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Sample records for acid-catalyzed polymerization reactions

  1. Enantioselective BINOL-phosphoric acid catalyzed Pictet-Spengler reactions of N-benzyltryptamine

    NARCIS (Netherlands)

    Sewgobind, N.V.; Wanner, M.J.; Ingemann, S.; de Gelder, R.; van Maarseveen, J.H.; Hiemstra, H.

    2008-01-01

    Optically active tetrahydro-beta-carbolines were synthesized via an (R)-BINOL-phosphoric acid-catalyzed asynunetric Pictet-Spengler reaction of N-benzyltryptamine with a series of aromatic and aliphatic aldehydes. The tetrahydro-beta-carbolines were obtained in yields ranging from 77% to 97% and wit

  2. Particle growth by acid-catalyzed heterogeneous reactions of organic carbonyls on preexisting aerosols.

    Science.gov (United States)

    Jang, Myoseon; Carroll, Brian; Chandramouli, Bharadwaj; Kamens, Richard M

    2003-09-01

    Aerosol growth by the heterogeneous reactions of different aliphatic and alpha,beta-unsaturated carbonyls in the presence/absence of acidified seed aerosols was studied in a 2 m long flow reactor (2.5 cm i.d.) and a 0.5-m3 Teflon film bag under darkness. For the flow reactor experiments, 2,4-hexadienal, 5-methyl-3-hexen-2-one, 2-cyclohexenone, 3-methyl-2-cyclopentenone, 3-methyl-2-cyclohexenone, and octanal were studied. The carbonyls were selected based on their reactivity for acid-catalyzed reactions, their proton affinity, and their similarity to the ring-opening products from the atmospheric oxidation of aromatics. To facilitate acid-catalyzed heterogeneous hemiacetal/acetal formation, glycerol was injected along with inorganic seed aerosols into the flow reactor system. Carbonyl heterogeneous reactions were accelerated in the presence of acid catalysts (H2SO4), leading to higher aerosol yields than in their absence. Aldehydes were more reactive than ketones for acid-catalyzed reactions. The conjugated functionality also resulted in higher organic aerosol yieldsthan saturated aliphatic carbonyls because conjugation with the olefinic bond increases the basicity of the carbonyl leading to increased stability of the protonated carbonyl. Aerosol population was measured from a series of sampling ports along the length of the flow reactor using a scanning mobility particle sizer. Fourier transform infrared spectrometry of either an impacted liquid aerosol layer or direct reaction of carbonyls as a thin liquid layer on a zinc selenide FTIR disk was employed to demonstrate the direct transformation of chemical functional groups via the acid-catalyzed reactions. These results strongly indicate that atmospheric multifunctional organic carbonyls, which are created by atmospheric photooxidation reactions, can contribute significantly to secondary organic aerosol formation through acid-catalyzed heterogeneous reactions. Exploratory studies in 25- and 190-m3 outdoor chambers

  3. Studies of Grafted and Sulfonated Spiro Poly(isatin-ethersulfone Membranes by Super Acid-Catalyzed Reaction

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    Lei Jin

    2016-03-01

    Full Text Available Spiro poly(isatin-ethersulfone polymers were prepared from isatin and bis-2,6-dimethylphenoxyphenylsulfone by super acid catalyzed polyhydroxyalkylation reactions. We designed and synthesized bis-2,6-dimethylphenoxyphenylsulfone, which is structured at the meta position steric hindrance by two methyl groups, because this structure minimized crosslinking reaction during super acid catalyzed polymerization. In addition, sulfonic acid groups were structured in both side chains and main chains to form better polymer chain morphology and improve proton conductivity. The sulfonation reactions were performed in two steps which are: in 3-bromo-1-propanesulfonic acid potassium salt and in con. sulfuric acid. The membrane morphology was studied by tapping mode atomic force microscope (AFM. The phase difference between the hydrophobic polymer main chain and hydrophilic sulfonated units of the polymer was shown to be the reasonable result of the well phase separated structure. The correlations of proton conductivity, ion exchange capacity (IEC and single cell performance were clearly described with the membrane morphology.

  4. Acid-catalyzed Furfuryl Alcohol Polymerization: Characterizations of Molecular Structure and Thermodynamic Properties

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Taejin; Assary, Rajeev A; Marshall, Christopher L; Gosztola, David J.; Curtiss, Larry A; Stair, Peter C

    2011-07-22

    The liquid-phase polymerization of furfuryl alcohol catalyzed by sulfuric acid catalysts and the identities of molecular intermediates were investigated by using Raman spectroscopy and density functional theory calculation. At room temperature, with an acid catalyst, a vigorous furfuryl alcohol polymerization reaction was observed, whereas even at a high water concentration, furfuryl alcohol was very stable in the absence of an acid catalyst. Theoretical studies were carried out to investigate the thermodynamics of protonation of furfuryl alcohol, initiation of polymerization, and formation of conjugated dienes and diketonic species by using the B3LYP level of theory. A strong aliphatic C=C band observed in the calculated and measured Raman spectra provided crucial evidence to understand the polymerization reaction mechanism. It is confirmed that the formation of a conjugated diene structure rather than a diketone structure is involved in the furfuryl alcohol polymerization reaction.

  5. Development of Fluorous Lewis Acid-Catalyzed Reactions

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    Joji Nishikido

    2006-08-01

    Full Text Available Organic synthetic methodology in the 21st century aims to conform to the principles of green sustainable chemistry (GSC and we may expect that in the future, the realization of GSC will be an important objective for chemical industries. An important aim of synthetic organic chemistry is to implement waste-free and environmentally-benign industrial processes using Lewis acids as versatile as aluminum choride. A key technological objective of our work in this area has been to achieve a “catalyst recycling system that utilizes the high activity and structural features of fluorous Lewis acid catalysts”. Thus, we have developed a series of novel fluorous Lewis acid catalysts, namely the ytterbium(III, scandium(III, tin(IV or hafnium(IV bis(perfluoroalkanesulfonylamides or tris(perfluoro- alkanesulfonylmethides. Our catalysts are recyclable and effective for acylations of alcohols and aromatics, Baeyer-Villiger reactions, direct esterifications and transesterifications in a fluorous biphasic system (FBS, in supercritical carbon dioxide and on fluorous silica gel supports.

  6. Stereoselectivities in α- and β-Amino Acids Catalyzed Mannich Reactions Involving Cyclohexanone

    Institute of Scientific and Technical Information of China (English)

    WANG Ying; FU Ai-ping; LI Hong-liang; TIAN Feng-hui; YUAN Shu-ping; SI Hong-zong; DUAN Yun-bo; WANG Zong-hua

    2011-01-01

    The effects of two different amino acid catalysts on the stereoselectivities in the direct Mannich reactions of cyclohexanone,p-anisidine and p-nitrobenzaldehyde were studied with the aid of density functional theory.Transition states of the stereo-determining C-C bond-forming step with the addition of enamine intermediate to the imine for the L-proline(α-amino acid) and (R)-3-pyrrolidinecarboxylic acid(β-amino acid)-catalyzed processes were reported.B3LYP/6-31G** calculations provide a good explanation for the opposite syn vs.anti diastereoselectivities of these two different kinds of catalysts(syn-selectivity for the α-amino acid catalysts,anti-selectivity for the β-amino acid catalysts).Calculated and observed diastereomeric ratio and enantiomeric excess values are in reasonable agreement.

  7. Acid-Catalyzed Transesterification Reaction of Beef Tallow For Biodiesel Production By Factor Variation

    Directory of Open Access Journals (Sweden)

    R.C. Ehiri

    2014-07-01

    Full Text Available Biodiesel is a diesel grade fuel made by transesterification reaction of vegetable oils and animal fats with alcohol. Three variable factors that affect the yield of biodiesel namely, reaction time, reaction temperature and catalyst concentration were studied in this work. The biodiesel was produced via a batchprocess acid-catalyzed transesterification reaction of beef tallow with methanol. Optimal conditions for the reaction were established in a three factor two-level (23 central composite design with the biodiesel pretreatment yield as the response surface. The results show that the mean yield of biodiesel was 92.04% with a standard deviation of 5.16. An optimal biodiesel yield of 96.30% occurred at 0.5% HCl catalyst concentration and at constant conditions of 1.5h reaction time, 60oC reaction temperature and 6:1 methanol: tallow volume ratio. Gas chromatographic analysis of the beef tallow identified palmitic, stearic and oleic acids in it while the fatty acid methyl esters in the biodiesel product were oleate and linoleate. Catalysis was the most significant factor in the transesterification process.

  8. Synthesis of deuterium-labeled imipramine using acid-catalyzed exchange reaction

    Energy Technology Data Exchange (ETDEWEB)

    Baba, S.; Furuta, T.; Sasaki, Y.; Kasuya, Y. (Tokyo Coll. of Pharmacy (Japan))

    1985-02-01

    Synthesis of three forms of selectively deuterated imipramine with high isotopic purity using acid catalyzed hydrogen-deuterium exchange reaction is described. Deuterated imipramine labeled at the positions of 2,4,6 and 8 (IP-d/sub 4/(I)) was prepared directly by heating imipramine in 10% DC1-D/sub 2/O at 80/sup 0/ for 8hr. Imipramine labeled at all of the eight aromatic positions (IP-d/sub 8/) was synthesized from iminodibenzyl-1,2,3,4,6,7,8,9-d/sub 8/ which was prepared by treating iminodibenzyl (IDB) in 37% DC1-D/sub 2/O at 160/sup 0/ for 24hr. An imipramine labeled at the positions of 1,3,7 and 9 (IP-d/sub 4/(II)) was obtained by ''back-exchange'' of IP-d/sub 8/ under the protio condition according to the exchange procedure of IP-d/sub 4/(I).

  9. The Nature of Acid-Catalyzed Acetalization Reaction of 1,2-Propylene Glycol and Acetaldehyde

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Chen; Chen, Hui; Li, Xia; Hu, Jianli; Liang, Baochen [Tianjin University of Technology, Tianjin (China)

    2015-08-15

    We investigated catalytic activity of ion-exchange resins in acetalization of 1,2-propylene glycol with acetaldehyde. The impacts of reaction variables, such as temperature, reaction time, catalyst loading and feedstock composition, on the conversion of 1,2-propylene glycol were measured. The life of the catalyst was also studied. Furthermore, the reaction kinetics of 1,2-propylene glycol acetalization was studied. It was found that reaction rate followed the first order kinetics to acetaldehyde and 1,2-propylene glycol, respectively. Therefore, overall acetalization reaction should follow the second-order reaction kinetics, expressed as r - kC{sup nA}{sub A}C{sup nB}{sub B} = 19.74e{sup -650/T}C{sup 1}{sub A}C{sup 1}{sub B}.

  10. Efficient Lewis Acids Catalyzed Aza-Michael Reactions of Enones with Carbamates

    Institute of Scientific and Technical Information of China (English)

    XIA Chun-Gu; XU Li-Wen

    2004-01-01

    The a-amino carbonyl functionality is not only a segment of biologically important natural products but also a versatile intermediate for the synthesis of nitrogen-containing compounds.1 The development of novel synthetic methods leading to a-amino ketone, a-amino acids or their derivatives has attracted much attention in organic synthesis.2 Among the traditional methods for generating a-amino carbonyl compounds, Mannich-type reaction is one of the classical and powerful methods.3 However, the classic Mannich reaction presents serious disadvantages, for example, there is still a drawback in that the silyl enolates have to be prepared from the corresponding carbonyl compounds. Alternatively, aza-Michael additions can be used to create carbon-heteroatom bonds by reaction of a,a-unsaturated carbonyl compounds with amines. Although recent advances have made this route more attractive, development of cheaper, simpler, and more efficient metal catalyst, especially which can be applied to chalcone, is highly desirable.In this paper, we demonstrated that the first aza-Michael reaction of chalcone with a less nucleophilic carbamates can be accomplished on Me3SiCFFeCl3 catalyst system under very mild conditions. Apart from experimental simplicity, the advantages of this methodology are the use of a very cheap Lewis acid catalyst and the insensitivity of the reaction mixture towards air and moisture.catalyst for aza-Michael reaction of chalcone and cyclic enones with carbamates. And with the cyclic enones with carbamates in dichloromethane at room temperature were also investigated. In this conjugate addition reaction, good to excellent yields of a-amino ketones were obtained with system could also mediates aza-Michael addition of carbamates to chalcone and derivatives.These new strategies opened efficient procedures for the synthesis of a-amino ketones under mild conditions.

  11. Graphene oxide for acid catalyzed-reactions: Effect of drying process

    Science.gov (United States)

    Gong, H. P.; Hua, W. M.; Yue, Y. H.; Gao, Z.

    2017-03-01

    Graphene oxides (GOs) were prepared by Hummers method through various drying processes, and characterized by XRD, SEM, FTIR, XPS and N2 adsorption. Their acidities were measured using potentiometric titration and acid-base titration. The catalytic properties were investigated in the alkylation of anisole with benzyl alcohol and transesterification of triacetin with methanol. GOs are active catalysts for both reaction, whose activity is greatly affected by their drying processes. Vacuum drying GO exhibits the best performance in transesterification while freezing drying GO is most active for alkylation. The excellent catalytic behavior comes from abundant surface acid sites as well as proper surface functional groups, which can be obtained by selecting appropriate drying process.

  12. Mechanism of arylboronic acid-catalyzed amidation reaction between carboxylic acids and amines.

    Science.gov (United States)

    Wang, Chen; Yu, Hai-Zhu; Fu, Yao; Guo, Qing-Xiang

    2013-04-07

    Arylboronic acids were found to be efficient catalysts for the amidation reactions between carboxylic acids and amines. Theoretical calculations have been carried out to investigate the mechanism of this catalytic process. It is found that the formation of the acyloxyboronic acid intermediates from the carboxylic acid and the arylboronic acid is kinetically facile but thermodynamically unfavorable. Removal of water (as experimentally accomplished by using molecular sieves) is therefore essential for overall transformation. Subsequently C-N bond formation between the acyloxyboronic acid intermediates and the amine occurs readily to generate the desired amide product. The cleavage of the C-O bond of the tetracoordinate acyl boronate intermediates is the rate-determining step in this process. Our analysis indicates that the mono(acyloxy)boronic acid is the key intermediate. The high catalytic activity of ortho-iodophenylboronic acid is attributed to the steric effect as well as the orbital interaction between the iodine atom and the boron atom.

  13. The acid-catalyzed hydrolysis of an α-pinene-derived organic nitrate: kinetics, products, reaction mechanisms, and atmospheric impact

    Science.gov (United States)

    Rindelaub, Joel D.; Borca, Carlos H.; Hostetler, Matthew A.; Slade, Jonathan H.; Lipton, Mark A.; Slipchenko, Lyudmila V.; Shepson, Paul B.

    2016-12-01

    data, product identification confirms that a unimolecular specific acid-catalyzed mechanism is responsible for organic nitrate hydrolysis under acidic conditions. The free energies and enthalpies of the isobutyl nitrate hydrolysis intermediates and products were calculated using a hybrid density functional (ωB97X-V) to support the proposed mechanisms. These findings provide valuable information regarding the organic nitrate hydrolysis mechanism and its contribution to the fate of atmospheric NOx, aerosol phase processing, and BSOA composition.

  14. Brønsted-acid-catalyzed asymmetric multicomponent reactions for the facile synthesis of highly enantioenriched structurally diverse nitrogenous heterocycles.

    Science.gov (United States)

    Yu, Jie; Shi, Feng; Gong, Liu-Zhu

    2011-11-15

    Optically pure nitrogenous compounds, and especially nitrogen-containing heterocycles, have drawn intense research attention because of their frequent isolation as natural products. These compounds have wide-ranging biological and pharmaceutical activities, offering potential as new drug candidates. Among the various synthetic approaches to nitrogenous heterocycles, the use of asymmetric multicomponent reactions (MCRs) catalyzed by chiral phosphoric acids has recently emerged as a particularly robust tool. This method combines the prominent merits of MCRs with organocatalysis, thus affording enantio-enriched nitrogenous heterocyclic compounds with excellent enantioselectivity, atom economy, bond-forming efficiency, structural diversity, and complexity. In this Account, we discuss a variety of asymmetric MCRs catalyzed by chiral phosphoric acids that lead to the production of structurally diverse nitrogenous heterocycles. In MCRs, three or more reagents are combined simultaneously to produce a single product containing structural contributions from all the components. These one-pot processes are especially useful in the construction of heterocyclic cores: they can provide a high degree of both complexity and diversity for a targeted set of scaffolds while minimizing the number of synthetic operations. Unfortunately, enantioselective MCRs have thus far been relatively underdeveloped. Particularly lacking are reactions that proceed through imine intermediates, which are formed from the condensation of carbonyls and amines. The concomitant generation of water in the condensation reaction can deactivate some Lewis acid catalysts, resulting in premature termination of the reaction. Thus, chiral catalysts typically must be compatible with water for MCRs to generate nitrogenous compounds. Recently, organocatalytic MCRs have proven valuable in this respect. Brønsted acids, an important class of organocatalysts, are highly compatible with water and thereby offer great

  15. Reaction Between U(Ⅳ)and Nitrous Acid Catalyzed by Plutonium%Pu催化HNO2氧化U(Ⅳ)的研究

    Institute of Scientific and Technical Information of China (English)

    王浩文; 周贤明; 李高亮; 兰天; 刘金平; 常尚文; 何辉; 段红卫

    2014-01-01

    The oxidation of U(Ⅳ)by nitrous acid in the present of plutonium was studied. The influence of the concentration of nitrous acid,nitric acid,plutonium on the oxidation of U(Ⅳ)was investigated.The results show that plutonium can catalyze the reaction between U(Ⅳ)and nitrous acid.And the rate equation of the reaction between U(Ⅳ)and nitrous acid catalyzed by plutonium was obtained:-dc(U(Ⅳ))/dt=kc(U(Ⅳ))c1.3 (HNO3 )c1.3 (NO-2 ), k=(0.69±0.04)L2.6/(mol2.6 ·min)when the temperature was 29 ℃.The mechanism of the oxidation of U(Ⅳ)was discussed.%研究了Pu存在条件下 HNO2氧化 U(Ⅳ)的反应,并考察了 HNO2浓度、反应温度、HNO3浓度、Pu 浓度对 U(Ⅳ)氧化速率的影响。结果表明:Pu对 HNO2氧化 U(Ⅳ)的反应具有显著催化作用;获得了 Pu催化条件下 HNO2氧化 U(Ⅳ)的动力学方程:-dc(U(Ⅳ))/dt=kc(U(Ⅳ))c1.3(HNO3)c1.3(NO-2),得到了29℃时的反应速率常数k=(0.69±0.04)L2.6/(mol2.6·min)。并对反应历程进行了探讨。

  16. Polymerization as a Model Chain Reaction

    Science.gov (United States)

    Morton, Maurice

    1973-01-01

    Describes the features of the free radical, anionic, and cationic mechanisms of chain addition polymerization. Indicates that the nature of chain reactions can be best taught through the study of macromolecules. (CC)

  17. Nucleotide Selectivity in Abiotic RNA Polymerization Reactions

    Science.gov (United States)

    Coari, Kristin M.; Martin, Rebecca C.; Jain, Kopal; McGown, Linda B.

    2017-02-01

    In order to establish an RNA world on early Earth, the nucleotides must form polymers through chemical rather than biochemical reactions. The polymerization products must be long enough to perform catalytic functions, including self-replication, and to preserve genetic information. These functions depend not only on the length of the polymers, but also on their sequences. To date, studies of abiotic RNA polymerization generally have focused on routes to polymerization of a single nucleotide and lengths of the homopolymer products. Less work has been done the selectivity of the reaction toward incorporation of some nucleotides over others in nucleotide mixtures. Such information is an essential step toward understanding the chemical evolution of RNA. To address this question, in the present work RNA polymerization reactions were performed in the presence of montmorillonite clay catalyst. The nucleotides included the monophosphates of adenosine, cytosine, guanosine, uridine and inosine. Experiments included reactions of mixtures of an imidazole-activated nucleotide (ImpX) with one or more unactivated nucleotides (XMP), of two or more ImpX, and of XMP that were activated in situ in the polymerization reaction itself. The reaction products were analyzed using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) to identify the lengths and nucleotide compositions of the polymerization products. The results show that the extent of polymerization, the degree of heteropolymerization vs. homopolymerization, and the composition of the polymeric products all vary among the different nucleotides and depend upon which nucleotides and how many different nucleotides are present in the mixture.

  18. Polyphosphorous acid catalyzed cyclization in the synthesis of cryptolepine derivatives

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    11-Oxo-10,11-dihydroxy-5H-indolo[3,2,b]quinoline7-carboxylic acid was obtained specifically by polyphosphorous acid catalyzed cyclization with optimal reaction conditions. Biological assays showed that it potentially inhibits the proteasomal chymotrypsin-like activity in vitro and suppresses breast cancer cell growth.

  19. Biodiesel by acid-catalyzed transesterification with butanol

    OpenAIRE

    Bynes, Adrian

    2012-01-01

    Jatropha oil and Rapeseed oil was transesterified with n-butanol by the use of H2SO4. Before conducting the experiments a review of the effect of alcohol type was preformed. Alcohols from methanol to butanol, branched and straight, were reviewed for the effect on the acid catalyzed transesterification reaction. From the review it was found that propanol and butanol were the best for the acidic transesterification reaction. Variables such as time, temperature, alcohol amount and catalyst c...

  20. Lewis acid catalyzed cyclization of glycals/2-deoxy-D-ribose with arylamines: additional findings on product structure and reaction diastereoselectivity.

    Science.gov (United States)

    Du, Chengtang; Li, Fulong; Zhang, Xuefeng; Hu, Wenxiang; Yao, Qizheng; Zhang, Ao

    2011-11-01

    The cyclization reactions of arylamines with 2-deoxy-D-ribose or glycals were reinvestigated in the current report. In the montmorillonite KSF- or InCl(3)-initiated reactions of 2-deoxy-D-ribose with arylamines, a pair of diastereomeric tetrahydro-2H-pyran-fused tetrahydroquinolines was obtained in a nearly 1:1 ratio where the structure of one diastereomer was incorrectly assigned in the literature. Meanwhile, the diastereoselectivity in InBr(3)-catalyzed cyclization of glycals with arylamines was also incorrectly reported previously. It was found that high diastereomeric selectivity was achieved only when a C5-substituted glycal was used; otherwise, a pair of diastereomers was obtained in moderate yield with 1:1 diastereomeric ratio. Furthermore, tetrahydrofuran-fused tetrahydroquinolines 5b and 5b' were also prepared successfully by using TBDPS-protected ribose as the glycal precursor and montmorillonite KSF as the activator.

  1. A Meldrum's Acid Catalyzed Synthesis of Bis (indolyl) methanes in Water under Ultrasonic Condition

    Institute of Scientific and Technical Information of China (English)

    WANG,Shun-Yi; JI,Shun-Jun; SU,Xiao-Ming

    2008-01-01

    A highly effective Meldrum's acid catalyzed synthesis of bis(indol-3-yl)methanes has been developed. This reaction provides the corresponding bis(indol-3-yl)methanes in high yields after short reaction time in the presence of 2 mol% catalyst in water under ultrasonic condition.

  2. Polymerization reaction in restricted space of layered double hydroxides (LDHs)

    Institute of Scientific and Technical Information of China (English)

    SI Lichun; WANG Ge; CAI Fuli; WANG Zhiqiang; DUAN Xue

    2004-01-01

    This paper reported the preparation of styrene sulfonate intercalated layered double hydroxides (LDHs) material, SS-LDHs by coprecipitation method, followed by in-situ polymerization of the monomers in the interlayer space of LDHs. The polymerization reaction was monitored by UV and NMR. It is confirmed that when the reaction occurred at 100℃ for 24 h, part of monomers did not react .When the reaction was carried out at 150℃, the polymeriza tion of the intercalated monomers is complete to afford the polymer intercalated product PSS-LDHs. During the polymerization process, the layered structure remains well. At thesame time the gallery height increases with the lengthening of reaction time. This is preliminarily because that the PSS becomes more swelling with the amount of water it absorbs due to its hygroscopicity property.

  3. Competition Between Hydrotreating and Polymerization Reactions During Pyrolysis Oil Hydrodeoxygenation

    NARCIS (Netherlands)

    Mercader, F. De Miguel; Koehorst, P. J. J.; Heeres, H. J.; Kersten, S. R. A.; Hogendoorn, J. A.

    2011-01-01

    Hydrodeoxygenation (HDO) of pyrolysis oil is an upgrading step that allows further coprocessing of the oil product in (laboratory-scale) standard refinery units to produce advanced biofuels. During HDO, desired hydrotreating reactions are in competition with polymerization reactions that can lead to

  4. Dispersion Polymerization of Polystyrene Particles Using Alcohol as Reaction Medium

    Science.gov (United States)

    Cho, Young-Sang; Shin, Cheol Hwan; Han, Sujin

    2016-02-01

    In this study, monodisperse polystyrene nanospheres were prepared by dispersion polymerization using alcohol as reaction medium to prepare colloidal clusters of the latex beads. Polyvinylpyrrolidone (PVP) and 2-(methacryloyloxy)ethyltrimethylammonium chloride (MTC) were used as dispersion stabilizer and comonomer, respectively. The particle size could be controlled by adjusting the reactant compositions such as the amount of stabilizer, comonomer, and water in the reactant mixture. The size and monodispersity of the polymeric particles could be also controlled by changing the reaction medium with different alcohols other than ethanol or adjusting the polymerization temperature. The synthesized particles could be self-organized inside water-in-oil emulsion droplets by evaporation-driven self-assembly to produce colloidal clusters of the polymeric nanospheres.

  5. Kinetics of Model Reactions for Interfacial Polymerization

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    Henry Hall

    2012-02-01

    Full Text Available To model the rates of interfacial polycondensations, the rates of reaction of benzoyl chloride and methyl chloroformate with various aliphatic monoamines in acetonitrile were determined at 25 °C. Buffering with picric acid slowed these extremely fast reactions so the rate constants could be determined from the rate of disappearance of picrate ion. The rates of the amine reactions correlated linearly with their Swain-Scott nucleophilicities.

  6. Dyes as Photoinitiators or Photosensitizers of Polymerization Reactions

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    Christian Ley

    2010-12-01

    Full Text Available A short but up-to-date review on the role of dyes in the photoinitiation processes of polymerization reactions is presented. Radical and cationic reactions are largely encountered in the radiation curing and the imaging areas for use in traditional coating applications as well as in high tech sectors such as nanofabrication, computer-to-plate processing, laser direct imaging, manufacture of optical elements, etc. Recent promising developments concerned with the introduction of the silyl radical chemistry that enhances the polymerization efficiency are also discussed.

  7. Reactions and Polymerizations at the Liquid-Liquid Interface.

    Science.gov (United States)

    Piradashvili, Keti; Alexandrino, Evandro M; Wurm, Frederik R; Landfester, Katharina

    2016-02-24

    Reactions and polymerizations at the interface of two immiscible liquids are reviewed. The confinement of two reactants at the interface to form a new product can be advantageous in terms of improved reaction kinetics, higher yields, and selectivity. The presence of the liquid-liquid interface can accelerate the reaction, or a phase-transfer catalyst is employed to draw the reaction in one phase of choice. Furthermore, the use of immiscible systems, e.g., in emulsions, offers an easy means of efficient product separation and heat dissipation. A general overview on low molecular weight organic chemistry is given, and the applications of heterophase polymerization, occurring at or in proximity of the interface, (mostly) in emulsions are presented. This strategy can be used for the efficient production of nano- and microcarriers for various applications.

  8. Acid-catalyzed production of biodiesel from waste frying oil

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, S.; Dube, M.A.; McLean, D.D. [Department of Chemical Engineering, University of Ottawa, Ottawa, ON (Canada); Kates, M. [Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, ON (Canada)

    2006-03-15

    The reaction kinetics of acid-catalyzed transesterification of waste frying oil in excess methanol to form fatty acid methyl esters (FAME), for possible use as biodiesel, was studied. Rate of mixing, feed composition (molar ratio oil:methanol:acid) and temperature were independent variables. There was no significant difference in the yield of FAME when the rate of mixing was in the turbulent range 100 to 600rpm. The oil:methanol:acid molar ratios and the temperature were the most significant factors affecting the yield of FAME. At 70{sup o}C with oil:methanol:acid molar ratios of 1:245:3.8, and at 80{sup o}C with oil:methanol:acid molar ratios in the range 1:74:1.9-1:245:3.8, the transesterification was essentially a pseudo-first-order reaction as a result of the large excess of methanol which drove the reaction to completion (99+/-1% at 4h). In the presence of the large excess of methanol, free fatty acids present in the waste oil were very rapidly converted to methyl esters in the first few minutes under the above conditions. Little or no monoglycerides were detected during the course of the reaction, and diglycerides present in the initial waste oil were rapidly converted to FAME. (author)

  9. Brønsted Acid-Catalyzed Direct Substitution of 2-Ethoxytetrahydrofuran with Trifluoroborate Salts

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    Kayla M. Fisher

    2016-06-01

    Full Text Available Metal-free transformations of organotrifluoroborates are advantageous since they avoid the use of frequently expensive and sensitive transition metals. Lewis acid-catalyzed reactions involving potassium trifluoroborate salts have emerged as an alternative to metal-catalyzed protocols. However, the drawbacks to these methods are that they rely on the generation of unstable boron dihalide species, thereby resulting in low functional group tolerance. Recently, we discovered that in the presence of a Brønsted acid, trifluoroborate salts react rapidly with in situ generated oxocarbenium ions. Here, we report Brønsted acid-catalyzed direct substitution of 2-ethoxytetrahydrofuran using potassium trifluoroborate salts. The reaction occurs when tetrafluoroboric acid is used as a catalyst to afford functionalized furans in moderate to excellent yields. A variety of alkenyl- and alkynyltrifluoroborate salts readily participate in this transformation.

  10. Comparison of techniques for the determination of conversion during suspension polymerization reactions

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    J. C. Santos

    2008-06-01

    Full Text Available The determination of conversion during suspension polymerization reactions is not an easy task due to the heterogeneity of the reaction medium and the tendency of particles to agglomerate rapidly when stirring is stopped. Usually, bulk polymerization in ampoules is employed to study the kinetics of suspension polymerization reactions. In this work, a comparison of different techniques for the determination of conversion during suspension polymerization reactions is presented. Results showed a good agreement between the conversion obtained by gravimetry during styrene suspension polymerization and on-line conversion monitoring data using fiber-optic based Raman Spectroscopy. Nevertheless, the polymerization rate of styrene bulk polymerization carried out in ampoules was higher than the real reaction rate of styrene suspension polymerization due to slightly higher reaction temperatures. Simulation results using the experimental temperature data in a mathematical model confirmed these results.

  11. Studies on the runaway reaction of ABS polymerization process.

    Science.gov (United States)

    Hu, Kwan-Hua; Kao, Chen-Shan; Duh, Yih-Shing

    2008-11-15

    Taiwan has the largest acrylonitrile-butadiene-styrene (ABS) copolymer production in the world. Preventing on unexpected exothermic reactions and related emergency relief hazard is essential in the safety control of ABS emulsion polymerization. A VSP2 (Vent Sizing Package 2) apparatus is capable of studying both normal and abnormal conditions (e.g., cooling failure, mischarge, etc.) of industrial process. In this study, the scenarios were verified from the following abnormal conditions: loss of cooling, double charge of initiator, overcharge of monomer, without charge of solvent, and external fire. An external fire with constant heating will promote higher self-heat rate and this is recommended as the worst case scenario of emulsion polymerization on butadiene. Cooling failure coupled with bulk system of reactant was determined to be the credible worst case in ABS emulsion polymerization. Finally, the emergency vent sizing based on thermokinetics from VSP associated with DIERS methodology were used for evaluating the vent sizing and compared to that of the industrial plants.

  12. Stability of prostacyclin analogues: an unusual lack of reactivity in acid-catalyzed alkene hydration.

    Science.gov (United States)

    Magill, A; O'Yang, C; Powell, M F

    1988-04-01

    Prostacyclin analogue 5 undergoes specific acid-catalyzed hydration (kH+ = 1.9 x 10(-7)M-1 sec-1 at 25 degrees C) and a pH-independent oxidation reaction (k0 = 1.2 x 10(-10) sec-1 at 25 degrees C) above pH approximately 5. The hydration reaction for 5 is much slower than for other structurally similar exocyclic alkenes, even though the rate-determining step is proton transfer. This slowness of reaction and an analysis of the pH-rate profile show that 5 does not exhibit significant intramolecular general acid catalysis, as does prostacyclin.

  13. An acid-catalyzed macrolactonization protocol.

    Science.gov (United States)

    Trost, Barry M; Chisholm, John D

    2002-10-17

    [reaction: see text] An efficient macrolactonization protocol devoid of any base was developed derived from the use of vinyl esters in transesterification. Subjecting a hydroxy acid and ethoxyacetylene to 2 mol % [RuCl(2)(p-cymene)](2) in toluene followed by addition of camphorsulfonic acid or inverse addition provided macrolactones in good yields.

  14. Pilot-scale study on the acid-catalyzed steam explosion of rice straw using a continuous pretreatment system.

    Science.gov (United States)

    Chen, Wen-Hua; Tsai, Chia-Chin; Lin, Chih-Feng; Tsai, Pei-Yuan; Hwang, Wen-Song

    2013-01-01

    A continuous acid-catalyzed steam explosion pretreatment process and system to produce cellulosic ethanol was developed at the pilot-scale. The effects of the following parameters on the pretreatment efficiency of rice straw feedstocks were investigated: the acid concentration, the reaction temperature, the residence time, the feedstock size, the explosion pressure and the screw speed. The optimal presteaming horizontal reactor conditions for the pretreatment process are as follows: 1.7 rpm and 100-110 °C with an acid concentration of 1.3% (w/w). An acid-catalyzed steam explosion is then performed in the vertical reactor at 185 °C for 2 min. Approximately 73% of the total saccharification yield was obtained after the rice straw was pretreated under optimal conditions and subsequent enzymatic hydrolysis at a combined severity factor of 0.4-0.7. Moreover, good long-term stability and durability of the pretreatment system under continuous operation was observed.

  15. Potential of phosphoric acid-catalyzed pretreatment and subsequent enzymatic hydrolysis for biosugar production from Gracilaria verrucosa.

    Science.gov (United States)

    Kwon, Oh-Min; Kim, Sung-Koo; Jeong, Gwi-Taek

    2016-07-01

    This study combined phosphoric acid-catalyzed pretreatment and enzymatic hydrolysis to produce biosugars from Gracilaria verrucosa as a potential renewable resource for bioenergy applications. We optimized phosphoric acid-catalyzed pretreatment conditions to 1:10 solid-to-liquid ratio, 1.5 % phosphoric acid, 140 °C, and 60 min reaction time, producing a 32.52 ± 0.06 % total reducing sugar (TRS) yield. By subsequent enzymatic hydrolysis, a 68.61 ± 0.90 % TRS yield was achieved. These results demonstrate the potential of phosphoric acid to produce biosugars for biofuel and biochemical production applications.

  16. Antibacterial properties of cyanoacrylate tissue adhesive: Does the polymerization reaction play a role?

    Directory of Open Access Journals (Sweden)

    Romero Ivana

    2009-01-01

    Full Text Available Purpose: To ascertain if the polymerization reaction also contributes additionally to the antibacterial effects of two commonly used cyanoacrylate tissue adhesives. Materials and Methods: Fresh liquid ethyl-cyanoacrylate (EC and N-butyl-cyanoacrylate (BC adhesives were applied onto 6-mm sterile filter paper discs. In the first group, the adhesive-soaked discs were immediately placed onto confluent monolayer cultures of bacteria, allowing the polymerization reaction to proceed while in culture. In the second group, the adhesive-soaked disc was allowed to first polymerize prior to being placed onto the bacterial cultures. Four types of bacteria were studied: Staphylococcus aureus , Streptococcus pneumoniae , Escherichia coli , and Pseudomonas aeruginosa . Immediately after the discs were applied, the cultures were incubated at 35° C for 24 h. Bacterial inhibitory halos were measured in the cultures at the end of the incubation period. Results: For EC, exposure of the bacteria to the cyanoacrylate polymerization reaction increased the bacterial inhibitory halos in Streptococcus pneumonia, Staphylococcus aureus and Escherichia coli. For BC, it increased the bacterial inhibitory halos in Staphylococcus aureus and Streptococcus pneumoniae . No inhibitory halos were observed in Pseudomonas aeruginosa. The bactericidal effect was higher in actively polymerizing EC, compared to previously polymerized EC in Staphylococcus aureus , Streptococcus pneumoniae, and Escherichia coli ; however, no such differences were observed for BC. Conclusions: The polymerization reaction may also be an important factor in the antibacterial properties of EC and BC.

  17. 氧化偶联反应和酸催化反应制备活性买麻藤醇二聚体衍生物%Preparation of Active Gnetol Dimers by Oxidative Coupling Reaction and Acid-Catalyzed Dimerization

    Institute of Scientific and Technical Information of China (English)

    姚春所; 林茂; 杨庆云

    2013-01-01

    Oxidative coupling reaction with FeCl3·6H2O as oxidant and acid-catalyzed dimerization of natural gnetol in methanol afforded two new gnetol dimers and one new phenyl naphthalene derivative: 4-[1-(2,6-dihydroxyphenyl)-2-(3,5-dihydroxyphenyl)ethyl]-2-[(lE)-2-(3,5-dihydroxyphenyl)ethenyl]-1,3-benzenediol (1),2-[1-(2,6-dihydroxyphenyl)-2-(3,5-di-hydroxyphenyl)ethyl]-5-f(1E)-2-(2,6-dihydroxyphenyl)ethenyl]-1,3-benzenediol (2) and 4-(6,8-dimethoxyl-2-naphthalenyl)-1,3-benzenediol (3). Their structures were elucidated on the basis of spectral analysis,and their possible formation mechanisms were discussed. 1 and 2 were new linear stilbene dimers synthesized for the first time. Pharmacological tests showed 1,2 and 3 to exhibit potent anti-oxidation activity with IC50 values of 6.29×10-9,4.19× 10-6,and 2.96×10-5 mol·L-1,respectively,and 2 was shown to have potent anti-inflammatory activity.%以天然得到的买麻藤醇为原料,以FeCl3·6H2O为氧化剂进行氧化偶联反应和酸催化二聚反应,获得了2个新的买麻藤醇二聚体及一个新的苯基萘衍生物:4-[1-(2,6-二羟基苯基)-2-(3,5-二羟基苯基)乙基]-2-[(1E)-2-(3,5-二 羟基苯基)乙烯基]-1,3-苯二醇(1),2-[1-(2,6-二羟基苯基)-2-(3,5-二羟基苯基)乙基]-5-[(1E)2-(2,6-二羟基苯基)乙烯基]-1,3-苯二醇(2)和4-(6,8-二甲氧基-2-萘基)-1,3-苯二醇(3).应用波谱分析的方法确定了它们的结构,并分别讨论了它们可能的形成机理.其中,化合物1和2首次为人工合成的二苯乙烯链状二聚体.活性测试结果表明,化合物1,2和3显示有较强的抗氧化活性,其IC50值分别为6.29×10-9,4.19×10-6和2.96×10-5 mol·L-1;化合物2还显示有较强的抗炎活性.

  18. 不同聚合机理的聚合反应速率串讲%Explain of Polymerization Reaction Rate of Different Polymerization Mechanism

    Institute of Scientific and Technical Information of China (English)

    赵文杰; 张会轩

    2013-01-01

    In the polymerization reaction engineering course,the polymerization reaction rate directly influences average polymerization degree of the polymerization products,and has the important position in the teaching material.The polymerization rate of different polymerization mechanisms is different,but they have high correlation.In this paper,The polymerization rate in the course of “polymerization reaction engineering” was detailed based on the clue of different mechanism of free radical polymerization,ion polymerization,coordination polymerization and the condensation polymerization.The similarities and differences among different polymerization rate were pointed out,aimed at improving students to understand and grasp the definition of the polymerizationrate.%在《聚合反应工程》课程中,聚合反应速率直接影响聚合产物的平均聚合度,是课程的一个核心内容,在教材中占有重要地位.不同聚合反应机理所对应的聚合反应速率不同,但它们具有很强的关联性.文中以自由基聚合、离子聚合、配位聚合以及缩聚的聚合机理为主线,把不同聚合机理中的聚合反应速率这一重要知识点做了串讲;指出了不同聚合反应速率之间的相同之处和不同之处.旨在使学生对聚合反应速率能有一个系统的认识和把握.

  19. Fixed Point Transformations Based Iterative Control of a Polymerization Reaction

    Science.gov (United States)

    Tar, József K.; Rudas, Imre J.

    As a paradigm of strongly coupled non-linear multi-variable dynamic systems the mathematical model of the free-radical polymerization of methyl-metachrylate with azobis (isobutyro-nitrile) as an initiator and toluene as a solvent taking place in a jacketed Continuous Stirred Tank Reactor (CSTR) is considered. In the adaptive control of this system only a single input variable is used as the control signal (the process input, i.e. dimensionless volumetric flow rate of the initiator), and a single output variable is observed (the process output, i.e. the number-average molecular weight of the polymer). Simulation examples illustrate that on the basis of a very rough and primitive model consisting of two scalar variables various fixed-point transformations based convergent iterations result in a novel, sophisticated adaptive control.

  20. Application of acid-catalyzed hydrolysis of dispersed organic solvent in developing new microencapsulation process technology.

    Science.gov (United States)

    Lee, Honghwa; Lee, Sunhwa; Bhattacharjee, Himanshu; Sah, Hongkee

    2012-01-01

    The aim of this study was to evaluate a new microencapsulation technology employing an acid-catalyzed solvent extraction method in conjunction to an emulsion-based microencapsulation process. Its process consisted of emulsifying a dispersed phase of poly(D,L-lactide-co-glycolide) and isopropyl formate in an aqueous phase. This step was followed by adding hydrochloric acid to the resulting oil-in-water emulsion, in order to initiate the hydrolysis of isopropyl formate dissolved in the aqueous phase. Its hydrolysis caused the liberation of water-soluble species, that is, isopropanol and formic acid. This event triggered continual solvent leaching out of emulsion droplets, thereby initiating microsphere solidification. This new processing worked well for encapsulation of progesterone and ketoprofen that were chosen as a nonionizable model drug and a weakly acidic one, respectively. Furthermore, the structural integrity of poly(D,L-lactide-co-glycolide) was retained during microencapsulation. The new microencapsulation technology, being conceptually different from previous approaches, might be useful in preparing various polymeric particles.

  1. Synthesis of ordered conjugated polycyclic aromatic hydrocarbon polymers through polymerization reaction on Au(111)

    DEFF Research Database (Denmark)

    Wang, Zhongping; Zhao, Huiling; Lu, Yan;

    2016-01-01

    One-dimensional pi-conjugated polymer chains with variable lengths have been synthesized successfully via thermal polymerization reaction on the Au(111) surface. Such polymer chains form parallel arrays along specific directions according to the initial assembly orientations of the close-packed Br...

  2. The Acid Catalyzed Nitration of Methanol: Formation of Methyl Nitrate via Aerosol Chemistry

    Science.gov (United States)

    Riffel, Brent G.; Michelsen, Rebecca R.; Iraci, Laura T.

    2004-01-01

    The liquid phase acid catalyzed reaction of methanol with nitric acid to yield methyl nitrate under atmospheric conditions has been investigated using gas phase infrared spectroscopy. This nitration reaction is expected to occur in acidic aerosol particles found in the upper troposphere/lower stratosphere as highly soluble methanol and nitric acid diffuse into these aerosols. Gaseous methyl nitrate is released upon formation, suggesting that some fraction of NO(x) may he liberated from nitric acid (methyl nitrate is later photolyzed to NO(x)) before it is removed from the atmosphere by wet deposition. Thus, this reaction may have important implications for the NO(x) budget. Reactions have been initiated in 45-62 wt% H2SO4 solutions at 10.0 C. Methyl nitrate production rates increased exponentially with acidity within the acidity regime studied. Preliminary calculations suggest that the nitronium ion (NO2(+) is the active nitrating agent under these conditions. The reaction order in methanol appears to depend on the water/methanol ratio and varies from first to zeroth order under conditions investigated. The nitration is first order in nitronium at all acidities investigated. A second order rate constant, kappa(sub 2), has been calculated to be 1 x 10(exp 8)/ M s when the reaction is first order in methanol. Calculations suggest the nitration is first order in methanol under tropospheric conditions. The infinitesimal percentage of nitric acid in the nitronium ion form in this acidity regime probably makes this reaction insignificant for the upper troposphere; however, this nitration may become significant in the mid stratosphere where colder temperatures increase nitric acid solubility and higher sulfuric acid content shifts nitric acid speciation toward the nitronium ion.

  3. Production of Biodiesel from High Acid Value Waste Cooking Oil Using an Optimized Lipase Enzyme/Acid-Catalyzed Hybrid Process

    Directory of Open Access Journals (Sweden)

    N. Saifuddin

    2009-01-01

    Full Text Available The present study is aimed at developing an enzymatic/acid-catalyzed hybrid process for biodiesel production using waste cooking oil with high acid value (poor quality as feedstock. Tuned enzyme was prepared using a rapid drying technique of microwave dehydration (time required around 15 minutes. Further enhancement was achieved by three phase partitioning (TPP method. The results on the lipase enzyme which was subjected to pH tuning and TPP, indicated remarkable increase in the initial rate of transesterification by 3.8 times. Microwave irradiation was found to increase the initial reaction rates by further 1.6 times, hence giving a combined increase in activity of about 5.4 times. The optimized enzyme was used for hydrolysis and 88% of the oil taken initially was hydrolyzed by the lipase. The hydrolysate was further used in acid-catalyzed esterification for biodiesel production. By using a feedstock to methanol molar ratio of 1:15 and a sulphuric acid concentration of 2.5%, a biodiesel conversion of 88% was obtained at 50 °C for an hour reaction time. This hybrid process may open a way for biodiesel production using unrefined and used oil with high acid value as feedstock.

  4. Reaction kinetics and modeling of photoinitiated cationic polymerization of an alicyclic based diglycidyl ether

    Energy Technology Data Exchange (ETDEWEB)

    Harikrishna, R., E-mail: r.harikrishna@ncl.res.in [Polymer Science and Engineering Division, National Chemical Laboratory, Pune 411008 (India); Ponrathnam, S. [Polymer Science and Engineering Division, National Chemical Laboratory, Pune 411008 (India); Tambe, S.S. [Chemical Engineering and Process Development Division, National Chemical Laboratory, Pune 411008 (India)

    2014-01-01

    Highlights: • Photocationic polymerization of alicyclic based diglycidyl ether was carried out. • Kinetic parameters were influenced by gelation and diffusional restrictions. • Applicability of autocatalytic model was established by nonlinear regression. • System showed higher activation energy than cycloaliphatic and aromatic diepoxides. -- Abstract: Photoinitiated cationic polymerization of cycloaliphatic diepoxides had received tremendous attention, while studies with lesser polymerizable diglycidyl ethers are comparatively less reported. The present work deals with the photoinitiated cationic polymerization of cyclohexane dimethanol diglycidyl ether followed by estimation of kinetic parameters. The effects of concentration of photoinitiator and temperature on curing performance were studied using photo differential scanning calorimeter or photo DSC with polychromatic radiation. It was observed that the rate of polymerization as well as ultimate conversion increased with increasing concentration of photoinitiator and temperature. The influences of gelation as well as diffusional restrictions have remarkable effect on cure performance. The kinetic parameters as per autocatalytic kinetic model were studied by Levenberg–Marquardt nonlinear regression method instead of conventional linear method for obtaining more accurate values of apparent rate constant. It was observed that the model fits with data from initial stages to almost towards the end of the reaction. The activation energy was found to be higher than the values reported for more reactive cycloaliphatic diepoxides. The value of pre-exponential factor increased with increase in activation energy showing influence of gelation at early stages of reaction.

  5. Role of keto–enol tautomerization in a chiral phosphoric acid catalyzed asymmetric thiocarboxylysis of meso-epoxide: a DFT study

    KAUST Repository

    Ajitha, Manjaly John

    2015-09-15

    The mechanism of a chiral phosphoric acid catalyzed thiocarboxylysis of meso-epoxide was investigated by density functional theory (DFT) calculations (M06-2X). The nucleophilic ring opening of epoxide by thiobenzoic acid was found to proceed via a concerted termolecular transition state with a simultaneous dual proton transfer to yield the β-hydroxy thioester product. Electrostatic interactions together with the steric environment inside the chiral catalyst play an important role in determining the enantioselectivity of the reaction.

  6. Emergent Properties of Giant Vesicles Formed by a Polymerization-Induced Self-Assembly (PISA) Reaction

    Science.gov (United States)

    Albertsen, Anders N.; Szymański, Jan K.; Pérez-Mercader, Juan

    2017-01-01

    Giant micrometer sized vesicles are of obvious interest to the natural sciences as well as engineering, having potential application in fields ranging from drug delivery to synthetic biology. Their formation often requires elaborate experimental techniques and attempts to obtain giant vesicles from chemical media in a one-pot fashion have so far led to much smaller nanoscale structures. Here we show that a tailored medium undergoing controlled radical polymerization is capable of forming giant polymer vesicles. Using a protocol which allows for an aqueous reaction under mild conditions, we observe the macroscale consequences of amphiphilic polymer synthesis and the resulting molecular self-assembly using fluorescence microscopy. The polymerization process is photoinitiated by blue light granting complete control of the reaction, including on the microscope stage. The self-assembly process leads to giant vesicles with radii larger than 10 microns, exhibiting several emergent properties, including periodic growth and collapse as well as phototaxis.

  7. Reaction monitoring of toluenediisocyanate (TDI) polymerization on a non-mixable aqueous surface by MALDI mass spectrometry.

    Science.gov (United States)

    Ahn, Yeong Hee; Kim, Ji Seok; Kim, Sung Ho

    2013-01-01

    The polymerization reaction of toluene diisocyanate (TDI) and hydroxyl compounds has been widely used for the production of polyurea resins. Since the composition and molecular-weight distribution of polymer adducts greatly influence the final properties of the resuting polymer, the development of analytical tools capable of monitoring the polyaddition reactions is important to control them as well as the properties of the resuting polymer. Here we report that matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI TOF MS) is useful to precisely monitor time-dependent dynamic events occurring in the polymerization reaction of TDI with water. For this purpose, the polymerization reactions were conducted in two different reaction systems, continuously supplying sufficient water and depleting water after an initial exposure of water to provide an anhydrous storage condition of prepolymer adducts. Samples prepared in a time course from the two different reaction systems were analyzed by a MALDI TOF mass spectrometer. The polymerization adducts of TDI and water were monitored and showed to consist of three structural types of polymer adduct series, including diisocyanate, monoamino, and diamino series. These MALDI mass data efficiently reflected changes in the reaction conditions of each TDI polymerization reaction, thereby providing precise information at the molecular level for time-dependent events occurring during the polymerization reaction. These events included changes between the polymer adduct series and in the molecular-weight distribution of each polymer adduct series. The results obtained in this study suggest that high-throughput MALDI MS-based dynamic monitoring of polymerization can be used to precisely control the polymerization reaction as well as to rapidly monitor the state of prepolymers in storage.

  8. The Comparison Between Ziegler-Natta and Zirconocene Catalyst on Reaction Conditions and Physical Properties of Polymer in Propylene Polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Lee, S.C.; Nam, Y.G.; Choung, S.J. [Kyunghee University, Suwon (Korea)

    2000-07-01

    Propylene polymerizations were carried out by using rac-Et(Ind){sub 2}ZrCl{sub 2} (Zirconocene catalyst) and a commercial third generation Ziegler-Natta catalyst in a semibatch reactor. From the polymerization reactions, the optimum reaction conditions and the physical properties of polymers produced from each catalyst system were investigated. The optimum reaction temperatures of rac-Et(Ind){sub 2}ZrCl{sub 2} and Ziegler-Natta catalyst were 50 deg. C, 40 deg. C, respectively. On the basis of the results for the produced polymer particle size distributions and the catalytic activities of polymerization reaction, the reaction temperature should be considered as an important factor for the successful polymerization reactions. Especially, the polymer was conglomerated in the higher reaction temperature. It was found that there was an upper limitation to co-catalyst concentration. Reaction rates and polymer yields rather decreased with increasing the concentration of co-catalyst, i.e., MAO and TEAl affected only polymerization activities, but the PEEB in Ziegler-Natta catalyst system affected isotactic indexes of produced polymer as well as activities. Based on these observations, the production yield seems to exhibit a first order linear relationship to the partial pressure of monomer. (author). 14 refs., 1 tab., 10 figs.

  9. Lactic Acid Yield Using Different Bacterial Strains, Its Purification, and Polymerization through Ring-Opening Reactions

    Directory of Open Access Journals (Sweden)

    F. G. Orozco

    2014-01-01

    Full Text Available Laboratory-scale anaerobic fermentation was performed to obtain lactic acid from lactose, using five lactic acid bacteria: Lactococcus lactis, Lactobacillus bulgaricus, L. delbrueckii, L. plantarum, and L. delbrueckii lactis. A yield of 0.99 g lactic acid/g lactose was obtained with L. delbrueckii, from which a final concentration of 80.95 g/L aqueous solution was obtained through microfiltration, nanofiltration, and inverse osmosis membranes. The lactic acid was polymerized by means of ring-opening reactions (ROP to obtain poly-DL-lactic acid (PDLLA, with a viscosity average molecular weight (Mv of 19,264 g/mol.

  10. Colloidal and micro-carbon spheres derived from low-temperature polymerization reactions.

    Science.gov (United States)

    Moreno-Castilla, Carlos

    2016-10-01

    Carbon spheres (CSs) have recently attracted major interest due to their new applications, mainly in energy storage and conversion but also in hard-templating, sorption/catalysis processes, and drug delivery systems. This is attributable to their physico-chemical properties, including their tunable morphology (solid, hollow and core-shell), size, surface area/porosity, good electrical conductivity, low external surface-to-volume ratio, high packing density, enhanced mass transport, robust mechanical stability, low cytotoxicity, and excellent biocompatibility. They can be obtained from a wide variety of carbon precursors and methods. This review covers their production by carbonization of polymer spheres from low-temperature polymerization reactions, considered here as below 250°C. This is a very important method because it allows the synthesis of CSs with different morphologies and doped with other elements or chemical compounds. The preparation of polymer spheres by this technique is well documented in the literature, and the objective of this review is to summarize and give an overview of the most significant publications, proposing a novel classification based on the formation mechanism of the polymer spheres. This classification includes the following polymerization processes: emulsion polymerization and its derivatives, seeded emulsion and inverse emulsion polymerization; precipitation polymerization and its derivative, dispersion polymerization; hard-templating; spray-drying; and hydrothermal or solvothermal treatment of carbohydrates and biomass in general. This review also reports on the morphology and surface characteristics of the CSs obtained by different synthetic approaches. The final section of the review describes the current applications of these CSs, notably in energy storage (supercapacitors and rechargeable batteries) and energy conversion (fuel cells and dye-sensitized solar cells). Besides the numerous applications listed above, they are

  11. Regioselective, borinic acid-catalyzed monoacylation, sulfonylation and alkylation of diols and carbohydrates: expansion of substrate scope and mechanistic studies.

    Science.gov (United States)

    Lee, Doris; Williamson, Caitlin L; Chan, Lina; Taylor, Mark S

    2012-05-16

    Synthetic and mechanistic aspects of the diarylborinic acid-catalyzed regioselective monofunctionalization of 1,2- and 1,3-diols are presented. Diarylborinic acid catalysis is shown to be an efficient and general method for monotosylation of pyranoside derivatives bearing three secondary hydroxyl groups (7 examples, 88% average yield). In addition, the scope of the selective acylation, sulfonylation, and alkylation is extended to 1,2- and 1,3-diols not derived from carbohydrates (28 examples); the efficiency, generality, and operational simplicity of this method are competitive with those of state-of-the-art protocols including the broadly applied organotin-catalyzed or -mediated reactions. Mechanistic details of the organoboron-catalyzed processes are explored using competition experiments, kinetics, and catalyst structure-activity relationships. These experiments are consistent with a mechanism in which a tetracoordinate borinate complex reacts with the electrophilic species in the turnover-limiting step of the catalytic cycle.

  12. Ruthenium Hydride/Brønsted Acid-Catalyzed Tandem Isomerization/N-Acyliminium Cyclization Sequence for the Synthesis of Tetrahydro-β-carbolines

    DEFF Research Database (Denmark)

    Hansen, Casper Lykke; Clausen, Janie Regitse Waël; Ohm, Ragnhild Gaard;

    2013-01-01

    This paper describes an efficient tandem sequence for the synthesis of 1,2,3,4-tetrahydro-β-carbolines (THBCs) relying on a ruthenium hydride/Brønsted acid- catalyzed isomerization of allylic amides to N-acyliminium ion intermediates which are trapped by a tethered indolenucleophile. The methodol...... the Suzuki cross-coupling reaction to the isomerization/N-acyliminium cyclization sequence. Finally, diastereo- and enantioselective versions of the title reaction have been examined using substrate control (with dr >15: 1) and asymmetric catalysis (ee up to 57%), respectively...

  13. Effect of reaction conditions on phenol removal by polymerization and precipitation using Coprinus cinereus peroxidase.

    Science.gov (United States)

    Masuda, M; Sakurai, A; Sakakibara, M

    2001-03-01

    The quantitative relationships between removal efficiency of phenol and reaction conditions were investigated using Coprinus cinereus peroxidase. The most effective ratio of hydrogen peroxide to phenol was nearly 1/1 (mol/mol) at an adequate enzyme dose. 12.2 U of the enzyme was needed to remove 1 mg of phenol when our peroxidase preparation was used. At an insufficient peroxidase dose, the optimum pH value was 9.0, and lowering the reaction temperature led to the improvement of removal efficiency. At an excess peroxidase dose, almost 100% removal of phenol was obtained over a wide range of pH (5-9) and temperature (0-60 degrees C). Despite the presence of culture medium components, it was shown that Coprinus cinereus peroxidase had the same phenol polymerization performance as horseradish peroxidase or Arthromyces ramosus peroxidase.

  14. Acid-Catalyzed Preparation of Biodiesel from Waste Vegetable Oil: An Experiment for the Undergraduate Organic Chemistry Laboratory

    Science.gov (United States)

    Bladt, Don; Murray, Steve; Gitch, Brittany; Trout, Haylee; Liberko, Charles

    2011-01-01

    This undergraduate organic laboratory exercise involves the sulfuric acid-catalyzed conversion of waste vegetable oil into biodiesel. The acid-catalyzed method, although inherently slower than the base-catalyzed methods, does not suffer from the loss of product or the creation of emulsion producing soap that plagues the base-catalyzed methods when…

  15. Optimizing the Acid Catalyzed Synthesis of Hyperbranched Poly(Glycerol-diacids) Oligomers

    Science.gov (United States)

    Oligomeric pre-polymers were synthesized by the acid-catalyzed condensation of glycerol with succinic acid, glutaric acid and azelaic acid in dimethylsulfoxide (DMSO) or dimethylformamide (DMF). The prepolymers were obtained, on average in 84% yield, and were characterized by proton NMR, MALDI-TOF ...

  16. Facile synthesis of small crystal ZSM-5 zeolite by acid-catalyzed hydrolysis of tetraethylorthosilicate

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Small crystal zeolites ZSM-5 with sizes of 150-300 nm were synthesized using the colloidal silicate precursors as the silica source created by the acid-catalyzed hydrolysis of tetraethylorthosilicate with tetrapropylammonium bromide as the structure-directing agent within a short crystallization time of 20-35 h. The precursors and final products were detected by XRD, SEM, ICP and DLS.

  17. Kinetics of acid-catalyzed cleavage of cumene hydroperoxide.

    Science.gov (United States)

    Levin, M E; Gonzales, N O; Zimmerman, L W; Yang, J

    2006-03-17

    The cleavage of cumene hydroperoxide, in the presence of sulfuric acid, to form phenol and acetone has been examined by adiabatic calorimetry. As expected, acid can catalyze cumene hydroperoxide reaction at temperatures below that of thermally-induced decomposition. At elevated acid concentrations, reactivity is also observed at or below room temperature. The exhibited reactivity behavior is complex and is significantly affected by the presence of other species (including the products). Several reaction models have been explored to explain the behavior and these are discussed.

  18. Furfural production from fruit shells by acid-catalyzed hydrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Demirbas, A. [Selcuk Univ., Konya (Turkey). Dept. of Chemical Engineering

    2006-01-21

    Pentosans are hydrolyzed to pentoses by dilute mineral acid hydrolysis. The main source of pentosans is hemicelluloses. Furfural can be produced by the acid hydrolysis of pentosan from fruit shells such as hazelnut, sunflower, walnut, and almond of agricultural wastes. Further dehydration reactions of the pentoses yield furfural. The hydrolysis of each shell sample was carried out in dilute sulfuric acid (0.05 to 0.200 mol/l), at high temperature (450-525 K), and short reaction times (from 30 to 600 s). (author)

  19. Esterification of phenolic acids catalyzed by lipases immobilized in organogels.

    Science.gov (United States)

    Zoumpanioti, M; Merianou, E; Karandreas, T; Stamatis, H; Xenakis, A

    2010-10-01

    Lipases from Rhizomucor miehei and Candida antarctica B were immobilized in hydroxypropylmethyl cellulose organogels based on surfactant-free microemulsions consisting of n-hexane, 1-propanol and water. Both lipases kept their catalytic activity, catalyzing the esterification reactions of various phenolic acids including cinnamic acid derivatives. High reaction rates and yields (up to 94%) were obtained when lipase from C. antarctica was used. Kinetic studies have been performed and apparent kinetic constants were determined showing that ester synthesis catalyzed by immobilized lipases occurs via the Michaelis-Menten mechanism.

  20. Modification of Clays by Sol-Gel Reaction and Their Use in the Ethylene In Situ Polymerization for Obtaining Nanocomposites

    Directory of Open Access Journals (Sweden)

    E. Moncada

    2012-01-01

    Full Text Available The nanocomposites formation by in situ polymerization used a metallocene catalyst (butyl-2-cyclopentadienyl zirconium 2-chlorines and a hectorite synthetic clay type which is discussed. This research was carried out in two phases. The first phase consisted of mixing the components of the metallocenic polymerization reaction (metallocene-methylaluminoxane-ethylene with clay in a reactor. In the second phase, the metallocenic catalytic system was supported by clay particles and then a polymerization reaction was made. In this second phase, the clay particles were modified using a sol-gel reaction with different pH values: pH = 3, pH = 8, and pH = 12. The results were compared in terms of the catalytic activity in the different systems (phase 1 and phase 2 and the nanoparticle morphology of nanocomposites generated in this study.

  1. System Identification for Experimental Study for Polymerization Catalyst Reaction in Fluidized Bed

    Directory of Open Access Journals (Sweden)

    Ahmmed Saadi Ibrehem

    2011-11-01

    Full Text Available In this work, system identification method is used to capture the reactor characteristics of production rate of polyethylene (PE based on published experimental data. The identification method is used to measure the percentage effect on the production rate of PE by measuring the effect of input factors of temperature of reaction, hydrogen concentration, and [Al]/[Ti] molar catalyst ratio. Temperature of reaction has big effects equal 52.4 % on the output of the system and 47.6 % on interaction of the system's parameters compare to other two factors. Also, hydrogen concentration has big effect equal 45.66 % on the output of the system and 14.7 % on interaction of the system's parameters. [Al]/[Ti] molar catalyst ratio has big effect on interaction of the system equal 28.6 and 1.94 % on the output of the system but less than the reaction temperature and hydrogen concentration. All these results depend on experiment results and these results are very important in industrial plants. ©2011 BCREC UNDIP. All rights reserved(Received: 13rd May 2011; Revised: 27th July 2011; Accepted: 22th September 2011[How to Cite: Ahmmed S. Ibrehem. (2011. System Identification for Experimental Study for Polymerization Catalyst Reaction in Fluidized Bed. Bulletin of Chemical Reaction Engineering & Catalysis, 6 (2: 137-146. doi:10.9767/bcrec.6.2.874.137-146][How to Link / DOI: http://dx,doi.org/10.9767/bcrec.6.2.874.137-146 || or local:  http://ejournal.undip.ac.id/index.php/bcrec/article/view/874 ] | View in 

  2. Lewis acid catalyzed transformations of Z-ligustilide

    Energy Technology Data Exchange (ETDEWEB)

    Rios, Maria Yolanda [Universidad Autonoma del Estado de Morelos, Cuernavaca, Morelos (Mexico); Delgado, Guillermo [Universidad Nacional Autonoma de Mexico, Mexico, D.F. (Mexico)

    1999-08-01

    Some Lewis acid mediated reactions of Z-ligustilide (1), a bioactive constituent of the medicinal species Ligusticum porteri, were investigated. These reactions provided varying mixtures of Z-butylidenephthalide (7), E-butylidenephthalide (8), n-butyphthalide (13), and novel linear dimeric phthalides (9-12) as the main products. The formation of the dimers occurred in low yields and with regio and situ-selectivity. Initial competitive O- and C- complexation of the Lewis acid with Z-ligustilide promoted the formation of the dimers occurred in low yields and with regio and situ- selectivity. Initial competitive O- and C- complexation of the Lewis acid with Z-ligustilide promoted the formation of carbocations at C(8), C(6) and C(7), which were stabilized by the addition of the C(6')-C(7') olefin of a second unit of the starting material, to provide cations at C(6') and C(7'). Subsequent isomerizations and elimination of the catalyst afforded the dimeric products 9-12. The yields and structure of the products are quite dependent on variations of the reaction conditions and the catalyst employed. [Spanish] Se investigaron algunas reacciones de Z-ligustilidas (1), un constituyente bioactivo de la planta medicinal Ligusticum porteri, catalizadas por acidos de Lewis. Estas reacciones produjeron mezclas variables de Z-butilidenftalida (7), E-butilidenftalida (8), n-butilftalida (13), y ftalidos dimetricos lineales novedosos (9-12) como productos principales. La formacion de los dimeros procedio en rendimientos bajos y con regio- y situ-selectividad. La O- y C- complejacion competitiva inicial del acido de Lewis con Z-lingustilida promueve la formacion de cationes en C(8), C(6) y C(7), los cuales son estabilizados por la adicion de la olefina C(6')-C(7') de una segunda unidad de la materia prima para generar los cationes en C(6')-C(7'). Isomerizaciones subsecuentes y la eliminacion del catalizador conducen a los productos dimericos 9

  3. Preparation of Polystyrenylphosphonous Acid of Low Polymerization Degree and Influence of Initiators upon the Free Radical Reaction Mechanism

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The polystyrenylphosphonous acid (PSPA) of low polymerization degree was prepared with one step reaction. The reaction mechanism was changed with different initiators. For the reaction with AIBN or BPO as the initiator, there are 2 or 3 series of radical reaction chains and 5 or 9 series of polystyrenyl products. The main products are PSPA without or with the fragment of the initiator H[CH(C6H5)-CH2]n-PO2H2 and C6H5CO2-[CH2CH (C6H5)]n-PO2H2 respectively.

  4. Preparation of Polystryenylphosphonous Acid of Low Polymerization Degree and Influence of Initiators upon the Free Radical Reaction Mechanism

    Institute of Scientific and Technical Information of China (English)

    XiangKaiFU; YanSUI; 等

    2002-01-01

    The polystyrenylphosphonous acid (PSPA) of low polymerization degress was prepared with one step reaction. The reaction mechanism was changed with different initiators. For the reaction with AIBN or BPO as the initiator, therer are 2 or 3 serives of radical reaction chains and 5 or 9 series of polystyrenyl products. The main products are PSPA without or with the fragment of the initiator H[CH(C6H5)-CH2]n-PO2H2 and C6H5CO2-[CH2CH(C6H5)]n-PO2H2 respectively.

  5. Polymerization of Acetonitrile via a Hydrogen Transfer Reaction from CH3 to CN under Extreme Conditions.

    Science.gov (United States)

    Zheng, Haiyan; Li, Kuo; Cody, George D; Tulk, Christopher A; Dong, Xiao; Gao, Guoying; Molaison, Jamie J; Liu, Zhenxian; Feygenson, Mikhail; Yang, Wenge; Ivanov, Ilia N; Basile, Leonardo; Idrobo, Juan-Carlos; Guthrie, Malcolm; Mao, Ho-Kwang

    2016-09-19

    Acetonitrile (CH3 CN) is the simplest and one of the most stable nitriles. Reactions usually occur on the C≡N triple bond, while the C-H bond is very inert and can only be activated by a very strong base or a metal catalyst. It is demonstrated that C-H bonds can be activated by the cyano group under high pressure, but at room temperature. The hydrogen atom transfers from the CH3 to CN along the CH⋅⋅⋅N hydrogen bond, which produces an amino group and initiates polymerization to form a dimer, 1D chain, and 2D nanoribbon with mixed sp(2) and sp(3) bonded carbon. Finally, it transforms into a graphitic polymer by eliminating ammonia. This study shows that applying pressure can induce a distinctive reaction which is guided by the structure of the molecular crystal. It highlights the fact that very inert C-H can be activated by high pressure, even at room temperature and without a catalyst.

  6. Nanosphere of Semicrystalline Polyaniline Powder: An Effective, Versatile, and Reusable Catalyst for Hantzsch Reaction

    Directory of Open Access Journals (Sweden)

    Ravi Bolagam

    2014-01-01

    Full Text Available Polyaniline salt containing 1-hydroxyethane-1,1-diphosphonic acid with nanosphere morphology in semicrystalline powder form was successfully synthesized by interfacial polymerization pathway and demonstrated as polymer based acid catalyzed in the synthesis of 1,4-dihydropyridines and polyhydroquinoline derivatives. This catalyst promotes the reaction under solvent free condition in excellent yield in 10 min with recyclability. The advantages of this methodology are the easy synthesis of polymer containing acid group catalyst in powder form having easily handlable, efficient, versatile, and reusable nature.

  7. On the Brønsted acid-catalyzed homogeneous hydrolysis of furans.

    Science.gov (United States)

    Nikbin, Nima; Caratzoulas, Stavros; Vlachos, Dionisios G

    2013-11-01

    Furan affairs: Electronic structure calculations of the homogeneous Brønsted acid-catalyzed hydrolysis of 2,5-dimethylfuran show that proton transfer to the β-position is rate-limiting and provides support that the hydrolysis follows general acid catalysis. By means of projected Fukui indices, we show this to be the case for unsubstituted, 2-, and 2,5-substituted furans with electron-donating groups.

  8. Initiator and Photocatalyst-Free Visible Light Induced One-Pot Reaction: Concurrent RAFT Polymerization and CuAAC Click Reaction.

    Science.gov (United States)

    Wang, Jie; Wang, Xinbo; Xue, Wentao; Chen, Gaojian; Zhang, Weidong; Zhu, Xiulin

    2016-05-01

    A new, visible light-catalyzed, one-pot and one-step reaction is successfully employed to design well-controlled side-chain functionalized polymers, by the combination of ambient temperature revisible addtion-fragmentation chain transfer (RAFT) polymerization and click chemistry. Polymerizations are well controlled in a living way under the irradiation of visible light-emitting diode (LED) light without photocatalyst and initiator, using the trithiocarbonate agent as iniferter (initiator-transfer agent-terminator) agent at ambient temperature. Fourier transfer infrared spectroscopy (FT-IR), NMR, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) data confirm the successful one-pot reaction. Compared to the reported zero-valent metal-catalyzed one-pot reaction, the polymerization rate is much faster than that of the click reaction, and the visible light-catalyzed one-pot reaction can be freely and easily regulated by turning on and off the light.

  9. 菊粉酸降解动力学研究%Kinetic Studies on Acid Catalyzed Hydrolysis of Inulin

    Institute of Scientific and Technical Information of China (English)

    许威; 罗登林; 陈瑞红; 刘建学

    2012-01-01

    通过考察温度、溶液pH值及水分含量对菊粉酸降解的影响,探索菊粉酸水解规律。结果表明:菊粉水溶液在pH 5.0~7.0、温度低于100℃时具有良好的稳定性;但当pH值低于4.0时,菊粉出现明显的水解反应。菊粉溶液在不同温度和pH值下的酸降解动力学表明,其水解反应遵循一级反应动力学方程。利用菊粉凝胶特性考察水分含量与菊粉酸降解的关系,发现相同pH值(pH=3)条件下,水分含量越高,菊粉降解速率越快,凝胶中菊粉降解速率低于菊粉水溶液降解速率。%The effects of temperature,pH and water content on inulin hydrolysis were studied to understand the acid catalyzed hydrolysis process of inulin for industrial production of high-fructose syrup.The results showed that inulin solution had a good thermal stability at a pH value in the range of 5.0-7.0 and a temperature below 100 ℃,while inulin degradation started to occur when the pH was lower than 4.0.The acid catalyzed hydrolysis dynamics of inulin at different levels of temperature and pH showed that the reaction followed the first-order kinetics well.The relation between inulin gel degradation induced by acid and water content was also investigated.At the same pH,the higher water content,the faster inulin hydrolysis,and the degradation rate of inulin was lower in gel than in aqueous solution.

  10. FLUORESCENCE STUDIES FOR IN SITU MONITORING OF THE HYDROLYSIS AND POLYMERIZATION REACTIONS OF ORGANICALLY –MODIFIED TETRAMETHYLORTHOSILICATE

    OpenAIRE

    Kunarti, Eko Sri

    2010-01-01

    Monitoring of hydrolysis and condensation polymerization reactions of tetramethylorthosilicate-organosiloxane have been carried out. Proton transfer from the excited state of 8-hydroxy-1,3,6-pyrenetrisulfonic acid trisodium salt (pyranine) to surrounding water molecules was used as a sensitive fluorescence method for following the kinetics of water consumption during the early stages of the sol-gel polymerisation process. Changes in water/silane ratio, type of organosiloxane, mol ratio of or...

  11. A Protons Exchanged Montmorillonite Clay as an Efficient Catalyst for the Reaction of Isobutylene Polymerization

    Directory of Open Access Journals (Sweden)

    Mohammed Belbachir

    2002-07-01

    Full Text Available Abstract: “Maghnite” a montmorillonite sheet silicate clay, exchanged with protons to produce “H-Maghnite” is an efficient catalyst for cationic polymerization of many vinylic and heterocyclic monomers (Belbachir, M. U.S. Patent. 066969.0101 –2001. The structure compositions of both “Maghnite” and “H-Maghnite” have been developed. Isobutylene monomer, wich is polymerizable only by cationic process (Odian,G. La Polymerisation :principes et Applications; Ed.Technica: New York, 1994; pp 222-226, was used to elucidate the cationic character of polymerization. The polymerization was performed under suitable conditions at isobutylene vaporization temperature (–7°C. Experiments revealed that polymerization induced by “H-Maghnite” proceed in bulk and in solution. In contrast to findings with methylene chloride CH2Cl2 as a polar solvent, polymerization yields with hexane C6H14 non-polar solvent is very significant. In bulk polymerization, Isobutylene conversion increases with increasing “H-Maghnite” proportion.

  12. Integrated Production of Xylonic Acid and Bioethanol from Acid-Catalyzed Steam-Exploded Corn Stover.

    Science.gov (United States)

    Zhu, Junjun; Rong, Yayun; Yang, Jinlong; Zhou, Xin; Xu, Yong; Zhang, Lingling; Chen, Jiahui; Yong, Qiang; Yu, Shiyuan

    2015-07-01

    High-efficiency xylose utilization is one of the restrictive factors of bioethanol industrialization. However, xylonic acid (XA) as a new bio-based platform chemical can be produced by oxidation of xylose with microbial. So, an applicable technology of XA bioconversion was integrated into the process of bioethanol production. After corn stover was pretreated with acid-catalyzed steam-explosion, solid and liquid fractions were obtained. The liquid fraction, also named as acid-catalyzed steam-exploded corn stover (ASC) prehydrolyzate (mainly containing xylose), was catalyzed with Gluconobacter oxydans NL71 to prepare XA. After 72 h of bioconversion of concentrated ASC prehydrolyzate (containing 55.0 g/L of xylose), the XA concentration reached a peak value of 54.97 g/L, the sugar utilization ratio and XA yield were 94.08 and 95.45 %, respectively. The solid fraction was hydrolyzed to produce glucose with cellulase and then fermented with Saccharomyces cerevisiae NL22 to produce ethanol. After 18 h of fermentation of concentrated enzymatic hydrolyzate (containing 86.22 g/L of glucose), the ethanol concentration reached its highest value of 41.48 g/L, the sugar utilization ratio and ethanol yield were 98.72 and 95.25 %, respectively. The mass balance showed that 1 t ethanol and 1.3 t XA were produced from 7.8 t oven dry corn stover.

  13. Self-Assembled DNA Hydrogel Based on Enzymatically Polymerized DNA for Protein Encapsulation and Enzyme/DNAzyme Hybrid Cascade Reaction.

    Science.gov (United States)

    Xiang, Binbin; He, Kaiyu; Zhu, Rong; Liu, Zhuoliang; Zeng, Shu; Huang, Yan; Nie, Zhou; Yao, Shouzhuo

    2016-09-07

    DNA hydrogel is a promising biomaterial for biological and medical applications due to its native biocompatibility and biodegradability. Herein, we provide a novel, versatile, and cost-effective approach for self-assembly of DNA hydrogel using the enzymatically polymerized DNA building blocks. The X-shaped DNA motif was elongated by terminal deoxynucleotidyl transferase (TdT) to form the building blocks, and hybridization between dual building blocks via their complementary TdT-polymerized DNA tails led to gel formation. TdT polymerization dramatically reduced the required amount of original DNA motifs, and the hybridization-mediated cross-linking of building blocks endows the gel with high mechanical strength. The DNA hydrogel can be applied for encapsulation and controllable release of protein cargos (for instance, green fluorescent protein) due to its enzymatic responsive properties. Moreover, this versatile strategy was extended to construct a functional DNAzyme hydrogel by integrating the peroxidase-mimicking DNAzyme into DNA motifs. Furthermore, a hybrid cascade enzymatic reaction system was constructed by coencapsulating glucose oxidase and β-galactosidase into DNAzyme hydrogel. This efficient cascade reaction provides not only a potential method for glucose/lactose detection by naked eye but also a promising modular platform for constructing a multiple enzyme or enzyme/DNAzyme hybrid system.

  14. The effect of high temperature sol-gel polymerization parameters on the microstructure and properties of hydrophobic phenol-formaldehyde/silica hybrid aerogels.

    Science.gov (United States)

    Seraji, Mohamad Mehdi; Sameri, Ghasem; Davarpanah, Jamal; Bahramian, Ahmad Reza

    2017-05-01

    Phenol-formaldehyde/silica hybrid aerogels with different degree of hydrophobicity were successfully synthesized via high temperature sol-gel polymerization. Tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES) were used as precursor and co-precursor of the hydrophobic silica-based phase, respectively. The hydrolysis step of silica based sols were conducted by acid catalyzed reactions and HCl was used as hydrolysis catalyst. The chemical structure of prepared hybrid aerogels was characterized by Fourier Transform Infrared spectroscopy (FT-IR). The effect of MTES/TEOS proportion and catalyst content on the morphology and microstructure of samples were investigated by FE-SEM and C, Si mapping analysis. The acid catalyzed hydrolysis of TEOS and MTES sols leads to formation of a sol with primarily silica particles in the organic-inorganic hybrid sol and varying colloid growth mechanisms were occurred with change in MTES and HCl molar ratio. With the increasing of MTES content, the microstructure of samples changed from uniform colloidal network, core-shell structure to polymeric structure with a huge phase separation. The increasing of HCl mole fraction leads to smaller particle size. Moreover, the shrinkage of samples was decreased and water contact angles of the resulted aerogels were increased from 40 to 156.8° with the increases of MTES content.

  15. Hybrid Polymer-Immobilized Nanosized Pd Catalysts for Hydrogenation Reaction Obtained via Frontal Polymerization

    OpenAIRE

    Anatolii D. Pomogailo; Gulzhian I. Dzhardimalieva

    2013-01-01

    A new approach to the synthesis of mixed-type immobilized catalysts by frontal polymerization of metal-containing monomer in the presence of highly dispersed mineral support has been developed. Synthesis of the acrylamide Pd(II) nitrate complex, Pd(CH2=CHCONH2)2 (NO3)2 (PdAAm), on the SiO2 (Al2O3, C) surface and its consequent frontal polymerization and reduction lead to the formation of organic-inorganic composites with polymer-stabilized Pd nanoparticles. The immobilized metal complexes and...

  16. Selective and recyclable depolymerization of cellulose to levulinic acid catalyzed by acidic ionic liquid.

    Science.gov (United States)

    Ren, Huifang; Girisuta, Buana; Zhou, Yonggui; Liu, Li

    2015-03-01

    Cellulose depolymerization to levulinic acid (LA) was catalyzed by acidic ionic liquids (ILs) selectively and recyclably under hydrothermal conditions. The effects of reaction temperature, time, water amount and cellulose intake were investigated. Dilution effect becomes more pronounced at lower cellulose intake, dramatically improving the yield of LA to 86.1%. A kinetic model has been developed based on experimental data, whereby a good fit was obtained and kinetic parameters were derived. The relationships between IL structure, polymeric structure and depolymerization efficiency were established, shedding light on the in-depth catalytic mechanism of IL, inclusive of acidity and hydrogen bonding ability. The LA product can be readily separated through extraction by methyl isobutyl ketone (MIBK) and IL can be reused over five cycles without loss of activity. This environmentally friendly methodology can be applied to selective production of LA from versatile biomass feedstocks, including cellulose and derivatives, glucose, fructose and HMF.

  17. The effect of a number of selective points in modeling of polymerization reacting Monte Carlo method: studying the initiation reaction

    CERN Document Server

    Sadi, M; Dabir, B

    2003-01-01

    Monte Carlo Method is one of the most powerful techniques to model different processes, such as polymerization reactions. By this method, without any need to solve moment equations, a very detailed information on the structure and properties of polymers are obtained. The number of algorithm repetitions (selected volumes of reactor for modelling which represent the number of initial molecules) is very important in this method. In Monte Carlo method calculations are based on the random number of generations and reaction probability determinations. so the number of algorithm repetition is very important. In this paper, the initiation reaction was considered alone and the importance of number of initiator molecules on the result were studied. It can be concluded that Monte Carlo method will not give accurate results if the number of molecules is not satisfied to be big enough, because in that case , selected volume would not be representative of the whole system.

  18. Acid-catalyzed hydrogenation of olefins. A theoretical study of the HF- and H/sub 3/O/sup +/-catalyzed hydrogenation of ethylene

    Energy Technology Data Exchange (ETDEWEB)

    Siria, J.C.; Duran, M.; Lledos, A.; Bertran, J.

    1987-12-09

    The HF- and H/sub 3/O/sup +/-catalyzed hydrogenation of ethylene and the direct addition of molecular hydrogen to ethylene have been studied theoretically by means of ab initio MO calculations using different levels of theory. The main results are that catalysis by HF lowers the potential energy barrier to a large extent, while catalysis by H/sub 3/O/sup +/ diminishes dramatically the barrier for the reaction. Entropic contributions leave these results unchanged. The mechanisms of the two acid-catalyzed hydrogenations are somewhat different. While catalysis by HF exhibits bifunctional characteristics, catalysis by H/sub 3/O/sup +/ proceeds via an initial formation of a carbocation. It is shown that catalysis by strong acids may be an alternate way for olefin hydrogenation.

  19. Determination of molecular weight and other characteristics of co- and terpolymers using automatic continuous online monitoring of polymerization reactions (ACOMP)

    Science.gov (United States)

    Enohnyaket, Pascal E. A.

    The Automatic Continuous Online Monitoring of Polymerization reactions (ACOMP), is a technique developed by the Reed Research Group at Tulane University. By simultaneously monitoring and combining signals from a continuously dilute reactor stream, detectors such as a multi-angle light scattering detector, near infra-red spectrometer, viscometer, differential refractive index, and a full wavelength UV/Visible detector were used in a model-independent fashion to follow the weight-average molecular weight, intrinsic viscosity, the concentrations of each comonomer, and hence the evolution of the average instantaneous and cumulative compositions along the chains as comonomers are consumed. The goal of this dissertation is to make the ACOMP system more useful in very complex polymerization situations by improving it with additional detectors and formalisms (such as a new expression for computing the molecular weight a copolymer of nth degree) and to exploit its robustness in situations where traditional routes fail or are of limited value. By providing a continuum of data, ACOMP allows polymer scientists to better understand and control new reaction schemes. At the pilot plant, it can be used to optimize reaction conditions. Because the ACOMP system is relatively cheap, user friendly, can be environmentally friendly, less bulky and very efficient, it is my desire to use ACOMP to solve some of the problems in the petroleum, plastic and drug manufacturing industries in Cameroon (and Africa).

  20. Kinetics of Acid-Catalyzed Dehydration of Cyclic Hemiacetals in Organic Aerosol Particles in Equilibrium with Nitric Acid Vapor.

    Science.gov (United States)

    Ranney, April P; Ziemann, Paul J

    2016-04-28

    Previous studies have shown that 1,4-hydroxycarbonyls, which are often major products of the atmospheric oxidation of hydrocarbons, can undergo acid-catalyzed cyclization and dehydration in aerosol particles to form highly reactive unsaturated dihydrofurans. In this study the kinetics of dehydration of cyclic hemiacetals, the rate-limiting step in this process, was investigated in a series of environmental chamber experiments in which secondary organic aerosol (SOA) containing cyclic hemiacetals was formed from the reaction of n-pentadecane with OH radicals in dry air in the presence of HNO3. A particle beam mass spectrometer was used to monitor the formation and dehydration of cyclic hemiacetals in real time, and SOA and HNO3 were quantified in filter samples by gravimetric analysis and ion chromatography. Measured dehydration rate constants increased linearly with increasing concentration of HNO3 in the gas phase and in SOA, corresponding to catalytic rate constants of 0.27 h(-1) ppmv(-1) and 7.0 h(-1) M(-1), respectively. The measured Henry's law constant for partitioning of HNO3 into SOA was 3.7 × 10(4) M atm(-1), ∼25% of the value for dissolution into water, and the acid dissociation constant was estimated to be water. The results indicate that HNO3 was only weakly dissociated in the SOA and that dehydration of cyclic hemiacetals was catalyzed by molecular HNO3 rather than by H(+). The Henry's law constant and kinetics relationships measured here can be used to improve mechanisms and models of SOA formation from the oxidation of hydrocarbons in dry air in the presence of NOx, which are conditions commonly used in laboratory studies. The fate of cyclic hemiacetals in the atmosphere, where the effects of higher relative humidity, organic/aqueous phase separation, and acid catalysis by molecular H2SO4 and/or H(+) are likely to be important, is discussed.

  1. Hybrid Polymer-Immobilized Nanosized Pd Catalysts for Hydrogenation Reaction Obtained via Frontal Polymerization

    Directory of Open Access Journals (Sweden)

    Anatolii D. Pomogailo

    2013-01-01

    Full Text Available A new approach to the synthesis of mixed-type immobilized catalysts by frontal polymerization of metal-containing monomer in the presence of highly dispersed mineral support has been developed. Synthesis of the acrylamide Pd(II nitrate complex, Pd(CH2=CHCONH22 (NO32 (PdAAm, on the SiO2 (Al2O3, C surface and its consequent frontal polymerization and reduction lead to the formation of organic-inorganic composites with polymer-stabilized Pd nanoparticles. The immobilized metal complexes and palladium nanoparticles were characterized by various physical and chemical methods. The synthesized hybrid nanocomposites are efficient and selective catalysts for hydrogenation of cyclohexene, alkene, and acetylene alcohols, as well as di- and trinitrotoluene. Catalyst intermediates separated by nondestructive testing method have been described and changing in the palladium charge during the catalytic process has been identified.

  2. Solid state polymerization of pet/pc extruded blend: effect of reaction temperature on thermal, morphological and viscosity properties

    Directory of Open Access Journals (Sweden)

    Luis Claudio Mendes

    2014-08-01

    Full Text Available A systematic study of solid state polymerization (SSP, concerning the melt extruded blend of poly(ethylene terephthalate/polycarbonate (catalyzed PET/PC, 80/20 wt %, as a function of temperature range (180-190°C for a fixed time (6 h is presented. The materials obtained were evaluated by differential scanning calorimetry (DSC, thermogravimetry/derivative thermogravimetry (TG/DTG, optical microscopy (OM and intrinsic viscosity (IV analysis. After SSP, at all reaction temperatures, PET glass transition and heating crystallization temperatures slightly decreased, melting temperature slightly increased, while degree of crystallinity was practically invariable. The DTG curves indicated that, at least, three phases remained. The OM images revealed that the morphology is constituted of a PET matrix and a PC dispersed phase. In the interfacial region we noticed the appearance of structures like bridges linking the matrix and the dispersed domains. These bridges were correlated to the PET/PC block copolymer obtained during blending in the molten state. IV increased for all polymerization temperatures, due to the occurrence of PET chain extension reactions - esterification and transesterification. The IV range for bottle grade PET was achieved.

  3. N, S co-doped carbon dots with orange luminescence synthesized through polymerization and carbonization reaction of amino acids

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Ya-Wen [Nanomaterials and Chemistry Key Laboratory, Wenzhou University, Wenzhou, Zhejiang 325027 (China); Ma, De-Kun, E-mail: dkma@wzu.edu.cn [Nanomaterials and Chemistry Key Laboratory, Wenzhou University, Wenzhou, Zhejiang 325027 (China); Wang, Wei; Chen, Jing-Jing; Zhou, Lin; Zheng, Yi-Zhou [Department of Hematology, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325027 (China); Yu, Kang, E-mail: yukang62@126.com [Department of Hematology, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325027 (China); Huang, Shao-Ming, E-mail: smhuang@wzu.edu.cn [Nanomaterials and Chemistry Key Laboratory, Wenzhou University, Wenzhou, Zhejiang 325027 (China)

    2015-07-01

    Graphical abstract: N, S co-doped CDs with orange luminescence were synthesized through one-pot polymerization and carbonization reactions under hydrothermal conditions, using two different amino acids as raw materials. - Highlights: • N, S co-doped CDs were synthesized by one-pot carbonization reactions, using two different amino acids as raw materials. • The as-obtained N, S co-doped CDs showed unique orange fluorescence under excitation at room temperature. • The products could be applied in the imaging of peritoneal macrophages of mice without any functionalization. - Abstract: For practical application, it is highly desirable to obtain carbon dots (CDs) through environmentally benign synthetic route, using green raw materials. On the other hand, at present, most of CDs reported in the literature showed blue, green and yellow emission. Therefore it is still necessary to develop new strategy to obtain CDs with longer wavelength emission in order to expand their application range. Toward this end, in this study, N, S co-doped CDs were synthesized through one-pot condensation polymerization and carbonization reactions under hydrothermal conditions, using two different amino acids as raw materials. Taking the reaction of L-serine with L-cystine as an example, the as-obtained products were characterized by various techniques such as transmission electron microscopy, elemental analysis, Fourier-transform infrared spectrum, X-ray photoelectron spectra, and so on. Interestingly, N, S co-doped CDs displayed unique orange emission at room temperature. The possible photoluminescence mechanism of N, S co-doped CDs was proposed. Furthermore, the as-synthesized N, S co-doped CDs were directly applied in the imaging of peritoneal macrophages of mice.

  4. Determination of Catalytic Coefficient for a First-Order Reaction

    Science.gov (United States)

    Fraga, E. R.; And Others

    1975-01-01

    Describes an undergraduate physical chemistry experiment in which the acid catalyzed hydrolysis of sucrose is used to determine the catalytic coefficient of the hydronium ion, the catalyst in this reaction. (MLH)

  5. Preparation and structural characterization of poly-mannose synthesized by phosphoric acid catalyzation under microwave irradiation.

    Science.gov (United States)

    Wang, Haisong; Cheng, Xiangrong; Shi, Yonghui; Le, Guowei

    2015-05-05

    Poly-mannose with molecular weight of 2.457 kDa was synthesized using d-mannose as substrate and phosphoric acid as catalyst under the condition of microwave irradiation for the first time. The optimum reaction conditions were microwave output power of 900 W, temperature 115°C, proton concentration 2.5 mol/L, and microwave irradiation time 5 min. The actual maximum yield was 91.46%. After purified by Sepherdex G-25 column chromatography, the structural features of poly-mannose were investigated by high-performance anion-exchange chromatography (HPAEC), high-performance gel-permeation chromatography (HPGPC), infrared (IR) spectroscopy, methylation analysis and NMR spectroscopy analysis ((1)H, (13)C, COSY, TOCSY, HMQC, and HMBC). HPAEC analysis showed that the composition of synthetic polysaccharides was d-mannose, its purity was demonstrated by HPGPC as a single symmetrical sharp peak, and additionally IR spectra demonstrated the polymerization of d-mannose. Methylation analysis and NMR spectroscopy revealed that the backbone of poly-mannose consisting of (1→3)-linked β-d-Manp, (1→3)-linked α-d-Manp, and (1→6)-linked α-d-Manp residues, and the main chain were branched at the O-2, O-3, O-4, O-6 position.

  6. Organic Electronics: An El Dorado in the Quest of New Photocatalysts for Polymerization Reactions.

    Science.gov (United States)

    Dumur, Frédéric; Gigmes, Didier; Fouassier, Jean-Pierre; Lalevée, Jacques

    2016-09-20

    Photoinitiated polymerization has been the subject of continued research efforts due to the numerous applications in which this polymerization technique is involved (coatings, inks, adhesives, optoelectronic, laser imaging, stereolithography, nanotechnology, etc.). More recently, photopolymerization has received renewed interest due to the emergence of 3D-printing technologies. However, despite current academic and industrial interest in photopolymerization methodologies, a major limitation lies in the slow rates of photopolymerization. The development of new photoinitiating systems aimed at addressing this limitation is an active area of research. Photopolymerization occurs through the exposure of a curable formulation to light, generating radical and/or cationic species to initiate polymerization. At present, photopolymerization is facing numerous challenges related to safety, economic and ecological concerns. Furthermore, practical considerations such as the curing depth and the competition for light absorption between the chromophores and other species in the formulation are key parameters drastically affecting the photopolymerization process. To address these issues, photoinitiating systems operating under low intensity visible light irradiation, in the absence of solvents are highly sought after. In this context, the use of photoredox catalysis can be highly advantageous; that is, photoredox catalysts can provide high reactivities with low catalyst loading, permitting access to high performance photoinitiating systems. However, to act as efficient photoredox catalysts, specific criteria have to be fulfilled. A strong absorption over the visible range, an ability to easily oxidize or reduce as well as sufficient photochemical stability are basic prerequisites to make these molecules desirable candidates for photoredox catalysis. Considering the similarity of requirements between organic electronics and photopolymerization, numerous materials initially designed

  7. A Protons Exchanged Montmorillonite Clay as an Efficient Catalyst for the Reaction of Isobutylene Polymerization

    OpenAIRE

    Mohammed Belbachir; Rachid Meghabar; Amine Harrane

    2002-01-01

    Abstract: “Maghnite†a montmorillonite sheet silicate clay, exchanged with protons to produce “H-Maghnite†is an efficient catalyst for cationic polymerization of many vinylic and heterocyclic monomers (Belbachir, M. U.S. Patent. 066969.0101 –2001). The structure compositions of both “Maghnite†and “H-Maghnite†have been developed. Isobutylene monomer, wich is polymerizable only by cationic process (Odian,G. La Polymerisation :principes et Applications...

  8. Acetic Acid Catalyzed Steam Explosion for Improving the Sugar Recovery of Wheat Straw

    Directory of Open Access Journals (Sweden)

    Mengru Liu

    2014-06-01

    Full Text Available Acetic acid-catalyzed steam explosion pretreatment was applied to wheat straw at temperatures of 190 and 210 °C for 2, 6, and 10 min of residence time. The effects of pretreatment conditions on the total gravimetric recovery, hemicellulose sugars, glucose content, and yield of the enzymatic hydrolysis of cellulose were studied. The results indicated that the total gravimetric recovery decreases while the solubility of hemicellulose and the yield of cellulose enzymatic hydrolysis increase as the pretreatment severity increases. Pretreatment at 190 °C with a 2-min residence time resulted in the highest total gravimetric recovery, 58.9%. The optimum defiberation, glucose content, and enzymatic hydrolysis yields of 70.4 and 79.6%, respectively, occurred following pretreatment at 210 °C with a 10-min residence time. The optimal pretreatment condition was determined to be 190 °C for 10 min. Under the optimum conditions, the recovery yield of all sugars reached 42.7%. This pretreatment resulted in the highest recovery yield of all sugars.

  9. Recovery of arabinan in acetic acid-catalyzed hydrothermal pretreatment on corn stover

    DEFF Research Database (Denmark)

    Xu, Jian; Hedegaard, Mette Christina; Thomsen, Anne Belinda

    2009-01-01

    Acetic acid-catalyzed hydrothermal pretreatment was done on corn stover under 195 °C, 15 min with the acetic acid ranging from 5 × 10−3 to 0.2 g g−1 corn stover. After pretreatment, the water-insoluble solids (WISs) and liquors were collected respectively. Arabinan recoveries from both WIS...... and liquors were investigated. The results indicate that there was no detectable arabinan left in the WIS when the acetic acid of 0.1 and 0.2 g g−1 corn stover were used in the pretreatment. The arabinan contents in the other WISs were not more than 10%. However, the arabinan found in the liquors...... was not covering the amount of arabinan released from the raw corn stover. For the arabinan recovery from liquor fractions, the highest of 43.57% was obtained by the pretreatment of acetic acid of 0.01 g g−1 of corn stover and the lowest was only 26.77% when the acetic acid of 0.2 g g−1 corn stover was used...

  10. Polymerization-induced phase separation in polyether-sulfone modified epoxy resin systems: effect of curing reaction mechanism

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Polyethersulfone (PES)-modified epoxy systems with stepwise reaction were studied throughout the entire curing process by using optical microscopes, time-resolved light scattering (TRLS), and a rheolometry instrument compared with that of chainwise polymerization. The results suggested that the phase separation process is mainly controlled by the diffusion of epoxy oligomers for stepwise mechanism system and by that of epoxy monomers for chainwise mechanism system. In case of high PES content (SPES-20%) light-scattering results showed a viscoelastic phase separation and the characteristic relaxation time of phase separation can be described well by the WLF equation. However, in the case of low PES content (SPES-14%) secondary phase separation phenomenon was observed by Optical Microscope and further demonstrated by rheological study.

  11. LEWIS ACID-CATALYZED REACTIONS IN PROTIC MEDIA - LANTHANIDE-CATALYZED REACTIONS OF INDOLES WITH ALDEHYDES OR KETONES. (R826123)

    Science.gov (United States)

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  12. Mechanistic Investigation of Acid-Catalyzed Cleavage of Aryl-Ether Linkages: Implications for Lignin Depolymerization

    Energy Technology Data Exchange (ETDEWEB)

    Sturgeon, M. R.; Kim, S.; Chmely, S. C.; Foust, T. D.; Beckham, G. T.

    2013-01-01

    Carbon-oxygen bonds are the primary inter-monomer linkages lignin polymers in plant cell walls, and as such, catalyst development to cleave these linkages is of paramount importance to deconstruct biomass to its constituent monomers for the production of renewable fuels and chemicals. For many decades, acid catalysis has been used to depolymerize lignin. Lignin is a primary component of plant cell walls, which is connected primarily by aryl-ether linkages, and the mechanism of its deconstruction by acid is not well understood, likely due to its heterogeneous and complex nature compared to cellulose. For effective biomass conversion strategies, utilization of lignin is of significant relevance and as such understanding the mechanisms of catalytic lignin deconstruction to constituent monomers and oligomers is of keen interest. Here, we present a comprehensive experimental and theoretical study of the acid catalysis of a range of dimeric species exhibiting the b-O-4 linkage, the most common inter-monomer linkage in lignin. We demonstrate that the presence of a phenolic species dramatically increases the rate of cleavage in acid at 150 degrees C. Quantum mechanical calculations on dimers with the para-hydroxyl group demonstrate that this acid-catalyzed pathway differs from the nonphenolic dimmers. Importantly, this result implies that depolymerization of native lignin in the plant cell wall will proceed via an unzipping mechanism wherein b-O-4 linkages will be cleaved from the ends of the branched, polymer chains inwards toward the center of the polymer. To test this hypothesis further, we synthesized a homopolymer of b-O-4 with a phenolic hydroxyl group, and demonstrate that it is cleaved in acid from the end containing the phenolic hydroxyl group. This result suggests that genetic modifications to lignin biosynthesis pathways in plants that will enable lower severity processes to fractionate lignin for upgrading and for easier access to the carbohydrate fraction of

  13. Electrical polymerization of a tetrazole polymer-modified electrode and its catalytic reaction toward dopamine

    Science.gov (United States)

    Hsieh, Mu-Tao; Whang, Thou-Jen

    2017-02-01

    A conducting polymer-modified electrode was proposed in this article, which was fabricated by electropolymerization of 5-amino-1H-tetrazole (ATet) on a glassy carbon electrode. Electrochemical studies such as differential pulse voltammetry and chronoamperometry were performed for the evaluation of the rate constant of the catalytic reaction, the diffusion coefficient of the analyte dopamine, and the linear dynamic range of the analyte determination. The film modified electrode has superior resolving power in quantitative determination from the mixture of analytes and it was found to be an efficient functionalized electrode for its sensitivity and selectivity toward the analyte of interest.

  14. 手性磷酸催化亚甲胺叶立德与吲哚-3-甲醇不对称[3+3]环加成反应:一步构建多取代四氢-β-咔啉%Chiral Br(o)nsted Acid Catalyzed Stereoselective [3+3] Cycloaddition Reaction of Azomethine Ylide to Vinylimine Intermediates:Constructing Fully Functionalized Chiral Tetrahydro-β-Carboline

    Institute of Scientific and Technical Information of China (English)

    黄建洲; 罗时玮; 龚流柱

    2013-01-01

    An asymmetric three-component formal [3 + 3] cycloaddition reaction of aldehyde,diethyl 2-aminomalonate and substituted indolyl alcohols,has been investigated with chiral BINOL-derived monophosphoric acids as catalysts.The active azomethine ylide intermediate can be readily formed from the condensation of aldehyde and diethyl 2-aminomalonate under the promotion of the chiral phosphoric acids and is thereby able to undergo nucleophilic addition reaction to electron-deficient carbon-carbon double bonds as reported previously in the multicomponent reactions.On the other hand,the indolyl alcohols are able to participate in a dehydration reaction in the presence of the phosphoric acids to generate transient vinyliminium intermediates,which are principally reactive toward nucleophiles.Thus,we envisioned that the two types of active intermediates could undergo an asymmetric formal [3 +3] cycloaddition to stereoselectively produce functionalized tetrahydro-β-carbolines under the catalysis of the chiral phosphoric acids.Consequently,a variety of 3,3'-disubstituted BINOL-phosphoric acids were initially evaluated for the reaction.As a result,the 3,3'-bis(p-CIPh) BINOL-phosphoric acid proved to perform most successfully in non-polar solvents,such as toluene.This reaction actually provides a highly straightforward access to functionalized tetrahydro-β-carboline derivatives.A number of substituted indolyl alcohols bearing either electronically donating or withdrawing groups are well tolerated,affording highly functionalized tetrahydro-β-carbolines in high yields ranging from 70% to 91% and with excellent enantioselectivities of up to 93% ee.A representative procedure for the enantioselective formal [3+3] cycloaddition reaction is as following:After a mixture of p-nitrobenzaldehyde (0.06 mmol),diethy1 2-amino-malonate (0.05 mmol),3 A MS (100 mg) and chiral phosphoric acid (10 mol%) in toluene (1.0 mL) was stirred at the r.t.for 15 min,the substituted indolyl acohol (0

  15. Probing chain-end functionalization reactions in living anionic polymerization via matrix-assisted laser desorption ionization time-of-flight mass spectrometry

    Science.gov (United States)

    Arnould, Mark A.; Polce, Michael J.; Quirk, Roderic P.; Wesdemiotis, Chrys

    2004-11-01

    Matrix-assisted laser desorption ionization (MALDI) time-of-flight (TOF) mass spectrometry (MS) is applied to examine the products arising upon the preparation of chain-end functional polymers via living anionic polymerization techniques. Both post-polymerization functionalizations as well as the use of functionalized initiators are investigated. MALDI-TOF MS is shown to be a sensitive probe for the qualitative analysis of the major and minor oligomers from novel functionalization reactions whose mechanisms are not yet well established. The method is particularly valuable for the identification of the end groups of the minor, and often unexpected, distributions that may be undetectable by other analytical means. Complete characterization of all oligomers generated during functionalization reactions provides an essential tool to the synthetic chemist for understanding the corresponding mechanisms. This insight is necessary for selecting alternative routes or making modifications to the reaction conditions. It is demonstrated that MALDI-TOF MS can convey quantitative information about the yields of the chain-end groups introduced during functionalization. From the cases presented it is evident that post-polymerization reactions allow for better control of chain-end functionality and molecular weight than functionalization with the limited number of currently available protected functionalized initiators.

  16. Polymeric reaction between aldehyde group in furfural and phenolic derivatives from liquefaction of oil palm empty fruit bunch fiber as phenol-furfural resin

    Science.gov (United States)

    Masli, M. Z.; Zakaria, S.; Chia, C. H.; Roslan, R.

    2016-11-01

    Resinification of liquefied empty fruit bunch with furfural (LEFB-Fu) was performed. During the resinification process, the samples were taken every hour up to 4 hours. FTIR analysis of the samples was conducted to understand the progress of the reaction. It showed that the bands of 1512 cm-1 and 1692 cm-1 evolving and diminishing respectively, indicating the consumption of furfural. The postulation of polymerization was also proven as the increasing extent of substitution of aromatic ring observed.

  17. Oxalic acid catalyzed solvent-free one pot synthesis of coumarins

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Oxalic acid was found to be an efficient catalyst for Pechmann condensation, which includes the reaction between phenols and β-keto esters leading to formation of coumarin derivatives. The advantages of present methods are the use of cheap and easy available catalyst, solvent-free reaction conditions, better yields and shorter reaction time.

  18. Ruthenium-catalyzed metathesis reactions of ortho- and meta-dialkenyl-carboranes: efficient ring-closing and acyclic diene polymerization reactions.

    Science.gov (United States)

    Guron, Marta; Wei, Xiaolan; Carroll, Patrick J; Sneddon, Larry G

    2010-07-05

    The ruthenium-catalyzed metathesis reactions of dialkenyl-substituted ortho- and meta-carboranes provide excellent routes to both cyclic-substituted o-carboranes and new types of main-chain m-carborane polymers. The adjacent positions of the two olefins in the 1,2-(alkenyl)(2)-o-carboranes strongly favor the formation of ring-closed (RCM) products with the reactions of 1,2-(CH(2)=CHCH(2))(2)-1,2-C(2)B(10)H(10) (1), 1,2-(CH(2)=CH(CH(2))(3)CH(2))(2)-1,2-C(2)B(10)H(10) (2), 1,2-(CH(2)=CHSiMe(2))(2)-1,2-C(2)B(10)H(10) (3), 1,2-(CH(2)=CHCH(2)SiMe(2))(2)-1,2-C(2)B(10)H(10) (4), and 1,2-[CH(2)=CH(CH(2))(4)SiMe(2)](2)-1,2-C(2)B(10)H(10) (5) affording 1,2-(-CH(2)CH=CHCH(2)-)-C(2)B(10)H(10) (10), 1,2-[-CH(2)(CH(2))(3)CH=CH(CH(2))(3)CH(2)-]-1,2-C(2)B(10)H(10) (11), 1,2-[-SiMe(2)CH=CHSiMe(2)-]-1,2-C(2)B(10)H(10) (12), 1,2-[-SiMe(2)CH(2)CH=CHCH(2)SMe(2)-]-C(2)B(10)H(10) (13), and 1,2-[-SiMe(2)(CH(2))(4)CH=CH(CH(2))(4)SiMe(2)-]-C(2)B(10)H(10) (14), respectively, in 72-97% yields. On the other hand, the reaction of 1,2-(CH(2)-CHCH(2)OC(=O))(2)-1,2-C(2)B(10)H(10) (6) gave cyclo-[1,2-(1',8'-C(=O)OCH(2)CH=CHCH(2)OC(=O))-1,2-C(2)B(10)H(10)](2) (15a) and polymer 15b resulting from intermolecular metathesis reactions. The nonadjacent positions of the alkenyl groups in the 1,7-(alkenyl)(2)-m-carboranes, 1,7-(CH(2)=CHCH(2))(2)-1,7-C(2)B(10)H(10) (7), 1,7-(CH(2)=CH(CH(2))(3)CH(2))(2)-1,7-C(2)B(10)H(10) (8), and 1,7-(CH(2)=CHCH(2)SiMe(2))(2)-1,7-C(2)B(10)H(10) (9), disfavor the formation of RCM products, and in these cases, acyclic diene metathesis polymerizations (ADMET) produced new types of main chain m-carborane polymers. The structures of 3, 9, 11, 12, 13, and 15a were crystallographically confirmed.

  19. Tannic acid Catalyzed an Efficient Synthesis of 2,4,5-Triaryl-1H-Imidazole

    Directory of Open Access Journals (Sweden)

    Shitole Nana Vikram

    2013-05-01

    Full Text Available Tannic acid (C76H52O46 has been found to be an efficient catalyst for one-pot synthesis of 2,4,5-triaryl substituted imidazoles by the reaction of an arylaldehyde, benzyl/benzoin and an ammonium acetate. The short reaction time and excellent yields making this protocol practical and economically attractive.

  20. Acid Catalyzed Condensation of Phenylethanal Enol or Thiol Enol Ether to 2-Phenylnaphthalene

    Institute of Scientific and Technical Information of China (English)

    CHANG, Yu-An

    2007-01-01

    Treatment of enol ether or thiol enol ether of phenylethanals with sulfuric or polyphosphoric acid in toluene or xylene gave 2-phenylnaphthalene in good yield. More importantly, a one-pot reaction has been developed.

  1. Experimental and theoretical analysis of polymerization reaction process on the polydopamine membranes and its corrosion protection properties for 304 Stainless Steel

    Science.gov (United States)

    Yu, Fei; Chen, Shougang; Chen, Yan; Li, Houmin; Yang, Lejiao; Chen, Yuanyuan; Yin, Yansheng

    2010-10-01

    Inspired by the bio-adhesion principle, polydopamine membrane was fabricated by dipping the 304 Stainless Steel (304 SS) substrate into an aqueous alkaline dopamine solution and its possible reaction mechanism and the temperature effect were studied. The membranes were characterized by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), surface reflection Fourier transform infrared spectrum (SR-FTIR), UV-visible spectrum. The polymerization reactions of dopamine in solution were also analyzed by the LUMO energies, simulated infrared spectrum and HOMO-LUMO energy gaps of selected structure models calculation, and the possible interfacial reaction mechanism was also discussed by the molecular orbital analysis of melanin clusters. Moreover, the corrosion behaviors of the polydopamine films prepared at different temperatures and dipping days were evaluated by the electrochemical impedance spectroscopy (EIS), as well as that of bare 304 SS, especially long stability in 3.5% NaCl solution.

  2. Radical routes to interstellar glycolaldehyde. The possibility of stereoselectivity in gas-phase polymerization reactions involving CH(2)O and ˙CH(2)OH.

    Science.gov (United States)

    Wang, Tianfang; Bowie, John H

    2010-10-21

    A previous report that the interstellar molecule glycolaldehyde (HOCH(2)CHO) can be made from hydroxymethylene (HOCH:) and formaldehyde has been revisited at the CCSD(T)/6-311++G(3df,2p)//MP2/6-311++G(3df,2p) level of theory. This reaction competes with the formation of acetic acid and methylformate, molecules which have also been detected in interstellar clouds. Other possible modes of formation of glycolaldehyde by radical/radical reactions have been shown to be viable theoretically as follows: HO˙+˙CH2CHO -->HOCH2CHO [ΔG(Γ)(298K)=-303kJ mol⁻¹] HOCH2˙+˙CHO-->HOCH2CHO (-259kJ mol⁻¹). The species in these two processes are known interstellar molecules. Key radicals ˙CH(2)CHO and ˙CH(2)OH in these sequences have been shown to be stable for the microsecond duration of neutralization/reionization experiments in the dual collision cells of a VG ZAB 2HF mass spectrometer. The polymerization reaction HOCH(2)CH˙OH + nCH(2)O → HOCH(2)[CH(OH)](n)˙CHOH (n = 1 to 3) has been studied theoretically and shown to be energetically feasible, as is the cyclization reaction of HOCH(2)[(CH(2)OH)(4)]˙CHOH (in the presence of one molecule of water at the reacting centre) to form glucose. The probability of such a reaction sequence is small even if polymerization were to occur in interstellar ice containing a significant concentration of CH(2)O. The large number of stereoisomers produced by such a reaction sequence makes the formation of a particular sugar, again for example glucose, an inefficient synthesis. The possibility of stereoselectivity occurring during the polymerization was investigated for two diastereoisomers of HOCH(2)[(CHOH)](2)˙CHOH. No significant difference was found in the transition state energies for addition of CH(2)O to these two diastereoisomers, but a barrier difference of 12 kJ mol(-1) was found for the H transfer reactions ˙OCH(2)[(CHOH)](2)CH(2)OH → HOCH(2)[(CHOH)(2)˙CHOH of the two diastereoisomers.

  3. EFFECTS OF REACTION AND PROCESSING PARAMETERS ON ETHYLENE POLYMERIZATION USING DIFFERENT ZIEGLER-NATTA CATALYSTS:EMPLOYMENT OF TAGUCHI EXPERIMENTAL DESIGN AND RESPONSE SURFACE METHOD

    Institute of Scientific and Technical Information of China (English)

    Mohammad Najafi; Vahid Haddadi-Asl

    2007-01-01

    Different Ziegler-Natta catalysts were employed to polymerize ethylene.To investigate the influences of reaction parameters,namely Al/Ti molar ratio,hydrogen and processing parameters,I.e.ethylene pressure and temperature,a Taguchi experimental design was worked out.An L27 orthogonal array was chosen to take the above-mentioned parameters and relevant interactions into account.Response surface method was the tool used to analyze the experimental design results.Al/Ti,ethylene pressure and temperature were selected as experimental design factors.and catalyst activity and polymerization yield were the response parameters.Increasing pressure,due to an increment in monomer accessibility,and rising Al/Ti,because of higher reduction in the catalysts,cause an increase in both polymerization yield and catalyst activity.Nonetheless,a higher temperature,thanks to reducing ethylene solubility in the slurry medium and partially catalyst destruction.lead to a reduction in both response parameters.A synergistic eflfect was also observed between temperature and pressure.All catalyst activities will reduce in the presence of hydrogen.Molecular weight also shows a decline in the presence of hydrogen as a transfer agent.However,the polydispersity index remains approximately intact.Using SEM,various morphologies,owing to different catalyst morphologies,were seen for the polyethylene.

  4. Lewis-acid catalyzed depolymerization of Protobind lignin in supercritical water and ethanol

    NARCIS (Netherlands)

    Guvenatam, Burcu; Heeres, Erik H.J.; Pidko, Evgeny A.; Hensen, Ernie J. M.

    2016-01-01

    The use of metal acetates, metal chlorides and metal triflates as Lewis acid catalysts for the depolymerization of soda lignin under supercritical conditions was investigated. The reactions were carried out at 400 degrees C in water and ethanol. Lignin conversion in supercritical water led to format

  5. Oxalic Acid Catalyzed Three Component One Pot Synthesis of 3,4-Dihydroquinazolin-4-ones

    Institute of Scientific and Technical Information of China (English)

    SANGSHETTI Jaiprakash-N.; KOKARE Nagnnath-D.; SHINDE Devanand-B.

    2008-01-01

    An efficient one-pot method for synthesis of an array of 3,4-dihydroquinazolin-4-ones from anthranilicacid, triethyl orthoformate, and anilines using oxalic acid as a catalyst was described. The present protocol offers im-provements for the synthesis of 3,4-dihydroquinazolin-4-ones with regard to short reaction time, high yields of products, and simplicity in operation.

  6. An Efficient Procedure for Esterification of Aryloxyacetic Acid and Arylthioacetic Acid Catalyzed by Silica Sulfuric Acid

    Institute of Scientific and Technical Information of China (English)

    LI,Hong-Ya; LI,Ji-Tai; LI,Hui-Zhang

    2004-01-01

    @@ Aryloxyacetate and arylthioacetate are wildly used in herbicides, plant regulator and insecticides. Recently, Wille et al. have reported that methyl aryloxyacetate is an efficient agent to prevent and treat allergic contact dermatitis.[1] The most popular synthesis is by heating sodium phenoxide (mercaptide) with ethyl chloroacetate in DMF,[2] or by the esterification of acid with alcohol using concentrated H2SO4 as catalyst.[3] In this paper, synthesis of aryloxyacetate and aryl thioacetate from aryloxyacetic acid and arylthioacetic acid respectively in ether catalyzed by silica sulfuric acid in 83%~94% yields is described. The catalyst is reused for 3 times without significant loss of activity (Entry 4). Compared with common procedures, the present procedure possesses the advantages of the operational simplicity, short reaction time,less-corrosion, high yield and reusable catalyst.

  7. Dietary phenolic acids and ascorbic acid: Influence on acid-catalyzed nitrosative chemistry in the presence and absence of lipids.

    Science.gov (United States)

    Combet, Emilie; El Mesmari, Aziza; Preston, Tom; Crozier, Alan; McColl, Kenneth E L

    2010-03-15

    Acid-catalyzed nitrosation and production of potentially carcinogenic nitrosative species is focused at the gastroesophageal junction, where salivary nitrite, derived from dietary nitrate, encounters the gastric juice. Ascorbic acid provides protection by converting nitrosative species to nitric oxide (NO). However, NO may diffuse into adjacent lipid, where it reacts with O(2) to re-form nitrosative species and N-nitrosocompounds (NOC). In this way, ascorbic acid promotes acid nitrosation. Using a novel benchtop model representing the gastroesophageal junction, this study aimed to clarify the action of a range of water-soluble antioxidants on the nitrosative mechanisms in the presence or absence of lipids. Caffeic, ferulic, gallic, or chlorogenic and ascorbic acids were added individually to simulated gastric juice containing secondary amines, with or without lipid. NO and O(2) levels were monitored by electrochemical detection. NOC were measured in both aqueous and lipid phases by gas chromatography-tandem mass spectrometry. In the absence of lipids, all antioxidants tested inhibited nitrosation, ranging from 35.9 + or - 7.4% with gallic acid to 93 + or - 0.6% with ferulic acid. In the presence of lipids, the impact of each antioxidant on nitrosation was inversely correlated with the levels of NO they generated (R(2) = 0.95, pascorbic acid promoted nitrosation, whereas ferulic and caffeic acids markedly inhibited nitrosation.

  8. [Asymmetric synthesis of aromatic L-amino acids catalyzed by transaminase].

    Science.gov (United States)

    Xia, Wenna; Sun, Yu; Min, Cong; Han, Wei; Wu, Sheng

    2012-11-01

    Aromatic L-Amino acids are important chiral building blocks for the synthesis of many drugs, pesticides, fine chemicals and food additives. Due to the high activity and steroselectivity, enzymatic synthesis of chiral building blocks has become the main research direction in asymmetric synthesis field. Guided by the phylogenetic analysis of transaminases from different sources, two representative aromatic transaminases TyrB and Aro8 in type I subfamily, from the prokaryote Escherichia coli and eukaryote Saccharomyces cerevisia, respectively, were applied for the comparative study of asymmetric transamination reaction process and catalytic efficiency of reversely converting keto acids to the corresponding aromatic L-amino acid. Both TyrB and Aro8 could efficiently synthesize the natural aromatic amino acids phenylalanine and tyrosine as well as non-natural amino acid phenylglycine. The chiral HPLC analysis showed the produced amino acids were L-configuration and the e.e value was 100%. L-alanine was the optimal amino donor, and the transaminase TyrB and Aro8 could not use D-amino acids as amino donor. The optimal molar ratio of amino donor (L-alanine) and amino acceptor (aromatic alpha-keto acids) was 4:1. Both of the substituted group on the aromatic ring and the length of fatty acid carbon chain part in the molecular structure of aromatic substrate alpha-keto acid have the significant impact on the enzyme-catalyzed transamination efficiency. In the experiments of preparative-scale transamination synthesis of L-phenylglycine, L-phenylalanine and L-tyrosine, the specific production rate catalyzed by TryB were 0.28 g/(g x h), 0.31 g/(g x h) and 0.60 g/(g x h) and the specific production rate catalyzed by Aro8 were 0.61 g/(g x h), 0.48 g/(g x h) and 0.59 g/(g x h). The results obtained here were useful for applying the transaminases to asymmetric synthesis of L-amino acids by reversing the reaction balance in industry.

  9. Lewis acid-catalyzed in situ transesterification/esterification of microalgae in supercritical ethanol.

    Science.gov (United States)

    Jin, Binbin; Duan, Peigao; Xu, Yuping; Wang, Bing; Wang, Feng; Zhang, Lei

    2014-06-01

    The activities of several Lewis acid catalysts such SnCl2, FeCl3, ZnCl2, AlCl3, and NbCl5 for the in situ transesterification/esterification of lipid contained within a microalga (Chlorella pyrenoidosa) in ethanol at 350°C were examined to identify the most suitable catalyst in term of crude biodiesel (CBD) yield. Of those catalysts tested, ZnCl2 showed the highest performance toward the CBD production. Using ZnCl2 as catalyst, effects of reaction temperature (200-370 °C), time (0-120 min), ethanol to microalga ratio (EtOH:MA) (5/5-40/5), catalyst loading (0-30 wt.%), and algae moisture (0-80 wt.%) on the yields of product fractions and the properties of CBD were studied. The presence of ZnCl2 not only promoted the production of CBD but also showed activities toward the deoxygenation and denitrogenation of CBD. The moisture content in the starting material is the most influential factor affecting the yield and properties of CBD.

  10. Glycolic Acid-Catalyzed Deamidation of Asparagine Residues in Degrading PLGA Matrices: A Computational Study

    Directory of Open Access Journals (Sweden)

    Noriyoshi Manabe

    2015-03-01

    Full Text Available Poly(lactic-co-glycolic acid (PLGA is a strong candidate for being a drug carrier in drug delivery systems because of its biocompatibility and biodegradability. However, in degrading PLGA matrices, the encapsulated peptide and protein drugs can undergo various degradation reactions, including deamidation at asparagine (Asn residues to give a succinimide species, which may affect their potency and/or safety. Here, we show computationally that glycolic acid (GA in its undissociated form, which can exist in high concentration in degrading PLGA matrices, can catalyze the succinimide formation from Asn residues by acting as a proton-transfer mediator. A two-step mechanism was studied by quantum-chemical calculations using Ace-Asn-Nme (Ace = acetyl, Nme = NHCH3 as a model compound. The first step is cyclization (intramolecular addition to form a tetrahedral intermediate, and the second step is elimination of ammonia from the intermediate. Both steps involve an extensive bond reorganization mediated by a GA molecule, and the first step was predicted to be rate-determining. The present findings are expected to be useful in the design of more effective and safe PLGA devices.

  11. Glycolic acid-catalyzed deamidation of asparagine residues in degrading PLGA matrices: a computational study.

    Science.gov (United States)

    Manabe, Noriyoshi; Kirikoshi, Ryota; Takahashi, Ohgi

    2015-03-31

    Poly(lactic-co-glycolic acid) (PLGA) is a strong candidate for being a drug carrier in drug delivery systems because of its biocompatibility and biodegradability. However, in degrading PLGA matrices, the encapsulated peptide and protein drugs can undergo various degradation reactions, including deamidation at asparagine (Asn) residues to give a succinimide species, which may affect their potency and/or safety. Here, we show computationally that glycolic acid (GA) in its undissociated form, which can exist in high concentration in degrading PLGA matrices, can catalyze the succinimide formation from Asn residues by acting as a proton-transfer mediator. A two-step mechanism was studied by quantum-chemical calculations using Ace-Asn-Nme (Ace = acetyl, Nme = NHCH3) as a model compound. The first step is cyclization (intramolecular addition) to form a tetrahedral intermediate, and the second step is elimination of ammonia from the intermediate. Both steps involve an extensive bond reorganization mediated by a GA molecule, and the first step was predicted to be rate-determining. The present findings are expected to be useful in the design of more effective and safe PLGA devices.

  12. Optimization of Two-Step Acid-Catalyzed Hydrolysis of Oil Palm Empty Fruit Bunch for High Sugar Concentration in Hydrolysate

    Directory of Open Access Journals (Sweden)

    Dongxu Zhang

    2014-01-01

    Full Text Available Getting high sugar concentrations in lignocellulosic biomass hydrolysate with reasonable yields of sugars is commercially attractive but very challenging. Two-step acid-catalyzed hydrolysis of oil palm empty fruit bunch (EFB was conducted to get high sugar concentrations in the hydrolysate. The biphasic kinetic model was used to guide the optimization of the first step dilute acid-catalyzed hydrolysis of EFB. A total sugar concentration of 83.0 g/L with a xylose concentration of 69.5 g/L and a xylose yield of 84.0% was experimentally achieved, which is in well agreement with the model predictions under optimal conditions (3% H2SO4 and 1.2% H3PO4, w/v, liquid to solid ratio 3 mL/g, 130°C, and 36 min. To further increase total sugar and xylose concentrations in hydrolysate, a second step hydrolysis was performed by adding fresh EFB to the hydrolysate at 130°C for 30 min, giving a total sugar concentration of 114.4 g/L with a xylose concentration of 93.5 g/L and a xylose yield of 56.5%. To the best of our knowledge, the total sugar and xylose concentrations are the highest among those ever reported for acid-catalyzed hydrolysis of lignocellulose.

  13. EPR Spectroscopy of catalytic systems based on nickel complexes of 1,4-diaza-1,3-butadiene (α-diimine) ligands in hydrogenation and polymerization reactions

    Science.gov (United States)

    Titova, Yu. Yu.; Belykh, L. B.; Schmidt, F. K.

    2015-01-01

    EPR spectroscopy is used to study catalytic hydration and polymerization reaction systems based on α-diimine complexes of Ni(0) and Ni(II) with the general formula NiBr2(DAD-R) (R = -C3H7 or -CH3) or Ni(DAD-CH3)2 (DAD(-C3H7) = 1,4-bis(2,6-diiso-propylphenyl)-2,3-(dimethyl-1,4-diazabuta-1,3-diene, DAD(-CH3) = 1,4-bis(2,6-dimethylphenyl)-2,3-dimethyl-1,4-diazabuta-1,3-diene)), in combination with Lewis acids (AlEt3, AlEt2Cl, AlEtCl2, B(F5C6)3, BF3.OEt2). Ni(I) complexes of the form (DAD-R)NiX2AlX'y(C2H5)3-y composition (an aluminum atom can be replaced by a boron atom) were identified, where R = -CH3 or -C3H7, X = Br, and X' = Cl or -C2H5 and α-diimine anion radicals are included in derivatives of aluminum or boron. Oxidation reactions of the Ni(DAD-CH3)2 complex with aluminum alkyl halides and boron derivatives with formation of paramagnetic nickel complexes are observed. It is found that there is no direct relationship between the polymerization activity of ethylene or hydration of the alkenes and the concentration of paramagnetic particles.

  14. Determination of glucose using a coupled-enzymatic reaction with new fluoride selective optical sensing polymeric film coated in microtiter plate wells.

    Science.gov (United States)

    Abd-Rabboh, Hisham S M; Meyerhoff, Mark E

    2007-05-15

    The determination of glucose in beverages is demonstrated using newly developed fluoride selective optical sensing polymeric film that contains aluminum (III) octaethylporphyrin (Al[OEP]) ionophore and the chromoionophore ETH7075 cast at the bottom of wells of a 96-well polypropylene microtiter plate. The method uses a dual enzymatic reaction involving glucose oxidase enzyme (GOD) and horseradish peroxidase (HRP), along with an organofluoro-substrate (4-fluorophenol) as the source of fluoride ions. The concentration of fluoride ions after enzymatic reaction is directly proportional to the glucose level in the sample. The method has a detection limit of 0.8 mmol L(-1), a linear range of 0.9- 40 mmol L(-1) and a sensitivity of 0.125 absorbance unit/decade of glucose concentration. Glucose levels in several beverage samples determined using the proposed method correlate well with a reference spectrophotometric enzyme method based on detection of hydrogen peroxide using bromopyrogallol red dye (BPR). The new method can also be used to determine H(2)O(2) concentrations in the 0.1 - 50 mmol L(-1) range using a single enzymatic reaction involving H(2)O(2) oxidation of 4-fluorophenol catalyzed by HRP. The methodology could potentially be used to detect a wide range of substrates for which selective oxidase enzymes exist (to generate H(2)O(2)), with the high throughput of simple microtiter plate detection scheme.

  15. Polymeric microspheres

    Science.gov (United States)

    Walt, David R.; Mandal, Tarun K.; Fleming, Michael S.

    2004-04-13

    The invention features core-shell microsphere compositions, hollow polymeric microspheres, and methods for making the microspheres. The microspheres are characterized as having a polymeric shell with consistent shell thickness.

  16. Amino acid-catalyzed seed regrowth synthesis of photostable high fluorescent silica nanoparticles with tunable sizes for intracellular studies

    Energy Technology Data Exchange (ETDEWEB)

    Shahabi, Shakiba; Treccani, Laura, E-mail: treccani@uni-bremen.de; Rezwan, Kurosch [University of Bremen, Advanced Ceramics (Germany)

    2015-06-15

    Size-controlled fluorescence silica nanoparticles (NPs) are widely used for nanotoxicological studies, and diagnostic and targeted therapies. Such particles can be easily visualized and localized within cell environments and their interactions with cellular components can be monitored. We developed an amino acid-catalyzed seed regrowth technique (ACSRT) to synthesize spherical rhodamine-doped silica NPs with tunable sizes, low polydispersity index as well as high labeling efficiency and enhanced fluorescence photostability. Via ACSRT, fluorescent silica NPs can be obtained by introducing the fluorophore in seed formation step, while a precise control over particle size can be achieved by simply adjusting the concentration of reactants in the regrowth step. Unlike the conventional methods, the proposed ACSRT permits the synthesis of fluorescent silica NPs in a water-based system, without the use of any surfactants and co-surfactants. By this approach, additional linkers for covalent coupling of the fluorophore to silica matrix can be omitted, while a remarkable doping efficiency is achieved. The suitability of these particles for biomedical application is demonstrated by in vitro tests with normal and malignant bone cells. We show that the particles can be easily and unambiguously visualized by a conventional fluorescence microscope, localized, and distinguished within intracellular components. In addition, it is presented that the cellular uptake and cytotoxic profile of silica NPs are strongly correlated to the particle size, concentration, and cell line. The results of in vitro experiments demonstrate that tunable fluorescent silica NPs synthesized with ACSRT can be potentially used for toxicological assessments and nanomedical studies.

  17. The Effect of Limited Diffusion and Wet–Dry Cycling on Reversible Polymerization Reactions: Implications for Prebiotic Synthesis of Nucleic Acids

    Directory of Open Access Journals (Sweden)

    Paul G. Higgs

    2016-06-01

    Full Text Available A long-standing problem for the origins of life is that polymerization of many biopolymers, including nucleic acids and peptides, is thermodynamically unfavourable in aqueous solution. If bond making and breaking is reversible, monomers and very short oligomers predominate. Recent experiments have shown that wetting and drying cycles can overcome this problem and drive the formation of longer polymers. In the dry phase, bond formation is favourable, but diffusion is restricted, and bonds only form between monomers that are initially close together. In the wet phase, some of the bonds are hydrolyzed. However, repositioning of the molecules allows new bonds to form in the next dry phase, leading to an increase in mean polymer length. Here, we consider a simple theoretical model that explains the effect of cycling. There is an equilibrium length distribution with a high mean length that could be achieved if diffusion occurred freely in the dry phase. This equilibrium is inaccessible without diffusion. A single dry cycle without diffusion leads to mean lengths much shorter than this. Repeated cycling leads to a significant increase in polymerization relative to a single cycle. In the most favourable case, cycling leads to the same equilibrium length distribution as would be achieved if free diffusion were possible in the dry phase. These results support the RNA World scenario by explaining a potential route to synthesis of long RNAs; however, they also imply that cycling would be beneficial to the synthesis of other kinds of polymers, including peptides, where bond formation involves a condensation reaction.

  18. Cyclization Phenomena in the Sol-Gel Polymerization of a,w-Bis(triethoxysilyl)alkanes and Incorporation of the Cyclic Structures into Network Silsesquioxane Polymers

    Energy Technology Data Exchange (ETDEWEB)

    Alam, T.M.; Carpenter, J.P.; Dorhout, P.K.; Greaves, J.; Loy, D.A.; Shaltout, R.; Shea, K.J.; Small, J.H.

    1999-01-04

    Intramolecular cyclizations during acid-catalyzed, sol-gel polymerizations of ct,co- bis(tietioxysilyl)aWmes substintidly lengtien gelties formonomers witietiylene- (l), propylene- (2), and butylene-(3)-bridging groups. These cyclizations reactions were found, using mass spectrometry and %i NMR spectroscopy, to lead preferentially to monomeric and dimeric products based on six and seven membered disilsesquioxane rings. 1,2- Bis(triethoxysilyl)ethane (1) reacts under acidic conditions to give a bicyclic drier (5) that is composed of two annelated seven membered rings. Under the same conditions, 1,3- bis(triethoxysilyl)propane (2), 1,4-bis(triethoxysilyl)butane (3), and z-1,4- bis(triethoxysilyl)but-2-ene (10) undergo an intramolecular condensation reaction to give the six membemd and seven membered cyclic disilsesquioxanes 6, 7, and 11. Subsequently, these cyclic monomers slowly react to form the tricyclic dirners 8,9 and 12. With NaOH as polymerization catalyst these cyclic silsesquioxanes readily ~aeted to afford gels that were shown by CP MAS z%i NMR and infr=d spectroscopes to retain some cyclic structures. Comparison of the porosity and microstructwe of xerogels prepared from the cyclic monomers 6 and 7 with gels prepared directly from their acyclic precursors 2 and 3, indicate that the final pore structure of the xerogels is markedly dependent on the nature of the precursor. In addition, despite the fact that the monomeric cyclic disilsesquioxane species can not be isolated from 1-3 under basic conditions due to their rapid rate of gelation, spectroscopic techniques also detected the presence of the cyclic structures in the resulting polymeric gels.

  19. Constructing Competitive Reverse Transcription Polymerize Chain Reaction Inter-Reference of PC mRNA by Intron Approach

    Institute of Scientific and Technical Information of China (English)

    XU Chuang; XIA Cheng; LIU Guo-wen; WANG Zhe; JIANG Yu-fu; ZHANG Nai-sheng; FU Shi-xin

    2004-01-01

    Inter-reference ofcompetitive reverse transcription polymerase chain reaction(RT-PCR)was constructed by intron method to detect the change of PC mRNA level in the pathway of carbohydrate metabolism.The experiment based on the principle that 81bp intron sequence was deleted in PC mRNA compared with PC DNA sequence.The 466bp competitive DNA template recombinant plasmid of PC mRNAwas successfully built by a pair of primer and was cloned once,PC DNA and PC mRNA could be inter-referred each other.The intron approach used in the experiment has broken through the traditional method of constructing competitive template.

  20. Separation of transition metals on a poly-iminodiacetic acid grafted polymeric resin column with post-column reaction detection utilising a paired emitter-detector diode system.

    Science.gov (United States)

    Barron, Leon; O'Toole, Martina; Diamond, Dermot; Nesterenko, Pavel N; Paull, Brett

    2008-12-05

    The selectivity, retention and separation of transition metals on a short (2 mm x 50 mm) column packed with a poly-iminodiacetic acid functionalised polymer 10 microm resin (Dionex ProPac IMAC-10) are presented. This stationary phase, typically used for the separation of proteins, is composed of long chain poly-iminodiacetic acid groups grafted to a hydrophilic layer surrounding a 10 microm polymeric bead. Through the use of a combination of a multi-step pH and picolinic acid gradient, the separation of magnesium, iron, cobalt, cadmium, zinc, lead and copper was possible, followed by post-column reaction with 4-(2-pyridylazo) resorcinol (PAR) and absorbance detection at 510 nm using a novel and inexpensive optical detector, comprised of two light emitting diodes with one acting as a light source and the other as a detector. Column efficiency for selective transition metals was in excess of N=10,000, with the baseline separation of seven metal cations in <3 min possible under optimised conditions. Detection limits of between 5 and 81 microg/L were possible based upon a 50 microL injection volume.

  1. Synthesis of 1,1-Diphenylethylene (DPE): The Marriage of a Grignard Reaction and a Column Chromatography Experiment

    Science.gov (United States)

    Alty, Lisa T.; France, Marcia B.; Alty, Isaac G.; Saber, Christine A.; Smith, Donna M.

    2016-01-01

    The synthesis of 1,1-diphenylethylene (DPE) via a Grignard reaction, followed by an acid-catalyzed dehydration reaction, yields a mixture of compounds. DPE is a high boiling liquid that cannot be purified using simple distillation. However, it is easily separated from the more polar starting material and intermediate alcohol using both thin layer…

  2. Oxa-Pictet-Spengler reaction in water.Synthesis of some(±)-1-aryl-6,7-dimethoxyisochromans

    Institute of Scientific and Technical Information of China (English)

    Aamer; Saeed

    2010-01-01

    An acid catalyzed oxa-Pictet-Spengler reaction‘on water' leading to the synthesis of a variety of l-aryl-6,7-dimethoxyisochro-mans is described.The aqueous chemistry is a much cleaner,efficient,cheaper and simple method for synthesis.The scope of reactions was extended to thia-Pictet-Spengler reaction to afford the some isothiochromans.

  3. Polymerization rate and mechanism of ultrasonically initiated emulsion polymerization of n-butyl acrylate.

    Science.gov (United States)

    Xia, Hesheng; Wang, Qi; Liao, Yongqin; Xu, Xi; Baxter, Steven M; Slone, Robert V; Wu, Shuguang; Swift, Graham; Westmoreland, David G

    2002-07-01

    The factors affecting the induction period and polymerization rate in ultrasonically initiated emulsion polymerization of n-butyl acrylate (BA) were investigated. The induction period takes only an instant in ultrasonically initiated emulsion polymerization of BA without any added initiator by enhancing the N2 flow rate. Increasing temperature, power output and SDS concentration, decreasing the monomer concentration results in further decreasing induction period and enhanced polymerization rate. Under optimized reaction conditions the conversion of BA reaches 92% in 11 min. The polymerization rate can be controlled by varying reaction parameters. The apparatus of ultrasonically initiated semi-continuous and continuous emulsion polymerization were set up and the feasibility was first studied. Based on the experimental results, a free radical polymerization mechanism for ultrasonically initiated emulsion polymerization was proposed, including the sources of the radicals, the process of radical formation, the locus of polymerization and the polymerization process. Compared with conventional emulsion polymerization, where the radicals come from thermal decomposition of a chemical initiator, ultrasonically initiated emulsion polymerization has attractive features such as no need for a chemical initiator, lower reaction temperature, faster polymerization rate, and higher molecular weight of the polymer prepared.

  4. Twin screw extruders as polymerization reactors for a free radical homo polymerization

    NARCIS (Netherlands)

    Ganzeveld, K.J.; Janssen, L.P.B.M.

    1993-01-01

    The bulk polymerization of n-butylmethacrylate was investigated in a counter-rotating twin screw extruder. It appeared that the gel effect, occurring with bulk polymerizations, affected the polymerization progress very strongly. Due to this effect the conversion of the reaction is independent of the

  5. Cause analysis of the effects of acid-catalyzed steam-exploded corn stover prehydrolyzate on ethanol fermentation by Pichia stipitis CBS 5776.

    Science.gov (United States)

    Zhu, Junjun; Yang, Jinlong; Zhu, Yuanyuan; Zhang, Lingling; Yong, Qiang; Xu, Yong; Li, Xin; Yu, Shiyuan

    2014-11-01

    The prehydrolyzate obtained from acid-catalyzed steam-exploded corn stover (ASC) mainly contains xylose and a number of inhibitory compounds that inhibit ethanol fermentation by Pichia stipitis. In this study, the effects of the ASC prehydrolyzate, specifically those of the carbohydrate-degradation products, lignin-degradation products (which were extracted from ASC prehydrolyzate using ethyl acetate), and six major phenolic compounds (added to pure-sugar media individually or in combination), on ethanol fermentation were investigated. Results indicate that the effects of the carbohydrate-degradation products were negligible (10 h delayed) compared with those of pure-sugar fermentation, whereas the effects of the lignin-degradation products were significant (52 h delayed). Meanwhile, the inhibitory effects of the major phenolic compounds were not caused by certain types of inhibitors, but were due to the synergistic effects of various inhibitors.

  6. Difference analysis of the enzymatic hydrolysis performance of acid-catalyzed steam-exploded corn stover before and after washing with water.

    Science.gov (United States)

    Zhu, Junjun; Shi, Linli; Zhang, Lingling; Xu, Yong; Yong, Qiang; Ouyang, Jia; Yu, Shiyuan

    2016-10-01

    The difference in the enzymatic hydrolysis yield of acid-catalyzed steam-exploded corn stover (ASC) before and after washing with water reached approximately 15 % under the same conditions. The reasons for the difference in the yield between ASC and washed ASC (wASC) were determined through the analysis of the composition of ASC prehydrolyzate and sugar concentration of enzymatic hydrolyzate. Salts produced by neutralization (CaSO4, Na2SO4, K2SO4, and (NH4)2SO4), sugars (polysaccharides, oligosaccharides, and monosaccharides), sugar-degradation products (weak acids and furans), and lignin-degradation products (ethyl acetate extracts and nine main lignin-degradation products) were back-added to wASC. Results showed that these products, except furans, exerted negative effect on enzymatic hydrolysis. According to the characteristics of acid-catalyzed steam explosion pretreatment, the five sugar-degradation products' mixture and salts [Na2SO4, (NH4)2SO4] showed minimal negative inhibition effect on enzymatic hydrolysis. By contrast, furans demonstrated a promotion effect. Moreover, soluble sugars, such as 13 g/L xylose (decreased by 6.38 %), 5 g/L cellobiose (5.36 %), 10 g/L glucose (3.67 %), as well as lignin-degradation products, and ethyl acetate extracts (4.87 %), exhibited evident inhibition effect on enzymatic hydrolysis. Therefore, removal of soluble sugars and lignin-degradation products could effectively promote the enzymatic hydrolysis performance.

  7. An efficient synthesis of isocoumarins via a CuI catalyzed cascade reaction process

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    3-Alkyl isocoumarins are provided by CuI/amino acid-catalyzed Sonogashira coupling reaction of o-bromo benzoic acids and terminal alkynes and the subsequent additive cyclization. This cascade process allows synthesis of diverse isocoumarins by varying both coupling partners bearing a wide range of functional groups.

  8. Preparation of conducting polymer patterns using photochemical reaction of oxidation polymerization agents; Sanka jugozai no hikarikagaku henka wo riyoshita dodensei kobunshi patan no seisaku hoho

    Energy Technology Data Exchange (ETDEWEB)

    Onishi, Yasushi; Naruse, Tsutomu; Yoshimoto, Shoji; Kimura, Kazuyuki [Aichi Prefectura Goverment, Aichi (Japan). Institute of Industrial Research; Natsume, Yukihiro [Aica Kogyo Corp., Aichi (Japan)

    1999-09-10

    Preparation of conducting polymer patterns using the photochemical oxidizing ability changes of an oxidation polymerization agent has been investigated. Photoreactive metal salts such as iron (3) chloride were used for oxidation polymerization of conducting polymers such as polymers such as polypyrrole. Metal salts were reduced by exposing to ultra-violet (UV) light and missed the ability of oxidation polymerization. Therefore, conducting polypyrrole patterns have been prepared on the unirradiated part by exposing films containing iron (3) chloride to UV light through the pattern mask and then contacting with pyrrole vapor or dipping in pyrrole solution. By this method, large and fine conducting polymer patterns can easily be prepared on plastics, ceramics, papers, clothes, woods, etc. In addition, it may be able to prepare patterns with partially different conductivity by controlling the irradiation time of UV light and/or shades of the pattern masks. (author)

  9. Experimental and modeling studies on the acid-catalyzed conversion of inulin to 5-hydroxymethylfurfural in water

    NARCIS (Netherlands)

    Fachri, B.A.; Abdilla, R. M.; Rasrendra, C. B.; Heeres, Hero

    2016-01-01

    Inulin is considered as an attractive feed for the synthesis of 5-hydroxymethylfurfural (HMF), an important biobased platform chemical with high application potential. We here report a systematic study to optimize the HMF yield from inulin in a batch reactor for reactions in water using sulphuric ac

  10. Microwave-Assisted Resolution of α-Lipoic Acid Catalyzed by an Ionic Liquid Co-Lyophilized Lipase

    Directory of Open Access Journals (Sweden)

    Ning Liu

    2015-05-01

    Full Text Available The combination of the ionic liquid co-lyophilized lipase and microwave irradiation was used to improve enzyme performance in enantioselective esterification of α-lipoic acid. Effects of various reaction conditions on enzyme activity and enantioselectivity were investigated. Under optimal condition, the highest enantioselectivity (E = 41.2 was observed with a high enzyme activity (178.1 μmol/h/mg when using the ionic liquid co-lyophilized lipase with microwave assistance. Furthermore, the ionic liquid co-lyophilized lipase exhibited excellent reusability under low power microwave.

  11. The Formation of Pyrroline and Tetrahydropyridine Rings in Amino Acids Catalyzed by Pyrrolysine Synthase (PylD)

    KAUST Repository

    Quitterer, Felix

    2014-06-10

    The dehydrogenase PylD catalyzes the ultimate step of the pyrrolysine pathway by converting the isopeptide L-lysine-Nε-3R-methyl-D-ornithine to the 22nd proteinogenic amino acid. In this study, we demonstrate how PylD can be harnessed to oxidize various isopeptides to novel amino acids by combining chemical synthesis with enzyme kinetics and X-ray crystallography. The data enable a detailed description of the PylD reaction trajectory for the biosynthesis of pyrroline and tetrahydropyridine rings as constituents of pyrrolysine analogues. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Catalytic Conversion of Bio-Oil to Oxygen-Containing Fuels by Acid-Catalyzed Reaction with Olefins and Alcohols over Silica Sulfuric Acid

    Directory of Open Access Journals (Sweden)

    Qingwen Wang

    2013-09-01

    Full Text Available Crude bio-oil from pine chip fast pyrolysis was upgraded with olefins (1-octene, cyclohexene, 1,7-octadiene, and 2,4,4-trimethylpentene plus 1-butanol (iso-butanol, t-butanol and ethanol at 120 °C using a silica sulfuric acid (SSA catalyst that possesses a good catalytic activity and stability. Gas chromatography-mass spectrometry (GC-MS, Fourier transform infrared spectroscopy (FT-IR and proton nuclear magnetic resonance (1H-NMR analysis showed that upgrading sharply increased ester content and decreased the amounts of levoglucosan, phenols, polyhydric alcohols and carboxylic acids. Upgrading lowered acidity (pH value rose from 2.5 to >3.5, removed the unpleasant odor and increased hydrocarbon solubility. Water content dramatically decreased from 37.2% to about 7.0% and the heating value increased from 12.6 MJ·kg−1 to about 31.9 MJ·kg−1. This work has proved that bio-oil upgrading with a primary olefin plus 1-butanol is a feasible route where all the original heating value of the bio-oil plus the added olefin and alcohol are present in the resulting fuel.

  13. Advanced Model Compounds for Understanding Acid-Catalyzed Lignin Depolymerization: Identification of Renewable Aromatics and a Lignin-Derived Solvent.

    Science.gov (United States)

    Lahive, Ciaran W; Deuss, Peter J; Lancefield, Christopher S; Sun, Zhuohua; Cordes, David B; Young, Claire M; Tran, Fanny; Slawin, Alexandra M Z; de Vries, Johannes G; Kamer, Paul C J; Westwood, Nicholas J; Barta, Katalin

    2016-07-20

    The development of fundamentally new approaches for lignin depolymerization is challenged by the complexity of this aromatic biopolymer. While overly simplified model compounds often lack relevance to the chemistry of lignin, the direct use of lignin streams poses significant analytical challenges to methodology development. Ideally, new methods should be tested on model compounds that are complex enough to mirror the structural diversity in lignin but still of sufficiently low molecular weight to enable facile analysis. In this contribution, we present a new class of advanced (β-O-4)-(β-5) dilinkage models that are highly realistic representations of a lignin fragment. Together with selected β-O-4, β-5, and β-β structures, these compounds provide a detailed understanding of the reactivity of various types of lignin linkages in acid catalysis in conjunction with stabilization of reactive intermediates using ethylene glycol. The use of these new models has allowed for identification of novel reaction pathways and intermediates and led to the characterization of new dimeric products in subsequent lignin depolymerization studies. The excellent correlation between model and lignin experiments highlights the relevance of this new class of model compounds for broader use in catalysis studies. Only by understanding the reactivity of the linkages in lignin at this level of detail can fully optimized lignin depolymerization strategies be developed.

  14. Living olefin polymerization processes

    Science.gov (United States)

    Schrock, Richard R.; Baumann, Robert

    1999-01-01

    Processes for the living polymerization of olefin monomers with terminal carbon-carbon double bonds are disclosed. The processes employ initiators that include a metal atom and a ligand having two group 15 atoms and a group 16 atom or three group 15 atoms. The ligand is bonded to the metal atom through two anionic or covalent bonds and a dative bond. The initiators are particularly stable under reaction conditions in the absence of olefin monomer. The processes provide polymers having low polydispersities, especially block copolymers having low polydispersities. It is an additional advantage of these processes that, during block copolymer synthesis, a relatively small amount of homopolymer is formed.

  15. High Vacuum Techniques for Anionic Polymerization

    KAUST Repository

    Ratkanthwar, Kedar

    2015-09-01

    Anionic polymerization high vacuum techniques (HVTs) are the most suitable for the preparation of polymer samples with well-defined complex macromolecular architectures. Though HVTs require glassblowing skill for designing and making polymerization reactor, it is the best way to avoid any termination of living polymers during the number of steps for the synthesis of polymers with complex structure. In this chapter, we describe the different polymerization reactors and HVTs for the purification of monomers, solvents, and other reagents for anionic polymerization as well as few model reactions for the synthesis of polymers with simple to complex structure.

  16. Biokompatible Polymere

    Science.gov (United States)

    Ha, Suk-Woo; Wintermantel, Erich; Maier, Gerhard

    Der klinische Einsatz von synthetischen Polymeren begann in den 60-er Jahren in Form von Einwegartikeln, wie beispielsweise Spritzen und Kathetern, vor allem aufgrund der Tatsache, dass Infektionen infolge nicht ausreichender Sterilität der wiederverwendbaren Artikel aus Glas und metallischen Werkstoffen durch den Einsatz von sterilen Einwegartikeln signifikant reduziert werden konnten [1]. Die Einführung der medizinischen Einwegartikel aus Polymeren erfolgte somit nicht nur aus ökonomischen, sondern auch aus hygienischen Gründen. Wegen der steigenden Anzahl synthetischer Polymere und dem zunehmenden Bedarf an ärztlicher Versorgung reicht die Anwendung von Polymeren in der Medizin von preisgünstigen Einwegartikeln, die nur kurzzeitig intrakorporal eingesetzt werden, bis hin zu Implantaten, welche über eine längere Zeit grossen Beanspruchungen im menschlichen Körper ausgesetzt sind. Die steigende Verbreitung von klinisch eingesetzten Polymeren ist auf ihre einfache und preisgünstige Verarbeitbarkeit in eine Vielzahl von Formen und Geometrien sowie auf ihr breites Eigenschaftsspektrum zurückzuführen. Polymere werden daher in fast allen medizinischen Bereichen eingesetzt.

  17. Novel polymeric materials from triglycerides

    Science.gov (United States)

    Triglycerides are good platforms for new polymeric products that can substitute for petroleum-based materials. As part of our research emphasis in sustainability and green polymer chemistry, we have explored a number of reactions in efforts to produce a wide range of value-added products. In this ...

  18. Effect of acid-catalyzed formation rates of benzimidazole-linked polymers on porosity and selective CO2 capture from gas mixtures.

    Science.gov (United States)

    Altarawneh, Suha; İslamoğlu, Timur; Sekizkardes, Ali Kemal; El-Kaderi, Hani M

    2015-04-01

    Benzimidazole-linked polymers (BILPs) are emerging candidates for gas storage and separation applications; however, their current synthetic methods offer limited control over textural properties which are vital for their multifaceted use. In this study, we investigate the impact of acid-catalyzed formation rates of the imidazole units on the porosity levels of BILPs and subsequent effects on CO2 and CH4 binding affinities and selective uptake of CO2 over CH4 and N2. Treatment of 3,3'-Diaminobenzidine tetrahydrochloride hydrate with 1,2,4,5-tetrakis(4-formylphenyl)benzene and 1,3,5-(4-formylphenyl)-benzene in anhydrous DMF afforded porous BILP-15 (448 m(2) g(-1)) and BILP-16 (435 m(2) g(-1)), respectively. Alternatively, the same polymers were prepared from the neutral 3,3'-Diaminobenzidine and catalytic amounts of aqueous HCl. The resulting polymers denoted BILP-15(AC) and BILP-16(AC) exhibited optimal surface areas; 862 m(2) g(-1) and 643 m(2) g(-1), respectively, only when 2 equiv of HCl (0.22 M) was used. In contrast, the CO2 binding affinity (Qst) dropped from 33.0 to 28.9 kJ mol(-1) for BILP-15 and from 32.0 to 31.6 kJ mol(-1) for BILP-16. According to initial slope calculations at 273 K/298 K, a notable change in CO2/N2 selectivity was observed for BILP-15(AC) (61/50) compared to BILP-15 (83/63). Similarly, ideal adsorbed solution theory (IAST) calculations also show the higher specific surface area of BILP-15(AC) and BILP-16(AC) compromises their CO2/N2 selectivity.

  19. Synthesis of Highly Polymerized Water-soluble Cellulose Acetate by the Side Reaction in Carboxylate Ionic Liquid 1-ethyl-3-methylimidazolium Acetate

    Science.gov (United States)

    Pang, Jinhui; Liu, Xin; Yang, Jun; Lu, Fachuang; Wang, Bo; Xu, Feng; Ma, Mingguo; Zhang, Xueming

    2016-09-01

    In the present study, we describe a novel one-step method to prepare water-soluble cellulose acetate (WSCA) with higher degree of polymerization values (DP = 650–680) by in situ activation of carboxyl group in ionic liquid. First of all, cellulose was dissolved in 1-ethyl-3-methylimidazolium acetate (EmimAc) and reacted with dichloroacetyl chloride (Cl2AcCl) in order to make cellulose dichloroacetate. Under various conditions, a series of water soluble products were produced. Elemental analysis and NMR results confirmed that they were cellulose acetate with DS (degree of substitution) values in the range from 0.30 to 0.63. NMR studies demonstrated that Cl2AcCl reacted with acetate anion of EmimAc producing a mixed anhydride that acetylated cellulose. Other acylating reagents such as benzoyl chloride, chloroacetyl chloride can also work similarly. 2D NMR characterization suggested that 6-mono-O-acetyl moiety, 3,6-di-O-acetylcellulose and 2,6-di-O-acetyl cellulose were all synthesized and the reactivity of hydroxyl groups in anhydro-glucose units was in the order C-6>C-3>C-2. This work provides an alternative way to make WSCA, meanwhile, also services as a reminder that the activity of EmimAc toward carbohydrate as acylating reagents could be a problem, because the expected acylated products may not be resulted and recycling of this ionic liquid could also be difficult.

  20. Synthesis of Highly Polymerized Water-soluble Cellulose Acetate by the Side Reaction in Carboxylate Ionic Liquid 1-ethyl-3-methylimidazolium Acetate

    Science.gov (United States)

    Pang, Jinhui; Liu, Xin; Yang, Jun; Lu, Fachuang; Wang, Bo; Xu, Feng; Ma, Mingguo; Zhang, Xueming

    2016-01-01

    In the present study, we describe a novel one-step method to prepare water-soluble cellulose acetate (WSCA) with higher degree of polymerization values (DP = 650–680) by in situ activation of carboxyl group in ionic liquid. First of all, cellulose was dissolved in 1-ethyl-3-methylimidazolium acetate (EmimAc) and reacted with dichloroacetyl chloride (Cl2AcCl) in order to make cellulose dichloroacetate. Under various conditions, a series of water soluble products were produced. Elemental analysis and NMR results confirmed that they were cellulose acetate with DS (degree of substitution) values in the range from 0.30 to 0.63. NMR studies demonstrated that Cl2AcCl reacted with acetate anion of EmimAc producing a mixed anhydride that acetylated cellulose. Other acylating reagents such as benzoyl chloride, chloroacetyl chloride can also work similarly. 2D NMR characterization suggested that 6-mono-O-acetyl moiety, 3,6-di-O-acetylcellulose and 2,6-di-O-acetyl cellulose were all synthesized and the reactivity of hydroxyl groups in anhydro-glucose units was in the order C-6>C-3>C-2. This work provides an alternative way to make WSCA, meanwhile, also services as a reminder that the activity of EmimAc toward carbohydrate as acylating reagents could be a problem, because the expected acylated products may not be resulted and recycling of this ionic liquid could also be difficult. PMID:27644545

  1. Polymerization Simulator for Introductory Polymer and Material Science Courses

    Science.gov (United States)

    Chirdon, William M.

    2010-01-01

    This work describes how molecular simulation of polymerization reactions can be used to enrich introductory polymer or material science courses to give students a deeper understanding of free-radical chain and stepwise growth polymerization reactions. These simulations have proven to be effective media for instruction that do not require material…

  2. Aza‐Michael addition reaction: Post‐polymerization modification and preparation of PEI/PEG‐based polyester hydrogels from enzymatically synthesized reactive polymers

    DEFF Research Database (Denmark)

    Hoffmann, Christian; Stuparu, Mihaiela C.; Daugaard, Anders Egede;

    2015-01-01

    monomers provides the polyesters, which carry an activated carbon‐carbon double bond in the polymer backbone. These electron deficient alkenes represent suitable aza‐Michael acceptors and can be engaged in a nucleophilic addition reaction with small molecular mono‐amines (aza‐Michael donors) to yield...... functionalized linear polyesters. Employing a poly‐amine as the aza‐Michael donor, on the other hand, results in the formation of hydrophilic polymer networks....

  3. Study of the Chain Transfer Reaction of 3-Mercaptohexanol in the Styrene Polymerization%3-巯基己醇在苯乙烯聚合体系中的链转移反应行为

    Institute of Scientific and Technical Information of China (English)

    张薇; 黄文艳; 李少杰; 薛小强; 蒋必彪

    2011-01-01

    The polymerization of styrene was carried out in the presence of 3 - mercaptohexanol at different temperature with AIBN as the initiator and toluene as the internal standard. The chain transfer constant of 3 - mercaptohexanol under the experimental condition was obtained by the Mayo equation. It is 3. 99, 3. 58 and 2. 24 at the polymerization temperature of 60 ℃ , 70 ℃ and 80 ℃ respectively. As the temperature increased, the chain transfer constant of 3 - mercaptohexanol decreased. Further research showed that; under the polymerization condition, the products with very low molecular weight were formed from the 3-mercaptohexanol transferring to styrene radical. The dimer and trimer of these products were obtained by high performance liquid chromatography and confirmed by proton nuclear magnetic resonance (1H NMR) and liquid chromatography-mass spectrometry (LC - MS). The productivity of these products increased significantly as the reaction temperature increased. Therefore, the obtained chain transfer constant is only the apparent value because of the formation of the molecules with very low molecular weight.%以偶氯二异丁腈(AIBN)为引发剂,甲苯为内标,3-巯基己醇为链转移剂进行苯乙烯(St)聚合.根据Mayo等式,求出了60℃,70℃和80℃下的链转移常数,分别为3.99,3.58和2.24,表明链转移常数随着温度的升高而减小.采用制备色谱分离得到了聚合初期的产物,并且由核磁共振(1H NMR)和液-质联用(LC-MS)确证了生成的小分子产物的结构.定量分析结果表明:在相同的巯基醇转化率下,相对分子质量低的产物的生成量随反应温度的升高而显著增加,以聚合物相对分子质量为基础计算得到的表观链转移常数则变小.

  4. Carborane complexes of ruthenium(III): studies on thermal reaction chemistry and the catalyst design for atom transfer radical polymerization of methyl methacrylate.

    Science.gov (United States)

    Grishin, Ivan D; D'yachihin, Dmitrii I; Piskunov, Alexander V; Dolgushin, Fedor M; Smol'yakov, Alexander F; Il'in, Mikhail M; Davankov, Vadim A; Chizhevsky, Igor T; Grishin, Dmitry F

    2011-08-15

    The heating of the 18-electron complex [3,3-(dppb)-3-H-3-Cl-closo-3,1,2-RuC(2)B(9)H(11)] (3) in benzene at 80 °C in the presence of a small amount of CCl(4) as initiator afforded paramagnetic 17-electron species [3,3-(dppb)-3-Cl-closo-3,1,2-RuC(2)B(9)H(11)] (4) along with minor amounts of two P-phenylene ortho-cycloboronated derivatives [3-Cl-3,3,8-{Ph(2)P(CH(2))(4)PPh-μ-(C(6)H(4)-ortho)}-closo-3,1,2-RuC(2)B(9)H(10)] (5) and [3,7-Cl(2)-3,3,8-{Ph(2)P(CH(2))(4)PPh-μ-(C(6)H(4)-ortho)}-closo-3,1,2-RuC(2)B(9)H(10)] (6) in total yield of ca. 80%. The heating of either 3 or 4 in toluene at 95 °C in the absence of CCl(4) led to the selective formation of 5, which was isolated in 64% and 46% yield, respectively. Thermolysis of 3 at higher temperatures (boiling toluene, 110 °C) gives novel paramagnetic species [3-Cl-3,3,7,8-{Ph(2)P(CH(2))(4)P-μ-(C(6)H(4)-ortho)(2)}-closo-3,1,2-RuC(2)B(9)H(9)] (7) featuring bis(ortho-cycloboronation) of both P-phenyl groups at the same phosphorus atom of the ruthenium-bound dppb ligand. All new paramagnetic complexes 4-7, as well as starting diamagnetic species 3, were characterized by single-crystal X-ray diffraction and, in addition, by EPR spectroscopic studies of odd-electron complexes. Ruthenacarboranes 3-5 and 7 all display high efficiency as catalysts for the atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA). Complex 5 gave the best catalyst performance in terms of polydispersity; the PDI (M(w)/M(n)) of the polymer samples is as low as 1.15.

  5. Functionalized polymer networks: synthesis of microporous polymers by frontal polymerization

    Indian Academy of Sciences (India)

    N S Pujari; A R Vishwakarma; T S Pathak; A M Kotha; S Ponrathnam

    2004-12-01

    A series of glycidyl methacrylate (GMA)–ethylene dimethacrylate (EGDM) copolymers of varying compositions were synthesized by free-radically triggered thermal frontal polymerization (FP) as well as by suspension polymerization (SP) using azobisisobutyronitrile [AIBN] as initiator. The two sets of copolymers were characterized by IR spectroscopy and mercury intrusion porosimetry, for determination of epoxy number and specific surface area. Frontal polymerization was more efficient, yielding greater conversions at much shorter reaction times. The self-propagating frontal polymerization also generates microporous material with narrow pore size distribution. It yields higher internal pore volume and surface area than suspension polymerization, surface morphologies are, however, inferior.

  6. SYNTHESIS AND POLYMERIZATION OF BISPHENYLENE ORTHOCARBONATE

    Institute of Scientific and Technical Information of China (English)

    PAN Caiyuan; ZHAO Yulong; William J. Bailey

    1988-01-01

    Bisphenylene orthocarbonate (Ⅱ) was synthesized by the reaction of dicopper catecholate with carbon tetrachloride, and underwent cationic ring-opening polymerization with the introduction of phenyl group into the main ehain. The obtained polymer with ester and ether group was verified by IR and 1H NMR spectra.Based on the analysis of the polymer structures, the polymerization mechanism was proposed. Its Tm and Tg are 254℃ and 160℃ respectively. No decomposition of the polymer was observed below 320℃. The volume expansion property of the monomer during polymerization was studied by measuring the density difference between I and its polymer at various temperatures.

  7. AZIDE-ALKYNE CLICK POLYMERIZATION: AN UPDATE

    Institute of Scientific and Technical Information of China (English)

    Hong-kun Li; Jing-zhi Sun; An-jun Qin; Ben Zhong Tang

    2012-01-01

    The great achievements of click chemistry have encouraged polymer scientists to use this reaction in their field.This review assembles an update of the advances of using azide-alkyne click polymerization to prepare functional polytriazoles (PTAs) with linear and hyperbranched structures.The Cu(Ⅰ)-mediated click polymerization furnishes 1,4-regioregular PTAs,whereas,the metal-free click polymerization of propiolates and azides produces PTAs with 1,4-regioisomer contents up to 90%.The PTAs display advanced functions,such as aggregation-induced emission,thermal stability,biocompatibility and optical nonlinearity.

  8. Online observation of emulsion polymerization by fluorescence technique

    CERN Document Server

    Rudschuck, S; Fuhrmann, J

    1999-01-01

    An online observation of local polarity via fluorescence spectroscopy was used to study the formation and growth of polymer particles during an emulsifier-free heterogeneous polymerization. The reaction mixture consisted of styrene dispersed in water and the polymerization was initiated by a macro-initiator (hydrolyzed propene-maleic acid copolymer with t-butyl perester groups). Pyrenyl probes were attached to the backbone of the initiator to analyze the heterogeneous reaction. The experimental results allow a clear distinction of different time regions during the heterogeneous polymerization. Information about the heating period, the latex formation, the particle growth and the final stage of the polymerization process (gel point) were obtained. (11 refs).

  9. The Lewis Acid-promoted Novel Cyclization Reactions Towards N-adn O-Containing Heterocycles

    Institute of Scientific and Technical Information of China (English)

    Shoko; Yamazaki

    2007-01-01

    1 Results Nitrogen and oxygen-containing heterocyclic systems are important structures in organic chemistry because of their presence in many biologically active compounds.In this work,a new zinc and indium-promoted conjugate addition-cyclization reaction to afford nitrogen and oxygen-containing five-membered heterocycles has been developed.A Lewis acid-catalyzed cyclization of an ethenetricarboxylate derivative with propargylamines or propargyl alcohols to give methylenepyrrolidines and methylenetetrah...

  10. Survey and research on precision polymerization polymeric materials; Seimitsu jugo kobunshi zairyo ni kansuru chosa kenkyu

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-03-01

    Survey and research on the precision control of primary structure of polymeric materials and the precision evaluation technology have been conducted to develop advanced polymeric materials. It is proposed that the three basic processes of polymer synthesis, i.e., addition, condensation, and biomimesis, in forming the precision polymerization skeleton are to be covered through a centralized joint research effort with participation of industry, academia, and the government institute and under the leadership of researchers from academic institutions as the team leaders. For the study of technology trends, international conferences held in UK, Germany, and Hawaii are introduced, and domestic meetings, i.e., Annual Polymer Congress and Polymer Conference, are summarized. In addition, Precision Polymerization Forum and International Workshop on Precision Polymerization were held. The basic studies include a quantum-chemical elucidation of the elementary process in polymerization reaction, time-resolved analysis of polymerization process and polymer properties, synthesis of polymers with controlled microstructures by coordination polymerization using metal complexes, synthesis of polymer with controlled microstructures by precision polycondensation, molecular recognition in catalyst-reaction site, and synthesis of imprinting polymers. 246 refs., 117 figs., 14 tabs.

  11. Combining RAFT polymerization and thiol-ene click reaction for core-shell structured polymer@BaTiO3 nanodielectrics with high dielectric constant, low dielectric loss, and high energy storage capability.

    Science.gov (United States)

    Yang, Ke; Huang, Xingyi; Zhu, Ming; Xie, Liyuan; Tanaka, Toshikatsu; Jiang, Pingkai

    2014-02-12

    Nanodielectric materials with high dielectric constant, low dielectric loss, and high energy storage capability are highly desirable in modern electric and electronics industries. It has been proved that the preparation of core-shell structured dielectric polymer nanocomposites via "grafting from" method is an effective approach to these materials. However, by using this approach, the deep understanding of the structure-dielectric property relationship of the core-shell structured nanodielectrics has been limited because of the lack of detailed information (e.g., molecular weight, grafting density) about the macromolecules grafted onto the nanoparticle surfaces. In this work, by the combination of reversible addition-fragmentation chain transfer (RAFT) polymerization and thiol-ene click reaction, two types of core-shell structured polymer@BaTiO3 (polymer@BT) nanocomposites with high dielectric constant and low dielectric loss were successfully prepared via a "grafting to" method. Compared with the "grafting from" method, this "grafting to" method has two merits: the molecular weight of the polymer chains in the shell layer can be easily controlled and the grafting density can be tailored by changing the molecular weight of the grafting polymer. Moreover, a clear insight into the relationship among the dielectric properties and energy storage capability of the core-shell structured polymer@BT nanocomposites, the molecular weight of the polymer chains, and the grafting density of the core-shell structured nanoparticles was achieved. The study provides new insights into the design and preparation of nanodielectric materials with desirable dielectric properties.

  12. Preparation of a poly(3'-azido-3'-deoxythymidine-co-propargyl methacrylate-co-pentaerythritol triacrylate) monolithic column by in situ polymerization and a click reaction for capillary liquid chromatography of small molecules and proteins.

    Science.gov (United States)

    Lin, Zian; Yu, Ruifang; Hu, Wenli; Zheng, Jiangnan; Tong, Ping; Zhao, Hongzhi; Cai, Zongwei

    2015-07-01

    Combining free radical polymerization with click chemistry via a copper-mediated azide/alkyne cycloaddition (CuAAC) reaction in a "one-pot" process, a facile approach was developed for the preparation of a poly(3'-azido-3'-deoxythymidine-co-propargyl methacrylate-co-pentaerythritol triacrylate) (AZT-co-PMA-co-PETA) monolithic column. The resulting poly(AZT-co-PMA-co-PETA) monolith showed a relatively homogeneous monolithic structure, good permeability and mechanical stability. Different ratios of monomers and porogens were used for optimizing the properties of a monolithic column. A series of alkylbenzenes, amides, anilines, and benzoic acids were used to evaluate the chromatographic properties of the polymer monolith in terms of hydrophobic, hydrophilic and cation-exchange interactions, and the results showed that the poly(AZT-co-PMA-co-PETA) monolith exhibited more flexible adjustment in chromatographic selectivity than that of the parent poly(PMA-co-PETA) and AZT-modified poly(PMA-co-PETA) monoliths. Column efficiencies for toluene, DMF, and formamide with 35,000-48,000 theoretical plates per m could be obtained at a linear velocity of 0.17 mm s(-1). The run-to-run, column-to-column, and batch-to-batch repeatabilities of the retention factors were less than 4.2%. In addition, the proposed monolith was also applied to efficient separation of sulfonamides, nucleobases and nucleosides, anesthetics and proteins for demonstrating its potential.

  13. Facile synthesis of N-rich carbon quantum dots by spontaneous polymerization and incision of solvents as efficient bioimaging probes and advanced electrocatalysts for oxygen reduction reaction

    Science.gov (United States)

    Lei, Zhouyue; Xu, Shengjie; Wan, Jiaxun; Wu, Peiyi

    2016-01-01

    In this study, uniform nitrogen-doped carbon quantum dots (N-CDs) were synthesized through a one-step solvothermal process of cyclic and nitrogen-rich solvents, such as N-methyl-2-pyrrolidone (NMP) and dimethyl-imidazolidinone (DMEU), under mild conditions. The products exhibited strong light blue fluorescence, good cell permeability and low cytotoxicity. Moreover, after a facile post-thermal treatment, it developed a lotus seedpod surface-like structure of seed-like N-CDs decorating on the surface of carbon layers with a high proportion of quaternary nitrogen moieties that exhibited excellent electrocatalytic activity and long-term durability towards the oxygen reduction reaction (ORR). The peak potential was -160 mV, which was comparable to or even lower than commercial Pt/C catalysts. Therefore, this study provides an alternative facile approach to the synthesis of versatile carbon quantum dots (CDs) with widespread commercial application prospects, not only as bioimaging probes but also as promising electrocatalysts for the metal-free ORR.In this study, uniform nitrogen-doped carbon quantum dots (N-CDs) were synthesized through a one-step solvothermal process of cyclic and nitrogen-rich solvents, such as N-methyl-2-pyrrolidone (NMP) and dimethyl-imidazolidinone (DMEU), under mild conditions. The products exhibited strong light blue fluorescence, good cell permeability and low cytotoxicity. Moreover, after a facile post-thermal treatment, it developed a lotus seedpod surface-like structure of seed-like N-CDs decorating on the surface of carbon layers with a high proportion of quaternary nitrogen moieties that exhibited excellent electrocatalytic activity and long-term durability towards the oxygen reduction reaction (ORR). The peak potential was -160 mV, which was comparable to or even lower than commercial Pt/C catalysts. Therefore, this study provides an alternative facile approach to the synthesis of versatile carbon quantum dots (CDs) with widespread

  14. Enzymatic reaction of ethanol and oleic acid by lipase and lignin peroxidase in rhamnolipid (RL) reversed micelles

    Institute of Scientific and Technical Information of China (English)

    包珊; 吴秀莲; 武海鹏; 袁兴中; 王侯; 彭馨; 刘欢; 曾光明; 马玉洁; 崔凯龙

    2015-01-01

    An environment friendly bio-surfactant of rhamnolipid (RL) was used as a solvent. The enzymatic reaction of oleic acid catalyzed by lipase and lignin peroxidase (lip) was evaluated. The optimum conditions of enzymatic reaction catalyzed by lipase (lip) were water to amphiphile molar ratio of 30 (20), RL of 60 (60) critical micelle concentration (CMC), pH of 7.0 (3.0) and temperature of 40 (30) °C, respectively. The change of enzyme conformation indicates that, for catalytic of lipase, water content is the most important factor of the enzymatic reaction of oleic acid, and pH for lip. With individual optimum conditions, the enzymatic efficiency of oleic acid catalyzed by lipase is higher than that by lip. In the presence of ethanol, the enzymatic reaction of oleic acid catalyzed by lipase suits Ping-Pong Bi-Bi mechanism. As an alternative to chemical reversed micelles, the RL reversed micelles are promising methods to enzymatic reaction of oleic acid.

  15. Regio-, Diastereo-, and Enantioselective Nitroso-Diels-Alder Reaction of 1,3-Diene-1-carbamates Catalyzed by Chiral Phosphoric Acids.

    Science.gov (United States)

    Pous, Jonathan; Courant, Thibaut; Bernadat, Guillaume; Iorga, Bogdan I; Blanchard, Florent; Masson, Géraldine

    2015-09-23

    Chiral phosphoric acid-catalyzed asymmetric nitroso-Diels-Alder reaction of nitrosoarenes with carbamate-dienes afforded cis-3,6-disubstituted dihydro-1,2-oxazines in high yields with excellent regio-, diastereo-, and enantioselectivities. Interestingly, we observed that the catalyst is able not only to control the enantioselectivity but also to reverse the regioselectivity of the noncatalyzed nitroso-Diels-Alder reaction. The regiochemistry reversal and asynchronous concerted mechanism were confirmed by DFT calculations.

  16. 一种超支化聚酯的合成及反应动力学%Synthesis and Reaction Kinetics of Hyperbranched Polyester

    Institute of Scientific and Technical Information of China (English)

    张新荔

    2011-01-01

    以等物质的量比的间苯二甲酸(A2型单体)和三羟甲基丙烷(B3型单体)为原料,采用熔融聚合工艺制备了一种具有芳香-脂肪骨架的新型超支化聚酯(HBPE)。利用红外光谱、核磁共振、凝胶渗透色谱和热分析等手段对HBPE进行了表征。同时对合成HBPE的反应动力学进行了研究,建立了适合该体系的反应动力学方程,实验结果与理论研究符合良好。研究结果表明,该缩聚反应为外加酸的催化反应过程,反应级数为二级,反应速率由羧基浓度和羟基浓度共同决定。%A new hyperbranched polyester(HBPE) with aromatic-aliphatic skeleton was prepared by melt polymerization of isophthalic acid(A2 type monomer) and trimethylolpropane(B3 type monomer) with equimolar ratio,and the HBPE was characterized using Fourier transform infrared spectroscopy,nuclear magnetic resonance,gel permeation chromatography and thermal analyzer.A suitable kinetics equation of the system was established.It is found that the experimental results are in good agreement with theory.The research results show that the reaction is a second order.The condensation reaction is a acid-catalyzed process,and reaction rate is decided by the concentrations of carboxyl and hydroxyl together.

  17. 玉米秸秆稀酸蒸汽爆破协同作用机制研究%Research on Synergism of Acid-catalyzed Steam Explosion of Corn Stalk

    Institute of Scientific and Technical Information of China (English)

    贾天宇; 廖克俭; 佟名友; 王鑫; 李秀铭

    2011-01-01

    以玉米秸秆原料,进行蒸汽爆破处理,比较了水蒸气蒸爆、稀酸和稀酸蒸爆3种预处理方法,通过对3种预处理过程中米秸秆纤维组分变化、纤维素和半纤维素降解产物和玉米秸秆结构分析以及酶解试验,探讨稀酸蒸汽爆破的协同作用机制.结果表明,稀酸蒸爆协同作用包括稀酸的软化和蒸汽爆破的活化两种机制:一是通过稀酸脱除大部分的半纤维素破坏了半纤维素与木质素间的相互作用,软化了纤维组织;二是软化的纤维通过蒸汽爆破冻结其活性纤维素超分子结构,增加了纤维素与纤维素酶的接触面积.%Using corn stalk as raw material, three pretreatments including water vapor steam explosion, dilute acid catalysis and dilute acid-catalyzed steam explosion were carried out in order to investigate.synergy effect of steam explosion and dilute acid catalysis. For the purpose, effects of acid-catalyzed steam explosion on corn stalk were analyzed and characterized, such as composition, structure, property of the matter, forming degradable products after pretreatments and enzymatic hydrolysis. The results show that the positive effect of acid-catalyzed steam explosion attributes to,the synergistic interactions of acid-softening and steam activation. First, the hemicellulose removal with acid can break the interaction between cellulose and ligin, and soften lignocellulosic structure. Second, steam explosion of acid- softened matter can lead to the forming of an active supramolecular structure, which can increase the accessibility of cellulase to celluloses.

  18. Microstructure Control in the emulsion polymerization of fluorinated monomers

    Energy Technology Data Exchange (ETDEWEB)

    Apostolo, Marco [Ausimont R and D, Bollate (Italy); Morbidelli, Massimo [ETH Zentrum, Zuerich (Switzerland)

    1997-03-01

    In this paper a mathematical model able to evaluate the microstructure of fluorinated polymers is presented. The model uses the pseudo-homo polymerization approach to describe the kinetic evolution of polymerization reactions involving any number of monomer species. The molecular weight distribution is evaluated combining the classical leading moments method with a recently proposed model based on the numerical fractionation technique.

  19. SYNTHESIS AND POLYMERIZATION OF OLIGO (OXYETHYLENE) MACROMONOMER

    Institute of Scientific and Technical Information of China (English)

    ZHANG Shengshui; LIU Qingguo; YANG Leiling; FARRINGTON; Gregory C.

    1993-01-01

    This paper reports the synthesis of methoxyoligo (oxyethylene) methacrylate (MEOn , n is the repeating unit number of (CH2CH2O) in the macromonomer),and its polymerization in different solvents. MEOn is prepared through such two independent reactions as (1) anionic polymerization of oxirane initiated by potassium alkoxide and (2) end-capping of methoxy oligo(oxyethylene) by methacrylic group. The n value can be conveniently controlled over the range of 5~30 by varying the molar ratio of oxirane to initiator and the molecular weight distribution of MEOn be narrowed by increasing reaction time only in step (1). MEOn thus obtained shows a rapid polymerization in water and benzene respectively, and both give water-soluble polymers as long as suitable conditions are used.

  20. Polymerization Using Phosphazene Bases

    KAUST Repository

    Zhao, Junpeng

    2015-09-01

    In the recent rise of metal-free polymerization techniques, organic phosphazene superbases have shown their remarkable strength as promoter/catalyst for the anionic polymerization of various types of monomers. Generally, the complexation of phosphazene base with the counterion (proton or lithium cation) significantly improves the nucleophilicity of the initiator/chain end resulting in highly enhanced polymerization rates, as compared with conventional metalbased initiating systems. In this chapter, the general features of phosphazenepromoted/catalyzed polymerizations and the applications in macromolecular engineering (synthesis of functionalized polymers, block copolymers, and macromolecular architectures) are discussed with challenges and perspectives being pointed out.

  1. Kinetics of silica polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Weres, O.; Yee, A.; Tsao, L.

    1980-05-01

    The polymerization of silicic acid in geothermal brine-like aqueous solutions to produce amorphous silica in colloidal form has been studied experimentally and theoretically. A large amount of high quality experimental data has been generated over the temperature rang 23 to 100{sup 0}C. Wide ranges of dissolved silica concentration, pH, and sodium chloride concentration were covered. The catalytic effects of fluoride and the reaction inhibiting effects of aluminum and boron were studied also. Two basic processes have been separately studied: the formation of new colloidal particles by the homogeneous nucleation process and the deposition of dissolved silica on pre-existing colloidal particles. A rigorous theory of the formation of colloidal particles of amorphous silica by homogeneous nucleation was developed. This theory employs the Lothe-Pound formalism, and is embodied in the computer code SILNUC which quantitatively models the homogeneous nucleation and growth of colloidal silica particles in more than enough detail for practical application. The theory and code were extensively used in planning the experimental work and analyzing the data produced. The code is now complete and running in its final form. It is capable of reproducing most of the experimental results to within experimental error. It is also capable of extrapolation to experimentally inaccessible conditions, i.e., high temperatures, rapidly varying temperature and pH, etc.

  2. Kinetics of phosphotungstic acid catalyzed oxidation of propan-1,3-diol and butan-1,4-diol by N-chlorosaccharin

    Directory of Open Access Journals (Sweden)

    Sanjay Kumar Singh

    2011-09-01

    Full Text Available The kinetic studies of N-chlorosaccharin (NCSA oxidation of propan-1,3-diol and butan-1,4-diol have been reported in presence of phophotungstic acid and in aqueous acetic acid medium. The reactions follow first-order in NCSA and one to zero order with respect to substrate and phosphotungstic acid. Increase in the concentration of added perchloric acid increases the rate of oxidation. A negative effect on the oxidation rate is observed for solvent whereas the ionic strength does not influence the rate of reaction. Addition of the reaction product, saccharin, exhibited retarding effect. Various activation parameters have been evaluated. The products of the reactions were identified as the corresponding aldehydes. A suitable scheme of mechanism consistent with the experimental results has been proposed.

  3. Polymerization of epoxidized triglycerides with fluorosulfonic acid

    Science.gov (United States)

    The use of triglycerides as agri-based renewable raw materials for the development of new products is highly desirable in view of uncertain future petroleum prices. A new method of polymerizing epoxidized soybean oil has been devised with the use of fluorosulfonic acid. Depending on the reaction con...

  4. Selective Condensation Reaction of Phenol Using A Micromixer

    Institute of Scientific and Technical Information of China (English)

    N.Daito; J.Yoshida; K.Mae

    2007-01-01

    1 Results Bisphenol-F,which is synthesized by the acid catalyzed condensation reaction of phenols and form aldehyde is a useful raw material of epoxy resins having superior heat resistance and low viscosity. The commodity bisphenol,however,includes high molecular weight compounds,which are derived from tris-phenols and other highly condensed compounds.Such contaminants impair largely the feature of low viscosity which the bisphenol-F epoxy resin has.To overcome this problem,the molar ratio of phenol/for...

  5. Making Polymeric Microspheres

    Science.gov (United States)

    Rhim, Won-Kyu; Hyson, Michael T.; Chung, Sang-Kun; Colvin, Michael S.; Chang, Manchium

    1989-01-01

    Combination of advanced techniques yields uniform particles for biomedical applications. Process combines ink-jet and irradiation/freeze-polymerization techniques to make polymeric microspheres of uniform size in diameters from 100 to 400 micrometer. Microspheres used in chromatography, cell sorting, cell labeling, and manufacture of pharmaceutical materials.

  6. Applied bioactive polymeric materials

    CERN Document Server

    Carraher, Charles; Foster, Van

    1988-01-01

    The biological and biomedical applications of polymeric materials have increased greatly in the past few years. This book will detail some, but not all, of these recent developments. There would not be enough space in this book to cover, even lightly, all of the major advances that have occurred. Some earlier books and summaries are available by two of this book's Editors (Gebelein & Carraher) and these should be consul ted for additional information. The books are: "Bioactive Polymeric Systems" (Plenum, 1985); "Polymeric Materials In Medication" (Plenum, 1985); "Biological Acti vi ties of Polymers" (American Chemical Society, 1982). Of these three, "Bioacti ve Polymeric Systems" should be the most useful to a person who is new to this field because it only contains review articles written at an introductory level. The present book primarily consists of recent research results and applications, with only a few review or summary articles. Bioactive polymeric materials have existed from the creation of life...

  7. POLYMERIZATION MECHANISM OF DIENES WITH HOMOGENEOUS RARE EARTH CATALYSTS

    Institute of Scientific and Technical Information of China (English)

    JIN Yingtai; ZHANG Xitian; PEI Fengkui; WU Yue

    1990-01-01

    The reaction mechanisms ofdiene polymerization with homogeneous rare earth catalyst are studied by means of the spectra of 1H- NM R, one- and two- dimensions 13C-NMR. Based on the data of above NMR spectra, it is proposed that the polymerization reaction proceeds according to the following mechanism: η4-diene (cis- (→)trans- )and η3-allyl (syn- (→)anti- ).

  8. NATO Advanced Study Institute on Ring-opening Metathesis Polymerization of Olefins and Polymerization of Alkynes

    CERN Document Server

    1998-01-01

    The first NATO Advanced Study Institute on Olefin Metathesis and Polymerization Catalysts was held on September 10-22, 1989 in Akcay, Turkey. Based on the fundamental research of RRSchrock, RGrubbs and K.B.Wagener in the field of ring opening metathesis polymerization (ROMP), acyclic diene metathesis (ADMET) and alkyne polymerization, these areas gained growing interest within the last years. Therefore the second NATO-ASI held on metathesis reactions was on Ring Opening Metathesis Po­ lymerization of Olefins and Polymerization of Alkynes on September 3-16, 1995 in Akcay, Turkey. The course joined inorganic, organic and polymer chemists to exchange their knowledge in this field. This volume contains the main and short lectures held in Akcay. To include ADMET reactions better into the title of this volume we changed it into: Metathesis Polymerization of Olefins and Alkyne Polymerization. This volume is addressed to research scientists, but also to those who start to work in the area of olefin metathesis and al...

  9. Synthesis of bio-based methacrylic acid by decarboxylation of itaconic acid and citric acid catalyzed by solid transition-metal catalysts

    NARCIS (Netherlands)

    Notre, le J.E.L.; Witte-van Dijk, S.C.M.; Haveren, van J.; Scott, E.L.; Sanders, J.P.M.

    2014-01-01

    Methacrylic acid, an important monomer for the plastics industry, was obtained in high selectivity (up to 84%) by the decarboxylation of itaconic acid using heterogeneous catalysts based on Pd, Pt and Ru. The reaction takes place in water at 200–2508C without any external added pressure, conditions

  10. The continuous acid-catalyzed dehydration of alcohols in supercritical fluids: A new approach to the cleaner synthesis of acetals, ketals, and ethers with high selectivity

    Energy Technology Data Exchange (ETDEWEB)

    Gray, W.K.; Smail, F.R.; Hitzler, M.G.; Ross, S.K.; Poliakoff, M.

    1999-11-24

    This report describes a new a continuous method for forming ethers, acetals and ketals using solid acid catalysts, DELOXAN ASP or AMBERLYST 15, and supercritical fluid solvents. In the case of ether formation, the authors observe a high selectivity for linear alkyl ethers with little rearrangement to give branches ethers. Such rearrangement is common in conventional synthesis. The approach is effective for a range of n-alcohols up to n-octanol and also for the secondary alcohol 2-propanol. In the reaction of phenol with an alkylating agent, the continuous reaction can be tuned to give preferential O- or C-alkylation with up to 49% O-alkylation with supercritical propene. The authors also investigate the synthesis of a range of cyclic ethers and show an improved method for the synthesis of THF from 1,4-butandiol under very mild conditions.

  11. Highly efficient epoxidation of alkenes with m-chloroperbenzoic acid catalyzed by nanomagnetic Co(III)@Fe₃O₄/SiO₂ salen complex

    Indian Academy of Sciences (India)

    ALI ALLAHRESANI; MOHAMMAD ALI NASSERI

    2017-03-01

    A new type of heterogeneous Co(III) complex was synthesized by covalent grafting of homogeneous Co(III) salen complex onto the surface of Fe₃O₄/SiO₂ nanoparticle (NP). The heterogeneous nanocatalyst was characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), Fourier transform infrared spectra (FT-IR), atomic absorption spectroscopy (AAS), vibrating sample magnetometer (VSM) and nitrogen adsorption–desorption isotherm (BET). The catalytic activitywas investigated for the epoxidation of alkenes using m-chloroperbenzoic acid as oxidant at room temperature and the corresponding epoxide was achieved with excellent yields and selectivity. In addition, the effect of axial ligand was studied on the epoxidation reaction and pyridine N-oxide (PNO) was chosen as an excellent axial ligand in dichloromethane. Furthermore, the heterogeneous catalyst showed good stability and the magnetic properties (which made possible the easy recovery of catalyst with external magnet) without significant decrease in the activity in the epoxidation reaction.

  12. Solvent effects in acid-catalyzed dehydration of the Diels-Alder cycloadduct between 2,5-dimethylfuran and maleic anhydride

    Science.gov (United States)

    Salavati-fard, Taha; Caratzoulas, Stavros; Doren, Douglas J.

    2017-03-01

    Dehydration of the cycloadduct produced from the Diels-Alder reaction between 2,5-dimethylfuran and maleic anhydride to 3,6-dimethylphthalic anhydride exemplifies an important step in producing platform chemicals from biomass. The mechanisms of dehydration and catalytic effects of Lewis and Brønsted acids are investigated with density functional theory. The uncatalyzed reaction has a very high activation barrier (68.7 kcal/mol) in the gas phase and it is not significantly affected by solvation. With a Lewis acid catalyst, modeled as an alkali ion, the activation barriers are reduced, but intermediates are also stabilized. The net effect in vacuum is that the energetic span, or apparent activation energy of the catalytic cycle, is 77.9 kcal/mol, even higher than the barrier in the uncatalyzed case. In solution, however, the energetic span is reduced by as much as 20 kcal/mol, due to differences in the solvation energy of the transition states and intermediates. In the case of a Brønsted acid catalyst, modeled as a proton, the gas phase transition state energies are reduced even more than in the Lewis acid case, and there is no strong stabilization of the intermediates. The energetic span in vacuum is only 13.8 kcal/mol and is reduced even further in solution. Brønsted acid catalysis appears to be the preferred mechanism for dehydration of this cycloadduct. Since the Diels-Alder reaction that produced the molecule has previously been shown to be catalyzed by Brønsted acids, this suggests that a single catalyst could be used to accelerate both steps.

  13. Synthesis of ferulic acid catalyzed by ammonium acetate%乙酸铵催化合成阿魏酸的工艺研究

    Institute of Scientific and Technical Information of China (English)

    梁红冬; 蔡庆荣

    2011-01-01

    以香草醛和丙二酸为原料,乙酸铵为催化剂,合成阿魏酸.考察反应时间、投料物质的量比、催化剂用量和溶剂体积比等因素对收率的影响.结果表明,N,N-二甲基甲酰胺作溶剂,环已烷作带水剂,在V(环己烷)∶以N,N-二甲基甲酰胺)=2∶1、催化剂用量占香草醛质量的6%、n(香草醛)∶n(丙二酸)=1∶1.3和反应时间4h条件下,阿魏酸收率为70.87%.%Ferulic acid was synthesized by using vanillic aldehyde and malonic acid as raw materials, and ammonium acetate as the catalyst. The influence of reaction time, molar ratio of reactants, catalyst dosage and volume ratio of cyclohexane to N ,N-dimethylformamide( DMF) on ferulic acid yield was investigated. The experimental results indicated that ferulic acid yield of 70. 87% was attained under the optimum reaction condition as follows;DMF as the solvent,cyclohexane as the water carrying agent,volume ratio of cyclohexane to DMF =2∶1, catalyst dosage 6% of mass of vanillic aldehyde, molar ratio of vanillic aldehyde to malonic acid 1∶1∶3, and reaction time 4 h.

  14. Chelating polymeric membranes

    KAUST Repository

    Peinemann, Klaus-Viktor

    2015-01-22

    The present application offers a solution to the current problems associated with recovery and recycling of precious metals from scrap material, discard articles, and other items comprising one or more precious metals. The solution is premised on a microporous chelating polymeric membrane. Embodiments include, but are not limited to, microporous chelating polymeric membranes, device comprising the membranes, and methods of using and making the same.

  15. Understanding the Mechanism of the Hydrogen Abstraction from Arachidonic Acid Catalyzed by the Human Enzyme 15-Lipoxygenase-2. A Quantum Mechanics/Molecular Mechanics Free Energy Simulation.

    Science.gov (United States)

    Suardíaz, Reynier; Jambrina, Pablo G; Masgrau, Laura; González-Lafont, Àngels; Rosta, Edina; Lluch, José M

    2016-04-12

    Lipoxygenases (LOXs) are a family of enzymes involved in the biosynthesis of several lipid mediators. In the case of human 15-LOX, the 15-LOX-1 and 15-LOX-2 isoforms show slightly different reaction regiospecificity and substrate specificity, indicating that substrate binding and recognition may be different, a fact that could be related to their different biological role. Here, we have used long molecular dynamics simulations, QM(DFT)/MM potential energy and free energy calculations (using the newly developed DHAM method), to investigate the binding mode of the arachidonic acid (AA) substrate into 15-LOX-2 and the rate-limiting hydrogen-abstraction reaction 15-LOX-2 catalyzes. Our results strongly indicate that hydrogen abstraction from C13 in 15-LOX-2 is only consistent with the "tail-first" orientation of AA, with its carboxylate group interacting with Arg429, and that only the pro-S H13 hydrogen will be abstracted (being the pro-R H13 and H10 too far from the acceptor oxygen atom). At the B3LYP/6-31G(d) level the potential and free energy barriers for the pro-S H13 abstraction of AA by 15-LOX-2 are 18.0 and 18.6 kcal/mol, respectively. To analyze the kinetics of the hydrogen abstraction process, we determined a Markov model corresponding to the unbiased simulations along the state-discretized reaction coordinate. The calculated rates based on the second largest eigenvalue of the Markov matrices agree well with experimental measurements, and also provide the means to directly determine the pre-exponential factor for the reaction by comparing with the free energy barrier height. Our calculated pre-exponential factor is close to the value of kBT/h. On the other hand, our results suggest that the spin inversion of the complete system (including the O2 molecule) that is required to happen at some point along the full process to lead to the final hydroperoxide product, is likely to take place during the hydrogen transfer, which is a proton coupled electron transfer

  16. Reactions of the radical cations of methylated benzene derivatives in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Sehested, K.; Holcman, J.

    1978-03-23

    The radical cations of methylated benzene decompose in acid solution into the corresponding methylbenzyl radical and a proton. The rate constant for this reaction decreases by three orders of magnitude as the number of methyl groups increases from one to five. The rate constants can be correlated with the ionization potential of the parent compound. In neutral solution the reverse reaction to the acid-catalyzed OH adduct conversion occurs and the radical cations react with water to form the OH adduct. In slightly alkaline solution the radical cations of the higher methylated benzenes (n greater than or equal to 3) react with hydroxide ions forming the OH adduct.

  17. Clickable Polylactic Acids by Fast Organocatalytic Ring-Opening Polymerization in Continuous Flow

    NARCIS (Netherlands)

    Berg, van den Sebastiaan A.; Zuilhof, Han; Wennekes, Tom

    2016-01-01

    The use of microreactor technology for the ring-opening polymerization of l-lactide catalyzed by 1,5,7-triazabicyclo[4.4.0]dec-5-ene allows for rapid optimization of reaction parameters (reaction temperature and residence time). At moderate catalyst loading, good control over the polymerization i

  18. Reaction kinetics of polybutylene terephthalate polycondensation reaction

    NARCIS (Netherlands)

    Darda, P. J.; Hogendoorn, J. A.; Versteeg, G. F.; Souren, F.

    2005-01-01

    The kinetics of the forward polycondensation reaction of polybutylene terephthalate (PBT) has been investigated using thermogravimetric analysis (TGA). PBT - prepolymer with an initial degree of polymerization of 5.5 was used as starting material. The PBT prepolymer was prepared from dimethyl tereph

  19. Controlled free radical polymerization of vinyl acetate with cobalt acetoacetonate

    Indian Academy of Sciences (India)

    Mohammad Ali Semsarzadeh; Sahar Amiri

    2012-03-01

    The polymerization of vinyl acetate with the complex catalyst of cobalt acetoacetonate [Co (acac)2] and DMF ligand with benzoyl peroxide initiator has been successfully carried out in bulk and in solution. The bulk polymerization has been used in a new route consisting of a one-step polymer formation in a fine capillary tube. In this process, the high rate of propagation was used to carry out the reaction in a microcapillary tube. Under 60°C, the colour-free reaction without solid catalyst impurity was 95% complete within a few hours. The high molecular weight of polyvinyl acetate (PVAc) with its relatively low molecular distribution without unreacted monomer provided a new method in microprocessing of the controlled radical polymerization of vinyl acetate in a one-step polymerization process. PVAc polymerization systems showed induction time, which was reduced in this reaction with using complex of DMF/ Co(acac)2. The kinetics of the reaction with a smaller degree of branching from this catalyst indicated that the electronegativity of the transition metal and diffusion of the homogeneous catalyst with DMF are important factors of fast polymerization in the bulk. Thermal properties of the polymer indicated a lower glass transition state. The easily reformed or stretched microsolid polymer demonstrated 20% crystallinity.

  20. Synthesis of acetylsalicylic acid catalyzed by carbon-based solid acid%碳基固体酸催化合成乙酰水杨酸

    Institute of Scientific and Technical Information of China (English)

    占昌朝; 曹小华; 严平; 王剑波; 余祖进; 江小平

    2012-01-01

    Carbon-based solid acid catalysts synthesized from starch andp-toluene sulphonic acid were characterized by FTIR, TG, BET, SEM and EDS. Its catalytic activity and effect of conventional heat and microwave heat on yield of acetylsalicylic acid were studied. The better condition was determined with single factor tests, which is as follows: the molar ratio of acetic anhydride to salicylic acid was 1.5 : 1, the weight ratio of carbon-based solid acid to salicylic acid was 5.8%, acylation reaction temperature was 76--80 ~C, reaction time was 25 min under conventional heat. The yield of acetylsalicylic acid was 82.1% and kept 78.2% after used five times under conventional heat. The carbon-based solid acid catalyst has high catalytic activity and retrievability under conventional heat, which are better than that of microwave heat.%以淀粉和对甲苯磺酸为原料合成了碳基固体酸催化剂,并采用FTIR、TG、BET、SEM和EDS对催化剂进行了表征。研究了催化剂对乙酰水杨酸合成反应的催化活性,并比较了常规加热和微波加热方式对反应的影响。通过单因素试验确定了较佳工艺条件为:乙酸酐与水杨酸物质的量比为1.5∶1,催化剂用量为水杨酸质量的5.8%,反应时间25 min,反应温度76~80℃。常规加热条件下收率82.1%,使用5次后,收率仍保持在78.2%。碳基固体酸催化剂在常规加热条件下催化性能和重复使用性能均优于微波加热条件反应。

  1. Syntheses and Crystal Structures of Chiral BINOL Derivatives and Their Applications in Enantioselective Lewis Acid Catalyzed Addition of Diethylzinc to Aldehydes

    Institute of Scientific and Technical Information of China (English)

    LIU Guo-Hua; YU Han; Yang Liang-Zhun; YAO Mei; FANG Hai-Bin; XUE Yun-Ning

    2007-01-01

    Two novel chiral BINOL derivatives with bis(benzylamine) groups at the 3,3' positions have been synthesized through the condensation reaction between 2,2'-bis(methoxy- methyleneoxy)-1,1'-binaphthyl-3,3'-dicarboxylic acid and benzylamine or N-phenyl benzylamine in the presence of triethylamine. Suitable single crystal of (R)-N,N'-dibenzyl-2,2'-dihydroxy-1,1'-binaphthly-3,3'-diformamide (R)-3 for X-ray diffraction was obtained by recrystallization at room temperature from the mixture solvents. Crystallographic data of (R)-3: C40H36N2O6, Mr=640.71, monoclinic, space group P21, a=6.746(3), b=21.883(9), c=11.723(5) (A), β=104.605(7)°, Z=2, V=1674.7(12) (A)3, Dc=1.271 g/cm3, F(000)=676, R=0.0729, Wr=0.1687 and μ(MoKα)=0.086 mm-1. Two chiral BINOL ligands were found to be effective in the enantioselective addition of diethylzinc to aldehydes and much different enantioselectivity was observed both in the presence and absence of Ti(OiPr)4. In the former case, (R)-3 showed moderate enantioselectivity, which was lower than that of (R)-BINOL's; and in the latter case, (R)-4 gave the highest enantioselectivity up to 93.3% ee.*

  2. Biodegradable Shape Memory Polymeric Material from Epoxidized Soybean Oil and Polycaprolactone

    Directory of Open Access Journals (Sweden)

    Takashi Tsujimoto

    2015-10-01

    Full Text Available This article deals with the synthesis of plant oil-based shape memory materials from epoxidized soybean oil (ESO and polycaprolactone (PCL. PolyESO/PCLs were synthesized by an acid-catalyzed curing in the presence of PCL. During the reaction, PCL scarcely reacted with ESO and the crystallinity of the PCL component decreased to form a semi-interpenetrating network structure. The incorporation of the PCL components improved the maximum stress and strain at break of ESO-based network polymer. The polyESO/PCL was gradually degraded by Pseudomonas cepasia lipase. Furthermore, the polyESO/PCLs exhibited excellent shape memory properties, and the strain fixity depended on the feed ratio of ESO and PCL. The shape memory-recovery behaviors were repeatedly practicable. The resulting materials are expected to contribute to the development of biodegradable intelligent materials.

  3. Plasma polymerization by Softplasma

    DEFF Research Database (Denmark)

    Jiang, J.; Wu, Zhenning; Benter, Maike

    2008-01-01

    In the late 19th century, the first depositions - known today as plasma polymers, were reported. In the last century, more and more research has been put into plasma polymers. Many different deposition systems have been developed. [1, 2] Shi F. F. broadly classified them into internal electrode......, external electrode, and electrodeless microwave or high frequency reactors. [3] Softplasma™ is an internal electrode plasma setup powered by low frequenc~ gower supply. It was developed in late 90s for surface treatment of silicone rubber. [ ]- 5] It is a low pressure, low electron density, 3D homogenous...... plasma. In this study, we are presenting the surface modification"pf polymers by plasma polymerization using Softplasma™. Softplasma™ can be used for two major types of polymerization: polymerization of vinyl monomers, where plasma acts as initiator; chemical vapour deposition, where plasma acts...

  4. Personal Cooling Fabric Based on Polymeric Thermoelectrics

    Science.gov (United States)

    2016-07-28

    mercury , etc.), and an essentially unlimited material supply at low to moderate cost. The objective of that relatively limited work has been to...was then expanded to include investigation of the TE properties of the additional compounds . This chapter describes the process for synthesizing the p...in subsequent polymerization reactions with dialdehydes to afford the various 2.5 PPV-4OEt polymers. This compound was prepared in several steps

  5. Light induced polymerization of resin composite restorative materials

    Directory of Open Access Journals (Sweden)

    Blažić Larisa

    2004-01-01

    Full Text Available Introduction Dimensional stability of polymer-based dental materials is compromised by polymerization reaction of the monomer. The conversion into a polymer is accompanied by a closer packing of molecules, which leads to volume reduction called curing contraction or polymerization shrinkage. Curing contraction may break the adhesion between the adhesive system and hard tooth tissues forming micrographs which may result in marginal deterioration, recurrent caries and pulp injury. Polymerization shrinkage of resin-based restorative dental materials Polymerization of the organic phase (monomer molecules of resin-based dental materials causes shrinkage. The space occupied by filler particles is not associated with polymerization shrinkage. However, high filler loading within certain limits, can contribute to a lesser curing contraction. Polymerization shrinkage stress and stress reduction possibilities Polymerization shrinkage stress of polymer-based dental resins can be controlled in various ways. The adhesive bond in tooth-restoration interface guides the contraction forces to cavity walls. If leakage occurs, complications like secondary caries and pulpal irritation may jeopardize the longevity of a restoration. Stress relieve can be obtained by modifications of the monomer and photoinitiator, or by specially designed tooth preparation and application of bases and liners of low modulus of elasticity. The polymerization contraction can be compensated by water absorption due to oral cavity surrounding. The newest approach to stress relief is based on modulation of polymerization initiation. Conclusion This work deals with polymerization contraction and how to achieve leak-proof restoration. Restorative techniques that may reduce the negative effect of polymerization shrinkage stress need further research in order to confirm up-to-date findings.

  6. Conducting Polymeric Materials

    DEFF Research Database (Denmark)

    Hvilsted, Søren

    2016-01-01

    The overall objective of this collection is to provide the most recent developments within the various areas of conducting polymeric materials. The conductivity of polymeric materials is caused by electrically charged particles, ions, protons and electrons. Materials in which electrons...... are the charge transfer elements are intrinsically conducting polymers, where the electrical conductivity is a result of delocalized electrons along the polymer backbone, with polyaniline, polypyrrole, and PEDOT as prominent examples. Already in 2000 Alan Heeger, Alan MacDiarmid, and Hideki Shirakawa were...

  7. POLYMERIC SURFACTANT STRUCTURE

    Institute of Scientific and Technical Information of China (English)

    P.M. Saville; J.W. White

    2001-01-01

    Polymeric surfactants are amongst the most widespread of all polymers. In nature, proteins and polysaccharides cause self organization as a result of this surfactancy; in industry, polymeric surfactants play key roles in the food, explosives and surface coatings sectors. The generation of useful nano- and micro-structures in films and emulsions as a result of polymer amphiphilicity and the application of mechanical stress is discussed. The use of X-ray and neutron small angle scattering and reflectivity to measure these structures and their dynamic properties will be described. New results on linear and dendritic polymer surfactants are presented.

  8. PHOTOINDUCED CHARGE TRANSFER POLYMERIZATION OF STYRENE INITIATED BY ELECTRON ACCEPTOR

    Institute of Scientific and Technical Information of China (English)

    CAO Weixiao; ZHANG Peng; FENG Xinde

    1995-01-01

    Photoinduced charge transfer polymerization of styrene(St) with electron acceptor as initiator was investigated. In case of fumaronitrile (FN) or maleic anhydride (MA) as initiator the polymerization takes place regularly, whereas the tetrachloro-1, 4-benzenequinone (TCQ), 2, 3-dichloro-5, 6-dicyano-1, 4-benzenequinone (DDQ) . or tetracyano ethylene (TCNE) as initiator the polymerization proceeds reluctantly only after the photoaddition reaction. A mechanism was proposed that free radicals would be formed following the charge and proton transfer in the exciplex formed between St and electron acceptors.

  9. Measurement of in vitro microtubule polymerization by turbidity and fluorescence.

    Science.gov (United States)

    Mirigian, Matthew; Mukherjee, Kamalika; Bane, Susan L; Sackett, Dan L

    2013-01-01

    Tubulin polymerization may be conveniently monitored by the increase in turbidity (optical density, or OD) or by the increase in fluorescence intensity of diamidino-phenylindole. The resulting data can be a quantitative measure of microtubule (MT) assembly, but some care is needed in interpretation, especially of OD data. Buffer formulations used for the assembly reaction significantly influence the polymerization, both by altering the critical concentration for polymerization and by altering the exact polymer produced-for example, by increasing the production of sheet polymers in addition to MT. Both the turbidity and the fluorescence methods are useful for demonstrating the effect of MT-stabilizing or -destabilizing additives.

  10. Influence of Cyclodextrin on the Styrene Polymerization

    Institute of Scientific and Technical Information of China (English)

    HU Jie; LIU Bai-ling

    2004-01-01

    Cyclodextrin (CD) are oligosaccharides consisting of 6( α ), 7( β ), 8( γ ) units of1,4-linked glucose. Due to their polar hydrophilic outer shell and relatively hydrophobic cavity, theyare able to build up host-guest complexes by inclusion of suitable hydrophobic molecules. Theformation of these complexes leads to significant changes of the solubility and reactivity of the guestmolecules, but without any chemical modification. Thus, water insoluble molecules may becomecompletely water soluble simply by mixing with an aqueous solution of native CD or CD-derivatives.Hydrogen bonds or hydrophobic interactions are responsible for the stability of the complexes and itturned out that the complexed monomers could be successfully polymerized by free radicalpolymerization in water.In our present work, using styrene as monomer, potassium peroxodisulfate as radical initiator thatreacted in water in the presence ofβ-CD but without any additional surfactant, the effect ofcyclodextrin on the polymerization was described. Additionally, the acceleration mechanism ofcyclodextrin in the polymerization was also explained based on dynamic study.Table 1 Effect of CD on the monomer reactivityIt is found that β -CD could greatly accelerate the polymerization, enhance the final conversion ofmonomer. And the more the amount of β-CD was introduced, the faster the polymerization wasobtained. From Figure 1, after 5 hours reaction at 80℃, the monomer conversion in the presence of1.0g cyclodextrin reached to 95%. However, that in absence of cyclodextrin was only 60%. And themonomer conversion was not to exceed 75% even reacted for 8 hours when no CD in reactionsystem.In order to describe the acceleration of CD in the polymerization quantitatively, based onCD and without CD. As shown in Table 1, CD produced significant effect on the monomer reactivity.The relative relativities of monomer were greatly increased with the increase of the amount of CD.

  11. Investigation on the Inverse Emulsion Polymerization of Acrylic Acid

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Polyacrylic acid particles in nano-scale were synthesized using an inverse (W/O) emulsion polymerization method. The particle size and size change of inverse micelles which solubilize a part of monomer solution was monitored by PCS (photon correlation spectroscopy) and the particles of polyacrylic acid were viewed in scanning electron microscope for the first time. It was concluded that the inverse micelles were primarily the polymerization reaction sites.

  12. POLYMER-SUPPORTED RARE EARTH CATALYSTS FOR STYRENE POLYMERIZATION

    Institute of Scientific and Technical Information of China (English)

    ZHAO Jian; YANG Mujie; ZHENG Yi; SHEN Zhiquan

    1991-01-01

    The neodymium complex supported on styrene-maleic anhydride copolymer (SMA·Nd) has been prepared for the first time and found to be a highly effective catalyst for the polymerization of styrene. The SMA · Nd polymeric complex is characterized by IR and its catalytic activity, and the polymerization features have been investigated in comparison with that of the conventional Ziegler-Natta catalysts. When [Nd] = 1×10-3 mol/L, [M]=5 mol/L, Al/Nd = 170 (mol ratio ) and CCl4/Nd=50(mol ratio), the polymerization conversion of styrene gets to 51.6% in six hours, and the catalytic activity reaches 1852 gPS/gNd, which is much higher than that of conventional rare earth catalysts. The polymerization reaction has an induction period and shows some characteristics of chain polymerization. The polymerization rate is the first order with respect to the concentration of styrene monomer. Addition of FeCl3 does not suppress the polymerization.

  13. Polymerized and functionalized triglycerides

    Science.gov (United States)

    Plant oils are useful sustainable raw materials for the development of new chemical products. As part of our research emphasis in sustainability and green polymer chemistry, we have explored a new method for polymerizing epoxidized triglycerides with the use of fluorosulfonic acid. Depending on the ...

  14. Waterborne Polymeric Films.

    Science.gov (United States)

    1981-02-01

    Skydrol 500B is a fire resistant hydraulic fluid available from Monsanto and which is primarily tricresyl phosphate. In most cases, the above table...Makromol. Chem. 1979, 82 149.- 23. Ger. Offen 2,804,609; (8/9/79). Bayer AG. 24. Odian, G. "Principles of Polymerization; "McGraw-Hill Book Co.: New York

  15. Organic plasma process for simple and substrate-independent surface modification of polymeric BioMEMS devices.

    Science.gov (United States)

    Hiratsuka, Atsunori; Muguruma, Hitoshi; Lee, Kyong-Hoon; Karube, Isao

    2004-07-15

    A polymeric bio micro electromechanical systems (BioMEMS) device was fabricated using organic plasma polymerization, by which the surface of a polymeric substrate could easily be modified through vapor-phase deposition of organic thin films. This technique, capable of polymeric deposition of any kind of monomer, can serve the purpose of anti-fouling coating, wettability control, or layer-to-layer interface creation, on the surface of any given chemically-inert polymeric substrate without involving cumbersome surface organic reactions. A prototype device was fabricated to have an array of electrochemical glucose biosensors with the three electrode configuration, each of which has a microfluidic channel (500 microm x 800 microm) for capillary-action-driven sample delivery and the concerned enzymatic reaction. Stressing the advantages of the plasma polymerization process using a polymeric substrate together with some additional features accomplished in our device fabrication, new possibilities in the field of polymeric BioMEMS are discussed.

  16. Studies on the Self-condensing Vinyl Living Radical Polymerization of a Novel Acrylate Inimer

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A novel acrylate inimer, 2-(2-chloroacetyloxy) ethyl acrylate, was prepared by the reaction of 2-hydroxyethyl acrylate with chloroacetyl chloride in the presence of triethylamine. The self-condensing vinyl living radical polymerization of the inimer was studied and the hyperbranched macromolecules containing ester linkages on their backbone were prepared. All the polymerization products were characterized by 1H NMR. The polymerization degree and the branching parameter were calculated based on the 1H NMR spectra. It has been shown that this inimer exhibits a very distinctive polymerization behavior. Similar to step-growth polymerization, the polymerization degree of the products formed increased exponentially during the early stage of the polymerization, and then the increasing rate slowed down. However, the inimer remained present throughout the polymerization consistent with conventional free radical polymerization. Also, if much longer polymerization time was used, the polymerization system would become gel due to the crosslinking reaction derived from radical-radical recombination. As a result of the unequal reactivity of -CH2Cl and >CHCl, an almost linear product was obtained at a molar ratio of bipy to inimer=0.05, while a relatively high ratio of bipy to inimer 1 favored the formation of the branched structure. The macromolecules formed at a high ratio of bipy to inimer 1 exhibited an excellent solubility in organic solvents such as acetone.

  17. Iptycene synthesis: A new method for attaching a 2,3-anthracene moiety to the 9,10-positions of another anthracene moiety - Exceptional conditions for a Lewis acid catalyzed Diels-Alder reaction

    Science.gov (United States)

    Chen, Yong-Shing; Hart, Harold

    1989-01-01

    An efficient three-step method for appending a 2,3-anthracene moiety to the 9,10-positions of an existing anthracene moiety is described. The first step uses excess 1,4-anthraquinone (3 equiv) and aluminum chloride (6 equiv) to obtain the anthracene-quinone cycloadduct (omission of the AlCl3 resulted in no adduct). The resulting diketone was reduced to the corresponding diol (excess LiAlH4), which was dehydrated to the arene with phosphorus oxychloride and pyridine. Specific examples include the preparation of heptipycene 8 from pentiptycene 6 (66 percent overall yield) and a similar conversion of 8 to the noniptycene 13 (75 percent overall yield). The methodology led to a markedly improved synthesis of tritriptycene 9 and the first synthesis of undecaiptycene 14.

  18. The acid-catalyzed rearrangement CH3Oo --> oCH2OH and its involvement in the dissociation of the methanol dimer radical cation; A Quid pro Quo reaction

    NARCIS (Netherlands)

    Burgers, P.C.; Ruttink, P.J.A.

    2005-01-01

    The barrier for the radical isomerization CH3Oo --> oCH2OH is calculated by CBS-QB3 to be 29.7 kcal mol-1 and lies higher (by 5.7 kcal mol-1) than the dissociation limit CH2O+Ho. Hence, CH3Oo does not isomerize to the more stable oCH2OH on its own. However, this barrier is reduced to 15.8 kcal mol-1

  19. Biodiesel forming reactions using heterogeneous catalysis

    Science.gov (United States)

    Liu, Yijun

    other comparisons between the catalytic behaviors of liquid and solid acids suggests a common mode of operation of their Bronsted acid sites in carrying out esterification of a carboxylic acid with alcohol. The hypothesized Eley-Rideal type heterogeneous reaction mechanism involving a nucleophilic attack between adsorbed carboxylic acid and unadsorbed alcohol as the rate-limiting step was found to fit well the experimental observations and successfully predict the esterification rate obtained with SAC-13 as reaction progresses. The SAC-13 catalysis assay was also extended to carboxylic acids of higher molecular weights. A set of carboxylic acids with various alkyl chain lengths was used to investigate the structural effect of reacting carboxylic acids on heterogeneous catalyzed esterification. It was found that the reactivity of carboxylic acids was controlled by steric factors as the alkyl chain linearly lengthened. Despite their increased hydrophobicity, large carboxylic acids hardly impacted the deactivating effect of water on Bronsted acid sites. However, catalyst reusability and regeneration showed significant dependency on the size of the carboxylic acid used. With the use of larger reacting carboxylic acids, SAC-13 underwent more significant activity loss in consecutive reaction cycles due to stronger adsorption of the larger organics in the polymeric domains of the Nafion resin. In parallel to the research activity on acid catalyzed esterification, the use of strong solid bases with organic functionality (quarternary ammonium, QN+) was investigated from a fundamental perspective. Using triacetin as a model compound for TG molecules, the effectiveness of this Bronsted base functionality in transesterification was demonstrated even at mild reaction conditions. But its catalytic behavior including catalyst selectivity and deactivation was significantly affected by the nature of the adopted support. A purposive design of the immobilizing matrix is expected to

  20. EFFECT OF POLYMERIZATION CONDITIONS ON THE MOLECULAR WEIGHT OF POLYPHENYLSILSISQUIOXANE

    Institute of Scientific and Technical Information of China (English)

    LI Guizhi; YE Meiling; SHI Lianghe

    1994-01-01

    Samples of polyphenylsilsisquioxane (PPSQ)using CaF2 or MgF2 as the main catalysts had been prepared under different polymerization conditions. The results were treated on an orthogonal design L9 (34). All weight-average molecular weights Mw of PPSQ had been measured by gel permeation chromatography (GPC). Effects of polymerization conditions including reaction temperature, composition of the dual catalysts (CaF2 or MgF2 and DCC),mixture of solvents and reaction time on Mw of PPSQ have been discussed. The quantity of the catalysts is the most important factor that affects Mw of PPSQ. Reaction temperature is the second important factor. Appropriate polymerization condition has been established to get PPSQ with high Mw.

  1. Dynamic Monte Carlo simulation of chain growth polymerization and its concentration effect

    Institute of Scientific and Technical Information of China (English)

    L(U) Wenqi; DING Jiandong

    2005-01-01

    Free radical polymerization and living ion polymerization have been simulated via the dynamic Monte Carlo method with the bond-fluctuation model in this paper. The polymerization-related parameters such as conversion of monomers, degree of polymerization, average molecular weight and its distribution are obtained by statistics. The simulation outputs are consistent with the corresponding theoretical predictions. The scaling relationships of the coil size versus chain length are also confirmed at different volume fractions. Furthermore, the effect of diffusion on polymerization is revealed preliminarily in our simulation. Hence the simulation approach has been proven to be feasible to investigate polymerization reactions with the advantages that configuration and diffusion of polymer chains can be examined together with polymerization kinetics.

  2. [Study of "living" radical polymerization by FTIR in situ].

    Science.gov (United States)

    Chen, J; Hua, F; Qiu, J; Yang, Y

    2001-02-01

    Three types of living radical polymerization processes were monitored by means of FTIR spectrometer with handful diamond detector called as Dicomp in situ. It was found that both styrene and styrene/hydroxylpropyl methyacrylate (HPMA) could polymerize according to stable free radical polymerization (SFRP) mechanism in presence of 4-hydroxyl tetramethypiperidiyl-1-oxy(HTEMPO). For styrene/HPMA system, the styrene and HPMA conversion monitored by FTIR were linear with increase of molecular weight, but it gave longer induction period compared with that for St bulk polymerization. It was related to the hydrogen-transfer reaction between the propagating radicals with the end HPMA unit and HTEMPO. Furthermore, This following method in situ could be introduced into monitoring heterogeneous polymerization of styrene during atom transfer radical polymerization (ATRP). The apparent kinetics was found to be about zero order and not 1.0 order, due to propagating on the complex including radicals, CuX and bpy in heterogeneous interface. The polymerization rate will be not related to the St in bulk St phase.

  3. Therapeutic Strategies Based on Polymeric Microparticles

    Directory of Open Access Journals (Sweden)

    C. Vilos

    2012-01-01

    Full Text Available The development of the field of materials science, the ability to perform multidisciplinary scientific work, and the need for novel administration technologies that maximize therapeutic effects and minimize adverse reactions to readily available drugs have led to the development of delivery systems based on microencapsulation, which has taken one step closer to the target of personalized medicine. Drug delivery systems based on polymeric microparticles are generating a strong impact on preclinical and clinical drug development and have reached a broad development in different fields supporting a critical role in the near future of medical practice. This paper presents the foundations of polymeric microparticles based on their formulation, mechanisms of drug release and some of their innovative therapeutic strategies to board multiple diseases.

  4. Gas Phase Polymerization of Ethylene with Supported Titanium-Nickel Catalysts

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A new ditransition-metal catalyst system TiCl4-NiCl2/MgCl2-SiO2/AlR3 was prepared.Gas phase polymerization of ethylene with the catalysts has been studied.The kinetic curves of gas phase polymerization showed a decline.The catalystic efficiency and polymerization reaction rates have a optimum value when Ni content of the catalysts was 12.5%(mol).The products obtained are branched polyethylene.

  5. A Transient Cell-shielding Method for Viable MSC Delivery Within Hydrophobic Scaffolds Polymerized in situ

    Science.gov (United States)

    2015-03-27

    A transient cell-shielding method for viable MSC delivery within hydrophobic scaffolds polymerized in situ Ruijing Guo a, b, Catherine L. Ward c...SUBTITLE A transient cell-shielding method for viable MSC delivery within hydrophobic scaffolds polymerized in situ 5a. CONTRACT NUMBER 5b. GRANT...To overcome cell death caused by reaction products from in situ polymerization , we encapsu- lated bone marrow-derived stem cells (BMSCs) in

  6. Mathematical modeling of polystyrene particle size distribution produced by suspension polymerization

    Directory of Open Access Journals (Sweden)

    Machado R.A.F.

    2000-01-01

    Full Text Available Particle size distribution (PSD of polystyrene particles produced by suspension polymerization is of fundamental importance in determining suspension stability and product quality attributes. Within a population balance framework, a model is proposed for suspension polymerization reactors to describe the evolution of the PSD. The model includes description of breakage and coalescence rates in terms of reaction kinetics and rheology of the dispersed phase. The model is validated with experimental data of styrene suspension polymerization.

  7. Growth Kinetics of Monodisperse Polystyrene Microspheres Prepared by Dispersion Polymerization

    Directory of Open Access Journals (Sweden)

    Fan Li

    2013-01-01

    Full Text Available Dispersion polymerization has been widely applied to the synthesis of monodisperse micron-sized polymer colloidal spheres. Many efforts have been devoted to studying the influence of initial conditions on the size and uniformity of the resultant microspheres, aiming to synthesize micron-size monodisperse colloidal spheres. However, the inner contradiction between the size and the size distribution of colloidal spheres hinders the realization of this goal. In this work, we drew our attention from the initial conditions to the growth stage of dispersion polymerization. We tracked the size evolution of colloidal sphere during the dispersion polymerization, through which we established a kinetic model that described the relationship between the monomer concentration and the reaction time. The model may provide a guideline to prepare large polymer colloidal spheres with good monodispersity by continuous monomer feeding during the growth stage to maintain the concentration of monomer at a constant value in a dispersion polymerization process.

  8. Tandem ring-opening/ring-closing metathesis polymerization: relationship between monomer structure and reactivity.

    Science.gov (United States)

    Park, Hyeon; Lee, Ho-Keun; Choi, Tae-Lim

    2013-07-24

    Monomers containing either cycloalkenes with low ring strain or 1-alkynes are poor monomers for olefin metathesis polymerization. Ironically, keeping two inactive functional groups in proximity within one molecule can make it an excellent monomer for metathesis polymerization. Recently, we demonstrated that monomer 1 having cyclohexene and propargyl moieties underwent rapid tandem ring-opening/ring-closing metathesis (RO/RCM) polymerization via relay-type mechanism. Furthermore, living polymerization was achieved when a third-generation Grubbs catalyst was used. Here, we present a full account on this tandem polymerization by investigating how various structural modifications of the monomers affected the reactivity of the tandem polymerization. We observed that changing the ring size of the cycloalkene moieties, the length of the alkynes, and linker units influenced not only the polymerization rates but also the reactivities of Diels-Alder reaction, which is a post-modification reaction of the resulting polymers. Also, the mechanism of tandem polymerization was studied by conducting end-group analysis using (1)H NMR analysis, thereby concluding that the polymerization occurred by the alkyne-first pathway. With this mechanistic conclusion, factors responsible for the dramatic structure-reactivity relationship were proposed. Lastly, tandem RO/RCM polymerization of monomers containing sterically challenging trisubstituted cycloalkenes was successfully carried out to give polymer repeat units having tetrasubstituted cycloalkenes.

  9. Studies on Macro—kinetics of Gas Phase Polymerization of Butadiene with Rare—earch Catalyst

    Institute of Scientific and Technical Information of China (English)

    FANGDonyu; SUNJianzhong; 等

    2002-01-01

    The study of the kinetics of gas phase polymerization of butadiene with heterogeneous catalyst based on neodymium(Nd) was carried out.The effects of reaction temperature,reaction pressure,dispersing medium, and types of catalyst on kinetics of polymerization were investigated .A kinetic model with two kinds of active sites was proposed.The results show that the effects of the reaction temperature and the types of dispersing medium and catalyst on the kinetic performance of polymerization are significant,and that the combined model of first and second order decay of active site of catalyst can be used to describe the phenomena.

  10. Linear interfacial polymerization: theory and simulations with dissipative particle dynamics.

    Science.gov (United States)

    Berezkin, Anatoly V; Kudryavtsev, Yaroslav V

    2014-11-21

    Step-growth alternating interfacial polymerization between two miscible or immiscible monomer melts is investigated theoretically and by dissipative particle dynamics simulations. In both cases the kinetics for an initially bilayer system passes from the reaction to diffusion control. The polymer composed of immiscible monomers precipitates at the interface forming a film of nearly uniform density. It is demonstrated that the reaction proceeds in a narrow zone, which expands much slower than the whole film, so that newly formed polymer is extruded from the reaction zone. This concept of "reactive extrusion" is used to analytically predict the degree of polymerization and distribution of all components (monomers, polymer, and end groups) within the film in close agreement with the simulations. Increasing the comonomer incompatibility leads to thinner and more uniform films with the higher average degree of polymerization. The final product is considerably more polydisperse than expected for the homogeneous step-growth polymerization. The results extend the previous theoretical reports on interfacial polymerization and provide new insights into the internal film structure and polymer characteristics, which are important for membrane preparation, microencapsulation, and 3D printing technologies. A systematic way of mapping the simulation data onto laboratory scales is discussed.

  11. Synthesis of Polymeric Microcapsule Arrays and Their Use for Enzyme Immobilization

    Science.gov (United States)

    1994-04-01

    acetyl L-phenyl alanine ethyl ester and propanol; subtilisin should catalyze the transesterification reaction. Transesterification is 3 observed when...template- based synthetic method that yields hollow polymeric microcapsules of uniform diameter and length. These microcapsules are arranged in a high...immobilization that satisfies all of these criteria. We have developed a template- based synthetic method that yields hollow polymeric microcapsules of

  12. Ring-Opening Polymerization of Lactide to Form a Biodegradable Polymer

    Science.gov (United States)

    Robert, Jennifer L.; Aubrecht, Katherine B.

    2008-01-01

    In this laboratory activity for introductory organic chemistry, students carry out the tin(II) bis(2-ethylhexanoate)/benzyl alcohol mediated ring-opening polymerization of lactide to form the biodegradable polymer polylactide (PLA). As the mechanism of the polymerization is analogous to that of a transesterification reaction, the experiment can be…

  13. Towards copper-free nanocapsules obtained by orthogonal interfacial "click" polymerization in miniemulsion.

    Science.gov (United States)

    Siebert, Joerg Max; Baier, Grit; Musyanovych, Anna; Landfester, Katharina

    2012-06-01

    A facile method to produce nanocapsules by copper-free interfacial "click"-polymerization as orthogonal reaction for the encapsulation of functional molecules is successfully performed using stable miniemulsion droplets. Difunctional azides and alkynes have been used for polymerization around the miniemulsion droplets, leading to the formation of nanocapsules. The results were compared with copper-catalyzed systems.

  14. Effect of ultrasonic pretreatment on emulsion polymerization of styrene.

    Science.gov (United States)

    Nagatomo, Daichi; Horie, Takafumi; Hongo, Chizuru; Ohmura, Naoto

    2016-07-01

    This study investigated the effect of pretreatment of ultrasonic irradiation on emulsion polymerization of styrene to propose a process intensification method which gives high conversion, high reaction rate, and high energy efficiency. The solution containing styrene monomer was irradiated by a horn mounted on the ultrasonic transducer with the diameter of 5mm diameter and the frequency of 28 kHz before starting polymerization. The pretreatment of ultrasound irradiation as short as 1 min drastically improved monomer dispersion and increased reaction rate even under the agitation condition with low rotational speed of impeller. Furthermore, the ultrasonic pretreatment resulted in higher monomer concentration in polymer particles and produced larger polymer particles than conventional polymerization without ultrasonic pretreatment.

  15. Phosphazene-promoted anionic polymerization

    KAUST Repository

    Zhao, Junpeng

    2014-01-01

    In the recent surge of metal-free polymerization techniques, phosphazene bases have shown their remarkable potential as organic promoters/catalysts for the anionic polymerization of various types of monomers. By complexation with the counterion (e.g. proton or lithium cation), phosphazene base significantly improve the nucleophilicity of the initiator/chain-end resulting in rapid and usually controlled anionic/quasi-anionic polymerization. In this review, we will introduce the general mechanism, i.e. in situ activation (of initiating sites) and polymerization, and summarize the applications of such a mechanism on macromolecular engineering toward functionalized polymers, block copolymers and complex macromolecular architectures.

  16. Reaction Mechanism of Terephthaloyl Chloride/N-Methyl-2-pyrrolidone and the Effect on Poly(p-phenylene terephthalamide) Polymerization%对苯二甲酰氯与N-甲基吡咯烷酮反应机理以及对聚对苯二甲酰对苯二胺聚合的影响

    Institute of Scientific and Technical Information of China (English)

    郭澄龙; 许甲; 王力慧; 庹新林; 王罗新

    2014-01-01

    Stable synthesis of high molecular weight of poly(p-phenylene terephthalamide) (PPTA) resin is the basis for the production of high-performance aramid fibers. In PPTA polymerization process, the feeding method of the monomer terephthaloyl chloride (TPC) has important influence on the molecular weight. In theory, using TPC/N-methyl-2-pyrrolidone (NMP) solution and monomer p-phenylene diamine (PPD)/NMP solution for solution polycondensation is the most ideal and effective way, but in real polymerization process, it is difficult to synthesize high molecular weight PPTA due to some un-known interaction between TPC and NMP. This article combines experiments and molecular stimulation together, using Fron-tier infrared spectroscopy (FTIR), 1H NMR, the time of flight mass spectrometer (TOF-MS) and differential scanning calo-rimetric analysis (DSC), analyzing the reaction between TPC and NMP, and verified that TPC and NMP has obvious reaction similar to Vilsmeier-Haack reaction through molecular stimulation, which may cause the chloride group on the TPC deactivat-ing, and seriously influence its reactivity. And the conclusion is verified through PPTA polymerization experiments, and the longer TPC/NMP solution is prepared, the worse of the polymerization effect is. These observations and experiments suggest that it is not feasible to synthesize high molecular weight PPTA in industry using TPC/NMP solution feeding method.%稳定合成高分子量聚对苯二甲酰对苯二胺(PPTA)树脂是生产高性能芳纶纤维的基础。在 PPTA 聚合过程中,以单体对苯二甲酰氯(TPC)/N-甲基吡咯烷酮(NMP)溶液与单体对苯二胺(PPD)/NMP 溶液进行溶液缩聚反应是最理想高效的方式,但是因为TPC/NMP间未知的相互作用导致这种聚合方式难以实现。通过实验与计算模拟相结合的方式,利用红外光谱(FTIR)、核磁共振(1H NMR)、飞行时间质谱及示差扫描量热分析对TPC/NMP间的反应进行了分析,并通

  17. One-Pot Synthesis of N-(α-Peroxy)Indole/Carbazole via Chemoselective Three-Component Condensation Reaction in Open Atmosphere

    KAUST Repository

    Wang, Xinbo

    2015-11-06

    A facile one-pot synthesis of N-(α-peroxy)indole and N-(α-peroxy)carbazole has been developed using metal-free, organo-acid-catalyzed three-component condensation reactions of indole/carbazole, aldehyde, and peroxide. Based on the reaction discovered, a new synthetic proposal for Fumitremorgin A and Verruculogen is introduced. Such a protocol could be easily handled and scaled up in an open atmosphere with a wide substrate scope, enabling the construction of a new molecule library.

  18. Interfacial polymerization of conductive polymers: Generation of polymeric nanostructures in a 2-D space.

    Science.gov (United States)

    Dallas, Panagiotis; Georgakilas, Vasilios

    2015-10-01

    In the recent advances in the field of conductive polymers, the fibrillar or needle shaped nanostructures of polyaniline and polypyrrole have attracted significant attention due to the potential advantages of organic conductors that exhibit low-dimensionality, uniform size distribution, high crystallinity and improved physical properties compared to their bulk or spherically shaped counterparts. Carrying the polymerization reaction in a restricted two dimensional space, instead of the three dimensional space of the one phase solution is an efficient method for the synthesis of polymeric nanostructures with narrow size distribution and small diameter. Ultra-thin nanowires and nanofibers, single crystal nanoneedles, nanocomposites with noble metals or carbon nanotubes and layered materials can be efficiently synthesized with high yield and display superior performance in sensors and energy storage applications. In this critical review we will focus not only on the interfacial polymerization methods that leads to polymeric nanostructures and composites and their properties, but also on the mechanism and the physico-chemical processes that govern the diffusion and reactivity of molecules and nanomaterials at an interface. Recent advances for the synthesis of conductive polymer composites with an interfacial method for energy storage applications and future perspectives are presented.

  19. Polyamide-6 Polymerization in the VK Tube Reactor with Baffle Structure

    Institute of Scientific and Technical Information of China (English)

    WANG Xia-qin; TANG Zhi-lian

    2002-01-01

    The melt flow mechanism of polyamide-6 (PA6) was simulated with the mathematical flow model and tested by Particle Image Velotrimitry (PIV). The complete mathematical model for PA6 polymerization while flowing through the VK tube reactor was established according to PA6 hydrolytic polymerization kinetics. The characteristic data such as residence time, caprolactam conversion and the degree of polymerization (D. P.), at every stage of polymerization reaction and at every point of the VK tube were presented for the melt flowing through ten alternate conical baffles in VK tube.

  20. A STUDY OF THE POLYMERIZATION MECHANISM OF ACETONITRILE IN GLOW DISCHARGE

    Institute of Scientific and Technical Information of China (English)

    YU Qingsong; YE Mu; LU Lizhen; CHEN Jie; WANG Fosong; Yoshihito Osada

    1988-01-01

    Plasma polymerization of acetonitrile was carried out by a capacitively coupled RF plasma apparatus with external electrodes under some different reaction conditions such as discharge power. By investigating the informations provided by the polymer deposition regularities, IR spectra and elementary analysis results,the polymerization mechanism of acetonitrile in glow discharge have been investigated. The results show that acetonitrile polymerized in glow discharge mainly through hydrogen detachment for initiation at lower energy levels and the role that opening C = N triple bond played in polymerization became more important at higher energy levels.

  1. Gratings in polymeric waveguides

    Science.gov (United States)

    Mishakov, G.; Sokolov, V.; Kocabas, A.; Aydinli, A.

    2007-04-01

    Laser-induced formation of polymer Bragg grating filters for Dense Wavelength Division Multiplexing (DWDM) applications is discussed. Acrylate monomers halogenated with both fluorine and chlorine, which possess absorption losses less than 0.25 dB/cm and wide choice of refractive indices (from 1.3 to 1.5) in the 1.5 μm telecom wavelength region were used. The monomers are highly intermixable thus permitting to adjust the refractive index of the composition within +/-0.0001. Moreover they are photocurable under UV exposure and exhibit high contrast in polymerization. These properties make halogenated acrylates very promising for fabricating polymeric waveguides and photonic circuits. Single-mode polymer waveguides were fabricated on silicon wafers using resistless contact lithography. Submicron index gratings have been written in polymer waveguides using holographic exposure with He-Cd laser beam (325 nm) through a phase mask. Both uniform and apodized gratings have been fabricated. The gratings are stable and are not erased by uniform UV exposure. The waveguide gratings possess narrowband reflection spectra in the 1.5 μm wavelength region of 0.4 nm width, nearly rectangular shape of the stopband and reflectivity R > 99%. The fabricated Bragg grating filters can be used for multiplexing/demultiplexing optical signals in high-speed DWDM optical fiber networks.

  2. Polymeric Amines by chemical modifications of alternating aliphatic polyketones

    NARCIS (Netherlands)

    Zhang, Youchun; Broekhuis, A. A.; Stuart, Marc C. A.; Picchioni, F.

    2008-01-01

    Alternating, aliphatic polyketones were chemically modified by using di-amines to obtain polymeric products having pendant amino groups. The used reaction, Paal-Knorr, involves the formation of pyrrole rings along the polyketone backbone. The corresponding kinetics and final conversions are clearly

  3. Complex Macromolecular Architectures by Living Cationic Polymerization

    KAUST Repository

    Alghamdi, Reem D.

    2015-05-01

    Poly (vinyl ether)-based graft polymers have been synthesized by the combination of living cationic polymerization of vinyl ethers with other living or controlled/ living polymerization techniques (anionic and ATRP). The process involves the synthesis of well-defined homopolymers (PnBVE) and co/terpolymers [PnBVE-b-PCEVE-b-PSiDEGVE (ABC type) and PSiDEGVE-b-PnBVE-b-PSiDEGVE (CAC type)] by sequential living cationic polymerization of n-butyl vinyl ether (nBVE), 2-chloroethyl vinyl ether (CEVE) and tert-butyldimethylsilyl ethylene glycol vinyl ether (SiDEGVE), using mono-functional {[n-butoxyethyl acetate (nBEA)], [1-(2-chloroethoxy) ethyl acetate (CEEA)], [1-(2-(2-(t-butyldimethylsilyloxy)ethoxy) ethoxy) ethyl acetate (SiDEGEA)]} or di-functional [1,4-cyclohexanedimethanol di(1-ethyl acetate) (cHMDEA), (VEMOA)] initiators. The living cationic polymerizations of those monomers were conducted in hexane at -20 0C using Et3Al2Cl3 (catalyst) in the presence of 1 M AcOEt base.[1] The PCEVE segments of the synthesized block terpolymers were then used to react with living macroanions (PS-DPE-Li; poly styrene diphenyl ethylene lithium) to afford graft polymers. The quantitative desilylation of PSiDEGVE segments by n-Bu4N+F- in THF at 0 °C led to graft co- and terpolymers in which the polyalcohol is the outer block. These co-/terpolymers were subsequently subjected to “grafting-from” reactions by atom transfer radical polymerization (ATRP) of styrene to afford more complex macromolecular architectures. The base assisted living cationic polymerization of vinyl ethers were also used to synthesize well-defined α-hydroxyl polyvinylether (PnBVE-OH). The resulting polymers were then modified into an ATRP macro-initiator for the synthesis of well-defined block copolymers (PnBVE-b-PS). Bifunctional PnBVE with terminal malonate groups was also synthesized and used as a precursor for more complex architectures such as H-shaped block copolymer by “grafting-from” or

  4. Chemical Oxidative Polymerization of 2-Aminothiazole in Aqueous Solution: Synthesis, Characterization and Kinetics Study

    Directory of Open Access Journals (Sweden)

    Hua Zou

    2016-11-01

    Full Text Available The chemical oxidative polymerization of 2-aminothiazole (AT was studied in aqueous solution using copper chloride (CuCl2 as an oxidant. The effect of varying the reaction temperature, reaction time and oxidant/monomer molar ratio on the polymer yield was investigated. The resulting poly(2-aminothiazoles (PATs were characterized by FTIR, 1H NMR, UV-vis, gel permeation chromatography, scanning electron microscopy, thermogravimetric analysis and four-point probe electrical conductivity measurements. Compared with a previous study, PATs with higher yield (81% and better thermal stability could be synthesized. The chemical oxidative polymerization kinetics of AT were studied for the first time. The orders of the polymerization reaction with respect to monomer concentration and oxidant concentration were found to be 1.14 and 0.97, respectively, and the apparent activation energy of the polymerization reaction was determined to be 21.57 kJ/mol.

  5. The counter-rotating twin screw extruder as a polymerization reactor

    NARCIS (Netherlands)

    Ganzeveld, Klaassien Jakoba

    1992-01-01

    The goal of the research was to examine the possibilities of this type of extruder as a polymerization reactor, and to develop models of the extruder reactor which accurately describe the reaction progress in the extruder. See summary

  6. POLYMERIZATION OF BUTYL METHACRYLATE BY IRON PYRIDINEBISIMINE COMPLEXES

    Institute of Scientific and Technical Information of China (English)

    Jing-yu Liu; Yan-guo Li; Yi Zheng; Yue-sheng Li

    2005-01-01

    Fe(Ⅱ) pyridinebisimine complexes activated with trialkylaluminium or modified methylaluminoxane (MMAO) as catalysts were employed for the polymerization of butyl methacrylate (BMA). Polymer yields, catalytic activities and molecular weights as well as molecular weight distributions of BMA can be controlled over a wide range by varying the reaction parameters such as cocatalyst, A1/Fe molar ratio, monomer/catalyst molar ratio, monomer concentration and reaction yield could reach 99.1% under optimum condition.

  7. INVESTIGATION OF THE SURFACE PROPERTIES OF POLYMERIC SOAPS OBTAINED BY RING-OPENING POLYMERIZATION OF EPOXIDIZED SOYBEAN OIL

    Science.gov (United States)

    Epoxidized soybean oil (ESO) was converted to a polysoap via a two-step synthetic procedure of catalytic ring-opening polymerization (PESO), followed by hydrolysis with a base (HPESO). Various molecular weights of PESO and HPESO were prepared by varying the reaction temperature and/or catalyst conc...

  8. Monte Carlo simulation on kinetics of batch and semi-batch free radical polymerization

    KAUST Repository

    Shao, Jing

    2015-10-27

    Based on Monte Carlo simulation technology, we proposed a hybrid routine which combines reaction mechanism together with coarse-grained molecular simulation to study the kinetics of free radical polymerization. By comparing with previous experimental and simulation studies, we showed the capability of our Monte Carlo scheme on representing polymerization kinetics in batch and semi-batch processes. Various kinetics information, such as instant monomer conversion, molecular weight, and polydispersity etc. are readily calculated from Monte Carlo simulation. The kinetic constants such as polymerization rate k p is determined in the simulation without of “steady-state” hypothesis. We explored the mechanism for the variation of polymerization kinetics those observed in previous studies, as well as polymerization-induced phase separation. Our Monte Carlo simulation scheme is versatile on studying polymerization kinetics in batch and semi-batch processes.

  9. Polymerization of chloro-p-xylylenes, quantum-chemical study.

    Science.gov (United States)

    Czaplewski, Cezary; Smalara, Krzysztof; Giełdoń, Artur; Bobrowski, Maciej

    2017-02-01

    The p-xylylene monomers of parylene N, C and D have similar high polymerization reactivity. For effective copolymerization processes this fact is basically a drawback and for instance the copolymerization with styrene doesn't go at all (Corley et al. J Pol Sc 13(68):137-156, [15]). Substitution of terminal hydrogen atoms by chlorine atoms reduces reactivity dramatically. 7,7,8,8-tetrachloro-p-xylylene and 2,5,7,7,8,8-hexachloro-p-xylylene can be isolated as yellow crystals. These crystals can be kept without any change in temperature below 0 (∘)C, but they polymerize slowly at room temperature. Perchloro-p-xylylene is stable even at elevated temperatures and does not polymerize under any conditions. Both 7,7,8,8-tetrachloro-p-xylylene and 2,5,7,7,8,8-hexachloro-p-xylylene copolymerize with various vinyl monomers, such as styrene and others. In this work the polymerization reactions of different chloro-derivatives of p-xylylene were modeled by means of the DFT method with hybrid correlation functionals (B3LYP and PBE0) and, for comparison, by means of the Hartree Fock methods. We inquired both initiation as well as elongation polymeric reactions for each of the reactants. We survied their reactivity analytically examining energetics and configurations in Szwarc-like process. The quantitative influence of chlorine atoms on the reactivity in polymerization steps, their location in the reactants' structure (aromatic and/or aliphatic) as well as their number, were reviewed. The polymerizations of p-xylylenes with chlorine atoms as terminal aliphatic substituents yet revealed one more access path for parylenes' in situ functionalization.

  10. In-situ polymerization behaviour of bone cements.

    Science.gov (United States)

    Maffezzoli, A; Ronca, D; Guida, G; Pochini, I; Nicolais, L

    1997-02-01

    The polymerization behaviour of bone cements during total hip replacements is characterized by a fast and highly non-isothermal bulk reaction. In the first part of this paper the reaction kinetics are analysed by calorimetric analysis in order to determine the rates of polymerization in isothermal and non-isothermal conditions. A phenomenological kinetic model, accounting for the effects of autoacceleration and vitrification, is presented. This model, integrated with an energy balance, is capable of predicting the temperature across the prosthesis, the cement and the bone and the degree of reaction in the cement, during in situ polymerization. The temperature and the degree of reaction profiles are calculated, as a function of the setting time, taking into account the system geometry, the thermal diffusivity of bone, prosthesis and cement, and the heat rate generated by the reaction according to the kinetic model. Material properties, boundary and initial conditions are the input data of the heat transfer model. Kinetic and heat transfer models are coupled and a numerical solution method is used. The model is applied in order to study the effects of different application procedures on temperature and degree of reaction profiles across the bone-cement-prosthesis system.

  11. NATO Advanced Research Workshop on Frontiers in Polymerization Catalysis and Polymer Synthesis

    CERN Document Server

    Guyot, A

    1987-01-01

    Due to their specific properties, polymers with well-defined structures have been receiving increasing attention over the last several years. Owing to the wide variability of their properties, these specialty polymers have been used in various areas from biomedical engineering to electronics or energy applications. The synthesis of such polymers necessi­ tates the use of new methods of polymerization which derived from an insight into the mechanism of polymerization reactions. A NATO Advanced Research Workshop on "Frontiers in Polymerization Catalysis and Polymer Synthesis" was held in BANDOl (FRANCE) in February 1987. Its aim was to assess the new polymerization methods, as well as the latest advances in the mechanisms of conventional polymerization reactions together with their applications to the synthesis of new macromolecular structures. The financial support from the NATO Scientific Affairs Division which covered the "lecturers' accomodation and travel expenses as well as the organization charges of th...

  12. Electron-beam curing of epoxy resins: effect of alcohols on cationic polymerization

    Indian Academy of Sciences (India)

    N N Ghosh; G R Palmese

    2005-10-01

    Electron-beam (e-beam) induced polymerization of epoxy resins proceeds via cationic mechanism in presence of suitable photoinitiator. Despite good thermal properties and significant processing advantages, epoxy-based composites manufactured using e-beam curing suffer from low compressive strength, poor interlaminar shear strength, and low fracture toughness. A detailed understanding of the reaction mechanism involving e-beam induced polymerization is required to properly address the shortcomings associated with ebeam curable resin systems. This work investigated the effect of hydroxyl containing materials on the reaction mechanism of e-beam induced cationic polymerization of phenyl glycidyl ether (PGE). The alcohols were found to play important roles in polymerization. Compared to hydroxyl group of aliphatic alcohol, phenolic hydroxyl group is significantly less reactive with the oxonium active centre, generated during e-beam induced polymerization of epoxy resin system.

  13. Effect of enzyme impurities on phenol removal by the method of polymerization and precipitation catalyzed by Coprinus cinereus peroxidase.

    Science.gov (United States)

    Masuda, M; Sakurai, A; Sakakibara, M

    2001-11-01

    The removal of phenol by peroxidase-catalyzed polymerization was examined using the Coprinus cinereus peroxidases at different levels of impurity with respect to contamination. The phenol removal efficiency was improved by lowering the peroxidase purity. Acidic and high molecular weight proteins present as impurities in the peroxidase solution had some positive effect on the phenol-polymerizing reaction. The residual enzyme activity, either only in the solution or both in the solution and on the precipitate during the polymerizing reaction, was measured. The results indicate that the main effect of impurities in the peroxidase solution was the suppression of the adsorption of peroxidase molecules on the polymerized precipitate.

  14. 杂交杨木纤维中碳水化合物的稀酸催化分离%Dilute Acid-catalyzed Fractionation of Carbohydrates in Hybrid Poplar Fibers

    Institute of Scientific and Technical Information of China (English)

    张春辉; Troy Runge; 詹怀宇

    2012-01-01

    In this paper, the acid-catalyzed fractionation of pentosans and hexosans from hybrid poplar fibers was studied using a circulation reactor. Kinetic models of both pentosan and hexosan hydrolysis/degradation were crea- ted to predict the hydrolysis yield of both substances. The extraction conditions were varied, including a tempera- ture range of 140 - 170℃ , a sulfuric acid concentration range of 0.1% - 0.9% wt with a constant liquor-to-wood ratio of 6: 1. The yields of both substances were favored at high acid concentration and temperature, while pentosan being considerable more reactive. Under optimal conditions, 91 percent of pentosan could be separated from the fi- ber, while more than 93 percent of hexosan was retained in the solids. This study demonstrates that pentosan and hexosans could be fractionated from poplar fibers using acid hydrolysis and converted into liquid fuel and valued chemicals separately.%本文采用循环式反应器研究了杂交杨木纤维中聚戊糖和聚己糖在稀酸条件下的催化分离,分别得出了聚戊糖和聚己糖稀酸水解/降解的动力学模型,以预测在不同反应条件下戊糖和己糖的水解得率。反应条件为温度140~170℃,硫酸浓度0.1%~0.9%wt,液比为6:1。研究发现,较高的酸浓和温度对提高戊糖和己糖的得率都有利,但相同条件下聚戊糖的反应活性更高。经动力学模型优化得出,在较佳条件下有91%的聚戊糖可以以单体、低聚体及其降解产物的形式从杨木纤维中分离出来,同时超过93%的聚己糖可以以固体的形式保留在纤维中。研究表明,在适宜的稀酸催化条件下杂交杨木纤维中的碳水化合物可以得到很好的分离,为下一步戊糖和聚己糖的分别单独转化打下了基础,不仅可以充分利用木材生物质资源,而且为反应提供了相对均一的条件,从而提高反应选择性和产物的纯度。

  15. Diacetylene mixed Langmuir monolayers for interfacial polymerization.

    Science.gov (United States)

    Ariza-Carmona, Luisa; Rubia-Payá, Carlos; García-Espejo, G; Martín-Romero, María T; Giner-Casares, Juan J; Camacho, Luis

    2015-05-19

    Polydiacetylene (PDA) and its derivatives are promising materials for applications in a vast number of fields, from organic electronics to biosensing. PDA is obtained through polymerization of diacetylene (DA) monomers, typically using UV irradiation. DA polymerization is a 1-4 addition reaction with both initiation and growth steps with topochemical control, leading to the "blue" polymer form as primary reaction product in bulk and at interfaces. Herein, the diacetylene monomer 10,12-pentacosadiynoic acid (DA) and the amphiphilic cationic N,N'-dioctadecylthiapentacarbocyanine (OTCC) have been used to build a mixed Langmuir monolayer. The presence of OTCC imposes a monolayer supramolecular structure instead of the typical trilayer of pure DA. Surface pressure, Brewster angle microscopy, and UV-vis reflection spectroscopy measurements, as well as computer simulations, have been used to assess in detail the supramolecular structure of the DA:OTCC Langmuir monolayer. Our experimental results indicate that the DA and OTCC molecules are sequentially arranged, with the two OTCC alkyl chains acting as spacing diacetylene units. Despite this configuration is expected to prevent photopolymerization of DA, the polymerization takes place without phase segregation, thus exclusively leading to the red polydiacetylene form. We propose a simple model for the initial formation of the "blue" or "red" PDA forms as a function of the relative orientation of the DA units. The structural insights and the proposed model concerning the supramolecular structure of the "blue" and "red" forms of the PDA are aimed at the understanding of the relation between the molecular and macroscopical features of PDAs.

  16. Sterically and electrosterically stabilized emulsion polymerization. Kinetics and preparation.

    Science.gov (United States)

    Capek, Ignác

    2002-10-21

    The principal subject discussed in the current paper is the radical polymerization in the aqueous emulsions of unsaturated monomers (styrene, alkyl (meth)acrylates, etc.) stabilized by non-ionic and ionic/non-ionic emulsifiers. The sterically and electrosterically stabilized emulsion polymerization is a classical method which allows to prepare polymer lattices with large particles and a narrow particle size distribution. In spite of the similarities between electrostatically and sterically stabilized emulsion polymerizations, there are large differences in the polymerization rate, particle size and nucleation mode due to varying solubility of emulsifiers in oil and water phases, micelle sizes and thickness of the interfacial layer at the particle surface. The well-known Smith-Ewart theory mostly applicable for ionic emulsifier, predicts that the number of particles nucleated is proportional to the concentration of emulsifier up to 0.6. The thin interfacial layer at the particle surface, the large surface area of relatively small polymer particles and high stability of small particles lead to rapid polymerization. In the sterically stabilized emulsion polymerization the reaction order is significantly above 0.6. This was ascribed to limited flocculation of polymer particles at low concentration of emulsifier, due to preferential location of emulsifier in the monomer phase. Polymerization in the large particles deviates from the zero-one approach but the pseudo-bulk kinetics can be operative. The thick interfacial layer can act as a barrier for entering radicals due to which the radical entry efficiency and also the rate of polymerization are depressed. The high oil-solubility of non-ionic emulsifier decreases the initial micellar amount of emulsifier available for particle nucleation, which induces non-stationary state polymerization. The continuous release of emulsifier from the monomer phase and dismantling of the non-micellar aggregates maintained a high level of

  17. Theoretical Study of 1,8-Diaminonaphthalene Polymerization

    Science.gov (United States)

    Nateghi, Mohammad R.; Kalantari, F.

    2007-12-01

    The polymerization of 1,8-diaminonaphthalene (1,8-DAN) was studied by a theoretical approach based on Hartree-Fock calculations. Investigation of relative stability of most possible dimers, trimers and tetramers yields very useful data concerning the regioselectivity of the coupling reaction as well as the final structures of the polymeric chains. The mechanism is more likely to occur via a radical-radical pathway and leads to mixture of compounds through ortho-C-C and para-C-N linkages.

  18. Kinetics of phenolic polymerization catalyzed by peroxidase in organic media

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Y.P.; Huang, G.L; Yu, Y.T. [Nankai Univ., Tianjin (China). Inst. for Molecular Biology

    1995-07-05

    Phenolic polymerization was carried out by enzymatic catalysis in organic media, and its kinetics was studied by using high-pressure liquid chromatography (HPLC). Phenols and aromatic amines with electron-withdrawing groups could hardly be polymerized by HRP catalysis, but phenols and aromatic amines with electron-donating groups could easily by polymerized. The reaction rate of either the para-substituted substrate or meta-substituted substrate was higher than that of ortho-substituted substrate. When ortho-position of hydroxy group of phenols was occupied by an electron-donating group and if another electron-donating group occupied para-position of hydroxy group, the reaction rate increased. Horseradish peroxidase and lactoperoxidase could easily catalyze the polymerization, but chloroperoxidase and laccase failed to yield polymers. Metallic ions such as Mn{sup 2+}, Fe{sup 2+}, or Fe{sup 3+}, and Cu{sup 2+} could poison horseradish peroxidase to various extents, but ions such as Co{sup 2+}, Cd{sup 2+}, Zn{sup 2+}, and K{sup +} were not found to inhibit the reaction.

  19. Enhance decarboxylation reaction of carboxylic acids in clay minerals

    Energy Technology Data Exchange (ETDEWEB)

    Negron-Mendoza, A.; Ramos, S.; Albarran, G. [Instituto de Ciencias y Artes, Chiapas (Mexico). Escuela de Biologia

    1995-10-01

    Clay minerals are important constituents of the Earth`s crust. These minerals catalyze reactions in several ways: by energy transfer processes, redox reactions, stabilization of intermediates and by Broensted or Lewis acidity behavior. Important set of organic reactions can be improved in the precedence of clay minerals. Besides the properties of clays to catalyze chemical reactions, it is possible to enhance some of its reactions by using ionizing radiation. The phenomenon of radiation-induced catalysis may be connected with ionizing process in the solid and with the trapped non-equilibrium charge carriers. In this paper we are reporting the decarboxylation reaction of carboxylic acids catalyzed by clay and by irradiation of the system acid-clay. We studied the behaviour of several carboxylic acids and analyzed them by gas chromatography, X-ray and infrared spectroscopy. The results showed that decarboxylation of the target compound is the dominating pathway. The reaction is enhanced by gamma radiation in several orders of magnitude. (author).

  20. Reaction mechanism and structure-reactivity relationships in the stereospecific 1,4-polymerization of butadiene catalyzed by neutral dimeric allylnickel(II) halides [Ni(C3H5)X]2 (X- = Cl-, Br-, I-): a comprehensive density functional theory study.

    Science.gov (United States)

    Tobisch, S; Taube, R

    2001-09-03

    For the first time, a comprehensive and consistent picture of the catalytic cycle of 1,4-polymerization of butadiene with neutral dimeric allylnickel(II) halides [Ni(C3H5)X]2 (X = Cl- (I), Br- (II), and I- (III)) as single-site catalysts has been derived by means of quantum chemical calculations that employ a gradient-corrected density-functional method. All crucial reaction steps of the entire catalytic course have been scrutinized, taking into account butadiene pi complex formation, symmetrical and asymmetrical splitting of dimeric pi complexes, cis-butadiene insertion, and anti-syn isomerization. The present investigation examines, in terms of located structures, energies and activation barriers, the participation of postulated intermediates, in particular it aimed to clarify whether monomeric or dimeric species are the catalytically active species. Prior qualitative mechanistic assumptions are substituted by the presented theoretically well-founded and detailed analysis of both the thermodynamic and the kinetic aspects, that substantially improve the insight into the reaction course and enlarge them with novel mechanistic proposals. From a mechanistic point of view, all three catalysts exhibit common characteristics. First, chain propagation occurs by cis-butadiene insertion into the pi-butenylnickel(II) bond with nearly identical intrinsic free-energy activation barriers. Second, the reactivity of syn-butenyl forms is distinctly higher than that of anti forms. Third, the chain-propagation step is rate-determining in the entire polymerization process, and the pre-established anti-syn equilibrium can always be regarded as attained. Accordingly, neutral dimeric allylnickel(II) halides catalyze the formation of a stereo-regular trans-1,4-polymer under kinetic control following the k1t channel with butenyl(halide)(butadiene)NiII complexes being the catalytically active species. Production of a stereoregular cis-1,4-polymer with allylnickel chloride can only be

  1. Organometallic Polymeric Conductors

    Science.gov (United States)

    Youngs, Wiley J.

    1997-01-01

    For aerospace applications, the use of polymers can result in tremendous weight savings over metals. Suitable polymeric materials for some applications like EMI shielding, spacecraft grounding, and charge dissipation must combine high electrical conductivity with long-term environmental stability, good processability, and good mechanical properties. Recently, other investigators have reported hybrid films made from an electrically conductive polymer combined with insulating polymers. In all of these instances, the films were prepared by infiltrating an insulating polymer with a precursor for a conductive polymer (either polypyrrole or polythiophene), and oxidatively polymerizing the precursor in situ. The resulting composite films have good electrical conductivity, while overcoming the brittleness inherent in most conductive polymers. Many aerospace applications require a combination of properties. Thus, hybrid films made from polyimides or other engineering resins are of primary interest, but only if conductivities on the same order as those obtained with a polystyrene base could be obtained. Hence, a series of experiments was performed to optimize the conductivity of polyimide-based composite films. The polyimide base chosen for this study was Kapton. 3-MethylThiophene (3MT) was used for the conductive phase. Three processing variables were identified for producing these composite films, namely time, temperature, and oxidant concentration for the in situ oxidation. Statistically designed experiments were used to examine the effects of these variables and synergistic/interactive effects among variables on the electrical conductivity and mechanical strength of the films. Multiple linear regression analysis of the tensile data revealed that temperature and time have the greatest effect on maximum stress. The response surface of maximum stress vs. temperature and time (for oxidant concentration at 1.2 M) is shown. Conductivity of the composite films was measured for

  2. High temperature structural, polymeric foams from high internal emulsion polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Hoisington, M.A.; Duke, J.R.; Apen, P.G.

    1996-02-01

    In 1982, a high internal phase emulsion (HIPE) polymerization process to manufacture microcellular, polymeric foam systems was patented by Unilever. This patent discloses a polymerization process that occurs in a water-in-oil emulsion in which the water represents at least 76% of the emulsion by volume. The oil phase consists of vinyl monomers such as styrene and acrylates that are crosslinked by divinyl monomers during polymerization. After polymerization and drying to remove the water phase, the result is a crosslinked polymer foam with an open cell microstructure that is homogeneous throughout in terms of morphology, density, and mechanical properties. Since 1982, numerous patents have examined various HIPE polymerized foam processing techniques and applications that include absorbents for body fluids, cleaning materials, and ion exchange systems. All the published HIPE polymerized foams have concentrated on materials for low temperature applications. Copolymerization of styrene with maleic anhydride and N-substituted maleimides to produce heat resistant thermoplastics has been studied extensively. These investigations have shown that styrene will free radically copolymerize with N-substituted maleimides to create an alternating thermoplastic copolymer with a Tg of approximately 200{degrees}C. However, there are many difficulties in attempting the maleimide styrene copolymerization in a HIPE such as lower polymerization temperatures, maleimide solubility difficulties in both styrene and water, and difficulty obtaining a stable HIPE with a styrene/maleimide oil phase. This work describes the preparation of copolymer foams from N-ethylmaleimide and Bis(3-ethyl-5-methyl-4-maleimide-phenyl)methane with styrene based monomers and crosslinking agents.

  3. Catalytic Activity of Dual Metal Cyanide Complex in Multi-component Coupling Reactions

    Institute of Scientific and Technical Information of China (English)

    Anaswara RAVINDRAN; Rajendra SRIVASTAVA

    2011-01-01

    Several dual metal cyanide catalysts were prepared from potassium ferrocyanide,metal chloride (where metal =Zn2+,Mn2+,Ni2+,Co2+ and Fe2+),t-butanol (complexing agent) and PEG-4000 (co-complexing agent).The catalysts were characterized by elemental analysis (CHN and X-ray fluorescence),X-ray diffraction,N2 adsorption-desorption,scanning electron microscopy,Fourier-transform infiared spectroscopy,and UV-Visible spectroscopy.The dual metal cyanide catalysts were used in several acid catalyzed multi-component coupling reactions for the synthesis of pharmaceutically important organic derivatives.In all these reactions,the Fe-Fe containing dual metal cyanide catalyst was the best catalyst.The catalysts can be recycled without loss in catalytic activity.The advantage of this method is the use of mild,efficient and reusable catalysts for various reactions,which makes them candidates for commercial use.

  4. Proton transfer reactions between nitric acid and acetone, hydroxyacetone, acetaldehyde and benzaldehyde in the solid phase.

    Science.gov (United States)

    Lasne, Jérôme; Laffon, Carine; Parent, Philippe

    2012-12-01

    The heterogeneous and homogeneous reactions of acetone, hydroxyacetone, acetaldehyde and benzaldehyde with solid nitric acid (HNO(3)) films have been studied with Reflection-Absorption Infrared Spectroscopy (RAIRS) under Ultra-High Vacuum (UHV) conditions in the 90-170 K temperature range. In the bulk or at the surface of the films, nitric acid transfers its proton to the carbonyl function of the organic molecules, producing protonated acetone-H(+), hydroxyacetone-H(+), acetaldehyde-H(+) and benzaldehyde-H(+), and nitrate anions NO(3)(-), a reaction not observed when nitric acid is previously hydrated [J. Lasne, C. Laffon and Ph. Parent, Phys. Chem. Chem. Phys., 2012, 14, 697]. This provides a molecular-scale description of the carbonyl protonation reaction in an acid medium, the first step of the acid-catalyzed condensation of carbonyl compounds, fuelling the growth of secondary organic aerosols (SOA) in the atmosphere.

  5. Advanced Polymeric Materials for High-tech Innovations

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    @@ High technology is advancing our society and modernizing our life and advanced materials play an important role in the technological innovations. My research group has been working on the development of advanced polymeric materials and in this talk I will report our recent work on the creation of new conjugated polymers with novel molecular structures and unique materials properties.1-18 Our work include the design of molecular structures of monomeric building blocks, development of stable, effective and environmentally benign "green” polymerization catalysts, discovery of new polymerization reactions, synthesis of functional macromolecules, fabrication of nanodimensional composites, assembly and control of hierarchical structures, and construction of electrooptical devices. We have revealed the liquid crystallinity, light emission, photoconductivity, optical limiting, nano-hybridization, solvatochromism, optical activity, self-organization, and biological activity of the linear polyacetylenes and hyperbranched polyarylenes. The utilization of the advanced polymers and their interesting materials properties for high-tech innovations will be discussed.

  6. Advanced Polymeric Materials for High-tech Innovations

    Institute of Scientific and Technical Information of China (English)

    TANG; BenZhong

    2001-01-01

    High technology is advancing our society and modernizing our life and advanced materials play an important role in the technological innovations. My research group has been working on the development of advanced polymeric materials and in this talk I will report our recent work on the creation of new conjugated polymers with novel molecular structures and unique materials properties.1-18 Our work include the design of molecular structures of monomeric building blocks, development of stable, effective and environmentally benign "green” polymerization catalysts, discovery of new polymerization reactions, synthesis of functional macromolecules, fabrication of nanodimensional composites, assembly and control of hierarchical structures, and construction of electrooptical devices. We have revealed the liquid crystallinity, light emission, photoconductivity, optical limiting, nano-hybridization, solvatochromism, optical activity, self-organization, and biological activity of the linear polyacetylenes and hyperbranched polyarylenes. The utilization of the advanced polymers and their interesting materials properties for high-tech innovations will be discussed.  ……

  7. Recent advances on polymeric membranes for membrane reactors

    KAUST Repository

    Buonomenna, M. G.

    2012-06-24

    Membrane reactors are generally applied in high temperature reactions (>400 °C). In the field of fine chemical synthesis, however, much milder conditions are generally applicable and polymeric membranes were applied without their damage. The successful use of membranes in membrane reactors is primary the result of two developments concerning: (i) membrane materials and (ii) membrane structures. The selection of a suited material and preparation technique depends on the application the membrane is to be used in. In this chapter a review of up to date literature about polymers and configuration catalyst/ membranes used in some recent polymeric membrane reactors is given. The new emerging concept of polymeric microcapsules as catalytic microreactors has been proposed. © 2012 Bentham Science Publishers. All rights reserved.

  8. Enzyme-catalysis breathes new life into polyester condensation polymerizations.

    Science.gov (United States)

    Gross, Richard A; Ganesh, Manoj; Lu, Wenhua

    2010-08-01

    Traditional chemical catalysts for polyester synthesis have enabled the generation of important commercial products. Undesirable characteristics of chemically catalyzed condensation polymerizations include the need to conduct reactions at high temperatures (150-280 degrees C) with metal catalysts that are toxic and lack selectivity. The latter is limiting when aspiring towards synthesis of increasingly complex and well-defined polyesters. This review describes an exciting technology that makes use of immobilized enzyme-catalysts for condensation polyester synthesis. Unlike chemical catalysts, enzymes function under mild conditions (< or =100 degrees C), which enables structure retention when polymerizing unstable monomers, circumvents the introduction of metals, and also provides selectivity that avoids protection-deprotection steps and presents unique options for structural control. Examples are provided that describe the progress made in enzyme-catalyzed polymerizations, as well as current limitations and future prospects for developing more efficient enzyme-catalysts for industrial processes.

  9. Novel hybrid polymeric materials for barrier coatings

    Science.gov (United States)

    Pavlacky, Erin Christine

    Polymer-clay nanocomposites, described as the inclusion of nanometer-sized layered silicates into polymeric materials, have been widely researched due to significant enhancements in material properties with the incorporation of small levels of filler (1--5 wt.%) compared to conventional micro- and macro-composites (20--30 wt.%). One of the most promising applications for polymer-clay nanocomposites is in the field of barrier coatings. The development of UV-curable polymer-clay nanocomposite barrier coatings was explored by employing a novel in situ preparation technique. Unsaturated polyesters were synthesized in the presence of organomodified clays by in situ intercalative polymerization to create highly dispersed clays in a precursor resin. The resulting clay-containing polyesters were crosslinked via UV-irradiation using donor-acceptor chemistry to create polymer-clay nanocomposites which exhibited significantly enhanced barrier properties compared to alternative clay dispersion techniques. The impact of the quaternary alkylammonium organic modifiers, used to increase compatibility between the inorganic clay and organic polymer, was studied to explore influence of the organic modifier structure on the nanocomposite material properties. By incorporating just the organic modifiers, no layered silicates, into the polyester resins, reductions in film mechanical and thermal properties were observed, a strong indicator of film plasticization. An alternative in situ preparation method was explored to further increase the dispersion of organomodified clay within the precursor polyester resins. In stark contrast to traditional in situ polymerization methods, a novel "reverse" in situ preparation method was developed, where unmodified montmorillonite clay was added during polyesterification to a reaction mixture containing the alkylammonium organic modifier. The resulting nanocomposite films exhibited reduced water vapor permeability and increased mechanical properties

  10. Ring-opening polymerization of cyclic esters by cyclodextrins.

    Science.gov (United States)

    Harada, Akira; Osaki, Motofumi; Takashima, Yoshinori; Yamaguchi, Hiroyasu

    2008-09-01

    Synthetic polymers, typically prepared by addition polymerization or stepwise polymerization, are used constantly in our daily lives. In recent years, polymer scientists have focused on more environmentally friendly synthetic methods such as mild reaction conditions and biodegradable condensation polymers, including polyesters and polyamides. However, challenges remain in finding greener methods for the synthesis of polymers. Although reactions carried out in water are more environmentally friendly than those in organic solvents, aqueous media can lead to the hydrolysis of condensation polymers. Furthermore, bulk polymerizations are difficult to control. In biological systems, enzymes synthesize most polymers (proteins, DNAs, RNAs, and polysaccharides) in aqueous environments or in condensed phases (membranes). Most enzymes, such as DNA polymerases, RNA polymerases, and ribosomes, form doughnutlike shapes, which encircle the growing polymer chain. As biopolymers form, the active sites and the substrate-combining sites are located at the end of the growing polymer chain and carefully control the polymerization. Therefore, a synthetic catalyst that could insert the monomers between the active site and binding site would create an ideal biomimetic polymerization system. In this Account, we describe cyclodextrins (CDs) as catalysts that can polymerize cyclic esters (lactones and lactides). CDs can initiate polymerizations of cyclic esters in bulk without solvents (even water) to give products in high yields. During our studies on the polymerization of lactones by CDs in bulk, we found that CDs function not only as initiators (catalysts) but also as supporting architectures similar to chaperone proteins. CDs encircle a linear polymer chain so that the chain assumes the proper conformation and avoids coagulation. The CDs can mimic the strategy that living systems use to prepare polymers. Thus, we can obtain polyesters tethered to CDs without employing additional solvents

  11. Electroactivity in Polymeric Materials

    CERN Document Server

    2012-01-01

    Electroactivity in Polymeric Materials provides an in-depth view of the theory of electroactivity and explores exactly how and why various electroactive phenomena occur. The book explains the theory behind electroactive bending (including ion-polymer-metal-composites –IPMCs), dielectric elastomers, electroactive contraction, and electroactive contraction-expansion cycles.  The book also balances theory with applications – how electroactivity can be used – drawing inspiration from the manmade mechanical world and the natural world around us.  This book captures: A complete introduction to electroactive materials including examples and recent developments The theory and applications of numerous topics like electroactive bending of dielectric elastomers and electroactive contraction and expansion New topics, such as biomimetic applications and energy harvesting This is a must-read within the electroactive community, particularly for professionals and graduate students who are interested in the ...

  12. Polymerization of anionic wormlike micelles.

    Science.gov (United States)

    Zhu, Zhiyuan; González, Yamaira I; Xu, Hangxun; Kaler, Eric W; Liu, Shiyong

    2006-01-31

    Polymerizable anionic wormlike micelles are obtained upon mixing the hydrotropic salt p-toluidine hydrochloride (PTHC) with the reactive anionic surfactant sodium 4-(8-methacryloyloxyoctyl)oxybenzene sulfonate (MOBS). Polymerization captures the cross-sectional radius of the micelles (approximately 2 nm), induces micellar growth, and leads to the formation of a stable single-phase dispersion of wormlike micellar polymers. The unpolymerized and polymerized micelles were characterized using static and dynamic laser light scattering, small-angle neutron scattering, 1H NMR, and stopped-flow light scattering. Stopped-flow light scattering was also used to measure the average lifetime of the unpolymerized wormlike micelles. A comparison of the average lifetime of unpolymerized wormlike micelles with the surfactant monomer propagation rate was used to elucidate the mechanism of polymerization. There is a significant correlation between the ratio of the average lifetime to the monomer propagation rate and the average aggregation number of the polymerized wormlike micelles.

  13. Surface glycosylation of polymeric membranes

    Institute of Scientific and Technical Information of China (English)

    DAI ZhengWei; WAN LingShu; XU ZhiKang

    2008-01-01

    Surface glycosylation of polymeric membranes has been inspired by the structure of natural biomembranes. It refers to that glycosyl groups are introduced onto the membrane surface by various strategies, which combine the separation function of the membrane with the biological function of the saccharides in one system. In this review, progress in the surface glycosylation of polymeric membranes is highlighted in two aspects, i.e. the glycosylation methods and the potential applications of the surface-glycosylated membranes.

  14. RING OPENING POLYMERIZATION OF TETRAHYDROFURAN CATALYSED BY MAGHNITE-H+

    Institute of Scientific and Technical Information of China (English)

    Khadidja Benkenfoud; Amine Harrane; Mohammed Belbachir

    2012-01-01

    The cationic ring-opening polymerization of tetrahydrofuran using maghnite-H- is reported.Maghnite-H+,is a non-toxic solid catalyst issued from proton exchanged montmorillonite clay.Polytetrahydrofuran,also called "poly(butandiol) ether",with acetate and hydroxyl end groups was successfully synthesized.Effects of reaction temperature,weight ratio of initiator/monomer and reaction time on the conversion of monomer and on the molecular weight are investigated.A cationic mechanism of the reaction was proposed.This chemistry can be considered as a suitable route for preparing poly(THF) as a soft segment for thermoplastic elastomers.

  15. Calix[4]arene methylenebisphosphonic acids as inhibitors of fibrin polymerization.

    Science.gov (United States)

    Lugovskoy, Eduard V; Gritsenko, Pavel G; Koshel, Tatyana A; Koliesnik, Ievgen O; Cherenok, Serhey O; Kalchenko, Olga I; Kalchenko, Vitaliy I; Komisarenko, Serhey V

    2011-04-01

    Calix[4]arenes bearing two or four methylenebisphosphonic acid groups at the macrocyclic upper rim have been studied with respect to their effects on fibrin polymerization. The most potent inhibitor proved to be calix[4]arene tetrakis-methylene-bis-phosphonic acid (C-192), in which case the maximum rate of fibrin polymerization in the fibrinogen + thrombin reaction decreased by 50% at concentrations of 0.52 × 10(-6) M (IC(50)). At this concentration, the molar ratio of the compound to fibrinogen was 1.7 : 1. For the case of desAABB fibrin polymerization, the IC(50) was 1.26 × 10(-6) M at a molar ratio of C-192 to fibrin monomer of 4 : 1. Dipropoxycalix[4]arene bis-methylene-bis-phosphonic acid (C-98) inhibited fibrin desAABB polymerization with an IC(50) = 1.31 × 10(-4) M. We hypothesized that C-192 blocks fibrin formation by combining with polymerization site 'A' (Aα17-19), which ordinarily initiates protofibril formation in a 'knob-hole' manner. This suggestion was confirmed by an HPLC assay, which showed a host-guest inclusion complex of C-192 with the synthetic peptide Gly-Pro-Arg-Pro, an analogue of site 'A'. Further confirmation that the inhibitor was acting at the initial step of the reaction was obtained by electron microscopy, with no evidence of protofibril formation being evident. Calixarene C-192 also doubled both the prothrombin time and the activated partial thromboplastin time in normal human blood plasma at concentrations of 7.13 × 10(-5) M and 1.10 × 10(-5) M, respectively. These experiments demonstrate that C-192 is a specific inhibitor of fibrin polymerization and blood coagulation and can be used for the design of a new class of antithrombotic agents.

  16. Pressure polymerization of polyester

    Science.gov (United States)

    Maurer, Charles J.; Shaw, Gordon; Smith, Vicky S.; Buelow, Steven J.; Tumas, William; Contreras, Veronica; Martinez, Ronald J.

    2000-08-29

    A process is disclosed for the preparation of a polyester polymer or polyester copolymer under superatmospheric pressure conditions in a pipe or tubular reaction under turbannular flow conditions. Reaction material having a glycol equivalents to carboxylic acid equivalents mole ratio of from 1.0:1 to 1.2:1, together with a superatmospheric dense gaseous medium are fed co-currently to the reactor. Dicarboxylic acid and/or diol raw materials may be injected into any of the reaction zones in the process during operation to achieve the overall desired mole ratio balance. The process operates at temperatures of from about 220.degree. C. to about 320.degree. C., with turbannular flow achieved before the polymer product and gas exit the reactor process. The pressure in the reaction zones can be in the range from 15 psia to 2500 psia. A polymer product having a DP of a greater than 40, more preferably at least about 70, is achieved by the transfer of water from the reacting material polymer melt to the gaseous medium in the reactor.

  17. AQUEOUS STABLE FREE RADICAL POLYMERIZATION PROCESSES

    Institute of Scientific and Technical Information of China (English)

    Andrea R. Szkurhan; Michael K. Georges

    2004-01-01

    An overview of aqueous polymerizations, which include emulsion, miniemulsion and suspension polymerizations,under stable free radical polymerization (SFRP) conditions is presented. The success of miniemulsion and suspension SFRP polymerizations is contrasted with the difficulties associated with obtaining a stable emulsion polymerization. A recently developed unique microprecipitation technique is referenced as a means of making submicron sized particles that can be used to achieve a stable emulsion SFRP process.

  18. Recent Developments of Versatile Photoinitiating Systems for Cationic Ring Opening Polymerization Operating at Any Wavelengths and under Low Light Intensity Sources.

    Science.gov (United States)

    Lalevée, Jacques; Mokbel, Haifaa; Fouassier, Jean-Pierre

    2015-04-20

    Photoinitiators (PI) or photoinitiating systems (PIS) usable in light induced cationic polymerization (CP) and free radical promoted cationic polymerization (FRPCP) reactions (more specifically for cationic ring opening polymerization (ROP)) together with the involved mechanisms are briefly reviewed. The recent developments of novel two- and three-component PISs for CP and FRPCP upon exposure to low intensity blue to red lights is emphasized in details. Examples of such reactions under various experimental conditions are provided.

  19. Polymeric materials for neovascularization

    Science.gov (United States)

    DeVolder, Ross John

    Revascularization therapies have emerged as a promising strategy to treat various acute and chronic wounds, cardiovascular diseases, and tissue defects. It is common to either administer proangiogenic growth factors, such as vascular endothelial growth factor (VEGF), or transplant cells that endogenously express multiple proangiogenic factors. Additionally, these strategies utilize a wide variety of polymeric systems, including hydrogels and biodegradable plastics, to deliver proangiogenic factors in a sophisticated manner to maintain a sustained proangiogenic environment. Despite some impressive results in rebuilding vascular networks, it is still a challenging task to engineer mature and functional neovessels in target tissues, because of the increasing complexities involved with neovascularization applications. To resolve these challenges, this work aims to design a wide variety of proangiogenic biomaterial systems with tunable properties used for neovascularization therapies. This thesis describes the design of several biomaterial systems used for the delivery of proangiogenic factors in neovascularization therapies, including: an electrospun/electrosprayed biodegradable plastic patch used for directional blood vessel growth (Chapter 2), an alginate-g-pyrrole hydrogel system that biochemically stimulates cellular endogenous proangiogenic factor expression (Chapter 3), an enzyme-catalyzed alginate-g-pyrrole hydrogel system for VEGF delivery (Chapter 4), an enzyme-activated alginate-g-pyrrole hydrogel system with systematically controllable electrical and mechanical properties (Chapter 5), and an alginate-g-pyrrole hydrogel that enables the decoupled control of electrical conductivity and mechanical rigidity and is use to electrically stimulate cellular endogenous proangiogenic factor expression (Chapter 6). Overall, the biomaterial systems developed in this thesis will be broadly useful for improving the quality of a wide array of molecular and cellular based

  20. Towards the Valorization of Humin By-products: Characterization, Solubilization and Catalysis

    NARCIS (Netherlands)

    Zandvoort, I. van

    2015-01-01

    During the acid-catalyzed dehydration of carbohydrates for the production of renewable bulk chemicals, such as furfural, hydroxymethylfurfural (HMF) and levulinic acid, large amounts of carbonaceous, insoluble by-products are typically formed by cross-polymerization reactions of HMF and several suga

  1. Visualization and characterization of interfacial polymerization layer formation.

    Science.gov (United States)

    Zhang, Yali; Benes, Nieck E; Lammertink, Rob G H

    2015-01-21

    We present a microfluidic platform to visualize the formation of free-standing films by interfacial polymerization. A microfluidic device is fabricated, with an array of micropillars to stabilize an aqueous-organic interface that allows a direct observation of the films formation process via optical microscopy. Three different amines are selected to react with trimesoyl chloride: piperazine, JEFFAMINE(®)D-230, and an ammonium functionalized polyhedral oligomeric silsesquioxane. Tracking the formation of the free-standing films in time reveals strong effects of the characteristics of the amine precursor on the morphological evolution of the films. Piperazine exhibits a rapid reaction with trimesoyl chloride, forming a film up to 20 μm thick within half a minute. JEFFAMINE(®)D-230 displays much slower film formation kinetics. The location of the polymerization reaction was initially in the aqueous phase and then shifted into the organic phase. Our in situ real-time observations provide information on the kinetics and the changing location of the polymerization. This provides insights with important implications for fine-tuning of interfacial polymerizations for various applications.

  2. Stereoselectivity in metallocene-catalyzed coordination polymerization of renewable methylene butyrolactones: From stereo-random to stereo-perfect polymers

    KAUST Repository

    Chen, Xia

    2012-05-02

    Coordination polymerization of renewable α-methylene-γ-(methyl) butyrolactones by chiral C 2-symmetric zirconocene catalysts produces stereo-random, highly stereo-regular, or perfectly stereo-regular polymers, depending on the monomer and catalyst structures. Computational studies yield a fundamental understanding of the stereocontrol mechanism governing these new polymerization reactions mediated by chiral metallocenium catalysts. © 2012 American Chemical Society.

  3. Highly efficient and selective pressure-assisted photon-induced polymerization of styrene

    Science.gov (United States)

    Guan, Jiwen; Song, Yang

    2016-06-01

    The polymerization process of condensed styrene to produce polystyrene as an industrially important polymeric material was investigated using a novel approach by combining external compression with ultraviolet radiation. The reaction evolution was monitored as a function of time and the reaction products were characterized by in situ Fourier transform infrared spectroscopy. By optimizing the loading pressures, we observed highly efficient and selective production of polystyrene of different tacticities. Specifically, at relatively low loading pressures, infrared spectra suggest that styrene monomers transform to amorphous atactic polystyrene (APS) with minor crystalline isotactic polystyrene. In contrast, APS was found to be the sole product when polymerization occurs at relatively higher loading pressures. The time-dependent reaction profiles allow the examination of the polymerization kinetics by analyzing the rate constant and activation volume as a function of pressure. As a result, an optimized pressure condition, which allows a barrierless reaction to proceed, was identified and attributed to the very desirable reaction yield and kinetics. Finally, the photoinitiated reaction mechanism and the growth geometry of the polymer chains were investigated from the energy diagram of styrene and by the topology analysis of the crystal styrene. This study shows strong promise to produce functional polymeric materials in a highly efficient and controlled manner.

  4. VINYL RADICAL POLYMERIZATION INITIATED WITH CERIC ION AND ETHYL N,N-DIETHYLDITHIOCARBAMYL ACETATE SYSTEM

    Institute of Scientific and Technical Information of China (English)

    XU Shoujun; QIU Kunyuan

    1997-01-01

    Acrylamide polymerization initiated with a redox initiation system consisting of ceric ion and ethyl N, N-diethyldithiocarbamyl acetate (EDCA) has been studied. It was found that the polymerization rate equation is in good agreement with that of a redox initiated polymerization, and the overall activation energy of the polymerization was determined to be 25.2 kJ·mol-1. Accordingly, the system belongs to a redox initiator. The initiation mechanism was proposed based on the end group analysis using FT-IR, UV spectroscopies.Analysis results revealed that the N, N-diethyldithiocarbamyl radical produced from the redox reaction of EDCA with ceric ion can initiate acrylonitrile (AN) polymerization and form the end group on PAN. The resulting PAN was photopolymerized with butyl acrylate (BA) to form PAN-b-PBA block copolymer.

  5. Kinetics and Mechanism of Bulk Polymerization of Styrene Catalyzed by Rare Earth Catalyst

    Institute of Scientific and Technical Information of China (English)

    吴林波; 李伯耿; 李宝芳; 曹堃

    2001-01-01

    The bulk polymerization of styrene catalyzed by Nd(P204)3/MgBu2/HMPA (hexamethyl phospho-ramide) was carried out in capped glass tubes. The effects of reaction conditions on polymerization conversion and molecular weight in the range of high conversion were investigated. The molecular weight of the resultant polymers is dramatically high and its distribution is relatively narrow. The polymerization process demonstrates the feature of living polymerization and auto-acceleration phenomenon. The auto-acceleration phenomenon is attributed to the non-instantaneous formation of the active species. The experimental data suggest that chain transfer to MgBu2 is one of the factors governing the molecular weight development. A mechanism of polymerization is presented with the chain transfer process incorporated.

  6. Stereospecific olefin polymerization catalysts

    Science.gov (United States)

    Bercaw, John E.; Herzog, Timothy A.

    1998-01-01

    A metallocene catalyst system for the polymerization of .alpha.-olefins to yield stereospecific polymers including syndiotactic, and isotactic polymers. The catalyst system includes a metal and a ligand of the formula ##STR1## wherein: R.sup.1, R.sup.2, and R.sup.3 are independently selected from the group consisting of hydrogen, C.sub.1 to C.sub.10 alkyl, 5 to 7 membered cycloalkyl, which in turn may have from 1 to 3 C.sub.1 to C.sub.10 alkyls as a substituent, C.sub.6 to C.sub.15 aryl or arylalkyl in which two adjacent radicals may together stand for cyclic groups having 4 to 15 carbon atoms which in turn may be substituted, or Si(R.sup.8).sub.3 where R.sup.8 is selected from the group consisting of C.sub.1 to C.sub.10 alkyl, C.sub.6 to C.sub.15 aryl or C.sub.3 to C.sub.10 cycloalkyl; R.sup.4 and R.sup.6 are substituents both having van der Waals radii larger than the van der Waals radii of groups R.sup.1 and R.sup.3 ; R.sup.5 is a substituent having a van der Waals radius less than about the van der Waals radius of a methyl group; E.sup.1, E.sup.2 are independently selected from the group consisting of Si(R.sup.9).sub.2, Si(R.sup.9).sub.2 --Si(R.sup.9).sub.2, Ge(R.sup.9).sub.2, Sn(R.sup.9).sub.2, C(R.sup.9).sub.2, C(R.sup.9).sub.2 --C(R.sup.9).sub.2, where R.sup.9 is C.sub.1 to C.sub.10 alkyl, C.sub.6 to C.sub.15 aryl or C.sub.3 to C.sub.10 cycloalkyl; and the ligand may have C.sub.S or C.sub.1 -symmetry. Preferred metals are selected from the group consisting of group III, group IV, group V or lanthanide group elements. The catalysts are used to prepare stereoregular polymers including polypropylene from .alpha.-olefin monomers.

  7. Horseradish peroxidase catalyzed free radical cannot free move in reaction solution

    Directory of Open Access Journals (Sweden)

    Cai Xialing

    2009-08-01

    Full Text Available Mechanism of Horseradish Peroxidase -catalyzed phenol compound oxidizing reaction is a radical polymerization. Many polymer preparation are also carry on through the radical polymerization mechanism We deduce if free radical produced by peroxidasecatalyzed phenol polymerization could apply on polymer preparation? Could the phenol–oxygen free radical leave off the peroxidase and catalyze other compounds polymerization? The free radical in phenol oxidation process was investigated in homogeneous reaction and in immobilized HRP catalyzed reaction. The results showed the free radical produced by peroxidase only move on the surface of enzyme, can’t free move in solution in both experiment. Evidence showed the phenol polymerization is enzyme reaction process, different from general chemistry free radical chain reaction.Keywords: Horseradish Peroxidase, free radical polymerization, mechanismReceived: 17 March 2008 / Received in revised form: 5 February 2009, Accepted: 31 April 2009 Published online: 14 May 2009

  8. Fire-Retardant Polymeric Additives

    Science.gov (United States)

    Williams, Martha K.; Smith, Trent M.

    2011-01-01

    component forms polybenzoxazole (PBO) in a reaction that absorbs heat from its surroundings. PBO under thermal stress cross-links, forming a protective char layer, which thermally insulates the polymer. Thus, the formation of the char layer further assists to extinguish the fire by preventing vaporization of the polymeric fuel.

  9. Surface Initiated Polymerizations via e-ATRP in Pure Water

    Directory of Open Access Journals (Sweden)

    Seyed Schwan Hosseiny

    2013-10-01

    Full Text Available Here we describe the combined process of surface modification with electrochemical atom transfer radical polymerization (e-ATRP initiated from the surface of a modified gold-electrode in a pure aqueous solution without any additional supporting electrolyte. This approach allows for a very controlled growth of the polymer chains leading towards a steady increase in film thickness. Electrochemical quartz crystal microbalance displayed a highly regular increase in surface confined mass only after the addition of the pre-copper catalyst which is reduced in situ and transformed into the catalyst. Even after isolation and washing of the modified electrode surface, reinitiation was achieved with retention of the controlled electrochemical ATRP reaction. This reinitiation after isolation proves the livingness of the polymerization. This approach has interesting potential for smart thin film materials and offers also the possibility of post-modification via additional electrochemical induced reactions.

  10. Polymerization in emulsion microdroplet reactors

    Science.gov (United States)

    Carroll, Nick J.

    The goal of this research project is to utilize emulsion droplets as chemical reactors for execution of complex polymerization chemistries to develop unique and functional particle materials. Emulsions are dispersions of immiscible fluids where one fluid usually exists in the form of drops. Not surprisingly, if a liquid-to-solid chemical reaction proceeds to completion within these drops, the resultant solid particles will possess the shape and relative size distribution of the drops. The two immiscible liquid phases required for emulsion polymerization provide unique and complex chemical and physical environments suitable for the engineering of novel materials. The development of novel non-ionic fluorosurfactants allows fluorocarbon oils to be used as the continuous phase in a water-free emulsion. Such emulsions enable the encapsulation of almost any hydrocarbon compound in droplets that may be used as separate compartments for water-sensitive syntheses. Here, we exemplify the promise of this approach by suspension polymerization of polyurethanes (PU), in which the liquid precursor is emulsified into droplets that are then converted 1:1 into polymer particles. The stability of the droplets against coalescence upon removal of the continuous phase by evaporation confirms the formation of solid PU particles. These results prove that the water-free environment of fluorocarbon based emulsions enables high conversion. We produce monodisperse, cross-linked, and fluorescently labeled PU-latexes with controllable mesh size through microfluidic emulsification in a simple one-step process. A novel method for the fabrication of monodisperse mesoporous silica particles is presented. It is based on the formation of well-defined equally sized emulsion droplets using a microfluidic approach. The droplets contain the silica precursor/surfactant solution and are suspended in hexadecane as the continuous oil phase. The solvent is then expelled from the droplets, leading to

  11. Multiphase surfactant-assisted reaction-separation system in a microchannel reactor

    Institute of Scientific and Technical Information of China (English)

    Salah ALJBOUR; Tomohiko TAGAWA; Mohammad MATOUQ; Hiroshi YAMADA

    2009-01-01

    The Lewis acid-catalyzed addition of tri-methylsilyl cyanide to p-chlorobenzaldehyde in a micro-channel reactor was investigated. The microchannel was integrated to promote both reaction and separation of the biphase system. FeF3 and Cu(triflate)2 were used as water-stable Lewis acid catalysts. Sodium dodecyl sulfate was incorporated in the organic-aqueous system to enhance the reactivity and to manipulate the multiphase flow inside the microchannel. It was found that the dynamics and the kinetics of the multiphase reaction were affected by the new micellar system. Parallel multiphase flow inside the microchannel was obtained, allowing for continuous and acceptable phase separation. Enhanced selectivity was achieved by operating at lower conversion values.

  12. Dipeptide catalysed prebiotic polymerization of RNA

    DEFF Research Database (Denmark)

    Wieczorek, Rafal; Luisi, Pier Luigi; Monnard, Pierre-Alain

    2011-01-01

    toward more peptide synthesis. In the present work we describe a prebiotically plausible system in which the SerHis dipeptide acts as catalyst for the formation of RNA oligomers from imidazole derivatives of mononucleotides. The thermodynamic shift towards condensation was achieved using water......-concentrated in the remaining liquid microinclusions, thus creating an environment with low water activity in which condensation reactions can occur. Successful oligomerization of RNA monomers catalysed by the SerHis dipeptide was observed in a broad range of pH, and with all four natural nucleobases. The isomeric dipeptide...... HisSer did not exhibit any catalytic properties thus indicating that the specific, spatial arrangement of amino acid residues in the SerHis structure is responsible for its catalytic activity. Establishing novel synthetic pathways to RNA polymerization is important, as to date no convincing prebiotic...

  13. Preparation of Stable Photopatternable Polymeric Materials for Non- linear Optics

    Science.gov (United States)

    1993-05-01

    of limited versatility and is incompatible with the azobenzene and stilbene based chromo- phores.6’ 7 In addition it has proven extremely difficult...could not be achieved using dibutyltin dilaurate as a catalyst due to the occurrence of a trou- blesome transesterification side reaction of the...methacrylate moiety. Therefore, diazab- icyclo[2.2.2]-octane was used to catalyze the polymerization of monomer Q with iso- phorone diisocyanate. After

  14. Optimal control of batch emulsion polymerization of vinyl chloride

    Energy Technology Data Exchange (ETDEWEB)

    Damslora, Andre Johan

    1998-12-31

    The highly exothermic polymerization of vinyl chloride (VC) is carried out in large vessels where the heat removal represents a major limitation of the production rate. Many emulsion polymerization reactors are operated in such a way that a substantial part of the heat transfer capacity is left unused for a significant part of the total batch time. To increase the reaction rate so that it matches the heat removal capacity during the course of the reaction, this thesis proposes the use of a sufficiently flexible initiator system to obtain a reaction rate which is high throughout the reaction and real-time optimization to compute the addition policy for the initiator. This optimization based approach provides a basis for an interplay between design and control and between production and research. A simple model is developed for predicting the polymerization rate. The model is highly nonlinear and open-loop unstable and may serve as an interesting case for comparison of nonlinear control strategies. The model is fitted to data obtained in a laboratory scale reactor. Finally, the thesis discusses optimal control of the emulsion polymerization reactor. Reduction of the batch cycle time is of major economic importance, as long as the quality parameters are within their specifications. The control parameterization had a major influence on the performance. A differentiable spline parameterization was applied and the optimization is illustrated in a number of cases. The best performance is obtained when the reactor temperature is obtained when the optimization is combined with some form of closed-loop control of the reactor temperature. 112 refs., 48 figs., 4 tabs.

  15. Polymerization monitoring in plasma etching systems

    Science.gov (United States)

    Kim, Jinsoo

    1999-11-01

    In plasma etching processes, the polymers used to enhance etch anisotropy and selectivity also deposit on various parts of the reaction chamber. This polymerization on reactor surface not only strongly affects the concentration of reactants in the plasma discharge, eventually changing the etching characteristics, but also can produce particulates which lower yield. This thesis explores the development of a direct in-situ polymerization monitoring sensor to minimize the drifts in plasma etching processes. In addition, polymerization dependencies on basic processing parameters and polymerization effects on etching characteristics have been explored for the first time using a direct in-situ sensor. The polymer buildup process is a strong function of parameters such as power, base pressure, and flow rate, and is also dependent on the reactor materials used, temperature, and the hydrogen/oxygen concentrations present. Experiments performed in an Applied Materials 8300 plasma etcher show a significant increase in polymerization with increased pressure and flow rates and a decrease as a function of power. These experiments provide insight into how the chamber state changes under the different processing recipes used for etching specific material layers and also suggest how the chamber seasoning process can best be carried out. The reactor surface, which serves as both a source and a sink for reactive gas species, not only strongly affects the concentration of reactants in the plasma discharge, eventually changing the etching characteristics, but also can produce particulates which lower yield. The etch rate and selectivity variations for specific silicon dioxide and silicon nitride etching recipes have been explored as a function of the polymer thickness on the reactor walls. The etch rates of nitride and polysilicon decrease dramatically with polymer thickness up to a thickness of 60nm, while the oxide etch rate remains virtually constant due to the polymerization

  16. Horseradish peroxidase catalyzed free radical cannot free move in reaction solution

    OpenAIRE

    2009-01-01

    Mechanism of Horseradish Peroxidase -catalyzed phenol compound oxidizing reaction is a radical polymerization. Many polymer preparation are also carry on through the radical polymerization mechanism We deduce if free radical produced by peroxidasecatalyzed phenol polymerization could apply on polymer preparation? Could the phenol–oxygen free radical leave off the peroxidase and catalyze other compounds polymerization? The free radical in phenol oxidation process was investigated in homo...

  17. Surface glycosylation of polymeric membranes

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Surface glycosylation of polymeric membranes has been inspired by the structure of natural biomem-branes. It refers to that glycosyl groups are introduced onto the membrane surface by various strate-gies, which combine the separation function of the membrane with the biological function of the sac-charides in one system. In this review, progress in the surface glycosylation of polymeric membranes is highlighted in two aspects, i.e. the glycosylation methods and the potential applications of the sur-face-glycosylated membranes.

  18. Synthesis of two carbazole-based dyes and application of two-photon initiating polymerization

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Two carbazole-based polymerization initiators possessing blue fluorescence emission have been synthesized via Wittig reaction in the solid phase at room temperature.Two-photon excited fluorescence(TPEF) spectra for them were investigated under 800 nm fs laser pulse and two-photon absorption cross sections were determined by the Z-scan technique.Then two-photon initiating polymerization(TPIP) microfabrication experiments were successfully carried out.Three-dimensional lattice and artificial defects were gained,indicating that they were viable candidates for the two-photon polymerization initiator in practical application of microfabrication.

  19. Pre-irradiation induced emulsion graft polymerization of acrylonitrile onto polyethylene nonwoven fabric

    Science.gov (United States)

    Liu, Hanzhou; Yu, Ming; Deng, Bo; Li, Linfan; Jiang, Haiqing; Li, Jingye

    2012-01-01

    Acrylonitrile has been widely used in the modification of polymers by graft polymerization. In the present work, pre-irradiation induced emulsion graft polymerization method is used to introduce acrylonitrile onto PE nonwoven fabric instead of the traditional reaction in organic solvents system. The degree of grafting (DG) is measured by gravimetric method and the kinetics of the graft polymerization is studied. The existence of the graft chains is proven by Fourier transform infrared spectroscopy (FT-IR) analysis. Thermal stability of the grafted polymer is measured by Thermogravimetric analysis (TGA).

  20. STUDIES ON THE POLYMERIZATION OF ACRYLONITRILE INITIATED BY METAVANADATE- CONTAINING ANION EXCHANGER-THIOUREA REDOX SYSTEM

    Institute of Scientific and Technical Information of China (English)

    YANG Chaoxiong; WU Jinyuan; WU Yuxian

    1991-01-01

    The polymerization of acrylonitrile (AN) in aqueous nitric acid initiated by metavanadate-containing anion exchange resin (PV)-thiourea (TU) redox system at 20- 40 ℃. has been investigated. The overall rate of polymerization (Rp) is given by Rp= 1.92 × 104 e -6,860/RT [AN]1.2[PV]0.44[TU]1.0[HNO3]1.0 The kinetic parameters differed from those of V5+-TU system indicated that the generation of the primary radicals is mainly a difffusion-controlled reaction . The effect of macromolecular field arisen from the polymer matrix exerts a great influence on the polymerization process.

  1. Synthesis of two carbazole-based dyes and application of two-photon initiating polymerization

    Institute of Scientific and Technical Information of China (English)

    HU RenTao; LU LiangFei; RUAN BanFeng; WANG Peng; ZHANG MingLiang; ZHOU HongPing; LI ShengLi; WU JieYing; TIAN YuPeng

    2009-01-01

    Two carbazole-based polymerization initiators possessing blue fluorescence emission have been synthesized via Wittig reaction in the solid phase at room temperature.Two-photon excited fluorescence (TPEF) spectra for them were investigated under 800 nm fs laser pulse and two-photon absorption cross sections were determined by the Z-scan technique.Then two-photon initiating polymerization (TPIP) microfabrication experiments were successfully carried out.Three-dimensional lattice and artificial defects were gained,indicating that they were viable candidates for the two-photon polymerization initiator in practical application of microfabrication.

  2. The reversible addition-fragmentation chain transfer (RAFT) miniemulsion polymerization of vinyl acetate mediated by xanthate

    Institute of Scientific and Technical Information of China (English)

    Bo Jiang; Qing Hua Zhang; Xiao Li Zhan; Feng Qiu Chen

    2009-01-01

    The reversible addition-fragmentation chain transfer (RAFT) miniemulsion polymerization of vinyl acetate (VAt) mediated by methyl (methoxycarbonothioyl) sulfanyl acetate (MMSA) was carried out. The results showed that polymerizations initiated by AIBN and KPS proceeded in a controlled way. The RAFT miniemulsion polymerization of VAc initiated by KPS showed the shorter inhibition period, higher propagation rate coefficient and final conversion than those in experiment initiated by AIBN. When the monomer conversion reached 25%, the polydispersity index (PDI) of polymer became broad, which was related to chain transfer reaction in RAFT miniemulsion of VAc.

  3. Polypropylene/graphite nanocomposites by in situ polymerization; Nanocompositos polipropileno/grafite via polimerizacao in situ

    Energy Technology Data Exchange (ETDEWEB)

    Milani, Marceo A.; Galland, Giselda B., E-mail: griselda@iq.ufrgs.br [Instituto de Quimica, UFRGS, Porto Alegre, RS (Brazil); Quijada, Raul [Universidade de Chile, Santiago (Chile). Centro de Ciencias de los Materiales; Basso, Nara R.S. [Fac. de Quimica, PUCRS, Porto Alegre, RS (Brazil)

    2011-07-01

    This work presents the synthesis of nanocomposites of polypropylene/graphite by in situ polymerization using metallocene catalyst and graphene nanosheets. Initially was analyzed which of the metallocene catalysts rac-Et(Ind){sub 2}ZrCl{sub 2} or rac-Me{sub 2}Si(Ind){sub 2}ZrCl{sub 2} produces polypropylene with mechanical properties more relevant. Then it were performed the in situ polymerization reactions to obtain the nanocomposites. The polymeric materials were characterized by XRD, DSC, GPC and DMTA. (author)

  4. Interaction of quantitative PCR components with polymeric surfaces.

    Science.gov (United States)

    Gonzalez, Asensio; Grimes, Ronan; Walsh, Edmond J; Dalton, Tara; Davies, Mark

    2007-04-01

    This study investigated the effect of exposing a polymerase chain reaction (PCR) mixture to capillary tubing of different materials and lengths, at different contact times and flow rates and the adsorption of major reaction components into the tubing wall. Using 0.5 mm ID tubing, lengths of 40 cm and residence times up to 45 min, none of the tested polymeric materials was found to affect subsequent PCR amplification. However, after exposure of the mixture to tubing lengths of 3 m or reduction of sample volume, PCR inhibition occurred, increasing with the volume to length ratio. Different flow velocities did not affect PCR yield. When the adsorption of individual PCR components was studied, significant DNA adsorption and even more significant adsorption of the fluorescent dye Sybr Green I was found. The results indicate that PCR inhibition in polymeric tubing results from adsorption of reaction components to wall surfaces, increasing substantially with tubing length or sample volume reduction, but not with contact time or flow velocities typical in dynamic PCR amplification. The data also highlight that chemical compatibility of polymeric capillaries with DNA dyes should be carefully considered for the design of quantitative microfluidic devices.

  5. Dynamic bioactive stimuli-responsive polymeric surfaces

    Science.gov (United States)

    Pearson, Heather Marie

    This dissertation focuses on the design, synthesis, and development of antimicrobial and anticoagulant surfaces of polyethylene (PE), polypropylene (PP), and poly(tetrafluoroethylene) (PTFE) polymers. Aliphatic polymeric surfaces of PE and PP polymers functionalized using click chemistry reactions by the attachment of --COOH groups via microwave plasma reactions followed by functionalization with alkyne moieties. Azide containing ampicillin (AMP) was synthesized and subsequently clicked into the alkyne prepared PE and PP surfaces. Compared to non-functionalized PP and PE surfaces, the AMP clicked surfaces exhibited substantially enhanced antimicrobial activity against Staphylococcus aureus bacteria. To expand the biocompatibility of polymeric surface anticoagulant attributes, PE and PTFE surfaces were functionalized with pH-responsive poly(2-vinyl pyridine) (P2VP) and poly(acrylic acid) (PAA) polyelectrolyte tethers terminated with NH2 and COOH groups. The goal of these studies was to develop switchable stimuli-responsive polymeric surfaces that interact with biological environments and display simultaneous antimicrobial and anticoagulant properties. Antimicrobial AMP was covalently attached to --COOH terminal ends of protected PAA, while anticoagulant heparin (HEP) was attached to terminal --NH2 groups of P2VP. When pH 5.5, they collapse while the PAA segments extend. Such surfaces, when exposed to Staphylococcus aureus, inhibit bacterial growth due to the presence of AMP, as well as are effective anticoagulants due to the presence of covalently attached HEP. Comparison of these "dynamic" pH responsive surfaces with "static" surfaces terminated with AMP entities show significant enhancement of longevity and surface activity against microbial film formation. The last portion of this dissertation focuses on the covalent attachment of living T1 and Φ11 bacteriophages (phages) on PE and PTFE surface. This was accomplished by carbodiimide coupling between --COOH

  6. Effect of Cross-Linking on the Structure and Growth of Polymer Films Prepared by Interfacial Polymerization.

    Science.gov (United States)

    Berezkin, Anatoly V; Kudryavtsev, Yaroslav V

    2015-11-10

    Interfacial polymerization of tri- and bifunctional monomers (A3B2 polymerization) is investigated by dissipative particle dynamics to reveal an effect of cross-linking on the reaction kinetics and structure of the growing polymer film. Regardless of the comonomer reactivity and miscibility, the kinetics in an initially bilayer melt passes from the reaction to diffusion control. Within the crossover period, branched macromolecules undergo gelation, which drastically changes the scenario of the polymerization process. Comparison with the previously studied linear interfacial polymerization (Berezkin, A. V.; Kudryavtsev, Y. V. Linear Interfacial Polymerization: Theory and Simulations with Dissipative Particle Dynamics J. Chem. Phys. 2014, 141, 194906) shows similar conversion rates but very different product characteristics. Cross-linked polymer films are markedly heterogeneous in density, their average polymerization degree grows with the comonomer miscibility, and end groups are mostly trapped deeply in the film core. Products of linear interfacial polymerization demonstrate opposite trends as they are spontaneously homogenized by a convective flow of macromolecules expelled from the reactive zone to the film periphery, which we call the reactive extrusion effect and which is hampered in branched polymerization. Influence of the comonomer architecture on the polymer film characteristics could be used in various practical applications of interfacial polymerization, such as fabrication of membranes, micro- and nanocapsules and 3D printing.

  7. Estudo da polimerização do 2-metil, 1,3-butadieno via catalisadores lantanídicos: influência do tipo de alquilalumínio, da temperatura reacional e da concentração do catalisador Polymerization of 2-methyl, 1,3-butadiene via lanthanides catalysts: influence from the type of alkylaluminum, concentration and reaction temperature and catalyst

    Directory of Open Access Journals (Sweden)

    André L. C. Simões

    2011-01-01

    Full Text Available Os catalisadores lantanídicos são muito eficientes na polimerização estereoespecífica de dienos, principalmente aqueles à base de neodímio. Neste trabalho será apresentado o estudo da polimerização do 2-metil, 1,3-butadieno com catalisadores à base de neodímio, utilizados comercialmente na polimerização do 1,3-butadieno. Foi estudado o efeito da temperatura, do tipo de alquilalumínio e da concentração de catalisador. As reações foram realizadas em reator de aço inox sob atmosfera inerte, usando como solvente o hexano e uma concentração de 2-metil, 1,3-butadieno de 12%. Foram obtidos polímeros com massas molares na faixa de 1,0 a 1,5 × 105 e teor de unidades repetitivas cis em torno de 97%.The rare earth metals catalysts are very efficient in stereospecific polymerization of dienes, especially those of neodymium. This paper reports on the polymerization of 2-methyl, 1,3-butadiene with catalysts of neodymium, used commercially in polymerization of 1,3-butadiene. Effects were studied from the temperature, type of alkylaluminum, and from the concentration of catalyst. The reactions were carried out in a stainless steel reactor under an inert atmosphere, using hexane as the solvent and a concentration of 12% of 2-methyl, 1,3-butadiene. Polymers were obtained with molecular weight from 1.0 to 1.5 × 105, with ca. 97% of cis repeating units.

  8. Functionalization and Polymerization on the CNT Surfaces

    KAUST Repository

    Albuerne, Julio

    2013-07-01

    In this review we focus on the current status of using carbon nanotube (CNT) as a filler for polymer nanocomposites. Starting with the historical background of CNT, its distinct properties and the surface functionalization of the nanotube, the three different surface polymerization techniques, namely grafting "from", "to" and "through/in between" were discussed. Wider focus has been given on "grafting from" surface initiated polymerizations, including atom transfer radical polymerization (ATRP), reversible addition fragmentation chain-transfer (RAFT) Polymerization, nitroxide mediated polymerization (NMP), ring opening polymerization (ROP) and other miscellaneous polymerization methods. The grafting "to" and "through / in between" also discussed and compared with grafting from polymerization. The merits and shortcomings of all three grafting methods were discussed and the bottleneck issue in grafting from method has been highlighted. Furthermore the current and potential future industrial applications were deliberated. Finally the toxicity issue of CNTs in the final product has been reviewed with the limited available literature knowledge. © 2013 Bentham Science Publishers.

  9. Modeling intraparticle transports during propylene polymerizations using supported metallocene and dual function metallocene as catalysts: Single particle model

    Directory of Open Access Journals (Sweden)

    Li Hua-Rong

    2014-01-01

    Full Text Available Two improved multigrain models (MGMs for preparing homopolypropylene and long chain branched polypropylene via propylene polymerization using silica-supported metallocene or dual function metallocene as catalysts are presented in this paper. The presented models are used to predict the intraparticle flow fields involved in the polymerizations. The simulation results show that the flow field distributions involve dare basically identical. The results also show that both the two polymerization processes have an initiation stage and the controlling step for them is reaction-diffusion-reaction with the polymerization proceeding. Furthermore, the simulation results show that the intra particle mass transfer resistance has significant effect on the polymerization but the heat transfer resistance can be ignored.

  10. Biodegradable polymeric prodrugs of naltrexone

    NARCIS (Netherlands)

    Bennet, D.B.; Li, X.; Adams, N.W.; Kim, S.W.; Hoes, C.J.T.; Feijen, J.

    1991-01-01

    The development of a biodegradable polymeric drug delivery system for the narcotic antagonist naltrexone may improve patient compliance in the treatment of opiate addiction. Random copolymers consisting of the ¿-amino acids N5-(3-hydroxypropyl--glutamine and -leucine were synthesized with equimolar

  11. Buckling of polymerized monomolecular films

    Science.gov (United States)

    Bourdieu, L.; Daillant, J.; Chatenay, D.; Braslau, A.; Colson, D.

    1994-03-01

    The buckling of a two-dimensional polymer network at the air-water interface has been evidenced by grazing incidence x-ray scattering. A comprehensive description of the inhomogeneous octadecyltrichlorosilane polymerized film was obtained by atomic force microscopy and x-ray scattering measurements. The buckling occurs with a characteristic wavelength ~=10 μm.

  12. The Viscosity of Polymeric Fluids.

    Science.gov (United States)

    Perrin, J. E.; Martin, G. C.

    1983-01-01

    To illustrate the behavior of polymeric fluids and in what respects they differ from Newtonian liquids, an experiment was developed to account for the shear-rate dependence of non-Newtonian fluids. Background information, procedures, and results are provided for the experiment. Useful in transport processes, fluid mechanics, or physical chemistry…

  13. The absorption of polymeric composites

    Science.gov (United States)

    Řídký, R.; Popovič, M.; Rolc, S.; Drdlová, M.; Krátký, J.

    2016-06-01

    An absorption capacity of soft, viscoelastic materials at high strain rates is important for wide range of practical applications. Nowadays there are many variants of numerical models suitable for this kind of analysis. The main difficulty is in selection of the most realistic numerical model and a correct setup of many unknown material constants. Cooperation between theoretical simulations and real testing is next crucial point in the investigation process. Standard open source material database offer material properties valid for strain rates less than 250 s-1. There are experiments suitable for analysis of material properties with strain rates close to 2000 s-1. The high strain-rate characteristics of a specific porous blast energy absorbing material measured by modified Split Hopkinson Pressure Bar apparatus is presented in this study. Testing these low impedance materials using a metallic split Hopkinson pressure bar setup results in poor signal to noise ratios due to impedance mismatching. These difficulties are overcome by using polymeric Hopkinson bars. Conventional Hopkinson bar analysis cannot be used on the polymeric bars due to the viscoelastic nature of the bar material. One of the possible solution leads to complex and frequency depended Young modulus of testing bars material. This testing technique was applied to materials composed of porous glass/ceramic filler and polymeric binder, with density of 125 - 300 kg/m3 and particle size in range of 50 µm - 2 mm. The achieved material model was verified in practical application of sandwich structure includes polymeric composites under a blast test.

  14. Theoretical analysis of kinetic isotope effects on proton transfer reactions between substituted alpha-methoxystyrenes and substituted acetic acids.

    Science.gov (United States)

    Wong, Kin-Yiu; Richard, John P; Gao, Jiali

    2009-10-01

    Primary kinetic isotope effects (KIEs) on a series of carboxylic acid-catalyzed protonation reactions of aryl-substituted alpha-methoxystyrenes (X-1) to form oxocarbenium ions have been computed using the second-order Kleinert variational perturbation theory (KP2) in the framework of Feynman path integrals (PI) along with the potential energy surface obtained at the B3LYP/6-31+G(d,p) level. Good agreement with the experimental data was obtained, demonstrating that this novel computational approach for computing KIEs of organic reactions is a viable alternative to the traditional method employing Bigeleisen equation and harmonic vibrational frequencies. Although tunneling makes relatively small contributions to the lowering of the free energy barriers for the carboxylic acid catalyzed protonation reaction, it is necessary to include tunneling contributions to obtain quantitative estimates of the KIEs. Consideration of anharmonicity can further improve the calculated KIEs for the protonation of substituted alpha-methoxystyrenes by chloroacetic acid, but for the reactions of the parent and 4-NO(2) substituted alpha-methoxystyrene with substituted carboxylic acids, the correction of anharmonicity overestimates the computed KIEs for strong acid catalysts. In agreement with experimental findings, the largest KIEs are found in nearly ergoneutral reactions, DeltaG(o) approximately 0, where the transition structures are nearly symmetric and the reaction barriers are relatively low. Furthermore, the optimized transition structures are strongly dependent on the free energy for the formation of the carbocation intermediate, that is, the driving force DeltaG(o), along with a good correlation of Hammond shift in the transition state structure.

  15. A new metalation complex for organic synthesis and polymerization reactions

    Science.gov (United States)

    Hirshfield, S. M.

    1971-01-01

    Organometallic complex of N,N,N',N' tetramethyl ethylene diamine /TMEDA/ and lithium acts as metalation intermediate for controlled systhesis of aromatic organic compounds and polymer formation. Complex of TMEDA and lithium aids in preparation of various organic lithium compounds.

  16. THE POLYMERIZATION OF AROMATIC AND HETEROCYCLIC DINITRILES

    Institute of Scientific and Technical Information of China (English)

    HUANG Zhitang

    1988-01-01

    This review is a concise survey about the works in our laboratory on the polymerization of aromatic and heterocyclic dinitriles, including the polymerization kinetics and mechanism, synthesis of heterocyclic dinitriles, the structure of polymers, and the correlation between the structures of dinitriles and polymerization rates and thermal performances of polymers.

  17. Polymeric amines and biomedical uses thereof

    NARCIS (Netherlands)

    Broekhuis, Antonius; Zhang, Youchum; Picchioni, Francesco; Roks, Antonius

    2010-01-01

    The invention relates to the field of polymers and biomedical applications thereof. In particular, it relates to the use of polymeric amines derived from alternating polyketones.Provided is the use of a polymeric amine for modulating or supporting cellular behavior, said polymeric amine being an alt

  18. Nanoscale Polymeric Amphiphiles by Combination of Controlled Polymerizations and "Click" Reactions: Implications for Drug Delivery

    DEFF Research Database (Denmark)

    Javakhishvili, Irakli

    af guld nanopartikler med slimhinde vedhæftende egenskaber med mulige drug delivery perspektiver. Ligeledes er en række sammenkoblinger med mindre molekyler med biologisk aktivitet gennemført ved udstrakt brug af nye effektive ”klik”-koblingsreaktioner. De anvendte kontrollerede...

  19. Glycine Polymerization on Oxide Minerals

    Science.gov (United States)

    Kitadai, Norio; Oonishi, Hiroyuki; Umemoto, Koichiro; Usui, Tomohiro; Fukushi, Keisuke; Nakashima, Satoru

    2016-07-01

    It has long been suggested that mineral surfaces played an important role in peptide bond formation on the primitive Earth. However, it remains unclear which mineral species was key to the prebiotic processes. This is because great discrepancies exist among the reported catalytic efficiencies of minerals for amino acid polymerizations, owing to mutually different experimental conditions. This study examined polymerization of glycine (Gly) on nine oxide minerals (amorphous silica, quartz, α-alumina and γ-alumina, anatase, rutile, hematite, magnetite, and forsterite) using identical preparation, heating, and analytical procedures. Results showed that a rutile surface is the most effective site for Gly polymerization in terms of both amounts and lengths of Gly polymers synthesized. The catalytic efficiency decreased as rutile > anatase > γ-alumina > forsterite > α- alumina > magnetite > hematite > quartz > amorphous silica. Based on reported molecular-level information for adsorption of Gly on these minerals, polymerization activation was inferred to have arisen from deprotonation of the NH3 + group of adsorbed Gly to the nucleophilic NH2 group, and from withdrawal of electron density from the carboxyl carbon to the surface metal ions. The orientation of adsorbed Gly on minerals is also a factor influencing the Gly reactivity. The examination of Gly-mineral interactions under identical experimental conditions has enabled the direct comparison of various minerals' catalytic efficiencies and has made discussion of polymerization mechanisms and their relative influences possible Further systematic investigations using the approach reported herein (which are expected to be fruitful) combined with future microscopic surface analyses will elucidate the role of minerals in the process of abiotic peptide bond formation.

  20. Multiple Olefin Metathesis Polymerization That Combines All Three Olefin Metathesis Transformations: Ring-Opening, Ring-Closing, and Cross Metathesis.

    Science.gov (United States)

    Lee, Ho-Keun; Bang, Ki-Taek; Hess, Andreas; Grubbs, Robert H; Choi, Tae-Lim

    2015-07-29

    We demonstrated tandem ring-opening/ring-closing metathesis (RO/RCM) polymerization of monomers containing two cyclopentene moieties and postmodification via insertion polymerization. In this system, well-defined polymers were efficiently formed by tandem cascade RO/RCM reaction pathway. Furthermore, these polymers could be transformed to new A,B-alternating copolymers via a sequential cross metathesis reaction with a diacrylate. Additionally, we demonstrated the concept of multiple olefin metathesis polymerization in which the dicyclopentene and diacrylate monomers underwent all three olefin metathesis transformations (ring-opening, ring-closing, and cross metathesis) in one shot to produce A,B-alternating copolymer.

  1. Pigment encapsulation by emulsion polymerization using macro-RAFT copolymers.

    Science.gov (United States)

    Nguyen, Duc; Zondanos, Hollie S; Farrugia, Jason M; Serelis, Algirdas K; Such, Chris H; Hawkett, Brian S

    2008-03-04

    A new method is described, based on living amphipathic random macro-RAFT copolymers, which enables the efficient polymeric encapsulation of both inorganic and organic particulate materials via free-radical polymerization. The mechanism for this new approach is examined in the context of the polymer coating of zirconia- and alumina-coated titanium dioxide particles and its breadth of application demonstrated by the coating of organic phthalocyanine blue pigment particles. The particulate materials were first dispersed in water using a macro-RAFT copolymer as a stabilizer. Monomer and water-soluble initiator were then added to the system, and the monomer polymerized to form the coating. If nucleation of new polymer particles in the aqueous phase was to be avoided, it was found necessary to use a macro-RAFT copolymer that did not form micelles; within this constraint, a broad range of RAFT agents could be used. The macro-RAFT agents used in this work were found not to transfer competitively in the aqueous phase and therefore did not support growth of aqueous-phase polymer. Successful encapsulation of particles was demonstrated by TEM. The process described enables 100% of the particles to be encapsulated with greater than 95% of the polymer finishing up in the polymeric shells around the particles. Moreover, the coating reaction can be carried out at greater than 50% solids in many cases and avoids the agglomeration of particles during the coating step.

  2. Monolithic molecularly imprinted polymeric capillary columns for isolation of aflatoxins.

    Science.gov (United States)

    Szumski, Michał; Grzywiński, Damian; Prus, Wojciech; Buszewski, Bogusław

    2014-10-17

    Monolithic molecularly imprinted polymers extraction columns have been prepared in fused-silica capillaries by UV or thermal polymerization in a two-step process. First, a poly-(trimethylolpropane trimethacrylate) (polyTRIM) core monolith was synthesized either by UV or thermal polymerization. Then it was grafted with the mixture of methacrylic acid (MAA) as a functional monomer, ethylene dimethacrylate (EDMA) as a cross-linking agent, 5,7-dimethoxycoumarin (DMC) as an aflatoxin-mimicking template, toluene as a porogen solvent and 2,2-azobis-(2-methylpropionitrile) (AIBN) as an initiator of the polymerization reaction. Different thermal condition of the photografting and different concentrations of the grafting mixture were tested during polymerization. The extraction capillary columns were evaluated in the terms of their hydrodynamic and chromatographic properties. Retention coefficients for aflatoxin B1 and DMC were used for assessment of the selectivity and imprinting factor. The obtained results indicate that the temperature of photografting and concentration of the grafting mixture are key parameters that determine the quality of the prepared MIPs. From the MIP columns characterized by the highest permeability the column of the highest imprinting factor was applied for isolation of aflatoxins B1, B2, G1 and G2 from the model aqueous sample followed by on-line chromatographic separation. The process was performed using a micro-MISPE-microLC-LIF system of a novel design, which allowed for detection of the eluates from the sample preparation part as well as from the chromatographic separation.

  3. The Research on Modeling and Simulation of TFE Polymerization Process

    Directory of Open Access Journals (Sweden)

    Jing Gao Sun

    2014-01-01

    Full Text Available PTFE (polytetrafluoroethylene is the fluorinated straight-chain polymer, made by the polymerization of tetrafluoroethylene monomer; it is used widely because of its excellent performance and can be obtained by the polymerization of body, solutions, suspensions, and emulsions. But only the last two are the main ways. This research paper makes simulation based on Polymer Plus. It uses the emulsion polymerization method at background to carry out a semibatch reactor system. Upon the actual production conditions, simulation process under the steady state conditions is used to analyze the effects of the changes on operating conditions; the corresponding dynamic model is created to analyze the impact of the changes of conditions on the entire system. Moreover, the amount of APS which plays an important part in this reaction is discussed for getting the most suitable amount of initiator. Because of less research work on this job, it is so difficult to find the related data from the literature. Therefore, this research will have a great significance for the process of the tetrafluoroethylene emulsion polymerization in the future.

  4. Analysis of beer volatiles by polymeric imidazolium-solid phase microextraction coatings: Synthesis and characterization of polymeric imidazolium ionic liquids.

    Science.gov (United States)

    González-Álvarez, Jaime; Blanco-Gomis, Domingo; Arias-Abrodo, Pilar; Pello-Palma, Jairo; Ríos-Lombardía, Nicolás; Busto, Eduardo; Gotor-Fernández, Vicente; Gutiérrez-Álvarez, María Dolores

    2013-08-30

    Two polymeric ionic liquids, 3-(but-3″-en-1″-yl)-1-[2'-hydroxycyclohexyl]-1H-imidazol-3-ium bis(trifluoromethanesulfonyl)imide (IL-1) and 1-(2'-hydroxycyclohexyl)-3-(4″-vinylbenzyl)-1H-imidazol-3-ium bis(trifluoromethylsulfonyl)imide (IL-2), have been synthesized by a free radical polymerization reaction and used as coatings for solid-phase microextraction (SPME). These new fibers exhibit good film stability, high thermal stability (270-290°C) and long lifetimes, and are used for the extraction of volatile compounds in lemon beer using gas chromatography separation and flame ionization detection. The scanning electron micrographs of the fiber surface revealed a polymeric ionic liquid (PIL) film, which is distributed homogeneously on the fiber. The developed PIL fiber showed good linearity between 50 and 2000μg/L with regression coefficients in the range of 0.996-0.999. The relative standard deviations (RSD) obtained in the peak area were found to vary between 1% and 12%, which assured that adequate repeatability was achieved. The spiked recoveries for three beer samples ranged from 78.4% to 123.6%. Experimental design has been employed in the optimization of extraction factors and robustness assessment. The polymeric IL-1 butenyl fiber showed a greater efficiency compared to the PDMS-DVB (65μm) and CAR-PDMS (75μm) for the extraction of all of the analytes studied.

  5. Heterogeneous reactions of epoxides in acidic media.

    Science.gov (United States)

    Lal, Vinita; Khalizov, Alexei F; Lin, Yun; Galvan, Maria D; Connell, Brian T; Zhang, Renyi

    2012-06-21

    Epoxides have recently been identified as important intermediates in the gas phase oxidation of hydrocarbons, and their hydrolysis products have been observed in ambient aerosols. To evaluate the role of epoxides in the formation of secondary organic aerosols (SOA), the kinetics and mechanism of heterogeneous reactions of two model epoxides, isoprene oxide and α-pinene oxide, with sulfuric acid, ammonium bisulfate, and ammonium sulfate have been investigated using complementary experimental techniques. Kinetic experiments using a fast flow reactor coupled to an ion drift-chemical ionization mass spectrometer (ID-CIMS) show a fast irreversible loss of the epoxides with the uptake coefficients (γ) of (1.7 ± 0.1) × 10(-2) and (4.6 ± 0.3) × 10(-2) for isoprene oxide and α-pinene oxide, respectively, for 90 wt % H(2)SO(4) and at room temperature. Experiments using attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) reveal that diols are the major products in ammonium bisulfate and dilute H(2)SO(4) (65 wt %), acetals are formed from isoprene oxide, whereas organosulfates are produced from α-pinene oxide. The reaction of the epoxides with ammonium sulfate is slow and no products are observed. The epoxide reactions using bulk samples and Nuclear Magnetic Resonance (NMR) spectroscopy reveal the presence of diols as the major products for isoprene oxide, accompanied by aldehyde formation. For α-pinene oxide, organosulfate formation is observed with a yield increasing with the acidity. Large yields of organosulfates in all NMR experiments with α-pinene oxide are attributed to the kinetic isotope effect (KIE) from the use of deuterated sulfuric acid and water. Our results suggest that acid-catalyzed hydrolysis of epoxides results in the formation of a wide range of products, and some of the products have low volatility and contribute to SOA growth under ambient conditions prevailing in the urban atmosphere.

  6. 离子液体催化合成阻燃剂3-羟基苯膦酰丙酸%Synthesis of Flame Retardants 3-(Hydroxyphenylphosphinyl) Propionic Acid Catalyzed by Ionic Liquid

    Institute of Scientific and Technical Information of China (English)

    罗轩; 史红丽; 周浩; 张士磊; 杨锦飞; 职慧珍

    2012-01-01

    3-(hydroxyphenylphosphinyl) propionic acid ( CEPPA) was synthesized by a two-step procedure; Phenyl phosphonic dichloride ( DCPP) was first synthesized using phosphorus trichloride and benzene as raw materials, and tri-ethyl benzyl ammonium chloride-aluminum chloride ( [ BnEt3N]Cl -xA1C13 )as catalyst. The optimum conditions for the first step are as follows: re ( PC13 ) :n( C6 H6 ) :n( [ BnEt3 N ] Cl - xA1C13 ) = 3:1:0.025, At the reflux stage, the reaction temperature was 72℃-76℃, the reaction time was 6 h, and the yield of DCPP was up to 81. 1% . The optimum conditions for the second step by changing the order of the reactants and adjusting the reaction temperature were as follows; re (acrylic acid): n( DCPP) = 1. 30: 1. 00; the reaction temperature was 70℃ -80℃ and the reaction time was 1. 5 h -2h at the dropping stage; then reacting at 90℃ for 1 h; at the hydrolysis reaction stage, the reaction temperature was 92℃ - 95℃ , and the reaction time was 4 h, the yield of CEPPA was up to 91 %. The problem of agglomeration was easy to be solved in this procedure.%采用两步法合成3-羟基苯膦酰丙酸(CEPPA),即以三氯化磷与苯为原料,在离子液体三乙基苄基氯化铵氯化铝([ BnEt3N]Cl - xAlCl3)催化下,合成苯膦二氯(DCPP),再用DCPP与丙烯酸合成3-羟基苯膦酰丙酸(CEPPA).确定第一步最佳反应条件为:n(三氯化磷)∶n(苯)∶n([BnEt3N]Cl - xAlCl3)=3∶1∶0.025,同流温度为72℃~ 76℃,反应时间为6h,产率达81.1%;第二步通过改变反应物滴加顺序及调整反应温度,得到最佳反应条件为:n(丙烯酸)∶n(DCPP)=1.30∶1.00;滴加反应阶段,控制在70℃~80℃,反应1.5 ~2h后,在90℃保温反应1h;水解反应阶段,控制在92℃~95℃反应4h,CEPPA的产率可达91%,并解决了反应中易结块问题.

  7. Effect of temperature on the mechanism of actin polymerization.

    Science.gov (United States)

    Zimmerle, C T; Frieden, C

    1986-10-21

    The rate of the Mg2+-induced polymerization of rabbit skeletal muscle G-actin has been measured as as function of temperature at pH 8 by using various concentrations of Mg2+, Ca2+, and G-actin. A polymerization mechanism similar to that proposed at this pH [Frieden, C. (1983) Proc. Natl. Acad. Sci. U.S.A. 80, 6513-6517] was found to fit the data from 10 to 35 degrees C. From the kinetic data, no evidence for actin filament fragmentation was found at any temperature. Dimer formation is the most temperature-sensitive step, with the ratio of forward and reverse rate constants changing 4 orders of magnitude from 10 to 35 degrees C. Over this temperature change, all other ratios of forward and reverse rate constants change 7-fold or less, and the critical concentration remains nearly constant. The reversible Mg2+-induced isomerization of G-actin monomer occurs to a greater extent with increasing temperature, measured either by using N-(iodoacetyl)-N'-(5-sulfo-1-naphthyl)ethylenediamine-labeled actin or by simulation of the full-time course of the polymerization reaction. This is partially due to Mg2+ binding becoming tighter, and Ca2+ binding becoming weaker, with increasing temperature. Elongation rates from the filament-pointed end, determined by using actin nucleated by plasma gelsolin, show a temperature dependence slightly larger than that expected for a diffusion-limited reaction.

  8. Polymerization of Polar Monomers from a Theoretical Perspective

    KAUST Repository

    Alghamdi, Miasser

    2016-10-11

    Density functional theory calculations have been used to investigate catalytic mechanism of polymer formation containing polar groups, from the synthesis of the monomer to the synthesis of the macromolecule. In the spirit of a sustainable and green chemistry, we initially focused attention on the coupling of CO2 as economically convenient and recyclable C1 source with C2H4 to form acrylate and/or butirro-lactone, two important polar monomers. In this process formation of a mettallolactone via oxidative coupling of CO2 and C2H4 is an important intermediate. Given this background, we explored in detail (chapter-3) several Ni based catalysts for CO2 coupling with C2H4 to form acrylate. In this thesis we report on the competitive reaction mechanisms (inner vs outer sphere) for the oxidative coupling of CO2 and ethylene for a set of 11 Ni-based complexes containing bisphosphine ligands. In another effort, considering incorporation of a C=C bond into a metal-oxygen-Functional-Group moiety is a challenging step in several polymerization reactions, we explored the details of this reaction (chapter4) using two different catalysts that are capable to perform this reaction in the synthesis of heterocycles. Specifically, the [Rh]-catalyzed intramolecular alkoxyacylation ([Rh] = [RhI(dppp)+] (dppp, 1,3-Bis-diphenylphosphino-propane), and the [Pd]/BPh3 intramolecular alkoxyfunctionalizations. Rest of the thesis we worked on understanding the details of the polymerization of polar monomers using organocatalysts based on N-heterocyclic carbenes (NHC) or N-heterocyclic olefins (NHO). In particular (chapter-5) we studied the polymerization of N-methyl N-carboxy- anhydrides, towards cyclic poly(N-substituted glycine)s, promoted by NHC catalysts. In good agreement with the experimental findings, we demonstrated that NHC promoted ring opening polymerization of N-Me N-Carboxyanhydrides may proceed via two different catalytic pathways. In a similar effort we studied polymerization of

  9. SCATTERING FROM RAMIFIED POLYMERIC SYSTEMS

    Directory of Open Access Journals (Sweden)

    M.Benhamou

    2004-01-01

    Full Text Available Here, of great interest to us is a quantitative study of the scattering properties from ramified polymeric systems of arbitrary topology. We consider three types of systems, namely ramified polymers in solution, ramified polymer blends, or ternary mixtures made of two ramified polymers of different chemical nature immersed in a good solvent. To achieve the goal of the study, use is made of the Random Phase Approximation. First we determine the exact expression of the form factor of an ideal ramified polymer of any topology, from which we extract the exact expression of its gyration radius. Using the classical Zimm's formulae and the exact form factor, we determine all scattering properties of these three types of ramified polymeric systems. The main conclusion is that ramification of the chains induces drastic changes of the scattering properties.

  10. Magnetic properties of polymerized diphenyloctatetrayne

    Energy Technology Data Exchange (ETDEWEB)

    Beristain, Miriam F.; Jimenez-Solomon, Maria F.; Ortega, Alejandra; Escudero, Roberto [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-360, Ciudad Universitaria, Mexico DF 04510 (Mexico); Munoz, Eduardo [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, Apartado Postal 20-364, Ciudad Universitaria, Mexico DF 01000 (Mexico); Maekawa, Yasunari; Koshikawa, Hiroshi [High Performance Polymer Group, Quantum Beam Science Directorate, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Ogawa, Takeshi, E-mail: ogawa@unam.mx [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-360, Ciudad Universitaria, Mexico DF 04510 (Mexico)

    2012-10-15

    A new type of metal-free ferromagnetic carbon material was obtained by thermal polymerization and electron beam irradiation of diphenyloctatetrayne (DPOT). The isothermal magnetic measurements showed hysteresis loops indicating weak but intrinsic ferromagnetism with Curie temperatures of around 600 K. Electron spin resonance spectroscopy showed that the material contained stable free radicals in the range of 10{sup 17}-10{sup 20} radicals g{sup -1} depending on the polymerization process. The ferromagnetism should be due to high radical concentration although no correlation was observed between them. It was shown that an amorphous ferromagnetic carbon could be obtained from a simple crystalline solid by heating at moderate temperatures. Highlights: Black-Right-Pointing-Pointer Diphenyloctatetrayne as a precursor for carbon with high radical concentration. Black-Right-Pointing-Pointer The carbon material consists of sp{sup 2} configuration. Black-Right-Pointing-Pointer A weak intrinsic metal-free ferromagnetism was observed for the carbon products.

  11. Polymerization of liquid propylene with a 4th generation Ziegler-Natta catalyst-influence of temperature, hydrogen and monomer concentration and prepolymerization method on polymerization kinetics

    NARCIS (Netherlands)

    Pater, Jochem T.M.; Weickert, Günter; Swaaij, van Wim P.M.

    2002-01-01

    In a batch-wise operated autoclave reactor, liquid propylene was polymerized using a 4th generation, TiCl4/MgCl2/phthalate ester-AlEt3-R2Si(OMe)2, Ziegler-Natta catalyst system. By using a calorimetric principle it was possible to measure full reaction rate versus time curves for obtaining data on p

  12. Esterification with ethanol to produce biodiesel from high acidity raw materials. Kinetic studies and analysis of secondary reactions

    Energy Technology Data Exchange (ETDEWEB)

    Pisarello, M.L.; Dalla Costa, B.; Mendow, G.; Querini, C.A. [Instituto de Investigaciones en Catalisis y Petroquimica (INCAPE)-(FIQ-UNL, CONICET), Santiago del Estero 2654-Santa Fe, S3000AOJ (Argentina)

    2010-09-15

    In this work, the esterification reaction of free fatty acids (FFA) in sunflower oil, coconut oil and concentrated FFA, with ethanol, methanol and ethanol 96%, using homogeneous acid catalysts to produce biodiesel is studied. Kinetic parameters are estimated with a simplified model, and then used to predict the reaction behavior. Reactions other than the reversible esterification are considered to explain the behavior that this system displays. Such reactions are the triglycerides conversion by acid catalyzed transesterification and hydrolysis. In addition, we include kinetic studies of the reaction that occur between the sulphuric acid and methanol (or ethanol), forming mono and dialkylsulphates. This reaction produces water and consumes methanol (or ethanol), and consequently has a direct impact in the esterification reaction rate and equilibrium conversion. The concentration of sulphuric acid decreases to less than 50% of the initial value due to the reaction with the alcohol. A minimum in the acidity due to the free fatty acids as a function of time was clearly observed during the reaction, which has not been reported earlier. This behavior is related to the consecutive reactions that take place during the esterification of FFA in the presence of triglycerides. The phase separation due to the presence of water, which is generated during the reaction, is also studied. (author)

  13. Polymeric Microspheres for Medical Applications

    Directory of Open Access Journals (Sweden)

    Ketie Saralidze

    2010-06-01

    Full Text Available Synthetic polymeric microspheres find application in a wide range of medical applications. Among other applications, microspheres are being used as bulking agents, embolic- or drug-delivery particles. The exact composition of the spheres varies with the application and therefore a large array of materials has been used to produce microspheres. In this review, the relation between microsphere synthesis and application is discussed for a number of microspheres that are used for different treatment strategies.

  14. Controlled aniline polymerization strategies for polyaniline micro- and nano self-assembling into practical electronic devices.

    Science.gov (United States)

    Yunus, Sami; Attout, Anne; Bertrand, Patrick

    2009-02-03

    Electroless polymerization of aniline on platinum is investigated for polyaniline micro- and nanostructuring into practical electronic devices. This type of reaction is adapted to estimate its usefulness in a lithographic process. For practical electronic device fabrication, electroless polymerization of aniline can be used to electrically bridge initially independent platinum electrodes. As this application requires a polyaniline bridge to form over a nonconductive material before an electrical contact is obtained, polyaniline growth using chemical oxidative reaction is investigated on substrates presenting surface-tension contrast patterns.

  15. An unprecedented, tandem Aldol-Grob reaction sequence

    Energy Technology Data Exchange (ETDEWEB)

    Kabalka, G.W.; Tejedor, D.; Li, N.S.; Malladi, R.R.; Trotman, S. [Univ. of Tennessee, Knoxville, TN (United States)

    1998-09-18

    The authors report an unprecedented, tandem Aldol-Grob sequence involving the reaction of ketones with aromatic aldehydes in nonnucleophilic solvents in the presence of boron trifluoride. Although a detailed study of the reaction mechanism has not yet been completed, the consistent formation of (E)-alkene products, as well as the fact that aromatic aldehydes appear to be required, would point toward the intermediacy of a carbocation derivative. A reasonable mechanism would involve the formation of the mixed aldol followed by the formation and subsequent nonsynchronous ring opening of a lactol. The proposed fragmentation is reminiscent of two-step Grob fragmentations that have been reported for N-halo-{alpha}-amino acids and cyclobutane hemiacetals as well as the acid-catalyzed fragmentation of {beta}-hydroxy acetals. The authors examined the effect of various acids on the reaction sequence in order to ascertain which would be most efficient. They conclude that boron trifluoride is the most effective of the acids studied in achieving the new tandem condensation-cleavage sequence.

  16. Non-Isocyanate Polyurethane Soft Nanoparticles Obtained by Surfactant-Assisted Interfacial Polymerization.

    Science.gov (United States)

    Bossion, Amaury; Jones, Gavin O; Taton, Daniel; Mecerreyes, David; Hedrick, James L; Ong, Zhan Yuin; Yang, Yi Yan; Sardon, Haritz

    2017-02-28

    Polyurethanes (PUs) are considered ideal candidates for drug delivery applications due to their easy synthesis, excellent mechanical properties, and biodegradability. Unfortunately, methods for preparing well-defined PU nanoparticles required miniemulsion polymerization techniques with a nontrivial control of the polymerization conditions due to the inherent incompatibility of isocyanate-containing monomers and water. In this work, we report the preparation of soft PU nanoparticles in a one-pot process using interfacial polymerization that employs a non-isocyanate polymerization route that minimizes side reactions with water. Activated pentafluorophenyl dicarbonates were polymerized with diamines and/or triamines by interfacial polymerization in the presence of an anionic emulsifier, which afforded non-isocyanate polyurethane (NIPU) nanoparticles with sizes in the range of 200-300 nm. Notably, 5 wt % of emulsifier was required in combination with a trifunctional amine to achieve stable PU dispersions and avoid particle aggregation. The versatility of this polymerization process allows for incorporation of functional groups into the PU nanoparticles, such as carboxylic acids, which can encapsulate the chemotherapeutic doxorubicin through ionic interactions. Altogether, this waterborne synthetic method for functionalized NIPU soft nanoparticles holds great promise for the preparation of drug delivery nanocarriers.

  17. Simulation of nylon 6 polymerization in tubular reactors with recycle

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, S.K.; Kunzru, D.; Kumar, A.; Agarwal, K.K.

    1983-05-01

    In the hydrolytic polymerization of epsilon-caprolactam, the ring opening of the monomer is much slower than the polyaddition reaction. Hence, the mixing of aminocaproic acid to the feed results in a faster conversion of the monomer. Industrially, this fact is exploited by using a recycle stream. An isothermal plug flow reactor (PFR) with a recycle is simulated in this study, using two techniques: the method of successive substitutions and Wegstein's method. It is found that, under certain operating conditions, the use of a recycle stream gives higher monomer conversions and lower cyclic dimer concentrations than either a PFR or a homogeneous continuous flow stirred tank reactor (HCSTR), with the degree of polymerization almost the same as that obtained in an HCSTR, and thus offers a considerable advantage. However, when a recycle reactor is coupled with a subsequent flashing operation and a finishing reactor, these advantages are considerably reduced.

  18. Solid coatings deposited from liquid methyl methacrylate via Plasma Polymerization

    Science.gov (United States)

    Wurlitzer, Lisa; Maus-Friedrichs, Wolfgang; Dahle, Sebastian

    2016-09-01

    The polymerization of methyl methacrylate via plasma discharges is well known today. Usually, plasma-enhanced chemical vapor deposition (PECVD) is used to deposit polymer coatings. Solid coatings are formed out of the liquid phase from methyl methacrylate via dielectric barrier discharge. The formation of the coating proceeds in the gas and the liquid phase. To learn more about the reactions in the two phases, the coatings from MMA monomer will be compared to those from MMA resin. Finally, attenuated total reflection infrared spectroscopy, confocal laser scanning microscopy and X-ray photoelectron spectroscopy are employed to characterize the solid coatings. In conclusion, the plasma enhanced chemical solution deposition is compared to the classical thermal polymerization of MMA.

  19. Functional bio-based polyesters by enzymatic polymerization

    DEFF Research Database (Denmark)

    Daugaard, Anders Egede; Hoffmann, Christian; Andersen, Christian

    During recent years enzymatic polymerization has become increasingly popular as an alternative to classical polyesterification processes. The high regioselectivity observed for lipases permits preparation of novel polyesters with a high number of functional groups.1 This is particularly interesting...... polymerization was applied to prepare functional water soluble polyesters based on dimethyl itaconate and poly(ethyleneglycol).2 The monomer permits postfunctionalization using thiol-ene chemistry or aza-michael additions, which was used to illustrate the possibilites of preparing functional hydrogels. Hydrogels...... based on the polyesters were shown to be degradable and could be prepared either from the pure polyester or from prefunctionalized polyesters, though the thiol-ene reactions were found to be less effective. Since then a new monomer, trans-2,5-dihydroxy-3-pentenoic acid methyl ester (DPM) has been...

  20. Polymerization of phenols catalyzed by peroxidase in nonaqueous media

    Energy Technology Data Exchange (ETDEWEB)

    Dordick, J.S.; Marletta, M.A.; Klibanov, A.M.

    1987-01-01

    Polymers produced by horseradish-peroxidase-catalyzed coupling of phenols have been explored as potential substitutes for phenol-formaldehyde resins. To overcome low substrate solubilities and product molecular weights in water, enzymatic polymerizations in aqueous-organic mixtures have been examined. Peroxidase vigorously polymerizes a number of phenols in mixtures of water with water-miscible solvents such as dioxane, acetone, dimethylformamide, and methyl formate with the solvent content up to 95%. As a result, various phenolic polymers with average molecular weights from 400 to 2.6 x 10/sup 4/ D were obtained depending on the reaction medium composition and the nature of the phenol. Peroxidase-catalyzed copolymerization of different phenols in 85% dioxane was demonstrated. Poly(p-phenylphenol) and poly(p-cresol) were enzymatically prepared on a gram scale. They had much higher melting points, and in addition, poly(p-phenylphenol) was found to have a much higher electrical conductivity than phenol-formaldehyde resins.

  1. Kinetics of Vinyl Polymerization of Methyl Methacrylate Initiated by Ce(IV-Vanillin Redox System

    Directory of Open Access Journals (Sweden)

    M. Palanivelu

    2012-01-01

    Full Text Available The kinetics of polymerization of methyl methacrylate initiated by Ce(IV-Vanillin redox system was studied in aqueous solution of sulfuric acid at 40°C. The rate of polymerization (Rp and the reaction orders with respect to monomer, initiator and ligand have been determined and found to be 1.5, 0.5 and 0.5 respectively. The effect of concentration of sulfuric acid on the polymerization was also studied. The rate of polymerization was found to increase with increasing temperature 30–60°C and decreases at higher temperature (>60°C. The overall activation energy (Ea was found to be 36.7 kJ/mol. A suitable kinetic scheme has been proposed.

  2. Salicylaldimine Copper(II) complex catalyst: Pioneer for ring opening Polymerization of Lactide

    Indian Academy of Sciences (India)

    ANITA ROUTARAY; NIBEDITA NATH; TUNGABIDYA MAHARANA; PRATAP KUMAR SAHOO; JAYA PRAKASH DAS; ALEKHA KUMAR SUTAR

    2016-06-01

    Salicylaldimine copper complex has been synthesized and its reactivity for the ring-opening polymerization(ROP) of lactide has been studied. This monomeric copper complex was prepared by the reaction ofcopper(II) solution with one molar equivalent of salicylaldimine Schiff-base ligand in methanol under nitrogenatmosphere. This copper complex has been characterized by different spectroscopic methods, which showedsquare planar geometry. The molecular structure of the salicylaldimine Schiff-base has been determined byX-ray diffraction studies. The complex was tested as the initiator for the ring-opening polymerization of lactide,with variation in diamine group in ligand. The rate of polymerization is dependent on the diamine groupin the following order: ethylene > propylene > phenyl. The salicylaldimine copper complex allows controlledring-opening polymerization as indicated by the linear relationship between the percentage conversion and thenumber-average molecular weight. On the basis of literature reports, a mechanism for ROP of lactide has beenproposed.

  3. Highly Defined Multiblock Copolypeptoids: Pushing the Limits of Living Nucleophilic Ring-Opening Polymerization

    KAUST Repository

    Fetsch, Corinna

    2012-06-05

    Advanced macromolecular engineering requires excellent control over the polymerization reaction. Living polymerization methods are notoriously sensitive to impurities, which makes a practical realization of such control very challenging. Reversible-deactivation radical polymerization methods are typically more robust, but have other limitations. Here, we demonstrate by repeated (ge;10 times) chain extension the extraordinary robustness of the living nucleophilic ring-opening polymerization of N-substituted glycine N-carboxyanhydrides, which yields polypeptoids. We observe essentially quantitative end-group fidelity under experimental conditions that are comparatively easily managed. This is employed to synthesize a pentablock quinquiespolymer with high definition. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Surface-initiated atom transfer radical polymerization of methyl methacrylate from magnetite nanoparticles at ambient temperature.

    Science.gov (United States)

    Raghuraman, G K; Dhamodharan, R

    2006-07-01

    The synthesis of methyl methacrylate (MMA) brush from the surface of magnetite nanoparticles (core-shell structure), from initiator moieties anchored covalently to the nanoparticles, via room temperature atom transfer radical polymerization (ATRP) is described. The surface-initiated polymerization was carried out from a surface-confined initiator containing a 2-bromoisobutyrate moiety with Cu(I)Br/PMDETA catalytic system. The initiator moiety was covalently anchored to the nanoparticles via a two step modification reaction scheme. Controlled polymerization was observed if ethyl-2-bromoisobutyrate (2-EiBrB) was added as a free/sacrificial initiator. A linear increase of molecular weight and a narrow molecular weight distribution of the PMMA formed in solution, provide evidence for a controlled surface-initiated polymerization, leading to surface-attached polymer brushes under mild conditions. The grafted PMMA provides good stability and dispersibility for the nanoparticles in organic solvents.

  5. Synthesis of functional poly(disubstituted acetylene)s through the post-polymerization modification route.

    Science.gov (United States)

    Gao, Yuan; Wang, Xiao; Sun, Jing Zhi; Tang, Ben Zhong

    2015-04-01

    We report the recent progress in the preparation of functional poly(disubstituted acetylene)s (PDSAs) through post-polymerization modification routes. The metathesis polymerization of disubstituted acetylene monomers activated by Mo/W-Sn complex catalysts, which do not tolerate highly polar functionalities, was assumed to be a key step in the polymer synthetic procedures. We and other groups have explored several approaches to prepare PDSAs with latent reactive functionalities, which are inactive to Mo/W-Sn complex catalysts but can be used as highly reactive sites for post-polymerization modification. Click chemistry, Michael-type addition reactions, the use of activated esters and other strategies are demonstrated by recently published examples. These works indicate that post-polymerization modification is an efficient route to the synthesis of various functional PDSAs.

  6. Studies in reactive extrusion processing of biodegradable polymeric materials

    Science.gov (United States)

    Balakrishnan, Sunder

    Various reaction chemistries such as Polymerization, Polymer cross-linking and Reactive grafting were investigated in twin-screw extruders. Poly (1,4-dioxan-2-one) (PPDX) was manufactured in melt by the continuous polymerization of 1,4-dioxan-2-one (PDX) monomer in a twin-screw extruder using Aluminum tri-sec butoxide (ATSB) initiator. Good and accurate control over molecular weight was obtained by controlling the ratio of monomer to initiator. A screw configuration consisting of only conveying elements was used for the polymerization. The polymerization reaction was characterized by a monomer-polymer dynamic equilibrium, above the melting temperature of the polymer, limiting the equilibrium conversion to 78-percent. Near complete (˜100-percent) conversion was obtained on co-polymerizing PDX monomer with a few mol-percent (around 8-percent) Caprolactone (CL) monomer in a twin-screw extruder using ATSB initiator. The co-polymers exhibited improved thermal stability with reduction in glass transition temperature. The extruder was modeled as an Axial Dispersed Plug Flow Reactor for the polymerization of CL monomer using Residence Time Distribution (RTD) Analysis. The model provided a good fit to the experimental RTD and conversion data. Aliphatic and aliphatic-aromatic co-polyesters, namely Polycaprolactone (PCL) and Poly butylenes (adipate-co-terephthalate) (Ecoflex) were cross-linked in a twin-screw extruder using radical initiator to form micro-gel reinforced biodegradable polyesters. Cross-linked Ecoflex was further extrusion blended with talc to form blends suitable to be blown into films. A screw configuration consisting of conveying and kneading elements was found to be effective in dispersion of the talc particles (5--10 microns) in the polyester matrix. While the rates of crystallization increased for the talc filled polyester blends, overall crystallinity reduced. Mechanical, tear and puncture properties of films made using the talc filled polyester blends

  7. Ultrasound-Mediated Polymeric Micelle Drug Delivery.

    Science.gov (United States)

    Xia, Hesheng; Zhao, Yue; Tong, Rui

    2016-01-01

    The synthesis of multi-functional nanocarriers and the design of new stimuli-responsive means are equally important for drug delivery. Ultrasound can be used as a remote, non-invasive and controllable trigger for the stimuli-responsive release of nanocarriers. Polymeric micelles are one kind of potential drug nanocarrier. By combining ultrasound and polymeric micelles, a new modality (i.e., ultrasound-mediated polymeric micelle drug delivery) has been developed and has recently received increasing attention. A major challenge remaining in developing ultrasound-responsive polymeric micelles is the improvement of the sensitivity or responsiveness of polymeric micelles to ultrasound. This chapter reviews the recent advance in this field. In order to understand the interaction mechanism between ultrasound stimulus and polymeric micelles, ultrasound effects, such as thermal effect, cavitation effect, ultrasound sonochemistry (including ultrasonic degradation, ultrasound-initiated polymerization, ultrasonic in-situ polymerization and ultrasound site-specific degradation), as well as basic micellar knowledge are introduced. Ultrasound-mediated polymeric micelle drug delivery has been classified into two main streams based on the different interaction mechanism between ultrasound and polymeric micelles; one is based on the ultrasound-induced physical disruption of the micelle and reversible release of payload. The other is based on micellar ultrasound mechanochemical disruption and irreversible release of payload.

  8. Novel Reaction of N,N'-Bisarylmethanediamines with Formaldehyde. Synthesis of Some New 1,3,5-Triaryl-1,3,5-hexahydrotriazines

    Directory of Open Access Journals (Sweden)

    Abolfazl Olyaei

    2006-07-01

    Full Text Available The acid-catalyzed cyclocondensation of N,N'-bisaryl (aryl = 2-pyrimidinyl, 2- pyrazinyl and 4-nitrophenyl methanediamines 5a-c with aqueous formaldehyde in refluxing acetonitrile leads to the formation of the corresponding 1,3,5-triaryl-1,3,5-hexa- hydrotriazines 6a-c. The stoichiometric reactions of 2-aminopyrimidine and 2-amino- pyrazine with aqueous formaldehyde in acetonitrile under reflux conditions also afforded 6a and 6b, respectively. Treatment of 2-aminopyrimidine with aqueous formaldehyde in a 3:2 ratio yielded N,N',N"-tris(2-pyrimidinyldimethylenetriamine (7a as a sole product, which upon subsequent reaction with formaldehyde also afforded 6a. The reaction of N,N'-biphenylmethanediamine with formaldehyde was also investigated.

  9. Investigation of Four Different Laponite Clays as Stabilizers in Pickering Emulsion Polymerization.

    Science.gov (United States)

    Brunier, Barthélémy; Sheibat-Othman, Nida; Chniguir, Mehdi; Chevalier, Yves; Bourgeat-Lami, Elodie

    2016-06-21

    Clay-armored polymer particles were prepared by emulsion polymerization in the presence of Laponite platelets that adsorb at the surface of latex particles and act as stabilizers during the course of the polymerization. While Laponite RDS clay platelets are most often used, the choice of the type of clay still remains an open issue that is addressed in the present article. Four different grades of Laponite were investigated as stabilizers in the emulsion polymerization of styrene. First, the adsorption isotherms of the clays, on preformed polystyrene particles, were determined by ICP-AES analysis of the residual clay in the aqueous phase. Adsorption of clay depended on the type of clay at low concentrations corresponding to adsorption as a monolayer. Adsorption of clay particles as multilayers was observed for all the grades above a certain concentration under the considered ionic strength (mainly due to the initiator ionic species). The stabilization efficiency of these clays was investigated during the polymerization reaction (free of any other stabilizer). The clays did not have the same effect on stabilization, which was related to differences in their compositions and in their adsorption isotherms. The different grades led to different polymer particles sizes and therefore to different polymerization reaction rates. Laponite RDS and S482 gave similar results, ensuring the best stabilization efficiency and the fastest reaction rate; the number of particles increased as the clay concentration increased. Stabilization with Laponite XLS gave the same particles size and number as the latter two clays at low clay concentrations, but it reached an upper limit in the number of nucleated polymer particles at higher concentrations indicating a decrease of stabilization efficiency at high concentrations. Laponite JS did not ensure a sufficient stability of the polymer particles, as the polymerization results were comparable to a stabilizer-free polymerization system.

  10. PHOTOSENSITIVITY OF CERIC ION INITIATED ACRYLAMIDE POLYMERIZATION

    Institute of Scientific and Technical Information of China (English)

    DONG Jianhua; QIU Kunyuan; FENG Xinde

    1992-01-01

    Polymerization of acrylamide initiated by ceric ammonium nitrate alone has been studied in aqueous medium. The effects of UV light irradiation on the initial rates of polymerization, the activation energy and on the polymer molecular weights have been investigated. Compared with that in the dark, the rate of polymerization under UV light was accelerated to eleven times higher, and the overall activation energy was lowered markedly.

  11. POLYMERIZATION OF ETHYLENE WITH UNSYMMETRIC 2,6-BIS(IMINO)PYRIDINE IRON(Ⅱ) COMPLEX

    Institute of Scientific and Technical Information of China (English)

    Zhi Ma; Wen-hua Sun; Zi-long Li; Chang-xing Shao; You-liang Hu

    2002-01-01

    An unsymmetric 2,6-bis(imino)pyridine iron(Ⅱ) complex 1' was synthesized. The relationship between catalyst structure and its activity in ethylene polymerization is discussed. The kinetic behavior of ethylene polymerization and the effects of polymerization conditions such as temperature, aluminum/iron molar ratio on the activity of catalyst and the characteristics of polyethylene were reported. The unsymmetric catalyst 1' has a good catalytic performance of 3.47 ×106 gPE @ mol-1 @ Fe @ h-1 at 40℃ with aluminum/iron molar ratio = 2500. A dependence of catalyst activity on the methylaluminoxane (MAO) concentration and reaction temperature was found. The molecular weight (MW) of polyethylene with broad dispersity is about 104-105 g/mol. The melting temperature and branching of polyethylenes vary with changing reaction temperature and aluminum/iron molar ratio.

  12. Romp as a versatile method for the obtention of differentiated polymeric materials

    Directory of Open Access Journals (Sweden)

    Valdemiro P. Carvalho Jr.

    2012-01-01

    Full Text Available Ring Opening Metathesis Polymerization (ROMP of cyclic olefins is a powerful transition metal-catalyzed reaction for syntheses of polymers and copolymers. The key feature of this reaction is the [2+2]-cycloaddition mechanism, with retention of the olefinic unsaturation in the polymer chain and occurrence of living polymerization. With the development of metal-carbene type catalysts for this process, many addressed polymeric materials have been successfully prepared to be employed in several fields of the science and technology. This review summarizes recent examples of syntheses of polymers with amphiphilic features such as block, graft, brush or star copolymers; as well syntheses of biomaterials, dendronized architectures, photoactive polymers, cross-linked or self-healing materials, and polymers from renewed supplies.

  13. Charge transport in polymeric transistors

    Directory of Open Access Journals (Sweden)

    Alberto Salleo

    2007-03-01

    Full Text Available Polymeric semiconductors have attracted much attention because of their possible use as active materials in printed electronics. Thin-film transistors (TFTs are a convenient tool for studying charge-transport physics in conjugated polymers. Two families of materials are reviewed here: fluorene copolymers and polythiophenes. Because charge transport is highly anisotropic in molecular conductors, the electrical properties of conjugated polymers are strongly dependent on microstructure. Molecular weight, polydispersity, and regioregularity all affect morphology and charge-transport in these materials. Charge transport models based on microstructure are instrumental in identifying the electrical bottlenecks in these materials.

  14. Directional Growth of Polymeric Nanowires

    Science.gov (United States)

    Thapa, Prem; Flanders, Bret

    2009-03-01

    This work establishes an innovative electrochemical approach to the template free growth of conducting polypyrrole and polythiophene wires. These polymeric wires exhibit a knobby structure, but persistent growth in a given direction up to 30 μm in length. A long-range component of the applied voltage signal defines the growth-path. Moreover, the presence of this component enables the growth of amorphous nanowires with wire-like geometries. Such wires are employed in a non-invasive methodology for attaining strong mechanical attachments to live cells. This capability is of potential use in the electro-mechanical probing of cell physiological processes.

  15. Marketing NASA Langley Polymeric Materials

    Science.gov (United States)

    Flynn, Diane M.

    1995-01-01

    A marketing tool was created to expand the knowledge of LaRC developed polymeric materials, in order to facilitate the technology transfer process and increase technology commercialization awareness among a non-technical audience. The created brochure features four materials, LaRC-CP, LaRC-RP46, LaRC-SI, and LaRC-IA, and highlights their competitive strengths in potential commercial applications. Excellent opportunities exist in the $40 million per year microelectronics market and the $6 billion adhesives market. It is hoped that the created brochure will generate inquiries regarding the use of the above materials in markets such as these.

  16. Preparing polymeric biomaterials using "click" chemistry techniques

    Science.gov (United States)

    Lin, Fei

    Significant efforts have been focused on preparing degradable polymeric biomaterials with controllable properties, which have the potential to stimulate specific cellular responses at the molecular level. Click reactions provide a universal tool box to achieve that goal through molecular level design and modification. This dissertation demonstrates multiple methodologies and techniques to develop advanced biomaterials through combining degradable polymers and click chemistry. In my initial work, a novel class of amino acid-based poly(ester urea)s (PEU) materials was designed and prepared for potential applications in bone defect treatment. PEUs were synthesized via interfacial polycondensation, and showed degradability in vivo and possessed mechanical strength superior to conventionally used polyesters. Further mechanical enhancement was achieved after covalent crosslinking with a short peptide crosslinker derived from osteogenic growth peptide (OGP). The in vitro and in an in vivo subcutaneous rat model demonstrated that the OGP-based crosslinkers promoted proliferative activity of cells and accelerated degradation properties of PEUs. As a continuous study, extra efforts were focused on the development of PEUs with functional pendant groups, including alkyne, azide, alkene, tyrosine phenol, and ketone groups. PEUs with Mw exceeding to 100K Da were obtained via interfacial polycondensation, and the concentration of pendent groups was varied using a copolymerization strategy. Electrospinning was used to fabricate PEU nanofiber matrices with mechanical strengths suitable for tissue engineering. A series of biomolecules were conjugated to nanofiber surface following electrospinning using click reactions in aqueous media. The ability to derivatize PEUs with biological motifs using high efficient chemical reactions will significantly expand their use in vitro and in vivo. Based on similar principles, a series of mono- and multifunctionalized polycaprolactone (PCL

  17. Kinetics of vinyl acetate emulsion polymerization in a pulsed tubular reactor: comparison between experimental and simulation results

    Directory of Open Access Journals (Sweden)

    Sayer C.

    2002-01-01

    Full Text Available A new reactor, the pulsed sieve plate column (PSPC, was developed to perform continuous emulsion polymerization reactions. This reactor combines the enhanced flexibility of tubular reactors with the mixing behavior provided by sieved plates and by the introduction of pulses that is important to prevent emulsion destabilization. The main objective of this work is to study the kinetics of vinyl acetate (VA emulsion polymerization reactions performed in this PSPC. Therefore, both experimental studies and reaction simulations were performed. Results showed that it is possible to obtain high conversions with rather low residence times in the PSPC.

  18. Effect of Polymerization Condition on Particle Size Distribution in St/BA/MAA Emulsion Polymerization Process

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A series of St/BA/MAA emulsion polymerizations was carried out. By using PCS (photon correlation spectroscopy), the particle size distribution(PSD) of the whole St/BA/MAA emulsion polymerization process was gotten easily and quickly. The effect of polymerization condition on PSD in St/BA/MAA emulsion process was discussed.

  19. Transition metal-free olefin polymerization catalyst

    Science.gov (United States)

    Sen, Ayusman; Wojcinski, II, Louis M.; Liu, Shengsheng

    2001-01-01

    Ethylene and/or propylene are polymerized to form high molecular weight, linear polymers by contacting ethylene and/or propylene monomer, in the presence of an inert reaction medium, with a catalyst system which consists essentially of (1) an aluminum alkyl component, such as trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-octylaluminum and diethylaluminum hydride and (2) a Lewis acid or Lewis acid derivative component, such as B (C.sub.6 F.sub.5).sub.3, [(CH.sub.3).sub.2 N (H) (C.sub.6 H.sub.5)].sup.+ [B (C.sub.6 F.sub.5)4].sup.-, [(C.sub.2 H.sub.5).sub.3 NH].sup.+ [B C.sub.6 F.sub.5).sub.4 ],.sup.-, [C(C.sub.6 F.sub.5).sub.3 ].sup.+ [B(C.sub.6 F.sub.5).sub.4 ].sup.-, (C.sub.2 H.sub.5).sub.2 Al(OCH.sub.3), (C.sub.2 H.sub.5).sub.2 Al(2,6-di-t-butyl-4-methylphenoxide), (C.sub.2 H.sub.5)Al(2,6 -di-t-butylphenoxide).sub.2, (C.sub.2 H.sub.5).sub.2 Al(2,6-di-t-butylphonoxide) , 2,6 -di-t-butylphenol.multidot.methylaluminoxane or an alkylaluminoxane, and which may be completely free any transition metal component(s).

  20. Polymeric Biodegradable Stent Insertion in the Esophagus

    Directory of Open Access Journals (Sweden)

    Kai Yang

    2016-04-01

    Full Text Available Esophageal stent insertion has been used as a well-accepted and effective alternative to manage and improve the quality of life for patients diagnosed with esophageal diseases and disorders. Current stents are either permanent or temporary and are fabricated from either metal or plastic. The partially covered self-expanding metal stent (SEMS has a firm anchoring effect and prevent stent migration, however, the hyperplastic tissue reaction cause stent restenosis and make it difficult to remove. A fully covered SEMS and self-expanding plastic stent (SEPS reduced reactive hyperplasia but has a high migration rate. The main advantage that polymeric biodegradable stents (BDSs have over metal or plastic stents is that removal is not require and reduce the need for repeated stent insertion. But the slightly lower radial force of BDS may be its main shortcoming and a post-implant problem. Thus, strengthening support of BDS is a content of the research in the future. BDSs are often temporarily effective in esophageal stricture to relieve dysphagia. In the future, it can be expect that biodegradable drug-eluting stents (DES will be available to treat benign esophageal stricture, perforations or leaks with additional use as palliative modalities for treating malignant esophageal stricture, as the bridge to surgery or to maintain luminal patency during neoadjuvant chemoradiation.

  1. Enzyme-Catalyzed Polymerization of Beta-alanine Esters, A Sustainable Route Towards the Formation of Poly-Beta-alanine

    NARCIS (Netherlands)

    Steunenberg, P.; Uiterweerd, M.; Sijm, M.; Scott, E.L.; Zuilhof, H.; Sanders, J.P.M.; Franssen, M.C.R.

    2013-01-01

    The synthesis of poly-ß-alanine by a lipase catalyzed polycondensation reaction between ß-alanine esters is reported. The effect of different solvents, reaction temperatures and substrate/enzyme concentrations on polymer yield and degree of polymerization (DP) was determined. Also the effect of meth

  2. Synthesis of Thiourea Derivatives on Soluble Polymeric Support

    Institute of Scientific and Technical Information of China (English)

    YANG,Gui-Chun(杨桂春); CHEN,Zu-Xing(陈祖兴); ZHANG,Zhao-Jun(张照军)

    2002-01-01

    A modified poly(ethylene glycol) ( PEG ) has been developed as the soluble polymeric supports for liquid phase synthesis of novel thiourea derivatives. In each step of the sequence, the PEG-bound products were precipitated in cold Et2O and the unreacted materials and by-products were removed by simple filtration. The progress of reaction, purity of the isolation and the structure of the PEG-bound products were easily monitored by TLC, IR and 1H NMR spectra. Representative thiourea derivatives were obtained in moderate yields with excellent purity from this modified PEG-bound product by the cleavage with 50% TFA/H2O.

  3. Electrochemical Polymerization of Methylene Green

    Institute of Scientific and Technical Information of China (English)

    ZHU,Hong-Ping; MU,Shao-Lin

    2001-01-01

    The electrochemical polymerization of methylene green has been carried out using cyclic voltammetry. The electrolytic so lution consisted of 4 × 10-3 mol/L methylene green, 0.1 mol/L NaNO3 and 1 × 10-2 mol/L sodium tetraborate with pH 11.0. The temperature for polymerization is controlled at 60℃. The scan potential is set between -0.2 and 1.2 V (vs. Ag/AgCl with saturated KCl solution). There are an anodic peak and a cathodic peak on the cyclic voltammogram of poly(methylene green) at pH≤3.8. Both peak potentials shift towards nega tive potentials with increasing pH value, and their peak cur rents decrease with increasing pH value. Poly(methylene green) has a good electrochemical activity and stability in aqueous solutions with pH ≤ 3.8. The UV-Visible spectrum and FTIR spectrum of poly (methylene green) are different from those of methylene green.

  4. Schlenk Techniques for Anionic Polymerization

    KAUST Repository

    Ratkanthwar, Kedar

    2015-09-01

    Anionic polymerization-high vacuum techniques (HVTs) are doubtlessly the most prominent and reliable experimental tools to prepare polymer samples with well-defined and, in many cases, complex macromolecular architectures. Due to the high demands for time and skilled technical personnel, HVTs are currently used in only a few research laboratories worldwide. Instead, most researchers in this filed are attracted to more facile Schlenk techniques. The basic principle of this technique followed in all laboratories is substantially the same, i.e. the use of alternate vacuum and inert gas atmosphere in glass apparatus for the purification/charging of monomer, solvents, additives, and for the manipulation of air-sensitive compounds such as alkyl metal initiators, organometallic or organic catalysts. However, it is executed quite differently in each research group in terms of the structure of Schlenk apparatus (manifolds, connections, purification/storage flasks, reactors, etc.), the use of small supplementary devices (soft tubing, cannulas, stopcocks, etc.) and experimental procedures. The operational methods are partly purpose-oriented while also featured by a high flexibility, which makes it impossible to describe in detail each specific one. In this chapter we will briefly exemplify the application of Schlenk techniques for anionic polymerization by describing the performance of a few experiments from our own work.

  5. Partitioning of Laponite Clay Platelets in Pickering Emulsion Polymerization.

    Science.gov (United States)

    Brunier, Barthélémy; Sheibat-Othman, Nida; Chevalier, Yves; Bourgeat-Lami, Elodie

    2016-01-12

    Partitioning of laponite disklike clay platelets between polymer particles and bulk aqueous phase was investigated in Pickering surfactant-free emulsion polymerization of styrene. Adsorption of laponite clay platelets plays an important role in the stabilization of this system, influencing the particle size and the number of particles, and, hence, the reaction rate. Adsorption isotherms show that, while the laponite clay platelets are almost fully exfoliated in water, they form multilayers on the surface of the polymer particles by the end of polymerization, as confirmed by transmission electron microscopy (TEM). This observation is supported by quartz crystal microbalance, conductivity, and TEM measurements, which reveal interactions between the clay and polystyrene, as a function of the ionic strength. The strong adsorption of clay platelets leaves a low residual concentration in the aqueous phase that cannot cause further nucleation of polymer particles, as demonstrated during seeded emulsion polymerization experiments in the presence of a high excess of clay. A Brunauer-Emmett-Teller (BET)-type model for laponite adsorption on polystyrene particles matches the adsorption isotherms.

  6. Morphological control of conductive polymers utilized electrolysis polymerization technique: trial of fabricating biocircuit.

    Science.gov (United States)

    Onoda, Mitsuyoshi

    2014-10-01

    Conductive polymers are a strong contender for making electronic circuits. The growth pattern in conductive polymer synthesis by the electrolysis polymerization method was examined. The growth pattern is deeply related to the coupling reaction of the radical cation and the deprotonation reaction following it and changes suddenly depending on the kind and concentration of the supporting electrolyte and the solvent used. That is, when the electrophilic substitution coupling reaction becomes predominant, the three-dimensional growth form is observed, and when the radical coupling reaction becomes predominant, the two-dimensional growth morphology is observed. In addition, the growth pattern can be comparatively easily controlled by changing the value of the polymerization constant current, and it is considered that the indicator and development for biocircuit research with neuron-type devices made of conjugated polymers was obtained.

  7. QSRR correlation of free-radical polymerization chain-transfer constants for styrene.

    Science.gov (United States)

    Ignatz-Hoover, F; Petrukhin, R; Karelson, M; Katritzky, A R

    2001-01-01

    Quantitative structure-reactivity relationships (QSRR) are deduced for kinetic chain-transfer constants for 90 agents on styrene polymerization at 60 degrees C. Three- and five-parameter correlations were obtained with R2 of 0.725 and 0.818, respectively. The descriptors involved in the correlations are consistent with the proposed mechanism of the chain-transfer reactions.

  8. Radical polymerization by a supramolecular catalyst: cyclodextrin with a RAFT reagent

    Directory of Open Access Journals (Sweden)

    Kohei Koyanagi

    2016-11-01

    Full Text Available Supramolecular catalysts have received a great deal of attention because they improve the selectivity and efficiency of reactions. Catalysts with host molecules exhibit specific reaction properties and recognize substrates via host–guest interactions. Here, we examined radical polymerization reactions with a chain transfer agent (CTA that has α-cyclodextrin (α-CD as a host molecule (α-CD-CTA. Prior to the polymerization of N,N-dimethylacrylamide (DMA, we investigated the complex formation of α-CD with DMA. Single X-ray analysis demonstrated that α-CD includes DMA inside its cavity. When DMA was polymerized in the presence of α-CD-CTA using 2,2'-azobis[2-(2-imidazolin-2-ylpropane dihydrochloride (VA-044 as an initiator in an aqueous solution, poly(DMA was obtained in good yield and with narrow molecular weight distribution. In contrast, the polymerization of DMA without α-CD-CTA produced more widely distributed polymers. In the presence of 1,6-hexanediol (C6 diol which works as a competitive molecule by being included in the α-CD cavity, the reaction yield was lower than that without C6 diol.

  9. Stereoselective synthesis of 3,3-diarylacrylonitriles as tubulin polymerization inhibitors.

    Science.gov (United States)

    Fang, Zhenglai; Song, Yunlong; Sarkar, Taradas; Hamel, Ernest; Fogler, William E; Agoston, Gregory E; Fanwick, Phillip E; Cushman, Mark

    2008-06-06

    A series of 3,3-diarylacrylonitriles were synthesized stereoselectively as tubulin polymerization inhibitors for potential use in cancer chemotherapy. This synthetic route features stannylcupration and palladium-catalyzed Stille cross-coupling chemistry, allowing both E and Z isomers of 3,3-diarylacrylonitriles to be prepared in a very short sequence of reactions.

  10. Modeling of branching density and branching distribution in low-density polyethylene polymerization

    NARCIS (Netherlands)

    Kim, D.M.; Iedema, P.D.

    2008-01-01

    Low-density polyethylene (ldPE) is a general purpose polymer with various applications. By this reason, many publications can be found on the ldPE polymerization modeling. However, scission reaction and branching distribution are only recently considered in the modeling studies due to difficulties i

  11. Thermally Self-Healing Polymeric Materials : The Next Step to Recycling Thermoset Polymers?

    NARCIS (Netherlands)

    Zhang, Youchun; Broekhuis, Antonius A.; Picchioni, Francesco

    2009-01-01

    We developed thermally self-healing polymeric materials on the basis of furan-functionalized, alternating thermosetting polyketones (PK-furan) and bis-maleimide by using the Diels-Alder (DA) and Retro-Diels-Alder (RDA) reaction sequence. PK-furan can be easily obtained under mild conditions by the P

  12. A new multifunctional initiator system for the living cationic polymerization of vinyl ethers

    NARCIS (Netherlands)

    Zhang, Xiaochun; Goethals, Eric J.; Loontjens, Ton; Derks, Frank

    2000-01-01

    Combination of hexa(chloromethyl)melamine (HCMM) and zinc chloride was found to be a multifunctional initiator system for the living cationic polymerization of isobutyl vinyl ether. HCMM was synthesized by reaction of hexa(methoxymethyl)melamine and boron trichloride. Characterization of the polymer

  13. Free radical suspension polymerization kinetics of styrene up to high conversion

    NARCIS (Netherlands)

    Tefera, Nurelegne; Weickert, Günter; Bloodworth, Robert; Schweer, Johannes

    1994-01-01

    Styrene was polymerized using different amounts of azoisobutyronitrile as initiator at temperatures of 70°C, 75°C and 80°C in suspension. The course of reaction up to almost complete conversion was modeled within a classical kinetic framework. Optimal simultaneous descriptions of both conversion and

  14. INTERACTIONS BETWEEN KETONES AND AMINES IN PHOTOINITIATING SYSTEMS USED FOR RADICAL POLYMERIZATION

    Institute of Scientific and Technical Information of China (English)

    WU Shikang; FOUASSIER ,J. P.

    1990-01-01

    Time resolved laser spectroscopy and GC/MS were used to investigate the primary processes and the side reactions occurring in benzophenone and chlorothioxanthone/amine systems used as photoinitiators of radical polymerization. The discrepancy observed between the experimental data and the expected behaviour is accounted for by detrimental chemicalreaction involving the ketone triplet state, the ketyl radical and the amine - derived radical.

  15. Hydrolysis of 4-Acetoxystyrene Polymers Prepared by Atom Transfer Radical Polymerization

    DEFF Research Database (Denmark)

    Chen, Xianyi; Jankova, Katja; Kops, Jørgen

    1999-01-01

    Hydrolysis of 4-acetoxystyrene polymers prepared by atom transfer radical polymerization was carried out under various reaction conditions. It was found that hydrazinolysis of 4-acetoxystyrene homopolymers, random and block copolymers with styrene in 1,4-dioxane, afforded the corresponding narrow...

  16. Metal-catalyzed simultaneous chain- and step-growth radical polymerization: marriage of vinyl polymers and polyesters.

    Science.gov (United States)

    Mizutani, Masato; Satoh, Kotaro; Kamigaito, Masami

    2010-06-02

    All polymerization reactions are categorized into two large different families, chain- and step-growth polymerizations, which are typically incompatible. Here, we report the simultaneous chain- and step-growth polymerization via the metal-catalyzed radical copolymerization of conjugated vinyl monomers and designed monomers possessing unconjugated C horizontal lineC and active C-Cl bonds. Especially, almost ideal linear random copolymers containing both vinyl polymer and polyester units in a single polymer chain were formed by the CuCl/1,1,4,7,10,10-hexamethyltriethylenetetramine- or RuCp*Cl(PPh(3))(2)-catalyzed copolymerization of methyl acrylate (MA) for the chain-growth polymerization and 3-butenyl 2-chloropropionate (1) for the step-growth polymerization. In contrast, other transition metal catalysts, such as CuCl with tris[2-(dimethylamino)ethyl]amine or N,N,N',N'',N''-pentamethyldiethylenetriamine and FeCl(2)/PnBu(3), resulted in branched structures via the concomitant chain-growth copolymerization of 1 with MA. The polymerization mechanism was studied in detail by NMR and MALDI-TOF-MS analyses of the polymerizations as well as the model reactions. Furthermore, a series of copolymers changing from random to multiblock polymer structures were obtained by varying the feed ratios of the two monomers. These copolymers can be easily degraded into lower molecular weight oligomers or polymers via methanolysis of the ester-linkages in the main chain using sodium carbonate.

  17. POLYMERIC NANOPARTICLES FROM SUPERCRITICAL CO2 MICROEMULSION POLYMERIZATION

    Institute of Scientific and Technical Information of China (English)

    Wei-jun Ye; Jason S. Keiper; Joseph M. DeSimone

    2006-01-01

    Herein, we reported the microemulsion polymerization in supercritical carbon dioxide. With the aid of an anionic phosphate fluorosurfactant (bis-[2-(F-hexyl)ethyl]phosphate sodium), water-soluble/CO2-insoluble acryloxyethyltrimethyl ammonium chloride monomer and N,N'-methylene-bisacrylamide cross-linker were solubilized into CO2 continuous phase via the formation of water-in-CO2 (w/c) microemulsion water pools. Initiated by a CO2-soluble initiator, 2,2'-azo-bisisobutyronitrile (AIBN), cross-linked poly(acryloxyethyltrimethyl ammonium chloride) particles were produced and stabilized in these w/c internal water pools. Nano-sized particles with sizes less than 20 nm in diameter and narrow particle size distributions were obtained.

  18. Three-dimensional microfabrication using two-photon polymerization

    Science.gov (United States)

    Cumpston, Brian H.; Ehrlich, Jeffrey E.; Kuebler, Stephen M.; Lipson, Matthew; Marder, Seth R.; McCord-Maughon, D.; Perry, Joseph W.; Roeckel, Harold; Rumi, Maria Cristina

    1998-09-01

    Photopolymerization initiated by the simultaneous absorption of two photons is unique in its ability to produce complex three-dimensional (3D) structures from a single, thick photopolymer film. Strong 3D confinement of the polymerization process is not possible in other polymer microfabrication techniques such as LIGA, rapid prototyping, and conventional photoresist technology. Two-photon polymerization also permits the fabrication of 3D structures and the definition of lithographic features on non-planar surfaces. We have developed a wide array of chromophores which hold great promise for 3D microfabrication, as well as other applications, such as two-photon fluorescence imaging and 3D optical data storage. These materials are based on a donor- (pi) -donor, donor-acceptor-donor, or acceptor-donor-acceptor structural motif. The magnitude of the two-photon absorption cross-section, (delta) , and the position of the two-photon absorption maximum, (lambda) (2)max, can be controlled by varying the length of the conjugated bridge and by varying the strength of the donor/acceptor groups. In this way, chromophores have been developed which exhibit strong two- photon absorption in the range of 500 - 975 nm, in some cases as high as 4400 X 10-50 cm4 s/photon-molecule. In the case of donor-(pi) -donor structures, quantum-chemical calculations show that the large absorption cross-sections arise from the symmetric re-distribution of charge from the donor end-groups to the conjugated bridge, resulting in an electronic excited-state which is more delocalized than the ground state. For many of these molecules, two-photon excitation populates a state which is sufficiently reducing that a charge transfer reaction can occur with acrylate monomers. The efficiency of these processes can be described using Marcus theory. Under suitable conditions, such reactions can induce radical polymerization of acrylate resins. Polymerization rates have been measured, and we show that these two

  19. Role of a waste-derived polymeric biosurfactant in the sol-gel synthesis of nanocrystalline titanium dioxide

    OpenAIRE

    Boffa, Vittorio; Perrone, Daniele G.; MAGNACCA, Giuliana; Montoneri, Enzo

    2014-01-01

    An inexpensive polymeric biosurfactant isolated from urban bio-wastes is shown to be a useful chemical aid in the synthesis of nanostructured materials with tunable pore size and surface hydrophilicity. Photocatalytic active TiO2 powders were prepared by sol–gel reaction in the presence of variable amounts of a waste-derived polymeric biosurfactant. The products were characterized for morphology, crystal structures and surface hydrophilicity. The porosity data indicate that an increase of the...

  20. RADICAL POLYMERIZATION OF N, N-DI(2-2 '-METHYL-ACRYLOYLOXY-PROPYL) -PARA-TOLUIDINE FUNCTIONAL MONOMER

    Institute of Scientific and Technical Information of China (English)

    QIU Kunyuan; FU Jie

    1989-01-01

    Functional monomer ( MP )2PT having tertiary aromatic amino group was systhesized from the reaction of N, N-di ( 2 -hydroxypropyl )-p-toluidine with 2-methyl acryloyl chloride. In the presence of organic peroxide, the radical polymerization of ( MP )2PT in toluene took place. The kinetics of ( MP )2PT polymerization and the ESR spectra ofLPO-( MP )2PT-MNP systems were determined respectively.

  1. Rapid "one-pot" preparation of polymeric monolith via photo-initiated thiol-acrylate polymerization for capillary liquid chromatography.

    Science.gov (United States)

    Bai, Jingyao; Wang, Hongwei; Ou, Junjie; Liu, Zhongshan; Shen, Yehua; Zou, Hanfa

    2016-06-21

    A facile approach was exploited for fast preparation of polymer-based monoliths in UV-transparent fused-silica capillaries via "one-pot" photo-initiated thiol-acrylate polymerization reaction of dipentaerythritolpenta-/hexaacrylate (DPEPA) and 1-octadecanethiol (ODT) in the presence of porogenic solvents (1-butanol and ethylene glycol). Due to relative insensitivity of oxygen inhibition in thiol-ene free-radical polymerization, the polymerization could be performed within 5 min. The effects of composition of prepolymerization solution on the morphology and permeability of poly(ODT-co-DPEPA) monoliths were investigated in detail by adjusting the content of monomer and binary porogen ratio. The physical properties of poly(ODT-co-DPEPA) monoliths were characterized by Fourier transform infrared spectroscopy (FT-IR), mercury intrusion porosimetry (MIP) and nitrogen adsorption/desorption measurement. The evaluation of chromatographic performance was carried out by capillary liquid chromatography (cLC). The results indicated that the poly(ODT-co-DPEPA) monolith was homogeneous and permeable, and also possessed a typical reversed-phase retention mechanism in cLC with high efficiency (∼75,000 N m(-1)) for separation of alkylbenzenes. Eventually, the further separation of tryptic digest of proteins by cLC tandem mass spectrometry (cLC-MS/MS) demonstrated its potential in the analysis of biological samples.

  2. Polymerization of 5-alkyl δ-lactones catalyzed by diphenyl phosphate and their sequential organocatalytic polymerization with monosubstituted epoxides

    KAUST Repository

    Zhao, Junpeng

    2015-02-04

    Organocatalytic ring-opening polymerization (ROP) reactions of three renewable 5-alkyl δ-lactones, namely δ-hexalactone (HL), δ-nonalactone (NL) and δ-decalactone (DL), using diphenyl phosphate (DPP) were investigated. Room temperature, together with a relatively high monomer concentration (≥3 M), was demonstrated to be suitable for achieving a living ROP behavior, a high conversion of the lactone, a controlled molecular weight and a low dispersity of the polyester. HL, containing a 5-methyl substituent, showed a much higher reactivity (polymerization rate) and a slightly higher equilibrium conversion than the compounds with longer alkyl substituents (NL and DL). The effectiveness of DPP-catalyzed ROP of 5-alkyl δ-lactones facilitated the one-pot performance following the t-BuP4-promoted ROP of monosubstituted epoxides. It has been shown in an earlier study that substituted polyethers acted as "slow initiators" for non-substituted lactones. However, efficient initiations were observed in the present study as substituted lactones were polymerized from the substituted polyethers. Therefore, this reinforces the previously developed "catalyst switch" strategy, making it a more versatile tool for the synthesis of well-defined polyether-polyester block copolymers from a large variety of epoxide and lactone monomers. © The Royal Society of Chemistry 2015.

  3. Inflation and Instability of a Polymeric Membrane

    DEFF Research Database (Denmark)

    Hassager, Ole; Kristensen, Susanne Brogaard; Larsen, Johannes Ruben

    1999-01-01

    We consider an axisymmetric polymeric membrane inflated by a uniform pressure difference acting across the membrane. The polymeric material is described by an arbitrary combination of a viscoelastic and a purely viscous component to the stress. Some viscoelastic materials described by a Mooney...

  4. Inflation and Instability of a Polymeric Membrane

    DEFF Research Database (Denmark)

    Neergaard, Jesper; Hassager, Ole

    1999-01-01

    We consider an axisymmetric polymeric membrane inflated by a uniform pressure difference acting across the membrane. The polymeric materialis described by an arbitrary combination of a viscoelastic and a purely viscous component to the stress. Some viscoelastic materials described by a Mooney...

  5. Polymerization kinetics of boron carbide/epoxy composites

    Energy Technology Data Exchange (ETDEWEB)

    Abenojar, J., E-mail: abenojar@ing.uc3m.es [Materials Performance Group, Materials Science and Engineering Department, IAAB, Universidad Carlos III de Madrid, Av. Universidad, 30, 28911 Leganés (Spain); Encinas, N. [Materials Performance Group, Materials Science and Engineering Department, IAAB, Universidad Carlos III de Madrid, Av. Universidad, 30, 28911 Leganés (Spain); Real, J.C. del [Department of Mechanical Engineering, Universidad Pontificia Comillas, C/ Alberto Aguilera 23, 28015 Madrid (Spain); Martínez, M.A. [Materials Performance Group, Materials Science and Engineering Department, IAAB, Universidad Carlos III de Madrid, Av. Universidad, 30, 28911 Leganés (Spain)

    2014-01-10

    Graphical abstract: - Highlights: • Conversion degree and rate reaction of the curing reaction increase with temperature. • At low temperature, the particles exhibit catalytic effect, similar to the OH groups. • At high temperature, B{sub 4}C micro-particles increase the n-order rate reaction. • The diffusion constant diminishes with temperature for all the studied materials. • The autocatalytic reaction is favored by the effect of 6% nanoparticles. - Abstract: This study employs Differential Scanning Calorimetry (DSC) technique and focuses on the curing kinetics and the activation energy of the commercial epoxy resin (which cures at room temperature for 12 h) filled with boron carbide particles (B{sub 4}C) in different amount (6 and 12 wt%) and particle size (60 nm, 7 and 23 μm). An isothermal dwell at different temperatures (25, 35 and 50 °C) was used for 180 min. Thereafter, the temperature is increased by 5 °C min{sup −1} up to 200 °C to complete the curing process. Conversion degree is calculated by combining both methods. The kinetic constant and the reaction order are calculated using Kamal's equation with diffusion control. Consequently, the activation energy is computed assuming Arrhenius’ equation.The results show a significant influence of the temperature on the reaction mechanism. Furthermore, polymerization kinetics is affected by B{sub 4}C additions depending on the amount and size of the added particles.

  6. Kinetics of interfacial radical polymerization initiated by a glucose-oxidase mediated redox system.

    Science.gov (United States)

    Shenoy, Raveesh; Bowman, Christopher N

    2012-10-01

    The reaction and coating kinetics for the glucose oxidase initiated interfacial polymerization are elaborated. The interfacial film grows rapidly and linearly with time, producing time-dependent controllable conformal coating thicknesses of up to a millimeter in less than 4 min. Bulk polymerization was only observed when the immersing media was stirred to induce higher mass transport rates. The dramatically different film thicknesses observed between different concentrations of glucose in the hydrogel and iron in the bulk media are demonstrated to be a result of an initial rapid growth phase following which the film grows at the same rate nearly independent of either the glucose or iron concentration. The polymerization rate and hence the thickness growth rate in this initial phase saturate at glucose and iron concentrations above 0.8 M and 0.63 mM, respectively. At iron concentrations above 0.05 mM, the film thickness at the end of 3 h of reaction monotonically decreased with increasing iron concentration from 5.7 mm to 4.2 mm. The glucose oxidase is trapped by the growing polymerization front and can be used as the sole enzymatic precursor to coat a second polymeric layer. However, the rate of film growth of the second layer is 14-fold lower than the rate of film growth when bulk enzyme is present during the second stage coating process.

  7. Photoacoustic analysis of dental resin polymerization

    Science.gov (United States)

    Coloiano, E. C. R.; Rocha, R.; Martin, A. A.; da Silva, M. D.; Acosta-Avalos, D.; Barja, P. R.

    2005-06-01

    In this work, we use the photoacoustic technique to monitor the curing process of diverse dental materials, as the resins chemically activated (RCA). The results obtained reveal that the composition of a determined RCA significantly alters its activation kinetics. Photoacoustic data also show that temperature is a significant parameter in the activation kinetics of resins. The photoacoustic technique was also applied to evaluate the polymerization kinetics of photoactivated resins. Such resins are photoactivated by incidence of continuous light from a photodiode. This leads to the polymerization of the resin, modifying its thermal properties and, consequently, the level of the photoacoustic signal. Measurements show that the polymerization of the resin changes the photoacoustic signal amplitude, indicating that photoacoustic measurements can be utilized to monitor the polymerization kinetic and the degree of polymerization of photoactivated dental resins.

  8. Fluid Effects in Polymers and Polymeric Composites

    CERN Document Server

    Weitsman, Y Jack

    2012-01-01

    Fluid Effects in Polymers and Polymeric Composites, written by the late Dr. Y. Jack Weitsman, addresses the wide range of parameters that affect the interaction of fluids with polymers and polymeric composites. The book aims at broadening the scope of available data, mostly limited up to this time to weight-gain recordings of fluid ingress into polymers and composites, to the practical circumstances of fluctuating exposure. Various forms of experimental data are given, in conjunction with theoretical models derived from basic scientific principles, and correlated with severity of exposure conditions and interpreted by means of rationally based theoretical models. The practical implications of the effects of fluids are discussed. The issue of fluid effects on polymers and polymeric composites is of concern to engineers and scientists active in aerospace and naval structures, as an increasing portion of these structures are made of polymeric composites and employ polymeric adhesives as a joining device. While...

  9. Design and synthesis of structurally well-defined functional polypropylenes via transition metal-mediated olefin polymerization chemistry

    Institute of Scientific and Technical Information of China (English)

    Dong Jinyong

    2006-01-01

    Functionalization of polyolefins is an industrially important yet scientifically challenging research subject.This paper summarizes our recent effort to access structurally well-defined functional polypropylenes via transition metal-mediated olefin polymerization.In one approach,polypropylenes containing side chain functional groups of controlled concentrations were obtained by Ziegler-Natta-catalyzed copolymerization of propylene in combination with either living anionic or controlled radical polymerization of polar monomers.The copolymerization of propylene with 1,4-divinylbenzene using an isospecific MgC12-supported TIC14 catalyst yielded potypropylenes containing pendant styrene moieties.Both metalation reaction with n-butyllithium and hydrochlorination reaction with dry hydrogen chloride selectively and quantitatively occurred at the pendant reactive sites,generating polymeric benzyllithium and 1-chloroethylbenzene species.These species initiated living anionic polymerization of styrene(S)and atom transfer radical polymerization(in the presence of CuC1 and pentamethyldiethylenetriamine) of methyl methacrylate(MMA),respectively,resulting in functional polypropylene graft copolymers(PP-g-PS and PP-g-PMMA)with controllable graft lengths.In another approach,chain end-functionalized polypropylenes containing a terminal OH-group with controlled molecular weights were directly prepared by propylene polymerization with a metaUocene catalyst through a selective aluminum chain transfer reaction.Both approaches proved to be desirable polyolefin functionalization routes in terms of efficiency and polymer structure controllability.

  10. Synthesis of polystyrene with high melting temperature through BDE/CuCl catalyzed polymerization

    Institute of Scientific and Technical Information of China (English)

    WAN; Xiaolong

    2001-01-01

    [1]Ewen, J. A., Novel method for plastic production, Science (in Chinese), 1997, 9: 34.[2]Brintzinger, H. H., Fischer, D., Waymouth, R. M. et al., Stereospecific olefin polymerization with chiral metallocene catalysts, Angewandte Chemie International Edition in English, 1995, 34(11): 1143.[3]Matyjaszewski, K., Atom transfer radical polymerization, role of various components and reaction conditions, Polym. Prep., 1997, 38(2): 736.[4]Wang, J. S., Matyjaszewski, K., Controlled/"living" radical polymerization, atom transfer radical polymerization in the presence of transition-metal complex, J. Am. Soc., 1995, 117: 5614.[5]Wang, J. S., Matyjaszewski, K., Controlled/"living" radical polymerization, halogen atom transfer radical polymerization promoted by a Cu(I)/Cu(II) redox process, Macromolecules, 1995, 28: 7901.[6]Koto, M., Kamigaito, M., Sawamoto, M. et al., Polymerization of methyl methacrylate with the carbon tetrachloride/dichloro-tris(triphenyphosphine) ruthenium(II)/methylaluminum bis(2,6-di-tert-butylphenoxide) initiating system: possible of living radical polymerization, Macromolecules, 1995, 28: 1721.[7]Ando, T., Kato, M., Living radical polymerization of methyl methacrylate with Ruthenium complex: formation of polymers with controlled molecular weights and very narrow distributions, Macromolecules, 1996, 29: 1070.[8]Granel, C., Dubios, P., Jerome, R. et al., Controlled radical polymerization of methacrylic monomers in the presence of a bis(ortho-chelated) arylnickel(II) complex and different activated alkyl halides, Macromolecules, 1996, 29: 8576.[9]Granel, C., Moineau, G., Lecome, P. et al., (Meth)acrylates pseudo-living radical polymerization in the presence of transition metal complexes: the kharasch reaction revisited, Polym. Prep., 1997, 38(1): 450.[10]Ando, T., Kamigaito, M., Sawamoto, M., Iron(II) chloride complex for living radical polymerization of methyl methacrylate, Macromolecules, 1997, 30: 4507.[11

  11. Pressure induced polymerization of Formates

    Science.gov (United States)

    Tschauner, Oliver

    2004-03-01

    The discovery of pressure induced polymerization of CO2 inspired us to search for C-O based chain structures forming at high pressure. We used salts of carboxylic acids as starting materials and exposed them to pressures between 10 and 30 GPa. Upon heating to temperatures above 1800 K we observed deprotonation and significant changes in the Raman shifts of C-O streching modes. Structure analysis based on powder diffraction patterns collected at sector 16 of the APS showed formation of extended C-O chain structures with the cations of the salts residing in the interchain spaces. These new high pressure polymers are interesting by their mechanical strength and provide basic molecular patterns of organic metallic conductors.

  12. MESO—STRUCTURED POLYMERIC HYDROGELS

    Institute of Scientific and Technical Information of China (English)

    Zhen-zhongYang; Jian-huaRong; DanLi

    2003-01-01

    Meso-structured(opal and inverse opal) polymeric hydrogels of varied morphology and composition were prepared by using two methods:post-modification of the template-synthesized structured polymers and templatepolymerization of functional monomers.A polyacrylic acid based inverse opal hydrogel was chosen to demonstrate its fast pH response by changing color,which is important in designing tunable photonic crystals.Template effects of the hydrogels on controlling structure of the template-synthesized inorganic materials were discussed.The catalytic effect of acid groups in the templates was emphasized for a preferential formation of TiO2 in the region containing acid groups,which allowed duplicating inorganic colloidal crystals from colloidal crystal hydrogels (or macroporous products from macroporous hydrogels) via one step duplication.

  13. MESO-STRUCTURED POLYMERIC HYDROGELS

    Institute of Scientific and Technical Information of China (English)

    Zhen-zhong Yang; Jian-hua Rong; Dan Li

    2003-01-01

    Meso-structured (opal and inverse opal) polymeric hydrogels of varied morphology and composition were prepared by using two methods: post-modification of the template-synthesized structured polymers and templatepolymerization of functional monomers. A polyacrylic acid based inverse opal hydrogel was chosen to demonstrate its fast pH response by changing color, which is important in designing tunable photonic crystals. Template effects of the hydrogels on controlling structure of the template-synthesized inorganic materials were discussed. The catalytic effect of acid groups inthe templates was emphasized for a preferential formation of TiO2 in the region containing acid groups, which allowed duplicating inorganic colloidal crystals from colloidal crystal hydrogels (or macroporous products from macroporous hydrogels) via one step duplication.

  14. Environment-Responsive Polymeric Hydrogels

    Institute of Scientific and Technical Information of China (English)

    Zhn X. X.; M. Nichifor; Lin H.Y.; D. Avoce

    2004-01-01

    Some polymers may respond by changing their physico-chemical perperties when the environmental conditions such as pH, temperature and ionic strength are varied. For example,thermosensentive polymers can exhibit a sharp change in solubility in a solvent such as water at a certain temperature known as the lower critical solution temperature (LCST). The responsiveness of the polymeric materials has important technological implications since they can be employed for various applications. The responsiveness of such polymers can be varied by means of copolymerization, chemical modification of the polymer, or the addition of reagents into the solutions. It is interesting and important to tune predictably the responsiveness of the polymers for the different applications. The sensitivity towards the external environment can be modulated by the relative hydrophilicity of the copolymers, hence the chemical structure and composition of the comonomers used.

  15. Hemocompatibility of polymeric nanostructured surfaces.

    Science.gov (United States)

    Leszczak, Victoria; Smith, Barbara S; Popat, Ketul C

    2013-01-01

    Tissue integration is an important property when inducing transplant tolerance, however, the hemocompatibility of the biomaterial surface also plays an important role in the ultimate success of the implant. Therefore, in order to induce transplant tolerance, it is critical to understand the interaction of blood components with the material surfaces. In this study, we have investigated the adsorption of key blood serum proteins, in vitro adhesion and activation of platelets and clotting kinetics of whole blood on flat polycaprolactone (PCL) surfaces, nanowire (NW) surfaces and nanofiber (NF) surfaces. Previous studies have shown that polymeric nanostructured surfaces improve cell adhesion, proliferation and viability; however it is unclear how these polymeric nanostructured surfaces interact with the blood and its components. Protein adsorption results indicate that while there were no significant differences in total albumin (ALB) adsorption on PCL, NW and NF surfaces, NW surfaces had higher total fibrinogen (FIB) and immunoglobulin-G (IgG) adsorption compared to NF and PCL surfaces. In contrast, NF surfaces had higher surface FIB and IgG adsorption compared to PCL and NW surfaces. Platelet adhesion and viability studies show more adhesion and clustering of platelets on the NF surfaces as compared to PCL and NW surfaces. Platelet activation studies reveal that NW surfaces have the highest percentage of unactivated platelets, whereas NF surfaces have the highest percentage of fully activated platelets. Whole blood clotting results indicate that NW surfaces maintain an increased amount of free hemoglobin during the clotting process compared to PCL and NF surface, indicating less clotting and slower rate of clotting on their surfaces.

  16. Polymeric materials from renewable resources

    Science.gov (United States)

    Frollini, Elisabete; Rodrigues, Bruno V. M.; da Silva, Cristina G.; Castro, Daniele O.; Ramires, Elaine C.; de Oliveira, Fernando; Santos, Rachel P. O.

    2016-05-01

    The goals of our studies have been the use of renewable raw materials in the preparation of polymeric materials with diversified properties. In this context, lignosulfonate, which is produced in large scale around the world, but not widely used in the production of polymeric materials, was used to replace phenol and polyols in the preparation of phenolic- (Ligno-PH) and polyurethane-type (Ligno-PU) polymers, respectively. These polymers were used to prepare composites reinforced with sisal lignocellulosic fibers. The use of lignosulfonate in the formulation of both types of polymers was beneficial, because in general composites with improved properties, specially impact strength, were obtained. Composites were also prepared from the so called "biopolyethylene" (HDPE), curaua lignocellulosic fiber, and castor oil (CO). All composites HDBPE/CO/Fiber exhibited higher impact strength, when compared to those of the corresponding HDBPE/Fiber. These results, combined with others (eg SEM images of the fractured surfaces) indicated that, in addition to acting as a plasticizer, this oil may have acted as a compatibilizer of the hydrophilic fiber with the hydrophobic polymer. The set of results indicated that (i) mats with nano (diameter ≤ 100nm) and/or ultrafine (submicron scale) fibers were produced, (ii) hybrid fibers were produced (bio-based mats composites), (iii) cellulosic pulp (CP) and/or lignin (Lig) can be combined with PET matrices to control properties such as stiffness and hydrophilicity of the respective mats. Materials with diversified properties were prepared from high content of renewable raw materials, thus fulfilling the proposed targets.

  17. Free radical (co)polymerization of methyl methacrylate and styrene in room temperature ionic liquids

    Science.gov (United States)

    Zhang, Hongwei

    Conventional free radical polymerizations were carried out in a variety of room temperature ionic liquids (RTILs). Generally, methyl methacrylate (MMA) and styrene (St) were used as typical monomers to compare the polymerization behavior both in RTILs and in common volatile organic compound solvents (VOCs). In most cases, it was observed that both yields and molecular weights are enhanced in the RTIL. While we believe the "diffusion-controlled termination" mechanism makes the termination of the radical propagating chains difficult due to the highly viscous nature of RTIL, other researchers have suggested that the rapid polymerization rates are due to the high polarity of these reaction media. By employing more than a dozen RTILs with a wide range of anions and cations, we attempted to correlate the viscosity and polarity of the RTILs with the molecular weights and polymerization rates. This correlation was not successful, suggesting that other parameters may also play a role in affecting the polymerization behavior. Other kinds of polymerizations have also been attempted including nitroxide-mediated living radical polymerizations of St and MMA in 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF6), and redox initiation system initiated polymerization of MMA through redox pair formed by cation of trihexyl-tetradecyl-phosphonium bis(2,4,4-trimethylpentyl) phosphinate ([H3TDP] [(PM3) 2P]) and BPO. The formation of PSt-b-PMMA by sequential monomer addition through the standard free radical polymerization mechanism, using BPO as initiator, can be realized in [BMIM]PF6 due to the insolubility of polymerized first block---PSt in [BMIM]PF6. The macroradicals wrapped inside the chain coils have prolonged lifetimes because of the diminished termination, which allow some of these radicals to initiate polymerization of MMA at room temperature to form diblock copolymer. Solvents effects on reactivity ratios for free radical statistical copolymerization have been

  18. DEPENDENCE OF ACRYLONITRILE POLYMERIZATION KINETICS ON THE COMPOSITION OF POLYAMID OXIME -THIOUREA SYSTEM

    Institute of Scientific and Technical Information of China (English)

    WU Jinyuan; YANG Chaoxiong; ZHANG Guangzhao

    1993-01-01

    The polymerization of acrylonitrile (AN) initiated by polypropylene based-polyamidoxime (PPAO)- thiourea (TU) system was investigated at [ TU]/[ PPAO] > 0.5 molar ratio. It shows that the variation of the concentrations of PPAO, thiourea and nitric acid does not exert an observable influence on the reaction rate. The overall rate of polymerization (Rp) is Rp = 2.07e - 7,800/RT[AN] 2.0The zero order dependence on PPAO and thiourea concentrations and the lowest value of the collision frequence factor were considered to be a feature of the primary radical termination.

  19. Synthesis of Acrylic Acid/Kaoline Powder Superabsorbent Composite by Inverse-suspending Polymerization

    Institute of Scientific and Technical Information of China (English)

    ZHONG Jin-feng; XUE Yi-ming; WU Ji-huai; LIN Jian-ming; WEI Yue-lin

    2004-01-01

    An acrylic acid/kaoline powder superabsorbent composite with a water absorbency of the superabsorbent composite about 1/800 was synthesized by inverse-suspending polymerization reaction between acrylic acid monomer and kaoline ultrafine powder. The influence of the dispersant agent on the configuration of the products in the inverse suspension polymerization is investigated. The influences of the kaoline powder, cross-linker, initiator, neutralization degree and the volume ratio of oil to water phase on the water absorbency of the superabsorbent composites are discussed in the paper.

  20. Synthesis of NLO polycarbonates via the ring-opening polymerization of macrocyclic prepolymers

    Science.gov (United States)

    Kulig, Joseph B.; Moore, Collin G.; Brittain, William J.; Gilmour, Sandra; Perry, Joseph W.

    1994-05-01

    The synthesis and characterization of polycarbonates and polyformals is described. Copolymers of bisphenol A (BPA) and either a triphenyloxazole (1) or phenylquinoxaline (2) monomer were prepared. The polycarbonate copolymers were prepared by ring-opening polymerization of macrocyclic prepolymers using a solvent-free process. Preliminary electro- optic measurements have been performed on the polycarbonate copolymers of BPA and 1. Polyformals have also been prepared by a conventional polymerization process involving the reaction of dichloromethane with different feed ratios of BPA and either 1 or 2. The glass transition temperature of either the polyformals or polycarbonates is dramatically increased by increasing mole fractions of monomers 1 and 2.

  1. Molecular weight control in organochromium olefin polymerization catalysis by hemilabile ligand–metal interactions

    Science.gov (United States)

    Mark, Stefan; Wadepohl, Hubert

    2016-01-01

    Summary A series of Cr(III) complexes based on quinoline-cyclopentadienyl ligands with additional hemilabile side arms were prepared and used as single-site catalyst precursors for ethylene polymerization. The additional donor functions interact with the metal centers only after activation with the co-catalyst. Evidence for this comes from DFT-calculations and from the differing behavior of the complexes in ethylene polymerization. All complexes investigated show very high catalytic activity and the additional side arm minimizes chain-transfer reactions, leading to increase of molecular weights of the resulting polymers. PMID:27559387

  2. SIMULTANEOUS MEASUREMENT OF FREE RADICAL DECAY IN POLYMERIZATION OF MMA INITIATED BY AIBN USING ESR AND ITS KINETIC MODEL

    Institute of Scientific and Technical Information of China (English)

    Ping Xia; Qing-song Hu; Xiao-lan Qian; Xul-in Jiang; De-yue Yan

    2001-01-01

    The kinetics of free radical decay in the polymerization of MMA initiated by AIBN was studied by means of ESR spectroscopy. It was found that the curves of radical decay are strongly associated with the reaction temperature, the initiator concentration and the solvent. In the case of the radical polymerization carried out at high temperature or in solution, the radical concentration first reached a maximum, then declined monotonously with reaction time. It was also found that the greater the amount of initiator or the higher the temperature, the more rapidly the radicals decay. When the bulk polymerization was implemented at a relatively low temperature, the curves of radical decay became more complicated, i.e.,the radical concentration rapidly rose to a maximum, then dropped to a minimum, finally increased again with reaction time.Taking into account the diffusion effect, a semi-empirical equation is suggested to describe the kinetics of propagating radical decay.

  3. Programming magnetic anisotropy in polymeric microactuators.

    Science.gov (United States)

    Kim, Jiyun; Chung, Su Eun; Choi, Sung-Eun; Lee, Howon; Kim, Junhoi; Kwon, Sunghoon

    2011-10-01

    Polymeric microcomponents are widely used in microelectromechanical systems (MEMS) and lab-on-a-chip devices, but they suffer from the lack of complex motion, effective addressability and precise shape control. To address these needs, we fabricated polymeric nanocomposite microactuators driven by programmable heterogeneous magnetic anisotropy. Spatially modulated photopatterning was applied in a shape-independent manner to microactuator components by successive confinement of self-assembled magnetic nanoparticles in a fixed polymer matrix. By freely programming the rotational axis of each component, we demonstrate that the polymeric microactuators can undergo predesigned, complex two- and three-dimensional motion.

  4. Polymeric nanoparticles: the future of nanomedicine.

    Science.gov (United States)

    Banik, Brittany L; Fattahi, Pouria; Brown, Justin L

    2016-01-01

    Polymeric nanoparticles (NPs) are one of the most studied organic strategies for nanomedicine. Intense interest lies in the potential of polymeric NPs to revolutionize modern medicine. To determine the ideal nanosystem for more effective and distinctly targeted delivery of therapeutic applications, particle size, morphology, material choice, and processing techniques are all research areas of interest. Utilizations of polymeric NPs include drug delivery techniques such as conjugation and entrapment of drugs, prodrugs, stimuli-responsive systems, imaging modalities, and theranostics. Cancer, neurodegenerative disorders, and cardiovascular diseases are fields impacted by NP technologies that push scientific boundaries to the leading edge of transformative advances for nanomedicine.

  5. Exploring the Potential Formation of Organic Solids in Chondrites and Comets through Polymerization of Interstellar Formaldehyde

    Science.gov (United States)

    Kebukawa, Yoko; Kilcoyne, A. L. David; Cody, George D.

    2013-07-01

    Polymerization of interstellar formaldehyde, first through the formose reaction and then through subsequent condensation reactions, provides a plausible explanation for how abundant and highly chemically complex organic solids may have come to exist in primitive solar system objects. In order to gain better insight on the reaction, a systematic study of the relationship of synthesis temperature with resultant molecular structure was performed. In addition, the effect of the presence of ammonia on the reaction rate and molecular structure of the product was studied. The synthesized formaldehyde polymer is directly compared to chondritic insoluble organic matter (IOM) isolated from primitive meteorites using solid-state 13C nuclear magnetic resonance, Fourier transform infrared, and X-ray absorption near edge structure spectroscopy. The molecular structure of the formaldehyde polymer is shown to exhibit considerable similarity at the functional group level with primitive chondritic IOM. The addition of ammonia to the solution enhances the rate of polymerization reaction at lower temperatures and results in substantial incorporation of nitrogen into the polymer. Morphologically, the formaldehyde polymer exists as submicron to micron-sized spheroidal particles and spheroidal particle aggregates that bare considerable similarity to the organic nanoglobules commonly observed in chondritic IOM. These spectroscopic and morphological data support the hypothesis that IOM in chondrites and refractory organic carbon in comets may have formed through the polymerization of interstellar formaldehyde after planetesimal accretion, in the presence of liquid water, early in the history of the solar system.

  6. Supported Catalysts Useful in Ring-Closing Metathesis, Cross Metathesis, and Ring-Opening Metathesis Polymerization

    Directory of Open Access Journals (Sweden)

    Jakkrit Suriboot

    2016-04-01

    Full Text Available Ruthenium and molybdenum catalysts are widely used in synthesis of both small molecules and macromolecules. While major developments have led to new increasingly active catalysts that have high functional group compatibility and stereoselectivity, catalyst/product separation, catalyst recycling, and/or catalyst residue/product separation remain an issue in some applications of these catalysts. This review highlights some of the history of efforts to address these problems, first discussing the problem in the context of reactions like ring-closing metathesis and cross metathesis catalysis used in the synthesis of low molecular weight compounds. It then discusses in more detail progress in dealing with these issues in ring opening metathesis polymerization chemistry. Such approaches depend on a biphasic solid/liquid or liquid separation and can use either always biphasic or sometimes biphasic systems and approaches to this problem using insoluble inorganic supports, insoluble crosslinked polymeric organic supports, soluble polymeric supports, ionic liquids and fluorous phases are discussed.

  7. Cationic ring-opening polymerization of 3,3-bis(chloromethyl)oxacyclobutane in ionic liquids

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Cationic ring-opening polymerization of 3,3-bis(chloromethyl)oxacyclobutane catalyzed by BF3·OEt2 was carried out in ionic liquids [bmim]BF4 and [bmim]PF6. The influences of BCMO concentration and molar ratio of BCMO/BF3·OEt2 on the molecular weights and yield of PBCMO were investigated. The polymerization in ionic liquids proceed to high conversions, although molecular weights are limited, similar to polymerization in organic solvent such as CH2C12. Follow a viewpoint of green chemistry,we feel ionic liquid [bmim]BF4 is superior to [bmim]PF6. Extracting [bmim]PF6 from the product using organic solvent as extractant limits its advantage as a green reaction media.

  8. POLYMERIZATION OF ETHYLENE METHYL PHOSPHATE IN THE PRESENCE OF SODIUM POLY(ETHYLENE GLYCOL)ATE

    Institute of Scientific and Technical Information of China (English)

    Jie Wen; Ren-xi Zhuo; Lu Wang

    1999-01-01

    Poly(ethylene methyl phosphate)-poly(ethylene glycol)-poly(ethylene methyl phosphate) triblock copolymers carrying hydroxyl group at both chain ends were synthesized with sodium poly(ethylene glycol)ate as initiator. The effects of the factors such as solvent, amount of the initiator and reaction time were investigated. The copolymers were characterized by IR, 1H-NMR, 1H{31p}-NMR, 13C-NMR, 31P{1H}-NMR, and DSC. High molecular weight of the copolymer and high yield of the polymerization were achieved within 3 min at 25℃. The polymerization process was studied by 31P{1H}-NMR and transesterification was found during longer polymerization time.

  9. Dynamic Study of Polymer Particle Growth in Gas Phase Polymerization of Butadiene

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    An experimental apparatus composed of microscope, video camera. image-processing, and mini reactor which can be used for real-time measurement of the growth of polymer particle in gas phase polymerization was built up to carry out dynamic study of gas phase polymerization of butadiene by heterogeneous catalyst based on neodymium(Nd). The studies of the shape duplication of polymer particles and catalyst particles and the growth rate of polymer particle were made. Results show that the apparatus and procedure designed can be well utilized to make dynamic observation and data collection of the growth of polymer particle in gas phase polymerization. A phenomenon of shape duplication of polymer particles and catalyst particles was observed by the real-time measurement. The result also concludes that the activity of individual catalyst particle is different, and the effect of reaction pressure on the growth of polymer particle is significant.

  10. Polymerization of UDMA using zinc particles and 4-META with and without BPO.

    Science.gov (United States)

    Wanichacheva, N; Miyagawa, Y; Ogura, H

    2000-06-01

    The polymerization phenomena of zinc particles moistened with a small amount of water, 4-META, and UDMA without amine in the presence and absence of BPO were investigated. The effects of 4-META and BPO on the setting time and the degree of conversion (DC) were studied. Moreover, the effect of zinc ion amount on the setting time was investigated. As-received zinc particles could induce the polymerization either with or without BPO. A higher concentration of 4-META shortened the setting time and increased DC when BPO was absent. However, the presence of BPO generally retarded the setting time and decreased DC, although its effect was dependent on the 4-META concentration. A higher amount of zinc ion retarded the setting reaction in the presence of 4-META. The zinc particles mixed with 10% zinc sulfate and acetic acid solutions could induce the polymerization of UDMA containing BPO when the amine and 4-META were absent.

  11. Cytocompatible and multifunctional polymeric nanoparticles for transportation of bioactive molecules into and within cells

    Science.gov (United States)

    Ishihara, Kazuhiko; Chen, Weixin; Liu, Yihua; Tsukamoto, Yuriko; Inoue, Yuuki

    2016-01-01

    Abstract Multifunctional polymeric nanoparticles are materials with great potential for a wide range of biomedical applications. For progression in this area of research, unfavorable interactions of these nanoparticles with proteins and cells must be avoided in biological environments, for example, through treatment of the nanoparticle surfaces. Construction of an artificial cell membrane structure based on polymers bearing the zwitterionic phosphorylcholine group can prevent biological reactions at the surface effectively. In addition, certain bioactive molecules can be immobilized on the surface of the polymer to generate enough affinity to capture target biomolecules. Furthermore, entrapment of inorganic nanoparticles inside polymeric matrices enhances the nanoparticle functionality significantly. This review summarizes the preparation and characterization of cytocompatible and multifunctional polymeric nanoparticles; it analyzes the efficiency of their fluorescence function, the nature of the artificial cell membrane structure, and their performance as in-cell devices; and finally, it evaluates both their chemical reactivity and effects in cells. PMID:27877883

  12. Incorporation of 5-hydroxyindazole into the self-polymerization of dopamine for novel polymer synthesis.

    Science.gov (United States)

    Peterson, Matthew B; Le-Masurier, Solomon P; Lim, Khoon; Hook, James M; Martens, Penny; Granville, Anthony M

    2014-02-01

    Investigation into the mussel-inspired polymerization of dopamine has led to the realization that other compounds possessing potential quinone structures could undergo similar self-polymerizations in mild buffered aqueous conditions. To this end, 5-hydroxyindazole was added to a dopamine polymerization matrix in varying amounts, to study its incorporation into a polydopamine coating of silica particles. Solid-state (13) C NMR spectroscopy confirmed the presence of the indazole in the polymer shell when coated onto silica gel. SEM and DLS analysis also confirmed that the presence of the indazole in the reaction matrix yielded monodisperse polymer-coated particles, which retained their polymer shell upon HF etching, except when high levels of the indazole were used. Characterization data and examination of incorporation mechanism suggests that the 5-hydroxyindazole performs the function of a chain-terminating agent. Cytotoxicity studies of the polymer particles containing 5-hydroxyindazole showed dramatically lower toxicity levels compared to polydopamine alone.

  13. Polymerization of Various Lignins via Immobilized Myceliophthora thermophila Laccase (MtL

    Directory of Open Access Journals (Sweden)

    Daniela Huber

    2016-08-01

    Full Text Available Enzymatic polymerization of lignin is an environmentally-friendly and sustainable method that is investigated for its potential in opening-up new applications of one of the most abundant biopolymers on our planet. In this work, the laccase from Myceliophthora thermophila was successfully immobilized onto Accurel MP1000 beads (67% of protein bound to the polymeric carrier and the biocatalyzed oxidation of Kraft lignin (KL and lignosulfonate (LS were carried out. Fluorescence intensity determination, phenol content analysis and size exclusion chromatography were performed in order to elucidate the extent of the polymerization reaction. The collected results show an 8.5-fold decrease of the LS samples’ fluorescence intensity after laccase-mediated oxidation and a 12-fold increase of the weight average molecular weight was obtained.

  14. Detection of heavy metals in water using dye nano-complexants and a polymeric film.

    Science.gov (United States)

    Hadar, Hodayah Abuhatzira; Bulatov, Valery; Dolgin, Bella; Schechter, Israel

    2013-09-15

    An optical analytical method, based on complexation reactions of organic azo-dyes with heavy metals, is proposed. It is based on a specially designed polymeric film that when submerged in water contaminated with heavy metals it changes its color. The azo-dyes are injected into the tested water, resulting in formation of nano-particles of insoluble complexes. The polymeric film embeds and dissolves these nano-particles and thus allows for spectral and/or visual analysis. This film consists of a PVC polymeric skeleton and an organic solvent, bis(2-ethylhexyl)phthalate, which possesses high affinity to the heavy metal nano-complexes. The method was exemplified for Cd, Ni and Co ions. The method is sensitive in the sub-ppm range. The mechanism and kinetics of the film coloration were reported.

  15. Characterization of Polymeric Nanofiltration Membranes

    Directory of Open Access Journals (Sweden)

    Simoncic, B.

    2007-11-01

    Full Text Available As membrane processes are increasingly used in industrial applications, there is a growing interest in methods of membrane characterization. Traditional membrane characteristics, such as cut-off value and pore size distribution, are being supplemented by membrane surface characteristics, such as charge density or zeta potential and hydrophobicity. This study, therefore, characterizes the three different polymeric membranes used (NFT-50, DL and DK. The molecular mass cut-off (MMCO value was determined using a set of reference solutes within the molecular range 150-600 Da, whereas streaming potential measurements enabled quantification of the surface charge characteristics. Hydrophobicity was studied using contact angle measurements. The results indicated that even though all three membranes had very similar layer compositions which consisted of poly(piperazneamide, as top layers they showed different values of measured quantitive. The NFT-50 membrane had the lowest MMCO value and the most hydrophilic membrane surface, followed by DK and DL. Membrane fouling as measured by flux reduction was determined by streaming potential measurements and accompanied by a positive change in zeta potential.

  16. Isothermal Titration Calorimetry of Chiral Polymeric Nanoparticles.

    Science.gov (United States)

    Werber, Liora; Preiss, Laura C; Landfester, Katharina; Muñoz-Espí, Rafael; Mastai, Yitzhak

    2015-09-01

    Chiral polymeric nanoparticles are of prime importance, mainly due to their enantioselective potential, for many applications such as catalysis and chiral separation in chromatography. In this article we report on the preparation of chiral polymeric nanoparticles by miniemulsion polymerization. In addition, we describe the use of isothermal titration calorimetry (ITC) to measure the chiral interactions and the energetics of the adsorption of enantiomers from aqueous solutions onto chiral polymeric nanoparticles. The characterization of chirality in nano-systems is a very challenging task; here, we demonstrate that ITC can be used to accurately determine the thermodynamic parameters associated with the chiral interactions of nanoparticles. The use of ITC to measure the energetics of chiral interactions and recognition at the surfaces of chiral nanoparticles can be applied to other nanoscale chiral systems and can provide further insight into the chiral discrimination processes of nanomaterials.

  17. Deformation and flow of polymeric materials

    CERN Document Server

    Münstedt, Helmut

    2014-01-01

    This book describes the properties of single polymer molecules and polymeric materials and the methods how to characterize them. Molar masses, molar mass distributions and branching structure are discussed in detail. These properties are decisive for a deeper understanding of structure/properties relationships of polymeric materials. This book therefore describes and discusses them in detail. The mechanical behavior as a function of time and temperature is a key subject of the book. The authors present it on the basis of many original results they have obtained in their long research careers. They present the temperature dependence of mechanical properties of various polymeric materials in a wide temperature range: from cryogenic temperatures to the melt. Besides an extensive data collection on the transitions of various different polymeric materials, they also carefully present the physical explanations of the observed phenomena. Glass transition and melting temperatures are discussed, particularly, with the...

  18. Influence of ultrasonic condition on phase transfer catalyzed radical polymerization of methyl methacrylate in two phase system - A kinetic study.

    Science.gov (United States)

    Marimuthu, Elumalai; Murugesan, Vajjiravel

    2016-08-25

    An ultrasonic condition assisted phase transfer catalyzed radical polymerization of methyl methacrylate was investigated in an ethyl acetate/water two phase system at 60±1°C and 25kHz, 300W under inert atmosphere. The influence of monomer, initiator, catalyst and temperature, volume fraction of aqueous phase on the rate of polymerization was examined in detail. The reaction order was found to be unity for monomer, initiator and catalyst. Generally, the reaction rate was relatively fast in two phase system, when a catalytic amount of phase transfer catalyst was used. The combined approach, use of ultrasonic and PTC condition was significantly enhances the rate of polymerization. An ultrasonic and phase transfer catalyzed radical polymerization of methyl methacrylate has shown about three fold enhancements in the rate compared with silent polymerization of MMA using cetyltrimethylammonium bromide as PTC. The resultant kinetics was evaluated with silent polymerization and an important feature was discussed. The activation energy and other thermodynamic parameters were computed. Based on the obtained results an appropriate radical mechanism has been derived. TGA showed the polymer was stable up to 150°C. The FT-IR and DSC analysis validates the atactic nature of the obtained polymer. The XRD pattern reveals the amorphous nature of polymer was dominated.

  19. Volumetric polymerization shrinkage of contemporary composite resins

    Directory of Open Access Journals (Sweden)

    Halim Nagem Filho

    2007-10-01

    Full Text Available The polymerization shrinkage of composite resins may affect negatively the clinical outcome of the restoration. Extensive research has been carried out to develop new formulations of composite resins in order to provide good handling characteristics and some dimensional stability during polymerization. The purpose of this study was to analyze, in vitro, the magnitude of the volumetric polymerization shrinkage of 7 contemporary composite resins (Definite, Suprafill, SureFil, Filtek Z250, Fill Magic, Alert, and Solitaire to determine whether there are differences among these materials. The tests were conducted with precision of 0.1 mg. The volumetric shrinkage was measured by hydrostatic weighing before and after polymerization and calculated by known mathematical equations. One-way ANOVA (a or = 0.05 was used to determine statistically significant differences in volumetric shrinkage among the tested composite resins. Suprafill (1.87±0.01 and Definite (1.89±0.01 shrank significantly less than the other composite resins. SureFil (2.01±0.06, Filtek Z250 (1.99±0.03, and Fill Magic (2.02±0.02 presented intermediate levels of polymerization shrinkage. Alert and Solitaire presented the highest degree of polymerization shrinkage. Knowing the polymerization shrinkage rates of the commercially available composite resins, the dentist would be able to choose between using composite resins with lower polymerization shrinkage rates or adopting technical or operational procedures to minimize the adverse effects deriving from resin contraction during light-activation.

  20. Post polymerization cure shape memory polymers

    Science.gov (United States)

    Wilson, Thomas S; Hearon, Michael Keith; Bearinger, Jane P

    2014-11-11

    This invention relates to chemical polymer compositions, methods of synthesis, and fabrication methods for devices regarding polymers capable of displaying shape memory behavior (SMPs) and which can first be polymerized to a linear or branched polymeric structure, having thermoplastic properties, subsequently processed into a device through processes typical of polymer melts, solutions, and dispersions and then crossed linked to a shape memory thermoset polymer retaining the processed shape.

  1. DNA detection with a polymeric nanochannel device.

    Science.gov (United States)

    Fanzio, Paola; Mussi, Valentina; Manneschi, Chiara; Angeli, Elena; Firpo, Giuseppe; Repetto, Luca; Valbusa, Ugo

    2011-09-01

    We present the development and the electrical characterization of a polymeric nanochannel device. Standard microfabrication coupled to Focused Ion Beam (FIB) nanofabrication is used to fabricate a silicon master, which can be then replicated in a polymeric material by soft lithography. Such an elastomeric nanochannel device is used to study DNA translocation events during electrophoresis experiments. Our results demonstrate that an easy and low cost fabrication technique allows creation of a low noise device for single molecule analysis.

  2. Post polymerization cure shape memory polymers

    Energy Technology Data Exchange (ETDEWEB)

    Wilson, Thomas S.; Hearon, II, Michael Keith; Bearinger, Jane P.

    2017-01-10

    This invention relates to chemical polymer compositions, methods of synthesis, and fabrication methods for devices regarding polymers capable of displaying shape memory behavior (SMPs) and which can first be polymerized to a linear or branched polymeric structure, having thermoplastic properties, subsequently processed into a device through processes typical of polymer melts, solutions, and dispersions and then crossed linked to a shape memory thermoset polymer retaining the processed shape.

  3. Thermo-inelastic Response of Polymeric Solids

    Science.gov (United States)

    2014-08-11

    Public Release; Distribution Unlimited Final Report: Thermo -inelastic Response of Polymeric Solids The views, opinions and/or findings contained in this...in non peer-reviewed journals: Final Report: Thermo -inelastic Response of Polymeric Solids Report Title We the study the impact response of a large...none) Challenges and opportunities in the modeling of thermo -viscoelastic materials, Society of Experimental Mechanics, Greenville, North, Carolina

  4. Inflation and Failure of Polymeric Membranes

    DEFF Research Database (Denmark)

    Hassager, Ole; Neergaard, Jesper

    2000-01-01

    We consider the inflation of an axisymmetric polymeric membrane.Some membranes composed of viscoelastic materialsdescribed by a Mooney-Rivlin model show a monotone increasingpressure during inflation. These materialsdevelop a homogeneous membrane thickness in agreement with the Considere-Pearson ......We consider the inflation of an axisymmetric polymeric membrane.Some membranes composed of viscoelastic materialsdescribed by a Mooney-Rivlin model show a monotone increasingpressure during inflation. These materialsdevelop a homogeneous membrane thickness in agreement with the Considere...

  5. Polymeric micellar drug carriers with fluorescent properties

    OpenAIRE

    Abreu, Ana Sofia Lemos Machado; Sá, Arsénio Vasconcelos; Oliveira, Manuel; Moura, I; Machado, A.V.

    2015-01-01

    Self-assembling polymeric surfactants, based on amphiphilic block copolymers into nanosized aggregates in aqueous solution, are of great interest in the biomedical fields as one class of promising carrier systems, for drug delivery, gene therapy and diagnostic biosensors.[1] The incorporation of fluorescent probes into polymeric micelles has been fulfilled either by physically encapsulation or chemically attachment of fluorophores. [2] These micelle-based fluorescent probes not only facili...

  6. Detoxification of acidic catalyzed hydrolysate of Kappaphycus alvarezii (cottonii).

    Science.gov (United States)

    Meinita, Maria Dyah Nur; Hong, Yong-Ki; Jeong, Gwi-Taek

    2012-01-01

    Red seaweed, Kappaphycus alvarezii, holds great promise for use in biofuel production due to its high carbohydrate content. In this study, we investigated the effect of fermentation inhibitors to the K. alvarezii hydrolysate on cell growth and ethanol fermentation. In addition, detoxification of fermentation inhibitors was performed to decrease the fermentation inhibitory effect. 5-Hydroxymethylfurfural and levulinic acid, which are liberated from acidic hydrolysis, was also observed in the hydrolysate of K. alvarezii. These compounds inhibited ethanol fermentation. In order to remove these inhibitors, activated charcoal and calcium hydroxide were introduced. The efficiency of activated charcoals was examined and over-liming was used to remove the inhibitors. Activated charcoal was found to be more effective than calcium hydroxide to remove the inhibitors. Detoxification by activated charcoal strongly improved the fermentability of dilute acid hydrolysate in the production of bioethanol from K. alvarezii with Saccharomyces cerevisiae. The optimal detoxifying conditions were found to be below an activated charcoal concentration of 5%.

  7. A Mechanistic and Kinetic Study of the Photoinitiated Cationic Double Ring-opening Polymerization of 2-Methylene-7-phenyl-1,4,6,9-tetraoxa-spiro[4.4]nonane

    OpenAIRE

    2006-01-01

    Efficient photopolymerization of a potentially expandable monomer is of practical importance for a variety of polymeric applications demanding dimensional stability, particularly if the polymerization process is well controlled based on a detailed investigation of the reaction. In the current study, photoinitiated polymerization kinetics of 2-methylene-7-phenyl-1,4,6,9-tetraoxaspiro[4.4]nonane (MPN) either with cationic initiation alone or with combined cationic/free radical initiation was ex...

  8. The tempered polymerization of human neuroserpin.

    Directory of Open Access Journals (Sweden)

    Rosina Noto

    Full Text Available Neuroserpin, a member of the serpin protein superfamily, is an inhibitor of proteolytic activity that is involved in pathologies such as ischemia, Alzheimer's disease, and Familial Encephalopathy with Neuroserpin Inclusion Bodies (FENIB. The latter belongs to a class of conformational diseases, known as serpinopathies, which are related to the aberrant polymerization of serpin mutants. Neuroserpin is known to polymerize, even in its wild type form, under thermal stress. Here, we study the mechanism of neuroserpin polymerization over a wide range of temperatures by different techniques. Our experiments show how the onset of polymerization is dependent on the formation of an intermediate monomeric conformer, which then associates with a native monomer to yield a dimeric species. After the formation of small polymers, the aggregation proceeds via monomer addition as well as polymer-polymer association. No further secondary mechanism takes place up to very high temperatures, thus resulting in the formation of neuroserpin linear polymeric chains. Most interesting, the overall aggregation is tuned by the co-occurrence of monomer inactivation (i.e. the formation of latent neuroserpin and by a mechanism of fragmentation. The polymerization kinetics exhibit a unique modulation of the average mass and size of polymers, which might suggest synchronization among the different processes involved. Thus, fragmentation would control and temper the aggregation process, instead of enhancing it, as typically observed (e.g. for amyloid fibrillation.

  9. Polymeric micelles for acyclovir drug delivery.

    Science.gov (United States)

    Sawdon, Alicia J; Peng, Ching-An

    2014-10-01

    Polymeric prodrug micelles for delivery of acyclovir (ACV) were synthesized. First, ACV was used directly to initiate ring-opening polymerization of ɛ-caprolactone to form ACV-polycaprolactone (ACV-PCL). Through conjugation of hydrophobic ACV-PCL with hydrophilic methoxy poly(ethylene glycol) (MPEG) or chitosan, polymeric micelles for drug delivery were formed. (1)H NMR, FTIR, and gel permeation chromatography were employed to show successful conjugation of MPEG or chitosan to hydrophobic ACV-PCL. Through dynamic light scattering, zeta potential analysis, transmission electron microscopy, and critical micelle concentration (CMC), the synthesized ACV-tagged polymeric micelles were characterized. It was found that the average size of the polymeric micelles was under 200nm and the CMCs of ACV-PCL-MPEG and ACV-PCL-chitosan were 2.0mgL(-1) and 6.6mgL(-1), respectively. The drug release kinetics of ACV was investigated and cytotoxicity assay demonstrates that ACV-tagged polymeric micelles were non-toxic.

  10. Study of n-Butyl Acrylate Self-Initiation Reaction Experimentally and via Macroscopic Mechanistic Modeling

    Directory of Open Access Journals (Sweden)

    Ahmad Arabi Shamsabadi

    2016-04-01

    Full Text Available This paper presents an experimental study of the self-initiation reaction of n-butyl acrylate (n-BA in free-radical polymerization. For the first time, the frequency factor and activation energy of the monomer self-initiation reaction are estimated from measurements of n-BA conversion in free-radical homo-polymerization initiated only by the monomer. The estimation was carried out using a macroscopic mechanistic mathematical model of the reactor. In addition to already-known reactions that contribute to the polymerization, the model considers a n-BA self-initiation reaction mechanism that is based on our previous electronic-level first-principles theoretical study of the self-initiation reaction. Reaction rate equations are derived using the method of moments. The reaction-rate parameter estimates obtained from conversion measurements agree well with estimates obtained via our purely-theoretical quantum chemical calculations.

  11. Surface-Initiated Atom Transfer Radical Polymerization and Electrografting Technique as a Means For Attaining Tailor-Made Polymer Coatings

    DEFF Research Database (Denmark)

    Chernyy, Sergey

    2012-01-01

    Atom transfer radical polymerization initiated from a surface of various substrates (SI-ATRP) has become a progressively popular technique for obtaining thin polymer films with predetermined properties. The present work addresses the main features of SI-ATRP with respect to the controllability......, rates of polymerization, suitable monomers, reaction mixture compositions etc. An alternative potential-driven polymerization approach is discussed, although to a smaller extent. Chapter 1 provides an overview of controlled/living polymerization techniques with an accent made on ATRP. Different...... strategies for initiator grafting, physicochemical properties of polymer brushes and basic principles of quartz crystal microbalance technique (QCM) are discussed. In Chapter 2 various ATRP conditions are probed. The effects of solvent polarity, monomer concentration, initiator surface density, ligand nature...

  12. Surface characterization and platelet adhesion studies on fluorocarbons prepared by plasma-induced graft polymerization.

    Science.gov (United States)

    Lin, J C; Tiong, S L; Chen, C Y

    2000-01-01

    It is believed that the interactions between the biological environment and biomaterial surface are the key factors influencing its biocompatibility. Therefore, plasma processing, which can vary the surface properties without altering the bulk properties, has been considered as one of the important techniques for improving a materials' biocompatibility. In this investigation, plasma-induced grafting polymerization of vinylidene fluoride (VDF) and chlorotrifluoroethylene (CTFE), instead of direct plasma polymerization, was attempted with an aim to improve the substrate blood compatibility. Contact angle measurement indicated both fluorocarbon-grafted Pdyethylenes (PEs) are hydrophobic. Due to the additional fluorine and chlorine atoms on the CTFE chain, the PCTFE-grafted PE exhibited a higher hydrophobicity than the PVDF-grafted one. ESCA analysis has revealed that these two plasma-induced fluorocarbon deposits contain almost no CFx (x > 2) binding on the surface layer, indicating the grafting polymerization mainly follows the free radical mechanism instead of the molecule-highly-fragmented reaction steps commonly seen in the direct plasma polymerization treatment. In addition, ATR-FTIR has shown the surface chemical configuration of these PVDF- and PCTFE-grafted PEs to be very similar to those of the bulk samples of PVDF and PCTFE. The surface roughness decreased after oxygen plasma treatment and was further reduced by VDF and CTFE grafting polymerization. In vitro platelet adhesion testing indicated these two fluorocarbon grafted PEs are less platelet-activating than the nontreated PE control and oxygen plasma activated one.

  13. Comparative studies of chemically synthesized and RF plasma-polymerized poly(-toluidine)

    Indian Academy of Sciences (India)

    Shama Islam; G B V S Lakshmi; M Zulfequar; M Husain; Azher M Siddiqui

    2015-04-01

    Poly(-toluidine) (POT) polymer was synthesized by chemical method and RF plasma polymerization at a radio frequency (RF) power input of 15 W on ultrasonically cleaned glass and silicon wafer substrates. These samples were characterized by DC conductivity measurements, UV–visible, XRD and FTIR techniques. The DC-conductivity was measured at 410 K, which was found to increase by two orders of magnitude for thin film as compared to pellet samples. It has been observed that the activation energy increases for RF plasma-polymerized POT. Transmission and reflectance spectra were studied for measuring optical constants like absorption coefficient (), extinction coefficient (), optical band gap (g), Urbach energy (e), and refractive index (). From XRD studies, one can infer that the samples grown by both the methods are amorphous in nature. The results indicate that the structures of plasma-polymerized POT are rather different from polymers synthesized by conventional chemical methods, due to a higher degree of cross-linking and branching reactions in plasma polymerization. This makes them suitable for various electroactive devices. A higher and more stable conductivity can be obtained with RF plasma-polymerized POT which is much smoother and more uniform.

  14. Simulation of Rate Retardation in RAFT Polymerization of Styrene with Low RAFT-Initiator Ratio

    Institute of Scientific and Technical Information of China (English)

    WANG Yanjun; YUE Liying; CHEN Wenhao; YUAN Caideng

    2005-01-01

    Bulk polymerizations of styrene (St) were carried out in the presence of three reversible addition fragmentation chain transfer (RAFT) agents benzyl dithiobenzoate (BDB), cumyl dithiobenzoate(CDB), and 1-phenylethyl dithiobenzoate (PEDB) under low ratio of RAFT agent to initiator. The kinetic model was developed to predict polymerization rate, which indicates that the RAFT polymerization of St is a first-order reaction. In the range of experimental conversions, the plots of -ln(1-x) against time t are approximately linear (x is monomer conversion). The kinetic study reveals the existence of strong rate retardation in RAFT polymerization of styrene. A coefficient K r is defined to estimate the rate retardation in the RAFT system considering the assumption that the retardation in polymerization rate is mainly attributed to slow fragmentation of the intermediate radicals. K r relates to the structure of RAFT agents as well as the concentrations of RAFT agent and azobis isobutyronitrile (AIBN). For a certain RAFT agent, the value of K r is enhanced by the increase in the initial concentration of RAFT agent and the higher ratio of RAFT to AIBN. With the same recipe for different RAFT agents, the increasing trend for the values of K r is BDB

  15. Emulsion Polymerization of Tung Oil-Based Latexes with Asolectin as a Biorenewable Surfactant

    Directory of Open Access Journals (Sweden)

    Ashley Johns

    2016-11-01

    Full Text Available Bio-based vesicles, with potential application in drug delivery and/or catalyst encapsulation, have been prepared by the free radical emulsion co-polymerization of tung oil, divinylbenzene (DVB, n-butyl methacrylate (BMA, and asolectin in a xylene/water mixture. The free radical polymerization was initiated by di-tert-butyl peroxide (DTBP at 100 °C in a convection oven. Molecular weights of approximately 11,000 Da were measured by Matrix-assisted Laser Desorption/Ionization-Time of Flight (Maldi-TOF for tung oil-asolectin copolymers, verifying that significant polymerization occurs under the cure conditions employed. The cure of the co-monomer mixture employed in this work was monitored by Dielectric Analysis (DEA, while changes in the Raman spectrum of all co-monomers before and after the cure, along with differential scanning calorimetry (DSC analysis, have been used to verify the need of a post-cure step and completion of the polymerization reaction. Scanning Transmission Electron Microscopy (STEM images of the emulsion after polymerization indicate that vesicles were formed, and vesicle size distribution of samples prepared with different amounts of tung oil were determined using a Zetasizer.

  16. Supramolecular intermediates in the synthesis of polymeric carbon nitride from melamine cyanurate

    Energy Technology Data Exchange (ETDEWEB)

    Dante, Roberto C., E-mail: rcdante@yahoo.com [Facultad de Mecánica, Escuela Politécnica Nacional (EPN), Ladrón de Guevara E11-253, Quito (Ecuador); Sánchez-Arévalo, Francisco M. [Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de Mexico, Apdo. Postal 70-360, Cd. Universitaria, Mexico D.F. 04510 (Mexico); Chamorro-Posada, Pedro [Dpto. de Teoría de la Señal y Comunicaciones e IT, Universidad de Valladolid, ETSI Telecomunicación, Paseo Belén 15, 47011 Valladolid (Spain); Vázquez-Cabo, José [Dpto. de Teoría de la Señal y Comunicaciones, Universidad de Vigo, ETSI Telecomunicación, Lagoas Marcosende s/n, Vigo (Spain); Huerta, Lazaro [Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de Mexico, Apdo. Postal 70-360, Cd. Universitaria, Mexico D.F. 04510 (Mexico); Lartundo-Rojas, Luis [Centro de Nanociencias y Micro y Nanotecnologías—IPN, Luis Enrique Erro s/n, U. Prof. Adolfo López Mateos, 07738 Ciudad de Mexico, Distrito Federal (Mexico); Santoyo-Salazar, Jaime [Departamento de Física, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, CINVESTAV-IPN, Apdo. Postal 14-740, Mexico D.F. 07360 (Mexico); and others

    2015-03-15

    The adduct of melamine and cyanuric acid (MCA) was used in past research to produce polymeric carbon nitride and precursors. The reaction yield was considerably incremented by the addition of sulfuric acid. The polymeric carbon nitride formation occurs around 450 °C at temperatures above the sublimation of the adduct components, which occurs around 400 °C. In this report the effect of sulfuric acid on MCA was investigated. It was found that the MCA rosette supramolecular channel structures behave as a solid solvent able to host small molecules, such as sulfuric acid, inside these channels and interact with them. Therefore, the sulfuric acid effect was found to be close to that of a solute that causes a temperature increment of the “solvent sublimation” enough to allowing the formation of polymeric carbon nitride to occur. Sulfate ions are presumably hosted in the rosette channels of MCA as shown by simulations. - Graphical abstract: The blend of melamine cyanurate and sulfuric acid behaves like a solution so that melamine cyanurate decomposition is shifted to temperatures high enough to react and form polymeric carbon nitride. - Highlights: • The adduct of melamine and cyanuric acid behaves as a solid solvent. • The blend of sulfuric acid and melamine cyanurate behaves like a solution. • Melamine cyanurate decomposition is shifted to higher temperatures by sulfuric acid. • The formation of polymeric carbon nitride occurs for these higher temperatures.

  17. Genotoxic evaluation of polymeric nanoparticles

    Directory of Open Access Journals (Sweden)

    Tamara Iglesias Alonso

    2015-06-01

    Full Text Available An important strategy for optimizing the therapeutic efficacy of many conventional drugs is the development of polymeric nanoparticles (NPs, as it may expand their activities, reduce their toxicity, increase their bioactivity and improve biodistribution. The main objective of this study was to evaluate the genotoxicity of 8 different poly (anhydride NPs designed for the oral administration of therapeutic compounds by using the comet assay in combination with the enzyme formamidopypiridine DNA-glycosylase (FPG. Furthermore, the mitogen capacity of the NPs was evaluated by the proliferation assay. All NPs were tested at four concentrations (0, 0.5, 1 and 2 mg/mL in Caco-2 cells after 3 hours of treatment while selected NPs were also tested after 24 h. The comet assay was performed immediately after the treatment and cell proliferation was assessed by counting the treated cells after their incubation at 37 °C for 48h. Cells treated with 1 µM of the photosensitizer Ro 19-8022 plus 5 min of light, as well as cells treated with 100 µM H2O2 were included as positive controls in all the experiments. All NPs studied did not result in any increase in the frequency of strand breaks or alkali-labile sites in Caco-2 cells but they induced a slight concentration-dependent increase in net FPG sensitive sites (oxidized and/or alkylated bases. Furthermore, treated cells did not show changes in levels of proliferation in comparison with the negative control.

  18. Controlled synthesis of photochromic polymer brushes by atom transfer radical polymerization.

    Energy Technology Data Exchange (ETDEWEB)

    Piech, Marcin; Bell, Nelson Simmons; Long, Timothy Michael

    2005-06-01

    This work reports on the grafting of methyl methacrylate polymer brushes containing spirobenzopyran pendant groups from flat silica surfaces and colloidal particles utilizing atom transfer radical polymerization (ATRP). The reaction conditions were optimized with respect to the kind of surface bound initiator, the type of halide and ligand used in the catalytic complex, the presence/absence of untethered initiator, and solvent type. This enabled synthesis of coatings up to 80 {+-} 3 nm thick with controlled spirobenzopyran content. While polymerization kinetics indicate the presence of chain termination reactions, the 'living' character of the process is confirmed by controlled formation of block copolymer brushes. UV/vis spectroscopy was used to characterize the UV-induced isomerization of spirobenzopyran to zwitterionic merocyanine and the thermal back-reaction. Spectral and kinetic analyses of this latter bleaching process points to the existence of free and associated merocyanines in the polymeric brush in both tetrahydrofuran and toluene. However, stabilization of merocyanine species by the polymer matrix is considerably greater in toluene with thermal back-reaction rates approaching those determined for solid dry films.

  19. Reaction Graph

    Institute of Scientific and Technical Information of China (English)

    傅育熙

    1998-01-01

    The paper proposes reaction graphs as graphical representations of computational objects.A reaction graph is a directed graph with all its arrows and some of its nodes labeled.Computations are modled by graph rewriting of a simple nature.The basic rewriting rules embody the essence of both the communications among processes and cut-eliminations in proofs.Calculi of graphs are ideentified to give a formal and algebraic account of reaction graphs in the spirit of process algebra.With the help of the calculi,it is demonstrated that reaction graphs capture many interesting aspects of computations.

  20. Construction of Nontoxic Polymeric UV-Absorber with Great Resistance to UV-Photoaging

    Science.gov (United States)

    Huang, Zhong; Ding, Aishun; Guo, Hao; Lu, Guolin; Huang, Xiaoyu

    2016-05-01

    In this article, we developed a series of new nontoxic polymeric UV-absorbers through covalently attaching a benzophenone derivative onto the main chain of poly(vinyl chloride) (PVC) via mild and quantitative click chemistry. Azide groups were firstly introduced into the backbone of PVC via a nucleophilic reaction without affecting polymeric skeleton. Copper-catalyzed Husigen-Click cycloaddition reaction was performed between the pendant azide groups of PVC and alkynyl of (2-hydroxy-4-(prop-2-ynyloxy)phenyl)(phenyl)methanone at ambient temperature for affording the desired PVC-based UV-absorbers (PVC-UV) with different amounts of benzophenone moieties, which displayed great resistance to photoaging without degradation while exposed to UV irradiation. These polymeric UV-absorbers also showed good solubilities in common organic solvents and no cytotoxicity vs. HaCat cell. Small amounts of PVC-UV were homogeneously mixed with PVC as additive for stabilizing PVC against UV-photoaging without degradation and releasing small molecule even after 200 h while keeping thermal stability. This route of polymeric additive clearly paved an efficient way for solving the puzzle of separation of small molecule additive.

  1. Nature of the active sites in the polymerization of isoprene by the action of triphenylmethylneodymium chlorides

    Energy Technology Data Exchange (ETDEWEB)

    Audeeva, O.G.; Bondarenko, G.N.; Markevich, I.N.; Sharaev, O.K.; Tinyakova, E.I.

    1986-07-01

    The authors study the activity of triphenylmehtylneodymium chlorides and the nature of the polymerization reaction of isoprene by the action of RNdC1/sub 2/ and obtain experimental data revealing the nature of the cis-regulating sites. A graph is presented which incicates that the activities of the triphenylmethylneodymium dichloride and triphenylneodymium sesquichloride complexes become equal relative to the isomerization of isoprene when the concentration of R /SUB 1.5/ NdCl /SUB 1.5/ is twice as great as that of RNdCl/sub 2/. This finding indicates that R/sub 2/NdCl in the presence of trialkylaluminum does not participate in the polymerization of these dienes. The IR spectra of the Ph/sub 3/CNdCl /SUB 2./ nTHF complex and the products of its reaction with (iC/sub 4/H/sub 9/)/sub 3/Al and piperylene were studied. Another study was carried out on the isoprene polymerization kinetics upon the action of the NdCl /SUB 2./ R/sub 3/Al /SUP ./ aC/sub 5/H/sub 8/ complex in hexane. A derease in the polymerization rate was found in going from hexane to toluene and then to o-xylene.

  2. Copolymer Synthesis and Characterization by Post-Polymerization Modification

    Science.gov (United States)

    Galvin, Casey James

    This PhD thesis examines the physical behavior of surface-grafted polymer assemblies (SGPAs) derived from post-polymerization modification (PPM) reactions in aqueous and vapor enriched environments, and offers an alternative method of creating SGPAs using a PPM approach. SGPAs comprise typically polymer chains grafted covalently to solid substrates. These assemblies show promise in a number of applications and technologies due to the stability imparted by the covalent graft and ability to modify interfacial properties and stability. SGPAs also offer a set of rich physics to explore in fundamental investigations as a result of confining macromolecules to a solid substrate. PPM reactions (also called polymer analogous reactions) apply small molecule organic chemistry reactions to the repeat units of polymer chains in order to generate new chemistries. By applying a PPM strategy to SGPAs, a wide variety of functional groups can be introduced into a small number of well-studied and well-behaved model polymer systems. This approach offers the advantage of holding constant other properties of the SGPA (e.g., molecular weight, MW, and grafting density, sigma) to isolate the effect of chemistry on physical behavior. Using a combination of PPM and fabrication methods that facilitate the formation of SPGAs with position-dependent gradual variation of sigma on flat impenetrable substrate, the influence of polymer chemistry and sigma is examined on the stability of weak polyelectrolyte brushes in aqueous environments at different pH levels. Degrafting of polymer chains in SGPAs exhibits a complex dependence on side chain chemistry, sigma, pH and the charge fraction (alpha) within the brush. Results of these experiments support a proposed mechanism of degrafting, wherein extension of the grafted chains away from the substrate generates tension along the polymer backbone, which activates the grafting chemistry for hydrolysis. The implications of these findings are important in

  3. Untemplated nonenzymatic polymerization of 3',5'cGMP: a plausible route to 3',5'-linked oligonucleotides in primordia.

    Science.gov (United States)

    Šponer, Judit E; Šponer, Jiří; Giorgi, Alessandra; Di Mauro, Ernesto; Pino, Samanta; Costanzo, Giovanna

    2015-02-19

    The high-energy 3',5' phosphodiester linkages conserved in 3',5' cyclic GMPs offer a genuine solution for monomer activation required by the transphosphorylation reactions that could lead to the emergence of the first simple oligonucleotide sequences on the early Earth. In this work we provide an in-depth characterization of the effect of the reaction conditions on the yield of the polymerization reaction of 3',5' cyclic GMPs both in aqueous environment as well as under dehydrating conditions. We show that the threshold temperature of the polymerization is about 30 °C lower under dehydrating conditions than in solution. In addition, we present a plausible exergonic reaction pathway for the polymerization reaction, which involves transient formation of anionic centers at the O3' positions of the participating riboses. We suggest that excess Na(+) cations inhibit the polymerization reaction because they block the anionic mechanism via neutralizing the negatively charged O3'. Our experimental findings are compatible with a prebiotic scenario, where gradual desiccation of the environment could induce polymerization of 3',5' cyclic GMPs synthesized in liquid.

  4. RAFT Polymerization of Vinyl Esters: Synthesis and Applications

    Directory of Open Access Journals (Sweden)

    Simon Harrisson

    2014-05-01

    Full Text Available This article is the first comprehensive review on the study and use of vinyl ester monomers in reversible addition fragmentation chain transfer (RAFT polymerization. It covers all the synthetic aspects associated with the definition of precision polymers comprising poly(vinyl ester building blocks, such as the choice of RAFT agent and reaction conditions in order to progress from simple to complex macromolecular architectures. Although vinyl acetate was by far the most studied monomer of the range, many vinyl esters have been considered in order to tune various polymer properties, in particular, solubility in supercritical carbon dioxide (scCO2. A special emphasis is given to novel poly(vinyl alkylates with enhanced solubilities in scCO2, with applications as reactive stabilizers for dispersion polymerization and macromolecular surfactants for CO2 media. Other miscellaneous uses of poly(vinyl esters synthesized by RAFT, for instance as a means to produce poly(vinyl alcohol with controlled characteristics for use in the biomedical area, are also covered.

  5. Synthesis and characterization of hydrophobically modified polymeric betaines

    Directory of Open Access Journals (Sweden)

    Alexey Shakhvorostov

    2015-09-01

    Full Text Available Polymeric betaines containing long alkyl chains C12H25, C14H29, C16H33 and C18H37 were synthesized by Michael addition reaction of alkylaminocrotonates and methacrylic acid (MAA. They were characterized by FTIR, 13C NMR, DSC, DLS, GPC, cryo-TEM, viscometry and zeta-potential measurements. The polymers were fully soluble in DMF, THF and DMSO, partially dissolved in aromatic hydrocarbons (benzene, toluene, o-xylene and formed colloid solutions in aqueous KOH. In aqueous KOH and DMSO solutions, hydrophobically modified polymeric betaines behaved as polyelectrolytes. The average hydrodynamic size and zeta potential of diluted aqueous solutions of hydrophobic polybetainess containing dodecyl-, tetradecyl-, hexadecyl-, and octadecyl groups were studied as a function of pH. Anomalous low values of the isoelectric point (IEP of amphoteric macromolecules were found to be in the range of pH 2.7-3.4. According to DLS data, the average size of macromolecules tends to decrease with dilution. Zeta-potential of amphoteric macromolecules in aqueous solution is much higher than that in DMSO. The cryo-TEM results revealed that in both aqueous KOH and DMSO media, the micron- and nanosized vesicles existed. The structural organization of vesicles in water and DMSO is discussed. The wax inhibition effect of hydrophobic polybetaines at a decrease of the pour point temperatures of high paraffinic oils was better in comparison with commercial available ethylene-vinylacetate copolymers (EVA.

  6. Preparation of thiolated polymeric nanocomposite for sensitive electroanalysis of dopamine.

    Science.gov (United States)

    Su, Zhaohong; Liu, Ying; Xie, Qingji; Chen, Li; Zhang, Yi; Meng, Yue; Li, Yan; Fu, Yingchun; Ma, Ming; Yao, Shouzhuo

    2012-01-01

    We report on the thiol-ene chemistry guided preparation of novel thiolated polymeric nanocomposite films of abundant anionic carboxylic groups for electrostatic enrichment and sensitive electroanalysis of cationic dopamine (DA) in neutral solution. Briefly, the thiol-ene nucleophilic reaction of a carboxylated thiol with oxidized polypyrrole (PPy), which was electrosynthesized on an Au electrode in the presence of solution-dispersed acidified multiwalled carbon nanotubes (MWCNTs), produced an a PPy-thiol-MWCNTs/Au electrode, and the PPy can be electrochemically overoxidized (OPPy) to form an OPPy-thiol-MWCNTs/Au electrode. The carboxylic groups of the polymeric nanocomposite film originate from the acidified MWCNTs, PPy-tethered carboxylated thiol, and OPPy. The carboxylated thiols examined are mercaptosuccinic acid (MSA) and thioglycolic acid, with β-mercaptoethanol as a control. Electrochemical quartz crystal microbalance, scanning electron microscopy, Fourier transform infrared spectroscopy and ultraviolet-visible spectroscopy were used for film characterization and process monitoring. Under the optimized condition, the differential pulse voltammetry peak current of DA oxidation at OPPy-MSA-MWCNTs/Au electrode is linear with DA concentration from 1.00×10(-9) to 2.87×10(-6) mol L(-1), with a limit of detection of 0.4 nmol L(-1), good anti-interferent ability and stability.

  7. Mixing in polymeric microfluidic devices.

    Energy Technology Data Exchange (ETDEWEB)

    Schunk, Peter Randall; Sun, Amy Cha-Tien; Davis, Robert H. (University of Colorado at Boulder, Boulder, CO); Brotherton, Christopher M. (University of Colorado at Boulder, Boulder, CO)

    2006-04-01

    This SAND report describes progress made during a Sandia National Laboratories sponsored graduate fellowship. The fellowship was funded through an LDRD proposal. The goal of this project is development and characterization of mixing strategies for polymeric microfluidic devices. The mixing strategies under investigation include electroosmotic flow focusing, hydrodynamic focusing, physical constrictions and porous polymer monoliths. For electroosmotic flow focusing, simulations were performed to determine the effect of electroosmotic flow in a microchannel with heterogeneous surface potential. The heterogeneous surface potential caused recirculations to form within the microchannel. These recirculations could then be used to restrict two mixing streams and reduce the characteristic diffusion length. Maximum mixing occurred when the ratio of the mixing region surface potential to the average channel surface potential was made large in magnitude and negative in sign, and when the ratio of the characteristic convection time to the characteristic diffusion time was minimized. Based on these results, experiments were performed to evaluate the manipulation of surface potential using living-radical photopolymerization. The material chosen to manipulate typically exhibits a negative surface potential. Using living-radical surface grafting, a positive surface potential was produced using 2-(Dimethylamino)ethyl methacrylate and a neutral surface was produced using a poly(ethylene glycol) surface graft. Simulations investigating hydrodynamic focusing were also performed. For this technique, mixing is enhanced by using a tertiary fluid stream to constrict the two mixing streams and reduce the characteristic diffusion length. Maximum mixing occurred when the ratio of the tertiary flow stream flow-rate to the mixing streams flow-rate was maximized. Also, like the electroosmotic focusing mixer, mixing was also maximized when the ratio of the characteristic convection time to the

  8. A novel scalable synthesis process of PPTA by coupling n-pentane evaporation for polymerization heat removal

    Institute of Scientific and Technical Information of China (English)

    Tao Zhang; Guo Hua Luo; Fei Wei; Yan Yan Lu; Wei Zhong Qian; Xin Lin Tuo

    2011-01-01

    In this study, we compared the effect of n-pentane and ice-water bath on removing the thermal effect in the poly (p-phenylene terephthalamide) (PPTA) polymerization process. The results indicate that the n-pentane can help to transfer the reaction heat faster and better. Adding suitable amount of n-pentanes into the PPTA preparation process not only improve the heat transfer, but also reduce the motor power in the polymerization process. Moreover, the introduction of n-pentane properly does not result in decrease of the inherent viscosity (η7inh) of polymer. Instead, it leads to increased viscosity of polymer during the PPTA preparation process. The results indicate that n-pentane can effectively transfer the reaction heat and avoid overheating during the polymerization of PPTA.

  9. Monte Carlo simulation on kinetic behavior of one-pot hyperbranched polymerization based on AA*+CB2

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Monte Carlo simulation was applied to investigate the kinetic behavior of AA*+CB2 system.The algorithm consisted of two procedures to simulate the in-situ synthesis of AB2-like intermediate and the subsequent polymerization,respectively.In order to improve the accuracy of the prediction,the mobility distinction between different scale molecules in polymerization was taken into account by relating the reaction rate constants to the collision possibility of each pair of species.The feed ratio of initial monomers and the activity difference between the two functional groups within AA* were studied systematically to catch the essential features of the reaction.Simulation results have revealed that the achievable maximum conversion primarily depends on the extent of the reactivity difference between A and A*-groups,and it is suggested that A*-group should be at least 10 times more active than A-group to achieve high number-average degree of polymerization.

  10. REACTION CHEMISTRY RELATED TO FCC GASOLINE QUALITY

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    About 80% of the gasoline pool as a whole in China for supplying the domestic market at current stage directly originates from FCC units. Obviously, FCC gasoline quality is critical for refiners to meet the nations more and more stringent gasoline specifications. FCC process is expected to produce gasoline with reduced contents of olefins, aromatics, benzene, sulfur, and, contradictorily, still with high octane number.   Catalytic cracking process involves a series of acid catalyzed reactions. Bronsted acid sites dominate the surface of the catalyst used for FCC process. All the reactions of hydrocarbons in FCC process are based on carbonium ions of penta-coordinated, or carbenium ions of tri-coordinated. The monomolecular beta scission mechanism for alkane cracking explains that the cracking of carbon-carbon bonding occurs at the beta position to the carbon atom bearing positive charge, and hence forms two small hydrocarbon molecules: one alkane molecule and one olefin molecule. The molar ratio of alkane to olefin for the primary cracking product will be 1 and it will be less than 1 if the cracking reaction proceeds.   However, it is proved that bimolecular reaction pathways exist between surface carbenium ions and the feed molecules. The products of this bimolecular disproportionation reaction could be an alkane molecule and a newly formed carbenium ion. The better understanding of the reaction chemistry of FCC process based on monomolecular pathways and bimolecular pathways should be the basis for searching approaches to the improvement of FCC gasoline quality. In the complicated reaction scheme of the FCC process, the isomerization reaction leading to the formation of iso-alkanes is obviously a target reaction, which favors both olefin reduction and octane enhancement.   The cracking of small paraffin molecules, due to its limited number of reaction pathways and products, has been used to investigate cracking mechanism. In the present work the

  11. Delivery of antibiotics with polymeric particles.

    Science.gov (United States)

    Xiong, Meng-Hua; Bao, Yan; Yang, Xian-Zhu; Zhu, Yan-Hua; Wang, Jun

    2014-11-30

    Despite the wide use of antibiotics, bacterial infection is still one of the leading causes of hospitalization and mortality. The clinical failure of antibiotic therapy is linked with low bioavailability, poor penetration to bacterial infection sites, and the side effects of antibiotics, as well as the antibiotic resistance properties of bacteria. Antibiotics encapsulated in nanoparticles or microparticles made up of a biodegradable polymer have shown great potential in replacing the administration of antibiotics in their "free" form. Polymeric particles provide protection to antibiotics against environmental deactivation and alter antibiotic pharmacokinetics and biodistribution. Polymeric particles can overcome tissue and cellular barriers and deliver antibiotics into very dense tissues and inaccessible target cells. Polymeric particles can be modified to target or respond to particular tissues, cells, and even bacteria, and thereby facilitate the selective concentration or release of the antibiotic at infection sites, respectively. Thus, the delivery of antibiotics with polymeric particles augments the level of the bioactive drug at the site of infection while reducing the dosage and the dosing frequency. The end results are improved therapeutic effects as well as decreased "pill burden" and drug side effects in patients. The main objective of this review is to analyze recent advances and current perspectives in the use of polymeric antibiotic delivery systems in the treatment of bacterial infection.

  12. Stress and structure development in polymeric coatings

    Science.gov (United States)

    Vaessen, Diane Melissa

    2002-09-01

    The main goal of this research is to measure the stress evolution in various polymer coating systems to establish the mechanisms responsible for stress development, stress relaxation, and defect formation. Investigated systems include ultraviolet (UV)-curable coatings, dense and porous coatings from polymer solutions, and latex coatings. Coating stress was measured using a controlled environment stress apparatus based on a cantilever deflection principle. For acrylate coatings, it was found that by cycling a UV-lamp on and off, keeping the total dose constant, coating stress was lowered by 60% by decreasing the cycle period. A stress minimum was also found to exist for a given dose of radiation. The lower stress is attributed to stress relaxation and/or slower reaction during dark periods. A viscoelastic stress model of this process was formulated and predicted stress values close to those observed experimentally. During drying of cellulose acetate (CA) coatings cast in acetone, final stress increased from 10 to 45 MPa as coating thickness decreased from 60 to 10 mum. This thickness dependent coating stress for a solvent-cast polymer coating is a new finding and is attributed to (1) less shrinkage in thicker coatings due to more trapped solvent (from skinning) and (2) greater amounts of polymer stress relaxation in thicker coatings. For porous CA coatings prepared by dry-cast phase separation, final in-plane stresses ranged from 20 MPa for coatings containing small pores (˜1 mum) to 5 MPa for coatings containing small pores and macrovoids (˜200 mum). For these coatings, a small amount of stress relaxation occurs due to capillary pressure relief. A stress plateau for the macrovoid-containing coating is likely caused by stress-induced rupture of the polymer-rich phase. Measured stress in pigment-free latex coatings was much lower (˜0.3 MPa) than UV-curable and solvent-cast polymer coatings and was found to increase with increasing latex glass transition

  13. Electrochemically polymerized conjugated polymer films: Stability improvement and surface functionalization

    Science.gov (United States)

    Wei, Bin

    -functionalized variant of the ProDOT monomer. With the alkene side groups, highly efficient post-polymerization functionalization of the conducting film was successfully achieved via a radical-based thiol-ene "click" reaction with various terminal thiols, including alkanes, ethylene glycols, and ferrocenes. These surface modification led to dramatic changes in the charge transport and wetting behavior of the chemically functionalized films.

  14. Instantaneous Click Chemistry by a Copper-Containing Polymeric-Membrane-Installed Microflow Catalytic Reactor.

    Science.gov (United States)

    Yamada, Yoichi M A; Ohno, Aya; Sato, Takuma; Uozumi, Yasuhiro

    2015-11-23

    The copper(I)-catalyzed Huisgen cycloaddition (azide-alkyne cycloaddition) is an important reaction in click chemistry that ideally proceeds instantaneously. An instantaneous Huisgen cycloaddition has been developed that uses a novel catalytic dinuclear copper complex-containing polymeric membrane-installed microflow device. A polymeric membranous copper catalyst was prepared from poly(4-vinylpyridine), copper(II) sulfate, sodium chloride, and sodium ascorbate at the interface of two laminar flows inside microchannels. Elucidation of the structure by XANES, EXAFS, and elemental analysis, as well as second-order Møller-Plesset perturbation theory (MP2) calculations and density functional theory (DFT) calculations assigned the local structure near Cu as a μ-chloro dinuclear Cu(I) complex. The microflow device promotes the instantaneous click reaction of a variety of alkynes and organic azides to afford the corresponding triazoles in quantitative yield.

  15. About the activity and selectivity of less well-known metathesis catalysts during ADMET polymerizations

    Directory of Open Access Journals (Sweden)

    Hatice Mutlu

    2010-12-01

    Full Text Available We report on the catalytic activity of commercially available Ru-indenylidene and “boomerang” complexes C1, C2 and C3 in acyclic diene metathesis (ADMET polymerization of a fully renewable α,ω-diene. A high activity of these catalysts was observed for the synthesis of the desired renewable polyesters with molecular weights of up to 17000 Da, which is considerably higher than molecular weights obtained using the same monomer with previously studied catalysts. Moreover, olefin isomerization side reactions that occur during the ADMET polymerizations were studied in detail. The isomerization reactions were investigated by degradation of the prepared polyesters via transesterification with methanol, yielding diesters. These diesters, representing the repeat units of the polyesters, were then quantified by GC-MS.

  16. Advanced polymer-inorganic hybrid hard coatings utilizing in situ polymerization method.

    Science.gov (United States)

    Takaki, Toshihiko; Nishiura, Katsunori; Mizuta, Yasushi; Itou, Yuichi

    2006-12-01

    Hard coatings are frequently used to give plastics high scratch resistance. Coating hardness and adhesion to the substrate are considered to be key factors influencing scratch resistance, but it is difficult to produce coatings that have both properties. Hybridization of polymers and inorganic materials is a promising approach for solving this problem. We prepared polymer-silica hybrid coatings by using in situ polymerization to carry out radical polymerization of vinyl monomers in a sol-gel solution of alkoxysilanes, and measured the abrasion resistance of the coatings. However, the expected properties were not obtained because the sol-gel reaction did not perfectly proceed on the surface of the coatings under the N2 conditions. We found that curing the hybrid coatings by UV irradiation in air promoted the sol-gel reaction on the surface, resulting in coatings having excellent abrasion resistance.

  17. Preparation of polyamide 6/silica nanocomposites from silica surface initiated ring-opening anionic polymerization

    Directory of Open Access Journals (Sweden)

    2007-07-01

    Full Text Available Polyamide 6/silica nanocomposites were synthesized by in situ ring-opening anionic polymerization of ε-caprolactam in the presence of sodium caprolactamate as a catalyst and caprolactam-functionalized silica as an initiator. The initiator precursor, isocyanate-functionalized silica, was prepared by directly reacting commercial silica with excess toluene 2,4-diisocyanate. This polymerization was found to occur in a highly efficient manner at relatively low reaction temperature (170°C and short reaction times (6 h. FTIR spectroscopy was utilized to follow the introduction and consumption of isocyanate groups on the silica surface. Thermogravimetric analysis indicated that the polyamide 6 was successfully grown from the silica surface. Transmission electron microscopy was utilized to image polymer-functionalized silica, showing fine dispersion of silica particles and their size ranging from 20 to 40 nm.

  18. Role of the reaction intermediates in determining PHIP (parahydrogen induced polarization) effect in the hydrogenation of acetylene dicarboxylic acid with the complex [Rh (dppb)]{sup +} (dppb: 1,4-bis(diphenylphosphino)butane)

    Energy Technology Data Exchange (ETDEWEB)

    Reineri, F.; Aime, S. [Department of Molecular Biotechnologies and Health Sciences, University of Torino, Via Nizza 52, 10123 Torino (Italy); Gobetto, R.; Nervi, C. [Department of Chemistry, University of Torino, via P. Giuria 7, 10125 Torino (Italy)

    2014-03-07

    This study deals with the parahydrogenation of the symmetric substrate acetylene dicarboxylic acid catalyzed by a Rh(I) complex bearing the chelating diphosphine dppb (1,4-bis(diphenylphosphino)butane). The two magnetically equivalent protons of the product yield a hyperpolarized emission signal in the {sup 1}H-NMR spectrum. Their polarization intensity varies upon changing the reaction solvent from methanol to acetone. A detailed analysis of the hydrogenation pathway is carried out by means of density functional theory calculations to assess the structure of hydrogenation intermediates and their stability in the two solvents. The observed polarization effects have been accounted on the basis of the obtained structures. Insights into the lifetime of a short-lived reaction intermediate are also obtained.

  19. Role of the reaction intermediates in determining PHIP (parahydrogen induced polarization) effect in the hydrogenation of acetylene dicarboxylic acid with the complex [Rh (dppb)]+ (dppb: 1,4-bis(diphenylphosphino)butane).

    Science.gov (United States)

    Reineri, F; Aime, S; Gobetto, R; Nervi, C

    2014-03-07

    This study deals with the parahydrogenation of the symmetric substrate acetylene dicarboxylic acid catalyzed by a Rh(I) complex bearing the chelating diphosphine dppb (1,4-bis(diphenylphosphino)butane). The two magnetically equivalent protons of the product yield a hyperpolarized emission signal in the (1)H-NMR spectrum. Their polarization intensity varies upon changing the reaction solvent from methanol to acetone. A detailed analysis of the hydrogenation pathway is carried out by means of density functional theory calculations to assess the structure of hydrogenation intermediates and their stability in the two solvents. The observed polarization effects have been accounted on the basis of the obtained structures. Insights into the lifetime of a short-lived reaction intermediate are also obtained.

  20. Vinylic polymerization of Norbornenecarboxylic Acid Esters by Palladium Complexes

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    New thermoplastic norbornene polymers containing ester groups were prepared byvinylic polymerization of norbornene-carboxylic acid esters by Pd(Ⅱ)-based catalysts. Themonomers were obtained by Diels-Alder reaction of cyclopentadiene with acrylic acid esters(methyl and butyl) as mixtures of endo/exo (ratio 40/60)-isomers and were converted topolymers in 60%~70% conversion. The endo-isomer was less reactive than the exo-isomer.To obtain higher molecular weight the more reactive pure exo-isomer was prepared andpolymerized with the Pd (Ⅱ)-catalysts, tetrakis (acetonitrile) Pd (Ⅱ) bis (tetrafluoroborate)and (η3-allyl)Pd(Ⅱ)SbF6, in high conversion. These polymers showed high glass transitiontemperatures, high transparency and good solubility in common solvents.

  1. Organolanthanide Compounds Containing Methanesulfonate and Pyrazinamide Ligand in Styrene Polymerization

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The synthesis of organolanthanide compounds identified as LnCp*(MS)2PzA, Ln=Sm, Tb, Yb (MS=methanesulfonate, Cp*=pentamethylcyclopentadienyl, and PzA=pyrazinamide), by the reaction of coordination compounds Ln(MS)3(PzA)4 with NaCp in THF was reported. The complexes were formulated according to elemental analyses, complexometric titration with EDTA (%Ln), and 1H NMR. IR spectroscopy revealed that PzA coordinates with lanthanide(Ⅲ) ions and methanesulfonate coordinates via oxygen atoms in a non-equivalent manner. In preliminary catalytic studies, these compounds were active in styrene polymerization that used MAO as a cocatalyst with an activity of 12.3 kg PS mol Sm-1h-1. Differential scanning calorimetry (DSC) of polystyrene showed that the polymer was mainly atactic.

  2. The Olefin Metathesis Reactions in Dendrimers

    Science.gov (United States)

    Astruc, Didier

    Dendrimers containing terminal olefins or ruthenium-benzylidene terminal groups undergo olefin metathesis reactions (RCM and ROMP types), and essentially results from our group are reviewed here. Dendrimers have been loaded at their periphery with ruthenium-chelating bis-phosphines, which leads to the formation of dendrimer-cored stars by ring-opening-metathesis polymerization (ROMP). CpFe+-induced perallylation of polymethylaromatics (Cp = η5-C5H5) followed by ring-closing metathesis (RCM) and/or cross metathesis (CM) leads to poly-ring, cage, oligomeric and polymeric architectures. In the presence of acrylic acid or metha-crylate, stereospecific CM inhibits oligomerization, and dendritic olefins yield polyacid dendrimers. Finally, cros-metahesis reactions with dendronic acrylate allow dendritic construction and growth.

  3. Self-Healing of biocompatible polymeric nanocomposities

    Science.gov (United States)

    Espino, Omar; Chipara, Dorina

    2014-03-01

    Polymers are vulnerable to damage in form of cracks deep within the structure, where detection is difficult and repair is near to impossible. These cracks lead to mechanical degradation of the polymer. A method has been created to solve this problem named polymeric self healing. Self healing capabilities implies the dispersion within the polymeric matrix of microcapsules filled with a monomer and of catalyst. Poly urea-formaldehyde microcapsules used in this method are filled with dicyclopentadiene that is liberated after being ruptured by the crack propagation in the material. Polymerization is assisted by a catalyst FGGC that ignites the self healing process. Nanocomposites, such as titanium oxide, will be used as an integration of these polymers that will be tested by rupturing mechanically slowly. In order to prove the self healing process, Raman spectroscopy, FTIR, and SEM are used.

  4. Development of radioisotope labeled polymeric carriers

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Seung Jin; Jeong, Jea Min; Hwang, Hyun Jeong [Ewha Womans University, Seoul (Korea)

    2000-04-01

    This research was performed with the aim of developing polymeric radioisotope or drug carriers for obtaining efficient diagnostic therapeutic efficacy. As polymers, polyethylene oxides, polylactides, polycaprolactone were chosen to prepare the devices including micelle system, microemulsion, nanospheres. In addition, anticancer drug loaded polylactide microparticulates were fabricated as a regional chemotherapeutics for the treatment of cancer. Technetium or radioactive iodine was labeled to the polymeric carriers via ligands such as DTPA and HPP, respectively. Labeling efficiency was above 90% and stable enough up to 24 hours. Moreover, injected polymer carriers demonstrated higher blood maintenance and bone uptake than Tin colloid, a control. These results suggested that radioisotope carrying polymeric particulate are promising tools for diagnosing blood vessels or bones. Besides, anticancer drug loaded particulates demonstrated appropriate maintenance of therapeutic concentration and localization. Therefore it was proposed that this therapeutic system may be potential as a cancer therapy modality. 20 refs., 24 figs.,5 tabs. (Author)

  5. Medical prototyping using two photon polymerization

    Directory of Open Access Journals (Sweden)

    Roger J Narayan

    2010-12-01

    Full Text Available Two photon polymerization involves nearly simultaneous absorption of ultrashort laser pulses for selective curing of photosensitive material. This process has recently been used to create small-scale medical devices out of several classes of photosensitive materials, such as acrylate-based polymers, organically-modified ceramic materials, zirconium sol-gels, and titanium-containing hybrid materials. In this review, the use of two photon polymerization for fabrication of several types of small-scale medical devices, including microneedles, artificial tissues, microfluidic devices, pumps, sensors, and valves, from computer models is described. Necessary steps in the development of two photon polymerization as a commercially viable medical device manufacturing method are also considered.

  6. A necessary and sufficient condition for gelation of a reversible Markov process of polymerization

    CERN Document Server

    Han, D

    2003-01-01

    A reversible Markov process as a chemical polymerization model which permits the coagulation and fragmentation reactions is considered. We present a necessary and sufficient condition for the occurrence of a gelation in the process. We show that a gelation transition may or may not occur, depending on the value of the fragmentation strength, and, in the case that gelation takes place, a critical value for the occurrence of the gelation and the mass of the gel can be determined by close forms.

  7. Design and optimization of polymeric silole and boronate photoluminescent probes for improved explosives detection applications

    OpenAIRE

    Sanchez, Jason C.

    2008-01-01

    Hydrosilylation of silole and silafluorene fluorophores is an effective polymerization tool for the synthesis of [Sigma]*-[Pi]/[Pi]* delocalized structures. Improvements in molecular weights (4000-20 000), reaction conditions (0 -50 ⁰C), and functional group variety were obtained for 1, 1-polysilole and 1,1-polysilafluorene materials. The polymers were screened for their ability to detect organic based explosives by a fluorescence quenching mechanism. The explosives screened include the nitro...

  8. Effect of Chemical Parameters on the Properties of Hydrogels Prepared by using Gamma Radiation Polymerization

    Directory of Open Access Journals (Sweden)

    MOHAMMAD SADEGHI

    2012-12-01

    Full Text Available Several hydrogels were prepared using radiolytic polymerization of aqueous solutions of 2-acrylamido-2-methylpropanesulfonic acid containing appropriate comonomer such as acrylic acid and collagen. The hydrogels have been prepared at an irradiation dose of 25 kGy. The effects of the chemical structure of the monomer(s and crosslinking agent on the yield of homopolymer(s or copolymers and reaction time have been studied. This crosslinking agent include N, N’-methylene bisallyamide (MBA.

  9. Direct Arylation Strategies in the Synthesis of π-Extended Monomers for Organic Polymeric Solar Cells

    OpenAIRE

    Andrea Nitti; Riccardo Po; Gabriele Bianchi; Dario Pasini

    2016-01-01

    π-conjugated macromolecules for organic polymeric solar cells can be rationally engineered at the molecular level in order to tune the optical, electrochemical and solid-state morphology characteristics, and thus to address requirements for the efficient solid state device implementation. The synthetic accessibility of monomers and polymers required for the device is getting increasing attention. Direct arylation reactions for the production of the π-extended scaffolds are gaining importance,...

  10. Possible Role of Ice in the Synthesis of Polymeric Compounds

    Science.gov (United States)

    Monnard, Pierre-Alain; Doerr, Mark; Loeffler, Philipp, M. G.

    COSPAR Session F3.6, Bremen July 18-25, 2010 Possible role of ice in the synthesis of polymeric compounds Doerr, Mark, Loeffler, Philipp M.G and Monnard, Pierre-Alain, University of Southern Den-mark, FLinT Center, Odense M, Denmark. Email: monnard@ifk.sdu.dk Cellular life relies on a collection of linear polymers (among them DNA, RNA, proteins) to perform the functions necessary to its survival. It seems likely that catalytic and informational polymers played essential roles in the emergence of the first living entities, precursors of con-temporary cells. Thus, their detection on other planetary bodies might hint at either emerging, or extant, or past life in these environments. A non-enzymatic synthesis of such polymeric materials or their precursors likely had to rely on a supply of monomers dissolved at low concentrations in an aqueous medium. An aqueous environment represents a clear hurdle to the synthesis of long polymers as it tends to inhibit polymerization due to entropic effects and favors the reverse reaction (decomposition by hy-drolysis). It was therefore proposed that polymerization could occur in a distinct micro-or nanostructured environment that would permit a local increase in the monomer concentration, reduce water activity and protect monomers and polymers from hydrolysis. Several types of micro-or nanostructured environments, among them mineral surfaces [1], lattices of organic molecules, such as amphiphile bilayer structures [2], and the eutectic phase in water-ice [3-8] have been proposed to promote RNA and peptide formation. This last environment might be of particular interest since space exploration has established that water exists on Mars, Europa, Enceladus and comets, mostly as ice. Ice deposits may also have existed on the early Earth. When an aqueous solution is cooled below its freezing point, but above the eutectic point, two aqueous phases co-exist and form the eutectic phase system: a solid (the ice crystals made of pure water

  11. Carbonyl-Olefin Exchange Reaction: Present State and Outlook

    Science.gov (United States)

    Kalinova, Radostina; Jossifov, Christo

    The carbonyl-olefin exchange reaction (COER) is a new reaction between carbonyl group and olefin double bond, which has a formal similarity with the olefin metathesis (OM) - one carbon atom in the latter is replaced with an oxygen atom. Till now the new reaction is performed successfully only when the two functional groups (carbonyl group and olefin double bond) are in one molecule and are conjugated. The α, β-unsaturated carbonyl compounds (substituted propenones) are the compounds with such a structure. They polymerize giving substituted polyacetylenes. The chain propagation step of this polymerization is in fact the COER. The question arises: is it possible the COER to take place when the two functional groups are not in one molecule and are not conjugated, and could this reaction became an alternative of the existing carbonyl olefination reactions?

  12. Tetramethyl-1-silacycloprop-2-ene: its characterization and reactions

    Energy Technology Data Exchange (ETDEWEB)

    Cornett, B.J.

    1980-05-01

    The object of this research is to fully characterize and study some of the reactions of tetramethyl-1-silacycloprop-2-ene. The final characterization of this compound was accomplished by obtaining both Si29 and 13C nuclear magnetic resonance spectra. The reactions studied included those with fluorenone, acetone, styrene, phenylacetylene, acetonitrile, t-butylcyanide, methyl isocyanate, phenyl azide, and azobenzene. Product analyses suggest that aside from addition reactions tetramethylsilacyclopropene can react either via a radical chain polymerization or an anionic chain polymerization mechanism with the latter being the more prevalent. Other reactions studied included the photolysis of tetramethylsilacyclopropene and its reactions in the presence of Pd(PPh/sub 3/)/sub 2/Cl/sub 2/. An appendix includes a study of trimethylsilyl radical disproportionation in the liquid phase to a sila olefin. Trimethylsilyl radicals in solution undergo disproportionation as well as recombination in a 1:5 ratio. The sila olefin formed by disproportionation was trapped by alcohols.

  13. Thrombin interaction with fibrin polymerization sites.

    Science.gov (United States)

    Hsieh, K

    1997-05-15

    Thrombin is central to hemostasis, and postclotting fibrinolysis and wound healing. During clotting, thrombin transforms plasma fibrinogen into polymerizing fibrin, which selectively adsorbs the enzyme into the clot. This protects thrombin from heparin-antithrombin inactivation, thus preserving the enzyme for postclotting events. To determine how the fibrin N-terminal polymerization sites of A alpha 17-23 (GPRVVER) and B beta 15-25 (GHRPLDKKREE) and their analogs may interact with thrombin, amidolysis vs. plasma- and fibrinogen-clotting assays were used to differentiate blockade of catalytic site vs. other thrombin domains. Amidolysis studies suggest GPRVVER inhibition of thrombin catalytic site through hydrophobic interaction, and GPRVVER inhibited clotting. Neither GPRP nor VVER nor the B beta 15-25 homologs inhibited amidolysis. Contrary to heparin, acyl-DKKREE promoted plasma-clotting, but inhibited fibrinogen-clotting. In addition, acyl-DKKREE reversed the anticoagulant effect of heparin (0.1 U/ml) in plasma. The results suggest fibrin B beta 15-25 interaction with thrombin, possibly by blocking the heparin-binding site. Together with the reported fibrin A alpha 27-50 binding to thrombin, polymerizing fibrin appears to initially bind to thrombin catalytic site and exosite-1 through A alpha 17-50, and to another thrombin site through B beta 15-25. As these fibrin sites are also involved in polymerization, competition of the polymerization process with thrombin-binding could subsequently dislodge thrombin from fibrin alpha-chain. This may re-expose the catalytic site and exosite-1, thus explaining the thrombogenicity of clot-bound thrombin. The implications of these findings in polymerization mechanism and anticoagulant design are discussed.

  14. The flat phase of quantum polymerized membranes

    CERN Document Server

    Coquand, O

    2016-01-01

    We investigate the flat phase of quantum polymerized phantom membranes by means of a nonperturbative renormalization group approach. We first implement this formalism for general quantum polymerized membranes and derive the flow equations that encompass both quantum and thermal fluctuations. We then deduce and analyze the flow equations relevant to study the flat phase and discuss their salient features : quantum to classical crossover and, in each of these regimes, strong to weak coupling crossover. We finally illustrate these features in the context of free standing graphene physics.

  15. Polymeric matrix materials for infrared metamaterials

    Science.gov (United States)

    Dirk, Shawn M; Rasberry, Roger D; Rahimian, Kamyar

    2014-04-22

    A polymeric matrix material exhibits low loss at optical frequencies and facilitates the fabrication of all-dielectric metamaterials. The low-loss polymeric matrix material can be synthesized by providing an unsaturated polymer, comprising double or triple bonds; partially hydrogenating the unsaturated polymer; depositing a film of the partially hydrogenated polymer and a crosslinker on a substrate; and photopatterning the film by exposing the film to ultraviolet light through a patterning mask, thereby cross-linking at least some of the remaining unsaturated groups of the partially hydrogenated polymer in the exposed portions.

  16. Mechanism and kinetics of addition polymerizations

    CERN Document Server

    Kucera, M

    1991-01-01

    This volume presents an up-to-date survey of knowledge concerning addition type polymerizations. It contains nine chapters, each of which covers a particular basic term. Whenever necessary, the phenomena are discussed from the viewpoint of both stationary and non-stationary state of radical, ionic (i.e. anionic and cationic) and coordination polymerization. Special attention has been paid to the propagation process. It provides not only a general overview but also information on important special cases (theoretical conditions of propagation, influence of external factors, controlled propagatio

  17. Prebiotic Polymerization: Oxidative Polymerization of 2,3 Dimercapto-1- Propanol on the Surface of Iron(III) Hydroxide Oxide

    Science.gov (United States)

    Weber, Arthur L.

    1995-01-01

    The oxidation of 2,3-dimercapto-1-propanol by ferric ions on the surface of iron(III) hydroxide oxide (Fe(OH)O) yielded polydisulfide oligomers. This polymerization occurred readily at low dithiol concentration under mild aqueous conditions. Polydisulfide polymers up to the 15-mer were synthesized from 1 mM dithiol in 5 ml water reacted with iron(III) hydroxide oxide (20 mg, 160 micromole Fe) for 3 days under anaerobic conditions at 40 C and pH 4. About 91% of the dithiol was converted to short soluble oligomers and 9% to insoluble larger oligomers that were isolated with the FE(OH)O phase. Reactions carried out at the same ratio of dithiol to FE(OH)O but at higher dithiol concentrations gave higher yields of the larger insoluble oligomers. The relationship of these results to prebiotic polymer synthesis is discussed.

  18. Prebiotic polymerization: Oxidative polymerization of 2, 3-dimercapto-1-propanol on the surface of iron(III) hydroxide oxide

    Science.gov (United States)

    Weber, Arthur L.

    1995-01-01

    The oxidation of 2, 3-dimercapto-1-propanol by ferric ions on the surface of iron(III) hydroxide oxide (Fe(OH)O) yielded polydisulfide oligomers. This polymerization occurred readily at low dithiol concentration under mild aqueous conditions. Polydisulfide polymers up to the 15-mer were synthesized from 1 mM dithiol in 5 ml water reacted with iron(III) hydroxide oxide (20 mg, 160 micromole Fe) for 3 days under anaerobic conditions at 40 C and pH 4. About 91% of the dithiol was converted to short soluble oligomers and 9% to insoluble larger oligomers that were isolated with the Fe(OH)O phase. Reactions carried out at the same ratio of dithiol to Fe(OH)O but at higher dithiol concentrations gave higher yields of the larger insoluble oligomers. The relationship of these results to prebiotic polymer synthesis is discussed.

  19. Insights into relevant mechanistic aspects about the induction period of Cu(0)/Me(6)TREN-mediated reversible-deactivation radical polymerization.

    Science.gov (United States)

    Gao, Yongsheng; Zhao, Tianyu; Zhou, Dezhong; Greiser, Udo; Wang, Wenxin

    2015-10-04

    There is a controversial debate about the mechanism of the Cu(0)-catalyzed radical polymerization. Herein, a comparative analysis of a series of reactions catalyzed by different valent copper shows that the induction period and the subsequent autoaccelerated polymerization of a Cu(0)/Me6TREN-catalyzed system originate from the accumulation of soluble copper species, and Cu(I) is still a powerful activator under its disproportionation favored conditions.

  20. Controlled synthesis of biodegradable lactide polymers and copolymers using novel in situ generated or single-site stereoselective polymerization initiators.

    Science.gov (United States)

    Zhong, Zhiyuan; Dijkstra, Pieter J; Feijen, Jan

    2004-01-01

    Polylactides and their copolymers are key biodegradable polymers used widely in biomedical, pharmaceutical and ecological applications. The development of synthetic pathways and catalyst/initiator systems to produce pre-designed polylactides, as well as the fundamental understanding of the polymerization reactions, has continuously been an important topic. Here, we will address the recent advances in the ring-opening polymerization of lactides, with an emphasis on the highly versatile in situ generated initiator systems and single-site stereoselective initiators. The in situ generated initiators including in situ formed yttrium, calcium and zinc alkoxides all have been shown to bring about a rapid and living polymerization of lactides under mild conditions, which facilitated the preparation of a variety of advanced lactide-based biomaterials. For example, well-defined di- and tri-block copolymers consisting of hydrophilic poly(ethylene glycol) blocks and hydrophobic polyester blocks, which form novel biodegradable polymersomes or biodegradable thermosensitive hydrogels, have been prepared. In the past few years, significant progress has also been made in the area of stereoselective polymerization of lactides. This new generation of initiators has enabled the production of polylactide materials with novel microstructures and/or properties, such as heterotactic (--RRSSRRSSRRSS--) polylactide, crystalline syndiotactic (--RSRSRSRSRSRS--) polylactide and isotactic stereoblock (--Rn Sn Rn Sn--) polylactide, exhibiting a high melting temperature. The recently developed polymerizations using in situ generated initiators and stereoselective polymerizations have no doubt opened a brand-new avenue for the design and exploration of polylactides and their copolymers.

  1. Hydrophobic Coatings on Cotton Obtained by in Situ Plasma Polymerization of a Fluorinated Monomer in Ethanol Solutions.

    Science.gov (United States)

    Molina, Ricardo; Teixidó, Josep Maria; Kan, Chi-Wai; Jovančić, Petar

    2017-02-15

    Plasma polymerization using hydrophobic monomers in the gas phase is a well-known technology to generate hydrophobic coatings. However, synthesis of functional hydrophobic coatings using plasma technology in liquids has not yet been accomplished. This work is consequently focused on polymerization of a liquid fluorinated monomer on cotton fabric initiated by atmospheric plasma in a dielectric barrier discharge configuration. Functional hydrophobic coatings on cotton were successfully achieved using in situ atmospheric plasma-initiated polymerization of fluorinated monomer dissolved in ethanol. Gravimetric measurements reveal that the amount of polymer deposited on cotton substrates can be modulated with the concentration of monomer in ethanol solution, and cross-linking reactions occur during plasma polymerization of a fluorinated monomer even without the presence of a cross-linking agent. FTIR and XPS analysis were used to study the chemical composition of hydrophobic coatings and to get insights into the physicochemical processes involved in plasma treatment. SEM analysis reveals that at high monomer concentration, coatings possess a three-dimensional pattern with a characteristic interconnected porous network structure. EDX analysis reveals that plasma polymerization of fluorinated monomers takes place preferentially at the surface of cotton fabric and negligible polymerization takes place inside the cotton fabric. Wetting time measurements confirm the hydrophobicity of cotton coatings obtained although equilibrium moisture content was slightly decreased. Additionally, the abrasion behavior and resistance to washing of plasma-coated cotton has been evaluated.

  2. A Mechanistic and Kinetic Study of the Photoinitiated Cationic Double Ring-opening Polymerization of 2-Methylene-7-phenyl-1,4,6,9-tetraoxa-spiro[4.4]nonane.

    Science.gov (United States)

    Ge, Junhao; Trujillo-Lemon, Marianela; Stansbury, Jeffrey W

    2006-12-26

    Efficient photopolymerization of a potentially expandable monomer is of practical importance for a variety of polymeric applications demanding dimensional stability, particularly if the polymerization process is well controlled based on a detailed investigation of the reaction. In the current study, photoinitiated polymerization kinetics of 2-methylene-7-phenyl-1,4,6,9-tetraoxaspiro[4.4]nonane (MPN) either with cationic initiation alone or with combined cationic/free radical initiation was examined using real-time FT-IR. A proposed mechanism based on the simplified propagation steps of the cationic double ring-opening polymerization of MPN was confirmed by both computer modeling and NMR spectroscopic analysis of resulting polymers as well as the experimentally observed apparent activation energy. According to this mechanism, alpha-position attack is the predominant mode for the second ring opening during cationic polymerization of MPN. Further, cationic photopolymerization was performed along with a free radical co-initiator or with exposure to moisture to get an improved understanding of the complex cationic double ring-opening polymerization. As a result, free radical-promoted cationic polymerization helps increase the polymerization rate of MPN while even a trace amount of moisture was found to significantly impact both the reaction kinetics and the polymerization course.

  3. Preparation, Properties and Application of Polymeric Organic-Inorganic Nanocomposites

    Institute of Scientific and Technical Information of China (English)

    任杰; 刘艳; 唐小真

    2003-01-01

    Six preparation methods for polymeric organic-inorganic nanocomposites and their respective mechanisms and features are reviewed. The extraordinary properties of polymeric organic-inorganic nanocomposites are discussed,and their potential applications are evaluated.

  4. Polymerization Initiated at the Sidewalls of Carbon Nanotubes

    Science.gov (United States)

    Tour, James M.; Hudson, Jared L.

    2011-01-01

    A process has been developed for growing polymer chains via anionic, cationic, or radical polymerization from the side walls of functionalized carbon nanotubes, which will facilitate greater dispersion in polymer matrices, and will greatly enhance reinforcement ability in polymeric material.

  5. The Oxidative Coupling of 2,6-Xylenol Catalyzed by Polymeric Complexes of Copper, 1. Kinetic Study of the Catalysis by Copper(II)-Complexes of Partially Aminated Polystyrene

    NARCIS (Netherlands)

    Schouten, Arend Jan; Prak, Nanno; Challa, Ger

    1977-01-01

    The oxidative coupling reaction of 2,6-xylenol catalyzed by copper(II) complexes of chemically modified polystyrene was investigated. Under the applied reaction conditions the main reaction product was 2,6,2',6'-tetramethyl-1,1'-dioxo-4,4'-bicyclohexa-2,5-dienylidene. It was found that the polymeric

  6. Ribozyme Activity of RNA Nonenzymatically Polymerized from 3′,5′-Cyclic GMP

    Directory of Open Access Journals (Sweden)

    Samanta Pino

    2013-12-01

    Full Text Available 3′,5′-Cyclic GMP spontaneously nonenzymatically polymerizes in a base-catalyzed reaction affording G oligonucleotides. When reacted with fully or partially sequence-complementary RNA (oligo C, the abiotically generated oligo G RNA displays a typical ribozyme activity consisting of terminal ligation accompanied by cleavage of an internal phosphate site of the donor oligonucleotide stem upon attack of the acceptor 3′ terminal OH. This reaction is dubbed Ligation following Intermolecular Cleavage (LIC. In a prebiotic perspective, the ability of oligo G polynucleotides to react with other sequences outlines a simple and possible evolutionary scenario based on the autocatalytic properties of RNA.

  7. Solid state polymerization: its action on thermal and rheological properties of PET/PC reactive blends

    Directory of Open Access Journals (Sweden)

    Luis C. Mendes

    2013-01-01

    Full Text Available The solid state polymerization (SSP of PET/PC reactive extrusion blends - with and without cobalt catalyst - at different polymer ratios was studied. Thermal and rheological evaluations were performed. DSC results showed changes in the PET's Tg, Tch, Tm and Xc.. The melt flow rate (MFR decreased for PET and the blends. The intrinsic viscosity increased. The variation in calorimetric and rheological properties might be attributed to the PET's chain extension reactions - esterification and transesterification. These reactions led to an increase in the PET's molar mass, consequently shifting the PET's Tg to lower temperature and PET's crystallization, besides reducing the blend miscibility and flowability.

  8. Mechanistic investigation into cross-linking reactions in low rank coal: formation and pyrolysis of aryl esters

    Energy Technology Data Exchange (ETDEWEB)

    Britt, P.F.; Buchanan, A.C. III; Kiddern, M.K.; Skeen, J.D. [Oak Ridge National Lab. Oak Ridge, TN (USA). Chemical Sciences Division

    2003-07-01

    In this study, the sealed tube pyrolysis of mixtures of m-phenylphenol and benzoic acid have been investigated at 400{sup o}C to determine if cross-linking reactions can occur, and to determine the low temperature pyrolysis pathways of aryl esters, which are not known. Initial studies show that condensation reactions occur between carboxylic acids and phenols to form aryl esters at temperatures as low as 200{sup o}C. With a 3:1 ratio of m-phenylphenol to benzoic acid, yields of m-phenylphenyl benzoate were as high as 50% at 400{sup o}C. At short reaction times, the dominant products were the aryl ester and benzene, formed by the acid catalyzed decarboxylation of benzoic acid, but at longer times, other arylated products grew in indicating that radical reactions were occurring. These products appear to arise from the induced decomposition of benzoic anhydride to form phenyl radicals. The thermal stability of aryl esters was investigated through the pyrolysis of phenyl benzoate at 400{sup o}C. As predicted, the aryl ester appeared to be thermally stable but hydrolytically unstable. In general, formation of aryl esters could act as a low temperature cross-link in low rank coals. 19 refs., 3 figs., 1 tab.

  9. The Morphology of Emulsion Polymerized Latex Particles

    Science.gov (United States)

    Wignall, G. D.; Ramakrishnan, V. R.; Linne, M. A.; Klein, A.; Sperling, L. H.; Wai, M. P.; Gelman, R. A.; Fatica, M. G.; Hoerl, R. H.; Fisher, L. W.

    1987-11-01

    Under monomer starved feed conditions, emulsion polymerization of perdeuterated methyl methacrylate and styrene in the presence of preformed polymethylmethacrylate latexes resulted in particles with a core-shell morphology, as determined by small-angle neutron scattering (SANS) analysis for a hollow sphere. The locus of polymerization of the added deuterated monomer is therefore at the particle surface. In similar measurements a statistical copolymer of styrene and methyl methacrylate was used as seed particles for further polymerization of trideuteromethyl methacrylate. The resulting polymer latex was again shown to have a core-shell morphological structure as determined by SANS. SANS experiments were also undertaken on polystyrene latexes polymerized by equilibrium swelling methods, with deuterated polymer forming the first or second step. The experiments covered a molecular weight range of 6 x 10{sup 4} 10{sup 6} the molecular weights are consistent with the experimental errors, indicating that the deuterium labeled molecules are randomly distributed in the latex. These results led to the finding that the polymer chains were constrained in the latex particles by factors of 2 to 4 from the relaxed coil dimensions. For M < 10{sup 6} g/mol SANS gave zero angle scattering intensities much higher than expected on the basis of a random distribution of labeled molecules. Several models were examined, including the possible development of core-shell structures at lower molecular weights.

  10. Vibrating polymeric microsieves: Antifouling strategies for microfiltration

    NARCIS (Netherlands)

    Gironès i Nogué, M.; Akbarsyah, Imam J.; Bolhuis-Versteeg, Lydia A.M.; Lammertink, Rob G.H.; Wessling, Matthias

    2006-01-01

    Constant flux performance in time is achieved with polyethersulfone (PES) polymeric microsieves when filtering protein solutions, skimmed milk and white beer in combination with backpulsing. Such microsieves are fabricated by phase separation micromolding (PSμM) and possess pores around 2 μm. The fi

  11. Olefin polymerization over supported chromium oxide catalysts

    NARCIS (Netherlands)

    Weckhuysen, B.M.; Schoonheydt, R.A.

    1999-01-01

    Cr/SiO2 or Phillips-type catalysts are nowadays responsible for a large fraction of all polyethylene (HDPE and LLDPE) worldwide produced. In this review, several key-properties of Cr/SiO2 catalysts will be discussed in relation to their polymerization characteristics. It will be shown how the polyol

  12. Forming of Polymeric Tubular Micro-components

    DEFF Research Database (Denmark)

    Qin, Yi; Zhao, Jie; Anyasodor, Gerald;

    2015-01-01

    This chapter is intended to provide an overview of three nontraditional shaping technologies for the forming of polymeric micro-tubes, which are hot embossing, blow molding, and cross rolling, as well as realization of a process chain and the integration of a modular machine-based manufacturing...

  13. Structure-properties relationships in polymeric fibres

    NARCIS (Netherlands)

    Penning, Jan Paul

    1994-01-01

    Dit proefschrift beschrijft een onderzoek naar de samenhang tussen de struktuur en de mechanische eigenschappen van polymere vezels, met als centrale vraag hoe men deze eigenschappen het best kan beschrijven op grond van de vezelstruktuur en hoe deze struktuur onstaat tijdens de diverse stappen van

  14. Proteins and Peptides in Biomimetic Polymeric Membranes

    DEFF Research Database (Denmark)

    Perez, Alfredo Gonzalez

    2013-01-01

    This chapter discusses recent advances and the main advantages of block copolymers for functional membrane protein reconstitution in biomimetic polymeric membranes. A rational approach to the reconstitution of membrane proteins in a functional form can be addressed by a more holistic view by usin...

  15. Bioactive Polymeric Materials for Tissue Repair

    Directory of Open Access Journals (Sweden)

    Diane R. Bienek

    2017-01-01

    Full Text Available Bioactive polymeric materials based on calcium phosphates have tremendous appeal for hard tissue repair because of their well-documented biocompatibility. Amorphous calcium phosphate (ACP-based ones additionally protect against unwanted demineralization and actively support regeneration of hard tissue minerals. Our group has been investigating the structure/composition/property relationships of ACP polymeric composites for the last two decades. Here, we present ACP’s dispersion in a polymer matrix and the fine-tuning of the resin affects the physicochemical, mechanical, and biological properties of ACP polymeric composites. These studies illustrate how the filler/resin interface and monomer/polymer molecular structure affect the material’s critical properties, such as ion release and mechanical strength. We also present evidence of the remineralization efficacy of ACP composites when exposed to accelerated acidic challenges representative of oral environment conditions. The utility of ACP has recently been extended to include airbrushing as a platform technology for fabrication of nanofiber scaffolds. These studies, focused on assessing the feasibility of incorporating ACP into various polymer fibers, also included the release kinetics of bioactive calcium and phosphate ions from nanofibers and evaluate the biorelevance of the polymeric ACP fiber networks. We also discuss the potential for future integration of the existing ACP scaffolds into therapeutic delivery systems used in the precision medicine field.

  16. Polymerization of different lignins by laccase

    NARCIS (Netherlands)

    Mattinen, M.L.; Suortti, T.; Gosselink, R.J.A.; Argyropoulos, D.S.; Evtuguin, D.; Suurnäkki, A.; Jong, de E.; Tamminen, T.

    2008-01-01

    In this study the oxidative polymerization of different lignins, i.e. Flax Soda lignin, Spruce EMAL, and Eucalyptus Dioxane lignin by Trametes hirsuta laccase was compared. Initially the structures of the different lignins were compared by Fourier transform infrared spectroscopy. The reactivity of l

  17. Kinetics of crosslinking in emulsion polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Ghielmi, A.; Fiorentino, S.; Morbidelli, M. [Universitaetstrasse Zuerich (Switzerland)] [and others

    1996-12-31

    A mathematical model for evaluating the chain length distribution of nonlinear polymers produced in emulsions is presented. The heterogeneous emulsion polymerization process is described. The aim of the analysis is the distribution of active polymer chains and pairs of chains with a given growth time in latex particles in state.

  18. Controlled Cationic Polymerization of N-Vinylcarbazol

    NARCIS (Netherlands)

    Nuyken, O.; Rieß, G.; Loontjens, J.A.

    1995-01-01

    Cationic polymerization of N-Vinylcarbazol (NVC) was initiated with 1-iodo-1-(2-methylpropyloxy)ethane in the presence of N(n-Bu)4ClO4 and without addition of this activator. Furthermore, 1-chloro-1-(2-methylpropyloxy) ethane, with and without activator has been applied as initiator for NVC. These i

  19. Operating Modes Of Chemical Reactors Of Polymerization

    Directory of Open Access Journals (Sweden)

    Meruyert Berdieva

    2012-05-01

    Full Text Available In the work the issues of stable technological modes of operation of main devices of producing polysterol reactors have been researched as well as modes of stable operation of a chemical reactor have been presented, which enables to create optimum mode parameters of polymerization process, to prevent emergency situations of chemical reactor operation in industrial conditions.

  20. Planar elongation of soft polymeric networks

    DEFF Research Database (Denmark)

    Jensen, Mette Krog; Hassager, Ole; Rasmussen, Henrik K.

    2010-01-01

    A new test fixture for the filament stretch rheometer (FSR) has been developed to measure planar elongation of soft polymeric networks with application towards pressure-sensitive adhesives (PSAs). The concept of this new geometry is to elongate a tube-like sample by keeping the perimeter constant...

  1. SYNTHESIS OF BLOCK COPOLYMER BY INTEGRATED LIVING ANIONIC POLYMERIZATION-ATOM TRANSFER RADICAL POLYMERIZATION (ATRP)

    Institute of Scientific and Technical Information of China (English)

    Bing Liu; Feng Liu; Ning Luo; Sheng-kang Ying; Qing Liu

    2000-01-01

    Alpha-trichloroacetoxy terminated polystyrene oligomer (PS-CH2CH2OCOCCl3) and poly-(styrene-b-butadiene)oligomer [P(S-b-B)-CH2CH2OCOCCl3)] were synthesized by living anionic polymeri-zation using n-butyllithium as initiator.Then the PS-CH2CH2OCOCCl3 (PS-Cl3) or P(S-b-B)-CH2CH2O-COCCl3 (PSB-Cl3) was used as the macroinitiator in the polymerization of (meth)acrylates in the presence of CuX/bpy. AB diblock and ABC triblock copolymers were prepared by the integrated living anionic polymerization (LAP)-atom transfer radical polymerization (ATRP). The structures of the PSB-Cl3 and the P(S-b-MMA) were identified by FTIR and 1H-NMR spectrum, respectively. A new way to design block copolymers (the combination of LAP and ATRP) was developed.

  2. Preparation of Functional Polymeric Microspheres

    Institute of Scientific and Technical Information of China (English)

    Changchun Wang; Yonghui Deng; Wuli Yang; Shoukuang Fu

    2005-01-01

    @@ 1Introduction Because of the wide applications in the area of biomedical and biotechnological fields, a great efforts have been done to fabricate different kinds of microspheres with tailored structural and surface properties over the last decade[1]. Among them, stimuli responsive microspheres are microspheres that show ability to change their physical-chemical properties and colloidal properties in response to environmental stimuli such as changes of temperature, pH, chemicals, light, electrical field, magnetic field or mechanic stress, etc. These microspheres have been under intensive study for their high potential applications in biomedical and biotechnological fields such as controlled drug delivery[2], biosensor[3], chemical isolation[4], cell culture substrates[5], enzyme immobilization[6], bioelectrocatalysis[7], and magnetically controlled electrochemical reaction[8]. However,most of the reported stimuli responsive microspheres only show response to one specific stimulus. Up to now,to the best of our knowledge, only a few works have been directed to the fabrication of microspheres which show response to more than one stimulus[9]. In this paper, a system synthesis method for stimuli responsive microspheres with more useful properties was reported, and the simple application in biomedical area have been mentioned.

  3. Mechanism and Modeling for Polymerization of Acrylamide in Inverse Microemulsions

    Institute of Scientific and Technical Information of China (English)

    LiXiao; ZhangWeiying; YuanHuigen

    2004-01-01

    After discussion on the mechanism of polymer particle nucleation and growth in inverse microemulsion polymerization, a schematic physical model for polymerization of acrylamide in inverse microemulsions was presented. Furthermore, several key problems in mathematically modeling of inverse microemulsion polymerization were pointed out.

  4. Mechanism and Kinetics of Nitroxide-Controlled Free Radical Polymerization (ORGANIC MATERIALS CHEMISTRY-Polymeric Materials)

    OpenAIRE

    1997-01-01

    In the nitroxide-mediated free radical polymerization, the rate of polymerization is determined by the balance of the rates of thermal initiation and bialkyl termination, just like in the conventional system, while the polydispersity is determined by the dissociation-combination frequency of the polymer-nitroxyl adduct and the rate of decomposition of the adduct. These mechanisms were quantitatively confirmed by both experiments and computer simulations.

  5. Free heme and sickle hemoglobin polymerization

    Science.gov (United States)

    Uzunova, Veselina V.

    This work investigates further the mechanism of one of the most interesting of the protein self-assembly systems---the polymerization of sickle hemoglobin and the role of free heme in it. Polymerization of sickle hemoglobin is the primary event in the pathology of a chronic hemolytic condition called sickle cell anemia with complex pathogenesis, unexplained variability and symptomatic treatment. Auto-oxidation develops in hemoglobin solutions exposed to room temperature and causes release of ferriheme. The composition of such solutions is investigated by mass spectrometry. Heme dimers whose amount corresponds to the initial amounts of heme released from the protein are followed. Differences in the dimer peak height are established for hemoglobin variants A, S and C and depending on the exposure duration. The effects of free heme on polymerization kinetics are studied. Growth rates and two characteristic parameters of nucleation are measured for stored Hb S. After dialysis of polymerizing solutions, no spherulites are detected at moderately high supersaturation and prolonged exposure times. The addition of 0.16-0.26 mM amounts of heme to dialyzed solutions leads to restoration of polymerization. The measured kinetic parameters have higher values compared to the ones before dialysis. The amount of heme in non-dialyzed aged solution is characterized using spectrophotometry. Three methods are used: difference in absorbance of dialyzed and non-dialyzed solutions, characteristic absorbance of heme-albumin complex and absorbance of non-dialyzed solutions with added potassium cyanide. The various approaches suggest the presence of 0.12 to 0.18 mM of free ferriheme in such solutions. Open questions are whether the same amounts of free heme are present in vivo and whether the same mechanism operates intracellulary. If the answer to those questions is positive, then removal of free heme from erythrocytes can influence their readiness to sickle.

  6. Polyethylene/Clay Nanocomposites Produced by In Situ Polymerization with Zirconocene/MAO Catalyst

    Directory of Open Access Journals (Sweden)

    Pimpatima Panupakorn

    2013-01-01

    Full Text Available Two commercial nanoclays were used here as catalytic fillers for production of polyethylene (PE and linear low-density polyethylene (LLDPE nanocomposites via in situ polymerization with zirconocene/MAO catalyst. It was found that both types of nanoclays designated as clay A and clay B can improve thermal stability to the host polymers as observed from a thermal gravimetric analysis (TGA. The distribution of the clays inside the polymer matrices appeared good due to the in situ polymerization system into which the clays were introduced during the polymer forming reaction. Upon investigating the clays by X-ray diffractometer (XRD and Fourier transform infrared spectroscopy (FTIR, it was observed that the crucial differences between the two clays are the crystallite sizes (A < B and the amounts of amine group (A < B. The higher amount of amine group in clay B was supposed to be a major reason for the lower catalytic activity of the polymerization systems compared to clay A resulting from its deactivating effect on zirconocene catalyst. However, for both clays, increasing their contents in the polymerization systems reduced the catalytic activity due to the higher steric hindrance occurring.

  7. Synthesis of Mixed-ring Zirconocene Complexes Containing Alkenyl Group and Ethylene Polymerization Catalyzed with Them

    Institute of Scientific and Technical Information of China (English)

    钱延龙; 孙俊全; 等

    2003-01-01

    Four new mixed-ring zirconium complexes,[CH2=CH(CH2)n·C5H4](RC5H4)ZrCl2[n=1,R=CH3OCH2CH2(3);n=2,R=CH3OCH2CH2(4);n=2,R=Me3Si(5);n=2,R=allyl(6)],have been prepared by the reaction of CH2=CH(CH2)nC5H4ZrCl3·DME[n=1(1);n=2(2)] with RC5H4Li.When activated with methylaluminoxane(MAO),the catalytic activities of the above complexes in ethylene polymerization were tested.Complexes 5 and 6 show high activities similar to Cp2ZrCl2.Introduction of methoxyethyl group into Cp-ligand dramatically decreases the catalytic activities of complexes 3 and 4,which can be overcome by increasing the amount of MAO.For complex 5,the dependence of activity and molecular weight(Mη) on the Al/Zr ratio,the polymerization time(tp).polymerization temperature(Tp) and the polymerization solvent volume(V) was investigated.

  8. Kinetics of Atom Transfer Radical Polymerization of Methyl Methacrylate Initiated by Cellulose Chloroacetate in BMIMCI

    Institute of Scientific and Technical Information of China (English)

    LIN Chun-xiang; ZHAN Huai-yu; LIU Ming-hua; FU Shi-yu; LUCIA Lucian

    2013-01-01

    The kinetics of atom transfer radical polymerization(ATRP) of methyl methacrylate(MMA) initiated by cellulose based macroinitator,cellulose chloroacetate,performed in ionic liquid(1-N-butyl-3-methylimidazolium chloride,BMIMCl),dimethyl sulfoxide(DMSO) and dimethyl formamide(DMF) were respectively studied in detail.The polymerizations were carried out under homogeneous conditions with CuBr as catalyst and 2,2'-bipyridine(bpy)as ligand.The dependences of the rate of polymerization on solvent,temperature,monomer/initiator ratio and catalyst/ligand ratio were presented.Plots of ln([M]0/[M]t) vs.time and molecular weight vs.conversion showed a linear dependence,indicating a constant number of propagating species throughout the polymerization as well as a negligible contribution of termination or transfer reactions.On the basis of an Arrhenius plot,the apparent energy of activation(△Eaapp) for ATRP of MMA in BMIMC1 was 16.6 kJ/mol which is much lower than that in diphenyl ether.

  9. Synthesis and crystal structure and nonlinear optical properties of polymeric W (Mo)-Cu-S cluster

    Institute of Scientific and Technical Information of China (English)

    ZHOU Jian-liang; CHEN Qi-yuan; GU Ying-ying; ZHONG Shi-an

    2006-01-01

    The polymeric chalcogenide [W2O2S6Cu4(NCMe)4]n (compound 1) was synthesized by the self-assembly reaction of (NH4)2(WOS3) with CuBr in MeCN in the presence of tricyclohexylphosphane (PCy3) under a purified nitrogen atmosphere using standard Schlenk techniques. It gives rise to a novel 1D polymeric compound 1 with solvent MeCN coordinated to the copper atom. This situation is unprecedented in the W(Mo)/Cu/S system. The crystals were characterized by elemental analysis,IR and single-crystal X-ray crystallography. The configuration of the polymeric compound can be viewed as a helical chain which is propagated along the crystallographic c axis. The excited state absorption and refraction of compound 1 in CH3CN solution were studied by using the Z-scan technique with laser pulses of 40 ps pulse-width at a wavelength of 532 nm. The polymeric compound possesses an optical self-focusing performance. The positive nonlinear refraction is attributed to population transitions between singlet states. Compound 1 displays a strong excited-state absorption.

  10. Poly-amido-saccharides: synthesis via anionic polymerization of a β-lactam sugar monomer.

    Science.gov (United States)

    Dane, Eric L; Grinstaff, Mark W

    2012-10-01

    Enantiopure poly-amido-saccharides (PASs) with a defined molecular weight and narrow dispersity are synthesized using an anionic ring-opening polymerization of a β-lactam sugar monomer. The PASs have a previously unreported main chain structure that is composed of pyranose rings linked through the 1- and 2-positions by an amide with α-stereochemistry. The monomer is synthesized in one-step from benzyl-protected D-glucal and polymerized using mild reaction conditions to give degrees of polymerization ranging from 25 to >120 in high yield. Computational modeling reveals how the monomer's structure and steric bulk affect the thermodynamics and kinetics of polymerization. Protected and deprotected polymers and model compounds are characterized using a variety of methods (NMR, GPC, IR, DLS, etc.). On the basis of circular dichroism, the deprotected polymer possesses a regular secondary structure in aqueous solution, which agrees favorably with the prediction of a helical structure using molecular modeling. Furthermore, we provide evidence suggesting that the polymers bind the lectin concanavalin A at the same site as natural carbohydrates, showing the potential of these polymers to mimic natural polysaccharides. PASs offer the advantages associated with synthetic polymers, such as greater control over structure and derivitization. At the same time, they preserve many of the structural features of natural polysaccharides, such as a stereochemically regular, rigid pyranose backbone, that make natural carbohydrate polymers important materials both for their unique properties and useful applications.

  11. Synthesis of polyanthranilic acid–Au nanocomposites by emulsion polymerization: development of dopamine sensor

    Indian Academy of Sciences (India)

    Bhavana Gupta; Ambrose Melvin; Rajiv Prakash

    2014-10-01

    Polyanthranilic acid (PANA) and polyanthranilic acid–gold (PANA–Au) nanocomposites have been synthesized through emulsion polymerization technique. Use of gold chloride as an oxidant for anthranilic acid not only provides a new route for chemical synthesis of PANA, but also explores a facile method for the formation of nanocomposites. Emulsion polymerization helps in slowing down kinetics of polymerization in comparison to one-phase polymerization and thereby induces formation of monodispersed, both pure and Au nanoparticles, embedded PANA sphere. Reaction progress of nanocomposite formation is studied by UV–Vis spectroscopy for 0–24 h. PANA–Au nanocomposites are characterized by SEM, equipped with EDS, TGA, FT–IR, XRD and electrochemical techniques. XRD of nanocomposites depicts the amorphous nature of polymer and crystalline nature of Au with crystallite size of ∼ 24 nm. Differential pulse voltammetry has shown the electro-active nature of PANA. The nanocomposites with improved thermal properties show good dispersion in common organic solvents, and it can be explored for application in interference-free dopamine sensors with sensitivity 12.5 A/mM. Acidic group (–COOH) on the polymer makes the sensor free from ascorbic acid interference.

  12. Constructing Functional Ionic Membrane Surface by Electrochemically Mediated Atom Transfer Radical Polymerization

    Directory of Open Access Journals (Sweden)

    Fen Ran

    2016-01-01

    Full Text Available The sodium polyacrylate (PAANa contained polyethersulfone membrane that was fabricated by preparation of PES-NH2 via nonsolvent phase separation method, the introduction of bromine groups as active sites by grafting α-Bromoisobutyryl bromide, and surface-initiated electrochemically atom transfer radical polymerization (SI-eATRP of sodium acrylate (AANa on the surface of PES membrane. The polymerization could be controlled by reaction condition, such as monomer concentration, electric potential, polymerization time, and modifier concentration. The membrane surface was uniform when the monomer concentration was 0.9 mol/L, the electric potential was −0.12 V, the polymerization time was 8 h, and the modifier concentration was 2 wt.%. The membrane showed excellent hydrophilicity and blood compatibility. The water contact angle decreased from 84° to 68° and activated partial thromboplastin increased from 51 s to 84 s after modification of the membranes.

  13. Cobalt-Mediated Radical Polymerization of Vinyl Acetate and Acrylonitrile in Supercritical Carbon Dioxide.

    Science.gov (United States)

    Kermagoret, Anthony; Chau, Ngoc Do Quyen; Grignard, Bruno; Cordella, Daniela; Debuigne, Antoine; Jérôme, Christine; Detrembleur, Christophe

    2016-03-01

    Cobalt-mediated radical polymerization (CMRP) of vinyl acetate (VAc) is successfully achieved in supercritical carbon dioxide (scCO2). CMRP of VAc is conducted using an alkyl-cobalt(III) adduct that is soluble in scCO2. Kinetics studies coupled to visual observations of the polymerization medium highlight that the melt viscosity and PVAc molar mass (Mn) are key parameters that affect the CMRP in scCO2. It is noticed that CMRP is controlled for Mn up to 10 000 g mol(-1), but loss of control is progressively observed for higher molar masses when PVAc precipitates in the polymerization medium. Low molar mass PVAc macroinitiator, prepared by CMRP in scCO2, is then successfully used to initiate the acrylonitrile polymerization. PVAc-b-PAN block copolymer is collected as a free flowing powder at the end of the process although the dispersity of the copolymer increases with the reaction time. Although optimization is required to decrease the dispersity of the polymer formed, this CMRP process opens new perspectives for macromolecular engineering in scCO2 without the utilization of fluorinated comonomers or organic solvents.

  14. Signal amplification strategies for DNA and protein detection based on polymeric nanocomposites and polymerization: A review

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Shaohong; Yuan, Liang; Hua, Xin; Xu, Lingling; Liu, Songqin, E-mail: liusq@seu.edu.cn

    2015-06-02

    Highlights: • We review the innovative advances in polymer-based signal amplification. • Conceptual connectivity between different amplified methodologies is illustrated. • Examples explain the mechanisms of polymers/polymerizations-based amplification. • Several elegant applications are summarized that illustrate underlying concept. - Abstract: Demand is increasing for ultrasensitive bioassays for disease diagnosis, environmental monitoring and other research areas. This requires novel signal amplification strategies to maximize the signal output. In this review, we focus on a series of significant signal amplification strategies based on polymeric nanocomposites and polymerization. Some common polymers are used as carriers to increase the local concentration of signal probes and/or biomolecules on their surfaces or in their interiors. Some polymers with special fluorescence and optical properties can efficiently transfer the excitation energy from a single site to the whole polymer backbone. This results in superior fluorescence signal amplification due to the resulting collective effort (integration of signal). Recent polymerization-based signal amplification strategies that employ atom transfer radical polymerization (ATRP) and photo-initiated polymerization are also summarized. Several distinctive applications of polymers in ultrasensitive bioanalysis are highlighted.

  15. Mechanistic study of secondary organic aerosol components formed from nucleophilic addition reactions of methacrylic acid epoxide

    Directory of Open Access Journals (Sweden)

    A. W. Birdsall

    2014-08-01

    Full Text Available Recently, methacrylic acid epoxide (MAE has been proposed as a precursor to an important class of isoprene-derived compounds found in secondary organic aerosol (SOA: 2-methylglyceric acid (2-MG and a set of oligomers, nitric acid esters and sulfuric acid esters related to 2-MG. However, the specific chemical mechanisms by which MAE could form these compounds have not been previously studied. In order to determine the relevance of these processes to atmospheric aerosol, MAE and 2-MG have been synthesized and a series of bulk solution-phase experiments aimed at studying the reactivity of MAE using nuclear magnetic resonance (NMR spectroscopy have been performed. The present results indicate that the acid-catalyzed MAE reaction is more than 600 times slower than a similar reaction of an important isoprene-derived epoxide, but is still expected to be kinetically feasible in the atmosphere on more acidic SOA. The specific mechanism by which MAE leads to oligomers was identified, and the reactions of MAE with a number of atmospherically relevant nucleophiles were also investigated. Because the nucleophilic strengths of water, sulfate, alcohols (including 2-MG, and acids (including MAE and 2-MG in their reactions with MAE were found to be of a similar magnitude, it is expected that a diverse variety of MAE + nucleophile product species may be formed on ambient SOA. Thus, the results indicate that epoxide chain reaction oligomerization will be limited by the presence of high concentrations of non-epoxide nucleophiles (such as water; this finding is consistent with previous environmental chamber investigations of the relative humidity-dependence of 2-MG-derived oligomerization processes and suggests that extensive oligomerization may not be likely on ambient SOA because of other competitive MAE reaction mechanisms.

  16. THE EFFECTS OF N-2-HYDROXYETHYL-N-METHYL-P-TOLUIDINE ON METHYL METHACRYLATE RADICAL POLYMERIZATION AND ACRYLONITRILE PHOTOINDUCED POLYMERIZATION

    Institute of Scientific and Technical Information of China (English)

    QIU Kunyuan; ZHANG Zhanghua; FENG Xinde

    1992-01-01

    The effects of N-2-hydroxyethyl-N-methyl-p-toluidine (HMT) on MMA polymerization using organic peroxide as an initiator and on AN photoinduced polymerization have been investigated respectively. The kinetics of polymerization and the overall activation energy of polymerization were determined. Based on kinetics study and the end group analysis of the polymer obtained by UV spectrum method, the initiation mechanism is proposed.

  17. Controlled radical polymerization of vinyl acetate in presence of mesoporous silica supported TiCl4 heterogeneous catalyst

    Indian Academy of Sciences (India)

    M A Semsarzadeh; S Amiri; M Azadeh

    2012-10-01

    The heterogeneous TiCl4 catalysts supported on mesoporous mobile composition of matter (MCM-41) and mesoporous silicone particles synthesized from block copolymer of PPG–PEG–PPG (SPB) complexed with dimethyl formamide (DMF) ligand were used in a controlled free radical reaction with benzoyl peroxide (BPO) initiator in bulk polymerization of vinyl acetate (VAc). In this polymerization process, mesoporous particle of SPB increased the reactivity of TiCl4 catalyst with DMF ligand. The active site formed on the surface and the pores of the catalyst produced specific sequences of VAc on the chain with different thermal and microstructural properties and crystallinity.

  18. Raspberry-like nanocomposite microsphere prepared by double in situ miniemulsion polymerization using interfacial redox initiator system

    Institute of Scientific and Technical Information of China (English)

    LIN Ji-zhi; WU Bo; ZHANG Jian-an; YANG Jian-jun; WU Qing-yun; WU Ming-yuan

    2012-01-01

    The butyl rubber was synthesized with acetone as the third component of initiating system by solution method, and the effect of acetone on the polymerization was investigated. The results showed that the acetone had a certain inhibition effect on the carboncation active center and reduced the side reactions in the later stage of polymerization, thus increasing the relative molecular mass of the polymer. The optimal molar ratio of ethylaluminium sesqui- chloride to water to acetone was 14. 1/1/0. 90, and under this condition, the polymer with higher relative molecular mass and narrow molecular weight distribution could be synthesized at a higher temperature.

  19. Capture reactions

    NARCIS (Netherlands)

    Endt, P.M.

    1956-01-01

    Capture reactions will be considered here from the viewpoint of the nuclear spectroscopist. Especially important to him are the capture of neutrons, protons, and alpha particles, which may proceed through narrow resonances, offering a well defined initial state for the subsequent deexcitation proces

  20. Wrinkling of solidifying polymeric coatings

    Science.gov (United States)

    Basu, Soumendra Kumar

    2005-07-01

    In coatings, wrinkles are viewed as defects or as desired features for low gloss, and texture. In either case, discovering the origin of wrinkles and the conditions that lead to their formation is important. This research examines what wrinkling requires and proposes a mechanism to explain the observations. All curing wrinkling coatings contain multi-functional reactants. Upon curing, all develop a depth-wise gradient in solidification that result in a cross-linked elastic skin atop a viscous bottom layer. It is hypothesized that compressive stress develops in the skin when liquid below diffuses up into the skin. High enough compressive stress buckles the skin to produce wrinkles. The hypothesis is substantiated by experimental and theoretical evidences. Effects of various application and compositional parameters on wrinkle size in a liquid-applied acrylic coating and a powder-applied epoxy coating were examined. All three components, namely resin, cross-linker and catalyst blocked with at least equimolar volatile blocker, proved to be required for wrinkling. The wrinkling phenomenon was modeled with a theory that accounts for gradient generation, cross-linking reaction and skinning; predictions compared well with observations. Two-layer non-curing coatings that have a stiff elastic layer atop a complaint elastic bottom layer wrinkled when the top layer is compressed. The top layer was compressed by either moisture absorption or differential thermal expansion. Experimental observations compared well with predictions from a theory based on force balance in multilayer systems subjected to differential contraction or expansion. A model based on the Flory-Rehner free energy of a constrained cross-linked gel was constructed that predicts the compressive stress generated in a coating when it absorbs solvent. Linear stability analysis predicts that when a compressed elastic layer is attached atop a viscous layer, it is always unstable to buckles whose wavelength exceeds a