Effect of side chain length and degree of polymerization on the decomposition and crystallization behaviour of chlorinated poly(vinyl ester) oligomers

International Nuclear Information System (INIS)

Heinze, D.; Mang, Th.; Popescu, C.; Weichold, O.

2016-01-01

Highlights: • Thermal behaviour of telomerized polyvinyl esters is investigated. • Thermal stability relies mainly on the contribution of side chains. • At equal molecular weights thermal stability is dictated by length of side chain. • Increasing the length of side chains improves also the packing degree of polymer. - Abstract: Four members of a homologous series of chlorinated poly(vinyl ester) oligomers CCl_3–(CH_2CH (OCO(CH_2)_mCH_3))_n–Cl with degrees of polymerization of 10 and 20 were prepared by telomerisation using carbon tetrachloride. The number of side chain carbon atoms ranges from 2 (poly(vinyl acetate) to 18 (poly(vinyl stearate)). The effect of the n-alkyl side chain length and of the degree of polymerization on the thermal stability and crystallization behaviour of the synthesized compounds was investigated. All oligomers degrade in two major steps by first losing HCl and side chains with subsequent breakdown of the backbone. The members with short side chains, up to poly(vinyl octanoate), are amorphous and show internal plasticization, whereas those with high number of side chain carbon atoms are semi-crystalline due to side-chain crystallization. A better packing for poly(vinyl stearate) is also noticeable. The glass transition and melting temperatures as well as the onset temperature of decomposition are influenced to a larger extent by the side chain length than by the degree of polymerization. Thermal stability is improved if both the size and number of side chains increase, but only a long side chain causes a significant increase of the resistance to degradation. This results in a stabilization of PVAc so that oligomers from poly(vinyl octanoate) on are stable under atmospheric conditions. Thus, the way to design stable, chlorinated PVEs oligomers is to use a long n-alkyl side chain.

Effect of side chain length and degree of polymerization on the decomposition and crystallization behaviour of chlorinated poly(vinyl ester) oligomers

Energy Technology Data Exchange (ETDEWEB)

Heinze, D.; Mang, Th. [Aachen University of Applied Sciences, Heinrich-Mussmann-Str. 1, 52428 Jülich (Germany); Popescu, C., E-mail: crisan.popescu@kao.com [KAO Germany GmbH, Pfungstädterstr. 98-100, 64297 Darmstadt (Germany); Weichold, O., E-mail: weichold@ibac.rwth-aachen.de [Institute of Building Materials Research, Schinkelstr. 3, 52062 Aachen (Germany)

2016-08-10

Highlights: • Thermal behaviour of telomerized polyvinyl esters is investigated. • Thermal stability relies mainly on the contribution of side chains. • At equal molecular weights thermal stability is dictated by length of side chain. • Increasing the length of side chains improves also the packing degree of polymer. - Abstract: Four members of a homologous series of chlorinated poly(vinyl ester) oligomers CCl{sub 3}–(CH{sub 2}CH (OCO(CH{sub 2}){sub m}CH{sub 3})){sub n}–Cl with degrees of polymerization of 10 and 20 were prepared by telomerisation using carbon tetrachloride. The number of side chain carbon atoms ranges from 2 (poly(vinyl acetate) to 18 (poly(vinyl stearate)). The effect of the n-alkyl side chain length and of the degree of polymerization on the thermal stability and crystallization behaviour of the synthesized compounds was investigated. All oligomers degrade in two major steps by first losing HCl and side chains with subsequent breakdown of the backbone. The members with short side chains, up to poly(vinyl octanoate), are amorphous and show internal plasticization, whereas those with high number of side chain carbon atoms are semi-crystalline due to side-chain crystallization. A better packing for poly(vinyl stearate) is also noticeable. The glass transition and melting temperatures as well as the onset temperature of decomposition are influenced to a larger extent by the side chain length than by the degree of polymerization. Thermal stability is improved if both the size and number of side chains increase, but only a long side chain causes a significant increase of the resistance to degradation. This results in a stabilization of PVAc so that oligomers from poly(vinyl octanoate) on are stable under atmospheric conditions. Thus, the way to design stable, chlorinated PVEs oligomers is to use a long n-alkyl side chain.

Enzymatic synthesis of 6-O-glucosyl-poly(3-hydroxyalkanoate) in organic solvents and their binary mixture.

Science.gov (United States)

Gumel, A M; Annuar, M S M; Heidelberg, T

2013-04-01

The effects of organic solvents and their binary mixture in the glucose functionalization of bacterial poly-3-hydroxyalkanoates catalyzed by Lecitase™ Ultra were studied. Equal volume binary mixture of DMSO and chloroform with moderate polarity was more effective for the enzyme catalyzed synthesis of the carbohydrate polymer at ≈38.2 (±0.8)% reactant conversion as compared to the mono-phasic and other binary solvents studied. The apparent reaction rate constant as a function of medium water activity (aw) was observed to increase with increasing solvent polarity, with optimum aw of 0.2, 0.4 and 0.7 (±0.1) observed in hydrophilic DMSO, binary mixture DMSO:isooctane and hydrophobic isooctane, respectively. Molecular sieve loading between 13 to 15gL(-1) (±0.2) and reaction temperature between 40 to 50°C were found optimal. Functionalized PHA polymer showed potential characteristics and biodegradability. Copyright © 2012 Elsevier B.V. All rights reserved.

Novel poly(hydroxyalkanoates)-based composites containing Bioglass® and calcium sulfate for bone tissue engineering

International Nuclear Information System (INIS)

García-García, J M; Boccaccini, A R; Garrido, L; Quijada-Garrido, I; Kaschta, J; Schubert, D W

2012-01-01

Three different poly(hydroxyalkanoates) (PHAs), copolymers of poly(3-hydroxybutyrate) (P3HB), have been used to make composites using two different fillers, bioactive glass (type 45S5 Bioglass®) and calcium sulfate dihydrate. The PHAs used were poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [PHBHV] and two copolymers of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) [PHBHHx]. The aim of the study was the fabrication and characterization of the new composites and the assessment of the influence of the particular filler combination on the physical properties and bioactivity of the films. The thermal behaviour was studied using differential scanning calorimetry while mechanical properties were evaluated using dynamic mechanic thermal analysis and tensile strength test. The mechanical and thermal properties were affected by particles addition. The distribution of the particles in the polymer matrix, observed by scanning electron microscopy, was directly related to the mechanical properties. The surface characteristics were investigated by contact angle measurements and Raman spectroscopy. The extent of formation of hydroxyapatite (HA) upon immersion in simulated body fluid (SBF) depended on the polymer used, the amount of fillers employed and the time of immersion in SBF. Bioactivity was enhanced in the composites with a rise of hydrophilicity. The HA formation was controllable with time in the case of PHBHHx composites. (paper)

Polymer chain alignment and transistor properties of nanochannel-templated poly(3-hexylthiophene) nanowires

Science.gov (United States)

Oh, Seungjun; Hayakawa, Ryoma; Pan, Chengjun; Sugiyasu, Kazunori; Wakayama, Yutaka

2016-08-01

Nanowires of semiconducting poly(3-hexylthiophene) (P3HT) were produced by a nanochannel-template technique. Polymer chain alignment in P3HT nanowires was investigated as a function of nanochannel widths (W) and polymer chain lengths (L). We found that the ratio between chain length and channel width (L/W) was a key parameter as regards promoting polymer chain alignment. Clear dichroism was observed in polarized ultraviolet-visible (UV-Vis) absorption spectra only at a ratio of approximately L/W = 2, indicating that the L/W ratio must be optimized to achieve uniaxial chain alignment in the nanochannel direction. We speculate that an appropriate L/W ratio is effective in confining the geometries and conformations of polymer chains. This discussion was supported by theoretical simulations based on molecular dynamics. That is, the geometry of the polymer chains, including the distance and tilting angles of the chains in relation to the nanochannel surface, was dominant in determining the longitudinal alignment along the nanochannels. Thus prepared highly aligned polymer nanowire is advantageous for electrical carrier transport and has great potential for improving the device performance of field-effect transistors. In fact, a one-order improvement in carrier mobility was observed in a P3HT nanowire transistor.

Burkholderia sacchari DSM 17165: A source of compositionally-tunable block-copolymeric short-chain poly(hydroxyalkanoates) from xylose and levulinic acid.

Science.gov (United States)

Ashby, Richard D; Solaiman, Daniel K Y; Nuñez, Alberto; Strahan, Gary D; Johnston, David B

2018-04-01

Burkholderia sacchari was used to produce poly-3-hydroxybutyrate-co-3-hydroxyvalerate block copolymers from xylose and levulinic acid. Levulinic acid was the preferred substrate resulting in 3-hydroxyvalerate (3HV) contents as high as 95 mol% at 24 h. The 3HB:3HV ratios were controlled by the initial levulinic acid media concentration and fermentation length. Higher levulinic acid concentrations and longer durations, resulted in polymers with two glass transition temperatures, each approximating those associated with poly-3HB and poly-3HV. 13 C NMR confirmed the presence of high concentrations of 3HB-3HB and 3HV-3HV homopolymeric dyads, while mass spectrometry of the partial hydrolysis products did not conform to Bernoullian statistics for randomness, confirming block sequences. MS/MS analysis of specific oligomers showed the mass-loss of 86 amu (a 3HB unit) and 100 amu (a 3HV unit) attesting to some randomness within the polymers. This study verifies the potential for producing Poly-3HB-block-3HV copolymers from inexpensive biorenewable feedstocks without sequential addition of carbon sources. Published by Elsevier Ltd.

The Role of Short-Chain Conjugated Poly-(R-3-Hydroxybutyrate (cPHB in Protein Folding

Directory of Open Access Journals (Sweden)

Rosetta N. Reusch

2013-05-01

Full Text Available Poly-(R-3-hydroxybutyrate (PHB, a linear polymer of R-3-hydroxybutyrate (R-3HB, is a fundamental constituent of biological cells. Certain prokaryotes accumulate PHB of very high molecular weight (10,000 to >1,000,000 residues, which is segregated within granular deposits in the cytoplasm; however, all prokaryotes and all eukaryotes synthesize PHB of medium-chain length (~100–200 residues which resides within lipid bilayers or lipid vesicles, and PHB of short-chain length (<12 residues which is conjugated to proteins (cPHB, primarily proteins in membranes and organelles. The physical properties of cPHB indicate it plays important roles in the targeting and folding of cPHB-proteins. Here we review the occurrence, physical properties and molecular characteristics of cPHB, and discuss its influence on the folding and structure of outer membrane protein A (OmpA of Escherichia coli.

Structure and polymer form of poly-3-hydroxyalkanoates produced by Pseudomonas oleovorans grown with mixture of sodium octanoate/undecylenic acid and sodium octanoate/5-phenylvaleric acid.

Science.gov (United States)

Ho, I-Ching; Yang, Sheng-Pin; Chiu, Wen-Yen; Huang, Shih-Yow

2007-01-30

PHAs (poly-3-hydroxyalkanoates) obtained by Pseudomonas oleovorans grown with mixed carbon sources were investigated. Mixed carbon sources were sodium octanoate/undecylenic acid and sodium octanoate/5-phenylvaleric acid. Effect of carbon source in pre-culture on PHAs structure was investigated. Main fermentation was conducted with mixture of sodium octanoate/undecylenic acid, and PHA contained both saturated and unsaturated units. When more undecylenic acid was used in the medium, the ratio of unsaturated unit increased and the T(g) of the products also changed. The PHA grown with mixture of sodium octanoate and undecylenic acid was a random copolymer, which was determined by DSC analysis. Using mixed carbon sources of sodium octanoate and 5-phenylvaleric acid, highest dry cell weight and PHA concentration were obtained when 0.02g or 0.04g of 5-phenylvaleric acid were added in 50mL medium. Cultured with sodium octanoate and 5-phenylvaleric acid, PHA containing HO (3-hydroxyoctanoate) unit and HPV (3-hydroxy-5-phenylvalerate) unit was produced. T(g) of the products fell between those of pure PHO and pure PHPV. By means of DSC analysis and fractionation method, the PHA obtained was regarded as a random copolymer.

Poly(hydroxyalkanoates for Food Packaging: Application and Attempts towards Implementation

Directory of Open Access Journals (Sweden)

M. Koller

2014-09-01

Full Text Available Plastics are well-established for convenient and safe packaging and distribution of food and feed goods. At present, this special sector of the plastic market displays remarkably increasing quantities of its annual production. Caused by the ongoing limitation and strongly fluctuating prices of fossil feedstocks, classically used for plastic production, there is an evident trend to switch towards so-called “bio-plastics”. Especially for bulk applications such as food packaging, a broad implementation of “bio-plastics” constitutes a future-oriented strategy to restrict the dependence of global industry on fossil feedstocks, and to diminish current problematic environmental issues arising from plastic disposal. However, food packaging demands a great deal of the utilized packaging material. This encompasses tailored mechanical properties such as low brittleness and adequate tensile strength, a sufficient barrier for oxygen, CO2, and aromatic flavors, high UV-resistance, and high water retention-capacity to block the food´s moisture content, or to prevent humidity, respectively. Due to their hydrophobic character and the broad flexibility of their mechanical features, prokaryotic poly(hydroxyalkanoates (PHAs are considered as promising materials to compete with petro-plastics on the food-packaging market. Nevertheless, short-comings in particular aspects of their material performance and economics of their biosynthesis and purification constitute stumbling blocks on the long way towards broad implementation of PHAs for food packaging. This article discusses advantages and drawbacks of PHAs as food packaging materials, and demonstrates how desired properties can be improved by the designing of novel composite materials, and also encompassing techniques by applying nanoparticles.

Synthesis of Diblock copolymer poly-3-hydroxybutyrate -block-poly-3-hydroxyhexanoate [PHB-b-PHHx] by a β-oxidation weakened Pseudomonas putida KT2442.

Science.gov (United States)

Tripathi, Lakshmi; Wu, Lin-Ping; Chen, Jinchun; Chen, Guo-Qiang

2012-04-05

Block polyhydroxyalkanoates (PHA) were reported to be resistant against polymer aging that negatively affects polymer properties. Recently, more and more attempts have been directed to make PHA block copolymers. Diblock copolymers PHB-b-PHHx consisting of poly-3-hydroxybutyrate (PHB) block covalently bonded with poly-3-hydroxyhexanoate (PHHx) block were for the first time produced successfully by a recombinant Pseudomonas putida KT2442 with its β-oxidation cycle deleted to its maximum. The chloroform extracted polymers were characterized by nuclear magnetic resonance (NMR), thermo- and mechanical analysis. NMR confirmed the existence of diblock copolymers consisting of 58 mol% PHB as the short chain length block with 42 mol% PHHx as the medium chain length block. The block copolymers had two glass transition temperatures (Tg) at 2.7°C and -16.4°C, one melting temperature (Tm) at 172.1°C and one cool crystallization temperature (Tc) at 69.1°C as revealed by differential scanning calorimetry (DSC), respectively. This is the first microbial short-chain-length (scl) and medium-chain-length (mcl) PHA block copolymer reported. It is possible to produce PHA block copolymers of various kinds using the recombinant Pseudomonas putida KT2442 with its β-oxidation cycle deleted to its maximum. In comparison to a random copolymer poly-3-hydroxybutyrate-co-3-hydroxyhexanoate (P(HB-co-HHx)) and a blend sample of PHB and PHHx, the PHB-b-PHHx showed improved structural related mechanical properties.

A life cycle assessment of poly-hydroxybutyrate extraction from microbial biomass using dimethyl carbonate

DEFF Research Database (Denmark)

Righi, Serena; Baioli, Filippo; Samorì, Chiara

2017-01-01

Poly-hydroxyalkanoates are an example of biodegradable and biocompatible polymers, produced from renewable raw materials. With respect to other bioplastics the market share of poly-hydroxyalkanoates is still limited because of their commercial costs. To develop more cost-effective processes, a mu...... by evaporation appears to be the most promising in terms of environmental sustainability performance....

Poly (3-hydroxyalkanoates)-co-(6-hydroxyhexanoate) hydrogel promotes angiogenesis and collagen deposition during cutaneous wound healing in rats.

Science.gov (United States)

Gumel, Ahmad Mohammed; Razaif-Mazinah, Mohd Rafais Mohd; Anis, Siti Nor Syairah; Annuar, Mohamad Suffian Mohamad

2015-07-08

Wound management and healing in several physiological or pathological conditions, particularly when comorbidities are involved, usually proves to be difficult. This presents complications leading to socio-economic and public health burdens. The accelerative wound healing potential of biocompatible poly(3-hydroxyalkanoates)-co-(6-hydroxyhexanoate) (PHA-PCL) composite hydrogel is reported herein. The biosynthesized PHA-PCL macromer was cross-linked with PEGMA to give a hydrogel. Twenty-four rats weighing 200-250 g each were randomly assigned to four groups of six rats. Rats in group I (negative control) were dressed with sterilized gum acacia paste in 10% normal saline while PEGMA-alone hydrogel (PH) was used to dress group II (secondary control) rats. Group III rats were dressed with PHAs-PCL cross-linked PEGMA hydrogel (PPH). For the positive control (group IV), the rats were dressed with Intrasite(®) gel. Biochemical, histomorphometric and immunohistomorphometric analyses revealed a significant difference in area closure and re-epithelialization on days 7 and 14 in PPH or Intrasite(®) gel groups compared to gum acacia or PEGMA-alone groups. Furthermore, wounds dressed with PPH or Intrasite(®) gel showed evident collagen deposition, enhanced fibrosis and extensively organized angiogenesis on day 14 compared to the negative control group. While improvement in wound healing of the PH dressed group could be observed, there was no significant difference between the negative control group and the PH dressed group in any of the tests. The findings suggested that topical application of PPH accelerated the rats' wound healing process by improving angiogenesis attributed to the increased microvessel density (MVD) and expressions of VEGF-A in tissue samples. Thus, PPH has been demonstrated to be effective in the treatment of cutaneous wounds in rats, and could be a potential novel agent in the management and acceleration of wound healing in humans and animals.

Individual Impact of Distinct Polysialic Acid Chain Lengths on the Cytotoxicity of Histone H1, H2A, H2B, H3 and H4

Directory of Open Access Journals (Sweden)

Kristina Zlatina

2017-12-01

Full Text Available Neutrophils are able to neutralize pathogens by phagocytosis, by the release of antimicrobial components, as well as by the formation of neutrophil extracellular traps (NETs. The latter possibility is a DNA-meshwork mainly consisting of highly concentrated extracellular histones, which are not only toxic for pathogens, but also for endogenous cells triggering several diseases. To reduce the negative outcomes initiated by extracellular histones, different approaches like antibodies against histones, proteases, and the polysaccharide polysialic acid (polySia were discussed. We examined whether each of the individual histones is a binding partner of polySia, and analyzed their respective cytotoxicity in the presence of this linear homopolymer. Interestingly, all of the histones (H1, H2A, H2B, H3, and H4 seem to interact with α2,8-linked sialic acids. However, we observed strong differences regarding the required chain length of polySia to bind histone H1, H2A, H2B, H3, and H4. Moreover, distinct degrees of polymerization were necessary to act as a cytoprotective agent in the presence of the individual histones. In sum, the outlined results described polySia-based strategies to bind and/or to reduce the cytotoxicity of individual histones using distinct polySia chain length settings.

The effect of poly-β-hydroxyalkanoates degradation rate on nitrous oxide production in a denitrifying phosphorus removal system.

Science.gov (United States)

Wei, Yan; Wang, Shuying; Ma, Bin; Li, Xiyao; Yuan, Zhiguo; He, Yuelan; Peng, Yongzhen

2014-10-01

Poly-β-hydroxyalkanoates (PHAs) and free nitrous acid (FNA) have been revealed as significant factors causing nitrous oxide (N2O) production in denitrifying phosphorus removal systems. In this study, the effect of PHA degradation rate on N2O production was studied at low FNA levels. N2O production always maintained at approximately 40% of the amount of nitrite reduced independent of the PHA degradation rate. The electrons distributed to nitrite reduction were 1.6 times that to N2O reduction. This indicated that electron competition between these two steps was not affected by the PHA degradation rate. Continuous feed of nitrate was proposed, and demonstrated to reduce N2O accumulation by 75%. While being kept low, a possible compounding effect of a low-level FNA could not be ruled out. The sludge used likely contained both polyphosphate- and glycogen-accumulating organisms, and the results could not be simply attributed to either group of organisms. Copyright © 2014 Elsevier Ltd. All rights reserved.

Rapid spectrofluorometric screening of poly-hydroxyalkanoate-producing bacteria from microbial mats.

Science.gov (United States)

Berlanga, Mercedes; Montero, M T; Fernández-Borrell, Jordi; Guerrero, Ricardo

2006-06-01

Microbial mat ecosystems are characterized by both seasonal and diel fluctuations in several physicochemical variables, so that resident microorganisms must frequently adapt to the changing conditions of their environment. It has been pointed out that, under stress conditions, bacterial cells with higher contents of poly-hydroxyalkanoates (PHA) survive longer than those with lower PHA content. In the present study, PHA-producing strains from Ebro Delta microbial mats were selected using the Nile red dying technique and the relative accumulation of PHA was monitored during further laboratory cultivation. The number of heterotrophic isolates in trypticase soy agar (TSA) was ca. 107 colony-forming units/g microbial mat. Of these, 100 randomly chosen colonies were replicated on mineral salt agar limited in nitrogen, and Nile red was added to the medium to detect PHA. Orange fluorescence, produced upon binding of the dye to polymer granules in the cell, was detected in approximately 10% of the replicated heterotrophic isolates. The kinetics of PHA accumulation in Pseudomonas putida, and P. oleovorans were compared with those of several of the environmental isolates spectrofluorometry. PHA accumulation, measured as relative fluorescence intensity, resulted in a steady-state concentration after 48 h of incubation in all strains assayed. At 72 h, the maximum fluorescence intensity of each strain incubated with glucose and fructose was usually similar. MAT-28 strain accumulated more PHA than the other isolates. The results show that data obtained from environmental isolates can highly improve studies based on modeling-simulation programs, and that microbial mats constitute an excellent source for the isolation of PHA-producing strains with industrial applications.

Recycling of Waste Streams of the Biotechnological Poly(hydroxyalkanoate Production by Haloferax mediterranei on Whey

Directory of Open Access Journals (Sweden)

Martin Koller

2015-01-01

Full Text Available For manufacturing “bioplastics” such as poly(hydroxyalkanoates (PHA, the combination of utilization of inexpensive carbon sources with the application of robust microbial production strains is considered a decisive step to make this process more cost-efficient and sustainable. PHA production based on surplus whey from dairy industry was accomplished by the extremely halophile archaeon Haloferax mediterranei. After fermentative production of PHA-rich biomass and the subsequent cell harvest and downstream processing for PHA recovery, environmentally hazardous, highly saline residues, namely spent fermentation broth and cell debris, remain as residues. These waste streams were used for recycling experiments to assess their recyclability in subsequent production processes. It was demonstrated that spent fermentation broth can be used to replace a considerable part of fresh saline fermentation medium in subsequent production processes. In addition, 29% of the expensive yeast extract, needed as nitrogen and phosphate source for efficient cultivation of the microorganism, can be replaced by cell debris from prior cultivations. The presented study provides strategies to combine the reduction of costs for biomediated PHA production with minimizing ecological risks by recycling precarious waste streams. Overall, the presented work shall contribute to the quick economic success of these promising biomaterials.

Synthesis of Diblock copolymer poly-3-hydroxybutyrate -block-poly-3-hydroxyhexanoate [PHB-b-PHHx] by a β-oxidation weakened Pseudomonas putida KT2442

DEFF Research Database (Denmark)

Tripathi, Lakshmi; Wu, Lin-Ping; Chen, Jinchun

2012-01-01

), thermo- and mechanical analysis. NMR confirmed the existence of diblock copolymers consisting of 58 mol% PHB as the short chain length block with 42 mol% PHHx as the medium chain length block. The block copolymers had two glass transition temperatures (Tg) at 2.7°C and -16.4°C, one melting temperature...... (Tm) at 172.1°C and one cool crystallization temperature (Tc) at 69.1°C as revealed by differential scanning calorimetry (DSC), respectively. This is the first microbial short-chain-length (scl) and medium-chain-length (mcl) PHA block copolymer reported. CONCLUSIONS: It is possible to produce PHA......BACKGROUND: Block polyhydroxyalkanoates (PHA) were reported to be resistant against polymer aging that negatively affects polymer properties. Recently, more and more attempts have been directed to make PHA block copolymers. Diblock copolymers PHB-b-PHHx consisting of poly-3-hydroxybutyrate (PHB...

Thermodynamic Interactions between Polystyrene and Long-Chain Poly(n-Alkyl Acrylates) Derived from Plant Oils.

Science.gov (United States)

Wang, Shu; Robertson, Megan L

2015-06-10

Vegetable oils and their fatty acids are promising sources for the derivation of polymers. Long-chain poly(n-alkyl acrylates) and poly(n-alkyl methacrylates) are readily derived from fatty acids through conversion of the carboxylic acid end-group to an acrylate or methacrylate group. The resulting polymers contain long alkyl side-chains with around 10-22 carbon atoms. Regardless of the monomer source, the presence of alkyl side-chains in poly(n-alkyl acrylates) and poly(n-alkyl methacrylates) provides a convenient mechanism for tuning their physical properties. The development of structured multicomponent materials, including block copolymers and blends, containing poly(n-alkyl acrylates) and poly(n-alkyl methacrylates) requires knowledge of the thermodynamic interactions governing their self-assembly, typically described by the Flory-Huggins interaction parameter χ. We have investigated the χ parameter between polystyrene and long-chain poly(n-alkyl acrylate) homopolymers and copolymers: specifically we have included poly(stearyl acrylate), poly(lauryl acrylate), and their random copolymers. Lauryl and stearyl acrylate were chosen as model alkyl acrylates derived from vegetable oils and have alkyl side-chain lengths of 12 and 18 carbon atoms, respectively. Polystyrene is included in this study as a model petroleum-sourced polymer, which has wide applicability in commercially relevant multicomponent polymeric materials. Two independent methods were employed to measure the χ parameter: cloud point measurements on binary blends and characterization of the order-disorder transition of triblock copolymers, which were in relatively good agreement with one another. The χ parameter was found to be independent of the alkyl side-chain length (n) for large values of n (i.e., n > 10). This behavior is in stark contrast to the n-dependence of the χ parameter predicted from solubility parameter theory. Our study complements prior work investigating the interactions between

Burkholderia sacchari DSM 17165: A source of compositionally-tunable block-copolymeric short-chain poly(hydroxyalkanoates) from xylose and levulinic acid

Science.gov (United States)

Burkholderia sacchari DSM 17165 was used as a biocatalyst for the production of poly-3-hydroxybutyrate-co-3-hydroxyvalerate block copolymers (Poly-3HB-block-3HV) from xylose and levulinic acid. Among the carbon source mixtures, levulinic acid was preferred and was consumed early in the fermentations...

Critical determinant of intestinal permeability and oral bioavailability of pegylated all trans-retinoic acid prodrug-based nanomicelles: Chain length of poly (ethylene glycol) corona.

Science.gov (United States)

Li, Zhenbao; Han, Xiaopeng; Zhai, Yinglei; Lian, He; Zhang, Dong; Zhang, Wenjuan; Wang, Yongjun; He, Zhonggui; Liu, Zheng; Sun, Jin

2015-06-01

Pegylation method is widely used to prolong the blood circulation time of proteins and nanoparticles after intravenous administration, but the effect of surface poly (ethylene glycol) (PEG) chain length on oral absorption of the pegylated nanoparticles is poorly reported. The aim of our study was to investigate the influence of PEG corona chain length on membrane permeability and oral bioavailability of the amphiphilic pegylated prodrug-based nanomicelles, taking all trans-retinoic acid (ATRA) as a model drug. The amphiphilic ATRA-PEG conjugates were synthesized by esterification reaction between all trans-retinoic acid and mPEGs (mPEG500, mPEG1000, mPEG2000, and mPEG5000). The conjugates could self-assemble in aqueous medium to form nanomicelles by emulsion-solvent evaporation method. The resultant nanomicelles were in spherical shape with an average diameter of 13-20 nm. The drug loading efficiency of ATRA-PEG500, ATRA-PEG1000, ATRA-PEG2000, and ATRA-PEG5000 was about 38.4, 26.6, 13.1, and 5.68 wt%, respectively. With PEG chain length ranging from 500 to 5000, ATRA-PEG nanomicelles exhibited a bell shape of chemical stability in different pH buffers, intestinal homogenate and plasma. More importantly, they were all rapidly hydrolyzed into the parent drug in hepatic homogenate, with the half-time values being 0.3-0.4h. In comparison to ATRA solution and ATRA prodrug-based nanomicelles, ATRA-PEG1000 showed the highest intestinal permeability. After oral administration, ATRA-PEG2000 and ATRA-PEG5000 nanomicelles were not nearly absorbed, while the oral bioavailability of ATRA-PEG500 and ATRA-PEG1000 demonstrated about 1.2- and 2.0-fold higher than ATRA solution. Our results indicated that PEG1000 chain length of ATRA-PEG prodrug nanomicelles has the optimal oral bioavailability probably due to improved stability and balanced mucus penetration capability and cell binding, and that the PEG chain length on a surface of nanoparticles cannot exceed a key threshold with

Photoluminescence Enhancement of Poly(3-methylthiophene Nanowires upon Length Variable DNA Hybridization

Directory of Open Access Journals (Sweden)

Jingyuan Huang

2018-01-01

Full Text Available The use of low-dimensional inorganic or organic nanomaterials has advantages for DNA and protein recognition due to their sensitivity, accuracy, and physical size matching. In this research, poly(3-methylthiophene (P3MT nanowires (NWs are electrochemically prepared with dopant followed by functionalization with probe DNA (pDNA sequence through electrostatic interaction. Various lengths of pDNA sequences (10-, 20- and 30-mer are conjugated to the P3MT NWs respectively followed with hybridization with their complementary target DNA (tDNA sequences. The nanoscale photoluminescence (PL properties of the P3MT NWs are studied throughout the whole process at solid state. In addition, the correlation between the PL enhancement and the double helix DNA with various lengths is demonstrated.

Poly A tail length analysis of in vitro transcribed mRNA by LC-MS.

Science.gov (United States)

Beverly, Michael; Hagen, Caitlin; Slack, Olga

2018-02-01

The 3'-polyadenosine (poly A) tail of in vitro transcribed (IVT) mRNA was studied using liquid chromatography coupled to mass spectrometry (LC-MS). Poly A tails were cleaved from the mRNA using ribonuclease T1 followed by isolation with dT magnetic beads. Extracted tails were then analyzed by LC-MS which provided tail length information at single-nucleotide resolution. A 2100-nt mRNA with plasmid-encoded poly A tail lengths of either 27, 64, 100, or 117 nucleotides was used for these studies as enzymatically added poly A tails showed significant length heterogeneity. The number of As observed in the tails closely matched Sanger sequencing results of the DNA template, and even minor plasmid populations with sequence variations were detected. When the plasmid sequence contained a discreet number of poly As in the tail, analysis revealed a distribution that included tails longer than the encoded tail lengths. These observations were consistent with transcriptional slippage of T7 RNAP taking place within a poly A sequence. The type of RNAP did not alter the observed tail distribution, and comparison of T3, T7, and SP6 showed all three RNAPs produced equivalent tail length distributions. The addition of a sequence at the 3' end of the poly A tail did, however, produce narrower tail length distributions which supports a previously described model of slippage where the 3' end can be locked in place by having a G or C after the poly nucleotide region. Graphical abstract Determination of mRNA poly A tail length using magnetic beads and LC-MS.

Thermoresponsive Poly(2-oxazoline) Molecular Brushes by Living Ionic Polymerization: Kinetic Investigations of Pendant Chain Grafting and Cloud Point Modulation by Backbone and Side Chain Length Variation

KAUST Repository

Zhang, Ning

2012-04-17

Molecular brushes of poly(2-oxazoline)s were prepared by living anionic polymerization of 2-iso-propenyl-2-oxazoline to form the backbone and subsequent living cationic ring-opening polymerization of 2-n- or 2-iso-propyl-2-oxazoline for pendant chain grafting. In situ kinetic studies indicate that the initiation efficiency and polymerization rates are independent from the number of initiator functions per initiator molecule. This was attributed to the high efficiency of oxazolinium salt and the stretched conformation of the backbone, which is caused by the electrostatic repulsion of the oxazolinium moieties along the macroinitiator. The resulting molecular brushes showed thermoresponsive properties, that is, having a defined cloud point (CP). The dependence of the CP as a function of backbone and side chain length as well as concentration was studied. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

How Does Poly(hydroxyalkanoate) Affect Methane Production from the Anaerobic Digestion of Waste-Activated Sludge?

Science.gov (United States)

Wang, Dongbo; Zhao, Jianwei; Zeng, Guangming; Chen, Yinguang; Bond, Philip L; Li, Xiaoming

2015-10-20

Recent studies demonstrate that, besides being used for production of biodegradable plastics, poly(hydroxyalkanoate) (PHA) that is accumulated in heterotrophic microorganisms during wastewater treatment has another novel application direction, i.e., being utilized for enhancing methane yield during the anaerobic digestion of waste-activated sludge (WAS). To date, however, the underlying mechanism of how PHA affects methane production remains largely unknown, and this limits optimization and application of the strategy. This study therefore aims to fill this knowledge gap. Experimental results showed that with the increase of sludge PHA levels from 21 to 184 mg/g of volatile suspended solids (VSS) the methane yield linearly increased from 168.0 to 246.1 mL/g of VSS (R(2) = 0.9834). Compared with protein and carbohydrate (the main components of a cell), PHA exhibited a higher biochemical methane potential on a unit VSS basis. It was also found that the increased PHA not only enhanced cell disruption of PHA cells but also benefited the soluble protein conversion of both PHA- and non-PHA cells. Moreover, the reactor fed with higher PHA sludge showed greater sludge hydrolysis and acidification than those fed with the lower PHA sludges. Further investigations using fluorescence in situ hybridization and enzyme analysis revealed that the increased PHA enhanced the abundance of methanogenic Archaea and increased the activities of protease, acetate kinase, and coenzyme F420, which were consistent with the observed methane yield. This work provides insights into PHA-involved WAS digestion systems and may have important implications for future operation of wastewater treatment plants.

Synthesis of Medium-Chain-Length Polyhydroxyalkanoate Homopolymers, Random Copolymers, and Block Copolymers by an Engineered Strain of Pseudomonas entomophila.

Science.gov (United States)

Wang, Ying; Chung, Ahleum; Chen, Guo-Qiang

2017-04-01

Medium-chain-length polyhydroxyalkanoates (mcl-PHAs), widely used in medical area, are commonly synthesized by Pseudomonas spp. This study tries to use β-oxidation pathways engineered P. entomophila to achieve single source of a series of mcl-monomers for microbial production of PHA homopolymers. The effort is proven successful for the first time to obtain a wide range of mcl-PHA homopolymers from engineered P. entomophila LAC23 grown on various fatty acids, respectively, ranging from poly(3-hydroxyheptanoate) to poly(3-hydroxytetradecanoate). Effects of a PHA monomer chain length on thermal and crystallization properties including the changes of T m , T g , and T d5% are investigated. Additionally, strain LAC23 is used to synthesize random copolymers of 3-hydroxyoctanoate (3HO) and 3-hydroxydodecanoate (3HDD) or 3-hydroxytetradecanoates, their compositions could be controlled by adjusting the ratios of two related fatty acids. Meanwhile, block copolymer P(3HO)-b-P(3HDD) is synthesized by the same strain. It is found for the first time that even- and odd number mcl-PHA homopolymers have different physical properties. When the gene of the PHA synthase in the engineered P. entomophila is replaced by phaC from Aeromonas hydrophila 4AK4, poly(3-hydroxybutyrate-co-30 mol%-3-hydroxyhexanoate) is synthesized. Therefore, P. entomophila can be used to synthesize the whole range of PHA (C7-C14) homopolymers, random- and block copolymers. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Studies on poly-3-hydroxyoctanoate biosynthesis by a consortium of microorganisms

Directory of Open Access Journals (Sweden)

Eremia Mihaela Carmen

2016-06-01

Full Text Available Polyhydroxyalcanoates (PHAs are specifically produced by a wide variety of bacteria, as an intracellular energy reserve in the form of homo- and copolymers of [R]-β-hydroxyalkanoic acids, depending on the C source used for microorganism growth, when the cells are grown under stressing conditions. In this paper we present microbiological accumulation of poly-3-hydroxyoctanoate (PHO by using a consortium of bacterial strains, Pseudomonas putida and Bacillus subtilis, in a rate of 3:1, grown on a fermentation medium based on sodium octanoate as the sole carbon source. The experiments performed in the above mentioned conditions led to the following results: from 18.70 g sodium octanoate (7.72 g/L in the fermentation medium used up during the bioprocess, 3.93-3.96 g/L dry bacterial biomass and 1.834 - 1.884 g/L PHA, containing 85.83 - 86.8% PHO, were obtained.

Well-defined block copolymers for gene delivery to dendritic cells: probing the effect of polycation chain-length.

Science.gov (United States)

Tang, Rupei; Palumbo, R Noelle; Nagarajan, Lakshmi; Krogstad, Emily; Wang, Chun

2010-03-03

The development of safe and efficient polymer carriers for DNA vaccine delivery requires mechanistic understanding of structure-function relationship of the polymer carriers and their interaction with antigen-presenting cells. Here we have synthesized a series of diblock copolymers with well-defined chain-length using atom transfer radical polymerization and characterized the influence of polycation chain-length on the physico-chemical properties of the polymer/DNA complexes as well as the interaction with dendritic cells. The copolymers consist of a hydrophilic poly(ethylene glycol) block and a cationic poly(aminoethyl methacrylate) (PAEM) block. The average degree of polymerization (DP) of the PAEM block was varied among 19, 39, and 75, with nearly uniform distribution. With increasing PAEM chain-length, polyplexes formed by the diblock copolymers and plasmid DNA had smaller average particle size and showed higher stability against electrostatic destabilization by salt and heparin. The polymers were not toxic to mouse dendritic cells (DCs) and only displayed chain-length-dependent toxicity at a high concentration (1mg/mL). In vitro gene transfection efficiency and polyplex uptake in DCs were also found to correlate with chain-length of the PAEM block with the longer polymer chain favoring transfection and cellular uptake. The polyplexes induced a modest up-regulation of surface markers for DC maturation that was not significantly dependent on PAEM chain-length. Finally, the polyplex prepared from the longest PAEM block (DP of 75) achieved an average of 20% enhancement over non-condensed anionic dextran in terms of uptake by DCs in the draining lymph nodes 24h after subcutaneous injection into mice. Insights gained from studying such structurally well-defined polymer carriers and their interaction with dendritic cells may contribute to improved design of practically useful DNA vaccine delivery systems. Copyright 2009 Elsevier B.V. All rights reserved.

Effect of Hydrophobic Chain Length on the Stability and Guest Exchange Behavior of Shell-Sheddable Micelles Formed by Disulfide-Linked Diblock Copolymers.

Science.gov (United States)

Fan, Haiyan; Li, Yixia; Yang, Jinxian; Ye, Xiaodong

2017-10-19

Reduction-responsive micelles hold enormous promise for application as drug carriers due to the fast drug release triggered by reducing conditions and high anticancer activity. However, the effect of hydrophobic chain length on the stability and guest exchange of reduction-responsive micelles, especially for the micelles formed by diblock copolymers containing single disulfide group, is not fully understood. Here, shell-sheddable micelles formed by a series of disulfide-linked copolymer poly(ethylene glycol)-b-poly(ε-caprolactone) (PEG-SS-PCL) containing the same chain length of PEG but different chain lengths of hydrophobic block PCL were prepared and well characterized. The influence of the chain length of hydrophobic PCL block on the stability and guest exchange of PEG-SS-PCL micelles was studied by the use of both dynamic laser light scattering (DLS) and fluorescence resonance energy transfer (FRET). The results show that longer PCL chains lead to a slower aggregation rate and guest exchange of micelles in the aqueous solutions containing 10 mM dithiothreitol (DTT). The cell uptake of the shell-sheddable PEG-SS-PCL micelles in vitro shows that the amount of internalization of dyes loaded in PEG-SS-PCL micelles increases with the chain length of hydrophobic PCL block investigated by flow cytometric analysis and confocal fluorescence microscopy.

Chain length dependence of the helix orientation in Langmuir-Blodgett monolayers of alpha-helical diblock copolypeptides

NARCIS (Netherlands)

Nguyen, Le-Thu T.; Ardana, Aditya; Vorenkamp, Eltjo J.; ten Brinke, Gerrit; Schouten, Arend J.

2010-01-01

The effect of chain length on the helix orientation of alpha-helical diblock copolypeptides in Langmuir and Langmuir-Blodgett monolayers is reported for the first time. Amphiphilic diblock copolypeptides (PLGA-b-PMLGSLGs) of poly(alpha-L-glutamic acid) (PLGA) and

Simulation study of the initial crystallization processes of poly(3-hexylthiophene) in solution: ordering dynamics of main chains and side chains.

Science.gov (United States)

Takizawa, Yuumi; Shimomura, Takeshi; Miura, Toshiaki

2013-05-23

We study the initial nucleation dynamics of poly(3-hexylthiophene) (P3HT) in solution, focusing on the relationship between the ordering process of main chains and that of side chains. We carried out Langevin dynamics simulation and found that the initial nucleation processes consist of three steps: the ordering of ring orientation, the ordering of main-chain vectors, and the ordering of side chains. At the start, the normal vectors of thiophene rings aligned in a very short time, followed by alignment of main-chain end-to-end vectors. The flexible side-chain ordering took almost 5 times longer than the rigid-main-chain ordering. The simulation results indicated that the ordering of side chains was induced after the formation of the regular stack structure of main chains. This slow ordering dynamics of flexible side chains is one of the factors that cause anisotropic nuclei growth, which would be closely related to the formation of nanofiber structures without external flow field. Our simulation results revealed how the combined structure of the planar and rigid-main-chain backbones and the sparse flexible side chains lead to specific ordering behaviors that are not observed in ordinary linear polymer crystallization processes.

Chloroform induces outstanding crystallization of poly(hydroxybutyrate) (PHB) vesicles within bacteria.

Science.gov (United States)

Rebois, Rolando; Onidas, Delphine; Marcott, Curtis; Noda, Isao; Dazzi, Alexandre

2017-03-01

Poly[(R)-3-hydroxyalkanoate]s or PHAs are aliphatic polyesters produced by numerous microorganisms. They are accumulated as energy and carbon reserve in the form of small intracellular vesicles. Poly[(R)-3-hydroxybutyrate] (PHB) is the most ubiquitous and simplest PHA. An atomic force microscope coupled with a tunable infrared laser (AFM-IR) was used to record highly spatially resolved infrared spectra of commercial purified PHB and native PHB within bacteria. For the first time, the crystallinity degree of native PHB within vesicle has been directly evaluated in situ without alteration due to the measure or extraction and purification steps of the polymer: native PHB is in crystalline state at 15% whereas crystallinity degree reaches 57% in commercial PHB. Chloroform addition on native PHB induces crystallization of the polymer within bacteria up to 60%. This possibility of probing and changing the physical state of polymer in situ could open alternative ways of production for PHB and others biopolymers. Graphical abstract An atomic force microscope coupled with a tunable infrared laser (AFM-IR) has been used to record local infrared spectra of biopolymer PHB within bacteria. Deconvolution of those spectra has allowed to determine in situ the crystallinity degree of native PHB.

A life-cycle assessment of poly-hydroxybutyrate extraction from microbial biomass using dimethylcarbonate

DEFF Research Database (Denmark)

Righi, Serena; Baioli, Filippo; Samorì, Chiara

2016-01-01

Plastic materials have wide commercial applicability. However, they are made from non-renewable resources and are characterised by resistance to degradation. Poly-hydroxyalkanoates (PHAs) provides one example of a polymer biodegradable, biocompatible and produced from renewable raw materials...

Open-chain poly(organophosphazenes). Synthesis and properties

International Nuclear Information System (INIS)

Vinogradova, Svetlana V; Tur, Dzidra R; Vasnev, Valery A

1998-01-01

Various methods for the synthesis of open-chain poly(organophosphazenes) are considered. The mechanism of polymerisation of hexachlorocyclotriphosphazene and the basic principles of formation of poly(organophosphazene) macromolecules by polymeranalogous reactions of poly(dichloro-phosphazene) with various nucleophilic reagents are analysed from a new viewpoint. The potential of this synthetic method for targeted design of poly(organophosphazenes) of various structures is shown. The possibility of synthesising poly(organophosphazenes) by polymerisation of cyclophosphazenes is also discussed. The problem of unit non-uniformity of poly(organophosphazenes) and its influence on the properties of these polymers are considered. The properties of poly(organophosphazenes) are considered in detail and it is shown that these polymers possess unusual valuable properties, which provide opportunities for their successful practical application. The bibliography includes 276 references.

The Inhibition of Aluminum Corrosion in Sulfuric Acid by Poly(1-vinyl-3-alkyl-imidazolium Hexafluorophosphate).

Science.gov (United States)

Arellanes-Lozada, Paulina; Olivares-Xometl, Octavio; Guzmán-Lucero, Diego; Likhanova, Natalya V; Domínguez-Aguilar, Marco A; Lijanova, Irina V; Arce-Estrada, Elsa

2014-08-07

Compounds of poly(ionic liquid)s (PILs), derived from imidazole with different alkylic chain lengths located in the third position of the imidazolium ring (poly(1-vinyl-3-dodecyl-imidazolium) (PImC 12 ), poly(1-vinyl-3-octylimidazolium) (PImC₈) and poly(1-vinyl-3-butylimidazolium) (PImC₄) hexafluorophosphate) were synthesized. These compounds were tested as corrosion inhibitors on aluminum alloy AA6061 in diluted sulfuric acid (0.1-1 M H₂SO₄) by weight loss tests, polarization resistance measurements and inductively coupled plasma optical emission spectroscopy. Langmuir's isotherms suggested film formation on bare alloy while standard free energy indicated inhibition by a physisorption process. However, compound efficiencies as inhibitors ranked low (PImC 12 > PImC₈ > PImC₄) to reach 61% for PImC 12 in highly diluted acidic solution. Apparently, the high mobility of sulfates favored their adsorption in comparison to PILs. The surface film displayed general corrosion, and pitting occurred as a consequence of PILs' partial inhibition along with a continuous dissolution of defective patchy film on formation. A slight improvement in efficiency was displayed by compounds having high molecular weight and a long alkyl chain, as a consequence of steric hindrance and PIL interactions.

Polyurethanes elastomers with amide chain extenders of uniform length

NARCIS (Netherlands)

van der Schuur, J.M.; Noordover, B.A.J.; Noordover, Bart; Gaymans, R.J.

2006-01-01

Toluene diisocyanate based polyurethanes with amide extenders were synthesized poly(propylene oxide) with a number average molecular weight of 2000 and endcapped with toluene diisocyanate was used as the polyether segment. The chain extenders were based on poly(hexamethylene terephthalamide):

Polyuretehane elastomers with amide chain extenders of uniform length

NARCIS (Netherlands)

Schuur, van der M.; Noordover, B.A.J.; Gaymans, R.J.

2006-01-01

Toluene diisocyanate based polyurethanes with amide extenders were synthesized poly(propylene oxide) with a number average molecular weight of 2000 and endcapped with toluene diisocyanate was used as the polyether segment. The chain extenders were based on poly(hexamethylene terephthalamide):

Effects of alkyl chain length and substituent pattern of fullerene bis-adducts on film structures and photovoltaic properties of bulk heterojunction solar cells.

Science.gov (United States)

Tao, Ran; Umeyama, Tomokazu; Kurotobi, Kei; Imahori, Hiroshi

2014-10-08

A series of alkoxycarbonyl-substituted dihydronaphthyl-based [60]fullerene bis-adduct derivatives (denoted as C2BA, C4BA, and C6BA with the alkyl chain of ethyl, n-butyl, and n-hexyl, respectively) have been synthesized to investigate the effects of alkyl chain length and substituent pattern of fullerene bis-adducts on the film structures and photovoltaic properties of bulk heterojunction polymer solar cells. The shorter alkyl chain length caused lower solubility of the fullerene bis-adducts (C6BA > C4BA > C2BA), thereby resulting in the increased separation difficulty of respective bis-adduct isomers. The device performance based on poly(3-hexylthiophene) (P3HT) and the fullerene bis-adduct regioisomer mixtures was enhanced by shortening the alkyl chain length. When using the regioisomerically separated fullerene bis-adducts, the devices based on trans-2 and a mixture of trans-4 and e of C4BA exhibited the highest power conversion efficiencies of ca. 2.4%, which are considerably higher than those of the C6BA counterparts (ca. 1.4%) and the C4BA regioisomer mixture (1.10%). The film morphologies as well as electron mobilities of the P3HT:bis-adduct blend films were found to affect the photovoltaic properties considerably. These results reveal that the alkyl chain length and substituent pattern of fullerene bis-adducts significantly influence the photovoltaic properties as well as the film structures of bulk heterojunction solar cells.

Proton conducting graft copolymers with tunable length and density of phosphonated side chains for fuel cell membranes

DEFF Research Database (Denmark)

Dimitrov, Ivaylo; Takamuku, Shogo; Jankova Atanasova, Katja

2014-01-01

Polysulfones functionalized with highly phosphonated poly(pentafluorostyrene) side chains of different lengths were synthesized applying controlled polymerization and modification methods. The graft copolymers' thermal properties were evaluated by differential scanning calorimetry and thermal...... gravimetrical analyses. The proton conductivity of membrane prepared from the graft copolymer with the shortest phosphonated side chains was 134 mS cm(-1) at 100 degrees C under fully immersed conditions. The graft copolymer TEM image shows a nanophase separation of ion-rich segments within the polysulfone...

Molecular Dynamics Simulations of Silica Nanoparticles Grafted with Poly(ethylene oxide) Oligomer Chains

KAUST Repository

Hong, Bingbing

2012-03-01

A molecular model of silica nanoparticles grafted with poly(ethylene oxide) oligomers has been developed for predicting the transport properties of nanoparticle organic-hybrid materials (NOHMs). Ungrafted silica nanoparticles in a medium of poly(ethylene oxide) oligomers were also simulated to clarify the effect of grafting on the dynamics of nanoparticles and chains. The model approximates nanoparticles as solid spheres and uses a united-atom representation for chains, including torsional and bond-bending interactions. The calculated viscosities from Green-Kubo relationships and temperature extrapolation are of the same order of magnitude as experimental data but show a smaller activation energy relative to real NOHMs systems. Grafted systems have higher viscosities, smaller diffusion coefficients, and slower chain dynamics than the ungrafted ones at high temperatures. At lower temperatures, grafted systems exhibit faster dynamics for both nanoparticles and chains relative to ungrafted systems, because of lower aggregation of particles and enhanced correlations between nanoparticles and chains. This agrees with the experimental observation that NOHMs have liquidlike behavior in the absence of a solvent. For both grafted and ungrafted systems at low temperatures, increasing chain length reduces the volume fraction of nanoparticles and accelerates the dynamics. However, at high temperatures, longer chains slow down nanoparticle diffusion. From the Stokes-Einstein relationship, it was determined that the coarse-grained treatment of nanoparticles leads to slip on the nanoparticle surfaces. Grafted systems obey the Stokes-Einstein relationship over the temperature range simulated, but ungrafted systems display deviations from it. © 2012 American Chemical Society.

The Inhibition of Aluminum Corrosion in Sulfuric Acid by Poly(1-vinyl-3-alkyl-imidazolium Hexafluorophosphate

Directory of Open Access Journals (Sweden)

Paulina Arellanes-Lozada

2014-08-01

Full Text Available Compounds of poly(ionic liquids (PILs, derived from imidazole with different alkylic chain lengths located in the third position of the imidazolium ring (poly(1-vinyl-3-dodecyl-imidazolium (PImC12, poly(1-vinyl-3-octylimidazolium (PImC8 and poly(1-vinyl-3-butylimidazolium (PImC4 hexafluorophosphate were synthesized. These compounds were tested as corrosion inhibitors on aluminum alloy AA6061 in diluted sulfuric acid (0.1–1 M H2SO4 by weight loss tests, polarization resistance measurements and inductively coupled plasma optical emission spectroscopy. Langmuir’s isotherms suggested film formation on bare alloy while standard free energy indicated inhibition by a physisorption process. However, compound efficiencies as inhibitors ranked low (PImC12 > PImC8 > PImC4 to reach 61% for PImC12 in highly diluted acidic solution. Apparently, the high mobility of sulfates favored their adsorption in comparison to PILs. The surface film displayed general corrosion, and pitting occurred as a consequence of PILs’ partial inhibition along with a continuous dissolution of defective patchy film on formation. A slight improvement in efficiency was displayed by compounds having high molecular weight and a long alkyl chain, as a consequence of steric hindrance and PIL interactions.

Roles of head group architecture and side chain length on colorimetric response of polydiacetylene vesicles to temperature, ethanol and pH.

Science.gov (United States)

Charoenthai, Nipaphat; Pattanatornchai, Thanutpon; Wacharasindhu, Sumrit; Sukwattanasinitt, Mongkol; Traiphol, Rakchart

2011-08-15

In this contribution, we report the relationship between molecular structures of polydiacetylene (PDA) vesicles, fabricated by using three monomers, 10,12-tricosadiynoic acid (TCDA), 10,12-pentacosadiynoic acid (PCDA) and N-(2-aminoethyl)pentacosa-10,12-diynamide (AEPCDA), and their color-transition behaviors. The modification of side chain length and head group of the PDA vesicles strongly affects the colorimetric response to temperature, ethanol and pH. A shorter side chain of poly(TCDA) yields weaker inter- and intra-chain dispersion interactions in the bilayers compared to the system of poly(PCDA), which in turn results in a faster color transition upon exposure to all stimuli. A change of head group in poly(AEPCDA) slightly reduces the transition temperature. Interestingly, the colorimetric response of poly(AEPCDA) vesicles to the addition of ethanol is found to occur in a two-step fashion while the response of poly(PCDA) vesicles takes place in a one-step process. The amount of ethanol required for inducing complete color-transition of poly(AEPCDA) vesicles is also much higher, about 87% v/v. The increase of pH to ~9 and ~10 causes a color-transition of poly(TCDA) and poly(PCDA) vesicles, respectively. The poly(AEPCDA) vesicles, on the other hand, change color upon decreasing pH to ~0. The colorimetric response also occurs in a multi-step fashion. These discrepancies are attributed to the architecture of surface layers of poly(AEPCDA), constituting amine and amide groups separated by ethyl linkers. Copyright © 2011 Elsevier Inc. All rights reserved.

In-silico-driven metabolic engineering of Pseudomonas putida for enhanced production of poly-hydroxyalkanoates

NARCIS (Netherlands)

Poblete-Castro, I.; Binger, D.; Rodrigues, A.; Becker, J.; Martins Dos Santos, V.A.P.; Wittmann, C.

2013-01-01

Here, we present systems metabolic engineering driven by in-silico modeling to tailor Pseudomonas putida for synthesis of medium chain length PHAs on glucose. Using physiological properties of the parent wild type as constraints, elementary flux mode analysis of a large-scale model of the metabolism

Hybrid bulk heterojunction solar cells based on poly(3-hexylthiophene) and ZnO nanoparticles modified by side-chain functional polythiophenes

International Nuclear Information System (INIS)

Li, Fan; Du, Yanhui; Chen, Yiwang

2012-01-01

We report the investigation of the hybrid bulk heterojunction solar cells based on the blend of poly(3-hexylthiophene) (P3HT) and ZnO nanoparticles modified by side-chain thiol functional poly(3-thiophenehexanethiol) (P3HT-SH). Grafting of P3HT-SH onto ZnO nanoparticles can promote the dispersion of ZnO nanoparticles within P3HT matrix and facilitate electron injection process into ZnO nanoparticles, resulting in a more efficient photoinduced charge transfer than that in simple physical mixture of P3HT and non-modified ZnO nanoparticles (P3HT/ZnO). Furthermore, the performance of hybrid photovoltaic device based on P3HT/P3HT-SH-modified ZnO blend exhibits an improved device efficiency compared with P3HT/ZnO even before thermal treatment. After being annealed at 80 °C, the P3HT/P3HT-SH-modified ZnO device shows the power conversion efficiency as high as 0.68%, with the short-circuit current density of 1.89 mA/cm 2 , the open-circuit voltage of 0.599 V and a fill factor of 60.5% under AM 1.5 G illumination with 100 mW/cm 2 light intensity. - Highlights: ► Hybrid solar cells based on poly(3-hexylthiophene) and modified ZnO nanoparticles ► ZnO nanoparticles modified by side-chain functional polythiophenes ► Uniform dispersion and intimate contact between polymers and nanoparticles ► Efficient charge transfer leading to the improvement of device efficiency

Dependence of adenine isolation efficiency on the chain length evidenced using paramagnetic particles and voltammetry measurements

International Nuclear Information System (INIS)

Huska, Dalibor; Adam, Vojtech; Trnkova, Libuse; Kizek, Rene

2009-01-01

The main aim of this work was to study the dependence of oligoadenine isolation efficiency on the chain length by using paramagnetic particles covered by homo-deoxythymidines ((dT)25) with subsequent detection by adsorptive transfer technique coupled with square wave voltammetry. For this purpose, the oligonucleotides of the length A5, A10, A15, A20, A25, A30, A35, A40 and poly(A) in various concentrations were chosen. We determined that the isolation efficiency defined as 'isolated oligonucleotide concentration'/'given oligonucleotide concentration' was about 55% on average. Sequence A25 demonstrated the best binding onto microparticles surface.

Finite fission chain length and symmetry around prompt-criticality

International Nuclear Information System (INIS)

Xie Qilin; Yin Yanpeng; Gao Hui; Huang Po; Fang Xiaoqiang

2012-01-01

Probability distribution of finite fission chain length was derived by assuming that all neutrons behave identically. Finite fission chain length was also calculated using a zero-dimension Monte-Carlo method based on point kinetics. Then symmetry of finite fission chain length probability distribution around prompt-criticality was deduced, which helps understanding the emission rate of delayed neutrons and initiation of fission chain in super-prompt-critical system. (authors)

Single-Chain Conformation for Interacting Poly(N-isopropylacrylamide in Aqueous Solution

Directory of Open Access Journals (Sweden)

Boualem Hammouda

2015-04-01

Full Text Available The demixing phase behavior of Poly(N-isopropylacrylamide (PNIPAM aqueous solution is investigated using small-angle neutron scattering. This polymer phase separates upon heating and demixes around 32 °C. The pre-transition temperature range is characterized by two scattering modes; a low-Q (large-scale signal and a high-Q dissolved chains signal. In order to get insight into this pre-transition region, especially the origin of the low-Q (large-scale structure, the zero average contrast method is used in order to isolate single-chain conformations even in the demixing polymers transition region. This method consists of measuring deuterated and non-deuterated polymers dissolved in mixtures of deuterated and non-deuterated water for which the polymer scattering length density matches the solvent scattering length density. A fixed 4% polymer mass fraction is used in a contrast variation series where the d-water/h-water fraction is varied in order to determine the match point. The zero average contrast (match point sample displays pure single-chain scattering with no interchain contributions. Our measurements prove that the large scale structure in this polymer solution is due to a transient polymer network formed through hydrophobic segment-segment interactions. Scattering intensity increases when the temperature gets close to the phase boundary. While the apparent radius of gyration increases substantially at the Lower Critical Solution Temperature (LCST transition due to strong interchain correlation, the single-chain true radius of gyration has been found to decrease slightly with temperature when approaching the transition.

Structure-guided investigation of lipopolysaccharide O-antigen chain length regulators reveals regions critical for modal length control.

Science.gov (United States)

Kalynych, Sergei; Ruan, Xiang; Valvano, Miguel A; Cygler, Miroslaw

2011-08-01

The O-antigen component of the lipopolysaccharide (LPS) represents a population of polysaccharide molecules with nonrandom (modal) chain length distribution. The number of the repeat O units in each individual O-antigen polymer depends on the Wzz chain length regulator, an inner membrane protein belonging to the polysaccharide copolymerase (PCP) family. Different Wzz proteins confer vastly different ranges of modal lengths (4 to >100 repeat units), despite having remarkably conserved structural folds. The molecular mechanism responsible for the selective preference for a certain number of O units is unknown. Guided by the three-dimensional structures of PCPs, we constructed a panel of chimeric molecules containing parts of two closely related Wzz proteins from Salmonella enterica and Shigella flexneri which confer different O-antigen chain length distributions. Analysis of the O-antigen length distribution imparted by each chimera revealed the region spanning amino acids 67 to 95 (region 67 to 95), region 200 to 255, and region 269 to 274 as primarily affecting the length distribution. We also showed that there is no synergy between these regions. In particular, region 269 to 274 also influenced chain length distribution mediated by two distantly related PCPs, WzzB and FepE. Furthermore, from the 3 regions uncovered in this study, region 269 to 274 appeared to be critical for the stability of the oligomeric form of Wzz, as determined by cross-linking experiments. Together, our data suggest that chain length determination depends on regions that likely contribute to stabilize a supramolecular complex.

Biodegradable block poly(ester-urethane)s based on poly(3-hydroxybutyrate-co-4-hydroxybutyrate) copolymers.

Science.gov (United States)

Ou, Wenfeng; Qiu, Handi; Chen, Zhifei; Xu, Kaitian

2011-04-01

composition and the chain-length of P3/4HB-diol prepolymers, the biocompatibility of the poly(ester-urethane)s can be tailored. Copyright © 2011 Elsevier Ltd. All rights reserved.

Dependence of adenine isolation efficiency on the chain length evidenced using paramagnetic particles and voltammetry measurements

Energy Technology Data Exchange (ETDEWEB)

Huska, Dalibor [Department of Chemistry and Biochemistry, Faculty of Agronomy, Mendel University of Agriculture and Forestry, Zemedelska 1, CZ-613 00 Brno (Czech Republic); Adam, Vojtech [Department of Chemistry and Biochemistry, Faculty of Agronomy, Mendel University of Agriculture and Forestry, Zemedelska 1, CZ-613 00 Brno (Czech Republic); Department of Animal Nutrition and Forage Production, Faculty of Agronomy, Mendel University of Agriculture and Forestry, Zemedelska 1, CZ-613 00 Brno (Czech Republic); Trnkova, Libuse [Department of Chemistry, Faculty of Science, Masaryk University, Kamenice 5, CZ-625 00 Brno (Czech Republic); Kizek, Rene [Department of Chemistry and Biochemistry, Faculty of Agronomy, Mendel University of Agriculture and Forestry, Zemedelska 1, CZ-613 00 Brno (Czech Republic)], E-mail: kizek@sci.muni.cz

2009-05-15

The main aim of this work was to study the dependence of oligoadenine isolation efficiency on the chain length by using paramagnetic particles covered by homo-deoxythymidines ((dT)25) with subsequent detection by adsorptive transfer technique coupled with square wave voltammetry. For this purpose, the oligonucleotides of the length A5, A10, A15, A20, A25, A30, A35, A40 and poly(A) in various concentrations were chosen. We determined that the isolation efficiency defined as 'isolated oligonucleotide concentration'/'given oligonucleotide concentration' was about 55% on average. Sequence A25 demonstrated the best binding onto microparticles surface.

Entanglement Length in Miscible Blends of cis-Polyisoprene and Poly(ptert-butylstyrene)

Science.gov (United States)

Watanabe, Hiroshi; Matsumiya, Yumi

In miscible polymer blends, the entanglement length is common for the components, but its changes with the composition w remain unclear. For this problem, this study analyzed viscoelastic data for miscible blends of cis-polyisoprene (PI) and poly(ptert-butylstyrene) (PtBS), considering the basic feature that the local relaxation is determined only by wPI. On the basis of this feature, a series of unentangled low- M PI/PtBS blends having various M and a given wPI were utilized as references for well-entangled high- M PI/PtBS blends having the same wPI, and the modulus data of the references were subtracted from the high- M blend data. For an optimally chosen reference, the storage modulus Ge'of the high- M blends obtained after the subtraction exhibited a clear entanglement plateau GN and the corresponding Ge' ' decreased in proportion to 1/ ω at high frequencies ω. Thus, the onset of entanglement relaxation was detected. The GN values were well described by a linear mixing rule of the entanglement length with the number fraction of Kuhn segments of the components being utilized as the averaging weight. This result, not explained by a mean-field picture of entanglement, is discussed in relation to local packing of bulky PtBS chains and skinny PI chains.

Probing the structural dependence of carbon space lengths of poly(N-hydroxyalkyl acrylamide)-based brushes on antifouling performance.

Science.gov (United States)

Yang, Jintao; Zhang, Mingzhen; Chen, Hong; Chang, Yung; Chen, Zhan; Zheng, Jie

2014-08-11

Numerous biocompatible antifouling polymers have been developed for a wide variety of fundamental and practical applications in drug delivery, biosensors, marine coatings, and many other areas. Several antifouling mechanisms have been proposed, but the exact relationship among molecular structure, surface hydration property, and antifouling performance of antifouling polymers still remains elusive. Here this work strives to provide a better understanding of the structure-property relationship of poly(N-hydroxyalkyl acrylamide)-based materials. We have designed, synthesized, and characterized a series of polyHAAA brushes of various carbon spacer lengths (CSLs), that is, poly(N-hydroxymethyl acrylamide) (polyHMAA), poly(N-(2-hydroxyethyl)acrylamide) (polyHEAA), poly(N-(3-hydroxypropyl)acrylamide) (polyHPAA), and poly(N-(5-hydroxypentyl)acrylamide) (polyHPenAA), to study the structural dependence of CSLs on their antifouling performance. HMAA, HEAA, HPAA, and HPenAA monomers contained one, two, three, and five methylene groups between hydroxyl and amide groups, while the other groups in polymer backbones were the same as each other. The relation of such small structural differences of polymer brushes to their surface hydration and antifouling performance was studied by combined experimental and computational methods including surface plasmon resonance sensors, sum frequency generation (SFG) vibrational spectroscopy, cell adhesion assay, and molecular simulations. Antifouling results showed that all polyHAAA-based brushes were highly surface resistant to protein adsorption from single protein solutions, undiluted blood serum and plasma, as well as cell adhesion up to 7 days. In particular, polyHMAA and polyHEAA with the shorter CSLs exhibited higher surface hydration and better antifouling ability than polyHPMA and polyHPenAA. SFG and molecular simulations further revealed that the variation of CSLs changed the ratio of hydrophobicity/hydrophilicity of polymers

Side chain variations radically alter the diffusion of poly(2-alkyl-2-oxazoline) functionalised nanoparticles through a mucosal barrier.

Science.gov (United States)

Mansfield, Edward D H; de la Rosa, Victor R; Kowalczyk, Radoslaw M; Grillo, Isabelle; Hoogenboom, Richard; Sillence, Katy; Hole, Patrick; Williams, Adrian C; Khutoryanskiy, Vitaliy V

2016-08-16

Functionalised nanomaterials are gaining popularity for use as drug delivery vehicles and, in particular, mucus penetrating nanoparticles may improve drug bioavailability via the oral route. To date, few polymers have been investigated for their muco-penetration, and the effects of systematic structural changes to polymer architectures on the penetration and diffusion of functionalised nanomaterials through mucosal tissue have not been reported. We investigated the influence of poly(2-oxazoline) alkyl side chain length on nanoparticle diffusion; poly(2-methyl-2-oxazoline), poly(2-ethyl-2-oxazoline), and poly(2-n-propyl-2-oxazoline) were grafted onto the surface of thiolated silica nanoparticles and characterised by FT-IR, Raman and NMR spectroscopy, thermogravimetric analysis, and small angle neutron scattering. Diffusion coefficients were determined in water and in a mucin dispersion (using Nanoparticle Tracking Analysis), and penetration through a mucosal barrier was assessed using an ex vivo fluorescence technique. The addition of a single methylene group in the side chain significantly altered the penetration and diffusion of the materials in both mucin dispersions and mucosal tissue. Nanoparticles functionalised with poly(2-methyl-2-oxazoline) were significantly more diffusive than particles with poly(2-ethyl-2-oxazoline) while particles with poly(2-n-propyl-2-oxazoline) showed no significant increase compared to the unfunctionalised particles. These data show that variations in the polymer structure can radically alter their diffusive properties with clear implications for the future design of mucus penetrating systems.

Study on the crystallization of multiarm stars with a poly(ethyleneimine) core and poly(ϵ-caprolactone) arms of different length

Energy Technology Data Exchange (ETDEWEB)

Díaz, Angélica; Bacaicoa, Anna; Casas, Maria Teresa; Franco, Lourdes [Departament d’Enginyeria Química, Universitat Politècnica de Catalunya, Av. Diagonal 647, Barcelona E-08028 (Spain); Serra, Angels [Departament de Química Analítica i Química Orgànica, Universitat Rovira i Virgili. C. Marcel.lí Domingo, s/n. Campus Sescelades, Tarragona 43007 (Spain); Puiggalí, Jordi, E-mail: Jordi.Puiggali@upc.edu [Departament d’Enginyeria Química, Universitat Politècnica de Catalunya, Av. Diagonal 647, Barcelona E-08028 (Spain)

2015-05-10

Highlights: • Isothermal crystallization kinetics of multiarm stars. • Influence of the length of poly(ϵ-caprolactone) arms on crystallization kinetics. • Influence of the length of poly(ϵ-caprolactone) arms on secondary nucleation constant. • Crystallization of mixtures of stars having different arm lengths. - Abstract: Crystallization of multiarm star systems constituted by a core of poly(ethyleneimine) (PEI) and arms of poly(ϵ-caprolactone) (PCL) was studied by transmission electron microscopy, calorimetry and optical microscopy techniques. Three systems differing on the degree of polymerization of PCL were studied as well as binary mixtures constituted by systems differing on the length of PCL arms. Samples were able to crystallize from both diluted solutions and the melt state giving rise to well-formed lamellae and spherulites, respectively. Lamellae of samples with large PCL arms were highly regular and corresponded to elongated hexagonal crystals with an aspect ratio that decreased with the length of PCL arms. A significant decrease on equilibrium melting temperatures, degree of crystallinity and glass transition temperature was detected for samples having short PCL arms. Crystallization kinetics were also highly influenced by the length of PCL arms, being both nucleation density and secondary nucleation constant increased as the length of PCL arms decreased. Crystallization of star mixtures having different PCL lengths was determined by the larger arms since they initiated the process and subsequently shorter arms were progressively incorporated. A thermal nucleation was characteristic of multiarm star mixtures due to the different crystallization temperature ranges of samples with large and short PCL arms, whereas samples with a homogeneous arm length rendered an athermal nucleation.

Effect of temperature on atom-atom collision chain length in metals

International Nuclear Information System (INIS)

Makarov, A.A.; Demkin, N.A.; Lyashchenko, B.G.

1981-01-01

Focused atom-atom collision chain lengths are calculated for fcc-crystals with account of thermal oscillations. The model of solid spheres with the Born-Merier potential has been used in the calculations. The dependence of chain lengths on the temperature, energy and movement direction of the first chain atom for Cu, Au, Ag, Pb, Ni is considered. The plot presented shows that the chain lengths strongly decrease with temperature growth, for example, for the gold at T=100 K the chain length equals up to 37 interatomic spacings, whereas at T=1000 K their length decreases down to 5 interatomic distances. The dependence of the energy loss by the chain atoms on the atom number in the chain is obtained in a wide range of crystal temperature and the primary chain atom energy [ru

Growth kinetics, effect of carbon substrate in biosynthesis of mcl-PHA by Pseudomonas putida Bet001.

Science.gov (United States)

Gumel, A M; Annuar, M S M; Heidelberg, T

2014-01-01

Growth associated biosynthesis of medium chain length poly-3-hydroxyalkanoates (mcl-PHA) in Pseudomonas putida Bet001 isolated from palm oil mill effluent was studied. Models with substrate inhibition terms described well the kinetics of its growth. Selected fatty acids (C8:0 to C18:1) and ammonium were used as carbon and nitrogen sources during growth and PHA biosynthesis, resulting in PHA accumulation of about 50 to 69% (w/w) and PHA yields ranging from 10.12 g L(-1) to 15.45 g L(-1), respectively. The monomer composition of the PHA ranges from C4 to C14, and was strongly influenced by the type of carbon substrate fed. Interestingly, an odd carbon chain length (C7) monomer was also detected when C18:1 was fed. Polymer showed melting temperature (T m) of 42.0 (± 0.2) °C, glass transition temperature (T g) of -1.0 (± 0.2) °C and endothermic melting enthalpy of fusion (ΔHf) of 110.3 (± 0.1) J g(-1). The molecular weight (M w) range of the polymer was relatively narrow between 55 to 77 kDa.

Growth kinetics, effect of carbon substrate in biosynthesis of mcl-PHA by Pseudomonas putida Bet001

Directory of Open Access Journals (Sweden)

A.M. Gumel

2014-06-01

Full Text Available Growth associated biosynthesis of medium chain length poly-3-hydroxyalkanoates (mcl-PHA in Pseudomonas putida Bet001 isolated from palm oil mill effluent was studied. Models with substrate inhibition terms described well the kinetics of its growth. Selected fatty acids (C8:0 to C18:1 and ammonium were used as carbon and nitrogen sources during growth and PHA biosynthesis, resulting in PHA accumulation of about 50 to 69% (w/w and PHA yields ranging from 10.12 g L-1 to 15.45 g L-1, respectively. The monomer composition of the PHA ranges from C4 to C14, and was strongly influenced by the type of carbon substrate fed. Interestingly, an odd carbon chain length (C7 monomer was also detected when C18:1 was fed. Polymer showed melting temperature (Tm of 42.0 (± 0.2 °C, glass transition temperature (Tg of -1.0 (± 0.2 °C and endothermic melting enthalpy of fusion (ΔHf of 110.3 (± 0.1 J g-1. The molecular weight (Mw range of the polymer was relatively narrow between 55 to 77 kDa.

Poly[n]catenanes: Synthesis of molecular interlocked chains

Science.gov (United States)

Wu, Qiong; Rauscher, Phillip M.; Lang, Xiaolong; Wojtecki, Rudy J.; de Pablo, Juan J.; Hore, Michael J. A.; Rowan, Stuart J.

2017-12-01

As the macromolecular version of mechanically interlocked molecules, mechanically interlocked polymers are promising candidates for the creation of sophisticated molecular machines and smart soft materials. Poly[n]catenanes, where the molecular chains consist solely of interlocked macrocycles, contain one of the highest concentrations of topological bonds. We report, herein, a synthetic approach toward this distinctive polymer architecture in high yield (~75%) via efficient ring closing of rationally designed metallosupramolecular polymers. Light-scattering, mass spectrometric, and nuclear magnetic resonance characterization of fractionated samples support assignment of the high-molar mass product (number-average molar mass ~21.4 kilograms per mole) to a mixture of linear poly[7-26]catenanes, branched poly[13-130]catenanes, and cyclic poly[4-7]catenanes. Increased hydrodynamic radius (in solution) and glass transition temperature (in bulk materials) were observed upon metallation with Zn2+.

Topological analysis of polymeric melts: chain-length effects and fast-converging estimators for entanglement length.

Science.gov (United States)

Hoy, Robert S; Foteinopoulou, Katerina; Kröger, Martin

2009-09-01

Primitive path analyses of entanglements are performed over a wide range of chain lengths for both bead spring and atomistic polyethylene polymer melts. Estimators for the entanglement length N_{e} which operate on results for a single chain length N are shown to produce systematic O(1/N) errors. The mathematical roots of these errors are identified as (a) treating chain ends as entanglements and (b) neglecting non-Gaussian corrections to chain and primitive path dimensions. The prefactors for the O(1/N) errors may be large; in general their magnitude depends both on the polymer model and the method used to obtain primitive paths. We propose, derive, and test new estimators which eliminate these systematic errors using information obtainable from the variation in entanglement characteristics with chain length. The new estimators produce accurate results for N_{e} from marginally entangled systems. Formulas based on direct enumeration of entanglements appear to converge faster and are simpler to apply.

Mechanism of Crystallization and Implications for Charge Transport in Poly(3-ethylhexylthiophene) Thin Films

KAUST Repository

Duong, Duc T.

2014-04-09

In this work, crystallization kinetics and aggregate growth of poly(3-ethylhexylthiophene) (P3EHT) thin films are studied as a function of film thickness. X-ray diffraction and optical absorption show that individual aggregates and crystallites grow anisotropically and mostly along only two packing directions: the alkyl stacking and the polymer chain backbone direction. Further, it is also determined that crystallization kinetics is limited by the reorganization of polymer chains and depends strongly on the film thickness and average molecular weight. Time-dependent, field-effect hole mobilities in thin films reveal a percolation threshold for both low and high molecular weight P3EHT. Structural analysis reveals that charge percolation requires bridged aggregates separated by a distance of ≈2-3 nm, which is on the order of the polymer persistence length. These results thus highlight the importance of tie molecules and inter-aggregate distance in supporting charge percolation in semiconducting polymer thin films. The study as a whole also demonstrates that P3EHT is an ideal model system for polythiophenes and should prove to be useful for future investigations into crystallization kinetics. Recrystallization kinetics and its relationship to charge transport in poly(3-ethylhexylthiophene) (P3EHT) thin films are investigated using a combination of grazing incidence X-ray diffraction, optical absorption, and field-effect transistor measurements. These results show that thin film crystallization kinetics is limited by polymer chain reorganization and that charge percolation depends strongly on the edge-to-edge distance between aggregates. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Short-chain fatty acids and poly-beta-hydroxyalkanoates: (New) Biocontrol agents for a sustainable animal production.

Science.gov (United States)

Defoirdt, Tom; Boon, Nico; Sorgeloos, Patrick; Verstraete, Willy; Bossier, Peter

2009-01-01

Because of the risk of antibiotic resistance development, there is a growing awareness that antibiotics should be used more carefully in animal production. However, a decreased use of antibiotics could result in a higher frequency of pathogenic bacteria, which in its turn could lead to a higher incidence of infections. Short-chain fatty acids (SCFAs) have long been known to exhibit bacteriostatic activity. These compounds also specifically downregulate virulence factor expression and positively influence the gastrointestinal health of the host. As a consequence, there is currently considerable interest in SCFAs as biocontrol agents in animal production. Polyhydroxyalkanoates (PHAs) are polymers of beta-hydroxy short-chain fatty acids. Currently, PHAs are applied as replacements for synthetic polymers. These biopolymers can be depolymerised by many different microorganisms that produce extracellular PHA depolymerases. Interestingly, different studies provided some evidence that PHAs can also be degraded upon passage through the gastrointestinal tract of animals and consequently, adding these compounds to the feed might result in biocontrol effects similar to those described for SCFAs.

Constraints on food chain length arising from regional metacommunity dynamics

Science.gov (United States)

Calcagno, Vincent; Massol, François; Mouquet, Nicolas; Jarne, Philippe; David, Patrice

2011-01-01

Classical ecological theory has proposed several determinants of food chain length, but the role of metacommunity dynamics has not yet been fully considered. By modelling patchy predator–prey metacommunities with extinction–colonization dynamics, we identify two distinct constraints on food chain length. First, finite colonization rates limit predator occupancy to a subset of prey-occupied sites. Second, intrinsic extinction rates accumulate along trophic chains. We show how both processes concur to decrease maximal and average food chain length in metacommunities. This decrease is mitigated if predators track their prey during colonization (habitat selection) and can be reinforced by top-down control of prey vital rates (especially extinction). Moreover, top-down control of colonization and habitat selection can interact to produce a counterintuitive positive relationship between perturbation rate and food chain length. Our results show how novel limits to food chain length emerge in spatially structured communities. We discuss the connections between these constraints and the ones commonly discussed, and suggest ways to test for metacommunity effects in food webs. PMID:21367786

Thermal studies of poly(esters) containing silicon or germanium in the main chain

International Nuclear Information System (INIS)

Tagle, L.H.; Terraza, C.; Valenzuela, P.; Leiva, A.; Urzua, M.

2005-01-01

The thermal properties of poly(esters) containing Si and/or Ge in the main chain derived from the acid dichlorides bis(4-chloroformyl-phenyl)-dimethyl-silane, bis(4-chloroformyl-phenyl)-dimethyl-germane, bis(4-chloroformyl-phenyl)-diphenyl-silane and bis(4-chloroformyl-phenyl)-diphenyl-silane, and the diphenols bis(4-hydroxyphenyl)-dimethyl-silane, bis(4-hydroxyphenyl)-dimethyl-germane, bis(4-hydroxyphenyl)-diphenyl-silane and bis(4-hydroxyphenyl)-diphenyl-germane were studied by differential scanning calorimetry and dynamic thermogravimetry. Poly(esters) with two Si atoms in the main chain showed higher values of T g than those with two Ge atoms, and the same was observed for poly(esters) with phenyl groups bonded to the heteroatoms, instead of those with methyl groups. Thermal decomposition temperatures were also higher for those poly(esters) with two Si atoms in the main chain and those in which the heteroatom is bonded to phenyl groups, due to the higher polarity of the Si-C bond in front of the Ge-C

The roles of productivity and ecosystem size in determining food chain length in tropical terrestrial ecosystems.

Science.gov (United States)

Young, Hillary S; McCauley, Douglas J; Dunbar, Robert B; Hutson, Michael S; Ter-Kuile, Ana Miller; Dirzo, Rodolfo

2013-03-01

Many different drivers, including productivity, ecosystem size, and disturbance, have been considered to explain natural variation in the length of food chains. Much remains unknown about the role of these various drivers in determining food chain length, and particularly about the mechanisms by which they may operate in terrestrial ecosystems, which have quite different ecological constraints than aquatic environments, where most food chain length studies have been thus far conducted. In this study, we tested the relative importance of ecosystem size and productivity in influencing food chain length in a terrestrial setting. We determined that (1) there is no effect of ecosystem size or productive space on food chain length; (2) rather, food chain length increases strongly and linearly with productivity; and (3) the observed changes in food chain length are likely achieved through a combination of changes in predator size, predator behavior, and consumer diversity along gradients in productivity. These results lend new insight into the mechanisms by which productivity can drive changes in food chain length, point to potential for systematic differences in the drivers of food web structure between terrestrial and aquatic systems, and challenge us to consider how ecological context may control the drivers that shape food chain length.

Studies on the solvation dynamics of coumarin 153 in 1-ethyl-3-methylimidazolium alkylsulfate ionic liquids: dependence on alkyl chain length.

Science.gov (United States)

Das, Sudhir Kumar; Sarkar, Moloy

2012-08-06

Steady-state and time-resolved fluorescence behavior of coumarin 153 (C153) is investigated in a series of 1-ethyl-3-methylimidazolium alkylsulfate ([C(2)mim][C(n)OSO(3)]) ionic liquids differing only in the length of the linear alkyl chain (n = 4, 6, and 8) in the anion. The aim of the present study is to understand the role of alkyl chain length in solute rotation and solvation dynamics of C153 in these ionic liquids. The blueshift observed in the steady-state absorption and emission maxima of C153 on going from the C(4)OSO(3) to the C(8)OSO(3) system indicates increasing nonpolar character of the microenvironment of the solute with increasing length of the alkyl side chain of the anion of the ionic liquids. The average solvation time is also found to increase on changing the substituent from butyl to octyl, and this is attributed to the increase in the bulk viscosity of the ILs. A steady blueshift of the time-zero maximum of the fluorescence spectrum with increasing alkyl chain length also indicates that the probe molecule experiences a less polar environment in the early part of the dynamics. Rotational dynamics of C153 are also analyzed by using the Stokes-Einstein-Debye (SED), Gierer-Wirtz (GW), and Dote-Kivelson-Schwartz (DKS) theories. Analyses of the results seem to suggest decoupling of the rotational motion of the probe from solvent viscosity. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Kinetics of Coil-to-Globule Transition of Dansyl-Labeled Poly(N-sopropylacrylamide) Chains in Aqueous Solution

Science.gov (United States)

Li, Chun-liang; Ye, Xiao-dong; Ding, Yan-wei; Liu, Shi-lin

2012-08-01

The coil-to-globule transition of thermally sensitive linear poly(N-isopropylacrylamide) (PNIPAM) labeled with dansyl group is induced by 1.54 μm laser pulses (width≈10 ns). The dansyl group is used to follow the transition kinetics because its fluorescence intensity is very sensitive to its micro-environment. As the molar ratio of NIPAM monomer to dansyl group increases from 110 to 300, the effect of covalently attached dansyl fluorophores on the transition decreases. In agreement with our previous study in which we used 8-anilino-1-naphthalensulfonic acid ammonium salt free in water as a fluorescent probe, the current study reveals that the transition has two distinct stages with two characteristic times, namely, τfast≈0.1 ms, which can be attributed to the nucleation and formation of some “pearls" (locally contracting segments) on the chain, and τslow≈0.5 ms, which is related to the merging and coarsening of the “pearls". τfast is independent of the PNIPAM chain length over a wide range (Mw=2.8×106-4.2×107 g/mol). On the other hand, τslow only slightly increases with the chain length.

Does the copolymer poly(vinylidene cyanide-tricyanoethylene) possess piezoelectricity?

Science.gov (United States)

Wang, Zhi-Yin; Su, Ke-He; Xu, Qiong

2012-10-01

The geometry, energy, internal rotation barrier, dipole moment, and molecular polarizability of the α- and β-chain models of poly(vinylidene cyanide-tricyanoethylene) [P(VDCN-TrCN)] were studied with density functional theory at the B3PW91/6-31G(d) level. The effects of the chain length and the TrCN content on the copolymer chain stability, the chain conformation, and the electrical properties of P(VDCN-TrCN) were examined and compared with those of poly(vinylidene fluoride-trifluoroethylene) and PVDCN to gauge whether P(VDCN-TrCN) would be expected to possess substantial piezoelectricity. The results of this study showed that the stability of the β conformation increases and the energy difference per monomer unit between the β- and α-chains decreases with increasing TrCN. However, introducing TrCN into VDCN will not significantly enhance the radius of curvature of the P(VDCN-TrCN) chains. The average dipole moment per monomer unit in the β-chain is affected by the chain curvature and the TrCN content. The amount of piezoelectricity present in P(VDCN-TrCN) is slightly smaller than that in PVDCN, and is less than that in poly(vinylidene fluoride-trifluoroethylene).

effect of side chain length on the stability and structural properties of 3

African Journals Online (AJOL)

Preferred Customer

We report on the effect of the alkoxy chain length on the thermodynamic ... studied by Hartree-Fock (HF) and Density Functional Theory (DFT) methods. ..... with longer alkoxy substituents on the phenyl ring have lesser value of change in Gibbs ...

Liquid-liquid phase separation in dilute solutions of poly(styrene sulfonate) with multivalent cations: Phase diagrams, chain morphology, and impact of temperature

Science.gov (United States)

Hansch, Markus; Hämisch, Benjamin; Schweins, Ralf; Prévost, Sylvain; Huber, Klaus

2018-01-01

The dilute solution behavior of sodium poly(styrene sulfonate) is studied in the presence of trivalent Al3+ and bivalent Ba2+ cations at various levels of excess NaCl. The study evaluates the phase behavior and the morphology of the polyelectrolyte chains with increasing extent of decoration with the Al3+ and Ba2+ cations and analyses the effect of temperature on these decorated chains. The phase behavior is presented in the form of the cation concentration versus the respective poly(styrene sulfonate) concentration, recorded at the onset of precipitation. Whereas poly(styrene sulfonate) with Al3+ exhibits a linear phase boundary, denoted as the "threshold line," which increases with increasing poly(styrene sulfonate) concentration, Ba2+ cations show a threshold line which is independent of the poly(styrene sulfonate) concentration. An additional re-entrant phase, at considerably higher cation content than those of the threshold lines, is observed with Al3+ cations but not with Ba2+ cations. The threshold line and the re-entrant phase boundary form parts of the liquid-liquid phase boundary observed at the limit of low polymer concentration. The dimensions of the polyelectrolyte chains shrink considerably while approaching the respective threshold lines on increase of the Al3+ and Ba2+ cation content. However, subtle differences occur between the morphological transformation induced by Al3+ and Ba2+. Most strikingly, coils decorated with Al3+ respond very differently to temperature variations than coils decorated with Ba2+ do. As the temperature increases, the poly(styrene sulfonate) chains decrease their size in the presence of Al3+ cations but increase in size in the presence of Ba2+ cations.

Dependence of the product chain-length on detergents for long-chain E-polyprenyl diphosphate synthases

Science.gov (United States)

Pan, Jian-Jung; Ramamoorthy, Gurusankar; Poulter, C. Dale

2013-01-01

Long-chain E-polyprenyl diphosphate synthases (E-PDS) catalyze repetitive addition of isopentenyl diphosphate (IPP) to the growing prenyl chain of an allylic diphosphate. The polyprenyl diphosphate products are required for the biosynthesis of ubiquinones and menaquinones required for electron transport during oxidative phosphorylation to generate ATP. In vitro, the long-chain PDSs require addition of phospholipids or detergents to the assay buffer to enhance product release and maintain efficient turnover. During preliminary assays of product chain-length with anionic, zwitterionic, and non-ionic detergents, we discovered considerable variability. Examination of a series of non-ionic PEG detergents with several long-chain E-PDSs from different organisms revealed that in vitro incubations with nonaethylene glycol monododecyl ether or Triton X-100 typically gave chain lengths that corresponded to those of the isoprenoid moieties in respiratory quinones synthesized in vivo. In contrast incubations in buffer with n-butanol, CHAPS, DMSO, n-octyl-β-glucopyranoside, or β-cyclodextrin or in buffer without detergent typically proceeded more slowly and gave a broad range of chain lengths. PMID:23802587

The Chain-Length Distribution in Subcritical Systems

International Nuclear Information System (INIS)

Nolen, Steven Douglas

2000-01-01

The individual fission chains that appear in any neutron multiplying system provide a means, via neutron noise analysis, to unlock a wealth of information regarding the nature of the system. This work begins by determining the probability density distributions for fission chain lengths in zero-dimensional systems over a range of prompt neutron multiplication constant (K) values. This section is followed by showing how the integral representation of the chain-length distribution can be used to obtain an estimate of the system's subcritical prompt multiplication (MP). The lifetime of the chains is then used to provide a basis for determining whether a neutron noise analysis will be successful in assessing the neutron multiplication constant, k, of the system in the presence of a strong intrinsic source. A Monte Carlo transport code, MC++, is used to model the evolution of the individual fission chains and to determine how they are influenced by spatial effects. The dissertation concludes by demonstrating how experimental validation of certain global system parameters by neutron noise analysis may be precluded in situations in which the system K is relatively low and in which realistic detector efficiencies are simulated

The Chain-Length Distribution in Subcritical Systems

Energy Technology Data Exchange (ETDEWEB)

Nolen, Steven Douglas [Texas A & M Univ., College Station, TX (United States)

2000-06-01

The individual fission chains that appear in any neutron multiplying system provide a means, via neutron noise analysis, to unlock a wealth of information regarding the nature of the system. This work begins by determining the probability density distributions for fission chain lengths in zero-dimensional systems over a range of prompt neutron multiplication constant (K) values. This section is followed by showing how the integral representation of the chain-length distribution can be used to obtain an estimate of the system's subcritical prompt multiplication (MP). The lifetime of the chains is then used to provide a basis for determining whether a neutron noise analysis will be successful in assessing the neutron multiplication constant, k, of the system in the presence of a strong intrinsic source. A Monte Carlo transport code, MC++, is used to model the evolution of the individual fission chains and to determine how they are influenced by spatial effects. The dissertation concludes by demonstrating how experimental validation of certain global system parameters by neutron noise analysis may be precluded in situations in which the system K is relatively low and in which realistic detector efficiencies are simulated.

Topochemical approach to efficiently produce main-chain poly(bile acid)s with high molecular weights.

Science.gov (United States)

Li, Weina; Li, Xuesong; Zhu, Wei; Li, Changxu; Xu, Dan; Ju, Yong; Li, Guangtao

2011-07-21

Based on a topochemical approach, a strategy for efficiently producing main-chain poly(bile acid)s in the solid state was developed. This strategy allows for facile and scalable synthesis of main-chain poly(bile acid)s not only with high molecular weights, but also with quantitative conversions and yields.

Novel odd/even effect of alkylene chain length on the photopolymerizability of organogelators.

Science.gov (United States)

Aoki, Ken'ichi; Kudo, Masabumi; Tamaoki, Nobuyuki

2004-10-28

[reaction: see text] Starting from diactylene diacarboxylic acids, we have synthesized a series of photopolymerizable organogelators that possess simple amide structures, different alkylene chain lengths, and either optically active or racemic 3,7-dimethyl-1-octylamine units. The alkylene chain length of these compounds exhibits a prominent odd/even effect with respect to the photopolymerization in the gel state and is accompanied by a stereostructural effect on the gelation ability.

Three-Dimensional Packing Structure and Electronic Properties of Biaxially Oriented Poly(2,5-bis(3-alkylthiophene-2-yl)thieno[3,2- b ]thiophene) Films

KAUST Repository

Cho, Eunkyung

2012-04-11

We use a systematic approach that combines experimental X-ray diffraction (XRD) and computational modeling based on molecular mechanics and two-dimensional XRD simulations to develop a detailed model of the molecular-scale packing structure of poly(2,5-bis (3-tetradecylthiophene-2-yl) thieno[3,2-b]thiophene) (PBTTT-C 14) films. Both uniaxially and biaxially aligned films are used in this comparison and lead to an improved understanding of the molecular-scale orientation and crystal structure. We then examine how individual polymer components (i.e., conjugated backbone and alkyl side chains) contribute to the complete diffraction pattern, and how modest changes to a particular component orientation (e.g., backbone or side-chain tilt) influence the diffraction pattern. The effects on the polymer crystal structure of varying the alkyl side-chain length from C 12 to C 14 and C 16 are also studied. The accurate determination of the three-dimensional polymer structure allows us to examine the PBTTT electronic band structure and intermolecular electronic couplings (transfer integrals) as a function of alkyl side-chain length. This combination of theoretical and experimental techniques proves to be an important tool to help establish the relationship between the structural and electronic properties of polymer thin films. © 2012 American Chemical Society.

The effect of gamma radiation on mechanical properties of biodegradable polymers poly(3-hydroxybutyrate and poly(3-hydroxybutyrate-co-3-hydroxyvalerate

Directory of Open Access Journals (Sweden)

Leticia Maria Oliveira

2013-02-01

Full Text Available Brazilian poly(3-hydroxybutyrate, P(3-HB, and its copolymer, poly (3-hydroxybutyrate-co-3-hydroxyvalerate, P(3-HB-co-3-HV were irradiated with gamma radiation (60Co at room temperature and in the presence of oxygen. The viscosity-average molar mass (Mv was analyzed by viscometry using an Ostwald-type capillary viscometer. Both polymers showed a decrease in molar mass with the increase in dose, reflecting that random main chain scissions occurred. The value G (scissions/100 eV of energy transferred to the system and the parameter α (scissions per original molecule were also determined. Mechanical properties decrease with the increase in dose, revealing that P(3-HB underwent significant changes, especially at doses higher than 50 kGy. Tensile at break and impact resistance properties were the most affected by radiation, while the elastic modulus remained virtually unaltered up to 100 kGy dose.

Tailored Poly(2-oxazoline) Polymer Brushes to Control Protein Adsorption and Cell Adhesion

KAUST Repository

Zhang, Ning

2012-05-18

POx bottle-brush brushes (BBBs) are synthesized by SIPGP of 2-isopropenyl-2-oxazoline and consecutive LCROP of 2-oxazolines on 3-aminopropyltrimethoxysilane-modified silicon substrates. The side chain hydrophilicity and polarity are varied. The impact of the chemical composition and architecture of the BBB upon protein (fibronectin) adsorption and endothelial cell adhesion are investigated and prove extremely low protein adsorption and cell adhesion on BBBs with hydrophilic side chains such as poly(2-methyl-2-oxazoline) and poly(2-ethyl-2-oxazoline). The influence of the POx side chain terminal function upon adsorption and adhesion is minor but the side chain length has a significant effect on bioadsorption. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tailored Poly(2-oxazoline) Polymer Brushes to Control Protein Adsorption and Cell Adhesion

KAUST Repository

Zhang, Ning; Pompe, Tilo; Amin, Ihsan; Luxenhofer, Robert; Werner, Carsten; Jordan, Rainer

2012-01-01

POx bottle-brush brushes (BBBs) are synthesized by SIPGP of 2-isopropenyl-2-oxazoline and consecutive LCROP of 2-oxazolines on 3-aminopropyltrimethoxysilane-modified silicon substrates. The side chain hydrophilicity and polarity are varied. The impact of the chemical composition and architecture of the BBB upon protein (fibronectin) adsorption and endothelial cell adhesion are investigated and prove extremely low protein adsorption and cell adhesion on BBBs with hydrophilic side chains such as poly(2-methyl-2-oxazoline) and poly(2-ethyl-2-oxazoline). The influence of the POx side chain terminal function upon adsorption and adhesion is minor but the side chain length has a significant effect on bioadsorption. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of Amphiphilic Alkyl Chain Length Upon Purified LATEX Stability

International Nuclear Information System (INIS)

Amira Amir Hassan; Amir Hashim Mohd Yatim

2015-01-01

Rubber particles in purified latex (PL) are stabilized by a film of protein and fatty acid soap (surfactant). Saturated straight-chain fatty acid soaps can assist an enhancement of latex stability. However, whether the alkyl chain length plays an important role in increasing the stability is still an issue. The aim of this study is to investigate the effect of alkyl chain length of anionic surfactant on the stability of purified latex. The fatty acid soap of decanoate (9), laurate (11), sodium dodecyl sulphate (SDS) (12) and palmitate (15) were used. The numbers in parentheses indicating the number of carbon present in alkyl chain of the soap. The results showed that the impact of alkyl chain length on the stability of latex is in the order of laurate > decanoate > SDS > palmitate > purified latex accordingly. The alkyl chain length does giving a significant effect on latex stability after longer stirring time. The particle size of latex with the presence of surfactant is greater compare to a single particle itself due to extension of particles diameter. Thus suitable interaction of the nonpolar tail of surfactant with the hydrophobic regions of latex surface played a major role in maintaining a stable latex system. (author)

Poly[ n ]catenanes: Synthesis of molecular interlocked chains

Energy Technology Data Exchange (ETDEWEB)

Wu, Qiong; Rauscher, Phillip M.; Lang, Xiaolong; Wojtecki, Rudy J.; de Pablo, Juan J.; Hore, Michael J. A.; Rowan, Stuart J.

2017-11-30

As the macromolecular version of mechanically interlocked molecules, mechanically interlocked polymers are promising candidates for the creation of sophisticated molecular machines and smart soft materials. Poly[n]catenanes, where the molecular chains consist solely of interlocked macrocycles, contain one of the highest concentrations of topological bonds. We report, herein, a synthetic approach toward this distinctive polymer architecture in high yield (similar to 75%) via efficient ring closing of rationally designed metallosupramolecular polymers. Light-scattering, mass spectrometric, and nuclear magnetic resonance characterization of fractionated samples support assignment of the high-molar mass product (number-average molar mass similar to 21.4 kilograms per mole) to a mixture of linear poly[7-26]catenanes, branched poly[13-130]catenanes, and cyclic poly[4-7]catenanes. Increased hydrodynamic radius (in solution) and glass transition temperature (in bulk materials) were observed upon metallation with Zn2+.

Amyloid-like fibril formation by polyQ proteins: a critical balance between the polyQ length and the constraints imposed by the host protein.

Directory of Open Access Journals (Sweden)

Natacha Scarafone

Full Text Available Nine neurodegenerative disorders, called polyglutamine (polyQ diseases, are characterized by the formation of intranuclear amyloid-like aggregates by nine proteins containing a polyQ tract above a threshold length. These insoluble aggregates and/or some of their soluble precursors are thought to play a role in the pathogenesis. The mechanism by which polyQ expansions trigger the aggregation of the relevant proteins remains, however, unclear. In this work, polyQ tracts of different lengths were inserted into a solvent-exposed loop of the β-lactamase BlaP and the effects of these insertions on the properties of BlaP were investigated by a range of biophysical techniques. The insertion of up to 79 glutamines does not modify the structure of BlaP; it does, however, significantly destabilize the enzyme. The extent of destabilization is largely independent of the polyQ length, allowing us to study independently the effects intrinsic to the polyQ length and those related to the structural integrity of BlaP on the aggregating properties of the chimeras. Only chimeras with 55Q and 79Q readily form amyloid-like fibrils; therefore, similarly to the proteins associated with diseases, there is a threshold number of glutamines above which the chimeras aggregate into amyloid-like fibrils. Most importantly, the chimera containing 79Q forms amyloid-like fibrils at the same rate whether BlaP is folded or not, whereas the 55Q chimera aggregates into amyloid-like fibrils only if BlaP is unfolded. The threshold value for amyloid-like fibril formation depends, therefore, on the structural integrity of the β-lactamase moiety and thus on the steric and/or conformational constraints applied to the polyQ tract. These constraints have, however, no significant effect on the propensity of the 79Q tract to trigger fibril formation. These results suggest that the influence of the protein context on the aggregating properties of polyQ disease-associated proteins could be

Stochastic Simulation of a Full-Chain Reptation Model with Constraint Release, Chain-Length Fluctuations and Chain Stretching

DEFF Research Database (Denmark)

Neergaard, Jesper; Schieber, Jay D.

1999-01-01

A self-consistent reptation model that includes chain stretching, chain-length fluctuations, segment connectivity and constraint release is used to predict transient and steady flows. Quantitative comparisons are made with entangledsolution data. The model is able to capture quantitatively all...

Comparison of Chain-Length Preferences and Glucan Specificities of Isoamylase-Type α-Glucan Debranching Enzymes from Rice, Cyanobacteria, and Bacteria.

Directory of Open Access Journals (Sweden)

Taiki Kobayashi

Full Text Available It has been believed that isoamylase (ISA-type α-glucan debranching enzymes (DBEs play crucial roles not only in α-glucan degradation but also in the biosynthesis by affecting the structure of glucans, although molecular basis on distinct roles of the individual DBEs has not fully understood. In an attempt to relate the roles of DBEs to their chain-length specificities, we analyzed the chain-length distribution of DBE enzymatic reaction products by using purified DBEs from various sources including rice, cyanobacteria, and bacteria. When DBEs were incubated with phytoglycogen, their chain-length specificities were divided into three groups. First, rice endosperm ISA3 (OsISA3 and Eschericia coli GlgX (EcoGlgX almost exclusively debranched chains having degree of polymerization (DP of 3 and 4. Second, OsISA1, Pseudomonas amyloderamosa ISA (PsaISA, and rice pullulanase (OsPUL could debranch a wide range of chains of DP≧3. Third, both cyanobacteria ISAs, Cyanothece ATCC 51142 ISA (CytISA and Synechococcus elongatus PCC7942 ISA (ScoISA, showed the intermediate chain-length preference, because they removed chains of mainly DP3-4 and DP3-6, respectively, while they could also react to chains of DP5-10 and 7-13 to some extent, respectively. In contrast, all these ISAs were reactive to various chains when incubated with amylopectin. In addition to a great variation in chain-length preferences among various ISAs, their activities greatly differed depending on a variety of glucans. Most strikingly, cyannobacteria ISAs could attack branch points of pullulan to a lesser extent although no such activity was found in OsISA1, OsISA3, EcoGlgX, and PsaISA. Thus, the present study shows the high possibility that varied chain-length specificities of ISA-type DBEs among sources and isozymes are responsible for their distinct functions in glucan metabolism.

Dynamic photoinduced realignment processes in photoresponsive block copolymer films: effects of the chain length and block copolymer architecture.

Science.gov (United States)

Sano, Masami; Shan, Feng; Hara, Mitsuo; Nagano, Shusaku; Shinohara, Yuya; Amemiya, Yoshiyuki; Seki, Takahiro

2015-08-07

A series of block copolymers composed of an amorphous poly(butyl methacrylate) (PBMA) block connected with an azobenzene (Az)-containing liquid crystalline (PAz) block were synthesized by changing the chain length and polymer architecture. With these block copolymer films, the dynamic realignment process of microphase separated (MPS) cylinder arrays of PBMA in the PAz matrix induced by irradiation with linearly polarized light was studied by UV-visible absorption spectroscopy, and time-resolved grazing incidence small angle X-ray scattering (GI-SAXS) measurements using a synchrotron beam. Unexpectedly, the change in the chain length hardly affected the realignment rate. In contrast, the architecture of the AB-type diblock or the ABA-type triblock essentially altered the realignment feature. The strongly cooperative motion with an induction period before realignment was characteristic only for the diblock copolymer series, and the LPL-induced alignment change immediately started for triblock copolymers and the PAz homopolymer. Additionally, a marked acceleration in the photoinduced dynamic motions was unveiled in comparison with a thermal randomization process.

Processing and characterization of recycled poly(ethylene terephthalate) blends with chain extenders, thermoplastic elastomer, and/or poly(butylene adipate-co-terephthalate)

Science.gov (United States)

Yottha Srithep; Alireza Javadi; Srikanth Pilla; Lih-Sheng Turng; Shaoqin Gong; Craig Clemons; Jun Peng

2011-01-01

Poly(ethylene terephthalate) (PET) resin is one of the most widely used thermoplastics, especially in packaging. Because thermal and hydrolytic degradations, recycled PET (RPET) exhibits poor mechanical properties and lacks moldability. The effects of adding elastomeric modifiers, chain extenders (CE), and poly(butylenes adipate-co-terephthalate), PBAT, as a toughener...

Preparation and Properties of Some Novel Poly benzoxazine Containing Pendent Aliphatic Chains

International Nuclear Information System (INIS)

Agag, T.; Akelah, A.; Rehaband, A.; Mostafa, S.

2005-01-01

Poly benzoxazine as a newly developed type of phenolic resin has an excellent properties-process ability-price balance. Despite having the usual characteristics of the typical phenolic resins, such as heat resistance, good electronic properties and flame retardance, poly benzoxazine have additional advantageous characteristics superior to the typical phenolic. These characteristics include low melt viscosity of the monomers, no strong acid or basic catalysts needed for the polymerization, and no by-products evolved during the polymerization as well as near-zero shrinkage or expansion upon curing. However, the brittleness is considered the main disadvantage of this new class of thermoset, like all the conventional resins. In the current study, we have prepared a series of new monofunctional and bifunctional benzoxazine monomers from different long chain aliphatic amines, paraformaldehyde and various phenols, using solventless method. The structure of the novel monomers was confirmed by IR and 1H-NMR, indicating the presence of cyclic benzoxazine structure. The thermoset obtained by the thermal cure of benzoxazine monomers showed improved toughness with lower glass transition temperatures than the typical known types of poly benzoxazine due to the flexibilizing effect of the long aliphatic chains in the novel poly benzoxazine

Solubilization of docetaxel in poly(ethylene oxide)-block-poly(butylene/styrene oxide) micelles.

Science.gov (United States)

Elsabahy, Mahmoud; Perron, Marie-Eve; Bertrand, Nicolas; Yu, Ga-Er; Leroux, Jean-Christophe

2007-07-01

Poly(ethylene oxide)-block-poly(styrene oxide) (PEO-b-PSO) and PEO-b-poly(butylene oxide) (PEO-b-PBO) of different chain lengths were synthesized and characterized for their self-assembling properties in water by dynamic/static light scattering, spectrofluorimetry, and transmission electron microscopy. The resulting polymeric micelles were evaluated for their ability to solubilize and protect the anticancer drug docetaxel (DCTX) from degradation. The drug release kinetics as well as the cytotoxicity of the loaded micelles were assessed in vitro. All polymers formed micelles with a highly viscous core at low critical association concentrations (hydrolysis under accelerated stability testing conditions. Only PEO-b-PBO bearing 24 BO units afforded significant protection against degradation. In vitro, DCTX was released slower from the latter micelles, but all formulations possessed a similar cytotoxic effect against PC-3 prostate cancer cells. These data suggest that PEO-b-P(SO/BO) micelles could be used as alternatives to conventional surfactants for the solubilization of taxanes.

Investigation of the role of hydrophilic chain length in amphiphilic perfluoropolyether/poly(ethylene glycol) networks: towards high-performance antifouling coatings

Energy Technology Data Exchange (ETDEWEB)

Wang, Yapei; Pitet, Louis M.; Finlay, John A.; Brewer, Lenora H.; Cone, Gemma; Betts, Douglas E.; Callow, Maureen E.; Callow, James A.; Wendt, Dean E.; Hillmyer, Marc A.; DeSimone, Joseph M. (Birmingham UK); (NCSU); (UNC); (Cal. Polytech.); (UMM)

2013-03-07

The facile preparation of amphiphilic network coatings having a hydrophobic dimethacryloxy-functionalized perfluoropolyether (PFPE-DMA; M{sub w} = 1500 g mol{sup -1}) crosslinked with hydrophilic monomethacryloxy functionalized poly(ethylene glycol) macromonomers (PEG-MA; M{sub w} = 300, 475, 1100 g mol{sup -1}), intended as non-toxic high-performance marine coatings exhibiting antifouling characteristics is demonstrated. The PFPE-DMA was found to be miscible with the PEG-MA. Photo-cured blends of these materials containing 10 wt% of PEG-MA oligomers did not swell significantly in water. PFPE-DMA crosslinked with the highest molecular weight PEG oligomer (ie PEG1100) deterred settlement (attachment) of algal cells and cypris larvae of barnacles compared to a PFPE control coating. Dynamic mechanical analysis of these networks revealed a flexible material. Preferential segregation of the PEG segments at the polymer/air interface resulted in enhanced antifouling performance. The cured amphiphilic PFPE/PEG films showed decreased advancing and receding contact angles with increasing PEG chain length. In particular, the PFPE/PEG1100 network had a much lower advancing contact angle than static contact angle, suggesting that the PEG1100 segments diffuse to the polymer/water interface quickly. The preferential interfacial aggregation of the larger PEG segments enables the coating surface to have a substantially enhanced resistance to settlement of spores of the green seaweed Ulva, cells of the diatom Navicula and cypris larvae of the barnacle Balanus amphitrite as well as low adhesion of sporelings (young plants) of Ulva, adhesion being lower than to a polydimethyl elastomer, Silastic T2.

Investigation of the role of hydrophilic chain length in amphiphilic perfluoropolyether/poly(ethylene glycol) networks: towards high-performance antifouling coatings.

Science.gov (United States)

Wang, Yapei; Pitet, Louis M; Finlay, John A; Brewer, Lenora H; Cone, Gemma; Betts, Douglas E; Callow, Maureen E; Callow, James A; Wendt, Dean E; Hillmyer, Marc A; DeSimonea, Joseph M

2011-01-01

The facile preparation of amphiphilic network coatings having a hydrophobic dimethacryloxy-functionalized perfluoropolyether (PFPE-DMA; M(w) = 1500 g mol(-1)) crosslinked with hydrophilic monomethacryloxy functionalized poly(ethylene glycol) macromonomers (PEG-MA; M(w) = 300, 475, 1100 g mol(-1)), intended as non-toxic high-performance marine coatings exhibiting antifouling characteristics is demonstrated. The PFPE-DMA was found to be miscible with the PEG-MA. Photo-cured blends of these materials containing 10 wt% of PEG-MA oligomers did not swell significantly in water. PFPE-DMA crosslinked with the highest molecular weight PEG oligomer (ie PEG1100) deterred settlement (attachment) of algal cells and cypris larvae of barnacles compared to a PFPE control coating. Dynamic mechanical analysis of these networks revealed a flexible material. Preferential segregation of the PEG segments at the polymer/air interface resulted in enhanced antifouling performance. The cured amphiphilic PFPE/PEG films showed decreased advancing and receding contact angles with increasing PEG chain length. In particular, the PFPE/PEG1100 network had a much lower advancing contact angle than static contact angle, suggesting that the PEG1100 segments diffuse to the polymer/water interface quickly. The preferential interfacial aggregation of the larger PEG segments enables the coating surface to have a substantially enhanced resistance to settlement of spores of the green seaweed Ulva, cells of the diatom Navicula and cypris larvae of the barnacle Balanus amphitrite as well as low adhesion of sporelings (young plants) of Ulva, adhesion being lower than to a polydimethyl elastomer, Silastic T2.

Tailor-made starch-based conjugates containing well-defined poly(vinyl acetate and its derivative poly(vinyl alcohol

Directory of Open Access Journals (Sweden)

2011-06-01

Full Text Available Reversible addition-fragmentation chain transfer (RAFT polymerization was adopted to synthesize starch-based conjugates that possessed controllable architecture and properties. Starch-based xanthate agent was prepared and applied as chain transfer agent to conduct the living/controlled polymerization (LCP of vinyl acetate, which generated tailor-made conjugates of starch and well-defined poly(vinyl acetate (SVAc. The relevant derivatives, conjugates of starch and chain length-controlled poly(vinyl alcohol (SVA, were obtained subsequently. Various characterizations such as Fourier transform infrared spectra (FTIR, ultraviolet-visible spectroscopy (UV, proton nuclear magnetic resonance (1H NMR, gel permeation chromatography (GPC, X-ray diffraction (XRD, Thermogravimetric analysis (TGA, and dynamic mechanical thermal analysis (DMTA were performed to examine the structure of intermediates and the starch-based conjugates. Static contact angle measurements revealed that the hydrophilic character of starch-based conjugates was tunable. Well-defined SVAc was amphiphilic and it was able to self-assemble into size controllable micelles, which was verified by contact angles, transmission electron microscopy (TEM and dynamic light scattering (DLS tests. SVA exhibited much higher capability to form physically cross-linked hydrogel than starch did. Both the characteristic of SVAc and SVA were chain length-dependent.

Vaporization enthalpies of imidazolium based ionic liquids. A thermogravimetric study of the alkyl chain length dependence

International Nuclear Information System (INIS)

Verevkin, Sergey P.; Zaitsau, Dzmitry H.; Emel’yanenko, Vladimir N.; Ralys, Ricardas V.; Yermalayeu, Andrei V.; Schick, Christoph

2012-01-01

Highlights: ► Enthalpies of vaporization of ionic liquids were measured with thermogravimetry. ► We studied 1-alkyl-3-methyl-imidazolium bis(trifluoromethanesulfonyl)imide. ► The linear alkyl chain length was 4, 6, 8, 10, 12, 14, 16, and 18 C-atoms. ► A linear dependence on the chain length of the alkyl-imidazolium cation was found. - Abstract: Vaporization enthalpies for a series of ten ionic liquids (ILs) 1-alkyl-3-methyl-imidazolium bis(trifluoromethanesulfonyl)imide [C n mim][NTf 2 ], with the alkyl chain length n = 4, 6, 8, 10, 12, 14, 16, and 18 were determined using the thermogravimetric method. An internally consistent set of experimental data and vaporization enthalpies at 540 K was obtained. Vaporization enthalpies at 540 K have shown a linear dependence on the chain length of the alkyl-imidazolium cation in agreement with the experimental results measured previously with a quartz crystal microbalance. Ambiguity of Δ l g C pm o -values required for the extrapolation of experimental vaporization enthalpies to the reference temperature 298 K has been discussed.

Uniaxial drawing and mechanical properties of poly[(R)-3-hydroxybutyrate]/poly(L-lactic acid) blends.

Science.gov (United States)

Park, Jun Wuk; Doi, Yoshiharu; Iwata, Tadahisa

2004-01-01

Blends of poly(L-lactic acid) (PLLA) with two kinds of poly[(R)-3-hydroxybutyrate] (PHB) having different molecular weights, commercial-grade bacterial PHB (bacterial-PHB) and ultrahigh molecular weight PHB (UHMW-PHB), were prepared by the solvent-casting method and uniaxially drawn at two drawing temperatures, around PHB's T(g) (2 degrees C) for PHB-rich blends and around PLLA's T(g) (60 degrees C) for PLLA-rich blends. Differential scanning calorimetry analysis showed that this system was immiscible over the entire composition range. Mechanical properties of all of the samples were improved in proportion to the draw ratio. Although PLLA domains in bacterial-PHB-rich blends remained almost unstretched during cold drawing, a good interfacial adhesion between two polymers and the reinforcing role of PLLA components led to enhanced mechanical properties proportionally to the PLLA content at the same draw ratio. On the contrary, in the case of UHMW-PHB-rich blends, the minor component PLLA was found to be also oriented by cold drawing in ice water due to an increase in the interfacial entanglements caused by the very long chain length of the matrix polymer. As a result, their mechanical properties were considerably improved with increasing PLLA content compared with the bacterial-PHB system. Scanning electron microscopy observations on the surface and cross-section revealed that a layered structure with uniformly oriented microporous in the interior was obtained by selectively removal of PLLA component after simple alkaline treatment.

Inhibition of nuclear T3 binding by fatty acids: dependence on chain length, unsaturated bonds, cis-trans configuration and esterification

NARCIS (Netherlands)

Wiersinga, W. M.; Platvoet-ter Schiphorst, M.

1990-01-01

1. Fatty acids have the capacity for inhibition of nuclear T3 binding (INB). The present studies were undertaken to describe the INB-activity of fatty acids as a function of chain length, unsaturated bonds, cis-trans configuration, and esterification. 2. Isolated rat liver nuclei were incubated with

Direct observation of the edge spin structure and chain length dependence of a finite haldane chain by high field ESR measurements

International Nuclear Information System (INIS)

Yoshida, Makoto; Ohta, Hitoshi; Ito, Toshimitsu; Ajiro, Yoshitami

2006-01-01

We have performed high field and multi-frequency ESR measurements of finite length S=1 antiferromagnetic chains in Y 2 BaNi 0.96 Mg 0.04 O 5 . Owing to the high spectral resolution by high fields and high frequencies, observed ESR signals can be separated into the contributions of the finite chains with various chain lengths. Our results clearly show that the edge spins actually interact with each other through the quantum spin chain and the interaction depends on the chain length N. (author)

Biophysical characterization of the strong stabilization of the RNA triplex poly(U•poly(A*poly(U by 9-O-(ω-amino alkyl ether berberine analogs.

Directory of Open Access Journals (Sweden)

Debipreeta Bhowmik

Full Text Available Binding of two 9-O-(ω-amino alkyl ether berberine analogs BC1 and BC2 to the RNA triplex poly(U(•poly(A(*poly(U was studied by various biophysical techniques.Berberine analogs bind to the RNA triplex non-cooperatively. The affinity of binding was remarkably high by about 5 and 15 times, respectively, for BC1 and BC2 compared to berberine. The site size for the binding was around 4.3 for all. Based on ferrocyanide quenching, fluorescence polarization, quantum yield values and viscosity results a strong intercalative binding of BC1 and BC2 to the RNA triplex has been demonstrated. BC1 and BC2 stabilized the Hoogsteen base paired third strand by about 18.1 and 20.5 °C compared to a 17.5 °C stabilization by berberine. The binding was entropy driven compared to the enthalpy driven binding of berbeine, most likely due to additional contacts within the grooves of the triplex and disruption of the water structure by the alkyl side chain.Remarkably higher binding affinity and stabilization effect of the RNA triplex by the amino alkyl berberine analogs was achieved compared to berberine. The length of the alkyl side chain influence in the triplex stabilization phenomena.

Effect of Chain-Extenders on the Properties and Hydrolytic Degradation Behavior of the Poly(lactide/ Poly(butylene adipate-co-terephthalate Blends

Directory of Open Access Journals (Sweden)

Mingqing Chen

2013-10-01

Full Text Available Biodegradable poly(lactide/poly(butylene adipate-co-terephthalate (PLA/PBAT blends were prepared by reactive blending in the presence of chain-extenders. Two chain-extenders with multi-epoxy groups were studied. The effect of chain-extenders on the morphology, mechanical properties, thermal behavior, and hydrolytic degradation of the blends was investigated. The compatibility between the PLA and PBAT was significantly improved by in situ formation of PLA-co-PBAT copolymers in the presence of the chain-extenders, results in an enhanced ductility of the blends, e.g., the elongation at break was increased to 500% without any decrease in the tensile strength. The differential scanning calorimeter (DSC results reveal that cold crystallization of PLA was enhanced due to heterogeneous nucleation effect of the in situ compatibilized PBAT domains. As known before, PLA is sensitive to hydrolysis and in the presence of PBAT and the chain-extenders, the hydrolytic degradation of the blend was evident. A three-stage hydrolysis mechanism for the system is proposed based on a study of weight loss and molecular weight reduction of the samples and the pH variation of the degradation medium.

A poly(alkyl methacrylate-divinylbenzene-vinylbenzyl trimethylammonium chloride) monolithic column for solid-phase microextraction.

Science.gov (United States)

Liu, Wan-Ling; Lirio, Stephen; Yang, Yicong; Wu, Lin-Tai; Hsiao, Shu-Ying; Huang, Hsi-Ya

2015-05-22

In this study, an organic polymer monolithic columns, which were prepared via in situ polymerization of alkyl methacrylate-ester (AMA), divinylbenzene (DVB) and vinylbenzyl trimethylammonium chloride (VBTA, charged monomer), were developed as adsorbent for solid-phase microextraction (SPME). Different parameters affecting the extraction efficiency for nine (9) non-steroidal anti-inflammatory drugs (NSAIDs) such as the ratio of the stearyl methacrylate (SMA) to DVB monomer, column length, sample pH, extraction flow rate and desorption solvent were investigated to obtain the optimal SPME condition. Also, the permeability for each poly(AMA-DVB-VBTA) monolithic column was investigated by adding porogenic solvent (poly(ethylene glycol), PEG). Using the optimized condition, a series of AMA-based poly(AMA-DVB-VBTA) monolith columns were developed to determine the effect the extraction efficiency of NSAIDs by varying the alkyl chain length of the methacrylate ester (methyl-, butyl-, octyl-, or lauryl-methacrylate; (MMA, BMA, OMA, LMA)). Results showed that decreasing the AMA chain length increases the extraction efficiency of some NSAIDs (i.e. sulindac (sul), naproxen (nap), ketoprofen (ket) and indomethacin (idm)). Among the poly(AMA-DVB-VBTA) monolithic columns, poly(BMA-DVB-VBTA) showed a highly repeatable extraction efficiency for NSAIDs with recoveries ranging from 85.0 to 100.2% with relative standard deviation (RSD) less than 6.8% (n=3). The poly(BMA-DVB-VBTA) can also be reused for at least 50 times without any significant effect in extraction efficiency for NSAIDs. Finally, using the established conditions, the poly(BMA-DVB-VBTA) was used to extract trace-level NSAIDs (100μgL(-1)) in river water with good recoveries ranging from 75.8 to 90.8% (RSD<14.9%). Copyright © 2015 Elsevier B.V. All rights reserved.

DNA compaction by poly (amido amine) dendrimers of ammonia cored and ethylene diamine cored

Science.gov (United States)

Qamhieh, K.; Al-Shawwa, J.

2017-06-01

The complexes build-up of DNA and soft particles poly amidoamine (PAMAM) dendrimers of ammonia cored of generations (G1-G6) and ethylenediamine cored of generations (G1-G10) have been studied, using a new theoretical model developed by Qamhieh and coworkers. The model describes the interaction between linear polyelectrolyte (LPE) chain and ion-penetrable spheres. Many factors affecting LPE/dendrimer complex have been investigated such as dendrimer generation, the Bjerrum length, salt concentration, and rigidity of the LPE chain represented by the persistence length. It is found that the wrapping chain length around dendrimer increases by increasing dendrimer`s generation, Bjerrum length, and salt concentration, while decreases by increasing the persistence length of the LPE chain. Also we can conclude that the wrapping length of LPE chain around ethylenediamine cored dendrimers is larger than its length around ammonia cored dendrimers.

Charge Delocalization in Oligomers of Poly(2,5-bis(3-alkylthiophene-2-yl)thieno[3,2-b]thiophene), PBTTT

KAUST Repository

Zhang, Yuexing

2016-04-25

We investigate theoretically charge delocalization in radical-cations, i.e., positive polarons, formed on oligomer chains of poly(2,5-bis(3-alkylthiophene-2-yl)thieno[3,2-b]thiophene), PBTTT. We use non-empirically tuned range-separated density functionals (TRS-DFT), including LC-ωPBE, LC-BLYP, and ωB97XD. We consider the evolution with oligomer length of the molecular geometric and electronic structures, optical absorption features, and spin densities. The TRS-DFT results indicate that a positive polaron can delocalize ideally over some 10 thiophene rings when the backbone is non-planar and up to 14 rings for a backbone forced to be completely planar. Interestingly, up to six polarons can co-exist side-by-side in a hexamer (which contains 24 thiophene rings), which is consistent with the highest degrees of doping (oxidation) experimentally achievable in polythiophene derivatives.

Charge Delocalization in Oligomers of Poly(2,5-bis(3-alkylthiophene-2-yl)thieno[3,2-b]thiophene), PBTTT

KAUST Repository

Zhang, Yuexing; Steyrleuthner, Robert; Bredas, Jean-Luc

2016-01-01

We investigate theoretically charge delocalization in radical-cations, i.e., positive polarons, formed on oligomer chains of poly(2,5-bis(3-alkylthiophene-2-yl)thieno[3,2-b]thiophene), PBTTT. We use non-empirically tuned range-separated density functionals (TRS-DFT), including LC-ωPBE, LC-BLYP, and ωB97XD. We consider the evolution with oligomer length of the molecular geometric and electronic structures, optical absorption features, and spin densities. The TRS-DFT results indicate that a positive polaron can delocalize ideally over some 10 thiophene rings when the backbone is non-planar and up to 14 rings for a backbone forced to be completely planar. Interestingly, up to six polarons can co-exist side-by-side in a hexamer (which contains 24 thiophene rings), which is consistent with the highest degrees of doping (oxidation) experimentally achievable in polythiophene derivatives.

Effect of side chain length on charge transport, morphology, and photovoltaic performance of conjugated polymers in bulk heterojunction solar cells

NARCIS (Netherlands)

Duan, C.; Willems, R.E.M.; van Franeker, J.J.; Bruijnaers, B.J.; Wienk, M.M.; Janssen, R.A.J.

2016-01-01

The effect of side chain length on the photovoltaic properties of conjugated polymers is systematically investigated with two sets of polymers that bear different alkyl side chain lengths based on benzodithiophene and benzo[2,1,3]thiadiazole or 5,6-difluorobenzo[2,1,3]thiadiazole. Characterization

Characterization of amylose nanoparticles prepared via nanoprecipitation: Influence of chain length distribution.

Science.gov (United States)

Chang, Yanjiao; Yang, Jingde; Ren, Lili; Zhou, Jiang

2018-08-15

The influence of chain length distribution of amylose on size and structure of the amylose nanoparticles (ANPs) prepared through nanoprecipitation was investigated. Amylose with different chain length distributions was obtained by β-amylase treating amylose paste for different times and measured by size exclusion chromatography (SEC) and fluorophore-assisted carbohydrate electrophoresis (FACE). ANPs prepared via precipitation were characterized by using dynamic light scattering (DLS), scanning electron microscopy (SEM) and X-ray diffraction (XRD). Results showed that the β-amylase treatments led to decrease in chain length of amylose, and it was the most important factor affecting size of ANPs. When hydrolysis degree of amylose was 52.8%, mean size of ANPs decreased from 206.4 nm to 102.7 nm. All the ANPs displayed a V-type crystalline structure and the effect of amylose chain length on crystallinity of the precipitated ANPs was negligible in the investigated range. Copyright © 2018 Elsevier Ltd. All rights reserved.

A fixed cations and low Tg polymer: the poly(4-vinyl-pyridine) quaternized by poly(ethylene oxide) links. Conductivity study; Un electrolyte polymere a cations fixes et bas Tg: les poly(4-vinylpyridine) quaternisees par des chainons de poly(oxyde d`ethylene). Etude de la conductivite

Energy Technology Data Exchange (ETDEWEB)

Gramain, Ph. [Ecole Nationale Superieure de Chimie de Montpellier, 34 (France); Frere, Y. [Centre National de la Recherche Scientifique (CNRS), 67 - Strasbourg (France). Institut Charles Sadron

1996-12-31

The spontaneous ionic polymerization of 4-vinyl-pyridine in presence of mono-tosylated or bromated short chains of poly(ethylene oxide)-(PEO) is used to prepare amorphous comb-like poly-cations with low Tg. The polymer electrolyte properties of these new structures have been studied without any addition of salts. The ionic conductivity of these fixed cation poly-electrolytes depends on the length of the grafted PEO and varies from 10{sup -7} to 10{sup -4} S/cm between 25 and 80 deg. C. It is only weakly dependent on the nature of the cation but it is controlled by the movements of the pyridinium cation which are facilitated by the plastifying effect of the POE chains which do not directly participate to the ionic transport. (J.S.) 17 refs.

A fixed cations and low Tg polymer: the poly(4-vinyl-pyridine) quaternized by poly(ethylene oxide) links. Conductivity study; Un electrolyte polymere a cations fixes et bas Tg: les poly(4-vinylpyridine) quaternisees par des chainons de poly(oxyde d`ethylene). Etude de la conductivite

Energy Technology Data Exchange (ETDEWEB)

Gramain, Ph [Ecole Nationale Superieure de Chimie de Montpellier, 34 (France); Frere, Y [Centre National de la Recherche Scientifique (CNRS), 67 - Strasbourg (France). Institut Charles Sadron

1997-12-31

The spontaneous ionic polymerization of 4-vinyl-pyridine in presence of mono-tosylated or bromated short chains of poly(ethylene oxide)-(PEO) is used to prepare amorphous comb-like poly-cations with low Tg. The polymer electrolyte properties of these new structures have been studied without any addition of salts. The ionic conductivity of these fixed cation poly-electrolytes depends on the length of the grafted PEO and varies from 10{sup -7} to 10{sup -4} S/cm between 25 and 80 deg. C. It is only weakly dependent on the nature of the cation but it is controlled by the movements of the pyridinium cation which are facilitated by the plastifying effect of the POE chains which do not directly participate to the ionic transport. (J.S.) 17 refs.

Polymer light-emitting diodes with thermal inkjet printed poly(3,4-ethylenedioxythiophene):polystyrenesulfonate as transparent anode

International Nuclear Information System (INIS)

Chou, W.-Y.; Lin, S.-T.; Cheng, H.-L.; Chang, M.-H.; Guo, H.-R.; Wen, T.-C.; Mai, Y.-S.; Horng, J.-B.; Kuo, C.-W.; Tang, F.-C.; Liao, C.-C.; Chiu, C.-L.

2007-01-01

Conjugated poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) films, prepared by inkjet-printing and spin-coating methods, have been studied using atomic force microscopy, micro-Raman spectroscopy, photoelectron spectroscopy, and four-point probe conductivity measurements. Electrical conductivity of the inkjet-printed film was enhanced by a factor of around 10 when compared to a spin-coating film. The improved conductivity was attributed to longer effective conjugation length of PEDOT chains in inkjet-printing PEDOT:PSS films as suggested by their micro-Raman spectroscopy. PEDOT:PSS films formed by the inkjet-printing method are appropriate for use as an anode for simplification of the fabrication process of polymer light-emitting diodes whose performance is about 1.2 cd/A

Abnormal glycogen chain length pattern, not hyperphosphorylation, is critical in Lafora disease.

Science.gov (United States)

Nitschke, Felix; Sullivan, Mitchell A; Wang, Peixiang; Zhao, Xiaochu; Chown, Erin E; Perri, Ami M; Israelian, Lori; Juana-López, Lucia; Bovolenta, Paola; Rodríguez de Córdoba, Santiago; Steup, Martin; Minassian, Berge A

2017-07-01

Lafora disease (LD) is a fatal progressive epilepsy essentially caused by loss-of-function mutations in the glycogen phosphatase laforin or the ubiquitin E3 ligase malin. Glycogen in LD is hyperphosphorylated and poorly hydrosoluble. It precipitates and accumulates into neurotoxic Lafora bodies (LBs). The leading LD hypothesis that hyperphosphorylation causes the insolubility was recently challenged by the observation that phosphatase-inactive laforin rescues the laforin-deficient LD mouse model, apparently through correction of a general autophagy impairment. We were for the first time able to quantify brain glycogen phosphate. We also measured glycogen content and chain lengths, LBs, and autophagy markers in several laforin- or malin-deficient mouse lines expressing phosphatase-inactive laforin. We find that: (i) in laforin-deficient mice, phosphatase-inactive laforin corrects glycogen chain lengths, and not hyperphosphorylation, which leads to correction of glycogen amounts and prevention of LBs; (ii) in malin-deficient mice, phosphatase-inactive laforin confers no correction; (iii) general impairment of autophagy is not necessary in LD We conclude that laforin's principle function is to control glycogen chain lengths, in a malin-dependent fashion, and that loss of this control underlies LD. © 2017 The Authors. Published under the terms of the CC BY 4.0 license.

Optimization of the alkyl side chain length of fluorine-18-labeled 7α-alkyl-fluoroestradiol

International Nuclear Information System (INIS)

Okamoto, Mayumi; Shibayama, Hiromitsu; Naka, Kyosuke; Kitagawa, Yuya; Ishiwata, Kiichi; Shimizu, Isao; Toyohara, Jun

2016-01-01

Introduction: Several lines of evidence suggest that 7α-substituted estradiol derivatives bind to the estrogen receptor (ER). In line with this hypothesis, we designed and synthesized 18 F-labeled 7α-fluoroalkylestradiol (Cn-7α-[ 18 F]FES) derivatives as molecular probes for visualizing ERs. Previously, we successfully synthesized 7α-(3-[ 18 F]fluoropropyl)estradiol (C3-7α-[ 18 F]FES) and showed promising results for quantification of ER density in vivo, although extensive metabolism was observed in rodents. Therefore, optimization of the alkyl side chain length is needed to obtain suitable radioligands based on Cn-7α-substituted estradiol pharmacophores. Methods: We synthesized fluoromethyl (23; C1-7α-[ 18 F]FES) to fluorohexyl (26; C6-7α-[ 18 F]FES) derivatives, except fluoropropyl (C3-7α-[ 18 F]FES) and fluoropentyl derivatives (C5-7α-[ 18 F]FES), which have been previously synthesized. In vitro binding to the α-subtype (ERα) isoform of ERs and in vivo biodistribution studies in mature female mice were carried out. Results: The in vitro IC 50 value of Cn-7α-FES tended to gradually decrease depending on the alkyl side chain length. C1-7α-[ 18 F]FES (23) showed the highest uptake in ER-rich tissues such as the uterus. Uterus uptake also gradually decreased depending on the alkyl side chain length. As a result, in vivo uterus uptake reflected the in vitro ERα affinity of each compound. Bone uptake, which indicates de-fluorination, was marked in 7α-(2-[ 18 F]fluoroethyl)estradiol (C2-7α-[ 18 F]FES) (24) and 7α-(4-[ 18 F]fluorobutyl)estradiol (C4-7α-[ 18 F]FES) (25) derivatives. However, C1-7α-[ 18 F]FES (23) and C6-7α-[ 18 F]FES (26) showed limited uptake in bone. As a result, in vivo bone uptake (de-fluorination) showed a bell-shaped pattern, depending on the alkyl side chain length. C1-7α-[ 18 F]FES (23) showed the same levels of uptake in uterus and bone compared with those of 16α-[ 18 F]fluoro-17β-estradiol. Conclusions: The optimal alkyl

Methanol-induced chain termination in poly(3-hydroxybutyrate) biopolymers: molecular weight control

Science.gov (United States)

A systematic study was performed to demonstrate the impact of methanol (MeOH) on poly(3-hydroxybutyrate) (PHB) synthesis and molecular weight (MW) control. Glycerine (init. conc. = 1.0%; w/v), was used as the primary carbon source in batch-culture fermentations with varying concentrations (0 to 0.85...

How Chain Length and Charge Affect Surfactant Denaturation of Acyl Coenzyme A Binding Protein (ACBP)

DEFF Research Database (Denmark)

Andersen, Kell Kleiner; Otzen, Daniel

2009-01-01

maltoside (DDM). The aim has been to determine how surfactant chain length and micellar charge affect the denaturation mechanism. ACBP denatures in two steps irrespective of surfactant chain length, but with increasing chain length, the potency of the denaturant rises more rapidly than the critical micelle......Using intrinsic tryptophan fluorescence, equilibria and kinetics of unfolding of acyl coenzyme A binding protein (ACBP) have been investigated in sodium alkyl sulfate surfactants of different chain length (8-16 carbon atoms) and with different proportions of the nonionic surfactant dodecyl...... constants increases linearly with denaturant concentration below the cmc but declines at higher concentrations. Both shortening chain length and decreasing micellar charge reduce the overall kinetics of unfolding and makes the dependence of unfolding rate constants on surfactant concentration more complex...

Ultrasonic Relaxation Study of 1-Alkyl-3-methylimidazolium-Based Room-Temperature Ionic Liquids: Probing the Role of Alkyl Chain Length in the Cation.

Science.gov (United States)

Zorębski, Michał; Zorębski, Edward; Dzida, Marzena; Skowronek, Justyna; Jężak, Sylwia; Goodrich, Peter; Jacquemin, Johan

2016-04-14

Ultrasound absorption spectra of four 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imides were determined as a function of the alkyl chain length on the cation from 1-propyl to 1-hexyl from 293.15 to 323.15 K at ambient pressure. Herein, the ultrasound absorption measurements were carried out using a standard pulse technique within a frequency range from 10 to 300 MHz. Additionally, the speed of sound, density, and viscosity have been measured. The presence of strong dissipative processes during the ultrasound wave propagation was found experimentally, i.e., relaxation processes in the megahertz range were observed for all compounds over the whole temperature range. The relaxation spectra (both relaxation amplitude and relaxation frequency) were shown to be dependent on the alkyl side chain length of the 1-alkyl-3-methylimidazolium ring. In most cases, a single-Debye model described the absorption spectra very well. However, a comparison of the determined spectra with the spectra of a few other imidazolium-based ionic liquids reported in the literature (in part recalculated in this work) shows that the complexity of the spectra increases rapidly with the elongation of the alkyl chain length on the cation. This complexity indicates that both the volume viscosity and the shear viscosity are involved in relaxation processes even in relatively low frequency ranges. As a consequence, the sound velocity dispersion is present at relatively low megahertz frequencies.

Electron beam irradiation of poly(perfluoro ethers): Identification of gaseous products as a result of main chain scission

International Nuclear Information System (INIS)

Pacansky, J.; Waltman, R.J.

1991-01-01

Several poly(perfluoro ethers) are exposed to electron beams to study the mechanism for main chain scission. Electron beam exposures were performed with the viscous poly(perfluoro ethers) under argon gas, and also at 9 K under vacuum, to determine mechanistic details for the chemical degradation. Here the authors report that, after main chain scission of the bulk poly(perfluoro ethers), sample weight loss is observed concomitant with evolution of gaseous products. Since this suggests that some unzipping of the polymer chain occurs, the products were identified and, most importantly, the efficiency for their formation was determined in terms of G values, and compared to known G values for main chain scission. The results show that COF 2 is the major gaseous product produced from unbranched ethers while CF 4 and COF 2 are the major products from branched polymers. The gaseous products were also exposed to the high-energy electron beam and the G values for decomposition are given

Photoluminescence and self-assembly of cesium lead halide perovskite nanocrystals: Effects of chain length of organic amines and reaction temperature

International Nuclear Information System (INIS)

Yuan, Yi; Liu, Zheming; Liu, Zhenyang; Peng, Lan; Li, Yongjie; Tang, Aiwei

2017-01-01

Highlights: • CsPbBr_3 perovskite nanocrystals have been synthesized in the presence of organic amines with different hydrocarbon length. • The photoluminescence of the CsPbBr_3 nanocrystals is affected by the varying the carbon length of the organic amines. • The lower reaction temperature and hydrocarbon chain length of the organic ligands play a significant role in the self-assembly of CsPbBr_3 nanocrystals. - Abstract: All-inorganic halide perovskites have become one of the most prospective materials for lightening and display technology due to their color-tunable and narrow-band emission. Herein, we have systematically studied the effects of organic amines with different hydrocarbon chain length on the optical properties and morphology as well as the crystal structure of colloidal CsPbBr_3 nanocrystals (NCs), which were synthesized in the presence of oleic acid (OA) and organic amines by using a simple hot-injection approach. The hydrocarbon chain length has shown an independent correlation to the morphology and crystal structure of the as-obtained CsPbBr_3 NCs at 160 °C, but their optical properties can be affected to some extent. The photoluminescence quantum yields (PLQYs) of the CsPbBr_3 NCs synthesized in the presence of organic amines with long carbon chain length are generally in the range of 55–80% for different reaction time, but the PLQYs of less than 20% are obtained for the products synthesized in the presence of octylamine (OTAm) with short carbon chain length. The effects of the reaction temperature on the optical properties, size and crystal structure of the CsPbBr_3 NCs synthesized in the presence of cetylamine (CTAm) are studied. Interestingly, some nanoplates also appear in these CsPbBr_3 NCs obtained at relatively low temperatures (120 and 140 °C), which have a strong tendency to self-assemble into face-to-face nanostructures. Such a similar self-assembly behavior is also observed in the product synthesized in the presence of

Photoluminescence and self-assembly of cesium lead halide perovskite nanocrystals: Effects of chain length of organic amines and reaction temperature

Energy Technology Data Exchange (ETDEWEB)

Yuan, Yi; Liu, Zheming; Liu, Zhenyang; Peng, Lan; Li, Yongjie; Tang, Aiwei, E-mail: awtang@bjtu.edu.cn

2017-05-31

Highlights: • CsPbBr{sub 3} perovskite nanocrystals have been synthesized in the presence of organic amines with different hydrocarbon length. • The photoluminescence of the CsPbBr{sub 3} nanocrystals is affected by the varying the carbon length of the organic amines. • The lower reaction temperature and hydrocarbon chain length of the organic ligands play a significant role in the self-assembly of CsPbBr{sub 3} nanocrystals. - Abstract: All-inorganic halide perovskites have become one of the most prospective materials for lightening and display technology due to their color-tunable and narrow-band emission. Herein, we have systematically studied the effects of organic amines with different hydrocarbon chain length on the optical properties and morphology as well as the crystal structure of colloidal CsPbBr{sub 3} nanocrystals (NCs), which were synthesized in the presence of oleic acid (OA) and organic amines by using a simple hot-injection approach. The hydrocarbon chain length has shown an independent correlation to the morphology and crystal structure of the as-obtained CsPbBr{sub 3} NCs at 160 °C, but their optical properties can be affected to some extent. The photoluminescence quantum yields (PLQYs) of the CsPbBr{sub 3} NCs synthesized in the presence of organic amines with long carbon chain length are generally in the range of 55–80% for different reaction time, but the PLQYs of less than 20% are obtained for the products synthesized in the presence of octylamine (OTAm) with short carbon chain length. The effects of the reaction temperature on the optical properties, size and crystal structure of the CsPbBr{sub 3} NCs synthesized in the presence of cetylamine (CTAm) are studied. Interestingly, some nanoplates also appear in these CsPbBr{sub 3} NCs obtained at relatively low temperatures (120 and 140 °C), which have a strong tendency to self-assemble into face-to-face nanostructures. Such a similar self-assembly behavior is also observed in the

Diffusivities and Viscosities of Poly(ethylene oxide) Oligomers †

KAUST Repository

Hong, Bingbing

2010-10-14

Diffusivities and viscosities of poly(ethylene oxide) (PEO) oligomer melts with 1 to 12 repeat units have been obtained from equilibrium molecular dynamics simulations using the TraPPE-UA force field. The simulations generated diffusion coefficients with high accuracy for all of the molar masses studied, but the statistical uncertainties in the viscosity calculations were significantly larger for longer chains. There is good agreement of the calculated viscosities and densities with available experimental data, and thus, the simulations can be used to bridge gaps in the data and for extrapolations with respect to chain length, temperature, and pressure. We explored the convergence characteristics of the Green-Kubo formulas for different chain lengths and propose minimal production times required for convergence of the transport properties. The chain-length dependence of the transport properties suggests that neither Rouse nor reptation models are applicable in the short-chain regime investigated. © 2010 American Chemical Society.

Exploring the impact of the side-chain length on peptide/RNA binding events.

Science.gov (United States)

Sbicca, Lola; González, Alejandro López; Gresika, Alexandra; Di Giorgio, Audrey; Closa, Jordi Teixido; Tejedor, Roger Estrada; Andréola, Marie-Line; Azoulay, Stéphane; Patino, Nadia

2017-07-19

The impact of the amino-acid side-chain length on peptide-RNA binding events has been investigated using HIV-1 Tat derived peptides as ligands and the HIV-1 TAR RNA element as an RNA model. Our studies demonstrate that increasing the length of all peptide side-chains improves unexpectedly the binding affinity (K D ) but reduces the degree of compactness of the peptide-RNA complex. Overall, the side-chain length appears to modulate in an unpredictable way the ability of the peptide to compete with the cognate TAR RNA partner. Beyond the establishment of non-intuitive fundamental relationships, our results open up new perspectives in the design of effective RNA ligand competitors, since a large number of them have already been identified but few studies report on the modulation of the biological activity by modifying in the same way the length of all chains connecting RNA recognition motives to the central scaffold of a ligand.

Studies on electrical conductivity of poly phenylene vinylene

International Nuclear Information System (INIS)

Khattab, Asaad F.; Ahmad, Saddam M.

2009-01-01

Four Pp polymers have been synthesized through Wit ting reaction, 1 poly(p-phenylene vinylene), 2 = poly(p phenylene vinylene-co-m-phenylene vinylene), 3 = poly(p-phenylene vinylene-co-o-phenylene vinylene) and 4 poly(p-phenylene-1,5-hexadiene). Electrical conductivity measurements show that the conductivity of polymer 3 is higher than that of polymers 1 and 2. The dihedral angle measurements indicates that the irregularity of polymer chains is the main reason for this fact. The interruption of chain conjugation by aliphatic segments (polymer 4) will increase the conductivity by increasing the chain mobility.The electrical conductivity of the polymers is increased by doping with iodine and by raising the temperature. The effect of annealing with different temperatures on conductivity was studied; the results show that structural conformation of polymeric chain is the main factor affecting electrical conductivity. (author)

Biosynthesis and characterization of polyhydroxyalkanoates copolymers produced by Pseudomonas putida Bet001 isolated from palm oil mill effluent.

Science.gov (United States)

Gumel, Ahmad Mohammed; Annuar, Mohamad Suffian Mohamad; Heidelberg, Thorsten

2012-01-01

The biosynthesis and characterization of medium chain length poly-3-hydroxyalkanoates (mcl-PHA) produced by Pseudomonas putida Bet001 isolated from palm oil mill effluent was studied. The biosynthesis of mcl-PHA in this newly isolated microorganism follows a growth-associated trend. Mcl-PHA accumulation ranging from 49.7 to 68.9% on cell dry weight (CDW) basis were observed when fatty acids ranging from octanoic acid (C(8:0)) to oleic acid (C(18:1)) were used as sole carbon and energy source. Molecular weight of the polymer was found to be ranging from 55.7 to 77.7 kDa. Depending on the type of fatty acid used, the (1)H NMR and GCMSMS analyses of the chiral polymer showed a composition of even and odd carbon atom chain with monomer length of C4 to C14 with C8 and C10 as the principal monomers. No unsaturated monomer was detected. Thermo-chemical analyses showed the accumulated PHA to be semi-crystalline polymer with good thermal stability, having a thermal degradation temperature (T(d)) of 264.6 to 318.8 (± 0.2) (o)C, melting temperature (T(m)) of 43. (± 0.2) (o)C, glass transition temperature (T(g)) of -1.0 (± 0.2) (o)C and apparent melting enthalpy of fusion (ΔH(f)) of 100.9 (± 0.1) J g(-1).

Nanophase separation in side chain polymers: new evidence from structure and dynamics

International Nuclear Information System (INIS)

Hiller, S; Pascui, O; Budde, H; Kabisch, O; Reichert, D; Beiner, M

2004-01-01

New evidence for a nanophase separation of incompatible main and side chain parts in amorphous poly(n-alkyl methacrylates) with long alkyl groups are presented. Independent indications for the existence of alkyl nanodomains with a typical dimension in the 1 nm range from studies on dynamics and structure are reported. Results from nuclear magnetic resonance (NMR) experiments are compared with data from different relaxation spectroscopy methods on poly(n-decyl methacrylate). The NMR results in combination with relaxation spectroscopy data support the existence of an independent polyethylene-like glass transition, α PE , within the alkyl nanodomains in addition to the conventional glass transition a at higher temperatures. X-ray scattering data show that the situation in homopolymers is similar to that for random poly(n-alkyl methacrylate) copolymers with the same average length of the alkyl group in the side chains. Scattering data for a series of n-butyl methacrylate samples with polymerization degrees reaching from P=1 to 405 indicate that nanophase separation is chain-length independent above P=25, while the nanophase separation tends to disappear below P=6. Insensitivity of structural aspects in nanophase-separated poly(n-alkyl methacrylates) to changes in the molecular microstructure and consistency of NMR results with independent conclusions from relaxation spectroscopy underline the general importance of nanophase separation effects in a broad class of side chain polymers

Infinite coherence time of edge spins in finite-length chains

Science.gov (United States)

Maceira, Ivo A.; Mila, Frédéric

2018-02-01

Motivated by the recent observation that exponentially long coherence times can be achieved for edge spins in models with strong zero modes, we study the impact of level crossings in finite-length spin chains on the dynamics of the edge spins. Focusing on the X Y spin-1 /2 chain with a transverse or longitudinal magnetic field, two models relevant to understanding recent experimental results on cobalt adatoms, we show that the edge spins can remain coherent for an infinite time even for a finite-length chain if the magnetic field is tuned to a value at which there is a level crossing. Furthermore, we show that the edge spins remain coherent for any initial state for the integrable case of a transverse field because all states have level crossings at the same value of the field, while the coherence time is increasingly large for lower temperatures in the case of a longitudinal field, which is nonintegrable.

Unraveling the Order and Disorder in Poly(3,4-ethylenedioxythiophene)/Poly(styrenesulfonate) Nanofilms

KAUST Repository

Zhou, Jian; Anjum, Dalaver H.; Lubineau, Gilles; Li, Erqiang; Thoroddsen, Sigurdur T

2015-01-01

Conductive polymer poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) exhibits a tunable conductivity ranging from 0.1 to 4380 S·cm–1 under different doping and/or dedoping strategies. However, the dependence of macroscopic electrical properties on the evolution of the microstructure is not clearly understood. This is the first study that systematically investigated the spatial arrangement of the ordered and disordered phases in PEDOT/PSS nanofilms by bright-field (BF), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) combined with electron energy loss spectroscopy (EELS) and element-thickness mapping. Our observations clarify how amorphous PSS hinders electrical transport at various length scales in the PEDOT/PSS films. Moreover, the mechanism for an enhancement in 3 orders of magnitude in electrical conductivity was proved by TEM investigation, which is mainly due to a more uniform dispersion by dedoping that opens PEDOT nanoparticle clusters in PEDOT/PSS films. Our microstructural and electrical studies show that the change in spatial arrangement and interaction of small PEDOT domains plays a considerable role in the final electron transport.

Unraveling the Order and Disorder in Poly(3,4-ethylenedioxythiophene)/Poly(styrenesulfonate) Nanofilms

KAUST Repository

Zhou, Jian

2015-08-03

Conductive polymer poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) exhibits a tunable conductivity ranging from 0.1 to 4380 S·cm–1 under different doping and/or dedoping strategies. However, the dependence of macroscopic electrical properties on the evolution of the microstructure is not clearly understood. This is the first study that systematically investigated the spatial arrangement of the ordered and disordered phases in PEDOT/PSS nanofilms by bright-field (BF), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) combined with electron energy loss spectroscopy (EELS) and element-thickness mapping. Our observations clarify how amorphous PSS hinders electrical transport at various length scales in the PEDOT/PSS films. Moreover, the mechanism for an enhancement in 3 orders of magnitude in electrical conductivity was proved by TEM investigation, which is mainly due to a more uniform dispersion by dedoping that opens PEDOT nanoparticle clusters in PEDOT/PSS films. Our microstructural and electrical studies show that the change in spatial arrangement and interaction of small PEDOT domains plays a considerable role in the final electron transport.

Photoluminescence and self-assembly of cesium lead halide perovskite nanocrystals: Effects of chain length of organic amines and reaction temperature

Science.gov (United States)

Yuan, Yi; Liu, Zheming; Liu, Zhenyang; Peng, Lan; Li, Yongjie; Tang, Aiwei

2017-05-01

All-inorganic halide perovskites have become one of the most prospective materials for lightening and display technology due to their color-tunable and narrow-band emission. Herein, we have systematically studied the effects of organic amines with different hydrocarbon chain length on the optical properties and morphology as well as the crystal structure of colloidal CsPbBr3 nanocrystals (NCs), which were synthesized in the presence of oleic acid (OA) and organic amines by using a simple hot-injection approach. The hydrocarbon chain length has shown an independent correlation to the morphology and crystal structure of the as-obtained CsPbBr3 NCs at 160 °C, but their optical properties can be affected to some extent. The photoluminescence quantum yields (PLQYs) of the CsPbBr3 NCs synthesized in the presence of organic amines with long carbon chain length are generally in the range of 55-80% for different reaction time, but the PLQYs of less than 20% are obtained for the products synthesized in the presence of octylamine (OTAm) with short carbon chain length. The effects of the reaction temperature on the optical properties, size and crystal structure of the CsPbBr3 NCs synthesized in the presence of cetylamine (CTAm) are studied. Interestingly, some nanoplates also appear in these CsPbBr3 NCs obtained at relatively low temperatures (120 and 140 °C), which have a strong tendency to self-assemble into face-to-face nanostructures. Such a similar self-assembly behavior is also observed in the product synthesized in the presence of oleylamine (OLAm), but only flat nanoplates are observed in the products in the presence of OTAm at 120 °C. The results indicate that the lower reaction temperature and hydrocarbon chain length of the organic ligands play a significant role in the self-assembly of CsPbBr3 NCs. This work opens up an alternative approach to controllable-synthesis of perovskite NCs through varying the carbon chain length of organic surfactants, and enlightens

Fabrication and tribological properties of self-assembled monolayer of n-alkyltrimethoxysilane on silicon: Effect of SAM alkyl chain length

International Nuclear Information System (INIS)

Huo, Lixia; Du, Pengcheng; Zhou, Hui; Zhang, Kaifeng; Liu, Peng

2017-01-01

Highlights: • n-Alkyltrimethoxysilanes with various chain lengths were self-assembled on silicon. • Effect of alkyl chain lengths (C6, C12, or C18) on the SAMs was investigated. • Surface roughness of the SAMs decreased with increasing the alkyl chain lengths. • The C 12 -SAM possessed superior friction reduction and wear resistance. - Abstract: It is well known that the self-assembled organic molecules on a solid surface exhibit the friction-reducing performance. However, the effect of the molecular size of the self-assembled organic molecules has not been established. In the present work, self-assembled monolayers (SAMs) of n-alkyltrimethoxysilanes with different alkyl chain lengths (C 6 , C 12 , or C 18 ) were fabricated on silicon substrate. The water contact angles of the SAMs increased from 26.8° of the hydroxylated silicon substrate to near 60° after self-assembly. The atomic force microscopy (AFM) analysis results showed that the mean roughness (R a ) of the SAMs decreased with increasing the alkyl chain length. The tribological properties of the SAMs sliding against Al 2 O 3 ball were evaluated on an UMT-2 tribometer, and the worn surfaces of the samples were analyzed by means of Nano Scratch Tester and surface profilometry. It was found that lowest friction coefficient and smallest width of wear were achieved with the SAMs of C 12 alkyl chain (C 12 -SAM). The superior friction reduction and wear resistance of the SAMs in comparison with the bare silicon substrate are attributed to good adhesion of the self-assembled films to the substrate, especially the C 12 -SAM with desirable alkyl chain length.

Neutron chain length distributions in subcritical systems

International Nuclear Information System (INIS)

Nolen, S.D.; Spriggs, G.

1999-01-01

In this paper, the authors present the results of the chain-length distribution as a function of k in subcritical systems. These results were obtained from a point Monte Carlo code and a three-dimensional Monte Carlo code, MC++. Based on these results, they then attempt to explain why several of the common neutron noise techniques, such as the Rossi-α and Feynman's variance-to-mean techniques, are difficult to perform in highly subcritical systems using low-efficiency detectors

Does alkyl chain length really matter? Structure–property relationships in thermochemistry of ionic liquids

International Nuclear Information System (INIS)

Verevkin, Sergey P.; Zaitsau, Dzmitry H.; Emel’yanenko, Vladimir N.; Ralys, Ricardas V.; Yermalayeu, Andrei V.; Schick, Christoph

2013-01-01

Graphical abstract: We have shown that enthalpies of formation, enthalpies of vaporization, and lattice potential energies of alkylsubstituted imidazolium, pyridinium, and pyrrolidinium based ionic liquids with Cl and Br anions are linearly dependant on the alkyl chain length. The thermochemical properties of ILs are generally obey the group additivity rules and the values of the additivity parameters for enthalpies of formation and vaporization are very close to those for molecular compounds. - Highlights: • Alkyl substituted imidazolium, pyridinium, and pyrrolidinium based ionic liquids with anions [Cl] and [Br] were studied using DSC and ab initio methods. • The thermochemical properties of ILs generally obey the group additivity rules. • A linear dependence on the chain length of the alkyl chain of cation was found. - Abstract: DSC was used for determination of reaction enthalpies of synthesis of ionic liquids [C n mim][Cl]. A combination of DSC with quantum chemical calculations presents an indirect way to study thermodynamics of ionic liquids. The indirect procedure for vaporization enthalpy was validated with the direct experimental measurements by using thermogravimetry. First-principles calculations of the enthalpy of formation in the gaseous phase have been performed for the ionic species using the CBS-QB3 and G3 (MP2) theory. Experimental DSC data for homologous series of alkyl substituted imidazolium, pyridinium, and pyrrolidinium based ionic liquids with anions [Cl] and [Br] were collected from the literature. We have shown that enthalpies of formation, enthalpies of vaporization, and lattice potential energies are linearly dependant on the alkyl chain length. The thermochemical properties of ILs generally obey the group additivity rules and the values of the additivity parameters for enthalpies of formation and vaporization seem to be very close to those for molecular compounds

New Flame-Retardant Poly(ester-imide)s Containing Phosphine Oxide Moieties in the Main Chain: Synthesis and Properties

OpenAIRE

FAGHIHI, Khalil

2014-01-01

Six new flame-retardant poly(ester-imide)s (9a-f) with high inherent viscosity and containing phosphine oxide moieties in the main chain were synthesized from the polycondensation reaction of N,N-(3,3-diphenylphenyl phosphine oxide) bistrimellitimide diacid chloride (7) with 6 aromatic diols (8a-f) by 2 different methods:--solution and microwave-assisted polycondensation. The results showed that compared to solution polycondensation, the microwave-assisted polycondensation reaction us...

Poly(Amido Amine)s Containing Agmatine and Butanol Side Chains as Efficient Gene Carriers.

Science.gov (United States)

Won, Young-Wook; Ankoné, Marc; Engbersen, Johan F J; Feijen, Jan; Kim, Sung Wan

2016-04-01

A new type of bioreducible poly(amido amine) copolymer is synthesized by the Michael addition polymerization of cystamine bisacrylamide (CBA) with 4-aminobutylguanidine (agmatine, AGM) and 4-aminobutanol (ABOL). Since the positively charged guanidinium groups of AGM and the hydroxybutyl groups of ABOL in the side chains have shown to improve the overall transfection efficiency of poly(amido amine)s, it is hypothesized that poly(CBA-ABOL/AGM) synthesized at the optimal ratio of both components would result in high transfection efficiency and minimal toxicity. In this study, a series of the poly(CBA-ABOL/AGM) copolymers is synthesized as gene carriers. The polymers are characterized and luciferase transfection efficiencies of the polymers in various cell lines are investigated to select the ideal ratio between AGM and ABOL. The poly(CBA-ABOL/AGM) containing 80% AGM and 20% ABOL has shown the best transfection efficiency with the lowest cytotoxicity, indicating that this polymer is very promising as a potent and nontoxic gene carrier. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis and aqueous phase behavior of thermoresponsive biodegradable poly(D,L-3-methylglycolide)-block-poly(ethyelene glycol)-block-poly(D,L-3-methylglycolide) triblock copolymers

NARCIS (Netherlands)

Zhong, Zhiyuan; Dijkstra, Pieter J.; Feijen, Jan; Kwon, Young-Min; Bae, You Han; Kim, Sung Wan

2002-01-01

Novel biodegradable thermosensitive triblock copolymers of poly(D,L-3-methylglycolide)-block-poly(ethylene glycol)-block-poly(D,L-3-methylglycolide) (PMG-PEG-PMG) have been synthesized. Ring-opening polymerization of D,L-3-methyl-glycolide (MG) initiated with poly(ethylene glycol) (PEG) and

PMMA-g-OEtOx Graft Copolymers: Influence of Grafting Degree and Side Chain Length on the Conformation in Aqueous Solution

Directory of Open Access Journals (Sweden)

Irina Muljajew

2018-03-01

Full Text Available Depending on the degree of grafting (DG and the side chain degree of polymerization (DP, graft copolymers may feature properties similar to statistical copolymers or to block copolymers. This issue is approached by studying aqueous solutions of PMMA-g-OEtOx graft copolymers comprising a hydrophobic poly(methyl methacrylate (PMMA backbone and hydrophilic oligo(2-ethyl-2-oxazoline (OEtOx side chains. The graft copolymers were synthesized via reversible addition-fragmentation chain transfer (RAFT copolymerization of methyl methacrylate (MMA and OEtOx-methacrylate macromonomers of varying DP. All aqueous solutions of PMMA-g-OEtOx (9% ≤ DG ≤ 34%; 5 ≤ side chain DP ≤ 24 revealed lower critical solution temperature behavior. The graft copolymer architecture significantly influenced the aggregation behavior, the conformation in aqueous solution and the coil to globule transition, as verified by means of turbidimetry, dynamic light scattering, nuclear magnetic resonance spectroscopy, and analytical ultracentrifugation. The aggregation behavior of graft copolymers with a side chain DP of 5 was significantly affected by small variations of the DG, occasionally forming mesoglobules above the cloud point temperature (Tcp, which was around human body temperature. On the other hand, PMMA-g-OEtOx with elongated side chains assembled into well-defined structures below the Tcp (apparent aggregation number (Nagg = 10 that were able to solubilize Disperse Orange 3. The thermoresponsive behavior of aqueous solutions thus resembled that of micelles comprising a poly(2-ethyl-2-oxazoline (PEtOx shell (Tcp > 60 °C.

Engineering of poly(ethylene glycol) chain-tethered surfaces to obtain high-performance bionanoparticles

International Nuclear Information System (INIS)

Nagasaki, Yukio

2010-01-01

A poly(ethylene glycol)-b-poly[2-(N,N-dimethylamino)ethyl methacrylate] block copolymer possessing a reactive acetal group at the end of the poly(ethylene glycol) (PEG) chain, that is, acetal-PEG-b-PAMA, was synthesized by a proprietary polymerization technique. Gold nanoparticles (GNPs) were prepared using the thus-synthesized acetal-PEG-b-PAMA block copolymer. The PEG-b-PAMA not only acted as a reducing agent of aurate ions but also attached to the nanoparticle surface. The GNPs obtained had controlled sizes and narrow size distributions. They also showed high dispersion stability owing to the presence of PEG tethering chains on the surface. The same strategy should also be applicable to the fabrication of semiconductor quantum dots and inorganic porous nanoparticles. The preparation of nanoparticles in situ, i.e. in the presence of acetal-PEG-b-PAMA, gave the most densely packed polymer layer on the nanoparticle surface; this was not observed when coating preformed nanoparticles. PEG/polyamine block copolymer was more functional on the metal surface than PEG/polyamine graft copolymer, as confirmed by angle-dependent x-ray photoelectron spectroscopy. We successfully solubilized the C 60 fullerene into aqueous media using acetal-PEG-b-PAMA. A C 60 /acetal-PEG-b-PAMA complex with a size below 5 nm was obtained by dialysis. The preparation and characterization of these materials are described in this review. (topical review)

Fabrication and tribological properties of self-assembled monolayer of n-alkyltrimethoxysilane on silicon: Effect of SAM alkyl chain length

Energy Technology Data Exchange (ETDEWEB)

Huo, Lixia [National Key Laboratory of Science and Technology on Vacuum Technology and Physics, Lanzhou Institute of Physics, Lanzhou, Gansu 730010 (China); Institute of Polymer Science and Engineering, College of Chemistry and Chemical Engineering, Lanzhou University, Gansu 730000 (China); Du, Pengcheng [Institute of Polymer Science and Engineering, College of Chemistry and Chemical Engineering, Lanzhou University, Gansu 730000 (China); Zhou, Hui; Zhang, Kaifeng [National Key Laboratory of Science and Technology on Vacuum Technology and Physics, Lanzhou Institute of Physics, Lanzhou, Gansu 730010 (China); Liu, Peng, E-mail: pliu@lzu.edu.cn [Institute of Polymer Science and Engineering, College of Chemistry and Chemical Engineering, Lanzhou University, Gansu 730000 (China)

2017-02-28

Highlights: • n-Alkyltrimethoxysilanes with various chain lengths were self-assembled on silicon. • Effect of alkyl chain lengths (C6, C12, or C18) on the SAMs was investigated. • Surface roughness of the SAMs decreased with increasing the alkyl chain lengths. • The C{sub 12}-SAM possessed superior friction reduction and wear resistance. - Abstract: It is well known that the self-assembled organic molecules on a solid surface exhibit the friction-reducing performance. However, the effect of the molecular size of the self-assembled organic molecules has not been established. In the present work, self-assembled monolayers (SAMs) of n-alkyltrimethoxysilanes with different alkyl chain lengths (C{sub 6}, C{sub 12}, or C{sub 18}) were fabricated on silicon substrate. The water contact angles of the SAMs increased from 26.8° of the hydroxylated silicon substrate to near 60° after self-assembly. The atomic force microscopy (AFM) analysis results showed that the mean roughness (R{sub a}) of the SAMs decreased with increasing the alkyl chain length. The tribological properties of the SAMs sliding against Al{sub 2}O{sub 3} ball were evaluated on an UMT-2 tribometer, and the worn surfaces of the samples were analyzed by means of Nano Scratch Tester and surface profilometry. It was found that lowest friction coefficient and smallest width of wear were achieved with the SAMs of C{sub 12} alkyl chain (C{sub 12}-SAM). The superior friction reduction and wear resistance of the SAMs in comparison with the bare silicon substrate are attributed to good adhesion of the self-assembled films to the substrate, especially the C{sub 12}-SAM with desirable alkyl chain length.

Synthesis and photophysical and electroluminescent properties of poly(1,4-phenylene–ethynylene)-alt-poly(1,4-phenylene–vinylene)s with various dissymmetric substitution of alkoxy side chains

Czech Academy of Sciences Publication Activity Database

Bouguerra, N.; Růžička, Aleš; Ulbricht, C.; Enengl, C.; Enengl, S.; Pokorná, Veronika; Výprachtický, Drahomír; Tordin, E.; Aitout, R.; Cimrová, Věra; Egbe, D. A. M.

2016-01-01

Roč. 49, č. 2 (2016), s. 455-464 ISSN 0024-9297 R&D Projects: GA ČR(CZ) GA13-26542S; GA ČR(CZ) GAP106/12/0827 Institutional support: RVO:61389013 Keywords : poly(1,4-phenylene-ethynylene)-alt-poly(1,4-phenylene-vinylene)s * dissymmetric side chains * synthesis Subject RIV: CD - Macromolecular Chemistry Impact factor: 5.835, year: 2016

The importance of chain length for the polyphosphate enhancement of acidic potassium permanganate chemiluminescence.

Science.gov (United States)

Holland, Brendan J; Adcock, Jacqui L; Nesterenko, Pavel N; Peristyy, Anton; Stevenson, Paul G; Barnett, Neil W; Conlan, Xavier A; Francis, Paul S

2014-09-09

Sodium polyphosphate is commonly used to enhance chemiluminescence reactions with acidic potassium permanganate through a dual enhancement mechanism, but commercially available polyphosphates vary greatly in composition. We have examined the influence of polyphosphate composition and concentration on both the dual enhancement mechanism of chemiluminescence intensity and the stability of the reagent under analytically useful conditions. The average chain length (n) provides a convenient characterisation, but materials with similar values can exhibit markedly different distributions of phosphate oligomers. There is a minimum polyphosphate chain length (∼6) required for a large enhancement of the emission intensity, but no further advantage was obtained using polyphosphate materials with much longer average chain lengths. Providing there is a sufficient average chain length, the optimum concentration of polyphosphate is dependent on the analyte and in some cases, may be lower than the quantities previously used in routine detection. However, the concentration of polyphosphate should not be lowered in permanganate reagents that have been partially reduced to form high concentrations of the key manganese(III) co-reactant, as this intermediate needs to be stabilised to prevent formation of insoluble manganese(IV). Copyright © 2014 Elsevier B.V. All rights reserved.

Synthesis and characterization of thermosensitive poly(organophosphazenes) with methoxy-poly(ethylene glycol) and alkylamines as side groups

International Nuclear Information System (INIS)

Lee, Bae Hoon; Song, Soo Chang; Lee, Young Moo; Sohn, Youn Soo

2002-01-01

Thermosensitive poly(organophosphazenes) bearing methoxy-poly(ethylene glycon) (MPEG) and alkylamine as substituents have been synthesized and characterized by elemental analysis, NMR spectroscopy, GPC, and DSC. All the polymers exhibited crystallinity, which was probably induced by the MPEG side chain of the polymers. All the polymers exhibited the lower critical solution temperature (LCSTs) in the range of 28 to 94 .deg. C depending on several factors such as mole ratio of the substituents, kinds of PEG and alkylamines. The higher content of MPEG and shorter chain length of alkylamines of the polymers afforded the higher LCST. The LCSTs of the polymers exhibited almost concentration-independent behavior in the range of 3-30 wt % of the polymers in aqueous solutions. The polymers showed the higher LCSTs in the acidic solutions than in the neutral and basic solutions. The ionic strength of the polymer solution affected the LCST,which decreased with increased NaCl concentration. The polymer bearing almost equimolar substituents with the -N-P-N unit has shown the LCST more sensitive to NaCl and pH than that with the -N-P-O- unit. The polymers were found to degrade in acidic solution but be very stable in alkali solution as well as in the buffer solution of pH 7.4

Effect of alkyl chain length on the rotational diffusion of nonpolar and ionic solutes in 1-alkyl-3-methylimidazolium-bis(trifluoromethylsulfonyl)imides.

Science.gov (United States)

Gangamallaiah, V; Dutt, G B

2013-10-10

Rotational diffusion of a nonpolar solute 9-phenylanthracene (9-PA) and a cationic solute rhodamine 110 (R110) has been examined in a series of 1-alkyl-3-methylimidazolium (alkyl = octyl, decyl, dodecyl, tetradecyl, hexadecyl, and octadecyl) bis(trifluoromethylsulfonyl)imides to understand the influence of alkyl chain length on solute rotation. In this study, reorientation times (τr) have been measured as a function of viscosity (η) by varying the temperature (T) of the solvents. These results have been analyzed using the Stokes-Einstein-Debye (SED) hydrodynamic theory along with the ones obtained for the same solutes in 1-alkyl-3-methylimidazolium (alkyl = methyl, ethyl, propyl, butyl, and hexyl) bis(trifluoromethylsulfonyl)imides (Gangamallaiah and Dutt, J. Phys. Chem. B 2012, 116, 12819-12825). It has been noticed that the data for 9-PA and R110 follows the relation τr = A(η/T)(n) with A being the ratio of hydrodynamic volume of the solute to the Boltzmann constant and n = 1 as envisaged by the SED theory. However, upon increasing the alkyl chain length from methyl to octadecyl significant deviations from the SED theory have been observed especially from the octyl derivative onward. From methyl to octadecyl derivatives, the value of A decreases by a factor of 3 for both the solutes and n by a factor of 1.4 and 1.6 for 9-PA and R110, respectively. These observations have been rationalized by taking into consideration the organized structure of the ionic liquids, whose influence appears to be pronounced when the number of carbon atoms in the alkyl chain attached to the imidazolium cation exceeds eight.

Biosynthesis of Colabomycin E, a New Manumycin-Family Metabolite, Involves an Unusual Chain-Length Factor

Czech Academy of Sciences Publication Activity Database

Petříčková, Kateřina; Pospíšil, Stanislav; Kuzma, Marek; Tylová, Tereza; Jágr, Michal; Tomek, P.; Chroňáková, Alica; Brabcová, E.; Anděra, Ladislav; Krištůfek, Václav; Petříček, Miroslav

2014-01-01

Roč. 15, č. 9 (2014), s. 1334-1345 ISSN 1439-4227 R&D Projects: GA MZd(CZ) NT13012 Institutional support: RVO:61388971 ; RVO:60077344 ; RVO:68378050 Keywords : biosynthesis * chain-length factors * manumycins Subject RIV: CE - Biochemistry Impact factor: 3.088, year: 2014

Biosynthesis and characterization of polyhydroxyalkanoates copolymers produced by Pseudomonas putida Bet001 isolated from palm oil mill effluent.

Directory of Open Access Journals (Sweden)

Ahmad Mohammed Gumel

Full Text Available The biosynthesis and characterization of medium chain length poly-3-hydroxyalkanoates (mcl-PHA produced by Pseudomonas putida Bet001 isolated from palm oil mill effluent was studied. The biosynthesis of mcl-PHA in this newly isolated microorganism follows a growth-associated trend. Mcl-PHA accumulation ranging from 49.7 to 68.9% on cell dry weight (CDW basis were observed when fatty acids ranging from octanoic acid (C(8:0 to oleic acid (C(18:1 were used as sole carbon and energy source. Molecular weight of the polymer was found to be ranging from 55.7 to 77.7 kDa. Depending on the type of fatty acid used, the (1H NMR and GCMSMS analyses of the chiral polymer showed a composition of even and odd carbon atom chain with monomer length of C4 to C14 with C8 and C10 as the principal monomers. No unsaturated monomer was detected. Thermo-chemical analyses showed the accumulated PHA to be semi-crystalline polymer with good thermal stability, having a thermal degradation temperature (T(d of 264.6 to 318.8 (± 0.2 (oC, melting temperature (T(m of 43. (± 0.2 (oC, glass transition temperature (T(g of -1.0 (± 0.2 (oC and apparent melting enthalpy of fusion (ΔH(f of 100.9 (± 0.1 J g(-1.

Thermally reversible cross-linked poly(ether-urethanes

Directory of Open Access Journals (Sweden)

V. Gaina

2013-07-01

Full Text Available Cross-linked poly(ether-urethanes were prepared by Diels-Alder (DA reaction of the furan-containing poly(ether-urethane to bismaleimides and showed thermal reversibility evidenced by differential scanning calorimetry and attenuated total reflectance in conjunction with Fourier transform infrared spectroscopy (ATR-FTIR. The furan-containing poly(ether-urethanes were synthesized by the polyaddition reaction of 1,6-hexamethylene diisocyanate (HMDI or 4,4'- dibenzyl diisocyanate (DBDI to poly(tetramethylene ether glycol (PTMEG having Mn = 250, 650, 1000, 1500 and 2000 and 2-[N,N-bis(2-methyl-2-hydroxyethylamino]furfuryl as chain extender by the solution prepolymer method. The molar ratio of isocyanate: PTMEG:chain extender varied from 2:1:1 to 4:1:3, which produces a molar concentration of furyl group ranging between 3.65•10–4 and 1.25•10–3 mol/g.

Effect of the alkyl chain length of the ionic liquid anion on polymer electrolytes properties

International Nuclear Information System (INIS)

Leones, Rita; Sentanin, Franciani; Nunes, Sílvia Cristina; Esperança, José M.S.S.; Gonçalves, Maria Cristina

2015-01-01

New polymer electrolytes (PEs) based on chitosan and three ionic liquid (IL) families ([C 2 mim][C n SO 3 ], [C 2 mim][C n SO 4 ] and [C 2 mim][diC n PO 4 ]) were synthesized by the solvent casting method. The effect of the length of the alkyl chain of the IL anion on the thermal, morphological and electrochemical properties of the PEs was studied. The solid polymer electrolytes SPE membranes were analyzed by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), polarized optical microscopy (POM), atomic force microscopy (AFM), complex impedance spectroscopy (ionic conductivity) and cyclic voltammetry (CV). The obtained results evidenced an influence of the alkyl chain length of the IL anion on the temperature of degradation, birefringence, surface roughness and ionic conductivity of the membranes. The DSC, XRD and CV results showed independency from the length of the IL-anion-alkyl chain. The PEs displayed an predominantly amorphous morphology, a minimum temperature of degradation of 135 °C, a room temperature (T = 25 °C) ionic conductivity of 7.78 × 10 −4 S cm −1 and a wide electrochemical window of ∼ 4.0 V.

Quantum discord length is enhanced while entanglement length is not by introducing disorder in a spin chain.

Science.gov (United States)

Sadhukhan, Debasis; Roy, Sudipto Singha; Rakshit, Debraj; Prabhu, R; Sen De, Aditi; Sen, Ujjwal

2016-01-01

Classical correlation functions of ground states typically decay exponentially and polynomially, respectively, for gapped and gapless short-range quantum spin systems. In such systems, entanglement decays exponentially even at the quantum critical points. However, quantum discord, an information-theoretic quantum correlation measure, survives long lattice distances. We investigate the effects of quenched disorder on quantum correlation lengths of quenched averaged entanglement and quantum discord, in the anisotropic XY and XYZ spin glass and random field chains. We find that there is virtually neither reduction nor enhancement in entanglement length while quantum discord length increases significantly with the introduction of the quenched disorder.

New Insights into the Mechanisms of Photodegradation/Stabilization of P3HT:PCBM Active Layers Using Poly(3-hexyl-d13-Thiophene)

DEFF Research Database (Denmark)

Tournebize, Aurelien; Bussiere, Pierre-Olivier; Rivaton, Agnes

2013-01-01

species involved in the chain radical oxidation of P3HT is a key characteristic in the underlying mechanism. The results obtained in this work advance the understanding of active layer stability and will help improve the design of long lifetime organic solar cells thanks to the use of cutoff filter......The photo-oxidation mechanism of thin-film blends based on poly(3-hexylthiophene):phenyl-C-61-butyric acid methyl ester (P3HT:PCBM) upon irradiation with ultraviolet-visible light (UV-Vis) was studied. The use of deuterated P3HT, i.e., poly(3-hexyl-d(13)-thiophene) (P3HdT), permitted discrimination...

Photoluminescence decay lifetime measurements of hemicyanine derivatives of different alkyl chain lengths

International Nuclear Information System (INIS)

Shim, Taekyu; Lee, Myounghee; Kim, Sungho; Sung, Jaeho; Rhee, Bum Ku; Kim, Doseok; Kim, Hyunsung; Yoon, Kyung Byung

2004-01-01

The fluorescence upconversion setup for the detection of photoluminescence (PL) decay lifetime with subpicosecond time resolution was constructed, and the photoluminescence phenomena of several hemicyanine dyes with alkyl chains of different chain lengths tethered to the N atom of the pyridine moiety (HC-n, n=6, 15, 22) in methanol were investigated. The average decay lifetimes of the solutions determined from the measured data by multi-order exponential decay curve fitting were ∼27 ps at the PL peak wavelength. It was found that the PL decay properties did not depend on the alkyl chain length in the molecule, implying that the twist of the alkylpyridinium ring of the molecule is not possible as a nonfluorescing relaxation pathway. The time-dependent PL spectra constructed from the PL lifetime data showed the dynamic Stokes shift of ∼1000 cm -1

Biosynthesis of medium chain length alkanes for bio-aviation fuel by metabolic engineered Escherichia coli.

Science.gov (United States)

Wang, Meng; Nie, Kaili; Cao, Hao; Xu, Haijun; Fang, Yunming; Tan, Tianwei; Baeyens, Jan; Liu, Luo

2017-09-01

The aim of this work was to study the synthesis of medium-chain length alkanes (MCLA), as bio-aviation product. To control the chain length of alkanes and increase the production of MCLA, Escherichia coli cells were engineered by incorporating (i) a chain length specific thioesterase from Umbellularia californica (UC), (ii) a plant origin acyl carrier protein (ACP) gene and (iii) the whole fatty acid synthesis system (FASs) from Jatropha curcas (JC). The genetic combination was designed to control the product spectrum towards optimum MCLA. Decanoic, lauric and myristic acid were produced at concentrations of 0.011, 0.093 and 1.657mg/g, respectively. The concentration of final products nonane, undecane and tridecane were 0.00062mg/g, 0.0052mg/g, and 0.249mg/g respectively. Thioesterase from UC controlled the fatty acid chain length in a range of 10-14 carbons and the ACP gene with whole FASs from JC significantly increased the production of MCLA. Copyright © 2017 Elsevier Ltd. All rights reserved.

Characterization and optimization of antibiotic resistant bacterial strains for polyhydroxyalkanoates (phas) production

International Nuclear Information System (INIS)

Rehman, S. U.; Jamil, N.; Hussain, S.

2005-01-01

In this investigation, sugarcane soil, sewage water and soil containing long chain hydrocarbons was screened to obtain bacterial strains that were able to synthesize poly-beta-hydroxyalkanoates (PHA). The potential to synthesize PHA was tested qualitatively by Sudan Black staining of colonies growing in glucose and sucrose. Sixteen bacterial strains were isolated, purified and characterized for Gram reaction, biochemical analysis and PHA production. Isolates showed a wide range of tolerance to different commonly used antibiotics. PHA extraction was done by solvent extraction and hypochlorite digestion method. PHA production was optimized for different nitrogen concentrations. (author)

Improving the Performances of Poly(vinylphosphonic acid) by Compositing or Copolymerization with Poly(4-(α-methyl)vinyl-1H-1,2,3-triazole)

International Nuclear Information System (INIS)

Han, Shuaiyuan; Yue, Baohua; Yan, Liuming

2014-01-01

Graphical abstract: - Highlights: • Poly(4-(α-methyl)vinyl-1H-1,2,3-triazole) is synthesized • PVPA/PMVTri polymeric composite proton conducting membranes are prepared • The proton conductivity of PVPA is improved by compositing with PMVTri • The water resistance of PVPA is improved by compositing with PMVTri • The oxidative stability is greatly improved - Abstract: The poly(vinylphosphonic acid) (PVPA), poly(4-(α-methyl)vinyl-1H-1,2,3-triazole) (PMVTri), and poly(VPA-co-MVTri) were synthesized, and proton exchange membranes were prepared based on the acid-base polymeric composite of PVPA and PMVTri, and acid-base amphoteric copolymer of poly(VPA-co-MVTri). The overall performances of PVPA, proton conductivity, thermal and oxidative stability, and water resistance, are greatly improved by compositing of PMVTri or copolymerization with 4-(α-methyl)vinyl-1H-1,2,3-triazole (MVTri). About four or eight folds improvement in maximum proton conductivity was observed in the polymeric composite of PVPA/PMVTri or acid-base amphoteric copolymer poly(VPA-co-MVTri) because of the redistribution of ions in the heterostructures of PVPA and PMVTri, respectively, compared with the pristine PVPA. At the same time, the oxidative stability and the water resistance of PVPA were also greatly improved attributing to the absent of α-H in the main chain of PMVTri and the acid-base interaction between the phosphonic acid groups and the triazolyl groups, respectively

Mutagenesis by alkylating agents: coding properties for DNA polymerase of poly (dC) template containing 3-methylcytosine

Energy Technology Data Exchange (ETDEWEB)

Boiteux, S.; Laval, J. (Institut Gustave-Roussy, 94 - Villejuif (France))

After treatment of poly(dC) by the simple alkylating agent (/sup 3/H)dimethylsulfate, 90 percent of the radioactivity cochromatographed with 3-methylcytosine and 10 percent with 5-methylcytosine which is the normally occurring methylated base. In order to study the influence of 3-methylcytosine on DNA replication, untreated and MDS-treated poly(dC) were used as templates for E. coli DNA polymerase I. The alkylation of poly(dC) inhibits DNA chain elongation, and does not induce any mispairing under high fidelity conditions. The alteration of DNA polymerase I fidelity by manganese ions allows some replication of 3-methylcytosine which mispairs with either dAMP or dTMP. Our results suggest that 3-methylcytosine could be responsible, at least partially, for killing and the mutagenesis observed after cell treatment by alkylating agents.

Fabrication and characterization of a novel hydrophobic CaCO{sub 3} grafted by hydroxylated poly(vinyl chloride) chains

Energy Technology Data Exchange (ETDEWEB)

Bao, Lixia [State Key Laboratory of Polymer Materials Engineering, Sichuan University (China); School of Chemical Science and Technology, Yunnan University (China); Yang, Simei; Luo, Xin [School of Chemical Science and Technology, Yunnan University (China); Lei, Jingxin [State Key Laboratory of Polymer Materials Engineering, Sichuan University (China); Cao, Qiue [School of Chemical Science and Technology, Yunnan University (China); Wang, Jiliang, E-mail: jlwang@ynu.edu.cn [School of Chemical Science and Technology, Yunnan University (China)

2015-12-01

Highlights: • Hydroxylated poly(vinyl chloride) (PVC-OH) with different molecular weight and hydroxyl value was successfully prepared by the suspension copolymerization. • PVC-OH was grafted onto the surface of CaCO{sub 3} particles by the urethane formation reaction. • The modified CaCO{sub 3} particles show excellent hydrophobicity. - Abstract: The hydroxylated PVC (PVC-OH) was successfully synthesized by a suspension polymerization of vinyl chloride (VC), butyl acrylate (BA) and hydroxyethyl acrylate (HEA). Novel hydrophobic CaCO{sub 3} was then prepared by a urethane formation reaction between methylene diphenyl diisocyanate (MDI) and the −OH groups both in the PVC-OH chains and on the surface of pristine CaCO{sub 3} particles. The effect of the PVC-OH content on the grafting ratio of treated CaCO{sub 3} particles was extensively investigated. Combining the result of Fourier transform infrared (FTIR) with that of water contact angle, it can be concluded that the hydrophobicity of CaCO{sub 3} had been efficiently improved by the PVC-OH segments grafted on the surface of CaCO{sub 3} particles. X-ray diffraction (XRD), thermal gravity analysis (TGA), scanning electron microscope (SEM) and transmission electron microscope (TEM) were also used to study crystalline behaviors, thermal stability and surface morphology of the modified CaCO{sub 3} particles, respectively. The change of specific surface area implying surface modification was investigated as well.

PEGylation on mixed monolayer gold nanoparticles: Effect of grafting density, chain length, and surface curvature.

Science.gov (United States)

Lin, Jiaqi; Zhang, Heng; Morovati, Vahid; Dargazany, Roozbeh

2017-10-15

PEGylation on nanoparticles (NPs) is widely used to prevent aggregation and to mask NPs from the fast clearance system in the body. Understanding the molecular details of the PEG layer could facilitate rational design of PEGylated NPs that maximize their solubility and stealth ability without significantly compromising the targeting efficiency and cellular uptake. Here, we use molecular dynamics (MD) simulation to understand the structural and dynamic the PEG coating of mixed monolayer gold NPs. Specifically, we modeled gold NPs with PEG grafting densities ranging from 0-2.76chain/nm 2 , chain length with 0-10 PEG monomers, NP core diameter from 5nm to 500nm. It is found that the area accessed by individual PEG chains gradually transits from a "mushroom" to a "brush" conformation as NP surface curvature become flatter, whereas such a transition is not evident on small NPs when grafting density increases. It is shown that moderate grafting density (∼1.0chain/nm 2 ) and short chain length are sufficient enough to prevent NPs from aggregating in an aqueous medium. The effect of grafting density on solubility is also validated by dynamic light scattering measurements of PEGylated 5nm gold NPs. With respect to the shielding ability, simulations predict that increase either grafting density, chain length, or NP diameter will reduce the accessibility of the protected content to a certain size molecule. Interestingly, reducing NP surface curvature is estimated to be most effective in promoting shielding ability. For shielding against small molecules, increasing PEG grafting density is more effective than increasing chain length. A simple model that includes these three investigated parameters is developed based on the simulations to roughly estimate the shielding ability of the PEG layer with respect to molecules of different sizes. The findings can help expand our current understanding of the PEG layer and guide rational design of PEGylated gold NPs for a particular

Influence of polymer chain architecture of poly(vinyl alcohol) on the inhibition of ice recrystallization

NARCIS (Netherlands)

Olijve, L.L.C.; Hendrix, M.M.R.M.; Voets, I.K.

2016-01-01

Poly(vinyl alcohol) (PVA) is a water-soluble synthetic polymer well-known to effectively block the recrystallization of ice. The effect of polymer chain architecture on the ice recrystallization inhibition (IRI) by PVA remains unexplored. In this work, the synthesis of PVA molecular bottlebrushes is

Catabolism of Branched Chain Amino Acids Contributes Significantly to Synthesis of Odd-Chain and Even-Chain Fatty Acids in 3T3-L1 Adipocytes.

Directory of Open Access Journals (Sweden)

Scott B Crown

Full Text Available The branched chain amino acids (BCAA valine, leucine and isoleucine have been implicated in a number of diseases including obesity, insulin resistance, and type 2 diabetes mellitus, although the mechanisms are still poorly understood. Adipose tissue plays an important role in BCAA homeostasis by actively metabolizing circulating BCAA. In this work, we have investigated the link between BCAA catabolism and fatty acid synthesis in 3T3-L1 adipocytes using parallel 13C-labeling experiments, mass spectrometry and model-based isotopomer data analysis. Specifically, we performed parallel labeling experiments with four fully 13C-labeled tracers, [U-13C]valine, [U-13C]leucine, [U-13C]isoleucine and [U-13C]glutamine. We measured mass isotopomer distributions of fatty acids and intracellular metabolites by GC-MS and analyzed the data using the isotopomer spectral analysis (ISA framework. We demonstrate that 3T3-L1 adipocytes accumulate significant amounts of even chain length (C14:0, C16:0 and C18:0 and odd chain length (C15:0 and C17:0 fatty acids under standard cell culture conditions. Using a novel GC-MS method, we demonstrate that propionyl-CoA acts as the primer on fatty acid synthase for the production of odd chain fatty acids. BCAA contributed significantly to the production of all fatty acids. Leucine and isoleucine contributed at least 25% to lipogenic acetyl-CoA pool, and valine and isoleucine contributed 100% to lipogenic propionyl-CoA pool. Our results further suggest that low activity of methylmalonyl-CoA mutase and mass action kinetics of propionyl-CoA on fatty acid synthase result in high rates of odd chain fatty acid synthesis in 3T3-L1 cells. Overall, this work provides important new insights into the connection between BCAA catabolism and fatty acid synthesis in adipocytes and underscores the high capacity of adipocytes for metabolizing BCAA.

New Aptes Cross-linked Polymers from Poly(ethylene oxide)s and Cyanuric Chloride for Lithium Batteries

Science.gov (United States)

Tigelaar, Dean M.; Meador, Mary Ann B.; Kinder, James D.; Bennett, William R.

2005-01-01

A new series of polymer electrolytes for use as membranes for lithium batteries are described. Electrolytes were made by polymerization between cyanuric chloride and diamino-terminated poly(ethylene oxide)s, followed by cross-linking via a sol-gel process. Thermal analysis and lithium conductivity of freestanding polymer films were studied. The effects of several variables on conductivity were investigated, such as length of backbone PEO chain, length of branching PEO chain, extent of branching, extent of cross-linking, salt content, and salt counterion. Polymer films with the highest percentage of PEO were found to be the most conductive, with a maximum lithium conductivity of 3.9 x 10(exp -5) S/cm at 25 C. Addition of plasticizer to the dry polymers increased conductivity by an order of magnitude.

Synthesis, characterizations and biocompatibility of novel biodegradable star block copolymers based on poly[(R)-3-hydroxybutyrate] and poly(epsilon-caprolactone)

DEFF Research Database (Denmark)

Wu, Linping; Wang, Liang; Wang, Xiaojuan

2010-01-01

Star block copolymers based on poly[(R)-3-hydroxybutyrate] (PHB) and poly(epsilon-caprolactone) (PCL), termed SPHBCL, were successfully synthesized with structural variation on arm numbers and lengths via coupling reactions and ring opening polymerizations. Arm numbers 3, 4 and 6 of SPHBCL were...... weights of the SPHBCL due to the discrepancy of star copolymer structures. The melting temperature of SPHBCL decreased with increasing degree of branching. Thermal decomposition temperature was revealed to be lower than that of linear block copolymer LPHBCL counterparts based on PHB and PCL. Films made...... from various SPHBCL copolymers had different porous or networking surface morphology, and all possessed improved biocompatibility in terms of less blood clotting and more osteoblast cell growth compared with their corresponding homopolymers PHB and PCL. Among them, it was found, however, that the 4-arm...

Comparison of Properties among Dendritic and Hyperbranched Poly(ether ether ketones and Linear Poly(ether ketones

Directory of Open Access Journals (Sweden)

Atsushi Morikawa

2016-02-01

Full Text Available Poly(ether ether ketone dendrimers and hyperbranched polymers were prepared from 3,5-dimethoxy-4′-(4-fluorobenzoyldiphenyl ether and 3,5-dihydroxy-4′-(4-fluorobenzoyldiphenyl ether through aromatic nucleophilic substitution reactions. 1-(tert-Butyldimethylsiloxy-3,5-bis(4-fluorobenzoylbenzene was polycondensed with bisphenols, followed by cleavage of the protective group to form linear poly(ether ketones having the same hydroxyl groups in the side chains as the chain ends of the dendrimer and hyperbranched polymers. Their properties, such as solubilities, reduced viscosities, and thermal properties, were compared with one another. Similar comparisons were also carried out among the corresponding methoxy group polymers, and the size of the molecules was shown to affect the properties.

Thermal depolymerization mechanisms of poly (3-hydroxybutyrate-co-3-hydroxyvalerate)

Institute of Scientific and Technical Information of China (English)

Hengxue Xiang; Xiaoshuang Wen; Xiaohui Miu; Yan Li; Zhe Zhou; Meifang Zhu

2016-01-01

Thermal degradation processes and decomposition mechanisms of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) were investigated by using thermal gravity analysis(TGA), Gel permeation chromatography (GPC), elemental analyzer, pyrolysis-gas chromatography-mass spectrometry (PyGC-MS) and 1H nuclear magnetic resonance (1H NMR). The degradation activation energy was calculated via the dependence of residual mass on isothermal temperature. 1H NMR and PyGC-MS were used to investigate the chemical structure and component proportion of volatile gases and degradation residues which were produced by thermal decomposition, and to infer the process of macromolecular chain scission. Besides, the influence of the factors, such as outfield atmosphere, residual metal ions, on the degradation behaviors of PHBV was also studied. Finally, the PHBV thermal decomposition mechanisms were speculated on the basis of the degradation behaviors of molecular and chemical structure.

Poly(3-hydroxybutyrate and Poly(3-hydroxybutyrate-co-3-hydroxyvalerate: Structure, Property, and Fiber

Directory of Open Access Journals (Sweden)

Qingsheng Liu

2014-01-01

Full Text Available Poly(3-hydroxybutyrate [P(3HB] and poly(3-hydroxybutyrate-co-3-hydroxyvalerate [P(3HB-co-3HV] are produced by various microorganisms as an intracellular carbon and energy reserve from agricultural feedstocks such as sugars and plant oils under unbalanced growth conditions. P(3HB and P(3HB-co-3HV have attracted the attention of academia and industry because of its biodegradability, biocompatibility, thermoplasticity, and plastic-like properties. This review first introduced the isodimorphism, spherulites, and molecular interaction of P(3HB and P(3HB-co-3HV. In addition, the effects of 3HV content on the melting temperature and crystallization rate were discussed. Then the drawbacks of P(3HB and P(3HB-co-3HV including brittleness, narrow melt processing window, low crystallization rate, slow biodegradation rate in body, and so on were summarized. At last, the preparation, structure, and properties of P(3HB and P(3HB-co-3HV fiber were introduced.

Effect of the Alkyl Chain Length on the Adsorption Properties of Malonamide Chelating Resins

International Nuclear Information System (INIS)

Ismail, I.M.; Nogami, M.; Suzuki, K.

2004-01-01

In order to investigate the effect of the alkyl chain length of malonamide chelating resins on the rate of uptake of U(VI) ions and Ce(III) Ions, lV,N,N',N'-tetraethyl malonamide (TEMA), N,N,N',N'-tetra-n-propyl malonamide (TPrMA), lV,lV,N',N'-tetra-n-butyl malonamide (TBMA) and N,l V,N',N'-tetra-n-pentyl malonamide (Tamp) chelating resins were synthesized by chemically bonding these function groups to CMS-DVB co-polymer beads. N,lV,N',N'-tetraphenyl malonamide (TPhMA) chelating resin was also investigated and the results of these resins were compared with those of N,lY,N',N-tetra methylmalonamide (TMMA) previously reported. The batch technique was used to study the thermodynamic equilibrium, in terms of distribution coefficient, and the kinetics of the adsorption U(VI) and Ce(III) ions from 3 M HNO 3 , Acid, and 3 M NaNO 3 + 0.05 M HNO 3 , Salt, media. The introduction ratio of the function group into the polymer base and the uptake of U(VI) ions and C(III) ions were found to decrease with the increase in the alkyl chain length. The uptake was found to diminish in case of TPhMA resin due to the decrease of the function group ratio and the steric-hinder effect

Application of nitrogen and carbon stable isotopes (δ(15N and δ(13C to quantify food chain length and trophic structure.

Directory of Open Access Journals (Sweden)

Matthew J Perkins

Full Text Available Increasingly, stable isotope ratios of nitrogen (δ(15N and carbon (δ(13C are used to quantify trophic structure, though relatively few studies have tested accuracy of isotopic structural measures. For laboratory-raised and wild-collected plant-invertebrate food chains spanning four trophic levels we estimated nitrogen range (NR using δ(15N, and carbon range (CR using δ(13C, which are used to quantify food chain length and breadth of trophic resources respectively. Across a range of known food chain lengths we examined how NR and CR changed within and between food chains. Our isotopic estimates of structure are robust because they were calculated using resampling procedures that propagate variance in sample means through to quantified uncertainty in final estimates. To identify origins of uncertainty in estimates of NR and CR, we additionally examined variation in discrimination (which is change in δ(15N or δ(13C from source to consumer between trophic levels and among food chains. δ(15N discrimination showed significant enrichment, while variation in enrichment was species and system specific, ranged broadly (1.4‰ to 3.3‰, and importantly, propagated variation to subsequent estimates of NR. However, NR proved robust to such variation and distinguished food chain length well, though some overlap between longer food chains infers a need for awareness of such limitations. δ(13C discrimination was inconsistent; generally no change or small significant enrichment was observed. Consequently, estimates of CR changed little with increasing food chain length, showing the potential utility of δ(13C as a tracer of energy pathways. This study serves as a robust test of isotopic quantification of food chain structure, and given global estimates of aquatic food chains approximate four trophic levels while many food chains include invertebrates, our use of four trophic level plant-invertebrate food chains makes our findings relevant for a majority

Application of Nitrogen and Carbon Stable Isotopes (δ15N and δ13C) to Quantify Food Chain Length and Trophic Structure

Science.gov (United States)

Perkins, Matthew J.; McDonald, Robbie A.; van Veen, F. J. Frank; Kelly, Simon D.; Rees, Gareth; Bearhop, Stuart

2014-01-01

Increasingly, stable isotope ratios of nitrogen (δ15N) and carbon (δ13C) are used to quantify trophic structure, though relatively few studies have tested accuracy of isotopic structural measures. For laboratory-raised and wild-collected plant-invertebrate food chains spanning four trophic levels we estimated nitrogen range (NR) using δ15N, and carbon range (CR) using δ13C, which are used to quantify food chain length and breadth of trophic resources respectively. Across a range of known food chain lengths we examined how NR and CR changed within and between food chains. Our isotopic estimates of structure are robust because they were calculated using resampling procedures that propagate variance in sample means through to quantified uncertainty in final estimates. To identify origins of uncertainty in estimates of NR and CR, we additionally examined variation in discrimination (which is change in δ15N or δ13C from source to consumer) between trophic levels and among food chains. δ15N discrimination showed significant enrichment, while variation in enrichment was species and system specific, ranged broadly (1.4‰ to 3.3‰), and importantly, propagated variation to subsequent estimates of NR. However, NR proved robust to such variation and distinguished food chain length well, though some overlap between longer food chains infers a need for awareness of such limitations. δ13C discrimination was inconsistent; generally no change or small significant enrichment was observed. Consequently, estimates of CR changed little with increasing food chain length, showing the potential utility of δ13C as a tracer of energy pathways. This study serves as a robust test of isotopic quantification of food chain structure, and given global estimates of aquatic food chains approximate four trophic levels while many food chains include invertebrates, our use of four trophic level plant-invertebrate food chains makes our findings relevant for a majority of ecological systems

Application of nitrogen and carbon stable isotopes (δ(15)N and δ(13)C) to quantify food chain length and trophic structure.

Science.gov (United States)

Perkins, Matthew J; McDonald, Robbie A; van Veen, F J Frank; Kelly, Simon D; Rees, Gareth; Bearhop, Stuart

2014-01-01

Increasingly, stable isotope ratios of nitrogen (δ(15)N) and carbon (δ(13)C) are used to quantify trophic structure, though relatively few studies have tested accuracy of isotopic structural measures. For laboratory-raised and wild-collected plant-invertebrate food chains spanning four trophic levels we estimated nitrogen range (NR) using δ(15)N, and carbon range (CR) using δ(13)C, which are used to quantify food chain length and breadth of trophic resources respectively. Across a range of known food chain lengths we examined how NR and CR changed within and between food chains. Our isotopic estimates of structure are robust because they were calculated using resampling procedures that propagate variance in sample means through to quantified uncertainty in final estimates. To identify origins of uncertainty in estimates of NR and CR, we additionally examined variation in discrimination (which is change in δ(15)N or δ(13)C from source to consumer) between trophic levels and among food chains. δ(15)N discrimination showed significant enrichment, while variation in enrichment was species and system specific, ranged broadly (1.4‰ to 3.3‰), and importantly, propagated variation to subsequent estimates of NR. However, NR proved robust to such variation and distinguished food chain length well, though some overlap between longer food chains infers a need for awareness of such limitations. δ(13)C discrimination was inconsistent; generally no change or small significant enrichment was observed. Consequently, estimates of CR changed little with increasing food chain length, showing the potential utility of δ(13)C as a tracer of energy pathways. This study serves as a robust test of isotopic quantification of food chain structure, and given global estimates of aquatic food chains approximate four trophic levels while many food chains include invertebrates, our use of four trophic level plant-invertebrate food chains makes our findings relevant for a majority of

Multifunctional poly(alkyl methacrylate) films for dental care

International Nuclear Information System (INIS)

Nielsen, Birthe V; Nevell, Thomas G; Barbu, Eugen; Smith, James R; Tsibouklis, John; Rees, Gareth D

2011-01-01

Towards the evaluation of non-permanent dental coatings for their capacity to impart dental-care benefits, thin films of a homologous series of comb-like poly(alkyl methacrylate)s (ethyl to octadecyl) have been deposited, from aqueous latex formulations, onto dentally relevant substrates. AFM studies have shown that the thickness (40-300 nm) and surface roughness (8-12 nm) of coherent polymer films are influenced by the degree of polymerization and by the length of the pendant chain. Of the polymers under consideration, poly(butyl methacrylate) formed a close-packed film that conferred to dental substrates a high degree of inhibition to acid-mediated erosion (about 27%), as evaluated by released-phosphate determinations. The potential utility of the coatings to act as anti-sensitivity barriers has been evaluated by determining the hydraulic conductance of coated bovine-dentine substrates; single treatments of dentine discs with poly(butyl methacrylate) or with poly(ethyl methacrylate) effected mean respective reductions in fluid flow of about 23% with respect to water-treated controls; repeated applications of the poly(butyl methacrylate) latex led to mean reductions in fluid flow of about 80%. Chromometric measurements have shown that pellicle-coated hydroxyapatite discs treated with poly(butyl methacrylate), poly(hexyl methacrylate) or poly(lauryl methacrylate) exhibit significant resistance to staining by food chromogens.

Multifunctional poly(alkyl methacrylate) films for dental care

Energy Technology Data Exchange (ETDEWEB)

Nielsen, Birthe V; Nevell, Thomas G; Barbu, Eugen; Smith, James R; Tsibouklis, John [School of Pharmacy and Biomedical Sciences, University of Portsmouth, Portsmouth, Hampshire, PO1 2DT (United Kingdom); Rees, Gareth D [GlaxoSmithKline R and D, St George' s Avenue, Weybridge, Surrey, KT13 0DE (United Kingdom)

2011-02-15

Towards the evaluation of non-permanent dental coatings for their capacity to impart dental-care benefits, thin films of a homologous series of comb-like poly(alkyl methacrylate)s (ethyl to octadecyl) have been deposited, from aqueous latex formulations, onto dentally relevant substrates. AFM studies have shown that the thickness (40-300 nm) and surface roughness (8-12 nm) of coherent polymer films are influenced by the degree of polymerization and by the length of the pendant chain. Of the polymers under consideration, poly(butyl methacrylate) formed a close-packed film that conferred to dental substrates a high degree of inhibition to acid-mediated erosion (about 27%), as evaluated by released-phosphate determinations. The potential utility of the coatings to act as anti-sensitivity barriers has been evaluated by determining the hydraulic conductance of coated bovine-dentine substrates; single treatments of dentine discs with poly(butyl methacrylate) or with poly(ethyl methacrylate) effected mean respective reductions in fluid flow of about 23% with respect to water-treated controls; repeated applications of the poly(butyl methacrylate) latex led to mean reductions in fluid flow of about 80%. Chromometric measurements have shown that pellicle-coated hydroxyapatite discs treated with poly(butyl methacrylate), poly(hexyl methacrylate) or poly(lauryl methacrylate) exhibit significant resistance to staining by food chromogens.

Self-assembling of poly(ε-caprolactone)-b-poly(ethylene oxide) diblock copolymers in aqueous solution and at the silica-water interface

International Nuclear Information System (INIS)

Leyh, B.; Vangeyte, P.; Heinrich, M.; Auvray, L.; De Clercq, C.; Jerome, R.

2004-01-01

Small-angle neutron scattering is used to investigate the self-assembling behaviour of poly(ε-caprolactone)-b-poly(ethylene oxide) diblock copolymers with various block lengths (i) in aqueous solution, (ii) in aqueous solution with the addition of sodium dodecyl sulphate (SDS) and (iii) at the silica-water interface. Micelles are observed under our experimental conditions due to the very small critical micellar concentration of these copolymers (0.01 g/l). The poly(ε-caprolactone) core is surrounded by a poly(ethylene oxide) corona. The micellar form factors have been measured at low copolymer concentrations (0.2 wt%) under selected contrast matching conditions. The data have been fitted to various analytical models to extract the micellar core and corona sizes. SDS is shown to induce partial micelle disruption together with an increase of the poly(ethylene oxide) corona extension from 25% (without SDS) to 70% (with SDS) of a completely extended PEO 114 chain. Our data at the silica-water interface are compatible with the adsorption of micelles

Order in poly(di-n-alkyl itaconate)s revealed by X-ray scattering experiments

International Nuclear Information System (INIS)

Holmes, P.F.; Arrighi, V.; McEwen, I.J.; Qian, H.; Terrill, N.J.

2003-01-01

The effects of both blending and copolymersiation on local ordering in poly(di-n-alkyl itaconate)s is investigated, as a function of side chain length, using small-angle X-ray scattering. Preliminary results show that local ordering is unaffected by blending in these immiscible materials, however copolymerisation leads to different behaviour. For short side chains the characteristic distance varies smoothly with copolymer composition, but with longer side chains the characteristic separations found for the homopolymers are observed, and these remain unchanged with composition

Order in poly(di-n-alkyl itaconate)s revealed by X-ray scattering experiments

Energy Technology Data Exchange (ETDEWEB)

Holmes, P.F.; Arrighi, V. E-mail: v.arrighi@hw.ac.uk; McEwen, I.J.; Qian, H.; Terrill, N.J

2003-01-01

The effects of both blending and copolymersiation on local ordering in poly(di-n-alkyl itaconate)s is investigated, as a function of side chain length, using small-angle X-ray scattering. Preliminary results show that local ordering is unaffected by blending in these immiscible materials, however copolymerisation leads to different behaviour. For short side chains the characteristic distance varies smoothly with copolymer composition, but with longer side chains the characteristic separations found for the homopolymers are observed, and these remain unchanged with composition.

Effect of crosslinker length on the elastic and compression modulus of poly(acrylamide) nanocomposite hydrogels

International Nuclear Information System (INIS)

Zaragoza, J; Chang, A; Asuri, P

2017-01-01

Polymer hydrogelshave shown to exhibit improved properties upon the addition of nanoparticles; however, the mechanical underpinnings behind these enhancements have not been fully elucidated. Moreover, fewer studies have focused on developing an understanding of how polymer parameters affect the nanoparticle-mediated enhancements. In this study, we investigated the elastic properties of silica nanoparticle-reinforced poly(acrylamide) hydrogels synthesized using crosslinkers of various lengths. Crosslinker length positively affected the mechanical properties of hydrogels that were synthesized with or without nanoparticles. However the degree of nanoparticle enhancement was negatively correlated to crosslinker length. Our findings enable the understanding of the respective roles of nanoparticle and polymer properties on nanoparticle-mediated enhancement of hydrogels and thereby the development of next-generation nanocomposite materials. (paper)

Effects of chain length, chlorination degree, and structure on the octanol-water partition coefficients of polychlorinated n-alkanes.

Science.gov (United States)

Hilger, Bettina; Fromme, Hermann; Völkel, Wolfgang; Coelhan, Mehmet

2011-04-01

Log octanol-water partition coefficients (log Kow) of 40 synthesized polychlorinated n-alkanes (PCAs) with different chlorination degrees were determined using reversed-phase high performance liquid chromatography (RP-HPLC). In addition, log Kow values of a technical mixture namely Cereclor 63L as well as 15 individual in house synthesized C10, C11, and C12 chloroalkanes with known chlorine positions were estimated. Based on these results, the effects of chain length, chlorination degree, and structure were explored. The estimated log Kow values ranged from 4.10 (polychlorinated n-decanes with 50.2% chlorine content) to 11.34 (polychlorinated n-octacosanes with 54.8% chlorine content) for PCAs and from 3.82 (1,2,5,6,9,10-hexachlorodecane) to 7.75 (1,1,1,3,9,11,11,11-octachlorododecane) for the individual chloroalkanes studied. The results showed that log Kow value was influenced linearly at a given chlorine content by chain length, while a polynominal effect was observed in dependence on the chlorination degree of an alkane chain. Chlorine substitution pattern influenced markedly the log Kow value of chloroalkanes.

Structural analysis of poly-SUMO chain recognition by the RNF4-SIMs domain.

Science.gov (United States)

Kung, Camy C-H; Naik, Mandar T; Wang, Szu-Huan; Shih, Hsiu-Ming; Chang, Che-Chang; Lin, Li-Ying; Chen, Chia-Lin; Ma, Che; Chang, Chi-Fon; Huang, Tai-Huang

2014-08-15

The E3 ubiquitin ligase RNF4 (RING finger protein 4) contains four tandem SIM [SUMO (small ubiquitin-like modifier)-interaction motif] repeats for selective interaction with poly-SUMO-modified proteins, which it targets for degradation. We employed a multi-faceted approach to characterize the structure of the RNF4-SIMs domain and the tetra-SUMO2 chain to elucidate the interaction between them. In solution, the SIM domain was intrinsically disordered and the linkers of the tetra-SUMO2 were highly flexible. Individual SIMs of the RNF4-SIMs domains bind to SUMO2 in the groove between the β2-strand and the α1-helix parallel to the β2-strand. SIM2 and SIM3 bound to SUMO with a high affinity and together constituted the recognition module necessary for SUMO binding. SIM4 alone bound to SUMO with low affinity; however, its contribution to tetra-SUMO2 binding avidity is comparable with that of SIM3 when in the RNF4-SIMs domain. The SAXS data of the tetra-SUMO2-RNF4-SIMs domain complex indicate that it exists as an ordered structure. The HADDOCK model showed that the tandem RNF4-SIMs domain bound antiparallel to the tetra-SUMO2 chain orientation and wrapped around the SUMO protamers in a superhelical turn without imposing steric hindrance on either molecule.

Chain length distribution and kinetic characteristics of an enzymatically produced polymer

NARCIS (Netherlands)

Mulders, K.J.M.; Beeftink, H.H.

2013-01-01

Non-processive enzymatic polymerization leads to a distribution of polymer chain lengths. A polymerization model was developed to investigate the relation between the extent of this distribution on one hand, and the polymerization start conditions and reaction kinetics on the other hand. The model

Topological characterization of nanocrystalline cellulose reinforced Poly (lactic acid) and Poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) bionanocomposites

Science.gov (United States)

Bhat, A. H.; Dasan, Y. K.; Khan, Ihsan Ullah; Ahmad, Faiz; Ayoub, Muhammad

2016-11-01

This study was conducted to evaluate the morphological and barrier properties of nanocrystalline cellulose reinforced Poly (lactic acid) and Poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) bionanocomposites. Nanocrystalline cellulose was isolated from waste oil palm empty fruit bunch fiber using Sulphuric acid hydrolysis. Chemical modifications of nanocrystalline cellulose was performed to allow good compatibilization between fiber and the polymer matrices and also to improve dispersion of fillers. Bionanocomposite materials were produced from these nanocrystalline cellulose reinforced Poly (lactic acid) and Poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) using solvent casting and evaporation techniques. The properties of extracted nanocrystalline cellulose were examined using FT-IR spectroscopy, X-ray diffractometer, TEM and AFM. Besides that, the properties of bionanocomposites were examined through FESEM and oxygen permeability properties analysis. Better barrier and morphological properties were obtained for nanocrystalline cellulose reinforced bionanocomposites than for neat polymer blend.

Poly-(R)-3-hydroxybutyrates (PHB) are Atherogenic Components of Lipoprotein Lp(a).

Science.gov (United States)

Reusch, Rosetta N

2015-12-01

The hypothesis is that poly-(R)-3-hydroxybutyrates (PHB), linear polymers of the ketone body, R-3-hydroxybutyrate (R-3HB), are atherogenic components of lipoprotein Lp(a). PHB are universal constituents of biological cells and are thus components of all foods. Medium chain-length PHB (PHB (PHB are highly insoluble in water, but soluble in lipids in which they exhibit a high intrinsic viscosity. They have a higher density than other cellular lipids and they are very adhesive, i.e. they engage in multiple noncovalent interactions with other molecules and salts via hydrogen, hydrophobic and coordinate bonds, thus producing insoluble deposits. Following digestive processes, PHB enter the circulation in chylomicrons and very low density lipoproteins (VLDL). The majority of the PHB (>70%) are absorbed by albumin, which transports them to the liver for disposal. When the amount of PHB in the diet exceed the capacity of albumin to safely remove them from the circulation, the excess PHB remain in the lipid core of LDL particles that become constituents of lipoprotein Lp(a), and contribute to the formation of arterial deposits. In summary, the presence of PHB – water-insoluble, dense, viscous, adhesive polymers – in the lipid cores of the LDL moieties of Lp(a) particles supports the hypothesis that PHB are atherogenic components of Lp(a).

Resonance chains in open systems, generalized zeta functions and clustering of the length spectrum

International Nuclear Information System (INIS)

Barkhofen, S; Faure, F; Weich, T

2014-01-01

In many non-integrable open systems in physics and mathematics, resonances have been found to be surprisingly ordered along curved lines in the complex plane. In this article we provide a unifying approach to these resonance chains by generalizing dynamical zeta functions. By means of a detailed numerical study we show that these generalized zeta functions explain the mechanism that creates the chains of quantum resonance and classical Ruelle resonances for three-disk systems as well as geometric resonances on Schottky surfaces. We also present a direct system-intrinsic definition of the continuous lines on which the resonances are strung together as a projection of an analytic variety. Additionally, this approach shows that the existence of resonance chains is directly related to a clustering of the classical length spectrum on multiples of a base length. Finally, this link is used to construct new examples where several different structures of resonance chains coexist. (paper)

Conformational studies of self-organized regioregular poly(3-dodecylthiophene)s using non-contact atomic force microscopy in ultra high vacuum condition

International Nuclear Information System (INIS)

Tanaka, Shukichi; Grevin, Benjamin; Rannou, Patrice; Suzuki, Hitoshi; Mashiko, Shinro

2006-01-01

Conformations of one of the variations of π-conjugated poly-alkylthiophene, poly(3-dodecylthiophene)s (P3DDT)s on the surface in ultra high vacuum (UHV) were investigated by non-contact atomic force microscopy (NC-AFM) operated by frequency-modulation mode (FM-mode). From individual molecules to several multi-layered ones, polymer chains on the surface were clearly resolved on conducting highly oriented pyrolytic graphite (HOPG) substrates and insulating mica ones, respectively. Solvent evaporation was found to have two stages, which influenced the diffusion, ordering, and adhesion processes of polymer chains on the substrate. To keep the ordered conformations of deposited polymer chains when they are transferred from ambient condition to UHV, these evaporation processes should be carefully considered. The initial conformation of polymers on the substrate was found to depend strongly on the lattice matching conditions and interactions between polymers and substrates. Formations of stripe-like structures of P3DDT polymers were found on the mica substrates, which is promising for device application

Effects of hydrophobic helix length and side chain chemistry on biomimicry in peptoid analogues of SP-C.

Science.gov (United States)

Brown, Nathan J; Wu, Cindy W; Seurynck-Servoss, Shannon L; Barron, Annelise E

2008-02-12

The hydrophobic proteins of lung surfactant (LS), SP-B and SP-C, are critical constituents of an effective surfactant replacement therapy for the treatment of respiratory distress syndrome. Because of concerns and difficulties associated with animal-derived surfactants, recent investigations have focused on the creation of synthetic analogues of the LS proteins. However, creating an accurate mimic of SP-C that retains its biophysical surface activity is extraordinarily challenging given the lipopeptide's extreme hydrophobicity and propensity to misfold and aggregate. One successful approach that overcomes these difficulties is the use of poly-N-substituted glycines, or peptoids, to mimic SP-C. To develop a non-natural, bioactive mimic of SP-C and to investigate the effects of side chain chemistry and length of the helical hydrophobic region, we synthesized, purified, and performed in vitro testing of two classes of peptoid SP-C mimics: those having a rigid alpha-chiral aromatic helix and those having a biomimetic alpha-chiral aliphatic helix. The length of the two classes of mimics was also systematically altered. Circular dichroism spectroscopy gave evidence that all of the peptoid-based mimics studied here emulated SP-C's secondary structure, forming stable helical structures in solution. Langmuir-Wilhelmy surface balance, fluorescence microscopy, and pulsating bubble surfactometry experiments provide evidence that the aromatic-based SP-C peptoid mimics, in conjunction with a synthetic lipid mixture, have superior surface activity and biomimetic film morphology in comparison to the aliphatic-based mimics and that there is an increase in surface activity corresponding to increasing helical length.

Development of allele-specific multiplex PCR to determine the length of poly-T in intron 8 of CFTR

Directory of Open Access Journals (Sweden)

Neng Chen

2014-07-01

Full Text Available Cystic fibrosis transmembrane conductance regulator (CFTR gene mutation analysis has been implemented for Cystic Fibrosis (CF carrier screening, and molecular diagnosis of CF and congenital bilateral absence of the vas deferens (CBAVD. Although poly-T allele analysis in intron 8 of CFTR is required when a patient is positive for R117H, it is not recommended for routine carrier screening. Therefore, commercial kits for CFTR mutation analysis were designed either to mask the poly-T allele results, unless a patient is R117H positive, or to have the poly-T analysis as a standalone reflex test using the same commercial platform. There are other standalone assays developed to detect poly-T alleles, such as heteroduplex analysis, High Resolution Melting (HRM curve analysis, allele-specific PCR (AS-PCR and Sanger sequencing. In this report, we developed a simple and easy-to-implement multiplex AS-PCR assay using unlabeled standard length primers, which can be used as a reflex or standalone test for CFTR poly-T track analysis. Out of 115 human gDNA samples tested, results from our new AS-PCR matched to the previous known poly-T results or results from Sanger sequencing.

Controlled synthesis of novel 3D dendritic Bi2S3 /cross-linked poly(vinyl alcohol) nanocomposites

International Nuclear Information System (INIS)

Wu, W-T; Shi Lei; Pang Wenmin; Wang Yusong; Zhu Qingren; Xu Guoyong

2006-01-01

Novel spherical three-dimensional (3D) dendritic Bi 2 S 3 /cross-linked poly(vinyl alcohol) (PVA) nanocomposites were successfully synthesized in aqueous solution of amphiphilic polyvinylacetone (PVKA) (ketalization degree D H = 0.549), via one-step in situ decomposition of the complex [Bi(Tu) x ] 3+ under γ-ray irradiation, utilizing the controllable hydrolysis property of PVKA in acidic solution. Herein, PVA chains are obtained from the hydrolysed PVKA. These uniform 3D spherical nanocomposites have a structure similar to that found in the natural lotus leaf, where every microscale papilla on the leaf surface is covered by nanoscale papillae

Synthesis, Characterization and Biocompatibility of Biodegradable Elastomeric Poly(ether-ester urethane)s Based on Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) and Poly(ethylene glycol) via Melting Polymerization

DEFF Research Database (Denmark)

Li, Zibiao; Yang, Xiaodi; Wu, Linping

2009-01-01

Poly(ether-ester urethane)s (PUs) multiblock co-polymers were synthesized from telechelic hydroxylated poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) and poly(ethylene glycol) (PEG) via a melting polymerization (MP) process using 1,6-hexamethylene diisocyanate (HDI) as a non-toxic couplin...

Knotting dynamics of DNA chains of different length confined in nanochannels

International Nuclear Information System (INIS)

Suma, Antonio; Micheletti, Cristian; Orlandini, Enzo

2015-01-01

Langevin dynamics simulations are used to characterize the typical mechanisms governing the spontaneous tying, untying and the dynamical evolution of knots in coarse-grained models of DNA chains confined in nanochannels. In particular we focus on how these mechanisms depend on the chain contour length, L c , at a fixed channel width D = 56 nm corresponding to the onset of the Odijk scaling regime where chain backfoldings and hence knots are disfavoured but not suppressed altogether. We find that the lifetime of knots grows significantly with L c , while that of unknots varies to a lesser extent. The underlying kinetic mechanisms are clarified by analysing the evolution of the knot position along the chain. At the considered confinement, in fact, knots are typically tied by local backfoldings of the chain termini where they are eventually untied after a stochastic motion along the chain. Consequently, the lifetime of unknots is mostly controlled by backfoldings events at the chain ends, which is largely independent of L c . The lifetime of knots, instead, increases significantly with L c because knots can, on average, travel farther along the chain before being untied. The observed interplay of knots and unknots lifetimes underpins the growth of the equilibrium knotting probability of longer and longer chains at fixed channel confinement. (paper)

Fabrication and tribological properties of self-assembled monolayer of n-alkyltrimethoxysilane on silicon: Effect of SAM alkyl chain length

Science.gov (United States)

Huo, Lixia; Du, Pengcheng; Zhou, Hui; Zhang, Kaifeng; Liu, Peng

2017-02-01

It is well known that the self-assembled organic molecules on a solid surface exhibit the friction-reducing performance. However, the effect of the molecular size of the self-assembled organic molecules has not been established. In the present work, self-assembled monolayers (SAMs) of n-alkyltrimethoxysilanes with different alkyl chain lengths (C6, C12, or C18) were fabricated on silicon substrate. The water contact angles of the SAMs increased from 26.8° of the hydroxylated silicon substrate to near 60° after self-assembly. The atomic force microscopy (AFM) analysis results showed that the mean roughness (Ra) of the SAMs decreased with increasing the alkyl chain length. The tribological properties of the SAMs sliding against Al2O3 ball were evaluated on an UMT-2 tribometer, and the worn surfaces of the samples were analyzed by means of Nano Scratch Tester and surface profilometry. It was found that lowest friction coefficient and smallest width of wear were achieved with the SAMs of C12 alkyl chain (C12-SAM). The superior friction reduction and wear resistance of the SAMs in comparison with the bare silicon substrate are attributed to good adhesion of the self-assembled films to the substrate, especially the C12-SAM with desirable alkyl chain length.

Expected value of finite fission chain lengths of pulse reactors

International Nuclear Information System (INIS)

Liu Jianjun; Zhou Zhigao; Zhang Ben'ai

2007-01-01

The average neutron population necessary for sponsoring a persistent fission chain in a multiplying system, is discussed. In the point reactor model, the probability function θ(n, t 0 , t) of a source neutron at time t 0 leading to n neutrons at time t is dealt with. The non-linear partial differential equation for the probability generating function G(z; t 0 , t) is derived. By solving the equation, we have obtained an approximate analytic solution for a slightly prompt supercritical system. For the pulse reactor Godiva-II, the mean value of finite fission chain lengths is estimated in this work and shows that the estimated value is reasonable for the experimental analysis. (authors)

Geometric distribution of CuO chains in YBa2Cu3O6+x

International Nuclear Information System (INIS)

Matic, V.M.; Lazarov, N.Dj.

2006-01-01

Statistics of CuO chains in basal planes of YBa 2 Cu 3 O 6+x high-T c superconductor has been studied in terms of two dimensional asymmetric next-to-nearest-neighbor Ising (ASYNNNI) model, with accentuation on distribution of CuO chains per different chain lengths. It has been shown that the fraction p(l) of CuO chains containing l oxygen ions (i.e., having the length equal to l), satisfies so-called ''law of geometric distribution''p(l)=ω(1-ω) l-1 , where the quantity ω is equal to the inverse of average chain length l av in the system, for given values of oxygen content x and temperature T. In the case of ortho-II (OII) structural phase, the geometric chain probability distribution is shown to hold separately for each of two different sublattices of oxygen sites, commonly known as α 1 and α 2 , with respectively defined l av α 1 (x,T) and l av α 2 (x,T). The theoretically derived result of the chain probability distribution p(l) is shown to be in a remarkable agreement with the results obtained out of extensive Monte Carlo calculations that were made within region of stability of orthorhombic structural phases in (x,T) space. The relevance of chain length distribution for accurate count of the number of transferred electronic holes to superconducting CuO 2 layers has been pointed out and expression for hole concentration has been derived. The concept of critical chain length for charge transfer mechanism was briefly discussed

Micellar dipolar rearrangement is sensitive to hydrophobic chain length: Implication for structural switchover of piroxicam.

Science.gov (United States)

Sethy, Dasaratha; Chakraborty, Hirak

2016-10-01

The interfacial properties of the membrane are exceptionally vital in drug-membrane interaction. They not only select out a particular prototropic form of the drug molecule for incorporation, but are also potent enough to induce structural switchover of these drugs in several cases. In this work, we quantitatively monitored the change in dipolar rearrangement of the micellar interface (as a simplified membrane mimic) by measuring the dielectric constant and dipole potential with the micellization of SDS at pH 3.6. The dielectric constant and dipole potential were measured utilizing the fluorescence of polarity sensitive probe, pyrene and potential-sensitive probe, di-8-ANEPPS, respectively. Our study demonstrates that the change in dipolar rearrangement directly influences the switchover equilibrium between the anionic and neutral from of piroxicam. We have further extended our work to evaluate the effect of hydrophobic chain length of the surfactants on the dipolar rearrangement and its effect on the structural switchover of piroxicam. It is interesting that the extent of switchover of piroxicam is directly correlated with the dipolar rearrangement induced bythe varying hydrophobic chain length of the surfactants. To the best of our knowledge, our results constitute the first report to show the dependence of dipole potential on the hydrophobic chain length of the surfactant and demonstrate that the dipolar rearrangement directly tunes the extent of structural switchover of piroxicam, which was so far only intuitive. We consider that this new finding would have promising implication in drug distribution and drug efficacy. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Spectral sensitization of TiO2 by new hemicyanine dyes in dye solar cell yielding enhanced photovoltage: Probing chain length effect on performance

International Nuclear Information System (INIS)

Fadadu, Kishan B.; Soni, Saurabh S.

2013-01-01

Graphical abstract: New hemicyanine dyes based on indolenine moiety were utilized as light harvesting materials in dye sensitized solar cell. Chain lengths of the molecules were varied in order to study its effect of chain length on the performance of DSSC. Electron transfer kinetic of the solar cell was studied and it was found that the chain length changes the electron transfer kinetic. We have achieved remarkable photovoltage and overall performance of DSSC. Highlights: ► New hemicyanine dyes based on indolenine moiety were utilized as light harvesting materials in dye sensitized solar cell. ► Chain lengths of the molecules were varied in order to study its effect of chain length on the performance of DSSC. ► Electron transfer kinetic of the solar cell was studied and it was found that the chain length changes the electron transfer kinetic. -- Abstract: New hemicyanine dyes having indole nucleus with different alkyl chain length were synthesized and characterized using 1 H NMR and mass spectroscopy. These dyes were used to sensitize the TiO 2 film in dye sensitized solar cell. Nanocrystalline dye solar cells were fabricated and characterized using various electrochemical techniques. It has been found that the alkyl chain length present in the dye molecules greatly affects the overall performance of dye solar cell. Molecules having longer alkyl chain are having better sensitizers which enhance V oc to significant extent. Chain length dependent performance was further investigated using Tafel polarization and impedance method. Hemicyanine dye having hexyl chain has outperformed by attaining 2.9% solar to electricity conversion efficiency

A model for the chain-to-plane charge transfer in YBa2Cu3O6+x

International Nuclear Information System (INIS)

Matic, V. M.; Lazarov, N. Dj.; Milic, M.

2012-01-01

A model for the chain-to-plane charge transfer is proposed to account for the two plateaus, at 60 K and at 90 K, of the T c (x) characteristics of the YBa 2 Cu 3 O 6+x high-T c superconductor. It is assumed that the number of holes transferred from a CuO chain of length l to two nearby CuO 2 sheets is proportional to l (that is, to the number of oxygen atoms in the chain), if the chain length is greater than, or equal to, a certain critical chain length, l cr , that is required to trigger the charge transfer process. No holes are assumed to have been transferred from chains of length l cr . The calculated T c (x) dependence is found to be in excellent agreement with the experimentally reported T c (x). The critical chain length parameter is estimated to be equal to l cr = 11 (eleven oxygen atoms in a chain), which is a greater value than that obtained in the previously proposed model for the chain-to-plane charge transfer (l cr = 4). The results obtained out of the proposed model are briefly discussed

Dynamic studies of poly(di-n-alkyl itaconate)s

CERN Document Server

Arrighi, V; Gagliardi, S; McEwen, I J; Telling, M T F

2002-01-01

We report a preliminary dynamic study of poly(di-n-alkyl itaconate)s with varying side chain length n. QENS measurements were carried out on two backscattering spectrometers, IRIS at ISIS and IN10 at the ILL in the temperature range of 4 to 350 K. We show that molecular motion can be detected well below the polymer glass transition for all samples. It is possible to distinguish different dynamic processes. The temperature range over which these are observed is dependent on the length of the side chain, n. The intermediate scattering function, I(Q,t), was determined from the IRIS and found to obey time-temperature superposition. We show that the I(Q,t) data at different temperatures can be overlapped using the same time-scale shift factors, indicating that the relaxation process is common to all the polymers investigated. (orig.)

Alkyl chain interaction at the surface of room temperature ionic liquids: systematic variation of alkyl chain length (R = C(1)-C(4), C(8)) in both cation and anion of [RMIM][R-OSO(3)] by sum frequency generation and surface tension.

Science.gov (United States)

Santos, Cherry S; Baldelli, Steven

2009-01-29

The gas-liquid interface of halide-free 1,3-dialkylimidazolium alkyl sulfates [RMIM][R-OSO(3)] with R chain length from C(1)-C(4) and C(8) has been studied systematically using the surface-specific sum frequency generation (SFG) vibrational spectroscopy and surface tension measurements. From the SFG spectra, vibrational modes from the methyl group of both cation and anion are observed for all ionic liquid samples considered in the present study. These results suggest the presence of both ions at the gas-liquid interface, which is further supported by surface tension measurements. Surface tension data show a decreasing trend as the alkyl chain in the imidazolium cation is varied from methyl to butyl chain, with a specific anion. A similar trend is observed when the alkyl chain of the anion is modified and the cation is fixed.

The effect of carbon chain length of starting materials on the formation of carbon dots and their optical properties

Science.gov (United States)

Pan, Xiaohua; Zhang, Yan; Sun, Xiaobo; Pan, Wei; Yu, Guifeng; Si, Shuxin; Wang, Jinping

2018-04-01

Carbon dots (CDs) have attracted increasing attention due to their high performances and potential applications in wide range of areas. However, their emission mechanism is not clear so far. In order to reveal more factors contributing to the emission of CDs, the effect of carbon chain length of starting materials on the formation of CDs and their optical properties was experimentally investigated in this work. In order to focus on the effect of carbon chain length, the starting materials with C, O, N in fully identical forms and only carbon chain lengths being different were selected for synthesizing CDs, including citric acid (CA) and adipic acid (AA) as carbon sources, and diamines with different carbon chain lengths (H2N(CH2)nNH2, n = 2, 4, 6) as nitrogen sources, as well as ethylenediamine (EDA) as nitrogen source and diacids with different carbon chain lengths (HOOC(CH2)nCOOH, n = 0, 2, 4, 6) as carbon sources. Therefore, the effect of carbon chain length of starting materials on the formation and optical properties of CDs can be systematically investigated by characterizing and comparing the structures and optical properties of as-prepared nine types of CDs. Moreover, the density of –NH2 on the surface of the CDs was quantitatively detected by a spectrophotometry so as to elucidate the relationship between the –NH2 related surface state and the optical properties.

Hydrophilization of poly(caprolactone copolymers through introduction of oligo(ethylene glycol moieties.

Directory of Open Access Journals (Sweden)

Jonathan J Wurth

Full Text Available In this study, a new family of poly(ε-caprolactone (PCL copolymers that bear oligo(ethylene glycol (OEG moieties is described. The synthesis of three different oligo(ethylene glycol functionalized epoxide monomers derived from 2-methyl-4-pentenoic acid, and their copolymerization with ε-caprolactone (CL to poly(CL-co-OEG-MPO copolymers is presented. The statistical copolymerization initiated with SnOct2/BnOH yielded the copolymers with varying OEG content and composition. The linear relationship between feed ratio and incorporation of the OEG co-monomer enables control over backbone functional group density. The introduction of OEG moieties influenced both the thermal and the hydrophilic characteristics of the copolymers. Both increasing OEG length and backbone content resulted in a decrease in static water contact angle. The introduction of OEG side chains in the PCL copolymers had no adverse influence on MC-3TE3-E1 cell interaction. However, changes to cell form factor (Φ were observed. While unmodified PCL promoted elongated (anisotropic morphologies (Φ = 0.094, PCL copolymer with tri-ethylene glycol side chains at or above seven percent backbone incorporation induced more isotropic cell morphologies (Φ = 0.184 similar to those observed on glass controls (Φ = 0.151.

The effect of the alkyl chain length on physicochemical features of (ionic liquids + γ-butyrolactone) binary mixtures

International Nuclear Information System (INIS)

Papović, Snežana; Bešter-Rogač, Marija; Vraneš, Milan; Gadžurić, Slobodan

2016-01-01

Highlights: • Influence of alkyl substituent length on IL properties was studied. • Nature of interactions between studied [C_nC_1im][NTf_2] and GBL were discussed. • Angell strength parameter indicates [C_nC_1im][NTf_2] are fragile liquids. • ILs properties regularly change with increase of the alkyl chain length. • Absence of GBL self-association upon addition of IL is observed. - Abstract: Densities and viscosities were determined and analysed for γ-butyrolactone (GBL) binary mixtures with 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquids (where alkyl = ethyl, hexyl, octyl) as a function of temperature at atmospheric pressure (p = 0.1 MPa) and over the whole composition range. Excess molar volumes have been calculated from the experimental densities and were fitted using Redlich–Kister’s polynomial equation. Other volumetric parameters have been also calculated in order to obtain information about interactions between GBL and imidazolium based ionic liquids with different alkyl chain length. From the viscosity measurements, the Angell strength parameter was calculated for pure ionic liquids indicating that all investigated electrolytes are “fragile” liquids.

The snakelike chain character of unstructured RNA.

Science.gov (United States)

Jacobson, David R; McIntosh, Dustin B; Saleh, Omar A

2013-12-03

In the absence of base-pairing and tertiary structure, ribonucleic acid (RNA) assumes a random-walk conformation, modulated by the electrostatic self-repulsion of the charged, flexible backbone. This behavior is often modeled as a Kratky-Porod "wormlike chain" (WLC) with a Barrat-Joanny scale-dependent persistence length. In this study we report measurements of the end-to-end extension of poly(U) RNA under 0.1 to 10 pN applied force and observe two distinct elastic-response regimes: a low-force, power-law regime characteristic of a chain of swollen blobs on long length scales and a high-force, salt-valence-dependent regime consistent with ion-stabilized crumpling on short length scales. This short-scale structure is additionally supported by force- and salt-dependent quantification of the RNA ion atmosphere composition, which shows that ions are liberated under stretching; the number of ions liberated increases with increasing bulk salt concentration. Both this result and the observation of two elastic-response regimes directly contradict the WLC model, which predicts a single elastic regime across all forces and, when accounting for scale-dependent persistence length, the opposite trend in ion release with salt concentration. We conclude that RNA is better described as a "snakelike chain," characterized by smooth bending on long length scales and ion-stabilized crumpling on short length scales. In monovalent salt, these two regimes are separated by a characteristic length that scales with the Debye screening length, highlighting the determining importance of electrostatics in RNA conformation. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Characterization of Binary Organogels Based on Some Azobenzene Compounds and Alkyloxybenzoic Acids with Different Chain Lengths

Directory of Open Access Journals (Sweden)

Yongmei Hu

2014-01-01

Full Text Available In this work the gelation behaviors of binary organogels composed of azobenzene amino derivatives and alkyloxybenzoic acids with different lengths of alkyl chains in various organic solvents were investigated and characterized. The corresponding gelation behaviors in 20 solvents were characterized and shown as new binary organic systems. It showed that the lengths of substituent alkyl chains in compounds have played an important role in the gelation formation of gelator mixtures in present tested organic solvents. Longer methylene chains in molecular skeletons in these gelators seem more suitable for the gelation of present solvents. Morphological characterization showed that these gelator molecules have the tendency to self-assemble into various aggregates from lamella, wrinkle, and belt to dot with change of solvents and gelator mixtures. Spectral characterization demonstrated different H-bond formation and hydrophobic force existing in gels, depending on different substituent chains in molecular skeletons. Meanwhile, these organogels can self-assemble to form monomolecular or multilayer nanostructures owing to the different lengths of due to alkyl substituent chains. Possible assembly modes for present xerogels were proposed. The present investigation is perspective to provide new clues for the design of new nanomaterials and functional textile materials with special microstructures.

Charge transfer and bond lengths in YBa2Cu3-xMxO6+y

International Nuclear Information System (INIS)

Jorgensen, J.D.; Rhyne, J.J.; Neumann, D.A.; Miceli, P.F.; Tarascon, J.M.; Greene, L.H.; Barboux, P.

1989-01-01

We discuss the effects of doping on the Cu chain sites in YBa 2 Cu 3-x M x O 6+y . The relationship between bond lengths obtained from neutron scattering and charge transfer is evaluated in terms of bond valence. In particular, it is concluded that removing an oxygen from the chains transfers one electron to the planes. 24 refs., 3 figs

Direct observation of backbone planarization via side-chain alignment in single bulky-substituted polythiophenes

Science.gov (United States)

Raithel, Dominic; Simine, Lena; Pickel, Sebastian; Schötz, Konstantin; Panzer, Fabian; Baderschneider, Sebastian; Schiefer, Daniel; Lohwasser, Ruth; Köhler, Jürgen; Thelakkat, Mukundan; Sommer, Michael; Köhler, Anna; Rossky, Peter J.; Hildner, Richard

2018-03-01

The backbone conformation of conjugated polymers affects, to a large extent, their optical and electronic properties. The usually flexible substituents provide solubility and influence the packing behavior of conjugated polymers in films or in bad solvents. However, the role of the side chains in determining and potentially controlling the backbone conformation, and thus the optical and electronic properties on the single polymer level, is currently under debate. Here, we investigate directly the impact of the side chains by studying the bulky-substituted poly(3-(2,5-dioctylphenyl)thiophene) (PDOPT) and the common poly(3-hexylthiophene) (P3HT), both with a defined molecular weight and high regioregularity, using low-temperature single-chain photoluminescence (PL) spectroscopy and quantum-classical simulations. Surprisingly, the optical transition energy of PDOPT is significantly (˜2,000 cm‑1 or 0.25 eV) red-shifted relative to P3HT despite a higher static and dynamic disorder in the former. We ascribe this red shift to a side-chain induced backbone planarization in PDOPT, supported by temperature-dependent ensemble PL spectroscopy. Our atomistic simulations reveal that the bulkier 2,5-dioctylphenyl side chains of PDOPT adopt a clear secondary helical structural motif and thus protect conjugation, i.e., enforce backbone planarity, whereas, for P3HT, this is not the case. These different degrees of planarity in both thiophenes do not result in different conjugation lengths, which we found to be similar. It is rather the stronger electronic coupling between the repeating units in the more planar PDOPT which gives rise to the observed spectral red shift as well as to a reduced calculated electron‑hole polarization.

Poly(aniline-co-m-aminobenzoic acid) deposited on poly(vinyl ...

Indian Academy of Sciences (India)

Abstract. In this work, we have deposited poly(aniline-co-m-aminobenzoic acid) on poly(vinyl alcohol) (PVA) by in situ ... along the polyaniline (PANI) chain results in self dop- ing of PANI and ..... The value of electrical conductivity is found to be ...

Lipid polymorphism of mixtures of dioleoylphosphatidylethanolamine and saturated and monounsaturated phosphatidylcholines of various chain lengths

International Nuclear Information System (INIS)

Tate, M.W.; Gruner, S.M.

1987-01-01

The L/sub α/-H/sub II/ phase transition behavior of many lipid-water liquid crystals is dominated by the competition between the tendency to curl the lipid layers to an intrinsic radius of curvature and opposing hydrocarbon packing constraints. In particular, packing constraints can increase the free energy of the inverted hexagonal (H/sub II/) phase as compared to that of the lamellar (L/sub α/) phase. This is especially true where the lipid molecule is not long enough to reach into the corners of the lattice in large hexagonal structures necessitated by a large radius of curvature.In this paper it is shown that the addition of a minor fraction long-chain lipid to a system of otherwise uniform chain composition can also relax packing constraints, thereby lowering the lamellar to hexagonal transition temperature. For the specific systems used, dioleoylphosphatidylethanolamine (di-18:1/sub c/-PE) with minor fractions of 1,2-diacyl-sn-glycero-3-phosphocholines [di-n:1/sub c/-PC (n = 14, 18, 22, and 24)], the observed H/sub II/lattices systematically increased in size with increasing chain length suggesting that the chain length also may affect the intrinsic curvature of the mixture. These experiments demonstrate that the lipid shape concept, which is a qualitative expression of the concept quantitatively described by the intrinsic radius of curvature, is insufficient to understand the L/sub α/-H/sub II/ transition. It is necessary to, at least, consider the competition between curvature and packing

The effect of the chain length distribution of free fatty acids on the mixing properties of stratum corneum model membranes.

Science.gov (United States)

Oguri, Masashi; Gooris, Gert S; Bito, Kotatsu; Bouwstra, Joke A

2014-07-01

The stratum corneum (SC) plays a fundamental role in the barrier function of the skin. The SC consists of corneocytes embedded in a lipid matrix. The main lipid classes in the lipid matrix are ceramides (CERs), cholesterol (CHOL) and free fatty acids (FFAs). The aim of this study was to examine the effect of the chain length of FFAs on the thermotropic phase behavior and mixing properties of SC lipids. Fourier transform infrared spectroscopy and Raman imaging spectroscopy were used to study the mixing properties using either protonated or deuterated FFAs. We selected SC model lipid mixtures containing only a single CER, CHOL and either a single FFA or a mixture of FFAs mimicking the FFA SC composition. The single CER consists of a sphingoid base with 18 carbon atoms and an acyl chain with a chain length of 24 carbon atoms. When using lignoceric acid (24 carbon atoms) or a mixture of FFAs, the CER and FFAs participated in mixed crystals, but hydration of the mixtures induced a slight phase separation between CER and FFA. The mixed crystalline structures did not phase separate during storage even up to a time period of 3months. When using palmitic acid (16 carbon atoms), a slight phase separation was observed between FFA and CER. This phase separation was clearly enhanced during hydration and storage. In conclusion, the thermotropic phase behavior and the mixing properties of the SC lipid mixtures were shown to strongly depend on the chain length and chain length distribution of FFAs, while hydration enhanced the phase separation. Copyright © 2014 Elsevier B.V. All rights reserved.

New Linear and Star-Shaped Thermogelling Poly([R]-3-hydroxybutyrate) Copolymers.

Science.gov (United States)

Barouti, Ghislaine; Liow, Sing Shy; Dou, Qingqing; Ye, Hongye; Orione, Clément; Guillaume, Sophie M; Loh, Xian Jun

2016-07-18

The synthesis of multi-arm poly([R]-3-hydroxybutyrate) (PHB)-based triblock copolymers (poly([R]-3-hydroxybutyrate)-b-poly(N-isopropylacrylamide)-b-[[poly(methyl ether methacrylate)-g-poly(ethylene glycol)]-co-[poly(methacrylate)-g-poly(propylene glycol)

Photocatalytic fixation of carbon dioxide with poly(3-alkylthiophene)

Energy Technology Data Exchange (ETDEWEB)

Kuwabara, T; Kawai, T; Yoshino, K [Osaka University, Osaka (Japan). Faculty of Engineering

1992-04-05

The photoirradiation effect of poly(3-hexylthiophene) (P3HT) were studied under CO{sub 2} atmosphere. P3HT film became soluble by photoirradiation in adequate solvents such as ethanol, CHC1{sub 3}, hexane and CH{sub 3}CN under CO{sub 2} atmosphere as well as O{sub 2} atmosphere. This photosolubilization reaction required higher photon energy than the band gap energy of P3HT, and the photoluminescence intensity of P3HT in solvent decreased under CO{sub 2} atmosphere. The solubilized P3HT had larger band gap energy and shorter effective conjugation length than those of original P3HT, and offered an IR absorption peak indicating formation of calbonyl group. These results suggested that electrons transferred from photoexcited P3HT to CO{sub 2} molecules in the first stage of photoinduced reaction. Salicylic acid was obtained by photoirradiation of P3HT in ethanol solution containing phenol indicating the photocatalysis of P3HT. 9 refs., 8 figs.

Atomistic simulation of CO 2 solubility in poly(ethylene oxide) oligomers

KAUST Repository

Hong, Bingbing

2013-10-02

We have performed atomistic molecular dynamics simulations coupled with thermodynamic integration to obtain the excess chemical potential and pressure-composition phase diagrams for CO2 in poly(ethylene oxide) oligomers. Poly(ethylene oxide) dimethyl ether, CH3O(CH 2CH2O)nCH3 (PEO for short) is a widely applied physical solvent that forms the major organic constituent of a class of novel nanoparticle-based absorbents. Good predictions were obtained for pressure-composition-density relations for CO2 + PEO oligomers (2 ≤ n ≤ 12), using the Potoff force field for PEO [J. Chem. Phys. 136, 044514 (2012)] together with the TraPPE model for CO2 [AIChE J. 47, 1676 (2001)]. Water effects on Henrys constant of CO2 in PEO have also been investigated. Addition of modest amounts of water in PEO produces a relatively small increase in Henrys constant. Dependence of the calculated Henrys constant on the weight percentage of water falls on a temperature-dependent master curve, irrespective of PEO chain length. © 2013 Taylor & Francis.

Electro-oxidation of chlorophenols on poly(3,4-ethylenedioxythiophene)-poly(styrene sulphonate) composite electrode

International Nuclear Information System (INIS)

Pigani, L.; Musiani, M.; Pirvu, C.; Terzi, F.; Zanardi, C.; Seeber, R.

2007-01-01

The electrochemical behaviour of chlorinated phenols on Pt/poly(3,4-ethylenedioxy)thiophene,LiClO 4 and on Pt/poly(3,4-ethylenedioxy)thiophene,poly(sodium-4-styrenesulphonate) electrodes has been investigated in phosphate buffer solution. Poly(sodium-4-styrenesulphonate) exerts remarkable effect against the electrode fouling induced by oxidation of chlorophenols, allowing us to record the relevant anodic response even after repeated potential cycles. Hypotheses about the role exerted by poly(sodium 4-styrenesulphonate) are made, on the basis of evidences provided by several techniques, such as cyclic voltammetry, electrochemical impedance spectroscopy, electrochemical microgravimetry and atomic force microscopy. Thanks to the fact that different chlorophenols show differences in the voltammetric responses, depending on number and position of the chloro substituents on the aromatic ring, applications of the modified electrode in the analysis of mixtures of chlorinated phenols are possible

Self-Assembly of Alkylammonium Chains on Montmorillonite: Effect of Interlayer Cations, CEC, and Chain Length

Science.gov (United States)

Chen, Hua; Li, Yingjun; Zhou, Yuanlin; Wang, Shanqiang; Zheng, Jian; He, Jiacai

2017-12-01

Recently, polymeric materials have been filled with synthetic or natural inorganic compounds in order to improve their properties. Especially, polymer clay nanocomposites have attracted both academic and industrial attention. Currently, the structure and physical phenomena of organoclays at molecular level are difficultly explained by existing experimental techniques. In this work, molecular dynamics (MD) simulation was executed using the CLAYFF and CHARMM force fields to evaluate the structural properties of organoclay such as basal spacing, interlayer density, energy and the arrangement of alkyl chains in the interlayer spacing. Our results are in good agreement with available experimental or other simulation data. The effects of interlayer cations (Na+, K+, Ca2+), the cation exchange capacity, and the alkyl chain length on the basal spacing and the structural properties are estimated. These simulations are expected to presage the microstructure of organo-montmorillonite and lead relevant engineering applications.

Rotational diffusion of nonpolar and ionic solutes in 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imides: is solute rotation always influenced by the length of the alkyl chain on the imidazolium cation?

Science.gov (United States)

Gangamallaiah, V; Dutt, G B

2012-10-25

In an attempt to find out whether the length of the alkyl chain on the imidazolium cation has a bearing on solute rotation, temperature-dependent fluorescence anisotropies of three structurally similar solutes have been measured in a series of 1-alkyl-3-methylimidazolium (alkyl = methyl, ethyl, propyl, butyl, and hexyl) bis(trifluoromethylsulfonyl)imides. Solute-solvent coupling constants obtained from the experimentally measured reorientation times with the aid of Stokes-Einstein-Debye hydrodynamic theory indicate that there is no influence of the length of the alkyl chain on the rotation of nonpolar, anionic, and cationic solutes 9-phenylanthracene (9-PA), fluorescein (FL), and rhodamine 110 (R110), respectively. It has also been noticed that the rotational diffusion of 9-PA is closer to the predictions of slip hydrodynamics, whereas the rotation of negatively charged FL and positively charged R110 is almost identical and follows stick hydrodynamics in these ionic liquids. Despite having similar shape and size, ionic solutes rotate slower by a factor of 3-4 compared to the nonpolar solute. Interplay of specific and electrostatic interactions between FL and the imidazolium cation of the ionic liquids, and between R110 and the bis(trifluoromethylsulfonyl)imide anion, appear to be responsible for the observed behavior. These results are an indication that the length of the alkyl chain on the imidazolium cation does not alter their physical properties in a manner that has an effect on solute rotation.

Thermosensitive mPEG-b-PA-g-PNIPAM comb block copolymer micelles: effect of hydrophilic chain length and camptothecin release behavior.

Science.gov (United States)

Yang, Xiao-Li; Luo, Yan-Ling; Xu, Feng; Chen, Ya-Shao

2014-02-01

Block copolymer micelles are extensively used as drug controlled release carriers, showing promising application prospects. The comb or brush copolymers are especially of great interest, whose densely-grafted side chains may be important for tuning the physicochemical properties and conformation in selective solvents, even in vitro drug release. The purpose of this work was to synthesize novel block copolymer combs via atom transfer radical polymerization, to evaluate its physicochemical features in solution, to improve drug release behavior and to enhance the bioavailablity, and to decrease cytotoxicity. The physicochemical properties of the copolymer micelles were examined by modulating the composition and the molecular weights of the building blocks. A dialysis method was used to load hydrophobic camptothecin (CPT), and the CPT release and stability were detected by UV-vis spectroscopy and high-performance liquid chromatography, and the cytotoxicity was evaluated by MTT assays. The copolymers could self-assemble into well-defined spherical core-shell micelle aggregates in aqueous solution, and showed thermo-induced micellization behavior, and the critical micelle concentration was 2.96-27.64 mg L(-1). The micelles were narrow-size-distribution, with hydrodynamic diameters about 128-193 nm, depending on the chain length of methoxy polyethylene glycol (mPEG) blocks and poly(N-isopropylacrylamide) (PNIPAM) graft chains or/and compositional ratios of mPEG to PNIPAM. The copolymer micelles could stably and effectively load CPT but avoid toxicity and side-effects, and exhibited thermo-dependent controlled and targeted drug release behavior. The copolymer micelles were safe, stable and effective, and could potentially be employed as CPT controlled release carriers.

Conductivity and long term stability of polypyrrole poly(styrene-co-methacrylic acid) core–shell particles at different polypyrrole loadings

Energy Technology Data Exchange (ETDEWEB)

Carrillo, I., E-mail: isabel.carrillo@upm.es [Dpto. Química Industrial y Polímeros, E.U.I.T. Industrial, Univ. Politécnica de Madrid, 28012 Madrid (Spain); Sanchez de la Blanca, E. [Dpto. Química Física I, Fac. Ciencias Químicas, Univ. Complutense, 28040 Madrid (Spain); Fierro, J.L.G. [Instituto de Catálisis y Petroquímica, CSIC, Cantoblanco, 28049 Madrid (Spain); Raso, M.A.; Acción, F.; Enciso, E.; Redondo, M.I. [Dpto. Química Física I, Fac. Ciencias Químicas, Univ. Complutense, 28040 Madrid (Spain)

2013-07-31

Conductive core–shell particles were obtained by chemical polymerization of pyrrole over monodisperse poly(styrene-co-methacrylic acid) particles. The surface composition has been studied by elemental analysis, Fourier Transform Infrared Spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS), scanning electron microscopy and transmission electron microscopy techniques. XPS, elemental analysis and FTIR results allowed determining doping level and conjugation length of the polypyrrole (PPy) chain deposited on the latex surface. It is shown that the chain conjugation length, and not the doping level, is the principal factor that influences the conductivity. Samples with low PPy loading have short conjugation length and so low conductivity independently of their doping level. The experimental conductivity decay with time has been analysed following the electron hopping model, from this model the characteristic time (τ) of the conductivity degradation process has been determined. - Highlights: • Polypyrrole coated latex were prepared. • Time-dependent conductivity was studied. • Composites conductivity depends on chain conjugation length and not on doping level.

Study of the chain microstructure effects on the resulting thermal properties of poly(L-lactide)/poly(N-isopropylacrylamide) biomedical materials

Energy Technology Data Exchange (ETDEWEB)

Lizundia, E., E-mail: erlantz.liizundia@ehu.es [Macromolecular Chemistry Research Group (LABQUIMAC), Dept. of Physical Chemistry, Faculty of Science and Technology, University of the Basque Country (UPV/EHU) (Spain); Meaurio, E., E-mail: emiliano.meaurio@ehu.es [Department of Mining-Metallurgy and Materials Science and BERC POLYMAT, School of Engineering, University of the Basque Country (UPV/EHU) (Spain); Laza, J.M., E-mail: josemanuel.laza@ehu.es [Macromolecular Chemistry Research Group (LABQUIMAC), Dept. of Physical Chemistry, Faculty of Science and Technology, University of the Basque Country (UPV/EHU) (Spain); Vilas, J.L., E-mail: joseluis.vilas@bcmaterials.net [Basque Center for Materials, Applications and Nanostructures (BCMaterials), Parque Tecnológico de Bizkaia, Ed. 500, Derio 48160 (Spain); León Isidro, L.M., E-mail: luismanuel.leon@ehu.es [Macromolecular Chemistry Research Group (LABQUIMAC), Dept. of Physical Chemistry, Faculty of Science and Technology, University of the Basque Country (UPV/EHU) (Spain); Basque Center for Materials, Applications and Nanostructures (BCMaterials), Parque Tecnológico de Bizkaia, Ed. 500, Derio 48160 (Spain)

2015-05-01

The development of thermally-sensitive poly(N-isopropylacrylamide) (PNIPAAm) and biocompatible/biodegradable poly(L-lactide) (PLLA) blends offers us an efficient strategy in order to obtain materials with improved functional properties to be used in the emerging field of biomedicine. In this sense, thermal properties of PLLA and PNIPAAm have been investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and wide angle X-ray diffraction (WAXD) were conducted to shed more light on the obtained results. For a better understanding of PLLA/PNIPAAm system, both low and high molecular weight PLLA and PNIPAAm have been synthesized by ring opening polymerization and aqueous redox polymerization respectively. Obtained results are interpreted from the viewpoint of chain microstructure of each homopolymer and the ratio between two constituent materials. DSC, SEM and WAXD results show a phase separation over the entire composition range irrespectively of the molecular weight of both homopolymers. Additionally, it was found a nucleating agent behavior of low molecular weight PNIPAAm, while high molecular weight PNIPAAm hinders the crystallization of PLLA. FTIR results suggest that the strong autoassociation present in PNIPAAm plays a key role impairing the miscibility of the whole system. Thermogravimetric analysis reveals that thermodegradation process of PLLA could be continuously delayed with the addition of PNIPAAm due to the increased thermal stability of N-isopropylacrylamide in regard to L-lactide sequences. - Highlights: • Poly(L-lactide)/poly(N-isopropylacrylamide) biomedical materials are synthesized. • Results are interpreted in terms of the building block nature of each constituent. • Phase separation behavior over the entire composition range is achieved. • Strong autoassociation present in PNIPAAm impairs the miscibility of the whole blend

Communication disruption of guava moth (Coscinoptycha improbana) using a pheromone analog based on chain length.

Science.gov (United States)

Suckling, D M; Dymock, J J; Park, K C; Wakelin, R H; Jamieson, L E

2013-09-01

The guava moth, Coscinoptycha improbana, an Australian species that infests fruit crops in commercial and home orchards, was first detected in New Zealand in 1997. A four-component pheromone blend was identified but is not yet commercially available. Using single sensillum recordings from male antennae, we established that the same olfactory receptor neurons responded to two guava moth sex pheromone components, (Z)-11-octadecen-8-one and (Z)-12-nonadecen-9-one, and to a chain length analog, (Z)-13-eicosen-10-one, the sex pheromone of the related peach fruit moth, Carposina sasakii. We then field tested whether this non-specificity of the olfactory neurons might enable disruption of sexual communication by the commercially available analog, using male catch to synthetic lures in traps in single-tree, nine-tree and 2-ha plots. A disruptive pheromone analog, based on chain length, is reported for the first time. Trap catches for guava moth were disrupted by three polyethylene tubing dispensers releasing the analog in single-tree plots (86% disruption of control catches) and in a plots of nine trees (99% disruption). Where peach fruit moth pheromone dispensers were deployed at a density of 1000/ha in two 2-ha areas, pheromone traps for guava moth were completely disrupted for an extended period (up to 470 days in peri-urban gardens in Mangonui and 422 days in macadamia nut orchards in Kerikeri). In contrast, traps in untreated areas over 100 m away caught 302.8 ± 128.1 moths/trap in Mangonui and 327.5 ± 78.5 moths/ trap in Kerikeri. The longer chain length in the pheromone analog has greater longevity than the natural pheromone due to its lower volatility. Chain length analogs may warrant further investigation for mating disruption in Lepidoptera, and screening using single-sensillum recording is recommended.

Influence of the chain length on the biological behaviour of 131I fatty acids

International Nuclear Information System (INIS)

Riche, F.; Mathieu, J.P.; Comet, M.; Vidal, M.; Pernin, C.; Marti-Batlle, D.; Busquet, G.; Bardy, A.

1983-01-01

Saturated and acetylenic fatty acids labeled with 131 I in ω position, differing by their chain length (C8 to C20) and the number odd or even of their carbon atoms are injected in mice. The evolution of the activity in myocardium, blood, liver and kidney is measured until 10 minutes after injection. The myocardial activity increases with chain length from C8 to C16 then decreases for C18 and C20. The odd or even number of carbon atoms does not influence myocardial activity but in the liver, activity is inferior with the odd fatty acids. The presence of a triple bond accelerates the output of activity from the myocardium and these fatty acids are not well suited for the study of myocardial metabolism [fr

Tuning the Mechanical Properties of Polymer Nanocomposites Filled with Grafted Nanoparticles by Varying the Grafted Chain Length and Flexibility

Directory of Open Access Journals (Sweden)

Zixuan Wang

2016-08-01

Full Text Available By employing coarse-grained molecular dynamics simulation, we simulate the spatial organization of the polymer-grafted nanoparticles (NPs in homopolymer matrix and the resulting mechanical performance, by particularly regulating the grafted chain length and flexibility. The morphologies ranging from the agglomerate, cylinder, sheet, and string to full dispersion are observed, by gradually increasing the grafted chain length. The radial distribution function and the total interaction energy between NPs are calculated. Meanwhile, the stress–strain behavior of each morphology and the morphological evolution during the uniaxial tension are simulated. In particular, the sheet structure exhibits the best mechanical reinforcement compared to other morphologies. In addition, the change of the grafted chain flexibility to semi-flexibility leads to the variation of the morphology. We also find that at long grafted chain length, the stress–strain behavior of the system with the semi-flexible grafted chain begins to exceed that of the system with the flexible grafted chain, attributed to the physical inter-locking interaction between the matrix and grafted polymer chains. A similar transition trend is as well found in the presence of the interfacial chemical couplings between grafted and matrix polymer chains. In general, this work is expected to help to design and fabricate high performance polymer nanocomposites filled with grafted NPs with excellent and controllable mechanical properties.

Investigating the nanostructure and thermal properties of chiral poly(amide-imide)/Al2O3 compatibilized with 3-aminopropyltriethoxysilane

International Nuclear Information System (INIS)

Mallakpour, Shadpour; Dinari, Mohammad

2013-01-01

Graphical abstract: - Highlights: • Chiral polymer with different functional groups was prepared in green route. • The surface of Al 2 O 3 -NPs was treated by KH550 as a silane coupling agent. • NCs of poly(amide-imide) and Al 2 O 3 were synthesized by ultrasonic irradiation. • TEM results show good dispersion of Al 2 O 3 -NPs in the poly(amide-imide) matrix. • The thermal and mechanical properties of the hybrid materials were improved. - Abstract: Novel chiral poly(amide-imide) (PAI)/Al 2 O 3 nanocomposites were prepared via incorporating surface modified Al 2 O 3 nanoparticles into polymer matrices for the first time. In the process of preparing the nanocomposites, severe aggregation of Al 2 O 3 nanoparticles could be reduced by surface modification and γ-aminopropyltriethoxysilane. The optically active PAI chains were formed from the polycondensation reaction of N,N′-(pyromellitoyl)-bis-phenylalanine diacid with 2-(3,5-diaminophenyl)-benzimidazole in green condition. The obtained polymer and inorganic metal oxide nanoparticles were used to prepare chiral PAI/Al 2 O 3 nanocomposites through ultrasonic irradiation. The resulting nanoparticle filled composites were also characterized by Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy and thermogravimetric analysis (TGA) techniques. TGA thermographs confirmed that the heat stability of the prepared nanoparticle-reinforced composites was improved. Mechanical properties showed that the film containing 10 wt% of modified Al 2 O 3 had a tensile strength of the order of 83.6 MPa, relative to the 64.3 MPa of the pure PAI

Effect of hydrocarbon chain length of aliphatic diluents on hydrodynamic properties of irradiated solutions of extractant

International Nuclear Information System (INIS)

Gumenyuk, V.E.; Pribush, A.G.; Egorov, G.F.

1990-01-01

To optimize the composition of n-paraffin mixtures with different molecular weight, used as a diluent (D) of extractant during extraction reprocessing of spent fuel, interrelation between D hydrocarbon chain length and change in hydrodynamic properties of extraction mixture on D basis depending on the dose has been considered. It is shown that the value of threshold dose loading (D crit ), at which a sharp change in hydrodynamic properties of tri-n-butyl phosphate solutions in D is observed, decreases with hydrocarbon chain length growth. Empiric ratio relating D crit value and the number of carbon atoms of D is obtained

Single-molecule study on polymer diffusion in a melt state: Effect of chain topology

KAUST Repository

Habuchi, Satoshi

2013-08-06

We report a new methodology for studying diffusion of individual polymer chains in a melt state, with special emphasis on the effect of chain topology. A perylene diimide fluorophore was incorporated into the linear and cyclic poly(THF)s, and real-time diffusion behavior of individual chains in a melt of linear poly(THF) was measured by means of a single-molecule fluorescence imaging technique. The combination of mean squared displacement (MSD) and cumulative distribution function (CDF) analysis demonstrated the broad distribution of diffusion coefficient of both the linear and cyclic polymer chains in the melt state. This indicates the presence of spatiotemporal heterogeneity of the polymer diffusion which occurs at much larger time and length scales than those expected from the current polymer physics theory. We further demonstrated that the cyclic chains showed marginally slower diffusion in comparison with the linear counterparts, to suggest the effective suppression of the translocation through the threading-entanglement with the linear matrix chains. This coincides with the higher activation energy for the diffusion of the cyclic chains than of the linear chains. These results suggest that the single-molecule imaging technique provides a powerful tool to analyze complicated polymer dynamics and contributes to the molecular level understanding of the chain interaction. © 2013 American Chemical Society.

Single-molecule study on polymer diffusion in a melt state: Effect of chain topology

KAUST Repository

Habuchi, Satoshi; Fujiwara, Susumu; Yamamoto, Takuya; Vá cha, Martin; Tezuka, Yasuyuki

2013-01-01

We report a new methodology for studying diffusion of individual polymer chains in a melt state, with special emphasis on the effect of chain topology. A perylene diimide fluorophore was incorporated into the linear and cyclic poly(THF)s, and real-time diffusion behavior of individual chains in a melt of linear poly(THF) was measured by means of a single-molecule fluorescence imaging technique. The combination of mean squared displacement (MSD) and cumulative distribution function (CDF) analysis demonstrated the broad distribution of diffusion coefficient of both the linear and cyclic polymer chains in the melt state. This indicates the presence of spatiotemporal heterogeneity of the polymer diffusion which occurs at much larger time and length scales than those expected from the current polymer physics theory. We further demonstrated that the cyclic chains showed marginally slower diffusion in comparison with the linear counterparts, to suggest the effective suppression of the translocation through the threading-entanglement with the linear matrix chains. This coincides with the higher activation energy for the diffusion of the cyclic chains than of the linear chains. These results suggest that the single-molecule imaging technique provides a powerful tool to analyze complicated polymer dynamics and contributes to the molecular level understanding of the chain interaction. © 2013 American Chemical Society.

Multifunctional chemical additives for hetero chain polymers; Khimikati-dobavki mnogofunkstional'nogo deystviya dlya geterostepnikh polimerov

Energy Technology Data Exchange (ETDEWEB)

Niyazi, F. F.; Kalontarov, I. Ya.; Chayko, Yu. V.; Kasimova, E. I. [V.I. Nikitin Institute of Chemistry, Academy of Sciences of the Republic of Tajikistan, Dushanbe, (Tajikistan)

1994-07-01

Indane and carbazole derivatives, poly conjugated azomethine, bis-benzimidazole were studied as chemical additives. Photo stabilizing effect was studied as well. It was found that photo stabilizing effect doesn't depend on nature of functional groups of substituent in aromatic nucleus and specified by length and efficiency of conjugation chains.

A Lactobacillus mutant capable of accumulating long-chain polyphosphates that enhance intestinal barrier function.

Science.gov (United States)

Saiki, Asako; Ishida, Yasuaki; Segawa, Shuichi; Hirota, Ryuichi; Nakamura, Takeshi; Kuroda, Akio

2016-05-01

Inorganic polyphosphate (polyP) was previously identified as a probiotic-derived substance that enhances intestinal barrier function. PolyP-accumulating bacteria are expected to have beneficial effects on the human gastrointestinal tract. In this study, we selected Lactobacillus paracasei JCM 1163 as a strain with the potential to accumulate polyP, because among the probiotic bacteria stored in our laboratory, it had the largest amount of polyP. The chain length of polyP accumulated in L. paracasei JCM 1163 was approximately 700 phosphate (Pi) residues. L. paracasei JCM 1163 accumulated polyP when Pi was added to Pi-starved cells. We further improved the ability of L. paracasei JCM 1163 to accumulate polyP by nitrosoguanidine mutagenesis. The mutant accumulated polyP at a level of 1500 nmol/mg protein-approximately 190 times that of the wild-type strain. PolyP extracted from the L. paracasei JCM 1163 significantly suppressed the oxidant-induced intestinal permeability in mouse small intestine. In conclusion, we have succeeded in breeding the polyP-accumulating Lactobacillus mutant that is expected to enhance intestinal barrier function.

3D FT-IR imaging spectroscopy of phase-separation in a poly(3-hydroxybutyrate)/poly(L-lactic acid) blend

Science.gov (United States)

Miriam Unger; Julia Sedlmair; Heinz W. Siesler; Carol Hirschmugl; Barbara Illman

2014-01-01

In the present study, 3D FT-IR spectroscopic imaging measurements were applied to study the phase separation of a poly(3-hydroxybutyrate) (PHB)/poly(L-lactic acid) (PLA) (50:50 wt.%) polymer blend film. While in 2D projection imaging the z-dependent information is overlapped, thereby complicating the analysis, FT-IR spectro-micro-tomography,...

Effects of solvents on the radiation grafting reaction of vinyl compounds on poly (3-hydroxybutyrate)

International Nuclear Information System (INIS)

Torres, Maykel González; Talavera, José Rogelio Rodríguez; Muñoz, Susana Vargas; Pérez, Manuel González; Castro, Ma. Pilar. Carreón.; Cortes, Jorge Cerna

2015-01-01

Vinyl Acetate was grafted onto poly (3-hydroxybutyrate) by the simultaneous gamma irradiation method using different types of solvents and in bulk (solvent free), at 10 kGy and 1.62 kGy/h dose and dose rate respectively. Subsequent complete hydrolysis allowed the conversion of grafted chains from poly (vinyl acetate) to poly (vinyl alcohol). The aim of this study is to determine the effect of solvent through the estimation of the dependence of the degree of grafting with the choice of solvent, the calculation of the degree of crystallinity, and to study the biodegradation of the products. The results showed a greater degree of grafting in bulk, while the more suitable solvent was hexane. Characterization of the grafted copolymer indicated that crystallinity percentage decreased by an increase in grafting, while the biodegradability was promoted by the increment in poly (vinyl alcohol) grafted. - Highlights: • PHB was indirectly grafted with PVA, by complete hydrolysis of grafted PVAc. • The effect of solvents on the grafting, crystallinity and biodegradation was studied. • The characterizations of the products were obtained by SEM, TGA, and DSC

Liquid mixtures for scintillation counters

International Nuclear Information System (INIS)

Kauffmann, J.M.

1975-01-01

Liquid scintillators contain emulsifiers or combinations of these which can be used over a wide temperature range for a multitude of aqueous samples. These emulsifiers are block-polymerides with a nonhygroscopic center part of the chain of oxypropylene combinations recieved by addition of propylene oxide to both hydroxyl groups of a propylene-glycol nucleus and both ends of the center part of the chain terminating in hygroscopic poly(oxyethylene) groups. The length of the nonhygroscopic center part of the chain varies from about 800 to 3,000 or 4,000 in molecular weight. The hygroscopic poly(oxyethylene) end groups have a controlled length constituting about 10 to 80wt.% of the finished molecule. The most useful members of this group of co-polymerides possess a length of their poly(oxypropylene) chains corresponding to a value of y of about 15 to 56 and a length of their poly(oxyethylene)chains corresponding to values of x and z between 1 and 35 . All known fluorines can be used. With the scintillators the radioimmunoassay can also be carried through. (DG/PB) [de

Poly(N-isopropylacrylamide)–poly(ferrocenylsilane) dual-responsive hydrogels: synthesis, characterization and antimicrobial applications

NARCIS (Netherlands)

Sui, Xiaofeng; Feng, Xueling; Di Luca, Andrea; van Blitterswijk, Clemens; Moroni, Lorenzo; Hempenius, Mark A.; Vancso, Gyula J.

2013-01-01

Novel hydrogels composed of thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) and redox-responsive poly(ferrocenylsilane) (PFS) macromolecules were formed by photopolymerization. PFS chains bearing acrylate side groups were copolymerized with NIPAM and N,N′-methylenebisacrylamide in

Critical temperatures and a critical chain length in saturated diacylphosphatidylcholines: calorimetric, ultrasonic and Monte Carlo simulation study of chain-melting/ordering in aqueous lipid dispersions.

Science.gov (United States)

Kharakoz, Dmitry P; Panchelyuga, Maria S; Tiktopulo, Elizaveta I; Shlyapnikova, Elena A

2007-12-01

Chain-ordering/melting transition in a series of saturated diacylphosphatidylcholines (PCs) in aqueous dispersions have been studied experimentally (calorimetric and ultrasonic techniques) and theoretically (an Ising-like lattice model). The shape of the calorimetric curves was compared with the theoretical data and interpreted in terms of the lateral interactions and critical temperatures determined for each lipid studied. A critical chain length has been found (between 16 and 17 C-atoms per chain) which subdivides PCs into two classes with different phase behavior. In shorter lipids, the transition takes place above their critical temperatures meaning that this is an intrinsically continuous transition. In longer lipids, the transition occurs below the critical temperatures of the lipids, meaning that the transition is intrinsically discontinuous (first-order). This conclusion was supported independently by the ultrasonic relaxation sensitive to density fluctuations. Interestingly, it is this length that is the most abundant among the saturated chains in biological membranes.

Modelling the effect of nonplanarity on charge transport along conjugated polymer chains

International Nuclear Information System (INIS)

Correia, Helena M.G.; Ramos, Marta M.D.

2007-01-01

Conjugated polymers show interesting properties that make them appropriated for nanoelectronics. Several studies of poly(p-phenylene vinylene) (PPV) have suggested that each polymer chain consists of several planar segments, with conjugation length of nanoscale dimension, linked by twists or kinks. A pronounced twist between two planar segments in a PPV chain not only causes loss of main-chain conjugation but it may also alter electron and hole mobility along the chain, which has further implications for the percolation of charge through the polymer film. We used self-consistent quantum molecular dynamics calculations to provide information on the electric field needed to move the injected charges (either electrons or holes) along the planar segments of PPV and to cross the twist between two planar segments perpendicular to each other. Field-dependent charge mobility was also estimated for conjugated segments of various lengths. Our results suggest that electrons can cross the twist between adjacent planar segments for lower applied electric fields than holes if there is no more than one electronic charge (electron or hole) on the PPV chain, otherwise similar fields are needed

Characterization and in vitro degradation of poly(2,3-(1,4-diethyl tartrate)-co-2,3-isopropyliden tartrate).

Science.gov (United States)

Schliecker, Gesine; Schmidt, Carsten; Fuchs, Stefan; Kissel, Thomas

2004-07-23

In the present study, a less known polyester based on tartaric acid was characterized with respect to its degradation mechanism. Poly(2,3-(1,4-diethyl tartrate)-co-2,3-isopropyliden tartrate) (PTA) differs from commonly used biodegradable polyesters, such as poly(lactides-co-glycolides) (PLGA) by the presence of additional cleavable bonds in the polymer side chains. This modification results in different polymer properties and influences polymer degradation. The hydrolytic degradation of PTA was studied in parallel to PLGA using disc-shape matrices, which were obtained by compression-molding. The discs were incubated in pH 7.4 phosphate buffer solution at 37 degrees C. The degraded samples were characterized for percentage mass loss, water absorption, decay of molecular weight and change in glass transition temperature. The results demonstrate that the degradation of PTA proceeds via bulk erosion similar to PLGA. However, the degradation of PTA implants is characterized by a rapid mass loss within a short period of time appearing after a definite lag phase without remarkable mass loss. This makes the polymer promising for pulsatile drug release systems.

Self-consistent field theoretic simulations of amphiphilic triblock copolymer solutions: Polymer concentration and chain length effects

Directory of Open Access Journals (Sweden)

X.-G. Han

2014-06-01

Full Text Available Using the self-consistent field lattice model, polymer concentration φP and chain length N (keeping the length ratio of hydrophobic to hydrophilic blocks constant the effects on temperature-dependent behavior of micelles are studied, in amphiphilic symmetric ABA triblock copolymer solutions. When chain length is increased, at fixed φP, micelles occur at higher temperature. The variations of average volume fraction of stickers φcos and the lattice site numbers Ncols at the micellar cores with temperature are dependent on N and φP, which demonstrates that the aggregation of micelles depends on N and φP. Moreover, when φP is increased, firstly a peak appears on the curve of specific heat CV for unimer-micelle transition, and then in addition a primary peak, the secondary peak, which results from the remicellization, is observed on the curve of CV. For a long chain, in intermediate and high concentration regimes, the shape of specific heat peak markedly changes, and the peak tends to be a more broad peak. Finally, the aggregation behavior of micelles is explained by the aggregation way of amphiphilic triblock copolymer. The obtained results are helpful in understanding the micellar aggregation process.

Anomaly in the Chain Length Dependence of n-Alkane Diffusion in ZIF-4 Metal-Organic Frameworks.

Science.gov (United States)

Hwang, Seungtaik; Gopalan, Arun; Hovestadt, Maximilian; Piepenbreier, Frank; Chmelik, Christian; Hartmann, Martin; Snurr, Randall Q; Kärger, Jörg

2018-03-15

Molecular diffusion is commonly found to slow down with increasing molecular size. Deviations from this pattern occur in some host materials with pore sizes approaching the diameters of the guest molecules. A variety of theoretical models have been suggested to explain deviations from this pattern, but robust experimental data are scarcely available. Here, we present such data, obtained by monitoring the chain length dependence of the uptake of n- alkanes in the zeolitic imidazolate framework ZIF-4. A monotonic decrease in diffusivity from ethane to n- butane was observed, followed by an increase for n- pentane, and another decrease for n- hexane. This observation was confirmed by uptake measurements with n- butane/ n -pentane mixtures, which yield faster uptake of n- pentane. Further evidence is provided by the observation of overshooting effects, i.e., by transient n- pentane concentrations exceeding the (eventually attained) equilibrium value. Accompanying grand canonical Monte Carlo simulations reveal, for the larger n- alkanes, significant differences between the adsorbed and gas phase molecular configurations, indicating strong confinement effects within ZIF-4, which, with increasing chain length, may be expected to give rise to configurational shifts facilitating molecular propagation at particular chain lengths.

Anomaly in the Chain Length Dependence of n-Alkane Diffusion in ZIF-4 Metal-Organic Frameworks

Directory of Open Access Journals (Sweden)

Seungtaik Hwang

2018-03-01

Full Text Available Molecular diffusion is commonly found to slow down with increasing molecular size. Deviations from this pattern occur in some host materials with pore sizes approaching the diameters of the guest molecules. A variety of theoretical models have been suggested to explain deviations from this pattern, but robust experimental data are scarcely available. Here, we present such data, obtained by monitoring the chain length dependence of the uptake of n-alkanes in the zeolitic imidazolate framework ZIF-4. A monotonic decrease in diffusivity from ethane to n-butane was observed, followed by an increase for n-pentane, and another decrease for n-hexane. This observation was confirmed by uptake measurements with n-butane/n-pentane mixtures, which yield faster uptake of n-pentane. Further evidence is provided by the observation of overshooting effects, i.e., by transient n-pentane concentrations exceeding the (eventually attained equilibrium value. Accompanying grand canonical Monte Carlo simulations reveal, for the larger n-alkanes, significant differences between the adsorbed and gas phase molecular configurations, indicating strong confinement effects within ZIF-4, which, with increasing chain length, may be expected to give rise to configurational shifts facilitating molecular propagation at particular chain lengths.

Characterization of a Bio-Based, Biodegradable Class of Copolymers, Poly[(R)-3-Hydroxybutyrate-Co-(R)-3- Hydroxyhexanoate], and Application Development

Science.gov (United States)

Sobieski, Brian

As modern society begins to focus on sustainability and renewable resources there is a growing need for the polymer industry to develop more environmentally friendly materials and practices. Part of this movement can be seen in the use of recycled materials in new products and in the development of bio-based, biodegradable polymers. Bio-based, biodegradable polymers are produced from renewable carbon sources, such as vegetable oils, typically polymerized using fermentation reactions via bacteria, and are able to be consumed by bacteria in landfills to completely convert the polymers to water and CO2. One class of such polymers are poly(hydroxyalkanoate)'s (PHAs), which are chiral, aliphatic polyesters. Within this class of polyesters are poly(hydroxybutyrate) (PHB) and the copolymer poly[(R)-3-hydroxybutyrate- co-(R)-3-hydroxyhexanoate] (PHBHx), which have received extensive study due to their material properties as thermoplastics. Although the properties of PHB have been widely explored, much still remains to be understood about these promising biodegradable polymers. Specifically, PHB and its copolymers exhibit physical gelation in most solvents, yet the origin and mechanism of gelation and the properties of the resulting gel state are unknown. This research effort was primarily focused on investigating the physical gel state of PHBHx. Five goals were laid out and completed: determining the origin of gelation, the mechanism of gelation, the structure of the gel state, the properties of the gel state, and the effects of gelation on electrospun fibers of PHBHx. These goals were achieved through material characterization of the gel state utilizing infrared spectroscopy/two-dimensional correlation spectroscopy, differential scanning calorimetry, X-ray diffraction, scanning electron microscopy, and many other analysis methods. Crystallization of the polymer in solution was found to cause gelation in PHBHx solutions, where the polymer crystals act as tie points forming

Non-Gaussian theory of rubberlike elasticity based on rotational isomeric state simulations of network chain configurations. II. Bimodal poly(dimethylsiloxane) networks

International Nuclear Information System (INIS)

Curro, J.G.; Mark, J.E.

1984-01-01

Bimodal, poly(dimethylsiloxane) (PDMS) networks containing a large mole fraction of very short chains have been shown to be unusually tough elastomers. The purpose of this investigation is to understand the rubber elasticity behavior of these bimodal networks. As a first approach, we have assumed that the average chain deformation is affine. This deformation, however, is partitioned nonaffinely between the long and short chains so that the free energy is minimized. Gaussian statistics are used for the long chains. The distribution function for the short chains is found from Monte Carlo calculations. This model predicts an upturn in the stress-strain curve, the steepness depending on the network composition, as is observed experimentally

Synthesis of microbial elastomers based on soybean oily acids. Biocompatibility studies

International Nuclear Information System (INIS)

Hazer, Derya Burcu; Hazer, Baki; Kaymaz, Figen

2009-01-01

Biocompatibility studies of the autoxidized and unoxidized unsaturated medium-long chain length (m-lcl) co-poly-3-hydroxyalkanoates (m-lclPHAs) derived from soya oily acids have been reported. Pseudomonas oleovorans was grown on a series of mixtures of octanoic acid (OA) and soya oily acids (Sy) with weight ratios of 20:80, 28:72 and 50:50 in order to obtain unsaturated m-lcl copolyesters coded PHO-Sy-2080, PHO-Sy-2872 and PHO-Sy-5050, respectively. The PHA films were obtained by solvent cast from CHCl 3 . They were all originally sticky and waxy except PHO-Sy-5050. Autoxidation of the unsaturated copolyester films was carried out on exposure to air at room temperature in order to obtain crosslinked polymers. They became a highly flexible elastomer after being autoxidized (about 40 days of autoxidation). The in vivo tissue reactions of the autoxidized PHAs were evaluated by subcutaneous implantation in rats. The rats appeared to be healthy throughout the implantation period. No symptom such as necrosis, abscess or tumorigenesis was observed in the vicinity of the implants. Retrieved materials varied in their physical appearance after 6 weeks of implantation. In vivo biocompatibility studies of the medical applications indicated that the microbial copolyesters obtained were all biocompatible and especially the PHOSy series of copolyesters had the highest biocompatibility among them.

Properties of Haldane Excitations and Multiparticle States in the Antiferromagnetic Spin-1 Chain Compound CsNiCl3

International Nuclear Information System (INIS)

Kenzelmann, M.; Cowley, R.A.; Buyers, W.J.L.; Tun, Z.; Coldea, Radu; Enderle, M.

2002-01-01

We report inelastic time-of-flight and triple-axis neutron scattering measurements of the excitation spectrum of the coupled antiferromagnetic spin-1 Heisenberg chain system CsNiCl 3 . Measurements over a wide range of wave-vector transfers along the chain confirm that above T N CsNiCl 3 is in a quantum-disordered phase with an energy gap in the excitation spectrum. The spin correlations fall off exponentially with increasing distance with a correlation length ζ = 4.0(2) sites at T = 6.2K. This is shorter than the correlation length for an antiferromagnetic spin-1 Heisenberg chain at this temperature, suggesting that the correlations perpendicular to the chain direction and associated with the interchain coupling lower the single-chain correlation length. A multiparticle continuum is observed in the quantum-disordered phase in the region in reciprocal space where antiferromagnetic fluctuations are strongest, extending in energy up to twice the maximum of the dispersion of the well-defined triplet excitations. We show that the continuum satisfies the Hohenberg-Brinkman sum rule. The dependence of the multiparticle continuum on the chain wave vector resembles that of the two-spinon continuum in antiferromagnetic spin-1/2 Heisenberg chains. This suggests the presence of spin-1/2 degrees of freedom in CsNiCl 3 for T ∼< 12 K, possibly caused by multiply frustrated interchain interactions.

Theoretical consideration on phase behaviors of poly(ethylene oxide-block-propylene oxide)/LiCF3SO3 systems in lithium battery

International Nuclear Information System (INIS)

Ko, Sung Jin; Kim, Sun Joon; Kong, Sung Ho; Bae, Young Chan

2004-01-01

A new thermodynamic model is developed based on the extended perturbed hard sphere chain (PHSC) model and melting point depression theory to describe the phase behaviors of copolymer electrolyte/salt systems. The phase behaviors of poly(ethylene oxide-block-propylene oxide)/LiCF 3 SO 3 systems are investigated by thermo-optical analysis (TOA) technique. Quantitative descriptions according to the proposed model are in good agreement with experimental data. The obtained results show that monomer ratio and sequence type of copolymers play a great role in determining eutectic points of the given systems

The Effect of the Chain Length on MMA Free Radicl Polymerization

Institute of Scientific and Technical Information of China (English)

无

2001-01-01

In the polymerization process of methyl methacrylate (MMA), the Arrhenius parameters (activation energy and frequency factor) of propagating reaction monotonically decrease with increasing monomer conversion. At the beginning and middle stage of the propagating reaction, the increase of radical chain length is the main reason of above mentioned change. And at the end stage, the sharp decrease of kp indicates that the activation energy is approximately incline to zero and the propagating reaction is controlled by molecular diffusion motion.

Immobilization of lipases on alkyl silane modified magnetic nanoparticles: effect of alkyl chain length on enzyme activity.

Directory of Open Access Journals (Sweden)

Jiqian Wang

Full Text Available BACKGROUND: Biocatalytic processes often require a full recycling of biocatalysts to optimize economic benefits and minimize waste disposal. Immobilization of biocatalysts onto particulate carriers has been widely explored as an option to meet these requirements. However, surface properties often affect the amount of biocatalysts immobilized, their bioactivity and stability, hampering their wide applications. The aim of this work is to explore how immobilization of lipases onto magnetite nanoparticles affects their biocatalytic performance under carefully controlled surface modification. METHODOLOGY/PRINCIPAL FINDINGS: Magnetite nanoparticles, prepared through a co-precipitation method, were coated with alkyl silanes of different alkyl chain lengths to modulate their surface hydrophobicity. Candida rugosa lipase was then directly immobilized onto the modified nanoparticles through hydrophobic interaction. Enzyme activity was assessed by catalytic hydrolysis of p-nitrophenyl acetate. The activity of immobilized lipases was found to increase with increasing chain length of the alkyl silane. Furthermore, the catalytic activities of lipases immobilized on trimethoxyl octadecyl silane (C18 modified Fe(3O(4 were a factor of 2 or more than the values reported from other surface immobilized systems. After 7 recycles, the activities of the lipases immobilized on C18 modified nanoparticles retained 65%, indicating significant enhancement of stability as well through hydrophobic interaction. Lipase immobilized magnetic nanoparticles facilitated easy separation and recycling with high activity retaining. CONCLUSIONS/SIGNIFICANCE: The activity of immobilized lipases increased with increasing alkyl chain length of the alkyl trimethoxy silanes used in the surface modification of magnetite nanoparticles. Lipase stability was also improved through hydrophobic interaction. Alkyl silane modified magnetite nanoparticles are thus highly attractive carriers for

Immobilization of lipases on alkyl silane modified magnetic nanoparticles: effect of alkyl chain length on enzyme activity.

Science.gov (United States)

Wang, Jiqian; Meng, Gang; Tao, Kai; Feng, Min; Zhao, Xiubo; Li, Zhen; Xu, Hai; Xia, Daohong; Lu, Jian R

2012-01-01

Biocatalytic processes often require a full recycling of biocatalysts to optimize economic benefits and minimize waste disposal. Immobilization of biocatalysts onto particulate carriers has been widely explored as an option to meet these requirements. However, surface properties often affect the amount of biocatalysts immobilized, their bioactivity and stability, hampering their wide applications. The aim of this work is to explore how immobilization of lipases onto magnetite nanoparticles affects their biocatalytic performance under carefully controlled surface modification. Magnetite nanoparticles, prepared through a co-precipitation method, were coated with alkyl silanes of different alkyl chain lengths to modulate their surface hydrophobicity. Candida rugosa lipase was then directly immobilized onto the modified nanoparticles through hydrophobic interaction. Enzyme activity was assessed by catalytic hydrolysis of p-nitrophenyl acetate. The activity of immobilized lipases was found to increase with increasing chain length of the alkyl silane. Furthermore, the catalytic activities of lipases immobilized on trimethoxyl octadecyl silane (C18) modified Fe(3)O(4) were a factor of 2 or more than the values reported from other surface immobilized systems. After 7 recycles, the activities of the lipases immobilized on C18 modified nanoparticles retained 65%, indicating significant enhancement of stability as well through hydrophobic interaction. Lipase immobilized magnetic nanoparticles facilitated easy separation and recycling with high activity retaining. The activity of immobilized lipases increased with increasing alkyl chain length of the alkyl trimethoxy silanes used in the surface modification of magnetite nanoparticles. Lipase stability was also improved through hydrophobic interaction. Alkyl silane modified magnetite nanoparticles are thus highly attractive carriers for enzyme immobilization enabling efficient enzyme recovery and recycling.

The Effects of Dilute Sulfuric Acid on Sheet Resistance and Transmittance in Poly(3,4-thylenedioxythiophene: Poly(styrenesulfonate Films

Directory of Open Access Journals (Sweden)

Teen-Hang Meen

2013-01-01

Full Text Available The conductivity of poly(3,4-thylenedioxythiophene: poly(styrenesulfonate (PEDOT: PSS films by adding various molar concentrations of sulfuric acid (H2SO4 was improved and studied in this paper. The sheet resistance of the doped PEDOT: PSS film was enhanced with increasing the ratio of H2SO4, but it drops after the maximum sheet resistance. The reason for this phenomenon is resulting from the fact that the H2SO4 preferentially react with the sorbitol which is so-called the pinacol rearrangement. The nonconductive anions of some PSS− were substituted by the conductive anions of hydrogen sulfate (HSO4- when the residual H2SO4 reacted with PSS. In addition to the substitution reaction, PEDOT chains were increasingly aggregated with increasing the ratio of H2SO4. After doped H2SO4, the sheet resistance of H2SO4-doped PEDOT: PSS film is improved nearly 36%; the surface roughness is reduced from 1.268 nm to 0.822 nm and the transmittance is up to 91.9% in the visible wavelength range from 400 to 700 nm.

Glycogen with short average chain length enhances bacterial durability

Science.gov (United States)

Wang, Liang; Wise, Michael J.

2011-09-01

Glycogen is conventionally viewed as an energy reserve that can be rapidly mobilized for ATP production in higher organisms. However, several studies have noted that glycogen with short average chain length in some bacteria is degraded very slowly. In addition, slow utilization of glycogen is correlated with bacterial viability, that is, the slower the glycogen breakdown rate, the longer the bacterial survival time in the external environment under starvation conditions. We call that a durable energy storage mechanism (DESM). In this review, evidence from microbiology, biochemistry, and molecular biology will be assembled to support the hypothesis of glycogen as a durable energy storage compound. One method for testing the DESM hypothesis is proposed.

Self-assembled H-aggregation induced high performance poly (3-hexylthiophene) Schottky diode

Science.gov (United States)

Chaudhary, Vivek; Pandey, Rajiv K.; Prakash, Rajiv; Singh, Arun Kumar

2017-12-01

The investigation of size confinement and chain orientation within the microstructure of a polymer thin film is very important for electronic device applications and fundamental research. Here, we present single step methodology for the synthesis of solution-processable poly (3-hexylthiophene) (P3HT) nanofibers via a self-assembly process. The formation of P3HT nanofibers is confirmed by atomic force microscopy. The synthesized nanofibers are characterized by UV-visible absorption, photoluminescence, and Raman spectroscopy. The aggregation type of self-assembled P3HT is studied by both UV-visible absorbance and photoluminescence spectroscopy. The exciton bandwidth in polymer films is calculated by following the Spano's H-aggregate model and found to be 28 meV. Raman spectroscopy is used to identify the various stretching modes present in nanofibers. The structural investigation using grazing angle X-ray diffraction of nanofibers reveals the presence of alkyl chain ordering. We have fabricated organic Schottky diodes with P3HT nanofibers on indium tin oxide (ITO) coated glass with configuration Al/P3HT/ITO, and current density-voltage characteristics are subsequently used for extracting the electronic parameters of the device. We have also discussed the charge transport mechanism at the metal/polymer interface.

Influence of the chain length on the biological behaviour of /sup 131/I fatty acids

Energy Technology Data Exchange (ETDEWEB)

Riche, F.; Mathieu, J.P.; Comet, M.; Vidal, M.; Pernin, C.; Marti-Batlle, D.; Busquet, G. (Universite de Grenoble, 38 (France)); Bardy, A. (C.E.A.-ORIS, 91 - Gif-sur-Yvette (France))

1983-01-01

Saturated and acetylenic fatty acids labeled with /sup 131/I in ..omega.. position, differing by their chain length (C8 to C20) and the number odd or even of their carbon atoms are injected in mice. The evolution of the activity in myocardium, blood, liver and kidney is measured until 10 minutes after injection. The myocardial activity increases with chain length from C8 to C16 then decreases for C18 and C20. The odd or even number of carbon atoms does not influence myocardial activity but in the liver, activity is inferior with the odd fatty acids. The presence of a triple bond accelerates the output of activity from the myocardium and these fatty acids are not well suited for the study of myocardial metabolism.

Effect of the different chain transfer agents on molecular weight and optical properties of poly(methyl methacrylate)

Science.gov (United States)

Çetinkaya, Onur; Demirci, Gökhan; Mergo, Paweł

2017-08-01

Investigation of molecular weight and optical properties of poly(methyl metacrylate) (PMMA) polymerized in house with different chain transfer agents was studied. Isopropyl alcohol (IPA), n-butyl mercaptan (nBMC) and pentamethyl disilane (PMDS) were used as chain transfer agents. The molecular weight (Mw) of PMMA samples were measured by Ostwald viscometer. Mw of bulk polymer samples were decreased with increase the concentration of chain transfer agents (CTA). Since reactivity of used CTAs is not same, molecular weights of samples which were produced with different type of CTA but same concentration of CTA was varied. Higher concentration of n-BMC showed higher scattering. Transmission of samples could not be correlated with different concentration of CTA. Refractive index of samples was not affected by concentration of CTA nevertheless higher molecular weight of CTA showed higher refractive index.

Synthesis of amphiphilic poly(ε-caprolactone)-b-poly( N-vinylcaprolactam) block copolymers via the combination of RAFT polymerization and click chemistry

International Nuclear Information System (INIS)

Assis, Paulo Henrique; Aguiar, Graziele Aparecida de Jesus; Moraes, Rodolfo Minto de; Medeiros, Simone de Fatima; Santos, Amilton Martins

2016-01-01

Full text: In recent years, well-defined block copolymers composed of a hydrophilic and hydrophobic segments have gained much interest as drug carriers, because of their enhanced solubility and sustained release of the drug in controlled delivery systems [1]. The development of strategies to obtain block copolymers has attracted considerable attention, due to the possibility to combine characteristic properties of the homopolymers. A wide variety of well-defined block copolymers have been successfully synthesized by combining the efficiency and selectivity of click chemistry with the powerful RAFT polymerization mechanism. In the present work, well-defined amphiphilic, biocompatible, partially biodegradable, and thermosensitive poly(ε-caprolactone)-b-poly(N-vinylcaprolactam) (PCL-b-PNVCL) block copolymers were synthesized by combining ring opening polymerization (ROP), reversible addition-fragmentation chain transfer (RAFT) polymerization and subsequent click chemistry reaction. Alkyne-terminated poly(ε-caprolactone) (alkyne-PCL) was obtained by the ring opening polymerization of ε-caprolactone (ε-CL) using propargyl alcohol as initiator and stannous-2-ethylhexanoate [Sn(Oct) 2 ] as catalyst. The azide end-capped-poly(N-vinylcaprolactam) (PNVCL-N 3 ) was synthesized by reversible addition-fragmentation chain transfer/macromolecular design via interchange of xanthates (RAFT/MADIX) polymerization of the N-vinylcaprolactam (NVCL) mediated by a novel chain transfer agent comprising an azide function , 2-azidoethyl[(ethoxycarbonothioyl)thio](phenyl)acetate. These functionalized homopolymers, alkyne-PCL and PNVCL-N 3 , were coupled by the 1,3 dipolar cycloaddition reaction in order to obtain the corresponding block copolymers. These (co)polymers were characterized by FTIR, 1 H NMR and GPC measurements. Reference: 1. RAMESH, K., SINGH, S., MITRA, K., CHATTOPADHYAY, D., MISRA, N., & RAY, B. (2015). Colloid and Polymer Science, 1-9. (author)

Gas-permeation properties of poly(ethylene oxide) poly(butylene terephthalate block copolymers

NARCIS (Netherlands)

Metz, S.J.; Mulder, M.H.V.; Wessling, Matthias

2004-01-01

This paper reports the gas-permeation properties of poly(ethylene oxide) (PEO) poly(butylene terephthalate) (PBT) segmented multiblock copolymers. These block copolymers allow a precise structural modification by the amount of PBT and the PEO segment length, enabling a systematic study of the

Supplemental Dietary Inulin of Variable Chain Lengths Alters Intestinal Bacterial Populations in Young Pigs123

Science.gov (United States)

Patterson, Jannine K.; Yasuda, Koji; Welch, Ross M.; Miller, Dennis D.; Lei, Xin Gen

2010-01-01

Previously, we showed that supplementation of diets with short-chain inulin (P95), long-chain inulin (HP), and a 50:50 mixture of both (Synergy 1) improved body iron status and altered expression of the genes involved in iron homeostasis and inflammation in young pigs. However, the effects of these 3 types of inulin on intestinal bacteria remain unknown. Applying terminal restriction fragment length polymorphism analysis, we determined the abundances of luminal and adherent bacterial populations from 6 segments of the small and large intestines of pigs (n = 4 for each group) fed an iron-deficient basal diet (BD) or the BD supplemented with 4% of P95, Synergy 1, or HP for 5 wk. Compared with BD, all 3 types of inulin enhanced (P inulin on bacterial populations in the lumen contents were found. Meanwhile, all 3 types of inulin suppressed the less desirable bacteria Clostridium spp. and members of the Enterobacteriaceae in the lumen and mucosa of various gut segments. Our findings suggest that the ability of dietary inulin to alter intestinal bacterial populations may partially account for its iron bioavailability-promoting effect and possibly other health benefits. PMID:20980641

A temperature-dependent coarse-grained model for the thermoresponsive polymer poly(N-isopropylacrylamide)

Energy Technology Data Exchange (ETDEWEB)

Abbott, Lauren J.; Stevens, Mark J., E-mail: msteve@sandia.gov [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)

2015-12-28

A coarse-grained (CG) model is developed for the thermoresponsive polymer poly(N-isopropylacrylamide) (PNIPAM), using a hybrid top-down and bottom-up approach. Nonbonded parameters are fit to experimental thermodynamic data following the procedures of the SDK (Shinoda, DeVane, and Klein) CG force field, with minor adjustments to provide better agreement with radial distribution functions from atomistic simulations. Bonded parameters are fit to probability distributions from atomistic simulations using multi-centered Gaussian-based potentials. The temperature-dependent potentials derived for the PNIPAM CG model in this work properly capture the coil–globule transition of PNIPAM single chains and yield a chain-length dependence consistent with atomistic simulations.

Entanglement Dynamics in Miscible Polyisoprene / Poly(p-tert-butyl styrene) Blends

Science.gov (United States)

Watanabe, Hiroshi

2011-03-01

Viscoelastic and dielectric behavior was examined for well entangled, miscible blends of high- M cis-polyisoprene (PI) and poly(p-tert-butyl styrene) (PtBS). The dielectric data of the blends, reflecting the global motion of the PI chains having the type-A dipoles, indicated that PI and PtBS were the fast and slow components therein. At high temperatures T , the blends exhibited two-step entanglement plateau. The high frequency (ω) plateau height was well described by a simple mixing rule of the entanglement length based on the number fraction of the Kuhn segments. At low T , the blend exhibited the Rouse-like power-law behavior of storage and loss moduli, G ' = G ~ω0.5 , in the range of ω where the high- ω plateau was supposed to emerge. This lack of the high- ω plateau was attributed to retardation of the Rouse equilibration of the PI chain over the entanglement length due to the hindrance from the slow PtBS chains: The PI and PtBS chains were equilibrated cooperatively, and the retardation due to PtBS shortened the plateau for PI to a width not resolved experimentally. A simple model for this cooperative equilibration formulated on the basis of the dielectric data described the viscoelastic data surprisingly well.

Effect of Difference in Fatty Acid Chain Lengths of Medium- Chain Lipids on Lipid/Surfactant/Water Phase Diagrams and Drug Solubility

Directory of Open Access Journals (Sweden)

Hetal N. Prajapati

2011-09-01

Full Text Available Lipids consisting of medium chain fatty acids are commonly used in the development of lipid-based selfemulsifying and self-microemulsifying drug delivery systems. However, no systematic approach to selecting one lipid over another has been reported in the literature. In this study, propylene glycol (PG monoester (PG monocaprylate, Capmul PG-8® and PG diester (PG dicaprylocaprate, Captex 200P® of C8-fatty acids were compared with PG monoester (PG monolaurate, Capmul PG-12® and PG diester (PG dilaurate, Capmul PG-2L® of C12-fatty acids with respect to their phase diagrams, and especially for their ability to form microemulsions in the presence of a common surfactant, Cremophor EL®, and water. The solubility of two model drugs, danazol and probucol, in the lipids and lipid/surfactant mixtures were also compared. The effect of the chain length of medium-chain fatty acids (C8 versus C12 on the phase diagrams of the lipids was minimal. Both shorter and longer chain lipids formed essentially similar microemulsion and emulsion regions in the presence of Cremophor EL® and water, although the C12-fatty acid esters formed larger gel regions in the phase diagrams than the C8-fatty acid esters. When monoesters were mixed with their respective diesters at 1:1 ratios, larger microemulsion regions with lower lipid particle sizes were observed compared to those obtained with individual lipids alone. While the solubility of both danazol and probucol increased greatly in all lipids studied, compared to their aqueous solubility, the solubility in C12-fatty acid esters was found to be lower than in C8-fatty acid esters when the lipids were used alone. This difference in solubility due to the difference in fatty acid chain length, practically disappeared when the lipids were combined with the surfactant.

Estratégias de cultivo para produção dos plásticos biodegradáveis poli(3-Hidroxibutirato e poli(3-hidroxibutirato-co-3-hidroxivalerato por bactérias Cultivation strategies for production of the biodegradable plastics poly(3-hydroxybutyrate and poly(3-hydroxybutyrate-co-3-hydroxyvalerate by bacteria

Directory of Open Access Journals (Sweden)

Cláudia Regina Squio

2004-08-01

Full Text Available Polyhydroxyalkanoates (PHAs are carbon and energy storage materials that are accumulated as intracellular granules in a variety of microorganisms during unbalanced growth. PHAs have drawn attention due to their properties similar to conventional plastics and complete biodegradability. They can be used for food and cosmetics packaging, and in medicine and agriculture. However, their applicability is reduced because of their high production cost compared to conventional plastics. An overview on production strategies of poly(3-hydroxybutyrate and poly(3-hydroxybutyrate-co-3-hydroxyvalerate aiming at reducing the production costs is presented.

Protein adsorption resistant surface on polymer composite based on 2D- and 3D-controlled grafting of phospholipid moieties

International Nuclear Information System (INIS)

Hoshi, Toru; Matsuno, Ryosuke; Sawaguchi, Takashi; Konno, Tomohiro; Takai, Madoka; Ishihara, Kazuhiko

2008-01-01

To prepare the biocompatible surface, a phosphorylcholine (PC) group was introduced on this hydroxyl group generated by surface hydrolysis on the polymer composite composed of polyethylene (PE) and poly (vinyl acetate) (PVAc) prepared by supercritical carbon dioxide. Two different procedures such as two-dimensional (2D) modification and three-dimensional (3D) modification were applied to obtain the steady biocompatible surface. 2D modification was that PC groups were directly anchored on the surface of the polymer composite. 3D modification was that phospholipid polymer was grafted from the surface of the polymer composite by surface-initiated atom transfer radical polymerization (SI-ATRP) of 2-methacryloyloxyethyl phosphorylcholine (MPC). The surfaces were characterized by X-ray photoelectron spectroscopy, dynamic water contact angle measurements, and atomic force microscope. The effects of the poly(MPC) chain length on the protein adsorption resistivity were investigated. The protein adsorption on the polymer composite surface with PC groups modified by 2D or 3D modification was significantly reduced as compared with that on the unmodified PE. Further, the amount of protein adsorbed on the 3D modified surface that is poly(MPC)-grafted surface decreased with an increase in the chain length of the poly(MPC). The surface with an arbitrary structure and the characteristic can be constructed by using 2D and 3D modification. We conclude that the polymer composites of PE/PVAc with PC groups on the surface are useful for fabricating biomedical devices due to their good mechanical and surface properties

Tuning Surface Properties of Poly(methyl methacrylate) Film Using Poly(perfluoromethyl methacrylate)s with Short Perfluorinated Side Chains.

Science.gov (United States)

Sohn, Eun-Ho; Ha, Jong-Wook; Lee, Soo-Bok; Park, In Jun

2016-09-27

To control the surface properties of a commonly used polymer, poly(methyl methacrylate) (PMMA), poly(perfluoromethyl methacrylate)s (PFMMAs) with short perfluorinated side groups (i.e., -CF3, -CF2CF3, -(CF3)2, -CF2CF2CF3) were used as blend components because of their good solubility in organic solvents, low surface energies, and high optical transmittance. The surface energies of the blend films of PFMMA with the -CF3 group and PMMA increased continuously with increasing PMMA contents from 17.6 to 26.0 mN/m, whereas those of the other polymer blend films remained at very low levels (10.2-12.6 mN/m), similar to those of pure PFMMAs, even when the blends contained 90 wt %PMMA. Surface morphology and composition measurements revealed that this result originated from the different blend structures, such as lateral and vertical phase separations. We expect that these PFMMAs will be useful in widening the applicable window of PMMA.

Microphase separation and the formation of ion conductivity channels in poly(ionic liquid)s: A coarse-grained molecular dynamics study

Science.gov (United States)

Weyman, Alexander; Bier, Markus; Holm, Christian; Smiatek, Jens

2018-05-01

We study generic properties of poly(ionic liquid)s (PILs) via coarse-grained molecular dynamics simulations in bulk solution and under confinement. The influence of different side chain lengths on the spatial properties of the PIL systems and on the ionic transport mechanism is investigated in detail. Our results reveal the formation of apolar and polar nanodomains with increasing side chain length in good agreement with previous results for molecular ionic liquids. The ion transport numbers are unaffected by the occurrence of these domains, and the corresponding values highlight the potential role of PILs as single-ion conductors in electrochemical devices. In contrast to bulk behavior, a pronounced formation of ion conductivity channels in confined systems is initiated in close vicinity to the boundaries. We observe higher ion conductivities in these channels for increasing PIL side chain lengths in comparison with bulk values and provide an explanation for this effect. The appearance of these domains points to an improved application of PILs in modern polymer electrolyte batteries.

Chemical modification of biodegradable polymer poly(3-hydroxybutyrate) by poly(ethylene oxide)

International Nuclear Information System (INIS)

Almeida, Lilian L.; Rocha, Gisele A.; Hui, Wang S.

2009-01-01

Catalyzed transesterification in the melt was used to produce triblock copolymers from poly(3-hydroxybutyrate) (PHB) and poly(ethyleneoxide) (PEG), in a simplified process. PHB of high molecular weight was depolymerized by pyrolysis and transesterification with dihydroxy terminated PEG occurred through consecutive and partly simultaneous reactions. The effectiveness of the process was verified by the characterization of the formed copolymers by Hydrogen and Carbon-13 Nuclear Magnetic Resonance Spectroscopies (NMR) and solubility analysis in a series of solvents. (author)

Linear side chains in benzo[1,2-b:4,5-b′]dithiophene-thieno[3,4-c] pyrrole-4,6-dione polymers direct self-assembly and solar cell performance

KAUST Repository

Cabanetos, Clement; El Labban, Abdulrahman; Bartelt, Jonathan A.; Douglas, Jessica D.; Mateker, William R.; Frechet, Jean; McGehee, Michael D.; Beaujuge, Pierre

2013-01-01

role that linear side-chain substituents play in poly(benzo[1,2-b:4,5-b′]dithiophene-thieno[3,4-c]pyrrole-4,6-dione) (PBDTTPD) polymers for bulk heterojunction (BHJ) solar cell applications. We show that replacing branched side chains by linear ones

Stability of polyelectrolyte-coated iron nanoparticles for T2-weighted magnetic resonance imaging

Science.gov (United States)

McGrath, Andrew J.; Dolan, Ciaran; Cheong, Soshan; Herman, David A. J.; Naysmith, Briar; Zong, Fangrong; Galvosas, Petrik; Farrand, Kathryn J.; Hermans, Ian F.; Brimble, Margaret; Williams, David E.; Jin, Jianyong; Tilley, Richard D.

2017-10-01

Iron nanoparticles are highly-effective magnetic nanoparticles for T2 magnetic resonance imaging (MRI). However, the stability of their magnetic properties is dependent on good protection of the iron core from oxidation in aqueous media. Here we report the synthesis of custom-synthesized phosphonate-grafted polyelectrolytes (PolyM3) of various chain lengths, for efficient coating of iron nanoparticles with a native iron oxide shell. The size of the nanoparticle-polyelectrolyte assemblies was investigated by transmission electron microscopy and dynamic light scattering, while surface attachment was confirmed by Fourier transform infrared spectroscopy. Low cytotoxicity was observed for each of the nanoparticle-polyelectrolyte ("Fe-PolyM3") assemblies, with good cell viability (>80%) remaining up to 100 μg mL-1 Fe in HeLa cells. When applied in T2-weighted MRI, corresponding T2 relaxivities (r2) of the Fe-PolyM3 assemblies were found to be dependent on the chain length of the polyelectrolyte. A significant increase in contrast was observed when polyelectrolyte chain length was increased from 6 to 65 repeating units, implying a critical chain length required for stabilization of the α-Fe nanoparticle core.

Scattering Study of Conductive-Dielectric Nano/Micro-Grained Single Crystals Based on Poly(ethylene glycol, Poly(3-hexyl thiophene and Polyaniline

Directory of Open Access Journals (Sweden)

Samira Agbolaghi

2017-12-01

Full Text Available Two types of rod-coil block copolymers including poly(3-hexylthiophene-block-poly(ethylene glycol (P3HT-b-PEG and PEG-block-polyaniline (PANI were synthesized using Grignard metathesis polymerization, Suzuki coupling, and interfacial polymerization. Afterward, two types of single crystals were grown by self-seeding methodology to investigate the coily and rod blocks in grafted brushes and ordered crystalline configurations. The conductive P3HT fibrillar single crystals covered by the dielectric coily PEG oligomers were grown from toluene, xylene, and anisole, and characterized by atomic force microscopy (AFM and grazing wide angle X-ray scattering (GIWAXS. Longer P3HT backbones resulted in folding, whereas shorter ones had a high tendency towards backbone lamination. The effective factors on folding of long P3HT backbones in the single crystal structures were the solvent quality and crystallization temperature. Better solvents due to decelerating the growth condition led to a higher number of foldings. Via increasing the crystallization temperature, the system decreased the folding number to maintain its stability. Poorer solvents also reflected a higher stacking in hexyl side chain and π-π stacking directions. The dielectric lamellar PEG single crystals sandwiched between the PANI nanorods were grown from amyl acetate, and analyzed using the interface distribution function (IDF of SAXS and AFM. The molecular weights of PANI and PEG blocks and crystallization temperature were focused while studying the grown single crystals.

Hypothalamic fatty acid sensing in Senegalese sole (Solea senegalensis): response to long-chain saturated, monounsaturated, and polyunsaturated (n-3) fatty acids.

Science.gov (United States)

Conde-Sieira, Marta; Bonacic, Kruno; Velasco, Cristina; Valente, Luisa M P; Morais, Sofia; Soengas, José L

2015-12-15

We assessed the presence of fatty acid (FA)-sensing mechanisms in hypothalamus of Senegalese sole (Solea senegalensis) and investigated their sensitivity to FA chain length and/or level of unsaturation. Stearate (SA, saturated FA), oleate (OA, monounsaturated FA of the same chain length), α-linolenate [ALA, a n-3 polyunsaturated fatty acid (PUFA) of the same chain length], and eicosapentanoate (EPA, a n-3 PUFA of a larger chain length) were injected intraperitoneally. Parameters related to FA sensing and neuropeptide expression in the hypothalamus were assessed after 3 h and changes in accumulated food intake after 4, 24, and 48 h. Three FA sensing systems characterized in rainbow trout were also found in Senegalese sole and were activated by OA in a way similar to that previously characterized in rainbow trout and mammals. These hypothalamic FA sensing systems were also activated by ALA, differing from mammals, where n-3 PUFAs do not seem to activate FA sensors. This might suggest additional roles and highlights the importance of n-3 PUFA in fish diets, especially in marine species. The activation of FA sensing seems to be partially dependent on acyl chain length and degree of saturation, as no major changes were observed after treating fish with SA or EPA. The activation of FA sensing systems by OA and ALA, but not SA or EPA, is further reflected in the expression of hypothalamic neuropeptides involved in the control of food intake. Both OA and ALA enhanced anorexigenic capacity compatible with the activation of FA sensing systems. Copyright © 2015 the American Physiological Society.

Fluorinated polyimides grafted with poly(ethylene glycol) side chains by the RAFT-mediated process and their membranes

International Nuclear Information System (INIS)

Chen Yiwang; Chen Lie; Nie Huarong; Kang, E.T.; Vora, R.H.

2005-01-01

Graft polymerization of poly(ethylene glycol) methyl ether methacrylate (PEGMA) from fluorinated polyimide (FPI) was carried out by the reversible addition-fragmentation chain transfer (RAFT)-mediated process. The peroxides generated by the ozone treatment on FPI facilitated the thermally-initiated graft copolymerization from FPI backbone. The 'living' character of the graft chain growing was ascertained in the subsequent chain extension of PEGMA. Nuclear magnetic resonance (NMR) and molecular weight measurements were used to characterize the chemical composition and structure of the copolymers. Microfiltration (MF) membranes were fabricated from the FPI-g-PEGMA comb copolymers by phase inversion in aqueous media. Surface composition analysis of the membranes scanned by X-ray photoelectron spectroscopy (XPS) revealed a substantial surface enrichment of the hydrophilic components. The pore size distribution of the resulting membranes was found to be much more uniform than that of the corresponding membranes cast from FPI-g-PEGMA prepared by the conventional radical polymerization process in the absence of the chain transfer agent. The morphology of the membranes was characterized by scanning electron microscopy (SEM)

Effect of co-substrate on production of poly-β- hydroxybutyrate (PHB and copolymer PHBV from newly identified mutant Rhodobacter sphaeroides U7 cultivated under aerobic-dark condition

Directory of Open Access Journals (Sweden)

Kemarajt Kemavongse

2007-07-01

Full Text Available Photosynthetic bacterial mutant strain U7 was identified using both classical and molecular (16S rDNA techniques to be Rhodobacter sphaeroides. The glutamate-acetate (GA medium containing sodium acetate and sodium glutamate as carbon and nitrogen sources was used for production of poly-β-hydroxybutyrate (PHB from R. sphaeroides U7 cultivated under aerobic-dark condition (200 rpm at 37oC. Effect of auxiliary carbon sources (propionate and valerate and concentrations (molar ratio of 40/0, 40/20, 40/40 and 40/80 on copolymer production were studied. Both combinations of acetate with valerate and acetate with propionate were found to induce the accumulation of poly-β-hydroxybutyrate-co-β-hydroxyvalerate (PHBV within the cell. Acetate with propionate in the molar ratio of 40/40 gave the highest poly-β-hydroxyalkanoates (PHA content (77.68%, followed by acetate with valerate at the same molar ratio (77.42%. Although their polymer contents were similar, the presence of 40 mM valerate gave more than 4 times higher hydroxyvalerate (HV fraction (84.77% than in the presence of 40 mM propionate (19.12% HV fraction.

Effect of alkyl chain length of imidazolium cations on the electron transport and recombination kinetics in ionic gel electrolytes based quasi-solid-state dye-sensitized solar cells

International Nuclear Information System (INIS)

Huo, Zhipeng; Tao, Li; Wang, Lu; Zhu, Jun; Chen, Shuanghong; Zhang, Changneng; Dai, Songyuan; Zhang, Bing

2015-01-01

Highlights: •A series of novel IGEs based on 12-hydroxystearicacid as LMOG were prepared. •The QS-DSSCs exhibit excellent stability during the accelerated aging tests. •The influence of Im + alkyl chain length on the electron kinetic process is investigated. -- Abstract: A series of stable quasi-solid-state dye-sensitized solar cells (QS-DSSCs) are prepared by the 12-hydroxystearicacid as low molecular mass organogelator (LMOG) to gelate the ionic liquid with different alkyl chain lengths (3, 4, and 7). The influence of alkyl chain length of imidazolium cations (Im + ) on the kinetic processes of electron transport and recombination are investigated by Electrochemical impedance spectroscopy (EIS) and intensity-modulated photocurrent spectroscopy/intensity-modulated photovoltage spectroscopy (IMPS/IMVS). It is found that the ionic gel electrolytes (IGEs) with different alkyl chain lengths of Im + can influence the competitive adsorption effects of imidazolium cations (Im + ) and Li + , and further affect the charge diffusion, the electron recombination/transport processes, the shift of TiO 2 conduction band edge and surface states distribution. The IGE with longer alkyl chain length of Im + can prolong the electron recombination lifetime, promote the incidental photon-to-electron conversion efficiency (IPCE) and the short circuit photocurrent density (J sc ). An excellent QS-DSSC based on the IGE with the longer alkyl chain of Im + gives the highest photoelectric conversion efficiency. Moreover, all the QS-DSSCs based on IGEs exhibit excellent durability without losing their photovoltaic performances during the accelerated thermal and light–soaking test. These results are very important to the researches on the electrochemical mechanism and application of QS-DSSCs based on IGEs

Comparison of immobilized poly-L-aspartic acid and poly-L-glutamic acid for chelation of metal cations

International Nuclear Information System (INIS)

Malachowski, Lisa; Holcombe, James A.

2004-01-01

Poly-L-aspartic acid (PLAsp) and poly-L-glutamic acid (PLGlu) were individually immobilized onto controlled pore glass (CPG) and compared according to their metal-binding capabilities in a solution of pH 7.0. The metal-binding capacities were calculated through the analysis of breakthrough curves generated by monitoring the metal concentrations on a flow injection-flame atomic absorption system. Capacities for individual metals were comparable and in the order of Cu 2+ >> Pb 2+ > Ni 2+ ∼ Cd 2+ > Co 2+ > Mn 2+ >> Na + . Elemental combustion analysis yielded polymer coverage on the CPG of approximately 4 x 10 12 to 5 x 10 12 chains/cm 2 , when average chain lengths were used in the calculations. Formation constants and site capacities of both polymers for Cd 2+ were determined through equilibrium and breakthrough studies. The maximum log K values for the strong sites were determined to be ∼13 for both PLAsp and for PLGlu. Additionally, the metal selectivity of PLAsp and PLGlu was evaluated when breakthrough curves were run with several metals present in solution at one time. Both polymers showed selectivities in the order of their single metal-binding capacities, i.e., Cu 2+ > Pb 2+ > Ni 2+ ∼ Cd 2+ . Both polymers exhibited similar binding trends and binding strengths for all of the metals studied. This likely reflects the absence of a predetermined tertiary structure of the polymers on the surface and the relatively high residue-per-metal ratio (∼20:1), which places less stringent requirements on the steric hindrance between the side chains and the resultant 'wrapping' of the peptide around the metal

The thermal degradation of poly(iso-butyl methacrylate and poly(sec-butyl methacrylate

Directory of Open Access Journals (Sweden)

IVANKA G. POPOVIC

2000-12-01

Full Text Available The non-oxidative thermal degradation of poly(iso-butyl methacrylate and poly(sec-butyl methacrylate was investigated by studying changes in the polymer residue. Due to the different number of b-hydrogens in their ester substituents, these two polymeric isomers behave differently when subjected to elevated temperatures. Poly(iso-butyl methacrylate degrades quantitatively by depolymerisation with zip lengths of the same order of magnitude as those of poly(methyl methacrylate. Poly(sec-butyl methacrylate degrades by a combined degradation mechanism of depolymerisation and de-esterification. De-esterification becomes a significant thermolysis route at temperatures higher than 240°C.

Oriented Poly(dialkylstannane)s

DEFF Research Database (Denmark)

Choffat, Fabien; Fornera, Sara; Smith, Paul

2008-01-01

The inorganic (or 'organometallic') polymers poly(dibutylstannane), poly(dioctylstannane), and poly(didodecylstannane) have been oriented by shear forces, the tensile drawing of blends with polyethylene, and deposition from solution onto glass slides coated with all oriented, friction-deposited p......The inorganic (or 'organometallic') polymers poly(dibutylstannane), poly(dioctylstannane), and poly(didodecylstannane) have been oriented by shear forces, the tensile drawing of blends with polyethylene, and deposition from solution onto glass slides coated with all oriented, friction......-deposited poly(tetrafluoroethylene) (PTFE) layer. Orientation of the polystannanes has been examined by polarization microscopy, UV-vis spectroscopy with polarized light, and X-ray diffraction and their direction is found to depend on the length of the alkyl side groups and the method of orientation. Remarkably...

Manipulating the morphology and textural property of γ-AlOOH by modulating the alkyl chain length of cation in ionic liquid

Energy Technology Data Exchange (ETDEWEB)

Tang, Zhe, E-mail: tangzhe1983@163.com; Hu, Xiaofu, E-mail: hjj19850922@126.cn; Liang, Jilei, E-mail: liang.jilei_ttplan@126.com; Zhao, Jinchong, E-mail: Dr.zhaojc@gmail.com; Liu, Yunqi, E-mail: liuyq@upc.edu.cn; Liu, Chenguang, E-mail: cgliu@upc.edu.cn

2013-06-01

Graphical abstract: - Highlights: • γ-AlOOH was the only product in all experiments. • Different morphology of γ-AlOOH was obtained according to the alkyl chain length. • The textural property of γ-AlOOH was changed according to the alkyl chain length. • The possible formation mechanisms for hollow sphere and microflower were proposed. - Abstract: We demonstrated that the morphology and textural property of γ-AlOOH can be tuned by modulating the alkyl chain length of cation in [C{sub n}mim]{sup +}Cl{sup −} (n = 4, 8, 16). Using the short alkyl chain length-based [C{sub 4}mim]{sup +}Cl{sup −} as the structure-directed reagent, the morphology of γ-AlOOH was not changed and preserved as the hollow sphere structure in all experiments. The specific area and the number of small meso-pores of γ-AlOOH increased with the increase of [C{sub 4}mim]{sup +}Cl{sup −} dosage. While, using the larger alkyl chain length-based ionic liquids as the soft-template, such as [C{sub 8}mim]{sup +}Cl{sup −} and [C{sub 16}mim]{sup +}Cl{sup −}, the morphologies of γ-AlOOH were changed from initiative hollow spheres into the final microflowers. The specific areas of γ-AlOOH firstly increased then decreased with the increase of their dosage. The samples were characterized by X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscope (SEM) and Transmission Electron Microscopy (TEM). Furthermore, the possible formation mechanisms of γ-AlOOH have been proposed.

Conformation of ionizable poly Para phenylene ethynylene in dilute solutions

International Nuclear Information System (INIS)

Wijesinghe, Sidath; Maskey, Sabina; Perahia, Dvora; Grest, Gary S.

2015-01-01

The conformation of dinonyl poly para phenylene ethynylenes (PPEs) with carboxylate side chains, equilibrated in solvents of different quality is studied using molecular dynamics simulations. PPEs are of interest because of their tunable electro-optical properties, chemical diversity, and functionality which are essential in wide range of applications. The polymer conformation determines the conjugation length and their assembly mode and affects electro-optical properties which are critical in their current and potential uses. The current study investigates the effect of carboxylate fraction on PPEs side chains on the conformation of chains in the dilute limit, in solvents of different quality. The dinonyl PPE chains are modeled atomistically, where the solvents are modeled both implicitly and explicitly. Dinonyl PPEs maintained a stretched out conformation up to a carboxylate fraction f of 0.7 in all solvents studied. The nonyl side chains are extended and oriented away from the PPE backbone in toluene and in implicit good solvent whereas in water and implicit poor solvent, the nonyl side chains are collapsed towards the PPE backbone. Thus, rotation around the aromatic ring is fast and no long range correlations are seen within the backbone

The color tuning of PS-b-P2VP lamellar films with changing the alkyl chain length of 1-iodoalkanes.

Science.gov (United States)

Shin, Sung-Eui; Kim, Su-Young; Shin, Dong-Myung

2011-05-01

Photonic crystals with tunability in the visible or near-infrared region have drawn increasing attention for controlling and processing light for the active components of future display. We prepared polystyrene-b-poly(2-vinyl pyridine) (PS-b-P2VP) lamellar films which is hydrophobic block-hydrophilic polyelectrolyte block polymer of 57 kg/mol-b-57 kg/mol. The lamellar stacks, which is alternating layer of hydrophilic and hydrophobic moiety of PS-b-P2VP, are obtained by exposing the spin coated film under chloroform vapor. The band gaps of the lamellar films interestingly varied after immersion into the quaternizing solvents containing 5 wt% of iodomethane, iodoethane, 1-iodobutane, 1-iodopentane, 1-iodohexane and 1-iodooctane solubilized in n-hexane. The iodoalkanes reacted with pyridine groups in PS-b-P2VP and generated the alkyl pyridinium salts readily. The degree of quaternization, alkyl chain length of iodoalkane and the salt water concentration affects the spacing of layer structure of PS-b-P2VP. The iodomethane and iodohexane produced similar band gaps and salt concentration dependence. These results are very much dependent on the hydrophobic-hydrophilic characters of PS-b-P2VP lamellar surface.

Molar mass fractionation in aqueous two-phase polymer solutions of dextran and poly(ethylene glycol).

Science.gov (United States)

Zhao, Ziliang; Li, Qi; Ji, Xiangling; Dimova, Rumiana; Lipowsky, Reinhard; Liu, Yonggang

2016-06-24

Dextran and poly(ethylene glycol) (PEG) in phase separated aqueous two-phase systems (ATPSs) of these two polymers, with a broad molar mass distribution for dextran and a narrow molar mass distribution for PEG, were separated and quantified by gel permeation chromatography (GPC). Tie lines constructed by GPC method are in excellent agreement with those established by the previously reported approach based on density measurements of the phases. The fractionation of dextran during phase separation of ATPS leads to the redistribution of dextran of different chain lengths between the two phases. The degree of fractionation for dextran decays exponentially as a function of chain length. The average separation parameters, for both dextran and PEG, show a crossover from mean field behavior to Ising model behavior, as the critical point is approached. Copyright © 2016 Elsevier B.V. All rights reserved.

SAN-b-P4VP block copolymer synthesis by chain extension from RAFT-functional poly(4-vinylpyridine) in solution and in emulsion

NARCIS (Netherlands)

Bozovic, J.S.; Tello Manon, H.M; Meuldijk, J.; Koning, C.E.; Klumperman, B.

2007-01-01

Reversible addition fragmentation chain transfer (RAFT)-mediated polymerization was successfully applied for the synthesis of poly(4-vinylpyridine) (P4VP) polymers of predetermined molar mass and of low polydispersity index. These RAFT end-functionalized polymers were then used as macro-RAFT agents

Expression of full-length and splice forms of FoxP3 in rheumatoid arthritis

DEFF Research Database (Denmark)

Ryder, L R; Woetmann, A; Madsen, H O

2010-01-01

OBJECTIVE: The aim of our study was to compare the presence of full-length and alternative splice forms of FoxP3 mRNA in CD4 cells from rheumatoid arthritis (RA) patients and healthy controls. METHODS: A quantitative real-time polymerase chain reaction (QRT-PCR) method was used to measure...... the amount of FoxP3 mRNA full-length and splice forms. CD4-positive T cells were isolated from peripheral blood from 50 RA patients by immunomagnetic separation, and the FoxP3 mRNA expression was compared with the results from 10 healthy controls. RESULTS: We observed an increased expression of full......-length FoxP3 mRNA in RA patients when compared to healthy controls, as well as an increase in CD25 mRNA expression, but no corresponding increase in CTLA-4 mRNA expression. The presence of an alternative splice form of FoxP3 lacking exon 2 was confirmed in both RA patients and healthy controls...

Impact of the alkyl chain length on binding of imidazolium-based ionic liquids to bovine serum albumin

Science.gov (United States)

Zhang, Mengyue; Wang, Ying; Zhang, Hongmei; Cao, Jian; Fei, Zhenghao; Wang, Yanqing

2018-05-01

The effects of six imidazolium-based ionic liquids (ILs) with different alkyl chain length ([CnMim]Cl, n = 2, 4, 6, 8, 10, 12) on the structure and functions of bovine serum albumin (BSA) were studied by multi-spectral methods and molecular docking. ILs with the longer alkyl chain length have the stronger binding interaction with BSA and the greater conformational damage to protein. The effects of ILs on the functional properties of BSA were further studied by the determination of non-enzyme esterase activity, β-fibrosis and other properties of BSA. The thermal stability of BSA was reduced, the rate of the formation of beta sheet structures of BSA was lowered, and the esterase-like activity of BSA were decreased with the increase of ILs concentration. Simultaneous molecular modeling technique revealed the favorable binding sites of ILs on protein. The hydrophobic force and polar interactions were the mainly binding forces of them. The calculated results are in a good agreement with the spectroscopic experiments. These studies on the impact of the alkyl chain length on binding of imidazolium-based ionic liquids to BSA are of great significance for understanding and developing the application of ionic liquid in life and physiological system.

Liposomes coated with hydrophobically modified hydroxyethyl cellulose: Influence of hydrophobic chain length and degree of modification.

Science.gov (United States)

Smistad, Gro; Nyström, Bo; Zhu, Kaizheng; Grønvold, Marthe Karoline; Røv-Johnsen, Anne; Hiorth, Marianne

2017-08-01

Nanoparticulate systems with an uncharged hydrophilic surface may have a great potential in mucosal drug delivery. In the present study liposomes were coated with hydrophobically modified hydroxyethyl cellulose (HM-HEC) to create a sterically stabilized liposomal system with an uncharged surface. The aim was to clarify the influence of the amount of hydrophobic modification of HEC and the length of the hydrophobic moiety, on the stability of the system and on the release properties. HM-HEC with different degrees of hydrophobic modification (1 and 2mol%) and hydrophobic groups with different chain lengths (C8, C12, C16) were included in the study, as well as fluid phase and gel phase liposomes. Both types of liposomes were successfully coated with HM-HEC containing 1mol% of hydrophobic groups, while 2mol% did not work for the intended pharmaceutical applications. The polymer coated gel phase liposomes were stable (size, zeta potential, leakage) for 24 weeks at 4°C, with no differences between the C8 and C16 HM-HEC coating. For the fluid phase liposomes a size increase was observed after 24 weeks at 4°C for all formulations; the C8 HM-HEC coated liposomes increased the most. No differences in the leakage during storage at 4°C or in the release at 35°C were observed between the fluid phase formulations. To conclude; HM-HEC with a shorter hydrophobic chain length resulted in a less stable product for the fluid phase liposomes, while no influence of the chain length was observed for the gel phase liposomes (1mol% HM). Copyright © 2017 Elsevier B.V. All rights reserved.

Molecular dynamics simulation of radiation grafted FEP films as proton exchange membranes: Effects of the side chain length

DEFF Research Database (Denmark)

Li, Xue; Zhao, Yang; Li, Weiwei

2017-01-01

In order to study the microstructure of the prepared potential proton exchange membrane (PEM), molecular dynamics (MD) simulations were used to lucubrate the transport behavior of water molecules and hydronium ions inside the hydrated sulfonated styrene grafted fluorinated ethylene propylene (FEP...... whereas larger water clusters formed. The results of the mean square displacements (MSDs) show that the proton conductivities of the membranes with the proposed side chain lengths were about three fifths of the experimental data, of which the membrane with side chain length of 7 sulfonic styrene units...... was supposed to exhibit the highest proton conductivity, that is 115.69 mS cm-1. All of the supposed membrane models presented good proton conductivity that could definitely meet the application requirements of the proton exchange membranes. The MD simulations can provide an insight to the chain structure...

Effects of cloud-point grafting, chain length, and density of PEG layers on competitive adsorption of ocular proteins

DEFF Research Database (Denmark)

Kingshott, P.; Thissen, H.; Griesser, H.J.

2002-01-01

The effects of pinning density, chain length, and 'cloud point' (CP) versus non-CP grafting conditions have been studied on the ability of polyethylene glycol (PEG) layers to minimize adsorption from a multicomponent (lysozyme, human serum albumin (HSA), IgG and lactoferrin) protein solution...... density) r.f.g.d. polymer layers. The PEG graft density was varied also by increasing the temperature and salt (K2SO4) content of the grafting solution; it reached a maximum at the CP of the PEGs. The CP reaction conditions were critical for producing PEG layers capable of minimizing protein adsorption. X...... density and chain length are interrelated, but the key factor is optimization of PEG chain density by use of the CP conditions, provided that a sufficient density of pinning sites exists. (C) 2002 Elsevier Science Ltd. Al l rights reserved....

Long-Chain Diacrylate Crosslinkers and Use of PEG Crosslinks in Poly(potassium acrylate-acrylic acid)/Kaolin Composite Superabsorbents

OpenAIRE

Koroush Kabiri; Siavash Nafisi; Mohammad jalaledin Zohuriaan-Mehr; Ali Akbar Yousefi

2013-01-01

Long-chain diacrylate crosslinkers based on linear α,ω-diols were synthesized and characterized using FTIR and 1H NMR spectroscopy. The highest reaction yield (99.5%) was due to polyethylene glycol diacrylate 1000 (PEGDA-1000). Then, kaolin-containing poly(potassium acrylate-acrylic acid) superabsorbent composites and kaolin-free counterparts were synthesized using PEGDA-1000.The effect of the crosslinker concentration on swelling, rheological and thermo-mechanical properties was investigated...

Phase behaviour of an ionic microemulsion system as a function of the cosurfactant chain length

NARCIS (Netherlands)

Kegel, W.K.; Lekkerkerker, H.N.W.

1993-01-01

The phase behaviour of a microemulsion system consisting of equal volumes of brine and oil, sodium dodecyl sulphate (SDS) as surfactant and alcohols of different chain lengths (pentanol, hexanol and heptanol) as cosurfactant was studied. In the case of pentanol, at low surfactant concentrations and

Controlled Release of Damascone from Poly(styrene-co-maleic anhydride-based Bioconjugates in Functional Perfumery

Directory of Open Access Journals (Sweden)

Andreas Herrmann

2013-02-01

Full Text Available Poly(styrene-co-maleic anhydrides were modified with poly(propylene oxide (PO-co-ethylene oxide (EO side chains (Jeffamine® with different EO/PO molar ratios, varying between 0.11 and 3.60. These copolymers were then further functionalized with a β-mercapto ketone of δ-damascone. The obtained poly(maleic acid monoamide-based β-mercapto ketones were then studied as delivery systems for the controlled release of δ-damascone by retro 1,4-addition. The release of δ-damascone, a volatile, bioactive molecule of the family of rose ketones, was studied by dynamic headspace analysis above a cotton surface after deposition of a cationic surfactant containing fabric softening formulation, as a function of the ethylene oxide (EO/propylene oxide (PO molar ratio of the grafted copolymer side chains. The polarity of the EO/PO side chain influenced the release efficiency of the damascone in a typical fabric softening application. PO-rich copolymers and the corresponding poly(styrene-co-maleic anhydride without Jeffamine® side chains were found to be less efficient for the desired fragrance release than the corresponding bioconjugate with a EO/PO ratio of 3.60 in the side chain. This copolymer conjugate seemed to represent a suitable balance between hydrophilicity and hydrophobicity to favor the release of the δ-damascone and to improve the deposition of the conjugate from an aqueous environment onto a cotton surface.

ESR and X-ray diffraction studies on thin films of poly-3-hexylthiophene: Molecular orientation and magnetic interactions

International Nuclear Information System (INIS)

Sugiyama, Keisuke; Kojima, Takashi; Fukuda, Hisashi; Yashiro, Hisashi; Matsuura, Toshihiko; Shimoyama, Yuhei

2008-01-01

Poly-3-hexylthiophene (P3HT) thin films were investigated by X-ray diffraction (XRD) and electron spin resonance (ESR) to reveal the film structure and molecular organization. The XRD data showed a diffraction pattern with a plane separation between the planes containing thiophene rings of 16.0 A. Comparison between the XRD patterns of powder and thin films of P3HT suggests that the main chains are folded on the substrate. Angular variation of the line position (g-value) of ESR spectra revealed that thiophene ring of P3HT orients along the substrate normal axis. The ESR linewidth varied by the angular rotation, indicating the one-dimensional spin-chain interactions in the P3HT thin films with a linear network of spin-chains. An organic thin-film transistor (OTFT) with P3HT film as a channel layer was then demonstrated. The P3HT films showed conducting characteristics with holes as carriers. The OTFTs indicated a field-effect mobility of 4.93 x 10 -3 cm 2 /Vs and an on/off ratio of 73 in the accumulation mode

Incipient microphase separation in short chain perfluoropolyether-block-poly(ethylene oxide) copolymers.

Science.gov (United States)

Chintapalli, Mahati; Timachova, Ksenia; Olson, Kevin R; Banaszak, Michał; Thelen, Jacob L; Mecham, Sue J; DeSimone, Joseph M; Balsara, Nitash P

2017-06-07

Incipient microphase separation is observed by wide angle X-ray scattering (WAXS) in short chain multiblock copolymers consisting of perfluoropolyether (PFPE) and poly(ethylene oxide) (PEO) segments. Two PFPE-PEO block copolymers were studied; one with dihydroxyl end groups and one with dimethyl carbonate end groups. Despite having a low degree of polymerization (N ∼ 10), these materials exhibited significant scattering intensity, due to disordered concentration fluctuations between their PFPE-rich and PEO-rich domains. The disordered scattering intensity was fit to a model based on a multicomponent random phase approximation to determine the value of the interaction parameter, χ, and the radius of gyration, R g . Over the temperature range 30-90 °C, the values of χ were determined to be very large (∼2-2.5), indicating a high degree of immiscibility between the PFPE and PEO blocks. In PFPE-PEO, due to the large electron density contrast between the fluorinated and non-fluorinated block and the high value of χ, disordered scattering was detected at intermediate scattering angles, (q ∼ 2 nm -1 ) for relatively small polymer chains. Our ability to detect concentration fluctuations was enabled by both a relatively large value of χ and significant scattering contrast.

A temperature-dependent coarse-grained model for the thermoresponsive polymer poly(N-isopropylacrylamide)

International Nuclear Information System (INIS)

Abbott, Lauren J.; Stevens, Mark J.

2015-01-01

In this study, a coarse-grained (CG) model is developed for the thermoresponsive polymer poly(N-isopropylacrylamide) (PNIPAM), using a hybrid top-down and bottom-up approach. Nonbonded parameters are fit to experimental thermodynamic data following the procedures of the SDK (Shinoda, DeVane, and Klein) CG force field, with minor adjustments to provide better agreement with radial distribution functions from atomistic simulations. Bonded parameters are fit to probability distributions from atomistic simulations using multi-centered Gaussian-based potentials. The temperature-dependent potentials derived for the PNIPAM CG model in this work properly capture the coil-globule transition of PNIPAM single chains and yield a chain-length dependence consistent with atomistic simulations

Dependence of micelle size and shape on detergent alkyl chain length and head group.

Directory of Open Access Journals (Sweden)

Ryan C Oliver

Full Text Available Micelle-forming detergents provide an amphipathic environment that can mimic lipid bilayers and are important tools for solubilizing membrane proteins for functional and structural investigations in vitro. However, the formation of a soluble protein-detergent complex (PDC currently relies on empirical screening of detergents, and a stable and functional PDC is often not obtained. To provide a foundation for systematic comparisons between the properties of the detergent micelle and the resulting PDC, a comprehensive set of detergents commonly used for membrane protein studies are systematically investigated. Using small-angle X-ray scattering (SAXS, micelle shapes and sizes are determined for phosphocholines with 10, 12, and 14 alkyl carbons, glucosides with 8, 9, and 10 alkyl carbons, maltosides with 8, 10, and 12 alkyl carbons, and lysophosphatidyl glycerols with 14 and 16 alkyl carbons. The SAXS profiles are well described by two-component ellipsoid models, with an electron rich outer shell corresponding to the detergent head groups and a less electron dense hydrophobic core composed of the alkyl chains. The minor axis of the elliptical micelle core from these models is constrained by the length of the alkyl chain, and increases by 1.2-1.5 Å per carbon addition to the alkyl chain. The major elliptical axis also increases with chain length; however, the ellipticity remains approximately constant for each detergent series. In addition, the aggregation number of these detergents increases by ∼16 monomers per micelle for each alkyl carbon added. The data provide a comprehensive view of the determinants of micelle shape and size and provide a baseline for correlating micelle properties with protein-detergent interactions.

Fatty acid biosynthesis VII. Substrate control of chain-length of products synthesised by rat liver fatty acid synthetase

DEFF Research Database (Denmark)

Hansen, Heinz Johs. Max; Carey, E.M.; Dils, R.

1970-01-01

- 1. Gas-liquid and paper chromatography have been used to determine the chain-lengths of fatty acids synthesised by purified rat liver fatty acid synthetase from [1-14C]acetyl-CoA, [1,3-14C2]malonyl-CoA and from [1-14C]acetyl-CoA plus partially purified rat liver acetyl-CoA carboxylase. - 2....... A wide range (C4:0–C18:0) of fatty acids was synthesised and the proportions were modified by substrate concentrations in the same manner as for purified rabbit mammary gland fatty acid synthetase. - 3. The relative amount of radioactivity incorporated from added acetyl-CoA and malonyl-CoA depended...... of long-chain fatty acids was synthesised from carboxylated acetyl-CoA than from added malonyl-CoA. - 5. It is suggested that acetyl-CoA carboxylase may carboxylate acetate bound to fatty acid synthetase....

Enhanced alpha-galactosidase expression in pseudomonas chlororaphis

Science.gov (United States)

Pseudomonas chlororaphis is a non-pathogenic bacterium useful for fermentative production of biopolymer (i.e., poly(hydroxyalkanoates); PHA) and biosurfactant (i.e., rhamnolipid; RhL). In order to enable P. chlororaphis to better fermentatively utilize the residual soy sugars in soy molasses – a lo...

Productivity, disturbance and ecosystem size have no influence on food chain length in seasonally connected rivers.

Science.gov (United States)

Warfe, Danielle M; Jardine, Timothy D; Pettit, Neil E; Hamilton, Stephen K; Pusey, Bradley J; Bunn, Stuart E; Davies, Peter M; Douglas, Michael M

2013-01-01

The food web is one of the oldest and most central organising concepts in ecology and for decades, food chain length has been hypothesised to be controlled by productivity, disturbance, and/or ecosystem size; each of which may be mediated by the functional trophic role of the top predator. We characterised aquatic food webs using carbon and nitrogen stable isotopes from 66 river and floodplain sites across the wet-dry tropics of northern Australia to determine the relative importance of productivity (indicated by nutrient concentrations), disturbance (indicated by hydrological isolation) and ecosystem size, and how they may be affected by food web architecture. We show that variation in food chain length was unrelated to these classic environmental determinants, and unrelated to the trophic role of the top predator. This finding is a striking exception to the literature and is the first published example of food chain length being unaffected by any of these determinants. We suggest the distinctive seasonal hydrology of northern Australia allows the movement of fish predators, linking isolated food webs and potentially creating a regional food web that overrides local effects of productivity, disturbance and ecosystem size. This finding supports ecological theory suggesting that mobile consumers promote more stable food webs. It also illustrates how food webs, and energy transfer, may function in the absence of the human modifications to landscape hydrological connectivity that are ubiquitous in more populated regions.

Productivity, disturbance and ecosystem size have no influence on food chain length in seasonally connected rivers.

Directory of Open Access Journals (Sweden)

Danielle M Warfe

Full Text Available The food web is one of the oldest and most central organising concepts in ecology and for decades, food chain length has been hypothesised to be controlled by productivity, disturbance, and/or ecosystem size; each of which may be mediated by the functional trophic role of the top predator. We characterised aquatic food webs using carbon and nitrogen stable isotopes from 66 river and floodplain sites across the wet-dry tropics of northern Australia to determine the relative importance of productivity (indicated by nutrient concentrations, disturbance (indicated by hydrological isolation and ecosystem size, and how they may be affected by food web architecture. We show that variation in food chain length was unrelated to these classic environmental determinants, and unrelated to the trophic role of the top predator. This finding is a striking exception to the literature and is the first published example of food chain length being unaffected by any of these determinants. We suggest the distinctive seasonal hydrology of northern Australia allows the movement of fish predators, linking isolated food webs and potentially creating a regional food web that overrides local effects of productivity, disturbance and ecosystem size. This finding supports ecological theory suggesting that mobile consumers promote more stable food webs. It also illustrates how food webs, and energy transfer, may function in the absence of the human modifications to landscape hydrological connectivity that are ubiquitous in more populated regions.

Phase Behavior and Evaporation Profile of Tween 20 - Eugenol System. Effect of Different Alkane Chain Length and Solvent System

International Nuclear Information System (INIS)

Kassim, A.; Lim, W.H.; Kuangl, D.; Rusmawati, W.W.M.; Abdullah, A.H.; Teoh, S.P.

2003-01-01

The isotropic region of Tween 20/eugenol/n-alkane in aqueous systems was determined. The solubilisation trend of isotropic solution formed in the presence of eugenol was studied as a function of different alkyl chain length of n-alkane. The solubility of solvent in surfactant solution is dependent on their molecular polarity. An increase in n-alkane chain length (lower polarity) lead to smaller isotropic region which will affect the surfactant partitioning between the interface, the oil phase and the aqueous phase of the microemulsion as the oil chain length is varied. The changes of evaporation behaviour were affected strongly by the types of phases existed in the systems. The increment of n-alkane and water content led to higher evaporation rate. But the formation of w/o microemulsion would lower the evaporation rate because water molecules were trapped in the core of aggregates. In solubilisation system, evaporation rate is dependent on the solvent content and the interaction between Tween 20 and solvent molecules in the mixed composition. (author)

Large electrically induced height and volume changes in poly(3,4- ethylenedioxythiophene) /poly(styrenesulfonate) thin films

NARCIS (Netherlands)

Charrier, D.S.H.; Janssen, R.A.J.; Kemerink, M.

2010-01-01

We demonstrate large, partly reversible height and volume changes of thin films of poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS) on the anode of interdigitating gold electrodes under ambient conditions by applying an electrical bias. The height and volume changes were monitored

Pseudomonas aeruginosa cytochrome c551 denaturation by five systematic urea derivatives that differ in the alkyl chain length.

Science.gov (United States)

Kobayashi, Shinya; Fujii, Sotaro; Koga, Aya; Wakai, Satoshi; Matubayasi, Nobuyuki; Sambongi, Yoshihiro

2017-07-01

Reversible denaturation of Pseudomonas aeruginosa cytochrome c 551 (PAc 551 ) could be followed using five systematic urea derivatives that differ in the alkyl chain length, i.e. urea, N-methylurea (MU), N-ethylurea (EU), N-propylurea (PU), and N-butylurea (BU). The BU concentration was the lowest required for the PAc 551 denaturation, those of PU, EU, MU, and urea being gradually higher. Furthermore, the accessible surface area difference upon PAc 551 denaturation caused by BU was found to be the highest, those by PU, EU, MU, and urea being gradually lower. These findings indicate that urea derivatives with longer alkyl chains are stronger denaturants. In this study, as many as five systematic urea derivatives could be applied for the reversible denaturation of a single protein, PAc 551 , for the first time, and the effects of the alkyl chain length on protein denaturation were systematically verified by means of thermodynamic parameters.

Preparation of poly (styrene)-b-poly (acrylic acid)/{gamma}-Fe{sub 2}O{sub 3} composites

Energy Technology Data Exchange (ETDEWEB)

Zhang, L.D. [School of Materials Science and Engineering, Shandong Polytechnic University, Key Laboratory of Processing and Testing Technology of Glass Functional Ceramics of Shandong Province, Daxue Road, Western University Science Park, Jinan 250353 (China); Liu, W.L., E-mail: wlliu@sdu.edu.cn [School of Materials Science and Engineering, Shandong Polytechnic University, Key Laboratory of Processing and Testing Technology of Glass Functional Ceramics of Shandong Province, Daxue Road, Western University Science Park, Jinan 250353 (China); Xiao, C.L.; Yao, J.S.; Fan, Z.P.; Sun, X.L.; Zhang, X.; Wang, L. [School of Materials Science and Engineering, Shandong Polytechnic University, Key Laboratory of Processing and Testing Technology of Glass Functional Ceramics of Shandong Province, Daxue Road, Western University Science Park, Jinan 250353 (China); Wang, X.Q. [State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 (China)

2011-12-15

The use of a block copolymer, poly (styrene)-b-poly (acrylic acid) (PS-b-PAA) to prepare a magnetic nanocomposite was investigated. Poly (styrene)-poly (t-butyl acrylate) block copolymer, being synthesized by atom transfer radical polymerization, was hydrolyzed with hydrochloric acid for obtaining PS-b-PAA. The obtained PS-b-PAA was then compounded with the modified {gamma}-Fe{sub 2}O{sub 3}, and subsequently the magnetic nanocomposite was achieved. The products were characterized by {sup 1}H NMR, FTIR, gel permeation chromatography, thermogravimetric analysis, transmission electron microscopy and vibrating sample magnetometer. The results showed that the nanocomposites exhibited soft magnetism, with the mean diameter of 100 nm approximately. - Highlights: > Magnetic composites were prepared using {gamma}-Fe{sub 2}O{sub 3} and PS-b-PAA. > PS-b-PAA was synthesized by atom transfer radical polymerization. > The obtained composite exhibited soft magnetism.

Soliton scatterings by impurities in a short-length sine-Gordon chain

International Nuclear Information System (INIS)

Dikande, A.M.; Kofane, T.C.

1995-07-01

The scattering of soliton by impurities at the frontiers of a finite-length region of an infinite sine-Gordon chain is analyzed. The impurities consist of two isotopic inhomogeneities installed at the boundaries of the finite-length region. The soliton solution in the region is found in term of snoidal sine-Gordon soliton which properly takes into account the effects of the boundaries. By contrast, the soliton solutions in the neighboring sides of the region are obtained in terms of the so-called large-amplitude, localized kinks with limiting spatial extensions at x → ± ∞, which is equal ±π. Using the continuity of these soliton solutions at the frontiers as well as appropriate boundary conditions, it is shown that the soliton may be either i) reflected by the incident impurity; ii) trapped (with oscillating motions) between the two impurities (i.e. inside the infinite region); or iii) transmitted by the second impurity into the third, infinitely extended region. The threshold velocities for the reflection and transmission into different regions are found and shown to vary exponentially as a function of the length of the bounded region. The frequency of soliton oscillations between the impurities has also been calculated in some acceptable limit. (author). 28 refs, 1 fig

Thermal stability of poly(3-hydroxybutyrate)/vegetable fiber composites

Science.gov (United States)

Cipriano, Pâmela Bento; de Sá, Mayelli Dantas; Andrade, André L. Simões; de Carvalho, Laura Hecker; Canedo, Eduardo Luis

2015-05-01

The present work deals with the thermal stability during and after processing of composites of poly(3-hydroxybutyrate) (PHB) - a fully biodegradable semi-crystalline thermoplastic obtained from renewable resources through low-impact biotechnological process, biocompatible and non-toxic - and vegetable fiber from the fruit (coconut) of babassu palm tree. PHB/babassu composites with 0, 5, 10 and 20% w/w load were prepared in a laboratory internal mixer. Two fractions of the mesocarp of babassu with different particle sizes were compounded with PHB and test specimens molded by compression. The effect of loading level and processing conditions on torque, temperature and mechanical energy dissipation were studied using a new engineering model. It was found that PHB degrades during processing at temperatures slightly above the melting point. To minimize thermal degradation stabilizer and chain extender additives were incorporated, with mixed results. These findings were confirmed by the dependence of the melt flow rate on the processing temperature.

3D scaffolds from vertically aligned carbon nanotubes/poly(methyl methacrylate) composites via atom transfer radical polymerization

Energy Technology Data Exchange (ETDEWEB)

Tebikachew, Behabtu; Magina, Sandra [CICECO, Department of Chemistry, University of Aveiro (Portugal); Mata, Diogo; Oliveira, Filipe J.; Silva, Rui F. [CICECO, Department of Materials and Ceramic Engineering, University of Aveiro (Portugal); Barros-Timmons, Ana, E-mail: anabarros@ua.pt [CICECO, Department of Chemistry, University of Aveiro (Portugal)

2015-01-15

Vertically aligned carbon nanotubes (VACNTs) synthesized by Thermal Chemical Vapour Deposition (TCVD) were modified using an Ar:O{sub 2} (97:3) plasma to generate oxygen-containing functional groups on the surface for subsequent modification. X-ray photo-emission spectroscopy (XPS) and micro-Raman analyses confirmed the grafting of those functional groups onto the surface of the nanotubes as well as the removal of amorphous carbon produced and deposited on the VACNT forests during the CVD process. The plasma treated VACNT forests were further modified with 2-bromo-2-methylpropionyl bromide, an atom transfer radical polymerization (ATRP) initiator, to grow poly(methyl methacrylate) (PMMA) chains from the forests via ATRP. Scanning transmission electron microscopy (STEM) of the ensuing VACNT/PMMA composites confirmed the coating of the nanotube forests with the PMMA polymer. 3D scaffolds of polymeric composites with honeycomb like structure were then obtained. Compressive tests have shown that the VACNT/PMMA composite has higher compressive strength than the pristine forest. - Highlights: • Vertically aligned carbon nanotubes (VACNTs) were synthesized and plasma modified. • X-ray photo-emission and Raman spectroscopies confirmed the VACNTs modification. • Poly(methyl methacrylate) chains were grown via ATRP from the VACNTs. • STEM of the VACNT/PMMA composites confirmed that PMMA surrounds the nanotubes. • VACNT/PMMA composite has higher compressive strength compared to the pristine forest.

3D scaffolds from vertically aligned carbon nanotubes/poly(methyl methacrylate) composites via atom transfer radical polymerization

International Nuclear Information System (INIS)

Tebikachew, Behabtu; Magina, Sandra; Mata, Diogo; Oliveira, Filipe J.; Silva, Rui F.; Barros-Timmons, Ana

2015-01-01

Vertically aligned carbon nanotubes (VACNTs) synthesized by Thermal Chemical Vapour Deposition (TCVD) were modified using an Ar:O 2 (97:3) plasma to generate oxygen-containing functional groups on the surface for subsequent modification. X-ray photo-emission spectroscopy (XPS) and micro-Raman analyses confirmed the grafting of those functional groups onto the surface of the nanotubes as well as the removal of amorphous carbon produced and deposited on the VACNT forests during the CVD process. The plasma treated VACNT forests were further modified with 2-bromo-2-methylpropionyl bromide, an atom transfer radical polymerization (ATRP) initiator, to grow poly(methyl methacrylate) (PMMA) chains from the forests via ATRP. Scanning transmission electron microscopy (STEM) of the ensuing VACNT/PMMA composites confirmed the coating of the nanotube forests with the PMMA polymer. 3D scaffolds of polymeric composites with honeycomb like structure were then obtained. Compressive tests have shown that the VACNT/PMMA composite has higher compressive strength than the pristine forest. - Highlights: • Vertically aligned carbon nanotubes (VACNTs) were synthesized and plasma modified. • X-ray photo-emission and Raman spectroscopies confirmed the VACNTs modification. • Poly(methyl methacrylate) chains were grown via ATRP from the VACNTs. • STEM of the VACNT/PMMA composites confirmed that PMMA surrounds the nanotubes. • VACNT/PMMA composite has higher compressive strength compared to the pristine forest

pEVL: A Linear Plasmid for Generating mRNA IVT Templates With Extended Encoded Poly(A Sequences

Directory of Open Access Journals (Sweden)

Alexandra E Grier

2016-01-01

Full Text Available Increasing demand for large-scale synthesis of in vitro transcribed (IVT mRNA is being driven by the increasing use of mRNA for transient gene expression in cell engineering and therapeutic applications. An important determinant of IVT mRNA potency is the 3′ polyadenosine (poly(A tail, the length of which correlates with translational efficiency. However, present methods for generation of IVT mRNA rely on templates derived from circular plasmids or PCR products, in which homopolymeric tracts are unstable, thus limiting encoded poly(A tail lengths to ≃120 base pairs (bp. Here, we have developed a novel method for generation of extended poly(A tracts using a previously described linear plasmid system, pJazz. We find that linear plasmids can successfully propagate poly(A tracts up to ≃500 bp in length for IVT mRNA production. We then modified pJazz by removing extraneous restriction sites, adding a T7 promoter sequence upstream from an extended multiple cloning site, and adding a unique type-IIS restriction site downstream from the encoded poly(A tract to facilitate generation of IVT mRNA with precisely defined encoded poly(A tracts and 3′ termini. The resulting plasmid, designated pEVL, can be used to generate IVT mRNA with consistent defined lengths and terminal residue(s.

Glycolysis of poly(3-hydroxybutyrate) via enzyme catalysis; Glicolise do poli(3-hidroxibutirato) por via enzimatica

Energy Technology Data Exchange (ETDEWEB)

Paula, Everton Luiz de, E-mail: everton2804@gmail.com [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Departamento de Quimica; Campos, Tiago Ferreira; Mano, Valdir [Universidade Federal de Sao Joao del-Rei (UFSJ), MG (Brazil). Departamento de Ciencias Naturais

2014-05-15

Poly(3-hydroxybutyrate), PHB, is a polymer with broad potential applications because of its biodegradability and biocompatibility. However, its high crystallinity is a limiting factor for many applications. To overcome this drawback, one strategy currently employed involves the reduction of the molecular weight of PHB with the concomitant formation of end-functionalized chains, such as those obtained via glycolysis. The glycolysis of PHB can be catalyzed by acid, base, or organometallic compounds. However, to our knowledge, there are no reports regarding PHB glycolysis catalyzed enzymatically. Among the major types of enzymes used in biocatalysis, the lipases stand out because they have the ability to catalyze reactions in both aqueous and organic media. Thus, in this study, we performed the enzymatic glycolysis of PHB using the lipase Amano PS (Pseudomonas cepacia) with ethane-1,2-diol (ethylene glycol) as the functionalizing agent. The results indicated that the glycolysis was successful and afforded hydroxyl-terminated oligomeric PHB polyols. Nuclear magnetic resonance spectra of the products showed characteristic signals for the terminal hydroxyl groups of the polyols, while thermogravimetric and differential scanning calorimetry analyses confirmed an increase in the thermal stability and a decrease in the crystallinity of the polyols compared with the starting PHB polymer, which were both attributed to the reduction in the molecular weight due to glycolysis. (author)

The effect of chain length and lipid phase transitions on the selective permeability properties of liposomes

NARCIS (Netherlands)

Blok, M.C.; Neut-Kok, E.C.M. van der; Deenen, L.L.M. van; Gier, J. de

1975-01-01

This paper describes experiments showing the importance of the fatty acid chain length on the barrier properties of liposomal bilayers, prepared from saturated lecithins, under conditions of lateral phase separation. 1. 1.|Above the gel to liquid crystalline phase transition temperature,

Modification of eucalyptus pulp fiber using silane coupling agents with aliphatic side chains of different length

Science.gov (United States)

The objective of this work was to evaluate the effect of three silane coupling agents with different aliphatic chain lengths on the hydrophobicity of eucalyptus pulp fiber. The three silanes coupling agents used (isobutyltrimethoxysilane, methyltrimethoxysilane, and n-octyltriethoxysilane [OTES]) we...

Effect of Chain Length Compatibility of Alcohols on Muscovite Flotation by Dodecyl Amine

Directory of Open Access Journals (Sweden)

Li Wang

2018-04-01

Full Text Available A portion of dodecyl amine (DDA in a muscovite flotation system was replaced with alcohols with different carbon-chain lengths. These alcohols included octanol (OCT; decanol (DEC; dodecanol (DOD; and tetradecanol (TER. The muscovite adsorption behavior of the mixed DDA and alcohol systems were investigated through zeta potential; contact angle; and adsorption quantity tests. Single-mineral flotation tests showed that the muscovite-collecting power of the mixed DDA/alcohol (OCT, DEC, or DOD system was stronger than that of the pure DDA system. The muscovite-collecting power of the collector systems decreased in the following order: DDA/DEC > DDA/OCT > DDA/DEC > DDA > DDA/TER. Zeta potential and contact angle analysis indicated that when combined with DDA; alcohols physically adsorbed on the surfaces of muscovite. This behavior improved the hydrophobicity of muscovite. Furthermore, adsorption analysis revealed that synergy between DDA and alcohol enhanced the adsorption of alcohol on muscovite. DDA has a dominant role in synergistic adsorption; whereas alcohol has a supporting role. Among all tested alcohols; DDA and DOD exhibit the highest synergetic adsorption effect because of their similar carbon-chain lengths. This similarity promotes the formation of a compact adsorption layer on the muscovite surface.

Comparison of Chain Conformation of Poly(vinyl alcohol) in Solutions and Melts from Quantum Chemistry Based Molecular Dynamics Simulations

Science.gov (United States)

Jaffe, Richard; Han, Jie; Matsuda, Tsunetoshi; Yoon, Do; Langhoff, Stephen R. (Technical Monitor)

1997-01-01

Confirmations of 2,4-dihydroxypentane (DHP), a model molecule for poly(vinyl alcohol), have been studied by quantum chemistry (QC) calculations and molecular dynamics (MD) simulations. QC calculations at the 6-311G MP2 level show the meso tt conformer to be lowest in energy followed by the racemic tg, due to intramolecular hydrogen bond between the hydroxy groups. The Dreiding force field has been modified to reproduce the QC conformer energies for DHP. MD simulations using this force field have been carried out for DHP molecules in the gas phase, melt, and CHCl3 and water solutions. Extensive intramolecular hydrogen bonding is observed for the gas phase and CHCl3 solution, but not for the melt or aqueous solution, Such a condensed phase effect due to intermolecular interactions results in a drastic change in chain conformations, in agreement with experiments.

Poly(glycolide multi-arm star polymers: Improved solubility via limited arm length

Directory of Open Access Journals (Sweden)

Florian K. Wolf

2010-06-01

Full Text Available Due to the low solubility of poly(glycolic acid (PGA, its use is generally limited to the synthesis of random copolyesters with other hydroxy acids, such as lactic acid, or to applications that permit direct processing from the polymer melt. Insolubility is generally observed for PGA when the degree of polymerization exceeds 20. Here we present a strategy that allows the preparation of PGA-based multi-arm structures which significantly exceed the molecular weight of processable oligomeric linear PGA (<1000 g/mol. This was achieved by the use of a multifunctional hyperbranched polyglycerol (PG macroinitiator and the tin(II-2-ethylhexanoate catalyzed ring-opening polymerization of glycolide in the melt. With this strategy it is possible to combine high molecular weight with good molecular weight control (up to 16,000 g/mol, PDI = 1.4–1.7, resulting in PGA multi-arm star block copolymers containing more than 90 wt % GA. The successful linkage of PGA arms and PG core via this core first/grafting from strategy was confirmed by detailed NMR and SEC characterization. Various PG/glycolide ratios were employed to vary the length of the PGA arms. Besides fluorinated solvents, the materials were soluble in DMF and DMSO up to an average arm length of 12 glycolic acid units. Reduction in the Tg and the melting temperature compared to the homopolymer PGA should lead to simplified processing conditions. The findings contribute to broadening the range of biomedical applications of PGA.

Interaction and dynamics of (alkylamide + electrolyte) deep eutectics: Dependence on alkyl chain-length, temperature, and anion identity

International Nuclear Information System (INIS)

Guchhait, Biswajit; Das, Suman; Daschakraborty, Snehasis; Biswas, Ranjit

2014-01-01

Here we investigate the solute-medium interaction and solute-centered dynamics in (RCONH 2 + LiX) deep eutectics (DEs) via carrying out time-resolved fluorescence measurements and all-atom molecular dynamics simulations at various temperatures. Alkylamides (RCONH 2 ) considered are acetamide (CH 3 CONH 2 ), propionamide (CH 3 CH 2 CONH 2 ), and butyramide (CH 3 CH 2 CH 2 CONH 2 ); the electrolytes (LiX) are lithium perchlorate (LiClO 4 ), lithium bromide (LiBr), and lithium nitrate (LiNO 3 ). Differential scanning calorimetric measurements reveal glass transition temperatures (T g ) of these DEs are ∼195 K and show a very weak dependence on alkyl chain-length and electrolyte identity. Time-resolved and steady state fluorescence measurements with these DEs have been carried out at six-to-nine different temperatures that are ∼100–150 K above their individual T g s. Four different solute probes providing a good spread of fluorescence lifetimes have been employed in steady state measurements, revealing strong excitation wavelength dependence of probe fluorescence emission peak frequencies. Extent of this dependence, which shows sensitivity to anion identity, has been found to increase with increase of amide chain-length and decrease of probe lifetime. Time-resolved measurements reveal strong fractional power dependence of average rates for solute solvation and rotation with fraction power being relatively smaller (stronger viscosity decoupling) for DEs containing longer amide and larger (weaker decoupling) for DEs containing perchlorate anion. Representative all-atom molecular dynamics simulations of (CH 3 CONH 2 + LiX) DEs at different temperatures reveal strongly stretched exponential relaxation of wavevector dependent acetamide self dynamic structure factor with time constants dependent both on ion identity and temperature, providing justification for explaining the fluorescence results in terms of temporal heterogeneity and amide clustering in these multi

Transformation from Nanofibers to Nanoribbons in Poly(3-hexylthiophene) Solution by Adding Alkylthiols.

Science.gov (United States)

Pan, Shuang; Zhu, Mingjing; He, Luze; Zhang, Hongdong; Qiu, Feng; Lin, Zhiqun; Peng, Juan

2018-05-10

An intriguing morphological transition from poly(3-hexylthiophene) (P3HT) 1D nanofibers to 2D nanoribbons enabled by the addition of a series of alkylthiols is reported. First, P3HT 1D nanofibers are formed due to strong anisotropic π-π stacking between planar rigid backbones. Upon the addition of alkylthiols, P3HT nanofibers are transformed into nanoribbons associated with the crystallographic transition from edge-on orientation to flat-on orientation. The content of alkylthiols has a great influence on the P3HT morphology in the solution. The mechanism of such a morphological transformation is discussed based on the interaction between alkylthiols and P3HT chains. This work offers an effective strategy to tailor the crystal morphology and dimension of P3HT, which not only improves the understanding of P3HT crystallization but also may enable such discovery into conjugated polymer-based optoelectronic devices. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Non-surface activity and micellization behavior of cationic amphiphilic block copolymer synthesized by reversible addition-fragmentation chain transfer process.

Science.gov (United States)

Ghosh, Arjun; Yusa, Shin-ichi; Matsuoka, Hideki; Saruwatari, Yoshiyuki

2011-08-02

Cationic amphiphilic diblock copolymers of poly(n-butylacrylate)-b-poly(3-(methacryloylamino)propyl)trimethylammonium chloride) (PBA-b-PMAPTAC) with various hydrophobic and hydrophilic chain lengths were synthesized by a reversible addition-fragmentation chain transfer (RAFT) process. Their molecular characteristics such as surface activity/nonactivity were investigated by surface tension measurements and foam formation observation. Their micelle formation behavior and micelle structure were investigated by fluorescence probe technique, static and dynamic light scattering (SLS and DLS), etc., as a function of hydrophilic and hydrophobic chain lengths. The block copolymers were found to be non-surface active because the surface tension of the aqueous solutions did not change with increasing polymer concentration. Critical micelle concentration (cmc) of the polymers could be determined by fluorescence and SLS measurements, which means that these polymers form micelles in bulk solution, although they were non-surface active. Above the cmc, the large blue shift of the emission maximum of N-phenyl-1-naphthylamine (NPN) probe and the low micropolarity value of the pyrene probe in polymer solution indicate the core of the micelle is nonpolar in nature. Also, the high value of the relative intensity of the NPN probe and the fluorescence anisotropy of the 1,6-diphenyl-1,3,5-hexatriene (DPH) probe indicated that the core of the micelle is highly viscous in nature. DLS was used to measure the average hydrodynamic radii and size distribution of the copolymer micelles. The copolymer with the longest PBA block had the poorest water solubility and consequently formed micelles with larger size while having a lower cmc. The "non-surface activity" was confirmed for cationic amphiphilic diblock copolymers in addition to anionic ones studied previously, indicating the universality of non-surface activity nature.

Preparation, characterization, and application of poly(vinyl alcohol)-graft-poly(ethylene glycol) resins: novel polymer matrices for solid-phase synthesis.

Science.gov (United States)

Luo, Juntao; Pardin, Christophe; Zhu, X X; Lubell, William D

2007-01-01

Spherical crosslinked poly(vinyl alcohol) (PVA) beads with good mechanical stability were prepared by reverse-suspension polymerization, using dimethyl sulfoxide (DMSO) as a cosolvent in an aqueous phase. Poly(ethylene glycol)s with varying chain lengths were grafted onto the PVA beads by anionic polymerization of ethylene oxide. The thermal behavior, morphology, and swelling were evaluated for each of the new polymer matrices. High loading and good swelling in water and organic solvents were characteristic of the PEG-grafted PVA beads. The polymer beads also exhibited good mechanical and chemical stability and were unaffected by treatment with 6 N HCl and with 6 N NaOH. The hydroxyl groups of the PVA-PEG beads were converted into aldehyde, carboxylic acid, and isocyanate functions to provide scavenger resins and were extended by way of a benzyl alcohol in a Wang linker. The transglutaminase substrates dipeptides (Z-Gln-Gly) and heptapeptides (Pro-Asn-Pro-Gln-Leu-Pro-Phe) were synthesized on PVA-PEG_5, PVA-PEG_20, and the Wang linker-derivatized PVA-PEG resins. The cleavage of the peptides from the resins using MeOH/NH3 mixture at different temperatures (0 degrees C and room temp) and 50% TFA/DCM provided, respectively, peptide methyl esters, amides, and acids in good yields and purity as assessed by LC-MS analysis.

Temperature Induced Solubility Transitions of Various Poly(2-oxazolines in Ethanol-Water Solvent Mixtures

Directory of Open Access Journals (Sweden)

Hanneke M. L. Lambermont-Thijs

2010-08-01

Full Text Available The solution behavior of a series of poly(2-oxazolines with different side chains, namely methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, pentyl, hexyl, heptyl, octyl, nonyl, phenyl and benzyl, are reported in ethanol-water solvent mixtures based on turbidimetry investigations. The LCST transitions of poly(2-oxazolines with propyl side chains and the UCST transitions of the poly(2-oxazolines with more hydrophobic side chains are discussed in relation to the ethanol-water solvent composition and structure. The poly(2-alkyl-2-oxazolines with side chains longer than propyl only dissolved during the first heating run, which is discussed and correlated to the melting transition of the polymers.

Thermo- and pH-responsive poly(A-ProOMe)-graft-poly(AAc) membrane for selective separation of metal ions

International Nuclear Information System (INIS)

Hasegawa, Shin; Maekawa, Yasunari; Yoshida, Masaru; Ohashi, Hitoshi; Katakai, Ryoichi

2009-01-01

We investigated the permeation behavior of Li, Co, and Ni ions through thermo- and pH-responsive gel membranes, which were prepared by γ-ray grafting of pH-responsive poly(acrylic acid) (poly(AAc)) onto a thermo-responsive polymer gel of acryloyl-L-proline methyl ester (A-ProOMe). Using 15% AAc grafted membranes, the permeation constants of Li ions are 2.8 and 3.5 times higher than those of Co and Ni ions in a pH 6.0 buffer solution at 30degC. These ratios are two and three times higher than those of 5 and 43% grafted gel membranes, respectively. By comparison with the permeation of metal ions through the non-thermo-responsive porous polyethylene membranes grafted with AAc chains or random copolymer gel membranes (poly(A-ProOMe-co-AAc)), it is clear that the structure in which adjacent carboxyl groups of poly(AAc) are surrounded by thermo-responsive A-ProOMe matrix causes selective permeability of Li ion over Co and Ni ions. The distributions of Co and Ni ions in the microscopic structures clearly show that the structure consisting of flexible chains of the carboxyl groups grafted onto the thermo-response gel membrane plays a decisive role in the superior selective permeation of a Li ion. (author)

Thrombin immobilization to methacrylic acid grafted poly(3-hydroxybutyrate) and its in vitro application.

Science.gov (United States)

Akkaya, Alper; Pazarlioglu, Nurdan

2013-01-01

Poly(3-hydroxybutyrate) is nontoxic and biodegradable, with good biocompatibility and potential support for long-term implants. For this reason, it is a good support for enzyme immobilization. Enzyme immobilization could not be done directly because poly(3-hydroxybutyrate) has no functional groups. Therefore, modification should be done for enzyme immobilization. In this study, methacrylic acid was graft polymerized to poly(3-hydroxybutyrate) and thrombin was immobilized to polymethacrylic acid grafted poly(3-hydroxybutyrate). In fact, graft polymerization of methacrylic acid to poly(3-hydroxybutyrate) and thrombin immobilization was a model study. Biomolecule immobilized poly(3-hydroxybutyrate) could be used as an implant. Thrombin was selected as a biomolecule for this model study and it was immobilized to methacrylic acid grafted poly(3-hydroxybutyrate). Then the developed product was used to stop bleeding.

Bioinspired Poly(2-oxazolines

Directory of Open Access Journals (Sweden)

Helmut Schlaad

2011-02-01

Full Text Available Poly(2-oxazolines are regarded as pseudopeptides, thus bioinspired polymers, due to their structural relationship to polypeptides. Materials and solution properties can be tuned by varying the side-chain (hydrophilic-hydrophobic, chiral, bioorganic, etc., opening the way to advanced stimulus-responsive materials and complex colloidal structures. The bioinspired “smart” solution and aggregation behavior of poly(2-oxazolines in aqueous environments are discussed in this review.

Scaling behaviour of the correlation length for the two-point correlation function in the random field Ising chain

Energy Technology Data Exchange (ETDEWEB)

Lange, Adrian; Stinchcombe, Robin [Theoretical Physics, University of Oxford, Oxford (United Kingdom)

1996-07-07

We study the general behaviour of the correlation length {zeta}(kT:h) for two-point correlation function of the local fields in an Ising chain with binary distributed fields. At zero field it is shown that {zeta} is the same as the zero-field correlation length for the spin-spin correlation function. For the field-dominated behaviour of {zeta} we find an exponent for the power-law divergence which is smaller than the exponent for the spin-spin correlation length. The entire behaviour of the correlation length can be described by a single crossover scaling function involving the new critical exponent. (author)

Mechanical and Morphological Properties of Poly-3-hydroxybutyrate/Poly(butyleneadipate-co-terephthalate)/Layered Double Hydroxide Nanocomposites

OpenAIRE

Pak, Yen Leng; Bin Ahmad, Mansor; Shameli, Kamyar; Yunus, Wan Md Zin Wan; Ibrahim, Nor Azowa; Zainuddin, Norhazlin

2013-01-01

Nanocomposites of poly-3-hydroxybutyrate/poly(butyleneadipate-co-terephthalate)/layered double hydroxide (PHB/PBAT/LDH) were prepared from a binary blend of PHB/PBAT and stearate-Zn3Al LDH via a solution casting method using chloroform as solvent in this study. The pristine Zn3Al LDH was synthesized from nitrate salts solution at pH 7 by using coprecipitation technique and then was modified by stearate anions surfactant via ion exchange reaction. As a result, the basal spacing of the LDH was ...

Surface zwitterionicalization of poly(vinylidene fluoride) membranes from the entrapped reactive core-shell silica nanoparticles.

Science.gov (United States)

Zhu, Li-Jing; Zhu, Li-Ping; Zhang, Pei-Bin; Zhu, Bao-Ku; Xu, You-Yi

2016-04-15

We demonstrate the preparation and properties of poly(vinylidene fluoride) (PVDF) filtration membranes modified via surface zwitterionicalization mediated by reactive core-shell silica nanoparticles (SiO2 NPs). The organic/inorganic hybrid SiO2 NPs grafted with poly(methyl meth acrylate)-block-poly(2-dimethylaminoethyl methacrylate) copolymer (PMMA-b-PDMAEMA) shell were prepared by surface-initiated reversible addition fragmentation chain transfer (SI-RAFT) polymerization and then used as a membrane-making additive of PVDF membranes. The PDMAEMA exposed on membrane surface and pore walls were quaternized into zwitterionic poly(sulfobetaine methacrylate) (PSBMA) using 1,3-propane sultone (1,3-PS) as the quaternization agent. The membrane surface chemistry and morphology were analyzed by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), respectively. The hydrophilicity, permeability and antifouling ability of the investigated membranes were evaluated in detail. It was found that the PSBMA chains brought highly-hydrophilic and strong fouling resistant characteristics to PVDF membranes due to the powerful hydration of zwitterionic surface. The SiO2 cores and PMMA chains in the hybrid NPs play a role of anchors for the linking of PSBMA chains to membrane surface. Compared to the traditional strategies for membrane hydrophilic modification, the developed method in this work combined the advantages of both blending and surface reaction. Copyright © 2016 Elsevier Inc. All rights reserved.

Benzene containing polyhydroxyalkanoates homo- and copolymers synthesized by genome edited Pseudomonas entomophila

DEFF Research Database (Denmark)

Shen, Rui; Cai, Longwei; Meng, Dechuan

2014-01-01

Microbial synthesis of functional polymers has become increasingly important for industrial biotechnology. For the first time, it became possible to synthesize controllable composition of poly(3-hydroxyalkanoate) (P3HA) consisting of 3-hydroxydodecanoate (3HDD) and phenyl group on the side......HPhV) and 3-hydroxydodecanoate (3HDD) were synthesized when the strain was grown on mixtures of PVA and dodecanoic acid (DDA). Compositions of 3HPhV in P(3HPhV-co-3HDD) were controllable ranging from 3% to 32% depending on DDDA/PVA ratios. Nuclear magnetic resonance (NMR) spectra clearly indicated...

Preparation, Characterization and Permeation Behavior of Poly(methyl acrylate-Poly(dimethyl siloxane-Poly(methyl acrylate Block Copolymer/Poly(vinyl acetate Blend Membranes

Directory of Open Access Journals (Sweden)

Mohammad Ali Semsarzadeh

2015-03-01

Full Text Available Structure of polymeric materials is of the most important factors in determination of the characteristics and properties of the membranes. Various research and developments on polymeric membranes confirm the direct correlation between structure-properties of polymeric membranes. In this research, the structural outcome of poly(methyl acrylate-poly(dimethyl siloxane-poly(methyl acrylate/poly(vinyl acetate blend membranes and its relationship with gas permeation behavior of the blends were investigated. The flexible block copolymer of poly(methyl acrylate-poly(dimethyl siloxane-poly(methyl acrylate (PMA-PDMS-PMA was synthesized via atom transfer radical polymerization. Morphology and chemical structure of the synthesized block copolymer was investigated by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, gel permeation chromatography, X-ray diffraction analysis, differential scanning calorimetry and scanning electron microscopy. Blend membranes of PMA-PDMS-PMA and poly(vinyl acetate (PVAc were prepared by solution casting method in different compositions. By adding poly(vinyl acetate to PMA-PDMS-PMA block copolymer, the selectivity of the membranes for carbon dioxide/methane pair gases were increased by 55%. Fractional free volume (an indication of chain packing efficiency in blend membranes and dielectric constant (an indication of the molar volume and molar polarization of the blend membranes were obtained as the factors reflected the microstructural effect of PMA-PDMS-PMA and PVAc blend membranes. The efforts were directed toward expressing more precise structure-properties relationship of PMA-PDMS-PMA/PVAc blend membranes. The experimental permeability values of the blend membranes reported in this research were compared with the modified logarithmic model. The modified logarithmic model was evaluated for other blend membranes.

Relationship between Length and Surface-Enhanced Raman Spectroscopy Signal Strength in Metal Nanoparticle Chains: Ideal Models versus Nanofabrication

Directory of Open Access Journals (Sweden)

Kristen D. Alexander

2012-01-01

Full Text Available We have employed capillary force deposition on ion beam patterned substrates to fabricate chains of 60 nm gold nanospheres ranging in length from 1 to 9 nanoparticles. Measurements of the surface-averaged SERS enhancement factor strength for these chains were then compared to the numerical predictions. The SERS enhancement conformed to theoretical predictions in the case of only a few chains, with the vast majority of chains tested not matching such behavior. Although all of the nanoparticle chains appear identical under electron microscope observation, the extreme sensitivity of the SERS enhancement to nanoscale morphology renders current nanofabrication methods insufficient for consistent production of coupled nanoparticle chains. Notwithstanding this fact, the aggregate data also confirmed that nanoparticle dimers offer a large improvement over the monomer enhancement while conclusively showing that, within the limitations imposed by current state-of-the-art nanofabrication techniques, chains comprising more than two nanoparticles provide only a marginal signal boost over the already considerable dimer enhancement.

Effect of the Alkyl Chain Length Incorporated into Donor Part on the Optoelectronic Properties of the Carbazole Based Dyes: Theoretical Study

Directory of Open Access Journals (Sweden)

Souad El Mzioui

2017-12-01

Full Text Available In this paper, we report a theoretical study using density functional theory (DFT and time-dependent (TD-DFT for R-D-π-A systems with various alkyl chains (R. Results show that the LUMO of the dye lies above the semiconductor conduction band, promoting the injection of electrons; the lower HOMO level promotes dye regeneration. The incorporation of methyl chain (CH3 has a significant reduction in the gap energy, improved red-shift absorption spectrum and increase the molar extinction coefficient at the maximum absorption wavelength compared to D. While, the increase in alkyl chain length from C2H5 to C6H13 present a relatively reduce of gap energies, low effect on the wavelength (438 nm and converged excitation energies. DOI: http://dx.doi.org/10.17807/orbital.v9i5.1003 

First detection of lamella-gyroid-cylinder phase transition of neat polyethylene-poly(ethylene oxide) diblock copolymers on the basis of synchrotron WAXD/SAXS and infrared/Raman spectral measurements

International Nuclear Information System (INIS)

Weiyu, Cao; Tashiro, Kohji; Hanesaka, Makoto; Takeda, Shinichi; Masunaga, Hiroyasu; Sasaki, Sono; Takata, Masaki

2009-01-01

The phase transition behaviour of polyethylene-b-poly(ethylene oxide) (PE-b-PEO) diblock copolymer with relatively short chain lengths has been studied on the basis of temperature dependent infrared and Raman spectral measurements and synchrotron WAXD/SAXS simultaneous measurements, from which the concrete structural changes were deduced successfully from the various levels of molecular chain conformation, chain packing mode and higher-order structure. The higher-order structure has been found to transform between lamella, perforated lamella, gyroid, cylinder and sphere structures. The inner structural changes occurring in the polyethylene and poly(ethylene oxide) parts have been related with these morphological changes. The morphological transition from lamella to gyroid occurs with keeping the crystalline state of polyethylene parts. This apparently curious transition can be interpreted reasonably by assuming the thermally-activated chain motion in the crystal lattice, which may play an important role as a trigger to induce the morphological change from lamella to gyroid. This idea was supported by the measurement of half-width of Raman anti-symmetric CH 2 stretching band sensitive to the thermal mobility of alkyl chains.

Simulated glass-forming polymer melts: dynamic scattering functions, chain length effects, and mode-coupling theory analysis.

Science.gov (United States)

Frey, S; Weysser, F; Meyer, H; Farago, J; Fuchs, M; Baschnagel, J

2015-02-01

We present molecular-dynamics simulations for a fully flexible model of polymer melts with different chain length N ranging from short oligomers (N = 4) to values near the entanglement length (N = 64). For these systems we explore the structural relaxation of the supercooled melt near the critical temperature T c of mode-coupling theory (MCT). Coherent and incoherent scattering functions are analyzed in terms of the idealized MCT. For temperatures T > T c we provide evidence for the space-time factorization property of the β relaxation and for the time-temperature superposition principle (TTSP) of the α relaxation, and we also discuss deviations from these predictions for T ≈ T c. For T larger than the smallest temperature where the TTSP holds we perform a quantitative analysis of the dynamics with the asymptotic MCT predictions for the late β regime. Within MCT a key quantity, in addition to T c, is the exponent parameter λ. For the fully flexible polymer models studied we find that λ is independent of N and has a value (λ = 0.735 ) typical of simple glass-forming liquids. On the other hand, the critical temperature increases with chain length toward an asymptotic value T c (∞) . This increase can be described by T c (∞) - T c(N) ∼ 1/N and may be interpreted in terms of the N dependence of the monomer density ρ, if we assume that the MCT glass transition is ruled by a soft-sphere-like constant coupling parameter Γ c = ρ c T c (-1/4), where ρ c is the monomer density at T c. In addition, we also estimate T c from a Hansen-Verlet-like criterion and MCT calculations based on structural input from the simulation. For our polymer model both the Hansen-Verlet criterion and the MCT calculations suggest T c to decrease with increasing chain length, in contrast to the direct analysis of the simulation data.

Comparative study: The effects of solvent on the morphology, optical and structural features of regioregular poly(3-hexylthiophene):fullerene thin films

CSIR Research Space (South Africa)

Motaung, DE

2010-01-01

Full Text Available preparation Sample preparations were done according to the following procedure. All chemicals used in this experiment were purchased from Sigma Aldrich. Regioregular poly (3-hexylthiophene) (rr-P3HT) was used as a light absorption and electron... the percentage of stereo-regular head-to-tail (HT) attachments of the hexyl side chains to the 4 3-position of the thiophene rings [17]. These materials were used as received, without any further purification. Indium tin oxide (ITO) coated on a 1 mm glass...

Rational Design of Coordination Polymers with Flexible Oxyethylene Side Chains

International Nuclear Information System (INIS)

Choi, Eun Young; Gao, Chunji; Lee, Suck Hyun; Kwon, O Pil

2012-01-01

We rationally designed and synthesized metallopolymers with organic 1,4-benzenedicarboxylic acid (BDC) linkers with different lengths of oxyethylene side chains in order to examine the influence of side chains on the coordination characteristics. While in a previous report the BDC linkers with alkyl side chains were found to form three-dimensional (3D) isoreticular metal-organic framework (IRMOF) structures or one-dimensional (1D) coordination polymeric structures with short -O(CH 2 ) 6 CH 3 or long -O(CH 2 ) 9 CH 3 side chains, respectively, new BDC linkers with oxyethylene side chains of the same lengths, -(OCH 2 CH 2 ) 2 CH 3 and -(OCH 2 CH 2 ) 3 CH 3 , form only 3D IRMOF structures. This result is attributed to the higher flexibility and smaller volume of oxyethylene side chains compared to alkyl side chains

Self-assembly behavior of well-defined polymethylene-block-poly(ethylene glycol) copolymers in aqueous solution

KAUST Repository

Alkayal, Nazeeha

2016-09-22

A series of well-defined amphiphilic polymethylene-b-poly(ethylene glycol) (PM-b-PEG) diblock copolymers, with different hydrophobic chain length, were synthesized by combining Diels-Alder reaction with polyhomologation. The successful synthetic procedure was confirmed by size-exclusion chromatography (SEC) and 1H NMR spectroscopy. These block copolymers self-assembled into spherical micelles in aqueous solutions and exhibit low critical micelle concentration (CMC) of 2–4 mg/mL, as determined by fluorescence spectroscopy using pyrene as a probe. Measurements of the micelle hydrodynamic diameters, performed by dynamic light scattering (DLS), cryo-transmission electron microscopy (cryo-TEM) and atomic force microscopy (AFM), revealed a direct dependence of the micelle size from the polymethylene block length.

Aggregation behavior and intermicellar interactions of cationic Gemini surfactants: Effects of alkyl chain, spacer lengths and temperature

International Nuclear Information System (INIS)

Hajy Alimohammadi, Marjan; Javadian, Soheila; Gharibi, Hussein; Tehrani-Bagha, Ali reza; Alavijeh, Mohammad Rashidi; Kakaei, Karim

2012-01-01

Graphical abstract: Highlights: → Enthalpy-entropy compensation relation was found between and for gemini surfactants. → The intermicellar interaction parameters are influenced with increasing the lengths of the tail and the spacer of gemini surfactants. → Increasing temperature decreases the intermicellar interaction parameters. → The changes in micellar surface charge density, and phase transition between spherical and rod geometries explain the data. - Abstract: The aggregation behavior of the cationic Gemini surfactants C m H 2m+1 N(CH 3 ) 2 (CH 2 ) S (CH 3 ) 2 N C m H 2m+1 ,2Br - with m = 12, 14 and s = 2, 4 were studied by performing surface tension, electrical conductivity, pulsed field gradient nuclear magnetic resonance (PFG-NMR), and cyclic voltammetry (CV) measurements over the temperature range 298 K to 323 K. The critical micelle concentration (CMC), surface excess (Γ max ), mean molecular surface area (A min ), degree of counter ion dissociation (α), and the thermodynamic parameters of micellization were determined from the surface tension and conductance data. An enthalpy-entropy compensation effect was observed and all the plots of enthalpy-entropy compensation exhibit excellent linearity. The micellar self-diffusion coefficients (D m ) and intermicellar interaction parameters (k d ) were obtained from the PFG-NMR and CV measurements. These results are discussed in terms of the intermicellar interactions, the effects of the chain and spacer lengths on the micellar surface charge density, and the phase transition between spherical and rod geometries. The intermicellar interaction parameters were found to decrease slightly with increasing temperature for 14-4-14, which suggests that the micellar surface charge density decreases with increasing temperature. The mean values of the hydrodynamic radius, R h , and the aggregation number, N agg , of the Gemini surfactants'm-4-m micelles were calculated from the micellar self-diffusion coefficient

Waste cooking oil as substrate for biosynthesis of poly(3-hydroxybutyrate and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate: Turning waste into a value-added product

Directory of Open Access Journals (Sweden)

Yang, T. A.

2013-01-01

Full Text Available Aims: Improper disposal of domestic wastes, such as waste cooking oil (WCO, contributes to the deterioration of the environment and may lead to health problems. In this study, we evaluated the potential of plant-based WCO as a carbon source for the commercial biosynthesis of the bio-plastics, poly(3-hydroxybutyrate and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate. The consumption of WCO for this purpose would mitigate their pollution of the environment at the same time.Methodology and Results: WCO collected from several cafeterias in USM was tested as the carbon source for polyhydroxyalkanoates (PHA production. A selection of suitable nitrogen source was first conducted in order to obtain an acceptable number of dry cell weight (DCW and PHA content. Urea was found to be a suitable nitrogen source for the two bacterial strains used in our study, Cupriavidus necator H16 and its transformed mutant, C. necator PHB¯4 harboring the PHA synthase gene of Aeromonas caviae (PHB¯4/pBBREE32d13. With WCO as the sole carbon source, C. necator H16 yielded a relatively good dry cell weight (DCW=25.4 g/L, with 71 wt% poly(3-hydroxybutyrate P(3HBcontent. In comparison, the DCW obtained with fresh cooking oil (FCO was 24.8 g/L. The production of poly(3 hydroxybutyrate-co-3- hydroxyhexanoate [P(3HB-co-3HHx] from WCO by the transformant C. necator PHB¯4 was comparable, yielding a DCW of 22.3 g/L and P(3HB-co-3HHx content of 85 wt%. Lipase activities for both bacterial strains reached a maximum after 72 h of cultivation when time profile was conducted. Conclusion, significance and impact of study: The use of WCO as a carbon source in the biosynthesis of the bioplastic, PHA, turns a polluting domestic waste into a value-added biodegradable product. This renewable source material can thus be exploited for the low cost production of PHA.

Well-Defined Poly(Ortho Ester Amides) for Potential Drug Carriers: Probing the Effect of Extra- and Intracellular Drug Release on Chemotherapeutic Efficacy.

Science.gov (United States)

Yan, Guoqing; Wang, Jun; Qin, Jiejie; Hu, Liefeng; Zhang, Panpan; Wang, Xin; Tang, Rupei

2017-07-01

To compare the chemotherapeutic efficacy determined by extra- and intracellular drug release strategies, poly(ortho ester amide)-based drug carriers (POEAd-C) with well-defined main-chain lengths, are successfully constructed by a facile method. POEAd-C3-doxorubicin (DOX) can be rapidly dissolved to release drug at tumoral extracellular pH (6.5-7.2), while POEAd-C6-DOX can rapidly release drug following gradual swelling at intracellular pH (5.0-6.0). In vitro cytotoxicity shows that POEAd-C3-DOX exhibits more toxic effect on tumor cells than POEAd-C6-DOX at extracellular pH, but POEAd-C6-DOX has stronger tumor penetration and inhibition in vitro and in vivo tumor models. So, POEAd-C6-DOX with the intracellular drug release strategy has stronger overall chemotherapeutic efficacy than POEAd-C3-DOX with extracellular drug release strategy. It is envisioned that these poly(ortho ester amides) can have great potential as drug carriers for efficient chemotherapy with further optimization. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

RAFT-mediated synthesis of cationic poly[(ar-vinylbenzyl)trimethylammonium chloride] brushes for quantitative DNA immobilization

International Nuclear Information System (INIS)

Demirci, Serkan; Caykara, Tuncer

2013-01-01

The synthesis of cationic poly[(ar-vinylbenzyl)trimethylammonium chloride)] [poly(VBTAC)] brushes was achieved via reversible addition-fragmentation chain transfer (RAFT) polymerization and used for quantitative DNA immobilization. Initially, silicon surfaces were modified with RAFT chain transfer agent by utilizing an amide reaction involving a silicon wafer modified with allylamine and 4-cyanopentanoic acid dithiobenzoate (CPAD). Poly(VBTAC) brushes were then prepared via RAFT-mediated polymerization from the surface immobilized CPAD. Various characterization techniques including ellipsometry, X-ray photoelectron spectroscopy, grazing angle-Fourier transform infrared spectroscopy, atomic force microscopy and contact-angle goniometer were used to characterize the immobilization of CPAD on the silicon wafer and the subsequent polymer formation. The addition of free CPAD was required for the formation of well-defined polymer brushes, which subsequently resulted in the presence of free polymer chains in solution. The free polymer chains were isolated and used to estimate the molecular weights and polydispersity index of chains attached to the surface. Moreover, from atomic force microscopy and ellipsometry measurements, it was also determined that the density of immobilized DNA on the cationic poly(VBTAC) brushes can be quantitatively controlled by adjusting the solution concentration. Highlights: ► The cationic poly(VBTAC) brushes were prepared by RAFT polymerization. ► Grafting density of cationic poly(VBTAC) brushes was as high as 0.76 chains/nm 2 . ► The cationic poly(VBTAC) brushes were used for quantitative DNA immobilization.

The Impact of the Polymer Chain Length on the Catalytic Activity of Poly(N-vinyl-2-pyrrolidone)-supported Gold Nanoclusters

OpenAIRE

Haesuwannakij, Setsiri; Kimura, Tetsunari; Furutani, Yuji; Okumura, Kazu; Kokubo, Ken; Sakata, Takao; Yasuda, Hidehiro; Yakiyama, Yumi; Sakurai, Hidehiro

2017-01-01

Poly(N-vinyl-2-pyrrolidone) (PVP) of varying molecular weight (M w ?=?40-360?kDa) were employed to stabilize gold nanoclusters of varying size. The resulting Au:PVP clusters were subsequently used as catalysts for a kinetic study on the sized-dependent aerobic oxidation of 1-indanol, which was monitored by time-resolved in situ infrared spectroscopy. The obtained results suggest that the catalytic behaviour is intimately correlated to the size of the clusters, which in turn depends on the mol...

Improvement of Accuracy in Flow Immunosensor System by Introduction of Poly-2-[3-(methacryloylaminopropylammonio]ethyl 3-aminopropyl Phosphate

Directory of Open Access Journals (Sweden)

Yusuke Fuchiwaki

2011-01-01

Full Text Available In order to improve the accuracy of immunosensor systems, poly-2-[3-(methacryloylaminopropylammonio]ethyl 3-aminopropyl phosphate (poly-3MAm3AP, which includes both phosphorylcholine and amino groups, was synthesized and applied to the preparation of antibody-immobilized beads. Acting as an antibody-immobilizing material, poly-3MAm3AP is expected to significantly lower nonspecific adsorption due to the presence of the phosphorylcholine group and recognize large numbers of analytes due to the increase in antibody-immobilizing sites. The elimination of nonspecific adsorption was compared between the formation of a blocking layer on antibody-immobilized beads and the introduction of a material to combine antibody with beads. Determination with specific and nonspecific antibodies was then investigated for the estimation of signal-to-noise ratio. Signal intensities with superior signal-to-noise ratios were obtained when poly-3MAm3AP was introduced. This may be due to the increase in antibody-immobilizing sites and the extended space for antigen-antibody interaction resulting from the electrostatic repulsion of poly-3MAm3AP. Thus, the application of poly-3MAm3AP coatings to immunoassay beads was able to improve the accuracy of flow immunosensor systems.

σ-Bond Electron Delocalization in Oligosilanes as Function of Substitution Pattern, Chain Length, and Spatial Orientation

Directory of Open Access Journals (Sweden)

Johann Hlina

2016-08-01

Full Text Available Polysilanes are known to exhibit the interesting property of σ-bond electron delocalization. By employing optical spectroscopy (UV-vis, it is possible to judge the degree of delocalization and also differentiate parts of the molecules which are conjugated or not. The current study compares oligosilanes of similar chain length but different substitution pattern. The size of the substituents determines the spatial orientation of the main chain and also controls the conformational flexibility. The chemical nature of the substituents affects the orbital energies of the molecules and thus the positions of the absorption bands.

Template-free electrosynthesis of aligned poly(p-phenylene) microtubules

Institute of Scientific and Technical Information of China (English)

无

2003-01-01

Poly(p-phenylene) (PPP) microtubules with diameters of 0.2-0.8μm and lengths of～10 (m have been synthesized by direct oxidation of benzene in the mixed electrolyte of boron trifluoride diethyl etherate (BFEE) and trifluoroacetic acid (TFA) (BFEE:TFA= 2:1, by volume), containing a certain amount of sodium dodecylbenzene- sulfonate (SDBS) as surfactant. The microtubules were grown vertically on the working electrode surface. The tubular morphology has been confirmed by scanning and transmission electron microscopies and the chain structure of the skin of the tubules has been characterized by Raman spectroscopy. The electrode property, monomer/surfactant molar ratio and the value of applied potential have strong effects on the morphology of the microtubules.

Poly (3,4-ethylenedioxythiophene) (PEDOT) and poly (3,4-ethylenedioxythiophene)-few walled carbon nanotube (PEDOT-FWCNT) nanocomposite based thin films for Schottky diode application

Energy Technology Data Exchange (ETDEWEB)

Gupta, Bhavana, E-mail: bgupta1206@gmail.com [Surface and Nanoscience Division, Materials Science Group, Indira Gandhi Centre of Atomic Research, Kalpakkam, Tamil Nadu 603102 (India); Mehta, Minisha, E-mail: mehta.mini@gmail.com [Surface and Nanoscience Division, Materials Science Group, Indira Gandhi Centre of Atomic Research, Kalpakkam, Tamil Nadu 603102 (India); Melvin, Ambrose [Catalysis Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha, Pune 411008 (India); Kamalakannan, R.; Dash, S.; Kamruddin, M.; Tyagi, A.K. [Surface and Nanoscience Division, Materials Science Group, Indira Gandhi Centre of Atomic Research, Kalpakkam, Tamil Nadu 603102 (India)

2014-10-15

Transparent, conductive films of poly (3,4-ethylenedioxythiophene) (PEDOT) and poly (3,4-ethylenedioxythiophene)-few walled carbon nanotube (PEDOT-FWCNT) nanocomposite were synthesized by in-situ oxidative polymerization and investigated for their Schottky diode property. The prepared films were characterized by UV–Vis spectroscopy, thermal gravimetric analysis (TGA), surface resistivity, cyclic voltametery, scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). SEM reveals the formation of homogeneous and adhesive polymer films while HRTEM confirms the uniform wrapping of polymer chains around the nanotube walls for PEDOT-FWCNT film. Improved thermal stability, conductivity and charge storage property of PEDOT in the presence of FWCNT is observed. Among different compositions, 5 wt. % of FWCNT is found to be optimum with sheet resistance and transmittance of 500 Ω sq{sup −1} and 77%, respectively. Moreover, the electronic and junction properties of polymer films were studied and compared by fabricating sandwich type devices with a configuration of Al/PEDOT or PEDOT-FWCNT nanocomposite/indium tin oxide (ITO) coated glass. The measured current density-voltage characteristics show typical rectifying behavior for both configurations. However, enhanced rectification ratio and higher forward current density is observed in case of PEDOT-FWCNT based Schottky diode. Furthermore, reliability test depicts smaller hysteresis effect and better performance of PEDOT-FWCNT based diodes. - Highlights: • Single step synthesis of PEDOT and PEDOT-FWCNT nanocomposites films via in-situ oxidative polymerization. • Thermal, electrical and electrochemical properties of films show positive effect of FWCNT on PEDOT films. • Schottky diodes based on metal Al/PEDOT or PEDOT-FWCNT composites/ITO glass are fabricated. • Improved electrical characteristics with better reliability is achieved for PEDOT-FWCNT based diodes.

Poly (3,4-ethylenedioxythiophene) (PEDOT) and poly (3,4-ethylenedioxythiophene)-few walled carbon nanotube (PEDOT-FWCNT) nanocomposite based thin films for Schottky diode application

International Nuclear Information System (INIS)

Gupta, Bhavana; Mehta, Minisha; Melvin, Ambrose; Kamalakannan, R.; Dash, S.; Kamruddin, M.; Tyagi, A.K.

2014-01-01

Transparent, conductive films of poly (3,4-ethylenedioxythiophene) (PEDOT) and poly (3,4-ethylenedioxythiophene)-few walled carbon nanotube (PEDOT-FWCNT) nanocomposite were synthesized by in-situ oxidative polymerization and investigated for their Schottky diode property. The prepared films were characterized by UV–Vis spectroscopy, thermal gravimetric analysis (TGA), surface resistivity, cyclic voltametery, scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). SEM reveals the formation of homogeneous and adhesive polymer films while HRTEM confirms the uniform wrapping of polymer chains around the nanotube walls for PEDOT-FWCNT film. Improved thermal stability, conductivity and charge storage property of PEDOT in the presence of FWCNT is observed. Among different compositions, 5 wt. % of FWCNT is found to be optimum with sheet resistance and transmittance of 500 Ω sq −1 and 77%, respectively. Moreover, the electronic and junction properties of polymer films were studied and compared by fabricating sandwich type devices with a configuration of Al/PEDOT or PEDOT-FWCNT nanocomposite/indium tin oxide (ITO) coated glass. The measured current density-voltage characteristics show typical rectifying behavior for both configurations. However, enhanced rectification ratio and higher forward current density is observed in case of PEDOT-FWCNT based Schottky diode. Furthermore, reliability test depicts smaller hysteresis effect and better performance of PEDOT-FWCNT based diodes. - Highlights: • Single step synthesis of PEDOT and PEDOT-FWCNT nanocomposites films via in-situ oxidative polymerization. • Thermal, electrical and electrochemical properties of films show positive effect of FWCNT on PEDOT films. • Schottky diodes based on metal Al/PEDOT or PEDOT-FWCNT composites/ITO glass are fabricated. • Improved electrical characteristics with better reliability is achieved for PEDOT-FWCNT based diodes

Biodegradability of poly(3-hydroxybutyrate) film grafted with vinyl acetate: Effect of grafting and saponification

Science.gov (United States)

Wada, Yuki; Seko, Noriaki; Nagasawa, Naotsugu; Tamada, Masao; Kasuya, Ken-ichi; Mitomo, Hiroshi

2007-06-01

Radiation-induced graft polymerization of vinyl acetate (VAc) onto poly(3-hydroxybutyrate) (PHB) film was carried out. At a degree of grafting higher than 5%, the grafted films (PHB-g-VAc) completely lost the enzymatic degradability that is characteristic of PHB due to the grafted VAc covering the surface of the PHB film. However, the biodegradability of the PHB-g-VAc films was recovered when the films were saponified in alkali solution under optimum conditions. Graft chains of the PHB-g-VAc film reacted selectively to become biodegradable polyvinyl alcohol (PVA). The biodegradability of the saponified PHB-g-VAc film increased rapidly with time.

Biodegradability of poly(3-hydroxybutyrate) film grafted with vinyl acetate: Effect of grafting and saponification

International Nuclear Information System (INIS)

Wada, Yuki; Seko, Noriaki; Nagasawa, Naotsugu; Tamada, Masao; Kasuya, Ken-ichi; Mitomo, Hiroshi

2007-01-01

Radiation-induced graft polymerization of vinyl acetate (VAc) onto poly(3-hydroxybutyrate) (PHB) film was carried out. At a degree of grafting higher than 5%, the grafted films (PHB-g-VAc) completely lost the enzymatic degradability that is characteristic of PHB due to the grafted VAc covering the surface of the PHB film. However, the biodegradability of the PHB-g-VAc films was recovered when the films were saponified in alkali solution under optimum conditions. Graft chains of the PHB-g-VAc film reacted selectively to become biodegradable polyvinyl alcohol (PVA). The biodegradability of the saponified PHB-g-VAc film increased rapidly with time

Self-assembly of poly(vinylidene fluoride–polystyrene block copolymers in solution: Effects of the length of polystyrene block and solvent compositions

Directory of Open Access Journals (Sweden)

Yao Wu

2017-09-01

Full Text Available We report the first preliminary and extensive study on the solution self-assembly behaviors of poly(vinylidene fluoride–b-polystyrene (PVDF–PS block copolymers. The two PVDF–PS polymers we examined have the same length of PVDF block with number averaged repeating unit of 180, but distinctly different lengths of PS block with number averaged repeating unit of 125 and 1202. The self-assembly experiments were carried out in a series of mixture solutions containing a good solvent N,N-dimethylformamide and a selective solvent with different ratios. Our results showed that the self-assembly process was greatly affected by the two factors we examined, i.e. the length of the PS block and the solvent composition. We hope that our study could stimulate more research on the self-assembly of PVDF-containing polymers in solution.

Preparation and Properties of Poly (vinylidene fluoride)/poly(dimethylsiloxane) graft (poly(propylene oxide)-block-poly(ethylene oxide)) blend porous separators and corresponding electrolytes

International Nuclear Information System (INIS)

Li, Hao; Zhang, Hong; Liang, Zhi-Ying; Chen, Yue-Ming; Zhu, Bao-Ku; Zhu, Li-Ping

2014-01-01

Highlights: •This work aims exploring microporous PVDF separators for lithium ion batteries. •Comb structure polymer PDMS-g-(PPO-PEO) was used in PVDF blend separators. •The influence of polyether side chains on interfacial resistance was studied. -- Abstract: This work aims exploring the high performance porous separators that can be activated into gel electrolyte membranes for lithium ion batteries. A comb-like copolymer poly (dimethylsiloxane) graft poly (propylene oxide)-block-poly (ethylene oxide) (PDMS-g-(PPO-PEO)) was synthesized and blended with poly (vinylidene fluoride) (PVDF) to fabricate porous separators via a typical phase inversion process, and then the separators absorbed liquid electrolyte solution and formed into polymer electrolyte membranes. By measuring the composition, morphology and ion conductivity etc, the influence of PDMS-g-(PPO-PEO) on structure and properties of blend separators were discussed. Compared with pure PVDF separator with comparable porous structure, the adoption of PDMS-g-(PPO-PEO) decreased the crystallinity and increased the liquid electrolyte uptake and stability effectively. It was also found that the electrode/electrolyte interfacial resistance could be reduced greatly. The resulting electrolyte membrane using separator with PVDF/PDMS-g-(PPO-PEO) mass ratio in 8/2 exhibited highest ionic conductivity in 4.5 × 10 −3 S/cm at room temperature, while the electrochemical stability was up to 4.7 V (vs. Li/Li + ). Coin cells assembled with such separators also exhibited stable cycle performance and improved rate capabilities, especially when discharge rate higher than 0.5 C

Diversion of phagosome trafficking by pathogenic Rhodococcus equi depends on mycolic acid chain length.

Science.gov (United States)

Sydor, Tobias; von Bargen, Kristine; Hsu, Fong-Fu; Huth, Gitta; Holst, Otto; Wohlmann, Jens; Becken, Ulrike; Dykstra, Tobias; Söhl, Kristina; Lindner, Buko; Prescott, John F; Schaible, Ulrich E; Utermöhlen, Olaf; Haas, Albert

2013-03-01

Rhodococcus equi is a close relative of Mycobacterium spp. and a facultative intracellular pathogen which arrests phagosome maturation in macrophages before the late endocytic stage. We have screened a transposon mutant library of R. equi for mutants with decreased capability to prevent phagolysosome formation. This screen yielded a mutant in the gene for β-ketoacyl-(acyl carrier protein)-synthase A (KasA), a key enzyme of the long-chain mycolic acid synthesizing FAS-II system. The longest kasA mutant mycolic acid chains were 10 carbon units shorter than those of wild-type bacteria. Coating of non-pathogenic E. coli with purified wild-type trehalose dimycolate reduced phagolysosome formation substantially which was not the case with shorter kasA mutant-derived trehalose dimycolate. The mutant was moderately attenuated in macrophages and in a mouse infection model, but was fully cytotoxic.Whereas loss of KasA is lethal in mycobacteria, R. equi kasA mutant multiplication in broth was normal proving that long-chain mycolic acid compounds are not necessarily required for cellular integrity and viability of the bacteria that typically produce them. This study demonstrates a central role of mycolic acid chain length in diversion of trafficking by R. equi. © 2012 Blackwell Publishing Ltd.

Dynamic crossovers and activated regimes in a narrow distribution poly(n-butyl acrylate): an ESR study

Energy Technology Data Exchange (ETDEWEB)

Andreozzi, Laura; Autiero, Ciro; Faetti, Massimo; Giordano, Marco; Zulli, Fabio [Department of Physics ' E Fermi' , University of Pisa, largo Pontecorvo 3, 56127 Pisa (Italy); polyLAB-CNR, largo Pontecorvo 3, 56127 Pisa (Italy)

2006-07-19

The rotational dynamics of the spin probe cholestane dissolved in a narrow distribution poly(n-butyl acrylate) sample has been investigated via electron spin resonance (ESR) spectroscopy. The measurements were carried out in a wide temperature range: different dynamic regions have been recognized, and the coupling of the probe dynamics to the {alpha} and secondary relaxations has been revealed. In particular, the coupling with the structural relaxation is ruled by two fractionary Vogel-Fulcher laws (VF). The crossover from one VF region to the other occurs at the temperature T{sub C} = 1.17T{sub g}, signalling the onset of the cooperativity in the dynamics and confirming a behaviour previously observed in ESR studies carried out on polymeric glass-formers. Furthermore, in this work we discuss the activated regime at the highest temperatures and show that the activation energy does not depend on the length of the polymer main- and side-chains, while its onset temperature linearly depends on the chain length.

Dynamic crossovers and activated regimes in a narrow distribution poly(n-butyl acrylate): an ESR study

International Nuclear Information System (INIS)

Andreozzi, Laura; Autiero, Ciro; Faetti, Massimo; Giordano, Marco; Zulli, Fabio

2006-01-01

The rotational dynamics of the spin probe cholestane dissolved in a narrow distribution poly(n-butyl acrylate) sample has been investigated via electron spin resonance (ESR) spectroscopy. The measurements were carried out in a wide temperature range: different dynamic regions have been recognized, and the coupling of the probe dynamics to the α and secondary relaxations has been revealed. In particular, the coupling with the structural relaxation is ruled by two fractionary Vogel-Fulcher laws (VF). The crossover from one VF region to the other occurs at the temperature T C = 1.17T g , signalling the onset of the cooperativity in the dynamics and confirming a behaviour previously observed in ESR studies carried out on polymeric glass-formers. Furthermore, in this work we discuss the activated regime at the highest temperatures and show that the activation energy does not depend on the length of the polymer main- and side-chains, while its onset temperature linearly depends on the chain length

Effect of side chain length on the stability and structural properties of 3

African Journals Online (AJOL)

thiophene (DOOPT) and their dimers studied by Hartree-Fock (HF) and Density Functional Theory (DFT) methods. The DFT calculations suggest that dimers of the dialkoxyphenylthiophenes with longer side chains are thermodynamically more ...

Poly(3,4-ethylenedioxythiophene)-based glucose biosensors

NARCIS (Netherlands)

Kros, A.; Hövell, W.F.M. van; Sommerdijk, N.A.J.M.; Nolte, R.J.M.

2001-01-01

Amperometric biosensors for the recognition of glucose oxidase (GOx) based on poly(3,4-ethylenedioxythiophene) (PEDOT) were fabricated for the first time. The resulting biosensor has potential applications for long-term glucose measurements.

Interaction and dynamics of (alkylamide + electrolyte) deep eutectics: Dependence on alkyl chain-length, temperature, and anion identity

Energy Technology Data Exchange (ETDEWEB)

Guchhait, Biswajit; Das, Suman; Daschakraborty, Snehasis; Biswas, Ranjit, E-mail: ranjit@bose.res.in [Department of Chemical, Biological and Macromolecular Sciences, S. N. Bose National Centre for Basic Sciences, Block-JD, Sector-III, Salt Lake, Kolkata 700098 (India)

2014-03-14

Here we investigate the solute-medium interaction and solute-centered dynamics in (RCONH{sub 2} + LiX) deep eutectics (DEs) via carrying out time-resolved fluorescence measurements and all-atom molecular dynamics simulations at various temperatures. Alkylamides (RCONH{sub 2}) considered are acetamide (CH{sub 3}CONH{sub 2}), propionamide (CH{sub 3}CH{sub 2}CONH{sub 2}), and butyramide (CH{sub 3}CH{sub 2}CH{sub 2}CONH{sub 2}); the electrolytes (LiX) are lithium perchlorate (LiClO{sub 4}), lithium bromide (LiBr), and lithium nitrate (LiNO{sub 3}). Differential scanning calorimetric measurements reveal glass transition temperatures (T{sub g}) of these DEs are ∼195 K and show a very weak dependence on alkyl chain-length and electrolyte identity. Time-resolved and steady state fluorescence measurements with these DEs have been carried out at six-to-nine different temperatures that are ∼100–150 K above their individual T{sub g}s. Four different solute probes providing a good spread of fluorescence lifetimes have been employed in steady state measurements, revealing strong excitation wavelength dependence of probe fluorescence emission peak frequencies. Extent of this dependence, which shows sensitivity to anion identity, has been found to increase with increase of amide chain-length and decrease of probe lifetime. Time-resolved measurements reveal strong fractional power dependence of average rates for solute solvation and rotation with fraction power being relatively smaller (stronger viscosity decoupling) for DEs containing longer amide and larger (weaker decoupling) for DEs containing perchlorate anion. Representative all-atom molecular dynamics simulations of (CH{sub 3}CONH{sub 2} + LiX) DEs at different temperatures reveal strongly stretched exponential relaxation of wavevector dependent acetamide self dynamic structure factor with time constants dependent both on ion identity and temperature, providing justification for explaining the fluorescence results in

Dip-coating of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) anodes for efficient polymer solar cells

International Nuclear Information System (INIS)

Huang, Like; Hu, Ziyang; Zhang, Ke; Chen, Peipei; Zhu, Yuejin

2015-01-01

The fabrication of anodes and active layers by dip-coating in indium tin oxide (ITO)-free polymer solar cells (PSCs) is investigated. A highly conductive poly(3, 4-ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS) layer was used as an anode while a blend film of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61 butyric acid methyl ester (PCBM) was employed as an active layer. The transmittance and sheet resistance of dip-coated PEDOT:PSS layers prepared with different thickness were studied. These layers were integrated into PSCs. The PSCs with the dip-coated PEDOT:PSS and P3HT:PCBM films exhibited power conversion efficiencies of 3.21% and 3.03% on glass and polyethylene terephthalate substrates, respectively, comparable to those of conventional ITO-based cells. Our research results suggest the feasibility of fabricating PSCs without a traditional spin-coating process and the possibility to substitute the ITO electrodes for conducting polymer films using the facile dip-coating method. - Highlights: • ITO-free polymer solar cells (PSCs) were fabricated by dip coating method. • Highly conductive PEDOT:PSS films used as anode were prepared. • The ITO-free PSCs performance was comparable with that of the spin coated devices. • Our results suggest the possibility of replacing ITO with dip coated PEDOT:PSS

Dip-coating of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) anodes for efficient polymer solar cells

Energy Technology Data Exchange (ETDEWEB)

Huang, Like; Hu, Ziyang, E-mail: huziyang@nbu.edu.cn; Zhang, Ke; Chen, Peipei; Zhu, Yuejin, E-mail: zhuyuejin@nbu.edu.cn

2015-03-02

The fabrication of anodes and active layers by dip-coating in indium tin oxide (ITO)-free polymer solar cells (PSCs) is investigated. A highly conductive poly(3, 4-ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS) layer was used as an anode while a blend film of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61 butyric acid methyl ester (PCBM) was employed as an active layer. The transmittance and sheet resistance of dip-coated PEDOT:PSS layers prepared with different thickness were studied. These layers were integrated into PSCs. The PSCs with the dip-coated PEDOT:PSS and P3HT:PCBM films exhibited power conversion efficiencies of 3.21% and 3.03% on glass and polyethylene terephthalate substrates, respectively, comparable to those of conventional ITO-based cells. Our research results suggest the feasibility of fabricating PSCs without a traditional spin-coating process and the possibility to substitute the ITO electrodes for conducting polymer films using the facile dip-coating method. - Highlights: • ITO-free polymer solar cells (PSCs) were fabricated by dip coating method. • Highly conductive PEDOT:PSS films used as anode were prepared. • The ITO-free PSCs performance was comparable with that of the spin coated devices. • Our results suggest the possibility of replacing ITO with dip coated PEDOT:PSS.

Synthesis and solution self-assembly of side-chain cobaltocenium-containing block copolymers.

Science.gov (United States)

Ren, Lixia; Hardy, Christopher G; Tang, Chuanbing

2010-07-07

The synthesis of side-chain cobaltocenium-containing block copolymers and their self-assembly in solution was studied. Highly pure monocarboxycobaltocenium was prepared and subsequently attached to side chains of poly(tert-butyl acrylate)-block-poly(2-hydroxyethyl acrylate), yielding poly(tert-butyl acrylate)-block-poly(2-acryloyloxyethyl cobaltoceniumcarboxylate). The cobaltocenium block copolymers exhibited vesicle morphology in the mixture of acetone and water, while micelles of nanotubes were formed in the mixture of acetone and chloroform.

Poly(3-hexylthiophene)/ZnO hybrid pn junctions for microelectronics applications

DEFF Research Database (Denmark)

Katsia, E.; Huby, N.; Tallarida, G.

2009-01-01

Hybrid poly(3-hexylthiophene)/ZnO devices are investigated as rectifying heterojunctions for microelectronics applications. A low-temperature atomic layer deposition of ZnO on top of poly(3-hexylthiophene) allows the fabrication of diodes featuring a rectification ratio of nearly 105 at ±4 V...

Vault-poly-ADP-ribose polymerase in the Octopus vulgaris brain: a regulatory factor of actin polymerization dynamic.

Science.gov (United States)

De Maio, Anna; Natale, Emiliana; Rotondo, Sergio; Di Cosmo, Anna; Faraone-Mennella, Maria Rosaria

2013-09-01

Our previous behavioural, biochemical and immunohistochemical analyses conducted in selected regions (supra/sub oesophageal masses) of the Octopus vulgaris brain detected a cytoplasmic poly-ADP-ribose polymerase (more than 90% of total enzyme activity). The protein was identified as the vault-free form of vault-poly-ADP-ribose polymerase. The present research extends and integrates the biochemical characterization of poly-ADP-ribosylation system, namely, reaction product, i.e., poly-ADP-ribose, and acceptor proteins, in the O. vulgaris brain. Immunochemical analyses evidenced that the sole poly-ADP-ribose acceptor was the octopus cytoskeleton 50-kDa actin. It was present in both free, endogenously poly-ADP-ribosylated form (70kDa) and in complex with V-poly-ADP-ribose polymerase and poly-ADP-ribose (260kDa). The components of this complex, alkali and high salt sensitive, were purified and characterized. The kind and the length of poly-ADP-ribose corresponded to linear chains of 30-35 ADP-ribose units, in accordance with the features of the polymer synthesized by the known vault-poly-ADP-ribose polymerase. In vitro experiments showed that V-poly-ADP-ribose polymerase activity of brain cytoplasmic fraction containing endogenous actin increased upon the addition of commercial actin and was highly reduced by ATP. Anti-actin immunoblot of the mixture in the presence and absence of ATP showed that the poly-ADP-ribosylation of octopus actin is a dynamic process balanced by the ATP-dependent polymerization of the cytoskeleton protein, a fundamental mechanism for synaptic plasticity. © 2013 Elsevier Inc. All rights reserved.

Fabrication of ultrahydrophobic poly(lauryl acrylate) brushes on silicon wafer via surface-initiated atom transfer radical polymerization

Energy Technology Data Exchange (ETDEWEB)

Oztuerk, Esra; Turan, Eylem [Department of Chemistry, Faculty of Art and Science, Gazi University, 06500 Besevler, Ankara (Turkey); Caykara, Tuncer, E-mail: caykara@gazi.edu.tr [Department of Chemistry, Faculty of Art and Science, Gazi University, 06500 Besevler, Ankara (Turkey)

2010-11-15

In this report, ultrahydrophobic poly(lauryl acrylate) [poly(LA)] brushes were synthesized by surface-initiated atom transfer radical polymerization (SI-ATRP) of lauryl acrylate (LA) in N,N-dimethylformamide (DMF) at 90 deg. C. The formation of ultrahydrophobic poly(LA) films, whose thickness can be turned by changing polymerization time, is evidenced by using the combination of ellipsometry, X-ray photoelectron spectroscopy (XPS), grazing angle attenuated total reflectance-Fourier transform infrared spectroscopy (GATR-FTIR), atomic force microscopy (AFM), gel permeation chromatography (GPC), and water contact angle measurements. The SI-ATRP can be conducted in a well-controlled manner, as revealed by the linear kinetic plot, linear evolution of number-average molecular weights (M-bar{sub n}) versus monomer conversions, and the relatively narrow PDI (<1.28) of the grafted poly(LA) chains. The calculation of grafting parameters from experimental measurements indicated the synthesis of densely grafted poly(LA) films and allowed us to predict a 'brushlike' conformation for the chains in good solvent. The poly(LA) brushes exhibited high water contact angle of 163.3 {+-} 2.8{sup o}.

Asymmetric Conjugated Molecules Based on [1]Benzothieno[3,2-b][1]benzothiophene for High-Mobility Organic Thin-Film Transistors: Influence of Alkyl Chain Length.

Science.gov (United States)

He, Keqiang; Li, Weili; Tian, Hongkun; Zhang, Jidong; Yan, Donghang; Geng, Yanhou; Wang, Fosong

2017-10-11

Herein, we report the synthesis and characterization of a series of [1]benzothieno[3,2-b][1]benzothiophene (BTBT)-based asymmetric conjugated molecules, that is, 2-(5-alkylthiophen-2-yl)[1]benzothieno[3,2-b][1]benzothiophene (BTBT-Tn, in which T and n represent thiophene and the number of carbons in the alkyl group, respectively). All of the molecules with n ≥ 4 show mesomorphism and display smectic A, smectic B (n = 4), or smectic E (n > 4) phases and then crystalline phases in succession upon cooling from the isotropic state. Alkyl chain length has a noticeable influence on the microstructures of vacuum-deposited films and therefore on the performance of the organic thin-film transistors (OTFTs). All molecules except for 2-(thiophen-2-yl)[1]benzothieno[3,2-b][1]benzothiophene and 2-(5-ethylthiophen-2-yl)[1]benzothieno[3,2-b][1]benzothiophene showed OTFT mobilities above 5 cm 2 V -1 s -1 . 2-(5-Hexylthiophen-2-yl)[1]benzothieno[3,2-b][1]benzothiophene and 2-(5-heptylthiophen-2-yl)[1]benzothieno[3,2-b][1]benzothiophene showed the greatest OTFT performance with reliable hole mobilities (μ) up to 10.5 cm 2 V -1 s -1 because they formed highly ordered and homogeneous films with diminished grain boundaries.

Micelle formation of nonionic surfactants in a room temperature ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate: surfactant chain length dependence of the critical micelle concentration.

Science.gov (United States)

Inoue, Tohru; Yamakawa, Haruka

2011-04-15

Micellization behavior was investigated for polyoxyethylene-type nonionic surfactants with varying chain length (C(n)E(m)) in a room temperature ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF(4)). Critical micelle concentration (cmc) was determined from the variation of (1)H NMR chemical shift with the surfactant concentration. The logarithmic value of cmc decreased linearly with the number of carbon atoms in the surfactant hydrocarbon chain, similarly to the case observed in aqueous surfactant solutions. However, the slope of the straight line is much smaller in bmimBF(4) than in aqueous solution. Thermodynamic parameters for micelle formation estimated from the temperature dependence of cmc showed that the micellization in bmimBF(4) is an entropy-driven process around room temperature. This behavior is also similar to the case in aqueous solution. However, the magnitude of the entropic contribution to the overall micellization free energy in bmimBF(4) is much smaller compared with that in aqueous solution. These results suggest that the micellization in bmimBF(4) proceeds through a mechanism similar to the hydrophobic interaction in aqueous surfactant solutions, although the solvophobic effect in bmimBF(4) is much weaker than the hydrophobic effect. Copyright © 2011 Elsevier Inc. All rights reserved.

Genipin-cross-linked poly(L-lysine)-based hydrogels: synthesis, characterization, and drug encapsulation.

Science.gov (United States)

Wang, Steven S S; Hsieh, Ping-Lun; Chen, Pei-Shan; Chen, Yu-Tien; Jan, Jeng-Shiung

2013-11-01

Genipin-cross-linked hydrogels composed of biodegradable and pH-sensitive cationic poly(L-lysine) (PLL), poly(L-lysine)-block-poly(L-alanine) (PLL-b-PLAla), and poly(L-lysine)-block-polyglycine (PLL-b-PGly) polypeptides were synthesized, characterized, and used as carriers for drug delivery. These polypeptide hydrogels can respond to pH-stimulus and their gelling and mechanical properties, degradation rate, and drug release behavior can be tuned by varying polypeptide composition and cross-linking degree. Comparing with natural polymers, the synthetic polypeptides with well-defined chain length and composition can warrant the preparation of the hydrogels with tunable properties to meet the criteria for specific biomedical applications. These hydrogels composed of natural building blocks exhibited good cell compatibility and enzyme degradability and can support cell attachment/proliferation. The evaluation of these hydrogels for in vitro drug release revealed that the controlled release profile was a biphasic pattern with a mild burst release and a moderate release rate thereafter, suggesting the drug molecules were encapsulated inside the gel matrix. With the versatility of polymer chemistry and conjugation of functional moieties, it is expected these hydrogels can be useful for biomedical applications such as polymer therapeutics and tissue engineering. Copyright © 2013 Elsevier B.V. All rights reserved.

Fabrication of honeycomb-structured poly(ethylene glycol)-block-poly(lactic acid) porous films and biomedical applications for cell growth

Energy Technology Data Exchange (ETDEWEB)

Yao, Bingjian [Key Laboratory of Special Functional Aggregated Materials, Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250199 (China); College of chemistry, Chemical Engineering and Materials Science, Collaborative Innovation Center of Functionalized Probes for Chemical Imaging, Key Laboratory of Molecular and Nano Probes, Ministry of Education, Shandong Normal University, Jinan 250014 (China); Zhu, Qingzeng, E-mail: qzzhu@sdu.edu.cn [Key Laboratory of Special Functional Aggregated Materials, Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250199 (China); Yao, Linli [Key Laboratory of the Ministry of Education for Experimental Teratology, Department of Histology and Embryology, Shandong University School of Medicine, 250012 Jinan (China); Hao, Jingcheng [Key Laboratory of Special Functional Aggregated Materials, Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250199 (China)

2015-03-30

Graphical abstract: - Highlights: • Honeycomb-structured PEG-PLA porous films were fabricated. • The organization of pores depends on molecular weight ratio of PEG-to-PLA block. • The pores in the film were internally decorated with a layer of PEG. • The honeycomb-structured PEG-PLA film was suitable as a substrate for cell growth. - Abstract: A series of poly(ethylene glycol)-block-poly(lactic acid) (PEG-PLA) copolymers with a hydrophobic PLA block of different molecular weights and a fixed length hydrophilic PEG were synthesized successfully and characterized. These amphiphilic block copolymers were used to fabricate honeycomb-structured porous films using the breath figure (BF) templating technique. The surface topology and composition of the highly ordered pattern film were further characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and fluorescence microscopy. The results indicated that the PEG-to-PLA block molecular weight ratio influenced the BF film surface topology. The film with the best ordered pores was obtained with a PEG-to-PLA ratio of 2.0 × 10{sup 3}:3.0 × 10{sup 4}. The self-organization of the hydrophilic PEG chains within the pores was confirmed by XPS and fluorescence labeled PEG. A model is proposed to elucidate the stabilization process of the amphiphilic PEG-PLA aggregated architecture on the water droplet-based templates. In addition, GFP-U87 cell viability has been investigated by MTS test and the cell morphology on the honeycomb-structured PEG-PLA porous film has been evaluated using phase-contrast microscope. This porous film is shown to be suitable as a matrix for cell growth.

Fabrication of honeycomb-structured poly(ethylene glycol)-block-poly(lactic acid) porous films and biomedical applications for cell growth

International Nuclear Information System (INIS)

Yao, Bingjian; Zhu, Qingzeng; Yao, Linli; Hao, Jingcheng

2015-01-01

Graphical abstract: - Highlights: • Honeycomb-structured PEG-PLA porous films were fabricated. • The organization of pores depends on molecular weight ratio of PEG-to-PLA block. • The pores in the film were internally decorated with a layer of PEG. • The honeycomb-structured PEG-PLA film was suitable as a substrate for cell growth. - Abstract: A series of poly(ethylene glycol)-block-poly(lactic acid) (PEG-PLA) copolymers with a hydrophobic PLA block of different molecular weights and a fixed length hydrophilic PEG were synthesized successfully and characterized. These amphiphilic block copolymers were used to fabricate honeycomb-structured porous films using the breath figure (BF) templating technique. The surface topology and composition of the highly ordered pattern film were further characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and fluorescence microscopy. The results indicated that the PEG-to-PLA block molecular weight ratio influenced the BF film surface topology. The film with the best ordered pores was obtained with a PEG-to-PLA ratio of 2.0 × 10 3 :3.0 × 10 4 . The self-organization of the hydrophilic PEG chains within the pores was confirmed by XPS and fluorescence labeled PEG. A model is proposed to elucidate the stabilization process of the amphiphilic PEG-PLA aggregated architecture on the water droplet-based templates. In addition, GFP-U87 cell viability has been investigated by MTS test and the cell morphology on the honeycomb-structured PEG-PLA porous film has been evaluated using phase-contrast microscope. This porous film is shown to be suitable as a matrix for cell growth

Multispectroscopic methods reveal different modes of interaction of anti cancer drug mitoxantrone with Poly(dG-dC).Poly(dG-dC) and Poly(dA-dT).Poly(dA-dT).

Science.gov (United States)

Awasthi, Pamita; Dogra, Shilpa; Barthwal, Ritu

2013-10-05

The interaction of mitoxantrone with alternating Poly(dG-dC).Poly(dG-dC) and Poly(dA-dT).Poly(dA-dT) duplex has been studied by absorption, fluorescence and Circular Dichroism (CD) spectroscopy at Drug to Phosphate base pair ratios D/P=20.0-0.04. Binding to GC polymer occurs in two distinct modes: partial stacking characterized by red shifts of 18-23nm at D/P=0.2-0.8 and external binding at D/P=1.0-20.0 whereas that to AT polymer occurs externally in the entire range of D/P. The binding constant and number of binding sites is 3.7×10(5)M(-1), 0.3 and 1.3× 10(4)M(-1), 1.5 in GC and AT polymers, respectively at low D/P ratios. CD binding isotherms show breakpoints at D/P=0.1, 0.5 and 0.25, 0.5 in GC and AT polymers, respectively. The intrinsic CD bands indicate that the distortions in GC polymer are significantly higher than that in AT polymer. Docking studies show partial insertion of mitoxantrone rings between to GC base pairs in alternating GC polymer. Side chains of mitoxantrone interact specifically with base pairs and DNA backbone. The studies are relevant to the understanding of suppression or inhibition of DNA cleavage on formation of ternary complex with topoisomerase-II enzyme and hence the anti cancer action. Copyright © 2013 Elsevier B.V. All rights reserved.

Unit and internal chain profiles of maca amylopectin.

Science.gov (United States)

Zhang, Ling; Li, Guantian; Yao, Weirong; Zhu, Fan

2018-03-01

Unit chain length distributions of amylopectin and its φ, β-limit dextrins, which reflect amylopectin internal structure from three maca starches, were determined by high-performance anion-exchange chromatography with pulsed amperometric detection after debranching, and the samples were compared with maize starch. The amylopectins exhibited average chain lengths ranging from 16.72 to 17.16, with ranges of total internal chain length, external chain length, and internal chain length of the maca amylopectins at 12.49 to 13.68, 11.24 to 11.89, and 4.27 to 4.48. The average chain length, external chain length, internal chain length, and total internal chain length were comparable in three maca amylopectins. Amylopectins of the three maca genotypes studied here presented no significant differences in their unit chain length profiles, but did show significant differences in their internal chain profiles. Additional genetic variations between different maca genotypes need to be studied to provide unit- and internal chain profiles of maca amylopectin. Copyright © 2017. Published by Elsevier Ltd.

Valorization of waste glycerol for the production of poly (3-hydroxybutyrate) and poly (3-hydroxybutyrate-co-3-hydroxyvalerate) copolymer by Cupriavidus necator and extraction in a sustainable manner.

Science.gov (United States)

Gahlawat, Geeta; Soni, Sanjeev Kumar

2017-11-01

Glycerol is a by-product of many industrial processes and huge amounts of it are generated in the form of waste, thereby necessitating a search for the method of its disposal. An interesting solution is the valorization of crude glycerol into value added product such as polyhydroxyalkanoates (PHAs). The feasibility of producing PHAs by Cupriavidus necator was evaluated using crude glycerol (WG). Various cultivation strategies were designed for the production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) copolymer by adding different organic acids as precursors at different concentrations levels. Batch cultivation of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) production showed accumulation of 6.76g/L biomass containing 4.84g/L copolymer on WG with a maximum 3-hydroxyvalerate content of 24.6mol%. PHAs extraction using a non-toxic and recyclable solvent, 1,2 propylene carbonate, showed the highest recovery yield (90%) and purity (93%) at 120°C temperature and 30min incubation. This is the first report on jatropha based glycerol valorization for poly(3-hydroxybutyrate-co-3-hydroxyvalerate) production coupled with extraction using non-toxic solvent. Copyright © 2017 Elsevier Ltd. All rights reserved.

All solid-state polymer electrolytes prepared from a hyper-branched graft polymer using atom transfer radical polymerization

International Nuclear Information System (INIS)

Higa, Mitsuru; Fujino, Yukiko; Koumoto, Taihei; Kitani, Ryousuke; Egashira, Satsuki

2005-01-01

We propose an all solid-state (liquid free) polymer electrolyte (SPE) prepared from a hyper-branched graft copolymer. The graft copolymer consisting of a poly(methyl methacrylate) main chain and poly(ethylene glycol) methyl ether methacrylate side chains was synthesized by atom transfer radical polymerization changing the average chain distance between side chains, side chain length and branched chain length of the proposed structure of the graft copolymer. The ionic conductivity of the SPEs increases with increasing the side chain length, branched chain length and/or average distance between the side chains. The ionic conductivity of the SPE prepared from POEM 9 whose POEM content = 51 wt% shows 2 x 10 -5 S/cm at 30 deg. C. The tensile strength of the SPEs decreases with increases the side chain length, branched chain length and/or average distance between the side chains. These results indicate that a SPE prepared from the hyper-branched graft copolymer has potential to be applied to an all-solid polymer electrolyte

Investigation of Poly(3,4-ethylenedioxythiophene:Poly(styrenesulfonate Hole Transport Layer for Solution-Processed Polymer Solar Cells

Directory of Open Access Journals (Sweden)

Chengxi Zhang

2015-01-01

Full Text Available The inverted polymer solar cell was prepared by self-made spray-coating system, and the poly(3,4-ethylenedioxythiophene:poly(styrenesulfonate (PEDOT:PSS hole transport layer was studied. 220 nm poly-(3-hexylthiophene:[6,6]-phenylC61butyric-acid methyl-ester (P3HT:PCBM and 40 nm PEDOT:PSS were deposited on ZnO thin film subsequently by solution spray coating. Different volume of isopropyl alcohol was introduced into PEDOT:PSS to decrease the contact angle and obtain the optimum Marangoni flow. The surface morphology and roughness of PEDOT:PSS films were characterized by atomic force microscopy with varied deposition temperature from 70°C to 160°C. The improvement of power conversion efficiency (PCE was attributed to the enhancement of vertical phase separation in PEDOT:PSS film, which improved the charge transfer in the bulk cell. The highest PCE of spray-coated PSCs reached 2.80% after postannealing for 10 min.

Prediction of Poly(A Sites by Poly(A Read Mapping.

Directory of Open Access Journals (Sweden)

Thomas Bonfert

Full Text Available RNA-seq reads containing part of the poly(A tail of transcripts (denoted as poly(A reads provide the most direct evidence for the position of poly(A sites in the genome. However, due to reduced coverage of poly(A tails by reads, poly(A reads are not routinely identified during RNA-seq mapping. Nevertheless, recent studies for several herpesviruses successfully employed mapping of poly(A reads to identify herpesvirus poly(A sites using different strategies and customized programs. To more easily allow such analyses without requiring additional programs, we integrated poly(A read mapping and prediction of poly(A sites into our RNA-seq mapping program ContextMap 2. The implemented approach essentially generalizes previously used poly(A read mapping approaches and combines them with the context-based approach of ContextMap 2 to take into account information provided by other reads aligned to the same location. Poly(A read mapping using ContextMap 2 was evaluated on real-life data from the ENCODE project and compared against a competing approach based on transcriptome assembly (KLEAT. This showed high positive predictive value for our approach, evidenced also by the presence of poly(A signals, and considerably lower runtime than KLEAT. Although sensitivity is low for both methods, we show that this is in part due to a high extent of spurious results in the gold standard set derived from RNA-PET data. Sensitivity improves for poly(A sites of known transcripts or determined with a more specific poly(A sequencing protocol and increases with read coverage on transcript ends. Finally, we illustrate the usefulness of the approach in a high read coverage scenario by a re-analysis of published data for herpes simplex virus 1. Thus, with current trends towards increasing sequencing depth and read length, poly(A read mapping will prove to be increasingly useful and can now be performed automatically during RNA-seq mapping with ContextMap 2.

Bacterial membrane activity of a-peptide/b-peptoid chimeras: Influence of amino acid composition and chain length on the activity against different bacterial strains

DEFF Research Database (Denmark)

Hein-Kristensen, Line; Knapp, Kolja M; Franzyk, Henrik

2011-01-01

and subsequent killing is usually not tested. In this report, six α-peptide/β-peptoid chimeras were examined for the effect of amino acid/peptoid substitutions and chain length on the membrane perturbation and subsequent killing of food-borne and clinical bacterial isolates. RESULTS: All six AMP analogues...... acid only had a minor effect on MIC values, whereas chain length had a profound influence on activity. All chimeras were less active against Serratia marcescens (MICs above 46 μM). The chimeras were bactericidal and induced leakage of ATP from Staphylococcus aureus and S. marcescens with similar time...... of onset and reduction in the number of viable cells. EDTA pre-treatment of S. marcescens and E. coli followed by treatment with chimeras resulted in pronounced killing indicating that disintegration of the Gram-negative outer membrane eliminated innate differences in susceptibility. Chimera chain length...

Overexpression of O-polysaccharide chain length regulators in Gram-negative bacteria using the Wzx-/Wzy-dependent pathway enhances production of defined modal length O-polysaccharide polymers for use as haptens in glycoconjugate vaccines.

Science.gov (United States)

Hegerle, N; Bose, J; Ramachandran, G; Galen, J E; Levine, M M; Simon, R; Tennant, S M

2018-03-30

O-polysaccharide (OPS) molecules are protective antigens for several bacterial pathogens, and have broad utility as components of glycoconjugate vaccines. Variability in the OPS chain length is one obstacle towards further development of these vaccines. Introduction of sizing steps during purification of OPS molecules of suboptimal or of mixed lengths introduces additional costs and complexity while decreasing the final yield. The overall goal of this study was to demonstrate the utility of engineering Gram-negative bacteria to produce homogenous O-polysaccharide populations that can be used as the basis of carbohydrate vaccines by overexpressing O-polysaccharide chain length regulators of the Wzx-/Wzy-dependent pathway. The O-polysaccharide chain length regulators wzzB and fepE from Salmonella Typhimurium I77 and wzz2 from Pseudomonas aeruginosa PAO1 were cloned and expressed in the homologous organism or in other Gram-negative bacteria. Overexpression of these Wzz proteins in the homologous organism significantly increased the proportion of long or very long chain O-polysaccharides. The same observation was made when wzzB was overexpressed in Salmonella Paratyphi A and Shigella flexneri, and wzz2 was overexpressed in two other strains of P. aeruginosa. Overexpression of Wzz proteins in Gram-negative bacteria using the Wzx/Wzy-dependant pathway for lipopolysaccharide synthesis provides a genetic method to increase the production of an O-polysaccharide population of a defined size. The methods presented herein represent a cost-effective and improved strategy for isolating preferred OPS vaccine haptens, and could facilitate the further use of O-polysaccharides in glycoconjugate vaccine development. © 2018 The Society for Applied Microbiology.

Shape Memory Properties and Enzymatic Degradability of Poly(ε-caprolactone)-Based Polyurethane Urea Containing Phenylalanine-Derived Chain Extender.

Science.gov (United States)

Wang, Rong; Zhang, Fanjun; Lin, Weiwei; Liu, Wenkai; Li, Jiehua; Luo, Feng; Wang, Yaning; Tan, Hong

2018-04-24

Biodegradable shape memory polymers are promising biomaterials for minimally invasive surgical procedures. Herein, a series of linear biodegradable shape memory poly(ε-caprolactone) (PCL)-based polyurethane ureas (PUUs) containing a novel phenylalanine-derived chain extender is synthesized. The phenylalanine-derived chain extender, phenylalanine-hexamethylenediamine-phenylalanine (PHP), contains two chymotrypsin cleaving sites to enhance the enzymatic degradation of PUUs. The degradation rate, the crystallinity, and mechanical properties of PUUs are tailored by the content of PHP. Meanwhile, semicrystalline PCL is not only hydrolytically degradable but also vital for shape memory. Good shape memory ability under body temperature is achieved for PUUs due to the strong interactions in hard segments for permanent crosslinking and the crystallization-melt transition of PCL to switch temporary shape. The PUUs would have a great potential in application as implanting stent. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

PolyUbiquitin chain linkage topology selects the functions from the underlying binding landscape.

Directory of Open Access Journals (Sweden)

Yong Wang

2014-07-01

Full Text Available Ubiquitin (Ub can generate versatile molecular signals and lead to different celluar fates. The functional poly-valence of Ub is believed to be resulted from its ability to form distinct polymerized chains with eight linkage types. To provide a full picture of ubiquitin code, we explore the binding landscape of two free Ub monomers and also the functional landscapes of of all eight linkage types by theoretical modeling. Remarkably, we found that most of the compact structures of covalently connected dimeric Ub chains (diUbs pre-exist on the binding landscape. These compact functional states were subsequently validated by corresponding linkage models. This leads to the proposal that the folding architecture of Ub monomer has encoded all functional states into its binding landscape, which is further selected by different topologies of polymeric Ub chains. Moreover, our results revealed that covalent linkage leads to symmetry breaking of interfacial interactions. We further propose that topological constraint not only limits the conformational space for effective switching between functional states, but also selects the local interactions for realizing the corresponding biological function. Therefore, the topological constraint provides a way for breaking the binding symmetry and reaching the functional specificity. The simulation results also provide several predictions that qualitatively and quantitatively consistent with experiments. Importantly, the K48 linkage model successfully predicted intermediate states. The resulting multi-state energy landscape was further employed to reconcile the seemingly contradictory experimental data on the conformational equilibrium of K48-diUb. Our results further suggest that hydrophobic interactions are dominant in the functional landscapes of K6-, K11-, K33- and K48 diUbs, while electrostatic interactions play a more important role in the functional landscapes of K27, K29, K63 and linear linkages.

PolyUbiquitin chain linkage topology selects the functions from the underlying binding landscape.

Science.gov (United States)

Wang, Yong; Tang, Chun; Wang, Erkang; Wang, Jin

2014-07-01

Ubiquitin (Ub) can generate versatile molecular signals and lead to different celluar fates. The functional poly-valence of Ub is believed to be resulted from its ability to form distinct polymerized chains with eight linkage types. To provide a full picture of ubiquitin code, we explore the binding landscape of two free Ub monomers and also the functional landscapes of of all eight linkage types by theoretical modeling. Remarkably, we found that most of the compact structures of covalently connected dimeric Ub chains (diUbs) pre-exist on the binding landscape. These compact functional states were subsequently validated by corresponding linkage models. This leads to the proposal that the folding architecture of Ub monomer has encoded all functional states into its binding landscape, which is further selected by different topologies of polymeric Ub chains. Moreover, our results revealed that covalent linkage leads to symmetry breaking of interfacial interactions. We further propose that topological constraint not only limits the conformational space for effective switching between functional states, but also selects the local interactions for realizing the corresponding biological function. Therefore, the topological constraint provides a way for breaking the binding symmetry and reaching the functional specificity. The simulation results also provide several predictions that qualitatively and quantitatively consistent with experiments. Importantly, the K48 linkage model successfully predicted intermediate states. The resulting multi-state energy landscape was further employed to reconcile the seemingly contradictory experimental data on the conformational equilibrium of K48-diUb. Our results further suggest that hydrophobic interactions are dominant in the functional landscapes of K6-, K11-, K33- and K48 diUbs, while electrostatic interactions play a more important role in the functional landscapes of K27, K29, K63 and linear linkages.

Surface functionalization of cellulose by grafting oligoether chains

International Nuclear Information System (INIS)

Ly, El hadji Babacar; Bras, Julien; Sadocco, Patrizia; Belgacem, Mohamed Naceur; Dufresne, Alain; Thielemans, Wim

2010-01-01

Two cellulosic substrates (Whatman paper and wood fibres) were chemically modified using different oligoether chains; poly(ethylene) (POE), poly(propylene) (PPG) and poly(tetrahydrofuran) (PTHF) glycols with different lengths were first converted into mono-NCO-terminating macromolecules to allow direct grafting to the cellulose substrates. This step was achieved by reacting the chosen oligoether with 2,4-toluene diisocyanate. The prepared macromolecular grafts were then coupled with the cellulose surface and the resulting treated substrates were fully characterized by contact angle measurements, elemental analysis, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Thus, all the techniques implemented showed clear evidence of successful grafting, namely: (i) when using PPG grafts, the polar contribution to the surface energy decreased from approximately 25 to virtually 0 mJ m -2 and the wettability by water decreased, as the water contact angle shifted from around 40 to above 90 o ; (ii) nitrogen atoms were detected by elemental analysis and XPS; (iii) the aliphatic carbon contents increased from 11 to about 39-50%, depending on the oligoether used; and (iv) small spheres having about 100 nm diameter were detected by SEM. Moreover, the grafted fibres were submitted to biodegradation tests which showed that they conserved their biodegradable character, although with a slower biodegradation rate. The novelty of the present paper is the direct grafting of the polymeric matrix onto the fibre surface thanks to a new modification strategy involving the use of a diisocyanate as a mediator between the matrix and the reinforcing elements. The covalently linked polymeric chains constituting the matrix could melt under heating, thus, yielding the interdiffusion of the macromolecular grafts and forming the composite.

The effect of the cation alkyl chain length on density and diffusion in dialkylpyrrolidinium bis(mandelato)borate ionic liquids.

Science.gov (United States)

Filippov, Andrei; Taher, Mamoun; Shah, Faiz Ullah; Glavatskih, Sergei; Antzutkin, Oleg N

2014-12-28

The physicochemical properties of ionic liquids are strongly affected by the selective combination of the cations and anions comprising the ionic liquid. In particular, the length of the alkyl chains of ions has a clear influence on the ionic liquid's performance. In this paper, we study the self-diffusion of ions in a series of halogen-free boron-based ionic liquids (hf-BILs) containing bis(mandelato)borate anions and dialkylpyrrolidinium cations with long alkyl chains CnH2n+1 with n from 4 to 14 within a temperature range of 293-373 K. It was found that the hf-BILs with n = 4-7 have very similar diffusion coefficients, while hf-BILs with n = 10-14 exhibit two liquid sub-phases in almost the entire temperature range studied (293-353 K). Both liquid sub-phases differ in their diffusion coefficients, while values of the slower diffusion coefficients are close to those of hf-BILs with shorter alkyl chains. To explain the particular dependence of diffusion on the alkyl chain length, we examined the densities of the hf-BILs studied here. It was shown that the dependence of the density on the number of CH2 groups in long alkyl chains of cations can be accurately described using a "mosaic type" model, where regions of long alkyl chains of cations (named 'aliphatic' regions) and the residual chemical moieties in both cations and anions (named 'ionic' regions) give additive contributions. Changes in density due to an increase in temperature and the number of CH2 groups in the long alkyl chains of cations are determined predominantly by changes in the free volume of the 'ionic' regions, while 'aliphatic' regions are already highly compressed by van der Waals forces, which results in only infinitesimal changes in their free volumes with temperature.

Equivalent chain lengths of all C4-C23 saturated monomethyl branched fatty acid methyl esters on methylsilicone OV-1 stationary phase.

Science.gov (United States)

Kubinec, Róbert; Blaško, Jaroslav; Górová, Renáta; Addová, Gabriela; Ostrovský, Ivan; Amann, Anton; Soják, Ladislav

2011-04-01

Isomer mixtures of monomethyl branched saturated C7-C23 fatty acid methyl esters (FAME) were prepared by performing a methylene insertion reaction to the straight chain FAME and this study model was completed by using commercially available standards of C4-C7 FAME. The equivalent chain lengths (ECL) of all 220 C4-C23 monomethyl branched FAME on OV-1 stationary phase were measured, achieving an average repeatability of ±0.0004 ECL units. The monomethyl branched FAME was identified by GC on the basis of regularity of the fractional chain lengths (FCL) dependence on the number of carbon atoms (C(z)) of individual homologous series of methyl 2-, 3-, …, 21-FAME. The prediction of retention of the first homologues, having the new position of methyl group beginning at higher carbon atoms number, and analogously for the second, third, fourth, and other members of the homologous series, allowed the dependence FCL=f(C(z)) for the first and subsequent members of beginning homologous of monomethyl derivatives of FAME. The identification was confirmed by mass spectrometry. All of the methyl isomers of FAME, which could not be completely separated by gas chromatography due to having a methyl group in surroundings of the middle of the carbon chain, were resolved by mass spectrometry using deconvolution in a SIM-mode. Measured gas chromatographic and mass spectrometric data were applied for identification of the monomethyl branched saturated FAME in tongue coating. Copyright © 2011 Elsevier B.V. All rights reserved.

Association mapping of starch chain length distribution and amylose content in pea (Pisum sativum L.) using carbohydrate metabolism candidate genes.

Science.gov (United States)

Carpenter, Margaret A; Shaw, Martin; Cooper, Rebecca D; Frew, Tonya J; Butler, Ruth C; Murray, Sarah R; Moya, Leire; Coyne, Clarice J; Timmerman-Vaughan, Gail M

2017-08-01

Although starch consists of large macromolecules composed of glucose units linked by α-1,4-glycosidic linkages with α-1,6-glycosidic branchpoints, variation in starch structural and functional properties is found both within and between species. Interest in starch genetics is based on the importance of starch in food and industrial processes, with the potential of genetics to provide novel starches. The starch metabolic pathway is complex but has been characterized in diverse plant species, including pea. To understand how allelic variation in the pea starch metabolic pathway affects starch structure and percent amylose, partial sequences of 25 candidate genes were characterized for polymorphisms using a panel of 92 diverse pea lines. Variation in the percent amylose composition of extracted seed starch and (amylopectin) chain length distribution, one measure of starch structure, were characterized for these lines. Association mapping was undertaken to identify polymorphisms associated with the variation in starch chain length distribution and percent amylose, using a mixed linear model that incorporated population structure and kinship. Associations were found for polymorphisms in seven candidate genes plus Mendel's r locus (which conditions the round versus wrinkled seed phenotype). The genes with associated polymorphisms are involved in the substrate supply, chain elongation and branching stages of the pea carbohydrate and starch metabolic pathways. The association of polymorphisms in carbohydrate and starch metabolic genes with variation in amylopectin chain length distribution and percent amylose may help to guide manipulation of pea seed starch structural and functional properties through plant breeding.

4-N, 4-S & 4-O Chloroquine Analogues: Influence of Side Chain Length and Quinolyl Nitrogen pKa on Activity vs. Chloroquine Resistant Malaria+, #

OpenAIRE

Natarajan, Jayakumar K.; Alumasa, John; Yearick, Kimberly; Ekoue-Kovi, Kekeli A.; Casabianca, Leah B.; de Dios, Angel C.; Wolf, Christian; Roepe, Paul D.

2008-01-01

Using predictions from heme – quinoline antimalarial complex structures, previous modifications of chloroquine (CQ), and hypotheses for chloroquine resistance (CQR), we synthesize and assay CQ analogues that test structure – function principles. We vary side chain length for both monoethyl and diethyl 4N CQ derivatives. We alter the pKa of the quinolyl N by introducing alkylthio or alkoxy substituents into the 4 position, and vary side chain length for these analogues. We introduce an additio...

PEGylation of Phytantriol-Based Lyotropic Liquid Crystalline Particles-The Effect of Lipid Composition, PEG Chain Length, and Temperature on the Internal Nanostructure

DEFF Research Database (Denmark)

Nilsson, Christa; Ostergaard, Jesper; Larsen, Susan Weng

2014-01-01

of these lipidic nonlamellar liquid crystalline particles by using DSPE-mPEGs with three different block lengths of the hydrophilic PEG segment. The effects of lipid composition, PEG chain length, and temperature on the morphology and internal nanostructure of these self-assembled lipidic aqueous dispersions based...

Fundamentals of poly(lactic acid) microstructure, crystallization behavior, and properties

Science.gov (United States)

Kang, Shuhui

Poly(lactic acid) is an environmentally-benign biodegradable and sustainable thermoplastic material, which has found broad applications as food packaging films and as non-woven fibers. The crystallization and deformation mechanisms of the polymer are largely determined by the distribution of conformation and configuration. Knowledge of these mechanisms is needed to understand the mechanical and thermal properties on which processing conditions mainly depend. In conjunction with laser light scattering, Raman spectroscopy and normal coordinate analysis are used in this thesis to elucidate these properties. Vibrational spectroscopic theory, Flory's rotational isomeric state (RIS) theory, Gaussian chain statistics and statistical mechanics are used to relate experimental data to molecular chain structure. A refined RIS model is proposed, chain rigidity recalculated and chain statistics discussed. A Raman spectroscopic characterization method for crystalline and amorphous phase orientation has been developed. A shrinkage model is also proposed to interpret the dimensional stability for fibers and uni- or biaxially stretched films. A study of stereocomplexation formed by poly(l-lactic acid) and poly(d-lactic acid) is also presented.

BCR CDR3 length distributions differ between blood and spleen and between old and young patients, and TCR distributions can be used to detect myelodysplastic syndrome

International Nuclear Information System (INIS)

Pickman, Yishai; Mehr, Ramit; Dunn-Walters, Deborah

2013-01-01

Complementarity-determining region 3 (CDR3) is the most hyper-variable region in B cell receptor (BCR) and T cell receptor (TCR) genes, and the most critical structure in antigen recognition and thereby in determining the fates of developing and responding lymphocytes. There are millions of different TCR Vβ chain or BCR heavy chain CDR3 sequences in human blood. Even now, when high-throughput sequencing becomes widely used, CDR3 length distributions (also called spectratypes) are still a much quicker and cheaper method of assessing repertoire diversity. However, distribution complexity and the large amount of information per sample (e.g. 32 distributions of the TCRα chain, and 24 of TCRβ) calls for the use of machine learning tools for full exploration. We have examined the ability of supervised machine learning, which uses computational models to find hidden patterns in predefined biological groups, to analyze CDR3 length distributions from various sources, and distinguish between experimental groups. We found that (a) splenic BCR CDR3 length distributions are characterized by low standard deviations and few local maxima, compared to peripheral blood distributions; (b) healthy elderly people's BCR CDR3 length distributions can be distinguished from those of the young; and (c) a machine learning model based on TCR CDR3 distribution features can detect myelodysplastic syndrome with approximately 93% accuracy. Overall, we demonstrate that using supervised machine learning methods can contribute to our understanding of lymphocyte repertoire diversity. (paper)

BCR CDR3 length distributions differ between blood and spleen and between old and young patients, and TCR distributions can be used to detect myelodysplastic syndrome

Science.gov (United States)

Pickman, Yishai; Dunn-Walters, Deborah; Mehr, Ramit

2013-10-01

Complementarity-determining region 3 (CDR3) is the most hyper-variable region in B cell receptor (BCR) and T cell receptor (TCR) genes, and the most critical structure in antigen recognition and thereby in determining the fates of developing and responding lymphocytes. There are millions of different TCR Vβ chain or BCR heavy chain CDR3 sequences in human blood. Even now, when high-throughput sequencing becomes widely used, CDR3 length distributions (also called spectratypes) are still a much quicker and cheaper method of assessing repertoire diversity. However, distribution complexity and the large amount of information per sample (e.g. 32 distributions of the TCRα chain, and 24 of TCRβ) calls for the use of machine learning tools for full exploration. We have examined the ability of supervised machine learning, which uses computational models to find hidden patterns in predefined biological groups, to analyze CDR3 length distributions from various sources, and distinguish between experimental groups. We found that (a) splenic BCR CDR3 length distributions are characterized by low standard deviations and few local maxima, compared to peripheral blood distributions; (b) healthy elderly people's BCR CDR3 length distributions can be distinguished from those of the young; and (c) a machine learning model based on TCR CDR3 distribution features can detect myelodysplastic syndrome with approximately 93% accuracy. Overall, we demonstrate that using supervised machine learning methods can contribute to our understanding of lymphocyte repertoire diversity.

Structure formation in fibrous materials based on poly-3-hydroxybutyrate for traumatology

Science.gov (United States)

Olkhov, A. A.; Sklyanchuk, E. D.; Staroverova, O. V.; Abbasov, T. A.; Guryev, V. V.; Akatov, V. S.; Fadeyeva, I. S.; Fesenko, N. I.; Filatov, Yu. N.; Iordanskii, A. L.

2015-10-01

The paper reviews the structure formation of fibrous materials based on poly-3-hydroxybutyrate depending on parameters of electrospinning and characteristics of polymer solution. Fiber structure was studied by DSC, ESR and SEM. The molecular weight affects the diameter and uniformity of the fiber. An electromechanical impact leads to an orientation of crystalline structure in the fiber. The design of an artificial bioresorbable implant based on nano- and microfibers of poly-3-hydroxybutyrate is created. Dynamics of growth of mesenchymal stem cells on poly-3-hydroxybutyrate scaffolds is studied. Successful field tests of implants of the Achilles tendon in Wistar rats are conducted.

Influence of trehalose 6,6'-diester (TDX) chain length on the physicochemical and immunopotentiating properties of DDA/TDX liposomes

DEFF Research Database (Denmark)

Kallerup, Rie Selchau; Madsen, Cecilie Maria; Schiøth, Mikkel Lohmann

2015-01-01

Linking physicochemical characterization to functional properties is crucial for defining critical quality attributes during development of subunit vaccines toward optimal safety and efficacy profiles. We investigated how the trehalose 6,6'-diester (TDX) chain length influenced the physicochemical...... and immunopotentiating properties of the clinically tested liposomal adjuvant composed of dimethyldioctadecylammonium (DDA) bromide and analogues of trehalose-6,6'-dibehenate (TDB). TDB analogues with symmetrically shortened acyl chains [denoted X: arachidate (A), stearate (S), palmitate (P), myristate (Myr) and laurate...

The role of discharge variation in scaling of drainage area and food chain length in rivers

Science.gov (United States)

Sabo, John L.; Finlay, Jacques C.; Kennedy, Theodore A.; Post, David M.

2010-01-01

Food chain length (FCL) is a fundamental component of food web structure. Studies in a variety of ecosystems suggest that FCL is determined by energy supply, environmental stability, and/or ecosystem size, but the nature of the relationship between environmental stability and FCL, and the mechanism linking ecosystem size to FCL, remain unclear. Here we show that FCL increases with drainage area and decreases with hydrologic variability and intermittency across 36 North American rivers. Our analysis further suggests that hydrologic variability is the mechanism underlying the correlation between ecosystem size and FCL in rivers. Ecosystem size lengthens river food chains by integrating and attenuating discharge variation through stream networks, thereby enhancing environmental stability in larger river systems.

Synthesis of Poly(3,4-Ethylenedioxy thiophene)-Poly(Styrene-4-Sulfonate) Composites for Support Fuel Cell Catalyst Layer

International Nuclear Information System (INIS)

Eko Sulistiyono; Murni Handayani

2009-01-01

Synthesis of poly(3,4-ethylenedioxy thiophene)-poly(styrene-4-sulfonate) composites for support fuel cell catalyst layer are synthesis composites which become fuel cell catalyst support so that catalyst has optimal performance. Main function of composites is support platinum particle for application in fuel cell. This article explains the result of composites production process from ( 3,4 Ethylenedioxy thiophene) and Sodium poly( styrene - 4-sulfonate) using two methods Jingning Shan method (method 1) and Zhigang Qi and Peter G.Pickup method (method 2). Analysis of the synthesis results used Scanning Electron Microscopic –Electron Dispersive X – Ray Spectrophotometer (SEM-EDS ). The analysis result show that both methods produce polymer agglomerate into a sponge-like morphology. Composite from method 1 has morphology, pores and proton transport better than composite produced by method 2. (author)

Effect of heat shock on poly(ADP-ribose) synthetase and DNA repair in Drosophila cells

Energy Technology Data Exchange (ETDEWEB)

Nolan, N.L.; Kidwell, W.R.

1982-04-01

Poly(ADP-ribose) synthetase, a chromatin-bound enzyme which attaches polyanionic chains of ADP-ribose to nuclear proteins, was found to be temperature sensitive in intact Drosophila melanogaster cells. The synthetase was completely inactivated by heat-shocking the cells at 37/sup 0/C for 5 min, a condition which had no appreciable effect on the subsequent growth of Drosophila cells at their physiological temperature. The heat-shock effect on synthetase was reversible; enzyme activity began to reappear about 2 hr post heat shock. During the 2-hr interval when poly(ADP-ribose) synthetase was absent, the cells were competent in repair of ..gamma..-ray-induced DNA strand breaks as shown by DNA sedimentation studies on alkaline sucrose gradients. It is thus concluded that poly(ADP-ribose) synthesis is unnecessary for repair of DNA strand breaks introduced by irradiation. The same conclusion was reached from the fact that two inhibitors of poly(ADP-ribose) synthetase 3-aminobenzamide and 5-methylnicotinamide, failed to block repair of ..gamma..-ray-induced DNA chain breaks even though both inhibitors reduced the amount of poly(ADP-ribose) synthesized in cells by 50-75%. Although it was found that the repair of DNA strand breaks is independent of poly(ADP-ribose) synthesis, irradiation does activate the synthetase in control cells, as shown by radioimmunoassay of poly(ADP-ribose) levels.

Effect of heat shock on poly(ADP-ribose) synthetase and DNA repair in Drosophila cells

International Nuclear Information System (INIS)

Nolan, N.L.; Kidwell, W.R.

1982-01-01

Poly(ADP-ribose) synthetase, a chromatin-bound enzyme which attaches polyanionic chains of ADP-ribose to nuclear proteins, was found to be temperature sensitive in intact Drosophila melanogaster cells. The synthetase was completely inactivated by heat-shocking the cells at 37 0 C for 5 min, a condition which had no appreciable effect on the subsequent growth of Drosophila cells at their physiological temperature. The heat-shock effect on synthetase was reversible; enzyme activity began to reappear about 2 hr post heat shock. During the 2-hr interval when poly(ADP-ribose) synthetase was absent, the cells were competent in repair of γ-ray-induced DNA strand breaks as shown by DNA sedimentation studies on alkaline sucrose gradients. It is thus concluded that poly(ADP-ribose) synthesis is unnecessary for repair of DNA strand breaks introduced by irradiation. The same conclusion was reached from the fact that two inhibitors of poly(ADP-ribose) synthetase 3-aminobenzamide and 5-methylnicotinamide, failed to block repair of γ-ray-induced DNA chain breaks even though both inhibitors reduced the amount of poly(ADP-ribose) synthesized in cells by 50-75%. Although it was found that the repair of DNA strand breaks is independent of poly(ADP-ribose) synthesis, irradiation does activate the synthetase in control cells, as shown by radioimmunoassay of poly(ADP-ribose) levels

Poly(organo phosphazene) nanoparticles surface modified with poly(ethylene oxide).

Science.gov (United States)

Vandorpe, J; Schacht, E; Stolnik, S; Garnett, M C; Davies, M C; Illum, L; Davis, S S

1996-10-05

The use of biodegradable derivatives of poly(organo phosphazenes) for the preparation of nanoparticles and their surface modification with the novel poly(ethylene oxide) derivative of poly(organo phosphazene) has been assessed using a range of in vitro characterization methods. The nanoparticles were produced by the precipitation solvent evaporation method from the derivative co-substituted with phenylalanine and glycine ethyl ester side groups. A reduction in particle size to less than 200 nm was achieved by an increase in pH of the preparation medium. The formation (and colloidal stability) of these nanoparticles seems to be controlled by two opposite effects: attractive hydrophobic interactions between phenylalanine ester groups and electrostatic repulsions arising from the carboxyl groups formed due to (partial) hydrolysis of the ester bond(s) at the high pH of the preparation medium. The poly[(glycine ethyl ester)phosphazene] derivative containing 5000-Da poly(ethylene oxide) as 5% of the side groups was used for the surface modification of nanoparticles. Adsorbed onto the particles, the polymer produced a thick coating layer of approximately 35 nm. The coated nanoparticles exhibited reduced surface negative potential and improved colloidal stability toward electrolyte-induced flocculation, relative to the uncoated system. However, the steric stabilization provided was less effective than that of a Poloxamine 908 coating. This difference in effectiveness of the steric stabilization might indicate that, although both the stabilizing polymers possess a 5000-Da poly(ethylene oxide) moiety, there is a difference in the arrangements of these poly(ethylene oxide) chains at the particle surface. (c) 1996 John Wiley & Sons, Inc.

Effect of the novel polysaccharide PolyGlycopleX® on short-chain fatty acid production in a computer-controlled in vitro model of the human large intestine

NARCIS (Netherlands)

Reimer, R.A.; Maathuis, A.J.H.; Venema, K.; Lyon, M.R.; Gahler, R.J.; Wood, S.

2014-01-01