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Sample records for acid-labile temperature-responsive copolymers

  1. Acid-Labile Amphiphilic PEO-b-PPO-b-PEO Copolymers: Degradable Poloxamer Analogs.

    Science.gov (United States)

    Worm, Matthias; Kang, Biao; Dingels, Carsten; Wurm, Frederik R; Frey, Holger

    2016-05-01

    Poly ((ethylene oxide)-b-(propylene oxide)-b-(ethylene oxide)) triblock copolymers commonly known as poloxamers or Pluronics constitute an important class of nonionic, biocompatible surfactants. Here, a method is reported to incorporate two acid-labile acetal moieties in the backbone of poloxamers to generate acid-cleavable nonionic surfactants. Poly(propylene oxide) is functionalized by means of an acetate-protected vinyl ether to introduce acetal units. Three cleavable PEO-PPO-PEO triblock copolymers (Mn,total = 6600, 8000, 9150 g·mol(-1) ; Mn,PEO = 2200, 3600, 4750 g·mol(-1) ) have been synthesized using anionic ring-opening polymerization. The amphiphilic copolymers exhibit narrow molecular weight distributions (Ð = 1.06-1.08). Surface tension measurements reveal surface-active behavior in aqueous solution comparable to established noncleavable poloxamers. Complete hydrolysis of the labile junctions after acidic treatment is verified by size exclusion chromatography. The block copolymers have been employed as surfactants in a miniemulsion polymerization to generate polystyrene (PS) nanoparticles with mean diameters of ≈200 nm and narrow size distribution, as determined by dynamic light scattering and scanning electron microscopy. Acid-triggered precipitation facilitates removal of surfactant fragments from the nanoparticles, which simplifies purification and enables nanoparticle precipitation "on demand."

  2. An acid-labile block copolymer of PDMAEMA and PEG as potential carrier for intelligent gene delivery systems.

    Science.gov (United States)

    Lin, Song; Du, Fusheng; Wang, Yang; Ji, Shouping; Liang, Dehai; Yu, Lei; Li, Zichen

    2008-01-01

    Intelligent gene delivery systems based on physiologically triggered reversible shielding technology have evinced enormous interest due to their potential in vivo applications. In the present work, an acid-labile block copolymer consisting of poly(ethylene glycol) and poly(2-(dimethylamino)ethyl methacrylate) segments connected through a cyclic ortho ester linkage (PEG- a-PDMAEMA) was synthesized by atom transfer radical polymerization of DMAEMA using a PEG macroinitiator with an acid-cleavable end group. PEG- a-PDMAEMA condensed with plasmid DNA formed polyplex nanoparticles with an acid-triggered reversible PEG shield. The pH-dependent shielding/deshielding effect of PEG chains on the polyplex particles were evaluated by zeta potential and size measurements. At pH 7.4, polyplexes generated from PEG- a-PDMAEMA exhibited smaller particle size, lower surface charge, reduced interaction with erythrocytes, and less cytotoxicity compared to PDMAEMA-derived polyplexes. At pH 5.0, zeta potential of polyplexes formed from PEG- a-PDMAEMA increased, leveled up after 2 h of incubation and gradual aggregation occurred in the presence of bovine serum albumin (BSA). In contrast, the stably shielded polyplexes formed by DNA and an acid-stable block copolymer, PEG- b-PDMAEMA, did not change in size and zeta potential in 6 h. In vitro transfection efficiency of the acid-labile copolymer greatly increased after 6 h incubation at pH 5.0, approaching the same level of PDMAEMA, whereas there was only slight increase in efficiency for the stable copolymer, PEG- b-PDMAEMA.

  3. Modulating rheological and degradation properties of temperature-responsive gelling systems composed of blends of PCLA-PEG-PCLA triblock copolymers and their fully hexanoyl-capped derivatives.

    Science.gov (United States)

    Petit, Audrey; Müller, Benno; Bruin, Peter; Meyboom, Ronald; Piest, Martin; Kroon-Batenburg, Loes M J; de Leede, Leo G J; Hennink, Wim E; Vermonden, Tina

    2012-12-01

    In this study, the ability to modulate rheological and degradation properties of temperature-responsive gelling systems composed of aqueous blends of poly(ε-caprolactone-co-lactide)-b-poly(ethylene glycol)-b-poly(ε-caprolactone-co-lactide) (PCLA-PEG-PCLA) triblock copolymers (i.e. uncapped) and their fully capped derivatives was investigated. Uncapped and capped PCLA-PEG-PCLA triblock copolymers, abbreviated as degree of modification 0 and 2 (DM0 and DM2, respectively), were composed of identical PCLA and PEG blocks but different end groups: namely hydroxyl and hexanoyl end groups. DM0 was synthesized by ring opening polymerization of l-lactide and ε-caprolactone in toluene using PEG as initiator and tin(II) 2-ethylhexanoate as the catalyst. A portion of DM0 was subsequently reacted with an excess of hexanoyl chloride in solution to yield DM2. The cloud point and phase behaviour of DM0 and DM2 in buffer as well as that of their blends were determined by light scattering in a diluted state and by vial tilting and rheological measurements in a concentrated state. Degradation/dissolution properties of temperature-responsive gelling systems were studied in vitro at pH 7.4 and 37°C. The cloud points of DM0/DM2 blends were ratio-dependent and could be tailored from 15 to 40°C for blends containing 15 to 100wt.% DM0. Vial tilting and rheological experiments showed that, with solid contents between 20 and 30wt.%, DM0/DM2 blends (15/85 to 25/75w/w) had a sol-to-gel transition temperature at 10-20°C, whereas blends with less than 15wt.% DM0 formed gels below 4°C and the ones with more than 25wt.% DM0 did not show a sol-to-gel transition up to 50°C. Complete degradation of temperature-responsive gelling systems took ∼100days, independent of the DM0 fraction and the initial solid content. Analysis of residual gels in time by GPC and (1)H-NMR showed no chemical polymer degradation, but indicated gel degradation by dissolution. Preferential dissolution of lactoyl

  4. pH-responsive biodegradable micelles based on acid-labile polycarbonate hydrophobe: synthesis and triggered drug release.

    Science.gov (United States)

    Chen, Wei; Meng, Fenghua; Li, Feng; Ji, Shun-Jun; Zhong, Zhiyuan

    2009-07-13

    pH-responsive biodegradable micelles were prepared from block copolymers comprising of a novel acid-labile polycarbonate hydrophobe and poly(ethylene glycol) (PEG). Two new cyclic aliphatic carbonate monomers, mono-2,4,6-trimethoxybenzylidene-pentaerythritol carbonate (TMBPEC, 2a) and mono-4-methoxybenzylidene-pentaerythritol carbonate (MBPEC, 2b) were designed and successfully synthesized via a two-step procedure. The ring-opening polymerization of 2a or 2b in the presence of methoxy PEG in dichloromethane at 50 °C using zinc bis[bis(trimethylsilyl)amide] as a catalyst yielded the corresponding block copolymers PEG-PTMBPEC (3a) or PEG-PMBPEC (3b) with low polydispersities (PDI 1.03-1.04). The copolymerization of D,L-lactide (DLLA) and 2a under otherwise the same conditions could also proceed smoothly to afford PEG-P(TMBPEC-co-DLLA) (3c) block copolymer. These block copolymers readily formed micelles in water with sizes of about 120 nm as determined by dynamic light scattering (DLS). The hydrolysis of the acetals of the polycarbonate was investigated using UV/vis spectroscopy. The results showed that the acetals of micelles 3a, while stable at pH 7.4 are prone to rapid hydrolysis at mildly acidic pH of 4.0 and 5.0, with a half-life of 1 and 6.5 h, respectively. The acetal hydrolysis resulted in significant swelling of micelles, as a result of change of hydrophobic polycarbonate to hydrophilic polycarbonate. In comparison, the acetals of PMBPEC of micelles 3b displayed obviously slower hydrolysis at the same pH. Both paclitaxel and doxorubicin could be efficiently encapsulated into micelles 3a achieving high drug loading content (13.0 and 11.7 wt %, respectively). The in vitro release studies showed clearly a pH dependent release behavior, that is, significantly faster drug release at mildly acidic pH of 4.0 and 5.0 compared to physiological pH. These pH-responsive biodegradable micelles are promising as smart nanovehicles for targeted delivery of anticancer drugs.

  5. The acid-labile subunit of the ternary insulin-like growth factor complex in cirrhosis

    DEFF Research Database (Denmark)

    Møller, S; Juul, A; Becker, U;

    2000-01-01

    In the circulation, insulin-like growth factor-I (IGF-I) is bound in a trimeric complex of 150 kDa with IGF binding protein-3 (IGFBP-3) and the acid-labile subunit (ALS). Whereas circulating IGF-I and IGFBP-3 are reported to be low in patients with chronic liver failure, the level of ALS has...... not been described in relation to hepatic dysfunction. The aim of the present study was therefore to measure circulating and hepatic venous concentrations of ALS in relation to hepatic function and the IGF axis....

  6. Temperature responsive hydrogel nanofibers and nanoparticles

    Science.gov (United States)

    Ruokolainen, Janne

    2011-03-01

    Poly(N-isopropylacrylamide) (PNIPAM) is one of the most extensively investigated synthetic temperature-responsive polymers. In this work temperature-responsive PNIPAM based triblock copolymer hydrogels, their self-assembly and phase behavior in bulk, are described. Additionally, recent results from responsive hydrogel nanofibers and hydrogel nanoparticles are shown. It is known that block copolymers form well-organized nano structures in bulk or thin films when annealed thermally or in solvent vapours. However, in the case of nanofibers or nanoparticles, the annealing leads in most cases to aggregation and particle sintering. This work utilizes aerosol-based gas phase method where the preparation and annealing of hydrogel nanoparticles with well-organized, hierarchical inner structures are performed without any particle coagulation or sintering. In the method, the block copolymers assemble within aerosol nanoparticles to form, for instance, lamellar onion-like or gyroid inner structures.

  7. The acid-labile subunit of human ternary insulin-like growth factor binding protein complex in serum

    DEFF Research Database (Denmark)

    Juul, A; Møller, S; Mosfeldt-Laursen, E;

    1998-01-01

    Circulating insulin-like growth factor-I (IGF-I) is predominantly bound in the trimeric complex comprised of IGF binding protein-3 (IGFBP-3) and acid-labile subunit (ALS). Circulating concentrations of IGF-I, IGFBP-3 and ALS are believed to reflect the GH secretory status, but the clinical use...... of ALS determination is not known. We therefore, determined the: 1) hepatosplanchnic release of ALS by liver vein catheterization (n=30); 2) 24-h diurnal variation of ALS (n=8); 3) normal age-related ranges of circulating ALS (n=1158); 4) diagnostic value of ALS in 108 patients with childhood-onset GH...... deficiency (GHD). We found: 1) no significant arteriovenous gradient over the liver ofALS, IGF-I, and IGFBP-3; 2) the diurnal variation of ALS was 12% (mean coefficient of variation percent); 3) ALS levels increased throughout childhood with maximal levels in puberty, with a subsequent decrease with age...

  8. The acid-labile subunit of the ternary insulin-like growth factor complex in cirrhosis: relation to liver dysfunction

    DEFF Research Database (Denmark)

    Møller, S; Juul, A; Becker, U;

    2000-01-01

    BACKGROUND/AIMS: In the circulation, insulin-like growth factor-I (IGF-I) is bound in a trimeric complex of 150 kDa with IGF binding protein-3 (IGFBP-3) and the acid-labile subunit (ALS). Whereas circulating IGF-I and IGFBP-3 are reported to be low in patients with chronic liver failure, the level...... of ALS has not been described in relation to hepatic dysfunction. The aim of the present study was therefore to measure circulating and hepatic venous concentrations of ALS in relation to hepatic function and the IGF axis. METHODS: Twenty-five patients with cirrhosis (Child class A/B/C:5/10/10) and 30...... controls with normal liver function were studied. During a haemodynamic investigation, blood samples were collected from the hepatic vein and femoral artery, and the plasma concentrations of ALS, IGF-I and IGFBP-3 were determined. RESULTS: Hepatic venous and arterial concentrations of ALS were...

  9. Molecular glass positive i-line photoresist materials containing 2,1,4-DNQ and acid labile group

    Science.gov (United States)

    Wang, Liyuan; Yu, Jinxing; Xu, Na

    2010-04-01

    Recent years increasing attention has been given to molecular glass resist materials. In this paper, maleopimaric acid, cycloaddition reaction product of rosin with maleic anhydride, was reacted with hydroxylamine and then further esterified with 2-diazo-1-naphthoquinone-4-sulfonyl chloride to give N-hydroxy maleopimarimide sulfonate. The carboxylic acid group of the compound was then protected by the reaction of this compound with vinyl ethyl ether or dihydropyran. Thus obtained compounds were amorphous. When irradiated with i-line light, the 2,1,4-DNQ group undergo photolysis not only to give off nitrogen gas but also generate sulfonic acid which can result in the decomposition of the acid labile group. So, a novel chemically amplified positive i-line molecular glass photoresists can be formed by the compound and other acidolytic molecular glass compounds. The lithographic performance of the resist materials is evaluated.

  10. Low Molecular Weight PEI-Based Vectors via Acid-Labile Ortho Ester Linkage for Improved Gene Delivery.

    Science.gov (United States)

    Zhang, Lei; Yu, Min; Wang, Jun; Tang, Rupei; Yan, Guoqing; Yao, Weijing; Wang, Xin

    2016-08-01

    A series of novel pH-sensitive gene delivery vectors (POEI 1, 2, and 3) are synthesized through Michael addition from low molecular weight PEI (LMW PEI) via acid-labile ortho ester linkage with terminal acrylates (OEAc) by various feed molar ratios. The obtained POEI 1 and POEI 2 can efficiently condense plasmid DNA into nanoparticles with size range of 200-300 nm and zeta-potentials of about +15 mV while protecting DNA from enzymatic digestion compared with POEI 3. Significantly, ortho ester groups of POEI main-chains can make an instantaneous degradation-response to acidic endosomal pH (≈5.0), resulting in accelerated disruption of polyplexes and intracellular DNA release. MTT assay reveals that all POEIs exhibit much lower cytotoxicity in different cells than branched PEI (25 KDa). As expected, POEI 1 and POEI 2 perform improved gene transfection in vitro, suggesting that such polycations might be promising gene vectors based on overcoming toxicity-efficiency contradiction.

  11. A simple and inexpensive enteric-coated capsule for delivery of acid-labile macromolecules to the small intestine.

    Science.gov (United States)

    Miller, Darren S; Parsons, Anne Michelle; Bresland, John; Herde, Paul; Pham, Duc Minh; Tan, Angel; Hsu, Hung-yao; Prestidge, Clive A; Kuchel, Tim; Begg, Rezaul; Aziz, Syed Mahfuzul; Butler, Ross N

    2015-07-01

    Understanding the ecology of the gastrointestinal tract and the impact of the contents on the host mucosa is emerging as an important area for defining both wellness and susceptibility to disease. Targeted delivery of drugs to treat specific small intestinal disorders such as small bowel bacterial overgrowth and targeting molecules to interrogate or to deliver vaccines to the remote regions of the small intestine has proven difficult. There is an unmet need for methodologies to release probes/drugs to remote regions of the gastrointestinal tract in furthering our understanding of gut health and pathogenesis. In order to address this concern, we need to know how the regional delivery of a surrogate labeled test compound is handled and in turn, if delivered locally as a liquid or powder, the dynamics of its subsequent handling and metabolism. In the studies we report on in this paper, we chose (13)C sodium acetate ((13)C-acetate), which is a stable isotope probe that once absorbed in the small intestine can be readily measured non-invasively by collection and analysis of (13)CO2 in the breath. This would provide information of gastric emptying rates and an indication of the site of release and absorptive capacity. In a series of in vitro and in vivo pig experiments, we assessed the enteric-protective properties of a commercially available polymer EUDRAGIT(®) L100-55 on gelatin capsules and also on DRcaps(®). Test results demonstrated that DRcaps(®) coated with EUDRAGIT(®) L100-55 possessed enhanced enteric-protective properties, particularly in vivo. These studies add to the body of knowledge regarding gastric emptying in pigs and also begin the process of gathering specifications for the design of a simple and cost-effective enteric-coated capsule for delivery of acid-labile macromolecules to the small intestine.

  12. Development of pH-sensitive self-nanoemulsifying drug delivery systems for acid-labile lipophilic drugs.

    Science.gov (United States)

    Zhao, Tianjing; Maniglio, Devid; Chen, Jie; Chen, Bin; Migliaresi, Claudio

    2016-03-01

    Oral administration is the most convenient way of all the drug delivery routes. Orally administered bioactive compounds must resist the harsh acidic fluids or enzyme digestion in stomach, to reach their absorbed destination in small intestine. This is the case for silibinin, a drug used to protect liver cells against toxins that has also been demonstrated in vitro to possess anti-cancer effects. However, as many other drugs, silibinin can degrade in the stomach due to the action of the gastric fluid. The use of pH-sensitive self-nanoemulsifying drug delivery systems (pH-SNEDDS) could overcome the drawback due to degradation of the drug in the stomach while enhancing its solubility and dissolution rate. In this paper we have investigated pH-sensitive self-nanoemulsifying formulations containing silibinin as model drug. Pseudo-ternary phase diagrams have been constructed in order to identify the self-emulsification regions under different pH. Solubility of silibinin in selected formulations has been assessed and stability of the pure drug and of the silibinin loaded pH-SNEDDS formulations in simulated gastric fluid had been compared. Droplet size of the optimized pH-SNEDDS has been correlated to pH, volume of dilution medium and silibinin loading amount. TEM (transmission electron microscopy) studies have shown that emulsion droplets had spherical shape and narrow size distribution. In vitro drug release studies of the optimal pH-SNEDDS indicated substantial increase of the drug release and release rate in comparison to pure silibinin and to the commercial silibinin tablet. The results indicated that pH-SNEDDS have potential to improve the biopharmaceutics properties of acid-labile lipophilic drugs.

  13. Detection of a variable intracellular acid-labile carbon pool in Thalassiosira weissflogii (Heterokontophyta) and Emiliania huxleyi (Haptophyta) in response to changes in the seawater carbon system.

    Science.gov (United States)

    Isensee, Kirsten; Erez, Jonathan; Stoll, Heather M

    2014-02-01

    Accumulation of an intracellular pool of carbon (C(i) pool) is one strategy by which marine algae overcome the low abundance of dissolved CO2 (CO2 (aq) ) in modern seawater. To identify the environmental conditions under which algae accumulate an acid-labile C(i) pool, we applied a (14) C pulse-chase method, used originally in dinoflagellates, to two new classes of algae, coccolithophorids and diatoms. This method measures the carbon accumulation inside the cells without altering the medium carbon chemistry or culture cell density. We found that the diatom Thalassiosira weissflogii [(Grunow) G. Fryxell & Hasle] and a calcifying strain of the coccolithophorid Emiliania huxleyi [(Lohmann) W. W. Hay & H. P. Mohler] develop significant acid-labile C(i) pools. C(i) pools are measureable in cells cultured in media with 2-30 µmol l(-1) CO2 (aq), corresponding to a medium pH of 8.6-7.9. The absolute C(i) pool was greater for the larger celled diatoms. For both algal classes, the C(i) pool became a negligible contributor to photosynthesis once CO2 (aq) exceeded 30 µmol l(-1) . Combining the (14) C pulse-chase method and (14) C disequilibrium method enabled us to assess whether E. huxleyi and T. weissflogii exhibited thresholds for foregoing accumulation of DIC or reduced the reliance on bicarbonate uptake with increasing CO2 (aq) . We showed that the C(i) pool decreases with higher CO2 :HCO3 (-) uptake rates.

  14. Mass spectrometry method to identify aging pathways of Sp- and Rp-tabun adducts on human butyrylcholinesterase based on the acid labile P-N bond.

    Science.gov (United States)

    Jiang, Wei; Cashman, John R; Nachon, Florian; Masson, Patrick; Schopfer, Lawrence M; Lockridge, Oksana

    2013-04-01

    The phosphoramidate nerve agent tabun inhibits butyrylcholinesterase (BChE) and acetylcholinesterase by making a covalent bond on the active site serine. The adduct loses an alkyl group in a process called aging. The mechanism of aging of the tabun adduct is controversial. Some studies claim that aging proceeds through deamination, whereas crystal structure studies show aging by O-dealkylation. Our goal was to develop a method that clearly distinguishes between deamination and O-dealkylation. We began by studying the tetraisopropyl pyrophosphoramide adduct of BChE because this adduct has two P-N bonds. Mass spectra showed that the P-N bonds were stable during trypsin digestion at pH 8 but were cleaved during pepsin digestion at pH 2. The P-N bond in tabun was also acid labile, whereas the P-O bond was stable. A scheme to distinguish aging by deamination from aging by O-dealkylation was based on the acid labile P-N bond. BChE was inhibited with Sp- and Rp-tabun thiocholine nerve agent model compounds to make adducts identical to those of tabun with known stereochemistry. After aging and digestion with pepsin at pH 2, peptide FGES198AGAAS from Sp-tabun thiocholine had a mass of 902.2 m/z in negative mode, indicating that it had aged by deamination, whereas peptide FGES198AGAAS from Rp-tabun thiocholine had a mass of 874.2 m/z in negative mode, indicating that it had aged by O-dealkylation. BChE inhibited by authentic, racemic tabun yielded both 902.2 and 874.2 m/z peptides, indicating that both stereoisomers reacted with BChE and aged either by deamination or dealkylation.

  15. Application of nanoparticles for oral delivery of acid-labile lansoprazole in the treatment of gastric ulcer: in vitro and in vivo evaluations.

    Science.gov (United States)

    Alai, Milind; Lin, Wen Jen

    2015-01-01

    The aim of this study was to develop nanoparticles for oral delivery of an acid-labile drug, lansoprazole (LPZ), for gastric ulcer therapy. LPZ-loaded positively charged Eudragit(®) RS100 nanoparticles (ERSNPs-LPZ) and negatively charged poly(lactic-co-glycolic acid) nanoparticles (PLGANPs-LPZ) were prepared. The effect of charge on nanoparticle deposition in ulcerated and non-ulcerated regions of the stomach was investigated. The cellular uptake of nanoparticles in the intestine was evaluated in a Caco-2 cell model. The pharmacokinetic performance and ulcer healing response of LPZ-loaded nanoparticles following oral administration were evaluated in Wistar rats with induced ulcers. The prepared drug-loaded ERSNPs-LPZ and PLGANPs-LPZ possessed opposite surface charge (+38.5±0.3 mV versus -27.3±0.3 mV, respectively) and the particle size was around 200 nm with a narrow size distribution. The negatively charged PLGANPs adhered more readily to the ulcerated region (7.22%±1.21% per cm(2)), whereas the positively charged ERSNPs preferentially distributed in the non-ulcerated region (8.29%±0.35% per cm(2)). Both ERSNPs and PLGANPs were prominent uptake in Caco-2 cells, too. The nanoparticles sustained and prolonged LPZ concentrations up to 24 hours, and the half-life and mean residence time of LPZ were prolonged by 3.5-fold and 4.5-fold, respectively, as compared with LPZ solution. Oral administration of LPZ-loaded nanoparticles healed 92.6%-95.7% of gastric ulcers in Wistar rats within 7 days.

  16. Application of nanoparticles for oral delivery of acid-labile lansoprazole in the treatment of gastric ulcer: in vitro and in vivo evaluations

    Directory of Open Access Journals (Sweden)

    Alai M

    2015-06-01

    Full Text Available Milind Alai,1 Wen Jen Lin1,2 1Graduate Institute of Pharmaceutical Sciences, School of Pharmacy, 2Drug Research Center, College of Medicine, National Taiwan University, Taipei, Taiwan Abstract: The aim of this study was to develop nanoparticles for oral delivery of an acid-labile drug, lansoprazole (LPZ, for gastric ulcer therapy. LPZ-loaded positively charged Eudragit® RS100 nanoparticles (ERSNPs-LPZ and negatively charged poly(lactic-co-glycolic acid nanoparticles (PLGANPs-LPZ were prepared. The effect of charge on nanoparticle deposition in ulcerated and non-ulcerated regions of the stomach was investigated. The cellular uptake of nanoparticles in the intestine was evaluated in a Caco-2 cell model. The pharmacokinetic performance and ulcer healing response of LPZ-loaded nanoparticles following oral administration were evaluated in Wistar rats with induced ulcers. The prepared drug-loaded ERSNPs-LPZ and PLGANPs-LPZ possessed opposite surface charge (+38.5±0.3 mV versus -27.3±0.3 mV, respectively and the particle size was around 200 nm with a narrow size distribution. The negatively charged PLGANPs adhered more readily to the ulcerated region (7.22%±1.21% per cm2, whereas the positively charged ERSNPs preferentially distributed in the non-ulcerated region (8.29%±0.35% per cm2. Both ERSNPs and PLGANPs were prominent uptake in Caco-2 cells, too. The nanoparticles sustained and prolonged LPZ concentrations up to 24 hours, and the half-life and mean residence time of LPZ were prolonged by 3.5-fold and 4.5-fold, respectively, as compared with LPZ solution. Oral administration of LPZ-loaded nanoparticles healed 92.6%–95.7% of gastric ulcers in Wistar rats within 7 days. Keywords: nanoparticles, lansoprazole, Eudragit® RS100, PLGA

  17. Temperature-responsive chromatography for the separation of biomolecules.

    Science.gov (United States)

    Kanazawa, Hideko; Okano, Teruo

    2011-12-09

    Temperature-responsive chromatography for the separation of biomolecules utilizing poly(N-isopropylacrylamide) (PNIPAAm) and its copolymer-modified stationary phase is performed with an aqueous mobile phase without using organic solvent. The surface properties and function of the stationary phase are controlled by external temperature changes without changing the mobile-phase composition. This analytical system is based on nonspecific adsorption by the reversible transition of a hydrophilic-hydrophobic PNIPAAm-grafted surface. The driving force for retention is hydrophobic interaction between the solute molecules and the hydrophobized polymer chains on the stationary phase surface. The separation of the biomolecules, such as nucleotides and proteins was achieved by a dual temperature- and pH-responsive chromatography system. The electrostatic and hydrophobic interactions could be modulated simultaneously with the temperature in an aqueous mobile phase, thus the separation system would have potential applications in the separation of biomolecules. Additionally, chromatographic matrices prepared by a surface-initiated atom transfer radical polymerization (ATRP) exhibit a strong interaction with analytes, because the polymerization procedure forms a densely packed polymer, called a polymer brush, on the surfaces. The copolymer brush grafted surfaces prepared by ATRP was an effective tool for separating basic biomolecules by modulating the electrostatic and hydrophobic interactions. Applications of thermally responsive columns for the separations of biomolecules are reviewed here.

  18. Normal growth spurt and final height despite low levels of all forms of circulating insulin-like growth factor-I in a patient with acid-labile subunit deficiency

    DEFF Research Database (Denmark)

    Domené, Horacio M; Martínez, Alicia S; Frystyk, Jan;

    2007-01-01

    of circulating versus locally produced IGF-I in skeletal growth in this patient, we now describe in detail growth changes and their relationship with several components of the circulating IGF system. DESIGN AND METHODS: We followed growth and development up to the final height in a patient with complete ALS...... deficiency and determined both spontaneous and growth hormone (GH)-stimulated changes in the IGF system, including measurements of total, free and bioactive IGF-I, total IGF-II and insulin-like growth factor binding protein (IGFBP)-1, IGFBP-2 and IGFBP-3. RESULTS: The patient had a delayed growth......BACKGROUND: In a recently described patient with acid-labile subunit (ALS) deficiency, the inability to form ternary complexes resulted in a marked reduction in circulating total insulin-like growth factor (IGF)-I, whereas skeletal growth was only marginally affected. To further study the role...

  19. Exploring the potential of self-assembled mixed micelles in enhancing the stability and oral bioavailability of an acid-labile drug.

    Science.gov (United States)

    Zhang, Xingwang; Wang, Huan; Zhang, Tianpeng; Zhou, Xiaotong; Wu, Baojian

    2014-10-01

    Oral delivery of many drugs is plagued with limited solubility and/or poor stability. This paper aimed to explore the performance of polymeric mixed micelles on solubilization, stabilization and bioavailability enhancement with stiripentol as model drug. Stiripentol-loaded mixed micelles were prepared by solvent-diffusion method: rapid dispersion of an ethanol solution containing stiripentol, monomethoxy poly(ethylene glycol)-b-poly(ε-caprolactone) and sodium oleate into water. Stiripentol micelles were characterized by the particle size, entrapment efficiency, in vitro drug release, TEM, DSC and FTIR. The pharmacokinetic profile of stiripentol was determined in rats after oral administration of stiripentol micelles. The obtained stiripentol micelles were 44.2 nm in size with an entrapment efficiency over 90%. It was shown that micelles substantially improved the solubility and gastric stability of stiripentol. The oral absorption of stiripentol was also enhanced to a great extent with a relative bioavailability of 157% and 444% to the commercial formulation (Diacomit®) and in-house suspensions. Mixed micelles assembled by di-block copolymer/sodium oleate exhibited a good potential in the improvement of drug stability and bioavailability. It should be a promising carrier for oral delivery of therapeuticals with solubility and stability issues.

  20. Meth math: modeling temperature responses to methamphetamine.

    Science.gov (United States)

    Molkov, Yaroslav I; Zaretskaia, Maria V; Zaretsky, Dmitry V

    2014-04-15

    Methamphetamine (Meth) can evoke extreme hyperthermia, which correlates with neurotoxicity and death in laboratory animals and humans. The objective of this study was to uncover the mechanisms of a complex dose dependence of temperature responses to Meth by mathematical modeling of the neuronal circuitry. On the basis of previous studies, we composed an artificial neural network with the core comprising three sequentially connected nodes: excitatory, medullary, and sympathetic preganglionic neuronal (SPN). Meth directly stimulated the excitatory node, an inhibitory drive targeted the medullary node, and, in high doses, an additional excitatory drive affected the SPN node. All model parameters (weights of connections, sensitivities, and time constants) were subject to fitting experimental time series of temperature responses to 1, 3, 5, and 10 mg/kg Meth. Modeling suggested that the temperature response to the lowest dose of Meth, which caused an immediate and short hyperthermia, involves neuronal excitation at a supramedullary level. The delay in response after the intermediate doses of Meth is a result of neuronal inhibition at the medullary level. Finally, the rapid and robust increase in body temperature induced by the highest dose of Meth involves activation of high-dose excitatory drive. The impairment in the inhibitory mechanism can provoke a life-threatening temperature rise and makes it a plausible cause of fatal hyperthermia in Meth users. We expect that studying putative neuronal sites of Meth action and the neuromediators involved in a detailed model of this system may lead to more effective strategies for prevention and treatment of hyperthermia induced by amphetamine-like stimulants.

  1. Temperature responsive hydroxypropyl cellulose for encapsulation

    Energy Technology Data Exchange (ETDEWEB)

    Heitfeld, Kevin A.; Guo, Tingtai; Yang, George; Schaefer, Dale W. (UCIN)

    2009-08-26

    This work focuses on the use of temperature responsive gels (TRGs) (polymeric hydrogels with a large temperature-dependent change in volume) for flavor retention at cooking temperatures. Specifically, we have studied a gel with a lower critical solution temperature (LCST) that swells at low temperatures and collapses at high temperatures. In the collapsed state, the polymer acts as a transport barrier, keeping the volatile flavors inside. We have successfully synthesized a cellulose gel that exhibits this volume change and have encapsulated an oil phase inside the gel. The flavor-loaded encapsulated oil exhibited an increased release time when compared to similar gelatin capsules.

  2. Self-assembled micelles composed of doxorubicin conjugated Y-shaped PEG-poly(glutamic acid)2 copolymers via hydrazone linkers.

    Science.gov (United States)

    Sui, Bowen; Xu, Hui; Jin, Jian; Gou, Jingxin; Liu, Jingshuo; Tang, Xing; Zhang, Yu; Xu, Jinghua; Zhang, Hongfeng; Jin, Xiangqun

    2014-08-11

    In this work, micelles composed of doxorubicin-conjugated Y-shaped copolymers (YMs) linked via an acid-labile linker were constructed. Y-shaped copolymers of mPEG-b-poly(glutamate-hydrazone-doxorubicin)2 and linear copolymers of mPEG-b-poly(glutamate-hydrazone-doxorubicin) were synthesized and characterized. Particle size, size distribution, morphology, drug loading content (DLC) and drug release of the micelles were determined. Alterations in size and DLC of the micelles could be achieved by varying the hydrophobic block lengths. Moreover, at fixed DLCs, YMs showed a smaller diameter than micelles composed of linear copolymers (LMs). Also, all prepared micelles showed sustained release behaviors under physiological conditions over 72 h. DOX loaded in YMs was released more completely, with 30% more drug released in acid. The anti-tumor efficacy of the micelles against HeLa cells was evaluated by MTT assays, and YMs exhibited stronger cytotoxic effects than LMs in a dose- and time-dependent manner. Cellular uptake studied by CLSM indicated that YMs and LMs were readily taken up by HeLa cells. According to the results of this study, doxorubicin-conjugated Y-shaped PEG-(polypeptide)2 copolymers showed advantages over linear copolymers, like assembling into smaller nanoparticles, faster drug release in acid, which may correspond to higher cellular uptake and enhanced extracellular/intracellular drug release, indicating their potential in constructing nano-sized drug delivery systems.

  3. Long-term effects of insulin-like growth factor (IGF)-I on serum IGF-I, IGF-binding protein-3 and acid labile subunit in Laron syndrome patients with normal growth hormone binding protein.

    Science.gov (United States)

    Kanety, H; Silbergeld, A; Klinger, B; Karasik, A; Baxter, R C; Laron, Z

    1997-12-01

    A minority of patients with Laron syndrome have normal serum GH binding protein (GHBP), indicating that the defect is elsewhere than in the extracellular domain of the GH receptor. We have evaluated the effect of long-term IGF-I treatment on serum IGF-binding protein (IGFBP)-3 and the acid-labile subunit (ALS) in three sibling with Laron syndrome caused by a GH post-receptor defect and with normal GHBP. The children (a boy aged 3 years, a girl aged 4 years and a boy aged 10 years) were treated by daily s.c. injection of IGF-I in a dose of 150 micrograms/kg. IGFBP-3 was measured by RIA and Western ligand blotting, ALS by RIA. Based values of IGFBP-3 and ALS were low. During IGF-I treatment, the IGFBP-3 concentrations in the girl gradually increased, whereas in the boys there was a 60% decrease during the first week, followed by gradual increase towards baseline. The ALS concentrations followed a similar pattern. We conclude that IGF-I treatment induces and initial suppression and then an increase in the IGFBP-3 and ALS concentrations, confirming data from animal experiments that IGFBP-3 synthesis is not solely under GH control. The differences in responsiveness between the female and male siblings may reflect genetic differences, or lower circulating concentrations of IGF-I in the boys compared with the girl.

  4. Acid-labile sulfides in shallow marine bottom sediments: A review of the impact on ecosystems in the Azov Sea, the NE Black Sea shelf and NW Adriatic lagoons

    Science.gov (United States)

    Sorokin, Yu. I.; Zakuskina, O. Yu

    2012-02-01

    Acid-labile sulfides (LS) increase in bottom sediments at sites in the Azov Sea, at the NE Black Sea shelf and in the coastal lagoons of NW Adriatic Sea experiencing direct impacts of anthropogenic pollution. Fresh anthropogenic organic matter stimulates the bacterial sulfate reduction and here the rate of the LS production overcomes their loss during the oxidation and pyritization. This results in the expansion of reduced sediment layer up to the bottom surface. The LS concentration in the reduced sediments varies between 300 and 2000 mg S l -1 of wet silt depending on the size of pollution loading and on the rate of sedimentation. In the oxidized sediments away from the direct pollution impact, the LS concentration did not exceed 100-150 mg S l -1. Being a strong cytochrome toxin, the LS adversely affect the coastal ecosystems. The concentrations over 600 mg S l -1 result in quasi total benthic mortality whereas >300-400 mg S l -1 depletes the benthic faunal abundance and taxonomic diversity. Accumulation of the LS in sediments also induces nocturnal hypoxia and stimulates domination of toxic cyanobacteria in the pelagic phytocenoses.

  5. Amphiphilic block copolymers bearing six-membered ortho ester ring in side chains as potential drug carriers: synthesis, characterization, and in vivo toxicity evaluation.

    Science.gov (United States)

    Luo, Shi; Tao, Yangyang; Tang, Rupei; Wang, Rui; Ji, Weihang; Wang, Chun; Zhao, Youliang

    2014-07-01

    A new type of amphiphilic block copolymers, poly(ethylene glycol)-block-poly(2-methyl-acrylicacid 2-methoxy-5-methyl-[1,3]dioxin-5-ylmethyl ester) (PEG-b-PMME), bearing acid-labile six-membered ortho ester rings in side chains was synthesized by reversible addition-fragmentation chain-transfer polymerization, and the influence of chain length of the hydrophobic PMME block on micelle properties was investigated. The PEG-b-PMME micelles were stable in aqueous buffer at physiological pH with a low critical micelle concentration. Nile Red as a model drug was encapsulated into the micelles to explore the release profiles. The Nile Red-loaded polymeric micelles showed rapid release of Nile Red in weakly acidic environments (pH 5) but slow release under physiological condition (pH 7.4), due to different hydrolysis rate of ortho ester side chains of PEG-b-PMME. The Paclitaxel (PTX)-loaded micelles retained potency in killing lung cancer cells (A549), compared with the free PTX. No obvious toxicity was found in vitro and in vivo after intraperitoneal injection of the micelles, which confirms that the PEG-b-PMME micelles with unique acid-labile characteristic have great potential as nano-scaled carriers for drug delivery.

  6. Synthesis and Characterization of Stimuli Responsive Block Copolymers, Self-Assembly Behavior and Applications

    Energy Technology Data Exchange (ETDEWEB)

    Determan, Michael Duane [Iowa State Univ., Ames, IA (United States)

    2005-12-17

    The central theme of this thesis work is to develop new block copolymer materials for biomedical applications. While there are many reports of stimuli-responsive amphiphilic [19-21] and crosslinked hydrogel materials [22], the development of an in situ gel forming, pH responsive pentablock copolymer is a novel contribution to the field, Figure 1.1 is a sketch of an ABCBA pentablock copolymer. The A blocks are cationic tertiary amine methacrylates blocked to a central Pluronic F127 triblock copolymer. In addition to the prerequisite synthetic and macromolecular characterization of these new materials, the self-assembled supramolecular structures formed by the pentablock were experimentally evaluated. This synthesis and characterization process serves to elucidate the important structure property relationships of these novel materials, The pH and temperature responsive behavior of the pentablock copolymer were explored especially with consideration towards injectable drug delivery applications. Future synthesis work will focus on enhancing and tuning the cell specific targeting of DNA/pentablock copolymer polyplexes. The specific goals of this research are: (1) Develop a synthetic route for gel forming pentablock block copolymers with pH and temperature sensitive properties. Synthesis of these novel copolymers is accomplished with ATRP, yielding low polydispersity and control of the block copolymer architecture. Well defined macromolecular characteristics are required to tailor the phase behavior of these materials. (2) Characterize relationship between the size and shape of pentablock copolymer micelles and gel structure and the pH and temperature of the copolymer solutions with SAXS, SANS and CryoTEM. (3) Evaluate the temperature and pH induced phase separation and macroscopic self-assembly phenomenon of the pentablock copolymer. (4) Utilize the knowledge gained from first three goals to design and formulate drug delivery formulations based on the multi

  7. Temperature responses of individual soil organic matter components

    Science.gov (United States)

    Feng, Xiaojuan; Simpson, Myrna J.

    2008-09-01

    Temperature responses of soil organic matter (SOM) remain unclear partly due to its chemical and compositional heterogeneity. In this study, the decomposition of SOM from two grassland soils was investigated in a 1-year laboratory incubation at six different temperatures. SOM was separated into solvent extractable compounds, suberin- and cutin-derived compounds, and lignin-derived monomers by solvent extraction, base hydrolysis, and CuO oxidation, respectively. These SOM components have distinct chemical structures and stabilities and their decomposition patterns over the course of the experiment were fitted with a two-pool exponential decay model. The stability of SOM components was also assessed using geochemical parameters and kinetic parameters derived from model fitting. Compared with the solvent extractable compounds, a low percentage of lignin monomers partitioned into the labile SOM pool. Suberin- and cutin-derived compounds were poorly fitted by the decay model, and their recalcitrance was shown by the geochemical degradation parameter (ω - C16/∑C16), which was observed to stabilize during the incubation. The temperature sensitivity of decomposition, expressed as Q10, was derived from the relationship between temperature and SOM decay rates. SOM components exhibited varying temperature responses and the decomposition of lignin monomers exhibited higher Q10 values than the decomposition of solvent extractable compounds. Our study shows that Q10 values derived from soil respiration measurements may not be reliable indicators of temperature responses of individual SOM components.

  8. New Polytetrahydrofuran Graft Copolymers.

    Science.gov (United States)

    1979-03-15

    chioroprene) , chiorobutyl - ~~~~~ rubber , bromobutyl rubber , chlorinated EPDM , chlorinated poly(buta— diene) and chlorinated butadiene styrene copolymer...for initial detailed studies (3 ,4 , 6 , 7 — 9 ) . Many soluble metal salts with cations capable of stabilizing an on].um ion polymerization (SO3CF 3

  9. Block coordination copolymers

    Energy Technology Data Exchange (ETDEWEB)

    Koh, Kyoung Moo; Wong-Foy, Antek G; Matzger, Adam J; Benin, Annabelle I; Willis, Richard R

    2014-11-11

    The present invention provides compositions of crystalline coordination copolymers wherein multiple organic molecules are assembled to produce porous framework materials with layered or core-shell structures. These materials are synthesized by sequential growth techniques such as the seed growth technique. In addition, the invention provides a simple procedure for controlling functionality.

  10. Block coordination copolymers

    Science.gov (United States)

    Koh, Kyoung Moo; Wong-Foy, Antek G; Matzger, Adam J; Benin, Annabelle I; Willis, Richard R

    2012-11-13

    The present invention provides compositions of crystalline coordination copolymers wherein multiple organic molecules are assembled to produce porous framework materials with layered or core-shell structures. These materials are synthesized by sequential growth techniques such as the seed growth technique. In addition, the invention provides a simple procedure for controlling functionality.

  11. STUDY ON PET-PA66 COPOLYMER

    Institute of Scientific and Technical Information of China (English)

    WU Rongrui; SHI Weitong

    1992-01-01

    In this work the PET-PA66 copolymers are obtained. The characterization of chemical structure of copolymer chain by NMR method is also given . It is shown that when the 66 Nylon salt is added in the copolycondensation, the adipic acid and hexamethylenediamine reacted mainly by itself and the obtained copolymer is a random copolymer, and when the Nylon 66 oligomer is added, the obtained copolymer is a block copolymer. The result of NMR analysis is demonstrated by properties investigation.

  12. Block copolymer battery separator

    Science.gov (United States)

    Wong, David; Balsara, Nitash Pervez

    2016-04-26

    The invention herein described is the use of a block copolymer/homopolymer blend for creating nanoporous materials for transport applications. Specifically, this is demonstrated by using the block copolymer poly(styrene-block-ethylene-block-styrene) (SES) and blending it with homopolymer polystyrene (PS). After blending the polymers, a film is cast, and the film is submerged in tetrahydrofuran, which removes the PS. This creates a nanoporous polymer film, whereby the holes are lined with PS. Control of morphology of the system is achieved by manipulating the amount of PS added and the relative size of the PS added. The porous nature of these films was demonstrated by measuring the ionic conductivity in a traditional battery electrolyte, 1M LiPF.sub.6 in EC/DEC (1:1 v/v) using AC impedance spectroscopy and comparing these results to commercially available battery separators.

  13. Synthesis and Thermosensitive Behavior of Polyacrylamide Copolymers and Their Applications in Smart Textiles

    Directory of Open Access Journals (Sweden)

    Tao Chen

    2015-05-01

    Full Text Available We tuned the lower critical solution temperature (LCST of amphiphilic poly(N-isopropylacrylamide (PNIPAAm via copolymerization with a hydrophilic comonomer of N-hydroxymethyl acrylamide (NHMAAm. A series of copolymers P(NIPAAm-co-NHMAAm were synthesized by atom transfer radical polymerization (ATRP using CuBr/(N,N,N',N',N''-Pentamethyldiethylenetriamine (PMDETA as a catalyst system and 2-bromo ethyl isobutyrate (EBiB as an initiator. The copolymers were well characterized by Fourier transform infrared spectroscopy (FT-IR, 1H Nuclear magnetic resonance (NMR, and Thermogravimetric analysis (TGA. The copolymers followed a simple rule in their thermosensitive behaviors and have a linear increase in the LCST as a function of NHMAAm mol%. The thermosensitive properties of the copolymer films were investigated and demonstrated hydrophilic-hydrophobic transitions. Finally, the copolymer was grafted onto cotton fabrics using citric acid (CA as a crosslinking agent and sodium hypophosphite (SHP as a catalyst following a two dipping, two padding process. The large number of hydroxyl groups in the copolymer makes grafting convenient and firm. The grafted cotton fabrics show obvious thermosensitive behaviors. The results demonstrate that the cotton fabrics become more hydrophobic when the temperature is higher than the LCST. This study presents a valuable route towards temperature-responsive smart textiles and their potential applications.

  14. Temperature response of soil respiration largely unaltered with experimental warming

    DEFF Research Database (Denmark)

    Carey, Joanna C; Tang, Jianwu; Templer, Pamela H

    2016-01-01

    considerably more responsive to increased ambient temperatures compared with warmer regions. Our analysis adds a unique cross-biome perspective on the temperature response of soil respiration, information critical to improving our mechanistic understanding of how soil carbon dynamics change with climatic......The respiratory release of carbon dioxide (CO2) from soil is a major yet poorly understood flux in the global carbon cycle. Climatic warming is hypothesized to increase rates of soil respiration, potentially fueling further increases in global temperatures. However, despite considerable scientific...... attention in recent decades, the overall response of soil respiration to anticipated climatic warming remains unclear. We synthesize the largest global dataset to date of soil respiration, moisture, and temperature measurements, totaling >3,800 observations representing 27 temperature manipulation studies...

  15. Polyether/Polyester Graft Copolymers

    Science.gov (United States)

    Bell, Vernon L., Jr.; Wakelyn, N.; Stoakley, D. M.; Proctor, K. M.

    1986-01-01

    Higher solvent resistance achieved along with lower melting temperature. New technique provides method of preparing copolymers with polypivalolactone segments grafted onto poly (2,6-dimethyl-phenylene oxide) backbone. Process makes strong materials with improved solvent resistance and crystalline, thermally-reversible crosslinks. Resulting graft copolymers easier to fabricate into useful articles, including thin films, sheets, fibers, foams, laminates, and moldings.

  16. Preparation and Characterization of Temperature-responsive Porous Monoliths

    Institute of Scientific and Technical Information of China (English)

    ZHANG, Rongyue; QI, Li; XIN, Peiyong; YANG, Gengliang; CHEN, Yi

    2009-01-01

    A new temperature-responsive porous monolith has been prepared by surface-initiated activators generated by electron transfer atom transfer radical polymerization (AGET ATRP) grafting poly(N-isopropylacrylamide) (PNIPAAm) within the pores of the porous polymer monolith. The grafting copolymerization was carried out by a method based on a continuous flow-through technique without special deoxygenation procedure needed in the general ATRP. The addition of ascorbic acid could counteract the oxidation effect of oxygen diffusing into the reaction system. The resulting grafted monolith was characterized by a mercury intrusion method and the size of macropore was 3.65 μm, which was suitable for flow through the monolith for HPLC. The thermally responsive property of the grafted monolith was evaluated by HPLC using steroids with various hydrophobicities as probes. Through determination of retention factor of each steroid on the grafted monolith at different temperatures using water as mobile phase, it was found that the slope of the plot of retention factor of each steroid versus the temperature changed around the low critical solution temperature (LCST, 32 ℃) of PNIPAAm in water. It was relative to the grafted PNIPAAm temperature sensitivity that a hydrophobic and hydrophilic alternation would take place around its LCST.Based on this thermally responsive property, the grafted monolith was used as stationary phase for HPLC and to separate the steroids using water as mobile phase by changing the column temperature. As a mobile phase, water is much better than organic solvents concerning the environment.

  17. Phase Transition and Micellization of Temperature Responsive Dextran-graft-poly (N-isopropylacrylamide) Polymers

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Phase behavior and micellization of dextran-graft-poly (N-isopropylacrylamide) (PNIPAAm) polymers in aqueous solution are investigated in this paper using DSC and AFM methods. It is found that with the increase of grafting (G%) of the copolymers the endothermic enthalpy during the phase transition increases significantly and the transition temperature decreases slightly. The phase transition behavior of the copolymers is scanning rate dependent. Micelles are formed whenever the solution temperature is raised above the LCST of the copolymers. It is proposed that by using this thermal responsive property of the copolymers, drugs could be incorporated into the micelles without employing any organic solvent.

  18. Temperature Responses of Soil Organic Matter Components With Varying Recalcitrance

    Science.gov (United States)

    Simpson, M. J.; Feng, X.

    2007-12-01

    The response of soil organic matter (SOM) to global warming remains unclear partly due to the chemical heterogeneity of SOM composition. In this study, the decomposition of SOM from two grassland soils was investigated in a one-year laboratory incubation at six different temperatures. SOM was separated into solvent- extractable compounds, suberin- and cutin-derived compounds, and lignin monomers by solvent extraction, base hydrolysis, and CuO oxidation, respectively. These SOM components had distinct chemical structures and recalcitrance, and their decomposition was fitted by a two-pool exponential decay model. The stability of SOM components was assessed using geochemical parameters and kinetic parameters derived from model fitting. Lignin monomers exhibited much lower decay rates than solvent-extractable compounds and a relatively low percentage of lignin monomers partitioned into the labile SOM pool, which confirmed the generally accepted recalcitrance of lignin compounds. Suberin- and cutin-derived compounds had a poor fitting for the exponential decay model, and their recalcitrance was shown by the geochemical degradation parameter which stabilized during the incubation. The aliphatic components of suberin degraded faster than cutin-derived compounds, suggesting that cutin-derived compounds in the soil may be at a higher stage of degradation than suberin- derived compounds. The temperature sensitivity of decomposition, expressed as Q10, was derived from the relationship between temperature and SOM decay rates. SOM components exhibited varying temperature responses and the decomposition of the recalcitrant lignin monomers had much higher Q10 values than soil respiration or the solvent-extractable compounds decomposition. Our study shows that the decomposition of recalcitrant SOM is highly sensitive to temperature, more so than bulk soil mineralization. This observation suggests a potential acceleration in the degradation of the recalcitrant SOM pool with global

  19. "Giant surfactants" created by the fast and efficient functionalization of a DNA tetrahedron with a temperature-responsive polymer.

    Science.gov (United States)

    Wilks, Thomas R; Bath, Jonathan; de Vries, Jan Willem; Raymond, Jeffery E; Herrmann, Andreas; Turberfield, Andrew J; O'Reilly, Rachel K

    2013-10-22

    Copper catalyzed azide-alkyne cycloaddition (CuAAC) was employed to synthesize DNA block copolymers (DBCs) with a range of polymer blocks including temperature-responsive poly(N-isoproylacrylamide) (poly(NIPAM)) and highly hydrophobic poly(styrene). Exceptionally high yields were achieved at low DNA concentrations, in organic solvents, and in the absence of any solid support. The DNA segment of the DBC remained capable of sequence-specific hybridization: it was used to assemble a precisely defined nanostructure, a DNA tetrahedron, with pendant poly(NIPAM) segments. In the presence of an excess of poly(NIPAM) homopolymer, the tetrahedron-poly(NIPAM) conjugate nucleated the formation of large, well-defined nanoparticles at 40 °C, a temperature at which the homopolymer precipitated from solution. These composite nanoparticles were observed by dynamic light scattering and cryoTEM, and their hybrid nature was confirmed by AFM imaging. As a result of the large effective surface area of the tetrahedron, only very low concentrations of the conjugate were required in order for this surfactant-like behavior to be observed.

  20. Greenland temperature response to climate forcing during the last deglaciation

    Science.gov (United States)

    Buizert, C.; Gkinis, V.; Severinghaus, J. P.; He, F.; Lecavalier, B.; Kindler, P.; Leuenberger, M.; Carlson, A. E.; Vinther, B.; White, J. W.; Liu, Z.; Otto-Bliesner, B. L.; Brook, E.

    2013-12-01

    Much of the regional and global climate variability during the last glacial termination (19-11 ka BP) can be explained as the superposition of two distinct modes (1, 2); a spatially uniform increase in global temperature correlated with greenhouse gas forcing, and a redistribution of heat associated with variability in the Atlantic meridional overturning circulation (AMOC) strength. The latter mode is expressed most clearly in the abrupt climate shifts recorded in the precipitation isotopic composition (δ18O) of Greenland ice cores, which are now widely used as a template for abrupt change in the northern hemisphere. Greenland δ18O is influenced by many factors, including source temperature, moisture transport and origin, and precipitation seasonality, complicating reconstruction of past temperatures. Here we use three non-δ18O temperature reconstructions from three ice cores and a general circulation model (GCM) to elucidate the (often abrupt) Greenland surface temperature response to external (insolation) and internal (CO2, AMOC, ice topography) climate forcings during the last termination. Our reconstructions are based on δ15N (NEEM, GISP2) and water isotope diffusion (NGRIP), both of which depend on physical processes in the firn column. The GCM and our reconstructions show excellent agreement on several key features. First, we find that the Younger Dryas (YD) period was 4-6oC warmer than the Oldest Dryas (OD) period in response to increased summer insolation and CO2 forcing. By contrast, δ18O-based reconstrucions from Greenland summit suggest the YD to be the colder of the two periods. Our finding is consistent with non-ice core NH proxy reconstructions, as well as with East Greenland deglacial moraine sequences that suggest only a modest glacial re-advance during the YD. Second, the YD-OD temperature difference shows a polar amplification signal, with warming being greatest at the northernmost NEEM site. By isolating different forcings in the GCM, we

  1. Skin delivery by block copolymer nanoparticles (block copolymer micelles).

    Science.gov (United States)

    Laredj-Bourezg, Faiza; Bolzinger, Marie-Alexandrine; Pelletier, Jocelyne; Valour, Jean-Pierre; Rovère, Marie-Rose; Smatti, Batoule; Chevalier, Yves

    2015-12-30

    Block copolymer nanoparticles often referred to as "block copolymer micelles" have been assessed as carriers for skin delivery of hydrophobic drugs. Such carriers are based on organic biocompatible and biodegradable materials loaded with hydrophobic drugs: poly(lactide)-block-poly(ethylene glycol) copolymer (PLA-b-PEG) nanoparticles that have a solid hydrophobic core made of glassy poly(d,l-lactide), and poly(caprolactone)-block-poly(ethylene glycol) copolymer (PCL-b-PEG) nanoparticles having a liquid core of polycaprolactone. In vitro skin absorption of all-trans retinol showed a large accumulation of retinol in stratum corneum from both block copolymer nanoparticles, higher by a factor 20 than Polysorbate 80 surfactant micelles and by a factor 80 than oil solution. Additionally, skin absorption from PLA-b-PEG nanoparticles was higher by one order of magnitude than PCL-b-PEG, although their sizes (65nm) and external surface (water-swollen PEG layer) were identical as revealed by detailed structural characterizations. Fluorescence microscopy of histological skin sections provided a non-destructive picture of the storage of Nile Red inside stratum corneum, epidermis and dermis. Though particle cores had a different physical states (solid or liquid as measured by (1)H NMR), the ability of nanoparticles for solubilization of the drug assessed from their Hildebrand solubility parameters appeared the parameter of best relevance regarding skin absorption.

  2. BARRIER PROPERTIES OF VINYLIDENE CHLORIDE COPOLYMERS

    Institute of Scientific and Technical Information of China (English)

    LI Yuesheng; WENG Zhixue; HUANG Zhiming; PAN Zuren

    1996-01-01

    The permeability coefficients of a series of copolymers of vinylidene chloride (VDC)with methyl acrylate (MA), butyl acrylate (BA) or vinyl chloride (VC) (as comonomer)to oxygen and carbon dioxide have been measured at 1.0 MPa and 30℃, while those to water vapor have been measured at 30℃ and 100% relative humidity. All the copolymers are semicrystalline. VDC/MA copolymers have lower melting temperature compared with VDC/BA copolymers, while that melting temperature of VDC/VC copolymer is higher than that of VDC/acrylate copolymers with the same VDC content. The barrier property of the copolymers is predominantly controlled by crystallite, free volume fraction, and cohesive energy. The permeability coefficients of VDC/MA copolymers to oxygen, carbon dioxide, and water vapor were successfully correlated with the ratio of free volume to cohesive energy.

  3. Lignin poly(lactic acid) copolymers

    Energy Technology Data Exchange (ETDEWEB)

    Olsson, Johan Vilhelm; Chung, Yi-Lin; Li, Russell Jingxian; Waymouth, Robert; Sattely, Elizabeth; Billington, Sarah; Frank, Curtis W.

    2017-02-14

    Provided herein are graft co-polymers of lignin and poly(lactic acid) (lignin-g-PLA copolymer), thermoset and thermoplastic polymers including them, methods of preparing these polymers, and articles of manufacture including such polymers.

  4. Micellization and Dynamics of a Block Copolymer

    DEFF Research Database (Denmark)

    Hvidt, Søren

    2006-01-01

    Triblock copolymers of the type EPE, where E and P denote ethylene oxide and propylene oxide blocks, respectively, are industrially important copolymers often called Pluronics or Poloxamers. EPE copolymers form micelles with a core of P blocks and different micellar shapes depending on block leng...

  5. Copolymers For Capillary Gel Electrophoresis

    Science.gov (United States)

    Liu, Changsheng; Li, Qingbo

    2005-08-09

    This invention relates to an electrophoresis separation medium having a gel matrix of at least one random, linear copolymer comprising a primary comonomer and at least one secondary comonomer, wherein the comonomers are randomly distributed along the copolymer chain. The primary comonomer is an acrylamide or an acrylamide derivative that provides the primary physical, chemical, and sieving properties of the gel matrix. The at least one secondary comonomer imparts an inherent physical, chemical, or sieving property to the copolymer chain. The primary and secondary comonomers are present in a ratio sufficient to induce desired properties that optimize electrophoresis performance. The invention also relates to a method of separating a mixture of biological molecules using this gel matrix, a method of preparing the novel electrophoresis separation medium, and a capillary tube filled with the electrophoresis separation medium.

  6. Polyether-polyester graft copolymer

    Science.gov (United States)

    Bell, Vernon L. (Inventor)

    1987-01-01

    Described is a polyether graft polymer having improved solvent resistance and crystalline thermally reversible crosslinks. The copolymer is prepared by a novel process of anionic copolymerization. These polymers exhibit good solvent resistance and are well suited for aircraft parts. Previous aromatic polyethers, also known as polyphenylene oxides, have certain deficiencies which detract from their usefulness. These commercial polymers are often soluble in common solvents including the halocarbon and aromatic hydrocarbon types of paint thinners and removers. This limitation prevents the use of these polyethers in structural articles requiring frequent painting. In addition, the most popular commercially available polyether is a very high melting plastic. This makes it considerably more difficult to fabricate finished parts from this material. These problems are solved by providing an aromatic polyether graft copolymer with improved solvent resistance and crystalline thermally reversible crosslinks. The graft copolymer is formed by converting the carboxyl groups of a carboxylated polyphenylene oxide polymer to ionic carbonyl groups in a suitable solvent, reacting pivalolactone with the dissolved polymer, and adding acid to the solution to produce the graft copolymer.

  7. Liquid ethylene-propylene copolymers

    Science.gov (United States)

    Rhein, R. A.; Ingham, J. D.; Humphrey, M. F.

    1975-01-01

    Oligomers are prepared by heating solid ethylene-propylene rubber in container that retains solid and permits liquid product to flow out as it is formed. Molecular weight and viscosity of liquids can be predetermined by process temperature. Copolymers have low viscosity for given molecular weight.

  8. Closely related freshwater macrophyte species, Ceratophyllum demersum and em>C. submersum, differ in temperature response

    DEFF Research Database (Denmark)

    Hyldgaard, Benita; Sorrell, Brian Keith; Brix, Hans

    2014-01-01

    1. The importance of temperature responses of photosynthesis and respiration in determining species distributions was compared in two closely related freshwater macrophytes, Ceratophyllum demersum and C. submersum. The two species differed significantly in response to temperature in the short and...

  9. The role of spatial scale and background climate in the latitudinal temperature response to deforestation

    OpenAIRE

    Li, Y.; N. de Noblet-Ducoudré; E. L. Davin; Zeng, N.; S. Motesharrei; Li, S.C.; Kalnay, E.

    2015-01-01

    Previous modeling and empirical studies have shown that the biophysical impact of deforestation is to warm the tropics and cool the extra-tropics. In this study, we use an earth system model to investigate how deforestation at various spatial scales affects ground temperature, with an emphasis on the latitudinal temperature response and its underlying mechanisms. Results show that the latitudinal pattern of temperature response depends non-linearly on the s...

  10. Impacts of Repeat Unit Structure and Copolymer Architecture on Thermal and Solution Properties in Homopolymers, Copolymers, and Copolymer Blends

    Science.gov (United States)

    Marrou, Stephen Raye

    Gradient copolymers are a relatively new type of copolymer architecture in which the distribution of comonomers gradually varies over the length of the copolymer chain, resulting in a number of unusual properties derived from the arrangement of repeat units. For example, nanophase-segregated gradient copolymers exhibit extremely broad glass transition temperatures (Tgs) resulting from the wide range of compositions present in the nanostructure. This dissertation presents a number of studies on how repeat unit structure and copolymer architecture dictate bulk and solution properties, specifically taking inspiration from the gradient copolymer architecture and comparing the response from this compositionally heterogeneous material to other more conventional materials. The glass transition behavior of a range of common homopolymers was studied to determine the effects of subunit structure on Tg breadth, observing a significant increase in T g breadth with increasing side chain length in methacrylate-based homopolymers and random copolymers. Additionally, increasing the composition distribution of copolymers, either by blending individual random copolymers of different overall composition or synthesizing random copolymers to high conversion, resulted in significant increases to Tg breadth. Plasticization of homopolymers and random copolymers with low molecular weight additives also served to increase the Tg breadth; the most dramatic effect was observed in the selective plasticization of a styrene/4-vinylpyridine gradient copolymer with increases in T g breadth to values above 100 °C. In addition, the effects of repeat unit structure and copolymer architecture on other polymer properties besides Tg were also investigated. The intrinsic fluorescence of styrene units in styrene-containing copolymers was studied, noting the impact of repeat unit structure and copolymer architecture on the resulting fluorescence spectra in solution. The impact of repeat unit structure on

  11. Design, syntheses, and properties of tunable, dual-stimuli (temperature and pH) responsive copolymers

    Science.gov (United States)

    Manokruang, Kiattikhun

    polymer aggregates for each pH, rather than random/polydisperse structures. TEM images of the collapsed morphology showed polymer aggregates that included numerous small hydrophobic cores, demonstrating that the phase transition of these copolymers involved the formation of micelles with many hydrophobic clusters. Finally, these copolymers were used to prepare hollow microcapsules that provided an exceptional protection and a prolonged stability of an encapsulated matter at acidic conditions (pH 2) and a sharp and fast pH-triggered release at physiological conditions (pH 7). A second series of copolymers was synthesized to compose of ethylene glycol oligomers (EOm) connected in an alternating fashion with hydrophobic alkyls (EEn), (EOm-alt-EE n). Also, terpolymers were synthesized to compose of EOm connected in an alternating fashion with EEn and lysine ethyl ester (LyE), (EOm-alt-(EEn;LyE). Both copolymers and terpolymers demonstrated temperature responsive LCST phase behavior in aqueous solution, whose critical temperature is dictated by the thermodynamics of the hydrophilic/hydrophobic balance. In addition, the terpolymers' LCST can be further tuned by tailoring the ratio of EEn to LyE yielding dual responsive, viz. temperature and pH responsive, polymers upon conversion of LyE to ionizable Lysine (Lys). These last polymers that included ionizable units showed a reversible temperature and pH sensitive phase transition, allowing for such polymers to exhibit a phase separation with both-or-either temperature increase and pH-decrease. The extended phase diagrams, collected from turbidity measurements and modulated differential scanning callorimetry (MDSC), showed that the phase diagram remained a genuine LCST binodal throughout the complete concentration range. In addition, 1H-NMR provided additional strong evidence that the phase transition proceeded without micelle formation. Finally, hydrogels were prepared from EOm-alt-EEn, which exhibited reversible swelling

  12. Volatile organic compound detection using nanostructured copolymers.

    Science.gov (United States)

    Li, Bo; Sauvé, Genevieve; Iovu, Mihaela C; Jeffries-El, Malika; Zhang, Rui; Cooper, Jessica; Santhanam, Suresh; Schultz, Lawrence; Revelli, Joseph C; Kusne, Aaron G; Kowalewski, Tomasz; Snyder, Jay L; Weiss, Lee E; Fedder, Gary K; McCullough, Richard D; Lambeth, David N

    2006-08-01

    Regioregular polythiophene-based conductive copolymers with highly crystalline nanostructures are shown to hold considerable promise as the active layer in volatile organic compound (VOC) chemresistor sensors. While the regioregular polythiophene polymer chain provides a charge conduction path, its chemical sensing selectivity and sensitivity can be altered either by incorporating a second polymer to form a block copolymer or by making a random copolymer of polythiophene with different alkyl side chains. The copolymers were exposed to a variety of VOC vapors, and the electrical conductivity of these copolymers increased or decreased depending upon the polymer composition and the specific analytes. Measurements were made at room temperature, and the responses were found to be fast and appeared to be completely reversible. Using various copolymers of polythiophene in a sensor array can provide much better discrimination to various analytes than existing solid state sensors. Our data strongly indicate that several sensing mechanisms are at play simultaneously, and we briefly discuss some of them.

  13. The influence of chain stretching on the phase behavior of multiblock copolymer and comb copolymer melts

    NARCIS (Netherlands)

    Angerman, HJ; ten Brinke, G

    2003-01-01

    The subject of this paper is inspired by microphase-separated copolymer melts in which a small-scale structure is present inside one of the phases of a large-scale structure. Such a situation can arise in a diblock copolymer melt, if one of the blocks of the diblock is in itself a multiblock copolym

  14. Copolymers of fluorinated polydienes and sulfonated polystyrene

    Science.gov (United States)

    Mays, Jimmy W.; Gido, Samuel P.; Huang, Tianzi; Hong, Kunlun

    2009-11-17

    Copolymers of fluorinated polydienes and sulfonated polystyrene and their use in fuel cell membranes, batteries, breathable chemical-biological protective materials, and templates for sol-gel polymerization.

  15. A simple and inexpensive enteric-coated capsule for delivery of acid-labile macromolecules to the small intestine%题目:一种用于递送酸度敏感大分子到小肠的简易且廉价的肠溶胶囊

    Institute of Scientific and Technical Information of China (English)

    Darren S MILLER; Rezaul BEGG; Syed Mahfuzul AZIZ; Ross N BUTLER; Anne Michelle PARSONS; John BRESLAND; Paul HERDE; Duc Minh PHAM; Angel TAN; Hung-yao HSU; Clive A PRESTIDGE; Tim KUCHEL

    2015-01-01

    Understanding the ecology of the gastrointestinal tract and the impact of the contents on the host mucosa is emerging as an important area for defining both welness and susceptibility to disease. Targeted delivery of drugs to treat specific smal intestinal disorders such as smal bowel bacterial overgrowth and targeting molecules to interrogate or to deliver vaccines to the remote regions of the smal intestine has proven difficult. There is an unmet need for methodologies to release probes/drugs to remote regions of the gastrointestinal tract in furthering our understanding of gut health and pathogenesis. In order to address this concern, we need to know how the regional delivery of a sur-rogate labeled test compound is handled and in turn, if delivered localy as a liquid or powder, the dynamics of its subsequent handling and metabolism. In the studies we report on in this paper, we chose13C sodium acetate (13C-acetate), which is a stable isotope probe that once absorbed in the smal intestine can be readily measured non-invasively by colection and analysis of13CO2 in the breath. This would provide information of gastric emptying rates and an indication of the site of release and absorptive capacity. In a series ofin vitro andin vivo pig experiments, we assessed the enteric-protective properties of a commercialy available polymer EUDRAGIT® L100-55 on gelatin capsules and also on DRcaps®. Test results demonstrated that DRcaps® coated with EUDRAGIT® L100-55 possessed enhanced enteric-protective properties, particularlyin vivo. These studies add to the body of knowledge regarding gastric emptying in pigs and also begin the process of gathering specifications for the design of a simple and cost-effective enteric-coated capsule for delivery of acid-labile macromolecules to the smal intestine.%目的:通过开展胃肠道远端释放药物的研究,以增加对肠道健康和发病机制的理解。创新点:本研究选择了13C醋酸钠作为同位素探针,

  16. A review of progress towards understanding the transient global mean surface temperature response to radiative perturbation

    Science.gov (United States)

    Yoshimori, Masakazu; Watanabe, Masahiro; Shiogama, Hideo; Oka, Akira; Abe-Ouchi, Ayako; Ohgaito, Rumi; Kamae, Youichi

    2016-12-01

    The correct understanding of the transient response to external radiative perturbation is important for the interpretation of observed climate change, the prediction of near-future climate change, and committed warming under climate stabilization scenarios, as well as the estimation of equilibrium climate sensitivity based on observation data. It has been known for some time that the radiative damping rate per unit of global mean surface temperature increase varies with time, and this inconstancy affects the transient response. Knowledge of the equilibrium response alone is insufficient, but understanding the transient response of the global mean surface temperature has made rapid progress. The recent progress accompanies the relatively new concept of the efficacies of ocean heat uptake and forcing. The ocean heat uptake efficacy associates the temperature response induced by ocean heat uptake with equilibrium temperature response, and the efficacy of forcing compares the temperature response caused by non-CO2 forcing with that by CO2 forcing.

  17. Orexinergic Neurotransmission in Temperature Responses to Methamphetamine and Stress: Mathematical Modeling as a Data Assimilation Approach

    Science.gov (United States)

    Behrouzvaziri, Abolhassan; Fu, Daniel; Tan, Patrick; Yoo, Yeonjoo; Zaretskaia, Maria V.; Rusyniak, Daniel E.; Molkov, Yaroslav I.; Zaretsky, Dmitry V.

    2015-01-01

    Experimental Data Orexinergic neurotransmission is involved in mediating temperature responses to methamphetamine (Meth). In experiments in rats, SB-334867 (SB), an antagonist of orexin receptors (OX1R), at a dose of 10 mg/kg decreases late temperature responses (t>60 min) to an intermediate dose of Meth (5 mg/kg). A higher dose of SB (30 mg/kg) attenuates temperature responses to low dose (1 mg/kg) of Meth and to stress. In contrast, it significantly exaggerates early responses (t<60 min) to intermediate and high doses (5 and 10 mg/kg) of Meth. As pretreatment with SB also inhibits temperature response to the stress of injection, traditional statistical analysis of temperature responses is difficult. Mathematical Modeling We have developed a mathematical model that explains the complexity of temperature responses to Meth as the interplay between excitatory and inhibitory nodes. We have extended the developed model to include the stress of manipulations and the effects of SB. Stress is synergistic with Meth on the action on excitatory node. Orexin receptors mediate an activation of on both excitatory and inhibitory nodes by low doses of Meth, but not on the node activated by high doses (HD). Exaggeration of early responses to high doses of Meth involves disinhibition: low dose of SB decreases tonic inhibition of HD and lowers the activation threshold, while the higher dose suppresses the inhibitory component. Using a modeling approach to data assimilation appears efficient in separating individual components of complex response with statistical analysis unachievable by traditional data processing methods. PMID:25993564

  18. Orexinergic neurotransmission in temperature responses to methamphetamine and stress: mathematical modeling as a data assimilation approach.

    Directory of Open Access Journals (Sweden)

    Abolhassan Behrouzvaziri

    Full Text Available Orexinergic neurotransmission is involved in mediating temperature responses to methamphetamine (Meth. In experiments in rats, SB-334867 (SB, an antagonist of orexin receptors (OX1R, at a dose of 10 mg/kg decreases late temperature responses (t > 60 min to an intermediate dose of Meth (5 mg/kg. A higher dose of SB (30 mg/kg attenuates temperature responses to low dose (1 mg/kg of Meth and to stress. In contrast, it significantly exaggerates early responses (t < 60 min to intermediate and high doses (5 and 10 mg/kg of Meth. As pretreatment with SB also inhibits temperature response to the stress of injection, traditional statistical analysis of temperature responses is difficult.We have developed a mathematical model that explains the complexity of temperature responses to Meth as the interplay between excitatory and inhibitory nodes. We have extended the developed model to include the stress of manipulations and the effects of SB. Stress is synergistic with Meth on the action on excitatory node. Orexin receptors mediate an activation of on both excitatory and inhibitory nodes by low doses of Meth, but not on the node activated by high doses (HD. Exaggeration of early responses to high doses of Meth involves disinhibition: low dose of SB decreases tonic inhibition of HD and lowers the activation threshold, while the higher dose suppresses the inhibitory component. Using a modeling approach to data assimilation appears efficient in separating individual components of complex response with statistical analysis unachievable by traditional data processing methods.

  19. Drug targeting to tumors using HPMA copolymers

    NARCIS (Netherlands)

    Lammers, T.G.G.M.

    2009-01-01

    Copolymers based on N-(2-hydroxypropyl)methacrylamide (HPMA) are prototypic and well-characterized polymeric drug carriers that have been broadly implemented in the delivery of anticancer agents. HPMA copolymers circulate for prolonged periods of time, and by means of the Enhance Permeability and Re

  20. PEO-related block copolymer surfactants

    DEFF Research Database (Denmark)

    Mortensen, K.

    2001-01-01

    Non-ionic block copolymer systems based on hydrophilic poly(ethylene oxide) and more hydrophobic co-polymer blocks are used intensively in a variety of industrial and personal applications. A brief description on the applications is presented. The physical properties of more simple model systems ...

  1. Micellization and Characterization of Block Copolymer Detergents

    DEFF Research Database (Denmark)

    Hvidt, Søren

    Triblock copolymers of the type EPE, where E and P denote ethylene oxide and propylene oxide blocks, respectively, are used widely in industry as emulsifiers, anti-foaming agents, and in delayed drug release. EPE copolymers form micelles with a core of P blocks and different micellar shapes depen...

  2. STUDY ON POLYSULFONE-POLYESTER BLOCK COPOLYMERS

    Institute of Scientific and Technical Information of China (English)

    DING Youjun; QI Daquan

    1988-01-01

    Synthesis and characterization of a series of Polysulfone (PSF)-Polyester (PEs) block copolymers were studied.The degree of randomness (B) of these block copolymers was calculated from the intensities of their proton signals in 1H NMR spectra and lies in the region of 0 < B < 1. It was shown that the degree of randomness (B) and the average sequence length (L) in block copolymers were relatively dependent on the reaction conditions, various feed ratios and structure of diols.The phenomenon was observed, when the PSF-PEs block copolymers dissolved in different solvents they had different viscosities and molecular conformations.The PSF-PEs block copolymers had better solvent resistance than homo-polysulfone.

  3. Rapid self-assembly of block copolymers to photonic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Xia, Yan; Sveinbjornsson, Benjamin R; Grubbs, Robert H; Weitekamp, Raymond; Miyake, Garret M; Atwater, Harry A; Piunova, Victoria; Daeffler, Christopher Scot; Hong, Sung Woo; Gu, Weiyin; Russell, Thomas P.

    2016-07-05

    The invention provides a class of copolymers having useful properties, including brush block copolymers, wedge-type block copolymers and hybrid wedge and polymer block copolymers. In an embodiment, for example, block copolymers of the invention incorporate chemically different blocks comprising polymer size chain groups and/or wedge groups that significantly inhibit chain entanglement, thereby enhancing molecular self-assembly processes for generating a range of supramolecular structures, such as periodic nanostructures and microstructures. The present invention also provides useful methods of making and using copolymers, including block copolymers.

  4. NANOSTRUCTURES OF FUNCTIONAL BLOCK COPOLYMERS

    Institute of Scientific and Technical Information of China (English)

    Guojun Liu

    2000-01-01

    Nanostructure fabrication from block copolymers in my group normally involves polymer design, synthesis, selfassembly, selective domain crosslinking, and sometimes selective domain removal. Preparation of thin films with nanochannels was used to illustrate the strategy we took. In this particular case, a linear triblock copolymer polyisopreneblock-poly(2-cinnamoylethyl methacrylate)-block-poly(t-butyl acrylate), PI-b-PCEMA-b-PtBA, was used. Films, 25 to50μm thick, were prepared from casting on glass slides a toluene solution of PI-b-PCEMA-b-PtBA and PtBA homopolymer,hPtBA, where hPtBA is shorter than the PtBA block. At the hPtBA mass fraction of 20% relative to the triblock or the total PtBA (hPtBA and PtBA block) volume fraction of 0.44, hPtBA and PtBA formed a seemingly continuous phase in the matrix of PCEMA and PI. Such a block segregation pattern was locked in by photocrosslinking the PCEMA domain. Nanochannels were formed by extracting out hPtBA with solvent. Alternatively, larger channels were obtained from extracting out hPtBA and hydrolyzing the t-butyl groups of the PtBA block. Such membranes were not liquid permeable but had gas permeability constants ~6 orders of magnitude higher than that of low-density polyethylene films.

  5. Coarse Grained Simulation of Lipid Membrane and Triblock Copolymers

    Science.gov (United States)

    Hatakeyama, Masaomi; Faller, Roland

    2008-02-01

    We investigated the interaction between DPPC (Dipalmitoyl phosphatidylcholine) bilayer and polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) triblock copolymers using coarse grained simulation. We simulated two systems of DPPC bilayer and PEO-PPO-PEO triblock copolymer containing different mole fractions, and simulated DPPC vesicle with the copolymers. We found different adsorption mechanisms of triblock copolymers depending on concentration. And we also observed docking process between a lipid vesicle and a micelle of the copolymers.

  6. Block copolymer membranes for aqueous solution applications

    KAUST Repository

    Nunes, Suzana Pereira

    2016-03-22

    Block copolymers are known for their intricate morphology. We review the state of the art of block copolymer membranes and discuss perspectives in this field. The main focus is on pore morphology tuning with a short introduction on non-porous membranes. The two main strategies for pore formation in block copolymer membranes are (i) film casting and selective block sacrifice and (ii) self-assembly and non-solvent induced phase separation (SNIPS). Different fundamental aspects involved in the manufacture of block copolymer membranes are considered, including factors affecting the equilibrium morphology in solid films, self-assembly of copolymer in solutions and macrophase separation by solvent-non-solvent exchange. Different mechanisms are proposed for different depths of the SNIPS membrane. Block copolymer membranes can be prepared with much narrower pore size distribution than homopolymer membranes. Open questions and indications of what we consider the next development steps are finally discussed. They include the synthesis and application of new copolymers and specific functionalization, adding characteristics to respond to stimuli and chemical environment, polymerization-induced phase separation, and the manufacture of organic-inorganic hybrids.

  7. Injectible bodily prosthetics employing methacrylic copolymer gels

    Science.gov (United States)

    Mallapragada, Surya K.; Anderson, Brian C.

    2007-02-27

    The present invention provides novel block copolymers as structural supplements for injectible bodily prosthetics employed in medical or cosmetic procedures. The invention also includes the use of such block copolymers as nucleus pulposus replacement materials for the treatment of degenerative disc disorders and spinal injuries. The copolymers are constructed by polymerization of a tertiary amine methacrylate with either a (poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) polymer, such as the commercially available Pluronic.RTM. polymers, or a poly(ethylene glycol) methyl ether polymer.

  8. Temperature response of a number of plastic dosimeters for radiation processing

    Science.gov (United States)

    Sohrabpour, M.; Kazemi, A. A.; Mousavi, H.; Solati, K.

    1993-10-01

    Various plastic dosemeters are employed for dosimetry control of radiation processing within gamma and electron irradiation facilities. The temperature response of a dosimeter is important when the dose to such a dosimeter is accumulated under varying irradiation temperatures. Such measurements would be significant for proper assessment of the dose for better process control, as well as, performance evaluation of dosimetry systems. In this work we have developed a high current peltier junction temperature controller system for our Gammacell-220. This system has been designed to regulate the operating temperature of the irradiation chamber in the range of 0 to 80 C this system has been applied to measure the temperature response of the red perspex, a local clear PMMA, Gammex, Gammachrome, and Gafchromic dosimeters. The curves of relative performance or variation of the induced optical densities of the above dosemeters versus the irradiation temperature at fixed dose values are obtained.

  9. Temperature-responsive chromatography using poly(N-isopropylacrylamide) hydrogel-modified silica.

    Science.gov (United States)

    Kanazawa, Hideko; Sunamoto, Tatsuo; Ayano, Eri; Matsushima, Yoshikazu; Kikuchi, Akihiko; Okano, Teruo

    2002-01-01

    Poly(N-isopropylacrylamide) (PNIPAAm) has the sharpest phase transition of the class of thermo-sensitive N-alkyl acrylamide polymers. We developed a new method of HPLC using packing materials modified with cross-linked poly(N-isopropylacrylamide) (PNIPAAm) hydrogel. A temperature-responsive surface was prepared by polymerization of NIPAAm in the presence of a cross-linker on the silica support. The surface properties and functions of the stationary phases change in response to the external temperature. Therefore it easily changes the interaction of a solute with the surface with a constant aqueous mobile phase. A temperature-responsive elution behavior was observed on the separation of steroids and PTH-amino acids. The method is expected to be applicable to separation in the pharmaceutical and biomedical fields.

  10. Preparation and properties of fast temperature-responsive soy protein/PNIPAAm IPN hydrogels

    Directory of Open Access Journals (Sweden)

    Liu Yong

    2014-01-01

    Full Text Available The interpenetrating polymer network of fast temperature-responsive hydrogels based on soy protein and poly(N-isopropylacrylamide were successfully prepared using the sodium bicarbonate (NaHCO3 solutions as the reaction medium. The structure and properties of the hydrogels were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry and thermal gravimetric analysis. The swelling and deswelling kinetics were also investigated in detail. The results have shown that the proposed hydrogels had high porous structure, good miscibility and thermal stability, and fast temperature responsivity. The presence of NaHCO3 had little effect on the volume phase transition temperature (VPTT of the hydrogels, and the VPTTs were at about 32°C. Compared with the traditional hydrogels, the proposed hydrogels had much faster swelling and deswelling rate. The swelling mechanism of the hydrogels was the non-Fickian diffusion. This fast temperature-responsive hydrogels may have potential applications in the field of biomedical materials.

  11. Cultured articular chondrocytes sheets for partial thickness cartilage defects utilizing temperature-responsive culture dishes

    Directory of Open Access Journals (Sweden)

    N Kaneshiro

    2007-05-01

    Full Text Available The extracellular matrix (ECM of articular cartilage has several functions that are unique to joints. Although a technique for transplanting cultured chondrocytes has already been introduced, it is difficult to collect intact ECM when using enzymes to harvest samples. Temperature-responsive culture dishes have already been clinically applied in the fields of myocardial and corneal transplantation. Earlier studies have shown that a sheet of cultured cells with intact ECM and adhesive factors can be harvested using such culture dishes, which allow the surface properties of the dish to be reversibly altered by changing the temperature. Human chondrocytes were subjected to enzymatic digestion and then were seeded in temperature-responsive culture dishes. A sheet of chondrocytes was harvested by only reducing the temperature after the cultured cells reached confluency. A real-time PCR analysis of the chondrocyte sheets confirmed that type II collagen, aggrecan, and fibronectin were present. These results suggested that, although chondrocytes undergo dedifferentiation in a monolayer culture, multilayer chondrocyte sheets grown in a similar environment to that of three-dimensional culture may be able to maintain a normal phenotype. A histological examination suggested that multilayer chondrocyte sheets could thus prevent the loss of proteoglycans because the area covered by the sheets was well stained by safranin-O. The present experiments suggested that temperature-responsive culture dishes are useful for obtaining cultured chondrocytes, which may then be clinically employed as a substitute for periosteal patches because such sheets can be applied without a scaffold.

  12. Convergence in the temperature response of leaf respiration across biomes and plant functional types.

    Science.gov (United States)

    Heskel, Mary A; O'Sullivan, Odhran S; Reich, Peter B; Tjoelker, Mark G; Weerasinghe, Lasantha K; Penillard, Aurore; Egerton, John J G; Creek, Danielle; Bloomfield, Keith J; Xiang, Jen; Sinca, Felipe; Stangl, Zsofia R; Martinez-de la Torre, Alberto; Griffin, Kevin L; Huntingford, Chris; Hurry, Vaughan; Meir, Patrick; Turnbull, Matthew H; Atkin, Owen K

    2016-04-05

    Plant respiration constitutes a massive carbon flux to the atmosphere, and a major control on the evolution of the global carbon cycle. It therefore has the potential to modulate levels of climate change due to the human burning of fossil fuels. Neither current physiological nor terrestrial biosphere models adequately describe its short-term temperature response, and even minor differences in the shape of the response curve can significantly impact estimates of ecosystem carbon release and/or storage. Given this, it is critical to establish whether there are predictable patterns in the shape of the respiration-temperature response curve, and thus in the intrinsic temperature sensitivity of respiration across the globe. Analyzing measurements in a comprehensive database for 231 species spanning 7 biomes, we demonstrate that temperature-dependent increases in leaf respiration do not follow a commonly used exponential function. Instead, we find a decelerating function as leaves warm, reflecting a declining sensitivity to higher temperatures that is remarkably uniform across all biomes and plant functional types. Such convergence in the temperature sensitivity of leaf respiration suggests that there are universally applicable controls on the temperature response of plant energy metabolism, such that a single new function can predict the temperature dependence of leaf respiration for global vegetation. This simple function enables straightforward description of plant respiration in the land-surface components of coupled earth system models. Our cross-biome analyses shows significant implications for such fluxes in cold climates, generally projecting lower values compared with previous estimates.

  13. The role of spatial scale and background climate in the latitudinal temperature response to deforestation

    Science.gov (United States)

    Li, Yan; De Noblet-Ducoudré, Nathalie; Davin, Edouard L.; Motesharrei, Safa; Zeng, Ning; Li, Shuangcheng; Kalnay, Eugenia

    2016-03-01

    Previous modeling and empirical studies have shown that the biophysical impact of deforestation is to warm the tropics and cool the extratropics. In this study, we use an earth system model of intermediate complexity to investigate how deforestation on various spatial scales affects ground temperature, with an emphasis on the latitudinal temperature response and its underlying mechanisms. Results show that the latitudinal pattern of temperature response depends nonlinearly on the spatial extent of deforestation and the fraction of vegetation change. Compared with regional deforestation, temperature change in global deforestation is greatly amplified in temperate and boreal regions but is dampened in tropical regions. Incremental forest removal leads to increasingly larger cooling in temperate and boreal regions, while the temperature increase saturates in tropical regions. The latitudinal and spatial patterns of the temperature response are driven by two processes with competing temperature effects: decrease in absorbed shortwave radiation due to increased albedo and decrease in evapotranspiration. These changes in the surface energy balance reflect the importance of the background climate in modifying the deforestation impact. Shortwave radiation and precipitation have an intrinsic geographical distribution that constrains the effects of biophysical changes and therefore leads to temperature changes that are spatially varying. For example, wet (dry) climate favors larger (smaller) evapotranspiration change; thus, warming (cooling) is more likely to occur. Our analysis reveals that the latitudinal temperature change largely results from the climate conditions in which deforestation occurs and is less influenced by the magnitude of individual biophysical changes such as albedo, roughness, and evapotranspiration efficiency.

  14. Temperature-Responsive Smart Nanocarriers for Delivery Of Therapeutic Agents: Applications and Recent Advances.

    Science.gov (United States)

    Karimi, Mahdi; Sahandi Zangabad, Parham; Ghasemi, Alireza; Amiri, Mohammad; Bahrami, Mohsen; Malekzad, Hedieh; Ghahramanzadeh Asl, Hadi; Mahdieh, Zahra; Bozorgomid, Mahnaz; Ghasemi, Amir; Rahmani Taji Boyuk, Mohammad Reza; Hamblin, Michael R

    2016-08-24

    Smart drug delivery systems (DDSs) have attracted the attention of many scientists, as carriers that can be stimulated by changes in environmental parameters such as temperature, pH, light, electromagnetic fields, mechanical forces, etc. These smart nanocarriers can release their cargo on demand when their target is reached and the stimulus is applied. Using the techniques of nanotechnology, these nanocarriers can be tailored to be target-specific, and exhibit delayed or controlled release of drugs. Temperature-responsive nanocarriers are one of most important groups of smart nanoparticles (NPs) that have been investigated during the past decades. Temperature can either act as an external stimulus when heat is applied from the outside, or can be internal when pathological lesions have a naturally elevated termperature. A low critical solution temperature (LCST) is a special feature of some polymeric materials, and most of the temperature-responsive nanocarriers have been designed based on this feature. In this review, we attempt to summarize recent efforts to prepare innovative temperature-responsive nanocarriers and discuss their novel applications.

  15. Silica reinforced triblock copolymer gels

    DEFF Research Database (Denmark)

    Theunissen, E.; Overbergh, N.; Reynaers, H.

    2004-01-01

    The effect of silica and polymer coated silica particles as reinforcing agents on the structural and mechanical properties of polystyrene-poly(ethylene/butylene)-polystyrene (PS-PEB-PS) triblock gel has been investigated. Different types of chemically modified silica have been compared in order...... to evaluate the influence of the compatibility between gel and filler. Time-resolved SANS and small-angle X-ray scattering (SAXS) shows that the presence of silica particles affects the ordering of the polystyrene domains during gelsetting. The scattering pattern of silica-reinforced gels reveals strong...... a viscoclastic rubber to a plastic fluid and from a plastic fluid to a viscoelastic liquid are shifted to more elevated temperatures when silica is added to the triblock copolymer gel. (C) 2004 Elsevier Ltd. All rights reserved....

  16. MISCIBILITY IN COPOLYMER/HOMOPOLYMER BLENDS

    Institute of Scientific and Technical Information of China (English)

    JIANG Ming

    1988-01-01

    In order to study the miscibility of a copolymer with its corresponding homopolymers, varieties of multicomponent polymers including simple graft, multibranch, diblock, triblock and four-arm block copolymers and so-called ABCPs were synthesized and characterized. The morphologies of the blends comprising the covolymers and the corresponding homopolymers were examined by electron microscopy. It is concluded that beeides molecular weight, architecture of a copolymers has apparent effect on the miscibility, i.e. the more complex is molecular architecture, the greater is conformation restriction in microdomain formation and the less is solubility of homopolymer in corresponding domains. In addition, a density gradient model is suggested for describing the segment distribution of the bound and free chains in block-homopolymer systems. Using this model, Helfand's theory is extended to the blends of copolymer and homopolymer predicting the miscibility which is in good agreement with the experimental results.

  17. Drug targeting to tumors using HPMA copolymers

    OpenAIRE

    Lammers, T.G.G.M.

    2009-01-01

    Copolymers based on N-(2-hydroxypropyl)methacrylamide (HPMA) are prototypic and well-characterized polymeric drug carriers that have been broadly implemented in the delivery of anticancer agents. HPMA copolymers circulate for prolonged periods of time, and by means of the Enhance Permeability and Retention (EPR) effect, they localize to tumors both effectively and selectively. As a consequence, the concentrations of attached active agents in tumors can be increased, and their accumulation in ...

  18. Amphiphilic diblock copolymers for molecular recognition

    OpenAIRE

    Nehring, Rainer

    2009-01-01

    In this thesis, the synthesis and the characterization of poly(butadiene)-blockpoly( ethylene oxide) copolymers with terminal Me2+-NTA groups (copper or nickel) is described for the first time. A convenient “one-pot” procedure that allows control over the individual block lengths of the copolymer and the end-group functionalization was successfully established. The formation of the metal-polymer complex has been confirmed by EPR and UV/VIS spectroscopy. Mixing of the Ni2+-NT...

  19. Silicone containing copolymers: Synthesis, properties and applications

    OpenAIRE

    Yılgör, Emel; Yılgör, İskender

    2013-01-01

    Accepted Manuscript Title: Silicone containing copolymers: Synthesis, properties and applications Author: Emel Yilgor Iskender Yilgor PII: S0079-6700(13)00141-X DOI: http://dx.doi.org/doi:10.1016/j.progpolymsci.2013.11.003 Reference: JPPS 848 To appear in: Progress in Polymer Science Received date: 1-8-2013 Revised date: 4-11-2013 Accepted date: 8-11-2013 Please cite this article as: Yilgor E, Yilgor I, Silicone containing copolymers: Synthesis, properties ...

  20. Responsive Copolymers for Enhanced Petroleum Recovery

    Energy Technology Data Exchange (ETDEWEB)

    McCormick, C.; Hester, R.

    2001-02-27

    The objectives of this work was to: synthesize responsive copolymer systems; characterize molecular structure and solution behavior; measure rheological properties of aqueous fluids in fixed geometry flow profiles; and to tailor final polymer compositions for in situ rheology control under simulated conditions. This report focuses on the synthesis and characterization of novel stimuli responsive copolymers, the investigation of dilute polymer solutions in extensional flow and the design of a rheometer capable of measuring very dilute aqueous polymer solutions at low torque.

  1. Polyhydroxyalkanoate copolymers from forest biomass.

    Science.gov (United States)

    Keenan, Thomas M; Nakas, James P; Tanenbaum, Stuart W

    2006-07-01

    The potential for the use of woody biomass in poly-beta-hydroxyalkanoate (PHA) biosynthesis is reviewed. Based on previously cited work indicating incorporation of xylose or levulinic acid (LA) into PHAs by several bacterial strains, we have initiated a study for exploring bioconversion of forest resources to technically relevant copolymers. Initially, PHA was synthesized in shake-flask cultures of Burkholderia cepacia grown on 2.2% (w/v) xylose, periodically amended with varying concentrations of levulinic acid [0.07-0.67% (w/v)]. Yields of poly(beta-hydroxybutyrate-co-beta-hydroxyvalerate) [P(3HB-co-3HV)] from 1.3 to 4.2 g/l were obtained and could be modulated to contain from 1.0 to 61 mol% 3-hydroxyvalerate (3HV), as determined by 1H and 13C NMR analyses. No evidence for either the 3HB or 4HV monomers was found. Characterization of these P(3HB-co-3HV) samples, which ranged in molecular mass (viscometric, Mv) from 511-919 kDa, by differential scanning calorimetry and thermogravimetric analyses (TGA) provided data which were in agreement for previously reported P(3HB-co-3HV) copolymers. For these samples, it was noted that melting temperature (Tm) and glass transition temperature (Tg) decreased as a function of 3HVcontent, with Tm demonstrating a pseudoeutectic profile as a function of mol% 3HV content. In order to extend these findings to the use of hemicellulosic process streams as an inexpensive carbon source, a detoxification procedure involving sequential overliming and activated charcoal treatments was developed. Two such detoxified process hydrolysates (NREL CF: aspen and CESF: maple) were each fermented with appropriate LA supplementation. For the NREL CF hydrolysate-based cultures amended with 0.25-0.5% LA, P(3HB-co-3HV) yields, PHA contents (PHA as percent of dry biomass), and mol% 3HV compositions of 2.0 g/l, 40% (w/w), and 16-52 mol% were obtained, respectively. Similarly, the CESF hydrolysate-based shake-flask cultures yielded 1.6 g/l PHA, 39% (w

  2. The role of spatial scale and background climate in the latitudinal temperature response to deforestation

    Directory of Open Access Journals (Sweden)

    Y. Li

    2015-10-01

    Full Text Available Previous modeling and empirical studies have shown that the biophysical impact of deforestation is to warm the tropics and cool the extra-tropics. In this study, we use an earth system model to investigate how deforestation at various spatial scales affects ground temperature, with an emphasis on the latitudinal temperature response and its underlying mechanisms. Results show that the latitudinal pattern of temperature response depends non-linearly on the spatial extent of deforestation and the fraction of vegetation change. Compared with regional deforestation, temperature change in global deforestation is greatly amplified in temperate and boreal regions, but is dampened in tropical regions. Incremental forest removal leads to increasingly larger cooling in temperate and boreal regions, while the temperature increase saturates in tropical regions. The latitudinal and spatial patterns of the temperature response are driven by two processes with competing temperature effects: decreases in absorbed shortwave radiation due to increased albedo and decreases in evapotranspiration. These changes in the surface energy balance reflect the importance of the background climate on modifying the deforestation impact. Shortwave radiation and precipitation have an intrinsic geographical distribution that constrains the effects of biophysical changes and therefore leads to temperature changes that are spatially varying. For example, wet (dry climate favors larger (smaller evapotranspiration change, thus warming (cooling is more likely to occur. Further analysis on the contribution of individual biophysical factors (albedo, roughness, and evapotranspiration efficiency reveals that the latitudinal signature embodied in the temperature change probably result from the background climate conditions rather than the initial biophysical perturbation.

  3. Differences between rice and wheat in temperature responses of photosynthesis and plant growth.

    Science.gov (United States)

    Nagai, Takeshi; Makino, Amane

    2009-04-01

    The temperature responses of photosynthesis (A) and growth were examined in rice and wheat grown hydroponically under day/night temperature regimes of 13/10, 19/16, 25/19, 30/24 and 37/31 degrees C. Irrespective of growth temperature, the maximal rates of A were found to be at 30-35 degrees C in rice and at 25-30 degrees C in wheat. Below 25 degrees C the rates were higher in wheat, while above 30 degrees C they were higher in rice. However, in both species, A measured at the growth temperature remained almost constant irrespective of temperature. Biomass production and relative growth rate (RGR) were greatest in rice grown at 30/24 degrees C and in wheat grown at 25/19 degrees C. Although there was no difference between the species in the optimal temperature of the leaf area ratios (LARs), the net assimilation rate (NAR) in rice decreased at low temperature (19/16 degrees C) while the NAR in wheat decreased at high temperature (37/31 degrees C). For both species, the N-use efficiency (NUE) for growth rate (GR), estimated by dividing the NAR by leaf-N content, correlated with GR and with biomass production. Similarly, when NUE for A at growth temperature was estimated, the temperature response of NUE for A was similar to that of NUE for GR in both species. The results suggest that the difference between rice and wheat in the temperature response of biomass production depends on the difference in temperature dependence of NUE for A.

  4. Regional and global temperature response to anthropogenic SO2 emissions from China in three climate models

    Science.gov (United States)

    Kasoar, Matthew; Voulgarakis, Apostolos; Lamarque, Jean-François; Shindell, Drew T.; Bellouin, Nicolas; Collins, William J.; Faluvegi, Greg; Tsigaridis, Kostas

    2016-08-01

    We use the HadGEM3-GA4, CESM1, and GISS ModelE2 climate models to investigate the global and regional aerosol burden, radiative flux, and surface temperature responses to removing anthropogenic sulfur dioxide (SO2) emissions from China. We find that the models differ by up to a factor of 6 in the simulated change in aerosol optical depth (AOD) and shortwave radiative flux over China that results from reduced sulfate aerosol, leading to a large range of magnitudes in the regional and global temperature responses. Two of the three models simulate a near-ubiquitous hemispheric warming due to the regional SO2 removal, with similarities in the local and remote pattern of response, but overall with a substantially different magnitude. The third model simulates almost no significant temperature response. We attribute the discrepancies in the response to a combination of substantial differences in the chemical conversion of SO2 to sulfate, translation of sulfate mass into AOD, cloud radiative interactions, and differences in the radiative forcing efficiency of sulfate aerosol in the models. The model with the strongest response (HadGEM3-GA4) compares best with observations of AOD regionally, however the other two models compare similarly (albeit poorly) and still disagree substantially in their simulated climate response, indicating that total AOD observations are far from sufficient to determine which model response is more plausible. Our results highlight that there remains a large uncertainty in the representation of both aerosol chemistry as well as direct and indirect aerosol radiative effects in current climate models, and reinforces that caution must be applied when interpreting the results of modelling studies of aerosol influences on climate. Model studies that implicate aerosols in climate responses should ideally explore a range of radiative forcing strengths representative of this uncertainty, in addition to thoroughly evaluating the models used against

  5. Effect of polymer composition on rheological and degradation properties of temperature-responsive gelling systems composed of acyl-capped PCLA-PEG-PCLA.

    Science.gov (United States)

    Petit, Audrey; Müller, Benno; Meijboom, Ronald; Bruin, Peter; van de Manakker, Frank; Versluijs-Helder, Marjan; de Leede, Leo G J; Doornbos, Albert; Landin, Mariana; Hennink, Wim E; Vermonden, Tina

    2013-09-09

    In this study, the ability to modulate the rheological and degradation properties of temperature-responsive gelling systems composed of acyl-capped poly(ε-caprolactone-co-lactide)-b-poly(ethylene glycol)-b-poly(ε-caprolactone-co-lactide) (PCLA-PEG-PCLA) triblock copolymers was investigated. Eight polymers with varying molecular weight of PCLA, caproyl/lactoyl ratio (CL/LA) and capped with either acetyl- or propionyl-groups were synthesized by ring-opening polymerization of L-lactide and ε-caprolactone in toluene using PEG as initiator and tin(II) 2-ethylhexanoate as catalyst, and subsequently reacted in solution with an excess of acyl chloride to yield fully acyl-capped PCLA-PEG-PCLA. The microstructure of the polymers was determined by (1)H NMR, and the thermal properties and crystallinity of the polymers in dry state and in 25 wt % aqueous systems were studied by differential scanning calorimetry and X-ray diffraction. Rheological and degradation/dissolution properties of aqueous systems composed of the polymers in 25 wt % aqueous systems were studied. (1)H NMR analysis revealed that the monomer sequence in the PCLA blocks was not fully random, resulting in relatively long CL sequences, even though transesterification was demonstrated by the enrichment with lactoyl units and the presence of PEG-OH end groups. Except the most hydrophilic polymer composed of acetyl-capped PCLA1400-PEG1500-PCLA1400 having a CL/LA molar ratio of 2.5, the polymers at 25 wt % in buffer were sols below room temperature and transformed into gels between room temperature and 37 °C, which makes them suitable as temperature-responsive gelling systems for drug delivery. Over a period of weeks at 37 °C, the systems containing polymers with long CL sequences (~8 CL) and propionyl end-groups became semicrystalline as shown by X-ray diffraction analysis. Degradation of the gels by dissolution at 37 °C took 100-150 days for the amorphous gels and 250-300 days for the semicrystalline gels

  6. Oil recovery with vinyl sulfonic acid-acrylamide copolymers

    Energy Technology Data Exchange (ETDEWEB)

    Norton, C.J.; Falk, D.O.

    1973-12-18

    An aqueous polymer flood containing sulfomethylated alkali metal vinyl sulfonate-acrylamide copolymers was proposed for use in secondary or tertiary enhanced oil recovery. The sulfonate groups on the copolymers sustain the viscosity of the flood in the presence of brine and lime. Injection of the copolymer solution into a waterflooded Berea core, produced 30.5 percent of the residual oil. It is preferred that the copolymers are partially hydrolyzed.

  7. Charge Transport in Conjugated Block Copolymers

    Science.gov (United States)

    Smith, Brandon; Le, Thinh; Lee, Youngmin; Gomez, Enrique

    Interest in conjugated block copolymers for high performance organic photovoltaic applications has increased considerably in recent years. Polymer/fullerene mixtures for conventional bulk heterojunction devices, such as P3HT:PCBM, are severely limited in control over interfaces and domain length scales. In contrast, microphase separated block copolymers self-assemble to form lamellar morphologies with alternating electron donor and acceptor domains, thereby maximizing electronic coupling and local order at interfaces. Efficiencies as high as 3% have been reported in solar cells for one block copolymer, P3HT-PFTBT, but the details concerning charge transport within copolymers have not been explored. To fill this gap, we probed the transport characteristics with thin-film transistors. Excellent charge mobility values for electron transport have been observed on aluminum source and drain contacts in a bottom gate, bottom contact transistor configuration. Evidence of high mobility in ordered PFTBT phases has also been obtained following thermal annealing. The insights gleaned from our investigation serve as useful guideposts, revealing the significance of the interplay between charge mobility, interfacial order, and optimal domain size in organic block copolymer semiconductors.

  8. Thermoreversible copolymer gels for extracellular matrix.

    Science.gov (United States)

    Vernon, B; Kim, S W; Bae, Y H

    2000-07-01

    To improve the properties of a reversible synthetic extracellular matrix based on a thermally reversible polymer, copolymers of N-isopropylacrylamide and acrylic acid were prepared in benzene with varying contents of acrylic acid (0 to 3%) and the thermal properties were evaluated. The poly(N-isopropylacrylamide) and copolymers made with acrylic acid had molecular weights from 0.8 to 1.7 x10(6) D. Differential scanning calorimetry (DSC) showed the high-molecular-weight acrylic acid copolymers had similar onset temperatures to the homopolymers, but the peak width was considerably increased with increasing acrylic acid content. DSC and cloud point measurements showed that polymers with 0 to 3% acrylic acid exhibit a lower critical solution temperature (LCST) transition between 30 degrees and 37 degrees C. In swelling studies, the homopolymer showed significant syneresis at temperatures above 31 degrees C. Copolymers with 1 and 1.5% showed syneresis beginning at 32 degrees and 37 degrees C, respectively. At 37 degrees C the copolymers with 1.5-3% acrylic acid showed little or no syneresis. Due to the high water content and a transition near physiologic conditions (below 37 degrees C), the polymers with 1.5-2.0% acrylic acid exhibited properties that would be useful in the development of a refillable synthetic extracellular matrix. Such a matrix could be applied to several cell types, including islets of Langerhans, for a biohybrid artificial pancreas.

  9. Chain exchange in block copolymer micelles

    Science.gov (United States)

    Lu, Jie; Bates, Frank; Lodge, Timothy

    2014-03-01

    Block copolymer micelles are aggregates formed by self-assembly of amphiphilic copolymers dispersed in a selective solvent, driven by unfavorable interactions between the solvent and the core-forming block. Due to the relatively long chains being subject to additional thermodynamic and dynamic constraints (e.g., entanglements, crystallinity, vitrification), block copolymer micelles exhibit significantly slower equilibration kinetics than small molecule surfactants. As a result, details of the mechanism(s) of equilibration in block copolymer micelles remain unclear. This present works focuses on the chain exchange kinetics of poly(styrene-b-ethylenepropylene) block copolymers in squalane (C30H62) using time-resolved small angle neutron scattering (TR-SANS). A mixture of h-squalane and d-squalane is chosen so that it contrast matches a mixed 50/50 h/d polystyrene micelle core. When the temperature is appropriate and isotopically labeled chains undergo mixing, the mean core contrast with respect to the solvent decreases, and the scattering intensity is therefore reduced. This strategy allows direct probing of chain exchange rate from the time dependent scattering intensity I(q, t).

  10. Mathematical model of cycad cones' thermogenic temperature responses: inverse calorimetry to estimate metabolic heating rates.

    Science.gov (United States)

    Roemer, R B; Booth, D; Bhavsar, A A; Walter, G H; Terry, L I

    2012-12-21

    A mathematical model based on conservation of energy has been developed and used to simulate the temperature responses of cones of the Australian cycads Macrozamia lucida and Macrozamia. macleayi during their daily thermogenic cycle. These cones generate diel midday thermogenic temperature increases as large as 12 °C above ambient during their approximately two week pollination period. The cone temperature response model is shown to accurately predict the cones' temperatures over multiple days as based on simulations of experimental results from 28 thermogenic events from 3 different cones, each simulated for either 9 or 10 sequential days. The verified model is then used as the foundation of a new, parameter estimation based technique (termed inverse calorimetry) that estimates the cones' daily metabolic heating rates from temperature measurements alone. The inverse calorimetry technique's predictions of the major features of the cones' thermogenic metabolism compare favorably with the estimates from conventional respirometry (indirect calorimetry). Because the new technique uses only temperature measurements, and does not require measurements of oxygen consumption, it provides a simple, inexpensive and portable complement to conventional respirometry for estimating metabolic heating rates. It thus provides an additional tool to facilitate field and laboratory investigations of the bio-physics of thermogenic plants.

  11. Global Temperature Response to the Major Volcanic Eruptions in Multiple Reanalysis Datasets

    Science.gov (United States)

    Fujiwara, M.; Hibino, T.; Mehta, S. K.; Gray, L. J.; Mitchell, D.; Anstey, J.

    2015-12-01

    Global temperature response to the eruptions of Mount Agung in 1963, El Chichón in 1982 and Mount Pinatubo in 1991 is investigated using nine reanalysis datasets (JRA-55, MERRA, ERA-Interim, NCEP-CFSR, JRA-25, ERA-40, NCEP-1, NCEP-2, and 20CR). Multiple linear regression is applied to the zonal and monthly mean time series of temperature for two periods, 1979-2009 (for eight reanalysis datasets) and 1958-2001 (for four reanalysis datasets), by considering explanatory factors of seasonal harmonics, linear trends, Quasi-Biennial Oscillation, solar cycle, and El Niño Southern Oscillation. The residuals are used to define the volcanic signals for the three eruptions separately. In response to the Mount Pinatubo eruption, most reanalysis datasets show strong warming signals (up to 2-3 K for one-year average) in the tropical lower stratosphere and weak cooling signals (down to -1 K) in the subtropical upper troposphere. For the El Chichón eruption, warming signals in the tropical lower stratosphere are somewhat smaller than those for the Mount Pinatubo eruption. The response to the Mount Agung eruption is asymmetric about the equator with strong warming in the Southern Hemisphere midlatitude upper troposphere to lower stratosphere. Comparison of the results from several different reanalysis datasets confirms the atmospheric temperature response to these major eruptions qualitatively, but also shows quantitative differences even among the most recent reanalysis datasets.

  12. Temperature response of methane production in liquid manures and co-digestates.

    Science.gov (United States)

    Elsgaard, Lars; Olsen, Anne B; Petersen, Søren O

    2016-01-01

    Intensification of livestock production makes correct estimation of methanogenesis in liquid manure increasingly important for inventories of CH4 emissions. Such inventories currently rely on fixed methane conversion factors as knowledge gaps remain with respect to detailed temperature responses of CH4 emissions from liquid manure. Here, we describe the temperature response of CH4 production in liquid cattle slurry, pig slurry, and fresh and stored co-digested slurry from a thermophilic biogas plant. Subsamples of slurry were anoxically incubated at 20 temperatures from 5-52°C in a temperature gradient incubator and CH4 production was measured by gas chromatographic analysis of headspace gas after a 17-h incubation period. Methane production potentials at 5-37°C were described by the Arrhenius equation (modelling efficiencies, 79.2-98.1%), and the four materials showed a consistent activation energy (Ea) which averaged 81.0kJmol(-1) (95% confidence interval, 74.9-87.1kJmol(-1)) corresponding to a temperature sensitivity (Q10) of 3.4. In contrast, the frequency factor (A) differed among the slurry materials (30.1emissions from livestock manure.

  13. SCATTERING BY CYCLIC POLYMERS AND COPOLYMERS AT LARGE SCATTERING VECTORS

    NARCIS (Netherlands)

    KOSMAS, M; BENOIT, H; HADZIIOANNOU, G

    1994-01-01

    General formulae allowing the evaluation of the form factors of cyclic block copolymers are established and graphs for cyclic copolymers of the form (A-B)(N) are shown. When N is large, the linear and the cyclic copolymer have the same behaviour. It is possible to extend at large angle an analytical

  14. Adsorption of graft copolymers onto silica and titania.

    NARCIS (Netherlands)

    Bijsterbosch, H.D.; Cohen Stuart, M.A.; Fleer, G.J.

    1998-01-01

    The adsorption of graft copolymers of poly(acrylamide) (PAAm, backbone) and poly(ethylene oxide) (PEO, side chains) from aqueous solution onto silica and titania was studied with reflectometry. Two high-molar-mass copolymers were used with different PEO graft densities (10 and 18% w/w PEO in copolym

  15. 21 CFR 181.32 - Acrylonitrile copolymers and resins.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Acrylonitrile copolymers and resins. 181.32 Section... Ingredients § 181.32 Acrylonitrile copolymers and resins. (a) Acrylonitrile copolymers and resins listed in... of the vinyl chloride resin) resin—for use only in contact with oleomargarine. (iv)...

  16. 21 CFR 175.210 - Acrylate ester copolymer coating.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Acrylate ester copolymer coating. 175.210 Section... COATINGS Substances for Use as Components of Coatings § 175.210 Acrylate ester copolymer coating. Acrylate ester copolymer coating may safely be used as a food-contact surface of articles intended for...

  17. 21 CFR 177.1350 - Ethylene-vinyl acetate copolymers.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Ethylene-vinyl acetate copolymers. 177.1350 Section... Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1350 Ethylene-vinyl acetate copolymers. Ethylene-vinyl acetate copolymers may be safely used as articles or components of...

  18. Magnetic nanoparticles (MNPs) covalently coated by PEO-PPO-PEO block copolymer for drug delivery.

    Science.gov (United States)

    Wang, Ning; Guan, Yueping; Yang, Liangrong; Jia, Lianwei; Wei, Xuetuan; Liu, Huizhou; Guo, Chen

    2013-04-01

    A stable drug carrier has been prepared by covalently coating magnetic nanoparticles (MNPs) with PEO-PPO-PEO block copolymer Pluronic P85. The particles were characterized by TEM, XRD, DLS, VSM, FTIR, and TGA. A typical product has a 15 nm magnetite core and a 100 nm hydrodynamic diameter with a narrow size distribution and is superparamagnetic with large saturation magnetization (57.102 emu/g) at room temperature. The covalently-coated Pluronic-MNPs (MagPluronics) were proven to be stable in different conditions, such as aqueous solution, 0.2 M PBS solution, and pH 13.5 solution, which would be significant for biological applications. Furthermore, MagPluronics also possess temperature-responsive property acquired from the Pluronic copolymer layer on their surface, which can cause conformational change of Pluronics and improve load and delivery efficiency of the particles. The temperature-controlled loading and releasing of hydrophobic model drug curcumin were tested with these particles. A loading efficiency of 81.3% and a sustained release of more than 4 days were achieved in simulated human body condition. It indicates that the covalently-coated MagPluronics are stable carriers with good drug-loading capacity and controlled-release property.

  19. Nanoscale Ionic Aggregate Morphology in Zwitterionic Copolymers

    Science.gov (United States)

    Choi, Jae-Hong; Huyck, Rebecca; Salas-de La Cruz, David; Long, Timothy E.; Winey, Karen I.

    2009-03-01

    The morphology of two different zwitterionic copolymers, poly(sulfobetaine methacrylate-ran-butyl acrylate), and poly(sulfobetaine methacrylamide-ran-butyl acrylate) are investigated as a function of the mol % content of SBMA (7 and 9 mol %) and SBMAm (6, 10 and 13 mol %), respectively. In both copolymers, X-ray scattering results show a new structure in the material arising from ionic aggregates. The sizes of the ionic aggregates are obtained through the scattering model. The sizes of the ionic aggregates increase as the ion content increases. The application of scanning transmission electron microscopy to the study of ionomer morphology has enabled direct, model-independent visualization of the ionic aggregates. The correlation between X-ray scattering results and the real space imaging for morphology of these zwitterionic copolymers will be presented.

  20. Functionalization of Block Copolymer Vesicle Surfaces

    Directory of Open Access Journals (Sweden)

    Wolfgang Meier

    2011-01-01

    Full Text Available In dilute aqueous solutions certain amphiphilic block copolymers self-assemble into vesicles that enclose a small pool of water with a membrane. Such polymersomes have promising applications ranging from targeted drug-delivery devices, to biosensors, and nanoreactors. Interactions between block copolymer membranes and their surroundings are important factors that determine their potential biomedical applications. Such interactions are influenced predominantly by the membrane surface. We review methods to functionalize block copolymer vesicle surfaces by chemical means with ligands such as antibodies, adhesion moieties, enzymes, carbohydrates and fluorophores. Furthermore, surface-functionalization can be achieved by self-assembly of polymers that carry ligands at their chain ends or in their hydrophilic blocks. While this review focuses on the strategies to functionalize vesicle surfaces, the applications realized by, and envisioned for, such functional polymersomes are also highlighted.

  1. Additive-driven assembly of block copolymers

    Science.gov (United States)

    Lin, Ying; Daga, Vikram; Anderson, Eric; Watkins, James

    2011-03-01

    One challenge to the formation of well ordered hybrid materials is the incorporation of nanoscale additives including metal, semiconductor and dielectric nanoparticles at high loadings while maintaining strong segregation. Here we describe the molecular and functional design of small molecule and nanoparticle additives that enhance phase segregation in their block copolymer host and enable high additive loadings. Our approach includes the use of hydrogen bond interactions between the functional groups on the additive or particle that serve as hydrogen bond donors and one segment of the block copolymer containing hydrogen bond acceptors. Further, the additives show strong selectively towards the targeted domains, leading to enhancements in contrast between properties of the phases. In addition to structural changes, we explore how large changes in the thermal and mechanical properties occur upon incorporation of the additives. Generalization of this additive-induced ordering strategy to various block copolymers will be discussed.

  2. Dynamics of Block Copolymer Nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Mochrie, Simon G. J.

    2014-09-09

    A detailed study of the dynamics of cadmium sulfide nanoparticles suspended in polystyrene homopolymer matrices was carried out using X-ray photon correlation spectroscopy for temperatures between 120 and 180 °C. For low molecular weight polystyrene homopolymers, the observed dynamics show a crossover from diffusive to hyper-diffusive behavior with decreasing temperatures. For higher molecular weight polystyrene, the nanoparticle dynamics appear hyper-diffusive at all temperatures studied. The relaxation time and characteristic velocity determined from the measured hyper-diffusive dynamics reveal that the activation energy and underlying forces determined are on the order of 2.14 × 10-19 J and 87 pN, respectively. We also carried out a detailed X-ray scattering study of the static and dynamic behavior of a styrene– isoprene diblock copolymer melt with a styrene volume fraction of 0.3468. At 115 and 120 °C, we observe splitting of the principal Bragg peak, which we attribute to phase coexistence of hexagonal cylindrical and cubic double- gyroid structure. In the disordered phase, above 130 °C, we have characterized the dynamics of composition fluctuations via X-ray photon correlation spectroscopy. Near the peak of the static structure factor, these fluctuations show stretched-exponential relaxations, characterized by a stretching exponent of about 0.36 for a range of temperatures immediately above the MST. The corresponding characteristic relaxation times vary exponentially with temperature, changing by a factor of 2 for each 2 °C change in temperature. At low wavevectors, the measured relaxations are diffusive with relaxation times that change by a factor of 2 for each 8 °C change in temperature.

  3. Lysozyme complexes with thermo- and pH-responsive PNIPAM- b-PAA block copolymer

    Science.gov (United States)

    Pippa, Natassa; Meristoudi, Anastasia; Pispas, Stergios; Demetzos, Costas

    2017-02-01

    Lysozyme is an enzyme responsible for the damage of bacterial cell walls and is abundant in a number of secretions such as tears and human milk. In the present study, we investigated the structure, the physicochemical characteristics, and the temperature-responsiveness of lysozyme complexes with poly( N-isopropylacrylamide)- b-poly(acrylic acid) block polyelectrolyte in aqueous media. A gamut of light-scattering techniques and fluorescence spectroscopy were used in order to examine the complexation process, as well as the structure, solution behavior, and temperature response of the nanosized complexes. The concentration of copolymer polyelectrolyte was kept constant. The values of the scattering intensity, I 90, which is proportional to the mass of the species in solution, increased gradually as a function of C LYS, providing proof of the occurring complexation, while the size of the nanostructures decreased. The structure of the complexes became more open as the C LYS increased. The increase of the salinity did not affect the structural characteristics of the supramolecular nanoparticulate aggregates. On the other hand, the physicochemical and structural characteristics of the complexes changed upon increasing temperature, and the changes depended on the initial ratio block polyelectrolyte/lysozyme. The knowledge on developing block polyelectrolyte/protein complexes through electrostatic interactions, obtained from this investigation, may be applied to the design of nutraceuticals.

  4. Co-polymer Films for Sensors

    Science.gov (United States)

    Ryan, Margaret A. (Inventor); Homer, Margie L. (Inventor); Yen, Shiao-Pin S. (Inventor); Kisor, Adam (Inventor); Jewell, April D. (Inventor); Shevade, Abhijit V. (Inventor); Manatt, Kenneth S. (Inventor); Taylor, Charles (Inventor); Blanco, Mario (Inventor); Goddard, William A. (Inventor)

    2012-01-01

    Embodiments include a sensor comprising a co-polymer, the co-polymer comprising a first monomer and a second monomer. For some embodiments, the first monomer is poly-4-vinyl pyridine, and the second monomer is poly-4-vinyl pyridinium propylamine chloride. For some embodiments, the first monomer is polystyrene and the second monomer is poly-2-vinyl pyridinium propylamine chloride. For some embodiments, the first monomer is poly-4-vinyl pyridine, and the second monomer is poly-4-vinyl pyridinium benzylamine chloride. Other embodiments are described and claimed.

  5. Polaronic Tunnelling in Organic Triblock Copolymers

    Institute of Scientific and Technical Information of China (English)

    LIU De-Sheng; ZHANG Da-Cheng; XIE Shi-Jie; MEI Liang-Mo

    2005-01-01

    @@ Polaron tunnelling is studied in xPA/nPPP/xPA (PA for polyacetylene and PPP poly (p-phenylene)) triblock copolymer, which has a well-barrier-well structure. An extended tight-binding Hamiltonian including external electric field is adopted. Without electric field, the injected electrons would not extend over the whole copolymer chain but instead be confined in the segments of PA. This is different from the behaviour of the traditional semiconductors. It is found that the polaron can transfer to the potential barrier-PPP segment when the applied electric field reaches a certain value. The critical polaron tunnelling electric fields depend upon the lengths of PPP segments.

  6. Ordering phenomena in ABA triblock copolymer gels

    DEFF Research Database (Denmark)

    Reynders, K.; Mischenko, N.; Kleppinger, R.

    1997-01-01

    Temperature and concentration dependencies of the degree of order in ABA triblock copolymer gels are discussed. Two factors can influence the ordering phenomena: the conformation of the midblocks (links of the network) and the polydispersity of the endblock domains (nodes of the network). The lat......Temperature and concentration dependencies of the degree of order in ABA triblock copolymer gels are discussed. Two factors can influence the ordering phenomena: the conformation of the midblocks (links of the network) and the polydispersity of the endblock domains (nodes of the network...

  7. Drug governs the morphology of polyalkylated block copolymer aggregates.

    Science.gov (United States)

    Le Dévédec, F; Her, S; Vogtt, K; Won, A; Li, X; Beaucage, G; Yip, C; Allen, C

    2017-02-16

    Polyalkylated copolymers based on mPEG-b-(AGE-C6,12 or 18)25 have been used to formulate clinically relevant concentrations of doxorubicin (DOX) and the impact of drug incorporation on copolymer aggregation behaviour was examined. The copolymer aggregates were analyzed by various microscopy techniques (TEM, cryo-TEM and AFM) and scattering methods (SANS, DLS). In the absence of the drug, the copolymers formed largely non-spherical aggregates (i.e. cylinders, vesicles). Drug incorporation during copolymer aggregate formation directed the formation of only spherical aggregates. As well, the nature of the core-forming block was found to influence drug release and cytotoxicity of the formulations.

  8. Temperature-Responsive Tensile Actuator Based on Multi-walled Carbon Nanotube Yarn

    Institute of Scientific and Technical Information of China (English)

    Hyunsoo Kim; Jae Ah Lee; Hyeon Jun Sim; Ma rcio D Lima; Ray H Baughman; Seon Jeong Kim

    2016-01-01

    Many temperature indicators or sensors show color changes for materials used in food and medical fields. However, they are not helpful for a color-blind person or children who lack judgment. In this paper, we introduce simply fabricated and more useful low-temperature indicator (*30 ?C) for devices that actuates using paraffin-infiltrated multi-walled carbon nanotube (MWCNT) coiled yarn. The density difference of MWCNT yarn provides large strain (*330%) when heat causes the melted polymer to move. Furthermore, the MWCNT yarn decreases the melting point of paraffin. These properties allow control of the actuating temperature. In addition, mechanical strength was enhanced by MWCNT than previously reported temperature-responsive actuators based on shape memory polymers. This simply fabricated temperature indicator can be applied in latching devices for medical and biological fields.

  9. Temperature response of methane production in liquid manures and co-digestates

    DEFF Research Database (Denmark)

    Elsgaard, Lars; Olsen, Anna Berg; Petersen, Søren O.

    2016-01-01

    of CH4 emissions fromliquid manure. Here, we describe the temperature response of CH4 production in liquid cattle slurry, pig slurry, and fresh and stored co-digested slurry from a thermophilic biogas plant. Subsamples of slurry were anoxically incubated at 20 temperatures from 5–52 °C in a temperature...... gradient incubator and CH4 production was measured by gas chromatographic analysis of headspace gas after a 17-h incubation period. Methane production potentials at 5–37 °C were described by the Arrhenius equation (modelling efficiencies, 79.2–98.1%), and the four materials showed a consistent activation...... of the manure affect this parameter. The Ea estimate, based on individual slurry materials,was intermediate when compared to published values of 63 and 112.7 kJ mol−1 derived from composite data, but was similar to Ea estimated for CH4 production at microbial community level across aquatic ecosystems, wetlands...

  10. Preparation and characterization of temperature-responsive magnetic composite particles for multi-modal cancer therapy.

    Science.gov (United States)

    Yao, Aihua; Chen, Qi; Ai, Fanrong; Wang, Deping; Huang, Wenhai

    2011-10-01

    The temperature-responsive magnetic composite particles were synthesized by emulsion-free polymerization of N-isopropylacrylamide (NIPAAm) and acrylamide (Am) in the presence of oleic acid-modified Fe(3)O(4) nanoparticles. The magnetic properties and heat generation ability of the composite particles were characterized. Furthermore, temperature and alternating magnetic field (AMF) triggered drug release behaviors of vitamin B(12)-loaded composite particles were also examined. It was found that composite particles enabled drug release to be controlled through temperature changes in the neighborhood of lower critical solution temperature. Continuous application of AMF resulted in an accelerated release of the loaded drug. On the other hand, intermittent AMF application to the composite particles resulted in an "on-off", stepwise release pattern. Longer release duration and larger overall release could be achieved by intermittent application of AMF as compared to continuous magnetic field. Such composite particles may be used for magnetic drug targeting followed by simultaneous hyperthermia and drug release.

  11. Kuosheng BWR/6 containment pressure and temperature responses after recirculation line break using GOTHIC code

    Energy Technology Data Exchange (ETDEWEB)

    Lin, A.; Wang, J-R.; Chen, Y-S., E-mail: samuellin1999@iner.gov.tw, E-mail: jrwang@iner.gov.tw, E-mail: yschen@iner.gov.tw [Inst. of Nuclear Energy Research Atomic Energy Council (China); Shih, C., E-mail: ckshih@ess.nthu.edu.tw [National Tsing Hua Univ., Dept. of Engineering and System Science (China)

    2011-07-01

    In this study, we presented the calculated results of the containment P/T (pressure and temperature) response after the recirculation line break (RCLB) accident of a GE-designed twin-unit BWR/6 plant, which can be served as the design basis for the containment system. During the simulation, a power of SPU (stretch power uprate) range was used and a model of the Mark III type containment was built using the GOTHIC (Generation of Thermal-Hydraulic Information for Containments) code. The calculated results, similar to the FSAR (Final Safety Analysis Report) results, indicate the GOTHIC code has the capability to simulate the containment P/T response to the RCLB accident. (author)

  12. Molecular Interaction Control in Diblock Copolymer Blends and Multiblock Copolymers with Opposite Phase Behaviors

    Science.gov (United States)

    Cho, Junhan

    2014-03-01

    Here we show how to control molecular interactions via mixing AB and AC diblock copolymers, where one copolymer exhibits upper order-disorder transition and the other does lower disorder-order transition. Linear ABC triblock copolymers possessing both barotropic and baroplastic pairs are also taken into account. A recently developed random-phase approximation (RPA) theory and the self-consistent field theory (SCFT) for general compressible mixtures are used to analyze stability criteria and morphologies for the given systems. It is demonstrated that the copolymer systems can yield a variety of phase behaviors in their temperature and pressure dependence upon proper mixing conditions and compositions, which is caused by the delicate force fields generated in the systems. We acknowledge the financial support from National Research Foundation of Korea and Center for Photofunctional Energy Materials.

  13. Block Copolymers of Ethylene Oxide and Styrene Oxide.New Copolymer Surfactants(Ⅱ)

    Institute of Scientific and Technical Information of China (English)

    Zhuo Yang; David Attwood; Colin Booth

    2003-01-01

    @@ 3.2. Association Number Figure 5 shows the dependence of the weight-average association number (Nw,measured by static light scattering, solution temperature 30 °C) on hydrophobe block length for ES and ESEblock copolymers.

  14. Temperature response functions introduce high uncertainty in modelled carbon stocks in cold temperature regimes

    Directory of Open Access Journals (Sweden)

    H. Portner

    2009-08-01

    Full Text Available Models of carbon cycling in terrestrial ecosystems contain formulations for the dependence of respiration on temperature, but the sensitivity of predicted carbon pools and fluxes to these formulations and their parameterization is not understood. Thus, we made an uncertainty analysis of soil organic matter decomposition with respect to its temperature dependency using the ecosystem model LPJ-GUESS.

    We used five temperature response functions (Exponential, Arrhenius, Lloyd-Taylor, Gaussian, Van't Hoff. We determined the parameter uncertainty ranges of the functions by nonlinear regression analysis based on eight experimental datasets from northern hemisphere ecosystems. We sampled over the uncertainty bounds of the parameters and run simulations for each pair of temperature response function and calibration site. The uncertainty in both long-term and short-term soil carbon dynamics was analyzed over an elevation gradient in southern Switzerland.

    The function of Lloyd-Taylor turned out to be adequate for modelling the temperature dependency of soil organic matter decomposition, whereas the other functions either resulted in poor fits (Exponential, Arrhenius or were not applicable for all datasets (Gaussian, Van't Hoff. There were two main sources of uncertainty for model simulations: (1 the uncertainty in the parameter estimates of the response functions, which increased with increasing temperature and (2 the uncertainty in the simulated size of carbon pools, which increased with elevation, as slower turn-over times lead to higher carbon stocks and higher associated uncertainties. The higher uncertainty in carbon pools with slow turn-over rates has important implications for the uncertainty in the projection of the change of soil carbon stocks driven by climate change, which turned out to be more uncertain for higher elevations and hence higher latitudes, which are of key importance for the global terrestrial carbon

  15. Global temperature response to the major volcanic eruptions in multiple reanalysis datasets

    Directory of Open Access Journals (Sweden)

    M. Fujiwara

    2015-05-01

    Full Text Available Global temperature response to the eruptions of Mount Agung in 1963, El Chichón in 1982 and Mount Pinatubo in 1991 is investigated using nine reanalysis datasets (JRA-55, MERRA, ERA-Interim, NCEP-CFSR, JRA-25, ERA-40, NCEP-1, NCEP-2, and 20CR. Multiple linear regression is applied to the zonal and monthly mean time series of temperature for two periods, 1979–2009 (for eight reanalysis datasets and 1958–2001 (for four reanalysis datasets, by considering explanatory factors of seasonal harmonics, linear trends, Quasi-Biennial Oscillation, solar cycle, and El Niño Southern Oscillation. The residuals are used to define the volcanic signals for the three eruptions separately. In response to the Mount Pinatubo eruption, most reanalysis datasets show strong warming signals (up to 2–3 K for one-year average in the tropical lower stratosphere and weak cooling signals (down to −1 K in the subtropical upper troposphere. For the El Chichón eruption, warming signals in the tropical lower stratosphere are somewhat smaller than those for the Mount Pinatubo eruption. The response to the Mount Agung eruption is asymmetric about the equator with strong warming in the Southern Hemisphere midlatitude upper troposphere to lower stratosphere. The response to three other smaller-scale eruptions in the 1960s and 1970s is also investigated. Comparison of the results from several different reanalysis datasets confirms the atmospheric temperature response to these major eruptions qualitatively, but also shows quantitative differences even among the most recent reanalysis datasets.

  16. A temperature-responsive network links cell shape and virulence traits in a primary fungal pathogen.

    Directory of Open Access Journals (Sweden)

    Sinem Beyhan

    2013-07-01

    Full Text Available Survival at host temperature is a critical trait for pathogenic microbes of humans. Thermally dimorphic fungal pathogens, including Histoplasma capsulatum, are soil fungi that undergo dramatic changes in cell shape and virulence gene expression in response to host temperature. How these organisms link changes in temperature to both morphologic development and expression of virulence traits is unknown. Here we elucidate a temperature-responsive transcriptional network in H. capsulatum, which switches from a filamentous form in the environment to a pathogenic yeast form at body temperature. The circuit is driven by three highly conserved factors, Ryp1, Ryp2, and Ryp3, that are required for yeast-phase growth at 37°C. Ryp factors belong to distinct families of proteins that control developmental transitions in fungi: Ryp1 is a member of the WOPR family of transcription factors, and Ryp2 and Ryp3 are both members of the Velvet family of proteins whose molecular function is unknown. Here we provide the first evidence that these WOPR and Velvet proteins interact, and that Velvet proteins associate with DNA to drive gene expression. Using genome-wide chromatin immunoprecipitation studies, we determine that Ryp1, Ryp2, and Ryp3 associate with a large common set of genomic loci that includes known virulence genes, indicating that the Ryp factors directly control genes required for pathogenicity in addition to their role in regulating cell morphology. We further dissect the Ryp regulatory circuit by determining that a fourth transcription factor, which we name Ryp4, is required for yeast-phase growth and gene expression, associates with DNA, and displays interdependent regulation with Ryp1, Ryp2, and Ryp3. Finally, we define cis-acting motifs that recruit the Ryp factors to their interwoven network of temperature-responsive target genes. Taken together, our results reveal a positive feedback circuit that directs a broad transcriptional switch between

  17. Gyroid Membranes made from Nanoporous Blck Copolymers

    DEFF Research Database (Denmark)

    Szewczykowski, Piotr Plzemystaw; Vigild, Martin Etchells; Ndoni, Sokol;

    2007-01-01

    of the membrane and its nanoporosity is e.g. obtained by cross-linking the majority blocks and selectively etching the minority blocks. Here we report on ultrafiltration membranes prepared from a 1,2-polybutadiene-b-polydimethylsiloxane diblock copolymer with gyroid structure. Different experimental methods...

  18. Substrate tolerant direct block copolymer nanolithography

    DEFF Research Database (Denmark)

    Li, Tao; Wang, Zhongli; Schulte, Lars

    2016-01-01

    simplifies the main stream BC lithography process, showing a broad substrate tolerance and allowing for efficient pattern transfer over wafer scale. PDMS-rich poly(styrene-b-dimethylsiloxane) (PS-b-PDMS) copolymers are directly applied on substrates including polymers, silicon and graphene. A single oxygen...

  19. LEDs based on conjugated PPV block copolymers

    NARCIS (Netherlands)

    Brouwer, H.J.; Hilberer, A.; Krasnikov, V.V.; Werts, M.; Wildeman, J.; Hadziioannou, G.

    1997-01-01

    A way to control the bandgap in semi-conducting polymers is by preparing polymers with a partially conjugated backbone. In our laboratory, three conjugated copolymers containing PPV trimers as light emitting chromophores have been synthesized, which emit in the blue, green and orange wavelength regi

  20. Chiral Block Copolymer Structures for Metamaterial Applications

    Science.gov (United States)

    2015-01-27

    MONITOR’S REPORT NUMBER(S) AOARD-114078 12. DISTRIBUTION/AVAILABILITY STATEMENT Distribution A: Approved for public release. Distribtion is...researchers focused o synthesis and processing, morphology and physical characterization of chiral block copolymer (BCP) materials. Such materials a...developed a platform process technology that can fabricate novel netwo morphologies from initial bicontinuous cubic phases through supergroup/subgroup

  1. Helical Ordering in Chiral Block Copolymers

    Science.gov (United States)

    Zhao, Wei; Hong, Sung Woo; Chen, Dian; Grason, Gregory; Russell, Thomas

    2012-02-01

    Introducing molecular chirality into the segments of block copolymers can influence the nature of the resultant morphology. Such an effect was found for poly(styrene-b-L-lactide) (PS-b-PLLA) diblock copolymers where hexagonally packed PLLA helical microdomains (H* phase) form in a PS matrix. However, molecular ordering of PLLA within the helical microdomains and the transfer of chirality from the segmental level to the mesoscale is still not well understood. We developed a field theoretic model to describe the interactions between segments of chiral blocks, which have the tendency to form a ``cholesteric'' texture. Based on the model, we calculated the bulk morphologies of chiral AB diblock copolymers using self-consistent field theory (SCFT). Experiments show that the H* phase only forms when microphase separation between PS and PLLA block happens first and crystallization of PLLA block is suppressed or happens within confined microdomain. Hence, crystalline ordering is not necessary for H* phase formation. The SCFT offers the chance to explore the range of thermodynamic stability of helical structures in the phase diagram of chiral block copolymer melts, by tuning parameters not only like the block segregation strength and composition, but also new parameters such as the ratio between preferred helical pitch to the radius of gyration and the Frank elastic constant for inter-segment distortions.

  2. CONJUGATED BLOCK-COPOLYMERS FOR ELECTROLUMINESCENT DIODES

    NARCIS (Netherlands)

    Hilberer, A; Gill, R.E; Herrema, J.K; Malliaras, G.G; Wildeman, J.; Hadziioannou, G

    1995-01-01

    In this article we review results obtained in our laboratory on the design and study of new light-emitting polymers. We are interested in the synthesis and characterisation of block copolymers with regularly alternating conjugated and non conjugated sequences. The blocks giving rise to luminescence

  3. Nylon 46-polytetramethylene oxide segmented block copolymers

    NARCIS (Netherlands)

    Gaymans, R.J.; Schwering, P.; Haan, de J.L.

    1989-01-01

    Block copolymers were synthesized from amine-terminated polytetramethylene oxide (PMTO) (Mw 800 and 1130) and polyamide 4,6 salt. First prepolymers were prepared at 200–210°C in the presence of a solvent (pyrrolidone). The prepolymers were postcondensed at 255°C (where possible in the solid state) t

  4. Glycine/Glycolic acid based copolymers

    NARCIS (Netherlands)

    Veld, in 't Peter J.A.; Shen, Zheng-Rong; Takens, Gijsbert A.J.; Dijkstra, Pieter J.; Feijen, Jan

    1994-01-01

    Glycine/glycolic acid based biodegradable copolymers have been prepared by ring-opening homopolymerization of morpholine-2,5-dione, and ring-opening copolymerization of morpholine-2,5-dione and glycolide. The homopolymerization of morpholine-2,5-dione was carried out in the melt at 200°C for 3 min u

  5. Block copolymer/ferroelectric nanoparticle nanocomposites

    Science.gov (United States)

    Pang, Xinchang; He, Yanjie; Jiang, Beibei; Iocozzia, James; Zhao, Lei; Guo, Hanzheng; Liu, Jin; Akinc, Mufit; Bowler, Nicola; Tan, Xiaoli; Lin, Zhiqun

    2013-08-01

    Nanocomposites composed of diblock copolymer/ferroelectric nanoparticles were formed by selectively constraining ferroelectric nanoparticles (NPs) within diblock copolymer nanodomains via judicious surface modification of ferroelectric NPs. Ferroelectric barium titanate (BaTiO3) NPs with different sizes that are permanently capped with polystyrene chains (i.e., PS-functionalized BaTiO3NPs) were first synthesized by exploiting amphiphilic unimolecular star-like poly(acrylic acid)-block-polystyrene (PAA-b-PS) diblock copolymers as nanoreactors. Subsequently, PS-functionalized BaTiO3 NPs were preferentially sequestered within PS nanocylinders in the linear cylinder-forming polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymer upon mixing the BaTiO3 NPs with PS-b-PMMA. The use of PS-b-PMMA diblock copolymers, rather than traditional homopolymers, offers the opportunity for controlling the spatial organization of PS-functionalized BaTiO3 NPs in the PS-b-PMMA/BaTiO3 NP nanocomposites. Selective solvent vapor annealing was utilized to control the nanodomain orientation in the nanocomposites. Vertically oriented PS nanocylinders containing PS-functionalized BaTiO3 NPs were yielded after exposing the PS-b-PMMA/BaTiO3 NP nanocomposite thin film to acetone vapor, which is a selective solvent for PMMA block. The dielectric properties of nanocomposites in the microwave frequency range were investigated. The molecular weight of PS-b-PMMA and the size of BaTiO3 NPs were found to exert an apparent influence on the dielectric properties of the resulting nanocomposites.Nanocomposites composed of diblock copolymer/ferroelectric nanoparticles were formed by selectively constraining ferroelectric nanoparticles (NPs) within diblock copolymer nanodomains via judicious surface modification of ferroelectric NPs. Ferroelectric barium titanate (BaTiO3) NPs with different sizes that are permanently capped with polystyrene chains (i.e., PS-functionalized BaTiO3NPs) were

  6. A temperature response function for modeling leaf growth and development of the African violet (Saintpaulia ionantha Wendl.

    Directory of Open Access Journals (Sweden)

    Streck Nereu Augusto

    2004-01-01

    Full Text Available Response functions used in crop simulation models are usually different for different physiological processes and cultivars, resulting in many unknown coefficients in the response functions. This is the case of African violet (Saintpaulia ionantha Wendl., where a generalized temperature response for leaf growth and development has not been developed yet. The objective of this study was to develop a generalized nonlinear temperature response function for leaf appearance rate and leaf elongation rate in African violet. The nonlinear function has three coefficients, which are the cardinal temperatures (minimum, optimum, and maximum temperatures. These coefficients were defined as 10, 24, and 33ºC, based on the cardinal temperatures of other tropical species. Data of temperature response of leaf appearance rate and leaf elongation rate in African violet, cultivar Utah, at different light levels, which are from published research, were used as independent data for evaluating the performance of the nonlinear temperature response function. The results showed that a generalized nonlinear response function can be used to describe the temperature response of leaf growth and development in African violet. These results imply that a reduction in the number of input data required in African violet simulation models is possible.

  7. An isotopic investigation of the temperature response of young and old soil organic matter respiration

    Science.gov (United States)

    Burns, Nancy; Cloy, Joanna; Garnett, Mark; Reay, David; Smith, Keith; Otten, Wilfred

    2010-05-01

    The effect of temperature on rates of soil respiration is critical to our understanding of the terrestrial carbon cycle and potential feedbacks to climate change. The relative temperature sensitivity of labile and recalcitrant soil organic matter (SOM) is still controversial; different studies have produced contrasting results, indicating limited understanding of the underlying relationships between stabilisation processes and temperature. Current global carbon cycle models still rely on the assumption that SOM pools with different decay rates have the same temperature response, yet small differences in temperature response between pools could lead to very different climate feedbacks. This study examined the temperature response of soil respiration and the age of soil carbon respired from radiocarbon dated fractions of SOM (free, intra-aggregate and mineral-bound) and whole soils (organic and mineral layers). Samples were collected from a peaty gley soil from Harwood Forest, Northumberland, UK. SOM fractions were isolated from organic layer (5 - 17 cm) material using high density flotation and ultrasonic disaggregation - designated as free ( 1.8 g cm-3) and mineral-bound (> 1.8 g cm-3) SOM. Fractions were analysed for chemical composition (FTIR, CHN analysis, ICP-OES), 14C (AMS), δ13C and δ15N (MS) and thermal properties (DSC). SOM fractions and bulk soil from the organic layer and the mineral layer (20 - 30 cm) were incubated in sealed vessels at 30 ° C and 10 ° C for 3 or 9 months to allow accumulation of CO2 sufficient for sampling. Accumulated respired CO2 samples were collected on zeolite molecular sieve cartridges and used for AMS radiocarbon dating. In parallel, material from the same fractions and layers were incubated at 10 ° C, 15 ° C, 25 ° C and 30 ° C for 6 months and sampled weekly for CO2 flux measurements using GC chromatography. Initial data have shown radiocarbon ages ranging from modern to 219 y BP in bulk soil from the organic layer (5

  8. Global temperature response to the major volcanic eruptions in multiple reanalysis data sets

    Science.gov (United States)

    Fujiwara, M.; Hibino, T.; Mehta, S. K.; Gray, L.; Mitchell, D.; Anstey, J.

    2015-12-01

    The global temperature responses to the eruptions of Mount Agung in 1963, El Chichón in 1982, and Mount Pinatubo in 1991 are investigated using nine currently available reanalysis data sets (JRA-55, MERRA, ERA-Interim, NCEP-CFSR, JRA-25, ERA-40, NCEP-1, NCEP-2, and 20CR). Multiple linear regression is applied to the zonal and monthly mean time series of temperature for two periods, 1979-2009 (for eight reanalysis data sets) and 1958-2001 (for four reanalysis data sets), by considering explanatory factors of seasonal harmonics, linear trends, Quasi-Biennial Oscillation, solar cycle, and El Niño Southern Oscillation. The residuals are used to define the volcanic signals for the three eruptions separately, and common and different responses among the older and newer reanalysis data sets are highlighted for each eruption. In response to the Mount Pinatubo eruption, most reanalysis data sets show strong warming signals (up to 2-3 K for 1-year average) in the tropical lower stratosphere and weak cooling signals (down to -1 K) in the subtropical upper troposphere. For the El Chichón eruption, warming signals in the tropical lower stratosphere are somewhat smaller than those for the Mount Pinatubo eruption. The response to the Mount Agung eruption is asymmetric about the equator with strong warming in the Southern Hemisphere midlatitude upper troposphere to lower stratosphere. Comparison of the results from several different reanalysis data sets confirms the atmospheric temperature response to these major eruptions qualitatively, but also shows quantitative differences even among the most recent reanalysis data sets. The consistencies and differences among different reanalysis data sets provide a measure of the confidence and uncertainty in our current understanding of the volcanic response. The results of this intercomparison study may be useful for validation of climate model responses to volcanic forcing and for assessing proposed geoengineering by stratospheric

  9. Global temperature response to the major volcanic eruptions in multiple reanalysis data sets

    Directory of Open Access Journals (Sweden)

    M. Fujiwara

    2015-12-01

    Full Text Available The global temperature responses to the eruptions of Mount Agung in 1963, El Chichón in 1982, and Mount Pinatubo in 1991 are investigated using nine currently available reanalysis data sets (JRA-55, MERRA, ERA-Interim, NCEP-CFSR, JRA-25, ERA-40, NCEP-1, NCEP-2, and 20CR. Multiple linear regression is applied to the zonal and monthly mean time series of temperature for two periods, 1979–2009 (for eight reanalysis data sets and 1958–2001 (for four reanalysis data sets, by considering explanatory factors of seasonal harmonics, linear trends, Quasi-Biennial Oscillation, solar cycle, and El Niño Southern Oscillation. The residuals are used to define the volcanic signals for the three eruptions separately, and common and different responses among the older and newer reanalysis data sets are highlighted for each eruption. In response to the Mount Pinatubo eruption, most reanalysis data sets show strong warming signals (up to 2–3 K for 1-year average in the tropical lower stratosphere and weak cooling signals (down to −1 K in the subtropical upper troposphere. For the El Chichón eruption, warming signals in the tropical lower stratosphere are somewhat smaller than those for the Mount Pinatubo eruption. The response to the Mount Agung eruption is asymmetric about the equator with strong warming in the Southern Hemisphere midlatitude upper troposphere to lower stratosphere. Comparison of the results from several different reanalysis data sets confirms the atmospheric temperature response to these major eruptions qualitatively, but also shows quantitative differences even among the most recent reanalysis data sets. The consistencies and differences among different reanalysis data sets provide a measure of the confidence and uncertainty in our current understanding of the volcanic response. The results of this intercomparison study may be useful for validation of climate model responses to volcanic forcing and for assessing proposed

  10. Comb-like temperature-responsive polyhydroxyalkanoate-graft-poly(2-dimethylamino-ethylmethacrylate) for controllable protein adsorption

    DEFF Research Database (Denmark)

    Yao, Hui; Wei, Daixu; Che, Xuemei

    2016-01-01

    %. Graft copolymer PHA-g-PDMAEMA showed enhanced thermal stability, biocompatibility and controllable hydrophilicity compared with non-grafted P(3HDD-co-3H9D). The grafted material presented an obvious tendency of increasing protein adsorptions over the lower critical solution temperature (LCST 47.5 °C...... controllable protein adsorption for biomedical usages....

  11. Temperature-responsive self-assembled monolayers of oligo(ethylene glycol): control of biomolecular recognition.

    Science.gov (United States)

    Zareie, Hadi M; Boyer, Cyrille; Bulmus, Volga; Nateghi, Ebrahim; Davis, Thomas P

    2008-04-01

    Self-assembled monolayers (SAMs) of oligo(ethylene glycol) (OEG)-tethered molecules on gold are important for various biorelevant applications ranging from biomaterials to bioanalytical devices, where surface resistance to nonspecific protein adsorption is needed. Incorporation of a stimuli-responsive character to the OEG SAMs enables the creation of nonfouling surfaces with switchable functionality. Here we present an OEG-derived structure that is highly responsive to temperature changes in the vicinity of the physiological temperature, 37 degrees C. The temperature-responsive solution behavior of this new compound was demonstrated by UV-vis and nuclear magnetic resonance spectroscopy. Its chemisorption onto gold(111), and the retention of responsive behavior after chemisorption have been demonstrated by surface plasmon resonance (SPR), X-ray photoelectron spectroscopy (XPS), and atomic force and scanning tunneling microscopy. The OEG-derived SAMs have been shown to reversibly switch the wettability of the surface, as determined by contact angle measurements. More importantly, SPR and AFM studies showed that the OEG SAMs can be utilized to control the affinity binding of streptavidin to the biotin-tethered surface in a temperature-dependent manner while still offering the nonspecific protein-resistance to the surface.

  12. Seasonal temperature responses to land-use change in the western United States

    Science.gov (United States)

    Kueppers, L.M.; Snyder, M.A.; Sloan, L.C.; Cayan, D.; Jin, J.; Kanamaru, H.; Kanamitsu, M.; Miller, N.L.; Tyree, Mary; Du, H.; Weare, B.

    2008-01-01

    In the western United States, more than 79 000??km2 has been converted to irrigated agriculture and urban areas. These changes have the potential to alter surface temperature by modifying the energy budget at the land-atmosphere interface. This study reports the seasonally varying temperature responses of four regional climate models (RCMs) - RSM, RegCM3, MM5-CLM3, and DRCM - to conversion of potential natural vegetation to modern land-cover and land-use over a 1-year period. Three of the RCMs supplemented soil moisture, producing large decreases in the August mean (- 1.4 to - 3.1????C) and maximum (- 2.9 to - 6.1????C) 2-m air temperatures where natural vegetation was converted to irrigated agriculture. Conversion to irrigated agriculture also resulted in large increases in relative humidity (9% to 36% absolute change). Modeled changes in the August minimum 2-m air temperature were not as pronounced or consistent across the models. Converting natural vegetation to urban land-cover produced less pronounced temperature effects in all models, with the magnitude of the effect dependent upon the preexisting vegetation type and urban parameterizations. Overall, the RCM results indicate that the temperature impacts of land-use change are most pronounced during the summer months, when surface heating is strongest and differences in surface soil moisture between irrigated land and natural vegetation are largest. ?? 2007 Elsevier B.V. All rights reserved.

  13. The use of infrared thermography to detect the skin temperature response to physical activity

    Science.gov (United States)

    Tanda, G.

    2015-11-01

    Physical activity has a noticeable effect on skin blood flow and temperature. The thermal regulatory and hemodynamic processes during physical activity are controlled by two conflicting mechanisms: the skin vasoconstriction induced by the blood flow demand to active muscles and the skin vasodilation required by thermoregulation to increase warm blood flow and heat conduction to the skin. The time-evolution of skin temperature during exercise can give useful information about the adaptation of the subject as a function of specific type, intensity and duration of exercise. In this paper, infrared thermography is used to investigate the thermal response of skin temperature during running exercise on treadmill for a group of seven healthy and trained runners. Two different treadmill exercises are considered: a graded load exercise and a constant load exercise; for both exercises the duration was 30 minutes. Within the limits due to the relatively small size of the sample group, results typically indicate a fall in skin temperature during the initial stage of running exercise. As the exercise progresses, the dynamics of the skin temperature response depends on the type of exercise (graded versus constant load) and probably on the level of training of the subject.

  14. Temperature responsive complex coacervate core micelles with a PEO and PNIPAAm corona.

    Science.gov (United States)

    Voets, Ilja K; Moll, Puck M; Aqil, Abdelhafid; Jérôme, Christine; Detrembleur, Christophe; Waard, Pieter de; Keizer, Arie de; Stuart, Martien A Cohen

    2008-09-01

    In aqueous solutions at room temperature, poly( N-methyl-2-vinyl pyridinium iodide)- block-poly(ethylene oxide), P2MVP 38- b-PEO 211 and poly(acrylic acid)- block-poly(isopropyl acrylamide), PAA 55- b-PNIPAAm 88 spontaneously coassemble into micelles, consisting of a mixed P2MVP/PAA polyelectrolyte core and a PEO/PNIPAAm corona. These so-called complex coacervate core micelles (C3Ms), also known as polyion complex (PIC) micelles, block ionomer complexes (BIC), and interpolyelectrolyte complexes (IPEC), respond to changes in solution pH and ionic strength as their micellization is electrostatically driven. Furthermore, the PNIPAAm segments ensure temperature responsiveness as they exhibit lower critical solution temperature (LCST) behavior. Light scattering, two-dimensional 1H NMR nuclear Overhauser effect spectrometry, and cryogenic transmission electron microscopy experiments were carried out to investigate micellar structure and solution behavior at 1 mM NaNO 3, T = 25, and 60 degrees C, that is, below and above the LCST of approximately 32 degrees C. At T = 25 degrees C, C3Ms were observed for 7 coacervate shell, and a PEO corona.

  15. Responsive copolymers for enhanced petroleum recovery. Quarterly technical progress report, December 22, 1993--March 21, 1994

    Energy Technology Data Exchange (ETDEWEB)

    McCormick, C.; Hester, R.

    1994-06-01

    The overall goal of this research is the development of advanced water-soluble copolymers for use in enhanced oil recovery. This report summarizes technical progress for the following tasks: advanced copolymer synthesis; and characterization of molecular structure of copolymers.

  16. COMPOSITIONAL HETEROGENEITY OF ETHYLENE OXIDE-BUTYLENE TEREPHTHALATE SEGMENTED COPOLYMER

    Institute of Scientific and Technical Information of China (English)

    De-zhu Ma; Dong-sheng Li; Ming-chuan Zhao; Mo-zhen Wang; Ran Ye; Xiao-lie Luo

    1999-01-01

    A series of ethylene oxide-butylene terephthalate (EOBT) segmented copolymers with different soft segment length and hard segment content were synthesized. The compositional heterogeneity was studied by solvent extraction. The results show that the compositional heterogeneity increases when soft segment length and hard segment content increase. The compositional heterogeneity is also reflected in the crystallization behavior and morphology of soft and hard segment in EOBT segmented copolymer. The more compositional heterogeneous the EOBT segmented copolymer is, the more different the morphology and the crystallization behavior between separated fractions. Compared with ethylene oxide-ethylene terephthalate (EOET) segmented copolymer, compositional heterogeneity in EOBT segmented copolymer is weaker. But the compositional heterogeneity in EOBT segmented copolymer with long soft segment and high hard segment content is still obvious.

  17. Imide/Arylene Ether Copolymers Containing Phosphine Oxide

    Science.gov (United States)

    Jensen, Brian J.; Partos, Richard D.

    1993-01-01

    Phosphine oxide groups react with oxygen to form protective phosphate surface layers. Series of imide/arylene ether block copolymers containing phosphine oxide units in backbone synthesized and characterized. In comparison with commercial polyimide, these copolymers display better resistance to etching by oxygen plasma. Tensile strengths and tensile moduli greater than those of polyarylene ether homopolymer. Combination of properties makes copolymers attractive for films, coatings, adhesives, and composite matrices where resistance to atomic oxygen needed.

  18. Development of a High-Frequency Multilayer Copolymer Acoustic Projector

    Science.gov (United States)

    1994-03-31

    Vinylidene Fluoride/Trifluoroethylene Copolymers in Relation to Their Structures," Japanese Journal of Applied Physics , vol. 103, 1987, p. 554. 4. R. AI... Journal of Applied Physics , vol. 21, 1982, p. L455. 17. K. Rittenmyer, *Report on the Electromechanical Evaluation of PVDF Copolymer Materials," U. S...Ohigashi and K. Koga, "Ferroelectric Copolymers of Vinylidene Fluoride and Trifluoroethylene with a Large Electromechanical Coupling Factor,* Japanese

  19. Formation of Anisotropic Block Copolymer Gels

    Science.gov (United States)

    Liaw, Chya Yan; Shull, Kenneth; Henderson, Kevin; Joester, Derk

    2011-03-01

    Anisotropic, fibrillar gels are important in a variety of processes. Biomineralization is one example, where the mineralization process often occurs within a matrix of collagen or chitin fibers that trap the mineral precursors and direct the mineralization process. We wish to replicate this type of behavior within block copolymer gels. Particularly, we are interested in employing gels composed of cylindrical micelles, which are anisotropic and closely mimic biological fibers. Micelle geometry is controlled in our system by manipulating the ratio of molecular weights of the two blocks and by controlling the detailed thermal processing history of the copolymer solutions. Small-Angle X-ray Scattering and Dynamic Light Scattering are used to determine the temperature dependence of the gel formation process. Initial experiments are based on a thermally-reversible alcohol-soluble system, that can be subsequently converted to a water soluble system by hydrolysis of a poly(t-butyl methacrylate) block to a poly (methacrylic acid) block. MRSEC.

  20. Rapid ordering of block copolymer thin films

    Science.gov (United States)

    Majewski, Pawel W.; Yager, Kevin G.

    2016-10-01

    Block-copolymers self-assemble into diverse morphologies, where nanoscale order can be finely tuned via block architecture and processing conditions. However, the ultimate usage of these materials in real-world applications may be hampered by the extremely long thermal annealing times—hours or days—required to achieve good order. Here, we provide an overview of the fundamentals of block-copolymer self-assembly kinetics, and review the techniques that have been demonstrated to influence, and enhance, these ordering kinetics. We discuss the inherent tradeoffs between oven annealing, solvent annealing, microwave annealing, zone annealing, and other directed self-assembly methods; including an assessment of spatial and temporal characteristics. We also review both real-space and reciprocal-space analysis techniques for quantifying order in these systems.

  1. Nanostructured Polysulfone-Based Block Copolymer Membranes

    KAUST Repository

    Xie, Yihui

    2016-05-01

    The aim of this work is to fabricate nanostructured membranes from polysulfone-based block copolymers through self-assembly and non-solvent induced phase separation. Block copolymers containing polysulfone are novel materials for this purpose providing better mechanical and thermal stability to membranes than polystyrene-based copolymers, which have been exclusively used now. Firstly, we synthesized a triblock copolymer, poly(tert-butyl acrylate)-b-polsulfone-b-poly(tert-butyl acrylate) through polycondensation and reversible addition-fragmentation chain-transfer polymerization. The obtained membrane has a highly porous interconnected skin layer composed of elongated micelles with a flower-like arrangement, on top of the graded finger-like macrovoids. Membrane surface hydrolysis was carried out in a combination with metal complexation to obtain metal-chelated membranes. The copper-containing membrane showed improved antibacterial capability. Secondly, a poly(acrylic acid)-b-polysulfone-b-poly(acrylic acid) triblock copolymer obtained by hydrolyzing poly(tert-butyl acrylate)-b-polsulfone-b-poly(tert-butyl acrylate) formed a thin film with cylindrical poly(acrylic acid) microdomains in polysulfone matrix through thermal annealing. A phase inversion membrane was prepared from the same polymer via self-assembly and chelation-assisted non-solvent induced phase separation. The spherical micelles pre-formed in a selective solvent mixture packed into an ordered lattice in aid of metal-poly(acrylic acid) complexation. The space between micelles was filled with poly(acrylic acid)-metal complexes acting as potential water channels. The silver0 nanoparticle-decorated membrane was obtained by surface reduction, having three distinct layers with different particle sizes. Other amphiphilic copolymers containing polysulfone and water-soluble segments such as poly(ethylene glycol) and poly(N-isopropylacrylamide) were also synthesized through coupling reaction and copper0-mediated

  2. Functional Nanoporous Polymers from Block Copolymer Precursors

    DEFF Research Database (Denmark)

    Guo, Fengxiao

    functionalities remains a great challenge due to the limitation of available polymer synthesis and the nanoscale confinement of the porous cavities. The main topic of this thesis is to develop methods for fabrication of functional nanoporous polymers from block copolymer precursors. A method has been developed...... functional nanoporous polymers based on nanoporous 1,2- polybuatdiene 1,2-PB, which is derived from a 1,2-PB-b-PDMS diblock copolymer precursor. As a result, nanoporous 1,2-PB with pores decorated of polyacrylates, sulfonated polymers and poly(ethylene glycol) are created. A method of vapor phase deposition...... has also been generated to obtain nanoporous polymers with functional coatings on pore walls. Vapor phase polymerization of pyrrole is performed to incorporate an ultra thin film of polypyrrole into nanoporous 1,2-PB. The preliminary test shows that nanoporous 1,2-PB gains conductivity. Generally...

  3. Photothermal degradation of ethylene/vinylacetate copolymer

    Science.gov (United States)

    Liang, R. H.; Chung, S.; Clayton, A.; Di Stefano, S.; Oda, K.; Hong, S. D.; Gupta, A.

    1983-01-01

    Photothermal degradation studies were conducted on a 'stabilized' formulation of ethylene/vinyl acetate copolymer (EVA) in the temperature range 25-105 C under three different oxygen environments (in open air, with limited access to O2, and in a dark closed stagnant oven). These studies were performed in order to evaluate the utility of EVA as an encapsulation material for photovoltaic modules. Results showed that at low temperature (25 C), slow photooxidation of the polymer occurred via electronic energy transfer involving the UV absorber incorporated in the polymer. However, no changes in the physical properties of the bulk polymer were detected up to 1500 hours of irradiation. At elevated temperatures, leaching and evaporation of the additives occurred, which ultimately resulted in the chemical crosslinking of the copolymer and the formation of volatile photoproducts such as acetic acid.

  4. Mechanism of Molecular Exchange in Copolymer Micelles

    Science.gov (United States)

    Choi, Soo-Hyung; Lodge, Timothy; Bates, Frank

    2010-03-01

    Compared to thermodynamic structure, much less has been known about the kinetics of block copolymer micelles which should underlay the attainment of thermodynamic equilibrium. In this presentation, molecular exchange between spherical micelles formed by isotopically labeled diblock copolymers was investigated using time-resolved small-angle neutron scattering. Two pairs of structurally matched poly(styrene-b-ethylene-alt-propylene) (PS-PEP) were synthesized and dispersed in isotopic mixture of squalane, highly selective to PEP block. Each pair includes polymers with fully deuterated (dPS-PEP) and a normal (hPS-PEP) PS blocks. Temperature dependence of the micelle exchange rate R(t) is consistent with melt dynamics for the core polymer. Furthermore, R(t) is significantly sensitive to the core block length N due to the thermodynamic penalty associated with ejecting a core block into the solvent. This hypersensitivity, combined with modest polydispersity in N, leads to an approximately logarithmic decay in R(t).

  5. Hybrid, Nanoscale Phospholipid/Block Copolymer Vesicles

    Directory of Open Access Journals (Sweden)

    Bo Liedberg

    2013-09-01

    Full Text Available Hybrid phospholipid/block copolymer vesicles, in which the polymeric membrane is blended with phospholipids, display interesting self-assembly behavior, incorporating the robustness and chemical versatility of polymersomes with the softness and biocompatibility of liposomes. Such structures can be conveniently characterized by preparing giant unilamellar vesicles (GUVs via electroformation. Here, we are interested in exploring the self-assembly and properties of the analogous nanoscale hybrid vesicles (ca. 100 nm in diameter of the same composition prepared by film-hydration and extrusion. We show that the self-assembly and content-release behavior of nanoscale polybutadiene-b-poly(ethylene oxide (PB-PEO/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC hybrid phospholipid/block copolymer vesicles can be tuned by the mixing ratio of the amphiphiles. In brief, these hybrids may provide alternative tools for drug delivery purposes and molecular imaging/sensing applications and clearly open up new avenues for further investigation.

  6. Parallel Computing Properties of Tail Copolymer Chain

    Directory of Open Access Journals (Sweden)

    Hong Li

    2013-08-01

    Full Text Available The properties of a AB diblock copolymer chain are calculated by Monte Carlo methods. Monomer A contacting to the surface has an adsorption energy E=-1 and monomer B E= 0. The polymer chain is simulated by self-avoiding walk in simple cubic lattice. The adsorption properties and the conformation properties of the polymer chain are computed by using message passing interface (MPI. The speedup is close to linear speedup by parallel computing independent samples.    

  7. Nanostructured Block Copolymer Coatings for Biofouling Inhibition

    Science.gov (United States)

    2015-06-30

    biofouling program contractors. 15. SUBJECT TERMS antifouling; coatings; block copolymers; IR nanoscale imaging ; biocides 16. SECURITY CLASSIFICATION OF...diagnostics and drug delivery. In our scanned probe microscopy studies on collaborator coatings and marine organisms, we have provided teamwork . We have...Studies of Organisms on model fouiants: • H. elegans studies 3. Testing of other contractor materials 4. Imaging technology. We applied our organic

  8. Block and Graft Copolymers of Polyhydroxyalkanoates

    Science.gov (United States)

    Marchessault, Robert H.; Ravenelle, François; Kawada, Jumpei

    2004-03-01

    Polyhydroxyalkanoates (PHAs) were modified for diblock copolymer and graft polymer by catalyzed transesterification in the melt and by chemical synthesis to extend the side chains of the PHAs, and the polymers were studied by transmission electron microscopy (TEM) X-ray diffraction, thermal analysis and nuclear magnetic resonance (NMR). Catalyzed transesterification in the melt is used to produce diblock copolymers of poly[3-hydroxybutyrate] (PHB) and monomethoxy poly[ethylene glycol] (mPEG) in a one-step process. The resulting diblock copolymers are amphiphilic and self-assemble into sterically stabilized colloidal suspensions of PHB crystalline lamellae. Graft polymer was synthesized in a two-step chemical synthesis from biosynthesized poly[3-hydroxyoctanoate-co-3-hydroxyundecenoate] (PHOU) containing ca. 25 mol chains. 11-mercaptoundecanoic acid reacts with the side chain alkenes of PHOU by the radical addition creating thioether linkage with terminal carboxyl functionalities. The latter groups were subsequently transformed into the amide or ester linkage by tridecylamine or octadecanol, respectively, producing new graft polymers. The polymers have different physical properties than poly[3-hydroxyoctanoate] (PHO) which is the main component of the PHOU, such as non-stickiness and higher thermal stability. The combination of biosynthesis and chemical synthesis produces a hybrid thermoplastic elastomer with partial biodegradability.

  9. Local Mechanical Stimulation of Mardin-Darby Canine Kidney Cell Sheets on Temperature-Responsive Hydrogel

    Directory of Open Access Journals (Sweden)

    Toshihiro Akaike

    2012-01-01

    Full Text Available Collective motion of cell sheets plays a role not only in development and repair, but also in devastating diseases such as cancer. However, unlike single-cell motility, collective motion of cell sheets involves complex cell-cell communication during migration; therefore, its mechanism is largely unknown. To elucidate propagation of signaling transduced by cell-cell interaction, we designed a hydrogel substrate that can cause local mechanical stretching of cell sheets. Poly (N-isopropyl acrylamide (PNIPAAm hydrogel is a temperature-responsive polymer gel whose volume changes isotropically in response to temperature changes below 37 °C. We designed a combined hydrogel substrate consisting of collagen-immobilized PNIPAAm as the local stimulation side and polyacrylamide (PAAm as the non-stimulation side to assess propagation of mechanical transduction. Mardin-Darby canine kidney (MDCK cells adhered to the collagen-immobilized PNIPAAm gel increased it area and were flattened as the gel swelled with temperature decrease. E-cadherin in these cells became undetectable in some domains, and actin stress fibers were more clearly observed at the cell base. In contrast, E-cadherin in cells adhered to the collagen-immobilized PAAm side was equally stained as that in cells adhered to the collagen-immobilized PAAm side even after temperature decrease. ERK1/2 MAPK activation of cells on the non-stimulated substrate occurred after partial stretching of the cell sheet suggesting the propagation of signaling. These results indicate that a change in the balance of mechanical tension induced by partial stretching of cell sheets leads to activation and propagation of the cell signaling.

  10. Temperature responsive hydrogel magnetic nanocomposites for hyperthermia and metal extraction applications

    Energy Technology Data Exchange (ETDEWEB)

    Reddy, N. Narayana, E-mail: nagireddynarayana@gmail.com [Center for Advanced Biomaterials for Healthcare, Istituto Italiano di Tecnologia@CRIB, Largo Barsanti e Matteucci 53, 80125 Napoli (Italy); Ravindra, S. [Department of Physics, College of Science, Engineering and Technology, University of South Africa, Johannesburg 1709 (South Africa); Reddy, N. Madhava [Department of Environmental Science, Gates Institute of Technology, NH-7, Gooty, Anantapuram, Andhra Pradesh (India); Rajinikanth, V. [Department of Physics, College of Science, Engineering and Technology, University of South Africa, Johannesburg 1709 (South Africa); Raju, K. Mohana [Synthetic Polymer Laboratory, Department of Polymer Science & Technology, S.K. University, Anantapuram, Andhra Pradesh (India); Vallabhapurapu, Vijaya Srinivasu [Department of Physics, College of Science, Engineering and Technology, University of South Africa, Johannesburg 1709 (South Africa)

    2015-11-15

    The present work deals with the development of temperature and magnetic responsive hydrogel networks based on poly (N-isopropylacrylamide)/acrylamido propane sulfonic acid. The hydrogel matrices are synthesized by polymerizing N-isopropylacrylamide (NIPAM) monomer in the presence of acrylamido propane sulphonicacid (AMPS) using a cross-linker (N,N-methylenebisacrylamide, MBA) and redox initiating system [ammonium persulphate (APS)/tetramethylethylenediamine (TMEDA)]. The magnetic nanoparticles are generated throughout the hydrogel networks using in situ method by incorporating iron ions and subsequent treatment with ammonia. A series of hydrogel-magnetic nanocomposites (HGMNC) are developed by varying AMPS composition. The synthesized hydrogel magnetic nanocomposites (HGMNC) are characterized by using Fourier Transform Infrared (FTIR) Spectroscopy, X-ray diffraction (XRD), Thermal Analyses and Electron Microscopy analysis (Scanning and Transmission Electron Microscope). The metal extraction capacities of the prepared hydrogel (HG) and hydrogel magnetic nanocomposites (HGMNC) were studied at different temperatures. The results suggest that HGMNCs have higher extraction capacity compared to HG and HG loaded iron ions. This data also reveals that the extraction of metals by hydrogel magnetic nanocomposites (HGMNCs) is higher at higher temperatures than room temperature. The prepared HGMNCs are also subjected to hyperthermia (cancer therapy) studies. - Highlights: • We have developed temperature responsive hydrogel magnetic nanocomposites. • Addition of AMPS monomer to this magnetic hydrogel enhances the temperature sensitivity to 40–43 °C. • Similarly the sulfonic groups present in the AMPS units enhances the swelling ratio of magnetic hydrogels. • AMPS acts as good stabilizing agent for nanoparticles in the magnetic nanogel.

  11. Temperature responses of carbon monoxide and hydrogen uptake by vegetated and unvegetated volcanic cinders.

    Science.gov (United States)

    King, Caitlin E; King, Gary M

    2012-08-01

    Ecosystem succession on a large deposit of volcanic cinders emplaced on Kilauea Volcano in 1959 has resulted in a mosaic of closed-canopy forested patches and contiguous unvegetated patches. Unvegetated and unshaded surface cinders (Bare) experience substantial diurnal temperature oscillations ranging from moderate (16 °C) to extreme (55 °C) conditions. The surface material of adjacent vegetated patches (Canopy) experiences much smaller fluctuations (14-25 °C) due to shading. To determine whether surface material from these sites showed adaptations by carbon monoxide (CO) and hydrogen (H(2)) consumption to changes in ambient temperature regimes accompanying succession, we measured responses of CO and H(2) uptake to short-term variations in temperature and long-term incubations at elevated temperature. Based on its broader temperature optimum and lower activation energy, Canopy H(2) uptake was less sensitive than Bare H(2) uptake to temperature changes. In contrast, Bare and Canopy CO uptake responded similarly to temperature during short-term incubations, indicating no differences in temperature sensitivity. However, during extended incubations at 55 °C, CO uptake increased for Canopy but not Bare material, which indicated that the former was capable of thermal adaptation. H(2) uptake for material from both sites was completely inhibited at 55 °C throughout extended incubations. These results indicated that plant development during succession did not elicit differences in short-term temperature responses for Bare and Canopy CO uptake, in spite of previously reported differences in CO oxidizer community composition, and differences in average daily and extreme temperatures. Differences associated with vegetation due to succession did, however, lead to a notable capacity for thermophilic CO uptake by Canopy but not Bare material.

  12. Temperature responses of carbon monoxide and hydrogen uptake by vegetated and unvegetated volcanic cinders

    Science.gov (United States)

    King, Caitlin E; King, Gary M

    2012-01-01

    Ecosystem succession on a large deposit of volcanic cinders emplaced on Kilauea Volcano in 1959 has resulted in a mosaic of closed-canopy forested patches and contiguous unvegetated patches. Unvegetated and unshaded surface cinders (Bare) experience substantial diurnal temperature oscillations ranging from moderate (16 °C) to extreme (55 °C) conditions. The surface material of adjacent vegetated patches (Canopy) experiences much smaller fluctuations (14–25 °C) due to shading. To determine whether surface material from these sites showed adaptations by carbon monoxide (CO) and hydrogen (H2) consumption to changes in ambient temperature regimes accompanying succession, we measured responses of CO and H2 uptake to short-term variations in temperature and long-term incubations at elevated temperature. Based on its broader temperature optimum and lower activation energy, Canopy H2 uptake was less sensitive than Bare H2 uptake to temperature changes. In contrast, Bare and Canopy CO uptake responded similarly to temperature during short-term incubations, indicating no differences in temperature sensitivity. However, during extended incubations at 55 °C, CO uptake increased for Canopy but not Bare material, which indicated that the former was capable of thermal adaptation. H2 uptake for material from both sites was completely inhibited at 55 °C throughout extended incubations. These results indicated that plant development during succession did not elicit differences in short-term temperature responses for Bare and Canopy CO uptake, in spite of previously reported differences in CO oxidizer community composition, and differences in average daily and extreme temperatures. Differences associated with vegetation due to succession did, however, lead to a notable capacity for thermophilic CO uptake by Canopy but not Bare material. PMID:22258097

  13. Rheological Properties with Temperature Response Characteristics and a Mechanism of Solid-Free Polymer Drilling Fluid at Low Temperatures

    Directory of Open Access Journals (Sweden)

    Sheng Wang

    2016-12-01

    Full Text Available The rheological properties of drilling fluid have important effects during drilling in natural gas hydrate at low temperatures. The present study was performed using theoretical analysis. Experiments and micro-analyses were carried out to determine the rheological properties with temperature response characteristics and the mechanism involved in solid-free polymer drilling fluid (SFPDF at low temperatures when drilling in permafrost with natural gas hydrates (NGH. The curves of shear stress with the shear rates of three kinds of polymer drilling fluids, Semen Lepidii natural vegetable gum, polyacrylamide, and xanthan gum, were drawn. Then, statistical and related analyses of test data were performed using Matlab ver. 8.0. Through regression analysis, the Herschel–Bulkley model was used to characterize the rheological characteristics of SFPDF. On this basis, the laws regarding the rheological properties of the three kinds of SFPDF under changing temperatures were analyzed and rheological properties with temperature response state equations were established. Next, the findings of previous studies on rheological properties with temperature response characteristics of the SFPDF were reviewed. Finally, the rheological properties with temperature response mechanisms were assessed using scanning electron microscopy and infrared spectrum analysis.

  14. Evolution of temperature responses in the Cladophora vagabunda complex and the C-albida/sericea complex (Chlorophyta)

    NARCIS (Netherlands)

    Breeman, AM; Oh, YS; Hwang, MS; Van den Hoek, C

    2002-01-01

    Differentiation in temperature responses (survival and growth) was investigated among isolates of two tropical to temperate green algal lineages: the Cladophora vagabunda complex and the C. albida/sericea complex. The results were analysed in relation to published data on 18S rRNA and ITS sequence d

  15. 21 CFR 177.1310 - Ethylene-acrylic acid copolymers.

    Science.gov (United States)

    2010-04-01

    ... (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) INDIRECT FOOD ADDITIVES: POLYMERS Substances for Use as... this section are not applicable to ethylene-acrylic acid copolymers used in food-packaging adhesives... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Ethylene-acrylic acid copolymers. 177.1310...

  16. 21 CFR 177.1980 - Vinyl chloride-propylene copolymers.

    Science.gov (United States)

    2010-04-01

    ... (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) INDIRECT FOOD ADDITIVES: POLYMERS Substances for Use as... applicable to vinyl chloride-propylene copolymers used in food-packaging adhesives complying with § 175.105... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Vinyl chloride-propylene copolymers....

  17. Surface morphology of PS-PDMS diblock copolymer films

    DEFF Research Database (Denmark)

    Andersen, T.H.; Tougaard, S.; Larsen, N.B.

    2001-01-01

    Spin coated thin films (∼400 Å) of poly(styrene)–poly(dimethylsiloxane) (PS–PDMS) diblock copolymers have been investigated using X-ray Photoelectron Spectroscopy and Atomic Force Microscopy. Surface segregation of the poly(dimethylsiloxane) blocks was studied for five diblock copolymers which...

  18. From Block Copolymers to Nano-porous Materials

    DEFF Research Database (Denmark)

    Vigild, Martin Etchells; Ndoni, Sokol; Berg, Rolf Henrik

    2003-01-01

    Quantitative etching of the polydimethylsiloxane block in a series of polystyrene-polydimethylsiloxane (PS-PDMS) block copolymers is reported. Reacting the block copolymer with anhydrous hydrogen fluoride (HF) renders a nanoporous material with the remaining PS maintaining the original morphology...

  19. Alternation and tunable composition in hydrogen bonded supramolecular copolymers.

    Science.gov (United States)

    Felder, Thorsten; de Greef, Tom F A; Nieuwenhuizen, Marko M L; Sijbesma, Rint P

    2014-03-07

    Sequence control in supramolecular copolymers is limited by the selectivity of the associating monomer end groups. Here we introduce the use of monomers with aminopyrimidinone and aminohydroxynaphthyridine quadruple hydrogen bonding end groups, which both homodimerize, but form even stronger heterodimers. These features allow the formation of supramolecular copolymers with a tunable composition and a preference for alternating sequences.

  20. Self-assembled materials from thermosensitive and biohybrid block copolymers

    NARCIS (Netherlands)

    de Graaf, A.J.

    2012-01-01

    In this research, several block copolymers were synthesized and characterized with regard to possible pharmaceutical applications. All block copolymers were thermosensitive and self-assembled at 37 °C into structures like micelles and hydrogels, which can be used for innovative drug delivery purpose

  1. Hierarchical structure formation in supramolecular comb-shaped block copolymers

    NARCIS (Netherlands)

    Hofman, Anton; ten Brinke, Gerrit; Loos, Katja

    2016-01-01

    Block copolymers are known to spontaneously form ordered structures at the nano-to mesoscale. Although the number of different morphologies is rather limited in diblock copolymer systems, their phase behavior becomes increasingly more complex with each additional building block. Synthesis of such al

  2. Morphological studies on block copolymer modified PA 6 blends

    Science.gov (United States)

    Poindl, M.; Bonten, C.

    2014-05-01

    Recent studies show that compounding polyamide 6 (PA 6) with a PA 6 polyether block copolymers made by reaction injection molding (RIM) or continuous anionic polymerization in a reactive extrusion process (REX) result in blends with high impact strength and high stiffness compared to conventional rubber blends. In this paper, different high impact PA 6 blends were prepared using a twin screw extruder. The different impact modifiers were an ethylene propylene copolymer, a PA PA 6 polyether block copolymer made by reaction injection molding and one made by reactive extrusion. To ensure good particle matrix bonding, the ethylene propylene copolymer was grafted with maleic anhydride (EPR-g-MA). Due to the molecular structure of the two block copolymers, a coupling agent was not necessary. The block copolymers are semi-crystalline and partially cross-linked in contrast to commonly used amorphous rubbers which are usually uncured. The combination of different analysis methods like atomic force microscopy (AFM), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) gave a detailed view in the structure of the blends. Due to the partial cross-linking, the particles of the block copolymers in the blends are not spherical like the ones of ethylene propylene copolymer. The differences in molecular structure, miscibility and grafting of the impact modifiers result in different mechanical properties and different blend morphologies.

  3. Antimicrobial activity of poly(acrylic acid) block copolymers

    Energy Technology Data Exchange (ETDEWEB)

    Gratzl, Günther, E-mail: guenther.gratzl@jku.at [Johannes Kepler University Linz, Institute for Chemical Technology of Organic Materials, Altenberger Str. 69, 4040 Linz (Austria); Paulik, Christian [Johannes Kepler University Linz, Institute for Chemical Technology of Organic Materials, Altenberger Str. 69, 4040 Linz (Austria); Hild, Sabine [Johannes Kepler University Linz, Institute of Polymer Science, Altenberger Str. 69, 4040 Linz (Austria); Guggenbichler, Josef P.; Lackner, Maximilian [AMiSTec GmbH and Co. KG, Leitweg 13, 6345 Kössen, Tirol (Austria)

    2014-05-01

    The increasing number of antibiotic-resistant bacterial strains has developed into a major health problem. In particular, biofilms are the main reason for hospital-acquired infections and diseases. Once formed, biofilms are difficult to remove as they have specific defense mechanisms against antimicrobial agents. Antimicrobial surfaces must therefore kill or repel bacteria before they can settle to form a biofilm. In this study, we describe that poly(acrylic acid) (PAA) containing diblock copolymers can kill bacteria and prevent from biofilm formation. The PAA diblock copolymers with poly(styrene) and poly(methyl methacrylate) were synthesized via anionic polymerization of tert-butyl acrylate with styrene or methyl methacrylate and subsequent acid-catalyzed hydrolysis of the tert-butyl ester. The copolymers were characterized via nuclear magnetic resonance spectroscopy (NMR), size-exclusion chromatography (SEC), Fourier transform infrared spectroscopy (FTIR), elemental analysis, and acid–base titrations. Copolymer films with a variety of acrylic acid contents were produced by solvent casting, characterized by atomic force microscopy (AFM) and tested for their antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. The antimicrobial activity of the acidic diblock copolymers increased with increasing acrylic acid content, independent of the copolymer-partner, the chain length and the nanostructure. - Highlights: • Acrylic acid diblock copolymers are antimicrobially active. • The antimicrobial activity depends on the acrylic acid content in the copolymer. • No salts, metals or other antimicrobial agents are needed.

  4. PREPARATION AND SURFACE PROPERTIES OF ACRYLIC COPOLYMERS CONTAINING FLUORINATED MONOMERS

    Institute of Scientific and Technical Information of China (English)

    Tai-jiang Gui; Hao Wei; Ying Zhao; Xiu-lin Wang; Du-jin Wang; Duan-fu Xu

    2006-01-01

    A series of copolymers comprising butylmethacrylate, styrene, butylacrylate, hydroxypropyl acrylate and perfluoroalkyl methacrylate were synthesized by the free radical polymerization using BPO as an initiator. The surface property of the copolymer films was subsequently characterized. The contact angle measurements and energy dispersive analysis of X-ray (EDAX) show that the length and content ofperfluoroalkyl side chains in the copolymers are crucial for the preparation of the film with low surface energy. At a given content of fluorinated monomers in the copolymers, the longer the perfluoroalkyl side chain, the larger the water contact angle of the copolymer films will be. On the other hand, the higher the content of fluorinated monomers, the lower the surface energy is. The water contact angle increases with the increase of the fluorinated monomer content and reaches a plateau at 3 wt% of fluorinated monomer content.

  5. Multicompartment Micelles From π-Shaped ABC Block Copolymers

    Institute of Scientific and Technical Information of China (English)

    XIA Jun; ZHONG Chong-Li

    2007-01-01

    Dissipative particle dynamics simulations were performed on the morphology and structure of multicompartment micelles formed from n-shaped ABC block copolymers in water. The influences of chain architectures were studied in a systematic way, and a rich variety of morphologies were observed, such as spherical, wormlike,X-shaped, Y-shaped, ribbon-like, layered rod-like, layered disk-like, as well as network morphologies. The simulations show that the distance between the two grafts plays an important role in control of the morphology. Since π-shaped ABC block copolymers can be reduced to linear ABC and star ABC block copolymers, they are good model copolymers for studying the self-assembly of complex block copolymers into micelles. The knowledge obtained in this work as well as the new morphologies identified provide useful information for future rational design and synthesis of novel multicompartment micelles.

  6. Sulfomethylated graft copolymers of xanthan gum and polyacrylamide

    Energy Technology Data Exchange (ETDEWEB)

    Cottrell, I.W.; Empey, R.A.; Racciato, J.S.

    1978-08-08

    A water-soluble anionic graft copolymer of xanthan gum and polyacrylamide is described in which at least part of the amide function of the acrylamide portion of the copolymer is sulfomethylated and the xanthan gum portion of the copolymer is unreacted with formaldehyde. The copolymer is sulfomethylated by reaction with formaldehyde and sodium metabisulfite. The formaldehyde does not cause any appreciable cross-linking between hydroxyl groups of the xanthan moieties. The sulfomethylation of the acrylamido group takes place at temperatures from 35 to 70 C. The pH is 10 or higher, typically from 12 to 13. The degree of anionic character may be varied by adjusting the molar ratio of formaldehyde and sodium metabisulfite with respect to the copolymer. 10 claims.

  7. Structure and Mechanical Properties of Ethylene-butene Copolymers

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The crystallinity of ethylene-butene copolymers prepared by copolymerization of ethylene and butene in the presence of a new highly active catalyst was studied by means of DSC, WAXD and DMA. The results show that the melting temperature, the crystallinity and the crystallite size decreased with increasing the content of butene in the copolymers. The copolymers have a high degree of branching, the butene segments are mainly in the amorphous regions of the copolymers, while the polyethylene sequence forms crystal phase acting as crosslinking bondage between the molecules at room temperature. The ethylene-butene copolymers have a low modulus, a low stress and a high strain analogous to the stress-strain behavior of non-cross thermoplastic elastomer.

  8. A Preliminary Study on Mechanisms of Well Water Temperature Responses Based on the Modes of Stress Loading

    Institute of Scientific and Technical Information of China (English)

    Chen Daqing; Wan Yongfang

    2011-01-01

    Based on the studies of the predecessors, and contrasting the modes of stress loading with water level and water temperature response characteristics of a well-aquifer system, this paper draws a preliminary conclusion on the mechanisms of water temperature responses in a well caused by three modes of stress loading, i.e. gas escape, heat dispersion and cold water penetration mechanisms for elastic seismic wave stress loading; the fracture seepage mechanism for seismic wave stress loading and the hydrodynamic mechanism for earth tide stress loading and stress-dissipative heat mechanism for long period slow stress loading in the earthquake preparation stage. This paper illustrates the typical observation examples for each mode of stress loading and makes a preliminary study on their mechanisms.

  9. Small domain-size multiblock copolymer electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Pistorino, Jonathan; Eitouni, Hany Basam

    2016-09-20

    New block polymer electrolytes have been developed which have higher conductivities than previously reported for other block copolymer electrolytes. The new materials are constructed of multiple blocks (>5) of relatively low domain size. The small domain size provides greater protection against formation of dendrites during cycling against lithium in an electrochemical cell, while the large total molecular weight insures poor long range alignment, which leads to higher conductivity. In addition to higher conductivity, these materials can be more easily synthesized because of reduced requirements on the purity level of the reagents.

  10. Preparation of Impact and Weather Resistant Copolymer

    Institute of Scientific and Technical Information of China (English)

    LIANG Tao

    2001-01-01

    @@ Synthesis method of the resin is that crosslinked polybutyl acrylate latex is used as base latex. Styrene (St) and acrylonitrile (AN) are grafted onto polybutyl acrylate latex particle and turn into core-shell copolymer. The resin is a good resin's impact modifier. There are study of influence regularity about additive emulsifier, initiator, monomer concentration, the ratio of St to AN, chain transfer to graft polymerization. A kind of core-shell resin used as impact modifier is obtained. (A) Preparation of Crosslinked Butyl Acrylate Rubber Latex

  11. Preparation of Impact and Weather Resistant Copolymer

    Institute of Scientific and Technical Information of China (English)

    LIANG; Tao

    2001-01-01

    Synthesis method of the resin is that crosslinked polybutyl acrylate latex is used as base latex. Styrene (St) and acrylonitrile (AN) are grafted onto polybutyl acrylate latex particle and turn into core-shell copolymer. The resin is a good resin's impact modifier. There are study of influence regularity about additive emulsifier, initiator, monomer concentration, the ratio of St to AN, chain transfer to graft polymerization. A kind of core-shell resin used as impact modifier is obtained. (A) Preparation of Crosslinked Butyl Acrylate Rubber Latex  ……

  12. 21 CFR 177.1360 - Ethylene-vinyl acetate-vinyl alcohol copolymers.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Ethylene-vinyl acetate-vinyl alcohol copolymers... acetate-vinyl alcohol copolymers. Ethylene-vinyl acetate-vinyl alcohol copolymers (CAS Reg. No. 26221-27-2... accordance with the following prescribed conditions: (a) Ethylene-vinyl acetate-vinyl alcohol copolymers...

  13. Temperature-Responsive Gelation of Type I Collagen Solutions Involving Fibril Formation and Genipin Crosslinking as a Potential Injectable Hydrogel

    Directory of Open Access Journals (Sweden)

    Shunji Yunoki

    2013-01-01

    Full Text Available We investigated the temperature-responsive gelation of collagen/genipin solutions using pepsin-solubilized collagen (PSC and acid-solubilized collagen (ASC as substrates. Gelation occurred in the PSC/genipin solutions at genipin concentrations 0–2 mM under moderate change in temperature from 25 to 37°C. The PSC/genipin solutions exhibited fluidity at room temperature for at least 30 min, whereas the ASC/genipin solutions rapidly reached gel points. In specific cases PSC would be preferred over ASC as an injectable gel system. The temperature-responsive gelation of PSC/genipin solutions was due to temperature responses to genipin crosslinking and collagen fibril formation. The elastic modulus of the 0.5% PSC/genipin gel system could be adjusted in a range of 2.5 to 50 kPa by the PSC and genipin concentrations, suggesting that a PSC/genipin solution is a potential injectable gel system for drug and cell carriers, with mechanical properties matching those of living tissues.

  14. The effects of CO2 and nutrient fertilisation on the growth and temperature response of the mangrove Avicennia germinans.

    Science.gov (United States)

    Reef, Ruth; Slot, Martijn; Motro, Uzi; Motro, Michal; Motro, Yoav; Adame, Maria F; Garcia, Milton; Aranda, Jorge; Lovelock, Catherine E; Winter, Klaus

    2016-08-01

    In order to understand plant responses to both the widespread phenomenon of increased nutrient inputs to coastal zones and the concurrent rise in atmospheric CO2 concentrations, CO2-nutrient interactions need to be considered. In addition to its potential stimulating effect on photosynthesis and growth, elevated CO2 affects the temperature response of photosynthesis. The scarcity of experiments testing how elevated CO2 affects the temperature response of tropical trees hinders our ability to model future primary productivity. In a glasshouse study, we examined the effects of elevated CO2 (800 ppm) and nutrient availability on seedlings of the widespread mangrove Avicennia germinans. We assessed photosynthetic performance, the temperature response of photosynthesis, seedling growth and biomass allocation. We found large synergistic gains in both growth (42 %) and photosynthesis (115 %) when seedlings grown under elevated CO2 were supplied with elevated nutrient concentrations relative to their ambient growing conditions. Growth was significantly enhanced under elevated CO2 only under high-nutrient conditions, mainly in above-ground tissues. Under low-nutrient conditions and elevated CO2, root volume was more than double that of seedlings grown under ambient CO2 levels. Elevated CO2 significantly increased the temperature optimum for photosynthesis by ca. 4 °C. Rising CO2 concentrations are likely to have a significant positive effect on the growth rate of A. germinans over the next century, especially in areas where nutrient availability is high.

  15. A method for achieving monotonic frequency-temperature response for langasite surface-acoustic-wave high-temperature sensor

    Science.gov (United States)

    Shaoming, Bao; Yabing, Ke; Yanqing, Zheng; Lina, Cheng; Honglang, Li

    2016-02-01

    To achieve the monotonic frequency-temperature response for a high-temperature langasite (LGS) surface-acoustic-wave (SAW) sensor in a wide temperature range, a method utilizing two substrate cuts with different propagation angles on the same substrate plane was proposed. In this method, the theory of effective permittivity is adopted to calculate the temperature coefficients of frequency (TCF), electromechanical coupling coefficients (k2), and power flow angle (PFA) for different propagation angles on the same substrate plane, and then the two substrate cuts were chosen to have large k2 and small PFA, as well as the difference in their TCFs (ΔTCF) to always have the same sign of their values. The Z-cut LGS substrate plane was taken as an example, and the two suitable substrate cuts with propagation angles of 74 and 80° were chosen to derive a monotonic frequency-temperature response for LGS SAW sensors at -50 to 540 °C. Experiments on a LGS SAW sensor using the above two substrate cuts were designed, and its measured frequency-temperature response at -50 to 540 °C agreed well with the theory, demonstrating the high accuracy of the proposed method.

  16. Controlling Structure in Sulfonated Block Copolymer Membranes

    Science.gov (United States)

    Truong, Phuc; Stein, Gila; Strzalka, Joe

    2015-03-01

    In many ionic block copolymer systems, the strong incompatibility between ionic and non-ionic segments will trap non-equilibrium structures in the film, making it difficult to engineer the optimal domain sizes and transport pathways. The goal of this work is to establish a framework for controlling the solid-state structure of sulfonated pentablock copolymer membranes. They have ABCBA block sequence, where A is poly(t-butyl styrene), B is poly(hydrogenated isoprene), and C is poly(styrene sulfonate). To process into films, the polymer is dissolved in toluene/n-propanol solvent mixtures, where the solvent proportions and the polymer loading were both varied. Solution-state structure was measured with small angle X-ray scattering (SAXS). We detected micelles with radii that depend on the solvent composition and polymer loading. Film structure was measured with grazing-incidence SAXS, which shows (i) domain periodicity is constant throughout film thickness; (ii) domain periodicity depends on solvent composition and polymer loading, and approximately matches the micelle radii in solutions. The solid-state packing is consistent with a hard sphere structure factor. Results suggest that solid-state structure can be tuned by manipulating the solution-state self-assembly.

  17. Chain exchange in triblock copolymer micelles

    Science.gov (United States)

    Lu, Jie; Lodge, Timothy; Bates, Frank

    2015-03-01

    Block polymer micelles offer a host of technological applications including drug delivery, viscosity modification, toughening of plastics, and colloidal stabilization. Molecular exchange between micelles directly influences the stability, structure and access to an equilibrium state in such systems and this property recently has been shown to be extraordinarily sensitive to the core block molecular weight in diblock copolymers. The dependence of micelle chain exchange dynamics on molecular architecture has not been reported. The present work conclusively addresses this issue using time-resolved small-angle neutron scattering (TR-SANS) applied to complimentary S-EP-S and EP-S-EP triblock copolymers dissolved in squalane, a selective solvent for the EP blocks, where S and EP refer to poly(styrene) and poly(ethylenepropylene), respectively. Following the overall SANS intensity as a function of time from judiciously deuterium labelled polymer and solvent mixtures directly probes the rate of molecular exchange. Remarkably, the two triblocks display exchange rates that differ by approximately ten orders of magnitude, even though the solvophobic S blocks are of comparable size. This discovery is considered in the context of a model that successfully explains S-EP diblock exchange dynamics.

  18. MOLECULAR DESIGN SYNTHESIS AND PROPERTIES OF SIX KINDS OF MULTIPHASE (STYRENE-ETHYLENE OXIDE) COPOLYMERS

    Institute of Scientific and Technical Information of China (English)

    XIE Hongquan; ZHOU Peiguang; SUN Wenbo; XIA Jun; LIU Jin; XIE Dong

    1991-01-01

    @@ Multiphase copolymers of styrene (S) and ethylene oxide (EO) are amphiphilic,because of the hydrophobic and amorphous polystyrene (PS) segments and the hydrophilic and crystalline polyoxyethylene (PEO). They have many uses including polymeric surfactants, electrostatic charge reducers, compatibilizer in polymer blending, phase transfer catalysts or solid polymer electrolytes. These copolymers include different types of block copolymers, graft copolymers and star-shaped block copolymers.

  19. Nanostructure controlled sustained delivery of human growth hormone using injectable, biodegradable, pH/temperature responsive nanobiohybrid hydrogel

    Science.gov (United States)

    Singh, Narendra K.; Nguyen, Quang Vinh; Kim, Bong Sup; Lee, Doo Sung

    2015-02-01

    The clinical efficacy of a therapeutic protein, the human growth hormone (hGH), is limited by its short plasma half-life and premature degradation. To overcome this limitation, we proposed a new protein delivery system by the self-assembly and intercalation of a negatively charged hGH onto a positively charged 2D-layered double hydroxide nanoparticle (LDH). The LDH-hGH ionic complex, with an average particle size of approximately 100 nm, retards hGH diffusion. Nanobiohybrid hydrogels (PAEU/LDH-hGH) were prepared by dispersing the LDH-hGH complex into a cationic pH- and temperature-sensitive injectable PAEU copolymer hydrogel to enhance sustained hGH release by dual ionic interactions. Biodegradable copolymer hydrogels comprising poly(β-amino ester urethane) and triblock poly(ε-caprolactone-lactide)-poly(ethylene glycol)-poly-(ε-caprolactone-lactide) (PCLA-PEG-PCLA) were synthesized and characterized. hGH was self-assembled and intercalated onto layered LDH nanoparticles through an anion exchange technique. X-ray diffraction and zeta potential results showed that the LDH-hGH complex was prepared successfully and that the PAEU/LDH-hGH nanobiohybrid hydrogel had a disordered intercalated nanostructure. The biocompatibility of the nanobiohybrid hydrogel was confirmed by an in vitro cytotoxicity test. The in vivo degradation of pure PAEU and its nanobiohybrid hydrogels was investigated and it showed a controlled degradation of the PAEU/LDH nanobiohybrids compared with the pristine PAEU copolymer hydrogel. The LDH-hGH loaded injectable hydrogels suppressed the initial burst release of hGH and extended the release period for 13 days in vitro and 5 days in vivo. The developed nanohybrid hydrogel has the potential for application as a protein carrier to improve patient compliance.The clinical efficacy of a therapeutic protein, the human growth hormone (hGH), is limited by its short plasma half-life and premature degradation. To overcome this limitation, we proposed a new

  20. Heat exchanger temperature response for duty-cycle transients in the NGNP/HTE.

    Energy Technology Data Exchange (ETDEWEB)

    Vilim, R. B.; Nuclear Engineering Division

    2009-03-12

    Control system studies were performed for the Next Generation Nuclear Plant (NGNP) interfaced to the High Temperature Electrolysis (HTE) plant. Temperature change and associated thermal stresses are important factors in determining plant lifetime. In the NGNP the design objective of a 40 year lifetime for the Intermediate Heat Exchanger (IHX) in particular is seen as a challenge. A control system was designed to minimize temperature changes in the IHX and more generally at all high-temperature locations in the plant for duty-cycle transients. In the NGNP this includes structures at the reactor outlet and at the inlet to the turbine. This problem was approached by identifying those high-level factors that determine temperature rates of change. First are the set of duty cycle transients over which the control engineer has little control but which none-the-less must be addressed. Second is the partitioning of the temperature response into a quasi-static component and a transient component. These two components are largely independent of each other and when addressed as such greater understanding of temperature change mechanisms and how to deal with them is achieved. Third is the manner in which energy and mass flow rates are managed. Generally one aims for a temperature distribution that minimizes spatial non-uniformity of thermal expansion in a component with time. This is can be achieved by maintaining a fixed spatial temperature distribution in a component during transients. A general rule of thumb for heat exchangers is to maintain flow rate proportional to thermal power. Additionally the product of instantaneous flow rate and heat capacity should be maintained the same on both sides of the heat exchanger. Fourth inherent mechanisms for stable behavior should not be compromised by active controllers that can introduce new feedback paths and potentially create under-damped response. Applications of these principles to the development of a plant control strategy for

  1. Supramolecular self-assembly and controllable drug release of thermosensitive hyperbranched multiarm copolymers

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    A novel temperature-responsive hyperbranched multiarm copolymer with a hydrophobic hyperbranched poly(3-ethyl-3-(hydroxymethyl)oxetane)(HBPO) core and thermosensitive poly(N-isopropylacrylamide)(PNIPAM) arms was synthesized via the atom transfer radical polymerization(ATRP) of NIPAM monomers from a hyperbranched HBPO macroinitiator.It was found that HBPO-star-PNIPAM self-assembled into multimolecular micelles(around 60 nm) in water at room temperature according to pyrene probe fluorescence spectrometry,1H NMR,TEM,and DLS measurements.The micelle solution showed a reversible thermosensitive phase transition at a lower critical solution temperature(LCST)(around 32°C) observed by variable temperature optical absorbance measurements.Variable temperature NMR and DLS analyses demonstrated that the LCST transition originated from the secondary aggregation of the micelles driven by increasing hydrophobic interaction due to the dehydration of PNIPAM shells upon heating.The drug loading and release properties of HBPO-star-PNIPAM micelles were also investigated using prednisone acetate as a model drug.The micelles showed a much improved drug encapsulation efficiency and temperature-dependent sustainable release behavior due to the special micellar structure.The micelles exhibited no apparent cytotoxicity against human HeLa cells.

  2. Synthesis and properties of polystyrene/polydimethylsiloxane graft copolymers

    Institute of Scientific and Technical Information of China (English)

    Wu Ningjing; Huang Likan; Zheng Anna

    2006-01-01

    Polystyrene-graft-polydimethylsiloxane (PS-g-PDMS) copolymers with different PDMS content were synthesized by the radical bulk copolymerization of PDMS macromonomer and styrene.The copolymers were characterized by Fourier transform infrared (FT-IR),1H-nuclear magnetic resonance (NMR),thermogravimetric analysis (TGA),dynamic mechanical analysis (DMA),transmission electron microscopy (TEM) and the mechanical properties of the copolymers were also carried out.It was indicated that the notched impact strength and elongation at break of the polymers increased with the increase of PDMS content.The thermal stability of PS-g-PDMS is better than that of PS.

  3. Self-assembled antimicrobial and biocompatible copolymer films on titanium.

    Science.gov (United States)

    Pfaffenroth, Cornelia; Winkel, Andreas; Dempwolf, Wibke; Gamble, Lara J; Castner, David G; Stiesch, Meike; Menzel, Henning

    2011-11-10

    Copolymers of 4-vinyl-N-hexylpyridinium bromide and dimethyl(2-methacryloyloxyethyl) phosphonate self-assemble to form ultrathin layers on titanium surfaces that show antimicrobial activity, and biocompatibility. The copolymer layers are characterized by contact angle measurements, ellipsometry and XPS. Antibacterial activity is assessed by investigation of adherence of S. mutans. Biocompatibility is rated based on human gingival fibroblast adhesion and proliferation. By balancing the opposing effects of the chemical composition on biocompatibility and antimicrobial activity, copolymer coatings are fabricated that are able to inhibit the growth of S. mutans on the surface but still show attachment of gingival fibroblasts, and therefore might prevent biofilm formation on implants.

  4. Phase Transition Induced by Small Molecules in Confined Copolymer Films

    Institute of Scientific and Technical Information of China (English)

    ZHOU Ling

    2007-01-01

    We investigate the phase transition induced by small molecules in confined copolymer films by using density functional theory.It is found that the addition of small molecules can effectively promote the phase separation of copolymers.In a symmetric diblock copolymer film,the affinity and concentration of small molecules play an important role in the structure transjtions.The disordered-lamellar transitions lamellar-lamellar transitions and the re-entrant transitions of the same structures are observed.Our results have potential applications in the fabrication of new functional materials.

  5. STUDY ON SOLID STATE POLYCONDENSATION OF POLYETHYLENE TEREPHTHALATE COPOLYMERS

    Institute of Scientific and Technical Information of China (English)

    WU Rongrui; DENG Yuan; HUANG Guanbao; DENG Jianyuan; LI Huiping

    1994-01-01

    The kinetic data of solid state polycondensation of PET and its copolymers are determined.It is shown that the reaction rate of copolycondensation is higher than that of PET polycondensation, and increases with the comonomers content. But the reaction rate of copolycondensation in melt state of this kind of copolymers is lower than that of PET. It is considered that the chemical reactivity of comonomer is the main factor which affect the polycondensation in melt state,whereas the aggregative structure of the polymer is the main factor in solid state. The crystallinity and crystallite size of the copolymers have been measured by X-ray method.

  6. Synthesis of amphiphilic diblock copolymer for surface modification of Ethylene-Norbornene copolymers

    DEFF Research Database (Denmark)

    Levinsen, Simon; Svendsen, Winnie Edith; Horsewell, Andy

    2014-01-01

    The aim of this work is to produce polymer modifiers in order to develop hydrophilic polymeric surfaces for use in microfluidics. The use of hydrophilic polymers in microfluidics will have many advantages e.g. preventing protein absorbance. Here we present an amphiphilic diblock copolymer......-norbornene copolymer TOPAS. Through matching of the radius of gyration for the model polymer and TOPAS the miscibility was achieved. The poly(ethylene-1-butene) polymer was synthesized from a hydrogenated anionic polymerized polybutadiene polymer. As hydrophilic block poly(ethylene oxide) was subsequently added also...... with anionic polymerization. Recent miscibility results between the model polymer and TOPAS will be presented, as well ongoing efforts to study the hydrophilic surface....

  7. Temperature-Responsive Gelation of Type I Collagen Solutions Involving Fibril Formation and Genipin Crosslinking as a Potential Injectable Hydrogel

    OpenAIRE

    Shunji Yunoki; Yoshimi Ohyabu; Hirosuke Hatayama

    2013-01-01

    We investigated the temperature-responsive gelation of collagen/genipin solutions using pepsin-solubilized collagen (PSC) and acid-solubilized collagen (ASC) as substrates. Gelation occurred in the PSC/genipin solutions at genipin concentrations 0–2 mM under moderate change in temperature from 25 to 37°C. The PSC/genipin solutions exhibited fluidity at room temperature for at least 30 min, whereas the ASC/genipin solutions rapidly reached gel points. In specific cases PSC would be preferred o...

  8. Block copolymer templated etching on silicon.

    Science.gov (United States)

    Qiao, Yinghong; Wang, Dong; Buriak, Jillian M

    2007-02-01

    The use of self-assembled polymer structures to direct the formation of mesoscopic (1-100 nm) features on silicon could provide a fabrication-compatible means to produce nanoscale patterns, supplementing conventional lithographic techniques. Here we demonstrate nanoscale etching of silicon, applying standard aqueous-based fluoride etchants, to produce three-dimensional nanoscale features with controllable shapes, sizes, average spacing, and chemical functionalization. The block copolymers serve to direct the silicon surface chemistry by controlling the spatial location of the reaction as well as concentration of reagents. The interiors of the resulting etched nanoscale features may be selectively functionalized with organic monolayers, metal nanoparticles, and other materials, leading to a range of ordered arrays on silicon.

  9. Concentration Dependent Structure of Block Copolymer Solutions

    Science.gov (United States)

    Choi, Soohyung; Bates, Frank S.; Lodge, Timothy P.

    2015-03-01

    Addition of solvent molecules into block copolymer can induce additional interactions between the solvent and both blocks, and therefore expands the range of accessible self-assembled morphologies. In particular, the distribution of solvent molecules plays a key role in determining the microstructure and its characteristic domain spacing. In this study, concentration dependent structures formed by poly(styrene-b-ethylene-alt-propylene) (PS-PEP) solution in squalane are investigated using small-angle X-ray scattering. This reveals that squalane is essentially completely segregated into the PEP domains. In addition, the conformation of the PS block changes from stretched to nearly fully relaxed (i.e., Gaussian conformation) as amounts of squalane increases. NRF

  10. Amphiphilic copolymers for fouling-release coatings

    DEFF Research Database (Denmark)

    Noguer, Albert Camós; Olsen, Stefan Møller; Hvilsted, Søren

    Polydimethylsiloxane (PDMS) resins are extensively used as binder in fouling-release coatings due to the low critical surface energy and low elastic modulus of PDMS. These properties result in poor adhesion of the fouling organisms, which are therefore detached by hydrodynamic forces during...... navigation [1,2,3]. Other compounds are usually mixed together with the binder (e.g. silica and pigments) in order to improve the mechanical, thixotropic and visual properties of the coatings. It has ben shown, however, that these ingredients have a negative effect on the fouling-release properties...... of the coatings [1,2,4]. Together with the PDMS-system, non-reactive polymers have been used to improve the fouling-release properties of the coatings. Initially, hydrophobic siloxane-based polymers were used, which aimed to increase the hydrophobicity of the PDMS surface [5,6]. However, copolymers comprising...

  11. Nanopatterned articles produced using surface-reconstructed block copolymer films

    Energy Technology Data Exchange (ETDEWEB)

    Russell, Thomas P.; Park, Soojin; Wang, Jia-Yu; Kim, Bokyung

    2016-06-07

    Nanopatterned surfaces are prepared by a method that includes forming a block copolymer film on a substrate, annealing and surface reconstructing the block copolymer film to create an array of cylindrical voids, depositing a metal on the surface-reconstructed block copolymer film, and heating the metal-coated block copolymer film to redistribute at least some of the metal into the cylindrical voids. When very thin metal layers and low heating temperatures are used, metal nanodots can be formed. When thicker metal layers and higher heating temperatures are used, the resulting metal structure includes nanoring-shaped voids. The nanopatterned surfaces can be transferred to the underlying substrates via etching, or used to prepare nanodot- or nanoring-decorated substrate surfaces.

  12. BARRIER PROPERTY AND STRUCTURE OF ACRYLONITRILE/ACRYLIC COPOLYMERS

    Institute of Scientific and Technical Information of China (English)

    YANG Zhenghua; LI Yuesheng

    1997-01-01

    A series of acrylonitrile (AN) copolymers with methyl acrylate (MA) or ethyl acrylate (EA) as comonomer (5-23 wt%) was prepared by free-radical copolymerization. The permeability coefficients of the copolymers to oxygen and carbon dioxide were measured at 1.0 MPa and at 30 ℃, and those to water vapor also measured at 100% relative humidity and at 30 ℃. All the AN/acrylic copolymers are semicrystalline. As the acrylate content increase, the permeability coefficients of the copolymers to oxygen and carbon dioxide are increased progressively, but those to water vapor are decreased progressively. The gas permeability coefficients of the polymers were correlated with free-volume fractions or the ratio of free volume to cohesive energy.

  13. Opto-electronic devices from block copolymers and their oligomers.

    NARCIS (Netherlands)

    Hadziioannou, G

    1997-01-01

    This paper presents research activities towards the development of polymer materials and devices for optoelectronics, An approach to controlling the conjugation length and transferring the luminescence properties of organic molecules to polymers through black copolymers containing well-defined conju

  14. Thermal analytical study of polyamide copolymer/Surlyn Ionomers Blends

    Energy Technology Data Exchange (ETDEWEB)

    Qin, C.; Ding, Y.P. [Baxter Healthcare Corp., Round Lake, IL (United States)

    1993-12-31

    Thermal analytical technique was used as a screening method to study polyamide(Nylon)/ethylene-co-methacrylic acid copolymer-based ionomer(Surlyn)blends. The retardation of crystallization process from molten state of Nylon-12 by the existence of the ionomer was observed, but the crystallization of Nylon-12 can not be thwarted even at high concentration of ionomers. Zinc ionomers shows stronger effect than sodium ionomers. A Nylon copolymer, polyamide-6,6-co-polyamide-6,10, was used to blend with different ionomers and the crystallization process from molten state of Nylon copolymer could be thwarted at high concentration of zinc ionomer even at very cooling rate. Interesting cold crystallization behavior of polyamide copolymer was observed during second DSC heating cycle in the temperature range of the melting process of ionomer.

  15. HPMA and HEMA copolymer bead interactions with eukaryotic cells

    Directory of Open Access Journals (Sweden)

    Cristina D. Vianna-Soares

    2004-09-01

    Full Text Available Two different hydrophilic acrylate beads were prepared via aqueous suspension polymerization. Beads produced of a hydroxypropyl methacrylate (HPMA and ethyleneglycol methacrylate (EDMA copolymer were obtained using a polyvinyl alcohol suspending medium. Copolymers of 2hydroxyethyl methacrylate (HEMA, methyl methacrylate (MMA and ethyleneglycol methacrylate (EDMA beads were obtained using magnesium hydroxide as the suspending agent. Following characterization by scanning electron microscopy (SEM, nitrogen sorption analysis (NSA and mercury intrusion porosimetry (MIP, the beads were cultured with monkey fibroblasts (COS7 to evaluate their ability to support cell growth, attachment and adhesion. Cell growth behavior onto small HPMA/EDMA copolymer beads and large HEMA/MMA/EDMA copolymer beads is evaluated regarding their hidrophilicity/hidrophobicity and surface roughness.

  16. Synthesis of Polyacrylate/Polysiloxane Copolymer and Its Damping Performance

    Institute of Scientific and Technical Information of China (English)

    夏宇正; 石淑先; 焦书科; 李素青

    2003-01-01

    The copolymer of polyacrylate/polysiloxane for vibration damping materials was synthesized through emulsion polymerization. The effects of the amount of methyl methacrylate (MMA),polysiloxane containing vinyl, initiator and emulsifier on the conversion, stability of polyacrylate/polysiloxane emulsion were discussed when the emulsion was prepared by pre-emulsifying half continuous method. The graft copolymer has good vibration damping performance. The widest glass transition region of the copolymer spans 100℃, and the highest value of tanδ reached 2.0. The glass transition of the samples was examined by dynamic mechanical analysis (DMA). The vibration damping performance of the graft copolymer was affected by the amount of poly-vinyl dimethylsiloxane (PVMS).

  17. 21 CFR 177.1950 - Vinyl chloride-ethylene copolymers.

    Science.gov (United States)

    2010-04-01

    ... the production of such basic copolymers. The optional adjuvant substances required in the production... is cooled and an equal volume of acetone is added. (e) The solution is titrated with 0.005 N...

  18. Composition fluctuations in homopolymer blends and diblock copolymers

    DEFF Research Database (Denmark)

    Frielinghaus, H.; Mortensen, K.; Almdal, K.

    2000-01-01

    The thermal composition fluctuations of a deuterogenous polystyrene/polyethyleneoxide (dPS/PEO) homopolymer blend and corresponding diblock copolymer have been investigated by small angle neutron scattering (SANS). The measured susceptibilities could be described by theories, which take strong...

  19. Thermal Stability of Poly (acrylonitrile-methyl acrylate) Copolymers

    Institute of Scientific and Technical Information of China (English)

    HAN Na; ZHANG Xing-xiang; WANG Xue-chen

    2008-01-01

    Poly (acrylonitrile-methyl acrylate) copolymer was synthesized by water depositing polymerization and has a typical feed ratio of 85/15. And then 1 - 3 wt% lauryl alcohol maleic anhydride (LAM) was adopted as stabilizer to mix with the acrylonitrile based copolymer. The mixtures were characterized by using Fourier Transform Infrared Spectroscopy (FTIR), Nuclear Magnetic Resonance (1H NMR ), Gel Permeation Chromatography ( GPC ), Differential Scanning Calorimetry (DSC), optic microscope and Ubbelohde viscosimetryr etc. The melting point (Tm) and glass transition temperature (Tg) of the 85/15 AN/MA copolymer mixed with LAM all decrease with the increase of stabilizer content. The lowest Tg and Tm were 116.1 ℃ and 209. 1℃ respectively at the heating rate of 100℃/min when the content of LAM is 2 wt%. The 85°/15 AN/MA copolymer mixed with 1 - 3 w t% LAM possess good thermal stability up to 30 min at 220 ℃.

  20. Synthesis of CO2 Copolymer Based Polyurethane Foams

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    CO2-copolymer based polyurethane foams were synthesized and characterized in this paper. The foams were found to have higher strength and lower heat of combustion than the conventional polyether polyurethane foams. They may find wide applications in many fields.

  1. Preparation and modification of itaconic anhydride–methyl methacrylate copolymers

    Directory of Open Access Journals (Sweden)

    MILOS B. MILOVANOVIC

    2007-12-01

    Full Text Available The free radical copolymerisation of itaconic anhydride and methyl methacrylate in solution was studied at 60 °C. The copolymer composition was determined by 1H-NMR spectroscopy and the obtained monomer reactivity ratios were calculated, rITA = 1.35±0.11; rMMA = 0.22±0.22 (by the Fineman–Ross method and rITA = 1.27±0.38; rMMA = 0.10±0.05 (by the Mayo–Lewis method. The synthesised copolymers were modified by reaction with di-n-butyl amine. The copolymer composition after amidation was determined by elemental analysis via the nitrogen content. Amidation of the anhydride units in the copolymers with di-n-butyl amine resulted in complete conversion to itaconamic acid.

  2. Fluctuations, conformational asymmetry and block copolymer phase behaviour

    DEFF Research Database (Denmark)

    Bates, F.S.; Schulz, M.F.; Khandpur, A.K.;

    1994-01-01

    Phase behaviour near the order-disorder transition (ODT) of 58 model hydrocarbon diblock copolymers, representing four different systems, is summarized. Six distinct ordered-state microstructures are reported, including hexagonally modulated lamellae (HML), hexagonally perforated layers (HPL) and...

  3. Multicompartmental Microcapsules from Star Copolymer Micelles

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Ikjun; Malak, Sidney T.; Xu, Weinan; Heller, William T.; Tsitsilianis, Constantinos; Tsukruk, Vladimir V.

    2013-02-26

    We present the layer-by-layer (LbL) assembly of amphiphilic heteroarm pH-sensitive star-shaped polystyrene-poly(2-pyridine) (PSnP2VPn) block copolymers to fabricate porous and multicompartmental microcapsules. Pyridine-containing star molecules forming a hydrophobic core/hydrophilic corona unimolecular micelle in acidic solution (pH 3) were alternately deposited with oppositely charged linear sulfonated polystyrene (PSS), yielding microcapsules with LbL shells containing hydrophobic micelles. The surface morphology and internal nanopore structure of the hollow microcapsules were comparatively investigated for shells formed from star polymers with a different numbers of arms (9 versus 22) and varied shell thickness (5, 8, and 11 bilayers). The successful integration of star unimers into the LbL shells was demonstrated by probing their buildup, surface segregation behavior, and porosity. The larger arm star copolymer (22 arms) with stretched conformation showed a higher increment in shell thickness due to the effective ionic complexation whereas a compact, uniform grainy morphology was observed regardless of the number of deposition cycles and arm numbers. Small-angle neutron scattering (SANS) revealed that microcapsules with hydrophobic domains showed different fractal properties depending upon the number of bilayers with a surface fractal morphology observed for the thinnest shells and a mass fractal morphology for the completed shells formed with the larger number of bilayers. Moreover, SANS provides support for the presence of relatively large pores (about 25 nm across) for the thinnest shells as suggested from permeability experiments. The formation of robust microcapsules with nanoporous shells composed of a hydrophilic polyelectrolyte with a densely packed hydrophobic core based on star amphiphiles represents an intriguing and novel case of compartmentalized microcapsules with an ability to simultaneously store different hydrophilic, charged, and hydrophobic

  4. Thin Film Assembly of Spider Silk-like Block Copolymers

    Science.gov (United States)

    2011-01-01

    Film Assembly of Spider Silk -like Block Copolymers Sreevidhya T. Krishnaji,†,‡ Wenwen Huang,§ Olena Rabotyagova,†,‡ Eugenia Kharlampieva, ) Ikjun Choi...Received November 26, 2010 We report the self-assembly of monolayers of spider silk -like block copolymers. Langmuir isotherms were obtained for a series of...bioengineered variants of the spider silks , and stable monolayers were generated. Langmuir-Blodgett films were prepared by transferring the monolayers

  5. SYNTHESIS OF A NEW SILICONE-CONTAINING BISMALEIMIDE COPOLYMER RESIN

    Institute of Scientific and Technical Information of China (English)

    KUANG Wenfeng; CAI Xingxian; JIANG Luxia

    1997-01-01

    A copolymer of bismaleimide-diallylbisphenol A-diphenylsilandiol was synthesized and the copolymerization was studied by using N-phenylmaleimide, bisphenol A and diphenylsilandiol as model compounds. The copolymer could be well cured around 200 ℃, and the cured resins had good thermal stability. In the range of 170-210 ℃, a higher curing temperature was favorable to obtain more thermal stable resin by reducing the content of diphenylsilandiol cyclo-homopolymer in resin which would spoil its thermal stability.

  6. Synthesis and characterization of HPMA copolymer-5-FU conjugates

    Institute of Scientific and Technical Information of China (English)

    Fang Yuan; Fu Chen; Qing Yu Xiang; Xuan Qin; Zhi Rong Zhang; Yuan Huang

    2008-01-01

    N-(2-Hydroxypropyl)methacrylamide copolymer-5-fluorouracil (PHPMA-FU)conjugates were synthesized by a novel and simplified synthetic mute,and characterized by UV,FTIR and HPLC analyses.The conjugated content of 5-fluorouracil (5-FU)was 3.41 ± 0.07 wt%.The stabilities of PHPMA-FU conjugates under different conditions were studied.The results showed that HPMA copolymer was a potential carrier for tumor-targeting delivery of 5-FU.

  7. Self-Assembled Antimicrobial and biocompatible copolymer films on Titanium

    OpenAIRE

    2011-01-01

    Biofilm formation on biomedical devices such as dental implants can result in serious infections and finally in device failure. Polymer coatings which provide antimicrobial action to surfaces without compromising the compatibility with human tissue are of great interest. Copolymers of 4-vinyl-N-hexylpyridinium bromide and dimethyl(2-methacryloyloxyethyl) phosphonate are interesting candidates in this respect. These copolymers form ultrathin polycationic layers on titanium surfaces. As the cop...

  8. MALDI-ToF Analysis of Model Copolymer Blends

    Science.gov (United States)

    Pan, David; Arnould, Mark

    2008-03-01

    MALDI-ToF mass spectrometry was used to determine the composition of a low MW styrene (S) / n-butyl acrylate (nBA) copolymer. Bernoullian chain statistics were used to predict the copolymer distribution and confirm that MALDI-ToF detects the correct composition. The copolymer was blended with a low MW polystyrene homopolymer having the same end group as the copolymer at several levels to determine if MALDI-ToF could be used to calculate the amount of homopolymer by subtracting homopolymer peak areas. It is found that, while MALDI-ToF can be used to monitor the amount of homopolymer blended into the copolymer, the observed increase is always greater than the actual amount added, e.g. up to 13% error. This could be due to the fact that the homopolymer ionizes more efficiently than the low MW copolymer. A model to improve the accuracy of the calculated amount of homopolymer in the blend is discussed.

  9. DNA Island Formation on Binary Block Copolymer Vesicles.

    Science.gov (United States)

    Luo, Qingjie; Shi, Zheng; Zhang, Yitao; Chen, Xi-Jun; Han, Seo-Yeon; Baumgart, Tobias; Chenoweth, David M; Park, So-Jung

    2016-08-17

    Here, we report DNA-induced polymer segregation and DNA island formation in binary block copolymer assemblies. A DNA diblock copolymer of polymethyl acrylate-block-DNA (PMA-b-DNA) and a triblock copolymer of poly(butadiene)-block-poly(ethylene oxide)-block-DNA (PBD-b-PEO-b-DNA) were synthesized, and each was coassembled with a prototypical amphiphilic polymer of poly(butadiene)-block-poly(ethylene oxide) (PBD-b-PEO). The binary self-assembly of PMA-b-DNA and PBD-b-PEO resulted in giant polymersomes with DNA uniformly distributed in the hydrophilic PEO shell. When giant polymersomes were connected through specific DNA interactions, DNA block copolymers migrated to the junction area, forming DNA islands within polymersomes. These results indicate that DNA hybridization can induce effective lateral polymer segregation in mixed polymer assemblies. The polymer segregation and local DNA enrichment have important implications in DNA melting properties, as mixed block copolymer assemblies with low DNA block copolymer contents can still exhibit useful DNA melting properties that are characteristic of DNA nanostructures with high DNA density.

  10. Influence of copolymer composition on the transport properties of conducting copolymers: poly(aniline-co-o-anisidine)

    Indian Academy of Sciences (India)

    S S Umare; A D Borkar; M C Gupta

    2002-06-01

    The effect of different compositions of monomers on the transport properties of copolymers by various techniques such as optical, electrical and magnetic has been investigated and compared with the homopolymers. The UV-visible absorption spectra show a hypsochromic shift with an increase in the o-anisidine content in copolymers indicating a decrease in the extent for conjugation (i.e. an increase in the bandgap). From temperature dependence of electrical conductivity the transport parameters such as charge localization length and average hopping distance are calculated and also the effect of the monomeric composition on the coherence length has been discussed. The magnetic studies show the paramagnetic and diamagnetic nature of homopolymers and copolymers. The X-ray diffraction pattern indicates that the copolymers are of amorphous nature.

  11. Functionalization of graphene and grafting of temperature-responsive surfaces from graphene by ATRP 'on water'

    Energy Technology Data Exchange (ETDEWEB)

    Ren Lulu; Huang Shu; Zhang Chao; Wang Ruiyu [Fudan University, State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science (China); Tjiu, Weng Weei [Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A-STAR) (Singapore); Liu Tianxi, E-mail: txliu@fudan.edu.cn [Fudan University, State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science (China)

    2012-06-15

    Water-dispersible graphene with temperature-responsive surfaces has successfully been synthesized by grafting poly(N-isopropylacrylamide) (PNIPAM) from graphene via surface-initiated atom transfer radical polymerization (ATRP). First, graphene surfaces are functionalized with aminophenol groups by diazonium reaction on water. Subsequently, bromoisobutyrate groups are covalently attached to the phenol-functionalized graphene (G-OH) surface by esterification of 2-bromoisobutyrate with the hydroxyl groups, forming bromoisobutyrate-functionalized graphene (G-Br). Finally, PNIPAM is then grafted from G-Br via ATRP. Data from Raman spectroscopy, {sup 1}H NMR, and transmission electron microscopy (TEM) confirm that PNIPAM chains grow from graphene by ATRP. Thermogravimetric analysis shows that the amount of PNIPAM grown from the graphene increases with the increase of monomer ratios. TEM images also show that functionalized polymer structures (PNIPAM cluster or agglutination) on graphene sheets can be well tuned by controlled polymerization. The obtained graphene-PNIPAM (G-PNIPAM) composite has PNIPAM surface which is highly sensitive to the temperature change. This temperature-responsive and water-dispersible G-PNIPAM composite may find potential applications in environmental devices as well as controlled release drug delivery.

  12. Temperature-responsive smart nanoreactors: poly(N-isopropylacrylamide)-coated Au@mesoporous-SiO2 hollow nanospheres.

    Science.gov (United States)

    Chen, Zhe; Cui, Zhi-Min; Cao, Chang-Yan; He, Wei-Dong; Jiang, Lei; Song, Wei-Guo

    2012-09-18

    A nanoreactor with temperature-responsive poly(N-isopopylacrylamide) (PNIPAM) coated on the external pore mouth of mesoporous silica hollow spheres and Au nanoparticles at the internal pore mouth were fabricated. Such spatial separation allows both Au nanoparticles and PNIPAM to function without interfering with each other. Transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectra, and temperature-dependent optical transmittance curves demonstrate successful grafting of PNIPAM. This nanoreactor shows repeated on/off catalytic activity switched by temperature control. It shows excellent catalytic activity toward 4-nitrophenol (4-NP) reduction at 30 °C [below lower critical solution temperature (LCST) of PNIPAM] with a turnover frequency (TOF) of 14.8 h(-1). However, when the temperature was 50 °C (above LCST), the TOF dropped to 2.4 h(-1). Kinetic studies indicated that diffusion into the mesopores of the catalyst was the key factor, and the temperature-responsive behavior of PNIPAM was able to control this diffusion.

  13. Comment on "Tropospheric temperature response to stratospheric ozone recovery in the 21st century" by Hu et al. (2011

    Directory of Open Access Journals (Sweden)

    C. McLandress

    2012-03-01

    Full Text Available In a recent paper Hu et al. (2011 suggest that the recovery of stratospheric ozone during the first half of this century will significantly enhance free tropospheric and surface warming caused by the anthropogenic increase of greenhouse gases, with the effects being most pronounced in Northern Hemisphere middle and high latitudes. These surprising results are based on a multi-model analysis of CMIP3 model simulations with and without prescribed stratospheric ozone recovery. Hu et al. suggest that in order to properly quantify the tropospheric and surface temperature response to stratospheric ozone recovery, it is necessary to run coupled atmosphere-ocean climate models with stratospheric ozone chemistry. The results of such an experiment are presented here, using a state-of-the-art chemistry-climate model coupled to a three-dimensional ocean model. In contrast to Hu et al., we find a much smaller Northern Hemisphere tropospheric temperature response to ozone recovery, which is of opposite sign. We suggest that their result is an artifact of the incomplete removal of the large effect of greenhouse gas warming between the two different sets of models.

  14. Effect of Water Vapor and Surface Morphology on the Low Temperature Response of Metal Oxide Semiconductor Gas Sensors

    Directory of Open Access Journals (Sweden)

    Konrad Maier

    2015-09-01

    Full Text Available In this work the low temperature response of metal oxide semiconductor gas sensors is analyzed. Important characteristics of this low-temperature response are a pronounced selectivity to acid- and base-forming gases and a large disparity of response and recovery time constants which often leads to an integrator-type of gas response. We show that this kind of sensor performance is related to the trend of semiconductor gas sensors to adsorb water vapor in multi-layer form and that this ability is sensitively influenced by the surface morphology. In particular we show that surface roughness in the nanometer range enhances desorption of water from multi-layer adsorbates, enabling them to respond more swiftly to changes in the ambient humidity. Further experiments reveal that reactive gases, such as NO2 and NH3, which are easily absorbed in the water adsorbate layers, are more easily exchanged across the liquid/air interface when the humidity in the ambient air is high.

  15. Fabrication and evaluation of temperature responsive molecularly imprinted sorbents based on surface of yeast via surface-initiated AGET ATRP

    Science.gov (United States)

    Pan, Jianming; Hang, Hui; Li, Xiuxiu; Zhu, Wenjing; Meng, Minjia; Dai, Xiaohui; Dai, Jiangdong; Yan, Yongsheng

    2013-12-01

    Temperature responsive molecularly imprinted polymers (T-MIPs) were prepared based on the surface of yeast by electron transfer atom transfer radical polymerization (AGET ATRP). The as-prepared T-MIPs were charcterized by FT-IR, SEM, TGA and elemental analysis, which indicated that T-MIPs exhibited thermal stability and composed of temperature responsive imprinted layer. Then T-MIPs were evaluated as sorbents to selectively recognise and release cefalexin (CFX) molecules. The results suggested binding properties of T-MIPs were related to the testing temperature. The maximum adsorption capacity of T-MIPs at 303 K was 59.4 mg g-1, and the maximum release proportion for T-MIPs at 293 K in water for 24 h was 71.08%. The selective recognition experiments demonstrated high affinity and selectivity of T-MIPs towards CFX over competitive compounds, and the specific recognition of binding sites may be based on the distinct size, structure and functional group to the template molecules.

  16. LOW DENSITY POLYETHYLENE/CLAY NANOCOMPOSITES MODIFIED BY ETHYLENE COPOLYMERS: EFFECTS OF FUNCTIONALIZED SEGMENTS ON MORPHOLOGY

    Institute of Scientific and Technical Information of China (English)

    Bo Xu; Yi-hu Song; Yong-gang ShangGuan; Qiang Zheng

    2006-01-01

    Melt extrusion was used to prepare binary nanocomposites of ethylene copolymers and organoclay and trinary nanocomposites of low-density polyethylene (LDPE), ethylene copolymer and organoclay. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to analyze the structure of the clay phase and the morphology of the nanocomposites. Influences of the comonomer in the copolymer and the content of the copolymer on the morphology of the resulting nanocomposites were discussed. The binary and the trinary composites may form intercalated or exfoliated structures depending on the interaction between the copolymer and the clay layers and the content of the copolymer.

  17. Real-time monitoring of the penetration of amphiphilic acrylate copolymer in leather using a fluorescent copolymer as tracer.

    Science.gov (United States)

    Du, Jin-Xia; Shi, Lu; Peng, Bi-Yu

    2015-12-01

    A fluorescent tracer, poly (acrylic-co-stearyl acrylate-co-3-acryloyl fluorescein) [poly (AA-co-SA-co-Ac-Flu)], used for real-time monitoring the penetration of amphiphilic acrylate copolymer, poly (acrylic-co-stearyl acrylate) [poly (AA-co-SA)], in leather was synthesized by radical polymerization of acrylic, stearyl acrylate and fluorescent monomer, 3-acryloyl fluorescein (Ac-Flu). The structure, molecular weight, introduced fluorescent group content and fluorescent characteristics of the fluorescent tracer and target copolymer, amphiphilic acrylate copolymer, were also characterized. The results show that the tracer presents the similar structural characteristics to the target and enough fluorescence intensity with 1.68 wt % of the fluorescent monomer introduced amount. The vertical section of the leather treated with the target copolymer mixing with 7% of the tracer exhibits evident fluorescence, and the change of fluorescence intensity along with the vertical section with treating time increasing can reflect the penetration depth of the target copolymer. The introduction of the fluorescent group in polymer structure through copolymerization with a limited amount of fluorescent monomer, Ac-Flu, is an effective way to make a tracer to monitor the penetration of the target in leather, which provides a new thought for the penetration research of syntans such as vinyl copolymer materials in leather manufacture.

  18. Shape memory rubber bands & supramolecular ionic copolymers

    Science.gov (United States)

    Brostowitz, Nicole

    subject covered in this dissertation is supra-molecular ionic copolymers. Supramolecular interactions are non-covalent; e.g. hydrogen bonding, ionic interactions, van der Waals forces. Supramolecular interactions in polymers can be used to tailor the thermo-mechanical properties by controlling bond association and dissociation. Recent research has focused on hydrogen bonded systems due to established synthesis mechanisms. Reversibility of the supramolecular interactions can be triggered by environmental changes. Ionic interactions would provide greater bond strength and more control over operating conditions. Research has been limited on ionic copolymers due to complicated synthesis methods needed to include functionalization. Low molecular weight polymers were synthesized by atom transfer radical polymerization with post polymerization conversion to phosphonium end-groups. Both polystyrene and poly(methyl acrylate) were investigated with similar reaction conditions. Chromatography measured the molecular weight and indicated a low polydispersity consistent with controlled reactions. Copolymers were formed by interfacial mixing of the cationic polymers with multifunctional, anionic oligomers. Oligomers containing sulfonate groups were used to create linear or three-dimensional polymer networks. NMR and rheology was used to characterize the presence and effect of ionic groups when compared to the neat polymer.

  19. Ion Transport in Nanostructured Block Copolymer/Ionic Liquid Membranes

    Science.gov (United States)

    Hoarfrost, Megan Lane

    Incorporating an ionic liquid into one block copolymer microphase provides a platform for combining the outstanding electrochemical properties of ionic liquids with a number of favorable attributes provided by block copolymers. In particular, block copolymers thermodynamically self-assemble into well-ordered nanostructures, which can be engineered to provide a durable mechanical scaffold and template the ionic liquid into continuous ion-conducting nanochannels. Understanding how the addition of an ionic liquid affects the thermodynamic self-assembly of block copolymers, and how the confinement of ionic liquids to block copolymer nanodomains affects their ion-conducting properties is essential for predictable structure-property control. The lyotropic phase behavior of block copolymer/ionic liquid mixtures is shown to be reminiscent of mixtures of block copolymers with selective molecular solvents. A variety of ordered microstructures corresponding to lamellae, hexagonally close-packed cylinders, body-centered cubic, and face-centered cubic oriented micelles are observed in a model system composed of mixtures of imidazolium bis(trifluoromethylsulfonyl)imide ([Im][TFSI]) and poly(styrene- b-2-vinyl pyridine) (PS-b-P2VP). In contrast to block copolymer/molecular solvent mixtures, the interfacial area occupied by each PS-b-P2VP chain decreases upon the addition of [Im][TFSI], indicating a considerable increase in the effective segregation strength of the PS-b-P2VP copolymer with ionic liquid addition. The relationship between membrane structure and ionic conductivity is illuminated through the development of scaling relationships that describe the ionic conductivity of block copolymer/ionic liquid mixtures as a function of membrane composition and temperature. It is shown that the dominant variable influencing conductivity is the overall volume fraction of ionic liquid in the mixture, which means there is incredible freedom in designing the block copolymer architecture

  20. New adhesive systems based on functionalized block copolymers

    Energy Technology Data Exchange (ETDEWEB)

    Kent, M.; Saunders, R.; Hurst, M.; Small, J.; Emerson, J.; Zamora, D.

    1997-05-01

    The goal of this work was to evaluate chemically-functionalized block copolymers as adhesion promoters for metal/thermoset resin interfaces. Novel block copolymers were synthesized which contain pendant functional groups reactive toward copper and epoxy resins. In particular, imidazole and triazole functionalities that chelate with copper were incorporated onto one block, while secondary amines were incorporated onto the second block. These copolymers were found to self-assemble from solution onto copper surfaces to form monolayers. The structure of the adsorbed monolayers were studied in detail by neutron reflection and time-of-flight secondary ion mass spectrometry. The monolayer structure was found to vary markedly with the solution conditions and adsorption protocol. Appropriate conditions were found for which the two blocks form separate layers on the surface with the amine functionalized block exposed at the air surface. Adhesion testing of block copolymer-coated copper with epoxy resins was performed in both lap shear and peel modes. Modest enhancements in bond strengths were observed with the block copolymer applied to the native oxide. However, it was discovered that the native oxide is the weak link, and that by simply removing the native oxide, and then applying an epoxy resin before the native oxide can reform, excellent bond strength in the as-prepared state as well as excellent retention of bond strength after exposure to solder in ambient conditions are obtained. It is recommended that long term aging studies be performed with and without the block copolymer. In addition, the functionalized block copolymer method should be evaluated for another system that has inherently poor bonding, such as the nickel/silicone interface, and for systems involving metals and alloys which form oxides very rapidly, such as aluminum and stainless steel, where bonding strategies involve stabilizing the native oxide.

  1. Monte Carlo simulations of the phase separation of a copolymer blend in a thin film

    KAUST Repository

    Wang, Zhexiao

    2014-12-11

    Monte Carlo simulations were carried out to study the phase separation of a copolymer blend comprising an alternating copolymer and/or block copolymer in a thin film, and a phase diagram was constructed with a series of composed recipes. The effects of composition and segregation strength on phase separation were discussed in detail. The chain conformation of the block copolymer and alternating copolymer were investigated with changes of the segregation strength. Our simulations revealed that the segment distribution along the copolymer chain and the segregation strength between coarse-grained beads are two important parameters controlling phase separation and chain conformation in thin films of a copolymer blend. A well-controlled phase separation in the copolymer blend can be used to fabricate novel nanostructures.

  2. A compendium of temperature responses of Rubisco kinetic traits: variability among and within photosynthetic groups and impacts on photosynthesis modeling.

    Science.gov (United States)

    Galmés, Jeroni; Hermida-Carrera, Carmen; Laanisto, Lauri; Niinemets, Ülo

    2016-09-01

    The present study provides a synthesis of the in vitro and in vivo temperature responses of Rubisco Michaelis-Menten constants for CO2 (Kc) and O2 (Ko), specificity factor (Sc,o) and maximum carboxylase turnover rate (kcatc) for 49 species from all the main photosynthetic kingdoms of life. Novel correction routines were developed for in vitro data to remove the effects of study-to-study differences in Rubisco assays. The compilation revealed differences in the energy of activation (∆Ha) of Rubisco kinetics between higher plants and other photosynthetic groups, although photosynthetic bacteria and algae were under-represented and very few species have been investigated so far. Within plants, the variation in Rubisco temperature responses was related to species' climate and photosynthetic mechanism, with differences in ∆Ha for kcatc among C3 plants from cool and warm environments, and in ∆Ha for kcatc and Kc among C3 and C4 plants. A negative correlation was observed among ∆Ha for Sc/o and species' growth temperature for all data pooled, supporting the convergent adjustment of the temperature sensitivity of Rubisco kinetics to species' thermal history. Simulations of the influence of varying temperature dependences of Rubisco kinetics on Rubisco-limited photosynthesis suggested improved photosynthetic performance of C3 plants from cool habitats at lower temperatures, and C3 plants from warm habitats at higher temperatures, especially at higher CO2 concentration. Thus, variation in Rubisco kinetics for different groups of photosynthetic organisms might need consideration to improve prediction of photosynthesis in future climates. Comparisons between in vitro and in vivo data revealed common trends, but also highlighted a large variability among both types of Rubisco kinetics currently used to simulate photosynthesis, emphasizing the need for more experimental work to fill in the gaps in Rubisco datasets and improve scaling from enzyme kinetics to realized

  3. Investigation on the structure of temperature-responsive N-isopropylacrylamide microgels containing a new hydrophobic crosslinker

    Directory of Open Access Journals (Sweden)

    G. Roshan Deen

    2015-12-01

    Full Text Available Temperature-responsive poly(N-isopropylacrylamide microgels crosslinked with a new hydrophobic chemical crosslinker was prepared by surfactant-mediated precipitation emulsion polymerization. The temperature-responsive property of the microgel and the influence of the crosslinker on the swelling behaviour was studied systematically by light scattering and small-angle X-ray scattering (SAXS. The radius of gyration (Rg and the hydrodynamic radius (Rh of the microgels decreased with increase in temperature due to the volume-phase transition from a swollen to a collapsed state. The ratio of Rg/Rh below the transition temperature was lower than that of hard-spheres due to the lower crosslinking density of the microgels. The SAXS data were analysed by a model in which the microgels were modelled as core-shell particles with a graded interface. The model at intermediate temperatures included a central core and a more diffuse outer layer describing pending polymer chains with a low crosslinking density. In the fully swollen state, the microgels were modelled with a single component with a broad graded surface. In the collapsed state, they were modelled as homogeneous and relatively compact particles. The polymer volume fraction inside the microgel was also derived based on the model and was found to increase with increase in the temperature as a result of collapse of the microgel to compact particles. The polymer volume fraction in the core of the microgel in the collapsed state was about 60% which is higher than that of similar microgels crosslinked with hydrophilic and flexible crosslinkers.

  4. Tunable Morphologies from Charged Block Copolymers

    Energy Technology Data Exchange (ETDEWEB)

    Goswami, Monojoy [ORNL; Sumpter, Bobby G [ORNL; Mays, Jimmy [ORNL; Messman, Jamie M [ORNL

    2010-01-01

    The bulk morphologies formed by a new class of charged block copolymers, 75 vol % fluorinated polyisoprene (FPI) 25 vol% sulfonated polystyrene (PSS) with 50% sulfonation, are characterized, and the fundamental underlying forces that promote the self-assembly processes are elucidated. The results show how the bulk morphologies are substantially different from their uncharged diblock counterparts (PS-PI) and also how morphology can be tuned with volume fraction of the charged block and the casting solvent. A physical understanding based on the underlying strong electrostatic interactions between the charged block and counterions is obtained using Monte Carlo (MC) and Molecular Dynamics (MD) simulations. The 75/25 FPI-PSS shows hexagonal morphologies with the minority blocks (PSS) forming the continuous phase due to charge percolation and the FPI blocks arranged in hexagonal cylinders. Some long-range order can be sustained even if lipophobicity is increased (addition of water), albeit with lower dimensional structures. However, thermal annealing provides sufficient energy to disrupt the percolated charges and promotes aggregation of ionic sites which leads to a disordered system. Diverse and atypical morphologies are readily accessible by simply changing the number distribution of the charges on PSS block.

  5. Morphologies of A_2B Simple Graft Copolymer Blends: Copolymer/Copolymer and Copolymer/Homopolymer Systems to Further Elucidate the Stability of Simple Graft Phase Behavior

    Science.gov (United States)

    Lee, Chin; Pochan, Darrin; Gido, Samuel P.; Pispas, Stergios; Mays, Jimmy; Tan, Nora Beck; Trevino, Samuel

    1997-03-01

    The morphological behavior of two series of binary blends of A_2B simple graft block copolymers (A is polyisoprene and B is polystyrene) was characterized via transmission electron microscopy (TEM) and small-angle neutron scattering (SANS). Binary blends of A_2B samples with other A_2B samples of similar relative volume fractions were composed to map out the volume fraction window of stability of the randomly oriented worm phase, or ROW. This novel equilibrium phase behavior was found to occur in a neat A_2B sample with a B volume fraction of 0.81. At this unique composition the single B graft chain first becomes large enough to force the two A chains to the concave side of the AB interface in the microphase separated state. Another set of binary blends of A_2B samples was composed with the respective homopolymers in order to more rigorously determine the phase boundaries relative to volume fraction of the respective microphase separated morphologies in the A_2B systems.

  6. Molecular Exchange in Ordered Diblock Copolymer Micelles

    Science.gov (United States)

    Choi, Soo-Hyung; Lodge, Timothy; Bates, Frank

    2011-03-01

    Previously, molecular exchange between spherical micelles in dilute solution (1 vol% polymer) was investigated using time-resolved small-angle neutron scattering (TR-SANS). As the concentration of spherical micelles formed by the diblock copolymers increases, the micelles begin to overlap and eventually pack onto body-centered cubic (BCC) lattice. In this study, concentrated, ordered micelles (15 vol% polymers) prepared by dispersing isotopically labeled poly(styrene- b -ethylene-alt-propylene) in an isotopic squalane mixture was investigated to understand the micellar concentration dependence of the molecular exchange. Perfectly random mixing of isotopically labeled micelles on the BCC lattice was confirmed by SANS patterns where the interparticle contribution vanishes, resulting in an intensity that directly relates to the exchange kinetics. The measured molecular exchange process for the concentrated, ordered system is qualitatively consistent with the previous observations, but the rate is more than an order of magnitude slower than that for the dilute, disordered system. Infineum(IPrime), MRSEC(NSF), NIST.

  7. Molecular Exchange Dynamics in Block Copolymer Micelles

    Science.gov (United States)

    Bates, Frank; Lu, Jie; Choi, Soohyung; Lodge, Timothy

    2012-02-01

    Poly(styrene-b-ethylene propylene) (PS-PEP) diblock copolymers were mixed with squalane (C30H62) at 1% by weight resulting in the formation of spherical micelles. The structure and dynamics of molecular exchange were characterized by synchrotron small-angle x-ray scattering (SAXS) and time resolved small-angle neutron scattering (TR-SANS), respectively, between 100 C and 160 C. TR-SANS measurements were performed with solutions initially containing deuterium labeled micelle cores and normal cores dispersed in a contrast matched squalane. Monitoring the reduction in scattering intensity as a function of time at various temperatures revealed molecular exchange dynamics highly sensitive to the core molecular weight and molecular weight distribution. Time-temperature superposition of data acquired at different temperatures produced a single master curve for all the mixtures. Experiments conducted with isotopically labeled micelle cores, each formed from two different but relatively mondisperse PS blocks, confirmed a simple dynamical model based on first order kinetics and core Rouse single chain relaxation. These findings demonstrate a dramatic transition to nonergodicity with increasing micelle core molecular weight and confirm the origins of the logarithmic exchange kinetics in such systems.

  8. Contrast variation SANS experiments to the study of detergent-induced micellization of block copolymers

    Indian Academy of Sciences (India)

    V K Aswal; J Kohlbrecher

    2004-08-01

    PEO-PPO-PEO triblock copolymer P85 [(EO)26 (PO)39 (EO)26] dissolves as unimers and detergent sodium dodecyl sulfate (SDS) forms micelles in aqueous solution at 20°C. The mixing of detergent with triblock copolymer induces the micellization of triblock copolymers. Contrast variation small-angle neutron scattering measurements show that triblock copolymer forms mixed micelles with detergent and the mixing of two components in the mixed micelles is uniform.

  9. Controlling block copolymer phase behavior using ionic surfactant

    Science.gov (United States)

    Ray, D.; Aswal, V. K.

    2016-05-01

    The phase behavior of poly(ethylene oxide)-poly(propylene oxide-poly(ethylene oxide) PEO-PPO-PEO triblock copolymer [P85 (EO26PO39EO26)] in presence of anionic surfactant sodium dodecyl sulfate (SDS) in aqueous solution as a function of temperature has been studied using dynamic light scattering (DLS) and small-angle neutron scattering (SANS). The measurements have been carried out for fixed concentrations (1 wt%) of block copolymer and surfactants. Each of the individual components (block copolymer and surfactant) and the nanoparticle-surfactant mixed system have been examined at varying temperature. The block copolymer P85 forms spherical micelles at room temperature whereas shows sphere-to-rod like micelle transition at higher temperatures. On the other hand, SDS surfactant forms ellipsoidal micelles over a wide temperature range. Interestingly, it is found that phase behavior of mixed micellar system (P85 + SDS) as a function of temperature is drastically different from that of P85, giving the control over the temperature-dependent phase behavior of block copolymers.

  10. Relaxation processes in a lower disorder order transition diblock copolymer

    Energy Technology Data Exchange (ETDEWEB)

    Sanz, Alejandro; Ezquerra, Tiberio A.; Nogales, Aurora, E-mail: aurora.nogales@csic.es [Instituto de Estructura de la Materia, IEM-CSIC. C/ Serrano 121, Madrid 28006 (Spain); Hernández, Rebeca [Instituto de Ciencia y Tecnología de Polímeros, ICTP-CSIC. C/ Juan de la Cierva 3, Madrid 28006 (Spain); Sprung, Michael [Petra III at DESY, Notkestr. 85, 22607 Hamburg (Germany)

    2015-02-14

    The dynamics of lower disorder-order temperature diblock copolymer leading to phase separation has been observed by X ray photon correlation spectroscopy. Two different modes have been characterized. A non-diffusive mode appears at temperatures below the disorder to order transition, which can be associated to compositional fluctuations, that becomes slower as the interaction parameter increases, in a similar way to the one observed for diblock copolymers exhibiting phase separation upon cooling. At temperatures above the disorder to order transition T{sub ODT}, the dynamics becomes diffusive, indicating that after phase separation in Lower Disorder-Order Transition (LDOT) diblock copolymers, the diffusion of chain segments across the interface is the governing dynamics. As the segregation is stronger, the diffusive process becomes slower. Both observed modes have been predicted by the theory describing upper order-disorder transition systems, assuming incompressibility. However, the present results indicate that the existence of these two modes is more universal as they are present also in compressible diblock copolymers exhibiting a lower disorder-order transition. No such a theory describing the dynamics in LDOT block copolymers is available, and these experimental results may offer some hints to understanding the dynamics in these systems. The dynamics has also been studied in the ordered state, and for the present system, the non-diffusive mode disappears and only a diffusive mode is observed. This mode is related to the transport of segment in the interphase, due to the weak segregation on this system.

  11. Design of block copolymer membranes using segregation strength trend lines

    KAUST Repository

    Sutisna, Burhannudin

    2016-05-18

    Block copolymer self-assembly and non-solvent induced phase separation are now being combined to fabricate membranes with narrow pore size distribution and high porosity. The method has the potential to be used with a broad range of tailor-made block copolymers to control functionality and selectivity for specific separations. However, the extension of this process to any new copolymer is challenging and time consuming, due to the complex interplay of influencing parameters, such as solvent composition, polymer molecular weights, casting solution concentration, and evaporation time. We propose here an effective method for designing new block copolymer membranes. The method consists of predetermining a trend line for the preparation of isoporous membranes, obtained by computing solvent properties, interactions and copolymer block sizes for a set of successful systems and using it as a guide to select the preparation conditions for new membranes. We applied the method to membranes based on poly(styrene-b-ethylene oxide) diblocks and extended it to newly synthesized poly(styrene-b-2-vinyl pyridine-b-ethylene oxide) (PS-b-P2VP-b-PEO) terpolymers. The trend line method can be generally applied to other new systems and is expected to dramatically shorten the path of isoporous membrane manufacture. The PS-b-P2VP-b-PEO membrane formation was investigated by in situ Grazing Incident Small Angle X-ray Scattering (GISAXS), which revealed a hexagonal micelle order with domain spacing clearly correlated to the membrane interpore distances.

  12. Perpendicularly Aligned, Anion Conducting Nanochannels in Block Copolymer Electrolyte Films

    Energy Technology Data Exchange (ETDEWEB)

    Arges, Christopher G.; Kambe, Yu; Suh, Hyo Seon; Ocola, Leonidas E.; Nealey, Paul F.

    2016-03-08

    Connecting structure and morphology to bulk transport properties, such as ionic conductivity, in nanostructured polymer electrolyte materials is a difficult proposition because of the challenge to precisely and accurately control order and the orientation of the ionic domains in such polymeric films. In this work, poly(styrene-block-2-vinylpyridine) (PSbP2VP) block copolymers were assembled perpendicularly to a substrate surface over large areas through chemical surface modification at the substrate and utilizing a versatile solvent vapor annealing (SVA) technique. After block copolymer assembly, a novel chemical vapor infiltration reaction (CVIR) technique selectively converted the 2-vinylpyridine block to 2-vinyl n-methylpyridinium (NMP+ X-) groups, which are anion charge carriers. The prepared block copolymer electrolytes maintained their orientation and ordered nanostructure upon the selective introduction of ion moieties into the P2VP block and post ion-exchange to other counterion forms (X- = chloride, hydroxide, etc.). The prepared block copolymer electrolyte films demonstrated high chloride ion conductivities, 45 mS cm(-1) at 20 degrees C in deionized water, the highest chloride ion conductivity for anion conducting polymer electrolyte films. Additionally, straight-line lamellae of block copolymer electrolytes were realized using chemoepitaxy and density multiplication. The devised scheme allowed for precise and accurate control of orientation of ionic domains in nanostructured polymer electrolyte films and enables a platform for future studies that examines the relationship between polymer electrolyte structure and ion transport.

  13. Preparation and icephobic properties of polymethyltrifluoropropylsiloxane-polyacrylate block copolymers

    Science.gov (United States)

    Li, Xiaohui; Zhao, Yunhui; Li, Hui; Yuan, Xiaoyan

    2014-10-01

    Five polymethyltrifluoropropylsiloxane (PMTFPS)-polyacrylate block copolymers (PMTFPS-b-polyacrylate) were synthesized by free radical polymerization of methyl methacrylate, n-butyl acrylate and hydroxyethyl methacrylate using PMTFPS macroazoinitiator (PMTFPS-MAI) in range of 10-50 mass percentages. The morphology, surface chemical composition and wettability of the prepared copolymer films were investigated by transmission electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and water contact angle measurement. Delayed icing time and ice shear strength of the films were also detected for the icephobic purpose. The surface morphologies of the copolymers were different from those of the bulk because of the migration of the PMTFPS segments to the air interface during the film formation. Maximal delayed icing time (186 s at -15 °C) and reduction of the ice shear strength (301 ± 10 kPa) which was significantly lower than that of polyacrylates (804 ± 37 kPa) were achieved when the content of PMTFPS-MAI was 20 wt%. The icephobicity of the copolymers was attributed primarily to the enrichment of PMTFPS on the film surface and synergistic effect of both silicone and fluorine. Thus, the results show that the PMTFPS-b-polyacrylate copolymer can be used as icephobic coating materials potentially.

  14. Synthesis, characterization and antimicrobial activity of important heterocyclic acrylic copolymers

    Directory of Open Access Journals (Sweden)

    2008-10-01

    Full Text Available The acrylate monomer, 7-acryloyloxy-4-methyl coumarin (AMC has been synthesized by reacting 7-hydroxy-4-methyl coumarin, with acryloyl chloride in the presence of NaOH at 0–5°C. Copolymers of 7-acryloyloxy-4-methyl coumarin (AMC with vinyl acetate (VAc were synthesized in DMF (dimethyl formamide solution at 70±1°C using 2,2′-azobisisobutyronitrile (AIBN as an initiator with different monomer-to-monomer ratios in the feed. The copolymers were characterized by Fourier transform infra red (FTIR spectroscopy. The copolymer composition was evaluated by 1H-NMR (proton nuclear magnetic resonance and was further used to determine reactivity ratios. The monomer reactivity ratios for AMC (M1-VAc (M2 pair were determined by the application of conventional linearization methods such as Fineman-Ross (r1 = 0.6924; r2 = 0.6431, Kelen-Tüdõs (r1 = 0.6776; r2 = 0.6374 and extended Kelen-Tüdõs (r1 = 0.6657; r2 = 0.6256. Thermo gravimetric analysis showed that thermal decomposition of the copolymers occurred in single stage in the temperature range of 263–458°C. The molecular weights of the polymers were determined using gel permeation chromatography. The homo and copolymers were tested for their antimicrobial properties against selected microorganisms.

  15. Plastic Deformation and Morphological Evolution of Precise Acid Copolymers

    Science.gov (United States)

    Middleton, L. Robert; Azoulay, Jason; Murtagh, Dustin; Cordaro, Joseph; Winey, Karen

    2014-03-01

    Acid- and ion-containing polymers have specific interactions that produce complex and hierarchical morphologies that provide remarkable mechanical properties. Historically, correlating the hierarchical structure and the mechanical properties of these polymers has been challenging due to the random arrangements of the polar groups along the backbone, ex situ characterization and the difficulty in deconvolution the effects of crystalline and amorphous regions along with secondary interactions between polymer chains. We address these challenges through in situ deformation of precise acid copolymers and relate the structural evolution to bulk properties by considering a series of copolymers with 9, 15 or 21 carbons between acid groups. Simultaneous synchrotron X-ray scattering and room temperature uniaxial tensile experiments of these precise acid copolymers were conducted. The different deformation mechanisms are compared and the microstructural evolution during deformation is discussed. For example, the liquid-like distribution of acid aggregates within the bulk copolymer transitions into a layered structure concurrent to a dramatic increase in tensile strength. Overall, we evaluate the effect and control of introducing acid groups on mechanical deformation of the bulk copolymers.

  16. STUDY ON THE SYNTHESIS OF COPOLYMER CONTAINING N-SUBSTITUTED ACRYLAMIDE COMPONENT

    Institute of Scientific and Technical Information of China (English)

    LI Xuefen; WANG Shenguo; LI Zhifen

    1984-01-01

    In this paper the synthesis of linear and crosslinked N-substituted acrylamide copolymer is reported. In order to obtain the terpolymer with appropriate hydrophilicity, the conditions of aminolysis of St-MMA copolymer have been selected.It is shown that the copolymer with predictable hydrophilicity possesses good blood compatibility.

  17. 21 CFR 177.1960 - Vinyl chloride-hexene-1 copolymers.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Vinyl chloride-hexene-1 copolymers. 177.1960... Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1960 Vinyl chloride-hexene-1 copolymers. The vinyl chloride-hexene-1 copolymers identified in paragraph (a) of this section or...

  18. 21 CFR 177.1970 - Vinyl chloride-lauryl vinyl ether copolymers.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Vinyl chloride-lauryl vinyl ether copolymers. 177... for Use as Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1970 Vinyl chloride-lauryl vinyl ether copolymers. The vinyl chloride-lauryl vinyl ether copolymers identified in...

  19. 40 CFR 180.1162 - Acrylate polymers and copolymers; exemption from the requirement of a tolerance.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 23 2010-07-01 2010-07-01 false Acrylate polymers and copolymers... RESIDUES IN FOOD Exemptions From Tolerances § 180.1162 Acrylate polymers and copolymers; exemption from the requirement of a tolerance. (a) Acrylate polymers and copolymers are exempt from the requirement of...

  20. 21 CFR 177.1480 - Nitrile rubber modified acrylonitrile-methyl acrylate copolymers.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Nitrile rubber modified acrylonitrile-methyl... Nitrile rubber modified acrylonitrile-methyl acrylate copolymers. Nitrile rubber modified acrylonitrile... rubber modified acrylonitrile-methyl acrylate copolymers consist of basic copolymers produced by...

  1. 21 CFR 177.1020 - Acrylonitrile/butadiene/sty-rene co-polymer.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Acrylonitrile/butadiene/sty-rene co-polymer. 177... SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) INDIRECT FOOD ADDITIVES: POLYMERS Substances.../butadiene/sty-rene co-polymer. Acrylonitrile/butadiene/styrene copolymer identified in this section may...

  2. Synthesis of imide/arylene ether copolymers for adhesives and composite matrices

    Science.gov (United States)

    Jensen, B. J.; Hergenrother, P. M.; Bass, R. G.

    1991-01-01

    A series of imide/arylene ether copolymers were prepared from the reaction of an amorphous arylene ether oligomer and a semi-crystalline imide oligomer. These copolymers were thermally characterized and mechanical properties were measured. One block copolymer was endcapped and the molecular weight was controlled to provide a material that displayed good compression moldability and attractive adhesion and composite properties.

  3. Realization of an integrated VDF/TrFE copolymer-on-silicon pyroelectric sensor

    NARCIS (Netherlands)

    Setiadi, D.; Regtien, P.P.L.; Sarro, P.M.

    1995-01-01

    An integrated pyroelectric sensor based on a vinylidene fluoride trifluoroethylene (VDF/TrFE) copolymer is presented. A silicon substrate that contains FET readout electronics is coated with the VDF/TrFE copolymer film using a spin-coating technique. On-chip poling of the copolymer has been applied

  4. A 3 x 1 Integrated Pyroelectric Sensor Based on VDF/TrFE Copolymer

    NARCIS (Netherlands)

    Setiadi, D.; Sarro, P.M.; Regtien, P.P.L.

    1995-01-01

    This paper presents an integrated pyroelectric sensor based on a Vinylidene Fluoride TriFluoroEthylene (VDF/TrFE) copolymer. A silicon substrate that contains FET readout electronics is coated with the VDF/TrFE copolymer film using a spin-coating technique. On-chip poling of the copolymer has been a

  5. 40 CFR 721.10179 - Copolymers of phenol and aromatic hydocarbon (generic).

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Copolymers of phenol and aromatic... Specific Chemical Substances § 721.10179 Copolymers of phenol and aromatic hydocarbon (generic). (a... generically as copolymers of phenol and aromatic hydocarbon (PMNs P-04-346 and P-04-347) are subject...

  6. Bandgap determination of P(VDF–TrFE) copolymer film by electron energy loss spectroscopy

    Indian Academy of Sciences (India)

    Dipankar Mandal; K Henkel; K Müller; D Schmeißer

    2010-08-01

    The ferroelectric of poly(vinylidene fluoride trifluoroethylene), P(VDF–TrFE) is confirmed for 100 nm thickness spin coated copolymer film. The homogeneous coverage of the copolymer film is investigated by the help of X-ray photoelectron spectroscopy (XPS). Most importantly, the existing bandgap in the crystalline phase of the copolymer is determined directly from the electron energy loss spectroscopy (EELS).

  7. Polystyrene-b-polyethylene oxide block copolymer membranes, methods of making, and methods of use

    KAUST Repository

    Peinemann, Klaus-Viktor

    2015-04-16

    Embodiments of the present disclosure provide for polystyrene-b-polyethylene oxide (PS-b-PEO) block copolymer nanoporous membranes, methods of making a PS-b-PEO block copolymer nanoporous membrane, methods of using PS-b-PEO block copolymer nanoporous membranes, and the like.

  8. 21 CFR 175.350 - Vinyl acetate/crotonic acid copolymer.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Vinyl acetate/crotonic acid copolymer. 175.350... COATINGS Substances for Use as Components of Coatings § 175.350 Vinyl acetate/crotonic acid copolymer. A copolymer of vinyl acetate and crotonic acid may be safely used as a coating or as a component of a...

  9. Compatibilizing Effect of Random or Block Copolymer Added to Binary Mixture of Homopolymers.

    Science.gov (United States)

    2014-09-26

    copolymer R50/50 (Mw 25000); filled squares: random copolymer RF50/50 (M 16300); filled diamonds : random copolymer SPP45 (Mw > 2.3 x 105); open squares...Pennsylvania 18015 Dr. R. S. Porter Professor Brian Newman Department of Polymer Science Department of Mechanics and and Engineering Materials Science

  10. Ordered nanoscale domains by infiltration of block copolymers

    Energy Technology Data Exchange (ETDEWEB)

    Darling, Seth B.; Elam, Jeffrey; Tseng, Yu-Chih; Peng, Qing

    2016-11-08

    A method of preparing tunable inorganic patterned nanofeatures by infiltration of a block copolymer scaffold having a plurality of self-assembled periodic polymer microdomains. The method may be used sequential infiltration synthesis (SIS), related to atomic layer deposition (ALD). The method includes selecting a metal precursor that is configured to selectively react with the copolymer unit defining the microdomain but is substantially non-reactive with another polymer unit of the copolymer. A tunable inorganic features is selectively formed on the microdomain to form a hybrid organic/inorganic composite material of the metal precursor and a co-reactant. The organic component may be optionally removed to obtain an inorganic features with patterned nanostructures defined by the configuration of the microdomain.

  11. Universality between Experiment and Simulation of a Diblock Copolymer Melt

    Science.gov (United States)

    Beardsley, Thomas M.; Matsen, Mark W.

    2016-11-01

    The equivalent behavior among analogous block copolymer systems involving chemically distinct molecules or mathematically different models has long hinted at an underlying universality, but only recently has it been rigorously demonstrated by matching results from different simulations. The profound implication of universality is that simple coarse-grained models can be calibrated so as to provide quantitatively accurate predictions to experiment. Here, we provide the first compelling demonstration of this by simulating a polyisoprene-polylactide diblock copolymer melt using a previously calibrated lattice model. The simulation successfully predicts the peak in the disordered-state structure function, the position of the order-disorder transition, and the latent heat of the transition in excellent quantitative agreement with experiment. This could mark a new era of precision in the field of block copolymer research.

  12. Mechanism for Rapid Self-Assembly of Block Copolymer Nanoparticles

    Science.gov (United States)

    Johnson, Brian K.; Prud'Homme, Robert K.

    2003-09-01

    Amphiphilic block copolymers in solution spontaneously self-assemble when the solvent quality for one block is selectively decreased. We demonstrate that, for supersaturation ratio changes [d(S)/dt] over 105 per second from equilibrium, nanoparticles are obtained with a formation mechanism and size dependent on the jumping rate and magnitude. The threshold rate for homogeneous precipitation is determined by the induction time of a particle, equivalent to the diffusion limited fusion of copolymer chains to form a corona of overlapping soluble brushes. Via determination of the induction time with a novel confined impinging jets mixer and use of a scaling relation, the interfacial free energy of a block copolymer nanoparticle was measured for the first time.

  13. Modification of ethylene-norbornene copolymer by Gamma irradiation

    Directory of Open Access Journals (Sweden)

    Kačarević-Popović Zorica M.

    2006-01-01

    Full Text Available The possibility of modifying polyethylene and many other polymers with high energy radiation has led to many useful applications. Due to their new combination of properties and the shortage of experimental data, the radiolysis of a new class of materials, cyclo-olefin copolymers (COC, polymerised from norbornene and ethylene using metallocene catalysts, is of great interest to the study of radiation chemistry and the physics of polymeric systems. Ethylenenorbornene copolymer, pristine and containing an antioxidant were subjected to gamma irradiation in the presence of air and in water. The irradiated copolymer was studied using IR and UV-vis spectrophotometric analysis. The radiation-induced changes in the molecular structure were correlated to changes in the glass transition temperature measured by the DSC method.

  14. Structure of Block Copolymer Hydrogel Formed by Complex Coacervate Process

    Science.gov (United States)

    Choi, Soohyung; Ortony, Julia; Krogstad, Daniel; Spruell, Jason; Lynd, Nathaniel; Han, Songi; Kramer, Edward

    2012-02-01

    Complex coacervation occurs when oppositely charged polyelectrolytes associate in solution, forming dense micron-sized droplets. Hydrogels with coacervate block domains were formed by mixing two ABA and A'BA' triblock copolymer solutions in water where the A and A' blocks are oppositely charged. Small-angle neutron scattering (SANS) was used to investigate the structure of hydrogels formed by ABA triblock copolymers (A block: poly(allyl glycidyl ether) functionalized with guanidinium (A) or sulfonate (A'), B block: poly(ethylene oxide)). By using an appropriate fitting model, structural information such as coacervate core block radius and water volume fraction w can be extracted from SANS data. The results reveal that w in the coacervate core block was significantly higher than in conventional triblock copolymer hydrogels where microphase separation is driven by the hydrophobicity of the core-forming blocks.

  15. Photophysical Study of Pyrene-labelled St/DVB Copolymers

    Institute of Scientific and Technical Information of China (English)

    何炳林; 王国昌; 李新松; 陈柳生; 杜金环

    1994-01-01

    The photophysical properties of a series of pyrene-labelled styrene/divinyl benzene (St/ DVB) copolymers have been studied for the first time by steady-state fluorescence spectra. The results indicate that when pyrenyl content (mol%) in the copolymer is lower than 0. 006% , the fluorescence spectra only show the pyrenyl monomer emission, while the 0-0 transition band is much suppressed and the vibronic structure is partially lost. However, in the fluorescence spectra of the copolymers with pyrenyl content higher than 0.3%, there appear some new emission bands at ca 420 nm, 440 nm and 475 nm. These results are explained in terms of the formation of ground-state and excited-state aggregates, which reveals the heterogeneity of the crosslinked networks.

  16. Self-assembly of semiflexible-flexible block copolymers

    Science.gov (United States)

    Kumar, Arun; Ganesan, Venkat

    2012-02-01

    We apply self-consistent Brownian dynamics simulations to study the self-assembly behavior of semiflexible-flexible block copolymers. A Maier-Saupe interaction model was applied for the orientational interactions between the semiflexible polymers, while the enthalpic interactions between semiflexible and flexible polymers were modeled through a standard Flory-Huggins approach. To develop a physical understanding of the phases and their regimes of occurrence as a function of varying persistence length of the semiflexible block, we computed the 2D phase diagram for our model. We quantify the progression of the self-assembly morphologies in transitioning from coil-coil block copolymers on the one hand to rod-coil block copolymers on the other hand. The results obtained are in qualitative agreement with the existing experimental and numerical results.

  17. STRUCTURE OF CRYSTALLINE DOMAINS IN SEMICRYSTALLINE BLOCK COPOLYMER THIN FILMS

    Institute of Scientific and Technical Information of China (English)

    Guo-dong Liang; Jun-ting Xu; Zhi-qiang Fan

    2006-01-01

    Thin film morphology of a symmetric semicrystalline oxyethylene/oxybutylene diblock copolymer (E76B38) on silicon was investigated by tapping mode atomic force microscopy (AFM). It is found that the nascent thin film is composed of multiple polymer layers having mixed thicknesses of L ≈ L0 and L ≈ L0/2 (L0 is the long period of the block copolymer in bulk) besides the first layer near the substrate. This shows that the crystalline domain in the block copolymer consists of double poly(oxyethylene) layers. Annealing leads to disappearance of the polymer layers with thickness L ≈ L0/2, indicating that such polymer layers are metastable.

  18. Solubility of dense CO2 in two biocompatible acrylate copolymers

    Directory of Open Access Journals (Sweden)

    A. R. C. Duarte

    2006-06-01

    Full Text Available Biocompatible polymers and copolymers are frequently being used as part of controlled delivery systems. These systems can be prepared using a "clean and environment friendly" technology like supercritical fluids. One great advantage of this process is that compressed carbon dioxide has excellent plasticizing properties and can swell most biocompatible polymeric matrixes, thus promoting drug impregnation processes. Mass sorption of two acrylate biocompatible copolymers contact with supercritical carbon dioxide is reported. Equilibrium solubility of dense carbon dioxide in poly(methylmethacrylate-co-ethylhexylacrylate and poly(methylmethacrylate-co-ethylhexylacrylate-co-ethyleneglycoldimethacrylate was studied by a static method at 10.0 MPa and 313 K. The reticulated copolymer had Fickean behavior and its diffusion coefficient was calculated, under operating conditions.

  19. Acrylate Copolymers as Impact Modiifer for Epoxy Resin

    Institute of Scientific and Technical Information of China (English)

    WANG Tao; WANG Jun; CHEN Wei; DUAN Huajun; YANG Shuang; CHEN Xi; ZHANG Bin

    2015-01-01

    P(BA-GMA) (PBG), having various molecular weights, was synthesized by in situ polymerization of butyl acrylate (BA) and glycidyl methacrylate (GMA), and further used as a modifier to improve the comprehensive properties of the epoxy curing system. The copolymers were characterized by gel permeation chromatography (GPC). The effects of various molecular weights of copolymers on the mechanical properties, thermal performance, and phase behavior of the curing system were carefully evaluated. The experimental results of differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) showed that glass transition temperature decreased and the tan δ peak shifted to a lower temperature with decreasing molecular weight of copolymer. Mechanical properties analysis of curing films showed that the impact strength and fracture toughness increased significantly upon the addition of PBG, indicating good toughness of the modified epoxy resins. From scanning electron microscopy (SEM) studies of the fracture surfaces of ER/PBG systems, the fracture behavior of epoxy matrix was changed from brittleness to toughness.

  20. Performance behavior of modified cellulosic fabrics using polyurethane acrylate copolymer.

    Science.gov (United States)

    Zuber, Mohammad; Shah, Sayyed Asim Ali; Jamil, Tahir; Asghar, Muhammad Irfan

    2014-06-01

    The surface of the cellulosic fabrics was modified using self-prepared emulsions of polyurethane acrylate copolymers (PUACs). PUACs were prepared by varying the molecular weight of polycaprolactone diol (PCL). The PCL was reacted with isophorone diisocyanate (IPDI) and chain was extended with 2-hydroxy ethyl acrylate (HEA) to form vinyl terminated polyurethane (VTPU) preploymer. The VTPU was further co-polymerized through free radical polymerization with butyl acrylate in different proportions. The FT-IR spectra of monomers, prepolymers and copolymers assured the formation of proposed PUACs structure. The various concentrations of prepared PUACs were applied onto the different fabric samples using dip-padding techniques. The results revealed that the application of polyurethane butyl acrylate copolymer showed a pronounced effect on the tear strength and pilling resistance of the treated fabrics.

  1. A Photosensitive Copolymer for UV-curable Eleetrodeposition Coatings

    Institute of Scientific and Technical Information of China (English)

    LIU Ren; LI Xiaojie; AN Fenglci; ZHANG Shengwen; LIU Xiaoya

    2011-01-01

    A series of photosensitive random copolymers (UPDHES) were prepared by introducing acrylate groups onto the side chain of the copolymer backbone of N,N-domethyl amimethyl methacrylate (DMAEMA),2-hydroxypropyl acrylate (HEA),2-ethylhexyl acrylate (EHA),and styrene (St) (PDHES).The molecular structure of UPDHES was characterized by FTIR,1HNMR and GPC.The photopolymerization kinetics of UPDHES with different C=C content was investigated using real time FTIR in which it was found that the UPDHES system had notable photosensitivity.The effect of C=C content on the properties of cured films were studied by evaluating various film properties such as thermal stability,glass transition temperature and tensile properties.The thermal degradation of cured films was investigated via thermogravimetric analysis/infrared spectrometry (TGA-IR).Thus a series of UV-curable electrodeposition coatings with good photosensitivity and mechanical properties were prepared from a low-cost photosensitive random copolymer.

  2. Studies on N-vinylformamide cross-linked copolymers

    Science.gov (United States)

    Świder, Joanna; Tąta, Agnieszka; Sokołowska, Katarzyna; Witek, Ewa; Proniewicz, Edyta

    2015-12-01

    Copolymers of N-vinylformamide (NVF) cross-linked with three multifunctional monomers, including divinylbenzene (DVB), ethylene glycol dimethacrylate (EGDMA), and N,N‧-methylenebisacrylamide (MBA) were synthetized by a three-dimensional free radical polymerization in inverse suspension using 2,2‧-azobis(2-methylpropionamide) dihydrochloride (AIBA) as an initiator. Methyl silicon oil was used as the continuous phase during the polymerization processes. Fourier-transform adsorption infrared (FT-IR) spectra revealed the presence of silicone oil traces and suggested that silicone oil strongly interacted with the copolymers surface. Purification procedure allowed to completely remove the silicon oil traces from P(NVF-co-DVB) only. The morphology and the structure of the investigated copolymers were examined by optical microscopy, FT-IR, and FT-Raman (Fourier-transform Raman spectroscopy) methods.

  3. Block copolymer/homopolymer dual-layer hollow fiber membranes

    KAUST Repository

    Hilke, Roland

    2014-12-01

    We manufactured the first time block copolymer dual-layer hollow fiber membranes and dual layer flat sheet membranes manufactured by double solution casting and phase inversion in water. The support porous layer was based on polystyrene and the selective layer with isopores was formed by micelle assembly of polystyrene-. b-poly-4-vinyl pyridine. The dual layers had an excellent interfacial adhesion and pore interconnectivity. The dual membranes showed pH response behavior like single layer block copolymer membranes with a low flux for pH values less than 3, a fast increase between pH4 and pH6 and a constant high flux level for pH values above 7. The dry/wet spinning process was optimized to produce dual layer hollow fiber membranes with polystyrene internal support layer and a shell block copolymer selective layer.

  4. Responsive copolymers for enhanced petroleum recovery. Second annual report

    Energy Technology Data Exchange (ETDEWEB)

    McCormick, C.; Hester, R.

    1995-05-01

    The authors describe second year efforts in synthesis, characterization, and rheology to develop polymers with significantly improved efficiency in mobility control and conformance. These advanced polymer systems would maintain high viscosities or behave as virtual gels under low shear conditions and at elevated electrolyte concentrations. At high fluid shear rates, associates would deaggregate yielding low viscosity solutions, reducing problems of shear degradation or face plugging during injection. Polymeric surfactants were also developed with potential for use in higher salt, higher temperature reservoirs for mobilization of entrapped oil. Chapters include: Ampholytic terpolymers of acrylamide with sodium 3-acrylamido-3-methylbutanoate and 2-acrylamido-2-methylpropanetrimethylammonium chloride; Hydrophilic sulfobetaine copolymers of acrylamide and 3-(2-acrylamido-methylpropane-dimethylammonio)-1-propanesulfonate; Copolymerization of maleic anhydride and N-vinylformamide; Reactivity ratio of N-vinylformamide with acrylamide, sodium acrylate, and n-butyl acrylate; Effect of the distribution of the hydrophobic cationic monomer dimethyldodecyl(2-acrylamidoethyl)ammonium bromide on the solution behavior of associating acrylamide copolymers; Effect of surfactants on the solution properties of amphipathic copolymers of acrylamide and N,N-dimethyl-N-dodecyl-N-(2-acrylamidoethyl)ammonium bromide; Associative interactions and photophysical behavior of amphiphilic terpolymers prepared by modification of maleic anhydride/ethyl vinyl ether copolymers; Copolymer compositions of high-molecular-weight functional acrylamido water-soluble polymers using direct-polarization magic-angle spinning {sup 13}C NMR; Use of factorial experimental design in static and dynamic light scattering characterization of water soluble polymers; and Porous medium elongational rheometer studies of NaAMB/AM copolymer solutions.

  5. Stability of ordered phases in block copolymer melts and solutions

    Indian Academy of Sciences (India)

    Kell Mortensen

    2008-11-01

    Block copolymer melts and solutions assemble into nanosized objects that order into a variety of phases, depending on molecular parameters and mutual interactions. Beyond the classical phases of lamella ordered sheets, hexagonally ordered cylinders and cubic ordered spheres, the complex bicontinuous gyroid phase and the modulated lamellar phase are observed near the phase boundaries. The stability of these phases has been discussed on the basis of theoretical calculations. Here, we will discuss new experimental results showing that the given ordered phase depends critically on both molecular purity and mechanical treatment of the sample. While a variety of block copolymer micellar systems have been shown to undergo the liquid-to-bcc-to-fcc phase sequence upon varying micellar parameters (or temperature), we find for a purified system a different sequence, namely liquid-to-fcc-to-bcc [1]. The latter sequence is by the way the one predicted for pure block copolymer melts. External fields like shear or stress may also affect the ordered phase. Applying well-controlled large-amplitude oscillatory shear can be used to effectively control the texture of soft materials in the ordered states. As an example, we present results on a body-centred-cubic phase of a block copolymer system, showing how a given texture can be controlled with the application of specific shear rate and shear amplitude [2,3]. Shear may however also affect the thermodynamic ground state, causing shear-induced ordering and disordering (melting), and shear-induced order–order transitions. We will present data showing that the gyroid state of diblock copolymer melts is unstable when exposed to large amplitude/frequency shear, transforming into the hexagonal cylinder phase [4]. The transformation is completely reversible. With the rather slow kinetics in the transformation of copolymer systems, it is possible in detail to follow the complex transformation process, where we find transient ordered

  6. Preparation and icephobic properties of polymethyltrifluoropropylsiloxane–polyacrylate block copolymers

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xiaohui; Zhao, Yunhui [School of Materials Science and Engineering, and Tianjin Key Laboratory of Composite and Functional Materials, Tianjin University, Tianjin 300072 (China); Li, Hui [School of Chemistry and Chemical Engineering, Shandong Key Laboratory of Fluorine Chemistry and Chemical Engineering Materials, University of Jinan, Jinan 250022 (China); Yuan, Xiaoyan, E-mail: xyuan28@yahoo.com [School of Materials Science and Engineering, and Tianjin Key Laboratory of Composite and Functional Materials, Tianjin University, Tianjin 300072 (China)

    2014-10-15

    Highlights: • PMTFPS–b-polyacrylate copolymers in five different compositions were synthesized. • Enrichment of PMTFPS amounts at the surface made high F/Si value. • Icing delay time was related to the surface roughness. • Ice shear strength was decreased by the synergistic effect of silicone and fluorine. - Abstract: Five polymethyltrifluoropropylsiloxane (PMTFPS)–polyacrylate block copolymers (PMTFPS–b-polyacrylate) were synthesized by free radical polymerization of methyl methacrylate, n-butyl acrylate and hydroxyethyl methacrylate using PMTFPS macroazoinitiator (PMTFPS-MAI) in range of 10–50 mass percentages. The morphology, surface chemical composition and wettability of the prepared copolymer films were investigated by transmission electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and water contact angle measurement. Delayed icing time and ice shear strength of the films were also detected for the icephobic purpose. The surface morphologies of the copolymers were different from those of the bulk because of the migration of the PMTFPS segments to the air interface during the film formation. Maximal delayed icing time (186 s at −15 °C) and reduction of the ice shear strength (301 ± 10 kPa) which was significantly lower than that of polyacrylates (804 ± 37 kPa) were achieved when the content of PMTFPS-MAI was 20 wt%. The icephobicity of the copolymers was attributed primarily to the enrichment of PMTFPS on the film surface and synergistic effect of both silicone and fluorine. Thus, the results show that the PMTFPS–b-polyacrylate copolymer can be used as icephobic coating materials potentially.

  7. Photoexcitation dynamics in an alternating polyfluorene copolymer

    Science.gov (United States)

    Westerling, M.; Aarnio, H.; Österbacka, R.; Stubb, H.; King, S. M.; Monkman, A. P.; Andersson, M. R.; Jespersen, K.; Kesti, T.; Yartsev, A.; Sundström, V.

    2007-06-01

    We have used transient photoinduced absorption on femtosecond to nanosecond time scales as well as delayed fluorescence up to microseconds to study the photogeneration and recombination of charges in thin films of the alternating polyfluorene copolymer poly[2,7-(9,9-dioctylfluorene)-alt-5,5-( 4',7' -di-2-thienyl- 2',1',3' -benzothiadiazole)]. We interpret the results using a coupled rate equation model and find that we can fit all our experimental results with a single set of parameters. The model includes prompt (polaron pairs, respectively. The intrachain polaron pairs are promptly generated from vibronically excited (hot) primary singlet excitons S1* and recombine geminately back to the lowest singlet exciton state S1 with a lifetime distribution having a mean lifetime of ˜2.4ps . The interchain polaron pairs, which can be seen as precursors to free charges, are formed via two channels: via singlet excitons being dissociated with a linear rate constant of ˜5ns as well as via a time-dependent bimolecular exciton-exciton annihilation process generating higher-energy exciton states Sn* of which a fraction subsequently dissociates into interchain polaron pairs. We observe a total yield of 12%-23% interchain polaron pairs (a precursor to free polarons), depending on the excitation intensity used. This also defines the upper limit of the free polaron yield at zero electric field in this material. The long-lived interchain polaron pairs recombine geminately back to the ground state or to singlet excitons with a broad distribution of lifetimes having a mean lifetime of ˜0.27μs . The fraction of interchain polaron pairs recombining back to singlet excitons, with subsequent radiative decay back to the ground state, gives rise to delayed fluorescence extending to microsecond time scales.

  8. Polymers and block copolymers of fluorostyrenes by ATRP

    DEFF Research Database (Denmark)

    Hvilsted, Søren; Borkar, Sachin; Abildgaard, Lillian;

    2002-01-01

    Fully or partly fluorinated polymers have many desirable and intriguing properties. In the framework of a larger program on design and control of new functional block copolymers we recently employed the Atom Transfer Radical Polymerization (ATRP) protocol on 2,3,4,5,6-pentafluorostyrene (FS). We...... materials based on 2,3,5,6-tetrafiuoro-4-methoxy-styrene (TFMS). TFMS homopolymers as well as diblock copolymers with FS are produced by ATRP. Both types of novel polymers were subsequently demethylated and different side chains introduced on the resulting hydroxy sites....

  9. Nanoporous Crosslinked Polyisoprene from Polyisoprene-Polydimethylsiloxane Block Copolymer

    DEFF Research Database (Denmark)

    Hansen, Michael Steffen; Vigild, Martin Etchells; Berg, Rolf Henrik;

    2004-01-01

    The polyisoprene block of a polyisoprene-polydimethylsiloxane (PI-PDMS) diblock copolymer with 0.68 volume fraction of PI was tightly crosslinked with dicumylperoxide. The PDMS part of the obtained glassy material was subsequently quantitatively etched with anhydrous hydrogen fluoride or tetrabut......The polyisoprene block of a polyisoprene-polydimethylsiloxane (PI-PDMS) diblock copolymer with 0.68 volume fraction of PI was tightly crosslinked with dicumylperoxide. The PDMS part of the obtained glassy material was subsequently quantitatively etched with anhydrous hydrogen fluoride...

  10. Synthesis and Characterization of Organotin Containing Copolymers: Reactivity Ratio Studies

    Directory of Open Access Journals (Sweden)

    Mohamed H. El-Newehy

    2010-03-01

    Full Text Available Organotin monomers containing dibutyltin groups – dibutyltin citraconate (DBTC as a new monomer and dibutyltin maleate (DBTM – were synthesized. Free radical copolymerizations of the organotin monomers with styrene (ST and butyl acrylate (BA were performed. The overall conversion was kept low (≤15% wt/wt for all studied samples and the copolymers composition was determined from tin analysis using the Gillman and Rosenberg method. The reactivity ratios were calculated from the copolymer composition using the Fineman-Ross (FR method. The synthesized monomers were characterized by elemental analysis, 1H-, 13C-NMR and FTIR spectroscopy.

  11. Synthesis and infrared properties of ethylenedioxythiophene and octylthiophene based copolymers

    Science.gov (United States)

    Buvat, P.; Hourquebie, P.

    1998-06-01

    The control of the structural parameters and doping conditions of PATs lead to quasi-metallic materials. We have developed the synthesis of copolymers and PAT to enhance the metallic properties with conservation of the solubility. Le contrôle des paramètres physico-chimiques des PATs et des conditions de dopage conduit à des matériaux quasi-métalliques. Nous nous sommes ici orientés vers des copolymères du PEDOT et des PATs pour augmenter le caractère métallique tout en conservant les propriétés de solubilité.

  12. Stabilization and controlled association of superparamagnetic nanoparticles using block copolymers

    Energy Technology Data Exchange (ETDEWEB)

    Frka-Petesic, Bruno [UPMC Univ Paris 6, Lab. des Liquides Ioniques et Interfaces Chargees (LI2C), CNRS-ESPCI UMR 7612 case 51, 4 place Jussieu, F-75252 Paris Cedex 05 (France); Fresnais, Jerome; Berret, Jean-Francois [Laboratoire Matiere et Systemes Complexes (MSC), UMR 7057 CNRS and Universite Paris Diderot, Batiment Condorcet 10 rue Alice Domon et Leonie Duquet, F-75205 Paris Codex 13 (France); Dupuis, Vincent [UPMC Univ Paris 6, Lab. des Liquides Ioniques et Interfaces Chargees (LI2C), CNRS-ESPCI UMR 7612 case 51, 4 place Jussieu, F-75252 Paris Cedex 05 (France); Perzynski, Regine [UPMC Univ Paris 6, Lab. des Liquides Ioniques et Interfaces Chargees (LI2C), CNRS-ESPCI UMR 7612 case 51, 4 place Jussieu, F-75252 Paris Cedex 05 (France)], E-mail: regine.perzynski@upmc.fr; Sandre, Olivier [UPMC Univ Paris 6, Lab. des Liquides Ioniques et Interfaces Chargees (LI2C), CNRS-ESPCI UMR 7612 case 51, 4 place Jussieu, F-75252 Paris Cedex 05 (France)

    2009-04-15

    Mixing in aqueous solutions polyelectrolyte-neutral block copolymers with oppositely charged species, spontaneously forms stable core-shell complexes, which are electrostatically driven. We report here on the structural and orientational properties of such mixed magnetic nanoclusters made of magnetic iron oxide nanoparticles (MNPs) and polyelectrolyte-neutral block copolymers. Small angle neutron scattering and transmission electron microscopy experiments allows to probe the inner-core nanoparticle organization, leading to an average interparticle distance and confirming the hierarchical internal structure of the clusters. Thanks to the MNP optical anisotropy, we also probe the under-magnetic field orientational properties of the core-shell clusters and their dynamical rotational relaxation.

  13. Micellar structure of amphiphilic poly(2-oxazoline) diblock copolymers

    DEFF Research Database (Denmark)

    Papadakis, C.M.; Ivanova, R.; Lüdtke, K.

    2007-01-01

    Amphiphilic diblock copolymers from poly(2-oxazoline)s in aqueous solution can form micelles. By means of small-angle neutron scattering, we have found that poly[(n-nonyl-2-oxazoline)-b-(methyl-2-oxazoline)] {P[(NOx)-b-(MOx)]} diblock copolymers in aqueous solution form micelles of core-shell type....... We have determined the core radius and the shell thickness of the micelles. Comparing the values obtained to the stretched lengths of the blocks leads to the conclusion that the P(NOx) core blocks are stretched, whereas the P(MOx) shell blocks are coiled....

  14. Block copolymer adhesion promoters via ring-opening metathesis polymerization

    Science.gov (United States)

    Kent, M.S.; Saunders, R.

    1997-02-18

    Coupling agents are disclosed based on functionalized block copolymers for bonding thermoset polymers to solid materials. These are polymers which possess at least two types of functional groups, one which is able to attach to and react with solid surfaces, and another which can react with a thermoset resin, which are incorporated as pendant groups in monomers distributed in blocks (typically two) along the backbone of the chain. The block copolymers in this invention are synthesized by living ring-opening metathesis polymerization. 18 figs.

  15. Novel block, graft and random copolymers for biomedical applications

    DEFF Research Database (Denmark)

    Javakhishvili, Irakli; Jankova Atanasova, Katja; Tanaka, Masaru;

    roles for this [2]. An artificial lung (oxygenator), already in use, is coated with high MW PMEA prepared by radical polymerization with AIBN [2]. To broaden the possibilities for designing biomedical devices [3] and inspired from these findings we first prepared homo polymers of MEA and their block...... copolymers with MMA [4] utilizing ATRP. Here we present other block, graft and random copolymers of MEA intended for biomedical applications. These macromolecular architectures have been constructed by employing controlled radical polymerization methods such as RAFT and ATRP....

  16. Fabrication and Characterization of a Porous Silicon Drug Delivery System with an Initiated Chemical Vapor Deposition Temperature-Responsive Coating.

    Science.gov (United States)

    McInnes, Steven J P; Szili, Endre J; Al-Bataineh, Sameer A; Vasani, Roshan B; Xu, Jingjing; Alf, Mahriah E; Gleason, Karen K; Short, Robert D; Voelcker, Nicolas H

    2016-01-12

    This paper reports on the fabrication of a pSi-based drug delivery system, functionalized with an initiated chemical vapor deposition (iCVD) polymer film, for the sustainable and temperature-dependent delivery of drugs. The devices were prepared by loading biodegradable porous silicon (pSi) with a fluorescent anticancer drug camptothecin (CPT) and coating the surface with temperature-responsive poly(N-isopropylacrylamide-co-diethylene glycol divinyl ether) (pNIPAM-co-DEGDVE) or non-stimulus-responsive poly(aminostyrene) (pAS) via iCVD. CPT released from the uncoated oxidized pSi control with a burst release fashion (∼21 nmol/(cm(2) h)), and this was almost identical at temperatures both above (37 °C) and below (25 °C) the lower critical solution temperature (LCST) of the switchable polymer used, pNIPAM-co-DEGDVE (28.5 °C). In comparison, the burst release rate from the pSi-pNIPAM-co-DEGDVE sample was substantially slower at 6.12 and 9.19 nmol/(cm(2) h) at 25 and 37 °C, respectively. The final amount of CPT released over 16 h was 10% higher at 37 °C compared to 25 °C for pSi coated with pNIPAM-co-DEGDVE (46.29% vs 35.67%), indicating that this material can be used to deliver drugs on-demand at elevated temperatures. pSi coated with pAS also displayed sustainable drug delivery profiles, but these were independent of the release temperature. These data show that sustainable and temperature-responsive delivery systems can be produced by functionalization of pSi with iCVD polymer films. Benefits of the iCVD approach include the application of the iCVD coating after drug loading without causing degradation of the drug commonly caused by exposure to factors such as solvents or high temperatures. Importantly, the iCVD process is applicable to a wide array of surfaces as the process is independent of the surface chemistry and pore size of the nanoporous matrix being coated.

  17. Research Update: Triblock copolymers as templates to synthesize inorganic nanoporous materials

    Science.gov (United States)

    Li, Yunqi; Bastakoti, Bishnu Prasad; Yamauchi, Yusuke

    2016-04-01

    This review focuses on the application of triblock copolymers as designed templates to synthesize nanoporous materials with various compositions. Asymmetric triblock copolymers have several advantages compared with symmetric triblock copolymers and diblock copolymers, because the presence of three distinct domains can provide more functional features to direct the resultant nanoporous materials. Here we clearly describe significant contributions of asymmetric triblock copolymers, especially polystyrene-block-poly(2-vinylpyridine)-block-poly(ethylene oxide) (abbreviated as PS-b-P2VP-b-PEO).

  18. Chlorine resistant desalination membranes based on directly sulfonated poly(arylene ether sulfone) copolymers

    Science.gov (United States)

    McGrath, James E.; Park, Ho Bum; Freeman, Benny D.

    2011-10-04

    The present invention provides a membrane, kit, and method of making a hydrophilic-hydrophobic random copolymer membrane. The hydrophilic-hydrophobic random copolymer membrane includes a hydrophilic-hydrophobic random copolymer. The hydrophilic-hydrophobic random copolymer includes one or more hydrophilic monomers having a sulfonated polyarylsulfone monomer and a second monomer and one or more hydrophobic monomers having a non-sulfonated third monomer and a fourth monomer. The sulfonated polyarylsulfone monomer introduces a sulfonate into the hydrophilic-hydrophobic random copolymer prior to polymerization.

  19. SYNTHESIS AND CHARACTERIZATION OF HYDROPHOBIC-HYDROPHILIC MULTIBLOCK COPOLYMERS FOR BIOMEDICAL APPLICATIONS

    Institute of Scientific and Technical Information of China (English)

    Yong Kiel Sung; Yong Joo Kim; Sung Wan Kim

    1999-01-01

    The synthesis and characterization of amphiphilic copolymers of poly(dimethyl siloxane)(PDMS),poly(ethylene oxide)(PEO), and heparin(Hep) were investigated. These multiblock copolymers were identified using 1H-NMR, FTIR, end group analysis, and sulfur elemental analysis. The multiblock copolymers were characterized by using DSC and X-ray diffractometry. The glass transition temperature,crystalline melting characteristics, annealing effect, and cold crystallization of the block copolymers were determined by DSC. The crystallinity of the block copolymers was also determined by X-ray diffraction method.

  20. Surface energies and self-assembly of block copolymers on grafted surfaces.

    Science.gov (United States)

    Trombly, David M; Pryamitsyn, Victor; Ganesan, Venkat

    2011-09-30

    We present a theoretical analysis of the self-assembly of diblock copolymers on surfaces grafted with random copolymers. Our results demonstrate that the surface energies of homopolymeric components on grafted surfaces differ from the corresponding values for self-assembled morphologies. Moreover, grafted random copolymers are shown to adapt their conformations in response to the morphology of the overlaying block copolymer film to create chemical inhomogeneities which modulate the interfacial interactions. Consequently, the surface energy differences between the different components on the grafted substrate do not serve as a useful measure to predict the stability of self-assembly of the diblock copolymer film.

  1. SYNTHESIS OF STYRENE-METHYL METHACRYLATE BLOCK COPOLYMER BY POLYAZOAMIDE AS INITIATOR

    Institute of Scientific and Technical Information of China (English)

    WANG Zhongyi; WEI Jeqing

    1996-01-01

    Polyazoamide(PAA) was used as initiator to prepare block copolymer P(MMA-b-St) by free radical polymerization. The fraction of block copolymer was about 50%. The structure of the block-copolymer was characterized by IR and the results of 1H-NMR and GPC showed that the content of the block and the molecular weight (-Mw) of the prepolymer and block copolymer could be controlled by varying the mol ratio of styrene/PAA and MMA/prepolymer. DSC and TEM results revealed that the block copolymer has two separated glass transition temperatures and phase separation within the domain structure.

  2. Studies on Preparation of Poly(3,4-Dihydroxyphenylalanine-Polylactide Copolymers and the Effect of the Structure of the Copolymers on Their Properties

    Directory of Open Access Journals (Sweden)

    Dongjian Shi

    2016-03-01

    Full Text Available Properties of copolymers are generally influenced by the structure of the monomers and polymers. For the purpose of understanding the effect of polymer structure on the properties, two kinds of copolymers, poly(3,4-dihydroxyphenylalanine-g-polylactide and poly(3,4-dihydroxyphenylalanine-b-polylactide (PDOPA-g-PLA and PDOPA-b-PLA were designed and prepared by ring-opening polymerization of lactide with pre-prepared PDOPA as the initiator and the amidation of the functional PLA and PDOPA oligomer, respectively. The molecular weight and composition of the copolymers could be adjusted by changing the molar ratio of LA and DOPA and were confirmed by gel permeation chromatography (GPC and proton nuclear magnetic resonance (1H NMR spectra. The obtained copolymers with graft and block structures showed high solubility even in common organic solvents. The effects of the graft and block structures on the thermal and degradation properties were also detected. The PDOPA-g-PLA copolymers showed higher thermal stability than the PDOPA-b-PLA copolymers, due to the PDOPA-g-PLA copolymers with regular structure and strong π-π stacking interactions among the intermolecular and intramolecular chains. In addition, the degradation results showed that the PDOPA-g-PLA copolymers and the copolymers with higher DOPA composition had quicker degradation speeds. Interestingly, both two kinds of copolymers, after degradation, became undissolved in the organic solvents because of the oxidation and crosslinking formation of the catechol groups in the DOPA units during degradation in alkaline solution. Moreover, fluorescent microscopy results showed good biocompatibility of the PDOPA-g-PLA and PDOPA-b-PLA copolymers. The PDOPA and PLA copolymers have the potential applications to the biomedical and industrial fields.

  3. Anhydric maleic functionalization and polyethylene glycol grafting of lactide-co-trimethylene carbonate copolymers

    Energy Technology Data Exchange (ETDEWEB)

    Díaz, A.; Valle, L.; Franco, L. del [Departament d' Enginyeria Química, Universitat Politècnica de Catalunya, Av. Diagonal 647, Barcelona E-08028 (Spain); Sarasua, J.R. [Department of Mining-Metallurgy Engineering and Materials Science, University of the Basque Country (UPV/EHU), Bilbao (Spain); Estrany, F. [Departament d' Enginyeria Química, Universitat Politècnica de Catalunya, Av. Diagonal 647, Barcelona E-08028 (Spain); Puiggalí, J., E-mail: Jordi.Puiggali@upc.es [Department of Mining-Metallurgy Engineering and Materials Science, University of the Basque Country (UPV/EHU), Bilbao (Spain)

    2014-09-01

    Lactide and trimethylene carbonate copolymers were successfully grafted with polyethylene glycol via previous functionalization with maleic anhydride and using N,N′-diisopropylcarbodiimide as condensing agent. Maleinization led to moderate polymer degradation. Specifically, the weight average molecular weight decreased from 36,200 to 30,200 g/mol for the copolymer having 20 mol% of trimethylene carbonate units. Copolymers were characterized by differential scanning calorimetry, thermogravimetry and X-ray diffraction. Morphology of spherulites and lamellar crystals was evaluated with optical and atomic force microscopies, respectively. The studied copolymers were able to crystallize despite the randomness caused by the trimethylene carbonate units and the lateral groups. Contact angle measurements indicated that PEG grafted copolymers were more hydrophilic than parent copolymers. This feature justified that enzymatic degradation in lipase medium and proliferation of both epithelial-like and fibroblast-like cells were enhanced. Grafted copolymers were appropriate to prepare regular drug loaded microspheres by the oil-in-water emulsion method. Triclosan release from loaded microspheres was evaluated in two media. - Highlights: • Pegylated copolymers of lactide and trimethylene carbonate have been synthesized. • Grafting with polyethylene glycol was able via maleic anhydride functionalization. • Drug-loaded microspheres could be prepared from new pegylated copolymers. • Hydrophilicity of lactide/trimethylene carbonate copolymers increased by pegylation. • New pegylated copolymers supported cell adhesion and proliferation.

  4. Polystyrene-Polylactide Bottlebrush Block Copolymer at the Air/Water Interface

    Science.gov (United States)

    Zhao, Lei; Byun, Myunghwan; Rzayev, Javid; Lin, Zhiqun

    2010-03-01

    Hydrophobic ultrahigh molecular weight bottlebrush block copolymer and linear block copolymer of polystyrene-polylactide (PS-PLA) were shown to be capable of forming Langmuir monolayers and exhibiting unique assembly behaviors at the air/water interface, which cannot be addressed by the classic theory of Langmuir monolayer of amphiphilic copolymers. New models were proposed to illustrate these intriguing surface behaviors. The self-assembled structure of Langmuir monolayer of bottlebrush block copolymer was determined by a combination of AFM measurement, thermal annealing, and enzymatic degradation experiment. To the best of our knowledge, this is among few studies on hydrophobic block copolymers at the air/water interface. As such, it not only complements the well-known models of self-assembly of amphiphilic block copolymers at the air/water interface but also expands the use of Langmuir-Blodgett (LB) technique to hydrophobic block copolymers.

  5. Dominant role of wormlike micelles in temperature-responsive viscoelastic properties of their mixtures with polymeric chains

    KAUST Repository

    Molchanov, Vyacheslav S.

    2013-03-01

    Temperature effects on the rheological properties of viscoelastic solutions containing entangled wormlike micelles of potassium oleate and hydrophobically modified polyacrylamide were studied in a wide range of polymer concentrations. A very pronounced drop of viscosity by four orders of magnitude was observed at heating from 20 to 78 °C both in the presence and in the absence of polymer indicating that the wormlike micelles are mainly responsible for this effect. The highly thermosensitive behavior was attributed to the shortening of micellar chains induced by heating. Although the decrease in viscosity is almost the same for both surfactant and surfactant/polymer systems, the absolute values of the viscosity in the presence of polymer are by few orders of magnitude higher, which is due to the formation of a common network of entangled polymer and micellar chains. As a result, the added polymer allows one to get highly temperature responsive system that keeps viscoelastic properties in a much wider range of temperatures, which makes it very promising for various practical applications. © 2012 Elsevier Inc.

  6. Flocculation of copper(II) and tetracycline from water using a novel pH- and temperature-responsive flocculants.

    Science.gov (United States)

    Yang, Zhen; Jia, Shuying; Zhuo, Ning; Yang, Weiben; Wang, Yuping

    2015-12-01

    Insufficient research is available on flocculation of combined pollutants of heavy metals and antibiotics, which widely exist in livestock wastewaters. Aiming at solving difficulties in flocculation of this sort of combined pollution, a novel pH- and temperature-responsive biomass-based flocculant, carboxymethyl chitosan-graft-poly(N-isoproyl acrylamide-co-diallyl dimethyl ammonium chloride) (denoted as CND) with two responsive switches [lower critical solution temperature (LCST) and isoelectric point (IEP)], was designed and synthesized. Its flocculation performance at different temperatures and pHs was evaluated using copper(II) and tetracycline (TC) as model contaminants. CND exhibited high efficiency for coremoval of both contaminants, whereas two commercial flocculants (polyaluminum chloride and polyacrylamide) did not. Especially, flocculation performance of the dual-responsive flocculant under conditions of temperature>LCST and IEP(contaminants)flocculation mechanism via pH monitoring, zeta potential measurements, floc properties analyses and spectral characterization indicated that, pairwise interactions among CND, copper(II) and TC were present in bridging flocculation, including charge attraction, coordination and hydrophobic effect. Based on these pairwise interactions, copper(II) and TC exerted "aid" roles to each other's removal with the existence of CND, and preferable flocculation performance was thus achieved.

  7. Comment on "Tropospheric temperature response to stratospheric ozone recovery in the 21st century" by Hu et al. (2011

    Directory of Open Access Journals (Sweden)

    M. Previdi

    2012-01-01

    Full Text Available Stratospheric ozone recovery is expected to figure prominently in twenty-first century climate change. In a recent paper, Hu et al. (2011 argue that one impact of ozone recovery will be to enhance the warming of the surface-troposphere system produced by increases in well-mixed greenhouse gases; furthermore, this enhanced warming would be strongest in the Northern Hemisphere, which is surprising since previous studies have consistently shown the effects of stratospheric ozone changes to be most pronounced in the Southern Hemisphere. Hu et al. (2011 base their claims largely on differences in the simulated temperature change between two groups of IPCC climate models, one group which included stratospheric ozone recovery in its twenty-first century simulations and a second group which did not. Both groups of models were forced with the same increases in well-mixed greenhouse gases according to the A1B emissions scenario. In the current work, we compare the surface temperature responses of the same two groups of models in a different experiment in which atmospheric CO2 was increased by 1% per year until doubling. We find remarkably similar differences in the simulated surface temperature change between the two sets of models as Hu et al. (2011 found for the A1B experiment, suggesting that the enhanced warming which they attribute to stratospheric ozone recovery is actually a reflection of different responses of the two model groups to greenhouse gas forcing.

  8. Spatial and seasonal variability of temperature responses of biochemical photosynthesis parameters and leaf nitrogen content within a Pinus densiflora crown.

    Science.gov (United States)

    Han, Qingmin; Kawasaki, Tatsuro; Nakano, Takashi; Chiba, Yukihiro

    2004-07-01

    We measured seasonal variation in area-based nitrogen concentration (N), maximum rate of carboxylation (Vcmax) and maximum rate of electron transport (Jmax) in 1-year-old needles along four first-order branches within a Pinus densiflora Sieb. & Zucc. crown, and analyzed their relationships to growth irradiance and temperature. Each leaf light environment was expressed as a ratio of the monthly mean of daily integrated photosynthetically active irradiance (Iint) for the particular needle to Iint above the canopy (Irel). Needle N decreased in the upper crown during the development of new needles, whereas it remained fairly constant in the lower crown, reflecting differences between upper and lower crown needles in their contribution to the nitrogen of new needles. Gradients of N within the crown were correlated with Irel in all seasons (r2 = 0.40-0.78). Seasonal variation in N was weakly correlated with mean daily air minimum temperatures. Both Vcmax and Jmax showed seasonal variation in all first-order branches, and decreased to their lowest values in winter. The gradients of Vcmax and Jmax within the crown were not correlated with Irel in some seasons, but were correlated with changes in N in most months (r2 = 0.33-0.75), except in the winter. Furthermore, the regression slope of the relationship between N and Vcmax and the temperature response of Vcmax and Jmax exhibited seasonal variation.

  9. Characterization and micellization of a poloxamer block copolymer

    DEFF Research Database (Denmark)

    Hvidt, S.; Pedersen, Walther Batsberg

    2007-01-01

    Several poloxamers that are symmetrical EPE block copolymers (E and P are ethylene and propylene oxide, respectively) have been characterized by size exclusion chromatography on Superose columns in water. The poloxamers contain between 12 and 26 wt% of smaller-size UV-absorbing impurities...

  10. Bioactive, mechanically favorable, and biodegradable copolymer nanocomposites for orthopedic applications.

    Science.gov (United States)

    Victor, Sunita Prem; Muthu, Jayabalan

    2014-06-01

    We report the synthesis of mechanically favorable, bioactive, and biodegradable copolymer nanocomposites for potential bone applications. The nanocomposites consist of in situ polymerized biodegradable copolyester with hydroxyapatite (HA). Biodegradable copolyesters comprise carboxy terminated poly(propylene fumarate) (CT-PPF) and poly(trimethylol propane fumarate co mannitol sebacate) (TF-Co-MS). Raman spectral imaging clearly reveals a uniform homogenous distribution of HA in the copolymer matrix. The mechanical studies reveal that improved mechanical properties formed when crosslinked with methyl methacrylate (MMA) when compared to N-vinyl pyrrolidone (NVP). The SEM micrographs of the copolymer nanocomposites reveal a serrated structure reflecting higher mechanical strength, good dispersion, and good interfacial bonding of HA in the polymer matrix. In vitro degradation of the copolymer crosslinked with MMA is relatively more than that of NVP and the degradation decreases with an increase in the amount of the HA filler. The mechanically favorable and degradable MMA based nanocomposites also have favorable bioactivity, blood compatibility, cytocompatibility and cell adhesion. The present nanocomposite is a more promising material for orthopedic applications.

  11. Synthesis and photooxidation of styrene copolymer bearing camphorquinone pendant groups

    Directory of Open Access Journals (Sweden)

    Branislav Husár

    2012-03-01

    Full Text Available (±-10-Methacryloyloxycamphorquinone (MCQ was synthesized from (±-10-camphorsulfonic acid either by a known seven-step synthetic route or by a novel, shorter five-step synthetic route. MCQ was copolymerized with styrene (S and the photochemical behavior of the copolymer MCQ/S was compared with that of a formerly studied copolymer of styrene with monomers containing the benzil (BZ moiety (another 1,2-dicarbonyl. Irradiation (λ > 380 nm of aerated films of styrene copolymers with monomers containing the BZ moiety leads to the insertion of two oxygen atoms between the carbonyl groups of BZ and to the formation of benzoyl peroxide (BP as pendant groups on the polymer backbone. An equivalent irradiation of MCQ/S led mainly to the insertion of only one oxygen atom between the carbonyl groups of camphorquinone (CQ and to the formation of camphoric anhydride (11 covalently bound to the polymer backbone. While the decomposition of pendant BP groups formed in irradiated films of styrene copolymers with pendant BZ groups leads to crosslinking, only small molecular-weight changes in irradiated MCQ/S were observed.

  12. Pressure and temperature effects in homopolymer blends and diblock copolymers

    DEFF Research Database (Denmark)

    Frielinghaus, H.; Schwahn, D.; Mortensen, K.;

    1997-01-01

    contribution of the Flory-Huggins parameter at larger pressure fields. This gives rise to a shift of the phase boundaries to higher temperatures and to a strong reduction of the Ginzburg parameter. Diblock copolymers show a different behavior. Neither the entropic term of the Flory-Huggins parameter nor...

  13. Unexpected phase behavior of an asymmetric diblock copolymer

    DEFF Research Database (Denmark)

    Papadakis, Christine Maria; Almdal, Kristoffer; Mortensen, Kell;

    1999-01-01

    We report on measurements of the transmitted depolarized light intensity and on small-angle neutron scattering (SANS) measurements on a compositionally asymmetric poly(ethylene propylene)-poly(dimethylsiloxane) diblock copolymer studied in the bulk. SANS measurements were made both on isotropic a...

  14. Striped, Ellipsoidal Particles by Controlled Assembly of Diblock Copolymers

    Science.gov (United States)

    2013-04-17

    chloroform solutions were then mixed with deionized water containing 0.1 wt % amphiphilic cationic surfactant (CTAB), emulsified by ultrasonication, and...This block copolymer solution was emulsified by ultrasonication in 15 mL of deionized water containing CTAB (Sigma-Aldrich, 0.1 wt %) as a

  15. Copolymer-in-oil phantom materials for elastography.

    Science.gov (United States)

    Oudry, J; Bastard, C; Miette, V; Willinger, R; Sandrin, L

    2009-07-01

    Phantoms that mimic mechanical and acoustic properties of soft biological tissues are essential to elasticity imaging investigation and to elastography device characterization. Several materials including agar/gelatin, polyvinyl alcohol and polyacrylamide gels have been used successfully in the past to produce tissue phantoms, as reported in the literature. However, it is difficult to find a phantom material with a wide range of stiffness, good stability over time and high resistance to rupture. We aim at developing and testing a new copolymer-in-oil phantom material for elastography. The phantom is composed of a mixture of copolymer, mineral oil and additives for acoustic scattering. The mechanical properties of phantoms were evaluated with a mechanical test instrument and an ultrasound-based elastography technique. The acoustic properties were investigated using a through-transmission water-substituting method. We showed that copolymer-in-oil phantoms are stable over time. Their mechanical and acoustic properties mimic those of most soft tissues: the Young's modulus ranges from 2.2-150 kPa, the attenuation coefficient from 0.4-4.0 dB.cm(-1) and the ultrasound speed from 1420-1464 m/s. Their density is equal to 0.90 +/- 0.04 g/cm3. The results suggest that copolymer-in-oil phantoms are attractive materials for elastography.

  16. Multiple ordered phases in a block copolymer melt

    DEFF Research Database (Denmark)

    Almdal, K.; Koppi, K.A.; Bates, F.S.;

    1992-01-01

    A poly(ethylenepropylene)-poly(ethylethylene) (PEP-PEE) diblock copolymer containing 65% by volume PEP was investigated using small-angle neutron scattering (SANS) and rheological measurements. Four distinct phases have been identified as a function of temperature: three ordered phases at low tem...

  17. Organisation and shape of micellar solutions of block-copolymers

    NARCIS (Netherlands)

    Gaspard, J.P.; Creutz, S.; Bouchat, P.; Jerome, R.; Cohen Stuart, M.A.

    1997-01-01

    Diblock copolymers of polymethacrylic acid sodium salt, forming the hair, and styrene derivatives have been studied in aqueous solutions by SANS and SAXS. The influence of both the chemical nature and the length of the hydrophobic bloxk on the size and shape of micelles have been investigated. The m

  18. Controlled Synthesis of Fluorinated Copolymers with Pendant Sulfonates

    DEFF Research Database (Denmark)

    Dimitrov, Ivaylo; Jankova Atanasova, Katja; Hvilsted, Søren

    2008-01-01

    Novel fluorinated copolymers of different architectures and bearing sulfopropyl groups were synthesized by atom transfer radical polymerization (ATRP) of aromatic fluorinated monomers and two modification reactions performed on the polymer chain - demethylation followed by sulfopropylation. As a ...... characterized by size-exclusion chromatography, FTIR and IH NMR spectroscopy. Their thermal properties were investigated by differential scanning calorimetry and thermal gravimetric analyses....

  19. Free energy of a copolymer in a micro-emulsion

    CERN Document Server

    Hollander, Frank den

    2012-01-01

    In this paper we consider a two-dimensional model of a copolymer consisting of a random concatenation of hydrophilic and hydrophobic monomers, immersed in a micro-emulsion of random droplets of oil and water. The copolymer interacts with the micro-emulsion through an interaction Hamiltonian that favors matches and disfavors mismatches between the monomers and the solvents, in such a way that the interaction with the oil is stronger than with the water. The configurations of the copolymers are directed self-avoiding paths in which only steps up, down and right are allowed. The configurations of the micro-emulsion are square blocks with oil and water arranged in percolation-type fashion. The only restriction imposed on the path is that in every column of blocks its vertical displacement on the block scale is bounded. The way in which the copolymer enters and exits successive columns of blocks is a directed self-avoiding path as well, but on the block scale. We refer to this path as the coarse-grained self-avoid...

  20. CHARACTERIZATION OF RADIATION GRAFT COPOLYMER OF INORGANIC COMPOUND ONTO ALKENE

    Institute of Scientific and Technical Information of China (English)

    ZhangWanxi; CheJitai; 等

    1995-01-01

    In this paper,the radiation graft copolymer of MgO,SiO2 and Y-molecular sieve onto organic compounds,such as methacrylate,styrene and acrylomitrile obtained by per-radiation method were characterized by X-ray diffraction,pyrolysis gas chromatography,GPC and X-ray photoelectron spectroscopy.

  1. Copolymer adsorption and the effect on colloidal stability.

    NARCIS (Netherlands)

    Bijsterbosch, H.D.

    1998-01-01

    The main aim of the work described in this thesis is to study the effect of different types of copolymers on the stability of aqueous oxide dispersions. Such dispersions are a major component in water-borne paints. In order to obtain a better insight in steric stabilisation we first investigated the

  2. Bicontinuous Porous Carbon Films Templated with ABC Triblock Copolymers

    Science.gov (United States)

    Cavicchi, Kevin; Deng, Guodong; Vogt, Bryan

    2014-03-01

    Mesoporous carbons are useful for a range of applications such as separation and catalysis. A route to prepare porous materials is through cooperative self-assembly of a carbon precursor (e.g. phenolic resin) and a block copolymer, in which the precursor is selectively soluble, to drive mesophase formation. Typical soft templating uses AB or ABA block copolymers, which form classical morphologies, such as spheres, cylinders, and lamellae. Switching to an ABC type block copolymer provides greater flexibility in the design of the morphology potentially opening up larger processing windows for complex structures, such as bicontinuous morphologies. This presentation will discuss efforts to prepare bicontinuous porous carbon thin films using an ABC triblock copolymer of poly(ethylene oxide)-block-poly(ethyl acrylate)-block-polystyrene via spin-coating and a series of thermal annealing steps. It will be shown that direct thermal annealing can produce high porosity (~60%) carbon fiber networks. In addition, adding a solvent annealing step prior to the thermal annealing steps is able to produce longer range order structures with a small window of an ordered bicontinuous morphology. These high porosity films with organized fibers are promising for energy and separation applications.

  3. In vivo biocompatibility of radiation crosslinked acrylamide copolymers

    Energy Technology Data Exchange (ETDEWEB)

    Saraydin, Dursun E-mail: saraydin@cumhuriyet.edu.tr; Uenver-Saraydin, Serpil; Karadag, Erdener; Koptagel, Emel; Gueven, Olgun

    2004-04-01

    In vitro swelling and in vivo biocompatibility of radiation crosslinked acrylamide copolymers such as acrylamide/crotonic acid (AAm/CA) and acrylamide/itaconic acid (AAm/IA) were studied. The swelling kinetics of acrylamide copolymers were performed in distilled water, human serum and some simulated physiological fluids such as phosphate buffer, pH 7.4, glycine-HCl buffer, pH 1.1, physiological saline solution, and some swelling and diffusion parameters have been calculated. AAm/CA and AAm/IA hydrogels were subcutaneously implanted in rats for up to 10 weeks and the immediate short- and long-term tissue response to these implants were investigated. Histological analysis indicated that tissue reaction at the implant site progressed from an initial acute inflammatory response. No necrosis, tumorigenesis or infection was observed at the implant site up to 10 weeks. The radiation crosslinked AAm/CA and AAm/IA copolymers were found well tolerated, non-toxic and highly biocompatible. However, AAm/IA copolymer was not found to be compatible biomaterials, because one of the AAm/IA samples was disintegrated into small pieces in the rat.

  4. Micellization kinetics in block copolymer solutions : Scaling model

    NARCIS (Netherlands)

    Dormidontova, EE

    1999-01-01

    The kinetics of micelle evolution of diblock copolymers from unimers toward the equilibrium state is studied analytically on the basis of consideration of the kinetic equations. The association/dissociation rate constants for unimer insertion/expulsion and micelle fusion/fission are calculated by ap

  5. Heparin-containing block copolymers, Part I: Surface characterization

    NARCIS (Netherlands)

    Vulić, I.; Pijpers, A.P.; Okano, T.; Kim, S.W.; Feijen, J.

    1993-01-01

    Newly synthesized heparin-containing block copolymers, consisting of a hydrophobic block of polystyrene (PS), a hydrophilic spacer-block of poly(ethylene oxide) (PEO) and covalently bound heparin (Hep) as bioactive block, were coated on aluminium, glass, polydimethylsiloxane (PDMS), PS or Biomer sub

  6. Nanoporous Network Channels from Self-Assembled Triblock Copolymer Supramolecules

    NARCIS (Netherlands)

    du Sart, Gerrit Gobius; Vukovic, Ivana; Vukovic, Zorica; Polushkin, Evgeny; Hiekkataipale, Panu; Ruokolainen, Janne; Loos, Katja; ten Brinke, Gerrit

    2011-01-01

    Supramolecular complexes of a poly(tert-butoxystyrene)-block-polystyrene-block-poly(4-vinylpyridine) triblock copolymers and less than stoichiometric amounts of pentadecylphenol (PDP) are shown to self-assemble into a core-shell gyroid morphology with the core channels formed by the hydrogen-bonded

  7. 21 CFR 177.1211 - Cross-linked polyacrylate copolymers.

    Science.gov (United States)

    2010-04-01

    ... adjuvant substances required in the production of such copolymers. The optional adjuvant substances may... absorbent pad or in any suitable flexible porous article, (such as a “tea bag” or infuser), under an applied... are limited to use as a fluid absorbent in food-contact materials used in the packaging of frozen...

  8. A NEW PLLA PCL COPOLYMER FOR NERVE REGENERATION

    NARCIS (Netherlands)

    DENDUNNEN, WFA; SCHAKENRAAD, JM; ZONDERVAN, GJ; PENNINGS, AJ; VANDERLEI, B; ROBINSON, PH

    1993-01-01

    The aim of this study is to evaluate the functional and cell biological applicability of a two-ply nerve guide constructed of a PLLA/PCL (i.e. poly-L-lactide and poly-epsilon-caprolactone) copolymer. To do so, we performed a cytotoxicity test, a subcutaneous biodegradation test and an in situ implan

  9. Metal nanoparticle - block copolymer composite assembly and disassembly

    NARCIS (Netherlands)

    Li, Z.H.; Sai, H.; Warren, S.C.; Kamperman, M.M.G.; Arora, H.; Gruner, S.M.; Wiesner, U.

    2009-01-01

    Ligand-stabilized platinum nanoparticles (Pt NPs) were self-assembled with poly(isoprene-block-dimethylaminoethyl methacrylate) (PI-b-PDMAEMA) block copolymers to generate organic-inorganic hybrid materials. High loadings of NPs in hybrids were achieved through usage of N,N-di-(2-(allyloxy)ethyl)-N-

  10. Synthesis and properties of acrylic copolymers for ocular implants

    Science.gov (United States)

    Reboul, Adam C.

    There is a need for flexible polymers with higher refractive index and extended UV absorbing properties for improved intraocular lenses (IOLs). This research was devoted to the synthesis of new acrylic copolymers for foldable IOLs and to studies concerning IOL polymer properties. New polymers were synthesized from phenylated acrylates copolymerized with N-vinyl carbazole derivatives using bulk free radical addition methods. The copolymers had low Tg values, high refractive index, and were flexible. The N-vinyl carbazole derivatives were characterized by NMR and copolymers were characterized by DSC, UV-Vis, and refractometry. New phenothiazine based UV absorbers with high extinction coefficients were also synthesized for incorporation into ocular materials. Patent disclosures on UV absorbers and high refractive index polymers were prepared. A so called "glistening" phenomenon that occurs in all foldable intraocular lenses currently in clinical use is poorly understood and was studied. Research on this microvoid forming behavior included studies and development of methods to inhibit glistening in low Tg acrylic based copolymers. Glistenings were characterized using SEM and optical microscopy. A novel technique for inhibiting glistening was found and a patent disclosure was prepared.

  11. Responsive copolymers for enhanced petroleum recovery. Annual report

    Energy Technology Data Exchange (ETDEWEB)

    McCormick, C.; Hester, R.

    1994-08-01

    A coordinated research program involving synthesis, characterization, and rheology has been undertaken to develop advanced polymer system which should be significantly more efficient than polymers presently used for mobility control and conformance. Unlike the relatively inefficient, traditional EOR polymers, these advanced polymer systems possess microstructural features responsive to temperature, electrolyte concentration, and shear conditions. Contents of this report include the following chapters. (1) First annual report responsive copolymers for enhanced oil recovery. (2) Copolymers of acrylamide and sodium 3-acrylamido-3-methylbutanoate. (3) Terpolymers of NaAMB, Am, and n-decylacrylamide. (4) Synthesis and characterization of electrolyte responsive terpolymers of acrylamide, N-(4-butyl)phenylacrylamide, and sodium acrylate, sodium-2-acrylamido-2-methylpropanesulphonate or sodium-3-acrylamido-3-methylbutanoate. (5) Synthesis and solution properties of associative acrylamido copolymers with pyrensulfonamide fluorescence labels. (6) Photophysical studies of the solution behavior of associative pyrenesulfonamide-labeled polyacrylamides. (7) Ampholytic copolymers of sodium 2-(acrylamido)-2-methylpropanesulfonate with [2-(acrylamido)-2-methypropyl]trimethylammonium chloride. (8) Ampholytic terpolymers of acrylamide with sodium 2-acrylamido-2-methylpropanesulphoante and 2-acrylamido-2-methylpropanetrimethyl-ammonium chloride and (9) Polymer solution extensional behavior in porous media.

  12. Block copolymer-nanoparticle hybrid self-assembly

    KAUST Repository

    Hoheisel, Tobias N.

    2015-01-01

    © 2014 Published by Elsevier Ltd. Polymer-inorganic hybrid materials provide exciting opportunities as they may display favorable properties from both constituents that are desired in applications including catalysis and energy conversion and storage. For the preparation of hybrid materials with well-defined morphologies, block copolymer-directed nanoparticle hybrids present a particularly promising approach. As will be described in this review, once the fundamental characteristics for successful nanostructure formation at or close to the thermodynamic equilibrium of these nanocomposites are identified, the approach can be generalized to various materials classes. In addition to the discussion of recent materials developments based on the use of AB diblock copolymers as well as ABC triblock terpolymers, this review will therefore emphasize progress in the fundamental understanding of the underlying formation mechanisms of such hybrid materials. To this end, critical experiments for, as well as theoretical progress in the description of these nanostructured block copolymer-based hybrid materials will be discussed. Rather than providing a comprehensive overview, the review will emphasize work by the Wiesner group at Cornell University, US, on block copolymer-directed nanoparticle assemblies as well as their use in first potential application areas. The results provide powerful design criteria for wet-chemical synthesis methodologies for the generation of functional nanomaterials for applications ranging from microelectronics to catalysis to energy conversion and storage.

  13. Optical fibre Bragg grating recorded in TOPAS cyclic olefin copolymer

    DEFF Research Database (Denmark)

    Johnson, I.P.; Yuan, Scott Wu; Stefani, Alessio

    2011-01-01

    A report is presented on the inscription of a fibre Bragg grating into a microstructured polymer optical fibre fabricated from TOPAS cyclic olefin copolymer. This material offers two important advantages over poly (methyl methacrylate), which up to now has formed the basis for polymer fibre Bragg...

  14. Biocompatibility of poly (DL-lactic acid/glycine) copolymers

    NARCIS (Netherlands)

    Schakenraad, J.M.; Dijkstra, P.J.

    1991-01-01

    In this review the authors discuss the polymer chemical, physical and cell biological aspects of poly (DL-lactic acid/glycine) copolymers, both in vitro and in vivo. The mechanism and rate of degradation and the degree of foreign body reaction were evaluated as a function of the molecular compositi

  15. Structural study of symmetric diblock copolymer thin films

    DEFF Research Database (Denmark)

    Gadegaard, Nikolaj

    2000-01-01

    Thin diblock copolymer film have been investigated by x-ray and neutron reflectivity as well as small angle x-ray and neutron scattering. Two model systems have been investigated. PS-PDMS (25 kg/mol-25 kg/mol), which has a glass transition temperature ofca. 100 deg.C for the PS-block. This means...

  16. Control of Block Copolymer Morphology through End-functional Groups

    Science.gov (United States)

    Jo, Gyuha; Park, Moon Jeong

    2014-03-01

    Recently, poly(ethylene oxide) (PEO)-containing polymer electrolytes have attracted significant attention to be applied for lithium batteries. As the realization of high mechanical strength from the polymer electrolyte becomes of critical importance in high-energy lithium batteries, much effort has been devoted to developing PEO-based block copolymers comprising mechanically robust polymer chains. Interest in this topic has been further stimulated by multiple observations of significant electrolytic conductivity enhancement imparted by microphase separation of block copolymers. In the present study, we report an intriguing methodology for modulating the morphology of poly(styrene-ethylene oxide) (PS-PEO) block copolymers with a single ionic group tethered at the chain end of PEO. Unique intra- and inter-chain interactions deduced from the end functional group afforded enriched nanostructures, i.e. disorder, lamellae, hexagonal cylinder, and gyroid, with significant differences in conductivities depending on lithium salt concentration. In particular, a gyorid morphology with a twofold-enhanced lithium ion transport efficiency was found for the end-functionalized PS-PEO block copolymer, attributed to the structural advantages of the gyroid having co-continuous ionic channels.

  17. HIGH-STRENGTH POLY(METH)ACRYLAMIDE COPOLYMER HYDROGELS

    NARCIS (Netherlands)

    WIERSMA, JA; SOS, M; PENNINGS, AJ

    1994-01-01

    The hydrogels described here are copolymers of acrylamide and methacrylamide highly cross-linked with piperazine diacrylamide or 4,7,10-trioxa-1,13-tridecanediamine diacrylamide by radical polymerisation in highly concentrated aqueous and aqueous gelatin solutions. The hydrogels were characterised b

  18. Synthesis and characterization of ferrocene containing block copolymers

    DEFF Research Database (Denmark)

    Chernyy, Sergey; Wang, Zhongli; Kirkensgaard, Jacob Judas Kain

    2017-01-01

    Narrowly dispersed diblock copolymers containing poly(methyl methacrylate) [PMMA] or poly(nonafluorohexyl methacrylate) [PF9MA] as the first block and poly(ferrocenylmethyl methacrylate) [PFMMA] as the second block, were prepared by anionic polymerization for the first time. Disordered bulk morph...

  19. Physical properties of copolymer layers : Morphology, forces and rheology

    NARCIS (Netherlands)

    Stamouli, Amalia

    2000-01-01

    The aim of this thesis was to get a better understanding of the normal and lateral interactions of adsorbed diblock copolymer monolayers. The goal was to couple these interaction with the microscopic structural properties of the polymer layers. Therefore, two instruments were used, the Atomic Force

  20. Physical properties of copolymer layers : morphology, forces and rheology

    NARCIS (Netherlands)

    Stamouli, Amalia

    2000-01-01

    The aim of this thesis was to get a better understanding of the normal and lateral interactions of adsorbed diblock copolymer monolayers. The goal was to couple these interaction with the microscopic structural properties of the polymer layers. Therefore, two instruments were used, the Atomic Force

  1. Meter-long multiblock copolymer microfibers via interfacial bioorthogonal polymerization.

    Science.gov (United States)

    Liu, Shuang; Zhang, Han; Remy, Roddel A; Deng, Fei; Mackay, Michael E; Fox, Joseph M; Jia, Xinqiao

    2015-05-01

    High-molecular-weight multiblock copolymers are synthesized as robust polymer fibers via interfacial bioorthogonal polymerization employing the rapid cycloaddition of s-tetrazines with strained trans-cyclooctenes. When cell-adhesive peptide is incorporated in the tetrazine monomer, the resulting protein-mimetic polymer fibers provide guidance cues for cell attachment and elongation.

  2. Effects of copolymer component on the properties of phosphorylcholine micelles

    Directory of Open Access Journals (Sweden)

    Wu Z

    2017-01-01

    Full Text Available Zhengzhong Wu,1 Mengtan Cai,1 Jun Cao,2 Jiaxing Zhang,1 Xianglin Luo1,3 1College of Polymer Science and Engineering, 2National Engineering Research Center for Biomaterials, 3State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu, People’s Republic of China Abstract: Zwitterionic polymers have unique features, such as good compatibility, and show promise in the application of drug delivery. In this study, the zwitterionic copolymers, poly(ε-caprolactone-b-poly(2-methacryloyloxyethyl phosphorylcholine with disulfide (PCL-ss-PMPC or poly(ε-caprolactone-b-poly(2-methacryloyloxyethyl phosphorylcholine or without disulfide (PCL-PMPC and with different block lengths in PCL-ss-PMPC, were designed. The designed copolymers were obtained by a combination of ring-opening polymerization and atom transferring radical polymerization. The crystallization properties of these polymers were investigated. The micelles were prepared based on the obtained copolymers with zwitterionic phosphorylcholine as the hydrophilic shell and PCL as the hydrophobic core. The size distributions of the blank micelles and the doxorubicin (DOX-loaded micelles were uniform, and the micelle diameters were <100 nm. In vitro drug release and intracellular drug release results showed that DOX-loaded PCL-ss-PMPC micelles could release drugs faster responding to the reduction condition and the intracellular microenvironment in contrast to PCL-PMPC micelles. Moreover, in vitro cytotoxicity evaluation revealed that the designed copolymers possessed low cell toxicity, and the inhibiting effect of DOX-loaded phosphorylcholine micelles to tumor cells was related to the components of these copolymers. These results reveal that the reduction-responsive phosphorylcholine micelles with a suitable ratio of hydrophilic/hydrophobic units can serve as promising drug carriers. Keywords: zwitterionic, reduction-sensitive, disulfide, phosphorylcholine

  3. QSPR Analysis of Copolymers by Recursive Neural Networks: Prediction of the Glass Transition Temperature of (Meth)acrylic Random Copolymers.

    Science.gov (United States)

    Bertinetto, Carlo Giuseppe; Duce, Celia; Micheli, Alessio; Solaro, Roberto; Tiné, Maria Rosaria

    2010-09-17

    The glass transition temperature (Tg ) of acrylic and methacrylic random copolymers was investigated by means of Quantitative Structure-Property Relationship (QSPR) methodology based on Recursive Neural Networks (RNN). This method can directly take molecular structures as input, in the form of labelled trees, without needing predefined descriptors. It was applied to three data sets containing up to 615 polymers (340 homopolymers and 275 copolymers). The adopted representation was able to account for the structure of the repeating unit as well as average macromolecular characteristics, such as stereoregularity and molar composition. The best result, obtained on a data set focused on copolymers, showed a Mean Average Residual (MAR) of 4.9 K, a standard error of prediction (S) of 6.1 K and a squared correlation coefficient (R(2) ) of 0.98 for the test set, with an optimal rate with respect to the training error. Through the treatment of homopolymers and copolymers both as separated and merged data sets, we also showed that the proposed approach is particularly suited for generalizing prediction of polymer properties to various types of chemical structures in a uniform setting.

  4. Plantar Temperature Response to Walking in Diabetes with and without Acute Charcot: The Charcot Activity Response Test

    Directory of Open Access Journals (Sweden)

    Bijan Najafi

    2012-01-01

    Full Text Available Objective. Asymmetric plantar temperature differences secondary to inflammation is a hallmark for the diagnosis and treatment response of Charcot foot syndrome. However, little attention has been given to temperature response to activity. We examined dynamic changes in plantar temperature (PT as a function of graduated walking activity to quantify thermal responses during the first 200 steps. Methods. Fifteen individuals with Acute Charcot neuroarthropathy (CN and 17 non-CN participants with type 2 diabetes and peripheral neuropathy were recruited. All participants walked for two predefined paths of 50 and 150 steps. A thermal image was acquired at baseline after acclimatization and immediately after each walking trial. The PT response as a function of number of steps was examined using a validated wearable sensor technology. The hot spot temperature was identified by the 95th percentile of measured temperature at each anatomical region (hind/mid/forefoot. Results. During initial activity, the PT was reduced in all participants, but the temperature drop for the nonaffected foot was 1.9 times greater than the affected side in CN group (P=0.04. Interestingly, the PT in CN was sharply increased after 50 steps for both feet, while no difference was observed in non-CN between 50 and 200 steps. Conclusions. The variability in thermal response to the graduated walking activity between Charcot and non-Charcot feet warrants future investigation to provide further insight into the correlation between thermal response and ulcer/Charcot development. This stress test may be helpful to differentiate CN and its response to treatment earlier in its course.

  5. Temperature response of photosynthesis in C3, C4, and CAM plants: temperature acclimation and temperature adaptation.

    Science.gov (United States)

    Yamori, Wataru; Hikosaka, Kouki; Way, Danielle A

    2014-02-01

    Most plants show considerable capacity to adjust their photosynthetic characteristics to their growth temperatures (temperature acclimation). The most typical case is a shift in the optimum temperature for photosynthesis, which can maximize the photosynthetic rate at the growth temperature. These plastic adjustments can allow plants to photosynthesize more efficiently at their new growth temperatures. In this review article, we summarize the basic differences in photosynthetic reactions in C3, C4, and CAM plants. We review the current understanding of the temperature responses of C3, C4, and CAM photosynthesis, and then discuss the underlying physiological and biochemical mechanisms for temperature acclimation of photosynthesis in each photosynthetic type. Finally, we use the published data to evaluate the extent of photosynthetic temperature acclimation in higher plants, and analyze which plant groups (i.e., photosynthetic types and functional types) have a greater inherent ability for photosynthetic acclimation to temperature than others, since there have been reported interspecific variations in this ability. We found that the inherent ability for temperature acclimation of photosynthesis was different: (1) among C3, C4, and CAM species; and (2) among functional types within C3 plants. C3 plants generally had a greater ability for temperature acclimation of photosynthesis across a broad temperature range, CAM plants acclimated day and night photosynthetic process differentially to temperature, and C4 plants was adapted to warm environments. Moreover, within C3 species, evergreen woody plants and perennial herbaceous plants showed greater temperature homeostasis of photosynthesis (i.e., the photosynthetic rate at high-growth temperature divided by that at low-growth temperature was close to 1.0) than deciduous woody plants and annual herbaceous plants, indicating that photosynthetic acclimation would be particularly important in perennial, long-lived species that

  6. Topology and Shape Control for Assemblies of Block Copolymer Blends in Solution

    KAUST Repository

    Moreno, Nicolas

    2015-10-27

    We study binary blends of asymmetric diblock copolymers (AB/AC) in selective solvents with a mesoscale model. We investigate the morphological transitions induced by the concentration of the AC block copolymer and the difference in molecular weight between the AB and AC copolymers, when segments B and C exhibit hydrogen-bonding interactions. To the best of our knowledge, this is the first work modeling mixtures of block copolymers with large differences in molecular weight. The coassembly mechanism localizes the AC molecules at the interface of A and B domains and induces the swelling of the B-rich domains. The coil size of the large molecular weight block copolymer depends only on the concentration of the short block copolymer (AC or AB), regardless of the B–C interactions. However, the B–C interactions control the morphological transitions that occur in these blends.

  7. Synthesis and Characterization of Poly(L-lactide-co-ε-caprolactone) Copolymers

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    A series of random and block poly (L-lactide-co-ε-caprolactone) (PCLA) copolymers with different composition are prepared using starmous octaoate as catalyst. The effects of the amount of initiator on the intrinsic viscosity have been investigated. The structure of the PCLA copolymers is characterized by means of nuclear magnetic resonance (NMR), Fourier transform infrared spectrum (FTIR), differential scanning calorimetry(DSC) and X- ray diffraction (XRD) methods. It is shown that the synthesis condition and the composition of copolymers have obvious influence on the structure of PCLA copolymers. Hydrolytic degradation of the copolymers in a PBS solution of pH 7.4 at 37.0 ℃ shows that the copolymers of different compositions degrade at different rates .

  8. Electrochemical behavior and conductivity measurements of electropolymerized selenophene-based copolymers

    Directory of Open Access Journals (Sweden)

    Alakhras Fadi

    2015-03-01

    Full Text Available Electrochemical copolymerization of selenophene and thiophene was performed at a constant electrode potential. The obtained homopolymer films and copolymers were studied and characterized with cyclic voltammetry and conductivity measurements, from which conductivity values around 13.35 S · cm-1 were determined. The influence of the applied electropolymerization potential and the monomer feed ratio of selenophene and thiophene on the copolymers properties was investigated. The obtained copolymers showed good stability of the redox activity in an acetonitrile-based electrolyte solution. At higher polymerization potentials and at higher concentrations of thiophene in the feed, more thiophene units were incorporated into the copolymer chain. The conductivities of the copolymers were between those of homopolymers, implying that oxidation of both monomers was possible and the copolymer chains might accordingly be composed of both selenophene and thiophene units.

  9. Interaction between PEO-PPO-PEO copolymers and a hexapeptide in aqueous solutions.

    Science.gov (United States)

    Jia, Lianwei; Guo, Chen; Xiang, Junfeng; Wang, Ning; Yang, Liangrong; Tang, Yalin; Liu, Huizhou

    2012-01-24

    Interaction between PEO-PPO-PEO copolymers and a hexapeptide, growth hormone releasing peptide-6 (GHRP-6), was investigated by NMR to study the potential use of the copolymers in peptide drug delivery. (1)H NMR and nuclear Overhauser effect spectroscopy (NOESY) measurements determined that PO methyl protons interacted with methyl protons of the Ala moiety, aromatic protons of the Trp moiety, and some of the Phe aromatic protons. The Lys moiety and part of the Phe moiety entered the hydrophilic EO environment via hydrogen bonding. PEO-PPO-PEO copolymers and the peptide formed a complex in 1:1 stoichiometry. Binding constants between copolymers and GHRP-6 were determined, and it was indicated that the copolymers containing more EO and PO units will lead to greater affinity with the peptide. Isothermal titration calorimetry (ITC) measurements confirmed the results of NMR experiments. This study indicates that PEO-PPO-PEO copolymers have great potential in delivering peptide drugs.

  10. Novel fluorescent amphiphilic block copolymers: photophysics behavior and interactions with DNA

    Directory of Open Access Journals (Sweden)

    2007-06-01

    Full Text Available In this study, novel amphiphilic fluorescent copolymers poly(N-vinylpyrrolidone-b-poly(N-methacryloyl-N'-(α-naphthylthiourea (PVP-b-PNT were synthesized via ATRP with poly(N-vinylpyrrolidone-Cl as macroinitiator and N-methacryloyl-N'-α-naphthylthiourea (NT as hydrophobic segment. PVP-b-PNT copolymers were characterized by 1H NMR, GPC-MALLS and fluorescence measurements. The aggregation behavior of PVP-b-PNT in water was investigated by transmission electron microscope (TEM and dynamic light scattering (DLS measurement. The photophysics behavior of PVP-b-PNT showed that block copolymer formed strong excimer. The interaction of DNA with the block copolymer made the excimer of block copolymer quench. The cytotoxicity result of PVP-b-PNT in cell culture in vitro indicated that this copolymer PVP-b-PNT had good biocompatibility.

  11. Synthesis and Characterization of a Systematic Series of All-Conjugated Diblock Copolymers

    Science.gov (United States)

    Smith, Kendall; Verduzco, Rafael

    2012-02-01

    All-conjugated block copolymers can potentially self-assemble into nanoscale structures beneficial for charge separation and transport, but due to synthetic challenges a comprehensive investigation of all-conjugated block copolymers has not been carried out . Here we detail a novel synthetic approach to all-conjugated block copolymers and characterize the structure of a systematic series of materials. The materials are prepared via copper-catalyzed azide-alkyne click chemistry followed by selective solvent removal of homopolymer impurities. This allows us to readily vary the molecular weight and type of each block in order to systematically study the properties of a family of block copolymers. As a system relevant to organic photovoltatics, we investigate a series of diblock copolymers based on poly(9,9-dioctyl-fluorene) and poly(3-alkylthiophene). This series of block copolymers is characterized with respect to phase behavior, including micro-phase segregation and crystallinity, optical properties, and charge mobilities.

  12. Polymer Electrolyte Membrane Fuel Cell Performance of a Sulfonated Poly(Arylene Ether Benzimidazole Copolymer Membrane

    Directory of Open Access Journals (Sweden)

    Hasan Ferdi Gerçel

    2016-01-01

    Full Text Available Disodium-3,3′-disulfonate-4,4′-dichlorodiphenylsulfone (SDCDPS and 5,5′-bis[2-(4-hydroxyphenylbenzimidazole] (HPBI monomers were synthesized. Binding these monomers via nucleophilic aromatic polycondensation reaction, a sulfonated poly(arylene ether benzimidazole copolymer was synthesized. Structures of monomers and copolymer were confirmed by proton nuclear magnetic resonance spectroscopy (1H NMR and Fourier transform infrared (FTIR spectroscopy analyses. Proton exchange membrane was prepared by dissolving copolymer in dimethylacetamide (DMAc and casting onto a glass plate. Copolymer membrane was doped with sulfuric acid to ensure proton exchange character. Single cell performance of the copolymer membrane was tested in a polymer electrolyte membrane fuel cell test station. The highest power density of the membrane was measured as 23.7 mW cm−2 at 80°C. Thermogravimetric analysis (TGA showed that as the degree of disulfonation is increased thermal stability of the copolymer is increased.

  13. Effect of sequence features on assembly of spider silk block copolymers.

    Science.gov (United States)

    Tokareva, Olena S; Lin, Shangchao; Jacobsen, Matthew M; Huang, Wenwen; Rizzo, Daniel; Li, David; Simon, Marc; Staii, Cristian; Cebe, Peggy; Wong, Joyce Y; Buehler, Markus J; Kaplan, David L

    2014-06-01

    Bioengineered spider silk block copolymers were studied to understand the effect of protein chain length and sequence chemistry on the formation of secondary structure and materials assembly. Using a combination of in vitro protein design and assembly studies, we demonstrate that silk block copolymers possessing multiple repetitive units self-assemble into lamellar microstructures. Additionally, the study provides insights into the assembly behavior of spider silk block copolymers in concentrated salt solutions.

  14. Self-assembling Characteristics of Amphiphilic Star Block Copolymers with a Polyelectrolyte Shell

    Institute of Scientific and Technical Information of China (English)

    S.Strandman; A.Zarembo; V.Aseyev; S.J.Butcher; H.Tenhu

    2007-01-01

    1 Results Amphiphilic block copolymers are capable of forming supramolecular assemblies resembling those observed in nature,such as spherical micelles,worm micelles,and vesicles.Changing the solvent composition,ionic strength or pH of the polymer solution may induce the self-assembly of block copolymers or trigger the transition between the geometries of noncovalent assemblies.In the current work,we have synthesised starlike amphiphilic block copolymers having hydrophobic poly(methyl methacrylate),PMMA,...

  15. Block copolymers : controlling nanostructure to generate functional materials : synthesis, characterization, and engineering

    OpenAIRE

    Epps, Thomas H.; O'Reilly, Rachel K.

    2016-01-01

    n this perspective, we survey recent advances in the synthesis and characterization of block copolymers, discuss several key materials opportunities enabled by block copolymers, and highlight some of the challenges that currently limit further realization of block copolymers in promising nanoscale applications. One significant challenge, especially as the complexity and functionality of designer macromolecules increases, is the requirement of multiple complementary techniques to fully charact...

  16. New synthesis of amphiphilic copolymers PE-g-PEO via esterfication

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    A new series of high molecular weight amphiphilic graft copolymers PE-g-PEO has been prepared. The esterifications between PE-p-MS-g-MA and PEO with OH group at the chain end are carried out under different conditions. The compositions of these graft copolymers are studied by NMR and FTIR. It is found to be a convenient and efficient way to prepare high molecular weight PE-g-PEO graft copolymers.

  17. Evaluation of copolymer conformation states of vinylchloride-maleic anhydride

    Science.gov (United States)

    Ivanov, A. A.

    2016-11-01

    The quantum-chemical analysis and experimental study of alternating vinylchloride-maleic anhydride (VC-MA) copolymer macromolecules with polymerization degree 600 have been carried out. The VC-MA copolymer in solvents of different nature undergoes cycloanhydride-enol tautomerism and the macromolecules take the form of corrugated sticks according to viscometric measurements. The computer simulation has shown that the segment with polymerization degree n < 18 (model compound) is not a helix and rolls while if n = 18 the conformations get distorted. The model molecule optimal structure comprising a random sequence of alternating units of comonomers and their enol tautomers with minimal system total energy has been found by the semiempirical parametric method PM3.

  18. ETHYLENE OXIDE-ETHYLENE TEREPHTHALATE SEGMENTED COPOLYMER SOLID ELECTROLYTE

    Institute of Scientific and Technical Information of China (English)

    LUO Xiaolie; WANG Chuanqing; WANG Haiqian; HU Keliang; MA Dezhu

    1994-01-01

    A series of ethylene oxide-ethylene terephthalate segmented copolymers (EOET) were synthesized and complexed with LiClO4 to form some new polymer electrolytes. The EOET-LiClO4 electrolytes exhibit not only high ionic conductivity, but also good mechanical strength and toughness. The EOET 3400-25-LiClO4 complex possesses the highest conductivity (4. 65 ×10-5s·cm-1)at room temperature when the ratio [Li+]/[EO] equals 1/16.The structures of these electrolytes were examined with FTIR analysis, X-ray diffraction and DSC thermograms, and the results of high ionic conductivity of the segmented copolymers were discussed.

  19. Functional materials derived from block copolymer self-assembly

    DEFF Research Database (Denmark)

    Li, Tao

    is to fabricate interconnected and highly ordered metal oxide films by using a nano-porous polymer with gyroid morphology as the template. This unique structure is ideal for the solar cell application where a mesoscopic metal oxide scaffold functions as the electron collection and transport material. Two......The main objective of this project is to explore block copolymer self-assembly for generating functional materials with well-defined morphology on sub-20 nanometer length scale, which can be utilized in many important applications such as solar cells and nanolithography. One of the specific targets......-casting, the block copolymer self-organizes into monolayer packed sphere pattern, without any surface treatment of the substrate and annealing process. Arrays of nano-pillars and nanowells of various materials are fabricated in dry etch processes over wafer scale without defects. We also show an in situ Al2O3 hard...

  20. SYNTHESIS OF MACROPOROUS COPOLYMER OF VCA AND DVB

    Institute of Scientific and Technical Information of China (English)

    ZhuChangying; ZuoJu; 等

    1998-01-01

    The reactivity ratios of vinyl acetate(VAc) and divinyl benzene (DVB) were calculated from the Q and e values.The possibility of the copolymerization of these two monomers was predicted and the copolymerization was carried out by suspension polymerization technique in the presence of pore producing agent (toluene and gasoine).The relative ratio of acetoxy group and benzene ring in the copolymer were monitored by IR measurement during the polymerization.The variation of pore properties,such as spectific surface area,porosity and average pore diameter,with polymerization time were determined.The copolymers at various polymerization time were alcoholyzed and thus the variation of the hydroxyl group content with polymerization time was studied.

  1. Formulation and Characterization of Epoxy Resin Copolymer for Graphite Composites

    Science.gov (United States)

    Keck, F. L.

    1983-01-01

    Maximum char yield was obtained with a copolymer containing 25% mol fraction DGEBE and 75% mol fraction DGEBA (Epon 828). To achieve the high values (above 40%), a large quantity of catalyst (trimethoxyboroxine) was necessary. Although a graphite laminate 1/8" thick was successfully fabricated, the limited life of the catalyzed epoxy copolymer system precludes commercial application. Char yields of 45% can be achieved with phenolic cured epoxy systems as indicated by data generated under NAS2-10207 contract. A graphite laminate using this type of resin system was fabricated for comparison purposes. The resultant laminate was easier to process and because the graphite prepreg is more stable, the fabrication process could readily be adapted to commercial applications.

  2. Preparation of diarylethene copolymers and their photoinduced refractive index change

    Science.gov (United States)

    Cho, S. Y.; Yoo, M.; Shin, H.-W.; Ahn, K.-H.; Kim, Y.-R.; Kim, E.

    2003-01-01

    Diarylethene copolymers were synthesized from 1-(6 '-vinyl-2 '-methylbenzo[ b]thiophene-3 '-yl)-2-(2 ''-methylbenzo [ b]thiophene-3 ''-yl)hexafluorocyclopentene (VMBTF6) and 1-[6 '-(4 '''-vinylbenzoyl)-2 '-methylbenzo[ b]thiophene-3 '-yl]-2-(2 ''-methylbenzo[ b]thiophene-3 ''-yl)hexafluorocyclopentene (VBMBTF6) via living free radical techniques using stable TEMPO derivatives. The diarylethene content was controlled by the feed ratio of diarylethene derivatives and styrene. Transparent photochromic polymer films were prepared from the diarylethene copolymers with narrow molecular weight dispersion (PD˜1.3) by spin coating method. Photoinduced refractive index changes (Δ nTE) of the polymer films, with 25 mol% of diaryethene content, accompanied by the photochromic change were determined as 0.0009 and 0.0030 for poly(styrene- ran -VMBTF6) and poly(styrene- ran-VBMBTF6), respectively.

  3. Communication: Self-assembly of semiflexible-flexible block copolymers

    Science.gov (United States)

    Kumar, N. Arun; Ganesan, Venkat

    2012-03-01

    We apply the methodology of self-consistent Brownian dynamics simulations to study the self-assembly behavior in melts of semiflexible-flexible diblock copolymers as a function of the persistence length of the semiflexible block. Our results reveal a novel progression of morphologies in transitioning from the case of flexible-coil to rod-coil copolymers. At even moderate persistence lengths, the morphologies in the semiflexible-block rich region of the phase diagram transform to liquid crystalline phases. In contrast, the phases in the flexible-block rich region of the phase diagram persist up to much larger persistence lengths. Our analysis suggests that the development of orientational order in the semiflexible block to be a critical factor influencing the morphologies of self-assembly.

  4. Design and Application of Nanoscale Actuators Using Block-Copolymers

    Directory of Open Access Journals (Sweden)

    Paul D. Topham

    2010-10-01

    Full Text Available Block copolymers are versatile designer macromolecules where a “bottom-up” approach can be used to create tailored materials with unique properties. These simple building blocks allow us to create actuators that convert energy from a variety of sources (such as chemical, electrical and heat into mechanical energy. In this review we will discuss the advantages and potential pitfalls of using block copolymers to create actuators, putting emphasis on the ways in which these materials can be synthesised and processed. Particular attention will be given to the theoretical background of microphase separation and how the phase diagram can be used during the design process of actuators. Different types of actuation will be discussed throughout.

  5. Numerical investigation of local defectiveness control of diblock copolymer patterns

    Directory of Open Access Journals (Sweden)

    D. Jeong

    2016-09-01

    Full Text Available We numerically investigate local defectiveness control of self-assembled diblock copolymer patterns through appropriate substrate design. We use a nonlocal Cahn-Hilliard (CH equation for the phase separation dynamics of diblock copolymers. We discretize the nonlocal CH equation by an unconditionally stable finite difference scheme on a tapered trench design and, in particular, we use Dirichlet, Neumann, and periodic boundary conditions. The value at the Dirichlet boundary comes from an energy-minimizing equilibrium lamellar profile. We solve the resulting discrete equations using a Gauss-Seidel iterative method. We perform various numerical experiments such as effects of channel width, channel length, and angle on the phase separation dynamics. The simulation results are consistent with the previous experimental observations.

  6. New Fluorinated and Sulfonated Block Copolymers Final Report

    Science.gov (United States)

    2009-04-23

    serves as a plasticizer even in the hydrophobic FI domain. Similar glass transition reduction effects observed in other ionomer systems have been...Sulfonated Ionomer : Thermal Annealing and Solvent Effects.” American Physical Society National Meeting. Los Angeles, CA. March 21, 2005. 4. Akinbode...optimizing morphology and ultimately properties, membranes have been cast from relatively inexpensive block-copolymer ionomers of fluorinated poly

  7. Block copolymer libraries: modular versatility of the macromolecular Lego system.

    Science.gov (United States)

    Lohmeijer, Bas G G; Wouters, Daan; Yin, Zhihui; Schubert, Ulrich S

    2004-12-21

    The synthesis and characterization of a new 4 x 4 library of block copolymers based on polystyrene and poly(ethylene oxide) connected by an asymmetrical octahedral bis(terpyridine) ruthenium complex at the block junction are described, while initial studies on the thin film morphology of the components of the library are presented by the use of Atomic Force Microscopy, demonstrating the impact of a library approach to derive structure-property relationships.

  8. Poly(alkylene oxide) Copolymers for Nucleic Acid Delivery

    Science.gov (United States)

    2012-07-17

    Prescribed by ANSI Std Z39-18 parameter are discussed in the context of improving gene delivery processes , such as serum- stability and association with...is an entropy-driven process dominated by the hydrophobic block’s interactions with water as shown by applications of Flory-Huggins theory9,10 and...aqueous solution of PAO block copolymers, a critical gelation temperature (CGT) is observed above which the micellar liquid transitions into the

  9. Solid-supported biomimetic membranes based on amphiphilic block copolymers

    OpenAIRE

    Kowal, Justyna

    2015-01-01

    Planar artificial membranes based on amphiphilic block copolymers are of high interest due to their potential applications in catalysis, drug screening, sensing, etc. Such polymeric membranes can successfully mimic biological membranes, providing high robustness and stability, which makes them good candidates to be developed in direction of applications. Even though solid-supported polymer membranes have been already investigated to a certain extent, it is still an emerging area. This thesis ...

  10. Non-Surface Activity of Cationic Amphiphilic Diblock Copolymers

    Energy Technology Data Exchange (ETDEWEB)

    Nayak, Rati Ranjan; Yamada, Tasuku; Matsuoka, Hideki, E-mail: ratiranjan@immt.res.in, E-mail: matsuoka@star.polym.kyoto-u.ac.jp [Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan)

    2011-09-19

    Cationic amphiphilic diblock copolymers containing quaternized poly (2-vinylpyridine) chain as a hydrophilic segment (PIp-b-PNMe2VP) were synthesized by living anionic polymerization. By IR measurement, we confirmed the quaternization of the polymer (PIp-b-PNMe2VP), and determined the degree of quaternization by conductometric titration. The surface tension experiment showed that the polymers are non-surface active in nature. The foam formation of the polymer solutions was also investigated with or without added salt. Almost no foam formation behavior was observed without added salt, while a little foam was observed in the presence of 1M NaCl. The critical micelle concentration (cmc) of the diblock copolymers with 3 different chain lengths was measured by the static light scattering method. The cmc values obtained in this study were much lower than the values obtained for anionic non-surface active diblock polymers studied previously. The hydrodynamic radii of the polymer micelle increased slightly in the presence of 1 M NaCl. The transmission electron microscopic images revealed spherical micelles in pure water. In the presence of salt, the cmc values increased as was the case for anionic polymers, which is unlike conventional surfactant systems but consistent with non-surface active anionic block copolymers. The microviscosity of the micelle core was evaluated using Coumarin-153 as a fluorescent anisotropy probe using steady-sate fluorescence depolarization. Non-surface activity has been proved to be universal for ionic amphiphilic block copolymers both for anionic and cationic. Hence, the origin of non-surface activity is not the charged state of water surface itself, but should be an image charge repulsion at the air/water interface.

  11. Morphology Control of Copolymer Thin Films by Nanoparticles

    OpenAIRE

    Shagolsem, Lenin Singh

    2014-01-01

    Diblock-Copolymers (DBCs), created by covalently joining two chemically distinct polymer blocks, spontaneously form various nanoscale morphologies such as lamellae, cylinders, spheres, etc. due to the chemical incompatibility of its constituent blocks. This effect is called microphase separation in the literature. Because of this self-organizing property DBCs find applications in many areas e.g. in creating selective membranes, and in polymer based modern electronic devices like organic photo...

  12. Modification of isotactic polypropylene with styrene block-copolymers

    OpenAIRE

    DENAC, Matjaž; Musil, Vojko; Makarovič, Matjaž

    2015-01-01

    With a modification the current properties of polymeric material can be improved, and even some new properties can be obtained. The success of polymeric modifiers mostly depend on the interaction intensity at the phase boundary of the polymer/modifier. The influence of polymeric modifiers on polypropylene matrices were investigated. Different sorts and types of styrene block-copolymers were used in a concentration range up to 20 vol.%. Samples were prepared by melt-mixing in a Brabender knead...

  13. Synthesis of PET and Its Copolymer with Rare Earth Catalysts

    Institute of Scientific and Technical Information of China (English)

    张天骄; 武荣瑞

    2003-01-01

    A new catalyst system was used in the synthesis of polyethylene terephthalate(PET) and its copolymers, which involved a Ln3+ containing compound. The catalytic effects were studied, and it was found that the direct esterification reaction of terephthalate acid(TPA) with ethylene glycol(EG) can be accelerated by the addition of Ln3+ containing compound, which acts as a promoter of the catalyst Sb2O3 in polycondensation of bis hydroxyethyl terephthalate(BHET).

  14. THE STRUCTURE AND OPTICAL PROPERTIES OF COPOLYMER OF CHOLESTERIC ESTER

    Institute of Scientific and Technical Information of China (English)

    Zhou Enle; Zhang Yongqing; Zhao Xiaoguang; Xu Yang; Zhou Xingmao

    1988-01-01

    The structure and switching properties of liquid crystalline side chain copolymers of cholesteric ester of1,2-hydroxypropyl 2,4-di-isocyanatoluene methylmethacrylate (PHCPM) have been studied in detail. The cholesteric mesophase of PHCPM is shown by polarizing microscopy, X-ray diffraction and selective light reflection. Solution of PHCPM in CHCl3 is optically anisotropic; its optical properties were determined by specific rotation [α], circular dichroism (CD) and wide-angle light scattering (WALS) methods.

  15. CHARACTERISTICS OF STRUCTURE OF IMPACT COPOLYMERS OF POLYPROPYLENE WITH LOW ETHYLENE CONTENTS

    Institute of Scientific and Technical Information of China (English)

    MA Dezhu; LI Xiqiang; ZHANG Ruiyun; HONG Kunlun; LUO Xiaolie

    1994-01-01

    In the present work, the structure and impact properties of copolymers of polypropylene with low ethylene contents have been investigated. Based on the results of 13C-NMR, FTIR,WAXD, DSC, PLM and SEM, the relationship between impact properties and morphology of the copolymers has been discussed. The high impact properties of copolymer ICP2 may attribute to the relatively higher ethylene content and homogeneous ethylene unit distribution. The size and its distribution of spherulite in the copolymers and cycloid cavities dispersed in polypropylene continue phase may also be two important factors which affect the impact properties of these materials.

  16. The effect of heat treatment on the internal structure of nanostructured block copolymer films

    DEFF Research Database (Denmark)

    Sepe, Alessandro; Hoppe, E T; Jaksch, S

    2011-01-01

    We report on the temperature dependence of the nanostructure of thin block copolymer films, as studied using in situ grazing-incidence small-angle x-ray scattering (GISAXS). We focus on spin-coated poly(styrene-b-butadiene) diblock copolymer thin films featuring lamellae perpendicular to the subs......We report on the temperature dependence of the nanostructure of thin block copolymer films, as studied using in situ grazing-incidence small-angle x-ray scattering (GISAXS). We focus on spin-coated poly(styrene-b-butadiene) diblock copolymer thin films featuring lamellae perpendicular...

  17. Self-assembly of block copolymers on topographically patterned polymeric substrates

    Energy Technology Data Exchange (ETDEWEB)

    Russell, Thomas P.; Park, Soojin; Lee, Dong Hyun; Xu, Ting

    2016-05-10

    Highly-ordered block copolymer films are prepared by a method that includes forming a polymeric replica of a topographically patterned crystalline surface, forming a block copolymer film on the topographically patterned surface of the polymeric replica, and annealing the block copolymer film. The resulting structures can be used in a variety of different applications, including the fabrication of high density data storage media. The ability to use flexible polymers to form the polymeric replica facilitates industrial-scale processes utilizing the highly-ordered block copolymer films.

  18. Investigation of some copolymers based on acrylic salts as circulation loss control agents

    Directory of Open Access Journals (Sweden)

    Ahmed Mohamed Alsabagh

    2013-12-01

    The prepared copolymers were investigated as loss circulation control materials by measuring different filtration parameters such as; spurt loss, fluid loss and permeability plugging tester value according to the American Petroleum Institute (API standard. From the obtained data, it was found that the 0.6% from the poly[PA-co-AM](0.4:0.6 exhibited the best results of the filtration parameters among the other copolymers. At the same time all the studied copolymers enhanced the rheological properties of the drilling mud. These results were discussed on the light of the swelling capacity of the copolymers.

  19. In situ gelling stimuli-sensitive block copolymer hydrogels for drug delivery.

    Science.gov (United States)

    He, Chaoliang; Kim, Sung Wan; Lee, Doo Sung

    2008-05-08

    Stimuli-sensitive block copolymer hydrogels, which are reversible polymer networks formed by physical interactions and exhibit a sol-gel phase-transition in response to external stimuli, have great potential in biomedical and pharmaceutical applications, especially in site-specific controlled drug-delivery systems. The drug may be mixed with a polymer solution in vitro and the drug-loaded hydrogel can form in situ after the in vivo administration, such as injection; therefore, stimuli-sensitive block copolymer hydrogels have many advantages, such as simple drug formulation and administration procedures, no organic solvent, site-specificity, a sustained drug release behavior, less systemic toxicity and ability to deliver both hydrophilic and hydrophobic drugs. Among the stimuli in the biomedical applications, temperature and pH are the most popular physical and chemical stimuli, respectively. The temperature- and/or pH-sensitive block copolymer hydrogels for biomedical applications have been extensively developed in the past decade. This review focuses on recent development of the preparation and application for drug delivery of the block copolymer hydrogels that respond to temperature, pH or both stimuli, including poly(N-substituted acrylamide)-based block copolymers, poloxamers and their derivatives, poly(ethylene glycol)-polyester block copolymers, polyelectrolyte-based block copolymers and the polyelectrolyte-modified thermo-sensitive block copolymers. In addition, the hydrogels based on other stimuli-sensitive block copolymers are discussed.

  20. Studies on the heterogeneity of St/DVB copolymers by phenyl aggregate fluorescence

    Institute of Scientific and Technical Information of China (English)

    王国昌; 叶彦春; 高焕; 何炳林; 栗凤珍; 高传喜

    1995-01-01

    A new method for characterizing St/DVB copolymer heterogeneity by phenyl aggregatefluorescence has been developed and used to study the effects of crosslinking degree,crosslinker and diluent onthe heterogeneity of the copolyruer gels.The results show that St/m-DVB copolymer gel is more homogeneousin structure than St/p-DVB copolymer gel,whereas increasing crosslinking degree and the proportion of goodsolvent in diluent lead to an increase of gel heterogeneity.These results provide structural evidence which mayserve as a bridge between St/DVB crosslinking reaction and the copolymer properties.

  1. STUDY ON SOME PROPERTIES OF Si-CONTAINING POLYESTER-POLYETHER MULTIBLOCK COPOLYMERS

    Institute of Scientific and Technical Information of China (English)

    LI Zhenyi; ZHU Jin

    1997-01-01

    Some physical properties of the polyester-polyether multiblock copolymers with Si-containing hard segment were further examined by a series of physical methods. The hydrophobicity of the copolymers was improved with the incorporation of increasing amount of orgauosilicone, XPS test proved that silicon element was enriched at the surface of the Si-containing polyester-polyether copolymers. It was also found that their heat resistance and gas permeability for O2 and N2 were greatly improved. The study on semipermeability of films made of the Si-containing copolymers was also followed with interest.

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

    Science.gov (United States)

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

    2008-03-04

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

  3. Crystallization studies of polyethylene -poly(ethylene glycol) graft copolymers

    Science.gov (United States)

    Mark, P. R.; Hovey, G. E.; Murthy, N. S.; Breitenkamp, K.; Kade, M.; Emerick, T.

    2006-03-01

    Structure and crystallization behavior of three copolymers obtained by grafting poly (ethylene glycol) (PEG) chains to polyethylene (PE) main chain was investigated by variable temperature x-ray diffraction and thermal analysis. The results show that PEG side chains and PE main chains crystallize into separate domains. This is especially true when grafted chains are long (50 and 100 repeat units), in which the PEG domains are same as in PEG homopolymer both in structure and in melting behavior. In the copolymer with shorter chains (25 repeat units), the PEG crystals are not distinct and melting is broad. The PEG domains can be dissolved in water or ethanol without altering the mechanical integrity of the film. PE crystallites in both samples are similar to that in PE homopolymer. For instance, the thermal expansion of the basal cell plane (a- and b-axes) of the PE domains agrees well with that of PE homopolymer over the entire temperature range from ambient to melt. However, the chain-axis dimension PE-lattice in the copolymer is shorter by ˜ 0.05 å and the basal dimensions are larger by ˜ 0.05 å. The changes in these dimensions due to the changes in the length of the grafted PEG chains were investigated.

  4. Chain exchange kinetics of block copolymer micelles in ionic liquids

    Science.gov (United States)

    Ma, Yuanchi; Lodge, Timothy

    The chain exchange kinetics of block copolymer micelles has been studied using time-resolved small-angle neutron scattering (TR-SANS), a key tool in determining the average micelle composition in contrast-matched solvents. In this work, PMMA-block-PnBMA was selected as the model block copolymer, which has a LCST behavior in the common ionic liquids, [EMIM][TFSI] and [BMIM][TFSI]. We examined the chain exchange kinetics of three PMMA-block-PnBMA copolymers, with identical PMMA block length (MPMMA = 25000) and different PnBMA block lengths (MPnBMA = 24000, 35000 and 53000); the Flory-Huggins interaction parameter (χ) between the core (PnBMA) and the solvent were varied by mixing [EMIM][TFSI] and [BMIM][TFSI] in different ratios. We found that the relaxation of the initial segregation of h- and d- micelles followed the same form with the time as previously developed by our group. Assuming that single chain expulsion is the rate limiting step, the thermal barrier was found to depend linearly on the core block length (Ncore) . Furthermore, the effect of χ on the chain exchange kinetics will also be discussed.

  5. Electrically Tunable Soft-Solid Block Copolymer Structural Color.

    Science.gov (United States)

    Park, Tae Joon; Hwang, Sun Kak; Park, Sungmin; Cho, Sung Hwan; Park, Tae Hyun; Jeong, Beomjin; Kang, Han Sol; Ryu, Du Yeol; Huh, June; Thomas, Edwin L; Park, Cheolmin

    2015-12-22

    One-dimensional photonic crystals based on the periodic stacking of two different dielectric layers have been widely studied, but the fabrication of mechanically flexible polymer structural color (SC) films, with electro-active color switching, remains challenging. Here, we demonstrate free-standing electric field tunable ionic liquid (IL) swollen block copolymer (BCP) films. Placement of a polymer/ionic liquid film-reservoir adjacent to a self-assembled poly(styrene-block-quaternized 2-vinylpyridine) (PS-b-QP2VP) copolymer SC film allowed the development of red (R), green (G), and blue (B) full-color SC block copolymer films by swelling of the QP2VP domains by the ionic liquid associated with water molecules. The IL-polymer/BCP SC film is mechanically flexible with excellent color stability over several days at ambient conditions. The selective swelling of the QP2VP domains could be controlled by both the ratio of the IL to a polymer in the gel-like IL reservoir layer and by an applied voltage in the range of -3 to +6 V using a metal/IL reservoir/SC film/IL reservoir/metal capacitor type device.

  6. Surface Structure of Thin Films of Multifunctional Ionizable Copolymers

    Science.gov (United States)

    Wickramasinghe, Anuradhi; Perahia, Dvora

    Phase segregation results in a rich variety of structures in co-polymers where interfacial forces often dominate the structure of thin films. Introduction of ionizable segments often drives the formation of compounded structures with multiple blocks residing at the interfaces. Here we probe thin films, 40-50nm, of an A-B-C-B-A co-polymer where C is a randomly sulfonated polystyrene with sulfonation fractions of 0, 26 and 52 mole %, B is poly (ethylene-r-propylene), and A is poly (t-butyl styrene) as the sulfonation level and temperature are varied using Neutron Reflectivity AFM, and surface tension measurements. As cast films form layers with both hydrophobic blocks dominating the solid and air interfaces and the ionizable block segregating to the center. Following annealing at 1700C, above Tg of styrene sulfonate, the films coarsen, with surface aggregation dominating the structure, though interfacial regions remain dominated by the hydrophobic segments. We show that in contrast to non-ionic co-polymers, formation of micelles dominated the structure of these ionic structured films. Supported in part by DOE Grant No. DE-SC007908.

  7. Macroscopic lamellae orientations of diblock copolymer induced by dynamic shear

    Institute of Scientific and Technical Information of China (English)

    张红东; 杨玉良

    1997-01-01

    Computer simulation based on the coupled map lattices has been carried out for morphologies of the diblock copolymeric system under applied periodic shear deformation.The main effort is concentrated on the influence of pre-annenling history on the lamellae orientations in dynamically sheared diblock copolymers.It is found that whatever the quenching temperature is,the perpendicular orientation (i.e.the lamellae normal is parallel to the vorticity axis) is always observed if the dynamic shear deformation with shear amplitude F=1.0 and reduced shear frequency=0.005 is applied during annealing.In contrast to that,the parallel orientation (i.e.the lamellae normal is parallel to the velocity gradient direction) is observed if the dynamic shear with the same amplitude and frequency is applied to a thoroughly annealed (with the annealing time t>4 000) diblock copolymer.Therefore,it is pointed out that the selection of lamellar orientations in dynamically sheared diblock copolymers is not solely dependent on th

  8. Dielectric relaxation dynamics of high-temperature piezoelectric polyimide copolymers

    Science.gov (United States)

    Maceiras, A.; Costa, C. M.; Lopes, A. C.; San Sebastián, M.; Laza, J. M.; Vilas, J. L.; Ribelles, J. L. Gómez; Sabater i Serra, R.; Andrio Balado, A.; Lanceros-Méndez, S.; León, L. M.

    2015-08-01

    Polyimide copolymers have been prepared based on different diamines as comonomers: a diamine without CN groups and a novel synthesized diamine with two CN groups prepared by polycondensation reaction followed by thermal cyclodehydration. Dielectric spectroscopy measurements were performed, and the dielectric complex function, ac conductivity and electric modulus of the copolymers were investigated as a function of CN group content in the frequency range from 0.1 to 107 Hz at temperatures from 25 to 260 °C. For all samples and temperatures above 150 °C, the dielectric constant increases with increasing temperature due to increasing conductivity. The α-relaxation is just detected for the sample without CN groups, being this relaxation overlapped by the electrical conductivity contributions in the remaining samples. For the copolymer samples and the polymer with CN groups, an important Maxwell-Wagner-Sillars contribution is detected. The mechanisms responsible for the dielectric relaxation, conduction process and electric modulus response have been discussed as a function of the CN group content present in the samples.

  9. Donor-Acceptor Block Copolymers: Synthesis and Solar Cell Applications

    Directory of Open Access Journals (Sweden)

    Kazuhiro Nakabayashi

    2014-04-01

    Full Text Available Fullerene derivatives have been widely used for conventional acceptor materials in organic photovoltaics (OPVs because of their high electron mobility. However, there are also considerable drawbacks for use in OPVs, such as negligible light absorption in the visible-near-IR regions, less compatibility with donor polymeric materials and high cost for synthesis and purification. Therefore, the investigation of non-fullerene acceptor materials that can potentially replace fullerene derivatives in OPVs is increasingly necessary, which gives rise to the possibility of fabricating all-polymer (polymer/polymer solar cells that can deliver higher performance and that are potentially cheaper than fullerene-based OPVs. Recently, considerable attention has been paid to donor-acceptor (D-A block copolymers, because of their promising applications as fullerene alternative materials in all-polymer solar cells. However, the synthesis of D-A block copolymers is still a challenge, and therefore, the establishment of an efficient synthetic method is now essential. This review highlights the recent advances in D-A block copolymers synthesis and their applications in all-polymer solar cells.

  10. Surface Modification Using Photo-Crosslinkable Random Copolymers

    Science.gov (United States)

    Bae, Joonwon; Bang, Joona; Lowenhielm, Peter; Spiessberger, Christian; Russell, Thomas P.; Hawker, Craig J.

    2006-03-01

    We recently reported that poly(styrene-r-methyl methacrylate) (PS-r-PMMA) random copolymers containing benzocyclobutene (BCB) group can be used to modify the surface effectively by thermal crosslinking. It was demonstrated that this method is simple, rapid, and robust, and can be applied to various surfaces. However, it requires the large amount of heat for processing, and the BCB monomer itself involves a hard chemistry. An alternative way that can replace BCB with easier chemistry and lower cost, if possible, is highly desirable. We introduce the new functional group, azide group, which can be crosslinked simply by UV irradiation, for this purpose. PS-r-PMMA random copolymers, containing various amounts of azide groups, were synthesized via controlled living-radical polymerization. It was demonstrated that even after 1 minute of the UV irradiation can crosslink the materials effectively, so that they can be used as crosslinked random copolymer mat to control the surface energy. However, it was observed that the longer irradiation time causes the damages on the surface due to the other side reactions. Depending on the UV intensity, the UV irradiation time, and the amount of azide group, the effective processing window that leads to the crosslinking without any surface damages was optimized.

  11. Gas Permeation through Polystyrene-Poly(ethylene oxide) Block Copolymers

    Science.gov (United States)

    Hallinan, Daniel, Jr.; Minelli, Matteo; Giacinti-Baschetti, Marco; Balsara, Nitash

    2013-03-01

    Lithium air batteries are a potential technology for affordable energy storage. They consist of a lithium metal anode and a porous air cathode separated by a solid polymer electrolyte membrane, such as PEO/LiTFSI (PEO = poly(ethylene oxide), LiTFSI = lithium bis-trifluoromethane sulfonimide). For extended operation of such a battery, the polymer electrolyte must conduct lithium ions while blocking electrons and gases present in air. In order to maintain a pressure difference the membrane must be mechanically robust, which can be achieved by incorporating the PEO into a block copolymer with a glassy block such as PS (PS = polystyrene). To protect the lithium electrode, the membrane must have low permeability to gases in air such as CO2, N2, and O2. We have therefore studied the permeation of pure gases through a PS-PEO block copolymer. A high molecular weight, symmetric block copolymer with a lamellar morphology was used to cast free-standing membranes. Gas permeability was measured through these membranes with a standard, pressure-based technique. A model was developed to account for transport through the polymer membrane consisting of semi-crystalline PEO lamellae and amorphous PS lamellae. PEO crystallinity was extracted from the permeation model and compares well with values from differential scanning calorimetry measurements.

  12. Biological materials: (Part A): Temperature-responsive polymers and drug delivery, and, (Part B): Polymer modification of fish scale and their nano-mechanical properties

    Science.gov (United States)

    Xiang, Xu

    This research has three parts. Two parts deal with novel nanoparticle assemblies for drug delivery, and are described in Part A, while the third part looks at properties of fish scales, an abundant and little-used waste resource, that can be modified to have value in medical and other areas. Part A describes fundamental research into the affects of block sequence of amphiphilic block copolymers prepared from on a new and versatile class of monomers, oligo(ethylene glycol) methyl ether acrylate (OEGA) and the more hydrophobic di(ethylene glycol) methyl ether methacrylate (DEGMA). Polymers from these monomers are biologically safe and give polymers with thermoresponsive properties that can be manipulated over a broader temperature range than the more researched N-isopropylacrylamide polymers. Using RAFT polymerization and different Chain Transfer Agents (CTAs) amphiphilic block copolymers were prepared to study the effect of block sequence (hydrophilic OEGA and more hydrophobic DEGMA) on their thermo-responsive properties. Pairing hydrophilic chain ends to a hydrophobic DEGMA block and hydrophobic chain ends to hydrophilic blocks ("mis-matched polarity") significantly affected thermoresponsive properties for linear and star diblock copolymers, but little affected symmetric triblock copolymers. Specifically matching polarity in diblock copolymers yielded nanoparticles with higher cloud points (CP), narrow temperature ranges for coil collapse above CP, and smaller hydrodynamic diameter than mis-matched polarity. Using this knowledge two linear OEGA/DEGMA diblock copolymers were prepared with thiol end groups and assembled into hybrid nanoparticles with a gold nanoparticle core (GNP-polymer hybrids). This design was made using the hypothesis that a hybrid polymer drug carrier with a high CP (50-60 °C) and a diblock structure could be designed with low levels of drug release below 37 °C (body temperature) allowing the drug carrier to reach a target (tumor) site with

  13. DNA block copolymers: functional materials for nanoscience and biomedicine.

    Science.gov (United States)

    Schnitzler, Tobias; Herrmann, Andreas

    2012-09-18

    We live in a world full of synthetic materials, and the development of new technologies builds on the design and synthesis of new chemical structures, such as polymers. Synthetic macromolecules have changed the world and currently play a major role in all aspects of daily life. Due to their tailorable properties, these materials have fueled the invention of new techniques and goods, from the yogurt cup to the car seat belts. To fulfill the requirements of modern life, polymers and their composites have become increasingly complex. One strategy for altering polymer properties is to combine different polymer segments within one polymer, known as block copolymers. The microphase separation of the individual polymer components and the resulting formation of well defined nanosized domains provide a broad range of new materials with various properties. Block copolymers facilitated the development of innovative concepts in the fields of drug delivery, nanomedicine, organic electronics, and nanoscience. Block copolymers consist exclusively of organic polymers, but researchers are increasingly interested in materials that combine synthetic materials and biomacromolecules. Although many researchers have explored the combination of proteins with organic polymers, far fewer investigations have explored nucleic acid/polymer hybrids, known as DNA block copolymers (DBCs). DNA as a polymer block provides several advantages over other biopolymers. The availability of automated synthesis offers DNA segments with nucleotide precision, which facilitates the fabrication of hybrid materials with monodisperse biopolymer blocks. The directed functionalization of modified single-stranded DNA by Watson-Crick base-pairing is another key feature of DNA block copolymers. Furthermore, the appropriate selection of DNA sequence and organic polymer gives control over the material properties and their self-assembly into supramolecular structures. The introduction of a hydrophobic polymer into DBCs

  14. Morphology and Crystallization of Thin Films of Asymmetric Organic-Organometallic Diblock Copolymers of Isoprene and Ferrocenyldimethylsilane

    NARCIS (Netherlands)

    Lammertink, Rob G.H.; Hempenius, Mark A.; Vancso, G. Julius

    2000-01-01

    The morphology of thin films of asymmetric block copolymers of poly(isoprene-block-ferrocenyldimethylsilane) was studied using atomic force microscopy, transmission electron microscopy, and optical microscopy. Block copolymers with the organometallic (ferrocenylsilane) phase between 20 and 28 vol %

  15. Structure-Property Relationships of Poly(lactide)-based Triblock and Multiblock Copolymers

    Science.gov (United States)

    Panthani, Tessie Rose

    Replacing petroleum-based plastics with alternatives that are degradable and synthesized from annually renewable feedstocks is a critical goal for the polymer industry. Achieving this goal requires the development of sustainable analogs to commodity plastics which have equivalent or superior properties (e.g. mechanical, thermal, optical etc.) compared to their petroleum-based counterparts. This work focuses on improving and modulating the properties of a specific sustainable polymer, poly(lactide) (PLA), by incorporating it into triblock and multiblock copolymer architectures. The multiblock copolymers in this work are synthesized directly from dihydroxy-terminated triblock copolymers by a simple step-growth approach: the triblock copolymer serves as a macromonomer and addition of stoichiometric quantities of either an acid chloride or diisocyanate results in a multiblock copolymer. This work shows that over wide range of compositions, PLA-based multiblock copolymers have superior mechanical properties compared to triblock copolymers with equivalent chemical compositions and morphologies. The connectivity of the blocks within the multiblock copolymers has other interesting consequences on properties. For example, when crystallizable poly(L-lactide)-based triblock and multiblock copolymers are investigated, it is found that the multiblock copolymers have much slower crystallization kinetics. Additionally, the total number of blocks connected together is found to effect the linear viscoelastic properties as well as the alignment of lamellar domains under uniaxial extension. Finally, the synthesis and characterization of pressure-sensitive adhesives based upon renewable PLA-containing triblock copolymers and a renewable tackifier is detailed. Together, the results give insight into the effect of chain architecture, composition, and morphology on the mechanical behavior, thermal properties, and rheological properties of PLA-based materials.

  16. The synthesis and characterization of organometallic copolymers with Mn-Re binuclear transition-metal group in the side chain

    Institute of Scientific and Technical Information of China (English)

    XU; Zhi; FENG; Gang; BAI; Zhifeng; MA; Yongqiang; CHANG; Weixing; LI; Jing

    2006-01-01

    Novel organometallic copolymers with Mn-Re binuclear transition-metal groups in the side chain are synthesized and characterized. The structure and properties of the copolymers are characterized by GPC, DSC, TG, NMR, FT-IR, UV-Vis spectra and elemental analysis. The glass transition temperature and UV-Vis spectra properties of these three organometallic copolymers are found to be different from the normal polystyrene. New synthetic strategy for the synthesis of organometallic copolymer is developed.

  17. Synthesis and Characterization of a Biodegradable Copolymer: RGD Peptide Modification of Poly (lactic acid-co-lysine)

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The poly ( lactic acid- co-lysine ) was synthesized using IR and 1 H NMR to characterize the copolymer. And then the RGD modification copolymer RGD-PLAL was prepared. The contact angles were used to see the RGD modification occurrence. Also high molecular weight polymer was controlled to the reaction of polymerization of copolymer.

  18. Controlled Functionalization of Olefin/styrene Copolymers through Free Radical Processes

    NARCIS (Netherlands)

    Passaglia, Elisa; Aglietto, Mauro; Ciardelli, Francesco; Picchioni, Francesco

    2000-01-01

    The functionalization of styrene-b-(ethylene-co-1-butene)-b-styrene triblock copolymer (SEBS) and styrene-co-butadiene (SBR) random copolymer by free radical processes is presented. SEBS was functionalized in the melt with diethyl maleate (DEM) and dicumyl peroxide (DCP) as initiator. The functional

  19. Value of embolization of brain arteriovenous malformations with ethylene vinyl alcohol copolymer

    Institute of Scientific and Technical Information of China (English)

    YANG Xin-xin; SONG Lu; WU Na; LIU Zhen-guo

    2010-01-01

    @@ T° the Editor We are interested in a recent article "Embolization of brain arteriovenous malformations with ethylene vinyl alcohol copolymer: technical aspects" written by GAO et al.1 Ethylene vinyl alcohol copolymer (Onyx) is a novel liquid embolic material used to cure brain arteriovenous malformations. They performed the embolization on 115 patients and they found that the complications of the treatment are scarce.

  20. Mixing alternating copolymers containing fluorenyl groups with phospholipids to obtain Langmuir and Langmuir-Blodgett films.

    Science.gov (United States)

    Santos, Thays C F; Péres, Laura O; Wang, Shu H; Oliveira, Osvaldo N; Caseli, Luciano

    2010-04-20

    The control of molecular architectures may be essential to optimize materials properties for producing luminescent devices from polymers, especially in the blue region of the spectrum. In this Article, we report on the fabrication of Langmuir-Blodgett (LB) films of polyfluorene copolymers mixed with the phospholipid dimyristoyl phosphatidic acid (DMPA). The copolymers poly(9,9-dioctylfluorene)-co-phenylene (copolymer 1) and poly(9,9-dioctylfluorene)-co-quaterphenylene) (copolymer 2) were synthesized via Suzuki reaction. Copolymer 1 could not form a monolayer on its own, but it yielded stable films when mixed with DMPA. In contrast, Langmuir monolayers could be formed from either the neat copolymer 2 or when mixed with DMPA. The surface pressure and surface potential measurements, in addition to Brewster angle microscopy, indicated that DMPA provided a suitable matrix for copolymer 1 to form a stable Langmuir film, amenable to transfer as LB films, while enhancing the ability of copolymer 2 to form LB films with enhanced emission, as indicated by fluorescence spectroscopy. Because a high emission was obtained with the mixed LB films and since the molecular-level interactions between the film components can be tuned by changing the experimental conditions to allow for further optimization, one may envisage applications of these films in optical devices such as organic light-emitting diodes (OLEDs).

  1. 21 CFR 175.360 - Vinylidene chloride copolymer coatings for nylon film.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Vinylidene chloride copolymer coatings for nylon... coatings for nylon film. Vinylidene chloride copolymer coatings identified in this section and applied on nylon film may be safely used as food-contact surfaces, in accordance with the following...

  2. PRECISE SYNTHESIS OF OLEFIN BLOCK COPOLYMERS USING A SYNDIOSPECIFIC LIVING POLYMERIZATION SYSTEM

    Institute of Scientific and Technical Information of China (English)

    Zheng-guo Cai; Hai-hui Su; Takeshi Shiono

    2013-01-01

    This feature article summarizes the synthesis of novel olefin block copolymers using fast syndiospecific living homo-and copolymerization of propylene,higher 1-alkene,and norbomene with ansa-fluorenylamidodimethyltitaniumbased catalyst according to the authors' recent results.The catalytic synthesis of monodisperse polyolefin and olefin block copolymer was also described using this living system.

  3. Design of block-copolymer-based micelles for active and passive targeting

    NARCIS (Netherlands)

    Lebouille, Jérôme G.J.L.; Leermakers, Frans A.M.; Cohen Stuart, Martien A.; Tuinier, Remco

    2016-01-01

    A self-consistent field study is presented on the design of active and passive targeting block-copolymeric micelles. These micelles form in water by self-assembly of triblock copolymers with a hydrophilic middle block and two hydrophobic outer blocks. A minority amount of diblock copolymers with the

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

    NARCIS (Netherlands)

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

    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 relati

  5. Improved compositional analysis of block copolymers using diffusion ordered NMR spectroscopy.

    Science.gov (United States)

    Viel, Stéphane; Mazarin, Michaël; Giordanengo, Rémi; Phan, Trang N T; Charles, Laurence; Caldarelli, Stefano; Bertin, Denis

    2009-11-03

    Block copolymers constitute a fascinating class of polymeric materials that are used in a broad range of applications. The performance of these materials is highly coupled to the physical and chemical properties of the constituting block copolymers. Traditionally, the composition of block copolymers is obtained by 1H NMR spectroscopy on purified copolymer fractions. Specifically, the integrals of a properly selected set of 1H resonances are compared and used to infer the number average molecular weight (M(n)) of one of the block from the (typically known) M(n) value of the other. As a corollary, compositional determinations achieved on imperfectly purified samples lead to serious errors, especially when isolation of the block copolymer from the initial macro initiator is tedious. This investigation shows that Diffusion Ordered NMR Spectroscopy (DOSY) can be used to provide a way to assess the advancement degree of the copolymerization purification/reaction, in order to optimize it and hence contribute to an improved compositional analysis of the resulting copolymer. To this purpose, a series of amphiphilic polystyrene-b-poly(ethylene oxide) block copolymers, obtained by controlled free-radical nitroxide mediated polymerization, were analyzed and it is shown that, under proper experimental conditions, DOSY allows for an improved compositional analysis of these block copolymers.

  6. Block copolymer route towards poly(vinylidene fluoride)/poly(methacrylic acid)/nickel nanocomposites

    NARCIS (Netherlands)

    Voet, V.S.D.; Hermida-Merino, D.; Brinke, G. ten; Loos, K.

    2013-01-01

    PVDF-based block copolymers have been employed as precursors for the construction of PVDF/PMAA/Ni nanocomposites. New poly(tert-butyl methacrylate)-block-poly(vinylidene fluoride)-block-poly(tert-butyl methacrylate) (PtBMA-b-PVDF-b-PtBMA) triblock copolymers were synthesized via atom transfer radica

  7. Synthesis, Characterization and Photoinduction of Optical Anisotropy in Liquid Crystalline Diblock Azo-Copolymers

    DEFF Research Database (Denmark)

    Forcén, P; Oriol, L; Sánchez, C

    2007-01-01

    Diblock copolymers with polymethyl methacrylate and side chain liquid crystalline WC) azopolymethacrylate blocks were synthesized by atom transfer radical polymerization (ATRP). The azobeazene content in these copolymers ranges from 52 to 7 wt %. For an azo conteat dowri to 20% they exhibit a LC ...

  8. A 3x1 integrated pyroelectric sensor based on VDF/TrFE copolymer

    NARCIS (Netherlands)

    Setiadi, D.; Sarro, P.M.; Regtien, P.P.L.

    1996-01-01

    This paper presents an integrated pyroelectric sensor based on a vinylidene fluoride¿trifluoroethylene (VDF/TrFE) copolymer. A silicon substrate that contains field-effect transistor (FET) readout electronics is coated with the VDF/TrFE copolymer film using a spin-coating technique. On-chip poling o

  9. 40 CFR 721.7210 - Epoxidized copolymer of phenol and substituted phenol.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Epoxidized copolymer of phenol and substituted phenol. 721.7210 Section 721.7210 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.7210 Epoxidized copolymer of phenol and substituted phenol. (a)...

  10. Adsorption of charged di-block copolymers : effect on colloidal stability.

    NARCIS (Netherlands)

    Israëls, R.

    1994-01-01

    In this thesis we present Scheutjens-Fleer (SF) calculations on the adsorption of diblock copolymers. More specifically, we restrict ourselves to adsorption at uncharged surfaces, while the specific type of block copolymers we consider have one uncharged adsorbing "anchor" block and one non-adsorbin

  11. PREPARATION AND PROPERTIES OF ABSORBABLE FIBERS FROM L-LACTIDE COPOLYMERS

    NARCIS (Netherlands)

    PENNING, JP; PENNINGS, AJ

    1993-01-01

    Absorbable fibres have been prepared from various copolymers Of L-lactide with either D-lactide or epsilon-caprolactone. The lower crystallinity of these copolymers, compared with the homopolymer, is desirable in the light of their potential use as an absorbable suture material and has a pronounced

  12. Structure–property relations of segmented block copolymers with liquid–liquid demixed morphologies

    NARCIS (Netherlands)

    Schuur, van der Martijn; Heide, van der Evert; Feijen, Jan; Gaymans, Reinoud J.

    2005-01-01

    Poly(propylene oxide) based polyether(ester-amide)s (PEEA) with non-crystallisable amide segments were synthesized and their structure–property relations studied. These model segmented block copolymers were used to gain insight in the structure–property relations of block copolymers with liquid–liqu

  13. Segmented copolymers of uniform tetra-amide units and poly(phenylene oxide) by direct coupling

    NARCIS (Netherlands)

    Krijgsman, J.; Biemond, G.J.E.; Gaymans, R.J.

    2007-01-01

    Segmented copolymers with telechelic poly(2,6-dimethyl-1,4-phenylene ether) (PPE) segments and crystallizable bisester tetra-amide units (two-and-a-half repeating unit of nylon-6,T) were studied. The copolymers were synthesized by reacting bifunctional PPE with hydroxylic end groups with an average

  14. 76 FR 30604 - National Emission Standards for Hazardous Air Pollutants for Polyvinyl Chloride and Copolymers...

    Science.gov (United States)

    2011-05-26

    ... Polyvinyl Chloride and Copolymers Production AGENCY: Environmental Protection Agency (EPA). ACTION: Proposed..., the proposed rule, National Emission Standards for Hazardous Air Pollutants for Polyvinyl Chloride and... Polyvinyl Chloride and Copolymers Production, under Docket ID No. EPA-HQ-OAR-2002-0037 (available at...

  15. 76 FR 42613 - National Emission Standards for Hazardous Air Pollutants for Polyvinyl Chloride and Copolymers...

    Science.gov (United States)

    2011-07-19

    ... Polyvinyl Chloride and Copolymers Production; Extension of Comment Period AGENCY: Environmental Protection... for Hazardous Air Pollutants for Polyvinyl Chloride and Copolymers Production is being extended for 14... extend the public comment period for the May 20, 2011, Proposed Polyvinyl Chloride and...

  16. Effect of nanoscale morphology on selective ethanol transport through block copolymer membranes

    Science.gov (United States)

    We report on the effect of block copolymer domain size on transport of liquid mixtures through the membranes by presenting pervaporation data of an 8 wt% ethanol/water mixture through A-B-A and B-A-B triblock copolymer membranes. The A-block was chosen to facilitate ethanol transport while the B-blo...

  17. Novel fluorinated block copolymer architectures fuelled by atom transfer radical polymerization

    DEFF Research Database (Denmark)

    Jankova, Katja; Hvilsted, Søren

    2005-01-01

    Block copolymers based on poly(pentafluorostyrene), PFS, in various numbers and of different lengths, and polystyrene are prepared by atom transfer radical polymerization (ATRP). Di- and triblock copolymers with varying amounts of PFS were synthesized employing either I phenylethylbromide or 1,4-...

  18. 21 CFR 175.365 - Vinylidene chloride copolymer coatings for polycarbonate film.

    Science.gov (United States)

    2010-04-01

    ... polycarbonate film. 175.365 Section 175.365 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH... chloride copolymer coatings for polycarbonate film. Vinylidene chloride copolymer coatings identified in this section and applied on polycarbonate film may be safely used as food-contact surfaces,...

  19. Temperature effects on the stability of gold nanoparticles in the presence of a cationic thermoresponsive copolymer

    Science.gov (United States)

    Pamies, Ramón; Zhu, Kaizheng; Kjøniksen, Anna-Lena; Nyström, Bo

    2016-11-01

    New hybrid complexes composed by a thermoresponsive copolymer and gold nanoparticles (Rh = 22 nm) have been characterized by dynamic light scattering (DLS) and UV-visible spectroscopy. A cationic thermoresponsive triblock copolymer, methoxy-poly(ethylene glycol)- block-poly( N-isopropylacrylamide)- block-poly((3-acrylamidopropyl) trimethyl ammonium chloride), abbreviated as MPEG- b-PNIPAAM- b-PN(+), has been synthesized by atom transfer radical polymerization (ATRP). We have evaluated the thermal response at low concentrations of this triblock copolymer in bulk solution and the effect of concentration on the interaction between this thermosensitive copolymer and the gold nanoparticles (AuNPs) to form new hybrid complexes (60-1000 nm) at different temperatures. The thermosensitive nature of the copolymer causes both aggregation and contraction of the aggregates at elevated temperatures. The AuNPs were found to be separately embedded in the hybrid complexes. Interestingly, the AuNPs prevent macroscopic phase separation of the system at high temperatures.

  20. PERVAPORATION FOR SEPARATING BENZENE/CYCLOHEXANE MIXTURE BY P(AA-MA) COPOLYMER MEMBRANES

    Institute of Scientific and Technical Information of China (English)

    Gao-fei Xu; Wei-pu Zhu

    2011-01-01

    P(AA-MA) copolymers composed of acrylic acid and methyl acrylate with different molecular weights and sequence structures were synthesized by combination of ATRP and selective hydrolysis. These copolymers were used as membrane materials to separate benzene/cyclohexane mixture by pervaporation. The effects of molecular weight and sequence structure of the copolymers on the pervaporation performance were investigated in detail. For the random copolymers, the permeate flux decreased rapidly with the increasing of molecular weight. The separation factor was also influenced by the molecular weight, which was changed from no selectivity to cyclohexane selectivity with increasing the molecular weight. Contrarily, the block copolymer membrane showed good benzene selectivity with separation factor of 4.3 and permeate flux of 157 g/(m2h) to 50 wt% benzene/cyclohexane mixture.

  1. Experimental investigation of the behaviour and fate of block copolymers in fouling-release coatings

    DEFF Research Database (Denmark)

    Noguer, Albert Camós; Olsen, Stefan Møller

    in the worsening of the fouling-inhibition properties of these complex systems, specially focusing on the behaviour and fate of the block copolymers used as additives. The development of various methods to visualize and quantify processes involving these copolymers are presented. Chapter 1 provides an overview......-release coatings. A coating based on a PDMS binder has been employed as model system in the thesis. The effect of the addition of various PEG-based surfactants and copolymers (i.e. amphiphiles) was investigated by a novel method developed in this project, and the diffusion coefficient and biofouling...... coatings. Images obtained by confocal microscopy proved that the copolymer molecules assemble in spherical domains inside the PDMS coating. The domains are smaller close to the surface and larger in the bulk of the film (with domains as large as 7 µm in diameter). The diffusion of copolymer from the bulk...

  2. Branched Rod-Coil Polyimide-Poly(Alkylene Oxide) Copolymers and Electrolyte Compositions

    Science.gov (United States)

    Meador, Maryann B. (Inventor); Tigelaar, Dean M. (Inventor)

    2014-01-01

    Crosslinked polyimide-poly(alkylene oxide) copolymers capable of holding large volumes of liquid while maintaining good dimensional stability. Copolymers are derived at ambient temperatures from amine endcapped amic-acid oligomers subsequently imidized in solution at increased temperatures, followed by reaction with trifunctional compounds in the presence of various additives. Films of these copolymers hold over four times their weight at room temperature of liquids such as ionic liquids (RTIL) and/or carbonate solvents. These rod-coil polyimide copolymers are used to prepare polymeric electrolytes by adding to the copolymers various amounts of compounds such as ionic liquids (RTIL), lithium trifluoromethane-sulfonimide (LiTFSi) or other lithium salts, and alumina.

  3. Enzyme cleavable nanoparticles from peptide based triblock copolymers

    Science.gov (United States)

    Fuchs, Adrian V.; Kotman, Niklas; Andrieu, Julien; Mailänder, Volker; Weiss, Clemens K.; Landfester, Katharina

    2013-05-01

    A solid-phase synthesis based approach towards protease cleavable polystyrene-peptide-polystyrene triblock copolymers and their formulation to nanoparticulate systems is presented. These nanoparticles are suitable for the optical detection of an enzyme and have the potential for application as a drug delivery system. Two different peptide sequences, one cleaved by trypsin (GFF), the other by hepsin (RQLRVVGG), a protease overexpressed in early stages of prostate cancer, are used as the central part of the triblock. For optical detection a fluorophore-quencher pair is introduced around the cleavage sequence. The solid phase synthesis is conduced such that two identical sequences are synthesized from one branching point. Eventually, carboxy-terminated polystyrene is introduced into the peptide synthesizer and coupled to the amino-termini of the branched sequence. Upon cleavage, a fragment is released from the triblock copolymer, which has the potential for use in drug delivery applications. Conducting the whole synthesis on a solid phase in the peptide synthesizer avoids solubility issues and post-synthetic purification steps. Due to the hydrophobic PS-chains, the copolymer can easily be formulated to form nanoparticles using a nanoprecipitation process. Incubation of the nanoparticles with the respective enzymes leads to a significant increase of the fluorescence from the incorporated fluorophore, thereby indicating cleavage of the peptide sequence and decomposition of the particles.A solid-phase synthesis based approach towards protease cleavable polystyrene-peptide-polystyrene triblock copolymers and their formulation to nanoparticulate systems is presented. These nanoparticles are suitable for the optical detection of an enzyme and have the potential for application as a drug delivery system. Two different peptide sequences, one cleaved by trypsin (GFF), the other by hepsin (RQLRVVGG), a protease overexpressed in early stages of prostate cancer, are used as the

  4. Tough Block Copolymer Organogels and Elastomers as Short Fiber Composites

    Science.gov (United States)

    Kramer, Edward J.

    2012-02-01

    The origins of the exceptional toughness and elastomeric properties of gels and elastomers from block copolymers with semicrystalline syndiotactic polypropylene blocks will be discussed. Using synchrotron X-radiation small angle (SAXS) and wide angle X-ray scattering (WAXS) experiments were simultaneously performed during step cycle tensile deformation of these elastomers and gels. From these results the toughness can be attributed to the formation, orientation and elongation of the crystalline fibrils along the tensile direction. The true stress and true strain ɛH during each cycle were recorded, including the true strain at zero load ɛH,p after each cycle that resulted from the plastic deformation of the sPP crystals in the gel or elastomer. The initial Young's modulus Einit and maximum tangent modulus Emax in each cycle undergo dramatic changes as a function of ɛH,p, with Einit decreasing for ɛH,p 100 to 1000 at the highest maximum (nominal) strain. Based on SAXS patterns from the deformed and relaxed gels, as well as on previous results on deformation of semicrystalline random copolymers by Strobl and coworkers, we propose that the initial decrease in Einit and increase in Emax with ɛH,p are due to a breakup of the network of the original sPP crystal lamellae and the conversion of the sPP lamellae into fibrils whose aspect ratio increases with further plastic deformation, respectively. The gel elastic properties can be understood quantitatively as those of a short fiber composite with a highly deformable matrix. At zero stress the random copolymer midblock chains that connect the fibrils cause these to make all angles to the tensile axis (low Einit), while at the maximum strain the stiff, crystalline sPP fibrils align with the tensile axis producing a strong, relatively stiff gel. The evolution of the crystalline structure during deformation is confirmed by WAXS and FTIR measurements.

  5. Facile synthesis and characterization of novel biodegradable amphiphilic block copolymers bearing pendant hydroxyl groups

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Gaicen; Fan, Xiaoshan; Xu, Bingcan; Zhang, Delong; Hu, Zhiguo, E-mail: zghu@htu.cn

    2014-10-01

    Novel amphiphilic block copolymers bearing pendant hydroxyl groups polylactide-b–poly(3,3-bis(Hydroxymethyl–triazolylmethyl) oxetane)-b–polylactide (PLA-b–PHMTYO-b–PLA) were synthesized via a facile and efficient method. First, the block copolymer intermediates polylactide-b–poly(3,3-Diazidomethyloxetane)-b–polylactide (PLA-b–PBAMO-b–PLA) were synthesized through ring-opening polymerization of lactide using PBAMO as a macroinitiator. Following “Click” reaction of PLA-b–PBAMO-b–PLA with propargyl alcohol provided the targeted amphiphilic block copolymers PLA-b–PHMTYO-b–PLA with pendant hydroxyl groups. The composition and structure of prepared copolymers were characterized by {sup 1}H nuclear magnetic resonance ({sup 1}H NMR) spectroscopy, Fourier transform infrared (FT-IR) and gel permeation chromatography (GPC). The self-assembly behavior of the copolymers in water was investigated by transmission electron microscope (TEM), dynamic light scattering (DLS) and static light scattering (SLS). The results showed that the novel copolymers PLA-b–PHMTYO-b–PLA self-assembled into spherical micelles with diameters ranging from 100 nm to 200 nm in aqueous solution. These copolymers also exhibited low critical micellar concentrations (CMC: 6.9 × 10{sup −4} mg/mL and 3.9 × 10{sup −5} mg/mL, respectively). In addition, the in vitro cytotoxicity of these copolymers was determined in the presence of L929 cells. The results showed that the block copolymers PLA-b–PHMTYO-b–PLA exhibited better biocompatibility. Therefore, these well-defined copolymers are expected to find some applications in drug delivery or tissue engineering. - Highlights: • The method to synthesize PLA-b–PHMTYO-b–PLA is relatively facile and efficient. • PLA-b–PHMTYO-b–PLA self-assembles into spherical micelles with low CMC in water. • PLA-b–PHMTYO-b–PLA exhibits better biocompatibility and biodegradability.

  6. Thermoplastic Adhesives based on polyolefin and olefinic copolymers

    Science.gov (United States)

    Paul, Rituparna

    2014-03-01

    H.B. Fuller has been a leading global industrial adhesive manufacturer for over 125 years. It is a company with a rich history of consistently delivering adhesive innovations for enhancing product performance in the market place. H.B. Fuller technologies/products find application in several markets including packaging, personal hygiene and nonwovens, durable assembly and electronics. In this presentation, H. B. Fuller's technology innovation journey will be shared with emphasis on groundbreaking technologies/products based on polyolefin and olefin copolymers.

  7. PREPARATION AND PERVAPORATION PROPERTIES OF PROPENE/1-DECENE COPOLYMER MEMBRANES

    Institute of Scientific and Technical Information of China (English)

    Xiu-zhi Tian; Bao-ku Zhu; Xue Jiang; You-yi Xu

    2005-01-01

    Propene/1-decene copolymers (P-co-D) were synthesized by means of slurry polymerization process under atmospheric pressure using Ziegler-Natta catalyst (MgCl2/TiCl4/AlEt3). The random P-co-Ds were elastic, low-crystalline,thermally stable and therefore suitable to be used as membrane materials in organophilic pervaporation with chloroform/water mixture. Its mechanical strength is better than polydimethylsiloxane (PDMS). The correlation between structural parameters (glass transition temperature and crystallinity) and properties of organophilic pervaporation were investigated.

  8. Determination of cloud-point temperatures for different copolymers

    Directory of Open Access Journals (Sweden)

    G.M. Campese

    2003-09-01

    Full Text Available This paper describes a novel system which has a great potential for use for extractions in biotechnological processes as it uses only polymers and can be operated at moderate temperatures and salt concentrations. The polymers used in this work are ethylene oxide-propylene oxide 10:90 (w/w (EO10PO90 and ethylene oxide-propylene oxide 20:80 (w/w (EO20PO80. The temperature required for thermoseparation decreases with increasing PO content of the copolymer and increasing buffer concentration.

  9. Monte Carlo simulation of AB-copolymers with saturating bonds

    DEFF Research Database (Denmark)

    Chertovich, A.C.; Ivanov, V.A.; Khokhlov, A.R.;

    2003-01-01

    Structural transitions in a single AB-copolymer chain where saturating bonds can be formed between A- and B-units are studied by means of Monte Carlo computer simulations using the bond fluctuation model. Three transitions are found, coil-globule, coil-hairpin and globule-hairpin, depending...... on the nature of a particular AB-sequence: statistical random sequence, diblock sequence and 'random-complementary' sequence (one-half of such an AB-sequence is random with Bernoulli statistics while the other half is complementary to the first one). The properties of random-complementary sequences are closer...

  10. Gamma radiation induced degradation in PE-PP block copolymer

    Energy Technology Data Exchange (ETDEWEB)

    Ravi, H. R.; Sreepad, H. R.; Ahmed, Khaleel; Govindaiah, T. N. [P.G. Department of Physics, Government College (Autonomous), Mandya - 571401, Karnataka State (India)

    2012-06-05

    In the present investigation, effect of gamma irradiation on the PP-PE block copolymer has been studied. The polymer has been subjected to gamma irradiation from 100 to 500 Mrad dosages. Characterization of the polymer using XRD and FTIR was done both before irradiation and after irradiation in each step. Effect of irradiation on the electrical properties of the material has also been studied. FTIR study shows that the sample loses C - C stretching mode of vibration but gains C=C stretching mode of vibration after irradiation. Present investigation clearly indicates that though the electrical conductivity increases in the material, it undergoes degradation and shows brittleness due to irradiation.

  11. Multifunctional nanoassemblies of block copolymers for future cancer therapy

    Directory of Open Access Journals (Sweden)

    Horacio Cabral and Kazunori Kataoka

    2010-01-01

    Full Text Available Nanoassemblies from amphiphilic block copolymers are promising nanomedicine platforms for cancer diagnosis and therapy due to their relatively small size, high loading capacity of drugs, controlled drug release, in vivo stability and prolonged blood circulation. Recent clinical trials with self-assembled polymeric micelles incorporating anticancer drugs have shown improved antitumor activity and decreased side effects encouraging the further development of nanoassemblies for drug delivery. This review summarizes recent approaches considering stimuli-responsive, multifunctionality and more advanced architectures, such as vesicles or worm-like micelles, for tumor-specific drug and gene delivery.

  12. PREPARATION AND PROPERTIES OF SILICONE-ACRYLATE COPOLYMER LATEX

    Institute of Scientific and Technical Information of China (English)

    Mu-jie Yang; Wei Zhang

    2004-01-01

    Silicone-acrylate copolymer latex was prepared through three different polymerization processes, i.e., the batch process, preemulsified monomer addition and the monomer addition process. The results revealed that the monomer addition process is a desirable approach to produce narrow particle size distribution latex with higher polymerization conversion and less amount of coagulum. The effect of silicone content on the glossiness and water absorption of latex film was investigated and the results showed that the glossiness of latex film is improved up to a silicone content of 10% of total monomers, but becomes impaired thereafter, whereas water absorption is reduced accordingly.

  13. Analysis of Photosensitivity of Copolymer Optical Fibre Preform

    Institute of Scientific and Technical Information of China (English)

    MA Hui; LI Zeng-Chang; MING Hai; ZHANG Qi-Jin; TAM Hwa-Yaw; ZHANG Yong-Sheng; ZHANG Tao; WANG Pei; XIE Jian-Ping

    2004-01-01

    @@ The photosensitivity of copolymer optical fibre preform is analysed in comparison with the doped one. The effects of write conditions such as pump power and pump time have been studied. Then, the preform is drawn into single mode polymer optical fibre with core refractive index of 1.499, and core-cladding refractive-index difference of 0.008. Long-period birefringence gratings with period of 120um are fabricated in the fibre. The duty cycle is 50%, and the refractive index change in the exposed area is about 1 × 10-3.

  14. STUDY ON ACRYLAMIDE-SODIUM ACRYLATE COPOLYMER GELS

    Institute of Scientific and Technical Information of China (English)

    ZHOU Maotang; LI Qian; XU Jiping

    1990-01-01

    Acrylamide-sodium acrylate copolymer hydrogels have been obtained by radiation techniques.Two different methods have been used to introduce -COONa groups into polymer chains of the gels: (1) by partial hydrolysis of acrylamide homopolymer gel; (2) by direct copolymerization and crosslinking of acrylamide and sodium acrylate in aqueous solutions. It was found that the gels obtained in different ways had different properties, the swelling character of the gels obtained by partial hydrolysis were more sensitive to pH of swelling aqueous media. In order to explain these differences,13 C-NMR techniques were used to investigate the sequence distribution of monomer units of both gels.

  15. Self-assembly in casting solutions of block copolymer membranes

    KAUST Repository

    Marques, Debora S.

    2013-01-01

    Membranes with exceptional pore regularity and high porosity were obtained from block copolymer solutions. We demonstrate by small-angle X-ray scattering that the order which gives rise to the pore morphology is already incipient in the casting solution. Hexagonal order was confirmed in PS-b-P4VP 175k-b-65k solutions in DMF/THF/dioxane with concentrations as high as 24 wt%, while lamellar structures were obtained in more concentrated solutions in DMF or DMF/dioxane. The change in order has been understood with the support of dissipative particle dynamic modeling. © 2013 The Royal Society of Chemistry.

  16. Low molecular weight block copolymers as plasticizers for polystyrene

    DEFF Research Database (Denmark)

    Hansen, Kristoffer Karsten; Nielsen, Charlotte Juel; Hvilsted, Søren

    2005-01-01

    Polystyrene-b-alkyl, polystyrene-b-polybutadiene-b-polystyrene, and polystyrene-b-poly(propylene glycol)monotridecyl ether were synthesized using macro initiators and atom transfer radical polymerization or by esterifications of homopolymers. The aim was a maximum molecular weight of 4 kg...... for polystyrene-b-polyisoprene-b-polystyrene (SIS) block copolymers. The end use properties of SIS plasticized with polystyrene-b-alkyl, measured as tensile strength, is higher than for SIS plasticized with dioctyl adipate. The polystyrene-b-polybutadiene-b-polystyrene and polystyrene-bpoly(propylene glycol...

  17. Stability of the fcc structure in block copolymer systems.

    Science.gov (United States)

    Nonomura, Makiko

    2008-11-19

    The stability of the face-centered cubic (fcc) structure in microphase separated copolymers is investigated by a coarse-grained approach. Direct simulations of the equation for the microphase separation in three dimensions indicate that there is a narrow area above a certain degree of segregation in the phase diagram, where the fcc structure is the most stable structure. By employing the mode expansion, we have confirmed that the fcc structure can form as a metastable structure even in the weak segregation regime.

  18. SUBNANOMOLAR DETECTION OF ACID-LABILE SULFIDES BY THE CLASSICAL METHYLENE BLUE METHOD COUPLED TO HPLC. (R825395)

    Science.gov (United States)

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

  19. The acid-labile subunit of human ternary insulin-like growth factor binding protein complex in serum

    DEFF Research Database (Denmark)

    Juul, A; Møller, S; Mosfeldt-Laursen, E;

    1998-01-01

    of ALS determination is not known. We therefore, determined the: 1) hepatosplanchnic release of ALS by liver vein catheterization (n=30); 2) 24-h diurnal variation of ALS (n=8); 3) normal age-related ranges of circulating ALS (n=1158); 4) diagnostic value of ALS in 108 patients with childhood-onset GH...

  20. Thermal degradation behavior of methyl methacrylate derived copolymer.

    Science.gov (United States)

    Kaya, Esin; Kurt, Adnan; Er, Mustafa

    2012-11-01

    A novel copolymer of 2-hydroxy-3-menthyloxy-1-(4-methoxyphenyl)-3-oxopropyl methacrylate (HMOPMA) and methyl methacrylate (MMA), [poly(HMOPMA-co-MMA)], was synthesized by free radical polymerization. The percentages of HMOPMA and MMA units obtained in the copolymer composition were 19% and 81%, respectively. The solubility parameter of poly(HMOPMA-co-MMA) was found to be 10.3 cal(1/2) cm(-3/2) by turbidimetric titration method. Thermal degradation mechanism and activation energies for initial decomposition process under non-isothermal conditions were determined by integral approximation methods from the thermogravimetric study. The decomposition activation energies of poly(HMOPMA-co-MMA) using Kissinger and Flyn-Wall-Ozawa methods were calculated as 119.99 kJ/mol and 125.34 kJ/mol, respectively. The study of kinetic equations showed that the reaction mechanism of decomposition process in the conversion range studied progressed with D1 mechanism, one-dimensional diffusion of deceleration type of solid state mechanism.

  1. Phase Separation in Poly(urethane urea) Multiblock Copolymers

    Science.gov (United States)

    Garrett, J. T.; Xu, R.; Cho, J.; Runt, J.

    2002-03-01

    The current paper is a continuation of our research on microdomain morphology and phase separation of model poly(urethane urea) copolymers, complimenting our previous AFM and small-angle x-ray scattering studies. Phase transitions were monitored using both dynamic mechanical analysis and DSC, taking care to keep the temperature below where chemical degradation becomes significant. Surprisingly, soft phase Tgs were found to consistently decrease in temperature with increasing hard segment content in the copolymers. This is seemingly in contrast with an increase in unlike segment mixing in the domains with increasing hard segment content, as determined from SAXS. Several possible explanations for this behavior are proposed. The nature of the hard domains was also characterized using wide-angle x-ray diffraction experiments. Evidence of very weak crystalline diffraction peak(s) where found, superimposed on the amorphous halo. Finally, we also evaluated the sensitivity of Fourier transform infrared spectroscopy to hard/soft segment phase separation in these systems.

  2. Ethylene-Octene Copolymers/Organoclay Nanocomposites: Preparation and Properties

    Directory of Open Access Journals (Sweden)

    Alice Tesarikova

    2016-01-01

    Full Text Available Two ethylene-octene copolymers with 17 and 45 wt.% of octene (EOC-17 and EOC-45 were compared in nanocomposites with Cloisite 93A. EOC-45 nanocomposites have a higher elongation at break. Dynamical mechanical analysis (DMA showed a decrease of tan⁡δ with frequency for EOC-17 nanocomposites, but decrease is followed by an increase for EOC-45 nanocomposites; DMA showed also increased modulus for all nanocomposites compared to pure copolymers over a wide temperature range. Barrier properties were improved about 100% by addition of organoclay; they were better for EOC-17 nanocomposites due to higher crystallinity. X-ray diffraction (XRD together with transmission electron microscopy (TEM showed some intercalation for EOC-17 but much better dispersion for EOC-45 nanocomposites. Differential scanning calorimetry (DSC showed increased crystallization temperature Tc for EOC-17 nanocomposite (aggregates acted as nucleation agents but decrease Tc for EOC-45 nanocomposite together with greatly influenced melting peak. Accelerated UV aging showed smaller C=O peak for EOC-45 nanocomposites.

  3. Monte Carlo Simulation for the Adsorption of Symmetric Triblock Copolymers

    Institute of Scientific and Technical Information of China (English)

    彭昌军; 李健康; 刘洪来; 胡英

    2004-01-01

    The adsorption behavior of symmetric triblock copolymers, Am/2BnAm/2, from a nonselective solvent at solid-liquid interface has been studied by Monte Carlo simulations on a simple lattice model. Either segment A or segment B is attractive, while the other is non-attractive to the surface. Influences of the adsorption energy,bulk concentration, chain composition and chain length on the microstructure of adsorbed layers are presented.The results show that the total surface coverage and the adsorption amount increases monotonically as the bulk concentration increases. The larger the adsorption energy and the higher the fraction of adsorbing segments, the higher the total surface coverage is exhibited. The product of surface coverage and the proportion of non-attractive segments are nearly independent of the chain length, and the logarithm of the adsorption amount is a linear function of the reciprocal of the reduced temperature. When the adsorption energy is larger, the adsorption amount exhibits a maximum as the fraction of adsorbing segment increases. The adsorption isotherms of copolymers with different length of non-attractive segments can be mapped onto a single curve under given adsorption energy. The adsorption layer thickness decreases as the adsorption energy and the fraction of adsorbing segments increases, but it increhses as the length of non-attractive segments increases. The tails mainly govern the adsorption layer thickness.

  4. Complexation Between Cationic Diblock Copolymers and Plasmid DNA

    Science.gov (United States)

    Jung, Seyoung; Reineke, Theresa; Lodge, Timothy

    Deoxyribonucleic acids (DNA), as polyanions, can spontaneously bind with polycations to form polyelectrolyte complexes. When the polycation is a diblock copolymer with one cationic block and one uncharged hydrophilic block, the polyelectrolyte complexes formed with plasmid DNA (pDNA) are often colloidally stable, and show great promise in the field of polymeric gene therapy. While the resulting properties (size, stability, and toxicity to biological systems) of the complexes have been studied for numerous cationic diblocks, the fundamentals of the pDNA-diblock binding process have not been extensively investigated. Herein, we report how the cationic block content of a diblock influences the pDNA-diblock interactions. pDNA with 7164 base pairs and poly(2-deoxy-2-methacrylamido glucopyranose)-block-poly(N-(2-aminoethyl) methacrylamide) (PMAG-b-PAEMA) are used as the model pDNA and cationic diblock, respectively. To vary the cationic block content, two PMAG-b-PAEMA copolymers with similar PMAG block lengths but distinct PAEMA block lengths and a PAEMA homopolymer are utilized. We show that the enthalpy change from pDNA-diblock interactions is dependent on the cationic diblock composition, and is closely associated with both the binding strength and the pDNA tertiary structure.

  5. Clear antismudge unimolecular coatings of diblock copolymers on glass plates.

    Science.gov (United States)

    Macoretta, Danielle; Rabnawaz, Muhammad; Grozea, Claudia M; Liu, Guojun; Wang, Yu; Crumblehulme, Alison; Wyer, Martin

    2014-12-10

    Two poly[3-(triisopropyloxysilyl)propyl methacrylate]-block-poly[2-(perfluorooctyl)ethyl methacrylate] (PIPSMA-b-PFOEMA) samples and one poly(perfluoropropylene oxide)-block-poly-[3-(triisopropyloxysilyl)propyl methacrylate] (PFPO-b-PIPSMA) sample were synthesized, characterized, and used to coat glass plates. These coatings were formed by evaporating a dilute polymer solution containing HCl, which catalyzed PIPSMA's sol-gel chemistry. Polymer usage was minimized by targeting at diblock copolymer unimolecular (brush) layers that consisted of a sol-gelled grafted PIPSMA layer and an oil- and water-repellant fluorinated surface layer. Investigated is the effect of varying the catalyst amount, polymer amount, as well as block copolymer type and composition on the structure, morphology, and oil- and water-repellency of the coatings. Under optimized conditions, the prepared coatings were optically clear and resistant to writing by a permanent marker. The marker's trace was the faintest on PFPO-b-PIPSMA coatings. In addition, the PFPO-b-PIPSMA coatings were far more wear-resistant than the PIPSMA-b-PFOEMA coatings.

  6. Hollow ZIF-8 Nanoworms from Block Copolymer Templates

    KAUST Repository

    Yu, Haizhou

    2015-10-16

    Recently two quite different types of “nano-containers” have been recognized as attractive potential drug carriers; these are wormlike filamenteous micelles (“filomicelles”) on the one hand and metal organic frameworks on the other hand. In this work we combine these two concepts. We report for the first time the manufacturing of metal organic framework nanotubes with a hollow core. These worm-like tubes are about 200 nm thick and several μm long. The preparation is simple: we first produce long and flexible filament-shaped micelles by block copolymer self-assembly. These filomicelles serve as templates to grow a very thin layer of interconnected ZIF-8 crystals on their surface. Finally the block copolymer is removed by solvent extraction and the hollow ZIF-8 nanotubes remain. These ZIF-NTs are surprisingly stable and withstand purification by centrifugation. The synthesis method is straightforward and can easily be applied for other metal organic framework materials. The ZIF-8 NTs exhibit high loading capacity for the model anti cancer drug doxorubicin (DOX) with a pH-triggered release. Hence, a prolonged circulation in the blood stream and a targeted drug release behavior can be expected.

  7. Effect of solvents on the enzyme mediated degradation of copolymers

    Science.gov (United States)

    Banerjee, Aditi; Chatterjee, Kaushik; Madras, Giridhar

    2015-09-01

    The biodegradation of polycaprolactone (PCL), polylactic acid (PLA), polyglycolide (PGA) and their copolymers, poly (lactide-co-glycolide) and poly (D, L-lactide-co-caprolactone) (PLCL) was investigated. The influence of different solvents on the degradation of these polymers at 37 °C in the presence of two different lipases namely Novozym 435 and the free lipase of porcine pancreas was investigated. The rate coefficients for the polymer degradation and enzyme deactivation were determined using continuous distribution kinetics. Among the homopolymers, the degradation of PGA was nearly an order of magnitude lower than that for PCL and PLA. The overall rate coefficients of the copolymers were higher than their respective homopolymers. Thus, PLCL degraded faster than either PCL or PLA. The degradation was highly dependent on the viscosity of the solvent used with the highest degradation observed in acetone. The degradation of the polymers in acetone was nearly twice that observed in dimethyl sulfoxide indicating that the degradation decreases with increase in the solvent viscosity. The degradation of the polymers in water-solvent mixtures indicated an optimal water content of 2.5 wt% of water.

  8. Hollow ZIF-8 Nanoworms from Block Copolymer Templates

    Science.gov (United States)

    Yu, Haizhou; Qiu, Xiaoyan; Neelakanda, Pradeep; Deng, Lin; Khashab, Niveen M.; Nunes, Suzana P.; Peinemann, Klaus-Viktor

    2015-10-01

    Recently two quite different types of “nano-containers” have been recognized as attractive potential drug carriers; these are wormlike filamenteous micelles (“filomicelles”) on the one hand and metal organic frameworks on the other hand. In this work we combine these two concepts. We report for the first time the manufacturing of metal organic framework nanotubes with a hollow core. These worm-like tubes are about 200 nm thick and several μm long. The preparation is simple: we first produce long and flexible filament-shaped micelles by block copolymer self-assembly. These filomicelles serve as templates to grow a very thin layer of interconnected ZIF-8 crystals on their surface. Finally the block copolymer is removed by solvent extraction and the hollow ZIF-8 nanotubes remain. These ZIF-NTs are surprisingly stable and withstand purification by centrifugation. The synthesis method is straightforward and can easily be applied for other metal organic framework materials. The ZIF-8 NTs exhibit high loading capacity for the model anti cancer drug doxorubicin (DOX) with a pH-triggered release. Hence, a prolonged circulation in the blood stream and a targeted drug release behavior can be expected.

  9. Non-liftoff block copolymer nanolithography of magnetic nanodot arrays

    Science.gov (United States)

    Baruth, A.; Rodwogin, M. D.; Shankar, A.; Torija, M. A.; Erickson, M. J.; Hillmyer, M. A.; Leighton, C.

    2011-03-01

    Nanolithographic techniques based on self-assembled block copolymer templates offer exceptional potential for fabrication of large-area nanostructure arrays from a wide variety of functional materials. Despite significant progress with control of the template ordering, and development of pattern transfer schemes, significant issues exist with common techniques such as lift-off and etching. Here, we demonstrate successful execution of a nanolithographic process based on climate-controlled solvent annealing of easily degradable cylinder-forming poly(styrene- b -lactide) block copolymer films that avoids both lift-off and the most challenging aspects of etching. Essentially, we use an overfill/planarize/etch-back ``Damascene-type'' process, exploiting the large Ar ion beam etch rate contrast between polystyrene and typical metals. The process is demonstrated via formation of a large-area array of 12 nm thick, 25 +/- 3 nm diameter Ni 80 Fe 20 nanodots (~ 0.4 x 1012 dots/ in 2) with hexagonally-close-packed local order. Extensive microscopy, magnetometry, and electrical measurements provide detailed characterization of the pattern formation and fidelity. We argue that this generic approach can be applied to a wide variety of materials and is scalable to even smaller feature sizes. Funded by NSF MRSEC.

  10. Metal Nanoparticle/Block Copolymer Composite Assembly and Disassembly.

    Science.gov (United States)

    Li, Zihui; Sai, Hiroaki; Warren, Scott C; Kamperman, Marleen; Arora, Hitesh; Gruner, Sol M; Wiesner, Ulrich

    2009-01-01

    Ligand-stabilized platinum nanoparticles (Pt NPs) were self-assembled with poly(isoprene-block-dimethylaminoethyl methacrylate) (PI-b-PDMAEMA) block copolymers to generate organic-inorganic hybrid materials. High loadings of NPs in hybrids were achieved through usage of N,N-di-(2-(allyloxy)ethyl)-N-3-mercaptopropyl-N-3-methylammonium chloride as the ligand, which provided high solubility of NPs in various solvents as well as high affinity to PDMAEMA. From NP synthesis, existence of sub-1 nm Pt NPs was confirmed by high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) images. Estimations of the Pt NP ligand head group density based on HAADF-STEM images and thermogravimetric analysis (TGA) data yielded results comparable to what has been found for alkanethiol self-assembled monolayers (SAMs) on flat Pt {111} surfaces. Changing the volume fraction of Pt NPs in block copolymer-NP composites yielded hybrids with spherical micellar, wormlike micellar, lamellar and inverse hexagonal morphologies. Disassembly of hybrids with spherical, wormlike micellar, and lamellar morphologies generated isolated metal-NP based nano-spheres, cylinders and sheets, respectively. Results suggest the existence of powerful design criteria for the formation of metal-based nanostructures from designer blocked macromolecules.

  11. Designing block copolymer architectures for targeted membrane performance

    KAUST Repository

    Dorin, Rachel Mika

    2014-01-01

    Using a combination of block copolymer self-assembly and non-solvent induced phase separation, isoporous ultrafiltration membranes were fabricated from four poly(isoprene-b-styrene-b-4-vinylpyridine) triblock terpolymers with similar block volume fractions but varying in total molar mass from 43 kg/mol to 115 kg/mol to systematically study the effect of polymer size on membrane structure. Small-angle X-ray scattering was used to probe terpolymer solution structure in the dope. All four triblocks displayed solution scattering patterns consistent with a body-centered cubic morphology. After membrane formation, structures were characterized using a combination of scanning electron microscopy and filtration performance tests. Membrane pore densities that ranged from 4.53 × 1014 to 1.48 × 1015 pores/m 2 were observed, which are the highest pore densities yet reported for membranes using self-assembly and non-solvent induced phase separation. Hydraulic permeabilities ranging from 24 to 850 L m-2 h-1 bar-1 and pore diameters ranging from 7 to 36 nm were determined from permeation and rejection experiments. Both the hydraulic permeability and pore size increased with increasing molar mass of the parent terpolymer. The combination of polymer characterization and membrane transport tests described here demonstrates the ability to rationally design macromolecular structures to target specific performance characteristics in block copolymer derived ultrafiltration membranes. © 2013 Elsevier Ltd. All rights reserved.

  12. Transport of Water in Semicrystalline Block Copolymer Membranes

    Science.gov (United States)

    Hallinan, Daniel; Oparaji, Onyekachi

    Poly(styrene)-block-poly(ethylene oxide) (PS- b-PEO) is a semicrystalline block copolymer (BCP) with interesting properties. It is mechanically tough, amphiphilic, and has a polar phase. The mechanical toughness is due to the crystallinity of PEO and the high glass transition temperature of PS, as well as the morphological structure of the BCP. The polymer has high CO2, water, and salt solubility that derive from the polar PEO component. Potential applications include CO2 separation, water purification, and lithium air batteries. In all of the aforementioned applications, water transport is an important parameter. The presence of water can also affect thermal and mechanical properties. Water transport and thermal and mechanical properties of a lamellar PS- b-PEO copolymer have been measured as a function of water activity. Water transport can be affected by the heterogeneous nature of a semicrystalline BCP. Therefore, Fourier transform infrared - attenuated total reflectance (FTIR-ATR) spectroscopy has been employed, because water transport and polymer swelling can be measured simultaneously. The effect of BCP structure on transport has been investigated by comparing water transport in PS- b-PEO to a PEO homopolymer. The crystalline content of the PEO and the presence of glassy PS lamellae will be used to explain the transport results.

  13. PEGYLATED SINGLE-WALLED CARBON NANOTUBES WITH GELABLE BLOCK COPOLYMERS

    Institute of Scientific and Technical Information of China (English)

    Cheng Zhang; Wen Zhu; Lei Gao; Yong-ming Chen

    2011-01-01

    Functional amphiphilic block copolymer poly(ethylene glycol)-block-poly[(3-(triethoxysilyl)propyl methacrylate)-co-(1-pyrene-methyl) methacrylate], PEG113-b-P(TEPM26-co-PyMMA4),was synthesized via atom transfer radical polymerization (ATRP) initiated by monomethoxy capped poly(ethylene glycol) bromoisobutyrate.This polymer exhibited strong ability to disperse and exfoliate single-walled carbon nanotubes (SWNTs) in different solvents due to the adhesion of pyrene units to surface of SWNTs.In aqueous solution,the PTEPM segments that were located on the nanotube surfaces with the pyrene units could be gelated and,as a result,the silica oxide networks with PEG coronas were formed on the surface of nanotubes,which ensured the composites with a good dispersibility and stability.Furthermore,functional silane coupling agents,3-mercaptopropyltrimethoxysilane and 3-aminopropyltriethoxysilane,were introduced during dispersion of SWNTs using the block copolymers.They were co-gelated with PTEPM segments,and the -SH and -NH2 functionalitieswere introduced into the silica oxide coats respectively.

  14. Molecular exchange in block copolymer micelles: when corona chains overlap

    Science.gov (United States)

    Lu, Jie; Lodge, Timothy; Bates, Frank; Choi, Soohyung

    2013-03-01

    The chain exchange kinetics of poly(styrene-b-ethylenepropylene) (PS-PEP) diblock copolymer micelles in squalane (C30H62) was investigated using time-resolved small angle neutron scattering (TR-SANS). The solvent is a mixture of h-squalane and d-squalane that contrast-matches a mixed 50/50 h/d PS micelle core. As isotope labeled chains exchange, the core contrast decreases, leading to a reduction in scattering intensity. This strategy therefore allows direct probing of the chain exchange rate. Separate copolymer micellar solutions containing either deuterium labeled (dPS) or normal (hPS) poly(styrene) core blocks were prepared and mixed at room temperature, below the core glass transition temperature. The samples were heated to several temperatures (around 100 °C) and monitored by TR-SANS every 5 min. As polymer concentration was increased from 1% to 15% by volume, we observed a significant slowing down of chain exchange rate. Similar retarded kinetics was found when part of the solvent in the 1% solution was replaced by homopolymer PEP (comparable size as corona block). Furthermore, if all the solvent is replaced with PEP, no exchange was detected for up to 3hr at 200 °C. These results will be discussed in terms of a molecular model for chain exchange Infineum, Iprime, NIST, ORNL

  15. DEFORMATION OF COPOLYMER MICELLES INDUCED BY AMPHIPHILIC DIMER PARTICLES

    Institute of Scientific and Technical Information of China (English)

    Xiao-chun Qin; Chun-lai Ren

    2012-01-01

    Combining self-consistent-field theory and density-functional theory,we systematically study the deformation of copolymer micelles induced by the presence of amphiphilic dimer particles.Due to the amphiphilic nature,dimer particles tend to accumulate onto the interface of the copolymer micelle.With increasing concentration of the symmetric dimer particles,which are made of two identical spherical particles,the micelle deforms from the initial sphere to ellipse,dumbbell,and finally separates into two micelles.Furthermore,asymmetric dimer particles,composed by two particles with different sizes,are considered to investigate the influence of geometry of dimer particles on the deformation of the micelle.It is found that the micelle inclines to deform into dumbbell due to the additional curvature originating in the gathering of asymmetric dimer particles onto the interface of the micelle.The present study on the deformation of micelles is useful to understand the possible shape variation in the course of cell division/fusion.

  16. Crystalline free energies of micelles of diblock copolymer solutions

    CERN Document Server

    D'Adamo, Giuseppe; 10.1063/1.3509391

    2012-01-01

    We report a characterization of the relative stability and structural behavior of various micellar crystals of an athermal model of AB-diblock copolymers in solution. We adopt a previously devel- oped coarse-graining representation of the chains which maps each copolymer on a soft dumbbell. Thanks to this strong reduction of degrees of freedom, we are able to investigate large aggregated systems, and for a specific length ratio of the blocks f = MA/(MA + MB) = 0.6, to locate the order-disorder transition of the system of micelles. Above the transition, mechanical and thermal properties are found to depend on the number of particles per lattice site in the simulation box, and the application of a recent methodology for multiple occupancy crystals (B.M. Mladek et al., Phys. Rev. Lett. 99, 235702 (2007)) is necessary to correctly define the equilibrium state. Within this scheme we have performed free energy calculations at two reduced density {\\rho}/{\\rho}\\ast = 4,5 and for several cubic structures as FCC,BCC,A1...

  17. Perfluorocyclobutyl-containing Amphiphilic Block Copolymers Synthesized by RAFT Polymerization

    Institute of Scientific and Technical Information of China (English)

    LI, Yongjun; ZHANG, Sen; FENG, Chun; ZHANG, Yaqin; LI, Qingnuan; LI, Wenxin; HUANG, Xiaoyu

    2009-01-01

    Amphiphilic block copolymers containing hydrophobic perfluorocyclobutyl-based (PFCB) polyacrylate and hydrophilic poly(ethylene glycol) (PEG) segments were prepared via reversible addition-fragmentation chain transfer (RAP-T) polymerization. The PFCB-containing acrylate monomer, p-(2-(p-tolyloxy)perfluorocyclobutoxy)phenyl acrylate, was first synthesized from commercially available compounds in good yields, and this kind of acrylate monomer can be homopolymerized by free radical polymerization or RAFT polymerization. Kinetic study showed the 2,2'-azobis(isobutyronitrile) (AIBN) initiated and cumyl dithiobenzoate (CDB) mediated RAFT polymerization was in a living fashion, as suggested by the fact that the number-average molecular weights (M_n) increased linearly with the conversions of the monomer, while the polydispersity indices kept less than 1.10. The block polymers with narrow molecular weight distributions (M_w/M_n≤1.21) were prepared through RAFT polymerization using PEG monomethyl ether capped with 4-cyanopentanoic acid dithiobenzoate end group as the macro chain transfer agent (mPEG-CTA). The length of the hydrophobic segment can be tuned by the feed ratio of the PFCB-based acrylate monomer and the extending of the polymerization time. The micellization behavior of the block copolymers in aqueous media was investigated by the fluorescence probe technique.

  18. Responsive block copolymer photonics triggered by protein-polyelectrolyte coacervation.

    Science.gov (United States)

    Fan, Yin; Tang, Shengchang; Thomas, Edwin L; Olsen, Bradley D

    2014-11-25

    Ionic interactions between proteins and polyelectrolytes are demonstrated as a method to trigger responsive transitions in block copolymer (BCP) photonic gels containing one neutral hydrophobic block and one cationic hydrophilic block. Poly(2-vinylpyridine) (P2VP) blocks in lamellar poly(styrene-b-2-vinylpyridine) block copolymer thin films are quaternized with primary bromides to yield swollen gels that show strong reflectivity peaks in the visible range; exposure to aqueous solutions of various proteins alters the swelling ratios of the quaternized P2VP (QP2VP) gel layers in the PS-QP2VP materials due to the ionic interactions between proteins and the polyelectrolyte. Parameters such as charge density, hydrophobicity, and cross-link density of the QP2VP gel layers as well as the charge and size of the proteins play significant roles on the photonic responses of the BCP gels. Differences in the size and pH-dependent charge of proteins provide a basis for fingerprinting proteins based on their temporal and equilibrium photonic response. The results demonstrate that the BCP gels and their photonic effect provide a robust and visually interpretable method to differentiate different proteins.

  19. Fabrication of Bioactive Surfaces by Functionalization of Electroactive and Surface-Active Block Copolymers

    Directory of Open Access Journals (Sweden)

    Omotunde Olubi

    2014-08-01

    Full Text Available Biofunctional block copolymers are becoming increasingly attractive materials as active components in biosensors and other nanoscale electronic devices. We have described two different classes of block copolymers with biofuctional properties. Biofunctionality for block copolymers is achieved through functionalization with appropriate biospecific ligands. We have synthesized block copolymers of electroactive poly(3-decylthiophene and 2-hydroxyethyl methacrylate by atom transfer radical polymerization. The block copolymers were functionalized with the dinitrophenyl (DNP groups, which are capable of binding to Immunoglobulin E (IgE on cell surfaces. The block copolymers were shown to be redox active. Additionally, the triblock copolymer of α, ω-bi-biotin (poly(ethylene oxide-b-poly (styrene-b-poly(ethylene oxide was also synthesized to study their capacity to bind fluorescently tagged avidin. The surface-active property of the poly(ethylene oxide block improved the availability of the biotin functional groups on the polymer surfaces. Fluorescence microscopy observations confirm the specific binding of biotin with avidin.

  20. Effect of Copolymer Chain Architecture on Active Layer Morphology and Device Performance

    Science.gov (United States)

    Amonoo, Jojo; Li, Anton; Sykes, Matthew; Huang, Bingyuan; Palermo, Edmund; McNeil, Anne; Shtein, Max; Green, Peter

    2014-03-01

    The optimum morphological structure that determines the device performance of bulk heterojunction thin film polymer solar cells is greatly influenced by the extent of phase separation between the polymer and fullerene components, which ultimately defines the length scales and purity of the donor- and acceptor-rich phases. Block copolymer thin films have been widely studied for their ability to microphase separate into well-defined nanostructures. Nickel-catalyzed chain-growth copolymerizations of thiophene and selenophene derivatives afforded well-defined π-conjugated copolymers of poly(3-hexylthiophene) (P3HT) and poly(3-hexylselenophene) (P3HS) to achieve diblock, random and gradient copolymer chain architectures. This allowed us to study the effect of copolymer sequence and nanoscale morphology of P3HT-P3HS copolymer/[6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) on device performance. With the use of energy-filtered transmission electron microscopy and conductive and photoconductive atomic force microscopy we found that copolymer sequence strongly influences the phase separation capabilities of the copolymer-fullerene blend in bulk heterojunction organic photovoltaic devices.

  1. Block copolymer morphologies confined by square-shaped particle: Hard and soft confinement

    Science.gov (United States)

    Zhang, Qiyi; Yang, Wenyan; Hu, Kaiyan

    2016-11-01

    The self-assembly of diblock copolymers confined around one square-shaped particle is studied systematically within two-dimensional self-consistent field theory (SCFT). In this model, we assume that the thin block copolymer film is confined in the vicinity of a square-shaped particle by a homopolymer melt, which is equivalent to the poor solvents. Multiple sequences of square-shaped particle-induced copolymer aggregates with different shapes and self-assembled internal morphologies are predicted as functions of the particle size, the structural portion of the copolymer, and the volume fraction of the copolymer. A rich variety of aggregates are found with complex internal self-assembled morphologies including complex structures of the vesicle, with one or several inverted micelle surrounded by the outer monolayer with the particle confined in the core. These results demonstrate that the assemblies of diblock copolymers formed around the square-shaped particle in poor solvents are of immediate interest to the assembly of copolymer and the morphology of biomembrane in the confined environment, as well as to the transitions of vesicles to micelles. Project supported by the National Natural Science Foundation of China (Grant No. 20804060) and the Research Foundation of Chongqing University of Science and Technology, China (Grant No. CK2013B16).

  2. Surface functionalization of carbon nanotubes by direct encapsulation with varying dosages of amphiphilic block copolymers

    Science.gov (United States)

    Yao, Xueping; Li, Jie; Kong, Liang; Wang, Yong

    2015-08-01

    Encapsulation of carbon nanotubes (CNTs) by amphiphilic block copolymers is an efficient way to stabilize CNTs in solvents. However, the appropriate dosages of copolymers and the assembled structures are difficult to predict and control because of the insufficient understanding on the encapsulation process. We encapsulate multiwalled CNTs with polystyrene-block-poly (4-vinyl pyridine) (PS-b-P4VP) by directly mixing them in acetic acid under sonication. The copolymer forms a lamellar structure along the surface of CNTs with the PS blocks anchoring on the tube wall and the P4VP blocks exposed to the outside. The encapsulated CNTs achieve good dispersibility in polar solvents over long periods. To increase our understanding of the encapsulation process we investigate the assembled structures and stability of copolymer/CNTs mixtures with changing mass ratios. Stable dispersions are obtained at high mass ratios between the copolymer and CNTs, i.e. 2 or 3, with the presence of free spherical micelles. Transmission electron microscopy and thermal gravimetric analysis determine that the threshold for the complete coverage of CNTs by the copolymer occurs at the mass ratio of 1.5. The coated copolymer layer activates the surface of CNTs, enabling further functionalization of CNTs. For instance, atomic layer deposition of TiO2 produces conformal thin layers on the encapsulated CNTs while isolated TiO2 bumps are produced on the pristine, inert CNTs.

  3. Mechanical properties of designed multicompartment gels formed by ABC graft copolymers.

    Science.gov (United States)

    Jiang, Tao; Wang, Liquan; Lin, Jiaping

    2013-10-01

    In the present work, we designed a multicompartment gel by taking advantage of the ABC graft copolymer with a solvophilic A backbone and solvophobic B and C grafts. The mechanical properties of such designed gels were investigated by a combination of dissipative particle dynamics simulation and a nonequilibrium deformation technique. The extensional moduli of multicompartment gels were found to be dependent on polymer concentration and architectural parameters of the graft copolymers (the sequence of graft arms and the position of the graft points). The graft copolymer solutions undergo a sol-gel transition as the polymer concentration increases. This leads to an abrupt increase in the extensional modulus. The studies also revealed that the multicompartment gels of graft copolymers exhibit higher extensional moduli than those of nonmulticompartment gels of graft copolymers and triblock copolymer gels. The position of graft points plays another important role in determining the extensional moduli of the multicompartment gels. The effects of graft positions on the gel modulus were found to be associated with the bridging fraction of graft copolymer chains. The results gained through the present work may provide useful guidance for designing high-performance gels.

  4. Synthesis, Micellization and Characterization of Novel Amphiphilic β-Cyclodextrin/Poly(L-aspartate) Copolymer

    Institute of Scientific and Technical Information of China (English)

    GUO Yan-ling; CUI Zhao-shan; HAN Min

    2013-01-01

    A novel amphiphilic β-cyclodextrin/poly(L-aspartate)(β-CD-PASP) copolymer was prepared by ringopening polymerization of polysuccinimide(PSI).This copolymer bears β-CD units along the macromolecular chain and the structure was characterized by infrared(IR) and proton nuclear magnetic resonance(1H NMR).The molecular weight of the copolymer was determined by gel permeation chromatography(GPC).The copolymer micelle were prepared by direct dissolution method.The critical micelle concentration(CMC) of the copolymer micelle was measured by flourescence technique with pyrene as probe.The size distribution of micelle was characterized on a dynamic laser light scattering particle size analyzer and its shape was observed by transmission electron microscopy(TEM).The results show that the copolymer could self-assemble into micelle with a low CMC,and the effective diameter of the micelle was 116.3 nm.The methotrexate(MTX)-loaded micelle were prepared and the drug loading content(DLC) was 22.86%.The MTX-loaded copolymer exhibited a better water-solubility than the free drug.

  5. How to Place Block Copolymer Molecules at the Interface of a Binary Blend

    Science.gov (United States)

    Chen, Zhong-Ren; Xu, Yuci; Zhong, Shuo

    2015-03-01

    Block copolymers have been used to reduce the domain size of immiscible polymer blends and thus improve the mechanical and other properties. The effectiveness of this method, however, depends on the percentage of these polymeric surfactants residing at the interface of the blend. In fact, theoretical as well as experimental work indicate that a large percentage of block copolymers form micelles in the bulk of one or both of the component polymers. These micelles may serve as weak spots initiating crack propagation. Previous work have been focused on the design of molecular architecture and synthesis of new block copolymers to address this problem. In this presentation, a simple mixing strategy is applied to make each block copolymer molecule stay at the interface. As one example, when this strategy is used to mix natural rubber (NR) with butadiene rubber (BR), a small amount of low molecular weight block copolymer (LIR) improves both processing characteristics such as melt viscosity and mechanical properties of cured samples, such as crack resistance. AFM micrographs show the much smaller domain size; and an original real-time monitoring system reveals the lowest crack growth rate. Using a model A/B/A-B binary blend, we have witnessed by microscopy that all block copolymer molecules form micelles at the first mixing step, and all of these micelles are disappeared and all block copolymer molecules stay at the interface after the second mixing step.

  6. Anti-plasticizing effect of amorphous indomethacin induced by specific intermolecular interactions with PVA copolymer.

    Science.gov (United States)

    Ueda, Hiroshi; Aikawa, Shohei; Kashima, Yousuke; Kikuchi, Junko; Ida, Yasuo; Tanino, Tadatsugu; Kadota, Kazunori; Tozuka, Yuichi

    2014-09-01

    The mechanism of how poly(vinyl alcohol-co-acrylic acid-co-methyl methacrylate) (PVA copolymer) stabilizes an amorphous drug was investigated. Solid dispersions of PVA copolymer, poly(vinyl pyrrolidone) (PVP), and poly(vinyl pyrrolidone-co-vinyl acetate) (PVPVA) with indomethacin (IMC) were prepared. The glass transition temperature (Tg)-proportion profiles were evaluated by differential scanning calorimetry (DSC). General Tg profiles decreasing with the IMC ratio were observed for IMC-PVP and IMC-PVPVA samples. An interesting antiplasticizing effect of IMC on PVA copolymer was observed; Tg increased up to 20% IMC ratio. Further addition of IMC caused moderate reduction with positive deviation from theoretical values. Specific hydrophilic and hydrophobic interactions between IMC and PVA copolymer were revealed by infrared spectra. The indole amide of IMC played an important role in hydrogen bonding with PVA copolymer, but not with PVP and PVPVA. X-ray diffraction findings and the endotherm on DSC profiles suggested that PVA copolymer could form a semicrystalline structure and a possibility of correlation of the crystallographic nature with its low hygroscopicity was suggested. PVA copolymer was able to prevent crystallization of amorphous IMC through both low hygroscopicity and the formation of a specific intermolecular interaction compared with that with PVP and PVPVA.

  7. Synthesis and characterization of a novel PNIPAAm-based copolymer with hydrolysis-dependent thermosensitivity.

    Science.gov (United States)

    Rosellini, Elisabetta; Cristallini, Caterina; Guerra, Giulio D; Barbani, Niccoletta; Giusti, Paolo

    2010-06-01

    The aim of this work was the synthesis and characterization of a novel poly(N-isopropylacrylamide)-based copolymer, with hydrolysis-dependent thermosensitivity, for bioengineering applications. For this purpose, N-isopropylacrylamide (NIPAAm) and 2-hydroxyethylmethacrylate-6-hydroxyhexanoate (HEMAHex) monomers were chosen. The poly(NIPAAm-co-HEMAHex) copolymer was synthesized by radical polymerization. The physicochemical, mechanical, functional and biological properties of the copolymer were investigated. The physicochemical characterization confirmed that the copolymerization was successfully carried out. In addition, the newly synthesized poly(NIPAAm-co-HEMAHex) copolymer showed temperature sensitivity, with a phase separation temperature under body temperature (at 23 °C). Fourier transform infrared spectroscopy and differential scanning calorimetry results after hydrolysis tests indicated that the incorporation of the HEMAHex ester groups provides the cleavage of the lateral chain, which leads to an increase in the hydrophilicity of the copolymer and, consequently, to an increase in the lower critical solution temperature (LCST) with time. Since the LCST increases above body temperature (up to 40.4 °C), the copolymer becomes soluble again and diffuses away. It was also demonstrated that the hydrolysis occurred on the peripheral ester bond of the lateral chain, with the release of 6-hydroxyhexanoic acid, whose bioresorbibility has been reported in the literature. Therefore, the properties of this copolymer are very interesting and make it particularly attractive for biomedical applications.

  8. Preparation and characterization of lignin based macromonomer and its copolymers with butyl methacrylate.

    Science.gov (United States)

    Liu, Xiaohuan; Wang, Jifu; Yu, Juan; Zhang, Mingming; Wang, Chunpeng; Xu, Yuzhi; Chu, Fuxiang

    2013-09-01

    Copolymerization of butyl methacrylate (BMA) with biobutanol lignin (BBL) was achieved by free-radical polymerization (FRP) using a lignin-based macromonomer. The lignin-based macromonomer containing acrylic groups was prepared by reacting acryloyl chloride with biobutanol lignin using triethylamine (TEA) as absorb acid agentin. From the results of elemental analysis and GPC, the average degree of polymerization (DP) of BBL was estimated to be five. A detailed molecular characterization has been performed, including techniques such as (1)H NMR, (13)C NMR and UV-vis spectroscopies, which provided quantitative information about the composition of the copolymers. The changes in the solubility of lignin-g-poly(BMA) copolymers in ethyl ether were dependent on the length of poly(BMA) side chain. TGA analysis indicated that the lignin-containing poly(BMA) graft copolymers exhibited high thermal stability. The bulky aromatic group of lignin increased the glass-transition temperature of poly(BMA). In order to confirm the main structure of copolymer, (AC-g-BBL)-co-BMA copolymer was also synthesized by atom transfer radical polymerization (ATRP), and the results revealed that the copolymer prepared by ATRP had the same solution behavior as that prepared by FRP, and the lignin-based macromonomer showed no homopolymerizability due to the steric hindrance. In addition, the lignin-co-BMA copolymer had a surprisingly higher molecular weight than poly(BMA) under the same reaction condition, suggesting that a branched lignin based polymer could be formed.

  9. Morphology and electrical properties of electrochemically synthesized pyrrole-formyl pyrrole copolymer

    Science.gov (United States)

    Gholami, Mehrdad; Nia, Pooria Moozarm; Alias, Yatimah

    2015-12-01

    A direct electrochemical copolymerization of pyrrole-formyl pyrrole (Py-co-FPy) was carried out by oxidative copolymerization of formyl pyrrole and pyrrole in LiClO4 aqueous solution through galvanostatic method. The (Py-co-FPy) copolymer was characterized using Fourier-transform infrared spectroscopy (FT-IR), field emission scanning electron microscope (FESEM), energy-filtering transmission electron microscope (EFTEM), thermal gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The FESEM images showed that the synthesized copolymer had a hollow whelk-like helixes structure, which justifies the enhancement of charge transportation through the copolymer film. Cyclic voltammetry studies revealed that the electrocatalytic activity of synthesized copolymer has improved and the surface coverage in copolymer enhanced 1.6 times compared to polypyrrole alone. Besides, (Py-co-FPy) copolymer showed 2.5 times lower electrochemical charge transfer resistance (Rct) value in impedance spectroscopy. Therefore, this copolymer has a strong potential to be used in several applications such as sensor applications.

  10. Diverging temperature responses of CO2 assimilation and plant development explain the overall effect of temperature on biomass accumulation in wheat leaves and grains.

    Science.gov (United States)

    Collins, Nicholas C; Parent, Boris

    2017-01-09

    There is a growing consensus in the literature that rising temperatures influence the rate of biomass accumulation by shortening the development of plant organs and the whole plant and by altering rates of respiration and photosynthesis. A model describing the net effects of these processes on biomass would be useful, but would need to reconcile reported differences in the effects of night and day temperature on plant productivity. In this study, the working hypothesis was that the temperature responses of CO2 assimilation and plant development rates were divergent, and that their net effects could explain observed differences in biomass accumulation. In wheat (Triticum aestivum) plants, we followed the temperature responses of photosynthesis, respiration and leaf elongation, and confirmed that their responses diverged. We measured the amount of carbon assimilated per "unit of plant development" in each scenario and compared it to the biomass that accumulated in growing leaves and grains. Our results suggested that, up to a temperature optimum, the rate of any developmental process increased with temperature more rapidly than that of CO2 assimilation and that this discrepancy, summarised by the CO2 assimilation rate per unit of plant development, could explain the observed reductions in biomass accumulation in plant organs under high temperatures. The model described the effects of night and day temperature equally well, and offers a simple framework for describing the effects of temperature on plant growth.

  11. Photosynthetic temperature responses of tree species in Rwanda: evidence of pronounced negative effects of high temperature in montane rainforest climax species

    Science.gov (United States)

    Vårhammar, Angelica; Wallin, Göran; McLean, Christopher M.; Dusenge, Mirindi Eric; Medlyn, Belinda E.; Hasper, Thomas B.; Nsabimana, Donat; Uddling, Johan

    2015-04-01

    The sensitivity of photosynthetic metabolism to temperature has been identified as a key uncertainty for projecting the magnitude of the terrestrial feedback on future climate change. While temperature responses of photosynthetic capacities have been comparatively well investigated in temperate species, the responses of tropical tree species remain unexplored. We compared the responses of seedlings of native cold-adapted tropical montane rainforest tree species to exotic warm-adapted plantation species, all growing in an intermediate temperature common garden in Rwanda. Leaf gas exchange responses to CO2 at different temperatures (20 - 40 C) were used to assess the temperature responses of biochemical photosynthetic capacities. Analyses revealed a lower optimum temperature for photosynthetic electron transport rates than for Rubisco carboxylation rates, along with lower electron transport optima in the native cold-adapted than in the exotic warm-adapted species. The photosynthetic optimum temperatures were generally exceeded by daytime peak leaf temperatures, in particular in the native montane rainforest climax species. This study thus provides evidence of pronounced negative effects of high temperature in tropical trees and indicates high susceptibility of montane rainforest climax species to future global warming. (Reference: New Phytologist, in press)

  12. Morphologies of diblock copolymer confined in a slit with patterned surfaces studied by dissipative particle dynamics

    Institute of Scientific and Technical Information of China (English)

    FENG Jian; HUANG Yongmin; LIU Honglai; HU Ying

    2007-01-01

    Diblock copolymers with ordered mesophase structures have been used as templates for nano-fabrication.Unfortunately,the ordered structure only exists at micrometerscale areas,which precludes its use in many advanced applications.To overcome this disadvantage,the diblock copolymer confined in a restricted system with a patterned surface is proved to be an effective means to prohibit the formation of defects and obtain perfect ordered domains.In this work,the morphologies of a thin film of diblock copolymer confined between patterned and neutral surfaces were studied by dissipative particle dynamics.It is shown that the morphology of the symmetric diblock copolymer is affected by the ratio of the pattern period on the surface to the lamellar period of the symmetric diblock copolymer and by the repulsion parameters between blocks and wall particles.To eliminate the defects in the lamellar phase,the pattern period on the surface must match the lamellar period.The difference in the interface energy of different compartments of the pattern should increase with increasing film thickness.The pattern period on the surface has a scaling relationship with the chain length,which is the same as that between the lamellar period and the chain length.The lamellar period is also affected by the polydispersity of the symmetric diblock copolymer.The total period is the average of the period of each component multiplied by the weight of its volume ratio.The morphologies of asymmetric diblock copolymers are also affected by the pattern on the surface,especially when the matching period of the asymmetric diblock copolymer is equal to the pattern period,which is approximately equal to the lamellar period of a symmetric diblock copolymer with the same chain length.

  13. Fluorosilicone multi-block copolymers tethering quaternary ammonium salt groups for antimicrobial purpose

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Fang; Qin, Xiaoshuai; Li, Yancai; Ren, Lixia; Zhao, Yunhui, E-mail: zhaoyunhui@tju.edu.cn; Yuan, Xiaoyan

    2015-08-30

    Highlights: • QAS-containing fluorosilicone multi-block copolymers were synthesized. • The block length of PHFBMA in the copolymers was tailored via RAFT polymerization. • Surface roughness of the copolymers decreased with the increased PHFBMA content. • A certain length of PHFBMA block enhanced C−N{sup +} percentage on the surface. - Abstract: Symmetrically structured fluorosilicone multi-block copolymers containing poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and poly(hexafluorobutyl methacrylate) (PHFBMA) were sequentially synthesized via reversible addition–fragmentation chain transfer polymerization, using a polydimethylsiloxane (PDMS) chain transfer agent with dithiocarbonate groups at both ends. Then, the CBABC-type block copolymers were quaternized with n-octyliodide to tether quaternary ammonium salt (QAS) groups in the PDMAEMA blocks for the antimicrobial use. The obtained fluorosilicone copolymers showed clear variations in the C-N{sup +} composition and surface morphology on their films depending on the content of the PHFBMA blocks, which were characterized by X-ray photoelectron spectroscopy and atomic force microscopy, respectively. The results indicated that the symmetrical CBABC structure favored PDMS and QAS tethered blocks migrating to the film surface. With the mass percentage of the PHFBMA increased from 0 to 32.5%, the surface roughness of the copolymer film decreased gradually with a tendency to form a smooth surface. Owing to the surface properties, fluorosilicone multi-block copolymers containing a certain amount of PHFBMA with higher C-N{sup +} content and relatively smooth morphology demonstrated obvious antimicrobial activity against Gram-positive bacteria, Bacillus subtilis and Gram-negative bacteria, Escherichia coli. The functionalized multi-block copolymers based on fluorosilicone and QAS groups would have potential applications in antimicrobial coatings.

  14. On the Use of Self-Assembling Block Copolymers to Toughen A Model Epoxy

    Science.gov (United States)

    Chen, Yilin

    Block copolymers have been receiving considerable attention in toughening epoxy due to their ability to form a wide variety of nanostructures. This study focuses on using both triblock and diblock copolymers to improve the fracture toughness of an aromatic-amine cured epoxy system. The curing system consisted of 1,3- phenylenediamine (mPDA) as curing agent and aniline as a chain extender. Three triblock copolymers and three diblock copolymers were incorporated in the same lightly crosslinked model epoxy system, which was chosen to mimic an underfill material in flip-chip packaging for the microelectronics industry. In this research, rubber particles were formed in situ using self-assembling block copolymers. Mechanical, thermal and microscopic studies were conducted with the main goal to study the relationship between the block parameters and the final morphologies and their effects on static and dynamic mechanical properties of the toughened resin, especially fracture toughness. In these block-copolymer-modified epoxies, spherical micelles and wormlike micelles were obtained by varying block lengths, molecular weight, polarities and compositions. It was found that miscibility of the epoxy-miscible block played a crucial role in the formation of different types of morphologies. At a low loading level, diblock copolymers were able to toughen the model epoxy as effectively as triblock copolymers. The fracture toughness was improved to almost three times with respect to that of the neat resin with addition of 10 phr AM*-27. At the same time, other mechanical properties, such as yield strength and modulus, were well retained. Incorporation of block copolymers did not have a significant effect on glass transition temperature but caused an increase in coefficient of thermal expansion (CTE) of the modified epoxy. Particle cavitation and matrix void growth were proved to be the toughening mechanisms for SBM-Modified epoxies. However, these typical toughening mechanisms for

  15. SYNTHESIS AND PROPERTIES OF COPOLYMERS CONTAINING CUCURBIT[6]URIL-BASED PSEUDOROTAXANE STRUCTURE

    Institute of Scientific and Technical Information of China (English)

    Qiang Ma; Hui Yang; Kimoon Kim; Ye-bang Tan

    2012-01-01

    Novel copolymers based on acrylamide (AM) and complex pseudorotaxane monomer N'-(3-vinylbenzyl)-l,4-diaminobutane dihydrochloride with cucurbit[6]uril (CB[6]) (3VBCB) were prepared via free-radical polymerization in aqueous solution,and characterized by 1H-NMR,FT-IR,elemental analysis and static light scattering.The compositions of the copolymers (PAM3VBCB) with pseudorotaxane units were determined by 1H-NMR and elemental analysis.Thermal properties of the copolymers were studied by TGA,and the effects of the copolymer concentration and pH on the average hydrodynamic radius (Rh) of the copolymer molecules were studied by dynamic light scattering (DLS).The experiment data show that CB[6] beads are localized on 1,4-diaminobutane units in side chains of the copolymers.TGA results show that thermal stability of the copolymer increases with increasing the content of pseudorotaxane unit because of the enhanced rigidity and the bulky steric hindrance of 3VBCB in side chains of PAM3VBCB.DLS data show that the average hydrodynamic radius of copolymer molecules increases with the increase in the copolymer concentration,and both the pH and electrical conductivity of PAM3VBCB solutions demonstrate an acute change with addition of NaOH because of CB[6]dethreading from the side chains of PAM3VBCB.CB[6] threading and dethreading of PAM3VBCB could be controlled by addition of BaCl2 and Na2SO4.

  16. Collaborative Research: Process-Resolving Decomposition of the Global Temperature Response to Modes of Low Frequency Variability in a Changing Climate

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Yi

    2014-11-24

    DOE-GTRC-05596 11/24/2104 Collaborative Research: Process-Resolving Decomposition of the Global Temperature Response to Modes of Low Frequency Variability in a Changing Climate PI: Dr. Yi Deng (PI) School of Earth and Atmospheric Sciences Georgia Institute of Technology 404-385-1821, yi.deng@eas.gatech.edu El Niño-Southern Oscillation (ENSO) and Annular Modes (AMs) represent respectively the most important modes of low frequency variability in the tropical and extratropical circulations. The projection of future changes in the ENSO and AM variability, however, remains highly uncertain with the state-of-the-science climate models. This project conducted a process-resolving, quantitative evaluations of the ENSO and AM variability in the modern reanalysis observations and in climate model simulations. The goal is to identify and understand the sources of uncertainty and biases in models’ representation of ENSO and AM variability. Using a feedback analysis method originally formulated by one of the collaborative PIs, we partitioned the 3D atmospheric temperature anomalies and surface temperature anomalies associated with ENSO and AM variability into components linked to 1) radiation-related thermodynamic processes such as cloud and water vapor feedbacks, 2) local dynamical processes including convection and turbulent/diffusive energy transfer and 3) non-local dynamical processes such as the horizontal energy transport in the oceans and atmosphere. In the past 4 years, the research conducted at Georgia Tech under the support of this project has led to 15 peer-reviewed publications and 9 conference/workshop presentations. Two graduate students and one postdoctoral fellow also received research training through participating the project activities. This final technical report summarizes key scientific discoveries we made and provides also a list of all publications and conference presentations resulted from research activities at Georgia Tech. The main findings include

  17. Preparation and Characterization of Copolymer Micelles Formed by Poly(ethylene glycol)-Polylactide Block Copolymers as Novel Drug Carriers

    Institute of Scientific and Technical Information of China (English)

    姜维; 王运东; 甘泉; 张建铮; 赵秀文; 费维扬; 贝建中; 王身国

    2006-01-01

    Diblock copolymer poly(ethylene glycol) methyl ether-polylactide (MePEG-PLA) micelles were prepared by dialysis against water. Indomethacin (IMC) as a model drug was entrapped into the micelles by dialysis method. The critical micelle concentration (CMC) of the prepared micelles in distilled water investigated by fluorescence spectroscopy was 0.0051mg/mL which is lower than that of common low molecular weight surfactants. The diameters of MePEG-PLA micelles and IMC loaded MePEG-PLA micelles in a number-averaged scale measured by dynamic light scattering were 52.4 and 53.7 nm respectively. The observation with transmission electron microscope and scanning electron microscope showed that the appearance of MePEG-PLA micelles was in a spherical shape. The content of IMC incorporated in the core portion of the micelles was 18% (ω). The effects of the synthesis method of the copolymer on the polydispersity of the micelles and the yield of the micelles formation were discussed.

  18. SYNTHESIS AND CHARACTERIZATION OF REACTIVE GRAFT COPOLYMER PDMS-g- (PEO-OH)

    Institute of Scientific and Technical Information of China (English)

    QIU Yongxing; YU Xiaojie; FENG Lingxian

    1995-01-01

    A new reactive graft copolymer, poly (dimethyl siloxane)-graft-ω-hydroxyl-poly (ethylene oxide) (PDMS-g-(PEO-OH)), was synthesized by the hydrosilylation reaction of α, ω-bifunctional PEO macromonomer (CH2=CH-CH2-PEO-OH) with poly (hydromethylsiloxane) (PHMS). The obtained copolymer, exhibited the expected comblike structure as indicated by the result of detailed characterization and the needed reactivity as demonstrated by the result of esterification between PDMS-g-(PEO-OH)and aminoacetic acid. This reactive graft copolymer is expected to be very useful in the preparation of new bioactive polymer materials.

  19. POTENTIAL USE OF GRAFT COPOLYMERS OF MERCERIZED FLAX AS FILLER IN POLYSTYRENE COMPOSITE MATERIALS

    Directory of Open Access Journals (Sweden)

    Susheel Kalia

    2008-11-01

    Full Text Available Graft copolymerization of binary vinyl monomers onto mercerized flax fiber was carried out for the enhancement of mechanical properties of polystyrene composites. Binary vinyl monomer mixture of AA+AN has been found to show maximum grafting (33.55% onto mercerized flax. Graft copolymers thus synthesized were characterized with FT-IR spectroscopy, SEM, and TGA techniques. Mercerized flax (MF showed maximum thermal stability in comparison to graft copolymers. It has been found that polystyrene composites reinforced with graft copolymers showed improvement in mechanical properties such as wear resistance, compressive strength, and tensile strength.

  20. Synthesis and Characterization of Amphiphilic Block Copolymer Containing PVP and Poly(5-benzyloxytrimethylene carbonate)

    Institute of Scientific and Technical Information of China (English)

    Ying Xia WANG; Feng HE; Ren Xi ZHUO

    2006-01-01

    Amphiphilic copolymer of 5-benzyloxytrimethylene carbonate (BTMC) with poly (vinyl pyrrolidone) (PVP) was successfully synthesized using immobilized porcine pancreas lipase (IPPL) or SnOct2 as catalyst. Hydroxyl terminated PVP, synthesized with 2-mercaptoethanol as a chain transfer reagent, was employed as a macroinitiator. The resulting copolymers were characterized by GPC, 1H NMR and IR. Increasing the BTMC/PVP-OH feed ratio ([B]/[P])resulted in the increase of Mn of corresponding copolymers and the decrease of Mw/Mn.Immobilized enzyme has comparable catalytic activity to SnOct2 for the copolymerization.

  1. Compositional Analysis of the High Molecular Weight Ethylene Oxide Propylene Oxide Copolymer by MALDI Mass Spectrometry

    CERN Document Server

    Houshia, Orwa Jaber

    2012-01-01

    The composition of narrow distribution poly ethylene oxide-propylene oxide copolymer (Mw ~ 8700 Da) was studied using matrix assisted laser desorption ionization (MALDI) mass spectrometry. The ethylene oxide-propylene oxide copolymer produced oligomers separated by 14 Da. The average resolving power over the entire spectrum was 28,000. Approximately 448 isotopically resolved peaks representing about 56 oligomers are identified. Although agreement between experimental and calculated isotopic distributions was strong, the compositional assignment was difficult. This is due to the large number of possible isobaric components. The purpose of this research is to resolve and study the composition of high mass copolymer such as ethylene oxide-propylene oxide.

  2. THE EFFECTS OF PATTERNED SURFACES ON THE PHASE SEPARATION FOR DIBLOCK COPOLYMERS

    Institute of Scientific and Technical Information of China (English)

    Lin-li He; Lin-xi Zhang

    2009-01-01

    The phase behaviors of symmetric diblock copolymer thin films confined between two hard, parallel and diversified patterned surfaces are investigated by three-dimensional dissipative particle dynamics (DPD) simulations. The induction of diversified patterned surfaces on phase separation of symmetric diblock copolymer films in snapshots, density profiles and concentration diagrams of the simulated systems are presented. The phase separations can be controlled by the patterned surfaces. In the meantime, the mean-square end-to-end distance of the confined polymer chains (R2) is also discussed. Surface-induced phase separation for diblock copolymers can help us to create novel and controlled nanostructured materials.

  3. GRAFTED STYRENE-DIVINYLBENZENE COPOLYMERS CONTAINING BENZALDEHYDES AND THEIR WITTIG REACTIONS WITH VARIOUS PHOSPHONIUM SALTS

    Institute of Scientific and Technical Information of China (English)

    Adriana Popa; Gheorghe Ilia; Aurelia Pascariu; Smaranda Iliescu; Nicoleta Plesu

    2005-01-01

    A chloromethylated styrene-divinylbenzene copolymer support system functionalized with 4-benzaldehyde and 2-benzaldehyde was prepared. The degree of functionalization with aldehyde groups is well suited for the subsequent use of the products as Wittig reagents. The polymer bound aldehyde was reacted with Wittig reagents to give olefin groups grafted on styrene-divinylbenzene copolymers. The reactions were carried out in phase transfer catalysis conditions. A simple procedure for the calculation of the degree of functionalization and the statistical modeling of the structural repetitive unit of the copolymer are reported.

  4. Non-random crosslinking of polysulphone-polysiloxane alternating block copolymers under irradiation

    Science.gov (United States)

    Xinfang, Chen; Chunshan, Zhang

    In this paper the effects of radiation on polysulphone-polysiloxane segmented copolymers have been investigated. The experimental observations indicate that the crosslinking reaction occurs primarily between siloxane segments and the intermolecular crosslinking of isopropylidene groups of adjacent polysulphone segments also takes place after the irradiation of higher doses. From the non-randon radiation crosslinking model which the block copolymer follows, the relationship between sol fraction and crosslink density is derived by a statistical method. The radiation crosslinking structure of block copolymers prepared by polycondensation of prepolymers, polysulphone and polysiloxane, can be controled by changing the average molecular weights of two prepolymers and the ratio of one component to the other.

  5. STUDY ON THE SYNTHESIS AND PROPERTIES OF POLY(ESTER-IMIDE-ETHER) MULTIBLOCK COPOLYMERS

    Institute of Scientific and Technical Information of China (English)

    Zu-yao Shan; Zhen-yi Li

    2000-01-01

    A new class of poly(ester-imide-ether) multiblock copolymers was synthesized by transes-terification and melt copolymerization of dimethyl terephthalate (DMT) and N-(4-carbomethoxyphenyl)-4-(carbomethoxy)-phthalimide with ethylene glycol (EG) and polytetramethylene glycol (PTMG). The structure of the above copolymers was characterized by 1H-NMR and IR spectroscopy. Some properties of the coplymers were also examined. It was found that their mechanical properties and heat stability, compared with poly(ether-ester) copolymers, were obviously improved.

  6. Synthesis and physicochemical characterization of copolymers of 3-octylthiophene and thiophene functionalized with azo chromophore

    Energy Technology Data Exchange (ETDEWEB)

    Nicho, M.E., E-mail: menicho@uaem.mx [Centro de Investigacion en Ingenieria y Ciencias Aplicadas, Universidad Autonoma del Estado de Morelos (UAEM), Av. Universidad 1001, Col. Chamilpa, C.P. 62209, Cuernavaca, Morelos (Mexico); Garcia-Carvajal, S.; Marquez-Aguilar, P.A.; Gueizado-Rodriguez, M. [Centro de Investigacion en Ingenieria y Ciencias Aplicadas, Universidad Autonoma del Estado de Morelos (UAEM), Av. Universidad 1001, Col. Chamilpa, C.P. 62209, Cuernavaca, Morelos (Mexico); Escalante-Garcia, J. [Centro de Investigaciones Quimicas, UAEM, C.P. 62210, Cuernavaca, Morelos (Mexico); Medrano-Baca, G. [Centro de Investigacion en Ingenieria y Ciencias Aplicadas, Universidad Autonoma del Estado de Morelos (UAEM), Av. Universidad 1001, Col. Chamilpa, C.P. 62209, Cuernavaca, Morelos (Mexico)

    2011-10-03

    Highlights: {yields} Azo chromophore in the copolymer showed an additional color to the P3OT. {yields} Non-linear optical properties by Z-scan technique in states: neutral and oxidized. {yields} The copolymers showed a change of non-linearity sign when the films were doped. {yields} We determined that the nonlinearity of the polymer films was a Kerr type. {yields} This study is the first report of NLO characterization of this material. - Abstract: Polythiophene derivatives with azo chromophore were synthesized via copolymerization of 3-octylthiophene (3OT) and 2-[N-ethyl-N-[4-[(4-nitrophenyl)azo]phenyl]amino]ethyl 3-thienylacetate (3-DRT). This copolymer has interesting optoelectronic properties and a variety of applications such as electrochromic and electronic devices. The polymerization process of 3OT and the functionalized thiophene was carried out via FeCl{sub 3} oxidative polymerization. Thin films of poly(3OT-co-3-DRT) copolymer were prepared by spin-coating technique from toluene. FTIR and {sup 1}H NMR spectroscopy revealed the presence of chromophore groups in the copolymer chain. Molecular weight and polydispersity of the polymers were measured by size exclusion chromatography. Changes in the surface topography of copolymers were analyzed by atomic force microscopy; the results showed that the copolymers presented some protuberances of variable size unlike the homogeneous granular morphology of P3OT. It is believed that these changes appeared by the incorporation of 3-DRT in the polymer. P3ATs are electrochromic materials that show color change upon oxidation-reduction process. We report that electrochemical characterization of poly(3OT-co-3-DRT) copolymer films synthesized chemically on indium-tin oxide (ITO) glass substrates showed an additional color to the P3OT homopolymer. Optical absorption properties of the polymer films were analyzed in the undoped and doped states and as a function of 3-DRT concentration in the copolymer. The nonlinear optical

  7. Formation of nanophases in epoxy thermosets containing amphiphilic block copolymers with linear and star-like topologies.

    Science.gov (United States)

    Wang, Lei; Zhang, Chongyin; Cong, Houluo; Li, Lei; Zheng, Sixun; Li, Xiuhong; Wang, Jie

    2013-07-11

    In this work, we investigated the effect of topological structures of block copolymers on the formation of the nanophase in epoxy thermosets containing amphiphilic block copolymers. Two block copolymers composed of poly(ε-caprolactone) (PCL) and poly(2,2,2-trifluoroethyl acrylate) (PTFEA) blocks were synthesized to possess linear and star-shaped topologies. The star-shaped block copolymer composed a polyhedral oligomeric silsesquioxane (POSS) core and eight poly(ε-caprolactone)-block-poly(2,2,2-trifluoroethyl acrylate) (PCL-b-PTFEA) diblock copolymer arms. Both block copolymers were synthesized via the combination of ring-opening polymerization and reversible addition-fragmentation chain transfer/macromolecular design via the interchange of xanthate (RAFT/MADIX) process; they were controlled to have identical compositions of copolymerization and lengths of blocks. Upon incorporating both block copolymers into epoxy thermosets, the spherical PTFEA nanophases were formed in all the cases. However, the sizes of PTFEA nanophases from the star-like block copolymer were significantly lower than those from the linear diblock copolymer. The difference in the nanostructures gave rise to the different glass transition behavior of the nanostructured thermosets. The dependence of PTFEA nanophases on the topologies of block copolymers is interpreted in terms of the conformation of the miscible subchain (viz. PCL) at the surface of PTFEA microdomains and the restriction of POSS cages on the demixing of the thermoset-philic block (viz. PCL).

  8. Ordered phases of diblock copolymers in selective solvent.

    Science.gov (United States)

    Grason, Gregory M

    2007-03-21

    The authors propose a mean-field model to explore the equilibrium coupling between micelle aggregation and lattice choice in neutral copolymer and selective solvent mixtures. They find both thermotropic and lyotropic transitions from face-centered cubic to body-centered cubic ordered phases of spherical micelles, in agreement with experimental observations of these systems over a broad range of conditions. The stability of the nonclosed packed phase can be attributed to two physical mechanisms: the large entropy of lattice phonons near crystal melting and the preference of the intermicelle repulsions for the body-centered cubic structure when the lattice becomes sufficiently dense at higher solution concentrations. Both mechanisms are controlled by the decrease of micelle aggregation and subsequent increase of lattice density as solvent selectivity is reduced. These results shed new light on the relationship between micelle structure--"crewcut" or "hairy"--and long-range order in micelle solutions.

  9. Extensible collagen in mussel byssus: a natural block copolymer.

    Science.gov (United States)

    Coyne, K J; Qin, X X; Waite, J H

    1997-09-19

    To adhere to solid surfaces, marine mussels produce byssal threads, each of which is a stiff tether at one end and a shock absorber with 160 percent extensibility at the other end. The elastic extensibility of proximal byssus is extraordinary given its construction of collagen and the limited extension (less than 10 percent) of most collagenous materials. From the complementary DNA, we deduced that the primary structure of a collagenous protein (preCol-P) predominating in the extensible proximal portion of the threads encodes an unprecedented natural block copolymer with three major domain types: a central collagen domain, flanking elastic domains, and histidine-rich terminal domains. The elastic domains have sequence motifs that strongly resemble those of elastin and the amorphous glycine-rich regions of spider silk fibroins. Byssal thread extensibility may be imparted by the elastic domains of preCol-P.

  10. Electrochemical synthesis and surface characterization of (pyrrole+2-methylfuran) copolymer

    Science.gov (United States)

    Djaouane, Linda; Nessark, Belkacem; Sibous, Lakhdar

    2017-02-01

    Electrochemical copolymerization of pyrrole (Py) and 2-methylfuran (2 MF) was performed on platinum and ITO substrates in acetonitrile/lithium perchlorate solution, using cyclic voltammetry method. The electrochemical behavior of the modified electrode surface by polypyrrole, poly(2-methylfuran) homopolymers and (pyrrole+2-methylfuran) copolymer was characterized by cyclic voltammetry, electrochemical impedance spectroscopy (EIS), UV-visible spectroscopy, atomic force microscopy (AFM) and scanning electron microscopy (SEM). The cyclic voltammetry shows anodic and cathodic peaks which are characteristic of the oxidation and the reduction of the formed films. The electrochemical impedance spectroscopy confirmed the results obtained by cyclic voltammetry. AFM and SEM analyses proved as well that the morphology and the electrochemical properties of the polypyrrole film are modified in the presence of 2-methylfuran.

  11. Influence of solvent on micellar morphologies of semifluorinated block copolymers.

    Science.gov (United States)

    Lee, Min Young; Kim, Sang Jae; Jeong, Yeon Tae; Kim, Joo Hyun; Gal, Yeong-Soon; Lim, Kwon Taek

    2009-12-01

    The influence of solvents on micellar architectures of block copolymers composed of poly(1H,1H-dihydroperfluorooctyl methacrylate) and poly(ethylene oxide) was investigated. In this study, binary solvents with desired proportions were chosen, which had remarkable influence on the morphology of the resulting micelles. With simple adjusting the composition of the binary solvent of chloroform and trichlorofluoromethane, interesting shapes of micelle-like aggregates, such as core-shell, cylinder, worm-like and inverted micelles were formed with sizes of 15, 70, 30 and 250 nm, respectively. In the case of methanol/water system, core-shell spheres and vesicles were produced by varying the proportion of the contents. The morphologies were also tuned to honeycomb-like and bowl-shaped micelles as well as large planar lamellae with holes in DMF and water binary solvent.

  12. A tri-block copolymer templated synthesis of gold nanostructures.

    Science.gov (United States)

    Falletta, Ester; Ridi, Francesca; Fratini, Emiliano; Vannucci, Chiara; Canton, Patrizia; Bianchi, Sabrina; Castelvetro, Valter; Baglioni, Piero

    2011-05-01

    Stable ultra-small gold nanoparticles have been synthesized in aqueous phase by using a tri-block copolymer (BMB) as a templating agent consisting of two PEG-methylacrylate chains (B blocks) anchored to a poly(methacrylic) moiety containing a trithiocarbonate unit (M block). The effect of the BMB/Au molar ratios on the final particle size, shape and monodispersity has been investigated. The synthesized nanosols have been characterized by means of Visible Absorption, Small Angle X-ray Scattering (SAXS), and Transmission Electron Microscopy (TEM). Results clearly indicate that the polymer plays a key role in determining the size and shape of gold particles, from fractal-like structures to monodisperse spherical particles with a mean diameter of about 3 nm. The aggregation behavior of these nanostructures has been characterized both in solution (SAXS) as well as on mica substrate (AFM) and has been proven to be driven by the polymer to gold concentration ratio.

  13. Lamellae orientation in dynamically sheared diblock copolymer melts

    Science.gov (United States)

    Koppi, Kurt A.; Tirrell, Matthew; Bates, Frank S.; Almdal, Kristoffer; Colby, Ralph H.

    1992-11-01

    Two distinct lamellae orientaitons have been identified by small-angle neutron scattering (SANS) in dynamically sheared poly(ethylene-propylene)-poly(ethylethylene) (PEP-PEE) diblock copolymer melts. Near the order-disorder transition temperature, Tto T_ODT, and at low shear frequencies, the lamellae arrange with unit normal perpendicular to the flow direction and parallel to the velocity gradient direction (parallel orientation). Higher frequency processing leads to lamellae with unit normal permendicular to both the flow and velocity gradient directions (perpendicular orientation). The crossover from low to high frequency behavior occurs at ω≈tau^{-1} where tau is the relaxation time for local domain deformations. At temperatures further from the ODT, Torientation is obtained at all shearing frequencies. Based on dynamic and steady shear rheological measurements we propose two mechanisms to account for these results. The perpendicular orientation is proposed to arise from shear-induced disordering, followed by reordering in the perpendicular direction due to the effect of vorticity. Parallel lamellae are believed to be a manifestation of defect mediated stress relaxation. These findings are supported by additional experiments on various other shear-oriented polyolefin diblock copolymers. Nous avons identifié, par diffusion de neutrons aux petits angles, deux orientation différentes des lamelles dans des échantillons de copolymères séquencés poly(éthylène-propylène)- poly(éthylétylène) (PEP-PEE) qui ont été cisaillés dynamiquement. A des températures proches de la transition ordre-désordre et aux fréquences de cisaillement faibles, la normale aux couches est perpendiculaire à la direction d'écoulement et parallèle au gradient de vitesse (orientation parllèle). Aux fréquences plus élevées, la normale est perpendiculaire à la direction d'écoulement et au gradient de vitesse (orientation perpendiculaire). Le changement d

  14. Viscoelastic Properties of Fluorinated Ethylene-Propylene (FEP) Random Copolymers

    Science.gov (United States)

    Curtin, Megan; Wright, Benjamin; Ozisik, Rahmi

    Florinated ethylene-propylene (FEP) random copolymers contain tetrafluoroethylene (TFE) and hexafluoropropylene (HFP) repeat units. FEP is an excellent alternative to poly(tetrafluoroethylene), PTFE, which cannot be melt processed due to its high molecular weight and extensive crystallinity. On the other hand, FEP is a melt processible polymer and offers similar if not the same properties as PTFE. Many studies have been performed on FEP over the years, however, the properties of these polymers strongly depend on the HFP concentration and molecular weight (distribution). Just like PTFE, FEP cannot be dissolved in many solvents, therefore, obtaining molecular weight distribution of these polymers is not possible with commonly used methods. In the current study, we perform rheological analysis of various FEPs and obtain their molecular weight distributions by employing the Tuminello method. This material is based upon work supported by the National Science Foundation under Grant No. CMMI-1538730.

  15. Correlative infrared nanospectroscopic and nanomechanical imaging of block copolymer microdomains

    Directory of Open Access Journals (Sweden)

    Benjamin Pollard

    2016-04-01

    Full Text Available Intermolecular interactions and nanoscale phase separation govern the properties of many molecular soft-matter systems. Here, we combine infrared vibrational scattering scanning near-field optical microscopy (IR s-SNOM with force–distance spectroscopy for simultaneous characterization of both nanoscale optical and nanomechanical molecular properties through hybrid imaging. The resulting multichannel images and correlative analysis of chemical composition, spectral IR line shape, modulus, adhesion, deformation, and dissipation acquired for a thin film of a nanophase separated block copolymer (PS-b-PMMA reveal complex structural variations, in particular at domain interfaces, not resolved in any individual signal channel alone. These variations suggest that regions of multicomponent chemical composition, such as the interfacial mixing regions between microdomains, are correlated with high spatial heterogeneity in nanoscale material properties.

  16. Bulk modification of PDMS microchips by an amphiphilic copolymer.

    Science.gov (United States)

    Xiao, Yan; Yu, Xiao-Dong; Xu, Jing-Juan; Chen, Hong-Yuan

    2007-09-01

    A simple and rapid bulk-modification method based on adding an amphiphilic copolymer during the fabrication process was employed to modify PDMS microchips. Poly(lactic acid)-poly(ethylene glycol) (PLA-PEG) was used as the additive substance. Compared to the native PDMS microchips, both the contact angle and the EOF of the bulk-modified PDMS microchips decreased. The effects of the additive loading and the pH on the EOF were investigated in detail. The bulk-modified PDMS microchips exhibited reproducible and stable EOF behavior. The application of the bulk-modified PDMS microchips was also studied and the results indicated that they could be successfully used to separate amino acids and to suppress protein adsorption.

  17. Functional Block Copolymers as Compatibilizers for Nanoclays in Polypropylene Nanocomposites

    DEFF Research Database (Denmark)

    Jankova Atanasova, Katja; Daugaard, Anders Egede; Stribeck, Norbert;

    With the aim of creating tough nanocomposits (NC) [1] based on polypropylene (PP) and nanoclay (NCl) in the framework of the 7th EU program NANOTOUGH we have designed amphiphilic block copolymers utilizing Atom Transfer Radical Polymerization (ATRP) [2]. They consist of a hydrophobic block of Kra...... crystallites) is replaced by alien-reinforcement (of the MMT). Furthermore, the results from the impact strength and cyclic test of the prepared PP nanocomposites [3] are promicing....... to the structural data derived from SAXS [4] the MMT acts like a nucleating agent to the PP that starts competitive nucleation of crystallites in the PP during manufacturing. Consequently, the PP crystallites in the composites are small and imperfect. This means that the self-reinforcement of the PP (by its...

  18. Positronium lifetime in porous VP-DVB copolymer

    Energy Technology Data Exchange (ETDEWEB)

    Zaleski, Radoslaw [Institute of Physics, Maria Curie-Sklodowska University, Lublin (Poland); Goworek, Jacek; Maciejewska, Malgorzata [Faculty of Chemistry, Maria Curie-Sklodowska University, Lublin (Poland)

    2009-11-15

    Porous 1-vinyl-2-pyrrolidone-divinylbenzene copolymer was studied using Positron Annihilation Lifetime Spectroscopy. A set of spectra measured at various temperatures was analysed using two methods: model parameters fitting and quantified maximum entropy. Similarity of the results obtained by entirely different methods ensure that distortion of the results arisen from inappropriate data processing was minimized. Temperature dependence of the experimental ortho-positronium lifetimes was compared to predictions of the Extended Tao-Eldrup model. Very good agreement in whole temperature range was found for empirical parameter {delta}=0.15 nm. Basing on PALS data and the Extended Tao-Eldrup model the distribution of free volume sizes was derived. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Ultraporous films with uniform nanochannels by block copolymer micelles assembly

    KAUST Repository

    Nunes, Suzana Pereira

    2010-10-12

    Films with high pore density and regularity that are easy to manufacture by conventional large-scale technology are key components aimed for fabrication of new generations of magnetic arrays for storage media, medical scaffolds, and artificial membranes. However, potential manufacture strategies like the self-assembly of block copolymers, which lead to amazing regular patterns, could be hardly reproduced up to now using commercially feasible methods. Here we report a unique production method of nanoporous films based on the self-assembly of copper(II) ion-polystyrene-b-poly(4-vinylpyridine) complexes and nonsolvent induced phase separation. Extremely high pore densities and uniformity were achieved. Water fluxes of 890 L m-2 h-1 bar-1 were obtained, which are at least 1 order of magnitude higher than those of commercially available membranes with comparable pore size. The pores are also stimuli (pH)-responsive. © 2010 American Chemical Society.

  20. Fabrication of biomolecule copolymer hybrid nanovesicles as energy conversion systems

    Science.gov (United States)

    Ho, Dean; Chu, Benjamin; Lee, Hyeseung; Brooks, Evan K.; Kuo, Karen; Montemagno, Carlo D.

    2005-12-01

    This work demonstrates the integration of the energy-transducing proteins bacteriorhodopsin (BR) from Halobacterium halobium and cytochrome c oxidase (COX) from Rhodobacter sphaeroides into block copolymeric vesicles towards the demonstration of coupled protein functionality. An ABA triblock copolymer-based biomimetic membrane possessing UV-curable acrylate endgroups was synthesized to serve as a robust matrix for protein reconstitution. BR-functionalized polymers were shown to generate light-driven transmembrane pH gradients while pH gradient-induced electron release was observed from COX-functionalized polymers. Cooperative behaviour observed from composite membrane functionalized by both proteins revealed the generation of microamp-range currents with no applied voltage. As such, it has been shown that the fruition of technologies based upon bio-functionalizing abiotic materials may contribute to the realization of high power density devices inspired by nature.

  1. Rapid Mercury(II Removal by Electrospun Sulfur Copolymers

    Directory of Open Access Journals (Sweden)

    Michael W. Thielke

    2016-07-01

    Full Text Available Electrospinning was performed with a blend of commercially available poly(methyl methacrylate (PMMA and a sulfur-rich copolymer based on poly(sulfur-statistical-diisopropenylbenzene, which was synthesized via inverse vulcanization. The polysulfide backbone of sulfur-containing polymers is known to bind mercury from aqueous solutions and can be utilized for recycling water. Increasing the surface area by electrospinning can maximize the effect of binding mercury regarding the rate and maximum uptake. These fibers showed a mercury decrease of more than 98% after a few seconds and a maximum uptake of 440 mg of mercury per gram of electrospun fibers. These polymeric fibers represent a new class of efficient water filtering systems that show one of the highest and fastest mercury uptakes for electrospun fibers reported.

  2. Ultrafast Optical Response from a Novel Tri-Branched Copolymer

    Institute of Scientific and Technical Information of China (English)

    李波; 米君; 孟凡顺; 田禾; 钱士雄

    2004-01-01

    A novel tri-branched copolymer is synthesized to show strong two-photon absorption and intense two-photon absorption induced fluorescence emission under the excitation of the femtosecond laser pulses at wavelength of 800 nm. The dynamics of the excited state was measured by the pump-probe technique. In a one-colour pump-probe experiment at 800 nm, there was an ultrafast transient absorption, followed by other two relaxation processes. The two-photon absorption process could be one origin for this ultrafast photoabsorption signal, which was further proven by two-colour pump-probe experiments. The other two decaying processes in the transient absorption dynamics have lifetime of about 15 ps and 129ps, which reflect the intraband vibrational relaxation and the decay of two-photon excited state, respectively.

  3. PRELIMINARY STUDY OF EXTRACTABLE PROTEIN BINDING USING MALEIC ANHYDRIDE COPOLYMER

    Institute of Scientific and Technical Information of China (English)

    Thirawan Nipithakul; Ladawan Watthanachote; Nanticha Kalapat

    2012-01-01

    A preliminary study of using maleic anhydride copolymer for protein binding has been carried out.The polymeric films were prepared by compression of the purified resin and annealing the film to induce efficient back formation of the anhydride groups.The properties of the film surface were analyzed by attenuated total reflection Fourier transforms infrared spectroscopy and water contact angle measurements.The protein content was determined by Bradford assay.To obtain optimum conditions,immersion time for protein binding was examined.Results revealed that proteins can be successfully immobilized onto the film surface via covalent linkage.The efficiency of the covalent binding of the extractable protein to maleic anhydride-polyethylene film was estimated at 69.87 μtg/cm2,although the film had low anhydride content (3%) on the surface.

  4. Reinvestigation of the Block Copolymer Modulated Lamellar Structure

    DEFF Research Database (Denmark)

    Mortensen, K.; Vigild, Martin Etchells

    2009-01-01

    We report extended crystallographic studies on shear-aligned block copolymer systems within the metastable modulated lamellae (ML) state. With studies limited to the "classical" orientations parallel and perpendicular to shear plane, the apparent modulated state would likely have been assigned...... simple lamellar. Surprisingly, upon rotating the sample to intermediate angles additional scattering reflections appear, which reveal the apparent ML phase much beyond what was expected. The modulated structure is a slightly distorted fcc structure. With the sample sheared at relatively low temperature......, presumably below the stable gyroid phase. we find a very well resolved ML texture corresponding to a simple twin structure of the distorted fcc structure. When shear-aligned within the hexagonal cylinder phase, and quenced to the gyroid phase or slightly below. we find ML alignment into a two...

  5. Synthesis and Analysis of Resorcinol-Acetone Copolymer

    Directory of Open Access Journals (Sweden)

    Gen-ichi Konishi

    2009-01-01

    Full Text Available Synthesis and characterization of resorcinol-acetone copolymer is described. The polymer was prepared by trifluoroacetic acid-catalyzed polymerization of resorcinol with acetone. According to the 1H-NMR, 13C-NMR, and MALDI-TOF Mass spectra data, the obtained polymer had three types of repeating units: isopropylidene bridged-resorcinol, chromane ring, and spiro-shaped double chromane ring, indicating that polymerization proceeded via simultaneous addition-condensation and cyclization of resorcinol with acetone. The obtained polymer can be useful not only for the development of plastic materials such as thermosets, adhesives, and coatings but also for the synthesis of biomaterials such as antimicrobial agents, pesticides, and medicines.

  6. Nanometer TiO2 Modified Polyacrylic Copolymer Sizing Agent

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A series of new-type nanometer TiO2 modified polyacrylic copolymer sizing agent were synthesized from acrylic acid, ethyl acrylate, nanometer TiO2, oleic acid etc.by orthogonal design method. Results of the studies show that the synthetic method used in this paper was a new way and had never been found in the synthesis of acrylate sizing agent, and that the properties of those new-type size-agent were be improved, which had potential for substituting PVA (polyvinyl alcohol) sizing agent. The technology for solving the problem of nano-scale powder agglomeration and dispersion were also studied. The transmission electron microscope (TEM) observation showed that nano-TiO2 had good dispersion and stability in aqueous solution and in sizing agent solution.

  7. Silver-enhanced block copolymer membranes with biocidal activity

    KAUST Repository

    Madhavan, Poornima

    2014-11-12

    Silver nanoparticles were deposited on the surface and pore walls of block copolymer membranes with highly ordered pore structure. Pyridine blocks constitute the pore surfaces, complexing silver ions and promoting a homogeneous distribution. Nanoparticles were then formed by reduction with sodium borohydride. The morphology varied with the preparation conditions (pH and silver ion concentration), as confirmed by field emission scanning and transmission electron microscopy. Silver has a strong biocide activity, which for membranes can bring the advantage of minimizing the growth of bacteria and formation of biofilm. The membranes with nanoparticles prepared under different pH values and ion concentrations were incubated with Pseudomonas aeruginosa and compared with the control. The strongest biocidal activity was achieved with membranes containing membranes prepared under pH 9. Under these conditions, the best distribution with small particle size was observed by microscopy.

  8. Synthesis and Characterization of ABBA Block Copolymer of Glycolide and ε-Caprolactone

    Institute of Scientific and Technical Information of China (English)

    CHEN Li; CHEN Xue-si; DENG Ming-xiao; JING Xia-bin

    2005-01-01

    A biodegradable ABBA block copolymer was synthesized via the ring-opening co-polymerization of ε-caprolactone(CL, B) and glycolide(A) by means of step polymerization in the presence of ethylene glycol as an initiator and stannous octanoate as a catalyst at 110 ℃ for 48 h. The molecular length of the PCL pre-polymer(BB) could be adjusted by controlling the molar ratio of the ethylene glycol initiator to ε-caprolactone monomer. The structure and the composition of the block copolymer were determined by the weight ratio of the monomer glycolide(A) to PCL pre-polymer(BB). The block copolymers were characterized by 1H NMR, GPC, DSC and X-ray. The results confirm the successful synthesis of an ABBA block copolymer.

  9. Novel Blue Light-emitting PPV-based Copolymer Containing Triazole and Carbazole Units

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A novel alternating conjugated copolymer containing triazole and carbazole units was synthesized by the Wittig reaction. The resulting bipolar conjugated polymer emits a pure light with good thermal stability, which is a promising candidate for polymer light emitting display.

  10. Basic Research of Vibration Energy Harvesting Micro Device using Vinylidene Fluoride / Trifluoroethylene Copolymer Thin Film

    Science.gov (United States)

    Takiguchi, T.; Sasaki, T.; Nakajima, T.; Yamaura, S.; Sekiguchi, T.; Shoji, S.

    2014-11-01

    Basic research of MEMS based micro devices for vibration energy harvesting using vinylidene fluoride / trifluoroethylene (VDF/TrFE) copolymer thin film was investigated. The VDF/TrFE copolymer thin film was formed by spin coating. Thickness of VDF/TrFE copolymer thin film was ranged from 375 nm to 2793 nm. Impedance of VDF/TrFE copolymer thin film was measured by LCR meter. Thin film in each thickness was fully poled by voltage based on C-V characteristics result. Generated power of the devices under applied vibration was observed by an oscilloscope. When the film thickness is 2793 nm, the generated power was about 0.815 μJ.

  11. Synthesis and Surface Tension Properties of Polyethyleneimine—Polyethylene Oxide Block Copolymers

    Institute of Scientific and Technical Information of China (English)

    张剑; LONNIE,Bryant

    2003-01-01

    This peper describes the synthesis,surface tension and dispersancy properties of block copolymer nonionic surfactants comprised of polyethyleneimine(PEI) and polyethlene oxide(PEO) blocks of selected lengths.These block copolymers were prepared by a threestep synthetic sequence.Firstly,PEO glycol was converted to its dimethanesulphonylester (dimesyl) derivative by reacting with methanesulphonyl chloride.Then a tri-block polymer was preparaed by the ring-opening polymerization of 2-methly-2-oxazoline(MeOZO)with the dimesyl PEO derivative.Lastly,linear PEI blocks were obtained by subsequent hydrolysis and purification.1H NMR spectra confirmed the structures of the intermediate,final products and their purities(>99%).The utility of these block copolymers is described in terms of their surface tension and clay dispersancy measurements as a function of copolymer chain and block length.

  12. RANDOM COPOLYMER OF PROPYLENE OXIDE AND ETHYLENE OXIDE PREPARED BY DOUBLE METAL CYANIDE COMPLEX CATALYST

    Institute of Scientific and Technical Information of China (English)

    Yi-jun Huang; Guo-rong Qi; Guan-xi Chen

    2002-01-01

    Copolymerization of propylene oxide (PO) and ethylene oxide (EO) using double metal cyanide (DMC) complex as the catalyst was carried out. The structure of random copolymers was confirmed by 13C-NMR and IR spectra. 1H-NMR analysis shows that the EO content in the copolymer is the same as that in the initial monomer feed. Moderate molecular weight copolymers with various EO content were obtained and their values of molecular weight distribution (MWD) fell in the range of 1.21-1.55. It was found that the molecular weight of copolymers is controlled by the mass ratio ofEO + PO to initiator moles used. The reaction rate as well as polymer yield decrease with increasing EO content in the feed composition.

  13. New routes to the synthesis of amylose-block-polystyrene rod-coil block copolymers

    NARCIS (Netherlands)

    Loos, Katja; Müller, Axel H.E.

    2002-01-01

    Hybrid block copolymers amylose-block-polystyrene were synthesized by covalent attachment of maltoheptaose derivatives to end-functionalized polystyrene and subsequent enzymatic grafting from polymerization. The maltoheptaose derivatives were attached by reductive amination or hydrosilation to amino

  14. Synthesis, Thermal Processing, and Thin Film Morphology of Poly(3-hexylthiophene)-Poly(styrenesulfonate) Block Copolymers

    NARCIS (Netherlands)

    Erothu, Harikrishna; Kolomanska, Joanna; Johnston, Priscilla; Schumann, Stefan; Deribew, Dargie; Toolan, Daniel T. W.; Gregori, Alberto; Dagron-Lartigau, Christine; Portale, Giuseppe; Bras, Wim; Arnold, Thomas; Distler, Andreas; Hiorns, Roger C.; Mokarian-Tabari, Parvaneh; Collins, Timothy W.; Howse, Jonathan R.; Topham, Paul D.

    2015-01-01

    A series of novel block copolymers, processable from single organic solvents and subsequently rendered amphiphilic by thermolysis, have been synthesized using Grignard metathesis (GRIM) and reversible addition-fragmentation chain transfer (RAFT) polymerizations and azide-alkyne click chemistry. This

  15. Novel Blue Light—emitting PPV—based Copolymer Containing Trazole and Carbazole Units

    Institute of Scientific and Technical Information of China (English)

    ZeLIU; LiXiangWANG; 等

    2002-01-01

    A novel alternating conjugated copolymer containing triazole and carbazole units was synthesized by the Witting reaction. The resulting bipolar conjugated polymer emits a pure light with good thermal stability, which is a promising candidate for polymer light emitting display.

  16. Dual hydrophilic and salt responsive schizophrenic block copolymers – synthesis and study of self-assembly

    NARCIS (Netherlands)

    Vasantha, Vivek Arjunan; Jana, Satyasankar; Lee, Serina Siew Chen; Lim, Chin-Sing; Teo, Serena Lay Ming; Parthiban, Anbanandam; Vancso, Julius G.

    2015-01-01

    A new class of dual hydrophilic diblock copolymers (BCPs) possessing poly(ethylene glycol) (PEG) and zwitterionic polysulfabetaine (PSB) was synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization. These BCPs formed schizophrenic micelles undergoing core–shell transitio

  17. Inducing Order from Disordered Copolymers: On Demand Generation of Triblock Morphologies Including Networks

    Energy Technology Data Exchange (ETDEWEB)

    Tureau, Maëva S.; Kuan, Wei-Fan; Rong, Lixia; Hsiao, Benjamin S.; Epps, III, Thomas H. (Delaware); (Buffalo)

    2015-10-15

    Disordered block copolymers are generally impractical in nanopatterning applications due to their inability to self-assemble into well-defined nanostructures. However, inducing order in low molecular weight disordered systems permits the design of periodic structures with smaller characteristic sizes. Here, we have induced nanoscale phase separation from disordered triblock copolymer melts to form well-ordered lamellae, hexagonally packed cylinders, and a triply periodic gyroid network structure, using a copolymer/homopolymer blending approach, which incorporates constituent homopolymers into selective block domains. This versatile blending approach allows one to precisely target multiple nanostructures from a single disordered material and can be applied to a wide variety of triblock copolymer systems for nanotemplating and nanoscale separation applications requiring nanoscale feature sizes and/or high areal feature densities.

  18. Synthesis and Characterization of Quinoxaline-Based Low-Bandgap Copolymers for Bulk Heterojunction Solar Cells

    Science.gov (United States)

    Lee, Yoonkyoo; Jo, Won Ho

    2011-03-01

    A series of low-bandgap alternating copolymers consisting of quinoxaline derivatives and electron-donating carbazole or fluorene were synthesized via the Suzuki coupling reaction. For the purpose to improve the molecular packing of polymer chains and to enhance the charge carrier mobility in the packing direction, a new quinoxaline derivative, 5,8-dithien-2-yl-dibenzophenazine which has perfectly planar polycyclic structure, was synthesized and introduced as a new building block for alternating copolymers instead of frequently-used 5,8-dithien-2-yl-2,3-diphenylquinoxaline. The use of planar quinoxaline derivative exhibited better optical, electrochemical, and structural properties of the resulting copolymers as compared to those of polymers with less planar quinoxaline derivatives. Charge transport and photovoltaic properties of these two classes of copolymers are compared and discussed.

  19. Nanoscale characterization of carbazole-indole copolymers modified carbon fiber surfaces.

    Science.gov (United States)

    Sarac, A Sezai; Serantoni, Marina; Tofail, Syed A M; Cunnane, Vincent J

    2005-10-01

    Polycarbazole, carbazole and indole containing copolymers were electrochemically coated onto carbon fiber. The resulting polymers and copolymers were characterized by scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. Characterization of the thin polymer films were performed on the polymer-coated surface of the carbon fiber. Therefore, the results obtained could elucidate the relationship between the initial feed monomer ratio, the resulting polymer/copolymer film morphology and the surface structure formed. The thickness increase (in diameter) was 0.3 and 0.9 microm, for two different composition of carbazole/indole on the carbon fiber. The carbon fibers coated with copolymer thin films were from 6.5 to 8.2 microm in diameter (from AFM measurement).

  20. Effects of PEO-PPO-PEO triblock copolymers on phospholipid membrane integrity under osmotic stress.

    Science.gov (United States)

    Wang, Jia-Yu; Chin, Jaemin; Marks, Jeremy D; Lee, Ka Yee C

    2010-08-03

    The effects of PEO-PPO-PEO triblock copolymers, mainly Poloxamer 188, on phospholipid membrane integrity under osmotic gradients were explored using giant unilamellar vesicles (GUVs). Fluorescence leakage assays showed two opposing effects of P188 on the structural integrity of GUVs depending on the duration of their incubation time. A two-state transition mechanism of interaction between the triblock copolymers and the phospholipid membrane is proposed: an adsorption (I) and an insertion (II) state. While the triblock copolymer in state I acts to moderately retard the leakage, their insertion in state II perturbs the lipid packing, thus increasing the membrane permeability. Our results suggest that the biomedical application of PEO-PPO-PEO triblock copolymers, either as cell membrane resealing agents or as accelerators for drug delivery, is directed by the delicate balance between these two states.