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Sample records for acid-labile temperature-responsive copolymers

  1. Poly(ortho ester amides): Acid-labile Temperature-responsive Copolymers for Potential Biomedical Applications

    PubMed Central

    Tang, Rupei; Palumbo, R. Noelle; Ji, Weihang; Wang, Chun

    2009-01-01

    A new, convenient pathway is developed to synthesize highly hydrolytically labile poly(ortho ester amide) (POEA) copolymers that overcomes some of the major weaknesses of the traditional methods of synthesizing poly(ortho esters) and their derivatives. A diamine monomer containing a built-in, stabilized ortho ester group was synthesized and was used for polycondensation with diacid esters, giving rise to a series of POEA copolymers with unique stimuli-responsive properties. The POEA undergoes temperature-responsive, reversible sol-gel phase transition in water. Phase diagrams of the POEA/H2O mixture reveal the concentration-dependent existence of different phases, including hydrogel and opaque or clear solution. Such behavior may be attributed to the temperature-dependent hydrogen-bonding involving the amide groups in the POEA backbone and hydrophobic interactions between POEA chains, and it is tunable by selecting diacid monomers with different chemical structures. The kinetics of POEA mass loss in physiological aqueous buffers and release of a model macromolecular drug, fluorescently labeled dextran, are nearly zero-order, suggesting predominantly surface-restricted polymer erosion. The rates of polymer erosion and drug release are much faster at pH 5.0 than pH 7.4. No cytotoxicity was found for the polymer extracts and the polymer degradation products at concentrations as high as 1 mg/ml. The normal morphology of fibroblasts cultured directly in contact with POEA films was not altered. These novel acid-labile temperature-responsive POEA copolymers may be potentially useful for a wide range of biomedical applications such as minimal invasive delivery of controlled-release drug formulations that respond to biological temperature and acidic-pH environments in cells and tissues. PMID:19281150

  2. Poly(ortho ester amides): acid-labile temperature-responsive copolymers for potential biomedical applications.

    PubMed

    Tang, Rupei; Palumbo, R Noelle; Ji, Weihang; Wang, Chun

    2009-04-13

    A new, convenient pathway is developed to synthesize highly hydrolytically labile poly(ortho ester amide) (POEA) copolymers that overcomes some of the major weaknesses of the traditional methods of synthesizing poly(ortho esters) and their derivatives. A diamine monomer containing a built-in, stabilized ortho ester group was synthesized and was used for polycondensation with diacid esters, giving rise to a series of POEA copolymers with unique stimuli-responsive properties. The POEA undergoes temperature-responsive, reversible sol-gel phase transition in water. Phase diagrams of the POEA/H(2)O mixture reveal the concentration-dependent existence of different phases, including hydrogel and opaque or clear solution. Such behavior may be attributed to the temperature-dependent hydrogen-bonding involving the amide groups in the POEA backbone and hydrophobic interactions between POEA chains, and it is tunable by selecting diacid monomers with different chemical structures. The kinetics of POEA mass loss in physiological aqueous buffers and release of a model macromolecular drug, fluorescently labeled dextran, are nearly zero-order, suggesting predominantly surface-restricted polymer erosion. The rates of polymer erosion and drug release are much faster at pH 5.0 than pH 7.4. No cytotoxicity was found for the polymer extracts and the polymer degradation products at concentrations as high as 1 mg/mL. The normal morphology of fibroblasts cultured directly in contact with POEA films was not altered. These novel acid-labile temperature-responsive POEA copolymers may be potentially useful for a wide range of biomedical applications such as minimal invasive delivery of controlled-release drug formulations that respond to biological temperature and acidic-pH environments in cells and tissues.

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

    PubMed

    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."

  4. PEG-detachable and acid-labile cross-linked micelles based on orthoester linked graft copolymer for paclitaxel release

    NASA Astrophysics Data System (ADS)

    Yuan, Zhefan; Huang, Jingyi; Liu, Jing; Cheng, Sixue; Zhuo, Renxi; Li, Feng

    2011-08-01

    Polyethylene glycol detachable graft copolymer, mPEG-g-p(NAS-co-BMA), was synthesized by grafting 2-(ω-methoxy)PEGyl-1,3-dioxan-5-ylamine onto poly(N-(acryloyloxy)succinimide-co-butyl methacrylate). Pseudo in situ cross-linking of the mPEG-g-p(NAS-co-BMA) was performed in dimethylformamide phosphate buffer (v/v = 1/1) by an acid-labile diamine cross-linker bearing two symmetrical cyclic orthoesters. The cross-linked (CL) micelles with different contents of mPEG segments represented different morphologies. The CL micelles containing approximately one mPEG segment exhibited 'echini' morphology whereas the CL micelle with approximately three mPEG segments formed nanowires. The hydrolysis rate of the CL micelles is highly pH-dependent and much more rapid at mild acid than physiological conditions. Hydrolyzates of the CL micelles formed vesicles because new amphiphilic copolymers were formed. Paclitaxel (PTX) was successfully loaded into the CL micelles and a controlled and pH-dependent release behavior was observed. No obvious cytotoxicity was found for the CL micelles at concentration as high as 800 mg l - 1.

  5. Block copolymer micelles with acid-labile ortho ester side-chains: Synthesis, characterization, and enhanced drug delivery to human glioma cells.

    PubMed

    Tang, Rupei; Ji, Weihang; Panus, David; Palumbo, R Noelle; Wang, Chun

    2011-04-10

    A new type of block copolymer micelles for pH-triggered delivery of poorly water-soluble anticancer drugs has been synthesized and characterized. The micelles were formed by the self-assembly of an amphiphilic diblock copolymer consisting of a hydrophilic poly(ethylene glycol) (PEG) block and a hydrophobic polymethacrylate block (PEYM) bearing acid-labile ortho ester side-chains. The diblock copolymer was synthesized by atom transfer radical polymerization (ATRP) from a PEG macro-initiator to obtain well-defined polymer chain-length. The PEG-b-PEYM micelles assumed a stable core-shell structure in aqueous buffer at physiological pH with a low critical micelle concentration as determined by proton NMR and pyrene fluorescence spectroscopy. The hydrolysis of the ortho ester side-chain at physiological pH was minimal yet much accelerated at mildly acidic pHs. Doxorubicin (Dox) was successfully loaded into the micelles at pH 7.4 and was released at a much higher rate in response to slight acidification to pH 5. Interestingly, the release of Dox at pH 5 followed apparently a biphasic profile, consisting of an initial fast phase of several hours followed by a sustained release period of several days. Dox loaded in the micelles was rapidly taken up by human glioma (T98G) cells in vitro, accumulating in the endolysosome and subsequently in the nucleus in a few hours, in contrast to the very low uptake of free drug at the same dose. The dose-dependent cytotoxicity of the Dox-loaded micelles was determined by the MTT assay and compared with that of the free Dox. While the empty micelles themselves were not toxic, the IC(50) values of the Dox-loaded micelles were approximately ten-times (by 24h) and three-times (by 48h) lower than the free drug. The much enhanced potency in killing the multi-drug-resistant human glioma cells by Dox loaded in the micelles could be attributed to high intracellular drug concentration and the subsequent pH-triggered drug release. These results

  6. Gradient structure-induced temperature responsiveness in styrene/methyl methacrylate gradient copolymers micelles.

    PubMed

    Zheng, Chao; Huang, Haiying; He, Tianbai

    2014-02-01

    In this work, micelles are formed by gradient copolymer of styrene and methyl methacrylate in acetone-water mixture and their temperature responsiveness is investigated in a narrow range near room temperature. Three different kinds of structural transitions could be induced by temperature: unimers to micelle transition, shrinkage/stretching of micelles, and morphological transition from spherical micelles to vesicles. In addition, a model analysis on the interface of gradient copolymer micelle is made to better understand these phenomena. It is found that both position and composition of the interface could alter in response to the change in temperature. According to the experiments and model analysis, it is proposed that temperature responsiveness might be an intrinsic and universal property of gradient copolymer micelles, which only originates from the gradient structure.

  7. Injectable biodegradable temperature-responsive PLGA-PEG-PLGA copolymers: synthesis and effect of copolymer composition on the drug release from the copolymer-based hydrogels.

    PubMed

    Qiao, Mingxi; Chen, Dawei; Ma, Xichen; Liu, Yanjun

    2005-04-27

    Injectable biodegradable temperature-responsive poly(DL-lactide-co-glycolide-b-ethylene glycol-b-DL-lactide-co-glycolide) (PLGA-PEG-PLGA) triblock copolymers with DL-lactide/glycolide molar ratio ranging from 6/1 to 15/l were synthesized from monomers of DL-lactide, glycolide and polyethylene glycol and characterized by 1H NMR. The resulting copolymers are soluble in water to form free flowing fluid at room temperature but become hydrogels at body temperature. The hydrophobicity of the copolymer increased with the increasing of DL-lactide/glycolide molar ratio. In vitro dissolution studies with two different hydrophobic drugs (5-fluorouracil and indomethacin) were performed to study the effect of DL-lactide/glycolide molar ratio on drug release and to elucidate drug release mechanism. The release mechanism for hydrophilic 5-fluorouracil was diffusion-controlled, while hydrophobic indomethacin showed an biphasic profile comprising of an initial diffusion-controlled stage followed by the hydrogel erosion-dominated stage. The effect of DL-lactide/glycolide molar ratio on drug release seemed to be dependent on the drug release mechanism. It has less effect on the drug release during the diffusion-controlled stage, but significantly affected drug release during the hydrogel erosion-controlled stage. Compared with ReGel system, the synthesized copolymers showed a higher gelation temperature and longer period of drug release. The copolymers can solubilize the hydrophobic indomethacin and the solubility (13.7 mg/ml) was increased 3425-fold compared to that in water (4 microg/ml, 25 degrees C). Two methods of physical mixing method and solvent evaporation method were used for drug solubilization and the latter method showed higher solubilization efficiency.

  8. Polyelectrolyte multilayers of diblock copolymer micelles with temperature-responsive cores.

    PubMed

    Xu, Li; Zhu, Zhichen; Sukhishvili, Svetlana A

    2011-01-04

    We report on assembly and stimuli-response behavior of layer-by-layer (LbL) films of pH- and temperature-responsive cationic diblock copolymer micelles (BCMs) of poly(2-(dimethylamino)ethyl methacrylate)-block-poly(N-isopropylacrylamide) (PDMA-b-PNIPAM) and a linear polyanion polystyrene sulfonate (PSS). As a function of solution pH at temperatures above lower critical solution temperature (LCST) of PNIPAM, PDMA-b-PNIPAM micelles have been demonstrated earlier to exhibit an abrupt change in micellar aggregation number and hydrodynamic size between larger and smaller BCMs (LBCMs and SBCMs, respectively). Here, LBCMs or SBCMs were included within LbL films through self-assembly with a polyanion, and film pH and temperature responses were studied using ellipsometry and atomic force microscopy (AFM). Both types of micelle preserved their micellar morphology when adsorbed at the surface of oxidized silicon wafers coated with PSS-terminated precursor layer at a constant pH. Response of adsorbed BCMs to temperature and pH variations was strongly dependent on whether or not BCMs were coated with the PSS layer. While monolayers of LBCMs lost their original dry morphology in response to pH or temperature variations, depositing a PSS layer atop LBCMs inhibited such irreversible restructuring. As a result of wrapping around and strong binding of PSS chains with LBCM micelles, BCM/PSS assemblies preserved their original dry state morphology despite the application of pH and temperature triggers. However, the wet-state film response to pH and temperature stimuli was drastically different. Swelling of BCM/PSS multilayers was strongly affected by temperature but was almost independent of pH due to neutralization of BCM PDMA's coronal charge with PSS. Cycling the temperature below and above PNIPAM's LCST caused PNIPAM chains within BCM cores to swell or collapse, resulting in reversible swelling transitions in the entire BCM/PSS assemblies. Temperature-controlled switching between

  9. Synthesis and self-assembly of temperature-responsive copolymers based on N-vinylpyrrolidone and triethylene glycol methacrylate

    PubMed Central

    Jumeaux, Coline; Chapman, Robert; Chandrawati, Rona; Stevens, Molly M.

    2017-01-01

    Polyvinylpyrrolidone (PVP) is a biocompatible, water-soluble polymer with unique physicochemical properties and attractive biological features that has found widespread use in several industries. Owing to advances in controlled polymerisation techniques, PVP can be easily synthesised with robust control over its architecture. However, the synthesis of PVP copolymers, which can allow tailoring of its properties and expand the scope of this polymeric material, is challenging and rarely reported. Here, we demonstrate the synthesis of well-defined, temperature-responsive polyvinylpyrrolidone-co-poly(triethylene glycol methacrylate) (PVP-co-pTEGMA) block copolymers via successive Reversible Addition-Fragmentation chain Transfer (RAFT) and Activators ReGenerated by Electron Transfer Atom Transfer Radical Polymerisation (ARGET-ATRP) techniques. We show that PVP-co-pTEGMA block copolymers display temperature-responsive behaviour and self-assemble above their cloud point temperature (Tcp) to form spherical nanostructures of 100-200 nm in diameter. Finally, we demonstrate stabilisation of these assemblies below their Tcp by cross-linking through the PVP block. PMID:28458725

  10. Structural and Rheological Properties of Temperature-Responsive Amphiphilic Triblock Copolymers in Aqueous Media.

    PubMed

    Nielsen, Josefine Eilsø; Zhu, Kaizheng; Sande, Sverre Arne; Kováčik, Lubomír; Cmarko, Dušan; Knudsen, Kenneth D; Nyström, Bo

    2017-05-11

    Thermoresponsive amphiphilic biodegradable block copolymers of the type poly(ε-caprolactone-co-lactide)-poly(ethylene glycol)-poly(ε-caprolactone-co-lactide) (PCLA-PEGm-PCLA) have great potential for various biomedical applications. In the present study, we have surveyed the effects of PEG spacer length (m = 1000 and 1500), temperature, and polymer concentration on the self-assembling process to form supramolecular structures in aqueous solutions of the PCLA-PEGm-PCLA copolymer. This copolymer has a lower critical solution temperature, and the cloud point depends on both concentration and PEG length. Thermoreversible hydrogels are formed in the semidilute regime; the gel windows in the phase diagrams can be tuned by the concentration and length of the PEG spacer. The rheological properties of both dilute and semidilute samples were characterized; especially the sol-to-gel transition was examined. Small-angle neutron scattering (SANS) experiments reveal fundamental structural differences between the two copolymers for both dilute and semidilute samples. The intensity profiles for the copolymer with the long PEG spacer could be described by a spherical core-shell model over a broad temperature domain, whereas the copolymer with the short hydrophilic spacer forms rod-like species over an extended temperature range. This finding is supported by cryo-TEM images. At temperatures approaching macroscopic phase separation, both copolymers seem to assume extended rod-like structures.

  11. Behavior of temperature-responsive copolymer microgels at the oil/water interface.

    PubMed

    Wu, Yaodong; Wiese, Susanne; Balaceanu, Andreea; Richtering, Walter; Pich, Andrij

    2014-07-08

    Herein, we investigate the interfacial behavior of temperature-sensitive aqueous microgels on the toluene/water interface. Copolymer microgels based on N-vinylcaprolactam (VCL) and two acrylamides, N-isopropylacrylamide (NIPAm) and N-isopropylmethacrylamide (NIPMAm), with various copolymer compositions were used in this study. It is revealed that these copolymer microgels have the similar internal structure, regardless of the chemical composition. A classic kinetics of interfacial tension with three distinct regimes is found in the dynamic interfacial tension plots of copolymer microgels, which is similar to inorganic nanoparticles and proteins. The influences of the copolymer composition and the temperature on the interfacial behavior of microgels are investigated. The results show that the interfacial behavior of copolymer microgels at the toluene/water interface follows exactly the trend of the volume phase behavior of microgels but, on the other hand, strongly depends upon the chemical compositions of copolymer microgels. In contrast, with respect to the size range of microgels studied here (50-500 nm), the size of the microgel has no influence on the interfacial tension. Below the volume phase transition temperature (VPTT), the equilibrium interfacial tensions of all microgel systems decrease as the temperature increases. Above VPTT, the equilibrium interfacial tension remains at a certain level for poly(N-vinylcaprolactam) (PVCL)- and poly(N-isopropylmethacrylamide) (PNIPMAm)-rich microgel systems and increases slightly for poly(N-isopropylacrylamide) (PNIPAm)-rich microgel systems. The evolution of dynamic interfacial tension for microgel solutions against toluene at T < VPTT is faster than that at T > VPTT, because of the reduced deformability of the microgel with the increase of the temperature. The softer microgels with lower cross-linking degrees exhibit faster kinetics of reduction of interfacial tension compared to those with more cross-linked degrees

  12. Micellar electrokinetic chromatography with acid labile surfactant.

    PubMed

    Stanley, Bob; Lucy, Charles A

    2012-02-24

    We present a study of a degradable surfactant, sodium 4-[(2-methyl-2-undecyl-1,3-dioxolan-4-yl)methoxy]-1-propane sulfonate that is also known as an acid-labile surfactant (ALS). The performance of ALS as a pseudostationary phase is assessed and compared with established pseudostationary phases such as sodium dodecyl sulphate (SDS), volatile surfactants and polymeric micelles. ALS achieves separation efficiency of 100,000-145,000 theoretical plates and relative standard deviation (RSD) of electrophoretic mobility (n=5) of less than 3%. Retention factors with ALS are strongly correlated with those with SDS. This is shown by the R2=0.79 for all eleven analytes and an R2=0.992 for specifically the non-hydrogen bonding (NHB) analytes. However, ALS displays different selectivity than SDS for hydrogen bond donor (HBD) and hydrogen bond acceptor (HBA) solutes (R2 of 0.74 and 0.88, respectively). ALS is degraded to less surface active compounds in acidic solution. These less surface-active compounds are more compatible with the electrospray ionization mass spectrometry (ESI-MS). ALS has a half-life of 48 min at pH 4. ALS has the potential to couple micellar electrokinetic chromatography (MEKC) with the ESI-MS. ALS can be used as a pseudostationary phase for a high efficiency separation and later acid hydrolyzed to enable an ESI-MS analysis. Copyright © 2011 Elsevier B.V. All rights reserved.

  13. 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.

    PubMed

    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

  14. The effects of anionic electrolytes and human serum albumin on the LCST of poly(N-isopropylacrylamide)-based temperature-responsive copolymers.

    PubMed

    Hiruta, Yuki; Nagumo, Yuhei; Suzuki, Yuichi; Funatsu, Takaaki; Ishikawa, Yuki; Kanazawa, Hideko

    2015-08-01

    Poly(N-isopropylacrylamide) (PNIPAm) is one of the most widely studied temperature-responsive polymers among those that have been applied to biomaterials science and technology. Here, we investigated the importance of interactions between PNIPAm-based copolymers and biological factors. The effects of a series of major anionic electrolytes in biological environments and of human serum albumin (HSA) on the lower critical solution temperature (LCST) of homo-PNIPAm and PNIPAm copolymers were studied, using either a hydrophobic monomer or a cationic monomer. We synthesized P(NIPAm-co-BMA3%) with butyl methacrylate (BMA) as a hydrophobic monomer and P(NIPAm-co-DMAPAm2%) with N,N-dimethylaminopropyl acrylamide (DMAPAm) as a cationic monomer. The LCST of PNIPAm and P(NIPAm-co-DMAPAm2%) decreased with increasing salt concentrations, and the effects of anions on each polymer corresponded to the Hofmeister series. The LCST of P(NIPAm-co-DMAPAm2%) was greatly affected by anionic electrolytes compared with those of homo-PNIPAm and P(NIPAm-co-BMA3%). While the LCST of homo-PNIPAm was not affected by HSA, the LCST of P(NIPAm-co-DMAPAm2%) decreased non-linearly with increasing HSA concentrations. These effects were due to the electrostatic interactions between the positively charged polymer chains and the negatively charged HSA, as well as the stabilization of polymer aggregations with HSA. Under physiological buffer conditions, the LCST of P(NIPAm-co-DMAPAm2%) was not significantly affected by the HSA concentration. These results indicated that depending on the types of copolymers used for biological applications, it is necessary to take into account the effect of biological media while designing polymers. Copyright © 2015 Elsevier B.V. All rights reserved.

  15. Novel alicyclic polymers having 7,7-dimethyloxepan-2-one acid labile groups for ArF lithography

    NASA Astrophysics Data System (ADS)

    Lee, Jae-Jun; Kim, Jin-Baek; Honda, Kenji

    2002-07-01

    The present paper describes a novel class of norbornene- based copolymers containing 7,7-dimethyloxepan-2-one acid labile groups. Poly(3-(bicyclo[2.2.1]hept-5-en-2- ylhydroxymethyl)-7,7-dimethyloxepan-2-one-co-5-((2- decahydronaphth-yl)oxycarbonyl)-norbornene-co-5-norbornene- 2-carboxxylic acid-co-maleic anhydride) was synthesized and evaluated as a potential chemically amplified resist for ArF lithography. The 7,7-dimethyloxepan-2-one group of the matrix polymer was readily cleaved and the carboxylic acid functionality was formed by acid-catalyzed ring-opening reaction in the exposed region after post-exposure bake. 0.12micrometers line and space patterns were obtained at a dose of 10 mJ cm-2 with a conventional developer, 2.38 wt% tetramethylammonium hydroxide aqueous solution, using an ArF excimer laser stepper.

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

    PubMed

    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.

  17. Synthesis and characterization of new poly(ortho ester amidine) copolymers for nonviral gene delivery

    PubMed Central

    Tang, Rupei; Ji, Weihang; Wang, Chun

    2011-01-01

    A new type of pH-labile cationic polymers, poly(ortho ester amidine) (POEAmd) copolymers, has been synthesized and characterized with potential future application as gene delivery carriers. The acid-labile POEAmd copolymer was synthesized by polycondensation of a new ortho ester diamine monomer with dimethylaliphatimidates, and a non-acid-labile polyamidine (PAmd) copolymer was also synthesized for comparison using a triethylene glycol diamine monomer. Both copolymers were easily dissolved in water, and can efficiently bind and condense plasmid DNA at neutral pH, forming nano-scale polyplexes. The physico-chemical properties of the polyplexes have been studied using dynamic light scattering, gel electrophoresis, ethidium bromide exclusion, and heparin competition. The average size of the polyplexes was dependent on the amidine: phosphate (N:P) ratio of the polymers to DNA. Polyplexes containing the acid-labile POEAmd or the non-acid-labile PAmd showed similar average particle size, comparable strength of condensing DNA, and resistance to electrostatic destabilization. They also share similar metabolic toxicity to cells as measured by MTT assay. Importantly, the acid-labile polyplexes undergo accelerated polymer degradation at mildly-acid-pHs, resulting in increasing particle size and the release of intact DNA plasmid. Polyplexes from both types of polyamidines caused distinct changes in the scattering properties of Baby Hamster Kidney (BHK-21) cells, showing swelling and increasing intracellular granularity. These cellular responses are uniquely different from other cationic polymers such as polyethylenimine and point to stress-related mechanisms specific to the polyamidines. Gene transfection of BHK-21 cells was evaluated by flow cytometry. The positive yet modest transfection efficiency by the polyamidines (acid-labile and non-acid-labile alike) underscores the importance of balancing polymer degradation and DNA release with endosomal escape. Insights gained from

  18. Enantiomeric Excesses of Acid Labile Amino Acid Precursors of the Murchison Meteorite

    NASA Technical Reports Server (NTRS)

    Pizzarello, Sandra

    1998-01-01

    Amino acids present in carbonaceous chondrite are extracted in water in part as free compounds and in approximately equal part as acid labile precursors. On the assumption that they would be free of contamination, the precursors of two Murchison amino acids that have terrestrial occurrence, alanine and glutamic acid, have been targeted for analysis of their enantiomeric ratios. Pyroglutamic acid, the precursor of glutamic acid, was found with an L-enantiomeric excess comparable to that of the free acid, while alanine's precursor, N-acetyl alanine, appears approximately racemic. Also alpha-imino propioacetic acid, a proposed end product of alanine synthesis in the meteorite, was analyzed and found racemic.

  19. Enantiomeric Excesses of Acid Labile Amino Acid Precursors of the Murchison Meteorite

    NASA Astrophysics Data System (ADS)

    Pizzarello, Sandra

    1998-10-01

    Amino acids present in carbonaceous chondrite are extracted in water in part as free compounds and in approximately equal part as acid labile precursors. On the assumption that they would be free of contamination, the precursors of two Murchison amino acids that have terrestrial occurrence, alanine and glutamic acid, have been targeted for analysis of their enantiomeric ratios. Pyroglutamic acid, the precursor of glutamic acid, was found with an L-enantiomeric excess comparable to that of the free acid, while alanine's precursor, N-acetyl alanine, appears approximately racemic. Also alpha-imino propioacetic acid, a proposed end product of alanine synthesis in the meteorite, was analyzed and found racemic.

  20. Enantiomeric Excesses of Acid Labile Amino Acid Precursors of the Murchison Meteorite

    NASA Technical Reports Server (NTRS)

    Pizzarello, Sandra

    1998-01-01

    Amino acids present in carbonaceous chondrite are extracted in water in part as free compounds and in approximately equal part as acid labile precursors. On the assumption that they would be free of contamination, the precursors of two Murchison amino acids that have terrestrial occurrence, alanine and glutamic acid, have been targeted for analysis of their enantiomeric ratios. Pyroglutamic acid, the precursor of glutamic acid, was found with an L-enantiomeric excess comparable to that of the free acid, while alanine's precursor, N-acetyl alanine, appears approximately racemic. Also alpha-imino propioacetic acid, a proposed end product of alanine synthesis in the meteorite, was analyzed and found racemic.

  1. Analysis of acid-labile subunit and its usefulness in pediatrics.

    PubMed

    Zaidman, Verónica E

    2017-08-01

    The acid-labile subunit (ALS) is an 85 kDa glycoprotein that belongs to the leucine-rich repeat superfamily. It mainly circulates in serum bound to a high molecular weight ternary complex. The main and most widely studied function of ALS is to prolong the half-life of the binary complex formed by insulin-like growth factors type 1 and 2 and its transport proteins 3 and 5. ALS serum levels are lower in neonates, reach a peak in late puberty, and then slowly decrease throughout adulthood. ALS deficiency has consequences on growth, hydrocarbon and bone metabolism, and, in some cases, it affects pubertal development. To date, 25 patients with complete ALS deficiency due to IGFALS gene mutations have been found. Sociedad Argentina de Pediatría.

  2. Microenvironmental Control of MUC1 Aptamer-Guided Acid-Labile Nanoconjugate within Injectable Microporous Hydrogels.

    PubMed

    Xu, Chenchen; Han, Xiu; Jiang, Yujie; Yuan, Shengxiao; Wu, Ziheng; Wu, Zhenghong; Qi, Xiaole

    2017-10-05

    Although aptamers are well-known as cell-specific membrane biomarkers for tumor-targeted therapy, it is important to avoid their degradation by nucleases in vivo. In this study, we developed a MUC1 aptamer-doxorubicin nanoconjugate (APT-DOX) through an acid-labile linkage and embedded APT-DOX into a thermosensitive hydrogel for antitumor therapy. The hydrogels exhibit a sol-gel transition upon intratumoral injection, resulting in the protection and controlled release control of APT-DOX with the shielding of the gel network. Moreover, the released APT-DOX was prone to be enriched at the tumor cells due to specific intracellular transport by the overexpressing MUC1 protein; however, APT-DOX regained the free DOX form via the rupture of the linkage under tumor cells lysosome acidic conditions and achieved increased concentration in the nucleus for antitumor treatment.

  3. Multiple peptide synthesis on acid-labile handle derivatized polyethylene supports.

    PubMed

    Valerio, R M; Bray, A M; Maeji, N J

    1994-08-01

    Using the multipin peptide synthesis approach, a range of peptides with native amide and carboxylate C-termini were generated using an acid-labile approach. Polyethylene crowns grafted with hydroxyethylmethacrylate (HEMA) polymer were functionalized with either 4-hydroxymethylphenoxyacetic acid for the generation of peptide-carboxylate or p-[(R,S)-alpha-[1-(9H-fluoren-9-yl)methoxyformamido]-2,4-dim ethoxy- benzyl]phenoxyacetic acid for peptide-amide. A range of known peptide hormone sequences and other peptides with native C-termini were assembled by sequential incorporation of N alpha-Fmoc protected amino acids. Peptides were sidechain deprotected and cleaved from crowns with TFA/scavengers within 2 mL centrifuge tubes, and isolated by a series of ether/petrol wash and centrifugation steps. In this way it was possible to avoid a cleavage and isolation botteneck, allowing rapid processing of large numbers of peptides.

  4. Facile synthesis of acid-labile polymers with pendent ortho esters.

    PubMed

    Cheng, Jing; Ji, Ran; Gao, Shi-Juan; Du, Fu-Sheng; Li, Zi-Chen

    2012-01-09

    This work presents a facile approach for preparation of acid-labile and biocompatible polymers with pendent cyclic ortho esters, which is based on the efficient and mild reactions between cyclic ketene acetal (CKA) and hydroxyl groups. Three CKAs, 2-ethylidene-1,3-dioxane (EDO), 2-ethylidene-1,3-dioxolane (EDL), and 2-ethylidene-4- methyl-1,3-dioxolane (EMD) were prepared from the corresponding cyclic vinyl acetals by catalytic isomerization of the double bond. The reaction of CKAs with different alcohols and diols was examined using trace of p-toluenesulfonic acid as a catalyst. For the monohydroxyl alcohols, cyclic ortho esters were formed by simple addition of the hydroxyl group toward CKAs with ethanol showing a much greater reactivity than iso-propanol. When 1,2- or 1,3-diols were used to react with the CKAs, we observed the isomerized cyclic ortho esters besides the simple addition products. Biocompatible polyols, that is, poly(2-hydroxyethyl acrylate) (PHEA) and poly(vinyl alcohol) (PVA) were then modified with CKAs, and the degree of substitution of the pendent ortho esters can be easily tuned by changing feed ratio. Both the small molecule ortho esters and the CKA-modified polymers demonstrate the pH-dependent hydrolysis profiles, which depend also on the chemical structure of the ortho esters as well as the polymer hydrophobicity.

  5. Sex-specific Regulation of Body Size and Bone Slenderness by the Acid Labile Subunit

    PubMed Central

    Courtland, Hayden-William; DeMambro, Victoria; Maynard, Jane; Sun, Hui; Elis, Sebastien; Rosen, Clifford; Yakar, Shoshana

    2011-01-01

    Insulin-like growth factor-1 (IGF-1) is a crucial mediator of body size and bone mass during growth and development. In serum, IGF-1 is stabilized by several IGF-1 binding proteins (IGFBPs) and the acid labile subunit (ALS). Previous research using ALS knockout (ALSKO) mice indicated a growth retardation phenotype and clinical reports of humans have indicated short stature and low bone mineral density (BMD) in patients with ALS deficiency. To determine the temporal and sex-specific effects of ALS deficiency on body size and skeletal development during growth we characterized control and ALSKO mice from 4 to 16 weeks of age. We found that female ALSKO mice had an earlier onset reduction in body size (4 weeks), but that both female and male ALSKO mice were consistently smaller than control mice. Interestingly, skeletal analyses at multiple ages showed increased slenderness of ALSKO femora that was more severe in females than in males. Both male and female ALSKO mice appeared to compensate for their more slender bones through increased bone formation on their endosteal surfaces during growth, but ALSKO females had increased endosteal bone formation compared to ALSKO males. This study revealed age and sex-specific dependencies of ALS deficiency on body size and bone size. These findings may explain the heterogeneity in growth and BMD measurements reported in human ALS deficient patients. PMID:20499371

  6. Acetalated Dextran: A Tunable and Acid-Labile Biopolymer with Facile Synthesis and a Range of Applications.

    PubMed

    Bachelder, Eric M; Pino, Erica N; Ainslie, Kristy M

    2017-02-08

    Acetalated dextran (Ac-DEX) is a tunable acid-labile biopolymer with facile synthesis, aptly designed for the formulation of microparticles for vaccines and immune modulation. Tunability of degradation is achieved based on the kinetics of reaction and the molecular weight of the parent dextran polymer. This tunability translated to differential rates of activation of CD8+ T cells in an in vitro ovalbumin model and illustrated that acid-labile polymer can activate CD8+ T cells at an increased rate compared to acid-insensitive polymers. In addition, Ac-DEX has been used to encapsulate small molecules, deliver nucleotides, transport inorganic molecules, formulate immune modulating therapies and vaccines, and trigger pH responsive constructs for therapy. Here we highlight the properties and results of Ac-DEX nano-/microparticles as well as the use of the polymer in other constructs and chemistries.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    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.

  9. Temperature responsive transmitter

    NASA Technical Reports Server (NTRS)

    Kleinberg, Leonard L. (Inventor)

    1987-01-01

    A temperature responsive transmitter is provided in which frequency varies linearly with temperature. The transmitter includes two identically biased transistors connected in parallel. A capacitor, which reflects into the common bases to generate negative resistance effectively in parallel with the capacitor, is connected to the common emitters. A crystal is effectively in parallel with the capacitor and the negative resistance. Oscillations occur if the magnitude of the absolute value of the negative resistance is less than the positive resistive impedance of the capacitor and the inductance of the crystal. The crystal has a large linear temperature coefficient and a resonant frequency which is substantially less than the gain-bandwidth product of the transistors to ensure that the crystal primarily determines the frequency of oscillation. A high-Q tank circuit having an inductor and a capacitor is connected to the common collectors to increase the collector current flow which in turn enhances the radiation of the oscillator frequency by the inductor.

  10. Improving the performance of an acid-labile 4-hydroxymethyl phenoxyacetic acid (HMP) linker on resin and SynPhase grafted solid-supports.

    PubMed

    Bui, C T; Ercole, F; Pham, Y; Campbell, R; Rasoul, F A; Maeji, N J; Ede, N J

    2000-10-01

    A replacement of the acetic acid moiety by valeric acid within the 4-hydroxymethylphenoxyacetic acid (HMP) linker (Sheppard RC, Williams BJ. Acid-labile resin linkage agents for use in solid phase peptide synthesis. Int. J. Peptide Protein Res. 1982; 20: 451-454) significantly improved its performance in terms of loading capacity, yield and purity of the final products. The results indicated the spacer-linker combination and type of solid supports are important factors for solid-phase synthesis.

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

    PubMed

    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.

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

    PubMed Central

    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.

    2015-01-01

    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 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 13C sodium acetate (13C-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 13CO2 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. PMID:26160716

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

    PubMed

    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.

  14. Evaluation of acid-labile S-protecting groups to prevent Cys racemization in Fmoc solid-phase peptide synthesis

    PubMed Central

    Hibino, Hajime; Miki, Yasuyoshi; Nishiuchi, Yuji

    2014-01-01

    Phosphonium and uronium salt-based reagents enable efficient and effective coupling reactions and are indispensable in peptide chemistry, especially in machine-assisted SPPS. However, after the activating and coupling steps with these reagents in the presence of tertiary amines, Fmoc derivatives of Cys are known to be considerably racemized during their incorporation. To avoid this side reaction, a coupling method mediated by phosphonium/uronium reagents with a weaker base, such as 2,4,6-trimethylpyridine, than the ordinarily used DIEA or that by carbodiimide has been recommended. However, these methods are appreciably inferior to the standard protocol applied for SPPS, that is, a 1 min preactivation procedure of coupling with phosphonium or uronium reagents/DIEA in DMF, in terms of coupling efficiency, and also the former method cannot reduce racemization of Cys(Trt) to an acceptable level (<1.0%) even when the preactivation procedure is omitted. Here, the 4,4′-dimethoxydiphenylmethyl and 4-methoxybenzyloxymethyl groups were demonstrated to be acid-labile S-protecting groups that can suppress racemization of Cys to an acceptable level (<1.0%) when the respective Fmoc derivatives are incorporated via the standard SPPS protocol of phosphonium or uronium reagents with the aid of DIEA in DMF. Furthermore, these protecting groups significantly reduced the rate of racemization compared to the Trt group even in the case of microwave-assisted SPPS performed at a high temperature. © 2013 The Authors. European Peptide Society published by John Wiley & Sons, Ltd. PMID:24357151

  15. Endosomal Escape and Transfection Efficiency of PEGylated Cationic Lipid–DNA Complexes Prepared with an Acid-Labile PEG-Lipid

    PubMed Central

    Chan, Chia-Ling; Majzoub, Ramsey N.; Shirazi, Rahau S.; Ewert, Kai K.; Chen, Yen-Ju; Liang, Keng S.

    2012-01-01

    Cationic liposome–DNA (CL–DNA) complexes are being pursued as nonviral gene delivery systems for use in applications that include clinic trials. However, to compete with viral vectors for systemic delivery in vivo, their efficiencies and pharmacokinetics need to be improved. The addition of poly (ethylene glycol)-lipids (PEGylation) prolongs circulation lifetimes of liposomes, but inhibits cellular uptake and endosomal escape of CL–DNA complexes. We show that this limits their transfection efficiency (TE) in a manner dependent on the amount of PEG-lipid, the lipid/DNA charge ratio, and the lipid membrane charge density. To improve endosomal escape of PEGylated CL–DNA complexes, we prepared an acid-labile PEG-lipid (HPEG2K-lipid, PEG MW 2000) which is designed to lose its PEG chains at the pH of late endosomes. The HPEG2K-lipid and a similar but acid-stable PEG-lipid were used to prepare PEGylated CL–DNA complexes. TLC and dynamic light scattering showed that HPEG2K-CL–DNA complexes are stable at pH 7.4 for more than 24 hours, but the PEG chains are cleaved at pH 5 within one hour, leading to complex aggregation. The acid-labile HPEG2K-CL–DNA complexes showed enhanced TE over complexes stabilized with the acid-stable PEG-lipid. Live-cell imaging showed that both types of complexes were internalized to quantitatively similar particle distributions within the first 2 hours of incubation with cells. Thus, we attribute the increased TE of the HPEG2K-CL–DNA complexes to efficient endosomal escape, enabled by the acid-labile HPEG2K-lipid which sheds its PEG chains in the low-pH environment of late endosomes, effectively switching on the electrostatic interactions that promote fusion of the membranes of complex and endosome. PMID:22469293

  16. Acid-labile pHPMA modification of four-arm oligoaminoamide pDNA polyplexes balances shielding and gene transfer activity in vitro and in vivo.

    PubMed

    Beckert, Linda; Kostka, Libor; Kessel, Eva; Krhac Levacic, Ana; Kostkova, Hana; Etrych, Tomas; Lächelt, Ulrich; Wagner, Ernst

    2016-08-01

    We report novel pH-reversibly surface-shielded polyplexes with enhanced gene transfer activity upon systemic administration. A four-arm-structured sequence-defined cationic oligomer KK[HK[(H-Sph-K)3HC]2]2 was designed and synthesized on solid-phase, containing additional lysine residues not only for improved pDNA polyplex stability, but also providing attachment points for subsequent polyplex functionalization with amine-reactive shielding polymers. Herein, the surface of polyplexes was shielded with hydrophilic polymers, monovalent PEG or monovalent and multivalent pHPMA, optionally attached to the polyplex via the acid-labile linker AzMMMan. Overall, surface modification with PEG or pHPMA resulted in a decrease in the zeta potential of polyplexes, consistent with the degree of surface shielding. At pH 6.0, only polyplexes modified via the acid-labile linkage showed an increase in zeta potential, consistent with a "deshielding" in acidic environment, expected as beneficial for endosomal escape. Shielding was more efficient for multivalent pHPMA (20kDa, 30kDa) as compared to monovalent pHPMA (10kDa, 20kDa, 30kDa) or PEG (5kDa). In vitro transfection studies revealed higher gene expression by the polyplexes with the acid-labile shield as compared to their irreversibly shielded counterparts. Intravenous administration of AzMMMan-pHPMA modified polyplexes in an in vivo tumor mouse model mediated enhanced gene expression in the subcutaneous tumor and reduced undesirable expression in the liver.

  17. Efficacy and pharmacokinetics of a modified acid-labile docetaxel-PRINT® nanoparticle formulation against non-small-cell lung cancer brain metastases

    PubMed Central

    Sambade, Maria; Deal, Allison; Schorzman, Allison; Luft, J Christopher; Bowerman, Charles; Chu, Kevin; Karginova, Olga; Swearingen, Amanda Van; Zamboni, William; DeSimone, Joseph; Anders, Carey K

    2016-01-01

    Aim: Particle Replication in Nonwetting Templates (PRINT®) PLGA nanoparticles of docetaxel and acid-labile C2-dimethyl-Si-Docetaxel were evaluated with small molecule docetaxel as treatments for non-small-cell lung cancer brain metastases. Materials & methods: Pharmacokinetics, survival, tumor growth and mice weight change were efficacy measures against intracranial A549 tumors in nude mice. Treatments were administered by intravenous injection. Results: Intracranial tumor concentrations of PRINT-docetaxel and PRINT-C2-docetaxel were 13- and sevenfold greater, respectively, than SM-docetaxel. C2-docetaxel conversion to docetaxel was threefold higher in intracranial tumor as compared with nontumor tissues. PRINT-C2-docetaxel increased median survival by 35% with less toxicity as compared with other treatments. Conclusion: The decreased toxicity of the PRINT-C2-docetaxel improved treatment efficacy against non-small-cell lung cancer brain metastasis. PMID:27456556

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

    PubMed

    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.

  19. 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.

    PubMed

    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. © 2013 Scandinavian Plant Physiology Society.

  20. Mass Spectrometry Method to Identify Aging Pathways of Sp- and Rp-Tabun Adducts on Human Butyrylcholinesterase Based on the Acid Labile P-N Bond

    PubMed Central

    Lockridge, Oksana

    2013-01-01

    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. PMID:23345579

  1. Serological studies of an acid-labile O-polysaccharide of Proteus vulgaris OX19 lipopolysaccharide using human and rabbit antibodies.

    PubMed

    Kaca, W; Swierzko, A S; Ziolkowski, A; Amano, K; Senchenkova, S N; Knirel, Y A

    1998-01-01

    In a Weil-Felix test, sera from patients infected with Rickettsia sp. agglutinate Proteus OX types of bacteria and Proteus lipopolysaccharide (LPS) are responsible for the cross-reaction. Data on the character of LPS of one of the OX group strains, Proteus vulgaris OX19, are contradictory, and it remained unclear whether it has an O-polysaccharide (OPS) and is thus LPS of the smooth type (S) or not (rough-type LPS). Our studies showed that P. vulgaris OX19 (strain PZH-24) produces a smooth-type LPS that contains a long-chain OPS, but it undergoes depolymerization during mild acid hydrolysis conventionally used for LPS delipidation and loses the serological activity. An elucidation of the complete structure of OPS demonstrated the presence of a glycosyl phosphate linkage responsible for the acid-lability of the polysaccharide chain. In ELISA, both IgM type antibodies in a Weil-Felix test with human anti-Rickettsia typhi sera and rabbit anti-P. vulgaris OX19 antibodies reacted with OPS. Rabbit antibodies did not inhibit the cross-reaction with human antibodies and thus bind to different epitopes.

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

    PubMed

    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.

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

    PubMed Central

    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 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. PMID:26124659

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

    PubMed

    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. Copyright © 2011 Elsevier B.V. All rights reserved.

  5. Temperature-responsive copolymeric hydrogel systems synthetized by ionizing radiation

    NASA Astrophysics Data System (ADS)

    López-Barriguete, Jesús Eduardo; Bucio, Emilio

    2017-06-01

    Eight different systems of hydrogel copolymers with diverse temperature responsiveness were prepared to elaborate membranes for their biomedical application. The hydrogels were synthesized using poly(N-isopropylacrylamide) (PNIPAAm) and poly(N-vinylcaprolactam) (PNVCL), which have a low critical solution temperature (LCST) close to that of the human body temperature. The networks were synthesized using gamma radiation at a dose rate of 11.2 kGy h-1, and dose of 50 kGy. The LCST of each system was measured by differential scanning calorimetry (DSC). The effect of using hydrophilic monomers of acrylic acid (AAc), methacrylic acid (MAAc), dimethyl acrylamide (DMAAm), and hydroxyethyl methacrylate (HEMA) for the copolymerization on the critical point was evaluated. Five viable systems were obtained, with the best hydrogel being that of poly(NIPAAm-co-DMAAm), which an LCST at 39.8 °C. All the samples were characterized by FTIR-ATR, DSC, TGA, X-Ray Diffraction, and SEM. The proportion of monomers during the formation of the copolymers was decisive in the displacement of the LCST.

  6. Active thermal isolation for temperature responsive sensors

    NASA Technical Reports Server (NTRS)

    Martinson, Scott D. (Inventor); Gray, David L. (Inventor); Carraway, Debra L. (Inventor); Reda, Daniel C. (Inventor)

    1994-01-01

    A temperature responsive sensor is located in the airflow over the specified surface of a body and is maintained at a constant temperature. An active thermal isolator is located between this temperature responsive sensor and the specified surface of the body. The temperature of this isolator is controlled to reduce conductive heat flow from the temperature responsive sensor to the body. This temperature control includes: (1) operating the isolator at the same temperature as the constant temperature of the sensor and (2) establishing a fixed boundary temperature which is either less than or equal to or slightly greater than the sensor constant temperature.

  7. Acid-labile formylation of amino terminal proline of human immunodeficiency virus type 1 p24(gag) was found by proteomics using two-dimensional gel electrophoresis and matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry.

    PubMed

    Fuchigami, Takashi; Misumi, Shogo; Takamune, Nobutoki; Takahashi, Ichiro; Takama, Michiho; Shoji, Shozo

    2002-05-10

    HIV-1(LAV-1) particles were collected by ultracentrifugation, treated with subtilisin, and then purified by Sepharose CL-4B column chromatography to remove microvesicles. The lysate of the purified human immunodeficiency virus type 1 (HIV-1) particles was subjected to two-dimensional (2D) gel electrophoresis and stained, and the stained spots were excised and digested with trypsin. The resulting peptide fragments were characterized by matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS). Twenty-five proteins were identified as the proteins inside the virion and the acid-labile formyl group of an amino terminal proline residue of HIV-1(LAV-1) p24(gag) was determined by MALDI-TOF MS before and after weak-acid treatments (0.6 N hydrochloric acid) and confirmed by post-source decay (PSD) of the N-formylated N-terminal tryptic peptide (N-formylated Pro(1)-Arg(18)). The role of formylation has been unclear so far, but it is surmised that the acid-labile formylation of HIV-1(LAV-1) p24(gag) may play a critical role in the formation of the HIV-1 core for conferring HIV-1 infectivity.

  8. N,N'-methylenebis(acrylamide)-crosslinked poly(acrylic acid) particles as doxorubicin carriers: A comparison between release behavior of physically loaded drug and conjugated drug via acid-labile hydrazone linkage.

    PubMed

    Modarresi-Saryazdi, Seyedeh Mahnaz; Haddadi-Asl, Vahid; Salami-Kalajahi, Mehdi

    2017-09-18

    N,N'-methylenebis(acrylamide) (MBA)-crosslinked poly(acrylic acid) (PAA) particles with low degree of cross-linking were synthesized using distillation precipitation polymerization. Size and size distribution of particles were obtained using dynamic light scattering and field emission scanning electron microscopy( and results showed that microspheres had a narrow size dispersity. Proton nuclear magnetic resonance results indicated that amount of cross-linker in structure of particles is a little more than the molar percentage of feeded MBA because of greater activity ratio of MBA than AA. pH-responsive behavior of samples was investigated using UV-vis. absorption at 480 nm where each sample showed a sudden deplete in UV absorbance at a peculiar pH. Synthesized particles were used as carriers of anti-cancer drug doxorubicin using two different approaches including physically loading of drug and drug conjugation via an acid-labile hydrazone linkage. Release results showed that in the first case, amount of released drug has an inverse relationship with the amount of cross-linker in the structure and also, by adding an acid-labile linkage, the amount of burst release decreased drastically. Also, the amount of released drug for conjugated systems was much lesser than particles with physically loaded drug. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2017. © 2017 Wiley Periodicals, Inc.

  9. Active thermal isolation for temperature responsive sensors

    NASA Technical Reports Server (NTRS)

    Martinson, Scott D. (Inventor); Gray, David L. (Inventor); Carraway, Debra L. (Inventor); Reda, Daniel C. (Inventor)

    1994-01-01

    The detection of flow transition between laminar and turbulent flow and of shear stress or skin friction of airfoils is important in basic research for validation of airfoil theory and design. These values are conventionally measured using hot film nickel sensors deposited on a polyimide substrate. The substrate electrically insulates the sensor and underlying airfoil but is prevented from thermally isolating the sensor by thickness constraints necessary to avoid flow contamination. Proposed heating of the model surface is difficult to control, requires significant energy expenditures, and may alter the basic flow state of the airfoil. A temperature responsive sensor is located in the airflow over the specified surface of a body and is maintained at a constant temperature. An active thermal isolator is located between this temperature responsive sensor and the specific surface of the body. The total thickness of the isolator and sensor avoid any contamination of the flow. The temperature of this isolator is controlled to reduce conductive heat flow from the temperature responsive sensor to the body. This temperature control includes (1) operating the isolator at the same temperature as the constant temperature of the sensor; and (2) establishing a fixed boundary temperature which is either less than or equal to, or slightly greater than the sensor constant temperature. The present invention accordingly thermally isolates a temperature responsive sensor in an energy efficient, controllable manner while avoiding any contamination of the flow.

  10. Temperature-responsive intelligent interfaces for biomolecular separation and cell sheet engineering

    PubMed Central

    Nagase, Kenichi; Kobayashi, Jun; Okano, Teruo

    2009-01-01

    Temperature-responsive intelligent surfaces, prepared by the modification of an interface with poly(N-isopropylacrylamide) and its derivatives, have been used for biomedical applications. Such surfaces exhibit temperature-responsive hydrophilic/hydrophobic alterations with external temperature changes, which, in turn, result in thermally modulated interactions with biomolecules and cells. In this review, we focus on the application of these intelligent surfaces to chromatographic separation and cell cultures. Chromatographic separations using several types of intelligent surfaces are mentioned briefly, and various effects related to the separation of bioactive compounds are discussed, including wettability, copolymer composition and graft polymer architecture. Similarly, we also summarize temperature-responsive cell culture substrates that allow the recovery of confluent cell monolayers as contiguous living cell sheets for tissue-engineering applications. The key factors in temperature-dependent cell adhesion/detachment control are discussed from the viewpoint of grafting temperature-responsive polymers, and new methodologies for effective cell sheet culturing and the construction of thick tissues are summarized. PMID:19324682

  11. Meth math: modeling temperature responses to methamphetamine.

    PubMed

    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.

  12. Meth math: modeling temperature responses to methamphetamine

    PubMed Central

    Molkov, Yaroslav I.; Zaretskaia, Maria V.

    2014-01-01

    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. PMID:24500434

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

    PubMed

    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.

  14. Temperature responsive hydroxypropyl cellulose for encapsulation

    SciTech Connect

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

    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.

  15. Lysosomal pH-inducible supramolecular dissociation of polyrotaxanes possessing acid-labile N-triphenylmethyl end groups and their therapeutic potential for Niemann-Pick type C disease

    PubMed Central

    Tamura, Atsushi; Nishida, Kei; Yui, Nobuhiko

    2016-01-01

    Abstract Niemann-Pick type C (NPC) disease is characterized by the accumulation of cholesterol in lysosomes. We have previously reported that biocleavable polyrotaxanes (PRXs) composed of β-cyclodextrins (β-CDs) threaded onto a linear polymer capped with bulky stopper molecules via intracellularly cleavable linkers show remarkable cholesterol reducing effects in NPC disease patient-derived fibroblasts owing to the stimuli-responsive intracellular dissociation of PRXs and subsequent β-CD release from the PRXs. Herein, we describe a series of novel acid-labile 2-(2-hydroxyethoxy)ethyl group-modified PRXs (HEE-PRXs) bearing terminal N-triphenylmethyl (N-Trt) groups as a cleavable component for the treatment of NPC disease. The N-Trt end groups of the HEE-PRXs underwent acidic pH-induced cleavage and led to the dissociation of their supramolecular structure. A kinetic study revealed that the number of HEE groups on the PRX did not affect the cleavage kinetics of the N-Trt end groups of the HEE-PRXs. The effect of the number of HEE groups of the HEE-PRXs, which was modified to impart water solubility to the PRXs, on cellular internalization efficiency, lysosomal localization efficiency, and cholesterol reduction ability in NPC disease-derived fibroblasts (NPC1 fibroblasts) was also investigated. The cellular uptake and lysosomal localization efficiency were almost equivalent for HEE-PRXs with different numbers of HEE groups. However, the cholesterol reducing ability of the HEE-PRXs in NPC1 fibroblasts was affected by the number of HEE groups, and HEE-PRXs with a high number of HEE groups were unable to reduce lysosomal cholesterol accumulation. This deficiency is most likely due to the cholesterol-solubilizing ability of HEE-modified β-CDs released from the HEE-PRXs. We conclude that the N-Trt group acts as a cleavable component to induce the lysosomal dissociation of HEE-PRXs, and acid-labile HEE-PRXs with an optimal number of HEE groups (4.1 to 5.4 HEE groups per

  16. Novel temperature-responsive polymer brushes with carbohydrate residues facilitate selective adhesion and collection of hepatocytes

    PubMed Central

    Idota, Naokazu; Ebara, Mitsuhiro; Kotsuchibashi, Yohei; Narain, Ravin; Aoyagi, Takao

    2012-01-01

    Temperature-responsive glycopolymer brushes were designed to investigate the effects of grafting architectures of the copolymers on the selective adhesion and collection of hypatocytes. Homo, random and block sequences of N-isopropylacrylamide and 2-lactobionamidoethyl methacrylate were grafted on glass substrates via surface-initiated atom transfer radical polymerization. The galactose/lactose-specific lectin RCA120 and HepG2 cells were used to test for specific recognition of the polymer brushes containing galactose residues over the lower critical solution temperatures (LCSTs). RCA120 showed a specific binding to the brush surfaces at 37 °C. These brush surfaces also facilitated the adhesion of HepG2 cells at 37 °C under nonserum conditions, whereas no adhesion was observed for NIH-3T3 fibroblasts. When the temperature was decreased to 25 °C, almost all the HepG2 cells detached from the block copolymer brush, whereas the random copolymer brush did not release the cells. The difference in releasing kinetics of cells from the surfaces with different grafting architectures can be explained by the correlated effects of significant changes in LCST, mobility, hydrophilicity and mechanical properties of the grafted polymer chains. These findings are important for designing ‘on–off’ cell capture/release substrates for various biomedical applications such as selective cell separation. PMID:27877533

  17. Novel temperature-responsive polymer brushes with carbohydrate residues facilitate selective adhesion and collection of hepatocytes

    NASA Astrophysics Data System (ADS)

    Idota, Naokazu; Ebara, Mitsuhiro; Kotsuchibashi, Yohei; Narain, Ravin; Aoyagi, Takao

    2012-12-01

    Temperature-responsive glycopolymer brushes were designed to investigate the effects of grafting architectures of the copolymers on the selective adhesion and collection of hypatocytes. Homo, random and block sequences of N-isopropylacrylamide and 2-lactobionamidoethyl methacrylate were grafted on glass substrates via surface-initiated atom transfer radical polymerization. The galactose/lactose-specific lectin RCA120 and HepG2 cells were used to test for specific recognition of the polymer brushes containing galactose residues over the lower critical solution temperatures (LCSTs). RCA120 showed a specific binding to the brush surfaces at 37 °C. These brush surfaces also facilitated the adhesion of HepG2 cells at 37 °C under nonserum conditions, whereas no adhesion was observed for NIH-3T3 fibroblasts. When the temperature was decreased to 25 °C, almost all the HepG2 cells detached from the block copolymer brush, whereas the random copolymer brush did not release the cells. The difference in releasing kinetics of cells from the surfaces with different grafting architectures can be explained by the correlated effects of significant changes in LCST, mobility, hydrophilicity and mechanical properties of the grafted polymer chains. These findings are important for designing ‘on-off’ cell capture/release substrates for various biomedical applications such as selective cell separation.

  18. Phase separations in a copolymer copolymer mixture

    NASA Astrophysics Data System (ADS)

    Zhang, Jin-Jun; Jin, Guojun; Ma, Yuqiang

    2006-01-01

    We propose a three-order-parameter model to study the phase separations in a diblock copolymer-diblock copolymer mixture. The cell dynamical simulations provide rich information about the phase evolution and structural formation, especially the appearance of onion-rings. The parametric dependence and physical reason for the domain growth of onion-rings are discussed.

  19. 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.

    PubMed

    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.

  20. 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

    NASA Astrophysics Data System (ADS)

    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.

  1. The temperature response of fungal enzyme kinetics

    NASA Astrophysics Data System (ADS)

    Curran, M.; Lu, Y.; Taylor, J.; Allison, S. D.

    2013-12-01

    Extracellular enzymes produced and excreted by microbes mediate the decomposition of carbon (C), nitrogen (N), and phosphorus (P) -containing compounds in their environment. Climate change has the potential to alter the rate of decomposition especially in high latitude regions where stocks of recalcitrant, or long-lived, C are abundant. This project compares extracellular enzyme activity (EEA) across ten fungi strains within the model family Neurospora in order to assess the range of variation in temperature sensitivities of fungal enzyme Vmax and Km. Vmax values of most enzymes tested increased exponentially,which was hypothesized and consistant with thermodynamic principles. We also hypothesized that Neurospora strains would exhibit different EEA temperature sensitivities based on their native climate. We observed strain-dependent variation in enzyme temperature responses consistent with strain-specific adaptation to local conditions. Since fungi are the major decomposers of organic carbon in high-latitude ecosystems, an increase in EEA in-situ would result in higher carbon dioxide emissions. These findings suggest a shift in fungal processing of soil organic carbon and nutrients in response to changing climate.

  2. Protein based Block Copolymers

    PubMed Central

    Rabotyagova, Olena S.; Cebe, Peggy; Kaplan, David L.

    2011-01-01

    Advances in genetic engineering have led to the synthesis of protein-based block copolymers with control of chemistry and molecular weight, resulting in unique physical and biological properties. The benefits from incorporating peptide blocks into copolymer designs arise from the fundamental properties of proteins to adopt ordered conformations and to undergo self-assembly, providing control over structure formation at various length scales when compared to conventional block copolymers. This review covers the synthesis, structure, assembly, properties, and applications of protein-based block copolymers. PMID:21235251

  3. Temperature responsive hydrogels enable transient three-dimensional tumor cultures via rapid cell recovery.

    PubMed

    Heffernan, John M; Overstreet, Derek J; Srinivasan, Sanjay; Le, Long D; Vernon, Brent L; Sirianni, Rachael W

    2016-01-01

    Recovery of live cells from three-dimensional (3D) culture would improve analysis of cell behaviors in tissue engineered microenvironments. In this work, we developed a temperature responsive hydrogel to enable transient 3D culture of human glioblastoma (GBM) cells. N-isopropylacrylamide was copolymerized with hydrophilic grafts and functionalized with the cell adhesion peptide RGD to yield the novel copolymer poly(N-isopropylacrylamide-co-Jeffamine(®) M-1000 acrylamide-co-hydroxyethylmethacrylate-RGD), or PNJ-RGD. This copolymer reversibly gels in aqueous solutions when heated under normal cell culture conditions (37°C). Moreover, these gels redissolve within 70 s when cooled to room temperature without the addition of any agents to degrade the synthetic scaffold, thereby enabling rapid recollection of viable cells after 3D culture. We tested the efficiency of cell recovery following extended 3D culture and were able to recover more than 50% of viable GBM cells after up to 7 days in culture. These data demonstrate the utility of physically crosslinked PNJ-RGD hydrogels as a platform for culture and recollection of cells in 3D. © 2015 Wiley Periodicals, Inc.

  4. Design and synthesis of temperature-responsive polymer/silica hybrid nanoparticles and application to thermally controlled cellular uptake.

    PubMed

    Hiruta, Yuki; Nemoto, Ryo; Kanazawa, Hideko

    2017-02-04

    This study reports the development of temperature-responsive polymer/silica hybrid nanoparticles and their application to temperature-dependent intracellular uptake of hydrophobic encapsulated fluorescence molecules. Amphiphilic diblock copolymer comprising a temperature-responsive segment, poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) [P(NIPAAm-co-DMAAm)] and a trimethyoxysilyl-containing hydrophobic segment was synthesized (PBM-b-ND); this amphiphilic diblock copolymer self-assembled in an aqueous solution, and temperature-responsive polymer/silica hybrid fluorescence nanoparticles were fabricated via a base-catalyzed sol-gel process. The fluorescence probe rhodamine DHPE or boron dipyrromethene derivative was encapsulated into the polymer core with a silica network in a stable manner. Other types of polymer/silica hybrid fluorescence nanoparticles were also developed using either homo-PNIPAAm (PBM-b-N) or homo-PDMAAm (PBM-b-D) segments, instead of P(NIPAAm-co-DMAAm). While PBM-b-D did not exhibit a temperature-dependent phase transition (hydrophilic characteristic), PBM-b-N and PBM-b-ND exhibited temperature-dependent phase transition (hydrophilic/hydrophobic) at 32°C and 38°C, respectively. The cellular uptake of PBM-b-N was clearly observed at both 37°C and 42°C, while the cellular uptake of PBM-b-D was minimal at these temperatures. On the other hand, significant enhancement in the intracellular uptake of PBM-b-ND was observed at 42°C, compared to its uptake at a lower temperature of 37°C. These results indicated that temperature-responsive polymer/silica hybrid nanoparticle, PBM-b-ND demonstrate potential for applications in theranostics with cancer therapy via the combination of local drug delivery and local hyperthermia, as well as for monitoring treatment effectiveness with fluorescence imaging.

  5. Temperature-responsive smart packing materials utilizing multi-functional polymers.

    PubMed

    Ayano, Eri; Kanazawa, Hideko

    2014-01-01

    Polymers that respond to small changes in environmental stimuli with large, sometimes discontinuous changes in their physical state or properties, are often called "smart" polymers. Poly(N-isopropylacrylamide), PNIPAAm, is one of the most representative smart polymer that exhibits a thermally reversible soluble-insoluble change in the vicinity of its lower critical solution temperature (LCST) at 32°C in aqueous solution. Temperature-responsive chromatography for the separation of biomolecules utilizing the poly(N-isopropylacrylamide) (PNIPAAm)-modified stationary phase is performed with an aqueous mobile phase without using an organic solvent. The surface properties and function of the stationary phase are controlled by external temperature changes without changing the mobile-phase composition. The separation of the biomolecules, such as nucleotides, 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. Additionally, we also prepared functional copolymers composed of N-isopropylacrylamide (NIPAAm) and amino acid derivative or naphthyl alanine derivative, which have temperature-responsiveness and molecular recognition. These separation systems would have potential applications in the separation of biomolecules.

  6. New Polytetrahydrofuran Graft Copolymers.

    DTIC Science & Technology

    1979-03-15

    chioroprene) , chiorobutyl - ~~~~~ rubber , bromobutyl rubber , chlorinated EPDM , chlorinated poly(buta— diene) and chlorinated butadiene styrene copolymer...bromobutyl rubber , which after dehalogenation is unstable with respect to conjugated dienes, the yields of graft copolymer are low. With poly(chloroprerte

  7. Silicone/Acrylate Copolymers

    NASA Technical Reports Server (NTRS)

    Dennis, W. E.

    1982-01-01

    Two-step process forms silicone/acrylate copolymers. Resulting acrylate functional fluid is reacted with other ingredients to produce copolymer. Films of polymer were formed by simply pouring or spraying mixture and allowing solvent to evaporate. Films showed good weatherability. Durable, clear polymer films protect photovoltaic cells.

  8. N-Isopropylacrylamide-Based Copolymers with Time-Dependent LCST for a Bioresorbable Carrier

    DTIC Science & Technology

    2005-01-01

    temperature responsive and biodegradable poly(N- isopropylacrylamide-co-caprolactone) [2]; partially degradable dextran -maleic anhydride/ poly(N...isopropylacrylamide) hybrid hydrogels [3]. Also, Nevadovic et al. designed new types of thermosensitive NIPAAm-based polymers such as a copolymer of NIPAAm and 2

  9. Temperature response of bundle-sheath conductance in maize leaves

    PubMed Central

    Yin, Xinyou; van der Putten, Peter E.L.; Driever, Steven M.; Struik, Paul C.

    2016-01-01

    A small bundle-sheath conductance (g bs) is essential for the C4 CO2-concentrating mechanism to suppress photorespiration effectively. To predict the productivity of C4 crops accurately under global warming, it is necessary to examine whether and how g bs responds to temperature. We investigated the temperature response of g bs in maize by fitting a C4 photosynthesis model to combined gas exchange and chlorophyll fluorescence measurements of irradiance and CO2 response curves at 21% and 2% O2 within the range of 13.5–39 °C. The analysis was based on reported kinetic constants of C4 Rubisco and phosphoenolpyruvate carboxylase and temperature responses of C3 mesophyll conductance (g m). The estimates of g bs varied greatly with leaf temperature. The temperature response of g bs was well described by the peaked Arrhenius equation, with the optimum temperature being ~34 °C. The assumed temperature responses of g m had only a slight impact on the temperature response of g bs. In contrast, using extreme values of some enzyme kinetic constants changed the shape of the response, from the peaked optimum response to the non-peaked Arrhenius pattern. Further studies are needed to confirm such an Arrhenius response pattern from independent measurement techniques and to assess whether it is common across C4 species. PMID:26969744

  10. Temperature responses of exercizing dogs to infusion of electrolytes

    NASA Technical Reports Server (NTRS)

    Greenleaf, J. E.; Kozlowski, S.; Nazar, K.; Kaciuba-Uscilko, H.; Brzezinska, Z.

    1974-01-01

    The effect of infusions with solutions of various ionic and osmotic composition on exercise temperature responses was studied in dogs who do not regulate their temperature by sweating. The results suggest an association between plasma Na+ and Ca++ level within the normal physiological range and the control of body temperature during exercise.

  11. Temperature responses of exercizing dogs to infusion of electrolytes

    NASA Technical Reports Server (NTRS)

    Greenleaf, J. E.; Kozlowski, S.; Nazar, K.; Kaciuba-Uscilko, H.; Brzezinska, Z.

    1974-01-01

    The effect of infusions with solutions of various ionic and osmotic composition on exercise temperature responses was studied in dogs who do not regulate their temperature by sweating. The results suggest an association between plasma Na+ and Ca++ level within the normal physiological range and the control of body temperature during exercise.

  12. Preparation of temperature responsive fragrance release membranes by UV curing

    NASA Astrophysics Data System (ADS)

    Nakayama, Hiroshi; Kaetsu, Isao; Uchida, Kumao; Okuda, Jyunya; Kitami, Toshiaki; Matsubara, Yoshio

    2003-06-01

    The authors have studied the preparation and the function of intelligent drug release membranes by UV curing. Temperature responsive fragrance release membranes were prepared by UV curing process and the release functions were investigated as the function of thickness and composition of membrane. Microscopic observations were used to prove the postulated release mechanism.

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

    SciTech Connect

    Determan, Michael Duane

    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

  14. Synthesis of norbornene copolymers with diazo groups and their application as DUV resists

    NASA Astrophysics Data System (ADS)

    Kim, Jin-Baek; Kim, Kyoung Seon

    2003-06-01

    We synthesized a new type of norbornene-maleic anhydride copolymer which as diazoketo groups instead of acid labile protecting groups. The matrix polymer does not need a photoacid generator for the lithographic evaluation. And there is no necessity for the post-exposure bake step that is the cause of PED effects. Methyl 5-norbornenyl-3-oxopropionate was prepared by the reaction of acetyl norbornene with dimethyl carbonate in the presence of sodium hydride. And methyl 5-norbornenyl-2-diazo-3-oxopropionate was synthesized from the reaction between methyl 5-norbornenyl-3-oxopropionate and p-carboxybenzenesulfonyl azide. The polymer was prepared by free radical polymerization. Upon exposure to DUV light, diazoketo groups undergo a series of reactions that culminate in the formation of a carboxylic acid. The matrix polymer in the exposed region becomes soluble in the aqueous base developer. The polymer showed bleaching effect after exposure. Thermal stability of the polymer is measured by TGA and DSC. Characterization of the polymer is achieved using other techniques such as FT-IR, NMR, GPC, and UV. The resist patterns of 0.6 μm feature size were resolved using a KrF exposure tool and with a conventional developer, 2.38 wt% TMAH aqueous solution.

  15. Block coordination copolymers

    DOEpatents

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

    2012-12-04

    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.

  16. Block coordination copolymers

    DOEpatents

    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.

  17. Block coordination copolymers

    DOEpatents

    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.

  18. Ultraviolet absorbing copolymers

    DOEpatents

    Gupta, Amitava; Yavrouian, Andre H.

    1982-01-01

    Photostable and weather stable absorping copolymers have been prepared from acrylic esters such as methyl methacrylate containing 0.1 to 5% of an 2-hydroxy-allyl benzophenone, preferably the 4,4' dimethoxy derivative thereof. The pendant benzophenone chromophores protect the acrylic backbone and when photoexcited do not degrade the ester side chain, nor abstract hydrogen from the backbone.

  19. Steps towards a mechanistic understanding of respiratory temperature responses.

    PubMed

    Kruse, Jörg; Rennenberg, Heinz; Adams, Mark A

    2011-02-01

    Temperature crucially affects the speed of metabolic processes in poikilotherm organisms, including plants. The instantaneous temperature responses of O(2)-reduction and CO(2)-release can be approximated by Arrhenius kinetics, even though respiratory gas exchange of plants is the net effect of many constituent biochemical processes. Nonetheless, the classical Arrhenius equation must be modified to account for a dynamic response to measurement temperatures. We show that this dynamic response is readily explained by combining Arrhenius and Michaelis-Menten kinetics, as part of a fresh appraisal of metabolic interpretations of instantaneous temperature responses. In combination with recent experimental findings, we argue that control of mitochondrial electron flow is shared among cytochrome oxidase and alternative oxidase under in vivo conditions, and is continuously coordinated. In this way, upstream carbohydrate metabolism and downstream electron transport appear to be optimized according to the demand of ATP, TCA-cycle intermediates and anabolic reducing power under differing metabolic states. We provide a link to the 'Growth and Maintenance Paradigm' of respiration and argue that respiratory temperature responses can be used as a tool to probe metabolic states of plant tissue, such that we can learn more about the mechanisms that govern longer-term acclimatization responses of plant metabolism.

  20. Temperature responses of individual soil organic matter components

    NASA Astrophysics Data System (ADS)

    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.

  1. Imide/arylene ether copolymers

    NASA Technical Reports Server (NTRS)

    Jensen, Brian J. (Inventor); Hergenrother, Paul M. (Inventor); Bass, Robert G. (Inventor)

    1992-01-01

    Imide/arylene ether block copolymers are prepared by reacting anhydride terminated poly(amic acids) with amine terminated poly(arylene ethers) in polar aprotic solvents and by chemically or thermally cyclodehydrating the resulting intermediate poly(amic acids). The resulting block copolymers have one glass transition temperature or two, depending upon the particular structure and/or the compatibility of the block units. Most of these block copolymers form tough, solvent resistant films with high tensile properties.

  2. Block copolymer battery separator

    DOEpatents

    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.

  3. Clickable Amphiphilic Triblock Copolymers.

    PubMed

    Isaacman, Michael J; Barron, Kathryn A; Theogarajan, Luke S

    2012-06-15

    Amphiphilic polymers have recently garnered much attention due to their potential use in drug-delivery and other biomedical applications. A modular synthesis of these polymers is extremely desirable since it offers precise individual block characterization and increased yields. We present here for the first time a modular synthesis of poly(oxazoline)-poly(siloxane)-poly(oxazoline) block copolymers that have been clicked together using the copper-catalyzed azide-alkyne cycloaddition reaction. Various click methodologies for the synthesis of these polymers have been carefully evaluated and optimized. The approach using copper nanoparticles was found to be the most optimal among the methods evaluated. Furthermore, these results were extended to allow for a reactive Si-H group-based siloxane middle block to be successfully clicked. This enables the design of more complex amphiphilic block copolymers that have additional functionality, such as stimuli responsiveness, to be synthesized via a simple hydrosilylation reaction.

  4. Baroplastic Block copolymers

    NASA Astrophysics Data System (ADS)

    Hewlett, Sheldon A.

    2005-03-01

    Block copolymers with rubbery and glassy components have been observed to have pressure induced miscibility. These microphase-separated materials, termed baroplastics, were able to flow and be processed at temperatures below the Tg of the glassy component by simple compression molding and extrusion. Diblock and triblock copolymers of polystyrene and poly(butyl acrylate) or poly(2-ethyl hexyl acrylate) were synthesized by atom transfer radical polymerization (ATRP) and processed at room temperature into well defined transparent objects. SAXS and SANS measurements demonstrated partial mixing between components as a result of pressure during processing. DSC results also show the presence of distinct domains even after several processing cycles. Their mechanical properties after processing were tested and compared with commercial thermoplastic elastomers.

  5. Imide/Arylene Ether Copolymers

    NASA Technical Reports Server (NTRS)

    Jensen, Brian J.; Hergenrother, Paul M.; Bass, Robert G.

    1991-01-01

    New imide/arylene ether copolymers prepared by reacting anhydride-terminated poly(amic acids) with amine-terminated poly(arylene ethers) in polar aprotic solvents. Each resulting copolymer may have one glass-transition temperature or two, depending on chemical structure and/or compatibility of block units. Most of copolymers form tough, solvent-resistant films with high tensile properties. Films cast from solution tough and flexible, and exhibit useful thermal and mechanical properties. Potentially useful as moldings, adhesives, or composite matrices. Because of flexible arylene ether blocks, these copolymers easier to process than polyimides.

  6. Analysis of melt copolymers.

    PubMed

    Montaudo, Maurizio S

    2007-01-01

    Melt copolymer chains are the main (most abundant) reaction product obtained when heating a blend of two (or more) condensation polymers (such as polyester + polycarbonate or polyester + polyamide or polyester + polyester) in which exchange reactions occur. In fact, during the melt-mixing reaction, an AB copolymer is formed and, as a consequence, the sample is a complex mixture made of three components or simply "parts", referred to as Z1, Z2 and Z3, where Z1 and Z2 are the parts for unreacted homopolymers (A and B), whereas Z3 is the part for the copolymer. In this paper, it is shown that matrix-assisted laser desorption/ionization mass spectrometry (and mass spectrometry in general) can be used to monitor the yield of the reactive blending reaction, YR, by measuring the amount of unreacted homopolymer (Z1 and Z2). In order to allow for comparisons, the paper also discusses conventional methods for measuring Z1 and Z2, such as liquid chromatography and nuclear magnetic resonance.

  7. Structure-Performance Relationships of Temperature-Responsive PLGA-PEG-PLGA Gels for Sustained Release of Bone Morphogenetic Protein-2.

    PubMed

    Santoveña, Ana; Monzón, Cecilia; Alvarez-Lorenzo, Carmen; Del Rosario, Carlos; Delgado, Araceli; Evora, Carmen; Concheiro, Angel; Llabrés, Matias; Fariña, José B

    2017-07-19

    PLGA (poly(lactic-co-glycolic) acid)-PEG (polyethylene glycol)-PLGA synthesis conditions have an impact on the physicochemical features of the copolymer and its usefulness as biomaterial. This study reports on an analysis of the composition and structural properties of PLGA-PEG-PLGA copolymers applying a variety of analytical techniques. Viscoelastic properties and particularly the temperature-responsive behavior of PLGA-PEG-PLGA showed a marked dependence on copolymer structural features. Physicochemical and biological properties, such as bioadhesion, biocompatibility and cell viability, of the raw copolymers and their gels were also evaluated. The most promising copolymer was chosen to formulate the osteoinductive protein bone morphogenetic protein-2 ((125)I-BMP-2), and the ability of its gels to sustain the release both in vitro and in vivo was monitored in situ using a gamma counter. In vitro diffusion studies were carried out using a bioinspired set-up that included a biorelevant receptor medium. In vivo release tests after implantation in a critical-size calvarial defect model showed an important burst, but then the release fitted well to the square-root kinetics. Importantly, the release rate constants recorded in vitro and in vivo matched each other suggesting close in vitro-in vivo correlation. Overall, the information gathered opens new perspectives in the biomedical application of these temperature-sensitive materials. Copyright © 2017 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

  8. Block copolymer investigations

    NASA Astrophysics Data System (ADS)

    Yufa, Nataliya A.

    The research presented in this thesis deals with various aspects of block copolymers on the nanoscale: their behavior at a range of temperatures, their use as scaffolds, or for creation of chemically striped surfaces, as well as the behavior of metals on block copolymers under the influence of UV light, and the healing behavior of copolymers. Invented around the time of World War II, copolymers have been used for decades due to their macroscopic properties, such as their ability to be molded without vulcanization, and the fact that, unlike rubber, they can be recycled. In recent years, block copolymers (BCPs) have been used for lithography, as scaffolds for nano-objects, to create a magnetic hard drive, as well as in photonic and other applications. In this work we used primarily atomic force microscopy (AFM) and transmission electron microscopy (TEM), described in Chapter II, to conduct our studies. In Chapter III we demonstrate a new and general method for positioning nanoparticles within nanoscale grooves. This technique is suitable for nanodots, nanocrystals, as well as DNA. We use AFM and TEM to demonstrate selective decoration. In Chapters IV and V we use AFM and TEM to study the structure of polymer surfaces coated with metals and self-assembled monolayers. We describe how the surfaces were created, exhibit their structure on the nanoscale, and prove that their macroscopic wetting properties have been altered compared to the original polymer structures. Finally, Chapters VI and VII report out in-situ AFM studies of BCP at high temperatures, made possible only recently with the invention of air-tight high-temperature AFM imaging cells. We locate the transition between disordered films and cylinders during initial ordering. Fluctuations of existing domains leading to domain coarsening are also described, and are shown to be consistent with reptation and curvature minimization. Chapter VII deals with the healing of PS-b-PMMA following AFM-tip lithography or

  9. Controlled Delivery of Human Cells by Temperature Responsive Microcapsules

    PubMed Central

    Mak, W.C.; Olesen, K.; Sivlér, P.; Lee, C.J.; Moreno-Jimenez, I.; Edin, J.; Courtman, D.; Skog, M.; Griffith, M.

    2015-01-01

    Cell therapy is one of the most promising areas within regenerative medicine. However, its full potential is limited by the rapid loss of introduced therapeutic cells before their full effects can be exploited, due in part to anoikis, and in part to the adverse environments often found within the pathologic tissues that the cells have been grafted into. Encapsulation of individual cells has been proposed as a means of increasing cell viability. In this study, we developed a facile, high throughput method for creating temperature responsive microcapsules comprising agarose, gelatin and fibrinogen for delivery and subsequent controlled release of cells. We verified the hypothesis that composite capsules combining agarose and gelatin, which possess different phase transition temperatures from solid to liquid, facilitated the destabilization of the capsules for cell release. Cell encapsulation and controlled release was demonstrated using human fibroblasts as model cells, as well as a therapeutically relevant cell line—human umbilical vein endothelial cells (HUVECs). While such temperature responsive cell microcapsules promise effective, controlled release of potential therapeutic cells at physiological temperatures, further work will be needed to augment the composition of the microcapsules and optimize the numbers of cells per capsule prior to clinical evaluation. PMID:26096147

  10. Temperature-responsive PLLA/PNIPAM nanofibers for switchable release.

    PubMed

    Elashnikov, Roman; Slepička, Petr; Rimpelova, Silvie; Ulbrich, Pavel; Švorčík, Vaclav; Lyutakov, Oleksiy

    2017-03-01

    Smart antimicrobial materials with on-demand drug release are highly desired for biomedical applications. Herein, we report about temperature-responsive poly(N-isopropylacrylamide) (PNIPAM) nanospheres doped with crystal violet (CV) and incorporated into the poly-l-lactide (PLLA) nanofibers. The nanofibers were prepared by electrospinning, using different initial polymers ratios. The morphology of the nanofibers and polymers distribution in the nanofibers were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The interaction between PNIPAM and PLLA in the nanofibers was studied by Fourier transform infrared spectroscopy (FTIR) and its effect on the PNIPAM phase transition was also investigated. It was shown that by the changing of the environmental temperature across the lower critical solution temperature (LCST) of PNIPAM, the switchable wettability and controlled CV release can be achieved. The temperature-dependent release kinetics of CV from polymer nanofibers was investigated by ultraviolet-visible spectroscopy (UV-Vis). The temperature-responsive release of antibacterial CV was also tested for triggering of antibacterial activity, which was examined on Staphylococcus epidermidis (S. epidermidis) and Escherichia coli (E. coli). Thus, the proposed material is promising value for controllable drug-release. Copyright © 2016 Elsevier B.V. All rights reserved.

  11. Synthesis of temperature-responsive anion exchanger via click reaction.

    PubMed

    Murakami, Kenji; Yu, Xue; Kato, Takahiro; Inoue, Yukihiko; Sugawara, Katsuyasu

    2012-06-15

    The temperature-responsive anion exchanger was synthesized by immobilizing the poly(N-isopropylacrylamide) (PNIPAM), a kind of the temperature-responsive polymer, on the external surface of mesoporous silica via click reaction. The structure of this synthesized composite was characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), elemental analysis, and nitrogen adsorption experiment. The amount of PNIPAM immobilized on the external surface of mesoporous silica, which was calculated from the weight loss measured by thermogravimetry, increased from 5.3 wt.% to 12.9 wt.% (dry) depending on the amount of PNIPAM added in the click reaction. The adsorption-desorption behavior of methyl orange (MO) ions in this synthesized anion exchanger was affected by the temperature of aqueous solution: the MO ions were adsorbed and desorbed reversibly and repeatedly with changing the pH of the solution at 25 °C, while the amount of adsorbed MO ions remained nearly constant at about 0.05 mmol/g independent of the pH of the solution at 40 °C. Also, the amount of PNIPAM immobilized on the mesoporous silica influenced the adsorption rate of MO ions, suggesting that the adsorption rate in this composite is controlled by the diffusion of MO ions through the PNIPAM layer.

  12. Childhood fever: correlation of diagnosis with temperature response to acetaminophen.

    PubMed

    Baker, M D; Fosarelli, P D; Carpenter, R O

    1987-09-01

    Many people believe that temperature response to antipyretics in febrile children varies according to diagnosis. To evaluate the validity of this premise, we prospectively studied the temperature response to acetaminophen of febrile children who came to an urban pediatric emergency and walk-in facility. The study group consisted of 1,559 patients between the ages of 8 weeks and 6 years whose temperatures when seen were greater than 38.4 degrees C and who had not received antipyretic treatment within the previous four hours. Acetaminophen (15 mg/kg) was administered to each child and repeat temperatures were taken one and two hours later. Patient management was unaffected by the study, and physicians were unaware of the repeat temperature measurements. Telephone follow-up was conducted with the parents of each child within five days of the initial visit. Children with cultures positive for bacterial disease or chest x-ray films positive for pneumonia had slightly greater one- and two-hour temperature decreases compared with children with other diagnoses. Although statistically significant, we do not consider these differences in response to be clinically useful. We conclude that fever response to acetaminophen is not a clinically useful indicator by which to differentiate the causes of febrile illnesses in young children.

  13. Interfacial Modification by Copolymers: The Importance of Copolymer Microstructure

    NASA Astrophysics Data System (ADS)

    Dadmun, Mark; Eastwood, Eric

    2002-03-01

    The dispersion of nanoscale particles or domains in a polymer matrix can readily lead to nonlinear enhancement of material properties. Our research group has been examining two primary methods to improve the properties of multicomponent polymer systems: compatibilization of a blend with an interfacial modifier or improving the miscibility and properties of polymer blends with specific interactions. In this talk, the importance of specific copolymer microstructure on its ability to strengthen a biphasic interface will be discussed. Atom transfer radical polymerization has been utilized to polymerize a series of multiblock copolymers containing styrene and methyl methacrylate. This, in turn, has allowed the synthesis of a series of copolymers with careful control of the sequence distribution. Subsequent experiments that determine the interfacial strength between two polymers in the presence and absence of these copolymers has provided critical information that documents the importance of copolymer sequence distribution on its ability to strengthen a biphasic interface.

  14. Extemporaneously preparative biodegradable injectable polymer systems exhibiting temperature-responsive irreversible gelation.

    PubMed

    Yoshida, Yasuyuki; Takata, Kazuyuki; Takai, Hiroki; Kawahara, Keisuke; Kuzuya, Akinori; Ohya, Yuichi

    2017-10-01

    On clinical application of biodegradable injectable polymer (IP) systems, quick extemporaneous preparation of IP formulations and longer duration time gel state after injection into the body are the important targets to be developed. Previously, we had reported temperature-responsive covalent gelation systems via bio-orthogonal thiol-ene reaction by 'mixing strategy' of amphiphilic biodegradable tri-block copolymer (tri-PCG) attaching acryloyl groups on both termini (tri-PCG-Acryl) with reactive polythiol. In other previous works, we found 'freeze-dry with PEG/dispersion' method as quick extemporaneous preparation method of biodegradable IP formulations. In this study, we applied this quick preparative method to the temperature-triggered covalent gelation system. The instant formulation (D-sample) could be prepared by 'freeze-dry with PEG/dispersion' just mixing of tri-PCG-Acryl micelle dispersion and tri-PCG/DPMP micelle dispersion with PEG, that can be prepared in 30 s from the dried samples. The obtained D-sample showed irreversible gelation and long duration time of gel state, which was basically the same as the formulations prepared by the usual heating dissolution method (S-sample). Interestingly, the D-sample could maintain its sol state for a longer time (24 h) after preparing the formulation at r.t. compared with the S-sample, which became a gel in 3 h after preparing. The IP system showed good biocompatibility and long duration time of the gel state after subcutaneous implantation. These characteristics of D-samples, quick extemporaneous preparation and high stability in the sol state before injection, would be very convenient in a clinical setting.

  15. Polyether/Polyester Graft Copolymers

    NASA Technical Reports Server (NTRS)

    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. Humidity and temperature response of photopolymer-based holographic gratings

    NASA Astrophysics Data System (ADS)

    Mikulchyk, Tatsiana; Walshe, James; Cody, Dervil; Martin, Suzanne; Naydenova, Izabela

    2015-05-01

    Holographic sensors have significant potential in various applications ranging from in vitro diagnostics to optical security. They are capable of providing fast, real-time, reversible or irreversible, visual colorimetric or optical readouts. The main challenge in the development of holographic sensors is to improve their selectivity by functionalizing the holographic recording material and achieve a response to a specific analyte. This material should be permeable to the analyte and its properties should change under exposure to the analyte. This work explores the humidity and temperature response of volume phase gratings recorded in photopolymers containing acrylamide and diacetone acrylamide as monomers, and triethanolamine and N-phenylglycine as photoinitiators. Characterization of the humidity response of photopolymer-based gratings in the relative humidity (RH) range of 20-90 % was carried out by measuring the diffraction efficiency of slanted transmission gratings and the position of the maximum intensity in the spectral response of reflection gratings. A strong humidity dependence of the diffraction efficiency of diacetone acrylamide-based transmission gratings was observed at RH=20-90%. The humidity dependence of the spectral response of the reflection gratings showed that photopolymers containing triethanolamine are more hydrophilic than photopolymers containing N-phenylglycine. The temperature response of slanted transmission gratings was investigated in the temperature (T) range of 20-60 °C. Exposure of the photopolymer layers containing triethanolamine to elevated temperature showed that the observed Bragg angle shift was caused by layer shrinkage due to water evaporation. The application of a sealing technique allowed for the observation of the photopolymer layer swelling due to the layer's thermal expansion. The results demonstrate an effective approach to obtaining photopolymer-based gratings with tuneable temperature and humidity sensitivity.

  17. Second generation copolymers for EOR

    SciTech Connect

    McCormick, C.L.

    1988-05-01

    In this report, the authors review four types of acrylamide-based copolymers with distinctly different dilute solutions and rheological behavior. Each of these ''second generation'' systems possesses characteristics which, in theory, should be superior to conventional polymers under certain operational conditions. Type I copolymers are prepared from acrylamide (AM) and sodium-3-acrylamido-3-methylbutanoate (NaAMB). The high molecular weight, viscosity maintenance, and phase stability in the presence of divalent ions make these copolymers especially attractive for mobility control in EOR. Type II copolymers address the problems of entrapment, pore clogging, and shear degradation often encountered with ultrahigh molecular weight copolymers. The copolymers of this type are lower molecular weight than Type 1 but associate in a cooperative manner in semi-dilute solutions to enhance solution viscoscity. In this report, the authors discuss associative polymers of acrylamide/N-alkyl acrylamides which contain low mole percentages of C/sub 8/, C/sub 10/, or C/sub 12/ comonomers. In practice, a third charged comonomer such as carboxylated or sulfonated one, might be necessary to reduce adsorption to reservoir rock. Type III systems are relatively low molecular weight and hyrophibically modified in order to bring about intramolecular micelle-like association in aqueous solution. The aqueous solutions are non-viscous; viscosification occurs upon solubilization of hydrocarbons in the hydrophobic domains. Copolymers of acrylamide with N-propyl diacetone acrylamide are examples of Type III.

  18. Tensile actuators of carbon nanotube coiled yarn based on polydiacetylene-pluronic copolymers as temperature indicators

    NASA Astrophysics Data System (ADS)

    Lee, Hee Uk; Kim, Hyunsoo; Chun, Kyoung-Yong; Kwon, Cheong Hoon; Lima, Márcio D.; Baughman, Ray H.; Kim, Seon Jeong

    2016-07-01

    Most polydiacetylenes (PDAs) have been studied as chromatic sensors or temperature indicators because of their phase transition that is accompanied by a color change from blue to red. Here, we focus on the structural change based on the polydiacetylene phase transition for a temperature-responsive tensile actuator at low temperature using a copolymer composed of PDA and pluronic in a multi-walled carbon nanotube (MWCNT) coiled yarn. In this paper, we do not focus on the general color change phenomenon of PDA. We demonstrate that the volume change of PDA in the MWCNT coiled yarn provides ˜180% tensile strain at low temperature (˜53 °C). Insertion of the pluronic copolymer into the coiled yarn composed of PDA and MWCNT caused the tensile actuation temperature to decrease by ˜6 °C (with tensile actuation of ˜230%) compared to an actuator without pluronic copolymer. Furthermore, we could verify that the large tensile actuation was also predominantly affected by the melting of the nonpolymerized diacetylene (DA) monomer and the pluronic copolymer. MWCNT coiled yarn actuators with PDA-pluronic copolymer can be easily prepared, have a large tensile actuation, and are actuated at low temperature. It could be used as temperature indicators in the food, drugs, and medical fields.

  19. Hyperviscous diblock copolymer vesicles

    NASA Astrophysics Data System (ADS)

    Dimova, R.; Seifert, U.; Pouligny, B.; Förster, S.; Döbereiner, H.-G.

    2002-03-01

    Giant vesicles prepared from the diblock copolymer polybutadien-b-polyethyleneoxide (PB-PEO) exhibit a shear surface viscosity, which is about 500 times higher than those found in common phospholipid bilayers. Our result constitutes the first direct measurement of the shear surface viscosity of such polymersomes. At the same time, we measure bending and stretching elastic constants, which fall in the range of values typical for lipid membranes. Pulling out a tether from an immobilized polymersome and following its relaxation back to the vesicle body provides an estimate of the viscous coupling between the two monolayers composing the polymer membrane. The detected intermonolayer friction is about an order of magnitude higher than the characteristic one for phospholipid membranes. Polymersomes are tough vesicles with a high lysis tension. This, together with their robust rheological properties, makes them interesting candidates for a number of technological applications.

  20. Global temperature responses to current emissions from the transport sectors

    PubMed Central

    Berntsen, Terje; Fuglestvedt, Jan

    2008-01-01

    Transport affects climate directly and indirectly through mechanisms that cause both warming and cooling of climate, and the effects operate on very different timescales. We calculate climate responses in terms of global mean temperature and find large differences between the transport sectors with respect to the size and mix of short- and long-lived effects, and even the sign of the temperature response. For year 2000 emissions, road transport has the largest effect on global mean temperature. After 20 and 100 years the response in net temperature is 7 and 6 times higher, respectively, than for aviation. Aviation and shipping have strong but quite uncertain short-lived warming and cooling effects, respectively, that dominate during the first decades after the emissions. For shipping the net cooling during the first 4 decades is due to emissions of SO2 and NOx. On a longer timescale, the current emissions from shipping cause net warming due to the persistence of the CO2 perturbation. If emissions stay constant at 2000 levels, the warming effect from road transport will continue to increase and will be almost 4 times larger than that of aviation by the end of the century. PMID:19047640

  1. Global temperature responses to current emissions from the transport sectors.

    PubMed

    Berntsen, Terje; Fuglestvedt, Jan

    2008-12-09

    Transport affects climate directly and indirectly through mechanisms that cause both warming and cooling of climate, and the effects operate on very different timescales. We calculate climate responses in terms of global mean temperature and find large differences between the transport sectors with respect to the size and mix of short- and long-lived effects, and even the sign of the temperature response. For year 2000 emissions, road transport has the largest effect on global mean temperature. After 20 and 100 years the response in net temperature is 7 and 6 times higher, respectively, than for aviation. Aviation and shipping have strong but quite uncertain short-lived warming and cooling effects, respectively, that dominate during the first decades after the emissions. For shipping the net cooling during the first 4 decades is due to emissions of SO(2) and NOx. On a longer timescale, the current emissions from shipping cause net warming due to the persistence of the CO(2) perturbation. If emissions stay constant at 2000 levels, the warming effect from road transport will continue to increase and will be almost 4 times larger than that of aviation by the end of the century.

  2. Rubisco Catalytic Properties and Temperature Response in Crops1

    PubMed Central

    2016-01-01

    Rubisco catalytic traits and their thermal dependence are two major factors limiting the CO2 assimilation potential of plants. In this study, we present the profile of Rubisco kinetics for 20 crop species at three different temperatures. The results largely confirmed the existence of significant variation in the Rubisco kinetics among species. Although some of the species tended to present Rubisco with higher thermal sensitivity (e.g. Oryza sativa) than others (e.g. Lactuca sativa), interspecific differences depended on the kinetic parameter. Comparing the temperature response of the different kinetic parameters, the Rubisco Km for CO2 presented higher energy of activation than the maximum carboxylation rate and the CO2 compensation point in the absence of mitochondrial respiration. The analysis of the Rubisco large subunit sequence revealed the existence of some sites under adaptive evolution in branches with specific kinetic traits. Because Rubisco kinetics and their temperature dependency were species specific, they largely affected the assimilation potential of Rubisco from the different crops, especially under those conditions (i.e. low CO2 availability at the site of carboxylation and high temperature) inducing Rubisco-limited photosynthesis. As an example, at 25°C, Rubisco from Hordeum vulgare and Glycine max presented, respectively, the highest and lowest potential for CO2 assimilation at both high and low chloroplastic CO2 concentrations. In our opinion, this information is relevant to improve photosynthesis models and should be considered in future attempts to design more efficient Rubiscos. PMID:27329223

  3. Global Patterns in Leaf Respiration and its Temperature Response

    NASA Astrophysics Data System (ADS)

    Heskel, M.; Atkin, O. K.; O'Sullivan, O. S.; Reich, P. B.; Tjoelker, M. G.; Weerasinghe, L. K.; Penillard, A.; Egerton, J. J. G.; Creek, D.; Bloomfield, K. J.; Xiang, J.; Sinca, F.; Stangl, Z.; Martinez-de la Torre, A.; Griffin, K. L.; Huntingford, C.; Hurry, V.; Meir, P.; Turnbull, M.

    2015-12-01

    Leaf respiration (R) represents a massive flux of carbon to the atmosphere. Currently, neither physiological models nor terrestrial biosphere models are able to disentangle sources of variation in leaf R among different plant species and contrasting environments. Similarly, such models do not adequately describe the short-term temperature (T) response of R, which can lead to inaccurate representation of leaf R in simulation models of regional and global terrestrial carbon cyling. Even minor differences in the underlying basal rate of leaf R and/or shape of the T-response curve can significantly impact estimates of carbon released and stored in ecosystems. Given this, we recently assembled and analyzed two new global databases (arctic-to-tropics) of leaf R and its short-term T-dependence. The results highlight variation in basal leaf R among species and across global gradients in T and aridity, with leaf R at a standard T (e.g. 25°C) being greatest in plants growing in the cold, dry Arctic and lowest in the warm, moist tropics. Arctic plants also exhibit higher rates of leaf R at a given photosynthetic capacity or leaf N concentration than their tropical counterparts. The results also point to convergence in the short-term temperature response of respiration across biomes and plant functional types. The applicability and significance of the short-term T-response of R for simulation models of plant and ecosystem carbon fluxes will be discussed.

  4. Global Surface Temperature Response Explained by Multibox Energy Balance Models

    NASA Astrophysics Data System (ADS)

    Fredriksen, H. B.; Rypdal, M.

    2016-12-01

    We formulate a multibox energy balance model, from which global temperature evolution can be described by convolving a linear response function and a forcing record. We estimate parameters in the response function from instrumental data and historic forcing, such that our model can produce a response to both deterministic forcing and stochastic weather forcing consistent with observations. Furthermore, if we make separate boxes for upper ocean layer and atmosphere over land, we can also make separate response functions for global land and sea surface temperature. By describing internal variability as a linear response to white noise, we demonstrate that the power-law form of the observed temperature spectra can be described by linear dynamics, contrary to a common belief that these power-law spectra must arise from nonlinear processes. In our multibox model, the power-law form can arise due to the multiple response times. While one of our main points is that the climate system responds over a wide range of time scales, we cannot find one set of time scales that can be preferred compared to other choices. Hence we think the temperature response can best be characterized as something that is scale-free, but still possible to approximate by a set of well separated time scales.

  5. Temperature-Responsive Ionic Liquids: Fundamental Behaviors and Catalytic Applications.

    PubMed

    Qiao, Yunxiang; Ma, Wenbao; Theyssen, Nils; Chen, Chen; Hou, Zhenshan

    2017-05-24

    Temperature-responsive ionic liquids (ILs), their fundanmental behaviors, and catalytic applications were introduced, especially the concepts of upper critical solution temperature (UCST) and lower critical solution temperature (LCST). It is described that, during a catalytic reaction, they form a homogeneous mixture with the reactants and products at reaction temperature but separate from them afterward at ambient conditions. It is shown that this behavior offers an effective alternative approach to overcome gas/liquid-solid interface mass transfer limitations in many catalytic transformations. It should be noted that IL-based thermomorphic systems are rarely elaborated until now, especially in the field of catalytic applications. The aim of this article is to provide a comprehensive review about thermomorphic mixtures of an IL with H2O and/or organic compounds. Special focus is laid on their temperature dependence concerning UCST and LCST behavior, including systems with conventional ILs, metal-containing ILs, polymerized ILs, as well as the thermomorphic behavior induced via host-guest complexation. A wide range of applications using thermoregulated IL systems in chemical catalytic reactions as well as enzymatic catalysis were also demonstrated in detail. The conclusion is drawn that, due to their highly attractive behavior, thermoregulated ILs have already and will find more applications, not only in catalysis but also in other areas.

  6. Temperature Responses to Spectral Solar Variability on Decadal Time Scales

    NASA Technical Reports Server (NTRS)

    Cahalan, Robert F.; Wen, Guoyong; Harder, Jerald W.; Pilewskie, Peter

    2010-01-01

    Two scenarios of spectral solar forcing, namely Spectral Irradiance Monitor (SIM)-based out-of-phase variations and conventional in-phase variations, are input to a time-dependent radiative-convective model (RCM), and to the GISS modelE. Both scenarios and models give maximum temperature responses in the upper stratosphere, decreasing to the surface. Upper stratospheric peak-to-peak responses to out-of-phase forcing are approx.0.6 K and approx.0.9 K in RCM and modelE, approx.5 times larger than responses to in-phase forcing. Stratospheric responses are in-phase with TSI and UV variations, and resemble HALOE observed 11-year temperature variations. For in-phase forcing, ocean mixed layer response lags surface air response by approx.2 years, and is approx.0.06 K compared to approx.0.14 K for atmosphere. For out-of-phase forcing, lags are similar, but surface responses are significantly smaller. For both scenarios, modelE surface responses are less than 0.1 K in the tropics, and display similar patterns over oceanic regions, but complex responses over land.

  7. The effects of molecular structure on sol-to-gel transition of biodegradable poly(depsipeptide-co-lactide)-g-PEG copolymers.

    PubMed

    Takahashi, Akihiro; Umezaki, Masaya; Yoshida, Yasuyuki; Kuzuya, Akinori; Ohya, Yuichi

    2014-01-01

    We report on the effects of number and length of PEG chains in poly(depsipeptide-co-dl-lactide)-g-poly(ethylene glycol) (P(DG-dl-LA)-g-PEG) copolymers on their sol-to-gel transition behavior. The graft-type copolymer is suitable for the systematic study of the effects of molecular structure and hydrophilic/hydrophobic balance on its sol-to-gel transition. We prepared various P(DG-dl-LA)-g-PEG copolymers through coupling reactions between the pendant carboxylic acid groups of P(GD-dl-LA) and the end hydroxyl group of MeO-PEG having various molecular weights. Temperature-responsive sol-to-gel transition of the obtained copolymer solution in phosphate-buffered solution (pH 7.4, ionic strength = 0.14) was investigated by the test tube inverting method and rheological measurements. P(GD-dl-LA)-g-PEG copolymer prepared from higher molecular weight PEG showed higher sol-to-gel transition temperatures compared with the copolymers prepared from lower molecular weight PEG, although these copolymers have similar weight content of PEG (23-24 wt.%). Similar trends were observed for groups of copolymers whose PEG contents were 27 or 30 wt.%. These results are informative for providing strategies on rational design of thermo-gelling polymers.

  8. RAFT polymerization of temperature- and salt-responsive block copolymers as reversible hydrogels

    PubMed Central

    Hemp, Sean T.; Smith, Adam E.; Bunyard, W. Clayton; Rubinstein, Michael H.; Long, Timothy E.

    2016-01-01

    Reversible-addition fragmentation chain transfer (RAFT) polymerization enabled the synthesis of novel, stimuli-responsive, AB and ABA block copolymers. The B block contained oligo(ethylene glycol) methyl ether methacrylate (OEG) and was permanently hydrophilic in the conditions examined. The A block consisted of diethylene glycol methyl ether methacrylate (DEG) and [2-(methacryloyloxy)ethyl]trimethylammonium chloride (TMA). The A block displayed both salt- and temperature-response with lower critical solution temperatures (LCSTs) dependent on the molar content of TMA and the presence of salt. Higher TMA content in the AB diblock copolymers increased the critical micelle temperatures (CMT) in HPLC-grade water due to an increased hydrophilicity of the A block. Upon addition of 0.9 wt% NaCl, the CMTs of poly(OEG-b-DEG95TMA5) decreased from 50 °C to 36 °C due to screening of electrostatic repulsion between the TMA units. ABA triblock copolymers displayed excellent hydrogel properties with salt- and temperature-dependent gel points. TMA incorporation in the A block increased the gel points for all triblock copolymers, and salt-response increased with higher TMA composition in the A block. For example, poly(DEG98TMA2-b-OEG-b-DEG98TMA2) formed a hydrogel at 40 °C in HPLC-grade water and 26 °C in 0.9 wt% NaCl aqueous solution. These salt- and temperature-responsive AB diblock and ABA triblock copolymers find applications as drug delivery vehicles, adhesives, and hydrogels. PMID:27041771

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

    PubMed Central

    Carey, Joanna C.; Tang, Jianwu; Templer, Pamela H.; Kroeger, Kevin D.; Crowther, Thomas W.; Burton, Andrew J.; Dukes, Jeffrey S.; Emmett, Bridget; Frey, Serita D.; Heskel, Mary A.; Jiang, Lifen; Machmuller, Megan B.; Mohan, Jacqueline; Panetta, Anne Marie; Reich, Peter B.; Reinsch, Sabine; Wang, Xin; Allison, Steven D.; Bamminger, Chris; Bridgham, Scott; de Dato, Giovanbattista; Eddy, William C.; Enquist, Brian J.; Estiarte, Marc; Harte, John; Henderson, Amanda; Johnson, Bart R.; Luo, Yiqi; Marhan, Sven; Melillo, Jerry M.; Peñuelas, Josep; Pfeifer-Meister, Laurel; Poll, Christian; Rastetter, Edward; Reinmann, Andrew B.; Reynolds, Lorien L.; Schmidt, Inger K.; Shaver, Gaius R.; Strong, Aaron L.; Suseela, Vidya; Tietema, Albert

    2016-01-01

    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, spanning nine biomes and over 2 decades of warming. Our analysis reveals no significant differences in the temperature sensitivity of soil respiration between control and warmed plots in all biomes, with the exception of deserts and boreal forests. Thus, our data provide limited evidence of acclimation of soil respiration to experimental warming in several major biome types, contrary to the results from multiple single-site studies. Moreover, across all nondesert biomes, respiration rates with and without experimental warming follow a Gaussian response, increasing with soil temperature up to a threshold of ∼25 °C, above which respiration rates decrease with further increases in temperature. This consistent decrease in temperature sensitivity at higher temperatures demonstrates that rising global temperatures may result in regionally variable responses in soil respiration, with colder climates being 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 warming. PMID:27849609

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

    USGS Publications Warehouse

    Carey, Joanna C.; Tang, Jianwu; Templer, Pamela H.; Kroeger, Kevin D.; Crowther, Thomas W.; Burton, Andrew J.; Dukes, Jeffrey S.; Emmett, Bridget; Frey, Serita D.; Heskel, Mary A.; Jiang, Lifen; Machmuller, Megan B.; Mohan, Jacqueline; Panetta, Anne Marie; Reich, Peter B.; Reinsch, Sabine; Wang, Xin; Allison, Steven D.; Bamminger, Chris; Bridgham, Scott; Collins, Scott L.; de Dato, Giovanbattista; Eddy, William C.; Enquist, Brian J.; Estiarte, Marc; Harte, John; Henderson, Amanda; Johnson, Bart R.; Steenberg Larsen, Klaus; Luo, Yiqi; Marhan, Sven; Melillo, Jerry M.; Penuelas, Josep; Pfeifer-Meister, Laurel; Poll, Christian; Rastetter, Edward B.; Reinmann, Andrew B.; Reynolds, Lorien L.; Schmidt, Inger K.; Shaver, Gaius R.; Strong, Aaron L.; Suseela, Vidya; Tietema, Albert

    2016-01-01

    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, spanning nine biomes and over 2 decades of warming. Our analysis reveals no significant differences in the temperature sensitivity of soil respiration between control and warmed plots in all biomes, with the exception of deserts and boreal forests. Thus, our data provide limited evidence of acclimation of soil respiration to experimental warming in several major biome types, contrary to the results from multiple single-site studies. Moreover, across all nondesert biomes, respiration rates with and without experimental warming follow a Gaussian response, increasing with soil temperature up to a threshold of ∼25 °C, above which respiration rates decrease with further increases in temperature. This consistent decrease in temperature sensitivity at higher temperatures demonstrates that rising global temperatures may result in regionally variable responses in soil respiration, with colder climates being 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 warming.

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

    PubMed

    Carey, Joanna C; Tang, Jianwu; Templer, Pamela H; Kroeger, Kevin D; Crowther, Thomas W; Burton, Andrew J; Dukes, Jeffrey S; Emmett, Bridget; Frey, Serita D; Heskel, Mary A; Jiang, Lifen; Machmuller, Megan B; Mohan, Jacqueline; Panetta, Anne Marie; Reich, Peter B; Reinsch, Sabine; Wang, Xin; Allison, Steven D; Bamminger, Chris; Bridgham, Scott; Collins, Scott L; de Dato, Giovanbattista; Eddy, William C; Enquist, Brian J; Estiarte, Marc; Harte, John; Henderson, Amanda; Johnson, Bart R; Larsen, Klaus Steenberg; Luo, Yiqi; Marhan, Sven; Melillo, Jerry M; Peñuelas, Josep; Pfeifer-Meister, Laurel; Poll, Christian; Rastetter, Edward; Reinmann, Andrew B; Reynolds, Lorien L; Schmidt, Inger K; Shaver, Gaius R; Strong, Aaron L; Suseela, Vidya; Tietema, Albert

    2016-11-29

    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, spanning nine biomes and over 2 decades of warming. Our analysis reveals no significant differences in the temperature sensitivity of soil respiration between control and warmed plots in all biomes, with the exception of deserts and boreal forests. Thus, our data provide limited evidence of acclimation of soil respiration to experimental warming in several major biome types, contrary to the results from multiple single-site studies. Moreover, across all nondesert biomes, respiration rates with and without experimental warming follow a Gaussian response, increasing with soil temperature up to a threshold of ∼25 °C, above which respiration rates decrease with further increases in temperature. This consistent decrease in temperature sensitivity at higher temperatures demonstrates that rising global temperatures may result in regionally variable responses in soil respiration, with colder climates being 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 warming.

  12. Temperature Responses of Mice to Escherichia Coli Endotoxin

    PubMed Central

    Prashker, D.; Wardlaw, A. C.

    1971-01-01

    SJL mice kept in a 23° environment and injected intravenously with Escherichia coli endotoxin developed a marked hypothermia compared with animals given pyrogen-free saline (PFS). In contrast, giving endotoxin to SJL mice which had been “pre-conditioned” for 4 hr at 36° caused relative hyperthermia. Both responses were best observed at 1½ hr after injection. An endotoxin dose of 0·02 μg. was at the threshold of detectability in mice pre-conditioned at 36°, while with 23° animals, the threshold dose was 0·2 μg. Dose-response curves, with an index of precision (λ) of about 0·73, were obtained for mice in both environments, endotoxin doses of about 20 μg. being in the plateau regions of maximum responses. Mouse strains SWR/J and CMRL behaved similarly to SJL, but the temperature responses at both 23° and 36° were smaller. BALB/cJ and AKR/J mice showed a hyperthermic response to endotoxin at 36° but no hypothermia at 23°, while ST/bJ mice showed the converse pattern of hypothermia after endotoxin at 23° but no hyperthermia at 36°. Thus the strain of mouse is an important variable. We suggest that a hypothermia test in SJL mice may provide a simple and convenient bioassay procedure for endotoxin. Although its sensitivity is much less than the rabbit pyrogenicity test, it may be useful for the quantitative measurement of endotoxin activity of such preparations as typhoid, pertussis and cholera vaccines which are rich in endotoxin. PMID:4926536

  13. European temperature responses to blocking and ridge regional patterns

    NASA Astrophysics Data System (ADS)

    Sousa, Pedro M.; Trigo, Ricardo M.; Barriopedro, David; Soares, Pedro M. M.; Santos, João A.

    2017-03-01

    Blocking occurrence and its impacts on European temperature have been studied in the last decade. However, most previous studies on blocking impacts have focused on winter only, disregarding its fingerprint in summer and differences with other synoptic patterns that also trigger temperature extremes. In this work, we provide a clear distinction between high-latitude blocking and sub-tropical ridges occurring in three sectors of the Euro-Atlantic region, describing their climatology and consequent impacts on European temperature during both winter and summer. Winter blocks (ridges) are generally associated to colder (warmer) than average conditions over large regions of Europe, in some areas with anomalies larger than 5 °C, particularly for the patterns occurring in the Atlantic and Central European sectors. During summer, there is a more regional response characterized by above average temperature for both blocking and ridge patterns, especially those occurring in continental areas, although negative temperature anomalies persist in southernmost areas during blocking. An objective analysis of the different forcing mechanisms associated to each considered weather regime has been performed, quantifying the importance of the following processes in causing the temperature anomalies: horizontal advection, vertical advection and diabatic heating. While during winter advection processes tend to be more relevant to explain temperature responses, in summer radiative heating under enhanced insolation plays a crucial role for both blocking and ridges. Finally, the changes in the distributions of seasonal temperature and in the frequencies of extreme temperature indices were also examined for specific areas of Europe. Winter blocking and ridge patterns are key drivers in the occurrence of regional cold and warm extreme temperatures, respectively. In summer, they are associated with substantial changes in the frequency of extremely warm days, but with different signatures in

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

    NASA Astrophysics Data System (ADS)

    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

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

    PubMed

    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.

  16. Lignin poly(lactic acid) copolymers

    DOEpatents

    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.

  17. Copolymers For Capillary Gel Electrophoresis

    DOEpatents

    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.

  18. Self-assembly of poly(lauryl methacrylate)-b-poly(benzyl methacrylate) nano-objects synthesised by ATRP and their temperature-responsive dispersion properties.

    PubMed

    Obeng, Melody; Milani, Amir H; Musa, Muhamad S; Cui, Zhengxing; Fielding, Lee A; Farrand, Louise; Goulding, Mark; Saunders, Brian R

    2017-03-15

    Self-assembling poly(lauryl methacrylate)-b-poly(benzyl methacrylate) (PLMAx-PBzMAy) diblock copolymers were synthesised for the first time using solution atom transfer radical polymerisation (ATRP). The PLMA degree of polymerisation (x) was fixed at 14 and the PBzMA degree of polymerisation (y) was varied from 34 to 74. Post-polymerisation transfer of this new series of diblock copolymers from chloroform into n-dodecane (a poor solvent for PBzMA) resulted in self-assembly of polymeric nano-objects. The morphologies for the latter (spheres, worms and vesicles) were controlled by y. The observed morphologies generally agreed with those reported for related PLMAx-PBzMAy diblock copolymers (x ≥ 16) prepared by polymerisation induced self-assembly (PISA) via reversible addition-fragmentation chain transfer (RAFT) polymerisation (Fielding et al., J. Am. Chem. Soc., 2014, 136, 5790). However, a number of differences were observed such as de-gelation behaviour and the phase boundary positions compared to those expected from Fielding et al. Variable-temperature dynamic light scattering studies for the PLMA14-PBzMA34 spheres revealed that the aggregation number was unaffected by a temperature increase over the range of 20-90 °C, which differed markedly from the behaviour observed for PLMA14-PBzMA64 worms. This difference is a new observation with mechanistic importance for the worm-to-sphere breakdown mechanism. We show that concentrated PLMA14-PBzMAy dispersions (20% w/w) in n-dodecane can be prepared using post-polymerisation transfer. The dispersion with a mixed spherical and worm-like copolymer phase exhibited reversible de-gelation when heated. Surprisingly, the dispersions containing only the worm phase remained as gels (which were white) at temperatures up to 90 °C. Our new ATRP approach for preparing temperature-responsive non-aqueous nano-object dispersions presented here decoupled chain growth and self-assembly and will apply to other copolymer dispersions.

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

    NASA Astrophysics Data System (ADS)

    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

  20. Individual chromosomes as viscoelastic copolymers

    NASA Astrophysics Data System (ADS)

    Almagro, S.; Dimitrov, S.; Hirano, T.; Vallade, M.; Riveline, D.

    2003-09-01

    We report elastic measurements of individual chromosomes observed in vitro. Free fluctuations of shapes show that a chromosome can be seen as a copolymer, exhibiting rigid regions alternating with semi-flexible regions. We characterize this behavior and compare it with known biopolymers. We further show that the inner part of a chromosome exhibits viscoelasticity, as extracted by the loading rate dependence of the stretch modulus. Taken together, these data suggest an organization for the chromosome as a copolymer composed of an inner rigid core exhibiting viscoelasticity surrounded by an elastic soft envelope.

  1. Gradient copolymers - a new class of materials

    SciTech Connect

    Greszta, D.; Matyjaszewski, K.

    1996-10-01

    In this work preparation of a new class of copolymers, namely gradient copolymers via controlled Atom Transfer Radical Polymerization (ATRP) is described. Due to the compositional gradient along the chain, gradient copolymers are expected to exhibit unique physical characteristics as compared to block and random copolymers with similar composition and molecular weight. These include unusual phase separation behavior, and mechanical and thermal properties. Using ATRP one can prepare gradient copolymers via two routes. The first one is the one-pot copolymerization of monomers with different reactitvity ratios r{sub 1}{much_gt}r{sub 2}. The second one is a copolymerization while continuously changing the comonomers feed composition.

  2. Crystalline imide/arylene ether copolymers

    NASA Technical Reports Server (NTRS)

    Jensen, Brian J. (Inventor); Hergenrother, Paul M. (Inventor); Bass, Robert G. (Inventor)

    1995-01-01

    Crystalline imide/arylene ether block copolymers are prepared by reacting anhydride terminated poly(amic acids) with amine terminated poly)arylene ethers) in polar aprotic solvents and chemically or thermally cyclodehydrating the resulting intermediate poly(amic acids). The block copolymers of the invention have one glass transition temperature or two, depending on the particular structure and/or the compatibility of the block units. Most of these crystalline block copolymers for tough, solvent resistant films with high tensile properties. While all of the copolymers produced by the present invention are crystalline, testing reveals that copolymers with longer imide blocks or higher imide content have increased crystallinity.

  3. Instantaneous Directional Growth of Block Copolymer Nanowires During Heterogeneous Radical Polymerization (HRP).

    PubMed

    Lu, Chunliang; Urban, Marek W

    2016-04-13

    Polymeric nanowires that consist of ultrahigh molecular weight block copolymers were instantaneously prepared via one-step surfactant-free heterogeneous radical polymerization (HRP). Under heterogeneous reaction and initiator-starvation conditions, the sequential copolymerization of hydrophilic and hydrophobic monomers facilitates the formation of amphiphilic ultrahigh molecular weight block copolymers, which instantaneously assemble to polymeric nanowires. As polymerization progresses, initially formed nanoparticles exhibit the directional growth due to localized repulsive forces of hydrophilic blocks and confinement of the hydrophobic blocks that adopt favorable high aspect ratio nanowire morphologies. Using one-step synthetic approach that requires only four ingredients (water as a solvent, two polymerizable monomers (one hydrophilic and one hydrophobic), and water-soluble initiator), block copolymer nanowires ∼70 nm in diameter and hundreds of microns in length are instantaneously grown. For example, when 2-(N,N-dimethylamino)ethyl methacrylate (DMAEMA) and styrene (St) were copolymerized, high aspect ratio nanowires consist of ultrahigh (>10(6) g/mol) molecular weight pDMAEMA-b-St block copolymers and the presence of temperature responsive pDMAEMA blocks facilitates nanowire diameter changes as a function of temperature. These morphologies may serve as structural components of the higher order biological constructs at micro and larger length scales, ranging from single strand nanowires to engineered biomolecular networks capable of responding to diverse and transient environmental signals, and capable of dimensional changes triggered by external stimuli.

  4. Liquid ethylene-propylene copolymers

    NASA Technical Reports Server (NTRS)

    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.

  5. Polyether-polyester graft copolymer

    NASA Technical Reports Server (NTRS)

    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.

  6. Electrochemical Deposition Of Conductive Copolymers

    NASA Technical Reports Server (NTRS)

    Nagasubramanian, Ganesan; Distefano, Salvador; Liang, Ranty H.

    1991-01-01

    Experiments show electrically conductive films are deposited on glassy carbon or indium tin oxide substrates by electrochemical polymerization of N-{(3-trimethoxy silyl) propyl} pyrrole or copolymerization with pyrrole. Copolymers of monomer I and pyrrole exhibit desired electrical conductivity as well as desired adhesion and other mechanical properties. When fully developed, new copolymerization process useful in making surface films of selectable conductivity.

  7. Microwave-induced synthesis of alginate-graft-poly(N-isopropylacrylamide) and drug release properties of dual pH- and temperature-responsive beads.

    PubMed

    Işıklan, Nuran; Küçükbalcı, Gülcan

    2012-10-01

    The first decade of the 21st century saw an increasing interest in the development of devices and biomaterials for delivery of bioactive substances that can be controlled by external stimuli. This study deals with the production of novel pH and temperature responsive beads for colon-specific delivery of indomethacine (IM). For this purpose, N-isopropylacrylamide (NIPAAm) was grafted onto sodium alginate (NaAlg) with microwave radiation in aqueous solution. The graft copolymer (NaAlg-g-PNIPAAm) was characterized by using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), elemental analysis, differential scanning calorimetry (DSC), and thermogravimetric analysis. A series of pH- and temperature-responsive NaAlg-g-PNIPAAm beads were prepared as drug delivery matrices of indomethacine cross-linked by glutaraldehyde (GA) in the hydrochloric acid catalyst. Preparation condition of the beads was optimized by considering the percentage entrapment efficiency, particle size, swelling capacity of beads, and their release data. Effects of variables such as graft yield, drug/polymer ratio, exposure time to GA, and concentration of GA on the release of IM were investigated and discussed at two different pH values (1.2 and 7.4) and temperatures (25°C and 37°C). It was observed that IM release from the beads decreased when the grafting of NIPAAm, drug/polymer ratio (d/p), and extent of cross-linking were increased. The results also showed that NaAlg-g-PIPAAm beads were positive pH and temperature responsive. The release of IM from grafted beads was slower for the pH 1.2 solution than that of the pH 7.4 buffer solution, whereas the release rate was higher at 37°C than at 25°C. Copyright © 2012 Elsevier B.V. All rights reserved.

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

    NASA Astrophysics Data System (ADS)

    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

  9. Protein-like copolymers: computer simulation

    NASA Astrophysics Data System (ADS)

    Khokhlov, Alexei R.; Khalatur, Pavel G.

    The notion of protein-like AB copolymers is introduced. Such copolymers can be generated with the help of the “ instant image” of a dense homopolymer globule by assigning that the monomeric units closer to the globular surface are of A type, while the core is formed by the B type units. After that the primary structure of the chain is fixed, and one introduces different interaction potentials for A and B units. In doing so, we have in mind mainly aqueous systems and analogy with globular proteins, therefore A units are regarded as hydrophilic, and B units as hydrophobic. By means of Monte Carlo simulation using the bond fluctuation model we study the coil-globule transition for a protein-like copolymer upon the increase of attraction of hydrophobic B units, and compare the results with those for random AB copolymers. From the analysis of the primary structure of protein-like copolymers one can see that the “ degree of blockiness” of the protein-like sequence is higher than for random copolymers, therefore the copolymers with the “ random-block” primary structure are generated for comparison as well (the average length of A and B sequences being the same as for protein-like copolymers). It is shown that the coil-globule transition in protein-like copolymers occurs at higher temperatures, is more abrupt and has faster kinetics than for random copolymers with the same A/ B composition and for random-block copolymers with the same A/ B composition and “ degree of blockiness”. The globules of protein-like copolymers exhibit a dense micelle-like core of hydrophobic B units stabilized by the long dangling loops of hydrophilic A units. Apparently, a protein-like copolymer “ inherits” some of the properties of the “ parent globule” which is reflected in the special long-range correlations in primary structure.

  10. Temperature responsive fluorescent polymer nanoparticles (TRFNPs) for cellular imaging and controlled releasing of drug to living cells.

    PubMed

    Zhang, Ziang; Zhang, Di; Wei, Lin; Wang, Xi; Xu, Yueling; Li, Hung-Wing; Ma, Ming; Chen, Bo; Xiao, Lehui

    2017-09-01

    Recent studies have demonstrated that drug delivery by using functional nanomaterials with imaging capability could afford plenty of insightful information for the better control of the delivery process. In this work, we developed temperature responsive fluorescent nanoparticles (TRFNPs) for drug delivery and cellular imaging. The TRFNP was fabricated by one-pot co-precipitation of thermal sensitive amphiphilic block copolymers polystyrene-b-poly(N-isopropyl acrylamide) (PS-b-PNIPAM) and fluorescent conjugated polymer poly [(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(1,4-benzo(2,1',3)-thiadiazole)] (PFBT) in the presence of desired small guest molecules. The dynamic light scattering (DLS) measurements verified that this functional nanoparticle exhibited temperature dependent size variation, which could therefore regulate the releasing rate of loaded guest molecules (e.g. drugs) inside the polymer core. Besides, the TRFNPs displayed good photostability in terms of optical characterization. The cellular cytotoxicity characterization demonstrated that this nanoparticle exhibited good biocompatibility even under the mass concentration of 10μg/mL. By using Nile Red as a model molecule, the temperature-controlled releasing process from TRFNPs in solution as well as inside living cells was monitored directly according to the spectroscopic and microscopic characterizations. Furthermore, anti-cancer drug was successfully delivered into living cells via TRFNPs and released in a temperature dependent manner. As a consequence, owing the attractive merits as mentioned above, this nanostructure would find broad applications in nanomedicine in the future. Copyright © 2017. Published by Elsevier B.V.

  11. Bioinspired catecholic copolymers for antifouling surface coatings.

    PubMed

    Cho, Joon Hee; Shanmuganathan, Kadhiravan; Ellison, Christopher J

    2013-05-01

    We report here a synthetic approach to prepare poly(methyl methacrylate)-polydopamine diblock (PMMA-PDA) and triblock (PDA-PMMA-PDA) copolymers combining mussel-inspired catecholic oxidative chemistry and atom transfer radical polymerization (ATRP). These copolymers display very good solubility in a range of organic solvents and also a broad band photo absorbance that increases with increasing PDA content in the copolymer. Spin-cast thin films of the copolymer were stable in water and showed a sharp reduction (by up to 50%) in protein adsorption compared to those of neat PMMA. Also the peak decomposition temperature of the copolymers was up to 43°C higher than neat PMMA. The enhanced solvent processability, thermal stability and low protein adsorption characteristics of this copolymer makes it attractive for variety of applications including antifouling coatings on large surfaces such as ship hulls, buoys, and wave energy converters.

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

    NASA Astrophysics Data System (ADS)

    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

  13. Crystalline Imide/Arylene Ether Copolymers

    NASA Technical Reports Server (NTRS)

    Jensen, Brian J.; Hergenrother, Paul M.; Bass, Robert G.

    1991-01-01

    Series of imide/arylene ether block copolymers prepared by using arylene ether blocks to impart low melt viscosity, and imide blocks to provide high strength and other desirable mechanical properties. Work represents extension of LAR-14159 on imide/arylene ether copolymers in form of films, moldings, adhesives, and composite matrices. Copolymers potentially useful in variety of high-temperature aerospace and microelectronic applications.

  14. Phase Behavior of Symmetric Sulfonated Block Copolymers

    SciTech Connect

    Park, Moon Jeong; Balsara, Nitash P.

    2008-08-21

    Phase behavior of poly(styrenesulfonate-methylbutylene) (PSS-PMB) block copolymers was studied by varying molecular weight, sulfonation level, and temperature. Molecular weights of the copolymers range from 2.9 to 117 kg/mol. Ordered lamellar, gyroid, hexagonally perforated lamellae, and hexagonally packed cylinder phases were observed in spite of the fact that the copolymers are nearly symmetric with PSS volume fractions between 0.45 and 0.50. The wide variety of morphologies seen in our copolymers is inconsistent with current theories on block copolymer phase behavior such as self-consistent field theory. Low molecular weight PSS-PMB copolymers (<6.2 kg/mol) show order-order and order-disorder phase transitions as a function of temperature. In contrast, the phase behavior of high molecular weight PSS-PMB copolymers (>7.7 kg/mol) is independent of temperature. Due to the large value of Flory-Huggins interaction parameter, x, between the sulfonated and non-sulfonated blocks, PSS-PMB copolymers with PSS and PMB molecular weights of 1.8 and 1.4 kg/mol, respectively, show the presence of an ordered gyroid phase with a 2.5 nm diameter PSS network. A variety of methods are used to estimate x between PSS and PMB chains as a function of sulfonation level. Some aspects of the observed phase behavior of PSS-PMB copolymers can be rationalized using x.

  15. Self-assembly of Random Copolymers

    PubMed Central

    Li, Longyu; Raghupathi, Kishore; Song, Cunfeng; Prasad, Priyaa; Thayumanavan, S.

    2014-01-01

    Self-assembly of random copolymers has attracted considerable attention recently. In this feature article, we highlight the use of random copolymers to prepare nanostructures with different morphologies and to prepare nanomaterials that are responsive to single or multiple stimuli. The synthesis of single-chain nanoparticles and their potential applications from random copolymers are also discussed in some detail. We aim to draw more attention to these easily accessible copolymers, which are likely to play an important role in translational polymer research. PMID:25036552

  16. Copolymers of fluorinated polydienes and sulfonated polystyrene

    DOEpatents

    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.

  17. Scanning probe block copolymer lithography

    PubMed Central

    Chai, Jinan; Huo, Fengwei; Zheng, Zijian; Giam, Louise R.; Shim, Wooyoung; Mirkin, Chad A.

    2010-01-01

    Integration of individual nanoparticles into desired spatial arrangements over large areas is a prerequisite for exploiting their unique electrical, optical, and chemical properties. However, positioning single sub-10-nm nanoparticles in a specific location individually on a substrate remains challenging. Herein we have developed a unique approach, termed scanning probe block copolymer lithography, which enables one to control the growth and position of individual nanoparticles in situ. This technique relies on either dip-pen nanolithography (DPN) or polymer pen lithography (PPL) to transfer phase-separating block copolymer inks in the form of 100 or more nanometer features on an underlying substrate. Reduction of the metal ions via plasma results in the high-yield formation of single crystal nanoparticles per block copolymer feature. Because the size of each feature controls the number of metal atoms within it, the DPN or PPL step can be used to control precisely the size of each nanocrystal down to 4.8 ± 0.2 nm. PMID:21059942

  18. Interfaces between Block Copolymer Domains

    NASA Astrophysics Data System (ADS)

    Kim, Jaeup; Jeong, Seong-Jun; Kim, Sang Ouk

    2011-03-01

    Block copolymers naturally form nanometer scale structures which repeat their geometry on a larger scale. Such a small scale periodic pattern can be used for various applications such as storage media, nano-circuits and optical filters. However, perfect alignment of block copolymer domains in the macroscopic scale is still a distant dream. The nanostructure formation usually occurs with spontaneously broken symmetry; hence it is easily infected by topological defects which sneak in due to entropic fluctuation and incomplete annealing. Careful annealing can gradually reduce the number of defects, but once kinetically trapped, it is extremely difficult to remove all the defects. One of the main reasons is that the defect finds a locally metastable morphology whose potential depth is large enough to prohibit further morphology evolution. In this work, the domain boundaries between differently oriented lamellar structures in thin film are studied. For the first time, it became possible to quantitatively study the block copolymer morphology in the transitional region, and it was shown that the twisted grain boundary is energetically favorable compared to the T-junction grain boundary. [Nano Letters, 9, 2300 (2010)]. This theoretical method successfully explained the experimental results.

  19. Responsive copolymers for enhanced petroleum recovery

    SciTech Connect

    McCormick, C.; Hester, R.

    1992-01-01

    The overall goal of this research is the development of advanced water-soluble copolymers for use in enhanced oil recovery which rely on reversible microheterogeneous associations for mobility control and reservoir conformance. Technical progress is summarized for the following tasks: advanced copolymer synthesis; characterization of macromolecular structure and properties; and solution rheology in a porous media.

  20. Thermochemical characteristics of chitosan-polylactide copolymers

    NASA Astrophysics Data System (ADS)

    Goruynova, P. E.; Larina, V. N.; Smirnova, N. N.; Tsverova, N. E.; Smirnova, L. A.

    2016-05-01

    The energies of combustion of chitosan and its block-copolymers with different polylactide contents are determined in a static bomb calorimeter. Standard enthalpies of combustion and formation are calculated for these substances. The dependences of the thermochemical characteristics on block-copolymer composition are determined and discussed.

  1. Dimensionally Stable Ether-Containing Polyimide Copolymers

    NASA Technical Reports Server (NTRS)

    Fay, Catharine C. (Inventor); St.Clair, Anne K. (Inventor)

    1999-01-01

    Novel polyimide copolymers containing ether linkages were prepared by the reaction of an equimolar amount of dianhydride and a combination of diamines. The polyimide copolymers described herein possess the unique features of low moisture uptake, dimensional stability, good mechanical properties, and moderate glass transition temperatures. These materials have potential application as encapsulants and interlayer dielectrics.

  2. Process-Accessible States of Block Copolymers

    NASA Astrophysics Data System (ADS)

    Sun, De-Wen; Müller, Marcus

    2017-02-01

    Process-directed self-assembly of block copolymers refers to thermodynamic processes that reproducibly direct the kinetics of structure formation from a starting, unstable state into a selected, metastable mesostructure. We investigate the kinetics of self-assembly of linear A C B triblock copolymers after a rapid transformation of the middle C block from B to A . This prototypical process (e.g., photochemical transformation) converts the initial, equilibrium mesophase of the A B B copolymer into a well-defined but unstable, starting state of the A A B copolymer. The spontaneous structure formation that ensues from this unstable state becomes trapped in a metastable mesostructure, and we systematically explore which metastable mesostructures can be fabricated by varying the block copolymer composition of the initial and final states. In addition to the equilibrium mesophases of linear A B diblock copolymers, this diagram of process-accessible states includes 7 metastable periodic mesostructures, inter alia, Schoen's F-RD periodic minimal surface. Generally, we observe that the final, metastable mesostructure of the A A B copolymer possesses the same symmetry as the initial, equilibrium mesophase of the A B B copolymer.

  3. Nanostructured high-performance dielectric block copolymers.

    PubMed

    Liu, Wenmei; Liao, Xiaojuan; Li, Yawei; Zhao, Qiuhua; Xie, Meiran; Sun, Ruyi

    2015-10-25

    A new type of insulating-conductive block copolymer was synthesized by metathesis polymerization. The copolymer can self-assemble into unique nanostructures of micelles or hollow spheres. It exhibits a high dielectric constant, low dielectric loss, and high stored/released energy density due to the strong dipolar and nano-interfacial polarization contributions.

  4. Process-Accessible States of Block Copolymers.

    PubMed

    Sun, De-Wen; Müller, Marcus

    2017-02-10

    Process-directed self-assembly of block copolymers refers to thermodynamic processes that reproducibly direct the kinetics of structure formation from a starting, unstable state into a selected, metastable mesostructure. We investigate the kinetics of self-assembly of linear ACB triblock copolymers after a rapid transformation of the middle C block from B to A. This prototypical process (e.g., photochemical transformation) converts the initial, equilibrium mesophase of the ABB copolymer into a well-defined but unstable, starting state of the AAB copolymer. The spontaneous structure formation that ensues from this unstable state becomes trapped in a metastable mesostructure, and we systematically explore which metastable mesostructures can be fabricated by varying the block copolymer composition of the initial and final states. In addition to the equilibrium mesophases of linear AB diblock copolymers, this diagram of process-accessible states includes 7 metastable periodic mesostructures, inter alia, Schoen's F-RD periodic minimal surface. Generally, we observe that the final, metastable mesostructure of the AAB copolymer possesses the same symmetry as the initial, equilibrium mesophase of the ABB copolymer.

  5. Synthesis and Characterization of Block Copolymers.

    DTIC Science & Technology

    1987-07-01

    Polyether-Polyimide Block Copolymers; Three series of Polyether-Polyimide (PEPI) block copolymers were synthesized. Soft segments were poly( propylene ... glycol ) (PPO) Mn = 2,000 and 4,000. Hard segments were pyromellitic dianhydride (PMDA) and di-(2-hydroxyethyl)-dimethylhydantoin (H). The hard

  6. Imide/arylene ether block copolymers

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

    Two series of imide/arylene either block copolymers were prepared using an arylene ether block and either an amorphous or semi-crystalline imide block. The resulting copolymers were characterized and selected physical and mechanical properties were determined. These results, as well as comparisons to the homopolymer properties, are discussed.

  7. Fabrication of transplantable corneal epithelial and oral mucosal epithelial cell sheets using a novel temperature-responsive closed culture device.

    PubMed

    Nakajima, Ryota; Kobayashi, Toyoshige; Kikuchi, Tetsutaro; Kitano, Yuriko; Watanabe, Hiroya; Mizutani, Manabu; Nozaki, Takayuki; Senda, Naoko; Saitoh, Kazuo; Takagi, Ryo; Yamato, Masayuki; Okano, Teruo; Takeda, Shizu

    2015-05-01

    Temperature-responsive culture surfaces make it possible to harvest transplantable carrier-free cell sheets. Here, we applied temperature-responsive polymer for polycarbonate surfaces with previously developed closed culture devices for an automated culture system in order to fabricate transplantable stratified epithelial cell sheets. Histological and immunohistochemical analyses and colony-forming assays revealed that corneal epithelial and oral mucosal epithelial cell sheets could be harvested with the temperature-responsive closed culture devices. The results were similar to those obtained using temperature-responsive culture inserts. These results indicate that the novel temperature-responsive closed culture device is useful for fabricating transplantable stratified epithelial cell sheets.

  8. Processible Polyaniline Copolymers and Complexes.

    NASA Astrophysics Data System (ADS)

    Liao, Yun-Hsin

    1995-01-01

    Polyaniline (PANI) is an intractable polymer due to the difficulty of melt processing or dissolving it in common solvents. The purpose of the present investigation was to prepare a new class of conducting polyanilines with better solubility both in base and dope forms by (1) adding external salt to break aggregated chains, (2) introducing ring substituted units onto the backbone without disturbing the coplanar structure, and (3) complexing with polymeric dopants to form a soluble polymer complex. Aggregation of PANI chains in dilute solution was investigated in N-methyl-2-pyrrolidinone (NMP) by light scattering, gel permeation chromatography, and viscosity measurements. The aggregation of chains resulted in a negative second virial coefficient in light scattering measurement, a bimodal molecular weight distribution in gel permeation chromatography, and concave reduced viscosity curves. The aggregates can be broken by adding external salt, which resulting in a higher reduced viscosity. The driving force for aggregation is assumed to be a combination of hydrogen bonding between the imine and amine groups, and the rigidity of backbone. The aggregation was modeled to occur via side-on packing of PANI chains. The ring substituted PANI copolymers, poly(aniline -co-phenetidine) were synthesized by chemical oxidation copolymerization using ammonium persulfate as an oxidant. The degree of copolymerization declined with an increasing feed of o-phenetidine in the reaction mixture. The o-phenetidine had a higher reactivity than aniline in copolymerization resulting in a higher content of o-phenetidine in copolymers. The resulting copolymers can be readily dissolved in NMP up to 20% (w/w), and other common solvents, and solutions possess a longer gelation time. The highly soluble copolymer with 20 mole % o-phenetidine in the backbone has same order of conductivity as the unsubstituted PANI after it is doped by HCl. Complexation of PANI and polymeric dopant, poly

  9. Hybridization of Block Copolymer Micelles

    DTIC Science & Technology

    1993-01-01

    J. Macromol. Sci., Part A 1973, 7,601. (10) Tiara, M.; Ramireddy, C.; Webber, S. K; Munk,P. Collect. Czer" (14) 0snford, C. In The Hydrophobic Effect ...equilibrate In the first series of experiments we have studied the within 20 min, similarly as ASA-10 micelles do. However, effect of the copolymer...high. This may happen after a sudden The Johnston-Ogston effect 2’ 6- also may play a role in jump in temperature or in the composition of the mixed

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

    NASA Astrophysics Data System (ADS)

    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.

  11. The uncertainty of crop yield projections is reduced by improved temperature response functions.

    PubMed

    Wang, Enli; Martre, Pierre; Zhao, Zhigan; Ewert, Frank; Maiorano, Andrea; Rötter, Reimund P; Kimball, Bruce A; Ottman, Michael J; Wall, Gerard W; White, Jeffrey W; Reynolds, Matthew P; Alderman, Phillip D; Aggarwal, Pramod K; Anothai, Jakarat; Basso, Bruno; Biernath, Christian; Cammarano, Davide; Challinor, Andrew J; De Sanctis, Giacomo; Doltra, Jordi; Fereres, Elias; Garcia-Vila, Margarita; Gayler, Sebastian; Hoogenboom, Gerrit; Hunt, Leslie A; Izaurralde, Roberto C; Jabloun, Mohamed; Jones, Curtis D; Kersebaum, Kurt C; Koehler, Ann-Kristin; Liu, Leilei; Müller, Christoph; Naresh Kumar, Soora; Nendel, Claas; O'Leary, Garry; Olesen, Jørgen E; Palosuo, Taru; Priesack, Eckart; Eyshi Rezaei, Ehsan; Ripoche, Dominique; Ruane, Alex C; Semenov, Mikhail A; Shcherbak, Iurii; Stöckle, Claudio; Stratonovitch, Pierre; Streck, Thilo; Supit, Iwan; Tao, Fulu; Thorburn, Peter; Waha, Katharina; Wallach, Daniel; Wang, Zhimin; Wolf, Joost; Zhu, Yan; Asseng, Senthold

    2017-07-17

    Increasing the accuracy of crop productivity estimates is a key element in planning adaptation strategies to ensure global food security under climate change. Process-based crop models are effective means to project climate impact on crop yield, but have large uncertainty in yield simulations. Here, we show that variations in the mathematical functions currently used to simulate temperature responses of physiological processes in 29 wheat models account for >50% of uncertainty in simulated grain yields for mean growing season temperatures from 14 °C to 33 °C. We derived a set of new temperature response functions that when substituted in four wheat models reduced the error in grain yield simulations across seven global sites with different temperature regimes by 19% to 50% (42% average). We anticipate the improved temperature responses to be a key step to improve modelling of crops under rising temperature and climate change, leading to higher skill of crop yield projections.

  12. The Uncertainty of Crop Yield Projections Is Reduced by Improved Temperature Response Functions

    NASA Technical Reports Server (NTRS)

    Wang, Enli; Martre, Pierre; Zhao, Zhigan; Ewert, Frank; Maiorano, Andrea; Rotter, Reimund P.; Kimball, Bruce A.; Ottman, Michael J.; White, Jeffrey W.; Reynolds, Matthew P.; hide

    2017-01-01

    Increasing the accuracy of crop productivity estimates is a key element in planning adaptation strategies to ensure global food security under climate change. Process-based crop models are effective means to project climate impact on crop yield, but have large uncertainty in yield simulations. Here, we show that variations in the mathematical functions currently used to simulate temperature responses of physiological processes in 29 wheat models account for is greater than 50% of uncertainty in simulated grain yields for mean growing season temperatures from 14 C to 33 C. We derived a set of new temperature response functions that when substituted in four wheat models reduced the error in grain yield simulations across seven global sites with different temperature regimes by 19% to 50% (42% average). We anticipate the improved temperature responses to be a key step to improve modelling of crops under rising temperature and climate change, leading to higher skill of crop yield projections.

  13. 21 CFR 177.1060 - n-Alkylglutarimide/acrylic copolymers.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false n-Alkylglutarimide/acrylic copolymers. 177.1060... Use Food Contact Surfaces § 177.1060 n-Alkylglutarimide/acrylic copolymers. n-Alkylglutarimide/acrylic...) Identity. For the purpose of this section, n-alkylglutarimide/acrylic copolymers are copolymers obtained by...

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

    PubMed Central

    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

  15. Temperature-responsive cross-linked poly(epsilon-caprolactone) membrane that functions near body temperature.

    PubMed

    Uto, Koichiro; Yamamoto, Kazuya; Hirase, Shohei; Aoyagi, Takao

    2006-01-10

    The objective of this study is to develop a sensitive temperature-responsive material that would function near body temperature. To achieve this purpose, we compounded 2-branched and 4-branched poly(epsilon-caprolactone) macromonomers to modulate the transition temperatures of the resulting cross-linked materials. The temperature-responsive properties were studied using differential scanning calorimetry and X-ray diffraction measurements. As a result, the mixing ratios of each macromonomer or the total macromonomer concentrations were very dominant in modulating the transition temperatures. The materials could successfully control the permeation of the model drug, prednisolone, near body temperature.

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

    DOEpatents

    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.

  17. Microphase separation in random multiblock copolymers

    NASA Astrophysics Data System (ADS)

    Govorun, E. N.; Chertovich, A. V.

    2017-01-01

    Microphase separation in random multiblock copolymers is studied with the mean-field theory assuming that long blocks of a copolymer are strongly segregated, whereas short blocks are able to penetrate into "alien" domains and exchange between the domains and interfacial layer. A bidisperse copolymer with blocks of only two sizes (long and short) is considered as a model of multiblock copolymers with high polydispersity in the block size. Short blocks of the copolymer play an important role in the microphase separation. First, their penetration into the "alien" domains leads to the formation of joint long blocks in their own domains. Second, short blocks localized at the interface considerably change the interfacial tension. The possibility of penetration of short blocks into the "alien" domains is controlled by the product χ Nsh (χ is the Flory-Huggins interaction parameter and Nsh is the short block length). At not very large χ Nsh , the domain size is larger than that for a regular copolymer consisting of the same long blocks as in the considered random copolymer. At a fixed mean block size, the domain size grows with an increase in the block size dispersity, the rate of the growth being dependent of the more detailed parameters of the block size distribution.

  18. Seasonal changes in metabolic and temperature responses to cold air in humans.

    PubMed

    van Ooijen, A M J; van Marken Lichtenbelt, W D; van Steenhoven, A A; Westerterp, K R

    2004-09-15

    The metabolic and temperature response to mild cold were investigated in summer and winter in a moderate oceanic climate. Subjects were 10 women and 10 men, aged 19-36 years and BMI 17-32 kg/m2. Metabolic rate (MR) and body temperatures were measured continuously in a climate chamber with an ambient temperature of 22 degrees C for 1 h and subsequently 3 h of 15 degrees C. The average metabolic response during cold exposure, measured as the increase in kJ/min over time, was significantly higher in winter (11.5%) compared to summer (7.0%, P < .05). The temperature response was comparable in both seasons. The metabolic response in winter was significantly related to the response in summer (r2 = .47, P < .001). Total heat production during cold exposure was inversely related to the temperature response in both seasons (summer, r2 = .39, P < .01; winter r2 = .32, P < .05). In conclusion, the observed higher metabolic response in winter compared to summer indicates cold adaptation. The magnitude of the cold response varies, but the relative contribution of metabolic and temperature response was subject specific and consistent throughout the seasons, which can have implications for energy balance and body composition.

  19. LaRC-ITPI/arylene ether copolymers

    NASA Technical Reports Server (NTRS)

    Jensen, Brian J.; Working, Dennis C.

    1991-01-01

    As part of an effort to develop high performance structural resins for aerospace applications, work has continued on block copolymers containing imide and arylene ether segments. The arylene ether block used in this study contains a bulky fluorene group in the polymer backbone while the imide block contains an arylene ketone segment similar to that in the arylene ether block and has been named LaRC-ITPI. A series of imide/arylene ether block and segmented copolymers were prepared and characterized. Films were prepared from these copolymers and mechanical properties were measured.

  20. Block Copolymer Membranes for Biofuel Purification

    NASA Astrophysics Data System (ADS)

    Evren Ozcam, Ali; Balsara, Nitash

    2012-02-01

    Purification of biofuels such as ethanol is a matter of considerable concern as they are produced in complex multicomponent fermentation broths. Our objective is to design pervaporation membranes for concentrating ethanol from dilute aqueous mixtures. Polystyrene-b-polydimethylsiloxane-b-polystyrene block copolymers were synthesized by anionic polymerization. The polydimethylsiloxane domains provide ethanol-transporting pathways, while the polystyrene domains provide structural integrity for the membrane. The morphology of the membranes is governed by the composition of the block copolymer while the size of the domains is governed by the molecular weight of the block copolymer. Pervaporation data as a function of these two parameters will be presented.

  1. Injectible bodily prosthetics employing methacrylic copolymer gels

    DOEpatents

    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.

  2. Organosilane Polymers. III. Block Copolymers.

    DTIC Science & Technology

    1980-04-01

    5446 (1969) 9) R. West, J. Polym. Sci., C, 29, 65 (1970) 10) V.F. Traven and R. West, J. Am. Chem. Soc., 95, 6824 (1973) 11) W.G. Boberski and-A.L...COMPOSITION Alkyl H/Aryl H (2 ) Copolymer Method,1 , Calculated Found 111-3 A 0.72 0.73 B 0.72 0.73 111-5 A 0.80 0.85 B 0.80 0.80 111-8 A 1.0 1.4 B 1.0...1.1 (1) A: Chloro-oligomer added to lithio-oligomer. B : Lithio-oligomer added to chloro-oligomer. (2) By HI-NMR TABLE 2 INFRA-RED ABSORPTIONS

  3. Curable polyphosphazene copolymers and terpolymers

    NASA Technical Reports Server (NTRS)

    Reynard, Kennard A. (Inventor); Rose, Selwyn H. (Inventor)

    1976-01-01

    Copolymers and terpolymers comprising randomly repeating units represented by the general formulae ##EQU1## wherein the R' radicals contain OH functionality and R being at least one member of the group of monovalent radicals selected from alkyl, substituted alkyl, aryl, substituted aryl and arylalkyl, and R' is represented by ##EQU2## wherein Q represents either --(CH.sub.2).sub. n or --C.sub.6 H.sub.4 X(CH.sub.2).sub. m, the --X(CH.sub.2).sub. m group being either meta or para and n is an integer from 1 to 6, m is an integer from 1 to 3, X is O or CH.sub.2, and R is H or a lower alkyl radical with up to four carbon atoms (methyl, ethyl, etc.). The ratio of R to R' is between 99.5 to 0.5 and 65 to 35.

  4. Salt Complexation in Block Copolymer Thin Films

    SciTech Connect

    Kim,S.; Misner, M.; Yang, L.; Gang, O.; Ocko, B.; Russell, T.

    2006-01-01

    Ion complexation within cylinder-forming block copolymer thin films was found to affect the ordering process of the copolymer films during solvent annealing, significantly enhancing the long-range positional order. Small amounts of alkali halide or metal salts were added to PS-b-PEO, on the order of a few ions per chain, where the salt complexed with the PEO block. The orientation of the cylindrical microdomains strongly depended on the salt concentration and the ability of the ions to complex with PEO. The process shows large flexibility in the choice of salt used, including gold or cobalt salts, whereby well-organized patterns of nanoparticles can be generated inside the copolymer microdomains. By further increasing the amount of added salts, the copolymer remained highly ordered at large degrees of swelling and demonstrated long-range positional correlations of the microdomains in the swollen state, which holds promise as a route to addressable media.

  5. Electrostatic control of block copolymer morphology

    NASA Astrophysics Data System (ADS)

    Sing, Charles E.; Zwanikken, Jos W.; Olvera de La Cruz, Monica

    2014-07-01

    Energy storage is at present one of the foremost issues society faces. However, material challenges now serve as bottlenecks in technological progress. Lithium-ion batteries are the current gold standard to meet energy storage needs; however, they are limited owing to the inherent instability of liquid electrolytes. Block copolymers can self-assemble into nanostructures that simultaneously facilitate ion transport and provide mechanical stability. The ions themselves have a profound, yet previously unpredictable, effect on how these nanostructures assemble and thus the efficiency of ion transport. Here we demonstrate that varying the charge of a block copolymer is a powerful mechanism to predictably tune nanostructures. In particular, we demonstrate that highly asymmetric charge cohesion effects can induce the formation of nanostructures that are inaccessible to conventional uncharged block copolymers, including percolated phases desired for ion transport. This vastly expands the design space for block copolymer materials and is informative for the versatile design of battery electrolyte materials.

  6. Arbitrary lattice symmetries via block copolymer nanomeshes

    PubMed Central

    Majewski, Pawel W.; Rahman, Atikur; Black, Charles T.; Yager, Kevin G.

    2015-01-01

    Self-assembly of block copolymers is a powerful motif for spontaneously forming well-defined nanostructures over macroscopic areas. Yet, the inherent energy minimization criteria of self-assembly give rise to a limited library of structures; diblock copolymers naturally form spheres on a cubic lattice, hexagonally packed cylinders and alternating lamellae. Here, we demonstrate multicomponent nanomeshes with any desired lattice symmetry. We exploit photothermal annealing to rapidly order and align block copolymer phases over macroscopic areas, combined with conversion of the self-assembled organic phase into inorganic replicas. Repeated photothermal processing independently aligns successive layers, providing full control of the size, symmetry and composition of the nanoscale unit cell. We construct a variety of symmetries, most of which are not natively formed by block copolymers, including squares, rhombuses, rectangles and triangles. In fact, we demonstrate all possible two-dimensional Bravais lattices. Finally, we elucidate the influence of nanostructure on the electrical and optical properties of nanomeshes. PMID:26100566

  7. Morphologies in Sulfonated Styrenic Pentablock Copolymer Membranes

    NASA Astrophysics Data System (ADS)

    Choi, Jae-Hong; Bramson, Matt; Winey, Karen I.

    2010-03-01

    Membranes of pentablock and triblock copolymers consisting of poly(tert-butyl styrene) (TBS), hydrogenated polyisoprene (HI), and partially sulfonated poly(styrene-ran-styrene sulfonate) (SS) were studied using small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). The TBS-HI-SS-HI-TBS pentablock and TBS-HI-SS triblock copolymer membranes exhibit anisotropic microphase separated morphologies. Because the pentablock and triblock copolymers can be expected to have complex morphologies, thermal annealing was conducted to promote well-defined morphologies. The annealed membranes exhibit stronger peaks and more high order reflections in SAXS patterns, as well as better defined microstructures in the TEM. Electron microcopy studies with various staining protocols are underway to establish the morphology of the pentablock copolymer membranes including the size and shape of the three microdomains (TBS, HI and SS). We gratefully acknowledge Kraton Polymers, Inc. for materials.

  8. Block copolymer structures in nano-pores

    NASA Astrophysics Data System (ADS)

    Pinna, Marco; Guo, Xiaohu; Zvelindovsky, Andrei

    2010-03-01

    We present results of coarse-grained computer modelling of block copolymer systems in cylindrical and spherical nanopores on Cell Dynamics Simulation. We study both cylindrical and spherical pores and systematically investigate structures formed by lamellar, cylinders and spherical block copolymer systems for various pore radii and affinity of block copolymer blocks to the pore walls. The obtained structures include: standing lamellae and cylinders, ``onions,'' cylinder ``knitting balls,'' ``golf-ball,'' layered spherical, ``virus''-like and mixed morphologies with T-junctions and U-type defects [1]. Kinetics of the structure formation and the differences with planar films are discussed. Our simulations suggest that novel porous nano-containers can be formed by confining block copolymers in pores of different geometries [1,2]. [4pt] [1] M. Pinna, X. Guo, A.V. Zvelindovsky, Polymer 49, 2797 (2008).[0pt] [2] M. Pinna, X. Guo, A.V. Zvelindovsky, J. Chem. Phys. 131, 214902 (2009).

  9. Temperature-responsive electrospun nanofibers for ‘on-off’ switchable release of dextran

    NASA Astrophysics Data System (ADS)

    Kim, Young-Jin; Ebara, Mitsuhiro; Aoyagi, Takao

    2012-12-01

    We propose a new type of ‘smart’ nanofiber (NF) with dynamically and reversibly tunable properties for the ‘on-off’ controlled release of the polysaccharide dextran. The fibers are produced by electrospinning copolymers of N-isopropylacrylamide (NIPAAm) and N-hydroxymethylacrylamide (HMAAm). The OH groups of HMAAm are subsequently crosslinked by thermal curing. The copolymers were successfully fabricated into a well-defined nanofibrous structure with a diameter of about 600-700 nm, and the fibers preserved their morphology even after thermal curing. The resulting crosslinked NFs showed rapid and reversible volume changes in aqueous media in response to cycles of temperature alternation. The fibrous morphology was maintained for the crosslinked NFs even after the cycles of temperature alternation, while non-crosslinked NFs collapsed and dispersed quickly in the aqueous solution. Dextran-containing NFs were prepared by electrospinning the copolymers blended with fluorescein isothiocyanate (FITC)-dextran, and the ‘on-off’ switchable release of FITC-dextran from the crosslinked NFs was observed. Almost all the FITC-dextran was released from the NFs after six heating cycles, whereas only a negligible amount of FITC-dextran was evolved during the cooling process. The reported incorporation of smart properties into NFs takes advantage of their extremely large surface area and porosity and is expected to provide a simple platform for on-off drug delivery.

  10. Method for making block siloxane copolymers

    DOEpatents

    Butler, N.L.; Jessop, E.S.; Kolb, J.R.

    1981-02-25

    A method for synthesizing block polysiloxane copolymers is disclosed. Diorganoscyclosiloxanes and an end-blocking compound are interacted in the presence of a ring opening polymerization catalyst, producing a blocked prepolymer. The prepolymer is then interacted with a silanediol, resulting in condensation polymerization of the prepolymers. A second end-blocking compound is subsequently introduced to end-cap the polymers and copolymers formed from the condensation polymerization.

  11. Responsive Copolymers for Enhanced Petroleum Recovery

    SciTech Connect

    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.

  12. Reactivity ratios for organotin copolymer systems.

    PubMed

    El-Newehy, Mohamed H; Al-Deyab, Salem S; Al-Hazmi, Ali Mohsen Ali

    2010-04-15

    Di(tri-n-butyltin) itaconate (DTBTI) and monoethyl tributyltin fumarate (METBTF) were synthesized as organotin monomers. The organotin monomers were copolymerized with styrene (ST) and methyl methacrylate (MMA) via a free radical polymerization technique. The overall conversion was kept low (copolymer composition was determined from tin analysis. The synthesized monomers and copolymers were characterized by elemental analysis, 1H- and 13C-NMR, and FTIR spectroscopy.

  13. Method for making block siloxane copolymers

    DOEpatents

    Butler, Nora; Jessop, Edward S.; Kolb, John R.

    1982-01-01

    A method for synthesizing block polysiloxane copolymers. Diorganoscyclosiloxanes and an end-blocking compound are interacted in the presence of a ring opening polymerization catalyst, producing a blocked prepolymer. The prepolymer is then interacted with a silanediol, resulting in condensation polymerization of the prepolymers. A second end-blocking compound is subsequently introduced to end-cap the polymers and copolymers formed from the condensation polymerization.

  14. Diffusion of copolymers composed of monomers with drastically different friction factors in copolymer/homopolymer blends

    NASA Astrophysics Data System (ADS)

    Duranty, Edward R.; Baschnagel, Jörg; Dadmun, Mark

    2017-02-01

    Copolymers are commonly used as interface modifiers that allow for the compatibilization of polymer components in a blend. For copolymers to function as a compatibilizer, they must diffuse through the matrix of the blend to the interface between the two blend components. The diffusivity of a copolymer in a blend matrix therefore becomes important in determining good candidates for use as compatibilizers. In this work, coarse-grained Monte Carlo simulations using the bond fluctuation model modified with an overlap penalty have been developed to study the diffusive behavior of PS/PMMA random copolymers in a PMMA homopolymer blend. The simulations vary the connectivity between different monomers, the thermodynamic interactions between the monomers which manifest within a chain, and between copolymer and homopolymer matrix and define the monomer friction coefficient of each component independently, allowing for the determination of the combined effect of these parameters on copolymer chain diffusion. The results of this work indicate that PS-r-PMMA copolymer diffusion is not linearly dependent on the copolymer composition on a logarithmic scale, but its diffusion is a balance of the kinetics governed by the dominant motion of the faster styrene monomers and thermodynamics, which are governed by the concentration of styrene monomer within a given monomer's local volume.

  15. Diffusion of copolymers composed of monomers with drastically different friction factors in copolymer/homopolymer blends

    DOE PAGES

    Duranty, Edward R.; Baschnagel, Jörg; Dadmun, Mark

    2017-02-07

    Copolymers are commonly used as interface modifiers that allow for the compatibilization of polymer components in a blend. For copolymers to function as a compatibilizer, they must diffuse through the matrix of the blend to the interface between the two blend components. The diffusivity of a copolymer in a blend matrix therefore becomes important in determining good candidates for use as compatibilizers. In this paper, coarse-grained Monte Carlo simulations using the bond fluctuation model modified with an overlap penalty have been developed to study the diffusive behavior of PS/PMMA random copolymers in a PMMA homopolymer blend. The simulations vary themore » connectivity between different monomers, the thermodynamic interactions between the monomers which manifest within a chain, and between copolymer and homopolymer matrix and define the monomer friction coefficient of each component independently, allowing for the determination of the combined effect of these parameters on copolymer chain diffusion. Finally, the results of this work indicate that PS-r-PMMA copolymer diffusion is not linearly dependent on the copolymer composition on a logarithmic scale, but its diffusion is a balance of the kinetics governed by the dominant motion of the faster styrene monomers and thermodynamics, which are governed by the concentration of styrene monomer within a given monomer’s local volume.« less

  16. Why does the locally induced temperature response to land cover change differ across scenarios?

    NASA Astrophysics Data System (ADS)

    Winckler, J.; Reick, C. H.; Pongratz, J.

    2017-04-01

    Land cover change (LCC) affects temperature locally. The underlying biogeophysical effects are influenced not only by land use (location and extent) but also by natural biogeographic shifts and background climate. We examine the contributions of these three factors to surface temperature changes upon LCC and compare them across Coupled Model Intercomparison Project phase 5 (CMIP5) scenarios. To this end, we perform global deforestation simulations with an Earth system model to deduce locally induced changes in surface temperature for historical and projected forest cover changes. We find that the dominant factors differ between historical and future scenarios: the local temperature response is historically dominated by the factor land use change, but the two other factors become just as important in scenarios of future land use and climate. An additional factor contributing to differences across scenarios is the dependence on the extent of forests before LCC happens: For most locations, the temperature response is strongest when starting deforestation from low forest cover fractions.

  17. A universal approach to predicting temperature response of metallic parts to spray quenching

    NASA Astrophysics Data System (ADS)

    Mudawar, Issam; Deiters, Thomas A.

    1995-02-01

    A new method was developed to predict the temperature response of metallic parts to spray quenching below the film boiling regime. Local heat flux measurements in surfaces subjected to full cone and hollow cone sprays revealed existing correlations based on local values of volumetric spray flux, Sauter mean diameter, and mean drop velocity are both accurate and spatially independent in the transition boiling and nucleate boiling regimes, but less accurate in the single-phase regime due to liquid run-off effects. It is shown how the instantaneous spatial distribution of the heat transfer coefficient can be predicted from a mapping of the spatial distribution of the spray hydrodynamic parameters. The validity of this approach is demonstrated by comparing numerical predictions to the temperature response of a large rectangular aluminum block subjected on one surface to a nonuniform water spray. It is shown that the new method is universally applicable to sprays having drastically different patterns.

  18. Novel multi-responsive P2VP-block-PNIPAAm block copolymers via nitroxide-mediated radical polymerization

    PubMed Central

    Corten, Cathrin; Kretschmer, Katja

    2010-01-01

    Summary Linear soluble multi-responsive block copolymers are able to form so called schizophrenic micelles in aqueous solution. Here, such polymers are prepared via nitroxide-mediated radical polymerization (NMRP). In a first step nitroxide-terminated poly(2-vinylpyridine) (P2VP) was prepared with different molecular weights and narrow molecular weight distributions. The best reaction conditions, optimized by kinetic studies, were bulk polymerization at 110 °C. Using P2VP as a macroinitiator, the synthesis of new soluble linear block copolymers of P2VP and poly(N-isopropylacrylamide) (PNIPAAm) (P2VP-block-PNIPAAm) was possible. The nitroxide terminated polymers were characterized by nuclear magnetic resonance (NMR) spectroscopy, size exclusion chromatography (SEC) and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). Thermal properties were investigated by the differential scanning calorimetry (DSC). Block copolymers showed pH- and temperature-responsive solubility in aqueous media. By increasing the P2VP content, the phase transition temperature shifted to lower temperatures (e.g. 26 °C for P2VP114-block-PNIPAAm180). Depending on the resulting block length, temperature and pH value of aqueous solution, the block copolymers form so called schizophrenic micelles. The hydrodynamic radius R h of these micelles associated with pH values and temperature was analyzed by dynamic light scattering (DLS). Such kind of block copolymers has potential for many applications, such as controlled drug delivery systems. PMID:20978627

  19. Preparation and drug release behavior of temperature-responsive mesoporous carbons

    SciTech Connect

    Wang Xiufang; Liu Ping; Tian Yong

    2011-06-15

    A temperature-responsive composite based on poly (N-isopropylacrylamide) (PNIPAAm) and ordered mesoporous carbons (OMCs) has been successfully prepared by a simple wetness impregnation technique. The structures and properties of the composite were characterized by infrared spectroscopy (IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), N{sub 2} sorption, thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). The results showed that the inclusion of PNIPAAm had not greatly changed the basic ordered pore structure of the OMCs. Ibuprofen (IBU) was selected as model drug, and in vitro test of IBU release exhibited a temperature-responsive controlled release delivery. - Graphical abstract: The bands located at 1650 and 1549 cm{sup -1} could be assigned to C=O stretching and N-H bending vibrations for polymer PNIPAAm (a). The bands at 1388 and 1369 cm{sup -1} were due to isopropyl group, and the band at 1459 cm{sup -1} was related to the bending vibration of C-H (a). For the PNIPAAm/OMCs composite, the characteristic bands of polymer were still observed besides those for carbon materials and the bands at around 1585 cm{sup -1} and a broad band at about 1100 cm{sup -1} were characteristics for the carbon materials(c). In addition, little shifts of C=O and N-H bands compared to the pure PNIPAAm were also observed (b), indicating a weak interaction between the polymer and carbon material. These results could be a proof that the PNIPAAm has been incorporated into the carbon material. Highlights: > A temperature-responsive PNIPAAm/OMCs composite was successfully synthesized by a simple wetness impregnation technique for the first time. > The inclusion of PNIPAAm had not greatly changed the basic ordered pore structure of the OMCs. > In vitro test of IBU release exhibited a temperature-responsive controlled release delivery.

  20. Temperature responses of dark respiration in relation to leaf sugar concentration.

    PubMed

    Hüve, Katja; Bichele, Irina; Ivanova, Hiie; Keerberg, Olav; Pärnik, Tiit; Rasulov, Bahtijor; Tobias, Mari; Niinemets, Ulo

    2012-04-01

    Changes in leaf sugar concentrations are a possible mechanism of short-term adaptation to temperature changes, with natural fluctuations in sugar concentrations in the field expected to modify the heat sensitivity of respiration. We studied temperature-response curves of leaf dark respiration in the temperate tree Populus tremula (L.) in relation to leaf sugar concentration (1) under natural conditions or (2) leaves with artificially enhanced sugar concentration. Temperature-response curves were obtained by increasing the leaf temperature at a rate of 1°C min⁻¹. We demonstrate that respiration, similarly to chlorophyll fluorescence, has a break-point at high temperature, where respiration starts to increase with a faster rate. The average break-point temperature (T(RD) ) was 48.6 ± 0.7°C at natural sugar concentration. Pulse-chase experiments with ¹⁴CO₂ demonstrated that substrates of respiration were derived mainly from the products of starch degradation. Starch degradation exhibited a similar temperature-response curve as respiration with a break-point at high temperatures. Acceleration of starch breakdown may be one of the reasons for the observed high-temperature rise in respiration. We also demonstrate that enhanced leaf sugar concentrations or enhanced osmotic potential may protect leaf cells from heat stress, i.e. higher sugar concentrations significantly modify the temperature-response curve of respiration, abolishing the fast increase of respiration. Sugars or enhanced osmotic potential may non-specifically protect respiratory membranes or may block the high-temperature increase in starch degradation and consumption in respiratory processes, thus eliminating the break-points in temperature curves of respiration in sugar-fed leaves. Copyright © Physiologia Plantarum 2011.

  1. Sensitivity of Regional Radiative Forcing and Temperature Response to Aviation-induced Ozone

    NASA Astrophysics Data System (ADS)

    Lund, M. T.; Fuglestvedt, J. S.; Berntsen, T.

    2015-12-01

    Aviation emissions affect the atmosphere and climate through a number of mechanisms. One important mechanism is the change in ozone budged resulting from emissions of nitrogen oxides (NOx) and other precursor gases. Significant spatial heterogeneity exists in the aviation-induced ozone changes and consequent climate impact, which may have important implications for the design and evaluation of mitigation strategies for the sector. However, further studies are needed to increase the knowledge of regional impacts. This study investigates spatial variability - from emissions to temperature response - of aviation ozone perturbations. Using the AEDT year 2006 and 2050 aviation emission inventory in the chemistry-transport model OsloCTM3, we quantify the radiative forcing (RF) due to regional aviation NOx emissions. In addition to the information provided by RF, there is an increasing need to also quantify the temperature impacts. In order to examine the sensitivity of regional temperature response to aviation-induced ozone perturbations, we perform simulations with the Community Earth System model (CESM). Results are compared to estimates of temperature response calculated using the Regional Temperature change Potential (RTP) metric with aviation RF results from the Aviation Climate Change Research Initiative (ACCRI). Furthermore, we focus in particular on the vertical sensitivity in the ozone forcing-response relationship, especially at higher latitudes where the short-wave component of the ozone RF becomes more important than globally. This also allows for an investigation of potential differences between the temperature response sensitivity to ozone changes caused by aviation emissions and by lower-altitude emissions from other sectors.

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

    PubMed Central

    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.

    2016-01-01

    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. PMID:27001849

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

    NASA Astrophysics Data System (ADS)

    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.

  5. Transportation of transplantable cell sheets fabricated with temperature-responsive culture surfaces for regenerative medicine.

    PubMed

    Nozaki, Takayuki; Yamato, Masayuki; Inuma, Toshiaki; Nishida, Kohji; Okano, Teruo

    2008-06-01

    Here we report transportation of cell sheets fabricated on temperature-responsive culture surfaces for regenerative medicine. On the surfaces cells adhere, spread and proliferate at 37 degrees C, but upon temperature reduction below 32 degrees C all the cells are spontaneously detached. When cells on the surfaces are challenged by long distance transportation, maintaining the temperature is critical. Therefore, we developed a portable homothermal container to keep the inner temperature at 36 degrees C for > 30 h without any need for batteries or energy supply. We transported and compared fibroblast sheets cultured on temperature-responsive surfaces in the container, at room temperature in a car, or on ice. After 8 h transportation by car, all cells at room temperature and on ice were detached from the surfaces and some were folded and broken into tiny pieces. On the other hand, fibroblast sheets transported in the container retained their adhesion to the dish surfaces and intact cell sheets were successfully harvested by temperature reduction. During the transportation, cell viability and histology were not impaired. This unique transportation device would be useful for cell sheet-based regenerative medicine utilizing temperature-responsive culture surfaces. Copyright (c) 2008 John Wiley & Sons, Ltd.

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

    PubMed

    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.

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

    PubMed

    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.

  8. Polyhydroxyalkanoate copolymers from forest biomass.

    PubMed

    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

  9. Random hydrophilic-hydrophobic copolymers

    NASA Astrophysics Data System (ADS)

    Garel, T.; Leibler, L.; Orland, H.

    1994-12-01

    We study a single statistical amphiphilic copolymer chain AB in a selective solvent (e.g. water). Two situations are considered. In the annealed case, hydrophilic (A) and hydrophobic (B) monomers are at local chemical equilibrium and both the fraction of A monomers and their location along the chain can vary, whereas in the quenched case (which is relevant to proteins), the chemical sequence along the chain is fixed by synthesis. In both cases, the physical behaviour depends on the average hydrophobicity of the polymer chain. For a strongly hydrophobic chain (large fraction of B), we find an ordinary continuous θ collapse, with a large conformational entropy in the collapsed phase. For a weakly hydrophobic, or a hydrophilic chain, there is an unusual first-order collapse transition. In particular, for the case of Gaussian disorder, this discontinuous transition is driven by a change of sign of the third virial coefficient. The entropy of this collapsed phase is strongly reduced with respect to the θ collapsed phase. Nous étudions un copolymère aléatoire amphiphile AB dans un solvant sélectif (par exemple, de l'eau). Nous considérons deux cas. Dans le cas du désordre mobile, les monomères hydrophiles (A) et hydrophobes (B) sont à l'équilibre chimique local, et la fraction de monomères A ainsi que leur position dans l'espace peuvent varier, alors que dans le cas du désordre gelé (qui est relié au problème des protéines), la séquence chimique est fixée par synthèse. Dans les deux cas, le comportement de la chaîne depend de son hydrophobicité moyenne. Pour une chaîne fortement hydrophobe (grande fraction de B), on trouve un point d'effondrement θ continu ordinaire, avec une grande entropie conformationnelle. Pour une chaîne faiblement hydrophobe ou hydrophile, on trouve une transition inhabituelle du premier ordre. En particulier, dans le cas du désordre gaussien, cette transition discontinue est pilotée par un changement de signe du troisi

  10. Initiator Effects in Reactive Extrusion of Starch Graft Copolymers

    USDA-ARS?s Scientific Manuscript database

    Graft copolymers of starch with water-soluble polymers such as polyacrylamide have potential applications including hydrogels, superabsorbents, and thickening agents. Reactive extrusion is a rapid, continuous method for production of starch graft copolymers with high reaction and grafting efficienc...

  11. Polyamide copolymers having 2,5-furan dicarboxamide units

    DOEpatents

    Chisholm, Bret Ja; Samanta, Satyabrata

    2017-09-19

    Polyamide copolymers, and methods of making and using polyamide copolymers, having 2,5-furan dicarboxamide units are disclosed herein. Such polymers can be useful for engineering thermoplastics having advantageous physical and/or chemical properties.

  12. Hydrogen-bonded aggregates in precise acid copolymers

    SciTech Connect

    Lueth, Christopher A.; Bolintineanu, Dan S.; Stevens, Mark J. Frischknecht, Amalie L.

    2014-02-07

    We perform atomistic molecular dynamics simulations of melts of four precise acid copolymers, two poly(ethylene-co-acrylic acid) (PEAA) copolymers, and two poly(ethylene-co-sulfonic acid) (PESA) copolymers. The acid groups are spaced by either 9 or 21 carbons along the polymer backbones. Hydrogen bonding causes the acid groups to form aggregates. These aggregates give rise to a low wavevector peak in the structure factors, in agreement with X-ray scattering data for the PEAA materials. The structure factors for the PESA copolymers are very similar to those for the PEAA copolymers, indicating a similar distance between aggregates which depends on the spacer length but not on the nature of the acid group. The PEAA copolymers are found to form more dimers and other small aggregates than do the PESA copolymers, while the PESA copolymers have both more free acid groups and more large aggregates.

  13. Adhesion promotion with random copolymers

    NASA Astrophysics Data System (ADS)

    Simmons, Edward Read

    This thesis presents a study of adhesion promotion with random copolymers (RCP's). Monte Carlo (MC) simulations are used to study the potential use of RCP's as interfacial strengtheners at a homopolymer-solid interface. We discuss the effect of varying several design parameters of the RCP chains on interfacial strength. We find that RCP's can promote adhesion dependent upon careful selection of the parameters such as the RCP composition, blockiness, and concentration. We draw our conclusions from both equilibrium and non-equilibrium MC simulations in which we impose a normal stress on the interfacial chain system and observe the response as the system is deformed. These simulations are designed to reflect experimentally realizable conditions as closely as possible. The ultimate goal of our work is to guide experimentalists in the design and selection of the best adhesion promoter for a given system. With this goal in mind, we suggest several extensions of our methodology to further tighten the connection between simulation and experiment.

  14. Melt Rheology of Block Copolymers in Relation to Melt Structure.

    DTIC Science & Technology

    1980-06-23

    According to their theory, (A-B-A) type block copolymer melts are expected to exhibit a network response including a yield stress at very low shear rates ...observed the following very unusual flow behavior with SBS block copolymers . 1. The viscosities of SBS block copolymers at low shear rates go...unusual flow properties. One can expect from the probable two-phase structure in the melt that block copolymer melts would exhibit strong elastic

  15. Charge Transport in Conjugated Block Copolymers

    NASA Astrophysics Data System (ADS)

    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.

  16. Morphology study in block copolymer electrolytes

    NASA Astrophysics Data System (ADS)

    Mullin, Scott; Wanakule, Nisita; Balsara, Nitash

    2008-03-01

    Poly(styrene-b-ethylene oxide)/lithium bis(trifluoromethane)sulfonimide (SEO/LiTFSI) is of interest in battery applications since the doped PEO phase can conduct ions and the glassy PS phase can prevent dendrite growth upon recharging. It is believed that the LiTFSI molecules are localized in the PEO microphases. Previous studies have shown that highly conducting electrolytes can be made from symmetric SEO copolymers. The purpose of this study is to explore the conductivity of asymmetric SEO copolymer systems doped with LiTFSI. Our studies encompass both neat asymmetric SEO copolymers and SEO copolymers blended with PS homopolymers to separate the effects of architecture of the copolymer molecules and morphology adopted by the system in the melt state. Conductivity is measured by AC impedance, morphology is determined by small angle X-ray scattering, and crystallinity of the PEO chains is determined by differential scanning calorimetry. All samples were prepared in hermetically sealed sample cells in an Argon glovebox.

  17. 21 CFR 172.775 - Methacrylic acid-divinylbenzene copolymer.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Methacrylic acid-divinylbenzene copolymer. 172.775... HUMAN CONSUMPTION Other Specific Usage Additives § 172.775 Methacrylic acid-divinylbenzene copolymer. Methacrylic acid-divinylbenzene copolymer may be safely used in food in accordance with the following...

  18. 21 CFR 177.1310 - Ethylene-acrylic acid copolymers.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Ethylene-acrylic acid copolymers. 177.1310 Section... Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1310 Ethylene-acrylic acid copolymers. The ethylene-acrylic acid copolymers identified in paragraph (a) of this section may be safely...

  19. 21 CFR 172.775 - Methacrylic acid-divinylbenzene copolymer.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Methacrylic acid-divinylbenzene copolymer. 172.775... Additives § 172.775 Methacrylic acid-divinylbenzene copolymer. Methacrylic acid-divinylbenzene copolymer may... produced by the polymerization of methacrylic acid and divinylbenzene. The divinylbenzene functions as a...

  20. 21 CFR 177.1310 - Ethylene-acrylic acid copolymers.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Ethylene-acrylic acid copolymers. 177.1310 Section... Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1310 Ethylene-acrylic acid copolymers. The ethylene-acrylic acid copolymers identified in paragraph (a) of this section may be safely...

  1. 21 CFR 177.1310 - Ethylene-acrylic acid copolymers.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Ethylene-acrylic acid copolymers. 177.1310 Section... Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1310 Ethylene-acrylic acid copolymers. The ethylene-acrylic acid copolymers identified in paragraph (a) of this section may be safely...

  2. 21 CFR 172.775 - Methacrylic acid-divinylbenzene copolymer.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Methacrylic acid-divinylbenzene copolymer. 172.775... HUMAN CONSUMPTION Other Specific Usage Additives § 172.775 Methacrylic acid-divinylbenzene copolymer. Methacrylic acid-divinylbenzene copolymer may be safely used in food in accordance with the following...

  3. 21 CFR 172.775 - Methacrylic acid-divinylbenzene copolymer.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Methacrylic acid-divinylbenzene copolymer. 172.775... HUMAN CONSUMPTION Other Specific Usage Additives § 172.775 Methacrylic acid-divinylbenzene copolymer. Methacrylic acid-divinylbenzene copolymer may be safely used in food in accordance with the following...

  4. 21 CFR 177.1312 - Ethylene-carbon monoxide copolymers.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Ethylene-carbon monoxide copolymers. 177.1312... Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1312 Ethylene-carbon monoxide copolymers. The ethylene-carbon monoxide copolymers identified in paragraph (a) of this section may be...

  5. 21 CFR 177.1312 - Ethylene-carbon monoxide copolymers.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Ethylene-carbon monoxide copolymers. 177.1312... Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1312 Ethylene-carbon monoxide copolymers. The ethylene-carbon monoxide copolymers identified in paragraph (a) of this section may be...

  6. 21 CFR 177.1312 - Ethylene-carbon monoxide copolymers.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Ethylene-carbon monoxide copolymers. 177.1312... Use Food Contact Surfaces § 177.1312 Ethylene-carbon monoxide copolymers. The ethylene-carbon monoxide... of this section, ethylene-carbon monoxide copolymers (CAS Reg. No. 25052-62-4) consist of the...

  7. 21 CFR 177.1312 - Ethylene-carbon monoxide copolymers.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Ethylene-carbon monoxide copolymers. 177.1312... Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1312 Ethylene-carbon monoxide copolymers. The ethylene-carbon monoxide copolymers identified in paragraph (a) of this section may be...

  8. 21 CFR 177.1312 - Ethylene-carbon monoxide copolymers.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Ethylene-carbon monoxide copolymers. 177.1312... Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1312 Ethylene-carbon monoxide copolymers. The ethylene-carbon monoxide copolymers identified in paragraph (a) of this section may be...

  9. 21 CFR 177.1820 - Styrene-maleic anhydride copolymers.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Styrene-maleic anhydride copolymers. 177.1820... Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1820 Styrene-maleic anhydride copolymers. Styrene-maleic anhydride copolymers identified in paragraph (a) of this section may be...

  10. 40 CFR 721.484 - Fluorinated acrylic copolymer (generic name).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Fluorinated acrylic copolymer (generic... Specific Chemical Substances § 721.484 Fluorinated acrylic copolymer (generic name). (a) Chemical substance... fluorinated acrylic copolymer (PMN P-95-1208) is subject to reporting under this section for the...

  11. 40 CFR 721.484 - Fluorinated acrylic copolymer (generic name).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Fluorinated acrylic copolymer (generic... Specific Chemical Substances § 721.484 Fluorinated acrylic copolymer (generic name). (a) Chemical substance... fluorinated acrylic copolymer (PMN P-95-1208) is subject to reporting under this section for the...

  12. 40 CFR 721.10519 - Perfluoroalkyl acrylate copolymer (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Perfluoroalkyl acrylate copolymer... Specific Chemical Substances § 721.10519 Perfluoroalkyl acrylate copolymer (generic). (a) Chemical... as perfluoroalkyl acrylate copolymer (PMN P-11-63) is subject to reporting under this section for the...

  13. 40 CFR 721.10519 - Perfluoroalkyl acrylate copolymer (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Perfluoroalkyl acrylate copolymer... Specific Chemical Substances § 721.10519 Perfluoroalkyl acrylate copolymer (generic). (a) Chemical... as perfluoroalkyl acrylate copolymer (PMN P-11-63) is subject to reporting under this section for the...

  14. 21 CFR 177.1060 - n-Alkylglutarimide/acrylic copolymers.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false n-Alkylglutarimide/acrylic copolymers. 177.1060... Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1060 n-Alkylglutarimide/acrylic copolymers. n-Alkylglutarimide/acrylic copolymers identified in this section may be safely used as articles...

  15. 21 CFR 177.1060 - n-Alkylglutarimide/acrylic copolymers.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false n-Alkylglutarimide/acrylic copolymers. 177.1060... Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1060 n-Alkylglutarimide/acrylic copolymers. n-Alkylglutarimide/acrylic copolymers identified in this section may be safely used as articles...

  16. Structure Confirmation and Properties of Poly(Dimethylsiloxaneco-diethylsiloxane) Copolymer

    NASA Astrophysics Data System (ADS)

    Gao, Li-Juan; Ma, De-Peng; Feng, Sheng-Yu

    2016-05-01

    High molecular weight poly (dimethylsiloxane-co-diethylsiloxane) (PMES) copolymer was synthesized by anionic ring opening polymerization. Its composition and structures was determined by 29Si NMR spectroscopy. A random microstructure of copolymer was observed in the 29Si NMR spectrum. Further, PMES was characterized by GPC and DSC. The results show that PMES is crystallization-free copolymer with low glass transition temperatures.

  17. pH-sensitive methacrylic copolymers and the production thereof

    DOEpatents

    Mallapragada, Surya K.; Anderson, Brian C.; Bloom, Paul D.; Sheares Ashby, Valerie V.

    2007-01-09

    The present invention provides novel multi-functional methacrylic copolymers that exhibit cationic pH-sensitive behavior as well as good water solubility under acidic conditions. The copolymers are constructed from tertiary amine methacrylates and poly(ethylene glycol) containing methacrylates. The copolymers are useful as gene vectors, pharmaceutical carriers, and in protein separation applications.

  18. pH-sensitive methacrylic copolymers and the production thereof

    DOEpatents

    Mallapragada, Surya K.; Anderson, Brian C.; Bloom, Paul D.; Sheares Ashby, Valerie V.

    2006-02-14

    The present invention provides novel multi-functional methacrylic copolymers that exhibit cationic pH-sensitive behavior as well as good water solubility under acidic conditions. The copolymers are constructed from tertiary amine methacrylates and poly(ethylene glycol) containing methacrylates. The copolymers are useful as gene vectors, pharmaceutical carriers, and in protein separation applications.

  19. 21 CFR 177.1320 - Ethylene-ethyl acrylate copolymers.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Ethylene-ethyl acrylate copolymers. 177.1320... Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1320 Ethylene-ethyl acrylate copolymers. Ethylene-ethyl acrylate copolymers may be safely used to produce packaging materials,...

  20. 21 CFR 177.1350 - Ethylene-vinyl acetate copolymers.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Ethylene-vinyl acetate copolymers. 177.1350... 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...

  1. 21 CFR 177.1950 - Vinyl chloride-ethylene copolymers.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Vinyl chloride-ethylene copolymers. 177.1950... Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1950 Vinyl chloride-ethylene copolymers. The vinyl chloride-ethylene copolymers identified in paragraph (a) of this section may be...

  2. 21 CFR 177.1310 - Ethylene-acrylic acid copolymers.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Ethylene-acrylic acid copolymers. 177.1310 Section... Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1310 Ethylene-acrylic acid copolymers. The ethylene-acrylic acid copolymers identified in paragraph (a) of this section may be...

  3. 21 CFR 177.1350 - Ethylene-vinyl acetate copolymers.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Ethylene-vinyl acetate copolymers. 177.1350... 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...

  4. 21 CFR 177.1320 - Ethylene-ethyl acrylate copolymers.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Ethylene-ethyl acrylate copolymers. 177.1320... Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1320 Ethylene-ethyl acrylate copolymers. Ethylene-ethyl acrylate copolymers may be safely used to produce packaging materials,...

  5. 21 CFR 177.1320 - Ethylene-ethyl acrylate copolymers.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Ethylene-ethyl acrylate copolymers. 177.1320... Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1320 Ethylene-ethyl acrylate copolymers. Ethylene-ethyl acrylate copolymers may be safely used to produce packaging materials,...

  6. 21 CFR 177.1350 - Ethylene-vinyl acetate copolymers.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Ethylene-vinyl acetate copolymers. 177.1350... Use Food Contact Surfaces § 177.1350 Ethylene-vinyl acetate copolymers. Ethylene-vinyl acetate... with the following prescribed conditions: (a)(1) Ethylene-vinyl acetate copolymers consist of...

  7. 21 CFR 177.1060 - n-Alkylglutarimide/acrylic copolymers.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false n-Alkylglutarimide/acrylic copolymers. 177.1060... Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1060 n-Alkylglutarimide/acrylic copolymers. n-Alkylglutarimide/acrylic copolymers identified in this section may be safely used as...

  8. 21 CFR 177.1060 - n-Alkylglutarimide/acrylic copolymers.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true n-Alkylglutarimide/acrylic copolymers. 177.1060... Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1060 n-Alkylglutarimide/acrylic copolymers. n-Alkylglutarimide/acrylic copolymers identified in this section may be safely used as articles...

  9. Block copolymer blend phase behavior: Binary diblock blends and amphiphilic block copolymer/epoxy mixtures

    NASA Astrophysics Data System (ADS)

    Lipic, Paul Martin

    The phase behavior of block copolymers and block copolymer blends has provided an extensive amount of exciting research and industrial applications for over thirty years. However, the unique nanoscale morphologies of microphase separated block copolymer systems is still not completely understood. This thesis examines the phase behavior of diblock copolymers and binary diblock copolymer blends in the strong segregation limit (SSL), and blends of an amphiphilic diblock copolymer with an epoxy resin. Studies of high molecular weight (˜84,000 g/mole) poly(ethylene)-poly(ethyl ethylene) (PE-PEE) diblock copolymers probed the ability of block copolymers to reach equilibrium in the SSL. Samples of pure diblocks or binary diblock blends prepared using different preparation techniques (solvent casting or precipitation) had different phase behaviors, as identified with transmission electron microscopy (TEM) and small-angle x-ray scattering (SAXS), confirming non-equilibrium phase behavior. This non-equilibrium behavior was metastable, and these results identify the caution that should be used when claiming equilibrium phase behavior in the SSL. Blends of an amphiphilic diblock copolymer, poly(ethylene oxide)-poly(ethylene-alt-propylene) (PEO-PEP) with a polymerizable epoxy resin selectively miscible with PEO, poly(Bisphenol-A-co-epichlorohydrin), supported theoretical calculations and increased the understanding of block copolymer/homopolymer blends. These blends formed different ordered structures (lamellae, bicontinuous cubic gyroid, hexagonally packed cylinders, cubic and hexagonally packed spheres) as well as a disordered spherical micellar structure, identified with SAXS and rheological measurements. Addition of hardener, methylene dianiline, to the system resulted in cross-linking of the epoxy resin and formation of a thermoset material. Macrophase separation between the epoxy and block copolymer did not occur, but local expulsion of the PEO from the epoxy was

  10. Microbial Cometabolism and Polyhydroxyalkanoate Co-polymers.

    PubMed

    Ray, Subhasree; Kalia, Vipin Chandra

    2017-03-01

    Polyhydroxyalkanoate (PHAs) are natural, biodegradable biopolymers, which can be produced from renewable materials. PHAs have potential to replace petroleum derived plastics. Quite a few bacteria can produce PHA under nutritional stress. They generally produce homopolymers of butyrate i.e., polyhydroxybutyrate (PHB), as a storage material. The biochemical characteristics of PHB such as brittleness, low strength, low elasticity, etc. make these unsuitable for commercial applications. Co-polymers of PHA, have high commercial value as they overcome the limitations of PHBs. Co-polymers can be produced by supplementing the feed with volatile fatty acids or through hydrolysates of different biowastes. In this review, we have listed the potential bacterial candidates and the substrates, which can be co-metabolized to produce PHA co-polymers.

  11. Rod-Coil Block Polyimide Copolymers

    NASA Technical Reports Server (NTRS)

    Meador, Mary Ann B. (Inventor); Kinder, James D. (Inventor)

    2005-01-01

    This invention is a series of rod-coil block polyimide copolymers that are easy to fabricate into mechanically resilient films with acceptable ionic or protonic conductivity at a variety of temperatures. The copolymers consist of short-rigid polyimide rod segments alternating with polyether coil segments. The rods and coil segments can be linear, branched or mixtures of linear and branched segments. The highly incompatible rods and coil segments phase separate, providing nanoscale channels for ion conduction. The polyimide segments provide dimensional and mechanical stability and can be functionalized in a number of ways to provide specialized functions for a given application. These rod-coil black polyimide copolymers are particularly useful in the preparation of ion conductive membranes for use in the manufacture of fuel cells and lithium based polymer batteries.

  12. Rod-Coil Block Polyimide Copolymers

    NASA Technical Reports Server (NTRS)

    Meador, Mary Ann B. (Inventor); Kinder, James D. (Inventor)

    2005-01-01

    This invention is a series of rod-coil block polyimide copolymers that are easy to fabricate into mechanically resilient films with acceptable ionic or protonic conductivity at a variety of temperatures. The copolymers consist of short-rigid polyimide rod segments alternating with polyether coil segments. The rods and coil segments can be linear, branched or mixtures of linear and branched segments. The highly incompatible rods and coil segments phase separate, providing nanoscale channels for ion conduction. The polyimide segments provide dimensional and mechanical stability and can be functionalized in a number of ways to provide specialized functions for a given application. These rod-coil black polyimide copolymers are particularly useful in the preparation of ion conductive membranes for use in the manufacture of fuel cells and lithium based polymer batteries.

  13. Additive-driven assembly of block copolymers

    NASA Astrophysics Data System (ADS)

    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.

  14. Microphase segregation in molten randomly grafted copolymers

    NASA Astrophysics Data System (ADS)

    Qi, Shuyan; Chakraborty, Arup K.; Balsara, Nitash P.

    2001-08-01

    We study microphase ordering of molten randomly grafted copolymers (RGCs) by using a mean field theory and the replica method to calculate the quenched average. Our results illustrate that in the weak segregation limit (WSI), the optimal wave vector q* of the lamellar phase formed by molten RGCs, has a temperature dependence different from either linear random copolymers (LRCs) or diblock copolymers (DCPs): when close, but below the microphase separation transition (MST) temperature, q* increases sharply with decreasing temperature; then q* gradually acquires an asymptotic value determined by the length of the branch and the average distance between branch points on the backbone. Our results are compared with recent experiments, and the effects of chain architecture on the microphase separation characteristics of RGCs are delineated. Our results suggest a new method for controlling the microphase spacing by exploiting quenched disorder.

  15. Nanoscale Ionic Aggregate Morphology in Zwitterionic Copolymers

    NASA Astrophysics Data System (ADS)

    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.

  16. Structure-property relationships in block copolymers

    NASA Technical Reports Server (NTRS)

    Mcgrath, J. E.

    1976-01-01

    Block copolymers are a class of relatively new materials which contain long sequences of two (or more) chemically different repeat units. Unlike random copolymers, each segment may retain some properties which are characteristic of its homopolymer. It is well known that most physical blends of two different homopolymers are incompatible on a macro-scale. By contrast most block copolymers display only a microphase (eg. 100-200 A domains) separation. Complete separation is restricted because of a loss in configurational entropy. The latter is due to presence of chemical bond(s) between the segments. Novel physical properties can be obtained because it is possible to prepare any desired combination of rubber-like, glassy, or crystalline blocks. The architecture and sequential arrangement of the segments can strongly influence mechanical behavior.

  17. Optical properties of coumarins containing copolymers

    NASA Astrophysics Data System (ADS)

    Skowronski, L.; Krupka, O.; Smokal, V.; Grabowski, A.; Naparty, M.; Derkowska-Zielinska, B.

    2015-09-01

    We investigate the optical properties such as absorption coefficient, refractive index, real and imaginary parts of dielectric function and energy band gap of coumarin-containing copolymers thin films by means of spectroscopic ellipsometry (SE) combined with transmittance measurements (T) and atomic force microscopy (AFM). We found that the optical properties of coumarin-containing copolymers strongly depend from length of alkyl spacer as well as the type of substitution in coumarin moiety. In our case the refractive index as well as the energy band gap of coumarin-containing copolymer decrease with increase the length of alkyl spacer. Additionally, the lengthening of the alkyl spacer brings the bathochromic shifts of the absorption spectra towards longer wavelengths.

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

    NASA Astrophysics Data System (ADS)

    Portner, H.; Bugmann, H.; Wolf, A.

    2010-11-01

    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 well understood. Thus, we performed 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 confidence ranges of the formulations by nonlinear regression analysis based on eight experimental datasets from Northern Hemisphere ecosystems. We sampled over the confidence ranges of the parameters and ran simulations for each pair of temperature response function and calibration site. We analyzed both the long-term and the short-term heterotrophic soil carbon dynamics over a virtual elevation gradient in southern Switzerland. The temperature relationship of Lloyd-Taylor fitted the overall data set best as 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 lack of confidence in the parameter estimates of the temperature response, which increased with increasing temperature, and (2) the size of the simulated soil carbon pools, which increased with elevation, as slower turn-over times lead to higher carbon stocks and higher associated uncertainties. Our results therefore indicate that such projections are more uncertain for higher elevations and hence also higher latitudes, which are of key importance for the global terrestrial carbon budget.

  19. Modeling the Temperature Responses to Spectral Solar Variability on Decadal and Centennial Time Scales

    NASA Astrophysics Data System (ADS)

    Cahalan, R. F.; Wen, G.; Pilewskie, P.; Harder, J. W.

    2010-12-01

    Atmospheric temperature responses to decadal solar variations are computed for two scenarios of solar spectral irradiance (SSI), SIM-based out-of-phase and proxy-based in-phase variations, using a time-dependent radiative-convective model (RCM), and also GISS modelE (GCM.) For both scenarios and both models, maximum responses occur in upper stratosphere, decreasing downward to the surface. Upper stratospheric temperature peak-to-peak responses to out-of-phase forcing are ~0.6 K in RCM and ~0.9 K over tropics in GCM, ~5x as large as responses to in-phase forcing. Stratospheric responses are in-phase with TSI (Total Solar Irradiance). Modeled upper stratospheric temperature responses to SIM-based forcing are similar to 11-year temperature variations observed with HALOE (Halogen Occultation Experiment). For both RCM and GCM, surface responses to the two scenarios are significantly smaller than stratospheric responses. On centennial timescales, SSI variations are poorly known. However, two scenarios of reconstructed TSI, one based on 11-year cycle with background [Lean 2000] and the other on flux transport with much less background [Wang, Lean, and Sheeley, 2005], provide a potential range of TSI variations. We apply phase relations among different SSI bands both from SIM observations and proxy reconstructions to the two scenarios of historical TSI to derive associated historical SSI, which then drives the RCM. The updated atmosphere and ocean mixed coupled RCM including diffusion to deep-ocean provide a first order estimate of temperature responses to SSI variations on centennial time scales. We discuss potential mechanisms for atmosphere-ocean and stratosphere-troposphere couplings responsible for the climate responses to spectral solar variations.

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

    NASA Astrophysics Data System (ADS)

    Li, Y.; De Noblet-Decoudre, N.; Davin, E.; Zeng, N.; Motesharrei, S.; Li, S.; Kalnay, E.; Guo, S.

    2015-12-01

    Previous modeling and observational studies have shown that the biophysical impact of deforestation is warming in the tropics and cooling in extra-tropics. In this study, we performed experiments with an earth system model to investigate how deforestation at various spatial scales affects ground temperature, with emphasis on the latitudinal temperature response and the underlining mechanisms. Results show that the latitudinal pattern of temperature response non-linearly depends 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 region. Incremental forest removal fraction leads to increasingly larger cooling under higher removal fraction in temperate and boreal regions, while the temperature increase saturates in tropical region. The latitudinal and spatial patterns of the temperature response are mainly determined by two processes with competing temperature effects, i.e., decreases in absorbed shortwave radiation and in evapotranspiration (ET). These changes in surface energy balance reflect the important role of background climate on modifying the deforestation impact, because shortwave radiation and precipitation have intrinsic geographical distribution, which constrain the effects of biophysical changes and therefore lead to spatially varying temperature change. For example, wet (dry) climate favors larger (smaller) ET change, thus warming (cooling) is more likely to occur. Further analysis on the contribution of individual biophysical factor (albedo, roughness, and evapotranspiration efficiency) reveals that the latitudinal signature embodied in the temperature change likely arises from background climate conditions rather than from the initial biophysical perturbation.

  1. Long- and short-term temperature responses of microbially-mediated boreal soil organic matter transformations

    NASA Astrophysics Data System (ADS)

    Min, K.; Buckeridge, K. M.; Edwards, K. A.; Ziegler, S. E.; Billings, S. A.

    2015-12-01

    Microorganisms use exoenzymes to decay soil organic matter into assimilable substrates, some of which are transformed into CO2. Microbial CO2 efflux contributes up to 60% of soil respiration, a feature that can change with temperature due to altered exoenzyme activities (short-term) and microbial communities producing different exoenzymes (longer-term). Often, however, microbial temperature responses are masked by factors that also change with temperature in soil, making accurate projections of microbial CO2 efflux with warming challenging. Using soils along a natural climate gradient similar in most respects except for temperature regime (Newfoundland Labrador Boreal Ecosystem Latitudinal Transect), we investigated short-vs. long-term temperature responses of microbially-mediated organic matter transformations. While incubating soils at 5, 15, and 25°C for 84 days, we measured exoenzyme activities, CO2 efflux rates and biomass, and extracted DNA at multiple times. We hypothesized that short-term, temperature-induced increases in exoenzyme activities and CO2 losses would be smaller in soils from warmer regions, because microbes presumably adapted to warmer regions should use assimilable substrates more efficiently and thus produce exoenzymes at a lower rate. While incubation temperature generally induced greater exoenzyme activities (p<0.001), exoenzymes' temperature responses depended on enzymes and regions (p<0.001). Rate of CO2 efflux was affected by incubation temperature (P<0.001), but not by region. Microbial biomass and DNA sequencing will reveal how microbial community abundance and composition change with short-vs. longer-term temperature change. Though short-term microbial responses to temperature suggest higher CO2 efflux and thus lower efficiency of resource use with warming, longer-term adaptations of microbial communities to warmer climates remain unknown; this work helps fill that knowledge gap.

  2. Studies on the application of temperature-responsive ion exchange polymers with whey proteins.

    PubMed

    Maharjan, Pankaj; Campi, Eva M; De Silva, Kirthi; Woonton, Brad W; Jackson, W Roy; Hearn, Milton T W

    2016-03-18

    Several new types of temperature-responsive ion exchange resins of different polymer composition have been prepared by grafting the products from the co-polymerisation of N-phenylacrylamide, N-iso-propylacrylamide and acrylic acid derivatives onto cross-linked agarose. Analysis of the binding isotherms for these different resins obtained under batch adsorption conditions indicated that the resin based on N-iso-propylacrylamide containing 5% (w/w) N-phenylacrylamide and 5% (w/w) acrylic acid resulted in the highest adsorption capacity, Bmax, for the whey protein, bovine lactoferrin, e.g. 14 mg bovine lactoferrin/mL resin at 4 °C and 62 mg bovine lactoferrin/mL resin at 40 °C, respectively. Under dynamic loading conditions at 40 °C, 94% of the loaded bovine lactoferrin on a normalised mg protein per mL resin basis was adsorbed by this new temperature-responsive ion-exchanger, and 76% was eluted by a single cycle temperature shift to 4 °C without varying the composition of the 10mM sodium dihydrogen phosphate buffer, pH 6.5, or the flow rate. The binding characteristics of these different ion exchange resins with bovine lactoferrin were also compared to results obtained using other resins based on N-isopropylacrylamide but contained N-tert-butylacrylamide rather than N-phenylacrylamide, where the corresponding dynamic capture and release properties for bovine lactoferrin required different temperature conditions of 20 °C and 50 °C, respectively for optimal desorption/adsorption. The cationic protein, bovine lactoperoxidase, was also adsorbed and desorbed with these temperature-responsive resins under similar conditions of changing temperature, whereas the anionic protein, bovine β-lactoglobulin, was not adsorbed under this regime of temperature conditions but instead eluted in the flow-through.

  3. Altitudinal changes in temperature responses of net photosynthesis and dark respiration in tropical bryophytes.

    PubMed

    Wagner, Sebastian; Zotz, Gerhard; Salazar Allen, Noris; Bader, Maaike Y

    2013-03-01

    There is a conspicuous increase of poikilohydric organisms (mosses, liverworts and macrolichens) with altitude in the tropics. This study addresses the hypothesis that the lack of bryophytes in the lowlands is due to high-temperature effects on the carbon balance. In particular, it is tested experimentally whether temperature responses of CO(2)-exchange rates would lead to higher respiratory carbon losses at night, relative to potential daily gains, in lowland compared with lower montane forests. Gas-exchange measurements were used to determine water-, light-, CO(2)- and temperature-response curves of net photosynthesis and dark respiration of 18 tropical bryophyte species from three altitudes (sea level, 500 m and 1200 m) in Panama. Optimum temperatures of net photosynthesis were closely related to mean temperatures in the habitats in which the species grew at the different altitudes. The ratio of dark respiration to net photosynthesis at mean ambient night and day temperatures did not, as expected, decrease with altitude. Water-, light- and CO(2)-responses varied between species but not systematically with altitude. Drivers other than temperature-dependent metabolic rates must be more important in explaining the altitudinal gradient in bryophyte abundance. This does not discard near-zero carbon balances as a major problem for lowland species, but the main effect of temperature probably lies in increasing evaporation rates, thus restricting the time available for photosynthetic carbon gain, rather than in increasing nightly respiration rates. Since optimum temperatures for photosynthesis were so fine tuned to habitat temperatures we analysed published temperature responses of bryophyte species worldwide and found the same pattern on the large scale as we found along the tropical mountain slope we studied.

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

    NASA Astrophysics Data System (ADS)

    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. Altitudinal changes in temperature responses of net photosynthesis and dark respiration in tropical bryophytes

    PubMed Central

    Wagner, Sebastian; Zotz, Gerhard; Salazar Allen, Noris; Bader, Maaike Y.

    2013-01-01

    Background and Aims There is a conspicuous increase of poikilohydric organisms (mosses, liverworts and macrolichens) with altitude in the tropics. This study addresses the hypothesis that the lack of bryophytes in the lowlands is due to high-temperature effects on the carbon balance. In particular, it is tested experimentally whether temperature responses of CO2-exchange rates would lead to higher respiratory carbon losses at night, relative to potential daily gains, in lowland compared with lower montane forests. Methods Gas-exchange measurements were used to determine water-, light-, CO2- and temperature-response curves of net photosynthesis and dark respiration of 18 tropical bryophyte species from three altitudes (sea level, 500 m and 1200 m) in Panama. Key Results Optimum temperatures of net photosynthesis were closely related to mean temperatures in the habitats in which the species grew at the different altitudes. The ratio of dark respiration to net photosynthesis at mean ambient night and day temperatures did not, as expected, decrease with altitude. Water-, light- and CO2-responses varied between species but not systematically with altitude. Conclusions Drivers other than temperature-dependent metabolic rates must be more important in explaining the altitudinal gradient in bryophyte abundance. This does not discard near-zero carbon balances as a major problem for lowland species, but the main effect of temperature probably lies in increasing evaporation rates, thus restricting the time available for photosynthetic carbon gain, rather than in increasing nightly respiration rates. Since optimum temperatures for photosynthesis were so fine tuned to habitat temperatures we analysed published temperature responses of bryophyte species worldwide and found the same pattern on the large scale as we found along the tropical mountain slope we studied. PMID:23258418

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

    PubMed

    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.

  7. Simulation of pressure and temperature responses for the 20 Inch Supersonic Wind Tunnel

    NASA Technical Reports Server (NTRS)

    Motter, Mark A.

    1990-01-01

    A simulation of the pressure and temperature responses of the 20 inch Supersonic Wind Tunnel (SWT) is developed. The simulation models the tunnel system as a set of lumped parameter volumes connected by flow regulating elements such as valves and nozzles. Simulated transient responses of temperature and pressure for the five boundary points of the 20 inch SWT operating map are produced from their respective initial conditions, tunnel operating conditions, heater input power, and valve positions. Upon reaching steady state, a linearized model for each operating point is determined. Both simulated and actual tunnel responses are presented for comparison.

  8. Temperature response of denitrification rate and greenhouse gas production in agricultural river marginal wetland soils.

    PubMed

    Bonnett, S A F; Blackwell, M S A; Leah, R; Cook, V; O'Connor, M; Maltby, E

    2013-05-01

    Soils are predicted to exhibit significant feedback to global warming via the temperature response of greenhouse gas (GHG) production. However, the temperature response of hydromorphic wetland soils is complicated by confounding factors such as oxygen (O2 ), nitrate (NO3-) and soil carbon (C). We examined the effect of a temperature gradient (2-25 °C) on denitrification rates and net nitrous oxide (N2 O), methane (CH4 ) production and heterotrophic respiration in mineral (Eutric cambisol and Fluvisol) and organic (Histosol) soil types in a river marginal landscape of the Tamar catchment, Devon, UK, under non-flooded and flooded with enriched NO3- conditions. It was hypothesized that the temperature response is dependent on interactions with NO3--enriched flooding, and the physicochemical conditions of these soil types. Denitrification rate (mean, 746 ± 97.3 μg m(-2)  h(-1) ), net N2 O production (mean, 180 ± 26.6 μg m(-2)  h(-1) ) and net CH4 production (mean, 1065 ± 183 μg m(-2)  h(-1) ) were highest in the organic Histosol, with higher organic matter, ammonium and moisture, and lower NO3- concentrations. Heterotrophic respiration (mean, 127 ± 4.6 mg m(-2)  h(-1) ) was not significantly different between soil types and dominated total GHG (CO2 eq) production in all soil types. Generally, the temperature responses of denitrification rate and net N2 O production were exponential, whilst net CH4 production was unresponsive, possibly due to substrate limitation, and heterotrophic respiration was exponential but limited in summer at higher temperatures. Flooding with NO3- increased denitrification rate, net N2 O production and heterotrophic respiration, but a reduction in net CH4 production suggests inhibition of methanogenesis by NO3- or N2 O produced from denitrification. Implications for management and policy are that warming and flood events may promote microbial interactions in soil between distinct microbial communities and increase

  9. Application of the Taylor transformation to the transient temperature response of an annular fin

    SciTech Connect

    Yu, L.T.; Chen, C.K.

    1999-01-01

    This article presents the transient temperature response of a convective-radiative rectangular profile annular fin under a step temperature change occurring in its base. A convection-radiation fin tip is considered. The nonlinear transient heat transfer and boundary conditions are solved by using the hybrid method of Taylor transformation and finite-difference approximation. Also, time domain is controlled by Taylor transformation, and the spatial coordinates are handled by finite-difference approximation. Temperature distribution is implemented by employing natural cubic spline fitting.

  10. [Hydrodynamic properties of exopolysaccharide-acrylamide copolymer].

    PubMed

    Votselko, S K

    2000-01-01

    The method for producing copolymer EPAA of exopolysaccharide (EPS)--polyacrylamide (PAA) has been presented which was based on microbial exopolysaccharides (enposane, xampane), their mixture and model EPS (xanthane sigma, rodopol P-23). The copolymer was produced by acrylamide polymerization in 1-2% water solutions of polysaccharides, the concentration of acrylamide in the reaction mixture being 4.7-2% and that of polysaccharides 0.1-1% of the weight. Hydrodynamic parameters of the studied polymers have been determined, their heterogenity as to molecular-weight characteristics has been demonstrated. Molecular-weight distribution of copolymers showed that the content of low-molecular fractions decreased, thus the Mw values were (0.08-0.2) x 10(6) Da in contrast to that of exopolysaccharides possessing Mw (1.2-0.4) x 10(6) Da and of polyacrylamide possessing Mw within (2-30) x 10(6) Da. The value of efficient viscosity of copolymers ranged from 120 to 131 mPa.s that was lower than that of polyacrylamide (500 mPa.s), and higher than that of exopolysaccharides (42 mPa.s), and it depended on the sample, raw material, production conditions. A possibility has been shown to produce a new copolymer based on microbial polysaccharides enposane and xampane in the process of acrylamide polymerization. It has been found out that the studied copolymers EPAA differ from initial ones as to their hydrodynamical properties, which determines their preference: better solubility, good glueing properties, prolonged term of preservation, resistance to bacterial pollution.

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

    PubMed

    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

  12. Dynamics of Block Copolymer Nanocomposites

    SciTech Connect

    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.

  13. Simultaneously Physically and Chemically Gelling Polymer System utilizing a poly(NIPAAm-co-cysteamine) Based Copolymer

    PubMed Central

    Robb, Stephanie A.; Lee, Bae Hoon; McLemore, Ryan; Vernon, Brent L.

    2010-01-01

    The objective of this work is to create an in situ physically and chemically cross-linking hydrogel for in vivo applications. N-isopropylacrylamide (NIPAAm) was copolymerized with N-acryloxysuccinimide (NASI) via free radical polymerization. Poly(NIPAAm-co-NASI) was further modified to obtain Poly(NIPAAm-co-cysteamine) through a nucleophilic attack on the carbonyl group of the NASI by the amine group of the cysteamine. Modification was verified by nuclear magnetic resonance. In addition to thermo-responsive physical gelling due to the presence of NIPAAm, this system also chemically gels via a Michael-Type addition reaction when mixed with poly(ethylene glycol) diacrylate (PEGDA). The presence of both physical and chemical gelation resulted in material properties that are much improved compared to purely physical gels. The chemical gelation time of the copolymers was not significantly affected by the amount of thiol present due to the increased pKa of the copolymer containing more thiols. In addition, the swelling of the copolymers was highly dependent on temperature and thiol content. Lastly, the rate of nucleophilic attack in the Michael-Type addition reaction was shown to be highly dependent on pH and on the mole ratio of thiol to acrylate. Due to the improved mechanical properties, this material may be better suited for long-term functional replacement applications than other thermo-sensitive physical gels. With further development and biocompatibility testing, this material could potentially be applied as a temperature-responsive injectable biomaterial for functional embolization. PMID:17567067

  14. Co-polymer Films for Sensors

    NASA Technical Reports Server (NTRS)

    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.

  15. Co-polymer films for sensors

    NASA Technical Reports Server (NTRS)

    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)

    2010-01-01

    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.

  16. New functionalized block copolymers for bonding copper to epoxy

    SciTech Connect

    Kent, M.; Saunders, R.; Emerson, J.; Hurst, M.

    1995-11-01

    The authors are exploring the use of functionalized block copolymers for bonding copper to epoxy in printed wiring boards. The program involves four key elements: (i) synthesis of suitable functionalized block copolymers; (ii) characterization of the conformation of the copolymers at the relevant interfaces by neutron reflectivity; (iii) spectroscopic measurements of chemical bonding, and (iv) measurement of the mechanical properties of the interfaces. The copolymers are synthesized by living, ring-opening metathesis polymerization. This relatively new technique allows great flexibility for synthesis of functionalized block copolymers in that the initiators are relatively insensitive to a wide range of functional groups. Significant adhesion enhancement has been observed in lap shear tests.

  17. Electrochemical and spectroscopic characterization of poly (bithiophene + 2-methylfuran) copolymer

    NASA Astrophysics Data System (ADS)

    Lamiri, Leila; Nessark, Belkacem; Habelhames, Farid; Sibous, Lakhdar

    2017-09-01

    In this work, Poly(bithiophene + 2-methylfuran) copolymer was successfully synthetized by an electrochemical polymerization of two monomers, bithiophene and 2-methylfuran in acetonitrile containing lithium perchlorate. The obtained copolymer was characterized via cyclic voltammetry, impedance spectroscopy, UV-visible, scanning electron microscope, conductivity and photocurrent measurements. The cyclic voltammetry study showed two redox couples characteristic of Poly (bithiophene + 2-methylfuran) copolymer. The impedance spectroscopy study revealed that the resistance of the copolymer film increases with the addition of 2-methylfuran. The photocurrent measurement showed good photoelectrochemical properties, making this copolymer an ideal candidate for photovoltaic cell applications.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  20. Modeling and Experimental Analysis on the Temperature Response of AlN-Film Based SAWRs

    PubMed Central

    Chen, Shuo; You, Zheng

    2016-01-01

    The temperature responses of aluminum nitride (AlN) based surface acoustic wave resonator (SAWR) are modeled and tested. The modeling of the electrical performance is based on a modified equivalent circuit model introduced in this work. For SAWR consisting of piezoelectric film and semiconducting substrate, parasitic parameters from the substrate is taken into consideration for the modeling. By utilizing the modified model, the high temperature electrical performance of the AlN/Si and AlN/6H-SiC based SAWRs can be predicted, indicating that a substrate with a wider band gap will lead to a more stable high temperature behavior, which is further confirmed experimentally by high temperature testing from 300 K to 725 K with SAWRs having a wavelength of 12 μm. Temperature responses of SAWR’s center frequency are also calculated and tested, with experimental temperature coefficient factors (TCF) of center frequency being −29 ppm/K and −26 ppm/K for the AlN/Si and AlN/6H-SiC based SAWRs, which are close to the predicted values. PMID:27483286

  1. Plant nanobionic materials with a giant temperature response mediated by pectin-Ca2+.

    PubMed

    Di Giacomo, Raffaele; Daraio, Chiara; Maresca, Bruno

    2015-04-14

    Conventional approaches to create biomaterials rely on reverse engineering of biological structures, on biomimicking, and on bioinspiration. Plant nanobionics is a recent approach to engineer new materials combining plant organelles with synthetic nanoparticles to enhance, for example, photosynthesis. Biological structures often outperform man-made materials. For example, higher plants sense temperature changes with high responsivity. However, these properties do not persist after cell death. Here, we permanently stabilize the temperature response of isolated plant cells adding carbon nanotubes (CNTs). Interconnecting cells, we create materials with an effective temperature coefficient of electrical resistance (TCR) of -1,730% K(-1), ∼2 orders of magnitude higher than the best available sensors. This extreme temperature response is due to metal ions contained in the egg-box structure of the pectin backbone, lodged between cellulose microfibrils. The presence of a network of CNTs stabilizes the response of cells at high temperatures without decreasing the activation energy of the material. CNTs also increase the background conductivity, making these materials suitable elements for thermal and distance sensors.

  2. Plant nanobionic materials with a giant temperature response mediated by pectin-Ca2+

    PubMed Central

    Di Giacomo, Raffaele; Daraio, Chiara; Maresca, Bruno

    2015-01-01

    Conventional approaches to create biomaterials rely on reverse engineering of biological structures, on biomimicking, and on bioinspiration. Plant nanobionics is a recent approach to engineer new materials combining plant organelles with synthetic nanoparticles to enhance, for example, photosynthesis. Biological structures often outperform man-made materials. For example, higher plants sense temperature changes with high responsivity. However, these properties do not persist after cell death. Here, we permanently stabilize the temperature response of isolated plant cells adding carbon nanotubes (CNTs). Interconnecting cells, we create materials with an effective temperature coefficient of electrical resistance (TCR) of −1,730% K−1, ∼2 orders of magnitude higher than the best available sensors. This extreme temperature response is due to metal ions contained in the egg-box structure of the pectin backbone, lodged between cellulose microfibrils. The presence of a network of CNTs stabilizes the response of cells at high temperatures without decreasing the activation energy of the material. CNTs also increase the background conductivity, making these materials suitable elements for thermal and distance sensors. PMID:25825744

  3. Direct measurement of transcription rates reveals multiple mechanisms for configuration of the Arabidopsis ambient temperature response.

    PubMed

    Sidaway-Lee, Kate; Costa, Maria J; Rand, David A; Finkenstadt, Bärbel; Penfield, Steven

    2014-03-03

    Sensing and responding to ambient temperature is important for controlling growth and development of many organisms, in part by regulating mRNA levels. mRNA abundance can change with temperature, but it is unclear whether this results from changes in transcription or decay rates, and whether passive or active temperature regulation is involved. Using a base analog labelling method, we directly measured the temperature coefficient, Q10, of mRNA synthesis and degradation rates of the Arabidopsis transcriptome. We show that for most genes, transcript levels are buffered against passive increases in transcription rates by balancing passive increases in the rate of decay. Strikingly, for temperature-responsive transcripts, increasing temperature raises transcript abundance primarily by promoting faster transcription relative to decay and not vice versa, suggesting a global transcriptional process exists that controls mRNA abundance by temperature. This is partly accounted for by gene body H2A.Z which is associated with low transcription rate Q10, but is also influenced by other marks and transcription factor activities. Our data show that less frequent chromatin states can produce temperature responses simply by virtue of their rarity and the difference between their thermal properties and those of the most common states, and underline the advantages of directly measuring transcription rate changes in dynamic systems, rather than inferring rates from changes in mRNA abundance.

  4. Recent development of temperature-responsive surfaces and their application for cell sheet engineering

    PubMed Central

    Tang, Zhonglan; Okano, Teruo

    2014-01-01

    Cell sheet engineering, which fabricates sheet-like tissues without biodegradable scaffolds, has been proposed as a novel approach for tissue engineering. Cells have been cultured and proliferate to confluence on a temperature-responsive cell culture surface at 37°C. By decreasing temperature to 20°C, an intact cell sheet can be harvested from the culture surface without enzymatic treatment. This new approach enables cells to keep their cell–cell junction, cell surface proteins and extracellular matrix. Therefore, recovered cell sheet can be easily not only transplanted to host tissue, but also constructed a three-dimensional (3D) tissue by layering cell sheets. Moreover, cell sheet manipulation technology and bioreactor have been combined with the cell sheet technology to fabricate a complex and functional 3D tissue in vitro. So far, cell sheet technology has been applied in regenerative medicine for several tissues, and a number of clinical studies have been performed. In this review, recent advances in the preparation of temperature-responsive cell culture surface, the fabrication of organ-like tissue and the clinical application of cell sheet engineering are summarized and discussed. PMID:26816628

  5. Phenotyping carrot (Daucus carota L.) for yield-determining temperature response by calorespirometry.

    PubMed

    Nogales, Amaia; Muñoz-Sanhueza, Luz; Hansen, Lee D; Arnholdt-Schmitt, Birgit

    2015-02-01

    Calorespirometric measurements proved to be useful for phenotyping temperature response in terms of optimum temperatures for growth and low temperature limits for growth respiration in diverse carrot genotypes. High and low-temperature tolerance is an important trait in many breeding programs, but to date, improvement strategies have had limited success. Developing new, cost efficient and reliable screening tools to identify and select the most tolerant crop plant genotypes is necessary to assist plant breeding on cold and heat tolerance, and calorespirometry is proposed for this. Calorespirometry is a technique to simultaneously measure metabolic heat rates and CO2 emission rates of respiring tissues and can be used as a rapid method to determine how changes in the environment (e.g., temperature) influence plant growth. The main aim of this work was, therefore, to test the usefulness of calorespirometry as a phenotyping tool for carrot taproot growth in response to temperature. Calorespirometric measurements in the carrot taproot meristems of plants from eight carrot inbred lines allowed identification of optimum and minimum temperatures for growth of plants and to distinguish between phenotypes based on those characteristics. The technique proved to be useful for predicting yield-determining temperature responses in diverse carrot genotypes. Preliminary screening of new crop plant genotypes with calorespirometry based on their temperature adaptation and acclimation capability could make the screening process much less laborious by allowing selection of genotypes presenting the best growth performance under particular biotic or abiotic conditions before field tests.

  6. Quantifying stream temperature response to environmental change in a groundwater-dominated catchment, Alberta, Canada

    NASA Astrophysics Data System (ADS)

    MacDonald, R.; Byrne, J. M.; Boon, S.

    2012-12-01

    The ecological significance of steam temperature response to environmental change has been discussed in many recent studies across a range of disciplines. We couple a stream energy and mass balance model with a catchment-scale hydrometeorological model to quantify stream temperature response to environmental change in a groundwater-dominated catchment. Given the importance of surface-subsurface interactions in simulating stream temperature, we propose a baseflow separation technique to parameterize these interactions within the model. This method forms the basis of a catchment-scale modelling approach designed specifically for data sparse regions. Using this approach we applied a sensitivity analysis to examine the effects of forest disturbance (harvest with riparian buffer) and climate change (mean air temperature and precipitation change for the 2040-2069 period) on stream temperature. We find that stream temperature following forest disturbance and climate change is primarily affected by a predicted shift towards earlier snowmelt runoff timing, which advances subsurface recharge early in the spring and subsequently decreases subsurface discharge in the summer, fall and winter. Changes in seasonal stream temperature regime may have important ecological consequences, particularly during the spawning and rearing stages of the salmonid lifecycle.

  7. Surveying Rubisco Diversity and Temperature Response to Improve Crop Photosynthetic Efficiency.

    PubMed

    Orr, Douglas J; Alcântara, André; Kapralov, Maxim V; Andralojc, P John; Carmo-Silva, Elizabete; Parry, Martin A J

    2016-10-01

    The threat to global food security of stagnating yields and population growth makes increasing crop productivity a critical goal over the coming decades. One key target for improving crop productivity and yields is increasing the efficiency of photosynthesis. Central to photosynthesis is Rubisco, which is a critical but often rate-limiting component. Here, we present full Rubisco catalytic properties measured at three temperatures for 75 plants species representing both crops and undomesticated plants from diverse climates. Some newly characterized Rubiscos were naturally "better" compared to crop enzymes and have the potential to improve crop photosynthetic efficiency. The temperature response of the various catalytic parameters was largely consistent across the diverse range of species, though absolute values showed significant variation in Rubisco catalysis, even between closely related species. An analysis of residue differences among the species characterized identified a number of candidate amino acid substitutions that will aid in advancing engineering of improved Rubisco in crop systems. This study provides new insights on the range of Rubisco catalysis and temperature response present in nature, and provides new information to include in models from leaf to canopy and ecosystem scale.

  8. Surveying Rubisco Diversity and Temperature Response to Improve Crop Photosynthetic Efficiency1[OPEN

    PubMed Central

    Andralojc, P. John

    2016-01-01

    The threat to global food security of stagnating yields and population growth makes increasing crop productivity a critical goal over the coming decades. One key target for improving crop productivity and yields is increasing the efficiency of photosynthesis. Central to photosynthesis is Rubisco, which is a critical but often rate-limiting component. Here, we present full Rubisco catalytic properties measured at three temperatures for 75 plants species representing both crops and undomesticated plants from diverse climates. Some newly characterized Rubiscos were naturally “better” compared to crop enzymes and have the potential to improve crop photosynthetic efficiency. The temperature response of the various catalytic parameters was largely consistent across the diverse range of species, though absolute values showed significant variation in Rubisco catalysis, even between closely related species. An analysis of residue differences among the species characterized identified a number of candidate amino acid substitutions that will aid in advancing engineering of improved Rubisco in crop systems. This study provides new insights on the range of Rubisco catalysis and temperature response present in nature, and provides new information to include in models from leaf to canopy and ecosystem scale. PMID:27342312

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

    PubMed

    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.

  10. Mixing thermodynamics of block-random copolymers

    NASA Astrophysics Data System (ADS)

    Beckingham, Bryan Scott

    Random copolymerization of A and B monomers represents a versatile method to tune interaction strengths between polymers, as ArB random copolymers will exhibit a smaller effective Flory interaction parameter chi; (or interaction energy density X) upon mixing with A or B homopolymers than upon mixing A and B homopolymers with each other, and the ArB composition can be tuned continuously. Thus, the incorporation of a random copolymer block into the classical block copolymer architecture to yield "block-random" copolymers introduces an additional tuning mechanism for the control of structure-property relationships, as the interblock interactions and physical properties can be tuned continuously through the random block's composition. However, typical living or controlled polymerizations produce compositional gradients along the "random" block, which can in turn influence the phase behavior. This dissertation demonstrates a method by which narrow-distribution copolymers of styrene and isoprene of any desired composition, with no measurable down-chain gradient, are synthesized. This synthetic method is then utilized to incorporate random copolymers of styrene and isoprene as blocks into block-random copolymers in order to examine the resulting interblock mixing thermodynamics. A series of well-defined near-symmetric block and block-random copolymers (S-I, Bd-S, I-SrI, S-SrI and Bd-S rI diblocks, where S is polystyrene, I is polyisoprene and Bd is polybutadiene), with varying molecular weight and random-block composition are synthesized and the mixing thermodynamics---via comparison of their interaction energy densities, X---of their hydrogenated derivatives is examined through measurement of the order-disorder transition (ODT) temperature. Hydrogenated derivatives of I-SrI and S-SrI block-random copolymers, both wherein the styrene aromaticity is retained and derivatives wherein the styrene units are saturated to vinylcyclohexane (VCH), are found to hew closely to the

  11. Block copolymer nanolithography for the fabrication of patterned media.

    SciTech Connect

    Warke, Vishal V; Bakker, Martin G; Hong, Kunlun; Mays, Jimmy; Britt, Phillip F; Li, Xuefa; Wang, Jin

    2008-01-01

    Abstract Bit patterned perpendicular media has the potential to increase the density of magnetic recording beyond what can be achieved by granular media. Self assembling diblock copolymers are of interest as templates for patterned media, as they potentially provide a low cost fabrication route. A method to fabricate the desired pattern using cylinder forming diblock copolymers of (PS-b-PMMA) as template is reported. Upon phase separation hexagonally packed cylinders of the minority phase (PMMA) surrounded by the continuous majority phase (PS) are obtained. The processing sequence began with spin coating the block copolymer on a suitable substrate, followed by annealing the block copolymer thin film in vacuum to orient it perpendicular to the substrate. Block copolymer templates were obtained by glacial acetic acid treatment which opened the pores in the block copolymer thin film. Ni was electrodeposited in the block copolymer templates and this pattern was then transferred onto the underlying substrate by ion milling

  12. Acrylamide/acrylic acid copolymers for cement fluid loss control

    SciTech Connect

    McKenzie, L.F.; McElfresh, P.M.

    1982-01-01

    Acrylamide/acrylic acid copolymers are considered as effective fluid loss control additives in a wide range of oil well cements. Unlike HEC based fluid loss aditives, these copolymers can be used with calcium chloride accelerator without significantly influencing fluid loss control. Another advantage of the copolymers is that the amount of fluid loss for a given concentration of polymer remains relatively constant over a wide range of temperatures. The use of acrylamide/acrylic acid copolymers has generally been restricted to wells below 60 degree C BHCT. Above that temperature chemical changes in the copolymer often lead to retardation of the cement. This paper presents data related to the use of acrylamide/acrylic acid copolymers as fluid loss control agents in oil well cementing. A comparison of these polymers with HEC based fluid loss control additives is made. In addition, data related to the cause of acrylamide/acrylic acid copolymer retarding effects is presented. 4 refs.

  13. Solid-supported block copolymer membranes through interfacial adsorption of charged block copolymer vesicles.

    PubMed

    Rakhmatullina, Ekaterina; Meier, Wolfgang

    2008-06-17

    The properties of amphiphilic block copolymer membranes can be tailored within a wide range of physical parameters. This makes them promising candidates for the development of new (bio)sensors based on solid-supported biomimetic membranes. Here we investigated the interfacial adsorption of polyelectrolyte vesicles on three different model substrates to find the optimum conditions for formation of planar membranes. The polymer vesicles were made from amphiphilic ABA triblock copolymers with short, positively charged poly(2,2-dimethylaminoethyl methacrylate) (PDMAEMA) end blocks and a hydrophobic poly( n-butyl methacrylate) (PBMA) middle block. We observed reorganization of the amphiphilic copolymer chains from vesicular structures into a 1.5+/-0.04 nm thick layer on the hydrophobic HOPG surface. However, this film starts disrupting and dewetting upon drying. In contrast, adsorption of the vesicles on the negatively charged SiO2 and mica substrates induced vesicle fusion and formation of planar, supported block copolymer films. This process seems to be controlled by the surface charge density of the substrate and concentration of the block copolymers in solution. The thickness of the copolymer membrane on mica was comparable to the thickness of phospholipid bilayers.

  14. Chiral Block Copolymer Structures for Metamaterial Applications

    DTIC Science & Technology

    2015-01-27

    transformation. 15. SUBJECT TERMS Block Copolymers, Chiral Metamaterials, Gyroids, Nanotechnology, Nanoporous Materials , Networks...Chiral Metamaterials, Gyroids, Nanotechnology, Nanoporous Materials , Networks 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT Same as... nanoporous materials for templating, in particular with network morphologies, as templates could be developed. BCPs comprising chiral entities were

  15. 21 CFR 173.65 - Divinylbenzene copolymer.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... subjected to pre-use extraction with a water soluble alcohol until the level of divinylbenzene in the..._locations.html. The copolymer is then treated with water according to the manufacturer's recommendation to remove the extraction solvent to guarantee a food-grade purity of the resin at the time of use, in...

  16. 21 CFR 173.65 - Divinylbenzene copolymer.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... subjected to pre-use extraction with a water soluble alcohol until the level of divinylbenzene in the..._locations.html. The copolymer is then treated with water according to the manufacturer's recommendation to remove the extraction solvent to guarantee a food-grade purity of the resin at the time of use, in...

  17. 21 CFR 173.65 - Divinylbenzene copolymer.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... subjected to pre-use extraction with a water soluble alcohol until the level of divinylbenzene in the..._locations.html. The copolymer is then treated with water according to the manufacturer's recommendation to remove the extraction solvent to guarantee a food-grade purity of the resin at the time of use, in...

  18. Copolymer sealant compositions and method for making

    NASA Technical Reports Server (NTRS)

    Singh, Navjot (Inventor); Leman, John Thomas (Inventor); Whitney, John M. (Inventor); Krabbenhoft, Herman Otto (Inventor)

    2003-01-01

    Condensation curable poly(fluoroorgano)siloxane-poly(silarylene)siloxane block copolymer compositions having a glass transition temperature not exceeding about -54.degree. C. and excellent solvent resistance have been found useful as sealants. Polyalkoxysilylorgano compounds, such as 1,4-bis[trimethoxysilyl(ethyl)]benzene have been found to be effective as cross-linkers.

  19. Copolymer sealant compositions and method for making

    NASA Technical Reports Server (NTRS)

    Singh, Navjot (Inventor); Leman, John Thomas (Inventor); Whitney, John M. (Inventor); Krabbenhoft, Herman Otto (Inventor)

    2004-01-01

    Condensation curable poly(fluoroorgano)siloxane-poly(silarylene)siloxane block copolymer compositions having a glass transition temperature not exceeding about -54.degree. C. and excellent solvent resistance have been found useful as sealants. Polyalkoxysilylorgano compounds, such as 1,4-bis[trimethoxysilyl(ethyl)]benzene have been found to be effective as cross-linkers.

  20. Copolymer sealant compositions and method for making

    NASA Technical Reports Server (NTRS)

    Singh, Navjot (Inventor); Leman, John Thomas (Inventor); Whitney, John M. (Inventor); Krabbenhoft, Herman Otto (Inventor)

    2002-01-01

    Condensation curable poly(fluoroorgano)siloxane-poly(silarylene)siloxane block copolymer compositions having a glass transition temperature not exceeding about -54.degree. C. and excellent solvent resistance have been found useful as sealants. Polyalkoxysilylorgano compounds, such as 1,4-bis[trimethoxysilyl(ethyl)]benzene have been found to be effective as cross-linkers.

  1. 21 CFR 173.65 - Divinylbenzene copolymer.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... subjected to pre-use extraction with a water soluble alcohol until the level of divinylbenzene in the..._locations.html. The copolymer is then treated with water according to the manufacturer's recommendation to... with food only of Types I, II, and VI-B (excluding carbonated beverages) described in table 1 of...

  2. Amphiphilic block copolymer nanocontainers as bioreactors

    NASA Astrophysics Data System (ADS)

    Nardin, C.; Widmer, J.; Winterhalter, M.; Meier, W.

    2001-04-01

    Self-assembly of an amphiphilic triblock copolymer carrying polymerizable end-groups is used to prepare nanometer-sized vesicular structures in aqueous solution. The triblock copolymer shells of the vesicles can be regarded as a mimetic of biological membranes although they are 2 to 3 times thicker than a conventional lipid bilayer. Nevertheless, they can serve as a matrix for membrane-spanning proteins. Surprisingly, the proteins remain functional despite the extreme thickness of the membranes and that even after polymerization of the reactive triblock copolymers. This opens a new field to create mechanically stable protein/polymer hybrid membranes. As a representative example we functionalize (polymerized) triblock copolymer vesicles by reconstituting a channel-forming protein from the outer cell wall of Gram-negative bacteria. The protein used (OmpF) acts as a size-selective filter, which allows only for passage of molecules with a molecular weight below 400 g mol^{-1}. Therefore substrates may still have access to enzymes encapsulated in such protein/polymer hybrid nanocontainers. We demonstrate this using the enzyme β -lactamase which is able to hydrolyze the antibiotic ampicillin. In addition, a transmembrane voltage above a given threshold causes a reversible gating transition of OmpF. This can be used to reversibly activate or deactivate the resulting nanoreactors.

  3. 21 CFR 173.65 - Divinylbenzene copolymer.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Divinylbenzene copolymer. 173.65 Section 173.65 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) SECONDARY DIRECT FOOD ADDITIVES PERMITTED IN FOOD FOR HUMAN CONSUMPTION Polymer Substances and Polymer...

  4. 21 CFR 180.22 - Acrylonitrile copolymers.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Acrylonitrile copolymers. 180.22 Section 180.22 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD ADDITIVES PERMITTED IN FOOD OR IN CONTACT WITH FOOD ON AN INTERIM BASIS PENDING ADDITIONAL STUDY Specific...

  5. 21 CFR 177.2470 - Polyoxymethylene copolymer.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... molecular weight of the copolymer is 15,000 as determined by a method titled “Number Average Molecular... particles that pass through a U.S.A. Standard Sieve No. 6 and that are retained on a U.S.A. Standard Sieve...

  6. 21 CFR 177.2470 - Polyoxymethylene copolymer.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... molecular weight of the copolymer is 15,000 as determined by a method titled “Number Average Molecular... particles that pass through a U.S.A. Standard Sieve No. 6 and that are retained on a U.S.A. Standard Sieve...

  7. Block copolymer/ferroelectric nanoparticle nanocomposites

    NASA Astrophysics Data System (ADS)

    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

  8. Temperature Responses to Spectral Solar Variability on Decadal and Centennial Time Scales

    NASA Astrophysics Data System (ADS)

    Cahalan, Robert; Wen, Guoyong; Pilewskie, Peter; Harder, Jerald

    2010-05-01

    We apply two scenarios of 11-year solar spectral forcing, namely SIM-based out-of-phase variations and proxy-based in-phase variations, as input to a time-dependent radiative-convective model (RCM), and also to the GISS modelE GCM. For both scenarios, and both models, we find that the maximum temperature response occurs in the upper stratosphere, and temperature responses decrease downward to the surface. The upper stratospheric temperature peak-to-peak responses to out-of-phase solar forcing are ~0.6 K in RCM and ~0.9 K over the tropical region in GCM simulations, a factor of ~5 times as large as responses to in-phase solar forcing. Stratospheric responses are in-phase with TSI (Total Solar Irradiance) variations. The modeled upper stratospheric temperature response to the SORCE SIM observed SSI (Spectral Solar Irradiance) forcing resembles 11-year temperature variations observed with HALOE (Halogen Occultation Experiment). Surface responses to the two SSI scenarios are small for both RCM and GCM studies, as compared to stratospheric responses. Though solar irradiance variations on centennial time scale are not well known, the two scenarios of reconstructed TSI time series (i.e., one based on 11-year cycles with background [Lean 2000] and the second from flux transport that has much less background change [Wang, Lean, and Sheeley, 2005]) provide a range of variations of TSI on centennial time scales. We apply phase relations among different spectral irradiance bands both from SIM observation and proxy reconstructions to the two scenarios of historical TSI. The spectral solar forcing is used to drive the RCM. The updated atmosphere and ocean mixed coupled RCM including diffusion to deep-ocean provides a first-order estimate of climate response. We report the different responses of stratosphere, troposphere, and ocean surface to these 4 scenarios of centennial spectral solar forcing. We further discuss the mechanisms for atmosphere-ocean and stratosphere

  9. Regional aerosol emissions and temperature response: Local and remote climate impacts of regional aerosol forcing

    NASA Astrophysics Data System (ADS)

    Lewinschal, Anna; Ekman, Annica; Hansson, Hans-Christen

    2017-04-01

    Emissions of anthropogenic aerosols vary substantially over the globe and the short atmospheric residence time of aerosols leads to a highly uneven radiative forcing distribution, both spatially and temporally. Regional aerosol radiative forcing can, nevertheless, exert a large influence on the temperature field away from the forcing region through changes in heat transport or the atmospheric or ocean circulation. Moreover, the global temperature response distribution to aerosol forcing may vary depending on the geographical location of the forcing. In other words, the climate sensitivity in one region can vary depending on the location of the forcing. The surface temperature distribution response to changes in sulphate aerosol forcing caused by sulphur dioxide (SO2) emission perturbations in four different regions is investigated using the Norwegian Earth System Model (NorESM). The four regions, Europe, North America, East and South Asia, are all regions with historically high aerosol emissions and are relevant from both an air-quality and climate policy perspective. All emission perturbations are defined relative to the year 2000 emissions provided for the Coupled Model Intercomparison Project phase 5. The global mean temperature change per unit SO2 emission change is similar for all four regions for similar magnitudes of emissions changes. However, the global temperature change per unit SO2 emission in simulations where regional SO2 emission were removed is substantially higher than that obtained in simulations where regional SO2 emissions were increased. Thus, the climate sensitivity to regional SO2 emissions perturbations depends on the magnitude of the emission perturbation in NorESM. On regional scale, on the other hand, the emission perturbations in different geographical locations lead to different regional temperature responses, both locally and in remote regions. The results from the model simulations are used to construct regional temperature potential

  10. Block copolymer/ferroelectric nanoparticle nanocomposites.

    PubMed

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

    2013-09-21

    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.

  11. Cycloolefin effect in cycloolefin-(meth)acryl copolymer

    NASA Astrophysics Data System (ADS)

    Lim, Hyun Soon; Seo, Dong Chul; Lee, Chang Soo; Park, Sang Wok; Kim, Sang Jin; Shin, Dae Hyeon; Shin, Jin Bong; Park, Joo Hyun

    2008-11-01

    One of the most important factors in ArF resist development is a resin platform, which dominates a lot of parts of resist characteristics. It has been much changed in order to improve their physical properties such as resolution, pattern profile, etch resistance and line edge roughness. Through the low etch resistance in ArF initial (meth)acryl type copolymer and low transmittance in COMA type copolymer most researchers were interested in developing of (meth)acryl type copolymer again for ArF photoresist. On the other hand, we have studied various polymer platforms suitable ArF photoresist except for meth(acryl) type copolymer. As a result of this study we had developed ROMA type polymers and cycloolefin-(meth)acryl type copolymers. Among the polymers cycloolefin-(meth)acryl type copolymer has many attractions such as etch roughness, resist reflow which needs low glass transition temperature and solvent solubility. In this study, we intend to find out cycloolefin-(meth)acryl copolymer characteristics compared with (meth)acryl copolymer. And, we have tried to find out any differences between acrylate type copolymer and cycloolefin-(meth)acrylate type copolymer with various evaluation results. As a result of this study we are going to talk about the reason that the resist using acrylate type copolymer and cycloolefin-(meth)acryl type copolymer show good pattern profile while acrylate type copolymer show poor pattern profile. We also intend to explain the role of cycloolefin as a function of molecular weight variation and substitution ratio variation of cycloolefin in cycloolefin-(meth)acrylate resin.One of the most important factors in ArF resist development is a resin platform, which dominates a lot of parts of resist characteristics. It has been much changed in order to improve their physical properties such as resolution, pattern profile, etch resistance and line edge roughness. Through the low etch resistance in ArF initial (meth)acryl type copolymer and low

  12. Synthesis, characterization and drug delivery application of the temperature responsive pNIPA hydrogel

    NASA Astrophysics Data System (ADS)

    Craciunescu, I.; Nan, A.; Turcu, R.; Kacso, I.; Bratu, I.; Leostean, C.; Vekas, L.

    2009-08-01

    Temperature - sensitive poly (N-isopropyl acrylamide) pNIPA gels were synthesized with nano size iron oxide ferrofluids (Fe3O4) using N, N'-methylene bis-acrylamide (BIS) as the crosslinking agent, obtaining a new type of material, named ferrogel. The swelling characteristics of these ferrogels at distinct compositions, as a function of temperature were investigated. It was found that the pNIPA ferrogels demonstrated the temperature - responsive nature, and it also showed good reversibility. The FTIR spectra of pNIPA ferrogel samples, showed the absorption region of the specific chemical groups associated with pNIPA and the Fe3O4 magnetic nanoparticles. The drug release experiments were performed using atenolol (AT) in simulated gastric and intestinal media. The amount of released drug was determined by UV spectroscopy at characteristic wavelength of the drug, using a calibration curve obtained from a series of drug solution with standard concentration.

  13. Temperature response of 129Xe depolarization transfer and its application for ultra-sensitive NMR detection

    SciTech Connect

    Schroeder, Leif; Schroder, Leif; Meldrum, Tyler; Smith, Monica; Lowery, Thomas J.; Wemmer, David E.; Pines, Alexander

    2008-03-20

    Temporary trapping of atomic xenon in functionalized cryptophane cages makes the high sensitivity of hyperpolarized (hp) 129Xe available for highly specific NMR detection of biomolecules like proteins in solution. Here, we study the signal transfer onto a reservoir of unbound hp xenon by gating the residence time of the nuclei in the cage through the temperature-dependent exchange rate. Temperature changes were detectable immediately as an altered reservoir signal and yielded a sensitivity of 0.6 K. The temperature response is adjustable with lower concentrations of caged xenon providing more sensitivity at higher temperatures and allows ultra-sensitive detection of such molecular cages at 310 K. Functionalized cryptophane could be detected at concentrations as low as 10nM which corresponds to a 4000-fold sensitivity enhancement compared to conventional detection. This sensitivity makes hp-NMR capable of detecting such constructs in concentrations far belowthe detection limit by UV-visible light absorbance.

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

    PubMed

    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.

  15. Temperature response of biological materials to pulsed non-ablative CO2 laser irradiation.

    PubMed

    Brugmans, M J; Kemper, J; Gijsbers, G H; van der Meulen, F W; van Gemert, M J

    1991-01-01

    This paper presents surface temperature responses of various tissue phantoms and in vitro and in vivo biological materials in air to non-ablative pulsed CO2 laser irradiation, measured with a thermocamera. We studied cooling off behavior of the materials after a laser pulse, to come to an understanding of heat accumulation and related thermal damage during (super) pulsed CO2 laser irradiation. The experiments show a very slow decay of temperatures in the longer time regime. This behavior is well predicted by a simple model for one-dimensional heat flow that considers the CO2 laser radiation as producing a heat flux on the material surface. The critical pulse repetition frequency for which temperature accumulation is sufficiently low is estimated at about 5 Hz. Although we have not investigated the ablative situation, our results suggest that very low pulse frequencies in microsurgical procedures may be recommended.

  16. Overview of the Temperature Response in the Mesosphere and Lower Thermosphere to Solar Activity

    NASA Technical Reports Server (NTRS)

    Beig, Gufran; Scheer, Juergen; Mlynczak, Martin G.; Keckhut, Philippe

    2008-01-01

    The natural variability in the terrestrial mesosphere needs to be known to correctly quantify global change. The response of the thermal structure to solar activity variations is an important factor. Some of the earlier studies highly overestimated the mesospheric solar response. Modeling of the mesospheric temperature response to solar activity has evolved in recent years, and measurement techniques as well as the amount of data have improved. Recent investigations revealed much smaller solar signatures and in some case no significant solar signal at all. However, not much effort has been made to synthesize the results available so far. This article presents an overview of the energy budget of the mesosphere and lower thermosphere (MLT) and an up-to-date status of solar response in temperature structure based on recently available observational data. An objective evaluation of the data sets is attempted and important factors of uncertainty are discussed.

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

    NASA Astrophysics Data System (ADS)

    Portner, H.; Bugmann, H.; Wolf, A.

    2009-08-01

    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 budget.

  18. Acute Effects of Normobaric Hypoxia on Hand-Temperature Responses During and After Local Cold Stress

    PubMed Central

    Kölegård, Roger; Mekjavic, Igor B.; Eiken, Ola

    2014-01-01

    Abstract Keramidas, Michail E, Roger Kölegård, Igor B. Mekjavic, and Ola Eiken. Acute effects of normobaric hypoxia on hand-temperature responses during and after local cold stress. High Alt Med Biol. 15:183–191, 2014.—The purpose was to investigate acute effects of normobaric hypoxia on hand-temperature responses during and after a cold-water hand immersion test. Fifteen males performed two right-hand immersion tests in 8°C water, during which they were inspiring either room air (Fio2: 0.21; AIR), or a hypoxic gas mixture (Fio2: 0.14; HYPO). The tests were conducted in a counterbalanced order and separated by a 1-hour interval. Throughout the 30-min cold-water immersion (CWI) and the 15-min spontaneous rewarming (RW) phases, finger-skin temperatures were measured continuously with thermocouple probes; infrared thermography was also employed during the RW phase to map all segments of the hand. During the CWI phase, the average skin temperature (Tavg) of the fingers did not differ between the conditions (AIR: 10.2±0.5°C, HYPO: 10.0±0.5°C; p=0.67). However, Tavg was lower in the HYPO than the AIR RW phase (AIR: 24.5±3.4°C; HYPO: 22.0±3.8°C; p=0.002); a response that was alike in all regions of the immersed hand. Accordingly, present findings suggest that acute exposure to normobaric hypoxia does not aggravate the cold-induced drop in hand temperature of normothermic males. Still, hypoxia markedly impairs the rewarming responses of the hand. PMID:24666109

  19. A Temperature-Responsive Network Links Cell Shape and Virulence Traits in a Primary Fungal Pathogen

    PubMed Central

    Beyhan, Sinem; Gutierrez, Matias; Voorhies, Mark; Sil, Anita

    2013-01-01

    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 environmental and

  20. Future CO2 concentrations, though not warmer temperatures, enhance wheat photosynthesis temperature responses.

    PubMed

    Alonso, Aitor; Pérez, Pilar; Morcuende, Rosa; Martinez-Carrasco, Rafael

    2008-01-01

    The temperature dependence of C3 photosynthesis is known to vary according to the growth environment. Atmospheric CO2 concentration and temperature are predicted to increase with climate change. To test whether long-term growth in elevated CO2 and temperature modifies photosynthesis temperature response, wheat (Triticum aestivum L.) was grown in ambient CO2 (370 micromol mol(-1)) and elevated CO2 (700 micromol mol(-1)) combined with ambient temperatures and 4 degrees C warmer ones, using temperature gradient chambers in the field. Flag leaf photosynthesis was measured at temperatures ranging from 20 to 35 degrees C and varying CO2 concentrations between ear emergence and anthesis. The maximum rate of carboxylation was determined in vitro in the first year of the experiment and from the photosynthesis-intercellular CO2 response in the second year. With measurement CO2 concentrations of 330 micromol mol(-1) or lower, growth temperature had no effect on flag leaf photosynthesis in plants grown in ambient CO2, while it increased photosynthesis in elevated growth CO2. However, warmer growth temperatures did not modify the response of photosynthesis to measurement temperatures from 20 to 35 degrees C. A central finding of this study was that the increase with temperature in photosynthesis and the photosynthesis temperature optimum were significantly higher in plants grown in elevated rather than ambient CO2. In association with this, growth in elevated CO2 increased the temperature response (activation energy) of the maximum rate of carboxylation. The results provide field evidence that growth under CO2 enrichment enhances the response of Rubisco activity to temperature in wheat.

  1. Vertical and seasonal variations in temperature responses of leaf respiration in a Chamaecyparis obtusa canopy.

    PubMed

    Araki, Masatake G; Gyokusen, Koichiro; Kajimoto, Takuya

    2017-02-23

    Leaf respiration (R) is a major component of carbon balance in forest ecosystems. Clarifying the variability of leaf R within a canopy is essential for predicting the impact of global warming on forest productivity and the potential future function of the forest ecosystem as a carbon sink. We examined vertical and seasonal variations in short-term temperature responses of leaf R as well as environmental factors (light and mean air temperature) and physiological factors [leaf nitrogen (N), leaf mass per area (LMA), and shoot growth] in the canopy of a 10-year-old stand of hinoki cypress [Chamaecyparis obtusa (Sieb. et Zucc.) Endl.] in Kyushu, Japan. Leaf respiration rate adjusted to 20 °C (R20) exhibited evident vertical gradients in each season and was correlated with light, LMA and leaf N. In contrast, the temperature sensitivity of leaf R (Q10) did not vary vertically throughout the seasons. Seasonally, Q10 was higher in winter than in summer and was strongly negatively correlated to mean air temperature. A negative correlation of R20 with mean air temperature was also observed for each of the three canopy layers. These results clearly indicate that leaf R was able to adjust to seasonal changes in ambient temperature under field conditions and down-regulate during warmer periods. We also found that the degree of thermal acclimation did not vary with canopy position. Overall, our results suggest that vertical and seasonal variations in temperature responses of leaf R within a hinoki cypress canopy could be predicted by relatively simple parameters (light and temperature). There was an exception of extremely high R20 values in April that may have been due to the onset of shoot growth in spring. Understanding thermal acclimation and variations in leaf R within forest canopies will improve global terrestrial carbon cycle models. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

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

    PubMed

    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 (30.1

  3. Solvent enhanced block copolymer ordering in thin films

    NASA Astrophysics Data System (ADS)

    Misner, Matthew J.

    Diblock copolymer self-assembly of materials is emerging as a key element in the fabrication of functional nanostructured materials. By solvent casting or solvent annealing block copolymer thin films, we have demonstrated methods to produce diblock copolymer films with highly oriented, close-packed arrays of nanoscopic cylindrical domains with a high degree of long-range lateral order with few defects. The solvent imparts a high degree of mobility in the microphase-separated copolymer that enables a rapid removal of defects and a high degree of lateral order. Though the use of a selective cosolvent during solvent casting, it was found that the microdomain size and spacing could be increased, leading to a size-tunable system. Additionally, the presence of water also led to the ability to control the microdomain orientation during solvent annealing. Ionic complexation within cylinder-forming PS- b-EO block copolymer thin films was also investigated, where added salts bind PEO block as the minor component. Small amounts of added salts, on the order a few ions per chain, show large effects on the ordering of the copolymer films during solvent annealing. By using gold or cobalt salts, well-organized patterns of nanoparticles can be generated in the copolymer microdomains. Topographically and chemically patterned surfaces were used as a route to sectorizing and controlling the lattice orientation of copolymer films. Topographically patterned surfaces allow well-defined boundaries to confine the copolymer microdomains on a surface and effectively direct the ordering and grain orientation of the copolymer microdomains. Chemically patterned surfaces provide a route to direct the block copolymer ordering on completely flat surface, which may have advantages in applications where adding additional topography may be undesirable. To generate nanoporous templates from PS-b-PEO bases materials several routs were followed. The first route was through the addition and selective

  4. 21 CFR 872.3500 - Polyvinylmethylether maleic anhydride (PVM-MA), acid copolymer, and carboxymethylcellulose sodium...

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...), acid copolymer, and carboxymethylcellulose sodium (NACMC) denture adhesive. 872.3500 Section 872.3500...), acid copolymer, and carboxymethylcellulose sodium (NACMC) denture adhesive. (a) Identification. Polyvinylmethylether maleic anhydride (PVM-MA), acid copolymer, and carboxymethylcellulose sodium (NACMC) denture...

  5. 21 CFR 872.3500 - Polyvinylmethylether maleic anhydride (PVM-MA), acid copolymer, and carboxymethylcellulose sodium...

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...), acid copolymer, and carboxymethylcellulose sodium (NACMC) denture adhesive. 872.3500 Section 872.3500...), acid copolymer, and carboxymethylcellulose sodium (NACMC) denture adhesive. (a) Identification. Polyvinylmethylether maleic anhydride (PVM-MA), acid copolymer, and carboxymethylcellulose sodium (NACMC) denture...

  6. 21 CFR 872.3500 - Polyvinylmethylether maleic anhydride (PVM-MA), acid copolymer, and carboxymethylcellulose sodium...

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...), acid copolymer, and carboxymethylcellulose sodium (NACMC) denture adhesive. 872.3500 Section 872.3500...), acid copolymer, and carboxymethylcellulose sodium (NACMC) denture adhesive. (a) Identification. Polyvinylmethylether maleic anhydride (PVM-MA), acid copolymer, and carboxymethylcellulose sodium (NACMC) denture...

  7. 21 CFR 872.3500 - Polyvinylmethylether maleic anhydride (PVM-MA), acid copolymer, and carboxymethylcellulose sodium...

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...), acid copolymer, and carboxymethylcellulose sodium (NACMC) denture adhesive. 872.3500 Section 872.3500...), acid copolymer, and carboxymethylcellulose sodium (NACMC) denture adhesive. (a) Identification. Polyvinylmethylether maleic anhydride (PVM-MA), acid copolymer, and carboxymethylcellulose sodium (NACMC) denture...

  8. 21 CFR 872.3500 - Polyvinylmethylether maleic anhydride (PVM-MA), acid copolymer, and carboxymethylcellulose sodium...

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...), acid copolymer, and carboxymethylcellulose sodium (NACMC) denture adhesive. 872.3500 Section 872.3500...), acid copolymer, and carboxymethylcellulose sodium (NACMC) denture adhesive. (a) Identification. Polyvinylmethylether maleic anhydride (PVM-MA), acid copolymer, and carboxymethylcellulose sodium (NACMC) denture...

  9. 40 CFR 721.10523 - Perfluoroalkylethyl methacrylate copolymer with hydroxymethyl acrylamide, vinyl chloride and long...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... copolymer with hydroxymethyl acrylamide, vinyl chloride and long chain fatty alkyl acrylate (generic). 721... Substances § 721.10523 Perfluoroalkylethyl methacrylate copolymer with hydroxymethyl acrylamide, vinyl... methacrylate copolymer with hydroxymethyl acrylamide, vinyl chloride and long chain fatty alkyl acrylate (PMN...

  10. 40 CFR 721.10523 - Perfluoroalkylethyl methacrylate copolymer with hydroxymethyl acrylamide, vinyl chloride and long...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... copolymer with hydroxymethyl acrylamide, vinyl chloride and long chain fatty alkyl acrylate (generic). 721... Substances § 721.10523 Perfluoroalkylethyl methacrylate copolymer with hydroxymethyl acrylamide, vinyl... methacrylate copolymer with hydroxymethyl acrylamide, vinyl chloride and long chain fatty alkyl acrylate (PMN...

  11. Interaction of poloxamine block copolymers with lipid membranes: Role of copolymer structure and membrane cholesterol content.

    PubMed

    Sandez-Macho, Isabel; Casas, Matilde; Lage, Emilio V; Rial-Hermida, M Isabel; Concheiro, Angel; Alvarez-Lorenzo, Carmen

    2015-09-01

    Interactions of X-shaped poly(ethylene oxide)-poly(propylene oxide) (PEO-PPO) block copolymers with cell membranes were investigated recording the π-A isotherms of monolayer systems of dipalmitoylphosphatidylcholine (DPPC):cholesterol 100:0; 80:20 and 60:40 mol ratio and evaluating the capability of the copolymers to trigger haemolysis or to protect from haemolytic agents. Four varieties of poloxamine (Tetronic 904, 908, 1107 and 1307) were chosen in order to cover a wide range of EO and PO units contents and molecular weights, and compared to a variety of poloxamer (Pluronic P85). The π-A isotherms revealed that the greater the content in cholesterol, the stronger the interaction of the block copolymers with the lipids monolayer. The interactions were particularly relevant at low pressures and low lipid proportions, mimicking the conditions of damaged membranes. Relatively hydrophobic copolymers bearing short PEO blocks (e.g., T904 and P85) intercalated among the lipids expanding the surface area (ΔGexc) but not effectively sealing the pores. These varieties showed haemolytic behavior. Oppositely, highly hydrophilic copolymers bearing long PEO blocks (e.g., T908, T1107 and T1307) caused membrane contraction and outer leaflet sealing due to strong interactions of PEO with cholesterol and diamine core with phospholipids. These later varieties were not haemolytic and exerted a certain protective effect against spontaneous haemolysis for both intact erythrocytes and cholesterol-depleted erythrocytes.

  12. Phase Behavior of Neat Triblock Copolymers and Copolymer/Homopolymer Blends Near Network Phase Windows

    SciTech Connect

    M Tureau; L Rong; B Hsiao; T Epps

    2011-12-31

    The phase behavior of poly(isoprene-b-styrene-b-methyl methacrylate) (ISM) copolymers near the styrene-rich network phase window was examined through the use of neat triblock copolymers and copolymer/homopolymer blends. Both end-block and middle-block blending protocols were employed using poly(isoprene) (PI), poly(methyl methacrylate) (PMMA), and poly(styrene) (PS) homopolymers. Blended specimens exhibited phase transformations to well-ordered nanostructures (at homopolymer loadings up to 26 vol % of the total blend volume). Morphological consistency between neat and blended specimens was established at various locations in the ISM phase space. Copolymer/homopolymer blending permitted the refinement of lamellar, hexagonally packed cylinder, and disordered melt phase boundaries as well as the identification of double gyroid (Q{sup 230}), alternating gyroid (Q{sup 214}), and orthorhombic (O{sup 70}) network regimes. Additionally, the experimental phase diagram exhibited similar trends to those found in a theoretical ABC triblock copolymer phase diagram with symmetric interactions and statistical segments lengths generated by Tyler et al.

  13. Oxygen plasma resistant phosphine oxide containing imide/arylene copolymers

    NASA Technical Reports Server (NTRS)

    Jensen, Brian J.

    1993-01-01

    A series of oxygen plasma resistant imide/arylene ether copolymers were prepared by reacting anhydride-terminated poly(amide acids) and amine-terminated polyarylene ethers containing phosphine oxide units. Inherent viscosities for these copolymers ranged from 0.42 to 0.80 dL/g. After curing, the resulting copolymers had glass transition temperatures ranging from 224 C to 228 C. Solution cast films of the block copolymers were tough and flexible with tensile strength, tensile moduli, and elongation at break up to 16.1 ksi, 439 ksi, and 23 percent, respectively at 25 C and 9.1 ksi, 308 ksi and 97 percent, respectively at 150 C. The copolymers show a significant improvement in resistance to oxygen plasma when compared to the commercial polyimide Kapton. The imide/arylene ether copolymers containing phosphine oxide units are suitable as coatings, films, adhesives, and composite matrices.

  14. Amphiphilic block copolymer membrane for vanadium redox flow battery

    NASA Astrophysics Data System (ADS)

    Wang, Fei; Sylvia, James M.; Jacob, Monsy M.; Peramunage, Dharmasena

    2013-11-01

    An amphiphilic block copolymer comprised of hydrophobic polyaryletherketone (PAEK) and hydrophilic sulfonated polyaryletherketone (SPAEK) blocks has been synthesized and characterized. A membrane prepared from the block copolymer is used as the separator in a single cell vanadium redox flow battery (VRB). The proton conductivity, mechanical property, VO2+ permeability and single VRB cell performance of this block copolymer membrane are investigated and compared to Nafion™ 117. The block copolymer membrane showed significantly improved vanadium ion selectivity, higher mechanical strength and lower conductivity than Nafion™ 117. The VRB containing the block copolymer membrane exhibits higher coulombic efficiency and similar energy efficiency compared to a VRB using Nafion™ 117. The better vanadium ion selectivity of the block copolymer membrane has led to a much smaller capacity loss during 50 charge-discharge cycles for the VRB.

  15. Enhanced cellular uptake and gene silencing activity of siRNA using temperature-responsive polymer-modified liposome.

    PubMed

    Wang, Jian; Ayano, Eri; Maitani, Yoshie; Kanazawa, Hideko

    2017-05-15

    Short interfering RNA (siRNA) delivery systems using nanoparticle carriers have been limited by inefficient intracellular delivery. One drawback is the poor cellular uptake of siRNA/particle complexes through the plasma membrane and release of the nucleic acids into the cytosol. In this study, to develop the temperature-responsive liposome as a novel carrier for siRNA delivery, we prepared lipoplexes and assessed cellular uptake of siRNA and gene silencing activity of target genes, compared with those of a commercial transfection reagent, Lipofectamine RNAiMAX, and non-modified or PEGylated liposomes. The temperature-responsive polymer, N-isopropylacrylamide-co-N,N'-dimethylaminopropylacrylamide [P(NIPAAm-co-DMAPAAm)]-modified liposome induced faster intracellular delivery because P(NIPAAm-co-DMAPAAm) exhibits a lower critical solution temperature (LCST) changing its nature from hydrophilic to hydrophobic above the LCST. The temperature-responsive liposomes showed significantly higher gene silencing activity than other carriers with less cytotoxicity. Furthermore, we showed that the temperature-responsive lipoplexes were internalized mainly via microtubule-dependent transport and also by the clathrin-mediated endocytosis pathway. This is the first report that temperature-responsive polymer-modified liposomes thermally enhanced silencing activity of siRNA. The dehydrated polymer on the liposomes, and its aggregation caused around the LCST, can probably be attributed to effective cellular uptake of the lipoplexes for gene silencing activity by interaction with the cell membrane. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Reversible geling co-polymer and method of making

    DOEpatents

    Gutowska, Anna

    2005-12-27

    The present invention is a thereapeutic agent carrier having a thermally reversible gel or geling copolymer that is a linear random copolymer of an [meth-]acrylamide derivative and a hydrophilic comonomer, wherein the linear random copolymer is in the form of a plurality of linear chains having a plurality of molecular weights greater than or equal to a minimum geling molecular weight cutoff and a therapeutic agent.

  17. ROMP from ROMP: A New Approach to Graft Copolymer Synthesis

    PubMed Central

    Allen, Matthew J.; Wangkanont, Kittikhun; Raines, Ronald T.; Kiessling, Laura L.

    2009-01-01

    A new strategy is presented for the synthesis of graft copolymers using only the ring-opening metathesis polymerization (ROMP). From a ROMP-derived main chain, pendant maleimide functional groups are converted into norbornene moieties via a Diels–Alder reaction with cyclopentadiene. The norbornene groups serve as sites of initiation, and subsequent ROMP from the main chain yields graft copolymers with both main and side chains derived from ROMP. This strategy offers ready access to defined graft copolymers. PMID:20161406

  18. On the birefringence of multilayered symmetric diblock copolymer films

    SciTech Connect

    Kim, J.; Chin, I.; Smith, B.A.; Russell, T.P. ); Mays, J.W. . Dept. of Chemistry)

    1993-09-27

    The chain extension at lamellar interfaces was studied in thin films of symmetric diblock copolymers on gold substrates. The first copolymer consisted of blocks of polystyrene (PS) and poly(2-vinylpyridine) (P2VP), denoted P(S-b-2VP). The second was a diblock copolymer of PS and poly(methyl methacrylate) (PMMA), denoted P(S-b-MMA), on a gold substrate. Using attenuated total reflectance spectroscopy, the refractive indices parallel, n[sub [parallel

  19. Imide/Arylene Ether Copolymers Containing Phosphine Oxide

    NASA Technical Reports Server (NTRS)

    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.

  20. Multigraft Copolymer Superelastomers: Synthesis Morphology, and Properties

    SciTech Connect

    Uhrig, David; Schlegel, Ralf; Weidisch, Roland; Mays, Jimmy

    2011-01-01

    The synthesis of well-defined multigraft copolymers having a polydiene backbone with polystyrene side chains is briefly reviewed, with particular focus on controlling branch point spacing and branch point functionality. Use of living anionic polymerization and chlorosilane linking chemistry has led to the synthesis of series of materials having regularly spaced trifunctional (comb), tetrafunctional (centipede), and hexafunctional (barbwire) branch points. The morphologies of these materials were characterized by transmission electron microscopy and small-angle X-ray scattering, and it was found that the morphologies were controlled by the local architectural asymmetry associated with each branch point. Mechanical properties studies revealed that such multigraft copolymers represent a new class of thermoplastic elastomers (TPEs) with superior elongation at break and low residual strains as compared to conventional TPEs.

  1. "Clickable" PEG-dendritic block copolymers.

    PubMed

    Fernandez-Megia, Eduardo; Correa, Juan; Riguera, Ricardo

    2006-11-01

    Three generations of azido-terminated PEG-dendritic block copolymers have been synthesized and completely characterized by NMR and MALDI-TOF. A radial decrease of density, leading to more mobile protons at the outermost periphery, and an increasingly higher compactness of the core with generation have been determined by T(1) and T(2) relaxation time studies. The efficient surface decoration of these dendritic polymers by means of click chemistry has been demonstrated by the incorporation of unprotected carbohydrate units in very good to excellent yields. The reaction proceeds at room temperature, under aqueous conditions, and requires just catalytic amounts of Cu. The modified block copolymers are conveniently purified by ultrafiltration. The glycodendrimers functionalized with alpha-mannose form aggregates with concanavalin A as determined by absorbance experiments at 400 nm. This aggregation ability increases with generation.

  2. Rapid ordering of block copolymer thin films

    DOE PAGES

    Majewski, Pawel W.; Yager, Kevin G.

    2016-08-18

    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. Here, wemore » also review both real-space and reciprocal-space analysis techniques for quantifying order in these systems.« less

  3. Rapid ordering of block copolymer thin films

    SciTech Connect

    Majewski, Pawel W.; Yager, Kevin G.

    2016-08-18

    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. Here, we also review both real-space and reciprocal-space analysis techniques for quantifying order in these systems.

  4. Biofilaments as annealed semi-flexible copolymers

    NASA Astrophysics Data System (ADS)

    Fierling, Julien; Mohrbach, Hervé; Kulic, Igor; Lee, Nam-Kyung; Johner, Albert

    2014-06-01

    In many in vivo or in vitro situations, biofilaments manifest some annealed heterogeneity and should be considered as annealed random copolymers. The building blocks of the filaments differ from each other, for example, by the internal structure of the monomer, by the presence of some adsorbed species or by the curvature. Based on the copolymer concept, we embed the description of these systems in a common formalism. We demonstrate how the annealed heterogeneous nature of the filament is reflected by statistical correlations like the tangent-tangent correlation function or the cyclization probability. Our results show that annealed filaments adapt cooperatively to external constraints. This could contribute to explain anomalous elasticity manifested by biofilaments.

  5. Photothermal degradation of ethylene/vinylacetate copolymer

    NASA Technical Reports Server (NTRS)

    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.

  6. Defect trapping in ABC block copolymers

    NASA Astrophysics Data System (ADS)

    Corte, Laurent; Yamauchi, Kazuhiro; Court, Francois; Cloitre, Michel; Hashimoto, Takeji; Leibler, Ludwik

    2004-03-01

    Equilibrium morphologies in molten ABC triblock terpolymers are much more difficult to attain than in AB diblocks. In practice, it is important to know whether and how synthesis conditions influence the morphology and properties of copolymer materials. It is also relevant to understand the mechanisms of defect formation and annihilation. Indeed, a potential use of copolymers in new applications such as lithography highly depends on the ability to produce regular structures with no or few defects. We show that even the simplest lamellar structures exhibit high sensitivity to preparation conditions and that strongly trapped structural defects inherent to ABC triblock architecture cannot be removed by long annealing. Annealing can induce a transition from a lamellar structure in which A and C blocks are mixed to a lamellar structure where A, B and C are segregated. We propose reorganization mechanisms that are at the origin of some characteristic defects.

  7. [Researches on PEG-modified copolymer nanoparticle].

    PubMed

    Chen, Wei; Yang, Xiangliang

    2003-03-01

    Biodegradable polymeric nanoparticles acting as drug carrier have important potential applications such as site-specific drug delivery and controllable drug delivery. However, these carriers cannot generally be used because they are eliminated by the reticulo-endothelial system within seconds or minutes after intravenous injection. To overcome this limitation, more and more researchers introduce hydrophilic polyethylene glyeol(PEG) to modify polymeric nanoparticles for avoiding their uptake by reticulo-endothelial system. Introducing PEG not only changes polymer nanoparticles' biodegradation in vivo, but also influences drug's properties such as drug release, in vivo biodistribution, et. al. In this paper are reviewed the researches of PEG-modified copolymer nanoparticles, including their preparation and size distribution, stability, drug incorporation, drug release, in vivo biodistribution, in vitro cytotoxicty. A prospect for the researches and developments of the PEG-modified copolymer nanoparticles was also made.

  8. Amine-reactive biodegradable diblock copolymers.

    PubMed

    Tessmar, Jörg K; Mikos, Antonios G; Göpferich, Achim

    2002-01-01

    A new class of diblock copolymers was synthesized from biodegradable poly(lactic acid) and poly(ethylene glycol)minus signmonoamine. These polymers were activated by covalently attaching linkers such as disuccinimidyl tartrate or disuccinimidyl succinate to the hydrophilic polymer chain. The polymers were characterized by (1)H NMR spectroscopy, (13)C NMR spectroscopy and gel permeation chromatography (GPC). These investigations indicated that the polymers were obtained with the correct composition, in high purities, and the expected molecular weight. By using dyes containing primary amine groups such as 5-aminoeosin as model substrates, it was possible to show that the polymers are able to bind such compounds covalently. The diblock copolymers were developed to suppress unspecific protein adsorption and allow the binding of bioactive molecules by instant surface modification. The polymers are intended to be used for tissue engineering applications where surface immobilized cell adhesion peptides or growth factors are needed to control cell behavior.

  9. Rapid ordering of block copolymer thin films

    SciTech Connect

    Majewski, Pawel W.; Yager, Kevin G.

    2016-08-18

    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. Here, we also review both real-space and reciprocal-space analysis techniques for quantifying order in these systems.

  10. Photothermal degradation of ethylene/vinylacetate copolymer

    NASA Technical Reports Server (NTRS)

    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.

  11. Formation of Anisotropic Block Copolymer Gels

    NASA Astrophysics Data System (ADS)

    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.

  12. Hierarchical porous polymer scaffolds from block copolymers.

    PubMed

    Sai, Hiroaki; Tan, Kwan Wee; Hur, Kahyun; Asenath-Smith, Emily; Hovden, Robert; Jiang, Yi; Riccio, Mark; Muller, David A; Elser, Veit; Estroff, Lara A; Gruner, Sol M; Wiesner, Ulrich

    2013-08-02

    Hierarchical porous polymer materials are of increasing importance because of their potential application in catalysis, separation technology, or bioengineering. Examples for their synthesis exist, but there is a need for a facile yet versatile conceptual approach to such hierarchical scaffolds and quantitative characterization of their nonperiodic pore systems. Here, we introduce a synthesis method combining well-established concepts of macroscale spinodal decomposition and nanoscale block copolymer self-assembly with porosity formation on both length scales via rinsing with protic solvents. We used scanning electron microscopy, small-angle x-ray scattering, transmission electron tomography, and nanoscale x-ray computed tomography for quantitative pore-structure characterization. The method was demonstrated for AB- and ABC-type block copolymers, and resulting materials were used as scaffolds for calcite crystal growth.

  13. Rapid ordering of block copolymer thin films

    NASA Astrophysics Data System (ADS)

    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.

  14. Hierarchical Structures of a Multiblock Copolymer Melt

    NASA Astrophysics Data System (ADS)

    Li, Weihua; Shi, An-Chang

    2007-03-01

    Hierarchical structures of a multiblock copolymer melt are investigated using real-space self-consistent mean-field theory. The polymer, A(BC)nBA, is composed of three species A, B, and C. The parameter n indicates the number of short BC blocks with equal lengths. Hierarchical lamellar structures with parallel double periodicity have been observed in very recent experiments done by Masuda, et al. in this type of multiblock copolymer melts. These heirachical structures are reproduced in our one-dimensional calculations. We locate the transitions between hierarchical lamellar phase and single lamellar phase as the composition fA is varied for two types of hierarchical lamellae with five and seven thin layers, respectively. In addition, we explore hierarchical cylindrical structures using two-dimensional calculations.

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

    NASA Astrophysics Data System (ADS)

    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), intra-aggregate (< 1.8 g cm-3 within aggregates > 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

  16. ``Sequence space soup'' of proteins and copolymers

    NASA Astrophysics Data System (ADS)

    Chan, Hue Sun; Dill, Ken A.

    1991-09-01

    To study the protein folding problem, we use exhaustive computer enumeration to explore ``sequence space soup,'' an imaginary solution containing the ``native'' conformations (i.e., of lowest free energy) under folding conditions, of every possible copolymer sequence. The model is of short self-avoiding chains of hydrophobic (H) and polar (P) monomers configured on the two-dimensional square lattice. By exhaustive enumeration, we identify all native structures for every possible sequence. We find that random sequences of H/P copolymers will bear striking resemblance to known proteins: Most sequences under folding conditions will be approximately as compact as known proteins, will have considerable amounts of secondary structure, and it is most probable that an arbitrary sequence will fold to a number of lowest free energy conformations that is of order one. In these respects, this simple model shows that proteinlike behavior should arise simply in copolymers in which one monomer type is highly solvent averse. It suggests that the structures and uniquenesses of native proteins are not consequences of having 20 different monomer types, or of unique properties of amino acid monomers with regard to special packing or interactions, and thus that simple copolymers might be designable to collapse to proteinlike structures and properties. A good strategy for designing a sequence to have a minimum possible number of native states is to strategically insert many P monomers. Thus known proteins may be marginally stable due to a balance: More H residues stabilize the desired native state, but more P residues prevent simultaneous stabilization of undesired native states.

  17. Viscoelastic Properties of Some Alkyl Disulfide Copolymers

    DTIC Science & Technology

    1963-12-01

    disulfide polymer in this paper. Polymer sheets were prepared by molding the rubber crumb in a hydraulic press. Ten second torsion modulus...DISULFIDE COPOLYMERS by ¥. J. MacKnight, M. Takahashi and A. V. Tobolsky Introduction Polysulfide polymers were the first synthetic rubbers produced in...Gaylord, ed., Interscience, New York, 1962, Chap. XIII, contains many references to the original literature. 2. Gee, G., Trans. Inst. Rubber Ind

  18. Critical adsorption of copolymer tethered on selective surfaces

    NASA Astrophysics Data System (ADS)

    Li, Hong; Qian, Chang-Ji; Luo, Meng-Bo

    2016-04-01

    Critical adsorption behaviors of flexible copolymer chains tethered to a flat homogeneous surface are studied by using Monte Carlo simulations. We have compared the critical adsorption temperature Tc, estimated by a finite-size scaling method, for different AB copolymer sequences with A the attractive monomer and B the inert monomer. We find that Tc increases with an increase in the fraction of monomers A, fA, in copolymers, and it increases with an increase in the length of block A for the same fA. In particular, Tc of copolymer (AnBn)r can be expressed as a function of the block length, n, and Tc of copolymer (AnB)r and (ABm)r can be expressed as a linear function of fA. Tc of random copolymer chains also can be expressed as a linear function of fA and it can be estimated by using weight-average of Tc of different diblocks in the random copolymer. However, the crossover exponent is roughly independent of AB sequence distributions either for block copolymers or for random copolymers.

  19. Asymmetric block copolymers for supramolecular templating of inorganic nanospace materials.

    PubMed

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

    2015-05-06

    This review focuses on polymeric micelles consisting of asymmetric block copolymers as designed templates for several inorganic nanospace materials with a wide variety of compositions. The presence of chemically distinct domains of asymmetric triblock and diblock copolymers provide self-assemblies with more diverse morphological and functional features than those constructed by EOn POm EOn type symmetric triblock copolymers, thereby affording well-designed nanospace materials. This strategy can produce unprecedented nanospace materials, which are very difficult to prepare through other conventional organic templating approaches. Here, the recent development on the synthesis of inorganic nanospace materials are mainly focused on, such as hollow spheres, tubes, and porous oxides, using asymmetric triblock copolymers.

  20. Comparing the morphology and phase diagram of H-shaped ABC block copolymers and linear ABC block copolymers.

    PubMed

    Ye, Xianggui; Yu, Xifei; Sun, Zhaoyan; An, Lijia

    2006-06-22

    By using a combinatorial screening method based on the self-consistent field theory (SCFT) for polymers, we have investigated the morphology of H-shaped ABC block copolymers (A2BC2) and compared them with those of the linear ABC block copolymers. By changing the ratios of the volume fractions of two A arms and two C arms, one can obtain block copolymers with different architectures ranging from linear block copolymer to H-shaped block copolymer. By systematically varying the volume fractions of block A, B, and C, the triangle phase diagrams of the H-shaped ABC block copolymer with equal interactions among the three species are constructed. In this study, we find four different morphologies (lamellar phase (LAM), hexagonal lattice phase (HEX), core-shell hexagonal lattice phase (CSH), and two interpenetrating tetragonal lattice (TET2)). Furthermore, the order-order transitions driven by architectural change are discussed.

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

    NASA Astrophysics Data System (ADS)

    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

  2. Re-visiting our understanding of surface temperature response to climate forcing

    NASA Astrophysics Data System (ADS)

    Outten, S.; Davy, R.; Chen, L.

    2015-12-01

    We know that the surface temperature response, dT, to a perturbation in the climate forcing is determined by (1) the magnitude of the forcing, (2) any feedback effects and (3) the effective heat capacity of the system. These three components can be related through an energy budget model of the form dT = dQ/C, where dQ is the net heat perturbation from the combination of the forcing perturbation and the feedback processes, and C is the effective heat capacity of the system. On long, multi-decadal to centennial timescales, C is defined by the ocean. But on shorter timescales, the effective heat capacity in the atmosphere can determine the pattern of the surface temperature change. It has been demonstrated that the effective heat capacity of the atmosphere is defined by the volume of air through which that heat is distributed i.e. defined by the planetary boundary layer depth, h. The boundary-layer depth can vary from ~100 m to a few km across different locations, and during the seasonal and diurnal cycles. So even under a uniform forcing we can expect a strongly asymmetrical warming (or cooling) based on the climatology of h. We demonstrate this relationship in the recent warming period using a combination of surface observations and reanalysis products and find that it is the climatology of h which is the strongest predictor of the pattern of warming during the satellite era (1979-present). This has important implications for the detection of climate forcing and feedback signals through the surface temperature. In many current detection and attribution studies of climate feedback processes we assume a linear relationship between a perturbation in the forcing, dQ, and the corresponding change in temperature, dT. However, the inverse relationship between h and the strength of dT means that we can get strongly amplified temperature responses in conditions with shallow h, and this linear relationship breaks down. We demonstrate that these conditions where h

  3. Block and Graft Copolymers of Polyhydroxyalkanoates

    NASA Astrophysics Data System (ADS)

    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.

  4. Gyroid nickel nanostructures from diblock copolymer supramolecules.

    PubMed

    Vukovic, Ivana; Punzhin, Sergey; Voet, Vincent S D; Vukovic, Zorica; de Hosson, Jeff Th M; ten Brinke, Gerrit; Loos, Katja

    2014-04-28

    Nanoporous metal foams possess a unique combination of properties - they are catalytically active, thermally and electrically conductive, and furthermore, have high porosity, high surface-to-volume and strength-to-weight ratio. Unfortunately, common approaches for preparation of metallic nanostructures render materials with highly disordered architecture, which might have an adverse effect on their mechanical properties. Block copolymers have the ability to self-assemble into ordered nanostructures and can be applied as templates for the preparation of well-ordered metal nanofoams. Here we describe the application of a block copolymer-based supramolecular complex - polystyrene-block-poly(4-vinylpyridine)(pentadecylphenol) PS-b-P4VP(PDP) - as a precursor for well-ordered nickel nanofoam. The supramolecular complexes exhibit a phase behavior similar to conventional block copolymers and can self-assemble into the bicontinuous gyroid morphology with two PS networks placed in a P4VP(PDP) matrix. PDP can be dissolved in ethanol leading to the formation of a porous structure that can be backfilled with metal. Using electroless plating technique, nickel can be inserted into the template's channels. Finally, the remaining polymer can be removed via pyrolysis from the polymer/inorganic nanohybrid resulting in nanoporous nickel foam with inverse gyroid morphology.

  5. Gyroid Nickel Nanostructures from Diblock Copolymer Supramolecules

    PubMed Central

    Vukovic, Ivana; Punzhin, Sergey; Voet, Vincent S. D.; Vukovic, Zorica; de Hosson, Jeff Th. M.; ten Brinke, Gerrit; Loos, Katja

    2014-01-01

    Nanoporous metal foams possess a unique combination of properties - they are catalytically active, thermally and electrically conductive, and furthermore, have high porosity, high surface-to-volume and strength-to-weight ratio. Unfortunately, common approaches for preparation of metallic nanostructures render materials with highly disordered architecture, which might have an adverse effect on their mechanical properties. Block copolymers have the ability to self-assemble into ordered nanostructures and can be applied as templates for the preparation of well-ordered metal nanofoams. Here we describe the application of a block copolymer-based supramolecular complex - polystyrene-block-poly(4-vinylpyridine)(pentadecylphenol) PS-b-P4VP(PDP) - as a precursor for well-ordered nickel nanofoam. The supramolecular complexes exhibit a phase behavior similar to conventional block copolymers and can self-assemble into the bicontinuous gyroid morphology with two PS networks placed in a P4VP(PDP) matrix. PDP can be dissolved in ethanol leading to the formation of a porous structure that can be backfilled with metal. Using electroless plating technique, nickel can be inserted into the template's channels. Finally, the remaining polymer can be removed via pyrolysis from the polymer/inorganic nanohybrid resulting in nanoporous nickel foam with inverse gyroid morphology. PMID:24797367

  6. Crystallization in Ordered Polydisperse Polyolefin Diblock Copolymers

    SciTech Connect

    Li, Sheng; Register, Richard A.; Landes, Brian G.; Hustad, Phillip D.; Weinhold, Jeffrey D.

    2010-12-07

    The morphologies of polydisperse ethylene-octene diblock copolymers, synthesized via a novel coordinative chain transfer polymerization process, are examined using two-dimensional synchrotron small-angle and wide-angle X-ray scattering on flow-aligned specimens. The diblock copolymers comprise one amorphous block with high 1-octene content and one semicrystalline block with relatively low 1-octene content, and each block ideally exhibits the most-probable distribution. Near-symmetric diblocks with a sufficiently large octene differential between the amorphous and semicrystalline blocks show well-ordered lamellar domain structures with long periods exceeding 100 nm. Orientation of these domain structures persists through multiple melting/recrystallization cycles, reflecting a robust structure which self-assembles in the melt. The domain spacings are nearly 3-fold larger than those in near-monodisperse polyethylene block copolymers of similar molecular weights. Although the well-ordered lamellar domain structure established in the melt is preserved in the solid state, the crystallites are isotropic in orientation. These materials display crystallization kinetics consistent with a spreading growth habit, indicating that the lamellae do not confine or template the growing crystals. The exceptionally large domain spacings and isotropic crystal growth are attributed to interblock mixing resulting from the large polydispersity; short hard blocks dissolved in the soft-block-rich domains swell the domain spacing in the melt and allow hard block crystallization to proceed across the lamellar domain interfaces.

  7. Cavitation in block copolymer modified epoxy

    NASA Astrophysics Data System (ADS)

    Declet-Perez, Carmelo; Francis, Lorraine; Bates, Frank

    2013-03-01

    Today, brittleness in epoxy networks limits most commercial applications. Significant toughness can be imparted by adding small amounts of micelle forming block copolymers (BCP) without compromising critical properties such as high use temperature and modulus. Curing the network locks in the self-assembled BCP micellar structures formed in the monomer resin providing control of the resulting morphology. Despite significant research over the last decade, a complete description of the parameters influencing toughness in block copolymer modified epoxies is still lacking. In this presentation we compare the ultimate mechanical behavior of epoxies modified with spherical micelle forming BCP's containing rubbery and glassy cores using real-time in-situ small-angle X-ray scattering (SAXS) performed during tensile deformation. Striking differences in the 2D SAXS patterns were documented for epoxies modified with rubbery (PEP) versus glassy (PS) micelle cores. Rubbery cores dilate by 100% in volume upon specimen yielding, while the glassy micelle cores deform at approximately constant volume. These results provide direct evidence of a cavitation mediated mechanism for toughness in block copolymer modified epoxies. We further interpret characteristic butterfly features in the 2D SAXS patterns in terms of epoxy network deformation. Support was provided by the NSF sponsored MRSEC at the University of Minnesota

  8. Sulfur copolymers for infrared optical imaging

    NASA Astrophysics Data System (ADS)

    Namnabat, S.; Gabriel, J. J.; Pyun, J.; Norwood, R. A.; Dereniak, E. L.; van der Laan, J.

    2014-06-01

    The development of organic polymers with low infrared absorption has been investigated as a possible alternative to inorganic metal oxide, semiconductor, or chalcogenide-based materials for a variety of optical devices and components, such as lenses, goggles, thermal imaging cameras and optical fibers. In principle, organic-based polymers are attractive for these applications because of their low weight, ease of processing, mechanical toughness, and facile chemical variation using commercially available precursors. Herein we report on the optical characterization of a new class of sulfur copolymers that are readily moldable, transparent above 500 nm, possess high refractive index (n > 1.8) and take advantage of the low infrared absorption of S-S bonds for potential use in the mid-infrared at 3-5 microns. These materials are largely made from elemental sulfur by an inverse vulcanization process; in the current study we focus on the properties of a chemically stable, branched copolymer of poly(sulfur-random-1,3-diisopropenylbenzene) (poly(S-r- DIB). Copolymers with elemental sulfur content ranging from 50% to 80% by weight were studied by UV-VIS spectroscopy, FTIR, and prism coupling for refractive index measurement. Clear correlation between material composition and the optical properties was established, confirming that the high polarizability of the sulfur atom leads to high refractive index while also maintaining low optical loss in the infrared.

  9. Regulating block copolymer phases via selective homopolymers

    SciTech Connect

    Yang, Shuang E-mail: eqchen@pku.edu.cn; Lei, Zhen; Hu, Nan; Chen, Er-Qiang E-mail: eqchen@pku.edu.cn; Shi, An-Chang

    2015-03-28

    The phase behavior of strongly segregated AB diblock copolymer and selective C homopolymer blends is examined theoretically using a combination of strong stretching theory (SST) and self-consistent field theory (SCFT). The C-homopolymer is immiscible with the B-blocks but strongly attractive with the A-blocks. The effect of homopolymer content on the order-order phase transitions is analyzed. It is observed that, for AB diblock copolymers with majority A-blocks, the addition of the C-homopolymers results in lamellar to cylindrical to spherical phase transitions because of the A/C complexation. For diblock copolymers with minor A-blocks, adding C-homopolymers leads to transitions from spherical or cylindrical morphology with A-rich core to lamellae to inverted cylindrical and spherical morphologies with B-rich core. The results from analytical SST and numerical SCFT are in good agreement within most regions of the phase diagram. But the deviation becomes more obvious when the composition of A-blocks is too small and the content of added C-homopolymers is large enough, where the SCFT predicts a narrow co-existence region between different ordered phases. Furthermore, it is found that the phase behavior of the system is insensitive to the molecular weight of C-homopolymer.

  10. Comparing Fluid and Elastic Block Copolymer Shells

    NASA Astrophysics Data System (ADS)

    Rozairo, Damith; Croll, Andrew B.

    2014-03-01

    Emulsions can be stabilized with the addition of an amphiphilic diblock copolymer, resulting in droplets surrounded and protected by a polymer monolayer. Such droplets show considerable promise as advanced cargo carriers in pharmaceuticals or cosmetics due to their strength and responsiveness. Diblock copolymer interfaces remain mostly fluid and may not be able to attain the mechanical performance desired by industry. To strengthen block copolymer emulsion droplets we have developed a novel method for creating thin elastic shells using polystyrene-b-poly(acrylic acid)-b-polystyrene (PS-PAA-PS). Characterization of the fluid filled elastic shells is difficult with traditional means which lead us to develop a new and general method of mechanical measurement. Specifically, we use laser scanning confocal microscopy to achieve a high resolution measure of the deformation of soft spheres under the influence of gravity. To prove the resilience of the technique we examine both a polystyrene-b-poly(ethylene oxide) (PS-PEO) stabilized emulsion and the PS-PAA-PS emulsion. The mechanical measurement allows the physics of the polymer at the interface to be examined, which will ultimately lead to the rational development of these technologies.

  11. Surface modification of uniaxial cyclic strain cell culture platform with temperature-responsive polymer for cell sheet detachment†

    PubMed Central

    Lee, E. L.; Bendre, H. H.; Kalmykov, A.

    2015-01-01

    Current cell sheet-based blood vessels lack biomimetic structure and require excessively long culture times that may compromise smooth muscle cell phenotype. We modified a commercially available product for uniaxial cell sheet conditioning with thermoresponsive copolymers. Thus, culture of detachable conditioned cell sheets is shortened while retaining structural integrity and contractility. PMID:26660468

  12. Surface modification of uniaxial cyclic strain cell culture platform with temperature-responsive polymer for cell sheet detachment.

    PubMed

    Lee, E L; Bendre, H H; Kalmykov, A; Wong, J Y

    2015-10-28

    Current cell sheet-based blood vessels lack biomimetic structure and require excessively long culture times that may compromise smooth muscle cell phenotype. We modified a commercially available product for uniaxial cell sheet conditioning with thermoresponsive copolymers. Thus, culture of detachable conditioned cell sheets is shortened while retaining structural integrity and contractility.

  13. Are block copolymer worms more effective Pickering emulsifiers than block copolymer spheres?

    PubMed

    Thompson, K L; Mable, C J; Cockram, A; Warren, N J; Cunningham, V J; Jones, E R; Verber, R; Armes, S P

    2014-11-21

    RAFT-mediated polymerisation-induced self-assembly (PISA) is used to prepare six types of amphiphilic block copolymer nanoparticles which were subsequently evaluated as putative Pickering emulsifiers for the stabilisation of n-dodecane-in-water emulsions. It was found that linear poly(glycerol monomethacrylate)-poly(2-hydroxypropyl methacrylate) (PGMA-PHPMA) diblock copolymer spheres and worms do not survive the high shear homogenisation conditions used for emulsification. Stable emulsions are obtained, but the copolymer acts as a polymeric surfactant; individual chains rather than particles are adsorbed at the oil-water interface. Particle dissociation during emulsification is attributed to the weakly hydrophobic character of the PHPMA block. Covalent stabilisation of these copolymer spheres or worms can be readily achieved by addition of ethylene glycol dimethacrylate (EGDMA) during the PISA synthesis. TEM studies confirm that the resulting cross-linked spherical or worm-like nanoparticles survive emulsification and produce genuine Pickering emulsions. Alternatively, stabilisation can be achieved by either replacing or supplementing the PHPMA block with the more hydrophobic poly(benzyl methacrylate) (PBzMA). The resulting linear spheres or worms also survive emulsification and produce stable n-dodecane-in-water Pickering emulsions. The intrinsic advantages of anisotropic worms over isotropic spheres for the preparation of Pickering emulsions are highlighted. The former particles are more strongly adsorbed at similar efficiencies compared to spheres and also enable smaller oil droplets to be produced for a given copolymer concentration. The scalable nature of PISA formulations augurs well for potential applications of anisotropic block copolymer nanoparticles as Pickering emulsifiers.

  14. Effects of temperature-responsive hydrogel on viscosity of denture adhesives.

    PubMed

    Zhao, Huizi; Akiba, Norihisa; Tanimoto, Hiroyuki; Yoshizaki, Taro; Yalikun, Kaidiliya; Minakuchi, Shunsuke

    2016-01-01

    The cream type of denture adhesives after use cannot be easily removed from oral mucosa and have the potential risk to change the oral flora. The effects of the temperature-responsive hydrogel Pluronic F-127 (PF) on the complex viscosity of denture adhesives were evaluated. Carboxy methylcellulose (CMC) mass fractions (1, 2, 3 and 4%) were added to 20 and 25% PF hydrogels. Complex viscosity was measured over a temperature cycle (40→10→40°C) and fixed temperature points (23 and 37°C). Adhesive strength tests were performed with 2 resin plates at 23 and 37°C. One commercial cream-type denture adhesive, New Poligrip® (NP), was evaluated as a control. Complex viscosity values for PF20% groups at 23°C were lower than those for NP at 37°C. Adhesive strength of PF20% with CMC2%, was higher at 23°C when compared to NP at 37°C, which suggests that PF20%CMC2% is an effective adhesive and is easily removed after mouth rinsing.

  15. Application of polymeric macroporous supports for temperature-responsive chromatography of pharmaceuticals.

    PubMed

    Lamprou, Alexandros; Gavriilidou, Agni-Faviola-Mika; Storti, Giuseppe; Soos, Miroslav; Morbidelli, Massimo

    2015-08-14

    A macroporous particulate support prepared previously by reactive gelation under shear and functionalized with poly(N-isopropylacrylamide), PNIPAM, brushes of variable length is applied for temperature-responsive chromatography, whereby temperature modulates hydrophobic interactions. Several different analytes, including small pharmaceuticals, peptides, proteins and monoclonal antibodies are employed. Contrary to the most commonly observed behavior in conventional chromatography, increasing retention is observed at elevated temperatures. Peak broadening is quantified using the peak standard deviation, which depends on both the polymer chain conformation and analyte adsorptivity. The favorable effect of grafted polymer thickness on retention becomes progressively less pronounced for thicker grafted PNIPAM layers. The effect of eluent composition on solute-sorbent interactions was investigated by introducing NaCl, methanol, dioxane and by varying the pH. Salt or organic solvent addition affects apart from the analytes solution properties, the hydrophobicity of the stationary phase itself. Frontal analyses performed at different temperatures to determine dynamic binding capacities, indicate small mass transfer resistances imposed by this novel packing material. Copyright © 2015 Elsevier B.V. All rights reserved.

  16. Controllable and switchable drug delivery of ibuprofen from temperature responsive composite nanofibers

    NASA Astrophysics Data System (ADS)

    Tran, Toan; Hernandez, Mariana; Patel, Dhruvil; Burns, Elena; Peterman, Vanessa; Wu, Ji

    2015-08-01

    Composited electrospun nanofibers made of temperature-responsive poly(N-isopropylacrylamide) (pNIPAM) and biodegradable poly (ɛ-caprolactone) (PCL) can be utilized for `on-demand' and controlled drug release of ibuprofen without burst effect for potential pharmaceutical applications. Three types of nanofibers, PCL, pNIPAM and pNIPAM/PCL composite NFs containing ibuprofen were fabricated using electrospinning techniques. Ibuprofen release rates from PCL NFs are not affected by the temperature in the range of 22-34°C (less than 10%). In contrast, the ibuprofen release rates from pNIPAM NFs are very sensitive to the change in temperature, which is five times higher at 22°C compared to 34°C. However, there is a serious burst effect at 22°C. Compared to other two types of NFs, pNIPAM/PCL composite NFs prepared demonstrated a variable and controlled release at both room and higher temperature, due to the extra protection from the hydrophobic poly (ɛ-caprolactone). The rate at 22°C is 75% faster compared to that at 34°C. This kind of composite design can provide a novel approach to suppress the burst effect in drug delivery systems for potential pharmaceutical applications.

  17. Temperature responsive porous silicon nanoparticles for cancer therapy - spatiotemporal triggering through infrared and radiofrequency electromagnetic heating.

    PubMed

    Tamarov, Konstantin; Xu, Wujun; Osminkina, Liubov; Zinovyev, Sergey; Soininen, Pasi; Kudryavtsev, Andrey; Gongalsky, Maxim; Gaydarova, Azha; Närvänen, Ale; Timoshenko, Victor; Lehto, Vesa-Pekka

    2016-11-10

    One critical functionality of the carrier system utilized in targeted drug delivery is its ability to trigger the release of the therapeutic cargo once the carrier has reached its target. External triggering is an alluring approach as it can be applied in a precise spatiotemporal manner. In the present study, we achieved external triggering through the porous silicon (PSi) nanoparticles (NPs) by providing a pulse of infrared or radiofrequency radiation. The NPs were grafted with a temperature responsive polymer whose critical temperature was tailored to be slightly above 37°C. The polymer coating improved the biocompatibility of the NPs significantly in comparison with their uncoated counterparts. Radiation induced a rapid temperature rise, which resulted in the collapse of the polymer chains facilitating the cargo release. Both infrared and radiofrequency radiation were able to efficiently trigger the release of the encapsulated drug in vitro and induce significant cell death in comparison to the control groups. Radiofrequency radiation was found to be more efficient in vitro, and the treatment efficacy was verified in vivo in a lung carcinoma (3LL) mice model. After a single intratumoral administration of the carrier system combined with radiofrequency radiation, there was clear suppression of the growth of the carcinoma and a prolongation of the survival time of the animals.

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

    NASA Astrophysics Data System (ADS)

    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.

  19. Self-Assembly of Temperature-Responsive Protein–Polymer Bioconjugates

    PubMed Central

    2015-01-01

    We report a simple temperature-responsive bioconjugate system comprising superfolder green fluorescent protein (sfGFP) decorated with poly[(oligo ethylene glycol) methyl ether methacrylate] (PEGMA) polymers. We used amber suppression to site-specifically incorporate the non-canonical azide-functional amino acid p-azidophenylalanine (pAzF) into sfGFP at different positions. The azide moiety on modified sfGFP was then coupled using copper-catalyzed “click” chemistry with the alkyne terminus of a PEGMA synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization. The protein in the resulting bioconjugate was found to remain functionally active (i.e., fluorescent) after conjugation. Turbidity measurements revealed that the point of attachment of the polymer onto the protein scaffold has an impact on the thermoresponsive behavior of the resultant bioconjugate. Furthermore, small-angle X-ray scattering analysis showed the wrapping of the polymer around the protein in a temperature-dependent fashion. Our work demonstrates that standard genetic manipulation combined with an expanded genetic code provides an easy way to construct functional hybrid biomaterials where the location of the conjugation site on the protein plays an important role in determining material properties. We anticipate that our approach could be generalized for the synthesis of complex functional materials with precisely defined domain orientation, connectivity, and composition. PMID:26083370

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

    USGS Publications Warehouse

    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.

  1. Acute effects of normobaric hypoxia on hand-temperature responses during and after local cold stress.

    PubMed

    Keramidas, Michail E; Kölegård, Roger; Mekjavic, Igor B; Eiken, Ola

    2014-06-01

    The purpose was to investigate acute effects of normobaric hypoxia on hand-temperature responses during and after a cold-water hand immersion test. Fifteen males performed two right-hand immersion tests in 8°C water, during which they were inspiring either room air (Fio2: 0.21; AIR), or a hypoxic gas mixture (Fio2: 0.14; HYPO). The tests were conducted in a counterbalanced order and separated by a 1-hour interval. Throughout the 30-min cold-water immersion (CWI) and the 15-min spontaneous rewarming (RW) phases, finger-skin temperatures were measured continuously with thermocouple probes; infrared thermography was also employed during the RW phase to map all segments of the hand. During the CWI phase, the average skin temperature (Tavg) of the fingers did not differ between the conditions (AIR: 10.2 ± 0.5°C, HYPO: 10.0 ± 0.5°C; p = 0.67). However, Tavg was lower in the HYPO than the AIR RW phase (AIR: 24.5 ± 3.4°C; HYPO: 22.0 ± 3.8°C; p = 0.002); a response that was alike in all regions of the immersed hand. Accordingly, present findings suggest that acute exposure to normobaric hypoxia does not aggravate the cold-induced drop in hand temperature of normothermic males. Still, hypoxia markedly impairs the rewarming responses of the hand.

  2. Temperature-responsive size-exclusion chromatography using poly(N-isopropylacrylamide) grafted silica.

    PubMed

    Lakhiari, H; Okano, T; Nurdin, N; Luthi, C; Descouts, P; Muller, D; Jozefonvicz, J

    1998-03-02

    Silica-based packing materials induce non-specific interactions with proteins in aqueous media because of the nature of their surface, mainly silanol groups. Therefore, the silica surface has to be modified in order to be used as stationary phase for the High Performance Size-Exclusion Chromatography (HPSEC) of proteins. For this purpose, porous silica beads were coated with hydrophilic polymer gels (dextrans of different molecular weights) carrying a calculated amount of diethyl-aminoethyl groups (DEAE). Actually, as shown by HPSEC, these dextran modified supports minimize non-specific adsorption for proteins and pullulans in aqueous solution. Then, in order to change the pore size in response to temperature, temperature responsive polymer of poly(N-isopropylacrylamide) (PIPAAm) was introduced into the surface of dextran-DEAE on porous silica beads. The structure of these supports before and after modification was alternately studied by Scanning Electronic Microscopy (SEM) and Scanning Force Microscopy (SFM). An adsorption of radiolabelled albumin was performed to complete our study. Silica modifications by dextran-DEAE and PIPAAm improve the neutrality of the support and minimize the non-specific interactions between the solid support and proteins in solution. At low temperature, the support having PIPAAm exhibits a high resolution domain in HPSEC and finally permits a better resolution of proteins and pullulans. At higher temperature, hydrophobic properties of PIPAAm produce interactions with some proteins and trigger off a slight delay of their elution time.

  3. Body temperature responses of Savanna Brown goat to the harmattan and hot-dry season

    NASA Astrophysics Data System (ADS)

    Igono, M. O.; Molokwu, E. C. I.; Aliu, Y. O.

    1982-09-01

    Rectal and vaginal temperature responses of the Savanna Brown goat indigenous to the Nigerian guinea savanna were determined during the harmattan and the hot-dry season. Measurements were made at 06:00h and at 14:00h after 8h exposure to field conditions. At the 06:00h measurements during the harmattan, all animals were observed to shiver. A significant (P<0.01) positive correlation was found between rectal (Tre) and vaginal temperatures. During the harmattan, mean Tre was 38.2‡C at 06:00h and 39.7‡C at 14:00h; the mean difference, δTre was 1.5‡C. During the hot-dry season, Tre at 06:00h was 38.1‡C, and at 14:00h, 38.7; δTre was 0.6‡C. It is concluded that the harmattan is thermally more stressful than the hot-dry season and that passive thermolability may not be an important mechanism in the Savanna Brown goat in adaptation to thermal stress.

  4. Acclimation of respiratory temperature responses in northern and southern populations of Pinus banksiana.

    PubMed

    Tjoelker, M G; Oleksyn, J; Lorenc-Plucinska, G; Reich, P B

    2009-01-01

    Temperature acclimation of respiration may contribute to climatic adaptation and thus differ among populations from contrasting climates. Short-term temperature responses of foliar dark respiration were measured in 33-yr-old trees of jack pine (Pinus banksiana) in eight populations of wide-ranging origin (44-55 degrees N) grown in a common garden at 46.7 degrees N. It was tested whether seasonal adjustments in respiration and population differences in this regard resulted from changes in base respiration rate at 5 degrees C (R(5)) or Q(10) (temperature sensitivity) and covaried with nitrogen and soluble sugars. In all populations, acclimation was manifest primarily through shifts in R(5) rather than altered Q(10). R(5) was higher in cooler periods in late autumn and winter and lower in spring and summer, inversely tracking variation in ambient air temperature. Overall, R(5) covaried with sugars and not with nitrogen. Although acclimation was comparable among all populations, the observed seasonal ranges in R(5) and Q(10) were greater in populations originating from warmer than from colder sites. Population differences in respiratory traits appeared associated with autumnal cold hardening. Common patterns of respiratory temperature acclimation among biogeographically diverse populations provide a basis for predicting respiratory carbon fluxes in a wide-ranging species.

  5. pH- and temperature-sensitive polymeric microspheres for drug delivery: the dissolution of copolymers modulates drug release.

    PubMed

    Fundueanu, Gheorghe; Constantin, Marieta; Stanciu, Cristina; Theodoridis, Georgios; Ascenzi, Paolo

    2009-12-01

    Most pH-/temperature-responsive polymers for controlled release of drugs are used as cross-linked hydrogels. However, the solubility properties of the linear polymers below and above the lower critical solution temperature (LCST) are not exploited. Here, the preparation and characterization of poly (N-isopropylacrylamide-co-methacrylic acid-co-methyl methacrylate) (poly (NIPAAm-co-MA-co-MM)) and poly (N-isopropylacrylamide-co-acrylamide) (poly (NIPAAm-co-AAm)), known as "smart" polymers (SP), is reported. Both poly (NIPAAm-co-MA-co-MM) and poly (NIPAAm-co-AAm) display pH- and temperature-responsive properties. Poly (NIPAAm-co-MA-co-MM) was designed to be insoluble in the gastric fluid (pH = 1.2), but soluble in the intestinal fluid (pH = 6.8 and 7.4), at the body temperature (37 degrees C). Poly (NIPAAm-co-AAm) was designed to have a lower critical solution temperature (LCST) corresponding to 37 degrees C at pH = 7.4, therefore it is not soluble above the LCST. The solubility characteristics of these copolymers were exploited to modulate the rate of release of drugs by changing pH and/or temperature. These copolymers were solubilized with hydrophobic cellulose acetate butyrate (CAB) and vitamin B(12) (taken as a water soluble drug model system) in an acetone/methanol mixture and dispersed in mineral oil. By a progressive evaporation of the solvent, the liquid droplets were transformed into loaded CAB/SP microspheres. Differential scanning calorimetric studies and scanning electron microscopy analysis demonstrated that the polymeric components of the microspheres precipitated separately during solvent evaporation forming small microdomains. Moreover, vitamin B(12) was found to be molecularly dispersed in both microdomains with no specific affinity for any polymeric component of microspheres. The release of vitamin B(12) was investigated as a function of temperature, pH, and the CAB/SP ratio.

  6. 21 CFR 177.1310 - Ethylene-acrylic acid copolymers.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Ethylene-acrylic acid copolymers. 177.1310 Section... Use Food Contact Surfaces § 177.1310 Ethylene-acrylic acid copolymers. The ethylene-acrylic acid... for use in contact with food subject to the provisions of this section. (a) The ethylene-acrylic acid...

  7. Piezoelectric Properties of Non-Polar Block Copolymers

    SciTech Connect

    Pester, Christian; Ruppel, Markus A; Schoberth, Heiko; Schmidt, K.; Liedel, Clemens; Van Rijn, Patrick; Littrell, Ken; Schindler, Kerstin; Hiltl, Stephanie; Czubak, Thomas; Mays, Jimmy; Urban, Volker S; Boker, Alexander

    2011-01-01

    Piezoelectric properties in non-polar block copolymers are a novelty in the field of electroactive polymers. The piezoelectric susceptibility of poly(styrene-b-isoprene) block copolymer lamellae is found to be up to an order of magnitude higher when compared to classic piezoelectric materials. The electroactive response increases with temperature and is found to be strongest in the disordered phase.

  8. 21 CFR 177.1211 - Cross-linked polyacrylate copolymers.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... polyacrylate copolymers consist of: (1) The grafted copolymer of cross-linked sodium polyacrylate identified as 2-propenoic acid, polymers with N,N-di-2-propenyl-2-propen-1-amine and hydrolyzed polyvinyl acetate, sodium salts, graft (CAS Reg. No. 166164-74-5); or (2) 2-propenoic acid, polymer with 2-ethyl-2-(((1-oxo...

  9. 21 CFR 177.1211 - Cross-linked polyacrylate copolymers.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... polyacrylate copolymers consist of: (1) The grafted copolymer of cross-linked sodium polyacrylate identified as 2-propenoic acid, polymers with N,N-di-2-propenyl-2-propen-1-amine and hydrolyzed polyvinyl acetate, sodium salts, graft (CAS Reg. No. 166164-74-5); or (2) 2-propenoic acid, polymer with 2-ethyl-2-(((1-oxo...

  10. 21 CFR 177.1211 - Cross-linked polyacrylate copolymers.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... grafted copolymer of cross-linked sodium polyacrylate identified as 2-propenoic acid, polymers with N,N-di-2-propenyl-2-propen-1-amine and hydrolyzed polyvinyl acetate, sodium salts, graft (CAS Reg. No...-propanediyl di-2-propenoate and sodium 2-propenoate (CAS Reg. No. 76774-25-9). (b) Adjuvants. The copolymers...

  11. 21 CFR 177.1211 - Cross-linked polyacrylate copolymers.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... polyacrylate copolymers consist of: (1) The grafted copolymer of cross-linked sodium polyacrylate identified as 2-propenoic acid, polymers with N,N-di-2-propenyl-2-propen-1-amine and hydrolyzed polyvinyl acetate, sodium salts, graft (CAS Reg. No. 166164-74-5); or (2) 2-propenoic acid, polymer with 2-ethyl-2-(((1-oxo...

  12. 21 CFR 177.1211 - Cross-linked polyacrylate copolymers.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... polyacrylate copolymers consist of: (1) The grafted copolymer of cross-linked sodium polyacrylate identified as 2-propenoic acid, polymers with N,N-di-2-propenyl-2-propen-1-amine and hydrolyzed polyvinyl acetate, sodium salts, graft (CAS Reg. No. 166164-74-5); or (2) 2-propenoic acid, polymer with 2-ethyl-2-(((1-oxo...

  13. Morphological studies on block copolymer modified PA 6 blends

    NASA Astrophysics Data System (ADS)

    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.

  14. Morphological studies on block copolymer modified PA 6 blends

    SciTech Connect

    Poindl, M. E-mail: christian.bonten@ikt.uni-stuttgart.de; Bonten, C. E-mail: christian.bonten@ikt.uni-stuttgart.de

    2014-05-15

    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.

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

    PubMed

    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.

  16. 21 CFR 177.1320 - Ethylene-ethyl acrylate copolymers.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... blended with polyethylene or with one or more olefin copolymers complying with § 177.1520 or with a mixture of polyethylene and one or more olefin copolymers, in such proportions that the ethyl acrylate... prescribed in paragraph (c)(2) of this section, when tested by the methods prescribed for polyethylene...

  17. 21 CFR 177.1320 - Ethylene-ethyl acrylate copolymers.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... percent by weight unless it is blended with polyethylene or with one or more olefin copolymers complying with § 177.1520 or with a mixture of polyethylene and one or more olefin copolymers, in such... prescribed for polyethylene in § 177.1520. (1) Specifications—(i) Infrared identification....

  18. Block Copolymer Directed Assembly for Nanomaterials and Nanodevices

    NASA Astrophysics Data System (ADS)

    Kim, Sang

    2013-03-01

    Block copolymer nanopatterning is a promising technology that can complement the inherent limitations of conventional photolithography. The spontaneous and parallel assembly of block copolymers may generate densely packed, periodic 10-nm-scale nanodomains in a scalable way. Furthermore, laterally ordered, device-oriented nanostructures are attainable by the directed self-assembly principles employing prepatterned substrates. In this presentation, the overview of my research achievements associated to block copolymer nanopatterning will be presented. My research group demonstrated the world-first successful integration of block copolymer nanopatterning with 193 nm ArF lithography. We also developed soft-graphoepitaxy, which generates highly aligned nanoscale metal and semiconductor nanostructures without any trace of structure-directing topographic pattern. Soft-graphoepitaxy could be further developed to ultralarge-area nanopatterning, where micrometer scale photoresist pattern can be completely transformed into large-area block copolymer nanopattern. My research group also developed various pattern transfer methods for block copolymer nanopatterning. Mussel-inspired block copolymer nanopatterning exploiting universal natural adhesive of mussel polydopamine enables the nanopatterning of low surface energy materials, such as gold, Teflon and graphene. Our recent transferrable and flexible nanopatterning employing chemically modified graphene films as pattern substrates makes it possible to apply block copolymer nanopatterning onto arbitrary nonplanar and flexible geometries and generates ideal three-dimensional assembly of carbon nanotubes and graphene.

  19. 40 CFR 721.10213 - Polyether polyester copolymer phosphate (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... phosphate (generic). 721.10213 Section 721.10213 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.10213 Polyether polyester copolymer phosphate (generic). (a) Chemical... as polyether polyester copolymer phosphate (PMN P-09-253) is subject to reporting under this section...

  20. 40 CFR 721.10213 - Polyether polyester copolymer phosphate (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... phosphate (generic). 721.10213 Section 721.10213 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.10213 Polyether polyester copolymer phosphate (generic). (a) Chemical... as polyether polyester copolymer phosphate (PMN P-09-253) is subject to reporting under this section...

  1. 40 CFR 721.10213 - Polyether polyester copolymer phosphate (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... phosphate (generic). 721.10213 Section 721.10213 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.10213 Polyether polyester copolymer phosphate (generic). (a) Chemical... as polyether polyester copolymer phosphate (PMN P-09-253) is subject to reporting under this section...

  2. 40 CFR 721.10213 - Polyether polyester copolymer phosphate (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... phosphate (generic). 721.10213 Section 721.10213 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.10213 Polyether polyester copolymer phosphate (generic). (a) Chemical... as polyether polyester copolymer phosphate (PMN P-09-253) is subject to reporting under this section...

  3. Block Copolymers for Alkaline Fuel Cell Membrane Materials

    DTIC Science & Technology

    2014-07-30

    113 CHAPTER 5 MONO METHOXY POLY( ETHYLENE GLYCOL) GRAFTED BLOCK COPOLYMERS FOR ALKALINE EXCHANGE MEMBRANE...polystyrene-poly( ethylene -co-butylene)-polystyrene (SEBS) copolymer.[37, 42] Chloromethylation of the polystyrene block and trimethylamine...temperature. The same graft and functionalization strategy was applied to poly( ethylene -co- tetrafluoroethylene) (ETFE) film leading to a promising

  4. Temperature response of photosynthesis in different drug and fiber varieties of Cannabis sativa L.

    PubMed

    Chandra, Suman; Lata, Hemant; Khan, Ikhlas A; Elsohly, Mahmoud A

    2011-07-01

    The temperature response on gas and water vapour exchange characteristics of three medicinal drug type (HP Mexican, MX and W1) and four industrial fiber type (Felinq 34, Kompolty, Zolo 11 and Zolo 15) varieties of Cannabis sativa, originally from different agro-climatic zones worldwide, were studied. Among the drug type varieties, optimum temperature for photosynthesis (Topt) was observed in the range of 30-35 °C in high potency Mexican HPM whereas, it was in the range of 25-30 °C in W1. A comparatively lower value (25 °C) for Topt was observed in MX. Among fiber type varieties, Topt was around 30 °C in Zolo 11 and Zolo 15 whereas, it was near 25 °C in Felinq 34 and Kompolty. Varieties having higher maximum photosynthesis (PN max) had higher chlorophyll content as compared to those having lower PN max. Differences in water use efficiency (WUE) were also observed within and among the drug and fiber type plants. However, differences became less pronounced at higher temperatures. Both stomatal and mesophyll components seem to be responsible for the temperature dependence of photosynthesis (PN) in this species, however, their magnitude varied with the variety. In general, a two fold increase in dark respiration with increase in temperature (from 20 °C to 40 °C) was observed in all the varieties. However, a greater increase was associated with the variety having higher rate of photosynthesis, indicating a strong association between photosynthetic and respiratory rates. The results provide a valuable indication regarding variations in temperature dependence of PN in different varieties of Cannabis sativa L.

  5. Voluntary fluid intake and core temperature responses in adolescent tennis players: sports beverage versus water

    PubMed Central

    Bergeron, M F; Waller, J L; Marinik, E L

    2006-01-01

    Objective To examine differences in ad libitum fluid intake, comparing a 6% carbohydrate/electrolyte drink (CHO‐E) and water, and associated differences in core temperature and other selected physiological and perceptual responses in adolescent athletes during tennis training in the heat. Methods Fourteen healthy, fit, young tennis players (nine male; five female; mean (SD) age 15.1 (1.4) years; weight 60.6 (8.3) kg; height 172.8 (8.6) cm) completed two 120 minute tennis specific training sessions on separate days (randomised, crossover design) in a warm environment (wet bulb globe temperature: CHO‐E, 79.3 (2.6) °F; water, 79.9 (2.2) °F; p>0.05). Results There were no significant differences (p>0.05) between the trials with respect to fluid intake, urine volume, fluid retention, sweat loss, perceived exertion, thirst, or gastrointestinal discomfort. However, there was a difference (p<0.05) in the percentage body weight change after training (CHO‐E, −0.5 (0.7)%; water, −0.9 (0.6)%). Urine specific gravity before training (CHO‐E, 1.024 (0.006); water, 1.025 (0.005)) did not correlate significantly (p>0.05) with any of these measurements or with core body temperature. In examining the main effect for trial, the CHO‐E trial showed a significantly lower (p<0.001) mean body temperature (irrespective of measurement time) than the water trial. However, the mean body temperature in each trial was not associated (p>0.05) with fluid intake, fluid retention, sweat loss, or percentage body weight change. Conclusion Ad libitum consumption of a CHO‐E drink may be more effective than water in minimising fluid deficits and mean core temperature responses during tennis and other similar training in adolescent athletes. PMID:16632570

  6. Temperature responses of some North Atlantic Cladophora species (Chlorophyceae) in relation to their geographic distribution

    NASA Astrophysics Data System (ADS)

    Cambridge, M.; Breeman, A. M.; van Oosterwijk, R.; van den Hoek, C.

    1984-09-01

    The temperature responses for growth and survival have been experimentally tested for 6 species of the green algal genus Cladophora (Chlorophyceae; Cladophorales) (all isolated from Roscoff, Brittany, France, one also from Connecticut, USA), selected from 4 distribution groups, in order to determine which phase in the annual temperature regime might prevent the spread of a species beyond its present latitudinal range on the N. Atlantic coasts. For five species geographic limits could be specifically defined as due to a growth limit in the growing season or to a lethal limit in the adverse season. These species were: (1) C. coelothrix (Amphiatlantic tropical to warm temperate), with a northern boundary on the European coasts formed by a summer growth limit near the 12°C August isotherm. On the American coasts sea temperatures should allow its occurrence further north. (2) C. vagabunda (Amphiatlantic tropical to temperate), with a northern boundary formed by a summer growth limit near the 15°C August isotherm on both sides of the Atlantic. (3) C. dalmatica, as for C. vagabunda. (4) C. hutchinsiae (Mediterranean-Atlantic warm temperate), with a northern boundary formed by a summer growth limit near the 12°C August isotherm, and possibly also a winter lethal limit near the 6°C February isotherm; and a southern boundary formed by a southern lethal limit near the 26°C August isotherm. It is absent from the warm temperate American coast because its lethal limits, 5° and 30°C, are regularly reached there. (5) Preliminary data for C. rupestris (Amphiatlantic temperate), suggest the southeastern boundary on the African coast to be a summer lethal limit near the 26°C August isotherm; the southwestern boundary on the American coast lies on the 20°C August isotherm. For one species, C. albida, the experimental growth and survival range was wider than expected from its geographic distribution, and reasons to account for this are suggested.

  7. Linking altitudinal gradients and temperature responses of plant phenology in the Bavarian Alps.

    PubMed

    Cornelius, C; Estrella, N; Franz, H; Menzel, A

    2013-01-01

    Global climate change influences ecosystems across the world. Alpine plant communities have already experienced serious impacts, and will continue to do so as climate change continues. The aim of our study was to determine the sensitivity of woody and herbaceous species to shifts in temperature along an altitudinal gradient. Since 1994, park rangers have been making phenological observations at 24 sites from 680 to 1425 m a.s.l. Each year 21 plant species were observed once or twice weekly from March to July; with a main focus on flowering and leaf unfolding. Our study showed a very high degree of dependence of phenophases and species on inter-annual temperature variation and altitude. Averaged over all species and phenophases, there was a delay of 3.8 days with every 100 m increase in altitude and, across all elevations, an advance of phenophases of 6 days per 1 °C increase in temperature. Temperature lapse rates assessed indirectly by phenology, as the quotient of altitudinal to temperature response coefficients, were higher than directly calculated from March to July mean temperatures, most likely due to snow effects. Furthermore, a significant difference in sensitivity to temperature change was found between growth forms (herbs versus trees). Sensitivity was less pronounced in events occurring later in the season. Our results show that species reactions will differ in magnitude during global warming. Consequently, impacts of shifts in the timing of phenological events on plant migration and plant-pollinator interactions due to rising temperatures should be considered at the species level. © 2012 German Botanical Society and The Royal Botanical Society of the Netherlands.

  8. Temperature responses of photosynthesis and respiration in Populus balsamifera L.: acclimation versus adaptation.

    PubMed

    Silim, Salim N; Ryan, Natalie; Kubien, David S

    2010-04-01

    To examine the role of acclimation versus adaptation on the temperature responses of CO(2) assimilation, we measured dark respiration (R(n)) and the CO(2) response of net photosynthesis (A) in Populus balsamifera collected from warm and cool habitats and grown at warm and cool temperatures. R(n) and the rate of photosynthetic electron transport (J) are significantly higher in plants grown at 19 versus 27 degrees C; R(n) is not affected by the native thermal habitat. By contrast, both the maximum capacity of rubisco (V(cmax)) and A are relatively insensitive to growth temperature, but both parameters are slightly higher in plants from cool habitats. A is limited by rubisco capacity from 17-37 degrees C regardless of growth temperature, and there is little evidence for an electron-transport limitation. Stomatal conductance (g(s)) is higher in warm-grown plants, but declines with increasing measurement temperature from 17 to 37 degrees C, regardless of growth temperature. The mesophyll conductance (g(m)) is relatively temperature insensitive below 25 degrees C, but g(m) declines at 37 degrees C in cool-grown plants. Plants acclimated to cool temperatures have increased R(n)/A, but this response does not differ between warm- and cool-adapted populations. Primary carbon metabolism clearly acclimates to growth temperature in P. balsamifera, but the ecotypic differences in A suggest that global warming scenarios might affect populations at the northern and southern edges of the boreal forest in different ways.

  9. pH- and temperature-responsive aqueous foams stabilized by hairy latex particles.

    PubMed

    Fujii, Syuji; Akiyama, Ko; Nakayama, Saori; Hamasaki, Sho; Yusa, Shin-ichi; Nakamura, Yoshinobu

    2015-01-21

    Polystyrene (PS) particles carrying pH- and temperature-responsive poly[2-(dimethylamino)ethyl methacrylate] (PDMA) hairs (PDMA-PS particles) were synthesized by dispersion polymerization. The diameter, diameter distribution, morphology, chemical composition and surface chemistry of the particles were characterized using scanning electron microscopy (SEM), elemental microanalysis, dynamic light scattering and zeta potential measurements. The hydrophilicity-hydrophobicity balance of the PDMA could be tuned by varying both pH and temperature and therefore these sterically stabilized particles acted as doubly stimuli-responsive stabilizers for aqueous foams by adsorption and desorption to/from the air-water interface. At and above pH 6.0, in which range the PDMA hairs were either non-protonated or partially protonated, particle-stabilized foams were formed at both 23 and 55 °C. The foam prepared at 55 °C was the more stable of the two, lasting for at least 24 h, whereas the 23 °C foam destabilized within 24 h. SEM studies indicated that the particles adsorbed at the air-water interface as monolayers at 23 °C and as multilayers at 55 °C. At and below pH 5, in which range the hairs were cationic, hydrophilic and water-soluble, no foam was formed irrespective of temperature. Rapid defoaming could be induced by lowering the solution pH at both temperatures, due to rapid in situ protonation of the PDMA hairs, prompting the PDMA-PS particles to desorb from the air-water interface. The foaming and defoaming cycles could be repeated at least five times.

  10. Global satellite data highlights the diurnal asymmetry of the surface temperature response to deforestation

    NASA Astrophysics Data System (ADS)

    Schultz, Natalie M.; Lawrence, Peter J.; Lee, Xuhui

    2017-04-01

    Uncertainties remain about the spatial pattern and magnitude of the biophysical effects of deforestation. In particular, a diurnal asymmetry in the magnitude and sign of the surface temperature response to deforestation (ΔTS) has been observed, but the biophysical processes that contribute to day and nighttime ΔTS are not fully understood. In this study, we use a space-for-time approach with satellite and reanalysis data to investigate the biophysical processes that control the day and nighttime ΔTS. Additionally, we incorporate flux-tower data to examine two hypotheses for nighttime forest warming relative to open lands: (1) that forests generate turbulence in the stable nocturnal boundary layer, which brings heat aloft down to the surface, and (2) that forests store more heat during the day and release it at night. Our results confirm a diurnal asymmetry in ΔTS. Over most regions of the world, deforestation results in daytime warming and nighttime cooling. The strongest daytime warming is in the tropics, where the average ΔTS is 4.4 ± 0.07 K. The strongest nighttime cooling is observed in the boreal zone, where open lands are cooler than forests by an average of 1.4 ± 0.04 K. Daytime patterns of ΔTS are explained by differences in the latent heat flux (ΔLE) and absorbed solar radiation (ΔKa). We find that nighttime ΔTS is related to the strength of the nocturnal temperature inversion, with stronger temperature inversions at high latitudes and weak inversions in the tropics. Forest turbulence at night combined with stored heat release drives nighttime ΔTS patterns.

  11. Voluntary fluid intake and core temperature responses in adolescent tennis players: sports beverage versus water.

    PubMed

    Bergeron, M F; Waller, J L; Marinik, E L

    2006-05-01

    To examine differences in ad libitum fluid intake, comparing a 6% carbohydrate/electrolyte drink (CHO-E) and water, and associated differences in core temperature and other selected physiological and perceptual responses in adolescent athletes during tennis training in the heat. Fourteen healthy, fit, young tennis players (nine male; five female; mean (SD) age 15.1 (1.4) years; weight 60.6 (8.3) kg; height 172.8 (8.6) cm) completed two 120 minute tennis specific training sessions on separate days (randomised, crossover design) in a warm environment (wet bulb globe temperature: CHO-E, 79.3 (2.6) degrees F; water, 79.9 (2.2) degrees F; p>0.05). There were no significant differences (p>0.05) between the trials with respect to fluid intake, urine volume, fluid retention, sweat loss, perceived exertion, thirst, or gastrointestinal discomfort. However, there was a difference (p<0.05) in the percentage body weight change after training (CHO-E, -0.5 (0.7)%; water, -0.9 (0.6)%). Urine specific gravity before training (CHO-E, 1.024 (0.006); water, 1.025 (0.005)) did not correlate significantly (p>0.05) with any of these measurements or with core body temperature. In examining the main effect for trial, the CHO-E trial showed a significantly lower (p<0.001) mean body temperature (irrespective of measurement time) than the water trial. However, the mean body temperature in each trial was not associated (p>0.05) with fluid intake, fluid retention, sweat loss, or percentage body weight change. Ad libitum consumption of a CHO-E drink may be more effective than water in minimising fluid deficits and mean core temperature responses during tennis and other similar training in adolescent athletes.

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

    PubMed Central

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

    PubMed

    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.

  14. Dual magnetic-/temperature-responsive nanoparticles for microfluidic separations and assays.

    PubMed

    Lai, James J; Hoffman, John M; Ebara, Mitsuhiro; Hoffman, Allan S; Estournès, Claude; Wattiaux, Alain; Stayton, Patrick S

    2007-06-19

    A stimuli-responsive magnetic nanoparticle system for diagnostic target capture and concentration has been developed for microfluidic lab card settings. Telechelic poly(N-isopropylacrylamide) (PNIPAAm) polymer chains were synthesized with dodecyl tails at one end and a reactive carboxylate at the opposite end by the reversible addition fragmentation transfer technique. These PNIPAAm chains self-associate into nanoscale micelles that were used as dimensional confinements to synthesize the magnetic nanoparticles. The resulting superparamagnetic nanoparticles exhibit a gamma-Fe2O3 core ( approximately 5 nm) with a layer of carboxylate-terminated PNIPAAm chains as a corona on the surface. The carboxylate group was used to functionalize the magnetic nanoparticles with biotin and subsequently with streptavidin. The functionalized magnetic nanoparticles can be reversibly aggregated in solution as the temperature is cycled through the PNIPAAm lower critical solution temperature (LCST). While the magnetophoretic mobility of the individual nanoparticles below the LCST is negligible, the aggregates formed above the LCST are large enough to respond to an applied magnetic field. The magnetic nanoparticles can associate with biotinylated targets as individual particles, and then subsequent application of a combined temperature increase and magnetic field can be used to magnetically separate the aggregated particles onto the poly(ethylene glycol)-modified polydimethylsiloxane channel walls of a microfluidic device. When the magnetic field is turned off and the temperature is reversed, the captured aggregates redisperse into the channel flow stream for further downstream processing. The dual magnetic- and temperature-responsive nanoparticles can thus be used as soluble reagents to capture diagnostic targets at a controlled time point and channel position. They can then be isolated and released after the nanoparticles have captured target molecules, overcoming the problem of low

  15. Temperature Responses of C4 Photosynthesis: Biochemical Analysis of Rubisco, Phosphoenolpyruvate Carboxylase, and Carbonic Anhydrase in Setaria viridis1[OPEN

    PubMed Central

    Boyd, Ryan A.; Gandin, Anthony; Cousins, Asaph B.

    2015-01-01

    The photosynthetic assimilation of CO2 in C4 plants is potentially limited by the enzymatic rates of Rubisco, phosphoenolpyruvate carboxylase (PEPc), and carbonic anhydrase (CA). Therefore, the activity and kinetic properties of these enzymes are needed to accurately parameterize C4 biochemical models of leaf CO2 exchange in response to changes in CO2 availability and temperature. There are currently no published temperature responses of both Rubisco carboxylation and oxygenation kinetics from a C4 plant, nor are there known measurements of the temperature dependency of the PEPc Michaelis-Menten constant for its substrate HCO3−, and there is little information on the temperature response of plant CA activity. Here, we used membrane inlet mass spectrometry to measure the temperature responses of Rubisco carboxylation and oxygenation kinetics, PEPc carboxylation kinetics, and the activity and first-order rate constant for the CA hydration reaction from 10°C to 40°C using crude leaf extracts from the C4 plant Setaria viridis. The temperature dependencies of Rubisco, PEPc, and CA kinetic parameters are provided. These findings describe a new method for the investigation of PEPc kinetics, suggest an HCO3− limitation imposed by CA, and show similarities between the Rubisco temperature responses of previously measured C3 species and the C4 plant S. viridis. PMID:26373659

  16. Temperature Responses of C4 Photosynthesis: Biochemical Analysis of Rubisco, Phosphoenolpyruvate Carboxylase, and Carbonic Anhydrase in Setaria viridis.

    PubMed

    Boyd, Ryan A; Gandin, Anthony; Cousins, Asaph B

    2015-11-01

    The photosynthetic assimilation of CO2 in C4 plants is potentially limited by the enzymatic rates of Rubisco, phosphoenolpyruvate carboxylase (PEPc), and carbonic anhydrase (CA). Therefore, the activity and kinetic properties of these enzymes are needed to accurately parameterize C4 biochemical models of leaf CO2 exchange in response to changes in CO2 availability and temperature. There are currently no published temperature responses of both Rubisco carboxylation and oxygenation kinetics from a C4 plant, nor are there known measurements of the temperature dependency of the PEPc Michaelis-Menten constant for its substrate HCO3 (-), and there is little information on the temperature response of plant CA activity. Here, we used membrane inlet mass spectrometry to measure the temperature responses of Rubisco carboxylation and oxygenation kinetics, PEPc carboxylation kinetics, and the activity and first-order rate constant for the CA hydration reaction from 10°C to 40°C using crude leaf extracts from the C4 plant Setaria viridis. The temperature dependencies of Rubisco, PEPc, and CA kinetic parameters are provided. These findings describe a new method for the investigation of PEPc kinetics, suggest an HCO3 (-) limitation imposed by CA, and show similarities between the Rubisco temperature responses of previously measured C3 species and the C4 plant S. viridis. © 2015 American Society of Plant Biologists. All Rights Reserved.

  17. Light-emitting block copolymers composition, process and use

    DOEpatents

    Ferraris, John P.; Gutierrez, Jose J.

    2006-11-14

    Generally, and in one form, the present invention is a composition of light-emitting block copolymer. In another form, the present invention is a process producing a light-emitting block copolymers that intends polymerizing a first di(halo-methyl) aromatic monomer compound in the presence of an anionic initiator and a base to form a polymer and contacting a second di(halo-methyl) aromatic monomer compound with the polymer to form a homopolymer or block copolymer wherein the block copolymer is a diblock, triblock, or star polymer. In yet another form, the present invention is an electroluminescent device comprising a light-emitting block copolymer, wherein the electroluminescent device is to be used in the manufacturing of optical and electrical devices.

  18. Block Copolymer Metastability: Scientific Nightmare or Engineering Dream?

    NASA Astrophysics Data System (ADS)

    Bates, Frank S.

    1997-03-01

    Most experimental studies and almost all theories that deal with block copolymers, or mixtures of block copolymers and homopolymers, have been designed from an equilibrium perspective. Yet a myriad of factors conspire to retard approach to equilibrium in these systems, including: subtle features in the free energy surface that are controlled by ordered state symmetry; a coupling between microphase separation and entanglement dynamics; complex molecular architectures such as multiblock, starblock, and miktoarm. Even unentangled low molecular weight diblock copolymers, the simplest and dynamically least encumbered materials, exhibit long-lived metastable states that confound attempts to validate equilibrium theories. However, this apparent dilemma can be exploited through clever processing strategies. This lecture will address two opposing consequences of block copolymer metastability. The first is a potential nightmare: Can we ever establish universal block copolymer phase diagrams? The second is the stuff of dreams: Self-assembled thermoset nanocomposites.

  19. Electric Field Induced Selective Disordering in Lamellar Block Copolymers

    SciTech Connect

    Ruppel, Markus A; Pester, Christian W; Langner, Karol M; Sevink, Geert; Schoberth, Heiko; Schmidt, Kristin; Urban, Volker S; Mays, Jimmy; Boker, Alexander

    2013-01-01

    External electric fields align nanostructured block copolymers by either rotation of grains or nucleation and growth depending on how strongly the chemically distinct block copolymer components are segregated. In close vicinity to the orderdisorder transition, theory and simulations suggest a third mechanism: selective disordering. We present a time-resolved small-angle X-ray scattering study that demonstrates how an electric field can indeed selectively disintegrate ill-aligned lamellae in a lyotropic block copolymer solution, while lamellae with interfaces oriented parallel to the applied field prevail. The present study adds an additional mechanism to the experimentally corroborated suite of mechanistic pathways, by which nanostructured block copolymers can align with an electric field. Our results further unveil the benefit of electric field assisted annealing for mitigating orientational disorder and topological defects in block copolymer mesophases, both in close vicinity to the orderdisorder transition and well below it.

  20. Electric field induced selective disordering in lamellar block copolymers.

    PubMed

    Ruppel, Markus; Pester, Christian W; Langner, Karol M; Sevink, Geert J A; Schoberth, Heiko G; Schmidt, Kristin; Urban, Volker S; Mays, Jimmy W; Böker, Alexander

    2013-05-28

    External electric fields align nanostructured block copolymers by either rotation of grains or nucleation and growth depending on how strongly the chemically distinct block copolymer components are segregated. In close vicinity to the order-disorder transition, theory and simulations suggest a third mechanism: selective disordering. We present a time-resolved small-angle X-ray scattering study that demonstrates how an electric field can indeed selectively disintegrate ill-aligned lamellae in a lyotropic block copolymer solution, while lamellae with interfaces oriented parallel to the applied field prevail. The present study adds an additional mechanism to the experimentally corroborated suite of mechanistic pathways, by which nanostructured block copolymers can align with an electric field. Our results further unveil the benefit of electric field assisted annealing for mitigating orientational disorder and topological defects in block copolymer mesophases, both in close vicinity to the order-disorder transition and well below it.

  1. In situ-Gelling, Erodible N-Isopropylacrylamide Copolymers

    PubMed Central

    Lee, Bae Hoon; Vernon, Brent

    2005-01-01

    Summary Copolymers of N-isopropylacrylamide, 2-hydroxyethyl methacryl lactate and acrylic acid were prepared with varying mole ratios of monomers to develop copolymers with gelation properties above a certain concentration for a bioerodible, in-situ gelling material. The copolymers formed gels in situ under physiological condition. The gelation temperature of the copolymers decreased as the HEMA-lactate content of the copolymers increased due to the hydrophobicity of HEMA-lactate, and increased as the AAc content increased due to the hydrophilicity of AAc. The gels redissolve at 37 °C as their LCSTs increase above 37°C due to the hydrolysis of the HEMA-lactate pendant groups. PMID:15997439

  2. Fabrication routes for one-dimensional nanostructures via block copolymers

    NASA Astrophysics Data System (ADS)

    Tharmavaram, Maithri; Rawtani, Deepak; Pandey, Gaurav

    2017-05-01

    Nanotechnology is the field which deals with fabrication of materials with dimensions in the nanometer range by manipulating atoms and molecules. Various synthesis routes exist for the one, two and three dimensional nanostructures. Recent advancements in nanotechnology have enabled the usage of block copolymers for the synthesis of such nanostructures. Block copolymers are versatile polymers with unique properties and come in many types and shapes. Their properties are highly dependent on the blocks of the copolymers, thus allowing easy tunability of its properties. This review briefly focusses on the use of block copolymers for synthesizing one-dimensional nanostructures especially nanowires, nanorods, nanoribbons and nanofibers. Template based, lithographic, and solution based approaches are common approaches in the synthesis of nanowires, nanorods, nanoribbons, and nanofibers. Synthesis of metal, metal oxides, metal oxalates, polymer, and graphene one dimensional nanostructures using block copolymers have been discussed as well.

  3. N-halamine copolymers for use in antimicrobial paints.

    PubMed

    Kocer, Hasan B; Cerkez, Idris; Worley, S D; Broughton, R M; Huang, T S

    2011-08-01

    A series of copolymers containing units of a novel hydantoinylacrylamide and the sodium salt of 2-(acrylamido)-2-methylpropanesulfonic acid have been synthesized. The homopolymer of the hydantoinylacrylamide compound was insoluble in water, while the copolymers with the sulfonic acid sodium salt were water-dispersible/soluble, with the solution becoming completely transparent when the feed ratio for the copolymer contained 7 parts of the hydantoin moiety to 3 parts of the sodium sulfonate moiety. The polymers were added into a commercial water-based latex paint, and upon drying, the painted surfaces treated with the water-miscible copolymers were rendered antimicrobial following chlorination with dilute household bleach. The chlorinated homopolymer failed to provide an antimicrobial property for the paint because of its tendency to isolate into aggregates in the paint, while the completely miscible copolymers were capable of 6-log inactivation of Staphylococcus aureus and Escherichia coli O157:H7 within 5 min of contact time.

  4. First-principles investigation of PVDF and its copolymers

    NASA Astrophysics Data System (ADS)

    Ranjan, V.; Yu, Liping; Buongiorno Nardelli, Marco; Bernholc, J.

    2009-03-01

    Recently, PVDF and its copolymers have generated significant interest due to their electroactive properties [1] and potential for ultra-high energy-storage applications [2]. In this talk, we present the results of first-principles calculations of stable phases and dielectric properties of different copolymers and terpolymers of PVDF at varying concentrations. Our results show that at very high concentrations of Chloro-trifluoroethylene (CTFE), PVDF/CTFE displays sharp transitions between non-polar (α) and polar (β) phases. On the contrary, the same transitions in copolymers with trifluoroethylene (TrFE) and tetrafluoroethylene (TeFE) are not sharp and happen at lower concentrations. We discuss the interplay of copolymer admixture on the dielectric properties of PVDF and discuss the suitability of copolymers for energy storage and electroactive applications. [1] S. G. Lu et al., App. Phys. Lett. 93, 042905 (2008). [2] V. Ranjan et al., Phys. Rev. Lett. 99, 047801 (2007).

  5. Poly(methyl methacrylate)-cellulose nitrate copolymers. I. Preparation

    SciTech Connect

    Badran, B.M.; Sherif, S.; Abu-Sedira, A.A.

    1981-03-01

    Poly(methyl methacrylate)-cellulose nitrate copolymers were prepared in the form of rods and sheets by bulk polymerization using benzoyl peroxide as initiator. Suspension polymerization did not succeed in preparing poly(methyl methacrylate)-cellulose nitrate copolymers, especially when cellulose nitrate of 11.4% nitrogen content was used. The parameters such as cellulose nitrate concentration, nitrogen content of cellulose nitrate, the amount of initiator and the reaction time, and the temperature are discussed. The prepared copolymers were irradiated for specified periods of up to 11.83 Mrad. It was found that poly(methyl methacrylate)-cellulose nitrate copolymers did not dissolve in any conventional solvent, but they swelled. Swelling decreases with increasing cellulose nitrate concentrations, nitrogen content of cellulose nitrate, and irradiation dose, indicating the crosslinked structure of the prepared copolymers.

  6. Similar temperature responses suggest future climate warming will not alter partitioning between denitrification and anammox in temperate marine sediments.

    PubMed

    Brin, Lindsay D; Giblin, Anne E; Rich, Jeremy J

    2017-01-01

    Removal of biologically available nitrogen (N) by the microbially mediated processes denitrification and anaerobic ammonium oxidation (anammox) affects ecosystem N availability. Although few studies have examined temperature responses of denitrification and anammox, previous work suggests that denitrification could become more important than anammox in response to climate warming. To test this hypothesis, we determined whether temperature responses of denitrification and anammox differed in shelf and estuarine sediments from coastal Rhode Island over a seasonal cycle. The influence of temperature and organic C availability was further assessed in a 12-week laboratory microcosm experiment. Temperature responses, as characterized by thermal optima (Topt ) and apparent activation energy (Ea ), were determined by measuring potential rates of denitrification and anammox at 31 discrete temperatures ranging from 3 to 59 °C. With a few exceptions, Topt and Ea of denitrification and anammox did not differ in Rhode Island sediments over the seasonal cycle. In microcosm sediments, Ea  was somewhat lower for anammox compared to denitrification across all treatments. However, Topt  did not differ between processes, and neither Ea  nor Topt  changed with warming or carbon addition. Thus, the two processes behaved similarly in terms of temperature responses, and these responses were not influenced by warming. This led us to reject the hypothesis that anammox is more cold-adapted than denitrification in our study system. Overall, our study suggests that temperature responses of both processes can be accurately modeled for temperate regions in the future using a single set of parameters, which are likely not to change over the next century as a result of predicted climate warming. We further conclude that climate warming will not directly alter the partitioning of N flow through anammox and denitrification. © 2016 John Wiley & Sons Ltd.

  7. Hand temperature responses to local cooling after a 10-day confinement to normobaric hypoxia with and without exercise.

    PubMed

    Keramidas, M E; Kölegård, R; Mekjavic, I B; Eiken, O

    2015-10-01

    The study examined the effects of a 10-day normobaric hypoxic confinement (FiO2: 0.14), with [hypoxic exercise training (HT); n = 8)] or without [hypoxic ambulatory (HA; n = 6)] exercise, on the hand temperature responses during and after local cold stress. Before and after the confinement, subjects immersed their right hand for 30 min in 8 °C water [cold water immersion (CWI)], followed by a 15-min spontaneous rewarming (RW), while breathing either room air (AIR), or a hypoxic gas mixture (HYPO). The hand temperature responses were monitored with thermocouples and infrared thermography. The confinement did not influence the hand temperature responses of the HA group during the AIR and HYPO CWI and the HYPO RW phases; but it impaired the AIR RW response (-1.3 °C; P = 0.05). After the confinement, the hand temperature responses were unaltered in the HT group throughout the AIR trial. However, the average hand temperature was increased during the HYPO CWI (+0.5 °C; P ≤ 0.05) and RW (+2.4 °C; P ≤ 0.001) phases. Accordingly, present findings suggest that prolonged exposure to normobaric hypoxia per se does not alter the hand temperature responses to local cooling; yet, it impairs the normoxic RW response. Conversely, the combined stimuli of continuous hypoxia and exercise enhance the finger cold-induced vasodilatation and hand RW responses, specifically, under hypoxic conditions. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  8. Dielectric properties of thermo-reversible hydrogels: the case of a dextran copolymer grafted with poly(N-isopropylacrylamide).

    PubMed

    Masci, Giancarlo; Cametti, Cesare

    2009-08-20

    We investigated the dielectric properties of aqueous solutions of a grafted copolymer, consisting of a polysaccharide, Dextran, grafted with a thermo-sensitive polymer, poly(N-isopropylacrylamide), [pNIPAAM], over broad temperature and frequency ranges. The graft copolymers, prepared by atom-transfer radical polymerization [ATRP], form temperature-responsive materials that represent a class of self-assembled structures in water of great interest because of their potential use as drug delivery formulations and in diverse biotechnological applications. In these systems, in the dilute regime and below the lower critical solution temperature, relaxation modes corresponding to two different length-scales have been observed and analyzed in terms of ion fluctuation dielectric models specifically developed to describe the dielectric relaxation in highly charged polyion aqueous solutions. Regardless of whether the ions were produced by the ionization of the polymer chain, as in polyelectrolyte solutions, or not, as in the present case, they represent a probe at a microscopic level that is expected to reveal the structural characteristics of the system at different scales. We have identified a characteristic length associated with the size of the polymer coil in the dilute regime and a length due to fixed cross-links, where ions are partially localized by the local profile of the Coulombic field. These lengths are in reasonable agreement with analogous lengths derived from structural information and from the hydrodynamic radius of the polymer coils, measured by means of a dynamic light-scattering technique.

  9. Ionization of amphiphilic acidic block copolymers.

    PubMed

    Colombani, Olivier; Lejeune, Elise; Charbonneau, Céline; Chassenieux, Christophe; Nicolai, Taco

    2012-06-28

    The ionization behavior of an amphiphilic diblock copolymer poly(n-butyl acrylate(50%)-stat-acrylic acid(50%))(100)-block-poly(acrylic acid)(100) (P(nBA(50%)-stat-AA(50%))(100)-b-PAA(100), DH50) and of its equivalent triblock copolymer P(nBA(50%)-stat-AA(50%))(100)-b-PAA(200)-b-P(nBA(50%)-stat-AA(50%))(100) (TH50) were studied by potentiometric titration either in pure water or in 0.5 M NaCl. These polymers consist of a hydrophilic acidic block (PAA) connected to a hydrophobic block, P(nBA(50%)-stat-AA(50%))(100), whose hydrophobic character has been mitigated by copolymerization with hydrophilic units. We show that all AA units, even those in the hydrophobic block could be ionized. However, the AA units within the hydrophobic block were less acidic than those in the hydrophilic block, resulting in the preferential ionization of the latter block. The preferential ionization of PAA over that of P(nBA(50%)-stat-AA(50%))(100) was stronger at higher ionic strength. Remarkably, the covalent bonds between the PAA and P(nBA(50%)-stat-AA(50%))(100) blocks in the diblock or the triblock did not affect the ionization of each block, although the self-association of the block copolymers into spherical aggregates modified the environment of the PAA blocks compared to when PAA was molecularly dispersed.

  10. Nanostructured Block Copolymer Coatings for Biofouling Inhibition

    DTIC Science & Technology

    2015-06-30

    we hoped. Inhibition, but not highly tunable by change of MW ratio The inhibition of diatoms by the diblocks was not significant (See figure 13). M...OH O a. £ o EC o a. in £ 0 Cu Figure 13 - The initial attachment density of the diatom Navicula on PS-b-PMMA coatings after gentle...washing on glass-nylon supports. Diatom Settlement: no effect of diblock copolymer We did have some success with triblocks, and that work is on-going. We

  11. Corrugational Instabilities of Thin Copolymer Films

    NASA Astrophysics Data System (ADS)

    Williams, D. R. M.

    1995-07-01

    We study the equilibrium configurations of thin films of diblock copolymers, in the strong segregation limit, resting on a flat surface. The top surface is free. Such films are geometrically frustrated and possess an inherent strain. Here we show how this strain induces an undulational instability in the film. The existence of this instability is very sensitive to the chain end distribution within the bilayers, and a macroscopic observation of this instability on a length scale of 1000 Å gives an indication of the chain end distribution on the scale of 5 Å.

  12. Small domain-size multiblock copolymer electrolytes

    DOEpatents

    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.

  13. 21 CFR 177.1340 - Ethylene-methyl acrylate copolymer resins.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Ethylene-methyl acrylate copolymer resins. 177... Repeated Use Food Contact Surfaces § 177.1340 Ethylene-methyl acrylate copolymer resins. Ethylene-methyl... section, the ethylene-methyl acrylate copolymer resins consist of basic copolymers produced by...

  14. Multidimensional chromatographic techniques for hydrophilic copolymers II. Analysis of poly(ethylene glycol)-poly(vinyl acetate) graft copolymers.

    PubMed

    Knecht, Daniela; Rittig, Frank; Lange, Ronald F M; Pasch, Harald

    2006-10-13

    A large variety of hydrophilic copolymers is applied in different fields of chemical industry including bio, pharma and pharmaceutical applications. For example, poly(ethylene glycol)-poly(vinyl alcohol) graft copolymers that are used as tablet coatings are responsible for the controlled release of the active compounds. These copolymers are produced by grafting of vinyl acetate onto polyethylene glycol (PEG) and subsequent hydrolysis of the poly(ethylene glycol)-poly(vinyl acetate) graft copolymers. The poly(ethylene glycol)-poly(vinyl acetate) copolymers are distributed with regard to molar mass and chemical composition. In addition, they frequently contain the homopolymers polyethylene glycol and polyvinyl acetate. The comprehensive analysis of such complex systems requires hyphenated analytical techniques, including two-dimensional liquid chromatography and combined LC and nuclear magnetic resonance spectroscopy. The development and application of these techniques are discussed in the present paper.

  15. Borehole temperature response for competing models of Laurentide ice sheet dynamics

    NASA Astrophysics Data System (ADS)

    Rath, Volker; Alvarez-Solas, Jorge; Robinson, Alex; Montoya-Redondo, Marisa

    2013-04-01

    borehole data (including the corresponding metadata) still have to be collected and need to undergo strict quality control before being used. In addition, a methodological concept fora regional interpretation is missing. In this contribution we will compare the borehole temperature response for two ice sheet models of the Laurentide glaciation, differing in their dynamics. Both were realized by running the hybrid SIA/SSA code GRISLI in different modes. The subsurface temperature anomalies thus generated are significant. Unfortunately the existing deep boreholes in the area are not placed in areas of high sensitivity (e.g., Northern Quebec, Canadian Archipelago). Notwithstanding these difficulties, we will present results for some of these available boreholes in central and northern Canada and Alaska.

  16. A sandwich-designed temperature-gradient incubator for studies of microbial temperature responses.

    PubMed

    Elsgaard, Lars; Jørgensen, Leif Wagner

    2002-03-01

    A temperature-gradient incubator (TGI) is described, which produces a thermal gradient over 34 aluminium modules (15x30x5 cm) intersected by 2-mm layers of partly insulating graphite foil (SigraFlex Universal). The new, sandwich-designed TGI has 30 rows of six replicate sample wells for incubation of 28-ml test tubes. An electric plate heats one end of the TGI, and the other end is cooled by thermoelectric Peltier elements in combination with a liquid cooling system. The TGI is equipped with 24 calibrated Pt-100 temperature sensors and insulated by polyurethane plates. A PC-operated SCADA (Supervisory Control And Data Acquisition) software (Genesis 4.20) is applied for temperature control using three advanced control loops. The precision of the TGI temperature measurements was better than +/-0.12 degrees C, and for a 0-40 degrees C gradient, the temperature at the six replicate sample wells varied less than +/-0.04 degrees C. Temperatures measured in incubated water samples closely matched the TGI temperatures, which showed a linear relationship to the sample row number. During operation for 8 days with a gradient of 0-40 degrees C, the temperature at the cold end was stable within +/-0.02 degrees C, while the temperatures at the middle and the warm end were stable within +/-0.08 degrees C (n=2370). Using the new TGI, it was shown that the fine-scale (1 degrees C) temperature dependence of S(o) oxidation rates in agricultural soil (0-29 degrees C) could be described by the Arrhenius relationship. The apparent activation energy (E(a)) for S(o) oxidation was 79 kJ mol(-1), which corresponded to a temperature coefficient (Q(10)) of 3.1. These data demonstrated that oxidation of S(o) in soil is strongly temperature-dependent. In conclusion, the new TGI allowed a detailed study of microbial temperature responses as it produced a precise, stable, and certifiable temperature gradient by the new and combined use of sandwich-design, thermoelectric cooling, and advanced

  17. Nongrafted Skin Area Best Predicts Exercise Core Temperature Responses in Burned Humans

    PubMed Central

    Ganio, Matthew S.; Schlader, Zachary J.; Pearson, James; Lucas, Rebekah A.I.; Gagnon, Daniel; Rivas, Eric; Kowalske, Karen J.; Crandall, Craig G.

    2015-01-01

    Grafted skin impairs heat dissipation, but it is unknown to what extent this impacts body temperature during exercise in the heat. PURPOSE We examined core body temperature responses during exercise in the heat in a group of individuals with a large range of grafts covering their body surface area (BSA; 0-75%). METHODS Forty-three individuals (19 females) were stratified into groups based upon BSA grafted: Control (0% grafted, n=9), 17-40% (n=19), and >40% (n=15). Subjects exercised at a fixed rate of metabolic heat production (339 ± 70 W; 4.3 ± 0.8 W/kg) in an environmental chamber set at 40°C, 30% RH for 90 min or until exhaustion (n=8). Whole-body sweat rate and core temperatures were measured. RESULTS Whole body sweat rates were similar between groups (Control: 14.7±3.4 ml/min, 17-40%: 12.6±4.0 ml/min, and >40%: 11.7±4.4 ml/min, P>0.05), but the increase in core temperature at the end of exercise in the >40% BSA grafted group (1.6±0.5°C) was greater than the 17-40% (1.2±0.3°C) and Control (0.9±0.2°C) groups (P<0.05). Absolute BSA of non-grafted skin (expressed in m2) was the strongest independent predictor of the core temperature increase (r2=0.41). When re-grouping all subjects, individuals with the lowest BSA of non-grafted skin (<1.0 m2) had greater increases in core temperature (1.6±0.5°C) than those with >1.5 m2 non-grafted skin (1.0±0.3°C, P<0.05). CONCLUSIONS These data imply that individuals with grafted skin have greater increases in core temperature when exercising in the heat and that the magnitude of this increase is best explained by the amount of non-grafted skin available for heat dissipation. PMID:26378947

  18. Hollow flower micelles from a diblock copolymer

    NASA Astrophysics Data System (ADS)

    Changez, Mohammad; Kang, Nam-Goo; Kim, Dong Woo; Lee, Jae-Suk

    2013-11-01

    A poly(2-vinylpyridine)-block-poly(2-(4-vinylphenyl)pyridine) (P2VP106-b-PVPPy95) coil-coil diblock copolymer forms hollow flower micelles in a mixed solvent of methanol and water (95/5, v/v) in a one step process. The geometry and composition of the micelles allow formation of a Pt-Au bimetallic dendritic nanocatalyst with a Pt leaf at room temperature.A poly(2-vinylpyridine)-block-poly(2-(4-vinylphenyl)pyridine) (P2VP106-b-PVPPy95) coil-coil diblock copolymer forms hollow flower micelles in a mixed solvent of methanol and water (95/5, v/v) in a one step process. The geometry and composition of the micelles allow formation of a Pt-Au bimetallic dendritic nanocatalyst with a Pt leaf at room temperature. Electronic supplementary information (ESI) available: Experimental details. See DOI: 10.1039/c3nr03063f

  19. Anomalous Micellization of Pluronic Block Copolymers

    NASA Astrophysics Data System (ADS)

    Leonardi, Amanda; Ryu, Chang Y.

    2014-03-01

    Poly(ethylene oxide) - poly(propylene oxide) - poly(ethylene oxide) (PEO-PPO-PEO) block copolymers, commercially known as Pluronics, are a unique family of amphiphilic triblock polymers, which self-assemble into micelles in aqueous solution. These copolymers have shown promise in therapeutic, biomedical, cosmetic, and nanotech applications. As-received samples of Pluronics contain low molecular weight impurities (introduced during the manufacturing and processing), that are ignored in most applications. It has been observed, however, that in semi-dilute aqueous solutions, at concentrations above 1 wt%, the temperature dependent micellization behavior of the Pluronics is altered. Anomalous behavior includes a shift of the critical micellization temperature and formation of large aggregates at intermediate temperatures before stable sized micelles form. We attribute this behavior to the low molecular weight impurities that are inherent to the Pluronics which interfere with the micellization process. Through the use of Dynamic Light Scattering and HPLC, we compared the anomalous behavior of different Pluronics of different impurity levels to their purified counterparts.

  20. Interface-enforced complexation between copolymer blocks.

    PubMed

    Steinschulte, Alexander A; Xu, Weinan; Draber, Fabian; Hebbeker, Pascal; Jung, Andre; Bogdanovski, Dimitri; Schneider, Stefanie; Tsukruk, Vladimir V; Plamper, Felix A

    2015-05-14

    Binary diblock copolymers and corresponding ternary miktoarm stars are studied at oil-water interfaces. All polymers contain oil-soluble poly(propylene oxide) PPO, water-soluble poly(dimethylaminoethyl methacrylate) PDMAEMA and/or poly(ethylene oxide) PEO. The features of their Langmuir compression isotherms are well related to the ones of the corresponding homopolymers. Within the Langmuir-trough, PEO-b-PPO acts as the most effective amphiphile compared to the other PPO-containing copolymers. In contrast, the compression isotherms show a complexation of PPO and PDMAEMA for PPO-b-PDMAEMA and the star, reducing their overall amphiphilicity. Such complex formation between the blocks of PPO-b-PDMAEMA is prevented in bulk water but facilitated at the interface. The weakly-interacting blocks of PPO-b-PDMAEMA form a complex due to their enhanced proximity in such confined environments. Scanning force microscopy and Monte Carlo simulations with varying confinement support our results, which are regarded as compliant with the mathematical random walk theorem by Pólya. Finally, the results are expected to be of relevance for e.g. emulsion formulation and macromolecular engineering.

  1. Controlling Structure in Sulfonated Block Copolymer Membranes

    NASA Astrophysics Data System (ADS)

    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.

  2. Responsive linear-dendritic block copolymers.

    PubMed

    Blasco, Eva; Piñol, Milagros; Oriol, Luis

    2014-06-01

    The combination of dendritic and linear polymeric structures in the same macromolecule opens up new possibilities for the design of block copolymers and for applications of functional polymers that have self-assembly properties. There are three main strategies for the synthesis of linear-dendritic block copolymers (LDBCs) and, in particular, the emergence of click chemistry has made the coupling of preformed blocks one of the most efficient ways of obtaining libraries of LDBCs. In these materials, the periphery of the dendron can be precisely functionalised to obtain functional LDBCs with self-assembly properties of interest in different technological areas. The incorporation of stimuli-responsive moieties gives rise to smart materials that are generally processed as self-assemblies of amphiphilic LDBCs with a morphology that can be controlled by an external stimulus. Particular emphasis is placed on light-responsive LDBCs. Furthermore, a brief review of the biomedical or materials science applications of LDBCs is presented. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Hydrogen-bonded polymer complexes and nanocages of weak polyacids templated by a Pluronic® block copolymer.

    PubMed

    Wang, Yuhao; Sukhishvili, Svetlana A

    2016-10-26

    We investigate the phase behavior, morphology, and temperature response of hydrogen-bonded assemblies formed by a triblock copolymer Pluronic® F127 (F127) and polycarboxylic acids of varied hydrophobicity and chain lengths. As confirmed by FTIR, the complexes of poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA) with F127 at acidic pH were stabilized by multiple hydrogen bonding between carboxylic acid groups of polyacids and ether groups of F127. The colloidal stability of the polyacid/F127 complexes (their occurrence as stable dispersions, slowly coagulating dispersions or precipitates) was dependent on the composition of complexes, polyacid molecular weight and hydrophobicity, as well as temperature. For both polyacids, complexes could not be solubilized in excess of polyacids, but excess of F127 resulted in the formation of colloidally stable nanostructured clusters whose size could be controlled from tens to hundreds of nanometers by the polyacid-to-F127 ratio, temperature, and the polyacid molecular weight. Hydrophobicity of polyacids had a dramatic effect on the temperature response of Pluronic®-enriched assemblies. While PMAA suppressed the LCST behavior of F127 due to binding within the temperature-responsive PPO core of F127, more hydrophilic PAA allowed F127 micellization and supported reversible, temperature-induced re-structuring of PAA-F127 clusters. At temperatures above the LCST of Pluronic®, low-molecular-weight PAA formed nanosized dispersed complexes, in which the polyacid chains were wrapped around individual F127 micelles. Chemical crosslinking of PAA in the shells of these complexes followed by removal of the templating F127 cores resulted in easy-to-prepare monodisperse pH-responsive polymer nanocages with controllable size and swelling amplitude.

  4. Benzodithiophene and Imide-Based Copolymers for Photovoltaic; Applications

    SciTech Connect

    Braunecker, W. A.; Owczarczyk, Z. R.; Garcia, A.; Kopidakis, N.; Larsen, R. E.; Hammond, S. R.; Ginley, D. S.; Olson, D. C.

    2012-04-10

    Conjugated alternating copolymers were designed with low optical band gaps for organic photovoltaic (OPV) applications by considering quinoid resonance stabilization. Copolymers of thienoisoindoledione (TID) and benzodithiophene (BDT) had appreciably lower band gaps (by {approx}0.4 eV) than copolymers of thienopyrroledione (TPD) and BDT. In addition to intramolecular charge transfer stabilization (i.e., the 'push-pull' effect), the former copolymer's quinoid resonance structure is stabilized by a gain in aromatic resonance energy in the isoindole unit. Additionally, the HOMO levels of the copolymers could be tuned with chemical modifications to the BDT monomer, resulting in open circuit voltages of greater than 1 V in photovoltaic devices. Despite the optimized band gap, TID containing polymers displayed lower photoconductance, as determined by time-resolved microwave conductivity, and decreased device efficiency (2.1% vs 4.8%) as compared with TPD analogues. These results were partially attributed to morphology, as computational modeling suggests TID copolymers have a twisted backbone, and X-ray diffraction data indicate the polymer films do not form ordered domains, whereas TPD copolymers are considerably more planar and are shown to form partially ordered domains.

  5. Manipulating Ordering Transitions in Interfacially Modified Block Copolymers

    SciTech Connect

    Singh, N.; Tureau, M; Epps, T

    2009-01-01

    We report a synthetic strategy that allows us to manipulate the interfacial region between blocks and control ordering transitions in poly(isoprene-b-styrene) [P(I-S)] block copolymers. This interfacial modification is accomplished by combining a semi-batch feed with anionic polymerization techniques. Using this approach, we are able to control the segmental composition and molecular interactions in our phase-separated block copolymers, independent of molecular weight and block constituents. A library of copolymers is prepared with various interfacial modifications to examine the effect of interfacial composition on copolymer self-assembly. The morphological characteristics of the self-assembled structures are investigated using small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), and dynamic mechanical analysis (DMA). Normal and inverse tapered block copolymers, containing approximately 15-35 vol% tapered material, show a measurable decrease in the order-disorder transition temperature (TODT) relative to the corresponding non-tapered diblock copolymers, with the inverse tapered materials showing the greatest deviation in TODT. Additionally, TODT was inversely related to the volume fraction of the tapered region in both normal and inverse tapered copolymer materials.

  6. Effects of Blockiness on the phase behavior of random copolymers

    NASA Astrophysics Data System (ADS)

    Vanderwoude, Gordon; Shi, An-Chang

    Theoretical study of random block copolymers remains a challenging topic due in part to the sheer enormity of their phase space. In this study we use the self-consistent field theory to investigate the phase behaviour of linear (AB)n-type and (AB)n-C-type multiblock copolymers with randomly distributed A and B blocks. In particular, we examine the effect of ``blockiness'' of the random copolymers on the formation of ordered phases. The blockiness can be quantified by the average length of individual A or B blocks, which can be taken as a measure of the heterogeneity of the random copolymers. We observed that the critical value of the χ parameter, at which the order-disorder transition occurs, decreases with increasing blockiness in the (AB)n copolymers. We also observed that the phase behaviour of the (AB)n-C copolymers depends strongly on the blockiness of the random chain. In particular, the blockiness governs whether or not the A/B blocks can phase separate within the A/B domains, thus dictating whether the (AB)n-C behaves as A/B-C diblock copolymers or as ABC terpolymers. The theoretical phase diagrams will be compared with available experiments.

  7. Nanopatterning of recombinant proteins and viruses using block copolymer templates

    NASA Astrophysics Data System (ADS)

    Cresce, Arthur Von Wald

    The study of interfaces is important in understanding biological interactions, including cellular signaling and virus infection. This thesis is an original effort to examine the interaction between a block copolymer and both a protein and a virus. Block copolymers intrinsically form nanometer-scale structures over large areas without expensive processing, making them ideal for the synthesis of the nanopatterned surfaces used in this study. The geometry of these nanostructures can be easily tuned for different applications by altering the block ratio and composition of the block copolymer. Block copolymers can be used for controlled uptake of metal ions, where one block selectively binds metal ions while the other does not. 5-norbornene-2,3-dicarboxylic acid is synthesized through ring-opening metathesis polymerization. It formed spherical domains with spheres approximately 30 nm in diameter, and these spheres were then subsequently loaded with nickel ion. This norbornene block copolymer was tested for its ability to bind histidine-tagged green fluorescent protein (hisGFP), and it was found that the nickel-loaded copolymer was able to retain hisGFP through chelation between the histidine tag and the metal-containing portions of the copolymer surface. Poly(styrene-b-4-vinylpyridine) (PS/P4VP) was also loaded with nickel, forming a cylindrical microstructure. The binding of Tobacco mosaic virus and Tobacco necrosis virus was tested through Tween 20 detergent washes. Electron microscopy allowed for observation of both block copolymer nanostructures and virus particles. Results showed that Tween washes could not remove bound Tobacco mosaic virus from the surface of PS/P4VP. It was also seen that the size and tunability of block copolymers and the lack of processing needed to attain different structures makes them attractive for many applications, including microfluidic devices, surfaces to influence cellular signaling and growth, and as a nanopatterning surface for

  8. Degradation of PCL-MPEG diblock copolymer in rat plasma.

    PubMed

    Lin, Wen-Jen; Chang, Kai-Ling

    2008-06-01

    The poly(epsilon-caprolactone)-co-poly(ethylene glycol) (PCL-MPEG) amphiphilic diblock copolymer with molar ratio of epsilon-CL to MPEG 81:1 is synthesized via a ring-opening polymerization without a catalyst. The M(w) and M(n) molecular weights and the polydispersities are 18,000, 11,000 g/mole and 1.55, respectively. The pegylated amphiphilic copolymer forms micelles with a low critical micelle concentration 6.71 x 10(-8) mole/L, and the average particle size of copolymeric micelles is 62.3 +/- 12.9 nm. The degradation behavior of diblock copolymer was studied in rat plasma at 37 degrees C for 90 days. The changes of mass, composition, morphology, molecular weight, and thermal property of PCL-MPEG copolymer were investigated. The decrease of copolymer mass shows two phases with rate constants of 1.91 x 10(-1) day(-1) in the first-phase (1-24 h) and 1.77 x 10(-3) day(-1) in the second-phase (1-90 days). The degradation of labile ester linkage between PCL block and MPEG block accounts for continuous decrease of copolymer mass in plasma. The decrease of EG molar ratio from 1.30 to 0.67 and prominent reduction of enthalpy of fusion of remained copolymer from 116.5 to 85.2 J/g provide evidences of PCL-MPEG chain scission. On the other hand, the presence of partially degraded copolymers in the residuals results in its polydispersity increased from 1.55 to 2.24 at the end of 90 days. Nevertheless, the surface erosion of copolymer makes the molecular weight not quite different from its original value. Copyright 2007 Wiley Periodicals, Inc.

  9. Electrochemically controlled self-assembly of block copolymer nanostructures

    NASA Astrophysics Data System (ADS)

    Eitouni, Hany Basam

    Organometallic block copolymers, wherein one block is composed of alternating ferrocene and dialkylsilane units in the main chain, undergo self-assembly to form microphase-separated ordered structures similarly to typical organic block copolymers. The 1,1'-dimethylsilylferrocenophane monomer was synthesized and polymerized anionically with other monomers to make a variety of different organometallic block copolymers. The phase behavior and thermodynamic interactions of anionically synthesized poly(styrene-block-ferrocenyldimethylsilane) (SF) and poly(isoprene-block-ferrocenyldimethylsilane) (IF) copolymers were examined using depolarized light scattering, small angle x-ray and neutron scattering (SAXS and SANS), and transmission electron microscopy. The temperature-dependence of the Flory-Huggins parameter, chi, and the statistical segment lengths of SF and IF copolymers were determined by SAXS and SANS using the random phase approximation. The thermodynamic interactions in poly(ferrocenyldimethylsilane) diblock copolymers were systematically adjusted by oxidizing the ferrocene moieties with silver salts and examined using SAXS and depolarized light scattering. The polymers retained microphase separated ordered structures upon oxidation and showed systematic changes in the location of the order-disorder transition as a function of extent of oxidation. By controlling the redox properties of the ferrocene moiety in the backbone of the polymer, we present a method for controlling the self-assembled microstructure and hence bulk material properties. Using electrochemical techniques, a novel means of controlling the order-disorder transition of block copolymers was discovered. By applying very small electrical potentials to disordered solutions of organometallic block copolymers, oriented ordered grains were formed near one electrode, the result of electrochemical reactions. After reversing the electrical bias on the system, the ordered grains disappeared and new

  10. Improvement in transdermal drug delivery performance by graphite oxide/temperature-responsive hydrogel composites with micro heater.

    PubMed

    Yun, Jumi; Lee, Dae Hoon; Im, Ji Sun; Kim, Hyung-Il

    2012-08-01

    Transdermal drug delivery system (TDDS) was prepared with temperature-responsive hydrogel. The graphite was oxidized and incorporated into hydrogel matrix to improve the thermal response of hydrogel. The micro heater was fabricated to control the temperature precisely by adopting a joule heating method. The drug in hydrogel was delivered through a hairless mouse skin by controlling temperature. The efficiency of drug delivery was improved obviously by incorporation of graphite oxide due to the excellent thermal conductivity and the increased interfacial affinity between graphite oxide and hydrogel matrix. The fabricated micro heater was effective in controlling the temperature over lower critical solution temperature of hydrogel precisely with a small voltage less than 1 V. The cell viability test on graphite oxide composite hydrogel showed enough safety for using as a transdermal drug delivery patch. The performance of TDDS could be improved noticeably based on temperature-responsive hydrogel, thermally conductive graphite oxide, and efficient micro heater.

  11. Temperature-responsiveness and biocompatibility of DEGMA/OEGMA radiation-grafted onto PP and LDPE films

    NASA Astrophysics Data System (ADS)

    Ramírez-Jiménez, Alejandro; Alvarez-Lorenzo, Carmen; Concheiro, Angel; Bucio, Emilio

    2014-06-01

    Polypropylene (PP) and low density polyethylene (LDPE) were modified by γ-ray grafting of di(ethylene glycol) methyl ether methacrylate (DEGMA) and oligo (ethylene glycol) methyl ether methacrylate (OEGMA300 or OEGMA475 with Mn 300 and 475 respectively) with different monomer concentrations and mol ratios. The grafting percentage was evaluated as a function of the solvent, irradiation dose, reaction time, temperature, and monomers concentration. The grafted materials were more hydrophilic than the pristine polymers, as observed by contact angle and swelling in water. Temperature-responsive behavior was evaluated using DSC showing transitions between 34 and 48 °C. In vitro hemocompatibility, protein adsorption, cytotoxicity and bacteria adhesion tests were also carried out. Overall, the DEGMA/OEGMA grafting provides hemo and cytocompatible materials that exhibit temperature-responsive hydrophilic features and decreased protein adsorption.

  12. Microphase Separated Block Copolymers in Pervaporation Membranes for Biofuels Processing

    NASA Astrophysics Data System (ADS)

    Greer, Douglas; Shin, Chae-Young; Ozcam, Evren; Skerker, Jeffrey; Basso, Thalita; Leon, Dacia; Bauer, Stefan; Balsara, Nitash; Energy Biosciences Institute Collaboration

    2014-03-01

    The production of transportation biofuels requires numerous continuous separation processes. We designed block copolymer membranes for pervaporation as a means to achieve these separations. These block copolymers contain a glassy structure block for support and a rubbery transport block for sorption and diffusion. We create membranes with nanoscale conducting channels using the unique trait of block copolymers to assemble into ordered morphologies. We have previously used nanostructured membranes to separate ethanol/water binary mixtures [J. Membr. Sci. 373, 112 (2011)], [J. Membr. Sci. 401, 125 (2012)]. We report this type of membranes is effective in other, more complex separations important to biofuel production. These separations increase yield and decrease process time.

  13. Verapamil hydrochloride release characteristics from new copolymer zwitterionic matrix tablets.

    PubMed

    Kostova, Bistra; Kamenska, Elena; Ivanov, Ivo; Momekov, George; Rachev, Dimitar; Georgiev, George

    2008-01-01

    The aim of this study was to synthesize stable copolymer (vinyl acetate-co-3-dimethyl[methacryloyloxyethyl] ammonium propane sulfinate) zwitterionic latex with different compositions for the first time by emulsifier-free emulsion copolymerization. Throughout the course of the study, a proposal was made for the explanation of the relationship between the "overshooting" phenomenon (a swelling kinetics with a maximum) and the specific self-association of the zwitterionic copolymers. The zwitterionic monomer unit mole fraction, pH, and ionic strength effects on this relationship, on the swelling kinetics of the zwitterionic copolymers, and on the sustained verapamil hydrochloride release from the model tablets were established by the study's authors.

  14. Photocrosslinkable copolymers for non-linear optical applications

    SciTech Connect

    Kawatsuki, N.; Pakbaz, K.; Schmidt, H.W.

    1993-12-31

    New photocrosslinkable copolymers have been synthesized and applied as non-linear optical materials. The copolymers are based on methyl methacrylate, a photo-excitable benzophenone monomer, a non-linear optical active 4`-[(2-hydroxyethyl)ethylamino]-4-nitro-azobenzene (disperse red 1) side chain monomer and a crosslinkable 2-butenyl monomer. These copolymers can be crosslinked by UV light at 366 nm in the poled state and show a stable alignment of NLO chromophore by monitoring the adsorption spectra. The crosslinked and poled film did not change its alignment after storing 4 weeks at room temperature.

  15. Polysaccharide based Copolymers as Supramolecular Systems in Biomedical Applications.

    PubMed

    Célia Monteiro de Paula, Regina; Andrade Feitosa, Judith Pessoa; Beserra Paula, Haroldo César

    2015-01-01

    Polysaccharides are natural polymers, obtained from a large variety of sources ranging from fungi to more complex organisms such as birds and whales. Their use for pharmaceutical and biomedical applications has been the subject of numerous researches by the world´s academia. Polysaccharide chemical/physical modifications leading to graft copolymers are discussed in this review, focusing on those nanosystems that are potential candidates for drug delivery applications. Therefore, this review focuses on the biomedical application of polysaccharide based copolymers, particularly as nanocarriers. Copolymer of polysaccharides such as alginate, cellulose, chitosan, dextran, guar, hyaluronic acid, pullulan and starch as drug delivery nanocarriers will be discussed.

  16. Thin membranes of new hard/soft segment copolymers

    SciTech Connect

    Ho, W.S.; Sartori, G.; Thaler, W.A.

    1996-12-31

    Thin membranes of new hard/soft segment copolymers have been synthesized for the separation of aromatics from saturates through high temperature pervaporation. In the membranes, hard segments provide temperature stability and solvent resistance, while soft segments govern aromatic/saturate selectivity and flux. We have synthesized new chlorinated polyurethane/polyester and polyimide/polyester copolymers. Based on a polyimide copolymer membrane, a new technology has been developed recently to separate heavy catalytically cracked naphtha into an aromatics-rich permeate and an aromatics-lean retentate.

  17. Electrically conductive doped block copolymer of polyacetylene and polyisoprene

    DOEpatents

    Aldissi, Mahmoud

    1985-01-01

    An electrically conductive block copolymer of polyisoprene and polyacetyl and a method of making the same are disclosed. The polymer is prepared by first polymerizing isoprene with n-butyllithium in a toluene solution to form an active isoprenyllithium polymer. The active polymer is reacted with an equimolar amount of titanium butoxide and subsequently exposed to gaseous acetylene. A block copolymer of polyisoprene and polyacetylene is formed. The copolymer is soluble in common solvents and may be doped with I.sub.2 to give it an electrical conductivity in the metallic regime.

  18. Global Average Upper Ocean Temperature Response To Changing Solar Irradiance: Exciting The Internal Decadal Mode

    NASA Astrophysics Data System (ADS)

    White, W. B.; Dettinger, M. D.; Cayan, D. R.; White, Warren B.; Dettinger, Michael D.; Cayan, Daniel R.

    Global average upper ocean temperatures anomalies of +/-0.05°K fluctuate in fixed phase with decadal signals in the Sun's irradiance of +/-0.5 Watts m-2 over the past 100 years (White et al., 1997), but its amplitude is 2 to 3 times that expected from the transient Stefan-Boltzmann radiation balance (White et al., 1988). Examining global patterns of upper ocean temperature and lower troposphere winds, we find the internal interannual mode of variability in Earth's ocean-atmosphere-terrestrial system with global-average upper ocean temperature anomalies of +/-0.05°K occurring naturally, independent of changing solar irradiance (White et al., 2000). Yet coherence and phase statistics indicate that the observed internal decadal mode in Earth's ocean -atmosphere terrestrial system is excited by the decadal signal in the Sun's irradiance. To understand the thermodynamics of this association we conduct a global-average upper ocean heat budget utilizing upper ocean temperatures from the SIO reanalysis and air-sea heat and momentum fluxes from the COADS reanalysis, finding the source of decadal global warming to be the reduction in trade wind intensity across the tropics, decreasing global average latent heat flux out of the ocean. We demonstrate that this reduction in trade wind intensity in the Pacific Ocean is governed by a delayed action oscillator mechanism in the ocean-atmosphere system differing little from that used to explain the El Niño-Southern Oscillation (Graham and White, 1988). We operate an intermediate coupled model of this delayed action oscillator, normally driven by white noise, by superimposing the Stefan-Boltzmann upper ocean temperature response to decadal changes in the Sun's irradiance. We find the latter, with weak amplitude of +/-0.02°K and non-random phase, is able to excite a decadal signal in this delayed action oscillator, yielding a damped resonance response of +/-0.1°K in the equatorial Pacific Ocean, with dissipation provided by

  19. Effect of water uptake on morphology of polymerized ionic liquid block copolymers and random copolymers

    NASA Astrophysics Data System (ADS)

    Wang, Tsen-Shan; Ye, Yuesheng; Elabd, Yossef; Winey, Karen

    2012-02-01

    Dynamic studies of polymer morphology probe how the physical properties of polymerized ionic liquids are affected by the environment, such as temperature or moisture. For a series of poly(methyl methacrylate-b-1-[2-(methacryloyloxy)ethyl]-3-Butylimidazolium X^-) block and random copolymers with hydrophilic counterions (X^- = Br^-, HCO3^-, OH^-), the introduction of water vapor to the system can swell the ionic liquid block, causing enlarged hydrophilic domains and swollen channels for ion conduction. This expected expansion of ionic liquid domains in humid environments can be used to intelligently design these copolymers for use in technological applications. The effect of water vapor exposure in these imidazolium-based acrylate polymers is studied by small-angle X-ray scattering. These morphology results will be discussed alongside complementary studies of water uptake and ion conductivity.

  20. Implication of Prostaglandins and Histamine H1 and H2 Receptors in Radiation-Induced Temperature Responses of Rats

    DTIC Science & Technology

    1988-05-01

    1988) S Implication of Prostaglandins and Histamine H1 and H 2 Receptors in Radiation-Induced Temperature Responses of Rats SATHASIVA B. KANDASAMY ... KANDASAMY , S. B., HUNT. W. A., AND MICKLEY, G. A. Implications of Prostaglandins and Histamine H I and H2 Receptors in Radiation-Induced Temperature...lateral ventricle according to coordinates derived from the atlas of Pelligrino et al. (31): 0.8 mm posterior to bregma. 2.5 mm lateral. 44 KANDASAMY , HUNT

  1. Temperature response of litter and soil organic matter decomposition is determined by chemical composition of organic material.

    PubMed

    Erhagen, Björn; Öquist, Mats; Sparrman, Tobias; Haei, Mahsa; Ilstedt, Ulrik; Hedenström, Mattias; Schleucher, Jürgen; Nilsson, Mats B

    2013-12-01

    The global soil carbon pool is approximately three times larger than the contemporary atmospheric pool, therefore even minor changes to its integrity may have major implications for atmospheric CO2 concentrations. While theory predicts that the chemical composition of organic matter should constitute a master control on the temperature response of its decomposition, this relationship has not yet been fully demonstrated. We used laboratory incubations of forest soil organic matter (SOM) and fresh litter material together with NMR spectroscopy to make this connection between organic chemical composition and temperature sensitivity of decomposition. Temperature response of decomposition in both fresh litter and SOM was directly related to the chemical composition of the constituent organic matter, explaining 90% and 70% of the variance in Q10 in litter and SOM, respectively. The Q10 of litter decreased with increasing proportions of aromatic and O-aromatic compounds, and increased with increased contents of alkyl- and O-alkyl carbons. In contrast, in SOM, decomposition was affected only by carbonyl compounds. To reveal why a certain group of organic chemical compounds affected the temperature sensitivity of organic matter decomposition in litter and SOM, a more detailed characterization of the (13) C aromatic region using Heteronuclear Single Quantum Coherence (HSQC) was conducted. The results revealed considerable differences in the aromatic region between litter and SOM. This suggests that the correlation between chemical composition of organic matter and the temperature response of decomposition differed between litter and SOM. The temperature response of soil decomposition processes can thus be described by the chemical composition of its constituent organic matter, this paves the way for improved ecosystem modeling of biosphere feedbacks under a changing climate.

  2. Leaf-age effects on temperature responses of photosynthesis and respiration of an alpine oak, Quercus aquifolioides, in southwestern China.

    PubMed

    Zhou, Haoran; Xu, Ming; Pan, Hongli; Yu, Xiubo

    2015-11-01

    Temperature responses and sensitivity of photosynthesis (A(n_)T) and respiration for leaves at different ages are crucial to modeling ecosystem carbon (C) cycles and productivity of evergreen forests. Understanding the mechanisms and processes of temperature sensitivity may further shed lights on temperature acclimation of photosynthesis and respiration with leaf aging. The current study examined temperature responses of photosynthesis and respiration of young leaves (YLs) (fully expanded in current growth season) and old leaves (OLs) (fully expanded in last growth season) of Quercus aquifolioides Rehder and E.H. Wilson in an alpine oak forest, southwestern China. Temperature responses of dark respiration (R(dark)), net assimilation (A(n)), maximal velocity of carboxylation (V(cmax)) and maximum rate of electron transport (J(max)) were significantly different between the two leaf ages. Those differences implied different temperature response parameters should be used for leaves of different ages in modeling vegetation productivity and ecosystem C cycles in Q. aquifolioides forests and other evergreen forests. We found that RuBP carboxylation determined the downward shift of A(n_)T in OLs, while RuBP regeneration and the balance between Rubisco carboxylation and RuBP regeneration made little contribution. Sensitivity of stomatal conductance to vapor pressure deficit changed in OLs and compensated part of the downward shift. We also found that OLs of Q. aquifolioides had lower An due to lower stomatal conductance, higher stomatal conductance limitation and deactivation of the biochemical processes. In addition, the balance between R(dark) and A(n) changed between OLs and YLs, which was represented by a higher R(dark)/A(n) ratio for OLs.

  3. Bicomponent Block Copolymers Derived from One or More Random Copolymers as an Alternative Route to Controllable Phase Behavior.

    PubMed

    Ashraf, Arman R; Ryan, Justin J; Satkowski, Michael M; Lee, Byeongdu; Smith, Steven D; Spontak, Richard J

    2017-09-01

    Block copolymers have been extensively studied due to their ability to spontaneously self-organize into a wide variety of morphologies that are valuable in energy-, medical-, and conservation-related (nano)technologies. While the phase behavior of bicomponent diblock and triblock copolymers is conventionally governed by temperature and individual block masses, it is demonstrated here that their phase behavior can alternatively be controlled through the use of blocks with random monomer sequencing. Block random copolymers (BRCs), i.e., diblock copolymers wherein one or both blocks are a random copolymer comprised of A and B repeat units, have been synthesized, and their phase behavior, expressed in terms of the order-disorder transition (ODT), has been investigated. The results establish that, depending on the block composition contrast and molecular weight, BRCs can microphase-separate. We also report that large variation in incompatibility can be generated at relatively constant molecular weight and temperature with these new soft materials. This sequence-controlled synthetic strategy is extended to thermoplastic elastomeric triblock copolymers differing in chemistry and possessing a random-copolymer midblock. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Temperature response of denitrification and anaerobic ammonium oxidation rates and microbial community structure in Arctic fjord sediments.

    PubMed

    Canion, Andy; Overholt, Will A; Kostka, Joel E; Huettel, Markus; Lavik, Gaute; Kuypers, Marcel M M

    2014-10-01

    The temperature dependency of denitrification and anaerobic ammonium oxidation (anammox) rates from Arctic fjord sediments was investigated in a temperature gradient block incubator for temperatures ranging from -1 to 40°C. Community structure in intact sediments and slurry incubations was determined using Illumina SSU rRNA gene sequencing. The optimal temperature (Topt ) for denitrification was 25-27°C, whereas anammox rates were optimal at 12-17°C. Both denitrification and anammox exhibited temperature responses consistent with a psychrophilic community, but anammox bacteria may be more specialized for psychrophilic activity. Long-term (1-2 months) warming experiments indicated that temperature increases of 5-10°C above in situ had little effect on the microbial community structure or the temperature response of denitrification and anammox. Increases of 25°C shifted denitrification temperature responses to mesophilic with concurrent community shifts, and anammox activity was eliminated above 25°C. Additions of low molecular weight organic substrates (acetate and lactate) caused increases in denitrification rates, corroborating the hypothesis that the supply of organic substrates is a more dominant control of respiration rates than low temperature. These results suggest that climate-related changes in sinking particulate flux will likely alter rates of N removal more rapidly than warming.

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

    PubMed Central

    Yunoki, Shunji

    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 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. PMID:24222766

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

    PubMed

    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.

  7. Morphology and phase diagram of complex block copolymers: ABC linear triblock copolymers.

    PubMed

    Tang, Ping; Qiu, Feng; Zhang, Hongdong; Yang, Yuliang

    2004-03-01

    Using a real space implementation of the self-consistent field theory for the polymeric system, we explore microphases of ABC linear triblock copolymers. For the sake of numerical tractability, the calculation is carried out in a two-dimensional (2D) space. Seven microphases are found to be stable for the ABC triblock copolymer in 2D, which include lamellae, hexagonal lattice, core-shell hexagonal lattice, tetragonal lattice, lamellae with beads inside, lamellae with beads at the interface, and hexagonal phase with beads at the interface. By systematically varying the composition, triangle phase diagrams are constructed for four classes of typical triblock polymers in terms of the relative strengths of the interaction energies between different species. In general, when both volume fractions and interaction energies of the three species are comparable, lamellar phases are found to be the most stable. While one of the volume fractions is large, core-shell hexagonal or tetragonal phases can be formed, depending on which of the blocks dominates. Furthermore, more complex morphologies, such as lamellae with beads inside, lamellae with beads at the interface, and hexagonal phases with beads at the interface compete for stability with lamellae structures, as the interaction energies between distinct blocks become asymmetric. Our study provides guidance for the design of microstructures in complex block copolymers.

  8. Characterization of copolymer latexes by capillary electrophoresis.

    PubMed

    Anik, Nadia; Airiau, Marc; Labeau, Marie-Pierre; Bzducha, Wojciech; Cottet, Hervé

    2010-02-02

    Latexes are widely used for industrial applications, including decorative paints, binders for the papermaking industry, and drilling fluids for oil-field applications. In this work, the interest of capillary zone electrophoresis (CE) for the characterization of hydrophobic block copolymer latexes obtained by the conventional emulsion polymerization technique consisting of a core of polystyrene (PS) surrounded by a layer of poly(ethyl acrylate) (PEA) has been investigated. The PEA part of the copolymer can be partially hydrolyzed in poly(acrylic acid) (PAA) leading to PS-PEA-AA water-soluble amphiphilic copolymer having high viscosifying properties. The main purpose of this work was to evaluate the potential of CE for the characterization of the latexes at the different stages of the synthesis (PS core, PS-PEA diblock latex, and hydrolyzed PS-PEA-AA gel). The main analytical issues were to state (i) if there was free PS or PEA homopolymer latexes in the PS-PEA latex sample and (ii) if there was free PS, PEA, PS-PEA latexes, or free PAA chains in the PS-PEA-AA gel. Within this scope, this work describes the optimization of the selectivity of the separation between the different species (PS, PEA particles in the not hydrolyzed diblock latex and PS, PEA, PS-PEA particles as well as the polymer PAA chains in the PS-PEA-AA diblock gel sample obtained by latter latex hydrolysis). For that purpose, several experimental parameters were investigated such as pH and ionic strength of the background electrolyte (BGE) or the concentration of neutral surfactant added in the BGE. A challenging issue was to overcome the high viscosity of the PS-PEA-AA gel. This was resolved by the addition of 10 mM neutral surfactant in the gel sample and in the BGE. Finally, it is demonstrated that, within the detection limits, CE is a suitable analytical tool for controlling and monitoring the syntheses of these latexes and for intrinsically characterizing the distribution in charge density of

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

    NASA Astrophysics Data System (ADS)

    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

  10. Nanoparticle-Loaded Multifunctional Block Copolymer Micelles

    NASA Astrophysics Data System (ADS)

    Bae, Jinhye; Lawrence, Jimmy; Miesch, Caroline; Ribbe, Alexander; Li, Weikun; Emrick, Todd; Zhu, Jintao; Hayward, Ryan

    2012-02-01

    We have studied the incorporation of pre-synthesized hydrophobic inorganic nanoparticles within the cores of amphiphilic polystyrene-block-poly(ethylene oxide) (PS-PEO) diblock copolymer micelles formed through solvent-evaporation-induced interfacial instabilities of emulsion droplets. Using iron oxide, gold, and cadmium selenide nanoparticles coated with native alkane ligands, highly uniform encapsulation is obtained for cylindrical micelles, while spherical micelles can be enriched to ˜ 90 % of loaded micelles through simple magnetic or centrifugal purification steps. Multiple different types of nanoparticles can easily be incorporated into each micelle, yielding multi-functional micelles. The ability to encapsulate both spherical and rod-like particles of different core chemistries and sizes ranging from ˜ 1 to 20 nm, without the necessity of coating particles with specially designed ligands, makes this a versatile route to prepare hybrid micelle structures.

  11. Ion transport through block copolymer electrolytes

    NASA Astrophysics Data System (ADS)

    Mullin, Scott; Panday, Ashoutosh; Balsara, Nitash

    2009-03-01

    Poly(styrene)-block-poly(ethylene oxide) (SEO) is a candidate material for electrolytes for rechargeable lithium metal batteries. The PS phase suppresses lithium dendrite growth on the anode during recharge, and the PEO phase solvates lithium bis(trifluoromethane)sulfonimide (LiTFSI) salt to form conducting pathways. Complete electrochemical characterization of PEO/LiTFSI mixtures requires measurement of conductivity, salt diffusion coefficient, and lithium ion transference number. The present study covers SEO copolymers that exhibit lamellar and cylindrical morphologies in the absence of salt. The addition of salt affects morphology but the relationships between morphology and electrochemical characteristics have not yet been clarified. Some aspects of these relationships will be presented.

  12. Cationic vinyl pyridine copolymers and products thereof

    NASA Technical Reports Server (NTRS)

    Rembaum, Alan (Inventor)

    1978-01-01

    Quaternized, cross-linked, insoluble copolymers of unsubstituted and substituted vinyl pyridines and a dihalo organic compound are spontaneously formed at ambient temperature on mixing the two monomers in bulk, in solution or in suspension. The amount of cross-linking may be varied according to the composition and reaction conditions. The polymer product exhibits ion exchange capacity and undergoes a reversible color change from black at a pH above 7 to yellow at a pH below 7. The polymer may be formed in the presence of preformed polymers, substrates such as porous or impervious particles or films to deposit an ion exchange film in situ or on the surface of the substrate. The coated or resin impregnated substrate may be utilized for separation of anionic species from aqueous solution.

  13. Computational engineering of low bandgap copolymers

    PubMed Central

    Wykes, Michael; Milián-Medina, Begoña; Gierschner, Johannes

    2013-01-01

    We present a conceptual approach to low bandgap copolymers, in which we clarify the physical parameters which control the optical bandgap, develop a fundamental understanding of bandgap tuning, unify the terminology, and outline the minimum requirements for accurate prediction of polymer bandgaps from those of finite length oligomers via extrapolation. We then test the predictive power of several popular hybrid and long-range corrected (LC) DFT functionals when applied to this task by careful comparison to experimental studies of homo- and co-oligomer series. These tests identify offset-corrected M06HF, with 100% HF exchange, as a useful alternative to the poor performance of tested hybrid and LC functionals with lower fractions of HF exchange (B3LYP, CAM-B3LYP, optimally-tuned LC-BLYP, BHLYP), which all significantly overestimate changes in bandgap as a function of system size. PMID:24790963

  14. Triblock Copolymer Theory: Ordered ABC Lamellar Phase

    NASA Astrophysics Data System (ADS)

    Ren, G.; Wei, J. A.

    2003-04-01

    The ABC lamellar phase of a triblock copolymer in the strong segregation region is studied on periodic and bounded intervals. In the periodic case we find a family of local minimizers of the free energy functional all with a fine lamellar structure. Among these local minimizers we identify the one most favored by the free energy, and hence determine the thickness of lamellar microdomains. In the bounded interval case we show that perfect lamellar structure does not exist due to the boundary effect. We view the strong segregation limit as a Γ -limit of the free energy by a proper choice of the material sample size. The key step is the spectral analysis of a large matrix resulting from the second derivative of the Γ -limit.

  15. Block and graft copolymers and NanoGel copolymer networks for DNA delivery into cell.

    PubMed

    Lemieux, P; Vinogradov, S V; Gebhart, C L; Guérin, N; Paradis, G; Nguyen, H K; Ochietti, B; Suzdaltseva, Y G; Bartakova, E V; Bronich, T K; St-Pierre, Y; Alakhov, V Y; Kabanov, A V

    2000-01-01

    Self-assembling complexes from nucleic acids and synthetic polymers are evaluated for plasmid and oligonucleotide (oligo) delivery. Polycations having linear, branched, dendritic. block- or graft copolymer architectures are used in these studies. All these molecules bind to nucleic acids due to formation of cooperative systems of salt bonds between the cationic groups of the polycation and phosphate groups of the DNA. To improve solubility of the DNA/polycation complexes, cationic block and graft copolymers containing segments from polycations and non-ionic soluble polymers, for example, poly(ethylene oxide) (PEO) were developed. Binding of these copolymers with short DNA chains, such as oligos, results in formation of species containing hydrophobic sites from neutralized DNA polycation complex and hydrophilic sites from PEO. These species spontaneously associate into polyion complex micelles with a hydrophobic core from neutralized polyions and a hydrophilic shell from PEO. Such complexes are very small (10-40 nm) and stable in solution despite complete neutralization of charge. They reveal significant activity with oligos in vitro and in vivo. Binding of cationic copolymers to plasmid DNA forms larger (70-200 nm) complexes. which are practically inactive in cell transfection studies. It is likely that PEO prevents binding of these complexes with the cell membranes ("stealth effect"). However attaching specific ligands to the PEO-corona can produce complexes, which are both stable in solution and bind to target cells. The most efficient complexes were obtained when PEO in the cationic copolymer was replaced with membrane-active PEO-b-poly(propylene oxide)-b-PEO molecules (Pluronic 123). Such complexes exhibited elevated levels of transgene expression in liver following systemic administration in mice. To increase stability of the complexes, NanoGel carriers were developed that represent small hydrogel particles synthesized by cross-linking of PEI with double end

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

    SciTech Connect

    Qin, C.; Ding, Y.P.

    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.

  17. Self-Assembly of Block Copolymers in an Ionic Liquid

    NASA Astrophysics Data System (ADS)

    He, Yiyong; Li, Zhibo; Lodge, Timothy P.

    2006-03-01

    Amphiphilic diblock copolymers poly((1,2-butadiene)-b-ethylene oxide) (PB-PEO) were shown to aggregate and form well-defined micelles in an ionic liquid, 1-butyl-3-methyl imidazolium hexafluorophosphate ([BMIM][PF6]). The universal sequence of micellar structures (spherical micelle, wormlike micelle, and bilayered vesicle) were all resolved by varying the block copolymer composition. For the first time, the nanostructures of PB-PEO micelles formed in an ionic liquid were directly visualized by cryogenic transmission electron microscopy (cryo-TEM). The detailed micelle structure information was extracted from cryo-TEM and dynamic light scattering (DLS) measurements, and compared to their aqueous counterparts. The work demonstrates the feasibility of controlling micellar nanostructures of amphiphilic block copolymers in ionic liquids, and also provides important knowledge for further applications of copolymers for forming microemulsions and ion gels.

  18. Surface Characterization of Aliphatic Polyester -g- Phosphorylcholine Copolymers

    NASA Astrophysics Data System (ADS)

    Zhang, Xiongfei; Emrick, Todd; Hsu, Shaw L.

    2007-03-01

    In order to control biodegradation behavior of a class of polyesters, hydrophilic functional groups were grafted onto the main chains. Phosphorylcholine (PC) molecules with azide attached at the end were synthesized. Due to their excellent biocompatibility and hydrophilicity, they have been covalently coupled to biodegradable aliphatic polyesters via a ``click'' cycloaddition reaction to produce amphiphilic graft copolymers. A series of copolymers were prepared by varying the molar incorporation of PC groups. Surface properties of the copolymers were examined to further explore their applications in drug delivery systems. Grazing angle reflection infrared spectroscopy was employed to determine segmental orientation at the film surface. XPS was used to verify surface composition. A water adsorption experiment was carried out to determine the water permeation rate. The improvement in hydrophilicity was confirmed by a water contact experiment. Results indicate that the graft copolymers were promising in drug delivery systems.

  19. Nanostructured photovoltaic materials using conjugated block copolymer assemblies

    NASA Astrophysics Data System (ADS)

    Mastroianni, Sarah E.; Epps, Thomas H., III

    2011-03-01

    Block copolymers containing a conjugated block offer attractive possibilities for creating nanostructured organic photovoltaic (OPV) devices. Current OPV materials suffer from efficiency losses primarily due to a size-scale discrepancy between exciton diffusion length and domain sizes; excitons that do not reach the interface between electron and hole-conducting materials recombine, preventing charge carrier separation. The inherent nature of block-copolymers to self-assemble into well-defined nanoscale structures with domain spacings on the order of exciton diffusion length offers a potential solution for reducing exciton recombination. In this work, allyl-terminated poly(3-hexyl thiophene) or poly(3-decyl thiophene) acting as electron donors are incorporated into the block copolymer chain via a coupling reaction with poly(styrene) or poly(isoprene- b -styrene) derivatives synthesized by anionic polymerization. The resulting block copolymer morphologies are characterized by small angle X-ray scattering and transmission electron microscopy.

  20. Sequence transferable coarse-grained model of amphiphilic copolymers

    NASA Astrophysics Data System (ADS)

    De Silva, Chathuranga C.; Leophairatana, Porakrit; Ohkuma, Takahiro; Koberstein, Jeffrey T.; Kremer, Kurt; Mukherji, Debashish

    2017-08-01

    Polymer properties are inherently multi-scale in nature, where delicate local interaction details play a key role in describing their global conformational behavior. In this context, deriving coarse-grained (CG) multi-scale models for polymeric liquids is a non-trivial task. Further complexities arise when dealing with copolymer systems with varying microscopic sequences, especially when they are of amphiphilic nature. In this work, we derive a segment-based generic CG model for amphiphilic copolymers consisting of repeat units of hydrophobic (methylene) and hydrophilic (ethylene oxide) monomers. The system is a simulation analogue of polyacetal copolymers [S. Samanta et al., Macromolecules 49, 1858 (2016)]. The CG model is found to be transferable over a wide range of copolymer sequences and also to be consistent with existing experimental data.

  1. Electrode coating composed of copolymers derived from diacetone acrylamide

    SciTech Connect

    Rampel, G.

    1985-07-23

    An improved electrode coating and separator coating derived from a copolymer of diacetone acrylamide and a polymerizable monomer. This invention relates to novel rechargeable electrodes, separators and processes for preparing same.

  2. HPMA copolymers: Origins, early developments, present, and future☆

    PubMed Central

    Kopeček, Jindřich; Kopečková, Pavla

    2010-01-01

    The overview covers the discovery of N-(2-hydroxypropyl)methacrylamide (HPMA) copolymers, initial studies on their synthesis, evaluation of biological properties, and explorations of their potential as carriers of biologically active compounds in general and anticancer drugs in particular. The focus is on the research in the authors’ laboratory – the development of macromolecular therapeutics for the treatment of cancer and musculoskeletal diseases. In addition, the evaluation of HPMA (co)polymers as building blocks of mod and new biomaterials is presented: the utilization of semitelechelic poly(HPMA) and HPMA copolymers for the modification of biomaterial and protein surfaces and the design of hybrid block and graft HPMA copolymers that self-assemble into smart hydrogels. Finally, suggestions for the design of second-generation macromolecular therapeutics are portrayed. PMID:19919846

  3. Crystalline Morphology of Propylene 1-Octene Random Copolymers

    NASA Astrophysics Data System (ADS)

    Jeon, Keesu; Alamo, Rufina G.

    2008-03-01

    The morphology of isotactic propylene 1-octene random copolymers has been studied by AFM, DSC, WAXS, and FTIR in an octene range of 10-20 mol %. Different morphologies were observed below and above 15 mol %. The morphological components in the higher counit copolymers are not of the lamellae-type, thicker than lamellae observed below 15 mol %, connected and isotropic in their orientation. Their global morphology is developed via nucleation and growth (NG) of spherulitic aggregates. The evolution of heat of fusion with time is also sigmoidal shape, typical of NG-type crystallization mechanism. WAXS diffractograms for the higher counit copolymers are devoid of crystalline reflections, except for small and broad peaks suggesting mesomorphic-like structures, which by FTIR show small contents of the 840 cm-1, 12 and higher units regularity bands, and hence formed of short helical sequences. The PO morphology is additionally compared with copolymers with ethylene, 1-butene and 1-hexene counits at matched contents.

  4. Insensitive explosive composition of halogenated copolymer and triaminotrinitrobenzene

    DOEpatents

    Benziger, Theodore M.

    1976-01-01

    A highly insensitive and heat resistant plastic-bonded explosive containing 90 wt % triaminotrinitrobenzene and 10 wt % of a fully saturated copolymer of chlorotrifluoroethylene and vinylidene fluoride is readily manufactured by the slurry process.

  5. Self-assembled architectures from biohybrid triblock copolymers.

    PubMed

    Reynhout, Irene C; Cornelissen, Jeroen J L M; Nolte, Roeland J M

    2007-02-28

    The synthesis and self-assembly behavior of biohybrid ABC triblock copolymers consisting of a synthetic diblock, polystyrene-b-polyethylene glycol (PSm-b-PEG113), where m is varied, and a hemeprotein, myoglobin (Mb) or horse radish peroxidase (HRP), is described. The synthetic diblock copolymer is first functionalized with the heme cofactor and subsequently reconstituted with the apoprotein or the apoenzyme to yield the protein-containing ABC triblock copolymer. The obtained amphiphilic block copolymers self-assemble in aqueous solution into a large variety of aggregate structures. Depending on the protein and the polystyrene block length, micellar rods, vesicles, toroids, figure eight structures, octopus structures, and spheres with a lamellar surface are formed.

  6. Electrode coating composed of copolymers derived from diacetone acrylamide

    SciTech Connect

    Rampel, G.

    1981-01-13

    An improved electrode coating and separator coating derived from a copolymer of diacetone acrylamide and a polymerizable monomer are disclosed. This invention relates to novel rechargeable electrodes, separators and processes for preparing same.

  7. Stepwise Activation of Switchable Glazing by Compositional Gradient of Copolymers.

    PubMed

    Lee, Eunsu; Kim, Dowan; Yoon, Jinhwan

    2016-10-05

    Thermotropic glazing is one of the most promising developments for adaptive solar control; however, a monotonic transparent-opaque transition limits its practical application. In this work, to render stepwise activation of the switchable glazing, we prepared multicomposition copolymers having a compositional gradient. By slow addition of the monomers in the reaction mixture during free-radical polymerization, the blend of copolymers with each polymer having different compositions of the monomers could be prepared. We found that the developed copolymers exhibit different thermal behaviors according to the monomer composition, yielding the nearly linear transmittance change over a wide temperature range due to the gradient hydrophilic-hydrophobic balances. By combining prepared copolymers with photothermal graphene oxide as a heat transducer, we demonstrated gradual solar control of the smart window in response to sunlight intensity in outdoor testing.

  8. Fluorescence properties of PEN and PET/PEN copolymers

    SciTech Connect

    Jones, A.S.; Dickson, T.J.; Wilson, B.E.

    1996-10-01

    The fluorescence properties of PEN (polyethylene napthalate) and PET (polyethylene terephthalate)/PEN copolymers were studied using time-resolved and steady-state fluorescence. Excimer and monomer emission are probed.

  9. Organically modified aluminosilicate mesostructures from block copolymer phases

    PubMed

    Templin; Franck; Du Chesne A; Leist; Zhang; Ulrich; Schadler; Wiesner

    1997-12-05

    Organically modified aluminosilicate mesostructures were synthesized from two metal alkoxides with the use of poly(isoprene-b-ethyleneoxide) block copolymers (PI-b-PEO) as the structure-directing molecules. By increasing the fraction of the inorganic precursors with respect to the polymer, morphologies expected from the phase diagrams of diblock copolymers were obtained. The length scale of the microstructures and the state of alignment were varied using concepts known from the study of block copolymers. These results suggest that the use of higher molecular weight block copolymer mesophases instead of conventional low-molecular weight surfactants may provide a simple, easily controlled pathway for the preparation of various silica-type mesostructures that extends the accessible length scale of these structures by about an order of magnitude.

  10. Multicompartmental Microcapsules from Star Copolymer Micelles

    SciTech Connect

    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

  11. Supramolecular Multiblock Copolymers Featuring Complex Secondary Structures.

    PubMed

    Elacqua, Elizabeth; Manning, Kylie B; Lye, Diane S; Pomarico, Scott K; Morgia, Federica; Weck, Marcus

    2017-09-06

    This contribution introduces main-chain supramolecular ABC and ABB'A block copolymers sustained by orthogonal metal coordination and hydrogen bonding between telechelic polymers that feature distinct secondary structure motifs. Controlled polymerization techniques in combination with supramolecular assembly are used to engineer heterotelechelic π-sheets that undergo high-fidelity association with both helical and coil-forming synthetic polymers. Our design features multiple advances to achieve our targeted structures, in particular, those emulating sheet-like structural aspects using poly(p-phenylenevinylene)s (PPVs). To engineer heterotelechelic PPVs in a sheet-like design, we engineer an iterative one-pot cross metathesis-ring-opening metathesis polymerization (CM-ROMP) strategy that affords functionalized Grubbs-II initiators that subsequently polymerize a paracyclophanediene. Supramolecular assembly of two heterotelechelic PPVs is used to realize a parallel π-sheet, wherein further orthogonal assembly with helical motifs is possible. We also construct an antiparallel π-sheet, wherein terminal PPV blocks are adjacent to a flexible coil-like poly(norbornene) (PNB). The PNB is designed, through supramolecular chain collapse, to expose benzene and perfluorobenzene motifs that promote a hairpin turn via charge-transfer-aided folding. We demonstrate that targeted helix-(π-sheet)-helix and helix-(π-sheet)-coil assemblies occur without compromising intrinsic helicity, while both parallel and antiparallel β-sheet-like structures are realized. Our main-chain orthogonal assembly approach allows the engineering of multiblock copolymer scaffolds featuring diverse secondary structures via the directional assembly of telechelic building blocks. The targeted assemblies, a mix of sequence-defined helix-sheet-coil and helix-sheet-helix architectures, are Nature-inspired synthetic mimics that expose α/β and α+β protein classes via de novo design and cooperative assembly

  12. Interfacial properties of semifluorinated alkane diblock copolymers

    NASA Astrophysics Data System (ADS)

    Pierce, Flint; Tsige, Mesfin; Borodin, Oleg; Perahia, Dvora; Grest, Gary S.

    2008-06-01

    The liquid-vapor interfacial properties of semifluorinated linear alkane diblock copolymers of the form F3C(CF2)n-1(CH2)m-1CH3 are studied by fully atomistic molecular dynamics simulations. The chemical composition and the conformation of the molecules at the interface are identified and correlated with the interfacial energies. A modified form of the Optimized Parameter for Liquid Simulation All-Atom (OPLS-AA) force field of Jorgensen and co-workers [J. Am. Chem. Soc. 106, 6638 (1984); 118, 11225 (1996); J. Phys. Chem. A 105, 4118 (2001)], which includes specific dihedral terms for H-F blocks-and corrections to the H-F nonbonded interaction, is used together with a new version of the exp-6 force field developed in this work. Both force fields yield good agreement with the available experimental liquid density and surface tension data as well as each other over significant temperature ranges and for a variety of chain lengths and compositions. The interfacial regions of semifluorinated alkanes are found to be rich in fluorinated groups compared to hydrogenated groups, an effect that decreases with increasing temperature but is independent of the fractional length of the fluorinated segments. The proliferation of fluorine at the surface substantially lowers the surface tension of the diblock copolymers, yielding values near those of perfluorinated alkanes and distinct from those of protonated alkanes of the same chain length. With decreasing temperatures within the liquid state, chains are found to preferentially align perpendicular to the interface, as previously seen.

  13. Block Copolymer Thin Films: Patterns and Patterning

    NASA Astrophysics Data System (ADS)

    Register, Richard A.

    2001-03-01

    The nanostructures ("microdomains") in thin block copolymer films make excellent contact masks for surface patterning on the nanoscale. Using these thin films as templates, we have developed techniques based on reactive ion etching to uniformly and completely pattern the underlying substrate with a dense periodic pattern of dots, holes, or lines, with widths of order 20 nm. In addition, we have fabricated arrays of metal dots by backfilling these holes, and GaAs quantum dots by regrowth onto patterned GaAs substrates. A key issue in this nanopatterning approach is controlling the pattern which forms within the mask. While the local structure of the pattern (e.g., spheres vs. cylinders) is easily controlled through block copolymer composition, the long-range order ("grain size") is more difficult to manipulate. For cylinder-forming diblocks, we find that the correlation length of the microdomains grows as a weak power of annealing time, approximately 1/4. The principal types of defects which destroy the long-range order of the microdomains are disclinations. Sequential AFM images taken on the same region of the film after varying annealing times can be strung together into "movies" (to be shown at the talk) which directly show that the principal mode of defect annihilation (and hence grain growth) is the annihilation of disclination quadrupoles (pairs of +1/2 and -1/2 disclinations). We propose a model for quadrupole annihilation which reproduces the 1/4 exponent. Preliminary results for sphere-forming systems suggest that the exponent there is even lower than 1/4, making it difficult to achieve a significant degree of coarsening by extending the annealing time. * in collaboration with D.H. Adamson, P.M. Chaikin, Z. Cheng, P.D. Dapkus (USC), C.K. Harrison, D.A. Huse, R.R. Li (USC), and M. Park.

  14. Melt structure and self-nucleation of ethylene copolymers

    NASA Astrophysics Data System (ADS)

    Alamo, Rufina G.

    A strong memory effect of crystallization has been observed in melts of random ethylene copolymers well above the equilibrium melting temperature. These studies have been carried out by DSC, x-ray, TEM and optical microscopy on a large number of model, narrow, and broad copolymers with different comonomer types and contents. Melt memory is correlated with self-seeds that increase the crystallization rate of ethylene copolymers. The seeds are associated with molten ethylene sequences from the initial crystals that remain in close proximity and lower the nucleation barrier. Diffusion of all sequences to a randomized melt state is a slow process, restricted by topological chain constraints (loops, knots, and other entanglements) that build in the intercrystalline region during crystallization. Self-seeds dissolve above a critical melt temperature that demarcates homogeneity of the copolymer melt. There is a critical threshold level of crystallinity to observe the effect of melt memory on crystallization rate, thus supporting the correlation between melt memory and the change in melt structure during copolymer crystallization. Unlike binary blends, commercial ethylene-1-alkene copolymers with a range in inter-chain comonomer composition between 1 and about 15 mol % display an inversion of the crystallization rate in a range of melt temperatures where narrow copolymers show a continuous acceleration of the rate. With decreasing the initial melt temperature, broadly distributed copolymers show enhanced crystallization followed by a decrease of crystallization rate. The inversion demarcates the onset of liquid-liquid phase separation (LLPS) and a reduction of self-nuclei due to the strong thermodynamic drive for molecular segregation inside the binodal. The strong effect of melt memory on crystallization rate can be used to identify liquid-liquid phase separation in broadly distributed copolymers, and offers strategies to control the state of copolymer melts in ways of

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

    SciTech Connect

    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

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

    DOEpatents

    Kent, Michael S.; Saunders, Randall

    1997-01-01

    Coupling agents 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.

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

    DTIC Science & Technology

    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

  18. Thin Films of Bottlebrush Block Copolymers with Homopolymer

    NASA Astrophysics Data System (ADS)

    Jeong, Gajin; Sveinbjornsson, Benjamin R.; Grubbs, Robert Howard; Russell, Thomas P.; Polymer science; engineering department, University of Massachusetts Amherst Team; Chemistry department, California Institute of Technology Team

    2015-03-01

    We have investigated the self assembled structures of bottlebrush block copolymers (BrBCPs) in thin films by blending deuterated homopolymer. By use of neutron reflectivity (NR), the assemblies with microdomain oriented parallel to the substrate, the distribution of the homopolymer in the bottlebrush block copolymer was obtained. Polynorbornene-backbone-based bottlebrush BCPs with polylactide (PLA) and polystyrene (PS) side chains of different molecular weights were investigated. Small angle x-ray scattering was used to complement the NR studies.

  19. Photooxidative degradation of clear ultraviolet absorbing acrylic copolymer surfaces

    NASA Technical Reports Server (NTRS)

    Gupta, A.; Liang, R. H.; Vogl, O.; Pradellok, W.; Huston, A. L.; Scott, G. W.

    1983-01-01

    Photodegradation of copolymer of methyl methacrylate and 2(2'-hydroxy 5'vinyl-phenyl) 2H-benzotriazole has been investigated in order to determine the changes in the chemical composition of the surface of the copolymer on photooxidation. An electronic energy transfer mechanism has been postulated in order to interpret the observed photochemical changes in the polymer. Preliminary examination of the photophysical properties of the chromophore provides support for such a mechanism.

  20. Thermoreversible, epitaxial fcc<-->bcc transitions in block copolymer solutions.

    PubMed

    Bang, Joona; Lodge, Timothy P; Wang, Xiaohui; Brinker, Kristin L; Burghardt, Wesley R

    2002-11-18

    Uncharged block copolymer micelles display thermoreversible transitions between close-packed and bcc lattices for a range of concentration, solvent selectivity, and copolymer composition. Using small-angle x-ray scattering on shear-oriented solutions, highly aligned fcc crystals are seen to transform epitaxially to bcc crystals, with fcc/bcc orientational relationships that are well established in martensitic transformations in metals. The transition is driven by decreasing solvent selectivity with increasing temperature, inducing solvent penetration of the micellar core.

  1. Complex copolymers for mobility control, water purification, and surface activity

    SciTech Connect

    Meister, J.J.

    1988-05-01

    Many processes that are basic to the extraction of natural resources are facilitated by addition of polymers. To be useful, the polymers must meet an interrelated list of chemical and physical properties as well as economic criteria. Two important properties demanded of the polymers are: 1. Rheology. Polymers are often added to change solvent or process flow properties. The addition of polymers almost always causes non-Newtonian flow behavior in the resulting fluid. Methods of controlling surface behavior are to: 1) create polar and nonpolar regions in the molecule thus producing a hydrophilic-lipophilic balance in the molecule, 2) charge the molecule by introducing ionic sites with the same or opposite charge as the boundary, or 3) introduce or remove functional groups in the molecule which produce binding reactions, such as a) hydrogen bond creation of b) nitrogen lone-pair donation, with the surface. This multitude of properties the polymer must possess dictate that better polymer performance is obtained from materials with complicated structures. Such polymers are complex polymers: random copolymers, block copolymers, graft copolymers, micellizing copolymers, and network copolymers. There has been a dramatic increase in the past decade in the number and complexity of these copolymers and it is these newly discovered polymers and their chemistry which will be described here. The synthesis, analysis, and testing of these polymers, with particular emphasis on those polymers designed for enhanced oil recovery, is presented.

  2. Carboxymethylbetaine copolymer layer covalently fixed to a glass substrate.

    PubMed

    Suzuki, Hisatomo; Li, Lifu; Nakaji-Hirabayashi, Tadashi; Kitano, Hiromi; Ohno, Kohji; Matsuoka, Kazuyoshi; Saruwatari, Yoshiyuki

    2012-06-01

    A random copolymer of zwitterionic monomer, carboxymethylbetaine (CMB), and 3-methacryloyloxypropyl trimethoxysilane was prepared in ethanol using 2,2'-azobisisobutyronitrile as initiator. The incubation of ethanol solution of the copolymer with a glass plate gave a layer of the copolymer with a thickness of about 2-3 nm. The copolymer-modified glass substrate became highly hydrophilic upon immersion in water, and showed a resistance against non-specific adsorption of proteins, and the degree of resistance increased with the content of CMB residues in the copolymer and leveled off. The adhesion of various cells to the glass substrate was also strongly suppressed by the surface modification with the copolymer layer. Further introduction of PolyCMB graft chains on the surface of the layer enhanced the suppression of cell adhesion due to the steric hindrance for the cells to approach the layer. The usefulness of the combination of zwitterionic polymer layer and graft chains to afford anti-biofouling properties to a solid surface of metal oxides was shown.

  3. Theory for the aggregation of proteins and copolymers

    SciTech Connect

    Fields, G.B.; Alonso, D.O.V.; Stigter, D.; Dill, K.A.

    1992-05-14

    We develop mean-field lattice statistical mechanics theory for the equilibrium between denatured and aggregated states of proteins and other random copolymers of hydrophobic and polar monomers in aqueous solution. We suppose that the aggregated state is a mixture of amorphous polymer plus solvent and that the driving forces are the hydrophobic interaction, which favors aggregation, and conformational and translational entropies, which favor disaggregation. The theory predicts that the phase diagram for thermal aggregation is an asymmetric closed loop, and for denaturants (guanidinium hydrochloride of urea) it is asymmetric with an upper consolute point. The theory predicts that a copolymer in a poor solvent will expand with increasing polymer concentration because of {open_quotes}screening{close_quotes} of the solvent interactions by the other chains; the chain ultimately reaches a theta-like state in the absence of solvent. The screening concentration depends strongly on the copolymer composition. We find two striking features of these copolymer phase diagrams. First, they are extraordinarily sensitive to the copolymer composition; a change of one amino acid can substantially change the aggregation behavior. Second, relative to homopolymers, copolymers should be stable against aggregation at concentrations that are higher by many orders of magnitude. 43 refs., 13 figs.

  4. Nanopatterning of Viruses and Proteins Using Microphase Separated Block Copolymers

    NASA Astrophysics Data System (ADS)

    Cresce, Arthur; Lewandowski, Angela; Bentley, William; Kofinas, Peter

    2006-03-01

    Diblock copolymers containing nickel ions have been prepared that are capable of selectively adsorbing histidine-tagged green fluorescent protein (hisGFP), and also binding tobacco mosaic virus (TMV). A block copolymer of norbornene and norbornene dicarboxylic acid was synthesized using ring-opening metathesis polymerization. A 400/50 block ratio achieved a spherical microphase-separated morphology with roughly 20 nm diameter dicarboxylic acid spheres. The spherical phase was exposed to nickel ions in solution, templating the formation of nickel nanoparticles. This process gave a nickel-loaded diblock copolymer film whose surface was used to chelate hisGFP. Fluorescence spectroscopy and TEM confirmed the presence of the protein on the polymer surface. A sulfonated triblock copolymer was loaded with nickel ions using a similar solution-doping procedure. The morphology of this copolymer was lamellar, and its sulfonated block was loaded with nickel ions. TEM studies revealed the presence of the virus on the surface of the copolymer and showed that the bond between the TMV and the polymer surface can withstand severe detergent washes.

  5. Field-theoretic simulations of random copolymers with structural rigidity.

    PubMed

    Mao, Shifan; MacPherson, Quinn; Qin, Jian; Spakowitz, Andrew J

    2017-04-12

    Copolymers play an important role in a range of soft-materials applications and biological phenomena. Prevalent works on block copolymer phase behavior use flexible chain models and incorporate interactions using a mean-field approximation. However, when phase separation takes place on length scales comparable to a few monomers, the structural rigidity of the monomers becomes important. In addition, concentration fluctuations become significant at short length scales, rendering the mean-field approximation invalid. In this work, we use simulation to address the role of finite monomer rigidity and concentration fluctuations in microphase segregation of random copolymers. Using a field-theoretic Monte-Carlo simulation of semiflexible polymers with random chemical sequences, we generate phase diagrams for random copolymers. We find that the melt morphology of random copolymers strongly depends on chain flexibility and chemical sequence correlation. Chemically anti-correlated copolymers undergo first-order phase transitions to local lamellar structures. With increasing degree of chemical correlation, this first-order phase transition is softened, and melts form microphases with irregular shaped domains. Our simulations in the homogeneous phase exhibit agreement with the density-density correlation from mean-field theory. However, conditions near a phase transition result in deviations between simulation and mean-field theory for the density-density correlation and the critical wavemode. Chain rigidity and sequence randomness lead to frustration in the segregated phase, introducing heterogeneity in the resulting morphologies.

  6. Thermodynamics of block copolymers with and without salt.

    PubMed

    Teran, Alexander A; Balsara, Nitash P

    2014-01-09

    Ion-containing block copolymers are of interest for applications such as electrolytes in rechargeable lithium batteries. The addition of salt to these materials is necessary to make them conductive; however, even small amounts of salt can have significant effects on the phase behavior of these materials and consequently on their ion-transport and mechanical properties. As a result, the effect of salt addition on block copolymer thermodynamics has been the subject of significant interest over the past decade. This feature article describes a comprehensive study of the thermodynamics of block copolymer/salt mixtures over a wide range of molecular weights, compositions, salt concentrations, and temperatures. The Flory-Huggins interaction parameter was determined by fitting small-angle X-ray scattering data of disordered systems to predictions based on the random phase approximation. Experiments on neat block copolymers revealed that the Flory-Huggins parameter is a strong function of chain length. Experiments on block copolymer/salt mixtures revealed a highly nonlinear dependence of the Flory-Huggins parameter on salt concentration. These findings are a significant departure from previous results and indicate the need for improved theories for describing thermodynamic interactions in neat and salt-containing block copolymers.

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

    PubMed

    Gratzl, Günther; Paulik, Christian; Hild, Sabine; Guggenbichler, Josef P; Lackner, Maximilian

    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. Copyright © 2014 Elsevier B.V. All rights reserved.

  8. MALDI-ToF Analysis of Model Copolymer Blends

    NASA Astrophysics Data System (ADS)

    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. Radical-cured block copolymer-modified thermosets

    SciTech Connect

    Redline, Erica M.; Francis, Lorraine F.; Bates, Frank S.

    2013-01-10

    Poly(ethylene-alt-propylene)-b-poly(ethylene oxide) (PEP-PEO) diblock copolymers were synthesized and added at 4 wt % to 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane (BisGMA), a monomer that cures using free radical chemistry. In separate experiments, poly(ethylene glycol) dimethacrylate (PEGDMA) was combined as a secondary monomer with BisGMA and the monomers were loaded with 4 wt % PEP-PEO. The diblock copolymers self-assembled into well-dispersed spherical micelles with PEP cores and PEO coronas. No appreciable change in the final extent of cure of the thermosets was caused by the addition of diblock copolymer, except in the case of BisGMA, where the addition of the block copolymer increased extent of cure by 12%. Furthermore, the extent of cure was increased by 29% and 37% with the addition of 25 and 50 wt % PEGDMA, respectively. Elastic modulus and fracture resistance were also determined, and the values indicate that the addition of block copolymers does not significantly toughen the thermoset materials. This finding is surprising when compared with the large increase in fracture resistance seen in block copolymer-modified epoxies, and an explanation is proposed.

  10. Properties of radiation cured vinyl-divinyl copolymers. [Gamma rays

    SciTech Connect

    Micko, M.M.; Paszner, L.

    1980-04-01

    Analysis of compression stress-strain curves of radiation-cured vinyl methacrylate copolymers shows that addition of small concentrations of vinyl comonomers significantly alter all mechanical strength properties in compression. Stress-strain behavior is found to be a function of the copolymer composition. Best strength results are limited to a narrow comonomer concentration region; between 5 to 10% of divinyl monomer (DVM) for the four systems studied. This concentration range broadens with increasing molecular bridge length of the crosslinking agent being narrowest for ethylene glycol dimethylacrylate and broadest for tetraethylene glycol dimethacrylate. Copolymer connection number (CN/sub co/), as introduced earlier, is found to be useful structural parameter for crosslinked copolymers in that it correlates quantitatively mechanical or thermomechanical properties with crosslink densities within copolymers. The Methyl methacrylate-TEGDMA comonomer system was found to be the most suitable and economically attractive. It represents a well balanced compromise of improved polymerization parameters and copolymer properties desirable in many polymeric products. 9 figures, 2 tables.

  11. The alpha-glycosidic bonds of poly(ADP-ribose) are acid-labile.

    PubMed

    Panzeter, P L; Zweifel, B; Althaus, F R

    1992-04-15

    The poly(ADP-ribosyl)ation system of higher eukaryotes produces multiple ADP-ribose polymers of distinct sizes which exhibit different binding affinities for histones. Although precipitation with trichloroacetic acid (TCA) is the standard procedure for isolation of poly(ADP-ribose) from biological material, we show here that poly(ADP-ribose) is not stable under acidic conditions. Storage of poly(ADP-ribose) as TCA pellets results in acid hydrolysis of polymers, the extent of which is dependent on storage time and temperature. The alpha-glycosidic, inter-residue bonds are the preferred sites of attack, thus reducing polymer sizes by integral numbers of ADP-ribose to yield artefactually more and smaller polymers than originally present. Therefore, poly(ADP-ribosyl)ation studies involving TCA precipitation, histone extraction with acids, or acidic incubations of ADP-ribose polymers must account for the impact of acids on resulting polymer populations.

  12. Functional Polymers and Sequential Copolymers by Phase Transfer Catalysis. 30. Synthesis of Liquid Crystalline Poly(epichlorohydrin) and Copolymers.

    DTIC Science & Technology

    1986-10-01

    Copolymers K0 By Coleen Pugh and V. Percec Department of Macromolecular Science Case Western Reserve University Cleveland, OH 44106 Submitted for... Coleen Pugh and V. Percec Department of Macromolecular Science Case Western Reserve University Cleveland, OH 44106 f ABSTRACT/ -Poly(epichlotohydrin...Catalysis. 30. Synthesis of Liquid Crystalline Poly(epichlorohydrin) and Copolymers 12 PERSONAL AUTIIOR(S C Coleen Pugh and V. Percec 13a TYPE OF

  13. Method of forming oriented block copolymer line patterns, block copolymer line patterns formed thereby, and their use to form patterned articles

    DOEpatents

    Russell, Thomas P.; Hong, Sung Woo; Lee, Doug Hyun; Park, Soojin; Xu, Ting

    2015-10-13

    A block copolymer film having a line pattern with a high degree of long-range order is formed by a method that includes forming a block copolymer film on a substrate surface with parallel facets, and annealing the block copolymer film to form an annealed block copolymer film having linear microdomains parallel to the substrate surface and orthogonal to the parallel facets of the substrate. The line-patterned block copolymer films are useful for the fabrication of magnetic storage media, polarizing devices, and arrays of nanowires.

  14. Method of forming oriented block copolymer line patterns, block copolymer line patterns formed thereby, and their use to form patterned articles

    DOEpatents

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

    2017-08-01

    A block copolymer film having a line pattern with a high degree of long-range order is formed by a method that includes forming a block copolymer film on a substrate surface with parallel facets, and annealing the block copolymer film to form an annealed block copolymer film having linear microdomains parallel to the substrate surface and orthogonal to the parallel facets of the substrate. The line-patterned block copolymer films are useful for the fabrication of magnetic storage media, polarizing devices, and arrays of nanowires.

  15. Structural determinants of miR156a precursor processing in temperature-responsive flowering in Arabidopsis

    PubMed Central

    Kim, Wanhui; Kim, Hee-Eun; Jun, A Rim; Jung, Myeong Gyo; Jin, Suhyun; Lee, Joon-Hwa; Ahn, Ji Hoon

    2016-01-01

    MicroRNAs originate from primary transcripts (pri-miRNAs) containing hairpin structures. Plant pri-miRNAs have highly variable structures and little is known about the information encoded in their secondary structures. Arabidopsis miR156 is an ambient temperature-responsive miRNA and plays an important role in regulating flowering time. To identify the structural determinants for miR156 processing, we analyzed the effects of mutations introduced in the upper stem of pri-miR156a on its temperature-dependent processing and flowering time. The levels of pri-miR156a and mature miR156 were opposite at different temperatures. Mutations in the upper stem, especially the region closer to the miR156a/miR156a* duplex, reduced miR156 processing at 23 °C and 16 °C and caused a less severe phenotype compared with the un-mutated construct. Mutation in the second stem near the first cleavage site of pri-miR156a affected miR156 processing at 23 °C, but not at 16 °C. This was also seen in pri-miR172a, another ambient temperature-responsive miRNA. Replacement of the upper stem of pri-miR156a with that of pri-miR172a severely affected miR156 processing and flowering time. These results suggested that the upper stem of pri-miR156a is important for miR156 processing at different temperatures. In particular, the second stem adjacent to the first cleavage site plays a role in the regulation of ambient temperature-responsive flowering. PMID:27335452

  16. Synthesis, morphologies and applications of polyoxometalate-containing diblock copolymers

    NASA Astrophysics Data System (ADS)

    Chakraborty, Sanjiban

    Block copolymers by virtue of their ability to self assemble and microphase-separation due to the contrast in chemical and physical properties of the covalently linked blocks constitute the essential building blocks towards various nano or micro sized architectures. Polyoxometalates (POM), on the other hand, being an interesting class of metal-oxygen nanometer-sized anionic clusters, are regarded highly due to their excellent electron accepting capability. Combining POM clusters with diblock copolymers can lead to a fascinating class of hybrid materials where the POM cluster not only affect the self-assembly process of various diblock copolymers but also brings its unique electronic properties into the hybrid system. Herein we report the detailed synthesis and characterizations of two hybrid coil-coil diblock copolymers along with two hybrid rod-coil diblock copolymers through polymerization-hybridization approach. The coil-coil diblocks were synthesized via atom transfer radial polymerization (ATRP) of styryl-type monomers and 4-vinylpyridine in sequence. For rod-coil diblock copolymers, the coil block was synthesized through ATRP, followed by the conversion of the terminal bromide to an azide. Ethynyl terminated poly (p-phenylenevinylene) (PPV) and poly (3-hexylthiophene) (P3HT) were prepared separately as the rod blocks. The rod block and the coil block were connected through click chemistry to yield rod-coil diblock copolymers. After removing the phthalimide protecting groups to regenerate aryl amines, POM clusters were finally linked to the coil block of all diblock copolymers to yield the targeted hybrid diblock copolymers. The covalent cluster attachment was confirmed by UV-Vis spectroscopy, FTIR and cyclovoltammetry measurements. The structures, solution and film optical properties, self-assembled morphologies and solar cell performances of these hybrids have been studied. It has been found that solar cell devices based on hybrid P3HT exhibited rather poor

  17. Shape memory rubber bands & supramolecular ionic copolymers

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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

  19. Disulfide-Functionalized Diblock Copolymer Worm Gels.

    PubMed

    Warren, Nicholas J; Rosselgong, Julien; Madsen, Jeppe; Armes, Steven P

    2015-08-10

    Two strategies for introducing disulfide groups at the outer surface of RAFT-synthesized poly(glycerol monomethacrylate)-poly(2-hydroxypropyl methacrylate) (PGMA-PHPMA, or Gx-Hy for brevity) diblock copolymer worms are investigated. The first approach involved statistical copolymerization of GMA with a small amount of disulfide dimethacrylate (DSDMA, or D) comonomer to afford a G54-D0.50 macromolecular chain transfer agent (macro-CTA); this synthesis was conducted in relatively dilute solution in order to ensure mainly intramolecular cyclization and hence the formation of linear chains. Alternatively, a new disulfide-based bifunctional RAFT agent (DSDB) was used to prepare a G45-S-S-G45 (or (G45-S)2) macro-CTA. A binary mixture of a non-functionalized G55 macro-CTA was utilized with each of these two disulfide-based macro-CTAs in turn for the RAFT aqueous dispersion polymerization of 2-hydroxypropyl methacrylate (HPMA). By targeting a PHPMA DP of 130 and systematically varying the molar ratio of the two macro-CTAs, a series of disulfide-functionalized diblock copolymer worm gels were obtained. For both formulations, oscillatory rheology studies confirmed that higher disulfide contents led to stronger gels, presumably as a result of inter-worm covalent bond formation via disulfide/thiol exchange. Using the DSDB-based macro-CTA led to the strongest worm gels, and this formulation also proved to be more effective in suppressing the thermosensitive behavior that is observed for the nondisulfide-functionalized control worm gel. However, macroscopic precipitation occurred when the proportion of DSDB-based macro-CTA was increased to 50 mol %, whereas the DSDMA-based macro-CTA could be utilized at up to 80 mol %. Finally, the worm gel modulus could be reduced to that of a nondisulfide-containing worm gel by reductive cleavage of the inter-worm disulfide bonds using excess tris(2-carboxyethyl)phosphine (TCEP) to yield thiol groups. These new biomimetic worm gels are

  20. New adhesive systems based on functionalized block copolymers

    SciTech Connect

    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.