Home About us Contact
|
Home About us Contact | ||
|
|
||
Low Glass Transition Temperature (low + glass_transition_temperature)
Selected AbstractsFabrication of Reversibly Crosslinkable, 3-Dimensionally Conformal Polymeric Microstructures,ADVANCED FUNCTIONAL MATERIALS, Issue 20 2008Luke A. Connal Abstract Multifaceted porous materials were prepared through careful design of star polymer functionality and properties. Functionalized core crosslinked star (CCS) polymers with a low glass transition temperature (Tg) based on poly(methyl acrylate) were prepared having a multitude of hydroxyl groups at the chain ends. Modification of these chain ends with 9-anthracene carbonyl chloride introduces the ability to reversibly photocrosslink these systems after the star polymers were self-assembled by the breath figure technique to create porous, micro-structured films. The properties of the low Tg CCS polymer allow for the formation of porous films on non-planar substrates without cracking and photo-crosslinking allows the creation of stabilized honeycomb films while also permitting a secondary level of patterning on the film, using photo-lithographic techniques. These multifaceted porous polymer films represent a new generation of well-defined, 3D microstructures. [source] Synthesis of networked polymers with lithium counter cations from a difunctional epoxide containing poly(ethylene glycol) and an epoxide monomer carrying a lithium sulfonate salt moietyJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 14 2010Kozo Matsumoto Abstract Poly(ethylene glycol)-based networked polymers that had lithium sulfonate salt structures on the network were prepared by heating a mixture of poly(ethylene glycol) diglycidyl ether (PEGGE), poly(ethylene glycol) bis(3-aminopropyl) terminated (PEGBA), and an ionic epoxy monomer, lithium 3-glycidyloxypropanesulfonate (LiGPS). Flexible self-standing networked polymer films showed high thermal stability, low crystallinity, low glass transition temperature, and good mechanical strength. The materials were ion conductive at room temperature even under a dry condition, although the ionic conductivity was rather low (10,6 to 10,5 S/m). The ionic conductivity increased with the increase in temperature to above 1 × 10,4 S/m at 90 °C. The film samples became swollen by immersing in propylene carbonate (PC) or PC solution of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). The samples swollen in PC showed higher ionic conductivity (ca.1 × 10,3 S/m at room temperature), and the samples swollen in LiTFSI/PC showed much higher ionic conductivity (nearly 1 S/m at room temperature). © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3113,3118, 2010 [source] Synthesis of azobenzene-functionalized two-arm, three-arm and four-arm telomers using polyfunctional chain transfer agentsPOLYMER INTERNATIONAL, Issue 11 2009Md Zahangir Alam Abstract BACKGROUND: Star-shaped polymers are very attractive because of their interesting properties such as reduced viscosity, good solubility, low glass transition temperature and fast response to external stimuli. The incorporation of azobenzene moieties in star-shaped polymers could significantly widen their potential applications in various optical devices. One of the most important properties of the azobenzene chromophore is its reversible trans,cis photoisomerization induced by UV or visible light. Photoisomerization induces conformational changes in azopolymer chains, which in turn lead to macroscopic variations in chemical and physical properties of the surroundings and media. RESULTS: This study reports the synthesis of azobenzene-functionalized two-, three- and four-arm telomers via free radical telomerization using the di-, tri- and tetrafunctional chain transfer agents 1,2- and 1,4-benzenedimethanethiol, trimethylolpropane-tris(2-mercaptoacetate) and pentaerythritol-tetrakis(3-mercaptopropionate), respectively, in the presence of azobisisobutyronitrile. Azotelomers were characterized using gel permeation chromatography and 1H NMR and Fourier transform infrared spectroscopy. Thermal phase transition behaviors were investigated using differential scanning calorimetry and polarized optical microscopy. Azotelomers synthesized in this study showed reversible photoisomerization and a fast generation of birefringence. CONCLUSION: Considering the photoisomerization behavior and birefringence of the two-, three- and four-arm azotelomers, it can be concluded that they could be potential candidates for use in various optical devices. Copyright © 2009 Society of Chemical Industry [source] Novel polymer electrolytes prepared by copolymerization of ionic liquid monomersPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 8 2002Masahiro Yoshizawa Abstract Ionic liquid monomer couples were prepared by the neutralization of 1-vinylimidazole with vinylsulfonic acid or 3-sulfopropyl acrylate. These ionic liquid monomer couples were viscous liquid at room temperature and showed low glass transition temperature (Tg) at ,83,°C and ,73,°C, respectively. These monomer couples were copolymerized to prepare ion conductive polymer matrix. Thus prepared ionic liquid copolymers had no carrier ions, and they showed very low ionic conductivity of below 10,9 S,cm,1. Equimolar amount of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to imidazolium salt unit was then added to generate carrier ions in the ionic liquid copolymers. Poly(vinylimidazolium-co-vinylsulfonate) containing equimolar LiTFSI showed the ionic conductivity of 4,×,10,8 S,cm,1 at 30,°C. Advanced copolymer, poly(vinylimidazolium-co-3-sulfopropyl acrylate) which has flexible spacer between the anionic charge and polymer main chain, showed the ionic conductivity of about 10,6 S,cm,1 at 30,°C, which is 100 times higher than that of copolymer without spacer. Even an excess amount of LiTFSI was added, the ionic conductivity of the copolymer kept this conductivity. This tendency is completely different from the typical polyether systems. Copyright © 2002 John Wiley & Sons, Ltd. [source] Relationship among drug delivery behavior, degradation behavior and morphology of copolylactones derived from glycolide, l -lactide and ,-caprolactonePOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 2 2002Qing Cai Abstract A series of copolylactones was synthesized by ring-opening copolymerization of glycolide, L -lactide and ,-caprolactone, using stannous octoate as catalyst. The in vitro degradation behaviors of them were studied and data demonstrated different degradation rates which mainly depended on the compositions. Investigation of the 5-fluorouracil (5-Fu) release from these copolylactones revealed that the composition, degradation rate and the morphology of the polymeric matrix played an important role on the drug release kinetics. A sustained 5-Fu release without initial time lag was obtained from random poly(lactide-co-glycolide-co-caprolactone) (r-PGLC) drug carrier, and it differed from the cases of polylactide (PLA) or random poly(lactide-co-glycolide) (PLGA), which usually showed an initial time lag or biphasic drug release behavior. It was due to the low glass transition temperature (Tg) of the r-PGLC and the drug would diffuse faster in rubbery state under the experimental temperature. Furthermore, a significant change in the drug release behavior of r-PGLC was observed when the temperatures were changed around the Tg of the drug carrier, which implied that the drug release behavior could be regulated by adjusting the morphology of the drug carrier. Copyright © 2002 John Wiley & Sons, Ltd. [source] Layer-by-Layer Hydrogen-Bonded Polymer Films: From Fundamentals to ApplicationsADVANCED MATERIALS, Issue 30 2009Eugenia Kharlampieva Abstract Recent years have seen increasing interest in the construction of nanoscopically layered materials involving aqueous-based sequential assembly of polymers on solid substrates. In the booming research area of layer-by-layer (LbL) assembly of oppositely charged polymers, self-assembly driven by hydrogen bond formation emerges as a powerful technique. Hydrogen-bonded (HB) LbL materials open new opportunities for LbL films, which are more difficult to produce than their electrostatically assembled counterparts. Specifically, the new properties associated with HB assembly include: 1) the ease of producing films responsive to environmental pH at mild pH values, 2) numerous possibilities for converting HB films into single- or two-component ultrathin hydrogel materials, and 3) the inclusion of polymers with low glass transition temperatures (e.g., poly(ethylene oxide)) within ultrathin films. These properties can lead to new applications for HB LbL films, such as pH- and/or temperature-responsive drug delivery systems, materials with tunable mechanical properties, release films dissolvable under physiological conditions, and proton-exchange membranes for fuel cells. In this report, we discuss the recent developments in the synthesis of LbL materials based on HB assembly, the study of their structure,property relationships, and the prospective applications of HB LbL constructs in biotechnology and biomedicine. [source] Segmented Block Copolymers with Monodisperse Hard Segments: The Influence of H-Bonding on Various PropertiesMACROMOLECULAR MATERIALS & ENGINEERING, Issue 8 2009Gerard J. E. Biemond Abstract The properties of segmented-copolymer-based H-bonding and non-H-bonding crystallisable segments and poly(tetramethylene oxide) segments were studied. The crystallisable segments were monodisperse in length and the non-hydrogen-bonding segments were made of tetraamidepiperazineterephthalamide (TPTPT). The polymers were characterised by DSC, FT-IR, SAXS and DMTA. The mechanical properties were studied by tensile, compression set and tensile set measurements. The TPTPT segmented copolymers displayed low glass transition temperatures (Tg, ,70,°C), good low-temperature properties, moderate moduli (G,,,,10,33 MPa) and high melting temperatures (185,220,°C). However, as compared to H-bonded segments, both the modulus and the yield stress were relatively low. [source] Synthesis, characterization, in vitro degradation and cytotoxicity of polyphosphazenes containing N -ethoxypyrrolidone side groupsPOLYMER INTERNATIONAL, Issue 2 2010Yunmei Bi Abstract A new biodegradable polyphosphazene (PYRMP) containing N -ethoxypyrrolidone and methoxyethoxyethoxy side groups was synthesized via a route of macromolecular substitution. The synthetic method of poly{bis[2-(2-oxo-1-pyrrolidinyl)ethoxy]phosphazene} (PYRP) was improved. The thermal properties of the polymers were investigated using differential scanning calorimetry. Degradation studies were carried out in vitro with varying pH conditions. The in vitro cytotoxicity of PYRMP and its hydrolysis products was evaluated using the methyl tetrazolium (MTT) cytotoxicity test in HepG2 cell culture. PYRMP and PYRP have low glass transition temperatures of ,68.8 and ,59.6 °C, respectively. The polymers show a higher degradation rate at pH = 5.0 than at both pH = 7.4 and 8.0. The degradation process of PYRMP in different buffer solutions is discussed. The MTT test reveals that PYRMP at concentrations below 800 µg mL,1 and its hydrolysis products are non-toxic to HepG2 cells. Moreover, the hydrolysis products diluted 10 times are able to promote cell proliferation. This study shows that polyphosphazene containing N -ethoxypyrrolidone subsituents provides interesting perspectives for various biomedical applications. Copyright © 2009 Society of Chemical Industry [source] Novel epoxy compositions for vibration damping applicationsPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 10 2004D. Ratna Abstract Three epoxy compositions have been developed by using polyether amine hardeners having varying chain lengths of polyethers. Unlike normal epoxies, the compositions show low glass transition temperatures (0,45°C). Dynamic mechanical analysis and time,temperature superposition of the isotherms indicate that they have broad and high loss factor values over broad frequency and temperature ranges suggesting their application as viscoelastic materials in constrained layer damping of structural vibrations. Copyright © 2004 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||