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Reactive Polymer (reactive + polymer)
Selected AbstractsInterface Structure between Immiscible Reactive Polymers under Transreaction: a Monte Carlo SimulationMACROMOLECULAR THEORY AND SIMULATIONS, Issue 5 2005Xuehao He Abstract Summary: The interface structure between two immiscible melts, a polycondensate polymer A (e.g., polycarbonate, polyester or polyamide) and a polymer B, was studied by means of Monte Carlo simulations using the bond fluctuation model. Polymer B contained a reactive end group (e.g., OH, NH2 or COOH). Copolymers were generated in-situ at the interfaces by transreactions (alcoholysis, aminolysis or acidolysis), composing of various length of block A, depending on the position of transreaction in the polycondensate chain A. The content of copolymer at the interface increased with the time, particular fast at the early stage. Fragments of polymers A were released with an end group, reactive to polymers A. This resulted in the proceeding of internal transreactions. An asymmetric interface structure was formed. The simulation also showed that copolymers generated by interfacial transreactions increased the compatibility of the two polymers and enhanced the adhesion strength at the interfaces. [source] A reactive polymer for toughening epoxy resinJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Hsu-Chiang Kuan Abstract Epoxy resins are hardly toughened by low weight content of tougheners. In this study, 5 wt % polyurea was adopted to significantly toughen piperidine-cured epoxy, as fracture toughness improved from 0.78 to 1.98 MPa m1/2. We focused on the reactions and morphology evolution of epoxy/polyurea mixture. The polyurea molecular weight was reduced by the exchange reactions of polyurea with epoxy during mixing, as evidenced by gel permeation chromatograph and Fourier transform infrared spectroscopy. As a result, epoxy molecules were chemically bonded with polyurea, improving particle content and interface thickness. Transmission electron microscope observation shows that (a) polyurea in situ formed nanoparticles in matrix which subsequently aggregate into micron-sized particles of thick interface with matrix; and (b) the particles became less stainable with increasing the mixing time, because the reactions promoted high levels of crosslink density of the particles which were thus more resistant to the diffusion of staining chemicals. Longer mixing time improved, obviously, the fracture toughness of epoxy/polyurea composite. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Mixed matrix membrane materials with glassy polymers.POLYMER ENGINEERING & SCIENCE, Issue 7 2002Part Analysis presented in Part 1 of this paper indicated the importance of optimization of the transport properties of the interfacial region to achieve ideal mixed matrix materials. This insight is used in this paper to guide mixed matrix material formation with more conventional gas separation polymers. Conventional gas separation materials are rigid, and, as seen earlier, lead to the formation of an undesirable interphase under conventional casting techniques. We show in this study that if flexibility can be maintained during membrane formation with a polymer that interacts favorably with the sieve, successful mixed matrix materials result, even with rigid polymeric materials. Flexibility during membrane formation can be achieved by formation of films at temperatures close to the glass transition temperature of the polymer. Moreover, combination of chemical coupling and flexibility during membrane formation produces even more significant improvements in membrane performance. This approach leads to the formation of mixed matrix material with transport properties exceeding the upper bound currently achieved by conventional membrane materials. Another approach to form successful mixed matrix materials involves tailoring the interface by use of integral chemical linkages that are intrinsically part of the chain backbone. Such linkages appear to tighten the interface sufficiently to prevent "nonselective leakage" along the interface. This approach is demonstrated by directly bonding a reactive polymer onto the sieve surface under proper processing conditions. [source] Modification of pLL/DNA complexes with a multivalent hydrophilic polymer permits folate-mediated targeting in vitro and prolonged plasma circulation in vivoTHE JOURNAL OF GENE MEDICINE, Issue 5 2002Christopher M. Ward Abstract Background Gene delivery vectors based on poly(L -lysine) and DNA (pLL/DNA complexes) have limited use for targeted systemic application in vivo since they bind cells and proteins non-specifically. In this study we have attempted to form folate-targeted vectors with extended systemic circulation by surface modification of pLL/DNA complexes with hydrophilic polymers. Methods pLL/DNA complexes were stabilised by surface modification with a multivalent reactive polymer based on alternating segments of poly(ethylene glycol) and tripeptides bearing reactive ester groups. Folate moieties were incorporated into the vectors either by direct attachment of folate to the polymer or via intermediate poly(ethylene glycol) spacers of 800 and 3400,Da. Results Polymer-coated complexes show similar morphology to uncoated complexes, their zeta potential is decreased towards zero, serum protein binding is inhibited and aqueous solubility is substantially increased. Intravenous (i.v.) administration to mice of coated complexes produced extended systemic circulation, with up to 2000-fold more DNA measured in the bloodstream after 30,min compared with simple pLL/DNA complexes. In further contrast to simple pLL/DNA complexes, coated complexes do not bind blood cells in vivo. Folate receptor targeting is shown to mediate targeted association with HeLa cells in vitro, leading to increased transgene expression. We demonstrate for the first time that DNA uptake via the folate receptor is dependent on pEG spacer length, with the transgene expression relatively independent of the level of internalised DNA. Conclusions We show increased systemic circulation, decreased blood cell and protein binding, and folate-targeted transgene expression using pLL/DNA complexes surface-modified with a novel multireactive hydrophilic polymer. This work provides the basis for the development of plasma-circulating targeted vectors for in vivo applications. Copyright © 2002 John Wiley & Sons, Ltd. [source] Long-term stability of an ambient self-curable latex based on colloidal dispersions in water of two reactive polymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2005Xiaonong Chen Abstract An ambient self-curable latex (ASCL) was prepared via the blending of colloidal dispersions in water of a chloromethylstyrene-functionalized copolymer and a tertiary-amine-functionalized copolymer. Upon casting and drying under ambient conditions, the ASCL could generate crosslinked continuous polymer films. The crosslinking occurred via the Menschutkin reaction (quaternization) between the two types of functional groups. Because this reaction was reversible at high temperatures, the films could be decrosslinked and hence were self-curable. The prepared ASCL exhibited excellent colloidal and chemical stability during long-term storage: no significant changes in the colloidal properties, such as the particle size, electrophoretic mobility, and crosslinking reactivity, were observed after 48 months of storage. The electrophoretic measurements indicated that the electrostatic repulsion between the negatively charged particles of the ASCL was responsible for the excellent stability. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2598,2605, 2005 [source] | ||||||||||