Strain-induced crystallization in elastomeric polymer networks prepared in solution and sol-gel derived high-temperature organic-inorganic hybrid materials.

摘要

Cross-linking polymer chains in solution should bring about fewer inter-chain entanglements in the resulting network. The subsequent drying of this network should compress the chains into a "super-contracted" state. The opposing effects of these changes on strain-induced crystallization in cis-1,4-polyisoprene networks formed in solution were investigated. Higher elongations were required to achieve strain-induced crystallinity in the networks prepared at higher dilutions, suggesting that in this regard the compressed states of the chains was more important than their reduced entangling.; The constrained-junction theory was applied to strain-induced crystallization in the above networks. The stress-strain isotherms generated from this theory were in satisfactory agreement with experiment. It was found that the constraint parameter {dollar}kappa{dollar} decreases with increase in dilution during cross-linking mainly due to the fact that cross-linking in solution decreases chain interpenetration.; The dependence of hydrolysis and condensation of {dollar}gamma{dollar}-ureidopropyltrimethoxysilane on pH in the water-methanol system at 23{dollar}spcirc{dollar}C was investigated by FTIR spectroscopy. Quantitative analysis of rates of hydrolysis showed that {dollar}gamma{dollar}-ureidopropyltrimethoxysilane is most stable in the water-methanol system at pH 7.7. The rate of overall condensation of silanols produced by the hydrolysis was qualitatively analyzed. These silanol groups are relatively more stable around pH 4.87.; The mechanical properties, thermal stability and water absorption of high-temperature sulfopolybenzobisthiazole-silica hybrid materials were investigated. The use of a bonding agent N,N-diethylaminopropyltrimethoxysilane facilitated the interfacial bonding between the organic and inorganic phases in these materials prepared through the sol-gel process. Tensile modulus, thermal stability and the resistant to water absorption were increased with increase in silica content in the resulting composites.; Sulfobiphenylpolybenzobisthiazole-silica hybrid aerogels were prepared using the sol-gel process and supercritical drying processes. The organic high-temperature polymer phase was bonded to the inorganic silica phase by a silane coupling agent. Increase in the amount of polymer present in the resulting materials decreased the compressional moduli but increased the deformability. Values of the longitudinal sound velocity generally increased with increase in amount of silica.