文献类型：期刊文献

英文题名：Stiffening of semirigid polymer chains before the isotropic-aniostropic transition

作者：Lin, JP; Zhou, DF

机构：[1]E China Univ Sci & Technol, Dept Polymer Sci & Engn, Shanghai 200237, Peoples R China

年份：2000

卷号：16

期号：2

起止页码：169

外文期刊名：CHEMICAL RESEARCH IN CHINESE UNIVERSITIES

收录：;WOS:【SCI-EXPANDED(收录号:WOS:000087467300014)】；

语种：英文

外文关键词：polypeptide; helix-coil transition; NMR

摘要：The phase behavior of a semirigid polymer manifested by the polypeptide such as poly(beta-phenethyl L-aspartate)(PPLA) in a mixed solvent system containing a denaturant acid was studied. The obtained results suggest that there is a marked enhancement of the propensity for the semirigid polymer chain to adopt a rigid conformation upon increasing polymer concentration before the critical value for the incipience of a liquid crystal phase, which has been firmly confirmed both theoretically and experimentally. In consideration of the first order estimation of polymer-polymer interaction, a theoretical approach was attempted within the framework of a helix-coil transition model proposed by Rajan and Woo. According to the analysis, the semirigid chains could become rather rigid before reaching liquid crystal phase. Such a kind of chain stiffening effect was verified by H-1 NMR and C-13 NMR measurements. The experimental results show that the PPLA molecules convert gradually from the random coil to the rigid rod conformation as polymer concentration turns higher in the isotropic phase.