Stiffening of Semirigid Polymer Chains Before the Isotropic-Aniostropic Transition  

作　　者：LIN Jiaping ZHOU Dafei 

出　　处：《Chemical Research in Chinese Universities》2000年第2期169-175,共7页高等学校化学研究（英文版）

基　　金：Supported by the National Natural Science Foundation of China(Grant No.59803002)

摘　　要：The phase behavior of a semirigid polymer manifested by the polypeptide such as poly(βphenethyl Laspartate)(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 polymerpolymer interaction, a theoretical approach was attempted within the framework of a helixcoil 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 1H NMR and 13 C 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.The phase behavior of a semirigid polymer manifested by the polypeptide such as poly(βphenethyl Laspartate)(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 polymerpolymer interaction, a theoretical approach was attempted within the framework of a helixcoil 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 1H NMR and 13 C 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.

关 键 词：POLYPEPTIDE Helix-coil transition NMR 

分 类 号：O631[理学—高分子化学]