Molecular Weight Dependence of Phase Behavior in Side-Chain Liquid Crystalline Polymer Which Exhibits Reentrant Nematic Phase

摘要

We prepared poly(6-[4-(4'-cyanophenyl)phenoxy]hexyl acrylate)s with various molecular weights (M_n) and narrow molecular weight distributions, and examined the M_n dependence of phase behavior which includes the reentrant nematic (RN) phase. Polymers with M_n lower than 20,000 form nematic (N), smectic A (SmA) and RN phases as temperature decreases, while ones with M_n higher than 20,000 form only N phase. The disappearance of SmA in longer chains is caused by the decrease in N-SmA temperature and the increase of SmA-RN one with increasing M_n. Result indicates that the polymer length is one of the significant factors affecting the reentrant behavior in side-chain liquid crystalline (LC) polymers.