Abstract
We examined the molecular weight dependence of phase transition behavior for poly(6-[4-(4'-cyanophenyl) phonoxy] hexyl acrylate) prepared by ATRP, which shows reentrant polymorphism with the variation of degree of polymerization (Dp). For the samples with moderate molecular weight (Mn 7,900~20,000) nematic, smectic A and reentrant nematic (RN) phase were exhibited whereas that with higher molecular weight only nematic phase was observed. Furthermore, the difference of dynamics in these two nematic phase has been confirmed by dynamic light scattering (DLS) measurements. The two types of nematic phase is found to be definitely distinguished each other with the two characteristics. This result is ascribed to that the increasing of dimerized mesogen acting as physically linking agents of polymer chains. On the basis of the knowledge, the direct RN-N transition is strongly suggested by DLS measurement for the samples with higher molecular weight.
