Investigation of the Nematic-Isotropic Biphase in Thermotropic Main Chain Polymers. Homogeneity of the Pure Isotropic and Nematic Phases. Part III: NMR Study

Abstract

Abstract Nematic fraction fN and biphase width are measured by combination of broad line PMR and DMR experiments and the data compared with microscopy and DSC results. Time dependence of fN was monitored isothermally. Preliminary data suggest that: i) equilibrium distribution of chain lengths between I and N components is established rapidly; ii) supercooling at the I/N transition is of thermo-dynamic rather than kinetic origin. The DMR spectrum of PAAd14 is used to probe heterogeneity and isothermal evolution of molecular morphology in the pure N phase (model system of small molecules and polymers). Dynamics of homogenization of the N phase on the molecular level is extremely slow under normal laboratory conditions.