Investigation of the Nematic-Isotropic Biphase in Thermotropic Main Chain Polymers. Homogeneity of the Pure Nematic and Isotropic Phases. Part I: Microscopy and Fractionation

Abstract

Two moderately low melting main chain nematic polymers with flexible spacers are investigated (spacers (CH₂)₇ and (CH₂)₁₀). Isothermal evolution in the N+I biphase is considered as an orientational ordering stage followed by macroscopic demixing of the N and I domains and homogenization of their respective chain length distributions. Segregation according to chain length is studied by means of polarizing microscopy and fractionation. A method for delineation of equilibrium biphase width is presented, for masses ranging up to Mn=37,000. Evolution of the gross morphology of the pure nematic and solid phases as a function of thermal history in the biphase is illustrated.