LIQUID-CRYSTALLINE PROPERTIES OF A SERIES OF THERMOTROPIC COPOLYESTERS CONTAINING BOTH MESOGENIC AND NOMESOGENIC UNITS

A series of copolymers containing triad ester mesogenic units, with pendent n-octyl substituents, and triad ester nonmesogenic units, both with flexible spacer groups, was prepared and characterized for the effect of the nonmesogenic unit content on transition temperatures and thermodynamic parameters. The mesophase temperature range increased, but temperature, enthalpy, and entropy of isotropization decreased in a linear manner with increasing nonmesogen comonomer content. The entropy of isotropization is considered to be a quantitative measure of the degree of order of the nematic phase, but this order may include both the amount and the order parameter of the mesophase if, as proposed, both the isotropic and nematic phase exist below the isotropization temperatures of the copolymers.