Physical-Chemical Properties of Articulated Rodlike Polymers

摘要

Rheological and rheo-optical studies are reported on solutions of rodlike poly (1,4-phenylene 2,6-benzobisthiazole), PBT. Both isotropic and nematic solutions are studied, over a range of polymer concentration c, weight average chain length, and temperature. A single-integral constitutive equation is given that describes the rheological and rheo-optical properties of the isotropic solution. It is based on a memory function based on linear viscoelastic behavior and a strain measure that introduces nonlinear viscoelastic behavior under appropriate strain history. The behavior for the nematic fluid exhibits both similarities and differences with that given by the single-integral relation. In particular, the steady-state behavior at small shear rate is markedly different than that predicted, perhaps related to unstable shear flow of the nematic fluid Rheological data are also given for mixtures of PBT and a nylon in solution. The results reveal marked effects on the rheological properties of the PBT solution, dependent on the nylon concentration.