Interplay of Phase Separations and Aggregations in Solutions of Rodlike Polymers

Abstract

A theory is introduced to describe phase separations in solutions of end-to-end aggregates which are formed by intermolecuar physical bonding between rodlike molecules. In these solutions we have three different phase transitions: self-associations, phase separations and molecular orientations. On the basis of the Flory-Abe theory for polydisperse systems of rodlike particles, we examine the equilibrium solution properties. By using the multiple-chemical equilibrium conditions for the molecular associations, we derive the size distribution of the end-to-end aggregates in an isotropic and in a nematic phase. We show that the end-to-end aggregates cause an nematic-isotropic phase transition as well as the new types of phase separations. For various values of the association constant, we calculate phase diagrams in the temperature-concentration plane.