Anomalous Phase Behavior of Ionic Polymer Blends and Ionic Copolymers

Abstract

Nonionic diblock copolymers, with a highly asymmetric relative composition (f), microphase segregate into structures in which the minority component always forms cylindrical or spherical domains that are embedded in the majority component continuous matrix phase. Recently, a hybrid liquid state theory (called the DHEMSA approximation) and self-consistent field approach for ionic diblock copolymers have demonstrated the possible existence of “inverted” phases in which the minority ionic component forms the continuous matrix phase and the majority nonionic component forms cylindrical domains. We find that such anomalous behavior is closely related to the thermodynamics of phase segregation found in a blend of an ionic polymer and a nonionic polymer at the electrostatic coupling values typical of polymers in the molten state, at which nonionic and ionic polymers segregate into two partially miscible phases. This partial miscibility holds even across infinite molecular weights of the polymers. Such partial mi...