Dynamics at Internal Interfaces in Ionizable Polymer Blends*

Ionizable polymers have found a large number of applications in the water-energy nexus, enabled by the segregation of the polymers into ionic and non-ionic domains. The morphology of the ionic domains varies as a function of numerous factors, among them are the number of ionic groups, their distribution and the topology of the polymers. To understand the segregation process, we probe the evolution and dynamics of internal interfaces formed by blends of polystyrene (PS) and polystyrene sulfonate (PSS) below their entanglement length using atomistic molecular dynamic simulations for temperatures above the glass transition temperature of either polymer. Melts of PS and PSS blends with varying sulfonation fractions with Na⁺ and N(CH₃)₄⁺ counterions were followed as a function of time. The development of the internal interface of the charged and the non-charged polymers will be discussed. We will compare blends of PS and PSS which can globally phase separate with diblock copolymers of PS and PSS which phase separate only locally.