Compatibility and Morphology in Polyurethane and Polystyrene Ionomeric Interpenetrating Polymer Networks

Interpenetrating Polymer Networks (IPNs), composed of polyurethane (PU) and poly(styrene-acrylic acid) (PSAA), with containing mutual opposite charge groups, i.e., tertiary amine group in PU and carboxyl groups in PSAA, were prepared in PU/PSAA ratio of 75/25 (PU-dominated), and 25/75 (PSAA-dominated). The compatibility and morphology of these IPNs were investigated through dynamic mechanical analysis and scanning electronic microscopy studies. Compatibility of IPNs was greatly enhanced through the introduction of charge groups into the system. There are different morphology and dynamic mechanical behaviours for PU/PSAA alloys between PU-dominated and PSAA-dominated alloys. PSAA in the PU-dominated alloys was found to aggregate to the hard segment of the PU matrix, resulting in heterogeneous distribution of hard/soft segments in morphology and having little effect on the shift of the temperature transition while PU in PSAA-dominated alloys was found to be distributed homogeneously in the PSAA matrix.