Surface Segregation in Miscible Blends of Polystyrene and Poly(vinylmethyl ether): Comparison of Theory and Experiment

摘要

The surface segregation behavior for dPS/PVME and PS/PVME blends is nearly identical, illustrating that surface free energy reduction is the dominant factor controlling surface segregation for this system. The Schmidt-Binder square gradient theory, utilizing the Sanchez-Lacombe-Balazs equation of state, overestimates the surface composition and surface decay lengths at low PVME concentration, however the agreement improves with PVME concentration. Consideration of experimental trends suggests two possible origins for the discrepancy between theory and experiment: that the interaction parameter within the surface gradient has a much stronger concentration dependence than the bulk interaction parameter, and that surface adsorbed PVME chains flatten out to cover more surface area, particularly at low surface compositions.