Surface formation and environmental responses on polyurethane-polystyrene graft copolymers

Abstract

The surfaces of polyurethane (PU)-polystyrene (PS) graft copolymers having a defined content of uniform-size polystyrene graft segments were studied in both dry and wet states. XPS inspection of PU-PS graft copolymer film samples indicated the enrichment of the PS component at the surface in the dry state. The sample films were then immersed in water, and the environmental response at the surface was examined by means of a contact angle measurement using a CCI4 in water technique. The contact angle underwent a slow, but measurable change from one near to that of the PS homopolymer toward that of the PU homopolymer within a 3 h period for the graft copolymer samples annealed at 80 C. On the other hand, the contact angle remained close to that of the PU homopolymer within a 3 h period for samples annealed at 120'C.