AFM study of surface morphology of segmented polyurethane block copolymers and their blends with phenoxy

AFM was used to investigate the surface morphology and surface modification effects of newly developed segmented polyurethanes and their mixture with phenoxy homopolymer. The polyurethanes were methylene diisocyanate (MDI) and polytetramethyleneoxide (PTMO) based polymer with low surface tension end groups of polydimethysiloxane (PDMS). Two types of surface structures were observed from polyurethanes, a number of holes with a wide range of sizes, presumably due to the large soft segment molecular weight, and fine granular structures on the terraces. The PDMS end groups formed these fine granular structure and made the surface roughness smaller compared to polyurethanes without PDMS. The surface modification effect of polyurethanes was also investigated. The polymer mixtures of polyurethane and phenoxy indicated phase separation of the blends. The surface was composed of two phases, honeycomb polyurethane rich phase and dispersed phenoxy rich phase. The polyurethane rich phase tended to segregate on the surface. The honeycomb phase increased in thickness and area fraction when the polyurethane concentration was increased.