XPS STUDY OF SURFACE-COMPOSITION OF A SEGMENTED POLYURETHANE BLOCK-COPOLYMER MODIFIED BY PDMS END-GROUPS AND ITS BLENDS WITH PHENOXY

Quantitative angle-resolved X-ray photoelectron spectroscopy (XPS) was used to investigate surface modification of a newly developed biomate rial, segmented polyurethane capped with poly-(dimethylsiloxane) (PDMS ) end groups, and its blends with phenoxy. The composition of the fres hly prepared films are not in equilibrium but they can be equilibrated both in air and in water. The surface segregation of PDMS is found bo th in nonequilibrium and in equilibrium states, XPS data also indicate that the PDMS is enriched in the film surfaces of both air/polymer an d glass substrate/polymer interfaces for the pure segmented polyuretha ne and its blends. The surface composition is affected by annealing te mperature and water. Below the polymer glass transition temperature, t here is a small increase in PDMS surface concentration during annealin g. Above Tg, PDMS surface concentration can increase by a factor of 2. The presence of water will decrease the PDMS surface segregation at t emperatures both below and above Tg.