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