The objective of this work is to develop nonfouling biornaterials by blending polyethylene oxide (PEO)-containing block copolymers with a polyurethane (PU) matrix; it is expected that the PEO component will migrate to the tissue-material interface. Three amphiphilic triblock copolymers, PEO-PU-PEO, in which the PEO MW was 550 (copolymer 1), 2000 (copolymer 2), and 5000 (copolymer 3), respectively, were synthesized. XPS data showed that the polymer/vacuum interfaces of copolymers 2 and 3 were enriched in the PU block, whereas that of copolymer I was enriched in the PEO block. In contact with water, the PEO blocks for all three copolymers migrated to the surface as indicated by water contact angles. Blends of the copolymers with a segmented polyurethane were investigated. Surface enrichment of the copolymers occurred and increased over time up to a limit; the degree of enrichment was dependent on PEO block size and copolymer content. At copolymer content <10%, enrichment decreased with increasing PEO block size. For the copolymer 2 and copolymer 3 blends, enrichment increased with increasing copolymer content; at 20% copolymer the surfaces consisted essentially of pure copolymer. For the copolymer I blends, the surface was completely covered by copolymer at content >= 1%. (c) 2008 Wiley Periodicals, Inc.