Surface characterization of blood compatible amphiphilic graft copolymers having uniform poly(ethylene oxide) side chains

The surface characterization of poly(methyl methacrylate)-graft-poly(ethyle ne oxide) (PMMA-g-PEO) was investigated by XPS and contact-angle measuremen t, and its in vitro blood compatibility was assessed by plasma recalcificat ion time measurement. The surface and bulk composition of different PMMA-g- PEO graft copolymer showed that PMMA segments were always enriched at the c opolymer-air interface, but surface enrichment of PEO segments could occur in films of copolymers with longer PEO side chain (M-n of PEG, 3200) and a higher bulk PEO content. Contact-angle studies indicated that the surface h ydrophilicity increased as the surface PEO content increased. The contact a ngles of water on the copolymer decreased linearly with contact time until they reached a balance value theta (e) or 0, and the relationship between t heta (from the static contact angle, theta (s) to theta (e)) and contact ti me(t) can be expressed by: theta = -kt. The proportionality constant k and Delta theta (theta (s) - theta (e)) depended on the bulk structural paramet ers (the bulk composition and PEO side chain length). The microphase-separa ted structure of copolymers was also observed by transmission electron micr oscopy (TEM). The relationship between the surface properties of PMMA-g PEO graft copolymer and its blood compatibility was addressed. (C) 2000 Publis hed by Elsevier Science Ltd.