VARIATIONS BETWEEN BIOMER LOTS .1. SIGNIFICANT DIFFERENCES IN THE SURFACE-CHEMISTRY OF 2 LOTS OF A COMMERCIAL POLY(ETHER URETHANE)

We have studied the surface chemistry of two lots of Biomer(TM) (BSP067 and BSUA001), a widely used commercial poly(ether urethane) (PEU). Although transmission infrared adsorption studies revealed no differences in the bulk chemistry of the two lots, the surface chemistry, as seen by x-ray photoelectron spectroscopy (XPS) and static secondary ion mass spectrometry (SIMS), was different. Lot BSP067 showed soft-segment enrichment at the surface, which is typical of PEU. Lot BSUA001 showed no evidence of either hard- or soft-segment PEU components at the surface. The surface of this lot was completely covered with a nonextractable additive identified as poly(diisopropyl amino ethyl methacrylate). Small amounts of a low-molecular-weight antioxidant were observed at the surface of both samples. Because the biological response to polymers is dependent on surface structure, these results are of considerable importance to biomaterials research.