ROLE OF OXYGEN IN BIODEGRADATION OF POLY(ETHERURETHANE UREA) ELASTOMERS

It is generally accepted that biodegradation of poly(etheruethane urea ) (PEUU) involves oxidation of the polyether segments on the surface w here leukocytes are adhered. The influence of dissolved oxygen, which is known to control oxidation of polymers in more traditional environm ents, was explored in this study. Specimens treated in vitro with hydr ogen peroxide-cobalt chloride for 12 days exhibited a brittle, degrade d surface layer about 10 mu m thick. Attenuated total reflectance-Four ier transform infrared spectroscopy of the surface revealed that the e ther absorbance at 1110 cm(-1) gradually decreased with in vitro treat ment time to 30% of its initial value after 12 days. In contrast, 6 da ys in vitro followed by 6 days in air produced a decrease to 12% of th e initial volume. Therefore, removing a specimen from the in vitro sol ution after 6 days and exposing it to air for the remainder of the 12 days actually resulted in more oxidation than leaving it in the in vit ro solution for the entire 12 days. These results suggest that PEUU de grades by an autooxidation mechanism sustained by oxygen. By successfu lly modeling the depth of the surface degraded layer with a diffusion- reaction model, it was demonstrated that PEUU biodegradation is contro lled by diffusion of oxygen into the polymer. (C) 1997 John Wiley & So ns, Inc.