OXIDATIVE-DEGRADATION OF BIOMER(TM) FRACTIONS PREPARED BY USING PREPARATIVE-SCALE GEL-PERMEATION CHROMATOGRAPHY

The possibility that some macromolecular chains within a chemically he terogeneous polyether-urethane (PEU) may be more susceptible to degrad ation than others has been investigated. Preparative scale gel permeat ion chromatography has been used to separate chemically different frac tions of a sample of the commercial PEU, Biomer(TM). The fractions wer e characterized and then tested for susceptibility to oxidative degrad ation by exposing them to hydrogen peroxide. After exposure to hydroge n peroxide, the samples were analyzed using high pressure gel permeati on chromatography (HPGPC), Fourier transform infrared spectroscopy (FT IR), and X-ray photoelectron spectroscopy (XPS). By using these method s, we were able to identify chemical changes in some of the Biomer(TM) fractions but not in others. Clear differences in the chemistry and r eactivity of the fractions were observed. Changes in the weight averag e molecular weight varied from a decrease of 55.8% to an increase of 3 .9%. A decrease in hard segment content at the surface and in the bulk was observed in some samples, but opposite trends were observed in ot hers. The evidence suggests that there may be a number of mechanisms b y which hydrogen peroxide can react with PEUs. Some fractions separate d from the Biomer(TM) were not significantly affected by concentrated hydrogen peroxide solutions. This suggests an intrinsic stability in s ome PEUs and points the way to the development of more degradation-res istant PEUs.