Probing the surface chemistry of a hydrated segmented polyurethane and a comparison with its dry surface chemical structure

A biochemical approach has been used to analyze the surface chemistry of a hydrated polyester-urea-urethane. Using an enzyme-catalyzed hydrolysis reac tion, the surface chemistry of the polyurethane was probed by having the en zyme remove the polymer chain components making up the surface. The surface -derived products were analyzed using high performance liquid chromatograph y (HPLC), and product identification was carried out by mass spectrometry. The qualitative and quantitative analysis of the removed surface-derived pr oducts provided the necessary information required to reconstruct the chemi stry of the hydrated polymer surface. The results indicated that methane an d urea linkages were present on the hydrated surface. However, their concen trations were lower than in the bulk polymer. In addition, the ratio of ure a to methane groups was substantially reduced at the hydrated surface relat ive to the bulk polymer stoichiometry. The data obtained for the hydrated s urface were also compared to the analysis of the dry surface, carried out u sing X-ray photoelectron spectroscopy (XPS). The hydrated polymers containe d higher urethane and ester groups than that shown on the dry surface. Whil e XPS was able to identify the presence of urethane linkages on the dry sur face, these could not be accurately quantified. Furthermore, the content of urea linkages could not be specifically determined by XPS because they wer e masked by the ester groups.