SURFACE PROPERTIES OF POLY(VINYL ALCOHOL-CO-N-VINYL - 2-PYRROLIDONE) HYDROGELS FOR BLOOD COMPATIBILITY STUDIES
Abstract
A copolymer of P(VAc-co-NVP) was synthesized with f(,1) = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0. The copolymer was converted to P(VA-co-NVP) by alkaline methanolysis in 0.1 N NaOH at ambient temperature for 36 hours. The degree of conversion of VAc units to VA was greater than 97 mole %. Hydrogels were produced by crosslinking with ('60)Co irradiation at 35(DEGREES)C. Bulk composition analysis was evaluated by IR, NMR, and elemental analysis. The reactivity ratios obtained were r(,1) = 0.477 and r(,2) = 3.17. Surface topology of the hydrogels was studied by SEM, the surface roughness scale evaluated to be of the order of 10 (mu)m and macro-syneresis observed with freeze etching. Surface region composition was evaluated by XPS of freeze dried samples of the hydrogels. Quantitative XPS analysis demonstrated an enrichment of the VA units in the surface region for copolymers with F(,1) < 0.34 which were formed on a glass surface. The effect of freeze drying on XPS analysis was investigated by surface esterification of the VA units of the hydrogels before freeze drying. XPS penetration depth in freeze dried materials was discussed. Sputtering of polymer surfaces and the effect of crosslinking on surface compositions was investigated. Adsorption of ('125)I-Albumin on PVA hydrogels was studied for 0.5 to 256 min at 37(DEGREES)C. The protein adsorption was not diffusion limited; formation of a protein gel phase limiting the protein uptake was observed. The protein adsorption was found to be completely reversible within the accuracy of the experiment. A Mathematical model of the alteration of polarized light at the protein layer/hydrogel interface was developed for applications to ellipsometric measurements. The model incorporates the affect of all important parameters (excluding optical cell) on ellipsometry readings for the system studied.
Degree
Ph.D.
Subject Area
Biomedical research
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