Amphiphilic Polymers as Additives in Biomedical Polyurethanes. Surface Properties and Morphology

Sammanfattning: The aim of this work was to achieve surface modification of two biomedical polyurethanes and one poly(urethane urea) through the addition of small amounts of amphiphilic copolymers in solution. The matrix polymers used were the poly(ether urethane)s Pellethane 2363-80AE (P80) and 2363-75D (P75) and a poly(ether urethane urea) similar to Biomer (PUUR). The amphiphilic additives consisted of segmented polyurethanes, designated Polymers A, B, and C, commercial ABA block copolymers, Pluronic PE9400 (PE94) and PE6800, and a graft copolymer designated ACRY. Polymers A, B and C were prepared from methylene diphenylene di-isocyanate, poly(ethylene oxide) (PEO) and a fatty acid monoglyceride and/or diethylene glycol as chain extenders. The block copolymers were composed of PEO as A-blocks and poly(propylene oxide) as B-blocks. ACRY consisted of a poly(methyl methacrylate-co-2-ethyl-hexyl acrylate) backbone and poly(ethylene oxide) monomethyl ether (MPEO) as side chains. The addition of amphiphilic polymers into the matrixes, caused considerable changes in the surface properties of the blends compared with the unmodified materials. The mobility of the matrixes , the hydrophilic/hydrophobic balance of the additives and the compatibility between the matrix and additive were shown to be of importance for the surface accumulation of the additives in the blends. High temperatures and water treatment increased the mobility of the additives in the matrixes, especially in the matrix having a glass transition around room temperature, and the affect was permanent for the time period examined. Non-water-soluble amphiphiles were found to be more effective than water-soluble additives. It was found that ACRY formed micellar structures in the P75 and P80 matrixes, with central cores probably consisting of the ACRY backbone and shells consisting of MPEO grafts. Brief protein adsorption measurements and blood coagulation experiments showed that the modified surfaces were generally more biocompatible than the matrixes.