Polydimethylsiloxane/polyether-mixed macrodiol-based polyurethane elastomers: biostability

A series of four thermoplastic polyurethane elastomers were synthesized wit h varying proportions of poly(hexamethylene oxide) (PHMO) and poly(dimethyl siloxane) (PDMS) macrodiols. The macrodiol ratios (by weight) employed were (% PDMS: %PHMO) 100 :0, 80: 20, 50: 50 and 20: 80. The weight fraction of macrodiol in each polymer was fixed at 60%. The mixed macrodiols were react ed with 4,4'-methylenediphenyl diisocyanate (MDI) and 1,4-butanediol (BDO) chain extender. The biostability of these polymers was assessed by strained subcutaneous implantation in sheep for three months followed by microscopi c examination. Pellethane 2363-80A and 2363-55D were employed as control ma terials. The mechanical properties of the polymers were tested and discusse d along with the biostability results. The results showed that soft, flexib le PDMS-based polyurethanes with very promising biostability can be success fully produced using the mixed macrodiol approach. The formulation with 80% PDMS macrodiol produced the best result in terms of a combination of flexi bility, strength and biostability. (C) 2000 Elsevier Science Ltd. All right s reserved.