SYNTHESIS, PROPERTIES, AND BIODEGRADATION OF POLY(1,3-TRIMETHYLENE CARBONATE)

Poly(1,3-trimethylene carbonate) (PTMC) was synthesized by diethylzinc-catalyzed ring-opening polymerization of 1,3-trimethylene carbonate. The polymer was characterized by measurement of its thermal and mechanical properties, permeability, and susceptibility to hydrolytic chain scission in vitro and in vivo. Molecular weights were determined by GPC using the universal calibration method. Mark-Houwink coefficients were derived from viscometry and GPC measurements: K = 1.986 x 10(-4), a = 0.789 (CHCl3); K = 2.77 x 10(-4), a = 0.677 (THF). The rate of hydrolytic chain scission of solid PTMC in phosphate-buffered saline at 37-degrees-C, pH 7.4, was approximately 20 times less than that of poly(epsilon-caprolactone); this rate difference was eliminated when the two polymers were compared in solution in aqueous THF. Degradation of PTMC implanted subcutaneously in rats was manifested by an increase in the molecular weight distribution at the implant surface, a decrease in the molecular weight, and substantial weight loss during a 6-month period. These observations, and the fact that the rate of chain cleavage in vivo was much more rapid than that observed in vitro, were indicative of an enzymatic degradation process.