Synthesis of Bioabsorbable Networks From Methacrylate-Endcapped Polyesters

A low-molecular-weight poly(epsilon-caprolactone) triol (M(n) = 540) was reacted with an excess of methacryloyl chloride to give a 3-arm methacrylate-endcapped polyester. The loss of the hydroxyl endgroups, which are capable of hydrogen bonding, lowered the viscosity of the polymer, thus enabling the formation of networks without solvent processing. The prepolymer was free radically homopolymerized, and copolymerized with methyl methacrylate, styrene, and 2-methylene-1,3-dioxepane to give a series of twelve biodegradable networks. Extraction studies indicated substantial network formation for all of the networks except those in which 2-methylene-1,3-dioxepane was used as the reactive diluent. A series of three low-molecular-weight poly(D,L-lactide) triols (M(n) \u3c 1 0 000) was synthesized by the trimethylolpropane-initiated ring-opening polymerization Of D,L-lactide. Number-average molecular weights of the triols were estimated to be 2300, 5100, and 8700, by using gel permeation chromatography (g.p.c.), calibrated with polystyrene standards. The triols were reacted with excess methacryloyl chloride to produce a series of low-molecular-weight 3-arm methacrylate-endcapped polyesters. These prepolymers were free radically homopolymerized, and copolymerized with methyl methacrylate and styrene to give a series of twenty-seven biodegradable networks. Extraction studies indicated substantial network formation for all of these systems. The T(g) values of each of the three homopolymer networks were higher than the corresponding T(g) values of either of their respective copolymer networks, thus illustrating substantial network formation in the absence of reactive diluents. The ultimate strengths and tensile modulii of the homopolymer networks synthesized from the higher-molecular-weight prepolymers (M(n) = 5100 and 8700) were higher than those measured for corresponding copolymer networks