POLY(L-LACTIDE) CROSS-LINKED WITH SPIRO-BIS-DIMETHYLENE-CARBONATE

Poly(L-lactide) and other poly(lactones) can be crosslinked by ring opening polymerization of the corresponding cyclic esters in the presence of a tetrafunctional bicyclic biscarbonate. Spiro-bis-dimethylene-carbonate was synthesized from pentaerythritol and diethylene-carbonate and used to prepare polyester networks for use in biomedical applications. Bulk copolymerization Of L-lactide with only small amounts of this crosslinker leads to networks with very high gel percentages of up to 100%. The initial crystallinity of these crosslinked poly(L-lactides), as well as the melting temperature, is very much reduced when compared with the homo poly(L-lactide). The degradation of the polymer in vivo is therefore expected to be enhanced and more benign at longer durations. Tensile strength and impact resistance are also greatly influenced by copolymerization with spiro-bis-dimethylene-carbonate. Much tougher and stronger materials can be obtained in this way. These favourable properties allow the material to be used in the preparation of degradable implants such as fracture fixation devices.