COPOLYMERS OF L-LACTIDE AND D,L-LACTIDE WITH 6-CAPROLACTONE - SYNTHESIS AND CHARACTERIZATION

L- and D,L-lactide copolymers with 6-caprolactone were synthesized and characterized in a wide range of compositions. The polymerizations were carried out in batch at 130-degrees-C, with Sn(II) octoate as a catalyst, a monomers/initiator mole ratio of 5000/1 and a reaction time of 48 h. The copolymers having from 5 to 40 wt.-% of 6-caprolactone are characterized by higher values of non-reacted monomers and deviations of the polymer composition from the feed ratio. In the same interval of compositions, L-lactide copolymers showed progressive hardening with time at room temperature, attributable to the tendency to crystallization of homopolymeric sequences. This behaviour was more deeply studied in the case of poly(L-lactide-co-6-caprolactone) with 30 wt.-% of 6-caprolactone. H-1 NMR at 300 MHz appeared to be a suitable method for the determination of the monomer sequence.