SYNTHESIS AND DEGRADABILITY OF A NOVEL ALIPHATIC POLYESTER - POLY(BETA-METHYL-DELTA-VALEROLACTONE-CO-L-LACTIDE)

Biodegradable polyesters were synthesized by ring-opening copolymeriza tion of L-lactide (LA) with DL-beta-methyl-delta-valerolactone (MV). H -1 and C-13 nuclear magnetic resonance analyses showed that these copo lymers were statistical and that their number-average molecular weight s were within the range of (3-5) x 10(4). The melting temperatures of these polyesters were dependent upon the LA content in the copolymers, thus showing that high LA composition resulted in higher T-m. The cop olymers containing more than 90 mol% LA formed tough and hard films, w hereas those with less than 80 mol% LA formed flexible films similar t o natural rubber. Accelerated hydrolysis was carried out with copolyme rs of various compositions at 70 degrees C for 18 days. The hydrolysis rates were much faster than that of poly(LA), which is well known to be a hydrolysable polymer. The copolymers were easily hydrolysed with lipases from Rhizopus arrhizus, R. delemar, Pseudomonas sp. and Candid a cylindracea. In particular, the lipases from R. arrhizus and R. dele mar proved to be very effective in promoting hydrolysis.