NOVEL STAR-SHAPED POLYLACTIDE WITH GLYCEROL USING STANNOUS OCTOATE ORTETRAPHENYL TIN AS CATALYST .1. SYNTHESIS, CHARACTERIZATION AND STUDYOF THEIR BIODEGRADABILITY

Novel star-shaped polyesters were synthesized by reacting L-lactide (L LA) with glycerol (GL) in the presence of stannous octoate or tetraphe nyltin as catalyst. These polymers were characterized by nuclear magne tic resonance, Fourier-transform infra-red spectroscopy, differential scanning calorimetry (d.s.c.) and thermogravimetric analysis. D.s.c. c urves showed that these polymers are semicrystalline when the ratio LL A/GL is higher than 20/1 (mol/mol). When this molar ratio falls below 20/1, the polymers are amorphous. The molecular-weight distribution of these polymers was studied with gel permeation chromatography measure ments, which showed that the M(n) decreased proportionally to the glyc erol content in the polymer. The potential biodegradability of these p olymers was assessed with the aid of enzymatic and alkali hydrolysis.