EFFECTS OF RESIDUAL MONOMER ON THE DEGRADATION OF DL-LACTIDE POLYMER

The effects of remaining monomer on hydrolysis of poly(DL-lactide) wer e examined by adding different amounts of monomer to purified polymer samples. The existence of monomer in the polymerization products was f ound to enhance hydrolytic degradation of the polymer. A porous textur e was observed on the SEM photographs of degraded materials, which led to the conclusion that the remaining monomer enabled water molecules to gain better access to the polymer matrix through this porous struct ure. The effects of molecular weight and chemical composition of polyl actides on the hydrolytic degradation were also studied. Poly(DL-lacti c acid) with higher molecular weights showed longer retention of the i nitial properties such as molecular weight and tensile strength. Copol ymerization of DL-lactide with glycolide enhanced the hydrolysis, prob ably because of increased hydrophilicity of the polymers. (C) 1998 SCI .