l-Lactide Additive and in Vitro Degradation Performance of Poly(l-lactide) Films

Polylactide as a valuable biodegradable polymer is being widely investigated with respect to its synthesis, physical properties, biodegradation and application. The aim of this study is to evaluate hydrolytic degradation of poly(l-lactide) (PLLA) in the presence of added l-lactide dimer. High molecular weight PLLA was synthesized in presence of stannous octoate through the ring opening polymerization of l-lactide. PLLA films, containing 0, 1, 3 and 5% (w/w) l-lactide (as additive), were prepared by solution casting. In vitro degradation of the PLLA matrices were carried out in distilled water at 37°C for the definite periods. The degraded polymer matrices have been characterized by SEC, SEM and DSC techniques after periods of 3 and 6 months degradation time. It was found that during the first 3 months of degradation period, the number average molecular weight (Mn) of each PLLA film containing l-lactide reduced slower than the control sample. Also, it is shown that the films containing l-lactide have higher crystallinity and melting point in comparison with non-containing l-lactide samples. However, after 6 months, degradation rate of PLLA matrices containing l-lactide increased due to penetration of water by eluting and removal of l-lactide from PLLA matrices.