L-Lactide Polymerization in the Presence of Gaseous Nitrogen

During the ring opening polymerization of L-lactide the presence of water must be avoided since even small amounts can influence negatively on the reaction kinetic behavior. An effective way of removing water from the reaction system should be easy to implement and have comparatively low cost. The objective of the work was to obtain poly (L-lactic acid) at different conditions of temperature and catalyst concentration when gaseous nitrogen is used to purge the reactor comparing the resulting conversion profiles and final average molar masses. Results showed that a long induction period was observed when no gaseous nitrogen was used. It suggests that nitrogen was effective in removing the water from the reaction system since induction periods were not observed when it was injected before polymerization. Depolymerization was avoided when gaseous nitrogen was used resulting in higher molar masses than the case when no purging was carried out.