Ring-Opening Polymerization of l-Lactide Catalyzed by an Organocatalytic System Combining Acidic and Basic Sites

In this study, organocatalytic systems containing both basic and acidic sites, which can activate simultaneously the chain end and the monomer, were investigated in the ring-opening polymerization of l -lactide. To this end, equivalent amounts of ( N, N -dimethylamino)pyridine (DMAP) and of its protonated form (DMAP·HX) were used as a dual catalytic system for l -lactide polymerization initiated by different alcohols. It is shown that the corresponding DMAP/DMAP·HX systems are significantly more active than DMAP alone, and yield well-controlled poly( l -lactide). Depending on the reaction conditions, the transesterification reaction can be prevented.