Mechanism of Propagation in the Cationic Polymerization of L,L-Lactide

The mechanism of propagation in the cationic polymerization of L, L-Lactide in the absence of the hydroxyl group containing compounds that is at conditions when cationic polymerization of oxygen-containing heterocyclic monomers was studied. The study was to find the reasons of dominance of the AM (Activated Monomer) mechanism when all the oxygen containing heterocyclic monomers are introduced at the beginning of the cationic polymerization when concentration of hydroxyl group is much lower than the concentration of monomer. Several experiments were conducted in sealed-in vacuum reaction vessels using vacuum line technique. A series of the polymerizations at room temperature were used to compare polymerization rates at the conditions when the possibility of any side reactions involving initiators is minimized, and proceeded with reasonable rate only in the presence of strong protic acid, such as triflic acid.