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The kinetics of ring-opening polymerization of D,L-lactide with 2-ethylhexanoic acid zinc (II) salt as catalyst and methanol as co-catalyst at different temperatures is investigated. A previously proposed kinetic model accounting for reactions such as activation, propagation, chain transfer, transesterification and thermal non-radical random chain scission has been applied to simulate the experimental results of conversion and average molecular weights. The relevance of some side reactions, mainly transesterifications and chain scission, has been verified all over the studied temperature range and the corresponding rate constants have been estimated.

The homopolymerizations of D,L‐lactide and glycolide catalyzed by ZnOct2 were studied by DSC. The kinetic parameters obtained are compared with those obtained from conversion data of bulk polymerizations. For the glycolide, the respective values of the calculated rate constants were quite similar. For the lactide polymerization, however, the agreement between the values obtained was not so good because the kinetics is affected by thermodynamics in the DSC experiments. As a result, the kinetics can not be studied by DSC. The degree of aggregation of the catalyst, the reaction order with respect to it, and the initiator influence were determined for glycolide homopolymerization.magnified image