Kinetics of Ring-Opening Polymerization of L,L-Lactide

The ring-opening polymerization of L,L-lactide with 2-ethylhexanoic acid tin(II) salt as catalyst, and 1-dodecanol as cocatalyst, is investigated at temperatures ranging from 140 to 180 degrees C and various operating conditions such as different ratios of monomer to catalyst as well as catalyst to cocatalyst amounts. Average molecular weights and byproduct formation have been measured as a function of monomer conversion. A complete kinetic model including intra- and intermolecular transesterifications as well as random chain scission has been developed. All experimental data have been compared with the predictions of the model, which is coherent with the one developed for lower temperature values in a previous work [Yu, Y. C.; Storti, G.; Morbidelli, M. Macromolecules 2009, 42, 8187]. This results in a reliable estimation of the rate coefficients of all involved reactions in a relatively large range of temperatures (130-180 degrees C).