Control of Molecular Mass Distributions in Enzymatic Lactone Polymerizations
Santanu S. Kundu, Peter M. Johnson, Kathryn L. Beers
Using a model developed for the enzyme catalyzed polymerization and degradation of poly(caprolactone), we illustrate methods and the kinetic mechanisms necessary to improve molecular mass distributions by manipulating equilibrium reactions in the kinetic pathway. For these polymerization/degradation reactions, a water and linear chain equilibrium controls the number of chains in solution. Here, we control the equilibrium by adding water trapping molecular sieves in the batch polymerization reactions of ε-caprolactone. While ring opening rates were mostly unaffected, the molecular mass distribution shifted to higher molecular masses after complete conversion was reached and a good agreement between the experimental and modeling results was found. These results provide a framework to improve the molecular mass and its distributions for ring opening polymerization of lactone.