Ring-Opening Polymerization of Ethylene Carbonate and Depolymerization of Poly(ethylene oxide-co-ethylene carbonate)

The ring-opening polymerization of ethylene carbonate (EC) using KOH as initiator was investigated by changing the EC/KOH ratios and the reaction temperatures. The ratio of the rate of polymerization to chain scission increases as the temperature rises. Hydrolysis results and polymer composition data indicate that polymer chains are formed initially by attack of the active polymer chain end (the alcoholate anion) on ethylene carbonate: one attack at the carbonyl group followed by two attacks at the methylene group. Reactions that decrease the molecular weight and carbonate content in the polymer continue as long as the carbonate links are present. A relationship between carbonate content and degree of polymerization was derived using both decarboxylation and bimolecular elimination reactions for the kinetic equations; this fit the experimental data very well.