Functional biorenewable polyesters from carvone-derived lactones

Abstract

To expand the palette of renewable resource derived monomers that incorporate reactive functionality, the natural product carvone was transformed into two polymerizable lactones, carvomenthide, containing only pendent alkyl groups, and dihydrocarvide, containing an unsaturated moiety. These lactones were polymerized using the catalyst/initiating system diethyl zinc/benzyl alcohol to give aliphatic polyesters with low glass transition temperatures. Good control of the polymer molar masses up to approximately 50 kg mol⁻¹ and products with polydispersity indices below 1.3 were achieved in all cases. Copolymerization of the two lactones was successfully carried out at feed compositions ranging from 3–80 mol% dihydrocarvide, and the ultimate level of dihydrocarvide incorporated into the copolymers was proportional to the feed composition. The pendant double bonds in poly(dihydrocarvide) and copolymers that contain dihydrocarvide were modified by post-polymerization reactions, including epoxidation and radical-induced crosslinking.