Oxidized dihydrocarvone as a renewable multifunctional monomer for the synthesis of shape memory polyesters

The natural product dihydrocarvone, found in caraway oil, was oxidized to an epoxylactone on a multigram scale. The resulting epoxylactone was used as a multifunctional monomer and cross-linker in ring-opening polymerizations. Homopolymerization using diethylzinc and tin(II) 2-ethylhexanoate gave only low molecular weight oligomers (apparent M_n less than 2.5 kg/mol). Copolymerizations of ε-caprolactone and 0.3 to 50% of the epoxylactone gave flexible cross-linked materials on a multigram scale in a one-step synthesis. The gel fraction of these copolymers was determined. These copolymers showed near perfect shape memory properties even after repeated bending.