Renewable Polycarbonates Based on Erythrodiol

The naturally occurring pentacyclic, triterpenoidic, hydroxyacid oleanolic acid (OA) was reduced to yield erythrodiol (ErDO), a rigid and polychiral diol. Consequently, poly(erythrodiol carbonate), a novel bio-based polycarbonate, could be synthesized by polycondensation with dimethyl carbonate (DMC) or diphenyl carbonate (DPC), yet with low molecular weights (Mw up to 10 kg mol–1). Potential explanations are the low reactivity of the secondary alcohol, as well as the bulky structure and the high melting point of ErDO. By introducing 1,6-hexanediol as a further bio-based diol comonomer, a copolymer with a content of 37 mol% ErDO showed a significant increase in Mw up to 74 kg mol–1. The homopolymer shows a remarkably high glass-transition temperature (Tg) for polycarbonates, at 232 °C, and could be effectively tuned by copolymerization with HDO (e.g., 109 °C for 37 mol% ErDO). All (co)polymers are thermally stable until at least 300 °C.