Ring-Opening Copolymerization of a CO2/Butadiene-Derived Epoxide with CO2 or Cyclic Anhydrides Leading to High CO2 Content Polycarbonates and High Tg Polyesters.

An epoxide 3-ethyl-6-(oxiran-2-yl)tetrahydro-2H-pyran-2-one (EtOP) synthesized from a CO2/butadiene-derived lactone (3-ethylidene-6-vinyltetrahydro-2H-pyran-2-one, EVP) is used in ring-opening copolymerization (ROCOP) with a series of anhydrides and carbon dioxide. Anhydride copolymerizations were carried out using the catalyst N,N-bis(salicylidene)-cyclohexanediamine chromium(III) chloride ((salen)CrCl) in combination with bis(triphenylphosphine)iminium chloride (PPNCl), resulting in high yields (>75%) of moderate molar mass (20-40 kDa) polyesters. The glass transition temperatures (Tg) of the polyesters could be modulated from 75 °C (maleic anhydride, MA) to 112 °C (norbornene anhydride, NA) while maintaining good thermal stability (Td > 180 °C). These glass transition temperatures are significantly higher than other polyesters derived from EVP, which are typically <0 °C. Reactions of EtOP with CO2 catalyzed by (salen)Co(OAc)/[PPN]TFA afforded polycarbonates with >99% selectivity. The resultant polycarbonate has a CO2 content of 41 wt %, and its Tg value of 73 °C represents the highest Tg reported for a material with a CO2 wt % above 40%.