Controlled Catalysis Delivering High Molecular Weight Polyesters as Recyclable Alternatives to Polystyrenes

An organometallic Al(III)K(I) catalyst shows exceptional control in the epoxide/anhydride ring opening copolymerization (ROCOP), producing high molecular weight polyesters (M_n ∼ 100 kg·mol^-1). The catalysis is highly effective using cyclohexene oxide, cyclopentane oxide, substituted cyclohexene oxide, and butylene oxide, each combined with phthalic anhydride. The polyesters show entanglement molecular weights, determined by oscillatory shear rheology, from 13 to 50 kg·mol^-1 with cyclopentene and substituted cyclohexene moieties being particularly effective (highly entangled). The lead polyesters show high glass transition temperatures (94 °C < T_g< 137 °C), high tensile strengths (40 MPa < σ < 47 MPa) and tensile modulii (0.6 GPa < E_y< 0.9 GPa); their properties are similar to polystyrene. The polyesters are all recyclable by repeated cycles of compression molding, and show equivalently high thermal-mechanical performances even over repeated recycles.