Alternating Poly(ether-alt-ester)s with High Glass Transition Temperature Enabled by Rotationally Constrained Biaryl Units

Abstract

Incorporating different structural units into the polyester backbone constitutes a powerful strategy to tailor material performances. The integration of ether and ester moieties affords poly(ether-alt-ester)s with enhanced mechanical flexibility and tunable thermal properties. Nevertheless, the substrate scope available for the alternating copolymerization of epoxides with lactones remains considerably restricted, and the resulting polymers still suffer from inferior thermal resistance. Herein, we design a typical Bringmann’s lactone bearing a conformationally constrained biaryl axis and a helically distorted six-membered bridging scaffold. A binary catalyst system composed of simple Salen-Cr(III)-Cl and 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD) enables strictly alternating and controlled copolymerization with meso-epoxides, effectively suppressing the formation of ether-ether or ester-ester linked homopolymer sequences. This protocol yields alternating poly(ether-alt-ester)s with a high glass transition temperature of 114 °C, an enhancement of 57 °C relative to alternating copolymer derived from the flexible 3,4-dihydrocoumarin monomer. This approach provides a facile and practical strategy for advancing the performance of alternating poly(ether-alt-ester)s.