Ring-Opening Copolymerization of (Dihydro)levoglucosenone-Derived Spiro-Epoxides and Cyclic Anhydrides

Abstract

Ring-opening copolymerization (ROCOP) of epoxides with cyclic anhydrides is a powerful strategy for synthesis of structure-controlled polyesters with tunable properties. Although considerable efforts have been devoted to expanding the monomer scope by introducing specific side groups or utilizing new biomass-derived feedstocks, the influence of monomer substitution patterns has received far less attention. In particular, in contrast to the well-studied mono- and 1,2-disubstituted epoxides, 1,1-disubstituted epoxides have been much less explored. Herein, we report cellulose-derived spiro-epoxides DBOO and DBOOPh as a new class of 1,1-disubstituted epoxide monomers for ROCOP with cyclic anhydrides. ROCOP of DBOO with phthalic anhydride proceeds in a living/controlled manner, affording polyesters with predominantly alternating structures, as confirmed by NMR and MALDI-TOF MS analyses. By varying the monomer combinations, a series of polyesters bearing spirocyclic backbones were synthesized. Thermal analyses revealed sufficient thermal stability and widely tunable glass-transition temperatures ranging from 29 to 130 °C. Moreover, the chirality of DBOO and DBOOPh induced chiral environments along the polymer chain, as evidenced by the circular dichroism spectra of the resulting polyesters. It may further induce the polymer chains to adopt a biased one-handed helical conformation. This work not only expands the monomer scope of ROCOP to biomass-derived spiro-epoxides, thus providing access to polyesters with unique rigid spirocyclic backbones, but also demonstrates the potential of polyesters synthesized via ROCOP as new chiral materials.