High-T g Furanoate and Terephthalate Polyesters from Branched Diols, 1,2-Propanediol, and 2,3-Butanediol, via a Traceless Linker

Abstract The branched diols, 1,2-propylene glycol (1,2-PG) and 2,3-butanediol (2,3-BDO), can be derived from renewable feedstocks and offer the potential to enhance the glass transition temperature (T g) of polyesters when used as replacements for ethylene glycol in poly(ethylene terephthalate) (PET) or poly(ethylene furanoate) (PEF). In addition, incorporation of these monomers reduces the crystallinity of the polyester. Their low reactivity and reduced thermal stability during polycondensation present significant challenges in achieving high molecular weights using conventional methods. Diphenyl oxalate (DPO) and diguaiacyl oxalate (DGO) can serve as a traceless linker to enable the synthesis of polyesters with high number-average molecular weights (M̅ n). Using this strategy, poly(1,2-propylene furanoate) (P12PF) and poly(2,3-butylene terephthalate) (P23BT) were synthesized with M̅ n values exceeding 20 kg/mol and T g values of 94 and 123 °C, respectively, surpassing previously reported values. Notably, P12PF reached an M̅ n of 27 kg/mol. Three polyesters, P12PT, P12PF, and P23BT, were successfully scaled to ~40 g quantities needed for processing and mechanical property testing. Overall, the linker approach provides an effective strategy for accelerating the synthesis of renewable-based, high-T g polyesters from branched glycols and holds promise for broader application to other challenging polyesters.