Toward Fully Biobased Polyesters With Spiroacetal Units: Synthesis and Enzymatic Depolymerization

ABSTRACT There has been active research in the development of new rigid biobased aromatic dicarboxylate monomers that can replace the widely used fossil‐based dimethyl terephthalate in polyester production. In this work, a new biobased dicarboxylate monomer with a spiroacetal unit was synthesized from biobased vanillin and pentaerythritol, which aims to partially or completely replace the fossil‐based dimethyl terephthalate monomer in the production of polyesters. Polyesterification of the new spirocetal diester monomer, 1,6‐hexanediol, in the presence or absence of dimethyl terephthalate, yielded a series of copolyesters with a tunable monomer composition and properties. The incorporated rigid spiroacetal units in the polyesters significantly enhanced the glass transition temperature T g (up to 72°C) and the storage moduli according to differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) measurements, respectively. Furthermore, the obtained polymer films displayed improved oxygen gas barrier by the incorporation of spiroacetal structures, which indicated their potential toward food packaging. Finally, we discovered that the obtained polyesters could be enzymatically depolymerized by the cutinase HiCut from Humicola insolens , indicating potential biodegradability or enzymatic recyclability.