Fully Biobased Unsaturated Aliphatic Polyesters from Renewable Resources: Enzymatic Synthesis, Characterization, and Properties

Abstract

Fully biobased saturated and unsaturated aliphatic polyesters and oligoesters are successfully prepared by Candida antarctica lipase B (CALB)‐catalyzed polycondensations of succinate, itaconate, and 1,4‐butanediol. The effects of monomer substrates and polymerization methods on enzymatic polycondensation are investigated. The CALB‐catalyzed polycondensations of succinic acid, itaconic acid, and 1,4‐butanediol only yield oligomers. By replacing the unactivated dicarboxylic acids with the alkyl diesters, polyesters with various chemical compositions are successfully obtained. The molar compositions and molecular weights of poly(butylene succinate‐co‐itaconate) (PBSI) are significantly affected by the applied polymerization method. Compared with the two‐stage enzymatic polymerization in bulk and in diphenyl ether, the enzymatic azeotropic polymerization in the mixture of cyclohexane and toluene is the best method to synthesize high‐molecular‐weight PBSI with tunable molar compositions. The 13C NMR study reveals that CALB is capable of producing more I‐B‐I‐3 microstructures in the mixture of cyclohexane and toluene by azeotropic distillation. Moreover, the crystalline properties of the obtained polyesters are characterized by wide‐angle X‐ray diffraction (WAXD) and DSC. Furthermore, the thermal and mechanical properties of the crosslinked PBSI are studied. image