Enzymatic prepolymerization combined with bulk post-polymerization towards the production of bio-based polyesters: The case of poly(butylene succinate)

Abstract

An alternative process for the production of poly(butylene succinate) (PBS) was herein applied, divided in two stages, both sustainable and in accordance with the principles of green polymerization. The first stage involved the enzymatic polycondensation of 1,4-butanediol and diethyl succinate, using immobilized Candida antarctica lipase B as a biocatalyst. The suitability of two different solvents (isooctane, toluene), as well as the bulk (solvent-free) system were examined at different reaction temperatures (40 °C, 50 °C, 60 °C), leading to the selection of isooctane as solvent and 50 °C as reaction temperature for the enzymatic prepolymerization step. The formed prepolymers were then submitted to bulk post-polymerization in order to upgrade their quality in terms of molecular weight and thermal properties. The final product was a PBS grade with weight-average molecular weight at ca. 5000 g/mol, melting point at 104 °C and mass fraction crystallinity at 70%, free of thermal degradation and metal catalyst residues.