Empowering green polymerization: Enzymatic polymerization and low-temperature post-polymerization to produce poly(butylene 2,5-furandicarboxylate)

Poly(butylene 2,5-furandicarboxylate), PBF, is a bio-based polymer originating from the 2,5 furan dicarboxylic acid (2,5 FDCA). PBF has shown promising barrier properties, especially CO₂ and O₂ permeability, rendering it a promising candidate for sustainable packaging. However, its chemical synthesis requires metal catalysts and high temperature. A sustainable approach to produce PBF was herein established as an alternative to chemical polymerization: enzymatic polymerization was applied in the presence of the biocatalyst Candida antarctica Lipase B via a two-stage, solventless process of enhanced sustainability and scaling-up potential. The most critical parameters were investigated (reaction temperature, pressure and time) and PBF oligoesters ($\overline{M_n}$ 1600 g·mol⁻¹, $\overline{M_w}$ 1700 g·mol⁻¹) were easily synthesized thanks to the process’s simplicity. The PBF prepolymer was subsequently submitted to low-temperature post-polymerization, aiming for a molecular weight increase while maintaining its green character. The reaction temperature and time were fine-tuned to reach increased polymerization rates, avoiding thermal degradation, and the received PBF presented $\overline{M_w}$ of ca. 5000 g·mol⁻¹ after 16 h of post-polymerization at 125 °C. The suggested approach produces the upcoming bio-based polymer PBF as a promising candidate for applications requiring high purity and a precisely controlled molecular weight.