Greener Synthesis Route for Furanic-Aliphatic Polyester: Enzymatic Polymerization in Ionic Liquids and Deep Eutectic Solvents

Abstract

The development of bio-based polymers is growing not only due to their abundance in nature but also mainly because of the current issues with fossil-based plastics. Enzymatic polymerizations are a promising way to produce such polymers since they are known to be environmentally friendly. Sustainable polymers that require a greener production process can be realized easily via this polymerization route. However, the use of organic solvents is often one of the drawbacks in developing pathways toward fully green enzymatic polymerization methods. Therefore, in the present work, a series of fully bio-based polyesters based on 2,5-furandicarboxylic acid (FDCA), namely, furanic-aliphatic polyesters (FPEs), were enzymatically synthesized using greener solvents, such as ionic liquids (ILs) and deep eutectic solvents (DESs). The enzymatic polymerization in ILs and DESs effectively leads to the FDCA-based polyesters without any byproduct, which frequently causes coloration using traditional polymerization methods. FPEs with M_w up to 5.4 kg mol^–1 were successfully achieved by Novozyme 435-catalyzed polycondensation of dimethyl 2,5-furandicarboxylate (DMFDCA) with aliphatic diols in BMIMPF₆. Polymerization in DESs was also successfully conducted, resulting in the synthesis of bio-based polyesters, which can be further functionalized. Characterization using TGA, DSC, and WAXD showed that all obtained FPEs are semi-crystalline materials, which decomposed around 390 °C with a T_m of 68–123 °C and T_g of 3–12 °C. With this, we successfully developed more eco-friendly enzymatic synthesis routes for the production of sustainable polyesters