Highly efficient mechanochemical depolymerisation of bio-based polyethylene furanoate and polybutylene furanoate†

Abstract

The challenge of producing new environmentally friendly and fossil-free polyesters has strongly encouraged the development of bio-based alternatives such as polyethylene furanoate (PEF) and polybutylene furanoate (PBF) as alternatives to commodity plastics such as polyethylene terephthalate (PET) for everyday applications. In this contribution, we report the mechanochemical depolymerisation of these polymers using NaOH in the presence of NaCl as an additive along with the synthesis of high-molecular weight PEF and PBF. Efficient depolymerisation, producing 2,5-furandicarboxylic acid (FDCA) and the corresponding diols in quantitative yields after aqueous acidic workup, is possible within 30 minutes milling time. Using slightly modified reaction conditions, transesterification with MeOH produces the 2,5-furandicarboxylic acid dimethyl ester (FuMe₂), which can potentially be reused for polymer synthesis. Notably, the furan ring remains stable under the mechanochemical conditions used. The applicability of these straight-forward, environmentally friendly protocols on a large scale is demonstrated through multigram scale reactions.