Enzymatic Ring-Opening Polymerization of ε-Caprolactone in Novel Green Solvents: from Batch Systems to Continuous Flow Mesoreactors

The transition toward sustainable alternatives in polymeric material production is a critical step in reducing the environmental impact of the traditional plastic industry. In this work, a novel synthetic pathway for the synthesis of poly(caprolactone) (PCL) was developed combining three present day sustainable technologies: enzymatic catalysis, biomass-derived solvents, and flow processing. The ring-opening polymerization (ROP) of epsilon-caprolactone was catalyzed by Candida antarctica lipase B (CaLB). The reaction conditions were first optimized in batch mode by tuning the amount of used monomer, initiator (0%-10%) and evaluating different reaction solvents (anisole, eucalyptol, 2,2,5,5-tetramethyltetrahydrofuran, phenetole and 2-methyltetrahydrofuran). The best batch conditions (no initiator and phenetole as solvent) yielding PCL with Mn up to similar to 8000 g mol-1 were successfully translated to flow systems where the reaction time was dramatically reduced from 24 h to 5 min while maintaining comparable Mn value (7800 g mol-1). These findings demonstrate the potential of integrating biocatalysis, renewable solvents, and flow technology for the development of scalable, eco-friendly processes paving the way for future innovations in sustainable polymer synthesis.