Preparation of chemically recyclable bio-based semi-aromatic polyamides using continuous flow technology under mild conditions

2,5-Furandicarboxylic acid (FDCA) from carbohydrate refining has been a promising bio-based building block for the construction of high-performance polymers. Herein, we not only choose renewable monomers, but employ an eco-friendly continuous flow approach to synthesize furan-based semi-aromatic polyamides (FPAs). The characteristics of the polycondensation reaction are firstly explored by regulating the operating parameters. Using esterified derivatives of FDCA and linear aliphatic diamines, structure-property analysis of synthesized FPAs is performed. The molecular weights, thermal properties and stability exceed those previously reported in the literature for both melt and enzymatic polycondensation. Furthermore, a variable-temperature two-step synthesis procedure is employed to improve the isolated yield of FPAs by removing by-products in the form of gas-liquid slug flow. The N-methylation rate and terminated end-groups uncover the advantages of continuous flow synthesis in terms of preventing side reactions, which promotes the growth of molecular weight. Finally, the FPAs are selectively hydrolyzed under acidic conditions. A closed loop cycle for recycling can be completed when the monomers are further polymerized back to a polyamide. Compared to traditional fossil-based manufacturing processes, the use of renewable resources and continuous flow technology in the production of value-added polymers provides a novel approach for the development of sustainable, carbon-dioxide-neutral industries.