Bio-based, closed-loop chemical recyclable aromatic polyamide from 2,5-furandicarboxylic acid: Synthesis, high performances, and degradation mechanism

A bio-based, closed-loop recyclable aromatic polyamide with high performances and recovery yield was synthesized, and the degradation mechanism was proposed. [Display omitted] •Bio-based, closed-loop chemical recyclable aromatic polyamide with high thermal, mechanical, and barrier properties comparable to or superior to those of fossil derived isophthalic acid based polyamide was synthesized from 2,5-furandicarboxylic acid.•For the first time, a closed-loop chemical recycling strategy for aromatic polyamides based on amide bond degradation with high recovery yield of initial monomer was proposed.•A simple and efficient method for separating and extracting initial monomer to achieve closed-loop chemical recycling was developed.•The hydrolysis reaction sites and energy barriers were calculated. The resource and environmental challenges posed by the extensive use and disposal of plastics have increased the urgency of research into plastic recycling and the hunt for bio-based alternative feedstocks. As one of the five general engineering polymers, polyamide has not yet been systematically explored in terms of its recycling performance or mechanism, especially aromatic polyamides. In addition, research on novel structured bio-based aromatic polyamides has not received sufficient attention due to the harsh polymerization conditions. In this work, bio-based fully aromatic polyamides based on 2,5-furandicarboxylic acid (FDCA) was successfully synthesized through the acyl chloride method, exhibiting thermal, mechanical, and barrier properties comparable to or superior to those of fossil derived isophthalic acid based polyamides. Moreover, both synthesized polyamides could be hydrolyzed in alkaline environments through the cleavage of amide bonds, as demonstrated by molecular dynamics simulations. The presence of furan rings lowered the energy barrier of hydrolysis as compared to benzene rings. Furthermore, a simple and efficient acidification followed by filtration approach with high recovery yields was developed to recover initial monomers from degradation solutions, thus achieving closed-loop chemical recovery of two polyamides. This work will further expand the application of bio-based feedstock, FDCA, and open new avenues for polyamide recycling research.