Optimization of intermolecular interactions in poly(propylene 2,4-furanoate) copolymers: an ecodesign case study towards high-performance, biobased, biodegradable food packaging

Biobased 2,4-furandicarboxylic acid (2,4-FDCA), a structural isomer of 2,5-FDCA, has recently led to the synthesis of high molecular weight polyesters with promising properties for food packaging. Among them, poly(propylene 2,4-furanoate) (2,4-PPF), the only polymer in the glassy state at room temperature, showed limited functional performance, attributed to its reduced macromolecular mobility. To address this, 2,4-PPF was copolymerized with biobased poly(propylene succinate) (PPS) via reactive blending, aiming to optimize Tg and chain flexibility. A physical blend, block and random copolymers were processed into freestanding films and thoroughly characterized (NMR, GPC, WAXD, DSC, TGA, tensile and gas permeability tests). Block and random copolymers showed excellent mechanical properties, including elongation at break exceeding 2400%, and outstanding gas barrier, competitive with commercial poly(ethylene vinyl alcohol). These enhancements are attributed to the predicted enhancement intermolecular interactions caused by the Tg close to room temperature, which increased chain mobility, thus optimized interchain hydrogen bonding and π–π interactions. Biodegradation under composting conditions was also assessed. Gravimetric, NMR, GPC, DSC, and WAXD analyses revealed preferential degradation of PPS segments and significant molecular weight reduction in the copolymers. Overall, our results demonstrate the potential of copolymers based on 2,4-PPF as biobased, flexible, monolayer and partially biodegradable materials for sustainable food packaging. Most importantly, this work highlights the critical importance of intermolecular interactions as a tool for the ecodesign of furan-based polymers, to unlock higher levels of functional and sustainable performance.