Ecofriendly synthetic strategies for the realization of FDCA-based polymer films for sustainable, flexible and recyclable/compostable food packaging

Novel 2,5-furandicarboxylic acid-based polyesters, by combining poly(octylene 2,5-furanoate) and poly(triethylene 2,5-furanoate), were successfully synthesized, characterized and evaluated for sustainable and flexible food packaging application. Three eco-friendly and solvent-free synthetic approaches, such as melt polycondensation, physical blending and reactive blending were employed to prepare: equimolar physical blend, 50 mol% of poly(octylene 2,5-furanoate) block and random copolymers, 80 mol% of poly(octylene 2,5-furanoate) random copolymer. After molecular characterization, by nuclear magnetic resonance spectroscopy and gel permeation chromatography, confirming the good control of synthesis parameters, the polymers were processed in form of films and subjected to solid-state properties characterization. High thermal stability was evidenced by thermogravimetric analysis, while the characteristic temperatures were determined through differential scanning calorimetry showing all the polymers, with the exception of poly (triethylene 2,5-furanoate), are capable of developing ordered structures. Diffractometric measurements showed poly(octylene 2,5-furanoate) crystals, in comparable amount but with different perfections degree, formed in all the crystalline samples. Scanning electron microscopy was employed to assess film microstructure, distribution and continuity. Functional properties, such as mechanical behavior and gas barrier capability, were tested and correlated with chemical, structural/microstructural and thermal characteristics of the polymer films. Surface wettability was measured and correlated with the composting ability and kinetics. In general, flexibility was enhanced while keeping the gas barrier ability even under humid conditions, while degradation rate in compost was properly tuned in the perspective of different end of life management of the polymer films.