Synthesis of Biobased Polyamides Containing a Bifuran Moiety and Comparison of Their Properties with Those of Polyamides Based on a Single Furan Ring

Future biobased building blocks are required to create biobased polymers with superior properties to petroleum-based polymers. Bifuran monomers prepared from inedible biomass represent promising biobased building blocks to endow polymers with excellent thermal and optical properties. In this study, we prepared bifurfurylamine, which is characterized by a bifuran moiety, and polymerized it with seven diacid chlorides to give a series of polyamides that contain a bifuran moiety. The chemical structures of these polyamides were carefully determined using 1H NMR spectroscopy on a model compound. The glass-transition temperature of the polyamide composed of bifurfurylamine and 2,5-furan dicarboxylic acid (Tg = 193 °C), which is a fully furan-based polyamide, revealed that the bifuran monomer is suitable as a comonomer unit for 2,5-furan dicarboxylic acid. A comparative study between a polyamide containing this bifuran moiety and a polyamide based on a single furan ring indicated that the bifuran moiety acts as a rigid unit to increase the relaxation temperature and expand the π-conjugation of the furan ring to strongly absorb UV radiation.