Closing the loop: polyimine thermosets from furfural derived bioresources†

Over the past few decades, thermosetting plastics have emerged as indispensable materials in both industrial applications and our daily lives, primarily due to their exceptional thermal and mechanical properties resulting from their covalently crosslinked structures. Nevertheless, conventional thermosets face a significant environmental challenge due to their inability to be recycled and reliance on the petroleum resources. Consequently, there is an urgent need to develop innovative, biobased thermosetting materials that are smartly designed to enable efficient chemical recycling, thus contributing to the realization of a circular plastic economy. Here, we present synthesis of a biobased di-furfural monomer and its polymerization with mixtures of various biobased multi-functional amines to construct a library of polyimines. These polyimine thermosets displayed tailor-made thermal and mechanical properties, featuring a wide range of glass transition temperatures from 8 °C to 60 °C and tensile strength spanning from 6.5 to 77.8 MPa. They also demonstrated high char yields, reaching 57% at 800 °C. Notably, these novel polyimines exhibit high bio-content (in the range of 78% to 90%) and closed-loop recyclability under mildly acidic and energy-efficient conditions. This unique property enables the recovery of monomers on demand with high yields and purity. The findings presented in this work represent a valuable contribution in the field of biobased thermosetting polymers with circular economy potential, offering new possibilities for sustainable material design.