Unlocking sustainable, aromatic, and versatile materials through transurethanization: development of non-isocyanate polyurethanes from lignins

Abstract

Polyurethanes (PUs) are nowadays essential for a wide range of key applications, thanks to their exceptional and adaptable properties, which arise from their wide variety of macromolecular architectures. However, conventional PUs are predominantly fossil-based, synthesized from highly toxic isocyanates, and are difficult to recycle since most of them are thermosets. This study presents a novel approach to address these issues by developing bio-based, aromatic, and crosslinked non-isocyanate polyurethanes (NIPUs) derived from lignin, which are synthesized for the first time via transurethanization. This reaction was used as a simple, powerful and safe polymerization process. This method eliminates the need for lignin purification and requires only widely available compounds. A comprehensive analysis of the polymerization process and the resulting NIPU materials was conducted. It was observed that lignin could be introduced in the crosslinked architectures up to 32 wt%, and these aromatic NIPUs showed elastomeric behaviors with tunable properties. Additionally, two end-of-life management strategies based on mechanical and chemical recycling were also evaluated. These bio-based and aromatic materials offer a promising pathway toward sustainable and easy production of NIPU from lignin while adhering to multiple green chemistry principles, including the use of renewable feedstocks, safe reagents, limited synthesis steps, and waste prevention.