Polyurethanes (PU) rank as the fifth most widely used class of polymeric materials, with extensive applications in insulation, construction, furniture, and medical devices. However, conventional PU synthesis relies heavily on petroleum-based polyols and highly toxic isocyanates, both of which pose significant environmental and health risks. In particular, the use of isocyanates, a group of volatile and reactive compounds, raises serious concerns due to their toxicity, flammability, and potential for occupational exposure. As the demand for sustainable and safer alternatives intensifies, the valorization of lignin, an abundant and underutilized biopolymer derived from lignocellulosic biomass, has emerged as a promising strategy for the development of renewable, non-isocyanate-based polyurethanes (NIPUs). In this study, we developed a fully biobased, isocyanate-free approach to PU synthesis using lignin as the core building block. Lignin was initially extracted through a co-solvent enhanced lignocellulosic fractionation (CELF) process, then further chemically modified through a one-step epoxidation followed by CO₂ cycloaddition to yield carbonated CELF lignin. A green, non-toxic synthesis of NIPU was then achieved via polyaddition of the tailored carbonated lignin with commercially available diamines. This green and non-toxic synthesis route eliminates the need for hazardous isocyanates while enabling tunable polymer architectures through the inherent structural diversity of lignin.
