Synthesis of novel bio-based and degradable polyurethanes using lignin oligomers

Bio-based and degradable materials were proposed to challenge the major problem of plastic disposal in the environment. In this context, polyurethane production was re-evaluated, encouraging the search for replacing both petroleum components and highly toxic species. A novel synthesis route is explored in this work, aimed to produce degradable lignin-based polyurethanes. Oligomers from steam-exploded lignin were extracted and used with ε-caprolactone (ε-CL) to generate a fully bio-based pre-polymer (oligomer-grafted-poly(ε-CL)), exploiting ring-opening polymerization. We demonstrated that tuning the main reaction parameters, such as ε-CL:oligomer and catalyst:ε-CL mass ratios, and reaction time, it is possible to obtain different pre-polymers enabling the synthesis of bio-based polyurethanes with variable physicochemical properties. In particular, the oligomeric content modulates the thermal and mechanical properties of the polymer (melting point range: 54–62 °C; Young modulus range: 3–7 kPa) and enhances the degradability (up to 13 % wt, in acid environment), highlighting the potential of the material for possible applications.