Functional bio-based polyurethanes from lignin oligomer-initiated ring-opening polymerization of cyclic esters

Recyclability and sustainability in polymer development are essential to addressing pollution and waste accumulation, for which bio-based polymers could be a credible candidate to enhance plastic circularity. In this work, lignin oligomers obtained from a steam-explosion process were employed as initiators for the ring-opening polymerization (ROP) of cyclic esters, such as lactone and lactide, enabling the synthesis of bio-based polyesters that were subsequently used as building blocks for polyurethane production. Key synthesis parameters, such as oligomers concentration (expressed as ester-to-oligomers mass ratio) and reaction time, were systematically investigated at a fixed catalyst loading (1 wt%) to achieve high yields and controlled molecular weight distributions. The production of oligomer-grafted-poly(ε-caprolactone) (PCL), oligomer-grafted-poly(lactic acid) (PLA), and oligomer-grafted-PCL-co-PLA were performed via three distinct polymerization routes, yielding random, di-block, and multiblock lignin-based architectures, respectively. These copolymers were further used in polyurethane syntheses through activation with isocyanate moieties, resulting in materials with tunable physicochemical, thermal, and mechanical properties, depending on the selected polyester polyol characteristics. Furthermore, the antimicrobial efficacy of the resulting polyurethanes was demonstrated, and their hydrolytic degradation behavior was assessed, underscoring the potential of these bio-based materials for antimicrobial applications with tailored degradability.