Lignin-based Film with Tunable Mechanical Properties Enabled by Polyether Amine Incorporation

Abstract

To achieve high-value utilization of lignin and develop high bio-based content materials, flexible films were prepared via Schiff base reaction of levulinic acid-esterified lignin with castor oil amine and varying amounts of polyether amine (0 to 50 wt.%). The incorporation of polyether amine as a flexible plasticizing component effectively addressed the inherent brittleness of high-lignin-content films, resulting in tunable mechanical properties. Tensile testing showed that V-3 (15% polyether amine) exhibited the highest tensile strength (12.0 MPa) and Young's modulus (7.19 GPa), representing increases of 51% and 318% compared to V-1 (the 0% polyether amine), while maintaining an elongation at break of 75.9%. All films exhibited good thermal stability with T_d 5% above 272 °C. Swelling ratio measurements increased from 109% (V-1) to 209% (V-5), indicating decreasing crosslinking density with higher polyether amine content. Notably, V-3 exhibited a T_g of 35.8 °C. This study demonstrates a simple strategy for tuning the mechanical properties of lignin-based films for potential biomedical and soft robotics applications.