Synthesis of Modified Lignin as an Antiplasticizer for Strengthening Poly(vinyl alcohol)–Lignin Interactions toward Quality Gel-Spun Fibers

Chemical modification is a viable strategy to tune the polarity of lignin and broaden lignin's application in different fields. To explore chemically modified lignin's role as an antiplasticizer and improve its interaction with poly(vinyl alcohol) (PVA), modified lignin (ML) was synthesized with d-gluconic acid acting as both the reagent and catalyst at different reaction durations. Quality gel-spun PVA fibers were prepared with the incorporation of 5 wt % ML. The fabricated PVA fiber with 5% ML obtained after 48 h of reaction time exhibits the best mechanical properties. The optimal tensile strength is 1.3 GPa, Young's modulus is 20.7 GPa, and toughness is 24.2 J g–1. The outstanding mechanical properties are attributed to the strong antiplasticization effect of ML, which results in high crystallinity in gel-spun PVA fibers. This work provides a facile approach to valorize modified lignin in the application of quality polymeric fibers.