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.