Tailoring Native Lignin through Click Chemistry for Electrospun Poly(vinyl alcohol) Nanofibers: A Proof-of-Concept toward Organic Contaminant Adsorption

Abstract

Lignin is an abundant, renewable aromatic biopolymer whose structural complexity and limited functionality often restrict its direct use in advanced materials. In this work, a synthetic strategy based on copper(I)-catalyzed azide–alkyne cycloaddition (CuAAC) was developed to obtain a family of click-functionalized lignins from native lignin isolated from Tacuara cane. Native lignin was first functionalized with azide groups and subsequently reacted with a series of di- and tetra-functional terminal alkynes, yielding structurally tailored derivatives. The modified lignins were comprehensively characterized by FTIR, 1H and 13C NMR, GPC, ICP-OES and thermogravimetric analysis, confirming successful functionalization and revealing how the introduced moieties influence the structural and thermal properties of lignin. The resulting derivatives were incorporated into electrospun poly(vinyl alcohol) nanofibers to obtain composite mats while preserving a homogeneous nanofibrous morphology. As a proof-of-concept of their potential application, the materials were subjected to a preliminary adsorption evaluation using representative pharmaceutical compounds and aromatic carbonyl pollutants. The results indicate that click functionalization modulates the interaction of lignin-based nanofibers with contaminants of different chemical natures, suggesting that the introduced functionalities influence adsorption behavior. This study establishes a versatile platform for tailoring lignin toward functional polymeric materials with potential applications in selective adsorption.