Reactive SAH-Based Deep Eutectic Solvent Enables Efficient Carboxylation of Bamboo Fibers with Preserved Structure and Conductive Functionality

Selective chemical modification of cellulose in lignocellulosic fibers without disrupting the native hierarchical structure remains a central challenge in polysaccharide chemistry. Herein, we report a reactive succinic anhydride-based deep eutectic solvent (SAH-DES) strategy. The SAH-DES system, comprising choline chloride, succinic anhydride, and water (1:1:1 molar ratio), forms a robust hydrogen-bonded network to stabilize anhydride reactivity and suppress hydrolysis. Under optimized conditions (100 ° C, 3 h), carboxylated bamboo fibers (C-BFs) achieved a high carboxyl content of 1.01 ± 0.03 mmol/g while retaining excellent tensile strength (2104 ± 237 MPa). The introduced carboxyl groups enabled uniform deposition of conductive materials (Ag/Ni nanoparticles, polypyrrole), resulting in a high electrical conductivity of 34,271 ± 1266 S/m. This study demonstrates that water-regulated reactivity in deep eutectic solvents provides a pathway for selective cellulose esterification, offering mechanistic insight into structure–reactivity relationships of polysaccharides in confined solvent systems.