Tuning the morphology and ionic conductivity of cellulose nanocrystals through ionic liquid plasticization and hydrogen peroxide oxidation

Cellulose nanocrystals (CNCs) are attractive renewable nanomaterials owing to their high crystallinity, mechanical strength, and surface functionality; however, their inherent rigidity and low ionic conductivity limit their application in flexible and ion-conducting materials. This study investigates the combined effects of ionic liquid (IL) plasticization and hydrogen peroxide (H₂O₂) oxidation on the structural, morphological, thermal, and ion-transport properties of CNCs using two imidazolium-based ionic liquids. The objective was to elucidate how IL anion chemistry and oxidative treatment influence the structure–property relationships governing CNC performance. Comprehensive characterization using FTIR, TEM, AFM, WAXS/SAXS, TGA, DSC, and dielectric relaxation spectroscopy revealed pronounced anion-dependent behavior. EMIMCl preserved the native CNC structure and promoted more ordered organization, whereas EMIMAc induced greater structural disruption, increased molecular mobility, and more extensive morphological reorganization, particularly under oxidative conditions. These differences were consistently reflected in the crystallinity, thermal behavior, and ionic conductivity of the resulting films. The combined results demonstrate that the combination of ionic liquid anion chemistry and H₂O₂ oxidation govern hydrogen-bonding interactions, structural organization, and ion transport within CNC networks. These findings demonstrate that IL anion chemistry provides a powerful design parameter for engineering the structure and functionality of CNCs, opening new opportunities for sustainable advanced materials.