Cellulose acetate composites with bamboo cellulose nanofibers: crystallinity preservation during tetrabutylammonium salt-catalyzed surface acetylation

Abstract

Conventional ionic liquids (ILs) used for cellulose modification, while effective in dissolving cellulose, often induce a transition from the robust cellulose I crystalline structure to the weaker cellulose II crystalline phase, compromising material strength. To overcome this limitation, we developed six types of tetrabutylammonium (TBA)-based organic salts, including TBA acetate, aimed at modifying the cellulose surface while preserving its native crystalline structure. Regenerated cellulose nanofibers (CNFs) treated with these TBA-based salts were analyzed via X-ray diffraction and scanning electron microscopy, revealing that TBA maleate minimally affected crystallinity and retained the cellulose I crystalline structure. Subsequently, TBA maleate was employed as the solvent medium for the surface modification (acetylation) of CNFs, achieving a degree of substitution of 0.5. The modified CNF acetate (CNF-ac) was blended with commercial cellulose acetate (CA) at ratios of 1, 3, and 5 wt% to evaluate its reinforcing potential. The cellulose I-rich CNF derivative exhibited superior dispersion within the CA matrix, leading to a 46% enhancement in mechanical properties. Overall, this study highlights the potential of crystalline structure-preserving organic salts for the development of high-performance cellulose-based composite materials.