Influence of the Geographical Origin on Properties and Chiral Nematic Self-Assembly of Carboxylated Cellulose Nanocrystals from Degreased Cotton

Abstract The intrinsic properties of cellulose are influenced by the geographical origin of its raw material, which in turn significantly affect the characteristics of cellulose nanocrystals (CNCs) derived from organic acid hydrolysis and consequently their chiral self-assembly behavior. In this study, carboxylated cellulose nanocrystals (C-CNCs) were prepared from degreased cotton sourced from six different regions in China via oxalic acid hydrolysis. The influence of geographical origin on the physicochemical properties of the resulting C-CNCs and their chiral nematic self-assembly behavior was systematically investigated. The results revealed that variations were observed among the six C-CNC samples in aspect ratio, carboxyl group content, and Zeta potential. Samples with higher aspect ratios and more negative zeta potentials could develop well-defined chiral nematic liquid crystalline fingerprint textures. And the second critical concentration (C 2 ) for complete anisotropy decreased with the increasing aspect ratio, while the helical pitch at C 2 increased with both aspect ratio and carboxyl content. Alkaline pretreatment was adopted to pretreat the samples that failed to form chiral nematic phases, aiming to enhance I β content, crystallinity, and hydroxy-group accessibility by disrupting the hydrogen-bonding network. The resulting N-CNCs exhibited smaller dimensions, higher aspect ratios, and more negative zeta potentials, successfully self-assembling into chiral nematic phases with fingerprint textures and iridescent films.