Mechanistic insights into the molecular structure and physicochemical properties of carboxymethyl sugarcane bagasse cellulose improved by barrier discharge plasma modification

Cellulose derivatization has long been hindered by low accessibility and restricted modification. In this study, dielectric barrier discharge plasma (DBD) pretreatment was integrated with carboxymethyl modification to improve the derivatization of sugarcane bagasse cellulose (BC). BC samples were treated with DBD for 0, 5, 10, and 15 min and then subjected to carboxymethyl modification at two different concentrations, so as to investigate the resulting structure and physicochemical properties. DBD generated high-energy active species that initially etched the BC surface, supplying energy for oxidation and the cleavage of glycosidic bonds. This process increased sample accessibility and created favorable conditions for the subsequent introduction of carboxymethylation reagents. Thereafter, carboxymethylation was performed to graft highly hydrophilic carboxymethyl groups onto cellulose, thereby reducing the water-insolubility of the original fibers. The combined effects of plasma activation and chemical substitution led to a marked increase in the degree of substitution (DS) as the DBD treatment time increased, reaching 0.61 and 0.59 after 15 min. In parallel, DBD disrupted the dense crystalline regions, resulting in a decrease in crystallinity to 48.6% and 41.56%. X-ray photoelectron spectroscopy (XPS) further confirmed the modification, as reflected by the increased proportion of the C2 peak associated with hydroxyl groups (C–OH), which rose to 60.38% and 58.7%. Meanwhile, prolonged DBD exposure also intensified depolymerization. Overall, DBD pretreatment effectively altered the physicochemical properties of the resulting cellulose derivatives, significantly expanding the potential application scope of sugarcane bagasse carboxymethyl cellulose.