Antibacterial and barrier coatings based on quaternized cellulose nanofibrils towards sustainable packaging

The growing demand for sustainable and biodegradable alternatives to plastic packaging has spurred interest in bio-based functional coatings for paper substrates. Cellulose nanofibrils (CNFs), due to their renewable origin and tunable surface chemistry, have emerged as promising candidates for such applications. In this study, quaternized cellulose nanofibrils (Quaternized CNFs) with different cationic group contents were prepared by adjusting the dosage of glycidyltrimethylammonium chloride (GMA) and evaluated as multifunctional coating agents for sustainable paper packaging applications. The effect of cationic group contents on the morphology, rheology, barrier properties, and antibacterial performance of quaternized CNF-coated papers was investigated. As the cationic group contents increased, the degree of polymerization CNFs decreased, resulting in lower viscosity and yield stress. These changes contributed to the formation of more homogeneous and continuous coating layers, which improved surface coverage. Consequently, the air permeability and water resistance of the coated papers were significantly enhanced. Antibacterial tests demonstrated that the quaternized CNF coatings exhibited strong contact-active antibacterial activity against Gram-positive bacteria, particularly with higher cationic group contents and increased coating layers. In contrast, the antibacterial effect on Gram-negative bacteria was negligible due to the presence of an outer membrane that limits cationic interaction. This is expected to contribute to the potential application of quaternized CNFs as biodegradable coating agents that can simultaneously enhance the barrier and antibacterial properties of paper substrates.