Selective reducing end modification of cellulose nanocrystal with tailoring amphiphilicity toward enhanced Pickering emulsion stabilization

Cellulose nanocrystal (CNC) is regarded as a promising bio-based material for emulsion stabilization owing to its high specific surface area, abundant hydroxyl groups, and tunable surface chemistry. However, the inherent hydrophilicity of CNC considerably limits interfacial activity at oil-water interfaces, posing a significant challenge for practical emulsion applications. In this study, the amphiphilicity of CNC was engineered through selective reducing end modification to enhance Pickering emulsion stabilization. Structural and chemical analyses confirmed the successful introduction of amine without disrupting the native crystalline structure of CNC. The conversion rate was dependent on the synergistic effects of amine nucleophilicity and solvent polarity, with an optimal conversion rate of 61.17%. Notably, the modified CNC exhibited tunable surface wettability (water contact angle increased to 45.5°) and colloidal stability (zeta potential ranging from −20.31 to −24.89 mV), enabling effective modulation over hydrophilic–hydrophobic balance. As a proof-of-concept, the amphiphilic CNC was capable of stabilizing Pickering emulsions featuring uniformly dispersed droplets, indicative of favorable interfacial activity. Rheological behavior further revealed an elastic-dominated behavior, corroborating the high stability of the interfacial layer. These findings open up new avenues for broadening the application of CNC in emulsion formulations across the fields of food science, cosmetics, pharmaceutics, and waterborne coatings.