Sustainable Approach for the Direct Functionalization of Cellulose Nanocrystals Dispersed in Water by Transesterification of Vinyl Acetate

Herein we report a novel method for a high-yield surface esterification of cellulose nanocrystals (CNCs) in water, by transesterification of vinyl esters. The esterified nanoparticles were simply produced by heating under stirring a water dispersion of CNCs in heterogeneous mixture with vinyl acetate, with potassium carbonate as catalyst. Reactions were performed in different conditions, to investigate the impact of different parameters, such as the amount of reagent, temperature and reaction time. In optimized conditions, the grafting level could be easily tailored by controlling the reaction time, and up to 90% of the accessible hydroxyl groups at the surface of the CNCs could be esterified. The acetylated CNCs retained their rod-like shape, while their dimensions, crystallinity and thermal stability were marginally affected by the treatment. Turbiscan analysis finally revealed that the hydrophobic character at the surface of the modified particles increased with the acetylation level, leading to a comm...