Localized surface acetylation of aqueous counter collision cellulose nanofibrils using a Pickering emulsion as an interfacial reaction platform

The self-organization of nano-sized fibrous building blocks is essential for the construction of biomimetic architectonics and hierarchically constructed bio-based materials. The localization of hydrophobic moieties on the surfaces of such nanofibrils is key to hierarchical assembly in aqueous systems. In this study, unique selfassembling fibrous building blocks comprising amphiphilic cellulose nanofibrils (CNFs) were prepared by aqueous counter collision (ACC). The purpose of the study was to control the surface properties of ACC-CNFs by selectively acetylating their surfaces at the oil/water interfaces of a Pickering emulsion. Localized interfacial reactions occurred when the ACC-CNFs were adsorbed onto the surfaces of oil droplets containing the reaction reagents. Such acetylation reactions were achieved whilst maintaining the crystallinity and fibrous morphology of the original CNFs. The surfaces of films cast from the acetylated ACC-CNFs described herein had unique selfaggregation properties that contrasted markedly with those of films cast from acetylated ACC-CNFs prepared in homogenous dispersions.