Cellulosic colloidal nanorods of different origins were used in order to investigate the effect of various elongated shapes adsorbed at the oil–water interface for Pickering emulsion characteristics. Nanocrystals of length ranging from 185 nm to 4 μm were obtained from the hydrolysis of cellulose microfibrils of three different biological origins: cotton (CCN), bacterial cellulose (BCN) and Cladophora (ClaCN) leading to aspect ratios ranging from 13 to 160. These nanocrystals are irreversibly adsorbed at the oil–water interface and form ultrastable emulsions. Individual droplets of similar diameter were obtained under diluted conditions, illustrating both similar wetting properties and nanocrystal flexibility for the three different types of nanocrystals. However, it was shown that the aspect ratio directly influences the coverage ratio giving rise, on the one hand to a dense organisation (coverage >80%) with short nanocrystals and on the other hand to an interconnected network of low covered droplets (40%) when longer nanocrystals are used. An estimation is made showing that for the longer nanocrystals, 55% of the nanocrystals introduced are involved in the network of the material. The capillary force that promotes attractive interactions between nanocrystals was also addressed. These results lead to a better understanding of the adsorption process for rod-like particles of various aspect ratios for the elaboration of a controlled surface architecture, from a homogeneous monolayer to interconnected porous multilayered interfaces.

Lightweight cellular foams were prepared by freeze-drying oil-in-water emulsions stabilized with cellulose nanocrystals (CNCs). Oil and water were removed while preserving the cellular emulsion template without any shrinkage or deformation both at the internal cell and bulk foam scales. This versatile process proved to be relevant for controlling the pore size of the foam with respect to emulsion droplets. Moreover, the composite foams could easily be obtained as shown here by the addition of polyelectrolytes. Mechanical properties of the foam were investigated and they were found to be reinforced by chitosan addition. Thus, our finding opens new routes to a broad range of cellulose-based porous materials.