Nanocellulose–surfactant interactions

Biomass-derived nanomaterials, such as cellulose nanocrystals and nanofibrils, are attractive building blocks for the formulation of foams, emulsions, suspensions and multiphase systems. Depending on their surface chemistry, aspect ratio and crystallinity, nanocelluloses can control the rheology and stability of dispersions; they can also confer robust mechanical properties to composites. Synthetic modification of fibrillar cellulose is an option to achieve chemical compatibility in related systems, in the formation of composites, etc. However, this can also limit the environmental benefits gained from the use of the cellulosic component. Thus, an attractive mean to compatibilize and to further expand the applications of nanocelluloses is through the use of surfactants. The chemical toolbox of surfactants developed over the last 60 years allows for a large versatility while their environmental impact can also be minimized. Furthermore, relatively small amounts of surfactants are sufficient to significantly impact the interfacial forces, which has implications in material development, from the colloidal scale to the macro-scale. In this review we attempt to cover the literature pertaining to the combined uses of surfactants and nanocelluloses. We summarize reports on the incorporation with nanocellulose of nonionic, anionic, amphoteric and cationic surfactants. With the ever-expanding interest in the use of renewable materials in a vast range of applications, we hope to provide insights into the application of surfactants as a tool to tailor the compatibility and the surface chemistry of nanocelluloses.