New Functional Materials Formed by Self-Assembly of Nano-Cellulose

Over the last few years the interest in so-called cellulose nanocrystals (CNC) has increased dramatically, largely driven by the recognition of CNC as a sustainably produced high-performance nanoparticle class, highly attractive for new advanced functional materials. A unique aspect of CNC is that, apart from the excellent mechanical and optical properties of the individual rods, they are easy to disperse in aqueous solvents, and already at low concentrations such a suspension forms a cholesteric LC phase. This makes it possible to produce photonic crystal films consisting to 100% of cellulose by evaporating the water. Moreover, taking inspiration from extreme-performance composites in Nature, e.g. in crustaceans, one can envision the development of light-weight high-strength composites by combining CNC with an appropriate secondary phase, e.g. a polymerizable precursor.

An important challenge that hampers this development, however, is that the LC ordering competes with a tendency of CNC to jam into a non-equilibrium kinetically arrested state. If properly understood, the jamming transition can however be very helpful, as it captures and in some sense 'protects' the helical cholesteric liquid crystalline state formed at low CNC concentration, even as all the solvent is evaporated. With a better understanding of the balance between jamming and liquid crystal formation, and of the events taking place during the evaporation of the water remaining after the system enters the jammed state, we may thus be able to tailor the optical and mechanical properties of CNC-based materials. It is such an understanding that my group strives to develop within our research dealing with CNC.

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