Cellulose nanocrystals (CNCs) are bio-sourced chiral nanorods that are known to spontaneously self-organize in water into a cholesteric liquid crystalline phase. Upon evaporation, this helicoidal arrangement can be retained in the solid-state in order to produce films that strongly reflect visible light. While the strong chiroptical properties and non-fading character of bio-compatible CNC films has generated considerable interest within the cosmetics, food and security industries; an alternative self-assembly route that leads directly to a dispersable photonic pigment would be much more desirable. Inspired by the helicoidal architectures found in the plant cell wall, we report the self-assembly of cellulose nanocrystals (CNCs) into hierarchical cholesteric architectures within micron-sized aqueous droplets (Fig. A). This confined, spherical geometry drastically affects the self-organisation of the colloidal liquid crystal, resulting in concentric "Frank-Pryce" ordering within the droplet, as confirmed by simulation (Fig. B). This hierarchical architecture can be retained upon conversion to the solid-state to produce buckled microparticles (Fig. C). By using a sustainable bio-polymer, such nanostructured microparticles offer a scalable route to sustainable photonic pigments. Furthermore, the unusual isotropic compression in spherical microdroplets offers an unique advantage to explore the fundamental behavior of such colloidal systems. Namely, the pitch evolution allows for in situ visualization of the kinetic arrest occurring as the concentration increases, offering significant advantages over the conventional planar geometry (cf. films) or sample-consuming rheology measurements.

Hierarchical self-assembly of cellulose in a confined geometry

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.