Bruno Frka-Petešić (U of Cambridge) Cellulose nanocrystals: from self-assembly to optical properties

Cellulose is the most naturally abundant polymer on the planet and represents an ideal choice for sourcing materials. In its native form, it is usually found as part of plant cell walls arranged in highly crystalline microfibrils, which can be further processed to produce, after chemical treatment, stable suspensions of slender, splinter-like and chiral particles, termed ‘Cellulose Nanocrystals’. [1] These bio-sourced and highly polydisperse suspensions (with dimensions of ca. 200±100 nm in length and 15±10 nm in width) present fascinating properties: above a critical concentration, they form left-handed cholesteric colloidal liquid crystalline suspensions, with a pitch in the micron range. When these suspensions are left to dry in a shallow dish, they lead to the formation of a film displaying strong reflection of left-circularly polarised light of specific wavelength adjustable within the visible range. While the use of these particles is promising for a variety of applications in effect pigments industry, the optical properties of these films are impacted by many parameters that remain still unclear.

In this talk, I will present our recent progress on the understanding of the mechanisms of their self-assembly and how to control them to produce a variety of optically interesting effects. [2–5] 

References

[1]      R. M. Parker, G. Guidetti, C. A. Williams, T. Zhao, A. Narkevicius, S. Vignolini, and B. Frka-Petesic, The Self-Assembly of Cellulose Nanocrystals: Hierarchical Design of Visual Appearance, Advanced Materials 30, 1704477 (2018).

[2]      T. H. Zhao, R. M. Parker, C. A. Williams, K. T. P. Lim, B. Frka-Petesic, and S. Vignolini, Printing of Responsive Photonic Cellulose Nanocrystal Microfilm Arrays, Advanced Functional Materials 29, 1804531 (2019).

[3]      B. Frka-Petesic, G. Kamita, G. Guidetti, and S. Vignolini, Angular Optical Response of Cellulose Nanocrystal Films Explained by the Distortion of the Arrested Suspension upon Drying, Physical Review Materials 3, 045601 (2019).

[4]      B. Droguet, H.-L. Liang, R. M. Parker, B. Frka-Petesic, M. de Volder, J. Baumberg, and S. Vignolini, Large-Scale Fabrication of Structurally Coloured Cellulose Nanocrystal Films and Effect Pigments, Nature Materials 21, 352 (2022).

[5]      M. R. Parker, T. H. Zhao, B. Frka-Petesic, and S. Vignolini, Cellulose Photonic Pigments, Nature Communications, 13, 3378 (2022).