Regensburg 2022 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

CPP: Fachverband Chemische Physik und Polymerphysik

CPP 8: Focus Session: Photonic Structures from Polymer and Colloidal Self-Assembly

CPP 8.4: Vortrag

Montag, 5. September 2022, 16:15–16:30, H38

Elucidating the chiral self-assembly of cellulose nanocrystals for photonic films — •Thomas Parton, Richard Parker, Gea van de Kerkhof, Aurimas Narkevicius, Johannes Haataja, Bruno Frka-Petesic, and Silvia Vignolini — Department of Chemistry, University of Cambridge, United Kingdom

Cellulose nanocrystals (CNCs) are naturally-sourced elongated nanoparticles that form a cholesteric colloidal liquid crystal phase in suspension. Interestingly, this helicoidal arrangement can be preserved upon drying to create films with vibrant structural colour. However, while CNCs have drawn significant attention as a way to produce sustainable photonic materials, the underlying mechanism by which chirality arises in the mesophase remains unclear. Although the morphology of individual CNCs is believed to play an important role, most particles are not strongly twisted, and the suspensions exhibit considerable polydispersity in both particle size and shape.

In this study, we performed an in-depth morphological analysis of CNCs observed using transmission electron microscopy (TEM) and atomic force microscopy (AFM). We sequentially tuned the size and shape of the CNCs using ultrasonication and correlated the morphology of individual nanoparticles with their ensemble liquid crystalline behaviour and photonic response. This analysis revealed that a sub-population of CNC ``bundles'' (i.e. clusters of laterally-bound elementary crystallites) act as chiral dopants, analogous to those used for molecular liquid crystals, and are therefore essential for the formation of the cholesteric phase.