Thursday 12 Dec 2013: Chiral Nematic Properties of Cellulosic Materials
Professor Derek Gray - Department of Chemistry, McGill University
HAR/170 (3D Visualisation Suite) 14:00-15:00
Despite its simple chemical structure and long history as a useful material, cellulose can still exhibit unexpected properties. Some time ago, many cellulose derivatives in concentrated solution were found to form chiral nematic liquid crystalline phases with optical reflection bands across the visible spectrum. Perhaps more surprisingly, cellulose nanocrystals (rod-shaped particles of crystalline cellulose I prepared from natural cellulose fibres) form stable aqueous colloidal suspensions with chiral nematic properties. These suspensions also display the optical properties of the familiar cholesteric liquid crystals, but contain up to 95% water. Remarkably, the order observed in the suspensions is maintained when the water is removed by evaporation, leading to iridescent solid films. The chiral nematic structure of self-assembled cellulose nanocrystals suspensions and films has recently been reported to template similar structures in silica and other inorganic materials.