Liquid crystalline structuring in dilute suspensions of high aspect ratio clay nanosheets

Abstract Aqueous liquid suspensions of high-aspect ratio 2D clay nanosheets were investigated using small angle X-ray scattering (SAXS). The high aspect ratio of synthetic fluorohectorite clays allows for investigation of liquid crystalline orientational order for relatively large nanosheet spacings, in the range which can produce structural coloration, thus providing two handles for determining the nanosheet spacings: SAXS and visible color. Various clay concentrations were investigated, and good agreement with previous work on structural coloration from such suspensions, was obtained. Particular attention is given to the confinement caused by the container geometry, where both cylindrical and flat confinements were investigated. In both cases, the SAXS data suggest coherent regions that have a nematic inter-orientational distribution that surprisingly is linked to the container geometry, which apparently determines the efficiency of packing of the suspension. For both geometries the analysis suggests that these coherent regions have a 1D lamellar periodic intra-structure with uniform nanosheet spacing determined by the clay concentration and a typical coherence length in the range of 200 to 500 nm.