On the dynamics of surface layer in octylcyanobiphenyl-aerosil systems
National Institute of Materials Physics PO Box Mg07, R-76900
2 Federal Institute of Materials Research and Testing Unter den Eichen 87, D-12205 Berlin, Germany
Accepted: 26 September 2001
A broadband dielectric study of the dispersions of silica spheres (Aerosil 380) in octylcyanobiphenyl (8CB) with densities between 0.083 and of silica per of liquid crystal (LC) is reported. High values of silica densities were achieved for the first time to observe the behaviour of the LC monolayer on the surface of the silica particles. The relaxation characteristic of the bulk LC is noticed especially for the samples with low silica densities. Additionally, a slow relaxation was detected, even at temperatures for which the bulk LC is in the crystalline state. It was assigned to the surface layer of LC molecules. Remarkably, the temperature dependence of the relaxation rates for this slow process shows a behaviour typical for glass-forming liquids.
PACS: 61.30.Hn – Surface phenomena: alignment, anchoring, anchoring transitions, surface-induced layering, surface-induced ordering, wetting, prewetting transitions and wetting transitions / 61.30.Pq – Microconfined liquid crystals, droplets, cylinders, randomly confined liquid crystals, polymer dispersed liquid crystals, and porous systems / 61.30.Gd – Orientational order of liquid crystals; electric and magnetic field effects on order
© EDP Sciences, 2001