Influence of Solid Support Sorptive Properties on the Color of Cholesteric Liquid Crystals

Abstract

This work is a continuation of that published in Part I [Mol. Cryst. Liq. Cryst., 61, 31 (1980)] under the same title, where the qualitative influence of the solid support sorptive properties on the reflected wavelengths from cholesteric liquid crystals has been for the first time reported. It was visually observed that the reflected light band shifted to longer wavelengths as the sorptive abilities of the solid support increased.

In the present work, quantitative measurements (visible diffuse reflectance spectroscopy) at several temperatures on bare metal (Zn, Fe, Cu, Al) surfaces mechanically treated, on chemically and electrolytically prepared ZnO and Fe₃O₄, on electrolytically prepared γ₁- and γ₂–Al₂O₃, on copper surfaces electroplated with copper and on electiolytically prepared γ₁-Al₂O₃ under several current densities, covered with the same mixture of cholesterics as the one used in the previous work, were carried out. Thus, the results of the visual observations of the previous work were checked and the following relationship between the reflected wavelength at the peaks (λ) from the examined cholesteric system on γ₁-Al₂O₃ and on blackened glass (λ′) and the physical sorptive abilities of the γ₁-Al₂O₃ (s') as a function of temperature [T(°K)] was temporarily established: