Helical Twisting Power in Mixtures of Nematic and Cholesteric Liquid Crystals

Abstract

The helical twisting power in nematic ($\mathrm{methoxybenzylidene} p\ensuremath{-}\mathrm{aminophenyl}\mathrm{acetate}$)-cholesteric (cholesteryl propionate) mixtures as a function of cholesteric material concentration is studied by measuring the circular dichroism, the wavelength of selective reflection, and the Grandjean fringes. It is found that as the cholesteric material concentration increases, the twisting power of the mixtures increases linearly up to a certain concentration, beyond which, however, it increases more slowly, taking a maximum value at some specific concentration which normally falls in the high-concentration region.