Solute and Temperature Induced Pitch Changes and Pretransitional Effects in Cholesteric Liquid Crystals

The effect of non-chiralic solute molecules on the pitch of cholesteric mixtures of cholesteryl chloride and cholesteryl nonanoate has been studied as a function of the composition and the temperature. The occurrence of a pretransition to the smectic state at low CC content is established. In the pretransitional state the pitch decreases exponentially with increasing temperature and is extremely sensitive against the addition of most organic molecules. In the normal cholesteric state the pitch increases with increasing temperature. In this state only a very limited number of non-chiralic molecules exert an appreciable influence on the pitch.