Viscous Behaviour of Cholesteric Liquid Crystals

Investigations as carried out on the viscous behaviour of liquid crystals of the cholesteric type viz., cholesteryl acetate, cholesteryl formate and cholesteryl benzoate throughout their anisotropic and isotropic phase using a cone-and-plate viscometer. It is observed that there is a noticeable abrupt change in the viscosity at the transition temperature in the case of cholesteryl acetate and cholesteryl benzoate, whereas a very slight variation is observed in the case of cholesteryl formate. The activation energies are calculated for the cholesteric and isotropic phase and the abrupt change in viscosity at the transition temperature is attributed to the hige mobility of the cholesteric mesophase of these esters.