Abstract
The temperature dependence of the induced helical pitch is reported for cholesteric and reentrant cholesteric phases of liquid crystal systems comprising 4-n-hexyloxy and 4-n-octyloxy-4′-cyanobiphenyl with a non-mesogenic optically active dopant. It was found that on adding small quantities of the dopant that the temperature range of the SA phase is narrowed and subsequently disappears, while short range smectic fluctuations persist, influencing the helical twisting features. Critical index values were determined from the temperature dependence of the pitch.