Smectic A-Cholesteric liquid crystal phase transition: A density study

The present work is focused on density measurements near the smectic A-cholesteric liquid crystal phase transition for cholesteryl myristate (C14), cholesteryl nonanoate (C9) and binary mixtures of C14 and C9 and cholesteryl caproate (C6) and C9. The results have evidenced that the transition crosses over from first to second order when both the mean molecular length and the reduced temperature, r (ratio between the smectic A-cholesteric and cholesteric-isotropic phase transition temperatures), decrease in the system. The occurrence of a second order phase transition is observed for a concentration very near 63.1 molar percent of C9 in the C6−C9 mixture at r≅ 0.92.