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 (C<Subscript>14</Subscript>), cholesteryl nonanoate (C<Subscript>9</Subscript>) and binary mixtures of C<Subscript>14</Subscript> and C<Subscript>9</Subscript> and cholesteryl caproate (C<Subscript>6</Subscript>) and C<Subscript>9</Subscript>. 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 C<Subscript>9</Subscript> in the C<Subscript>6</Subscript>−C<Subscript>9</Subscript> mixture at r≅ 0.92. Copyright EDP Sciences, Springer-Verlag 1998