Mixed Mesomorphism in Binary Systems Forming Smectic-Nematic Phases

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Abstract
A number of binary systems have been investigated with p-n-dodecyloxybenzal-p-n-butoxyaniline—a mesomorphic component exhibiting both smectic and nematic phases—and other non-liquid crystalline solutes. When the transition temperatures of such binary systems are plotted against the mole per cent composition of the liquid crystalline component, two types of curve are obtained: (1) A usual curve where the transition lines are depressed regularly and (2) a rising curve exhibiting only a smectic phase and a maximum. The latter type of curve indicates an enhancement in the smectic thermal stability while the former shows a decrease in the mesomorphic thermal stability during the course of mixed liquid crystal formation; the range of temperature over which the nematic phase exists increases at the cost of the smectic mesophase. It is observed that in such a binary mixture, if at least the first few compositions chosen melt to give the isotropic liquid at a temperature higher than the mesomorphic-isotropic liquid transition temperature of the pure liquid crystalline component, the mesomorphic-isotropic liquid transition curve exhibits a maximum and the mixture exhibits only a smectic phase.

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