Binary Mesogenic Systems Comprised of Ester Mesogens and Non-Mesogens

Abstract

With a view to evaluate the effect of non-mesogen or mesogen on the binary systems comprised of a nematogon or a polymesomorph, the present study was undertaken where the compounds have general structure (I):

The binary systems are selected with variation in R and R′ (I). The binary phase diagrams have very interesting behaviour. One most common feature is rounded minimum of melting point curve suggesting large depression and resulting into ambient temperature mesophase. A non-mesogen as one of the components decreased the mesomorphic tendency of the system and, in some cases, rendered the enantiotropic phase to monotropic phase with one exception. The binary systems comprised of mesogen and polymesogen exhibited interesting behaviour. The nematic phase remained enantiotropic for most of the compositions but the nematic-smectic curve went on falling up to about 50% concentration and then the phase was eliminated from the system. Whereas in the second binary system, the monotropic- smectic phase is converted to enantiotropic phase. The common feature with one exception is that the difference in the value of R(I) in binary system depresses the solid-mesomorphic transition temperatures markedly. The smectogenic tendencies are enhanced with increasing carbon chain of alkoxy and ester substituent keeping with the trend observed in homologous series.

Key Words:

• ester mesogens
• induced smectic phase
• polymesogenic