Abstract

A NOVEL MESOMORPHIC HOMOLOGOUS SERIES OF ESTER DERIVATIVES P (P’-N-ALKOXY BENZOYLOXY) N-HEPTYL BENZOATES

Pandya S. N. and Chauhan M. L.*

Abstract

A new homologous series of non amphiphilic liquid crystals p(p’-n- Alkoxy Benzoyloxy) n-Heptyl Benzoates with configuration is synthesized and studied with a view to understand the effect of molecular structure on mesomorphic properties of substances which may be useful to the various fields of applications. Methyl to Pentyl homologues are nonmesomorphic but hexyl octyl, decyl, dodecyl, tetradecyl and hexadecyl homologues are mesomorphic i.e. nematogenic in character without exhibition of any smectic character. A phase diagram is drawn from the transition temperatures as determined from hot stage polarizing microscope of homologues against the number of carbon atoms in n-alkyl chain of left n-alkoxy terminal end group. Solid-isotropic or solid nematic transition temperature curve follows a zigzag path of rising and falling throughout the series as series is ascended in normal manner. Nematic isotropic transition curve initially rises and then, shows descending tendency as series is ascended. Thus, it follows usual established trend as expected. Not shown odd-even effect for nematicisotropic transition curve. Analytical data support the structures of molecules. The enantiotropic nematic mesophase appeared for all the homologues, is of threaded type as determined from miscibility method. Thermal stability for nematic is 143.6 ºC and mesomorphic range is short which varies from 8.0 ºC to 20.0 ºC. mesomorphic properties of titled homologous series are compared with structurally similar homologous series.

Keywords: Liquid Crystal, Smectic, Nematic, Mesogen, Thermotropic, Mesomorphic.