Synthesis and Study of Mesogenic Material Through Homologous Series: n-pentyl-p-(p/-n-alkoxy cinnamoyloxy) Cinnamates

Patel R.B.; Doshi A. V.

Abstract

Synthesis and Study of Mesogenic Material Through Homologous Series: n-pentyl-p-(p/-n-alkoxy cinnamoyloxy) Cinnamates

Author(s): Patel R.B. and Doshi A. V.*

The titled new homologous series of twelve mesogens is synthesized by usual established method with, a view to understand and establish the relation between mesogenic properties of the substances and their molecular structure. Methyl to butyl derivatives of the homologous series are nonmesogenic, while pentyl, hexyl, octyl, decyl, dodecyl, tetradecyl and hexadecyl derivatives are enantiotropically mesogenic in character. Pentyl, tetradecyl, hexadecyl derivatives are nematogenic only, while, hexyl to dodecyl derivatives are polymesomorphic i.e. smectic and nematic, both mesophases are exhibited enantiotropically by hexyl to dodecyl homologues. Transitions and melting temperatures of homologues are determined by the polarizing microscope with heating stage. Transition temperatures are plotted versus number of carbon atoms in n-alkyl chain of left n- alkoxy terminal end group. A phase diagram is obtained by joining like points. Solid–mesomorphic or solid–isotropic transition curve initially follows zigzag path of rising and falling upto butyl homologue and then falls gradually upto decyl homologue and again rises steeply to a hexadecyl homologue in a rounded shape from decyl to hexadecyl derivative of the series. Smectic–nematic transition curve, behaves in normal manner and merges solid–mesomorphic / isotropic transition curve at the tetradecyl derivative of homologue, with showing up of odd-even effect. Nematic-isotropic transition curve wonderfully show rising tendency as series is ascended with alternation of transition temperatures, showing odd-even effect. Texture of nematic mesophase is of threaded type and that of smectic mesophase is focal conic fan shaped of the type-A. Analytical data support the structure of the molecules.

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