Liquid Crystalline Properties of Dissymmetric Molecules Part 5: the Effects of Alkyl Chain Length and Linkages on Thermal Properties of Smectic A and C Phases in Three Aromatic Ring Systems

Abstract

This paper describes the effect of alkyl and alkoxy chain lengths on the thermal properties of four isomeric systems; 4-R-phenyl 4-(4-octyloxybenzoyloxy)benzoates ( 1 ), 4-octyloxyphenyl 4-(4-R-benzoyloxy)benzoates ( 2 ), 4-(4-R-benzoyloxy)phenyl 4-octyloxybenzoates ( 3 ), and 4-R-phenyl 4-octyloxyphenyl terephthalates ( 4 ) (R=alkoxy, alkyl). The smectic properties for 1 and 2 are fairly different when both terminal alkyl and alkoxyl groups are short, while both have the same liquid crystalline core. The homologs of 3 exhibit only a smectic C phase even in the higher homologs. The homologs of 4 preferentially exhibit smectic A and C phases from the earlier homologs. The difference in the smectic properties will be discussed in terms of their molecular characteristics.

Key Words:

• liquid crystals
• ester compounds
• thermal properties
• smectic properties
• chain length effect