The Synthesis and Liquid Crystal Properties of Some Laterally Fluorinated trans-Cyclohexane-1-carboxylate and Benzoate Esters

Abstract

A large number of laterally fluorinated 4-n-alkyl- and -alkoxy-phenyl 4'-n-alkyl- and -alkoxy-benzoates and 4-n-alkylphenyl trans-4'-n-alkyl- and -alkoxy-cyclohexane-1-carboxylates were synthesised. In these compounds, the lateral fluoro-substituent was situated in either the phenol or the carboxylic acid moiety of the molecules for the benzoate esters, but only in the phenol moeity for the trans-cyclohexane-1-carboxylate esters. The nematic thermal stabilities for the fluorophenyl benzoate and trans-cyclohexane-1-carboxylate esters and the fiuorobenzoate esters were compared with those for the corresponding non-fluorinated analogues. A nematic thermal efficiency order was derived for the 4-n-alkyl-fluorophenyl 4-n-alkylbenzoate and trans4-n-alkylcyclohexane-1-carboxylate esters, but only in the case of the latter esters, which were extensively examined, was the smectic tendency of the system investigated.

Explanations are given for the observed nematic and smectic thermal stabilities of the titled esters, and some of their physical properties are discussed.