Twist grain boundary A phase in [R]-[-]-1-methyl-heptyl 4'-(3''-chloro-4''-n-alkoxybenzoyloxy) biphenyl-4-carboxylates

Abstract

Six chiral compounds belonging to the l-methylheptyl 4'-(3''-chloro-4''-n- alkoxybenzoyloxy) biphenyl-4-carboxylates have been synthesized. Twist grain boundary A phase was observed in five of the compounds including [R]-[-] and [S]-[+] enantiomers of the n-tetradecyloxy derivatives. All these five compounds also show smectic A and chiral smectic C phases. The nature of the helical smectic phases has been characterized by using different techniques viz. optical polarized light microscopy, differential scanning calorimetry, binary mixture studies and helical pitch measurements.