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

Six chiral compounds belonging to the 1-methylheptyl 4'-(3 "-chloro-4 "-n-a lkoxybenzoyloxy) biphenyl-4-carboxylates have been synthesized. Twist grain boundary A phase was observed in five of the compounds including [R]-[-] a nd [S]-[+] enantiomers of the n-tetradecyloxy derivatives. All these five c ompounds also show smectic A and chiral smectic C phases. The nature of the helical smectic phases has been characterized by using different technique s viz. optical polarized light microscopy, differential scanning calorimetr y, binary mixture studies and helical pitch measurements.