Studies on the liquid crystalline behaviour of novel N-alkyl-substituted ester imides

Abstract

Three new series of N-alkyl-substituted ester imide derivatives, which differ in the polarity of their mesogenic groups; specifically, either cholesteryl, 4′-undecyloxybiphenyl or 4′-cyanobiphenyl, have been synthesized. For the N-alkyl-[4-(cholesteryloxycarbonyl)]phthalimides the chiral nematic N* phase and the monolayer SmA1 phase have been observed up to the dodecyl homologue. The pentadecyl and octadecyl members of this series show only the SmA1 phase. The monolayer smectic A1 phase was also observed for all members of the N-alkyl-4-[(4′-undecyloxybiphenyl-4-yl)oxycarbonyl]phthalimide series while the longer homologues (with n>5) exhibited SmA–SmC dimorphism. In the case of the N-alkyl-4-[(4′-cyanobiphenyl-4-yl)oxycarbonyl]phthalimides, the short homologues exhibited only a nematic phase, while for the butyl homologue in addition to the nematic phase the bilayered SmA2 phase was observed. The smectic phase vanished for the pentyl and hexyl members but reappeared as a partially bilayered smectic Ad phase for the longer homologues.