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 A_d phase for the longer homologues.