Thermotropic liquid crystals of 1 H-imidazole amphiphiles showing hexagonal columnar and micellar cubic phases

Abstract

The linear and polycatenar type 1 H-imidazole amphiphiles showing a strong self-assembly tendency to build various supramolecular structures in bulk were synthesized by the esterification reaction of 4′-alkyloxy phenols (for 1– 4) and hydroxyphenyl trialkyloxybenzoates (for 5– 7) with 4-chlorocarbonyl imidazole. The linear 1 H-imidazole amphiphiles formed thermotropic smectic phases, but compound 4 with an ethyl group instead of hydrogen on 1 N did not show a mesophase. The polycatenar type 1 H-imidazole amphiphiles ( 5– 7) formed thermotropic hexagonal columnar and cubic phases. A phase transition was observed from a columnar phase to a cubic phase as the temperature increased on heating, and vice versa on cooling. In the POM study for compounds 5– 7, optically isotropic phases first appeared on cooling from the isotropic melts, and then birefringent mesophases with a nonspecific texture appeared on further cooling. The X-ray analysis shows that the optically isotropic phases were very likely micellar cubic phases with Pm3 n symmetry. The birefringent phases were confirmed as hexagonal columnar phases.