Lyotropic columnar liquid crystals based on polycatenar 1H-imidazoleamphiphiles and their assembly into bundles at the surface of silicon

Abstract

Polycatenar 1H-imidazole amphiphiles, consisting of a 1H-imidazole head connected through a benzene ring to a trialkyloxyphenyl tail, were synthesized and their self-assembling properties investigated. The ¹H NMR and fluorescence spectroscopy studies showed that in nonpolar solvents, the amphiphiles formed reverse micelles in which the hydrophilic imidazole heads aggregated inside the micelles through intermolecular hydrogen bonding and the nonpolar alkyl chains were located at the periphery of the micelles. In concentrated solutions, they formed lyotropic liquid crystals having columnar hexagonal structures. The molecules were arranged in a disk via hydrogen bonding between successive imidazole moieties. When dilute solutions of the amphiphiles in n-hexane (0.1 wt%) were spin-coated on to a plasma-cleaned Si wafer, a band-like structure with a width of 60–100 nm was imaged by AFM. Microscopic fiber bundles with a diameter as large as 13 µm were observed by SEM when the lyotropic liquid crystals in 30 wt% hexane solution were dried on the glass.