Smectic Mesophases from Dihydroxy Derivatives of Quaternary Alkylammonium Salts

Long alkyl-chain quaternary ammonium salts bearing two hydroxyethyl groups at the polar head group form smectic A mesophases at high temperatures and ordered smectic T mesophases of tetragonal symmetry at lower temperatures. The latter phase resembles a supermolecular grid (figure); it is formed by a hydrogen-bonding network between the hydroxy groups themselves on the one hand, and between the hydroxy groups and the bromide anions on the other, which is perfectly congruous with the tetragonal packing of the quaternary ammonium groups.