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A series of amphotropic bis[w-[4(4'-cyanobiphenylyl)oxy] alkyl] dimethylammonium bromides with alkyl spacers of 6-12 methylene units were synthesized. All these new compounds show monotropic liquidcrystalline behavior. UV absorption maxima of vesicles of these compounds are strongly blue shifted relative to the monomer absorption. Upon increasing the temperature the "monomern absorption reappears. Differential scanning calorimetry measurements clearly show a phase transition. This phase behavior is associated with a transition from a "stacked" gel phase to a more mobile liquid-crystalline phase of the vesicle bilayers. Upon spreading these molecules at the water-air interface of a Langmuir-Blodgett trough, an unusually high lift-off area of about 200-250 A2/molecule is observed in the surface pressure-area isotherms. This is associated with a situation in which the molecules are completely stretched on the surface. When the available area is reduced to about 40 AZ/molecule, a situation is obtained in which the tails in a close-packed crystallike arrangement.

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Two novel polymerizable double-chained ammonium amphiphiles carrying mesogenic cyanobiphenylyloxy units have been synthesized containing methacrylate in the headgroup or diacetylene groups in the hydrophobic tails. These compounds form bilayer vesicles upon dispersion in water. Polymerization increases the vesicle stability toward solubilization by a nonionic surfactant. The stacking of the cyanobiphenylyloxy units in the bilayer is directly monitored by the extent of the blue shift of the absorption maximum. Upon polymerization a decrease in blue shift is observed, reflecting a decrease in the ordering of the amphiphile molecules. This effect is stronger when polymerization occurs in the hydrophobic tails than in the headgroup region.

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