Amphitropic liquid crystals. Two lamellar phases in a surfactant containing thermotropic and lyotropic mesogenic groups

The lyotropic liq.-cryst. behavior of cationic surfactants contg. a potentially thermotropic moiety, a terminal cyanobiphenyloxy group, was studied. Both mono-alkyl and mid-chain substituted dialkyl surfactants were examd. using optical microscopy and NMR spectroscopy. Incorporation of the cyanobiphenyloxy group destabilizes the hexagonal and bicontinuous cubic phases, with only an extensive lamellar region being obsd. For the dialkyl surfactant there is a range of compns. where 2 lamellar phases coexist, one water-rich and the second surfactant-rich.