Optical microscopy and deuterium N.M.R. of non-ionic amphiphiles which exhibit thermotropic and aqueous lyotropic mesophases

Abstract

Abstract Tetrabenzocyclododecatetraene (I) substituted with eight methoxy-mono-, di-, and triethyleneoxide side chains exhibit the same highly ordered thermotropic mesophase, M. In the methoxydiethyleneoxide (I-2), and methoxytriethyleneoxide (I-3) derivatives this mesophase is also lyotropic and can sustain (at room temperature) up to 40 wt per cent water. The homologue (I-2) exhibits at higher water content another lyomesophase, MF , which is more fluid and nematic-like. Optical microscopy, differential scanning calorimetry and deuterium N.M.R. of both labelled (I-2) and water as well as of the water 17O were used to construct the (I-2)-water phase diagram and to characterize the various mesophases. It is found that both M and MF are uniaxial with negative birefringence and negative anisotropic magnetic susceptibility. The MF phase readily aligns in a magnetic field and is characterized by fast (∼ 107 s−1) reorientation of the mesogen molecules about the director. The M phase is apparently columnar, hig...