Layer-Dependent Surface-Induced Tilt, Hexatic, and Positional Orders in Free-Standing 7O.7 Films

Electron diffraction in free-standing films of 4-n-heptyloxybenzylidene-4-n-heptylaniline of up to 25 molecular layers has revealed the coexistence, as a function of distance from the surface, of three distinct phases: an outermost smectic-I layer, several layers of a middle phase, and a smectic-A interior. The middle phase is a novel tilted liquid, with hexaticlike positional correlations but no long-range bond-orientational order, which transforms to the smectic-I at a lower temperature.