New hexatic liquid phase observed in lyotropic thin films.

An intermediate surface hexatic phase between the liquid and the crystalline phases has been found for the first time in a lyotropic lamellar liquid-crystal system. This phase is highly unusual in that it has long-range sixfold bond-orientational order but liquidlike nearest-neighbor positional correlations, and could represent a significant departure from our current understanding of defect-mediated melting in two dimensions.

Multiple electron diffraction and two-dimensional crystalline order in liquid-crystal thin films.

Electron diffraction in freestanding thin films in the crystal-B phase reveals extensive multiple diffraction in films of 14S5 but not of 4O.8, suggesting an important difference in the structural order in these films despite the similarities in their positional correlations found in earlier experiments. The result in a two-layer 14S5 film indicates surprisingly that secondary diffraction can occur in a crystal with only pseudo-long-range positional order.

Surface phase transitions in free-standing films of nonchiral tilted hexatic liquid crystals.

Surface freezing transitions in free-standing films of achiral Schiff's-base liquid crystals 5O.6 and 7O.7 exhibiting tilted hexatic phases have been studied using optical textures.