X-ray characterization of two cubic phases and a structured liquid phase of 4 '-n-alkoxy-3 '-nitrobiphenyl-4-carboxylic acids (ANBC-n)

The cubic D (CubD) and structured liquid (I-1) phases of 4'-n-alkoxy-3'-nit robiphenyl-4-carboxylic acids (ANBC-n, where n is the number of carbons in the alkoxy group) have been investigated by X-ray diffraction techniques. T he type of the CubD phase was identified as Ia3d for the homologues with n= 15, 19, 20, 22, and 26, similarly to those of n=16 and 18. On the basis of the model proposed by Luzzati and Spegt, the diameter (D/Angstrom) and the length (L/Angstrom) of the constituent rod are estimated and discussed. The structure of the I1 phase and its dependence on n are also discussed. For n=26, very surprisingly, another cubic phase with Im3m symmetry was observe d at the lower temperature side of the Ia3d cubic phase on heating.