  Recently we have observed in compounds of the 4,n-alkyloxybenzoic acid
series, with the homologous index n ranging from 6 to 9, a texture transition
in the nematic range which subdivides the nematic phase in two sub-phases
displaying different textures in polarised light analysis. To investigate a
persistence of texture transitions in nematic phases, we prepared binary
mixtures of 4,6-alkyloxybenzoic acid (6OBAC) with other members (7-,8-,9-,12-,
16OBAC) of its homologous series. Binary mixtures exhibit a broadening in the
temperature ranges of both smectic and nematic phases. A nematic temperature
range of 75 C is observed. In the nematic phase, in spite of the microscopic
disorder introduced by mixing two components, the polarised light optics
analysis of the liquid crystal cells reveals a texture transition. In the case
of the binary mixture of 6OBAC with 12OBAC and with 16OBAC, that is of
compounds with monomers of rather different lengths, the texture transition
temperature is not homogeneous in the cell, probably due to a local variation
in the relative concentrations of compounds.
