Morphology, surface-induced orientational properties and phase transition peculiarities of lyotropic nematic mesophases in pentadecane solutions of tetranuclear platinum mesogens

We have investigated the surface-induced orientational properties and peculiarities of the phase transitions of a lyotropic system, composed of a sheet-shaped tetranuclear platinum organyl in pentadecane, and exhibiting two different lyotropic nematic mesophases (N1 and N2). Corrugated YBa2Cu3O7−x surfaces with a sinusoidal profile have been used to induce planar orientation of these two nematic lyomesophases, which differ significantly with their orientational behavior. We have also measured the birefringence of these nematic mesophases. Based on high-accuracy determinations of the transition temperatures, we are discussing some peculiarities of the phase transitions between the two nematic mesophases and between N2 mesophase and isotropic liquid, in particular, the width of the heterophase regions between them.