Formation of columnar mesophases by rodlike molecules

Novel amphotropic liquid crystals have been synthesized and their thermotropic and lyotropic phase behaviour was investigated by polarizing microscopy? and X-ray scattering. These compounds are biphenyl derivatives with a terminally attached hydrophilic 1,2-diol group and 4,4 "-didecyloxyterphenyl derivatives with a laterally attached diol group. The diol groups are separated from the rigid cores by means of polyether chains of different length. In dependence of the length of these polyether chains smectic and columnar mesophases have been found. The columnar mesophases may be regarded as ribbon phases resulting Born the collapse of a smectic layer structure into band-like segments. Columnar phases were also found in binary mixtures consist;ng of conventional amphiphiles and bolaamphiphiles as intermediate phases between the smectic double layer and the smectic single layer phase. We can conclude, that the formation of columnar mesophase by rod-like molecules is a more general phenomenon which occurs if strong intermolecular interactions force the molecules to arrange in layers and simultaneously the molecular architecture is not compatible with a smectic layer structure due to steric repulsion or unfavorable dipolar interactions.