Thermotropic columnar mesophases of wedge-shaped benzenesulfonic acid mesogens

The synthesis and characterisation are reported of two groups of new amphiphilic sulfonate compounds, 2,3,4-tris(dodecyloxy)benzenesulfonates, 2,3,4-tris(dodecyloxy)benzenesulfonamide and the isomeric 3,4,5-tris(dodecyloxy)benzenesulfonates. As revealed by a combination of thermo-optical microscopy, differential scanning calorimetry and X-ray scattering techniques, the occurrence of mesophases is controlled by the radius of the cation and the symmetry of the molecule. The sulfonates exhibited a rich phase behaviour involving cubic, ordered and disordered columnar mesophases, depending on the counter ion and the type of substitution. It is proposed that the term 'cunitic' molecules should be introduced as a class descriptor for wedge-shaped molecules and their columnar phases.