Liquid crystals from linked discs

In the burgeoning field of organic semiconducting devices, molecules able to self-assemble into columnar liquid crystal phases are being investigated due to the unique directional conductivity of their structures. Knowledge of how molecule-level structural features impact the formation of the larger columnar assemblies is of considerable interest. Studies of liquid crystal phases are already informally divided into shape categories, arising from molecules that are either rod-shaped or disc-shaped. Our interest lay in the middle ground where the basic disc-shape is elongated to a more elliptical one. In pursuit of this goal, a series of rigid dimers were prepared by condensation of 3,3’-diaminobenzidine with various 2,3,6,7-tetralkyloxyphenanthrene-9,10-diones. Investigation revealed that these dimers assemble into a number of unusual phases, including nematic and columnar oblique mesophases. In addition, a series of monomeric amide derivatives were synthesized by amidation of 2,3,6,7-Tetrakis(heptyloxy)dibenzo[a,c]phenazine-11-carboxylic acid. These molecules were found to spontaneously align in a homeotropic manner. They also supercooled into persistent glassy phases that preserved their alignment.