The Synthesis, Mesomorphism, and Characterization by X-ray Diffraction and Freeze-Fracture Electron Microscopy of Polycatenar Liquid Crystals of Silver(I) Showing Columnar and Cubic Mesophases

Complexation of 3,4-dialkoxystilbazoles to Ag I has led to a new series of polycatenar, metal-containing liquid crystals. The complexes were found to show mainly cubic and columnar mesophases, although short-chain homologues showed a different behavior due to a dissociation of one ligand in the melt. On cooling from the mesophase, some of the complexes formed a glassy state, rather than crystallizing. The mesophases were characterized by a combination of optical microscopy, differential scanning calorimetry, X-ray diffraction and freeze-fracture electron microscopy. Freeze-fracture electron microscopy was successful in identifying the symmetry of the cubic phase as Ia 3̄ d, while the transition between the cubic and columnar phase was studied by a combination of X-ray diffraction and dilatometry, allowing the proposal of a model for the transition between these two phases using their observed epitaxial relationship and requiring undulation of the columnar phase as proposed previously for lyotropic mesophases.