Thermotropic columnar mesophases from N-H•••O, and N•••H-O hydrogen bond supramolecular mesogenes

The structures of supramolecular columnar mesophases that depend on the presence of either >N-H...O=, or >N...H-O-hydrogen bonds (subsumed under the term 'N\H\O-bonds') are reviewed. The thesis is supported that supramolecular mesogenes bridge different fields of liquid crystal research, offering the opportunity to create a unified picture of thermotropic, and lyotropic mesomorphism. With the examples of N\H\O hydrogen bond mesogenes the molecular structures of the respective mesogenes are presented, and general principles to rationally construct such molecules are discussed. A connection is drawn to systems from isolated columns as found in low molecular weight organogels. Perspectives, and outlooks for possible applications of N\H\O hydrogen bonded columnar phases are given. (C) 2003 Elsevier Science Ltd. All rights reserved.