Urea derivative with double long alkyl chains and the corresponding rare-earth metal complex were prepared and their
thermotropic liquid-crystalline behavior was evaluated by differential scanning calorimetry, polarizing optical
microscopy, X-ray diffractometry, electron microscopy. It was found that in spite of the compounds without disk-like
molecular shape, they exhibit a columnar phase with two-dimensional rectangular lattice in which each column is built
up from one-dimensional molecular chains, i.e., non-covalently linked polymer architectures on the basis of one-dimensional
hydrogen bond. In the columnar liquid-crystalline materials, we predicted that delocalization of protons along the one-dimensional self-assembled molecular chains is induced, resulting in useful channels for prototropy. To verify this prediction, we evaluated preliminarily the electric conductivity of the urea
liquid-crystalline thin films by electrochemical impedance spectroscopy. The solid-state films retaining a columnar structure showed a protonic conductivity even under dry conditions.
Photochemically induced nematic (N)-isotropic (I) phase transition behavior and domain formation of the azobenzene/liquid crystal (LC) mixtures in the presence of non-mesogenic dopants were evaluated. When a bent-shaped non-mesogenic molecule was added to the azobenzene LCs, formation of I domains was formed effectively on photoirradiation to cause the trans-cis isomerization of the azobenzene. The domain formation results from the aggregation of cis isomers, which could be enhanced to more extent with the aid of the bent-shaped dopant with a common structural feature to the cis-azobenzene. When the formation of the I domain proceeds quickly upon photoirradiation, the photochemical phase transition is induced more effectively.
Manipulation of light by light as a stimulus by the use of liquid-crystalline materials was explored, which was aimed at optical switching, optical image storage and optical display. Two types of the liquid-crystalline materials are used: nematic liquid crystals and ferroelectric liquid (FLCs). Several kinds of optical switching and image storage systems were demonstrated by means of photochromic molecules and photosensitive LC alignment layer to induce the change in alignment of the LCs: 1) Fast nematic to isotropic phase transition of azobenzene LCs was induced by the laser pulse in two modes of analysis, transmission mode and reflection mode. 2) Optical switching in FLCs doped with the azobenzene was investigated with regard to photochemical flip of polarization of the FLCs. 3) Optical control of polymer- dispersed LC was explored by means of the azobenzene LC. 4) Optical switching and fabrication of nonrubbed alignment layer based on the novel photophysical principle was achieved in terms of photosensitive polyimide as an LC alignment layer. 5) Optical control of conductivity was performed by the use of LC thiophene derivatives.