Our research program ranges from molecular design and synthesis of highly photofunctional and high-performance polymer materials to fabrication of optical devices for holographic, photomechanical, and micro-optical applications, by taking advantage of the distinct photosensitivity of the polymers. We focus on fundamental understanding of the interaction between light and polymer materials from the viewpoint of innovative photonic applications, and create photofunctional polymer materials with precisely controlled molecular alignment.

１. Photomobile Smart Materials Based on Crosslinked Azobenzene Liquid-Crystalline Polymers

Photomobile smart materials that can undergo a shape or volume change in response to light have attracted much attention. Recently, we have successfully achieved photoinduced bending by using crosslinked azobenzene liquid-crystalline polymer films with alignment of azobenzene mesogens either in a whole area (monodomain film) or in a small domain (polydomain film). Depending on the manner of alignment of mesogens, the bending behavior can be controlled: bending along the alignment direction of mesogens in the monodomain films or bending along the polarization direction of linearly polarized actinic light in the polydomain films. Various modes of photoinduced motion such as expansion, contraction, bending and rotation are now being investigated. These materials enable us to convert light energy directly to mechanical energy, which leads to such applications as micromechanical machines and all-plastic motors.

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2. Liquid-Crystalline Polymer Materials for Holographic Applications

Hologram are expected as one of high-density optical data storage devices in the next generation. In holograms, materials in which refractive index is efficiently induced by writing beams are required. For twenty years, we have investigated photoinduced changes in the molecular alignment such as photochemical phase transition and molecular realignment, with a series of azobenzene liquid-crystalline polymers. As a result, we have found that the rapid (<200 ns) and large changes in refractive index were induced by cooperative molecular motion in the liquid-crystalline polymers. Recently, holograms with 55 angular multiplicities have been achieved. Towards high-performance holograms, we have synthesized novel liquid-crystalline polymers with exceptionally high birefringence (>0.7) and block copolymers with a photocontrollable nano-cylinder structure.

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3. Novel Polarization-Selective Liquid-Crystalline Materials

Various optical devices with polarization selectivity have been of great interest. We have designed and synthesized electroluminescent polymers, which emit linearly polarized light by controlling their macroscopic molecular alignment. Microlens arrays with polarization selectivity have also been fabricated by combination of photophysically induced molecular alignment of liquid-crystalline monomers and their simultaneous photopolymerization.