POLYMERS　Vol.64　No.4
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COVER STORY
Magical Polymers with Photo-Functional Properties
COVER STORY: Highlight Reviews
Future Prospect of Artificial Photosynthesis as an Ideal System for Chemical Conversion of Sun Light Energy Haruo INOUE
<Abstract> Mankind has been faced with many serious issues to be resolved in the present global situation for energy and environment. Sun light energy in ca. ten thousand times larger amount than it consumed by mankind should be a most promising source of energy in future. State of the art and the future prospect of artificial photosynthesis is here reviewed.
Keywords: Photosynthesis / Artificial Photosynthesis / Chemical Conversion of Sun Light Energy / Solar Fuel / Solar Energy Conversion / Photocatalysis
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Advanced Polymeric Materials Based on Interaction with Photons Toshihiko NAGAMURA
<Abstract> Recent advances on polymeric and organic materials are reviewed from viewpoints of photoresponses and change or control of optical properties by various stimuli. The former includes photonic upconversion with noncoherent light based on tripet-triplet annihilation, ultrafast photoinduced electrochromism for all-optical signal processing in the optical telecommunication wavelength region, real-time holographic display by fast photochromism and photorefractive effects, optical polarization switching in chiral photomagnet, photoinduced changes in macroscopic shapes for future photo-driven motors, and photochemically reversible liquefaction and solidification. The latter includes a thermochromic coordination polymer with high thermal stabililty for temperature sensitive paints, high-performance electro-optic polymer modulators superior to conventional inorganic crystals, various chemical- and bio-sensing properties based on amplified fluorescence quenching or color changes in polymeric photonic crystals, mechanochromism due to stress-induced ring-opening, polymer chain dissociation, or changes in aggregation. Highly ordered photonic crystal films of block copolymers recently commercialized as notch filters for Raman spectroscopy are also shown. Efforts to fully utilize many useful properties of light are further expected.
Keywords: Advanced Polymer Materials / Responses to Photons and Various Stimuli
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Organic Molecular Materials with Photomechanical Functions Hideyuki NAKANO
<Abstract> Recently, studies of photomechanical functions of organic photochromic materials have attracted a great deal of attentions. For example, reversible shape change of microcrystals of diarylethene-based materials, bending motions of azobenene-based liquid crystalline polymer films, surface relief grating formation for azobenzene-based amorphous polymer films have been reported. In addition, the movement of the fragments of molecular glasses of azobenzene-based amorphous molecular materials has been achieved by angled irradiation from their bottom.
Keywords: Photochromism / Photomechanical Function / Photoinduced Mass Transport / Microcrystal / Liquid Crystal / Amorphous Film / Diarylethene / Azobenzene
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COVER STORY: Topics and Products
Magneto-Optical Property of Lantanide Cluster with Ln-O Lattice Structure Takayuki NAKANISHI, Yasuchika HASEGAWA
<Abstract> Lanthanide(Ln)-complexes with organic ligands have attracted much interest for optical, electronic and magnetic applications. In particular, poly-nuclear lanthanide complexes with a Ln-O inorganic lattice have been reported to show characteristic chemical and physical properties such as catalytic reactions, acting as single-molecular magnets, and photo-sensitized luminescence. The molecular design and synthesis of poly-nuclear lanthanide complexes is expected to open up a new field of advanced molecular science.
In this article, we describe the magneto-optical properties of novel terbium nona-nuclear complexes with a sandglass shaped Tb-O lattice structure. Effective Faraday rotation was observed in nona-nuclear terbium complexes in the visible region for the first time.
Keywords: Lanthanide Cluster / Faraday Effect
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Molecular Domino with Emission Color Change upon Applying Mechanical Stimulus Tomohiro SEKI, Hajime ITO
<Abstract> Aryl gold isocyanide complexes exhibit interesting phase transition behaviors and photoluminescence properties in the solid state. During the course of our investigation on luminescent mechanochromism, we found that some aryl gold isocyanide complexes show mechanical force-induced single-crystal-to-single-crystal phase transition. This can be called “molecular domino” because even a small mechanical stimulus on a local area of the crystal can trigger the structure change of the entire crystal. This spontaneous molecular rearrangement proceeds in a single-crystal-to-single-crystal fashion with a dramatic emission color change. These features enable sub-molecular-level structure investigation with single crystal X-ray diffraction analyses and visual observation of the phase transition under UV light irradiation. This type of stimuli-responsive materials will provide us with deep understanding of their structure-property relationships.
Keywords: Mechanochromism / Photoluminescence / Molecular Domino / Gold Complex / Phase Transition
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Photochromism that Plays an Important Role in Information Transmission Kenji MATSUDA
<Abstract> Photochromic compounds change their molecular structure along with the photoinduced color change. Therefore, this category of compounds can be used as a switching unit in molecular electronics and molecular spintronics. Based on the topological change of π-system between diarylethene open- and closed-ring isomers, we have developed a switching system for magnetic exchange interaction and molecular conductance. To control molecular alignment at the surface or the interface by self-assembly is very important. We have developed systems which show photoswitching of a chiral structure and lower critical solution temperature using amphiphilic photochromic diarylethene derivatives.
Self-assembly at solid/liquid interface can be studied by STM. A diarylethene-pyrene-diarylethene triad showed photoinduced two-dimensional ordering change at a liquid/solid interface upon in situ photoirradiation. An open-ring isomer of a 2-thienyl-type diarylethene having an amide group showed abrupt increase of surface coverage at certain concentration. This abrupt increase can be explained by the cooperative model. A highly-sensitive system achieved by highly-cooperative system is an interesting topic.
Keywords: Photochromism / Molecular Electronics / Molecular Spintronics / Diarylethene / STM / Self-Assembly / Cooperativity
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Polymer Science and I: A Personal Account
Experiments are My Inspiration ! Yasuhiro KOHSAKA
<Abstract> No matter how great the idea is, no success comes without an experiment. Although the time of difficulty occupies most of my memories, I have made many experiments so as to make an exciting discovery. Now, at the start of my new laboratory, I remind myself about the importance of experiments again.
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Front-Line Polymer Science
Hydration of Polymeric Materials Toshiyuki SHIKATA
<Abstract> Hydration behavior is essential information for the discussion of physicochemical characteristics of polymeric materials in aqueous solution. In addition to a classical acoustic method, dielectric spectroscopic experiments over an extremely high frequency range beyond the relaxation frequency of water molecules, and depolarized Raman scattering measurements in an extremely low frequency range have been useful techniques to determine hydration numbers of solute molecules recently. Since these techniques also provide information about how long hydrated water molecules stay in their sites, i.e. hydration lifetime, more detailed consideration of hydration behavior has been developed in aqueous systems.
Keywords: Hydration Number / Acoustic Method / Dielectric Spectroscopy / Depolarized Raman Scattering / Hydration Lifetime
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