POLYMERS Vol.61 No.10
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COVER STORY
Chirality in the Macromolecules
COVER STORY: Topics and Products
Emergence of Chirality Induced by Vortex Mixing Takashi YAMASHITA, Kunihiko OKANO
<Abstract> Chirality of biopolymers is the fundamental feature of their higher structure formation, which is the origin of homochirality. How was homochirality established after the birth of the universe 14 billion years ago? There have been many explanations for homochirality such as the reaction induced by circular dichroic light, rotation of universe, and so on. Recently we have found vortex mixing of polymer solution induces chirality, which has been proven by extracting pure CD signal measuring muller matrix of the stirring solution. The induced chirality can be successfully transferred to a guest molecule, which is added in the polymer solution. With fluorescent dye as the guest molecule, circular dichroic emission is observed after vortex mixing of the polymer solution. Thus macroscopic rotation is proved as the one of the chiral inducing forces and can be converted to the chirality of the guest molecules or emission of light. Those phenomena are expected to be used as novel techniques in asymmetric synthesis and clues to the mystery of the origin of life.
Keywords: Vortex Mixing / Polymer Solution / Stir-Induced Chirality / Supramolecular Interaction / Circularly Polarized Emission / Homochirality
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Light Creates Polymer Helicity Tamaki NAKANO
<Abstract> A preferred-handed helical conformation was reversibly induced to poly(9,9-dioctylfluoren-2,7-diyl) in a thin film form upon irradiation by single-handed circularly polarized light. The induction mechanism is proposed to be based on a photo resolution process including a predominant excitation of right- or left-handed twist conformation in the ground state into an achiral coplanar form in excited states. The coplanar form is deactivated into right- and left-handed forms, resulting in enrichment of one twist form with less likelihood of excitation by the single-handed CPL than the antipode. Deactivation may tend to form a twist of which handedness is the same as single-handed twists in the vicinity that have been formed previously in earlier excitation-deactivation events. This effect should be more obvious when the difference in the populations of P- and M-twists is larger, bringing about an apparent amplification. This is the first example of helix chirality induction to a main-chain conjugated polymer using CPL.
Keywords: Chirality / Helix / Circularly Polarized Light / Photo Resolution Process / Twist / Copolanar / Main-Chain Conjugated Polymer / Amplification
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Chiral Mesoporous Materials Toshiyuki YOKOI, Takashi TATSUMI
<Abstract> Recently the use of a chiral anionic surfactant derived from amino acid, N-myristoyl-L-alanine sodium salt, has enabled us to obtain a chiral mesoporous silica (CMS). CMS has a twisted hexagonal rod-like morphology with hexagonally well-ordered mesopores. The predominant handedness of helices is directed by the handedness of the surfactants. CMS can be applied to the enantioselective separation of racemic solutions; the helical rod-shaped CMS is found to be effective for asymmetric separation of racemic N-trifluoroacetylalanine ethyl ester. Furthermore. The preparation of chiral periodic mesoporous organosilica with helicity perfectly controlled has been first achieved by using the chiral anionic surfactant and 1,2-bis(triethoxysilyl)ethylene in the presence of L-arginine. The success of chiral mesoporous silica could lead to new uses of mesoporous silica and other chiral pore materials for catalysis and separation media, in which both shape selectivity and enantio-selectivity have potential applications in the manufacturing of enantiomerically pure chemicals and pharmaceuticals.
Keywords: Chiral Mesoporous Silica / Anionic Surfactant / Chiral Mesopores / Amino Acid
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Asymmetric Polymerizations in Liquid Crystals Hiromasa GOTO
<Abstract> Asymmetric electrochemical polymerizations in chiral liquid crystals with electrochemical methods and chemical methods by using catalysts were developed by the author. These methods are referred to as liquid crystal electro-asymmetric polymerization and liquid crystal solvent asymmetric
polymerization. Background of the research, technical points of the present methods, and future perspective are reported.
Keywords: Liquid Crystals / Electrochemical Polymerization / Polycondensation / Helical Strucure / Chiral Aggregarion
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Stereo-Selective Synthesis and Chemical Reforming of A Chiral Biopolymer, Poly-γ-Glutamate Makoto ASHIUCHI
<Abstract> Poly-γ-glutamate (PGA) is a chiral polyamide material that possesses a chemically synthesized nylon-like backbone. The stereo-selective synthesis of PGA has been achieved using microbial chemistry. Nowadays a stereo-regular PGA, namely L-PGA, is commercially available. We further succeeded in synthesizing useful PGA-based poly-ion-complex materials (PGAIC). Hereafter, novel bio-thermoplastics and bio-nanofibers could be developed from PGAIC. An epoch-making technique for PGA-reforming, which creates a high-performance bio-gel material from PGAIC, was established as well.
Keywords: Poly-γ-Glutamate / Chiral Polyamide / Stereo-Selective Synthesis / Microbial Chemistry / Thermoplastics / Nanofibers / High-Performance Gels / Chemical Reforming
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Circulary Polarized Luminescent Quantum Dot Prepared in Protein Cage Masanobu NAITO
<Abstract> Semiconductor quantum dots (QD)s have attracted a great deal of attention because of their optically tunable light emissions, which are derived from the quantum confinement effect. Unlike bulk materials, QDs utilizing these unique optical properties have a wide range of potential applications, especially in light emitting devices, sensory materials, and bioassays. In this work, we first demonstrated that a water-soluble CdS-QD prepared in ferritin (CdS@ferritin) exhibits significant left-handed CPL emissions from direct transition and surface-trapping sites of the CdS-QDs. Furthermore, wavelengths of the photoluminescence (PL) / CPL were modulated by laser photoetching.
Keywords: Circularly Polarized Luminescence / Biomineralization / Ferritin / Quantum Dot / Nano Particle / Composite Semiconductor
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Generalized High-Accuracy Universal Polarimeter (G-HAUP) and Its Application Toru ASAHI, Masahito TANAKA
<Abstract> The generalized high-accuracy universal polarimeter (G-HAUP) is the optical apparatus to enable us to make simultaneous measurements of linear birefringence (LB), linear dichroism (LD), circular birefringence (CB), and circular dichroism (CD) for solid materials. The G-HAUP has been applied to observe anisotropic and chiroptical properties of an intercalated dye (cationic azobenzene derivative) compound into K4Nb6O17 crystals. Kramers-Kronig relationships between the observed CB and CD spectra as well as in the case of LB and LD indicate that LB, LD, CB, CD spectra are successfully obtained by the G-HAUP method. The strong LD and CD peaks have originate respectively from the preferred orientation and induced chirality of the dyes that are intercalated into K4Nb6O17 crystal.
Keywords: Generalized High Accuracy Universal Polarimeter / G-HAUP / Circular Birefringence / Linear Birefringence / Circular Dichroism / Linear Dichroism / Intercalated Compound / K4Nb6O17
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Exciton Chirality Method in Vibrational Circular Dichroism Kenji MONDE
<Abstract> The use of VCD technique based on ab initio theoretical calculation has been hampered by the low sensitivity of vibrational absorption and by the computational demand. In exploration of a more universal, sensitive method to determine molecular stereostructure, we found a new approach that requires only the observation of a strong VCD couplet originating from the interaction of two IR chromophores. The interaction of two IR chromophores yields a strong vibrational circular dichroism couplet whose sign reflects the absolute configuration of the molecule. This review describes a method to determine absolute configuration of a chiral molecule based on this couplet without need of theoretical calculation. Not only can this method analyze various molecules whose absolute configuration is difficult to determine by other spectroscopic methods, but also it can significantly enhance VCD signals. This method is the first VCD nonempirical method to determine absolute configuration without calculation.
Keywords: VCD / Vibrational Circular Dichroism / Couplet / Bisignate / Absolute Configuration
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Magneto-Chiral Dichroism of Organic Compounds Kazuyuki ISHII, Yuichi KITAGAWA
<Abstract> By using porphyrin J-aggregates, the magneto-chiral dichroism of organic compounds was observed for the first time, which is important for studying the contribution of MChD towards the homochirality of life.
Keywords: Magneto-Chiral Dichroism / Homochirality / Porphyrin / Aggregates
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Enantiomer Separation with Ice as a Functional Material-Chiral Ice Chromatography Tetsuo OKADA
<Abstract> We have devised ice chromatography, in which ice particles are used as the liquid chromatographic stationary phase. This method has allowed separation of various solutes through the hydrogen bond formation between the polar groups in a solute molecule and the OH dangling bonds on the ice surfaces. When an appropriate dopant is incorporated in the ice stationary phase, a liquid phase emerges, to which a solute is partitioned. The entire retention of the solute is determined both by the adsorption on the ice surface and by the partitioning to the liquid phase in such cases. When a chiral selector is added to the ice stationary phase together with a salt as an auxiliary dopant, chiral recognition occurs in the liquid phase rather than the surface of the ice stationary phase. This scheme has been successfully applied to chiral ice chromatographic separation with cyclodextrin as a chiral selector.
Keywords: Ice / Chiral Separation / Chromatography / Liquid Phase Coexisten with Ice / Cyclodextrin
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Polymer Science and I: A Personal Account
Research of a Principle Hidden in Polymer Processing Hideyuki UEMATSU
<Abstract> It is not easy to understand the principle in polymer processing although a polymer is changed to a product by a simple process. Research of a principle hidden in polymer processing is one of my passions.
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Front-Line Polymer Science
Dilute Solution Properties of Self-Assembled Molecules Kazuo SAKURAI
<Abstract> Characterizing self-assembled molecules in solutions is a rather open field since traditional techniques for polymers in dilute solutions are difficult to use for aggregates. By combining synchrotron small angle X-ray scattering and light scattering coupled with field flow fractionation, it becomes possible to look at their inner structures. The present report briefly reviews our recent studies on polymer micelles and a shape persistent calixarene micelle.
Keywords: Self-Assembly / Scattering / SAXS / FFF/MALS / Micelle
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