| POLYMERS Vol.61 No.10 |
| >> Japanese | >> English |
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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| Copyright(C) 2012 The Society of Polymer Science, Japan All Rights Reserved. |