The Experts below are selected from a list of 1698 Experts worldwide ranked by ideXlab platform
Takashi Harayama - One of the best experts on this subject based on the ideXlab platform.
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Regioselectivity of the intramolecular biaryl coupling reaction of 3-substituted Phenyl 2-iodoBenzoate using a palladium reagent
HETEROCYCLES, 2014Co-Authors: Hitoshi Abe, Takashi Harayama, Yasuo Takeuchi, Kazuhiro Maeda, Takuya Matsukihira, Shumpei Saga, Yoshikazu HorinoAbstract:This study investigated the regioselectivity of the intramolecular coupling reaction of the Phenyl Benzoate derivative which possesses a methyl or methoxy group at the meta-position of the phenoxy moiety. The type of base and the presence/absence of the phosphine ligand influenced the product ratio. A transition state model and the regioselectivity of the reaction are discussed
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synthesis of highly oxygenated biPhenyl derivative in an optically active form through palladium mediated intramolecular biaryl coupling reaction
Heterocycles, 2008Co-Authors: Hitoshi Abe, Yasuo Takeuchi, Masatsugu Arai, Keisuke Nishioka, Tatsuya Kida, Kazuma Shioe, Takashi HarayamaAbstract:Optically active 6,6'-dihydroxymethyl-2,2'-3,3'-4,4'-hexamethoxybiPhenyl (1) was prepared via the Pd-mediated biaryl coupling reaction of a Phenyl Benzoate derivative and the following enantioselective lactone opening reaction.
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synthesis of alternariol through an intramolecular biaryl coupling reaction using palladium reagent
Heterocycles, 2007Co-Authors: Hitoshi Abe, Yasuo Takeuchi, Tomoko Fukumoto, Takashi HarayamaAbstract:The facile synthesis of altemariol was accomplished through an intramolecular biaryl coupling reaction of the Phenyl Benzoate derivative, which was prepared by the simple esterification of the corresponding phenol and benzoic acid using a palladium reagent. The regioselectivity during the biaryl coupling reaction was also investigated.
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intramolecular biaryl coupling reaction of benzyl Benzoate and Phenyl Benzoate derivatives and its application to the formal synthesis of steganone
Tetrahedron, 2007Co-Authors: Shigemitsu Takeda, Yasuo Takeuchi, Takashi HarayamaAbstract:Abstract Construction of the biaryl moiety of stegane and related compounds through an intramolecular biaryl coupling reaction is described. Undesired products were obtained by the intramolecular coupling reaction of benzyl Benzoates ( 8 , 13 , and 14 ) because of their steric and electrostatic properties, and only that of Phenyl Benzoates ( 26b and 26c ) afforded the desired biaryl lactones in good yields. An asymmetric formal synthesis of the title compound has been achieved using an enantioselective lactone-opening reaction followed by a four-step conversion to the known compound.
Mizuho Kondo - One of the best experts on this subject based on the ideXlab platform.
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photoinduced reorientation of a liquid crystalline polymer with Phenyl Benzoate mesogenic side groups on the basis of an axis selective photo fries rearrangement
Macromolecules, 2012Co-Authors: Nobuhiro Kawatsuki, Mami Kurita, Hitomi Matsushita, Teppei Washio, Mizuho KondoAbstract:Many types of photoreactive polymers have been investigated to regulate their molecularly orientated structures for polarization-controlled optical and display applications. Herein, we demonstrate the axis-selective photoreaction of thin films and their molecular reorientation behaviors using four types liquid crystalline poly(meth)acrylates with Phenyl Benzoate side groups and linearly polarized (LP) 248 nm light. These simple liquid crystalline polymers (LCPs) exhibit sufficient photoinduced molecular reorientations. Photoinduced molecular reorientation based on an axis-selective photo-Fries rearrangement is simultaneously generated with an in-plane order parameter (S) up to 0.33 when the irradiation temperature is in the lower part of the LC temperature range of the material, but multidomain formation of the mesogenic groups inhibits reorientation. To prevent thermally generated multidomain formation, an axis-selective photoreaction of an amorphous film followed by thermally generated self-organization...
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Photoinduced Reorientation of a Liquid Crystalline Polymer with Phenyl Benzoate Mesogenic Side Groups on the Basis of an Axis-Selective Photo-Fries Rearrangement
2012Co-Authors: Nobuhiro Kawatsuki, Mami Kurita, Hitomi Matsushita, Teppei Washio, Mizuho KondoAbstract:Many types of photoreactive polymers have been investigated to regulate their molecularly orientated structures for polarization-controlled optical and display applications. Herein, we demonstrate the axis-selective photoreaction of thin films and their molecular reorientation behaviors using four types liquid crystalline poly(meth)acrylates with Phenyl Benzoate side groups and linearly polarized (LP) 248 nm light. These simple liquid crystalline polymers (LCPs) exhibit sufficient photoinduced molecular reorientations. Photoinduced molecular reorientation based on an axis-selective photo-Fries rearrangement is simultaneously generated with an in-plane order parameter (S) up to 0.33 when the irradiation temperature is in the lower part of the LC temperature range of the material, but multidomain formation of the mesogenic groups inhibits reorientation. To prevent thermally generated multidomain formation, an axis-selective photoreaction of an amorphous film followed by thermally generated self-organization processes effectively induce molecular reorientation with S up to 0.71 and birefringence (Δn) ∼ 0.16
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axis selective photo fries rearrangement and photoinduced molecular reorientation in liquid crystalline polymer films
Macromolecules, 2011Co-Authors: Nobuhiro Kawatsuki, Takuya Neko, Mami Kurita, Akinobu Nishiyama, Mizuho KondoAbstract:The thermally enhanced photoinduced molecular reorientation based on an axis-selective photo-Fries rearrangement was explored for the first time using three liquid crystalline polymethacrylates with 4-(2′-(4″-methoxyPhenyl)ethynyl)Phenyl Benzoate side groups (1a), 4-methoxybiPhenyl Benzoate side groups (1b), and 4-methoxyPhenyl Benzoate side groups (1c). All the polymeric films exhibited an axis-selective formation of the photo-Fries products at the Phenyl Benzoate derivatives side groups by irradiating with linearly polarized (LP) UV light. Annealing the films in the liquid crystalline temperature range of the material greatly amplified the photoinduced small optical anisotropy of the irradiated films. For 1a and 1b, the photoinduced small anisotropy was amplified in a direction parallel to the polarization (E) of LPUV light and the reorientational order (S) was greater than 0.7. In contrast, the orientation direction was perpendicular to E for 1c (S ∼ 0.57). Finally, a simple double-exposure method usin...
Colin Xavier - One of the best experts on this subject based on the ideXlab platform.
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Multi-scale and multi-technique analysis of the thermal degradation of poly(ether ether ketone)
'Elsevier BV', 2018Co-Authors: Courvoisier Emilie, Bicaba Yoann, Colin XavierAbstract:International audienceThe thermal degradation of PEEK has been studied in rubbery state in wide ranges of temperature (between 180 and 320 °C) and oxygen partial pressure (between 0.21 and 50 bars). On one hand, the thermal ageing mechanisms have been analysed and elucidated by FTIR spectrophotometry and by differential scanning calorimetry (DSC) on sufficiently thin PEEK films (between 10 and 60 μm thickness) to be totally free of the effects of oxygen diffusion. Oxidation occurs on aromatic rings causing the growth of five new IR absorption bands centered at 3650, 3525, 1780, 1740 et 1718 cm−1 and attributed to the stretching vibrations of the O-H bonds of phenol and benzoïc acid, and the C-O bonds of benzoïc anhydride, Phenyl Benzoate and fluorenone respectively. In addition, oxidation leads to a large predominance of crosslinking over chain scissions resulting in a sharp increase of Tg. This reduction in molecular mobility prevents the annealing of PEEK, in particular when the temperature of exposure is higher than the onset of the melting endotherm. On the other hand, the consequences of oxidation on the elastic properties have been analysed and elucidated by micro-indentation on polished cross-sections of PEEK plates of 3 mm thickness. The diffusion control of oxidation leads to the development of profiles of Young's modulus within the sample thickness, which correlate perfectly with the changes in crystallinity and macromolecular architecture determined at lower scales. The validity of the Tobolsky's relationship is demonstrated
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Analyse de la dégradation thermique du Poly(éther éther cétone)
'EDP Sciences', 2017Co-Authors: Courvoisier Emilie, Bicaba Yoann, Colin XavierAbstract:The thermal degradation of PEEK has been studied in rubbery state in wide ranges of temperature (between 180 and 320 °C) and oxygen partial pressure (between 0.21 and 50 bars). First of all, the thermal ageing mechanisms have been analysed and elucidated by FTIR spectroscopy and by differential scanning calorimetry (DSC) on sufficiently thin PEEK films (between 10 and 60 μm thickness) to be totally free of the effects of oxygen diffusion. Oxidation occurs on aromatic rings causing the growth of five new IR absorption bands centered at 3650, 3525, 1780, 1740 and 1718 cm -1 and attributed to the stretching vibrations of the O-H bonds of phenol and benzoïc acid, and the C-O bonds of benzoïc anhydride, Phenyl Benzoate and fluorenone respectively. In addition, oxidation leads to a large predominance of crosslinking over chain scissions (increase in T g ) preventing the annealing of PEEK, in particular when the temperature of exposure is higher than the onset of the melting endotherm. Finally, the consequences of oxidation on the elastic properties have been analysed and elucidated by micro-indentation on preliminarily polished cross-sections of PEEK plates of 3 mm thickness. The changes in Young's modulus and crystallinity ratio correlate perfectly, thus checking the Tobolsky's relationship
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Analyse de la dégradation thermique du Poly(éther éther cétone)
'EDP Sciences', 2017Co-Authors: Courvoisier Emilie, Bicaba Yoann, Colin XavierAbstract:Article number 403International audienceThe thermal degradation of PEEK has been studied in rubbery state in wide ranges of temperature (between 180 and 320 °C) and oxygen partial pressure (between 0.21 and 50 bars). First of all, the thermal ageing mechanisms have been analysed and elucidated by FTIR spectroscopy and by differential scanning calorimetry (DSC) on sufficiently thin PEEK films (between 10 and 60 μm thickness) to be totally free of the effects of oxygen diffusion. Oxidation occurs on aromatic rings causing the growth of five new IR absorption bands centered at 3650, 3525, 1780, 1740 and 1718 cm -1 and attributed to the stretching vibrations of the O-H bonds of phenol and benzoïc acid, and the C-O bonds of benzoïc anhydride, Phenyl Benzoate and fluorenone respectively. In addition, oxidation leads to a large predominance of crosslinking over chain scissions (increase in T g ) preventing the annealing of PEEK, in particular when the temperature of exposure is higher than the onset of the melting endotherm. Finally, the consequences of oxidation on the elastic properties have been analysed and elucidated by micro-indentation on preliminarily polished cross-sections of PEEK plates of 3 mm thickness. The changes in Young's modulus and crystallinity ratio correlate perfectly, thus checking the Tobolsky's relationship.La dégradation thermique du PEEK a été étudiée à l’état caoutchoutique dans de larges intervalles de température (entre 180 et 320 °C) et de pression partielle d’oxygène (entre 0,21 et 50 bars). Tout d’abord, les mécanismes de vieillissement thermique ont été analysés et élucidés par spectroscopie IRTF et par calorimétrie différentielle (DSC) sur des films de PEEK suffisamment minces (entre 10 et 60 μm d’épaisseur) pour s’affranchir totalement des effets de la diffusion d’oxygène. L’oxydation se produit sur les cycles aromatiques provoquant la croissance de cinq nouvelles bandes d’absorption IR centrées à 3650, 3525, 1780, 1740 et 1718 cm-1 et attribuées aux vibrations d’élongation des liaisons O–H du phénol et de l’acide benzoïque, et des liaisons C–O de l’anhydride benzoïque, du Benzoate de phényle et de la fluorénone respectivement. De plus, l’oxydation conduit à une large prédominance de la réticulation sur les coupures de chaîne (augmentation de Tg) empêchant le recuit du PEEK, en particulier lorsque la température d’exposition est supérieure au pied du pic de fusion. Enfin, les conséquences de l’oxydation sur les propriétés élastiques ont été analysées et élucidées par micro-indentation sur des sections droites préalablement polies de plaquettes de PEEK de 3 mm d’épaisseur. Les variations du module d’Young et du taux de cristallinité se corrèlent parfaitement, vérifiant ainsi la relation de Tobolsky
V P Shibaev - One of the best experts on this subject based on the ideXlab platform.
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phase structure recording in a nematic side chain liquid crystalline polymer
Polymers, 2020Co-Authors: I A Budagovsky, N I Boiko, Aleksey A Kuznetsov, S A Shvetsov, M P Smayev, A S Zolotko, Alexey Bobrovsky, V P ShibaevAbstract:Dye-doped nematic side-chain liquid-crystalline polymers possess extraordinary large optical nonlinearity and ability to store the induced orientational deformations in a glassy state, which makes them a very promising material for photonic applications. In this study, the phase structures were generated and recorded in the bulk of a 50-μm layer of a nematic liquid-crystalline side-chain polymer, containing polyacrylate backbone, spacer having five methylene groups, and Phenyl Benzoate mesogenic fragment. The polymer was doped with KD-1 azodye. The director field deformations induced by the light beam close to the TEM01 mode were studied for different geometries of light–polymer interaction. The phase modulation depth of 2π was obtained for the 18-μm spacing between intensity peaks. The experimental data were analyzed based on the elastic continuum theory of nematics. The possibility to induce and record positive and negative microlenses in the polymer bulk was shown experimentally.
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liquid crystalline side chain triblock copolymers consisting of a nematic central subblock edged by photochromic azobenzene containing fragments their synthesis structure and photooptical behaviour
Polymer Chemistry, 2015Co-Authors: N I Boiko, M A Bugakov, E V Chernikova, Alexey A Piryazev, Ya I Odarchenko, Dimitri A Ivanov, V P ShibaevAbstract:For the first time, symmetrical photosensitive fully liquid crystalline side chain triblock copolymers (pAzo-b-pPhM-b-pAzo) and random copolymers (pAzo-ran-pPhM) with nematogenic Phenyl Benzoate (PhM) and photosensitive smectogenic azobenzene containing groups (Azo) were synthesized by the combination of RAFT polymerization and subsequent chemical modification. The central block of synthesized photochromic block copolymers contains 80 PhM groups, while the length of “peripheral” blocks includes 4 or 10 Azo units. The microphase separation structure is observed in the block copolymer when the length of a subblock with Azo groups reaches ten monomeric units. The influence of photochromic polymers’ molecular architecture (homopolymer, block copolymer and random copolymer) on the photochemical and photoorientation processes induced by light in their amorphous films has been revealed. The optical anisotropy induced in block copolymer films by illumination with linearly polarized 546 nm light was studied and the results were compared with those of the Azo homopolymer and of a random copolymer with a similar composition. It was found that practically only Azo groups are included in the process of photoinduced orientation in films of block copolymers, whereas the orientational cooperative effect of both azobenzene chromophore and Phenyl Benzoate mesogenic groups is observed in the case of a random copolymer.
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a new type of multifunctional material based on dual photochromism of ternary chiral photochromic liquid crystalline copolymers for optical data recording and storage
Journal of Materials Chemistry, 2000Co-Authors: Alexey Bobrovsky, N I Boiko, V P ShibaevAbstract:An approach for the development of a new class of multifunctional photochromic liquid crystalline materials has been devised. Copolymerization of acrylic monomers allowed the preparation of ternary cholesteric copolymers containing nematogenic (Phenyl Benzoate), photochromic (azobenzene), and chiral photochromic side groups (benzylidene-p-menthanone). The phase behaviour and optical properties of such copolymers were studied. The synthesised copolymers are characterised by selective light reflection in the visible or IR spectral regions depending on the composition of the copolymers. The photochemical and photooptical properties of the synthesised copolymers were studied. The character of the photochemical processes in the above copolymers was shown to be controlled by wavelength λ of incident light: as a result of light irradiation with λ = 366 nm, films or dilute solutions of copolymers experience E–Z photoisomerization of the azobenzene groups, whereas at λ = 313 nm, isomerization of both azobenzene and benzylidene-p-menthanone groups takes place. The action of UV light on the plane oriented films of copolymers leads to the E–Z isomerization of the chiral photochromic groups, and this isomerization is accompanied by untwisting of the cholesteric helix and by a shift of the selective light reflection wavelength to a long wavelength spectral region. On the other hand, irradiation of such films by polarised light with λ = 514 nm leads to the appearance of induced birefringence due to the existence of azobenzene groups which are capable of isomerization. The synthesised copolymers were shown to constitute a new class of multifunctional materials for data recording and storage.
Nobuhiro Kawatsuki - One of the best experts on this subject based on the ideXlab platform.
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photoinduced reorientation of a liquid crystalline polymer with Phenyl Benzoate mesogenic side groups on the basis of an axis selective photo fries rearrangement
Macromolecules, 2012Co-Authors: Nobuhiro Kawatsuki, Mami Kurita, Hitomi Matsushita, Teppei Washio, Mizuho KondoAbstract:Many types of photoreactive polymers have been investigated to regulate their molecularly orientated structures for polarization-controlled optical and display applications. Herein, we demonstrate the axis-selective photoreaction of thin films and their molecular reorientation behaviors using four types liquid crystalline poly(meth)acrylates with Phenyl Benzoate side groups and linearly polarized (LP) 248 nm light. These simple liquid crystalline polymers (LCPs) exhibit sufficient photoinduced molecular reorientations. Photoinduced molecular reorientation based on an axis-selective photo-Fries rearrangement is simultaneously generated with an in-plane order parameter (S) up to 0.33 when the irradiation temperature is in the lower part of the LC temperature range of the material, but multidomain formation of the mesogenic groups inhibits reorientation. To prevent thermally generated multidomain formation, an axis-selective photoreaction of an amorphous film followed by thermally generated self-organization...
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Photoinduced Reorientation of a Liquid Crystalline Polymer with Phenyl Benzoate Mesogenic Side Groups on the Basis of an Axis-Selective Photo-Fries Rearrangement
2012Co-Authors: Nobuhiro Kawatsuki, Mami Kurita, Hitomi Matsushita, Teppei Washio, Mizuho KondoAbstract:Many types of photoreactive polymers have been investigated to regulate their molecularly orientated structures for polarization-controlled optical and display applications. Herein, we demonstrate the axis-selective photoreaction of thin films and their molecular reorientation behaviors using four types liquid crystalline poly(meth)acrylates with Phenyl Benzoate side groups and linearly polarized (LP) 248 nm light. These simple liquid crystalline polymers (LCPs) exhibit sufficient photoinduced molecular reorientations. Photoinduced molecular reorientation based on an axis-selective photo-Fries rearrangement is simultaneously generated with an in-plane order parameter (S) up to 0.33 when the irradiation temperature is in the lower part of the LC temperature range of the material, but multidomain formation of the mesogenic groups inhibits reorientation. To prevent thermally generated multidomain formation, an axis-selective photoreaction of an amorphous film followed by thermally generated self-organization processes effectively induce molecular reorientation with S up to 0.71 and birefringence (Δn) ∼ 0.16
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axis selective photo fries rearrangement and photoinduced molecular reorientation in liquid crystalline polymer films
Macromolecules, 2011Co-Authors: Nobuhiro Kawatsuki, Takuya Neko, Mami Kurita, Akinobu Nishiyama, Mizuho KondoAbstract:The thermally enhanced photoinduced molecular reorientation based on an axis-selective photo-Fries rearrangement was explored for the first time using three liquid crystalline polymethacrylates with 4-(2′-(4″-methoxyPhenyl)ethynyl)Phenyl Benzoate side groups (1a), 4-methoxybiPhenyl Benzoate side groups (1b), and 4-methoxyPhenyl Benzoate side groups (1c). All the polymeric films exhibited an axis-selective formation of the photo-Fries products at the Phenyl Benzoate derivatives side groups by irradiating with linearly polarized (LP) UV light. Annealing the films in the liquid crystalline temperature range of the material greatly amplified the photoinduced small optical anisotropy of the irradiated films. For 1a and 1b, the photoinduced small anisotropy was amplified in a direction parallel to the polarization (E) of LPUV light and the reorientational order (S) was greater than 0.7. In contrast, the orientation direction was perpendicular to E for 1c (S ∼ 0.57). Finally, a simple double-exposure method usin...