67 results on '"Atsushi Yoshizawa"'
Search Results
2. Machine extraction of polymer data from tables using XML versions of scientific articles
- Author
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Hiroyuki Oka, Atsushi Yoshizawa, Yuji Matsumoto, Masashi Ishii, and Hiroyuki Shindo
- Subjects
Disk formatting ,Information retrieval ,computer.internet_protocol ,Computer science ,Extraction (chemistry) ,Table (database) ,General Medicine ,Ontology (information science) ,Data structure ,computer ,XML - Abstract
In this study, we examined machine extraction of polymer data from tables in scientific articles. The extraction system consists of five processes: table extraction, data formatting, polymer name r...
- Published
- 2021
3. Nanostructured assemblies of liquid-crystalline supermolecules: from display to medicine
- Author
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Atsushi Yoshizawa
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Materials science ,010405 organic chemistry ,Liquid crystalline ,Mesogen ,fungi ,food and beverages ,02 engineering and technology ,General Chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Crystal ,Crystallography ,Liquid crystal ,General Materials Science ,0210 nano-technology ,Chirality (chemistry) - Abstract
Liquid crystal oligomers have a supermolecular structure in which two or more mesogenic units are interconnected through flexible spacers. They can form various molecular packing structures...
- Published
- 2019
4. H-shaped liquid crystals inducing nematic order in the isotropic liquid
- Author
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Shoumi Sayama, Ryosuke Muraki, and Atsushi Yoshizawa
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Phase transition ,Materials science ,Kerr effect ,010405 organic chemistry ,H shaped ,Isotropy ,Physics::Optics ,02 engineering and technology ,General Chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,law.invention ,Homologous series ,chemistry.chemical_compound ,Crystallography ,Differential scanning calorimetry ,chemistry ,Optical microscope ,Liquid crystal ,law ,General Materials Science ,0210 nano-technology - Abstract
We prepared a homologous series of H-shaped liquid crystals I-n and investigated their phase transition properties using optical microscopy and differential scanning calorimetry. All the compounds ...
- Published
- 2019
5. Coexistence of nematic and chiral nematic phases of an achiral liquid crystal trimer possessing an octafluorobiphenyl unit
- Author
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Atsushi Yoshizawa and Hirona Kato
- Subjects
Phase transition ,Materials science ,Trimer ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,law.invention ,Crystallography ,Differential scanning calorimetry ,Optical microscope ,Homogeneous ,Liquid crystal ,law ,General Materials Science ,0210 nano-technology ,Chirality (chemistry) - Abstract
We prepared some achiral flexible liquid crystal oligomers possessing an octafluorobiphenyl unit and investigated their phase transition properties using polarising optical microscopy and differential scanning calorimetry. All the compounds showed nematic phases. The trimer with even-numbered spacers was found to exhibit coexistence of the nematic regions and the chiral nematic regions with opposite twist senses of a sample contained in a homogeneous aligned cell during a cooling process, whilst that with odd-numbered spacers did not. We discuss how the even-numbered trimer produces the helical state.
- Published
- 2018
6. Molecular design of flexible liquid crystal oligomers stabilising the chiral frustrated phases
- Author
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Atsushi Yoshizawa
- Subjects
Materials science ,Mesogen ,media_common.quotation_subject ,Intermolecular force ,Frustration ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Condensed Matter::Soft Condensed Matter ,Crystallography ,Liquid crystal ,Molecule ,General Materials Science ,Grain boundary ,0210 nano-technology ,Chirality (chemistry) ,media_common - Abstract
Chirality induces structural frustration in liquid crystal systems, producing various kinds of chiral frustrated phases, for example, twist grain boundary (TGB) phases, blue phases (BPs) and dark conglomerate (DC) phases. Almost all molecules exhibiting these frustrated phases have a rigid shape. Especially, a bent–core unit is regarded as a key structure for BPs and DC phases. This paper describes that some flexible liquid crystal oligomers being far from a rigid bent–core molecule stabilise these phases. The LC oligomers have a supermolecular structure in which mesogenic units are connected via flexible spacers. By designing intermolecular interactions, they can exhibit various molecular packing structures in the liquid-crystalline phases as follows: chiral dimers inducing TGB phases, U-shaped and T-shaped oligomers stabilising BPs and achiral liquid crystal trimers exhibiting DC phases. I discuss how the designed liquid crystal oligomers produce the chiral frustrated phases.
- Published
- 2017
7. Crystal–nematic phase separation in an asymmetric liquid crystal dimer possessing a terminal hydroxyl group
- Author
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Haruna Sasaki, Atsushi Yoshizawa, and Yukiko Kondo
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Phase transition ,Materials science ,Dimer ,Intermolecular force ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,law.invention ,Crystal ,chemistry.chemical_compound ,Crystallography ,Differential scanning calorimetry ,chemistry ,Optical microscope ,Liquid crystal ,law ,Phase (matter) ,Organic chemistry ,General Materials Science ,0210 nano-technology - Abstract
We prepared an asymmetric liquid crystal dimer possessing a terminal hydroxyl group, 2-{4-{7-[4-(4-cyanophenyl)phenyloxy]heptyloxy}phenyl}-5-(6-hydroxyhexyloxy)pyrimidine, and investigated the phase transition behaviour using polarising optical microscopy and differential scanning calorimetry. The compound exhibited an enantiotropic nematic phase. On cooling, two distinct domains were formed during the nematic-to-crystal phase transition. During heating, one domain melted at 126.4°C to the N phase, whereas the other domain changed to the N phase at 144.6°C. Therefore, the crystal and nematic phases coexisted at a temperature of 18.2 K. The coexistence behaviour characteristics depend on the cooling rate. We discuss the manner in which intermolecular interactions affect the phase transition behaviour.
- Published
- 2016
8. Effects of liquid crystallinity on anticancer activity of benzoate derivatives possessing a terminal hydroxyl group
- Author
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Atsushi Yoshizawa, Yukako Fukushi, Ikuo Kashiwakura, Junya Ishikawa, Masanobu Sagisaka, and Hironori Yoshino
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Materials science ,Mesogen ,General Chemistry ,Condensed Matter Physics ,Thermotropic crystal ,Polar surface area ,Crystallinity ,Crystallography ,Dynamic light scattering ,Liquid crystal ,Lyotropic ,Organic chemistry ,Molecule ,General Materials Science - Abstract
To elucidate the effects of liquid crystallinity on the anticancer activity of a small mesogenic molecule, we prepared some benzoate derivatives possessing a terminal hydroxyl group and investigated their anti-proliferative activity against A549 human lung cancer cells. We also observed their molecular aggregation properties using polarised optical microscopy, differential scanning microscopy and dynamic light scattering. We discuss the structure–property relation of the benzoate derivatives. The results are explained in terms of the octanol–water partition coefficient, topological polar surface area (tPSA) and molecular aggregation ability.
- Published
- 2014
9. Flexible taper-shaped liquid crystal trimer exhibiting a modulated smectic phase
- Author
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Shinya Kashima, Atsushi Yoshizawa, Yoichi Takanishi, and Jun Yamamoto
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Diffraction ,Conformational change ,Materials science ,Intermolecular force ,Trimer ,General Chemistry ,Condensed Matter Physics ,law.invention ,Crystallography ,chemistry.chemical_compound ,chemistry ,Optical microscope ,law ,Liquid crystal ,Monolayer ,Organic chemistry ,General Materials Science ,Benzoic acid - Abstract
We prepared some taper-shaped liquid-crystalline trimers in which two phenylpyrimidine units and a 1,4-diphenyl-2,3-difluorobenzene unit are connected to 2,4-dihdroxy benzoic acid via flexible spacers. We then investigated their liquid-crystalline properties using polarised optical microscopy, differential scanning microscopy and X-ray diffraction. 6-[4–(5-Octylpyrimidin-2-yl)phenyloxy]hexyl 2-{7-{4-[4–(4-hexylphenyl)-2,3-difluorophenyl]phenyloxy}heptanoyloxy}-4-{6-[4–(5-octylpyrimidin-2-yl)phenyloxy]hexyloxy}benzoate (1) was found to exhibit a phase sequence of isotropic liquid – nematic – intercalated smectic A – intercalated anticlinic smectic C – modulated smectic C. The structure–property relation in the taper-shaped trimers reveals that the modulated phase is induced by competition between an intercalated structure stabilised by dipole–dipole interaction and a monolayer structure by packing entropy effects. Conformational change of compound 1 induced by intermolecular interactions plays an important...
- Published
- 2014
10. Molecular Design of Blue Phase Materials for Display Devices
- Author
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Atsushi Yoshizawa
- Subjects
Chemical substance ,Materials science ,Ternary numeral system ,Dopant ,business.industry ,General Chemistry ,Condensed Matter Physics ,Amorphous solid ,Condensed Matter::Materials Science ,Liquid crystal ,Phase (matter) ,Optoelectronics ,General Materials Science ,business ,Chirality (chemistry) ,Science, technology and society - Abstract
We report that coupling of molecular biaxiality and chirality is effective for blue phase stabilization. We show a U-shaped binaphthyl derivative with a cubic blue phase and some T-shaped compounds with an amorphous blue phase III (BPIII). We designed a ternary system consisting of a conventional nematic mixture, a T-shaped BPIII stabilizer, and a chiral dopant. BPIII of the system exhibited high transmittance, submillisecond response, and hysteresis-free switching at room temperature. Amorphous BPIII, with a level of symmetry equal to that of an isotropic liquid, is thought to have a superior potential for use in next-generation displays.
- Published
- 2014
11. Dielectric pre-transitional behavior in the vicinity of isotropic–blue phase III transition
- Author
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Manoj Marik, Muklesur Rahman, B. K. Chaudhuri, and Atsushi Yoshizawa
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Phase transition ,Materials science ,Condensed matter physics ,Internal energy ,Isotropy ,Thermodynamics ,Dielectric ,Dielectric spectroscopy ,symbols.namesake ,Liquid crystal ,Helmholtz free energy ,symbols ,General Materials Science ,Instrumentation ,Critical exponent - Abstract
Pre-transitional effects have been observed from the study of static dielectric permittivity ( ) and its temperature derivatives ( ) near the isotropic to blue phase-III (I–BPIII) transition in a highly polar T-shaped liquid crystalline material having a stable BPIII phase which persists over a comparatively wide range of temperature (∼8°C). The pre-transitional behavior near I–BPIII transition is found to be very similar to that observed in isotropic–nematic (I–N) transition. Landau–de Genes and Maier–Saupe approaches, used earlier to describe anomalous behavior of eS near the I–N transition, have been implemented to investigate the present pre-transitional behavior near the I–BPIII transition. The value of critical exponent (α) for the I–BPIII transition is found to be close to that of the reported I–N transition. Temperature-dependent behavior of and have also been interpreted in terms of field-induced increments of basic thermodynamic quantities, namely internal energy, entropy, and Helmholtz free energy.
- Published
- 2012
12. Competition between micro-segregation and anti-parallel alignment of an amphiphilic rod-like liquid crystal
- Author
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Ayumi Nishizawa, Jun Yamamoto, Yoichi Takanishi, and Atsushi Yoshizawa
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Materials science ,Hydrogen bond ,General Chemistry ,Condensed Matter Physics ,Crystallography ,chemistry.chemical_compound ,Homologous series ,Differential scanning calorimetry ,chemistry ,Liquid crystal ,Phase (matter) ,Amphiphile ,Molecule ,Organic chemistry ,General Materials Science ,Methylene - Abstract
Recently, we reported that a rod-like molecule, 4-[4-(7-hydroxyheptyloxy)phenyl]-1-(4-hexylphenyl)-2,3-difluorobenzene, exhibited a nematic phase with a layered structure and smectic C phases consisting of three states. We prepared a homologous series of the rod-like molecules in which a 2,3-difluoro-1,4-diphenylbenzene unit and a hydroxyl unit are connected via a flexible methylene spacer. We investigated their physical properties using polarised optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). Although they showed nematic, smectic A and smectic C phases, the phase structures were found to depend on the flexible spacer length. Those compounds possessing a shorter spacer length than a heptyl unit exhibited bilayered smectic A and smectic C phases, whereas those possessing a longer spacer length than a heptyl unit showed conventional monolayered smectic A and smectic C phases. A nematic phase with a smectic-like layer ordering was observed for the compound poss...
- Published
- 2011
13. Preorganised effects of a tetramesogenic supermolecule on supramolecular assembly in the liquid crystalline phases
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Tomohiro Ashina, Atsushi Yoshizawa, Yuki Miura, and Tsuyoshi Narumi
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chemistry.chemical_classification ,Materials science ,Mesogen ,General Chemistry ,Condensed Matter Physics ,Supermolecule ,Supramolecular assembly ,Homologous series ,chemistry.chemical_compound ,Crystallography ,chemistry ,Liquid crystal ,Phase (matter) ,Organic chemistry ,Molecule ,General Materials Science ,Alkyl - Abstract
After preparing a homologous series of tetrameric mesogenic compounds in which two U-shaped molecules were connected via a rigid benzene derivative or a flexible alkyl chain, we investigated their phase transition behaviour using optical microscopy, differential scanning calorimetry and X-ray diffraction analysis. The compounds possessing an alkyl spacer as the central group exhibited nematic and smectic A phases just as the corresponding U-shaped molecule did. The compound possessing a 1,2-benzene unit as the connecting group showed nematic and smectic A phases, although the compound possessing a 1,3-benzene unit exhibited only an anticlinic smectic C phase. Structure–property relations of the liquid crystalline tetramers are interpreted in terms of preorganised effects of the four mesogenic units.
- Published
- 2011
14. Chiral effects of blue phase stabilisation of a binaphthyl derivative
- Author
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Atsushi Yoshizawa and Yutaro Kogawa
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Phase transition ,Materials science ,General Chemistry ,Atmospheric temperature range ,Condensed Matter Physics ,Homologous series ,chemistry.chemical_compound ,Crystallography ,chemistry ,Liquid crystal ,Phase (matter) ,Organic chemistry ,General Materials Science ,Chirality (chemistry) - Abstract
We have recently reported a binaphthyl liquid crystal exhibiting on cooling a cubic blue phase over a wide temperature range. On heating, however, a chiral nematic phase appeared in place of the blue phase. To elucidate the origin of blue phase stabilisation we have prepared a homologous series of binaphthyl derivatives possessing two 2,3-difluoro-1,4-diphenylbenzene units and have investigated the phase transition behaviour and helical twisting power. A binaphthyl derivative exhibiting the blue phase was found to induce helical twist inversion in a chiral nematic mixture with a host liquid crystal, whereas other compounds without the blue phase induced short helical pitches independently of temperature. The blue phase material is thought to have two possible origins for its twisting power, which are able to stabilise the double-twist structure of the phase.
- Published
- 2011
15. Amphiphilic taper-shaped oligomer exhibiting a monolayer smectic A to columnar phase transition
- Author
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Yoichi Takanishi, Jun Yamamoto, Kazuhito Takeuchi, and Atsushi Yoshizawa
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chemistry.chemical_classification ,Materials science ,Mesogen ,General Chemistry ,Condensed Matter Physics ,Oligomer ,chemistry.chemical_compound ,Crystallography ,chemistry ,Liquid crystal ,Phase (matter) ,Monolayer ,Amphiphile ,Organic chemistry ,General Materials Science ,Columnar phase ,Alkyl - Abstract
We prepared two series of liquid-crystalline oligomers composed of phenylpyrimidine based mesogenic cores, alkyl spacers and semiperfluorinated alkyl chains in one series and only alkyl chains in the second series. Their physical properties were investigated using optical microscopy, differential scanning calorimetry and X-ray diffraction measurements. The oligomers possessing a semiperfluorinated alkyl chain show a phase sequence of SmC–SmA–Col when the number of phenylpyrimidine moieties was increased. The compound possessing three phenylpyrimidine cores was found to exhibit monolayer SmA and Col phases. On the other hand, the oligomer composed of an alkyl chain and three phenylpyrimidine cores showed only a nematic phase. We discuss effects of the shape amphiphilicity and the hydrocarbon–fluorocarbon amphiphilicity on phase transition behaviour of the amphiphilic oligomers.
- Published
- 2010
16. Alignment Structure of Dimeric Liquid Crystal Molecules Having Bent Molecular Structure
- Author
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Ayano Ito, Hirokazu Furue, Atsushi Yoshizawa, and Masaya Furutani
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Materials science ,business.industry ,Bent molecular geometry ,Bragg's law ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,Crystallography ,Molecular geometry ,Optics ,Liquid crystal ,Phase (matter) ,Antiferroelectricity ,Molecule ,Fourier transform infrared spectroscopy ,business - Abstract
Antiferroelectric liquid crystals (AFLCs) composed of low-mass mesogens do not show the nematic (N) phase. Recently, it has been reported that an AFLC containig dimeric molecules may show the N phase. However, it is not obvious why the antiferroelectric SmC (SmCA) and N phases may coexist in the phase sequence of the dimeric LCS. In this study, the molecular alignment structure has been investigated by X-ray diffractometry (XRD) and polarized Fourier transform infrared spectroscopy (FT-IR). As a result, It is found that dimeric LCs, mPY11OCB (m = 6 and 8), have the same layer spacing between the SmA and SmCA phases, and therefore, the molecular shape is bent even in the SmA phase. The difference between both phases is due to the thermal motion of bent molecules around the molecular axis. Furthermore, it is obvious that in the SmCA phase, the alignment of dimeric LC molecules can be localized in two directions in a cell with rubbed alignment films. Furthermore, we tried to estimate the bent angle of the di...
- Published
- 2010
17. Dielectric Spectroscopy of a Dichiral Mesogen with a Unique Phase Sequence
- Author
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B. K. Chaudhuri, Surjya Sarathi Bhattacharyya, Atsushi Yoshizawa, and Amrita Mukherjee
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Range (particle radiation) ,Materials science ,Mesogen ,Isotropy ,Physics::Optics ,General Chemistry ,Dielectric ,Condensed Matter Physics ,Molecular physics ,Dielectric spectroscopy ,Nuclear magnetic resonance ,Liquid crystal ,Phase (matter) ,General Materials Science ,Chirality (chemistry) - Abstract
Dielectric relaxation behavior of a dichiral mesogenic liquid crystal material, viz. (R,S)-FPPY, having anomalous phase sequence has been studied over a wide range of frequency. Measured dielectric spectra show a new relaxation process, in addition to the usual Goldstone mode, in the SmC* phase, which has been assigned to the relaxation process originating from the dichirality of the compound. The overlapping of two molecular modes has been observed in the dielectric spectrum of both isotropic and optically isotropic (IsoX) phases. The present detailed dielectric spectroscopic studies also establish an interesting ferroelectric-like ordering in the unknown SmX* phase.
- Published
- 2010
18. Liquid Crystal Oligomers Exhibiting a Blue Phase
- Author
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Atsushi Yoshizawa
- Subjects
Crystallography ,Materials science ,Liquid crystal ,Stereochemistry ,Lattice (order) ,Isotropy ,Polar ,General Materials Science ,General Chemistry ,Atmospheric temperature range ,Condensed Matter Physics ,Chirality (chemistry) - Abstract
Liquid crystal blue phases have a fluid lattice whose structure is stabilized by cubic defects. Blue phases, which are classified as BPIII, BPII and BPI observed on cooling, exist over a small temperature range (ca. 1 K) between isotropic and chiral nematic phases. Recently, we reported electro-optical switching with a response time of the order of 10−2 s for the BPIII exhibited by a polar chiral T-shaped compound. We describe molecular design of a liquid crystal stabilizing a blue phase III, and discuss electro-optical switching in the blue phase.
- Published
- 2010
19. Structure-Property Correlations of Novel S-Shaped Liquid Crystal Oligomers
- Author
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Fumitaka Ogasawara, Tetsuya Kawaguchi, Hisashi Kasai, Yoshihiro Nagashima, and Atsushi Yoshizawa
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Phase transition ,Materials science ,Mesogen ,Mesophase ,Condensed Matter Physics ,Oligomer ,Electronic, Optical and Magnetic Materials ,Homologous series ,chemistry.chemical_compound ,Crystallography ,chemistry ,Liquid crystal ,Phase (matter) ,Intramolecular force - Abstract
Transition properties of a homologous series of novel S-shaped oligomers on varying the spacer length, core structure and linking group were investigated. All the S-shaped oligomers showed a nematic (N) phase on cooling. Formation of the N phase is interpreted in terms of the length to diameter (L/D) ratio, indicating that intramolecular core-core interaction plays an important role in stabilizing N phases. A non-symmetric S-shaped oligomer possessing cyanobiphenyl and phenylpyrimidine moieties exhibited enantiotropic N and smectic A (SmA) phases. The high stability of the SmA phase results from intermolecular interactions between the unlike mesogenic moieties. We discuss physical properties of the S shaped system that has structure within structure.
- Published
- 2008
20. Alignment Structure Formed in Dimeric Liquid Crystal Molecules
- Author
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Hirokazu Furue, Atsushi Yoshizawa, Masaya Furutani, Teruki Niori, Hitoshi Sasaki, Junji Watanabe, Isa Nishiyama, and Tatsuya Izumi
- Subjects
Materials science ,business.industry ,Mesogen ,Bent molecular geometry ,Mesophase ,Infrared spectroscopy ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,Crystallography ,Molecular geometry ,Optics ,Liquid crystal ,Phase (matter) ,Fourier transform infrared spectroscopy ,business - Abstract
An antiferroelectric liquid crystal (AFLC) with dimeric molecules which take a bent molecular structure may show the nematic (N) phase. However, it has not been obvious yet why the antiferroelectric chiral SmC (SmC* A ) and N phases may coexist in the phase sequences of the dimeric AFLC. In this study, the molecular alignment structure of both liquid-crystalline phases has been researched in detail with a polarized Fourier transform infrared spectroscopy (FT-IR). In 8PY11OCB, the directors of both mesogenic moieties are oriented to the rubbing direction due to high thermal motion in the N and SmA phases, that is the molecular shape is almost rod like. In the SmC A phase, a herringbone alignment of the mesogenic moieties appears because the bent molecular structure becomes stable due to lower thermal motion. In the case of OBnCB, we obtain also almost the same results and discussion.
- Published
- 2008
21. Synthesis and Physical Properties of Novel Dimesogenic Compounds Possessing both Lateral and Terminal Polar Groups
- Author
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Atsushi Yoshizawa and Shota Chiba
- Subjects
Permittivity ,Materials science ,business.industry ,Condensed Matter Physics ,Oligomer ,Electronic, Optical and Magnetic Materials ,Crystallography ,chemistry.chemical_compound ,Homologous series ,Optics ,chemistry ,Liquid crystal ,Phase (matter) ,Molecule ,Polar ,business ,Benzene - Abstract
We prepared a homologous series of non-symmetric dimesogenic compounds 1-(4- fluorophenyl)-4-{ω -{4-[4-(4-hexylphenyl)-2,3-difluorophenyl]phenyloxy}alkyloxy} benzene ( I-n ) and investigated the physical properties. For comparison, we also prepared a compound ( II-6 ) possessing a 4-(4-cyanophenyl)benzene unit instead of the 4-(4- fluorophenyl)benzene unit. All the compounds exhibited an enantiotropic nematic phase. When an electric AC field was applied, a striped pattern that was similar to Williams domain appeared in the nematic phases of compounds I-n , whereas such a pattern was not observed in the nematic phase of II-6 . We discuss structure-property correlations of the polar liquid crystal oligomers.
- Published
- 2008
22. Synthesis and Physical Properties of Novel T-Shaped Chiral Liquid Crystal Oligomers Possessing Terminal Cyano Groups
- Author
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Masatada Sato and Atsushi Yoshizawa
- Subjects
inorganic chemicals ,Phase transition ,Materials science ,organic chemicals ,High Energy Physics::Lattice ,Mesogen ,High Energy Physics::Phenomenology ,Mesophase ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,Crystallography ,Liquid crystal ,Phase (matter) ,health occupations ,polycyclic compounds ,Moiety ,Molecule ,heterocyclic compounds ,Chirality (chemistry) - Abstract
Recently we found that some chiral compounds possessing molecular biaxiality can stabilize an amorphous blue phase III. We introduced a polar group into the chiral T-shaped molecule in order to couple the molecule with an electric field. We prepared some novel T-shaped chiral compounds possessing a 4-cyanobiphenyl moiety and a mesogenic unit with a chiral center. We investigated their phase transition temperatures and induced helical pitches. We discuss structure-property correlations of the newly designed T-shaped chiral oligomers.
- Published
- 2008
23. Helical Structure Induced by a Binaphthyl Derivative Possessing Two Biphenyl Moieties
- Author
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Yutaro Kogawa, Atsushi Yoshizawa, and Keiko Kobayashi
- Subjects
Biphenyl ,Materials science ,Infrared spectroscopy ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,Crystallography ,Chain length ,Nuclear magnetic resonance ,chemistry ,Liquid crystal ,Axial chirality ,Helix ,Molecule ,Chirality (chemistry) - Abstract
We prepared (R)-2, 2′-bis{6-[4-(4-(octyloxycarbonyl)phenyl)phenyloxycarbonyl] hexyloxy}-1, 1′-binaphthyl [(R) -Bi-I(8) ] and the monobiphenyl derivative [(R) -M-I(8) ], and investigated their induced helical senses and pitches in different nematic liquid crystals. With respect to each mixture with 5-heptyl-2-(4-hexyloxypheyl)primidine, a right-handed helix was induced in the mixture with (R)-Bi-I(8) , whereas a left-handed helix was observed in the mixture with (R){-M-I(8)}. On the other hand, a left-handed helix was induced in each mixture with 4-methyloxyphenyl 4-penthlcyclohexane. Furthermore, we investigated the effects of axial chirality and terminal chain length on the twisting power of the binaphthyl derivatives.
- Published
- 2008
24. Novel T-shaped Chiral Oligomers with a Wide Temperature Range of a Blue Phase
- Author
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Fumitaka Ogasawara, Atsushi Yoshizawa, and Masatada Sato
- Subjects
Stereochemistry ,Transition temperature ,General Chemistry ,Crystal structure ,Atmospheric temperature range ,Condensed Matter Physics ,Homologous series ,chemistry.chemical_compound ,Crystallography ,chemistry ,Liquid crystal ,Phase (matter) ,Molecule ,General Materials Science ,Chirality (chemistry) - Abstract
The crystal structure of (S)-1-methylheptyl-4′-{4-octyloxy-2-{11-[4-(5-hexylpyrimidin-2-yl)phenoxy]undecanoyloxy}benzoyloxy}biphenyl-4-carboxylate, which has a relatively wide temperature range of blue phase III on cooling, has been determined. The molecule was found to form a λ-shaped structure. We have prepared a homologous series of the chiral oligomers and investigated effects of structure on appearance of the blue phase. All compounds were found to show a phase sequence of Iso-BP-N*-glass on cooling. The structure-property correlations reveal that (1) chirality does not affect on the Iso-BP transition temperature, (2) increasing chirality destabilizes the N* phase, and (3) the longer spacer lowers the BP-N* transition temperature.
- Published
- 2007
25. Two origins for twisting power of a binaphthyl derivative in a host nematic liquid crystal
- Author
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Keiko Kobayashi and Atsushi Yoshizawa
- Subjects
Materials science ,Pyrimidine ,Doping ,General Chemistry ,Condensed Matter Physics ,chemistry.chemical_compound ,Crystallography ,chemistry ,Liquid crystal ,Helix ,Organic chemistry ,General Materials Science ,Twist ,Chirality (chemistry) - Abstract
We prepare a series of homologues of novel binaphthyl derivatives, (R)‐2, 2′‐bis{ω‐[4‐(4‐(octyloxycarbonyl)phenyl)phenyloxycabonyl]alkyloxy}‐1, 1′‐binaphthyl [(R)‐Bi‐n], and investigate their induced helical senses and pitches in different host nematic liquid‐crystalline compounds. Pronounced odd–even effects were observed for the induced helical structure in each mixture with 5‐heptyl‐2‐(4‐hexyloxyphenyl)pyrimidine. Temperature‐dependent helical twist inversion was observed for the mixture doped with the odd members, whereas a right‐handed helix was observed for the mixture doped with the even members. On the other hand, a left‐handed helix was induced in each mixture with 4‐methyloxyphenyl 4‐pentylcyclohexane. We discuss the change in sign of the induced pitch in terms of chirality transfer from the binaphthyl derivative to a host nematic liquid crystal.
- Published
- 2007
26. The role of a liquid crystal oligomer in stabilizing blue phases
- Author
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Masatada Sato, Shinpei Segawa, Atsushi Yoshizawa, and Hirotoshi Iwamochi
- Subjects
chemistry.chemical_compound ,Crystallography ,Materials science ,Molecular geometry ,chemistry ,Liquid crystal ,Phase (matter) ,Organic chemistry ,General Materials Science ,General Chemistry ,Atmospheric temperature range ,Condensed Matter Physics ,Oligomer - Abstract
A novel liquid crystal oligomer, 4‐(4‐cyanophenyl)phenyl 4‐octyloxy‐2‐{7‐{4‐[4‐(4‐hexylphenyl)‐2,3‐difluorophenyl]phenyloxy}heptanoyloxy}benzoate, was prepared and found to exhibit a wide temperature range of a nematic phase in spite of being far from a rod‐like structure. Furthermore, the compound induced blue phases in the mixture with a chiral smectic liquid crystal. The molecular shape and its 2,3‐difluorophenyl unit play a role in stabilizing the blue phases.
- Published
- 2007
27. Dielectric spectroscopy of a smectic liquid crystal
- Author
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Shyamal Kumar Kundu, Shin Yagihara, and Atsushi Yoshizawa
- Subjects
Phase transition ,Materials science ,Condensed matter physics ,Dielectric strength ,Relaxation (NMR) ,General Chemistry ,Condensed Matter Physics ,Ferroelectricity ,Dielectric spectroscopy ,Dipole ,Molecular dynamics ,Nuclear magnetic resonance ,Liquid crystal ,General Materials Science - Abstract
Complex dielectric spectroscopy (frequency range 5 Hz–13 MHz) has been used to analyse the frequency, temperature and bias‐field dependences of the molecular dynamics of a very high‐spontaneous‐polarization ferroelectric liquid crystalline material exhibiting SmA, SmC* and unknown SmX smectic phases. Different smectic phase transition temperatures have been observed from the study of the temperature dependence of the dielectric strength and the relaxation frequency. The phase transition temperatures (crystalline to isotropic phases) have also been described very accurately from the temperature‐dependent symmetric and asymmetric shape parameters of the relaxation function and also the dc conductivity. In a planar aligned cell, two symmetric modes (Goldstone mode and domain mode) have been observed in both the SmX and SmC* phases. One asymmetric mode (X‐mode) observed in the SmC* and SmA phases could be related to the interaction of dipoles of the ferroelectric liquid crystals being affected by the surface ...
- Published
- 2007
28. Odd–even effects in the phase transition behaviour of novel U‐shaped liquid crystals
- Author
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Akihisa Yamaguchi, Mitsutoshi Watanabe, and Atsushi Yoshizawa
- Subjects
chemistry.chemical_classification ,Phase transition ,Materials science ,Mesogen ,General Chemistry ,Condensed Matter Physics ,law.invention ,Homologous series ,chemistry.chemical_compound ,Crystallography ,Differential scanning calorimetry ,Molecular geometry ,chemistry ,Optical microscope ,Liquid crystal ,law ,General Materials Science ,Alkyl - Abstract
A homologous series of U‐shaped dimeric liquid crystals in which two mesogenic groups are connected via catechol has been prepared and the effects of terminal alkyl chains, alkyl spacers and core structures on the transition properties investigated by means of optical microscopy and differential scanning calorimetry. The phase sequence exhibits a pronounced odd–even effect as the length and parity of the spacers is varied, in which the even members favour the nematic and smectic C phases, whereas the odd members favour the nematic and smectic A phases. We discuss the transition behaviour of the U‐shaped compounds in terms of molecular shape.
- Published
- 2007
29. Synthesis and phase transition behaviour of novel liquid crystal trimers
- Author
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Tsuyoshi Narumi, Atsushi Yoshizawa, and Masashi Miyamoto
- Subjects
Crystallography ,Phase transition ,Materials science ,Liquid crystal ,Phase (matter) ,Mesogen ,Intermolecular force ,Organic chemistry ,General Materials Science ,General Chemistry ,Condensed Matter Physics ,Supercooling - Abstract
Novel oligomeric compounds in which three mesogenic moieties are connected via 3,4‐dihydroxybenzoic acid or 3,5‐dihydroxybenzoic acid were prepared and the physical properties investigated. Some of the compounds were found to have a tendency to form glassy states. With respect to 4‐cyanobiphenyl‐4′‐yl 4‐octyloxy‐2‐(3,4‐bis{6‐[4‐(5‐octylpyrimidine‐2‐yl)phenyloxy]hexyloxybenzoyloxy)benzoate, it is possible to obtain a supercooled nematic phase despite it deviating from a strongly rod‐like structure. We discuss intermolecular interactions between neighbouring mesogenic parts for the appearance of the nematic phase.
- Published
- 2007
30. Synthesis and physical properties of novel S‐shaped liquid crystal oligomers
- Author
-
Tetsuya Kawaguchi, Fumitaka Ogasawara, Hisashi Kasai, Nagashima Yoshihiro, and Atsushi Yoshizawa
- Subjects
chemistry.chemical_compound ,Crystallography ,Materials science ,Monomer ,Molecular geometry ,chemistry ,Liquid crystal ,Organic chemistry ,General Materials Science ,General Chemistry ,Condensed Matter Physics ,Oligomer ,Entropy (order and disorder) - Abstract
We prepared novel S‐shaped liquid crystal oligomers, the 4,4′‐bis(ω‐(2‐(ω‐(4‐(cyanophenyl)phenyloxy)alkyloxy)phenyloxy)alkyloxybiphenyls (S‐n ), and investigated their transition behaviour. The oligomer with even‐numbered spacers (S‐6) exhibited a nematic phase, whereas the oligomer with odd‐numbered spacers (S‐7) exhibited nematic and smectic A phases. Transition properties of the S‐shaped oligomers are compared with those of the corresponding monomeric and U‐shaped dimeric compounds. The entropy changes associated with the I–N transition for the oligomers were found to have small values, similar to that of the monomeric compound. A biaxial smectic phase was induced below the SmA phase in some binary mixtures of S‐6 and a phenylpyrimidine derivative (8‐PYP‐6O). On the other hand, the SmA phase was stabilized in the mixtures of S‐7 and 8‐PYP‐6O. We discuss the transition behaivour of the S‐shaped oligomers in terms of their molecular shape.
- Published
- 2007
31. Synthesis and physical properties of novel liquid crystal oligomers possessing polar terminal groups
- Author
-
Shota Chiba, Atsushi Yoshizawa, and Fumitaka Ogasawara
- Subjects
Phase transition ,Materials science ,Mesogen ,General Chemistry ,Condensed Matter Physics ,Benzoates ,Homologous series ,chemistry.chemical_compound ,Crystallography ,chemistry ,Liquid crystal ,Phase (matter) ,Alkoxy group ,Organic chemistry ,Polar ,General Materials Science - Abstract
A homologous series of novel liquid crystal oligomers possessing 4‐fluorobiphenyl and 4‐trifluoromethoxyphenyl benzoate moieties was prepared and the physical properties investigated. The dimesogenic compounds, 4‐trifluoromethoxyphenyl 4‐{6‐[4‐(4‐fluorophenyl)phenyloxy]alkoxy}benzoates, exhibited nematic (N) and smectic A (SmA) phases. Pronounced odd–even effects were seen, not only for the phase transition but also for the induced dielectric anisotropy in the N phase of the mixture with a host material, on varying the spacer length of the dimeric compounds. The λ–shaped trimesogenic compound, 4‐trifluoromethoxyphenyl 3,4‐bis{6‐[4‐(4‐fluorophenyl)phenyloxy]hexyloxy}benzoate, was found to show monotropic N and SmA phases. We discuss oligomeric effects of the mesogenic moieties on the phase transition behaviour, and on the induced dielectric anisotropy.
- Published
- 2007
32. Synthesis and transition properties of novel dimesogenic compounds possessingcis‐1, 4‐dioxa‐2‐butene as a linking group
- Author
-
Atsushi Yoshizawa and Tetsuya Kawaguchi
- Subjects
Materials science ,Liquid crystalline ,Mesogen ,Diol ,General Chemistry ,Condensed Matter Physics ,2-Butene ,chemistry.chemical_compound ,Crystallography ,chemistry ,Liquid crystal ,Group (periodic table) ,Phase (matter) ,Organic chemistry ,General Materials Science - Abstract
We have designed novel liquid crystalline compounds in which two mesogenic units are connected via cis‐2‐buten‐1,4‐diol. We prepared cis‐4‐{6‐[4‐(4‐cyanophenyl)phenyloxy]hexyloxy}‐1‐{6‐[4‐(4‐methyloxy)phenyloxy]hexyloxy}‐2‐butene (6OCMBCB), cis‐1,4‐bis{6‐[4‐(4‐cyanophenyl)phenyloxy]hexyloxy}‐2‐butene (6OCCBCB) and cis‐1,4‐bis{6‐[4‐(4‐methyloxy)phenyloxy]hexyloxy}‐2‐butene (6OMMBCB), and investigated their transition properties. 6OCMBCB and 6OCCBCB exhibited nematic phases whereas 6OMMBCB showed no liquid crystalline phase. We discuss the effects of the mesogenic structure and linkage group on the transition behaviour of the dimesogenic compounds.
- Published
- 2007
33. Phase behaviour under pressure of a dichiral liquid crystal with an optically isotropic cubic phase: 2‐{4‐[(R)‐2‐fluorohexyloxy]phenyl}‐5‐{4‐[(S)‐2‐fluoro‐2‐methyldecanoyloxy]phenyl}pyrimidine
- Author
-
Atsushi Yoshizawa, Hiroshi Yokoyama, Tetsuo Kusumoto, and Yoji Maeda
- Subjects
Materials science ,Pyrimidine ,Triple point ,Isotropy ,General Chemistry ,Pressure differential ,Condensed Matter Physics ,Endothermic process ,law.invention ,Crystallography ,chemistry.chemical_compound ,Optical microscope ,chemistry ,law ,Liquid crystal ,Phase (matter) ,General Materials Science - Abstract
The phase behaviour of a dichiral liquid crystalline compound with an optically isotropic cubic phase, 2‐{4‐[(R)‐2‐fluorohexyloxy]phenyl}‐5‐{4‐[(S)‐2‐fluoro‐2‐methyldecanoyloxy]phenyl}pyrimidine, (R,S)‐FPPY, was investigated under pressures up to 100 MPa using a polarizing optical microscope equipped with a high pressure optical cell and a high pressure differential thermal analyser. (R,S)‐FPPY exhibits the isotropic liquid (I)–chiral smectic C (SmC*)–optically isotropic cubic (Cub)–chiral smectic X (SmX*)–crystal (Cr) transition sequence on cooling at pressures up to about 13 MPa, in which the SmC*–Cub transition occurs with an associated endothermic peak. The heating process of the (R,S)‐FPPY crystals showed the Cr–SmX*–Cub–I and Cr–SmX*–SmC*–I phase sequences under pressures below and above about 50 MPa, respectively. The triple point for the SmX*, Cub and isotropic liquid phases was estimated to be about 52±1 MPa, 143.0±0.5°C, indicating the upper limit of pressure for the formation of the cubic phase...
- Published
- 2007
34. Synthesis and physical properties ofα‐(4‐cyanobiphenyl‐4′‐yloxy)‐ω‐[4‐(5‐alkylpyrimidine‐2‐yl)phenyloxy]alkanes
- Author
-
Kazuyuki Yamamoto, Isa Nishiyama, Harutada Dewa, Hiroshi Yokoyama, Yoshimitsu Kohama, Jun Yamamoto, Atsushi Yoshizawa, Mariko Kurauchi, and Takahiro Yamamoto
- Subjects
Homologous series ,chemistry.chemical_compound ,Crystallography ,Materials science ,chemistry ,Liquid crystal ,Phase (matter) ,Organic chemistry ,General Materials Science ,General Chemistry ,Condensed Matter Physics - Abstract
We prepared a homologous series of dimeric liquid crystals, α‐(4‐cyanobiphenyl‐4′‐yloxy)‐ω‐[4‐(5‐alkylpyrimidine‐2‐yl)phenyloxy]alkanes (mPYnOCB), in which cyanobiphenyl and phenylpyrimidine moieties are connected via a flexible central spacer. We investigated the physical properties of mPYnOCB and of binary mixtures between the dimeric compounds. The interdigitated anticlinic smectic C (SmCanti) phase was found to be induced for some binary mixtures between the dimers with a different odd‐numbered spacer. Furthermore, a striped pattern was observed in the SmCanti phase of a homeotropically aligned sample. The striped pattern was propagated when the temperature of the sample was varied. We discuss the correlation between the structure of the SmCanti phase and the appearance of the striped pattern.
- Published
- 2006
35. Phase transition behaviour of novel Y‐shaped liquid crystal oligomers
- Author
-
Akihisa Yamaguchi, Atsushi Yoshizawa, and Megumi Nakata
- Subjects
Phase transition ,Materials science ,Mesogen ,Isotropy ,General Chemistry ,Condensed Matter Physics ,law.invention ,Crystallography ,Differential scanning calorimetry ,Optical microscope ,Liquid crystal ,law ,Phase (matter) ,Organic chemistry ,General Materials Science - Abstract
We have designed novel liquid crystal oligomers in which three mesogenic units are connected via 3,5‐dihydroxybenzoic acid. 4‐Cyanobiphenyl‐4′‐yl 3,5‐bis{6‐[4‐(5‐octylpyrimidin‐2‐yl)phenyloxy]hexyloxy}benzoate and 4‐(5‐octylpyrimidine‐2‐yl)phenyl 3,5‐bis{6‐[4‐(5‐octylpyrimidine‐2‐yl)phenyloxy]hexyloxy}benzoate have been prepared, and their physical properties investigated by optical microscopy and differential scanning calorimetry. The Y‐shaped liquid crystal oligomers were found to show a direct phase transition from isotropic liquid to anticlinic SmC (SmCanti) phase.
- Published
- 2006
36. Synthesis and physical properties of novel liquid crystal trimers containing resorcinol as a linking unit
- Author
-
Hiroshi Kinbara, Atsushi Yoshizawa, Akihisa Yamaguchi, Harutada Dewa, and Tsuyoshi Narumi
- Subjects
Phase transition ,Materials science ,Mesogen ,General Chemistry ,Resorcinol ,Condensed Matter Physics ,Crystallinity ,chemistry.chemical_compound ,Crystallography ,Homologous series ,chemistry ,Liquid crystal ,Phase (matter) ,Organic chemistry ,General Materials Science ,Benzene - Abstract
A homologous series of novel liquid crystal trimers in which cyanobiphenyl and phenylpyrimidine moieties are connected via resorcinol was prepared and their physical properties investigated. 3‐{6‐[4‐(4‐Cyanophenyl)phenyl]hexyloxy}‐1‐{6‐[4‐(5‐octylpyrimidine‐2‐yl)phenyl]hexyloxy}benzene, compound I‐(6,6), was found to show monotropic nematic, smectic A and anticlinic smectic C (SmCanti) phases. We investigated the effects of the spacer length and the linking group on the phase transition behaviour. In addition, trimers with identical mesogenic units were prepared and their physical properties compared with those containing two different mesogens. Only the meta‐substituted trimers showed the SmCanti phase despite its reduced tendency to exhibit liquid crystallinity than the ortho‐ and para‐substituted trimers.
- Published
- 2005
37. Physical properties of a novel chiral material possessing a binaphthyl group
- Author
-
Atsushi Yoshizawa, Juri Rokunohe, and Akihisa Yamaguchi
- Subjects
Materials science ,Pyrimidine ,Dimer ,General Chemistry ,Condensed Matter Physics ,chemistry.chemical_compound ,Crystallography ,Monomer ,chemistry ,Liquid crystal ,Axial chirality ,Phase (matter) ,Organic chemistry ,General Materials Science ,Grain boundary ,Twist - Abstract
A novel chiral dimeric compound, (R)‐2,2′‐bis{6‐[4‐(5‐octylpyrimidine‐2‐yl)phenyloxy]hexyloxy}‐1,1′‐binaphthyl (1), has been prepared and its physical properties investigated. Compound 1 was found to show a monotropic smectic A phase. A twist grain boundary phase was observed in binary mixtures of compound 1 and its corresponding monomeric liquid crystal, 5‐octyl‐2‐(4‐hexyloxyphenyl)pyrimidine (8‐PYP‐6O). Pitch measurements in a mixture with a host material revealed that the binaphthyl dimer induces a stronger helical structure in the N* phase than in the SmC* phase. We also measured helical pitch values in N* and SmC* phases induced by other twin materials with a chiral centre. We discuss characteristic effects of axial chirality in liquid crystalline phases in comparison with that of centres of chilarity.
- Published
- 2005
38. Frustration Caused by Competition Between Interlayer and Intralayer Interactions in a Dichiral Liquid Crystal
- Author
-
Akihisa Yamaguchi, Tetsuo Kusumoto, and Atsushi Yoshizawa
- Subjects
Phase transition ,Chemistry ,Stereochemistry ,media_common.quotation_subject ,Frustration ,General Chemistry ,Condensed Matter Physics ,Endothermic process ,Hysteresis ,Crystallography ,Liquid crystal ,Phase (matter) ,General Materials Science ,Chirality (chemistry) ,Phase diagram ,media_common - Abstract
We reported that a dichiral liquid crystal 2-{4-[(R)-2-fluorohexyloxy]phenyl}-5-4-[(S)-2-fluoro-2-methyldecanoy]phenyl}pyrimidine (1) upon cooling exhibits an endothermic transition from a chiral smectic C phase to an optically isotropic phase (IsoX). We have investigated transition behaviour of a binary mixture between 1 and the corresponding monochiral liquid crystal without the IsoX phase, 2-[4-[hexyloxy]phenyl}-5-4-{[(S)-2-fluoro-2-methylnonanoyl]phenyl}pyrimidine (2). In the phase diagram clear hysteresis was observed in appearance of the IsoX phase between heating and cooling.
- Published
- 2004
39. Phase Transition Behaviour of Symmetric and Non-Symmetric Dimeric Liquid Crystals
- Author
-
Atsushi Yoshizawa and Shinobu Hatai
- Subjects
Phase transition ,Chemistry ,Dimer ,Non symmetric ,General Chemistry ,Condensed Matter Physics ,Antiparallel (biochemistry) ,chemistry.chemical_compound ,Crystallography ,Liquid crystal ,Intermolecular interaction ,Phase (matter) ,Moiety ,General Materials Science - Abstract
We have prepared novel symmetric and non-symmetric dimeric liquid crystals possessing a phenylpyrimidine moiety and investigated the transition behaviour. We discuss effect of the spacer length and the core structure on the transition behaviour. The present system is thought to be a model to investigate molecular packing in SmA and SmC phases of 2-ring phenylpyrimidine liquid crystals. Results of binary mixture systems between the dimeric materials indicate that intermolecular interaction organized by antiparallel packing of the phenylpyrimidine group increases the stability of the SmC phase.
- Published
- 2004
40. CUBIC AND BLUE PHASES IN A FLUORINE-CONTAINING DICHIRAL COMPOUND
- Author
-
Yoichi Takanishi, Kenji Ema, Atsushi Yoshizawa, Shohei Yoshida, Tamejiro Hiyama, Haruhiko Yao, Ken Ishikawa, Tetsuo Kusumoto, Hideo Takezoe, and Toyokazu Ogasawara
- Subjects
Diffraction ,Crystallography ,Blue colored ,Differential scanning calorimetry ,Liquid crystal ,Chemistry ,Phase (matter) ,General Materials Science ,General Chemistry ,Calorimetry ,Dielectric ,Texture (crystalline) ,Condensed Matter Physics - Abstract
The structure and dynamics in an optically isotropic liquid crystalline phase exhibited in a dichiral compound with fluorines have been investigated using X-ray, 19 F-NMR and dielectric measurements. Results in the dielectric measurement and 19 F-NMR measurements clearly show that molecular motion in this phase is just like in the isotropic phase as observed by texture. However several X-ray diffraction peaks observed in a small angle range indicate a kind of cubic phase (Cub). Based on the X-ray diffraction patterns together with the existence of circular dichroism, the phase is assigned to a chiral cubic structure belonging to crystallographic spacegroup I432. Moreover, the exotic phase with blue colored and foggy texture was found in the lower temperature range of isotropic liquid. X-ray diffraction in this phase clearly shows a diffraction ring corresponding to a layer structure, indicating that this blue-colored phase is assignable to a smectic blue phase (BP sm ). It was also found that the layer correlation length is remarkably long compared with the previously reported BP sm phases. We want to emphasize that the present material is quite unique in the sense that both cubic phases, BP sm and Cub, appear. The influence of cell thickness and incubation time on the emergence of the smectic C * phase is also discussed based on dielectric measurements and AC calorimetry.
- Published
- 2003
41. Anomalous behaviours of the heat capacity in a liquid crystal showing a re-entrant isotropic phase
- Author
-
Tetsuo Kusumoto, Yoichi Takanishi, Haruhiko Yao, Tamejiro Hiyama, Hideo Takezoe, Kenji Ema, and Atsushi Yoshizawa
- Subjects
Phase transition ,Materials science ,Liquid crystal ,Phase (matter) ,Isotropy ,Thermodynamics ,High resolution ,General Materials Science ,Re entrant ,General Chemistry ,Atmospheric temperature range ,Condensed Matter Physics ,Heat capacity - Abstract
High resolution a.c. calorimetric measurements have been carried out on a liquid crystal 2-{4-[(R)-2-fluorohexyloxy]phenyl}-5-{4-[(S)-2-fluoro-2-methyldecanoyloxy]phenyl}pyrimidine (RSFPPY), determined the present measurement revealed precise temperature dependence of the heat capacity over a wide temperature range including the phase transition temperatures. The isotropic-chiral smectic C transition was anomalous in that it showed quite different behaviours depending on whether the measurement was made on heating or cooling; that is attributed to the relaxational character of the transition. A new non-transitional feature in the isotropic phase was found, corresponding to a very broad heat capacity peak over a 30 K temperature range. This indicates an existence of a new phase, possibly some kind of blue phase, at the lower temperature side of the isotropic phase. (RSFPPY), determined the present measurement revealed precise temperature dependence of
- Published
- 2002
42. Chiral recognition in the crystal structure of a dichiral mesogen with a unique isotropic mesophase: 2-{4-[(R)-2-fluorohexyloxy]phenyl}-5-{4-[(S)-2-fluoro-2-methyldecanoyloxy]phenyl}pyrimidine
- Author
-
Tetsuo Kusumoto, Kayako Hori, Atsushi Yoshizawa, and Yasuko Matsunaga
- Subjects
Materials science ,Mesogen ,Mesophase ,General Chemistry ,Crystal structure ,Condensed Matter Physics ,Crystal ,Crystallography ,symbols.namesake ,Liquid crystal ,Phase (matter) ,symbols ,Organic chemistry ,Molecule ,General Materials Science ,Van der Waals radius - Abstract
The crystal structure of the title compound, which has an optically isotropic IsoX phase with an endothermic transition on cooling from an Sm*C phase, has been determined at 230 K. The crystal has a smectic-like layer structure composed of four crystallographically independent molecules. In the layer, one-dimensional chains of tightly fitted pyrimidine rings, with N... H distances shorter than the van der Waals radii, result in the large overlapping of core moieties and further induce close contacts and stereo-specific F-methyl interactions between the chiral groups; this is considered to be responsible for the uniquely organized IsoX phase.
- Published
- 2001
43. Isotropic Cubic Phase Organized by Chiral Molecular Recognition
- Author
-
Yoichi Takanishi, Tetsuo Kusumoto, Tamejiro Hiyama, Noriko Ise, Atsushi Yoshizawa, and Hideo Takezoe
- Subjects
Crystallography ,chemistry.chemical_compound ,chemistry ,Stereochemistry ,Liquid crystal ,Phase (matter) ,Intermolecular force ,Mesophase ,Enantiomer ,Condensed Matter Physics ,Chirality (chemistry) ,Derivative (chemistry) ,Phase diagram - Abstract
We investigated property-structure relations in a dichiral compound which exhibits an optically isotropic phase (IsoX). Slight modification of the molecular structure except the chain length suppressed the IsoX phase. A phase diagram between enantiomers suggests that chiral recognition induces the IsoX phase. A miscibility study between the dichiral compound (R, S) and a hydrazine derivative (BABH8) with a cubic phase was performed Both the IsoX phase and the cubic phase of BABH8 were suppressed, while the SmC* phase of (R, S) was miscible with the SmC phase of BABH8. The phase diagram reflects the competition between different intermolecular interactions. We discuss the novel chiral effect on mesophase formation.
- Published
- 2001
44. Formation of Optically Isotropic Cubic Phase Based on Chiral Recognition in Dichiral Compounds
- Author
-
Atsushi Yoshizawa, Yoichi Takanishi, Hideo Takezoe, Tetsuo Kusumoto, and Tamejiro Hiyama
- Subjects
Crystallography ,Molecular dynamics ,Chemistry ,Liquid crystal ,Phase (matter) ,Isotropy ,Mesophase ,Organic chemistry ,Dielectric ,Condensed Matter Physics ,Chirality (chemistry) ,Phase diagram - Abstract
Dielectric and 13C-NMR measurements have been made to investigate the optically isotropic (IsoX) phase in dichiral compounds. The dielectric dispersions in the IsoX phase was found to be almost the...
- Published
- 2000
45. Molecular Recognition of the Dichiral Liquid Crystals Containing Fluorines
- Author
-
Tamejiro Hiyama, Junko Umezawa, Miho Katoh, Hiroshi Matsutani, Yoichi Takanishi, Tetsuo Kusumoto, Atsushi Yoshizawa, Noriko Ise, Hideo Takezoe, and Ken-ichi Sato
- Subjects
Molecular aggregation ,Crystallography ,chemistry.chemical_compound ,Molecular recognition ,Liquid crystal ,Stereochemistry ,Chemistry ,Phase (matter) ,Enthalpy ,Ether ,Condensed Matter Physics ,Endothermic process ,Ferroelectricity - Abstract
Novel dichiral liquid crystal compound 2-[4-((R)-2-fluorohexyloxy)phenyl]-5-[4-((S)-2-fluoro-2-methyldecanoyloxy)phenyl]-pyrimidine((R,S)-1) exhibits new optically isotropic phase (IsoX) with an endothermic transition enthalpy on cooling. In contrast, (S,S)-1 did not show the unusual transition. However, a 1:1 mixture of (S,S)-1 and (R,R)-1 exhibited IsoX phase. These results suggest that the appearance of IsoX phase is attributed to a chirality-dependent molecular recognition.
- Published
- 1999
46. Physical properties of non-symmetric dimeric liquid crystals
- Author
-
Okada Tomomi, Atsushi Yoshizawa, and Noriko Ise
- Subjects
Alkane ,chemistry.chemical_classification ,Crystallography ,Phase transition ,Homologous series ,chemistry.chemical_compound ,Materials science ,chemistry ,Liquid crystal ,Intermolecular force ,Non symmetric ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials - Abstract
A homologous series of novel non-symmetric dimeric liquid crystals, α-(4-cyanobiphenyl-4'-yloxy)-ω-[4-(5-octylpyrimidine-2-yl)phenyl-4''-oxy] alkane, has been prepared and the physical properties investigated. C-13 NMR measurements revealed the relationship between intermolecular interactions and phase transition behavior for the dimeric liquid crystal.
- Published
- 1998
47. Amplification of the twisting power by modification of the chiral spacer in a smectic liquid-crystalline phase
- Author
-
Atsushi Yoshizawa
- Subjects
Crystallography ,Materials science ,Liquid crystalline ,Liquid crystal ,Phase (matter) ,Molecule ,Condensed Matter Physics ,Chirality (chemistry) ,Electronic, Optical and Magnetic Materials - Abstract
We investigated twisting power of chiral twin molecules, (S)-2-methylnonanedioic acid bis[4-(5-octyl-2-pyrimidinyl)phenyl]ester (MNB-8-PYP) and (S)-2-methyldecanedioic acid bis[4-(5-octyl-2-pyrimidinyl)phenyl] ester (MDB-8-PYP), in N* and SmC* phases. The inverse of the SmC* pitch induced by MDB-8-PYP was found to vary non-linearly as a function of changing concentration, indicating cooperative twisting mechanism for MDB-8-PYP which induces stronger helical structure than MNB-8-PYP.
- Published
- 1998
48. Chirality in liquid-crystalline twin materials
- Author
-
Isa Nishiyama and Atsushi Yoshizawa
- Subjects
Condensed Matter::Soft Condensed Matter ,Condensed Matter::Materials Science ,Materials science ,Chemical physics ,Liquid crystalline ,High Energy Physics::Lattice ,Condensed Matter Physics ,Chirality (chemistry) ,Electronic, Optical and Magnetic Materials - Abstract
Helical macrostructures in the liquid-crystalline phases induced by chiral twin materials where the chiral centre was introduced at the central spacer are investigated. Relationships between molecular structures and the twisting power are reported and discussed in two different types of helical liquid-crystalline phases, i.e., the cholesteric and chiral smectic C phases.
- Published
- 1996
49. New Chiral Dopants Based on the 2-Fluoro-2-Methylalkoxy Tail for Use in Ferroelectric Liquid Crystal Mixtures
- Author
-
William N. Thurmes, Rohini T. Vohra, Toshihiro Hirai, Michael D. Wand, Junko Umezawa, Atsushi Yoshizawa, and Kundalika M. More
- Subjects
Crystallography ,chemistry.chemical_compound ,Materials science ,Dopant ,chemistry ,Liquid crystal ,Stereochemistry ,Condensed Matter Physics ,Polarization (electrochemistry) ,Ferroelectricity ,Sign (mathematics) ,Methyl group - Abstract
A new class of FLC materials based on the 2-fluoro-2-methylalkoxy tail is reported. This new class of materials consistently shows an N* helical pitch opposite in sign to that of the polarization. These materials are compared to their 2-fluoroalkoxy analogs to explore the methyl group's effect on the N* pitch and polarization.
- Published
- 1995
50. Ferro-, Ferri- and Antiferroelectric Phases of an Optically Active Benzoate
- Author
-
Atsushi Yoshizawa, Isa Nishiyama, and Masayuki Saito
- Subjects
Crystallography ,Chemistry ,Chemical shift ,Analytical chemistry ,Antiferroelectricity ,Optically active ,Fourier transform infrared spectroscopy ,Condensed Matter Physics - Abstract
Ferro, ferri and antiferroelectric phases of an optically active benzoate, (R)-1-methylheptyl 4‘-(4“-n-decyloxybenzoyloxy)biphenyl-4-carboxylate, have been investigated by means of solid-state C-13 NMR and FTIR spectroscopy. Results obtained by C-13 NMR on the chemical shifts, T1 values and shapes of peaks have been reported. The shapes and intensities for the peaks corresponding to two ester groups, obtained by FTIR measurement, have also been compared between smectic phases.
- Published
- 1995
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