LIQUID CRYSTALS
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2015
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IF 2.486
Feng Li,Zhongwei An,Xinbing Chen,Pei Chen
A series of 2,3-difluoro tolane allyloxy-based liquid crystals (LCs), which are composed of the tolane unit, lateral fluoro substituents, alkoxy and allyloxy terminal groups, were synthesised with 4-bromo-2,3-difluorophenol as the starting material via a five-step reaction. Their structures were confirmed by infrared spectroscopy (IR), mass spectroscopy (MS) and nuclear magnetic resonance (NMR). The mesomorphic properties were investigated by differential scanning calorimetry (DSC) and polarising optical microscopy (POM). The dielectric measurement was performed using an independent analyser EC-1 and the birefringence was determined using an Abbe refractometer. The results reveal that LCs have large negative dielectric anisotropy and high birefringence, which are potentially important for the fast response displays and liquid crystal photonic devices (LCDs).
研究领域:
材料科学
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化学
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DOI
高影响因子
JOURNAL OF MOLECULAR LIQUIDS
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2024
·
IF 5.3
Ran Chen,Junyu Zou,Zihao Mao,Zhongwei An,Pei Chen,Xinbing Chen
Laser display technology can enhance the image quality of liquid–crystal on silicon (LCoS) devices in AR displays. High birefringence (Δ n ), large dielectric anisotropy (Δ ε ), low rotational viscosity ( γ 1 ) and good blue-light stability are inevitable performance requirements for achieving fast response time, low voltage and 2π phase modulation in LCoS devices based on laser display technology. However, people lack attention to how to obtain liquid crystal compounds with above properties. In this work, we propose to utilize one fluorinated terphenyl unit with excellent blue-light stability as the molecular skeleton, and then employ large polar terminal groups to modulate the molecular polarizability and dipole moment , and finally screen to obtain the LCs with high Δ n and large Δ ε . The effects of methyl, fluorinated, chlorinated and cyano terminal groups on the mesomorphic and electro-optical properties of fluorinated terphenyl LCs were systematically studied. Experimental and theoretical results show that the target compounds exhibit wide LC phase intervals, and could enhance the Δ n , Δ ε of the parent LC mixture and reduce its viscoelastic constant, further meaning that they would help to improve the electro-optical properties of LC mixtures for AR displays. Our results would provide experimental data and technical support for the future development of LC mixtures with high blue-light stability for AR displays.
研究领域:
材料科学
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光学
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显示技术
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DOI
高影响因子
Journal of Materials Chemistry C
·
2015
·Vol. 3
·期 33
·8706-8711
·
IF 4.696
Ran Chen,Yi Jiang,Jian Li,Zhongwei An,Xinbing Chen,Pei Chen
Four series of 1,3-dioxolane-terminated liquid crystals were prepared via multi-step reactions based on 4-alkylcyclohexanecarboxylic acids. Their structures were confirmed by infrared spectrometry (IR), nuclear magnetic resonance (NMR) and mass spectrometry (MS). Their properties were measured by differential scanning calorimetry (DSC), polarising optical microscopy (POM), X-ray diffraction (XRD), Abbe refractometer and an electrical constants instrument. The results show that the positive dielectric anisotropy and birefringence of the tolane-liquid crystals are increased significantly by an introduction of 1,3-dioxolane as a terminal group. The application of the 1,3-dioxolane-terminated liquid crystals in the mixture was investigated and the results show that lower threshold voltage, wider nematic range and higher birefringence are obtained when compared to the mixture containing liquid crystals with buty-3-enyl as a terminal group. The lateral fluoro substituent, alkyne-bridge and 1,3-dioxolane terminal group enhance the stability of the nematic mesophase and the solubility of the corresponding compounds in the common host liquid crystal mixture. Meanwhile, DFT calculations of dipole moments and molecular polarizabilities were used to correlate the experimental findings.
研究领域:
材料科学
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化学
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产品关联
DOI
高影响因子
LIQUID CRYSTALS
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2023
·
IF 2.2
Tong Zhang,Fanghua Liang,Xurui Li,Hongfei Lin,Ran Chen,Pei Chen,Xinbing Chen,Zhongwei An
A series of new liquid crystal compounds with negative dielectric anisotropy was synthesised by regulating the orientation of the substituents on the benzoxazole ring, namely, 5–4-(2-(4-(alkoxy)phenyl)-2,3-difluorophenyl)benzo[d]oxazole derivatives (nPP(2,3)FO). These compounds mainly display enantiotropic nematic mesophases in the ranges of 8.62–16.09°C (heating process) and 23.98–30.32°C (cooling process), moderate birefringence (Δn) ranging from 0.25–0.32 (DFT theoretical calculation) and 0.22–0.28 (experimental measurement), as well as negative dielectric anisotropy (Δɛ) ranging from −2.77 to −2.94. These characterises are ascribed to the larger perpendicular dipole moments and orientation angles of benzoxazole. This work provides new ideas for the rational design of negative dielectric anisotropy liquid crystals.
研究领域:
材料科学
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化学
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DOI
高影响因子
LIQUID CRYSTALS
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2020
·
IF 2.908
Kun Hu,Qiang Weng,Ran Chen,Jian Li,Dingqian Shi,Pei Chen,Aiai Gao,Xinbing Chen,Zhongwei An
Six benzoxazole-terminated mesogenic compounds with fluoro substituent at different positions were prepared and their properties investigated. The compounds give a high birefringence (Δn~ 0.45) and a large-dielectric anisotropy (Δε~ 26), indicating a possible application in liquid-crystal mixture as a dopant to enhance performance of the host mixture. In accordance with conventional high Δn liquid crystals containing triple carbon-carbon bonds, lateral fluoro substituents and terminal groups can alter the Δn and Δε of benzoxazole-terminated liquid crystals. Meanwhile, some parameters such as dipole moment, polarisability, dihedral angles are calculated with density functional theory (DFT) methods to relate to the experimental Δn and Δε. It is noted that the introduction of the benzoxazole unit is an effective method to enhance Δn and Δε values of the rodlike molecule, this is ascribed to its π-conjugated benzene-fused heterocycle and large dipole moment.
研究领域:
材料科学
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化学
✓ 已验证
DOI
高影响因子
LIQUID CRYSTALS
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2016
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IF 2.244
Ran Chen,Zhongwei An,Feng Li,Xinbing Chen,Pei Chen
Four series of tolane liquid crystals containing 2,3-difluorophenylene and terminated by a tetrahydropyran (THP) moiety have been synthesised via multistep reactions based on 4-alkylcyclohexanecarboxylic acids and 4-bromo-2,3-difluorophenol. Their properties were measured by differential scanning calorimetry, polarising optical microscopy, Abbe refractometer and an electrical constants instrument. The results show that the THP-based liquid crystals nT reveal a relatively high value of the birefringence, negative dielectric anisotropy, good solubility and a broad nematic mesophase. The effects of the terminal alkyl chain, the lateral fluoro substituents and the THP terminal group on the mesomorphic and physical properties are discussed. Meanwhile, density functional theory calculations of molecular conformation and polarisability were conducted to correlate the experimental findings.
研究领域:
材料科学
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物理化学
✓ 已验证
产品关联
DOI
高影响因子
MOLECULES
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2023
·Vol. 28
·期 7
·3019
·
IF 4.6
Ran Chen,Zihao Mao,Zhongwei An,Xinbing Chen,Pei Chen
Aromatic heterocyclic liquid crystal (LC) materials have received much attention from LC chemists for their high birefringence and large dielectric anisotropy, yet few have reported their properties in LC mixtures. In this work, a series of fluorinated benzoxazole liquid crystal compounds were synthesized to evaluate their electro-optical properties in high birefringence LC mixtures, with the expectation of further establishing the theoretical basis and experimental evidence for their applications in LC photonics. Firstly, the effects of the lateral fluorine substituent positions on the molecular synthetic yield, mesomorphic and solubility properties were comparatively investigated. Afterwards, we focused on the fluorination effects on the core electro-optical properties, including birefringence, dielectric anisotropy and further investigation of the viscoelastic coefficient of high birefringence LC mixtures. Research results showed that the benzoxazole liquid crystal compounds possess low melting points, wide nematic phase intervals and good solubility by appropriate lateral fluorine substitution, which is beneficial to further improve the electro-optical properties of high birefringence LC mixtures. Meanwhile, the theoretical and experimental results corroborate each other to well reveal the structure–property relationship. This study demonstrates that fluorination would promote promising applications of benzoxazole-terminated liquid crystals in emerging LC optical devices.Keywords:liquid crystal mixture;high birefringence;benzoxazole;large dielectric anisotropy;DFT calculations
研究领域:
材料科学
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化学
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产品关联
DOI
PubMed
高影响因子
LIQUID CRYSTALS
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2021
·
IF 0
Ning Xie,Shenghua Du,Ran Chen,Guoqing Liu,Pei Chen,Qiang Weng,Jie Wang,Aiai Gao,Xinbing Chen,Zhongwei An
New benzoxazole-terminated mesogenic compounds containing tolane moiety with high birefringence and large dielectric anisotropy, namely, 2-[4-[2-[4-alkoxyphenyl]ethynyl]-2,6-difluoro-phenyl]-benzoxazole derivatives (nPEDFPBx), were synthesised and investigated. Among them, the ones bearing methyl and nitro substituents at 5-position of benzoxazole moiety exhibit stable mesophase ranges of 30–71°C and 55–81°C during heating and cooling processes, respectively, while the non-substituted compounds exhibit no mesophase except the ones with long terminal alkoxy chain (n = 10, 12). Birefringence of nPEDFPBx is obtained from DFT theoretical calculation (0.446–0.583) and experimental measurement (0.395–0.499), respectively, where high birefringence is ascribed to their large π-conjugated molecule composed of benzene ring, acetylene linkage and benzoxazole moiety. Meanwhile, it is found that nPEDFPBx displays large dielectric anisotropy because of their high dipole moment. As an example, the compound 5PEDFPBM is doped into the liquid crystalline mixture as an additive, the properties of the resulting mixture, such as birefringence, dielectric anisotropy, clearing point and response time, are improved obviously, indicating high potential application for liquid crystalline mixture.
研究领域:
材料科学
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化学
✓ 已验证
DOI
LIQUID CRYSTALS
·
2023
·
IF 2.2
Jiaxing Tang,Chenhe Yao,Zhongwei An,Ran Chen,Zihao Mao,Xinbing Chen,Pei Chen
A series of liquid crystals containing one n-propyl/n-propoxy, lateral fluorine substituent, a tolane mesophase unit, and a 2,2-difluorovinyl terminal group were designed and synthesised. Their chemical structures were characterised and confirmed by nuclear magnetic resonance (NMR), mass spectrometry and Fourier transform infrared spectrometry (FTIR) instruments. Meanwhile, the position and number effects of lateral fluorine substituents on the thermal, mesomorphic, and electro-optical properties of these compounds were explored. Furthermore, density functional theory (DFT) calculations of molecular conformation, polarisability components and dipole moment were utilised to correlate the experimental results. Research results show that the 2,2-difluorovinyl-terminated liquid crystal compounds possess excellent properties of low melting point, wide nematic-phase temperature interval, high birefringence, large dielectric anisotropy and low rotational viscosity. This molecular splicing strategy is an effective method to balance the trade-offs between high birefringence, large dielectric anisotropy, and low viscosity in nematic liquid crystals.
研究领域:
材料科学
·
化学
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产品关联
DOI
高影响因子
JOURNAL OF MOLECULAR LIQUIDS
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2023
·
IF 6
Tong Zhang,Fanghua Liang,Hongfei lin,Xurui li,Ran Chen,Pei Chen,Xinbing Chen,Zhongwei An
We synthesized heterocyclic liquid crystals with large birefringence and negative dielectric anisotropy, namely, 5–4-(2-(4-(alkoxy)phenyl)-2,3-difluorophenyl)benzo(d)oxazole derivatives ( nPFO ). These compounds display enantiotropic nematic mesophases with wide mesophase range of 45.9–84.0 °C (heating process) and 61.3–119.6 °C (cooling process). Compared with reference analogues of traditional benzoxazole compound 6PFB with different orientation of benzoxazole-terminated structure, the compounds nPFO roughly give lower melting points and clearing points because of their increased dihedral angle. Meanwhile, compounds nPFO show obviously large birefringence ( Δn, 0.28–0.39 and 0.39–0.48 for experimental measurement and DFT theoretical calculation, respectively) due to the enhanced π-conjugation caused by the ethynyl bridge group in molecules. Benefitting from the larger perpendicular dipole moments and orientation angles, nPFO displays negative dielectric anisotropy ( Δɛ ) ranging from −3.60 to −4.10. These compounds can endow a commercial negative LC mixture the larger Δ n and higher values of figure of merit, suggesting they are suitable dopant to further improve the performance of some commercial LC mixtures.
研究领域:
材料科学
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化学
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DOI
高影响因子
LIQUID CRYSTALS
·
2017
·
IF 2.661
Ran Chen,Liang Zhao,Zhongwei An,Xinbing Chen,Pei Chen
A series of tolane liquid crystals (LCs) containing 2,3-difluorophenyl and allyloxy terminal groups have been synthesised via multi-step reactions. Their thermotropic mesophases, birefringences and dielectric anisotropy properties are discussed by comparison with the non-fluorinated analog. The results show that the allyloxy-based tolane LC 3TOV reveals a high value of the birefringence (0.29), negative dielectric anisotropy (−4.44) and a broad nematic mesophase with a low melting point and high clearing point. The effects of the terminal alkyl chains, the lateral fluoro substituents, the allyloxy terminal group and alkyne bridge on the mesomorphic and physical properties were also discussed. Meanwhile, Density Functional Theory (DFT) calculations of molecular conformation and polarisability were used to correlate the experimental findings.
研究领域:
材料科学
·
化学
✓ 已验证
DOI
高影响因子
JOURNAL OF MOLECULAR LIQUIDS
·
2023
·
IF 6
Chenhe Yao,Jiaxing Tang,Ran Chen,Zihao Mao,Xinbing Chen,Pei Chen,Zhongwei An
A series of liquid crystals (LCs) containing bis-tolane, lateral fluorine substituents and 2,2-difluorovinyloxyl group were designed and synthesized. Their LC phase behavior, birefringence, dielectric anisotropy and viscosity properties were discussed by comparing with previously reported LCs with high birefringence and large electrical anisotropy. Meanwhile, the effects of lateral fluorine numbers on the melting point, birefringence and dielectric anisotropy of these LCs were explored, and density functional theory (DFT) calculations of molecular conformation and polarizability were used to correlate the experimental results. Research results indicated that the 2,2-difluorovinyloxyl terminal group decreased the melting points of these LCs, and these LCs showed relatively low melting point (<113.7 ℃), broad nematic-phase temperature interval, high birefringence (>0.4), and large dielectric anisotropy (35.87). Furthermore, performance in high birefringence LC mixture demonstrated that they could effectively improve the birefringence and dielectric anisotropy, and maintain low viscosity, which is expected to possess widespread applications in fast response LC optical devices.
研究领域:
材料科学
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物理化学
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产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）