LIQUID CRYSTALS
·
2022
·
IF 2.676
Tong Zhang,Yuyu He,Fanghua Liang,Ran Chen,Pei Chen,Xinbing Chen,Zhongwei An
A series of benzimidazole-based liquid crystal compounds containing laterally difluoro-substituted and ethynyl linking groups, namely, 2-(4-(2-(2,3-difluoro-4-(alkoxy) phenyl)ethynyl)phenyl)-1-methyl-1 H-benzimidazolem derivatives (nPF(2,3)EPMx), are synthesised and investigated for their mesomorphic properties. These compounds mainly display enantiotropic nematic mesophases in the ranges of 32.0–44.5°C (heating process) and 50.0–64.0°C (cooling process). 10PF(2,3)EPMx exhibits lower clearing points and broader nematic phase ranges than nonfluorinated reference compound 10PEPMx, because of their slightly increased dipole moment. nPF(2,3)EPMx displays much larger theoretical birefringence (0.43–0.55) and experimental birefringence (0.42–0.53) than the common tolane-based liquid crystals, which is ascribed to its large π-conjugated molecule composed of benzene core, ethynyl linking group and benzimidazole terminated unit. The theory results of three-dimensional molecular conformations with dipole moment (µ), ratio of length to width (L/W), polarisability anisotropy (Δα) and average polarisability (Δα) calculated with density functional theory are also helpful in explaining the experimental results.
研究领域:
材料科学
·
化学
✓ 已验证
DOI
高影响因子
ChemSusChem
·
2024
·
IF 7.5
Jiaqi Zhao,Zhanwei Xu,Yujiao Zhang,Jin QingZhu,Longhua Guo,Siyu Chen,Xuetao Shen,Jiayin Li,Zhi Li
The sluggish transition and shuttle of polysulfides (LiPS) significantly hinder the application and commercialization of Li-S batteries. Herein, carbon nanotubes (CNTs) supported 10 nm sized iron Hexadecafluorophthalocyanine (FePcF16/CNTs) are prepared using a solid synthesis approach. The well-exposed FePcF16 molecular improve the LiPS capture efficiency and redox kinetics by its central Fe-N4 units and F functional groups. The strong electron withdraw F groups significantly promote the conjugate effect and decrease the steric hindrance during mass migration procedure. Distribution of relaxation time (DRT) analysis shows that the Fe-N4 units exhibit strong affinity towards LiPS and the F groups further improve the Li+ diffusion rate in Li2S nucleation and oxidation procedure, accomplishing a porous surface on cathode. As a result, the FePcF16/CNTs separator exhibits a high initial capacity of 1136.2 mAh g-1 at 0.2 C, outstanding rate capacity of 624.9 mAh g-1 at 5 C and superior long-term stability at 2 C surviving 300 cycles with a low capacity decay of 0.43‰ per cycle.
研究领域:
材料科学
·
电化学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
LIQUID CRYSTALS
·
2015
·
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
·
化学
✓ 已验证
DOI
高影响因子
JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
·
2023
·
IF 5.7
Kui Liu,Dainan Zhang,Yuran Yang,Qisheng Yin,Yida Lei,Cheng Liu,Jie Li,Lichuan Jin,Yulong Liao,Huaiwu Zhang
Herein, the sintering behavior, structural evolution, microstructure, and dielectric properties of Li 2+ x MgTiO 4 F x (0 ≤ x ≤ 5) ceramics were investigated. At x ≤ 0.75, Li 2+ x MgTiO 4 F x ceramics formed a continuous solid solution with a cubic rock salt structure. Subsequently, a composite ceramic of Li 2+ x MgTiO 4 F x and LiF was formed. It was found that the maximum mass percentage of LiF required to fully form a solid solution was between 11% and 13%. The Li 2.75 MgTiO 4 F 0.75 exhibited the best dielectric properties: ε r = 16.52, Q × f = 123,574 GHz, and τ f = −18.11 ppm/°C. The substitution of F - for O 2- resulted in a lower sintering temperature of 875 °C, which slightly suppressed the volatilization of Li, and thus optimized the dielectric properties. The decrease in lattice vibration damping behavior and the increase in electron cloud density resulted in lower dielectric losses. The reduction in molecular polarization rate led to a reduction in ε r , and the increase in bond energy optimized τ f . Good chemical compatibility with Ag electrode was demonstrated, indicating that Li 2+ x MgTiO 4 F x ceramics have unlimited potential for LTCC applications.
研究领域:
材料科学
·
电子工程
✓ 已验证
DOI
高影响因子
LIQUID CRYSTALS
·
2016
·
IF 2.244
Dingqian Shi,Kun Hu,Pei Chen,Aiai Gao,Weisong Du,Ran Chen,Xinbing Chen,Zhongwei An
Fluorine is widely used as a lateral substituent to modify the physical properties of liquid crystals. Here, laterally monofluorinated compounds, 2-(4ʹ-alkoxy-2-fluorobiphenyl-4-yl)-benzoxazole derivatives (nPPF(2)Bx) bearing different substituents (H, CH3, NO2, coded as nPPF(2)BH, nPPF(2)BM and nPPF(2)BN, respectively) at 5-position, were synthesised and characterised. It is interesting to note that these only display enantiotropic nematic mesophases with mesophase ranges of 12–28°C and 13–45°C on heating and cooling for nPPF(2)BH, 46–97°C and 62–120°C for nPPF(2)BM and 82–108°C and 87–113°C for nPPF(2)BN, which are very different from the corresponding monofluorine-substituted analogue (compounds I) with enantiotropic smectic or smectic/nematic mesophases. The enhanced nematic mesophase is attributed to the reduced π–π interaction/conjugation resulting from the twisted structure of the molecule caused by the introduction of a fluorine atom into the inter-ring of the biphenyl unit. These results suggest that modification of the monofluorine substituent position is an effective method to improve the nematic mesophase in benzoxazole-liquid crystals.
研究领域:
材料科学
·
有机化学
✓ 已验证
DOI
高影响因子
LIQUID CRYSTALS
·
2016
·
IF 2.244
Dingqian Shi,Kun Hu,Pei Chen,Weisong Du,Aiai Gao,Ran Chen,Xinbing Chen,Zhongwei An
A series of nematic heterocyclic liquid crystals, 2-(2ʹ-fluoro-4ʹ-alkoxy-1,1ʹ-biphenyl-4-yl)-benzoxazole derivatives (coded as nPF(2)PBx) bearing hydrogen (nPF(2)PBH), methyl (nPF(2)PBM) and nitro (nPF(2)PBN) terminal groups, respectively, are developped and investigated. The results show that the nematic mesophase stability is obviously improved via a slightly increase in the inter-ring twist angle between the planes of two phenyl rings in the biphenyl unit, where modification of the twist angle can be achieved by adjusting the position of the lateral monofluorine substituent from the outer to the inter ring of the biphenyl mesogenic core unit. Meanwhile, the inter-ring lateral fluorine substituent results in a decrease in both melting and clearing points but only a nematic mesophase with an acceptably wide mesophase range for nPF(2)PBx, and thus a potential application in liquid crystal display mixtures is expected, especially for the compounds nPF(2)PBM and nPF(2)PBN. The reduced π–π interaction/conjugation caused by the increased twist angle is considered as one of the possible reasons for the formation of a nematic mesophase.
研究领域:
材料科学
·
液晶化学
✓ 已验证
DOI
高影响因子
JOURNAL OF SOLID STATE ELECTROCHEMISTRY
·
2023
·Vol. 27
·期 5
·1269-1278
·
IF 2.5
Li Minzhang,Xu Junyuan,Qi Fei,Wang Yu,Yan Chunliu,Xu Jiaju
A tetrafluoro substituted CoPc (CoF 4 Pc), which is well dispersed in N,N-dimethylformamide (DMF), was used to modify carbon nanotubes (CNTs) via a facile sonication method, resulting in CoF 4 Pc nanorods with the length lower than 30 nm on the CNT surface. The as-fabricated CoF 4 Pc-CNT composites showed superior CO 2 RR catalytic activity compared with that of individual CoF 4 Pc, due to enhanced mass transfer and electrical conductivity arising from the CNT substrate. The CoF 4 Pc-CNT composite with the CoF 4 Pc/CNT weight ratio of 2:30 exhibited the highest CO current density of 29.0 mA cm −2 and CO selectivity of 91.8% at − 0.85 V vs. reversible hydrogen electrode (RHE) in a flow cell setup containing 0.5 M KHCO 3 , which was ascribed to enhanced charge transfer induced by highly dispersion of CoF 4 Pc nanorods, and good conductivity of CNT substrates. The work provides new insights for developing low-cost, effective, phthalocyanine-based catalysts for electrochemical CO 2 RR.
研究领域:
材料科学
·
电化学
·
环境科学
✓ 已验证
产品关联
DOI
高影响因子
LIQUID CRYSTALS
·
2018
·
IF 2.636
Qiang Weng,Longyan Duan,Pei Chen,Dingqian Shi,Aiai Gao,Xinbing Chen,Zhongwei An
Fluorinated aromatics is generally chosen as mesogenic cores to design novel liquid crystal compounds. Here, a series of benzoxazole derivatives with laterally multifluorinated biphenyl units, 2-(3′,3-difluoro −4′-alkoxy-1,1′-biphenyl-4-yl)-benzoxazole derivatives (coded as nPF(3)PF(3)Bx), are synthesized and characterized, where methyl and nitro moieties are selected as terminal groups to investigate the effects of different polar substituents on the liquid crystal properties. The compounds nPF(3)PF(3)Bx show enantiotropic mesophases with mesophase ranges of 0–40°C and 0–63°C on heating and cooling for hydrogen-terminated derivatives (nPF(3)PF(3)BH), 43–93°C and 54–123°C for methyl-terminated ones (nPF(3)PF(3)BM), 60–108°C and 74–152°C for nitro terminated ones (nPF(3)PF(3)BN), respectively. They exhibit photoluminescence emission peaks at 390–392 nm and UV–vis absorption bands with maxima at 327–330 nm, respectively. The results reveal that lateral multifluoro substituents lead to a decrease in melting/clearing points, while electron-withdrawing terminal nitro moiety results in increases in both melting point and mesophase range.
研究领域:
材料化学
·
液晶科学
·
有机合成
✓ 已验证
DOI
高影响因子
COMPOSITES PART B-ENGINEERING
·
2022
·
IF 11.322
Song Zhang,Weijiang Chen,Yushun Zhao,Lijian Ding,Xiaofeng Pan,Bin Du,Hao Shen,Chao Gong,Wei Yang,Kerong Yang,Xin Chen
Multi-aromatic ring epoxy composites (MAREC) are prospective electronic packaging materials owing to their high heat resistance. However, the presence of numerous conjugated π bonds lead to poor insulation performance of MAREC, limiting its further application. Here, we propose a unique strategy to design MAREC to integrate high insulation and high heat resistance performances by electron-induced effect. The results show that the substitution of H atoms of benzidine by F atoms and –CF 3 groups can lead to strong electron-induction effect. When all H atoms on the aromatic ring of benzidine are replaced by F atoms (8F), the electron-induced effect is the strongest (energy gap = 5.56 eV). The highest occupied molecular orbital of fluorenyl biphenyl exists by head to head overlap (similar to a σ bond), which significantly weakens the free sharing ability of the electrons on the conjugate π bonds of the aromatic ring. Although the reaction activity of –NH 2 groups of 8F is low, the strong electron-induction effect of 8F can be fully harnessed by combining CF (two –CF 3 groups replacing the H atoms of benzidine). The designed MAREC shows excellent insulation performance (AC breakdown strength = 39.18 kV/mm) and heat resistance performance ( T g = 234.5 °C, T d = 396.6 °C). Furthermore, the dielectric constant and dielectric loss are low ( [email protected] and [email protected] , respectively). We successfully fabricated materials with enhanced insulation and heat resistance performances, which can be used as packaging materials for large-scale integrated circuits, new energy power equipment, and energy storage devices.
研究领域:
材料科学
·
电子工程
✓ 已验证
产品关联
DOI
高影响因子
LIQUID CRYSTALS
·
2015
·
IF 2.486
Kun Hu,Pei Chen,Qiang Weng,Dingqian Shi,Ran Chen,Xinbing Chen,Zhongwei An
A series of 2-(3ʹ-fluoro-4ʹ-alkoxy-1,1ʹ-biphenyl-4-yl)-benzoxazole liquid crystals (coded as nPF(3)PBx) were prepared, where a lateral fluorine substituent, as well as methyl, chlorine and nitro terminal groups, was introduced into the molecules to investigate the effects of different polar substituents on the liquid crystal properties. The mesomorphic and photophysical properties were investigated. The results show that compounds nPF(3)PBx have enantiotropic mesophases; meanwhile, they exhibit UV–vis absorption bands with maxima at 323–326 nm and photoluminescence emission peaks at 389–395 nm, respectively. It is noted that nPF(3)PBx with terminal polar groups or electron-withdrawing groups (NO2, Cl) display higher clearing temperatures and wider mesophase range than those of the corresponding homologues with terminal non-polar groups or electron-donating groups (CH3, H). Meanwhile, compared with two lateral fluorine-substituted analogues containing 3,5-difluorophenyl unit, lateral monofluoro-substituted nPF(3)PBx display enhanced mesophase range both in heating and cooling except for terminal methyl-substituted compounds, as well as show obvious red-shifted UV–vis absorption bands and photoluminescence emission, which are attributed to the enhanced dipole–dipole interaction caused by increased dipole moment.
研究领域:
材料化学
·
物理化学
✓ 已验证
产品关联
DOI
高影响因子
DYES AND PIGMENTS
·
2016
·
IF 4.055
Qing Bao,Hua Li,Yang Li,Jinghui He,Qingfeng Xu,Najun Li,Dongyun Chen,Lihua Wang,Jianmei Lu
In this paper, two acceptor-donor-acceptor (A-D-A) type organic small molecules, 4,4'-(5,5'-(benzo[c] [1,2,5]thiadiazole-4,7-diyl)bis(3-hexylthiophene-5,2-diyl))bis(N-(4-nitrophenyl)-N-phenylaniline) (NTPA 2 TBT) and 4,4'-(5,6-difluorobenzo[c] [1,2,5]thiadiazole-4,7-diyl)bis(N-(4-nitrophenyl)-N-phenylaniline) (NTPA 2 BTF 2 ), were synthesized and fabricated into resistive random access memory devices. Compared with our previously reported molecule NTPA 2 BT, NTPA 2 TBT has 3-hexylthiophene linkages bridging its donor and acceptor, while there are two additional fluorine atoms in the benzothiadiazole moiety for NTPA 2 BTF 2. Both the fabricated memory devices based on these two new molecules perform nonvolatile ternary memory characteristics with lower threshold voltages , higher reproducibility and better stability. The addition of 3-hexylthiophene bridges significantly promotes the planarity of the conjugation backbone and facilitates the molecular stacking, while the substitution hydrogen by fluorine improves the intermolecular interaction , and thus also induces an ordered molecular stacking. The insertion of 3-hexylthiophene bridges or fluorine atoms could be an effective strategy of tailoring organic molecules to improve data storage performance with lower power consumption.
研究领域:
材料科学
·
有机电子学
·
分子器件
·
非易失性存储器
·
高分子化学
✓ 已验证
DOI
高影响因子
RSC Advances
·
2022
·Vol. 12
·期 19
·11715-11721
·
IF 4.036
Baokang Zou,Yipeng Zhan,Xiuli Xie,TongTong Zhang,Runkai Qiu,Fangming Zhu
Two salalen titanium(IV) complexes ((H-salalen)TiCl2 and (F-salalen)TiCl2) containing hydrogen and fluorine respectively on the phenolate ring close to the imine were synthesized for the copolymerization of ethylene with 1-octene to prepare poly(ethylene-co-1-octene) in the presence of methylaluminoxane (MAO). The (F-salalen)TiCl2/MAO showed higher catalytic activity and better copolymer characteristics such as a higher molecular weight, narrower molecular weight distribution, and higher 1-octene incorporation than (H-salalen)TiCl2/MAO, which revealed that the electron-withdrawing conjugated effect introduced by fluorine substituents led to improvements on catalytic performance and thermal stability. The influences of copolymerization conditions including temperature, Al/Ti molar ratios and comonomer feed ratios on the copolymerization behavior of (F-salalen)TiCl2/MAO and the copolymer microstructure were investigated in detail. Under the activation of MAO, the (F-salalen)TiCl2 could produce ultrahigh molecular weight poly(ethylene-co-1-octene) with 1-octene incorporation ratios in the range of 0.9–3.1 mol% and exhibit relatively high activity. It could be inferred that long ethylene sequences in the copolymer were segregated by the isolated 1-octene units based on the 13C NMR characterization of the copolymer. Moreover, the thermal properties and crystallization of copolymers were determined by DSC and XRD and correlated to the ethylene sequence length distribution. The reactivity ratios calculated by the triad distribution in 13C NMR revealed the random comonomer distribution in the copolymer chain.
研究领域:
高分子化学
·
配位聚合
·
催化化学
·
材料科学
·
高分子物理
✓ 已验证
DOI
高影响因子
危险品化学品经营许可证（带存储）