POLYMER
·
2024
·
IF 4.1
Shiliang Liu,Rui Yang,Qixin Zhuang,Guozhu Zhan,Peiyuan Zuo,Xiaoyun Liu
In this study, six thermosetting benzoxazole monomers with endo-alkynyl groups are prepared, and the effect of the endo-alkynyl groups and substituent group on the curing behavior and solubility of monomers, and on the thermal properties and dielectric properties of polybenzoxazoles are investigated. Our findings reveal that incorporating endo-alkynyl groups enhances the cross-linked network in the benzoxazole monomers, thereby improving their thermal stability, hydrophobicity , and dielectric constant . However, this modification also results in decreased solubility and curing properties of the monomers. In addition, the position of the fluorine atoms can affect the curing behavior of monomer and the dielectric properties of polybenzoxazoles. When a fluorine atom is positioned ortho to the cyano group , it impedes the curing of the cyanide group, which increases the curing reaction temperature. Moreover, while it is generally believed that the addition of fluorine typically lowers the dielectric constant of a material, the placement of fluorine atoms ortho to the cyano group can lead to overlapping electronic effects. This overlap may increase the polarity of the curing network, which increases the dielectric constant and dielectric loss of the polybenzoxazoles. Among the six thermosetting benzoxazole monomers studied, poly (2 F-JQ) containing m -diethynyl groups exhibit a 5 % thermal decomposition temperature (Td 5 ) of 610 °C, and a low dielectric loss of 0.0045 at 1 MHz. Compared with other polybenzoxazoles, poly (2 F-JQ) possesses a moderate dielectric constant, excellent thermal stability, and extremely low dielectric loss. In summary, this study provides a new approach for preparing resins that feature high-temperature resistance and low dielectric loss.
研究领域:
材料科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
LIQUID CRYSTALS
·
2020
·
IF 2.908
Guoqing Liu,Liyuan Ren,Mengting Zhang,Shenghua Du,Pei Chen,Aiai Gao,Xinbing Chen,Zhongwei An
Series of heterocyclic compounds containing ethynyl group, 2-[4-[2-[4-(alkoxy)phenyl]ethynyl]phenyl] -benzoxazole derivatives (nPEPBx), are prepared and investigated. They display enantiotropic nematic and smectic mesophases with large mesophase ranges of 30–133°C (heating) and 31–141°C (cooling). Compared with reference analogues without ethynyl group, the compounds nPEPBx roughly give lower melting points and much higher nematic mesophase stability because of the introduction of triple carbon-carbon bond. Meanwhile, they show much higher birefringence (Δn, 0.50–0.65 and 0.55–0.68 for experimental and calculated values with density functional theory (DFT), respectively) than common tolane-based liquid crystals, which indicates that the introduction of benzoxazole unit is an effective method to enhance Δn values of the rod-like molecule. It is concluded that nPEPBx has a potential application in liquid crystal mixture as a dopant to enhance the performance of the host mixture.
研究领域:
材料化学
·
液晶物理
✓ 已验证
DOI
高影响因子
LIQUID CRYSTALS
·
2020
·
IF 2.908
Jiazhen Dang,Shenghua Du,Liyuan Ren,Mengting Zhang,Pei Chen,Aiai Gao,Weisong Du,Xinbing Chen,Zhongwei An
Heterocyclic mesogenic compounds are one of the interesting liquid crystals. Here, a series of 1-methyl-1H- benzimidazole-based mesogenic compounds incorporating ethynyl moiety, 2-[4-[2-[4-(alkoxy)phenyl]ethynyl]phenyl]-1-methyl-1H-1,3-benzimidazole derivatives (nPEPMx) with terminal groups of H, CH3 and NO2 (coded as nPEPMH, nPEPMM and nPEPMN, respectively), are synthesised and their properties are evaluated. It is noted that the compounds nPEPMx with short alkoxy chain less than 9 carbon atoms display enantiotropic nematic mesophases, whereas corresponding reference compounds without ethynyl moiety have enantiotropic smectic mesophases. The mesophase ranges of compounds nPEPMx 50–70°C and 55–108°C on heating and cooling for nPEPMH, 76–106°C and 98–142°C for nPEPMM, and 78–132°C and 130–166°C for nPEPMN, respectively. Besides, compounds nPEPMx show obviously large birefringence of 0.501–0.641, suggesting a potential application in liquid crystal mixture. The high birefringence may result from its large π-conjugated molecule structure incorporating ethynyl and benzimidazole π-conjugated mesogenic unit.
研究领域:
材料化学
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液晶科学
·
有机合成化学
✓ 已验证
DOI
高影响因子
LIQUID CRYSTALS
·
2020
·
IF 2.908
Shenghua Du,Mengting Zhang,Pei Chen,Jiazhen Dang,Aiai Gao,Weisong Du,Xinbing Chen,Zhongwei An
With altering molecular dipole moments via lateral fluoro atom and π-conjugation through carbon–carbon triple bond, improved mesomorphic behaviour is achieved for new kind of fluorinated mesogenic compounds containing ethynyl and 1-methyl-1H-benzimidazole moieties, namely, 2-[4-[2-[4-(alkoxy) phenyl]ethynyl]-3-fluorophenyl]-1-methyl-1H-benzimidazole derivatives (nPEF(3)PMx). The compounds nPEF(3)PMx mainly display enantiotropic nematic mesophases with mesophase ranges of 27.1–59.1 °C and 62.7–96.7°C on heating and cooling for nPEF(3)PMH, 59.499.1°C and 96.2–144.6°C for nPEF(3)PMM, and 101.6–109.4°C and 104.9–157.2°C for nPEF(3)PMN (n < 8), respectively. Compared with nonfluorinated reference analogues I, nPEF(3)PMx give obviously lower melting points and much wider or comparable nematic mesophase ranges, meanwhile, they show much lower melting points and higher nematic mesophase stability than reference analogues II because of their reduced molecular dipole moments and enhanced π-conjugation. In addition, the compounds nPEF(3)PMx are composed of benzene ring, ethynyl bridge and benzimidazole mesogenic unit, therefore, they have high birefringence of 0.48–0.62 resulted from their large π-conjugated molecule. The result indicates that nPEF(3)PMx has a potential application in liquid crystal mixture.
研究领域:
材料科学
·
化学
✓ 已验证
产品关联
DOI
高影响因子
INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES
·
2024
·
IF 7.7
Miao Zhang,Peng Zhu,Jianxin Liu,Huapeng Zhang,Yanjun Tang
In recent years, click reactions with cellulose nanocrystals (CNC) participation have gradually become a research hotspot. Carboxylamine condensation is the most used method to introduce terminal alkyne groups at the reducing end of CNC as reaction sites for click reactions. However, hydroxyl groups on CNC surface would be slightly oxidized during the carboxyamine condensation process , inducing the potential positions of introduced alkynes would be not only at the reducing end but also on CNC surface. Here, aldimine condensation was proposed to introduce terminal alkyne groups just at the reducing end of CNC, and a systematic comparison analysis was conducted with carboxylamine condensation. Firstly, the selectivity and extent of alkynylation were characterized by XPS and EA. Secondly, the end aldehyde content in these CNC samples was measured by the BCA method, which quantitatively explained the grafting efficiency of aldimine condensation and further verified its feasibility. Thirdly, the clickability of the modified CNC samples was confirmed through XPS analysis of the products after a pre-designed click reaction. In sum, aldimine condensation was proven to be a simple and effective strategy for introducing terminal alkyne groups at the reducing end of CNC, which could be used as reaction sites for further click reactions.
研究领域:
材料科学
·
化学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
JOURNAL OF MATERIALS SCIENCE
·
2020
·Vol. 56
·期 1
·870-885
·
IF 3.553
Jia Daikun,Yang Jianxiao,He Jiyu,Li Xiangmei,Yang Rongjie
Abstract The rapid depletion of energy resources is the most serious challenge facing humanity today. Energy consumption by buildings is the largest component of energy consumption, and most of it is in the form of heat loss. Therefore, many buildings use rigid polyurethane foam (PUF) as thermal insulation material to effectively reduce heat loss. However, the greatest disadvantage of PUF is its high flammability. In this work, to reduce the risk of fire caused by PUF, melamine-based polyol containing phosphonate and alkynyl groups (MF 3.5 and MB 3 F 3 ) is synthesized and used to improve the flame retardancy of PUF by replacing common polyether polyol. The effects of MF 3.5 and MB 3 F 3 on the physical and mechanical properties, cell morphology, thermal stability and flame retardancy of PUF are systematically studied. The research results show that the flame-retardant polyols have no effect on the thermal insulation properties of PUF, but result in a slight decrease in compressive strength. Thermogravimetric analysis proves that MF 3.5 and MB 3 F 3 can increase the temperature of the maximum mass loss rate and reduce the maximum mass loss rate, and significantly increase the char yield at 800 °C. The limiting oxygen index (LOI) value is increased to 24.3%. Cone calorimetry experiments show that MB 3 F 3 reduces the peak heat release rate and total heat release by 28.2% and 30.5%, respectively. Vertical combustion tests show that the average burning rate of the flame-retardant PUF is much slower, and melt-dripping behavior is eliminated. The flame retardancy of PUF is improved mainly through a condensed phase mechanism. Graphic abstract
研究领域:
材料科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
Catalysis Science & Technology
·
2024
·
IF 4.4
Pengken Li,Hui Zhao,Rong Ji,Wenwen Chi,Xinyu Sun,Yuming Dong,Yongfa Zhu
A one-step two-electron oxygen reduction pathway is crucial for the stable and efficient photosynthesis of hydrogen peroxide. However, the lower oxygen adsorption and activation capacity significantly restrict the ability of the one-step two-electron oxygen reduction pathway. In this work, a covalent organic framework containing a diacetylene unit (COF-Tfp-BDDA) as an efficient oxygen reduction active site was designed for the photosynthesis of hydrogen peroxide. This work demonstrates that the introduction of the diacetylene unit efficiently improved the oxygen adsorption and activation capacity of the COF. Additionally, the introduction of a diacetylene unit effectively promoted charge separation. COF-Tfp-BDDA exhibited a superior rate of H2O2 preparation (880 μmol g−1 h−1) under visible light irradiation from pure water and oxygen, better than most COF-based photocatalysts. The catalyst exhibited a stable hydrogen peroxide photosynthesis efficiency above 100 hours in cycling experiments. Based on the experimental and DFT calculation results, the introduction of a diacetylene unit not only enhances the adsorption and activation of oxygen but also alters the reduction pathway of oxygen, leading to effective charge separation. These factors contribute to the efficient photosynthesis of hydrogen peroxide in pure water. This work provides a novel idea regarding the application of COFs in the field of solar energy conversion.
研究领域:
材料科学
·
光催化
·
太阳能转化
✓ 已验证
产品关联
DOI
高影响因子
POLYMER
·
2017
·
IF 3.684
Hongyan Yao,Na Zhang,Kunzhi Shen,Ningning Song,Kaixiang Shi,Shiyang Zhu,Yunhe Zhang,Shaowei Guan
A dianhydride monomer 2, 5-bis(3, 4-dicarboxyphenoxy)-4′-phenylethynyl biphenyl (PEPHQDA) containing a chain extendable phenylethynyl pendant group has been successfully synthesized via successive nucleophilic substitution , Sonogashira cross-coupling, hydrolysis and dehydration reactions. A flexible microporous polyimide network has been prepared based on the use of triamine (TAPOB), affording hyperbranched polyimide, followed by the curing of phenylethynyl groups to give network structure. Specifically microporous features such as a well-defined surface morphology , microporous structure and nanometer-sized pore channels have been introduced to the flexible polyimide networks through this two-step pathway. This network exhibit a BET surface area (322 m 2 g −1 ) as well as a comparable CO 2 uptake (1.25 mmol g −1 at 273 K and 1 bar) and enthalpy of adsorption (30.3 kJ mol −1 ) to that of other microporous polyimides derived from rigid tridimensional monomers.
研究领域:
高分子科学
·
材料科学
·
环境科学
✓ 已验证
产品关联
DOI
高影响因子
SENSORS AND ACTUATORS B-CHEMICAL
·
2021
·
IF 7.46
Qian Liu,Fang Wu,Huixia Di,Yingna Bi,Meng Meng,Dingbin Liu,Yongmei Yin,Rimo Xi
Developing highly sensitive and specific method is essential for trace Hg 2+ quantifying. Herein, we established a background-free surface-enhanced Raman scattering (SERS) platform which allows not only the detection of Hg 2+ in homogeneous samples, but also high-precision profiling of Hg 2+ distribution in zebrafish. Its superior anti-interference capability is due to the introduction of a high signal-to-noise-ratio (SNR) Raman reporter with an acetylenyl group, which present single nonoverlapping peak at 2125 cm −1 , avoiding interference from other substances. Additionally, the specific recognition of Hg 2+ -bis-thymine complexes and the signal amplified hybridization chain reaction (HCR) were effectively utilized in this design. Benefited from the above strategies, a detection range for Hg 2+ from 1.0 fM to 100 pM was achieved with a detection limit of 0.2 fM. Additionally, Raman imaging was first performed in zebrafish sections to study Hg 2+ distribution which provided a reference for the detection of Hg 2+ pollution in fish. This approach could be extended to target other interested analytes both in simple and biological samples for various purposes.
研究领域:
分析化学
·
环境科学
·
生物技术
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
TALANTA
·
2021
·
IF 6.057
Xin Zhu,Zenghui Liu,Jinge Li,Zutian Li,Fuchun Si,Huaixia Yang,Jinming Kong
Exosomes, as a biomarker with enhancing tumor invasion and spread, play an essential role for lung cancer diagnosis, therapy, and prognosis. In this work, a novel electrochemical sensor was fabricated for detecting exosomes secreted by lung cancer cells based on polysaccharide-initiated ring-opening polymerization (ROP) and click polymerization. First, MPA formed a self-assembled monolayer on the gold electrode surface, and then anti-EGFR was immobilized on the electrode surface by amide bond. Subsequently, a lot of phosphate groups were introduced by the specific recognition between anti-EGFR and exosomes, then sodium alginate grafted Glycidyl propargyl ether (SA- g -GPE) prepared via ROP was attached to the exosomes through PO 4 3- Zr 4+ -COOH coordination bond. After that, click polymerization was initiated by alkyne groups on the SA- g -GPE polymerization chain to realize highly sensitive detection of A549 exosomes. Under the optimum conditions, the fabricated sensor showed a good linear relationship between the logarithm of exosomes concentration and peak current in the range of 5 × 10 3 - 5 × 10 9 particles/mL, and the limit of detection (LOD) was as low as 1.49 × 10 2 particles/mL. In addition, this method had the advantages of high specificity, anti-interference, high sensitivity, simplicity, rapidity and green economy, which proposed a novel avenue for the detection of exosomes, and also had potential applications in early cancer diagnosis and biomedicine.
研究领域:
生物标志物研究
·
癌症诊断
·
电化学
·
聚合物科学
·
生物医学工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
危险品化学品经营许可证（带存储）