JOURNAL OF MATERIALS SCIENCE
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2023
·Vol. 58
·期 22
·9181-9195
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IF 4.5
Yu Jiaqi,Li Yuqi,Qin Feng,Lu Shaorong,Yang Chao,Li Yang,Zhou Wei
In this work, 1-aminoethyl-3-methylimidazolium bromide ionic liquid was used to modify the surface of graphene nanosheets (GNs) through “π–π” interaction to achieve good dispersion and conductivity. By introducing ionic liquid-modified graphene nanosheets (IGNs) into the PI matrix, the ultra-lightweight and multifunctional IGNs/PI aerogels were prepared via freeze-drying and thermal imidization. Benefiting from the porous structure and the introduction of conductive IGNs, the IGNs/PI aerogels exhibit excellent electromagnetic wave (EMW) absorption properties, compression properties, thermal insulation properties and thermal stability. Notably, when the volume content of IGNs is 10%, the IGNs/PI-10 aerogels show the best EMW absorption performance with a minimum reflection loss (RL min ) of −24.8 dB at 2.44 mm and an effective absorption bandwidth (EAB) of 3.6 GHz at 3.00 mm. These promising characteristics including excellent EMW absorption, compression properties and thermal insulation endow IGNs/PI aerogels great application prospects as multifunctional EMW absorbers.
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ELECTROCHIMICA ACTA
·
2023
·
IF 6.6
Qiuyitong Zhang,Yuexin Xu,Ning Lv,Hanyang Li,Zijie Wei,Tian Tian,Yadong Wang,Haolin Tang
A simplified and greener procedure for in-situ obtaining polyimide anode materials for lithium-ion battery electrodes is developed. The combined polyimide material synthesis and electrode preparation reduces the number of processing steps and treatment duration and decreases the energy required for heat treatment, solvent evaporation , and organic solvent use. More importantly, polymerization in situ on the electrode surface render the polyimide particles a sea urchin-like structure, leading to fast electrochemical kinetics, and significant improvement in discharge capacity and cycling performance compared with materials obtained using traditional procedures. Specific capacities of 1870 mAh g − 1 and 2277 mAh g − 1 at 30 °C and 60 °C, respectively, are obtained. A capacity of 1774 mAh g − 1 is retained after 500 cycles at high current density of 1000 mA g − 1 at 60 °C. This new preparation process not only simplifies the preparation process and makes it greener, but also significantly improves the battery performance, providing new possibilities for the preparation of high-performance low-cost lithium-ion battery electrodes.
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Polymers
·
2023
·Vol. 15
·期 12
·2609
·
IF 5
Shuhuan Yun,Xianzhe Sheng,Shengli Wang,Xing Miao,Xuetao Shi,Yongsheng Zhao,Jianbin Qin,Guangcheng Zhang
Polyimide foam (PIF) is a rising star in high-end applications such as aerospace thermal insulation and military sound absorption. However, the basic rule on molecular backbone design and uniform pore formation of PIF still need to be explored. In this work, polyester ammonium salt (PEAS) precursor powders are synthesized between alcoholysis ester of 3, 3′, 4, 4′-benzophenone tetracarboxylic dianhydride (BTDE) and aromatic diamines with different chain flexibility and conformation symmetry. Then, a standard “stepwise heating” thermo-foaming approach is used to prepare PIF with comprehensive properties. A rational thermo-foaming program is designed based on in situ observation of pore formation during heating. The fabricated PIFs have uniform pore structure, and PIFBTDA-PDAshows the smallest size (147 μm) and narrow distribution. Interestingly, PIFBTDA-PDAalso presents a balanced strain recovery rate (SR = 91%) and mechanical robustness (0.051 MPa at 25% strain) and its pore structure maintains regularity after 10 compression–recovery cycles, mainly due to high rigidity of the chains. Furthermore, all the PIFs possess lightweight feature (15–20 kg∙m−3), good heat resistance (Tgat 270–340 °C), thermal stability (T5%at 480–530 °C), thermal insulation properties (λ = 0.046–0.053 W∙m−1K−1at 20 °C, λ = 0.078–0.089 W∙m−1K−1at 200 °C), and excellent flame retardancy (LOI > 40%). The reported monomer-mediated pore-structure control strategy can provide guidelines for the preparation of high-performance PIF and its industrial applications.Keywords:polyimide foams;molecular structures;thermo-foaming;flame retardant;thermal insulation
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JOURNAL OF MEMBRANE SCIENCE
·
2023
·
IF 9.5
Shuyue Pang,Yanhong Li,Xiaofang Chen,Aisheng Huang
The fabrication of mixed matrix membranes (MMMs) by intermixing suitable fillers with organic polymers is an effective strategy to surmount the well-known trade-off effect between gas permeability and selectivity, which can promote separation performance of membranes to a great extent. Two-dimensional (2D) metal-organic frameworks (MOFs) are considered as potential fillers for strengthening the separation performance of MMMs as they possess high aspect ratio and distinctive chemical characteristics. However, it remains challenging in engineering the morphology of the MOFs with desired pore structure and high aspect ratio. In this study, we firstly prepare c-axis oriented ZIF-95 sheets with lateral dimension exceeding 22 μm and thickness of around 3 μm by the solvothermal method. And then the ZIF-95 sheets are incorporated into the polyimide (PI) matrix to fabricate highly c -axis oriented ZIF-95@PI MMMs (denoted as COZIF-95@PI MMMs thereafter). Attributing to the straight permeation channel of ZIF-95 (3.6 Å) for gas permeation as well as its high compatibility with polyimide substrates, the COZIF-95@PI MMMs show a high gas separation capability. At 373 K and 100 kPa for the COZIF-95@PI MMM with 40 wt% loading, the mixture separation factors of H 2 /CH 4 and H 2 /CO 2 are 134 and 58, respectively, and the H 2 permeability exceeds 967 barrer , which is hopeful for the separation and purification of hydrogen.
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Surfaces and Interfaces
·
2023
·
IF 6.2
Chengfeng Xiong,Yu Wang,Liangliang Lin,Ming Gao,Yifan Huang,Paul K Chu
The increasing demand for flexible electronics has spurred the development of flexible substrates with high thermal conductivity . Herein, nanocomposite coatings based on aluminum nitride (AlN) and siloxane matrix are deposited on polyimide (PI) films by atmospheric pressure plasma for improved thermal conductivity. Commercially available aluminum nitride powders are incorporated into methyltrimethoxysilane (MTMS) precursor to form nanocomposite coatings at atmospheric pressure. The evolution of the as-prepared coatings is systematically investigated upon the variations of the deposition time. The smooth surface is transformed into a rough surface with spherical nanoparticles , and the silicon containing functional groups with AlN nanoparticles are introduced into the surface. After 6 min deposition, the surface energies of the PI film can be improved to 32.8 mJ/m 2 , and the thermal conductivity can be enhanced to 1.68 W/mK with a coating hardness of 2H. The results demonstrate that the nanocomposite coatings prepared by plasma deposition are an efficient way to modify flexible materials with improved thermal conductivity.
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ACS Applied Materials & Interfaces
·
2019
·
IF 8.456
Zhimin Hao,Juntao Wu,Chaolu Wang,Jingang Liu
Particulate matter (PM) pollution is a serious threat to human health. Zeolitic imidazolate framework-8 (ZIF-8) is a kind of metal-organic framework, and ZIF-8 not only can capture PM2.5 efficiently but also possesses excellent chemical and thermal stability. In this study, ZIF-8-modified soluble polyimide (PI) nanofibrous membranes were prepared via an electrospinning process. As a result, the PI-ZIF membrane shows high PM2.5 filtration efficiency (up to 96.6 ± 2.9%), superior thermal stability (up to 300 °C), good transmittance, excellent mechanical properties, and low pressure drop. The prepared PI-ZIF membrane with excellent comprehensive property shows a promising application in PM2.5 capture, especially in harsh conditions.
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DYES AND PIGMENTS
·
2018
·
IF 3.767
Ye Tian,Ying Song,Hongyan Yao,Huaxuan Yu,Haiwei Tan,Ningning Song,Kaixiang Shi,Bo Zhang,Shiyang Zhu,Shaowei Guan
Two novel solution-processable polyimide (PI-6FDA) and co-polyimide (CoPI-6FDA), with triphenylamine (TPA)-derived structure as electron donor units and trifluoromethyl-containing phthalimide as electron acceptor units, were designed and synthesized for polymer memory device application. The TPA branched structure was introduced into the CoPI-6FDA to modify the performance of the polymer memory devices. Compared with PI-6FDA, CoPI-6FDA based memory devices exhibit better memory performance in lower threshold voltage of −3.1 V, higher ON/OFF current ratios of 10 5 , and better operation stability and charge transfer complex stability. The effect of TPA branched structures on memory performance has been further explored by optoelectronic measurements and theoretical calculation. Moreover, the optical and electrochemical measurements reveal the charge transfer mechanism of the CoPI-6FDA and PI-6FDA, which is related to the electrical bistability. The introduction of TPA branched structures was proved as a suitable strategy to fabricate the polymer memory devices with high performance.
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ACS Sustainable Chemistry & Engineering
·
2018
·
IF 6.14
Qingguo Chi,Zhiyou Gao,Tiandong Zhang,Changhai Zhang,Yue Zhang,Qingguo Chen,Xuan Wang,Qingquan Lei
In recent years, polymer-based dielectric capacitors have attracted much more attention due to the advantages of excellent flexibility, light weight, and high power density. However, most studies focus on energy storage performances of polymer-based dielectrics at room temperature, and there have been relatively fewer investigations on polymer-based dielectrics working under high-temperature conditions, which is much closer to the practical applications. Besides, dielectric capacitors operating in a high-temperature environment require excellent temperature stability of structure and performance. In this paper, high-temperature-resistant polyimide (PI) is selected as the matrix material, and 0.5Ba(Zr0.2Ti0.8)O3–0.5(Ba0.7Ca0.3)TiO3 (BZT–BCT) nanofibers are used as the filling phase. By analyzing the energy storage behaviors of BZT–BCT/PI composites at different temperatures, it can be found that when the doping content of BZT–BCT nanofibers is more than 1 vol % the dielectric strength of the composites drops sharply when the temperature increases from 25 to 150 °C, resulting in serious deterioration of energy storage properties. On the basis of this, a composite film with a sandwich structure has been designed, where BZT–BCT/PI with different volume fractions is the intermediate layer and hexagonal boron nitride (h-BN) with good thermal and insulating properties is introduced in the top and bottom layers with a content of 5 vol %. Consequently, the results have shown that the energy storage properties of the constructed sandwiched dielectric composite films exhibit excellent temperature stability. The maximum field strength of the composite film with a BZT–BCT content of 1 vol % in the intermediate layer is 360 and 350 kV/mm under temperatures of 25 and 150 °C, and the storage density is 2.3 and 1.83 J/cm3 respectively.
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Polymer-Plastics Technology and Materials
·
2019
·
IF 0
Linshuang Li,Yong Xu,Jianfei Che,Liu Xiaohong,Wei Zhao,Zhifeng Ye
A series of white fluorinated polyimide/TiO2 composite films were prepared by a solution mixing method. They showed high tensile strength beyond 95.1MPa and excellent insulting property with surface and volume resistances exceeding 1.9 × 1011Ω and 2.3 × 1012 Ω cm, respectively, coupled with water absorptions below 1.1%, water contact angles up to 95.9 and whiteness beyond 58.5. It was found that their optical transparency decreased dramatically with the increasing doping of TiO2. The thermal degradation of pure fluorinated polyimide (FPI) and representative polyimide/TiO2 composite film with 5 wt% of TiO2 (PI/TiO2-5 wt%) was also studied.
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SURFACE & COATINGS TECHNOLOGY
·
2019
·
IF 3.192
Jialong Li,Chen Yang,Na Li,Jinghua Yin,Yu Feng,Yuanyuan Liu,He Zhao,Yanpeng Li,Congcong Zhu,Dong Yue,Xiaoxu Liu
Two-dimension (2D) graphene-like nanosheets with small thickness and large lateral size attract tremendous attention in the application of high-K materials. In this paper, 2D aluminum oxide coated reduced graphene oxide nanosheet (Al 2 O 3 @rGO) were fabricated via bottom-up method in expectation of being a kind of promising dielectric filler. Polyimide (PI) based composites filled by different Al 2 O 3 @rGO contents were prepared via in-situ polymerization. The characterization results of the composites indicate that strong filler-matrix bonding contributes to improve the compatibility of Al 2 O 3 @rGO in PI. Besides, the orientation of Al 2 O 3 @rGO nanosheets in the composites is detected by SAXS and SEM . For the composites, the dielectric behaviors, thermal stabilities and mechanical properties were investigated. The results show that the composites possess high dielectric constant and low dielectric loss. Additionally, the composites have good electrical insulation properties. Furthermore, the enhancements in thermal stabilities and mechanical properties of the composites are also observed attribute to the strong interactions between PI and Al 2 O 3 @rGO. Consequently, it is hoped that the composites would be possessing potential applications in flexible dielectric materials owing to its enhanced dielectric constant, thermal stabilities and mechanical performances.
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JOURNAL OF MATERIALS SCIENCE
·
2018
·Vol. 53
·期 18
·12885-12893
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IF 2.993
Fei Zhifang,Yang Zichun,Chen Guobing,Li Kunfeng,Zhao Shuang,Su Gaohui
A glass fiber/polyimide (PI)/SiO 2 composite aerogel (FPS aerogel) was prepared by dispersing glass fibers in PI/SiO 2 hybrid sol derived from 4,4′-oxydianiline (ODA), pyromellitic dianhydride (PMDA) and tetraethoxysilane (TEOS) with supercritical CO 2 fluid drying technology. The SiO 2 primary particles were combined with PI chains which improved the strength of the composite aerogel, and the glass fibers inhibited the shrinkage deformation during the drying process by acting as the supporting skeletons. Effects of PI contents on the density, shrinkage, thermal conductivity and mechanical properties of the FPS aerogels were investigated. The as-prepared FPS aerogels had low densities (0.116–0.145 g/cm 3 ), high specific surface area (844–963 m 2 /g), low thermal conductivity (0.0268–0.0280 W m −1 K −1 at room temperature) and relatively high compression strength (0.12–0.29 MPa) with integrated nanostructures, fewer powders and stronger fiber/aerogel matrix interfaces. The density, the shrinkage, the thermal conductivity and the compression strength of the FPS aerogels increased with the increasing PI content. This research provided a new method employing PIs and glass fibers as strengthening phases to improve the mechanical properties of SiO 2 -based aerogels.
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RSC Advances
·
2018
·Vol. 8
·期 20
·11119-11126
·
IF 2.936
Faqin Tong,Shuangshuang Chen,Zhao Chen,Xuemin Lu,Qinghua Lu
Enhancing the azimuthal anchoring energy of the aligning film is a key requirement to improve the quality of liquid-crystal displays. Based on the assumption of mesogenic side groups being able to align liquid-crystal (LC) molecules, we have designed a novel transparent polyimide bearing cyanobiphenyl mesogenic side chains, which has a similar structure to that of liquid crystal 5CB. A pyrimidyl diamine monomer with a cyanobiphenyl mesogenic unit was first synthesized, and then co-polymerized with 4,4′-diaminodiphenyl ether and 4,4′-oxydiphthalic anhydride. The obtained polyimide (PI) exhibited good thermal stability and mechanical properties, as well as high optical transparency with transmittance of up to 86% in the wavelength range 450–700 nm. By evaluating the adhesion force between PI films and LCs with a super-sensitive microelectro-mechanical balance system, we have verified that appending mesogenic groups on the side chains of PI strengthens intermolecular interactions between the LC and PI surfaces, thereby enhancing the surface anchoring energy. Compared with the unmodified PI, the anchoring energy of the derivatized PI was improved more than 2.2-fold. By virtue of its good transparency and strong anchoring energy, this PI would seem to be an ideal candidate as a LC alignment film, and the concept of mesogens aligning LCs may open a new door in the design of LC alignment films.
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