RSC Advances
·
2024
·Vol. 14
·期 14
·9716-9724
·
IF 3.9
Wentao Yu,Jiahui Lin,Zhaozhang Zhao,Jiyong Fang,Ziqing Wang,Jintao Huang,Yonggang Min
This study successfully utilized a straightforward approach, choosing liquid–liquid phase separation to build a porous structure and synthesize composite absorbers based on polyimide-based porous carbon and cobalt nanoparticles (designated as PPC/Co-700 and PPC/Co-800). A fine porous structure was achieved as a result of the excellent heat resistance of polyimide resulting in an excellent electromagnetic wave absorption ability of PPC/Co composites. The results obtained clearly indicated that PPC/Co-700 and PPC/Co-800 exhibit a porous structure with coral-like pores, enhancing both impedance matching properties and microwave attenuation abilities. This improvement in impedance matching conditions and dissipation capability is attributed to the synergistic effect of dielectric loss induced by carbon and magnetic loss induced by Co nanoparticles. PPC/Co-700 showed the strongest absorption performance with a minimum reflection loss of −59.85 dB (30 wt% loading, thickness of 3.42 mm) and an effective absorption bandwidth (EABW, RL ≤ −10 dB) of 6.24 GHz (30 wt% loading, thickness of 2.78 mm). Therefore, this work provides a facile strategy for the development of a promising absorbing material with outstanding electromagnetic wave absorption performance.
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DOI
PubMed
高影响因子
MACROMOLECULAR CHEMISTRY AND PHYSICS
·
2024
·
IF 2.5
Zhigeng Chen,Yu Chen,Ling Lin,Gongpeng Lin,Zhenxun Huang
Polyimide films with low dielectric loss (D f ) at high frequencies are urgently needed owing to the rapid development of high-frequency communication technologies. Herein, various polyimide films with rigid mesogenic units are prepared to address this issue. Improving molecular flexibility has been found to promote crystallization during thermal imidization and, consequently, the formation of liquid-crystal-like polyimide (LCPI) films. The optimal LCPI film exhibits an ultralow D f value of 0.00178 at 10 GHz owing to the limited intermolecular friction. Furthermore, this LCPI film absorbs significantly less water (0.59%), which endows it with favorable durability of low D f value in a humid environment. The D f value of the LCPI film at 10 GHz is only 0.00288 after 24 h of exposure to 60% relative humidity. In addition, the LCPI film exhibits a glass transition temperature, coefficient of thermal expansion, and tensile strength of 371 °C, 21.8 ppm K −1 , and 240 MPa respectively, and is therefore a suitable low-dielectric-material candidate.
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高影响因子
CHEMICAL ENGINEERING SCIENCE
·
2024
·
IF 4.1
Yisa Zhou,Kunyan He,Yutong Lou,Jian Xue,Haihui Wang
Membrane separation offers an efficient and energy-saving process for extracting rare helium from natural gas. Among them, mixed matrix membranes (MMMs) containing two-dimensional (2D) materials are considered potential gas separation membranes. Herein, 2D g-C 3 N 4 nanosheets with nanoporous structure are incorporated into the polyimide (PI) matrix to prepare MMMs for efficient He separation. The incorporated g-C 3 N 4 nanosheets generate additional gas transport and sieving channels in MMMs. As a result, the PI/g-C 3 N 4 MMM comprising 0.5 wt% g-C 3 N 4 nanosheets exhibits a He/CH 4 selectivity of 160.4 with He permeability of 40.7 Barrer, which are 2.0 and 3.2 times higher than the pure PI membrane, respectively. Moreover, the membrane also shows good stability at elevated temperatures or a continuous 150 h long-term operation. Therefore, the remarkable gas separation performance and excellent stability make the membrane promising for gathering helium from natural gas.
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DOI
高影响因子
ACS Applied Polymer Materials
·
2024
·
IF 4.4
Qiyun Lin,Wenhao Zhang,Lingcheng Chen,Yifan Li,Zhipeng Ning,Xinfu Zhang,Yi Xiao
Epoxy acrylate (EA) resins have excellent light-curing properties and play a crucial role in UV-curable resins, but poor mechanical properties, lower thermal stability, and stronger hydrophilicity hinder their applications in high technic areas such as circuit board printing and electronic packaging. In this study, to enhance UV-curing EA resins, a photosensitive polyimide (PSPI) with a highly rigid and twisted skeleton was developed as a macromolecular cross-linker. This PSPI is featured with a unique diamine monomer that possesses a spirocyclic fluorene-xanthene core double-grafted with methacryloylamino groups. Commercial EA resins (EB600) were blended with varying levels of PSPI to modify the density and structure of the cross-linked network of the EB resins. The methylacrylamide groups branching on xanthene rings in the PSPI participate in radical UV-curing by crossing over with the main-chain helixes, resulting in three-dimensional cross-cured networks and unique structural rigidity of the resins. EB resins with different PSPI contents demonstrate apparently improved overall properties, compared with the nonmodified EB600. Among these cured resins, the overall performance of EB10PSPI1 (weight ratio of EB/PSPI 10/1) was superior. The initial thermal decomposition temperature (Td5%) of EB10PSPI1 resin is 353 °C, 78 °C higher than that of EB1PSPI0 (without PSPI), and the residual carbon rate is increased by 12.36% at 600 °C. The Tg of EB10PSPI1 resin was 122 °C, while that of EB1PSPI0 resin is only 87 °C. The tensile strength and modulus of elasticity of EB10PSPI1 resin increased by 162 and 246%, respectively, and the hardness increased by 291 MPa compared with EB1PSPI0 resin. In addition, the surface of EB10PSPI1 resin exhibited good hydrophobicity with significantly lower water absorption and swelling rate than that of EB1PSPI0. Also, EB10PSPI1 exhibits good adhesion capability. Finally, the curing performance of the EB10PSPI1 resin is better, almost doubling the curing speed at weak UV-light irradiation intensities, demonstrating the excellent sensitivity of the PSPI in radical polymerization reactions and the enhancement of the UV-curing network of the EB resin. This study opens a way to comprehensively enhance the thermodynamic and mechanical properties of EB1PSPI0 resins, which is promising in circuit board printing and electronic packaging.
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高影响因子
TRIBOLOGY INTERNATIONAL
·
2025
·
IF 6.9
Wangfei Shen,Qingzhe Zhang,Yingying Wang,Pu Zhang,Xiaoliang Zhang,Chunxia Wu,Cunxin Jia,Jingkang Liu,Xudong Xue,Yanming Wang
Two-dimensional lubricating fillers play a crucial role in strengthening the tribological performance of polymer coatings. In this study, MXene-PDA-Bi 6 O 7 (MXene/Bi 6 O 7 ) heterostructured composite nanofillers were prepared via a mussel-inspired chemical method. Polyimide (PI) composite coatings with varying MXene:Bi₆O₇ mass ratios were fabricated, and their microstructure, mechanical properties, and tribological performance were systematically characterized. The loading of Bi 6 O 7 nanoflowers onto the surface of PDA-modified MXene was achieved through in situ assembly, resulting in the formation of MXene/Bi 6 O 7 heterostructures. The experimental results demonstrated that the synergistic effect of MXene and Bi 6 O 7 significantly enhanced the properties of the PI composite coatings. Specifically, when the MXene-to-Bi₆O₇ mass ratio was 4:6, the PI composite coatings exhibited an 11.2 % reduction in friction coefficient and a 70.5 % decrease in wear rate compared with pure PI. Additionally, the tensile strength of the PI matrix was increased to 185.99 MPa. The MXene/Bi 6 O 7 heterostructure effectively reduced direct contact between the friction pairs by forming a dense transfer membrane, thereby maintaining stable lubrication performance under a broad range of conditions. The study elucidates the role of two-dimensional heterostructures in enhancing the interfacial mechanics and tribological properties of polymers, providing theoretical guidance and technical routes for the development of high-performance abrasion-resistant polymer coating materials.
研究领域:
材料科学
·
摩擦学
·
纳米复合材料
·
聚合物涂层
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DOI
高影响因子
ChemistrySelect
·
2025
·Vol. 10
·期 38
·e05310
·
IF 2
Deyu Yi,Zhongliang Zuo,Kai Wang,Ruochen Pan,Xiaomeng Chu,Zhi Li,Shaojie Liu,Zhenhua Shang
The transparent flexible substrate is vital for flexible displays, acting as both a carrier and a support. This study presents a molecular design strategy to enhance the optical and dielectric properties of colourless polyimide (CPI) films by incorporating flexible alkyl segments. First, we designed and synthesized three diamine monomers with varying alkyl chain lengths, and then polymerized them with commercially available 6FDA (2,2′-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride) via solution polycondensation to produce a series of colorless polyimide films. To further fine-tune the material properties, controlled copolymerization with fluorinated diamine TFMB (2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl) was performed, resulting in advanced CPIs with superior optical clarity and dielectric properties (ε = 2.8 ∼ 3.5, tanδ = 0.01 ∼ 0.02 at 1 MHz). The TDA-CPI-2 film (18 µm) demonstrated high optical transparency ( T 400 = 82.9%, haze = 0.28, YI = 0.73) with a UV cut-off at 340 nm. It exhibited low water absorption (1.89%) and a hydrophobic surface (contact angle of 80.84°), ensuring stable dielectric performance under varying humidity conditions. The film maintained excellent thermal ( T g = 172.4 °C, Td5% = 491.4 °C) and mechanical properties (tensile strength of 74.5 MPa, modulus of 1.37 GPa), while being solution-processable for practical applications. This work offers a versatile approach to developing high-performance CPI films for advanced optoelectronic flexible display devices. Graphical The three series of transparent and colorless polyimide films (EDA-CPI-X, HAD-CPI-X, TDA-CPI-X) exhibit exceptional optical clarity and outstanding dielectric properties (dielectric constant ε = 2.8~3.5, dissipation factor tanδ = 0.01~0.02 at 1 MHz).
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高影响因子
JOURNAL OF MEMBRANE SCIENCE
·
2025
·
IF 9
Jiayou Liao,Zhiyuan Wu,Zhe Meng,ChengYun Gao,Jinping Li,Yong Wang,Xianjie Meng,Jiwei Ma,Lijing Yuan,Xingzhong Cao,Xu Wu
A novel methodology was proposed to simultaneously enhance both permeability and selectivity of polyimide membranes through the synergistic regulation of interchain spacing, inter-chain interactions, and functional groups, collectively referred to as 'interchain microenvironment regulation'. Through reacting the -NH 2 group on the bulky diamines with the C-Br group on the polymer chains, we successfully linked the chains by bulky diamines. The results confirmed that the introduction of bulky groups inhibited chain stacking, increased d-spacing and free volume, resulting in enhanced permeability. Moreover, the CO 2 /CH 4 selectivity was significantly enhanced due to the synergistic effect between interchain interactions and the amino groups. In particular, the PI-Br-6%-NAPD membrane demonstrated a permeability coefficient 5 times greater than that of pure PI, reaching 311.71 Barrer. And its CO 2 /CH 4 selectivity was 3.87 times higher than pure PI, with a value of 74.88. It exceeded the 2008 Robeson upper bound for gas separation performance. In addition, enhanced interchain interactions endowed the membrane with good plasticization resistance, with a plasticization pressure of up to 450 psi. Membranes modified with other diamines also exhibited excellent gas separation performance. This study provided a feasible method for effectively regulating the interchain microenvironment to achieve high-performance gas separation.
研究领域:
高分子科学
·
膜分离技术
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材料科学
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气体分离
·
化学工程
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DOI
高影响因子
APPLIED CATALYSIS B-ENVIRONMENTAL
·
2020
·
IF 16.683
Peng Kong,Hao Tan,Tingyu Lei,Jie Wang,Wenjun Yan,Ruiyi Wang,Eric R. Waclawik,Zhanfeng Zheng,Zhong Li
Conjugated polyimide (R-PI) containing triazine ring was synthesized by a modified thermal solid-state polymerization of the salt monomer. The structure of the as-prepared R-PI was characterized by FTIR, XPS, EPR, EA and solid-state 13 C NMR, which is rich in oxygen vacancies (OVs). The R-PI exhibits excellent catalytic performance for selective benzylamine oxidation reactions under visible light. Both experimental and theoretical calculation results indicated that the introduction of OVs could increase the level of electron delocalization of R-PI. R-PI possess more excitable electrons and a narrower band gap, which expands the absorption of long-wavelength light. The surface OVs also serve as excellent sites for molecular O 2 adsorption and activation. Chemisorbed O 2 spatially builds up a channel for the delivery of photoexcited electrons to O 2 , which effectively enhanced separation efficiency of photogenerated charge carriers. These results indicate that OVs-rich conjugated polyimides can be efficient visible light-responsive photocatalysts for green synthesis.
研究领域:
材料科学
·
光催化化学
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DOI
高影响因子
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION
·
2025
·
IF 3.1
Shengrui Zhou,Zhang Li,Guan Wang,Qinkun Yang,Bilal Iqbal Ayubi
Under vacuum high-frequency electrical stress, polyimide (PI) films face severe surface discharge risks, which significantly affect their insulation stability in spacecraft dielectric systems. In this study, fluorinated polyimide (FPI) films with different fluorine contents were prepared, and a vacuum high-frequency surface discharge testing platform was established to systematically investigate their discharge characteristics. The results show that the introduction of fluorinated groups increases the surface electrical conductivity and thermal conductivity of the films. The discharge inception voltage increased from 1.88 kV for pure PI to 2.38 kV for 50% FPI, with a 26.6% increase. In addition, a non-equilibrium plasma model was constructed to dynamically simulate the formation process of discharge channels and the multiphysical evolution mechanisms. The results reveal that the front region of the discharge channel exhibits a coupled feature of “high density-low temperature-high reaction rate,” with significant electric field shielding and energy dissipation observed at the electron avalanche position. Fluorinated groups effectively suppress the establishment of surface discharge channels by reducing the secondary electron emission yield (SEEY) and dielectric constant, thereby weakening the electron multiplication effect and space charge accumulation. This study, from the perspectives of material regulation and physical mechanisms, provides theoretical support for optimizing the insulation performance of polyimide materials under vacuum high-frequency conditions.
研究领域:
高分子材料科学
·
电气绝缘工程
·
真空放电物理
·
介电材料
·
空间环境效应
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高影响因子
POLYMER INTERNATIONAL
·
2011
·Vol. 61
·期 1
·111-117
·
IF 2.056
Bing Fang,Kai Pan,Qinghan Meng,Bing Cao
This study investigated the preparation of polyimide solvent-resistant nanofiltration membranes by a two-step method (casting the membrane first and then crosslinking by the thermal imidization method). The influences of polymer concentration, thickness of membranes, temperature of the imidization, phase inversion time and thermal imidization procedure were studied. The membranes with the highest rejection rate of Fast Green FCF (molecular weight 808.86 g mol −1 ) were prepared in the following conditions: polymer concentration 13 wt%, phase inversion time 1 h, membrane thickness 150 µm and thermal imidization procedure 200 °C for 2.5 h, 250 °C for 2 h and 300 °C for 2 h in a vacuum environment; the heating rate was 5 °C min −1 . The membrane was stable in most of the solvents tested and the fluxes of some common solvents were equal to or higher than a number of commercial solvent-resistant nanofiltration membranes. A much higher rejection of dyes in water than in methanol was observed in the filtration experiments and a new way to explain it was developed. Copyright © 2011 Society of Chemical Industry
研究领域:
材料科学
·
化学工程
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DOI
高影响因子
COMPOSITES PART B-ENGINEERING
·
2021
·
IF 9.078
Jundong Zhu,Fuxing Zhao,Tangping Peng,Hao Liu,Le Xie,Chongwen Jiang
Advanced composite aerogel materials have attracted much attention due to the unique structure and properties. However, the efficient manufacturing process and structural stability were still a challenge. Herein, a novel hydroxyapatite nanowires/polyimide (HAnws/PI) composite aerogel was synthesized by the ultralong HAnws combined with polyamic acid via directional freezing and thermal imidization. Among them, the HAnws and PI intertwined to form a three-dimensional network structure, which decreased the volume shrinkage of aerogel in thermal imidization from 42.9% to 12.6%, resulting in high porosity (>96%) and low density (0.0329–0.0431 g cm −3 ). In addition, the HAnws/PI aerogel with layered porous structure exhibits obvious anisotropic mechanical properties. The axial specific modulus as high as 78.05 kN m kg −1 and radial high elasticity can withstand 100 cycles of fatigue resistance . Moreover, the lowest radial thermal conductivity at 32.21 mW m −1 K −1 and the maximum of the anisotropy factor was 2.2, which was very suitable for insulation pipes to prevent additional heat loss. Therefore, the novel nanofibers reinforced organic aerogel was expected to provide more abundant functional applications in energy efficiency.
研究领域:
材料科学
·
纳米技术
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DOI
高影响因子
TRIBOLOGY LETTERS
·
2017
·Vol. 66
·期 1
·1-18
·
IF 1.891
Xin Yuanshi,Xu Fanglin,Wang Mingming,Li Tongsheng
Modified carbon nanotube/nano-MoS 2 (CMS) hybrid as a self-lubricating and anti-wear nanofiller was prepared through chemical compounding and then incorporated into polyimide (PI) matrix to yield CMS/PI composite by in situ polymerization. For comparison, carbon nanotube (CNT), nano-MoS 2 as well as the mixture of them (CNT-MoS 2 ) were also incorporated into PI matrix separately to evaluate the superior performance of CMS hybrid. Morphology, mechanical capacity and tribological behavior of the as-prepared nanocomposites were investigated, and the discrepancies on the above-mentioned properties caused by the different structures between CMS hybrid and CNT-MoS 2 mixture were discussed in detail. With only 0.5 wt% addition of CMS, the friction coefficient and wear rate of CMS/PI composite decreased by 31 and 84%, respectively, compared to virgin PI. The results showed that the combinational structure of CMS hybrid, as CNT-coated few-layer MoS 2 nanosheet, which took the advantage of both CNT and nano-MoS 2 , contributed to the synergistic effect on the tribological properties.
研究领域:
材料科学
·
摩擦学
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高影响因子
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