MACROMOLECULAR CHEMISTRY AND PHYSICS
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2019
·Vol. 220
·期 15
·1900017
·
IF 2.622
Chuqi Shi,Shumei Liu,Yancheng Wu,Kai Cheng,Jianqing Zhao,Yi Fu
Ladder-like polypropylsilsesquioxane (LPSQ) with inorganic Si O Si double-stranded skeleton in situ growth is incorporated into 18-crown-6-polyimide (CE6-PI) chains by coupling effect of aminopropyltrimethoxysilane to build ladder-like polypropylsilsesquioxane/18-crown-6-polyimide (LPSQ/CE6-PI) nanocomposites. The dielectric constant is evidently decreased, and the strength, toughness, and thermal stability of CE6-PI are greatly improved. A low dielectric constant of 2.71 as well as high tensile strength of 133.7 MPa and toughness of 29.7 MJ m −3 are achieved for the LPSQ/CE6-PI nanocomposite with 23.2 wt% LPSQ. Meanwhile, its glass transition temperature and 5% weight loss temperature exhibit an increase of 23.1 °C and 68.8 °C, respectively, based on CE6-PI. Positron annihilation lifetime spectroscopy, X-ray diffraction patterns, dynamic mechanical analysis, and scanning electron microscope images are applied to investigate the effect of LPSQ on the structure of LPSQ/CE6-PI nanocomposites.
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高影响因子
COMPOSITES SCIENCE AND TECHNOLOGY
·
2019
·
IF 6.309
Zhigeng Chen,Yubin Zhou,Yancheng Wu,Shumei Liu,Haohao Huang,Jianqing Zhao
An amphiphilic alternating copolymer with hydrophobic polyhedral oligomeric silsesquioxane (POSS) segments and hydrophilic anhydride segments, which is able to self-assemble into nanoscale POSS aggregates, is introduced into fluorinated polyimide (FPI) films to polish up their toughness while lowering their dielectric constant. The dielectric constant of POSS/FPI composite films with 2.8 wt% amphiphilic alternating copolymer significantly decreases to 2.09 from 3.14 for pure FPI. Furthermore, a sharp brittle-ductile transition is observed in the tensile energy to break versus interparticle distance curve. When the interparticle distance is reduced to 215 nm, the elongation at break and tensile energy to break of POSS/FPI composite films increase to 27.5% and 23.5 MJ/m 3 from 8.3% to 6.8 MJ/m 3 respectively. The tensile-fractured surfaces of POSS/FPI composite films reveal that the toughening mechanism is mainly attributed to the prevention of crack propagation and the debonding of POSS aggregates with a plastic void growth .
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高影响因子
JOURNAL OF POWER SOURCES
·
2019
·
IF 7.467
Pan Yang,Jun Long,Sensen Xuan,Yanlin Wang,Yaping Zhang,Jinchao Li,Hongping Zhang
The trade-off between high proton conductivity and low vanadium ion permeability needs to be overcome urgently for membrane in vanadium redox flow battery (VRFB). A series of fluorine-containing branched sulfonated polyimide membranes with ionic cross-linking (c-FbSPI) and different degrees of sulfonation (40–70%) are prepared through polycondensation by introducing –CF 3 group, branched structure and ionic cross-linking. The c-FbSPI membranes have much lower vanadium ion permeabilities (0.36–3.87 ✕ 10 −7 cm 2 min −1 ) and higher proton selectivities (0.89–4.20 ✕ 10 5 S min cm −3 ) comparing with Nafion 115 membrane, respectively. Besides, c-FbSPI membranes have outstanding chemical stabilities when immersing in strong acidic and oxidizing solution for 38 days. The VRFB with selected c-FbSPI-60 membrane shows lower self-discharge speed and higher charge-discharge capacity and energy comparing to those with Nafion 115 membrane. During 300-time cyclical charge-discharge measurement, the VRFB assembled with c-FbSPI-60 membrane shows higher coulombic efficiency (97–99.5%), energy efficiency (68.2–75.1%) and capacity retention (50.5–55.1%) compared with the VRFB using Nafion 115 membrane at 80–60 mA cm −2 . This work provides a new approach for preparing high cost-performance aromatic polymer membrane, which is significant for accelerating the industrialization process of VRFB.
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高影响因子
HIGH PERFORMANCE POLYMERS
·
2018
·
IF 1.047
Lei Wang,Guifen Gong,Junyao Shen,Jinsong Leng
Polyimide (PI)/titanium dioxide (TiO2) composite nanofibers (NFs) with average diameters of 200–250 nm were synthesized via electrospinning. The total number density of dipoles decreased significantly, owing to the porous structures and compact interface between TiO2 NPs and PI matrix. All PI/TiO2 NFs maintain low dielectric constants and losses. For example, the dielectric constants of PI/TiO2-6% NFs are all lower than 2.6, being exposed to temperatures from 25°C to 200°C. Meantime, the dielectric losses of PI/TiO2-6% NFs are below 0.005. For ultraviolet (UV)-light shielding performance, the PI/TiO2 NFs exhibited good UV-light shielding and corresponding anti-photoaging properties. The reason can be ascribed from high UV-light absorption and scattering ability in the TiO2 NPs. The best UV-light absorption (average: 3.71) and corresponding absorption decay (15.13%) were achieved for optimized PI/TiO2-6% NFs. Other fundamental characteristics, such as the thermal stability, mechanical tensile property, and hydrophobicity, were also investigated. Such low dielectric constant PI/TiO2 composite NFs can be alternatively chosen under a longtime UV-light exposing condition.
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JOURNAL OF PHYSICS D-APPLIED PHYSICS
·
2018
·Vol. 51
·期 21
·215305
·
IF 2.373
Panpan Zhang,Jiupeng Zhao,Ke Zhang,Yiyong Wu,Yao Li
A series of porous polyimide (PI) membranes with 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) and 4,4'-diaminodiphenyl ether (ODA) in the different ratio of co-solvent (N, N-dimethylacetamide (DMAC)/1, 4-butyrolactone (GBL)) were prepared by a novel wet phase inversion method. The influence of co-solvent on the structure and dielectric properties of membranes were investigated. PI membranes changed from finger-like structure to spongy-like structure with the increasing of the GBL content since the intermolecular interaction between PI induced by GBL. The proportion and size of finger-like structure gradually decreased with the increase of GBL content in DMAC/GBL co-solvent. Although PI membranes exhibited low dielectric permittivity ranges from 1.7–2.5, the dielectric breakdown strengths were also relatively low. In particular, the PI from pure GBL yielded the highest breakdown strength (260.05 kV mm−1) since the low proportion of macrovoids and defects. Moreover, when the ratio of GBL/DAMC was 84/16, the resultant PI membrane possessed a low dielectric constant (1.99) as well as relatively high breakdown strength (100.53 kV mm−1). Therefore, porous PI membraness may be potential in many applications of electronics and microelectronics.
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JOURNAL OF APPLIED POLYMER SCIENCE
·
2019
·Vol. 136
·期 34
·47883
·
IF 2.188
Hui Tong,Aftab Ahmad,Jing Fu,Hongyan Xu,Tao Fan,Yudong Hou,Ju Xu
Polymer dielectrics with outstanding heat resistance and advanced dielectric properties are of great importance for high-temperature capacitors in the applications of hostile circumstances. In this work, a series of aromatic carbonyl-containing polyimides (CPI) are prepared from the carbonyl dianhydride and different diamines. The correlation between molecular structure (i.e., different linked structure (─O─, ─CH2─, ─SO2─) in diamines, the length of repeating unit and the linked position (para-para or meta-meta), and properties is revealed in detail to obtain CPI dielectrics with excellent thermal resistance (glass transition temperature, T g : 241~352°C), reasonably high dielectric constant (3.99~5.23), low dissipation factor (0.00307~0.00395), and admirable breakdown strength (425~552 MV/m) simultaneously. Particularly, CPI-5 with carbonyl structure in dianhydride and sulfonyl group in diamine proves to exhibit discharged energy density and charge–discharge efficiency of 6.34 J/cm 3 and 92.3% at 500 MV/m, respectively. In addition, CPI-5 also displays stable dielectric properties in temperature range of −50‑200°C. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136 , 47883.
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POLYMER COMPOSITES
·
2015
·Vol. 38
·期 10
·2321-2331
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IF 1.632
Peijiang Liu,Zhengjun Yao,Jintang Zhou
In this article, reduced graphene oxide/polyimide resin composites which exhibited enhancements in mechanical properties were successfully fabricated by hot-pressing, and reduced graphene oxide nanosheets were synthesized by thermal reduced method, which can readily mix with PI powders in aqueous solution by sonication process. The chemical structures of rGO were carefully characterized by X-ray diffraction, Fourier transfer infrared spectroscopy and X-ray photoelectron spectroscopy. The field emission scanning electron microscopy observations showed that the rGO displayed excellent dispersibility and compatibility with the PI matrix. The mechanical analysis indicated that the tensile and flexural strength values of the rGO/PI resin composite with 1.5 wt% rGO loading reached 80.7 and 133.3 MPa, respectively. Compared with pure PI, the optimized rGO/PI resin composite exhibited an enhancement of 30% in tensile strength, 19% in flexural strength and 27% in impact strength, due to the fine dispersion of high specific surface area of graphene nanosheets and the good adhesion between the rGO and the matrix. In addition, thermogravimetric analysis, dynamic mechanical analysis, and dielectric properties were also investigated. POLYM. COMPOS., 38:2321–2331, 2017. © 2015 Society of Plastics Engineers
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高影响因子
RSC Advances
·
2015
·Vol. 5
·期 89
·72971-72980
·
IF 3.84
Zenghui Yang,Qihua Wang,Yongkang Bai,Tingmei Wang
Shape memory polyimide/silica (PI/silica) composites with atomic oxygen resistance, good thermal stability and mechanical properties are synthesized by co-condensation of poly(amic acid) terminated with (3-aminopropy)triethoxysilane (APTES) and tetraethoxysliane (TEOS) via a sol–gel method. The silica networks formed in the hybrid films act not only as permanent crosslink points, but as atomic oxygen (AO) resistant moieties. The results show that the PI/silica composite films possess high thermal decomposition temperature (Td > 550 °C), high glass transition temperature (Tg > 265 °C) as well as good shape fixation ratio (Rf > 98%) and shape recovery ratio (Rr > 90%). The mechanical properties, surface topography and shape memory performance of PI/silica composite films were evaluated before and after AO irradiation in simulated space environment. Compared to pristine PI, the mechanical properties, surface topography, and shape memory performances of PI–SiO2-15 were less affected by AO exposure, which results from the silica protective layer formed on the composite film surface, indicating good AO-resistant ability of PI/silica composite films. This work may provide a strategy toward the design of promising shape memory materials for applications in the field of severe conditions.
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高影响因子
RSC Advances
·
2015
·Vol. 5
·期 16
·11980-11988
·
IF 3.84
Guanghe Song,Xuesong Li,Qiyang Jiang,Jianxin Mu,Zhenhua Jiang
A series of novel structural phosphorus-containing polyimide–polyhedral oligomeric silsesquioxane (POSS) nanocomposites with varying phosphorus contents were synthesized. The nanocomposites displayed outstanding thermal properties. The glass transition temperature was increased to 294.87 °C when the phosphorus content was 1.61 wt% and the anti-degradation properties were also obviously enhanced. Moreover, the nanocomposites presented much higher atomic oxygen (AO) durability compared with pure polyimide because of the incorporation of special functional groups of phosphorus oxide and POSS. The AO erosion yields decreased to 51.9% of pure polyimide–POSS nanocomposites when the phosphorus content was increased to 1.61 wt%. Furthermore, the mechanism of phosphorus and POSS synergistic AO resistance was explored via XPS and SEM. Three kinds of silicon particles with different binding energies and two kinds of phosphorus elements with different binding energies were formed because of AO exposure and the phosphorus and POSS synergy. Highly effective self-passivating layers were formed to protect the underlying material from AO attack.
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JOURNAL OF ALLOYS AND COMPOUNDS
·
2016
·
IF 3.014
Lingpu Jia,Yaxin Zhou,Yimin Jiang,Aihua Zhang,Xin Li,Chunming Wang
A novel Mo doped reduced graphene oxide/polyimide (Mo-rGO/PI) composite membrane sensor for dopamine (DA) has been successfully prepared by a simple and effective method. In this work, the rGO was doped into PI to prepare polymer composite membrane . Although rGO has a certain degree of catalytic activity for DA, more important is Mo doped rGO/PI film can enhance its electrocatalytic activity towards the oxidation of DA, and so far there is almost no report that MoO 2 can catalyze DA. In order to find the best film, different doped ratios of Mo powder are further investigated, and the combined characterization by X-ray photoelectron spectra and energy-dispersive X-ray spectroscopy indicate that Mo exist in rGO/PI film in the form of MoO 2 . Under optimal conditions, the Mo doped rGO/PI film exhibits excellent catalytic activity to DA, with a linear response throughout the concentration range from 0.1 to 2000 μM, it also shows long-term stability and good reproducibility, and performs well for detection of DA in human blood serums and injection. These results suggest that the novel Mo-rGO/PI film is a promising candidate for the accurate and reliable detection of DA signals in biological samples.
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高影响因子
POLYMER COMPOSITES
·
2024
·
IF 4.8
Baokai Zhang,Xianqiang Pei,Yanming Wang,Shanhong Wan,Juan Yang,Gai Zhao,Qihua Wang,Tingmei Wang
A novel organic coating was created by dispersing solvent-free covalent graphene oxide nanofluids (GO NFs) into a polyimide (PI) matrix. The tribological properties of GO NFs/PI composite coatings was tested against ball-on-disk tribometer. Even a low loading of GO NFs significantly improve the tribological properties of PI. MD simulation and nanoindentation tests reveal that GO NFs adsorbs the PI molecular chains, enhancing the composites' mechanical properties. Moreover, a stable tribofilm develops on the steel ball surface lubricated with the GO NFs/PI composite coating, with analyses indicating that the GO NFs promote its growth. The enhancement of mechanical properties and the formation of this tribofilm are essential for the improved tribological performance of the composite. This research aims to contribute to the development of novel PI composite coatings with superior anti-friction and wear-resistant properties. Highlights The GO NFs exhibited excellent dispersion stability and tribological properties. Novel GO NFs/PI composite coating with significantly enhanced tribological properties. A carbon-based tribofilm forms on the steel ball. The strengthening mechanisms of composites were revealed by MD simulation.
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高影响因子
ACS Applied Materials & Interfaces
·
2024
·
IF 8.3
Haolin Xie,Qingqing Qiu,Huan Li,Ping Liu,Putrakumar Balla,Xiaopeng Qi,Tongxiang Liang,Jinming Zeng
Two dimensional covalent organic framework (2D COF) films based on triphenylamine are considered to be promising electrochromic and energy-storage materials owing to their interlayer π–π electron delocalization, one-dimensional (1D) nanopores, and stable chemical structures. Triphenylamine-based 2D COF electrochromic films, nevertheless, rarely exhibit transparency and high optical contrast, which severely limited the scope of their application. In this work, two directly grown triphenylamine-based polyimide 2D COF films, TAPA-PMDA and TAPA-NTCDA PI COF, were prepared through solvothermal technology. Their morphologies were assembled into hierarchical nanoporous structures in the form of strips and gravel-like nanograins, respectively. Both the TAPA-PMDA and TAPA-NTCDA PI COF films exhibited a transparent bleached state and high optical contrast. Their optical contrasts were 77.6% at 752 nm and 60.4% at 708 nm, respectively. Interestingly, the TAPA-NTCDA PI COF film could exhibit multicolors (transparent, red-gray, and blue-gray) through regulating the contributions of the electron transition from HOMO to SOMO and HOMO-1 to SOMO of TPA+•. In addition, the TAPA-PMDA and TAPA-NTCDA PI COF films also displayed fast switching and colored/bleached times of 7.3/2.7 and 5.3/8.1 s, respectively. Remarkably, the TAPA-PMDA PI COF film also demonstrated large specific capacitance and excellent charge–discharge rate capabilities. The directly grown polyimide 2D COF films are enormously promising for high-performance electrochromic and energy-storage materials.
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PubMed
高影响因子
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