Jiashuang Luan

Ultra low dielectric constant soluble polyhedral oligomeric silsesquioxane (POSS)–poly(aryl ether ketone) nanocomposites with excellent thermal and mechanical properties

A series of novel ultra low dielectric constant soluble organic–inorganic nanocomposites in which nanoscale octa-aminophenyl polyhedral oligomeric silsesquioxanes (octaAmino POSS-Ph8) were covalently linked onto the fluoropoly(ether ether ketone)s (PEEK-CF3-COOH) were prepared and characterized. The chemical structures of the polymer matrix and nanocomposites were confirmed by 1H NMR and FT-IR spectra. The analysis of wide-angle X-ray diffraction (WAXD) and X-ray photoelectron spectra (XPS) indicated that the POSS clusters were successfully incorporated into the polymer matrix and the homogeneous dispersion of POSS cages in the polymer matrix was evidenced by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) (Si-mapping). Furthermore, the influence of the incorporation of POSS particles on the properties of nanocomposites is investigated. The dielectric constants of the organic–inorganic nanocomposites were drastically reduced relative to neat PEEK-CF3-COOH films and the dielectric constant could achieve as low as 1.71 (1 MHz). Besides, the thermal and mechanical properties of the nanocomposites were significantly improved by incorporation of octaAmino POSS-Ph8 moieties. Meanwhile, the nanocomposite thin films still retained the good transparency.

Design and preparation of graphene/poly(ether ether ketone) composites with excellent electrical conductivity

Graphene/poly(ether ether ketone) (m-TRG/PEEK) composites with excellent electrical conductivity were fabricated by hot pressing technique with thermally reduced graphene nanosheets (m-TRG) which were modified by poly(ether sulfone). Moreover, the conductive, thermal, and mechanical properties of PEEK/m-TRG composites were investigated by the precision impedance analyzer, thermal gravimetric analyzer, differential scanning calorimetry, and universal tester, respectively. The electrical conductivity of m-TRG/PEEK composites was greatly improved by incorporating graphene, resulting in a sharp transition from electrical insulator to semiconductor with a low percolation threshold of 0.76 vol.%. A high electrical conductivity of 0.18 S m−1 was achieved with 3.84 vol.% of m-TRG. The data were compared with those of composites reduced chemically, and the results showed that thermal reduction was an effective method to acquire higher electrical conductive composites. The excellent electrical property should be attributed to the large specific surface area of m-TRG, well dispersion of m-TRG in PEEK matrix, and good compatibility of m-TRG with PEEK matrix, as proven by scanning electron microscope. Besides, m-TRG/PEEK composites also exhibited relatively good thermal and mechanical properties.

Ultra low dielectric constant hybrid films via side chain grafting reaction of poly(ether ether ketone) and phosphotungstic acid

The novel ultra low dielectric constant poly(ether ether ketone) hybrid films in which nanoscale phosphotungstic acid (PWA) clusters were grafted onto the side chains of poly(ether ether ketone) containing (3-trifluoromethyl) phenyl groups and carboxyl groups (PEEK–CF3–COOH) in the presence the silane coupling agent γ-aminopropyltriethoxysilane (KH-550) were prepared and characterized. The chemical structures of the PWA/PEEK–CF3–COOH hybrid films were confirmed by FT-IR spectroscopy and 1H-NMR. The analysis of wide-angle X-ray diffraction (WAXD) indicated that the PWA clusters could not form crystalline structures in the PEEK–CF3–COOH matrix, and the investigation of the scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) (W-mapping) revealed that the PWA particles were well dispersed in the PEEK–CF3–COOH matrix with nanoscale. The influence of the incorporation of PWA particles by side chain grafting reaction on the properties of PEEK–CF3–COOH was studied. The dielectric constants of the PWA/PEEK–CF3–COOH hybrid films were remarkably lower than that of the neat PEEK–CF3–COOH film and the lowest value their dielectric constant could achieve was as low as 1.96 (1 MHz) when the content of grafted PWA reached 10 wt%. Meanwhile, the hybrid films still retain the excellent thermal and mechanical properties as well as the good transparency.

A novel poly(ethylene glycol)–grafted poly(arylene ether ketone) blend micro-porous polymer electrolyte for solid-state electric double layer capacitors formed by incorporating a chitosan-based LiClO4 gel electrolyte

A novel strategy was used to prepare a high performance micro-porous polymer electrolyte (MPE) from a poly(arylene ether ketone) (PAEK)/poly(ethylene glycol) grafted poly(arylene ether ketone) (PAEK-g-PEG) polymer composite membrane matrix incorporating a chitosan based LiClO4 gel electrolyte. The morphology, porosity, and thermal and mechanical properties of the PAEK/PAEK-g-PEG polymer blend membrane matrix were investigated. To improve the liquid retention capacity of the MPE, a simple but effective method involving the addition of chitosan was implemented. The effects of chitosan concentration on the liquid uptake and leakage behaviors as well as the ionic conductivity of the electrolyte were also evaluated. The synthesized MPE exhibited an ionic conductivity as high as 8 × 10−3 S cm−1 at room temperature. More importantly, a novel solid-state electric double layer capacitor (S-EDLC) could be fabricated using the synthesized MPE and activated carbon electrodes. For comparison, an EDLC was also assembled using the corresponding aqueous electrolyte and a commercial separator (NKK-MPF30AC-100). Alternating current (AC) impedance measurement results showed that the interfacial compatibility of the MPE and the activated carbon electrodes was high. Meanwhile, the as-prepared S-EDLC showed a specific capacitance of 118.63 F g−1, with an energy density of 7.87 W h kg−1 and power density being 95.97 W kg−1 at a current density of 1 A g−1. Furthermore, the S-EDLC exhibited greater cell-cycling stability after 5000 charge/discharge cycles than did the EDLC, indicating that this novel MPE should be suitable for use in EDLCs and other energy storage systems.

A flexible solid-state supercapacitor based on a poly(aryl ether ketone)–poly(ethylene glycol) copolymer solid polymer electrolyte for high temperature applications

In order to meet the requirement of high temperature applications, a high thermal stability solid polymer electrolyte is prepared with a poly(aryl ether ketone)–poly(ethylene glycol) copolymer (i.e., PAEK–PEG) as a polymer host, and LiClO4 as an electrolyte salt. A novel flexible solid-state supercapacitor is then assembled by the resultant solid polymer electrolyte and activated carbon electrodes. The electrochemical properties of the supercapacitor are analyzed over a wide temperature range of 30–120 °C. The fabricated supercapacitor has excellent electrochemical performance especially at high temperature (e.g. high specific capacitance of 103.17 F g−1 at 0.1 A g−1 and an energy density of 6.76 W h kg−1 with a power density of 9.55 W kg−1 at 120 °C). Simultaneously, this solid polymer electrolyte based supercapacitor possesses excellent flexible bending properties and outstanding cycle stability of negligible specific capacitance loss after 2000 cycles at various temperatures, demonstrating its feasibility as an energy device for high temperature applications.

Porphyrin–poly(arylene ether sulfone) covalently functionalized multi-walled carbon nanotubes: synthesis and enhanced broadband nonlinear optical properties

A novel multi-walled carbon nanotube (MWNT) hybrid was synthesized by covalently attaching a porphyrinated poly(arylene ether sulfone) onto the surface of carbon nanotubes. The polymer functionalized nanotube exhibited excellent solubility in organic solvents, and the weight% of MWNTs in the resulting hybrid was found to be 36%. Considerable fluorescence quenching and shortened fluorescence lifetime were observed in the MWNT hybrid due to the photo-induced electron/energy transfer behavior from porphyrin moieties to MWNTs. Z-scan measurements demonstrated the improved broadband nonlinear optical performance of the MWNT hybrid at both 532 and 1064 nm in nanoseconds, which is attributed to the accumulation effect of nonlinear absorption and scattering, and a remarkable photo-induced electron/energy transfer process. Meanwhile, the MWNT hybrid can be homogeneously dispersed in a polymer matrix, further fabricated into a uniform film with high transparency and ultrafast optical limiting response under femtosecond laser pulses.

Influence of processing conditions on tensile property of continuous glass fiber–reinforced PEEK composites fabricated by the co-wrapped yarn method

This study focused on the effect of processing conditions on the tensile properties of continuous glass fiber–reinforced polyether ether ketone composites, fabricated by co-wrapped yarn method, under different conditions. Their tensile properties were investigated in terms of thermal and fracture characterizations. The cooling rate significantly affected only the tensile modulus. However, both holding temperature and holding time had a significant effect on the tensile strengths and modulus. Although the effects of both were the same, the optimal increase of the holding time was found to be more beneficial.

Bending property and fracture behavior of continuous glass fiber-reinforced PEEK composites fabricated by the wrapped yarn method

The purpose of this study was to investigate bending properties and fracture behavior of the unidirectional continuous glass fiber-reinforced poly(ether ether ketone) composites based on the wrapped yarn method and to obtain an optimum fabrication condition. The composite plates were fabricated at different processing conditions, and their bending properties and fracture behaviors were investigated in terms of thermal, morphology, and fracture characterizations. The results indicate that the cooling rate lightly affected the bending performance; however, both molding temperature and holding time had a significant effect on the bending performance. Specifically, increasing the molding temperature or the holding time was conductive to reducing the delamination.

Preparation and properties of a novel, high-performance polyether ether ketone fabric

In this study, polyether ether ketone (PEEK) fibers were produced by melt spinning method and woven to form fabrics. Several characterization tests were conducted with fiber tensile testing machine, scanning electron microscope, and differential scanning calorimeter to investigate the basic properties of PEEK fibers. Electric fabric strength, thermal performance, and corrosion resistance of PEEK fabric were also investigated. The commercial samples of NomexIIIA (imported) and Aramid1313 fabrics (made in China) were selected as control groups to evaluate the performance of developed fabrics. The results indicate that the PEEK fabrics have higher breaking strength, better corrosion resistance, and greater thermal stability than the other two commercial fabrics in the control group. The total friction of the PEEK fabric reached 30,000 times when two separate yarns in fabric were broken completely, and the breaking strength was in the range of 830–1422 N. The surface of PEEK fibers remained smooth, and there was no deformation after handling by 30% sodium hydroxide and 36% hydrochloric acid for 48 h; additionally, there was no weight loss. The melting point of PEEK fabric was 342.89°C, and it lost 5% of its weight at 574°C. The research shows that as a novel high-performance textile, PEEK fabrics with a long service temperature of 260°C have significant advantages in the improvement of corrosion resistance and mechanical properties of textiles, especially enhancing the stability under high-concentration alkaline environment. This work can provide novel avenues for the development of high-performance fibers and products with applications in special harsh environments.

Influence of selective solvents on self-assembly behaviors of amphiphilic hyperbranched poly(aryl ether ketone)-graft-poly(ethylene glycol) rod–coil copolymer

An amphiphilic hyperbranched poly(aryl ether ketone)-graft-poly(ethylene glycol) (HPAEK-graft-PEG) rod–coil copolymer was synthesized by grafting linear PEG onto hydroxyl-terminated HPAEK (OH-HPAEK). The molecular structure, the number-average molecular weight and the thermal properties of HPAEK-graft-PEG were characterized by proton nuclear magnetic resonance and Fourier transform infrared spectroscopies, gel permeation chromatography, differential scanning calorimetry, and thermogravimetric analysis, respectively. The self-assembly behaviors of HPAEK-graft-PEG in the mixed solvents were investigated by transmission electron microscopy and scanning electron microscopy. The results demonstrated that the selective solvent in the used mixed solvents exerted remarkable influence on the morphology of the resulting micelles. When the mixed solvents were water/tetrahydrofuran (THF), trichloromethane/THF, and toluene/THF, that is, with the decrease of the selective solvents in polarity, HPAEK-graft-PEG could self-assemble into the regular microspheres with obvious core–shell structure, the similar quadrilateral-shaped micelles with the dimension of about 20 nm and the large complicated clew-shaped micelles, as well as the irregular large compound micelles, respectively. It is worth mentioning that the similar quadrilateral-shaped micelles were different from the toroidal micelles reported already, which had relatively obvious “angle”. The phenomenon may be ascribed that the rigid characteristic of rod HAPEK segment was conducive to the maintenance of the metastable state.