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A series of novel cross-linkable PSF-6AF/DBA copolymers with different structure were successfully synthesized via nucleophilic aromatic substitution stepwise polymerization of 4,4′-dichlorodiphenyl sulfone (DCS) with hexafluorobisphenol A (6AF) and 4,4′-(propane-2,2-diyl)bis(2-allylphenol) (DBA) monomer. The 6AF and DBA moieties with a large number of pendant groups had been successfully introduced into the PSF polymer chain. Then, the PSF-6AF/DBA films were fabricated by casting the PSF-6AF/DBA/DMF solutions with the concentration of 10% on the clean glass plates, followed by heat-treating all the films at 300 °C for 4 h. The effects of both the component and cross-linking on the thermal, mechanical and dielectric properties of the obtained films were investigated in detail. Compared to PSF-6AF/DBA films, the cross-linked PSF-6AF/DBA (CS-PSF-6AF/DBA) films show high glass transition temperature (Tg= 184–197 °C) and outstanding mechanical strength (64–77 MPa). More importantly, all CS-PSF-6AF/DBA films display stable dielectric properties in the temperature range of 20–200 °C. The permittivity of CS-PSE-6AF/DBA film at 1 kHz is as low as 2.1, while the dielectric loss is only 0.007.

Polyarylene ether nitrile (PEN) random copolymers were prepared from 6AF, BHPF, and 2, 6-dichlorobenzonitrile according to the nucleophilic aromatic substitution polymerization. The chemical structure of PEN random copolymers was characterized by the FT-IR and 1H-NMR spectrum, respectively. The thermal properties of the PEN random copolymers were investigated by using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The resulting PEN copolymers have excellent thermal stability with high glass transition temperature (Tg) ranging from 187℃ to 271℃ and the 5% weight loss temperature (T5%) of PEN copolymers greater than 490℃ in nitrogen atmospheres. Meanwhile, the PEN films have excellent mechanical property, the tensile strength ranges from 55 to 95 MPa. Moreover, the dielectric properties of the PEN random copolymers were investigated by dielectric tests. The dielectric constants (k) and loss tangent (tan δ) of PEN (PEN-6-AF/BHPF100) film is only 2.3 and 0.03 at 1 kHz, respectively. More importantly, the dielectric properties were found to be relatively stable until the Tg, which can be attributed to the existence of BHPF units in the molecular backbone.

Composite materials applied to capacitors with high dielectric constant, low dielectric loss and outstanding thermal stability are concerned widely in the field of dielectrics. So committed to the development of dielectric materials with excellent performance is the key factor. In this work, the barium titanate/polyether sulfone (BaTiO3/PES) composite films were prepared by a physical dispersion technology, which utilized a ball milling machine by high-speed circulation, scattered the PES solution contained BaTiO3 in deionized water with the aid of a surfactant. Then, the BaTiO3/PES composite films were obtained through a series of operations, containing reclaimed organic solvent, washed with deionized water, filtered, dried and hot pressed. The morphology of the BaTiO3/PES emulsion was investigated by TEM and SEM. The results showed that the BaTiO3 particles were covered in the PES resin matrix homogeneously. For 50 wt% BaTiO3 reinforced PES composite film. The dielectric constant increased by ~ 227% compared with pure PES resin (4.1 at 1 kHz) and the dielectric loss maintained around 10−2 magnitude, which performed better dielectric properties. The tensile strength of 10 wt% BaTiO3/PES composite films (72 MPa) reached the highest value in comparison with those of pure PES (58 MPa) due to the strengthened interaction between particles and matrix. Further increase of BaTiO3 content, the tensile strength and elongation at break decreased slightly but remained an excellent flexibility from the PES matrix. The temperature at weight loss 5% (T5%) of composite film with 40 wt% of BaTiO3 content reached up to 503 °C in N2 atmosphere. All the BaTiO3/PES composite films performed the concentrated glass transition temperature (Tg) around 229 °C. In sum, excellent thermal stability and dielectric properties would make the BaTiO3/PES composite films become the fine potential candidates for dielectric composites in the capacitors.

To develop high performance of polymer-based composites, the dispersion state and interfacial interaction of nano-fillers are two key issues to be considered. Herein, we report the surface decoration of basalt fibers (BF) with nano-sized barium titanate (BT) particles and their dielectric application in poly(ether sulfone)-based composite laminates (PBCLs) was investigated in detail. Firstly, the nano-sized BT particles uniformly deposited along the BF surface through a simple and effective solvothermal method, as confirmed by SEM and XRD measurement. Then, novel ternary dielectric polymer-based composite laminates, consisting of BT particles decorated BF and poly(ether sulfone) (BT–BF/PES), were fabricated by hot-pressing method. Compared to raw BF filled PBCLs, the SEM images of BT–BF fibers reinforced PBCLs showed that all the BT–BF fibers strongly adhere to the PES matrix, and obscure fiber/PES interfaces are present without visible boundaries, indicating a improved interfacial interactions in this case. Thus, the mechanical, thermal and dielectric properties of the resultant PBCLs were characterized and results indicated that the BF and BT particles show enhanced synergistic effects. Following this strategy, the flexural strength and dielectric constant of BT–BF/PES blend with 40 wt% of BT were increased by 28 and 350%, respectively, in comparison with those of BF/PES composite laminates.

A novel soluble poly(aryl ether ketone) (PAEK) terminated with 4-nitrophthalonitrile was designed and synthesized, which was used to solve the problem of difficult solution processing. Then, a series of cross-linked PAEK films with different thermal treatment temperatures were fabricated by using 4,4-bis(3,4-dicyanophenoxy)biphenyl (BPH) as a novel cross-linking agent, improving the glass transition temperature (Tg) of the traditional PAEK. Then, the fourier transform infrared (FT-IR) spectrum, X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermo gravimetric analysis (TGA), dynamic mechanical analysis (DMA), mechanical testing machine and LCR meter were used to investigate the microstructure, thermal, mechanical and dielectric properties of PAEK films, respectively. The results indicated that the increase in heat-treatment time and temperature are beneficial for the improvement of the value of Tg and T5%, and the excellent thermal stability and mechanical properties of PAEK films are demonstrated. Compared to PAEK-1 film, the Tg and T5% both increased by 63 °C for PAEK-4 film. Significantly, the tensile strength of PAEK-3 film (42 MPa) reaches the highest value in comparison with other samples. In addition, the dielectric constants (e) and loss tangent (tan δ) of PAEK-4 film is as low as 3.67 and 0.001 at 1 kHz, respectively. More importantly, the dielectric properties are found to be relatively stable to near the Tg value, which can be widely used for applications in dielectric energy storage at high temperatures.

In this work, a series of novel organosoluble copoly(arylene ether nitriles) containing thioether moiety (PENS) were synthesized via nucleophilic aromatic substitution polymerization of 2,6-dichlorobenzonitrile with bisphenol A and sodium sulfide nonahydrate, using N-Methyl-2-Pyrrolidone as solvent in the presence of anhydrous potassium carbonate. The chemical structures of PENS were characterized by FTIR and 1H NMR. The derived copolymers showed high glass transition temperatures in the range of 167–178 °C and excellent thermal stability with the 5% weight loss temperatures ranging from 465 °C to 503 °C. Meanwhile, all of the PENS were amorphous and can be readily cast into transparent films with a tensile strength exceeding 77 MPa and a breaking elongation over 4.8%.In addition, the dielectric constant of all the PENS copolymers showed weak frequency dependence, the dielectric loss showed slight decrease with increasing frequency over the range of 100 Hz to 200 kHz. Therefore, this kind of organosoluble copoly(arylene ether nitriles) containing thioether moiety could be a good candidate as matrix resins for high-performance polymeric materials.