Mengna Feng

In situ fabrication of MWCNTs reinforce dielectric performances of polyarylene ether nitrile nanocomposite

In this report, the dielectric properties of polyarylene ether nitrile (PEN)/multi-walled carbon nanotubes (MWCNTs) polymer composites were reinforced via in situ fabrication protocol for MWCNTs. The silanized MWCNTs were surface grafted with phenolphthalin (PPL), which is also one monomer involved in PEN synthesis. This is the premise for PPL can initiate cross-link behavior with the complex PEN and we called it as reactive MWCNTs. Therefore, the composite of PEN and reactive MWCNTs was readily fabricated by solution-casting method and the performance of this unique system was characterized by a range of different techniques. Fourier transform infrared spectroscopy confirmed that the MWCNTs have been bonded with PPL and silane functionalization agent. Based on the observation of scanning electron microscope, it was noted that the forming of reactive MWCNTs could improve the dispersion interfacial compatibility of PEN/MWCNTs nanocomposites. Consequently, the dielectric properties were improved, as lower dielectric loss and higher dielectric constant simultaneously obtained using reactive MWCNTs filler. Moreover, the results of thermal and mechanical performance tests provided additional evidences that the reactive MWCNTs synthesized via in situ fabrication can better reinforce PEN nanocomposites.

Design of bristle-like TiO2–MWCNT nanotubes to improve the dielectric and interfacial properties of polymer-based composite films

TiO2–MWCNT heterostructure nanotubes have been fabricated via a solvent-thermal method. Energy dispersive spectrometer and X-ray diffraction analysis revealed that the nanotubes are composed of C, Ti and O elements and TiO2 only contains the tetragonal anatase phase. SEM and TEM results show that most of the TiO2 bristles are vertically studded on the surface of the MWCNT. Subsequently, TiO2–MWCNT/polyarylene ether nitrile (PEN) composite films were prepared in order to investigate the effect of TiO2–MWCNT on the PEN matrix. SEM images exhibit that there is strong interfacial adhesion between the PEN matrix and fillers owing to the special bristle-like structure. Thermal analysis results show that TiO2–MWCNT/PEN composite films possess excellent thermal properties endowed by the PEN matrix. Besides, the dielectric constant of the composite films increases from 4 to 109 at 100 Hz when the TiO2–MWCNT loading reaches 8 wt%. Rheology measurements reveal that there is an obvious difference between the rheological percolation threshold and the electrical percolation threshold.

Influence of hyperbranched copper phthalocyanine grafted carbon nanotubes on the dielectric and rheological properties of polyarylene ether nitriles

Novel hyperbranched copper phthalocyanine covalently grafted carbon nanotube/polyarylene ether nitrile (HBCuPc-CNT/PAEN) flexile composite films were prepared via solution casting. The CNTs are enwrapped by a functional intermediate HBCuPc thin layer which forms a rough shell on the surface of the CNTs to ensure a good dispersion of CNTs in the PAEN matrix. The dielectric layer (HBCuPc-CNTs) is intercalated by insulating layers (pure PAEN, acting as the isolating layer). Due to the high capacitance of the dielectric layer and the effective blocking of the mobility of free charge carriers by the insulating layers, the polymer-based composite films exhibit not only a high permittivity but also an extremely low dielectric loss and excellent breakdown strength. SEM images show that HBCuPc-CNTs are perfectly embedded in the matrix and no pull-out phenomenon can be observed. In addition, the rheological properties of the resulting composite films also indicate that the grafted CNTs present a good dispersion and strong interactions with the PAEN resin, thus resulting in a significant improvement of the mechanical and thermal properties of the PAEN composite films.

Synergistic enhancement of dielectric constant of novel core/shell BaTiO3@MWCNTs/PEN nanocomposites with high thermal stability

In this work, the multi-walled carbon nanotubes (MWCNTs) cores were coated with inorganic BaTiO3 (denoted as BaTiO3@MWCNTs) via solvent-thermal method. Then, BaTiO3@MWCNTs/polyarylene ether nitriles (PEN) nanocomposite films embedded with core/shell BaTiO3@MWCNTs nanotubes were successfully prepared by solution-casting method. Pure PEN film, MWCNTs/PEN and BaTiO3/PEN films were prepared for comparison. The micromorphology, thermal, and dielectric properties of the nanocomposite films were investigated. All the nanocomposite films exhibited excellent thermal stability endowed by PEN matrix. Interestingly, it was found that core/shell BaTiO3@MWCNTs exhibited synergistic enhancement of dielectric constant of BaTiO3@MWCNTs/PEN nanocomposite films.

Sulfonated carbon nanotubes synergistically enhanced the proton conductivity of sulfonated polyarylene ether nitriles

The addition of a small amount of sulfonated multi-walled carbon nanotubes (3 wt%) to a sulfonated polyarylene ether nitriles (SPEN) proton exchange membrane using an acyl chloride method was proved to be an effective way to improve the mechanical behaviour and proton conductivity performance.

Mechanical, dielectric, and rheological properties of poly(arylene ether nitrile)–reinforced poly(vinylidene fluoride)

In this study, poly(vinylidene fluoride) (PVDF) and poly(arylene ether nitrile) (PEN) polymer alloys with different mass ratios were prepared by solution casting method. The morphological, thermal, dielectric, mechanical, and rheological properties of the obtained polymer alloys were systematically studied. Scanning electron microscopic images showed that the polymer alloys exhibited two-phase system with PEN dispersed in PVDF matrix, which was consistent with the Cole–Cole plots obtained from rheological study. With the introduction of PEN, the crystallinity of the alloys decreased obviously, the dielectric properties of the alloys were stable before the melting temperature. When the content of PEN increased to 7 wt%, both the tensile strength and elastic modulus reached the maximum values (35.1 MPa and 1545.3 MPa), with an increment of 24% and 31% compared with those of PVDF, respectively. Rheological studies showed that the addition of PEN could obviously broaden the linear viscoelastic region of PVDF. Furthermore, the complex viscosities and storage modulus of polymer alloys increased obviously with the addition of PEN.

Nitrile functionalized graphene oxide for highly selective sulfonated poly(arylene ether nitrile)-based proton-conducting membranes

4-(3-Aminophenoxy)phthalonitrile grafted graphene oxide (APN-GO) was employed as the filler incorporated into a sulfonated poly(arylene ether nitrile) (SPEN) matrix. The resulting composite membranes show good dispersion and compatibility, which is confirmed through scanning electron microscope. In this process, the existence of hydrogen bonds between amide and sulfonic acid groups can improve the interfacial adhesion and compatibility between the filler and the matrix. Besides, the newly introduced polar nitrile of APN-GO also can increase the intermolecular interaction and make the membranes more compact, which is favorable for the reduction of methanol permeability. Moreover, the composite membranes exhibit improved dimensional stability, proton conductivity and methanol permeability compared to that of a pure SPEN membrane. Furthermore, the composite membrane with 2 wt% filler achieves a high proton conductivity (0.124 S cm−1 at 20 °C and 0.240 S cm−1 at 80 °C) and low methanol permeability (0.117 × 10−6 cm2 s−1 at 20 °C) simultaneously, and exhibits a much higher selectivity (10.598 × 105 S s cm−3) than that of Nafion 117 (0.45 × 105 S s cm−3). All results indicate the potential of the as-prepared composite membranes for direct methanol fuel cell applications.

SGO/SPEN-based highly selective polymer electrolyte membranes for direct methanol fuel cells

In this study, proton-exchange membranes (PEMs) consisting of sulfonated poly(arylene ether nitrile) (SPEN) have been successfully prepared by incorporating a different amount of sulfonated graphene oxide (SGO). Incorporation of SGO can improve proton conductivity and reduce the methanol permeability. Besides, the existence of the intermolecular interactions between SPEN and SGO can improve the interfacial compatibility between filler and matrix. The resulting composite membranes show better mechanical property, proton conductivity and lower methanol permeability compared to that of pure SPEN. Furthermore, the composite membrane with 1 wt% SGO possesses good interfacial compatibility, exhibiting excellent proton conductivity (0.109 S/cm at 20 °C and 0.265 S/cm at 80 °C) and low methanol permeability (0.17×10−6 cm2·s−1 at 20 °C). So it achieves the highest selectivity (6.412×105 S·s·cm−3), which is about 14 times higher than that of Nafion 117. All these data indicate that the SPEN/SGO composite membranes have good potential for applications in direct methanol fuel cells.

Sulfonated copoly(arylene ether nitriles) as proton exchange membrane with excellent mechanical and thermal properties

A series of sulfonated biphenol poly(arylene ether nitriles) (BP-SPEN) copolymers were synthesized by the nucleophilic aromatic substitution polymerization of 2,6-difluorobenzonitrile with different ratios of hydroquinonesulfonic acid potassium salt and biphenol in the presence of potassium carbonate. The composition and structures of the BP-SPEN copolymers were characterized by Fourier transform infrared spectroscopy. Thermal properties, mechanical properties, proton conductivity, and water uptake of copolymer membranes were also investigated. The results showed that they present high glass transition temperature ranging from 131°C to 180°C and good thermal stability with the 5% weight loss temperatures in the range of 284–287°C under nitrogen atmosphere. They also exhibited good mechanical property with the tensile strength in the range of 68–109 MPa in the dry state and 31–72 MPa in the wet state. Furthermore, these copolymer membranes exhibited good water uptake ranging from 8.8% to 39.9%. Thus, the membranes had good proton conductivities in the range of 1.09 × 10−5–1.54 × 10−3 S cm−1 at room temperature and 100% relative humidity. The influence of temperature on water uptakes, tensile strength, and proton conductivity was also investigated.

Rheology, morphology, and properties of polyarylene ether nitrile blends

Polyarylene ether nitrile (PEN) blends with different mass ratios of PEN bisphenol (BP) to PEN bisphenol A (BPA) were prepared by solution casting method. The morphological, rheological, thermal, dielectric, and mechanical properties of the resulted blends were systematically studied. Rheological studies show that the addition of PEN (BPA) could improve the flowability of blends except that of 90/10 (BP/BPA). Meanwhile, the crystallization degree of blends also decreases except that of 90/10 (BP/BPA). Mechanical measurement results indicate that the PEN blend (PEN (BP):PEN (BPA) of 90:10) possesses highest tensile strength of 119.7 MPa, increased by 28.6% than PEN blends (PEN(BP):PEN(BPA) of 50:50). Besides, the scanning electron microscopic images show that there exists phase separation in the PEN blends (PEN (BP):PEN (BPA) of 50:50), which is well consistent with the Cole–Cole plots obtained from rheological studies. Moreover, the phenomenon of phase separation will lead to interfacial polarization between the two different phases, which is a significant factor to induce the transformation of dielectric constant. Furthermore, all blends possess high thermal stability (initial decomposition temperature over 470°C) and high mechanical property (tensile strength over 93 MPa), suggesting that PEN blends (BP/BPA) have a good prospect of extension and application.