Yumin Huang

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.

Plasmon enhanced fluorescence of a bisphthalonitrile-based dye via a dopamine mediated interfacial crosslinking reaction on silver nanoparticles

A fluorescent dye of a phenolphthalein derivative containing bisphthalonitrile groups was synthesized and subsequently chemically grafted onto dopamine modified silver nanoparticles via the interfacial crosslinking reaction, leading to enhanced fluorescent emission of dye molecules in a solution phase. Specifically, the non-fluorescent phenolphthalein (PP) molecule was end-capped with bisphthalonitrile (BPH) groups through nucleophilic substitution to obtain a violet/blue-emitting fluorescent dye PP-BPH due to the restriction of inter-molecular rotation. Furthermore, the PP-BPH dye can be immobilized on the surface of the dopamine modified silver nanoparticles, given the fact that bisphthalonitrile based monomers can be readily crosslinked in the presence of aromatic amine or phenol compounds (i.e. dopamine). Consequently, the fluorescent emission of the PP-BPH dye can be further enhanced via the plasmonic enhancement effects of silver nanoparticles. The preliminary results obtained in this communication will pave the way for the plasmon controlled photonic properties of PP-BPH based multifunctional polymers.

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.

Curing behaviors of cyanate ester/epoxy copolymers and their dielectric properties

The curing behavior and dielectric properties of cyanate ester/epoxy (EP) with a latent initiator imidazole was investigated as a function of blend composition. Differential scanning calorimetry (DSC) was used to investigate the dynamic cure behavior of the blends. Multiheating rate DSC, peak fitting, and iso-conversion method were applied to analyze the curing kinetic parameters. Two distinct peaks were fitted from the dynamic DSC curve and the activation energies of each reaction varied with the increase of curing degrees. Fourier transform infrared spectra revealed that several reactions coexisted during the curing processes of cyanate and EP, resulting in the coexistence of the polymers and copolymers in the final composites. The dielectric properties of the composites were studied and the phenomenon that the dielectric constants for all of the composites are independent of frequency was observed. The thermal decomposition characteristics of the blends were investigated using thermogravimetric analysis. By increasing the content of EP, the thermal properties of the cured blends were improved to a small extent, while the char yield markedly decreased.

The effect of bismaleimide on thermal, mechanical, and dielectric properties of allyl-functional bisphthalonitrile/bismaleimide system

Allyl-functional phthalonitrile (DBPA-Ph) and bismaleimide (BMI) have been considered as advanced composite-matrix resins applied in various fields. In this work, self-promoted polymerization behavior and processability of DBPA-Ph/BMI system were investigated in detail. To further reveal the effect of BMI on the properties of DBPA-Ph/BMI system, the blends and the prepolymers of DBPA-Ph/BMI were prepared in different proportions. Their curing and rheological behaviors were investigated by differential scanning calorimetry and dynamic rheological analysis. The results further confirmed the possible reaction mechanisms and demonstrated that DBPA-Ph/BMI prepolymers exhibited good processability, which included wide processing window (approximately 75°C), low melting viscosity (<0.2 Pa·s), and better reactivity. The copolymers exhibited satisfactory thermal stabilities (T 5% > 421°C, char yield at 600°C >70%). Moreover, the DBPA-Ph/BMI/glass fiber composite laminates were prepared and the effect of the curing temperature and BMI content on mechanical properties and dielectric properties were also investigated. The results show that the composite laminates exhibit favorable mechanical properties and weak frequency dependence of dielectric properties over a wide frequency range. Above all, the research on DBPA-Ph/BMI system could expand its applications in industry, especially in the areas, which require high temperature resistance and excellent mechanical and dielectric properties.

Constructing Continuous Proton-Conducting Highways within Sulfonated Poly(Arylene Ether Nitrile) Composite Membrane by Incorporating Amino-Sulfo-Bifunctionalized GO

To obtain a proton exchange membrane (PEM) with high proton conductivity and low methanol permeability, a novel amino-sulfo-bifunctionalized GO (NSGO) was synthesized and explored as a filler for sulfonated poly(arylene ether nitrile) (SPEN). The result indicated that the microstructure of composite membranes was rearranged by NSGO and strong acid–base interactions were formed between fillers and the SPEN matrix, affording enhanced thermal, mechanical, and dimensional stabilities. Moreover, it was found that NSGO fillers were uniformly dispersed in the SPEN matrix, generating efficient proton-conducting paths along the SPEN/NSGO interface. Meanwhile, the sulfonic and amino groups of NSGO served as additional proton hopping sites to connect the ionic clusters in the SPEN matrix, creating interconnected and long-range ionic pathways. In such a way, proton-conducting highways with low energy barriers are constructed, which enhance the proton conductivity of the composite membranes via the Grotthuss mechanism. Furthermore, the composite membranes also effectively prevent methanol permeation, and therefore high selectivity (the ratio of proton conductivity and methanol permeability) is endowed. Compared to SPEN membrane, a 3.6-fold increase in selectivity is obtained for the optimal composite membrane. This study will provide a new strategy for the preparation of high-performance PEM.

Electrospun nanofiber enhanced sulfonated poly(arylene ether nitriles)-based proton conducting membrane

To study the effect of electrospun nanofiber on proton conductivity of sulfonated poly(arylene ether nitriles) (SPEN), the nanofiber mats were prepared by the electrospinning technology and the nanofiber/SPEN proton conducting membranes with different SHQ content were fabricated via impregnation method. For comparison, the casting SPEN membrane was also prepared by the solution-casting method. The scanning electron microscope (SEM) was used to observe the morphologies of electrospinning nanofiber mats. The water uptake, thermal and oxidative stability of casting SPEN and the nanofiber/SPEN membranes were also detailed studied. Besides, the nanofiber/SPEN membranes possess the higher proton conductivity than that of casting SPEN. The SPEN composite membrane with 5 wt% SHQ nanofiber exhibits the highest proton conductivity of 0.044 S/cm and 0.0865 S/cm at 20 °C and 80 °C, respectively. However, after second times water treatment, the conductivities of nanofiber/SPEN membranes are all lower than that of orig...