NiO hierarchical hollow nanofibers (hhNFs) consisting of nanosized NiO particles have been synthesized with electrospun poly(amic acid) nanofiber templates through a simple ion-exchange process and subsequent thermal annealing. By virtue of the hierarchical porous fiber-like morphology, as confirmed by the microstructure analysis, the hhNFs possess dense ion transportation channels, interconnected electron diffusion paths, as well as good structure stability, which are conducive to electrochemical capacitor (i.e., supercapacitor) applications. Electrochemical measurements have validated the excellent electrochemical performance of as-prepared hhNFs, including a high specific capacitance of 700 F g−1 at a discharge current of 2 A g−1, a good cyclic stability (96% capacity retention after 5000 cycles at 5 A g−1), and a remarkable rate capability (80% capacitance retention with the current density increasing from 1 to 5 A g−1). These results along with the simplicity and high efficiency of the material preparation demonstrate that NiO hhNFs are promising electrode materials for high-performance supercapacitor applications. The method presented in this work could be extended to the fabrication of other hierarchical fiber-like nanomaterials for applications including electrochemical capacitors and secondary batteries.

NiO hierarchical hollow nanofibers as high-performance supercapacitor electrodes

A highly efficient one-pot synthesis of polysubstituted pyridine has been achieved through copper-catalyzed oxidative sp3 C−H coupling of acetophenones with toluene derivatives. Besides, the polysubstituted benzene was obtained through copper-catalyzed coupling of acetophenones. Both of the reactions exhibited a good functional group tolerance to produce a 2,4,6-triphenylpyridine or 1,3,5-triarylbenzene in high yields. Compared with previous methods, these transformations allow a highly flexible and efficient preparation of substituted pyridines and benzenes.

One-Pot Synthesis of Benzene and Pyridine Derivatives via Copper-Catalyzed Coupling Reactions

Different polyamic acid (PAA) modified sensors for hydrogen peroxide (H2O2) detection were prepared and characterized. Electro-deposition of a chemically synthesized PAA solution was used for modification of glassy-carbon electrode, while drop-casting was used for carbon (CSPE), gold (Au-SPE) and gold nanoparticles (AuNPs-SPE) screen-printed electrodes modification. All the studies performed, including the cyclic voltammetry, electrochemical impedance spectroscopy, amperometry revealed the best analytical performances of the PAA/Au-SPE electrode with a specific sensitivity of 899 μA mM−1 cm−2 and a detection limit of 2 μM hydrogen peroxide. The PAA/Au-SPE sensor exhibited a good selectivity for the determination of H2O2 in synthetic urine samples, and could be used to control the oxidative stress of the body.

Non-enzymatic polyamic acid sensors for hydrogen peroxide detection

Electrical and mechanical property study on three-component polyimide nanocomposite films with titanium dioxide and montmorillonite

We have developed green, efficient and powerful protocols for the preparation of 2,4,6-triarylpyridines and 1,8-dioxodecahydroacridines in the presence of Fe3O4@TiO2@O2PO2(CH2)2NHSO3H as a sulfonic acid-functionalized titana-coated magnetic nanoparticle catalyst under mild and solvent-free reaction conditions. These protocols furnished the desired products in short reaction times with good to high yields (20–40 min and 80–86% in the case of 2,4,6-triarylpyridines; 15–90 min and 80–93% in the case of 1,8-dioxodecahydroacridines). The final step of the mechanistic route in the synthesis of 2,4,6-triarylpyridines proceeds via an anomeric-based oxidation. Also, the nanomagnetic core–shell catalyst can be recycled and reused in both cases of the scrutinized one-pot multicomponent reactions with high turnover number and turnover frequency.

Catalytic application of sulfonic acid-functionalized titana-coated magnetic nanoparticles for the preparation of 1,8-dioxodecahydroacridines and 2,4,6-triarylpyridines via anomeric-based oxidation

A novel pyridine-containing aromatic diamine monomer, 4-phenyl-2,6-bis[3-(4-aminophenoxy)phenyl]pyridine (m,p-PAPP), was successfully synthesized by a modified Chichibabin reaction of benzaldehyde and a substituted acetophenone, 3-(4-nitrophenoxy)acetophenone (m,p-NPAP), followed by a reduction of the resulting dinitro compound 4-phenyl-2,6-bis[3-(4-nitrophenoxy)phenyl]pyridine (m,p-PNPP) with Pd/C and hydrazine monohydrate. The aromatic diamine was employed to synthesize a series of pyridine-containing polyimides (PIs) by polycondensation with various aromatic dianhydrides in N,N-dimethylformamide (DMF) via the conventional two-step method, and further thermal or chemical imidization forming PIs. The inherent viscosities of the resulting poly(amic acid)s and PIs were 0.59–0.73 and 0.56–0.68 dL/g; most of the PIs obtained by chemical imidization were readily soluble in common organic solvents such as DMF, N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), tetrahydrofuran (THF), etc. Meanwhile, strong and flexible PI films were obtained, which had good thermal stability, with the glass transition temperature (Tg) of 204.5–237.4 °C and the temperature at 10% weight loss of 527.7–552.0 °C in nitrogen atmosphere, as well as outstanding mechanical properties with tensile strengths of 88.6–90.4 MPa, a tensile moduli of 1.04–1.56 GPa, and elongations at break of 7.2–8.7%. The PI films also were found to possess low water uptake of 0.89–0.98%.

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Soluble polyimides based on a novel pyridine-containing diamine m,p-PAPP and various aromatic dianhydrides

A copolycondesation-type poly (amic acid) (PAA) was synthesized using pyromellitic dianhydride (PMDA) and 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) as dianhydride monomers, and 4,4'-oxydianiline (ODA) as a diamine monomer under microwave irradiation in dimethylformamide (DMF). PAA was then converted into a polyimide (PI) by an imidization. The structure and performance of the polymer were characterized by Fourier-transform infrared (FT-IR) spectroscopy, Proton nuclear magnetic resonance ( 1 H NMR) spectrometry, viscosity, X-ray diffraction (XRD), and thermogravimetric (TG) analyses. The results showed that under microwave irradiation, the intrinsic viscosity and the yield of PAA were increases, and the reaction time was shortened. The FT-IR spectra of the polymer revealed characteristic peaks for PI around 1778 - and 1723 cm -1 . TG curves indicated that the obtained PI began to lose weight at 535 °C, and its 10% thermal decomposition temperature under N 2 was 587°C.

Preparation of poly(amic acid) and polyimide via microwave assisted polycondensation of aromatic dianhydrides and diamines

Microwave-assisted synthesis and optical properties of hyperbranched polyimides containing triphenylpyridine structure: microwave-assisted synthesis and optical properties of hyperbranched polyimides containing triphenylpyridine structure

Xiaojin Yang

Papers

Soluble polyimides based on a novel pyridine-containing diamine m,p-PAPP and various aromatic dianhydrides

Preparation of poly(amic acid) and polyimide via microwave assisted polycondensation of aromatic dianhydrides and diamines

Microwave-assisted synthesis and optical properties of hyperbranched polyimides containing triphenylpyridine structure: microwave-assisted synthesis and optical properties of hyperbranched polyimides containing triphenylpyridine structure