Zhongjie Du

Carbon nanotube reinforced polypyrrole nanowire network as a high-performance supercapacitor electrode

A carbon nanotube reinforced polypyrrole nanowire network was constructed by in situ polymerization of pyrrole in the presence of carbon nanotubes using cetyltrimethylammonium bromide micelles as a soft template. Carbon nanotubes as a reinforcer were embedded into a network of polypyrrole nanowires, thus retaining in the latter a complete network. The resulting network possessed a specific surface area of 112.1 m2 g−1 and a rough porous structure. The embedding of carbon nanotubes decreased the charge transfer resistance in the polypyrrole nanowires and allowed easy access and rapid diffusion of ions/electrons. When applied as a capacitive electrode, a specific capacitance of 183.2 F g−1 was observed at a current density of 8 A g−1. The specific capacitance retention was 85% after 1000 cycles at 1 A g−1. An asymmetric supercapacitor was fabricated using the network as a positive electrode and active carbon as a negative electrode, and when operated at a maximum voltage of 1.5 V, had a high energy density (15.1 W h kg−1 at 3000 W kg−1). A long-term cycling test of the asymmetric supercapacitor at a current density of 1 A g−1 displayed a capacitance retention of 72% even after 3000 cycles of charge and discharge.

Fabrication of interfacial functionalized porous polymer monolith and its adsorption properties of copper ions.

The interfacial functionalized poly (glycidyl methacrylate) (PGMA) porous monolith was fabricated and applied as a novel porous adsorbent for copper ions (Cu(2+)). PGMA porous material with highly interconnected pore network was prepared by concentrated emulsion polymerization template. Then polyacrylic acid (PAA) was grafted onto the interface of the porous monolith by the reaction between the epoxy group on PGMA and a carboxyl group on PAA. Finally, the porous monolith was interfacial functionalized by rich amount of carboxyl groups and could adsorb copper ions effectively. The chemical structure and porous morphology of the porous monolith were measured by Fourier transform infrared spectroscopy and scanning electron microscopy. Moreover, the effects of pore size distribution, pH value, co-existing ions, contacting time, and initial concentrations of copper ions on the adsorption capacity of the porous adsorbents were studied.

A transparent and luminescent epoxy nanocomposite containing CdSe QDs with amido group-functionalized ligands

A highly transparent and luminescent CdSe quantum dot (QD)/epoxy nanocomposite was prepared by mixing amido-functionalized QDs with an epoxy matrix. The original oleic acid ligand on the QDs was replaced by thioglycolic acid, and then primary amine groups were introduced via a reaction between the carboxyl group of thioglycolic acid and Schiff’s base. The QDs with amido-functionalized ligands showed a better dispersibility and higher optical properties in the epoxy matrix. It was found that the nanocomposite filled with 0.3 wt% modified green light-emitting QDs had a similar transparency to the neat epoxy and twice the luminescence intensity of nanocomposite-filled 0.3 wt% original QDs. Moreover, a QD/epoxy nanocomposite, which could emit clear white light by combining the unabsorbed blue excitation light and the re-emitted yellow light, was successfully fabricated by following the same strategy. The as-prepared QD/epoxy nanocomposite has potential applications in encapsulating materials in light-emitting diode.

Carbon dioxide adsorbent based on rich amines loaded nano-silica.

An easy strategy to obtain an effective carbon dioxide adsorbent based on rich amines functionalized nano-silica was proposed. Polyacrylic acid (PAA), acted as a multi-functional bridge, was firstly immobilized onto the surface of silica nanoparticles. Each carboxylic acid group was subsequently reacted with an amine group of alkylamines, and plenty of remained amines groups could be coated onto silica nanoparticles. As a result, the rich amines loaded nano-silica was fabricated and applied as CO2 adsorbent. The structures and morphologies of amines modified nano-silica were characterized by FTIR, TGA, TEM, and CHNS elemental analysis. Moreover, the effect of molecular weight of PAA and that of alkylamine on CO2 absorption capacity was discussed. As expected, SiO2-PAA(3000)-PEI(10000) adsorbent possessed remarkably high CO2 uptake of approximately 3.8 mmol/g-adsorbent at 100 KPa CO2, 40°C. Moreover, it was found that the adsorbent exhibited a high CO2 adsorption rate, a good selectivity for CO2-N2 separation, and could be easily regenerated.

Formation of porous epoxy monolith via concentrated emulsion polymerization.

Step polymerization was introduced into the concentrated emulsion templating method and was illustrated with the preparation of porous epoxy monolith. A solution of diglycidyl ether of bisphenol-A (DGEBA), its curing agent low molecular weight polyamide resin, and surfactant nonyl phenol polyoxyethylene ether in 4-methyl-2-pentanon as a solvent was used as the continuous phase, an aqueous suspension of colloidal silica as the dispersed phase of the concentrated emulsion. After the continuous phase polymerized and the dispersed phase removed, a porous material is obtained. The key point in this work is to find a compromise between the rates of curing and phase separating and thus achieve a kinetic stability of the concentrated emulsion. The effects of loading of colloidal silica, the pre-curing of the epoxy precursors, and the volume fraction of the dispersed phase were systematically investigated.

Acrylonitrile-co-vinyl acetate with uniform composition via adiabatic, self-heating copolymerization in a concentrated emulsion

A copolymer of acrylonitrile and vinyl acetate was prepared via the room temperature-initiated, self-heating polymerization of a concentrated emulsion. A mixture of the monomers containing an oxidant was first dispersed in an aqueous solution of surfactants to generate a concentrated emulsion with a volume fraction of 0.8 of the dispersed phase. An aqueous solution of reductants was subsequently introduced into the concentrated emulsion to initiate polymerization together with the oxidant. Since the container was properly insulated, the system self-heated because of the energy released from polymerization, and achieved a high conversion in 30 min. The molecular weight distribution was determined using the gel permeation chromatography (GPC), and the composition of the product was determined via elemental analysis. The GPC traces indicated that the molecular weight was a function of time. The longer the polymerization time, the greater the molecular weight. During polymerization, the composition remained almost unchanged. These two results differ from those of the traditional radical polymerization.

Control of Uniform and Interconnected Macroporous Structure in PolyHIPE for Enhanced CO2 Adsorption/Desorption Kinetics.

The highly uniform and interconnected macroporous polymer materials were prepared within the high internal phase hydrosol-in-oil emulsions (HIPEs). Impregnated with polyethylenimine (PEI), the polyHIPEs were then employed as solid adsorbents for CO2 capture. Thermodynamic and kinetic capture-and-release tests were performed with pure CO2, 10% CO2/N2, and moist CO2, respectively. It has shown that the polyHIPE with suitable surface area and PEI impregnation exhibits high CO2 adsorption capacity, remarkable CO2/N2 selectivity, excellent adsorption/desorption kinetics, enhanced efficiency in the presence of water, and admirable stability in capture and release cycles. The results demonstrate the superior comprehensive performance of the present PEI-impregnated polyHIPE for CO2 capture from the postcombustion flue gas.

Thermal Degradation of Bisphenol A Type Novolac Epoxy Resin Cured with 4,4′-Diaminodiphenyl Sulfone

Abstract The curing reaction of bisphenol A type novolac epoxy resin (bis-ANER) with 4,4′-diaminodiphenyl sulfone (DDS) was investigated with Fourier-transform infrared (FTIR) spectroscopy. It was found that the obvious structure changes involve the disappearance of epoxide groups and increase of hydroxyls. Thermal degradation of the bis-ANER/DDS network was studied with thermogravimetry in both dynamic air and nitrogen atmospheres. The degradation takes place in two steps in air but in only one step in nitrogen. FTIR measurement was carried out to identify the changes in the structure during the degradation at different steps. In addition, the thermal degradation reaction mechanism of bis-ANER/DDS with the Coats-Redfern method showed that the kinetic model function of the thermal degradation obeys the Avrami-Erofeev model equation, that is, g(α) = [−ln(1 − α)]2/3.

Structure and Properties of Poly (Vinyl Alcohol)/Soy Protein Isolate Blend Film Fabricated Through Melt Processing

Poly (vinyl alcohol) (PVA)/soy protein isolate (SPI) blend film plasticized with glycerol is fabricated by melting processing in presence of water. The structure and properties are investigated by Fourier-transform infrared spectroscopy, X-ray diffraction, differential scanning calorimeter, scanning electron microscope (SEM), mechanical testing, and thermo-gravimetric analysis (TGA). It is found that strong hydrogen bonds between soy protein and PVA macromolecules are formed. The incorporation of soy protein into PVA decreases the crystallinity of the latter. The crystallization and melting temperatures decrease with increasing SPI content. SEM shows that certain degree of phase separation occurs in the blend film, with soy protein phase finely dispersed in the PVA matrix. The PVA/SPI blend film possesses high flexibility even at high protein content, which ensures its potential applications as packaging film. TGA experiments shows that the incorporation of soy protein rendered the thermostability of the blend film.

β-Cyclodextrin functionalized polystyrene porous monoliths for separating phenol from wastewater

A β-cyclodextrin (β-CD) functionalized polystyrene porous monolith was prepared by the following procedure: First, β-CD was modified with allyl bromide leading to allyl-β-cyclodextrin (allyl-β-CD); then a concentrated emulsion was prepared using a mixture of allyl-β-CD, styrene, and divinyl benzene as the continuous phase and water as the dispersed phase. In the third step, a β-cyclodextrin (β-CD) functionalized polystyrene porous monolith was obtained by copolymerization of allyl-β-CD and styrene followed by removal of the water phase. Since the allyl-β-CD contained both hydrophilic and hydrophobic groups, it tended to move towards the water/oil interface. As a result, the internal surfaces of the porous monolith were enriched with β-CD. This enrichment was indicated by X-ray photoelectron spectroscopy characterization. The high content of β-CD and the high specific surface area of the porous monolith both contributed to a high adsorption capacity. For example, the maximum adsorption of phenol was 5.74 mg/g. Importantly, the porous monolith could be easily regenerated and recycled through desorption with ethanol and it was found that the adsorption properties remained stable for at least five adsorption/desorption cycles.