Hangquan Li

A Polyethylene Nanocomposite Prepared via In-Situ Polymerization

A novel organic/inorganic nanocomposites of polyethylene (PE) was prepared via in-situ coordination polymerization. The Ziegler-Natta catalyst was first supported on the surface of silicate nanowhiskers to subsequently initiate the polymerization of ethylene on the surface of these nanowhiskers. The nanowhiskers were encapsulated by polyethylene and became reinforcement fibers of the composite. The strong interaction between the uniformly dispersed nanowhiskers and the resin matrix resulted in the formation of a kind of organic/inorganic network providing good mechanical properties.

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.

Cooperative toughening and cooperative compatibilization: the nylon 6/ethylene-co-vinyl acetate/ethylene-co-acrylic acid blends

Abstract A polymer blend consisting of nylon 6 and ethylene–vinyl acetate copolymer (EVA) was compatibilized with an ethylene–acrylic acid copolymer (EAA). Neither EVA nor EAA are compatible with nylon 6; however, the combination of the two resulted in a toughened nylon 6. The compatibilization was revealed by the dramatic increase in impact strength, and the smaller particle size and finer dispersion of EVA in the nylon 6 matrix in the presence of EAA. The degree of toughening was evaluated through its effect on the mechanical, morphological and rheological properties, by changing the proportion of the components in the nylon 6/EVA/EAA blends. Because EAA is a compatibilizer for nylon 6/EVA and EVA a compatibilizer for nylon 6/EAA, both the toughening and the compatibilization are cooperative.

Compatibilizing effect of diglycidyl ether of bisphenol-A in polymer blend system : Nylon 6 combined with poly(butyl acrylate) core and poly(methyl methacrylate) shell particles

A polymeric blend system of nylon 6 and a core-shell impact modifier was studied. The modifier had a poly(butyl acrylate) core and a poly(methyl methacrylate) (PMMA) shell compatibilized with an epoxy resin, diglycidyl ether of bisphenol-A (DGEBA). The compatibilization of DGEBA is achieved by the reaction of its glycidyl group with the amine groups of nylon 6, and hydrogen bonds may be generated between the hydroxyl groups and the carbonyl groups on PMMA. The effect of compatibilization was verified by the dramatic increase in impact strength and the finer dispersing of the core-shell particles in the nylon 6 matrix. The effects of compatibilization on other properties of the blend, such as the tensile and rheological properties, were also investigated.

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.

AB crosslinked polymer latexes via concentrated emulsion polymerization

Abstract A series of polycaprolactone (PCL)/poly(methyl methacrylate) (PMMA) AB crosslinked polymers (ABCP) in the form of latexes were prepared via the concentrated emulsion polymerization method. PCL diols were first reacted with acryloyl chloride in toluene to form a solution of vinyl-terminated PCL. Dissolving the methyl methacrylate monomer and a suitable initiator in this solution, the solution was employed to prepare a concentrated emulsion in water. After completing the polymerization of the concentrated emulsion, latexes of ABCP were obtained, which, depending on their composition, can be either elastomers or tough plastic materials. The toughness of PMMA is greatly improved in both cases. The effects of the PCL chain-length, composition and self-crosslinking of PCL on the mechanical properties were investigated.

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.