Xinjian Cheng

A highly sensitive sensor based on hollow particles for the detection, adsorption and removal of Hg2+ ions

A simple and facile method has been developed for the preparation of highly sensitive hollow spheric chemosensors. In this method, positively charged polystyrene (PS) particles were employed as templates to prepare silica hollow microspheres, and then the micro-sensors were grafted onto the hollow spheres to obtain hollow-chemosensors. A series of different SiO2 hollow spheres could be prepared by tuning the preparation conditions, and were used to carry the sensors. The hollow-chemosensors could not only detect Hg2+ ions, but were also able to separate them with high efficiency. When the hollow-chemosensors were added to Hg2+ ion solutions, the color of solution instantly changed from red to yellow and could be seen by naked eye. The adsorption capacity did not vary significantly over a wide pH range from 3 to 8. The hollow-chemosensors exhibited high selectivity for the detection of Hg2+ ions over other heavy metal ions. In addition, the superiority of using hollow silica spheres as carriers, which was promising for chemosensor detection, adsorption and removal of heavy metal ions in solution, could be clearly seen.

The effect of molecular weight of hyperbranched epoxy resins with a silicone skeleton on performance

Hyperbranched epoxy resins with a silicone skeleton (HERSS) obtained by us through an environmentally-friendly synthetic method have shown a prominent comprehensive performance in modifying the diglycidyl ether of bisphenol-A (DGEBA). However, controlling the performance of the HERSS is still a challenge. In this paper, we report the preparation of three other kinds of HERSS with various molecular weights via hydrosilylation, in order to study the effect of the molecular weights of the HERSS on the degree of branching (DB), the viscosity and the mechanical performance, the thermal properties and the micro-phase separation behavior of cured HERSS–DGEBA composites, which contain the HERSS prepared recently. The degree of branching and viscosities of the HERSS are 0.71–0.84 and 103.5–697.4 mPa s, respectively. An increase in the molecular weight of the HERSS results in a decrease in the DB and an appearance of a maximum viscosity. Accordingly, the mechanical properties of the cured HERSS–DGEBA composites, including the tensile, flexural and impact strength, increase first and then decrease, and their glass transition temperatures decrease weakly. Both the average diameters of 3.62–4.75 μm and the distribution of the islands in the “sea–island” structure of all the cured composites show an increase. Compared with those of DGEBA, the tensile, flexural and impact strength could be increased by about 76.4–88.6%, 25.3–36.0% and 78.4–92.1%, respectively, but their glass transition temperature was impaired only by about 6.3–6.8%.

Environment-friendly synthesis and performance of a novel hyperbranched epoxy resin with a silicone skeleton

Hyperbranched epoxy resins have attracted increasing attention for their excellent comprehensive performance in toughening and reinforcing the diglycidyl ether of bisphenol-A (DGEBA). However, the tedious synthetic procedure, high cost, and the use of large amounts of organic solvents have hampered their industrial application. This paper presents an environment-friendly method to synthesize a novel hyperbranched epoxy resin with a silicone skeleton (HERSS) through a hydrosilylation reaction catalyzed by a heterogeneous halloysite-supported platinum catalyst. The reaction involves only one solvent and affords a high yield (>90%). The chemical structure, molecular weight, and degree of branching of the HERSS were characterized by FT-IR, GPC and NMR. The resulting HERSS was used to modify a DGEBA based epoxy resin and showed excellent performance. With the incorporation of 9 wt% HERSS, the impact, flexural and tensile strength of DGEBA are increased by about 92.5%, 36.0% and 88.6%, respectively. The toughening and reinforcing mechanism was attributed to the “sea-island” structure of the cure composite, as shown by the SEM micrographs of the fractured surfaces. An initial thermal decomposition temperature of about 380.0 °C of the cured HERSS/methyl nadic anhydride resin also indicates promising applications with regard to high-temperature-resistance.

Surface Hybrid Self-Assembly, Mechanism, and Crystalline Behavior of a Carboxyl-Ended Hyperbranched Polyester/Platinum Complex

The self-assembly of hyperbranched polymers has attracted much attention because of their wide application. In this article, we report a new facile surface self-assembly method for a carboxyl-ended hyperbranched polyester/platinum complex (HTD-3-Pt) and obtain ordered structural microrods with a length of 10-20 μm and a width of 1 μm. The length and diameter of the self-assembled microrods could be increased to 300-600 μm and 4-5 μm, respectively, by hierarchical self-assembly. The main factors affecting the morphology of the self-assemblies, including temperature, time, solvent and solubility parameter, and relative humidity were discussed by transmission/reflection polarizing optical microscopy (TRPOM), SEM, and HRSEM. The indications for the coordination bond (-COOPt) included the appearance of a new peak at 1606 cm(-1) and its shifting to 1634 cm(-1) in the FT-IR spectra, the disappearance of the C 1s peak at about 288.6 eV, and the increase in the O 1s electron binding energy in the XPS spectra. Furthermore, an interesting crystal property of the HTD-3-Pt self-assemblies was discovered and confirmed by XRD. The study results from the surface self-assembly mechanism suggest that the coordination induction of the platinum ion play a key role in driving microphase separation between the intermolecular chains and end groups of the HTD-3-Pt to form the microrod self-assemblies. Another interesting finding was that HTD-3-Pt showed a higher catalytic activity for hydrosilylation than did a traditional homogeneous catalyst.

TOUGHNESS AND REINFORCEMENT OF LINEAR UNSATURATED POLYESTER RESINS BY UNSATURATED HYPERBRANCHED POLYMER AND MECHANISM ANALYSIS

Unsaturated hyperbranched polyester resin (UHPR) prepared by ourselves shows best comprehensive performance in linear unsaturated polyester resin (UP-191) curing system and is considered as a kind of toughness and reinforcement additive. The effect of molecular weight and content of the UHPR on the performance of the UHPR/UP-191 hybrid materials are discussed in detail, and their performance has maximum with the increase of content and molecular weight of UHPR. The impact strength of the hybrid materials containing 10–15 wt% UHPR-2 is 1.86 kJ/m2, and which almost is 1.69 times of UP-191 performance, furthermore, the tensile and flexural strength can also be enhanced about 45.71% and 23.66%, respectively. The fracture surface micrograph of hybrid materials show non micro-phase separation of the UHPR/UP-191 blends which facilitates an enhanced interaction to achieve excellent toughness and strength of the cured systems by SEM and the results also are explained by a novel situ reinforcing and toughening mechanism.

Synthesis of heterogeneous shape-controllable nano-hyperbranched polymer/Pt(0) catalyst with high catalytic activity in hydrosilylation

Abstract

A high-performance polyurethane sponge for the detection, adsorption and separation of Cu2+ ions

The simultaneous detection and separation of copper ions is important. In this study, a fluorescent chemosensor (a copper sensitive molecule), was prepared using 6-bromo-benzo[de]isochromene-1,3-dione as a precursor. The as-prepared fluorescent molecule contains a hydroxyl group and an aminoquinoline moiety. The hydroxyl group enables the fluorescent molecule to anchor to a porous polyurethane (PU) sponge. The chemosensors still retained their recognition ability after they were introduced to PU. Upon the addition of Cu2+ ions to the PU sponge, both the color and the fluorescence intensity changed, suggesting that the chemosensor-functionalized PU sponges could be used as a Cu2+ ion sensor. The copper ions could also accumulate and be enriched on the sponges. The adsorption capacity of the PU sponge (containing 2 wt% of the chemosensor) reached 97.26 mg g−1, which was higher than that of the solid PU membranes (52.62 mg g−1). These polymeric, highly sensitive chemosensors may potentially be applied in the detection of water pollution generated by sources such as electroplating and drain outflow.

A facile method to prepare monodispersed CdS/SiO2 composite microspheres and investigation on their photocatalytic properties.

This article presents a facile method to prepare CdS/SiO2 composite microspheres and their good catalytic properties. In our method, monodispersed SiO2 particles bearing amino groups (–NH2) were synthesized at first and then used as carriers to load nanosized CdS particles to form CdS/SiO2 composite microspheres. With the addition of CdAc2 solution to the SiO2 dispersion, Cd2+ was attracted to the surfaces of the SiO2 particles through coordination interaction, and then thioacetamide was added to the dispersion. By heating, S2− released and reacted with the Cd2+, CdS/SiO2 composite microspheres were obtained accordingly. The photocatalytic properties of the as‐prepared composite microspheres were investigated as well. It was found that the composite microspheres have excellent photocatalytic activities for the degradation of dyes comparing with the commercial P‐25 TiO2 catalysts. After using and recycling for three times, the photocatalytic performance still remained very well.

A facile method to prepare composite and porous polyphosphazene membranes and investigation of their properties

Polyphosphazene/SiO2 composite membranes and porous polyphosphazene membranes were prepared and their properties were studied in detail. In this work, linear polyphosphazenes with 3-aminopropyltriethoxysilane (APTS) and n-butylamino side groups were prepared via the nucleophilic substitution reaction. The substituted polyphosphazenes were cross-linked by the hydrolysis of triethoxysilanes to form polyphosphazene/SiO2 composite membranes. When the as-prepared polyphosphazene/SiO2 composites were treated with HF, the silica dissolved and porous polyphosphazene membranes formed subsequently. Their structures and morphologies were studied by IR, DSA, DMA, XPS and SEM. And their mechanical properties were investigated as well. It could be seen that the thermal stability, the contact angles and the mechanical properties changed with the ratio of APTS. Namely, the contact angle changed from 74° to 96°, and the initial decomposition temperature increased from 170 °C to 225 °C when the ratio of APTS increased. Besides, the glass transition temperature increased from −48 °C to 31 °C after the membranes were cross-linked.

Synthesis of hybrid crosslinked polyphosphazenes and investigation of their properties

Novel organic/inorganic hybrid polyphosphazenes were prepared by free radical UV copolymerization of linear polyphosphazenes and vinyl monomers. In this work, linear polyphosphazenes grafted by allyl amino and n-butylamino groups have been synthesized via nucleophilic substitution reaction at an anhydrous and anaerobic atmosphere. By regulating the molar ratio of allyl amino and n-butylamino groups, five different linear polyphosphazenes were prepared. The hybrid polyphosphazenes have been crosslinked using the linear polyphosphazenes and vinyl monomers including styrene, methyl methacrylate, and lauryl methacrylate as intermediates via free radical UV copolymerization. By changing the quantity of vinyl monomers participating in the crosslinking reaction, series of hybrid polyphosphazene membranes were obtained. The linear polyphosphazenes have been characterized by Nuclear magnetic resonance, Fourier transform infrared (FTIR), Thermogravimetric analysis (TGA), Differential scanning calorimeter, Dynamic mechanical analyzer and Drop Shape Analysis (DSA). The hybrid polyphosphazenes have also been studied via FTIR, TGA and DSA. The test results proved that the linear polymers were successfully synthesized. Moreover, the water contact angles showed that the hybrid crosslinked polyphosphazenes had a better hydrophobicity and thermal stability than the linear polyphosphazenes and the hydrophobicity of hybrid membranes have a regular changing tendency with the quantities of UV-monomers and ratio of allylamino. The initial decomposition temperatures of the hybrid polymers also had a regular change due to the difference and quantities of vinyl monomers.