Hepeng Zhang

Synthesis of raspberry-like poly(styrene-glycidyl methacrylate) particles via a one-step soap-free emulsion polymerization process accompanied by phase separation.

We herein report a facile method to prepare raspberry-like poly(styrene-glycidyl methacrylate) [P(S-GMA)] particles with controllable structure via a one-step soap-free emulsion polymerization process accompanied by phase separation. In this method, corona particles with a size of 10-20 nm were produced in situ in the later polymerization stage by the migrating of S-enriched polymers from GMA-enriched core particles. The size of the corona particles and the roughness of the raspberry-like particles can be easily controlled by adjusting the amount of styrene (S), glycidyl methacrylate (GMA), and divinylbenzene (DVB). The structure of raspberry-like P(S-GMA) particles was confirmed by transmission electron microscopy, scanning electron microscopy, and atomic force microscopy. A possible mechanism of the formation of raspberry-like particles was proposed.

Synthesis of BSA/Fe3O4 magnetic composite microspheres for adsorption of antibiotics

BSA/Fe3O4 magnetic composite microspheres with high saturation magnetization and paramagnetic property were prepared via inverse emulsion technology at room temperature, bovine serum albumin (BSA, 60 KD), magnetic nanoparticles (Fe3O4) and glutaraldehyde as macromonomer, inorganic particles and cross-linking agent, respectively. Fourier transform infrared (FTIR), scanning electron microscope (SEM), metalloscope, and particle size analyzer were used to characterize morphology and structure of composite microspheres. Vibrating sample magnetometer (VSM) and thermogravimetric analysis (TGA) were used to test magnetic properties of the synthesized samples, adsorption capacity of microspheres was determined by ultraviolet spectrophotometer (UV). The results showed that BSA/Fe3O4 microspheres were 43 μm with relatively narrow particle size distribution, perfect sphere-shaped morphologies, superparamagnetism with a saturation magnetization of 11 emu/g, and high magnetic content with a value of 57.29%. The main factors influencing properties of microspheres including raw material ratio, the amount of emulsifier and cross-linking agent, agitation speed were investigated and optimized. Furthermore, these microspheres accompanying with high separable and reusable efficient may have great potential application in the field of separation, in particular, removal of antibiotics. Adsorption capacities of the microspheres of four different kinds of antibiotics (erythromycin, streptomycin, tetracycline and chloramphenicol) ranging from 69.35 mg/g to 147.83 mg/g were obtained, and Langmuir isotherm model coincided with equilibrium data than that of the Freundlich model.

Preparation of thermoresponsive Fe3O4/P(acrylic acid–methyl methacrylate–N-isopropylacrylamide) magnetic composite microspheres with controlled shell thickness and its releasing property for phenolphthalein

In this work, Fe3O4/P(acrylic acid-methyl methacrylate-N-isopropylacrylamide) (Fe3O4/P(AA-MMA-NIPAm)) thermoresponsive magnetic composite microspheres have been prepared by controlled radical polymerization in the presence of 1,1-diphenylethene (DPE). The shell thickness of thermosensitive polymer (PNIPAm), which was on the surface of the microspheres, can be controlled by using DPE method. The morphology and thermosensitive properties of the composite microspheres, polymerization mechanism of the shell were characterized by TEM, FTIR, VSM, Laser Particle Sizer, TGA, NMR, and GPC. The microspheres with narrow particle size distribution show high saturation magnetization and superparamagnetism. The thermosensitive properties of the composite microspheres can be adjusted indirectly via controlling the addition amount of monomer (NIPAm) in the second step during controlled radical polymerization. Phenolphthalein was chosen as a model drug to investigate drug release behavior of the thermoresponsive magnetic composite microspheres with different shell thickness. Controlled drug release testing reveals that the release behavior depends on the thickness of polymer on the surface of the microspheres.

Fabrication of one-dimensional Fe3O4/P(GMA-DVB) nanochains by magnetic-field-induced precipitation polymerization.

One-dimensional (1D) magnetic Fe(3)O(4)/P(GMA-DVB) peapod-like nanochains have been successfully synthesized by magnetic-field-induced precipitation polymerization using Fe(3)O(4) as building blocks and P(GMA-DVB) as linker. The Fe(3)O(4) microspheres without surface modification can be arranged with the direction of the external magnetic field in a line via the dipolar interaction between Fe(3)O(4) microspheres and linked permanently via P(GMA-DVB) coating during precipitation polymerization. The length of peapod-like nanochains can be controlled by magnetic field intensity, and the thickness of polymer shell can be tuned by the amount of monomers. Magnetic measurement revealed that these 1D peapod-like nanochains showed highly magnetic sensitivity. In the presence of magnetic field, 1D magnetic Fe(3)O(4)/P(GMA-DVB) peapod-like nanochains can be oriented and aligned along the direction of external magnetic field.

Fabrication of PEI grafted Fe3O4/SiO2/P(GMA-co-EGDMA) nanoparticle anchored palladium nanocatalyst and its application in Sonogashira cross-coupling reactions

Novel magnetic Fe3O4/SiO2/P(GMA-co-EGDMA) composite nanoparticles grafted with hyperbranched/linear polyethylenimine ligands were fabricated. Subsequently, nano palladium was effectively anchored on this carrier through complexation between Pd2+ ions and multifunctional organic ligands, then a novel supported Pd nanoparticle catalyst with good dispersion and high loading of Pd nanoparticles was successfully prepared after the following reduction process. Afterwards, the as-prepared supported Pd nanoparticle catalyst was characterized by SEM, TEM, XRD, FTIR, TG and ICP-AES. Ultimately, the catalytic performance of the supported Pd nanoparticle catalyst was investigated by catalysing the Sonogashira cross-coupling reaction between aryl halides and arylacetylene. Research shows that the novel supported Pd nanoparticle catalyst exhibits very superior catalytic activity in catalysing the Sonogashira cross-coupling reaction between aryl halides and arylacetylene, even in the absence of the cocatalyst (CuI), and the side reaction producing the by-product (1,3-diyne) can be inhibited effectively. In addition, this supported Pd nanoparticle catalyst exhibits stable recovery and high catalytic activity, for it can be effectively reused 8 times without obvious loss of catalytic activity. Furthermore, the yields of the target products of the Sonogashira cross-coupling reaction between iodobenzene and phenylacetylene, 3-aminophenylacetylene and 4-(ethynyl)phthalic anhydride can reach approximately 79%, 78% and 95% after this novel supported Pd nanoparticle catalyst has been used eight times, respectively.

Papain/Zn3(PO4)2 hybrid nanoflower: preparation, characterization and its enhanced catalytic activity as an immobilized enzyme

Flower-like papain/Zn3(PO4)2 hybrid materials are synthesized via a facile, rapid and low-cost method in this study. The growth process of the nanoflowers has been studied in detail and a four-step formation mechanism, including coordination, precipitation, self-assembly and size growth, has been clarified. The concentration of papain mainly affects the morphology of the products by regulating the assembly and crystal growth. The enzyme activity of papain/Zn3(PO4)2 hybrid nanoflowers, a novel immobilized enzyme, was calculated by monitoring the hydrolysis reaction of casein. The results show that the catalytic properties of papain immobilized on hybrid nanoflowers are enhanced compared with that of free papain. The as-prepared hybrid nanoflowers exhibited excellent reusability, high thermo stability and long storage life. The results indicate that the well-designed materials have great potential in industrial applications.

Atomic oxygen resistance of polyimide/silicon hybrid thin films with different compositions and architectures

Silicon (Si)-containing polyimides (PIs) with superior atomic oxygen (AO) resistance are promising materials for space applications. Here, in this study, we present the synthesis and characterization of eight Si-containing PI thin films and evaluate their AO durability. The resulting PI films exhibited high thermal stability and preferable AO resistance but showed slightly reduced mechanical performance relative to pristine PI. The highest optical transparency at 550 nm was observed for PI/octaaminopropylsilsesquioxane, while the lowest value was observed for PI/silica (SiO2) hybrids. X-Ray photoelectron spectroscopic study suggested that the topmost surface of PI was degraded at the early stage and an SiO2 inert protective layer was finally formed on the surface of hybrid films after AO exposure. It is found that Si-containing units of higher oxidation states and with higher Si/O molar ratio are favorable to improve the AO resistance. Dispersion of Si at molecular level contributes to improving anti-AO property as well as optical transparency of the prepared films. The characterization of scanning electron microscopy indicated a continuous SiO2 protective layer was crucial to prevent AO from eroding the bulk matrix.

Tunable wettability of hierarchical structured coatings derived from one-step synthesized raspberry-like poly(styrene-acrylic acid) particles

A facile one-step method to fabricate hierarchical structured coatings whose wettability could be easily tuned from hydrophilic (water contact angle, 9.3°) to superhydrophobic (water contact angle, 154.2°) by controlling the assembly temperature without any specialized equipment or additional modification is reported. The building blocks for the coatings, hierarchically raspberry-like poly(styrene-acrylic acid) (P(S-AA)) particles with 10 nm corona particles on the core, were produced via a one-step soap-free emulsion polymerization process accompanied by phase separation. The morphology and roughness of the raspberry-like particles can be conveniently regulated by adjusting the amount of S, AA and divinylbenzene (DVB). The chemical composition, crosslinking degree, hierarchical structure and roughness of the raspberry-like particles have significant influence on the wettability of the coatings. The transition of the wettability was attributed to a thermodynamic-driven process that hydrophobic components of the particles migrate toward the surface of the coatings and a decrease of the roughness of the hierarchical structure that was a result of softening and fusing of the particles at temperatures above the Tg of the copolymers.

Synthesis of poly (methyl methacrylate)-b-polystyrene with high molecular weight by DPE seeded emulsion polymerization and its application in proton exchange membrane.

In this article, we present poly (methyl methacrylate)-b-polystyrene (PMMA-b-PS) with different block ratios and high molecular weight, which was synthesized by environmentally friendly seeded emulsion polymerization with 1,1-diphenylethylene (DPE) as a chain transfer agent. Polymerization kinetics in the first and second stage was investigated. Stable latex and homogeneous latex particles were obtained with the characterization of laser light scattering (LLS) and transmission electron microscopy (TEM). SEC and (1)H NMR revealed the successful preparation of block copolymers with high molecular weight and two different block ratios. The morphology of microphase separation of block copolymer thin films was investigated by AFM, and long-range order lamellar morphology was observed after vapor-annealing. The block copolymer with block ratio of almost 1:1 and higher molecular weight than that of previous PMMA-b-PS was sulfonated with acetyl sulfate, and the sulfonation was confirmed by FTIR, (1)H NMR, and TGA. Then, the sulfonated PMMA-b-PS was casted as membranes. The electrochemical impedance spectroscopy displayed that membranes possessed favorable proton conductivity and fine dimensional stability, and they could be candidates as proton exchange membranes.

Water-borne thiol–isocyanate click chemistry in microfluidics: rapid and energy-efficient preparation of uniform particles

A nucleophile-catalyzed thiol–isocyanate reaction has been exploited as an efficient route to fabricate uniform particles in a water-borne system. Droplets were generated in a simple microfluidic setup from stoichiometric thiol and isocyanate monomers, thereby creating an oil-in-water emulsion, and polymer particles were obtained once the monomer droplets were exposed to a nucleophile. This is the first report of thiol–isocyanate polymerization in a water-borne system, which shows great promise in the manufacture of particles for its mild conditions, rapid rate and high conversion. Notably, heat, UV, anhydrous or oxygen-free conditions are not required. It is demonstrated that particles with sizes ranging from 40 to 250 μm can be prepared via adjusting the flow rate of continuous and disperse phases. In addition, the functionality of the thiol monomer has a profound effect on the morphology of particles. This method opens up possibilities for nucleophile-catalyzed thiol–isocyanate click chemistry in water-borne and heterogeneous polymerization.