Dezhong Yin

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.

Thiol–isocyanate click reaction in a Pickering emulsion: a rapid and efficient route to encapsulation of healing agents

An innovative, rapid and efficient route is developed to fabricate ene loaded microcapsules via a thiol–isocyanate click reaction based on a hydrolyzed poly(glycidyl methacrylate) (PGMA) particle stabilized oil-in-water Pickering emulsion. The whole process for the reaction only requires 10 min, opening up a new, time-saving and energy-efficient strategy. The oil droplets contain isophorone diisocyanate (IPDI), trimethylolpropane tris(3-mercaptopropionate) (TMMP) and 1,3,5-tri-2-propenyl-1,3,5-triazine-2,4,6 (1H, 3H, 5H)-trione (TTT), in which IPDI and TMMP are subsequently catalyzed by triethylamine (TEA) to produce a polythiourethane network, forming microcapsules. From scanning electron microscopy (SEM) and optical microscopy (OM), the resulting microcapsules are in good spherical shape and their outer surface is coated with a compact PGMA particle layer. The mean diameter of the TTT loaded microcapsules decreases from 238.8 to 110 μm with increasing the particle stabilizer concentration. Solid-state 13C NMR measurement proves that almost no side reactions exist in the base-catalyzed thiol–isocyanate reaction. Moreover, the core content (up to 67.8%) and the thickness of the shell wall (8–36 μm) can be adjusted by the feeding amount of core materials. These microcapsules with an outer PGMA layer disperse well and maintain their integrity in the epoxy coating, and no agglomeration is observed. Even though being encapsulated, the core ingredient maintains high reactivity as its raw version and exhibits favorable healing capability. Furthermore, besides TTT, the proposed method is versatile and applicable to the encapsulation of SR833S and diallyl phthalate.

Synthesis and characterization of brush-like multigraft copolymers PnBA-g-PMMA by a combination of emulsion AGET ATRP and emulsion polymerization

In this paper, poly(n-butyl acrylate)-g-poly(methyl methacrylate) multigraft copolymers were synthesized by macromonomer technique and miniemulsion copolymerization. The PMMA macromonomers were obtained by an activator generated by electron transfer atom transfer radical polymerization (AGET ATRP) in emulsion system and subsequent allylation. Then the copolymerization of different macromonomers with nBA was carried out in miniemulsion system, obtaining multigraft copolymers with high molecular weight. The latex particles and distribution of emulsion AGET ATRP and miniemulsion copolymerization were characterized using laser light scattering. The molecular weight and polydispersity indices of macromonomers and multigraft copolymers were analyzed by gel permeation chromatography, and the number-average molecular weight range is 187,600-554,800 g/mol for PnBA-g-PMMA copolymers. In addition, the structural characteristics of macromonomer and brush-like copolymers were determined by infrared spectra and (1)H nuclear magnetic resonance spectroscopy. The thermal performance of brush-like copolymers were characterized by differential scanning calorimetry and thermogravimetric analysis. Atomic force microscopy results showed that the degree of microphase separation was varying with increasing PMMA content in PnBA-g-PMMA. The dynamic rheometer analysis revealed that multigraft copolymer with PMMA content of 31.4% exhibited good elastomeric properties to function as a TPE. These multigraft copolymers show a promising low cost and environmental friendly thermoplastic elastomer.

Microencapsulation of hexadecane by surface-initiated atom transfer radical polymerization on a Pickering stabilizer

Hexadecane-loaded microcapsules with SiO2–poly(methyl methacrylate) (PMMA) hybrids as shells were prepared by surface-initiated atom transfer radical polymerization (SI-ATRP) in an oil-in-water Pickering emulsion. ATRP-initiators were introduced onto SiO2 particles by a homemade silane coupling reagent containing a 2-bromoisobutyrate group. SI-ATRP polymerization was conducted on Pickering stabilizers based on activators regenerated by electron transfer (ARGET). TGA results indicated that 80.3% of PMMA chains in the shell were covalently-bonded to SiO2, which was formed by SI-ATRP polymerization. The microcapsules show excellent potential for thermal energy storage, as evidenced by a high melting enthalpy of 161.7 J g−1.

Fabrication of 1D Fe3O4/P(NIPAM-MBA) thermosensitive nanochains by magnetic-field-induced precipitation polymerization

One-dimensional (ID) magnetic thermosensitive Fe3O4/poly(N-isopropylacrylamide–N,N′-methylenebisacrylamide) (P(NIPAM-MBA)) peapod-like nanochains have been successfully synthesized by magnetic-field-induced precipitation polymerization using Fe3O4 as building blocks and P(NIPAM-MBA) as linker. Fe3O4 microspheres can be arranged with the direction of an external magnetic field in a line via the dipolar interaction between Fe3O4 microspheres and linked permanently via P(NIPAM-MBA) coating during precipitation polymerization. 1D magnetic Fe3O4/P(NIPAM-MBA) peapod-like nanochains can be oriented and aligned along the direction of the external magnetic field. More interestingly, Fe3O4 microspheres in each peapod were regularly arranged in a line and periodically separated through the P(NIPAM-MBA) layers with a visible interparticle spacing.

Effects of Carbon Black on the Properties of HNBR Reinforced by in-situ Prepared ZDMA

Hydrogenated nitrile rubber (HNBR) filled with carbon black (CB) and in-situ prepared zinc dimethacrylate (ZDMA) was prepared by mechanical mixing method. The effects of carbon black on the vulcanization characteristics, physical and dynamic mechanical properties, thermal stability and the fracture surface morphologies of HNBR reinforced by in-situ prepared ZDMA (HNBR/ZDMA) were investigated. The results showed that, for given ZDMA loading (50 phr), with the increasing CB content, the scorch time extended, tensile strength, tear strength and elongation at break increased at first and then decreased, while the modulus at 100% and hardness increased. The comprehensive properties of the HNBR/ZDMA/CB was optimal, when the content of CB was 10 phr. DMA analysis showed that the addition of CB could enhance the storage modulus (E’) & loss modulus (E”), and decreased the glass transition temperature (Tg) of HNBR/ZDMA. TGA analysis revealed that the addition of CB could improve the thermal stability of HNBR/ZDMA. SEM analysis showed that the CB dispersed well in the HNBR/ZDMA, and the CB could improve the dispersion of ZDMA effectively.

Structural diversity of multi-hollow microspheres via multiple Pickering emulsion co-stabilized by surfactant

This paper presented a facile approach to fabricate interconnected multi-hollow polymer microspheres by water-in-oil-in-water (W/O/W) multiple emulsions co-stabilized by SiO2 and Span80. Two-step emulsification was employed to obtain W/O/W emulsion, followed by polymerizing the monomer into the skeleton of microspheres. The inner structure of microspheres was successfully regulated by adjusting the relative amount of SiO2 to Span80. A large range of microspheres with different inner structures was obtained, including close-celled microspheres, interior hollowed microspheres, interconnected microspheres by single channel or multi-channels, and bicontinuous structure. A formation mechanism of microspheres with different inner structure was proposed and verified by the characteristic of released Ca2+ from inner aqueous phase to outer aqueous phase. These microspheres have advantages of high surface area, high porosity, and multi-hollow structure.

BiOBr/BiOCl/carbon quantum dot microspheres with superior visible light-driven photocatalysis

In this paper, BiOBr/BiOCl/CQDs heterostructure microspheres were successfully synthesized via a facile solvothermal method. Then, the structures, morphologies, optical properties and photocatalytic performances were investigated. This research showed that the BiOBr/BiOCl/CQDs microspheres exhibited significantly enhanced photocatalytic performance compared with BiOBr/BiOCl. In the photocatalysis process of rhodamine B (RhB) under visible light irradiation, the highest photodegradation rate (0.0609 min−1) would be obtained when the weight percentage of CQDs was appropriate, which was about 2.8 times higher than that of BiOBr/BiOCl (0.0217 min−1). In this photocatalytic system, the enhanced photoactivity was mainly attributed to the heterojunction interface among CQDs, BiOBr and BiOCl, and enhanced light harvesting for the appropriate CQD introduction. The radical trapping experiments revealed that O2˙−, e− and h+ were the main active species during the photocatalysis process.