Preparation and Characterization of Non-porous Superparamagnetic Microspheres with Epoxy Groups by Dispersion Polymerization

Non-porous superparamagnetic polymer microspheres with epoxy groups were prepared by dispersion polymerization of glycidyl methacrylate (GMA) in the presence of magnetic iron oxide (Fe3O4) nanoparticles coated with oleic acid. The polymerization was carried out in the ethanol/water medium using polyvinylpyrrolidone (PVP) and 2,2’-azobisisobutyronitrile (AIBN) as stabilizer and initiator, respectively. The magnetic microspheres obtained were characterized with scanning electron microscopy (SEM), vibrating sample magnetometry (VSM) and Fourier transform infrared spectroscopy (FTIR). The results showed that the magnetic microspheres had an average size of-1μm with superparamagnetic characteristics. The saturation magnetization was found to be 4.5emu.g-1. There was abundance of epoxy groups with density of 0.028 mmol·g^-1 in microspheres. The magnetic PGMA microspheres have extensive potential uses in magnetic bioseparation and biotechnology.

An efficient synthesis of ampicillin on magnetically separable immobilized penicillin G acylase

Penicillin G acylase(PGA) was immobilized on the magnetic hydrophilic polymer microspheres with average pore size of 17.1 nm,specific surface area of 128.2 m2/g and saturate magnetization of 6.4 emu/g.The 96.7%ampicillin yield with 1.60 of the synthesis/hydrolysis(S/H) ratio from 6-aminopenicillanic acid(6-APA) and D-(-)-alpha-phenylglycine methyl ester(D-PGME) can be achieved using the resultant magnetic biocatalyst in ethylene glycol,where only 82.1%yield with 1.40 of the S/H ratio was obtained using the free PGA under the identical reaction conditions.The immobilized PGA can be separated magnetically and recycled for five times without obvious loss of its catalytic activity.

Preparation of Dysprosium Ferrite/Polyacrylamide Magnetic Composite Microsphere and Its Characterization

Using the technique of microemulsion polymerization with nano-reactor, dysprosium ferrite/polyacrylamide magnetic composite microsphere was prepared by one-step method in a single inverse microemulsion. The structure, average particle size, morphology of composite microsphere were characterized by FTIR, XRD, TEM and TGA. The magnetic responsibility of composite microsphere was also investigated. The results indicate that the magnetic composite microsphere possess high magnetic responsibility and suspension stability.

MAGNETIC POLYMER MICROSPHERE STABILIZED GOLD NANOCOLLOIDS AS A FACILELY RECOVERABLE CATALYST

Magnetically responsive hierarchical magnetite/silica/poly（ethyleneglycol dimethacrylate-co-4-vinylpyridine） （Fe3O4/SiO2/P（EGDMA-co-VPy）） tri-layer microspheres were used as stabilizers for gold metallic nanoeolloids as a facilely recoverable catalyst with the reduction of 4-nitrophenol to 4-aminophenol as a model reaction. The magnetic microsphere stabilized gold metallic nanocolloids were prepared by in situ reduction of gold chloride trihydrate with borohydride as reductant via the stabilization effect of the pyridyl groups to gold nanoparticles on the surface of the outer shell-layer of the inorganic/polymer tri-layer microspheres.

Influence of surface modification of SrFe12O19 particles with oleic acid on magnetic microsphere preparation

Oleic acid was used as surface modification agent to improve the hydrophobicity of magnetic strontium hexaferrite particles. The structure and properties of treated magnetic particles were characterized by scanning electronic microscopy （SEM）, Fourier transform infrared spectra （FTIR）, powder X-ray diffraction （XRD） and magnetic property measurement system （MPMS）. The results show that oleic acid is chemically enwrapped on the surface of SrFe12O19 particles. Magnetic particles modified by oleic acid are highly dispersible and strongly responsive to magnetism but with slight decrease in saturated magnetization. The affinity between magnetic particles and monomers is improved by surface modification, resulting in increased particle incorporation in magnetic polymeric microspheres. The surface modification mechanism of magnetic particles by oleic acid is addressed in this work.