大粒径磁性高分子微球的合成

本文研究了苯乙烯、丙烯酸等单体在磁性氧化铁(E_((?)3)O_4)的醇/水分散体系中的聚合行为。为了改善磁性氧化铁粒子与苯乙烯单体间的亲合性,加入聚乙二醇作为分散剂和稳定剂,制备出粒径为30～1000μm的具有磁响应性的聚苯乙烯微球。研究了控制聚合区域的方法,考察了分散稳定剂、分散介质、引发剂种类和用量、反应时间等因素对聚合行为及微球形成的影响。     

Functionalization of Magnetite Nanoparticles as Oil Spill Collector

In the present study, a new magnetic powder based on magnetite can be used as a petroleum crude oil collector. Amidoximes based on rosin as a natural product can be prepared from a reaction between hydroxylamine and rosin/acrylonitrile adducts. The produced rosin amidoximes were used as capping agents for magnetite nanoparticles to prepare hydrophobic coated magnetic powders. A new class of monodisperse hydrophobic magnetite nanoparticles was prepared by a simple and inexpensive co-precipitation method. Iron ions and iodine were prepared by the reaction between ferric chloride and potassium iodide. The structure and morphology of magnetite capped with rosin amidoxime were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), zeta potential, thermogravimetric analysis (TGA) and dynamic light scattering (DLS). The magnetic properties were determined from vibrating sample magnetometer (VSM) analyses. These prepared magnetite nanoparticles were tested as bioactive nanosystems and their antimicrobial effects were investigated. The prepared nanomaterials were examined as a crude oil collector using magnetic fields. The results show promising data for the separation of the petroleum crude oil from aqueous solution in environmental pollution cleanup.     

Producing PLGA fine particles containing high magnetite nanoparticles by using the electrospray technique

Loading magnetite (Fe₃O₄) nanoparticles (NPs), extensively using magnetic agents in magnetic resonance imaging (MRI) and drug delivery in a matrix of polymeric fine particles (FPs), can optimize not only the delivery of these diagnostic and therapeutic agents but also the design of multifunctional drugs. In an effort to use a new method for producing high magnetite loaded polymeric particles, oleic acid (OA) capped magnetite NPs were synthesized and loaded into biocompatible and biodegradable FPs of poly lactic-co-glycolic acid (PLGA) by using the electrospray (ES) technique; and the effect of voltage, flow rate and magnetite content on the morphology, size, size distribution, uniformity and magnetic properties of fabricated magnetic FPs (MFPs) were studied. Results of SEM images and calculations showed that solution flow rate is a major factor in ES and the particle size of magnetite loaded PLGA FPs increases considerably as the flow rate increases. Particle size did not change considerably due to an increase in voltage; however, particle uniformity first increased and then decreased due to an increase in flow rate or voltage. High magnetite content of 72% was achieved for magnetite loaded PLGA FPs and an increase in the magnetite content resulted in an increase in the saturation magnetization of magnetite loaded PLGA FPs; though, their sphericity decreased.     

Electrodeposition of copper–magnetite magnetic composite films

Electrodeposition was demonstrated to be useful for the preparation of copper–magnetite magnetic composites. An acidic bath was tested for the incorporation of nanometric magnetite (Fe₃O₄) particles into an electrodeposited copper matrix. Cationic surfactant (dodecyltrimethylammonium chloride—DTAC) was used to keep particles suspended in the electrolyte as well as to assist magnetite incorporation. The influence of several parameters (bath temperature, deposition technique, stirring regimes and deposition conditions) on composites composition was analysed. Low stirring rate, moderate temperature (15 °C) and an applied magnetic field provided a greater incorporation of magnetite. Field emission scanning electron microscopy revealed magnetite distribution through the deposit thickness. Electrodeposited composites showed ferromagnetic behaviour. Magnetic force microscopy showed a magnetic response for the composites.     

Preparation and characterization of some ferromagnetic glass–ceramics contains high quantity of magnetite

Ferrimagnetic glass–ceramics are promising candidates for magnetic induction hyperthermia, which is one form of inducing deep-regional hyperthermia, by using a magnetic field. The aim of this work was to study the effect of increasing the amount of crystallized magnetite on the magnetic properties of glass–ceramic samples. Two different ferrimagnetic glass–ceramics with the composition based on wollastonite or hardystonite with high quantity (∼60%) of magnetite were prepared by melting the starting materials at 1450 °C for 2 h. The influences of chemical composition, amount of crystallized magnetite and microstructure of ferrimagnetic glass–ceramics on magnetic properties of ferromagnetic glass–ceramics were investigated using differential thermal analysis (DTA), X-ray diffraction (XRD), transmission electron microscope (TEM) and scanning electron microscope (SEM). The X-ray diffraction patterns show the presence of nanometric magnetite crystals in a glassy matrix after cooling from melting temperature. The amount of crystallized magnetite varies as a function of the chemical composition and heat treatment schedule. The presence of ZnO in the glass–ceramics was found to decrease the viscosity and so cases higher degree of mobility of ions leading to higher degree of crystallinity. The higher heat treatment parameters and so the lower viscosity of the glass containing ZnO are assumed to allow the magnetite to grow to larger crystallite size. Glass transition temperature and thermal stability were found to be functions of chemical composition. Magnetic hysteresis cycles were analyzed using a vibrating sample magnetometer (VSM) with a maximum applied field of 15 kOe at room temperature in quasi-static conditions. From the obtained hysteresis loops, the saturation magnetization (Ms), remanance magnetization (Mr) and coercivity (Hc) were determined. The results showed that these materials are expected to be useful in the localised treatment of cancer.     

Contributions of TMAH Surfactant on Hierarchical Structures of PVA/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>–TMAH Ferrogels by Using SAXS Instrument

The magnetic hydrogels combining polyvinyl-alcohol (PVA) and Fe₃O₄ (magnetite)–TMAH (tetra-methyl ammonium hydroxide) have been successfully fabricated via a Freezing-thawing route. The magnetite nanoparticles were prepared from iron sands by using coprecipitation method. The transmission electron microscopy image revealed that the magnetite nanoparticles with a reaction temperature of 30 °C had the average particle size of 12 nm in clusters of aggregation. The result was similar to the particle size obtained from X-ray diffraction data analyzed by Scherer equation. Furthermore, synchrotron small angle X-ray scattering data were analyzed by using two lognormal distributions to calculate the distribution of the individual magnetite particles. Meanwhile, Teubner-Strey and Beaucage models were employed to observe the distribution of magnetite particles coated by TMAH as a surfactant. The data analysis showed that the magnetite particles within the magnetic hydrogels formed aggregations with diameters of cluster particles in the range from 13.1 to 31.8 nm. Interestingly, the diameter of clusters particle increased from 13.1 to 31.8 nm along with the increasing concentration of ferrofluids from 1 to 15 wt%. This phenomenon was predicted to result from the effect of TMAH as a surface reactant agent that prevented the aggregation by coating the surface of the magnetite nanoparticles.     

Magnetic Characteristics of Ferrimagnetic Microspheres Prepared by Dispersion Polymerization

Summary: A magnetite‐based colloid was obtained by chemical co‐precipitation of iron(II) and iron(III) salts in alkaline medium and stabilized with oleic acid. Magnetic micron‐size poly(2‐hydroxyethyl methacrylate) (PHEMA)‐based latex particles of narrow size distribution were prepared by dispersion polymerization in toluene/2‐methylpropan‐1‐ol in the presence of three kinds of ferrimagnetic nanoparticles: chromium dioxide, maghemite, and magnetite. Cellulose acetate butyrate and dibenzoyl peroxide were used as the stabilizer and the initiator, respectively. The magnetic characteristics were examined with respect to behavior in the magnetic field and thermal stability. Our results show that chromium dioxide and derived PHEMA particles are magnetically stable in moderate temperatures up to about 100 °C. Maghemite particles are thermally stable up to 500 °C. Measurements of the hysteresis loops and remanent magnetization showed that embedment of magnetic particles in organic polymer has practically no effect on their magnetic hysteresis. All the samples reached magnetic saturation in fields below 0.3 T (saturation of magnetite). Regarding separation by the magnetic field, ultrafine, superparamagnetic magnetite particles show the best performance because of their magnetic susceptibility, the highest measured here, and the absence of coercive force.

Scanning electron micrograph of magnetite‐containing P(HEMA‐co‐25% GMA) microspheres.     

Fe_3O_4/P(St-CBA)核壳磁性复合微球的制备及性质

运用分散聚合法制备出Fe3O4 /P(St -CBA)核壳磁性复合微球。该微球粒径为 0 .0 75～0 .70 0 μm、w(Fe3O4 ) =0 .0 5 %～ 0 .90 % ,呈规整球型 ,表面光滑 ,在 0 .0 5T磁场中的磁响应性为3.0cm/min。制备微球的最佳条件为 :w(磁流体 ) =0 .5 %～ 3 .0 %、w(马来酸酐 ) =0 .0 %～2 .0 %、w(无水乙醇 ) =30 .0 %～ 70 .0 %。     

Efficient Dispersion of Magnetite Nanoparticles in the Polyurethane Matrix Through Solution Mixing and Investigation of the Nanocomposite Properties

Recent studies on inorganic/polymer nanocomposites have shown enhancements in thermal, mechanical, and chemical properties over the neat polymer without compromising density, toughness, and processibility. When nanoparticles are incorporated into the polymer matrix, significant enhancements in thermal and mechanical properties of the nanocomposite are observed. The present study is focused on the preparation and characterization of nanosize magnetite-reinforced PU composites, which induces magnetic properties to a specific thermoplastic polyurethane elastomer. The nanocomposites are prepared and the effects of magnetite content on thermal, mechanical, and magnetic properties of the nanocomposites are evaluated. Ultrasonication was used to disperse the nanoparticles and break up any large clumps and aggregates and followed by mechanical mixing. The magnetic nanocomposites were characterized by FT-IR spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and vibrating sample magnetometry (VSM). Characterization of the magnetic nanocomposite by FT-IR showed a successful incorporation of magnetite nanoparticles into the polymeric matrix. TGA and magnetometry of the magnetic nanocomposites revealed the amount of magnetite that was incorporated into the polymeric phase. Finally, the corresponding magnetization behavior of the nanocomposites was studied.     

NEW MAGNETIC FIELD-ENHANCED PROCESS FOR THE TREATMENT OF AQUEOUS WASTES

ABSTRACT

A new magnetic adsorbent material, called magnetic polyamine-epichlorohydrin (MPE) resin, was prepared by attaching activated magnetite to the outer surface of polyamine-epichlorohydrin resin beads. Experiments were carried out in the presence of a 0.3-tesla magnetic field to investigate the removal of actinides (plutonium and americium) from pH 12 wastewater using this new resin. The results demonstrated that the MPE resin has a significantly enhanced capacity for actinides over conventional ferrite-based surface complexation adsorption processes (where no field is applied) and over traditional high-gradient magnetic separation (HGMS) processes that remove suspended particles. This enhancement was attributed to the presence and subsequent removal of suspended actinide nanoparticles through an HGMS effect, with the magnetite acting as a very effective HGMS element. A theoretical analysis verified this supposition by showing that under adequate pHs and particle-particle separations, the attractive long-ranged magnetic force exerted by magnetite on suspended particles of plutonium hydroxide was greater in magnitude than other forces (e.g., van der Waals, electrostatic, viscous, and Brownian forces).     

Preparation and characterization of magnetite/dextran nanocomposite used as a precursor of magnetic fluid

Magnetic nanoparticles were synthesized by the co-precipitation of Fe²⁺ and Fe³⁺ using ammonium hydroxide (NH₄OH). The obtained nanoparticles were characterized by X-ray powder diffraction, transmission electron microscopy, scanning electron microscopy, Fourier transform infrared (FT-IR) spectroscopy and vibrating sample magnetometer. In order to prepare a biocompatible water-based magnetic fluid, the nanoparticles were modified by dextran through a two-step method. The influences of dextran molecular weight on the size, morphology, coating efficiency and magnetic property of magnetite/dextran nanocomposite were investigated. The magnetite/dextran nanocomposite was dispersed in water to form a magnetic fluid by ball milling. The rheological property of magnetic fluids was investigated using a rotating rheometer.     

Synthesis of polyvinyl alcohol hydrogel grafted by modified Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles: characterization and doxorubicin delivery studies

During the last two decades, serious efforts have been directed towards the synthesis and coating magnetic nanoparticles for biomedical applications. Among many different types of polymeric coating materials that have been utilized in previous studies, we have selected polyvinyl alcohol (PVA). In this study, we report a novel type of magnetite nanocomposite-based PVA hydrogel. For this purpose, first, Fe₃O₄ nanoparticles were modified through hexamethylene diisocyanate (HMDI) and then PVA was modified by bromoacetyl bromide to produce bromoacetylated PVA. The modified PVA was cross-linked through various diamines such as ethylene-diamine, propylene-diamine and hexamethylenediamine. The prepared weak tridimensional PVA hydrogels were further reacted through unreacted hydroxyl groups with Fe₃O₄, modified by HMDI to form magnetite hard tridimensional hydrogels. The swelling behavior of the prepared magnetite nanocomposites were investigated and showed a fast initial swelling followed by a mild increase until attaining equilibrium. The structural, morphological, thermal and magnetic properties of the synthesized magnetite nanocomposites were confirmed by FTIR, thermal gravimetric analysis, vibrating sample magnetometer and scanning electron microscopy. The doxorubicin anti-tumor drug was loaded on a selected synthesized magnetic hydrogel and in vitro drug release studies were done in phosphate buffer solution in 37 °C.     

Synthesis of core-shell gold coated magnetic nanoparticles and their interaction with thiolated DNA

Core-shell magnetic nanoparticles have received significant attention recently and are actively investigated owing to their large potential for a variety of applications. Here, the synthesis and characterization of bimetallic nanoparticles containing a magnetic core and a gold shell are discussed. The gold shell facilitates, for example, the conjugation of thiolated biological molecules to the surface of the nanoparticles. The composite nanoparticles were produced by the reduction of a gold salt on the surface of pre-formed cobalt or magnetite nanoparticles. The synthesized nanoparticles were characterized using ultraviolet-visible absorption spectroscopy, transmission electron microscopy, energy dispersion X-ray spectroscopy, X-ray diffraction and super-conducting quantum interference device magnetometry. The spectrographic data revealed the simultaneous presence of cobalt and gold in 5.6±0.8 nm alloy nanoparticles, and demonstrated the presence of distinct magnetite and gold phases in 9.2±1.3 nm core-shell magnetic nanoparticles. The cobalt-gold nanoparticles were of similar size to the cobalt seed, while the magnetite-gold nanoparticles were significantly larger than the magnetic seeds, indicating that different processes are responsible for the addition of the gold shell. The effect on the magnetic properties by adding a layer of gold to the cobalt and magnetite nanoparticles was studied. The functionalization of the magnetic nanoparticles is demonstrated through the conjugation of thiolated DNA to the gold shell.     

A multiple emulsion method for loading 5‐fluorouracil into a magnetite‐loaded nanocapsule: a physicochemical investigation

The preparation of 5‐fluorouracil (5‐FU) loaded poly(lactic‐co‐glycolic acid) (PLGA) biodegradable nanocapsules containing magnetite nanoparticles was studied through the modified multiple emulsion solvent evaporation method for magnetically controlled delivery of anticancer drugs. The morphology and size distribution of the prepared magnetite/PLGA nanocapsules were investigated by transmission and scanning electron microscopy. The micrographs showed that the magnetic nanocapsules were almost spherical in shape and their mean diameter was in the nanometer range with a narrow size distribution. Fourier transform infrared and ultraviolet–visible spectroscopy confirmed incorporation of 5‐FU molecules into the PLGA matrix. The magnetite content was assessed by thermogravimetric and magnetometry analysis and the results showed a magnetite content of 35 wt% with high magnetic responsivity. Magnetometry measurements showed superparamagnetic properties of the magnetic nanocapsules with a saturation magnetization of 13.7 emu g^?1. Such biodegradable magnetic nanocapsules could be considered as an appropriate choice for drug targeting. Furthermore, the influence of some important processing parameters such as PLGA concentration, initial loading of 5‐FU and poly(vinyl alcohol) concentration on drug content, encapsulation efficiency and in vitro drug release kinetics was investigated and optimized. The drug content and encapsulation efficiency of the magnetic nanocapsules were 4–7 wt% and 60%–80%, respectively, and the nanocapsules demonstrated controlled release of 5‐FU at 37 °C in a buffer solution. All samples exhibited a burst release at the initial stage and this burst release showed its close dependence on the formulation parameters. Copyright © 2012 Society of Chemical Industry     

Preparation of magnetic ion‐exchange resins by the suspension polymerization of styrene with magnetite

Magnetic polymer microspheres composed of magnetite, styrene, and divinylbenzene were prepared by suspension polymerization to produce magnetic ion‐exchange resins (MIEXs). The magnetite was grafted with oleic acid to improve the magnetic properties of the MIEXs and to prevent the magnetite from flushing out of the MIEXs. The shape and magnetic properties of the magnetic microspheres were investigated with scanning electron microscopy and vibrating‐sample magnetometry. The average diameter of the prepared magnetic polymer microspheres was about 219 μm. The two types of MIEXs were prepared, magnetic cation‐exchange resins (MCEXs) and magnetic anion‐exchange resins (MAEXs). MCEX was prepared by sulfonation of magnetic polymer microspheres, and MAEX was made by a quaternization reaction with triethylamine of chloromethylated magnetic polymer microspheres. With diffuse‐reflectance Fourier transform infrared spectroscopy, elemental analysis, and acid–base titration, the degree of substitution and ion‐exchange capacity of the MIEXs were assessed. The efficiency of each MCEX and MAEX for the purification of contaminated water was examined with Co²⁺ and NO solutions, respectively. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2058–2067, 2003     

Fe3O4水基磁流体的制备及其分散性能研究

采用共沉淀法制备了纯Fe3O4纳米粒子,分别用高氯酸、四甲基羟胺和油酸/十二烷基苯磺酸钠为表面活性剂对其进行表面处理后分散在水中,得到了3种水基磁流体,对这3种磁流体的浓度及稳定性进行了测定。实验结果显示:酸性、碱性和中性水基磁流体中Fe3O4的浓度分别为4.8%、5.8%和8.1%,其中中性水基磁流体中粒子的分散性能最佳;经过离心后,3种水基磁流体中的粒子均产生了沉降,且酸性和碱性磁流体中的粒子比中性磁流体中的粒子沉降的多。在此基础上,对影响粒子分散稳定性的机理进行了初步探讨。     

Composite magnetic particles: 1. Deposition of magnetite by heterocoagulation method

In this paper we report synthesis and characterization of composite polymeric particles bearing magnetite inclusions and reactive β-diketone groups on the surface. Composites were prepared by two-step method in which first step requires preparation of the functionalized polystyrene core and during second step magnetite was deposited onto core particle surface. This procedure gives a possibility to obtain composite particles with core-shell morphology and both the core size and magnetite shell thickness can be varied. Highly monodisperse PS/AAEM microspheres were synthesized by surfactant-free emulsion polymerization. Change of monomer fleet-ratio gives a possibility to change effectively the final particle size of dispersions without strong changes in particle size distribution. PS/AAEM particles were characterized by light scattering techniques (DLS, SLS) and electron microscopy (SEM) with respect to their particle size and morphology of the surface layer. Magnetite was deposited in form of nano-crystals onto PS-AAEM particle surface by heterocoagulation process. It has been established that more uniform magnetite coating was obtained at lower base amounts used for synthesis of magnetite. Amount of the magnetite on the polymeric particle surface can be effectively controlled by changing the initial FeCl₂ and FeCl₃ concentrations and/or variation of the PS/AAEM core dimensions. It has been confirmed by separation centrifugation technique, that stepwise increase of the magnetite content on the particle surface decrease gradually the stability of colloidal system. Magnetization curves for composite particles indicate that deposited magnetite content is high enough to achieve considerable magnetic response to external magnetic field.     

Polypropylene-based ferromagnetic composites

Microcomposites of polypropylene (PP) and magnetite (Fe₃O₄) in different concentration were prepared by one-step melt blending of magnetite powders and polypropylene. Morphology of the composites was studied by means of scanning electron microscope (SEM) to investigate magnetite dispersion within the polypropylene matrix. Thermoxidative stability and mechanical properties were investigated, showing improved thermal stability and enhanced stiffness. Magnetic properties characterization showed a ferromagnetic behavior with coercive field of 116 Oe and saturation magnetizations linearly dependent on the content of magnetic phase.     

Rupture Force of Magnetite Chain in a Uniform Magnetic Field

The rupture forces of breaking down a magnetite chain in a uniform magnetic field were measured by using a water flow under microscope observation with a video camera. The experimental results have shown that there was a linear relationship between the rupture force and the field intensity, which was expressed by F_M = kH. The value of the slope (k) was dependent on the magnetite particle size in the chain. It was found that the rupture force was very weak in a low-intensity magnetic field, around 0.01-0.1 mN, indicating that the chains must be kept in a very weak turbulence of suspension.     

α‐Amylase immobilized by Fe3O4/poly(styrene‐co‐maleic anhydride) magnetic composite microspheres: Preparation and characterization

Fe₃O₄/poly(styrene‐co‐maleic anhydride) core–shell composite microspheres, suitable for binding enzymes, were prepared using magnetite particles as seeds by copolymerization of styrene and maleic anhydride. The magnetite particles were encapsulated by polyethylene glycol, which improved the affinity between the magnetite particles and the monomers, thus showing that the size of the microspheres, the amount of the surface anhydrides, and the magnetite content in the composite are highly dependent on magnetite particles, comonomer ratio, and dispersion medium used in the polymerization. The composite microspheres, having 0.08–0.8 μm diameter and containing 100–800 μg magnetite/g microspheres and 0–18 mmol surface‐anhydride groups/g microsphere, were obtained. Free α‐amylase was immobilized on the microspheres containing reactive surface‐anhydride groups by covalent binding. The effects of immobilization on the properties of the immobilized α‐amylase [magnetic immobilized enzyme (MIE)] were studied. The activity of MIE and protein binding capacity reached 113,800 U and 544.3 mg/g dry microspheres, respectively. The activity recovery was 47.2%. The MIE had higher optimum temperature and pH compared with those of free α‐amylase and showed excellent thermal, storage, pH, and operational stability. Furthermore, it can be easily separated in a magnetic field and reused repeatedly. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 328–335, 2005