Polystyrene/Fe3O4 composite latex via miniemulsion polymerization‐nucleation mechanism and morphology

In this research, oil‐based Fe₃O₄ nanoparticles were prepared by means of coprecipitation method followed by a surface modification using lauric acid. Oil‐based Fe₃O₄ could disperse in styrene, and polystyrene/Fe₃O₄ (PS/Fe₃O₄) composite particles were prepared via miniemulsion polymerization in the presence of potassium peroxide (KPS) as an initiator, sodium dodecyl sulphate as a surfactant, hexadecane or sorbitan monolaurate(Span 20) as a costabilizer. The effects of Fe₃O₄ content, homogenization energy, amount of initiator, amount of surfactant and costabilizer on the conversion, size distributions of droplets and latex particles, nucleation mechanism and morphology of composite latex particles were investigated. The results showed that different nucleation mechanisms dominated during the course of reaction when polymerization conditions changed. The most important two key factors to influence the nucleation mechanism were homogenization energy and initiator. High homogenization energy provided critically stabilized size of droplets. Otherwise, secondary nucleation, including micellar and/or homogeneous nucleation, would take place rather than droplet nucleation when a water‐soluble initiator, KPS, was used. It resulted in two populations of latex particles, pure PS particles in smaller size and PS/Fe₃O₄ composite particles in larger size. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1014–1024, 2008     

Preparation of magnetic polystyrene latex via the miniemulsion polymerization technique

Magnetic iron oxide (magnetite, Fe₃O₄) nanoparticles were encapsulated with polystyrene to give a stable water‐based magnetic polymer latex, using the miniemulsion polymerization technique. The resulting magnetic latexes were characterized with transmission electron microscopy (TEM), dynamic light scattering (DLS), vibrating sample magnetometer measurements (VSM), and ⁵⁷Fe Mössbauer spectroscopy measurements. TEM revealed that all magnetite nanoparticles were embedded in the polymer spheres, leaving no empty polystyrene particles. The distribution of magnetite particles within the polystyrene spheres was inhomogeneous, showing an uneven polar appearance. The DLS measurements indicated a bimodal size distribution for the particles in the latexes. According to our magnetometry and Mössbauer spectroscopy data, the encapsulated magnetite particles conserve their superparamagnetic feature when they are separated in the polymer matrix. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4802–4808, 2004     

Preparation and clinical application of immunomagnetic latex

Magnetic poly(methyl methacrylate) (PMMA)/poly(methyl methacrylate‐co‐methacrylic acid) [P(MMA–MAA)] composite polymer latices were synthesized by two‐stage soapless emulsion polymerization in the presence of magnetite (Fe₃O₄) ferrofluids. Different types and concentrations of fatty acids were reacted with the Fe₃O₄ particles, which were prepared by the coprecipitation of Fe(II) and Fe(III) salts to obtain stable Fe₃O₄ ferrofluids. The Fe₃O₄/polymer particles were monodisperse, and the composite polymer particle size was approximately 100 nm. The morphology of the magnetic composite polymer latex particles was a core–shell structure. The core was PMMA encapsulating Fe₃O₄ particles, and the shell was the P(MMA–MAA) copolymer. The carboxylic acid functional groups (COOH) of methacrylic acid (MAA) were mostly distributed on the surface of the composite polymer latex particles. Antibodies (anti‐human immunoglobulin G) were then chemically bound with COOH groups onto the surface of the magnetic core–shell composite latices through the medium of carbodiimide to form the antibody‐coated magnetic latices (magnetic immunolatices). The MAA shell composition of the composite latex could be adjusted to control the number of COOH groups and thus the number of antibody molecules on the magnetic composite latex particles. With a magnetic sorting device, the magnetic immunolatices derived from the magnetic PMMA/P(MMA–MAA) core–shell composite polymer latex performed well in cell‐separation experiments based on the antigen–antibody reaction. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1342–1356, 2005     

Nanocomposite particles with core-shell morphology II. An investigation into the affecting parameters on preparation of Fe3O4-poly (butyl acrylate-styrene) particles via miniemulsion polymerization

The encapsulation of inorganic particles with polymers is desirable for many applications in order to improve the stability of the encapsulated products and disperse ability in different media. Colloidal particles with magnetic properties have become increasingly important both technologically and for fundamental studies. This is due to their tunable anisotropic. In the absence of an applied magnetic field, the particles have isotropic sphere dispersion, whereas in an external magnetic field the particles form anisotropic structures. Here, latexes containing nanocomposite particles of styrene-butyl acrylate/Fe₃O₄ with core-shell structure were prepared through miniemulsion polymerization technique. Magnetic composite nanospheres with high magnetic content were synthesized through miniemulsion polymerization using a new process based on a three-steps preparation route including two miniemulsion processes: (1) preparing a dispersion of oleic acid coated magnetite particles in water; (2) mixing of modified magnetite particles with styrene/butyl acrylate in the presence of sodium dodecyl sulfate (SDS), sorbitane mono oleate (Span 80), hexadecane (HD) and (3) miniemulsification of the modified Fe₃O₄ into the monomer droplets to reach to complete encapsulation. Subsequent polymerization generated magnetic nanocomposite spheres. Hence, the copolymerization reaction was performed on the surface of such particles in order to obtain core-shell morphology for these nanoparticles, which were characterized by several techniques such as TEM, SEM, DLS, TGA, VSM and FT-IR. The magnetic copolymer particles with diameter of 120-170 nm were obtained. The effect of several parameters such as magnetite, surfactants and hydrophobe amounts on the stability, particle size and magnetization were investigated and also optimized.     

Synthesis and morphology of an iron oxide/polystyrene/poly(isopropylacrylamide‐co‐methacrylic acid) thermosensitive magnetic composite latex with potassium persulfate as the initiator

In this work, an iron oxide (Fe₃O₄)/polystyrene (PS)/poly(N‐isopropylacryl amide‐co‐methacrylic acid) [P(NIPAAM–MAA)] thermosensitive magnetic composite latex was synthesized by the method of two‐stage emulsion polymerization. The Fe₃O₄ particles were prepared by a traditional coprecipitation method and then surface‐treated with either a PAA oligomer or lauric acid to form a stable ferrofluid. The first stage for the synthesis of the thermosensitive magnetic composite latex was to synthesize PS in the presence of a ferrofluid by emulsion polymerization to form Fe₃O₄/PS composite latex particles. Following the first stage of reaction, the second stage of polymerization was carried out with N‐isopropylacryl amide and methacrylic acid as monomers and with Fe₃O₄/PS latex as seeds. The Fe₃O₄/PS/[P(NIPAAM–MAA)] thermosensitive magnetic particles were thus obtained. The effects of the ferrofluids on the reaction kinetics, morphology, and particle size of the latex were discussed. A reaction mechanism was proposed in accordance with the morphology observation of the latex particles. The thermosensitive property of the thermosensitive magnetic composite latex was also studied. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3062–3072, 2007     

Highly magnetic latexes from submicrometer oil in water ferrofluid emulsions

The synthesis of functionalized submicrometer magnetic latex particles is described as obtained from a preformed magnetic emulsion composed of organic ferrofluid droplets dispersed in water. Composite (polystyrene/γ‐Fe₂O₃) particles were prepared according to a two‐step procedure including the swelling of ferrofluid droplets with styrene and a crosslinking agent (divinyl benzene) followed by seeded emulsion polymerization with either an oil‐soluble [2,2′‐azobis(2‐isobutyronitrile)] or water‐soluble (potassium persulfate) initiator. Depending on the polymerization conditions, various particle morphologies were obtained, ranging from asymmetric structures, for which the polymer phase was separated from the inorganic magnetic phase, to regular core–shell morphologies showing a homogeneous encapsulation of the magnetic pigment by a crosslinked polymeric shell. The magnetic latexes were extensively characterized to determine their colloidal and magnetic properties. The desired core–shell structure was efficiently achieved with a given styrene/divinyl benzene ratio, potassium persulfate as the initiator, and an amphiphilic functional copolymer as the ferrofluid droplet stabilizer. Under these conditions, ferrofluid droplets were successfully turned into superparamagnetic polystyrene latex particles, about 200 nm in size, containing a large amount of iron oxide (60 wt %) and bearing carboxylic surface charges. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2642–2656, 2006     

Preparation of sulfate- and carboxyl-functionalized magnetite/polystyrene spheres for further deposition of gold nanoparticles

A synthetic method developed for preparation of sulfate- and carboxyl-functionalized magnetite/polystyrene (Fe₃O₄/PS) spheres that can be further decorated with gold (Au) nanoparticles is reported. By using emulsifier-free emulsion polymerization based on potassium persulfate (KPS)/methyl acrylic acid (MAA)/water system in the presence of Fe₃O₄/PS spheres used as the seeds, PMAA-coated magnetic Fe₃O₄-PS spheres were readily obtained. The sulfate group is inherent in KPS for initiating the polymerization of PMAA, and eventually it acts as the reducing agent for the deposition of Au nanoparticles. The carboxyl group, on the other hand, could seemingly contribute to immobilize Au nanoparticles precipitated. The morphologies, magnetic properties, and characteristics of oleate-stabilized Fe₃O₄ nanoparticles, Fe₃O₄/PS spheres, PMAA-coated Fe₃O₄/PS spheres, and Au-decorated resultant spheres were respectively studied using transmission electron microscopy, X-ray diffraction, Fourier transform infrared, and superconducting quantum interference device magnetometer.     

Synthesis and morphology of Fe3O4/polystyrene/poly(isopropylacrylamide‐co‐methyl acrylate acid) magnetic composite latex – 2,2′‐azobis (2‐methylpropionamidine) dihydrochloride as initiator

In this work, Fe₃O₄/polystyrene/poly(N‐isopropylacryl amide‐co‐methylacrylate acid) (Fe₃O₄/PS/P(NIPAAM‐co‐MAA)) magnetic composite latex was synthesized by the method of two stage emulsion polymerization. In this reaction system, 2,2′‐azobis(2‐methyl propionamidine) dihydrochloride (AIBA) was used as initiator to initiate the first stage reaction and second stage reaction. The Fe₃O₄ particles were prepared by a traditional coprecipitation method. Fe₃O₄ particles were surface treated by either PAA oligomer or lauric acid to form the stable ferrofluid. The first stage for the synthesis of magnetic composite latex was to synthesize PS in the presence of ferrofluid by soapless emulsion polymerization to form the Fe₃O₄/PS composite latex particles. Following the first stage of reaction, the second stage of polymerization was carried out by the method of soapless emulsion polymerization with NIPAAM and MAA as monomers and Fe₃O₄/PS latex as seeds. The magnetic composite particles, Fe₃O₄/PS/P(NIPAAM‐co‐MAA), were thus obtained. The mechanism of the first stage reaction and second stage reaction were investigated. Moreover, the effects of PAA and lauric acid on the reaction kinetics, morphology, and particle size distribution were studied. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3912–3921, 2007     

Magnetic poly(N‐propargylacrylamide) microspheres: Preparation by precipitation polymerization and use in model click reactions

Magnetic poly(N‐propargylacrylamide) (PPRAAm) microspheres were prepared by the precipitation polymerization of N‐propargylacrylamide (PRAAm) in a toluene/propan‐2‐ol medium in the presence of magnetic nanoparticles (oleic acid‐coated Fe₃O₄). The effects of several polymerization parameters, including the polarity of the medium, polymerization temperature, the concentration of monomer, and the amount of magnetite (Fe₃O₄) in the polymerization feed, were examined. The microspheres were characterized in terms of their morphology, size, particle‐size distribution, and iron content using transmission and scanning electron microscopies (TEM and SEM) and atomic absorption spectroscopy (AAS). A medium polarity was identified in which magnetic particles with a narrow size distribution were formed. As expected, oleic acid‐coated Fe₃O₄ nanoparticles contributed to the stabilization of the polymerized magnetic microspheres. Alkyne groups in magnetic PPRAAm microspheres were detected by infrared spectroscopy. Magnetic PPRAAm microspheres were successfully used as the anchor to enable a “click” reaction with an azido‐end‐functionalized model peptide (radiolabeled azidopentanoyl‐GGGRGDSGGGY(¹²⁵I)‐NH₂) and 4‐azidophenylalanine using a Cu(I)‐catalyzed 1,3‐dipolar azide‐alkyne cycloaddition reaction in water. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.     

A facile route to hollow superparamagnetic magnetite/polystyrene nanocomposite microspheres via inverse miniemulsion polymerization

In this article, we report a facile route to the preparation of hollow superparamagnetic magnetite/polystyrene nanocomposite microspheres via inverse miniemulsion polymerization at room temperature and under ambient pressure. Water droplets act as a soft template for the formation of hollow structure. Meanwhile, the existence of amphipathic magnetite nanoparticles (MPs) which can assemble at the interface of W/O is favorable to the interfacial polymerization of styrene, ensuring the formation of hollow nanocomposite microspheres. The final products were thoroughly characterized by X‐ray powder diffraction (XRD), fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), field‐emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), and X‐ray photoelectron spectroscopy (XPS), which showed the formation of hollow magnetite/polystyrene nanocomposite microspheres. Magnetic hysteresis loop measurements revealed that both MPs and hollow nanocomposite microspheres displayed superparamagnetism. The effects of the content of H₂O, sorbitan monooleate (Span 80) and styrene and the dose rate on the morphology of nanocomposite microspheres were studied. Furthermore, the mechanism of the formation of the hollow magnetic microspheres was also discussed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3900–3910, 2008     

Synthesis of large,high‐solid‐content latexes by miniemulsion polymerization

Multiple and diverse applications have been recently found for miniemulsions and miniemulsion polymerization. In this work, miniemulsion polymerization is presented as a suitable technique for the preparation of high‐solid‐content latices with large particle sizes. Monomer miniemulsions were prepared with a high‐pressure homogenizer, and droplet sizes of 200–700 nm were obtained. Latexes with particle sizes larger than the sizes commonly accepted for miniemulsion polymerization were obtained. With fixed operational conditions of the homogenizer, the type of stabilizer was the key parameter determining the droplet size and the droplet size distribution. The particle size of the latices obtained by miniemulsion polymerization indicated that the particles were mainly formed by droplet nucleation. Latexes obtained by this process have multiple applications, including use as seeds in the polymerization of high‐solid‐content latices. This article shows that potential new applications for miniemulsion polymerization are far from being exhausted. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4222–4227, 2004     

Synthesis and characterization of micron‐sized monodisperse superparamagnetic polymer particles with amino groups

Micron‐sized monodisperse superparamagnetic polyglycidyl methacrylate (PGMA) particles with functional amino groups were prepared by a process involving: (1) preparation of parent monodisperse PGMA particles by the dispersion polymerization method, (2) chemical modification of the PGMA particles with ethylenediamine (EDA) to yield amino groups, and (3) impregnation of iron ions (Fe²⁺ and Fe³⁺) inside the particles and subsequently precipitating them with ammonium hydroxide to form magnetite (Fe₃O₄) nanoparticles within the polymer particles. The resultant magnetic PGMA particles with amino groups were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X‐ray diffractometry (XRD), and vibrating sample magnetometry (VSM). SEM showed that the magnetic particles had an average size of 2.6 μm and were highly monodisperse. TEM demonstrated that the magnetite nanoparticles distributed evenly within the polymer particles. The existence of amino groups in the magnetic polymer particles was confirmed by FTIR. XRD indicated that the magnetic nanoparticles within the polymer were pure Fe₃O₄ with a spinel structure. VSM results showed that the magnetic polymer particles were superparamagnetic, and saturation magnetization was found to be 16.3 emu/g. The Fe₃O₄ content of the magnetic particles was 24.3% based on total weight. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3433–3439, 2005     

Impact of initiators in preparing magnetic polymer particles by miniemulsion polymerization

Sub-micron sized polystyrene particles containing magnetite more than 30 wt.% were prepared by miniemulsion polymerization with commercially available ferricolloid. The effects of some water-soluble initiators and/or oil-soluble initiators on the particles characteristics, such as the size, morphology, magnetic properties and colloidal stability, were studied. The size of monomer droplets/polymer particles increased from 60 to 300 nm during polymerization, keeping magnetic in core when potassium persulfate (KPS) or ammonium persulfate (APS) was used as the sole initiator. These particles were easily separated from the medium within short time scale in external magnetic field, while such characteristics were controlled by the amount of persulfate used for the polymerization. In contrast, when 2,2′-azobis isobutyronitrile (AIBN) was used as the initiator, the size of droplets/particles was retained to be 90 nm at the most and magnetite nanoparticles located at the surface of polystyrene particles, which were so colloidally stable that they were not separated in external magnetic field. The above-mentioned effect of initiators on particle size in persulfate system was likely originated from the decrease of pH value and the increase of ionic strength, which induced the fusion of droplets/particles containing magnetite. Mixed-initiators system resulted in intermediate characteristics, compared with each initiator system. The location of magnetite in the particle seems to depend on where initiation/polymerization occurred in each initiator system.     

Emulsion and miniemulsion polymerizations with an oil‐soluble initiator in the presence and absence of an aqueous‐phase radical scavenger

Butyl acrylate conventional emulsion (macroemulsion) and miniemulsion polymerizations were carried out with an oil‐soluble initiator (azobisisobutyronitrile) in the presence or absence of an aqueous‐phase radical scavenger. For macroemulsion polymerization, in the presence of an aqueous‐phase radical scavenger, no particle nucleation occurred, whereas in the absence of an aqueous‐phase radical scavenger, particle nucleation proceeded as expected. For miniemulsion polymerization, the rate of polymerization was much higher in the absence of an aqueous‐phase radical scavenger than in its presence. Furthermore, in the absence of an aqueous‐phase radical scavenger, the miniemulsion polymerization rate increased with reduced droplet size, whereas in the presence of an aqueous‐phase radical scavenger, the trend was reversed. It is concluded that (1) for macroemulsion polymerization, the contribution from free radicals originating in the aqueous‐phase is predominant in the micellar nucleation of particles; (2) free radicals originating in the particle phase contribute to the rate of polymerization and the contribution increases with an increase in the particle size; and (3) for polymer particles with diameters of up to approximately 100 nm, polymerization is initiated from free radicals originating in the aqueous phase. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3200–3211, 2002     

Preparation and characterization of magnetic polymeric composite particles by miniemulsion polymerization

A water‐based magnetite ferrofluid, with an average size of about 10 nm, was prepared in a first step by the chemical coprecipitation of ferrous and ferric salts. Oil‐based styrene (St) magnetite ferrofluid was obtained by the acidification of the water‐based magnetite ferrofluid and the dispersion of the acidified magnetite in St. Magnetic polymeric composite particles (MPCPs) were prepared by miniemulsion polymerization in the presence of the oil‐based St magnetite ferrofluid with hexadecane as a hydrophobe, 2,2′‐azobisisobutyronitrile as an initiator, and sodium dodecyl sulfate as an emulsifier. Methacrylic acid was used as a comonomer, and hydroxyethyl cellulose and polyvinylpyrrolidone were used as aid stabilizers subsequently. With the aim of improving the encapsulation degree of magnetite, avoiding pure polymer particles and exposed magnetite particles, and obtaining the narrowest particle size distributions, the encapsulation conditions of magnetite were investigated in detail. The results show that miniemulsion polymerization is an effective method for encapsulating magnetite into a hydrophobic polymer successfully. Exposed magnetite particles and pure polymer particles can be avoided completely by the selection of the appropriate preparation conditions. All the resulting MPCPs exhibited superparamagnetism and possessed some magnetic response. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4187–4203, 2006     

Preparation of monodispersed polystyrene microspheres uniformly coated by magnetite via heterogeneous polymerization

Composite microspheres of core-shell type were prepared by a seeded polymerization using monodispersed polystyrene seed latex (Ps) combined with an in situ dispersion of magnetite (Fe₃O₄) fine particles. The heterogeneous polymerization was carried out in aqueous dispersions of the Fe₃O₄ particles modified with sodium oleate. All the synthetic processes were carried out in a wet state to avoid serious agglomeration. The morphology of the composite particle and the size distribution were examined to discuss the effects on the polymerization parameters, such as monomer concentration, type and concentration of an initiator, magnetite particle concentration and the method of surface modification of Fe₃O₄.     

Synthesis of raspberry‐like silica/polystyrene/silica multilayer hybrid particles via miniemulsion polymerization

Organic–inorganic hybrid particles have many potential applications, but almost all research has been focused on hybrid particles with one kind of inorganic nanoparticle. This article presents a novel and facile preparation approach for raspberry‐like silica/polystyrene/silica multilayer hybrid particles via miniemulsion polymerization. In this method, larger, surface‐modified silica particles are first dispersed into monomer droplets to form a miniemulsion, and then raspberry‐like silica/polystyrene/silica multilayer hybrid particles are directly obtained when miniemulsion polymerization is performed in the presence of smaller, unmodified silica particles with 4‐vinylpyridine as an auxiliary monomer. Influential parameters such as the amount of 4‐vinylpyridine, the surfactant concentration, and the pH value of the system have been investigated. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1028–1037, 2007     

Reversible addition–fragmentation chain transfer/miniemulsion polymerization of butyl methacrylate in the presence of β‐cyclodextrin

In the presence of β‐cyclodextrin (β‐CD), reversible addition–fragmentation chain transfer (RAFT) polymerization has been successfully applied to control the molecular weight and polydispersity [weight‐average molecular weight/number‐average molecular weight (M_w/M_n)] in the miniemulsion polymerization of butyl methacrylate, with 2‐cyanoprop‐2‐yl dithiobenzoate as a chain‐transfer agent (or RAFT agent) and 2,2′‐azoisobutyronitrile (AIBN) as an initiator. β‐CD acted as both a stabilizer and a solubilizer, assisting the transportation of the water‐insoluble, low‐molecular‐weight RAFT agent into the polymerization loca (i.e., droplets or latex particles) and thereby ensuring that the RAFT agent was homogeneous in the polymerization loca. The polymers produced in the system of β‐CD exhibited narrower polydispersity (1.2 < M_w/M_n < 1.3) than those without β‐CD. Moreover, the number‐average molecular weight in the former case could be controlled by a definite amount of the RAFT agent. Significantly, β‐CD was proved to have a favorable effect on the stability of polymer latex, and no coagulum was observed. The effects of the concentrations of the RAFT agent and AIBN on the conversion, the molecular weight and its distribution, and the particle size of latices were investigated in detail. Furthermore, the influences of the variations of the surfactant (sodium dodecyl sulfate) and costabilizer (hexadecane) on the RAFT/miniemulsion polymerization were also studied. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2931–2940, 2005     

Surface modification of iron oxide nanoparticles by a phosphate‐based macromonomer and further encapsulation into submicrometer polystyrene particles by miniemulsion polymerization

A new strategy relying on the use of a phosphate‐based macromonomer (PAM200) to modify the surface of iron oxide nanoparticles was developed for the synthesis of submicrometer polystyrene (PS) magnetic particles. First, iron oxide nanoparticles were synthesized using the coprecipitation of ferrous and ferric salts in alkaline medium. Besides the classical oleic acid (OA)/octane‐based ferrofluid, styrene‐based ferrofluids were elaborated with either OA or PAM200 as the stabilizer. In all cases, maghemite (γ‐Fe₂O₃) was clearly identified, with nanoparticles rather spherical in shape but exhibiting broad particle size distribution (PSD). Both OA and PAM200 led to stable maghemite‐based ferrofluids showing superparamagnetic properties. Further use of these ferrofluids in styrene miniemulsion polymerization resulted in inhomogeneous distribution of maghemite among and inside the polymer particles with OA‐based ferrofluids, whereas PAM200/styrene‐based ferrofluids led to magnetic particles with homogeneous distribution of maghemite inside PS particles. Broad PSD and small nonmagnetic particles were however observed. The true mechanisms operating in these systems are still to elucidate, but this study validates PAM200 as an efficient compatibilizing agent between hydrophilic maghemite and hydrophobic PS. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 327–340, 2008     

Preparation of composite particles with magnetic silica core and fluorescent polymer shell

Dual functions of magnetic and fluorescent properties were created in composite particles that incorporated magnetite (Fe₃O₄) nanoparticles in particle cores of silica and fluorescent pyrene in particle shells of polystyrene. The Fe₃O₄ nanoparticles were prepared with a conventional homogeneous precipitation method and surface modified with a coupling agent of carboxyethylsilanetriol. The silica particles incorporating Fe₃O₄ nanoparticles were synthesized with a modified Stöber method in which the Fe₃O₄ nanoparticles were added to a system of tetraethylorthosilicate (TEOS)/ammonia/water/ethanol. Then, the magnetite/silica composite particles were coated with the pyrene/polystyrene shell in a soap-free emulsion polymerization, which was conducted in the presence of pyrene in a mixed solvent of water/ethanol. The composite particles prepared in the mixed solvent had both magnetic and fluorescent properties. The fluorescent spectrum of the particles with Fe₃O₄ was very similar to that without Fe₃O₄, indicating that the magnetic component within the core particles scarcely interfered with the fluorescent emission from the polymer shell.