SYNTHESIS OF MAGNETIC BEADS FOR BIO-SEPARATION USING THE SOLUTION METHOD

A modified solution process is used to produce super-paramagnetic nanocomposite particles containing functional groups for adsorption application. The powder is produced in a spray tower. The feed is a polymer solution containing two fractions of different particles: magnetite (14 nm) and polymer ion exchanger (150 nm). The spray-magnetic beads are submitted to different characterization methods: confocal laser scanning microscopy (CLSM), small-angle X-ray scattering (SAXS), and alternating gradient magnetometry (AGM). The characterization clearly proves the super-paramagnetic properties at room temperature of the composite particles, even at a high filling degree of 30 wt.%. The evaluation of the protein binding capacity of the composite material shows excellent values, which are comparable to other ion exchange resins. Compared to the conventional methods, the solution process has a high potential in scale-up. Thus a potential application of magnetic separation technology in technical scale is possible.     

SYNTHESIS OF MAGNETIC BEADS FOR BIO-SEPARATION USING THE SOLUTION METHOD

A modified solution process is used to produce super-paramagnetic nanocomposite particles containing functional groups for adsorption application. The powder is produced in a spray tower. The feed is a polymer solution containing two fractions of different particles: magnetite (14 nm) and polymer ion exchanger (150 nm). The spray-magnetic beads are submitted to different characterization methods: confocal laser scanning microscopy (CLSM), small-angle X-ray scattering (SAXS), and alternating gradient magnetometry (AGM). The characterization clearly proves the super-paramagnetic properties at room temperature of the composite particles, even at a high filling degree of 30 wt.%. The evaluation of the protein binding capacity of the composite material shows excellent values, which are comparable to other ion exchange resins. Compared to the conventional methods, the solution process has a high potential in scale-up. Thus a potential application of magnetic separation technology in technical scale is possible.     

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     

Porous magnetic chelator support for albumin adsorption by immobilized metal affinity separation

Magnetic poly(2‐hydroxyethylmethacrylate) (mPHEMA) beads are modified by iminodiacetic acid (IDA) to implify the reactive groups and subsequent binding of Cu²⁺ ions to form metal chelate. mPHEMA beads, in the size range of 80–120 μm, were produced by a modified suspension polymerization technique. mPHEMA beads were characterized by swelling tests, electron spin resonance (ESR), FTIR, and scanning electron microscopy (SEM). Important results obtained in this study are as follows. The swelling ratio of mPHEMA beads was 34%. The presence of magnetite particles in the polymeric structure was confirmed by ESR. FTIR data confirmed that the magnetic polymer beads were modified with functional groups IDA. The mPHEMA beads have a spherical shape and porous structure. The effect of pH and concentration of human serum albumin (HSA), on the adsorption of HSA to the metal‐chelated magnetic beads, were examined in a batch reactor. Most importantly, the magnetic beads had little nonspecific adsorption for HSA (0.5 mg/g) before introducing IDA groups. Cu²⁺ chelation increased the HSA adsorption up to 28.4 mg/g. Adsorption behavior can be described at least approximately with the Langmuir equation. Regeneration of the metal‐chelated magnetic beads was easily performed with 1.0M NaSCN, pH 8.0, followed by washing with distilled water and reloading with Cu²⁺. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2501–2510, 2004     

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.     

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     

Double‐miniemulsion preparation of Fe3O4/poly(methyl methacrylate) magnetic latex

Magnetic poly(methyl methacrylate) (PMMA) microspheres were prepared by double‐miniemulsion polymerization. First, oleic acid coated magnetite particles synthesized by means of coprecipitation were dispersed into octane to obtain a ferrofluid. The ferrofluid and MMA were emulsified to form O/W emulsion, respectively. Subsequently two miniemulsions were mixed together for polymerization. The obtained magnetic polymer particles were characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy, X‐ray powder diffraction, and thermogravimetry. The results showed that oleic acid coated magnetite particles were well encapsulated in PMMA. The effects of initiator dosage and monomer concentration on the conversion of MMA were also investigated. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

A novel method to prepare magnetic polymer‐based anion exchangers and their application

Magnetic microspheres with ion‐exchange features were prepared by applying a swelling and penetration process using polystyrene–divinylbenzene‐based anion‐exchange resins as starting materials. The polymeric anion‐exchange particles were swollen with an aqueous solution of N‐methyl‐2‐pyrrolidone, followed by incubation with superparamagnetic iron oxide nanoparticles to allow them to penetrate into the swollen particles. The pH value in the solution of magnetic nanoparticles could significantly influence the uptake of magnetic nanoparticles by the swollen anion‐exchange particles. Higher amounts of magnetic nanoparticles entrapped within anion exchangers could be achieved at pH 10–12. An increase in the concentration of magnetic nanoparticles led to a higher density of magnetic nanoparticles entrapped within the interior of anion exchangers and, thus, higher magnetization of the magnetic anion exchangers. Loading of the magnetic nanoparticles onto the exchanger had no effect on anion‐exchange functionality. The utility of the resulting magnetic anion‐exchange resins was demonstrated for the isolation of plasmid pEGFP‐C1 from Escherichia coli cell lysates. The magnetic anion‐exchange microspheres could be easily collected within a few seconds in a magnetic field. Thus, automation of the protocol for DNA isolation using these magnetic anion‐exchange resins has a high potential. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40725.     

Sol–gel synthesis,physicochemical characterization,and analytical applications of copper selective composite cation exchanger: Polyvinyl alcohol Ce(IV) phosphate

An organic–inorganic composite cation exchanger polyvinyl alcohol Ce(IV) phosphate was prepared by the sol–gel method. The composite cation exchanger was characterized by some physicochemical properties like FTIR, TGA/DTA/DTG, XRD, SEM, TEM, EDX, and ion exchange properties to validate the structure and the ion exchange behavior. Ion exchange parameters indicated that the composite material is suitable for column operation. The ion exchange capacity of the composite ion exchanger is higher than that of the inorganic counterpart which showed that the incorporation of organic polymer polyvinyl alcohol (PVA) is responsible for prevention of the leaching of inorganic ion exchanger thereby proving mechanical stability and enhanced ion exchange properties. The distribution studies showed the selectivity toward Cu(II) ions, a heavy toxic metal ion. It was also observed that the selectivity depended upon the nature and composition of contacting solvents. The binary separation of a mixture of heavy metal ions Cu(II)–Zn(II), Cu(II)–Cd(II), and Cu(II)–Ni(II) also achieved thus composite cation exchanger proved excellent material could be effectively utilized in the treatment of discharge from copper plating, copper alloy, copper batteries, and smelting industries, whereas outstanding thermal stability of this composite ion exchanger could be utilized for the treatment of wastewater having Cu(II) ions with high temperature such as power generation and desalination plants. This composite ion exchanger with outstanding properties have potential to deal with aquatic toxicology caused by Cu(II) ions in future. POLYM. COMPOS., 38:332–340, 2017. © 2015 Society of Plastics Engineers     

Removal of heavy‐metal ions by magnetic beads containing triazole chelating groups

The aim of this study was to prepare magnetic beads that could be used for the removal of heavy‐metal ions from synthetic solutions. Magnetic poly(ethylene glycol dimethacrylate–1‐vinyl‐1,2,4‐triazole) [m‐poly(EGDMA–VTAZ)] beads were produced by suspension polymerization in the presence of a magnetite Fe₃O₄ nanopowder. The specific surface area of the m‐poly(EGDMA–VTAZ) beads was 74.8 m²/g with a diameter range of 150–200 μm, and the swelling ratio was 84%. The average Fe₃O₄ content of the resulting m‐poly(EGDMA–VTAZ) beads was 14.8%. The maximum binding capacities of the m‐poly(EGDMA–VTAZ) beads from aquous solution were 284.3 mg/g for Hg²⁺, 193.8 mg/g for Pb²⁺, 151.5 mg/g for Cu²⁺, 128.1 mg/g for Cd²⁺, and 99.4 mg/g for Zn²⁺. The affinity order on a mass basis was Hg²⁺ > Pb²⁺ > Cu²⁺ > Cd²⁺> Zn²⁺. The binding capacities from synthetic waste water were 178.1 mg/g for Hg²⁺, 132.4 mg/g for Pb²⁺, 83.5 mg/g for Cu²⁺, 54.1 mg/g for Cd²⁺, and 32.4 mg/g for Zn²⁺. The magnetic beads could be regenerated (up to ca. 97%) by a treatment with 0.1M HNO₃. These features make m‐poly(EGDMA–VTAZ) beads potential supports for heavy‐metal removal under a magnetic field. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation of magnetic poly(vinyl alcohol) (PVA) materials by in situ synthesis of magnetite in a PVA matrix

An easy method for manufacturing homogeneous inorganic–organic materials, especially composite fibers, was obtained by the in situ synthesis of inorganic particles within polymer matrices. In this article, nanosized magnetite particles were synthesized in situ within poly(vinyl alcohol) (PVA) solutions by precipitating Fe²⁺ ions or a mixture of Fe²⁺ and Fe³⁺ ions with NaOH solution. As a result, magnetite particles with an average diameter of 20 nm were obtained homogeneously within the solutions because of the tridimensional structure and chelating capacities of PVA. Transparent films were obtained by a casting method, and six kinds of magnetic PVA fibers were also prepared by a wet‐spinning method from the solutions containing magnetite nanoparticles. The mechanical properties and the saturation magnetization of the fibers were measured. These fibers, which contain iron ions with a maximum content of 17.63 wt %, can be successfully fabricated by the in situ synthesis and they exhibit excellent magnetization properties (i.e., the largest saturation magnetization is 13.38 emu/g). © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1239–1247, 2003     

Synthesis and characterization of magnetic porous clay heterostructure

Magnetic porous clay heterostructure (magnetic PCH) was successfully synthesized using a simple precipitation method of applying magnetite onto a PCH surface. X-ray techniques were used to confirm the presence of magnetite in the composite. The magnetite particles, as investigated by the transmission electron microscopy, were spherical nanoparticles (~12.07 nm). The magnetic PCH exhibited characteristics of mesoporous material type IV, similar to PCH. Significant enhancement of the magnetic and dielectric properties in the high frequency range was also observed.     

Magnetic polymer microspheres with azidocarbonyl groups: Synthesis,characterization and application in protein immobilization

A novel magnetic polymer microsphere with amide groups and carboxyl groups was synthesized and reported here. The azidocarbonyl groups were derived from amide groups and linked to the proteins to investigate their immobilization capacity. The morphology, size, functional groups and magnetic properties of magnetic microspheres were characterized by optical microscopy, particle size analyzer, atom force microscopy, magnetic force microscopy, fourier transform infrared spectrometer, vibrating‐sample magnetometer and thermal gravimetric analysis. The results indicated that the magnetic polymer microspheres had a well spherical shape with the size ranging from 1 to 10 μm, highly reactive functional groups, superparamagnetism and strong magnetic responsibility with saturation magnetization of 18.443 emu/g and Fe₃O₄ content around 21%. The immobilization capacity (η) was over 70%. The novel azidocarbonyl magnetic polymer microspheres showed potentials to be a good magnetic support and promising applications in bioseparation and biomedical fields. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation of halogen-free flame-retardant expandable polystyrene foam by suspension polymerization

In this research, using hexaphenoxycyclotriphosphazene (HPCTP) as the halogen-free flame retardant, we prepared flame-retardant expandable polystyrene (EPS) beads by suspension polymerization. The effects of process parameters and the amount of flame retardant on polystyrene (PS)/HPCTP composite beads were investigated. The results show that the change in HPCTP content has little effect on the particle size distribution of composite beads. When the oil–water ratio is 1/4, TCP dosage is 3 wt %, stirring rate is 350 rpm, initiator dosage is 1.25 wt %, and HPCTP dosage is 15 wt %, the size of the composite beads is uniform, and the average particle size is 1.12 mm. HPCTP formed nanodispersed particles in the PS matrix with an average particle size of 44.86 nm. In addition, the thermogravimetric behavior and heat-release properties of composite beads were evaluated. The results showed that HPCTP mainly acted in the gaseous phase, which can effectively decrease the maximum mass-loss rate of the PS/HPTCP composite beads and significantly reduce the heat-release rate and heat-release capacity. The EPS foams were obtained by a prefoaming method. The average cell diameter was 62.15 μm, and the foaming ratio was 11 times. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47779.     

Effect of Palladium on Thermal Degradation of Fiban K-1 Fibrous Sulfonic Cation Exchanger. Study by Thermal Analysis, Epr Spectroscopy, and Mass Spectrometry

Thermal degradation of palladium-containing samples of Fiban K-1 fibrous sulfonic cation exchanger in the H form fabricated by ion exchange and reduced with hydrazine hydrate was investigated by methods of DTA, x-ray phase analysis, mass spectrometry, and EPR spectroscopy. It was found that palladium in the reduced state added to the cation exchanger in relatively small amounts, 1.5-2.5 wt. %, stabilizes the hydrocarbon matrix (increases the temperature of the onset of desulfurization of the sulfonic cation exchanger and thermal degradation of the hydrocarbon matrix). With a higher content (14%), palladium significantly changes these characteristics, manifested by a decrease in the temperature of the onset of desulfurization of the ion exchanger and thermal degradation of the hydrocarbon matrix.     

Morphology and mechanical properties of Nylon 6 toughened with waste poly(vinyl butyral) film

Phase morphology and mechanical properties of the blends of Nylon 6 with scrap poly(vinyl butyral) (PVB) film and poly[styrene-block-(ethylene-co-butene)-block-styrene] (SEBS) have been investigated. Scanning electron microscopic photographs revealed that the spherical PVB particles are finely and uniformly dispersed in the Nylon 6 matrix without changing the shape of the particles. The average particle sizes in all over the blend compositions for Nylon 6/PVB were slightly increased with PVB content, but the dispersed phase is tightly adhered to the matrix phase, with PVB content in the range of 20–35 wt % PVB. Elongation at break and notched Izod impact strength of all the blends were enhanced, which implies good interfacial adhesion. The rubberlike PVB film adhering to the Nylon 6 phase is suggested to give an improved impact strength and toughness. In particular, the optimum PVB content for the best impact strength is found to be in the vicinity of 20–35 wt %, and this composition exhibits better moisture resistance than the other blend compositions. All of the blends up to 35 wt % PVB show higher mechanical properties than those of Nylon 6 blended with conventional impact modifier SEBS. Thus, plasticized PVB film, which is recycled from the process of automobile safety glasses, is applicable as an impact modifier or a toughening agent of Nylon 6. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1531–1540, 1998     

Preparation of micrometer‐sized,monodisperse, magnetic polymer particles

Micrometer‐sized, monodisperse, magnetic composite particles were prepared by heating micrometer‐sized, monodisperse, hollow polystyrene/polydivinylbenzene composite polymer particles at 200°C for 4 h (particles had been dipped in pentacarbonyliron) and then washed in 12 N HCl and water. The hollow polymer particles were produced by seeded polymerization by the dynamic swelling method that was proposed by authors. The magnetic composite particles contained Fe₃O₄, the content of which was 49% based on total weight, and were attracted easily in water by a 1650 G magnet. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 428–433, 2003     

Synthesis and Characterization of Anionic Exchange Resins with a Gradient in Polymer Composition for the PS-co-DVB/PDEAMA-co-DVB System

Summary Anionic exchange resins with a gradient in polymer composition were prepared in two stages. After P(S-co-DVB) suspension beads were obtained, N,N-diethylaminoethyl methacrylate monomer was let to diffuse into the beads at 25 °C, and immediately photopolymerized to fix the gradient polymer composition with high surface concentration of ion exchanger. Chemical composition through the radial position was estimated by means of a mathematical algorithm and using UV spectroscopy. Resin characterization included particle size distribution, “settled” density and total anion exchange capacity, following ASTM D-2187. Values were compared with a porous commercial resin (Amberlite IRA900RF Cl). Since non porous structure with high ion exchange capacity resins were obtained, useful resins for ion exchange with long term stability can be prepared with this methodology.     

Structural and magnetic behavior of zirconia-magnetic particles and zirconia-graphene composite ceramics

Incorporating magnetic materials in ceramic matrices becomes an attractive topic due to its versatility and wide range of applications. Therefore, this work aims to produce zirconia-magnetic particles and zirconia-graphene composites, investigating their structural and magnetic properties. The ceramic composites were produced by the tape casting technique and characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and magnetic measurements. The microstructural characterization showed monoclinic and tetragonal zirconia phases from the zirconia powder and the magnetite and hematite phases from the magnetic particles. Three peaks of characteristics known as band D, G, and 2D evidenced the presence of graphene. The morphology of the zirconia-magnetic particles and zirconia-graphene composites showed grains with irregular shapes and varying sizes; however, the zirconia-graphene composite showed the presence of pores and agglomerates due to the plasma heat-treatment process. The uniform dispersion of the elements in both ceramic composites confirmed the efficiency of the applied method. The magnetic characterizations of the green and sintered zirconia-magnetic particles and zirconia-graphene composites were studied in a wide range of magnetic fields and temperatures (5 to 300 K). Before sintering, the magnetite phase commanded the magnetic response of the zirconia-magnetic particles composite, showing a ferrimagnetic behavior, after sintering, the hematite phase content increased by approximately 27%, causing a change in the ferrimagnetic order to antiferromagnetic. It was found that the 1% graphene insertion in the zirconia ceramic composite was responsible for the ferromagnetic behavior of the sintered composite. Ceramic composites become future candidates for technological applications in spintronic devices and magnetic storage.