Polypyrrole‐Fe3O4 Magnetic Nanocomposite Prepared by Ultrasonic Irradiation

Summary: Ultrasonic irradiation was employed to prepare polypyrrole (PPY)/Fe₃O₄ magnetic nanocomposite by chemical oxidative polymerization of pyrrole in the presence of Fe₃O₄ nanoparticles. This approach can solve the problem in the dispersion and stabilization of inorganic nanoparticles in polymer. The structure and properties of PPY/Fe₃O₄ nanocomposite were characterized by TEM, XPS, FT‐IR, TG, and XRD. PPY deposits on the surface of Fe₃O₄ nanoparticles while Fe₃O₄ nanoparticles are dispersed at the nanoscale by ultrasonic irradiation, which leads to the formation of polypyrrole‐encapsulated Fe₃O₄ composite particles. The doping level of PPY in PPY/Fe₃O₄ nanocomposite is higher than that of neat PPY. The composites possess good electrical and magnetic properties. With the increase in the Fe₃O₄ content, the magnetization increases and the conductivity first increases and then decreases. When the Fe₃O₄ content is 40 wt.‐%, the conductivity reaches a maximum value of 11.26 S · cm^?1, about nine times higher than that of neat PPY, and the saturation magnetization is 23 emu · g^?1. Also, the introduction of Fe₃O₄ nanoparticles enhances the thermal stability of PPY/Fe₃O₄ composite.

Conductivity of PPY/Fe₃O₄ composite at different Fe₃O₄ content.     

Preparation and sedimentation behavior of conductive polymeric nanoparticles

A facile route to prepare Fe₃O₄/polypyrrole (PPY) core-shell magnetic nanoparticles was developed. Fe₃O₄ nanoparticles were first prepared by a chemical co-precipitation method, and then Fe₃O₄/PPY coreshell magnetic composite nanoparticles were prepared by in-situ polymerization of pyrrole in the presence of Fe₃O₄ nanoparticles. The obtained nanoparticles were characterized by scanning electronic microscopy (SEM), transmission electronic microscopy (TEM) and laser particle size analyzer. The images indicate that the size of Fe₃O₄ particles is about 10 nanometers, and the particles are completely covered by PPY. The Fe₃O₄/PPY core-shell magnetic composite nanoparticles are about 100 nanometers and there are several Fe₃O₄ particles in one composite nanoparticle. The yield of the composite nanoparticles was about 50%. The sedimentation behavior of Fe₃O₄/PPY core-shell magnetic nanoparticles in electrolyte and soluble polymer solutions was characterized. The experimental results indicate that the sedimentation of particles can be controlled by adjusting electrolyte concentration, solvable polymers and by applying a foreign field. This result is useful in preparing gradient materials and improving the stability of suspensions.     

Phase Transformation of Iron Oxide Nanoparticles by Varying the Molar Ratio of Fe2+:Fe3+

Co‐precipitation from a solution of ferrous/ferric mixed salt with the ratio of Fe²⁺:Fe³⁺ = 1:2 in air atmosphere is not a reliable method to synthesize magnetite (Fe₃O₄) nanoparticles because of the fact that Fe²⁺ oxidizes to Fe³⁺ and the molar ratio of Fe²⁺:Fe³⁺ changes. Therefore, the phase composition changes from magnetite to maghemite (γ‐Fe₂O₃). The influence of the initial molar ratio of Fe²⁺:Fe³⁺ on the phase composition of nanoparticles, their crystallinity and magnetic properties was studied. Experimental data from XRD, FTIR, SEM, and VSM reveal that the appropriate method to synthesize magnetite nanoparticles is reverse precipitation from only ferrous salt. It is found that by decreasing the synthesis temperature and by increasing the concentration of alkaline solution and the ratio of Fe²⁺:Fe³⁺ the crystallinity and the specific saturation magnetization (σ_s) are increased.     

Synthesis and characterization of novel core‐shell magnetic nanogels based on 2‐acrylamido‐2‐methylpropane sulfonic acid in aqueous media

Ultrafine well‐dispersed Fe₃O₄ magnetic nanoparticles were directly prepared in aqueous solution using controlled coprecipitation method. The synthesis of Fe₃O₄/poly (2‐acrylamido‐2‐methylpropane sulfonic acid) (PAMPS), Fe₃O₄/poly (acrylamide‐co‐2‐acrylamido‐2‐methylpropane sulfonic acid) poly(AM‐co‐AMPS) and Fe₃O₄/poly (acrylic acid‐co‐2‐acrylamido‐2‐methylpropane sulfonic acid) poly(AA‐co‐AMPS) ‐core/shell nanogels are reported. The nanogels were prepared via crosslinking copolymerization of 2‐acrylamido‐2‐methylpropane sulfonic acid, acrylamide and acrylic acid monomers in the presence of Fe₃O₄ nanoparticles, N,N′‐methylenebisacrylamide (MBA) as a crosslinker, N,N,N′,N′‐tetramethylethylenediamine (TEMED) and potassium peroxydisulfate (KPS) as redox initiator system. The results of FTIR and ¹H‐NMR spectra indicated that the compositions of the prepared nanogels are consistent with the designed structure. X‐ray powder diffraction (XRD) and transmission electron microscope (TEM) measurements were used to determine the size of both magnetite and stabilized polymer coated magnetite nanoparticles. The data showed that the mean particle size of synthesized magnetite (Fe₃O₄) nanoparticles was about 10 nm. The diameter of the stabilized polymer coated Fe₃O₄ nanogels ranged from 50 to 250 nm based on polymer type. TEM micrographs proved that nanogels possess the spherical morphology before and after swelling. These nanogels exhibited pH‐induced phase transition due to protonation of AMPS copolymer chains. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Efficient visible light magnetic modified iron oxide photocatalysts

Magnetite iron oxide (Fe₃O₄) nanoparticles were synthesized via simple co-precipitation method using ferrous and ferric ions salts. Fe₃O₄ nanoparticles were modified by silica and titania. Pure and modified nanoparticles were employed for dye degradation under visible light. X-ray diffraction analysis indicated inverse spinel structure of Fe₃O₄ nanoparticles. The particle size of magnetite nanoparticles is decreased due to coating of silica and titania. Scanning and transmission electron microscopy indicated the spherical morphology for all samples. The synthesized Fe₃O₄ nanoparticles were ferromagnetic in nature with highest saturation magnetization value of 1.1034 emu as compared to silica and titania coated samples. Fourier transform infra-red spectra confirmed the incorporation of magnetite nanoparticles with silica and titania. Titania modified magnetite sample showed the highest photocatalytic activity as compared to silica modified magnetite nanoparticles and bare iron oxide under visible light irradiations.     

Magnetic and optical properties of poly(vinylidene difluoride)/Fe3O4 nanocomposite prepared by coprecipitation approach

Poly(vinylidene difluoride) (PVDF)/Fe₃O₄ magnetic nanocomposite was prepared by a simple coprecipitation method, and was characterized by scanning electron microscope (SEM), X‐ray diffraction (XRD), vibrating sample magnetometer (VSM), and ultraviolet visible spectroscopy (UV‐Vis). The SEM images showed that Fe₃O₄ nanoparticles were dispersed in the PVDF matrix as some aggregates with the sizes of 50 nm–2 μm, and the XRD curves showed the incorporation of the Fe₃O₄ nanoparticles in PVDF matrices and the decrease of the crystallinity of the PVDF. VSM results showed that the saturation magnetization (M_s) and remnant magnetization (M_r) of the PVDF/Fe₃O₄ nanocomposite increased with the increase of the Fe₃O₄ content, and that M_s and M_r along the parallel direction were higher than those along the perpendicular direction at the same Fe₃O₄ content. The coercive force (H_c) of the nanocomposite was independent of the Fe₃O₄ content and approximately equal along the parallel and perpendicular direction at the same Fe₃O₄ content. The optical band gap (E_g) of the PVDF/Fe₃O₄ nanocomposite was influenced by the Fe₃O₄ content, and decreased by 0.75 eV compared with that of pure PVDF when the Fe₃O₄ content was 3 wt %. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation of chitosan‐coated magnetite nanoparticles and application for immobilization of laccase

In this study, immobilization of laccase (L) enzyme on magnetite (Fe₃O₄) nanoparticles was achieved, so that the immobilized enzyme could be used repeatedly. For this purpose, Fe₃O₄ nanoparticles were coated and functionalized with chitosan (CS) and laccase from Trametes versicolor was immobilized onto chitosan‐coated magnetic nanoparticles (Fe₃O₄‐CS) by adsorption or covalent binding after activating the hydroxyl groups of chitosan with carbodiimide (EDAC) or cyanuric chloride (CC). For chitosan‐coated magnetic nanoparticles, the thickness of CS layer was estimated as 1.0–4.8 nm by TEM, isoelectric point was detected as 6.86 by zeta (ζ)‐potential measurements, and the saturation magnetization was determined as 25.2 emu g^?1 by VSM, indicating that these nanoparticles were almost superparamagnetic. For free laccase and immobilized laccase systems, the optimum pH, temperature, and kinetic parameters were investigated; and the change of the activity against repeated use of the immobilized systems were examined. The results indicated that all immobilized systems retained more than 71% of their initial activity at the end of 30 batch uses. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

One-Pot Green Synthesis and Bioapplication of<Emphasis Type="SmallCaps">l</Emphasis>-Arginine-Capped Superparamagnetic Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> Nanoparticles

Water-soluble l-arginine-capped Fe₃O₄ nanoparticles were synthesized using a one-pot and green method. Nontoxic, renewable and inexpensive reagents including FeCl₃, l-arginine, glycerol and water were chosen as raw materials. Fe₃O₄ nanoparticles show different dispersive states in acidic and alkaline solutions for the two distinct forms of surface binding l-arginine. Powder X-ray diffraction and X-ray photoelectron spectroscopy were used to identify the structure of Fe₃O₄ nanocrystals. The products behave like superparamagnetism at room temperature with saturation magnetization of 49.9 emu g⁻¹ and negligible remanence or coercivity. In the presence of 1-ethyl-3-(dimethylaminopropyl) carbodiimide hydrochloride, the anti-chloramphenicol monoclonal antibodies were connected to the l-arginine-capped magnetite nanoparticles. The as-prepared conjugates could be used in immunomagnetic assay.     

Application of magnetite modified with aluminum/silica to adsorb phosphate in aqueous solution

BACKGROUND: Phosphate is one of the main contaminants responsible for the eutrophication of surface waters, and adsorption is a potential treatment method for this pollutant. A magnetic adsorbent manufactured from magnetite (Fe₃O₄) can be recovered easily from treated water by magnetic force, without requiring further downstream treatment. In this research, the surface of magnetite modified with aluminum and silica (Al/SiO₂/Fe₃O₄) was used to adsorb phosphate in an aqueous solution in a batch system. RESULTS: The optimum solution pH for phosphate adsorption by Al/SiO₂/Fe₃O₄ was found to be 4.5. The phosphate adsorption behavior of Al/SiO₂/Fe₃O₄ was in good agreement with both the Langmuir and Freundlich adsorption isotherm, and the maximum adsorption capacity (q_m) and Gibbs free energy of phosphate was 25.64 mg g^?1 and ? 21.47 kJ mol^?1, respectively. A pseudo‐second‐order model could best describe the adsorption kinetics, and the derived activation energy was 3.52 kJ mol^?1. The optimum condition to desorb phosphate from Al/SiO₂/Fe₃O₄ is provided by a solution with 0.05 mol L^?1 NaOH. CONCLUSIONS: Magnetic adsorbent is a potential material for a water treatment method. The results of this study will be helpful in the development of aluminum modified silica magnetic adsorbents that can be used to remove phosphate in aqueous solution. Copyright © 2011 Society of Chemical Industry     

Oxidation-precipitation of magnetic Fe3O4/AC nanocomposite as a heterogeneous catalyst for electro-Fenton treatment

Abstract

The oxidation-precipitation method was used for the synthesis of Fe₃O₄/AC. The characterization of the catalyst was accomplished by XRD, FT-IR, FE-SEM, BET, and VSM techniques. The obtained results indicated that magnetite nanoparticles were successfully prepared with cubic spinel structures and uniform distribution on the surface of activated carbon by the oxidation-precipitation method. The effect of operating parameters was evaluated to determine the optimum operating condition for the electro-Fenton (EF) removal of catechol as a phenolic pollutant model. At the optimum operating conditions (pH 3, Fe₃O₄/AC: 0.9?g L^?1, Catechol: 8.0?×?10^?4?mol L^?1 at I: 120?mA), the catechol and COD removal reached 98.2 and 76.1% in 120?min, respectively. Only 2.1% of ferrous and 3.44% of ferric ions were leached into the solution. Regarding the results from utilization of oxidant scavengers (isopropanol and BQ), it can be inferred that hydroxyl radical (responsible for 57% catechol removal) and superoxide anion radical (responsible for 40% catechol removal) is the main oxidants in acidic (pH 3) and basic (pH 10) conditions, respectively. The kinetics of EF removal of catechol was studied and the rate constant for the pseudo-first-order kinetic model was found to be 3.37?×?10^?2min^?1 (R² = 0.9924). The GC-MS analysis was carried out to detect the intermediate products and a possible degradation mechanism was proposed. The reusability of Fe₃O₄/AC was examined for six cycles. It can be concluded that Fe₃O₄/AC is an applicable ultimate catalyst for EF removal of organic pollutants.     

Fabrication of PMMA/PANI/Fe3O4 as a Novel Conducting Hybrid Coating

In this paper, an excellent new hybrid coating including poly(methyl methacrylate) (PMMA), polyaniline (PANI), and magnetite nanoparticles (Fe₃O₄) was obtained. Fe₃O₄ nanoparticles were synthesized using coprecipitation method, and then magnetite nanoparticles have been dispersed into the PANI to increase compatibility with PMMA. Also, PANI/Fe₃O₄ nanocomposites were synthesized through in situ emulsion polymerization, and then PMMA/PANI/Fe₃O₄ hybrid coating was successfully synthesized using batch emulsion polymerization method. Structure, morphology and thermal stability of the samples were characterized using Fourier transform infrared, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and thermal gravimetric analysis (TGA). The synthesized samples were well distributed with an average diameter smaller than 20?nm. Microscopy and X-ray photoelectron spectroscopy results illustrated a great dispersion of magnetite nanoparticles in hybrid matrix. Moreover, the TGA results demonstrated that the PMMA/PANI/Fe₃O₄ hybrid coating nanoparticle is an excellent hybrid coating with high thermal resistance.     

Gold deposition on Fe3O4/(co)Poly(N‐octadecyl methacrylate) hybrid particles to obtain nanocomposites With ternary intrinsic features

Here, nanocomposite particles with three domains including magnetite nanoparticles, poly(N‐octadecyl methacrylate) (PODMA) or poly(N‐octadecyl methacrylate‐co‐1‐vinylimidazole) (P(ODMA‐co‐VIMZ)), and gold nanoparticles were prepared. Fe₃O₄ nanoparticles with narrow particle size distribution were prepared through a synthetic route in an organic phase in order to achieve good control of the size and size distribution and prevent their aggregation during their preparation. These magnetite nanoparticles, ～ 5 nm in size, were then encapsulated and well‐dispersed in PODMA and P(ODMA‐co‐VIMZ) matrices via a miniemulsion polymerization process to obtain the corresponding nanocomposite particles. The results revealed that Fe₃O₄ nanoparticles were encapsulated and did not migrate towards the monomer/water interface during polymerization. The resulting latex was used as a precursor for the adsorption of Au³⁺ ions on the surface of the polymeric particles and subsequent reduction to produce Fe₃O₄/P(ODMA‐co‐VIMZ)/Au nanocomposite particles. The morphology of the particles from each step was fully characterized by TEM and AFM, and the results of DLS analysis showed their size and size distribution. Measurement of magnetic properties illustrated the superparamagnetic characteristic of the products and it was observed that the encapsulation process and deposition of gold had no effect on the magnetic properties of the resulting particles. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Novel electrically conductive and ferromagnetic composites of poly(aniline‐co‐aminonaphthalenesulfonic acid) with iron oxide nanoparticles: Synthesis and characterization

Nanocomposites of iron oxide (Fe₃O₄) with a sulfonated polyaniline, poly(aniline‐co‐aminonaphthalenesulfonic acid) [SPAN(ANSA)], were synthesized through chemical oxidative copolymerization of aniline and 5‐amino‐2‐naphthalenesulfonic acid/1‐amino‐5‐naphthalenesulfonic acid in the presence of Fe₃O₄ nanoparticles. The nanocomposites [Fe₃O₄/SPAN(ANSA)‐NCs] were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X‐ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, elemental analysis, UV–visible spectroscopy, thermogravimetric analysis (TGA), superconductor quantum interference device (SQUID), and electrical conductivity measurements. The TEM images reveal that nanocrystalline Fe₃O₄ particles were homogeneously incorporated within the polymer matrix with the sizes in the range of 10–15 nm. XRD pattern reveals that pure Fe₃O₄ particles are having spinel structure, and nanocomposites are more crystalline in comparison to pristine polymers. Differential thermogravimetric (DTG) curves obtained through TGA informs that polymer chains in the composites have better thermal stability than that of the pristine copolymers. FTIR spectra provide information on the structure of the composites. The conductivity of the nanocomposites (～ 0.5 S cm^?1) is higher than that of pristine PANI (～ 10^?3 S cm^?1). The charge transport behavior of the composites is explained through temperature difference of conductivity. The temperature dependence of conductivity fits with the quasi‐1D variable range hopping (quasi‐1D VRH) model. SQUID analysis reveals that the composites show ferromagnetic behavior at room temperature. The maximum saturation magnetization of the composite is 9.7 emu g^?1. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Immobilization of serum albumin on the synthesized three layers core–shell structures of super-paramagnetic iron oxide nanoparticles

In this study, the synthesis of four layer structures coated on magnetite nanoparticles such that Fe₃O₄/SiO₂/APTES/PEG/BSA was investigated. Magnetite nanoparticles were synthesized by co-precipitating Fe²⁺ and Fe³⁺ in an ammonia solution with the average size of 25 nm. To fabricate Fe₃O₄/SiO₂ core–shells, the magnetite nanoparticles coated by silica with Stöber method. The fabricated nanoparticles were treated by 3-aminopropyl-triethoxysilane to achieve Fe₃O₄/SiO₂/APTES nanostructures. Moreover, the nanoparticles were also attached to reactive polyethylene glycol chains. Eventually, the nanoparticles activated with bovine serum albumin for bio-application. X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, UV–vis spectroscopy and vibrating sample magnetometer were used to support the characterization.     

Synthesis and characterization of Sr2+ and Gd3+ doped magnetite nanoparticles for magnetic hyperthermia and drug delivery application

Commendable efforts have been gingered towards the fight against cancer. Nevertheless, it remains a major public health concern due to its predominant cause of death globally. Given this, we synthesized two different nanoparticles, Sr²⁺ and Gd³⁺ doped magnetite for magnetic hyperthermia and drug delivery application. Based on the characterization, the diffractogram shows that only one phase related to magnetite with a crystallite size of 10 nm was formed. TEM images revealed nanoparticles of spherical shapes of approximately 12 nm. There is no difference in magnetic saturation of the as-received synthesized samples (Fe₃O₄@Sr and Fe₃O₄@Gd), while the BET-specific surface area of Fe₃O₄@Gd is 8 m² g⁻¹ higher than Fe₃O₄@Sr. The heat generation in alternating magnetic field (the magnetic hyperthermia) of Fe₃O₄@Sr functionalized with citric acid and loaded with 5- fluorouracil (Fe₃O₄@Sr@CA@5-flu) is slower than Fe₃O₄@Gd@CA@5-flu. The specific absorption rate (SAR) of Fe₃O₄@Gd@CA@5-flu, 112.0 ± 10.4 W g⁻¹ was found to be higher than that of Fe₃O₄@Sr@CA@5-flu. The thermogram shows that 11% of the drug was successfully loaded on Fe₃O₄@Gd@CA@5-flu. The release of the antitumor drug by the synthesized nanoparticle drug carriers for ovarian cancer (SKOV-3 cells) therapy showed that more than 50% of the cancer cell’s viability was reduced after 72 h of incubation. The synthesized nanoparticles demonstrated a promising drug carrier for the treatment of SKOV-3 cells.     

Synthesis and characterization of (Fe3O4/MWCNTs)/ epoxy nanocomposites

A sonochemical technique is used for in situ coating of iron oxide (Fe₃O₄) nanoparticles on outer surface of MWCNTs. These Fe₃O₄/MWCNTs were characterized using a high‐resolution transmission electron microscope (HRTEM), X‐ray diffraction, and thermogravimetric analysis. The as‐prepared Fe₃O₄/MWCNTs composite nanoparticles were further used as reinforcing fillers in epoxy‐based resin (Epon‐828). The nanocomposites of epoxy were prepared by infusion of (0.5 and 1.0 wt %) pristine MWCNTs and Fe₃O₄/MWCNTs composite nanoparticles. For comparison purposes, the neat epoxy resin was also prepared in the same procedure as the nanocomposites, only without nanoparticles. The thermal, mechanical, and morphological tests were carried out for neat and nanocomposites. The compression test results show that the highest improvements in compressive modulus (38%) and strength (8%) were observed for 0.5 wt % loading of Fe₃O₄/MWCNTs. HRTEM results show the uniform dispersion of Fe₃O₄/MWCNTs nanoparticles in epoxy when compared with the dispersion of MWCNTs. These Fe₃O₄/MWCNTs nanoparticles‐infused epoxy nanocomposite shows an increase in glass transition (T_g) temperature. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synergistic effect in structural and supercapacitor performance of well dispersed CoFe2O4/Co3O4 nano-hetrostructures

Herein, we report a facile homogeneous urea – assisted hydrothermal approach for the design of CoFe₂O₄/Co₃O₄ nano hetrostructure. A variation in Co concentration leads to smartly designed composite material namely CFC-11 and CFC-12 where CFC-12 appreciates the benefits of both CoFe₂O₄ and Co₃O₄ nanoparticles. The physico – chemical properties of as developed materials were investigated by X-ray diffraction (XRD), field emission electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM), X-ray photoelectron microscopy (XPS) and Raman spectroscopy. The specific surface area and pore size distribution was determined by Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halendo (BJH) respectively. Magnetic measurements via. vibrating sample magnetometer (VSM) demonstrate that saturation magnetization decreases with the incorporation of Co₃O₄ antiferromagnetic nanoparticles. To explore the utility of as designed nano-hetrostructures as supercapacitor electrodes, we employed cyclic voltammetry (CV) and electrochemical impedence spectroscopy (EIS) measurements. A high specific capacitance of 761.1?F?g^?1 at 10?mV?s^?1, admirable cyclic durability of 92.2% and a low resistance value obtained from impedence measurements was observed for CFC-12. The favorable performance demonstrates the synergistic effect of CoFe₂O₄ and Co₃O₄ nanoparticles and thus promise an excellent material for energy storage devices.     

Biodegradable magnetic‐sensitive shape memory poly(ɛ‐caprolactone)/Fe3O4 nanocomposites

A novel biodegradable magnetic‐sensitive shape memory poly(?‐caprolactone) nanocomposites, which were crosslinked with functionalized Fe₃O₄ magnetic nanoparticles (MNPs), were synthesized via in situ polymerization method. Fe₃O₄ MNPs pretreated with γ‐(methacryloyloxy) propyl trimethoxy silane (KH570) were used as crosslinking agents. Because of the crosslinking of functionalized Fe₃O₄ MNPs with poly(?‐caprolactone) prepolymer, the properties of the nanocomposites with different content of functionalized Fe₃O₄ MNPs, especially the mechanical properties, were significantly improved. The nanocomposites also showed excellent shape memory properties in both 60 °C hot water and alternating magnetic field (f = 60, 90 kHz, H = 38.7, 59.8 kA m^?1). In hot water bath, all the samples had shape recovery rate (R_r) higher than 98% and shape fixed rate (R_f) nearly 100%. In alternating magnetic field, the R_r of composites was over 85% with the highest at 95.3%. In addition, the nanocomposites also have good biodegradability. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45652.     

Shape‐memory polymer networks with Fe3O4 nanoparticles for remote activation

Shape‐memory polymers (SMPs) have recently shown the capacity to actuate by remote heating via the incorporation of magnetic nanoparticles into the polymer matrix and exposure to an alternating magnetic field. In this study, methacrylate‐based thermoset SMP networks were synthesized through free‐radical polymerization with varying amounts of Fe₃O₄ magnetite (0, 1, and 2.5 wt %). Furthermore, the chemistry of the networks was controlled to maintain a constant glass transition temperature (T_g) while varying the degree of chemical crosslinking. Remote heating of the networks was shown to be a direct function of the nanoparticle concentration and independent of the chemistry. Magnetite reinforcement was shown to influence the thermomechanical properties of the networks; increasing Fe₃O₄ concentrations led to decreases in T_g and rubbery modulus. However, networks with a higher degree of crosslinking were more resistant to thermomechanical changes with respect to magnetite concentration. Strain to failure was shown to decrease with the addition of nanoparticles and the free‐strain shape‐memory cycle was investigated for all of the networks. Networks with lower degrees of crosslinking and high magnetite concentrations showed a significant amount of irrecoverable strain. Last, the use of remotely heated shape‐memory materials is discussed in light of potential biomedical applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Modification of Mg<Subscript>3</Subscript>Si<Subscript>2</Subscript>O<Subscript>5</Subscript>(OH)<Subscript>4</Subscript> nanotubes by magnetite nanoparticles

The magnetite nanoparticles and nanocomposite “Nanotube of hydrosilicate Mg—magnetite nanoparticles—Mg-ChR-NT/Fe₃O₄-NP” were obtained by coprecipitation. The composition of the synthesized samples has been established by X-ray diffraction. Using transmission electron microscopy, the presence of magnetite nanoparticles has been detected both inside the NTs and at the external surface of the NT walls. The specific surface of the NTs, nanoparticles, and composite is determined.