Synthesis of two novel acenaphthyl-quinoxaline based low-band gap polymers and its electrochromic properties

Dispersion stability and electrokinetic properties of TiO₂ nanoparticles, dispersed in aqueous solution of polyallylamine hydrochloride (PAAm.HCl) and polyvinyl alcohol (PVA) blends was examined. The electrophoresis method was employed to study electrokinetic properties of nanodispersion by varying pH and temperature with an emphasis on dispersion stability. The measurements were performed over a wide range of pH from 2–12 and temperature from 25–65 °C and the isoelectric points (IEPs) of nanodispersions were determined. The concentration of TiO₂ was varied from 2–12 wt%. The dispersions were found to be quite stable (no sedimentation) over a period of two months. The zeta potential of nanodispersions decreases as the pH increases. When temperature increases, a more distinct decrease in the zeta potential was observed. Such behavior may be due to the changes occurring in the linear dimension of adsorbing macromolecules with increasing temperature. As temperatures increases, the adsorption of polymers causes a decrease in the diffuse layer charge, which leads to a decrease in zeta potential. Also, the increase in ionic strength leads to a compression of the diffuse layer and reduction in the zeta potential. The conductivity of nanodispersions increases for all pH and temperatures studied.     

Aqueous Colloidal Stability Evaluated by Zeta Potential Measurement and Resultant TiO2 for Superior Photovoltaic Performance

Controlling the morphological structure of titanium dioxide (TiO₂) is crucial for obtaining superior power conversion efficiency for dye‐sensitized solar cells. Although the sol–gel‐based process has been developed for this purpose, there has been limited success in resisting the aggregation of nanostructured TiO₂, which could act as an obstacle for mass production. Herein, we report a simple approach to improve the efficiency of dye‐sensitized solar cells (DSSC) by controlling the degree of aggregation and particle surface charge through zeta potential analysis. We found that different aqueous colloidal conditions, i.e., potential of hydrogen (pH), water/titanium alkoxide (titanium isopropoxide) ratio, and surface charge, obviously led to different particle sizes in the range of 10–500 nm. We have also shown that particles prepared under acidic conditions are more effective for DSSC application regarding the modification of surface charges to improve dye loading and electron injection rate properties. Power conversion efficiency of 6.54%, open‐circuit voltage of 0.73 V, short‐circuit current density of 15.32 mA/cm², and fill factor of 0.73 were obtained using anatase TiO₂ optimized to 10–20 nm in size, as well as by the use of a compact TiO₂ blocking layer.     

Electrokinetic potential of kaolinite clay in the presence of polystyrene sulfonate

The determination of the electrokinetic potential of clay is very important in many applications. Therefore, this work was aimed at studying the effect of poly(4‐ sodium styrene sulfonate) on the electrokinetic potential and the sedimentation behavior of kaolinite clays at different pH values and/or in the presence of sodium or calcium chlorides. At pH values lower than the point of zero charge (PZC) of the kaolinite clay, the zeta potential of Na‐ or Ca‐kaolinite in CaCl₂ solutions was higher than that in NaCl solutions at the same concentration. Above the PZC, the zeta potential of Na‐ or Ca‐kaolinite in NaCl solution was higher than that in CaCl₂ at the same electrolyte concentration. These results reflect the ability of calcium cations to compress the double layer of the kaolinite clay better than sodium cations. Also, below the PZC and at low concentrations of poly(4‐sodium styrene sulfonate), the zeta potential of the kaolinite clay suspensions had low value, while the sediment volumes had higher values. On the other hand, above the PZC at increasing polymer concentrations, the zeta potentials increased but the sediment volumes had lower values compared to those produced below the PZC. The data showed the zeta potential of Na‐kaolinite suspensions are higher than Ca‐kaolinite, producing lower sediment volumes of Na‐kaolinite compared to Ca‐kaolinite at the same concentrations of polymer and/or pHs. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1705–1711, 2006     

Limiting flux in skimmed milk ultrafiltration: impact of electrostatic repulsion due to casein micelles

The variations of the limiting flux during skimmed milk ultrafiltration were studied under various physicochemical environments (pH, ionic strength, chemical nature of added salts). The evolutions were explained taking into account the physicochemical characteristics (size distribution, zeta potential) of the casein micelles, that is the main components of the fouling layer formed at the membrane surface. It was shown than in the pH range from 5.6 to 6.7, the limiting flux was linearly related to the zeta potential of the casein micelles regardless of the way used to obtain the zeta potential variation (addition of HCl, CaCl₂ or NaH₂PO₄): the higher the zeta potential of casein micelles (neutral pH), the greater the limiting flux. Under these operating conditions, the variations of hydrophobic interactions were negligible. The variation of the permeability of the deposit layer, composed of retained casein micelles, was therefore mainly governed by electrostatic interactions due to the casein micelles.     

Electrokinetics and stability of a cellulose acetate phthalate latex

An experimental investigation is described on the surface electric characterization of a commercially available latex, Aquateric, composed of cellulose acetate phthalate polymer particles, and used in enteric-controlled drug release. Since the surface charge of dispersed systems is an essential parameter governing most of their behavior, it is of fundamental importance to characterize how that quantity changes in the different environments in which the colloids could be used. The experimental method used in this work is electrophoresis; we report measurements of electrophoretic mobility of the latex as a function of pH and ionic concentration in the dispersion medium. It is shown that the zeta potential of the polymer particles is negative for the whole pH range studied and increases with pH as the dissociation of surface acetic acid groups proceeds. A plateau value is found for pH > 5, corresponding to complete dissociation of available ionizable sites. The values of the electrophoretic mobility (μ_e) and the zeta potential (ζ) of Aquateric are also analyzed as a function of the concentration of 1-1 (NaCl) and 2-1 (CaCl₂) concentration. The anomalous surface conductance (associated to the mobility of counterions adsorbed in the inner part of the electric double layer of the particles) manifests in a maximum in the |μ_e|-NaCl concentration plot for 10⁻³M concentration. No such behavior is observed in the presence of CaCl₂ solutions, where only a decrease of the mobility with ionic strength is observed. The effect of AlCl₃ concentration on the mobility is also considered; it is found that at pH 2 aluminum ions adsorb on the particles and render them positively charged. When the pH of the suspensions is not maintained constant, the hydrolysis of aluminum gives rise to a less efficient control of the charge of the particles and no positive mobilities are observed. Electrophoretic mobility measurements as a function of pH at constant AlCl₃ concentration show an abrupt change of μ_e from negative to positive, interpreted as due to surface precipitation of Al(OH)₃. When the pH is further increased, a second charge reversal is found, corresponding to the isoelectric point (pH of zero zeta potential) of Al(OH)₃. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2721–2726, 1997     

Effects of ethyl acetate on the soap‐free emulsion polymerization of 4‐vinylpyridine and styrene

The properties and morphologies of poly(4‐vinylpyridine‐co‐styrene) [P(4VP/St)] lattices, prepared by soap‐free emulsion polymerization using the water‐soluble initiator 2,2′‐azobis(2‐amidinopropane) · 2HCl (V50), were greatly affected by the addition of ethyl acetate (EA). The properties and morphologies of the resultant lattices were characterized by measuring the zeta potential, viscosity average molecular weight, particle size and distribution, glass‐transition temperature (T_g), and photographs taken by SEM and TEM. The effects of two kinds of monomer feeding modes, that is, the batch and semicontinuous emulsion copolymerization, were also investigated. For batch emulsion copolymerization, by charging EA, the core–shell morphology resulting from the disparate reactivity ratios of the 4VP(1)/St(2) copolymerization system (r₁ = 1.04, r₂ = ?0.73) disappeared. Instead, first a bimodal particle size distribution, with an apparently asymmetric composition structure, and then spherical microspheres were obtained as the amount of EA charged increased from 2 to 10 wt %. The particle size increased twofold by the addition of EA. The zeta potential of particles increased from +64.4 to more than +100 mV, and viscosity average molecular weight decreased from 9.70 to 0.97 × 10⁵ g/mol, as EA increased from 0 to 8 wt %. With the semicontinuous copolymerization, raspberry‐like particles were obtained by charging 10 wt % EA, whereas a sandwich‐like morphology was obtained without EA. The DSC curves showed one T_g for all the lattices prepared with charging EA, but two T_g's for the latex prepared without using EA, regardless of the monomer feeding modes. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1988–2001, 2001     

Yield stress of oxide dispersions—intermolecular forces of adsorbed small ionic additives and particle surface roughness

The yield stress‐pH and zeta potential‐pH behaviour of α‐alumina and zirconia dispersions with adsorbed small ionic molecular additives such as phosphate and pyrophosphate were determined. The result for adsorbed citrate was included for comparison. Adsorbed phosphate at high surface coverage increased the maximum yield stress of low surface area α‐Al₂O₃ (AKP30 and AA07) dispersions slightly. This increase is attributed to the intermolecular hydrogen bonding between phosphates adsorbed on interacting particles. With high surface area ZrO₂ (Tosoh) dispersions, however, the adsorbed phosphate decreased the maximum yield stress. This is due to its very rough surface morphology limiting the extent of intermolecular hydrogen bonding between adsorbed phosphate layers. Unlike phosphate, pyrophosphate reduces the maximum yield stress of AKP30 α‐Al₂O₃. This is due to the presence of intramolecular hydrogen bonding, thereby impeding effective bridging. A similar result is observed with citrate. The adsorbed pyrophosphate acts as an effective steric barrier keeping interacting particles further apart, thereby weakening the van de Waals attraction. These dispersions with the presence of non‐DLVO forces, that is bridging and steric, did not affect the linear relationship between yield stress and the square of the zeta potential as predicted by the yield stress–DLVO force model. However the relative importance of these non‐DLVO forces affect the value of the critical zeta potential at the point of transition from flocculated to dispersed state. © 2011 Canadian Society for Chemical Engineering     

Microcapsules prepared from a polycondensate‐based cement dispersant via layer‐by‐layer self‐assembly on melamine‐formaldehyde core templates

Novel microcapsules were prepared from colloidal core–shell particles by acid dissolution of the organic core. Weakly crosslinked, monodisperse and spherical melamine‐formaldehyde polycondensate particles (diameter ～ 1 μm) were synthesized as core template and coated with multilayers of an anionic polyelectrolyte via layer‐by‐layer deposition technique. As polyelectrolytes, an anionic naphthalenesulfonate formaldehyde polycondensate that is a common concrete superplasticizer and thus industrially available, and cationic poly(allylamine hydrochloride) were used. Core removal was achieved by soaking the core–shell particles in aqueous hydrochloric acid at pH 1.6, resulting in hollow microcapsules consisting of the polyelectrolytes. Characterization of the template, the core–shell particles, and the microcapsules plus tracking of the layer‐by‐layer polyelectrolyte deposition was performed by means of zeta potential measurement and scanning electron microscopy. The microcapsules might be useful as microcontainers for cement additives. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Layer‐by‐layer modification of porous polybenzoxazine with silver nanoparticles for enhanced CO2 storage

Polybenzoxazine (PBZ) xerogels have been synthesized via quasi solventless method and coated with silver nanoparticles using the layer‐by‐layer (LbL) deposition method. After coating, the samples were carbonized at 800 °C to obtain high surface area porous carbon materials to be used for CO₂ storage. Evidences of the successful LbL deposition of the coating was provided by ultraviolet–visible and attenuated total reflection–Fourier transform infrared spectroscopy and the silver nanoparticles top layer was confirmed by scanning electron microscopy–energy‐dispersive X‐ray spectroscopy, transmission electron microscopy, X‐ray diffraction, and X‐ray photoelectron spectroscopy. Results showed that the samples coated with silver nanoparticles displayed an increased CO₂ capacity from 3.02 to 3.39 mmol g^?1 when compared with the plain carbon PBZ. The LbL method for the modification of the pore surface in porous PBZ is simple and allows the facile tuning of the inner PBZ pore's surface chemistry with metallic nanoparticles that could be enhanced CO₂ storage capacity. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45097.     

Pristine point of zero charge (p.p.z.c.) and zeta potentials of boehmite’s nanolayer and nanofiber surfaces

The pristine point of zero charge (p.p.z.c) and zeta potential as a function of pH of boehmite oxide/hydroxide (α-Al₂O₃·H₂O) have been determined for three filter media. The active component in the first two filter media is boehmite nanofibers, only 2 nm in diameter and about 300 nm long. Boehmite nanofibers create high zeta potential (ζ_true≥46 mV) in aqueous solutions in the pH range of 3–8. The p.p.z.c. values were determined to be 11.60 ± 0.15 for nanofibers grafted onto microglass fibers and 11.40 ± 0.15 for agglomerated nanofibers. In the third filter media, a boehmite nanolayer in the form of monocrystalline oxide/hydroxide with a thickness of approximately 1.2 nm is electroadhesively deposited onto siliceous support material with large surface area of about 50 m²/g, therefore forming a highly electropositive composite of boehmite nanolayer on the second highly electronegative solid. Boehmite’s oxide-hydroxide nanolayer surface creates high zeta potential (ζ_true≥50 mV) in aqueous solutions in the pH range of 3–8. The p.p.z.c. value was determined to be 11.38 ± 0.15. The reported values are within accuracy, but they are much higher than the values reported in the literature. X-ray powder diffraction data were supplemented by microscopy, infrared spectroscopy in order to characterize fully synthetic boehmite surfaces.     

Physicochemical Characterization of Granular Ferric Hydroxide (GFH) for Arsenic(V) Sorption from Water

Abstract

Physical and chemical characterization of granular ferric hydroxide (GFH) [e.g., scanning electron micrographs (SEM), X‐ray diffraction (XRD) analysis, Brunauer‐Emmett‐Teller (BET) and Langmuir surface area measurements, pore size distribution, pH titration, and zeta potential measurements] were conducted to determine its performance as an adsorbent for trace arsenic(V) removal. Speciation diagrams for arsenate and phosphate were produced for the present system. The equilibrium adsorption isotherms were measured over initial arsenate concentrations ranging from 100–750 µg/L and the pH range of 4–9. The adsorption of arsenate was found to decrease as the pH of the solution was increased, thus giving the optimal adsorption of arsenate onto GFH at pH 4. Adherence to the Langmuir isotherm was found at all pHs for the arsenate adsorption. The competitive effect of phosphate on the uptake of arsenate at pH 4 by GFH was investigated, outlining the greater affinity of GFH for arsenate adsorption compared to phosphate. The kinetic performance of GFH was assessed and the results were analyzed by applying a particle diffusion model.     

Relationship between surface μ‐roughness and interface slurry particle spatial distribution during glass polishing

During optical glass polishing, a number of interactions between the workpiece (i.e., glass), polishing slurry, and pad can influence the resulting workpiece roughness at different spatial scale lengths. In our previous studies, the particle size distribution of the slurry, the pad topography, and the amount of material removed by a single particle on the workpiece were shown to strongly correlate with roughness at AFM scale lengths (nm‐μm) and weakly at μ‐roughness scale lengths (μm‐mm). In this study, the polishing slurry pH and the generation of glass removal products are shown to influence the slurry particle spatial and height distribution at the polishing interface and the resulting μ‐roughness of the glass workpiece. A series of fused silica and phosphate glass samples were polished with various ceria and colloidal silica slurries over a range of slurry pH, and the resulting AFM roughness and μ‐roughness were measured. The AFM roughness was largely invariant with pH, suggesting that the removal function of a single particle is unchanged with pH. However, the μ‐roughness changed significantly, increasing linearly with pH for phosphate glass and having a maximum at an intermediate pH for fused silica. In addition, the spatial and height distribution of slurry particles on the pad (as measured by laser confocal microscopy) was determined to be distinctly different at low and high pH during phosphate glass polishing. Also, the zeta potential as a function of pH was measured for the workpiece, slurry, and pad with and without surrogate glass products (K₃PO₄ for phosphate glass and Si(OH)₄ for silica) to assess the role of interfacial charge during polishing. The addition of K₃PO₄ significantly raised the zeta potential, whereas addition of Si(OH)₄ had little effect on the zeta potential. An electrostatic DLVO three‐body force model, using the measured zeta potentials, was used to calculate the particle–particle, particle–workpiece, and particle–pad attractive and repulsive forces as a function of pH and the incorporation of glass products at the interface. The model predicted an increase in particle–pad attraction with an increase in pH and phosphate glass products consistent with the measured slurry distribution on the pads during phosphate glass polishing. Finally, a slurry “island” distribution gap (IDG) model has been formulated which utilizes the measured interface slurry distributions and a load balance to determine the interface gap, the contact area fraction, and the load on each slurry “island”. The IDG model was then used to simulate the workpiece surface topography and μ‐roughness; the results show an increase in roughness with pH similar to that observed experimentally.     

Oxidation of cod phospholipids in liposomes: Effects of salts,pH and zeta potential

This work examines how different salts and pH influence both the zeta potential and the lipid oxidation rate of liposomes made from cod phospholipids. The rate of Fe²⁺‐induced lipid oxidation was measured by consumption of dissolved oxygen by liposomes in a closed vessel. Cations (Na⁺, K⁺, Ca⁺, Mg⁺) did not influence the rate of oxidation in the tested range [ionic strength (I) 0–0.14 M). Among the tested anions, sulphates and nitrates did not significantly change the oxygen uptake rate, but chlorides (KCl, NaCl, CaCl₂) reduced the oxidation rate down to approximately 45%, and dihydrogen phosphate down to 14%, when I = 0.14 M. The effect of Cl^? and H₂PO4₄^? was additive. Addition of salts increased the zeta potential of the liposomes, divalent cation salts even resulted in a positive zeta potential. When the liposomes contained different concentrations of chlorides, a linear relationship between oxygen uptake rate and zeta potential was observed. When phosphate was added, the oxygen uptake rate was not related to the changes in zeta potential. The decrease in pH was followed by an increase in zeta potential. The oxygen uptake rate did not change significantly at different positive zeta potentials (pH <3). When the zeta potential was negative, the oxygen uptake rate was influenced by the zeta potential and may also be influenced by iron solubility. Absolute values of the zeta potential alone cannot be used to predict oxidation rates.     

Surface force arising from adsorbed graphene oxide in alumina suspensions with different shape and size

The effects of graphene oxide (GO) on the yield stress‐pH of α‐Al₂O₃ (alumina) suspensions were investigated. For micron‐sized platelet alumina suspensions, micron‐sized GO additive increased the maximum yield stress by as much as six‐folds. This was attributed to GO‐mediated bridging interactions between the platelet particles. This type of bridging interactions was much less effective with submicron‐sized, spherical, and irregular shape alumina. Adsorption of the anionic GO reflected by the shift of pH of zero zeta potential to a lower pH is particularly high for platelet alumina. The 1.0 dwb % GO concentration added is sufficient to reinforce each platelet particle–particle bond, assisted by a directed GO–platelet interaction configuration. This is, however, not true with submicron‐sized particles as the particle concentration increases sharply with the inverse of the particle diameter to power of 3. Moreover, a GO sheet can adsorb several submicron‐sized particles and this does not produce the right interaction configuration. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3633–3641, 2013     

Bioactive glass nanoparticles with negative zeta potential

The purpose of this work was to produce and characterize SiO₂–CaO–P₂O₅ bioactive glass nanoparticles with negative zeta potential for possible use in biomedical applications. 63S bioactive glass was obtained using the sol–gel method. X-ray fluorescence (XRF) spectroscopy and dispersive X-ray analysis (EDX) confirmed the preparation of the 63S bioactive glass with 62.17% SiO₂, 28.47% CaO and 9.25% P₂O₅ (in molar percentage). The in vitro apatite forming ability of prepared bioactive glass was evaluated by Fourier transform infrared spectroscopy (FTIR) after immersion in simulated body fluid (SBF). The result showed that high crystalline hydroxyapatite can form on glass particles. By the gas adsorption (BET method), particle specific surface area and theoretical particle size were 223.6 ± 0.5 m²/g and ∼24 nm, respectively. Laser dynamic light scattering (DLS) indicated particles were mostly agglomerated and had an average diameter between 100 and 500 nm. Finally, using laser Doppler electrophoresis (LDE) the zeta potential of bioactive glass nanoparticles suspended in physiological saline was determined. The zeta potential was negative for acidic, neutral and basic pH values and was −16.18 ± 1.8 mV at pH 7.4. In summary, the sol–gel derived nanoparticles revealed in vitro bioactivity in SBF and had a negative zeta potential in physiological saline solution. This negative surface charge is due to the amount and kind of the ions in glass structure and according to the literature, promotes cell attachment and facilitates osteogenesis. The nanometric particle size, bioactivity and negative zeta potential make this material a possible candidate for bone tissue engineering.     

Layer‐by‐layer assembled hydrogel nanocomposite film with a high loading capacity

The layer‐by‐layer assembly technique is a method that widely used in the preparation of nanostructured multilayer ultrathin films. We fabricated a hydrogel nanocomposite film by alternating the deposition of a core–shell poly[(dimethylimino)(2‐hydroxy‐1,3‐propanedily) chloride] (PDMIHPC)–laponite solution and poly(acrylic acid). The growth of the deposition procedure was proven by ultraviolet–visible spectroscopy and spectroscopic ellipsometry. The surface morphology of the films was observed by scanning electron microscopy. The films could reversibly load and release methylene blue (MB) dye, which was used as an indicator. It took about 4.5 h to reach loading equilibrium at pH 9.0. The loading capacity of the film for MB was as large as 4.48 μg/cm² per bilayer because of the introduction of the core–shell PDMIHPC–laponite as a film component. Nearly 90% of MB was released at pH 3.0 or in a 300 mM NaCl solution within 2.5 h. The loading and release processes were greatly influenced by the ionic strength and pH value of the MB solution. The hydrogel nanocomposite film showed good pH‐triggered loading‐release reversibility and suggested potential applications in controlled drug‐delivery systems and smart materials. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39352.     

Micellization of pH‐sensitive poly(butadiene)‐block‐poly(2 vinylpyridine)‐block‐poly(ethylene oxide) triblock copolymers: Complex formation with anionic surfactants

The micellization of three tailor‐made triblock copolymers, such as PB₁₀₀–P2VP₁₀₀–PEO₁₀₄, PB₁₈₅–P2VP₁₀₈–PEO₁₅₄, and PB₃₇–P2VP₁₁₅–PEO₂₄₁, having similar total molecular weights and constant poly(2‐vinylpyridine) (P2VP) sequence lengths, was investigated as a function of pH and sodium dodecyl sulfate (SDS) concentration. At pH 7 the formation of intermicellar aggregates was observed, especially for copolymers of low poly(ethylene oxide) (PEO) content. A pH decrease from 7 to 3 leads to a particle size increase due to the electrostatic repulsion of the protonated P2VP chains. The influence of the PEO sequence length was also observed for zeta potential values. At pH 3, in the absence of SDS, core–shell–corona micelles are formed whereas in the presence of small amount of SDS (degree of neutralization DN = 0%–50%), a complex is formed between SDS and the protonated P2VP which leads to the shrinkage of the shell and thus to a decrease of the micellar sizes. For higher DN values, the micellar sizes increase due to the formation of large agglomerates and a transition occurs from a monomodal to a bimodal size distribution. Furthermore, it turned out that secondary aggregation, such as intermicellar aggregation, can completely be avoided if the degree of polymerization (DPn) of the water‐soluble block is significantly higher than the DPn of the water‐insoluble sequence. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45313.     

Characterization of stabilized porous magnetite core–shell nanogel composites based on crosslinked acrylamide/sodium acrylate copolymers

Stabilized and dispersed superparamagnetic porous nanogels based on sodium acrylate (AA‐Na) and acrylamide (AM) in a surfactant‐free aqueous system were synthesized via solution polymerization at room temperature. The formation of magnetite nanoparticles was confirmed and their properties characterized using Fourier transform infrared spectroscopy. Extensive characterization of the magnetic polymer particles using transmission electron microscopy (TEM), dynamic light scattering and zeta potential measurements revealed that Fe₃O₄ nanoparticles were incorporated into the shells of poly(AM/AA‐Na). The average particle size was 5–8 nm as determined from TEM. AM/AA‐Na nanoparticles with a diameter of about 11 nm were effectively assembled onto the negatively charged surface of the as‐synthesized Fe₃O₄ nanoparticles via electrostatic interaction. Crosslinked magnetite nanocomposites were prepared by in situ development of surface‐modified magnetite nanoparticles in an AM/AA‐Na hydrogel. Scanning electron microscopy was used to study the surface morphology of the prepared composites. The morphology, phase composition and crystallinity of the prepared nanocomposites were characterized. Atomic force microscopy and argon adsorption–desorption measurements of Fe₃O₄.AM/AA indicated that the architecture of the polymer network can be a hollow porous sphere or a solid phase, depending on the AA‐Na content. © 2013 Society of Chemical Industry     

Synthesis of tercopolymer BA–MMA–VTES and surface modification of nano‐size Si3N4 with this macromolecular coupling agent

A new macromolecular coupling agent butyl acrylate (BA)‐methyl methacrylate (MMA)‐vinyl triethoxy silane (VTES) tercopolymer was synthesized using solution polymerization initiated by free radical initiator benzoyl peroxide (BPO) and dicumyl peroxide (DCP). Dodecylthiol is choosed as the chain transfer to control the molecule weight of this tercopolymer. The terpolymer's molecular structure was confirmed by FTIR and NMR, and its average molecular weight was determined by GPC. In this work, the tercopolymer BA–MMA–VTES is used for surface modification of silicon nitride (Si₃N₄) nanopowder. The structure surface properties and thermal stability of modified nano‐Si₃N₄ were systematically investigated by FTIR, TGA, TEM, and size distribution analyzer. The results show that the macromolecular coupling agent bonds covalently on the surface of nano‐sized Si₃N₄ particles and an organic coating layer is formed. The optimum loading of this macromolecular coupling agent BA–MMA–VTES tercopolymer is 5% (wt %) of nano‐sized Si₃N₄. TEM also reveals that modified nano‐Si₃N₄ possesses good dispersibility. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Adsorption of Cd(II) ions at the hydroxyapatite/electrolyte solution interface

The study of the Cd(II) ions adsorption at the hydroxyapatite/electrolyte solution interface and the changes of the electrical double layer (EDL) structure in this system are presented. The adsorption of Cd(II) ions was calculated from the loss of their concentration from the solution using the radioisotope method. The adsorption was studied in the range of the initial concentration from 0.000001 to 0.001mol/dm³ and as the function of pH. The results of measurements of Cd(II) ions adsorption kinetics on hydroxyapatite were fitted using the pseudo-first, pseudo-second, and multiexponential modes to check which model describes this process in the best way. In addition, the main properties of the EDL, i.e., surface charge density and zeta potential were determined by the potentiometeric titration and electrophoresis measurements, respectively. The adsorption of Cd(II) ions at hydroxyapatite contributed to the increase of the zeta potential and also to the change of the double electrical layer structure.