Synthesis and characterization of polyaniline/silicon dioxide composites and preparation of conductive films

The focus of this study was to synthesize the inherently conductive polymer polyaniline using an optimized process to prepare polyaniline/silicon dioxide (PANI/SiO₂) composites by in situ polymerization and ex situ solution mixing. PANI and PANI/SiO₂ composite films were prepared by drop‐by‐drop and spin coating methods. The electrical conductivities of HCl doped PANI film and PANI/SiO₂ composite films were measured according to the standard four‐point‐probe technique. The composite films exhibited an increase in electrical conductivity over neat PANI. PANI and PANI/SiO₂ composites were also investigated by spectroscopic methods including UV‐Vis, FT‐IR, and Photoluminescence. UV‐Vis and FT‐IR studies showed that SiO₂ particles affect the quinoid units along the polymer backbone and indicate strong interactions between the SiO₂ particles and the quinoidal sites of PANI (doping effect). The photoluminescence properties of PANI and PANI/SiO₂ composites were studied and the PANI/SiO₂ composites showed increased intensity as compared to neat PANI. The increase of conductivity of PANI/SiO₂ composite may be partially due to the doping or impurity effect of SiO₂ where the silicon dioxides compete with chloride ions. The morphology of particles and films were examined by a scanning electron microscope (SEM). SEM measurements indicated that the SiO₂ were well dispersed and isolated in composite films. Copyright © 2009 John Wiley & Sons, Ltd.     

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     

Effects of surfactants on the morphology of composite polymer particles produced by two‐stage seeded emulsion polymerization

Poly(methyl methacrylate) (PMMA)–polystyrene (PS) composite polymer particles were synthesized in the presence of a surfactant by two‐stage seeded emulsion polymerization. The first stage was the synthesis of PMMA particles by soapless emulsion polymerization; the second stage was the synthesis of the PMMA–PS composite polymer particles with the PMMA particles as seeds. In the second stage of the reaction, three kinds of surfactants—sodium laurate sulfate (SLS), polyoxyethylene (POE) sorbitan monolaurate (Tween 20), and sorbitan monolaurate (Span 20)—were used to synthesize the PMMA–PS composite particles. Both the properties and concentrations of the surfactants influenced the morphology of the composite particles significantly. Core–shell composite particles, with PS as the shell and PMMA as the core, were synthesized in the presence of a low concentration of the hydrophilic surfactant SLS. This result was the same as that in the absence of the surfactant. However, a low concentration of Tween 20 led to composite particles with a core/strawberry‐like shell morphology; the core region was a PS phase, and the strawberry‐like shell was a PS phase dispersed in a PMMA phase. With an increase in the concentration of SLS, the morphology of the composite particles changed from core (PMMA)–shell (PS) to core (PS)–shell (PMMA). Moreover, the effects of a high concentration of Tween 20 or Span 20 on the morphology of the PMMA–PS composite particles were investigated in this study. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2224–2236, 2005     

Ni@Pd core–shell nanoparticles immobilized on yolk–shell Fe3O4@polyaniline composites as a highly efficient,magnetically separable and atom‐economical catalyst for reduction of nitrobenzenes

The preparation of Ni@Pd core–shell nanoparticles immobilized on yolk–shell Fe₃O₄@polyaniline composites is reported. Fe₃O₄ nanoclusters were first synthesized through the solvothermal method and then the SiO₂ shell was coated on the Fe₃O₄ surface via a sol–gel process. To prepare Fe₃O₄@SiO₂@polyaniline composites, polyvinylpyrrolidone was first grafted on to the surface of Fe₃O₄@SiO₂ composites and subsequently polymerization of aniline was carried out via an ultrasound‐assisted in situ surface polymerization method. Selective etching of the middle SiO₂ layer was then accomplished to obtain the yolk–shell Fe₃O₄@polyaniline composites. The approach uses polyaniline (PANI) conductive polymer as a template for the synthesis of Ni@Pd core–shell nanoparticles. The catalytic activity of the synthesized yolk–shell Fe₃O₄@PANI/Ni@Pd composite was investigated in the reduction of o‐nitroaniline to benzenediamine by NaBH₄, which exhibited conversion of 99% in 3 min with a very low content of the catalyst. Transmission electron microscopy, X‐ray photoelectron spectroscopy, TGA, X‐ray diffraction, UV–visible, scanning electron microscopy, X‐ray energy dispersion spectroscopy and FT‐IR were employed to characterize the synthesized nanocatalyst. Copyright © 2014 John Wiley & Sons, Ltd.     

Production of electrically conductive, core/shell polystyrene/polyaniline composite particles by chemical oxidative seeded dispersion polymerization

Micron-sized, monodispersed, electrically conductive polystyrene (PS)/polyaniline (PAn) composite particles were produced by chemical oxidative seeded dispersion polymerization of aniline at 0 °C with 1.37-μm-sized, monodispersed PS seed particles in HCl aqueous solution, where the pH value was kept at 2.5 with a pH stat. The composite particles consisted of a PS core and a PAn shell. A pellet of the composite particles had a conductivity of 3.4 × 10⁻³ S/cm. Received: 5 April 2000 Accepted: 10 August 2000     

Preparation and characterization of conducting polyaniline layered magnetic nano composite polymer particles

Considering the application potentials of organic materials possessing both conducting and ferromagnetic functions in various electronic devices, an attempt was made to prepare conducting polyaniline (PANI) layered magnetic nano composite polymer particles. Two routes were used to modify magnetic Fe₃O₄ core particles. In one route, seeded emulsion polymerization of methyl methacrylate (MMA) was carried out in presence of nano‐sized Fe₃O₄ core particles. In another route, cross‐linker ethyleneglycol dimethacrylate (EGDM) was used in addition to MMA. The modified composite particles were named as Fe₃O₄/PMMA and Fe₃O₄/P(MMA‐EGDM), respectively. Finally, seeded chemical oxidative polymerization of aniline was carried out in the presence of Fe₃O₄/PMMA and Fe₃O₄/P(MMA‐EGDM) composite seed particles to obtain Fe₃O₄/PMMA/PANI and Fe₃O₄/P(MMA‐EGDM)/PANI composite polymer particles. The modification of Fe₃O₄ core particles was confirmed by electron micrographs, FTIR, UV–visible spectra, X‐ray photoelectron spectra, X‐ray diffraction pattern and thermogravimetric analyses. A comparative study showed that crosslinking of intermediate shell improved the magnetic susceptibility and electrical conductivity of PANI layered magnetic nano composite particles. Copyright © 2013 John Wiley & Sons, Ltd.     

聚苯胺/聚苯乙烯复合Janus颗粒的制备

利用有机溶剂溶胀磺化聚苯乙烯@二氧化钛(SPS@TiO₂)核壳粒子制得二氧化钛/聚苯乙烯(TiO₂/PS)双面神(Janus)颗粒, 并在TiO₂端进行改性, 得到墨绿色的聚苯胺/聚苯乙烯(PANi/PS) Janus颗粒. 用扫描电子显微镜(SEM)、电子能谱(EDS)、元素分析、透射电子显微镜(TEM)、红外光谱(IR)、热重分析(TGA)、固体紫外-可见分析(UV-Vis)和四探针法考察Janus颗粒组成、微结构和Janus性质. 结果表明, Janus颗粒为雪人状结构, PS端的平均粒径为228 nm, PANi端的平均粒径从TiO₂的258 nm增大为295 nm; 并且在EDS谱上可以观察到N元素, 而未观察到Ti元素; 包覆的PANi的质量分数为23.7%. 掺杂后PANi/PS Janus颗粒的导电性能较好, 电导率为0.247 S/cm.     

Reverse Atom Transfer Radical Polymerization of MMA in the Presence of CaCO3/SiO2 Two-Component Composite Particles

Summary: We previously discovered that structurally well-defined polymer/inorganic composite particles, i.e., poly(methyl methacrylate) (PMMA)/CaCO₃/SiO₂ three-component composite particles, can be achieved via reverse atom transfer radical polymerization (ATRP), using 2,2′-azo-bis-isobutyronitrile as initiator and Cu^II bromide as catalyst. In the present study, the influence of the mass ratio of CaCO₃/SiO₂ two-component composite particles to methyl methacrylate (MMA) on the rate and behavior of the polymerization was studied in detail. The results illustrate that increasing the mass ratio of CaCO₃/SiO₂ two-component composite particles will decrease the overall rate of polymerization of MMA under standard reverse ATRP conditions. Thermal properties of the obtained well-defined particles were characterized and determined by thermogravimetric analysis (TGA). The results indicate that well-defined PMMA chains grafted on the surface of CaCO₃/SiO₂ particles were only degraded by random chain scission of C C linkages within the PMMA chain, which is different from the degradation of PMMA chains prepared via traditional radical polymerization. This difference is reasonably ascribed to the difference between the end groups of PMMA prepared via reverse ATRP and that via traditional radical polymerization, which has been confirmed by end group analysis measured by ¹H–NMR spectroscopy.     

Radar Absorption Properties of Ni0.5Zn0.5Fe2O4/PANI/epoxy Nanocomposites

A nitrate? citrate gel was prepared from metallic nitrates and citric acid by sol? gel process and was further used to synthesize Ni_0.5Zn_0.5Fe₂O₄ nanocrystalline powder by auto‐combustion. Then, two novel 15 and 35% (w/w) magnetic Ni_0.5Zn_0.5Fe₂O₄ containing polyaniline nanocomposites, named as PANI‐Ni15 and PANI‐Ni35, respectively, were prepared via in‐situ polymerization of aniline in an aqueous solution containing proper amount of Ni_0.5Zn_0.5Fe₂O₄ magnetic powder. The incorporation of the nanopowders to PANI matrix was confirmed by X‐ray diffraction (XRD), IR and SEM. Synthesized PANI‐NiZn ferrite composite particles were subsequently added to an epoxy resin matrix to produce related nanocomposites. The morphological properties of these nanocomposite materials were investigated by SEM and TEM. The electromagnetic‐absorbing properties were studied by measuring the reflection loss in the frequency range of 8.0 to 12.0 GHz. Results showed the reflection loss of the PANI‐Ni35 composite is higher than pure polyaniline and PANI‐Ni15. The good reflection loss of the nanocomposites suggests their potential applicability as radar absorber.     

A facile strategy for synthesis of multilayer and conductive organo-silica/polystyrene/polyaniline composite particles

By means of a facilely designed strategy, we successfully fabricated the multilayer and conductive organo-silica/polystyrene/polyaniline (organo-silica/PS/PANi) composite particles. First, organo-silica/PS core/shell composite particles were synthesized by seeded emulsion polymerization and the vinyl groups located on the surface of organo-silica nanoparticles were used to induce in situ polymerization of styrene. The influence of the route of the addition of styrene on the morphology of organo-silica/PS composite particles was investigated. Then, the coating of organo-silica/PS composite particles with PANi was achieved by virtue of the "Swelling-Diffusion-Interfacial-Polymerization Method" (SDIPM). The whole preparation process was monitored by transmission electron microscope, scanning electron microscope, Fourier transform infrared, Raman spectroscopy, dynamic light scattering, and thermogravimetry. As a result, the multilayer and conductive organo-silica/PS/PANi nanocomposites possessed of a uniform size and well-defined morphology, and furthermore, their structure could be well controlled by simply changing the weight ratio of aniline/PS.     

Preparation of poly(methyl methacrylate)/CaCO3/SiO2 composite particles via emulsion polymerization

A novel method to prepare organic/inorganic composite particles, i.e. poly(methyl methacrylate)/CaCO₃/SiO₂ three-component composite particles, using emulsion polymerization of methyl methacrylate with sodium lauryl sulfate as a surfactant in an aqueous medium was reported. CaCO₃/SiO₂ two-component inorganic composite particles were obtained firstly by the reaction between Na₂CO₃ and CaCl₂ in porous silica (submicrometer size) aqueous sol and the specific surface area of the particles was measured by the Brunauer–Emmett–Teller (BET) method. The results show that the BET specific surface area of the CaCO₃/SiO₂ composite particle is much smaller than that of the silica particle, indicating that CaCO₃ particles were adsorbed by porous silica and that two-component inorganic composite particles were formed. Before copolymerization with methyl methacrylate, the inorganic composite particles were coated with a modifying agent through covalent attachment. The chemical structures of the poly(methyl methacrylate)/CaCO₃/SiO₂ composite particles obtained were characterized by Fourier transform IR spectroscopy and thermogravimetric analysis. The results show that the surface of the modified inorganic particles is grafted by the methyl methacrylate molecules and that the grafting percentage is about 15.2%.     

The morphology of composite polymer particles produced by multistage soapless seeded emulsion polymerization

 Composite polymer particles which contain poly(methyl methacrylate) (PMMA) and polystyrene (PS) components (PMMA/PS composite particle) were synthesized by the method of multistage soapless seeded emulsion polymerization. In this study, the process of multistage soapless seeded emulsion polymerization included two-stage polymerization, three-stage polymerization or four-stage polymerization. The morphologies of the PMMA/PS composite particles were studied. The kinetic factor was the main force to control the morphology of the linear PMMA–PS composite particles which were synthesized by the method of two-stage reaction. Both the kinetic factor and the thermodynamic factor decide the morphology of the linear composite particles which were synthesized by the method of either three-stage or four-stage reaction. However, the thermodynamic factor cannot influence the morphology of the PMMA/PS composite particles with a cross-linked structure which were synthesized by the method of three-stage reaction. The cross-linked composite polymer particles had the morphology of a multilayer structure, which showed that the polymer layers accumulated in their order of production. Received: 9 January 2001 Accepted: 14 June 2001     

Graphene oxide‐induced polymerization and crystallization to produce highly conductive polyaniline/graphene oxide composite

Graphene oxide (GO)–polyaniline (PANI) composite is synthesized by in situ polymerization of aniline in the presence of GO as oxidant, resulting in highly crystalline and conductive composite. Fourier transform infrared spectrum confirms aniline polymerization in the presence of GO without using conventional oxidants. Scanning electron microscopic images show the formation of PANI nanofibers attached to GO sheets. X‐ray diffraction (XRD) patterns indicate the presence of highly crystalline PANI. The sharp peaks in XRD pattern suggest GO sheets not only play an important role in the polymerization of aniline but also in inducing highly crystalline phase of PANI in the final composite. Electrical conductivity of doped GO–PANI composite is 582.73 S m^?1, compared with 20.3 S m^?1 for GO–PANI obtained by ammonium persulfate assisted polymerization. The higher conductivity appears to be the result of higher crystallinity and/or chemical grafting of PANI to GO, which creates common conjugated paths between GO and PANI. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1545–1554     

Preparation of magnetically doped multilayered functional silica particles via surface modification with organic polymer

Magnetically modified functional particles are emerging as one of the most promising candidate in numerous multidisciplinary applications. In this research, a simple process has been developed to prepare magnetically modified aminated silica (SiO₂) particles. Herein, submicron‐sized SiO₂ particles were modified with poly(methylmethacrylate‐methacrylic acid) by seeded polymerization without any stabilizer. The carboxyl groups localized near the particles surface were then covalently linked with ethylene diamine to prepare aminated composite particles. Iron ions were then precipitated on the surface of aminated composite particles to obtain magnetically doped functional SiO₂ particles. The preparation of such particles was confirmed by scanning electron microscopy, Fourier transform infrared, ¹H NMR, X‐ray photoelectron spectroscopy and thermogravemetric analyses. Relative measurement of adsorption study of different biomolecules suggested that magnetically doped functional silica particles are comparatively hydrophobic. Copyright © 2012 John Wiley & Sons, Ltd.     

Influence of the swelling state of seed polymer particles with monomer on the morphology of micron-sized monodispersed composite polymer particles produced by seeded polymerization utilizing the dynamic swelling method

 Micron-sized mono-dispersed polystyrene (PS)/poly(n-butyl methacrylate) (PBMA) composite particles (PS/PBMA=2/1 by weight) having a heterogeneous structure in which many fine PBMA domains dispersed in a PS matrix near the particle surface were produced by seeded polymerization of n-butyl methacrylate (BMA) of which almost all had been absorbed by 1.8 μm-sized monodispersed PS seed particles utilizing the dynamic swelling method. The morphology was varied by changing the PS/BMA ratio and polymerization temperature. It was concluded that the swelling state of 2 μm-sized BMA-swollen PS particles in the seeded polymerization process is one of the important factors to control the morphology of the composite particles. Received: 27 November 1996 Accepted: 21 March 1997     

Dispersion stability and rheological behavior of suspensions of polystyrene coated fumed silica particles in polystyrene solutions

Polystyrene coated silica（SiO₂@PS） core-shell composite particles with averaged diameter of about 290 nm were prepared by in situ emulsion polymerization of styrene on the surface ofγ-methacryloxypropyltrimethoxysilane grafted SiO₂ nanoparticles of 20-50 nm in diameter.Rheological behavior and dispersion stability of SiO₂@PS suspension in 10 wt%PS solution were compared with suspensions of untreated SiO₂ and silane modified SiO₂ nanoparticles.Suspensions of the untreated and the silane modified SiO₂ exhibited obvious shear thinning.The SiO-2@PS suspension exhibits shear viscosity considerably smaller than suspensions of untreated and silane modified SiO₂ at low shear rates.Transmission electron microscopy showed that the composite particles can uniformly and stably disperse in PS solution compared to other suspensions,implying that the PS shell can effectively enhance the particle compatibility with PS macromolecules in solution.     

Synthesis of iron oxide/poly(methyl methacrylate) composite latex particles: Nucleation mechanism and morphology

A magnetic poly(methyl methacrylate) (PMMA) composite latex was prepared by soapless emulsion polymerization in the presence of ferrofluid, and the ferrofluid was prepared by means of a coprecipitation method. The effects of various polymerization parameters, such as the monomer concentration, ferrofluid content, and initiator concentration, on the conversion curve and particle size of the magnetic composite latex particles were examined in detail. The results showed that two nucleation mechanisms were involved according to the polymerization conditions. In the monomer‐rich and less ferrofluid system, self‐nucleation of PMMA was dominant over the entire course of emulsion polymerization. In the ferrofluid‐rich system, seeded emulsion polymerization was the main course to form the magnetic composite latex particles. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5695–5705, 2004     

An Advanced NiCoFeO/Polyaniline Composite for High‐Performance Supercapacitors

To reduce the charge‐transfer resistance of supercapacitors and achieve faster reversible redox reactions, ternary Ni‐Co‐Fe layered double hydroxide was prepared by using the urea method and then calcined to give NiCoFe oxide (NiCoFeO). To enhance conductivity, a polyaniline (PANI) conductive layer was assembled on the surface of the NiCoFeO particles by in situ oxidative polymerization of aniline monomers. The as‐prepared NiCoFeO/PANI composite was successful employed as a supercapacitor electrode. It was found that the NiCoFeO/PANI composite displayed good cycling stability, with a capacity loss of only 29.54 % after 5000 cycles. Furthermore, the NiCoFeO/PANI composite also exhibited excellent supercapacitor performance, with a high specific capacity of 843 F g^?1 at a current density of 2 A g^?1, whereas NiCoFeO showed a specific capacity of only 478 F g^?1. This result was attributed to the synergistic effect between NiCoFeO and PANI. The facile synthesis strategy and excellent electrochemical performance suggest that NiCoFeO/PANI is a promising economical electrode material for applications in supercapacitors.     

Production of micron-sized monodispersed core/shell polymethyl methacrylate/polystyrene particles by seeded dispersion polymerization

 Micron-sized monodispersed polymethyl methacrylate (PMMA)/polystyrene (PS) (PMMA/PS=2/1, wt ratio) composite particles consisting of PMMA-core and PS-shell were successfully produced by seeded dispersion polymerization of styrene in a methanol/water medium in the presence of about 2 μm-sized monodispersed PMMA particles. From the view point of thermodynamic equilibrium, such a morphology is difficult to form by usual seeded polymerization in a polar medium such as water. It is concluded that seeded dispersion polymerization in which almost all monomers and initiators exist in the medium has an advantage to produce core/shell polymer particles in which polymer layers accumulate in their order of the production regardless of the hydrophobicity of polymers, because of high viscosity in polymerizing particles. Received: 9 December 1996 Accepted: 26 February 1997     

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