Polyaniline-coated silver nanowires

Two non-conducting chemicals, aniline and silver nitrate, dissolved in formic acid solutions, yielded a composite of two conducting products, polyaniline and silver. As the concentration of formic acid increased, an alternative reaction, the reduction of silver nitrate with formic acid to silver became dominant, and the content of silver in the composites increased. The formation of polyaniline was confirmed by UV–visible, FTIR, and Raman spectroscopies. The typical conductivity of composites was 43 S cm^?1 at 84 wt.% of silver. Silver nanowires coated with polyaniline nanobrushes are produced at low concentrations of formic acid, the granular silver particles covered with polyaniline dominate at high acid concentrations.     

The oxidation of aniline with silver nitrate to polyaniline-silver composites

Silver nitrate oxidizes aniline in the solutions of nitric acid to conducting nanofibrillar polyaniline. Nanofibres of 10-20 nm thickness are assembled to brushes. Nanotubes, having cavities of various diameters, and nanorods have also been present in the oxidation products, as well as other morphologies. Metallic silver is obtained as nanoparticles of ∼50 nm size accompanying macroscopic silver flakes. The reaction in 0.4 M nitric acid is slow and takes several weeks to reach 10-15% yield. It is faster in 1 M nitric acid; a high yield, 89% of theory, has been found after two weeks oxidation of 0.8 M aniline. The emeraldine structure of polyaniline has been confirmed by FTIR and UV-vis spectra. The resulting polyaniline-silver composites contain 50-80 wt.% of silver, close to the theoretical expectation of 68.9 wt.% of silver. The highest conductivity was 2250 S cm⁻¹. The yield of a composite is lower when the reaction is carried out in dark, the effect of daylight being less pronounced at higher concentrations of reactants.     

Polyaniline–silver composites prepared by the oxidation of aniline with silver nitrate in solutions of sulfonic acids

Aniline was oxidized with silver nitrate in aqueous solutions of sulfonic acids: camphorsulfonic, methanesulfonic, sulfamic, or toluenesulfonic acids. Polyaniline–silver composites were produced slowly in 4 weeks in good yield, except for the reaction, which took place in sulfamic acid solution, where the yield was low. Polyaniline in the emeraldine form was identified with UV–visible, FTIR, and Raman spectra. Thermogravimetric analysis was used to determine the silver content, which was close to the theoretical prediction of 68.9 wt.%. Transmission electron microscopy demonstrated the presence of silver nanoparticles of ca 50 nm average sizes as the dominating species, and hairy polyaniline nanorods having diameter 150–250 nm accompanied them. The highest conductivity of 880 S cm⁻¹ was found with the composite prepared in methanesulfonic acid solution. Its conductivity decreased with temperature increasing in the 70–315 K range, which is typical of metals such as silver. The conductivity of composites prepared in solutions of other acids was lower and increased with increasing temperature. Such dependence is typical of semiconductors, reflecting the dominating role of polyaniline in the conductivity behaviour. It is proposed that interfaces between the polyaniline matrix and dispersed silver nanoparticles play a dominating role in macroscopic level of conductivity.     

Growth of silver nanowires on carbon fiber to produce hybrid/waterborne polyurethane composites with improved electrical properties

One dimensional silver nanowires (AgNWs) were grown on carbon fiber (CF) by a facile polyol method. Fourier transform infrared spectrometer (FTIR), laser Raman spectrometer (Raman), field‐emission scanning electron microscopy (FESEM), X ray diffraction instrument (XRD), energy dispersive spectrometer (EDS), and X‐ray photoelectron spectrometer (XPS) were carried out to reveal the structure, morphology, and formation mechanism of the CF‐AgNWs. It was found that AgNO₃ concentration of 1.5 mM, reaction temperature of 160°C, and reaction time of 120 min were appropriate conditions for growth of AgNWs on CF. Moreover, a mechanism was suggested that the cysteamine on CF acted as nucleation centers for growth of silver nanoparticles and then small sized silver nanoparticles reduced from silver nitrate were grown on CF via the silver bonding to sulfur. Through an Ostwald ripening process, small sized silver nanoparticles were grown into larger particles. With the assistance of polyvinylpyrolidone (PVP), these larger particles were directed to grow in a definite direction to form nanowires. It was found that the resistance of CF‐AgNWs was decreased to 19.5 Ω, compared with that of CF (102.6 Ω) with the same quality. Thus, the CF‐AgNWs was added into waterborne polyurethane (WPU) to improve the electrical and dielectric properties of WPU. Results showed the WPU/CF‐AgNWs composite presented a lower percolation threshold than WPU/CF composite. When the content was 2.5 wt %, the volume resistivity of the WPU/CF‐AgNWs (1.90 × 10⁴ Ω cm^?1) was lower by approximately three orders of magnitude than that of WPU/CF (4.19 × 10⁷ Ω cm^?1). When the content was 2.5 wt %, the dielectric constant and dielectric loss of the WPU/CF‐AgNWs were improved to 15.24 and 0.21, which were 34.5 and 40.8% higher than that of WPU/CF. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43056.     

Polyaniline-silver composites prepared by the oxidation of aniline with mixed oxidants, silver nitrate and ammonium peroxydisulfate: The control of silver content

Aniline was oxidized with mixtures of two oxidants, ammonium peroxydisulfate and silver nitrate, to give polyaniline-silver composites with variable content of silver in the composites. The presence of peroxydisulfate has a marked accelerating effect on the oxidation of aniline with silver nitrate. Oxidations in 1 M methanesulfonic acid produced composites in high yield. The molecular structure of the polyaniline was confirmed by UV-visible and FTIR spectra, and the polymeric character was established by gel-permeation chromatography. The content of silver varied between 0 and 70 wt.%. The silver nanoparticles were smaller than 100 nm. The conductivity of the composites was of the order of units S cm⁻¹. Only at high silver nitrate contents in the reaction mixture, the conductivity of products exceeded 100 S cm⁻¹. The conductivity of the composites sometimes increased after deprotonation of the polyaniline salt to a non-conducting base. Such conductivity behaviour is discussed in terms of the percolation model.     

Conducting composites prepared by the reduction of silver ions with poly(p‐phenylenediamine)

Poly(p‐phenylenediamine) (PPDA) and also its ladder‐like analogue were prepared by oxidation of p‐phenylenediamine with ammonium peroxydisulfate in an aqueous solution of 0.4 mol L^?1 hydrochloric acid and converted to PPDA bases. These were used as reductants of silver nitrate to silver nanoparticles in 1 mol L^?1 methanesulfonic acid or in water at various mole ratios of silver nitrate to p‐phenylenediamine units from 0 to 1.8. The original conductivity of the PPDA, 10^?12 S cm^?1, increased to the order of 100 S cm^?1 for the PPDA–silver composites containing 27–40 wt% (i.e. 4.5–6.6 vol%) silver. Fourier transform infrared spectra indicated a practically unchanged molecular structure of PPDA in the composites. In contrast, Raman spectroscopy showed the existence of regions with unchanged molecular structure of PPDA as well as the presence of regions containing silver particles and oxidized PPDA moieties. © 2014 Society of Chemical Industry     

Preparation and properties of nanocomposite hydrogels containing silver nanoparticles by ex situ polymerization

A series of composite hydrogels containing silver nanoparticle used for bioadhesives were prepared from acrylic acid, poly(ethylene glycol) methyl ether acrylate, and silver nanoparticles through ex situ polymerization. Silver nanoparticles with a narrow size distribution were prepared by the reduction of a silver nitrate solution with ascorbic acid. The influence of the content of the silver nanoparticles in the hydrogels on the equilibrium swelling ratio, mechanical properties, electrical conductivity, and inactivation of Escherichia coli (E. coli) was investigated in this study. The results showed that the swelling ratios of the composite gels were reduced by silver nanoparticles in the gels but were not reduced with an increase in the content of silver nanoparticles. In addition, the crosslinking density and shear modulus of these hydrogels did not increase with an increase in the content of silver nanoparticles. The adhesive force of these hydrogels (the APECAg series) was not obviously changed. Finally, the initial rate of E. coli inactivation for the APECAg series hydrogels showed excellent antibacterial properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3653–3661, 2006     

Synthesis and characterization of polyaniline derivative and silver nanoparticle composites

BACKGROUND: There has been a recent surge of interest in the synthesis and applications of electroactive polymers with incorporated metal nanoparticles. These hybrid systems are expected to display synergistic properties between the conjugated polymers and the metal nanoparticles, making them potential candidates for applications in sensors and electronic devices. RESULTS: Composites of polyaniline derivatives—polyaniline, poly(2,5‐dimethoxyaniline) and poly(aniline‐2,5‐dimethoxyaniline)—and silver nanoparticles were prepared through simultaneous polymerization of aniline derivative and reduction of AgNO₃ in the presence of poly(styrene sulfonic acid) (PSS). We used AgNO₃ as one of the initial components (1) to form the silver nanoparticles and (2) as an oxidizing agent for initiation of the polymerization reaction. UV‐visible spectra of the synthesized nanocomposites reveal the synchronized formation of silver nanoparticles and polymer matrix. The morphology of the silver nanoparticles and degree of their dispersion in the nanocomposites were characterized by transmission electron microscopy. Thermogravimetric analysis and differential scanning calorimetry results indicate an enhancement of the thermal stability of the nanocomposites compared to the pure polymers. The electrical conductivity of the nanocomposites is in the range 10^?4 to 10^?2 S cm^?1. CONCLUSION: A single‐step process for the synthesis of silver nanoparticle–polyaniline derivative nanocomposites doped with PSS has been demonstrated. The approach in which silver nanoparticles are formed simultaneously during the polymerization process results in a good dispersion of the nanoparticles in the conductive polymer matrix. Copyright © 2008 Society of Chemical Industry     

Conductivity and structure of a polyamide/silver iodide nanocomposite

In this study, the structure and properties of an organic–inorganic composite material prepared from nylon 6 doped with fine particles of silver iodide (AgI) were examined. The preparation of the composite involved the complexation of nylon 6 with polyiodide ions such as I and I by immersion in an iodine/potassium iodide (I₂–KI) aqueous solution followed by reaction in a silver nitrate (AgNO₃) aqueous solution; this resulted in the in situ formation of β-AgI fine particles within the nylon 6 matrix. The AgI content formed in the composite was dependent on the immersion temperatures of the I₂–KI and AgNO₃ solutions. Lower solution temperatures resulted in larger amounts of AgI in the composite. This method readily provided a composite with a high content of AgI in nylon 6 and a conductivity of approximately 10⁻⁵ Ω⁻¹ cm⁻¹. In a uniaxially oriented nylon 6 matrix, AgI particles precipitated with anisotropic shape, which was caused by the orientation of the precursor polyiodide ions. The structure of the oriented composite provided the anisotropic conductivity. Additionally, the composite exhibited high antibacterial properties. The procedure used in this study is considered a unique method for the preparation of organic–inorganic composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

在NiCl2、MnCl2或FeCl3存在下用多元醇法高浓度合成银纳米线

报道了一种用于高浓度制备银纳米线的改性多元醇法。在NiCl₂、MnCl₂或FeCl₃存在下高浓度地制得了具有均一尺寸和形貌的银纳米线。所得银纳米线的直径约为60～100 nm、长度约30～60 μm。研究了AgNO₃溶液浓度、PVP和AgNO₃比例和控制剂浓度等对所得银纳米线形貌的影响。研究发现可以通过反应条件的改变来调节所得银纳米线的形貌。本方法的可能机理是由于引入的金属阳离子可以除掉吸附在晶种表面的氧,从而促进银纳米线的生长。     

Preparation of polyaniline/nylon conducting fabric by layer‐by‐layer assembly method

In this article, layer‐by‐layer assembly technology was used to prepare polyaniline (PANI)/nylon conducting fabrics. PANI/nylon conductive composite fabrics were prepared by deposition of polyanion (PSS) and polycation (aniline cation) alternately. The pretreatment with PSS was discussed. The influence of the reaction time, aniline concentration, acid concentration and assembly time on the conductivity, and K/S values of composite fabric was studied. The optical reaction condition of assembly should be: the concentration of PSS was 20 g/L, the PSS‐treated nylon immersion in blended bath for 24 min, ammonium persulfate 0.1 mol/L, aniline 0.1 mol/L, p‐toluene sulfonic acid 0.3 mol/L. In the end, the conductive composite fabrics were characterized by fourier transformed Infrared‐attenuated total reflection spectroscopy and compared with pure nylon fabrics. At the same time, scanning electron microscopy, atomic force microscope (AFM), thermogravimetric analysis (TG), and mechanical properties were studied. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Influence of reaction conditions on the formation of nanotubes/nanoparticles of polyaniline in the presence of 1‐amino‐2‐naphthol‐4‐sulfonic acid and applications as electrostatic charge dissipation material

BACKGROUND: Poly(1‐amino‐2‐naphthol‐4‐sulfonic acid) and its copolymers with aniline are a new class of conducting polymers which can acquire intrinsic protonic doping ability, leading to the formation of highly soluble self‐doped homopolymers and copolymers. Free ? OH and ? NH₂ groups in the polymer chain can combine with other functional groups that could be present in protective paints which can thus be successfully used as antistatic materials. RESULTS: This paper reports the formation of nanotubes of polyaniline on carrying out oxidative polymerization of aniline in the presence of 1‐amino‐2‐naphthol‐4‐sulfonic acid (ANSA) in p‐toluenesulfonic acid (PTSA) as an external dopant. The presence of ? SO₃H groups in the ANSA comonomer allows the copolymer to acquire intrinsic protonic doping ability. The polymerization mechanism was investigated by analysing the ¹H NMR, ¹³C NMR, Fourier transform infrared and X‐ray photoelectron spectra of the copolymers and homopolymers, which revealed the involvement of ? OH/? NH₂ in the reaction mechanism. Scanning and transmission electron microscopy showed how the reaction route and the presence of a dopant can affect the morphology and size of the polymers. Static decay time measurements were also carried out on conducting copolymer films prepared by blending of 1 wt% of copolymers of ANSA and aniline with low‐density polyethylene (LDPE) which showed a static decay time of 0.1 to 0.31 s on dissipating a charge from 5000 to 500 V. CONCLUSION: Copolymers of ANSA with aniline were synthesized in different reaction media, leading to the formation of nanotubes and nanoparticles of copolymer. Blends of 1 wt% of PTSA‐ and self‐doped copolymers of ANSA and aniline with LDPE can be formulated into films with effective antistatic properties. Copyright © 2009 Society of Chemical Industry     

Fabrication of super water repellent silver flake/copolymer blend films and their potential as smart fabrics

A facile technique is demonstrated for the fabrication of super water repellent co‐polymer blend‐silver composite films from fatty acid surface functionalized fine silver flakes. Initially, high concentrations of surface functionalized silver flakes were dispersed in poly(vinyl chloride‐co‐vinyl acetate‐co‐vinyl alcohol) copolymer in solution to form electrically conducting adhesives/paints (ECAs) with a bulk resistivity of ∼3 × 10⁻⁵ Ω cm. The solvent‐borne ECAs were then blended with a water‐dispersed perfluoromethacrylate copolymer (Zonyl 8740) using a simple solvent‐inversion process to obtain super water‐repellent colloidal copolymer blend‐silver emulsions. The colloidal emulsions could be spray‐deposited on a number of fibrous substrates including fabrics and paper. A particular example is demonstrated herein by spray‐depositing these emulsions onto molten paraffin wax‐based laminates (60°C), which were partially impregnated into fabrics to fabricate highly water repellent, flexible, and thermoresponsive fabrics. A paraffin wax/polyolefin blend base film was used for the purpose. The surface topology of the superhydrophobic copolymer/silver composite films displayed fractal‐like hierarchical structures ideal for self‐cleaning hydrophobicity. On relatively low‐absorbent permeable porous surfaces such as cellulosic films (paper) impregnated with wax/polyolefin films, self‐cleaning ability of the coatings was maintained even for temperatures at which paraffin wax component of the laminated film was molten indicated by low‐water roll‐off angles. Hence, the composites have excellent compatibility with organic phase change materials such as paraffin wax and wax/polyolefin blends, and they can be used to fabricate nonwetting, thermoregulated, and electroactive fabrics. Antimicrobial properties of silver offer additional advantages for potential biomedical applications. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Influence of nitrate ions on silver electrocrystallization

The influence of nitrate anions on the reduction of silver ions on a silver cathode from a silver nitrate solution was studied with three different experimental methods: potentiokinetic curves, chronopotentiometry and impedance measurements. It was concluded that charge transfer of the Ag⁺ ions is certainly not the rate determining step of the reaction. It was clearly shown with the three methods that an increase in the nitrate ion concentration activates the reduction of the Ag⁺ ions; the overvoltage of the reaction decreases markedly. With the aid of an equivalent circuit it is possible to quantify the activation of the electrode, in particular through the determination of the charge transfer resistance and the resistance and the capacity of adsorbed species.     

Synthesis of highly conducting nylon-6 composites and their electrical properties

Highly conducting nylon-6 composites are synthesized by exposing nylon-6 films or fabrics impregnated with an oxidizing agent, cupric chloride, simultaneously to aniline and hydrochloric acid vapors. The conductivity of composite films reaches up to 10^?2 S/cm and can be controlled by varying the experimental conditions for the composite synthesis. The effects of the concentration of cupric chloride, exposure time to aniline and hydrochloric acid vapors, and concentration of hydrochloric acid to the polyaniline content and the conductivity of nylon-6/polyaniline composites are analyzed by means of statistical F test. The morphology change of composite films resulting from the synthesis conditions, conductivity in relation to the morphology, and stability of conductivity to ambient air exposure have been investigated.     

Preparation and properties of polyimide/silver foams using a direct ion exchange method

A novel polyimide/silver (PI/Ag) foam was prepared by isocyanate foaming and direct ion exchange between Ag⁺ ions from silver nitrate and the H⁺ ions in the carboxyl (–COOH) groups of the polyamide molecular chain. The microstructures, chemical and phase composition of the PI/Ag foams were tested by SEM, FT-IR and XRD. The properties were tested by TG, DSC and UV spectrophotometer. The effects of different Ag contents on the microstructures and properties were analysized. SEM results showed that the PI/Ag foams had present the opened-cells type. With the increase in the Ag⁺ ions contents, both the amount of silver particles and the UV reflectivity of the PI/Ag foams increased, as the size of silver particles decreased. FT-IR test results show that the introduction of the silver nano-particles have no significant effect on the chemical structure of the PI foams. XRD results indicate that the silver nano-particles are face-centered cubic structure and have good crystalline properties. Thermal tests results show that the PI/Ag foams maintain the excellent thermal stability. Based on the above experimental results, the reaction mechanism during the foaming and curing process were also analysized.     

Novel antibacterial composite of coal/LLDPE loaded with silver ions

A novel antibacterial composite of coal/LLDPE (linear low density polyethylene) loaded with silver ions (ACCPE) was prepared by means of solid–liquid phase adsorption and extrusion. The composite was characterized by IR, XRD and SEM, and the mechanical, rheological, and Ag⁺‐releasing, and antibacterial properties of the composite were investigated. We discover that the ACCPE shows favorable mechanical properties, features a higher processability and antibacterial activity, and the coal and silver ion possess superimposed effect on antibacterial activity against Escherichia coli. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

A convenient approach to synthesize stable silver nanoparticles and silver/polystyrene nanocomposite particles

In this study, silver nanoparticles were prepared by the reduction of silver nitrate in SDS+ isopentanol/styrene/H₂O reverse microemulsion system using sodium citrate as reducing agent. The Ag/PS nanocomposite particles were prepared by in situ emulsion polymerization of the styrene system containing silver nanoparticles that did not separate from the reaction solution. The polymerization dynamic characteristic was studied, at the same time, silver nanparticles and the encapsulation of composite particles were characterized by Fourier‐transform‐infrared spectroscopy (FTIR), transmission electron microscopy (TEM), X‐ray diffraction (XRD) measurement, UV–vis diffuse reflectance spectroscopy, and X‐ray photoelectron spectroscopy (XPS). The results of TEM and UV–vis absorption spectra showed that well‐dispersed silver nanoparticles have a narrow size distribution. XRD showed that Ag and Ag/PS nanocomposite particles were less than 10 and 20 nm in size, which is similar to those observed by TEM. The results of XPS spectra revealed that the microemulsion system can stabilize the silver nanoparticles from aggregation and provided supporting evidence for the polystyrene encapsulated silver nanoparticle structure. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008.     

Synthesis and applications of polyacrylamide gels catalyzed by silver nitrate

Polyacrylamide gels are widely used as matrices for biomolecular analysis and fractionation, and they are being developed as biomaterials for diverse medical and industrial applications. This study reports silver nitrate as a novel catalyst for the synthesis of polyacrylamide gels from acrylamide and N,N‐methylene bisacrylamide monomers. The conditions were defined for silver‐catalyzed, free‐radical‐induced polymerization, and a suitable buffer system was devised for the electrophoretic resolution of nucleic acids. A silver‐staining procedure was modified for these gels, and they were compared with N,N,N′,N′‐tetramethylethylenediamine‐catalyzed gels for sensitivity and gel background. Silver nitrate and ammonium persulfate at final concentrations of 100 and 625 μg/mL, respectively, polymerized the resolving gels within 20 min at room temperature. These gels exhibited antimicrobial properties. The gels with ≥10 μg/mL silver nitrate showed a zone of complete inhibition of Staphylococcus aureus growth on a Luria–Bertani agar plate. The silver‐catalyzed gels were also suitable as antigen‐ and drug‐delivery devices. Silver, acting as both a catalyst and a microbicidal agent, was better than N,N,N′,N′‐tetramethylethylenediamine for the synthesis of polyacrylamide gels as drug‐ and oxygen‐delivery devices for topical applications. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Relaxation mechanism in silver borate glasses

The electrical properties of silver ion conducting borate glasses are investigated by impedance spectroscopy in the temperature range 303–453 K. Impedance data are presented in the Nyquist plots. This representation allows the determination of the relaxation frequencies of the samples. The relaxation frequency follows an Arrhenius behavior. X-ray diffraction analysis shows that, due to the hygroscopic behavior of borate glasses, boric acid crystals are formed. In AgI-containing silver borate glasses, the β-AgI phase is formed and its structure mostly depends on the glass formation process, i.e., quenching or thermal treatment during melt quenching. In AgBr-containing glasses, a phase of AgBr is formed. The electrical properties of these glass systems can be described as a parallel RC circuit in which R represents the bulk resistance R _B and C represents the bulk geometric capacitance C _B of the sample. Impedance spectroscopy shows the Cole-Davidson type behavior. Published in Russian in Fizika i Khimiya Stekla. The text was submitted by the authors in English.