Formation Of Polyaniline Research Articles

Cr(VI) adsorption by the polyanyline and zeolite/polyaniline–sulphuric acid composite

The adsorption properties of the samples of polyaniline (PAn) and zeolite/polyaniline (Zt/PAn) composite regard to Cr(VI) have been studied. The samples of the PAn and Zt/PAn composite were prepared in the 0.5 M sulfuric acid aqueous solution by oxidative polycondensation of aniline by ammonium peroxydisulfate respectively under the presence and absence of the zeolite powder in the reaction mixture. The molar ratio of aniline to ammonium peroxydisulfate during synthesis was 1 : 1.1, while the weight ratio of aniline to zeolite was equal to 1 : 1. The formation of PAn and Zt/PAn composite was confirmed by X-ray phase analysis, FT-IR spectroscopy, thermogravimetric studies and results of electrical conductivity measurements. Analysis of the spectral, thermal and electrical properties of the synthesized samples of Zt/PAn composites showed their essential differences in relation to individual samples of the zeolite and polyaniline. It was determined that the structure of polyaniline in the synthesized samples of PAn and Zt/PAn is amorphous with insignificant inclusions of polyaniline crystallites (in the form of emeraldine salt of sulfuric acid) deposited on polycrystalline zeolite particles as carrier-matrices. Thermogravimetric studies of PAn samples and Zt/PAn composites confirmed the composition of composites and the dependence of their thermal stability on the content of natural mineral. The defined values of the specific conductivity for the synthesized samples of zeolite/polyaniline composites confirmed the presence of sulfuric acid in the composites. It is determined the availability and high efficiency of the use of PAn and Zt/PAn composites, in which polyaniline is doped by sulfuric acid during synthesis, for Cr(VI) sorption from aqueous solutions. It was demonstrated that Cr(VI) adsorption by produced samples can be described sufficiently good by Langmuir or Freundlich adsorption isotherms, while the kinetics of process is in good agreement with the model of pseudo second order. Keywords : polyaniline, zeolite/polyaniline, properties, adsorption of Cr(VI).

Structure of the polyaniline-carbon nanotube interface

The analysis of the structure and chemical state of the polyaniline/multi-walled carbon nanotube interface layer was carried out using the both methods of Near Edge X-Ray Absorption Fine Structure and X-Ray Photoelectron Spectroscopy. An analysis of the photoelectron spectra showed an increase in the content of covalently bound chlorine, which may be due to the functionalization of nanotubes during the polymer synthesis. The spectrum shows two states of the chloride anion, which are assigned to the polaron (Cl*) and bipolaron (Cl-) forms of polyaniline. The content of Cl* increases in the interface layer, which indicates an increase in its electrical conductivity. Keywords: polyaniline, multi-walled carbon nanotubes, composites, X-ray spectroscopy.

Hemin-catalyzed oxidative oligomerization of p-aminodiphenylamine (PADPA) in the presence of aqueous sodium dodecylbenzenesulfonate (SDBS) micelles.

In a previous report on the enzymatic synthesis of the conductive emeraldine salt form of polyaniline (PANI-ES) in aqueous solution using PADPA (p-aminodiphenylamine) as monomer, horseradish peroxidase isoenzyme C (HRPC) was applied as a catalyst at pH = 4.3 with H2O2 as a terminal oxidant. In that work, anionic vesicles were added to the reaction mixture for (i) guiding the reaction to obtain poly(PADPA) products that resemble PANI-ES, and for (ii) preventing product precipitation (known as the “template effect”). In the work now presented, instead of native HRPC, only its prosthetic group ferric heme b (= hemin) was utilized as a catalyst, and micelles formed from SDBS (sodium dodecylbenzenesulfonate) served as templates. For the elaborated optimal reaction conditions, complementary UV/vis/NIR, EPR, and Raman spectroscopy measurements clearly showed that the reaction mixture obtained after completion of the reaction contained PANI-ES-like products as dominating species, very similar to the products formed with HRPC as catalyst. HEPES (4-(2-hydroxyethyl)-1-piperazineethanesulfonate) was found to have a positive effect on the reaction rate as compared to dihydrogenphosphate. This work is the first on the template-assisted formation of PANI-ES type products under mild, environmentally friendly conditions using hemin as a cost-effective catalyst.

Recent advancements in synthesis, properties, and applications of conductive polymers for electrochemical energy storage devices: A review

AbstractConductive polymer (CP) research has exploded in popularity over the years, with applications ranging from nanoelectronics to material science. CPs are, for all sorts of purposes, Nobel Prize‐winning compounds, as their inventors received the Nobel Prize in Chemistry in 2000. Conducting polymers have sparked a lot of interest in academic and industrial sectors because they combine the electrical characteristics of semiconductors and metals with the typical benefits of ordinary polymers, such as ease of preparation and low cost production. Conducting polymers have also received a lot of attention because of their unique characteristics, which include customizable electrical properties, excellent optical and mechanical capabilities, ease of synthesis and manufacturing, and superior environmental durability to traditional inorganic materials. In this study, the molecular structures and behaviors of the most common forms of CPs, namely, polyacetylene, polyaniline, polypyrrole, and polythiophene and derivatives of polythiophene are discussed. The transport phenomenon that allow to understand the conduction process, are also described in this review. An in‐depth investigation of conducting polymer‐based binary, ternary, and quaternary composites with carbon‐based materials, metal oxides, transition metals, and inorganic particles is utilized to analyze their applications as supercapacitors and batteries. There are also explanations of recent advancements in their applications in the areas of energy storage systems including batteries and supercapacitors. The development of their applications in the energy storage devices such as supercapacitors, lithium, and other ‐ions batteries, as well as their current issues and future prospect to advance energy storage systems are broadly discussed. This review is intended to contribute to a better understanding of this conducting polymer and, as a result, to the development of new research areas.

Synthesis of Blend Polymer (PVA / PANI)/Copper (1) Oxide Nanocomposite: Thermal Analysis and UV-Vis Spectra Specifications

Copper (1) oxide nanoparticles together with matrix polymers of polyvinyl alcohol (PVA) and polyaniline (PANI) composite films were synthesized, as these materials are of importance in optoelectronic applications. ‎Nanoparticles of Cu2O were produced by chemical precipitation. Polymerization of aniline was carried out through polymerization in an acidic medium. Structural, thermal, and optical properties of PVA+PANI/Cu2O nanocomposite were inspected by x-ray diffraction (XRD), scanning electron microscopy (SEM), fourier-transform infrared (FTIR), differential scanning calorimeter (DSC) and ultraviolet-visible spectroscopy (UV-Vis spectroscopy). X-ray diffraction peaks at 29.53°, 36.34°, and 42.22° indicated the presence of cuprous oxide nanoparticles, having high dispersions and limited size distributions. The estimated average size of Cu2O nanoparticles was ~ 17.1525 nm. A characteristic peak at around 2θ = 18.5° was attributed to periodical parallel and perpendicular polymer chains, which denoted the formation of PANI. SEM results indicated the symmetrical dispersion of Cu2O nanoparticles inside the hybrid polymer of PVA and PANI matrix, being potentially useful for encapsulation and acting as a good capping agent. FTIR results established the formation of PANI and Cu2O with nanocrystalline nature. DSC results revealed the appearance of one single peak of Tg which decreased with Cu2O content of 4% wt, followed by an increase of that value by increasing Cu2O content up to 16%wt. Thermogram analysis of the PANI and PVA embedded with Cu2O form showed an exothermic peak at (240-292)℃ affiliated to the cross-linking reaction, while the Tm value of prepared nanocomposites is just about close to that of PVA polymer. The results indicated that there is an increase in thermal stability due to the presence of Cu2O NPS within the matrix of polymers. The distinguishing peaks at 330, 347, and 457 nm which refer to PANI are assigned to π−π* electron transitions among the benzenoid rings. The high absorption intensity of the peak at 470 nm for the blended PVA+PANI having 12% wt of Cu2O NPS is assigned due to the inter-band transitions for electrons of the core copper as well as copper oxide. This points out that the increasing quantity of Cu2O NPs leads to increases in the amounts of highly oxidized structures in PANI and decreases in the doping electrons and length of conjugation throughout the incorporation of Cu2O NPs into PANI matrix. Depending on the practical results, it can be said that these polymeric nanocomposites can be efficiently used in photovoltaic technology applications.

DFT modeling of polyaniline: a computational investigation into the structure and band gap of polyaniline

The band gaps of three forms of polyaniline (PANI) are calculated using the DFT method with the B3LYP functional and SV(P) basis set. This marks the first time that the band gap for this polymer has been calculated using this DFT method. The calculations include an investigation of the effect of varying the benzoid–quinoid structural units, the effect of increasing oligomer length, and the inclusion of Michael’s addition structures, which could be residual in the polymer depending on the chosen synthetic method. All results were compared with the experimentally determined band gap of 1.5 eV as typically reported in the literature. A commonly used structural motif of alternating benzoid–quinoid units and a ratio of 0.5:0.5 benzoid–quinoid resulted in a computed band gap of 1.9 eV. Inclusion of one extra quinoid unit gave rise to a band gap of 1.3 eV. Incorporation of a Michael’s addition structure was found to dominate the band gap calculation, yielding a localized LUMO and a band gap of 1.3 eV that was insensitive to the polymer chain length and composition.

Revisiting the Redox Transitions of Polyaniline. Semiquantitative Interpretation of Electrochemically Induced IR Bands

• Quantification of redox forms of polyaniline. • Octameric model for PANI transitions. • Back to aniline-black structures. The redox transitions of PANI in acidic medium have been monitored by a combination of cyclic voltammetry, in situ conductance and in situ FTIR spectroscopy. The results of the semiquantitative analysis strongly suggest that the classical tetrameric model of PANI does not satisfactorily describe the actual structures of the polymer at different redox states. An octameric model is revisited, with the inclusion of essential resonant structures, to provide an appropriate prediction of the relative IR intensity changes of the aromatic C C stretching (at around 1520 cm −1 ) and the quinoid C C stretching (at around 1590 cm −1 ) vibrations observed by FTIR, which are difficult to interpret by considering only 4 aniline rings. Particularly, it is found that the emeraldine state is better described as a resonance hybrid of the classical bipolaronic and semiquinoid (polaron lattice) structures, while most of the charge transferred at the onset of the second voltammetric peak comes from the additional oxidation of this hybrid, which becomes unstable in the electrochemical environment producing mineralization to CO 2 and release of soluble quinones.

Polimeryzacja aniliny w środowisku stałego pola magnetycznego

Polyaniline is an example of an electronically conducting polymer. During the oxidation of the polymer, positive charges appear in its structure, which must be compensated for e.g. by the presence of anions in the polymer layer. The form of polyaniline depends on both the degree of oxidation and the degree of protonation of the polymer, i.e. the pH of the solution. Due to the ease of electrochemical preparation of polyaniline, as well as the possibility of full control of the course of the process, the influence of the constant magnetic field (s.p.m.) on the reaction of its preparation was additionally investigated. The cyclic voltammetry (CV) method was used for this purpose. Aniline polymerization processes were carried out on platinum, plate electrodes, not insulated (A) and insulated on two different sides with Teflon, with surfaces directed parallel to the line of force of the s.p.m. (To beat). Research on the electrochemical preparation of polyaniline in s.p.m. allowed to conclude that the following factors affect the magnitude of the current in the tested process: (i) the magnitude of the magnetic induction vector B, (ii) the position of the electrode plane in relation to the direction of the vector B, (iii) the type of electrode (insulated on one side or not). Impact on the impact of s.p.m. the magnetic properties (e.g. paramagnetic, diamagnetic) of the particles participating in the electrochemical reaction, as well as their charge (+/-), also had an effect on the electrochemical polymerization processes. Based on the experimental results, the mechanism of the influence of s.p.m. was proposed. on the tested electrochemical reactions. This mechanism was based, inter alia, on the formation of the magnetohydrodynamic effect (MHD), which causes a change in the speed of transport of the reacting substances to the electrode, the magnetohydrodynamic movement of the electrolyte and the change in the kinetics of electrode processes. For the tested process, changes in the rate constants of electrochemical reactions (ks) as a result of external action of s.p.m. were around 30%.

Synthesis and Characterization of Bacterial Cellulose-Polyaniline Composite with Variation of Dopant Concentration

Polyaniline is a type of conductive polymer. Bacterial cellulose has high mechanical properties, so it can be made into polyaniline base composite materials. A stable form of polyaniline oxidation at room temperature is emeraldine base. The emeraldine base has a conductivity value of 10-6 S/cm. Dopants can change the shape of emeraldine base to emeraldine salt by protonation process. Emeraldine salt is a conductive form of polyaniline. The conductivity value of emeraldine salt is 0,03-0,07 S/cm. The addition of dopan in synthesis of polymer was carried out to determine its effect on the conductivity value. The disadvantage of polyaniline is that its mechanical properties are weak and easily brittle. Modifications are needed to improve the mechanical properties of polyaniline, one of which is the manufacture of composite. Bacterial celluloce has high mechanical properties so it can be made into polyaniline base composite materials. Synthesis of bacterial cellulose-polyaniline composites by in situ chemical polymerization methods. Syntehsis is started with BC membrane was dipped into aniline solution for about 2h with stirring at room temperature. The BC was immersed into ammonium peroxydisulfate solution for about 30m with stirring. The bacterial cellulose-polyaniline compositions obtained are black color which is characteristic of the emeraldine salt. The highest conductivity value of composite was obtained from the addition of 3,5M HCl dopant which was 4,70x10-4 S/cm. FTIR analysis of composite obtained peak of the characteristic polyanilin was conductive at 1565,92 cm-1 as C=C quinoid ring and 1442,95 cm-1 as C=C benzoid ring.

Two-Dimensional CVD-Graphene/Polyaniline Supercapacitors: Synthesis Strategy and Electrochemical Operation.

Nanocomposites of graphene materials and conducting polymers have been extensively studied as promising materials for electrodes of supercapacitors. Here, we present a graphene/polyaniline heterostructure consisting of a CVD-graphene and polyaniline monolayer and its electrochemical operation in a supercapacitor. The synthesis employs functionalization of graphene by p-phenylene sulfonic groups and oxidative polymerization of anilinium by ammonium persulfate under reaction conditions, providing no bulk polyaniline. Scanning electron microscopy, atomic force microscopy, and Raman spectroscopy showed the selective formation of polyaniline on the graphene. In situ Raman spectroelectrochemistry and cyclic voltammetry (both in a microdroplet setup) confirm the reversibility of polyaniline redox transitions and graphene electrochemical doping. After an increase within the initial 200 cycles due to the formation of benzoquinone-hydroquinone defects in polyaniline, the specific areal capacitance remained for 2400 cycles with ±1% retention at 21.2 μF cm-2, one order of magnitude higher than the capacitance of pristine graphene.

Macroporous silicon/polyaniline Schottky contacts: Fabrication and electrical characterization in air and liquid solution

The chemical and electrical properties of polyaniline/macroporous silicon heterojunction were investigated. It was found that this device is constituted by pores with an effective diameter ranging from 0.4 to 1.3 μm and length from 1.3 to 4.5 μm as established by scanning electron microscopy, while Energy-dispersive X-ray and infrared spectroscopies reveal that during polyaniline synthesis silicon oxide grows at the pore surface walls. The electrical characterization through the current-potential and impedance measurements shows non-homogeneous polyaniline formation through the samples. The modeling of the current-potential curves was performed using the thermionic model where the ideality coefficient was assumed to be dependent on the applied potential, being higher for the Schottky junctions measured through two contacts on the polyaniline/macroporous silicon surface, which was attributed to the higher thickness of silicon oxide between the two contacts at this region, as suggested by the higher flat band potential obtained from the Mott-Schottky analysis. Analogous results were achieved through the impedance electrochemical measurements. The analysis in ethanol containing low amounts of naphthalene shown an almost linear relationship between the current intensity and the naphthalene concentration (or pH level of the solution). A comparable behavior was found by plotting impedance and phase shift versus naphthalene concentration.

Chiral Charge Carriers Chiralions for Polyaniline Examined with Optical Rotation Spectroelectrochemistry

In this study, the optical active polyaniline film was examined with optical rotatory dispersion (ORD) through change in potential with spectroelectrochemical method. Polyaniline is one of the representative conducting polymers. Preparation of polyaniline is convenient because synthesis of polyaniline can perform in water medium. Conducting polymers shows electrochromism via change in the electronic state upon electrochemical redox process. Polyaniline forms various electronic states such as emeraldine base, emeraldine salt, and pernigraniline. This change allows to color tuning through electrochemical method. Further, optically active polyanilines have been synthesized in the presence of (+) or (-)-camphorsulfonic acid (CSA) by electrochemical polymerization or chemical polymerization with ammonium persulfate (oxidizing agent). Both electrochemical method and chemical method produce polyaniline through radical polymerization process. Polyaniline emeraldine salt as prepared form of polyaniline is doped with CSA, showing optical activity in the circular dichroism. In this research, we carried out to synthesis of polyaniline in the presence of optically active CSA, according to previously reported method (by Wallace et al). Here, we have found that the polyaniline thus prepared showed optically active electrochromism via electrochemical redox process in circular dichroism spectroscopy measurements. In our previous study, we calculated the ORD spectra for the polymer by Kramars - Kronich (K-K) conversion from circular dichromism. In the present research, we successfully obtained experimental data of optical rotation-spectroelectrochemical result, as a first example of optical rotation control of natural optical activity for conjugated polymers based on electrochemical method. In the case of low potential for the polymer in the electrochemical redox process, the polymer shows intense optical rotation at visible wavelength range. On the other hands, higher potential at around 1 V affords to give doping process for the polymer, resulting generation of polaron as charge carrier, which shows optical activity at near infrared region. We referred this optical charge carrier as “chiral charge carrier chiralions”. The electrochemical oxidation equivalents to electrochemical doping from the polymer. In other words, electrochemical oxidation gives electrochemical doping which results change in degree of optical rotation for the polymer. The control of optical ration for materials can be driven by magnetic field (Faraday rotation), and electric field (Kerr rotation). We propose a new phenomenon as ‘‘electrochemical optical rotation’’. The electro-conductivity of the polymer is measured with four-probe method. The polymer which is electronic doped state with (+)-CSA as electric dopant for production of radical cation (polarons) or dication (bipolarons) as charge carriers and chiral inducer for twisting main-chain. The polymer film was synthesized as followed. First, electrochemical polymerization of aniline as a monomer was carried out in excessive optically active (+)-CSA with three electrode system consisting of working electrode (indium-tin oxide coated glass), counter electrode (platinum wire), and reference electrode (SCE) in water. The polymerization reaction is rapidly progressed with formation of polymer thin film onto the counter electrode. The polymer was washed with excess amount of water, acetone. The electroactive polymer film was thus deposited on the electrode was used for optical activity measurements. Cyclic voltammetry (CV) measurements were carried out for the resultant polymer (monomer free) deposited on to the ITO coated glass electrode. The CV results with change in scan rate from 10-100 mV/s indicates electroactive. Increase of scan rate increases current density for the polymer due to increase of diffusion of ion in the electrolyte solution. Oxidation signals of the polymer are observed due to change in electronic state of the polymer. Corresponding reduction signals against oxidation process are observed, indicating reversible redox activity for the polymer. ORD measurement reveled that the polymer film thus obtained is optically active. The polyaniline can be formed helical structure due to doping of optically active CSA. We carried out in-situ ORD measurement with potential change, evaluating electrochemical driven change in optical rotation. Chemical structure of the double layer polymer is examined with Fourie transform infrared optical absorption spectroscopy measurements which reveled this polymer is polyaniline, and CSA as a dopant. Ultra-violet optical absorption measurements for the polymer film indicates intense and wide range absorptions from invisible to infrared range as charge carriers the delocalized along the main-chain, indicating the polymers are conductive materials. The advantages of the polymer film are formation of self-standing redox activity, tuning of optical activity and color coordination. This paper reports novel function of control optical rotation with electrochemical method examined with spectroelectrochemistry. This concept can be a first example as optical rotation effect of electro-optically active conducting polymers. This paper reports the charge carries of helical polyaniline as chiralions can tune via electrochemical method.

Bacterial Cellulose Reinforced Polyaniline Electroconductive Hydrogel with Multiple Weak H‐Bonds as Flexible and Sensitive Strain Sensor

AbstractHydrogel, as a promising soft material, possesses many functional advantages such as stretchability, viscoelasticity, and biocompatibility. An advanced electronic platform for strain sensor is constructed by modifying hydrogels with various doping techniques. Herein, a novel flexible conductive hydrogel is synthesized by combination of bacterial cellulose/sodium alginate/polyacrylamide with the polyaniline (BSP‐PANI) through multiple intermolecular interactions. In the obtained BSP‐PANI hydrogel system, the incorporated BC serves the function of mechanically toughening and the formation of polyaniline conducting network endows the hydrogels electrical conductivity. The assembled hydrogel strain sensor can detect electrical response under different applied strains (1–200%) and monitor human motion in real time. Therefore, it is believed that the BSP‐PANI hydrogel prepared by the feasible synergetic strategy proposed in this work has greatly diversified application in smart epidermal sensors and artificial intelligence devices.

Application of an enzymatic cascade reaction for the synthesis of the emeraldine salt form of polyaniline

The synthesis of the emeraldine salt form of polyaniline (PANI-ES) from aniline with Aspergillus sp. glucose oxidase (GOD), d-glucose, dissolved O2, and horseradish peroxidase isoenzyme C (HRPC) in the presence of large unilamellar vesicles of AOT (sodium bis-(2-ethylhexyl)sulfosuccinate) as templates at pH = 4.3 and T ~ 25 °C was investigated in a systematic way. In this cascade reaction mixture, the oxidation of aniline is catalyzed by HRPC with H2O2 that is formed in situ as byproduct of the GOD-catalyzed oxidation of d-glucose with O2. Under the elaborated experimental conditions which we considered ideal, the formation of PANI-ES products is evident, as judged by UV/Vis/NIR and EPR measurements. Comparison was made with a reference reaction, which was run under similar conditions with added H2O2 instead of GOD and d-glucose. Although the reference reaction was found to be superior, with the cascade reaction, PANI-ES products can still be obtained with high aniline conversion (> 90%) within 24 h as stable dark green PANI-ES/AOT vesicle dispersion. Our results show that the in situ formation of H2O2 does not prevent the inactivation of HRPC known to occur in the reference reaction. Moreover, the GOD used in the cascade reaction is inactivated as well by polymerization intermediates.

Preparation of proton block and highly conductive AEM by creating PANI dominated and hydrophobicity ion channels for sulfuric acid enrichment

AbstractElectrodialysis is widely used to separate and concentrate sulfuric acid from industrial wastewater. Nevertheless, owing to the proton leakage of anion‐exchange membrane (AEM), the concentration of recycled sulfuric acid is typically less than 20 wt.%. What is more, the restraining of proton leakage would sacrifice the conductivity of membrane, leading to the increasing of energy consumption (EC). In this work, a proton block and highly conductive polyaniline (PANI)/polyvinylidene fluoride (PVDF) membrane were prepared by creating PANI dominated and hydrophobicity ion channels through etching. The variations of solubility, structure, and electrical performance of membrane during etching process were investigated. As a result, the electrical performance of membrane, especially for the conductivity, was significantly improved owning to the formation of PANI dominated ion channels and spaces. Meanwhile, even the porosity and water content of etched membrane were improved, the anions were mainly migrated through molecular chains of PANI; the protons were still blocked by the hydrophobic pores. Further, the etched membranes with different porosities were used to enrich sulfuric acid (1 wt.%) through electrodialysis. As a result, the proton leakage was proved to be the major limitative factor of acid solution enrichment. By using the optimal etched membrane, concentrated acid (41 wt.%) was obtained with a less energy consume (EC), compared with commercial AEM.

Studies on Synthesis, Characterization and Transport Properties of Ta2O5 Doped Polyaniline Composites

Polyaniline (PANI) and PANI/Ta2O5 composite samples were prepared using chemical oxidative polymerization technique in the presence of hydrochloric acid (HCl) at room temperature. The effect of Ta2O5 on surface morphology and structural changes have been investigated and evaluated by X-ray diffraction (XRD) and scanning electron microscope (SEM) techniques. The XRD pattern of the PANI and PANI/Ta2O5 confirm the formation of PANI and its composite. The average crystallite size of the PANI is 2.86 nm which is increased to 46.80 nm when Ta2O5 was doped in the PANI matrix. SEM micrographs of the composite confirm the morphological changes in the composite materials. In the electrical conductivity studies, ac conductivity was carried as function of frequency and dc conductivity was studied as a function of temperature. Further to describe the dielectric properties of the PANI and composite, dielectric constant and dielectric loss was studied as a function of frequency.

Selective Formation of Polyaniline Confined in the Nanopores of a Metal-Organic Framework for Supercapacitors.

In this study, a strategy that can result in the polyaniline (PANI) solely confined within the nanopores of a metal-organic framework (MOF) without forming obvious bulk PANI between MOF crystals is developed. A water-stable zirconium-based MOF, UiO-66-NH2 , is selected as the MOF material. The polymerization of aniline is initiated in the acidic suspension of UiO-66-NH2 nanocrystals in the presence of excess poly(sodium 4-styrenesulfonate) (PSS). Since the pore size of UiO-66-NH2 is too small to enable the insertion of the bulky PSS, the quick formation of pore-confined solid PANI and the slower formation of well dispersed PANI:PSS occur within the MOF crystals and in the bulk solution, respectively. By taking advantage of the resulting homogeneous PANI:PSS polymer solution, the bulk PANI:PSS can be removed from the PANI/UiO-66-NH2 solid by successive washing the sample with fresh acidic solutions through centrifugation. As this is the first time reporting the PANI solely confined in the pores of a MOF, as a demonstration, the obtained PANI/UiO-66-NH2 composite material is applied as the electrode material for supercapacitors. The PANI/UiO-66-NH2 thin films exhibit a pseudocapacitive electrochemical characteristic, and their resulting electrochemical activity and charge-storage capacities are remarkably higher than those of the bulk PANI thin films.

Studies on Electrical and Optical Property of Polyaniline/ZnO Nanocomposites

The conducting polymer polyaniline and PANI/ZnO nanocomposites were synthesized by in-situ polymerization method at 0-5 °C temperature with ammonium persulphate as an oxidising agent. The optical band gap of PANI/ZnO nanocomposites have been studied at different weight percentage such as 10%, 30% and 50%, at room temperature. The XRD pattern confirmed the hexagonal wurtzite structure of the ZnO product. The particle size was calculated by using the Debye-Scherrer relation and it was found to be in the range of 20-50 nm. The obtained absorption spectra at 385 nm is the charectestic peak of ZnO and observed for all weight percentages of nanocomposites. The peaks occured at 300 nm and 470 nm confirms the formation of polyaniline in the nanocomposites. Further the dielectric properties such as dielectric constant, dielectric loss and AC conductivity for the PANI with PANI/ZnO composites at different weight percentages are studied as a function of frequency in the range 5 Hz–35 MHz at room temperature.

Synthesis and corrosion resistance properties of novel conjugated polymer-Cu2Cl4L3 composites

A novel conjugated polyaniline (PANI)-[Cu2Cl4(m-aminophenylbenzimidazole)3] hybrid nanocomposites were prepared by using novel benzoyl peroxide as an organic oxidant by Inverse emulsion polymerization technique. The FTIR spectra of nanocomposites revealed the vibrational bands due to N–H stretching (3437 cm−1), quinoid (1487 cm−1) and benzenoid ring stretching (1384 cm−1). The conductivity of nanocomposites increases with PANI content. TGA thermogram nanocomposites (50/50) undergoes two-step weight loss in the temperature range 38–279 °C and 279–791 °C for first and second with a mass loss of 18 and 42% respectively. Thermograms reveal that the thermal stability of pure polyaniline was slightly enhanced by the incorporation of [Cu2Cl4L3]·2H2O complex. The formation of PANI-[Cu2Cl4L3]·2H2O nanocomposite was confirmed by FESEM pictures. Potentiodynamic polarization results show that the prepared nanocomposite shows mixed type corrosion inhibitor in 0.1 M HCl on steel-316 surface.

Kinetics of peroxide bleaching of azorubin in the presence of polyaniline-mangane oxide composite (IV)

Purification of aquatic ecological systems from residues of synthetic dyes used in the textile and printing industry is an urgent problem. Researchers are successfully studying the possibilities of using Fenton and Raff reagents to decolorize aqueous solutions of dyes, they offer various compounds of metals with variable valence, whose ions can serve as catalysts for the decomposition of H 2 O 2 to HO • radicals, which are powerful oxidants. However, the separation of such homogeneous catalysts after interaction with industrial dyes is technically and economically impractical, so there is a need to create insoluble solid catalysts with high adsorption capacity, as exemplified by polymer composites polyaniline - MnO 2 . After the process of purification of water from the dye residues, the solid phase catalyst together with the adsorbed purification products is removed by filtration. We investigated the kinetics of oxidative decolorization of the synthetic dye azorubin in the presence of an adsorbent agent–polyaniline, which was used in the form of its composite with manganese (IV) oxide. The catalytic action of MnO 2 causes the decomposition of hydrogen peroxide to HO• radicals, with their participation the oxidation of dye molecules takes place, products that have almost no color are formed. The polyaniline–MnO 2 composite was synthesized by oxidative polycondensation by adding aniline to a reaction vessel containing a certain amount of MnO 2 powder, which was ground in an aqueous solution of sulfuric acid, the molar ratio of MnO 2 :An = 1:3. Infrared spectroscopy showed that the composition of the polyaniline–MnO 2 composite includes quinoid and benzoid groups of polyaniline and groups of atoms (Mn–O). A number of adsorption absorption peaks between 500 and 800 cm -1 are attributed to the oscillations of Mn–O atoms in MnO 6 octahedra, valence oscillations for quinoid and benzoid forms of PAN are traced at 1 575 and 1 495 cm -1 , peaks at 1 300 and 1 243 cm -1 belong to C–N valence oscillations of the benzoid form (secondary aromatic amine), and the peak at 1 142–1 153 cm -1 is attributed to the quinoid form of doped PAN, the peak at 800 – to the oscillations of atoms in the C–C and C–H bonds of the benzoid form of polyaniline. The kinetics of oxidative decolorization of the dye solution in the presence of equal amounts of the synthesized composite (PAN–MnO 2 ) or mechanical mixtures of the original manganese oxide with pure polyaniline (PAN+MnO 2 ) was studied by UV spectroscopy. It is shown that the rate constants of catalytic decolorization of azorubin with hydrogen peroxide (T = 20 C) when using such catalysts have numerical values of the same order (≈ 10 -5 c -1 ). Increasing the content of PAN in the mechanical mixture from (MnO 2 :PAN = 1:3; k 1 = 6,67 10 -5 s -1 ) to (MnO 2 :PAN = 1:30; k 2 = 8.17 10 -5 s -1 ) leads to some increase in the rate constant of azorubin decolorization reaction, however, in the case of the synthesized composite (MnO 2 :PAN = 1:3; k 3 = 3,17 10 -5 s -1 ) the catalysis efficiency decreases. This fact can be explained by the restriction of access of reagents to the catalytic centers on the surface of manganese oxide particles during the encapsulation of MnO 2 inside the polyaniline matrix during the synthesis of the composite. Keywords : polyaniline, composite, MnO 2 , catalysis, dye azorubin