Aniline Monomer Concentration Research Articles

Influence of the aniline concentration on the morphology and property of polyaniline nanotubes and their polymerization mechanism

Polyaniline is a kind of polymer material with excellent electrochemical performance, and it stands out among a number of conductive polymer materials owing to its low cost, easy availability of raw materials, and excellent physical and chemical properties. However, the poor processability of polyaniline impedes its broad application. Preparing nanosized structure and introducing big molecular organic acids as dopant are practical strategies to solve this problem. Here using ammonium persulfate as oxidant, sodium dodecyl sulfate as surfactant, and 3,5-dinitrobenzoic acid as doping acid, polyaniline nanotubes were successfully prepared via emulsion polymerization method and characterized by various measurements. The influence of aniline concentration on the morphology and property of the product was explored. The polymerization mechanism of polyaniline nanotubes was discussed in detail based on the analysis of the microscopic morphology. As the concentration of aniline monomer increases, the position of the characteristic absorption peak in the infrared spectrum of the polyaniline main chain remains almost unchanged, but the ratio of benzene to quinone gradually increases. Along with the increasing aniline concentration, the crystallinity of polyaniline gradually decreases from 56.21% to 40.37%. In addition, the optimal conductivity is 2.05×10−2 S/cm when the concentration of aniline monomer is 0.5 mol/L.

Polyaniline grafted pullulan: Optical, thermal, structural, and electrical characterization studies in combination withdensity functional theorycalculations

AbstractPolyaniline (PANI), a conducting polymer, has great interest for a large number of applications. However, poor processability and mechanical properties limits its usage and many methods like blending, grafting etc. are used to overcome this disadvantage. We have carried out grafting of PANI onto pullulan (PULL) via chemical oxidative polymerization technique. The percentage of grafting is favored by increasing concentration of aniline monomer. The formation of PANI is confirmed through UV–Vis spectroscopic studies. The possible grafting mechanism is studied using Fourier transform infrared spectroscopy and validated by Hartree‐Fock density functional theory (HF‐DFT) calculations. Further, thermal properties of grafted polymers are studied using differential scanning calorimetry and thermo gravimetric analysis. Using FESEM and x‐ray diffraction, structural properties of graft polymer were studied. DC electrical conductivity of grafted polymer is measured from I‐V characteristics, shows a significant conductivity which is the highlight of this work.

Enhancement of Electrical Conductivity of Polyaniline Synthesized by using Carbon Nanofiber

Carbon nanofiber (CNF) is a very useful additive for improving the performance of polymer matrix composites, but the performance has sometimes been interrupted by limits appear within composite processing. Recently, CNF based polymer composites are intensely considered as promising materials in many application fields, such as electrical devices, electrode materials for batteries, supercapacitors, sensors, etc. Among these, the electrical conductivity is always the first priority need to be considered. Polyaniline (PANI) and PANI-CNF composites are synthesized by chemical oxidative polymerization of aniline monomers in acidic media. The electrical conductivity of PANI-CNF composites were found varies with the degree of amount of CNF under the effect of multiple factors such as the concentration of aniline monomer, reaction media, oxidant, reaction temperature, reaction time, etc. The maximum electrical conductivity was found 3.7131 S/cm of the PANI-CNF composite coming from the polymerization of aniline with 0.05 g CNF. The results of the synthesis also demonstrated that CNF can be an effective material to prepare electrically conducting polymer composites with ordered nanostructures.

Polyaniline on Poly (3,4-ethylenedioxythiophene) Screen Printed Electrode as Dissolved Ammonia Sensor

Abstract Polyaniline (PANI) is a suitable material to be used as sensor for dissolved ammonia (DA) detection. PANI has conducting properties based on the fact that PANI structure contains pi (π) electron. In this study, polyaniline was synthesized from aniline monomer by cyclic voltammetry method on Poly (3,4-ethylenedioxythiophene) (PEDOT) screen printed electrode (SPE). The optimum concentration of aniline monomer was 0.5 M in 1.0 M sulphuric acid (H2SO4) which gave the highest current density (38 mAcm-2) upon electropolymerization on PEDOT SPE. The deposition of emeraldine salt (ES) of PANI was observed at +0.5 V (oxidation) and -0.2V (reduction). ES was then reacted with DA producing emeraldine blue (EB). The calibration of PANI sensors to DA solution (10 - 250 ppb) showed that the current density increased linearly with the rising trace amount of DA concentration. In terms of reproducibility, PANI sensor showed consistency in DA detection of 7.47 % deviation of mean current density readings towards 10 ppb DA solution. Here, PANI-PEDOT DA sensor was able to detect the trace DA concentration (10 ppb) which Nessler method unable to detect at this very low concentration of DA. Hence, this sensor was applied in DA detection in fish aquarium water samples. Thus, PANI-PEDOT SPE was able to perform as a DA sensor and can be further developed and commercialized for future uses.

Nanocomposite Sheets Composed of Polyaniline Nanoparticles and Graphene Oxide as Electrode Materials for High-performance Supercapacitor

Composite materials based on the combination of graphene oxide and PANI are expected not only to improve the PANI conductivity, but also relieve graphene oxide aggregation via a synergistic effect. We report an easy synthesis of a polyaniline/graphene oxide (PGO) composite with a relatively high specific capacitance by chemical oxidation polymerization. As the employ of phytic acid and increasing aniline monomer concentration, more and more PANI nanoparticles deposited into the interval between GO layers. PGO3 composite exhibits the largest specific capacitance (349 F·g-1) and PGO4 composite follows (314 F·g-1), whereas PGO has a minimal specific capacitance (206 F·g-1). The enhanced capacitance originates from the high capacitance of more PANI nanoparticles and better configuration as well as higher surface area of PGO3 and PGO4 composites for fast ion transport. The as-prepared PGO3 sheets composite with improved electrochemical performance is a promising electrode material for supercapacitor.

Effect of aniline monomer concentration on PANI electropolymerization process and its influence for applications in chemical sensors

Galvanostatic electrodeposited polyaniline thin films were studied and analysed, focusing on the influence of aniline concentration in the polymerization process and hence the answer of Extended-Gate Field-Effect-Transistor pH chemical sensor. A competition between the deposition efficiency and deposition rate was observed in the polymerization process according to aniline monomer concentration. This competition influences the structure-property relationship of polyaniline thin films. The polymerization occurred over fluorine doped tin oxide substrates and the polymerization solution contained aniline monomer in four concentrations from 0.10 to 0.25 M. The current density was 1.0 mA/cm2, the deposition time was 300 s, resulting in a deposited charge of 300 mC/cm2. The thickness of the PANI thin films presented a dual behaviour, increasing up to 121 ± 5 nm for 0.20 M (sample PANI20), and then, decreasing down to 68 ± 3 nm for 0.25 M (sample PANI25). The optical properties presented an inverse behaviour compared to the thickness, as expected, with small brightness and optical reflectance for sample PANI20, once that it is the thicker sample and absorbs more light. PANI20 presented the optimized relation between deposition rate and deposition efficiency. The sensitivity depends on chemically-sensitive film’s surface quality, which is determined by the deposition efficiency.

Fabrication of highly ordered polyaniline nanocone on pristine graphene for high-performance supercapacitor electrodes

The hybrids of pristine graphene with polyaniline were synthesized by in situ polymerizations for making a high-performance supercapacitor. The formed high-ordered PANI nanocones were vertically aligned on the graphene sheets. The length of the PANI nanocones increased with the concentration of aniline monomer. The specific capacitance of the hybrids electrode in the three-electrode system was measured as high as 481 F/g at a current density of 0.1 A/g, and its stability remained 87% after constant charge-discharge 10000 cycles at a current density of 1 A/g. This outstanding performance is attributed to the coupling effects of the pristine graphene and the hierarchical structure of the PANI possessing high specific surface area. The unique structure of the PANI provided more charge transmission pathways and fast charge-transfer speed of electrons to the pristine graphene because of its large specific area exposed to the electrolyte. The hybrid is expected to have potential applications in supercapacitor electrodes.

Facile fabrication of conductive polyaniline nanoflower modified electrode and its application for microbial energy harvesting

A facile strategy for fabrication of conductive polyaniline (PANI) nanoflower modified carbon cloth electrode was developed and its application for microbial energy harvesting was also demonstrated. By simply tuning the concentration of aniline monomer, uniformly distributed PANI nanoflowers assembled from PANI nanoflakes anchored on the surface of carbon cloth electrode were fabricated with in-situ polymerization. Electrochemical and spectral analyses indicated that the synthesized PANI nanoflower was in conductive emeraldine salt form. Electrochemical impedance spectroscopy (EIS) analysis revealed PANI nanoflower modification reduced the charge transfer resistance of carbon cloth electrode, indicating the PANI nanoflower had excellent electrochemical activity. Furthermore, the PANI nanoflower modified electrode was used as the anode of microbial fuel cells (MFC), which delivered 2.6 and 6.5 times higher voltage and power output than these of pristine carbon cloth electrode, respectively. This work provided a controllable synthesis strategy for PANI nanostructure and demonstrated its promise in microbial energy harvesting.

Preparation of pseudocapacitor electrodes via electrodeposition of polyaniline on nonwoven carbon fiber fabrics

ABSTRACTAniline has been polymerized via electrodeposition onto various nonwoven carbon fiber fabric (CFF) substrates for use as a pseudocapacitive electrochemical capacitor. Four types of CFF were initially tested for double layer capacitance before polyaniline deposition, and again for specific capacitance after deposition. A binder‐free CFF was selected for further analysis due to its high capacitance change following PANI deposition (three orders of magnitude). The aniline monomer concentration, deposition potential, and deposition time were varied and resulting materials were characterized using chrono‐potentiometry, cyclic voltammetry, and scanning electron microscopy. The deposition potential range yielding highest capacitance was found to be between 0.744 and 0.777 V. A solution concentration of 0.5M aniline at a 20 min deposition time resulted in the highest specific capacitance (>80 F/g based on total electrode mass and >300 F/g based on PANI mass) within this study. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43315.

Flexible transparent electrode based on PANi nanowire/nylon nanofiber reinforced cellulose acetate thin film as supercapacitor

Highly uniform, flexible, and transparent electrodes based on in situ polymerization of PANi nanowires on nylon nanofiber-reinforced cellulose acetate thin film substrates were reported in this study. At first, the nylon nanofibers were electrospun followed by infiltration with cellulose acetate to get highly transparent substrate. Then PANi nanowires were grown uniformly on the transparent substrate by an in situ polymerization technique. The resulting thin films showed transparency from 39% to 82% and sheet resistivity between 188 and 8700Ω/sq depending on the aniline monomer concentration. In addition, the transparent electrode exhibited outstanding toughness during bending cycles. Further, the transparent electrode showed excellent capacitive performance with specific capacitance of 402F/g. These promising results highlight the importance of PANi nanowires and nylon reinforced cellulose acetate film as potential materials for optoelectronic devices.

Effect of Electrochemical Synthesis Conditions on Capacitor Performance of Polyaniline Electrodes

Abstract: Polyaniline was electrochemically synthesized on stainless steel using sulfuric acid as the doping agent through cyclic voltammetry. The influences of the aniline monomer concentration and cycle number on electrochemical performance were investigated by cyclic voltammetry and the electrochemical impedance spectra. The results show that increasing aniline concentration leads to the increase of aniline electrochemical polymerization rate. The mass specific capacitance of polyaniline electrode increases with the increase of aniline concentration for 10 cycles and it reaches 769.55 F/g at the aniline concentration of 0.3mol/L. However, the capacitances of polyaniline prepared at different aniline concentrations display no apparent differences for 15 or 20 cycles. Furthermore, the capacitance decreases with the increase of cycling number. Electrochemical impedance spectroscopes show that the polyaniline keeps superior conducting performance in the potential range of 0.1V~0.4V

A Room Temperature Conductometric Hydrogen Sensor with Polyaniline/WO3 Nanocomposite

Polyaniline/W03 nanocomposite with high volume of W03 compared to polyaniline has been synthesized through a template-free synthetic route. Characterization of the developed nanomaterial was conducted through Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FT-IR). A conductometric transducer was fabricated and used to measure the resistance of polyaniline/W03 nanofiber films during interaction with different concentrations of hydrogen gas at room temperature. The concentration of aniline monomer to W03 was 1 to 8 on the solution. It was observed that the sensor has a stable baseline of 33.2 KO under synthetic air. A decrease in the sensitive film resistance of i .4 K!l was noticed during the Interaction with 1% H2 with 90% response time of 60 seconds. Due to the high operating temperature of ali metal oxides based gas sensors, this sensor offers low power consumption because of its room temperature operation.

Fabrication, Characterization and Application of Polyaniline-Polyelectrolyte Coated CaCO3 Microparticles Core-Shell Structure

Polyaniline(PAN) was in-situ formed around calcium carbonate(CaCO3) microparticles previously stabilized with polyelectrolyte layers(PEs),generating PAN/(PEs) 6/CaCO3 hybrid microparticles.The effects of PEs and concentration of aniline monomer on the stability and morphology of the hybrid microparticles were studied.The obtained hybrid microparticles were characterized by SEM,FT-IR,UV-Vis,etc.Furthermore,the hybrid microparticles were deposited on glassy carbon electrode,which displayed high electrocatalytical activity toward the oxidation of dopamine(DA).The oxidized peak potential was negatively shifted with a value of 130 mV,compared with that using pure CaCO3 microparticles.The modified electrode showed good reproducibility,and the relative standard deviation(RSD) was estimated to be about 4.2% in 4.0 mmol/L DA aqueous solution(n =5).The obtained hybrid microparticles have great potential in construction of biosensors.The linear range was in the range of 0.5~10.0 mmol/L,with the detection limit of 0.2 mmol/L(3 S/N).

Characterization of Reaction Intermediate Aggregates in Aniline Oxidative Polymerization at Low Proton Concentration

Aggregates of reaction intermediates form during the early stages of aniline oxidative polymerization whenever the initial mole ratio of proton concentration to aniline monomer concentration is low ([H(+)](0)/[An](0) <or= 1.0). Detailed characterization is carried out on those aggregates. The intermediate aggregates show a UV-Vis absorption peak at around 410 nm when dispersed in aqueous solution, whereas the peak is centered on 370 nm when dissolved in an organic solvent such as N-methylpyrrolidone. The electronic band gap decreases when the intermediates aggregate to form a solid, and thus, the absorption peak is red-shifted. Gel permeation chromatography (GPC) shows the aggregates contain a major low molecular weight peak with a long tail. The oligoanilines with low molecular weights consistently show a UV-Vis absorption peak at around 370 nm. Mass spectrometry confirms that the intermediate aggregates contain mainly a component with mass number 363 (M + H(+)), likely a tetramer. UV-Vis, GPC, mass spectrometry, NMR, FTIR, and XRD characterization results are presented and chemical structures for the tetramer are proposed. The major components of the intermediate aggregates are likely highly symmetric phenazine- and dihydrophenazine-containing structures. These particular organic compounds have not been identified before as intermediates. The aggregation and precipitation of the tetramers apparently stabilizes these intermediates. The aggregates are highly crystalline, as evidenced by powder X-ray diffraction. A new reaction mechanism for the formation of these intermediates is proposed.

Photocatalytic degradation of Allura red and Quinoline yellow with Polyaniline/TiO2 nanocomposite

A series of polyaniline/TiO2 (PANI/TiO2) composites has been prepared from aniline and TiO2 under various polymerization conditions. Among these conditions are the concentrations of aniline, ammonium persulfate, HCl, sodium dodecyl sulfate, and the amount of TiO2. More composites were obtained by replacing HCl with H2SO4, H3PO4, and HNO3 as dopant acids. Scanning electron microscopy, UV/vis-diffuse reflectance spectroscopy, FTIR and TGA were used to characterize some of these composites. The rate of degradation of dyes with these composites followed first-order kinetics in the dye concentration. The activity of the composite towards the degradation process differs according to the experimental polymerization conditions. The activity increased with the increase in the concentration of aniline monomer and persulfate, but decreased with increasing the concentration of HCl, sodium dodecyl sulfate, and the amount of TiO2. The activity of composites formed in the presence of different acids followed the order H2SO4>H3PO4>HCl>HNO3. The rate of composite/dye interaction was enhanced with the UV-irradiation, increasing load of composite, and temperature. It was retarded with the increase in initial dye concentration and pH. The activation parameters were determined and a plausible mechanism was proposed.

Polyaniline Nanofibers: Synthesis, Characterization, and Application to Direct Electron Transfer of Glucose Oxidase

Polyaniline nanofibers are synthesized by interfacial polymerization and confirmed by scanning electron microscopy. These nanofibers are characterized by XRD, FTIR, UV−vis spectroscopy, and voltammetry. A detailed study is conducted on the influence of a variety of synthetic conditions on the morphology of the polyaniline nanostructure. These conditions include organic solvents, acid dopants, concentration of dopants, the reaction time, and the concentration of aniline monomer and oxidant. The polyaniline nanofibers are used as an electrode substrate for immobilization and facilitating the direct electron transfer (DET) of redox proteins/enzymes with glucose oxidase (GOx) as a model. After immobilized on the nanofibers, GOx can keep its natural structure and undergoes effective DET reaction with a pair of well-defined, quasi-reversible redox peaks at −418 mV (pH 7.0, 10 mV/s). The apparent electron transfer rate constant is (6.3 ± 1.6) s−1. The GOx-nanoPANI/GC electrode displays good features in electroca...

THE CONTROLLED SYNTHESIS OF POLYANILINE MICROTUBES WITH SQUARE INNER CROSS SECTION AND POLYAZANE SQUARE MICROBARS

Controlled micro/nanostructures of polyaniline(PANI)were obtained through a chemical oxidative polymerization by changing the concentration of aniline monomer in the presence of citric acid as dopant.It was found that conducting PANI microtubes with square inner cross-section(580～300 nm in diameter and 80 nm in wall thickness) were obtained at a relatively high aniline concentration.When the solution was sufficiently dilute,the polyazane microbars with square cross-section(690～290 nm in side length and 1～40 μm in length) can be made by self-assembly.Structural characterizations of the microbars with square cross-section showed that aniline polymerized product by this method was a new material containing N—N single bonds rather than PANI,which was defined as polyazane by A.G.MacDiarmid.The aniline/citric acid salts are proposed as the templates in the formation of the microtubes with square inner cross-section and microbars with square cross-section based on XRD and SEM measurements.Interestingly,it was found that morphology and molecular structure of the microbars were strongly affected by the reaction time and the concentration of aniline.The molecular structure of the microbars with square cross-section was changed from polyazane to PANI,for instance,when the reaction time increased from 5 h to 168 h.Moreover,the microbars with square cross-section were varied from solid to hollow with square cross-section and which was accompanied by a molecular structural change from polyazane to conductive PANI when the concentration of aniline increased by one order of magnitude(from 1.75×10-2 to 1.75×10-1mol/L).

Electrochemical synthesis and characterization of chloride doped polyaniline

Chloride doped polyaniline conducting polymer films have been prepared in a protic acid medium (HCl) by potentiodynamic method in an electrochemical cell and studied by cyclic voltammetry and FTIR techniques. The FTIR spectra confirmed Cl- ion doping in the polymers. The polymerization rate was found to increase with increasing concentration of aniline monomer. But the films obtained at high monomer concentration were rough having a nonuniform flaky polyaniline distribution. Results showed that the polymerization rate did not increase beyond a critical HCl concentration. Cyclic voltammetry suggested that, the oxidation-reduction current increased with an increase in scan rate and that the undoped polyaniline films were not hygroscopic whereas chloride doped polyaniline films were found to be highly hygroscopic.