Conventional Polyaniline Research Articles

Carbon dots functionalized polyaniline as efficient sensing platform for cancer biomarker detection

Implementing simple and rapid detection of cancer biomarker using biosensors has the potential to contribute greatly to basic biological research and early detection of cancer. Tailoring of biosensor matrix based on conducting polymers has gained significant attention in recent years due to its electroactivity, redox property and biocompatibility. Herein, biomass derived carbon dots (CDs) were anchored on polyaniline (PANI) surface to get biocompatible and fluorescent, carbon dots functionalized polyaniline (CDs@PANI) that enable binding of large amount of prostate cancer biomarker, prostate specific antigen (PSA) antibody on its surface via active functional groups. Immobilization efficiency of CDs@PANI was investigated by electrochemical methods which revealed dense immobilization of biomolecules on CDs@PANI as compared to conventional PANI. A sandwich electrochemical biosensor was constructed using CDs@PANI as immobilization matrix for detection of prostate cancer biomarker PSA. The sensor displayed good sensitivity, specificity, stability, reproducibility, wide linear range (0.01–60 ng/ml) and a low detection limit of 20 pg/ml. The importance of CDs in improving the sensor performance was demonstrated by carrying out detailed electrochemical studies using glucose oxidase as a model biomolecule. Biocompatibility of sensing matrix was assessed by performing 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay for cell viability using WI26 cells. The sensing platform demonstrated herein provides great potential for the detection of different cancer biomarkers and metabolites.

Sulfuric acid-doped conjugated microporous poly(aniline)s enabled unconventional Hg (II) adsorption from aqueous solution

New strategies are required to modify adsorbents that possess numerous accessible chelating sites with high utilization, in order to achieve both rapid uptake and high capacity for the contaminants, which are still urgently needed. This study introduces a novel integration of a conjugated microporous polymer (CMP) material with conventional polyaniline, representing the first instance of such a combination. By amalgamating the doping properties of polyaniline with the highly stable structure and extensive microporous attributes of CMP, we achieve a synergistic effect. The conjugated microporous polyaniline is subjected to a concentrated sulfuric acid modification (SD-CMPA), enabling simultaneous oxidation, doping, and pore channel modification in a single step. The resulting SD-CMPA exhibits a record-breaking maximum adsorption capacity for Hg2+, reaching as high as 1720 mg·g−1, as well as a benchmark distribution coefficient of 2.5 × 108 mL·g−1. Moreover, it demonstrates robust reusability, retaining over 96% of its adsorption capacity for at least six cycles. These remarkable features enable the achievement of ultra-deep-water purification to 0.452 ppb in an effective manner. The impressive performance of SD-CMPA can be attributed to the abundance of nitrogen-containing groups, particularly the tertiary amine nitrogen in the material skeleton, as supported by X-ray photoelectron spectroscopy and density functional theory calculations. The results presented in this study demonstrate the exceptional potential of SD-CMPA for high-performance environmental remediation.

Redox-labelled detection probe enabled immunoassay for simultaneous detection of multiple cancer biomarkers.

Some of the cancer biomarkers often lack specificity and sensitivity; thus, simultaneous detection of multiple biomarkers can make the diagnosis more accurate. Also, simple sensing system without utilization of extra reagents like mediator or substrate during detection event is desirable for point-of-care testing. To address this, mediator and substrate-free amperometric biosensor for simultaneous detection of cancer biomarkers carcinoembryonic antigen (CEA) and alpha-fetoprotein (AFP) have been demonstrated by designing two different redox-labelled detection probes. Colloidal nanoparticles of polyaniline-pectin conjugated with AFP antibody along with ferrocene and silver nanoparticles conjugated with CEA antibody along with anthraquinone were used as redox probes to bind with AFP and CEA during the detection event. Sensor constructed using carboxylic acid tethered polyaniline as immobilization matrix displayed 5 times wider linear range than conventional polyaniline for AFP and CEA detection by sandwich electrochemical assay. The detection limit was 30pgmL-1 for AFP and 80pgmL-1 for CEA. The biosensor displayed appropriate sensitivity, good specificity, and negligible cross-reactivity between the two targets. The proposed sensor was used to determine APF and CEA in human blood serum. The strategy demonstrated can be further extended for detection of panel of cancer biomarkers by designing appropriate redox probes.

Electrochemical properties of aluminum ion batteries with emeraldine base polyaniline as cathode material

Aluminum ion batteries (AIBs) are currently attracting widespread interest due to their high capacity, low price and high safety, while practical applications are severely hampered by the lack of suitable cathodes and the relatively complex and divergent energy storage mechanisms. Polyaniline has shown considerable promise for application in various rechargeable batteries, however, little research has been conducted on the application to AIBs. Here, the emeraldine base polyaniline (PANI) using a chemical oxidation method is synthesized and then assembled in an Al/PANI cell with a chloroaluminate ionic liquid as the electrolyte. Compared with the conventional protonated polyaniline cathode, the PANI cathode shows better electrochemical performance during the 0–2.4 V charging/discharging process, exhibiting a discharge specific capacity of 155 mAh g-1 at a current density of 1 A g -1and capacity retention of 80% after 2000 cycles. Meanwhile, ex-situ characterization reveals a novel conversion process of this system different from that of conventional proton-doped polyaniline materials, in which the electrolyte is spontaneously complexed with the PANI cathode. This is followed by reversible doping of the chloroaluminate anion in the –NH- group of the PANI-AlCl3 complex, yielding high reversible capacity and long cycle life. These findings have made new attempts and laid the foundation for the development of high-performance aluminum ion batteries with conducting polymers as the cathode material and further clarification of their charge storage and reaction mechanisms.

Assembly of symmetric supercapacitor based on alginate hydrogel electrolyte and polyaniline modified electrodes

Biopolymer-based hydrogel electrolytes can be described as alternative materials for supercapacitors due to their good ionic conductivity, no liquid leakage, and no toxicity, allowing the construction of flexible devices. This work reports the preparation of alginate gels crosslinked with Ca2+, H+, and a combination of Ca2+ and H+, for use as electrolytes in a symmetric supercapacitor with polyaniline (PANI) films as electrodes. Results indicated that the gel formed with both Ca2+ and H+ showed to be the most appropriate for supercapacitor development for presenting the better electrochemical performance of PANI electrodes, higher values of ionic conductivity and capacitance, also presenting good cycling stability. The symmetrical supercapacitor assembled with the alginate gel and conventional PANI electrodes provided a specific capacitance of 15.08 F g−1 at 0.05 mA cm−2 and exhibited good cycling stability with 92% capacitance retention after 1100 cycles. Three supercapacitor devices fabricated with 3D printing were connected in series and used to power a red LED.

Brush-like Polyaniline with Optical and Electroactive Properties at Neutral pH and High Temperature.

In this research, a brush-like polyaniline (poly(2-acrylamide-2-methyl-1-propanesulfonate)-g-polyaniline)-b-poly(N-vinylcarbazole) (BL PAni) was developed as a strategy to overcome the limited processability and dedoping above pH 4 of conventional polyaniline (PAni). For the BL PAni synthesis, RAFT polymerization (homopolymer), RAFT-mediated surfactant-free emulsion polymerization (block copolymer), and interfacial oxidative polymerization were applied to graft the PAni chains. NMR and FT-IR spectroscopies were performed to confirm the structural elucidation of the reaction pathways, while the thermal properties were analyzed by TGA and DSC. Notably, the BL PAni presents absorption throughout the visible region and up to the near-infrared, showing dedoping resistance at up to 80 °C and at a neutral pH. The absorption range of the BL PAni, block copolymer, and homopolymer were studied by UV–Vis spectroscopy in solid-state and dispersion/solution, highlighting BL PAni and poly(anilinium 2-acrylamide-2-methyl-1-propanesulfonate)-b-poly(N-vinylcarbazole) (PAAMP-b-PVK) due to the π-stacking between the anilinium and carbazole groups. The cyclic voltammetry confirmed the persistence of electroactivity at a pH near 7.

Carboxylic acid-tethered polyaniline as a generic immobilization matrix for electrochemical bioassays.

Polyaniline (PANI) was functionalized by thiol-ene click chemistry to obtain carboxylic acid-tethered polyaniline (PCOOH). The versatility of PCOOH as an immobilization matrix was demonstrated by constructing four different biosensors for detection of metabolites and cancer biomarker. Immobilization efficiency of PCOOH was investigated by surface plasmon resonance and fluorescence microscopic analysis which revealed dense immobilization of biomolecules on PCOOH as compared to conventional PANI. A sandwich electrochemical biosensor was constructed using PCOOH for detection of liver cancer biomarker, α-fetoprotein (AFP). The sensor displayed sensitivity of 15.24 µA (ng mL-1)-1cm-2, with good specificity, reproducibility (RSD 3.4%), wide linear range (0.25-40ngmL-1) at - 0.1V (vs. Ag/AgCl), and a low detection limit of 2pgmL-1. The sensor was validated by estimating AFP in human blood serum samples where the AFP concentrations obtained are consistent with the values estimated using ELISA. Furthermore, utilization of PCOOH for construction of enzymatic biosensor was demonstrated by covalent immobilization of glucose oxidase, uricase, and horseradish peroxidase (HRP) for detection of glucose, uric acid, and H2O2, respectively. The biosensors displayed reasonable sensitivity (50, 148, 127 µA mM-1cm-2), and linear ranges (0.1-5, 0.1-6, 0.1-7mM) with a detection limit of 10, 1, and 8µM for glucose, uric acid, and H2O2, respectively. The present study demonstrates the capability of PCOOH to support and enable oxidation of H2O2 generated by oxidase enzymes as well as HRP enzyme catalyzed reduction of H2O2. Thus, PCOOH offers a great promise as an immobilization matrix for development of high-performance biosensors to quantify a variety of other disease biomarkers. Carboxylic acid-tethered polyaniline synthesized by thiol-ene click chemistry was used as matrix to construct four different electrochemical biosensors for detection of cancer biomarker α-fetoprotein, glucose, uric acid, and H2O2.

Preparation of porous polyaniline/RGO composite and its application in improving the electrochemical properties of Co9S8 hydrogen storage alloy

The sea urchin-like porous polyaniline (PPANI) is prepared by a facile saturated solution synthetic route. The porous polyaniline/reduced graphene oxide composite (PPANI/RGO) is synthesized via a solution-assisted self-assembly method. Mechanical alloying is used to obtain the Co9S8 alloy. Composites of Co9S8 mixed with PPANI and PPANI/RGO are fabricated through ball-milling to improve the electrochemical performance of Co9S8 alloy. The structures and morphologies of the composite alloys are studied by XRD, SEM and BET. The electrochemical properties of alloys are tested as negative electrodes of Ni-MH batteries by the LAND CT2001A tester and three-electrode system. For comparison, Co9S8 alloys doped with conventional polyaniline (CPANI) and RGO are also prepared. Ultimately, the Co9S8 + PPANI composite shows preferable discharge capacity compared with CPANI modified Co9S8 and matrix alloy. In addition, the PPANI/RGO composite modified Co9S8 electrode exhibits superior discharge capacity than separate PPANI and RGO coated alloys. A maximum discharge capacity (701.4 mAh/g) is achieved for Co9S8 + PPANI/RGO electrode. Furthermore, the Co9S8 + PPANI/RGO composite materials exhibit preferable high-rate dischargeability, improved corrosion and oxidation resistance and excellent kinetics properties. The PPANI material with special porous structure and unique morphology displays better performance than CPANI. Moreover, a synergistic effect between PPANI and RGO species in the PPANI/RGO material may provide a rapid passageway for charge transfer and accelerate the hydrogen transmission. Accordingly, the electrochemical activity and kinetic properties are improved for Co9S8 + PPANI/RGO composite electrode.

Enhanced Storage Performance of PANI and PANI/Graphene Composites Synthesized in Protic Ionic Liquids.

Polyaniline (PANI) was synthesized using oxidative polymerization in a mixture of water with pyrrolidinium hydrogen sulfate [Pyrr][HSO4], which is a protic ionic liquid PIL. The obtained PANI (PANI/PIL) was compared with conventional PANI (PANI/HCl and PANI/HSO4) in terms of their morphological, structural, and storage properties. The results demonstrate that the addition of this PIL to a polymerization medium leads to a fiber-like morphology, instead of a spherical-like morphology, of PANI/HSO4 or an agglomerated morphology of PANI/HCl. In addition, PAN/PIL exhibits an improvement of the charge transfer kinetic and storage capability in H2SO4 1 mol·L−1, compared to PANI/HCl. The combination of PANI/PIL and graphene oxide (GO), on the other hand, was investigated by optimizing the PANI/GO weight ratio to achieve the nanocomposite material with the best performance. Our results indicate that the PANI/PIL/GO containing 16 wt% of GO material exhibits a high performance and stability (223 F·g−1 at 10 A·g−1 in H2SO4 1 mol·L−1, 4.9 Wh·Kg−1, and 3700 W·Kg−1 @ 10 A·g−1). The obtained results highlight the beneficial role of PIL in building PANI and PANI/GO nanocomposites with excellent performances for supercapacitor applications.

Synthesis of the novel binary composite of self-suspended polyaniline (S-PANI) and functionalized multi-walled carbon nanotubes for high-performance supercapacitors

To push the upper limit of capacitive materials, the integration of multi-modal capacitive materials has emerged as a potential solution. In this regard, we reported the novel binary composite of self-suspended polyaniline (S-PANI) and multi-walled carbon nanotubes (MWNTs). Compared with conventional polyaniline, S-PANI offers higher porosity and fibrillar polymeric network, which was achieved by doping long-chain protonic acid during in situ polymerization. S-PANI was loaded on oxidized carbon nanotubes (OCNTs) and sulfonated carbon nanotubes (SCNTs) to prepare S-PANI/OCNT and S-PANI/SCNT composite electrodes, respectively. The conductive and exclusive fibrillar S-PANI provide unobstructed channels for charge transport and electrolyte infiltration. Preliminary electrochemical studies revealed that the capacitance of the composite electrode reached 316.8 F g−1 and 345.4 F g−1, and established exceptional capacitance retention rates of 92.8% and 93.7% after 5000 cycles for S-PANI/OCNT and S-PANI/SCNT composite, respectively, making it a potential candidate for imminent energy storage devices.

Interfacial growth of free-standing PANI films: toward high-performance all-polymer supercapacitors.

Along with high power capability and energy density, long cycle life is regarded an essential performance requirement for energy storage devices. The rapid capacitance decline of conducting polymer-based electrodes remains a major technical challenge and precludes their practical applications in supercapacitors. In this work, a polyaniline (PANI) network is synthesized via interfacial Buchwald–Hartwig polymerization for the first time, facilitating the construction of covalently connected PANI networks by ligand-promoted C–N bond formation. Particularly, the interfacial synthesis and subsequent gas release from pre-anchored protecting groups allow bottom-up and efficient access to porous cross-linked PANI (PCL-PANI) films that are free-standing and solvent-resistant. Upon assembling into supercapacitors, the PCL-PANI material enables an unprecedent long-term charge–discharge cycling performance (>18 000 times) without clear capacitance loss for an additive-free pseudocapacitive system. In addition, this synthesis affords electrodes entirely consisting of conducting polymers, yielding highly reversible gravimetric capacitance at 435 F gelectrode−1 in a two-electrode system, and a high gravimetric energy of 12.5 W h kgelectrode−1 while delivering an outstanding power density of 16 000 W kgelectrode−1, which is 10-fold higher than those of conventional linear PANI composite supercapacitors. This synthetic approach represents a novel and versatile strategy to generate additive/binder-free and high-performance conducting thin-films for energy storage.

Electrochemical polymerization of para-chloroaniline as highly redox-active poly(para-chloroaniline) on graphitized mesoporous carbon surface

Owing to the high demand of conducting molecular systems for various electronics and technological applications, development of new polyaniline (PANI)/carbon nanomaterial is a continued research interest in cross-disciplinary area of material chemistry. In the literature, for the preparation of PANI/carbon nanomaterial composite electrode systems ex-situ preparation method, in which, chemical oxidation of aniline in presence of carbon nanomaterial, followed by modification on solid substrate has been widely adopted. In this work, a systematic study has been carried out for in-situ electrochemical polymerization of 4-chloroaniline and other substituted aniline monomers to respective PANI on graphitized mesoporous carbon (GMC), that show porous structure and enormous sp2 sites to aniline and PANI for π-π interaction, unusually in neutral pH condition. The new GMC@PANI modified electrode showed a highly redox active peak at Eo’ = 0.12 V vs Ag/AgCl in pH 7 phosphate buffer solution. No such behaviour was noticed when an unmodified glassy carbon was used as working electrode for the polymerization in the above mentioned condition. The redox peak is found to be stable, surface-confined and Nernstian type of proton-coupled electron-transfer in nature. Based on the physicochemical characterization techniques using Raman, IR, X-Ray photoelectron-spectroscopy, scanning electron-microscope and scanning electrochemical microscope (SECM) instruments and electrochemical studies with several ortho, para and meta substituted aniline monomers, mechanism for the in-situ polymerization has been revealed that 4-chloroaniline monomer has undergone a surface-confined electrochemical oxidation reaction with involvement of aniline(4-Cl)-cation radical species, anti-orientation of the monomer (that exist in solution phase), head-to-tail collision (C-N bonding), ejection of the para-substituents as Cl- and Cl•, partial chlorination and PANI(4-Cl) formation mechanism. Such a PANI(4-Cl) film showed a wave-like 2D molecular film structure with enhanced redox and electrical property over the conventional PANI system.

Synthesis of novel fluorescent molecule and its polymeric form with aniline as fluorescent and supercapacitor electrode materials

AbstractIn this study, a fluorescent material, 2‐naphthyl‐4‐amino benzoate, is synthesized by the esterification of 4‐aminobenzoic acid with 2‐naphthol. This molecule is used in the bulk polymerization of aniline, which results in the formation of poly(aniline‐2‐naphthyl‐4‐aminobenzoate). For comparison, polyaniline and also poly(aniline‐4‐aminobenzoic acid) salts are prepared via bulk polymerization. Formation and properties of these polymeric materials are evaluated by Fourier‐transform infrared (FT‐IR), 13C nuclear magnetic resonance, matrix‐assisted laser desorption ionization, UV‐Vis, Fluorescence, X‐ray diffraction (XRD), Field emission‐scanning electron microscopy (FE‐SEM), Differential scanning calorimetry (DSC), thermogravimetric analysis, electrical resistance and electrochemical techniques. P(ANI‐2NA4ABA) is obtained in nanofiber morphology in 106 wt% yield with respect to the amount of aniline used with comparable conductivity of conventional polyaniline salts. This polymer salt is stable up to 220°C and indicates melting at 146°C on heating and crystal formation at 128°C on cooling. This polymer shows higher wavelength fluorescence compared to the conventional polyaniline salts. This polymer is used as an electrode material without binder, which shows a specific capacitance of 360 F g−1 at 0.25 A g−1.

Photocatalytic and Oxidative Synthetic Pathways for Highly Efficient PANI-TiO2 Nanocomposites as Organic and Inorganic Pollutant Sorbents

Polyaniline (PANI)-materials have recently been proposed for environmental remediation applications thanks to PANI stability and sorption properties. As an alternative to conventional PANI oxidative syntheses, which involve toxic carcinogenic compounds, an eco-friendly procedure was here adopted starting from benign reactants (aniline-dimer and H2O2) and initiated by ultraviolet (UV)-irradiated TiO2. To unlock the full potential of this procedure, we investigated the roles of TiO2 and H2O2 in the nanocomposites synthesis, with the aim of tailoring the properties of the final material to the desired application. The nanocomposites prepared by varying the TiO2:H2O2:aniline-dimer molar ratios were characterized for their thermal, optical, morphological, structural and surface properties. The reaction mechanism was investigated via mass analyses and X-ray photoelectron spectroscopy. The nanocomposites were tested on both methyl orange and hexavalent chromium removal. A fast dye-sorption was achieved also in the presence of interferents and the recovery of the dye was obtained upon eco-friendly conditions. An efficient Cr(VI) abatement was obtained also after consecutive tests and without any regeneration treatment. The fine understanding of the reaction mechanism allowed us to interpret the pollutant-removal performances of the different materials, leading to tailored nanocomposites in terms of maximum sorption and reduction capability upon consecutive tests even in simulated drinking water.

Thermal behavior of functionalized conventional polyaniline with hydrothermally synthesized graphene/carbon nanotubes

Conventional polyaniline (PANI) was mixed as a binder polymer matrix with carbonous materials. Hydrothermal technique was utilized to fabricate a nanocomposite of graphene (G)/carbon nanotubes (CNTs). The morphological features and quality of the synthesized PANI, G/CNTs, and their mixtures were investigated. Scanning electron microscopy (SEM) images confirm the formation of wide area graphene sheets with folds around the edges. In addition, the hydrothermally fabricated G/CNTs exhibited a uniform distribution with partial agglomeration. However, adding their mixture to PANI generated a mesh like porous morphology which demonstrates an enhancement in surface area and providing 3D conduction network. Moreover, Raman spectra confirm the quality of the synthesized samples. The generated disorder and defects within the structure, and the ratio of quinoid ring (Q) to benzenoid (B) ring in the fabricated samples were depicted. In addition, the enhancement in thermal parameters and reversing the thermo-electric carrier type into N-type after doping were attributed to the generated facile conduction paths of G/CNTs.

Electrochemical and X-ray photoelectron spectroscopic investigations of conductive polymers

We report the synthesis of high soluble poly(aniline-co-o-hydroxyaniline) copolymers with varying the amount of o-hydroxyaniline (20, 40, 60, and 80 %) and referred as PA-co-o-HA20, PA-co-o-HA40, PA-co-o-HA60, and PA-co-o-HA80 respectively. The chemical and structural composition of the polymers and copolymers were determined by XPS, UV–Vis, and FE-SEM analysis. Electrochemical studies of the as-prepared polymers showed two single-electron oxidations and two single-electron reductions reversibly at various scan rates ranging from 20 to 50 mV and results reveals that the current density of the copolymer was lesser than the conventional polyaniline (PA). This is due to increasing the hydroxyl (-OH) branching on the polymer backbone in the polymer chain. The current density decreases from PA-co-o-HA20 to PA-co-o-HA80 by increasing the weight percentage of o-hydroxyaniline in the polymeric backbone.

Redox-Active Gel Electrolyte Combined with Branched Polyaniline Nanofibers Doped with Ferrous Ions for Ultra-High-Performance Flexible Supercapacitors.

In this work, the effects of utilizing an Fe2+/Fe3+ redox-active electrolyte and Fe2+-doped polyaniline (PANI) electrode material on the performance of an assembled supercapacitor (SC) were studied. The concentration of the redox couple additive in the electrolyte of the SC was optimized to be 0.5 M. With the optimized concentration of 0.4 M Fe2+, the doped PANI branched nanofibers electropolymerized onto titanium mesh were much thinner, cleaner, and more branched than normal PANI. A specific capacitance (Cs) of 8468 F g−1 for the 0.4 M Fe2+/PANI electrode in the 1 M H2SO4 + 0.5 M Fe2+/Fe3+ gel electrolyte and an energy density of 218.1 Wh kg−1 at a power density of 1854.4 W kg−1 for the resultant SC were achieved, which were much higher than those of the conventional PANI electrode tested in a normal H2SO4 electrolyte (404 F g−1 and 24.9 Wh kg−1). These results are among the highest reported for PANI-based SCs in the literature so far and demonstrate the potential effectiveness of this strategy to improve the electrochemical performance of flexible SCs by modifying both the electrode and electrolyte.

Chiral polyaniline with superhelical structures for enhancement in microwave absorption

Chiral polyaniline (PANI) with superhelical structure is successfully synthesized via in situ polymerization using chiral acid as dopant and self-assembly technique. The morphology and structure were characterized by scanning electron microcopy, transmission electron microscopy, fourier transform infrared spectra, circular dichroism, X-ray diffractometer and X-ray photoelectron spectra, which demonstrate polyaniline has chirality and superhelical structure. A possible formation process of the superhelical structure was also discussed. The microwave absorption properties of superhelical chiral PANI was investigated in the frequency range of 2–18 GHz. The results indicated that the superhelical chiral PANI exhibit substantially enhanced electromagnetic losses compared to conventional PANI. The minimum reflection loss (RL) of the superhelical chiral PANI can reach −31.7 dB at 11.7 GHz, and the bandwidth less than −10 dB is 3.8 GHz with absorber thickness of 1.7 mm. The enhanced microwave absorbing property can be attributed to multi-loss mechanisms, good impedance matching and the cross-polarization effects resulting from the superhelical structure and chirality.

Impedance Analysis of Polyaniline in Comparison with Some Conventional Solid Electrolytes.

Doped polyaniline (PANI) is well-known as an electronic (polaronic) conductor and mostly is used as semiconductor in various applications. However, in the literature there are examples of employment of the acid doped form of PANI as electrolytic filler in proton exchange membranes. In order to distinguish between two types of conduction, in the present study powdered samples of polyaniline, either in the form of emeraldine base (PANI-EB) or in the form doped with camphorsulfonic acid (PANI-CSA), were investigated using impedance spectroscopy both in the dry state and in contact with liquid water. The obtained spectra were compared with the spectra of such conventional solid electrolytes, as zeolites X and ZSM5 and a strong electrolyte boron orthophosphate, acquired in identical conditions. The most important dissimilarity between conventional electrolytes and PANI was that ion diffusion dominates in the impedance response of the formers, whereas the behavior of PANI is under control of electron/hole displacement and the diffusion part is quite inessential. This corroborates the results of analysis of temperature dependence of PANI conductivity, which revealed values of activation energy twice as large as typical solid electrolytes. Equivalent circuits, simulating the impedance responses of all materials, were built up and used to estimate a possible diffusion coefficient of cations in the comparable solids. It was found that the diffusion in a strong electrolyte such as BPO4 is ∼2 orders of magnitude faster than evaluated for zeolites and ∼4 orders higher than what was PANI estimation. A conclusion was made that the slow cation diffusion both in protonated and in base form of PANI makes them less efficient solid electrolytes than conventional materials.

Synthesis of Villi-Structured Polyaniline Sheets Using Organic Single Crystal Surface-Induced Polymerization.

Villi-structured polyaniline sheets (VPASs) were synthesized by the organic single-crystal surface-induced polymerization (OCSP) method using sodium decanesulfonate as a template. Aniline hydrochloride is used as a monomer instead of aniline to improve the electrostatic interaction between monomers and hydrated crystals, which reveals that the mechanism of OCSP occurs from the electrostatic force between positively charged monomers and the negatively charged surface of hydrated crystals. Compared with conventional polyaniline (3.13 × 10–2 S/cm), VPASs showed higher electrical conductivity (1.07 × 10–1 S/cm). The thickness of double-layered VPASs is about 136 nm, and the surface of VPASs shows a random porous structure with a villi-like morphology. This morphological property provides a large surface area, which can be advantageous to various electrochemical applications. The process yields mass-producible inexpensive materials, and the products are suitable for flexible devices because of their characteristic morphology.