The genesis of polyaniline nanotubes

Fabrication of a tailor-made conductive polyaniline/ascorbic acid-coated nanofibrous mat as a conductive and antioxidant cell-free cardiac patch

Polyaniline (PANI) wasin-situpolymerized on nanofibrous polycaprolactone mats as cell-free antioxidant cardiac patches (CPs), providing electrical conductivity and antioxidant properties. The fabricated CPs took advantage of intrinsic and additive antioxidant properties in the presence of PANI backbone and ascorbic acid as a biocompatible dopant of PANI. The antioxidant nature of CPs may reduce the serious repercussions of oxidative stress, produced during the ischemia-reperfusion (I/R) process following myocardial infarction. The polymerization parameters were considered as aniline (60 mM, 90 mM, and 120 mM), ascorbic acid concentrations ([aniline]:[ascorbic acid] = 3:0, 3:0.5, 3:1, 3:3), and polymerization time (1 h and 3 h). Mainly, the more aniline concentrations and polymerization time, the less sheet resistance was obtained. 1,1 diphenyl-2-picrylhydrazyl (DPPH) assay confirmed the dual antioxidant properties of prepared samples. The advantage of the employedin-situpolymerization was confirmed by the de-doping/re-doping process. Non-desirable groups were excluded based on their electrical conductivity, antioxidant properties, and biocompatibility. The remained groups protected H9c2 cells against oxidative stress and hypoxia conditions. Selected CPs reduced the intracellular reactive oxygen species content and mRNA level of caspase-3 while the Bcl-2 mRNA level was improved. Also, the selected cardiac patch could attenuate the hypertrophic impact of hydrogen peroxide on H9c2 cells. Thein vivoresults of the skin flap model confirmed the CP potency to attenuate the harmful impact of I/R.

Preparation and evaluation of some nanocarbon (NC) based composites for optoelectronic applications

Polyaniline/nanocarbon (PANI/NC) nanocomposites have been prepared by in situ polymerization of aniline monomer in the presence of a stable colloidal solution of nanocarbon NC using ammonium persulfate as an initiator and silver ions (Ag⁺) as oxidizing agents to produce PANI/NC and PANI/NC/Ag₂O nanocomposites, respectively. The morphological studies of the formed nanocomposites have been elucidated via transmission and scanning electron microscopes (TEM and SEM). Further characterization of the prepared nanocomposites has been done via infrared spectroscopy (IR), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), particle size distribution analysis (PSD), fluorescence microscope (FM), UV-VIS spectroscopy, and finally surface analysis. XRD results confirmed the presence of silver oxide Ag₂O nanoparticles, and the obtained data is well matched with the JCPDS card number 76-1393 of silver oxide. XPS analyses have shown two prevailing characteristic peaks for Ag 3d5/2 and Ag 3d3/2 at 367.1 and 373 eV, respectively, representing Ag₂O nanoparticles, which are matchable with the XRD analysis. The PSD analysis revealed that the sizes of the prepared nanocomposites are in the size range from 60 to 140 nm. The FM measurements showed luminescence from the prepared nanocomposites upon irradiation with different lights. This recommends that the fluorophores present in the prepared nanocomposites have the potential to both absorb and emit light. The AC conductivity and the dielectric permittivity of the obtained nanocomposites at room temperature and at different frequency ranges have been investigated. At higher frequency ranges, the maximum ac conductivity obtained was 1.06 × 10^-2 and 2.5 × 10^-2 S.Cm^-1 for the PANI/NC and PANI/NC/Ag₂O, respectively. As far as we know, these new nanocomposites with superior optical and electrical characteristics have not been described yet in the literature.

A New Method to Prepare Stable Polyaniline Dispersions for Highly Loaded Cathodes of All-Polymer Li-Ion Batteries

A new method for the preparation of polyaniline (PANI) films that have a 2D structure and can record high active mass loading (up to 30 mg cm^-2) via acid-assisted polymerization in the presence of concentrated formic acid was developed. This new approach represents a simple reaction pathway that proceeds quickly at room temperature in quantitative isolated yield with the absence of any byproducts and leads to the formation of a stable suspension that can be stored for a prolonged time without sedimentation. The observed stability was explained by two factors: (a) the small size of the obtained rod-like particles (50 nm) and (b) the change of the surface of colloidal PANI particles to a positively charged form by protonation with concentrated formic acid. The films cast from the concentrated suspension were composed of amorphous PANI chains assembled into 2D structures with nanofibrillar morphology. Such PANI films demonstrated fast and efficient diffusion of the ions in liquid electrolyte and showed a pair of revisable oxidation and reduction peaks in cyclic voltammetry. Furthermore, owing to the high mass loading, specific morphology, and porosity, the synthesized polyaniline film was impregnated by a single-ion conducting polyelectrolyte-poly(LiM_n-r-PEGM_m) and characterized as a novel lightweight all-polymeric cathode material for solid-state Li batteries by cyclic voltammetry and electrochemical impedance spectroscopy techniques.

Preparation of One-Dimensional Polyaniline Nanotubes as Anticorrosion Coatings

Uniform polyaniline (PANI) nanotubes were synthesized by a self-assembly method under relatively dilute hydrochloric acid (HCl) solution. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and UV-Vis-NIR spectroscopy were employed to characterize the morphology and molecular structure of the PANI products. SEM images show that the PANI nanotubes have uniform morphology and form compact coating on the substrate surface. For comparison, aggregated PANI was also synthesized by conventional polymerization method. The performance of the PANI products on carbon steel was studied using eletrochemical measurement and immersion corrosion experiment in 3.5 wt% NaCl aqueous solution. The corrosion potentials of carbon steel samples increase by 0.196 V and 0.060 V after coated with PANI nanotubes and aggregated PANI, respectively, and the corrosion currents density decrease by about 76.32% and 36.64%, respectively. The 6-day immersion experiment showed that the carbon steel samples coated by PANI nanotubes showed more excellent anticorrosion performance, because the more compact coating formed by PANI nanotubes may inhibit the corrosion process between the anodic and cathodic.

Conjugated Molecules and Polymers in Secondary Batteries: A Perspective

Intrinsically conducting polymers constituting a subclass of macromolecules, as well as a still growing family of large, conjugated molecules, oligomers, and polymers, have attracted research interest for the recent decades. Closely corresponding to the fascination of these materials, combining typical properties of organic polymers and metallic materials, numerous applications have been suggested, explored, and sometimes transferred into products. In electrochemistry, they have been used in various functions beyond the initially proposed and obvious application as active masses in devices for electrochemical energy conversion and storage. This perspective contribution wraps up basic facts that are necessary to understand the behavior and properties of the oligo and polymers and their behavior in electrochemical cells for energy conversion by electrode reactions and associated energy storage. Representative examples are presented and discussed, and an overview of the state of research and development is provided. Particular attention is paid to stability and related aspects of practical importance. Future trends and perspectives are indicated.

Impact of Acidity Profile on Nascent Polyaniline in the Modified Rapid Mixing Process-Material Electrical Conductivity and Morphological Study

Polyaniline (PANI) was synthesized chemically with the modified rapid mixing protocol in the presence of sulfuric acid of various concentrations. A two-step synthetic procedure was utilized maintaining low-temperature conditions. Application of the modified rapid mixing protocol allowed obtaining a material with local ordering. A higher concentration of acid allowed obtaining a higher yield of the reaction. Structural characterization performed with Fourier-transform infrared (FTIR) analysis showed the vibration bands characteristic of the formation of the emeraldine salt in both products. Ultraviolet-visible light (UV-Vis) spectroscopy was used for the polaronic band and the p-p* band determination. The absorption result served to estimate the average oxidation level of PANI by comparison of the ratio of the absorbance of the polaronic band to that of the π-π* transition. The absorbance ratio index was higher for PANI synthesized in a more acidic solution, which showed a higher doping level for this polymer. For final powder products, particle size distributions were also estimated, proving that PANI (5.0 M) is characterized by a larger number of small particles; however, these particles can more easily agglomerate and form larger structures. The X-ray diffraction (XRD) patterns revealed an equilibrium between the amorphous and semicrystalline phase in the doped PANI. A higher electrical conductivity value was measured for polymer synthesized in a higher acid concentration. The time-of-flight secondary ion mass spectrometry (TOF-SIMS) analysis showed that the molecular composition of the polymers was the same; hence, the difference in properties was a result of local ordering.

Conducting polyaniline prepared in the solutions of formic acid: Does functionalization with carboxyl groups occur?

Polyaniline is a conducting polymer with an application potential in the field of biomedical engineering. By employing FTIR spectroscopy and conductivity measurements, it has been shown that the oxidation at stoichiometric peroxydisulfate-to-aniline mole ratio 1.25 in the solutions of formic acid in the range 0-10 M provides samples of a moderate conductivity of the orders 0.01-0.1 S cm^-1. They consist of polyaniline and aniline oligomers as typical of the aniline oxidation in weak acids. The detailed investigation of the infrared spectra indicates a partial ring-carboxylation of polyaniline at high acid concentrations. The extent of structural defects is higher for a series prepared at over-stoichiometric peroxydisulfate-to-aniline mole ratio 2.5, which provided only non-conducting samples. The reference sample series represented by poly(aniline-co-o-aminobenzoic acid) was also prepared and is used in the discussion of the infrared spectra.

A Textile-Based Microfluidic Platform for the Detection of Cytostatic Drug Concentration in Sweat Samples

This work presents a new multilayered microfluidic platform, manufactured using a rapid and cost-effective xurography technique, for the detection of drug concentrations in sweat. Textile fabrics made of cotton and polyester were used as a component of the platform, and they were positioned in the middle of the microfluidic device. In order to obtain a highly conductive textile, the fabrics were in situ coated with different amounts of polyaniline and titanium dioxide nanocomposite. This portable microfluidic platform comprises at least three layers of optically transparent and flexible PVC foils which were stacked one on top of the other. Electrical contacts were provided from the edge of the textile material when a microfluidic variable resistor was actually created. The platform was tested in plain artificial sweat and in artificial sweat with a dissolved cytostatic test drug, cyclophosphamide, of different concentrations. The proposed microfluidic device decreased in resistance when the sweat was applied. In addition, it could successfully detect different concentrations of cytostatic medication in the sweat, which could make it a very useful tool for simple, reliable, and fast diagnostics.

The Applications of Solid-State NMR to Conducting Polymers. The Special Case on Polyaniline

Polyaniline is one of the most well studied conducting polymers due to its advanced electrical, chemical, redox and morphological properties. The high conductivity of regular polyaniline, when partially oxidized and doped under acidic conditions, has been associated with the formation of unique electronic states known as polarons and bipolarons. Alternative aniline oxidation products and interesting nanotube and nanorod forms have been observed as the synthesis conditions are varied. Solid-state NMR has offered great opportunities for structural investigations and the determination of molecular dynamics in such a complex and diverse material. This review summarizes various applications of solid-state NMR techniques to polyaniline and its derivatives and the information that can be obtained by solid-state NMR.

Chiral Polyaniline Hollow Nanotwists toward Efficient Enantioselective Separation of Amino Acids

Controllable fabrication of complex chiral nanostructures of functional materials from achiral systems remains a great challenge. Herein, polyaniline (PANI) hollow nanotwists as complex chiral nanostructures have been prepared by chemical oxidation of aniline in an achiral HCl/isopropyl alcohol/water mixed solvent. The chiral oligoaniline twisted nanoribbons generated at the early reaction stage have been established to act as reactive sacrificial templates for inducing the growth of PANI hollow nanotwists. Single-handed PANI hollow nanotwists achieved by tuning the alcohol content in the solvent have been applied to separate several chiral amino acids from their racemic mixtures with high performance, indicating their high potential for enantioselective separation applications.

Comparable investigation of polyaniline behavior towards gaseous ammonia and toluene adsorption

With raising awareness of gaseous air pollutants and their harmful impact, adsorption is considered one of the most prominent techniques for gaseous emissions control. The usage of polyaniline as a gas adsorbent is an innovative idea. This work aims to compare the efficacy of synthesized polyaniline nanotubes (PANT) as a novel adsorbent towards inorganic gases (ammonia NH₃) and volatile organic compounds (toluene vapor). PANT was prepared via a sol-gel preparation technique. The molecular structure of prepared PANT was characterized by Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The morphological structure was confirmed using transmission electron microscopy (TEM) and scanning electron microscope (SEM). The PANT adsorbent surface area was determined using Brunner Emmett Teller (BET). Dynamic behavior of simulated feed gas mixture of NH₃ and toluene in air were examined using a fixed bed adsorption arrangement. The same adsorption conditions (inlet concentration, gas mixture feed flow rate, and a fixed amount of adsorbent) were applied for both NH₃ and toluene adsorption test. The NH₃ and toluene removal efficiencies were 100% and 96% respectively. Consequently, PANT is an auspicious adsorbent that can be utilized to control the indoor and outdoor gaseous air emissions. Graphical Abstracts ᅟ.

Graphene Oxide Membranes with Conical Nanochannels for Ultrafast Water Transport

Membrane-based separations have been increasingly utilized to address global energy crisis and water scarcity. However, the separation efficiency often suffers from the trade-off between membrane permeability and selectivity. Although great efforts have been devoted, a membrane with both high permeability and high selectivity remains a distant prospect. Inspired by the hourglass structure and ultrafast water transport in aquaporins, we propose a novel approach to fabricating membranes with conical nanochannels to reduce the mass transfer resistance and to introduce Laplace pressure as the internal driving force, which successfully breaks the permeability/selectivity trade-off. First, sulfonated polyaniline (SPANI) nanorods were in situ-synthesized and vertically aligned on sulfonated graphene oxide (SGO) nanosheets, forming SGO-SPANI _X composites. Then, the graphene oxide (GO) membranes were fabricated by assembling SGO-SPANI _X composites through pressure-assisted filtration, in which the SPANI nanorods would bend and flatten on the SGO nanosheets under low shear force, forming stripe arrays on SGO nanosheets. The tilted stripe arrays between the adjacent SGO nanosheets form the conical nanochannels inside GO membranes. The conical nanochannels significantly decreased the steric hindrance and enabled the generation of Laplace pressure as the internal driving force within membranes. Consequently, the resulting membranes exhibit an ultrahigh water permeability of 1222.77 L·m^-2·h^-1·bar^-1 and high efficiency in dye removal from water with a rejection of 90.44% and permeability of 528 L·m^-2·h^-1·bar^-1.

Free-Standing Single-Molecule Thick Crystals Consisting of Linear Long-Chain Polymers

Organic two-dimensional (2D) crystals are fundamentally important for development of future devices. Despite that more than a half of man-made products contain polymers, 2D crystals consisting of long linear chains have yet to be explored. Here we report on the fabrication of 2D polyaniline (PANI) crystals via rational electrochemical polymerization followed by liquid-phase exfoliation. The 2D PANI is molecularly thin (∼0.8 nm) and composed of PANI chains with a number-average molecular weight of ∼31 000. The chains are parallel to each other with the benzene rings standing almost vertically to the surface, implying a face-to-face arrangement of the neighboring chains held together by abundant π-π interactions augmented with hydrogen bonds. The 2D PANI can be readily transferred to various solid surfaces and exhibit interesting electrical and optical properties, suggesting that they would be potentially useful in photoelectronic devices and other applications.

Interaction of Polyaniline with Surface of Carbon Steel

The structure and barrier properties of the oxyhydroxide layers on a carbon steel surface covered with electroactive polyaniline were investigated. Two types of polymer structure differing in degree of macromolecular order were prepared by simultaneous (fast polymerization) or dropwise (slow polymerization) mixing of reagents. A larger amount of the most stable FeOOH modification was formed on steel covered with slowly polymerized sample during treatment in the corrosion-active medium. Amorphous rust products with weak barrier properties were observed in the sample prepared by fast polymerization. Additionally, barrier activity of dedoped polyaniline was studied with SEM, WAXD, and electrochemical methods.

Spectroscopic study of the highly homogeneous polyaniline film formation on gold support

The oxidation of aniline with ammonium peroxydisulfate in the aqueous solution of acetic acid has two subsequent phases: the oxidation of the neutral aniline molecules at low acidity, which was followed by the oxidation of the anilinium cations after the acidity became higher. The final polyaniline film deposited on immersed surfaces is usually contaminated with semi-crystalline oligomers which precipitated during induction period from the reaction medium. To obtain a homogeneous film, which is important in the fabrication of many molecular electronic devices, we have studied the course of aniline oxidation in a view of new experimental evidence. In the unique series of experiments, the silicon or gold supports have been immersed in the reaction mixture at crucial stages of oxidation reaction, and the deposits at the end of the reaction were analyzed. The growth of a highly homogenous film on the gold-coated glass substrate immersed in the reaction mixture at the end of the polymerization period has been observed. The molecular structure of the products was monitored with UV-visible, infrared, and Raman spectroscopies. The possible mechanism of the film formation and the molecular mechanism of the surface interaction of chemisorbed aniline oligomers with gold support are proposed.

Ethanol-guided synthesis of (flower-on-leaf)-like aniline oligomers with excellent adsorption properties

A novel oligoaniline with hierarchical flower-on-leaf microstructures and excellent adsorption properties has been fabricated via the oxidation of aniline in EtOH/water (3 : 7, v/v) mixtures.

Polyaniline–RuO2 composite for high performance supercapacitors: chemical synthesis and properties

Polyaniline–ruthenium oxide (PANI–RuO₂) composite thin films prepared by a chemical bath deposition (CBD) method for supercapacitor application.

Controlled synthesis of tower-like aniline oligomers with excellent adsorption properties

Nanoplate-based tower-like oligoaniline as a new nano-architecture was tailored via the oxidation polymerization of aniline in NaOH medium at 35 °C.

Seeded swelling polymerized sea urchin-like core–shell typed polystyrene/polyaniline particles and their electric stimuli-response

Sea urchin-like polystyrene/polyaniline particles were synthesized by a seeded swelling polymerization. When dispersed in silicone oil to produce an electrorheological (ER) fluid, they exhibit typical ER behaviors with better dispersion stability.

In Situ Infrared Spectroscopy of Oligoaniline Intermediates Created under Alkaline Conditions

The progress of the oxidation of aniline with ammonium peroxydisulfate in an alkaline aqueous medium has been monitored in situ by attenuated total reflection (ATR) Fourier transform infrared spectroscopy. The growth of the microspheres and of the film at the ATR crystal surface, as well as the changes proceeding in the surrounding aqueous medium, are reflected in the spectra. The evolution of the spectra and the changes in the molecular structure occurring during aniline oxidation in alkaline medium are discussed with the help of differential spectra. Several processes connected with the various stages of aniline oxidation were distinguished. The progress of hydrolysis of the aniline in water and further an oxidation of aminophenol to benzoquinone imines in the presence of peroxydisulfate in alkaline medium have been detected in the spectra in real time. The precipitated solid oxidation product was analyzed by mass spectrometry. It is composed of oligomers, mainly trimers to octamers, of various molecular structures incorporating in addition to aniline constitutional units also p-benzoquinone or p-benzoquinoneimine moieties.

One-step synthesis of graphene/polyaniline hybrids by in situ intercalation polymerization and their electromagnetic properties

A new method is introduced for the preparation of graphene/polyaniline hybrids using a one-step intercalation polymerization of aniline inside the expanded graphite. The structural and morphological characterizations were performed by X-ray diffraction analysis, transmission electron microscopy and field emission scanning electron microscopy. Both the experimental and first-principles simulated results show that the aniline cation formed by aniline and H(+) tends to be drawn towards the electron-enriched zone and to intercalate into the interlayer of graphite. Subsequently, an in situ polymerization leads to the separation of graphite into graphene sheet, resulting from the exothermic effect and more vigorous movements of the chain molecules of polyaniline. The interactions between polyaniline and graphene were confirmed by Fourier transform infrared spectroscopy and Raman spectra. In addition, the graphene/polyaniline hybrid exhibited a breakthrough in the improvement of microwave absorption.