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Method for deposition of layers of the organic semiconductor polyaniline onto various kinds of supports was developed. The method enables control over the layer thickness and morphology. It is based on formation of a polymeric layer on the support in the course of a heterophase in situ polymerization of aniline. Processes of self-organization of po...
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... The rate of ux decrease is directly linked to the surface layer deposition extent and density. Denser and thicker PANI layer on prolonging polymerization time exponentially reduces membrane ux as can be seen in Table 3. 77,78 On the other hand, explaining salt and water permeation through nanoltration membranes using solution-diffusion mechanism necessitates that the surface of nanoltration membranes should be hydrophilic in nature that can facilitate water molecules to be (1) absorbed on the surface, (2) diffused through the thickness on the basis of chemical potential difference on either sides and (3) desorbed on the downstream side. PES is intrinsically hydrophobic in nature therefore the modication with NaOH imparts some hydrophilicity. ...
In this research, novel polyaniline-layered nanofiltration membranes were prepared by phase inversion of base polyethersulfone (PES) membranes and subsequent in situ solution-phase deposition of polyaniline as a thin surface layer. In these composite membranes, the impact of the polyaniline deposition time on steric hindrance and electrostatic interactions during permeation was elucidated. The chemical structure, thermal stability, and mechanical properties of the PES and PANI-PES membranes were investigated using Fourier-transform infrared spectroscopy (ATR-FTIR), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA), respectively. The membranes' porosity and pore size decreased as PANI deposition time increased. As PANI deposition time increased, PANI layered nanofiltration membranes exhibited improved thermal stability but deteriorated mechanical characteristics due to free radical destruction from prolonged exposure to the oxidant. These PANI-PES membranes showed 43% rejection (NaCl) at 1.7 bar coupled with a flux of 11.59 L h-1 m2 that is quite promising when comparing with similar Nanofilteration (NF) membranes in the literature and commercial NF membranes, as well. As the deposited layer, PANI is partially doped; hence, permeation results have been interpreted in terms of steric hindrance and electrostatic repulsion by electrochemical PANI layering.
... Another promising way to increase the conductivity, sensing and catalytic properties of PANI layers is doping them with noble metal nanoparticles (Pd, Pt, Au), for which methods of electrochemical polymerization [11,12], including in-situ [13], solution preparation methods [4,14,15], self-assembly method [15], Langmuir-Blodgett [4] and etc., are applied. ...
... The methods of electrochemical polymerization that combine the synthesis of PANI composite materials are widely applied [5,12,13]. However, the reactions underlying the method are complex, multistage, and they proceed simultaneously with the oxidative polymerization of aniline, which also complicates the control of the conditions for the preparation of composites. ...
... However, the reactions underlying the method are complex, multistage, and they proceed simultaneously with the oxidative polymerization of aniline, which also complicates the control of the conditions for the preparation of composites. In addition, there remains the problem of transferring the formed layer from the electrodes to the working surface, using easily oxidized substrates [13]. This problem is solved by methods of selforganization from solutions for example Langmuir-Blodgett [4]. ...
Highly ordered conductive polyaniline (PANI) coatings containing gold nanoparticles were prepared by low-energy electron beam deposition method, with emeraldine base and chloroauric acid used as target materials. The molecular and chemical structure of the layers was studied by Fourier transform infrared, Raman, UV–vis and X-ray photoelectron spectroscopy. The morphology of the coatings was investigated by atomic force and transmission electron microscopy. Conductive properties were obtained by impedance spectroscopy method and scanning spreading resistance microscopy mode at the micro- and nanoscale.
It was found that the emeraldine base layers formed from the products of electron-beam dispersion have extended, non-conductive polymer chains with partially reduced structure, with the ratio of imine and amine groups equal to 0.54. In case of electron-beam dispersion of the emeraldine base and chloroauric acid, a protoemeraldine structure is formed with conductivity 0.1 S/cm. The doping of this structure was carried out due to hydrochloric acid vapor and gold nanoparticles formed by decomposition of chloroauric acid, which have a narrow size distribution, with the most probable diameter about 40 nm. These gold nanoparticles improve the conductivity of the thin layers of PANI + Au composite, promoting intra- and intermolecular charge transfer of the PANI macromolecules aligned along the coating surface both at direct and alternating voltage.
The proposed deposition method of highly oriented, conductive nanocomposite PANI-based coatings may be used in the direct formation of functional layers on conductive and non-conductive substrates.
... Mostly nano-sized PANI was used as an electrode material for the reason of electrodeelectrolyte interface, the easy pathway of ion/electron transport system with fast and better electrochemical response when compared to bulk PANI materials [6,7]. There are numerous reports existing for the dissimilar structure and morphology with controllable doping of PANI [8,9]. So far, diverse structured PANI materials were synthesized such as nano-sized particles, wires, helix, tubes, belts, plates and 3-dimensional (3D) flower [6,7,[10][11][12][13]. ...
Block copolymer (P-123) assisted nanohybrid of Polyaniline embraced Carbon nanotubes (PANI@CNT) with outcropping whiskers at the edge were synthesized to facilitates simple charge and ion transport at the electrode interface. Structural and morphological portrayals of the as-synthesized materials were realized by numerous techniques and their energy storage performance was electrochemically assessed. The nanohybrid electrode reveals remarkable electrochemical possessions with superior charge storage capacitance, rapid rate responsiveness and sustained cycling performance owing to its exploited chemistry and nano-architecture. Based on the insight acquired from super capacitance values, PANI@CNT nanohybrid material provided the highest capacitance of 348.9 F g⁻¹, which is 2.7 times superior to that of CNT and 1.5 times better than that of pure PANI, suggesting that a simplistic pathway for tailoring insertion/de-insertion of ions through high roughness in electrodes. In this nanohybrid, CNTs possibly acts as a backbone material for facile electron transfer and the porous PANI perform duties for the capacitance enhancement.
... Only the initiation step of the chain growth has a high energetic barrier which corresponds to a potential of +1.05 V. 54,69,70 The initial oligomers aggregate in the reaction phase and form a non-conducting layer on the surface in contact with the reaction medium or aggregate in the bulk of reaction phase. 71,72 Further growth of polymer chains proceeds heterogeneously at the interface of solid and liquid phases. Therefore it depends on the quality of the surface. ...
The mechanism of the oxidative polymerization of aniline is reviewed on the basis of the experimental evidence and reaction schemes proposed in the literature. It is demonstrated that the balance between the non-protonated and protonated forms of the monomer and the growing chain are responsible for the diversity of the molecular structure, morphology, and properties of aniline oxidation products. Various forms are oxidized by two oxidation mechanisms: (1) chain reaction of electrophilic substitution and (2) coupling of cation-radical centres. At pH>2.5, the non-protonated reagents are oxidized with a chain reaction controlled by electrophilic substitution of the aromatic ring. The reaction leads to the formation of non-conducting aniline oligomers with heterogeneous molecular structures. At pH 2.5–4, the electrophilic substitution is reduced because of the protonation of the aniline, and the cyclic dimer, phenazine, becomes the main product of the oxidation. The growth of the conjugated chain proceeds at pH<2.5, when the reactants are protonated. The reaction proceeds through coupling between the terminal cation-radical and the monomer cation-radical with formation of a π-complex. The transformation of the π-complex into a para-substituted monomer unit is thermodynamically controlled and is produced through an intramolecular benzidine (semidine) rearrangement. The regular structure of the growing chains is a result of the high regioselectivity of the sigmatropic rearrangements and significant energy gain attained by the formation of protonated polyconjugated chains in the agglomerated state.
Oxidative polymerization of aniline and 2‐(2‐chloro‐1‐methylbut‐2‐en‐1‐yl)aniline gave corresponding hitherto unknown copolymers with various compositions. The copolymers were studied by several techniques, including UV–visible spectroscopy, Fourier transform IR spectroscopy, cyclic voltammetry, thermal analysis and SEM. Copolymerization of aniline with an ortho‐substituted aniline derivative leads to the appearance of luminescence whose intensity increases with growth in the content of the substituted monomer units. It has been shown that the solubility of the copolymers obtained is determined by their composition. It has been found that the temperature of the start of thermal destruction of the copolymers increases with an increase in the content of a functionalized monomeric aniline therein. The solubility of the copolymers makes it possible to create homogeneous thin films and use them as the active layer in resistive gas sensors. © 2022 Society of Industrial Chemistry.
Pomegranate-like MnO2@polyaniline (PANI) sub-microspheres have been designed and successfully synthesized as a novel and highly effective sorbent material to remove heavy metal ions from water. Herein, pomegranate-like SiO2@PANI spheres were firstly fabricated by performing the oxidation polymerization of aniline in silica colloidal solution, followed by the removal of SiO2 and in situ redox reaction between KMnO4 and PANI. Compared with the mono-component PANI and MnO2 materials, the obtained pomegranate-like MnO2@PANI sub-microspheres exhibited superior adsorption ability towards Pb(II) ions due to the synergistic effect. Influencing factors, including pH, Pb(II) ions concentration, adsorbents content and other ions on the Pb(II) ion sorption onto the MnO2@PANI hybrid were systematically studied. The sorption isotherm, kinetics and thermodynamic properties of the hybrids for Pb(II) ions adsorption were reflected by different models. Moreover, the adsorption ability of pomegranate-like MnO2@PANI sub-microspheres towards other heavy metal ions was also explored. This work would provide new insight on the design of hierarchical inorganic/organic nanosorbent.
The sorption properties of polymers with a polyconjugated chain structure (polyaniline and polypyrrole) are considered. The molecular mechanism of sorption by these polymers of various compounds such as heavy metal ions, toxic organic compounds and micropathogens, which are the most hazardous and stubborn contaminants in water, is discussed. The use of such sorbents to purify water from micropathogens, including bacteria and viruses, is addressed for the first time. The adsorption capacity of polyconjugated polymers for these types of contaminants, the efficiency of water treatment by these sorbents and characteristics of the currently used sorbents are analyzed. The applicability of polyaniline and polypyrrole and composites based on them as high-performance versatile sorbents for water treatment is discussed, taking into account the sorbent properties such as high stability, lack of solubility, lack of toxicity and ability to be regenerated and reused.
The bibliography includes 194 references.
Detailed investigation has been made into the peculiarities of monomer sorption and desorption at different stages of aniline oxidative polymerization inside the perfluorinated membrane during preparation of composites with absorbance lower than 3 abs. units. The evaluation of the membrane saturation degree by monomer at every synthesis stage is performed, the mass fraction of the polyaniline in the composite membrane is estimated. The investigation into the kinetics of polyaniline synthesis with cationic and anionic oxidants in the membrane matrix has shown that the oxidant nature affects the polymerization rate and permitted to discover the limiting stage of the polymerization reaction. The limiting stage of polyaniline synthesis inside the membrane matrix is identified. The conditions to cease the polymerization reaction using oxidants of different nature are revealed. The opportunity to control the distribution of the modifier in the composite by choosing the appropriate oxidant is shown.
NSG01 industrial atomic force microscope probes were functionalized by the electrically conductive polymer, polyaniline, during in situ oxidative polymerization of aniline at the probe point, which was confirmed by scanning electron microscopy. The quality of the deposited polymer can be controlled by measuring the resonance frequency of the gauge during functionalization. The comparative test of the probes prior to and after functionalization was performed using a TGT01 calibration grate, as well as on a special polyaniline test layer with a complex nanosized morphology in the semicontact mode of surface relief study and the phase contrast mode. Local current spectroscopy showed that the functionalized probe can be converted repeatedly from the conducting to nonconducting state owing to a reversible change in the conductivity of the polymer coating.
It is shown that the method for the growth of conducting polyaniline nanotubes, based on the direct polymerization of aniline on the surface of channels in track membranes, can be used to produce nanotubes with a given conductivity. An island-type film with a channel resistance of ~10¹⁹ Ω is formed during the initial stage of polymerization (up to 2 min). As the polymerization duration increases to 3 min, the channel resistance falls by more than 10 orders of magnitude. This is attributed to the formation of a continuous film on the channel surface, i.e., a nanotube is formed. With the polymerization duration increasing further, the channel (nanotube) resistance gradually decreases to ~10¹⁹ Ω at 10 min. The conductivity of polyaniline during the formation of a hollow nanotube is estimated to be 0.01–0.04 S/cm. If the nanotube is completely filled with polyaniline, the conductivity increases to ~0.2 S/cm.
