Optically active electrochromism in polyanilines

The electrochemically driven control of the natural optical activity of polyanilines bearing chiral camphorsulfonic acid is reported. Aniline was polymerized in the presence of camphorsulfonic acid by oxidative electrochemical polymerization in water to afford polyanilines containing (+)- or (−)-camphorsulfonic acid. This research elucidated that the polymerization, with cyclic voltammetry scanning up to 1.1 V, produced consistent optically active polyanilines. The polyaniline films thus prepared showed intense and tunable optical activity based on electrochemical reduction/oxidation in a 0.1 M sulfuric acid aqueous solution. The circular dichroism and optical rotation angle of the polymer were tunable by the appropriate adjustment of an externally applied potential as a form of optical modulation. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2085–2090, 2007     

Electropolymerized coatings of polyaniline on copper by using the galvanostatic method and their corrosion protection performance in HCl medium

The synthesis of polyaniline coatings on the copper (Cu) surface has been investigated by using the galvanostatic method. The synthesized coatings were characterized by Fourier transform infrared spectroscopy, UV–visible absorption spectrometry and scanning electron microscopy. The anticorrosion performances of polyaniline coatings were investigated in 0.5 M HCl medium by the potentiodynamic polarization technique and electrochemical impedance spectroscopy. The corrosion rate of polyaniline‐coated Cu was found to be ～27 times lower than bare Cu, and potential corrosion increased from ?0.21 V versus Ag/AgCl for uncoated Cu to ?0.19 V versus Ag/AgCl for polyaniline‐coated Cu electrodes. Electrochemical measurements indicate that polyaniline coating has good inhibiting properties with a mean efficiency of ~96% at 10 mAcm^?2 current density applied on Cu corrosion in acid media. The results of this study clearly ascertain that the polyaniline has an outstanding potential to protect Cu against corrosion in an acidic environment. Copyright © 2014 John Wiley & Sons, Ltd.     

Influence of Cathodic Pretreatment in the Electrocatalytic Properties PANI Modified Electrodes

Herein, we reported the detection of dopamine (DA) based on use of a cathodically pretreated polyaniline (PANI) modified electrode. The PANI electrode presents a remarkable change in their electrocatalytic properties after a simple cathodic pretreatment, which consisted in applying a potential of ?0.7 V for 3 s. While the as‐prepared PANI shows no electrochemical response for DA, the cathodically pretreated PANI presented reversible electrochemical responses with well‐defined anodic and cathodic peaks. The electrochemical behavior of DA at the PANI electrode was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Under the optimized experimental conditions, the anodic peak currents increased proportionally to the DA concentration, displaying a linear relationship in the concentration range of 0.11 to 1.75×10^?4 M with a detection limit of 13.7 μM (3 σ/slope). Recovery studies in pharmaceutical formulations presented values between 98 % and 104 %. The cathodically pretreated PANI electrode was successfully applied for DA detection in real samples of pharmaceutical formulation showing good agreement with spectrometric comparative method. The unexpected easily capability of modulate the electrocatalytic properties of the electropolymerized PANI film using a simple pretreatement was successfully demonstrated. The cathodically pretreatment PANI electrode showed electrochemical responses for DA with excellent selectivity, sensitivity, and high stability.     

环取代基对金属化聚苯胺衍生物膜修饰电极性能的影响

通过比较聚2，5－二甲氧基苯胺（PDMAn）、聚邻甲基苯胺（POT）和聚间氯苯胺（PmClAn）膜修饰电极的氧化还原电位、沉积在这3种聚合物上的铂微粒的表面形态与晶面取向以及异丙醇在分散Pt微粒的聚苯胺膜修饰电极上的氧化行为，从电子效应和立体效应探讨了聚合物电化学性质与环取代基的关系以及不同聚合基质对Pt沉积机理和有催化性能的影响,结果表明，在硫酸溶液中PDMAn膜修饰电极的氧化还原电位最负、POT次之、PmClAn最正，Pt在PDMAn和POT膜上的电沉积机理与在PmClAn膜上的不同，聚合物膜上沉积的Pt微粒呈现（200)晶面择优取向，其中POT膜上择优取向度最大，PDMAn次之，Pm-ClAn最小，异丙醇在金属化聚合物膜电极上的氧化电位取决于聚苯胺的本质，在POT膜修饰电极上异丙醇的电氧化主要发生在POT的活性电位区，而在PDMAn与PmClAn膜上的电氧化则主要发生在Pt上的氧化电位区，说明聚合物膜不仅作为Pt微粒的分散介质，而且本身有产生催化作用。     

Combination of electrochemistry and the concurrent reduction and substitution chemistry to provide a facile and versatile tool for preparing functional polyanilines

Polyaniline as the first commercially available conducting polymer has recently received great attention from both academic and industrial communities. Although there have been quite a few reports on substituted polyanilines, none of them are concerning about the amino- and alkylthio-substituted polyanilines. Unlike other substituted polyanilines, the attempts in synthesizing poly(alkylthioaniline) directly from the alkylthioaniline monomer via chemical and electrochemical oxidative-coupling chemistry were all fail. On the other hand,we have recently discovered that the amino and alkylthio functional groups can be easily introduced to the backbone of emeraldine polyaniline via the concurrent reduction and substitution chemistry. Further combination of electrochemistry and the concurrent reduction and substitution chemistry can provide us a facile and versatile tool for preparing functional polyanilines. Different functional groups can be introduced sequentially to the same polymer backbone. The concentrations of each substituents can be easily controlled. This new process provides us a useful utility for tailoring the molecular and the electronic structures of polyanilines to render them with appropriate and possibly new material properties suitable for many different potential applications.     

Effect of chain aggregation on the conductivity and ESR spectra of polyaniline

Solutions of polyaniline in m-cresol with and without camphorsulfonic acid (CSA), as well as films cast from these solutions were studied by ESR spectroscopy at 133–423 K and by optical spectroscopy in the range λ = 350–1100 nm. An analysis of the optical and ESR spectra shows that in the solutions and films without CSA polyaniline is fully doped but the conductivity of these films is low (∼10⁻⁸ S cm⁻¹; cf. 100 S cm⁻¹ for the films with CSA). Compared with the CSA-containing samples, the samples without CSA are characterized by broader ESR lines and higher contribution of the Curie spins to the magnetic susceptibility. These facts indicate a weak aggregation of polyaniline chains without CSA, which leads to low conductivity. A formula was proposed, which describes the temperature dependence of the polyaniline ESR linewidth and allows the interchain distance and the mobility of electrons moving along polymer chains to be determined. The conductivity of polyaniline films is affected by moderate heating (363–388 K) of the films and solutions from which the films were cast. It was found that the interchain distances correlate with the conductivity of the films and with the broadening of their ESR lines caused by the effect of O₂. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2701–2711, December, 2005.     

Synthesis and characterization of N‐substituted polyaniline with mesogen molecules

The N‐substituted polyaniline (PANi) was synthesized by incorporation of bromine‐terminated mesogens onto the emeraldine form of polyaniline. Firsty three liquid crystalline molecules containing biphenyl units were synthesized. These mesogenic molecules are named as: 6‐bromo‐ (4‐hexyloxy‐biphenyl‐4′‐oxy) hexane (C₆? C₆Br), 5‐bromo‐(4‐hexyloxy‐biphenyl‐4′‐oxy) pentane (C₆? C₅Br), 6‐bromo‐(4‐octyloxy‐biphenyl‐4′‐oxy) hexane (C₈? C₆Br). Differential scanning calorimetry (DSC) in combination with polarizing optical microscopy (POM) were used to investigate the thermal properties of them. Optical microscopy showed focal conic texture characteristic of the Smectic A phase for (C₆? C₅Br) and (C₈? C₆Br). For (C₆? C₆? Br) smectic phase was determined. DSC experiments were also found in accord with mesophase formation. For the synthesis of N‐substituted polyaniline with these mesogen molecules, the emeraldine base polyaniline was reacted with BuLi to produce the N‐anionic polyaniline and then deprotonated polyaniline was reacted with bromine‐end mesogen to prepare mesogen‐substituted polyaniline through N‐substitution reaction. The degree of N‐substitution can be controlled by adjusting the molar feed ratio of mesogen to the number of repeat units of PANi. The microstructure and compositions of obtained polymers were characterized by FT‐IR, elemental analysis, DSC, and scanning electron microscopy (SEM). The cyclicvoltammetry show that the electroactivity of N‐substituted polyaniline is strongly dependent on the degree of N‐grafting. The solubility of mesogen‐substituted polyaniline in common organic solvents such as THF and chloroform was improved by increasing the degree of N‐substitution and also the samples are partially soluble in xylene. Liquid crystalline behavior of mesogen‐substituted polyanilines was investigated via POM, but no mesophase was observed. Copyright © 2008 John Wiley & Sons, Ltd.     

A Nanocomposite Containing Carbon Nano-onions and Polyaniline Nanotubes as a Novel Electrode Material for Electrochemical Sensing of Daidzein

Glassy carbon electrode (GCE) were modified with nanocomposites containing conductive polyaniline nanotubes (PANI_nt) and carbon nano-onions (CNOs). Herein we report a simple and sensitive way for daidzein (DA) determination at concentrations between 1 and 10 μM by linear sweep voltammetry using GCE/PANI_nt/CNOs system. The DA electrochemical behavior was examined in two buffer environments (pH 7.5 and 4.5) using electrodes modified with the oxidized CNOs or their derivatives containing carboxyl and benzylamino functional groups. The direct electrooxidation of DA was observed at +0.65 V and +0.8 V at pH 7.5 and at +0.7 V and +1.1 V vs. Ag/AgCl at pH 4.5.     

Polyaniline copolymers with solvent‐mimic side chains

We investigated new polyaniline copolymers with solvent‐mimic side chains for enhanced processability in various solvents. The solvent‐mimic side chains, benzyloxypropoxy (BOP), phenoxybutoxy (POB), and dihydroxypropoxy (DHP), were introduced into copolymers and used with nonpolar aromatic and polar alcoholic solvents, respectively. Compared to a polyaniline homopolymer, polyaniline copolymers with a small amount of side chains (<4 mol %) exhibit different physical properties, including film‐forming ability. This can be attributed to the solvent‐mimic side chains strongly interacting with the solvent and/or the polyaniline backbone. Especially, in nonpolar aromatic solvents, polyaniline copolymers with nonpolar aromatic BOP and POB side chains exhibit good film‐forming ability leading to high electrical conductivity, while the polyaniline homopolymer did not form a film. Therefore, introducing solvent‐mimic side chains in conducting polymers is a very attractive method of enhancing their processability and physical properties. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1986–1995     

Conformational Control of Oligo(p‐phenyleneethynylene)s with Intrinsic Substituent Electronic Effects: Origin of the Twist in Pentiptycene‐Containing Systems

Dependence of the backbone planarity of oligo(p‐phenyleneethynylene)s (OPEs) on the intrinsic electronic character of substituents and on the nature of the solvent has been experimentally demonstrated with a series of center‐symmetrical five‐ring systems, pentiptycene‐pentiptycene‐arene‐pentiptycene‐pentiptycene, differing in the substituents on the central arene. In frozen 2‐methyltetrahydrofuran (MTHF), the adjacent pentiptycene units prefer to be in a mutually twisted orientation when the substituents are electron‐withdrawing (F and amido), resulting in a TPPT or TTTT conformation, whereas a planarized PPPP backbone is favored in the case of electron‐donating substituents (alkyl and alkoxy). The propensity to adopt the PPPP form is generally enhanced by replacing MTHF with either methylcyclohexane or mixed ethanol/methanol as solvent. These observations reveal that the twist between adjacent pentiptycene units in OPEs is a consequence of the electronic rather than steric effects of iptycenyl substituents. The electronic effect of iptycenyl substituents is manifested in decreased phenylene π polarizability as the net effect of both electron‐donating hyperconjugation and an electron‐withdrawing inductive effect. Variable‐temperature electronic absorption and emission spectroscopies are the critical tools for this work. Our findings provide important guidelines for conformational and electronic engineering of OPEs and for the design of novel iptycene‐based organic electronic materials.     

Spectroelectrochemical Reactivities of Novel Polyaniline Nanotube Pesticide Biosensors

Summary: The preparation and characterisation of electrosynthetic polyaniline nanomaterials doped with phenanthrene sulphonic acid (PSA) is being presented. The polymeric nanomaterials prepared include processable poly(o-methoxy aniline) (POMA) and poly(2,5-dimethoxy aniline) (PDMA). Spectroelectrochemical reactivities of the electroactive polymeric nanotube systems as well as the nanobiosensor systems were studied by SEM, FTIR, UV-Vis and Subtractively Normalised Fourier Transformed Infrared Spectroscopy (SNIFTIRS) techniques. Furthermore, cyclic and differential pulse voltammetric studies of the nanomaterials were also performed using platinum or thiol-modulated gold electrodes. The SEM studies confirmed the nanorod morphology of the polyanilines. The heterogeneous rate constant, k_o, for the nanopolymeric material and the diffusion coefficient of electrons, D_e, was calculated and found to be in agreement with values expected for electron hopping along conducting polymer chains. Organophosphate pesticide nanobiosensor devices were prepared by encapsulating acetylcholinesterase (AChE) in the nanopolymeric composite. The biosensor amperometric response to the organophosphate pesticide called diazinon and the carbamate pesticide called carbofuran were studied. The sensor responses to pesticides followed typical electrochemical Michaelis-Menten kinetics.     

Preparation and characterization of polyaniline with high electrical conductivity

In the present paper, polyaniline (PANI) was polymerized by ammonium persulphate using a chemically oxidative process under mild tempertures ranging from ?5–20°C. Electrical conductivity of as synthesized PANI got enhanced gradually owing to the increase in molecular weight and crystallinity with decrease in synthesis temperature. Extraction with tetrahydrofuran (THF) was employed as the purification method of emeraldine base (EB) to enhance the electrical conductivity of PANI effectively attributed to the removal of the low molecular weight fractions and defective molecular chains. Methanesulfonic acid (MSA) was used to dope EB due to its strong acidity and small molecular size, and the amount of dopant versus EB was also optimized. Using a novel “synergistic doping” process with m‐cresol, electrical conductivity of PANI is further enhanced owing to more regular molecular chains which resulted in better interchain charge carriers' conduction. The emeraldine salts obtained finally have high electrical conductivity reaching up to 32.5 S cm^?1, which is much higher than that of the conventionally synthesized sample reported previously. Copyright © 2008 John Wiley & Sons, Ltd.     

Chemical synthesis and electric properties of the conducting copolymer of aniline and o‐aminophenol

A copolymer, poly(aniline‐co‐o‐aminophenol), was prepared chemically by using ammonium peroxydisulfate as an oxidant. The monomer concentration ratio of o‐aminophenol to aniline strongly influences the copolymerization rate and properties of the copolymer. The optimum composition of a mixture for the chemical copolymerization consisted of 0.3 M aniline, 0.021 M o‐aminophenol, 0.42 M ammonium peroxydisulfate, and 2 M H₂SO₄. The result of cyclic voltammograms in a potential region of ?0.20 to 0.80 V (vs.SCE) indicates that the electrochemical activity of the copolymer prepared under the optimum condition is similar to that of polyaniline in more acid solutions. However, the copolymer still holds the good electrochemical activity until pH 11.0. Therefore, the pH dependence of the electrochemical property of the copolymer is improved, compared with poly(aniline‐co‐o‐aminophenol) prepared electrochemically, and is much better than that of polyaniline. The spectra of IR and ¹H NMR confirm that o‐aminophenol units are included in the copolymer chain, which play a key role in extending the usable pH region of the copolymer. The visible spectra of the copolymers show that a high concentration ratio of o‐aminophenol to aniline in a mixture inhibits the chain growth. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5573–5582, 2007     

Electrochemical behavior of polyaniline synthesized by chemical oxidation

The slow voltammetry was taken on the paste electrode consisting of polyaniline powder and Teflon binder which was applied to pyrographite disc electrode. The potential cycle range was +0.6V→ ? 0.2V→+0.8V→+0.6V vs. SCE. It was found that the voltammetry curves are similar for both polyanilines obtained chemically and electrochemically. The difference of the voltammetry curves in various acids might be attributed to some exchange of doping anions in polyaniline. The first redox couple peaks shifted to positive potential direction with increase of pH and it might be associated with the proton addition-elimination reaction. It was shown that polyaniline prepared from very dilute or concentrated acid solution was electrochemically inactive.     

Nanocomposites of Sulfonic Polyaniline Nanoarrays on Graphene Nanosheets with an Improved Supercapacitor Performance

A new nanocomposite, poly(aniline‐co‐diphenylamine‐4‐sulfonic acid)/graphene (PANISP/rGO), was prepared by means of an in situ oxidation copolymerization of aniline (ANI) with diphenylamine‐4‐sulfonic acid (SP) in the presence of graphene oxide, followed by the chemical reduction of graphene oxide using hydrazine hydrate as a reductant. The morphology and structure of PANISP/rGO were characterized by field‐emission (FE) SEM, TEM, X‐ray photoelectron spectroscopy (XPS), Raman, FTIR, and UV/Vis spectra. The electrochemical performance was evaluated by cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy. The PANISP/rGO nanocomposite showed a nanosized structure, with sulfonic polyaniline nanoarrays coated homogeneously on the surface of graphene nanosheets. This special structure of the nanocomposite also facilitates the enhancement of the electrochemical performance of the electrodes. The PANISP/rGO nanocomposite exhibits a specific supercapacitance up to 1170 F g^?1 at the current density of 0.5 A g^?1. The as‐prepared electrodes show excellent supercapacitive performance because of the synergistic effects between graphene and the sulfonic polyaniline copolymer chains.     

二维高聚物振动谱的研究

聚乙炔和聚苯胺通常由于链间耦合比较弱 ,具有一维特性 .但在增加压力的条件下可以使其链间距b减少 ,当达到与晶格常数a相近的程度时 ,这时应考虑其晶格链间耦合作用 ,它们就具有二维复式晶格结构 ,由此会带来新的物理效应 .本文考虑了由于增压作用可以使高聚物晶格链间耦合作用增强 ,并使链间距b减少 ,当b达到与晶格常数a相比拟时 ,它们可以被看作具有二维晶格结构 .基于这种情况建立了理想的二维复式晶格链模型 ,利用晶格动力学的方法 ,计算其晶格链间及原子次近邻间的相互作用 ,借助计算机计算分别在几种晶格链耦合作用下和不同质量比时的色散关系 ,模拟色散曲线 ,讨论第一布里渊区BrillouinZone(BZ)中格波高对称线上频谱的变化 ,分析了由此会带来的新的物理效应 .     

Electrochemical study of polyaniline deposited on a titanium surface

The electrochemical synthesis of polyaniline on a titanium surface in aqueous sulfuric acid solutions with various concentrations of added aniline has been investigated by cyclic voltammetry. By utilizing a more cathodic potential range (up to −0.6 V) for the cyclization than is usual (up to −0.2 V) on Pt and Au electrodes, the new voltammetric waves have been deconvoluted from the already well-known ones for polyaniline. By simultaneous electrochemical and in situ Raman spectroscopic measurements, the Raman bands of polyaniline electrodeposited on a Ti electrode, were assigned for potentials of −0.15 V and −0.6 V. It was found that the new monitored waves were closely related to the so-called “middle” peaks and appear only when the polyaniline reaches an overoxidized state. Received: 7 August 1997 / Accepted: 4 November 1997     

Synthesis and Properties of Self‐doped Polyaniline with Polycationic Templates via Biocatalysis

The enzyme horseradish peroxidase (HRP) was used to polymerize acid‐functionalized anilines to make self‐doped polymer in the presence of a polycationic template. Anionic templates such as sulfonated polystyrene (SPS) could not function as a suitable template for the polymerization of acid‐functionalized aniline derivatives. Several types of polyelectrolytes were used as templates to observe the structural effects and doping behavior of polyaniline/template complexes. The synthesis is straightforward and the conditions are mild in that the polymerization of conducting polyanilines may be carried out in buffered solutions as high as pH 6, with a stoichiometric amount of hydrogen peroxide and catalytic amount of enzyme. The conductivity of these enzymatically synthesized self‐doped polymers was relatively high without additional doping due to the self‐doping of the acid moieties. The conductivity did not decrease dramatically at pH 3 as is the usual case of unsubstituted HCl‐doped polyaniline and maintained good conductivity even at pH 6. The measured conductivity at pH 4～pH 6 is around 10^?4 S/cm to 10^?6 S/cm.     

Selective Electrochemical Determination of Dopamine with Molecularly Imprinted Poly(Carbazole‐co‐Aniline) Electrode Decorated with Gold Nanoparticles

Dopamine (DA) is a significant neurotransmitter in the central nervous system, coexisting with uric acid (UA) and ascorbic acid (AA). UA and AA are easily oxidizable compounds having potentials close to that of DA for electrochemical analysis, resulting in overlapping voltammetric response. In this work, a novel molecularly imprinted (MI) electrochemical sensor was proposed for selective determination of DA (in the presence of up to 80‐fold excess of UA and AA), relying on gold nanoparticles (Au_nano)‐decorated glassy carbon (GC) electrode coated with poly(carbazole (Cz)‐co‐aniline (ANI)) copolymer film incorporating DA as template (DA imprinted‐GC/P(Cz‐co‐ANI)‐Au_nano electrode, DA‐MIP‐Au_nano electrode). The DA recognizing sensor electrode showed great electroactivity for analyte oxidation in 0.2 mol L^?1 pH 7 phosphate buffer. Square wave voltammetry (SWV) was performed within 10^?4–10^?5 mol L^?1 of DA, of which the oxidation peak potential was observed at 0.16 V. The limit of detection (LOD) and limit of quantification (LOQ) were 2.0×10^?6 and 6.7×10^?6 mol L^?1, respectively. Binary and ternary synthetic mixtures of DA‐UA, DA‐AA and DA‐UA‐AA yielded excellent recoveries for DA. Additionally, DA was quantitatively recovered from a real sample of bovine serum spiked with DA, and determined in concentrated dopamine injection solution. The developed SWV method was statistically validated against a literature potentiodynamic method using a caffeic acid modified‐GC electrode.     

Influence of phenylenediamine additions on the morphology and on the catalytic effect of polyaniline

The influence of para‐, ortho‐, and meta‐phenylenediamine (p‐, o‐, and m‐PDA) additions on the electrochemical synthesis of polyaniline has been investigated by the use of cyclic voltametry. It has been found that small additions (1 and 5 mmol L^?1) of PDA monomers influence significantly the polymerization rate. Whereas p‐PDA increases the polymerization rate, the addition of o‐ or m‐PDA slows it down. Therefore, a different number of potential cycling is necessary to obtain similar thickness of layers. The layers exhibit very different morphology, which changes from “spaghetti‐like” for polyaniline to “sponge‐like” for p‐PDA, to “pebble‐like” for o‐PDA and to “cauliflower‐like” for m‐PDA additions, respectively. The catalytic effect of the synthesized polymer layers has been tested. It has been found that all the layers exhibit catalytic effect in lowering the redox potential of hydroquinone/quinone tested reaction, but the rate of the electrocatalytic reaction varies depending on the PDA monomer added. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1599–1608, 2004