Electrochemical behaviour of polyaniline in aromatic sulphonic acids

This report describes the synthesis and redox behaviour of polyaniline in aqueous solutions of benzene sulphonic acid and 4-toluene sulphonic acid. The characterization of the polymer was carried out by electronic spectra, FTIR studies and ¹HNMR in DMSO-d₆.     

Thermal doping of polyaniline by sulfonic acids

The thermal doping of the emeraldine base (EB) form of polyaniline using two different sulfonic acids, dodecylbenzene sulfonic acid (DBSA) and p‐toluenesulfonic acid (pTSA) has been studied. Differential scanning calorimetry was used to record thermal events associated with the doping process. EB undergoes thermally induced doping with both acids at temperatures depending on the initial quantity of the dopant present. The doping temperatures show an increasing trend with increasing proportion of acid. The enthalpy of doping is also composition dependent. Conductivity values determined by the four‐probe method are given for each sample. The highest conductivities were attained at a mole ratio of 1 (dopant:EB) for both EB(DBSA) and EB(pTSA). © 2003 Society of Chemical Industry     

Enantioselective recognition of amino acids based on molecularly imprinted polyaniline electrode column

A novel molecularly imprinted polyaniline (PAn) electrode column is introduced as a new technique for the enantioselective recognition of amino acids. The principle of the molecularly imprinted electrode column is based on the reversible doping/de-doping property of PAn. PAn is an organic semiconductor and thus from an electrochemical point of view the column packed with PAn can be regarded as a packed-bed electrode of a three-electrode arrangement. The electric potential of this column can be easily controlled by a potentiostat. Various important factors influencing the performance of the molecularly imprinted PAn column have been investigated using fluorescence spectrometry in conjugation with the electrochemical quartz crystal microbalance (EQCM) technique. The advantage of this method proposed over previously reported is that the enantio-recognition can be performed in a high efficiency without requiring an expensive chiral column. Especially, the ejection and re-binding of amino acids can be accomplished by adjusting the potential applied on the column packed with molecularly imprinted PAn.     

Doping effect of organic sulphonic acids on the solid‐state synthesized polyaniline

Polyaniline (PANI) salts doped with organic sulfonic acids (methanesulfonicacid, p‐toluenesulphonic acid, and dodecylbenzenesulphonic acid) were first synthesized by using solid‐state polymerization method. The polymers were characterized by Fourier transform infrared (FTIR) spectra, ultraviolet‐visible spectrometry, X‐ray diffraction, cyclic voltammetry, scanning electron microscopy, transmission electron microscopy, and conductivity measurements. It was found that PANI doped with p‐toluenesulphonic acid is formed in conductive emeraldine oxidation state, and displayed higher doping level and cyrstallinity. On the contrary, PANI doped with dodecylbenzenesulphonic acid was lower at doping level and highly amorphous. In accordance with these results, the conductivity and electrochemical acitivity was also found to be higher in p‐toluenesulphonic acid‐doped PANI, and these properties were opposite in the case of dodecylbenzenesulphonic acid. The results also revealed that the morphology of dodecylbenzenesulphonic acid‐doped PANI was remarkably different from other PANI salts. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Study of polyaniline polyacrylamide composites by positron annihilation technique

Polyaniline doped with nonoxidizing Bronsted acids is recognized as a conducting material, as its electrical conductivity changes with percentage of doping. In the present work, different percentages of doped polyaniline were blended with polyacrylamide and their electrical conductivities as well as the positron annihilation lifetimes were measured. Analysis of data yielded three lifetime components. It was observed that the value of the short lifetime component remained constant for doping concentration, whereas that of the intermediate component τ₂ decreased. The relative intensity pertaining to τ₂, however, increased with the increase in doped PANI concentration. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 930–933, 2003     

Electrochromic properties of chemically prepared polyaniline

The electrochromic properties in non-aqueous medium of chemically prepared polyaniline films proved not to depend on the oxidizing agent used for the synthesis and were very similar to the properties of electrochemically prepared films. These properties were studied by measuring the optical contrast changes at fixed wavelengths in the uv/visible region during cyclic voltammetric scans and by applying 7 × 10³–8 × 10³ redox potential steps.     

Novel conducting polyaniline blends with cyanoresin

Novel conducting polyaniline (PANI)/cyanoresin (Cyan) blends were prepared by the addition of Cyan/dimethylformamide solutions to aniline monomer/dopant solutions and the in situ chemical oxidative polymerization of aniline with ammonium persulfate as an oxidant in aqueous p‐toluene sulfonic acid solutions. The PANI/Cyan blends were prepared with various compositions (5:95, 10:90, 20:80, 30:70, 40:60, 50:50, 60:40, and 70:30), and blend films of PANI/Cyan were obtained with a casting method. The conductivity of the PANI/Cyan blend films was 10^?7 to 10^?2 S/cm, which was measured by a four‐probe technique. The tensile strength of the blend films was maintained with an increasing amount of PANI (up to 50 wt %), and this was attributed to intermolecular interactions such as hydrogen bonding between PANI and Cyan and a reinforcing effect through blending. This hypothesis was corroborated by Fourier transform infrared spectroscopy. Field emission scanning electron microscopy and thermogravimetric analysis were also used to investigate the morphology and thermal properties of the conducting PANI/Cyan blend films, respectively. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1035–1042, 2005     

用于除草剂残留分析的分子印迹聚合物的制备

分子印迹聚合物（MIP）由于具有高度的特异性、亲和性、对光和热稳定以及耐酸碱性而广泛应用于环境、食品、药物、生物等领域样品的预处理。本文综述了近10a来,用于除草剂残留分析的分子印迹聚合物的制备。     

聚苯胺季铵盐的合成及其性能研究

以邻氨基苯甲酸为原料,与氯乙醇反应生成2-氨基苯甲酸氯乙酯,然后用三乙胺季铵化合成了苯胺季铵盐,并将其聚合,通过红外光谱、紫外-可见光谱、X-射线衍射、循环伏安法和热重分析等对其结构与性能进行了研究。     

Preparation and characterization of polyaniline powder synthesized on microstructured aluminium

Aluminium surfaces were microstructured in 0.1 M HNO₃ by potentiodynamic anodic activation to potentials generating pitting. This surface was then used as an electrode to prepare polyaniline powder. The number of pits is responsible for the amount of powder produced. Emeraldine salt powder was successfully prepared from 0.4 M aniline in 0.5 M H₂SO₄ solution. Other acid solutions for deposition are not convenient because powders are electrochemically inactive (e.g., in 1 M HNO₃) or the electrode is covered by a film (e.g., in 0.5 M H₂C₂O₄).     

Mixed electron and proton conductivity of polyaniline films in aqueous solutions of acids: beyond the 1000 S cm−1 limit

BACKGROUND: The application potential of conducting polymers depends on their conductivity. It is generally assumed that the conductivity determined in the dry state is a parameter that unambiguously characterizes them. RESULTS: The conductivity of polyaniline (PANI) films immersed in aqueous solutions of sulfuric acid may be more than 1000 times higher compared with that obtained by measurement of dry films in air, and is estimated to reach a value exceeding 3300 S cm^?1 in 1 mol L^?1 sulfuric acid. This is explained by the reduction of conductivity barriers between conducting PANI islands. CONCLUSION: The organized polymer chains in the conducting islands of a PANI film are separated by disordered regions of low conductivity in the dry state. The penetration of sulfuric acid solution into the disordered areas increases the overall conductivity of the PANI film by improving the electrical contact between the islands through ionic charge transport. The electronic conductivity of the PANI film in the dry state thus converts to mixed electron–proton conduction in acidic aqueous solutions, electron conductivity being dominant in ordered regions and ionic conductivity in disordered regions separating them. Weakly bound protons are the most important ionic charge carriers hopping along the PANI chains. Copyright © 2009 Society of Chemical Industry     

Effect of acids on in situ polyaniline film formation

The chemical oxidation of aniline with ammonium persulfate (APS) to form polyaniline (PANI) films has been studied in different aqueous acid media such as sulfuric, nitric, phosphoric and acetic acids. A comparison was made between the yields of PANI film deposition during the polymerization from these media with the corresponding one obtained previously from aqueous HCl solution. The degradation of the formed PANI films at the beginning of polymerization obtained at the higher concentrations of HCl is absent when the other acids under consideration were used. The effect of acid concentration on the yield and growth rate of the PANI film was studied. The variation in the yield and growth rate of the polymer films at different acid concentrations was explained on the basis of the electrostatic repulsion and the screening effects. Copyright © 2004 Society of Chemical Industry     

复合氧化剂在合成导电聚苯胺中的应用

以苯胺为单体,采用(NH4)2S2O8和抗坏血酸组成的复合氧化剂,在硫酸水溶液中,用化学氧化法直接合成导电聚苯胺。系统地研究了复合氧化剂配比、硫酸的浓度、氧化剂浓度等因素对苯胺聚合反应的影响。结果表明,该方法聚合反应的最佳条件为:在10~25℃的温度范围内,不加氮气保护条件下,苯胺1.0 mol/L,H2SO41 mol/L,(NH4)2S2O81 mol/L,(NH4)2S2O8/抗坏血酸(C6H8O6)的配比为10∶1,合成了电导率达1.33 S/cm、产率达82.17%的聚苯胺。通过红外光谱和X衍射研究了通过不同氧化剂聚合得到聚苯胺的结构变化,结果表明,复合氧化剂氧化聚合得到的聚苯胺结晶比通过过硫酸胺作氧化剂聚合得到的聚苯胺结晶好,并且相应基团在红外光谱上发生红移。     

A spectroelectrochemical study on polaron transformations in polyaniline in sulphuric and p-toluenesulphonic acids

The electrochemical processes involved in the oxidation of polyaniline in sulphuric and p-toluenesulphonic acids were studied under steady potential and during a potentiostatic current transient using UV-Vis absorption spectroscopy. It was found that sulphate ions are reversibly inserted into the polymer film on oxidation and removed during reduction, while tosylate ions are irreversibly accumulated slowly in the film and protons are exchange instead. The redox peaks involve two independent transformation equilibria of three main species: reduced species, polaron and bipolaron of different chain lengths. While the charge involved in the polaron transformation is less than 20% of the charge involved safely in the oxidation of polyaniline before the onset of degradation, a significant capacitive contribution 40–60% was detected before the start of further oxidation of the polaron to bipolarons. Nernstian analysis of the redox process was possible only for the reverse scan and with the absorption peak of the reduced form. The spectroscopic transients showed that the oxidation, which is much slower than the reduction, is essentially the same in both acids without a significant contribution of the diffusion of dopant species in contrast with the reduction process. ©1997 SCI     

制取聚苯胺-聚乙烯醇导电共混膜的条件研究

用共混浇铸法制备PAN-PVA共混膜,探讨了制膜液中PAN与PVA的质量比、成膜干燥温度和制膜液浓度对共混膜性能的影响,测定了膜的拉伸断裂强度和断裂伸长率。结果表明,制取电导率高、力学性能较好的适合作电磁屏蔽材料的PAN-PVA共混膜的条件为:制膜液内PVA的质量百分数为40%,成膜干燥温度为80℃,制膜液浓度为17.0 mg/mL。     

Control of polyaniline conductivity and contact angles by partial protonation

Many studies require a specific value of conductivity when investigating conducting polymers. The conductivity of polyaniline can efficiently be controlled by partial protonation of the polyaniline base. Although this is a simple task in principle, practical guidelines are missing. In the present study, the changes in the conductivity of polyaniline base after immersion in aqueous solutions of various acids are reported. Polyaniline base has been reprotonated in aqueous solutions of picric, camphorsulfonic and phosphoric acids. The conductivity of partially reprotonated polyaniline varied between 10⁻⁹ and 10⁰ S cm⁻¹. The relation between the pH of a phosphoric acid solution, which was in equilibrium with polyaniline, and the conductivity σ is pH = 0.77 − 0.64 log(σ [S cm⁻¹]). The wettability, i.e. water contact angles, can similarly be set by partial protonation to between 78° for polyaniline base and 44° for polyaniline reprotonated in 1 mol L⁻¹ phosphoric acid. In solutions of picric acid, the transition from the non‐conducting to the conducting state occurs over a narrow range of acid concentrations, and the tuning of conductivity is consequently difficult. Phosphoric acid is well suited for the control of conductivity of polyaniline because of the moderate dependence of the conductivity on the acid concentration or pH. Copyright © 2007 Society of Chemical Industry     

导电聚苯胺的研究进展

概述了聚苯胺的几种合成方法及其溶解性问胚,并介绍了聚苯胺复合材料及聚苯胺的应用。     

聚苯胺薄膜在不同质子酸溶液中的生长

在H2SO4、HCl、HNO3和H3PO4质子酸水溶液中采用原位聚合法在石英基片上制备了聚苯胺薄膜.通过对薄膜试样进行红外光谱(FT-IR)、紫外光谱、扫描电镜(SEM)、导电性能的测试研究不同种类质子酸对聚苯胺薄膜厚度及导电性能的影响.实验结果表明,试样的掺杂程度和薄膜分子链共轭长度是提高试样导电性能的重要因素,质子酸的氧化性对薄膜生长和导电性能也会产生影响.     

XPS study of aged polyaniline films

In this article, a study of the aging of conducting Polyaniline–Polystyrene blends using X‐ray photoelectron spectroscopy (XPS) and UV‐visible‐near IR analysis is presented. The physicochemical results are compared to those obtained by electrical measurements. XPS results confirm the existence of an oxidation process also deduced by the electrical conductivity studies. The N1s and S2p core level spectra decomposition allows to show that a deprotonation process and cyclization of tertiary amine occur during aging. The absorption spectrum shows a decrease of delocalized charges and the apparition of localized polarons after a long aging time. All these mechanisms are responsible of the electrical conductivity decrease observed during aging at elevated temperature. The results are presented for films of PANI–CSA–PSt blends, but the conclusions can be extended to pure conducting PANI–CSA films. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3730–3736, 2003     

Selective solid‐phase extraction of naphazoline using imprinted polymers as matrix prepared by precipitation polymerization

The molecularly imprinted polymers (MIP) for drug naphazoline (NAZ) have been synthesized by precipitation polymerization. The effect of the dispersive solvents dichloromethane (DCM), acetonitrile (ACN), and Methanol (MeOH) on particle size and morphology of MIP (P1, P2, and P3) was investigated by scanning electron microscopy (SEM). The selectivity of P1, compared with nonimprinted polymer (NIP), C₈ and C₁₈ were evaluated via static adsorption using UV spectrophotometer. The result showed that the bond amount of P1 for NAZ was significantly higher than other sorbents. The P1 were applied as a solid‐phase extraction (SPE) stationary phase to extract the NAZ from nasal drops and recoveries of more than 89% (relative standard deviations, RSD <5%) were obtained by high performance liquid chromatograph (HPLC) analyses. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010