Polyaniline film deposition from the oxidative polymerization of aniline using K2Cr2O7

The deposition of the polyaniline (PANI) films was monitored using the quartz crystal microbalance (QCM) technique. The films were grown from an aqueous dilute hydrochloric acid solution by the chemical oxidation of aniline using potassium dichromate (KDC). The effect of the initial molar ratio of the KDC/aniline on the yield and the growth rate of the PANI films were studied. There is no optimum initial molar ratio of KDC/aniline of PANI film deposition. Also there was a small depletion period and no degradation to the deposited PANI films. The order of the polymerization kinetics was studied with respect to KDC. The UV-visible spectra of the PANI films grown onto a glass support immersed into the bulk solution were measured. The absorption of the PANI film with the time of polymerization was compared to the growth of the PANI film thickness with time determined from the QCM technique. The characteristics of the PANI film deposition were compared to the corresponding ones that were observed during the oxidative polymerization of aniline with ammonium persulphate (APS).     

The kinetics and spectral studies of the in situ polyaniline film formation

The chemical oxidation of aniline with ammonium persulfate (APS) in an aqueous acidic solution to form polyaniline (PANI) films has been studied using the quartz crystal microbalance (QCM) technique. The kinetics of the film formation was investigated. The reaction exhibited half-order with respect to APS and first-order to aniline. The effect of temperature on the growth rate of PANI films was studied. The activation energy is 39.79 kJ/mol. This is in agreement with the corresponding one determined for the chemical polymerization of PANI in the bulk. The UV-visible spectra of the PANI films grown onto a glass support immersed into the bulk solution were measured. The absorption of the PANI film with time was also studied and compared to the growth of the PANI film thickness using the QCM technique.     

pH sensor based on polyaniline and aniline–anthranilic acid copolymer films using quartz crystal microbalance and electronic absorption spectroscopy

The pH sensitivity based on conducting polyaniline (PANI) and copolymer of aniline and o‐anthranilic acid (AA) films were studied using quartz crystal microbalance (QCM) technique and UV–Vis spectroscopy. The sensor was constructed from these polymer films coated on the electrode of the QCM. The resonant frequency changes as a function of pH in the range of 2–12 were measured. These changes are quantitative indication of the degree of dedoping or redoping of the polymer films upon the subsequent exposure of the electrode to 0.25 M sulfuric acid and different pH solutions. There are two linear regressions between the frequency change and pH with two different and opposite slopes in the regions from 2 to 9 and 9 to 12. The pH sensitivity of the copolymer film was found to be less than using the PANI film. Thin films of PANI and copolymer, which were chemically polymerized in a sulfuric acid solution, were deposited onto the inner walls of the quartz cuvettes. The UV–Vis absorption spectra of these films were measured in different pH solutions. Relations between the maximum absorption and its wavelength versus pH were constructed. The copolymer film shows some advantages over the PANI film. The difference between the PANI and copolymer films as pH sensors using the QCM and electronic absorption extends from the determination of pK_a for both films. Copyright © 2008 John Wiley & Sons, Ltd.     

乳液聚合中聚苯胺膜形成的动力学研究

以(NH4)2S2O8(APS)为氧化剂,十二烷基苯磺酸(DBSA)同时为乳化剂和掺杂剂,采用乳液聚合方法制备聚苯胺膜(PANIfilm),用石英晶体微天平(QCM)实时监测聚苯胺膜的形成过程,并对其动力学过程进行研究.结果表明,聚苯胺成膜反应对APS是0.5级,对苯胺是1级,聚苯胺膜增长速率随温度的升高而增加,而聚苯胺膜的最终沉积量却减小,表观活化能Ea=41.15kJ/mol,与均相溶液聚合成膜法的结果相近;随着DBSA浓度的增加,聚苯胺膜增长速率减小,而最终的沉积量增大.     

The effect of HCl on the polymerization of aniline with ferric chloride

The chemical oxidation of aniline with ferric chloride, FeCl₃ · 6H₂O in the HCl aqueous solutions to form polyaniline (PANI) powder and films has been investigated. The effect of acid concentration on the deposition of PANI film in situ was studied. The presence of an acid affects both the yield of the polymer and the growth rate of the film. This effect was corroborated by the UV-visible absorption studies of the films deposited on glass supports during the polymerization. The influence of the acid on the yield of the PANI powder formed in the bulk solution was also examined. We have found that the yield of the polymer formed either on the surface or in the bulk solution decreased with the increasing concentration of HCl. The effect of HCl concentration on the in situ UV-visible absorption at the early stages of aniline polymerization is also discussed. The text was submitted by the authors in English.     

Preparation and characterization of polyaniline films in the presence of N-phenyl-1,4-phenylenediamine

The chemical oxidation of aniline to form polyaniline (PANI) films was made in the presence of N-phenyl-1,4-phenylenediamine (PPDA) in aqueous hydrochloric acid medium. The PANI films were monitored by using the quartz crystal microbalance (QCM) technique. The effect of PPDA and its concentration on the film formation was investigated. It was found that PPDA decreases the yield of the PANI film, the induction period and the depletion time of the polymerization. However, the growth rate of the film formation was found to increase by increasing PPDA concentration. These results were justified by measuring the UV-VIS absorption spectra for the in situ PANI films and the in situ UV-VIS absorption spectra for the polymer in the bulk during the polymerization. The conductivity for the PANI films at different concentrations of PPDA was measured. Also, the IR spectra, X-ray and the thermal gravimetric analysis for the PANI powder formed in the bulk in the presence of PPDA were measured and discussed.     

Chemical synthesis and characterization of aniline and o-anthranilic acid copolymer

The chemical co-polymerization of aniline with o-anthranilic acid (AA) to form copolymer films has been made in aqueous hydrochloric acid medium. The copolymer films were monitored by using the quartz crystal microbalance (QCM) technique. The effect of AA and its concentrations on the film formation was investigated. The results were justified by measuring the UV-Vis absorption spectra for the in situ copolymer films grown onto glass slides immersed into the polymerization media and the in situ UV-Vis absorption spectra for the copolymer in the bulk during the co-polymerization. The conductivity for the copolymer films and powder pellets at different molar ratios of aniline/AA were measured. Also, the IR spectra, X-ray diffraction and the thermal gravimetric analysis for the copolymer powder formed in the bulk in the absence and presence of AA were measured and discussed. It is found that the presence of AA affects the yield, induction period, depletion time and growth rate of the film formation. It also affects the crystallinity, and conductivity as well as the solubility of the polymer. Finally, the dopant weight fraction (w) associated with the copolymer was determined. It is almost half the value determined for the polymer in absence of AA.     

Study the effect of inorganic salts on the chemically polymerized aniline films using quartz crystal microbalance

The chemical oxidation of aniline with ammonium peroxydisulfate to form polyaniline (PANI) films has been studied in different aqueous acid mediums such as HCl, HNO₃, and H₂SO₄. The yield and the growth rate of the PANI film deposition were measured using the quartz crystal microbalance (QCM) technique. The effect of different salts such as KCl, NaNO₃, and K₂SO₄ and their concentration on the yield and the growth rate of the film formation are investigated. The yield of PANI film deposition depends on the acid used and the type of salts as well as their concentrations. When HCl and HNO₃ were used as media, the addition of salts with the same anion has no effect. However, when H₂SO₄ was used as media, the addition of salts with the same anions as the medium enhances the yield of PANI film deposition. The UV–visible spectra of the produced PANI films in the absence and presence of the salts are also studied. Copyright © 2007 John Wiley & Sons, Ltd.     

石英晶体微天平技术在苯胺乳液聚合动力学研究中的应用

采用石英晶体微天平(QCM)技术, 探讨了在有无磁场条件下, 用过硫酸铵(APS)作为引发剂时苯胺的乳液聚合动力学行为. 研究结果表明, 苯胺的乳液聚合反应速率对苯胺(An)是一级反应; 对APS和十二烷基苯磺酸(DBSA)均为0.5级反应. 磁场环境中苯胺的聚合速率比在无磁环境中的要快. 在有无磁场条件下, 反应的表观活化能分别为40.4和41.6 kJ/mol. 结果表明, QCM技术可以作为研究An聚合动力学的一种有效方法.     

Influence of the magnitude and direction of electric field on the transport and growth property of deposited polyaniline films

Polyaniline (PANI) films were deposited by electrochemical polymerization of aniline monomer on a fluorine-doped glass substrate at room temperature under different electric field directions. The as-synthesized PANI films obtained at different growth cycles were characterized by AC impedance spectroscopy and scanning electron microscopy (SEM). The results revealed that the film morphology, transport kinetics, and electrical properties are strongly dependent on the electric field direction and magnitude of the applied field during electropolymerization. The SEM morphology and AC impedance (modulus spectroscopy) indicate that a more homogeneous, high-porous, and conducting PANI film is induced by horizontal electric field direction (HEFD) electrodeposition, whereas the modulus spectroscopy of the PANI film deposited by vertical electric field direction (VEFD) reveals that VEFD deposition favours two-dimensional growth of PANI. The obtained polymer is more of dielectric in nature due to preferable dendritic growth which is supported by SEM analysis.     

Voltammetric and waveguide spectroelectrochemical characterization of ultrathin poly(aniline)/poly(acrylic acid) films self-assembled on indium-tin oxide

We report on the spectroelectrochemical characterization of conducting polymer (CP) films, composed of alternating layers of poly(aniline) (PANI) and poly(acrylic acid) (PAA), deposited on ITO-coated, planar glass substrates using layer-by-layer self-assembly. Absorbance changes associated with voltammetrically induced redox changes in ultrathin films composed of only two bilayers (ITO/PANI/PAA/PANI/PAA) were monitored in real time using a unique multiple reflection, broadband attenuated total reflection (ATR) spectrometer. CP films in contact with pH 7 buffer undergo a single oxidation/reduction process, with ca. 12.5% of the aniline centers in the film being oxidized and reduced. The ATR spectra indicate that during an anodic sweep, the leucoemeraldine form of PANI in these films is oxidized to generate both the emeraldine and pernigraniline forms simultaneously. A comparison of the behavior observed during anodic and cathodic sweeps suggests that the rate of oxidation is limited by structural changes in the polymer film originating in electrostatic repulsion between positively charged PANI chains.     

In situ polymerized polyaniline films. 4. Film formation in dispersion polymerization of aniline

Polyaniline films were grown on glass supports during dispersion polymerizations of aniline using poly(N-vinylpyrrolidone) and hydroxypropylcellulose as stabilizers. The initiation of polyaniline chains is proposed to be heterogeneously catalyzed by the surfaces immersed in the reaction mixture. Film formations in dispersion and precipitation polymerizations are compared. Surfometry and optical absorption were used to assess the submicrometer film thickness, and FTIR spectroscopy was used to analyze the chemical structure of films and prove the absence of stabilizer. The film thickness was proportional to the dimensions of simultaneously produced colloidal polyaniline particles. The conductivity of films increased with increasing film thickness.     

层层自组装原位聚合聚苯胺复合膜成膜机理研究

从苯胺单体出发, 通过原位聚合、现场掺杂以及基于静电力的层层自组装制备了聚苯胺复合膜. 通过苯胺活性溶液的温度及颜色变化跟踪聚合反应进程, 同时考察不同聚合反应阶段所得聚苯胺复合膜的紫外-可见吸收, 并进一步探讨聚苯胺复合膜的成膜机理. 研究表明, 成膜机制是由聚合反应初始阶段的苯胺阳离子或苯胺阳离子自由基通过静电作用快速吸附到负电性的基片表面, 形成均匀的聚合中心, 链增长生成聚苯胺; 该聚苯胺在酸性条件下经现场掺杂显电正性, 可吸附电负性的聚苯乙烯磺酸钠(PSS), 以此循环层层组装得到多层聚苯胺复合膜.     

Nanomechanical properties of polyaniline and azo polyelectrolyte multilayer films

<正>Nanomechanical properties of multilayer films constructed of polyaniline(PANI) and azobeneze-containing polyelectrolytes(PNACN and PPAPE) were studied by using nanoindentation method.The multilayer films were prepared by the electrostatic layer-by-layer self-assembly through alternately dipping in the polymer solutions.The multilayer films deposited onto the glass slides after proper dry were used for the nanomechanical property testing.The nanomechanical measurement indicated that the PANI/PNACN and PANI/PPAPE multilayers possessed the mean elastic modulus of 5.42 GPa and 4.35 GPa,and hardness of 0.26 GPa and 0.18 GPa,respectively.The nanoscratch properties of the PANI/PNACN and PANI/PPAPE multilayer films were also measured.The critical loads of PANI/PNACN and PANI/PPAPE films were 103.52 mN and 100.59 mN.The degree of electrostatic cross-linking in the multilayers could be altered by exposing the films to aqueous solutions with different pH values.As a result,the modulus and hardness of the multilayer films were changed through the solvent treatment.Both modulus and hardness of the PANI/PNACN films obviously increased after dipping the multilayer films in solutions with pH in a range from 9 to 11.     

Conducting polymer films fabricated by oxidative graft copolymerization of aniline on poly(acrylic acid) grafted poly(ethylene terephthalate) surfaces

A conductive polyaniline/poly(ethylene terephthalate) (PANI/PET) composite film was fabricated via the oxidative graft copolymerization of aniline (ANI) onto the plasma-induced poly(acrylic acid) (PAAc) grafted PET surface. The attenuated total reflectance Fourier transform infrared spectroscopy spectra (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) results confirmed that PANI was successfully grafted onto the surface of the PAAc-g-PET films. The effects of the experimental conditions on the percentage of PANI grafted onto the PAAc-g-PET films were extensively investigated. A very high grafting percentage of ANI can be obtained through the acid-base reaction between the aniline monomer and PAAc on the PAAc-g-PET surface at high temperature. As a result, the grafting percentage of PANI can be increased to as high as 12.18 wt %, which causes the surface resistance of the PANI-g-PAAc-g-PET film to be reduced to about 1000 Omega/sq. We predicted that this is because of the high flexibility of the PAAc molecular chains and high solubility of aniline, both of which facilitate the binding of aniline to PAAc during this high temperature acid-base reaction. It was observed by atomic force microscopy (AFM) that the PANI-modified PET surface exhibits higher size irregularity and surface roughness, which further indicated that a much greater number of aniline molecules can be reactively bonded to and distributed along the grafted AAc chains and that the PANI-g-PAAc-g-PET surface resulting from the sequential oxidative graft copolymerization can possess higher electrical conductivity.     

纳米纤维聚苯胺膜在不锈钢电极表面的生长过程

研究了脉冲电流法(PGM)聚合苯胺时, 纳米纤维聚苯胺(PANI)膜在不锈钢(SS)电极表面的生长过程. 用计时电位法和扫描电子显微镜(SEM)表征了聚苯胺生长过程的电化学特征和微观形貌; 并通过循环伏安(CV)法研究了苯胺的聚合速率. 结果表明, 聚苯胺的生长经历了两个阶段, 首先是在裸不锈钢电极表面上形成颗粒状聚苯胺, 此时聚合电位约为1.10 V, 经历了30 s后, 电极表面被一层颗粒状聚苯胺膜所覆盖; 在此基础上, 聚苯胺以纳米纤维状结构继续生长, 当颗粒状聚苯胺被纳米纤维状聚苯胺膜完全覆盖时, 聚合电位降至0.75 V左右并保持稳定.     

A comparative study on the viscoelasticity and morphology of polyaniline films galvanostatically grown on bare and 4-aminothiophenol-modified gold electrodes using an electrochemical quartz crystal impedance system and SEM.

The equivalent-circuit parameters of the 9-MHz piezoelectric quartz crystal (PQC) resonance were measured in situ during the galvanostatic polymerization of aniline on 4-aminothiophenol(4-ATP)-modified and bare Au electrodes for ca. 2000 s, respectively. Two polymerization media, 0.100 mol L-1 aniline in 1.0 mol L-1 H2SO4 and in 2.0 mol L-1 HClO4 aqueous solutions, and two values of the current density, 12 and 36 microA cm-2, were used. At identical levels of the resonant frequency shifts in the solutions, obviously greater increases in the motional resistance (R1) were found after aniline polymerization on bare Au electrodes, though the absolute values of delta f0/delta R1 were all large; also, the resonant frequency shifts in air (delta f0g) were considerably smaller for PANI films grown on bare Au electrodes. It is thus concluded that, under identical polymerization conditions, (1) the PANI film grown on a bare gold electrode is rougher, less compact, and can entrap solution more notably; (2) the deposition efficiency of PANI is higher on a 4-ATP-modified Au electrode, owing to a significantly greater observed "dry" frequency shift, and thus a greater "net" mass value of the polyaniline backbone. SEM observations have confirmed that PANI films on 4-ATP-modified Au electrodes were smoother and more compact than those grown on bare Au ones under identical polymerization conditions. In addition, a technique of simultaneous measurements of the electroacoustic admittance of the PQC resonance and the electrochemical impedance was used to monitor the adsorption of 4-ATP onto a PQC gold electrode.     

聚苯胺/纳米二氧化锰复合材料Ⅰ.原位氧化合成制备

用固相合成法制备了纳米二氧化锰(nm-MnO2),并通过原位聚合法制备了聚苯胺／纳米二氧化锰复合材料。研究结果表明：在苯胺／nm-MnO2的盐酸反应体系中,nm-MnO2可以使苯胺氧化聚合。在一定的nm-MnO2用量下,聚苯胺的产率随苯胺添加量的增加而下降,nm-MnO2在产物中的含量也随之下降,且含量很低。在苯胺：／nm-MnO2／过硫酸铵的反应体系中,研究了Nm-MnO2通过两种不同的加料方式原位制备PA-NI／nm-MnO2复合材料的合成条件。第一种方式为nm-MnO2和过硫酸铵同时与苯胺混合,一起参与苯胺的氧化聚合。第二种方法是先将过硫酸铵和苯胺混合,3min后再将nm-MnO2加入反应体系中。研究表明：第一种加料方式得到的队NI／nm-MnO2中nm-MnO2的含量很低;第二种加料方式可以得到高nm-MnO2含量(w=0．14-0．73)的产物,其电导率约10^-4S／cm。     

Study of the growth process of in situ polyaniline deposited films

Polyaniline (PAni) thin films were deposited onto BK7 glass substrates using the in situ deposition technique. The control of the time and the aniline concentration in the PAni polymerization reaction on the film deposition allowed us to prepare films with different thickness, down to approximately 25 nm. The film growth process was monitored by measuring the UV-vis spectra and the AFM height profiles of the film surface. The curves of adsorption kinetics were analyzed with the Avrami's model, yielding an exponent n=3, thus indicating nucleation of spheroids at the initial stages of polymerization that grow through a diffusion process. AFM images of the surface height profiles corroborate this hypothesis, with spheroids growing with no preferred orientation during the in situ deposition.     

A study on the synthesis,characterization and properties of polyaniline using acrylic acid as a primary dopant. I: polymerization and polymer

In the presence of acrylic acid (AA) as a primary dopant, polyaniline (PANI) doped with poly(acrylic acid) was successfully synthesized by using ammonium persulfate (APS) as initiator and oxidizing agent. The effect of experimental conditions on the polymer yields was systematically studied. It was found that the polymer yield can be as high as 65%, and this value strongly depends on synthesis conditions, such as the reaction time, the molar ratio of oxidizing agent to aniline monomer, the concentration of reactants and reaction temperature. The molecular weight ( ) of main chains of the de‐doped PANI is estimated to be 32,000–53,000. Based on the data of FT‐IR, UV‐vis, ¹³C‐nuclear magnetic resonance (NMR), elemental analysis and electrical conductivity measurement, the emeraldine salt form of PANI was confirmed and the molecular structure of the resulting PANI‐AA was proposed. Accordingly the reaction mechanism was discussed and it was convinced that the polymerization reaction of AA is initiated by APS. Copyright © 2004 John Wiley & Sons, Ltd.