The development of conductive composite surfaces by a diffusion-limited in situ polymerization of pyrrole in sulfonated polystyrene ionomers

Electrically conductive composite surfaces were prepared by a diffusion-controlled in situ polymerization of pyrrole in the surface layer of sulfonated polystyrene ionomer films. Premolded films of the ionomer sulfonic acid derivatives were sequentially immersed in aqueous solutions of pyrrole and FeCl₃, and polymerization occurred only where both the monomer and the oxidant were present. The penetration of the polypyrrole (PPy) into the film was controlled by varying the immersion time in the monomer solution. The amount of PPy produced depended on the immersion time of the film in the monomer and the degree of sulfonation of the ionomer. Surface conductivities of 10⁻⁴-10⁻¹ S/cm were achieved with PPy concentrations from 2 to 22 wt % and composite layers as thin as 15 μm. Intermolecular interactions occurred between PPy and the ionomer by proton transfer. Incorporation of PPy also increased the tensile strength of the ionomer film, significantly increased its modulus above T_g, and inhibited melt flow. © 1997 John Wiley & Sons, Inc.     

Electropolymerization of polypyrrole, modified with germanium, on a passivated titanium electrode in aqueous nitrate solution: new results on catalytic reduction of protons and dissolved oxygen

Conductive polypyrrole (PPy) films and PPy films containing Ge microparticles were synthesized by anodic oxidation of pyrrole in acidic nitrate solutions using a bare passivated titanium electrode. Well-adhering black PPy films were obtained both under galvanostatic and potentiodynamic polarization. After the formation of the PPy film, during the first anodic cycle, an increase of the anodic deposition current with the number of cycles was observed, revealing the increase of conductivity of the growing film. The variations of the electrode surface area were estimated by impedance spectroscopy measurements. The kinetics of the PPy film formation is controlled by diffusion of the Py monomer in the solution. The diffusion coefficient, estimated by two different methods, was ca. 2×10^–6 cm² s^–1. The reduction rate of oxygen and protons at the Ti/PPy/Ge electrodes depends on how the Ge microparticles are incorporated in the PPy film. Optimum conditions for this incorporation are realized with thin PPy films and high Ge loading. Thermogravimetric analysis shows that the PPy film containing Ge microparticles is more thermally stable than the blank PPy film. Electronic Publication     

Preparation of conductive,flexible and transparent films by in situ deposition of polypyrrole nanoparticles on polyethylene terephthalate

In this study polypyrrole (PPy) nanoparticles were deposited as a thin film on the modified surface of polyethyleneterephthalate (PET) by in situ chemical polymerization in the presence of sodium dodecylsulfate (SDS), sodium dodecylbenzenesulfonate (DBSNa) and mixture of them as the surfactant. The surface of PET was modified by KOH before deposition and was investigated for conductivity and adhesion of PPy nanoparticles to PET. Resulting conductive flexible films were characterized by UV–Vis spectroscopy, fieldemission scanning electron microscopy, contact angle measurements and four-point-probe technique for conductivity. Direct morphological observation (FESEM) and electrical measurements indicated that the morphology, conductivity and the nature of deposited PPy films depend on surfactant, surface modification of PET and monomer concentration. In optimized process condition, uniform conductive films of PPy were obtained with good adhesion to PET.     

多次聚合法制备多孔聚吡咯厚膜及其电化学容量性能

为了得到高面积比容量的聚吡咯(PPy)膜超级电容器电极材料, 用多次聚合法合成了PPy厚膜, 聚合电量分别为8、10和12 mAh·cm-2, 掺杂离子分别为氯离子和对甲基苯磺酸根离子(TOS-). PPy膜的电化学性能采用恒电流充放电、循环伏安(CV)和电化学阻抗谱(EIS)等方法测试. 研究表明, 多次聚合法可以制备表面平整且内部均匀多孔的PPy厚膜. 在聚合电量为12 mAh·cm-2时, 用Cl-、TOS-两种离子掺杂的PPy厚膜的面积比容量高达5 F·cm-2, 并表现出理想的电化学容量性能. 同时PPy-Cl厚膜的质量比容量达到330 F·g-1, PPy-TOS厚膜的质量比容量略低(191 F·g-1), 但具有更快的充放电速率. 与一次聚合法合成的PPy 薄膜相比, 多次聚合法合成的PPy厚膜的质量比容量没有降低. 通过场发射扫描电镜(SEM)观察了一次聚合法和多次聚合法制备的PPy厚膜的截面形貌, 并讨论了多次聚合法的合成机理.     

Synthesis of electromagnetic functionalized nickel/polypyrrole core/shell composites

Microstructured Ni/PPy (PPy: polypyrrole) core/shell composites were prepared from an in situ chemical oxidative polymerization of pyrrole (Py) monomer in the presence of Ni powder, with ammonium persulfate (APS) as oxidant and citric acid (C6H8O7) as dopant. X-ray diffraction and Fourier transform infrared analyses indicate that there is no chemical interaction between Ni powder and protonated PPy. The mass percentages of PPy, calculated from the remanent weight percentages of Ni/PPy composites after thermogravimetric analysis, are in consistent with those as designed. The prepared Ni/PPy composites are soft and ferromagnetic materials, where a linear increase of saturation magnetization (MS) and remanent magnetization (MR) as a function of Ni powder content is proposed. The permeability of Ni/PPy composites presents a natural magnetic resonance at 6.0 GHz, and Cole-Cole semicircle was applied to explain the permittivity. Electromagnetic absorption less than -10 dB is found for Ni/Py=4:1 (11-15.4 GHz) and Ni/Py=2:1 (12-17.5 GHz). The ternary Debye relaxations for enhanced dielectric loss induced by PPy coatings and proper electromagnetic impedance matching due to the synergetic consequence of the Ni cores and PPy shells contribute to the improvement of the electromagnetic absorption of the Ni/PPy core/shell composites. It is important to notice that dielectric loss and electrical conductivity should be considered simultaneously in designing dielectric-type electromagnetic absorbing materials.     

Ultra low field emission characteristics of chloride doped polypyrrole films

Field emission characteristics of chloride doped polypyrrole (Cl‐PPy) films have been investigated. For this purpose, freestanding Cl‐PPy films have been synthesized by interfacial polymerization from two different monomer (pyrrole) concentrations (1 and 0.1 M), keeping the monomer to oxidant (FeCl₃) concentration ratio equal to 1. The surface morphology of these Cl‐PPy films, as revealed from scanning electron microscopy, was found to be granular in nature. The average grain size of films prepared using 1 and 0.1 M pyrrole concentrations were ～2.5 and ～1 µm, respectively. The measured threshold field, that is, field required to draw an emission current density of 10 µA/cm², for these two films were 0.27 and 0.15 V/µm, respectively. From these films, a maximum current density of 1 mA/cm² could be drawn at an electric field of 0.42 and 0.29 V/µm, respectively. The field emission current (investigated at a preset value of 1 µA) was found to be very stable up to 3h, suggesting utility of Cl‐PPy films as a novel material for field emission based applications. Copyright © 2010 John Wiley & Sons, Ltd.     

Formation of PPy/Ta2O5/Ta structure by electropolymerization

Electropolymerization of pyrrole on tantalum (Ta) electrodes was carried out in buffer solutions (0.04 M phosphoric acid, 0.04 M acetic acid, 0.04 M boric acid and 0.2 M sodium hydroxide) containing 0.1 M sodium ptoluenesulfonate (TsONa) under galvanostatic conditions and it was found that a polypyrrole (PPy) and a tantalum oxide (Ta₂O₅) layer are formed on a Ta electrode by an electrochemical oxidation process. The conditions of this simultaneous formation were studied in respect to current density (i_d), pyrrole concentration ([Py]), pH and the amount of electricity. Under certain conditions ([Py] = 0.25 M, pH = 1.8, i_d = 10–20 mA cm^?2, the amount of electricity = 1 C), 6–8 μm thick PPy films were efficiently formed on homogeneous 30–50 nm thick Ta₂O₅ layers. The PPy film showed a high electrical conductivity (110 s cm^?1), adhered well and covered the Ta₂O₅ layer. The resulting PPy/Ta₂O₅/Ta system is therefore proved to have excellent properties as a capacitor.     

Selective and sensitive determination of dopamine by composites of polypyrrole and graphene modified electrodes

A novel method is developed to fabricate the polypyrrole (PPy) and graphene thin films on electrodes by electrochemical polymerization of pyrrole with graphene oxide (GO) as a dopant, followed by electrochemical reduction of GO in the composite film. The composite of PPy and electrochemically reduced graphene oxide (eRGO)-modified electrode is highly sensitive and selective toward the detection of dopamine (DA) in the presence of high concentrations of ascorbic acid (AA) and uric acid (UA). The sensing performance of the PPy/eRGO-modified electrode is investigated by differential pulse voltammetry (DPV), revealing a linear range of 0.1-150 μM with a detection limit of 23 nM (S/N = 3). The practical application of the PPy/eRGO-modified electrode is successfully demonstrated for DA determination in human blood serum.     

聚ε-己内酯/聚吡咯电纺膜的制备与性能

以吡咯(Py)和聚ε-己内酯(PCL)为原料、氯仿为溶剂,并掺杂一定量的十二烷基硫酸钠制备电纺膜,利用三氯化铁的氧化作用原位生成聚吡咯(PPy).对所得到的PCL/PPy电纺膜用红外光谱进行表征,在扫描电镜和透射电镜下观察纤维形貌,并测定力学性能和体积电阻率.结果表明,所生成的PPy以纳米粒子形式附着在电纺纤维表面,随着Py相对于PCL的质量百分含量由0增加到20%,PCL/PPy电纺膜的纤维直径从(730±341)nm逐渐下降至(325±84)nm;膜的拉伸模量和拉伸强度由不含Py的(25.7±0.8)MPa和(2.48±0.14)MPa分别增加至含有20%Py的(48.4±7.6)MPa和(5.05±0.59)MPa,断裂伸长率由(129±27)%下降至(86.2±9.1)%;体积电阻率降低了2～3个数量级.该PCL/PPy电纺纤维膜以期可作为电活性材料用于功能或生物医用领域.     

Direct Visualization and Semi‐Quantitative Analysis of Payload Loading in the Case of Gold Nanocages

Upon incubation with Au nanocages, pyrrole (Py) molecules can enter the cavities by diffusing through the porous walls and then be polymerized to generate a polypyrrole (PPy) coating on the inner surface. The thicknesses of the PPy coating can serve as a direct indicator for the amount of Py molecules that diffuse into the cavity. Py molecules are able to diffuse into the cavities throughout the polymerization process, while a prolonged incubation time increases the amount of Py accumulated on both inner and outer surfaces of the nanocages. Furthermore, it is demonstrated that the dimensions of the cavity and the size of the pores in the wall are not critical parameters in determining the loading efficiency, as they do not affect the thickness of the PPy coating on the inner surface. These findings offer direct evidence to support the applications of Au nanocages as carriers for drug delivery and controlled release.     

Exploring the relationship between the surface chemistry and the corrosion behavior of electropolymerized polypyrrole films deposited on the surgical ISO 5832-1 stainless steel

In the present work, electropolymerized polypyrrole (PPy) films were obtained on the surface of the surgical ISO 5832-1 stainless steel. The films were obtained from solutions containing 0.1M and 0.5M of the monomer by cyclic voltammetry deposition. The correlation between the surface chemistry of the as-deposited films and the corrosion behavior of the coated substrate is explored. X-ray photoelectron spectroscopy was used to study the chemical state of the main elements in the PPy films. Electrochemical impedance spectroscopy and potentiodynamic polarization tests were employed to evaluate the corrosion resistance of the PPy-coated samples. The tests were conducted in phosphate-buffered saline solution at 37°C. The measured corrosion current densities were dependent on the doping level of the PPy film and decreased with the reduction of the doping level of the PPy layer.     

ELECTROCHEMICAL STUDIES ON CONDUCTING COMPOSITE FILMS FROM POLYURETHANE AND POLYPYRROLE

A study on the electrooxidative polymerization of pyrrole onto polyurethane-coated platinum electrodes and the electrochemical properties of the composite polyurethane/polypyrrole films (PU/PPy) as-prepared is presented. It is found that polypyrrole grows layer by layer from the polyurethane/platinum interface through the polyurethane matrix, and ca. 20 wt.% of polypyrrole will fill up the matrix. Cyclic voltemmograms show that the composite films are porous, and the reduction-reoxidation (redox) rate of the composite films is limited by the diffusion of counteranions through the films. Larger anion size leads to slower diffusion process. The composite films can also act as modified electrodes.     

A simple one-step electrosynthesis of poly(pyrrole-sulfated β-cyclodextrin) films

A functionalized stable film of poly(pyrrole-sulfated β-cyclodextrin) has been obtained electrochemically in LiClO₄ aqueous solution using a simple 1:1 mixture of pyrrole (Py) monomer and sulfated β-cyclodextrin (SβCD). Different cyclic voltammetric behavior is obtained for polypyrrole (PPy) and poly(Py-βSCD) during electrosynthesis. Scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX) measurements on the two films have confirmed the presence of CD in the films and show that CD preferentially dopes the polymer even in the presence of a large excess of perchlorate supporting electrolyte. The morphology of the new polymers shows a more organized system under SEM examination. Contrary to conventional PPy films, this new polymer offers a wide potential range for electroanalytical exploration from selective electrodes to preconcentration/sampling devices. Electronic Publication     

In situ AFM study of electrochemical synthesis of polypyrrole/Au nanocomposite

In this work, in situ AFM measurements with simultaneously electrochemical characterization were developed to study the mechanisms of both polypyrrole (PPy) and PPy/Au composite deposition. The nanoscale information derived from the in situ AFM images associated with theoretical simulation from the measured current–time transient (i–t) reveals that Au nanoparticles with negatively charged carboxylic groups can be the nuclei by both adsorption on the electrode surface and doping on PPy for the polymerization, and thus has faster nucleation and growth rate than Py alone at the early polymerization stage. The PPy/Au deposition shows parallel nucleation processes of Au nanoparticle and Py, and an instantaneous 3D nucleation mode. The work not only provides fundamental insights for PPy/Au nanocomposite deposition process, but also optimization approaches to fabricate a superior PPy/Au film with favorable features for greater potential applications.     

Controllable fabrication of porous free-standing polypyrrole films via a gas phase polymerization

A facile gas phase polymerization method has been proposed in this work to fabricate porous free-standing polypyrrole (PPy) films. In the presence of pyrrole vapor, the films are obtained in the gas/water interface spontaneously through the interface polymerization with the oxidant of FeCl(3) in the water. Both the thickness of the film and the size of the pores could be controlled by adjusting the concentrations of the oxidant and the reaction time. The as-prepared PPy films exhibited a superhydrophilic behavior due to its composition and porous structures. We have demonstrated a possible formation mechanism for the porous free-standing PPy films. This gas phase polymerization is shown to be readily scalable to prepare large area of PPy films.     

ZnO/PPy异质纳米复合材料的制备、表征及其气敏特性

室温下, 采用原位聚合法, 以吡咯(PY)为单体, 氯化铁(FeCl₃·6H₂O)为氧化剂, 在塑料基片上聚合生长了聚吡咯(PPy)纳米微球. 然后在聚吡咯基片上生长ZnO种子, 将表面种有ZnO种子的PPy元件置于六次甲基四胺与硝酸锌的混合溶液中, 90 ℃水浴中, 在PPy微球上生长了ZnO纳米棒, 合成了PPy/ZnO异质纳米复合材料. 分别通过X射线衍射仪(XRD)和场发射扫描电镜(FESEM)对PPy/ZnO异质纳米复合材料的结构和形貌进行了表征. 制备了塑料基的PPy/ZnO异质纳米复合材料气体传感器, 在室温下, 对10×10^-6-150×10^-6 (体积分数)浓度范围的氨气进行了气敏测试, PPy/ZnO气敏元件对氨气响应的灵敏度基本呈线性关系, 且对甲醇、丙酮、甲苯等有机气体表现出很好的选择性. 最后, 对PPy/ZnO异质纳米复合材料的形成机理进行了简要分析.     

Novel chemical synthesis of polypyrrole thin film electrodes for supercapacitor application

Present investigation describes the cost-effective, novel and simple chemical synthesis of polypyrrole (PPy) thin films for supercapacitor application. These PPy films are characterized by different techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The XRD pattern reveals the amorphous nature of PPy thin film, which is highly feasible for supercapacitors. Further, FTIR study confirms the formation of PPy. The surface morphological study exhibit the coverage of uniform and smooth morphology on thin film. The electrochemical supercapacitive properties of PPy thin films are evaluated using cyclic voltammetry (CV) in 0.5 M H₂SO₄ electrolyte, which exhibits the maximum specific capacitance of 329 Fg⁻¹ at the scan rate of 5 mV s⁻¹. Additionally, an equivalent series resistance (ESR) of PPy thin films is found to be 1.08 Ω using electrochemical impedance measurement.     

A spectroelectrochemical study of conducting pyrrole-N-methylpyrrole copolymers in nonaqueous solution

Conducting poly(pyrrole-N-methylpyrrole) (P(Py-NMPy)) was electrochemically synthesized on a gold electrode in a lithium perchlorate-containing acetonitrile electrolyte solution and compared with polypyrrole (PPy) and poly(N-methylpyrrole) (PNMPy) prepared under the same conditions. The obtained polymers were characterized with cyclic voltammetry, in situ resistance measurements, in situ UV–vis spectroscopy, FTIR spectroscopy, and scanning electron microscopy. The onset potentials for pyrrole and N-methylpyrrole monomer oxidation differ by about 0.1 V. Nucleation processes initiated by the radical cations are followed by growth of nuclei into continuous films. The oxidation and reduction peaks for the P(Py-NMPy) copolymer synthesized at 1:1 M concentration ratio of the comonomers are between those of PPy and PNMPy. A decreased [Py]/[NMPy] comonomer concentration ratio yields in the copolymers shifts of peak potentials to more positive values. The in situ resistance of copolymers measured from ?0.20 to 0.90 V vs. Ag/AgCl decreased with increasing [Py]/[NMPy] concentration ratio. In situ UV–vis and ex situ FTIR spectra of copolymers show spectroscopic behavior intermediate between those of the homopolymers. Scanning electron microscopy micrographs of the samples show fundamental differences between the morphology of the homo- and copolymers.     

Solid phase photopolymerization of pyrrole in poly(vinylchloride) matrix

Electrically conductive films were obtained by solid phase photopolymerization of pyrrole (Py) into a poly(vinylchloride) (PVC) matrix. We attempted to characterize the structure, electrochemical and thermal properties, and morphology of the resulting polypyrrole/PVC blend. The blend obtained has low conductivity and rather poor electroactivity due to the loss of conjugation length of polypyrrole (PPy) provoked by halogenation. Micrographs of cryofracture surface suggested two distinct phases, and thermogravimetric analysis revealed a low thermal stability of the blend. On the basis of our experimental results, we propose a reaction mechanism that explains the PPy formation in solid phase induced by UV light.     

Electrochemical supercapacitive properties of polypyrrole thin films: influence of the electropolymerization methods

A detailed study of the effects of different electropolymerization methods on the supercapacitive properties of polypyrrole (PPy) thin films deposited on carbon cloth is reported. Deposition mechanisms of PPy thin films through cyclic voltammetry (CV), potentiostatic (PS), and galvanostatic (GS) modes have been analyzed. The resulting PPy thin films have been characterized by X-ray photoelectron spectroscopy (XPS), SEM, and TEM. The electrochemical properties of PPy thin films were investigated by cyclic voltammetry and galvanostatic charge/discharge. The results showed that the different electrodeposition modes of synthesis significantly affect the supercapacitive properties of PPy thin films. Among different modes of electrodeposition, PPy synthesized by a potentiostatic mode exhibits maximum specific capacitance of 166 F/g with specific energy of 13 Wh/kg; this is attributed to equivalent proportions of the oxidized and neutral states of PPy. Thus, these results provide a useful orientation for the use of optimized electrodeposition modes for the growth of PPy thin films to be applied as electrode material in supercapacitors.