Solution-cast polypyrrole film: the electrical and thermal properties

Polypyrrole (PPy) solution has been prepared by dissolving PPy powder in m-cresol after doping with sodium dodecylbenzenesulfonate, and free-standing film of PPy has been cast from the solution. The PPy prepared in this way has very shiny smooth surfaces and contains approximately 13% of the solvent. The activation energy of electrical conduction was found to be 0.14 eV. It has been concluded that the solvent, i.e. m-cresol, plays an important role in electrical conduction as well as the enhancement of electrical conductivity during annealing at around 120 °C. The decrease in electrical conductivity as the PPy film is heated above 140 °C is due to the loss of solvent.     

Redox behavior and stability of polypyrrole film in sulfuric acid

Acid concentration can profoundly affect the redox behavior and stability of polypyrrole film in sulfuric acid solution. The electrochemical characteristics during the redox process of polypyrrole films prepared with p-toluenesulfonate were investigated by cyclic voltammetry. The redox stability was studied by recurrent potential pulses experiments in different concentrations of sulfuric acid. The reduction charge value (Q_red), the ratio of the reduction and oxidation charges (Q_red/Q_ox) were calculated from the experiments to exclude the polypyrrole films’ redox stability with the time and the reversibility of the reduction/oxidation process. FT-IR and SEM were used to study the structure and morphology change of ppy films treated by different concentrated sulfuric acid solutions, respectively.     

Spectroelectrochemical studies of the redox and kinetic behaviour of polypyrrole film

The kinetic study of electrochemical charge transfer in polypyrrole is aided by the determination of the apparent diffusion coefficient (D_app) of the transferred species by a chronoabsorptometric method. It is pointed out that D_app is a function of the electrolyte concentration (LiClO₄) in the solution in contact with the polymer film. A model for the time dependence of the concentration profiles of the species during oxidation and reduction is proposed, providing an estimation of the limiting process. The absorbance measurements performed at different potential steps upon polypyrrole allow one to establish a Nernstian relation between the relative oxidation state of the conducting polymer and its potential. A rapid and precise method using chronocoulometry is used in order to establish the maximum oxidation state (or level of doping) of conducting polymers.     

In situ AFM study of the surface morphology of polypyrrole film

In this paper we focus on the surface morphology of polypyrrole film by using in situ atomic force microscopy (AFM). The formation process of polypyrrole film and the transformation process of the film from the oxidized to reduced state were clearly observed.     

Study on polypyrrole film by electrochemical polymerization in aqueous solution

Electroactive polypyrrole (PPy) film was prepared by electrochemical polymerization in aqueous solution. E.s.r. analysis of the film showed that the peak-to-peak linewidth is related with heat treatment, standing time and environmental atmosphere of the film. Oxygen and water molecules participate in electrochemical polymerization of pyrrole (Py) from aqueous solution and introduce

and OH groups into the structure of PPy film, as has been verified by XPS and FT-i.r. spectroscopy. The conductivity of the film measured by the four-probe method is less than that of the films prepared in organic solvent. The mechanism of electrochemical polymerization to form PPy in aqueous solution has been proposed.     

Direct chemical functionalization of as-grown electroactive polypyrrole film containing leaving groups

A synthetic route for the functionalization of polypyrrole is described, which involves a direct chemical modification of as-grown polymer films containing labile groups, such as N-hydroxysuccinimide (NHS). Pyrrole is first substituted at the 3-position with NHS, and further electrochemically polymerized into a film of poly [3-NHS pyrrole]. A. direct chemical substitution of the easily leaving group NHS by another functional group is then carried out on the polymer film. β-Ferrocene ethylamine has been chosen as electrochemical probe, and the experimental conditions for substitution have been analyzed. Based on the ferrocene electroactivity, results show that substitution occurs with 100% yield on all the bulk of the polymer film, allowing the deposition of 10⁻⁶ mol cm⁻² of electroactive ferrocene linked to polypyrrole. This new approach toward the functionalization of polyheterocycles opens the way for an easy realization of elaborate electroactive architectures, involving fragile and expensive chemical or biochemicals groups, such as oligonucleotides, enzymes or hormones showing recognition properties.     

Corrosion protection of molybdate doped polypyrrole film prepared in succinic acid solution

ABSTRACT

Polypyrrole (PPy) was prepared on the mild steel substrate by electrochemical polymerisation in the solution containing pyrrole monomer and succinic acid. The mild steel surface could be passivated before and during electropolymerisation by molybdate. The morphology and structure of the PPy film were studied with SEM. The typical cauliflower structure of PPy was observed. Raman and IR spectroscopy showed that the obtained PPy was in an oxidised state. The thermal stability of PPy was investigated by the thermal gravimetric analysis, showing that PPy was stable at higher than 480°C. The electrochemical property of the PPy film was performed by open circuit potential, polarisation curves (I/E), and electrochemical impedance spectroscopy. The corrosion behaviour of mild steel (CT3) with PPy film in solution NaCl 3% was studied.

This paper is part of a supplementary issue from the 17th Asia-Pacific Corrosion Control Conference (APCCC-17).     

Enhancement of electrical conductivity of polypyrrole film by stretching: Counter ion effect

The effect of counter ions on the structure and properties of polypyrrole films was investigated. Various aliphatic and aromatic sulfonates as well as some typical inorganic ions such as BF₄⁻, ClO₄⁻and PF₆⁻ were employed as the counter ions. The films were prepared by anodic oxidation of pyrrole in propylene carbonate containing tetraethylammonium salt of the corresponding counter ion and 1 vol.% of water at −20 °C. The electrical conductivity and elongation of the films were highly dependent upon the structure of the counter ions. Among the counter ions investigated, PF₆⁻ gave a film with the highest conductivity (4.0 × 10² S/cm) and elongation (135%). The film stretched up to 2.5 times its original length showed a conductivity of 1.6 × 10³ S/cm in the stretch direction. A linear relationship was observed between the d-spacing measured by X-ray diffraction and the size of the counter ion. Films with smaller counter ions, both unstretched and stretched, showed higher conductivity, although the anisotropy in conductivity of the stretched films was independent of the size of the counter ion.     

Preparation and electrochemical performances of graphite oxide/polypyrrole composites

Graphite oxide/polypyrrole composites (GPys) were prepared by in situ polymerization and reduced by NaBH₄ to prepare reduced graphite oxide/polypyrrole composites (R-GPys). On the basis of the morphological and structural characterization of the composites by Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD) and transmission electron microscopy (TEM) tests, the electrochemical performances of the composites were investigated by cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance techniques. The experimental results showed that the specific capacitances of the composites before and after reduction (197 and 180 F/g) were highly improved compared with that of pristine graphite oxide (11 F/g) and polypyrrole (112 F/g), respectively. The capacitance retention of about 73% for R-GPys compared with 12% for PPy and 47% for GPys after 1200 cycles indicated the high cycle stability of the R-GPys and its potential as an electrode material for supercapacitor applications.     

Preparation of composite electroheat carbon film

1INTRODUCTIONThe electroheat carbon fil mis a newfunction-al electroheat fil m developed based on the electro-heat coating.Due to its good electroheat propertyand equivalent volume resistivity as nickel at roomtemperature,it can be widely used in electroheator relevant advanced technological fields such asportable low-voltage electric food warmer,ricecooker and heater,as a kind of lowvoltage electro-heat material[15].The existing electroheat coatingdeveloped by Acme chemicals&Insulating o…     

The effect of counter anions on corrosion resistance of steel covered by bi-layered polypyrrole film

The bi-layered polypyrrole (PPy) coatings were investigated for corrosion prevention of a carbon steel. The inner layer was doped with the Keggin structure anions of (PMo₁₂) and anions for stabilization of the passive oxide film at the metal-polymer interface, and the outer layer was doped with four organic anions of dihydroxynaphthalenedisulfonate (DHNDS), naphthalenedisulfonate (NDS), anthraquinonedisulfonate (AnqDS) or dodecylsulfate (DoS) for inhibition of the decomposition and release of PMo₁₂. The corrosion tests were performed in 3.5 wt.% NaCl aqueous solution. The corrosion resistance of the steels covered by the bi-layered PPy films was found in the following order: PPy-PMo₁₂/PPy-DHNDS < PPy-PMo₁₂/PPy-NDS < PPy-PMo₁₂/AnqDS < PPy-PMo₁₂/PPy-DoS. The performance of corrosion protection related to the oxidized state of the polymer was discussed.     

Study of lithium/polypyrrole secondary batteries with Lithium as cathode and polypyrrole anode

Lithium/polypyrrole (Li/PPy) batteries were fabricated using lithium sheet as cathode, PPy as anode, microporous membrane polypropylene/polyethylene/polypropylene (PP/PE/PP) composite as separator and LiPF6/ethylene carbonate-dimethyl carbonate-methyl ethyl carbonate (EC-DMC-EMC) as electrolyte. Polypyrrole was prepared by chemical polymerization. Certain fundamental electrochemical performances were investigated. Properties of the batteries were characterized and tested by SEM, galvanostatic charge/discharge tests, cyclic voltammetry (CV), and a.c. impedance spectroscopy. The influences of separator, morphology, and conductivity of PPy anode, cold-molded pressure, and electric current on the performances of the batteries were studied. Using PP/PE/PP membranes as separator, the battery showed good storage stability and cycling property. The conductivity of materials rather than morphology affected the behavior of the battery. The higher the conductivity, the better performances the cells had. Proper cold-molded pressure 20 MPa of the anode pellet would make the properties of the cells good and the fitted charge/discharge current was 0.1 mA. The cells showed excellent performance with 97%-100% coulombic efficiency. The highest discharge capacity of 95.2 mAh/g was obtained.     

纳米金刚石膜真空窗口的制备

使用自制的微波等离子体化学气相沉积装置,以乙醇为碳源在（100）硅表面制备了金刚石膜;然后用浓硝酸和氢氟酸的混合溶液腐蚀硅,制备出金刚石膜窗口。使用场发射扫描电镜（SEM）、X射线衍射、拉曼光谱（Raman）、原子力显微镜（AFM）表征和分析金刚石膜,并以自制的漏气率测量系统测量金刚石膜窗口的漏气率。结果表明:金刚石膜的厚度为15 μm,平均粗糙度值R_a为39.5 nm,晶粒的尺寸大小为30 nm,漏气率为8.8×10-9 Pa·m3/s。      

Preparation and characterization of a polypyrrole hybrid film with [Ni(dmit)2]2−, bis(1,3-dithiole-2-thione-4,5-dithiolate)nickellate(II)

The synthesis of a hybrid material obtained by electropolymerization of a solution of pyrrole and [NEt₄]₂[Ni(dmit)₂] (dmit = 1,3-dithiole-2-thione-4,5-dithiolato) in acetonitrile solution is reported. The material was characterized by cyclic voltammetry, UV–vis and infrared spectroscopies, scanning electron microscopy (SEM), atomic force microscopy (AFM) and thermal gravimetric analysis (TGA). The FTIR spectroscopy showed that the [Ni(dmit)₂]²⁻ anion has been inserted in the polypyrrole framework and was not destroyed or modified during the polymerization process. The voltammetric analysis indicated that the material has electroactivity and undergoes redox processes associated with the conducting polymer and the counteranion. The cyclic voltammetry results also suggest that the counteranion is not trapped in the PPy matrix undergoing anion exchange during the redox cycle of PPy. The PPy/[Ni(dmit)₂]²⁻ exhibits good thermal stability and a intrinsic conductivity value in the range of semiconductors (10⁻³ S cm⁻¹).     

高活性TiO_2薄膜电极的制备及其光电化学性能

以Ti(n-OC4H9)4和CH3COOK为原料,采用溶胶-凝胶法在导电玻璃基底上制备K2Ti2O5薄膜,进一步以K2Ti2O5薄膜为前躯体,用离子交换法获得TiO2纳米薄膜电极。利用X射线衍射(XRD)和扫描电子显微镜(SEM)分析薄膜的组成和表面特征;以草酸为有机污染物代表,通过光电化学技术考察薄膜的光电化学活性。结果表明:TiO2纳米薄膜具有锐钛矿晶型,其粒径随着K2Ti2O5薄膜制备温度的降低而减小,约为30～150nm;TiO2纳米薄膜在0.1mol/LNa2SO4溶液中具有典型的光电化学活性以及较高的稳定性,比在含少量草酸的溶液中采用溶胶-凝胶法制备的TiO2薄膜具有更强的光激发和更稳定的光电流响应性能,TiO2薄膜电极的平带电位发生负移,负移值为0.140V(vsSCE),饱和光电流密度为0.32mA/cm2。     

Preparation and properties of conducting composites of polypyrrole and porous cross-linked polystyrene with and without supercritical carbon dioxide

Composites of polypyrrole (PPy) and porous cross-linked polystyrene (PCPS) were prepared using a two-step batch method proposed by Ruckenstein and Park. However, the solvent employed by Ruckenstein and Park (methanol) in the polymerization step of their method was replaced with supercritical CO₂. For comparison purposes, PPy/PCPS composites were also prepared using no solvent in the polymerization step. Conductivities as high as 10⁻² S cm⁻¹ were obtained, with or without the use of supercritical CO₂. Uniformity of conductivity was determined via surface and bulk conductivity measurements, as well as by a new volume conductivity measurement that provides a measure of spatial (three-dimensional) distribution of the conducting component in the composite.The conductivity of composites prepared with or without the use of supercritical CO₂ conformed to the same percolation behavior with respect to the amount of PPy formed. The percolation threshold in all cases was as low as 4 wt.%. The mechanical strength of the composites was found to be about the same as that of the host PCPS, as was the thermal stability. Therefore, the conductive component did not appear to adversely affect these properties of the host. Finally, the temperature behavior of the conductivity could be correlated with Mott's variable-range hopping (VRH) model for three-dimensional electronic transport.     

Conducting polypyrrole with nanoscale hierarchical structure

Conducting polypyrrole (PPy) with nanoscale hierarchical structure is chemically synthesized in an aqueous solution in the presence of cetyltrimethylammonium bromide (CTAB) and 1,5-naphthalene disulfonic acid (1,5-NDA). The effect of synthetic conditions including concentration of CTAB and pyrrole, reaction temperature, oxidants and their introduced modes on the PPy hierarchical nanostructure is systematically investigated. A hypothesis for the hierarchical structure formation of PPy with the aid of CTAB/1,5-NDA/pyrrole supramolecular template is presented, in which the pyrrole is polymerized in imitation of the CTAB/1,5-NDA/pyrrole crystal shape. The electrochemical performances of representative PPy sample show that the PPy with hierarchical nanostructures has potential application as supercapacitor materials.     

空心聚吡咯/V_2O_5复合材料的制备及其电化学性能

为改善晶态V2O5（c-V2O5）正极材料实际容量较低、循环性能较差等问题,制备了空心球聚吡咯/V2O5复合材料。利用导电吡咯单体（Py）在中空型V2O5层间发生原位氧化聚合反应制备聚吡咯（PPy）/中空型V2O5复合材料（HS-PPy/V2O5）。采用X射线衍射仪（XRD）、扫描电镜（SEM）、透射电镜（TEM）对样品进行表征,采用恒流充放电测试和电化学阻抗（EIS）测试样品的电化学性能。结果表明,Py单体已插入中空型V2O5层间,与纯中空型V2O5相比,制备的HS-PPY/V2O5复合材料比容量虽然有所减小,但是循环稳定性有较大的提高。     

Photoinduced electron transfer at an ITO/C60 trapped in a thin polypyrrole film interface

The photoelectrochemical properties of C₆₀ entrapped in thin, functionalized polypyrrole films coated on indium-tin oxide (ITO) electrodes have been examined. A stable photocurrent is observed in the presence of an irreversible electron donor (ascorbic acid) in solution. Results suggest the coexistence of monomers and aggregates of C₆₀ in the polymeric matrix.     

MPCVD法制备金刚石膜的工艺

采用3 kW/2 450 MHz微波等离子体化学气相沉积(microwave plasma chemical vapor deposition, MPCVD)系统,以单晶硅为基底材料,采用单因素试验法研究微米级金刚石膜的生长工艺,分别探究衬底温度、腔体压强和甲烷体积分数对金刚石成膜过程的影响,获得微米级金刚石膜的最优生长工艺。结果表明:金刚石膜的生长速率与衬底温度、腔体压强、甲烷体积分数呈正相关;衬底温度和腔体压强对金刚石膜质量的影响存在最佳的临界值,甲烷体积分数过高不利于形成金刚石相。金刚石膜生长的最佳工艺参数为:功率为2 200 W,衬底温度为850 ℃,腔体压强为14 kPa,甲烷的体积分数为2.5%。在此条件下,金刚石膜生长速率为1.706 μm/h,金刚石相含量为87.92%。