Preparation and Properties of Water-based Conducting Polyaniline

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聚苯胺的电导率、电子顺磁共振和磁化率

本文报导了还原前后聚苯胺的电导率和电子顺磁共振强度随温度的变化。从logσ对1/T图得到了还原后的聚苯胺的能量间隙为0.252eV,它的不成对电子密度约为1.84×10~(23)m~(-3),或1.06×10~(20)kg~(-1),它的电导率与温度的关系式为σt=σ20-9.17×10~(-4)(20-t)Scm~(-1)。还原前的聚苯胺的电导率在20℃以上随温度升高而下降,在20℃以下,其电导率随温度升高而增加,它的不成对电子密度约为2.55×10~(27)m~(-3),或1.47×10~(24)kg~(-1)。两种聚苯胺的电子顺磁共振的强度和峰值-峰值之间的宽度△Hp-p都随温度而变化。还原前的聚苯胺的磁化率在不同温度下均为零。     

Surface modification of polyaniline using tetraethyl orthosilicate

A well-dispersible conducting polyaniline/silica hybrid is prepared by the hydrolysis and condensation of tetraethyl orthosilicate (TEOS) on the surface of polyaniline in water/ethanol solution. It provides a simple and environmentally sound route for preparing the processable conducting polyaniline/silica hybrid at the nanometre level. The conductivity of polyaniline/silica hybrid is 2.43 S cm(-1) at 25 degrees C, and its powder is easily dispersed in the anhydrous ethanol or aqueous solution without any stabilizer. In addition, the structure, morphology and cyclic voltammorgram of this hybrid are also reported.     

Helical conformational specificity of enzymatically synthesized water-soluble conducting polyaniline nanocomposites

A novel template guided enzymatic approach has been developed to synthesize optically active conducting polyaniline (PANI) nanocomposites in the presence of H2O2 as an oxidant, using (+) and (-) 10-camphorsulfonic acid (CSA) as a dopant and chiral inductor. The formation of chiral polyaniline in the nanocomposites was confirmed by circular dichroism (CD). Interestingly, the CD spectra of nanocomposites formed either with (+) or with (-) CSA show the enzyme itself plays a critical role in controlling the stereospecificity of the polyaniline (PANI) in the nanocomposite. The enzyme used for the polymerization of aniline in the nanocomposite was horseradish peroxidase (HRP). It was shown that this enzyme prefers a specific helical conformation, regardless of whether induced chirality in the complex CSA-aniline is from (+) or (-) CSA. UV-vis spectra show that the polyaniline is in the conducting form, and transmission electron micrographs (TEM) show that the nanocomposites are dispersed nicely with particle size dimensions in the range of 20-50 nm. Electron diffraction patterns of these chiral polymer nanocomposites suggest that these nanocomposites are in both crystalline and amorphous states.     

聚苯胺薄膜修饰电极对抗坏血酸的电催化氧化

本文表明聚苯胺(PAn)薄膜修饰电极对水溶液中的抗坏血酸(AH_2)在较宽的pH范围和较宽的浓度范围内均有良好的电催化氧化作用, 为EC平行催化过程。利用旋转圆盘电极(RDE)进行了催化过程动力学分析, 求出了催化反应动力学参数。在抗坏血酸浓度10~(-2)～10~(-6) mol·L~(-1)范围内, 催化峰电流与AH_2浓度均成良好的线性关系, 且PAn薄膜修饰电极具有很好的稳定性, 有应用分析抗坏血酸的意义。     

Conducting polyaniline/nano-zinc phosphate composite as a pigment for corrosion protection of low-carbon steel

Zinc phosphate (Zn₃(PO₄)₂) nanocrystals were synthesized and used for making conducting polyaniline/nano-zinc phosphate composite by chemical oxidative method. The product was characterized by UV–visible absorption spectroscopy. The crystal structure, morphology and thermal stability of the product were studied by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and thermo gravimetric analysis, respectively. The epoxy-based paint containing conducting polyaniline/nano-zinc phosphate composite pigment was applied on low-carbon steel samples. Corrosion protection performance of the painted low-carbon steel samples in 3.5 mass % sodium chloride solution was evaluated using electrochemical technique. Transmission electron microscopic image revealed the formation of core shell structure of the composite. Composite was found to be more thermally stable than the conducting polyaniline. The corrosion rate of conducting polyaniline/nano-zinc phosphate-painted low-carbon steel was found to be 5.1 × 10^?4 mm per year, about 34 times lower than that of unpainted low-carbon steel and 10 times lower than that of epoxy nano-zinc phosphate paint-coated steel. The study reveals the possibility of using conducting polyaniline/nano-zinc phosphate as a pigment for corrosion protection.     

Stability of polyaniline in air and acidic water

Polyaniline is a member of the class of electrically conducting polymers, having possible commercial applications such as coatings. Aqueous‐based polyaniline coatings are preferred over organic solvent or concentrated strong acid based coatings because water is not a pollutant. The overall goal of this study was to further the development of water‐based polyaniline coatings by an examination of the effect of acidic water (pH 1.18) and air on polyaniline. Knowledge of the effect of water on the structure, molecular weight, electrical conductivity, and diffusion of the dopant assisted in ascertaining whether polyaniline degraded with water exposure. Knowledge of how Fourier transform infrared (FTIR) spectra would be affected by dry air was important for determining if polyaniline was chemically stable with time. The results showed that the molecular weight, ultraviolet–visible and FTIR spectra, and carbon‐to‐nitrogen molar ratio in the polymer backbone all remained unchanged during acidic water immersion. The constant nature of these physical parameters showed a high degree of water stability. A chloride ion diffusion coefficient of 2.8 to 85 × 10^?9 cm²/h, the chloride concentration, and the electrical conductivity were also measured with the water immersion time. Aging polyaniline powders in a desiccator for 5 years showed no effect on the molecular structure, as indicated by the FTIR spectrum. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 807–822, 2003     

Conducting polyaniline prepared by the laccase-catalyzed method in a water dispersion of sodium dodecylbenzenesulfonate micellar solution

In the present work, physico-chemical properties of conducting polyaniline (PANI) prepared by laccase-catalyzed oxidative polymerization in water dispersions of sodium dodecylbenzenesulfonate micellar solutions were studied. The polymer was characterized using FTIR spectroscopy, cyclic voltammetry, termogravimetry, transmission electron microscopy, and electron diffraction. The antistatic properties of the obtained polyaniline were also studied.     

ELECTROSTATIC INTERACTION HYBRIDS FROM WATER-BORNE CONDUCTIVE POLYANILINE AND INORGANIC PRECURSOR CONTAINING CARBOXYL GROUP

Electrostatic interaction conductive hybrids were prepared in water/ethanol solution by the sol-gel process from inorganic sol containing carboxyl group and water-borne conductive polyaniline （cPANI）. The electrostatic interaction hybrids film displayed 1-2 orders of magnitude higher electrical conductivity in comparison with common hybrids film, showing remarkable conductivity stability against water soaking. Most strikingly, it displayed ideal electrochemical activity even in a solution with pH = 14, which enlarged the conducting polyaniline application window to strong alkaline media.     

氧化剂对PAn/PTFE复合导电膜结构和性能影响的研究

分别以过硫酸铵和正钒酸钠作氧化剂,应用膜相渗透原位化学聚合法制备聚苯胺(PAn)/聚四氟乙烯(PTFE)复合导电膜,比较考察了两种氧化剂条件下膜孔中苯胺的聚合生长行为.扫描电镜、孔径分布及电化学测试结果表明:选用两种氧化剂分别制备的复合膜,均具有较小的膜孔径;与过硫酸铵相比,使用正钒酸钠作氧化剂时,复合膜的结构更为致密,且在保持较高表面电导率(2.62S·cm-1)的同时,断面电导率提高了1～2个数量级,电化学活性增强.     

Sisal fibers coated with conducting polyaniline: Property and structural studies

Sisal (Agave sisalana) fiber was extracted by manual process. These fibers were subjected to surface coating with conducting polyaniline, through in situ oxidative polymerization. The polyaniline modified sisal fibers were characterized by thermal, spectroscopic and microscopic techniques. It was shown that the fiber was coated with polyaniline through in situ oxidative polymerization and the latter had a smoothing effect on the surface as compared to uncoated sisal fiber. Besides, it was confirmed that polyaniline was deposited in conductive form of emeraldine salt. This in turn verified the introduction of active functionalities to the system, which is helpful to tune up surface chemistry of polyaniline for water treatment applications.     

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。     

Conductive polymers as a new type of thermoelectric material

Thermoelectric properties were investigated for the films of electrically conductive doped polyanilines. The thermoelectric performance, evaluated by thermoelectric figure-of-merit (ZT = T (S² σ) / κ), of various protonic acid-doped polyaniline bulk films was found to depend on the electrical conductivity σ of the film. Thus, the higher the electrical conductivity, the higher the figure-of-merit is, because the thermal conductivity κ of polyaniline films does not depend on the electrical conductivity. Among the conductive bulk films of polyaniline, the highest figure-of-merit (ZT = 1 × 10⁻⁴) was observed for (±)-10-camphorsulfonic acid (CSA)-doped polyaniline in an emeraldine form (σ - 188 S cm⁻¹) at room temperature. The multilayered film, composed of electrically insulating emeraldine base layers and electrically conducting CSA-doped emeraldine salt layers, exhibited 6 times higher ZT at 300 K than that of a bulk film of CAS-doped polyaniline, showing the highest ZT value of 1.1 × 10⁻² at 423 K. Stretching of the CAS-doped polyaniline film also increased the figure-of-merit of doped polyaniline films along the direction of the stretching.     

自组装的氢氟酸掺杂的聚苯胺微/纳米管

以氢氟酸为掺杂剂,采用无模板法制得了高电导率(10-2-10-1S/cm)聚苯胺微/纳米管(d=85-420nm).当[HF]/[An]=0.5时所得微/纳米管的形成机率高达100%.发现微/纳米管的直径和电导率均随[HF]/[An]比例的增加而增加.FTIR,UV-Vis,XRD结构表征证明所得的聚苯胺微/纳米管为掺杂态.     

A mild, copper catalyzed route to conducting polyaniline

The aniline dimer, N-(4-aminophenyl)aniline has been polymerized cleanly under mild conditions to obtain an emeraldine base form of polyaniline using [MeB(3-(Mes)Pz)3]CuCl as the catalyst and H2O2 as the oxidant, while the subsequent acidification of the emeraldine base gives the conducting emeraldine salt form of polyaniline.     

New renewable resource amphiphilic molecular design for size-controlled and highly ordered polyaniline nanofibers

We demonstrate here, for the first time, a unique strategy for conducting polyaniline nanofibers based on renewable resources. Naturally available cardanol, which is an industrial waste and main pollutant from the cashew nut industry, is utilized for producing well-defined polyaniline nanofibers. A new amphiphilic molecule is designed and developed from cardanol, which forms a stable emulsion with aniline for a wide composition range in water (1:1 to 1:100 dopant/aniline mole ratio) to produce polyaniline nanofibers. The scanning electron microscopy and transmission electron microscopy analysis of the nanofibers reveals that the dopant/aniline ratio plays a major role in determining the shape and size of polyaniline nanofibers. The nanofiber length increases with the increase in the dopant/aniline ratio, and perfectly linear, well-defined nanofibers of lengths as long as 7-8 muM were produced. The amphiphilic dopant has a built-in head-to-tail geometry and effectively penetrates into the polyaniline chains to form highly organized nanofibers. Wide-angle X-ray diffraction (WXRD) spectra of the nanofibers showed a new peak at 2theta = 6.3 (d spacing = 13.9 A) corresponding to the three-dimensional solid-state ordering of polyaniline-dopant chains, and this peak intensity increases with increase in the nanofiber length. The comparison of morphology and WXRD reveals that high ordering in polyaniline chains results in the formation of long, well-defined nanofibers, and this direct correlation for the polyaniline nanofibers with solid-state ordering has been established. The conductivity of the polyaniline nanofibers also increases with increase in the solid-state ordering rather than increasing with the extent of doping. The polyaniline nanofibers are freely soluble in water and possess high environmental and thermal stability up to 300 degrees C for various applications.     

Enhanced conductivity of thin film polyaniline by self-assembled transition metal complexes

In a recent study, the transition metal complex, cis-dichlorobis(2-,2'-dipyridyl)ruthenium (II) (Ru(bpy)2Cl2), and the macrocycle Ru(TPP)CO (TPP:- tetraphenylporphine) were bound to pyridine terminated self-assembled monolayers on quartz. Following modification of the quartz surface with metal complexes, the conducting polymer polyaniline was deposited via in situ polymerization. The sheet conductivity (as measured by the four-probe method) of the resulting polyaniline films deposited onto Ru(bpy)2Cl2 and Ru(TPP)CO surfaces was significantly enhanced relative to films deposited onto unmodified quartz. It is postulated that either the macrocycle or the transition metal complex-modified surface interacts with the conducting polymer as it is forming, resulting in a more ordered expanded coil conformation for the polymer. The net result of such an interaction is a thin film possessing significantly greater electrical conductivity.     

Theoretical specific capacitance based on charge storage mechanisms of conducting polymers: comment on 'Vertically oriented arrays of polyaniline nanorods and their super electrochemical properties'

A recently claimed ultra high specific capacitance of 3407 F g(-1) for aligned polyaniline nanorods by the titled communication is shown to be contradictory to both the mechanism of charge storage in conducting polymers, and the experimental findings in other nanofibrils of polyaniline, and may thus stimulate debate.     

Coating of zinc ferrite particles with a conducting polymer, polyaniline

Particles of zinc ferrite, ZnOFe2O3, were coated with polyaniline (PANI) phosphate during the in situ polymerization of aniline in an aqueous solution of phosphoric acid. The PANI-ferrite composites were characterized by FTIR spectroscopy. X-ray photoelectron spectroscopy was used to determine the degree of coating with a conducting polymer. Even a low content of PANI, 1.4 wt%, resulted in the 45% coating of the particles' surface. On the other hand, even at high PANI content, the coating of ferrite surface did not exceeded 90%. This is explained by the clustering of hydrophobic aniline oligomers at the hydrophilic ferrite surface and the consequent irregular PANI coating. The conductivity increased from 2 x 10(-9) to 6.5 S cm(-1) with increasing fraction of PANI phosphate in the composite. The percolation threshold was located at 3-4 vol% of the conducting component. In the absence of any acid, a conducting product, 1.4 x 10(-2) Scm(-1), was also obtained. As the concentration of phosphoric acid increased to 3 M, the conductivity of the composites reached 1.8 S cm(-1) at 10-14 wt% of PANI. The ferrite alone can act as an oxidant for aniline; a product having a conductivity 0.11 S cm(-1) was obtained after a one-month immersion of ferrite in an acidic solution of aniline.     

Facile synthesis of processable conductive water solubilized polyaniline

Conductive polyaniline, polyemeraldine green, was synthesized in a water soluble form by an in situ method, using surfactants with strong acid functionalities as protonating agents. The clear green solution of conducting polyaniline, polyemeraldine green, can be diluted to any extent and stored. Thin and thick films can be easily processed from this solution by spin coating and solvent casting methods.