Preparation of polyaniline‐sulfate salt ­by emulsion and aqueous ­polymerization pathway without using ­protonic acid

Aniline was polymerized directly into polyaniline‐sulfate salt without using protonic acid in this work. Polyaniline‐sulfate salt was prepared by emulsion and aqueous polymerization pathways. The dopant i.e. sulfate ion in polyaniline‐sulfate salt was generated from ammonium persulfate which was used for oxidizing aniline. Ammonium persulfate acts both as oxidizing agent as well as protonating agent in the polymerization process of aniline to polyaniline salt. The efficiency of oxidizing and protonating power of ammonium persulfate is increased by the use of surfactant. The activity of ammonium persulfate is further increased by the use of sulfuric acid as protonic acid. It may be necessary to consider the effect of sulfate ion which is generated during the oxidation process of aniline in the chemical polymerization of aniline to polyaniline salt by ammonium persulfate either aqueous or emulsion polymerization pathway in the presence of protonic acid/functionalized protonic acid. Copyright © 2001 John Wiley & Sons, Ltd.     

Emulsion Polymerization Pathway for Preparation of Polyaniline‐Sulfate Salt,using Non Ionic Surfactant

In this work, aniline was polymerized directly to the polyaniline‐sulfate salt without using a protonic acid. The polyaniline‐sulfate salt was prepared by emulsion polymerization, using a non ionic surfactant such as poly(ethylene glycol)–block poly(propylene glycol)‐block poly(ethylene glycol). In the aniline oxidation process, to give the polyaniline salt by ammonium persulfate, the sulfate ion is generated from ammonium persulfate and doped on to the polyaniline. Ammonium persulfate acts both as an oxidizing agent, as well as the protonating agent in the aniline polymerization process, to give the polyaniline salt. This result indicates that the effect of sulfate ion, generated by ammonium persulfate during oxidation of aniline to the polyaniline salt, may be taken into consideration in the polymerization process of aniline.     

Enhancement of polyaniline’s electrical conductivity by coagulation polymerization

An effective and simple method was developed to prepare highly conductive polyaniline by coagulation polymerization. Depending on the coagulation reaction between aniline salts and lauryl sulfonate (SDS), not only was the polymerization rate of aniline monomers greatly decreased but also the doping efficiency of hydrochloric acid was effectively increased. Low polymerization rate provided enough time for the conformation adjustment of polyaniline chains and the diffusion of doping agent. Meanwhile, the doping efficiency of hydrochloric acid on polyaniline chains was effectively increased due to its easy diffusion among many vacancies, which were generated when SDS separated in the process of polymerization. Therefore, the electrical conductivity of polyaniline prepared by coagulation polymerization was increased more than ten times than that of polyaniline, which was prepared by conventional methods. In addition, the important factors to influence the preparation, such as SDS concentration, hydrochloride acid (HCl) concentration, content of ammonium persulfate (APS), and polymerization time were also investigated. When the molar ratio (aniline:SDS:HCl :APS) was set to 1.69:0.46:15.38:1, the conductivity of polyaniline reached 24.39 S/cm.     

Composition and spectral studies of polyaniline salts

Five different polyaniline salts have been prepared by chemical polymerization of aniline in aqueous solution of different acids. The polyaniline base was obtained from the corresponding polyaniline salt by dedoping using aqueous ammonium hydroxide solution. Electron paramagnetic, electronic absorption, infrared spectral and conductivity measurements have been performed on the polyaniline salts and polyaniline bases. This composition and the extent of dopant in polyaniline salt systems have been determined. There is no definite correlation between the conductivity and the stoichiometric ratio between the polyaniline base and the acid, and also the spin concentration.     

Spectral and thermal characterization of polyaniline–oxalic acid salt

Polyaniline–oxalic acid salts were prepared at 5 and 30°C by chemical polymerization of aniline using different concentration of oxalic acid. Polyaniline base was obtained from the corresponding polyaniline salt by dedoping using aqueous ammonium hydroxide solution. Conductivity measurements, elemental analysis, Infrared, electronic absorption, electron paramagnetic resonance spectral, and thermogravimetric analysis were performed on the polyaniline salts and bases. Composition and the extent of dopant in polyaniline salt systems where determined. The value of composition of polyaniline: oxalic acid is 4: 1.6 and the polymer yield is around 66%. The value of conductivity, polymer yield and composition of polyaniline–oxalic acid salt is independent of concentration of oxalic acid used and also the synthesis temperature. The results are compared with polyaniline–hydrochloride salt prepared by chemical polymerization. The conductivity of polyaniline–oxalic acid salt is three orders of magnitude lower than that of polyaniline-hydrocholoride salt. © 1995 John Wiley & Sons, Inc.     

Synthesis of nanostructured polyaniline via chemical oxidative polymerization: Investigation of morphology and conductivity of the prepared polymers

In this study, nanostructure polyaniline was prepared from aniline monomer via chemical oxidative polymerization in the presence of ammonium persulfate as an oxidizing agent. Interfacial, emulsion, rapid mixing and ultrasonic techniques are used for polymer synthesis. In the interfacial method, chloroform, n-hexane, hexanole and toluene were used as organic solvents and sulfuric acid, methane sulfonic acid and acetic acid were employed as electrolyte solutions. In the emulsion polymerization, dodecyl benzene sulfonic acid and aqueous solution of hydrochloric acid were used as emulsion agent and electrolyte solution respectively. In rapid mixing reaction and ultrasonic method, hydrochloric acid and salicylic acid were used as dopants. The structure, conductivity, morphology and particle size distribution of prepared polymers were investigated after purification and drying by FTIR spectroscopy, scanning electron microscopy and electrical conductivity measurements.     

Benzoyl peroxide oxidation route to polyaniline salts—Part I

Aniline was oxidized to polyaniline salt using benzoyl peroxide as an oxidizing agent in the presence of acids such as sulfuric, nitric, or hydrochloric acid by aqueous polymerization pathway. Polyaniline salts, their corresponding bases and redoped polyaniline salts were characterized by infrared, electronic absorption, x‐ray diffraction spectral techniques, elemental analysis and conductivity measurement. The result of this study indicates that both acid and surfactant group are present in the polyaniline salt as dopants. Polyaniline salts with reasonable yield (around 80%) and conductivity (0.04 S/cm) were prepared. Copyright © 2004 John Wiley & Sons, Ltd.     

原位聚合法制备聚酰胺/聚苯胺复合导电纤维

研究了原位聚合法制备聚酰胺/聚苯胺导电纤维,并对制备的复合纤维进行红外及光学显微镜测试,结果表明聚苯胺与纤维成功复合。对制备的复合纤维进行电导率测试,采用控制单一变量法探讨了苯胺单体在不同的条件下聚合对纤维电导率的影响,并讨论了反应温度对聚合过程和电导率的影响,得出最佳的工艺条件为:纤维经30%的甲酸溶液预处理20min,苯胺单体浓度为0.8M,氧化剂过硫酸铵浓度为1M,掺杂酸为盐酸,浓度为0.8M,冰水浴条件,反应时间为4h,得到的聚酰胺/聚苯胺导电纤维的电导率为3.7S/m。     

Self-supported bacterial cellulose polyaniline conducting membrane as electromagnetic interference shielding material: effect of the oxidizing agent

Conducting bacterial cellulose (BC) membranes coated with a high proportion of polyaniline (PAni) were prepared through in situ oxidative polymerization of aniline on the surface of the BC in the presence of acetic acid as the protonating agent. The effect of two different oxidizing agents, ammonium persulfate (APS) or iron(III) chloride (FeCl₃), on the mechanical performance, electrical conductivity, crystallinity, morphology and ability to absorb the electromagnetic radiation was investigated. BC/PAni membranes prepared with FeCl₃ displayed higher conductivity and better mechanical performance than those observed for pure BC or the BC/PAni membranes prepared with APS. Experiments related to the electromagnetic absorbing properties revealed that BC/PAni membranes prepared with FeCl₃ also present improved absorbing properties in the frequency range of 8–12 GHz. The morphology of the membranes, observed by field emission gun-scanning electron microscopy, is strongly affected by the oxidizing agent. Whereas the BC/PAni membranes prepared with APS present PAni nanoparticles attached on the fiber surface as agglomerates in the form of flakes, those prepared with FeCl₃ display a uniform and smooth coating of PAni on the BC fibers as hierarchical mode.     

Preparation of benzyl acetate using polyaniline salts as catalysts ‐ Part II

Polyaniline salts were prepared by oxidizing aniline in presence of acid using benzoyl peroxide as an oxidizing agent. Polyaniline salt was used as catalyst for the esterification reaction of phenyl acetic acid with methanol. The process is being reported for the first time. Preparation of catalyst, recovery and reusability of the catalyst were found to be good. Copyright © 2004 John Wiley & Sons, Ltd.     

氧化剂对聚苯胺性质的影响

当过硫酸铵与苯胺的摩尔量之比为1∶1至2∶1时,化学合成的聚苯胺具有高的产率,电导率也较高,过多的过硫酸铵存在,使聚苯胺的电导率明显下降,这是由于它氧化了不同的中间体使产物不同,及聚苯胺被进一步氧化而造成的。各种强的氧化剂虽能提高电化学合成的聚苯胺的电极电位,但都使它的电导率和电化学活性显著降低,这仅是由于聚苯胺的进一步氧化所引起的。为了保持聚苯胺高的电化学活性,应避免它与强氧化剂共存。     

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.     

Composite of conducting polyaniline-isobutylated urea formaldehyde: Preparation and characterization

Composite of conductive polyaniline-isobutylated urea formaldehyde have been prepared by chemical oxidative emulsion polymerization of aniline in the presence of isobutylated urea formaldehyde resin (BUFR) in toluene-water solvents at room temperature. The mass loading of polyaniline was controlled by varying the BUFR/aniline charging ratio as well as oxidant (ammonium persulfate)/aniline molar ratio. Some factors capable of affecting the yield and conductivity of composite, such as amount of the oxidant, type of the dispersants (span-80 and span-20), and amount of resin and organic acid (para-toluene sulfonic acid) were investigated. The prepared composites were characterized by FTIR spectroscopy and scanning electron microscopy (SEM).     

Synthesis of novel fluorescent molecule and its polymeric form with aniline as fluorescent and supercapacitor electrode materials

In this study, a fluorescent material, 2‐naphthyl‐4‐amino benzoate, is synthesized by the esterification of 4‐aminobenzoic acid with 2‐naphthol. This molecule is used in the bulk polymerization of aniline, which results in the formation of poly(aniline‐2‐naphthyl‐4‐aminobenzoate). For comparison, polyaniline and also poly(aniline‐4‐aminobenzoic acid) salts are prepared via bulk polymerization. Formation and properties of these polymeric materials are evaluated by Fourier‐transform infrared (FT‐IR), ¹³C nuclear magnetic resonance, matrix‐assisted laser desorption ionization, UV‐Vis, Fluorescence, X‐ray diffraction (XRD), Field emission‐scanning electron microscopy (FE‐SEM), Differential scanning calorimetry (DSC), thermogravimetric analysis, electrical resistance and electrochemical techniques. P(ANI‐2NA4ABA) is obtained in nanofiber morphology in 106 wt% yield with respect to the amount of aniline used with comparable conductivity of conventional polyaniline salts. This polymer salt is stable up to 220°C and indicates melting at 146°C on heating and crystal formation at 128°C on cooling. This polymer shows higher wavelength fluorescence compared to the conventional polyaniline salts. This polymer is used as an electrode material without binder, which shows a specific capacitance of 360 F g^?1 at 0.25 A g^?1.     

SYNTHESIS OF CONDUCTIVE POLYANILINE VIA OXIDATION BY MnO2

A unique process of chemical oxidation polymerization of aniline using manganese dioxide (MnO2) as the oxidizing agent in an aqueous medium is described. The reaction between aniline and MnO2 follows a mechanism by which the organic monomer is oxidized while the metal oxide undergoes reductive dissolution. The effects of the amount of oxidizing agent and aniline, pH and temperature of the reactive system, type of acid on the yield and conductivity of polyaniline are discussed. The resulting polyaniline was characterized by [R and UV-Vis spectrometry. Polyaniline with a conductivity of 12.5 S/cm was obtained using 0.033 tool of aniline oxidized by 0.023 tool MnO2 in the presence of 100 mL of 2.7 mol/L HCI at 25℃ for 4 h.     

Quinaldinium Chlorochromate Supported on Alumina: A New and Efficient Reagent for the Oxidation of Alcohols

The new, mild chromium(VI) oxidizing agent, quinaldinium chlorochromate supported on neutral alumina, was prepared as a stable yellow solid. The reagent is suitable to oxidize various primary and secondary alcohols to the corresponding carbonyl compounds and anthracene to anthraquinone in good yields.     

Conductive Cotton Prepared by Polyaniline In Situ Polymerization Using Laccase

The high-redox-potential catalyst laccase, isolated from Aspergillus, was first used as a biocatalyst in the oxidative polymerization of water-soluble conductive polyaniline, and then conductive cotton was prepared by in situ polymerization under the same conditions. The polymerization of aniline was performed in a water dispersion of sodium dodecylbenzenesulfonate (SDBS) micellar solution with atmospheric oxygen serving as the oxidizing agent. This method is ecologically clean and permits a greater degree of control over the kinetics of the reaction. The conditions for polyaniline synthesis were optimized. Characterizations of the conducting polyaniline and cotton were carried out using Fourier transform infrared spectroscopy, UV–vis spectroscopy, cyclic voltammetry, the fabric induction electrostatic tester, and the far-field EMC shielding effectiveness test fixture.     

Template Synthesis of Polyaniline in the Presence of Poly-(2-acrylamido-2-methyl-1-propanesulfonic Acid)

A template oxidative polymerization of aniline in aqueous solutions containing poly-(2-acrylamido-2-methyl-1-propanesulfonic acid) and ammonium persulfate yields a polyaniline complex with the polyacid soluble in water. According to the data of spectral measurements, the process of polymerization is of a pronounced autocatalytic nature. The consequences of this are both the formation of a nonuniform distribution of oxidized and nonoxidized fragments of the polymer chain and the formation of a macroscopic scale of redox nonuniformities in the reaction volume during the process of polymerization. The spectra of absorption of the polyaniline/polyacid films on transparent glass electrodes with a conductive layer of SnO₂ and the data of potentiodynamic measurements in the potential region 0–1.0 V (Ag/AgCl) are typical for polyaniline with moderate electroconduction.     

Quinaldinium Chlorochromate Supported on Alumina: A New and Efficient Reagent for the Oxidation of Alcohols

Summary. The new, mild chromium(VI) oxidizing agent, quinaldinium chlorochromate supported on neutral alumina, was prepared as a stable yellow solid. The reagent is suitable to oxidize various primary and secondary alcohols to the corresponding carbonyl compounds and anthracene to anthraquinone in good yields.     

掺杂质子酸的类型对聚苯胺结构和电导率的影响

采用化学氧化聚合法以苯胺为单体，过硫酸铵为氧化剂，在不同质子酸的水溶液中合成聚苯胺，考察质子酸对聚苯胺电性能影响，并通过傅立叶红外吸收光谱（FTIR）和紫外可见光吸收光谱（UV－vis)研究聚苯胺掺杂前后结构的变化。结果表明，龙质子酸掺杂后聚 胺具有导电性是因为其分子链上电荷离城形成了共轭结构，具有不同质子酸中生成的聚苯胺氧化程度不同；分子链共轭程度与掺杂酸对阴离子大小有关，掺杂质子酸对阴离子越大，聚苯胺分子链共轭程度越大，电导率也就越高。