The polymerization of aniline at a solution-gelatin gel interface

Gelatin gel swollen with the solution of aniline hydrochloride was exposed to a solution of ammonium peroxydisulfate. The reactants met at the gel interface, and the redox reaction between them produced a polyaniline (PANI) interlayer, a PANI membrane, at first. The electrons abstracted from the aniline molecules in the gel during the oxidation are transferred through a conducting PANI membrane to oxidant molecules in the external solution. The reaction between aniline and peroxydisulfate thus takes place without the need for the reactant molecules to physically meet. PANI, therefore, grows from the interface into the gelatin gel. When the loci of reactants are reversed, i.e. the oxidant is inside the gelatin gel and aniline hydrochloride in the surrounding solution, PANI grows from the gel interface into the aniline solution but some PANI is produced inside the gelatin gel, too. Composite PANI-gelatin gels were separated and gelatin was removed from them by acid hydrolysis. The resulting PANI had a granular morphology and a conductivity of the order of units S cm⁻¹, slightly lower compared with PANI prepared in a common way by mixing the solutions of reactants. The differences in the details of molecular structure are discussed on the basis of FTIR spectra.     

Synthesis and properties of a newly obtained sorbent based on silica gel coated with a polyaniline film as the stationary phase for non-suppressed ion chromatography

The new sorbent for non-suppressed ion chromatography based on silica gel coated with a film of polyaniline (PANI) was obtained in a process of in situ polymerization of aniline by oxidation with ammonium peroxydisulfate. Raman analyses performed using a Thermo Scientific DXR confocal Raman Microscope equipped with the Omnic 8 software from Thermo Fisher Scientific have proved a uniform distribution of PANI on the surface of chromatographic beads and in the pores of the particle.     

BrΦnsted酸性离子液体掺杂聚苯胺的无溶剂制备及其表征

首先合成了两种带—SO3H官能团的Brφnsted酸离子液体([MIMPS][HSO4]和[PYPS][HSO4]),然后分别以这两种带—SO3H官能团的Brφnsted酸性离子液体做为掺杂剂,在无溶剂条件下通过机械化学聚合反应制备了掺杂导电态聚苯胺.由于带—SO3H官能团的Brφnsted酸性离子液体中H+可以单独以离子形式存在,因此可形成质子化导电态的翠绿亚胺盐,并以红外光谱、紫外可见-近红外、X-射线衍射、循环伏安和四探针技术等测试方法对聚苯胺进行了结构和性能表征.PANI-[MIMPS][HSO4]的结晶性、电导率和电化学活性要优于PANI-[PYPS][HSO4].     

Synthesis of polyaniline and application in the design of formulations of conductive paints

Polyaniline (PANI) is prepared by chemical polymerization of aniline in acidic medium using ammonium peroxydisulfate ((NH₄)₂S₂O₈) as oxidant. The polymer, with a conductivity of 25–30 S/cm, is used to formulate conducting paints. A stable paint with a conductivity of 10^?3 S/cm is obtained. Copyright © 2004 John Wiley & Sons, Ltd.     

Synthesis and characterization of red mud/polyaniline composites: Electrical properties and thermal stability

New types of conducting composites using red mud as an inorganic substrate and polyaniline as the conducting phase were prepared. Red mud/polyaniline (RM/PANI) composites were synthesized in acidic aqueous solution by the chemical oxidative polymerization of aniline using ammonium peroxydisulfate as the oxidant. The composites exhibit conductivities in the 0.42-5.2 S cm⁻¹ range, depending on the amount of polyaniline. They were characterized by infrared and UV-vis spectroscopy, scanning electron microscopy and X-ray diffraction. The IR and X-ray results show that PANI is deposited on the RM surface. The composites have a globular structure and the PANI globules synthesized on the surface of RM are smaller than those prepared under the same conditions without the substrate. Thermogravimetric analysis was used for investigation of the thermal stability of the composites. The thermal stability of the conductivity of RM/PANI composites was studied by ageing at 125 °C, the conductivity being measured in situ during this process.     

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.     

Synthesis and characterization of C60/polyaniline composites from interfacial polymerization

C₆₀/polyaniline (PANI) nanocomposites have been synthesized by the oxidative polymerization of aniline with ammonium peroxydisulfate in the presence of C₆₀ by using an interfacial reaction. When compared with the pure PANI nanofibers from the similar process, the diameter of the obtained C₆₀/PANI nanofibers was increased because of the encapsulation of C₆₀ into PANI during aniline polymerization, which resulted from the charge‐transfer interactions between C₆₀ and aniline fragment in PANI. In addition, the resulting C₆₀/PANI nanocomposites synthesized from the low initial C₆₀/aniline molar ratio (less than 1:25) showed the homogenous morphology composed of fiber network structures, which has an electrical conductivity as high as 1.1 × 10^?4 S/cm. However, the C₆₀/PANI nanocomposites from the higher initial C₆₀/aniline molar ratio (more than 1:15) showed the nonuniformly distributed morphology, and the electrical conductivity was decreased to 3.5 × 10^?5 S/cm. Moreover, the C₆₀/PANI nanocomposites from the interfacial reaction showed a higher value of electrical conductivity than the mechanically mixed C₆₀/PANI blends with the same C₆₀ content, because of the more evenly distributed microstructures. FTIR, UV–vis, and CV data confirmed the presence of C₆₀ and the significant charge‐transfer interactions in the resultant nanocomposites, which was responsible for the morphology development of the C₆₀/PANI and the variation of the electrical conductivity. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

The oxidative polymerization of aniline as topochemical process. The statistical analysis of grain growth

The films of polyaniline (PANI) on the glass slides with granular morphology were prepared by oxidative polymerization with ammonium peroxydisulfate in strong acidic conditions. The kinetics of polymerization was monitored recording of scanning electron microscopy images of deposit PANI films on glass slides. Statistical analysis of the PANI grain size was successfully applied for characterization of the polymerization process. It was shown that oxidative PANI polymerization could be described as a topochemical process. This allowed us explaining the existence of three phase of process (induction period, acceleration stage and decay) and finding the kinetics parameters of these stages. The model of phenazine nucleates was used to described induction stage. It was shown that phenazine nucleation process can be described kinetically as zero-order reaction. The acceleration stage of PANI polymerization was connected with increase of PANI grain surface during reaction and the mechanism of this acceleration was discussed. The decay stage of process was attributed with formation fuse loose PANI film with reduced available interphase surface for polymerization process.     

Coating of multiwalled carbon nanotubes with polymer nanospheres through microemulsion polymerization

We report a simple and noncovalent method for coating multiwalled carbon nanotubes (MWCNTs) with polyaniline (PANI) nanospheres using a microemulsion polymerization method. In this method, aniline polymerization is performed with MWCNTs in the presence of sodium dodecyl sulfate (SDS), which serves as both a surfactant and a dopant. Morphological, structural, thermal, and electrical properties of MWCNT–PANI nanocomposites were analyzed. The TEM results of the nanocomposites prepared with surfactant reveal that 30–50-nm-diameter PANI nanospheres were coated on the surface of the MWCNTs. Composites prepared without surfactant were found to be in core–sheath-type cable structures. The conductivities of the nanocomposites synthesized through microemulsion polymerization were found to be one order of magnitude higher than both the conductivities of pure PANI and the composites prepared via in situ chemical polymerization without an assisting SDS surfactant. The mechanism for the formation of nanostructured composites is presented.     

Chemical Oxidative Polymerization of β-Cyclodextrin/Aniline Inclusion Complex

A β-cyclodextrin (β-CD)/aniline inclusion complex has been synthesized in aqueous solution and characterized by FT-IR and ¹H-NMR spectroscopy, chemical analysis and thermogravimetric method. By elemental analysis and ¹H-NMR spectroscopy a complex with stoichiometry 1:1.95 and 1:1.8 (β-CD/aniline) respectively, is found. The complexed aniline was polymerized by chemical oxidative polymerization using ammonium peroxydisulfate in water (pH = 7) and 1M HCl aqueous solution. In both cases, after an induction period, insoluble polyanilines (PANIs) are obtained, however, in water at pH = 7, a polypseudorotaxane architecture containing a β-CD molecule to ~14 aniline units has resulted. In acidic conditions, anilinium cation is highly hydrophilic and inclusion complex has a strong tendency to dissociate to free molecules and emeraldine salt of PANI, free of host molecules is synthesized.     

Preparation,morphology and electrical conductivity of polyaniline/polyoxyalkylene–montmorillonite exfoliated nanocomposites

Polyaniline (PANI)/organoclay exfoliated nanocomposites containing different organoclay contents (14–50 wt%) were prepared. PANI emeraldine base (EB) and oligomeric PANI (o‐PANI) were intercalated into montmorillonite (MMT) modified by four types of polyoxyalkylene diamine or triamine (organoclay) using N‐methyl pyrolidinone (NMP) as a solvent in the presence of 0.1 M HCl. o‐PANI and EB have been synthesized by oxidative polymerization of aniline using ammonium peroxydisulfate (APS). Infrared absorption spectra (IR) confirm the electrostatic interaction between negatively charged surface of MMT and positively charged sites in PANI. X‐ray diffraction (XRD) studies disclosed that the d₀₀₁ spacing between interlamellar surface disappeared at low content of the organoclay. The morphology of these materials was examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Electrical conductivities of the PANI‐organoclay and o‐PANI‐organoclay nanocomposites were 1.5 × 10^?3–2 × 10^?4 and 9.5 × 10^?7–1.8 × 10^?9 S/cm, respectively depending on the ratio of PANI. Copyright © 2007 John Wiley & Sons, Ltd.     

The role of acidity profile in the nanotubular growth of polyaniline

Conditions of polyaniline (PANI) nanotubes preparation were analyzed. Aniline was oxidized with ammonium peroxydisulfate in 0.4 M acetic acid. There are two subsequent oxidation steps and the products were collected after each of them. At pH > 3, neutral aniline molecules are oxidized to non-conducting aniline oligomers. These produce templates for the subsequent growth of PANI nanotubes, which takes place preferably at pH 2–3. At pH < 2, granular morphology of the conducting PANI is obtained. High final acidity of the medium should be avoided in the preparation of nanotubes, e.g., by reducing the amount of sulfuric acid which is a by-product. Reduction of the peroxydisulfate-to-aniline mole ratio was tested for this purpose in the present study. Lowering of the reaction temperature from 20°C to −4°C had a positive effect on the formation of nanotubes.     

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).     

Graphene oxide‐induced polymerization and crystallization to produce highly conductive polyaniline/graphene oxide composite

Graphene oxide (GO)–polyaniline (PANI) composite is synthesized by in situ polymerization of aniline in the presence of GO as oxidant, resulting in highly crystalline and conductive composite. Fourier transform infrared spectrum confirms aniline polymerization in the presence of GO without using conventional oxidants. Scanning electron microscopic images show the formation of PANI nanofibers attached to GO sheets. X‐ray diffraction (XRD) patterns indicate the presence of highly crystalline PANI. The sharp peaks in XRD pattern suggest GO sheets not only play an important role in the polymerization of aniline but also in inducing highly crystalline phase of PANI in the final composite. Electrical conductivity of doped GO–PANI composite is 582.73 S m^?1, compared with 20.3 S m^?1 for GO–PANI obtained by ammonium persulfate assisted polymerization. The higher conductivity appears to be the result of higher crystallinity and/or chemical grafting of PANI to GO, which creates common conjugated paths between GO and PANI. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1545–1554     

Nanocomposites of natural rubber and polyaniline-modified cellulose nanofibrils

Cellulose nanofibrils (CNF) were isolated from cotton microfibrils (CM) by acid hydrolysis and coated with polyaniline (PANI) by in situ polymerization of aniline onto CNF in the presence of hydrochloride acid and ammonium peroxydisulfate to produce CNF/PANI. Nanocomposites of natural rubber (NR) reinforced with CNF and CNF/PANI were obtained by casting/evaporation method. TG analyses showed that coating CNF with PANI resulted in a material with better thermal stability since PANI acted as a protective barrier against cellulose degradation. Nanocomposites and natural rubber showed the same thermal profiles to 200 °C, partly due to the relatively lower amount of CNF/PANI added as compared to conventional composites. On the other hand, mechanical properties of natural rubber were significantly improved with nanofibrils incorporation, i.e., Young’s modulus and tensile strength were higher for NR/CNF than NR/CNF/PANI nanocomposites. The electrical conductivity of natural rubber increased five orders of magnitude for NR with the addition of 10 mass% CNF/PANI. A partial PANI dedoping might be responsible for the low electrical conductivity of the nanocomposites.     

Thermal degradation of polyaniline films prepared in solutions of strong and weak acids and in water - FTIR and Raman spectroscopic studies

Polyaniline (PANI) films were prepared in situ on silicon windows during the oxidation of aniline with ammonium peroxydisulfate in aqueous solutions of strong (0.1 M sulfuric) or weak (0.4 M acetic) acid or without any acid. In solutions of sulfuric acid, a granular PANI is produced, in solutions of weak acids or without any acid, PANI nanotubes are obtained. The thermal stability and structural variation of the corresponding films produced on silicon windows during treatment at 80 °C for three months were studied by FTIR and Raman spectroscopies. The morphology of the films is preserved during the degradation but the molecular structure changes. The results indicate that the spectral changes correspond to deprotonation, oxidation and chemical crosslinking reactions. The films of PANI salts loose their protonating acid. PANI bases are more stable than the salt forms during thermal ageing. The films obtained in water or in the presence of acetic acid are more stable than those prepared in solutions of sulfuric acid. The protonated structure is more prone to crosslinking reactions than deprotonated one. The molecular structure corresponding to the nanotubular morphology, which contains the crosslinked phenazine- and oxazine-like groups, is more stable than the molecular structure of the granular morphology.     

Formation of polyaniline nanofibers: a morphological study

Polyaniline (PANI) powders were prepared by solution precipitation, rapid mixing polymerization, and interfacial polymerization to find the key factors that influence the formation and growth of PANI nanofibers. In chemical oxidative polymerization of aniline, the morphology of the product is mainly determined by aniline concentration. In the case of lower aniline concentration, PANI nanofibers were formed and can be preserved and collected as final product, while in the case of higher aniline concentration, larger sized PANI particles or agglomerates were obtained owing to the growth of the nanofibers. Without participation of the oxidizing step, solid PANI samples with compact structures and dissimilar morphologies were achieved by random accumulation of PANI molecules.     

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.     

An elastomeric conducting composite based on polyaniline coated nylon fiber and chloroprene rubber

Chloroprene rubber-polyaniline (PANI) coated nylon fiber composites containing PANI powder were prepared by mechanical mixing on a two-roll mill. PANI was synthesized by chemical polymerization of aniline in presence of hydrochloric acid. PANI coated nylon fiber was prepared by in situ polymerization of aniline on nylon fiber. The cure parameters cure kinetics, filler dispersion, mechanical properties, DC electrical conductivity and thermal degradation parameters of the composites were evaluated. Cure rate index and cure reaction constants indicated that the rate of cure reaction changes on filler addition. Filler addition at higher loadings led to agglomeration. The tensile strength and modulus values increased suggesting a reinforcement effect. The conductivity, thermal characteristics and thermal degradation kinetic parameters are also presented.