Polyaniline prepared in ethylene glycol or glycerol

Oxidations of aniline or aniline hydrochloride have been carried out in ethylene glycol or glycerol and in their mixtures with water. Ammonium peroxydisulfate was used as oxidant. The oxidation of aniline is exothermic and changes in temperature were monitored to follow its progress. The effect of the solvents on the course of oxidation, morphology, and properties of final products has been studied by scanning electron microscopy, FTIR spectroscopy, and conductivity measurements. It is proposed that the reduction of dielectric constant of the reaction medium results in the reduced dissociation of ionic species that take a part in oxidative polymerization. Consequently, the addition of an organic solvent has a similar effect as a decrease in the acidity of the reaction mixture. Conductivity and morphology depend on the mole ratio of oxidant and monomer, and the type and volume fractions of organic solvents, viz. ethylene glycol and glycerol, which were used in reactions.     

Morphology transition control of polyaniline from nanotubes to nanospheres in a soft template method

A soft template route is reported for the fabrication of polyaniline nanospheres via the oxidative polymerization of aniline in the presence of β‐naphthalenesulfonic acid (β‐NSA) as both surfactqant and dopant, and ammonium persulfate as oxidant at 2–5 °C. Control over the morphology and size of the nanoparticles was achieved by changing the reaction medium via addition of an organic cosolvent (i.e. ethanol or ethylene glycol) and by controlling the concentrations of aniline and β‐NSA and the molar ratio of β‐NSA to aniline. By this means the size of the β‐NSA–aniline micelles and the way that aniline monomer interacts with the micelles were controlled. In fact the lower dielectric constant of organic cosolvent, due to reduction of the possibility of dissociation of ionic species, causes the monomer to exist mostly as neutral aniline molecules rather than as anilinium cations. The neutral aniline molecules form aniline‐filled micelles with β‐NSA, which act as soft templates for the formation of polyaniline nanospheres. Scanning and transmission electron microscopies, dynamic light scattering, and Fourier transform infrared and UV‐visible spectroscopies were used to characterize the products. The mechanism of morphology transition from nanotubes to nanoparticles is discussed based on the experimental observations. © 2014 Society of Chemical Industry     

Adsorption behavior of monomers and formation of conducting polymers on polyester fibers

In situ adsorption of monomers on fibers plays a key role in fabricating highly conductive polyaniline (PANI)‐based textiles by two‐stage oxidation polymerization. Experiments were conducted in aniline monomer and hydrochloric acid solution with the variables such as contact time, initial concentration, and temperature, which can enhance the equilibrium adsorption capacity to aniline of poly(ethylene terephthalate) (PET) fibers. Equilibrium data were fit well by a Henry partition‐type isotherm equation. It was found that the kinetics of the adsorption of aniline onto PET fibers at different operating conditions was best described by the pseudo‐second‐order model. The rate parameters of the intraparticle diffusion model for adsorption were also evaluated and compared to identify the adsorption mechanisms. The monomer exhaustion increased with increasing the temperature. The value of electrical surface resistance of conductive textiles about 3.2 kΩ was obtained when the padder squeeze step was introduced, and the molar ratio of 0.6 between the oxidant concentration and the exhausted concentration of monomers at the adsorption equilibrium was applied. Scanning electron micrographs of PANI/PET composite surfaces were observed, conforming that smooth films were produced by surface polymerization of aniline monomers adsorbed previously on fibers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Conjugated polyaniline as a result of the benzidine rearrangement

The mechanism of the oxidative polymerization of aniline is reviewed on the basis of the experimental evidence and reaction schemes proposed in the literature. It is demonstrated that the balance between the non‐protonated and protonated forms of the monomer and the growing chain is responsible for the diversity of the molecular structure, morphology and properties of aniline oxidation products. Various forms are oxidized by two oxidation mechanisms: (1) chain reaction of electrophilic substitution and (2) coupling of cation‐radical centres. At pH > 2.5, the non‐protonated reagents are oxidized with a chain reaction controlled by electrophilic substitution of the aromatic ring. The reaction leads to the formation of non‐conducting aniline oligomers with heterogeneous molecular structures. At pH = 2.5–4, the electrophilic substitution is reduced because of the protonation of the aniline, and the cyclic dimer, phenazine, becomes the main product of the oxidation. The growth of the conjugated chain proceeds at pH < 2.5, when the reactants are protonated. The reaction proceeds through coupling between the terminal cation radical and the monomer cation radical with formation of a π‐complex. The transformation of the π‐complex into a para‐substituted monomer unit is thermodynamically controlled and is produced through an intramolecular benzidine (semidine) rearrangement. The regular structure of the growing chains is a result of the high regioselectivity of the sigmatropic rearrangements and significant energy gain attained by the formation of protonated polyconjugated chains in the agglomerated state. © 2015 Society of Chemical Industry     

Preparation and electrochemical capacitance of poly(pyrrole‐co‐aniline)

The copolymer of pyrrole and aniline, poly(pyrrole‐co‐aniline), has been prepared by chemical oxidation of corresponding monomer mixtures with ammonium peroxysulfate. Techniques of FTIR, SEM‐EDS, and BET surface area measurement were used to characterize the structure and morphology of the copolymer. The electrochemical properties of the copolymer were investigated by cyclic voltammetry, galvanostatic charge‐discharge, and electrochemical impedance spectroscopy. The results indicated that poly(pyrrole‐co‐aniline) was about 100–300 nm in diameter and showed better electrochemical capacitive performance than polypyrrole and polyaniline. The specific capacitance of the copolymer electrode was 827 F/g at a current of 8 mA/cm² in 1 mol/L Na₂SO₄ electrolyte. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Catalytic oxidization polymerization of aniline in an H2O2?Fe2+ system

Polyaniline is prepared by chemical polymerization of aniline in an acidic solution using H₂O₂ as an oxidant and ferrous chloride as a catalyst. A wide variety of synthesis parameters are studied, such as the amount of the catalyst, reaction temperature, reaction time, initial molar ratio of oxidant, monomer and catalyst, and aniline and HCl concentrations. The polymerization of aniline can be initiated by a very small amount of catalyst. The yield and the conductivity of product depend on the initial molar ratio of the oxidant and monomer. The polyaniline with a conductivity of about 10° S/cm and a yield of 60% is prepared under optimum conditions. The process of polymerization was studied by in situ ultraviolet–visible spectroscopy and open‐circuit potential technology. Compared to the polymerization process in a (NH₄)₂S₂O₈ system, the features of the H₂O₂ Fe²⁺ system are pointed out, and the chain growth mechanism is proposed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1077–1084, 1999     

Optimization of the conductivity and yield of chemically synthesized polyaniline using a design of experiments

The electrical conductivity and yield of polyaniline (PANi) were optimized using a design of experiments (DOE). PANi samples were synthesized by the chemical oxidative polymerization of aniline using methane sulfonic acid as the dopant acid and ammonium persulfate as the oxidant. The main factors in the synthesis of PANi that can affect the conductivity were identified as (i) the concentration of dopant acid, (ii) oxidant‐to‐monomer ratio, and (iii) the addition rate of oxidant to monomer. Using a Box‐Behnken DOE method the regression equation, main effects plots, contour plots, and optimization plots for conductivity and yield were generated and analyzed. Under the optimized conditions of dopant acid concentration of 0.9M, an oxidant addition rate of 30 mL/h and an OM ratio of 0.9, PANi with a conductivity of 1.95 S/cm and yield of 95% was obtained. The observed trends in the four‐point probe conductivity measurements were correlated with the polymer structure using fourier transform infrared spectroscopy, X‐ray diffraction studies, and scanning electron microscopy. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1047‐1057, 2013     

Novel oxidants for polymerization and crystallization of aniline

By using novel oxidants, namely, sodium salt of para‐toluene sulfonic acid, lithium perchlorate, and potassium ferricyanide, and varying the oxidant to monomer ratio from as low as 1/100 to 1/20 in the presence of concentrated HCl, it has been possible to simultaneously polymerize aniline and crystallize the polyaniline at room temperature. The crystals thus obtained have been characterized using FTIR, GPC, XRD, and Optical Microscope. It was found that highly crystalline substituted oligo‐polyanilines were obtained. The studies indicate that the use of even weaker oxidants, like pTS‐Na, LiClO₄, and K₃[Fe(CN)₆], can bring about simultaneous polymerization and crystallization of aniline, as we observed earlier using ammonium persulphate. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 640–646, 2005     

Polypyrrole–vinyl aniline modified cyclohexanone formaldehyde resin copolymers: a comparative study of the resin preparation

In this study, the synthesis of polypyrrole‐b‐vinyl aniline modified cyclohexanone formaldehyde resin (PPy‐b‐CFVAnR) block copolymers by a combination of condensation polymerization and chemical oxidative polymerization processes was examined. First, a cyclohexanone formaldehyde resin containing vinyl aniline units [4‐ vinyl aniline modified cycl?ohexanone formaldehyde resin (CFVAnR)] was prepared by a direct condensation reaction of 4‐vinyl aniline and cyclohexanone with formaldehyde in an in situ modification reaction. CFVAnR and pyrrole (Py) were then used with a conventional method of in situ chemical oxidative polymerization. The reactions were carried out with heat‐activated potassium persulfate salt in the presence of p‐toluene sulfonic acid in a dimethyl sulfoxide–water binary solvent system; this led to the formation of desired block copolymers. The effects of the oxidant–monomer molar ratio, dopant existence, addition order of the reactants, and reaction temperature on the yield, conductivity, and morphology of the resulting products were investigated. PPy‐b‐CFVAnR copolymers prepared with a resin‐to‐Py molar ratio of 1:40 showed conductivity in the range 3.7 × 10^?1 to 3.8 × 10^?2 S/cm. Oxidant‐to‐Py molar ratios of 0.5 and 1.0 were proposed to be the optimum stoichiometries for higher conductivity and yield, respectively, of the copolymer. The morphology of the copolymer (PPy‐b‐CFVAnR) was investigated with environmental scanning electron microscopy analyses. The results indicate that the surface of the copolymer was composed of well‐distributed nanospheres with average particle diameters of 60–85 nm. Also, the synthesized PPy‐b‐CFVAnR had a higher thermal stability than the pure CFVAnR. The chemical composition and structure of the PPy‐b‐CFVAnR copolymers were characterized by Fourier transform infrared spectroscopy and measurement. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 132, 42841.     

Expedient Synthesis of Functionalized Triarylmethanols through Tandem Formation of Geminal C?C and C?O Bonds

The rearrangement/oxidation of N,N‐disubstituted anilines and the formal dehydrogenative cross‐coupling of diarylmethanols with aniline derivatives have been developed for the preparation of symmetric and unsymmetric functionalized triarylmethanols. Both reactions proceed smoothly in trifluoroacetic acid in the presence of an inexpensive oxidant (manganese dioxide or potassium persulfate) and a catalytic amount of palladium diacetate to give a range of functionalized triarylmethanols in moderate to good yields and with extremely high regioselectivity. The two unprecedented reactions involve tandem formation of geminal C C and C O bonds, and they are synthetically useful, atom‐efficient, and operationally simple.     

Synthesis of needle‐like polyanilines

Needle‐like polyanilines were prepared in aqueous media by chemical oxidation. p‐Toluenesulfonic acid (pTSA) was used to protonate aniline (ANi) and readily made the anilinium complex. By slowly adding ammonium peroxydisulfate (APS) at 15°C, polyanilines were prepared in the micelles and grew to be needle‐like aggregates potentially useful as conductive fillers for electromagnetic interference shielding and radar‐absorbing materials. The needle‐like aggregates of protonated polyaniline prepared at 15°C and 0.5 M aniline concentration with 3 h of APS addition time showed conductivity up to 3 S/cm and a maximum aspect ratio of 26 L/D. They were observed by scanning electron microscopy to peel off partially into fibrils after washing. The needle‐like polyaniline‐pTSA complexes prepared with 0.5 M aniline concentration showed good thermal stability up to 200°C. The high conductivity of the needle‐like aggregates was ascribed to their well‐developed crystalline structures, compared with those of spherical particles. J. VINYL ADDIT. TECHNOL., 13:76–86, 2007. © 2007 Society of Plastics Engineers.     

Electrically conductive textiles by in situ polymerization of aniline

Two methods of obtaining electrically conductive fabrics by in situ polymerization of aniline were compared. Conductive fabrics were prepared by immersing the nylon 6 fabrics in 100% aniline or an aqueous hydrochloride solution of aniline followed by initiating successive polymerization in a separate bath (DPSB) or in a mixed bath (DPMB) of oxidant and dopant solution with aniline. In each case, the polymerization conditions were optimized to obtain the maximum quality of polyaniline (PAn) on the fabrics. The higher conductivity of composite fabrics, whose value reached up to 0.6 × 10⁻¹ s/cm, was obtained by the DPMB process. Moreover, this method induced the least decrease in the degree of crystallinity as compared to the DPSB process. The serviceability of the PAn–nylon 6 composite fabrics was also evaluated. No significant changes in the conductivity were observed after abrading the composite fabrics over 50 cycles and multiple acid and alkali treatment. The stability of conductivity was slightly decreased by less than 1 order after exposure to light for 100 h, but it was significantly decreased after washing with detergent. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2094–2101, 1999     

Solubility and electrochemical properties of chemically modified polyaniline‐gold/camphor sulfonic acid composites

Polyaniline nanocomposites encapsulating gold nanoparticles on camphor sulfonic acid (CSA) surface were prepared via the polymerization of aniline hydrochloride with different concentrations of CSA using HAuCl₄ as oxidant. The synthesized composites were characterized by Fourier transform infrared spectroscopy and UV–visible spectroscopy. Surface morphology was studied by scanning electron microscopy and transmission electron microscopy. The embedded crystallinity of the composites was investigated by X‐ray diffraction analysis. The solubility of the nanocomposites was studied using water, N‐methyl‐2‐pyrrolidinone, chloroform, and dimethylformamide solvents. The room temperature direct current conductivity of the composites was also observed in solution state. Electrical property of the composites was examined using cyclic voltammetric measurements at room temperature. The fabricated polymer nanocomposites with better solubility in water and some organic solvents will have various applications in electrical devices and biosensors. POLYM. COMPOS., 36:245–252, 2015. © 2014 Society of Plastics Engineers     

Synthesis,characterization and SEESR spectroscopic investigations of indole/aniline copolymers

Indole/aniline copolymers were synthesized electrochemically and the polymerization mechanism was investigated via in‐situ simultaneous electrochemical electron spin resonance (SEESR) spectroscopy. The Radical cationic intermediates of substituted indole and aniline were detected during the electrochemical oxidation. The resulting ESR‐spectra with hyperfine splitting were simulated and radicalic structures were identified. It was suggested that the polymerization occurs over positions C‐3 and C‐6 of indole molecule and over the nitrogen and para‐position of aniline. Furthermore, aniline, indole and aniline/indole copolymers were investigated depending on applied potential via electrochemical impedance spectroscopy (EIS). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and air separation of soluble terpolymers from Aniline,Toluidine, and Xylidine

A series of terpolymers were synthesized by oxidative polymerization of aniline, o-toluidine, and 2,3-xylidine with three monomer ratios using ammonium persulfate as an oxidant in two acidic media. The yield and intrinsic viscosity of the terpolymers were studied by changing the polymerization temperature and medium. The resulting terpolymers were characterized by ¹H–NMR, wide-angle X-ray diffraction, differential scanning calorimetry, thermogravimetry, and constant pressure-variable volume methods. The results showed that the terpolymers are amorphous and exhibit enhanced solubility, high thermostability, and high char yield, greater than 35 wt % at 900°C in nitrogen. A blend membrane of the terpolymer with ethyl cellulose shows good air-separation ability. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 790–798, 2001     

Electron transport properties of polyaniline composite films containing poly(3‐hydroxybutyric acid)

Polyaniline (PANI) composites containing poly(3‐hydroxybutyric acid) (PHB) were synthesized via in situ deposition technique. The oxidative polymerization of aniline hydrochloride was carried out by dissolving different weight percentages (10 wt%, 20 wt%, 30 wt%, 40 wt%, and 50 wt%) of PHB using ammonium persulfate as an oxidant. The as‐synthesized composites were characterized using Fourier‐transform infrared spectroscopy and X‐ray diffraction pattern. The surface morphology of the resulting composites was studied using transmission electron microscopy. The temperature‐dependent direct current conductivity of the synthesized composite films was measured, and the activation energy responsible for the conductivity was examined. Incorporation of the biodegradable polymer, PHB, during the preparation of new PANI composites significantly increased the conductivity of the resulting composites. POLYM. COMPOS., 34:1655–1662, 2013. © 2013 Society of Plastics Engineers     

Novel conducting polyaniline blends with cyanoresin

Novel conducting polyaniline (PANI)/cyanoresin (Cyan) blends were prepared by the addition of Cyan/dimethylformamide solutions to aniline monomer/dopant solutions and the in situ chemical oxidative polymerization of aniline with ammonium persulfate as an oxidant in aqueous p‐toluene sulfonic acid solutions. The PANI/Cyan blends were prepared with various compositions (5:95, 10:90, 20:80, 30:70, 40:60, 50:50, 60:40, and 70:30), and blend films of PANI/Cyan were obtained with a casting method. The conductivity of the PANI/Cyan blend films was 10^?7 to 10^?2 S/cm, which was measured by a four‐probe technique. The tensile strength of the blend films was maintained with an increasing amount of PANI (up to 50 wt %), and this was attributed to intermolecular interactions such as hydrogen bonding between PANI and Cyan and a reinforcing effect through blending. This hypothesis was corroborated by Fourier transform infrared spectroscopy. Field emission scanning electron microscopy and thermogravimetric analysis were also used to investigate the morphology and thermal properties of the conducting PANI/Cyan blend films, respectively. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1035–1042, 2005     

Doped polyaniline/multiwalled carbon nanotube composites: Preparation and characterization

Polyaniline (PANI)/multiwalled carbon nanotube (MWNT) composites with a uniform tubular structure were prepared from in situ polymerization by dissolving amino‐functionalized MWNT (a‐MWNT) in aniline monomer. For this the oxidized multiwalled nanotube was functionalized with ethylenediamine, which provided ethylenediamine functional group on the MWNT surface confirmed by Fourier‐transform infrared spectra (FT‐IR). The a‐MWNT was dissolved in aniline monomer, and the in situ polymerization of aniline in the presence of these well dispersed nanotubes yielded a novel tubular composite of carbon nanotube having an ordered uniform encapsulation of doped polyaniline. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed that the nanotubes were coated with a PANI layer. The thermal stability and electrical conductivity of the PANI /MWNTs composites were characterized by thermogravimetric analysis (TGA) and conventional four‐probe method respectively. Compared with pure PANI, the electrical conductivity and the decomposition temperature of the MWNTs/PANI composites increased with the enhancement of MWNT content in PANI matrix. POLYM. COMPOS., 34:1119–1125, 2013. © 2013 Society of Plastics Engineers     

Anthranilic acid assisted preparation of Fe3O4–poly(aniline‐co‐o‐anthranilic acid) nanoparticles

Magnetic Fe₃O₄–poly(aniline‐co‐o‐anthranilic acid) nanoparticles were prepared by a novel and simple method: anthranilic acid assisted polymerization. The synthetic strategy involved two steps. First, Fe₃O₄ nanoparticles capped by anthranilic acid were obtained by a chemical precipitation method, and then the aniline and oxidant were added to the modified Fe₃O₄ nanoparticles to prepare well‐dispersed Fe₃O₄–poly(aniline‐co‐o‐anthranilic acid) nanoparticles. Fe₃O₄–poly(aniline‐co‐o‐anthranilic acid) nanoparticles exhibited a superparamagnetic behavior (i.e., no hysteresis loop) and high‐saturated magnetization (M_s = 21.5 emu/g). The structure of the composite was characterized by Fourier‐transform infrared spectra, X‐ray powder diffraction patterns, and transmission electron microscopy, which proved that the Fe₃O₄–poly(aniline‐co‐o‐anthranilic acid) nanoparticles were about 20 nm. Moreover, the thermal properties of the composite were evaluated by thermogravimetric analysis, and it showed excellent thermal stability. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1666–1671, 2006     

Synthesis of soluble and thermally stable polyamides from diamine containing (quinolin‐8‐yloxy) aniline pendant group

A novel diamine monomer having pendant 4‐(quinolin‐8‐yloxy) aniline group was successfully synthesized via aromatic substitution reaction of 8‐quinolinol with p‐fluoronitrobenzene followed by Pd/C catalyzed hydrazine reduction, amidation reaction between 4‐(quinolin‐8‐yloxy) aniline and 3,5‐dinitrobenzoylcholoride followed by Pd/C catalyzed hydrazine reduction. The diamine monomer was fully characterized by using FTIR, ¹H‐NMR, ¹³C‐NMR, and elemental analysis. The diamine monomer was polymerized with various aromatic and aliphatic dicarboxylic acids to obtain the corresponding polyamides. The polyamides had inherent viscosity in the range of 0.30–0.41 dL/g and exhibited excellent solubility in the polar aprotic solvents such as DMAc, NMP, N,N‐dimethylformamide, Pyridine, and DMSO. The glass transition temperatures (T_g) of the polymers are high (up to 313°C) and the decomposition temperatures (T_i) range between 200 and 370°C, depending on the diacids residue in the polymers backbone. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010