Synthesis and characterization of polyanilines doped with several carboxylic acids and with a carboxylic acid equivalent

Polyanilines (PANIs) doped with several organic acids—maleic acid, squaric acid and 2‐propynoic acid—were chemically synthesized in good yields, while PANI doped with 2,6‐dihydroxybenzoic acid did not form under similar polymerization conditions. The resulting PANIs were characterized by spectroscopic and thermal analysis, and it was found that the spectroscopic and thermal properties of these PANIs were affected by the type of dopant ion. Formation of different oxidation states of these PANIs were confirmed by the spectroscopic (UV‐visible and FT‐IR) analysis. Thermogravimetric analysis suggested that PANI doped with maleic acid indicated higher thermal stability than those with the other dopants. The yield and conductivity of PANI doped with maleic acid were found to be higher than those with the other dopants. The PANI doped with 2‐propynoic acid was readily soluble in organic solvents including tetrahydrofuran and dioxane. Copyright © 2005 Society of Chemical Industry     

Electrical behavior of dual‐morphology polyaniline

An attempt was taken to synthesize two types of polyaniline (PANI) with and without solvent followed by drying in air and vacuum oven conditions resulting different morphologies. The PANIs were prepared by chemical oxidative polymerization and studied with respect to their morphological features. Scanning electron microscopy, thermogravimetric analysis, X‐ray diffractometry, Fourier transform infrared spectroscopy, and ultraviolet–visible spectroscopy techniques were used for the characterization studies. The PANI synthesized with a solvent had a mixed morphology (fibrillar and granular), whereas PANI synthesized without a solvent had only a granular morphology. The direct‐current electrical conductivities of the samples were evaluated with an electrometer. We observed that the PANIs with mixed morphology (with solvent) were more electrically conducting than those with a single morphology (without solvent). On drying in vacuo, the conductivity of PANI decreased from 3.3 × 10^?2 to 0.3 × 10^?2 S/cm with solvent treatment, whereas it decreased from 0.1 × 10^?2 to 0.3 × 10^?3 S/cm without solvent treatment. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44091.     

Preparation of polyaniline/phosphorylated poly(vinyl alcohol) nanoparticles and their aqueous redispersion stability

A novel approach for the preparation of the colloidal conducting polyaniline (PANI) nanoparticles was developed. The polyaniline/partially phosphorylated poly(vinyl alcohol)(PANI/P‐PVA) nanoparticles were prepared by the chemical oxidative dispersion polymerization of aniline monomer in 1.0 M HCl aqueous media with the partially phosphorylated poly(vinyl alcohol) (P‐PVA) as the stabilizer and codopant. The PANI/P‐PVA nanoparticles were characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR), thermal gravimetric analysis (TGA), electrical conductivity measurement, and redispersion stability testing. All the results were compared with the properties of the conventional polyaniline in the emeraldine salt form (PANI ES). It was found that the P‐PVA/aniline feeding ratio obviously affected the morphology, redispersion stability and electrical conductivity of the PANI/P‐PVA nanoparticles. When the P‐PVA/aniline feeding ratio ranged from 50 to 60 wt %, the PANI/P‐PVA nanoparticles showed spherical shape with good uniformity, significant redispersion stability in aqueous media, and good electrical conductivity up to 7 S/cm. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Tailoring of chiroptical properties of substituted polyanilines by controlling steric hindrance

Optically active polyorthoanisidine, polyorthotoluidine, polyorthoethylaniline and polyorthochloroaniline were synthesized with chemical polymerization of corresponding monomers in aqueous medium by using d- or l-camphorsulfonic acid (d- or l-CSA) as chiral dopant, ammonium persulfate as oxidant, and diaminodiphenylamine as initiator. By circular dichroism spectroscopic measurements, it was found that PANI exhibited generally a reversed chirality in comparison with the used chiral dopant, but the substituted PANIs had the same one as the chiral dopant. This revealed that the substituent at ortho position caused helical inversion of conformation in comparison with the parent PANI. Such effect was further confirmed by the influence of the copolymerization of aniline and its derivatives on the chirality of the copolymers. The effect of the substituent on the chirality of the copolymers was increased with the increase of the steric hindrance of the ortho substituent. A mechanism was proposed to explain the effects of steric hindrance on the chirality of PANIs. The clarified relationship between the steric hindrance and the chirality of the polymer can enable us to tailor the chiroptical properties of functional polymer materials for future application.     

Polyaniline benefited from poly(vinyl alcohol) in both conductivity and energy storage

Polyaniline (PANI) is an important conductive polymer because of its wide potential. In this article, we present a modified chemical polymerization method, which employs poly(vinyl alcohol) (PVA) as a doping assistant, for the synthesis of PANI. In this study, the introduced PVA contributed both to the conductivity and specific capacitance. The conductivity markedly increased more than two orders of magnitude from 5.2 to 1052 S/m after a small amount of PVA was introduced. A combination of the amphoteric polymer and acid together as the dopant extended the doping method for the synthesis of conductive PANI. The specific capacitance of PANI occurred up to 382.9 F/g at a current density of 0.5 A/g. The PANIs exhibited fast redox reactions, good ion response, and a short diffusion path of electronic transport. By feat of the hydrophilicity of PVA, the as‐prepared PANI showed a good dispersibility in aqueous solution; this is important for its potential applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42989.     

Crosslinked poly(vinyl alcohol)/carboxymethyl chitosan hydrogels for removal of metal ions and dyestuff from aqueous solutions

Hydrogels composed of poly(vinyl alcohol) (PVA) and carboxymethyl chitosan (CMCh) were synthesized via ultraviolet (UV) irradiation that can be used in several industrial fields. Several analysis tools were used to characterize the physical and thermal properties of CMCh/PVA hydrogels namely FT‐IR, scanning electron microscope (SEM), XRD, thermogravimetric analysis (TGA), and differential scanning calorimetery (DSC). TGA results showed that CMCh/PVA hydrogels are thermally more stable than CMCh and their thermal stability increases as PVA content increases in the hydrogel. Also, DSC results showed that CMCh/PVA hydrogels are at least partial miscible blends. Moreover, the swelling behavior of the CMCh/PVA hydrogels was studied in different buffered solutions and in different salt solutions at various concentrations. CMCh/PVA hydrogels swell much more than CMCh especially at alkaline pH. Both metal and dye uptake were studied for CMCh/PVA hydrogels. The hydrogels adsorb much more dyestuff and metal ions like Cu²⁺, Cd²⁺, and Co²⁺ than CMCh itself. Much dyestuff and metal ions are adsorbed by the hydrogels as PVA content increases in the hydrogel. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Electroactive polymer patterns with metal incorporation on a polymeric substrate

Electroactive polymer patterns on a polymeric substrate were fabricated using either a UV lithographic approach or plasma polymerization method. For the lithographic patterning technique, photosensitive thin films comprising polyaniline (PANI) coatings on viologen‐grafted low‐density polyethylene (LDPE) substrates were first prepared. The composite film was subsequently exposed to UV irradiation through a mask. Under UV irradiation, reactions between PANI and viologen occurred, resulting in the conversion of the PANI to a doped state. The PANI micropatterns were developed by using N‐methylpyrrolidinone (NMP) to dissolve the soluble‐unexposed (and hence undoped) parts. The use of Ar plasma treatment of the composite film instead of UV irradiation was not successful in inducing the doping reaction between PANI and viologen. On the other hand, plasma polymerization was shown to be another convenient way for the selective surface deposition of aniline polymer on the surface of the LDPE substrate through a mask. The further incorporation of metal/metal ions in both the PANI‐viologen and plasma polymerized aniline system was successfully carried out on the micropatterns. Polym. Eng. Sci. 44:2061–2069, 2004. © 2004 Society of Plastics Engineers.     

Nanofiber organic semiconductors: The effects of nanosize on the electrical charge transport and optical properties of bulk polyanilines

The electrical transport, optical, and microstructural properties of bulk polyaniline (PANI) and nano‐PANIs were investigated. A field emission scanning electron microscopy (SEM) image of bulk PANI showed macroscopic and aggregated granular particles. A SEM image of the nanostructured PANI showed the formation of one‐dimensional nano/microstructures. The formation of nanofibers was observed from the transmission electron microscopy image. The electrical conductivities of the bulk and nanostructured PANIs increased with increasing temperature, which indicated semiconductor behavior. The electrical conductivities of the bulk and nanostructured PANIs at room temperature were found to be 2.12 × 10^?5 and 1.80 × 10^?2 S/cm, respectively. The electrical conductivity of the nanostructured PANI was about 850 times higher than that of the bulk PANI. The obtained band gaps of the bulk and nanostructured PANIs were determined from diffuse reflectance measurements and were found to be 3.27 and 2.41 eV, respectively. The refractive index of the PANI samples changed from 1.3 to 1.61. The obtained results indicate that the electrical and optical properties of the PANI were inherently dependent on the nanostructure. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

O-carboxymethyl functionalization of chitosan: Complexation and adsorption of Cd (II) and Cr (VI) as heavy metal pollutant ions

Chitosan (CHI) is a biopolymer that can be used on complexation and adsorption of heavy metals in water. Chitosan can be chemically functionalized to modulate the pH range of solubility and favoring the complexation and adsorption processes with metal ions. Thus, in this study, it was investigated the synthesis and characterization of carboxymethyl-chitosan (CMC) as well as its application for the complexation and adsorption of Cd(II) and Cr(VI) ions at different pH conditions and compared to pristine chitosan. The properties of the synthesized derivative were extensively characterized by potentiometric titration, Fourier transform infrared spectroscopy (FTIR) and ultraviolet–visible (UV–vis) spectroscopy. The complexation and adsorption behaviors of CHI and CMC were assessed using atomic absorption spectrometer (AAS) and zeta potential analysis. The results demonstrated that O-carboxymethylation of chitosan has occurred with a degree of functionalization higher than 50% leading to the formation of CMC soluble in alkaline medium. In addition, the effective incorporation of carboxylic groups in the chitosan chain (CMC) has significantly altered the complexation and adsorption responses towards heavy metal cations (Cd^2 +) and anions (chromates) as compared to CHI. Therefore, these systems offer an attractive alternative as biosorbents for the removal of heavy metal pollutants from the wastewater.     

Effects of surfactants on the characteristics and biosensing properties of polyaniline

To investigate the effects of surfactants on the properties of polyaniline (PANI), a series of PANIs was synthesized in the presence of surfactants by chemical polymerization of aniline in an acidic medium, using (NH₄)₂S₂O₈ as oxidant. Three types of surfactant were used: (i) non‐ionic poly(ethylene oxide) (20) sorbitan monolaurate (Tween 20) and poly(ethylene oxide) (20) sorbitan monopalmitate (Tween 40); (ii) cationic (1‐tetradecyl)trimethylammonium bromide; and (iii) anionic sodium 1‐dodecanesulfonate and sodium 1‐pentanesulfonate. The structural, morphological and thermal properties of the various samples were characterized using Fourier transform infrared and UV‐visible spectroscopy, scanning electron microscopy and thermogravimetric analysis. Calorimetry was used to compare enthalpy changes during polymerization. The electrochemical and glucose biosensor properties of the PANIs were investigated using cyclic voltammetry and amperometric measurements. PANI‐Tween 20 and PANI‐Tween 40 were found to be good for immobilization of glucose oxidase enzymes and potential candidates for use in glucose biosensing. Copyright © 2010 Society of Chemical Industry     

Synthesis of dendritic polyaniline nanofibers by using soft template of sodium alginate

Highly crystallized polyaniline (PANI) nanofibers were synthesized by oxidative polymerization of aniline in the presence of sodium alginate as a soft template in HCl and ammonium peroxydisulfate (APS) acting as an oxidizing agent. Sodium alginate, in presence of a protonic acid like HCl, formed hydrogen bonds with anilium ions or oligomers. The formed hydrogen bonds provide the driving force to form PANI nanofibers. The nanofibers were separated from the alginate gel by degelling with ammonium hydroxide and during degelling emeraldine salt was converted into emeraldine base form. The polymerized PANI was characterized using ultraviolet (UV)–visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), and scanning electron microscopy (SEM). UV and FTIR spectra showed that the presence of sodium alginate had no effect on the electronic state and backbone structures of the resulting PANI products. It was evident from the XRD analysis that the obtained PANI nanofibers exhibit higher crystalline order. SEM micrographs showed that PANI nanofibers were just like a mat of interwoven twisted nanofibers. After magnification of the SEM image, it was found that most of the nanofibers were interconnected to form ramose structures rather than isolated nanofibers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Self‐doping of polyaniline prepared with the FeCl3/H2O2 system and the origin of the Raman band of emeraldine salt at around 1375 cm−1

Stepwise addition of H₂O₂ in small portions into the polymerization mixture reduces the number of defects in polyaniline (PANI) prepared with the Fe³⁺/H₂O₂ system, although it does not eliminate them completely. PANIs slightly self‐doped with phenolic groups are thus obtained, which show conductivity from 2.65 to 0.38 S cm^?1 as the total H₂O₂/aniline mole ratio is increased from 0.125 to 1.25. The conductivity shows a good correlation with the A_B/A₉₀₀ UV?visible absorbance ratio of the PANI emeraldine salt form (PANI ES), much better than with the A_B/A_Q ratio of the corresponding emeraldine base form. This corresponds well with the assignment of the band at 900 nm to polaronic transitions. Partial self‐doping of PANIs with weakly acidic phenolic groups allowed evidence to be obtained for the assignment of Raman bands at 1370 cm^?1 and 734 cm^?1 (for λ_exc = 780 nm) to vibrational modes of highly localized polarons. The presence of the band at 880 cm^?1 in the IR spectra of these PANI ES samples that are totally free of sulfate ions proves that this band is associated with a vibrational mode of PANI ES and need not be assigned to a mode of HSO₄^? ions, as has been suggested by some authors. © 2015 Society of Chemical Industry     

Polymeric ionic liquid—assisted polymerization for soluble polyaniline nanofibers

To enhance the solubility of polyanilines(PANI),polymeric ionic liquid(PIL)was introduced into the polymerization synthesis of PANI with various proportions.The structure and properties of the modified PANIs were characterized by 1H NMR,Fourier transform infrared spectroscopy,thermogravimetric analysis,ultraviolet-visible spectrum,etc.It was found that the obtained PANIs doped with PILs were soluble in various organic solvents such as N,N-dimethyl formamide and acetonitrile.Compared with the pure PANI,the PANIs doped by PILs showed remarkable solubility and their chemical structure and conductivity kept integrated.     

Pervaporation separation of water–ethanol mixtures using metal‐ion‐exchanged poly(vinyl alcohol) (PVA)/sulfosuccinic acid (SSA) membranes

Poly(vinyl alcohol)/sulfosuccinic acid (PVA/SSA) membranes in the hydrogen form were converted to monovalent metal ion forms Li⁺, Na⁺, and K⁺. The effect of exchange with metal ions was investigated by measuring the swelling of water–ethanol (10/90) mixtures at 30 °C and by the pervaporative dehydration performance test for aqueous ethanol solutions with various ethanol concentrations at 30, 40, and 50 °C. In addition, electron spectroscopy for chemical analysis (ESCA) analysis was carried out to study the quantity of metal ions in membranes. From the ESCA analysis, the lithium ion quantity in the resulting membranes is greater than that of any other metal ions in question because of the easy diffusion of a smaller metal ion into the membrane matrix. The swelling ratio was in the following order: PVA/SSA‐Li⁺ > PVA/SSA‐Na⁺ > PVA/SSA‐K⁺ membranes. For pervaporation, the PVA/SSA‐Na⁺ membrane showed the lowest flux and highest separation factor for all aqueous ethanol solutions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1867–1873, 2002     

Synthesis and characterization of tanninsulfonic acid doped polyaniline–metal oxide nanocomposites

Composites of conducting polymers and metal oxides have a potential role in electronic devices because of their enhanced physical and electronic properties. An in situ synthesis of metal oxide nanocomposites of polyaniline (PANI) and tanninsulfonic acid doped PANI was carried out at ?10°C with two different ratios of aniline to sodium persulfate (oxidant) and the simultaneous incorporation of TiO₂, Al₂O₃, and ZnO nanopowders. The products were characterized by X‐ray diffraction (XRD), thermal analysis, spectroscopy, and electrical conductivity measurements. XRD and thermogravimetric analysis confirmed the presence of the metal oxide in the final product, whereas the spectroscopic characterization revealed interactions among the tannin, metal oxides, and PANI. The electrical properties were determined by four‐point‐probe bulk conductivity measurements. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis,characterization, and catalytic activity of 4 mol % N,N′‐methylene bisacrylamide crosslinked poly(acrylic acid)–metal complexes

The metal‐ion complexation behavior and catalytic activity of 4 mol % N,N′‐methylene bisacrylamide crosslinked poly(acrylic acid) were investigated. The polymeric ligand was prepared by solution polymerization. The metal‐ion complexation was studied with Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), and Zn(II) ions. The metal uptake followed the order: Cu(II) > Cr(III) > Mn(II) > Co(II) > Fe(III) > Zn(II) > Ni(II). The polymeric ligand and the metal complexes were characterized by various spectral methods. The catalytic activity of the metal complexes were investigated toward the hydrolysis of p‐nitrophenyl acetate (NPA). The Co(II) complexes exhibited high catalytic activity. The kinetics of catalysis was first order. The hydrolysis was controlled by pH, time, amount of catalyst, and temperature. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 272–279, 2004     

Electrical and optical properties of polyaniline with a weblike morphology

We report on the preparation method of nanostructured polyaniline (PANI) via the oxidation polymerization of aniline hydrochloride in the presence of an anionic surfactant. Two solvents with different polarities were used for the synthesis of PANI. The polymers were characterized with ultraviolet–visible, infrared, Raman, and X‐ray photoelectron spectroscopy. The chemical structure derived from the optical characterization techniques and the electrical properties for the two polymers were almost identical. Transmission electron and scanning electron microscopy images revealed the morphological disparity between the PANIs synthesized under different solvent conditions: a microweb of nanofibers versus microtubes. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Molecularly imprinted polymer for solid phase extraction of nicotinamide in pork liver samples

Aromatic polyamides and polythioamides with pendent chlorobenzylidine rings were synthesized through direct polycondenzation of 2‐(p‐chlorobenzalimino) terephthalic acid with the diamines 4,4′‐oxidianiline (1a), 4,4′‐methylenediamide (1b), 4,4′‐diaminodiphenyl sulfone (1c), and thioamines 4,4′‐(bisthiourea) diphenyl ether (3a), 4,4′‐(bisthiourea) diphenyl methane (3b), 4,4′‐(bisthiourea) diphenyl sulfone (3c), respectively, in DMF using P(OPh)₃/pyridine. The polymers were precipitated using water as nonsolvent. FTIR and ¹H‐NMR spectroscopic analysis was used to characterize the monomers and polymers. Representative polyamides and polythioamides were used for the removal of heavy metal ions such as Pb(II), Cd(II), Cu(II), and Cr(III) from aqueous solutions. The effects of pH, contact time, and initial concentration on the uptake of metal ions have been investigated. The adsorption capacities under competitive conditions were in the order Pb (II) > Cu (II) > Cr (III) > Cd (II). The adsorbed ions were eluted by treatment with 2N HCl, and the activities of the polymers are retained after fourth regeneration. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Influence of the reaction temperature on polyaniline morphology and evaluation of their performance as supercapacitor electrode

The polyaniline (PANI) nanostructures of tubular, spherical, and granules morphologies were synthesized by chemical oxidation approach in different reaction temperatures and used as the active electrode materials of symmetric redox supercapacitors. X‐ray diffraction and scanning electron microscopy techniques are employed for characterization of these PANIs. With the initial and reaction temperature increase, the morphology of PANI turned from block to spherical and tubular. Electrochemical properties of these PANI electrodes are studied by cyclic voltammetry (CV), agalvanostatic charge–discharge test, and electrochemical impedance spectroscopy (EIS) in 1M H₂SO₄ aqueous solution. The highest electrochemical properties are obtained on the PANI with tubular morphology. The initial specific capacitance of tubular, spherical, and granules PANI are about 300, 300, and 290 F g^?1 at a constant current of 5 mA. Meanwhile, the retention of the tubular PANI capacitance after 500 charge–discharge cycles was 75%, whereas the spherical and granules PANI was only 35% and 57%. The results indicate that tubular PANI electrodes have potential applications as high‐performance supercapacitors electrode materials. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3753–3758, 2013     

The effect of transition metal ions (M2+=Mn2+, Ni2+, Co2+, Cu2+) on the chemical synthesis polyaniline as counter electrodes in dye-sensitized solar cells

The effect of transition metal ions(M~(2+)=Mn~(2+),Ni~(2+),Co~(2+),Cu~(2+)) on the chemical synthesis of polyaniline(PANI) used as a platinum-free counter electrode(CE) in dye-sensitized solar cells(DSSCs) was investigated.PANI was synthesized by co-polymerization of aniline in the presence of different transition metal ions by using potassium dichromate in acidic medium. It was found that the ion doping of PANI showed a certain catalytic activity for the regeneration of traditional iodide/triiodide(I~-/I_3~-) redox couples. The power conversion efficiency(η) of PANI CEs doped with Mn~(2+),Ni~(2+),Co~(2+) (4.41%, 2.36% and 2.10%, respectively) were higher than 1.94%, the value measured for PANI CE without doping. Doping with Cu~(2+)decreased the power conversion efficiency of PANI CE(PANI-Cu~(2+) η = 1.41%). The electrical properties of the PANI, PANI-Ni~(2+), PANI-Co~(2+),PANI-Mn~(2+) and PANI-Cu~(2+) were studied by cyclic voltammetry(CV), impedance(EIS), and Tafel polarization curve. The experimental results confirmed that PANI was affected by the doping of different transition metal ions(M~(2+)=Mn~(2+),Ni~(2+),Co~(2+),Cu~(2+)). These results indicate a potential application of ion doped PANI as counter electrode in cost-effective DSSCs.