Copolymerization of aniline and m-chloroaniline. Chlorine addition and structure of the resulting material

The copolymerization of aniline (Ani) and m-chloroaniline (mClA) in variable ratios was performed by chemical oxidation in HCl medium. The resulting copolymer composition was determined by elemental analysis and XPS. The results show the incorporation of additional Cl substituents in the polymer backbone when m-chloroaniline is present in the polymerization medium with a high mClA:Ani ratio. IR and NMR characterization confirms that finding. Conductivity measurements of the copolymers in salt form were also performed. UV–vis spectra for high mClA:Ani ratios show a main band centred ca. 380 nm. PM3-ZINDO/S spectra calculations suggest that the Cl substituents stabilize spinless semiquinone structures in the polymer chain which are responsible for the 380 nm band. Photoluminescence spectra are recorded and analyzed. The addition of chlorine is attributed to the lower reaction rate in high mClA:Ani ratio. Copolymers with high mClA:Ani ratio appear as materials very different from polyaniline, thus these differences should be considered regarding possible applications.     

Synthesis of novel calix[6]-1,4-crown-based netty polymer and its excellent adsorption capabilities for aniline derivatives

By introducing four ester groups on p-tert-butylcalix[6]-1,4-crown-4 and then ammonolysis with ethanolamine, p-tert-butylcalix[6]-1,4-crown-4 amido derivative with four terminal hydroxyl groups (4) was obtained in good yield. Further by reacting compound 4 with 1,1,1-tris(tosylatemethyl)propane (6) in NaH/THF system, the novel netty calix[6]-1,4-crown-based polymer 7 was prepared in ??4+3?? condensation mode. The structure of polymer 7 was confirmed by elemental analysis, IR and ¹H NMR spectra. The loose pores and cross-linked netty architecture were observed for polymer 7 in its SEM images. The M _n of polymer 7 was 39,816 which indicated an average of approximately 23 calixarene units in each polymer molecule. Polymer 7 exhibited outstanding adsorption abilities for series of aniline derivatives (aniline, o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, o-nitroaniline, m-nitroaniline and p-nitroaniline). The adsorption percentages for these aniline derivatives were above 90?%. The saturation adsorption capacities for aniline and p-nitroaniline were as high as 2.30 and 2.22?mmol/g, respectively. The adsorption abilities of polymer 7 kept stable at pH 6?C10 and it could be re-used after desorption of 10?% HCl. The high adsorption abilities of polymer 7 for aniline derivatives were not just because of ?ШC?? stack action of the phenyl groups and the hydrogen bond action, but also due to the stable conformation of calix[6]arene skeleton and big cavity, which were favorable for adsorption of aniline derivatives.     

Study on soluble polyaniline by positron annihilation technique

The solubility, electrical conductivity, and other properties of polyaniline (PANI) are highly dependent on its oxidation state. In this work, polyaniline (PANI1) prepared by peroxodisulphate induced polymerization of aniline in acidic aqueous medium in presence of benzenediazonium chloride salt was found to exist in lower oxidation state than emeraldine form of PANI and was highly soluble in common organic solvents. This polymer was subjected to positron annihilation spectroscopic study to investigate the correlation between the oxidation state of the polymer and defect sites generated by different degrees of protonation that in turn affect its electrical conductivity. The positron annihilation lifetime data were resolved to yield a three‐component fit for PANI1 subjected to different levels of protonation. The variation of positron annihilation parameters (τ_1,I₂) and Doppler broadening parameters (R, S) as a function of protonation level of the polymer indicate the dopant sites increase initially on protonation and reach a saturation value after a certain level of acidification. The lower value of electrical conductivity and the intensity of intermediate lifetime component (I₂) for PANI1 compared to PANI in emeraldine oxidation state indicate the presence of lesser number of quinoid–imine moieties that could undergo protonation and thus yield highly enriched trapping centers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and characterization of conducting copolymers from aniline and o‐anisidine in HCl solutions

Conducting poly(aniline‐co‐o‐anisidine) (PAS) films with different ratios of aniline units in the polymer chain were prepared by oxidative polymerization of different molar ratios of aniline and o‐anisidine in 1 M HCl using cyclic voltammetry. Due to the much higher reactivity of o‐anisidine, the structure and properties of PASs were found to be dominated by the o‐anisidine units. The polymerization of poly‐o‐anisidine and PASs followed zero‐order kinetics with respect to formation of the polymer (film thickness) and the autocatalytic polymerization of aniline was completely inhibited. In contrast to polyaniline, a decrease in the polymerization temperature was found to increase the amount of copolymer formed and its redox charge. The presence of aniline units in PASs led to a pronounced increase in the molecular weight and conductivity, and a decrease in the solubility in organic solvents. Repetitive charging/discharging cycles showed that PASs resist degradation more than polyaniline. Copyright © 2003 Society of Chemical Industry     

On the molecular properties of polyaniline: A comprehensive theoretical study

A comprehensive study about the molecular and electronic properties of the different forms of polyaniline has been developed using quantum mechanical calculations. Initially the performance of different ab initio and DFT quantum mechanical methods has been evaluated by comparing the results provided for small model compounds containing two repeating units. After this, calculations on the emeraldine base, leucoemeraldine base, pernigraniline base and emeraldine salt (monocationic and dicationic) forms of oligoanilines with n repeating units, where n ranged from 5 to 13, have been performed using the BH&H/6-31G(d) method, which was found to be a very suitable theoretical procedure. Interestingly, calculations indicate that the distribution in blocks of the repeating units containing amine and imine nitrogen is largely preferred for the emeraldine base form. On the other hand, the molecular structure and band gap of the emeraldine base, leucoemeraldine base and pernigraniline base forms have been rationalized according to their differences in the conjugation of the C₆H₄ rings. Calculations on cationic oligoanilines indicate that, when the emeraldine salt form presents a doublet electronic state, the positive charge and the spin density are located in the middle of the chain extending through five consecutive repeating units.     

Preparation and characterization of soluble polyaniline

Polyaniline, which is soluble in common organic solvents, has been synthesized through the oxidative chemical polymerization of aniline in the presence of benzene diazonium chloride salt in an aqueous HCl acid medium. The blue‐black polyaniline thus prepared exists in a lower oxidation state than emeraldine. An X‐ray photoelectron spectroscopy study has shown that the intrinsic oxidation state of the polymer is 0.38. An elemental analysis has shown that the fractional doping level or degree of oxidation of the blue‐black polyaniline is 0.26. The product is believed to consist of a lower number of imine nitrogens in comparison with the polyemeraldine base. This fact is also corroborated by the lower electrical conductivity of the polymer. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

A conducting nanocomposite via intercalative polymerisation of 2-methylaniline with aniline in montmorillonite cation-exchanged

Polymer/montmorillonite nanocomposites were prepared. Intercalation of 2-methylaniline with aniline monomers into montmorillonite modified by cation was followed by subsequent oxidative polymerization of the monomers in the interlayer spacing. The clay was prepared by cation exchange process between sodium cation in (M-Na) and copper cation (M-Cu). We prepared a series of polymer/clay nanocomposite materials that consisted of an emeraldine base of poly(2-MA), poly(2-MA-co-ANI) and PANI by layered copper montmorillonite. All organic monomers used were first intercalated into the interlayer regions of clay hosts followed by a one-step in situ oxidative polymerization. The unique properties of the as-synthesized nanocomposites materials are investigated by electronic conductivity measurements, X-ray diffraction, FTIR spectroscopy, UV-vis spectroscopy, thermogravimetric analysis and SEM, were also studied by cyclic voltammetry which indicates the electroactive effect of nanocomposite gradually increased with aniline in the polymer chain.     

Electrochemical copolymerization of aniline and para-phenylenediamine on IrO2-coated titanium electrode

Copolymerization of aniline (AN) and para-phenylenediamine (PPDA) was electrochemically performed by cyclic voltammetry on IrO₂-coated titanium electrodes in 0.5m H₂SO₄. The cyclic voltammograms, with and without a middle peak at about 580 mV, can be produced by controlling the PPDA concentration in the aniline solution during polymer preparation. The peak at about 580 mV corresponds to the para-aminophenol/benzoquinoneimine (PAP/QI) redox couple and crosslinking sites. The mass of polymer deposited on an IrO₂-coated titanium electrode is correlated with the polymer anodic peak current, which allows the rates of polymer deposition to be monitored by increases in the anodic peak current at various PPDA concentrations. SEM photographs show that the morphology of the polymer film depends dramatically on PPDA concentration. Stability test information can be used in generating an effective index to discern between the crosslinking and the PAP/QI reactions induced by PPDA. The linear relationship between the second redox process potential (E _1/2), corresponding to the oxidation and reduction between polaronic emeraldine and pernigraniline in PPDA-modified PANI films, and pH, possesses a slope of about -120 mV/pH.     

Effects of solvent interactions on the structure and properties of prepared PAni nanofibers

The changes of structure and properties of nanofibers were studied as a function of solubility parameters of the organic solvents that are used in interfacial polymerization of polyaniline (PAni) nanofibers. The presence of UV–visible absorbance at 340, 440, and 800 nm confirmed the formation of emeraldine salt structure of the prepared PAni nanofibers. Fourier transform infrared spectral results indicate an increasing trend of benzenoid to quinoid ratio with the decrease of interaction of the solvents with aniline. This can be correlated to the increase in the degree of conjugation of the polymer chain. Photoluminescence study revealed an increase in the density of defect state with the decrease of interaction. Single‐line approximation technique was used to analyze the broadening of the most intense X‐ray reflection peak corresponding to (110) plane of the nanofibers. The greater the solvent–monomer interaction, the lesser was the domain length and π‐stacking of the PAni chains. The study of this interaction is instrumental to precisely control the internal conformation of the PAni nanofibers. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Cationic phenyl-substituted poly(p-phenylenevinylene) related copolymers with efficient photoluminescence and synthetically tunable emissive colors

A series of amino-functionalized phenyl-substituted poly(p-phenylenevinylene) (PPV) related copolymers were synthesized by Wittig reaction. Their corresponding cationic conjugated polymers were successfully obtained via a post-polymerization approach. On the basis of FT-IR and ¹H NMR spectra, it was found that phenyl-substituted PPV related copolymers containing alkoxylated benzene (neutral polymer P1 and quaternized polymer P1′), phenylated benzene (neutral polymer P2 and quaternized polymer P2′) and fluorene (neutral polymer P3 and quaternized polymer P3′) moieties are of 55, 80, and 45% cis-vinylic linkage respectively while the polymer containing thiophene moiety (neutral polymer P4 and quaternized polymer P4′) is primarily of trans-vinylic linkage. Their photoluminescence (PL) were conveniently tuned from blue color to yellow color by introducing units with different optoelectronic properties into the PPV backbones. The polymer with fluorene unit and bulky phenylene-substituted benzene unit in the backbone exhibited the highest PL efficiency among these neutral and quaternized PPVs. P4′ containing little cis-vinylic linkage showed complete quenching while P1′-P3′ containing much more cis-vinylic linkage showed incomplete quenching, indicating that the quenching behavior of these cationic PPVs may be highly influenced by the content of cis-vinylic linkage in the PPV backbones.     

Preparation and characterization of a novel conducting nanocomposite blended with epoxy coating for antifouling and antibacterial applications

In this study, novel epoxy-based paint was synthesized to be applied on carbon steel. The composition of the paint mainly contains epoxy mixed with an electronically conductive polymer, polyaniline (PANI), alone and combined with its nanocomposite derivation containing ZnO nanorods as an additive. The antifouling properties of the paint applied on carbon steel were investigated. The conductive nanocomposite was synthesized by an in situ chemical oxidative method of aniline in the presence of ZnO nanorods and then well characterized. The antifouling behavior was evaluated for 9 months in the Caspian Sea and Persian Gulf. Results revealed that epoxy/PANI–ZnO nanocomposite coating can prevent accumulation of marine macroorganisms on the coated panel. In addition, the epoxy coating comprising PANI–ZnO nanocomposite as well as the epoxy/ZnO coating exhibit significant antibacterial characteristics against (E. coli and S. epi). We interpret the antifouling and antibacterial behavior of the paint with (i) the presence of emeraldine salt structure in PANI which develops a surface pH in a range of 4–5 preventing the adhesion of microorganisms on the surface and (ii) the antibacterial and antifouling properties of zinc oxide nanorods that occurred by the production of hydrogen peroxide on the surface of the coating.     

Synthesis of exfoliated polyaniline–clay nanocomposite in supercritical CO2

This paper presents the works done to synthesize fully exfoliated polyaniline–clay nanocomposites (PCNs) with high purity via in situ polymerization of aniline in Cloisite 30B nano-clay suspension in supercritical CO₂ (ScCO₂) medium. The Cloisite 30B was first delaminated with ScCO₂ treatment in the presence of aniline monomers. Ammonium peroxydisulfate (APS) solution was added rapidly into the mixture of delaminated Cloisite 30B and aniline monomers to produce PCNs. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), UV–vis spectroscopy and XRD analysis have been used to characterize the morphology and structure of the as-synthesized product. SEM results reveal that nano-clays are fully exfoliated in the final nanocomposite which is synthesized in ScCO₂. FTIR and UV–vis analysis showed that the resulted polyaniline (PANI) had been in highly conductive emeraldine salt state and ScCO₂ does not have any effect on chemical structures of the PANI.     

Thin film polyaniline-polyaniline electrochemical cells

Electrodeposited polyaniline (PANT) in the emeraldine oxidation state was used as the electrodes of open rechargeable cells containing 1 m HClO₄ as the electrolyte. The cells could be charged at very high hourly rates to 85% of the redox charge in the leucoemeraldine-emeraldine transition of the polymer. Contrary to normal behaviour of rechargeable cells, the coulombic efficiency improved with increasing rates of charge injection and withdrawal. This is attributed to less charge being dissipated by self-discharge at high rates of discharge. The poor charge retention was caused by reactions between the charged electrodes and their environment. The decrease in cell voltage on standing may also be induced by internal redox reactions of PANT of different oxidation states present at the electrodes as a result of incomplete oxidation or reduction during cell operation. Ultraviolet (u.v.) spectroscopy of the charged electrodes identified mostly protonated leucoemeraldine at the negative electrode and pernigraniline at the positive electrode. The irreversibility in the oxidation from the emeraldine state to the pernigraniline state accounts mostly for the degeneration of cell performance after prolonged cycling.     

Nanofibers of self-doped polyaniline

Self-doping polyaniline (SPANI) nanofibers were synthesized by using self-assembly process consisting of a self-doping monomer (o-aminobenzenesulfonic acid, SAN) and aniline (AN). SAN plays the key roles of a self-doping monomer and a surfactant in the process of forming nanofibers. TEM and SEM results revealed that the morphology, average diameter of the resulting nanofibers depended on the mole ratio of AN to SAN and reaction conditions. NMR, FTIR, XPS, UV-vis spectra were used to describe the molecular structures of the nanofibers. X-ray diffraction was used to characterize the crystallinity in these structures. Results revealed that the molecular structures of polymer chains were similar to those of the emeraldine form of polyaniline (PANI). The doping degree ranged from 21 to 27% corresponding to the AN/SAN mole ratio from 4 to 1.     

A correlation of electrochemical and spectroelectrochemical properties of poly(o-toluidine)

A comparative discussion of the electrochemical and spectroelectrochemical properties of poly(o-toluidine) POT, a methyl substituted derivative of polyaniline, PANI, is presented. POT exists in various oxidation states and shows an insulator to conductor transition when doped by electrooxidation. The transformation of the polymer film from its non-conducting leucoemeraldine to its conducting emeraldine state and further on to its again non-conducting pernigraniline form was observed with different techniques including cyclic voltammetry, in situ conductivity measurements and in situ UV-vis and Raman spectroelectrochemical methods. Results reveal that POT shows a good correlation between its electrochemical and spectroelectrochemical properties in its different oxidation states.     

Characterization of an electroactive polymer for overcharge protection in secondary lithium batteries

The optical, electronic, and electrochemical properties of thin films of the electroactive polymer, poly(3-butylthiophene) (P3BT), were studied in a lithium hexafluorophosphate electrolyte. Upon extraction of n electrons per polymer formula unit, anions are taken up to balance the charge, forming a polymer cation salt, (P3BT)^mn+(PF₆⁻)_mn (m is the number of formula units in the polymer chain), whose state of charge (SOC) varies with n. An in situ ac impedance method was developed to determine the electronic conductivity of the polymer at different states of charge. On oxidation of the insulating neutral P3BT polymer, the conductivity increased by eight orders of magnitude. The electrochemical potential, electronic conductivity, and optical spectrum at each state of charge were correlated, producing a color index of these primary characteristics. This allowed determination of the potential and state of charge as a function of location in transparent polymer films during propagation of an oxidation front across the film and during passage of steady-state currents through the polymer film.     

Degradation and geometric isomerization of poly(N-propargylamides)

The stability of several poly(N-propargylamides) was investigated in solution and in solid state on the basis of molecular weight change with time, and further their thermal stability was investigated by TGA. When the stability of poly(N-propargylamides) with varying pendent groups was compared, polymers with pendent groups of moderate size showed the highest stability in solution. Too short and too bulky pendent groups were not favorable for the stability of polymers. When poly(N-propargylheptanamide) (poly(6)) was stored in THF as solution at −20 °C in the absence of oxygen in dark, its degradation rate was the lowest. The degradation rate of poly(6) depended on the solvents used, which may be related to different solubility of oxygen in these solvents. Polymers with high cis contents degraded faster than polymers with low cis contents did. Addition of TEMPO and DPPH into the poly(6)/THF solution more or less depressed the degradation of poly(6). The degradation of polymer main chain in solution was always accompanied by the decrease of cis content, i.e. geometric isomerization from cis- to trans-structure. When the polymers were stored in the solid state at −20 °C, the polymers having alkyl pendent groups with moderate length were more stable than those with bulky pendent groups. Geometric isomerization occurred along with degradation in the solid state as well.     

Removal of Organic Compounds Containing a Benzene Ring from Water by Adsorptive Micellar Flocculation

The removal of low-molecular-weight benzoic acid (benzoic acid, p-toluic acid, and salicylic acid)-derived and aniline (aniline, 4-chloroaniline, and 2,6-dimethylaniline)-derived organic compounds through adsorptive micellar flocculation (AMF) with anionic surfactants (sodium dodecyl sulfate, SDS) and aluminum sulfate was demonstrated. The interactions between SDS and the organic compounds were studied using ¹H nuclear magnetic resonance (NMR) spectroscopy. Batch AMF experiments were conducted to study the influence of several factors on target pollutant removal. For benzoic acid derivatives, the removal rate was improved by increasing the SDS and Al concentrations, while increases in the concentrations of the organic pollutant tended to decrease the removal rate. The highest removal efficiencies were observed with p-toluic acid (95.4%) > salicylic acid (84.5%) > benzoic acid (76.5%) under weakly acidic conditions due to the greater hydrophobicity of p-toluic acid and the complexation of the Al salts and the salicylic acid. The removal rates of the aniline derivatives were positively related to the SDS concentration and negatively related to the pH. At a pH of 3.0, the highest removal rates of aniline, 4-chloroaniline, and 2,6-dimethylaniline (91.3%, 98.0%, and 97.6%, respectively) were observed. For aniline compounds, charge neutralization between the SDS anions and aniline cations dominated the removal process. These findings provide new insights for the development of further applications of AMF for the removal of benzoic acid and aniline derivatives.     

Influence of chemical polymerization conditions on the properties of polyaniline

The chemical polymerization of aniline in aqueous solutions was studied as a function of a wide variety of synthesis parameters, such as pH, relative concentration of reactants, polymerization temperature and time, etc. The polymer was synthesized using a number of different oxidizing agents and different protonic acids. It was found that the reaction yield was not sensitive to most variables. By contrast, the inherent viscosity of the polymer, measured in solutions in concentrated sulphuric acid, was strongly dependent on the synthesis parameters. Optimum reaction conditions are outlined for the chemical polymerization of aniline, for post-treatment with aqueous HCl solutions, and for compensation of the emeraldine salt into its base form. Under such conditions, high-quality polyaniline base was synthesized with an inherent viscosity (0.1% w/w polymer in sulphuric acid) as high as 2.32 dl g⁻¹.     

Purple red and luminescent polyiminoarylenes containing the 1,4-diketo-3,6-diphenylpyrrolo[3,4-c]pyrrole (DPP) chromophore

New DPP-containing polyiminoarylenes were prepared from 1,4-diketo-2,5-dihexyl-3,6-di(4′-bromophenyl)pyrrolo[3,4-c]pyrrole and various arylamine derivatives using palladium-catalyzed amination reactions. The arylamine comonomers were aniline (ANI), t-butylaniline (TBA), 2-aminoanthracene (AAN), 1-aminopyrene (APY) and N,N′-diphenyl-p-phenylenediamine (PDA). Purple red polymers with good solubility in common organic solvents and molecular weights between 4.4 and 35.8 kDa were obtained. Polymer solutions were readily fluorescent with quantum yields between 19 and 62%, while solution-cast films only showed a weak fluorescence. All polymers exhibit low band gaps of approximately 1.9 eV. Cyclovoltammetric studies indicate quasireversible oxidation for polymers with TBA, APY and PDA as comonomer units, and quasireversible reduction for the polymer with AAN comonomer unit. Polymers with APY and PDA comonomer units are electrochromic and can be switched between red in the neutral and greenish grey in the oxidized state.