Preparation, Properties, And Applications Of Conducting Polyaniline Nanocomposites

Among the available intrinsically conducting polymers, polyaniline is found to be the most promising because of its ease of synthesis, low cost monomer, tunable properties, and better stability compared to other intrinsically conducting polymer. However, the main problem associated with the effective utilization of polyaniline is inherent in their lower level of conductivity compared to metal, and their infusibility and poor solubility in all available solvents. In order to overcome these shortcomings, we proposed a novel idea in the preparation of the colloidal PANI nanoparticles, employing partially phosphorylated poly(vinyl alcohol) as both the stabilizer and co-dopant for the first time. And the applications of the prepared PANI nanoparticles were explored:Firstly, the polyaniline/partially phosphorylated poly(vinyl alcohol) nanoparticles were prepared by the chemical oxidative dispersion polymerization of aniline monomer in0.5M HC1aqueous media with the partially phosphorylated poly(vinyl alcohol) as the stabilizer and co-dopant. The prepared nanoparticles were characterized by transmission electron microscopy, Fourier transform infrared, thermal gravimetric analysis, electrical conductivity measurement, and re-dispersion stability testing. All the results were compared with the properties of the conventional polyaniline in the emeraldine salt form. It was found that the feeding ratio of partially phosphorylated poly(vinyl alcohol) obviously affected the morphology, re-dispersion stability and electrical conductivity of the prepared nanoparticles. When the feeding ratio of phosphorylated poly(vinyl alcohol) is40wt%, the polyaniline/partially phosphorylated poly(vinyl alcohol) nanoparticles showed spherical shape with good uniformity, significant re-dispersion stability in aqueous media, and good electrical conductivity (6.94S/cm).Next, conducting polyaniline/partially phosphorylated poly(vinyl alcohol)/polyacrylate composite nanoparticles were prepared by the encapsulation of the polyaniline/partially phosphorylated poly(vinyl alcohol) nanoparticles with polyacrylate via the emulsifier-free seeded emulsion polymerization. Transmission electron microscopy, scanning electron microscopy and X-ray photoelectron spectra analysis of the prepared composite nanoparticles showed that the polyaniline/partially phosphorylated poly(vinyl alcohol) nanoparticles were successfully encapsulated with the polyacrylate. With the increasing of the feeding ratio of acrylate monomers, the diameter of the polyaniline/partially phosphorylated poly(vinyl alcohol)/polyacrylate composite nanoparticles increased and their electrical conductivity decreased. Cyclic voltammogram revealed that the composite nanoparticles were electroactive. When the content of polyacrylate is50.93wt%, the prepared composite shows a electrical conductivity of0.41S/cm in pellet and0.05S/cm in powder. And good quality films with appreciable Young’s modulus (1.6MPa), tensile strength (17.6MPa), and elongation at break (125%) could be obtained from the prepared composite nanoparticlesThirdly, the waterborne corrosion protection polyaniline contained coatings was developed. The conducting polyaniline/partially phosphorylated poly(vinyl alcohol) spherical nanoparticles with significant dispersibility in aqueous media were prepared by the chemical oxidative dispersion polymerization in the presence of the partially phosphorylated poly(vinyl alcohol). Then the polyaniline contained coatings with different polyaniline/partially phosphorylated poly(vinyl alcohol) contents were prepared, employing waterborne epoxy resin as the matrix. The corrosion protection property of the polyaniline/partially phosphorylated poly(vinyl alcohol) contained coatings on mild steel was investigated by the salt spray test and electrochemical impedance spectroscopy technique in3.0wt%NaCl aqueous solution. The results indicated that the waterborne polyaniline/partially phosphorylated poly(vinyl alcohol) contained coatings could offer the high protection since the impedance values are remained at higher than107Ωcm2after30days of the salt spray tests. All the results were compared with these of the waterborne coatings containing the polyaniline nanoparticles in the emeraldine salt form and the protection mechanism was also proposed.Finally, a simultaneous reduction of graphene oxide/polyaniline flake composites by coating polyaniline onto graphene oxide sheets was developed to prepare the novel electrode materials for the high performance supercapacvitors. The graphene oxide/polyaniline composites were prepared by the chemical oxidation polymerization of aniline in the aqueous dispersion of graphene oxide. Then the reduced graphene oxide/Polyaniline composite flakes were obtained by the chemical reduction of the graphene oxide/polyaniline composites, with hydrazine hydrate as the reducing agent. Transmission electron microscopy, thermal gravimetric analysis and cyclic voltammogram were employed to investigate the surface, thermal property, and electroactivity of the samples. The results revealed that polyaniline was polymerized on the surface of graphene oxide sheets and after reduction there was still thin polyaniline coating on reduced graphene oxide sheets. The results also indicated that both the thermal stability and the electroactivity of the reduced graphene oxide/polyaniline flakes were distinctly enhanced than those of the graphene oxide/polyaniline composites. In the reduced graphene oxide/Polyaniline flakes, reduced graphene oxide played a dual role:as electron acceptor and also as a counterion to stabilize an atypical intermediate oxidation state of polyaniline. When hydrazine hydrate was introduced in to the system, the reduction of graphene oxide to reduced graphene oxide was taken place accompanied by the reduction of the polyaniline emeraldine salt to polyaniline leucosalt, and reduced graphene oxide subsequently played a role as a redoping agent and doped the polyaniline leucosalt to polyaniline emeraldine salt, which resulted in the high electroactivity of the reduced graphene oxide/polyaniline flakes. Cyclic voltammograms and galvanostatic charge-discharge technique indicated that the prepared graphene/polyaniline composites have high specific capacitances and good cycling stability, which are advantageous for their applications as electrode materials for supercapacitors.