Preparation And Properties Of Polyaniline / Silver Nanocomposites

Polyaniline powders have been synthesized via chemical oxidation polymerization of aniline in an acidic solution by a sonochemical method using ammonium perfulfate (APS) and hydrogen peroxide (H₂O₂) as oxidizing agents. Herein we developed a facile one-pot route to synthesize polyaniline/Ag nanocomposites by a sonochemical method with AgNO₃ and aniline as raw materials. The strucyure and morphology of the products were charactered by UV-visible spectra, Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectra, scanning electron microscopy and transmission electron microscopy. The conductive performance, thermal stability property and electrochemical behaviour of the Polyaniline/Ag nanocomposite were investigated by conductivity test, thermogravimetric analysis, cyclic voltammetry and electrochemical impedance spectroscopy. The following results can be summarized.(1) The results showed that when APS was used as an oxidant the reaction rates were quck and the products were emeraldine salt. The morphology of polyaniline was qusai-spherical shapes and microsize mass structure. When H₂O₂ was used as a sole oxidant the reaction rates were extremely slow and the polymerization degree was low, and thus an additive was a must.(2) Polyaniline/Ag nanocomposites have been synthesized via in-situ chemical oxidation polymerization of aniline in silver salt by sonochemical method using H₂O₂ as an external medium. AgNC>3 was used both as raw material and an additive oxidizing agent. H₂O₂ was used both to reduce AgNO₃ to Ag nanoparticles and to polymerize aniline in an acidic pH solution. This technique utilizes ultrasound radiation as an energy source to facilitate the reaction by enhancing rate, as well as significantly increasing the yield. X-ray diffraction measurement showed the presence of Ag in the composite in addition to indicating the formation of polyaniline with low crystalline phase in the case. UV-visible absorption spectra, FT-IR spectra and Raman spectra indicated the formation of emeraldine salt form in the polyaniline/Ag nanocomposite. The product exhibits a spherical and granular nature. The result indicated that the formation of aggregated silver nanoparticles, with the polyaniline formed around aggregated or individual nanoparticles.(3) The electrical conductivity of the composites was found to be more than 2 orders of the polyaniline only. The highest electrical conductivity of the polyaniline/Ag pellet was found 9.06 S/cm, whereas that of polyaniline was found to be 2.3×10^-2 S/cm. Thermal gravimetric analysis showed that the composites have a higher degradation temperature than polyaniline alone. The degradation temperature of PAn/Ag was found over 600℃, compared 375℃of polyaniline. The cyclic voltammetry and electrochemical impedance spectroscopy results showed that the polyaniline/Ag film exhibits considerably higher electroactivity compared with polyaniline film without Ag particles. The electrocatalytic oxidation of methanol of polyaniline was not changed by the embedment of silver particles inside the polyaniline matrix.