Controllable Interfacial Polymerization Of Poly Aniline And Its Nanostructure

Polyaniline(PANI)has received a great deal of attention in recent years because of its low cost,good electrical conductivity and environmental stability.The nanostructured PANI is an important field of conducting polymers.Various types of nanostructed PANI including nanofibers,nanotubes,nanorods and nanospheres,have been prepared,and their potential applications in supercapacitors,sensors,nano-optoelectronic devices and other fields have been exhibited.Therefore,how to control the growth of PANI nanostructure become more and more important.In this work,an improved method for interfacial polymerization was presented by using ferrous chloride and cumene hydroperoxide instead of traditional oxidants such as ammonium persulfate(APS)and ferric trichloride.The growth of PANI would be controlled by achieving slow nucleation for chemical oxidation polymerization of PANI through two-step reaction.The main results and conclusions are listed as follows:(1)Controllable growth of PANI nanostructure:Two-step reaction process was introduced for controlling the growth of nanostructured PANI,in which ferrous chloride was firstly oxidized to ferric trichloride by cumene hydroperoxide,and then ferric trichloride induced interfacial polymerization of aniline monomers.It is found that compared with polymerization of aniline monomers induced by APS or ferric trichloride,the nucleation in initial reaction stage was obviously delayed,and the oxidant efficiency of ferric ion was greatly improved,as a result,it became possible to efficiently control interfacial polymerization.Furthermore,the morphologies,yields and conductivities of nanostructured PANI were characterized,and reaction conditions of interfacial polymerization,such as monomer content,ratio of aniline monomer to ferrous chloride,ratio of aniline monomer to cumene hydroperoxide,nature of doping acid,concentration of HCl and interfacial reaction area were optimized to obtain the high conductivity of PANI with nanofibrous morphology.(2)Structures and properties of nanostructured PANI:The structure and properties of as-prepared nanostructured PANI were characterized by ultraviolet-visible absorption spectroscopy,Fourier transform infrared spectroscopy,X-Ray diffraction analysis,thermogravimetric analysis and electrical measurement.More attention was paid to the influence of reaction parameters for two-step oxidation reaction system on the structures and properties of PANI.It is demonstrated that PANI prepared by two-step reaction in aqueous solution of hydrochloric acid(HCl)exhibited highly ordered nanofibrous structure with large length and high thermal stability.Furthermore,under the reaction conditions with monomer concentration of 0.3 M,ratio of aniline monomer to ferrous chloride of 5:1 and ratio of aniline monomer to cumene hydroperoxide of 1:3,and acid concentration of 1 M HCl,aligned PANI nanofibers with high yield and smallest diameter of 30 nm could be obtained.In addition,different nanostructures of PANI would be formed in aqueous solution of different doping acids,such as HCl,sulphuric acid and nitric acid.(3)Electrochemical behaviors of nanostructured PANI:The electrochemical behaviors for different nanostructured PANI as electrode materials for supercapacitor were studied by cyclic voltammetry,galvanostatic charge-discharge measurement and electrochemical impedance spectroscopy.Moreover,an electrochemical dynamic model based on equivalent circuit was presented to describe electron transfer process.It is demonstrated highest specific capacitance can be achieved for PANI nanofibers prepared by two-step polymerization in aqueous solution of HC1.The improvement in energy storage ability of PANI is benefited from three-dimension innerpenetrating network formed by PANI nanofibers with longer length and smaller diameter,which would facilitate the penetration of electrolyte and ions intercalation/deintercalation and reduce the inner impedance.In addition,the hollow PANI microspheres prepared in aqueous solution of nitric acid favored the diffusion of the electrolyte ions.