Preparation And Characterization Of Low-Dimensional Strctures Of Pani

Polyaniline(PANI)has elicited the most interest due to its wide range of conductivity from insulating to metallicregime,unique redox tunability,good environmental stability,low cost,ease of synthesis,and promising applications in various fields,such as metallic corrosion protection,electromagnetic interference shielding,electrostatic discharge,sensors and actuators,and etc.Chiral PANI nanotubes with rectangular hollow interiors doped with (1S)-(+)-10-camphorsulfonic acid(D-CSA)as a chiral dopant were synthesized without aid of any surfactant.These nanotubes have 80 to 600 nm in outer diameter and 30 to 125 nm in wall thickness.The sructures of the synthesized samples were characterized by Fourier Transform Infrared spectroscopy(FTIR), Ultraviolet-visible spectroscopies(UV-vis)and X-ray diffraction(XRD).The four-probe conductivities of polyaniline naotubes doped with CSA were 10^-4～10⁰ S/cm.The effects of different synthesis conditions on the morphologies of polyaniline were analyzed,and the utmost conditions for synthesis of polyaniline nanostructures were as follows:the concentration of aniline was 0.05-0.1 mol/L;the molar ratios of CSA to ANI,and ammonium persulfate(APS)to ANI were about 1/8～1 and 1.2, respectly;the temperature was maintained in the range of 0～5℃and the reaction time was 15 h.Several kinds of polyaniline micro/nanostructures,such as tubes, fibers,networks,sheets,spheres and stars,were synthesized with the adjusting of reaction conditions,including the concentration of aniline,doping acid and oxidant, the the kind of doping acid and mixing speed,in the aqueous solution system.Nanostructured networks of PANI with conductivity of 10^-2～10^-1S/cm were synthesized via in situ polymerization of aniline using ferric chloride and APS as the co-oxidant through a "template-free" method.The further results showed that the ferric chloride played the roles of restraining the formation of PANI nanofibers and acting as both of oxidant and dopant at the same time,and the morphology and conductivity of the nanostructures could be controlled by adjusting the dosage of FeCl₃ or the molar ratios of APS to FeCl₃.The room temperature electromagnetic properties of polyaniline micro/nanotubes and nanostructured networks were studied.The tests of the eletromagnetic parameters of polyaniline nanostructures were evaluated,and it was found that polyaniline nanostructures exhibited dielectric loss and magnetic loss in the frequency range from 2 to 18 GHz.The electromagnetic absorption of polyaniline micro/nanostructures got well and the absorption peak shifted to low frequency with the ineases of molar ratios CSA to ANI.The maximal value of electromagnetic absorption was -19.1 dB at the frequency of 7.3 GHz.The dosage of FeCl₃ was good for widening the frequency band and enhancing the reflectivity of polyzniline.