Preparation And Characterization Of Polyaniline Micro/Nanometer Hollow Structures

It is thought that the polymer materials are not conductive, until the appearance of conducting polyacetylene. According to the level of conductivity, materials can be separated into four types: superconductor, conductor, semiconductor and insulator. Conductive polymers can change from insulator to conductor with changing the oxidation degree and doped level. The conductive polymers have become an important material in science, technology and economic construction for their changeable conductivity. With the discovery of conductivity of polyaniline, it is considered polyaniline is most likely to be large-scale application among the structured conductive polymers, due to their ease of processability, high environmental stability and special doping mechanism. However, the unsubstituted PANI is intractable and suffers from poor processability due to its rigid, highly conjugated backbones, which have hindered their application in many fields. To overcome this shortcoming, variety of morphologies of PANI (such as nanofibers, nanotubes and hollow microspheres) were prepared by changing the synthesis method. In addition, compared with random connected nanowires, well-ordered nanostructure can improve both the dispersion and electric property of polyaniline.This paper aims to provide some new ideas and methods to build polyaniline hollow constructs. These ideas and methods are as follows:(1)A template-based fabrication technique for PANI nanotubes with halloysite nanotubes (HNTs) as template. The HNTs associate the chemical properties of halloysite tubule's outermost surface with the properties of SiO2 and properties of the inner cylinder core with Al2O3. So the PANI nanotubes were obtained by etching the template with HCl/HF solution after the PANI layers were coated onto the template via in situ soapless emulsion polymerization. The coated polyaniline layers prepared with ultrasonic irradiation were more symmetrical and the PANI/HNTs hybrids had the better dispersibilities in water than those from the adsorption with stirring, which were conglomeration.(2)An ingenious strategy for the synthesis of the magnetic PANI functional hollow microspheres is explored, which combines the interfacial polymerization and Pickering emulsion techniques in an 0/W emulsion system, with Fe3O4-CA nanoparticles as cosurfactant. The effect of the amount of Fe3O4-CA nanoparticles on the formation of integrated Fe3O4-CA-PANI hollow microspheres was investigated. The amount of surfactant plays an important role on maintaining the size of PANI capsules. Toluene acts as the role of "soft-template" and storage of monomer.(3)Rod-shaped polyaniline nanocapsules were prepared via the in-situ chemical oxidative polymerization of aniline with a-Fe2O3 nanorods about 50nm in length and about 8nm in width as templates after being modified with p-aminobenzoic acid ion. When the weight ratio of aniline/Fe2O3 nanorods of 2:1 was adopted, the uniform rod-shaped PANI nanocapsules with length and diameter of about 80 and 5 nm were achieved. Above or below this ratio will not get complete PANI capsules.(4)Hollow polyaniline nanoparticles were fabricated via the facile chemical oxidative polymerization of aniline with y-Fe2O3 nanoparticle as the reactive template in the presence of the protonic acid. The effects of the reaction temperature and the kind of the protonic acid used on the formation of the hollow nanostructures were discussed.(5)Fe3O4@PS nanoparticles were used as "partial sacrificial templates", during the oxidation polymerization partial or all of the polystyrene can be dissolved. When polystyrene was prepared with low concentration of initiator, sandwich Fe3O4@PS@PANi nanoparticles were obtained; when polystyrene was prepared with high concentration of initiator, yolk/shell Fe3O4@PANI structures were prepared; when polystyrene was prepared with middle concentration of initiator, different size of holes presented in final composites. As the concentration of initiator increased, the size of holes increased. The possible process of the formation of hole has been given.