Studies On Synthesis And Properties Of Micro/Nanostructured Polyaniline And Their Composites

Owing to its easy preparation, cost-effective raw materials, diverse chemical structures, unique doping mechanism, and excellent environmental stability, polyaniline (PANI) has been extensively studied as an ingenerate conductive polymer in recent years. It is provided with great theoretical and applied significance to synthesize and characterize the micro/nanostructures of PANI and their composites. This dissertation follows with interest the issues of novel methods to prepare PANI and their composites with various micro/nanostructures, control their shapes and size, and self-assembly of the nano-building blocks into hierarchical microstructures. The structures, formation mechanism and the influences of synthesis parameters on them are also investigated.The micro/nanostructures of PANI could be controlled by simply adjusting the pH of the reactive media when aniline polymerization with APS as oxidation was carried out in aqueous system at various starting pH values. The geometric shapes of the as-fabricated PANI showed two-dimensional nanoplates, three-dimensional flower-like hierarchies, microspheres twisted with nanofibers, microspheres built by nanospheres, hollow microspheres and adherent hollow microspheres successively, while the media pH values were varied from mild acidities to super alkalinities. The performance presents the trends from disorder to order and from lower dimension to multidimension, and the sizes became relatively smaller. The molecular chains of PANI are made up primarily of alternating benzenoid and quinonoid rings, and phenazine-like segments. A part of aromatic rings was sulfonated. The primary forces of supramolecular assemblies are hydrogen bond and π-πstacking interactions.PANI doped with Zn2+and Cu2+was synthesized by H2O2oxidative polymerization of aniline in the presence of corresponding metal chloride in solution. Under the condition, the chainpropagation of PANI is electrophilic substitution-aromatization initiated by radical cations. The complexation occurs preferentially at imine nitrogen of PANI for Zn2+doping by a pseudo-protonation mechanism, while the complexation appears at both imine and amine for Cu2+doping by pseudo-protonation and redox mechanism. The cyclic voltammetric study has indicated that incorporation of metal ions in PANI backbone results in increasing of specific capacitance compared to that of HCl doping PANI.ZnO coated with PANI was prepared by one-step synergetic reaction using zinc salt and aniline as raw materials. Under the corporate effects on intrinsic polar-surface dominated growth and polymer localized crystal growth, PANI plays dual roles on hindering agglomeration as well as guiding oriented growth of ZnO nanocrystals. The coatings of PANI have evidently changed the dissoluble dynamics of ZnO nanosheets, and the dissoluble rate and the agglomeration of ZnO nanosheets in aqueous solution were inhibited well.