Construction And Characterization Of Polyaniline Micro/nanostructures

As an inherent conducting polymer, polyaniline (PANI) has attracted considerable attention because of its unique doping/dedoping process, good optical and electrical properties, as well as excellent environmental stability. The design and synthesis of PANI nanostructures have received great attention in nanoscience and nanotechnology based on their unique properties and potential applications. Therefore, developing a facile, efficient, and controlable process to construct PANI micro/nanostructures is desirable.The research of this dissertation is focused on the issues of new methods to synthesize PANI with various micro/nanostructures. The structures and formation mechanism of PANI micro/nanostructures are also investigated. The main contents are listed:1. Polyaniline nanostructures with sheet-, fiber- and particle-like morphologies are synthesized controllablely from p-toluene sulfonic acid (p-TSA) aqueous solution. The results demonstrate that the morphology of PANI nanostructures is significantly influenced by the molar ratio of aniline to p-TSA. The morphology of PANI can be controlled by adjusting the molar ratio of aniline to p-TSA. A rational mechanism based on the self-assembly of micelles is proposed for the formation of PANI nanostructures. Fourier transform infrared, UV-visible spectroscopy and X-ray diffraction are applied to characterize the products.2. Exclusive sheet-like PANI is successfully synthesized in ethanol solution by a template-free process using benzoyl peroxide as oxidant. Solvent plays an important role in the formation of exclusive PANI nanosheets. When the solvent is changed from water to ethanol, PANI nanosheets are obtained exclusively and the wettability of the surface constructed by PANI nanosheets changes obviously, which changes from hydrophilic to super-hydrophobic (with water contact angle of 145.0o).3. Polyaniline nanofibers accumulated by flake-like PANI are assembled in the presence of polyvinyl alcohol (PVA) in aqueous solution. Based on the experimental results, a formation mechanism of PANI nanofibers is proposed. The experimental results indicate that increasing the amount of aniline neutral molecules and decreasing the diffusion rate of reactive substances are benefit for the formation of PANI nanofibers. The morphology of PANI is significantly influenced by the concentration of HCl and the solution temperature. 4. Urchin-like polyaniline microspheres with an average diameter of 5-10μm have been successfully prepared by a template-free method. The surface of the obtained microspheres consists of highly oriented nanofibers with about 30 nm in diameter and 1μm in length as characterized by scanning electron microscopy and transmission electron microscope techniques. The experimental results indicate that the solvent composition plays an important role in the formation process of urchin-like PANI microspheres. Based on the experimental results, the formation mechanism of PANI microspheres is proposed.