Controlled Synthesis Of Low-dimensional Polyaniline Nanostructured (Composite) Materials And Study Of Its Formation Mechanism

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 and its composites have been becoming active in the field of nanoscience and nanotechnology based on their unique properties and potential applications. Therefore, developing a facile, efficient, and controllable process to construct PANI nanostructures and nano-composites is still a challenge.The research of this dissertation is focused on the issues of new methods to synthesize PANI and PANI-composites with various nanostructures. The structures and formation mechanism of these products are also investigated. The main results are listed:1. PANI nanostructures with various kinds of morphologies such as particles, fibers, fibers-micromats and disks, were synthesized via a process of self-assembly doped with salicylic acid (SA). The diameters of the synthesized fibers could be controlled by simply tuning the concentration of aniline. Micromats knitted by fibers were prepared on the appropriate concentration ratio of dopant to aniline. Furthermore, changing the concentration of ammonium persulfate (APS) to aniline, 3D interconnected disk-like nanostructures were formed. A rational mechanism based on the self-assembly of micelles is proposed for the formation of those PANI nanostructures above. This extensive approach for preparing nanostructure polymers has opened a controllable synthesis route in the development of advanced materials.2. Dendritic composite fibers of PANI/SiO₂ were prepared through a sol–gel process. The diameters of the PANI fibers could be controlled easily by changing reaction condition. We demonstrate a very easy approach to synthesize dendritic or network PANI composite fibers. Removed the PANI component of the composite fibers, mesoporous dendrtic SiO₂ fibers were obtained. This is a new technique to fabricate dendritic fibers of inorganic oxides.3. Silica nanofibers with ordered mesopores were synthesized by using a sol-gel method with aluminum oxide (AAO) membranes as template. Anline molecules were absorbed into these mesopores and polymerized therein. And mesoporou silica/PANI composite fibers were formed.4. We have prepared conductive TiO₂ (or Fe₃O₄)–PANI/PS composite capsules: hollow TiO₂ (or Fe₃O₄)–PANI spheres and hollow TiO₂ (or Fe₃O₄) spheres. The cavity size and shell thickness of the hollow spheres were uniform, and synchronously controlled by using core–shell structured sulfonated-PS spheres as templates. Conducting PANI was in situ doped with sulfonic acid, which made the composite spheres have good conductivity. This template method is very simple and reliable, which can be extended to prepare other capsules and hollow spheres with various functional compositions. The multi-functionality of these spheres may have many applications such as electronics, controlled delivery and microwave absorption.5. We have presented synthesis of flexible bicontinuous mesostructured PP/silica composite membranes by co-assemblies of template surfactants and sol-gel processes of inorganic materials inside pores of PP porous membranes. And PP/silica composite membranes were followed to combine with PANI for preparation of conductive PP/silica/PANI composite.