Study Of Conducting Polymers And Their Nanocomposites: Preparation And Properties

The development of materials science and nanotechnology has brought a great demand for new materials with excellent mechanical property, easy processibility and some functionality. Among these materials, one important class is that in which the organic part is conducting polymers, such as polyaniline or polypyrrole which have novel properties (novel doping mechanism, good environmental stability, ease of processability, low cost, etc.) and potential applications in batteries, sensors, light-emitting diodes, gas separation membranes, molecular electronic devices, etc.Polymeric materials in single component could not satisfy the need of the industry. In recent years, great efforts have been made in the preparation of nanocomposites of conducting polymers and inorganic materials. These materials exhibit unique physical properties which are useful for the development of novel enzyme-based electrochemical biosensors with rapid electron transfer at the electrode surface. The enzyme can be interacted directly into the conducting polymer to form a biosensor. The biosensor fabricated by conducting polymers has a good operational stability, long storage lifetime and fast response time.In this thesis, we succeeded in synthesizing multi-morphologies of polyaniline mi cro/nano structures by oxidative polymerization of aniline in amino acids aqueous solution without any external physical or chemical templates and additives. Spinous microspheres, smooth nanospheres and nanosticks were obtained successfully. A possible mechanism for the formation of PANI micro/nanostructures was proposed.Moreover, tetragonal starlike microstructures of PANI doped with aspartic acid have been synthesized under hydrothermal conditions. Hydrothermal synthesis by monitoring the reaction time provided a platform for understanding the polymerization process. Moreover, the tetragonal starlike PANI coated GCE exhibited higher electro catalytic activity for sensing dopamine than the PANI nanorods obtained under non-hydrothermal condition. This novel microstructure of PANI synthesized by hydrothermal method could be taken as an example of developing a possible application as a dopamine biosensor.Prussian blue (PB) covered multiwalled carbon nanotubes (MWCNTs)/polypyrrole (PPy) composite nanofibers with good dispersibility in water and ethanol have been prepared by directly mixing ferric-(III) chloride and potassium ferricyanide in the presence of MWCNT/PPy coaxial nanofibers. The MWCNT/PPy/PB composite nanofibers based electrochemical sensor in detection of H2O2 has been demonstrated. In comparison to bare GCE and MWCNT/PPy, the response current by MWCNT/PPy/PB composite nanofibers modified GCE was greatly enhanced. The electrode modified with MWCNT/PPy/PB composite nanofibers exhibited good sensitivity (345μA mM-1 cm-2), wide linear range (0.004-0.517 mM) and low detection limit (0.08μM) to detection of H2O2.We also used nanofibers deposited on the ITO glass produced by electrospinning as templates to prepared PPy/PB nanofibers. The electrochromic property and detection of H2O2 of the PPy/PB nanofibers were investigated. Compared to PPy, the PPy/PB nanocomposite gave a greater extent of electrochromism (33%) and higher electrocatalytic activity to the detection of H2O2 due to the incorporation of PB nanoparticles.We invented a new inverse interfacial polymerization method as an effective way to obtained uniform PANI nanofibers doped with different acids, such as HCl, H2SO4, HNO3, and HClO4. Unlike conventional interfacial polymerization, a new oxidant-CTAPS was used which was soluble in the bottom organic phase, while the monomer-aniline was dissolved in the top HCl solution. The morphology of the products was measured by TEM. The diameter of the nano fibers was 15-70 nm which were affected by the concentration and the kind of doping acids. The CV measurement showed that the obtained PANI nanofibers exhibited better electrochemical property than the bulk PANI synthesized by the conventional method, and may be probably applied to the detection of dopamine.We prepared PANI/Au nanocomposite via interfacial polymerization. Chloroauric acid dissolved in alkaline solution to form complex anion-Au(OH)4-. Using this new oxidant dissolved in oil phase, aniline hydrochloride dissolved in aqueous solution, and the polymerization took place at the interface. The concentration of HAuCl4 affected the size and amount of Au nanoparticles in the products. We also examined the electrochemical property of the products and found that the size and amount of Au nanoparticles affected the electrocatalytic activity for sensing dopamine.