Study Of Conducting Polymer And Azo Polyelectrolyte Multilayers And Micro-scale Structures

Conducting polymers (CPs) possess many unique electrical/optical properties and play an extremely important role as functional polymers. Azo polymers were well-known for their photoresponsive properties. Constructing novel composite materials such multilayers composed of both types of polymers and developing related nano/microstructures are important for potential applications in areas such as electrochromic displays, photonic crystals, micro-reactors, electro-optic modulators, and sensors. In this dissertation study, focusing on this new type of materials and structures, the methodology establishments, nano/microstructure control and electric/optical functions of the materials have been extensively investigated. The main achievements of the study are summarized as follows.Self-assembled multilayer films composed of alternate polyaniline (PANI) and azo polyelectrolytes (PPAPE, PNACN, PNANT and PNATZ) layers were fabricated through the electrostatic layer-by-layer (LBL) adsorption. The thickness contributed by each individual layer was found to be dependent on the concentrations and pH values of the PANI and azo polyelectrolytes dipping solutions. The multilayer films show interesting properties related with both components, such as conductivity, electrochemical redox, photoinduced dichroic and surface-relief-grating formation. The multilayer films possess the unique electrochromic function owning to the absorption bands of the azo chromophores and electrochromic variation of PANI. Using the azo polyelectrolytes with different hues, the electrochromic color variations can be dramatically enriched.A novel method to construct multilayer films through both the electrochemical polymerization and the electrostatic LBL self-assembly has been established. In the process, the conducting layers are built-up by the electrochemical polymerization and the polyelectrolyte layers are introduced through electrostatic adsorption. Multilayers composed of different conducting polymers (PANI, PPY and PEDOT) and polyelectrolytes (PNACN, PNANT, and PEDOT:PSS) as well as carboxyl-MWNT were fabricated by this method. Results show that the growth of multilayer films can be easily controlled by the currents and time period of the electrochemical polymerization process. By this method, multilayer composed of both CPs and azo polyelectrolytes can be feasibly fabricated, even for CPs lacking solubility in solvents.Nano/microstructures of related materials have been prepared through several methods. The honeycomb microporous conducting polymer (PEDOT) films were prepared through electrochemical polymerization of EDOT in acetonitrile and boron trifluoride ethyl ether (BFEE) solution by using polystyrene colloidal crystals as templates, which were obtained by vertical deposition on stainless steel electrodes. Uniform hollow capsules were fabricated from PTAA and a hyperbranched azobenzene-containing polymeric diazonium salt (HB-DAS) through LBL self-assembly on polystyrene (PS) colloidal spheres and removing templates after the deposition. Surface-relief-gratings of PANI were prepared through soft-lithography and studied for the optical sensor applications. The UV-vis spectra and complex refractive index of PANI change with the variations of pH and electrochemical potentials. Therefore, the diffraction efficiencies (DEs) of PANI gratings can sensing the redox and doping states. Lorentz model has been used to simulate and explain the complex refractive index changes of PANI after being treated in the different pH solutions.The LBL method has also been used in this study to prepare multilayer containing bioactive molecules. The electrostatic LBL self-assembled films composed of azobenzene polyelectrolytes PPAPE and enzyme (GLS) layers were prepared on the surfaces of PS colloidal particles. The relative activities of the immobilized GLS were measured in different pH and temperatures conditions and compared with the same enzyme in solution. The immobilized enzyme shows a wider range of environments adaption and smaller decrease of the catalysis activities. The influences of UV irradiation on enzyme activity of GLS/PPAPE-coated PS were investigated, which can result in the slight decrease of enzyme activity of immobilized GLS.