Controlled Synthesis Of Polyaniline Micro/Nanostructures With Assistance Of Dodecatungstosilic Acid And Its Properties

Nano/microstructures of polyaniline (PANI) have captivated a great deal of research interest with expectation that combination of organic conducting materials and nano/microstructure could yield functional materials or enable new physiochemical to be discovered. In this dissertation, ice-templating method developed by the author is introduced to synthesis of various morphologies of doped-PANI assisted by a milder polymerization initiator-ferric chloride (FeCl3) as oxidant. Here, we exploring these characteristics of doping acid (H4SiW12O40) and additive reagents in ice-template system, and taking full advantage of them to design and synthesize new morphology of PANI, such as PANI belts obtained by an interfacial controlled method. Application of PANI products with different morphologies on gas sensitivity, and conductivity were systematic demonstrated and the main achievement are summarized as follows:1. Chapter 2 introduces an green ice-templating method to make polyaniline microflakes stacked 1-D nanofiber with diameter range of 20-35 nm by using H4SiW12O40 as doping acid.The discovery of the microflakes formation mechanism is presented. The effect of reagents concentration on the morphology of PANI is discussed. Application of PANI fiber microflakes, such as in gas sensor, are examined owing to its high surface area and porous nature character.2. Chapter 3 designs a liquid droplet system in ice phase to get doped PANI hemisphere. A potential mechanism for forming PANI hemispheres is suggested and discussed elaborately. It is found that the solvent, the concentration of solution, and doping-acid affected the morphology and the diameter size of hemispheres. Furthermore, the high surface areas, super thin shell, and opening structure of PANI hemispheres appear to have super performance in both sensitivity and time response of NH3.we hope and believe that this work presented in this dissertation will open new research area for both functional materials with complex container structure and nanomaterials.3. The effects of various doping acid and the secondary solvent on the morphology of PANI are systematic demonstrated in Chapeter 4. All the results show that just the doping acids, POMs (H4SiW12O40) with unique nucleophilic oxygen-enriched surfaces, multi-hydrogen proton, and the binding capacity with the secondary solvent as a molecular template direct the growth of aniline monomer, and play a major role in determining the formation of various morphologies of PANI.4. Based on the mechanism discussed in Chapter 4, a simpler method for making polyaniline belts namely“interfacial controlled method”is introduced as described in Chapter 5. H4SiW12O40, with unique nucleophilic oxygen-enriched surfaces, and the binding capacity with water molecules play a major role in determining the formation of PANI belts except organic solvents. The conductivity of SiW12-doped PANI aligned belts is tested, which has a superior performance on the conductivity. These results show a more ordered structure of PANI will improve their conductive properties.5. In Chapter 6, H4SiW12O40-doped PANI/Ag nanobelts are synthesized by self assembly polymerization in the presence of ice crystals. There is a large concentration of trap in polyaniline owing to the disordered structure of it. With an assistance of Ag nanoparticles, the charge could be injected by Ag nanoparticls into PANI. Meanwhile, POMs (H4SiW12O40) is a good electron acceptor and charge transmitter. Hence, some the charge injected by Ag nanoparticls into PANI material could transfer from the PANI to the POMs and then be exported. The excited electrons transfer can reduce the recombination of electrons and holes in PANI, which results in enhancement of photovoltaic response of PANI.