Synthesis, Characterization And Properties Of Oriented Conjugated Polymer-Carbon Nanotube Nanocomposites

Conductive polymers as "fourth-generation polymers", not only have electrical properties of both metal and semiconductor, but also remain light, flexible and processability for general polymers, which have exhibit potential applications in various fields such as optoelectronic devices, sensor technology, molecular electronics, nano-devices and the drive device. However, poor stabilities limit theirmore practical applications. Designing and preparing conjugated poly mer composites with stable structure and high charge carrier mobility provide more effective way to overcome their defects. It not only can improve the thermal stability of conductive polymers, but also a substantial increase in conductive polymers-carbon nanotube composites for electrical and electrochemical properties. There is a strong conjugation between multi-walled carbon nanotubes and conductive polymers, which resulting in the orientation of conductive polymer coated on the surface of carbon nanotubes. Thus in such system, it is expected that the ability of charge transfer between carbon nanotubes and conductive polymers is promoted, and the resistance of composites are reduced significantly. In our work, three types of conductive polymers, i.e. PANI, PPy and POPV are prepared by in-situ chemical polymerization of conjugate monomers in the presence of multi-walled carbon nanotubes (MWCNTs) with less defective, respectively. Our main results are listed as following:1. Polyaniline-multi-wall carbon nanotubes composites with core-shell structures are synthesized, in which the commercial multi-wall carbon nanotubes treated in the condensed hydrochloric acid as template. The influence of second doping on the structure and properties are studied. The formation of Polyaniline layers with a tight structure on the surface of carbon nanotubes are achieved due to the existence of a strong conjugation between multi-walled carbon nanotubes and polyanilines. It is found that the thermal stabilities of the composites doped with organic acids are better that those composites doped with inorganic acids. Unfortunately, electrochemical properties of the composites are not improved significantly.2. A series of polypyrrole-multi-wall carbon nanotube composites with good core-shell structures are prepared by in-situ chemical polymerization, in which multi-wall carbon nanotubes with less defective are used as templates. By changing the ratio between the pyrrole monomer and carbon nanotube, the thickness of polypyrrole layers can be easily controlled. When the mass fraction of carbon nanotubes increases from 10 % to 40 %, the shell thickness of polypyrrole layer decreases from 60 nm to 30 nm. The thermal stabilities of the composites with various polypyrrole contents are improved due to the introducing of carbon nanotubes. Electrochemical analysis further shows that the capacitance of PPy-CNTs (20%) is up to 235.49F/g at 1mV/s.3. The poly 2,5-2-octyloxy-phenylene vinylene (POPV)-multi-wall carbon nanotubes nanocomposites with good core-shell structures is prepared by in-situ chemical polymerization in the presence of the multi-wall carbon nanotubes with less defective under ultrasonic irradiation and magnetic stirring. The optical properties of nanocomposites are studied by UV-Vis absorption spectroscopy and fluorescence spectroscopy. A significant blue-shift phenomenon can be observed, which attributed to the interaction between poly 2,5-2-octyloxy-p-phenylene acetylene (POPV) and multi-walled carbon nanotubes. Electrochemical analysis shows, more stable electrochemical behavior can be achieved in KCl electrolyte, and the capacitance of the composite is up to 146.34F/g at scan rate of 5mV.