Carbon Nanotube Surface Chemical Modification Of Its Performance

Carbon nanotubes (CNTs) have been investigated for both in theoretical understanding and in practical applications due to their unique structural and superior propertiesin numerous area, such as remarkable strength and high thermal and electrical conductivits. Nevertheless, the problem of insolubility in solvents because of high specific surface area remains a severe limitation to the extensive use. To expand the application of carbon nanotubes, functionalized CNTs, including noncovalent and covalent modification is studied.In this thesis, covalent modification of multi-walled carbon nanotubes(MWNTs) is the primary content. Some novel well-defined copolymer were successfully grafted onto MWNTs were prepared through different synthesis ways and were characterized by FTIR, TEM and TGA etc.1. MWNTs-g-PEG was achieved by the direct condensation reaction of carboxyl groups on the acids-treated carbon nanotubes (MWNTs-COOH) surface with hydroxyl groups of PEG using N,N-dicyclohexylcarbodiimide (DCC) and 4-dimethyl-aminopyridine (DMAP) as a condensing agent. Then, Ce4+/hydroxyl redox system initiated acrylonitrile (AN) or 2-(dimethylamino) ethyl methacrylate (DMAEMA) from MWNTs-g-PEG to get poly(ethylene glycol)-b-polyacrylonitrile (PEG-b-PAN) block copolymers or poly[(ethylene glycol)-b-poly2-(dimethylamino) ethyl meth- acrylate] (PEG-b-PDMAEMA) block copolymers functioned MWNTs [MWNTs-g-(PEG-b-PAN)] or [MWNTs-g-(PEG-b-PDMAEMA)] under the acidic condition. As-prepared block copolymers functionalized MWNTs were characterized with FTIR, TEM, TGA and SEM. In addition, the rheological behaviors of the DMF solution of the product were investigated, and the results showed that the highly-enriched of MWNTs (51%) [MWNTs51-g-(PEG2000-b-PAN)] showed shear thinning fluid, and the DMF solution of [MWNTs3o-g-(PEG2000-b-PAN)]/PAN (60/40, in which the content of MWNTs was 30%) showed pseudoplastic fluid, which indicated that the system of MWNTs and polymer formed a good network. MWNTs were dispersd well in the system and the content of MWNTs was much higher than that reported in the literature. On the other hand, the sensitivity of pH and temperature of the [MWNTs-g-(PEG-b-PDMAEMA)] aquesous solution was discussed through rheology means. The results manifested that the composites qualified the sensitivity of pH and temperature because of the properties of PDMAEMA. And the LCST of the composites decresed with the increase of the value of pH.2. The MWNTs/PAN composites were prepared through "one-pot" method. The cerium ammonium nitrate solution (Ce4+) not only oxidated the MWNTs dispersed well, but also formed Ce4+/OH redox system to introduce the free radical polymeri- zation of AN monomer. Therefore, the MWNTs/PAN composites were prepared and dispersed well, and the content of MWNTs could be controlled by changing the reaction feed ratio. The kinetic studied have shown that the MWNTs have a strong ability to capture free radical, and the induction period of the free polymerization increased with the addition of the MWNTs. When the MWNTs were 40wt%, the dispersivity was still fine. In addition, the SEM photos of the electrostatic spinning of composites showed that the morphology of the nanofiber sheets was good and the diameter of the nanofibers was uniform.3. The polyethylene glycol (PEG) grafted MWNTs was successfully produced by bromo-ended PEG (PEG-Br) and 2,2,6,6-tetramethylpiperidine (TEMPO) groups attached on the MWNTs surface via atom transfer nitroxide radical coupling (ATNRC) reaction. The results showed that the reaction efficiency of PEG-Br/MWNT-TEMPO was not high as expected because of PEG-Br, but was much higher than that of other ATRNC/PEG-Br system reported in the literature due to the strong free scavergency of MWNTs..