Preparation And Study Of Polymer Functionalized Multi-Walled Carbon Nanotubes And Its Nanocomposites

Carbon nanotubes (CNTs) have been used in various applications due to their excellent mechanical, thermal, electrical properties and so on. Achieving multi-function of carbon nanotubes through self-assembling on their surface is a challenge, because of their lazy surface, high aspect ratio, and likely aggregate. To solve the problems, chemical modification method was employed to graft polymer on the surface of carbon nanotubes. Simultaneously, the modified reactive sites can be used to obtain multi-function of carbon nanotubes. The main task of the paper as follows:1. Acid-treated MWCNTs were first reacted with poly(acryloyl chloride) (PAC1) leading to a grafted encapsulation, which were subsequently reacted with hydroxy ethyl acrylate (HEA) to generate vinyl groups. Thus obtained vinyl groups functionalized MWCNTs (vinyl-MWCNTs) were characterized using Fourier transform infrared spectroscopy, transmission electron microscopy, and thermogravimetric analysis. The vinyl-MWCNTs were blended with liquid-EPDM and subjected to co-curing; an intercrosslinked structure was obtained via the free radical polymerization among the vinyl groups on vinyl-MWCNTs and the double bonds on liquid-EPDM. As a result, the vinyl-MWCNTs and the cured EPDM matrix were covalently linked. The chemical interfacial interaction between vinyl-MWCNTs and the cured matrix were observed by scanning electron microscope, which provided obvious reinforcement of elastomer.2. Poly (acrylic acid) oligomer was first reacted with hydroxyl groups on acid-treated MWCNTs leading to a grafted encapsulation of the MWCNTs. These were subsequently reacted with 3-aminopropyltriethoxysilane (APTES) resulting sub-grafting of APTES on the MWCNTs. Such MWCNTs (siloxane-MWCNTs) were further hydrolyzed to make MWCNTs indirectly bearing Si-OH groups. Finally, a bud-like MWCNT/silica hybrid was obtained by forming a number of silica nanoparticles from Si-OH groups on the surface of MWCNTs by introducing siloxane-MWCNTs into a solution of tetraethyl orthosilicate, ammonia, and ethanol. The average size of the silica nanoparticles on the surface of the MWCNTs could be controlled by adjusting the concentration of ammonia and the reaction time. The hybrids were filled in the silicon rubber to increase the tensile strength of composites.3. Poly(acrylic acid) (PAA) oligomer was first reacted with hydroxyl-functionalized MWCNTs (MWCNTs-OH) forming PAA grafted MWCNTs (PAA-g-MWCNTs). Subsequently, Fe3O4 nanoparticles were attached onto the surface of PAA-g-MWCNTs through an amidation reaction between the amino groups on the surface of Fe3O4 nanoparticles and the carboxyl groups of PAA. Fourier transform infrared spectra confirmed that the Fe3O4 nanoparticles and PAA-g-MWCNTs were indeed chemically linked. The morphology of the nanocomposites was characterized using transmission electron microscope (TEM). The surface and bulk structure of the nanocomposites were examined using X-ray diffraction, X-ray photoelectron spectrometer (XPS), and thermogravimetric analysis (TGA). The magnetic performance was characterized by vibrating sample magnetometer (VSM) and the magnetic saturation value of the magnetic nanocomposites was 47 emu g'1. The resulting products could be separated from deionized water under an external magnetic field within about 15 s. Finally, the magnetorheological (MR) performances of the synthesized magnetic nanocomposites and pure Fe3O4 nanoparticles were examined using a rotational rheometer.4. Acid-treated multi-walled carbon nanotubes (MWCNTs) were first encapsulated with polyaniline (PANI) by an in-situ micro-emulsion polymerization and then reacted with aniline dimer modified with Fe3O4 (ADM-Fe3O4). Fourier transform infrared spectrometry demonstrated that there existed chemical linkages between the MWCNTs and the PANI as well as between the MWCNTs and the ADM-Fe3O4 nanoparticles. The morphology of the nano-absorber was examined using transmission electron microscopy. The surface and bulk structure of the nano-absorber were investigated with X-ray diffraction and X-ray photoelectron spectroscopy, respectively. The complex permeability and permittivity of the nano-absorber were measured in the range of 2-18 GHz. The real (ε') and imaginary (ε") parts of the permittivity of the nano-absorber were smaller than those of the pristine MWCNTs. On the other hand, the real (μ') and imaginary (μ") parts of the permeability and the magnetic dissipation factors tgδμ(μ"/μ') of the nano-absorber were greater than their counterparts for the pristine MWCNTs. For the MWCNT/PANI/Fe3O4 nano-absorber, the maximum reflection loss was approximately-15.01 dB at about 11 GHz and the reflection loss was less than-10 dB in the range of 9.6-12.2 GHz.5. First, poly (acrylic acid) (PAA) was grafted onto the surface of MWCNTs by in situ polymerization. Subsequently, Fe3O4 nanoparticles were anchored on PAA chains through amidation reactions between the amino groups on the surface of the Fe3O4 nanoparticles and the carboxyl groups of PAA. Finally, a TiO2 layer was coated onto the surface of the modified MWCNTs through hydrogen bonding between the hydroxyl groups on the surface of titanium dioxide and the carboxyl groups of PAA or the amino groups of Fe3O4. The morphology and structure of the intermediate and final hybrids were investigated by transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and x-ray photoelectron spectroscopy. The magnetism of the product was characterized using a vibrating sample magnetometer. In addition, the decoration with TiO2 extended the absorbance spectrum of the hybrid to the entire UV-visible region. The photo-catalytic function of the hybrid MWCNTs/Fe3O4/TiO2 was demonstrated for phenol degradation under irradiation of UV-visible light.