Graduation Year

2005

Document Type

Dissertation

Degree

Ph.D.

Degree Granting Department

Chemistry

Major Professor

Julie P. Harmon, Ph.D

Committee Member

Abdul Malik, Ph.D

Committee Member

Milton Johnston, Ph.D

Committee Member

Ralph W. Turner, Ph.D

Committee Member

Ashok Kumar, Ph.D

Keywords

Nanotechnology, Poly(methyl methacrylate), Poly(4-methyl-1-pentene), Interfacial polarization, Dielectric analysis

Abstract

The design, fabrication, and characterization of polymer-carbon nanotube (CNT) composites have generated a significant amount of attention in the fields of materials science and polymer chemistry. The challenge in fabricating composites that exploit the unique properties of the CNT and the ideal processing ability and low cost of the polymer is in achieving a uniform dispersion of the filler in the polymer matrix. This body of work focuses on (1) techniques employed to disperse CNTs into a polymer matrix and (2) the effects of CNTs on the mechanical and electrical properties of the polymer.

Poly (methyl methacrylate) (PMMA), an amorphous polymer, and poly (4-methyl-1-pentene) (P4M1P), a semi crystalline polymer, were chosen as the matrices. Non-functionalized single-walled carbon nanotubes and soot (unpurified carbon nanotubes) were chosen as the filler material. In the first study, single-walled carbon nanotubes (SWNTs) were sonicated in methyl methacrylate monomer and initiated via thermal energy, UV light, and gamma radiation. Composite films with increased dielectric constants and unique optical transparency were produced. Samples were characterized using differential scanning calorimetry, dielectric analysis, and dynamic mechanical analysis. Refractive Indices were obtained and correlated to the dielectric constant using Maxwells relationship. PMMA/soot composites were fabricated in the second study. Dispersion was accomplished by way of sonication and melt compounding. The PMMA/soot composites were exposed to gamma radiation, with a 137Cs gamma source, in order to investigate how the filler affects the polymers ability to resist radiation. Samples were characterized by differential scanning calorimetry, dielectric analysis, and dynamic mechanical.The third study involved dispersing nonfunctionalized nanotubes into P4M1P, a polymer without polar groups. The polar solvent N,N dimethylformamide (DMF) is known to be an ideal dispersing agent for carbon nanotubes. However, P4M1P does not dissolve in DMF. A series of solvents that would both dissolve the polymer and disperse the nanotubes were explored. A successful combination of pre-treating the nanotubes with DMF and then dispersing the nanotubes and dissolving the polymer in cyclohexyl chloride was achieved.

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