Etika, Krishna (2010-12). Stimuli-Tailored Dispersion State of Aqueous Carbon Nanotube Suspensions and Solid Polymer Nanocomposites. Doctoral Dissertation. Thesis uri icon

abstract

  • Nanoparticles (such as, carbon nanotubes, carbon black, clay etc.) have one or more dimensions of the order of 100 nm or less. Owing to very high van der Waals force of attraction, these nanoparticles exist in a highly aggregated state. It is often required to break these aggregates to truly experience the "nanosize" effect for any required end use. There are several strategies proposed for dispersing/exfoliating nanoparticles but limited progress has been made towards controlling their dispersion state. The ability to tailor nanoparticle dispersion state in liquid and solid media can ultimately provide a powerful method for tailoring the properties of solution processed nanoparticle-filled polymer composites. This dissertation reports the use of a variety of stimuli-responsive polymers to control the dispersion state of single-walled carbon nanotubes. Stimuli-responsive polymers exhibit conformational transitions as a function of applied stimulus (like pH, temp, chemical etc.). These variations in conformations of the polymer can be used tailor nanotube dispersion state in water and solid composites.The use of pH and temperature responsive polymers to stabilize/disperse single walled carbon nanotubes (SWNTs) in water is presented. Non-covalent functionalization of SWNTs using pH and temperature responsive polymer show tailored dispersion state as a function of pH and temperature, respectively. Carbon nanotube microstructure in these aqueous suspensions was characterized using several techniques (cryo-TEM, viscosity measurements, uv-vis spectroscopy, zeta potential measurements and settling behavior). Furthermore, nanotube dispersion state in aqueous suspensions is preserved to a large extent in the composites formed by drying these suspensions as evidenced by SEM images and electrical conductivity measurements. Based on the results obtained a mechanism is proposed to explain the tailored dispersion of SWNTs as a functions of applied external stimulus (i.e., pH, temperature). Such stimuli-controlled dispersion of carbon nanotubes could have a variety of applications in nanoelectronics, sensing, and drug and gene delivery systems. Furthermore, this dissertation also contains a published study focused on controlling the dispersion state of carbon black (CB) in epoxy composites using clay.
  • Nanoparticles (such as, carbon nanotubes, carbon black, clay etc.) have one or
    more dimensions of the order of 100 nm or less. Owing to very high van der Waals force
    of attraction, these nanoparticles exist in a highly aggregated state. It is often required to
    break these aggregates to truly experience the "nanosize" effect for any required end use.
    There are several strategies proposed for dispersing/exfoliating nanoparticles but limited
    progress has been made towards controlling their dispersion state. The ability to tailor
    nanoparticle dispersion state in liquid and solid media can ultimately provide a powerful
    method for tailoring the properties of solution processed nanoparticle-filled polymer
    composites.
    This dissertation reports the use of a variety of stimuli-responsive polymers to
    control the dispersion state of single-walled carbon nanotubes. Stimuli-responsive
    polymers exhibit conformational transitions as a function of applied stimulus (like pH,
    temp, chemical etc.). These variations in conformations of the polymer can be used tailor
    nanotube dispersion state in water and solid composites.The use of pH and temperature responsive polymers to stabilize/disperse single walled carbon nanotubes (SWNTs) in
    water is presented. Non-covalent functionalization of SWNTs using pH and temperature
    responsive polymer show tailored dispersion state as a function of pH and temperature,
    respectively. Carbon nanotube microstructure in these aqueous suspensions was
    characterized using several techniques (cryo-TEM, viscosity measurements, uv-vis
    spectroscopy, zeta potential measurements and settling behavior). Furthermore, nanotube
    dispersion state in aqueous suspensions is preserved to a large extent in the composites
    formed by drying these suspensions as evidenced by SEM images and electrical
    conductivity measurements. Based on the results obtained a mechanism is proposed to
    explain the tailored dispersion of SWNTs as a functions of applied external stimulus
    (i.e., pH, temperature). Such stimuli-controlled dispersion of carbon nanotubes could
    have a variety of applications in nanoelectronics, sensing, and drug and gene delivery
    systems. Furthermore, this dissertation also contains a published study focused on
    controlling the dispersion state of carbon black (CB) in epoxy composites using clay.

publication date

  • December 2010