Thesis (M.S.)--University of Kentucky, 2002. / Title from document title page. Document formatted into pages; contains xiii, 163 p. :ill. Includes abstract. Includes bibliographical references (p. 152-162).

In biotechnology, microelectronics, and materials science, many products require intimate attention to microscopic and sub-microscopic construction. Bulk properties of interest often depend on the system microstructure, leading researchers to strive to tailor custom microstructures and predict properties from microstructure—increasingly difficult tasks as component sizes shrink. A promising paradigm for engineering small systems is the idea of designing components which self-assemble into the structures desired, similar to the way that biological systems routinely build themselves from the molecular level up to the macroscopic. In this thesis, I use numerical simulation to study the structural evolution of colloidal and nanoscopic particulate systems. I focus on problems in rheology and adsorption. In the rheological study, I use Stokesian dynamics to investigate a transition where the shear rate qualitatively changes the trajectories of a lattice of particles and imparts a discontinuous, hysteretic viscosity jump. My model shows that a particular face-centered cubic crystal configuration is necessary to reproduce experimental findings. The adsorption studies are approached with two different models. First is a two-dimensional model for the random sequential adsorption of tethered nanoparticles. Tethers provide robust physical and/or electrical connections between particles and a substrate, but they also frustrate order. Hexatic and crystal structures form with surprisingly short tethers of one and four particle radii, respectively. Polydispersities of less than 5–7% (and sufficient tether length) are necessary to form crystal phases, and polydispersities of less than 7–8% are necessary to create hexatic phases. The second set of adsorption studies employs full three-dimensional Brownian dynamics simulations to model electrostatically-repulsive particles that are attracted to a substrate. The zeta-potential of the wall is the primary control of order formation on the surface, and the particle potentials are the primary control of surface coverage. Mixtures of particles that are bidisperse in surface zeta-potential can disrupt order for significant ratio of zeta-potentials, and at large ratios the process creates interesting patterns including dots, clusters, chains, and doped crystals. In each study, system history has a significant effect on the final state of the system; careful attention must be paid to the non-equilibrium process of assembling small systems. / text

Hydrogels containing of 2-dimethylaminoethyl methacrylate, DMAEMA, exhibit changes in their swelling properties in response to both pH and temperature. Accordingly, these materials are useful for a variety of applications, such as tissue scaffolds, responsive lenses, separations and drug delivery. The response of DMAEMAcontaining hydrogels can be tuned by copolymerization with other monomers, such as 2-hydroxyethyl methacrylate, HEMA. We have developed methodologies for the controlled synthesis of poly(HEMAco-DMAEMA), PHD, statistical copolymers with uniform composition distributions, controlled molecular weights, and narrow molecular weight distributions using controlled free-radical polymerization techniques, such as atom transfer radical polymerization and radical addition-fragmentation chain transfer polymerization. We have also investigated the controlled synthesis and characterization of amphiphilic block copolymers containing PHD statistical copolymers. These block copolymers microphase separate to form periodic nanostructures such as alternating lamellae, cylinders on a hexagonal lattice, or spheres on a body-centered cubic lattice, depending on the volume fraction of each block, the interblock segregation strength, and the choice of casting solvent. When swollen with water, these microphase-separated PHD-containing block copolymers form model hydrogels with uniform composition distributions. Model block copolymer hydrogels containing PHD statistical copolymers are responsive to changes in pH or temperature. The response of these model block copolymer hydrogels can be tuned by adjusting of the DMAEMA content within the PHD block. Moreover, the response can be tuned by changing the hydrophobic block. Specifically, the use of a glassy hydrophobic block, such as polystyrene or poly(tert-butyl acrylate) at temperatures below its glass transition temperature, resulted in the preservation of the original block copolymer morphology during swelling. In contrast, the use of a hydrophobic block that is rubbery during swelling, such as poly(methyl acrylate), enabled reversible morphological transformations. / text

We discuss digital holographic microscopy (DHM), a 3D imaging technique capable of measuring the positions of micron-sized colloidal particles with nanometer precision and sub-millisecond temporal resolution. We use exact electromagnetic scattering solutions to model holograms of multiple colloidal spheres. While the Lorenz-Mie solution for scattering by isolated spheres has previously been used to model digital holograms, we apply for the first time an exact multisphere superposition scattering model that is capable of modeling holograms from spheres that are sufficiently close together to exhibit optical coupling. / Physics

No description available.

No description available.

No description available.

A new process was developed for the filtration of hydrophobic colloids without the assistance of chemical coagulants. The process consists of passing the suspension through a bed of electrically conducting granules which are fluidized by the upward flow of the suspension and simultaneously exposed to a D.C. electric field. The process was demonstrated on an aqueous polystyrene latex of mean particle size 0.34 (mu)m. At optimum conditions a bed of iron granules retained 98% of the entering particles. / Experiments showed that the following variables increased the retention: increasing electric field strength, increasing static bed height, decreasing electrical conductivity of the feed, and decreasing the superficial velocity. Retention was independent of inlet particle concentration. / A model of the process was formulated including various mechanisms of deposition and surface forces. It contained no empirical factors from filtration experiments except the mean particle size in the effluent when electric field is applied. / Electrocoagulation of the polystyrene latex was observed under the microscope and the mechanisms involved were elucidated.

No description available.

No description available.