Date of Award

Fall 2005

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Environmental Science - (Ph.D.)

Department

Chemistry and Environmental Science

First Advisor

Michael Chien-Yueh Huang

Second Advisor

Robert Pfeffer

Third Advisor

Rajesh N. Dave

Fourth Advisor

S. Mitra

Fifth Advisor

Zafar Iqbal

Abstract

Microencapsulation means applying a shell-like coating to encapsulate the contents of interest in a particle form with a size range of few micrometers or below. In this work, aqueous liposome systems and polymer based encapsulation of fine particles in supercritical CO2 were studied. Compared to many other microencapsulation methods, these two methodologies feature reduction/prevention of using organic solvents, making them particularly attractive as green technology.

For polymer microencapsulation, a novel in situ polymerization based process to encapsulate various types of fine particles, include drugs, fire retardant, inorganic nanoparticles, and carbon nanotubes, was developed. In the process, host particles, monomers and other components are first mixed together followed by polymerization and encapsulation. Thin-film coating was achieved for particle size above 1 μm For nanoparticles, surface functionalization was employed for increasing interfacial interactions and dispersion. Under appropriate conditions, nano-silica particles were found undergoing sol-gel transition to form porous monoliths. Dispersion, debundling, and polymer encapsulation of single-walled carbon nanotubes (SWNTs) were also reported.

Despite the great potential posed by bio-mimetic phospholipids in drug delivery, commercial products are quite limited. To address the structure stability of liposome based microencapsulationm in a more fundamental level, we studied the mechanism of spontaneous formation of monodispersed unilamellar vesicles with scattering technique using neutron and light sources. Vesicle phase was studied systematically as a function of lipid concentration, salinity, temperature and time duration, etc. The results contribute to the understanding and selection of appropriate lipid system and process for microencapsulation of drugs.

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