Graduation Year

2011

Document Type

Dissertation

Degree

Ph.D.

Degree Granting Department

Chemical Engineering

Major Professor

Aydin K. Sunol, Ph.D.

Committee Member

Scott W. Campbell, Ph.D.

Committee Member

Shyam Mohapatra, Ph.D.

Committee Member

Douglas Shytle, Ph.D.

Committee Member

John T. Wolan, Ph.D.

Keywords

microparticle, coating, DMSO, Chitosan, biopolymer

Abstract

Coating of fine particles to produce tailored surface properties is currently a key development for supercritical fluids applications, in different areas such as: pharmaceutical, nutraceutical, cosmetic, agrochemical, electronic and specialty chemistry industries. During the encapsulation process the particles surface can be designed with specific properties by spreading a thin film coating material over the surface of the particles.

Chitosan, a natural polymer, was used in this work as the encapsulant material. Chitosan is biocompatible, biodegradable to normal body constituents, safe, non-toxic, bacteriostatic, anticancerogen, and versatile polymer. These attributes are among the properties that make Chitosan an attractive component of pharmaceutical products.

The main objective of this research was to encapsulate solid particles under 5fÝm with a biopolymer, Chitosan, using supercritical CO2 as one of the solvents. In order to reach this goal, some the following initial tasks were completed: the cloud point for the system DMSO-CO2 was determined and compared with published data to validate the experimental system. Subsequently the cloud point experiments were extended to include the ternary system Chitosan-DMSO-CO2, and a dynamic solubility experimental set-up was constructed and used to obtain solubility data for the same ternary system.

A novel SCF fluidized bed was used to micro encapsulate porous (TiO2) and non-porous particles (CaO) through a temperature swing with a Chitosan thin layer. DMSO was used as an entrainer to enable solubilization of Chitosan and removed within the supercritical carbon dioxide.

Several analytical methods were used to characterize these particles; SEM-EDS analysis was used to evaluate a group of particles, determining composition and particles diameter on samples up to 900 particles. TEM and AFM confirmed particles of one micron or less were encapsulated with a thickness of less than 5 nm. AFM shows particles roughness on the nanometer range, 46 nm or more for uncoated particles and 2-4 nm for the encapsulated ones.

FTIR, NMR and DSC-TGA analysis confirmed that the chemical structure of Chitosan remained constant before and after processing, and the changes observed were attributed to some DMSO and moisture adsorbed during the encapsulation process.

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