Title page for ETD etd-05052002-231800


Type of Document Dissertation
Author Harris, Linda Ann
Author's Email Address liharris@vt.edu
URN etd-05052002-231800
Title Polymer Stabilized Magnetite Nanoparticles and Poly(propylene oxide) Modified Styrene-Dimethacrylate Networks
Degree PhD
Department Chemistry
Advisory Committee
Advisor Name Title
Riffle, Judy S. Committee Chair
Dillard, John G. Committee Member
Lesko, John J. Committee Member
McGrath, James E. Committee Member
Ward, Thomas C. Committee Member
Keywords
  • phase separation
  • structural adhesive
  • vinyl ester
  • poly(ethylene oxide)
  • iron oxide
  • drug delivery
  • fiber reinforced polymer composite
  • carboxylic acid
  • nanoparticles
  • superparamagnetic
  • colloidal dispersion
Date of Defense 2002-04-19
Availability unrestricted
Abstract
Magnetic nanoparticles that display high saturation magnetization and high magnetic susceptibility are of great interest for medical applications. Nanomagnetite is particularly desirable because it displays strong ferrimagnetic behavior, and is less sensitive to oxidation than magnetic transition metals such as cobalt, iron, and nickel. Magnetite nanoparticles can be prepared by co-precipitating iron (II) and iron (III) chloride salts in the presence of ammonium hydroxide at pH 9-10. One goal of this work has been to develop a generalized methodology for stabilizing nanomagnetite dispersions using well-defined, non-toxic, block copolymers, so that the resultant magnetite-polymer complexes can be used in a range of biomedical materials.

Hydrophilic triblock copolymers with controlled concentrations of pendent carboxylic acids were prepared. The triblock copolymers contain carboxylic acids in the central urethane segments and controlled molecular weight poly(ethylene oxide) tail blocks. They were utilized to prepare hydrophilic-coated iron oxide nanoparticles with biocompatible materials for utility in magnetic field guidable drug delivery vehicles. The triblock copolymers synthesized contain 3, 5, or 10 carboxylic acids in the central segments with Mn values of 2000, 5000 or 15000 g/mol poly(ethylene oxide) tail blocks. A method was developed for preparing ~10 nm diameter magnetite surfaces stabilized with the triblock polymers. The carboxylic acid is proposed to covalently bind to the surface of the magnetite and form stable dispersions at neutral pH. The polymer-nanomagnetite conjugates described in this thesis have a maximum of 35 wt. % magnetite and the nano-magnetite particles have an excellent saturation magnetization of ~66 - 78 emu/g Fe3O4. Powder X-ray diffraction (XRD) confirms the magnetite crystal structure, which appears to be approximately single crystalline structures via electron diffraction spectroscopy analysis (EDS). These materials form stable magnetic dispersions in both water and organic solvents.

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