This dissertation focuses on the use of novel polyethers and polydimethylsiloxanes in the stabilization of magnetite nanoparticles as well as biomedical applications. The colloidal stabilities of magnetite nanoparticles coated with polyethers containing various functional endgroups were studied. Different variables (e.g. polymer loading, polyether molecular weight and type of functional anchor group) were investigated to determine their effect on the long-term physiological stability of the polyether magnetite complexes. One-part PDMS-magnetite nanoparticle fluids were synthesized using a high shear process and magnetic separation techniques. These one-part fluids are unique in the fact that they do not require the addition of a non-functional PDMS oligomer solvent to generate a magnetic hydrophobic fluid. A series of PDMS-magnetite nanoparticle fluids containing different molecular weight stabilizers were synthesized. A magnetic separation study was performed to determine if PDMS molecular weight influences the magnetic separation profiles of the fluids. Well-defined PDMS-b-PtBA and PDMS-b-poly(acrylic acid) copolymers were synthesized using living free radical techniques from novel PDMS precursors as well as PDMS-based ionenes with different hard segment groups. / Ph. D.

The functionalisation of silsesquioxanes results in materials with novel physical properties. A series of compounds has been coupled with silsesquioxanes [HSiO_3/2]₈ and [SiO_3/2]₈ [OSi(CH₃)₂H]₈ and the properties of the products investigated. Typically, coupling reactions involved hydrosilylation with H₂PtCl₆ or [Pt{(η-ViMe₂Si)₂O}(P^tBu₃)]. Mesogenic compounds have been shown to undergo a change in the liquid crystalline phase produced, once attached to the silsesquioxane core. A more ordered phase was observed due to the tethering of the mesogen to the cage. The silsesquioxanes core was considered to have been deformed in the production of this phase. Silsesquioxanes capable of complexing metal atoms have also been studied. Polyether derivatised cages were prepared and preliminary studies indicate potential for potassium complexation. Vinyl functionalised silsesquioxanes have also been shown to complex platinum, in an exchange reaction with [Pt{(η-ViMe₂Si)₂O}(P^tBu₃)]. Investigations into the hydrosilylation reaction have involved coupling triethylsilane, triethoxysilane and the silsesquioxanes with a variety of vinyl, allyl and alkenic compounds. The proportions of α and β adducts were considered. Particular substituents were found to encourage α addition, with species having an oxygen or phenyl group at the allylic position producing the α-regioisomer as well as the typical β product. It is suggested that such substitution affects the mode of cis ligand insertion in the Chalk Harrod mechanism. A preference for the α-regioisomer was also observed for the hydrosilylations of vinyl silsesquioxane compounds.

Includes bibliographical references (p. 44-47).

Thesis--Groningen. / In Periodical Room.

No description available.

No description available.

Thesis (M.S.)--University of North Carolina at Wilmington, 2005. / Includes bibliographical references (leaves: [50]-51)

The complexation properties of the two isomers of the cyclic polyether dicyclohexyl-18-crown-6 are examined in aqueous solution for a series of metal ions at various reaction temperatures. The results are discussed in terms of size relationships and salvation characteristics of both polyether and metal ions. ΔCp° values are determined from the temperature dependence of the ΔH° values. A discussion of the errors involved in the determination of ΔH° from the temperature dependence of log K values is also included. Comparisons are made between the results of this study and those of a similar study by H. K. Frensdorff, E. I. duPont de Nemours and Co., Wilmington, Delaware, in press. The complexation reactions of dicyclohexyl- and dibenzo-18-crown-6 and benzo-15-crown-5 with Na^+ and K^+ ions are reported in non-aqueous solvents and methanol-water mixtures. The results are discussed with reference to their application in model systems of ion transport. In general the stabilities of the polyether-cation complexes were found to increase with decreasing dielectric constant of the solvent medium. In the methanol-water mixtures large compensating ΔH° and ΔS° changes were observed above 70 weight percent methanol, while the log K values showed a nearly linear increase with increasing methanol concentration. Salvation of the polyethers and metal ions and complexation of ion pairs in non-aqueous solvents are discussed.

No description available.

No description available.