Master of Science / Department of Mechanical and Nuclear Engineering / Youqi Wang / Electrospinning is one of the most versatile methods used to fabricate nanofibers. Sub micron and nano level fibers can be continuously produced with the help of an external electric field induced on the polymer melt. These nanofibers can be used in a large variety of applications such as biosensors, three dimensional tissue scaffolds, composites, electronic devices, etc. A unique feature of electrospinning is its ability to work with different fiber assemblies. This helps in making application specific changes and also increases the quality and performance of the fibers. PEO (polyethylene oxide) and electrostrictive graft elastomer (an electroactive polymer developed by NASA) were used in our experiments which focus on controlling the shape and alignment of the fibers. Electroactive polymers (EAP’s) are seen as the basis for future artificial muscles because of their ability to deform when external voltage is applied and quickly recover to their original form when the polarity of the applied voltage is reversed. Hence, aligned fibers of the electrostrictive graft elastomer were produced to mimic the alignment in human muscle fibers. Alignment of fibers is the main objective of this research and was facilitated using vacuum technology. The research was basically divided into three phases, starting with checking of the repeatability of the previously developed techniques using polyethylene oxide. Next, the electrostrictive graft elastomer was spun using the electrospinning techniques and was checked for alignment using the Coaxial Electrode method and PLC controlled secondary electric field method. Finally, a vacuum chamber was designed and built with new components and the elastomer was tested for improved alignment in vacuum using the PLC controlled secondary electric field method.

Doctor of Philosophy / Department of Chemistry / Peter M.A. Sherwood / This dissertation will examine the fabrication of different phosphorus containing films and their use as corrosion preventative films and adhesion materials between polymers and metal and metal alloys. Orthophosphate films are used in several metals and metal alloys to prevent corrosion and promote adhesion between paints or polymers and metal substrates. One key component is to examine the use of different phosphorus containing acids that might lead to phosphorus containing films which would compliment the mainly orthophosphate films currently in use. The objectives of this study are to see if it is possible to fabricate different phosphorus containing films, use them to adhere polymers to metal and metal alloys, and test the phosphorus containing films’ and polymer films’ corrosion protection properties. The thermoplastic resin, Poly(ether ketone ketone), or PEKK was found to adhere well to different phosphorus containing films and protect the underlying layers from oxidation in 4-D water. The phosphorus containing films were created by electrochemical deposition in different 5 M phosphorus containing acids. The metal or metal alloy was abraded to remove the native oxide and treated in the electrochemical cell. The second, separate polymer films were created by dip coating the metal or metal alloy in a polymer solution. The film thickness in both cases was controlled to be less than 100Å to ensure that the underlying metal or metal alloy could be detected. The surface chemical analysis was collected using X-ray photoelectron spectroscopy, or XPS. Core level and valence band XPS were used to distinguish the differences in the chemistry at the surfaces. The valence band XPS spectra were interpreted using spectra generated by multiple scattered wave calculations and band structure calculations. In the cases were more than one film was present subtraction and addition spectrum were used to interpret the chemistry in the interface region of the films.

Doctor of Philosophy / Department of Chemistry / Duy H. Hua / I. Ovalicin is a natural product isolated from the culture of fungus Pseudorotium ovalis Stolk, it selectively inhibit type 2 methionine amino-peptidase (MetAP 2), which related to many physiological activities such as angiogenesis. Total synthesis of [plus or minus] ovalicin, its C4(S*), C4(S*)C5(S*) stereo-isomers, and C5 regio-isomer were synthesized via an intramolecular Heck reaction of (Z)-3-(t-butyldimethyl silyloxy)-1-iodo-1,6-heptadiene utilizing a catalytic amount of palladium acetate. Subsequent epoxidation, dihydroxylation, methylation (or stereochemistry inversion before or after methylation) and oxidation led to a variety of ketones, key intermediates for synthesis of ovalicin and its analogues. Introduction of side-chain to ketones by lithium (Z)-6-methylhepta-2,5-dien-2-ide and following functional group transformation led to ovalicin and its analogues. Anti-trypanosomal activities of various ovalicin analogues and synthetic intermediates were evaluated. II. Bio-based polymers from vegetable oils are renewable and environment-friendly materials. Dihydroxylated, trihydroxylate, tetrahydroxylated and hexahydroxylated triglycerides, triamino and triisopropylamino glycerides were synthesized from model triglyceride glyceryl trioleoate. These monomers were cross-linked with 1, 4-phenylene diisocynate to make polyurethanes and polyureas. The physical properties of these polymers were examined by gel content and swelling value measurements, thermodynamic and viscoelastic properties were studied from TGA, DSC and DMA measurements. The structure-property relationship was discussed based on these measurements. III. Diacetylenic fatty acids were widely applied in material science to regulate alignment on surface and stabilize self-assembled nanomaterials. A novel synthetic method of diacetylenic fatty acids from vegetable oils was developed. Its self-assembling properties on alumina surface were measured and discussed.

Master of Science / Department of Chemistry / Daniel A. Higgins / Three water-soluble perylene diimides (PDIs) were investigated to examine differences in their thin film forming properties. The PDI thin films investigated in this thesis are formed in an electrostatic-self-assembled (ESA) layer-by-layer (LBL) process by the use of a dip coater. The three PDIs employed are sodium bis (sulfonatopropyl) perylene diimide (PDISO[subscript]3[superscript]2-), bis (trimethylammonioethyl) perylene diimide diiodide (PDIDI[superscript]2+), and N-(butoxypropyl)-N'-(2-(N,N,N-trimethylammonio)-ethyl) perylene-3,4,9,10-tetracarboxylic diimide iodide (C[subscript]7OPDI[superscript]+). Thin films were made by alternately depositing the PDIs with counter polyelectrolyte (PEs). The PEs employed were poly(diallyldimethylammonium chloride) (PDDA[superscript]+) and poly(acrylic acid) (PA[superscript]-), depending on the charge of the PDI. PDIs were determined to be aggregated in all three PDI precursor solutions. The fraction of PDI aggregated in each was found to be 0.972, 0.903, and 0.993, for the PDISO[subscript]3[superscript]2-, PDIDI[superscript]2+, and C[subscript]7OPDI[superscript]+, respectively. The C[superscript]7OPDI[superscript]+ solution was the most aggregated only having one charge group, which makes it more hydrophobic. Thin films prepared from the solutions all displayed an absorbance spectrum similar to the aggregated form. All the composites displayed linear growth in film thickness and fiber width with bilayer number. However, the three composites gave unique surface morphologies. The PDISO[subscript]3[supercript]2-[dot in middle of line]PDDA+ composite was found to incorporate highly curled intertwined fibers compared to the PDIDI[superscript]2+[dot in middle of line]PA[superscript]- composite, where the fibers were not intertwined. The fiber structure was found to change after 15 bilayers. This change in morphology was attributed to the fibers grafting together and overlapping causing the loss of original fiber structure. The two symmetric composites differed in the film thickness with the PDISO[subscript]3[superscript]2-[dot in middle of line]PDDA[superscript]+ being thicker than the PDIDI[superscript]2+[dot in middle of line]PA[superscript]- composite. This was attributed to the molecular weights (MW) of the polyelectrolytes investigated during thin film deposition, with the PDDA[superscript]+ having a much higher MW. C[subscript]7OPDI[superscript]+[dot in middle of line]PA[superscript]- thin film composite had a film thickness approximately equal to the PDISO[subscript]3[superscript]2-[dot in middle of line]PDDA[superscript]+ composite, indicating precursor aggregation also influences deposition rate. The C[subscript]7OPDI[superscript]+[dot in middle of line]PA[superscript]- composite incorporated wavy thin fibers that appeared aligned in the dipping direction. This alignment was visible for bulk samples in UV-vis absorption dichroism studies. The alignment was parallel to the dipping direction of the substrate.