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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.

Detta examensarbete initierades och handledes av Mellifiq, ett företag som arbetar med rening av luft och vatten, där en applikation är rening av köksfrånluft med ozon. Ozon förhindrar att fettpartiklar i frånluften ansamlas på väggarna i kanalen och värmeväxlaren, vilket leder till högre brandsäkerhet och mer effektiv användning av värmeväxlaren. Syftet med detta examensarbete var att öka förståelsen av reaktionen mellan ozon och ytan av fettpartiklarna. Tunna fettsyrafilmer ovanpå ett fast underlag användes som modellsystem för att representera ytan av en fettpartikel. Tre fettsyror undersöktes, en mättad fettsyra, fettsyra A, en enkelomättad fettsyra, fettsyra B, och en fleromättad fettsyra, fettsyra C. TIR Raman-spektroskopi användes för att analysera effekten på fettsyrafilmen vid exponering av torr luft, fuktig luft med en relativ fuktighet på 80 % och fuktig luft med en konstant ozonkoncentration. Effekten av ozon undersöktes även med kontaktvinkelmätningar på fettsyrafilmerna. Resultaten från TIR Raman visade att torr luft och fuktig luft (RH 80 %) inte hade någon effekt på fettsyrafilmen, oberoende av vilken typ av fettsyra som användes. När det gäller effekterna av exponering för ozon kunde inga effekter observeras på filmen av fettsyra A i vare sig TIR Raman eller kontaktvinkelmätningar. Därför kunde ingen reaktion mellan fettsyra A och ozon bekräftas vid den ozonkoncentration som användes och de exponeringstiderna som undersöktes. Däremot oxiderades de omättade fettsyrafilmerna av fettsyra B och C när de exponerades för ozon, vilket bekräftades av den snabba minskningen av C-C-dubbelbindningarna i TIR Raman-spektra. Oxidationen av dubbelbindningar i fettsyra B verkade visa en mer komplex kinetik, med en tvåstegsprocess kopplad till en förändring av antalet molekyler vid ytan. Filmerna bestående av fettsyra C visade sig förlora materia när de exponerades för ozon, vilket tyder på att korta flyktiga ämnen bildades under oxidationsprocessen. Denna effekt observerades inte för fettsyra B, där även om den spektrala formen i CH-sträckningsområdet ändrades, vilket bevisade närvaron av nya arter, förblev den totala mängden material i filmen ungefär konstant. Dessutom gav både fettsyra B och C upphov till nya karbonyl-C=O-sträckningstoppar i spektra efter ozonisering, vilket visar att aldehyder, estrar eller båda bildas under processen. Slutligen bekräftade kontaktvinkelmätningarna med en minskning av statiska vinklar att ytan på filmerna av fettsyra B och C förändrades efter ozonisering. / This master thesis project was initiated and managed by Mellifiq, a company that works with purification of air and water, where one application is purification of kitchen exhaust air with ozone. Ozone prevents fat particles in the exhaust air from accumulating on the walls in the duct and the heat exchanger, reducing fire safety concerns and making the use of the heat exchanger more effective. The aim of this master thesis project was to further understand the reaction between ozone and the surface of the fat particles. Thin fatty acid films on top of a solid support were used as model systems to represent the surface of a fat particle. Three fatty acids were investigated, a saturated fatty acid, fatty acid A, a monounsaturated fatty acid, fatty acid B, and a polyunsaturated fatty acid, fatty acid C. TIR Raman spectroscopy was used to analyze the effect on the fatty acid film as it was exposed to dry air, humid air with a relative humidity of 80 %, and humid air with a fixed ozone concentration. The effect of ozone was also investigated with contact angle measurements on the fatty acid films. The results from TIR Raman showed that dry air and humid air (RH 80 %) had no effect on the fatty acid film, independent of the type of fatty acid used. Regarding the effects of exposure to ozone, no effects could be observed on the fatty acid A field in either the TIR Raman or contact angle measurements. Therefore, no reaction between fatty acid A and ozone could be confirmed at the fixed ozone concentration used and exposure times investigated. In contrast, the unsaturated fatty acid films of fatty acid B and fatty acid C were oxidized when exposed to ozone, as confirmed by the rapid decrease of the C-C double bonds in the TIR Raman spectra. However, the oxidation of double bonds in oleic acid appeared to show more complex kinetics, with a two-step process linked to a change in the number density of molecules at the surface. Interestingly, the films consisting of fatty acid C were shown to lose matter when exposed to ozone, indicating that short volatile species were formed during the oxidation process. This effect was not observed for fatty acid B, where though the spectral shape in the C-H stretching region changed, proving the presence of new species, the overall amount of material in the film remained approximately constant. Moreover, both fatty acid B and C gave rise to new carbonyl C=O stretching peaks in the spectra after ozonation, showing that aldehydes, esters, or both are formed during the process. Finally, the contact angle measurements confirmed with a decrease in static angles that the surface of the fatty acid B and C films changed after ozonation.

Improved fabrication of poly(vinylindenefluoride)-hexafluoropropylene (PVDF-HFP) thin films is of particular interest due to the high electric coercivity found in the beta-phase structure of the thin film. We show that it is possible to obtain high-quality, beta-phase dominant PVDF-HFP thin films using a direct approach to Langmuir-Blodgett deposition without the use of annealing or additives. To improve sample quality, an automated Langmuir-Blodgett thin film deposition system was developed; a custom dipping trough was fabricated, a sample dipping mechanism was designed and constructed, and the system was automated using custom LabVIEW software. Samples were fabricated in the form of ferroelectric capacitors on substrates of glass and silicon, and implement a unique step design with a bottom electrode of copper with an aluminum wetting layer and a top electrode of gold with an aluminum wetting layer. Samples were then characterized using a custom ferroelectric measurement program implemented in LabVIEW with a Keithley picoammeter/voltage supply to confirm electric coercivity properties. Further characterization using scanning electron microscopy and atomic force microscopy confirmed the improvement in thin film fabrication over previous methods.

Indiana University-Purdue University Indianapolis (IUPUI) / Improved fabrication of poly(vinylindenefluoride)-hexafluoropropylene (PVDF-HFP) thin films is of particular interest due to the high electric coercivity found in the beta-phase structure of the thin film. We show that it is possible to obtain high-quality, beta-phase dominant PVDF-HFP thin films using a direct approach to Langmuir-Blodgett deposition without the use of annealing or additives. To improve sample quality, an automated Langmuir-Blodgett thin film deposition system was developed; a custom dipping trough was fabricated, a sample dipping mechanism was designed and constructed, and the system was automated using custom LabVIEW software. Samples were fabricated in the form of ferroelectric capacitors on substrates of glass and silicon, and implement a unique step design with a bottom electrode of copper with an aluminum wetting layer and a top electrode of gold with an aluminum wetting layer. Samples were then characterized using a custom ferroelectric measurement program implemented in LabVIEW with a Keithley picoammeter/voltage supply to confirm electric coercivity properties. Further characterization using scanning electron microscopy and atomic force microscopy confirmed the improvement in thin film fabrication over previous methods.