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A new approach to the fabrication of polymeric thin films is presented. This approach, chemical vapor copolymerization (CVcP), has all the advantages of chemical vapor polymerization (CVP), including exceptional purity, highly conformal coatings, continuous films even when very thin, low stress, and low environmental impact. The range of film properties available by CVcP is much greater than by CVP. A specially modified deposition system was constructed to study deposition kinetics. A model was developed which allowed quantification of the order of initiation of paraxylylene (PX), which is the initiation system for all the work reported here. This model suggests a trimer diradical is the smallest stable diradical species formed by PX at room temperature, confirming thermodynamic predictions. This system also allows the calculation of reactivity ratios of PX with vinylic comonomers. A model is developed in which reactivity ratios can be determined if the following quantities are known: a) thickness vs. position of the final film; b) partial pressures of each reactive species entering the deposition chamber and c) composition vs. position in the final film. This model was tested yielded reasonable values for reactivity ratios. A polymeric film extremely low in refractive index (1.38-1.39 in the visible region) is presented. This film is formed by copolymerizing poly(parachloroxylylene), or PX-C, with perfluorooctyl methacrylate (PFOMA). The refractive index of the homopolymers, by contrast, are in the 1.60-1.68 range. Film growth rates are very low for this new material. Finally, a new deposition procedure is introduced in which a comonomer with a low vapor pressure is codeposited with PX. The reactor temperature is above the ceiling temperature of PX deposition, but at a temperature where the comonomer can condense. This makes the deposition environment extremely rich in comonomer, yielding films whose final properties are nearly identical to films composed entirely of the comonomer. The procedure is demonstrated using n-phenyl maleimide (NPMI) as a comonomer; films produced had thermal stabilities nearly matching those of poly(NPMI). This procedure has great promise for broadening the use of polymeric thin films in the microelectronics industry, as well as other fields. / Ph. D.

Ruthenium dioxide, zirconium dioxide and bismuth titanate thin films were deposited on Si, sapphire disks, and Pt/Ti/SiO₂/Si substrates by hot wall metalorganic chemical vapor deposition (MOCVD). Bis(cyclopentadienyl)ruthenium [Ru(C₅H₅)₂], zirconium tetramethylheptanedione [Zr(thd)₄], triphenylbismuth [Bi(C₆H₅)₃], and titanium ethoxide [Ti(C₂H₅O)₄] were used as precursors. MOCVD RuO₂ film structure was dependent on MOCVD process parameters such as bubbler temperature, dilute gas flow rates, deposition temperature, and total pressure. Either pure RuO₂, pure Ru, or a RuO₂ + Ru mixture was obtained under different deposition conditions. As-deposited pure RuO₂ films were specular, crack-free, and adhered well on the substrates. The Auger electron spectroscopy depth profile showed a good composition uniformity across the bulk of the films. The MOCVD RuO₂ thin films exhibited resistivities as low as 60 <i>μ</i>Ω-cm. In addition, the reflectance of RuO₂ in the NIR region showed a metallic character. Zr(thd)₄ was synthesized and the process was optimized. Purity of Zr(thd)₄ was confirmed by melting point determination, carbon and hydrogen elemental analysis and proton nuclear magnetic resonance spectrometer (NMR). The MOCVD ZrO₂ film deposition rates were very small (≤ 1 nm/min) for substrate temperatures below 530°C. The film deposition rates were significantly affected by: (1) source temperature, (2) substrate temperature, and (3) total pressure. As-deposited films are carbon free. Furthermore, only the tetragonal ZrO₂ phase was identified in as-deposited films. The tetragonal phase transformed progressively into the monoclinic phase as the films were subjected to high temperature post-deposition annealing. The optical properties of the ZrO₂ thin films as a function of wavelength, in the range of 200 nm to 2000 nm, were also reported. In addition, a simplified theoretical model which considers only a surface reaction was used to analyze the deposition of ZrO₂ film. The deposition rates can be predicted well for various deposition conditions in the hot wall reactor. The deposition rates of MOCVD Bi₄Ti₃O₁₂ were in the range of 3.9-12.5 nm/min. The Bi/Ti ratio was controlled by precursor temperature, carrier gas flow rate, and deposition temperature. As-deposited films were pure Bi₄Ti₃O₁₂ phase. The films were specular and showed uniform and fine-grain morphology. Optical constants as a function of wavelength were calculated from the film transmission characteristics in the UV-VIS-NIR region. The 550°C annealed film had a spontaneous polarization of 26.5 <i>μ</i>C/cm² and a coercive field of 244.3 kV/cm. / Master of Science

Metal alkoxides have been known for many years. Recently, a renewed interest in these compounds has arisen as they have been found to be viable precursors for metal oxide film synthesis. Lead zirconium titanate(PZT) films have shown promise for many applications in the electronics industry. Chemical vapor deposition(CVD) of PZT thin films has been hampered by the lack of a suitable zirconium precursor for low temperature chemical vapor deposition. Currently, both zircbnium alkoxides and zirconium β-diketonate complexes are employed in the CVD process of PZT films. The alkoxides, although volatile are moisture sensitive and are not easily handled under normal atmospheric conditions. Tetrakis β-diketonate complexes of zirconium are more stable than the alkoxides, but they have a deposition temperature that is too high for commercial use. A mixed (β-diketonate)zirconium alkoxide compound could provide the necessary stability while maintaining the volatility necessary for low temperature CVD. From the above reasoning, it was decided to prepare a zirconium di-(2,2,6,6 tetramethyl-3,5 heptadione) di-tert-butoxide compound. The compound was characterized and subjected to a variety of volatility studies. Thermogravimetric analysis provided evidence that the compound was volatile enough to be used in thin film synthesis. Initial attempts at film deposition, however, resulted in no film growth. Changing deposition parameters also resulted in no film growth. Visual inspection of the residue left after the deposition trials gave the first indication that the compound had undergone some change. Analysis of the material left in the reactor suggested the formation of a zirconium cluster compound. Further decomposition studies also resulted in the formation of the same zirconium cluster compound. Attempts to make the compound more stable at deposition temperatures centered on changing the alkoxide. Tri-tert-butyl alcohol(tritox) was prepared, however, the synthesis of the tritox - β-diketonate zirconium complex was unsuccessful. Other changes involved using pivalic acid to replace the alkoxide. Reactions with pivalic acid and zirconium di-(2,2,6,6 tetramethyl-3,5 heptadione) di-tert-butoxide resulted in the decomposition of the starting material. Other β-diketonate complexes were also investigated. Compounds synthesized from 2.4 pentadione(Acac), 1-benzoyl acetone(Bzac) and dibenzoyl methane(Dbzm) could not be purified in order to subject them to chemical vapor deposition. A zirconium complex with two different β-diketonate ligands was also synthesized. The complex was not investigated as a precursor for chemical vapor deposition because the isomers of the complex could not be separated. / Master of Science

Since 2006 there have been four Salmonella enterica and one Listeria monocytogenes foodborne outbreaks linked to whole cantaloupe fruit. No post-harvest intervention to reduce potential contamination on cantaloupe currently exists. The complex surface topography of netted cantaloupes aids bacterial attachment. This research evaluates the use of allyl isothiocyanate (AITC; a natural antimicrobial) to reduce populations of S. enterica Michigan and L. monocytogenes on the surface of cantaloupe. Fifty μl of S. Michigan or L. monocytogenes was inoculated onto whole ‗Athena‘ or ‗Hales Best Jumbo‘ (‗HBJ‘) cantaloupe fruit in 22 mm diameter circles and allowed to dry for 90 min. resulting in 6.60 log CFU/g. Cantaloupe received either AITC liquid or vapor, sterile deionized water, 200 ppm sodium hypochlorite per circle, or no treatment. All cantaloupes were stored in separate sealed glass desiccators for 1 or 24 h at 25°C or 35°C. To enumerate the bacteria following treatment, 22 mm sections of the rind were removed, homogenized and plated onto appropriate agar. Headspace analysis using Gas Chromatography-Mass Spectrometry (GC-MS) quantified the concentration of each AITC vapor treatment. The texture quality of the pericarp tissue of whole cantaloupes was evaluated after 24 h treatments, followed by two weeks of storage at 4°C. The concentration of vapor ranged from 3.4 to 19.6 μl AITC/L inside the desiccators. The liquid treatment reduced (P < 0.05) S. Michigan populations on ‗Athena‘ (3 log CFU/g) and L. monocytogenes on ‗HBJ‘ (2.6 log CFU/g). The longer exposure time to the AITC vapor (24 h versus 1 h) resulted in a greater reduction of both S. Michigan and L. monocytogenes on ‗Athena‘ and treatments at 35°C reduced microbial populations up to 4.5 times greater (P < 0.05). The highest vapor concentration reduced (P < 0.05) both pathogens at least 3.0 log CFU/g on ‗Athena‘ at 25°C. Generally, bacterial pathogens from the surface of ‗Athena‘ cantaloupe were reduced more than pathogens inoculated on the surface of ‗HBJ.‘ The application of AITC liquid or vapor is a natural alternative post-harvest treatment to 200 ppm free chlorine to reduce the level of bacterial contamination on cantaloupe surfaces for certified organic production. / Ph. D.

The first objective of this problem - thorough literature review - was conducted on all available references concerning humidity measurement, and visits were made to the American Instrument Company in Silver Springs, Maryland, and the National Bureau of Standards. The survey evaluated the instruments in use today and also explored many of the ideas and concepts that have been suggested in past years as possible means for humidity measurement. A summation of the survey indicated that the electric hygrometer with a ceramic element was a good basic theory for a humidity instrument, but still required development before it,would be of any practical use. The second objective - development of a useful hygrometer - was directed towards the development of the electric hygrometer using a ceramic element. The study that resulted included the evaluation of two methods for determining the change of resistance of the ceramic element, as well as a preliminary investigation of the characteristics of a ceramic element when employed as the sensing element for an electric hygrometer. The element intended for the initial tests, a porous ceramic containing mostly aluminum oxide, was the only material tested, but the tests included elements of the pure ceramic material and the same material after it was soaked in a saturated solution of lithium chloride. With the instruments used, the indications were that both elements were suited for determining the high humidities. The pure element had a lower limit of 50 percent relative humidity, and the coated element a lower limit of 20 percent. Two instruments were used for indicating the change of relative humidity. A vacuum tube voltmeter type instrument was tested, but found unsatisfactory due to variations of readings under the same conditions, drifting of the zero set, and excessive fluctuations of the indicating meter. The other instrument or method used was to apply an A-C voltage across the element, and to measure the resulting current flow. Because the current was maintained above 1 milliampere, heating of the element was caused, resulting in a change of element resistance. However, results with this instrument were sufficient to establish a calibration curve for the apparatus. A comparison of this device and a psychrometer indicated the usefulness of such an instrument, but confirmed that the development was not complete. The overall result of the research indicates that the selection of the ceramic sensing element for an electric hygrometer has merit, but more development is necessary. Two phases of any future work on the problem should be the development of the indicating instrument, and the selection and design of the sensing element. The need for a satisfactory instrument still exists, and the successful development of the type instrument described herein, would undoubtedly meet the requirements. / Master of Science

This study examined the effects of household fabric softeners on the thermal comfort and flammability of 100% cotton and 100% polyester fabrics after repeated laundering. Two fabric properties related to thermal comfort, water vapor transmission and air permeability, were examined. A 3 X 2 X 3 experimental design (i.e., 18 experimental cells) was developed to conduct the research. Three independent variables were selected: fabric softener treatments (i.e., rinse cycle softener, dryer sheet softener, no softener), fabric types (i.e., 100% cotton, 100% polyester), and number of laundering cycles (i.e., 1, 15, 25 cycles). Three dependent variables were tested: water vapor transmission, air permeability, and flammability. The test fabrics were purchased from Testfabrics, Inc. To examine the influence of the independent variables and their interactions on each dependent variable, two-way or three-way Analysis of Variance (ANOVA) tests were used to analyze the data. Results in this study showed that both the rinse cycle softener and the dryer sheet softener significantly decreased the water vapor transmission of test specimens to a similar degree. The rinse cycle softener decreased the air permeability of test specimens most and was followed by the dryer sheet softener. The rinse cycle softener increased the flammability of both cotton and polyester fabrics, but the dryer sheet softener had no significant effect on the flammability of both fabric types. Statistical analysis also indicated that the interactions were significant among the independent variables on water vapor transmission, air permeability, and flammability of the test specimens. For example, the rinse cycle softener significantly decreased the water vapor transmission and air permeability of cotton fabric but had no effect on polyester fabric. The dryer sheet softener also decreased the water vapor transmission of cotton fabric but had no effect on polyester fabric, and it had no effect on the air permeability of both cotton and polyester fabrics. In addition, the air permeability of cotton specimens treated with the rinse cycle softener continuously reduced after repeated laundering, but that of polyester fabrics treated with the rinse cycle softener only reduced after 15 laundering cycles and showed no continuous decrease when laundering cycles increased. When the influence of fabric softener treatments on flammability was examined, the results showed that the more the specimens were laundered with the rinse cycle softener, the greater the flammability of the test specimens. However, the dryer sheet softener did not have a significant effect on the flammability of the test fabrics even after repeated laundering. For the polyester fabric, all specimens treated with the dryer sheet softener or no softener passed the standard of children's sleepwear even after 25 laundering cycles, but those treated with the rinse cycle softener did not pass the standard. In conclusion, fabric softener treatment had a significant influence on the thermal comfort (i.e., water vapor transmission and air permeability) and flammability of 100% cotton and 100% polyester fabrics after repeated laundering cycles and the effects were significantly different among the three independent variables (i.e., fabric softener treatments, fabric types, and number of laundering cycles). The applications of these results were also discussed. / Master of Science

Yes / A composite silicone skin adhesive material was designed to improve its water vapor permeability to offer advantages to wearer comfort compared to existing skin adhesive dressings available (including perforated silicone and hydrocolloid products). The chemical and mechanical properties of this novel dressing were analyzed to show that it has a high creep compliance, offering anisotropic elasticity that is likely to place less stress on the skin. A participant study was carried out in which 31 participants wore a novel silicone skin adhesive (Sil2) and a hydrocolloid competitor and were monitored for physiological response to the dressings. Trans-epidermal water loss (TEWL) was measured pre- and postwear to determine impairment of skin barrier function. Sil2 exhibited a higher vapor permeability than the hydrocolloid dressings during wear. Peel strength measurements and dye counter staining of the removed dressings showed that the hydrocolloid had a higher adhesion to the participants’ skin, resulting in a greater removal of proteins from the stratum corneum and a higher pain rating from participants on removal. Once the dressings were removed, TEWL of the participants skin beneath the Sil2 was close to normal in comparison to the hydrocolloid dressings that showed an increase in skin TEWL, indicating that the skin had been highly occluded. Analysis of the skin immediately after removal showed a higher incidence of erythema following application of hydrocolloid dressings (>60%) compared to Sil2, ( / T.S. received partial funding to study skin adhesive materials from a Medical Research Council Confidence in Concept grant obtained by John Bridgeman at the University of Bradford (MC_PC_19030). Initial formulation and characterization work benchmarking the Sil2 material was funded in part by Trio Healthcare Ltd., who have had no role in the analysis or interpretation of the data presented. All data was obtained independently by staff at the University of Bradford. We also wish to thank the Royal Society of Chemistry for funding Edward Dyson’s position as a research technician via a Research Enablement Grant (E21-8346952505).

The purpose of this study was two-fold: firstly, the MOCVD deposition behavior of Pb(thd)2 was studied in detail and a one-dimensional kinetic model was proposed to successfully predict the effect of processing conditions on the deposition rate profile for PbO. Assuming the surface reaction is the rate-limiting step in the process, the effective activation energy for the process, Ea, was found to be 82 kJ/mol while the preexponential rate constant was found to be 33 g/cm2/min (0.15 moVcm2/min). The process was found to consistently produce a combination of the high temperature, orthorhombic modification of lead monoxide with randomly oriented plates of tetragonal lead monoxide. TEM electron diffraction was used to investigate the crystal orientation of the individual plates which was found to be in the plane normal to the <201> zone. Secondly, the deposition behavior of PbTi03 and the resulting film structure and properties were investigated. Pb(thd)2 was used in conjunction with titanium ethoxide (Ti(OEt)4) as a titanium source. Stoichiometric lead titanate films which were found to be smooth, specular and transparent, and well-adhered were deposited on a variety of substrates by careful control of the experimental conditions. Film structure, composition, and thickness were studied and correlated to changes in various experimental parameters. Additionally, a high temperature regime at which the film stoichiometry is relatively insensitive to experimental conditions was found to occur. The effects of post-annealing on the as-deposited films including compositional changes, morphological changes and crystal structure was also studied. Some problems were obtained with film peeling on the ruthenium oxide (Ru0₂)-coated substrates which could be alleviated somewhat by the use of (100) oriented silicon wafer rather than (111) oriented silicon; a possible mechanism to explain this behavior is also suggested. Optical properties were obtained using UV -VISNIR transmission and reflectance spectroscopy; the ferroelectric hysteresis behavior of the films was observed using standard R T -66 A test equipment. / Master of Science