▼ Greenhouse effect is the phenomenon of warming of the earth’s surface and its lower atmosphere due to increased levels of carbon dioxide and other gases, known as Greenhouse Gases (GHGs). It has been suggested that the release of greenhouse gases such as carbon dioxide, water vapor, nitrous oxide, methane, and ozone into the atmosphere by human activities (such as increased fossil fuel production and the growing use of automobiles) will trap more of the solar radiation that is reflected by the earth’s surface, causing rise in the atmospheric temperature over time. This is known as called global warming A novel and viable solution of mitigating two most important greenhouse gases, viz., carbon dioxide and water vapor by way of converting them into carbon monoxide and water individually or into syngas together has been described in this thesis, and the two gases were converted into carbon monoxide and hydrogen by using an oxide (waste from steel industry) or a metal as the reducing oxide. The resulting product was used as a fuel in running a single-button SOFC at 650°C with comparable efficiency. The spent oxide was highly magnetic in nature and could be used potentially in making ceramic ferrites for scores of applications. Advisors/Committee Members: Azad, Abdul-Majeed.

▼ The injection molding process of polyethylene terephthalate (PET) at 270 to 290 degree C generates parts per million concentration of acetaldehyde (AA), an undesirable chemical residual in food packaging applications. Over the last 60 years, researchers have been looking for the chemical reaction mechanisms of acetaldehyde generation behavior and the relationship with PET end groups such as carboxyl end group, hydroxyl end group, vinyl ester end group, and DEG components. Here, we develop techniques to quantitative determining end groups at low concentrations and establish the contributions of specific end groups to AA generation rates in PET resins. In order to study the effects of the contribution of hydroxyl and carboxyl end groups, we also produce and analyze end capped PET samples. As a result, it is concluded that the hydroxyl end group is one of the most significant factors that affect the acetaldehyde generation behavior, while the others groups such as carboxyl end group, vinyl ester end group, and DEG group do not affect AA generation directly. For short processing time (less than 20 minutes), acetaldehyde may come from two reactions: (1) Hydroxyl end groups reacting with vinyl end groups. Or (2) direct degradation of hydroxyl end groups. For long processing time (35 to 55 minutes), AA generation is mainly controlled by chain scission. Advisors/Committee Members: Jabarin, Saleh.

▼ In situ high-pressure Diffuse Reflectance Infrared Fourier Transform Spectroscopy was performed to investigate the hydroformylation of 1-hexene in supercritical carbon dioxide. A rhodium complex was immobilized on phosphinated silica and used as a catalyst. The changes in the infrared spectrum over time showed the reaction profile, which was used to evaluate the effect of pressure on the reaction mechanism. Increasing the reaction pressure by adding carbon dioxide increased 1-hexene conversion and hydroformylation activity. Specific changes observed in the infrared spectrum when the supported complex interacted with carbon monoxide, hydrogen and/or mixture of carbon monoxide and hydrogen in the presence and absence of carbon dioxide at elevated pressures revealed the nature of the reacting species over time and pressure, and clearly demonstrated the role of carbon dioxide when it was used as the solvent. The catalyst activity and structure were compared for reaction in supercritical carbon dioxide with that in nitrogen in order to more completely delineate the role of the supercritical solvent on the reaction mechanism. It was found that the resting state of the catalyst was HRh(CO) 2 L x , L=PPh 2 CH 2 CH 2 bound to silica, independent of the reaction pressure and the presence of carbon dioxide or nitrogen. Advisors/Committee Members: Abraham, Martin A.

▼ Electrodeposited porous Ni electrodes were fabricated to act as electrocatalysts in a photo water splitting reaction. The electrodes were made porous by incorporating various Zn, Mn, Co and NH4+ based precursors. A Watt’s bath was used to make electrodes at 60 °C and at 45 mA/cm2. Enhanced co-deposition of precursor ions was done at 50 mA/cm2. The precursor ions were leached out in 6M KOH for 48 hours to create porosity in the electrode. These electrodes were tested for their current densities against a Pt mesh in both anodic and cathodic conditions. It was observed that electrodes had enhanced anodic and cathodic properties. Some of the precursors favoured the OER and some favoured the HER. The electrode prepared using NH4Cl precursor gave anodic current densities up to 125 mA/cm2 and the electrodes prepared by (NH4)2SO4 generated cathodic current densities up to 200 mA/cm2. Long term stability test were done for 400 hours at 1.8 V and generated current densities of 12.5 mA/cm2. Once the performance of the electrodes was determined 1’ x 1’ electrodes were prepared. These electrodes were used as anode and cathode respectively in a substrate-type photoelectrochemical (PEC) cell used to produce hydrogen and oxygen from 6M KOH. The voltage required to split the water molecule in the electrolyte is generated by a 12” x 11” triple junction a-Si solar cell. The PEC cell gave an efficiency of 2.3 % under a tungsten filament lamp with an intefrated flux of 1000 Wm2. Advisors/Committee Members: Coleman, Dr. Maria.

▼ Biodiesel is a direct substitute for petroleum derived fules and can be utilized in diesel equipment with few or no modication (Ma, Hanna, 1999). Traditional sources for biodiesel include plant oils (such as soybean or canola) that are also important food sources; biodiesel derived from plants might therefore not result in substantial displacement of petroleum feedstocks. Algae may present itself as an alternate feedstock for biodiesel production that does not compete with the vital land and water resources needed for traditional agriculture. However, the production of fuels from algae is currently economically unviable due to several technological hurdles, including availability of efficient methods of converting cellular lipids to biodiesel. The research described herein describes the in-situ transesterification of soy flour triglycerides (surrogate for algal biomass) with methanol to fatty acid methyl esters using a novel ionic liquid (IL) comprised of 1-Ethyl-3-methylimidazolium chloride (EMIMCl) and the metal halide AlCl3. This IL exhibits Lewis acidity and has been shown to be an excellent nonvolatile solvent and catalyst for many chemical reactions including acylations, condensations, esterications, and polymerizations. However, it is now proposed that this IL catalyst is able to perform esterication reactions with the addition of an organic solvent that solubilizes the ionic liquid yet allows it to retain its catalytic properties. This method enables the reaction to experience the benefits of homogeneous catalysis while providing an opportunity for catalyst recovery and reuse. The influences of biomass concentration, catalyst volume, organic solvent/methanol ratios, reaction time, and temperature on the generation of the desired reaction products has been studied. A traditional mechanistic pathway to account for the observed production of fatty acid methyl esters is proposed and the triglyceride carbon mass balance is closed. The sustained catalytic ability of the ionic liquid was explored and the importance of ionic liquid recovery and reuse will be discussed. In addition, preliminary findings regarding the production of acrylates from biomass and Lewis acidic ionic liquids will be presented. Advisors/Committee Members: Viamajala, Dr. Sridhar.

▼ The concern over the increasing depletion of our nation’s fossil fuels, high oil prices and greenhouse gas emissions, has motivated research for alternative sources of energy. One alternative energy source, biofuels, provides liquid transportation fuels from biomass derived from plant or animal sources. First generation biofuels are produced from food crops abundant in sugars or lipids such as corn and soy. Second generation biofuels are produced from woody, inedible crops such as poplar and switchgrass. The third generation of biofuels is derived from algae and is of growing interest due to its high yield of energy per unit area, use of carbon dioxide for growth, and minimal contribution as a food product. The main carbon rich components of algal biomass include lipid, carbohydrates and protein. Products such as biodiesel and jet fuel can be derived from lipids. Carbohydrates, in the form of fermentable sugars, can be used to produce bioalcohols. Protein can be used as a dietary supplement or as feed for livestock. This work addresses algal characterization and processing techniques that are helpful in utilizing algae as a feedstock for bioproduct processing. Methods for lipid analysis are compared to select a technique for small sample sizes and ease of handling. The hydrolysis of soybean oil to convert triglycerides (lipids) to free fatty acids is evaluated. A kinetic model is developed to predict reaction behavior and serve as a platform for algal hydrolysis. Characterization techniques to determine the content of algal biopolymers; lipids, carbohydrates and protein are discussed and applied to multiple algal species. Lastly, protein extraction from alga is investigated to prepare species for successful algal hydrolysis. Advisors/Committee Members: Schall, Constance.

▼ Poly (Ethylene Terephthalate), PET, has become the packaging material of choice for many packaging applications. PET containers have virtually replaced glass bottles in many market segments. PET markets that require cold or hot products (up to 85°C) to be filled within have essentially reached commodity status. There are many applications that could be served by PET, if PET bottles with a higher degree of thermal stability could be commercially produced. Such non-commodity applications would provide added value to the marketplace, and enable more favorable economic return. Much work has been published regarding the kinetics of crystallization of PET, in both its oriented and unoriented states. Within the published volume of literature, there are key elements to the methods of processing PET that are disclosed and can be used to construct a new crystallization (heat set) process for the blow molding of PET bottles. For this work commercial stretch blow molding machines were adapted to accept a circulation of hot air on the interior of the bottle during the blow molding cycle. A combination of hot molds at the bottle exterior and heated compressed air at the interior bottle surface provide energy to the oriented bottle sidewall, with the energy sufficient to induce an increase in the crystalline structure of the PET. Additionally, the energy allows rearrangements of the morphology of the non-crystalline region from a stressed to a more relaxed structure, resulting in an improvement of bottle thermal stability up to 121°C. Once a process was established and performance of the bottles from the process was validated, the differential equation describing the energy transfer was written. Through numerical methods, this equation was solved for the temperature gradient, and PET kinetics were added to provide a final model that predicts both temperature and crystallinity gradients through the bottle sidewall as a function of the process parameters. The model predictions were tested against measured values, and reasonable agreement was found. The final model provides a means of describing the crystallization of PET that occurs immediately after formation of the bottle (i.e. as the bottle reaches the blow mold). Due to assumptions made during the modeling of the physical characteristics of PET (e.g. thermal conductivity, heat capacity), the model would only be valid for 100°C < T < 250°C. Once the process was designed, and the model describing the process was validated, the ultimate thermal properties of the resulting container were measured. Containers capable of withstanding a retorting process (e.g. filled package heated for 45 minutes at 121°C) were demonstrated. An assessment of level of crystallinity versus relaxation potential was performed. It has been clearly demonstrated that crystallinity is not an absolute predictor of thermal performance, as the relaxation potential is the key property to consider. Finally, the impact of increasing the amount of crystallinity on gas barrier is delineated. Advisors/Committee Members: Jabarin, Saleh.

▼ Biosolids are the solid byproduct resulting from the treatment of domestic sewage in a treatment facility. Biosolids contain large amounts of nutrients such as C and N making them an excellent fertilizer; however, they also contain trace amounts of heavy metals that can leach to the ground limiting their application rate. The leaching process of heavy metals from biosolids is dictated by the physical properties of the soil and by the solid/liquid partitioning of the metals. Biosolids contain multiple sorptive surfaces such as organic matter, iron, aluminum and manganese oxides, silicates and carbonates. To accurately predict leaching of metals from biosolids, the interaction of metals with these surfaces need to be considered. Beforehand, models have been developed to simulate the interactions of metals with individual sorptive surfaces such as hydrous ferric oxides and manganese oxides. The goal of this research was to develop a multisurface geochemical modeling approach to predict the release of As, Cd, Cr, Cu, Mo, Ni, Pb and Zn from biosolids and to determine the affinity of heavy metals for the different sorptive sites present in biosolids. First, pH dependent leaching and isotherm experiments were conducted on biosolids. A multisurface approach was implemented using the NICA-Donnan model to incorporate organic matter (OM) as a sorbent. The generalized two layer model was used to incorporate iron, aluminum and manganese oxides. Selective chemical extractions were conducted to determine the concentration of available surface sites. The multisurface geochemical model required a large number of laboratory measured input values that demanded extensive laboratory analysis and had an associated uncertainty for which there was little knowledge on its impact to the uncertainty of the output. A sampling based global sensitivity analysis was used to relate model output variability and uncertainty with the uncertainty of the input. The leaching pattern of the heavy metals showed strong pH dependence, similar to other waste materials. Overall, the model accurately predicted the release of metals over the pH range and the isotherms. The percentage of active dissolved organic matter (DOM) necessary to successfully model the leaching of metals under acidic conditions was significantly lower than under basic conditions; nevertheless, in the solution phase Cd, Cr, Cu, Ni, Pb and Zn complexes with DOM were predominant for the entire pH range. Organic matter (OM) was the predominant sorptive site in the matrix, however simulations of a case scenario in which OM was completely removed showed that biosolids still retained a large sorption capacity. The sensitivity analysis showed that the dissolved concentration of metals was not sensitive to variations of the input concentrations of: SO4-2, Na+1, NO3-1, Cl-1, Mg+2, K+1, F-1 and H4SiO4. In other words, the dissolved metal concentrations were not affected by the presence of SO4-2, Na+1, NO3-1, Cl-1, Mg+2, K+1, F-1 and H4SiO4. The dissolved metal concentrations leached from biosolids were sensitive to total metal concentrations, total sorptive sites available, and DOC, PO4-3, Al+3, Mn+2, and Fe+3 concentrations. The model uncertainty and sensitivity to the different input values varied with pH. Additionally, each metal input was only relevant for its own output suggesting that in these circumstances there was no competition effect among metals. The uncertainty of the output varied between 5 to 8 orders of magnitude depending on the metal. Advisors/Committee Members: Apul, Defne.

▼ Forward osmosis is the movement of water across a selectively permeable membrane. The driving force for water permeation through the membrane is the difference in osmotic pressure between the feed and draw solutions. Polybenzimidazole (PBI) is a material with excellent chemical resistance and high mechanical and thermal stability that is a promising material for forward osmosis separations. Drawbacks associated with the use of PBI as a membrane material include low hydrophilicity and surface charge neutrality at neutral pH values. These properties effect membrane wettability and solute rejection. In this study, PBI membranes were cast using the phase-inversion technique in the form of asymmetric flat sheets, and membrane surfaces were functionalized using different modifying agents with the goal of increasing hydrophilicity, increasing surface charge, and reducing membrane pore sizes. A charge increase of the membrane surface was expected to yield an increased rejection of ions and of charged species in the feed solution. An increase in hydrophilicity was expected to reduce fouling propensity and enhance wettability of the membrane surface. Lastly, a reduction in pore size was expected to allow for greater steric effects. In order to modify the membranes, the surfaces of the membranes were first activated with 4-(chloromethyl) benzoic acid (CMBA). The modifying agents selected for membrane functionalization included: taurine, para-phenylene diamine, ethylene diamine, and poly(acrylamide-co-acrylic acid). Membranes were characterized using Fourier transform infrared spectroscopy in attenuated reflectance mode (FTIR-ATR), zeta potential, environmental scanning electron microscopy (ESEM), contact angle measurements, and total organic carbon (TOC). Functionalization, surface charge, increased hydrophilicity, and reduced pore size were all verified. Pure water permeability and monovalent salt rejection were tested in a pressure driven mode for comparison between both virgin and modified membranes. Salt rejection was investigated using various sodium chloride feed concentrations, and a range of pH values. Flat sheet membranes were also tested in forward osmosis (FO) applications. The FO process involved use of an ammonium bicarbonate draw solution and a sodium chloride feed solution. All modified membranes showed enhanced water permeability and increased salt rejection over the unmodified membrane surface. Advisors/Committee Members: Escobar, Isabel.

▼ Blends of Poly (ethylene naphthalate) (PEN) and Poly (ethylene terephthalate) (PET) have attracted research interest because they combine the excellent properties of PEN with the economy of PET, and have commercial potential in the plastic packaging industry. The current work is a continuation of intensive research conducted on PEN/PET blends at the Polymer Institute at The University of Toledo. Acknowledging the effects of the transesterification levels and molecular weights of the blends, on the manufacturing of final products from PEN/PET blends, we brought solid state polymerization (SSP) into the PEN/PET blends processing cycle. After the blends were prepared using a twin screw extruder, they were subjected to SSP before the preform injection molding and bottle stretch blow molding processes. SSP has been proven to be a very effective method to both enhance the miscibility of the two polymer phases and upgrade the molecular weights of the blends. The solid stated blends were used to produce bottles with a conventional PET injection molding and stretch blow molding process, without any changes in the machinery design. Blend bottles with optimal mechanical, optical, and barrier properties were obtained. Systematic investigations were conducted on PEN/PET blends with PEN weight fractions of 5%, 10%, and 20%. Through approaches utilizing variation in IV and the end group concentrations, the kinetics and mechanisms of solid state polymerization reactions were investigated. Results have shown that the polymerization reactions were diffusion controlled rather than chemical reaction controlled. Important factors such as SSP temperatures, SSP times, blend compositions and initial precursor IV values of the precursor were investigated in terms of their effects on these reactions. Results obtained with 1H NMR showed that transesterification reactions between PET and PEN occurred during SSP. The transesterification reactions were investigated in terms of SSP times, temperatures, blend compositions and initial IV of blend precursor. By assuming a second order transesterification reaction the reaction rate constant and activation energy were obtained for each blend. Investigations were conducted on the blend samples to study the effects of SSP and transesterification reactions on several important thermal properties such as melting behavior, non-isothermal crystallization behavior, cold crystallization behavior and thermal stability of the blends. It has been found that crystallization ability of the blends during non-isothermal and cold crystallization was reduced as a result of SSP and transesterification reactions. By conducting AA generation experiments, we found that blend thermal stability was improved by the SSP process. Fabrication processes of injection molding and stretch blow molding of the blends were investigated. Minimum injection molding temperatures required to achieve optically clear preforms were shown to decrease for the solid stated blends as a result of enhanced miscibility between PET and PEN through the transesterification reaction during SSP. By monitoring the temperature profiles of the blend preforms, we found that the minimum stretching temperatures required to prevent stress whitening from occurring is about 22°C higher than Tg of each blend with different PEN weight fractions. An upper limit of stretching temperature was determined for each blend in order to obtain uniform thickness distributions in the bottle sidewalls. It has been found that the increased molecular weight of PEN/PET blends, as a result of SSP, is the key to producing good bottles from the PEN/PET blends. These bottles were characterized in terms of birefringence values, strain induced crystallinity levels, mechanical properties, and oxygen barrier properties. Advisors/Committee Members: Jabarin, Saleh A.

▼ Currently, transportation fuels are produced from continuously depleting fossil fuel sources. This calls for additional renewable sources that could be used for the production of high quality transportation fuel. Bio-diesel is one such alternative. Soybean, a food crop, has been used in the past as a source of lipids for the production of bio-diesel. Algae are an alternative non-food source of lipids for bio-diesel and/or carbohydrates for bio-ethanol. We have surveyed algae and phytoplankton in the western Lake Erie basin to identify the predominant algae species. The lipid, carbohydrate and the protein content of lake species were determined. Sampling at selected lake sites was performed at regular intervals of time in an attempt to correlate lake conditions (i.e. temperature, phosphorus and nitrogen) with the selection and composition of species. Based on the results of these analyses, native species were identified as candidates for bio-diesel or bio-ethanol production.Few preliminary experiments were performed to process soybean oil using a batch reactor to convert the triacylglycerides to free fatty acids which would then be converted to fatty acid methyl esters (bio-diesel) through transesterification. The optimized processing conditions can then be utilized to process algae. Advisors/Committee Members: Schall, Dr. Constance A.

▼ Although commercially available cellulose acetate membranes are characterized by having high fluxes during filtration as compared to other membrane materials, they are more prone to microbial attack and organic fouling because of their natural cellulose acetate backbone structures. Fouling, or the accumulation of foreign substances on the membrane surface, occurs mostly due to hydrophobic interactions between the membrane and the foreign substances, especially natural organic matter (NOM). In order to reduce the hydrophobic interactions and thereby fouling due to NOM, flexible hydrophilic poly(ethylene glycol) (PEG) monomer chains were grafted to the cellulose acetate membrane to increase its hydrophilicity. Two methods were used to achieve PEG grafting on the membrane surface. In Method I, grafting was achieved by the action of an oxidizing agent for free radical development, followed by monomer for polymerization, and a chain transfer agent (CTA) for termination of the polymerization. Two different techniques of introducing the chemicals to the membrane were investigated. These were a bulk approach, where membranes were immersed in the chemical solutions, and drop approach, where chemicals were added drop wise to the surface of the membrane to avoid polymerization within the pores. Both techniques led to improvements in membrane performance, as observed by lower fouling, lower flux declines and lower rates of flux decline, when compared to unmodified membranes. While the drop approach displayed slightly higher initial flux values, the bulk method was preferred for its ease of modification and replication. Method II was characterized by a greener solvent-free enzymatic polycondensation to graft PEG to the membrane surface. NOM feed solutions were used to compare organic fouling between the modified and unmodified membranes. Modification led to higher fluxes, lower flux declines, and a more reversible fouling layer easily removed by backwashing during operation. Method I and II led to 16 and 17% increase in the pure water flux of the cellulose acetate membrane, respectively. Both the methods resulted in improved membrane fouling resistance when using NOM as the feed content. Advisors/Committee Members: Escobar, Isabel.

▼ Polymer nanocomposites (PC) have gained considerable attention recently because of the wide range of properties they can provide. However, design of a high loading PC with uniform dispersion and good interfacial interaction between the nanofibers and polymer has been a challenging issue. In this work, techniques to develop and characterize a novel high loading functional nanofiber network (FNN) with enhanced mechanical strength, conductivity and improved gas transport properties are discussed. These FNN materials consist of polymer matrix, nanofiber network and bound functional groups to nanofiber surface. The nanofibers form a highly connected network or mesh, polymer matrix provides mechanical stability and processiblity to the resulting composite. Functional groups which are covalently bound to the surface of the nanofiber provide compatibility between nanofibers and polymer matrix and also desirable properties such as in the case of gas separation they react reversibly with the target species. Processing methods to in corporate functionalized carbon nanofiber (CNF) poly(dimethylsiloxane) (PDMS) were investigated. Possible applications for FNN were studied and a comprehensive characterization of the composite was performed in order to understand the impact of incorporation of CNF and different surface functionality on the physical and electrical properties on the PDMS matrix. Also, the CNF were functionalized with the following classes of groups to investigate the effect of surface chemistry of interfacial region on the transport properties: 1.No affinity group: this includes pristine CNF (CNF- P), oxidized CNF (CNF-OX) and PDMS (OH) functionalized CNF (CNF- PDMS (OH)). Inclusion of these fibers results in increase in stiffness of matrix and reduction in free volume. This is expected to translate to a decrease in permeability of all gases studied. 2.Small molecule with affinity groups: This includes ionic liquid functionalized CNF, PDMS (NH2) functionalized CNF (CNF- PDMS (NH2)). Small molecules with amine groups that exhibit affinity for CO2 can act as fixed carrier in the interfacial region to provide a second transport pathway. This may balance the decrease due to stiffness and reduced free volume of the matrix. 3.Polymer with high concentration of functional group (polyamidoamine (PAMAM) dendrimer functionalized CNF (CNF- PAMAM)): The polymer layer interfacial region likely exhibits properties similar to those of PAMAM with high CO2 permeability and sharp decrease in H2 and CH4 permeability. This is combined with the stiffness of matrix and reduced free volume. Carbodiimide and diimidazole chemistry were used in order to functionalize the surface of CNF with PDMS oligomers, ionic liquid monomers and polyamidoamine (PAMAM) dendrimer molecules. The bound PDMS groups improve the compatibility of the CNF with the polymer matrix. Also, PDMS with amine groups facilitated CO2 transport. Two different ionic liquid with different anions, 1,4-di[3-ethanol-imidazolium]butane taurate (IL [Taurine]) with taurine as anion and 1, 3-di (3-aminopropyl)-imidazolium bromide (IL [Br]) with bromine as anion, were synthesized and used in this project. These ionic liquids provided ion, electrical conductivity and helped with CO2 separation. PAMAM dendrimer with large concentration of affinity sites formed material with great transport properties. Functionalization was confirmed using X-ray photoelectron spectroscopy (XPS) and Thermo gravimetric analysis (TGA). Scanning Electron Microscopy (SEM) was used to study the dispersion and the interaction of the nanofibers within the polymer matrix. The SEM micrograph showed that FNN with pristine CNF had poor dispersion and interaction of the fibers with the polymer. With oxidation the fibers showed better dispersion, but the interaction with the polymer matrix was poor and discontinuity at the fiber-polymer interface was observed. Functionalization with PDMS and PAMAM dendrimer improved both the dispersion and adhesion of the fibers with polymer. However, PAMAM functionalized composites exhibited more entanglement between fibers within the polymer. Four point probe was used to measure the conductivity of FNN produced with oxidized and functionalized CNF at loading up to 17.7 vol% (30 wt%). An improvement in electrical conductivity was seen for samples made with CNF- IL [Br] and CNF- IL [Taurine] while CNF-PAMAM did not exhibit any conductivity. All the FNN except CNF-PAMAM showed threshold behavior and the percolation threshold was in the range of 3 to 5 vol%. Also, the application of FNN as electrochemical actuator was tested. Films made with pristine, CNF-OX and CNF-IL[Br] actuated with applying voltage in NaCl solution used as electrolyte. CNF-IL[Br] showed the largest displacement because of good electrical conductivity as well as its hydrophilicity. Carbon dioxide (CO2) capture is important for both energy production and environmental preservation. A key to reducing the cost of hydrogen production is development of energy efficient separations processes that can provide either preliminary bulk separations or deliver high pressure hydrogen streams by removing CO2. FNN with groups, such as PAMAM dendrimer and ionic liquids that exhibited affinity for the target gas species, CO2, were produced. The permeability of the pure CO2, H2, and CH4 were measured in FNN membranes at loadings up to 17.7 vol%. There was a decrease in permeability for all gases studied. Among FNN membranes with affinity sites, CNF- PAMAM showed the least decrease in CO2 permeability because it has many amines which can react with CO2. Moreover, CNF-PAMAM exhibited significant drop in permeability of H2 and CH4 especially at high loading relative to other FNN membranes. Consequently, a large increase in permselectivity of CO2/H2 and CO2/CH4 in CNF-PAMAM was seen. There are two potential pathways for transport within the proposed FNN membranes: (1) The matrix polymer: transport in dense polymer (PDMS) occurs through solution- diffusion mechanism, (2) The functional annular interfacial region: transport occurs in the annular region at the interface between some of the functionalized nanofiller surface and the matrix polymer. Affinity groups can be covalently bound to the nanofiller surface to form a functional interfacial region. In order to understand the pathway of gas transport in these membranes, the sorption measurement of CO2 and CH4 in selected FNN, CNF- ILTaurine], CNF-PAMAM and CNF-OX, was done along with simple modeling using Maxwell’s equation to predict the transport properties of FNN membranes. A reduction in solubility of CH4 and CO2 in CNF-OX was seen due to the a decrease in free volume and rigidifying effect of CNF in PDMS, while solubility of CH4 in CNF-IL[Taurine] and CNF-PAMAM remained unchanged due to solubility of CH4 in ionic liquid monomer and PAMAM molecule. CNF- IL [Taurine] and CNF- PAMAM exhibited an increase in solubility of CO2 in membrane which was attributed to the presence of affinity groups in those membranes. CNF- PAMAM. Significant improvements were observed for CO2/CH4 and CO2/H2 gas pairs and showed promising behaviors when plotted on the trade-off curve and compared against other researchers’ data. High temperature transport properties were consistent with proposed transport mechanism. CNF- OX as a representative of non-affinity FNN, CNF-IL[Taurine] representing medium affinity FNN and CNF-PAMAM with high affinity groups were chosen to perform permeation test. Increase in permeability of H2 and CH4 and decrease in permeability of CO2 with a decrease in selectivity was observed which is characteristic of transport through polymers. However, at any given temperature, CNF-PAMAM showed greater selectivity than other FNN membranes. The activation energies for permeation of CO2, H2 and CH4 in CNF-PAMAM with increasing CNF concentration and CNF-IL[Taurine] and CNF-OX were calculated. Furthermore, the effect of moisture on permeability of CO2, CH4 and H2 was investigated. 80°C showed an improvement in CO2 permeability for CNF-PAMAM and was favorable in gas transport properties. Advisors/Committee Members: Coleman, Maria.

▼ Hollow fiber membrane module is widely used for commercial gas separation, such as production of high purity of nitrogen and enriched oxygen gas from air, carbon dioxide removal from methane, carbon dioxide sequestration from flue gas and hydrogen purification. Membrane gas separation for air dehydration (AD) differs from other commercial applications in several ways. First, the component to be removed (water) possesses a permeability that may be more than three orders of magnitude greater than the other components in the feed (oxygen and nitrogen). Second, the feed concentration is small, less than 1% in a molar basis. Third, the product concentration may be two orders of magnitude less than the feed concentration. This work seeks to study the hollow fiber gas separation modules for air dehydration. The work evaluated potential module performance and the effect of the inefficiencies such as fiber property variability and deviation from ideal counter-current contacting. This research investigated the effect of sweep uniformity on gas dehydration module performance by assuming the sweep around each fiber is Gaussian sweep distribution. In addition, this work explicitly calculated sweep distribution and presented the effect of sweep distribution, effect of fiber packing variation along case. Compared to fiber size variation, non-uniform sweep distribution has little effect on module performance. Moreover, two fundamental issues for gas separation regarding the Hagen-Poiseuille law and boundary layer contributions on mass transfer coefficients were investigated. This works investigated the of the Hagen-Poiseuille law for pressure drop calculations in hollow fiber gas separation modules. In this work a two dimensional (2D) computational fluid dynamics (CFD) mathematical modeling was used to obtain the numerical approximations to the solutions of the conservation of mass and momentum equations in a single fiber that is assumed to be representative of all fibers in the fiber bundle. Hagen-posieuile law is a good approximate solution of pressure drop for sufficiently low Reynolds number of the feed and permeation fraction for compressible flows. For gas separations, concentration polarization can be significant when the fast gas permeance is greater than 1000 GPU. For air dehydration modules, the overall mass transfer coefficient is calculated by summing the lumen-side, membrane, and shell-side mass transfer resistances. In this work, effective mass transfer coefficients in the lumen and shell are calculated by using computational fluid dynamics (CFD) method and analytical method. The solutions will be obtained for a single fiber that is assumed to be representative of all fibers in the fiber bundle. The lumen mass transfer coefficient for constant wall permeance is 20% greater than that for constant wall concentration. The shell mass transfer coefficient in this research is 2-3 orders magnitude greater than the Donahue equation and the differences may arise from the complexity geometry of the shell fibers and the flows within it. A commercial air dehydration hollow fiber module was evaluated. The module properties were obtained from experiment. Experimental results are in good agreement in simulation results-sweep increases product flow rate significantly. Advisors/Committee Members: Lipscomb, G. Glenn.

▼ Implementation of nanofiltration (NF) and reverse osmosis (RO) processes in treating traditional water sources can provide a steady-state level of removal that eliminates the need for regeneration of ion exchange resins or granular activated carbon. Moreover, RO can help meet future potable water demands through desalination of seawater and brackish waters.The productivity of membrane filtration is severely lowered by fouling, which is caused by the accumulation of foreign substances on the surface and/or within pores of membranes. Microbial fouling, or biofouling, is the growth of microorganisms on the membrane surface and on the feedspacer as present between the envelopes. The fouling of membranes has demanded and continues to demand considerable attention from industry and research communities. Many of these applications use membranes in a spiral wound configuration that contains a feed spacer. The goal of this project was to develop low-biofouling polypropylene (PP) spacers through the functionalization of PP by a spacer arm with metal chelating ligands charged with biocidal metal ions, investigate the use of this metal-charged polypropylene (PP) feedspacers that target biofouling control, and to use some traditional and one novel techniques to autopsy the membranes after filtration to gain a better understanding of the biofouling mechanism and how the modified spacers are affecting it. Advisors/Committee Members: Escobar, Isabel.

▼ Commercial gas separation membranes are typically polymeric because of low cost, processibility and wide range of available properties. However, while much work has been done to develop improved polymers for membranes, these materials have limitations for many applications. Therefore, much work has been focused in post-formation modification of polymer membrane. In this work, two very different polymers were modified by ion irradiation to evaluate the evolution in chemical structure, microstructure and permeation properties. A specific focus was on the impact of ion choice on properties of a specific polymer The first part of study focused on evolution in a typical commercial membrane polymer, polysulfone, following H+ irradiation. Ion irradiation of polysulfone resulted in significant evolution in chemical structure at intermediate H+ doses. There was a general decrease in permeance with little improvement in selectivity following irradiation. Modification of asymmetric polysulfone membranes by H+ and C- irradiation resulted in significant damage to the porous substrate of the membranes. Therefore, these membranes exhibited larger decreases in permeance then could be attributed to changes in the selective layer. The polyimide, 6FDA-6FpDA, was irradiated with three different ions, (H+, N+ and F+) to investigate impact of ion mass and energy transfer mechanisms. As expected the polymer responded different to the different ions at similar overall doses and total energy transfer. In general, more damage to the polymer matrix was achieved with larger mass ions. The larger relative evolution to microstructure was attributed to the greater nuclear loss mechanism for N+ and F+ relative to H+. Significant evolution in permeation properties corresponded to this change in chemical structure and microstructure. While the ions exhibited similar trends in evolution in permeation properties, there were large differences in scale of modification. For example, at high dose H+ irradiation, the gas pair He/CH4 exhibited significant increase in both permeance and permselectivity. However, F+ irradiation at high doses exhibited drastic decreases in permeance for all gases. Several irradiated samples exhibited permeation properties that were beyond the trade-off curve for tradition polymers. Therefore, with additional research, ideal conditions may be selected to optimize the changes in permeation properties. Advisors/Committee Members: Coleman, Maria.

▼ This research aimed to develop hydrogels for agricultural and horticultural application. The most remarkable characteristic of hydrogels is their ability to absorb large amounts of aqueous solutions, such as pure water and nutrient solution. They could make plants grow at optimal environments as the release of water and nutrients is controlled into soils. The advantages not only keeps continuous optimal environment but also reduces the use of freshwater and associates labor cost, being compared to directly sprinkling water to plants. Currently, commercial hydrogels are being produced from these hydrogel advantages. However, there are a few drawbacks. Firstly, while these hydrogels can rapidly absorb large amounts of water, they also dehydrate very rapidly in a matter of hours. Secondly, they are fragile and break apart easily losing their water retention properties. In this study, we tried to overcome the weakness of commercial hydrogels. We researched the dehydration and mechanical characteristics of various types of hydrogels, such as pure hydrogels and ionic hydrogels. Based on these studies, we designed a double layer PAAm-based hydrogel to overcome the inherent weakness of pure and ionic hydrogels which are kinds of commercial hydrogels. The inner layer gel consists of soft, low crosslinked PAAm which retains the high water absorbing property, ensuring its ability is to supply sufficient water, while the outer layer is made up of either highly crosslinked PAAm or polyurethane (PU), providing low aqueous permeability and high mechanical strength. The dehydration rates of PU-PAAm double layer hydrogels could be controlled by the pore sizes of PU coating layer determined by the molecular weight of polyethylene glycol and by the thickness of coating layer. In addition, the cross-linking density of inner gel and the temperature of coating solution affected the dehydration rate of PU-PAAm double layer hydrogels. Such a double layer design resulted in mechanical stability for deployment in soils as well as continuous dehydration time over a week at a room atmosphere and nutrients release until one week in DI water. Advisors/Committee Members: Arun, Nadarajah.

▼ This research has concentrated on the development of methods for creating exfoliated clay nanocomposites with poly (ethylene terephthalate) (PET) for the purpose of improving barrier and other properties. For this purpose, extrusion blending and in situ polymerization were investigated. The melt extrusion was studied as a function of mobility of PET chain, affinity of clay modifier, and solid state polymerization (SSP). Three IVs of PET (0.48, 0.63, 0.74 dL/g) and three organic clays (Cloisite 10A, 15A, 30B) were melt blended with a twin screw extruder to evaluate variables on the properties. Addition of clay caused big molecular weight reduction after extrusion. Thermal stability experiments showed that the nanocomposites were sensitive to temperature. Fourier Transform Infrared (FTIR), however, indicated hydrolysis was the main reason for molecular weight reduction after extrusion. The SSP rate was decreased and crystallization rate became faster due to clay particles. There were basal spacing increases in PET/Cloisite 10A and PET/Cloisite 30B, but PET/Cloisite 15A did not show any change. After SSP reactions, PET/Cloisite 10A and PET/Cloisite 30B nanocomposites had a new peak at low angle in X-ray diffracton (XRD), indicating more expansion of basal spacing. In situ polymerization was investigated in detail as a function of time and temperature of polymerization, mode of addition of the clay in esterification and in polycondensation, ethylene glycol/terephthalic acid ratio (E/T), diethylene glycol (DEG) suppressor, reactor pressure, antioxidant, and metal stabilizer. There was a limitation to reach 0.60 dL/g IV when the clay was added into the reactor at PET melt polymerization conditions. Foam generation made the melt polymerization of nanocomposites difficult. The concentrations of carboxyl and hydroxyl end groups showed big differences from normal values of PET, due to severe thermal degradation during melt polymerization. This thermal degradation caused drastic decreases in melting points and made the SSP rates slower than the observed in the nanocomposites produced by the melt intercalation method. X-ray diffraction (XRD) results showed that Cloisite 30B had the best affinity with PET due to hydroxyl groups in PET and the modifier of clays, while strong hydrophobicity of Cloisite 15A caused the worst affinity with PET. Nanocomposites formed by the in situ polymerization method had more exfoliated nanostructures than those produced by the melt intercalation method, even though they had a small amount of clay agglomerations. Aluminium dish and reactor experiments implied the reason of foam generation and how to reduce the foam amount. Several additives were evaluated to improve the nanocomposite properties. Among them, melt polymerization of E/T=1.2 bishydroxy ethylene terephthalate (BHET) with Cloisite 30B at 270 °C was the best conditions for obtaining exfoliated nanostructures, considering all properties. The nanostructures analyzed by transmission electron microscopy (TEM) showed similar results with those of XRD, but TEM gave more detailed information compared with the results by XRD. Tactoid and exfoliated nanocomposites were selected to evaluate the relationship between nanostructures and properties. Exfoliated nanocomposite had 11% improvement in tensile modulus and 29% improvement in oxygen permeability at 3 wt% of clay, while tactoid nanocomposite showed 2~7% improvement in tensile modulus and no improvement in oxygen permeability. According to the above results, it was found that the dispersion of clay platelets into single layers can have great impact on the properties even though the amount of clay was small. After stretching, improvements by the addition of clay particles were reduced, due to the structure change in the nanocomposites. Density, microscopy, and differential scanning calorimetry (DSC) results implied micro void generation during stretching. The addition of 6 wt% clay in order to increase tortuous path length, was theoretically expected to produce 59% reduction in oxygen permeability, but only the permeability reduced by 37%, due to a small amount of intercalated nanostructure and more agglomeration of clay particles compared with that of 3 wt%. Low IV nanocomposite (0.39 dL/g), melt polymerized at 267 °C, improved the color of the nanocomposite. Cyclo hexane dimethanol (CHDM) was not a good monomer candidate for better nanocomposite, because color and oxygen permeability were worse than those of a control nanocomposite. Advisors/Committee Members: Jabarin, Saleh A.

▼ The effect of ion beam irradiation on the performance of two commercial nanofiltration membranes was investigated. This study focused on four major targets of water treatment: monovalent cations, divalent cations, dissolved organic carbon (DOC) and bacteria. Membrane performance was evaluated by measuring permeability, selectivity, and fouling. Irradiation of the polyether sulfone (PES) membrane revealed similar removal characteristics for all raw water components when compared to the unmodified membrane. There was a decrease in membrane permeability, while the resistance to fouling was improved. Irradiation of the polyamide (PA) membrane caused a slight reduction in selectivity for monovalent cations and a slight improvement for divalent cations and dissolved organic carbon. While selectivity slightly increased, the increase in membrane permeability suggested that a shift of the permeability/selectivity membrane-characteristic curve occurred due to irradiation. Advisors/Committee Members: Escobar, Isabel C.

▼ With the long term uncertainty of fossil fuels, their environmental repercussions, and supposed influence on global climate change, our world is arguably facing an impending energy crisis. Through the use of smart ceramics, materials may be created for the beneficiation and utilization of green house gases and, for the generation of electricity from benign sources. This paradigm was approached from two angles. In one case, magnetoelectric composites were created from the binary mixtures of a piezoelectric material (ZnO) and a ferromagnetic material (LSM; nominally La0.9Sr0.1MnO3-δ). The composites were fabricated through a bulk milling process as well as a wet chemical coating process, to yield a core-shell powder. Magnetoelectric properties of both composites were characterized. In the second case, the utilization of carbon dioxide was explored by utilizing a reaction media as a reversible catalyst. Reaction media formed through combustion and electrochemical synthesis were shown to decompose carbon dioxide, reducing some of it fully to its elemental state, as shown by Raman Spectroscopy and EDS. Catalyst (Ca2MnO4) was prepared via decomposition and calcination of metal salts. It was characterized for its propensity to reduce CO2, via thermogravimetric analysis under different temperature conditions over a number of cycles. The CO2-mediator was activated in pure nitrogen to create non-stoichiometric composition, and re-oxidized in carbon dioxide. Results show potential for converting carbon dioxide into carbon monoxide, for its use in the water-gas shift reaction to make hydrogen. Possible means of bypassing catalyst regeneration are explained and explored. Advisors/Committee Members: Azad, Abdul-Majeed.

▼ Hydroformylation reactions in supercritical carbon dioxide provide an environmentally conscious method of producing aldehydes for fine chemical and pharmaceutical products. Asymmetric ligands, such as (R)-BINAP, may be used to provide an enantioselective product. The benefits of producing a selective product include an overall reduction in costs, including those costs associated with separation and disposal of undesired and potentially harmful products. When these reactions are performed in environmentally benign solvents, such as supercritical carbon dioxide (scCO2), additional environmental benefits are derived, such as ease of recycling of the solvent and unconverted reactants and elimination of the need for organic solvents. In this study, rhodium based catalysts were prepared in supercritical carbon dioxide and evaluated for the hydroformylation of styrene to produce 2-phenylpropionaldheyde. Triphenylphosphine and (R)-BINAP were examined as ligands and their effects on the reaction were examined. The experiments showed that a catalyst is produced that promotes hydroformylation of styrene in supercritical carbon dioxide and that enantiomeric selectivity could be obtained using (R)-BINAP ligands. Advisors/Committee Members: Abraham, Martin A.

▼ The transport properties of gases in polyimide – polyhedral oligomeric silsesquioxane (POSS) mixed matrix membrane were determined based on pure gas permeation and sorption experiments. Gas permeabilities, solubilities, diffusivities and selectivities (CO2/CH4, He/CH4, O2/N2, He/N2) are reported over a wide pressure, temperature for polyimide-POSS mixed matrix membranes containing various loadings of POSS. Gas transport properties of mixed matrix membrane containing inorganic molecular sieving material depends on the sieving ability of the inorganic materials, the gas sorption capacity of the sieve, the interface between the sieve and the bulk polymer matrix and the inherent properties of the polymer matrix itself. Proper selection of both the polymer matrix and the molecular sieving materials is required to obtain mixed matrix membranes with enhanced gas transport properties. Increase in both, diffusivity of smaller penetrants and diffusivity selectivity and consequently in permeability and permselectivity will be obtained in mixed matrix membranes containing molecular sieves with precise pore openings. The properties of the bulk polymer such as excess free volume, relative flexibility/rigidity affect the gas transport properties of mixed matrix membranes. A good interface between the two phases eliminates the possibility of non-selective gas transport and maintains selectivity. Various inorganic materials such as zeolite, carbon molecular sieves are being incorporated into polymer matrices to form mixed matrix membranes. They possess precise pore openings and are mechanically and thermally stable. Polyhedral Oligomeric Silsesquioxanes (POSS) are three dimensional rigid cage structures made up of Si-O-Si linkages. They have dimensions in the nanometer range and possess a precise pore opening of 4.5 Å. They are also thermally and mechanically stable and hence are the inorganic filler of choice for this study. The impact of POSS on the physical, mechanical and thermal properties of 6FDA-MDA polyimide is determined. The effect of functionalization of POSS on the dispersion and morphology of the polyimide-POSS composites are reported. A thorough investigation into the properties of POSS and polymer-POSS composites was done to understand the observed gas transport behavior of these membranes. Pure gas permeation and sorption of penetrants was measured and analyzed based on understanding of pathways of gas transport in mixed matrix membranes. Specifically, pressure dependencies of gas permeabilities, solubilities and diffusivities are discussed in terms of pre-established solution diffusion and dual mode sorption theory. Temperature dependence was also determined to evaluate the performance of these mixed matrix membranes at elevated temperatures. In this study, the versatile properties of POSS particles were harnessed for yet another application. Octa functional POSS was covalently bound onto a carbon nanofiber to increase the overall functionality/reactivity of the fiber. The strong interface thereby generated would assist in effective load transfer under applied stress when incorporated within a polymer matrix. Confirmation of covalent attachment of POSS to the carbon nanofiber was obtained using various analytical techniques. Composites were formed using these functionalized carbon nanofibers within a polyimide matrix and their tensile properties were measured. Advisors/Committee Members: Coleman, Maria.

▼ Polymer nanocomposites are prepared by dispersing small quantities (0.5-10% by weight) of nano-sized particles which have high aspect ratios (100-1500) and high surface area (in excess of 750-800 m2/g) into the polymer matrices. Polymer nanocomposites offer improvements over conventional composites in mechanical, thermal and barrier properties without substantially increasing the density or affecting the light transmission properties of the base polymer. The objective of this project is to develop a new process for preparation of polyethylene terephthalate (PET)/montmorillonite (MMT/Na+MMT) nanocomposite and to characterize it. During the study, we tried to disperse natural clay (Na+MMT) in PET polymer monomers by different methods. Natural MMT clay has been chosen to prepare PET nanocomposites because previous studies with organoclays have shown that organically modified clays get thermally degraded at PET preparation and processing temperatures (~280 °C) and because of degradation, PET nanocomposites do not show expected improvement in properties. PET nanocomposites were prepared by dispersing pristine MMT (Na+MMT) clays into ethylene glycol (esterification-ES clay addition) and bishydroxy ethylene terephthalate (polycondensation-PC clay addition). Thermal, mechanical and barrier properties of these nanocomposites have been studied in comparison to those of neat PET. Differential scanning calorimetry (DSC) results were used to study thermal properties and it was observed that regardless of weight percentage of Na+MMT clay in PET matrices, there were no significant changes in glass transition temperatures (Tg) or melting temperatures (Tm) of the nanocomposites compared to neat PET. It was observed, however, that crystallization rate had increased at higher clay loading because of agglomeration of clay in the PET polymer matrices. For 0.5 wt% ES clay addition PET nanocomposite, tensile strength and tensile modulus observed to be increased by 85% and 92% respectively compared to that of neat PET. As clay percentage increased further, decrease in mechanical properties was noticed because of agglomeration of clay. Compared with neat PET, 0.5 wt% ES clay addition nanocomposite showed 30-40% increase in oxygen barrier properties. Different theoretical models were used to calculate values of tensile modulus and oxygen permeation for given clay content in the PET matrix and compared with experimental values of PET/ Na+MMT nanocomposites. It is concluded that the ES clay addition method resulted into better dispersion of Na+MMT clay into the PET matrices than the PC clay addition method. It is very easy and efficient method to prepare PET/Na+MMT nanocomposites and results into the nanocomposites having better properties than that of neat PET without organic modification of natural MMT. Advisors/Committee Members: Jabarin, Saleh.

▼ Two diamino room temperature ionic liquids, 1,3-di(3-aminopropyl)imidazolium bis[(trifluoromethyl)sulfonyl]imide (monocationic RTIL or mRTIL) and 1,12-di[3-(3- aminopropyl)imidazolium]dodecane bis[(trifluoromethyl)sulfonyl]imide (dicationic RTIL or diRTIL) were synthesized using a Boc protection method. The two RTILs were incorporated within the 6FDA-MDA backbones to tune the solubility properties and improve the separation of CO2 from CH4.The mRTIL was reacted with 2,2-bis(3,4-carboxylphenyl) hexafluoropropane dianhydride (6FDA) to produce 6FDA-RTIL oligomers. Two oligomers, one with 6.5 repeat units and another with 3.3 repeat units, were further reacted with 6FDA and m-phenylenediamine (MDA) where the compositions of RTIL ranged from 6.5 to 25.8 mol% to form block copolyimides. The diRTIL was successfully reacted with 6FDA and MDA and formed 6FDA-(MDA/diRTIL) random copolyimides with a concentration of diRTIL up to 30 mol%. An 8 mol% diRTIL based block copolyimide with an oligomer size of 9 repeat units was also synthesized. The separation performance of all RTIL based copolyimides followed a trade-off relationship and did not exhibit a significant improvement for CO2/CH4 gas pair. The incorporation of RTIL caused the change in the free volumes, free volume distributions of the copolyimides and did not increase the CO2 solubility of the polyimides. The increase in the RTIL mol% resulted in a decrease in molecular weight, 5% weight loss temperature, glass transition temperatures (Tg) and an increase in density. The long block copolyimides exhibited a higher d-spacing, fractional free volume (FFV) and specific free volume (SFV) than those of the short block copolyimides. The diRTIL based copolyimides exhibited smaller d-spacings, FFVs and SFVs with the increase in mol% of diRTIL. In addition, the 8 mol% diRTIL based block copolyimide exhibited a lower density, higher d-spacing, FFV and SFV than those of the 10 mol% random copolyimide. The RTIL monomers contain more alkyl groups than that of the MDA, which could increase the chain flexibility of the copolyimides. The incorporation of the RTILs in the 6FDA-MDA backbones caused denser packing that resulted in a lower permeability and higher selectivity compared with the pure 6FDA-MDA. For the mRTIL based block copolyimides, the gas permeability and diffusivity (H2, O2, N2, CH4 and CO2) decreased and the permeability and diffusivity selectivity for CO2/CH4 and O2/N2 gas pair increased with the increase in mol% of the mRTILs. The long block copolyimides have a lower permeability/diffusivity and higher permeability selectivity/ diffusivity selectivity than those of the short block copolyimides. The solubilities of varied gases of the long and short block copolyimides were similar. And the solubilities of O2, N2 and CH4 increased while that of CO2 decreased with the increase in mRTIL content. For the diRTIL based random copolyimides, the permeability, solubility and diffusivity of varied gases decreased with the increase in mol% of the RTIL. The permeability and diffusivity selectivity of CO2/CH4 and O2/N2 slightly increased while that of N2/CH4 decreased. The solubility selectivity of CO2/CH4 decreased. Advisors/Committee Members: Coleman, Maria.

▼ For many foods and beverages, a fundamental requirement for shelf stability is the minimization of oxygen exposure and thus minimal possible reaction with the food. Common problems associated with the presence of oxygen in food products include microbial spoilage, nutrient loss, as well as flavor and odor changes. There is a need in the industry to improve the oxygen barrier properties of polyesters. Among the approaches available to improve the barrier properties, one of the most promising approaches is the addition of an active oxygen scavenger directly into the poly(ethylene terephthalate) (PET) material. An active oxygen scavenger is a substance capable of intercepting and scavenging oxygen by undergoing a chemical reaction with it, as the oxygen permeates through the PET packaging wall. There is also a need to develop a methodology for determining the scavenging capacity of potential oxygen scavengers and to ultimately help in efficiently designing the copolymers of PET and potential scavengers with better barrier properties. The oxygen scavengers used in this research were two simple model compounds: monoolein (MO) and 3-cyclohexene-1,1-dimethanol (CHEDM). The new active barrier copolymers were synthesized by melt polymerizing PET with the oxygen scavengers (O2) in a batch scale polymerization system. It was found using proton NMR (1H NMR) and 2-D correlation spectroscopy (COSY) that PET has reacted with MO and CHEDM leading to the formation of the copolymers. The effect of oxygen scavengers on the physical properties (melting, crystallization, and rheological behavior) of PET was also studied. The effects of oxygen scavengers on the barrier properties of PET were evaluated by determining oxygen permeation rates. The oxygen barrier properties of copolymers of PET/MO and PET/CHEDM were respectively improved by about 30 and 40%. The oxidation by-products of the copolymers were determined by using gas chromatography-mass spectrometry (GC-MS). Finally, a methodology was developed to determine the scavenging capacity of potential oxygen scavengers by studying the oxidation kinetics followed by the calculation of Thiele modulus. The oxidation kinetics of the copolymers of PET and oxygen scavengers was determined by using nuclear magnetic resonance spectroscopy (NMR) and fourier transform infrared spectroscopy (FTIR). Advisors/Committee Members: Jabarin, Dr. Saleh A.

▼ This study attempted to determine if common processing parameters cause changes in the surface tension of the polymer. Initially, several contact angle techniques were tested to determine the optimal technique to be used for the remaining experiments. From these initial tests, the Harmonic Mean method was selected to determine the surface tension of the polymers. Flat parts were injection molded from both copolymer and homopolymer resins and aged at room temperature and humidity for two months. The surface tension of these parts was measured during several intervals throughout this storage time. The surface tensions of both materials dropped slightly for the first week of storage before leveling off to 44-47dynes/cm. Varying the injection molding conditions did not seem to cause the surface tension to change drastically. Some additional materials were aged for three weeks at 40°C to accelerate the aging process; however this also did not cause a significant change in the surface tension. Films were stretched under various conditions and it was found that increasing the planar extension decreased the surface tension. To determine if this was due to polar end group concentrations on the surface, films were exposed to UV light. The surface tension was found to increase with increased UV exposure time. The end group concentrations for the exposed samples were measured and it was found that the end group concentration increased with exposure time. For times up to 96 hours, the measured end group concentrations correlated well with intrinsic viscosity measurements. Bottles were blow molded under various conditions; it was found that the bottles blown from preforms having the highest temperature had the lowest surface tension. Storage of the bottles at room temperature and humidity caused the surface tension to decrease to around 45 dynes/cm. The films that were stretched to the same level as the bottles had similar surface tensions as the bottles after storage. Advisors/Committee Members: Jabarin, Saleh A.

▼ The goal of this project was to synthesize and characterize porous inorganic-organic hybrid particles using emulsion polymerization. Specifically, cross-linked poly(methyl methacryl) (PMMA)–poly(orthosiloxane) POSS (PMMA/POSS) particles were synthesized using two reaction approaches: (i) water phase free radical initiated reaction (WI) and (ii) organic phase free radical initiated reaction (OI). Particles were produced with concentrations of methyl-methacrylate (MMA) and methacryl functional POSS (MAPOSS) in the reaction mixtures from 40 to 100 wt% MAPOSS. MAPOSS was used to provide vinyl groups that could participate in the reaction and form a highly cross-linked, connected network of POSS molecules. The MMA was used to provide reactive groups that could link the POSS molecules. Following synthesis, the particles were washed with solvent to remove any unbound MMA, MAPOSS, or PMMA oligomers which was expected to provide more porous structure. The conversion of monomers to PMMA/POSS particles was monitored as a function of reaction method and initial MMA concentration. Scanning electron microscopy (SEM) was used to monitor the particle size and size distribution. The N2 sorption isotherms in the PMMA/POSS particles were characterized with a Micromeritics accelerated surface area and porosimetry system. The surface area and porosity of the PMMA/POSS particles were characterized using several different models for porous materials; such as, Brunauer-Emmet-Teller analysis, t-plot by Kruk-Jaroniec-Sayari analysis, and non local density functional theory by Tarazona. The particles synthesized formed hard-spheres with a broad size distribution, from about 100 nm to 15μm diameter, as shown by SEM micrographs. Particles were synthesized with greater than 90% conversion of monomers. The particles were washed with organic solvent and final mass or recovery was from 50% to 95% of prewashed values. There was a general trend of a decrease in surface area with increasing MMA concentration for samples produced using the OI method. The samples produced using OI method were generally higher porosity than those with the WI method. In most cases, the samples were characterized as having mesopores and some samples contained micropores. Advisors/Committee Members: Coleman, Maria.

▼ During the melting and processing of poly(ethylene terephthalate) (PET), degradation of the material may occur. One of the more common degradation products is acetaldehyde (AA). Due to its low boiling point, 21°C, AA is able to diffuse out of PET and into either the atmosphere or the packaged contents of the PET container. The diffusion of AA into packaged contents is of concern, because many food products have a limited threshold for the sweet, fruity taste and odor of AA. One of the ways to limit the AA affects is through the addition of AA scavenging agents. While these additives do not limit the generation of AA; they are designed to interact with and reduce the amount of AA that can be release from PET articles. The purpose of this study was not only to study these AA and AA scavenger interactions and quantify their abilities in reducing AA concentrations in PET; it was also to develop an initial model to predict effectiveness of adding AA scavengers to multi-cavity PET injection molding systems. Through this work, it was determined that anthranilamide and meta-xylenediamine (MXDA) reduce AA concentrations in PET by means of a reaction mechanism. Alpha-cyclodextrin, however, scavenges AA through a hydrogen bonding/size-enclosing scheme. Regardless of the mechanism, it was proven that these three scavengers are capable of reducing detectable AA concentrations in PET. It was generally found that the greater the AA scavenger concentration, the great the effect. Additionally, the changes in the physical properties of PET due to AA scavenger addition were studied. It was shown that melt-blending these additives into PET could adversely affect the intrinsic viscosity (I.V.) and color of the PET blend resin and/or container. The thermal properties and oxygen permeation of PET were not affected by AA scavenger addition. The modification of an existing multi-cavity injection molding program was applied to account for the addition of AA scavengers, to PET resin, when predicting the accumulation of AA within PET preforms. The approach to modify this original program and methodologies to quantify the appropriate kinetic terms has been described in detail. Finally, the modified simulation program was then used to predict the effectiveness of various AA scavenger/PET blends in reducing detectable AA concentrations in PET preforms. While complete agreement between the modeling results and observed trends from single-cavity injection molding was not achieved, the groundwork was laid to make further improvements and advance predictability for future modeling programs. Advisors/Committee Members: Jabarin, Saleh A.

▼ Membranes in the form of fine hollow fibers are used to perform a wide range of separations from hemodialysis to dehydration. The fibers commonly are fabricated into large bundles or modules for use in a separation process to facilitate handling and scale-up. Module performance depends strongly on membrane transport properties but other factors may be equally important including concentration and thermal boundary layers adjacent to the fiber surface as well as uniformity of the flow through a module. The introduction of a cross-flow component to the shell flow through a module can reduce the impact of shell concentration boundary layers. This can be done by placing baffles within the fiber bundle or other bundle structural features. Alternatively, one may crimp the fiber. Crimping transforms a straight fiber into a wavy fiber much like a permanent creates curly hair. iv Fiber bundles manufactured from crimped fibers intrinsically introduce a cross-flow component in the shell as fluid flows through it. The effect of crimping on shell side mass transfer coefficients is investigated here using computational fluid dynamics. Advisors/Committee Members: Lipscomb, Glenn.

▼ Spark ignition energies were examined for various small hydrocarbons in the 1940’s and 1950’s related to mine gas explosions. In 1996, the TWA flight 800 center wing tank explosion focused interest on the measurement of aviation fuel minimum ignition energy. The goal of this study is to obtain spark ignition energy data and acquire the resultant pressure rise for n-octane and i-octane combustion as the selected species of jet fuel. Using a composite electrical spark system, ignition energy was plotted versus dc-arc spark duration time while varying the fuel/air mixture equivalence ratio, φ. For rich mixtures of i-octane, the minimum ignition energy decreased with spark duration time, reached a minimum value, and then further increased as expected; while results for lean mixtures of n-octane are not so apparent, displaying abrupt irregular behavior. The minimum of the minimum ignition energy (commonly called minimum ignition energy, MIE) for i-octane at φ≈2 was 1.5 mJ which is close to the literature value of 1.35 mJ. Also, reducing the oxygen content appears to raise the minimum ignition energy and lessen the pressure rise. The ignition process (ignition + successful flame propagation) was analyzed by considering energy furnished from the composite spark and heat release from chemical reactions opposing heat conduction energy losses to the unburned gas and electrodes. Extending and preserving the ignition kernel (plasma kernel) with dc-arc energy is critical for successful flame propagation. In this regard, dc-arc energy deposition rate is more important than the absolute energy supply. Overall, it was shown that ignition energy is dependent upon equivalence ratio as well as spark duration time while pressure rise is also subject to the stoichiometry. Advisors/Committee Members: DeWitt, Kenneth J.