Master of Science, Miami University, 2009, Chemistry and Biochemistry

Polymeric polyimide capillary tubing, both uncoated and coated with stationary phases of two polarities, is explored for use as capillary columns for gas chromatography (GC). These glass-free polyimide columns are flexible and their small winding radius may enhance the design of portable GC instruments. Polyimide columns with dimensions of 0.32-mm ID x 3-m L are cleaned, baked out, and coated using the static method. Coating thickness is 0.5 - 1 µm. Separations of volatile organics are investigated isothermally on duplicate sets of polyimide columns by GC with a flame ionization detector, using split injection. The columns are characterized with a sample mass load study, a column reproducibility study, and a van Deemter study. The uncoated polyimide columns are minimally capable of GC separations. The coated polyimide columns successfully separate Grob test mix alkanes, bases, and fatty acid methyl esters, and are comparable to standard fused-silica capillary GC columns.

Committee: Neil Danielson PhD (Advisor); Susan Marine PhD (Committee Chair); Michael Novak PhD (Committee Member); Richard Taylor PhD (Committee Member) Subjects: Analytical Chemistry; Chemistry

Master of Sciences (Engineering), Case Western Reserve University, 2024, Materials Science and Engineering

The long-term durability of fexible printed circuit boards (PCBs) is essential for the microelectronics industry. The adhesive layer between the polyimide and the cop- per layers is of particular concern as failure in bonding properties leads to deadhe- sion and loss in performance. In this study, three groups of multilayer coupons with different combinations of polyimide, adhesive, and copper, were subjected to 1000 h of damp heat exposure (85 ◦C/85 %RH). The degradation pathway was modeled in a < Stressor|Mechanism|Response > framework using network structural equation modeling (netSEM). netSEM degradation modeling was used to visualize and predict the extent of materials degradation according to identifed degradation mechanisms and investigate the impact of the presence of copper on the adhesive bonding performance. Therefore, the inclusion of copper in the stack resulted in weakening of the interfacial adhesion and the identifed degradation pathway includes moisture and copper diffu- sion through the adhesive.

Committee: Laura Bruckman (Committee Chair); Roger French (Committee Member); Ina Martin (Committee Co-Chair) Subjects: Materials Science

PhD, University of Cincinnati, 2023, Engineering and Applied Science: Materials Science

Polyimides have gained more attention in recent years due to their high thermal stability, good interfacial bonding, light weight, and good wear resistance and corrosion, factors that make them find great applications in the field of aerospace and advanced equipment. Many advancements have been made in improving the thermal, mechanical, and wear properties of polyimides. The use of nanofillers such as carbon nanotubes, graphene, graphene oxide, clay, and alumina has been studied. Some challenges with nanofillers are dispersion in the polymer matrix and interfacial adhesion; this has led to surface modification of the fillers. Differential scanning calorimetry and thermogravimetric analysis were used to study the thermal degradation, stability, and the heat of decomposition of polyimide-graphene and polyimide-graphene-clay nanocomposites. Polyimide-graphene nanocomposites containing 10, 20, 30, 40, and 50 wt.% of multilayered graphene sheets were heated at a rate of 10 and 30 °C/min in air and in nitrogen atmosphere, respectively. The rate of mass loss was found to remarkably decrease by up to 198% for nanocomposites containing 50 wt.% of graphene. The enthalpy change resulting from the decomposition of the imide ring was found to decrease by 1166% in nitrogen atmosphere, indicating the outstanding heat-shielding properties of multilayered graphene sheets due to their high thermal conductivity. The enthalpy changes due to combustion, obtained from differential scanning calorimetry, were used to calculate the theoretical heat release rates, a major parameter in the determination of flammability of polymers. The heat release rate decreased by 62% for composites containing 10 wt.% of graphene compared to the neat polyimide matrix. The combined interaction of graphene and polyimide led to an overall decrease in the heat release rate. Thermogravimetric data was used to predict the limiting oxygen index of the neat polyimide and the nanocomposites. The limiting oxygen inde (open full item for complete abstract)

Committee: Jude Iroh Ph.D. (Committee Chair); Vesselin Shanov Ph.D. (Committee Member); Yoonjee Park Ph.D. (Committee Member); Peter Disimile Ph.D. (Committee Member) Subjects: Materials Science

PhD, University of Cincinnati, 2022, Engineering and Applied Science: Materials Science

The demand for newer, more efficient, and greener sources of energy storage materials has been a major focus of research today. With the rise in everyday gas prices and the imposition of stricter regulations on the use and eventual phasing out of fossil fuels, the electric age is brighter than ever. The challenges in technology faced in this transition have been the material limitations of storing large quantities of electrical charge and being able to dissipate it over a longer duration of time. Having an energy storage device with simultaneously high energy and power densities can make a positive global impact on the environment, and renewable energy systems. Lithium-ion batteries have evolved and transcended in the recent past to power almost every device across the spectrum, from watches to electrical vehicles and beyond. However, these batteries require expensive metal oxides that are rather heavy and have limited life cycles. This research looks at organic polymeric supercapacitors as an alternative form of energy storage material to address these limitations. The inherent advantages of supercapacitors include high power and energy densities, greater charge cyclability, longer service lifespans, and overall ease as well as the speed at which they can be charged over a wide range of temperatures. The high electrical conductivity and porosity of the electrodes contribute to the improved electrochemical performance of the supercapacitor. A multifunctional polyimide-based single-walled carbon nanotube (SWCNT/PI) nanocomposite is the focus of this research. This study investigates the effect of surface morphology on the electrochemical properties of the polymer nanocomposite prepared by the electrodeposition of doped polypyrrole (PPy) which is an inherently conducting polymer. The dopants used to enhance PPy are analyzed in this research and include p-Toluene sulfonic acid (TSA), Naphthalene disulfonic acid (NDSA), Naphthalene trisulfonic acid (NTSA), Dodec (open full item for complete abstract)

Committee: Jude Iroh Ph.D. (Committee Member); Randall Allemang Ph.D. (Committee Member); Mark Schulz Ph.D. (Committee Member); Yoonjee Park Ph.D. (Committee Member); Michael Mains M.S. (Committee Member) Subjects: Materials Science

Master of Science in Polymer Engineering, University of Akron, 2021, Polymer Engineering

In this study, high specific surface area syndiotactic polystyrene (sPS) and polyimide (PI) gels were used in dye adsorption from aqueous solutions. Gels in the form of monoliths and microparticles produced via microfluidic flows were used. Gel microparticles with multiple internal holes were fabricated by adjusting the buoyancy and surface forces. The gel particles and monoliths were supercritically dried for characterization purposes. The performance of such materials as adsorbents was evaluated by conducting dye adsorption experiments with factors such as dye concentration in solutions, pH values, nature of polymer in the gels, and adsorbent shape and size. Both methylene blue and Sudan III were used for adsorption experiments, although the mechanism of adsorption of methylene blue was elaborated. The results revealed that π-π interactions due to the presence of benzene rings played a role, while adsorption of a cationic dye was dependent on the electrostatic interactions between the dye molecules and the PI surface. The extent of adsorption of methylene blue on PI reduced with a reduction of pH. The adsorption mechanism was explained using the affinity between the adsorbents and the adsorbates. The adsorption kinetics of methylene blue was described using a pseudo-second order adsorption model.

Committee: Sadhan Jana PhD (Advisor); Fardin Khabaz PhD (Committee Chair); Weinan Xu PhD (Committee Member) Subjects: Polymers

Master of Science in Polymer Engineering, University of Akron, 2020, Polymer Engineering

In the recent years, thermoset powder coating has been overgrowing as a clean and environmentally friendly technology to respond increasing demands of environmental legislation and global regulatory attention for reducing Volatile Organic Compounds (VOC) in the coatings industry. It uses 100% solid components formulation including resins, pigments, fillers, curing agents, and other additives. Resins usually determine the properties of the coating such as abrasion resistance, corrosion protection, adhesion, and weatherability. Based on the resin or binder used in the powder coating, there are two coating systems: thermoplastic and thermoset. UV-powder coating was developed to achieve low-temperature thermoset curing. Incorporation of both powder curing and UV technologies provides rapid cure at lower temperatures which is suitable for heat-sensitive substrates like wood or plastic. In the UV-powder coating, the melt flow process is separated from the curing. When the coating applied on the substrate, it will be heated to the melt; then, cured by the UV light. Since the melt temperature is lower than usual, conventional cosmetic problems such as orange-peel effect and poor leveling are minimized in the UV-powder coating. In the present study a UV-curable bismaleimide methacrylated polyimide (BMI-PI-MA) was synthesized and fully characterized. BMIs are classified as thermoset polyimides (PI) with two maleimide end groups. These resins can do either thermal or UV curing. BMIs have high Tg, high thermal stability, high chemical resistance, and excellent mechanical properties. Synthesized BMI-PI-MA was mixed and formulated at different contents with a commercially available resin, UVECOAT, to study the application of UV powder coating. Resulted blends have shown the formation of polymer networks at the molten state and under UV light. Properties of UV cured films were investigated by thermomechanical analysis (TMA), differential scanning calorimetry (DSC), and dynam (open full item for complete abstract)

Committee: Mark D. Soucek PhD (Advisor); Kevin A. Cavicchi PhD (Committee Member); Thein Kyu PhD (Committee Member) Subjects: Chemical Engineering; Engineering; Polymer Chemistry; Polymers

MS, University of Cincinnati, 2019, Engineering and Applied Science: Materials Science

This research is focused on investigating the effect of ex-situ addition of Graphene (GR) on rheological, structural, mechanical and electrochemical properties of Polyimide/Poly (dimethyl siloxane) (PI/PDMS) copolymer. The composite is thereby characterized for electrochemical energy storage applications. Graphene-based polymers are widely being researched as high-performance electrode materials for supercapacitor and battery applications due to their unique properties such as high current density, high thermal conductivity and excellent mechanical behavior. PI/PDMS is a copolymer that combines the high thermal stability and chemical resistance of PI with excellent flexibility and hydrophobicity of PDMS. Herein, the performance of this flexible thin film nanocomposite as an electrode material with optimum graphene loading is evaluated and reported.

Committee: Jude Iroh Ph.D. (Committee Chair); Je-Hyeong Bahk Ph.D. (Committee Member); Woo Kyun Kim Ph.D. (Committee Member) Subjects: Engineering

MS, University of Cincinnati, 2019, Engineering and Applied Science: Materials Science

In this project the effect of polyacrylonitrile (PAN) on thermal and mechanical properties of polyimide (PI) was studied. The aim of this study is to formulate multifunctional polyimide/polyacrylonitrile film by combining excellent properties of polyimide such as high solvent and wear resistance, high dimensional stability, excellent thermal resistance and high modulus with the superior properties of polyacrylonitrile such as low density, thermal stability, high strength and modulus of elasticity. Polyacrylonitrile is a high-performance polymer that unlike others has the capability to form highly oriented molecular structure when subjected to a low temperature heat treatment. It has applications in ultra-filtration membranes, hollow fibers for reverse osmosis and fibers for textile. It is also pre-cursor material for the manufacture of carbon fibers which are characterized by high stiffness, high tensile strength, low weight, high chemical resistance, high temperature tolerance and low thermal expansion. In this study, a polyimide blend containing different weight percentages of polyacrylonitrile (0.1, 0.5, 1, 5 and 10 wt%) was fabricated into thin films and characterized for thermal properties using Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). Structural and mechanical properties were evaluated using Fourier Transform Infrared Spectroscopy (FTIR) and Dynamic Mechanical Analysis (DMA), respectively. Morphology was studied using an Optical Microscope. From FTIR, the degree of Imidization of the blend was found to be 97.5%. Tg of the copolymer was calculated to be ~370ºC from the tan d peak obtained from DMA. While the 10wt% PAN/PI blend exhibits the highest Tg, the 1% exhibits the highest damping ability. Rate of change of enthalpy was calculated using Differential Scanning Calorimetry which shows that increasing the content of PAN resulted in a decrease in heat release. Percentage mass retained and char retention calculations wer (open full item for complete abstract)

Committee: Jude Iroh Ph.D. (Committee Chair); Jonathan Nickels Ph.D. (Committee Member); Yoonjee Park Ph.D. (Committee Member) Subjects: Polymers

Doctor of Philosophy, University of Akron, 2019, Polymer Science

Within this thesis, a statistical design of experiments was employed to synthesize and analyze novel polyimide aerogels with enhanced, specific properties for aeronautic, aerospace, and commercial applications. The main objective of this research was to create a novel material combining chemistries that will result in improvement to physical and optical properties of polyimide aerogels. This study varied backbone chemistry of polyimide aerogels to tailor properties such as pore volume, pore size distribution, shrinkage, free volume, thermal stability, and optical transparency. Polymer aerogels exhibit a much higher structural integrity over silica-based counterparts; and polyimides offer a much higher temperature range than many polymers. However, the challenge with most conventional polyimides is the coloration from pale yellow to deep brown. Issues such as opacity, can be addressed by the incorporation of fluorocarbon monomers and bulky substituents into the polyimide backbone prior to gelation. In addition, characteristics such as shrinkage and onset of decomposition temperatures can be enhanced to more desirable ranges. Multiple routes were examined to study the effects of combining various diamines, dianhydrides, and multifunctional cross-linkers with the objective of producing high performance polyimide aerogels. Herein we examine the effect of fluorocarbon pendant groups on the backbone of the polymer matrix in regard to optical and physical properties

Committee: Coleen Pugh PhD (Advisor); Mary Ann Meador PhD (Committee Member); Kevin Cavicchi PhD (Committee Member); Sadhan Jana PhD (Committee Member); Yu Zhu PhD (Committee Member) Subjects: Aerospace Materials; Chemistry; Nanotechnology; Polymer Chemistry; Polymers

Doctor of Philosophy, University of Akron, 2019, Polymer Engineering

This research centers on combining different disparate technologies with the aerogel fabrication process to the control of nano, micro and macrostructure of aerogel morphology. It is envisioned that this control over structure at different length scales will enable aerogels to be used for various applications such as drug delivery, nanoparticle filtration or oil/water separation. Aerogels are a class of highly porous structures (>90% porosity) with inherently small pores with size typically in the range of 2-200 nm. These small pores are achieved through a combination of both the gel formation and supercritical drying steps, differentiating aerogels from other porous material counterparts (e.g. foams). The control of morphology is accomplished through manipulation of phase growth, introduction of dispersed phase liquids and templating of structures via 3D printing in conjunction with the aerogel fabrication process to produce a variety of aerogel structural forms such as foams, microparticles and mechanical metamaterials. In this work, two different polymeric material systems were studied, namely syndiotactic polystyrene and polyimide. Syndiotactic polystyrene was selected as it forms physically crosslinked, thermo-reversible gels which allow for on-demand gelation, as well as compatibility in water-in-oil emulsion systems. Polyimide was selected as a condensation sol-gel system provides increased flexibility in aerogel mechanical and chemical properties through different monomer selection. It was identified that chemical reaction kinetics, solvent effects, interfacial conditions and kinetics of phase separation all impact and control the structure-property relationships of aerogel materials. The body of work presented in this dissertation covers a wide variety of topics such as new synthesis of aerogel monoliths, microparticles and foams. The fabrication of these aerogel structures required thorough understanding of water-in-oil and oil-in-oil emulsion syst (open full item for complete abstract)

Committee: Sadhan Jana (Advisor); Younjin Min (Committee Chair); Bryan Vogt (Committee Member); Coleen Pugh (Committee Member); George Chase (Committee Member) Subjects: Polymer Chemistry; Polymers

Doctor of Philosophy (Ph.D.), University of Dayton, 2018, Materials Engineering

PMR-type polyimide prepregs are challenging to fabricate into high quality composites due to volatiles that are generated and must be removed in-situ during processing. Despite several decades of academic and industrial study, the core challenge of effective and repeatable volatile removal has still plagued manufacturers of polyimide composite structures. A method for the in-situ characterization and modeling of polyimide compaction during composite fabrication would greatly help in understanding and controlling the process. To this end, the current work was conducted to develop a polyimide prepreg compaction model, as well as practical characterization techniques for the resin rheology, volatile generation, and subsequent volatile removal from the prepreg stack during composite fabrication. Two PMR-type polyimide / carbon fiber prepreg systems were studied: one containing a simplified / model resin system, and one containing the commercially available RM-1100 resin system. Thermal analysis was used to characterize volatile generation, reaction rates, and rheology for each prepreg system. A novel approach was used to measure the thickness of a prepreg stack in-situ during vacuum bag / oven processing using a high-temperature LVDT. Neural networks were then used to model the volatile generation, rheology, and composite compaction. These tools were then combined in a global model that showed the key interrelationships in these coupled phenomena and how that information can be used to select the optimum temperature of pressure application to minimize void content. Two autoclave trials were conducted for RM-1100 which demonstrated the ability to reduce void content from 9.5% to 3.1% by using the information and criteria developed by this methodology. Overall the results showed that the methods developed in this study were able to accurately measure polyimide prepreg thickness in-situ during the imidization phase of the cure and were effective in cure cycle opt (open full item for complete abstract)

Committee: Donald Klosterman (Advisor) Subjects: Materials Science

Master of Science, University of Akron, 2018, Polymer Engineering

Oil or petroleum is one of the most important natural resources in the world today. However, there are associated risks with the transportation of oil. Since the beginning of oil exploitation, oil spills have occurred. An oil spill always brings about a deleterious impact to the environment and marine ecosystem, making oil cleanup an urgent requirement. There are many mature solutions for oil remediation, with absorption being one of the most efficient methods. The use of porous materials as absorbents has been widely investigated, and aerogels are good candidates, owing to their ultra-porosity and large surface area values. In the first part of this study, the potential of using polyimide (PI) aerogel and emulsion templated (ETPI) aerogel foams as absorbents for oil and water was investigated. PI and ETPI aerogels were fabricated from condensation polymerization between pyromellitic dianhydride (PMDA), 2,2'-dimethylbenzidine (DMBZ), and tris(2-aminoethyl) amine (TREN) dissolved in dimethyl formamide (DMF). Emulsion templating was also introduced by using an oil-in-oil emulsion system, stabilized by a non-ionic block copolymer surfactant F127® (trademark of BASF). The aerogel foams were obtained by supercritical drying of the corresponding organogels. The effect of surfactant concentration, polyimide concentration, and dispersed phase content on aerogel properties (density, porosity, surface area, oil and water absorption) was studied. The resulting ETPI aerogel foams displayed high surface area (239 m2/g to 782 m2/g), low bulk density (0.033 g/cm3 to 0.083 g/cm3) and high porosity (94.4% to 98.4%). Highest values of total oil absorption (30.00 mL/g) and initial rate (2.941 mL/g·s) was obtained from those ETPI aerogels with high dispersed phase (45%), low polyimide concentration (4 wt%), and low surfactant concentration (0.5 vol%). Aerogels with low polyimide concentration (4 wt%) showed water resistance ability. In the second part of this study, a novel syndiot (open full item for complete abstract)

Committee: Sadhan Jana (Advisor); Nicole Zacharia (Committee Chair); Younjin Min (Committee Member) Subjects: Chemical Engineering; Chemistry; Materials Science; Polymers

Master of Science, University of Akron, 2018, Polymer Engineering

This research concentrated on two parts. The first part focused on shrinkage reduction of polyimide (PI) aerogels using graphene oxide (GO) filler materials. Such materials are then used for enhanced oil absorption ability. The second part involved development of thermal stable solid-state ionogel electrolyte membrane materials for Li-ion batteries (LIBs). PI aerogels suffer from inevitable, high volume shrinkage during supercritical drying process, and its hydrophilic properties prevent potential applications as absorbents of oil and other non-polar organic liquids. A feasible method to tackle both the issues is to introduce GO into the PI aerogel structures. This was achieved first by allowing GO to react with pyromellitic dianhydride (PMDA) and obtaining GO-modified PMDA. These are used in synthesis of PI-GO composite gels through sol-gel polymerization process involving GO-modified PMDA and 2,2'-dimethybenzidine (DMBZ), together with 1, 3, 5-tris (4-aminophenyl) benzene (TAB) as the crosslinking agent. DMF was used as the solvent. The composite aerogel specimens were obtained through supercritical drying in liquid CO2. For comparison, the unmodified PI aerogel specimens were prepared using the same method minus the GO. The influence of content of GO on diameter shrinkage of the monoliths, oil absorption capacity, and other physical properties was investigated. The resulting composite aerogels showed high surface area (>505 m2/g), high porosity (>93%) and low bulk density (<0.0905 g/cm3). A strong relationship was observed between GO concentration in solutions and diameters shrinkage of aerogels. For example, a system with GO concentration of 0.55 wt% led to diameter shrinkage to 0.8 % compared to 9.0 % for unmodified monoliths. Meanwhile, oil absorption capacity of PI-GO composite aerogels was found to be greatly enhanced. To fully understand the reason behind oil absorption capacity enhancement, the surface energy of PI-GO composite aerogels and PI aerogels w (open full item for complete abstract)

Committee: Sadhan Jana (Advisor); Kevin Cavicchi (Committee Chair); Nicole Zacharia (Committee Member) Subjects: Energy; Materials Science; Polymers

Doctor of Philosophy, University of Akron, 2016, Polymer Engineering

This work is a part of collaborative project between Multidisciplinary University Research Initiative (MURI) through which an advanced polymeric capacitor films for military applications were designed. Two of those novel polymers were PPOH (hydroxyl functionalized isotactic polypropylene with comonomer of 10-hydroxy-1-undecen) and PI(BTDA-DAH) (Polyimide 3,',4,4'-benzophenone tetracarboxylic dianhydride and 1,6-diaminohexan). This dissertation focused on the effect of processing conditions on the mechano-optical behavior of PPOH and PI(BTDA-DAH). Firstly, the real-time mechano-optical behavior of PPOH containing 0.4 mol % comonomer and its comparison with unmodified polypropylene (PP) were studied in the partially molten state during processing cycle of heating, stretching, annealing, and cooling. It was revealed that the crystalline network dominated the material response during the processing cycle for both polymers. However, the presence of hydrogen bonding between the hydroxyl groups in PPOH was found to affect the structural evolution of the PPOH copolymer significantly more than compared to the PP homopolymer. Secondly, the real-time mechano-optical behavior of PI(BTDA-DAH) was studied in the glassy and the rubbery states as a function of processing temperature and stretching rate during uniaxial deformation. Thee regimes of stress optical behavior were revealed. First, at the early stage of deformation the stress optical rule is observed; birefringence linearly increased with a stress optical constant of 17.8 GPa-1 - regime I. Second, a deviation from linearity took place. At higher temperature and/or lower stretching rate the deviation is positive and the birefringence rapidly increases while the stress slowly increases- regime II. At lower temperature and/or higher stretching rate this deviation of linearity is negative- regime IIIa. Third, in cases where regime II is revealed, it was followed by a negative deviation of birefringence (open full item for complete abstract)

Committee: Mukerrem Cakmak Ph.D (Advisor); Robert Weiss Ph.D. (Advisor); Mark Soucek Ph.D (Committee Chair); Abraham Joy Ph.D (Committee Member); Chrys Wesdemiotis Ph.D (Committee Member) Subjects: Polymers

Doctor of Philosophy, University of Akron, 2016, Polymer Engineering

We investigated the effects of polymerization conditions, such as temperature, the polarity of the solvents, and microscale confinement during sol-gel transition, on the microstructure and physical properties of the resultant polymer aerogels. This work includes two main parts. (1) Studies of properties and formation mechanism of polybenzoxazine aerogels showing spherical and cylindrical building blocks; (2) Evaluation of properties of the aerogels obtained from the gel precursors synthesized in an oil-in-oil emulsion and a macroporous polymer host, in comparison to the normal aerogel monoliths. In the first part (Chapter III & Chapter IV), p-toluenesulfonic acid (TSA) was used as the catalyst for cationic ring opening polymerization of benzoxazine to produce polybenzoxazine (PBZ) aerogels. The PBZ aerogel building blocks (spheres vs. strands) and pore surface area show strong dependence on the solvent and the gelation temperature. The use of dimethyl sulfoxide (DMSO) and dimethylacetamide (DMA) led to spherical particle networks while fibrillar networks were obtained using N-methyl-2-pyrrolidone (NMP). In order to thoroughly understand the formation of these two types of networks, a combination of dynamic light scattering (DLS) and static light scattering (SLS) was used to monitor the growth of polymer networks during polymerization. The light scattering results revealed that polymer networks formed via nucleation and growth mechanism. In addition, the shape of building blocks was found to be associated with the concentration of the nuclei and the gelation time. In DMSO, a higher concentration of nuclei resulted a fast crowding of the building blocks that constituted the gel network. However, at low concentration of the nuclei and at long gelation times, the spherical building blocks evolved into cylinders by self-assembly and formed a fibrillar network when NMP was used as the solvent. Originally, the differences in the concentration of nuclei were due to the (open full item for complete abstract)

Committee: Sadhan Jana PhD (Advisor); Younjin Min PhD (Committee Chair); Bryan Vogt PhD (Committee Member); Li Jia PhD (Committee Member); Jiahua Zhu PhD (Committee Member) Subjects: Polymers

Doctor of Philosophy, Case Western Reserve University, 2016, Chemistry

Polycarbonate (PC)/poly(vinylidene fluoride) (PVDF) multilayer films (MLFs) with normal PC and high temperature PC (HTPC) were studied with broadband dielectric spectroscopy (BDS), electric displacement-electric field (D-E) loop, leakage current, and breakdown measurements to determine their high temperature performance and loss mechanism. The MLF containing HTPC performed better, which is attributed to its higher glass transition temperature (Tg), better maintaining interfacial polarization and providing a “blocking electrode” preventing charge carrier injection from PVDF into PC. Twelve (12) new polyimides (PIs) with nitrile (CN) groups attached to the polymer main chains were studied with BDS and D-E loop measurements. A ratio of experimental and theoretical dipolar polarization was calculated to estimate how easily the CN dipoles could rotate in response to the external electric field. Experimental results show that adding polar groups to PIs increased the permittivity but dielectric loss increased too because the dipoles in the rigid PI structures were difficult to rotate. An online mass spectrometry probe was developed for the detection of volatile reaction products and intermediates of electrochemical reactions in an aqueous solution. A wall-jet configuration was used to produce a laminar flow of electrolyte on the surface of a solid Au electrode in the center of the probe. The mass spectrometric ion current correlated well with the hydrazine oxidation current.

Committee: Lei Zhu (Advisor); Clemens Burda (Committee Chair); Anna Samia (Committee Member); Geneviève Sauvé (Committee Member); Donald Schuele (Committee Member) Subjects: Aerospace Materials; Automotive Materials; Chemistry; Energy; Polymers

Doctor of Philosophy, Case Western Reserve University, 2015, Macromolecular Science and Engineering

Aerogels are an interesting class of materials that possess many exotic and extreme properties. These properties are developed as the gel network is produced from solution. As the gel develops, it builds a hierarchical structure, possessing architectures at different size scales through molecular and macro-scale interactions. Once the solvent is removed, and the resultant aerogel is produced, the hierarchical nature of the material produces many desirable properties including: extremely high porosities (greater than 90% pore volume)[1], extremely low thermal conductivities (10-30 mW/m-k)[1], very low densities (as low as 0.002 g/cm3)[2], low refractive indices (as low as 1.01),[3] low dielectric constants (between 1.0 and 1.5),[4] high surface areas,[5,6] and the slowest speed of sound through a solid material. The first chapter of this thesis deals with the structure/property relationships of polymer/clay aerogels interfused with uniformly distributed air bubbles were examined. Through the incorporation of a polyelectrolyte in a montmorillonite (MMT) clay solution, the viscosity was systematically changed by the addition of ions with different charges. The bubbles were achieved via high speed mixing and were stabilized through the use of the surfactant sodium dodecyl sulfate (SDS). As the charge of the ion increased from +1 (Na+ ions) to +2 (Ca2+ ions) to finally +3 (Al3+ ions), the modulus of the resultant aerogels increased. The foamed polymer/clay aerogels showed a reduction in thermal conductivity while retaining similar mechanical properties to unfoamed polymer/clay aerogels. The most promising composition was one which contained 5% MMT clay/5% poly(vinyl alcohol)/0.5% xanthum gum/0.5% SDS/0.2% Al2(SO4)3·6(H2O) possessing a density of 0.083 g/cm3, an average modulus of 3.0 MPa, and a thermal conductivity of 41 mW/m·K. The second project investigated the feasibility of incorporating ground recycled polyurethane (PU) foam into clay/polymer aerog (open full item for complete abstract)

Committee: David Schiraldi Ph.D. (Advisor); Mary Ann Meador Ph.D. (Advisor); Gary Wnek Ph.D. (Committee Member); Eric Baer Ph.D. (Committee Member) Subjects: Aerospace Materials; Automotive Materials; Chemistry; Engineering; Experiments; Inorganic Chemistry; Materials Science; Organic Chemistry; Polymer Chemistry; Polymers

Doctor of Philosophy, University of Akron, 2015, Polymer Engineering

An array of mesoporous polymeric aerogels is synthesized in this work via gelation in condensation polymer systems. The monomers are chosen to yield softer, stiffer, or packable chains, and aerogel morphologies with controllable pore size distribution and surface area. A trifunctional amine crosslinker at low concentration (<1 wt%) is used in each case. The first system consists of polyurea aerogels with the porosity and shrinkage controlled via hydrogen bonding. These aerogels have mean pore diameters 9-16 nm, bulk density 0.19-0.26 g/cm3, porosity 79-86%, surface areas 106-309 m2/g, and compressive moduli of 12-69 MPa. The second system involves resilient poly(urethane urea) aerogels synthesized from aliphatic polyols. These aerogels are slightly more dense than polyurea aerogels (0.20-0.35 g/cm3) with similar porosity (71-85%), lower surface areas (47-163 m2/g), and similar compressive moduli (12-52 MPa). The polyol weight fraction can be used to control the extent of hydrogen bonding involving urea and urethane groups and consequently the aerogel shrinkage. In the third polymer system, polyimide and poly(urethane urea) segments are combined in the same poly(imide urethane urea) chains to yield aerogels with additional stiffness from the polyimide moieties. These aerogels are less dense (0.10-0.22 g/cm3) with higher porosity (82-92 %), and surface area between 117-358 m2/g. The surface area increases and the pore size distribution narrows as the polyol content is lowered. The fourth system focuses on translucent polyimide aerogels. These aerogels have low density (0.10-0.37 g/cm3), high porosity (73-93%), and high surface area (378-858 m2/g) due to rough fibrillar building blocks and narrow pore size distributions, and high compressive moduli (13-67 MPa). In the final system, a one-pot synthesis method is used to obtain fluorinated polyimide gels and aerogels. These polyimide aerogels are structurally uniformity at nano- and micro-scales, indicating that the fluo (open full item for complete abstract)

Committee: Sadhan Jana Dr. (Advisor); Mary Ann Meador Dr. (Advisor); Kevin Cavicchi Dr. (Committee Chair); Bryan Vogt Dr. (Committee Member); Mesfin Tsige Dr. (Committee Member); Gang Cheng Dr. (Committee Member) Subjects: Engineering; Materials Science; Polymer Chemistry; Polymers

Master of Science (MS), Wright State University, 2014, Chemistry

A series of oxyalkylene containing diamines, 1,4-bis(2-(4-aminophenoxy)-ethoxy)benzene, 2,2-bis[4-(2-(4-nitrophenoxy)ethoxy)phenyl]hexafluoropropane, 9,9-bis(4-(2-(4-nitrophenoxy)ethoxy)phenyl)fluorene, and bis(4-(2-(4-nitrophenoxy)ethoxy)-phenyl)diphenylmethane, has been synthesized from the reduction of 1,4-bis(2-(4-nitrophenoxy)ethoxy)benzene, 2,2-bis[4-(2-(4-nitrophenoxy)ethoxy)phenyl]-hexafluoropropane, 9,9-bis(4-(2-(4-nitrophenoxy)ethoxy)phenyl)fluorene, bis(4-(2-(4-nitrophenoxy)ethoxy)phenyl)diphenylmethane, respectively. The diamine compounds were reacted reacted with 6FDA to obtain the corresponding polyimide. The polymerization was done in a one-pot reaction with m-cresol and isoquinoline. The polyimides displayed glass transition temperatures ranging from 186-231°C and thermal stability >400°C.

Committee: William Feld Ph.D. (Advisor); Eric Fossum Ph.D. (Committee Member); David Grossie Ph.D. (Committee Member) Subjects: Chemistry

Doctor of Philosophy, University of Akron, 2013, Polymer Engineering

Physical and chemical changes during the complex multi-step thermal imidization reaction were investigated including all processing steps (solution casting, drying and imidization), using newly developed highly instrumented measurement systems. These instruments allowed us to observe the dynamic relationship between the bound solvent evaporation that causes relaxation and chain orientation during the imidization. Drying and imidization of PMDA-ODA solutions in NMP were investigated by a novel custom designed measurement system that tracks real time weight, thickness, surface temperature, in-plane and out-of-plane birefringence. At low temperature drying stage (T<120°C), the weight and thickness reductions occurred rapidly as a result of solvent evaporation. All the parameters started leveling off while the out of plane birefringence steadily increased and reached a plateau at longer drying times. When the temperature was increased for imidization reaction (T=200°C), additional weight loss accompanied by temporary reduction of birefringence was observed due to evaporation of bound solvent as solvent molecules decomplexed from the polymer chains and plasticized the film. During the latter stage, out-of-plane birefringence rose rapidly as the polymer chains increasingly became oriented with their chain axes were preferentially oriented in the film plane. Throughout the whole process the in-plane birefringence remained zero. For the first time, these real time measurements allowed us to quantitatively show the dynamics between chain relaxation due to evaporation of the decomplexed solvent molecules, and orientation development due to decreased chain mobility caused by imidization reaction and increasing Tg for the PMDA-ODA/NMP solutions. In addition, the dynamics of this interplay was investigated by varying the processing conditions: initial casting thickness and drying temperature. Chemical conversion, bound solvent and chain orientation that take place du (open full item for complete abstract)

Committee: Mukerrem Cakmak Dr. (Advisor); Mark Soucek Dr. (Committee Member); David Simmons Dr. (Committee Member); Coleen Pugh Dr. (Committee Member); Chrys Wesdemiotis Dr. (Committee Member) Subjects: Chemical Engineering; Chemistry; Materials Science; Polymer Chemistry; Polymers