PhD, University of Cincinnati, 2018, Pharmacy: Pharmaceutical Sciences/Biopharmaceutics

Controlled release oral dosage form offers great advantages over conventional dosage form by providing steady drug plasma concentration, decreasing the frequency of administration, and providing enhanced patient compliance. However, orally ingested tablet is exposed to varying pH conditions and fluctuating mechanical agitations during its travel through the gastrointestinal tract (GIT). Selection of materials that provide controlled release mechanism to the oral dosage form is important as they can a) minimize drug release rate fluctuations for ionizable drugs during its travel along the changing pH environment of the GIT and b) maintain the release rate mechanism even when subjected to the physiological mechanical agitation forces. To examine these two important requirements, matrix tablets prepared using low glass transition temperature (Tg) silicone pressure sensitive adhesive (PSA) were evaluated and compared with matrix tablets prepared using high Tg ethyl cellulose (EC). Specifically, the effect of dissolution medium pH on drug release from binary tablets consisting of the polymer and ionizable model drugs verapamil hydrochloride and diclofenac sodium was studied using USP dissolution apparatus (without mechanical stress). The effect of simulated physiological mechanical stress agitation on drug release was studied using dissolution stress test apparatus for non-ionizable model drug acetaminophen. Mechanical properties, physical structures, electrical resistance, water uptake, and contact angle of pure polymer films and of matrix tablets were studied to understand the relationships of these factors to drug release. Our study indicated that increasing polymer amount decreased drug release rate from both silicone PSA and EC tablets using USP dissolution apparatus. However, silicone PSA tablets showed lower friability compared to EC tablets. The application of physiological simulated mechanical stress affected drug release from high Tg EC tablets that resulte (open full item for complete abstract)

Committee: Kevin Li Ph.D. (Committee Chair); Pankaj Desai Ph.D. (Committee Member); Sergey Grinshpun Ph.D. (Committee Member); Gerald Kasting Ph.D. (Committee Member); Gary Kelm Ph.D. (Committee Member); R. Randall Wickett Ph.D. (Committee Member) Subjects: Pharmaceuticals

Doctor of Philosophy, University of Akron, 2024, Polymer Science

Polyethylene (PE) and isotactic polypropylene (iPP) are the two most abundant commodity plastics. However, these materials are incompatible in the melt blend due to the different surface energies owing to the difference in their microstructures. The transfer of stress between incompatible phases of these polymers is a challenge that contributes to mechanical recycling process losses. This prevents the mixed mechanical recycling of these polymers to yield commodity plastics for high performance applications compared to the virgin resins. As a result, there is a lack of incentive to recycle mixed plastic waste, thereby contributing to plastic pollution in the environment. Compatibilizer additives improve the performance of these blends, through non-covalent, supramolecular, and covalent interactions across PE/PP interfaces. By introducing a small amount of compatibilizer into recycled polyolefin blends, there is potential to enhance the properties, reduce waste plastic, and achieve these in economical fashions. This work investigates several methods of delivering copolymer reinforcing agents which include supramolecular coupling through diverse architectures, namely diblock structures that are proposed to form in-situ and preformed multiblock architecture. The first part of this work will highlight the synthesis of a compatibilizer system consisting of end-functionalized iPP and HDPE. These materials are referred to as Interfacial Supramolecular Coupling Agents (ISCAs) due to their proposed ability to form supramolecular H-bonds across the bulk PE/PP interfaces. The synthesis of high melting-temperature iPP with controlled molecular weight and end-group fidelity is described. Through a sequence of reactions, vinyl end-functionalized iPPs and PEs are converted to β-alanine trimer terminated polyolefins, which are being studied as potential compatibilizers for PE/PP blends. A second strategy describes the use of pre-synthesized multiblock compatibilizers which have hi (open full item for complete abstract)

Committee: Toshikazu Miyoshi Dr. (Committee Member); James Eagan Dr. (Advisor); Donald Quinn Dr. (Committee Member); Junpeng Wang Dr. (Committee Member); Mesfin Tsige Dr. (Committee Chair) Subjects: Chemical Engineering; Chemistry; Materials Science; Plastics

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

Effective utilization of biomass waste as a filler material to thermoplastic polymers has been a subject of interest for the recent years. Creating sustainable, renewable and eco-friendly filler to tailor the properties of the composite requires further processing. Thermal conversion using pyrolysis process was utilized to convert the unstable biomass filler Soybean hulls (SBHs) to more stable material. In this research, the SBHs were pyrolyzed at 500 °C then incorporated in Polyamide-6 (PA-6) by various particle sizes and loading levels. The intent of this research is to examine the mechanical, thermal, water absorption and morphological properties of the composite materials and compare them with PA6, Poylamide-66 (PA-66) and PA6 Carbon Black (CB) composite. Ball milling process was utilized to reduce the size of Pyrolyzed SBHs (PSBHs). Two batches of PSBHs named as PSBH-A and PSBH-T were used. PSBH-A refers to the as received particle sizes without any treatment which are in the range of 90 to more than 710 µm. PSBH-T refers to the treated particles by performing ball milling process. The sizes of PSBH-T particles were reduced to an average of 5 µm. 10, 20 and 30% of PSBH-A and PSBH-T were mixed with PA6, extruded and injection molded to create rectangular and dog bone shape samples. For mechanical properties, the addition of PSBH-T increases the tensile strength and modulus of the final composite reaching higher values compared to PA6, PA66, PSBH-A/PA6 and CB/PA6. Elongation at break and notched Izod impact were decreased with the addition of PSBH-A and PSBH-T. For the thermal properties, the addition of PSBH-A and PSBH-T increase the Heat Distortion Temperature (HDT) and decrease the Thermal Degradation Temperature (TDT) and heat of fusion. For water absorption, a slight increase was observed with the addition of PSBH-A and PSBH-T.

Committee: Sancaktar Erol (Advisor); Gong Xiong (Committee Chair); Eagan James (Committee Member) Subjects: Engineering; Environmental Engineering; Environmental Management; Polymers; Sustainability

Doctor of Philosophy, University of Akron, 2020, Polymer Engineering

Colors are ubiquitously present in nature and are used in several day-to-day applications such as paints, textiles, cosmetics and displays. Most of these colors are pigment-based and suffer from non-environment friendliness, toxicity and non-tunability. Structural colors have received significant attention as alternatives to degradation-prone pigment-based colors. Many non-iridescent (angle-independent) structural colors in nature are produced from porous bio-polymer nanostructures with multi-functional properties such as UV-protection and hydrophobicity. However, most bioinspired synthetic non-iridescent structural colors have been attained via self-assembly of colloids and 3D printing, but they suffer from poor adhesion and robustness. Non-iridescent structural colors in nature, on the other hand, are produced from quasi-ordered porous nanostructures and are thought to form by polymeric phase separation but have not yet been achieved artificially despite their advantages including scalability. The objective of this dissertation is to develop a polymeric phase-separation process that results in non-iridescent structural coloration. Here, we report, for the first time, fabrication of non-iridescent structural colors from porous polymers via temperature-induced phase-separation of compatibilized polymer blend films. By simply tuning the molecular parameters such as composition of the polymer blend (ϕ), the color of the films can be tuned from white to blue to transparent with underlying morphological transitions from a disordered to a quasi-ordered state. Control on brightness and color saturation can be achieved by tuning optical interfaces and structural order respectively at a molecular level without using any additives by tuning molecular weight of homopolymers and block co-polymer. Gradient non-iridescent structural colors were attained from films of differential thickness via tunable coffee ring effect. We further examined the absence of green and red c (open full item for complete abstract)

Committee: Alamgir Karim (Advisor); Matthew Shawkey (Advisor); Sadhan Jana (Committee Member); Xiong Gong (Committee Chair); Erol Sancaktar (Committee Member); Tianbo Liu (Committee Member) Subjects: Polymer Chemistry

Doctor of Philosophy, Case Western Reserve University, 2020, Materials Science and Engineering

Poly(methyl methacrylate), also know as acrylic, has excellent optical properties, light weight, good mechanical properties, and weatherability. Due to the balance of these outstanding properties with cost efficiency, poly(methyl methacrylate)s are widely used in architecture, medicine, electronics, agriculture, paints, aircraft, and automotive industries. However, the lifetime of poly(methyl methacrylate)(PMMA) is reduced in outdoor applications because of exposure to solar radiation, temperature, and moisture. During the polymer degradation process, a variety of environmental stressors act on the polymer leading to degradation of its properties. Although standardized durability and weathering tests are widely used to collect failure information and evaluate durability of materials based on the typical pass/fail criteria, degradation modes, mechanisms, and rates are not clearly understood. Therefore, a better understanding of degradation modes, mechanisms, and rates is critical. To optimize and extend the service life of polymer materials to more than 25 years in the outdoor environment, a domain knowledge-based and data-driven approach has been utilized to quantitatively investigate the temporal evolution of degradation modes, mechanisms and rates under various stepwise exposure conditions. Six grades of PMMA were studied, including one unstabilized and five stabilized PMMAs exposed 3200 hours in three weathering conditions. The unstabilized PMMA showed a significant YI increase of over 25, whereas a highly-stabilized PMMA showed a slight YI increase only between 0.5 to 0.7. The degradation of unstabilized acrylic, revealed by Urbach edge analysis, arises from the presence of residual MMA monomer, with a shift of absorption edge from 4.35 eV to 3.11 eV under UVA-340 irradiation. For unstabilized and partially-stabilized PMMA formulations, quantitative degradation rates (the Induced absorbance to dose (IAD)) indicates that the UVA-340 irradiation (Hot (open full item for complete abstract)

Committee: Roger French Dr. (Advisor); Mark De Guire Dr. (Committee Member); Laura Bruckman Dr. (Committee Member); Michael Hore Dr. (Committee Member) Subjects: Materials Science; Polymer Chemistry

Doctor of Philosophy, The Ohio State University, 2019, Chemical Engineering

When incorporated into polymers, nanoparticles are known to modify the structure and dynamics of nearby polymer chains. Because nanoparticles have a high surface area to volume ratio, the properties of the polymer-nanoparticle interphase region can have a significant effect on the overall composite properties even at relatively low nanoparticle loading. In this work, we study the polymer-nanoparticle interphase region using molecular dynamics simulations, and we analyze the impact of a nanoparticle on local structure, dynamics, and viscoelastic properties. Of particular interest here is a class of systems which consists of nanoparticles incorporated into two-component copolymers where one component of the copolymer interacts more favorably with the nanoparticle than the other. In these systems, modifying the particular copolymer sequence may modify the interphase properties, and composite properties may therefore be adjusted even while maintaining the same overall monomer ratio. These systems have been the subject of several simulation studies focused on nanoparticle dispersion and assembly; however, relatively little simulation work has focused specifically on the impact of copolymer sequence on properties of the copolymer-nanoparticle interphase. We simulate a simple nanocomposite consisting of a single spherical nanoparticle surrounded by coarse-grained polymer chains. The polymers are composed of two different monomer types that differ only in their interaction strengths with the nanoparticle. By studying a series of regular multiblock copolymers with adjustable block length as well as a random copolymer, we examine the effect of copolymer sequence blockiness on the structure as well as the end-to-end vector autocorrelation, bond vector autocorrelation, and self-intermediate scattering function relaxation times as a function of distance from the nanoparticle surface. We find that, depending on block length, blocky copolymers can have faster or slower inte (open full item for complete abstract)

Committee: Lisa Hall (Advisor); Isamu Kusaka (Committee Member); Kurt Koelling (Committee Member); Yiying Wu (Committee Member) Subjects: Chemical Engineering

Doctor of Philosophy, University of Akron, 2018, Polymer Engineering

Graphene and graphene oxide GO as Nano-fillers have been used in numerous applications. Reduced graphene oxide, for example, is one of the most attractive additives that have been targeted to use in polymer nanocomposites due to its strong mechanical properties, electric conductivity, and gas barrier properties. However, there are many of obstacles make it difficult to be produced in large quantity at low cost and safe processes. There are many methods to reduce graphene oxide rGO and one of the interesting one that used in this research project is solution reduction of graphene oxide using Microwave. In this project, we have investigated the time effect on reduction of graphene oxide in Microwave and its polymer application properties. We have three sub projects that have been studied for the comparison of adding graphene oxide to different time reduced graphene oxide at the same weight contents and conditions. The first project, the effect of GO and rGO on polymer thin films blend phase separation. We observed that the domain size of the polymer blend phase separation changed with adding graphene oxide comparing to reduced graphene oxide due to the interaction with polymer chain. The second project, we have investigated the addition of GO and rGO on polymer gas barrier properties. Two gases have been tested: Oxygen (O2) and Carbon dioxide (CO2) at two different pressures. The remarkable result of this project is that the addition of rGOs worked as a barrier for these gases comparing to GO and Pure films. The last- project, we have studied the effect of adding GO and rGO on polymer fibers for its oil sorption capacity application and the structure morphology of these fibers.

Committee: Karim Alamgir Dr. (Advisor); Kevin Cavicchi Dr. (Committee Chair); Joy Abraham Dr. (Committee Member); George Chase Dr. (Committee Member); Nicole Zacharia Dr. (Committee Member) Subjects: Polymers

Master of Sciences, Case Western Reserve University, 2018, Macromolecular Science and Engineering

A series of core-shell inorganic-organic hybrid nanomaterials have been proposed with gold nanoparticle as core, carbazole terminated star-like copolymer (h-PEI-b-PCL-Cbz) as shell which consist of hyper-branched polyethyleneimine (h-PEI) and three different chain lengths of poly(ε-caprolactone) (PCL). Electrostatic interaction between the PEI core and gold nanoparticles provides the possibility to form a core-shell nanomaterial by phase transfer method. By adjusting the degree of polymerization of PCL as well as the chain length of PCL, this core-shell nanomaterial has a controllability of energy transferring property and tunability of surface hydrophobicity as well as ionic probe diffusion property. These properties will help with further applications of formed core-shell hybrid system.

Committee: Rigoberto Advincula (Committee Chair); David Schiraldi (Committee Member); Lei Zhu (Committee Member); Alexander Jamieson (Committee Member) Subjects: Materials Science; Nanoscience; Polymer Chemistry

Doctor of Philosophy, Case Western Reserve University, 2016, Macromolecular Science and Engineering

CHAPTER1: A synthetic polymeric lens was designed and fabricated based on a bio-inspired, “Age=5” human eye lens design by utilizing a nanolayered polymer film-based technique. The internal refractive index distribution of an anterior and posterior GRIN lens were characterized and confirmed against design by µATR-FTIR. 3D surface topography of the fabricated aspheric anterior and posterior lenses was measured by placido-cone topography and exhibited confirmation of the desired aspheric surface shape. Furthermore, the wavefronts of aspheric posterior GRIN and PMMA lenses were measured and simulated by interferometry and Zemax software, respectively. Their results show that the gradient index distribution reduces the overall wavefront error as compared a homogenous PMMA lens of an identical geometry. Finally, the anterior and posterior GRIN lenses were assembled into a bio-inspired GRIN human eye lens through which a clear imaging was possible. CHAPTER 2: A nanolayered polymer films approach to designing and fabricating gradient refractive index lens (GRIN) lenses with designer refractive index distribution profiles and an independently prescribed lens surface geometry has been demonstrated to produce a new class of gradient index optics. This approach utilized nanolayered polymer composite materials from polymethylmethacrylate (PMMA) and a styrene-co-acrylonitrile copolymer (SAN) with a tailorable refractive index intermediate to bulk materials to fabricate discrete gradient refractive index profile materials. A process to fabricate nanolayered polymer GRIN optics from these materials through thermoforming and finishing steps is also described. A review of a collection of technology-demonstrating nanolayered GRIN case studies is which include: optical performance of an f/# 2.25 spherical GRIN plano-convex singlet 1/10 the weight of a similar BK7 lens and a bio-inspired aspheric human eye lens. Original research on the fabrication and characterization of a Lunebu (open full item for complete abstract)

Committee: Eric Baer Prof. (Committee Chair); Alexander Jamieson Prof. (Committee Member); Andrew Olah Dr. (Committee Member); Donald Schuele Prof. (Committee Member) Subjects: Polymers

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

Shape memory behavior of a partially zinc-neutralized, poly(ethylene-co-methacrylic acid) ionomer (i.e. PEMA) was investigated. The ionomer was semicrystalline ionomer with a broad melting transition in the range 60-100 °C. Physical crosslinks in the ionomer due to an ionic nanodomain structure provided a “permanent” crosslinked network, while polyethylene crystallinity provided a temporary network. The broad melting transition allowed one to tune the dual-shape memory behavior by choosing a switching temperature, Tc, anywhere within the melting transition. Similarly, multiple shape memory behavior was achieved by choosing two or more switching temperatures within the melting transition, though the effectiveness of shape fixation depended on how much materials was melted and recrystallized to support the specific temporary shape. Crosslinking improved the recovery efficiency and the crosslinked ionomer exhibited nearly ideal shape memory behavior in dual-shape memory cycle. Preparation of blends of PEMA with ZnSt extended the range of temperatures in which shape memory properties can be achieved. A temporary shape was achieved and fixed by heating and deforming the sample above the melting points (Tm) of the crosslinked ionomer and ZnSt and then cooling the material below Tm under stress. The original shape was restored by reheating the sample above the Tm of the ionomer and ZnSt. Shape memory fibers were made from the blends of Zn-SEPDM ionomer and lauric acid. Zn-SEPDM is an elastomeric amorphous ionomer, the zinc salt of sulfonated poly{ethylene-r-propylene-r-(5-ethylidene-2-norbornene). Shape recovery was triggered by the melting of lauric acid crystals at temperatures close to body temperature, i.e. ~ 40 °¿. Shape memory polymer with such a triggering temperature may have application as self-tightening sutures for biomedical applications. Triple shape memory behavior was also achieved with the blend of Zn-SEPDM with lauric ac (open full item for complete abstract)

Committee: Robert Weiss Dr. (Advisor); Kevin Cavicchi Dr. (Committee Member); Sadhan Jana Dr. (Committee Member); Matthew Becker Dr. (Committee Member); Chrys Wesdemiotis Dr. (Committee Member) Subjects: Chemical Engineering; Engineering; Plastics; Polymers

Master of Science in Chemical Engineering, University of Toledo, 2013, College of Engineering

Polyethylene terephthalate (PET) is a semi-crystalline polyester widely used in industry as a material for food and beverage containers. Although the properties of amorphous PET make it a poor material to use for this application, its properties can be improved through molecular orientation, which is accomplished by deforming the polymer while it is heated above its glass transition temperature (Tg). Orientation is frozen-in by cooling PET below Tg, and can be unfrozen and rapidly relaxed by raising the temperature above this point. Although orientation often results in some degree of strain-induced crystallization (SIC), completely crystalline PET is not possible, and some orientation will exist in the amorphous phase. Additionally, PET molecules retain a small degree of mobility below Tg. A concern for oriented PET, then, is the potential of orientation relaxation when the material is exposed to sub-Tg temperatures of 30-40 °C for extended periods of time. The goal of this study was to determine the extent of relaxation that occurs when oriented PET is exposed to sub-Tg temperatures, as well as how its physical and mechanical properties change correspondingly. Samples of extruded PET sheet were oriented above Tg by stretching them biaxially to two different stretch ratios and rapidly quenched to room temperature. As-quenched birefringence, film dimensions, and mechanical properties of the oriented films were measured. The films were then stored in an air circulating oven at 40, 50, or 60 °C for up to a week. Every 24 hours a film was removed from the oven, and post-exposure birefringence, dimensions and density were measured. Mechanical properties were measured after 7 days of exposure. Measurements of film dimensions provided noteworthy results, with all films experiencing a small degree of shrinkage. Films exposed at 60 °C exhibited the most shrinkage, with a 0.5% decrease in dimensions after a week. Shrinkage followed a trend of exponential decay, and it (open full item for complete abstract)

Committee: Saleh Jabarin PhD (Committee Chair); Maria Coleman PhD (Committee Member); Constance Schall PhD (Committee Member) Subjects: Chemical Engineering; Polymers

Doctor of Philosophy, University of Akron, 2013, Chemistry

Pure, sulfur rich and wurtzite phase CdS nanoparticles with average size ~4.7 nm were prepared in aqueous solution using thioglycerol as a capping ligand. Approximately 542 molecules of thioglycerol molecules were present on the surface of each CdS-TG nanoparticle. CdS-TG nanoparticles can trap a large amount of water molecules and the chemical shift of the trapped water molecules are dependent on the environment and the amount of water trapped. The presence of sodium ions in CdS-TG increases the order of thioglycerol molecules due to the interaction with ions. Relaxation values indicated the interaction between TSLi molecule and thioglycerol. Formation of the hydrophobic monolayer of TSLi on the outer surface of CdS-TG nanoparticles were confirmed by 2D-HETCOR studies. At the interface, cations are far from the aromatic ring and thioglycerol molecules and remain in water pockets with some motions. Pure, sulfur rich, wurtzite phase CdS-TEG nanoparticles with average size of ~4.5 nm were prepared using 2-mercaptoethanol (also known as thioethyleneglycol, TEG) as a capping ligand. Grafting of aromatic ring containing sulfonyl chloride with CdS-TEG nanoparticles through sulfonate ester was studied using benzene sulfonyl chloride in the basic aqueous medium. NMR studies confirmed the feasibility of the reaction and indicated that the rate of esterification reaction increased with increase in concentration of benzene sulfonyl chloride. Naphthalene sulfonyl chloride with CdS-TEG nanoparticles were used to study the photoluminescence behavior before and after the reaction. Quenching of the light observed in the naphthalene rings bonded to the nanoparticles and confirmed that electron or energy transfer took place easily in covalently bonded aromatic rings and nanoparticles. Grafting of polystyrene chain was done by changing polystyrene sulfonic acid to the polystyrene sulfonyl chloride. Some aromatic rings in polymer were bonded with nanoparticles through ester bo (open full item for complete abstract)

Committee: David Modarelli Dr. (Advisor); Matthew Espe Dr. (Committee Member); Claire Tessier Dr. (Committee Member); Thomas Leeper Dr. (Committee Member); Hendrik Heinz Dr. (Committee Member) Subjects: Chemistry

PhD, University of Cincinnati, 2009, Arts and Sciences : Chemistry

The rigid-rod polymeric fibers, such as Zylon (PBO, Poly(p-phenylenebenzobisoxazole), are exceptional with regard to their tensile properties, yet their poor to modest axial compressive properties have been their Achilles' heel, limiting their ultimate potential, especially for structural applications requiring tolerance to compressive loadings. The poor axial compressive strength of the polymer fibers is widely attributed to insufficient lateral interactions between the highly oriented rigid-rod molecules, causing the micro-fibrils to buckle under an axial compressive load.The main objective of this thesis is to provide an insightful review, based on investigation of some molecular/nano-level approaches, for the improvement of the axial compressive properties of these highly oriented polymeric fibers. The predominant molecular approaches discussed are based on the lateral stabilization of the rigid-rod polymer chains via thermal cross-linking or introduction of lateral association, such as inter-chain hydrogen bonding, to provide supramolecular structures. While examples of lateral hydrogen bonding in rigid-rod polymers invariably involve the benzobisimidazole structure in the polymer backbone, other rigid-rod molecular motifs such as benzobisthiazoles linked to a terphenyl system with aromatic heterocyclic pendants are also discussed from the viewpoint of enhancing polymer fiber compressive strength. It is presumed that the twisted terphenyl system with bulky substituents can disrupt molecular rigidity while facilitating strong lateral interactions between the aromatic heterocyclic pendants, leading to enhanced fiber compressive strength. In the context of the nano level approach to the problem of axial compressive strength, in situ polymerization of PBO in the presence of SWNTs (single-wall carbon nanotubes), the fabrication and characterization of PBO/SWNT hybrid polymer fibers as well as the evaluation of their mechanical properties are also discussed. Relative (open full item for complete abstract)

Committee: James Mark PhD (Committee Chair); Neil Ayres PhD (Committee Member); Estel Sprague PhD (Committee Member); James Mark PhD (Advisor) Subjects: Chemistry

PhD, University of Cincinnati, 2009, Engineering : Metallurgical Engineering

Conducting polymer composites (CPCs) have been studied since the 1950's and till date remain the focus of theoretical and experimental studies. With CPCs, the need often arises to preserve particular inherent properties of matrix and / or filler phase, such as mechanical, thermal or electrical properties in the final composite. Unfortunately, commonly used dispersion techniques fall short of assuring these goals because they alter the original polymer structure and require high filler loadings thereby compromising cohesive strengths, as is commonly observed with melt and solution mixing techniques. Even when component properties can be preserved and filler requirements are low, as in dry mixed systems, mechanical properties still remain poor. Therefore, a major challenge in processing CPCs is the need to balance high electrical conductivity with an acceptable mechanical performance, which sets the tone for this study. In this work, three commonly used blending techniques (dry, wet and complete solution methods) were optimized and the property results compared against a novel partial solubility mixing model based on the standard solubility parameter concept. The experimental design required a controlled swelling of the polymer particles, avoiding actual dissolution, such that filler particles of much smaller particle size can be embedded within the swelled polymer structure. The swelling parameter, developed as a function of mixing time, polymer particle size and solubility parameter, served as a useful tool for process control and property development. Powder compositions of poly(acrylonitrile butadiene styrene) and poly(styrene butadiene styrene) block copolymers were first classified into narrow size ranges. Using developed solvent solubility parameters (linked to swelling ratios), a controlled coating of conductive (graphite, polyaniline) and non-conductive fillers (alumina) was deployed over the polymer particles. These were dried and compression molded at 120-1 (open full item for complete abstract)

Committee: Relva Buchanan PhD (Committee Chair); Jude Iroh PhD (Committee Member); Raj Singh PhD (Committee Member); Rodney Roseman PhD (Committee Member) Subjects: Materials Science

MS, University of Cincinnati, 2005, Engineering : Mechanical Engineering

Carbon nanotubes (CNT) are being used extensively as reinforcing materials at nanoscale in developing new nanocomposites, because of their excellent mechanical properties. Incorporating CNTs in polymer matrices can potentially enhance the stiffness and strength of composites significantly when compared to those reinforced with conventional carbon fibers. However, retaining these outstanding properties at macro-scale poses a considerable challenge. To discover the ways for achieving this entails extensive experimental and simulation studies. Molecular dynamics (MD) simulations have been proved to be an excellent approach in characterizing nanocomposites. Nevertheless, MD is limited to nanoscale due to its extra-ordinary computational costs, which promoted the development and usage of alternate approaches for characterizing CNT reinforced composites at microscale. In this research one of these alternative approaches, the continuum mechanics approach using the finite element method, is employed to estimate the effective modulus of CNT reinforced composites and was successfully validated using other analytical (rule of mixtures) and MD methods. Large-scale models were developed, simulating CNTs using pipe elements for the first time. Results from these models reveal that there exists a limiting value for the length of long CNT, for effective load transfer. It was also observed that composites reinforced with long CNTs yield very high effective modulus compared to those with short CNTs. These results are found to be in good agreement with those obtained using MD and multi-scale constitutive modeling approaches.

Committee: Dr. Yijun Liu (Advisor) Subjects: Engineering, Mechanical

MS, University of Cincinnati, 2005, Engineering : Materials Science

Elastomers usually require the incorporation of reinforcing fillers in order to improve their mechanical properties. The resulting properties are very much dependent on the volume fraction, size and shape of the reinforcing agent. For commercial silicone systems silica and titania are typically used as fillers. Fumed and precipitated silica are made on an industrial scale for many applications however it was shown recently that biological and synthetic macromolecules can generate new silica structures using a bioinspired route. The morphology of these new silica structures being different than conventional silica fillers gives a wide scope for new synthetic composites and their study. Herein we have incorporated bioinspired silica fillers into poly(dimethylsiloxane) (PDMS) elastomers and investigated their mechanical, morphological and thermal properties as a function of filler loading. The equilibrium stress-strain characteristics of the elastomers were determined as a function of bioinspired filler loading and the Mooney-Rivlin constants (2C1 and 2C2) were calculated from the stress-strain isotherms. The thermal characteristics, in particular the glass transition temperature (Tg) and the melting point (Tm) of the elastomers were characterized using differential scanning calorimetry (DSC). We have also synthesized poly(propyleneoxide) (PPO) hybrid networks by incorporating bioinspired silica as a filler. The high temperature thermal stability of PDMS networks and PPO networks were investigated and compared using thermogravimetric analysis (TGA). In previous studies a mechanism was proposed explaining the formation of these new silica structures which is based on the silica incorporating the (bio)macromolecule. The results obtained from thermogravimetric analysis strengthen the “proposed mechanism” of formation of these new bioinspired silica structures. The morphology of the samples and the filler dispersion were characterized using Scanning Electron Microscopy (SE (open full item for complete abstract)

Committee: Dr. Stephen Clarson (Advisor) Subjects: Engineering, Materials Science

MS, University of Cincinnati, 2005, Engineering : Mechanical Engineering

Since their discovery in 1991, carbon nanotubes have been the focus of considerable research due to their remarkable physical and mechanical properties reported. This form of carbon has potential applications in numerous conventional and new areas - light-weight structural materials being just one of them. The strength to weight ratio of carbon nanotubes is higher than any currently known material; hence their use to reinforce polymers has been of great interest. This research concentrates on molecular mechanics simulations of carbon nanotubes and their application as reinforcing fibers in polymer composites. The systems being investigated consist of amorphous as well as crystalline polyethylene composites with embedded single-walled carbon nanotube. Various scenarios of deformation and fracture are observed, in accordance with experimental and previously published simulation results. Adhesion at the nanotube – polyethylene interface, the key to effective load transfer, is studied for crystalline as well as amorphous polyethylene systems. Further, fractures in carbon nanotube reinforced nanocomposites are simulated. The tensile properties of amorphous and crystalline polyethylene are studied and compared with nanotube-reinforced composites.

Committee: Dr. Dong Qian (Advisor) Subjects: Engineering, Mechanical

Doctor of Philosophy, The Ohio State University, 2010, Materials Science and Engineering

Electrospinning is a broadly useful manufacturing technique to create polymer fibers ranging in diameter from 20 nm to 20 µm. This size range is ideal for tissue engineering applications as these fibers can mimic the extracellular matrix found in vivo and provide suitable scaffolds for implantation in vivo or for more realistic in vitro models and diagnostics. Electrospinning is a process that involves dissolving a synthetic or natural polymer in a solvent and applying a large voltage bias, which leads to the formation of a Taylor cone and a small jet that ejects a thin stream of the polymer solution. This thin stream rapidly elongates while the solvent evaporates and solid fibers are collected on a grounded substrate. The electrospinning technique can be used to create a large number of nanofibers relatively cheaply and easily compared to other manufacturing methods used to create nanoscale features. While electrospun scaffolds are gaining popularity for cell culture and tissue engineering applications, relatively little is understood about the relationship between macroscopic properties and microscopic properties. Researchers need to understand that the bulk properties of a specific polymer are not the same properties that a cell cultured on the surface of a nanofiber are going to experience. To further complicate this issue, electrospun scaffolds are comprised of nanofibers that can act en masse and thus the macroscopic properties are more of a function determined by fiber-fiber interaction rather than individual fiber mechanical properties. This work strives to establish a baseline of mechanical properties for electrospun fiber scaffolds made of polycaprolactone and various blends of gelatin and relate the macroscopic tensile properties to the underlying microscopic behavior. To investigate how biological environments may affect these properties, scaffolds were subjected to various in vitro exposures and in vivo implantation and then further analyzed for mechani (open full item for complete abstract)

Committee: John Lannutti (Advisor); Heather Powell (Committee Member); Jianjun Guan (Committee Member); Young Lin (Committee Member); Kari Hoyt (Committee Member) Subjects: Materials Science

Master of Science, The Ohio State University, 2009, Mechanical Engineering

Conventional fiber reinforced plastics (FRP's) have long been important if not indispensable in many crucial applications such as transportation, renewable energy, defense applications, as well as many others. Composite materials are of interest to these industries due to their attractive properties including high strength to weight ratio and high modulus to weight ratio. Comprehensive research has been conducted on conventional composite materials to optimize their processing parameters as well as optimize their mechanical behavior and reliability. Although composites provide excellent mechanical properties, certain applications demand improved mechanical behavior as well as the presence of additional properties. Recent developments in polymers have developed nanocomposites, which are composites reinforced by nanoparticles. In these materials, the nanoparticles have shown great enhancements in mechanical properties, thermal properties, and electrical properties. Nevertheless, these composites lack the strength for applications where FRP's are currently used. The addition of nanoparticles as reinforcement to conventional composites shows great promise to not only enhance the existing properties of these composites, but also add many other properties that would maximize their applications. The promise of substantial multifunctional improvements to the behavior of conventional composites does not come without a cost. The effective reinforcement of the desired properties is a direct function of nanoparticle selection and proper dispersion of such nanoparticles. The objective of this research proposal is to develop long fiber reinforced polymer nanocomposites that combine conventional composites with the added benefits of nanocomposites. One of the main challenges involved in the successful enhancement of properties through the addition of nanoparticles is to overcome the problem of poor dispersion in the polymer matrix. Therefore novel state-of-the-art methods of inco (open full item for complete abstract)

Committee: Ly Lee PhD (Advisor); Jose Castro PhD (Committee Member) Subjects: Engineering; Plastics; Polymers

PHD, Kent State University, 2012, College of Arts and Sciences / Department of Physics

Liquid crystal devices are possible because of their large optical birefringence and dielectric anisotropy. They have become a part of modern life with the ubiquitous liquid crystal displays dominating the display industry. However, the need to enhance their physical properties is ever increasing and our research tried to provide as much information as possible to fill this void. In our recent studies, we showed by integrating non-liquid crystalline materials such as specialty particles or well-engineered polymers into a specific liquid crystal host, we could enhance the physical properties of the liquid crystal displays and devices. At the same time, it's possible to change how we perceive and use various types liquid crystals and related devices. In the dissertation, first, we present our work focusing on producing enhanced LC-polymer composites where we integrated custom-made polymer materials into unmodified 5CB to produce fast switching, high transparent LC-polymer composites. We developed high transmittance stressed liquid crystals (HTSLC) optimized for their ultra fast operation in the visible and NIR spectral range. The transmittance that is corrected for front and back surface reflections, of the device is more than 95% at 600nm and 99% in the near IR spectral range. The HTSLC produce large phase shifts. For example, an 18-micron thick HTSLC device can produce more than 1-micron phase shift in 1milli second. HTSLC devices have many potential optical applications for display, adaptable lenses and related electro-optic devices. In the dissertation, as second part, we present our work focusing on enhancing the physical properties of liquid crystals by integrating ferroelectric nano-particles into 5CB, where we achieve minimum of 2deg C and maximum of 4deg C increase in the clearing point of unmodified single component liquid crystal. In addition, we also present how to enhance the dielectric anisotropy and order parameter of the LC and present the results (open full item for complete abstract)

Committee: John West L (Advisor); David Allender (Advisor); Qi-Huo Wei (Committee Member); Elizabeth Mann (Committee Member); Alexander Seed (Committee Member) Subjects: Chemical Engineering; Chemistry; Engineering; Experiments; Materials Science; Optics; Physics