Doctor of Philosophy, Case Western Reserve University, 2024, Macromolecular Science and Engineering

Extensional flows control a variety of industrial processes that involve spraying, printing, and droplet deposition. Within these applications, polymers are used as rheology modifiers to control the flow and droplet breakup, properties which are largely dictated by the polymer's architecture. For example, high molecular weight polymers are often used because of the backbone's ability to deform under stress adds elasticity to solutions. But, by modifying the architecture of a polymer, these elastic contributions can be significantly altered. We have studied the extensional flows of graft polymers as a function of side chain density and length, and liquid crystalline rigid rods using drop-on-substrate rheology (DOSR), a technique that offers strong insights into the fluid dynamics of non-Newtonian droplet breakup. To understand the effects of polymer backbone extension and graft density on extensional flows, polyacrylamide-graft-poly(ethylene glycol) amine (PAM-g-PEGa) was synthesized at grafting densities of 2.5%, 5.5%, 8%, and 30% and characterized via NMR and light scattering. DOSR was then used to determine the extensional relaxation times as a function of concentration for each polymer. We find that as a function of grafting density, the trend in relaxation times is nonmonotonic. At low grafting densities, the viscous friction of the added side chains counteracts the effects of backbone extension, whereas at higher grafting densities, the effects of the extended backbone dominate extensional flow properties. In the continuation of our study of graft polymers in extensional flows, PAM-g-PEGa with varying side chain lengths at a fixed grafting density were also investigated. The trend in relaxation times were also found to be non-monotonic. In contrast to flexible PAM-g-PEGa, poly(γ-benzyl-L-glutamate) (PBLG) forms rigid rods. This conformation allows for PBLG to develop cholesteric liquid crystalline phases at high volume fractions, which can also be used (open full item for complete abstract)

Committee: Svetlana Morozova (Advisor); Metin Karayilan (Committee Member); Michael Hore (Committee Member); Ica Manas-Zloczower (Committee Member) Subjects: Fluid Dynamics; Materials Science; Organic Chemistry

Master of Science, University of Akron, 2024, Geology

Partial melting of hydrous phases such as amphibole, biotite, and muscovite occurs in orogens where distributed ductile thinning is causing exhumation of mid- to lower-crustal rocks. The partial melting of these hydrous phases contributes significantly to the physical and chemical evolution of the crust, as well as affecting the crust's strength. The Si-rich melts generated from partial melting reactions of mid- to lower-crustal assemblages migrate toward the upper crust leaving a more mafic restite. Previous laboratory experiments conducted on amphibole-, biotite-, or muscovite-bearing rocks performed at rapid strain rates (10-4/s to 10-5/s) result in brittle deformation due to high local pore pressures. These rapid experiments suggest this brittle behavior is the likely mechanism causing melt segregation in the crust. However, field evidence and slower strain rate experiments (10-6/s to 10-7/s) suggest that crystal plastic processes may be dominant during syndeformational partial melting. To investigate grain-scale melt segregation mechanisms in a common lower crustal protolith, I performed a suite of axial compression and general shear experiments on an amphibole-bearing source rock during syndeformational partial melting at T = 800-975°C, Pc = 1.5 GPa, at a strain rate (ε) of 1.6 x 10-6/s. I also performed axial compression experiments on a biotite-bearing gneiss and a muscovite-bearing quartzite at T = 950°C, Pc = 1.5 GPa, at a strain rate (ε) of 1.6 x 10-6/s to compare the differences in melt development depending on which hydrous phase is partially melting. The Nemo Amphibolite (d = 140 ± 85 μm) is composed of 62 vol% amphibole (Fe-hornblende), 27 vol% plagioclase (andesine; An30Ab69Or1), 8 vol% quartz, and 3 vol% titanite. The biotite-bearing gneiss (d = 80 +/- 40 microns) consists of quartz (43 vol%), plagioclase (andesine (An22Ab77Or1); 40 vol%), biotite (16 vol%), and ~1 vol% muscovite/Fe-Ti oxides. The muscovite-bearing quartzite is composed of 90 vol% q (open full item for complete abstract)

Committee: Caleb Holyoke (Advisor); Molly Witter-Shelleman (Committee Member); David Steer (Committee Member) Subjects: Earth; Experiments; Geochemistry; Geological; Geology; Mineralogy; Petrology; Plate Tectonics

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

A 3D printable functionalized polyester platform was developed using a coumarin pendant group as a photo-crosslinker. The coumarin pendant groups convert the copolyester from a viscous liquid to an elastomeric solid under 365 nm UV light at room temperature without the use of an initiator. Relatively hydrophobic variants of this platform (SC) was created using unsaturated aliphatic chains derived from soybean oil as pendant groups. A hydrogel variant (CPP) of this platform was created by using polyethylene glycol (PEG) as a backbone. Cell studies of the SC copolyester showed no toxic effects over short time scales. Rheological analysis demonstrated that all polymers over a range of molar feed ratios and molar masses were shear thinning. The SC platform has a very high entanglement molecular weight and has rheological behavior similar to that of an un-entangled brush. UV crosslinking of both SC and CPP platforms create thermosetting elastomeric solids. The relatively SC platform exhibits a high degree of fully reversible elastic deformation under shear due to chain extensibility and lack of trapped entanglements. Multiple pendant functional groups can be readily incorporated into this platform. Primary amine functionality was incorporated into the SC copolyester as a proof of concept. Extrusion based 3D printing (EBP) was successfully demonstrated on both platforms and FITC was successfully covalently clicked onto the primary amine functional group post-printing. Extrusion of the SC platform was accelerated due to UV extrusion. This might be due to Rouse-like behavior under shear coupled with excitation of cis double bonds in the unsaturated pendant groups. Examination of defects accumulated during the 3D printing process demonstrated that dynamic viscoelasticity due to print speed V affected the overall quality of the print. Interfacial chain relaxation institutes a lag-time between initial deposition and adhesion which increases with V. Deformability of the polyme (open full item for complete abstract)

Committee: Abraham Joy PhD (Advisor); Ali Dhinojwala PhD (Committee Chair); Mesfin Tsige PhD (Committee Member); Coleen Pugh PhD (Committee Member); Jae-Won Choi PhD (Committee Member) Subjects: Engineering; Materials Science; Physics; Polymer Chemistry; Polymers

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

This dissertation presents novel mechanical designs and advances in both polymer layer multiplication and extensional rheology. In Part I, advances in polymer layer multiplication include the investigation of typical thermoplastic layer multiplication extrusion dies and the redesign of such by means of experimental and computational investigation. Results show a decrease in flow instabilities including viscous encapsulation and elastic instabilities. Similarly, an innovative layer multiplication system for highly filled and elastic rubber compounds is presented. Both of these novel systems for thermoplastic and thermosetting polymer systems are validated and understood by numerical methods using ANSYS Polyflow and CFD-Post. These advances in multilayer coextrusion allow for layering of new families of rheologically complex and as well mismatched materials, thus widening the processing capabilities at the Center for Layered Polymeric Systems. In Part II, advances in extensional rheology include a newly developed extensional rheometer for achieving high Henky strains. The Meissner Extensional Rheometer Accessory or MERA is limited in strain only by sample rupture. Experimental validation is performed using two materials, a styrene-butadiene rubber (SBR) and a linear polystyrene (PS); the results are compared with those obtained using the well-known SER. Due to its design, it was possible to achieve homogeneous extensional flow up to unprecedented real Hencky strains in excess of 8. The second half of Part II covers a rheological understanding behind the mechanism of sharkskin, a melt fracture instability during extrusion. Solution-styrene-butadiene-styrene blended with various polybutadienes is studied. Experimental extrusion results show a behavior difference depending on the molecular architecture of the latter, polybutadiene. Extensional rheological techniques are used to investigate the behavior. Results show a higher sensitivity to stress relaxation after a step (open full item for complete abstract)

Committee: Joao Maia (Advisor); David Schiraldi (Committee Member); Roger Bonnecaze (Committee Member); Eric Baer (Committee Member) Subjects: Plastics; Polymers

Master of Science, The Ohio State University, 2009, Food Science and Nutrition

The pressure on food companies to quickly develop new products is increasing, and any tool that can decrease the time to market is valuable. This study is aimed to determine the feasibility of a centrifugation method developed to predict long term physical stability. A series of acidified beverages with various stabilizer systems were developed and were compared to the product without a stabilizer. The stabilizer systems for these beverages were 0.35% pectin, 0.40% Avicel BV2815, and a combination of 0.35% pectin and 0.40% Avicel BV2815. All of the formulations were manufactured using an ultra high temperature process and were filled under aseptic conditions. Avicel and pectin each function in different ways to stabilize the matrix. Centrifugation studies were conducted to accelerate sedimentation to predict the expected sedimentation during the storage relevant to shelf life of the product. Actual sediment was measured at several time points over shelf life and was compared with predicted sedimentation. Rheological data of products were collected to develop an understanding of the effect of stabilizers on sedimentation. Absence of a stabilizer resulted in high levels of whey layer and sediment; however, the combination of Avicel and pectin created the most physically stable product. Centrifugation studies were able predict the relative differences between the formulations with or without stabilizers based on the data collected immediately after the manufacturing of the product.

Committee: Gönül Kaletunc PhD (Advisor); Sheryl Barringer PhD (Committee Member); James Harper PhD (Committee Member) Subjects: Food Science

Master of Science, University of Akron, 0, Polymer Engineering

Soft Particle Glasses (SPGs) are jammed suspensions formed by packing soft and deformable particles above their random-close packing limit. These suspensions belong to a class of materials known as yield stress fluids, as they exhibit weak elastic solid-like properties at low strains and flow-like liquids at high strains above their yield stress limit. In these suspensions, the contact forces play a dominant role and are practically athermal. Due to the unique properties of these materials, they are widely used in industries as rheological modifiers in products like inks, pastes, drilling fluids, food products, and personal care products. These multifaceted practical applications make understanding the processing parameters, i.e., the rheological response and the dynamics of the system, of utmost importance. In our study, particle dynamic simulation is used to implement a 3-D simulation of SPGs, and a comprehensive analysis is made to understand the particles' motion and the changes in their microstructure under shear flow. These studies reveal that SPGs exhibit cage-like dynamics during motion, and the flow curve response for these materials is well-defined by the Herschel-Bulkley model. Our results indicate the presence of two distinct regimes, namely quasi-static and flow regimes. A constitutive equation is established between the macroscopic rheology and microscopic dynamics based on the constituent materials' intrinsic properties, like the compressibility of the particles and elastic modulus. A detailed analysis of the microscopic dynamics in the steady-state regime reveals the presence of heterogeneous flow in our suspensions. Analytical tools like the self-part of the van Hove function define the domain lengths of these heterogeneous flows. A qualitative analysis of these domains reveals that these heterogeneous flows exhibit localized dynamics at high shear rates and propagate as avalanches at low shear rates. Analysis of these mobile clusters quantifi (open full item for complete abstract)

Committee: Fardin Khabaz (Advisor); Kevin Cavicchi (Committee Member); Weinan Xu (Committee Chair) Subjects: Physics; Plastics

Doctor of Philosophy, Case Western Reserve University, 2024, Macromolecular Science and Engineering

Although thermoplastic polyurethane (TPU) is a widely used material, surprisingly little academic research has been conducted on it's synthesis under conditions similar to reactive extrusion (REX), one of the primary industrial production methods. This thesis delves into the bulk synthesis of TPU by investigating in-process reaction kinetics under flow conditions. Initially, the effect of HSC and shear rate on TPUs was scrutinized in a parallel plate rheometer. Innovative technology, namely a specialized bottom plate fixture with an inbuilt IR crystal, provided direct measurements of chemical conversion during synthesis, marking the pioneering use of this technology for TPU synthesis. Results showed that higher HSC leads to faster reaction kinetics, while increased shear rates accelerate kinetics by increasing the reaction surface area. Empirical modeling indicated the TPU reaction rates at new shear rates can be predicted based on data obtained at different rates, a promising lead for TPU REX processes. Expanding on these efforts, an on-line IR probe tracked TPU REX along the extruder barrel, a pioneering use of this technology in studying this process. Paired with RTD and off-line GPC measurements, it unveiled that subtle RTD alterations profoundly impact extruder conversion profiles. Both the effects of processing conditions such as screw speed and temperature profile, as well as TPU formulation changes were examined in this way. These findings aid in TPU REX process development, and pave the way for improved TPU REX process modeling. Furthermore, two industry collaboration projects were discussed. The first successfully developed a HEUR akin to TPU via REX, reducing trial and error through preliminary small-scale study. The second project showcased a proof-of-concept PVDC ostomy bag barrier film via layer multiplication extrusion, evaluating multiple resins, including TPU, for processability and resulting film barrier properties.

Committee: Joao Maia (Advisor); Donald Feke (Committee Member); Hatsuo Ishida (Committee Member); Ica Manas-Zlowczower (Committee Member) Subjects: Chemical Engineering; Chemistry; Engineering; Materials Science

PHD, Kent State University, 2024, College of Arts and Sciences / Department of Physics

Science of active matter is a multidisciplinary field that focuses on systems that consist of a large number of units converting the energy of the environment into motion. The main goals of this rapidly growing field are: (1) to understand the pattern formation in active systems, and (2) to design the environment to streamline the chaotic motion of active units into useful work. In this work, we pursue these goals through experimental studies of a living nematic (LN) representing dispersions of swimming bacteria B. Subtilis in a lyotropic chromonic liquid crystal (LCLC). LCLC is a biocompatible liquid crystal formed by an aqueous dispersion of disk-like organic molecules such as disodium cromoglycate (DSCG) Since the swimming bacteria impose shear on the surrounding LCLC, the first task of the dissertation is to explore how the externally imposed shear affects the LCLC director, by employing in-situ polarizing optical microscopy (POM), small-angle and wide-angle X-ray scattering (SAXS/WAXS). The LCLC response to shear depends on the shear rate, with the director realigning along the vorticity axis at low rates and parallel to the shear direction at higher shear rates. We use the higher-rate regime to uniformly align the LN. We demonstrate experimentally that upon shear cessation, the activity of the bacteria results in a cascade of structural transformations, which start with the enhancement and growth of bend fluctuations and continue with nucleation and proliferation of topological defects-disclinations, which drive the system to topological turbulence. To address the challenge of useful work extraction, we explore active droplets formed by bacterial dispersions and placed in a thermotropic liquid crystal. The surface anchoring of the droplet is designed to produce a fore-aft asymmetric director field around the droplet, which rectifies the chaotic flows inside the droplet into directional flows outside the droplet, which results in a ballistic unidirection (open full item for complete abstract)

Committee: Oleg Lavrentovich (Advisor); Sergij Shiyanovskii (Committee Member); John Portman (Committee Member); Elizabeth Mann (Committee Member); Elda Hegmann (Committee Member); Min-Ho Kim (Committee Chair) Subjects: Physics

Master of Science, The Ohio State University, 2024, Food Science and Technology

Two polymer coatings derived from spent coffee grounds were explored as a bio-sourced biodegradable alternative to traditional petroleum-based non-biodegradable plastic coatings used commonly in food packaging. The aim of this research is to formulate a bioplastic coating derived from spent coffee grounds that can serve as a viable alternative to current petroleum-based wax films used in the food packaging industry. Water vapor transmission rate (WVTR) and oxygen transmission rate (OTR) tests were conducted to assess the coatings' barrier properties. Results indicated inferior water vapor resistance compared to the control, yet an enhanced water barrier of the cardboard alone. The coffee oil coating demonstrated superior OTR performance compared to the other samples. Biodegradability experiments conducted over 73 days revealed partial degradation of the coffee oil coated cardboard, showing potential as a bio-sourced biodegradable alternative. However, challenges encountered in biodegradability testing methodology require further investigation. Crystallization and thermal analysis revealed differences between cured and uncured samples, indicating structural changes during curing. Rheological analysis demonstrated Newtonian behavior in uncured samples and shear thinning in cured samples, providing insights into material behavior under increased deformation rates. Adhesion tests confirmed polymer adhesion to cardboard, with no observed odor or microbial growth. Overall, the coffee oil coating presents a promising option for sustainable food packaging, but further research is necessary to optimize properties.

Committee: Yael Vodovotz (Advisor); Emmanuel Hatzakis (Committee Member); Katrina Cornish (Committee Member) Subjects: Food Science; Packaging; Plastics; Sustainability

Doctor of Philosophy, University of Akron, 2024, Mechanical Engineering

The rise of electric vehicles (EVs) has led to new engineering challenges for electric motors and new design opportunities for lubricants and tribological elements like bearings and gears. High power density EV motors require dual fluids: a high heat capacity, low viscosity coolant fluid and a highly effective lubricant capable of protecting ultra-high-speed bearings and gears. This dual fluid practice requires two different fluid systems (sumps, pumps, pipes, and filters) adding cost, weight and complexity. Compared to combustion engines, EVs fluids (oils and coolants) do not require similarly extreme high temperature capabilities. Thus, the opportunity exists to consider new fluids (coolants/lubricants) to enhance EV system performance. Towards this end, low viscosity, high heat capacity fluids such as water-based lubricants (WBLs) have gained popularity, as they can cool electric components and lubricate moving parts fulfilling the single fluid approach. However, WBLs have limitations such as low viscosity, evaporation, freezing point, microbiological growth, oxidation, corrosion, and high electrical conductivity. To mitigate these limitations, different additives such as ionic liquids, bio-based oils, and nanoparticles have been incorporated into WBLs. This has resulted in significant improvements in coefficient of friction and wear reduction. Limited literature is available on the rheological and tribological behavior of WBLs in steels, and the wear mechanisms for these lubricants are not fully understood. The proposed work aims to test different WBLs by characterizing their rheological properties and conducting tribological tests such as fretting and sliding experiments. Posttest analyses will be performed via SEM/EDX, XRD, and AFM to characterize the tribofilms and surface morphology. The results will be compared with traditional lubricants to gain a better understanding of the mechanisms and propose adjustments to current modeling tools. The study unders (open full item for complete abstract)

Committee: Christopher DellaCorte (Advisor); Yalin Dong (Committee Member); Nicholas G. Garafolo (Committee Member); Manigandan Kannan (Committee Member); Weinan Xu (Committee Member); Richard L. Einsporn (Committee Member) Subjects: Mechanical Engineering

Doctor of Philosophy, Case Western Reserve University, 2024, Macromolecular Science and Engineering

New processes and development of advanced technologies are essential for society to progress. The polymer field is vast and further expanding with the creation of new techniques and products. An advanced extrusion processing technique that has been beneficial in creating new products with very interesting properties takes the form of multi-layer co-extrusion. Initially multi-layer co-extrusion was and, in some cases, still is limited by the number of layers that can be achieved, the properties of different polymers can be combined to form products that are superior in different aspects due to the material selection. Layer multiplying co-extrusion was developed to achieve high layer numbers with the use of typically only two to three extruders. This work examines the layer multiplication technique capabilities for highly filled polymer layered systems and annular structures for pipe and blow molding applications. Limited work has been performed with filled polymer systems with using the layer multiplication technique. This work examines a model system to investigate effects of fillers at high loading levels on the stability of the layer structures created. The interface between filled and unfilled layers was examined xix to see the effect of particles at the interface. Along with this, particles with different rigidities were examined to investigate the effect of changing the rigidity of particles in confinement on the mechanical properties of the overall films. Previous work examined the creation of a tubing die for the layer multiplication technique to achieve high layer number annular structures. This work utilizes this tubing die to examine how angular rotation of the outer wall of the die land effects the weld line presence and pressure properties of the resultant tubes. The development of annular structures also allows for creation of blow molded structures. This work examines blow molding of high layer number bottles using a simple tabletop set-up and the (open full item for complete abstract)

Committee: João Maia (Committee Chair); Ica Manas-Zloczower (Committee Member); Gary Wnek (Committee Member); Alp Sehirlioglu (Committee Member) Subjects: Plastics

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

In this work, High Density Polyethylene (HDPE) composites were made using Torrefied Soybean Hulls (TSBH) and Carbon Black (CB) to study the interactions affiliated with the TSBH content for as-received as well as size-reduced particles. The Milled TSBH (MTSBH) was shown to integrate well at low loadings, but showed signs of favoring filler-filler interactions over filler-matrix interactions, reducing the overall effectiveness as the loadings increased. Rheological testing showed that the higher-loaded MTSBH composites behaved similar to composites with larger particles as the loading increased, indicating that clusters had formed. Unmilled TSBH (UTSBH) showed good mechanical strength, but the particle size was shown to limit its ability to integrate into the material, even at low loadings. The addition of CB was shown to have the most impact on the low loading MTSBH composites, where the MTSBH-CB interactions were shown to influence the filler network in electrical resistance testing where a nonlinear trend was observed in the composite resistivity with the addition of MTSBH. In UTSBH composites, there were less signs of CB-UTSBH interactions due to the relatively large particle size. To contrast the hydrophilic matrix behavior of HDPE, Nylon-6 (PA6) was used as a matrix for the TSBH composites. In cases where either TSBH filler was used, the composite performance was shown to improve to a greater degree than in the case of HDPE due to the hydrophilic groups contained in the PA6 backbone. Similar to the HDPE composites, the TSBH particles showed a lack of effectiveness at higher filler loadings, though MTSBH showed more effective integration which indicates that this is a result of particle size. The CB and MTSBH showed synergistic effects with high CB and low MTSBH loading during cyclic tension testing, where the increase in strain energy density required for a test was less when the CB was present that when it was not. This effect was seen throughout the mono (open full item for complete abstract)

Committee: Erol Sancaktar (Advisor); Kevin Cavicchi (Committee Chair); Wieslaw Binienda (Committee Member); Steven Chuang (Committee Member); James Eagan (Committee Member) Subjects: Chemical Engineering; Materials Science; Mechanics; Plastics

Doctor of Philosophy, The Ohio State University, 2023, Food Science and Technology

Consumer demands for ethically sourced and environmentally friendly food products have led to development efforts to replace animal-based proteins with plant-based alternatives. However, plant-based protein ingredients can be limited by their functional and sensory properties, and thus processing techniques to improve these properties must be explored. Enzymatic hydrolysis has been suggested to improve key functional properties, such as solubility, but the research methodology in this area is questionable and hydrolysis does not fully address sensory deficits in plant-protein ingredients, notably bitterness. In this dissertation, commercial extruded snack products containing soy protein hydrolysates were used as a model to quantify bitterness and test the viability of reformulation with flavor maskers or alternatively processed proteins to improve off-flavor. This study revealed that commercial flavor maskers are not effective at reducing bitterness in products containing soy hydrolysate, but soy protein hydrolysates made by different manufacturers with different processing methods proved a viable replacement with improved off-flavor. In search for conclusive evidence that enzymatic hydrolysis results in improved functionality, a review of literature was conducted. This review concluded that enzymatic hydrolysis process may result in the formation of insoluble aggregates, which in most studies are removed by centrifugation or filtration during processing, thus artificially increasing the reported solubility values for plant-protein hydrolysates. The phenomenon of hydrolysis induced aggregation was confirmed for protein isolates from soy and as well as a pulse protein alternative to soy, chickpea, which were hydrolyzed by Flavourzyme and Alcalase. Analysis of physical and structural properties of the hydrolyzed proteins revealed that hydrolysis led to protein destabilization, causing hydrogen-bond mediated aggregation during thermal enzyme inactivation. The knowledge (open full item for complete abstract)

Committee: Farnaz Maleky (Advisor); Osvaldo Campanella (Committee Member); Emmanuel Hatzakis (Committee Member); John Litchfield (Committee Member); Lynn Knipe (Committee Member) Subjects: Biochemistry; Food Science

Master of Science, The Ohio State University, 2023, Food Science and Technology

Plant proteins are gaining significant attention as a potential alternative to animal proteins in many food and beverage products. However, these proteins possess inferior functionality and physicochemical properties as compared to animal proteins. The primary goal of this investigation was to evaluate enzymatic hydrolysis as an approach to changing the structural and functional properties of pea proteins, specifically the gelling properties. Inulin is a neutral oligosaccharide and soluble fiber. It has bifidogenic properties that promotes gut health. Thus, gels containing a combination of hydrolyzed pea protein and inulin can serve as a model mixed food system that can be investigated. A specific objective of this research was to evaluate the degree of hydrolysis and inulin to pea protein ratio needed for the optimum structural and functional properties of the gels formed. Pea protein isolate (PPI) solutions (7.5%) were subjected to limited enzymatic hydrolysis prepared using the enzyme Alcalase® at three hydrolysis times (0, 3 and 6 mins). The hydrolyzed protein solutions were placed in an ice water bath to limit enzyme activity. At this stage, addition of inulin was done in different ratios to the pea protein present in the solution. Gels were prepared with these solutions and characterization of their viscoelastic properties was done by subjecting the gels to amplitude and frequency sweep. The gels formed by the pea protein samples hydrolyzed for 3 mins with inulin to pea protein ratio of 1:4 exhibited the highest gel strength as described by the storage modulus (G') values, out of all samples. Whereas the lowest gel strength was observed for the gels formed by samples hydrolyzed for 0 mins (unhydrolyzed samples). It was apparent that hydrolysis time controlled the ability of the gel to incorporate inulin and had a greater effect on gel strength, as compared to inulin addition. The frequency sweep results demonstrated that the gels formed by samples hydrolyz (open full item for complete abstract)

Committee: Dennis Heldman (Advisor); Valente Alvarez (Advisor); Osvaldo Campanella (Committee Member) Subjects: Food Science

Doctor of Philosophy, The Ohio State University, 2023, Food Science and Technology

Foods are composite biomaterials that are heterogenous and complex in nature. Investigating food systems with the general principles of physics provides the possibility to understand the relationship between food structure and function on a fundamental level. The physical properties of food materials are intrinsically determined by the molecular assembly of components which determine the interaction between the material and processing procedures, and ultimately affect consumers' acceptance. Measurement and quantification of the physical properties of food materials brings insights into the molecular interactions within the matrix. Bread dough, essentially a mixture of wheat flour and water, displays unique mechanical properties due to the viscoelasticity of the gluten proteins present in wheat flour. Rheology, the study of material deformation and flow, can be used to quantitatively demonstrate the interplay between water and other components present in dough. Frozen dough is widely used in the bakery industry for its economic benefits; however, freezing alters the state of water and adversely affects the dough quality. Examination of the frozen dough's rheological properties can shed light on the mechanism of interactional changes induced by the phase change of water in the dough matrix. Freezing is a heat transfer process with a significant enthalpy change derived from phase change, and particularly due to the significant latent heat involved in freezing or thawing processes. Food freezing can be represented by a physical model that is governed by a partial differential equation (PDE) that must be solved numerically. However, the achievement of an accurate solution requires careful handling of the thermophysical properties of the food material. Besides water, gluten also plays a predominant role in determining dough rheology, which brings challenges to the development of gluten-free dough with desirable performance. Through fibrillization, the structure of globula (open full item for complete abstract)

Committee: Osvaldo Campanella (Advisor); Sudhir Sastry (Committee Member); Senay Simsek (Committee Member); Dennis Heldman (Committee Member); Macdonald Wick (Committee Member) Subjects: Food Science

Doctor of Philosophy, University of Toledo, 2022, Chemical Engineering

Polysaccharides have attracted much attention in the field of bone tissue engineering as natural scaffolds that mimic the physiological structure of the extracellular matrix (ECM) and provide glycosaminoglycan-like environments with nontoxic degradation products. Moreover, the use of polysaccharides is not limited to mimicking the 3D structure of the ECM but also as bioactive natural macromolecules that can stimulate cell-signalling. Gellan gum (GAGR) is a naturally occurring polysaccharide with repeating units of D-glucose, D-glucuronic acid, and L-rhamnose. Due to its biocompatibility and biodegradability, GAGR has been investigated in biomedical applications, food processing, pharmaceutics, and tissue engineering. In this research, GAGR is investigated not only as a scaffold but also as a bioactive material that stimulates bone regeneration. Culturing pre-osteoblast cells with GAGR resulted in a significant upregulation of genes related to osteogenesis and chondrogenesis, in addition to collagen type I protein formation, which is the main component in the ECM. Thus, to deliver GAGR, various formulations of GAGR, hyaluronic acid, and β-tricalcium phosphate were fabricated. The objective was to develop an ionically crosslinked gel that can be injected and allows GAGR to disintegrate over time from its network structure. Then, the possibility of GAGR diffusion and adsorption in human bone was investigated in vitro by the standard diffusion cell chamber and adsorption isotherms. In vivo, the cross-linked GAGR gel was injected into the femur bone of an ovariectomized rat model. GAGR gel-injected sites showed a significant increase in inward bone growth, resulting in thicker cortical bone, as well as an increase in number of blood vessels. A simulation of the in vivo study using finite element model (COMSOL Multiphysics v 5.4) showed a qualitative agreement to the experimental results, and revealed a significant effect of GAGR molecular weight and adsorption on (open full item for complete abstract)

Committee: Dong-Shik Kim (Committee Chair); Joshua Park (Committee Member); Eda Yildirim-Ayan (Committee Member); Maria Coleman (Committee Member) Subjects: Chemical Engineering

Doctor of Philosophy, University of Akron, 0, Polymer Engineering

In contrast to conventional thermosets, vitrimers represent a new class of polymer networks that can exchange covalent bonds and adjust their topology without risking structural damage or permanent loss of material properties above a characteristic topology freezing temperature. This unique feature makes vitrimers perfect candidates to design self-healing polymer materials and improve the lifetime and circularity of plastics. However, due to their novelty, this unique dynamic behavior is not yet fully understood on a molecular level, and there is still a lack of theoretical research on the impact of the lifetime of the exchangeable bonds on the rheology and dynamics of vitrimers. In this study, a combination of coarse-grained molecular dynamics (MD) and Monte Carlo (MC) simulations are used to mimic the thermodynamic, microstructural, and rheological properties of vitrimers. The model captures the two characteristic transition temperatures of vitrimers: conventional glass transition temperature, Tg, and the topology freezing temperature, Tv, used to capture the thermoset-thermoplastic transition. The rheological data accurately describe the main feature of vitrimers, which is the terminal regime of the elastic modulus at low frequencies. Simulations reveal that the lifetime of the exchangeable bonds determines the rheology and dynamics of these networks. When the rate of the deformation is higher than the rate of the bond exchange, the system behaves as a typical thermoset, while at lower rates, the vitrimer behaves as a viscous liquid. The linkage between the microscopic dynamics and the linear rheology of vitrimers is established using the generalized Stokes-Einstein relationship, which efficiently extends the timescale of simulations and predicts the viscoelasticity. Additionally, the values of the shift factors are related to the characteristic decay time of the intermediate scattering function which is accessible in scattering experiments. This work provides (open full item for complete abstract)

Committee: Fardin Khabaz (Advisor); Sadhan Jana (Committee Chair); Yalin Dong (Committee Member); Mesfin Tsige (Committee Member); Kevin Cavicchi (Committee Member) Subjects: Physics; Political Science

Master of Science, University of Toledo, 2022, Chemical Engineering

The current study investigated the antibacterial activities of low acyl gellan gum (LA-GAGR) and its derivative, Mini-GAGR through two different methods. The first method involves the measurement of antibacterial activities of suspended LA-GAGR and Mini-GAGR in a liquid phase to determine their minimum inhibitory concentrations (MIC). The concentrations used for LA-GAGR and Mini-GAGR were 0.002 %, 0.003 %, and 0.015 %. As LA-GAGR and Mini-GAGR concentrations increased, their antibacterial activities became significantly high. The results also showed that LA-GAGR had a greater antibacterial activity than Mini-GAGR. The second method was via the growth inhibition experiment where 1.5% of LA-GAGR and 3% of Mini-GAGR in a gel phase were compared with two different types of polysaccharides, 2% chitosan and 7% dextran. Before running the growth inhibition experiment, confirmation of similar rheological properties for all samples was made. LA-GAGR, Mini-GAGR, chitosan and dextran showed similar rheological properties with gel-like behavior. The result of the growth inhibition experiment showed that the largest inhibition zone was formed in chitosan. While LA-GAGR has some inhibition zone, unlike Mini-GAGR where the gel is colorless, dextran did not inhibit the bacterial growth and allowed the bacteria to colonize on its gel.

Committee: Dong-Shik Kim Dr (Advisor); Joshua Park Dr (Committee Member); Maria Coleman Dr (Committee Member) Subjects: Biology; Biomedical Research; Chemical Engineering; Microbiology

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

In this dissertation, the sustainability of asphalt pavements was investigated in three different aspects. The first part presents the first research study to evaluate the effect of adding different contents of recycled Polyethylene Tetraphthalate (PETE) to the asphalt binder on the rheological and mechanical properties of the modified binder as well as the agglomeration behavior between PETE and asphalt binder at macro-, micro-, and atomistic scales using Superpave rheological tests, Atomic Force Microscope (AFM) testing, and molecular dynamics (MD) simulation, respectively. Results indicated that Addition of PETE enhanced the high and intermediate temperature rheological properties of the PG 64-22 binder. The low-temperature rheological properties and resistance to cracking decreased slightly with increasing the PETE content in the binder. However, this reduction was not remarkable when adding 4%, 8%, or 10% PETE contents. AFM results indicated that the inclusion of PETE improved the stiffness properties and increased the roughness, reduced modulus, and bonding energy of the modified binders as compared to the control binder. MD simulation indicated that the molecular agglomeration between PETE and light asphalt binder components increased when increasing the PETE content, with highest RDF values indicated for 10% PETE modified binder. The second part of this dissertation presents the first study to evaluate the effects using tack coat material and other factors on the interlayer bond strength between the field constructed or laboratory prepared micro-surfacing single or double layers and existing pavement surface. The bond strength between micro-surfacing layer(s) and the existing pavement surface was measured in the laboratory using two types of pull-off tests and a torque bond strength test. Results indicated that samples with no tack coat had significantly lower bond strength than those with tack coat with at least 0.05 gsy total application rate. Furthermore, (open full item for complete abstract)

Committee: Munir Nazzal Ph.D. (Committee Member); Matthew Steiner Ph.D. (Committee Member); Nabil Nassif (Committee Member); Sara Khoshnevisan Ph.D. (Committee Member) Subjects: Engineering

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

The characterization of the viscoelastic response of polymers and soft tissue is significant in several areas like biomedical engineering and material processing. Computational modeling of and experimentation with such rheological materials are complex due to their time- and temperature-dependent nature. There is a critical need for reliable computational models that account for the inherent variability in experimental data. Rheological constitutive models characterize the viscoelastic response of materials using discrete or continuous relaxation spectra. The spectra are characterized by parameters (time constants, elastic and shear moduli) representing the relaxation process, and contain information about the molecular structure of polymers and soft materials. We can estimate the viscoelastic model parameters from stress relaxation experiments, but several challenges exist. For discrete spectra, a challenge is a finite number of model parameters. In the case of continuous spectra, challenges include ill-posedness, the curse of dimensionality, parameter identifiability, as well as correlated and heteroscedastic data. For modeling temperature-dependent material behavior, the challenges include model complexity and limited availability of experimental data. To address these challenges, we aim to develop rigorous stochastic approaches. Bayesian methods offer a rigorous stochastic foundation and have gained significant interest due to the increasing availability of computational resources. The specific aims of this work are: Aim 1: Employ an information-theoretic approach, namely Fisher information, to develop criteria for evaluating experimental data to obtain an ideal range of parameters. Aim 2: Develop a hierarchical Bayesian (HB) approach to L2 regularization for inferring continuous spectra while considering heteroscedasticity. This approach applies to the general linear inverse problems involving regularization, and is not limited to (open full item for complete abstract)

Committee: Kumar Vemaganti Ph.D. (Committee Member); Gowtham Atluri Ph.D. (Committee Member); Sandeep Madireddy Ph.D. (Committee Member); Manish Kumar Ph.D. (Committee Member); Woo Kyun Kim Ph.D. (Committee Member) Subjects: Mechanical Engineering