Master of Science, University of Akron, 2017, Polymer Science

The objective of the research was to study the effects on surface segregation in binary polymer blends of both chain end functionalization of linear chains, and changes in architecture. An important question for the formation and application of a polymer thin film is the degree to which end group functionalization can influence the segregation of a chain to the air/polymer and polymer/substrate interfaces. For the first part of this study, well-defined polystyrene and hydroxyethylated functionalized polystyrene of exactly the same molecular weight (Mn = 6000 g/mol) were synthesized using anionic polymerization in order to minimize the impact of factors other than end group functionalization in the study of the segregation driven by the functionalization. Thin (90 nm) films of blends of these two chains spun cast on silicon substrates were investigated. Key to the study was use of a new method called Surface Layer Matrix Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry (SL-MALDI-TOF-MS) which determines the composition at the surface (< 2 nm depth) of entire polymer chains, rather than the segment or chain end composition measured with other techniques. This technique requires no isotopic labeling. The most striking finding is that the surface region is not only depleted in the high energy chain end functionality, but, in fact, depleted in chains containing the functional group. Thus, for the first time, depletion of the entire chain, driven by only a single functionalized end group, was observed directly. The depletion of the surface in functionalized chains varies with composition and is more pronounced for blends of near-symmetric composition. For the study of the effect of architecture on surface segregation, star-branched polymers with two different architectures were synthesized. Well-defined 5.5k 4-arm star was successfully synthesized using a combination of anionic polymerization and silane linking chemistry. The structure (open full item for complete abstract)

Committee: Mark Foster (Advisor); Li Jia (Committee Member) Subjects: Physics; Polymer Chemistry; Polymers

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

The swelling and deswelling of crosslinked polydimethylsiloxane (PDMS) pad adhered to a block copolymer (BCP) film during solvent vapor annealing (SVA) provides sufficient shear force to produce highly aligned domains over macroscopic dimensions in thin films. Here, we examine how far this alignment can propagate through the depth of a BCP film to understand the limits for efficacy of the SVA-S (SVA with shear) process. Films of cylinder-forming polystyrene-block-polyisoprene-block-polystyrene (SIS) ranging from 100 nm to more than 100 µm are examined using the same processing conditions. The SIS surface in contact with the PDMS is always well-aligned, with Herman's orientation parameter (S) exceeding 0.9 as determined from AFM micrographs, but the bottom surface in contact with the silicon wafer is not aligned for the thickest films. The average orientation through the film thickness was determined by transmission small angle x-ray scattering (SAXS), with S decreasing gradually with increasing thickness for SIS films thinner than 24 µm, but S remains > 0.8. S precipitously decreases for thicker films. A stop-etch-image approach allows the gradient in orientation through the thickness to be elucidated. The integration of this gradient agrees with the average S obtained from SAXS. These results demonstrate the effective alignment of supported thick BCP films of order 10 µm, which could be useful for BCP coatings for optical applications.

Committee: Bryan Vogt (Advisor); Kevin Cavicchi (Advisor); Thein Kyu (Committee Member) Subjects: Materials Science

Master of Science in Engineering, University of Akron, 2005, Biomedical Engineering

The purpose of this research was to investigate the potential of a laser-based optical polarimetric imaging system, operating under light backscattering geometry, for tumor detection utilizing an optical tumor phantom. Image plays a key role in tumor detection studies. The polarization state of the scattered light from a tumor-like structure and the discrimination of randomly polarized light from weakly polarized light can provide meaningful information regarding the nature of the tumor itself. This information can be both physiological and structural. In this research study, experiments were performed at two optical wavelengths, one visible and one near-infrared wavelength. The weakly scattered light from the tumor tissue like phantom had the necessary information relevant to the structure of the tumor. A Rotating Retarder Polarimeter was used to analyze this weakly scattered light from the phantom. The images obtained from the Rotating Retarder Polarimeter were then processed by means of a data reduction algorithm, based on Polarimetric Measurement matrix method to calculate the Degree of Linear Polarization (DOLP) image. Then, the DOLP images obtained from the two different wavelength lasers were subtracted to enhance the information present in the image. The Signal-to-Background ratio, a measure of contrast, was calculated to determine the quality of the image. Results from the experiments and the contrast analysis procedures showed that, the subtracted DOLP images provides better contrast in terms of higher numerical value compared to the single DOLP image. Overall, this optical imaging system combined with data reduction algorithm and image processing technique served as an effective imaging methodology in optical tumor phantom study.

Committee: George Giakos (Advisor) Subjects:

Master of Science, The Ohio State University, 1971, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, Miami University, 2021, Chemistry and Biochemistry

We have coated a typical C18 column with the inexpensive zwitterionic synthetic surfactant, cocamidopropyl betaine (CAPB), in order to generate a mixed mode reversed phase weak ion exchange column with a capacity of 0.29 mmoles. The addition of 8.8 x 10-4 M CAPB to the totally aqueous mobile phase ensured stability of the surfactant on the column and permitted separation of the four component sulfonamide mixture with micellar liquid chromatography (MLC) in under 11 min with baseline separation for all components. Comparatively, with a dilute H2SO4 mobile phase the sulfonamide mixture reached excessive run times of an hour on the bare C18 chains. A five component short chain carboxylic acid mixture was used to examine the ion exchange character of the column in pH environments of 2.3 and 4.6. Three phase MLC equilibrium experiments were also performed in these pH environments with the two sulfa drug and carboxylic acid mixtures to determine partition coefficients. Finally, two high molecular weight anionic compounds, polystyrene sulfonates, were characterized by MLC with CAPB and variable pH mobile phases; the optimal pH was determined to be 2.95. A totally aqueous mobile phase without CAPB was not suitable for profiling these polymers.

Committee: Neil Danielson (Advisor); Ellen Yezierski (Committee Chair); Andrea Kravats (Committee Member); David Tierney (Committee Member) Subjects: Analytical Chemistry; Chemistry

Master of Science, University of Akron, 2021, Physics

A previous study of low temperature photoluminescence (PL) in several common polymers revealed that photoluminescence intensity was, to a different degree, temperature dependent in all of them. Even though polystyrene showed only moderate temperature dependence, it was the only studied polymer in which the wavelength, and therefore, the energy of the photoluminescence peak changed with temperature. In this work I explored that effect in more details. A careful photoluminescence study was done of four polystyrene samples from different manufacturers. Samples were labeled PS1, PS2, PS3, and PS4, with measurements done at 77 K, 100 K, 200 K and 292 K. All samples showed that fluorescence quantum yield increased at cryogenic temperatures, causing the peak intensity to increase at temperatures below room temperature. However, only PS4 sample showed a peak shift, i.e. the energy of the peak changed with temperature. In PS1, PS2 and PS3 samples the peak position did not change with temperature. Therefore, I concluded that the effect was not an intrinsic property of polystyrene. Moreover, the data analysis revealed that the shift of the peak in PS4 was caused by a second photoluminescence peak, which displays a very strong temperature dependence. This second peak was not observed in PS1, PS2 and P3 and therefore is not intrinsic to polystyrene. I speculate that it is due to impurities.

Committee: Sasa Dordevic (Advisor); Robert Mallik (Committee Chair); Ben Hu (Committee Member) Subjects: Materials Science; Physics

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

Bachelor of Science, Ashland University, 2019, Biology/Toxicology

Plastic pollution has been a growing global issue since the production and widespread consumption of plastic began more than 60 years ago. Over time, detrimental impacts on ter-restrial and aquatic organisms have been observed. Microplastics are plastic pieces or fibers (less than 5 mm) that contaminate aquatic systems and may impact zooplankton, aquatic ani-mals that naturally ingest phytoplankton and other food particles of a similar size. Zooplankton are consumed by fish, so organisms higher in the food web are expected to be impacted by zo-oplankton ingestion of microplastics as those plastics consumed by zooplankton are trans-ferred to the predatory fish and thus bioaccumulate through the trophic food web. This study investigated the potential of the model zooplankton, Daphnia magna, to ingest microplastic spheres and microfibers through concentration and extended exposure experiments. D. magna are a large species and were found to readily ingest polystyrene spheres 50µm in size. Since D. magna demonstrated an affinity for sphere ingestion, animals were exposed to the more com-mon contaminant, microfibers, to determine if ingestion occurred and if there were impacts on survival and reproduction. Despite a lack of fiber ingestion, Daphnia exposure to low levels of microfibers over twenty days showed a reduction in the number of eggs generated in a clutch, reduction in the viability of neonates that gestate to term, and reduction in the overall number of neonates. Microplastics may pose a harm not only to organisms such as D. magna but also to organisms higher in the trophic system through bioaccumulation and reduction in available zooplankton as a food source if reproductive success is decreased when exposed. Further stud-ies of native organisms are necessary to establish the effects of microplastic pollution on freshwater systems and the organisms that rely on them.

Committee: Jenna Dolhi Binder Ph.D. (Advisor); Patricia Saunders Ph.D. (Advisor); Jeffrey Weidenhamer Ph.D. (Advisor) Subjects: Biology

Master of Science in Polymer Engineering, University of Akron, 2019, Polymer Engineering

This study focuses on fabrication and use of aerogel coatings on macroporous fabrics for the purpose of filtration of airborne nanometric particles. Filtering airborne particles is an important aspect due to their hazardous effects on human health. In this work, syndiotactic polystyrene (sPS) and polyimide (PI) aerogels were coated via a dip coating process on polyester woven fabric substrates and the resultant materials were evaluated to determine their effectiveness on air filtration. In addition, syndiotactic polystyrene aerogel monoliths were modified with triblock copolymer surfactants and the effects of the morphology on permeability and filtration efficiency were studied. In the first part of this study, thin films of syndiotactic polystyrene and polyimide aerogel were cast on fibrous substrates by a dip coating process. The results showed that syndiotactic polystyrene would be more suitable for the dip coating process. However, a reflection into fundamentals of dip coating process showed an imminent technical issue.. In sol-gel dip coating, the final step in producing a film is the evaporation of the solvent to leave the solid materials behind. This presents a serious challenge, as solvent evaporation from the gels destroys the pores in resultant aerogels. To correct this, an additional step was used in which the coated substrate was held in excess heated solvent vapor as the solution turned into a gel. In the second part of this study, syndiotactic polystyrene aerogel monoliths were modified by the addition of triblock copolymer surfactants during the synthesis step. Specifically, F108 and F127 Pluronic®, surfactants were dissolved in sPS solution in tetrahydrofuran before allowing sPS to gel. Monoliths modified with F108 surfactant were found to have unfavorable surface structure due to poor dispersion of the surfactant. The aerogels with F127 surfactant showed improved porous structures particularly at the surface where a fibrous structure was obse (open full item for complete abstract)

Committee: Sadhan Jana Dr. (Advisor); Kevin Cavicchi Dr. (Committee Chair); Erol Sancaktar Dr. (Committee Member) Subjects: Polymers

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

This dissertation describes the development of novel mass spectrometry (MS) methodologies and techniques to improve, simplify and allow for specific characterizations of synthetic materials. Successful MS analyses are governed by the mass spectrometry principles surrounding specific ionization sources, mass analyzers and ion detecters. The methods described within this dissertation provide information about polymer materials that is historically difficult to determine using other available analytical techniques. Self-assembled terpyridine (tpy)-based metallomacrocycles that are coordinatively-bound using various transition metals were investigated through the analysis of their collision cross-section (CCS) values obtained by travelling wave ion mobility (TWIM)-MS separation, and through comparison to modeled/simulated structures and theoretical CCS values. This work demonstrated the uniquely powerful ability of TWIM-MS separation for architectural verification in samples containing stoichiometrically-defined isobaric ion species ranging from dimeric macrocycles to hexameric macrocycles. Furthermore, TWIM-MS was utilized in a separate project which allowed for the development of a method to monitor concentration dependent supramolecular structural equilibria and conformational trends. Using the methodology in this work, equilibrium constants were derived from these data; this was illustrated for two equilibria concerning the self-assembly of a tpy-based ligand containing a flexible crown ether moiety with Zn2+ ions, and a tetrakisterpyridinyl ligand with Cd2+ ions, which have previously been shown to reversibly interconvert. Additionally, experimental CCS values were also derived from drift time measurements and compared with theoretical predictions for these complex self-assembled terpyridine-based supramolecules to provide insight into their size, stoichiometry and architecture. Parallel studies have focused on the development of methods that can obtain conne (open full item for complete abstract)

Committee: Chrys Wesdemiotis (Advisor); Mark Foster (Committee Chair); George Newkome (Committee Member); Matthew Becker (Committee Member); Kevin Cavicchi (Committee Member) Subjects: Analytical Chemistry; Chemistry; Materials Science; Polymer Chemistry; Polymers

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

The term `gel' encompasses a broad group of materials that range in application from topical ointments to contact lenses and beyond. Gels have been considered as drug delivery vehicles, as artificial tissue, and as scaffolds for bone and tissue growth. In some of these applications, the physical properties of the gels are paramount to the success of its implementation. However, the liquid component of these gels may change over the course of its lifetime due to natural diffusion with the surrounding environment or may be replaced strategically after the gels are synthesized. A serious design question must then be raised. Will this change affect the physical properties of the gel significantly? In the first part, this thesis seeks to determine if there are any changes in the material properties of a gel when different liquids are used to fill the porous solid networks. In the second part, the conductive properties of the iongels are investigated. An ionogel is obtained by replacing the original synthesis solvent with an ionic liquid. Thermoreversible syndiotactic polystyrene gels are fabricated and then used to create various gels by utilizing a simple method based on solvent exchange. This method isolates the solid component and allows the liquid component of the gel to be the sole variable. Five different gel types with various polymer contents for each are fabricated and tested – one aerogel as control material and four different liquid gels. The aerogels are found to have the largest compressive modulus value in uniaxial compression. The gels, in contrast, have widely varying moduli depending upon the liquid that fills the pores. The gels also exhibit different forms of mechanical failure during compression testing further showing that the uniqueness in mechanical properties is originating from the liquid components. Tests using differential scanning calorimetry do not yield any information on the changes in the solid material properties e.g., du (open full item for complete abstract)

Committee: Sadhan Jana Dr. (Advisor); Kevin Cavicchi Dr. (Committee Chair); Erol Sancaktar Dr. (Committee Member) Subjects: 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, 2018, Chemical Engineering

This dissertation presents the first report of local in vitro release of anti-inflammatory drugs, Zafirlukast and Aspirin, from an electrospun drug-eluting fiber mat made from novel non-commercialized, polyisobutylene-based thermoplastic elastomers. This drug-eluting fiber mat is a potential candidate for reducing the inflammatory response to silicone breast prosthesis. Linear poly(styrene-b-isobutylene-b-styrene) triblock copolymer (SIBS) is used in clinical practice as the drug-eluting polymeric coating on the TAXUSTM coronary stent for its excellent bioinertness and biostability. Over 6 million patients have benefited from this device, but due to the low permeability of the polymer, only ~10% of the encapsulated drug, Taxol, eluted from the coating in 330 days at 8.8 wt% loading. The next generation PIB-based thermoplastic elastomer (TPE), Arbomatrix with an arborescent polyisobutylene (PIB) core & poly(p-methyl styrene) (PMS) end blocks, was also shown to be bioinert in a rabbit model. Another novel PIB-based TPE, poly(alloocimene-b-isobutylene-b-alloocimene) (AIBA), which is a linear block copolymer developed by Puskas and coworkers, is also a suitable candidate for biomedical applications. Breast cancer is the most commonly diagnosed form of cancer and the second leading cause of cancer-related deaths in American women (246,660 new cases and 40,450 deaths in 2016). Approximately one-third of American women diagnosed with breast cancer undergo mastectomy, with approximately 70% of these women opting for silicone implant-based reconstruction. Capsular contracture is the most commonly reported problem with this approach. Capsular contracture is a distortion of an implant caused by tension resulting from the fibrous capsule forming around it due to an inflammatory response by the body against silicone rubber. Electrospinning is a versatile and unique process of creating fibers in the micron, sub-micron and nano diameter ranges with the help of electrostatic for (open full item for complete abstract)

Committee: Judit Puskas (Advisor); Teresa Cutright (Committee Member); Darrell Reneker (Committee Member); George Chase (Committee Member); Jie Zheng (Committee Member) Subjects: Biomedical Research; Chemical Engineering; Materials Science; Medicine; Morphology; Polymers; Textile Research

Master of Science, The Ohio State University, 2017, Chemical Engineering

Increased use of bio-based polymers and rubbers could help decrease our dependency on fossil fuel feedstocks. Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a semicrystalline polymer. PHBV gets its importace from being biocompatible and biodegradable. Virgin PHBV is a brittle thermoplastic with high water and oxygen transmission rates. Also, PHBV has poor thermal properties above 160ºC, thus limiting its packaging application. It has been previously demonstrated that improved bioplastic properties (increased softness and flexibility) can be achieved by blending natural high viscosity rubber (gel) extracted from natural rubber, with PHBV. These blended materials proved suitable for making TV trays and blown films. However, commercial sources of high viscosity natural rubber were found to no longer exist. The preliminary objective of this work was to manufacture peroxide cured high viscosity natural rubber matched to that of natural rubber gel so that the bioplastic-rubber blend could be scaled up to commercially meaningful volumes. A new organic peroxide cure system was sourced, which is completely consumed during an initial heating step and so can be used to induce controlled and complete crosslinking. Hence, organic peroxide cured matched viscosity natural rubber (MVNR) was developed to achieve properties comparable to that of high viscosity rubber (Hevea gel). Different lodgings of peroxide such as 0.5, 1, 1.5, 2 phr (parts per hundred rubber) were considered. Rheological and mechanical testing's were conducted on each of the peroxide cured natural rubber samples. 2phr peroxide (Luperox101XL45) cured natural rubber (SMR-L) at 180oC was found to have higher complex viscosity than Hevea gel. This matched viscosity natural rubber is referred as MVNR. Our next step was to incorporate this MVNR into a PHBV matrix. Dynamic vulcanization effectively dispersed and vulcanized the elastomeric (MVNR) phase within the thermoplastic (PHBV) matrix. Such systems (open full item for complete abstract)

Committee: Koelling Kurt PhD (Advisor); Cornish Katrina PhD (Committee Member); Vodovotz Yael PhD (Committee Member) Subjects: Chemical Engineering; Packaging; Plastics; Polymer Chemistry; Polymers

Doctor of Philosophy, The Ohio State University, 1973, Graduate School

Committee: Not Provided (Other) Subjects: Engineering

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

Ionomers are flexible polymers containing small amount of covalently attached ionic groups. Those polar groups tend to form ionic aggregates in low dielectric polymer medium due to their strong polar/ionic interactions. The ionic aggregates, serving as physical crosslinks, endow the ionomers with excellent physical and mechanical properties. Owing to the absence of chain entanglement, oligomeric sulfonated polystyrene (SPS) ionomers were selected as a model system to understand the dynamics of ionomers. Firstly, oligomeric SPS ionomers with different degrees of sulfonation (p) and metal cations were prepared from two oligomeric PS precursors. The gel point of SPS ionomers was determined as p = pc, corresponding to one ionic group per chain on average. Below the gel point, p < pc, the ionomer behaves like a sol with delayed Rouse relaxation. Close to the gel point, p ~ pc, characteristic power law relaxations occur with G'(ω) ~ G"(ω) ~ ω1 for mean field region, G'(ω) ~ G"(ω) ~ ω2/3 for critical percolation region, and G'(ω) ~ω2, G"(ω) ~ ω1 for terminal region. Above the gel point, p > pc, ionomers show a plateau in the G', and the plateau modulus increases with increasing p but remains constant for all different metal cations. Based on the mean field theory of Rubinstein and Semenov, a reversible gelation model was developed to analyze and predict the LVE behavior of SPS ionomers. This model, with only two parameters, the Rouse relaxation time of the Kuhn segment τ0 and ionic dissociation time τs, predicts well the LVE behavior of SPS ionomers with all different p and alkali cations. The obtained segment relaxation time, τ0, increases linearly with the increasing p but remains nearly unchanged for different metal cations. The ionic dissociation time, τs, however, highly depends on the type of metal cation, serving as an indicator for the strength of ionic interaction. For alkali metal cations, τsincreases with the decrease in cation radius due to the increased Coul (open full item for complete abstract)

Committee: Robert Weiss Dr. (Advisor); Kevin Cavicchi Dr. (Committee Chair); Bryan Vogt Dr. (Committee Member); Matthew Becker Dr. (Committee Member); Jiahua Zhu Dr. (Committee Member) Subjects: Polymers

Master of Fine Arts, The Ohio State University, 2016, Art

As a conceptual artist, I am constantly searching for a material form for my ideas. As a result, my portfolio appears inconsistent across materials and processes. In this thesis document I argue for a conceptual process by reading the thesis exhibition, Corridor #1, against a previous work, A Gesture Towards Zero. Articulating this approach is crucial to the progression of my practice beyond the Master of Fine Arts degree.

Committee: Roger Beebe (Committee Chair); Dani Leventhal (Advisor); Amy Youngs (Advisor) Subjects: Fine Arts

Master of Science, Miami University, 2015, Physics

This thesis presents the application of an empirical model of total internal reflection (TIR) we recently developed in conjunction with a home-built sensor to detect nanoaggregates in highly scattering opaque polystyrene colloidal suspensions. The nanoaggregates are detected directly without any sample dilution or special sample preparation. Additional results on nanoaggregate detection in gold nanoparticle suspensions are presented. Preliminary tests of our model and sensor in an absorbing dye solution are also presented.

Committee: Samir Bali PhD (Advisor); Lalit Bali PhD (Advisor); Jason Berberich PhD (Advisor); Jon Scaffidi PhD (Advisor); James Clemens PhD (Committee Member); Karthik Vishwanath PhD (Committee Member) Subjects: Analytical Chemistry; Biochemistry; Biomedical Engineering; Biomedical Research; Biophysics; Chemical Engineering; Chemistry; Experiments; Materials Science; Medical Imaging; Molecular Physics; Molecules; Nanoscience; Nanotechnology; Optics; Organic Chemistry; Physics; Polymer Chemistry; Polymers; Scientific Imaging

Master of Science, University of Akron, 2014, Polymer Science

Thermally stimulated fluctuations on polymer melts are important since they influence wetting, adhesion and friction. Study in this field has just begun recently. The most studied polymer is linear polystyrene (LPS) since it is easy to synthesize. A hydrodynamic continuum theory (HCT) that treats films as uniform layers of thickness, h, having bulk viscosity is able to explain surface fluctuations on melts of linear chains some times. The surface fluctuations can be characterized by a relaxation time, t, that varies with the value of the in-plane scattering vector, q. Kim and collaborators3 found that data for samples of different thicknesses, h(of which no confinement effect happens), collapse onto a single curve at a given temperature in the plot of t/h vs. qh, which is consistent with HCT model. However, deviations were observed in subsequent work at temperatures near Tg, for molecular weights, M, such that M > Mc, where Mc is the critical molecular weight for entanglements.1 Also, deviations were seen for very thin films with h<4 Rg, where Rg is radius of gyration.25 For very thin films, confinement effect induces the deviation. Wang and collaborators13 found that the confinement effect happens when the film is thinner than 10 Rg for 14k cyclic polystyrene (CPS). Subsequent work by He et al14. showed that for 6k CPS, data for films thinner than 20 Rg did not follow the HCT model, but no confinement effect was observed for the 6k LPS film even when thickness reaches 7 Rg. A tadpole-like polystyrene (TPS) has an architecture between that of CPS and LPS. It was synthesized using anionic polymerization via two synthetic approaches. The first route is to synthesize a functionalizable cyclic polystyrene with a silicon-hydrogen bond, which can be used for hydrosilylation to get the tadpole-like polystyrene. The second route is based on a metathesis ring-closure technique, which is used to cyclize two of the three arms in the 3-arms star precursor to create the tadp (open full item for complete abstract)

Committee: Mark Foster Dr. (Advisor); Roderic Quirk Dr. (Advisor) Subjects: Polymer Chemistry

Master of Science in Polymer Engineering, University of Akron, 2014, Polymer Engineering

This study focuses on hybrid aerogels of syndiotactic polystyrene (sPS) and silica where silica concentration is varied and silica condensation conditions are varied to produce various mesoporous materials. In addition, the study investigates hybrid materials obtained by coating sulfonated syndiotactic polystyrene on a cellulose filter paper. In first part of this study, syndiotactic polystyrene is modified by sulfonation to enable further chemical modifications. Specifically, sulfonated syndiotactic polystyrene (ssPS) is coated on macroporous cellulose filter paper using a dip coating process, ssPS is turned into gel by thermoreversible gelation, and finally aniline is polymerized on ssPS strands to obtain a hybrid aerogel with electrical conductivity. The aerogels are recoved by removing the solvents under supercritical conditions. The ssPS aerogels are coated on cellulose filter materials to derive two benefits: first, to capitalize on the large surface area of ssPS aerogels and second, to exploit the mechanical strength of the cellulose filter. In second part of this study, silane precursor is absorbed inside the macropores of sPS gels and silica gels are grown under both a two-step reaction and a one-step reaction. Type A silica aerogel is synthesized by acid-base catalyzed sol-gel method, while type B silica aerogel is prepared only by acid catalyzed sol-gel process. Type A silica gels exhibit pearl-necklace structure, while type B silica gels are composed of strand-like silica particles. In the process, the mesoporous hydrophilic silica particles are combined with macro- and microporous hydrophobic sPS in single articles. This unique combination of organic and inorganic materials and their associated surface area and surface energy offer a number of attractive properties. The sPS/silica hybrid aerogels are fabricated from different concentrations of sPS in solution and from different weight ratio of sPS to silica. The sPS/silica hybrid aeroge (open full item for complete abstract)

Committee: Sadhan C Jana Dr. (Advisor); Nicole Zacharia Dr. (Committee Member); Bryan Vogt Dr. (Committee Member) Subjects: Polymer Chemistry; Polymers