Doctor of Philosophy, Miami University, 2021, Chemistry and Biochemistry

This work is designed to understand how to efficiently synthesize polymers for and to understand two major biotechnology applications - protein-polymer conjugates, and macromolecular surfactants for favorable cell membrane interactions. Polymers are a ubiquitous class of molecules in the world due to the unique and complex properties that arise from combining simple building blocks in particular combinations. Nature has adopted proteins, amino acid polymers that fulfill myriad critical functions. In recent years, the biotechnology industry has begun to manipulate proteins by attaching synthetic polymers to them, conferring invisibility to the immune system for protein drugs, or enhanced stability, activity, or recyclability to enzymes for biocatalysis. A protein molecule on its own is sufficiently complex to require years-long research projects to fully understand. Thus, protein-polymer conjugates are still poorly understood. In this work, we present a technique for the study of conjugates, enabled by reversible deactivation radical polymerization, which by nuclear magnetic resonance allows for an atomic-level view. We also explored the challenge of attaching two distinct polymers to a single protein molecule in an efficient and well-defined manner, which would enable still more complex conjugates. Lipid membranes and the proteins that reside within them are another area of biotechnology that polymers have broken into. Cell membranes and the proteins within them experience a complex play of intermolecular forces. The unique location of membrane proteins makes them difficult to study, as they are not readily crystallized, and resuspension using traditional detergents can be detrimental to protein structure. Styrene-maleic acid copolymers and their relatives are known to form a belt containing lipids and membrane proteins in disk-shaped nanoparticles. These maintain the bilayer shape and avoid the use of detergents and have enabled characterization of previously (open full item for complete abstract)

Committee: Dominik Konkolewicz PhD (Advisor); Richard Page PhD (Advisor); Richard Taylor PhD (Committee Chair); Carole Dabney-Smith PhD (Committee Member); Jason Berberich PhD (Committee Member) Subjects: Biochemistry; Biophysics; Chemistry; Polymer Chemistry; Polymers

Master of Science, The Ohio State University, 2013, Horticulture and Crop Science

Grafting is a technique that has been used for fruit trees and vine crops for thousand years. Grafting to rootstocks is becoming popular in annual vegetable production to control soil-borne diseases, replace fumigation, increase yield, increase tolerance to abiotic stress, and impart vigor. Previous research indicates that inconsistent seed quality and lack of information about rootstock-scion compatibility affect the efficiency of grafting, raises cost, and inhibits adoption of the technology. The goals of this research were to address limitations in seed quality and graft efficiency. The specific objectives were: a) evaluate genetic and environmental factors affecting quality of seed in hybrids derived from interspecific crosses, b) improve grafting success through use of adhesives, and c) determine the genetic basis of graft failure between rootstock and scion. Tomato is a model for grafting annual vegetables due to the importance of the crop and the extensive genetic resources available. To assess the potential to select for improved seed quality, experimental rootstocks were developed through pollination of cultivated (Solanum lycopersicum L.) parental lines as female parents and 11 accessions of wild species as male parents. Seed quality was evaluated based on seed size (weight) and total germinability for each hybrid produced. Maternal effects and environment determined fruit set. Specific genotype combinations and environment determined seed yield. Seed size was mainly affected by genetic components, while seed germination was affected by both genetics and environmental factors. Seed size can be used as selection criterion in breeding program for early selection of rootstock seed quality. To improve graft success, nine different tomato rootstocks were grafted using the traditional tube method of grafting and using adhesives. Despite wide variation across rootstock genotypes and grafting environment, grafting using adhesives resulted in higher grafting suc (open full item for complete abstract)

Committee: David Francis M. Dr. (Advisor); Pablo Jourdan Dr. (Committee Member); Matthew Kleinhenz Dr. (Committee Member) Subjects: Agriculture; Agronomy; Horticulture; Plant Sciences

PhD, University of Cincinnati, 2024, Arts and Sciences: Chemistry

Carbon nanotubes (CNTs) hold immense promise in various technological applications, yet their efficacy has been hindered by challenges in establishing robust connections with metal surfaces. This study explores novel methods to address this limitation and enhance the electrical conductivity of CNT-metal interfaces. The resultant CNT-metal hybrid consists of strong bonding in between CNTs, and metal has been investigated in various applications such as sensors and energy storage devices. Covalent bond formation between open-ended CNTs and Cu surfaces is explored experimentally and theoretically. Vertical orientation of CNTs relative to the substrate, coupled with carboxylic functional groups on CNTs reacting with aminophenyl linkers on metal surfaces, facilitates amide bond formation at low temperatures. Theoretical analysis reveals bridge-like bond formations between carbon and adjacent Cu atoms, supporting the observed electrical conductivity enhancement. The robustness of covalent bonding is demonstrated through sonication tests. Due to the appealing nature of carbon nanotubes (CNT) in applications, the investigation extended on CNT films bonded to metal surfaces. Utilizing aligned CNT films, chemically covalent bonds are established between CNTs and various metal surfaces, including Cu, stainless steel, Au, indium tin oxide, and Al. Characterization techniques confirm the formation of robust bonds, with scanning electron microscopy validating their stability post-ultrasonication. Enhanced electrode performance suggests potential applications in sensor technology. Further, CNT bonded to metal electrodes were investigated in energy storage applications. Innovative fabrication of CNT-metal electrodes is achieved by forming chemical bonds between vertically aligned carbon nanotubes (VACNTs) and Au metal surfaces using linker molecules. Covalent bonds between CNTs and diazonium-based linker molecules on the Au surface result in highly conductive interfa (open full item for complete abstract)

Committee: Noe Alvarez Ph.D. (Committee Chair); Jianbing Jiang Ph.D. (Committee Member); Hairong Guan Ph.D. (Committee Member) Subjects: Chemistry

Master of Science, The Ohio State University, 1921, Graduate School

Committee: Not Provided (Other) Subjects:

Doctor of Philosophy, University of Akron, 2022, Polymer Science

Novel modifications of styrene-butadiene rubber were studied using conventional curatives, sulfur curing packages or peroxides, to efficiently utilize supramolecular reinforcement strategies that improve the mechanical properties of rubber. Thiol-ene coupling proved to be an effective method for modifying styrene-butadiene rubber during peroxide curing, but it was inadequate when attempted during sulfur vulcanization. Supramolecular reinforcement was achieved by grafting mercapto-functionalized sodium phosphate esters to styrene-butadiene rubber during peroxide curing which electrostatically associate. The association strength between these ionic grafts played a critical role in determining the degree of reinforcement. Possible mechanisms by which reinforcement occurs were discussed and, at low grafting densities, at least one mechanism was determined not to play a major role. It was shown that substantial modification of cis-1,4-polyisoprene does not occur by thiol-ene coupling and that another chemical means must be used to modify this substrate. Reagents consisting of thioaldehydes derived from thiosulfinates were used in Alder-ene reactions to modify cis-1,4-polyisoprene. Based on this chemistry, new grafting and crosslinking agents were developed that react quickly and at relatively low temperatures. Important elements in the molecular design of these curatives were discussed and it was demonstrated that good mechanical properties are attainable.

Committee: Li Jia (Advisor); Mark Foster (Committee Chair); Shing-Chung Wong (Committee Member); Tianbo Liu (Committee Member); James Eagan (Committee Member) Subjects: Chemistry; Materials Science; Molecular Chemistry; Morphology; Nanoscience; Nanotechnology; Organic Chemistry; Polymer Chemistry; Polymers

Doctor of Philosophy, Case Western Reserve University, 2023, Macromolecular Science and Engineering

Due to the effort in the past two decades, reversible addition-fragmentation chain transfer (RAFT) polymerization has developed into one of the most versatile and powerful living radical polymerization (LRP) for preparing polymers with different architectures. However, challenge remains because the presence of oxygen will quench the initiation and propagation radicals. In recent years, photoinduced electron/energy transfer-RAFT (PET-RAFT) polymerization has been developed. This technique uses visible light to initiate the reaction and is compatible with ambient condition and green solvents. It also maintains the ability of producing well-defined polymers and possess high potential as an alternative of conventional RAFT technique. Chapter 1 reviewed basics of Raft polymerization and recent efforts in developing PET-RAFT polymerization. In addition, applications of PET-RAFT in flow chemistry and on polymer brushes are also discussed. Chapter 2 reported synthesis of a series of hyperbranched polymers via PET-RAFT self-condensing vinyl polymerization (SCVP) in a flow reactor, which showed considerable controllability in molecular weight and branching density by adjusting the feeding ratio of monomer to transmer. The synthesis of block copolymers was also discussed. Chapter 3 demonstrated a new approach for preparing polymer brushes on conductive surface via surface-initiated PET-RAFT polymerization (SI-PET-RAFT), which showed capability of encapsulating gold nanoparticles. In chapter 4, four different architectures of linear or branched polymers were fabricated on conductive surface using SI-PET-RAFT. Their difference in morphology and encapsulation ability was also discussed. Finally in chapter 5, conclusion, perspectives, and future work based on chapter 2-4 is represented.

Committee: Rigoberto Advincula (Advisor); Gary Wnek (Committee Chair); Fu-sen Liang (Committee Member); Mike Hore (Committee Member); Valentin Rodionov (Committee Member) Subjects: Polymer Chemistry; Polymers

Doctor of Philosophy, The Ohio State University, 2021, Horticulture and Crop Science

Plant breeders have used wild relatives as a source of genetic diversity for biotic and abiotic stress mitigation since the early 20th century. This natural allelic diversity is a vital resource for crop improvement. The focus of this dissertation was to use tomato as a model to compare two methods of accessing trait diversity from wild relatives: introgression breeding and grafting. The specific aims were to estimate the genetic and environmental contributions to trait delivery methods and assess their relative efficacy and limitations. An accession of the endemic Galapagos tomato, S. galapagense LA1141, provided allelic variation for the genetic dissection of purple fruit pigmentation and tolerance to water deficit stress. Accessions of S. pimpinellifolium and S. habrochaites were used as parents to develop interspecific hybrid rootstock for multi-year, multi-location field trials. The first objective was to determine the chemical and genetic basis of purple pigmentation. Accession LA1141 and a processing tomato, OH8245, were used to develop populations for the simultaneous characterization and introgression of traits. The breeding strategy employed repeated backcrossing (BC) followed by inbreeding (S). The LA1141 × OH8245 populations provided plant materials to identify genetic factors that underlie quantitative trait loci (QTL) while introducing these traits into a commercially viable genetic background. I genotyped the LA1141 × OH8245 BC2S3 generation with single nucleotide polymorphisms, created a linkage map, and conducted composite interval mapping. Anthocyanins were identified as causal pigments, and QTL analysis revealed genetic regions that explained as much as 35% of the variation in color. These analyses led to the identification of candidate genes. Subsequent sequence and phylogenetic analyses supported a conservation of mechanism leading to purple fruit, while identifying novel alleles at the Anthocyanin fruit, atroviolacium, and uniform ripening l (open full item for complete abstract)

Committee: David Fancis PhD (Advisor); Jessica Cooperstone PhD (Committee Member); Mathew Kleinhenz PhD (Committee Member); Chieri Kubota PhD (Committee Member); Christine Spunrger PhD (Committee Member) Subjects: Horticulture; Plant Biology; Plant Sciences

Master of Science, The Ohio State University, 2020, Horticulture and Crop Science

In recent years, the North American region has seen increased usage of grafted vegetable transplants to reduce soil-borne disease incidence, increase tolerance to abiotic stress, enhance fruit quality, and increase yields over conventional nongrafted transplants. Grafting itself is a unique agrotechnology that merges a vegetable crop (scion) with the root system of another plant (rootstock) to form one transplant that benefits from both traits. In North America, a recent survey showed nearly 60 million grafted transplants are produced annually for fruiting vegetable crops, including tomato, watermelon, cucumber, pepper, eggplant, and muskmelon. Due to the limited number of nurseries in North America, transplants are commonly shipped 3-5 d to distant producers and have reportedly experienced chilling stress during transportation that reduces transplant quality and may affect post-transplanting performance. However, few studies have explored the specific effects of transport-related chilling stress on seedling quality and post-transplanting development. Using watermelon (Citrullus lanatus), a highly chilling sensitive member of the Cucurbitacea family, we examined effects of acute chilling stress on seedlings quality and post-transplanting development. When grafted and nongrafted seedlings were exposed to 0 - 48 h of 3 °C chilling, we found that seedling quality and post-transplanting development were unaffected by chilling. However, when the chilling temperature was reduced to 1 °C, seedlings exhibited increased visual damage of seedlings with longer durations, decreased chlorophyll fluorescence (Fv/Fm), and increased delays in the number of days it took for plants to reach male and female flower anthesis after transplanting. Nongrafted plants had longer delays in days to flower anthesis than grafted plants, indicating that grafted plants may have been more resistant to chilling or had enhanced flower primordia development that reduced the effects of acute chilling. (open full item for complete abstract)

Committee: Chieri Kubota (Advisor); Joseph Scheerens (Committee Member); Matthew Kleinhenz (Committee Member) Subjects: Agriculture; Horticulture; Physiology; Plant Biology; Plant Sciences

Doctor of Philosophy, The Ohio State University, 2018, Plant Pathology

Salmonellosis cases caused by Salmonella enterica through pre-harvest contamination of fresh produce represent a risk to human health worldwide; however, little is known about the interactions between Salmonella, phytopathogens, environment, and the plant host contributing to this food safety issue. Furthermore, the control of Salmonella from “farm to fork” is challenging due to the development of resistance mechanisms towards current control methods and restrictions on use of antimicrobials imposed by regulatory agencies. We investigated the effects of specific environmental conditions on the persistence and dissemination of Salmonella enterica subsp. enterica serotype Typhimurium (S. Typhimurium) following artificial contamination of `Tiny Tim' tomato plants. We found that higher temperatures (30°C day/25°C night) reduced the persistence of S. Typhimurium in the phyllosphere compared to lower temperatures (20°C day/15°C night) when plants were sprayed on the leaves with a S. Typhimurium -contaminated solution. Wounding cotyledons with contaminated tools increased S. Typhimurium persistence and internalization in planta compared to spray inoculation. Low relative humidity enhanced the dissemination of Salmonella into non-inoculated plant tissues. S. Typhimurium was detected in the root systems for at least 98 days-post inoculation. Further, we showed that splice-grafting (`Celebrity' with 'MaxiFort') is a major risk for the internalization and long-term survival of S. Typhimurium inside the tomato plant. S. Typhimurium was detected in the root system for over 137 days if at least 5 x 10^3 colony-forming units were introduced during grafting. The survival of S. Typhimurium in tomato foliage was also affected by the presence of phytopathogens, the genotype of S. Typhimurium and tomato variety used. We found that rfbV, involved in O antigen synthesis, might be essential for S. Typhimurium persistence in inoculated tomato plants and especially in `Tiny Tim' plants (open full item for complete abstract)

Committee: Gireesh Rajashekara (Advisor); Sally Miller (Advisor); Laurence Madden (Committee Member); Christopher Taylor (Committee Member); Corey Nislow (Committee Member) Subjects: Agriculture; Bioinformatics; Biology; Environmental Health; Molecular Biology; Plant Pathology; Public Health

Master of Science, The Ohio State University, 2017, Horticulture and Crop Science

Root systems are known to have profound influences on nearly every aspect of plant development and biology, including vegetative and reproductive capacity. However, the specific impacts of intra-specific combinations of root and shoot systems, when combined in physical hybrids, on important physical, chemical, and sensory properties of Capsicum annumm pepper fruit are largely unknown. Grafting was used to combine the canopy and root system of two types of Capsicum plants (producers and non-producers of capsaicin and small, more elongated versus large, blocky fruit), thereby making it possible to examine the separate and combined roles of variety-specific roots and shoots in shaping key fruit characteristics, among them the concentration of capsaicin. Capsaicin is an ideal metabolite to study root-shoot interaction and roles because early stages of its biosynthetic pathway occur in the roots, with final assembly in the fruit at advanced stages of development. Fruit size, shape, wall thickness, and soluble solids levels were similarly tracked as they and capsaicin influence consumer acceptability and fruit marketability. The overall program involved field studies in 2016 and 2017, a targeted wintertime greenhouse study, and consumer sensory analysis. Overall, it was found that the Capsicum variety supplying the root system of the grafted plant had little influence on the variables measured when a sweet pepper was used as a scion. When a hot pepper was used as a scion the root system played a large role in influencing the capsaicinoid profile of the fruit. Implications of this finding include: a) that the variables measured are influenced by more than the root systems used here and b) that it may possible to employ rootstock-scion combinations without concern over rootstock influence on fruit in commercial production.

Committee: Matthew Kleinhenz (Advisor); Joseph Scheerens (Advisor) Subjects: Biology; Botany; Food Science; Horticulture

Doctor of Philosophy, The Ohio State University, 1970, Graduate School

Committee: Not Provided (Other) Subjects: Biology

Doctor of Philosophy, The Ohio State University, 1963, Graduate School

Committee: Not Provided (Other) Subjects: Agriculture

Doctor of Philosophy, The Ohio State University, 2016, Horticulture and Crop Science

Seedling development is a period of dynamic change within the overall vegetable plant and crop development period. For example, leaf area, stem length, and above-ground biomass can increase several fold within 1-3 weeks of emergence, possibly signaling high rates of carbon fixation on a per gram fresh weight basis and prescribed patterns of primary growth. Still, while general patterns of seedling development are familiar and the influence of individual major environmental factors on it are well chronicled, a reliable, accessible, and highly repeatable approach to describe the efficiency with which seedlings convert growth factors into biomass and partition it is unavailable. We hypothesized that plant and environmental data could be integrated into a single “seedling vigor” value allowing for more direct and consistent comparisons of seedling growth within and across experiments. We tested this hypothesis in a greenhouse experiment involving the simultaneous tracking of seven parameters of seedling growth (above-ground biomass and growth pattern) in twenty-three commercial tomato varieties and four environmental variables through 18 d after seeding. A formula created for the test used the plant and environmental data in calculating seedling vigor values and the experiment was repeated twice over a four-month period in the spring. Minimum and maximum seedling vigor values differed 79- to 575-fold among cultivars in runs 1 and 2, respectively, although relative variety vigor values were generally consistent between runs. These results demonstrate: 1) that varieties differ in their primary growth capacities under identical growing conditions and 2) that calculations of vigor like the one demonstrated here can reliably differentiate these capacities and help standardize reports including them. Normal seedling development, perhaps especially root-shoot communication and root and shoot level (carbon) partitioning, is severely disrupted in the process of grafting. In f (open full item for complete abstract)

Committee: Matt Kleinhenz (Advisor) Subjects: Horticulture

Doctor of Philosophy in Engineering, University of Toledo, 2010, Chemical Engineering

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

Committee: Isabel Escobar PhD (Advisor); Sasidhar Varanasi PhD (Committee Member); Maria Coleman PhD (Committee Member); Dong-Shik Kim PhD (Committee Member); Jared Anderson PhD (Committee Member) Subjects: Chemical Engineering; Chemistry; Engineering; Environmental Engineering

Master of Science in Bioengineering, University of Toledo, 2005, Bioengineering

Annually, an estimated 1.2 million allografts are transplanted in the United States for repair or reconstruction of skeletal defects caused by disease, illness, or injury. Sterilization of these allografts must be performed to prevent disease transmission and reduce the inherent risk of infection. Currently, there is no single accepted sterilization technique in the bone and tissue banking industry. Gamma irradiation is the most popular and the safest form of allograft sterilization. However, to attain that level of sterility assurance, the biochemical and biomechanical integrity of the allograft is compromised, which is a serious concern since bone allografts are used in load bearing applications. Damage to allografts results in the radiolysis of water molecules during gamma irradiation. The water molecules bound to the tissue are essentially split into highly reactive, damaging free radical molecules. These free radicals cleave the collagen molecules in bone allograft tissues. One method to control the formation of these free radicals is to add a free radical scavenger to the bone allograft before gamma irradiation sterilization. However, while the free radical scavenger is protecting the collagen, is there the unintended consequence that the free radical scavenger is also protecting the pathogenetic organisms that should be eradicated? It was hypothesized that small, positively charged, globularly shaped free radical scavengers will protect bacteria more efficiently because the scavenger will be able to penetrate the intracellular space of the cell and thus scavenger for the free radicals that should be killing the bacteria. To test this hypothesis, viability tests were preformed with E. coli. Free radical scavengers were selected based on their charge, size, and shape. Solutions of these scavengers were added to E. coli suspended in media and incubated at time points of 0, 10, 20, and 40 hours and then subsequently irradiated to a dose of 500Gy. Results showed t (open full item for complete abstract)

Committee: Ozan Akkus (Advisor) Subjects: Engineering, Biomedical

Master of Science, The Ohio State University, 2012, Plant Pathology

Tomatoes are one of the most important crops in fresh market and processing industries. Due to fluctuating environment, plant diseases for instance, the production of tomatoes faces problems in both physiological growth and fruit morphology. In our study, we found that management practices (e.g. grafting) and environmental variation (across locations) affected both tomato physiology and fruit morphology. In the first study, grafting was found to affect biomass, leaf nutrient levels, and it also seemed to affect disease incidence, α-tomatine level and slightly impacted microbial community structure. Fresh and dry weight biomass of shoots of grafted plants tended to be less than ungrafted plants; however, differences were minimal in later phase of growth. Cross-grafted plants also had more leaf nutrient levels such as P, Ca and B in one or more rootstocks. α-tomatine, one disease resistance related compound in tomato leaves, also seemed to be higher in self-grafted plants. Although no significant differences were found, disease incidence of self-grafted plants tended to be less than the ungrafted plants. Grafting effects on tomato rhizosphere microbes and the contribution to disease resistance were also evaluated. Four 16S and three ITS TRFs (Terminal Restriction Fragments) were found significantly different in abundance between self-grafted and ungrafted plants. Two ITS TRFs were found significantly different in abundance between cross-grafted and ungrafted plants. In general, grafting affected tomato scion physiology and tended to reduced disease incidence, though this may be related to the small noted changes in microbial community structure. Environment impact in tomato fruit shape was evaluated in the second study. Variations in shape characteristics of 48 cultivars grown in three different locations (i.e. OH, NC, and NY) were investigated. Both cultivar and growing environment affected the relative proportion of malformed (MAL) fruit number and weight that deve (open full item for complete abstract)

Committee: Brian McSpadden Gardener PhD (Advisor); Esther Van der Knaap PhD (Committee Member); Terrence Graham PhD (Committee Member) Subjects: Plant Pathology

Doctor of Philosophy, University of Akron, 2008, Polymer Science

Poly(vinyl chloride), PVC, is a particularly important commodity polymer that accounts for an annual world-wide production of 26 million tons. It is used frequently in the medical field as blood storage bags, endotracheal and dialysis tubing and intravenous catheters. Common plasticizers, namely di(2-ethylhexyl) phthalate (DEHP), are added to PVC to improve the processability and flexibility by lowering the glass transition temperature. However, most phthalate plasticizers are potential carcinogens. There has been extensive research on PVC with surface coatings to improve biocompatibility, surface crosslinking to create a barrier to the plasticizer leaching and surface grafting of hydrophilic polymers for both biocompatibility and reduced plasticizer migration. A novel surface grafting technique is the grafting of hydrophilic monomers by physisorbed free radical initiators. This modification method can be applied to PVC to attach vinyl hydrophilic monomers by the “grafting from” method. This approach, extending on earlier work involving polymer brush formation on poly(dimethylsiloxane), involves a two-step process: physisorption of a hydrophobic free radical initiator onto a polymer surface followed by radical polymerization of hydrophilic monomers in water. The key step is creating a hydrophobic/hydrophilic diffusional barrier that promotes radical reactions at the polymer surface. Polymers that have been successfully grafted from PVC films and tubing include: poly(hydroxyethyl methacrylate) (PHEMA), poly(dimethylacrylamide) (PDMA), poly(hydroxyethyl acrylate) (PHEA), poly(dimethylaminoethyl methacrylate) (PDMAEMA), poly(acrylic acid) (PAA), and poly(4-vinylpyridine) (P4VP). Characterization methods performed include bulk chemical composition by transmission infrared spectroscopy, surface composition using X-ray photoelectron spectroscopy, surface wettability by tensiometry and capillary rise, film thickness determination by infrared, gravimetric analysis and UV- (open full item for complete abstract)

Committee: Roderic Quirk (Advisor) Subjects: Polymers

Doctor of Philosophy, University of Akron, 2008, Polymer Science

Surface modification of nanosized silica particles by polymer grafting is gaining attention. This can be attributed to the fact that it provides a unique opportunity to engineer the interfacial properties of these modified particles; at the same time the mechanical and thermal properties of the polymers can be improved. Controlled free radical polymerization is a versatile technique which affords control over molecular weight, molecular weight distribution, architecture and functionalities of the resulting polymer. Three commonly used controlled free radical polymerizations include nitroxide- mediated polymerization (NMP), atom transfer radical polymerization (ATRP) and reversible addition fragmentation transfer (RAFT) polymerization. ATRP and RAFT polymerization were explored in order to modify the silica surface with well-defined polymer brushes. A novel click-functionalized RAFT chain transfer agent (RAFT CTA) was synthesized which opened up the possibility of using RAFT polymerization and click chemistry together in surface modification. Using this RAFT CTA, the surface of silica nanoparticles was modified with polystyrene and polyacrylamide brushes via the “grafting to” approach. Both tethered polystyrene and polyacrylamide chains were found in the brush regime. The combination of ATRP and click chemistry was also explored for surface modification. A combination of RAFT polymerization and click chemistry was also studied to modify the surface via the “grafting from” approach. Our strategy included the (1) “grafting from” approach for brush formation (2) facile click reaction to immobilize the RAFT agent (3) synthesis of R-supported chain transfer agent and (4) use of the more active trithiocarbonate RAFT agent. Grafting density obtained by this method was significantly higher than reported values in the literature. Polystyrene (PS) grafted silica nanoparticles were also prepared by a tandem process that simultaneously employs reversible addition fragmentation t (open full item for complete abstract)

Committee: Roderic Quirk PhD (Advisor); Colleen Pugh PhD (Committee Chair); Ali Dhinojwala PhD (Committee Member); Scott Collins PhD (Committee Member); Bi-min Zhang Newby PhD (Committee Member) Subjects: Polymers