Doctor of Philosophy, Case Western Reserve University, 2009, Macromolecular Science and Engineering

Hyperbranched polymers, specifically hyperbranched poly(arylene ether ketone imide)s (HBPAEKI), are here studied as blend additives in thermoset composites to improve processing and ultimate performance properties of the composite. Monomer synthesis for HBPAEKI was further advanced in this work leading to higher yields, fewer reactions, and shorter production times. A five step synthetic method with an overall yield of 12% was reduced to a three step process with an overall yield of 38%. Polymer was synthesized under varying conditions and end group chemistry for use in thermoset blends. NMR characterization allowed for the assignment of chemical shifts in monomer and cataloguing of shifts in polymer for use in future work to characterize degree of branching.Cure kinetics of blends of HBPAEKI are explored through the use of differential scanning calorimetry (DSC) and chemorheology using small angle oscillatory shear. In a phenylethynyl terminated imide oligomer (PETI) thermoset resin, reactive phenylethynyl endcapped PAEKI (PEPAEKI) was found to retard cure while non reactive alkyl endcapped PAEKI was found to accelerate cure in DGEBA/DAH epoxy systems. Minimal effect was seen on early stage blend viscosity. Composite properties tested focused on the effect on bulk fracture and interfacial shear strength. No significant effect was seen in fracture toughness by SENB. XPS was used to verify that PEPAEKI was surface active to DGEBA/DDS epoxy/air interfaces to the complete exclusion of the epoxy at the surface. Evidence was also seen consistent with surface activity in alkyl endcapped PAEKI in DGEBA/DAH systems, although the contrast is much lower. Effect of alkyl endcapped HBPAEKI on interfacial shear strength was examined through the use of t-peel and single fiber fracture (SFF) techniques. In some systems, t-peel indicates a clear improvement in peel force, proportional to the blend concentration. In SFF, interfacial shear strength was found to be equal or slightly r (open full item for complete abstract)

Committee: Patrick T. Mather PhD (Committee Chair); J. Adin Mann Jr (Committee Member); Stuart J. Rowan PhD (Committee Member); David Schiraldi PhD (Committee Member) Subjects: Polymers

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

A new class of inimer (a molecule containing an initiating site and a polymerizable group in the same molecule) was synthesized from a key halohydrin-based intermediate, which was obtained from serine by a diazotization synthetic route. Polymerization of these inimers resulted in hyperbranched polyacrylates using the concepts of self-condensing vinyl polymerization (SCVP) and atom transfer radical polymerization (ATRP). These hyperbranched polyacrylates contain an ester group attached to every other carbon atom along the polymer backbone, with a non-initiator-containing alkyl ester attached as a free side chain. This is in contrast to previously reported hyperbranched polyacrylates, which have these ester groups along the polymer backbone upon reaction. The architecture of our new polymers is therefore more chemically analogous to linear polyacrylates. We have synthesized and characterized polyacrylates with different ester functional side chains such as alkyl, perfluoro, siloxane, oligo(oxyethylene) and mesogenic side chains . The hyperbranched side-chain liquid crystalline polyacrylates (SCLCPs) were synthesized and characterized intensively by 1H, 13C and 2D nuclear magnetic resonance (NMR) spectroscopy, matrix assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry, differential scanning calorimetry (DSC), polarized optical microscopy (POM), gel permeation chromatography (GPC), light scattering (LS), solution viscosity and rheological techniques. In this work, the structure was qualitatively analyzed by 1H, 13C and 2D NMR techniques to obtain the branching units . Solution properties, e.g. radius of gyration and intrinsic viscosity, thermal properties (glass transition and isotropization temperatures) and rhelogical peroperties (isotropic and anisotropic viscosity) of the hyperbranched side-chain liquid crystalline polyacrylate were compared with those of the linear , three-arm star , six-arm star and comb analogues. This work provides (open full item for complete abstract)

Committee: Coleen Pugh (Advisor); Stephen Cheng (Committee Chair); Peter Rinaldi (Committee Member); Roderic Quirk (Committee Member); Li Jia (Committee Member) Subjects: Polymers

PhD, University of Cincinnati, 2022, Arts and Sciences: Chemistry

Stimuli-responsive hydrogels that undergo a change in properties including stiffness and swelling in response to external stimuli are becoming important in many fields such as sensors, soft robots, and mimicking extracellular matrix (ECM) matrix for biomedical applications. However, it has been suggested that in order to observe meaningful changes differences in hydrogel stiffness of several kPa are required and are limited. To address this issue, we have tuned the polymer architecture and synthesized hydrogels using hyperbranched polymer and compared its properties with the conventional linear polymer. Hyperbranched polymer poly(2-hydroxypropyl methacrylate-stat-pyridyl disulfide ethyl methacrylate) (hb-poly(HPMA-stat-PDSEMA)) was synthesized using 2-((2-(((dodecylthio)carbonothioyl)thio)-2- methylpropanoyl)oxy)ethyl acrylate (ACDT) as a chain transfer monomer via reversible addition-fragmentation chain transfer polymerization (RAFT) technique. Thiol containing reduced hyperbranched polymer was crosslinked with poly(ethylene glycol)-dinorbornene (PEG-diNB) to prepare hydrogels. Hydrogels synthesized were softened using mercaptoethanol via thiol-disulfide exchange reactions and compared the results with the hydrogels prepared using linear polymer. Softening experiments with these gels resulted in stiffness changes of around 8.5 kPa after a thiol-disulfide exchange reaction using a small-molecule thiol, compared to only 4.5 kPa for similar gels prepared using linear polymers. Hydrogels with repair damage or healing ability are important in areas such as biomedical applications. Healing ability is restricted in the covalently crosslinked hydrogels due to permanent crosslinks and for these dynamic covalent linkages are required. In order to meet this challenge, we used our disulfide-containing dynamic hydrogels and introduced hydrogen peroxide (H2O2) as a healing agent, and fast healing was observed for around fifteen minutes. Healed hydrogels with higher values o (open full item for complete abstract)

Committee: Neil Ayres Ph.D. (Committee Member); David Smithrud Ph.D. (Committee Member); Hairong Guan Ph.D. (Committee Member) Subjects: Polymers

Master of Sciences (Engineering), Case Western Reserve University, 2020, Macromolecular Science and Engineering

A novel approach to develop well-defined hyperbranched star polymers is presented herein. The unique three-dimensional structures were synthesized by an arm-first star polymerization route, coupled with an A2 + B3 approach that utilized the copper-catalyzed azide-alkyne cycloaddition (CuAAC). The synthesis of these new materials is relatively straight-forward, and the size of the resultant stars can be easily tuned by varying the reaction conditions. Because the synthesis is tolerant of various different functional groups, there is potential to achieve access to a large library of distinctive star polymers with differing chemical properties. In this vein, the method was used to create stars from polystyrene and polyacrylonitrile starting materials. Moving forward, the unique properties of the materials–highly soluble polymers with both peripheral functional groups and many interior "pockets" offering potential spaces for site isolation– can be used to gain a better understanding of polymer-supported catalysis. Furthermore, it is the hope that these materials are the next step in bridging the gap between the catalytic ability and functional breadth of enzymes as compared to synthetic catalysts.

Committee: Valentin Rodionov (Committee Chair) Subjects: Organic Chemistry; Polymer Chemistry

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

Single chain nanoparticles (SCNPs) have recently achieved great success because of their significant potential in applications such as separation science and drug delivery. A major aim of these studies was to establish the factors that control their size. However, the effect of the spacer length between the polymer backbone and the cross-linkable site is not well established. This study presents the preparation of two series of linear polymers and their SCNPs with two different spacer lengths (3- and 11-carbons) in order to investigate the effect of the spacer on various properties of the nanoparticles. Sol-gel chemistry was used to crosslink single chains under conditions that prefer intramolecular cross-linking. The first series was poly[methyl methacrylate-co-3-(triisopropoxysilyl)propyl methacrylate]. Nanoparticles were prepared from copolymers containing 9 mol% silane monomer and with different molecular weights. Nanoparticles were also prepared from copolymers containing 22 and 31 mol% silane monomer. The second copolymer series was poly[methyl methacrylate-co-11-(triisopropoxysilyl)undecyl methacrylate]. The corresponding hyperbranched polymers were being prepared to determine the effect of polymer architecture on the preparation and properties of SCNPs. For this comparison. The silane-containing inimer, [2-bromo-2-(3'-triisopropoxysilyl)propan-1-oxycarbonyl]ethyl methacrylate was synthesized by hydrosilation of the allyl inimer, [2-bromo-2-(allyl-1-oxycarbonyl]ethyl methacrylate. The hyperbranched precursor polymers were prepared via atom transfer radical polymerization of the silyl inimer. Nanoparticles were produced by hydrolysis and condensation of the triisopropoxysilyl groups under pseudo-high dilution conditions to guarantee intramolecular crosslinking. To investigate the nanoparticle applicability as a stationary phase in chromatography, inverse gas chromatography (IGC) was used to thermodynamically characterize the prepared polymers and nanopart (open full item for complete abstract)

Committee: Coleen Pugh Ph. D. (Advisor); Yu Zhu Ph. D. (Committee Chair); Mesfin Tsige Ph. D. (Committee Member); Chrys Wesdemiotis Ph. D. (Committee Member); Sadhan Jana Ph. D. (Committee Member) Subjects: Analytical Chemistry; Chemistry; Materials Science; Organic Chemistry; Physical Chemistry; Polymer Chemistry; Polymers

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

Atom transfer radical polymerization (ATRP) of n-butyl acrylate (BA) was optimized in two different miniemulsion systems: using a nonionic surfactant with a hydrophobic ligand, and an anionic surfactant with a hydrophilic ligand. A series of fluorinated hyperbranched (co)polymers, and less branched (co)polymers were prepared from our AB* inimers, which are molecules with a double bond and an initiating site, by self-condensing vinyl polymerization (SCVP) in miniemulsion. In one series, different ratios (10 and 30 wt%) of both 2-bromo-3-oxo-3-(2,2,3,3,3-pentafluoropropoxy)propyl methacrylate/acrylate inimer (F2C1MAI) and 2-bromo-3-((7,7,8,8,9,9,10,10,11,11,12,12,13,13,14,14,14-heptadecafluorotetradecyl)oxy)-3-oxopropyl methacrylate/acrylate inimer (F8C6MAI) were copolymerized with the 2-bromo-3-butoxy-3-oxopropyl methacrylate/acrylate inimer (BMAI). In the other series, the F2C1MAI and F8C6MAI were copolymerized with n-butyl methacrylate monomer (BMA) with the same ratios to decrease the amount of branching in the hyperbranched architecture. The unwanted crosslinking was less of an issue when polymerizing methacrylate/acrylate inimers because methacrylate radicals do not terminate by radical-radical coupling as occurs with acrylates. The effective hydrophobicity of the fluorinated copolymers increased with increasing branching, such that smaller amounts of the fluorinated inimer are needed with the hyperbranched polymers to achieve nearly the same hydrophobicity as the fully fluorinated linear homopolymers.

Committee: Coleen Pugh (Advisor); Li Jia (Committee Chair); Yu Zhu (Committee Member); Mark Soucek (Committee Member); Chrys Wesdemiotis (Committee Member) Subjects: Chemistry; Materials Science; Nanoscience; Nanotechnology; Polymer Chemistry; Polymers

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

Hyperbranched polymers have unique physical and chemical properties that make them interesting to people in both academia and industry. One way to make hyperbranched polymers is to use self-condensing vinyl polymerization (SCVP).1 Hyperbranched polymethacrylates can be prepared from methacrylate inimers (inimers are monomers that contain both initiation and polymerizable groups) by atom transfer radical polymerization (ATRP)2 and self-condensing vinyl polymerization (SCVP).3 The methyl methacrylate inimer was synthesized by reacting the carboxylic acid group of 2-bromo-3-hydroxy-2- methylpropionic acid with methacrylic acid and esterifying the alcohol group with methanol.4 This methyl methacrylate inimer was then polymerized under atom transfer radical polymerization conditions. Post-polymerization functionalization is often used to change and/or improve the properties of polymers. For hyperbranched polymers made by atom transfer radical polymerization, the halogen atoms (chlorine or bromine) remaining in the polymer backbone provide sites for post-polymerization functionalization. The halogen atoms in polymethacrylates are bonded to tertiary carbons, which are more hindered and less electrophilic than the halogen sites in hyperbranched polyacrylates, but are presumably more susceptible to cationic rearrangement. The hyperbranched poly(methyl methacrylate) is rearrangeable with heating and to give a primary bromine.

Committee: Coleen Pugh (Advisor); Chrys Wesdemiotis (Committee Member) Subjects: Polymer Chemistry; Polymers

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

This research focused on the development of two different classes of gels: physically crosslinked hydrogel and covalently crosslinked organogel. Amphiphilic copolymers, composed of hydrophilic and hydrophobic monomers, have the potential to form physically crosslinked hydrogels depending on the hydrophobic monomer content in the backbone. The hydrophobic units form aggregates which act as physical crosslinking sites. The effect of methylene spacer and branched structure on the physical and viscoelastic properties of physically crosslinked hydrogels were investigated. Accurate values of the comonomer reactivity ratios are required to fully understand the properties of the amphiphilic copolymer hydrogels and to design new comonomer systems leading to advanced properties. A novel methodology was demonstrated to determine the reactivity ratios of chain copolymerizations that follow the terminal model with high precision. The St-MMA model system showed the validity of the novel technique. The methodology was applied to determine the reactivity ratios of two separate systems: N,N'-dimethylacrylamide (DMA) and 2-(N-ethylperfluorooctanesulfonamido)ethyl acrylate (FOSA) and N,N'-dimethylacrylamide (DMA) and 2-(N-ethylperfluorooctanesulfonamido)ethyl methacrylate (FOSM), which are very difficult to measure precisely using conventional technique due to the aggregating nature of FOSA and FOSM. During copolymerization DMA-FOSA should form slightly blocky morphology (rDMA, rFOSA > 1) if the copolymerization is living. On the other hand DMA-FOSM copolymer produced slightly gradient type chain morphology (rDMA < 1, rFOSM > 1) during living radical copolymerization. 7,7,8,8,9,9,10,10,11,11,12,12,13,13,14,14,14-Heptadecafluorotetradecyl acrylate (PFA) and 2-bromo-3-((7,7,8,8,9,9,10,10,11,11,12,12,13,13,14,14,14-heptadecafluorotetradecyl)oxy)-3-oxopropyl acrylate (PFI) were synthesized in high purity. PFA was copolymerized with DMA in three different ratio to obtain thre (open full item for complete abstract)

Committee: Dr. Coleen Pugh (Advisor); Dr. Abraham Joy (Committee Chair); Dr. Toshikazu Miyoshi (Committee Member); Dr. Tianbo Liu (Committee Member); Dr. Sadhan C. Jana (Committee Member) Subjects: Chemistry; Materials Science; Polymer Chemistry; Polymers

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

A series of new methacrylate inimers (a molecule having both an initiating site and a polymerizable group) was designed based on 2-bromo-3-hydroxy-2-methylpropionic acid. These inimers can be homopolymerized using self-condensing vinyl polymerization (SCVP) and atom transfer radical polymerization (ATRP), to produce hyperbranched polymethacrylates that are true architectural analogues of linear polymethacrylates. The polymers contain an ester group attached to every other carbon along the polymer backbone and each repeat unit contains a free ester pendant group. The synthetic pathway is suitable for different alkyl ester functional groups such as methyl, butyl, and dodecyl. The hyperbranched polymethacrylates were characterized by 1H nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography (GPC).

Committee: Coleen Pugh (Advisor); Chrys Wesdemiotis (Committee Member) Subjects: Polymer Chemistry; Polymers

Master of Science, University of Akron, 2016, Polymer Science

A series of branched L-valine based poly(ester urea)s with different branching degrees and molecular masss were synthesized and characterized. In this work, two monomers bis-L-valine-decane-1,10-diester (Diol-1-VAL-10) and tri-O-phenylalanine-1,1,1- trimethyl ethane-triester (Triol-PHE) were synthesized, along with copolymers made using various molar ratios of the two monomers during interfacial polymerization. It was found that high molecular mass branched L-valine-based PEUs exhibit higher glass transition temperature, higher elastic modulus and improve the stability of nanofibers throughout sterilization and in physiological conditions compared to their linear analogues. High molecular mass (MW = 379 kDa) PEU nanofibers containing 2% of the branching agent maintained their morphology in physiological conditions, which suggest that these materials can be developed further for biomedical applications such as drug delivery and tissue engineering.

Committee: Matthew Becker Dr. (Advisor); Abraham Joy Dr. (Committee Member) Subjects: Biomedical Engineering; Polymer Chemistry; Polymers

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

Recently nanoparticles made from linear polymers has achieved great success because of its significant potential in science, pharmaceutical and drug delivery fields, but seldom are nanoparticles made by hyperbranched polymers reported. In our project, we aimed to synthesize nanoparticles from hyperbranched polymers. In the synthesis of nanoparticles, there is a limitation in getting well-defined particles; that is, the particle structure is often uncontrollable. To solve this problem, single-chain collapse is applied here to provide an easy path to obtain particles with small diameters. In this project, we synthesized nanoparticles based on a hyperbranched copolymer poly[(methyl acrylate)-co-(3-(triethoxysilyl)propyl methacrylate)], which was prepared by the copolymerization of (2-bromo-2-methoxycarbonyl)ethyl acrylate, with 3-(triethoxysilyl)propyl methacrylate (TESPMA). With (2-bromo-2-methoxycarbonyl)ethyl acrylate, as an inimer, and 3-(trimethoxysilyl)propyl methacrylate (TMSPMA) as a silicon-containing monomer, the trialkoxysilyl groups provide crosslink sites for intarmolecular single-chain collapse by gelation. These highly branched polymers were snythesized by atom transfer radical polymerization (ATRP). The nanoparticles were produced later by gelation of the triethoxysilyl groups in dilute solution to guarantee intramolecular crosslink.

Committee: Coleen Pugh (Advisor) Subjects: Polymers

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

ABSTRACT A major thrust of polymer research in both industry and academia is being driven by the push for sustainable raw materials, environmentally friendly production processes and products that are biodegradable. Hyperbranched polyacrylates were synthesized by atom transfer radical polymerization by self-condensing vinyl polymerization (ATRP-SCVP) using a new class of inimers based on a naturally occurring amino acid, L-serine. The structure of these hyperbranched polyacrylates (HP) includes an ester group at the branch points and in the polymer backbone of many of the repeat units, which provide sites for biodegradation via hydrolysis. In contrast to previous studies, which were performed in bulk or solution and took long periods of time to reach high molecular weight (Mn), we synthesized our hyperbranched polyacrylate using emulsions and mainly miniemulsions polymerization techniques. This provides an environmentally friendly system, high number average molecular weight in the range of 105 to 106 Da, particle size distribution in the range of 50 to 500 nm, high functionality and high reactivity rate. The emulsion and/or miniemulsion conditions that were performed include normal ATRP, reverse ATRP, simultaneous reverse normal initiation SRNI-ATRP, and activator generated by electron transfer AGET-ATRP. The physical and chemical properties of the hyperbranched polyacrylates were studied in detail by 1H, and 13C 1D nuclear magnetic resonance (NMR) spectroscopies. The molecular weights were determined by gel permeation chromatography using light scattering (GPCLS) and reflactive index (GPCPSt) detectors. Thermal properties, such as glass transitions and melting temperatures were determined by differential scanning calorimetry, and the morphology by scanning electron microscopy (SEM). Emulsions and miniemulsions that were sonicated in OMNOVA were analyzed by traditional test methods, including particle size average distribution (number and volume) by D (open full item for complete abstract)

Committee: Coleen Pugh Dr. (Advisor); Abraham Joy Dr. (Committee Member); Chrys Wesdemiotis Dr. (Committee Member); Ali Dhinojwala Dr. (Committee Member); Mathew Espe Dr. (Committee Member) Subjects: Polymer Chemistry; Polymers

Master of Science (MS), Wright State University, 2009, Chemistry

The synthesis and characterization of hyperbranched poly(arylene ether)s with tailored degrees of branching has been explored via an A2+B3 approach. The reactivity of the individual electrophilic sites towards nucleophilic aromatic substitution, NAS, of the BB'B” monomers 4, 3', 5'-trifluorophenyl sulfone, 1 and 4, 3', 5'-trifluoro benzophenone, 2 were studied. The concentration, temperature and solvent conditions had an effect on the degree of branching, DB, in 1 and 2 and were probed via 13C and 19F NMR spectroscopy as well as a series of model reactions employing p-cresol 16, which acts as the nucleophile. Soluble, branched, poly (arylene ether)s, with controlled degrees of branching were prepared by performing the polycondensation reactions at higher temperatures with 1 leading to relatively higher DB values than 2. The glass transition, Tg and thermal stability of the soluble polymers increased as the degree of branching increased. Tg ranged from 126 °C to 177 °C, while 5% weight loss temperatures ranged from 372 °C to 514 °C under nitrogen and from 229 °C to 510 °C in air.

Committee: Eric Fossum PhD (Advisor); Kenneth Turnbull PhD (Committee Member); David Dolson PhD (Committee Member); Joseph F. Thomas, Jr. Phd (Other) Subjects: Chemistry

Master of Science (MS), Wright State University, 2007, Chemistry

Two different polymer systems have been studied in regards to their potential for functionalization to introduce new characteristics to the polymer. The first polymer system is a poly(arylene ether) with a truly pendant sulfone group from the monomer 3,5-difluorodiphenylsulfone. The work entails incorporating a bromine moiety onto the monomer for the versatile ability to bring in functional groups prior to or post the polymerization. The introduction of bromine onto the pendant ring had the best results from electrophilic bromine addition using N-bromosuccinimide in a mixture of sulfuric acid and acetic acid (80:20) yielding 76% of the desired material. Incorporation of the bromine moiety did not interfere with the nucleophilic aromatic substitution reaction utilized in the polymerization and modification was shown to proceed smoothly both prior and post polymerization. The second project involved the study and production of a poly(ester) hyperbranched system from glycerol and fumaric acid. These hyperbranched polymers were prepared using an A2 + B3 approach in a bulk synthesis. The study involves varying the molar ratio of A2 to B3 and temperature to control the polymerization and avoid gelation while pushing the polymerization to larger molecular weights. The two monomers bring the characteristic of biocompatibility with them into the polymer. In addition, the fumaric acid monomer unit brings an alkene bond available for modification. Average molecular weights achieved were around 5,000 daltons. Obtained PDI values were as low as 4.6, and DB values ranged from 0.26 to 0.38. Analysis on new compounds and polymers was done by NMR spectroscopy, GC/MS, and size exclusion chromatography where applicable.

Committee: Eric Fossum (Advisor) Subjects:

Doctor of Philosophy, University of Akron, 2011, Polymer Science

Synthesis of the reversible addition-fragmentation chain transfer (RAFT) based inimer (initiator-monomer) 4-vinylbenzyl dithiobenzoate (VBThB) and bulk copolymerization of this inimer with styrene was carried out at 110°C to synthesize high molecular weight arborescent (tree-like) polystyrenes (arbPS) with a branch-on-branch structure. The effect of the concentration of [VBThB] on the kinetics, molecular weight evolution, and branching were investigated. High-resolution, multi-detector size exclusion chromatography (SEC) was used to thoroughly characterize the polymers based on number-average and weight average molecular weights (Mn and Mw), radii of gyration (Rg), hydrodynamic radii (Rh), and reduced viscosity (ηw). Polymer architectural analysis was carried out based on the Rg and Rh data. The architecture of the arbPS was compared to that for arb-poly(isobutylene) and to theoretical calculations. The arborescent structure of these new materials was confirmed by atomic force microscopy (AFM). The arbPS was modified by a “molecular amplification” method to increase the size and hardness of the branches to a degree which makes visualization with AFM possible. Due to the preservation of the dithioester end group on the RAFT prepared arbPS, it was possible to chain extend the branches with vinylbenzyl chloride (VBCl) to make arb(PS-b¬-VBCl). Poly(styryl) diphenylethyl lithium (PSDPELi) of Mn = 11,000 g/mol was prepared by living anionic polymerization and used to graft onto the VBCl block making “bottle brush” chain ends on the branch. The “bottle brush” structure prevented coiling of the chain ends, and forced the molecule to spread out on a substrate for AFM analysis. The visualized structure of the polymers qualitatively correlated well with the predicted structure based on the mechanism of the inimer polymerization. Solution polymerizations of styrene mediated by VBThB were also performed. In this case, the polymers obtained had lower Mn and relatively narr (open full item for complete abstract)

Committee: Judit Puskas Dr. (Advisor); Chrys Wesdemiotis Dr. (Committee Chair); Gustavo Carri Dr. (Committee Member); Abraham Joy Dr. (Committee Member); Claire Tessier Dr. (Committee Member) Subjects: Polymer Chemistry

Doctor of Philosophy, University of Akron, 2009, Polymer Science

Polyisobutylene is fully saturated, therefore exhibits outstanding chemical, oxidative and thermal stability, which makes it ideally suitable as a model to study mechanical and viscoelastic properties of elastomers, and to correlate properties with structure. The main objective of this dissertation was to develop a fundamental understanding of the mechanism of the synthesis of arborescent (hyperbranched) polyisobutylene (arbPIB) by inimer-type (initiator-monomer) living carbocationic polymerization.The strategy for the effective synthesis of arbPIBs consists of copolymerizing the 4-(2-methoxyisopropyl)styrene inimer (MeOIM) and isobutylene (IB) via controlled/living carbocationic polymerization using TiCl4 coinitiator. In situ FTIR monitoring showed that the self-condensing vinyl polymerization (SCVP) of MeOIM is possible, and that when copolymerizing MeOIM and IB, a nearly alternating structure and multiple end groups are obtained. arbPIB was synthesized and the repeatability of the polymerization was demonstrated. It was found that higher branching was obtained with increasing [MeOIM] and that branching did not further increase if additional IB was added after the MeOIM had reacted completely. No evident changes were observed when switching solvents from Hx/MeCl to a MeCHx/MeCl mixture. Branching parameters showed that arbPIBs have a behavior between polydisperse stars and polycondensates with the number of branches increasing linearly with molecular weight. Novel arbPIB-based block copolymers (TPEs) were synthesized and it was found that copolymers with low Tg short end blocks and less than 5 mol% of a second monomer exhibit thermoplastic elastomeric properties. The materials were strongly reinforced when compounded with carbon black. arbPIB-b-PS are prospective biomaterials and the establishment of reliable methods for evaluating their short and long term properties is a subject of great importance. A dynamic fatigue testing methodology was developed for small, (open full item for complete abstract)

Committee: Judit Puskas PhD (Advisor) Subjects: Chemistry; Materials Science; Plastics; Polymers

Doctor of Philosophy, University of Akron, 2006, Polymer Science

Carbon nanofiber (CNF) and carbon nanotube (CNT) composites have interesting mechanical and electrical properties that make these composites interesting for reinforcing applications. These applications require good dispersion of CNF within a polymeric matrix. Presently high shear methods, such as twin screw extrusion, are used to make well dispersed CNF composites but these methods reduce the physical properties due to a reduction in the aspect ratio of the CNF. Low shear methods to functionalize CNT and CNF have been used to obtain good dispersion while maintaining the high aspect ratio. In this research three ways of making CNF/polymer composites by low shear methods were explored. The first reaction used bisphenol A cyclic carbonate oligomer as a low molecular weight precursor. The oligomers were polymerized to disperse the CNF within the matrix. These composites were characterized by electrical resistivity, transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermogravametric analysis (TGA) and gel permeation chromatography (GPC). The composites had a percolation threshold at 6 wt % CNF decreasing the resistivity to 10 4ohm•cm. The second way used heterocoagulation where a cationic polystyrene latex was combined with anionically charged oxidized CNF. The composites were melt pressed and characterized using electrical resistivity, SEM, and TGA. The percolation threshold was 2 wt % and the resitivity dropped to 10 6ohm•cm. Finally, it was found that synthesizing a hyperbranched polyol was possible by chemically modifying oxidized CNF with glycidol and BF 3OEt 2. The resulting polyol CNF were characterized by TGA, Fourier transform infrared spectroscopy (FTIR), TEM, and X-ray photoelectron spectroscopy (XPS). The OH groups were reacted with heptafluorobutyryl chloride to determine the amount of OH in the sample. The resulting fluorinated composite was characterized by FTIR and elemental analysis. The amount of OH for the polyol CNF increased (open full item for complete abstract)

Committee: William Brittain (Advisor) Subjects: Chemistry, Polymer