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

A variety of methods were used to make polymers with different architecture and functionalities. The linking chemistry of vinyldimethylchlorosilane (VDMCS) with poly(styryl)lithium (Mn = 1,700-3,000 g/mol) was studied. The average degree of branching varied from 7.5 to 9.4 with an increase in concentration of VDMCS (1.2 to 5.2 eq). The intrinsic viscosities and melt viscosities (at 160 °C) of the star polymers were found to be less than half of that of the corresponding linear polystyrenes. α-Pyrrolidine-functionalized polystyrene (Mn = 2,700 g/mol, Mw/Mn = 1.03, 92.5%) was successfully synthesized from α-chloromethyldimethylsilane-functionalized polystyrene(Mn = 2,600 g/mol, Mw/Mn = 1.02) based on NMR spectroscopy, MALDI-TOF and ESI mass spectrometry. The stability of silyl hydride groups under atom transfer radical polymerization conditions was proven by copolymerizing methyl methacrylate and (4-vinylphenyl)dimethylsilane (VPDS). Tapered block copolymers of isoprene, VPDS, and styrene with narrow molecular weight distributions (1.04 and 1.05) were synthesized via anionic polymerization. Evidence regarding the topology of cyclic polybutadienes was obtained by Atomic Force Microscopy of grafted polymers obtained by grafting an excess of silyl hydride functionalized polystyrene (Mn = 8,300 g/mol, Mw/Mn =1.01) onto cyclic polybutadiene(Mn=88,000 g/mol, Mw/Mn = 2.0). The reactivity of polyisobutylene carbocations was compared with respect to competitive electrophilic addition to a vinyl group versus silyl hydride transfer by investigating the reaction with VPDS. Based on GPC results, and 1H and 13C NMR spectroscopy, no evidence for any vinyl group addition was observed. A successful attempt was made to prepare electrospun fibers from fluorofunctionalized styrene-butadiene elastomers. The water contact angle of these surfaces was found to be 162.8o ± 3.8o for the fibrous mat of the fluorinated polymers as compared to 151.2o ± 2.4o for the analogous fibrous (open full item for complete abstract)

Committee: Roderic Quirk Dr. (Advisor); Mark Foster Dr. (Committee Chair); Judit Puskas Dr. (Committee Member); Chrys Wesdemiotis Dr. (Committee Member); Kevin Cavicchi Dr. (Committee Member) Subjects: Polymers

Doctor of Philosophy, University of Akron, 2023, Polymer Science

We have elucidated details of how the microscopic structure and dynamics of filler in reinforced rubbers influence mechanical properties. Studies were performed on highly loaded, silica-filled, crosslinked styrene-butadiene rubber (SBR). Properties of the compounds studied were varied by addition of silane coupling agents, silicas of different surface area, and by addition of well-characterized, anionically-polymerized, low molecular weight, dimethylamino end-functionalized SBR additives of linear or star molecular architecture. Samples were probed with a combination of Ultra-small Angle X-ray Scattering/Small Angle Scattering (USAXS/SAXS), X-ray Photon Correlation Spectroscopy (XPCS), and mechanical measurements. Investigation of samples with or without silane coupling agents confirms that coupling agents enhance filler dispersion. This enhanced dispersion leads to slower filler dynamics when the rubber is strained and a slower change in dynamics over time. These slower dynamics and slower evolution of dynamics correlate with slower macroscopic stress relaxation. Our work also examines the temporally heterogenous dynamics that underlie the stress relaxation process. During stress relaxation, filler dynamics intermittently speed up and slow down. These results indicate that while macroscopic stress relaxation appears to be a relatively simple process, the microscopic behavior is complex. Studies on rubbers containing high surface area, milled silica under dynamic strain reveal that while rubber containing milled silica and monosulfidic coupling agent shows a large Payne effect, the breakdown of filler is suppressed. We infer that debonding and/or yielding of bridging bound layers is responsible for the Payne effect in this sample. These bridging layers provide this rubber with a high modulus and low hysteresis. Addition of end-functionalized SBRs to rubber drastically affects mechanical properties. Rubber containing conventional silica and 20 kg/mol difunctio (open full item for complete abstract)

Committee: Mark Foster (Advisor); Roderic Quirk (Other); Jutta Luettmer-Strathmann (Committee Member); Mesfin Tsige (Committee Member); Junpeng Wang (Committee Member); Li Jia (Committee Chair) Subjects: Materials Science

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

The first efficient method for synthesis of well-defined, tadpole-shaped polystyrene has been developed using anionic polymerization, silicon chloride linking chemistry and metathesis ring closure. The difunctional macromolecular linking agent, ω-methyldichlorosilylpolystyrene, was formed by reacting sec-butyllithium-initiated poly(styryl)lithium with excess (30× molar) methyltrichlorosilane to eliminate formation of linear dimer and three-arm star polystyrene. The asymmetric, three-arm, star precursor was formed by linking excess α-4-pentenylpoly(styryl)lithium (α-PSLi) with the macromolecular linking agent, and the excess a-PSLi was functionalized with ethylene oxide before termination with methanol to facilitate column chromatographic separation of unlinked arm. Cyclization of the asymmetric, three-arm, star precursor to form the tadpole-shaped polystyrene was effected in methylene chloride at high dilution using the Grubbs first generation catalyst, bis(tricyclohexylphosphine)benzylidene ruthenium(IV) chloride. The tadpole product was uniquely characterized by MALDI-ToF MS in terms of peaks that appeared characteristically 28 m/z units lower than those of the corresponding asymmetric, three-arm, star precursor and corresponding to the loss of an ethylene unit. The MALDI-ToF MS results showed that the tadpole-shaped polystyrene was of high purity. MD simulations find a smaller hydrodynamic volume for the tadpole-shaped PS as compared to the three-arm star precursor, in quantitative agreement with GPC results. Incorporating one cycle in the molecule, while leaving one chain end, leads to an increase in Tg of only 2.7 ± 0.8°C, much smaller than the increase of 13.6 ± 0.8 °C seen when going from the linear chain to cyclic analog with no ends at all. These changes in Tg with architecture results are consistent with self-plasticization by free chain ends. Thermally stimulated surface fluctuations in polymer films are important from a fundamental perspective. The su (open full item for complete abstract)

Committee: Mark Foster Professor (Advisor) Subjects: Polymer Chemistry; Polymers

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

Doctor of Philosophy, University of Akron, 2015, Polymer Science

Oligomers of Nylon 3 (Oligo(β-alanine)) were used as monodisperse hard blocks in poly(butadiene) and poly(isoprene) based thermoplastic elastomers. All polymers were of linear ABA tri-block architecture. The dicarboxy or dihydroxy terminated diene mid-blocks were synthesized via anionic polymerization and served as the B block while oligo(β-alanine) served as the A block. A series of low-vinyl content (Mn ~60K, 12% vinyl) poly(butadiene)s were functionalized with oligo(β-alanine)n (n = 2, 3, 4) and hydrogenated, forming low-butyl content poly(ethylene-butylene) (PEB) polymers. To reduce the crystallinity of the hydrogenated mid-block, two other diene mid-blocks were synthesized. The first was a set of high-vinyl content, dicarboxy terminated poly(butadiene)s (A. Mn ~44K, 30% vinyl B. Mn ~116K, 46% vinyl). High-butyl content PEB polymers resulted after hydrogenation. The second was a set of dicarboxy terminated poly(isoprene)s (Mn ~15K, 44K, 98K), forming poly(ethylene-propylene) (PEP) polymers after hydrogenation. Another dihydroxy terminated poly(isoprene) (Mn ~18K) was synthesized. Each polymer was oligo(β-alanine)4 functionalized. FT-IR spectroscopy showed β-sheet formation for all of the synthesized polymers. The low-butyl set behaved as a physically cross-linked network and acted as an elastomeric solid at 105 °C by rheological measurements at ≤1.2 wt% of β-alanine peptide. These materials were classified as `solids'. The high-butyl content PEBs formed physically cross-linked networks but did not act as stable, elastomeric solids at 105 °C. The dihydroxy terminated PEP acted in similar fashion to the high-butyl PEB after oligo(β-alanine) functionalization. These were classified as `solid-liquid' materials. The remaining PEP samples did not form physically cross-linked networks and acted as higher molecular weight, chain-extended structures. They were classified as `liquid' materials. The sterics of the mid-block end-group immediately adjacent to the (open full item for complete abstract)

Committee: Li Jia Dr. (Advisor); Matthew Becker Dr. (Committee Member); Gary Hamed Dr. (Committee Member); Coleen Pugh Dr. (Committee Member); Kevin Cavicchi Dr. (Committee Member) Subjects: Chemistry; Polymer Chemistry; Polymers

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

Doctor of Philosophy, University of Akron, 2010, Polymer Science

The synthesis of well-defined functionalized polymers is an important area of research due to their wide array of applications. The work presented herein can be divided into three categories: a) functional initiator synthesis; b) chain-end and in-chain functionalization and c) functional monomer synthesis and polymerization. All three methods involve both anionic polymerization and hydrosilation. In this work, all anionic polymerizations were performed at room temperature in hydrocarbon solvent with an alkyllithium initiator. A functional 4-pentenyllithium initiator was prepared in 70% yield and was used for the synthesis of α and α,ω-functionalized polystyrene. 4-Pentenyllithium was used to initiate styrene polymerization in benzene in the presence of 5 equivalents of tetrahydrofuran. Narrow polydispersity indices and good agreement between calculated and observed molecular weights were observed for the methanol-terminated product. α-Triethoxysilyl-functionalized polystyrene was quantitatively prepared by hydrosilation with triethoxysilane and α-4-pentenylpolystyrene. α-4-Pentenyl-ω-silyl hydride-functionalized polystyrene and α-4-pentenyl-ω-thiol hydride functionalized polystyrene were quantitatively prepared by terminating α-4-pentenylpoly(styryl)lithium with chlorodimethylsilane and ethylene sulfide, respectively. The α-4-pentenyl-ω-silyl hydride-functionalized polystyrene showed good agreement between calculated and observed molecular weights and a narrow polydispersity. α-4-Pentenyl-ω-thiol-functionalized polystyrene showed a dimer peak due to oxidative coupling when quenched with methanol. Triethoxysilyl-functionalized, high-1,4-polybutadiene was prepared by reacting the pendant double bonds of the 1,2-units with triethoxysilane via hydrosilation. High-yielding reactions between the polymeric organolithium chain-ends and silyl chlorides were used to obtain the desired polymeric silyl hydrides for further functionalization. In-chain and chain-end cyano-funct (open full item for complete abstract)

Committee: Roderic Quirk Dr. (Advisor); Mark Foster Dr. (Committee Chair); Li Jia Dr. (Committee Member); Judit Puskas Dr. (Committee Member); Chrys Wesdemiotis Dr. (Committee Member) Subjects: Chemistry; Experiments; Molecules; Polymers

Doctor of Philosophy, University of Akron, 2010, Polymer Science

Anionic synthesis of well-defined polystyrene-block-polyvinylpyridine copolymers required the use of special conditions including lithium chloride and 1,1-diphenylethylene as additives, low temperature of reaction (-78 °C), highly diluted monomer at -78 °C and efficient stirring (Morton-type, creased reactor). Low molecular weight polystyrene-block-poly(2-vinylpyridine) copolymers (Mn = 6000 g/mol) were synthesized with average-molecular weights in agreement with the theoretically calculated Mns and narrow Mw/Mns (≤ 1.1). Polystyrene-block-polyvinylpyridine copolymers were selected for the fabrication of uniformly dispersed metal oxide nanoparticles (cobalt and iron oxides) due to the coordinating ligand character of the vinylpyridine units. The incorporation of the inorganic salts (1 mol-eq of inorg. salt per mol of vinylpyridine units) was 57 wt% when polystyrene-block-poly(2-vinylpyridine-co-4-vinylpyridine) (Mn= 59,000 g/mol, Mw/Mn = 1.09, fv PVP = 0.19) was used and 18 wt% when polystyrene-block-poly(2-vinylpyridine) (Mn= 39,000 g/mol, Mw/Mn = 1.07, fv PVP = 0.14) was used. The end-capping reaction of polymeric chain-ends with 1,1-diphenylethylene (DPE) was studied using 2D NMR spectroscopic and MALDI-TOF mass spectrometric analyses. Oligomerization of DPE was observed using a 15-fold excess of DPE in the end-capping of poly(butadienyl)lithium (Mn = 2,200 g/mol, Mw/Mn = 1.06) but not in the case of poly(styryl)lithium (Mn = 2,000 g/mol, Mw/Mn = 1.02). Although oligomerization of DPE has been previously reported in the synthesis of 1,1-diphenylhexyllithium (6-11% oligomer with 5.4-fold excess of DPE), there are no studies showing the presence of DPE oligomer in the end-capping reaction of polymeric living carbanions. Additionally, the synthesis of poly(para-phenylene) has been studied using different precursor polymers [poly(1,3-cyclohexadienes) (Mn = 1,600 and 3,100 g/mol, Mw/Mn = 1.1 and 1.03) and poly(2-phenyl-1,3-cyclohexadiene) (Mn = 10,000 g/mol, Mw/Mn = (open full item for complete abstract)

Committee: Roderic Quirk Dr. (Advisor) Subjects: Polymers

Master of Science, University of Akron, 2008, Polymer Science

The purpose of this research was to anionically prepare well-defined polystyrenes that had functional groups either at the chain end or in the middle of the chain. Functional groups were introduced by using a general functionalization method (GFM). For chain-end functionalizations, after poly(styryl)lithium was synthesized, it was terminated with chlorodimethylsilane. This produced chain-end, silyl hydride-functionalized polystyrene. Then, through a hydrosilation reaction between the silyl hydride group and the double bond of a substituted alkene, chain-end functional polystyrene was produced. For in-chain functionalizations, after poly(styryl)lithium was prepared, it was linked with dichloromethylsilane, which placed a silyl hydride functionality in the middle of the chain. This was then reacted with an alkene in a hydrosilation reaction to produce the in-chain functionalized polystyrene. Hydrosilations were performed using Karstedt…#8482;s catalyst in benzene at room temperature. Allyl acetate and methyl-3-butenoate were the alkenes used for both chain-end and in-chain functionalizations, as well as allyl alcohol for in-chain functionalizations. The functionalized polystyrenes were characterized by FTIR, 1H NMR and 13C NMR spectroscopy, and MALDI TOF MS.

Committee: Roderic Quirk PhD (Advisor) Subjects: Polymers

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

The synthesis of homopolymers and block copolymers containing metal coordinating ligands is an important area of research due to the potential applications of these polymers in the fields of optics, electronics, and photonics. Specifically, the terpyridine group is very useful, since it can act as a tridentate chelating ligand due to its strategically positioned, three nitrogen atoms. This allows it to form strong complexes with a variety of transition metal ions.The hydroxyl functionality is another important group due to numerous applications of well-defined hydroxyl-functionalized polymers. They can react with other functional groups on other polymers for chain extension, branching, or crosslinking. They can also be used as macroinitiators for the polymerization of other monomers such as lactide and lactone. Alkyllithium-initiated, living anionic polymerization offers excellent control over molecular weight and molecular weight distribution. The absence of termination and chain transfer steps makes these systems ideally suited for the preparation of chain-end functionalized polymers by the reaction of the living chain ends with appropriate monomers or terminating agents. A recently reported general anionic functionalization method was used to create well-defined terpyridine and hydroxyl end-functionalized polymers. In the first step, living polymeric organolithium compounds were reacted with silyl chlorides to form the corresponding silyl hydride-functionalized polymers. Then, these polymers were reacted with substituted alkenes in the presence of a hydrosilation catalyst to form the corresponding functionalized polymers. A new method was also developed, based on similar chemistry, to prepare an in-chain functionalized diblock copolymer where a variety of functional groups can be placed directly at the interface of the two blocks. This method was used to prepare both in-chain hydroxyl- and terpyridine-functionalized polystyrene-b-polyisoprene copolymers. Lewis (open full item for complete abstract)

Committee: Roderic Quirk Ph.D. (Advisor) Subjects: Chemistry; Polymers

Doctor of Philosophy, University of Akron, 2007, Polymer Science

Novel methods for the synthesis of chain-end and in-chain functionalized polymers, as well as star polymers, were developed using anionic polymerization techniques. A new mechanism for the reaction of polymeric organolithium compounds with thiiranes has been found. The reaction of poly(styryl)lithium and poly(butadienyl)lithium with propylene sulfide and ethylene sulfide was investigated in hydrocarbon solution for the preparation of thiol-functional polymers. It was found by MALDI-TOF mass spectral analysis of the reaction products that the reaction proceeded by attack of the anion on the methylene carbon atom of the thiirane ring followed by ring opening to form the thiol-functionalized polymer. The reaction of poly(styryl)lithium with trimethylene sulfide did not produce the corresponding thiol-functionalized polymer; the resulting methyl-terminated polymer was formed by attack of the anion on the sulfur atom followed by ring opening to form a primary carbanion. A new method for synthesis of alkoxysilyl-functionalized polymers was developed. Using a general functionalization methodology based on the hydrosilation of vinyltrimethoxysilane with w-silyl hydride-functionalized polystyrene, alkoxysilyl-functionalized polystyrene was obtained in high yield (83 %). The main side product was vinylsilane-functionalized polymer. A small amount of dimer (approximately 2 %) was formed from the hydrosilation reaction of silyl hydride-functionalized polymer and vinylsilane-functionalized polymer. Star polymers with an average number of 6.8 arms were obtained by reacting poly(styryl)lithium with 6.6 equivalents of vinyldimethylchlorosilane in benzene at 30 C. It was found that, in benzene at 30 C, vinyldimethylchlorosilane is an efficient linking agent for the preparation of well-defined star-branched polymers. In contrast, the reaction of poly(styryl)lithium with 5 equivalents of vinyldimethylchlorosilane in THF at -78 C produced vinylsilane-functionalized polymer in high yiel (open full item for complete abstract)

Committee: Roderic Quirk (Advisor) Subjects: Chemistry, Polymer

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

One of the unique features of living, alkyllithium-initiated, anionic polymerization is the ability to produce a stable carbanionic chain end after complete monomer consumption, which can be followed by reaction with electrophiles to form various end-functionalized polymers. Although a variety of functional polymers have been synthesized in the last few decades, each specific functionalization has had to be designed and optimized individually. Consequently, the development of general functionalization methodologies has drawn recent interest. However, even these general functionalization methods require the use of protecting groups, and the complexity in synthetic routes and the thermal/moisture instability of many protected functional agents have restricted their practical application. This thesis describes a new, general functionalization methodology, combining well-defined, living anionic polymerization with efficient and highly selective, platinum-catalyzed hydrosilation reactions with functionalized alkenes. Well-defined, Si-H functionalized polymers (P-SiH) have been synthesized by sec-butyllithium-initiated, living anionic polymerization in benzene followed by termination with dimethylchlorosilane. Even though the Si-H bond is polar and labile, it is stable with respect to reactions with organolithium compounds in hydrocarbon solvents. These Si-H bonds are also stable to oxygen and moisture in the atmosphere so that Si-H functionalized polymers can be isolated and handled in air. These silyl hydride-functionalized polymers were isolated simply by precipitation into methanol, in which they are also stable. Silyl hydride-functionalized polystyrenes and polyisoprenes have been prepared and characterized by SEC, 1H, 13C and 29Si NMR spectroscopy, FT-IR spectroscopy and MALDI-TOF mass spectrometry. For quantitative analysis, the ratio of the integration area of 1H NMR resonances for the six methyl protons of the dimethylsilane unit at a –0.1 ppm to the other six me (open full item for complete abstract)

Committee: Roderic Quirk (Advisor) Subjects: Chemistry, Polymer

Master of Science, University of Akron, 2005, Polymer Science

The linking reaction of poly(styryl)lithium with the difunctional epoxide linking agent, 1,3-butadiene diepoxide, was investigated. Poly(styryl)lithium was prepared by anionic polymerization in benzene at room temperature. The linked polymer was found to have in-chain hydroxyl groups. It was characterized by NMR spectroscopy, size exclusion chromatography, MALDI-TOF MS, as well as with thin layer and column chromatography. The coupled product containing in-chain alkoxylithium groups was used to initiate the polymerization of ethylene oxide in the presence of a phosphazene base with the objective of synthesizing a hetero, four-armed, (PS)2-star-(PEO)2 polymer. Ethylene oxide was polymerized at 45°C for two weeks. The product obtained was characterized by NMR spectroscopy, size exclusion chromatography and MALDI-TOF MS.

Committee: Roderic Quirk (Advisor) Subjects: Chemistry, Polymer