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Ring opening metathesis polymerization (ROMP) is established as one of the efficient controlled living polymerization methods which have various applications in polymer science and technology fields. The research presented in this dissertation addresses several applications of multifunctional well-defined norbornene-based block copolymers synthesized by ROMP using ruthenium-based Grubbs catalysts. These novel block copolymers were applied to stabilize maghemite nanoparticles, creating the superparamagnetic polymeric nanocomposites. The Jaggregation properties of the porphyrin dyes were improved via self-assembly with a customized norbornene polymer. Novel multimodal copolymer probes were synthesized for two-photon fluorescence integrin-targeted bioimaging. In Chapter 1 a brief overview of ROMP along with ruthenium metal catalysts and selected applications of the polymers related to this research is presented. Superparamagnetic maghemite nanoparticles are important in biotechnology fields, such as enhanced magnetic resonance imaging (MRI), magnetically controlled drug delivery, and biomimetics. However, cluster formation and eventual loss of nano-dimensions is a major obstacle for these materials. Chapter 2 presents a solution to this problem through nanoparticles stabiulized in a polymer matrix. The synthesis and chracterization of novel diblock copolymers, consisting of epoxy pendant anchoring groups to chelate maghemite nanoparticles and steric stabilizing groups, as well as generation of nanocomposites and their characterization, including surface morphologies and iv magnetic properties, is discussed in Chapter 2. In Chapter 3, further improvement of the nanocomposites by ligand modification and the synthesis of pyrazole-templated diblock copolymers and their impact to stabilize the maghemite nanocomposite are presented. Additionally, the organic soluble magnetic nanocomposites with high magnetizations were encapsulated in an amphiphilic copolymer and dispersed in water to assess their water stability by TEM. To gain a preliminary measure of biocopatibility of the micelle-encapsulated polymeric magnetic nanocomposites, cell-viability was determined. In Chapter 4, aggregation behaviors of two porphyrin-based dyes were investigated. A new amphiphilic homopolymer containing secondary amine moieties was synthesized and characterized. In low pH, the polymer became water soluble and initiated the stable Jaggregation of the porphyrin. Spectroscopic data supported the aggregation behavior. Two photon fluorescence microscopy (2PFM) has become a powerful technique in bioimaging for non-invasive imaging and potential diagnosis and treatment of a number of diseases via excitation in the near-infrared (NIR) region. The fluorescence emission upon two-photon absorption (2PA) is quadratically dependent with the intensity of excitation light (compared to the linear dependence in the case of one-photon absoprtion), offering several advantages for biological applications over the conventional one-photon absorption (1PA) due to the high 3D spatial resolution that is confined near the focal point along with less photodamage and interference from the biological tissues at longer wavelength (~700-900 nm). Hence, efficient 2PA absorbing fluorophores conjugated with specific targeting moieties provides an even better bioimaging probe to diagnose desired cellular processes or areas of interest The αVβ3 integrin v adhesive protein plays a significant role in regulating angiogenesis and is over-expressed in uncontrolled neovascularization during tumor growth, invasion, and metastasis. Cyclic-RGD peptides are well-known antagonists of αVβ3 integrin which suppress the angiogenesis process, thus preventing tumor growth. In Chapter 5 the synthesis, photophysical studies and bioimaging is reported for a versatile norbornene-based block copolymer multifunctional scaffold containing biocompatible (PEG), two-photon fluorescent (fluorenyl), and targeting (cyclic RGD peptide) moieties. This water-soluble polymeric multi scaffold probe with negligible cytotoxicity exhibited much stronger fluorescence and high localization in U87MG cells (that overexpress integrin) compared to control MCF7 cells. The norbornene-based polymers and copolymers have quite remarkable versatility for the creation of advanced functional magnetic, photonic, and biophotonic materials.

In this thesis, we use the self-consistent field theory (SCFT) to study neutral and charged block copolymer melts and blends in thin films and bulk. We showcase the utility of the SCFT by applying it to a number of different model systems. In our first study, we examined the elastic properties of multi-component bilayer membranes composed of amphiphilic AB/ED diblock copolymers. We focused on the effects of chain architecture and interactions between the amphiphilic molecules on the line tension or edge energy of a membrane pore. We discovered a direct relationship between the effective volume of the amphiphilic molecules, which is dictated by their architecture, and the line tension. We found that the addition of cone-shaped molecules to the membrane results in a decrease in the line tension. The opposite effect is seen for inverse cone-shaped amphiphiles, where an increase in their concentration results in an increase of the line tension. Studies two and three fall under the theme of directed self assembly of block copolymer thin films. First we examined the effects of ion concentration on the strength of the external electric field required to reori- ent lamellar domains from the parallel to the perpendicular orientation. The change in the critical electric field is found to be dependent on whether the neutral or charged polymer species is favoured by the top and bottom surfaces. In the second study, we examined the mechanism of using the entropic effect to direct the self assembly of micro domains in star block copolymer thin films. We control the architecture of star block copolymers by varying the number of arms, ranging from a linear chain with 1-arm to 4-arm star block copolymers. Using both experiments and SCFT, we showed that the entropic effect is enhanced in star block copolymer blends with greater number of arms. Furthermore, we showed that the entropic effect can be used to direct the self assembly of micro domains perpendicular to the substrate. In our last study, we examined the unbinding transition of the α-BN phase in pentablock terpolymer/ homopolymer blends. We constructed a phase diagram of the system as a function of homopolymer con- centration. We discovered that the unbinding transition is preempted by the macrophase separation of the blends into block copolymer rich/ homopolymer rich domains. The results presented in this thesis help advance our understanding of various properties of polymeric systems, such as the elastic properties of multi-component membranes, directed self assembly in block copolymer thin films and the phase behaviour of block copolymers in bulk. / Thesis / Doctor of Philosophy (PhD)

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The use of waste gas such as carbon dioxide (CO2) to prepare useful and valuable polymers benefits both the economy and the environment. Various strategies have been developed to reduce CO2 emission as well as to transfer CO2 into high-value products. CO2/epoxide copolymerization is one of the most promising methods of not only reducing the CO2 emission from the atmosphere but also producing biodegradable CO2-based materials that are CO2 as source-abundant, renewable, cheap, non-flammable and non-toxic. However, the activation of CO2 is one of several problems associated with the polymerization of CO2 due to its stability as a thermodynamic end product. Herein, my dissertation describes the effectiveness of new lithium/phosphazene complexes to generate highly active species for CO2/epoxide copolymerization and to capture/activate CO2 molecules for the nucleophilic attack of the active species. Well-defined polycarbonates and polycarbonate-based block copolymers are produced that have control of molecular weights, unimodal distributions and narrow molecular weight distributions (Chapter 3 and 4). Besides, these complexes provide access to prepare CO2-based triblock copolymers that are powerful candidates to serve as the next generation of thermoplastic elastomers (Chapter 4). Additionally, these complexes are applied for the anionic polymerization of petrochemical-based sources such as styrene and dienes producing polymers in faster rate of polymerization with control of molecular characteristics (Chapter 2). A general introduction of polymers and their classification based on composition, chemical structure, mechanical properties, degradability, source, applications, and preparative methods, is covered in Chapter 1

Segmented copolymer systems composed of an amorphous g1assy engineering polymer as one segment and a potentially anisotropic polyester as the second segment were synthesized and investigated. The engineering thermoplastic segment was based on various all aromatic poly(arylene ether sulfooes) derived from the nucleophilic aromatic substitution reaction between hydroquinone, biphenol, and dichlorodiphenylsulfone. This reaction was conducted in the presence of potassium carbonate and anhydrous aprotic dipolar solvents. Poly(biphenol terephthalate) and poly(oxybenzoate) were synthesized in situ as the second, potentially anisotropic, sem;crystalline segment. These segmented copolymers were synthesized either by solution t interfacial, or melt acidolysis techniques. The melt acidolysis technique was used to synthesize the segmented copolymers with high poly(arylate) contents. The morphology of the copolymers was found to be totally amorphous for those capolymers with low levels of the poly(arylates). They were semicrystalline when the poly(arylate) contents were increased beyond a critical value of about 15 weight percent. Differential scanning calorimetry, optical microscopy, and wide angle X-ray scattering were used to probe the copolymer morphology. The chemical structures of the segmented copolymers were studied through the use of Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy (both ¹H and ¹³C). As the weight percentage of the poly(arylate) was increased, a very significant improvement in the solvent resistance was noted. Evidence of anisotropy and liquid crystallinity in the copolymers was provided by optical microscopy, differential scanning calorimetry, and wide angle X-ray scattering. / Ph. D.

Novel, high molecular weight poly(dimethylsiloxane) / cycloaliphatic polyester segmented copolymers were prepared and characterized. Specifically, polyesters based on dimethyl 1,4-cyclohexane dicarboxylate and 1,4-butanediol were employed. The copolymers were synthesized via a melt process using a high trans content isomer which afforded semi-crystalline morphologies. Aminopropyl terminated poly(dimethylsiloxane) oligonlers of controlled molecular weight were synthesized and then end capped with excess diester to form a diester terminated amide linked oligomer. The latter was then incorporated into the copolymer via melt transesterification step reaction segmented copolymerization. The molecular weight of the polysiloxane and chemical composition of the copolymer were systematically varied to prepare a series of segmented polyester / poly(dimethylsiloxane) copolymers. / Ph. D.

The work presented in this dissertation revolves around the incorporation of t-butyl methacrylate into block copolymers utilizing anionic living polymerization techniques. The synthesis of t-butyl methacrylate/n-hexyl methacrylate and t-butyl methacrylate/2-ethylhexyl methacrylate di- and triblock copolymers was done by initiation with 2-methyl-1,1-diphenylpentyllithium in THF at -78°C by established techniques, and predictable molecular weights and narrow molecular weight distributions were obtained. Subsequent selective acid catalyzed hydrolysis of the t-butyl ester followed by neutralization with an appropriate base allowed the formation of block ioncontaining polymers. The synthesis of triblock polymers of t-butyl methacrylate with butadiene and styrene/butadiene systems and their analogous block ionomers was also carried out utilizing difunctional organolithium initiation of the hydrocarbon monomers in cyclohexane. For the polymerization of the tbma, it was found that the addition of large quantities of a polar solvent, such as THF, endcapping with diphenylethylene, and low temperatures (ca. -70 °C) were necessary to avoid side reactions which were theorized to be carbonyl attack by the dienyl- or styryllithium species. It was found that in the all methacrylic systems mentioned, when the t-butyl methacrylate blocks were in the ester form, i.e. not hydrolyzed to the acid or neutralized to the ionomer, the copolymers were phase mixed as evidenced by thermal analysis. Upon derivatization, however, the block polymers became phase separated. Morphological characterization of the block ionomers indicated that the morphology was dependent on both the ionic content and the ionic block length. Well defined, partially anisotropic, morphologies were observed by SAXS and TEM only in polymers that had both high ionic content and relatively large ionic block lengths. Elastomeric behavior was observed in copolymers with triblock architecture, but the materials degraded prior to plastic flow. On the other hand, all of the diene- and styrene/diene-methacrylates exhibited a multiphase morphology in the precursor state. Analogously to the all methacrylic system, the block ionomers were elastomeric, with the rubbery plateau extended ca. 60 °C relative to the non-ionic precursors. Crosslinking of the poly(butadiene) phase occurred at the onset of plastic flow, rendering the ionomers unable to be thermally processed. / The work presented in this dissertation revolves around the incorporation of t-butyl methacrylate into block copolymers utilizing anionic living polymerization techniques. The synthesis of t-butyl methacrylate/n-hexyl methacrylate and t-butyl methacrylate/2-ethylhexyl methacrylate di- and triblock copolymers was done by initiation with 2-methyl-1,1-diphenylpentyllithium in THF at -78°C by established techniques, and predictable molecular weights and narrow molecular weight distributions were obtained. Subsequent selective acid catalyzed hydrolysis of the t-butyl ester followed by neutralization with an appropriate base allowed the formation of block ioncontaining polymers. The synthesis of triblock polymers of t-butyl methacrylate with butadiene and styrene/butadiene systems and their analogous block ionomers was also carried out utilizing difunctional organolithium initiation of the hydrocarbon monomers in cyclohexane. For the polymerization of the tbma, it was found that the addition of large quantities of a polar solvent, such as THF, endcapping with diphenylethylene, and low temperatures (ca. -70 °C) were necessary to avoid side reactions which were theorized to be carbonyl attack by the dienyl- or styryllithium species. It was found that in the all methacrylic systems mentioned, when the t-butyl methacrylate blocks were in the ester form, i.e. not hydrolyzed to the acid or neutralized to the ionomer, the copolymers were phase mixed as evidenced by thermal analysis. Upon derivatization, however, the block polymers became phase separated. Morphological characterization of the block ionomers indicated that the morphology was dependent on both the ionic content and the ionic block length. Well defined, partially anisotropic, morphologies were observed by SAXS and TEM only in polymers that had both high ionic content and relatively large ionic block lengths. Elastomeric behavior was observed in copolymers with triblock architecture, but the materials degraded prior to plastic flow. On the other hand, all of the diene- and styrene/diene-methacrylates exhibited a multiphase morphology in the precursor state. Analogously to the all methacrylic system, the block ionomers were elastomeric, with the rubbery plateau extended ca. 60 °C relative to the non-ionic precursors. Crosslinking of the poly(butadiene) phase occurred at the onset of plastic flow, rendering the ionomers unable to be thermally processed. / Ph. D.

This work combines many characterization techniques in an effort to enhance understanding of molecular motions of polymers and. how they are influenced by' structure. The primary characterization method was dielectric spectroscopy which utilizes an AC electric field as the stress field. A variety of new, well controlled polymeric systems were studied. The first series included a number of radial starblock copolymers, styrene/isoprene, t-butyl- styrene/isoprene, and t-butyl-styrene/butadiene. These ABA copolymers consisted of hard and soft blocks, with the soft block comprising 75% by weight. The effect of microstructure of the soft block, casting solvent, hydrogenation, and chemical composition of the hard block were some of the variables studied. The amount of phase separation and the molecular motions occurring will be influenced by these parameters. Hydrogenation of the soft block increased the phase separation. Another system investigated included some stereospecific poly(alkyl methacrylates) which were synthesized anionically. In this series the alkyl group was systematically changed in order to study the effects of the bulkiness of the substituent and the tacticity on the a and ß transitions. The ß transition associated with side chain rotations was only observed in the case of the methyl and ethyl substituents. The Havriliak-Negami data analysis was used to evaluate the breadth and the skewness of the distribution of relaxation times. Finally, some high temperature thermoplastic polymers were evaluated with dielectric spectroscopy. The effect of the backbone composition, moisture, and fillers on the β transition was looked at. These studies showed that moisture and fillers play an important role on the magnitude and temperature of the observed β transition. / Ph. D.