This thesis describes the synthesis and applications of a new series of amphiphilic homopolymers and copolymers consisting of hydrophobic polyolefin backbone and hydrophilic phosphorylcholine (PC) pendant groups. These polymers are synthesized by ring opening metathesis polymerization (ROMP) of a novel PC- cyclooctene monomer, and copolymerization of various functionalized cyclooctene comonomers. Incorporation of different comonomers into the PC-polyolefin backbone affords copolymers with different functionalities, including crosslinkers, fluorophores, and other reactive groups, that tune the range of applications of these polymers, and their hydrophobic/hydrophilic balance. The amphiphilic nature of PC-polyolefins was exploited in oil-water interfacial assembly, providing robust polymer capsules to encapsulate and deliver nanoparticles to damaged regions of a substrate in a project termed `repair-and-go.' In repair-and-go, a flexible microcapsule filled with a solution of nanoparticles probes an imperfection-riddled substrate as it rolls over the surface. The thin capsule wall allows the nanoparticles to escape the capsules and enter into the cracks, driven in part by favorable interactions between the nanoparticle ligands and the cracked surface (i.e., hydrophobic-hydrophobic interactions). The capsules then continue their transport along the surface, filling more cracks and depositing particles into them. The amphiphilic nature of PC-polyolefins was also exploited in aqueous assembly, forming novel polymer vesicles in water. PC-polyolefin vesicles ranged in size from 50 nm to 30 µm. The mechanical properties of PC-polyolefin vesicles were measured by micropipette aspiration techniques, and found to be more robust than conventional liposomes or polymersomes prepared from block copolymers. PC-polyolefin vesicles have potential use in drug delivery; it was found that the cancer drug doxorubicin could be encapsulated efficiently in PC-polyolefin vesicles. In another application, PC-polyolefins were used as antifouling coatings for ultrafiltration (UF) and reverse osmosis (RO) water purification membranes. These polymers were found to reduce surface fouling in both UF and RO membranes. Finally, PC-substituted ruthenium benzylidene catalysts were synthesized and evaluated for ROMP in water. PC-substituted catalysts proved effective towards productive metathesis of water soluble cyclic olefins including PEG-substituted oxanorbornene.

Nanostructured magnetic materials are important for various applications, and hence their development is critical for the advancement of science and technology. Coupling self-assembly to the generation of magnetic materials in a simple, straight-forward manner has remained a challenge. Here, a series of novel cobalt-functionalized block copolymers (BCPs) with various block ratios were synthesized using ring-opening metathesis polymerization (ROMP). These BCPs self-assembled into different nanostructured morphologies, including cylindrical, lamellar, and inverted cylindrical phases. Upon a simple heat treatment, all these nanostructured materials exhibited room temperature ferromagnetic (RTF) behavior due to the nanoconfinement of the cobalt species within one phase. The effect of dimensionality, or the degree of nanoconfinement, on the macroscopic magnetic properties was studied using superconducting quantum interference device (SQUID) magnetometer. The most highly constrained cylindrical morphology yielded the highest coercivity. The inverted cylindrical morphology, analogous to antidot materials, in which a 3D magnetic matrix is confined between diamagnetic cylinders, showed the second highest coercivity, while the least confined lamellar morphology exhibited the lowest coercivity value. A series of metal-containing block-random copolymers composed of an alkyl-functionalized homo block (C16) and a random block of cobalt complex- (Co) and ferrocene-functionalized (Fe) units was synthesized via ROMP. Taking advantage of the block-random architecture, the influence of dipolar interactions on the magnetic properties of these nanostructured BCPs was studied by varying the molar ratio of the Co units to the Fe units, while maintaining the cylindrical phase-separated morphology. DC magnetic measurements, including magnetization versus field, zero-field-cooled and field cooled, as well as AC susceptibility measurements, showed that the magnetic properties of the nanostructured BCPs could be easily tuned by diluting the cobalt density with Fe units in the cylindrical domains. Decreasing the cobalt density weakened the dipolar interactions of the cobalt nanoparticles, leading to the transition from a room temperature ferromagnetic to a superparamagnetic material. These results confirmed that dipolar interactions of the cobalt nanoparticles within the phase-separated domains were responsible for the RTF properties of the nanostructured BCPs. The effect of domain size on the magnetic properties of these RTF materials was investigated using a series of five cobalt-containing BCPs with various molecular weights and constant block ratios. The BCPs self-assembled into cylindrical morphologies with different domain sizes upon solvent annealing, and then were converted to RTF materials upon a simple heat treatment. The domain sizes of these RTF materials did not show a significant impact on their coercivity values, possibly because the domain size range investigated was not large enough and the cobalt-cobalt dipolar interactions were nearly constant throughout. At the same time, this study confirms that the RTF materials generated from these novel BCPs are robust. (Abstract shortened by UMI.)

Model glassy polymers, polymethyl methacrylate (PMMA) and polycarbonate (PC) are used to experimentally probe several aspects of polymer fracture. In Chapter 1, the method of pre-stress is employed as a means of improving the fracture properites of brittle PMMA. Samples are tested under equi-biaxial compression, simple shear and a combination of biaxial compression and shear. Equi-biaxial compression is shown to increase the threshold stress level for projectile penetration whereas shear pre-stress has a large effect on the overall energy absorbed during an impact. There is also an apparent interaction observed between compression and shear to dramatically increase the threshold stress. Pre-stressed laminates of PMMA and PC show an increase in damage area because of the unique formation of a secondary cone. In Chapter 2, the effect of stress state on stress relaxation in PMMA and PC is investigated. Direct comparisons are made between uniaxial and biaxial loading conditions. The experimental methods used highlight the effect of hydrostatic stress on the relaxation process. The data shows an increase in relaxation time and increase in the breadth of the relaxation spectrum with increases in hydrostatic stress. This suggests that the stress state can have a significant effect on the useful lifetime of pre-stressed articles. In Chapter 3, Mode I and II fracture studies are performed from quasi-static to low velocity impact rates on PMMA and PC. Mode II testing utilizes an angled double-edge notched specimen loaded in compression. The shear banding response of PMMA is shown to be highly sensitive to rate, with diffuse shear bands forming at low rates and sharp distinct shear bands forming at high rates. As the rate increases, shear deformation becomes more localized to the point where Mode II fracture occurs. PC is much less rate dependent and stable shear band propagation is observed over the range of rates studied with lesser amounts of localization. A new theory is formulated relating orientation in a shear band to intrinsic material properties obtained from true-stress true-strain tests. In a qualitative sense the theory predicts the high rate sensitivity of PMMA. A kinematic limit for orientation within a shear band is also derived based on entanglement network parameters. Mode II fracture in PMMA is shown to occur at this kinematic limit. For the case of PC, the maximum impact rates were not high enough to reach the kinematic limit. In Chapter 4, the deformation response, as observed in a shear band is interpreted through the characterization of the "intrinsic material properties" obtained from true stress—true strain 8compression tests. The relatively high rate sensitivity of PMMA deformed at room temperature is related to the proximity of the beta transition to the test temperature. This is also shown in corollary experiments on PC where deformation near the beta transition is accompanied by an increase in rate sensitivity. Physical aging results in a more narrow alpha transition and is shown to increase strain localization and decrease rate sensitivity at low strain rates.

Higher coordination by donor atom interaction in phosphites and phosphates has until recently been a relatively unstudied aspect of phosphorus chemistry. The complexes involved are postulated as models for enzyme-phosphate substrates in phosphoryl transfer systems. Donor atoms employed in these compounds include sulfur and oxygen, which are typically present in enzyme residues at active sites of phosphoryl transfer enzymes. The degree of donor atom coordination is measured by the distance between the central phosphorus atom and the donor atom. This is reinforced by a measurement of the degree of distortion of the tetrahedron toward trigonal bipyramidal structures (in the case of phosphates) and pseudo-trigonal bipyramidal structures (in the case of phosphites). Hypercoordination by donor atom interaction in pentaoxyphosphoranes is well documented. Again, donor atoms used have included sulfur and oxygen. The degree to which the donor atom interacts with the phosphorus is obtained by measuring the distance between the two atoms and by the extent of distortion of the trigonal bipyramid toward an octahedral structure. These measurements are gathered from the molecular structures which are determined by X-ray crystallography. Other methods which are used for structure elucidation include $\sp1$H and $\sp{31}$P NMR spectroscopy. Six phosphites are synthesized, five of which contain the highly electronegative pentafluorophenoxy group. The effect of this group and of the varying aryl substituents on the coordination abilities of sulfur and sulfonyl oxygen atoms is discussed. Also included for comparison are two phosphites which contain no donor atom coordination. Three phosphates are synthesized, one of which contains a pentafluorophenoxy group. The effect on donor coordination by placing a phosphoryl oxygen atom in place of a lone pair in the analogous phosphite structure is discussed. Twelve phosphoranes are synthesized, eight of which exhibit donor atom coordination and are octahedral while four shown no donor interaction and are trigonal bipyramidal. Of the hexacoordinate phosphoranes, five were prepared via oxidative addition of a quinone and two via displacement reactions of monocyclic pentaoxyphosphoranes. Penta- and hexacoordinate phosphoranes are considered as models for activated states for phosphoryl transfer enzymes. The effect on reaction rate of tighter binding in the six-coordinate enzymatic transition state relative to both the five-coordinate transition state and the enzyme-phosphate substrate is discussed. The reactivities of a series of known oxyphosphoranes with respect to nucleophilic displacement by catechols is also described. The effect of varying substituents and extent of donor coordination on reaction rates are discussed.

The integration of non-covalent interactions in materials provides a direct mechanism to customize materials properties to specific applications and create novel nanostructures. Combining self-assembly with non-covalent interactions serves as a powerful tool in the creation of complex macromolecular structures with thermodynamically reversible contacts. With a host of non-covalent interactions available (e.g. dative bonding, hydrogen bonding, electrostatic pairings, π-stacking), tailoring the size and stability of self-assembled materials can be achieved through choice of interaction. This thesis describes two distinctive areas of research employing a rational combination of self-assembly and non-covalent interactions: (1) the synthesis and self-assembly of recognition unit functionalized Polyhedral Oligomeric Silsesquioxane (POSS) units and (2) the study of redox-modulated, molecular recognition in macromolecular systems. POSS units have long been employed as covalent additives in both polymeric and ceramic-based systems. Now, they have found alternative uses as non-covalent modifiers in multiple supramolecular systems. POSS units inherently feature a variety of attributes, which make them attractive as molecular recognition elements. These three-dimensional, nanoscale "building blocks" (∼0.6 nm inner silicate core) can easily be functionalized with a variety of recognition units. Through synthetic modification we were able to create a versatile component for non-covalent self-assembly with defined spacial orientations. To that end, recognition unit functionalized POSS units have been shown to serve as potent non-covalent modifiers for applications including surface modification, nanoparticle self-assembly, thermal enhancement in polymeric systems, and potential cellular delivery systems. Modulating non-covalent interactions via the reduction or oxidation of a molecule serves as an effective means in tuning the formation of supramolecular assemblies. Initial solution-based studies of both non-specific (urea-quinone) and specific, three-point (flavin-diamidopyridine) hydrogen bonding systems have been successful in understanding the complex behaviors, which govern redox-modulated molecular recognition. This understanding led to the incorporation of electrochemically tunable "host-guest" interactions on polymers and surfaces. Several interesting behaviors ranging from reversible redox-modulated recognition to induced proton transfer processes were observed and the ongoing focus of this research seeks to combine materials applications and redox-modulated recognition to create responsive, electrochemically tunable polymers and surfaces.

This thesis explores the effects of bilayer mechanics on the adhesion of biomimetic membranes and vesicles, establishing copolymer lamellae as versatile model membranes that more widely vary membrane mechanics and chemical functionalization than can be achieved using phospholipids. This new biomimetic system provides fundamental insight into cell adhesion, and motivates new design strategies for vesicles in applications such as targeted delivery.^ This study focused on the dynamic adhesion kinetics and spreading of vesicle pairs held in micropipettes at moderate tensions. The program employed two copolymers of different membrane stiffnesses, a graft copolymer of poly(dimethyl siloxane)-poly(ethylene oxide) [PDMS-PEO] and a diblock copolymer of poly(butadiene)-PEO [PBD-PEO]. The depletion-driven adhesion between pairs of these vesicles was studied, as was the avidin-biotin-driven adhesion between functionalized vesicles. This experimental grid therefore varied the membrane stiffness, adhesion strength, and point-wise versus laterally uniform application of adhesive forces.^ This study systematically demonstrated, for the first time, the activated nature of vesicle adhesion and spreading, with the bending cost of kink formation at the spreading front comprising a line tension that destabilizes adhesion nuclei. Despite modest differences between the bending moduli of phospholipid and stiffer copolymer vesicles, the effect was often sufficiently strong to prevent spreading, or at least produce a lag time prior to the onset of spreading. For instance, flexible membranes subject to depletion forces as small as 0.008 erg/cm2 responded instantaneous to changes in membrane tension, achieving the equilibrium contact angle in less than a second. Stiff vesicles, however, never spread over a substrate vesicle or displayed an equilibrium contact angle, even when depletion forces were increased to 0.35 erg/cm 2. Avidin-biotin functionalized flexible vesicles displayed a lag time prior to spreading while fully functionalized stiff vesicles never spread over substrate vesicles. Of note, in cases where spreading did not, or had not yet occurred, there was evidence for adhesion in a contact nucleus. For instance, avidin-biotin functionalized vesicles could not be separated, and unfunctionalized vesicles subject to depletion forces deformed momentarily upon separation.^ Estimates of the activation energy associated with spreading for depletion-driven adhesion were consistent with experimental observations, while a semi-quantitative treatment of avidin-biotin binding kinetics predicted the form of the concentration-dependence of the pre-spreading lag time. Once initiated, spreading kinetics were rapid and independent of membrane tension.^ These results find significance in the areas of fundamental membrane physics and in biology. As micropipette manipulation is becoming an increasingly popular tool for membrane characterization, the current thesis demonstrates that the approach to equilibrium, as measured through the contact angle, may be impeded by bending mechanics, rendering the Young's analysis of adhesion strength meaningless. The findings also suggest that in cell adhesion and processes involving sharp membrane curvature, such as endocytosis, membrane mechanics likely plays an important role in the dynamic mechanism.^

This thesis focuses on the manipulation of polymers and composites on length scales ranging from the nanoscopic to microscopic. In particular, on the microscopic length scale electric fields were used to produce instabilities at the air surface and at polymer interfaces that lead to novel three dimensional structures and patterns. On the nanoscopic length scale, the interaction of ligands attached to nanoparticles and polymer matrix were used to induce self-assembly processes that, in turn, lead to systems that self-heal, self-corral, or are patterned. For manipulation at the micron length scale, electrohydrodynamic instabilities were used in trilayer system composed of a layer of poly(methyl methacrylate) (PMMA), a second layer of polystyrene (PS) and a third layer of air. Dewetting of the polymer at the substrate at the polymer/polymer interface under an applied electric field was used to generate novel three dimensional structures. Also, electrohydrodynamic instabilities were used to pattern thin polymer films in conjunction with ultrasonic vibrations and patterned upper electrodes. Self-assembly processes involving polymers and nanoparticles offer a unique means of generating pattern materials or materials that self heal. Simple polymer/nanoparticle composites were investigated. Here, in the absence of interactions between the poly(ethylene oxide) ligands attached to the nanoparticles and PMMA polymer matrix, the opportunity to generate self-healing systems was opened. The size of the nanoparticle was varied and the effect on diffusion of nanoparticle in the polymer matrix was studied. CdSe nanorods were also assembled on a substrate templated with or guided by microphase separated diblock copolymers. The nanorods were incorporated in the diblock copolymer thin films by spin coating the co-solution of nanorods and polymer, surface adsorption of nanorods on to the patterned diblock copolymer films and surface reconstruction of PS/PMMA diblock copolymer thin film. Further, the interactions between the PMMA polymer matrix and the tri n-octyl phosphine oxide ligands attached to an anisotropic nanoparticle, i.e. nanorods, were used to influence the dispersion of the nanorods in the polymer. This led to a novel assembly, termed self-corralling where under an applied electric field highly oriented, highly ordered arrays of nanorods form. Further, self corralling of nanorods was directed by chemically patterned substrates.

This dissertation focuses on the fundamental understanding of the proton transfer process and translating the knowledge into design/development of new organic materials for efficient non-aqueous proton transport. For example, what controls the shuttling of a proton between two basic sites? a) Distance between two groups? or b) the basicity? c) What is the impact of protonation on molecular conformation when the basic sites are attached to rigid scaffolds? For this purpose, we developed several tunable proton sponges and studied proton transfer in these scaffolds theoretically as well as experimentally. Next we moved our attention to understand long-range proton conduction or proton transport. We introduced liquid crystalline (LC) proton conductor based on triphenylene molecule and established that activation energy barrier for proton transport is lower in the LC phase compared to the crystalline phase. Furthermore, we investigated the impact of several critical factors: the choice of the proton transferring groups, mobility of the charge carriers, intrinsic vs. extrinsic charge carrier concentrations and the molecular architectures on long-range proton transport. The outcome of this research will lead to a deeper understanding of non-aqueous proton transfer process and aid the design of next generation proton exchange membrane (PEM) for fuel cell.

Room temperature ionic liquids (ILs) are a unique class of solvents which are characterized by non-volatility, non-flammability, electrochemical stability and high ionic conductivity. These properties are highly desirable for ion-conducting electrolytes, and much work has focused on realizing their application in practical devices. In addition, hydrophilic and ionophilic polymers are generally miscible with ILs. The miscibility of ILs with ion-coordinating polymers makes ILs effective plasticizers for gel polymer electrolytes. Due to their unique properties, ILs present a means to realize the next generation of energy storage technology. In this dissertation, the fundamental interactions between poly(ethylene oxide) (PEO) and a variety of room temperature ILs were investigated. ILs with acidic protons were demonstrated to form a stronger interaction with PEO than ILs without such protons, suggesting that hydrogen bonding plays a dominant role for PEO miscibility with ILs. The hydrogen bonding interaction is selective for the PEO block of a PEO-b-PPO-b-PEO block copolymer (BCP). Therefore, blending these copolymers with the strongly interacting IL 1-butyl-3-methylimidazolium hexafluorophosphate ([BMI][PF6]) induced microphase separation into a well-ordered structure, whereas the neat copolymer is phase mixed. At sufficient quantities, the interaction between [BMI][PF6] and PEO suppresses PEO crystallinity entirely. In addition, the induced microphase separation may prove beneficial for ion conduction. Therefore, microphase separated copolymer/IL blends were investigated as potential gel polymer electrolytes. Cross-linkable block copolymers which microphase separate when blended with [BMI][PF6] were synthesized by modifying PPO-b-PEO-b-PPO copolymers with methacrylate end-groups. Cross-linking these copolymers while swollen with an IL generates ion gels with high ionic conductivities. The copolymer/IL blends vary from a well-ordered, strongly microphase separated state to a poorly ordered and weakly microphase separated state, depending upon the molecular weight. Stronger microphase separation results in higher mechanical strength upon cross-linking. However, this does not greatly affect ion conductivity. Nor is conductivity affected by forming gels from cross-linked PEO homopolymers when compared to BCPs. It was found that BCPs can be beneficial in producing gel electrolytes by allowing sequestration of phase selective cross-linkers away from the conducting block. Cross-linker molecules that are selective for the PPO blocks can be used to increase the mechanical strength of the gels with only a small effect on the conductivity. When cross-linkers that partition to the mixed PEO/IL block are used, the conductivity decreases by nearly a factor of 2. These studies show how ILs interact with PEO and how gel polymer electrolytes can be constructed with the IL [BMI][PF6]. While BCPs cannot directly be used to increase ion conductivity, they do allow for greater mechanical strength without sacrificing conductivity. This suggests many new approaches that may be used to simultaneously achieve high ionic conductivity and mechanical strength in solid and gel polymer electrolytes.

This thesis is divided into two research initiatives: The fabrication and study of bulk, co-continuous, cellulosic-polymer composites with the aid of supercritical CO2 (SC CO2); and the study of poly(vinyl alcohol) (PVOH) modification and surface activity in ionic liquids. The first part of this thesis utilizes the tunable solubility, gas-like diffusivity, and omniphilic wettability of SC CO2 to incorporate and subsequently polymerize silicone and poly(enemer) prepolymer mixtures throughout various cellulosic substrates. Chapters two and three investigate the mechanical properties of these composites and demonstrate that nearly every resulting composite demonstrates an improved flexural modulus and energy release rate upon splitting. Fire resistance of these composites was also investigated and indicates that the heat release rate, total heat released, and char yield were significantly improved upon for all silicone composites compared to the untreated cellulosic material. Chapter four looks specifically at aspen-silicone composites for thermo-oxidative studies under applied loads in order to study the effect of silicone incorporation on the failure kinetics of aspen. The aspen-silicone composites tested under these conditions demonstrated significantly longer lifetimes under the same loading and heating conditions compared with untreated aspen. The second part of this thesis focuses on studying ionic liquids as potentially useful solvents and reaction media for poly(vinyl alcohol). Two ionic liquids (1-Butyl-3-methylimidizolium chloride and tributylethylphosphonium diethylphosphate) were found to readily dissolve PVOH. More importantly, we have demonstrated that these solvents can be used as inert reaction media for PVOH modification. Both ionic liquids were found to facilitate the quantitative esterification of PVOH, while only the phosphonium ionic liquid supports the quantitative urethanation of the polymer. In an attempt to tune the surface properties of ionic liquid/polymer solutions, PVOH was also partially esterified with low surface energy substituents. Both surface tension and surface composition of the ionic liquid/polymer solutions can be manipulated by the stoichiometric addition of low surface energy acid chlorides. This work on the modification of PVOH can be directly applied to the modification of polysaccharides such as cellulose which could have important implications from a sustainability and energy standpoint.