The overall purpose of this dissertation is to develop new polymer materials containing ester functionalities. This document will be separated into two sections covering two synthetic research projects that I have worked on for my Ph.D. dissertation. Both projects involved chain polymerizations of ester-functionalized monomers. A key feature of this thesis was to gain an in-depth understanding of the individual chain polymerizations employed, namely, anionic ring-opening polymerization of dialkyl cyclopropane-1,1-dicarboxylates and radical polymerization of multifunctional captodative monomers. Part I focuses on developing a new synthetic methodology based on anionic ring-opening polymerizations of cyclopropanes geminally substituted on the cycle. The goal was to obtain carbon-chain polymers with ester substituents located on every third-carbon atom of the backbone, a substitution pattern that cannot be achieved by any other synthetic method. Ester groups are chosen not only because of their electron-withdrawing nature that ensures enough activation but also because the structural versatility offered by ester groups allows to tailor polymer properties in a very easy way. Conditions allowing this ring-opening polymerization to proceed in a living way are identified. By taking advantage of the living character of the anionic polymerization, a control over the polymer end-groups, molecular weight and molecular weight distribution of the polymers can be achieved. Tailoring the polymer properties is also possible by varying the ester groups. Chemical modification of the polymer offers another way to obtain new polymers such as polyelectrolyte having the same substitution pattern. In part II, a possible answer is proposed to the environmental issues the coating industry is currently facing which include the toxicity of acrylic monomers used and generation of volatile organic compounds during the process. New functionalized bis(α substituted acrylate)s were developed that can be assumed non/less toxic based on previous literature. The new functionalities introduced in the monomers are crucial in affecting not only their reactivity toward the photopolymerization involved in the coating production but also some properties of the final coatings. Both of these aspects are covered in the research.

This project involves the design, synthesis and characterization of a new class of carbon-chain polymers with substituents on every third and every fourth carbon along the backbone. 1,1-Dicyanocyclopropane 1, alkyl 1-cyanocyclopropanecarboxylates 2a–d and 1-phenylcyclopropanecarbonitrile 4 undergo ring-opening polymerization in the presence of thiophenolate anions at 60°C, yielding highly functionalized carbon-chain polymers of general structure (CH2CH2C(XY)) n. Monomer 1 is highly reactive, while 2a–d show intermediate reactivity between 1 and 4. GPC analysis indicated poly(2a–d) had narrow molecular weight distributions (M¯w/M¯n < 1.17). Due to the poor solubility of poly(1) and poly( 4), their molecular weights could not be measured. Thermogravimetric analysis (TGA) shows that poly(1) is highly stable up to 360°C, while poly(2a–d) and poly(4) are stable up to 200°C. X-ray analysis indicated that the polymers are all semi-crystalline, with melting temperatures above their decomposition temperatures. A detailed study of the crystal structure of poly(diethyl-1,1-cyclopropanecarboxylate) poly(3b) indicated that the conformation of the backbone is close to a TGG¯ TGG¯ structure. Similar attempts to ring-open polymerize dialkyl-1,1-cyclobutanedicarboxylates 5a–c and ethyl 1-cyanocyclobutanecarboxylate 6 using thiophenolate anions at temperatures ranging from 140 to 180°C were unsuccessful. For these reactions, the thiophenolate preferentially attacks the carbon on the ester substituent (Krapcho reaction) and not the ring-carbons. 1,1-Dicyanocyclobutane 8 ring-opens in the presence of potassium or sodium thiophenolate at 140°C, but only oligomers (X¯n < 5) were obtained after long reaction times. An alternative synthetic strategy to synthesize the desired poly(1,1-difunctionalized tetramethylene)s (CH2CH2CH2C(XY))n was attempted via the anionic polymerization of ethyl 2-cyano-2,4-pentadienoate 9 and diethyl 2-propeny-lidene malonate 10. NMR and IR analysis of samples (initiated with piperidine in benzene at 25°C) indicated that the microstructure of poly(9) consisted only of 1,4-addition units, but for poly(10), a mixture of 3,4- (66%), 1,4- (17%) and 1,2 (17%) units are obtained. Subsequent hydrogenation of a sample of poly(9) with only a 1,4-microstructure using diimide as a hydrogenation agent. The results indicated up to 80% hydrogenation was achieved. This strategy, although not direct, provides a feasible method to achieving our target carbon-chain polymers with substituents on every fourth carbon.

Various methods for modification of polymer surfaces were studied with the objective of controlling changes in wetting behavior. Random copolymers and block copolymers were synthesized by free radical polymerization and atom transfer radical polymerization, respectively, of methacryloxymethyl- or methacryloxypropyltiis(trimethylsiloxy)silane and methyl methacrylate. These polymers spontaneously rearrange to concentrate the low energy, non-wettable siloxane at the surface. The nanoporous nature of the surfaces of these polymers was confirmed using X-ray photoelectron spectroscopy (XPS) analysis and dynamic contact angle analysis. Another method for wettability modification that was studied was the selective modification of polymer surfaces using 3-aminopropyltriethoxysilane (APTES); this provided surfaces with silica-like reactivity. This surface chemistry had been reported for poly(ethylene terephthalate); this thesis work expands the reaction to many other polymers (ostensibly all that are H-bond acceptors). Variations in temperature, concentration, and solvent were studied as well as reagent mixtures with tetraethoxysilane. Our experiments led us to propose a new pathway for the reaction. Subsequently, polymers were hydrophobized by fluorination with a monochlorosilane. Argon plasma sputtering of polymers was investigated and a new mechanistic scheme was developed for non-classical polymer sputtering in which the polymer depolymerizes yielding gas-phase monomer which then re-polymerizes. This new understanding of the sputtering process was used to create ultrahydrophobic surfaces, which water drops were unstable on. Polymer surfaces were simultaneously roughened and hydrophobized to test the effect of roughness and topography on surface wettability. A new phenomenological model for wettability was developed with this knowledge in which wettability is treated as a one-dimensional contact line issue. For droplet motion to occur, an energy barrier to three phase contact line motion must be overcome, which can be accomplished by: (1) surface structures becoming smaller to lower barriers to motion and/or (2) contortion of the contact line to raise its ground state energy.

This thesis adapted tools of organic and organometallic chemistry to achieve control over synthetic macromolecular architectures, with a focus on the systematic incorporation of polar and nonpolar chemical entities into polymers, and test these amphiphilic polymers for their interactions with living cells, bacterial and mammalian. The development of highly active well-defined catalyst systems for olefin metathesis, and their influence on the development of ring-opening metathesis polymerization (ROMP) has been a major inspiration behind our synthetic strategy towards the preparation of model amphiphilic polymer architectures with a high level of structural control. The first synthetic approach was the investigation of ring-opening metathesis copolymerization of polar and nonpolar cyclic olefins as monomers. This study leads to the discovery of alternating copolymerizations of a series of polar cyclic olefins with nonpolar cyclic olefins using ruthenium-based homogeneous catalyst system. Mechanistic studies revealed that steric factors induced from comonomer structures and catalyst type affect the degree of alternation on the polymer backbone. This novel technique allows for the strictly alternating incorporation of polar and nonpolar monomeric units into polymer chains of various lengths, and facilitates the polymerization of sterically encumbered monomers and modification of final material properties. In a second synthetic approach, a general strategy was developed for the assembly of polar and nonpolar domains into a modular monomer structure. The character and size of each domain can be tuned independently and locked into the repeating unit of the amphiphilic polymers resulting from ROMP of the modular norbornene derivatives. Living ROMP of these monomers provided access to a large range of molecular weights with narrow molecular weight distributions. Lipid membrane disruption activities, a key feature of amphiphilic polymers used in many biomedical applications, were investigated for amphiphilic polynorbornene derivatives against liposomes. Water-soluble amphiphilic cationic polynorbornene derivatives, which exhibited the highest level of activities against liposome membranes, were then probed for their antibacterial activities in growth inhibition assays and hemolytic activities against human red blood cells in order to determine the selectivity of the polymers for bacterial over mammalian cells. By tuning the overall hydrophobicity of the polymer, highly selective, non-hemolytic antibacterial activities were obtained.

We developed an experimental approach that enables molecule visualizations of macromolecular diffusion and partitioning within well-defined pores. By colloidal templating, two-dimensional arrays of open, submicron cavities interconnected by small holes were created in dense polyacrylamide gels. Cavity size of the arrays varied from 600 to 1400 nm, with the corresponding holes about 4–5 times smaller. DNA molecules of sizes from 2.69 to 48.5 kbp were inserted into the cavity arrays and monitored by fluorescent microscopy. In video sequences, individual chain positions identified as the chains diffused under Brownian motion over a period of seconds to tens of minutes. For larger chains, dynamic configurations were resolved during the motion. Over full range of molecular and pore sizes, we found that chain dynamics could be understood through the entropic barriers transport mechanism. At high confinement (large molecules in small cavities), this mechanism produces unexpected trends, for example, independence of diffusion coefficient on molecular size or faster diffusion of molecules in smaller pores. These trends reflect segmental excluded volume. Complicated dynamics akin to motion of an inchworm characterized the largest DNA chains, those with radius of gyration larger than the cavity radius. Diffusion of linear and circular DNA molecules was compared for different molecular sizes, and the resulting differences in diffusion coefficient explained by differences in diffusion mechanism; linear molecules translocate through holes by forming loops, while linear chains predominantly translocate by threading one chain end. A similar colloidal templating approach was also employed to create isolated cavity pair interconnected by a small hole. When templated by bidisperse colloid, the two cavities have unequal diameters. A DNA chain trapped inside such pair partitions unevenly, preferring the larger cavity, which afford greater configurational freedom. This sort of partitioning underlies many separation technologies but had not been visualized previously. The partition coefficient between cavities was measured visually for many combinations of cavity and molecular sizes, trends in this coefficient were then compared to existing theories for polymer partitioning. Good agreement over a two orders-of-magnitude variation of partition coefficient was obtained when effect of excluded volume on confinement free energy was introduced in a mean-field manner.

Quantum dots are attractive potential components for next generation technologies such as light emitting diodes, sensors, and photovoltaic cells due to their unique and tunable electro-optical properties. The effective integration of quantum dots into devices requires a stable dispersion or self-assembly of the quantum dots in the solid-state. Such dispersions or assemblies are dictated by the interactions between the ligand environment of the quantum dots and the chosen polymer matrix. This thesis will highlight key contributions to the area of tailored cadmium selenide nanocrystals through the use of novel, functionalized ligands. This includes the utilization of ring-opening metathesis polymerization (ROMP), reversible addition fragmentation chain-transfer (RAFT) polymerization, and metal mediated couplings to control the polymer composition and molecular weight in radial polymerizations from CdSe nanocrystals. CdSe quantum dots were also found to assembly at the interface of immiscible fluids, and through appropriately functionalization these assemblies were effectively cross-linked. The key fording in this work is the retention of the inherent quantum dot fluorescence following these polymerization methods.

The goal of this research is to design molecules that capture the essential elements and biological properties of host defense peptides without the use of amino acids or peptide-like backbones. This is accomplished via a meta-phenylene ethynylene backbone with polar amine and nonpolar alkyl groups as side chains. These molecules are shown to form stable monolayers at the air-water interface with the polymer chains assuming an edge-on structure with the aromatic rings perpendicular to the water surface and the polar amines groups below the water surface. Furthermore, these molecules aggregate in solution with the addition of a non-solvent, as expected with facially amphiphilic molecules. When tested against biological systems, the result is promising: growth inhibition against a wide variety of bacteria at relatively low concentrations with minimal disruption towards red blood cells. The average minimal concentration needed to disrupt bacterial growth is 2 μg/mL and occurs in less than 5 minutes. Furthermore, tests indicate negligible evolution of bacterial resistance over a month-long experiment. Incorporation of these compounds into polymeric substrates proves to be an effective way of preventing bacterial growth on surfaces. Further probing the mode of action of these molecules shows results similar to many host defense peptides.

The fabrication of functional nanostructured materials for sensing, encapsulation and delivery requires practical approaches to self-assembly on multiple length scales and the synthesis of tough yet permeable structures. Here, ligand-stabilized nanoparticles assembled into three-dimensional constructs at fluid-fluid interfaces driven by the reduction in interfacial energy were investigated. Studies on the dynamics of the nanoparticles and the self-assembled structures formed at the interface, using fluorescence photobleaching methods and in-situ grazing incidence small angle x-ray scattering, suggest a liquid-like behavior and ordering at the interfaces. Cross-linking of the nanoparticle assembly using functional ligands, affords robust membranes that maintain their integrity even when they are removed from the interface. These composite membranes, nanometers in thickness, are elastic yet permeable. Combining other self-assembly processes on different length scale, i.e. "breath figures", with the self-assembly of nanoparticles at the oil-water interfaces lead to the formation of hierarchically structured nanoparticle arrays. The assembly of virus and other biological complexes at fluid interfaces was also investigated where interfacial assembly rendered an easy route to direct and assemble the bioparticles into 2-D and 3-D constructs with hierarchical ordering. These assemblies enable the potential use of the bioparticles as a natural supramolecular building block to obtain materials with well-defined biofunctionalities. Also, the organization of inorganic nanostructures within self-assembled organic or biological templates is receiving the attention of scientists interested in developing functional hybrid materials. Recent theoretical arguments have suggested that synergistic interactions between self-organizing particles and a self-assembling matrix material can lead to hierarchically ordered structures. Here we show that mixtures of diblock copolymers and either cadmium selenide- or ferritin- based nanoparticles exhibit cooperative, coupled self-assembly on the nanoscale. In thin films, the copolymers assemble into cylindrical domains, which dictate the spatial distribution of the nanoparticles; segregation of the particles to the interfaces mediates interfacial interactions and orients the copolymer domains normal to the surface, even when one of the blocks is strongly attracted to the substrate. Organization of both the polymeric and particulate entities is thus achieved without the use of external fields, opening a simple and general route for fabrication of nanostructured materials with hierarchical order.

The development of functional group tolerant ruthenium based ring-opening metathesis polymerization (ROMP) catalysts allows for the synthesis of a broad range of cyclic olefin based polymers. Highly robust ruthenium carbene catalysts allow for the ROMP of novel polymers at ambient conditions, that were not possible by previous organometallic catalysis. This research investigated the synthesis of crosslinked polyolefins by ROMP using ruthenium carbene catalysts. Specifically, polydicyclopentadiene (PDCPD) organic-inorganic copolymers were synthesized. An ultrasonic spectroscopy technique was utilized to quantify the reaction kinetics of the ROMP of dicyclopentadiene (DCPD) catalyzed by two different ruthenium catalysts. A reaction cell that held the reactants in a plane strain geometry, allowed the changes in density, acoustic velocity, acoustic modulus, and waveform attenuation to be accurately measured. It was determined that kinetic data for the crosslinking reaction could be calculated from the ultrasonic spectroscopy data. With the ability to measure the crosslinking kinetics of PDCPD homopolymer, PDCPD nanocomposites were prepared by copolymerization of DCPD and polyhedral oligomeric silsesquioxanes (POSS). The affects of the POSS functionality and the organic periphery on morphology were investigated. It was found that both the organic periphery and functionality of POSS could affect the morphology of the copolymer. Additionally, the affects of POSS functionality, on the physical and mechanical properties of the copolymer were evaluated. The thermal transitions and mechanical properties of the POSS copolymers decreased regardless of POSS functionality. Therefore, POSS acts much like a plasticizer in conventional thermosets. Additionally, POSS was found to decrease the dielectric constant of the copolymer. The dielectric constant could be further decreased by selectively degrading POSS from the matrix. A final aspect of the project utilized the catalysts' functional group tolerance to synthesize polymers containing reversible or physical crosslinks. These polymers possess the inherent shape memory characteristics of chemically crosslinked shape memory polymers and the processability of thermoplastics. Overall, this research advances our understanding of the utility of ruthenium catalyzed ROMP in thermoset polymerization through the creation of novel materials.

The synthesis, processing, and engineering of low heat release, ultra fire-resistant materials present an important challenge in polymer materials chemistry. One approach to this problem involves the use of materials that char upon decomposition rather than evolve flammable gas. Here, the synthesis and characterization of 1,1-dichloro-2,2-bis(4-hydroxyphenyl)ethene (bisphenol C or BPC) and deoxybenzoin containing polymers are described. Poly(aryletherketone)s containing 1,1-dichloro-2,2-bis(4-hydroxyphenyl)ethene (BPC) were synthesized by the cesium fluoride initiated polymerization of 1,1-dichloro-2,2-bis(4-t-butyldimethylsiloxyphenyl)ethane with 4,4′-difluorobenzophenone (BP-F). These polymers exhibit high char yields by thermogravimetric analysis (TGA), and low heat release capacities were measured by pyrolysis combustion flow calorimetry (PCFC). Poly(aryletherketone)s were prepared from BP-F and various ratios of BPC and bisphenol-A (BPA), and their thermal properties were characterized by TGA and PCFC. Fire-resistant bisphenol C and polydimethylsiloxane (PDMS) polyurethanes were prepared through the polycondensation of 1,1-dichloro-2,2-bis(4-isocyanatophenyl)-ethene (BPC-NCO) with BPC and 2000 g/mol hydroxybutyl-terminated PDMS (PDMS-BuOH). These polyurethanes showed increased char yields based on inclusion of BPC-NCO and PDMS-BuOH, and substantially reduced heat release capacities compared to similar polyurethanes prepared with 2,4-tolylene diisocyanate and poly(tetramethyleneoxide). Halogen-free, fire-resistant copolyarylates were prepared by interfacial copolymerization of isophthaloyl chloride and several relative ratios of 4,4 ′-bishydroxydeoxybenzoin and bisphenol A. The fire-resistance of these polyarylates was explored by TGA and PCFC, and char yields of nearly 40% were observed, twice that of bisphenol A polyarylate. Heat release capacities as low as 81 J/g·K were measured by PCFC. Thus, halogenation, often used to effect fire-resistance in materials, is eliminated all together. Hyperbranched polyphenylenes with bromine and boronic acid termination were prepared by Suzuki coupling polymerization. An exceptionally low heat release capacity of 6 J/g·K were measured by PCFC for bromine terminated polymers and char yields were shown to increase as a function of boronic acid termination due to the formation of a glassy network.