Membrane gas separation emerged as a commercial process on a large scale during the 1980s. When compared to other gas separation processes such as cryogenics, adsorption and absorption, membrane separation competes primarily on the basis of overall economics and convenience, but not on the basis of product purity. For example, membranes have been used for offshore natural gas processing because they reduce the size and the weight of the processing units, require less maintenance and less operator supervision. In order to improve product purity, development of new membrane materials, and modification of existing membrane material for better gas separation properties, is required. This research focused on preparation and characterization of new copolymers from the family of polyphenylene oxides. This family of polymers was chosen because of the properties of its best-known representative, poly(2,6-dimethyl-1,4-phenylene oxide), which shows one of the highest rates of permeability for gases among glassy polymers, exhibits excellent film-forming properties, and is resistant to a number of chemical agents. The study was divided into two parts: (1) homopolymers and both block and random copolymers of different composition were synthesized by oxidative coupling of 2,6-diphenylphenol and 2,6-dimethylphenol; (2) the physical and gas transport properties of the polymers were determined. (Abstract shortened by UMI.)

Nanotechnology is now a reality although it is still very much in its infancy. This being said much work still needs to be done. During the last past few decades, new experimental tools such as videomicroscopy and optical tweezers, which allow us to both visualize and manipulate in real time the dynamics of macromolecules, have emerged. These two tools alone provide endless possibilities. For example, it is now possible to tether a polymer at one end with optical tweezers while a constant flow of solvent extends it. If the chain is fluorescently labeled, dynamical properties can be extracted via videomicroscopy. In this thesis, we study a similar problem. With the help of Molecular Dynamics (MD) simulations, we examine the physics of a Freely Jointed Chain (FJC) tethered by one end to a hard surface while being submitted to a Poiseuille flow. A good solvent is used during the first part of this thesis, while for the second part, we look at the dynamics of the chain in poor solvents. In both cases, we compare actual stretching theories to our simulation data and extract the effects of Hydrodynamic Interactions (HI). For good solvents, we propose a new empirical equation which relates the unstretched fraction of the chain to the full range of shear rates. We also observe a peculiar cyclic motion of the chain which was first reported experimentally. For poor solvents, we study the collapsed chain properties while changing the strength of the shear flow linearly in time. A novel hysteretic effect for the chain extension as a function of shear rate is observed in our simulations.

Electrospray ionization (ESI) and matrix assisted laser desorption-ionization (MALDI) mass spectrometry were used to determine the composition (monomer ratios) and structure (end group analysis), relative to 1H NMR spectroscopy and theoretical predictions, for three different copolymers: poly(butyl acrylate/vinyl acetate) (PBA/PVAc), poly(methyl methacrylate/vinyl acetate) (PMMA/PVAc) and poly(butyl acrylate/methyl methacrylate) (PBA/PMMA). The ESI results were found to be in excellent agreement with 1H NMR spectroscopy for PBA/PVAc and PBA/PMMA copolymers whereas there was more divergence in the case of PMMA/PVAc. In the case of PBA/PMMA copolymers similar distributions of products were observed by ESI-MS and MALDI-MS; two major product classes were observed differing by their end-groups. One class has hydrogen and dodecylthio end groups while in the other the dodecylthio has been replaced by alpha-cyanoisopropyl from the initiator. The relative abundance of these distributions as a function of copolymer conversion for a series of reaction conditions was investigated by both ESI and MALDI. The collision-induced dissociation (CID) mass spectra for a variety of chain lengths of four ionized polymer samples have been quantified according to their observed total relative fragment ion abundances. The CID mass spectra of oligomers of ionized PMMA with three different types of end groups and polystyrene, PS, were obtained at fixed centre-of-mass collision energies and collision numbers. For the PMMA polymers, the total fragment ion abundance increases with increasing chain length, consistent with an increase in internal energy deposition with size of the ion. A discontinuity in the increase in total fragment ion abundance appears to correspond to a change in conformation of the polymer ions from linear (at short chain lengths) to cyclic (at long chain lengths). Ionized PS does not exhibit this change in conformation as all chain lengths show compact structures and accordingly the total fragment ion abundance does not change with increasing chain length. Protonation of polymers in the gas-phase was achieved by the dissociation of proton-bound complexes of the oligomers with small peptides and amino acids. Protonated PMMA and PBA oligomers were shown to fragment in unique pathways that involved losses of neutral molecules from their side chains, until all that is left is a hydrocarbon backbone. For PMMA the neutrals were primarily CO and methanol, while for PBA butyl ether is lost. We also explored the threshold fragmentation of the proton-bound complexes as a function of the amino acid used (and its proton affinity) which allowed a kinetic bracketing of the oligomer PA as a function of chain length. The results were consistent with a change from bidentate to tridentate binding of the proton with increasing length of the PMMA oligomers.

Most of the research presented in this thesis deals with photochemistry applied to optical lithography, a technology used to manufacture computer chips, memories, and integrated circuits in the micro- and nano-regime. Photochemical reactions induced in thin polymer films by laser radiation at 248, 193 and 157 nm were studied extensively, employing spectroscopy and microscopy techniques. Fluorescent dyes that would change their properties upon interaction with a chemical species were used to gain insights about the photoproducts formed during irradiation. Photolysis of photoacid generators (PAGs) leads to formation of acid, which will then catalyze deprotection of polymer pendant groups. The amount of acid formed as a function of incident dose was determined for different PAGs at various wavelengths and in different resist formulations using Coumarin 6, a fluorescent dye that changes its spectroscopic properties upon interaction with the proton. New and more transparent PAGs, obtained in the group, were characterized at different wavelengths. The amount of acid determined by in polymer titration was used in calculation of the catalytic chain length (CCL). This is a novel method which employs two fluorescent sensors embedded in a polymer film. Hydrofluoric acid (HF) was detected in films of fluorinated polymers exposed to laser radiation at 157 nm, using a fluorescent sensor especially designed and synthesized in the group. The influence of laser radiation on the polymer film was studied using pyrene as fluorescent probes sensitive to the environment changes. Formation of excimers was observed in exposed areas; a very interesting finding is that the molecules forming the excimers do not separate after they emit light, remaining in close proximity for days. The influence of temperature on the excimers in thin polymer films was studied, using polymers with different Tg.

This thesis describes the synthesis and application of a new series of amphiphilic graft copolymers with a hydrophobic polyolefin backbone and pendent hydrophilic poly(ethylene glycol) (PEG) grafts. These copolymers are synthesized by ruthenium benzylidene-catalyzed ring-opening metathesis polymerization (ROMP) of PEG-functionalized cyclic olefin macromonomers to afford polycyclooctene- graft-PEG (PCOE-g-PEG) copolymers with a number of tunable features, such as PEG graft density and length, crystallinity, and amphiphilicity. Macromonomers of this type were prepared first by coupling chemistry using commercially available PEG monomethyl ether derivatives and a carboxylic acid-functionalized cycloctene. In a second approach, macromonomers possessing a variety of PEG lengths were prepared by anionic polymerization of ethylene oxide initiated by cyclooctene alkoxide. This methodology affords a number of benefits compared to coupling chemistry including an expanded PEG molecular weight range, improved hydrolytic stability of the PEG-polycyclooctene linkage, and a reactive hydroxyl end-group functionality for optional attachment of biomolecules and probes. The amphiphilic nature of these graft copolymers was exploited in oil-water interfacial assembly, and the unsaturation present in the polycyclooctene backbone was utilized in covalent cross-linking reactions to afford hollow polymer capsules. In one approach, a bis-cyclooctene PEG derivative was synthesized and co-assembled with PCOE-g-PEG at the oil-water interface. Upon addition of a ruthenium benzylidene catalyst, a cross-linked polymer shell is formed through ring-opening cross-metathesis between the bis-cyclooctene cross-linker and the residual olefins in the graft copolymer. By incorporating a fluorescent-labeled cyclooctene into the graft copolymer, both oil-water interfacial segregation and effective cross-linking were confirmed using confocal laser scanning microscopy (CLSM). In a second approach, reactive functionality capable of chemical cross-linking was incorporated directly into the polymer backbone by synthesis and copolymerization of phenyl azide and acyl hydrazine-functional cyclooctene derivatives. Upon assembly, these reactive polymers were cross-linked by photolysis (in the phenyl azide case) or by addition of glutaraldehyde (in the acyl hydrazine case) to form mechanically robust polymer capsules with tunable degradability (i.e. non-degradable or pH-dependent degradability). This process permits the preparation of both oil-in-water and water-in-oil capsules, thus enabling the encapsulation of hydrophobic or hydrophilic reagents in the capsule core. Furthermore, the assemblies can be sized from tens of microns to the 150 nm - 1 µm size range by either membrane extrusion or ultrasonication techniques. These novel capsules may be well-suited for a number of controlled release applications, where the transport of encapsulated compounds can be regulated by factors such as cross-link density, hydrolytic stability, and environmental triggers such as changes in pH.

The rise in bacterial resistance and the declining approval rate of novel anti-infective drugs are a major threat to global public health. Antimicrobial peptides (AMPs), found in almost every multicellular organism, have attracted considerable attention as models for the design of new therapeutic agents due to their broad spectrum activity and reduced bacterial resistance development. This dissertation focuses on the development of a new series of synthetic mimics of antimicrobial peptides (SMAMPs) from simple aryl scaffolds using Suzuki Miyaura coupling. This novel design allows easy tuning of the conformation, overall hydrophobicity of the molecule, amphiphilicity, and the number of charges in order to develop a structure-activity relationship. The antimicrobial activities of the SMAMPs against both gram-positive and gram-negative bacteria suggest that improving the selectivity requires fine-tuning of one or more of these parameters, with overall hydrophobicity and charge having a more significant impact than conformational rigidity. Furthermore, comparing the activities of SMAMPS with facially amphiphilic and disrupted amphiphilic topologies confirmed that amphiphilicity is an important design parameter for attaining antimicrobial activity, especially against gram-negative bacteria. This aryl scaffold design has led to the development of several highly active SMAMPs with selectivities >200 against both gram-positive S. aureus and gram-negative E. coli, which is nearly 20 times higher than that of the conventional AMP, MSI-78. One of these SMAMPs also shows a unique immunomodulatory response involving the induction of both cytokines and chemokines, which can have significant therapeutic potential. Similar chemistry was employed in the development of novel lipopeptide mimics (LPMs), where the attachment of pendant aliphatic chains to the tri-aryl backbone structure can be used to modulate the activity. The second project in this dissertation concerns the investigation of the influence of the cobalt density in the phase-separated domains in the ferromagnetic block copolymer materials 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 complex-functionalized (Fe) units was synthesized via ring-opening metathesis polymerization (ROMP). Taking advantage of the block-random architecture, the influence of dipolar interactions on the magnetic properties of these nanostructured BCPs was studied by systematically varying the molar ratio of the Co units to the Fe units, while maintaining the cylindrical phase-separated morphology. A decrease in the cobalt density weakens the dipolar interactions between the cobalt nanoparticles, leading to the transition from a room temperature ferromagnetic material to a superparamagnetic material. These results confirm that the dipolar interactions of the cobalt nanoparticles within the phase-separated domains are responsible for the (unexpected) room temperature ferromagnetic properties of the nanostructured BCPs.

Analogous disproportionation processes lead to similarities in the structures present at incipient coacervation to those within the subsequent dense phase. Coacervation in polyelectrolyte/mixed micelle system is induced by temperature to explore structural evolution before, during and after coacervation. Assemblies of polyelectrolyte-micelle primary complexes appear to be governed by the interparticle interaction, a delicate balance between short-range attraction and long-range repulsion. Dilution-induced coacervation in opposite to self-suppression is facilitated by the presence of smaller particles in size but larger in number as a result of the favourable interparticle interaction. While dilution leads to formation of smaller particles that can phase separate easily, larger particles can achieve coacervation by increase in temperature, a greater entropy contribution. Dynamic light scattering reveals a progressive increase in aggregate size with temperature up to the phase transition at Tphi;, followed by splitting of these aggregates into respectively smaller and larger particles. The fact that the process of coacervation itself is accompanied by the expulsion of smaller aggregates to form near-neutral aggregates is known as a type of macroion disproportionation. At incipient coacervation, the transfer among soluble complexes of excess macroions to achieve near-neutrality is found to be analogous to the expulsion (with counterions) of excess macroions into dilute domains in the coacervates. The driving forces of ion-pairing and counterion release, in one-phase and dense phase states, use similar strategies of disproportionation and local charge neutralization to form analogous transient structures. The transient nature of coacervate structure is further investigated by rheology and total internal reflection microscopy in PDADMAC/BSA coacervates. While polyelectrolyte-colloid coacervates exhibit structural rearrangement in the coacervate correlated with the compositional difference between supernatant and coacervate, heteroprotein coacervation appears to have a fixed stoichiometry in both phases. The absence of disproportionation is suggested to be responsible for the highly limited conditions of pH, ionic strength I, total protein concentration Cp, and BLG:LF stoichiometry under which Lactoferrin (LF) and B-lactoglobulin (BLG) form optically clear coacervates. These constraints on conditions for pure coacervation were also attributed to the requirements for the formation of a basic primary unit, LF(BLG)4 , characterized in the supernatant and coacervate. Coacervate is characterized as a solidlike transient network of primary units embedded into a viscoelastic suspending fluid.

This dissertation explores the design, synthesis, and structure of aromatic molecules with the goal of understanding the forces which affect packing of conjugated molecules in the solid state. Two approaches were applied to direct the assembly of aromatic materials. The first one involved the use of coordination bonds between aromatic nitriles and silver(I) triflate. Several acridine-based ligands were synthesized and crystallized, alone and complexed to silver(I) triflate. Generally, ligands that possessed three peripheral coordination sites formed sheet-like crystal structures. Ligands with only one coordination site crystallized into columnar arrangements with significant edge-to-face interactions. The second approach studied the effect of mutually phobic side-chains on the properties of dyads - molecules comprised of linked electron-rich and electron-poor aromatic moieties. It was shown that, despite attractive electrostatic forces between electron-rich and electron-poor aromatic species, aliphatic hydrocarbon and fluorocarbon side-chains form segregated domains in single crystals. Finally, the mutually phobic side-chain approach was extended to materials based on oligo- or poly-thiophene and naphthalenediimide.

Materials with nanoscale dimensions display electronic, photonic, and magnetic properties different from those observed by their respective bulk materials. This thesis work has focused on the utilization of molecular recognition for modular self-assembly of nano-sized building blocks into two or three-dimensional aggregates and the precise control over their structural parameters and morphologies. Special attention will be given to the design and synthesis of molecular and macromolecular building blocks to generate micron and nanometer-scale order, to tailor local surface properties through site-selective immobilization, and to create responsive/adaptive functional materials in a controlled, reproducible, and reversible manner. The advantages, potential applications, and current challenges associated with this "bottom up" self-assembly approach will also be discussed. I am going to demonstrate in the following chapters how we synthesized functionalized Au and CdSe nanoparticles (NPs), styrene based block copolymer with pended recognition units, and diamidopyridine ( DAP)—thymine (Thy) three-point hydrogen bonding dyads that induced recognition-mediated self-assembly of polymers and NPs into ordered and tunable/responsive nanocomposites. The resultant composite materials were addressed onto photo-lithographically defined surface regions. Desired electrical conductivity, surface wettability and biocompatibility were achieved by choosing appropriate polymers and NPs—the versatile building blocks for nanocomposite functional materials.

The development of highly selective and very sensitive methods to detect peptides and proteins of interest in complex mixtures remains an important goal in proteomics applications. This dissertation focuses on the use of reverse-micelle forming amphiphilic homopolymers as part of liquid-liquid extraction to selectively extract and concentrate peptides from an aqueous solution into an immiscible organic phase. After extraction, the polymer-peptide mixtures are amenable to direct analysis by matrix assisted laser desorption ionization mass spectrometry (MALDI-MS). The charged interiors of the reverse micelles enable oppositely charged peptides to be selectively extracted into the aggregate’s cores via coulombic attraction. Reverse micelles formed by negatively charged carboxylic acid or positively charged quaternary amine groups can be used alone or in sequence to selectively extract and fractionate peptides according to their isoelectric points (pIs). Furthermore, the pI cutoff can be readily tuned by adjusting the extraction pH. The coalescence of polymer-peptide conjugates into hotspots on the MALDI target plate during MALDI-MS analysis results in significant signal enhancement for the enriched peptides, enabling reproducible ion signals at concentrations as low as 10 fM. Interestingly, reverse micelles formed by positively charged polymers with quaternary amine substituents can selectively enrich acidic peptides that are undetectable during regular MALDI-MS analysis. The extraction protocol along with MALDI-MS can also be used for the selective enrichment and detection of low abundance peptide/protein biomarkers in human serum at physiologically relevant concentrations. Overall, the results described in this dissertation reveal that this selective extraction protocol along with MALDI-MS analysis might have a significant impact on protein identification and early stage screening of biomarkers.