A variety of “clickable” self-assembling peptide-amphiphile hydrogel systems are reported. Covalently linked hydrogels were prepared using alkyne-azide “click” chemistry and thiolene photochemistry, which were used in combination with short self-assembling peptideamphiphile compounds. For alkyne-azide “click” hydrogels, samples were formed from a mixture of two peptideamphiphiles which were separately disubstituted with alkyne or azide functionalised amino acids. This allowed for production of an extensively triazole-linked hydrogel product when gelation was performed in combination with the appropriate “click” pre-catalyst and reductant. For thiol-ene photochemical hydrogels samples were formed from a mixture of two peptideamphiphiles which were separately disubstituted with cysteine or Alloc-protected lysine. UV exposure was used to catalyse the covalent linking of the asembled hydrogel. Michael addition thiol-ene reactions were also investigated as a potential covalent linking method. A number of model reactions were attempted on specially synthesised amino acids. Results were promising, but a number of difficulties were encountered which made them unsuitable for incorporation in a hydrogel system. The hydrogel samples produced were all found to be viscoelastic hydrogels through analysis by rheological methods. A variation in the stiffness of the samples was observed, with samples having Young’s modulus values in the soft to intermediate range when compared to that of various tissues. SEM analysis indicated the hydrogels exhibited a fibrous nanostructure. The biological activity of the hydrogel samples was investigated by 2D seeding of cells on hydrogel samples. A LIVE/DEAD assay was performed which indicated hydrogel samples were able to support cell attachment and growth in vitro.

Self-assembled monolayers have been proven to be well-ordered and to give stable ultrathin films. They show a remarkably high diversity with respect to their functionalisation giving rise to many possible applications. This thesis is focused on the potential use of these molecular thin films in life sciences. The reproduction of a membrane-like environment with these tightly packed and organized unimolecular layers has led to important breakthroughs in their nanotechnological application as biomaterials. Their straightforward modification allows the chemical and physical properties of biological interfaces to be altered. In particular, Oligo(ethylene glycol) based alkanethiol self-assembled monolayers were intensively studied as biointerfaces for their ability to resist the non specific adsorption of proteins. The electrostatic repulsion which originates from these monolayers was seen as one of the possible factors causing this protein repulsion. On the other hand proteins adsorb on alkanethiol self-assembled monolayers. This can be partially attributed to an attractive hydrophobic interaction between the biomolecules and the surface. As a result of the understanding of these two driving forces which are relevant for non-specific protein adsorption/repulsion, novel self-assembling molecules were tailored in an attempt to adjust the adsorption of proteins at the SAM-liquid interface. This was conceivable with these newly designed SAMs since they allow a combination of these forces. We have chosen the ionic strength of the liquid environment as the external parameter which could act on the amount of adsorbed proteins because the electrostatic force created by oligo(ethylene glycol) groups depends on it. In addition to the synthesis of six new molecules, the preparation and characterisation of the novel self-assembled monolayers are reported in this thesis. The density of the monolayers was estimated by X-ray photoelectron spectroscopy and ellipsometry, and the wettability properties were studied by measuring the contact angle. The total force acting on proteins from the SAMs was studied with an atomic force microscope, equipped with a tip mimicking proteins, by measuring force-distance curves. An in-situ technique was investigated in order to study the influence of the variation of this total force on the quantity of adsorbed proteins by varying the ionic strength.

This thesis describes the examination of novel block copolymers that contain Ru(bpy)32+ complexes incorporated into one block of diblock copolymers made by ROMP. With the intent of exploring the potential usefulness of these interesting materials in applications such as light-harvesting and sensing, a systematic study of the solution self-assembly, luminescence properties, and the ability of the metal complex to engage in electron and energy transfer reactions has been conducted. / The solution self-assembly of block copolymers that contain Ru(bpy) 32+ complexes was examined first. Using a series of these block copolymers, a detailed study of the effects of block length, block ratio, polymer concentration and solution conditions on the copolymer self-assembly is presented. Using TEM, a number of morphologies were reproducibly observed including star micelles, large compound micelles, tubules, and interestingly, vesicles. These structures all contain the metal complex Ru(bpy)3 2+ within their core domains. / The luminescence properties of two block copolymers containing Ru(bpy) 32+ were examined: one polymer self-assembled into star micelles, the other into vesicles. Comparison of the unassembled polymer chains and the self-assembled polymers indicated that self-assembly, and confinement of the Ru(bpy)32+ complexes into the core domains of the aggregates, did not seriously adversely affect the luminescence properties of the metal complex. Measurement of the luminescence lifetime decay of the polymers suggested that energy migration occurred among the metal complexes along the polymer chain. The ability of the metal complexes within self-assembled structures to participate in electron transfer reactions with small molecules was also explored. It was found that from within the core domains of self-assembled structures, the Ru(bpy)32+ complexes could still engage in electron transfer reactions with molecules on the outsides or the insides of the aggregates, likely a result of energy migration. / The ability of Ru(bpy)32+ complexes within the cores of micelles to participate in energy transfer was explored. Micelles were formed in aqueous solutions using polymers that possessed both the metal complex and a water-soluble block. Several methods were attempted to encapsulate two molecules, a derivative of coumarin 2 and an Os(bpy)3 2+-based molecule, inside these micelles. It was observed that Ru(bpy) 32+ could act as an energy acceptor from the coumarin derivative, and could act as an energy donor to the osmium-based complex. Encapsulation of the small molecules greatly enhanced the efficiency of energy transfer, by non-covalently bringing the small molecules in close proximity to the Ru(bpy)32+ complexes. / Polymers were synthesized that contained a Ru(bpy)3 2+-based block and were terminated with the molecular recognition unit biotin. These polymers, upon self-assembly, formed micelles with biotin groups on their periphery. The addition of the protein streptavidin, which has a strong binding affinity for biotin, resulted in the aggregation of the self-assembled structures. This established the potential for self-assembled metal-containing aggregates to form higher-order structures. / Early work is presented in Appendix A involving block copolymers that contain hydrogen-bonding groups. Several methods were attempted to elucidate the solution morphologies of these polymers, namely IR, 1H NMR, DLS, and pyrene fluorescence. The transition of this initial work to polymers that contain the Ru(bpy)32+ complex is also described.

Graphene is a two-dimensional sp2 hybridized carbon lattice that is also the fundamental building block of graphite. Graphene has attracted significant interest recently due to its distinctive electrical, optical and mechanical properties. These properties have spurred research directed at modifying graphene for use in a variety of electronic, optoelectronic, and sensor technologies. However, before graphene can be used in products, it is necessary to find methods to tune, modify, grow and integrate graphene features while substantially boosting device performance and maintaining current processing compatibility and ease of integration with existing manufacturing infrastructure. This dissertation focuses on developing techniques for controllably doping the graphene layer through scalable, industry friendly and simple chemical doping; using self-assembled monolayer compounds, photo-acid and photo-base generators, polymers and metal-organic species. We have, in fact, demonstrated simple p-n junctions fabricated in this manner. Characteristic I-V curves indicate the superposition of two separate Dirac points from the p and n regions, confirming an energy separation of neutrality points within the complementary regions; Raman studies of these methods have shown that these processes result in extremely low defect levels in the graphene. Our simple methods for producing patterned doping profiles in graphene films and devices open up a variety of new possibilities for forming complex doping profiles in a simple manner in graphene. This work can enable rapid testing, such as controlled work function tuning, complex doping profiles and simple post-fabrication tuning, of concepts for graphene that may be useful in both interconnect and transparent conductor applications. In addition to graphene doping, we also investigated approaches to the synthesis of few-layer graphene flakes, since current techniques still produce inferior materials. Exfoliation of Graphene Sheets by an Electron Donor Surfactant was demonstrated to generate few-layers graphene flakes that rival the electrical quality of reduce graphene-oxide (rGO) flakes. Last but not least, Diels-Alder adducts on silica were explored as a controllable carbon precursor for pristine graphene; these allow for a rational direct-growth-of-graphene-on-surface reaction mediated by copper catalyst, without the use of flammable precursors, such as methane, that are used in current methods of chemical vapor deposition synthesis of graphene.

The aim of this thesis is the study of protein resistant oligo(ethylene glycol) (OEG) self-assembled monolayers (SAMs) using in situ techniques, such as neutron reflectivity (NR), polarisation modulation infrared spectroscopy (PMIR) and small-angle x-ray scattering (SAXS). In order to elucidate the mechanisms that lead to the nonfouling properties of these SAMs, the SAM-water, protein-protein and protein-SAM interactions have been studied separately. NR measurements, focused on the solid-liquid interface between OEG SAMs and water, show clear evidence of an extended layer with reduced density water. The reduction in density is up to 10% compared to the bulk value, and extends up to 5 nm into the bulk. The effective area (density reduction x length) of this reduced density water layer did not significantly change when the temperature was reduced to 5°C. In a complementary study, the interaction of water with protein-resistant HS(CHV₂)₁₁(OCH₂CH₂)₃OMe monolayers was examined using in and ex situ PMIR. In particular, shifts in the position of the characteristic C-O-C stretching vibration were observed after the monolayers had been exposed to water. The shift in frequency increased when the SAM was observed in direct contact with a thin layer of water. It was found that the magnitude of the shift also depended on the surface coverage of the SAM. These results suggest a rather strong interaction of oligo(ethylene glycol) SAMs with water and indicate the penetration of water into the upper region of the monolayer. These findings indicate the presence of a tightly bound water layer at the SAM-water interface. Further NR studies of the interface between OEG SAMs and a highly concentrated protein solution revealed an oscillating protein density profile. A protein depleted region of about 4-5 nm close to the SAM was followed by a more densely populated region of 5-6 nm. These oscillations were then rapidly damped out until the bulk value was reached. The influence of temperature and salt concentration on the protein density profile was small, indicating a rather minor contribution of electrostatic interactions to the protein repulsive force. SAXS measurements of OEG coated gold colloids mixed with proteins in solution did also not show any pronounced salt concentration dependence of the colloid-protein interaction. The strong association of water with the SAM and the layer of tightly bound water, together with the lack of electrostatic repulsion, suggest that the adsorption of proteins is energetically hindered by the presence of a strongly bound hydration layer.

The research detailed in this dissertation is focused on the use of biomolecules (i.e., peptides and proteins) to form non-biologically produced materials under mild reaction conditions (i.e, neutral pH, aqueous solutions, and room temperature). The peptides utilized in the studies detailed in this dissertation were identified through the screening of single crystal rutile TiO2 substrates or Ge powder with a phage-displayed peptide library. Twenty-one peptides were identified which possessed an affinity for Ge. Those peptides possessing a basic isoelectric point as well as hydroxyl- and imidazole-containing amino acid residues were found to be the most effective in precipitating amorphous germania from an alkoxide precursor. The phage-displayed peptide library screening of TiO2 substrates yielded twenty peptides. The titania formation activity of these peptides was found to correlate with the number of positive charges they carried. The titania materials generated by the library-identified and designed peptides were found to be composed of amorphous titania as well as <10 nm anatase and/or monoclinic TiO2 crystallites. Four recombinant proteins, derived from the amino acid sequences of proteins (silaffins) associated with biosilicification in diatoms, were also investigated for titania precipitation activity. The two most basic of these recombinant silaffins, rSil1L and rSilC, were able to induce the formation of titania. The titania precipitates generated by rSil1L were found to be similar to those produced by the phage-displayed library identified peptides. The second recombinant silaffin, rSilC, was found to produce hollow spheres of titania, which, following dehydration, were observed to transform into larger, solid spheres composed of radially aligned columns of rutile TiO2. The highly repetitive nature of the rSilC s amino acid sequence is believed to be responsible for the differences in TiO2 polymorph generated by the different recombinant silaffins and peptides. This dissertation also details research conducted on the formation of titania utilizing rSilC conjugated to synthetic and biogenic silica surfaces. These silica surfaces were functionalized with a newly developed drendritic growth technique. The dendritic functional-group amplification process was demonstrated to increase the loading of hexahisitidine tagged proteins on silica surfaces by more than 40%, as compared to traditional immobilization procedures.

Poly(N-isopropylacrylamide-co-acrylic acid) (pNIPAm-AAc) copolymeric multi-responsive microgels demonstrate responsivity to temperature, pH, and ionic strength. A temperature-programmed polymerization protocol is proposed for the synthesis of large pNIPAm-AAc microgel particles with a hydrodynamic diameter of 2~5 μm. Immediately after preparation of concentrated pNIPAm-AAc dispersions in closed system, the average hydrodynamic diameter is smaller than the unperturbed diameter probably due to osmotic de-swelling effect. During the aging process, pNIPAm-AAc microgel particles start to swell while their dynamics slow down. The snapshots of phase behavior of pNIPAm-AAc microgel dispersions at different pH values are illustrated. The formation of crystalline phase should follow a nonergodic path in which microgel particles swell to the extent that they build up weak attractive interaction to allow them to associate while maintaining the opportunity of rearrangement to minimize local Gibbs free energy. The age-dependent thermostability of pNIPAm-AAc microgel dispersions suggests strong attractive interactions evolve between particles during aging-convoluted crystallization. Finally, to introduce multiple biological "handle"s on the microgel particles for biomedical applications, the Cu(I)-catalyzed azide-terminal alkyne 1,3-dipolar cycloaddition, also called Sharpless-Meldal "click" reaction, is used to functionalize pNIPAm-AAc microgel particles.

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 166-174).

Thesis (M.S.)--University of Texas at El Paso, 2007. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.