The work in this thesis was undertaken to explore both the effect of heteroatoms on the semiconducting properties of star-shaped thienoacenes, and to expand the scope of these materials to fields outside of organic semiconductors. Overall, new star-shaped molecules were prepared with a view towards applications such as thin film transistors, as the organic linker component in metal-organic frameworks, and as ligands that could coordinate to transition metals through the sulfur atom. The first chapter describes the properties of star-shaped molecules, the theory underlying their semiconducting behaviour, and the previous work that motivated the research contained herein. The second chapter of this thesis outlines the synthetic methodology that was utilized to achieve the molecular targets, as well as the characterization techniques that are used to reveal the properties of organic semiconductors. The third chapter of this thesis describes the synthesis and optoelectronic properties of novel nitrogen-containing semiconductor molecules called thienoacridines, and their comparison to carbon-and-sulfur based analogues, thienoanthracenes. The fourth and fifth chapters concern the synthesis of functionalized star shaped thienylbenzene molecules. In Chapter 4, these molecules are decorated with carboxylic acid groups so that they may act as tetrapodal MOF linkers. In Chapter 5, they are equipped with N-aryl(azomethine)thiophene moieties to explore sulfur coordination and act as ligands. The sixth chapter provides conclusion to this work, and possible future directions of the research conducted herein.

Fouling properties of materials such as polyethylene glycol (PEG) have been extensively studied over the past decades. Traditionally, the factors believed to result in protein adsorption resistance have included i) steric exclusion arising from the compression of longer chains and ii) grafting density contribution which may provide shielding from the underlying material. Recent studies have suggested that PEG interaction with water may also play a role in its ability to resist protein adsorption suggesting that steric exclusion may not be the only mechanism occurring during PEG/protein interactions. Star-shaped PEG polymers have been utilized in protein adsorption studies due to their high PEG segment concentration, which allows to increase the PEG chain grafting density compared to that achieved with linear PEG chains. Most studies that have investigated the interactions of tethered linear and star-shaped PEG layers with proteins have considered linear PEG molecules with molecular weights several orders of magnitude smaller than those considered for star-shaped PEG molecules (i.e. 10 000 g/mol vs. 200 000 g/mol, respectively). Additionally, the star-shaped PEG molecules which have been considered in the literature had up to ~70 arms and were therefore modeled by hard-sphere like structures and low chain densities near the surface due to steric hindrance. This resulted in some difficulties to achieve grafted PEG chain overlap for star molecules. Here, triethoxysilane end-functionalized linear PEG molecules have been synthesized and utilized to form star-shaped PEG derivatives based on ethoxy hydrolysis and condensation reactions. This resulted in PEG stars with up to ~4 arms, which were found to result in grafted star-shaped PEG chains with significant chain overlap. Linear PEG derivatives were synthesized so that their molecular weight would match the overall molecular weight of the star-shaped PEG molecules. These 2 PEG molecular architectures were covalently self-assembled to hydroxylated silicon wafers and the thickness, grafting density, and conformation of these films were studied. The adsorption of human albumin (serum protein) on linear and star-shaped PEG films was compared to that obtained on control samples, i.e. uncoated silicon wafers. Both film architectures were found to significantly lower albumin adsorption. / Ph. D.