Synthesis and Characterization of Novel Diphosphonium Polymers with the Emphasis on Supramolecular Assembly

Three different series of diphosphonium polymers were synthesized in order to analyze the supramolecular assembly of these polyelectrolytes with varying polyanions. Variation of the rigidity of the spacer between the phosphonium units determined that flexibility leads to increased absorption and consistency to film growth when observed through layer-by-layer assembly with UV-vis spectroscopy and atomic force microscopy. With the flexible ethylene spacer, films formed linearly up to 800 bilayers thick. An additional series of xylene based flexible diphosphonium polymers were synthesized with increasing numbers of methylene unit spacers. Analysis of materials was conducted through thermogravimetric analysis, X-ray crystallography, and layer-by-layer analysis tracked with UV-vis spectroscopy and atomic force microscopy. Consistency of film formation was dependent on even or odd number of the methylene spacer. Odd numbered methylene spacers lead to more consistent film growth with greater polythiophene deposition. Another series of polyelectrolytes were generated with the same methylene spacers, but with octyloxy units branching from the backbone to explore the influence of increased hydrophobicity on the previous study. Similar characterization was done with the addition of dip-cast films analyzed for critical surface energy and antimicrobial activity. The thermal stability of the octyloxy series was lower than their xylene counterparts and also demonstrated less dependence on the inter-ion spacing in the film growth formation. Extensive studies on the solvent systems for casting both the layer-by-layer films as well as the dip-cast films elucidated the high dependence and tune ability of these films by solvent systems. The presence of the hydrophobic side chain lead to an increased antibacterial activity especially when interacting with the gram-positive Staphylococcus aureus