Date of Award
Doctor of Philosophy (PhD)
Rhett C Smith
Andrew G Tennyson
Jason D McNeil
Daniel C Whitehead
Research on chromophores and polyelectrolytes incorporating main group elements has attracted tremendous research interest and been investigated extensively in the past few decades. In the current contribution, potential applications of polyelectrolytes in ion-conductive/exchange materials, optoelectronics and as antibacterial agents are studied systematically. Several new classes of chromophores based on heterocycle (thiophene and pyrrole) motifs have been developed in this work, with potential use in various areas including organic photovoltaics, organic light-emitting diodes, chemical/bio-sensors, bio-imaging/labeling, etc.
In Chapter 2, a series of ten polythiophene derivatives is discussed. Each polymer in the series has a different percentage of carboxylic acid-bearing repeat units. The properties of these polymers are explored under neutral and anionic forms. The properties that are examined include UV-vis absorption and photoluminescence spectroscopy of films and solutions as well as solution aggregation measured by dynamic light scattering. All of these properties are strongly dependent both on protonation state and percentage of carboxylic acid/carboxylate side chains along the polymer backbone. The anionic form of each polythiophene derivative was then employed for layer-by-layer (LbL) film deposition with a cationic phosphonium polyelectrolyte. The film growth process is studied by spectroscopic techniques and film morphologies are examined by atomic force microscopy.
In Chapters 3 and 4, two series of tetraarylphosphonium polyelectrolytes (TPELs) has been discussed. This work involved developing new polymerization protocols for using commercial diphenylphosphine and dihalides or readily-prepared bis(aryl triflate)s as monomers. The Ni- and Pd-catalyzed P–C coupling formation reactions produce degrees of polymerization up to 65. All TPELs have reasonable thermal stability in the range of 350-450 °C. The stability of the TPELs to alkaline solution is strongly depend on the spacer between adjacent phosphonium sites as well as counterions.
The work presented in Chapter 5 shows design and synthesis of two series of phosphonium polyelectrolytes (PELs) analogues. The polymerizations of diphosphines and α,α′-dibromo-p-xylene via SN2 reaction yielded phosphonium polymers with the degrees of polymerization higher than 10. The prepared polymers were employed for LbL self-assembly fabrication. The influences depending on spacer between charged sites and existence of hydrophobic side-chains have been investigated and compared systematically.
The Chapter 6 presents the work on a heavier analogue of BODIPY dye which presents strong visible light absorption and fluorescence emission. The new type of fluorescent dye has been prepared successfully with moderate yield ~ 44.2%. These new dyes exhibit strong visible light absorption and fluorescence emission (quantum yield up to 90 %). One member of this new chromophore family has been characterized by single crystal X-ray diffraction.
Wan, Wang, "Main Group Element-containing Chromophores and Polyelectrolytes: Sulfur, Phosphorus and Gallium" (2018). All Dissertations. 2407.