Polymeric, Wurster-Type Hosts For The Encapsulation Of Metal Cations And Molecular Guests




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Wurster crowns are a class of macrocyclic receptors based on N, N, N’, N’-tetramethyl-para-phenylenediamine (p-TMPD), commonly known as Wurster’s reagent. They are redox responsive hosts for a variety of guests spanning cationic, anionic, and neutral molecules. The goal of this work is to extend the well-studied Wurster’s reagent and its inspired molecular Wurster crown constructs, with their associated electrochemical and metal binding properties, into polymeric materials for eventual use in sensing and redox-switchable devices. Three projects involving the synthesis and electrochemical properties of new classes of polymers, linked by their polymer architectures and the incorporation of Wurster subunits, are described in this dissertation. The first involves the successful synthesis of polymers based on polystyrene with attached Wurster crown and Wurster’s reagent pendants. The electrochemical properties of these polymers were explored as well as the ability of the Wurster crown appended polystyrene to selectively coordinate with and sense alkali metal cations. While the synthesized polymers display reversible one electron oxidations, like Wurster’s reagent, the anticipated second reversible oxidation was less clear in its reversibility. Nevertheless, the polystyrene with pendant Wurster crowns maintains the ability to selectively bind and sense the presence of lithium and sodium alkali metal cations consistent with the free, monomeric Wurster crown ligand. The second project describes the synthesis of a triarylamine/divinylbenzene co-block polymer post-modified with 1,4,7,10-tetraoxa-13-azacyclopentadecane (aza 15-crown-5) to place a diarylated Wurster crown derivative in the backbone of the polymer. The resulting polymer compound’s electrochemical properties were studied using cyclic voltammetry. The polymer exhibits two reversible oxidations in accordance with its free, monomeric parent Wurster crown, though at higher potentials. Cation selectivity studies with a series of alkali metals were also performed revealing the polymer to have plateau selectivity for lithium and sodium cations, also in agreement with the free Wurster crown and the previously described Wurster crown appended polystyrene. The final project describes the development of a first generation dendritic compound composed of a pentamer of Wurster-type redox centers. The synthetic methodology is expandable to produce higher dendrimer generations with exponential increases in size. The electrochemical properties of the dendrimer were explored and compared to its monomeric analog, Wurster’s reagent. The dendritic structure maintains one reversible oxidation indicative of each of the five redox centers behaving independently. However, the second oxidation does not exhibit a discrete redox couple, indicating cooperative effects among the redox centers as charge density accumulates.



Polymers, Polymerization, Oxidation-reduction reaction