Probing the binding properties of polyelectrolytes as supramolecular hosts
The use of polyelectrolytes in the field of supramolecular chemistry has flourished in recent years. Specifically, commercially available PAMAM dendrimers have attracted attention due to their large globular structures and high loading capacities. In this dissertation, we focus on using optical spectroscopy to study the intermolecular interactions responsible when these charged polyelectrolytes, mainly PAMAM dendrimers, act as encapsulating agents for guest molecules in aqueous solutions. We found electrostatics, hydrogen bonding, and interactions mediated by aromatic moieties in the guest molecules to be the main drivers to complex formation in these systems. Chapter 2 and Chapter 3 details original research directed toward gaining insight about the intermolecular interactions and properties of these systems. Upon the discovery that aromatic moieties in guest molecules play a role in increased binding affinity to the dendritic scaffold, we conducted experiments, presented in Chapter 4, examining the ability of these polyelectrolytes to act as solubilizing agents for hydrophobic molecules. Through extensive dissolution studies using aromatic hydrocarbon probes we propose that cationic polyelectrolytes increase solubilization of the aromatic hydrocarbons by interactions with the ammonium cations located on their surface. These studies afforded a more complete understanding of the fundamental intermolecular interactions involved when cationic polyelectrolytes function as supramolecular hosts, a role they commonly assume in many of their applications e.g. as drug delivery vectors. Macrocycles have also attracted attention due to their symmetrical architecture and high count of functional sites. Chapter 5 introduces the preliminary studies on the preparation of amine macrocycles that are important for studying dicarboxylate recognition in aqueous solvent using optical techniques. These studies provide the synthesis of a series of the desired amine macrocycles and their stoichiometry upon binding copper(II).