Thrust 1 is motivated by two Research Questions:
1. How do electrostatics, hydrogen bonding, surface chemistry, and microstructure influence interfacial affinity and the organization of the solution’s boundary layers?
The interaction between an aqueous adsorbate and a binding site is dictated not just by the strength of a single, isolated bond, but also by numerous steric interactions, the electrical properties of the surface and solution, and the organization of water’s hydrogen-bond network at the interface and around the host-adsorbate complex. These properties also govern the organization and dynamics of solutes and ions in the interfacial boundary layers of the solution. In order to selectively control water/solid interfaces, we must understand how these effects collectively influence adsorption.
2. What principles govern selective, rapid, and reversible adsorption of ions and molecules on complex polymer structures in aqueous solutions?
Nature’s enzymes, receptors, and ion channels have evolved extraordinary capabilities to bind a specific target with incredible selectivity and high affinity, while maintaining reversibility and rapid turnover. For instance, ion channels typically contain a selectivity filter specific to a certain ion. In the case of the KcsA potassium ion channel, a four-site selectivity filter formed by protein backbone amide carbonyls passes K+ at rates >108 ions s-1 while retaining a 1000:1 discrimination over Na+. We know that such systems have optimally sized and flexible/dynamic binding sites, tailored electrostatic and hydrogen bonding interactions, and unusually small desolvation penalties, but we do not have the predictive understanding of how these principles work in concert to achieve remarkable selectivity. To develop versatile adsorption and sensing technologies, we must describe these cooperative effects systematically in the context of high surface-to-volume polymeric materials functionalized with novel binding moieties.