Single Molecule Studies of Dynamics at Polymeric Film Interfaces
Tauzin, Lawrence J
Landes, Christy F
Doctor of Philosophy
Filtration and separations play large roles in many industries yet no complete mechanistic interpretation of these phenomena exists. The development of experimental methods capable of characterizing dynamics at the single molecule level has opened the door to reexamining these heavily studied processes. By overcoming ensemble averaging mechanistic understandings that account for heterogeneities in these systems can be formulated. In this work, single molecule spectroscopic methods along with advanced particle tracking and localization algorithms are used to directly observe the interaction of single molecule probes with polymer films. The electrostatic contribution to interfacial interactions was evaluated by using the post-assembly tunability of polyelectrolyte multilayers and probes of varying charge. Multimodal transport mechanisms of protein interactions with functionalized nylon membranes were also discovered. Finally, the groundwork for a kinetic model of protein adsorption to a thin film was developed. A major conclusion was that even in ion-exchange systems in which electrostatic interactions are considered the most important variable, complex interactions between the adsorbents and the substrate are not insignificant in polymer membrane based systems. Additionally, interfacial transport in nearly all systems is characterized, not by 2 dimensional surface diffusion or activated hop diffusion, but by desorption mediated diffusion involving repeat adsorption events punctuated by periods of immobilization, the extent of which can be controlled using solution conditions.