Probing Nanoscale Environments in Polymeric Films One Molecule at a Time
Daniel A. Higgins, Kansas State University
Inorganic and composite organic/inorganic polymer films are now being employed in chemical separations, sensing, and catalysis applications. In order to optimize the performance of these materials, it is necessary to fully understand the relevant chemical and physical processes that occur within the films and on their surfaces. Historically, researchers have relied upon average materials data obtained by bulk spectroscopic methods to obtain such information. Unfortunately, bulk methods mask the role played by materials heterogeneity. Since many of the processes involved in separations, sensing and catalysis involve chemical or physical events occurring at the single molecule (or single site) level, a clear understanding of materials properties is best obtained one molecule at a time. The fact that many materials properties variations are nonrandom makes the argument for single molecule studies even stronger. Finally, rare sites/events also have a significant impact on materials performance, sometimes providing important functional characteristics and sometimes leading to materials failure. At present, these rare sites/events are also best probed by single molecule methods. This presentation will provide an introduction to single molecule spectroscopy and its application as a probe of individual nanoscale environments in and on polymeric thin films. Inorganic silica glass films will be discussed as will composite organic/inorganic films. Knowledge gleaned from these studies will also be described, including information on variations in the solvent properties of films, film acidity, molecular mobility and molecule-matrix interactions.