The Performance of Customized Molecular Coatings

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CTS-9615868 Quinn, J./Vanderlick, T.R. U of Penn Project Summary By exploiting the desire of certain organic molecules to spontaneously organize, it is possible to design and fabricate customized molecular coatings with unique architectures. One such coating process is the Langmuir-Blodgett (LB) deposition technique, a mechanical method used to build multi-layered molecular films. Another process is "self-assembled monolayer (SAM) formation," a chemical method based on chemisorption from solution. Over the last decade, substantial effort has been directed at expanding the sets of film forming molecule and characterizing the structure of the resultant coatings. On the other hand, little effort has been spent on evaluating the performance of these customized molecular coatings in different applications, or their response to changes in their surroundings. Measuring and understanding the ways in which these organic coatings interact with their environment is the central focus of this proposal. Experiments are designed to examine how coatings behave to the presence of different gases, liquids, and solids with which they come into contact. This work is divided into two branches. The first centers on the absorption characteristics of coatings with non-negligible volume (as formed from the LB method), establishing their performance as "molecular sponges" Here, cues will be taken from biological membranes to design films with different transport properties. Also, a novel method (using track-etched mica) will be developed to measure transport along/within the strata which comprise the LB films. The other branch of this proposal deals with the performance of nonmolecular films. Coatings of different molecular design will be fabricated using self-assembled monolayers derived from two different breeds-the well-known alkane-thiol based systems and a new class of film forming molecules based on aromatic thiols. The adhesion of SAMs to various surfaces(including other SAMs) will be investigated, thus evaluating the performance and reponsiveness of these coatings "molecular glue." The adsorption characteristics of different coatings will also be investigated, establishing their performance as "molecular tack-paper." A key objective of this work is compare the behavior of these different monolayer forming systems. The studies proposed herein will take advantage of two powerful tools: the surface forces apparatus to measure the forces of interaction between surfaces, and the quartz crystal microbalance to measure mass pickup. Although many groups are currently investigating self-assembled monolayers, the uniqueness of this approach rests both on techniques employed( in particular the SFA) and on systems proposed for study(including the new Class of SAMs)