Collaborative Research: Line-Active Amphiphiles for Nanostructure Stability

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This project aims to advance a fundamental understanding of how line-active molecules (which we call linactants) can be used to modify the line tension of nano- and meso-scale features within molecular monolayers. The ability to control line tension will be critical to the stabilization of objects created using next generation nanolithographic methods; in addition, linactants will permit the creation of self-organized 2D features that are analogous to 3D micelles or microemulsions. The strategy will be based on molecular aggregation within two- and three-component monomolecular films prepared by Langmuir-Blodgett (LB) deposition and related self-assembly methods. Key components include the rational design and synthesis of line-active molecular species that play a two-dimensional (2D) role analogous to that of amphiphilic surfactant molecules in three-dimensional (3D) micelles, bilayers, and microemulsions. In the same manner in which a 3D surfactant possesses hydrophobic and hydrophilic regions, these linactant molecules will possess two molecular "tails"; each tail will interact favorably with one of the other chemically dissimilar monolayer components. One approach will involve two-tailed 2D linactants having one hydrocarbon and one chemically and/or structurally dissimilar tail (e.g., partially fluorinated). Specific experiments include the systematic characterization of line activity (line tension isotherms), kinetic stabilization of 2D emulsions, as well as the exploration of two- and three-component monolayer phase diagrams. This collaborative research project, which encompasses two distinct disciplines at two separate universities, seeks to broaden the participation of both women and minorities in science and education. Proposed co-workers include three women (one undergraduate and two graduate students) and two minorities (one undergraduate and one graduate student). All participants will be encouraged to join their local professional societies and to attend local and national meetings to advance our dissemination efforts. As devices and materials are made smaller and smaller, the influence of surfaces and interfaces becomes increasingly important. In particular, the influence of surface tension leads to instabilities, such as coagulation or the degradation of nanoscale patterns. For this reason, the fabrication of nanoscale structures requires the addition of molecular stabilizers -- molecules that partition at surfaces and reduce the surface tension. The science behind such stabilizers is reasonably well understood for traditional three-dimensional materials, such as colloids and emulsions. However, no such science exists for molecules that are necessary to stabilize two-dimensional nanostructures (i.e., nanoscale patterns fabricated on surfaces). The stability of such surface nanopatterns is required for future applications in molecular electronics and biosensor technologies. This project will pursue a rational approach to develop this science of surface nanostructure stabilization. This collaborative research project, which encompasses two distinct disciplines at two separate universities, seeks to broaden the participation of both women and minorities in science and education.