Collaborative Research: Line-Active Amphiphiles for Nanostructure Stability

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TECHNICAL SUMMARYThe proposed research will develop a fundamental understanding of how line-active molecules (called linactants in the proposal) 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 necessary to stabilize objects created using next-generation nanolithographic methods; furthermore, development and use of linactants will permit the creation of self-organized 2D features that are analogous to 3D micelles or microemulsions. The proposed experimental strategy will rely 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 molecules that play roles in two-dimensions (2D) that are analogous to those 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 dissimilar hydrophobic molecular moieties (either distinct tails or blocks within a single tail); each moiety is designed to interact favorably with one of the respective components of a phase-separated two-component monolayer film. Previous work by this collaborative team focused on linactants having one hydrocarbon tail or block and one fluorinated tail or block. These compounds successfully reduced the line tension between hydrocarbon- and fluorocarbon-rich monolayer phases; distinctive 2D self-assembly of the linactants into nanometer-scale clusters analogous to micelles was also observed. The specific objectives of this project are (1) to obtain a clearer understanding of the molecular mechanisms leading to linactant behavior in fluorocarbon/hydrocarbon mixed monolayer systems, and (2) to generalize the linactant phenomenon beyond fluorocarbon/hydrocarbon systems by designing and synthesizing linactants for use in alternative binary monolayer mixtures, including hydrocarbon/silicone, saturated/unsaturated hydrocarbons, and cholesterol/lipid.NON-TECHNICAL SUMMARYThe fundamental scientific research outlined in this proposal will lead to advances in the technologically important and emerging field of nanotechnology. 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 that can instigate the degradation of nanoscale patterns and structural features. For this reason, the fabrication of functional nanoscale structures requires the addition of molecular stabilizers -- molecules that partition at surfaces and reduce the surface tension between edges and domain boundaries. The science behind such stabilizers is reasonably well understood for traditional three-dimensional materials, such as micelles, emulsions, and even nanoparticles. However, no such science exists for molecules that are needed 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, cataysis, biosensors, and biomaterials. This collaborative research project, which encompasses two distinct disciplines at two separate universities, will seek to broaden the participation of both women and minorities in science and education. All participants will be encouraged to join their local professional societies and to attend local and national meetings to advance our dissemination efforts. Also, through their participation in a variety of educational and outreach programs (e.g., REUs, RETs, NUE, GAANN, CU-Discovery Learning Center, Materials Science from CU K-12 outreach, Colorado High School Honors Institute, Houston Louis Stokes Alliance for Minority Participation, UH Latino Outreach, and Welch Summer Scholars), the researchers will continue to share this project with students, teachers, and members of the community at large. Furthermore, the proposed effort to link fundamental scientific discovery with technological and societal impact offers an ideal platform from which to communicate the benefits of research to the public.