Collaborative Research: Line-Active Amphiphiles for Nanostructure Stability

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TECHNICAL SUMMARYThis research project will advance the 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 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 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; also observed was distinctive 2D self-assembly of the linactants into nm-scale clusters that were analogous to micelles. The specific objectives of this project are (1) to obtain a deeper 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 other binary monolayer mixtures, including hydrocarbon/silicone, saturated/unsaturated hydrocarbons, and cholesterol/lipid.NON-TECHNICAL SUMMARYThis project involves fundamental scientific research that will enable advances related to 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, 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 or even nanoparticles. 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, 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, RET, 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 other community members. Furthermore, the integration of basic discovery and potential technological impact in this project will provide an ideal platform from which to communicate the excitement of research to the public.