Surface adsorption will be used to create bent-core layers on water via Langmuir techniques, as well as in free-standing films under water, with orientational order over centimeter ranges. These nanometer-thick ordered layers will be studied in situ, transferred to solid substrates (Langmuir/Blodgett and Langmuir/Schaeffer layers), and then used to align bulk bent-core mesophases. These systems will be analyzed with a multiscale approach, in which macroscopic and mesoscopic experiments are correlated with realistic molecular and mesoscopic simulations, where no one approach can cover the whole range of length scales. BLM-like films formed underwater will be stabilized by polymerization and tested as sensors for biological systems. The project will aim to understand the physics underlying these processes, and their sensitivity to small molecular changes and/or external stimuli. The knowledge gained will be used to optimize the self-organization of these molecules for diverse applications. The broader impacts of this project will include the enhanced ability to control surface properties which may lead to improved devices such as sensors, the training of students in a unique multidisciplinary environment, and the development of interdisciplinary teaching materials. NONTECHNICAL SUMMARY Throughout both nature and technology, the sensitivity of materials to external stimuli plays critical roles. For example, biological systems make extensive use of this sensitivity in endo- and exocytosis, the processes by which cells take in or expel materials. This sensitivity also lies behind the success of liquid crystals in electro-optical devices and other applications. This transformative project will use a combined experimental/computational approach to investigate how the properties of bent-core, banana-shaped molecules, are changed by interaction with a surface, and how these changes can be exploited to produce ordered bent-core liquid crystal materials for device applications, such as biosensors and smart biomaterials. More complex, but synthetically controllable molecular structures allow a much broader range of surface properties. Collaborations with international leaders in bent-core synthesis, to implement necessary modifications of the molecular structure of these complex molecules, plays an essential role in this project. Students ranging from high school to graduate level will receive interdisciplinary education in physics, chemistry, and engineering and be exposed to industrial contacts through the unique environment of the Liquid Crystal Institute at Kent State University.
Liquid crystal materials are widely used in many industries, with the most obvious example being display systems for televisions and computers. For liquid crystal materials to be useful, they must be aligned. Our project uses a combined experimental/simulation approach to develop a method to align a certain class of liquid crystal molecules -- "bent-core" liquid crystal molecules. The method involves depositing amphililic bent-core liquid crystals on water, where they will self-assemble into a monolayer. The structure and orientation of the monolayer can be controlled by adjusting the pressure. The monolayer is is transferred to a solid surface, where it then serves as an alignment layer for a bulk liquid crystal phase deposited above it -- ie, the alignment of the bulk liquid crystal phase is determined by this monolayer. Together with these experiments, we carry out molecular level simulations of the self-assembly of the monolayer, and of the development of an aligned liquid crystal phase above the monolayer. In the simulations, the system is modeled at the atomic level, and the dynamic trajectory of the molecules is followed. Our simulation results for the monolayer orientation as a function of pressure are in excellent agreement with experimental results. The experiments and simulations together allow an understanding of precisely how the alignment processes work.
