Phase Transitions in Colloidal Suspensions of Disks

Texas A&M Engineering Experiment Station, College Station TX

Investigators

Abstract

Non-Technical Abstract: Despite their natural abundance and wide industrial applications, such as red blood cells and clay, disks are least studied compared to spheres and rods. This condensed matter physics project will establish the long waited model micro-disks using unique methodology, shape transformation of liquid crystal emulsions and exfoliation of layered inorganic crystals. Micro-disks will be mass-produced with unprecedented uniformity in size and shape, and unprecedented flexibility in the control of size, shape, size-polydispersity and aspect ratio. Underlining the unique flow characteristics and applications of disk materials, the discotic liquid crystal phase transitions will be investigated experimentally and theoretically regarding their dependence on inter-disk interactions, disk aspect ratio and polydispersity. The achievement of controlled organization of discotic molecules and colloids will impact industries such as pharmaceuticals, medicine, oil refining, chemical process, solar energy, nano-composite engineering and photonics. Colloidal discotics will help to unleash the educational power of complex fluids as models of atomic discotic liquid crystals and tangible elements of the macroscopic world. This project will use visualization and multimedia tools to train graduates, to build educational modules for undergraduates, and to attract k-12 students into scientific research. It will also establish collaborations around the world to enhance the global impact of its research and education program. Technical Abstract: This condensed matter physics project will use unique methodology (shape transformation of liquid crystal emulsions and exfoliation of layered inorganic crystals) to mass-produce micro-disks with unprecedented uniformity in size and shape, and unprecedented flexibility in the control of size, shape, size-polydispersity and aspect ratio. The discotic liquid crystal phase transitions isotropic or liquid-like to orientationally order or nematic (I-N), nematic to crystal (N-C), and nematic to ordered layer-like or smectic (N-S) will be investigated experimentally. The nematic-to-smectic (N-S) transition is one of the main unsolved problems in statistical physics. Theory will be constructed and experimentally tested regarding the dependence of phase transitions on inter-disk interactions (screened electrostatic repulsion, depletion attraction), aspect ratio and polydispersity. The achievement of controlled organization of discotic molecules and colloids will impact industries such as pharmaceuticals, medicine, oil refining, chemical process, solar energy, nano-composite engineering and photonics. Colloidal discotics will help to unleash the educational power of complex fluids as models of atomic discotic liquid crystals and tangible elements of the macroscopic world. This project will use visualization and multimedia tools to train graduates, to build educational modules for undergraduates, and to attract K-12 students into scientific research. It will also establish collaborations around the world to enhance the global impact of its research and education program.