xli426 at uchicago.edu
- Liquid crystals (LCs) share the hierarchical structure of crystalline materials and the plasticity of liquids. These properties cause them to be very sensitive to external stimuli, which in turn makes LCs uniquely suited to applications such as low-concentration detection. The high sensitivity stems from the fact that in the presence of different chemical surfaces, LC molecules have different anchoring states such as planar or homeotropic. The boundaries between regions of different anchoring states are regions of high defectivity, a phenomenon which is poorly understood. Dr. Li is designing experimental techniques using patterned polymer surfaces to study the formation of these nanoscopic cores of topological defects, which can be precisely engineered by confining LC on micrometer and nanometer scales.
- In order to enable future technological devices such as semiconductor integrated circuits (ICs), patterned media, and capacitors, lithographic materials and techniques must be extended to the sub-10nm length scale. Block copolymers with high χ values allow for obtaining reduced feature sizes when the molecular weight is small; an example of one such high-χ material is PS-b-PLA. At the same time, PS and PLA blocks have similar surface energies which means that when a thin film of this material is annealed, neither block segregates to the free surface; instead a neutrality condition condition exists at the air/ film interface. Dr. Li is working to exploit these two properties of PS-b-PLA to form perpendicular lamellae structures of very small feature size through directed self-assembly.
Xiao Li received her BS degree in Polymer Materials and Engineering from the Wuhan University of Science and Technology, China. She received her PhD degree from Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, China, working on microphase separation of block copolymers for the preparation of antireflective films.