Structure transition of polymermediated colloidal crystals Chunrui Han

Structure transition of polymer-mediated colloidal crystals Chunrui Han et al. Supervisor: Luwei Zhou Department of Physics, Fudan University, Shanghai 200433, China The self-assembled colloidal crystals with tunable structures are realized experimentally on substrates with polymer brushes. Such polymer-mediated colloidal crystals were found to experience a series of in-layer structure transitions including stable columnar, polycrystalline, mixed square-hexagonal, square (body-centered tetragonal), hexagonal structures when the mass ratio of colloidal particles to free polymers is adjusted from 0. 125 to 10. Among these structures, a large area interfacial square structure which corresponds to the body-centered tetragonal (BCT) structure in three dimensions is first observed in the polymer-mediated colloidal crystals. Phase diagram of PCB colloidal crystal Morphology of Polymer brush Conclusions: 1. By using free polymers and polymer brushes, we have experimentally demonstrated a method for fabricating a class of colloidal crystals with stable tunable crystalline structures 2. Such polymer-mediated colloidal crystals were found to experience a series of in-layer structure transitions including a stable square structure when we adjusted the mass ratio of colloidal particles to free polymers 3. Reflectance spectrum of square and hexagon structure We have proved that the square structure is BCT structure in 3 -dimensions both in theory and experiment. Band structure of BCT and FCC lattice