Temperature-sensitive assembly of two-dimensional ionic crystals using polymer-grafted colloids*

Assembling two- and three-dimensional colloidal crystals of user-specified symmetries is of great scientific interest due to their broad technological and fundamental relevance. Among various pathways, Coulombic interactions are widely employed for assembling crystals of a range of symmetries. Despite notable progress, the experimental characterization of temperature-sensitive two-dimensional ionic crystals is underexplored. In this talk, I will describe a range of experiments designed to study the self-assembly of two-dimensional crystals composed of differently charged particles grafted with a neutral polymer. By varying two parameters—the particle size and the concentration ratio—we successfully construct a phase diagram containing distinct phases characterized by hexagonal and square symmetries. Furthermore, we investigate the crystallization dynamics of these different ionic crystals at the single-particle level, shedding new light on the coarsening and coexistence of square and hexagonal domains, the mobility of defects within attractive colloidal crystals, and the nature of crystal melting. These findings show how temperature-tunable Coulombic interactions can be used as a new route to investigating various physical phenomena in crystallization in time and space.