Influence of Core Surface Properties on the Formation of Liquid Photonic Crystals Based on Core–Shell Particles

The dispersibility and dispersion stability of colloidal particles in liquids are generally described using the Derjaguin-Landau-Verwey-Overbeek theory for bare solid particles without surface coatings. However, the surface properties of submicron-sized particles with high specific surface areas should not be ignored in understanding their dispersion behavior and the formation of ordered structures in liquids, and many aspects remain unknown. PS@PDA core-shell particles, where polystyrene (PS) core particles are coated with a melanin-mimetic polydopamine (PDA) shell, exhibit vivid structural color in both liquid and solid states and are widely employed as model systems of structural coloration. In this study, we investigated the effects of subtle differences in surface properties resulting from different PS core particle synthesis methods on the formation of liquid photonic crystals (LPCs) using PS@PDA particles. Detailed analyses of particle arrangements and properties revealed that an expanded layer on the core particle surface reduced electrostatic repulsive forces between particles in liquids. Furthermore, the particles formed at low particle concentrations were utilized to fabricate an electrophoretic display (EPD) device. This study demonstrates that the structural characteristics of the core particle surface govern the formation of LPCs composed of core-shell particles, offering fundamental insight for the rational design of structural color materials.