Structural Color Materials Using Polymer-Brush-Decorated Hybrid Particles

A structure with refractive-index periodicity of the same size as the wavelengths of visible light exhibits structural color. Here, we developed structural color materials with polymer-brush-decorated silica particles (PB-SiPs) as the primary component that formed bulk films and spherically integrated colloids (supracolloids). A bulk film of the PB-SiPs was prepared by drop-casting a particle suspension, followed by hot-pressing. The SiPs were located in a sea of the PB layer that constituted a film, maintaining a nearly constant interparticle spacing. The film exhibited a hazy unclear color; however, a bright color was developed upon the addition of only a small amount of carbon black nanoparticles grafted with the polymer brush. Moreover, the structural color tone significantly depended on the molecular weight and type of the polymer brush. In addition, structural color materials with a low dependence on the viewing angle were fabricated by mixing two types of hybrid particles with different molecular weights of the graft polymer; further, the color could be controlled by varying the particle ratio. Because of their ease of processing and color-tunability, the developed structural materials can be used in several practical applications such as cosmetics and paints.