Photonic Paints: Structural Pigments Combined with Water-Based Polymeric Film-Formers for Structurally Colored Coatings

Paints contain at least two components: a colorant and a polymeric binder, dispersed in a fluid medium. The first imparts color to the paint coating, while the second encapsulates the colorant upon drying in a robust polymeric film adherent to the surface substrate. Photonic pigments, inspired by nature's coloration strategy, hold promise as a replacement for toxic and fade-prone absorptive colorants, most prominently in the fabrication of stable and sustainable water-based paints. Crucially however, the step to combine photonic pigments with polymeric binders has not yet been taken. Here, a water-based paint is designed and realized containing both photonic pigments synthesized by a scalable emulsion process and commercial polymeric binders in an aqueous dispersion. The photonic pigments are silica spheres containing a close-packed array of air pores, of which both the periodicity and degree of long-range ordering can be controlled to produce pigments of varying colors and degrees of iridescence. The readiness of the photonic paints for application is demonstrated by applying them like traditional paints in homages of famous artistic paintings. These findings should stimulate widespread application of structural pigments as colorants in not only paints but also a variety of industrially important materials, such as plastics, inks, or cosmetics.