Switchable Full-Color Reflective Photonic Ellipsoidal Particles.

Full-color reflective photonic ellipsoidal polymer particles, capable of a dynamic color change, are created from dendronized brush block copolymers (den-BBCPs) self-assembled by solvent-evaporation from an emulsion. Surfactants composed of dendritic monomer units allow for the precise modulation of the interfacial properties of den-BBCP particles to transition in shape from spheres to striped ellipsoids. Strong steric repulsions between wedge-type monomers promote rapid self-assembly of polymers into large domains (i.e., 153 nm ≤ D ≤ 298 nm). Of note, highly ordered axially stacked lamellae (i.e., number of layers >100) within an ellipsoid give rise to a near-perfect photonic multilayer. The reflecting color is readily tunable across the entire visible spectrum by alteration of the molecular weight from 477 to 1144 kDa. Finally, the photonic ellipsoids are functionalized with magnetic nanoparticles organized into bands on the particle surface to produce real-time on/off coloration by magnetic field-assisted activation. In total, the reported photonic ellipsoidal particles represent a new class of switchable photonic materials.