Highly monodisperse zwitterion functionalized non-spherical polymer particles with tunable iridescence.

A facile and simple synthetic route towards functionalized non-spherical polymer particles (NSP) with tunable morphologies and iridescence is presented. Monodisperse particles with unique zwitterionic functionality were synthesized via emulsifier-free emulsion polymerization in a single step process. The sulfobetaine comonomer was utilized to induce phase separation in the course of polymerization to achieve anisotropic NSP with controlled morphologies such as quasi-spherical with protruding structures like bulge, eye-ball, and snowman-like nanostructures. Both SEM and TEM analyses revealed anisotropic particles, and phase-separated protrusion morphology with a small increase in aspect ratio. By taking advantage of the monodisperse, colloidally stable NSPs, template free photonic crystal arrays were fabricated through a bottom-up approach. The particles readily self-assemble and exhibit a photonic bandgap with vivid structural colors that arise from ordered structures of different morphologies. Additionally, the salt-responsive photonic crystals also possess tunable color-changing characteristics.