Biomimetic structural color through arrested phase separation

Structural colors are produced by light scattering from regular nanostructures. In bird feather barbs, these nanostructures appear to develop through phase separation. However, the mechanism that arrests phase separation at a precisely controlled length scale is unknown.
Recently, Style et al. (PRX 2018) showed that it is possible to obtain monodisperse micron-size droplets by inducing liquid-liquid phase separation inside networks with elastic moduli on the order of 0.1 MPa. Here, we attempt to scale this process down to the optical scale through polymerization-induced phase separation in a 0.1 GPa-scale network. As a result, we obtain stable polymer composites with modest structural correlations at optical length scales, and structural color through a combination of Rayleigh and coherent scattering.