Structural Color from Solid-State Polymerization-Induced Phase Separation

TL;DR

This paper introduces a novel solid-state polymerization method to create stable nanostructures for structural color, mimicking natural coloration processes with potential for versatile applications.

Contribution

It demonstrates a new approach to controlling phase separation at optical scales through polymerization-induced phase separation in solids.

Findings

Produced stable nanostructures with optical length scales

Achieved structural colors in various forms including filaments and sheets

Compared biomimetic structures to natural feather barbs

Abstract

Structural colors are produced by wavelength-dependent scattering of light from nanostructures. While living organisms often exploit phase separation to directly assemble structurally colored materials from macromolecules, synthetic structural colors are typically produced in a two-step process involving the sequential synthesis and assembly of building blocks. Phase separation is attractive for its simplicity, but applications are limited due to a lack of robust methods for its control. A central challenge is to arrest phase separation at the desired length scale. Here, we show that solid-state polymerization-induced phase separation can produce stable structures at optical length scales. In this process, a polymeric solid is swollen and softened with a second monomer. During its polymerization, the two polymers become immiscible and phase separate. As free monomer is depleted, the host matrix resolidifies and arrests coarsening. The resulting PS-PMMA composites have a blue or white appearance. We compare these biomimetic nanostructures to those in structurally-colored feather barbs, and demonstrate the flexibility of this approach by producing structural color in filaments and large sheets.