Angular Independent Photonic Pigments via the Controlled Micellization of Amphiphilic Bottlebrush Block Copolymers

TL;DR

This paper presents a scalable method to produce angular independent photonic pigments with isotropic nanoscale structures using controlled micellization of amphiphilic bottlebrush block copolymers, enabling broad-angle viewing and tunable color.

Contribution

It introduces a novel controlled micellization self-assembly process within emulsified droplets to create isotropic, porous microparticles that serve as non-iridescent, tunable photonic pigments.

Findings

Produced structurally coloured pigments with full visible spectrum reflection.

Achieved isotropic structural coloration suppressing iridescence.

Demonstrated scalable single-step fabrication process.

Abstract

Photonic materials with angular independent structural colour are highly desirable because they offer the broad viewing angles required for application as colorants in paints, cosmetics, textiles or displays. However, they are challenging to fabricate as they require isotropic nanoscale architectures with only short-range correlation. In this article, porous microparticles with such a structure are produced in a single, scalable step from an amphiphilic bottlebrush block copolymer. This is achieved by exploiting a novel controlled micellization self-assembly mechanism within emulsified toluene-in-water droplets. By restricting water permeation through the droplet interface, the size of the pores can be precisely addressed, resulting in structurally coloured pigments. Furthermore, the reflected colour can be tuned to reflect across the full visible spectrum using only a single polymer (Mn = 290 kDa) by altering the initial emulsification conditions. Such photonic pigments have several key advantages over their crystalline analogues, as they provide isotropic structural coloration that suppresses iridescence and improves colour purity without the need for either refractive index matching or the inclusion of a broadband absorber.