Oxidation Control of Bottlebrush Molecular Conformation for Producing Libraries of Photonic Structures

Abstract

Self‐assembly is important for creating photonic structures and structural color is typically tunable by varying the size of building blocks, which are themselves obtained after time‐consuming chemical syntheses. The molecular conformation of bottlebrush block copolymers (BBCPs) in solution can be manipulated to create libraries of photonic structures. Amphiphilic BBCPs bearing oxidation‐responsive ferrocene groups on the hydrophilic block are used to fabricate porous particles via evaporation‐induced self‐assembly of water‐in‐oil‐in‐water (W/O/W) double emulsions stabilized by the BBCP surfactant. In situ oxidation of the ferrocene groups by hydrogen peroxide at the W/O interface leads to enhanced hydrophilicity, more hydration, and chain extension of the hydrophilic block. Consequently, larger internal water droplets are spontaneously formed, yielding larger pores within the microparticles. The pore diameter is readily tunable from 144 to 301 nm with a single BBCP, thereby generating full‐spectrum structural colors. This work provides a straightforward method for fabrication of libraries of photonic pigments in an easy and scalable manner.

Self-assembly of colloidal particles into amorphous photonic crystals

“…6c and d). 123,[136][137][138] Using amphiphilic bottlebrush block copolymers (BBCPs) as surfactants, the controlled swelling of the reverse BBCPs micelles was induced by the confinement of toluene-water microdroplets to make the self-assembled droplets comparable in size to the visible light wavelength. With the evaporation of toluene, shortrange ordered porous structures with self-assembled water droplets as templates were formed.…”

Monodispersed polymer particles with tunable surface structures: Droplet microfluidic‐assisted fabrication and biomedical applications

“…Moreover, the structural color of particles could be tuned by varying the molecular weights and amphiphilicity of PNPS-b-PNPEO. 26,49 Similarly, the hydration of PEO also responded to salt ions. For example, they prepared PDMS-b-PEO BBCP microparticles, in which PDMS is cross-linked as a soft elastic skeleton.…”

Recent Advances in Block Copolymer Self‐Assembly for the Fabrication of Photonic Films and Pigments

“…Finally, oxidation can also be used to tune the structural color of porous BBCP particles. [170] In this case, a BBCP with an oxidation-responsive ferrocene group incorporated within an I-PEO layer was used to prepare inverse photonic glass pigments. When oxidized by hydrogen peroxide (H 2 O 2 ), the ferrocene cation enhanced the hydration of the hydrophilic I-PEO, causing the block to grow in size and occupy more space at the interface of the internal water droplet.…”