Precise Tailoring of Polyester Bottlebrush Amphiphiles toward Eco‐Friendly Photonic Pigments via Interfacial Self‐Assembly

Abstract

Biodegradable photonic microspheres with structural colors are promising substitutes to polluting microbeads and toxic dyes. Here, amphiphilic polyester‐block‐poly(ethylene glycol) bottlebrush block copolymers (BBCPs) with polylactic acid or poly(ϵ‐caprolactone) as the hydrophobic block are synthesized and used to fabricate eco‐friendly photonic pigments. Molecular parameters of BBCPs, including rigidity and symmetry, are precisely tailored by variation of side chain lengths, which enables effective manipulation of interfacial tension (γ). Organized spontaneous emulsion mechanism is enabled only when γ falls in a suitable range (10.6–14.3 mN m−1), producing ordered water‐in‐oil‐in‐water multiple emulsions and ordered porous structures. Consequently, highly saturated and tunable structural colors are observed due to coherent light scattering from the porous structures. Such photonic materials are nontoxic as confirmed by careful safety tests using aquatic model organisms.

Hierarchical Assemblies of Bottlebrush/Homopolymer Blends: Tailoring Phase Interfacial Curvature for Tunable Photonics†

“…[ 1‐3 ] In comparison with traditional pigments, structural colored materials have shown many attractive features including high saturation, high brightness, and stimuli responsive properties. [ 4‐7 ] Recently, polymeric photonic microspheres reflecting vivid structural colors have emerged as the next‐generation safe photonic pigments that may replace traditional toxic pigments or dyes in many important applications such as coatings, [ 8‐9 ] cosmetics, [ 10‐11 ] microsensors, [ 12‐13 ] anti‐counterfeiting, [ 14‐15 ] etc . Self‐assembly of block copolymers (BCPs) confined within oil‐in‐water (O/W) emulsion droplets provides a facile route to colloidal particles with diverse internal structures.…”

“…g ‐polyethylene oxide) (PS‐ b ‐PEO) BBCP. [ 11‐12,51‐56 ] Thermodynamically stable water‐in‐oil‐in‐water (W/O/W) multiple emulsion droplets were generated with the BBCP as the stabilizer. Benefiting from their rigid molecular conformation, saturated adsorption of the amphiphiles at the W/O interface enables the well‐control of spherical curvature of the internal droplets.…”

Responsive Structural Colors Derived from Geometrical Deformation of Synthetic Nanomaterials

“…In addition, biodegradable polymers can be introduced into the SCMs to obtain green photonic materials. [ 148 ] These types of SCMs are perfect substitutes for toxic dyes. Degradable inverse opals were developed by Tang et al through the ring‐opening polymerization of N ‐carboxyanhydrides (see Figure 3f).…”

Manufacturing Large-scale Materials with Structural Color

“…There has been significant interest in reproducing structural color synthetically and this has motivated scientists to use various methods to produce structurally colored films/coatings [22] and also pigments using colloidal assembly. These methods include colloidal assembly by using microfabricated templates, [14] external fields [23,24] or deposition techniques for coatings [22] and include microfluidic encapsulation and fabrication of supra-structures from polymers, [25] liquid crystals [26] and colloids. [27] Most of these demonstrations aimed for the production of the color, the colored surface or pigment particles and did not focus on the production of large-scale materials with color.…”