Responsive Block Copolymer Photonic Microspheres

Abstract

Responsive photonic crystals (PCs) have attracted much attention due to their broad applications in the field of chemical and physical sensing through varying optical properties when exposed to external stimuli. In particular, assembly of block copolymers (BCPs) has proven to be a robust platform for constructing PCs in the form of films or bulk. Here, the generation of BCPs photonic microspheres is presented with 3D periodical concentric lamellar structures through confined self-assembly. The structural color of the spherical PCs can be tuned by selective swelling of one block, yielding large change of optical property through varying both layer thickness and refraction index of the domains. The as-formed spherical PCs demonstrate large reflection wavelength shift (≈400-700 nm) under organic solvent permeation and pH adjustment. Spherical shape and structural symmetry endow the formed spherical PCs with rotation independence and monochrome, which is potentially useful in the fields of displays, sensing, and diagnostics.

Self‐Assembly of Multiblock Copolymers

“…The main factors influencing particle shape and inner structure are again the degree of confinement and surfactant properties, but also BCP composition, temperature, solvent evaporation rate, pH, polymer molecular weight, additives and so on . The shape and inner structure of the microparticles have been of particular interest as they play an important role in photonics and hybrid nanocomposites …”

“…[68] The main factors influencing particle shape and inner structure are again the degree of confinement and surfactant properties, but also BCP composition, temperature, solvent evaporation rate, pH, polymer molecular weight, additives and so on. [69,70] The shape and inner structure of the microparticles have been of particular interest as they play an important role in photonics [71] and hybrid nanocomposites. [72,73] Evaporation-induced confinement assembly (EICA) is an effective and simple method to fabricate microparticles with controlled size, shape, and highly ordered morphology (Figure 5).…”

“…With continuous droplet shrinking, BCP microphase separation propagates from the droplet surface to the droplet center yielding well‐ordered microparticles after complete drying. Traditional emulsification methods such as homogenizer, vortex, and membrane‐extrusion produce microparticles with a rather broad size distribution, while new methods such as microfluidics, and the Shirasu porous glass (SPG) membrane emulsification technique can generate quite monodisperse particles.…”

Supramolecular Modification of ABC Triblock Terpolymers in Confinement Assembly

“…While few examples exist for experimental phase diagrams in bulk [40,45,46,47], as well as examples that utilize supramolecular complexation with HB donors [48,49,50,51,52,53], the confinement assembly of ABC triblock terpolymers to multicompartment microparticles is still largely unexplored [54,55,56]. Yet, combining the 3D confinement assembly of the ABC triblock copolymers with supramolecular modification with the HB or XB donors should be very interesting and could lead to a range of functional microparticles [57,58,59].…”

Hierarchical Photonic Pigments via the Confined Self-Assembly of Bottlebrush Block Copolymers

“…Block copolymers provide a promising alternative for bottom-up fabrication of photonic structures. [18][19][20][21][22] In particular, bottlebrush block copolymers (BBCPs), where a highly extended backbone is densely grafted with polymer branches, are well-suited for photonic pigments as they can form lamellar structures with domain spacings large enough to produce a strong reflection in the visible spectrum. [23][24][25][26][27][28][29] However, to date, the photonic properties of BBCPs have mainly been investigated in the film geometry.…”