We introduce a method for the formation of block copolymer micelles through interfacial instabilities of emulsion droplets. Amphiphilic polystyrene-block-poly(ethylene oxide) (PS-PEO) copolymers are first dissolved in chloroform; this solution is then emulsified in water and chloroform is extracted by evaporation. As the droplets shrink, the organic solvent/water interface becomes unstable, spontaneously generating a new interface and leading to dispersion of the copolymer as micellar aggregates in the aqueous phase. Depending on the composition of the copolymer, spherical or cylindrical micelles are formed, and the method is shown to be general to polymers with several different hydrophobic blocks: poly(1,4-butadiene), poly(-caprolactone), and poly(methyl methacrylate). Using this method, hydrophobic species dissolved or suspended in the organic phase along with the amphiphilic copolymer can be incorporated into the resulting micelles. For example, addition of PS homopolymer, or a PS-PEO copolymer of different composition and molecular weight, allows the diameter and morphology of wormlike micelles to be tuned, while addition of hydrophobically coated iron oxide nanoparticles enables the preparation of magnetically loaded spherical and wormlike micelles.

A reversible transformation of overall shape and internal structure as well as surface composition of nanostructured block copolymer particles is demonstrated by solvent-adsorption annealing. Polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) pupa-like particles with PS and P4VP lamellar domains alternatively stacked can be obtained by self-assembly of the block copolymer under 3D soft confinement. Chloroform, a good solvent for both blocks, is selected to swell and anneal the pupa-like particles suspended in aqueous media. Reversible transformation between pupa-like and onion-like structures of the particles can be readily tuned by simply adjusting the particle/aqueous solution interfacial property. Interestingly, poly(vinyl alcohol) (PVA) concentration in the aqueous media plays a critical role in determining the particle morphology. High level of PVA concentration is favorable for pupa-like morphology, while extremely low concentration of PVA is favorable for the formation of onion-like particles. Moreover, the stimuli-response behavior of the particles can be highly suppressed through selective growth of Au nanoparticles within the P4VP domains. This strategy provides a new concept for the reversible transformation of nanostructured polymer particles, which will find potential applications in the field of sensing, detection, optical devices, drug delivery, and smart materials fabrication.

This color shifting of chameleon skin mainly relies on the active tuning of a nonclose-packed array of guanine nanocrystals within their iridophore cells, which can be regarded as mechanochromic PCs. [2b,3a,c] This fascinating phenomenon in nature has inspired the rapid development of mechanochromic photonic materials [3c,4] by combining PCs with elastomers [5] (i.e., photonic elastomers). For example, Inomata and co-workers [4a] reported structural colored elastomers with strainresponsive color shifting capability by fixing colloidal crystal of poly(ethyl acrylate-co-methyl methacrylate) in a poly(ethyl acrylate) elastomer. Recently, Kim and co-workers [2b] prepared iridophore photonic elastomers by embedding a well-ordered array of SiO 2 nanoparticles (NPs) in a poly(ethylene glycol)-based elastomer, which can change their structural color in the full-color range when being stretched. Such photonic elastomers show unique advantages over photonic hydrogels [6] or organogels, [7] such as improved elasticity, nonvolatility, and stability, thus facilitating their potential applications in visualized stress or strain sensors, display, and smart windows.Although these existing photonic elastomers have demonstrated the mechanochromic capability, several concerns may arise in their practical applications, [2b,4a,8] including: 1) accidentally cutting or scratching as well as aging of materials and structures over time, which deteriorates their performance particularly in optical devices; 2) angle-dependent variation in the colors of photonic elastomers because of the periodical long-range ordered structures, which brings inaccuracy in visualized sensing. An ideal photonic elastomer for visualized force and/or strain sensing should possess angle-independent structural colors as well as the mechanical durability or selfhealing capability. However, fabrication of the above-mentioned multifunctional elastomers remains challenging and is largely unexplored.Some natural organisms exhibit angle-independent structural colors because of their isotropic structures with short-range order. [3b] Angle-independent photonic materials have been reported by mimicking the natural isotropic structures. [2a,5f,9a-c] These findings suggested that incorporation of isotropic structures with short-range order into the elastomers would be a promising strategy for designing Photonic elastomers that can change colors like a chameleon have shown great promise in various applications. However, it still remains a challenge to produce artificial photonic elastomers with desired optical and mechanical properties. Here, the generation of metallosupramolecular polymer-based photonic elastomers with tunable mechanical strength, angle-independent structural color, and self-healing capability is reported. The photonic elastomers are prepared by incorporating isotropically arranged monodispersed SiO 2 nanoparticles within a supramolecular elastomeric matrix based on metal coordination interaction between amino-terminated poly(dimethylsiloxane) and...

A simple, yet robust route to prepare polymer nanoparticles with tunable internal structures through supramolecular assembly within emulsion droplets is presented. Nanoparticles with various internal morphologies, including dispersed spheres, dispersed spirals, stacked toroids, and concentric lamellae, are obtained due to the 3D confinement and variation of hydrogen-bonding agent. This method also allows us to form mesoporous particles through further disassembly of the supramoleclar assemblies by rupturing the hydrogen bonding.

Controlling the kinetics and gelation of photopolymerization is a significant challenge in the fabrication of complex three-dimensional (3D) objects as is critical in numerous imaging, lithography, and additive manufacturing techniques. We propose a novel, visible light sensitive "photoinitibitor" which simultaneously generates two distinct radicals, each with their own unique purpose-one radical each for initiation and inhibition. The Janus-faced functions of this photoinitibitor delay gelation and dramatically amplify the gelation time difference between the constructive and destructive interference regions of the exposed holographic pattern. This approach enhances the photopolymerization induced phase separation of liquid crystal/acrylate resins and the formation of fine holographic polymer dispersed liquid crystal (HPDLC) gratings. Moreover, we construct colored 3D holographic images that are visually recognizable to the naked eye under white light.