Preparation of Asymmetric Porous Janus Particles Using Microfluidics and Directional UV Curing

Abstract

Asymmetric porous Janus particles of poly(tripropylene glycol diacrylate) poly(TPGDA)) are prepared from TPGDA/4‐cyano‐4′‐pentylbiphenyl (5CB) mixtures using microfluidics and directional ultraviolet (UV) curing. Droplets of the TPGDA/5CB mixtures, which have been prepared successfully in the microfluidics channel, are photo‐polymerized in the off‐chip reservoir with a focused UV beam irradiated from beneath the reservoir. The isotropic TPGDA/5CB single phase is phase‐separated into two phases during the photopolymerization of TPGDA. The relative rate of photopolymerization compared with phase separation is different according to which hemisphere of the droplet is exposed to the UV beam. Rapid polymerization on the UV‐exposed hemisphere of the droplet produces small 5CB‐rich phase‐separated domains leading to a close and smooth structure, whereas slow polymerization on the opposite hemisphere produces large 5CB‐rich domains that induce an open and rough porous structure. These asymmetric porous Janus particles of poly(TPGDA) cause asymmetric swelling, in which the UV‐exposed hemisphere swell more than the other in the solvents due to the large porous surface area made by the small‐phase‐separated domain, which prevents the formation of a compact cross‐linked network structure. The complete dried droplet after the extraction of 5CB has an acorn‐like appearance, in which the swelled UV‐exposed hemisphere shrinks more than the other leading to a wrinkled structure. This new method combining microfluidics and directional UV curing provides a simple and unique way of fabricating asymmetric porous Janus particles and their functionalization with metal nanoparticles.

Nonspherical Nanoparticles with Controlled Morphologies via Seeded Surface-Initiated Single Electron Transfer Radical Polymerization in Soap-Free Emulsion

“…Nonspherical colloidal particles with asymmetric structures and different chemical functionalities have been widely researched because of their development prospects as functional surfactants, , compatibilizers, coatings, and catalysts . To date, various methods for the syntheses of asymmetric particles have been proposed, including microfluidic technique, toposelective modification, Pickering emulsion polymerization, seeded emulsion polymerization, self-assembly, controlled phase separation, , and surface nucleation . Among these, seeded emulsion polymerization has been proved to be efficient and flexible to prepare snowman-like, raspberry-like, and other nonspherical composite particles …”

Structures and alignment of anisotropic liquid crystal particles in a liquid crystal cell

“…We recently reported the preparation of functionalized LC droplets, in which steadystate droplet break-off in the microuidics channel was used to create monodisperse 5-cyanobiphenyl (5CB, a nematic LC at room temperature) droplets in water. [10][11][12][13] A droplet was formed at the channel junction. Its size was controlled by the competition between viscous drag and surface tension.…”

Microfluidic Methods in Janus Particle Synthesis

“…It was observed that the droplet hemisphere directly facing UV radiation swelled (and wrinkled when dried), while the other hemisphere remained smooth making the particle asymmetrically porous. 62 Li et al altered the contents of the dispersed phase from an organochloride compound (dichloromethane) to an organic compound (dimethyl carbonate) for phase separation-based Janus particle synthesis. They concluded that by changing the nature of the dispersed phase from an organochloride to an organic fluid, a morphology transition from core-shell microcapsule to Janus could be achieved.…”