Photocurable pickering emulsion for colloidal particles with structural complexity.

We prepared polymeric microparticles with coordinated patches using oil-in-water emulsion droplets which were stabilized by adsorbed colloidal polystyrene (PS) latex particles. The oil phase was photocurable ethoxylated trimethylolpropane triacrylate (ETPTA), and the particle-armored oil droplets were solidified by UV irradiation within a few seconds to produce ETPTA-PS composite microparticles without disturbing the structures. Large armored emulsion drops became raspberry-like particles, while small emulsion drops with a few anchored particles were transformed into colloidal clusters with well-coordinated patches. For high-molecular-weight PS particles with low chemical affinity to the ETPTA monomer, the morphology of the patchy particle was determined by the volume of the emulsion drop and the contact angle of the emulsion interface on the PS particle surface. Meanwhile, for low-molecular-weight PS particles with high affinity, the ETPTA monomers were likely to swell the adsorbed PS particles, and distinctive morphologies were induced during the shrinkage of emulsion drops and the phase separation of ETPTA from the swollen PS particles. In addition, colloidal particles with large open windows were produced by dissolving the PS particles from the patchy particles. We observed photoluminescent emission from the patchy particles in which dye molecules were dispersed in the ETPTA phase. Finally, we used Surface Evolver simulation to predict equilibrium structures of patchy particles and estimate surface energies which are essential to understand the underlying physics.