Colloidal Clusters by Using Emulsions and Dumbbell-Shaped Particles: Experiments and Simulations

摘要

In the last decade, there has been a significant increase in the complexity of colloidal building blocks, which were developed with self-assembly (SA) steps in mind. An important reason for this increase in complexity is the realization that with more complex, anisotropic building blocks significantly more potential structures and symmetries can be realized, thus increasing the ability to realize and optimize materials properties. Also, these particles are interesting model studies for answering questions which cannot be easily addressed with spheres. Emulsion droplets of a water phase in oil, the focus of this communication, or vice versa, are powerful platforms for the SA of colloidal particles. Velev et al.pioneered shells of many particles ( 10) which could be generated using droplets, and are now generally called "colloidosomes".Manoharan et al.investigated the limit of small numbers, N, of particles adsorbed onto droplets (N< 15) wherein the particles remained stable as the oil was slowly and completely evaporated. Surprisingly, this procedure, which has now been performed with quite a number of different particles, leads to regular clusters (for relatively small N values) where all clusters of the same N value have the same shape. It was noted already by Manoharan et al. that the structures of the packing of particles in the clusters seem to minimize the second moment (M2) of the mass distribution of each N-mer. The method of Manoharan et al. has been extended to binary systems, to more monodis-perse emulsion droplets made by shear as reported by Zerrouki et al., combined with the "over-swelling" method used in emulsion and dispersion polymerization to arrive at anisotropic particles,and to clusters of particles with a smaller size (< 200 nm) from smaller emulsion droplets as reported by the group of Wittemann.