Templated assembly of polymer particles into mesoscopic clusters with well-defined configurations

Abstract

We report on the fabrication of colloidal clusters through the combination of spherical particles. Polystyrene latex particles bearing amino groups on their surface were used as building blocks of the clusters. Packing of these particles with diameters of 91 and 154 nm into assemblies with defined configurations was accomplished using narrow dispersed emulsion droplets as templates. The building blocks of the clusters adhered to the oil-water interphase due to the Pickering effect. Subsequent evaporation of the dispersed phase forced them to pack into small clusters. Addition of the particles via the dispersed phase led to higher yields of clusters than if the building blocks were added via the continuous phase. All clusters had well-defined configurations. Because the dimensions of these clusters were below 400 nm, the colloidal assemblies underlay Brownian motion which resulted in stable suspensions. The number and yields of different species could be controlled via the concentration of the building blocks and surfactant within the emulsions. Moreover, the nature of the dispersed phase itself had a strong impact on the cluster formation. When cyclohexane was used as the dispersed phase, predominately particle doublets and triplets were obtained. The use of toluene-in-water emulsions resulted into a broader spectrum of clusters of up to 12 constituents. Such clusters could satisfy the demand for particles with complex but defined shapes and special symmetries for the fabrication of novel hierarchically organized materials.

Assembly of open clusters of colloidal dumbbells via droplet evaporation

“…6(c)] such as n c = 4, n b = 6 (tetrahedron); n c = 6, n b = 12 (octahedron); n c = 8, n b = 18 (snub disphenoid); n c = 10, n b = 22 (gyreoelongate square dipyramid). These structures are similar to the onecomponent structures that minimize the second moment of the mass distribution [20,23]. Figure 7 shows a stacked histogram of the number of clusters N nc with n c colloids.…”

“…Based on this technique, Manoharan et al [20] successfully prepared micrometer-sized clusters and found that the structures of particle packings seem to minimize the second moment of the mass distribution. Wittemann et al also produced clusters, but with a considerably smaller size of about 200nm [21][22][23]. Cho et al prepared binary clusters with different sizes or species from phase-inverted water-in-oil [24] and oil-in-water emulsion droplets [25].…”

Towards nanoscale composite particles of dual complexity

“…The size distribution of the templating emulsion droplets was controlled by ultrasound [39]. Evaporation of the dispersed phase creates capillary forces which pack the particles together into clusters that exhibit well-defined configurations, such as particle doublets, triplets, tetrahedrons, triangular dipyramids, and octahedrons, among others [32]. Because the dispersed phase presents a solvent for polystyrene, the cluster constituents are swollen during the assembly.…”

“…[32,39]. The cluster preparation is based on the agglomeration of the constituent particles while adsorbed onto the surface of emulsion droplets.…”

“…[32]. The spherical particles with an average diameter of 154 nm can be regarded as monodisperse (Fig.…”