Dimpled Polyhedral Colloids Formed by Colloidal Crystal Templating

Abstract

Many approaches to the self-assembly of interesting microstructures rely on particles with engineered shapes. We create dimpled solid particles by molding oil droplets in the interstices of a close-packed colloidal crystal and polymerizing them in situ, resulting in particles containing multiple spherical dimples arranged with various polyhedral symmetries. Monodisperse micrometer-sized droplets of 3-methacryloxypropyltrimethoxysilane (TPM) are mixed with an excess of polystyrene (PS) microspheres (2.58 μm) and allowed to sediment, forming colloidal crystals with TPM droplets inside their interstitial sites. When these crystals are compressed by partial drying, the trapped droplets wet the multiple microspheres surrounding them, forming a three-dimensional capillary bridge with the symmetry of the interstitial spaces, and then mild heating triggers polymerization in situ. Depending on the initial particle volume fraction and extent of drying, a high yield of dimpled particles having different symmetries including tetrahedra and cubes is obtained. The fractional yield of different shapes varies with the size ratio of the TPM droplets and the PS microspheres forming the template lattice. Sedimentation velocity fractionation methods are effective for enrichment of specific symmetries but not complete purification. Our approach for forming polyhedral particles should be readily scalable to larger samples and smaller sized particles if desired.

1D Colloidal chains: recent progress from formation to emergent properties and applications

“…However, hierarchical particles with relatively complex shapes and geometries can steer their self-assembly into higher level designated structures. These hierarchical particles include but are not limited to: porous particles, 59,113,114 core-shell particles, 33,115,116 microcapsules, 32,117,118 raspberryand onion-like particles, [119][120][121][122][123] Janus particles, 73,124,125 patchy particles, 98,126,127 and non-spherical particles including but not limited to ellipsoidal, [128][129][130] bicone, 131 dumbbell-shaped, [132][133][134] dimpled, 86,135,136 polyhedral, [137][138][139] and branched colloids (lower part of Fig. 2).…”

Synthetic Strategies for Polymer Particles with Surface Concavities

“…This is different to the above-mentioned one-step polymerization methods, in which the surface concavity is formed directly in the polymerization process. Both hard templates [140][141][142][143][144][145][146][147][148][149][150][151][152][153][154][155][156][157] and soft templates [158][159][160][161][162][163][164][165][166] have been used for the preparation of dimpled polymer particles.…”

“…A wide variety of post‐treatment techniques, including solvent‐absorbing/releasing, [ 109,110 ] general solvent evaporation, [ 111–121 ] microfluidic emulsification/emulsion–solvent evaporation, [ 122–128 ] electrospraying/solvent evaporation, [ 129–137 ] electrospinning/solvent evaporation, [ 138,139 ] templating method, [ 140–166 ] treatment on core–shell particles [ 167–173 ] and self‐assembly of polymer [ 174–176 ] have been developed for dimpled polymer particles syntheses.…”

Synthetic strategies for nonporous organosilica nanoparticles from organosilanes

“…In recent years, there has been increasing interest in the synthesis of organosilica particles based on spontaneous emulsification and subsequent radical polymerization of TPM. 82–123…”

“…TPM has been recognized as an extremely useful compound in colloidal chemistry, since it can transfer from liquid to solid on command by polymerization of its methacrylate moiety. In recent years, based on spontaneous emulsification and subsequent polymerization of TPM, a variety of complex colloids have been prepared, such as particles with multiple cavities, 91 shape-shifting particles, 92 bowl-shaped particles, 97 bifunctional patchy particles, 98 patchy particles with concave patches, 99 TPM–TPM dimers, 100 biphasic triblock PS–TPM–PS particles, 101 customized chiral particles, 102 di-patchy particles, 103 particles with triangular patches, 110 cubic diamonds, 111 faceted DNA patchy particles, 112 DNA-coated particles, 113 oil-containing particles with a single depression, 121 golf ball-like particles, 122 dimpled polyhedral particles, 123 etc . They are typically prepared by the seed-mediated heterogeneous nucleation and growth method, as proposed by Sacanna et al 90 In this method, colloidal seeds are used to induce heterogeneous nucleation of TPM monomers, which subsequently condense on the seed particles, forming liquid droplets; finally, solid colloids with desired shapes can be formed by polymerization of the droplets.…”