Nonspherical Colloidal Crystals Fabricated by the Thermal Pressing of Colloidal Crystal Chips

Abstract

Nonspherical colloids and their ordered arrays may be more attractive in applications such as photonic crystals than their spherical counterparts because of their lower symmetries, although such structures are difficult to achieve. In this letter, we describe the fabrication and characterization of colloidal crystals constructed from nonspherical polyhedrons. We fabricated such nonspherical colloidal crystals by pressing spherical polymer colloidal crystal chips at a temperature slightly lower than the glass-transition temperature (T(g)) of these polymer colloids. During this process, the polymer microspheres were distinctively transformed into polyhedrons according to their crystal structures, whereas the long-range order of the 3D lattice was essentially preserved. Because a working temperature lower than T(g) effectively prevented the colloidal crystals from fusing into films, the spherical colloidal crystals were transformed greatly under pressure, which lead to obvious change in the optical properties of colloidal crystals. Besides their special symmetry and optical properties, these nonspherical colloidal crystals can be used as templates for 2D or 3D structures of special symmetry, such as 2D nano-networks. We anticipate that this fabrication technique for nonspherical colloidal crystals can also be extended to nonspherical porous materials.

Silica Colloid Ordering in a Dynamic Sedimentary Environment

“…At a small shear force, the deformation of soft, ordered spheres into polyhedra decreases pore space and induces a blue-shift of the diffracted light [31]. Therefore, sheared sphere arrays may preserve their long-range order but lose their optical photonic character.…”

Ordered arrays of pumpkin-shaped Janus particles with tailored surface morphologies via microcontact hot embossing

“…However, the Janus particles modified above are principally spherical and have limited geometrical textures, yet there is also a growing need to generate nonspherical counterparts [1,29]. For instance, Yang et al obtained nonspherical polyhedrons by thermal pressing spherical colloidal crystals with planar plates [30]. In order to prevent the colloids from fusing into each other, the operation temperature was slightly lower than the corresponding glass transition temperature (T g ).…”

Preparation of hemispherical polystyrene particles utilizing the solvent evaporation method in aqueous dispersed systems

“…In general, polymer particles synthesized by heterogeneous polymerizations under thermodynamic control have a spherical shape because of interfacial free energy minimization. However, nonspherical polymer particles have been synthesized under kinetic control utilizing various seeded polymerization methods, [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] microfluidic techniques, [25][26][27][28] deformation of spherical polymer particles by external force, [29][30][31] the stepwise heterocoagulation method 32,33 and the self-organized precipitation method. 34 In a previous work, we proposed a novel approach for the preparation of micrometer-sized, monodisperse, nonspherical (i.e., dimpled and hemispherical) polystyrene (PS) particles by successive heating and cooling of spherical PS particles dispersed in a methanol/ water medium in the presence of droplets of decane.…”