Two-dimensional mixture of amphiphilic dimers and spheres: Self-assembly behaviour

Abstract

The emergence of supramolecular aggregates from simple microscopic interaction rules is a fascinating feature of complex fluids which, besides its fundamental interest, has potential applications in many areas, from biological self-assembly to smart material design. We here investigate by Monte Carlo simulation the equilibrium structure of a two-dimensional mixture of asymmetric dimers and spheres (disks). Dimers and disks are hard particles, with an additional short-range attraction between a disk and the smaller monomer of a dimer. The model parameters and thermodynamic conditions probed are typical of colloidal fluid mixtures. In spite of the minimalistic character of the interaction, we observe-upon varying the relative concentration and size of the two colloidal species-a rich inventory of mesoscale structures at low temperature, such as clusters, lamellæ (i.e., polymer-like chains), and gel-like networks. For colloidal species of similar size and near equimolar concentrations, a dilute fluid of clusters gives way to floating lamellæ upon cooling; at higher densities, the lamellæ percolate through the simulation box, giving rise to an extended network. A crystal-vapour phase-separation may occur for a mixture of dimers and much larger disks. Finally, when the fluid is brought in contact with a planar wall, further structures are obtained at the interface, from layers to branched patterns, depending on the nature of wall-particle interactions.

Self-Assembled Structures of Colloidal Dimers and Disks on a Spherical Surface

“…The investigated model is the curved-surface analog of the same mixture of dimers and spherical guest particles that was studied in [ 30 , 31 , 32 ]. A dimer consists of two tangent hard calottes (i.e., disks following the surface of the sphere) with curved diameters and , whereas guest particles are represented as hard calottes of size (below, we generically refer to these particles as “disks”).…”

“…Recently, we studied in 3D space [ 30 ] and on a plane [ 31 ] an implicit-solvent description of the dispersion of two colloidal species, namely, an amphiphilic dimer and a guest spherical/circular particle, where the smaller monomer in the dimer was solvophobic and had a strong affinity for the guest particle. In this paper, we consider the same system embedded in a spherical surface.…”

Janus dumbbells near surfaces modified with tethered chains

“…In the earlier works the behavior of Janus particles near solid surfaces has considered. Mixtures of Janus dumbbells with spherical particles at a bare substrate has been studied using computer simulations (Prestipino et al 2017). In this case the complex membrane-like structures have been found.…”

“…The encapsulating structures arise through self-assembly of amphiphilic molecules, Janus particles, lipids or protein-like copolymers. Among the wide range of Janus-like particles that can be used for the encapsulation, the dumbbell-shaped particles deserve a special interest (Munao et al 2016;O'Toole et al 2017;Prestipino et al 2017). Now, dumbbells of various geometrical and chemical properties can be produced (Skelton et al 2017;Wolters et al 2008).…”

“…The Janus dumbbells are usually constituted by two monomers, one of which is solvophilic and the other one is solvophobic. The molecular simulation study (Prestipino et al 2017) has shown that Janus dumbbells form different structures near solid surfaces. Adsorption of various heterogeneous dimers on bare solid surfaces has already been the subject of our research (Borówko and Rżysko 1996;Rżysko and Borówko 2003).…”