Phase Diagram of Janus Particles

Abstract

We thoroughly investigate a simple model representative of the recently synthesized Janus particles, i.e., colloidal spherical particles whose surface is divided into two areas of different chemical composition. When the two surfaces are solvophilic and solvophobic, these particles constitute the simplest example of surfactants. The phase diagram includes a colloidal-poor (gas), colloidal-rich (liquid) demixing region, which is progressively suppressed by the insurgence of micelles, providing the first model in which micellization and phase separation are simultaneously observed. The coexistence curve is found to be negatively sloped in the temperature-pressure plane, suggesting that Janus particles can provide a colloidal system with anomalous thermodynamic behavior.

Self-Assembly in Chains, Rings, and Branches: A Single Component System with Two Critical Points

“…The thermodynamic stability at low T is shown to arise from the building up of non interacting clusters of particles with low energy and low entropy. The theory also provides a theoretical foundation of the behavior numerically observed recently in models of Janus particles in three dimensions [15] and in 2D-simulations of limited valence particles on lattice [21]. In both cases, the gas reentrance is connected to the self assembly into weakly or non interacting saturated aggregates (micelles for the Janus particles and rings for the patchy particles).…”

“…The renewed focus on the role of directional interactions, stimulated by the synthesis of new-generation patchy colloids [10][11][12][13], has deepened our understanding not only of the role of the valence on the gas-liquid phase separation [14] but also on the competition between selfassembly and phase separation. Two recent investigations have provided insights particularly relevant for this work: (i) a numerical study of Janus colloids in which a gas-liquid critical point and a self-assembly process are simultaneously observed [15,16]. In this model, the formation of energetically stable vesicles stabilizes at low temperature T the gas-phase; (ii) a study of particles with dissimilar patches [17][18][19], promoting respectively chaining and branching, specifically designed to reproduce a mean-field model introduced by Safran and Tlustly [20] to describe the phase behavior of dipolar fluids.…”

Alignment of cylindrical colloids near chemically patterned substrates induced by critical Casimir torques

“…The experimental fabrication of such particles is of research interest in itself [48,58,59], as is the theoretical understanding of the interactions between spherical [60,61] or between non-spherical Janus particles [62,63], because they are considered to be promising building-blocks for selfassembling materials.…”

Inferring bulk self-assembly properties from simulations of small systems with multiple constituent species and small systems in the grand canonical ensemble

“…[15][16][17] With increased computing power and improved simulation techniques, it has become possible to simulate mesoscale models that reproduce such self-assembling behaviour. In recent years mesoscopic models have been used to assemble micelles, [18][19][20][21][22][23][24][25][26][27][28][29][30][31] vesicles, 29,32,33 hollow shells of specific symmetry analogous to virus capsids [34][35][36][37][38][39][40][41][42] and aggregates of particles which resemble protein clusters. 43 Additionally, reflecting the growth of DNA nanotechnology, 44 many coarse-grained models of DNA assembly have recently been proposed.…”