Effects of patch size and number within a simple model of patchy colloids

Abstract

We report on a computer simulation and integral equation study of a simple model of patchy spheres, each of whose surfaces is decorated with two opposite attractive caps, as a function of the fraction χ of covered attractive surface. The simple model explored -the two-patch Kern-Frenkel model -interpolates between a square-well and a hard-sphere potential on changing the coverage χ. We show that integral equation theory provides quantitative predictions in the entire explored region of temperatures and densities from the square-well limit χ = 1.0 down to χ ≈ 0.6. For smaller χ, good numerical convergence of the equations is achieved only at temperatures larger than the gasliquid critical point, where however integral equation theory provides a complete description of the angular dependence. These results are contrasted with those for the one-patch case. We investigate the remaining region of coverage via numerical simulation and show how the gas-liquid critical point moves to smaller densities and temperatures on decreasing χ. Below χ ≈ 0.3, crystallization prevents the possibility of observing the evolution of the line of critical points, providing the angular analog of the disappearance of the liquid as an equilibrium phase on decreasing the range for spherical potentials. Finally, we show that the stable ordered phase evolves on decreasing χ from a threedimensional crystal of interconnected planes to a two-dimensional independent-planes structure to a one-dimensional fluid of chains when the one-bond-per-patch limit is eventually reached.

Supercharging enables organized assembly of synthetic biomolecules

“…Given that both natural proteins 3-8 and synthetic colloids [18][19][20][21][22][23][24][25][26][27][28][29] have been shown to readily assemble into symmetric, higher order structures, we anticipate that our SuPrA strategy can now be generalized to create synthetic, scalable…”

“…16,17 In contrast, studies of simple synthetic colloids suggests that higher order structures can be derived based solely on packing and energetic and considerations. Computational and experimental studies of polyhedral or spherical colloids indicate that complementary particle shapes 18-24 and simple attractive "patches" [24][25][26][27][28][29] alone can enable formation of complex symmetrical assemblies. Shape complementarity has likewise been exploited to arrange synthetic linear biomolecules, i.e., double-stranded DNA strands, into distinct structures, demonstrating its utility for for the higher order arrangement of synthetic linear biomolecules, suggesting a utility beyond inorganic systems.…”

“…Notably, while some GFP variants, including the parent protein originally found in Aeqorea Victoria dimerize, the native dimer structure fits poorly into the electron density maps of the protomer, suggesting that the architecture of the protomer is completely novel. 54 The formation of SuPrA protomers appears to be largely independent of the placement of charges, suggesting that oppositely supercharging protein variants may generally drive formation into 'stacked' or brick-like structures whose overall form is determined by symmetric interactions.Given that both natural proteins 3-8 and synthetic colloids [18][19][20][21][22][23][24][25][26][27][28][29] have been shown to readily assemble into symmetric, higher order structures, we anticipate that our SuPrA strategy can now be generalized to create synthetic, scalableAll rights reserved. No reuse allowed without permission.…”

Janus fluid with fixed patch orientations: Theory and simulations

“…7 In fact, one of the most attractive features of the general model stems from the fact that it smoothly interpolates between an isotropic HS fluid (zero coverage) and an equally isotropic SW fluid (full coverage). 8,9 The thermophysical and structural properties of the Janus fluid have been recently investigated within the framework of the Kern-Frenkel model using numerical simulations, 7,10 thus rationalizing the cluster formation mechanism characteristic of the experiments. 3 The fluidfluid transition was found to display an unconventional and particularly interesting phase diagram, with a reentrant transition associated with the formation of a cluster phase at low temperatures and densities.…”

Second-order resummed thermodynamic perturbation theory for central-force associating potential: Multi-patch colloidal models

“…For future work we are planning to apply the version of our theory developed for the model with two patches to describe the phase behaviour of triblock Janus colloids. [39][40][41] …”