Two dimensional assembly of triblock Janus particles into crystal phases in the two bond per patch limit

Abstract

In recent experimental work on spherical colloidal particles decorated with two hydrophobic poles separated by an electrically charged middle band (triblock Janus particles)—when particles are confined by gravity at the bottom of the sample holder—self-assembly into a Kagome two dimensional lattice has been documented [Qian Chen, Sung Chul Bae and Steve Granick, Nature, 2011, 469, 381]. Here, we assess the ability of a simple two-patch effective potential to reproduce the experimental findings. The model parameters are selected to match the experimental values, with a short-range attraction mimicking hydrophobic interactions and a patch width that allows for a maximum of two contacts per patch. We show that the effective potential is able to reproduce the observed crystallisation pathway in the Kagome structure. On the basis of free energy calculations, we also show that the Kagome lattice is stable at low temperature and low pressure, but that it transforms into a hexagonal lattice with alternating attractive and repulsive bands on increasing pressure.