By: Cristovão Dias
From: CFTC - Universidade de Lisboa
At: Instituto de Investigação Interdisciplinar, Anfiteatro
The past few years have witnessed a sustained interest in the self-organization of patchy colloids, with the development of a wide range of techniques to synthesize them. Patchy colloids yield directionality of interactions being ideal building blocks for the rational development of self-assembled structures with novel physical properties. Studies of their equilibrium diagrams have revealed a myriad of possibilities as, for example, the capability of fine tuning the density and the temperature of gas-liquid and sol-gel transitions. However, the kinetics of self-organization and the feasibility of predicted structures are still poorly understood. Thus, to shed light on the aggregation of patchy colloids we have numerically studied their irreversible adsorption on substrates and analyzed the structure of the obtained colloidal networks. The interest in the aggregation on substrates is twofold. First, from the practical point of view, a substrate works as a nucleation center for growth improving the controllability over assembly. Second, with substrates it is possible to define a growth direction (away from the substrate) and characterize the time evolution of the structure. This possibility constitutes a powerful tool for a systematic theoretical study of non-equilibrium growth.
Our theoretical work considers two cases of experimental relevance: adsorption on a substrate and the aggregation at the edges of a drop. For the first case, we numerically investigate the irreversible adsorption of different types of patchy-colloids, namely, three- and two-patch colloids and Lisbon colloids and analyze the fractal network of connected particles that is formed [1,2,3]. For the second one, we show that the universality class of growth changes with the selectivity of patch-patch interactions.
 C. S. Dias et al., Phys. Rev. E 87, 032308 (2013).
 C. S. Dias et al., Soft Matter, 9, 5616 (2013).
 C. S. Dias et al., J. Chem. Phys. 139, 154903 (2013).