title: Cluster formation and phase separation in heteronuclear Janus dumbbells.
abstract: We have recently investigated the phase behavior of model colloidal dumbbells constituted by two identical tangent hard spheres, with the first being surrounded by an attractive square-well interaction (Janus dumbbells, Munaó et al 2014 Soft Matter 10 5269). Here we extend our previous analysis by introducing in the model the size asymmetry of the hard-core diameters and study the enriched phase scenario thereby obtained. By employing standard Monte Carlo simulations we show that in such 'heteronuclear Janus dumbbells' a larger hard-sphere site promotes the formation of clusters, whereas in the opposite condition a gas-liquid phase separation takes place, with a narrow interval of intermediate asymmetries wherein the two phase behaviors may compete. In addition, some peculiar geometrical arrangements, such as lamellæ, are observed only around the perfectly symmetric case. A qualitative agreement is found with recent experimental results, where it is shown that the roughness of molecular surfaces in heterogeneous dimers leads to the formation of colloidal micelles.
authors.affiliation: Dipartimento di Fisica e di Scienze della Terra, Università degli Studi di Messina, Viale F. Stagno d'Alcontres 31, 98166 Messina, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Munaò
authors.forename: P
authors.initials: P
authors.lastname: O'Toole
authors.forename: T S
authors.initials: TS
authors.lastname: Hudson
authors.forename: D
authors.initials: D
authors.lastname: Costa
authors.forename: C
authors.initials: C
authors.lastname: Caccamo
authors.forename: F
authors.initials: F
authors.lastname: Sciortino
authors.forename: A
authors.initials: A
authors.lastname: Giacometti