Coverage Dependent Evolution of Two-Dimensional Dendrimer/Mica Domain Patterns

Abstract

For a two-dimensional, two-phase system of A and B, with competing short-range attractive and long-range repulsive interactions, the evolution of domain patterns as a function of area fraction should follow the sequence circular islands of A in a matrix of B (the droplet phase), alternating elongated domains of A and B (the striped phase), and circular islands of B in a matrix of A (the inverted droplet phase). The predicted domain pattern evolution is experimentally verified here for the case of dendrimer molecules on mica, a materials system amenable to control of the competing interactions. This result, along with the coverage dependence of the characteristic domain length scale, is reported for the first time. The domain patterns are fabricated by simple aerosol deposition of dilute solutions of dendrimer molecules in pentanol onto mica followed by slow evaporation. The long-range repulsive interaction in this case is electrostatic in origin and is associated with the contact potential between the neg...