  We report a study of reversible adsorption of DNA-coated colloids on
complementary functionalized oil droplets. We show that it is possible to
control the surface coverage of oil droplets by colloidal particles, by
exploiting the fact that during slow adsorption, compositional arrest takes
place well before structural arrest occurs. As a consequence, we can prepare
colloid-coated oil droplets with a `frozen' degree of loading, but with fully
ergodic colloidal dynamics on the droplets. We illustrate the equilibrium
nature of the adsorbed colloidal phase by exploring the quasi two-dimensional
(2d) phase behaviour of the adsorbed colloids under the influence of depletion
interactions. We present simulations of a simple model that illustrates the
nature of the compositional arrest and the structural ergodicity.
