Immersion energy and polymer-mediated depletion interactions between nanocolloids as studied by analytic self-consistent field theory.

By applying the Edwards self-consistent field theory, we calculate the polymer density and free energy excesses caused by the presence of nanocolloids in the excluded volume polymer system. Using the obtained results, we have calculated the depletion potential U as a function of the separation between colloids, colloid radius, polymer volume fraction, and polymer gyration radius. Upon analyzing the obtained results against the known exact asymptotic small-separation limit and scaling relations, we propose an approximate expression for U that builds upon our exact result. This expression is shown to give excellent agreement with Monte Carlo simulations. Reliability of the derived analytical expression for the depletion potential and its relation to the previous theoretical and simulation work are thoroughly discussed.