Repulsion between Colloidal Particles Mediated by Nonadsorbing Polymers: Lattice Monte Carlo Simulations and the Corresponding Self-Consistent Field Calculations

Using a lattice self-consistent field (SCF) theory and the corresponding lattice Monte Carlo (MC) simulations combined with our recently proposed Z method [Zhang, P.; Wang, Q. Soft Matter 2015, 11, 862], we examined athermal homopolymer solutions confined between two parallel and nonabsorbing surfaces and in equilibrium with a bulk solution and accurately calculated the effective interaction between the two surfaces. By directly comparing our MC results with SCF predictions based on the same model system, we were able to quantitatively and unambiguously distinguish the mean-field and the fluctuation contributions to the effective interaction. We found for the first time the fluctuation-induced repulsion between the two confining surfaces at intermediate separation predicted by Semenov and Obukhov [Obukhov, S. P.; Semenov, A. N. Phys. Rev. Lett. 2005, 95, 038305; Semenov, A. N.; Obukhov, S. P. J. Phys.: Condens. Matter 2005, 17, S1747], which is about one order of magnitude stronger than that due solely to...