Entropic Surface Segregation from Athermal Polymer Blends of Slim and Bulky Polymers

Experiments, theory, and simulations have revealed an entropic preference at the surface of athermal blends for the component with the shorter statistical segment length. Here, we examined the resulting surface segregation for blends of slim and bulky polymers of equal molecular volume, using Monte Carlo simulations where the polymers are modeled as chains of impenetrable spheres. Comparing to analogous simulations for blends of stiff and flexible polymers [Spencer and Matsen, Macromolecules 2022, 55, 1120], we find that bulkiness has a considerably stronger effect on the surface segregation than stiffness, consistent with self-consistent field theory (SCFT) predictions for worm-like chains [Matsen, J. Chem. Phys. 2022, 156, 184901]. Furthermore, we demonstrate that, under special conditions, this mismatch in strength can lead to anomalous surface segregation of the component with the longer statistical segment length, as predicted by the SCFT.