Surface Segregation in Linear/Pompom and Linear/Cyclic Polymer Blends

Polymers with nonlinear architectures, such as branched or cyclic polymers, can segregate to both the surface and interfaces when blended with linear polymer. We use a self-consistent field theory (SCF) to model blends of a linear polymer with nonlinear polymer molecules with various architectures. The simulations predict how the total density and composition profiles vary with the molar ratio of nonlinear to linear species. The total surface excess of nonlinear species shows a quadratic dependence on composition with a maximum at 50% nonlinear polymer content. A comparison to experimentally determined surface excess of branched “pom-pom” and star polymers with different molecular weight of arms shows good qualitative agreement. We also compare our results with the analytical linear response theory of Wu and Fredrickson, and examine the deviations from linear response with increasing content of nonlinear polymer. In agreement with the predictions of the analytical theory, in the limit of high molecular weights, the integrated surface excess of cyclic polymers exceeds that of non-cyclic branched polymers of comparable molecular weight.