Entropic Segregation of Short Polymers to the Surface of a Polydisperse Blend

Surface effects become particularly important for micro-sized and even more so for nano-sized objects. Naturally, enthalpic preferences will cause certain components of a multi-component material to segregate to a surface, but in polymeric materials this can also happen as a result of purely entropic reasons. To demonstrate this, we consider the effect of a surface on a binary blend of chemically identical long and short polymers, using self-consistent field theory. Despite the absence of any enthalpic preference, the short polymers are found to segregate to the surface. We investigate how the amount of the surface excess and its decay length depends on the polymeric model, the molecular weights of the two polymers and the blend composition.