Microscopic approach to inhomogeneous polymeric liquids

We discuss a liquid-state theory for the equilibrium structure of inhomogeneous polymeric liquids. The theory consists of an equation for the density profile of a liquid in an external potential, which has been derived previously by density functional methods. In general, this equation must be solved by simulation techniques. However, if the chains are modeled as random walks—which is a reasonable approximation for flexible polymers at melt densities—we show that the theory reduces to a set of coupled integral equations which can be solved numerically. We present results for a single component liquid near a hard wall. Last, we show that, in the Gaussian thread limit, the theory reduces to a form that is very similar to Edwards–Helfand–Tagami ‘‘self-consistent field’’ theory. However, there are important differences between the two theories for multicomponent liquids (a blend for example) if the types of polymers are structurally dissimilar.