Generalized van der Waals density functional theory for nonuniform polymers

A density functional theory is presented for the effect of attractions on t he structure of polymers at surfaces. The theory treats the ideal gas funct ional exactly, and uses a weighted density approximation for the hard chain contribution to the excess free energy functional. The attractive interact ions are treated using a van der Waals approximation. The theory is in good agreement with computer simulations for the density profiles at surfaces f or a wide range of densities and temperatures, except for low polymer densi ties at low temperatures where it overestimates the depletion of chains fro m the surface. This deficiency is attributed to the neglect of liquid state correlations in the van der Waals term of the free energy functional. (C) 2000 American Institute of Physics. [S0021-9606(00)50203-7].