Local density distribution of nonuniform polymer melts at solid-fluid interfaces

We have developed the density functional theory (DFT) and density functional perturbation theory (DFPT) which are based both on the hybrid weighted-density approximation and on the higher-order weighted-density approximation, respectively, to study the structural and thermodynamic properties of polymer melts at interfaces. They were applied to predict the local density distributions, adsorption isotherms, surface excesses, and solvation forces of a freely jointed tangent hard-sphere chain in hard slit pores. The Wertheim's first-order perturbation theory extended by Yu and Wu [J. Chem. Phys. 117, 2368 (2002)] was used to calculate the excess free energy and second-order direct correlation function due to the chain connectivity. The weight functions were calculated from the second-order direct correlation functions. The calculated results show that the DFT is in excellent agreement with the computer simulations and slightly better than the DFPT.