A new lattice density functional theory for polymer adsorptionat solid-liquid interface

摘要

We report a new lattice density functional theory for polymer solutions at the solid-liquid interface.The theory accounts for the nearest-neighbor interactions and the long-range correlations due tochain connectivity. A Helmholtz free-energy functional is developed with an exact free-energyfunctional expression for the ideal chains and a thermodynamic model of lattice polymer solutionsfor the excess contributions. The local and weighted density approximations are used to calculate thecontributions due to the athermal entropy of mixing and the internal energy of mixing, respectively.Mayer function and propagator formalism are adopted to obtain the segment-density distributionsfor various conformations including adsorbed trains, tails, loops, and free polymers. The predicteddensity distributions of polymer adsorption are in good agreement with simulation results. Theresults imply that as a counterbalance between energy and conformational entropy, the weighteddensity approximation used in the functional can rationally capture the segment-segmentcorrelations.