Force-induced desorption of a linear polymer chain adsorbed on an attractive surface

Abstract

We consider a model of self-avoiding walk on a lattice with on-site repulsion and an attraction for every vertex of the walk visited on the surface to study force-induced desorption of a linear polymer chain adsorbed on an attractive surface and use the exact enumeration technique for analyzing how the critical force for desorption f_c(T) depends on the temperature. The curve f_c(T) gives the boundary separating the adsorbed phase from the desorbed phase. Our results show that in two dimensions, where surface is a line, the force f_c(T) increases monotonically as temperature is lowered and becomes almost constant at very low temperatures. In case of three dimensions we, however, find re-entrance, i.e. f_c(T) goes through a maximum as temperature is lowered. The behaviour of the polymer chain at different values of temperature and force is examined by calculating the probability distribution of the height from the surface of the vertex at which external force is applied.