The escape transition in a self-avoiding walk model of linear polymers

A linear polymer grafted to a hard wall and underneath an atomic force microscopy tip can be modeled in a lattice as a grafted lattice polymer (self-avoiding walk) compressed underneath a piston near the wall. As the piston approaches the wall the increasingly confined polymer escapes from the confined region to explore conformations beside the piston. This conformational change is believed to be a phase transition in the thermodynamic limit, and has been argued to be first order, based on numerical results in the literature. In this paper a lattice self-avoiding walk model of the escape transition is constructed. It is proven that this model has a critical point in the thermodynamic limit corresponding to the escape transition of compressed grafted linear polymers. This result relies on the analysis of self-avoiding walks in slits and slabs in the square and cubic lattices. Additionally, numerical estimates of the location of the escape transition critical point is reported based on Monte Carlo simulations of self-avoiding walks in slits and in slabs.