Pulling a polymer at an interface: directed walk models

We consider directed walk models of a homopolymer (in two dimensions) interacting with two immiscible liquids. The polymer is subject to a force, normal to the interface between the two liquid phases. We first consider the case where, in the absence of a force, the polymer is delocalized into the preferred bulk phase, but is pulled into the less favourable bulk phase by the applied force. We examine the temperature dependence of the critical force as a function of the relative quality of the two solvents. When both solvents are poor the polymer can localize at the interface and we also consider the temperature dependence of the critical force needed to pull the polymer out of the interface and into a bulk phase.