Pulling self-interacting polymers in two-dimensions

We investigate a two-dimensional problem of an isolated self-interacting end-grafted polymer, pulled by one end. In the thermodynamic limit, we find that the model has only two different phases, namely a collapsed phase and a stretched phase. We show that the phase diagram obtained by Kumar {\it at al.\} [Phys. Rev. Lett. {\bf 98}, 128101 (2007)] for small systems, where differences between various statistical ensembles play an important role, differ from the phase diagram obtained here in the thermodynamic limit.