The globule-coil transition in a mean field approach
  In this paper we study the unfolding transition observed in polymer stretching experiments. We use a known model and extend it with a mean-field-like interaction. Expressions for all necessary thermodynamic variables as a function of the model parameters are derived in closed form. To obtain the exact force-extension relation at constant temperature, we invert these relations numerically. Below a critical temperature the model exhibits a sharp first order phase transition. 
Erik Van der Straeten and Jan Naudts