2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/118821In 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.revtex, 9 pages, 4 figuresStatistical Mechanicstext