Polymers with self-attraction and stiffness: a generic phase structure

Recently it has been shown that a two-dimensional model of self-attracting polymers based on attracting segments displays two phase transitions, a theta-like collapse between swollen polymers and a globular state and another between the globular state and a polymer crystal. On the other hand, the canonical model based on attracting monomers on lattice sites displays only one: the standard tricritical theta collapse transition. Here we show that by considering both models with the addition of stiffness the two models display the same generic phase diagram. In fact we claim that any two-dimensional model of a self-attracting single polymer in solution based upon a fully volume-excluded backbone with isotropic short range attraction should show this same phase structure. We point to the model of hydrogen bonded polymers to demonstrate this observation. In three dimensions we note that more than one crystalline phase may occur.