New results on the collapse transition(s) of flexible homopolymers

We analyze the collapse transition of flexible homopolymer chains in the bond-fluctuation model employing the Wang-Landau Monte Carlo algorithm. The coil-globule transition is followed by a first order transition into a solid state occurring in the collapsed globule. in the thermodynamic limit (chain length to infinity) the topology of the phase diagram depends on the range of the attractive interaction between the monomers. For sufficiently large interaction range a normal behaviour of a continuous coil-globule transition at the Theta-temperature followed by a crystallization transition at lower temperature is observed. For short interaction range the first-order transition asymptotically can pre-empt the coil-globule transition such that a first-order collapse from a random-coil into a crystalline globule occurs. This vanishing of the liquid globule state is similar to the vanishing of the vapour-liquid coexistence found for colloidal suspensions interacting by a short-ranged attraction.