Zipping and collapse of diblock copolymers - art. no. 041801

Using exact enumeration methods and Monte Carlo simulations, we study the p hase diagram relative to the conformational transitions of a diblock copoly mer in two dimensions. The polymer is made of two homogeneous strands of mo nomers of different species which are joined to each other at one end. We f ind that, depending on the values of the energy parameters in the model, th ere is either a first order collapse from a swollen phase to a compact phas e of spiral type, or a continuous transition to an intermediate zipped phas e followed by a first order collapse at lower temperatures. Critical expone nts of the zipping transition are computed. and their exact values are conj ectured on the basis of a mapping onto percolation geometry, thanks to rece nt results on path-crossing probabilities.