Dynamic Transitions in Unzipping of an Adsorbed Polymer

Abstract

Abstact

We study, using Monte Carlo simulations, the unzipping of the adsorbed polymer from the wall whose one end is subjected to a time dependent periodic force with frequency (w) and amplitude (g0) and the other end is kept fixed. The polymer is modeled as a directed walk in (1+1)-dimensional square lattice and three different cases for the wall are considered: (1) soft-wall, (2) hard-wall, and (3) the wall separating two different media. In the static force limit, i.e., w = 0, this model has been solved exactly and the unzipping transition is a found to be a first order phase transition. The critical force obtained from the simulation matches excellently with the analytical phase boundary for all the three cases. For the dynamical case, i.e., w 6=0, we observed that the force-distance isotherms show hysteresis loops for all the three cases mentioned above . We obtained the area of the hysteresis loops Aloop and found that they satisfy scaling. We also study the probability distributions of the dynamical order parameter Q.