Behavior of a Grafted Flexible Homopolymer Under Applied Force

Manipulating individual polymer chains by means of experimental instruments such as optical tweezers has helped understand better the effects of molecular forces in macromolecular structures. In this study, we simulate the influence of the pulling force on structural phases of a coarse-grained model for flexible polymers using generalized-ensemble Monte Carlo methodologies. The recently introduced microcanonical inflection-point analysis method is employed to identify and classify structural phases of the system. The internal energy and structural order parameters are analyzed to help characterize the transition behavior in response to the applied pulling force. We show that, upon increasing the pulling strength, the coil-globule transition turns from second to first order, then merges with the liquid-solid transition. Transitions do not occur at all if the pulling force exceeds a certain threshold value.