Simulating the collapse transition of a two-dimensional semiflexible lattice polymer

Abstract

It has been revealed by mean-field theories and computer simulations that the nature of the collapse transition of a polymer is influenced by its bending stiffness epsilon(b). In two dimensions, a recent analytical work demonstrated that the collapse transition of a partially directed lattice polymer is always first order as long as epsilon(b) is positive [H. Zhou et al., Phys. Rev. Lett. 97, 158302 (2006)]. Here we employ Monte Carlo simulation to investigate systematically the effect of bending stiffness on the static properties of a two-dimensional lattice polymer. The system's phase diagram at zero force is obtained. Depending on epsilon(b) and the temperature T, the polymer can be in one of the three phases: crystal, disordered globule, or swollen coil. The crystal-globule transition is discontinuous and the globule-coil transition is continuous. At moderate or high values of epsilon(b) the intermediate globular phase disappears and the polymer has only a discontinuous crystal-coil transition. When an external force is applied, the force-induced collapse transition will either be continuous or discontinuous, depending on whether the polymer is originally in the globular or the crystal phase at zero force. The simulation results also demonstrate an interesting scaling behavior of the polymer at the force-induced globule-coil transition.

Monte Carlo simulations of polymers with nearest- and next nearest-neighbor interactions on square and cubic lattices

“…Therefore, a transition to a crystalline phase could be expected there, which we do not observe. However, the repulsive NNN interaction in our model is different from a bending energy of semiflexible models [19], since the first also inhibit the formation of pairs of nonconsecutive NN monomers in simple cubic lattices. Therefore, the change from a Θ-line to a direct (first-order) coil-crystal transition possible does not exists here, or appears in a region of |ǫ 1 | ≫ |ǫ 2 |, which is very difficult to be accessed with our simulation method.…”

“…Beyond the coil and globule phases (separated by a Θ-line), this model presents a crystalline phase and discontinuous globule-crystal (at small ǫ b ) and coil-crystal (at large ǫ b ) transitions are also present in its phase diagram [19].…”

“…A generalized ISAW model has also been used to model semiflexible polymers, where a repulsive bending force, associated to a bending energy ǫ b < 0, is introduced in the ISAW model (see [19] and references therein). Beyond the coil and globule phases (separated by a Θ-line), this model presents a crystalline phase and discontinuous globule-crystal (at small ǫ b ) and coil-crystal (at large ǫ b ) transitions are also present in its phase diagram [19].…”

Dynamics of Polymers in Flowing Colloidal Suspensions

“…because of the reduced number of contacts possible in 2D [19,20]. Previous studies have predicted a nucleation type mechanism for the unfolding of collapsed polymer chains in flow that relies on these thermally excited protrusions [6,8,21].…”

Polymers with nearest- and next nearest-neighbor interactions on the Husimi lattice

“…The more general case of semiflexible polymers has been modeled by introducing a bending energy ǫ b in the ISAW model (see for instance Refs. [7][8][9][10]). In this semiflexible-ISAW (sISAW) model, a stable crystalline (solid-like) phase also exists in the system (for low T and large ǫ b ), in addition to the coil and globule ones.…”