Phase transition of a single star polymer: A Wang-Landau sampling study

Abstract

Star polymers, as an important class of nonlinear macromolecules, process special thermodynamic properties for the existence of a common connecting point. The thermodynamic transitions of a single star polymer are systematically studied with the bond fluctuation model using Wang-Landau sampling techniques. A new analysis method employing the shape factor is proposed to locate the coil-globule (CG) and liquid-crystal (LC) transitions, which shows a higher efficiency and accuracy than the canonical specific heat function. The LC transition temperature is found to obey the identical scaling law as the linear polymers. However, the CG transition temperature shifts towards the LC transition with the increasing of the arm number. The reason is that for the star polymer a lower temperature is needed for the attractive force to overcome the excluded volume effect of the polymer chain because of its high arm density. This work clearly proves the structural distinction of the linear and star polymers can only affect the CG transition while has no influence on the LC transition.

Entropic sampling of star-shaped polymers with different number of arms: temperature dependencies of structural properties

“…The latter provides the increase of the total monomer density, such that it hinders the collapse of the coil-globule transition. Similar results were obtained in [4], where the fluctuating bond model was used. Additionally, we present several structural characteristics for our models.…”

“…The main aim of this paper is to observe how initial structural characteristics, such as the number of its arms, influence its equilibrium structural properties, including features of the coil-globule transition. This problem is also discussed in a number of papers [4,5] so it would be desirable to compare our data with that of [4]. It is known that in the star-like polymers, there can be observed transitions of two types: liquid-crystal (1st order) and the coil-globule (2nd order), wherein the second order transition is very sensitive to the polymer's topology.…”

“…This method was successfully applied in our previous works [13,15,[19][20][21] as well as by other authors [4,12,[22][23][24] in polymer studies. An important attractive feature of this method is in its ability to obtain statistics for very rare events with relative ease.…”

Equilibrium properties of 3-arm star-shaped polyions: an entropic sampling Monte Carlo study

“…The method that we used here is the entropic sampling (ES) method [23,24] within Wang-Landau (WL) algorithm [25] initially applied to polymers in our simulation group [26] and successfully used later by us [27-29, 34, 37, 40, 41] and by other researchs [30,33,[42][43][44][45] for studying different polymer systems. In the ES-WL computer experiment the density of states g(E) is calculated just as it was done in [27] (see [27] for details).…”

“…An additional advantage of the used approach is that it provides a means for obtaining results over a wide range of temperatures, including the area of possible structural transitions in a single computer run. Our independent data could be compared with the existing results of other authors obtained using different approaches [9,11,22,30].…”