Computer simulations of energetic and entropic changes of a single polymer chain under extension

Abstract

The changes in energy and entropy during the deformation of a single three-dimensional polymer chain above and below the Θ-temperature have been studied using the bond-fluctuation model. Above the Θ-temperature the deformation is controlled by the entropy. In contrast to that far below the Θ-temperature the energy is the dominating part of the deformation pattern. The deformation is represented by a coil–strand coexistence and is therefore inhomogeneous. During the coil–strand coexistence the total force, as well as its energetic and entropic parts, is independent of the extension. At large strains or higher temperatures the coil–strand system becomes unstable and the energy looses its dominance. During the disintegration of the coil–strand system the energetic part of the force exceeds the total force by a large extent and the entropic part of the force reaches pronounced negative values.