COMPUTER-SIMULATIONS OF ENERGETIC AND ENTROPIC CHANGES OF A SINGLE POLYMER-CHAIN UNDER EXTENSION

The changes in energy and entropy during the deformation of a single t hree-dimensional polymer chain above and below the Theta-temperature h ave been studied using the bond-fluctuation model. Above the Theta-tem perature the deformation is controlled by the entropy. In contrast to that far below the Theta-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-str and coexistence the total force, as well as its energetic and entropic parts, is independent of the extension. At large strains or higher te mperatures the coil-strand system becomes unstable and the energy loos es its dominance. During the disintegration of the coil-strand system the energetic part of the force exceeds the total force by a large ext ent and the entropic part of the force reaches pronounced negative val ues.