Breaking in polymer chains. II. The Lennard-Jones chain

Extensive simulations were performed in order to determine the conditions under which an anharmonic chain will break. The dynamics of a rectilinear chain of 100 monomers interacting via a Lennard-Jones potential were followed by solving a set of simultaneous Langevin equations. There are two principal results from this study. First, in order for irreversible breaking to occur in a stretched chain, a bond must be extended to a length considerably greater than the length at which the restoring force is maximized. Second, the breaking rate of a bond may be expressed in terms of the product of an attempt frequency and an Arrhenius factor. While the Arrhenius factor may be satisfactorily described in terms of the height of an effective energy barrier, the attempt frequency is found to be several orders of magnitude smaller than the dominant phonon frequencies.