Dynamical Monte Carlo study of equilibrium polymers: Effects of high density and ring formation

An off-lattice Monte Carlo algorithm for solutions of equilibrium polymers (EPs) is proposed. At low and moderate densities this is shown to reproduce faithfully the (static) properties found recently for flexible Linear EPs using a lattice model. The molecular weight distribution (MWD) is well desc ribed in the dilute limit by a Schultz-Zimm distribution and becomes purely exponential in the semidilute limit. Additionally, very concentrated molte n systems are studied. The MWD remains a pure exponential in contrast to re cent claims. The mean chain mass is found to increase faster with density t han in the semidilute regime due to additional entropic interactions genera ted by the dense packing of spheres. We also consider systems in which the formation of rings is allowed so that both the linear chains and the rings compete for the monomers. In agreement with earlier predictions the MWD of the rings reveals a strong singularity whereas the MWD of the coexisting li near chains remains essentially unaffected.