Elongational Flow of Ring Polymer Melts with Associating Groups

This study presents large-scale molecular dynamics simulations of associating ring polymer melts under elongational flow. Ring polymers are unique because they have no free ends and thus have very different behavior compared to their linear counterpart. Previous studies of elongational flow of ring polymer melts found that the rings form topological links that connect multiple chains, which lead to an unexpectedly large increase in the flow viscosity.  Here, using a coarse grain bead-spring model, we probe the response of ring polymers decorated with associate groups to extensional flow as the strength of the associative polymers is varied.  The fraction of associating groups was varied from 0.02 to 0.10, and association strength was varied from 1 – 8 k_BT.  We show that the chain stretching becomes more heterogeneous as the strength of the interaction between associating groups increases. In equilibrium, the associating groups form clusters, which increase in size as the strength of the associating groups increases. Under extensional flow, these clusters break up and reform only at very high associating strength. Even for a large interaction strength, some rings still form topological links, in which case the viscosity is due to a combination of these linked rings and the associating groups. This talk will further expound on the effect of flow on clustering, topological linking, and viscosity.