Elongational flow response of associative ring polymer melts.

Abstract

From polymers and biosystems to micelles and liquid crystals, when exposed to flow fields, soft matter exhibits fascinating responses leading to distinct structures. Here, using coarse-grained molecular dynamics simulations, we probe the flow response of compressible, associative ring polymer melts as the strength of the associative groups is varied; systems in which both the absence of ends and the interaction strength of the associative groups affect the motion of the macromolecules. Ring polymers with randomly distributed associating groups along the backbone with interaction strengths ranging from 1 to 8 <i>k</i>_B<i>T</i>, were studied over a broad range of accessible flow rates. Similar to their linear analogs, clusters of the associative beads break and reform into multiple groups, affecting their macroscopic properties. In contrast to linear chains, the flow viscosity and density are affected not only by the response of clusters of associating groups to flow, but also by topological links arising from the chains' topology. Overall, we show that the macroscopic response of these melts is a convoluted function of the strength of interchain interactions and the unique topological constraints resulting from the ring structure.