Topology effects on associative polymers

Tailoring the topology of associative polymers offers a means to control macromolecular responses that in turn enables the design of new responsive soft materials. The current study probes the conformation and response of ring associative polymers in comparison with their entangled linear analogues using molecular dynamics simulations of a coarse-grained bead-spring model. The uniqueness of ring polymers lies in their topology where the chains have no free ends, resulting in considerably faster dynamics compared to their linear analogs, whereas the associative groups drive assembly that constrains the polymer motion. Here, polymers consisting of randomly distributed associative groups, with a fraction <i>f</i> = 0.02 to 0.1 and interaction strength varying from 2 to 8<i>k</i>_B<i>T</i>, were studied. We find that with increasing <i>f</i> and association strength, larger clusters of associative groups are formed, where their size and dynamics are strongly affected by chain topology. While the associative groups do not impact the chain conformation, they slow stress relaxation, with a distinctively stronger effect on the linear chains. This is attributed to the lower number of unique chains associated with clusters of the same size in ring melts compared with linear ones. Overall, the coupling of associating groups with entanglements results in slower stress relaxation, where the distinctive topologies affect the association of the chains.