Chain Dynamics in Supramolecular Polymer Networks

Supramolecular polymer networks consist of macromolecules that are cross-linked by transient physical interactions such as hydrogen bonding or transition metal complexation. The utility of these networks is based on their mechanical properties, which lay between those of permanent networks and that of mechanically entangled, viscoelastic polymer solutions, depending on the strength of transient chain cross-linking. To benefit from this interplay, it is necessary to understand it. To promote this understanding, we use a modular toolkit to form supramolecular polymer networks that exhibit greatly varying strength of transient chain cross-linking but that are all derived from the very same precursor polymer. This strategy allows the impact of the strength of transient chain cross-linking on the network dynamics and mechanics to be studied with high consistency. We follow this approach to evaluate the diffusive mobility of labeled tracer chains within these transient networks. Our results reveal that the concentration dependence of the tracer-chain diffusivity is in agreement with theoretical predictions derived from the "sticky reptation" model by Rubinstein and Semenov, provided the chain association is stronger than a certain threshold.