Relaxation and Dynamics in Transient Polymer Model Networks

Supramolecular polymer networks have promising potential to serve as self-healing soft materials. To benefit from this ability, quantitative understanding of the underlying mechanisms of macromolecular dynamics and transient association must be achieved. A key to obtaining such understanding is to understand the dynamics and relaxation of supramolecular polymer networks, which is often complexed by inhomogeneous polymer-network structures. To overcome this limitation, we use a set of regular star-shaped poly(ethylene glycol) polymers end-capped with terpyridine groups that can transiently coordinate to different metal ions, thereby forming transient supramolecular polymer networks with determined homogeneous architectures and determined binding strength. We study these networks in view of their mechanics, dynamics, and from both macroscopic and microscopic perspectives through the use of rheology, dynamic light scattering, and fluorescence recovery after photobleaching. These studies reveal that whereas in a long-term average the networks exhibit percolated connectivity, temporal detachment of one of the arms of the star-polymer building blocks allows for their relocation within the networks, entailing relaxation and flow on long time scales.