Structure and Chain Dynamics of Self-Healing Telechelic Polymer Networks

The development of self-healing materials, which are capable of reforming into their original structure following rupture and damage, represents a fascinating and important area of research, with a wide range of potential applications. Telechelic polymers, defined as polymers with functional chain ends such as hydrophobically end-modified polymers, serve as prime examples of systems capable of forming hydrogel networks with transient bonding structures. In this study, we investigate the internal chain dynamics and self-diffusion of hydrogel networks made from telechelic polymers, employing selective contrast variation for small-angle neutron scattering and neutron spin echo spectroscopy. We show that the chain dynamics in the gel follow regular Zimm dynamics without any apparent evidence of restricted motion due to chain connectivity, possibly because the lifetime of the bonds is short. On the other hand, the micellar cores show slow relaxation, reflecting the restricted motion due to the connectivity and crowdedness of the system. The study highlights the decoupling between the slow dynamics of the micellar cores, which play a critical role in the rheological response, and the fast, relatively unconstrained chain dynamics that contribute to their "self-healing" properties. The results provide detailed insight into the multiscale dynamics in hydrogels with transient bonds useful for applications of these types of materials, natural or synthetic.