Mechanism for Energy Dissipation of Slide-Ring Elastomer Explored by Solid-State NMR and Rheology

Unconventional polymer networks (UPNs) have unique mechanical properties due to their special network structures, e.g., the rotaxane dissipates external energy during stretching through the sliding of the rings. In this work, we made a rubbery poly(thioctic acid) (PTA) network by a facile method cross-linked by rotaxanes, which were obtained by self-assembly of α-cyclodextrins (α-CDs) with poly(ethylene glycol) diacrylate (PEGDA). By master-curve from time–temperature superposition experiments and transient stress relaxation experiments, the consistent rheological behavior of slide-ring energy dissipation was found. The results of low-field solid-state nuclear magnetic resonance with an in situ stretching fixture suggested that 16.56% of the α-CDs could slide along the PEGDA chains during stretching, transforming from the rigid fraction to the relatively mobile fraction. The α-CDs threaded on PEGDA were verified by 1H–1H and 1H–13C high-field solid-state nuclear magnetic resonance experiments. Furthermore, the changes in the local dynamics due to the dipolar interaction of the α-CDs with PEGDA were identified by 2D proton wide-line separation experiments. This work provided a facile way to synthesize rotaxane-based elastomers, and the energy dissipation mechanism therein was clearly demonstrated, which may pave a new way to design UPNs with better energy dissipation.