Decoding the linear viscoelastic properties of model telechelic metallo-supramolecular polymers

Zhuge, Flanco [UCL] Hawke, Laurence George Demosthenis [UCL] Fustin, Charles-André [UCL] Gohy, Jean-François [UCL] Van Ruymbeke, Evelyne [UCL]

This work focuses on the linear viscoelastic properties of entangled telechelic bulk metallo-supramolecular polymers. The latter are based on linear and star poly(n-butyl acrylate)s functionalized with a terpyridine ligand at each chain extremity, in the presence of transition metal ion of varying nature. The systems are investigated both experimentally and theoretically using small amplitude oscillatory shear and a modified version of the tube-based time marching algorithm (TMA), respectively. The experimental data reveal that sample relaxation depends on both disentanglement and association dynamics, with the respective importance of these two processes depending on the nature of the metal ion and on the temperature. A good description of the data is achieved using the modified TMA model, provided that dissociation events of metal-ligand complexes occur via ligand exchange. The model contains two fitting parameters, i.e., the fraction of unassociated stickers and the longest time needed in order to ensure that all the chains were dissociated at least once. This latter time is found to be independent of the chain architecture and is well described by an Arrhenius equation, which allows the derivation of the related activation energy. This work provides the necessary framework to explore other metallo-supramolecular networks, built from different chain architectures, and exploit the large richness of their dynamics.