Dynamics of entangled metallosupramolecular polymer networks combining stickers with different lifetimes

Abstract

We study the linear viscoelastic properties of polymeric networks formed by poly(n-butyl acrylate) telechelic stars end-capped with 2,2:6,2″-terpyridine (Star-PnBA-tpy4) and two types of metal-ligand cross-links with different lifetimes. The influence of interactions, mediated by temperature, nature of metal ions, and ion content, on the linear viscoelastic behavior of both single and double dynamics transient networks is systematically investigated by small amplitude oscillatory shear and creep rheometry. The experimental results reveal that the dynamics of networks with two different metal-ligand cross-links is much faster than expected, characterized by the average sticker lifetime rather than a discrete contribution of each metal-ligand complex. We model the dynamics with the help of our modified tube-based time marching algorithm by accounting for both association/dissociation dynamics of metal-ligand coordination and the entanglement dynamics. Two parameters are defined in the model, namely, the proportion of dangling ends and the average time during which a sticker is free. This allows us to quantify the transient dynamics of the network and, in particular, to determine how the sticker dynamics depend on temperature and ion content.