Sticker Multivalency in Metallo-supramolecular Polymer Networks

Multivalency is a key concept in the supramolecular science; it allows an additive or even synergetic enhancement of association constants without the need to replace the basic binding motif. To understand the effects of multivalent binding on the mechanical and dynamic properties of metallo-supramolecular polymer gels, we investigate the concentration- and association strength-dependent linear viscoelasticity of two model systems in the semidilute regime, which are based on either telechelic star-poly(ethylene glycol)s (pEGs) or linear multiblock polyurethanes (PUs) with isolated, monotopic, or adjacent, ditopic terpyridine stickers. In the homogeneous star-pEG gels, the ditopic stickers increase the network strength at identical cross-linker concentrations through the formation of higher functional cross-linking junctions, whereas the mechanical enforcement of the partially clustered PU gels is less-pronounced. The ditopic stickers slow down the dynamics of both gel types to a similar extent by increasing the number of sticker-opening attempts required for network relaxation.