Rational control of viscoelastic properties in multicomponent associative polymer networks

We report here the formation and dynamic mechanical properties of metallo-supramolecular networks formed by mixtures of bis-Pd(II) and Pt(II) cross-linkers with poly(4-vinylpyridine) in DMSO. Precise control over the dynamic mechanical properties of the bulk materials is achieved through the dissociation kinetics of the metal-ligand coordination bond responsible for cross-linking, the density of the cross-links, and the relative amounts of multiple cross-links. In networks formed from multiple types of cross-linkers, discrete contributions from each type of cross-linker are evident in the bulk mechanical properties, rather than an average of the contributing species. The heterogeneous rheology is consistent with simple models, to the extent that complex viscoelastic responses can be rationally engineered.