For a system following the Maxwell model of viscoelasticity (Fig. ), the zero-shear viscosity 𝜂 + of a material is a function of the network elasticity 𝐺 + and the characteristic cross-over time 𝜏 -, such that 𝜂 + = 𝐺 + 𝜏 -. Here, we can recognize that 𝐺 + depends on the density of cross-links in the network (𝜌) and that 𝜏 -depends both on the dissociation rate (𝑘 / ) of the cross-links as well as 𝜌. Thus, we can surmise that 𝜂 + in our network is dependent on both 𝜌 and 𝑘 / of the crosslinking interactions. 𝜌 is a quantity related to the static equilibrium concentration of the cross-links, and thus related to the stability constant 𝐾, which is a measure of the thermodynamic free energy change Δ𝐺 + of the forward binding process between the metals and the histamine ligands. In contrast, 𝑘 / is a measure of the kinetic activation energy of the reverse binding process, 𝐸 0 (Fig. ).