We cannot decouple the contributions of 𝐺 + and 𝜏 -on the 𝜂 + of the material, since the cross-linker dynamics for the polymer networks (except the Ni 2+ His3 networks) are too fast for 𝜔 -to be measurable on the rheometer even at 𝑇 = 5 , 𝐶. Thus, we are not able to decouple the hierarchies of thermodynamic affinity and kinetic stability of the different histamine-M 2+ complexes which give rise to the different dissociation times. Nevertheless, we hypothesize that the observed 𝜂 + is dominated by the thermodynamic affinity of the histamine-M 2+ complexes (i.e. Δ𝐺 + in Fig. ). This is because the binding of histamine with these transition metals is spontaneous and occurs within seconds, evidenced by the rapid gelation of the system. Since the forward reaction is rapid, the forward activation energy 𝐸 1 should be small, and thus we expect Δ𝐺 + to be similar to the reverse activation energy 𝐸 0 (or at the very least, scale in a similar manner).