When writing chemical equations for reversible reactions, the usual one-way arrow is not used. Instead, two arrows are used, each with just half an arrowhead (⇌). The top one points right ...

Figure 1: Schematic of the reversible S–S bond formation and electronic reorganization within the cluster cage. Figure 4: Depiction of cluster 1 on a Au surface, generating an image charge.

Many reactions are irreversible. But in a reversible reaction, the products can react to produce the original reactants. At equilibrium, the concentrations of reactants and products do not change.

Their polymer is based on a network of reversible diketoenamine bonds formed in a ball mill using click chemistry reactions between triketones and polyamines like tris(2-aminoethyl)amine.