Kinetics of Dissolving Metal-Ligand Coordinated Dynamic Network in PDMS

Polydimethylsiloxane (PDMS) with metal-ligand coordinating bonds has shown exceptional mechanical properties like high stretchability and toughness, combined with advanced properties like self-healing and tunable stress relaxation. Being able to dissolve the network and reclaim PDMS is important, allowing us both to retrieve expensive metal ions at material's end-of-life and change properties by inserting different ions. Yet methods to realize metal removal without chemical change are unclear. We present a decantation-like method to measure the dissolution kinetics of metal-ligand coordinating network while preserving the PDMS chemical integrity. We find a similar dissolution rate regardless of dramatic mechanical response changes caused by different counterions. Compared to our reference zinc coordinated polymer, copper and higher molecular weight are shown to slow down dissolution process, while cobalt completely prevents it. The novel experimental method and results can lead to guidelines for design of dynamically adaptable metal-ligand coordination networks and specifically, for reclaimable PDMS.