Multipotent Elastomers via Tempering of Phase-Separated Dynamic Covalent Networks

Inspired by the concept of multipotent stem cells, this research explores the use of tempering to program the mechanical properties of elastomeric dynamic covalent networks (DCNs) that contain thia-Michael bonds. These DCNs are composed of benzalcyanoacetate-based Michael acceptors and thiol-functionalized poly(ethylene glycol) (PEG) derivatives of varying molecular weights and architectures. The impacts of tempering on the thia-Michael adduct formation and dynamic reaction-induced phase separation (DRIPS) morphology were investigated by Raman spectroscopy and atomic force microscopy. Uniaxial tensile testing revealed that increasing the tempering temperature reduced the Young's modulus and maximum stress while maintaining high elastic recovery and low energy dissipation as evidenced by cyclic loading-unloading experiments. The tempering process is completely reversible, and retempering the film at a different temperature allows the mechanical properties to be tuned. These findings establish a simple, reprogrammable strategy to access multipotent elastomers from a single feedstock through tempering of thia-Michael-based dynamic covalent networks.