Donor-Acceptor Stenhouse Adducts as Intrinsically Photoswitchable Dynamic Covalent Bonds

Combining dynamic covalent bonds with photoswitches allows the kinetics and thermodynamics of exchange to be controlled with light. However, this two-component strategy introduces synthetic and compatibility challenges. Here, we present a single-component strategy using donor-acceptor Stenhouse adducts (DASAs) as both the photoswitch and the dynamic covalent bond. DASAs isomerize from "open" to "closed" forms with light and heat, respectively. We discovered that open DASA isomers undergo dynamic covalent exchange of their amine donor via two pathways, reversible dissociation and conjugate transamination. Exchange can then be arrested upon irradiation to form the closed DASA isomer, offering a handle to gate dynamic behavior. Consequently, incorporating DASAs as cross-linkers in PDMS-based networks yields covalent adaptable networks (CANs) with viscoelastic behavior that can be tuned by light. We also identify degradation pathways that limit the reversibility of this system under extended heating. Overall, DASA exchange represents a synthetically accessible platform for photocontrolled soft materials. More broadly, this work introduces DASAs as a new class of intrinsically photoswitchable dynamic covalent bonds and lays the foundation for the discovery of other stimuli-gated dynamic bonds that combine reactivity and responsiveness in a single molecular unit.