Light-Driven, Reversible Spatiotemporal Control of Dynamic Covalent Polymers.

Dynamic covalent polymer networks exhibit a cross-linked structure like conventional thermosets and elastomers, although their topology can be reorganized through externally triggered bond exchange reactions. This characteristic enables a unique combination of repairability, recyclability and dimensional stability, crucial for a sustainable industrial economy. Herein the application of a photoswitchable nitrogen superbase is reported for the spatially resolved and reversible control over dynamic bond exchange within a thiol-ene photopolymer. By the exposure to UV or visible light, the associative exchange between thioester links and thiol groups is successfully gained control over, and thereby the macroscopic mechanical material properties, in a locally controlled manner. Consequently, the resulting reorganization of the global network topology enables to utilize this material for previously unrealizable advanced applications such as spatially resolved, reversible reshaping as well as micro-imprinting over multiple steps. Finally, the presented concept contributes fundamentally to the evolution of dynamic polymers and provides universal applicability in covalent adaptable networks relying on a base-catalyzed exchange mechanism.