(602h) Photoswitching Controlled Radical Polymerizations to Spatiotemporally Design Polymer Structures

Light-mediated 3D printing has gained significant interest due to the inherent advantages of light as external stimuli, including spatiotemporal control and easy access. Concurrently, there is an increased demand for novel chemistries that enable easy set-up and a broader spectrum of materials to be generated with pre-designed physical and chemical properties. As 3D printing processes require a rapid polymerization for practical applications, free radical or cationic polymerization methods are traditionally used. However, these polymerization reactions are highly exothermic, lead to immobilization of unreacted radical species within the network, resulting in mechanically weak structures, and are limited to the production of materials with properties that cannot be altered post-printing (i.e., not chemically reprocessable). Materials with mutable properties are useful as they can be recycled and repurposed for different applications via composition and shape change, repair, and chemical adhesion between chemically and mechanically distinct parts. The high chain-end fidelity of polymers synthesized via controlled radical polymerization (CRP) methods allows polymer networks to be reactivated and modified via post-functionalization. Despite many benefits of CRP techniques, slow polymerization rates and the general requirement for deoxygenation such as using a glovebox or freeze-pump-thaw degassing have placed significant limitations on widespread adaptation. This project reports the development of orthogonal chemistries based on photocontrolled CRP techniques for sustainable multimaterial 3D printing. This strategy leads to materials with discrete domains and mutable properties (i.e., properties that can be altered post-synthesis), allowing these materials to be recycled and repurposed via chemical processing.