Control of Crystallinity and Deformation in Polymer Networks Using Thiol-Thioester Dynamic Chemistry

Covalent adaptable networks (CANs) leverage exchangeable bonds to enable reconfigurability of cross-linked polymer networks. While several CANs systems have been developed containing a myriad of materials properties and capabilities ranging from soft dynamic cell scaffolds to rigid shape memory devices, new platforms are needed to exploit bond exchange to control material behavior. Towards this goal, we incorporated exchangeable thioester bonds into semi-crystalline thiol-ene networks to form tough and strong thermoplastics that can be dynamically reconfigured in the presence of catalytic nucleophiles via thiol-thioester exchange. By tailoring network composition and catalyst strength, we explore the interplay between bond exchange and crystallinity and how these processes can be used to program anisotropic crystallization under applied stress. Furthermore, we use these insights to construct shape-memory materials by leveraging directed crystallization and melting to drive controlled deformation. Finally, we show that the incorporation of photolatent catalysts affords spatiotemporal control over exchange and crystallization dynamics and enables hands-free manipulation and actuation.