Thermal Guanidine Metathesis for Covalent Adaptable Networks
Alberto J. Melchor Bañales, Michael B. Larsen
Abstract
We demonstrate that a dynamic chemical reaction that we term thermal guanidine metathesis (TGM) can serve as the basis for covalent adaptable network (CAN) materials. CANs are a class of cross-linked polymers that transition from thermoset to thermoplastic-like rheological behavior upon significant activation of reversible exchange reactions within the network and thus can be reprocessed. Small molecule studies indicate the TGM reaction proceeds by a dissociative mechanism, and guanidine-cross-linked network polymers can be reprocessed at elevated temperature. These TGM-based CANs exhibit dynamic behavior, such as dissolution in the presence of monofunctional exchange partners and stress relaxation above Tg. Additionally, differences in the activation energies obtained by small molecule kinetic studies and stress relaxation analysis are consistent with key predictions of the Semenov–Rubinstein model of thermoreversible gelation of highly cross-linked networks.