American Chemical Society
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Solvent-Triggered Chemical Recycling of Ion-Conductive and Self-Healable Polyurethane Covalent Adaptive Networks

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journal contribution
posted on 2023-12-22, 02:43 authored by Jihong Lyu, Gyujin Song, Hyocheol Jung, Young Il Park, Sang-Ho Lee, Ji-Eun Jeong, Jin Chul Kim
Given the substantial environmental challenge posed by global plastic waste, recycling technology for thermosetting polymers has become a huge research topic in the polymer industry. Covalent adaptive networks (CANs), which can reversibly dissociate and reconstruct their network structure, represent a key technology for the self-healing, reprocessing, and recycling of thermosetting polymers. In the present study, we introduce a new series of polyurethane CANs whose network structure can dissociate via the self-catalyzed formation of dithiolane from the CANs’ polydisulfide linkages when the CANs are treated in N,N-dimethylformamide (DMF) or dimethyl sulfoxide at 60 °C for 1 h. More interestingly, we found that this network dissociation even occurs in tetrahydrofuran–DMF solvent mixtures with low DMF concentrations. This feature enables a reduction in the use of high-boiling, toxic polar aprotic solvents. The dissociated network structure of the CANs was reconstructed under UV light at 365 nm with a high yield via ring-opening polydisulfide linkage formation from dithiolane pendant groups. These CAN films, which were prepared by a sequential organic synthesis and polymerization process, exhibited high thermal stability and good mechanical properties, recyclability, and self-healing performance. When lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt was added to the CAN films, the films exhibited a maximum ion conductivity of 7.48 × 10–4 S cm–1 because of the contribution of the high concentration of the pendant ethylene carbonate group in the CANs. The ion-conducting CAN films also showed excellent recyclability and a self-healing performance.