Tunable Mechanical and Dynamic Properties via Cross-Linker Length in Bis(hindered amino)Disulfide-Based Covalent...

Conventional cross-linked polymers are not recyclable or reprocessable due to the formation of permanent cross-links. Covalent adaptable networks (CANs) based on dynamic covalent chemistry attract great attention as materials that exhibit excellent stress relaxation, recyclability, reprocessability, and self-healing properties. Controlling the dynamic properties of CANs is important for both fundamental science and practical applications. Here, we report the relationship between the dynamic properties and the cross-linker length of CANs with bis(hindered amino)disulfide linkages introduced at the cross-link points. Viscoelasticity measurements, tensile tests, and reprocessing tests reveal that polymer-chain mobility and reprocessing rate increase with increasing cross-linker length. Furthermore, stress relaxation and reprocessing tests suggest that cross-linker length does not affect the flow activation energy but influences the reprocessing rate. These findings indicate that adjusting cross-linker length is an important factor in designing CAN-based materials with target dynamic properties.