Highly stretchable covalent adaptive networks enabled by dynamic boronic diester linkages with nitrogen→boron coordination

Covalent adaptive networks (CANs), which can be topologically rearranged, are of remarkable versatility. Here, the collaboration of dynamic boronic diester linkages with nitrogen -> boron coordination was used to develop catalyst-free, highly stretchable CANs. The CANs with different cross-link densities were prepared via one-pot synthesis of poly(propylene glycol) diglycidyl ether, 3-amino-1,2-propanediol and benzene-1,4-diboronic acid. They were found thermorheologically simple, of which the linear viscoelasticity obeyed the principle of time-temperature superposition. Their topological rearrangements activated by the reshuffling of dynamic linkages was slowed down, while the activation energy on complex viscosity decreased with increasing the cross-link density. The CANs demonstrated great stretchability, malleability and self-healing ability, which could be stretched to 15,000x its original length with no break at a strain rate up to 33.3 min(-1). Furthermore, the reshuffling of dynamic linkages contributed to efficient energy dissipation with a maximum efficiency of 91% at room temperature.

Automated summary

Covalent adaptive networks (CANs) are topologically rearrangeable and versatile, with high stretchability and self-healing ability. The collaboration of dynamic boronic diester linkages with nitrogen -> boron coordination enables the development of catalyst-free, highly stretchable CANs. CANs exhibit simple thermorheology with topological rearrangements activated by the reshuffling of dynamic linkages.