Sequence-controlled dynamic covalent units enable decoupling of mechanical and self-healing performance of polymers

Abstract

Sequence regulation provides an effective approach to controlling the properties of polymer materials. However, this approach remains an open question in the field of dynamic polymers, which emerge as more and more important new generation materials. Herein, we systematically investigate the effect of sequence control of dynamic covalent units in tuning the properties of materials. Different sequence-controlled poly(oxime-urethanes) are designed. The dynamic oxime-urethane groups are relatively dispersed (SCP-1) or concentrated (SCP-2) distributed in their molecular chains. The sequence control strategy provides an efficient way to decouple the mechanical and self-healing performance of polymers, which is one of the most pressing challenges in the field. The relatively dispersed oxime-urethane groups in SCP-1 not only facilitate the reorganization of the dynamic covalent bonds but also increase the probability of the reformation of hydrogen bonds. The reversible dissociation/reassociation of dynamic bonds is conducive to dissipating energy to enhance mechanical performance and promote self-healing properties. As a result, SCP-1 exhibits much faster self-healing than SCP-2, and its tensile strength is nearly twice that of SCP-2. In addition, energy dissipation capacity and degradation behavior also show significant sequence dependence. Overall, this work reveals a new molecular structure-property relationship and provides a powerful strategy to construct high-performance polymers.