Super Strong and Tough Polybenzimidazole/Metal Ions Coordination Networks: Reinforcing Mechanism, Recyclability, and Anti‐Counterfeiting Applications

Nature has provided many delicate strategies for optimizing the structural characteristics of biological materials. One such strategy is the strengthening and toughening of matrix materials by aduandant and hierarchically arranged non-covalent crosslinking. However, efficient strengthening and toughening of high-performance aromatic polymers by non-covalent bonds has rarely been reported yet. Herein, we report the preparation and characterizations of a metal coordination bonds crosslinked polybenzimidazole (PBI) network. By optimizing the synthetic parameters, the strength of copper ion (Cu2+ ) crosslinked PBI is improved from 87.8 to 218.4 MPa, and the toughness is increased from 19.4 to 111.9 MJ m-3 , corresponding to increments of 148.7 % and 476.8 %, respectively, which surpass all previously reported non-covalent bonds crosslinked high-performance polymers. PBI with varied chain flexibility are then synthesized to deeply understand the stregnening and toughening mechanism. In addition, the glass transition temperature of PBI is dramatically increased by 75 °C after Cu2+ crosslinking. Moreover, the chemical recycling of PBI from crosslinekd network, and the development of a novel high-temperature resistant or high-temperature rewritable anti-counterfeiting films based on Cu2+ crosslinked PBI are also demonstrated. This study is expected to shed light on design principle for future supramolecularly crosslinked and recyclable high-performance polymers.