Reversibly Interlocked Polymer Networks: Design, Preparation and Applications

Combining different polymers together to obtain multi-component polymer systems is an important and effective method for developing novel polymeric materials and regulating their properties. However, the synergistic effect between different components can hardly play its full role because of the ubiquitous phase separation. To solve this problem, we developed a novel strategy to prepare multi-component polymer systems as follows, in which phase separation can be suppressed. Firstly, two covalent adaptive networks respectively containing orthogonal reversible covalent bonds were synthesized. Next, the two single networks were dissolved in a co-solvent under proper stimulus as a result of the reversible reactions of the included reversible bonds. Accordingly, the solutions with the fragments of the single networks can be well mixed, and the latter were allowed to be reconstructed together through topological rearrangement with the assistance of inter-component secondary interactions during removal of the stimulus and co-solvent. Eventually, co-networks with relative independence, i. e. reversibly interlocked polymer networks, were obtained. Owing to the forced miscibility effect induced by the interlocked structure, even immiscible polymer pairs can be homogeneously interlaced with each other. In this context, there would be more freedom to choose the raw materials, and versatile multi-component polymer systems with high performance and novel functionalities can be developed. The paper introduces the material design and general preparation method of reversibly interlocked polymer networks. Afterwards, the structural features of the interlocked polymer networks, and a few applications of this type of material, including enhancement and regulation of mechanical properties, wide pH range underwater self-healability, improvement of intrinsic thermal conductivity, optimization of polymeric solid phase electrolyte, and controllable isolation/degradation and close-loop recycling of multi-component polymer systems, are discussed. Lastly, the difference between the interlocked networks and interpenetrating polymer networks (IPNs) is analyzed, and the future development in this aspect is prospected.