Mechanochromic polymers based on radical-type dynamic covalent chemistry

Polymer mechanochemistry has emerged as a field of considerable interest from both an academic and an industrial perspective. Mechanochromic polymers that show optical change in response to mechanical stimuli can be used to visualize the mechanical force applied to the materials, which provides a wide range of information from the nano- to the macroscale, and also enables damage detection to prevent critical failure of the materials. We have explored a wide variety of radical-type dynamic covalent chemistry in the field of polymer reactions and revealed its great potential in developing mechanochromic materials. This account describes our recent efforts in the precise design of mechanochromic polymers based on radical-type dynamic covalent chemistry to impart polymeric materials with bespoke chromic properties, and discusses their characteristics derived from the radical chemistry as well as potential applications. Graphical Abstract Mechanochromic polymers have emerged as a subject of considerable interest due to their capability of detecting damage in materials before they experience critical failure. Among the various approaches, radical-type dynamic covalent chemistry has demonstrated great potential in developing mechanoresponsive chromic materials. This chemistry involves simple homolysis and radical-radical coupling reactions, which eliminate the need for catalysts and the formation of by-products, and leads to observable color changes. Recent investigations have shed light on the significance of mechanophore design and precise control of the polymer structure to impart polymeric materials with the desired chromic properties. This account provides an overview of our research on radical-type mechanochromic polymers spanning approximately a decade, highlighting the advancements and potential applications in this field.