Mechanochromism and Mechanical‐Force‐Triggered Cross‐Linking from a Single Reactive Moiety Incorporated into Polymer Chains

Incorporation of small reactive moieties, the reactivity of which depends on externally imposed load (so‐called mechanophores) into polymer chains offers access to a broad range of stress‐responsive materials. Here, we report that polymers incorporating spirothiopyran (STP) manifest both green mechanochromism and load‐induced addition reactions in solution and solid. Stretching a macromolecule containing colorless STP converts it into green thiomerocyanine (TMC), the mechanically activated thiolate moiety of which undergoes rapid thiol–ene click reactions with certain reactive C=C bonds to form a graft or a cross‐link. The unique dual mechanochemical response of STP makes it of potentially great utility both for the design of new stress‐responsive materials and for fundamental studies in polymer physics, for example, the dynamics of physical and mechanochemical remodeling of loaded materials.