Shining under stress: hybrid coordination polymer as a multifunctional solution for mechanoluminochromic materials

Mechanochromic materials are studied as optical probes for mechanical stress in self-diagnostic devices. They rely on mechanoresponsive components undergoing structural changes (e.g. bond cleavage, conformational change, supramolecular rearrangement) upon application of a mechanical force. Depending on the active component, the state-of-the-art approaches face significant limitations: scarce optical changes, difficulty in detecting low stresses and deformation, response limited to specific deformation modes, and some lack scalability. This study proposes the use of mechanoluminochromic copper (I) iodide-based hybrid coordination polymers as a scalable and universal solution to achieve mechanoluminochromism across various polymer types and sensitivity to all deformation modes. [(CuI)3-Br-py]n is used as additive for developing highly sensitive mechanoluminochromic polymeric materials responding to both in-plane and out-of-plane mechanical stresses, including tensile, compression, impact, and scratching. The strong and persistent mechanoluminochromic response is found to linearly correlate to the strain (under tensile deformation) and to the force (under impact), independent from the additive concentration, and tunable by the polymer matrix features.