Photo-gated polymer mechanochromism from excited-state intramolecular proton transfer

Controlled polymer mechanochromism has large potential for new applications. We design a novel ESIPT mechanophore (HBIA-2OH) by three-step synthesis. Connected to polyurethane, it shows unique photo-gated mechanochromism from excited-state intramolecular proton transfer (ESIPT) via photo-induced formation and force-induced breaking of the intramolecular hydrogen bonds. As a control, HBIA@PU experiences no response to photo/force. Thus, HBIA-2OH is a rare mechanophore featuring photo-gated mechanochromism.