In Situ Reversible and Robust Mechano-Responsive Ultralong Phosphorescence of Polyurethane Elastomer

Though mechano-responsive luminescent materials obtained much attention, most of their responses are non-reversible, let alone in situ reversible. Here, the study presents a new strategy to push through this limitation for their applications, which relies on the reversible mechano-responsive (MR) hydrogen bonding interactions and polymer chain orientation among a doped polyurethane (PU) elastomer. The radiative and nonradiative transitions inside these phosphorescent triphenylene-based aromatic secondary amines (TpNP and TpNPO) doped in the PU matrix can be accordingly modulated by these MR variations, including the PU chains orientation and the interactions between emitters and PU, respectively. Surprisingly, the intensities, quantum yields, and even lifetimes of their ultralong phosphorescence correlate well with the stress of PU, showing triple mechano-enhancement with a small threshold value of 7.9 MPa. Importantly, these in situ and rapidly reversible MR phosphorescences possess excellent repeatability, which is still displayed even after >500 cycles of loading/unloading. Based on such a robust and highly sensitive MR afterglow, these PU materials have been demonstrated applications with no interruption of background in several fields, including micro-crack detection, material damage prediction, limb movement monitoring, and information encryption. This work provides new insights for developing innovative ultralong phosphorescence materials with improved luminescence and reversible mechano-responsive behavior.