Mechanochemical Activation of a Metal–Organic Framework Embedded within a Thermoplastic Polyurethane Matrix: Probing Fluorogenic Stress‐Sensing

Abstract

AbstractHere, a mechanochemically triggered Cu(I) bis(N‐heterocyclic carbene [NHC))‐based metal–organic framwork (MOF) embedded into a thermoplastic polyurethane (TPU)‐matrix is reported. The induced fluorogenic copper‐catalyzed azide–alkyne cycloaddition (CuAAC) reveals the stressed parts within the thermoplastic PU via a simple optical detection. As determined via oscillating tensile rheology on dumbbell‐shaped samples of TPU, a MOF, containing 4.66% copper, catalyzes the fluorogenic CuAAC between the nonfluorescent precursor dyes, 8‐azidonaphthalen‐2‐ol, and 3‐hydroxyphenylacetylene. After mechanical activation of the MOF situated inside the TPU, the fluorescent 8‐(4‐(3‐hydroxyphenyl)‐1,2,3‐triazol‐1‐yl)naphthalen‐2‐ol dye is formed. Monitoring the formation of the dye inside the TPU via fluorescence spectrometry at λex = 458 nm shows an increase of the fluorescence intensity up to 60–70%. It is demonstrated that a dumbbell‐shaped TPU, subjected to higher stress, displays higher fluorescence than the surrounding other areas, thus effectively functioning as a three‐in‐one stress‐sensor system.