A Chromic and Near-Infrared Emissive Mechanophore Serving as a Versatile Force Meter in Micelle-Hydrogel Composites.

Mechanofluorochromic polymers, which can indicate damage or excessive stress in highly polarized environments with a clearly perceptible optical signal, are potentially useful in a variety of exciting applications. However, most reported fluorochromic mechanophores exhibit poor color contrast and fluorescence penetration, or are irreversible in polarized phase after mechanical activation. Here, this challenge is tackled by designing and engineering a novel near-infrared (NIR) emissive, rhodanmin derived mechanophore (Rh-Co) in a kind of hydrogel composites. The ring-opened Rh-Co is unique in high molar extinction coefficient and bright NIR emission with such optical transition under force directly corresponding to covalent bond scission and reversibly switchable in an aqueous environment. The hydrogel composites thus can sensitively change their color from yellow to green and emit highly penetrated NIR fluorescence when different types of forces (tension, compression, and friction force) are applied, highlighting the potential applications of Rh-Co in biocompatible environments as a "force meter". [ABSTRACT FROM AUTHOR]