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Hybrid phenol-rhodamine dye based mechanochromic double network hydrogels with tunable stress sensitivity.

Mechanochromic hydrogels, which can switch their color in response to the applied external force, have shown great potential in the stress visualization and damage indication. However, the kinds of the colors in the reported mechanochromic hydrogels are limited. It is challenging to develop the mechanochromic hydrogels with new kinds of color change. Herein, we report a kind of mechanochromic double network (DN) hydrogel based on the hybrid phenol-rhodamine (HPR) mechanophore. The hydrogels turn into orange color with an emission wavelength of around 566/574 nm in response to tensile and compressive stress. The DN hydrogels show great reversibility. The color of DN hydrogels vanishes slowly after releasing the stress. The stress sensitivity can be tailored by the crosslinking density and the mechanophore concentration of the first network. In addition, the influence of the pH on the mechanochromic properties of DN hydrogels is also studied. This study provides an insightful study in tuning the stress sensitivity in the mechanochromic hydrogel, which would be beneficial for the development of the mechanochromic materials. This article is protected by copyright. All rights reserved.