Tunable Rhodamine Mechanophores: Designing a Mechanochromic Platform for Stress Mapping in Polymeric Materials

Mechanophores enable optical property switching in response to mechanical force, offering a powerful platform for stress visualization. Among emerging mechanophores, rhodamine mechanophores have garnered significant interest due to long emission wavelengths, high quantum efficiency, and excellent photostability. However, tuning their mechanochromic properties remains a significant challenge. Herein, we report a general method to modulate the mechanochromic behaviors of rhodamine mechanophores. The mechanochromic behavior, including the emission wavelength, strain threshold, force sensitivity, and fading kinetics, can be tailored by substituting or extending conjugation on the xanthene backbone of rhodamine dyes. Further experiments show that the tunable force sensitivity of mechanophores enables high-quality mapping for a wide range of stress in the polymeric materials. Our work provides a powerful platform for developing stress mapping molecular tools for the polymeric materials.