A stable and high-contrast color/fluorescence dual-mode stimuli-responsive poly (imino sulfone) for anti-counterfeiting and encryption

Counterfeiting and information leakage have become critical global challenges, exacerbated by rapid technological advancements. This study presents a novel stimuli-responsive polymer, poly(imino sulfone) (PIS), synthesized via a simple C-N coupling reaction. The findings reveal that PIS exhibits fast, high-contrast, reversible color and fluorescence dual-mode stimuli-response, driven by the protonation-deprotonation of imine groups under varying acid-base conditions. Additionally, the rigid polymer structure, coupled with strong hydrogen bonding, imparts PIS excellent thermally stable (T_5% = 463 °C, T_g = 245 °C), surpassing other polymers with stimulus-responsive discoloration capabilities. Notably, even at low concentrations (0.1 wt%), PIS demonstrates strong emission performance and stimulus-induced color-change behavior. The information encoded using PIS can be efficiently and repeatedly encrypted and decrypted under acid-base stimuli, thereby enhancing the confidentiality and security of the information. When integrated into polymer matrices, PIS not only imparts quick, stable and reversible dual-mode stimulus-responsive behavior but also enhances the thermal and mechanical properties of the host materials. The resultant PIS-based patterns exhibit excellent anti-counterfeiting performance. These unique properties position PIS as a promising candidate for advanced anti-counterfeiting and encryption applications.