Multimode information storage labels: light and temperature co-modulation based on photo-liquefiable crystal/waterborne polyurethane composites

The novel anti-counterfeiting label operates under synergistic logical modulation. • Multimode pattern storage relies on photo-liquefaction of azobenzene derivative. • Eco-friendly and crack-recovery composites show unique interfacial characteristic. Information storage labels that respond to multiple stimuli and enable multimode storage exhibit higher flexibility and security. However, this goal typically demands elaborate structural design and specialized storage strategies. In this study, a room-temperature photo-liquefiable crystal based on small-molecule azobenzene derivative was combined with an eco-friendly waterborne polyurethane (WPU) matrix, adopting the crystalline composite strategy. The results showed that the appropriate photo-liquefiable crystal can still retain sufficient solid-to-liquid phase transition ability in the encapsulated state, and can also solve the problem of leakage as well as the environmental pollution after liquefaction. The information storage labels fabricated from photo-liquefiable crystal and WPU matrix showed dual responsiveness to light and temperature, and featured multiple storage modes including short-term rewritable photochromic pattern storage mode and long-term anti-tampering light-scattering pattern storage mode, etc. It is presumably attributed to the synergistic effect between the photo-liquefiable crystal and WPU matrix. A variety of behaviors occurring within individual components and at their interfaces, including photochemical phase transition, interfacial microregional internal stress and polymer chain segment relaxation, jointly contribute to this effect. Furthermore, the information storage labels possessed intrinsic stimulus-responsive crack recovery ability, which further boosted the overall material properties. This study demonstrates the potential of the encapsulated photo-liquefiable crystal in information storage and provides a new strategy for synergistic interfacial regulation of composite materials. Download: Download high-res image (201KB) Download: Download full-size image