With the rapid development of information technology, data security has become a long-term global challenge, particularly in commercial and military fields. To address this challenge, various data protection materials have been developed. Among them, stimuli-responsive polymer materials have gained widespread attention due to their intelligent response to external stimuli and the advantage of being scalable for large-area fabrication. These materials can adjust their response characteristics by modifying the polymer chain structure or introducing specific functional groups, offering broad application prospects in the field of information security. Time-gated data encryption and dynamic multicolor anti-counterfeiting are two effective information protection strategies. However, traditional stimuli-responsive polymer materials often face challenges in achieving both functionalities simultaneously due to complex component assemblies or mutual interference.

In a study published in Angewandte Chemie International Edition, a research team led by HUANG Weiguo and FENG Shiyu from Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, developed a spiropyran-based stimuli-responsive polymer by designing the polymer structure and selecting appropriate molecules, thereby achieving both time-gated encryption and dynamic multicolor anti-counterfeiting capabilities, with great potential for advanced encryption and anti-counterfeiting applications.

The researchers synthesized a stimuli-responsive polymer material, pPFPA-co-SP, by covalently attaching spiropyran molecules (SP) to a crosslink density-tunable poly(pentafluorophenyl acrylate) (pPFPA) network. This material is not only sensitive to light and heat but also responds to acidic and basic stimuli. It exhibits excellent reversible photochromic and thermochromic properties in both solution and solid states.

By employing varying amounts of diamine crosslinkers, the researchers carried out aminolysis of the pentafluorophenyl ester side groups in pPFPA-co-SP, creating a polymer network with tunable crosslink density, which enabled the regulation of the isomerization rate between the SP and MC states of the spiropyran units. By adjusting the crosslink density, the researchers developed three types of copolymer inks with different fading rates, achieving time-gated data encryption. This allows correct information to be readable only within a specific time frame, while incorrect information is displayed at other times, significantly enhancing the security and concealment of encrypted data.

Furthermore, the researchers introduced a fluorescent probe, PTF1, which is sensitive to the rigidity of the polymer, and combined it with the multi-stimuli responsiveness of the pPFPA-co-SP polymer. This enabled dynamic, time-regulated multicolor anti-counterfeiting and was successfully applied to full-color transient information display and time-dependent pattern anti-counterfeiting.

This study utilizes the synergistic response of the spiropyran and PTF1 molecules to the rigidity of the polymer network. Through a “one stone, two birds” strategy, the researchers developed a multifunctional polymer that simultaneously achieves time-gated data encryption and dynamic multicolor anti-counterfeiting. This work overcomes the limitations of conventional responsive materials and provides new insights into the design of stimuli-responsive polymers.

Molecular Structure of Copolymer pPFPA-co-SP, Time-Gated Encryption, and Dynamic Multicolor Anti-Counterfeiting Schematic (Image by Prof. HUANG’s group)

Contact:

Prof. HUANG Weiguo

Fujian Institute of Research on the Structure of Matter

Chinese Academy of Sciences

Email: whuang@fjirsm.ac.cn