Fluorescent Organohydrogel with Thermal‐Induced Color Change for Anti‐counterfeiting

Dual-Mode Hydrogels with Structural and Fluorescent Colors toward Multistage Secure Information Encryption

Constructing an anti-counterfeiting material with non-interference dual optical modes is an effective way to improve information security. However, it remains challenging to achieve multistage secure information encryption due to the limited stimulus responsiveness and color tunability of the current dual-mode materials. Herein, a dual-mode hydrogel with both independently tunable structural and fluorescent colors toward multistage information encryption, is reported. In this hydrogel system, the rigid lamellar structure of poly(dodecylglyceryl itaconate) (pDGI) formed by shear flow-induced self-assembly provides the restricted domains wherein monomers undergo polymerization to form a hydrogel network, producing structural color. The introduction of fluorescent monomer 6-acrylamidopicolinate (6APA) as a complexation site provides the possibility of fluorescent color formation. The hydrogel's angle-dependent structural color can be controlled by adjusting the crosslinking density and water content. Additionally, the fluorescence color can be modulated by adjusting the ratio of lanthanide ions. Information of dual-mode can be displayed separately in different channels and synergistically overlayed to read the ultimate message. Thus, a multistage information encryption system based on this hydrogel is devised through the programed decryption process. This strategy holds tremendous potential as a platform for encrypting and safeguarding valuable and authentic information in the field of anti-counterfeiting.

Multifunctional Organohydrogels for pH-Responsive Fluorescent and Electrostimulus Writing

Hydrogels have attracted widespread attention in anticounterfeiting due to their unique physical/chemical properties and designability. However, hydrogels' poor mechanical properties and sluggish response to chemical stimuli pose challenges for their wide application. A fluorescent tough organohydrogel capable of freeform writing of information is reported in this work. By incorporation of the fluorescent monomer 7-methylacryloxy-4-methylcoumarin into the polyacrylamide network in a covalently cross-linked manner while intertwining with the carboxymethyl cellulose sodium network, a fluorescent tough organohydrogel with a dual-network structure is prepared. The organohydrogel shows acid-base-mediated adjustable fluorescence through the transformation of fluorescent monomers. Ion printing and electrical stimulation design achieved free information storage and encryption. In addition, the prepared organohydrogel has good antifreezing properties and can be encrypted and decrypted at subzero temperatures. The encrypted information in the organohydrogel can be read only after UV-light irradiation. These patterned fluorescent organohydrogels should find applications in protected message displays for improved information security.

High-contrast reversible multiple color-tunable solid luminescent ionic polymers for dynamic multilevel anti-counterfeiting

Dynamic color-tunable luminescent materials, which possess huge potential applications in advanced multilevel luminescence anti-counterfeiting, are of considerable interest. However, it remains challenging to develop simple high-contrast reversible multiple (triple or more than triple) color-tunable high-efficiency solid luminescent materials with low cost, facile synthesis, and good processability. Herein, by simply grafting charged multi-color AIEgen-based chromophores into polymers, a series of high-efficiency multiple color-tunable luminescent single ionic polymers are constructed through tuning feed ratios, counter anions and reaction solvents. Remarkably, some ionic polymers can not only achieve rare high-contrast reversible multiple color-tunable emission in solid states in response to different solvent stimuli, but also could realize excitation-dependent color-tunable emission. To the best of our knowledge, such charming multiple (triple or more than triple) color-tunable solid polymers responding to multiple external stimuli are still rare. Based on comparative studies of emission spectra, excitation spectra and fluorescence lifetimes before and after swelling, it could be inferred that solvent stimuli could induce microstructure changes of these ionic polymers and then change the aggregated-states of their corresponding AIE-active emission centers. Moreover, the different solvent stimuli could induce to produce different degrees of microstructure changes, resulting in their unique multiple color-tunable emission. More significantly, these smart color-tunable ionic polymers show great promise for applications in dynamic multilevel (three-level or even more than three-level) anti-counterfeiting.

Recent Progress in Smart Polymeric Gel-Based Information Storage for Anti-Counterfeiting

Information security protection has a tremendous impact on human life, social stability and national security, leading to the rapid development of anti-counterfeiting materials and related techniques. However, the traditional stored information on hard or dry media is often static and lacks functions, which makes it challenging to deal with increasing and powerful counterfeiting technologies. Modified intelligent polymeric gels exhibit color changes and shape morphing under external stimuli, which give them great potential for applications in information storage. This paper provides an overview of the latest progress in polymeric gel-based information storage materials in relation to counterfeiting. Following a brief introduction of anti-counterfeiting materials, the preparation methods for intelligent gels with adjustable colors (e.g., chemical colors and physical colors) and various encryption/decryption modes involving dimensions and diverse colors are outlined. Finally, the challenges and prospects for information storage and anti-counterfeiting based on smart gels are discussed.

Data storage and encryption with a high security level based on molecular configurational isomers

Developing advanced materials for highly secure data-encryption is crucial but very challenging, as most data-encryption materials (the message area) are chemically different from the substrates (the background) on which they are being written, leading to high risks of data leakage by deciphering via sophisticated instrumental analysis. Additionally, most materials require only one stimulus for decryption, resulting in a low-level of data-security. Here, a three configurational isomer-based data-encryption method is developed (i.e., propylamine, isopropylamine, and cyclopropylamine). Their similar molecular formulae, elemental constitution, and physiochemical properties make them ideal date-encryption materials. On the other hand, the significant differences in lower critical solution temperatures (LCST) of the corresponding polyacrylamides, i.e., 10 °C for poly(N-propylacrylamide), 32 °C for poly(N-isopropylacrylamide), and 53 °C for poly(N-cyclopropylacrylamide), respectively, render an effective method for data decryption. Relying on the above features, the data written by three isomers are well-hidden under given conditions. And a specific temperature range, rather than a simple temperature increase or decrease, would be required for decryption. Furthermore, undesired temperatures give wrong outputs, which is highly deceptive to the hacker. Therefore, a high-level of data security can be achieved. This result opens a new door for designing advanced materials for improving the data-security level.