A New Kind of Nonconventional Luminogen Based on Aliphatic Polyhydroxyurethane and Its Potential Application in Ink-Free Anticounterfeiting Printing

Abstract

Organic luminogens have extensive applications due to their unique photophysical properties. In recent years, nonconjugated organic luminogens, in contrast to traditional conjugated luminogens, have gained much attention because of their facile preparation, environmental friendliness, and biocompatibility. In this study, a new kind of nonconventional luminogen based on dynamic covalent cross-linked polyhydroxyurethane is reported for the first time. The new luminogen not only exhibits intrinsic strong fluorescent emission in the solid state but also possesses high mechanical properties along with good shape memory and self-healing properties. In addition, the new luminogens are synthesized from aliphatic polyfunctional cyclic carbonate and amines via a much more straightforward method, avoiding the use of toxic isocyanates. Investigations indicated that the intrinsic luminescence of the resultant luminogens was induced by the cross-linking of polymer chains and could be well tuned by controlling the degree of cross-linking. By taking advantage of the unique characteristics of the resultant polymer luminogens, we further developed a facile method, named "light-mediated ink-free screen printing", for anticounterfeiting paper fabrication. Different from traditional ink-based printing technology, the new method used UV-light instead of expensive security ink to encode anticounterfeiting information on natural cellulose paper. The anticounterfeiting information is stable under various wet conditions, showing promising applications in the fast-growing counterfeiting of pharmaceuticals, packaging, and the food industry.

Luminescence anti‐counterfeiting: From elementary to advanced

“…Recently, more and more materials with different luminescence modes have been applied into single‐level luminescence anti‐counterfeiting to improve the ability of single‐level luminescence anti‐counterfeiting and increase the difficulty of forgery. [ 19–34 ] According to the difference of luminescence modes, the single‐level luminescence anti‐counterfeiting can be divided into down‐conversion (DC) photoluminescence anti‐counterfeiting, [ 19,21–27,29,31 ] up‐conversion (UC) photoluminescence anti‐counterfeiting, [ 20,28,30,32,34 ] and chemiluminescence anti‐counterfeiting. [ 33 ]…”

“…DC photoluminescence anti‐counterfeiting is realized by absorbing one high‐energy photon and releasing one low‐energy photon. [ 35 ] At present, the materials used in single‐level DC photoluminescence anti‐counterfeiting include organic luminogens, [ 19 ] graphene quantum dots, [ 21 ] Ln‐carbon quantum dots, [ 22 ] cellulose nanofibrils/CdTe quantum dots, [ 23 ] carbon and oxygen co‐doped hexagonal boron nitride, [ 24 ] nitrogen‐doped carbon dots, [ 25 ] carbon dots/Ln‐MOFs hybrids, [ 26 ] Ln‐metal organic frameworks (Ln‐MOFs), [ 29 ] Tb 3+ /Eu 3+ ‐grafted melamine cyanurate, [ 31 ] and SrAl 2 O 4 :Eu 2+[ 36 ] . As shown in Figure 2A, Gao et al.…”

“…In addition, Feng et al. [ 19 ] adopted a kind of light‐mediated ink‐free screen‐printing technology to prepare a fluorescence anti‐counterfeiting label that was colorless under daylight, but displayed blue fluorescence under UV irradiation. This anti‐counterfeiting strategy was in favor of designing more complex anti‐counterfeiting patterns and decreasing cost by replacing expensive inks with UV lights.…”

Stimuli‐Responsive AIEgens

“…In fact, many nonaromatic systems such as poly[(maleic anhydride)‐ alt ‐(vinyl acetate)], poly(amidoamine), polypeptideshave, etc., have been found to exhibit attractive luminescence and this type of emission is described as clusteroluminescence. [ 128,129 ] As depicted in Figure a, the poly‐ l ‐proline (PPRO) film fluoresced quite weak purple light under 365 nm UV irradiation. [ 130 ] Interestingly, its emission could be gradually intensified when exerting pressure (set 1 and set 2).…”

Unique Property of Nontraditional Intrinsic Luminescence in the Transforming of Solution‐Hydrogel‐Solid and Its Applications

“…Unfortunately, although a lot of amine‐containing NTIL compounds including small molecules, oligomers, and polymers have been reported to possess remarkable fluorescence, [ 17–26 ] most of them were conducted in solution, and a few works in solid state. [ 9,27–29 ] Especially, a systematic research on the fluorescence variation from solution through gel to solid state has not been investigated.…”