A new multifunctional electrochromic material for hyperspectral stealth camouflage

Abstract

A kind of new multifunctional electrochromic material for hyperspectral stealth camouflage belongs to the technical field of hyperspectral stealth camouflage.The electrochromic material is composed of a core molecule and a functional branch connected to the active site of the core molecule, wherein the core molecule is 2,4,6-tris(4-pyridine)-1,3,5-triazine (TPT), and the triazine ring structure has abundant lone pair electrons, which increases the electron density and makes the grafting site have good reactivity, providing a good foundation for the integration of subsequent functional branches; the functional branch is composed of an anchoring branch, a color adjusting branch and a biomimetic branch, which are connected to the three active sites of the core molecule by covalent bond. The multifunctional electrochromic material is applied as an electrochromic layer in an electrochromic reflective device, and the dynamic spectral regulation ability and the biomimetic structure are deeply integrated through chemical bonding, which meets the demand of hyperspectral stealth in complex battlefield environment.

Description

Technical Field

[0001] This invention belongs to the field of hyperspectral stealth camouflage technology, specifically relating to a novel multifunctional electrochromic material for hyperspectral stealth camouflage. Background Technology

[0002] In recent years, the rapid development of hyperspectral detection technology has completely overturned the effectiveness of traditional camouflage systems. Hyperspectral equipment captures the fine spectral features of targets in the visible light (350-750 nm) and near-infrared (750-2500 nm) bands, forming a "spectral fingerprint." By combining image space with pixel-level spectral data, it can accurately identify "metachromatic" targets with a resolution of up to 10 nm.

[0003] In the complex and ever-changing battlefield environment, vegetation serves as a typical battlefield backdrop. Its unique spectral characteristics are manifested in several significant elements: the 550 nm visible light reflectance peak dominated by chlorophyll absorption, the "red edge effect" (a sudden increase in reflectance at 700-750 nm), the 850-1150 nm near-infrared plateau generated by the leaf porosity, and the 1450 / 1950 nm water absorption peaks regulated by leaf water content. Although traditional camouflage coatings can simulate visible light colors, they cannot reproduce the unique multi-level spectral characteristics of vegetation. This allows enemy satellites to easily detect targets with spectral anomalies through hyperspectral imaging, creating a "detect and destroy" situation. The application background of simulating plant hyperspectral camouflage emphasizes the adaptability of materials to two typical backgrounds: green leaves (spring and summer vegetation) and yellow leaves (autumn woodlands), to meet specific needs. Currently, biomimetic materials developed for specific backgrounds (such as a single yellow background) cannot achieve dynamic color changes. A color-changing hyperspectral camouflage material composed of thermochromic microcapsules and chromium titanium yellow pigment (Huang, Z.; Long, L.; Gao, Y.; Tang, Z.; Zhang, J.; Xu, K.; Ye, H.; Liu, MA Color-Changing Biomimetic Material Closely Resembling the Spectral Characteristics of Vegetation Foliage. Small 2024.) can achieve active camouflage against green and yellow leaf vegetation backgrounds. However, its application is limited by the need for an external temperature control device to trigger the color change in practical use. Researchers have also designed a biomimetic multilayer fiber material as a hyperspectral camouflage film (Jiang, C.; Wei, P.; Yuan, L.; Qing, X.; Ma, X.; Weng, X. An Intelligent Multi‐Band Camouflage Textile Inspired by Natural Leaves. Adv. Funct. Mater. 2025.), which can dynamically simulate the yellow and green states of natural leaves to achieve multi-band camouflage in vegetated environments. In a dry state, the film uses a precise pigment formulation to simulate the color and reflectance spectrum of yellow leaves, allowing it to blend into the background of autumn or arid vegetation. In a wet state, the film turns green, enabling it to evade visible light and hyperspectral detection against a forest or grassland background. However, the camouflage film exhibits significant deviations in its dry-state spectral simulation, resulting in excessively high near-infrared reflectance that makes it easily identifiable. Furthermore, its water dependence limits its application in arid environments.

[0004] The unique advantage of electrochromic materials lies in their ability to dynamically control spectral properties through electric field driving. Currently, while some progress has been made in hyperspectral dynamic camouflage materials based on electrochromism, their technological implementation largely relies on device architectures involving physical stacking or simple mixing of components. For example, a hyperspectral stealth camouflage electrochromic biomimetic leaf (publication number CN112198730B) uses a blend of Prussian blue and yellow dye to achieve a yellow-green transition, but the interface between the electrochromic dye and the porous nylon electrode relies solely on physical adsorption. Similarly, a color-changing film for hyperspectral stealth (publication number CN113606995A) constructs a color-changing layer by embedding viologen derivatives into a polyvinyl alcohol hydrogel. Although it can achieve green and black state switching to simulate the reflectance spectrum of vegetation and soil, the viologen molecules are trapped within the hydrogel pores solely through a physical cross-linking network. This makes it difficult to maintain molecular stability under long-term cycling or complex mechanical stress, leading to leakage or device failure, resulting in decreased optical performance and degraded camouflage function. Our research group has reported for the first time the research results combining electrochromic technology with the hyperspectral characteristics of plants (Tang, S.; Zhang, H.; Liu, Y.; Zheng, R.; Jia, C. Breakthrough in Anti-Reconnaissance Technology from a New Perspective: A Bio-Inspired Electrochromic Device with Hyperspectral Characteristics of Vegetation Foliage. Chemical Engineering Journal 2024.). The asymmetric violet molecules used in this study are usually dissolved in the electrolyte in a free state. Even with the use of a cellulose membrane as a structural support, the two still rely on weak interactions such as hydrogen bonds, which cannot maintain stable interfacial contact in complex and variable environments. Summary of the Invention

[0005] The purpose of this invention is to address the problems existing in the background technology by proposing a novel multifunctional electrochromic material for hyperspectral stealth camouflage. This invention provides a novel hyperspectral stealth camouflage material that combines anchoring substrate function with biomimetic color-changing properties. It is applied as an electrochromic layer in electrochromic reflective devices, deeply integrating dynamic spectral modulation capabilities (visible light color changing, near-infrared tuning, and water absorption peak simulation) with biomimetic structural support (microporous conductive gold film) through chemical bonding, thus adapting to the hyperspectral stealth requirements in complex battlefield environments.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A novel multifunctional electrochromic material for hyperspectral stealth camouflage is composed of a core molecule and functional side chains attached to the active sites of the core molecule.

[0008] The core molecule is 2,4,6-tris(4-pyridine)-1,3,5-triazine (TPT). The triazine ring structure has abundant lone pairs of electrons, which increases the electron density and makes the grafting site more reactive, providing a good foundation for the integration of subsequent functional branches.

[0009] The functional sidechain consists of anchoring sidechain R1, color-tuning sidechain R2, and biomimetic sidechain R3, which are covalently linked to the three active sites of the core molecule.

[0010] A novel multifunctional electrochromic material for hyperspectral stealth camouflage, with the following structural formula:

[0011]

[0012] Among them, R1 is the anchoring branch, R2 is the color-matching branch, and R3 is the biomimetic branch.

[0013] Furthermore, R1 is an anchoring branch, which, under heating conditions, integrates into the core molecule via a nucleophilic substitution reaction, enhancing the strong coupling effect at the molecule-electrode interface and constructing directional electron transport channels on the conductive substrate (gold electrode) through covalent bonds (gold-sulfur bonds). Specifically, the anchoring branch has a structure containing -SH groups, including but not limited to one of the following structures:

[0014] .

[0015] For example, 3-chloro-1-propanethiol, whose -SH group can form an Au-S bond with a gold electrode, and the nitrogen atom of the triazine core molecule has a lone pair of electrons, which can act as a nucleophile to attack the α-carbon of the haloalkanes and undergo a nucleophilic substitution reaction.

[0016] Furthermore, R2 is a chromatic side chain, which includes conjugated structures (such as carbon-carbon double bonds and benzene rings) and polar functional groups (such as halogens and nitro groups). By introducing conjugated ligand molecules formed by conjugated structures and polar functional groups, intramolecular charge transfer is regulated, thereby achieving precise control over spectral behavior. The conjugated structure can alter the molecular orbital energy levels and electron cloud density distribution, thus affecting the colorimetric properties of the material. It also helps stabilize free radical ions, promotes intramolecular charge transfer, and thus modulates the energy level difference between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), achieving a shift in the absorption spectrum. Polar functional groups include electron-donating groups and electron-attracting groups. Electron-donating groups (such as methyl and ethyl groups) can raise the HOMO energy level, reduce the band gap, and produce a red shift (such as red or brown); while electron-attracting groups (such as chlorine, fluorine, and nitro groups) lower the LUMO energy level, increase the band gap, and produce a blue shift (such as blue or purple). By adjusting the conjugated structure and polar functional groups in the color-tuning sidechain, the position of the reflection peak and the full width at half maximum (FWHM) can be controlled to achieve precise color switching. At the same time, through the synergistic effect of the conjugated structure and polar functional groups, the molecular orbital energy levels can be adjusted so that the maximum absorption wavelength falls within a specific visible light wavelength range (e.g., yellow or green).

[0017] Preferably, the color-tone branch can be selected from any of the following structures, but is not limited to:

[0018] .

[0019] Among them, halogen elements are nucleophilic reagent sites.

[0020] Furthermore, R3 is a biomimetic branch, specifically a cellulose supramolecular chain. This biomimetic branch replicates the natural spectrum through the physicochemical structure of the cellulose supramolecular chain, simulating the hyperspectral characteristic profile of plants. The oxygen-containing functional groups (such as COC and C-OH) on the surface of the cellulose supramolecular chain dynamically adsorb water molecules through a hydrogen bond network, matching the plant's water absorption band (1450 / 1950 nm); its multi-level porous structure simulates cell wall scattering, reproducing the near-infrared plateau region (800-1300 nm). The cellulose supramolecular chain's wide wavelength compatibility (380-2500 nm), dynamic water molecule adsorption capacity, and adaptability to environmental changes (such as humidity) enable it to possess the hyperspectral characteristic profile of plants, and its electrically neutral region ensures that the hyperspectral properties are not affected by visible light color modulation.

[0021] Preferably, R3 is one of the following structures:

[0022]

[0023]

[0024] .

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] This invention provides a novel multifunctional electrochromic material for hyperspectral camouflage, obtained by connecting anchoring branches, chromatic branches, and biomimetic branches to three active sites on a triazine ring structure. The anchoring branch, under heating conditions, integrates into the triazine ring structure via a nucleophilic substitution reaction, enhancing the strong coupling effect at the molecule-electrode interface and constructing directional electron transport channels on the gold electrode through gold-sulfur covalent bonds. The chromatic branch, based on the optimized electronic structure of conjugated ligands, achieves precise matching of chromaticity coordinates in the visible light band (380-780 nm). The biomimetic branch reproduces the natural spectrum through the physicochemical structure of cellulose supramolecular molecules, simulating the hyperspectral characteristic profiles of plants. Attached Figure Description

[0027] Figure 1 This is a design drawing of a novel multifunctional electrochromic material for hyperspectral stealth camouflage according to the present invention.

[0028] Figure 2 This is a schematic diagram showing the calculated charge density and electrostatic potential of the TPT triazine core molecule in the example.

[0029] Figure 3 This invention relates to several key cellulose supramolecular synthesis schemes;

[0030] Figure 4 This is a design diagram of a hyperspectral camouflage electrochromic molecule for an example.

[0031] Figure 5 The present invention provides a synthetic route for an electrochromic material according to one embodiment of the present invention. Detailed Implementation

[0032] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0033] This invention provides a novel multifunctional electrochromic material for hyperspectral stealth camouflage, such as... Figure 1 As shown, it includes a core molecule and "anchoring branches", "color-tuning branches" and "bionic branches" connected to three active sites of the core molecule. By integrating different functional branches, it achieves the functions of wide-band spectral modulation efficiency, precise chromaticity coordinate control and improvement of basic electrochromic performance parameters, thereby meeting the high-spectral camouflage performance requirements of electrochromic molecules. Figure 1 As shown, the device based on the electrochromic material of the present invention mainly includes the following functional layers:

[0034] Conductive substrate: The bottom layer is a conductive gold film, which serves as an electrode and is responsible for providing and conducting current for the electrochromic reaction. It is also an ideal substrate for fixing functional molecules through chemical bonds.

[0035] Multifunctional integrated molecular layer (multifunctional electrochromic layer): Through the formation of strong Au-S covalent bonds between its terminal thiol (-SH) groups and the surface of the conductive gold film, it self-assembles into a dense and ordered monolayer. This layer integrates anchoring, electrochromic (color adjustment), and subsequent bonding with biomimetic side chains.

[0036] Bionic scaffold layer (hydrogen bond network): Above the functional molecular layer, biomimetic side chains are formed by introducing polymers such as sodium carboxymethyl cellulose (CMC) through in-situ crosslinking. These side chains form an extensive hydrogen bond network through their abundant hydroxyl groups (-OH) with the pyridine nitrogen atoms of the TPT core in the functional molecular layer, as well as potential sites on the already integrated color-modulating side chains. This network mimics the cellulose skeleton of plant cell walls, playing multiple roles in structural support, stabilizing the overall architecture, providing a hydrophilic environment, and regulating interfacial optical properties.

[0037] Encapsulation layer: The outermost layer is a transparent encapsulation layer, which is used to protect the internal functional layers from environmental factors such as water and oxygen, and to ensure the long-term stability of the device.

[0038] This invention provides a novel multifunctional electrochromic material for hyperspectral stealth camouflage. 2,4,6-tris(4-pyridine)-1,3,5-triazine (TPT), possessing multiple reactive sites and high reactivity, is selected as the core molecule. Its triazine ring structure, with abundant lone pairs of electrons, increases the electron density, resulting in highly reactive grafting sites and providing a good foundation for the subsequent integration of functional branches. The charge density, electrostatic potential, and other properties of the TPT molecule were studied using DFT theoretical calculations. Figure 2 As shown, the left figure is an electron density isosurface plot (the physical morphology of the molecule), which uses a color change from blue to red to visually represent the shape of the molecule in three-dimensional space and the distribution of the electron cloud. The high electron density in the red area corresponds to nitrogen atoms, which have strong electronegativity. The right figure is a molecular orbital plot (the electronic properties and reaction potential of the molecule). The frontier orbitals HOMO or LUMO, which determine the chemical reactivity, reveal the probability of electron distribution in specific orbitals. An orbital can be understood as a "spatial region" where electrons exist in a molecule. It can be seen that the end groups of the TPT molecule have a rich charge distribution, which fully demonstrates the high reactivity at the molecule's ends.

[0039] Structures with -SH groups are selected as "anchoring branches" and, under heating conditions, are incorporated into the core molecule via nucleophilic substitution reactions. This enhances the strong coupling effect at the molecule-electrode interface, constructing directional electron transport channels on the conductive substrate (gold electrode) through covalent bonds (gold-sulfur bonds). This effectively improves charge transport efficiency, carrier migration order, and dimerization barrier, fundamentally improving the basic performance parameters of electrochromic molecules (response speed, coloring efficiency, and cycle stability), thereby endowing hyperspectral intelligent camouflage materials with excellent active control performance. During electrochromism, electrochromic molecules rely on an electric field applied by the conductive electrode to achieve electron transfer. Through covalent bonding, electrochromic molecules and the electrode surface can form stable electronic coupling. This tight bond promotes efficient charge transfer and improves the efficiency of electron conduction between molecules. Compared to physical adsorption or van der Waals forces, covalent bonds can more effectively transport electrons from the electrode to the electrochromic molecule or extract electrons from the molecule to the electrode, thereby improving the response speed, coloring efficiency, and uniformity during the electrochromic process. This highly efficient electron transfer capability reduces performance degradation caused by charge accumulation and increased resistance. Stable electron conduction reduces energy loss during the reaction process, allowing electrochromic materials to maintain high performance over long-term use. Simultaneously, anchoring electrochromic molecules to conductive electrodes via covalent bonds can, to some extent, improve molecular order, reduce side reactions, and enhance the cyclic stability of the molecules.

[0040] Choosing conjugated ligand molecules as "color-tuning branches," the band structure of electrochromic molecules is closely related to their intramolecular electron cloud density. By introducing electron-donating groups (such as methyl, ethyl, etc.) or electron-attracting groups (such as chlorine, fluorine, nitro, etc.) into electrochromic materials, the intramolecular electron density distribution can be directionally controlled, thereby changing its band structure to optimize visible light chromaticity coordinates and match typical camouflage colors. The color-tuning branches possess tunable electronic transition energy levels and high chromaticity contrast (such as switching from dark green to medium green). Through density functional theory optimization of ligands, and targeting typical plant environments (such as woodlands), they match dark green (chromaticity coordinates x=0.3, y=0.6) and medium green (x=0.35, y=0.5), ensuring precise coverage of the target color gamut in the electrochromic state (colored or faded state).

[0041] Cellulose supramolecular structures were chosen as "biomimetic side chains" to enable hyperspectral camouflage. The abundant oxygen-containing functional groups on the surface of cellulose supramolecular structures can simulate the chemical microenvironment of plants, constructing the characteristic spectrum of plants in the near-infrared region, which has a good match with the water absorption band of plants (1450 / 1950 nm). The hydrogen bond network can simulate the dynamic changes of plant water peaks through dynamic adsorption with water molecules. The multi-level porous structure can accurately simulate the micro- and nano-topological features of plants (such as the near-infrared plateau region caused by cell wall scattering: 800-1300 nm). The synergistic effect of both provides physicochemical support for the construction of hyperspectral camouflage function. The feasibility of this design is strongly supported by the group's previous representative research (Chem. Eng. J., 2024, 497, 154604). This study has successfully integrated regenerated cellulose membranes as functional components with an electrochromic system using a similar hydrogen-bonded self-assembly strategy. This not only achieved stable integration but, more importantly, successfully reproduced the characteristic spectral profiles of plants in the near-infrared band (800-2500 nm) while the electrochromic process occurred independently, including the water absorption bands at 1450 nm and 1950 nm and the plateau reflectance region at 800-1300 nm. This prior achievement fully demonstrates that the biomimetic branching integration strategy based on hydrogen bonding is an effective technical approach. It ensures that the biomimetic branches can impart excellent hyperspectral camouflage properties to the entire molecular system without degrading or destroying other functional groups under conditions of drastic chemical reactions. Figure 3 As shown, several key cellulose chemical modification reaction pathways involved in this invention are illustrated, which provide a foundation for the preparation of functional cellulose derivatives.

[0042] Reaction 1: Synthesis of cellulose Schiff bases

[0043] This reaction demonstrates the process of preparing Schiff base-type cellulose derivatives from cellulose via a condensation reaction with amino-containing compounds. Specifically, the aldehyde group (-CHO) inherent in the cellulose chain or introduced through oxidation undergoes a nucleophilic addition-elimination reaction with an organic amine (H2N-R). The amino group (-NH2) attacks the carbon atom of the aldehyde group, removing a water molecule (H2O) to form a Schiff base structure (Cellulose-N=CH-R) with a C=N double bond (imine bond). This reaction is a key step in constructing a functional platform for cellulose. By selecting different amine compounds (R groups), functional molecules can be covalently grafted onto the cellulose backbone, thereby introducing unique properties into cellulose materials.

[0044] Reaction 2: Synthesis of carboxymethyl cellulose

[0045] This reaction demonstrates the classic route for preparing carboxymethyl cellulose (CMC) via etherification. The hydroxyl group (-OH) on the cellulose chain acts as a nucleophile, undergoing a nucleophilic substitution reaction with chloroacetic acid (ClCH₂COOH). Under alkaline conditions (typically using sodium hydroxide), the cellulose hydroxyl group is deprotonated, forming the more reactive cellulose anion (Cellulose-O). - ), which then attacks the α-carbon atom of chloroacetic acid, replacing the chloride ion (Cl). - This forms an ether bond (-O-CH2-). Subsequent acid treatment converts the resulting carboxymethyl cellulic acid (Cellulose-O-CH2COOH) into its sodium salt form (Cellulose-O-CH2COO). - Na + This treatment improves the water solubility and thickening properties of cellulose, enabling the introduction of a water-soluble cellulose carrier in this invention and endowing the synthetic molecules with excellent biomimetic properties.

[0046] Reaction 3: Synthesis of porphyrin-functionalized cellulose

[0047] This reaction demonstrates a specific application example of Reaction 1, which involves covalently bonding macrocyclic porphyrin molecules to cellulose. Similarly, through Schiff base condensation, the aldehyde group of cellulose reacts with the amino group (H₂N-Porphyrin) contained in the porphyrin ring to generate a cellulose-porphyrin conjugate (Cellulose-N=CH-Porphyrin). Porphyrin compounds are known for their excellent photophysical and photochemical properties, such as the ability to generate reactive oxygen species. By immobilizing porphyrins on cellulose through this reaction, a recyclable and reusable solid-state photocatalyst or photodynamic antibacterial material has been successfully prepared.

[0048] This invention provides a novel multifunctional electrochromic material for hyperspectral stealth camouflage, with a simple and mild synthesis method. The designed functional branches can integrate with the core molecule under heating conditions through nucleophilic substitution reactions (“color-tuning branches”, “anchoring branches”) and hydrogen bond network crosslinking (“biomimetic branches”), such as… Figure 4 The diagram shown is a design overview of a hyperspectral camouflage electrochromic molecule, realizing the multifunctional integration of a hyperspectral camouflage electrochromic molecule. Figure 4The left side shows the nucleophilic substitution of the chromatic branch. A pyridine site in the TPT parent nucleus covalently bonds to the chromatic branch precursor (R1-X) via a nucleophilic substitution reaction. R1-X is typically a chlorinated or bromine-containing reactive aromatic hydrocarbon or alkene (e.g., 4-chloromethylstyrene). This reaction covalently integrates the electrochromic active unit (i.e., the chromatic branch) into the molecular system. This branch usually contains reversible redox centers (such as carboxyl or vinyl groups), which are key to achieving the electrochromic properties of the material in the visible light range (380-780 nm). By changing the structure of R1, the redox potential of the molecule can be precisely controlled, thereby altering its color. Figure 4 On the right is the nucleophilic substitution of the anchoring branch. At another pyridine site, the TPT parent nucleus undergoes a similar nucleophilic substitution reaction with the anchoring branch precursor (R2-X). R2-X is an alkane or aromatic hydrocarbon (e.g., 3-chloro-1-propanethiol) that contains a terminal halogen (-Cl, -Br) and a thiol group (-SH). This reaction covalently attaches the anchoring branch to the molecular system. The thiol group (-SH) at the end of this branch is key to the firm fixation of the molecule on the electrode surface. It can spontaneously and orderly assemble on the gold electrode surface through strong S-Au covalent bonds, forming a dense and stable monolayer, ensuring the mechanical and electrochemical stability of the device interface. Figure 4 The image below shows the in-situ cross-linking integration of biomimetic side chains. After successfully integrating the two covalent side chains mentioned above, the molecule retains the chemical activity of the third pyridine site and its nitrogen atom. Utilizing this site, the molecule is integrated with hydroxyl-rich natural polymers (such as sodium carboxymethyl cellulose) through a mild biomimetic side chain in-situ cross-linking strategy. This process is not traditional covalent grafting, but rather utilizes the pyridine nitrogen atom to form a dense hydrogen bond network with the hydroxyl groups (-OH) on the cellulose chain. A small amount of cross-linking agent (such as glutaraldehyde) can be used to cross-link the cellulose molecular chains, thereby constructing a three-dimensional biomimetic network encapsulating the functional molecule. The introduction of this biomimetic side chain greatly optimizes the spectral characteristics of the material in the near-infrared band (800-2500 nm), making it more similar to natural vegetation and achieving camouflage.

[0049] In the integration process of the hyperspectral camouflage electrochromic molecule, the integration sequence of the multifunctional branches is "anchoring branch - tinting branch - biomimetic branch". To prevent the "anchoring branch" from being oxidized in subsequent reactions, the entire reaction process is carried out in an N2 atmosphere, and the chemical reagents used are all non-oxidizing and non-electrophilic. The thiol group of the "anchoring branch" has an electron-withdrawing effect, which leads to a further reduction in the electron density of the remaining pyridine ring. The excessive electron-deficient state and the steric hindrance effect after substitution require higher energy to overcome the stability of the intermediate state in subsequent nucleophilic substitution reactions. Therefore, the integration process of the "tinting branch" requires higher thermodynamic conditions. Finally, the "biomimetic branch" is integrated into the remaining pyridine group of the TPT molecule through a hydrogen bonding network. This process has relatively mild reaction conditions to avoid destroying the already integrated branch structure. The activation energy barriers of the three functional branches are significantly different, ensuring that there are no repetitive branches on a single TPT molecule, thus guaranteeing the orderliness and controllability of the hyperspectral electrochromic molecule integration.

[0050] Preliminary theoretical calculations show that the hydrogen bond network of the "bionic branch" is mainly distributed on the periphery of the molecular plane, while the "color-tuning branch" and "anchoring branch" are oriented at the molecular end groups. Molecular dynamics simulations reveal significant differences in the conformational fluctuation energy barriers of each branch, indicating that their dynamic behavior is relatively independent. Frontier molecular orbital analysis shows that the electron cloud distribution of the "bionic branch" is concentrated in the hydrogen bond interaction region, the π-π transition orbitals of the "color-tuning branch" are localized in the conjugated framework, and the lone pair electrons of the "anchoring branch" are localized on the sulfur atom, forming functional partitions at the electronic structure level. This spatial-electronic dual decoupling design provides a theoretical basis for the parallel optimization of multifunctional branches.

[0051] like Figure 5The example illustrates a representative synthetic route of the present invention, in which the anchoring branch is 3-chloro-1-propanethiol, and the tinting branch is 4-chloro-1-butene or 4-chloromethylstyrene. The synthetic routes for other target molecules are similar. 2,4,6-tris(4-pyridine)-1,3,5-triazine (TPT), possessing three highly reactive sites, is selected as the core framework. The first synthetic step involves a nucleophilic substitution reaction between the TPT molecule and an equimolar amount of the "anchoring branch" precursor (e.g., 3-chloro-1-propanethiol) under an inert atmosphere. This reaction utilizes the electron-deficient nature of the pyridine ring of TPT, using chlorine from the thiol derivative as the leaving group to successfully attach the terminal thiol-terminated "anchoring branch" to a designated site on the core molecule via a stable C / C covalent bond, yielding intermediate I. This thiol group lays the foundation for the formation of a strong Au-S covalent bond with the gold electrode during subsequent molecular device fabrication. The second-step synthesis also employs a nucleophilic substitution mechanism, reacting intermediate I with an equimolar amount of another "chromatic side chain" precursor (e.g., 4-chloromethylstyrene) under heating conditions. The reaction conditions for this step were optimized (e.g., higher temperatures or stronger alkaline environments) to overcome the challenge of potentially reduced reactivity at remaining sites in the molecule after the first-step modification. This reaction successfully incorporated a conjugated structural unit containing a benzene ring and a vinyl group as a "chromatic side chain," covalently attaching it to the second site of the core molecule to obtain intermediate II. The introduction of this conjugated structure is crucial for achieving precise control of the molecular chromaticity coordinates in the visible light band.

[0052] The synergistic design of the "bionic branch" and the "color-tuning branch" achieves precise reproduction and dynamic adaptation of plant spectral characteristics through molecular-scale functional decoupling and dynamic complementarity mechanisms. The "bionic branch" reproduces the broad-spectrum characteristics of vegetation through multi-layered structures and surface functional groups: the multi-level porous structure accurately simulates the characteristic peaks of plant cell wall scattering (800-1300 nm), and oxygen-containing functional groups such as COC (1110 cm−1) and C-OH (1370 cm−1) show good matching with the plant's water absorption band (1450 / 1950 nm). The "color-tuning branch," on the other hand, regulates electronic transition energy levels through intramolecular charge transfer, independently adjusting chromaticity coordinates to dynamically match the color gamut of plants in different seasons. A typical chromaticity coordinate change is from dark green to medium green, overcoming the limitations of fixed color gamut and spectral distortion in traditional single-component materials. The "bionic branch" and the "color-tuning branch" ensure functional independence through spatial-electronic structure decoupling design. The "biomimetic branch" dominates the broad spectral profile, while the "color-tuning branch" modulates the chromaticity in the visible light band, avoiding mutual interference during spectral modulation. Simultaneously, the "anchoring branch" enhances the chemical bond strength between the material and the conductive substrate, improving charge transport efficiency and increasing the spectral dynamic response rate. The "color-tuning branch" and "anchoring branch" are covalently connected to TPT molecules, while the "biomimetic branch" forms an independent phase region through a hydrogen bond network. This ensures that charge transport during electrochromism primarily occurs in the covalent bond region, while the "biomimetic branch" region remains electrically neutral, and its hyperspectral characteristics are unaffected by changes in the chromaticity coordinates in the visible light band.

[0053] Example

[0054] A method for preparing a novel multifunctional electrochromic material for hyperspectral stealth camouflage, employing 2,4,6-tris(4-pyridine)-1,3,5-triazine (TPT) as the core molecule, 3-chloro-1-propanethiol (containing -SH groups) as the anchoring branch, 4-chloromethylstyrene (containing conjugated double bonds and chlorine substituents) as the color-tuning branch, and carboxymethyl cellulose supramolecular (containing COC and C-OH functional groups) as the biomimetic branch; specifically including the following steps:

[0055] Step 1. Anchoring support connection:

[0056] TPT (5 mmol) and 3-chloro-1-propanethiol (15 mmol) were dissolved in DMF and reacted at 80 °C under nitrogen protection for 12 hours. The thiol group was then inserted into the pyridine site of TPT via a nucleophilic substitution reaction to form an Au-S covalently anchored motif.

[0057] Step 2. Color grading support link:

[0058] 15 mmol of 4-chloromethylstyrene was added to the product from step 1, and the mixture was heated to 120 °C and reacted for 24 hours. The conjugated ligand was inserted into the remaining pyridine site via nucleophilic substitution, thereby modulating the molecular band gap (chromatic coordinates in the visible light region).

[0059] Step 3. Bionic branch integration:

[0060] Carboxymethyl cellulose (10 wt%) was mixed with glutaraldehyde crosslinking agent and added dropwise to the product of step 2. The mixture was then crosslinked in situ at 40°C for 2 hours. The cellulose supramolecular molecules were connected to TPT molecules via a hydrogen bond network, forming a multi-level porous structure, thus obtaining the novel multifunctional electrochromic material for hyperspectral camouflage.

[0061] Existing characterization equipment (such as near-infrared hyperspectral analyzers, electrochemical workstations, and in-situ infrared spectroscopy) can be used to test key performance parameters of hyperspectral camouflage electrochromic molecules. Density functional theory and molecular dynamics simulations can analyze the microscopic properties of branched molecules (such as HOMO / LUMO energy levels, charge distribution, and dipole moments), providing complete input parameters for model construction.

Claims

1. A novel multifunctional electrochromic material for hyperspectral stealth camouflage, characterized in that, It consists of a core molecule and functional side chains attached to the active sites of the core molecule; The core molecule is 2,4,6-tris(4-pyridine)-1,3,5-triazine, and the functional side chains consist of anchoring side chain R1, color-tuning side chain R2, and biomimetic side chain R3, which are covalently linked to the three active sites of the core molecule.

2. A novel multifunctional electrochromic material for hyperspectral stealth camouflage, characterized in that, The structural formula of the electrochromic material is: ； Among them, R1 is the anchoring branch, R2 is the color-matching branch, and R3 is the biomimetic branch.

3. The novel multifunctional electrochromic material for hyperspectral stealth camouflage according to claim 1 or 2, characterized in that, R1 is an anchoring branch that attaches to the core molecule via a nucleophilic substitution reaction under heating conditions, and constructs a directional electron transport channel on a conductive substrate through covalent bonds.

4. The novel multifunctional electrochromic material for hyperspectral stealth camouflage according to claim 1 or 2, characterized in that, The anchoring branch has a structure with -SH groups.

5. The novel multifunctional electrochromic material for hyperspectral stealth camouflage according to claim 1 or 2, characterized in that, The anchoring branch has one of the following structures: 。 6. The novel multifunctional electrochromic material for hyperspectral stealth camouflage according to claim 1 or 2, characterized in that, The color-matching side chain includes a conjugated structure and polar functional groups, which are either electron-donating or electron-attracting groups.

7. The novel multifunctional electrochromic material for hyperspectral stealth camouflage according to claim 1 or 2, characterized in that, The color-matching branch has one of the following structures: 。 8. The novel multifunctional electrochromic material for hyperspectral stealth camouflage according to claim 1 or 2, characterized in that, The biomimetic side chains are cellulose supramolecular chains.

9. The novel multifunctional electrochromic material for hyperspectral stealth camouflage according to claim 1 or 2, characterized in that, Bionic side chains are one of the following structures: ； ； 。

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