A plant-leaf-like hydrogel composite and a preparation method thereof

Abstract

The application discloses a kind of imitated plant leaf hydrogel composite material and preparation method thereof, belong to bionic composite material field.The application first by colorant compounding preparation printing paste, and fabric is printed, obtain the green fabric that can realize to plant leaf " green peak " and " red edge " spectral characteristic simulation, and with green fabric simulation leaf structure in fence organization and skeleton;Then with biomaterial polyvinyl alcohol (PVA) as base material, join with strong hygroscopic monomer and crosslinking agent, initiator blend preparation hydrogel prepolymer solution;Finally, hydrogel prepolymer solution is poured into the mold containing green fabric and copolymerization, it directly forms hydrogel in fabric surface and pore interior, obtains imitated plant leaf hydrogel composite material.The material gets rid of the dependence on hygroscopic salt, has water absorption and simulation effect stable, durability is good and the like advantages.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of imitated plant leaf hydrogel composite material and its preparation method, belong to bionic composite material field. BACKGROUND

[0002] Plant leaves are an important part of plants, and have become one of the typical bionic prototypes due to their diverse functional structures and survival functions. Currently, bionic structures and materials inspired by plant leaves have been widely used in various fields such as materials science, medicine, sensors, mechanics, and optics. Among them, bionic materials that simulate the spectral characteristics of plant leaves can counter high-spectral remote sensing detection technology, improve the survival ability and combat effectiveness of targets in a plant background, and play an important role in national defense and security. Although there are many types of plant leaves, their reflectance spectra all have four distinct spectral features: a "green peak", a "red edge", a "near-infrared plateau", and a "water absorption valley" between 400 and 2500 nm.

[0003] Currently, by using colorant compounding and material structure regulation, the "green peak", "red edge", and "near-infrared plateau" spectral characteristics of plant leaves can be effectively simulated. However, the simulation effect of the "water absorption valley" is still not ideal. The formation of the "water absorption valley" spectral feature is mainly related to the water content in plant leaves. In existing research, there are three main ways to give materials a "water absorption valley": mechanical water addition, internal water encapsulation, and self-driven water absorption. Among them, self-driven water absorption materials can adjust their water content according to environmental humidity, simulating the transpiration of plant leaves and becoming a research hotspot. However, existing self-driven water absorption bionic plant leaf materials, such as CN114214847A, usually use hygroscopic metal salts with high moisture absorption to absorb water from the air, enabling the material to simulate the "water absorption valley". However, in the application process, the hygroscopic salt in the material is prone to leakage, leading to unstable water absorption, poor simulation effect, and poor durability. Additionally, the material structure is complex, and the internal bonding strength is poor. SUMMARY

[0004] [TECHNICAL PROBLEM]

[0005] Existing self-driven water absorption bionic plant leaf materials that use hygroscopic salts are prone to salt leakage during application, leading to unstable water absorption, poor simulation effect of the "water absorption valley", poor durability, and complex material structure with poor internal bonding strength.

[0006] [TECHNICAL SCHEME]

[0007] To solve the above problems, the present application provides a kind of imitated plant leaf hydrogel composite material and its preparation method, which is free from the dependence on hygroscopic salt, with the advantages of stable water absorption and simulation effect, good durability and the like.The present application first prepares printing paste by compounding colorant, and prints fabric to obtain green fabric that can realize the simulation of the spectral characteristics of "green peak" and "red edge" of plant leaves, and imitates the palisade tissue and skeleton in leaf structure with green fabric;Then, with biological material polyvinyl alcohol (PVA) as base material, strong hygroscopic monomer, crosslinking agent and initiator are added to prepare hydrogel prepolymer solution;Finally, the hydrogel prepolymer solution is poured into a mold containing green fabric to copolymerize, so that hydrogel is directly formed on the surface and inside the pores of the fabric, and an imitated plant leaf hydrogel composite material is obtained.The imitated composite material obtained by the present application has all the spectral characteristics of plant leaves in the range of 400-2500 nm, and is similar to the structural characteristics of plant leaves.Meanwhile, the hydrogel with strong hygroscopicity in the composite material can self-drivenly absorb and release water according to the environmental humidity, realize the simulation of the transpiration of plant leaves, and avoid the problem of leakage of hygroscopic salt.In addition, the hydrogel has strong adhesion based on strong hydrogen bonding, and has excellent bonding fastness with the fabric inside it.

[0008] The first object of the present application is to provide a method for preparing an imitated plant leaf hydrogel composite material, comprising the following steps:

[0009] (1) Preparation of green fabric:

[0010] The colorant, printing aid and water are uniformly blended, and stirred to obtain green printing paste; then the printing paste is printed onto the surface of the fabric by screen printing to obtain green fabric;

[0011] (2) Preparation of hydrogel prepolymer solution:

[0012] PVA, strong hygroscopic monomer, crosslinking agent, initiator and water are uniformly blended and stirred to obtain hydrogel prepolymer solution;

[0013] (3) Preparation of imitated plant leaf hydrogel composite material:

[0014] The green fabric obtained in step (1) is mixed with the hydrogel prepolymer solution obtained in step (2), and heated to polymerize to obtain an imitated plant leaf hydrogel composite material.

[0015] In an embodiment of the present application, the colorant of step (1) comprises one or more of chromium oxide, disperse dye, vat dye, acid dye, reactive dye, dry leaf powder and copper sodium chlorophyll.

[0016] In an embodiment of the present application, the printing aid of step (1) comprises one or more of dispersing agent, thickening agent and adhesive.

[0017] In an embodiment of the present application, the dispersant includes one or more of BYK-190, 85A, AD-4600, 5080W, NNO, DM 1501, DM 1501N, PVP, BYK-190.

[0018] In an embodiment of the present application, the thickening agent includes one or more of TF-3181SS, TF-313E, TF-313B, TF-312NW, DM-5221G, DM-5228, DM-5298, sodium alginate.

[0019] In an embodiment of the present application, the binder includes one or more of TF-3211, TF-321A, TF-3201YD, TF-3201R, TEP, BST-N788, DM 5128A, DM 5120.

[0020] In an embodiment of the present application, the green printing paste of step (1) is prepared by uniformly blending and stirring the colorant, the printing aid and water into a paste; wherein the amount of the colorant in the green printing paste is 0.1-5.0wt%; the amount of the printing aid in the green printing paste is 5-40.0wt%.

[0021] In an embodiment of the present application, the fabric of step (1) includes one or more of polyester fabric, polyester-cotton blended fabric, cotton fabric, viscose fabric, nylon fabric.

[0022] In an embodiment of the present application, the PVA of step (2) includes one or more of polyvinyl alcohol 1788 type, polyvinyl alcohol 1788 low viscosity type, polyvinyl alcohol 1799 type, polyvinyl alcohol 1792 type, polyvinyl alcohol 0588 type, polyvinyl alcohol 0599 type, polyvinyl alcohol 1750±50 type, polyvinyl alcohol 124 type, polyvinyl alcohol 350 type.

[0023] In an embodiment of the present application, the strong hygroscopic monomer of step (2) includes one or more of acrylic acid, acrylic acid salt, acrylamide, acrylic acid-acrylamide copolymer, N-isopropyl acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer, sodium p-styrenesulfonate, lignin, chitosan, cellulose, carboxymethyl cellulose, sodium alginate, quaternary ammonium salt guar gum.

[0024] In an embodiment of the present application, the crosslinking agent of step (2) includes one or more of N,N-methylene bisacrylamide, glutaraldehyde, citric acid, ethylene glycol diacrylate.

[0025] In an embodiment of the present application, the initiator in step (2) comprises one or more of azobisisobutyronitrile, ammonium persulfate, potassium persulfate, epichlorohydrin, boric acid.

[0026] In an embodiment of the present application, in step (2), the mass ratio of PVA to the strong hygroscopic monomer in the hydrogel prepolymer solution is (0.4-0.8):1; further preferably 0.6:1.

[0027] In an embodiment of the present application, in step (2), the mass fraction of PVA in the hydrogel prepolymer solution is 10%-20%.

[0028] In an embodiment of the present application, in step (2), the mass fraction of the strong hygroscopic monomer in the hydrogel prepolymer solution is 0-50%. Preferably, it is 0-50% and not 0.

[0029] In an embodiment of the present application, in step (2), the mass fraction of the crosslinking agent in the hydrogel prepolymer solution is 0.1-1.0%.

[0030] In an embodiment of the present application, in step (2), the mass fraction of the initiator in the hydrogel prepolymer solution is 0.1-1.0%.

[0031] In an embodiment of the present application, in step (2), PVA is first dissolved in water to prepare a PVA solution, and then the obtained PVA solution is blended with the strong hygroscopic monomer, the crosslinking agent, the initiator, and water and stirred uniformly to obtain the hydrogel prepolymer solution.

[0032] In an embodiment of the present application, the PVA solution in step (2) is obtained by dissolving PVA in water; wherein the mass fraction of PVA in the PVA solution is 5-50%.

[0033] A second object of the present application is to provide a plant-leaf-imitating hydrogel composite prepared based on the above method.

[0034] A third object of the present application is to provide the use of the plant-leaf-imitating hydrogel composite in the field of national security.

[0035] [Advantages]

[0036] The plant leaf simulating hydrogel composite prepared in the application can realize the simulation of the "water absorption valley" of the plant leaf, and the spectral correlation coefficient with the real camellia leaf is as high as 0.98 or more. The plant leaf simulating composite prepared in the application does not use hygroscopic salt, but can simulate the transpiration of the plant leaf through the hydrogel with strong hydrophilicity, thereby avoiding the problems of unstable water absorption, poor simulation effect and poor durability caused by the leakage of the hygroscopic salt. The hydrogel has strong adhesion based on strong hydrogen bonding, and has excellent bonding fastness with the internal fabric. The plant leaf simulating composite prepared in the application has simple structure and simple preparation process, and has industrialization advantages. The plant leaf simulating hydrogel composite prepared in the application takes the textile material as the skeleton, takes the biological material PVA and the hygroscopic monomer as the hydrogel base material, and has good biocompatibility and degradability. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 FIG. 1 is a structural schematic diagram of the plant leaf simulating hydrogel composite of the application.

[0038] Figure 2 FIG. 3 is a spectral curve comparison schematic diagram of the plant leaf simulating hydrogel composite prepared in Example 1 and Comparative Example 1 and the camellia leaf. DETAILED DESCRIPTION

[0039] The outstanding advantages and significant features of the application are further illustrated by the following examples, but the application is not limited to the examples.

[0040] The plant leaf in the "plant leaf simulating" of the application includes but is not limited to flowers, schefflera, gold thread peach, cherry, Japanese beech, maple, evergreen, ginkgo, peach, camellia, magnolia, camphor leaf, etc.

[0041] The application relates to the following test method:

[0042] (1) Reflection spectral curve

[0043] The sample is placed in the solid reflectance sample test bin of the Lambda 950 ultraviolet-visible-near infrared spectrophotometer, and the reflection spectral curve of the sample in the range of 4000-1200 nm is tested, and the wavelength interval is 10 nm.

[0044] (2) Spectral correlation coefficient (γ)

[0045] The spectral correlation coefficient of the sample and the green plant leaf is calculated according to formula 1.

[0046]

[0047] In the formula, p is the sample spectrum vector; q is the reference standard spectrum vector; is the average spectrum; Covariance; α p Covariance; α q Standard deviation.

[0048] (3) Location of the "water absorption valley" of plant leaves and its reflectance range

[0049] The leaves of Camellia japonica, Cinnamomum camphora, Photinia serrulata, Osmanthus fragrans and Magnolia denudata in Wuxi were cleaned and their visible-near infrared reflectance spectra were tested. The results showed that the "water absorption valley" of plant leaves had two valleys at 1450 nm and 1930 nm, and their corresponding reflectance ranges were 10-30% and 4-10%, respectively.

[0050] Example 1

[0051] A method for preparing a plant leaf-like hydrogel composite material, comprising the following steps:

[0052] (1) Preparation of green fabric:

[0053] The colorant and printing aid were uniformly blended with water, and stirring was performed until a slurry was obtained to obtain a green printing paste. The mass fraction of each component in the printing paste was as follows: disperse blue NP-SBG 0.6%, disperse dark blue HGL 0.28%, disperse orange 30 0.50%, dispersing agent 85A 1.38%, thickening agent DM-5221G 6%, and the rest was water. The mass fraction of the above components was 100%. The printing paste was printed on the surface of the polyester fabric by flat screen printing, pre-dried at 80℃ for 5 min, baked at 180℃ for 2 min, and reduced and washed at 80℃ for 10 min. After washing, the fabric was dried at 80℃ to obtain green fabric.

[0054] (2) Preparation of hydrogel prepolymer solution:

[0055] 20 g of 1788 low viscosity type PVA was added to 80 g of water, and stirring was performed at 90℃ until complete dissolution and cooling to room temperature to obtain a PVA solution with a mass fraction of 20%. The PVA solution, hygroscopic monomer (2-acrylamido-2-methylpropanesulfonic acid), crosslinking agent (N,N-methylene bisacrylamide), initiator (ammonium persulfate), and water were uniformly blended and stirred, and nitrogen was blown for 20 min to prepare a hydrogel prepolymer solution. The mass fraction of each component in the prepolymer solution was as follows: PVA solution 60%, 2-acrylamido-2-methylpropanesulfonic acid 20% (the mass ratio of PVA to 2-acrylamido-2-methylpropanesulfonic acid was 0.6:1), N,N-methylene bisacrylamide 0.7%, ammonium persulfate 0.6%, and the rest was water. The mass fraction of the above components was 100%.

[0056] (3) Preparation of plant leaf-like hydrogel composite material:

[0057] The green fabric obtained in step (1) was cut into 10 cm*10 cm size and laid in a mold, 15 mL of the hydrogel prepolymer solution obtained in step (2) was added, and polymerization was carried out at 60 ℃ for 12 h to obtain a plant-leaf-like hydrogel composite.

[0058] The obtained biomimetic composite was placed at 25 ℃, 60% RH for 24 h to reach moisture equilibrium, and then spectral testing was performed, and the spectral curve of the biomimetic composite was drawn (Fig. 1), and the spectral correlation coefficient of the biomimetic composite and the camellia leaf was calculated according to formula 1, and the reflectivity of the biomimetic composite at the two "moisture absorption valleys" was recorded (Table 1). Figure 2

[0059] Figure 2 It can be seen that the spectral curve of the prepared biomimetic composite is similar to that of the camellia leaf, and the spectral correlation coefficient of the two is 0.984.

[0060] Example 2

[0061] A method for preparing a plant-leaf-like hydrogel composite, comprising the following steps:

[0062] (1) Preparation of green fabric:

[0063] The colorant, printing aid and water were uniformly blended to obtain a green printing paste, wherein the mass fraction of each component in the printing paste was 0.6% of disperse blue NP-SBG, 0.28% of disperse dark blue HGL, 0.50% of disperse orange 30, 1.38% of dispersing agent 85A, 6% of thickening agent DM-5221G, 30% of adhesive DM 5128A, and the rest was water. The mass fraction of the above components was 100%. The printing paste was printed on the surface of the cotton fabric by flat screen printing, pre-dried at 80 ℃ for 5 min, and baked at 180 ℃ for 2 min to obtain a green fabric.

[0064] (2) Preparation of hydrogel prepolymer solution:

[0065] The same as step (2) in Example 1.

[0066] (3) Preparation of plant-leaf-like hydrogel composite:

[0067] The same as step (3) in Example 1.

[0068] The obtained biomimetic composite was placed at 25 ℃, 60% RH for 24 h to reach moisture equilibrium, and then spectral testing was performed, and the spectral correlation coefficient of the biomimetic composite and the camellia leaf was calculated according to formula 1.

[0069] After testing and calculation, the spectral correlation coefficient of the biomimetic composite and the camellia leaf was 0.981.

[0070] Example 3​​

[0071] A method for preparing a plant-leaf-like hydrogel composite material, comprising the following steps:

[0072] (1) Preparation of green fabric:

[0073] The colorant, printing auxiliary and water were uniformly blended, and stirred to a slurry to obtain a green printing paste, wherein the mass fraction of each component in the printing paste was 3% of chromium oxide, 2% of dispersing agent 85A, 6% of thickening agent DM-5221G, 30% of adhesive DM5128A, and the rest was water, the sum of the mass fractions of the above components was 100%. The printing paste was printed on the surface of the polyester fabric by flat screen printing, and was dried at 80°C to obtain green fabric.

[0074] (2) Preparation of hydrogel prepolymer solution:

[0075] The same as step (2) in Example 1.

[0076] (3) Preparation of plant-leaf-like hydrogel composite material:

[0077] The same as step (3) in Example 1.

[0078] The obtained biomimetic composite material was placed at 25°C and 60% RH for 24h to reach moisture equilibrium, then it was subjected to spectral test, and the spectral correlation coefficient with camellia leaf was calculated according to formula 1.

[0079] Through testing and calculation, the spectral correlation coefficient of the biomimetic composite material with camellia leaf was 0.977.

[0080] Example 4

[0081] The biomimetic composite material prepared in Example 1 was dried at 60°C, and then was placed at 25°C under humidity of 30%, 60% and 90% RH respectively for 24h to reach moisture equilibrium.

[0082] The biomimetic composite materials under different humidity for moisture equilibrium were subjected to spectral test, and the reflectivity at two "moisture absorption valleys" was recorded (Table 1).

[0083] Table 1 Reflectivity of biomimetic composite material in Example 4 at "moisture absorption valley" under different humidity

[0084]

[0085] From Table 1, it can be seen that the plant leaf-like hydrogel composite prepared in Example 1 of the present application can meet the spectral characteristic requirements of the "water absorption valley" of the plant leaf under different humidity, and has good simulation effect. With the increase of humidity, the reflectivity of the biomimetic material in the "water absorption valley" gradually decreases, indicating that the material can regulate its water absorption amount with the change of humidity, and has good environmental adaptability.

[0086] Example 5

[0087] The biomimetic composite prepared in Example 1 was cut to 6cm*6cm and immersed in 250mL water for 6h, then taken out and dried at 60℃, and placed at 25℃, 60% RH for 24h to absorb moisture and balance.

[0088] The obtained biomimetic composite before and after immersion in water was subjected to spectral test, and the reflectivity at the two "water absorption valleys" was recorded (Table 2).

[0089] Comparative Example 1

[0090] A method for preparing a plant leaf-like hydrogel composite, comprising the following steps:

[0091] (1) Preparation of green fabric:

[0092] The same as step (1) in Example 1.

[0093] (2) Preparation of hydrogel prepolymer solution:

[0094] 20g of 1788 low viscosity type PVA was added to 80g of water, stirred to completely dissolve at 90℃ and cooled to room temperature to obtain a PVA solution with a mass fraction of 20%; the PVA solution, crosslinking agent (N,N-methylene bisacrylamide), initiator (ammonium persulfate) and water were blended and stirred uniformly, and nitrogen was blown for 20min to prepare a hydrogel prepolymer solution, wherein the mass fraction of each component in the prepolymer solution was PVA solution 80%, N,N-methylene bisacrylamide 0.7%, ammonium persulfate 0.6%, and the rest was water, and the sum of the mass fractions of the above components was 100%.

[0095] (3) Preparation of plant leaf-like hydrogel composite:

[0096] The same as step (3) in Example 1.

[0097] The obtained biomimetic composite was placed at 25℃, 60% RH for 24h to absorb moisture and balance, and then subjected to spectral test, and the spectral curve of the biomimetic composite and the camellia leaf was drawn (Fig. 1), and the spectral correlation coefficient of the two was calculated according to formula 1. Figure 2

[0098] From Table 3, it can be seen that the plant leaf-like hydrogel composite prepared in Example 5 of the present application can meet the spectral characteristic requirements of the "water absorption valley" of the plant leaf under different humidity, and has good simulation effect. With the increase of humidity, the reflectivity of the biomimetic material in the "water absorption valley" gradually decreases, indicating that the material can regulate its water absorption amount with the change of humidity, and has good environmental adaptability. Figure 2 ​It can be seen that the prepared biomimetic composite material has poor similarity with the spectral curve of camellia leaf, and the spectral correlation coefficient of the two is 0.640, and there is no "water absorption valley" spectral feature. Comparative example 1 can know that the hygroscopic monomer in the hydrogel has an important influence on the simulation effect of the "water absorption valley" of the biomimetic composite material.

[0099] Comparative example 2

[0100] According to the biomimetic material prepared by using hygroscopic metal salt in patent CN114214847A, the following steps are included:

[0101] (1) Preparation of green fabric:

[0102] The same as step (1) in example 1.

[0103] (2) Preparation of hydrogel prepolymer solution:

[0104] 1.0 g of sodium alginate powder was added to 100 mL of water and stirred until completely dissolved to obtain a sodium alginate aqueous solution; 10 g of calcium chloride was added to 90 g of water and mixed uniformly to obtain a calcium chloride solution with a mass fraction of 10%.

[0105] (3) Preparation of biomimetic material:

[0106] The green fabric obtained in step (1) was cut to the appropriate size and placed in a mold, and the sodium alginate aqueous solution obtained in step (2) was added to make its thickness reach 3 mm, then the calcium chloride solution obtained in step (2) was sprayed to make its thickness reach 6 mm, and it was placed at room temperature for 30 min, then dried at 50°C for 24 h to obtain the biomimetic material.

[0107] The biomimetic composite material prepared in step (3) was cut to 6 cm*6 cm and immersed in 250 mL of water for 6 h, then taken out and dried at 60°C, and placed at 25°C, 60% RH for 24 h to absorb moisture.

[0108] The obtained biomimetic material before and after soaking was tested by spectrum, and the reflectivity at two "water absorption valleys" was recorded (Table 2).

[0109] Table 2 Reflectivity of "water absorption valley" of biomimetic material prepared in example 5 and comparative example 2 before and after soaking

[0110]

[0111] As can be seen from Table 2, the reflectivity of the biomimetic composite prepared in Example 5 of the present application has no obvious change before and after being immersed in water, and has the characteristics of stable water absorption and good simulation effect and durability. The reflectivity of the biomimetic material prepared by using the hygroscopic metal salt in Comparative Example 2 is significantly increased after being immersed in water, the reflectivity at 1450 nm is close to the upper limit of the "water absorption valley" of the plant leaf, and the reflectivity at 1930 nm cannot meet the simulation requirements of the plant leaf, indicating that the hygroscopic salt calcium chloride in the material has been lost in a large amount, and the simulation effect is poor.

[0112] Comparative Example 3

[0113] (1) Preparation of green fabric:

[0114] The same as step (1) in Example 1.

[0115] (2) Preparation of hydrogel prepolymer solution:

[0116] 20 g of 1788 low viscosity type PVA was added to 80 g of water, and stirred to completely dissolve at 90°C and cooled to room temperature to obtain a PVA solution with a mass fraction of 20%; the PVA solution, hygroscopic monomer, crosslinking agent, initiator, and water were blended and uniformly stirred, and nitrogen was blown for 20 min to prepare a hydrogel prepolymer solution, wherein the mass fraction of each component in the prepolymer solution was PVA solution 40%, 2-acrylamide-2-methylpropanesulfonic acid 40% (the mass ratio of PVA to 2-acrylamide-2-methylpropanesulfonic acid was 0.2:1), N,N-methylenebisacrylamide 0.7%, ammonium persulfate 0.6%, and the rest was water, and the sum of the mass fractions of the above components was 100%.

[0117] (3) Preparation of plant leaf-like hydrogel composite:

[0118] The same as step (3) in Example 1.

[0119] The obtained biomimetic composite was placed at 25°C and 60% RH for 24 h to reach moisture equilibrium, and then spectral testing was performed thereon, the spectral correlation coefficient thereof with the camellia leaf was calculated according to Formula 1, and the reflectivity thereof at the two "water absorption valleys" was recorded.

[0120] Through testing and calculation, the spectral correlation coefficient of the material with the camellia leaf was 0.713, and the reflectivity of the spectral curve thereof at 1450 nm and 1930 nm was 3.29% and 2.94%, respectively. Compared with Example 1, when the amount of 2-acrylamide-2-methylpropanesulfonic acid is higher, the hygroscopicity of the biomimetic material is enhanced, resulting in too low reflectivity of the reflectivity curve thereof at 1450 nm and 1930 nm, and thus the spectral requirements of the plant leaf "water absorption valley" cannot be met.

[0121] Comparative Example 4

[0122] (1) Preparation of green fabric:

[0123] The same as step (1) in Example 1.

[0124] (2) Preparation of hydrogel prepolymer solution:

[0125] 20 g of 1788 low viscosity type PVA was added to 80 g of water, and stirred to completely dissolve at 90°C and cooled to room temperature to obtain a PVA solution with a mass fraction of 20%; the PVA solution, hygroscopic monomer, crosslinking agent, initiator, and water were blended and stirred uniformly, and nitrogen was blown for 20 min to prepare a hydrogel prepolymer solution, wherein the mass fraction of each component in the prepolymer solution was PVA solution 70%, 2-acrylamide-2-methylpropanesulfonic acid 10% (the mass ratio of PVA to 2-acrylamide-2-methylpropanesulfonic acid was 1.4:1), N,N-methylenebisacrylamide 0.7%, ammonium persulfate 0.6%, and the rest was water, the sum of the mass fractions of the above components was 100%.

[0126] (3) Preparation of hydrogel composite material imitating plant leaves:

[0127] The same as step (3) in Example 1.

[0128] The obtained biomimetic composite material was placed at 25°C and 60% RH for 24 h to reach moisture equilibrium, and then it was subjected to spectral testing, the spectral correlation coefficient with camellia leaves was calculated according to formula 1, and the reflectance at the two "water absorption valleys" was recorded.

[0129] Through testing and calculation, the spectral correlation coefficient of the material with camellia leaves was 0.811, and the reflectance of the spectral curve at 1450 nm and 1930 nm was 43.39% and 14.33%, respectively. Compared with Comparative Example 1, after adding 2-acrylamide-2-methylpropanesulfonic acid, the biomimetic material had certain hygroscopicity, and the spectral curve had two "water absorption valley" characteristics. Compared with Example 1, the amount of added 2-acrylamide-2-methylpropanesulfonic acid was less, and the reflectance of the biomimetic material reflectance curve at 1450 nm and 1930 nm was higher, so it could not meet the spectral requirements of the "water absorption valley" of plant leaves.

[0130] Comparative Example 5

[0131] (1) Preparation of green fabric:

[0132] The same as step (1) in Example 1.

[0133] (2) Preparation of hydrogel prepolymer solution:

[0134] 20 g of 1788 low viscosity type PVA was added to 80 g of water, stirred to completely dissolve at 90°C and cooled to room temperature to obtain a PVA solution with a mass fraction of 20%; the PVA solution, hygroscopic monomer (acrylamide), crosslinking agent (N,N-methylene bisacrylamide), initiator (ammonium persulfate), and water were blended and stirred uniformly, and a hydrogel prepolymer solution was prepared by nitrogen purging for 20 min, wherein the mass fraction of each component in the prepolymer solution was PVA solution 60%, acrylamide 20%, N,N-methylene bisacrylamide 0.7%, ammonium persulfate 0.6%, and the rest was water, and the sum of the mass fractions of the above components was 100%.

[0135] (3) Preparation of the hydrogel composite material simulating plant leaves:

[0136] The same as step (3) in Example 1.

[0137] The obtained biomimetic composite material was placed at 25°C and 60% RH for 24 h to reach moisture equilibrium, and then it was subjected to spectral testing, the spectral correlation coefficient with camellia leaves was calculated according to Formula 1, and the reflectance at the two “water absorption valleys” was recorded.

[0138] Through testing and calculation, the spectral correlation coefficient of the material with camellia leaves was 0.827, and the reflectance of the spectral curve at 1450 nm and 1930 nm was 25.46% and 12.08%, respectively. Compared with Example 1, the spectral correlation coefficient of the material with camellia leaves was reduced, and the reflectance at 1930 nm exceeded the spectral requirements of the “water absorption valley” of plant leaves.

[0139] Comparative Example 6

[0140] (1) Preparation of green fabric:

[0141] The same as step (1) in Example 1.

[0142] (2) Preparation of hydrogel prepolymer solution:

[0143] 20 g of acrylic acid was added to 80 g of water to obtain an acrylic acid solution with a mass fraction of 20%; the acrylic acid solution, hygroscopic monomer, crosslinking agent, initiator, and water were blended and stirred uniformly, and a hydrogel prepolymer solution was prepared by nitrogen purging for 20 min, wherein the mass fraction of each component in the prepolymer solution was acrylic acid solution 60%, 2-acrylamido-2-methylpropanesulfonic acid 20%, N,N-methylene bisacrylamide 0.7%, ammonium persulfate 0.6%, and the rest was water, and the sum of the mass fractions of the above components was 100%.

[0144] (3) Preparation of the hydrogel composite material simulating plant leaves:

[0145] The same as step (3) in Example 1.

[0146] The obtained biomimetic composite material was placed at 25°C, 60% RH for 24h to reach moisture equilibrium, and then subjected to spectral test, its spectral correlation coefficient with camellia leaf was calculated according to formula 1, and its reflectivity at two "water absorption valleys" was recorded.

[0147] Through test and calculation, the spectral correlation coefficient of the material with camellia leaf was 0.755, and the reflectivity of its spectral curve at 1450nm and 1930nm was 8.11% and 3.02% respectively. Compared with Example 1, the spectral correlation coefficient of the material with camellia leaf was reduced, and the reflectivity at 1450nm and 1930nm was too low to meet the spectral requirements of the "water absorption valley" of plant leaves.

[0148] Although the present application has been disclosed with the preferred embodiments as above, it is not intended to limit the present application, and any person skilled in the art can make various modifications and modifications without departing from the spirit and scope of the present application, therefore the protection scope of the present application should be defined by the claims.

Claims

1. A method of preparing a plant-mimicking leaf hydrogel composite material, characterized by, It comprises the following steps: (1) Preparation of green fabric: Mixing the colorant, printing auxiliary agent and water uniformly, stirring to paste to obtain green printing paste; then using silk screen printing method to print the printing paste on the surface of the fabric to obtain green fabric; (2) Preparation of hydrogel prepolymer solution: Mixing PVA, strong hygroscopic monomer, crosslinking agent, initiator and water uniformly and stirring to obtain hydrogel prepolymer solution; (3) Preparation of plant leaf-like hydrogel composite: Mixing the green fabric obtained in step (1) and the hydrogel prepolymer solution obtained in step (2), heating and polymerizing to obtain plant leaf-like hydrogel composite. The strong hygroscopic monomer in step (2) is 2-acrylamide-2-methylpropanesulfonic acid; the mass fraction of PVA in the hydrogel prepolymer solution is 10%-20%, and the mass ratio of PVA to strong hygroscopic monomer in the hydrogel prepolymer solution is (0.4-0.8):

1.

2. The method of claim 1, wherein, The colorant in step (1) comprises one or more of chromium oxide, disperse dye, vat dye, acid dye, reactive dye, dry leaf powder and copper sodium chlorophyll.

3. The method of claim 1, wherein, The printing auxiliary agent in step (1) comprises one or more of dispersing agent, thickening agent and adhesive.

4. The method of claim 3, wherein, The dispersing agent comprises one or more of 85A, AD-4600, NNO, DM1501, DM 1501N and BYK-190.

5. The method of claim 3, wherein, The thickening agent comprises one or more of TF-3181SS, TF-313E, TF-313B, TF-312NW, DM-5221G, DM-5228, DM-5298 and sodium alginate.

6. The method of claim 3, wherein, The adhesive comprises one or more of TF-3211, TF-321A, TF-3201YD, TF-3201R, BST-N788, DM 5128A and DM 5120.

7. The method of claim 1, wherein, The fabric in step (1) comprises one or more of polyester fabric, polyester-cotton blended fabric, cotton fabric, viscose fabric and nylon fabric.

8. The method of claim 1, wherein, The green printing paste in step (1) is prepared by mixing and stirring the colorant, printing auxiliary agent and water uniformly to paste; wherein the amount of the colorant in the green printing paste is 0.1-5.0 wt%, and the amount of the printing auxiliary agent in the green printing paste is 5-40.0 wt%.

9. The method of claim 1, wherein, In step (2), the mass fraction of the strong hygroscopic monomer is 20%.

10. The method according to any one of claims 1 to 9, characterized in that, The crosslinking agent in step (2) comprises one or more of N,N-methylenebisacrylamide, glutaraldehyde, citric acid and ethylene glycol diacrylate.

11. The method according to any one of claims 1 to 9, characterized in that, In step (2), the mass fraction of the crosslinking agent in the hydrogel prepolymer solution is 0.1-1.0%.

12. The method according to any one of claims 1 to 9, characterized in that, The initiator in step (2) comprises one or more of azobisisobutyronitrile, ammonium persulfate and potassium persulfate.

13. The method according to any one of claims 1 to 9, characterized in that, In step (2), the mass fraction of the initiator in the hydrogel prepolymer solution is 0.1-1.0%.

14. A plant leaf-like hydrogel composite prepared by the method of any one of claims 1-13.

15. Use of the plant leaf-like hydrogel composite of claim 14 in the field of national defense security.

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