Terpolymer and preparation method thereof and application thereof in antibacterial and water-retaining of wheat leaves

Abstract

The present invention discloses a ternary copolymer, a preparation method, and its application in the antibacterial and water-retaining properties of wheat leaves. The structural formula is as follows: wherein, x / x+y+z=0.05-0.25; y / x+y+z=0.05-0.25. After being atomized into a film on the leaves, the ternary copolymer strongly bonds to the plant surface, thereby enhancing the water-retaining capacity of the leaves, reducing stomatal transpiration, and maintaining a good moisture state for the leaves, providing important moisture support for crop photosynthesis. Affinity-repellency microphase separation channels are formed in the ternary copolymer coating, and the formed channels are conducive to the diffusion of gas molecules, achieving a breathable effect. The use of this coating can increase the antibacterial effect of plant leaves and reduce the incidence of stem and leaf diseases such as wheat powdery mildew, anthracnose, and rust. It can also overcome the phenomenon of easy agglomeration of small molecule antimicrobial agents, and has the advantages of long antibacterial time and not easy to lose.

Description

Technical Field

[0001] The invention belongs to the technical field of agricultural polymer material application, and particularly relates to a ternary copolymer, a preparation method thereof, and application thereof in the antibacterial and water-retaining properties of wheat leaves. Technical Background

[0002] Plant anti-transpiration agents are typically synthesized from polymeric reticular materials. They seal plant pores and slow metabolism. The reticular structure and its inter-molecular gaps are breathable, ensuring normal plant respiration and ventilation. They form an ultra-thin, translucent protective film on plant branches and leaves, effectively inhibiting excessive transpiration, minimizing damage to branches and leaves caused by transplanting, drought, and wind erosion, improving plant survival rates, and reducing maintenance costs.

[0003] Winter wheat is susceptible to dry, hot winds and drought during its mid-to-late growth period. During this period, the plant's water content decreases, and its stomata rapidly close to reduce transpiration and water loss. However, this closure inhibits CO2 assimilation and photosynthesis. Foliar application of a polymer coating containing a plant anti-transpiration agent can reduce leaf transpiration rates, mitigate photosynthesis resistance in both mild and severe drought conditions, and, to a certain extent, improve CO2 assimilation, thereby boosting photosynthesis rates.

[0004] However, existing anti-transpirants have drawbacks such as toxic side effects, high costs, or the potential to inhibit plant growth. Furthermore, some anti-transpirants are compounded from multiple ingredients, which can easily introduce non-essential metal elements into the soil, posing a potential safety hazard. For example, Chinese patent document CN108391659A (CN201810400963.9) discloses a plant anti-transpirant comprising the following components by weight: 10-30 parts aluminum salt; 5-10 parts organic polymer; and 0.5-1 parts nonionic surfactant. The aluminum salt is one or more combinations of aluminum sulfate, aluminum chloride, and basic aluminum chloride. The organic polymer is one or more combinations of polyacrylamide and polydimethylallyl ammonium chloride. The nonionic surfactant is one or more combinations of AEO 9 and JFC. However, this anti-transpirant has a complex composition and introduces substances that can be harmful to the soil. Summary of the Invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a ternary copolymer and a preparation method thereof and its application in the antibacterial and water-retaining properties of wheat leaves.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A vinylidene fluoride-acrylamide-quaternized polystyrene terpolymer, characterized in that the copolymer has a structural formula A2, and comprises structural unit A, structural unit B, and structural unit C;

[0008]

[0009] Among them, x / x+y+z = 0.05-0.25, preferably x / x+y+z = 0.08-0.25; y / x+y+z = 0.05-0.25, preferably y / x+y+z = 0.20-0.25; z / x+y+z = 0.50-0.72. More preferably, x / x+y+z = 0.08-0.20; y / x+y+z = 0.20; z / x+y+z = 0.60-0.72.

[0010] Preferably, the A unit is a vinylidene fluoride (PVDF) structural unit, and its monomer structure is CH2=CF2;

[0011] Unit B is an acrylamide structural unit, and its monomer structure is

[0012] Unit C is a quaternized styrene structural unit, and its monomer structure is

[0013] Preferably, the number average molecular weight of the terpolymer is 200,000 to 500,000; 0<x≤20. Preferably, the ion exchange capacity (IEC) value of the resulting terpolymer is 0.9 to 4.0 mmol / g, with a higher value indicating a greater number of quaternary ammonium groups. Further preferably, the number average molecular weight is 400,000 to 420,000, and the ion exchange capacity is 1 to 1.2 mmol / g.

[0014] The present invention also provides a method for preparing the above polymer, which is characterized by comprising the following steps:

[0015] (1) Add monomer acrylamide into the reaction vessel Vinylbenzyl chloride and an initiator, stirred, and filled with vinylidene fluoride (CH2=CF2) gas in a nitrogen atmosphere to carry out polymerization reaction. After the reaction is completed, it is cooled to room temperature and the unreacted gas is released to obtain a uniform terpolymer emulsion; after the emulsion is demulsified with an ethanol solution, it is washed several times to remove the emulsifier and unreacted monomer, and dried to obtain an intermediate product, named A1, as shown in Formula I:

[0016]

[0017] (2) The product A1 obtained in step (1) is immersed in a trimethylamine aqueous solution, reacted at a certain temperature, then cooled to room temperature, repeatedly washed with deionized water until neutral, and dried to obtain the target product A2. The reaction formula is shown in Formula II:

[0018]

[0019] Preferably, in step (1), the molar ratio of acrylamide, vinylbenzyl chloride, and initiator is (1-5): (5-25): 1; preferably 2: (8-20): 1. Preferably, in step (1), vinylidene fluoride is in excess relative to acrylamide and vinylbenzyl chloride, and the molar ratio of acrylamide to vinylidene fluoride is (0.4-5): 1; more preferably (0.5-4): 1. Further preferably, the molar ratio of acrylamide, vinylbenzyl chloride, initiator, and vinylidene fluoride is 2: (8-20): 1: (0.5-4).

[0020] Preferably, the polymerization reaction in step (1) is carried out at a pressure of 1.05 to 1.55 MPa, a temperature of 60 to 100° C., and a reaction time of 10 to 36 h. More preferably, the polymerization reaction is carried out at a pressure of 1.5 MPa, a temperature of 100° C., and a reaction time of 24 to 30 h.

[0021] Preferably, the initiator in step (1) comprises one of benzoyl peroxide, an azo compound or a persulfate. Further preferably, the initiator in step (1) is benzoyl peroxide.

[0022] Preferably, the drying temperature in step (1) is 60° C. and the drying time is 24 h.

[0023] In step (1), the hydrophobicity, hydrophilicity, bactericidal effect, and water retention capacity of the terpolymer coating are controlled by adjusting the mass feed ratio of the three monomers. As the proportion of unit A increases, the hydrophobicity of the terpolymer coating increases, while the light transmittance decreases; as the proportion of unit B increases, the hydrophilic and water retention properties of the coating increase, while the air permeability decreases; as the proportion of unit C increases, the antibacterial properties of the coating increase. According to the requirements of photosynthesis, transpiration, and water retention and antibacterial effects of crops, different functions of the coating can be achieved by adjusting the proportion of the terpolymer units.

[0024] Step (1) can be solution polymerization, with trifluorotrichloroethane (F113) as the dispersion medium, and the other reaction processes are the same as the emulsion polymerization step.

[0025] Preferably, in step (2), the mass percentage of the trimethylamine aqueous solution is 5 to 30%.

[0026] Preferably, in step (2), the reaction temperature is 30-60°C and the reaction time is 24-50 hours. Preferably, in step (2), the product drying temperature is 40-80°C and the drying time is 12-30 hours.

[0027] The present invention also provides a coating of a vinylidene fluoride-acrylamide-quaternized polystyrene-based terpolymer, wherein the thickness of the coating is 0.01 to 100 mm. The preparation method of the above coating comprises dissolving the above terpolymer in water or a hydroalcoholic solvent to obtain a solution with a copolymer concentration of 1.8 to 15 wt%, spraying the solution on a substrate, and air-drying or baking the solution. Preferably, the drying temperature is 30 to 50° C. Preferably, the alcohol in the hydroalcoholic solution is ethanol or isopropanol, and the volume ratio of water to alcohol is 1 to 2:8 to 9. Preferably, the substrate comprises one of crop leaves, metal materials, textile materials, and glass materials, and can be used as a coating for medical devices, etc.

[0028] The present invention also provides application of the terpolymer in antibacterial and water-retaining properties of crops.

[0029] Preferably, the crops include food crops and cash crops. Further preferably, the crops include wheat, corn, peanuts, soybeans, cotton, sugarcane, fruits, etc.

[0030] The present invention also provides an application of the terpolymer in the antibacterial and water-retaining properties of wheat leaves.

[0031] Preferably, the application method is:

[0032] After the terpolymer is evenly diluted with water at a mass ratio of 1:10 to 50, avoid rainy days and spray it evenly on the upper and lower surfaces of wheat leaves. The dosage each time is 40 to 50 L / mu.

[0033] Preferably, the mass ratio of the terpolymer to water is 1:15-25.

[0034] More preferably, the method of use is: spraying three times during the greening stage, jointing stage and flowering stage of wheat. More preferably, this method is more suitable for wheat planting in the North China Plain.

[0035] Beneficial effects of the present invention:

[0036] One or more technical solutions provided by the specific embodiments of the present invention have at least the following beneficial effects:

[0037] (1) The amide groups in the acrylamide units in the terpolymer can form hydrogen bonds, improving the hydrophilicity of the PVDF polymer and effectively increasing the water adsorption and water retention capacity of the copolymer coating. The use of this coating can effectively reduce the volatilization of water on the leaf surface, achieving the purpose of protecting the leaf moisture. In arid environments, the photosynthetic rate of crops will be significantly reduced. After the coating is atomized into a film on the leaves, it strongly bonds with the plant surface, forming a high-quality water-retaining and breathable protective film, which enhances the water retention capacity of the leaves, reduces stomatal transpiration, and keeps the leaves in a better water state, providing important water support for crop photosynthesis.

[0038] (2) The terpolymer and its coating of the present invention retain the PVDF advantage unit - (CH2CF2) x -, a hydrophobic phase can be formed in the terpolymer coating, which can form a hydrophilic-hydrophobic microphase separation channel with the hydrophilic acrylamide unit. The formed channel is conducive to the diffusion of gas molecules, achieving a breathable effect. The terpolymer also contains quaternary ammonium groups. The use of this coating can increase the antibacterial effect of plant leaves and reduce the incidence of stem and leaf diseases such as wheat powdery mildew, anthrax and rust. Compared with the phenomenon that small molecule antibacterial agents are easy to agglomerate, the polymer coating of the present invention is evenly dispersed after atomization and will not agglomerate; the antibacterial time of the coating is long after film formation and it will not be lost; there is a strong force between the coating and the base material, and it is resistant to erosion. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 3 is a contact angle picture of the terpolymer coating obtained in Example 1.

[0040] Figure 2 This is the infrared spectrum of the terpolymer obtained in Example 1. DETAILED DESCRIPTION

[0041] The technical solution of the present invention is described in detail below through specific embodiments.

[0042] The content of quaternary ammonium groups in the target product terpolymer structure can be determined by acid-base titration. The test method is as follows:

[0043] (1) Accurately weigh a certain weight of the target product, first soak it in a 2M KOH solution for 24 h, then neutralize it with deionized water, and finally dry it at 60°C to obtain the dry target product.

[0044] (2) The obtained dry target product was subjected to ion exchange with a 1 M NaCl aqueous solution for more than 12 h. The ion exchange solution was collected and titrated with a 0.1 M NaOH standard solution using phenolphthalein as an indicator until the solution turned pink. The ion exchange capacity (IEC) value of the target product can be calculated according to the following formula:

[0045] IEC=(V NaOH ×C NaOH ) / m

[0046] Where: V NaOH ——The volume of NaOH standard solution consumed, mL,

[0047] C NaOH ——The molar concentration of the NaOH standard solution, mmol / mL,

[0048] m——mass of dry target product, g.

[0049] Example 1

[0050] A vinylidene fluoride-acrylamide-quaternized polystyrene-based terpolymer, a coating, and a preparation method thereof, wherein the preparation method comprises the following steps:

[0051] (1) Adding monomer acrylamide into the high pressure reaction vessel 0.10 mol, vinylbenzyl chloride 1.0 mol and 0.05 mol of benzoyl peroxide were added, and the vacuum was repeatedly evacuated to remove oxygen; with stirring, the monomer vinylidene fluoride (CH2=CF2, 0.05 mol) gas was filled into the nitrogen atmosphere to carry out polymerization reaction, and the pressure was maintained at 1.5 MPa, and the temperature was slowly raised to 100°C, and the reaction was carried out under mechanical stirring for 24 hours.

[0052] After the reaction is completed, the mixture is cooled to room temperature to release unreacted vinylidene fluoride gas, thereby obtaining a uniform terpolymer emulsion. The emulsion is then demulsified with an ethanol solution, washed multiple times to remove the emulsifier and unreacted monomers, and dried at 60°C for 24 hours to obtain an intermediate product, designated a1.

[0053] (2) The product a1 obtained in step (1) was immersed in a 30% by mass aqueous solution of trimethylamine, reacted at 60° C. for 24 h, then cooled to room temperature, repeatedly washed with deionized water until neutral, and dried at 60° C. to obtain the target product a2.

[0054] In the target product a2 obtained in this example, x / x+y+z = 0.08, y / x+y+z = 0.20, and z / x+y+z = 0.72, with a number average molecular weight of 400,000. For agricultural applications, it is labeled as an antibacterial, water-retaining, and breathable coating (CA-4). The ion exchange capacity (IEC) value of the target product a2 is 1.20 mmol / g.

[0055] The target product a2 obtained in this example was sprayed on a glass sheet with a thickness of 5 to 10 mm to obtain a coating. The coating had a contact angle of 40° and had antibacterial and water-retaining properties. The contact angle test photo is shown in FIG. Figure 1 .

[0056] The target product a2 obtained in this example was tested by infrared spectroscopy. Figure 2 As shown in the figure, the characteristic peaks of CH, C=O, NH and CF bonds in the ternary polymer structural unit are at 3020 cm -1 、1710cm -1 、1640cm -1 and 1292cm -1 Nearby; infrared results proved that the target product a2 has been successfully synthesized.

[0057] Example 2

[0058] A vinylidene fluoride-acrylamide-quaternized polystyrene-based terpolymer and a preparation method thereof, wherein the preparation method comprises the following steps:

[0059] (1) Adding monomer acrylamide into the high pressure reaction vessel (0.10 molg), vinylbenzyl chloride (0.40 mol) and benzoyl peroxide (0.05 mol), stirred, and filled with monomer vinylidene fluoride (CH2=CF2, 0.20 mol) gas under nitrogen atmosphere to carry out polymerization reaction, maintaining the pressure. After the pressure is maintained at 1.5 MPa, slowly heat to 100°C and react for 30 hours under mechanical stirring.

[0060] After the reaction is completed, the mixture is cooled to room temperature to release unreacted vinylidene fluoride gas, thereby obtaining a uniform terpolymer emulsion. The emulsion is then demulsified with an ethanol solution, washed multiple times to remove the emulsifier and unreacted monomers, and dried at 60°C for 24 hours to obtain an intermediate product, designated a3.

[0061] (2) The product a3 obtained in step (1) was immersed in a 30% by mass aqueous solution of trimethylamine, reacted at 60° C. for 24 h, then cooled to room temperature, repeatedly washed with deionized water until neutral, and dried at 60° C. to obtain the target product a4.

[0062] In the target product a4 obtained in this example, x / x+y+z = 0.25, x / x+y+z = 0.25, and x / x+y+z = 0.50, and the number average molecular weight was 420,000. The ion exchange capacity (IEC) value of the target product a4 was 1.02 mmol / g. This product was designated as a water-retaining, breathable coating (CA-2).

[0063] Example 3

[0064] A vinylidene fluoride-acrylamide-quaternized polystyrene-based terpolymer and a preparation method thereof, wherein the preparation method comprises the following steps:

[0065] (1) Adding monomer acrylamide into the high pressure reaction vessel (0.20 mol), vinylbenzyl chloride (0.80 mol) and benzoyl peroxide (0.10 mol) were stirred, and monomer vinylidene fluoride (CH2=CF2, 0.05 mol) gas was introduced into a nitrogen atmosphere to carry out polymerization reaction. The pressure was maintained at 1.5 MPa, and then the temperature was slowly raised to 100°C and the reaction was carried out under mechanical stirring for 30 hours.

[0066] After the reaction is completed, the mixture is cooled to room temperature to release unreacted vinylidene fluoride gas, thereby obtaining a uniform terpolymer emulsion. The emulsion is then demulsified with an ethanol solution, washed multiple times to remove the emulsifier and unreacted monomers, and then dried at 60°C for 24 hours to obtain an intermediate product, designated a5.

[0067] (2) The product a5 obtained in step (1) was immersed in a 30% by mass aqueous solution of trimethylamine, reacted at 60° C. for 24 h, then cooled to room temperature, repeatedly washed with deionized water until neutral, and dried at 60° C. to obtain the target product a6.

[0068] In the target product a6 obtained in this example, x / x+y+z = 0.20, x / x+y+z = 0.20, and x / x+y+z = 0.60, and the number average molecular weight was 410,000. The target product a6 had an ion exchange capacity (IEC) of 1.10 mmol / g. This product was labeled as a water-retaining, breathable, and erosion-resistant coating (CA-3).

[0069] Comparative Example 1

[0070] A vinylidene fluoride-acrylamide binary copolymer and a preparation method thereof, wherein the preparation method comprises the following steps:

[0071] (1) Adding monomer acrylamide into the high pressure reaction vessel (0.20 mol) and benzoyl peroxide (0.10 mol), stirred, and filled with monomer vinylidene fluoride (CH2=CF2, 0.05 mol) gas under nitrogen atmosphere to carry out polymerization reaction, maintaining the pressure at 1.5 MPa, slowly raising the temperature to 100°C, and reacting for 30 hours under mechanical stirring.

[0072] (2) After the reaction is completed, the mixture is cooled to room temperature to release unreacted vinylidene fluoride gas, thereby obtaining a uniform binary copolymer emulsion. The emulsion is demulsified with an ethanol solution, washed multiple times to remove the emulsifier and unreacted monomers, and then dried at 60°C for 24 hours to obtain an intermediate product, designated a7, whose structure is shown below. In the target product a7 obtained in this example, m / m+n=0.20, n / m+n=0.80, and the number average molecular weight is 350,000. The resulting polymer coating is designated as coating CA-5.

[0073]

[0074] The terpolymers CA-2, CA-3, CA-4 and CA-5 of the present invention are applied to wheat for drought resistance and water retention, as shown in Application Examples 1 and 2.

[0075] Application Example 1

[0076] This application case experiment was conducted in 2020-2021 at the Jiyang Experimental Demonstration Base of the Shandong Academy of Agricultural Sciences. The soil type is fluvo-aquic soil with irrigation access. The wheat varieties tested were Jimai 22 (provided by the Crop Research Institute of the Shandong Academy of Agricultural Sciences) and Shimai 26 (provided by the Shijiazhuang Academy of Agriculture and Forestry Sciences), a drought-resistant variety with a thick waxy layer. Wheat was sown on October 20, 2020, with a row spacing of 20 cm, a sowing rate of 11 kg / mu, and a sowing depth of 4 cm.

[0077] The two wheat varieties were treated with three treatments: water-retaining and breathable coating (CA-2), water-retaining and breathable erosion-resistant coating (CA-3), and antibacterial water-retaining and breathable coating (CA-4). Each treatment was repeated three times. The experimental area was 2m*8m=16m 2 , random block arrangement. On March 16, 2020, after the wheat entered the greening period, the terpolymers obtained in Examples 1 to 3 and Comparative Example 4 were uniformly diluted with water at a mass ratio of 1:20, and then evenly sprayed on the upper and lower surfaces of the wheat leaves with a spraying pot, with a dosage of about 50 L / mu, avoiding rainy days. On April 10, the wheat entered the jointing stage, and the first topdressing was carried out with a dosage of about 50 L / mu. On May 6, the wheat began to enter the flowering stage, and the second supplementary spraying was carried out with a dosage of about 50 L / mu. This season's wheat was harvested on June 9.

[0078] The control treatments for this experiment used the same amount of water (CA-1) and antimicrobial water-retaining treatment (CA-5). All other treatments were identical. The wheat was sown at the same date and variety as in the previous experiment. The control treatments were sprayed with water at approximately 50 L / mu (approximately 50 L / mu) at the greening, jointing, and flowering stages.

[0079] The comparison of the experimental results of this experiment and the control experiment is as follows:

[0080] Table 1 Comparison of water production efficiency of tested wheat under different treatment modes

[0081]

[0082] Water use efficiency (WUE: kg hm –2 mm –1 ) = grain yield (kg hm –2) / crop water consumption during the entire growth period (mm). A comparison of wheat water production efficiency (Table 1) revealed that, compared to the control (CA-1), the three polymer coating material treatments (CA-2, CA-3, and CA-4) and the weakened treatment CA-5 increased water use efficiency (WUE) of Jimai 22 by 12.48%, 9.72%, 24.28%, and 2.61%, respectively. While CA-5 improved WUE, the effect was not significant. Water production efficiency was significantly improved under treatments CA-2, CA-3, and CA-4. Shimai 26, which has a thicker waxy layer, also showed similar results to Jimai 22. Compared to the plain water treatment, treatments with the polymer coating materials CA-2, CA-3, and CA-4 showed significant increases of 5.61%, 9.29%, 18.27%, and 1.18%, respectively. While WUE improved somewhat under CA-5, the effect was not significant. Experimental results indicate that polymer coating treatment can significantly improve crop water use efficiency, resulting in water conservation and increased yields. While CA-5 exhibits significant differences from CA-2, CA-3, and CA-4 due to its compositional differences, it does exhibit water conservation, albeit a less pronounced effect.

[0083] Table 2 Comparison of net photosynthetic rate of tested wheat under different treatment modes

[0084]

[0085] Comparisons (Table 2) revealed that the three polymer coatings described in this experiment (CA-2, CA-3, and CA-4) significantly increased the net photosynthetic rate of Jimai 22 at the heading stage (728%, 5.34%, and 11.65%) and mid-grain filling (28.25%, 13.97%, and 10.16%), and the net photosynthetic rate of Heshimai 26 at the heading stage (12.21%, 12.65%, and 8.27%) and mid-grain filling (22.66%, 6.05%, and 6.49%), compared to the control (CA-1). However, the improvement was less pronounced at the jointing and late grain filling stages, with photosynthesis showing a downward trend in the late grain filling stage. The coating's promoting effect also diminished with plant aging. Generally speaking, under drought stress, the photosynthetic rate of wheat populations and flag leaves is significantly inhibited. The heading and filling period of wheat coincides with the dry season from late April to mid-May in the North China Plain, with scarce precipitation, and wheat plants are easily affected by drought stress. The polymer coating used in the present invention is a hydrophobic, breathable, transparent coating that can lock in moisture on the leaf surface, reduce water loss from the leaf surface, enhance the water retention capacity of the flag leaf, reduce stomatal transpiration, and keep the leaves in a better moisture state, providing water support for plant photosynthesis. Therefore, compared with drought plants, the photosynthesis of plants sprayed with polymer coatings is improved. At the end of the growth period, with the end of the filling period of winter wheat, the leaves age, photosynthesis weakens, and the coating also begins to age and break, losing its original elasticity and water retention function. Therefore, the advantage of photosynthesis will also be weakened accordingly.

[0086] Table 3 Comparison of transpiration rates of wheat under different treatment modes

[0087]

[0088] By comparison (Table 3), it was found that the transpiration rate of Jimai 22 treated with the three polymer coating materials (CA-2, CA-3 and CA-4) in this experiment decreased by 36.51%, 15.90% and 40.98% respectively at the jointing stage, by 17.52%, 29.11% and 9.78% respectively at the heading stage, and by 13.46%, 20.41% and 34.10% respectively at the mid-graining stage, compared with the control (CA-1), all of which were significantly different. The transpiration rate of Shimai 26 was significantly reduced during the heading and mid-grain filling stages: by 42.85%, 31.05% and 42.41% at the jointing stage, by 30.88%, 33.96% and 16.63% at the heading stage, and by 5.26%, 12.22% and 14.99% at the mid-grain filling stage, all of which were significant differences. This indicates that the polymer coating can significantly reduce the transpiration rate of wheat plants during the heading and mid-grain filling stages, but has no significant effect on reducing the transpiration rate in the late grain filling stage. This indicates that the polymer coating can limit the transpiration of the plant during the jointing-mid-grain filling stage when wheat has a high water demand and vigorous growth, thereby conserving water for the leaves to promote plant growth.

[0089] Table 4 Comparison of powdery mildew incidence and disease index of wheat under different treatment modes

[0090]

[0091]

[0092] According to Table 4, among the three polymer coatings described in this experiment, CA-2, CA-3, and CA-4 all reduced the incidence and disease index of powdery mildew in wheat during both the middle and late stages of the disease. Because all four coatings contain antimicrobial ingredients, they all exhibited an inhibitory effect on the disease. However, CA-5's inhibitory effect was not significant. CA-2, CA-3, and CA-4 exhibited significant inhibitory effects on the incidence and disease index during the middle and late stages, particularly CA-4. This is because the coating contains a high concentration of quaternary ammonium groups, resulting in a stronger antimicrobial and bactericidal effect. This coating enhances the antimicrobial properties of plant leaves, reduces leaf water loss during the crop's growth period, and reduces leaf disease during the crop's growth period. In the early stages of the disease, shortly after application, the effects were not yet apparent, and the antimicrobial effect on the leaves was not significant. However, the antimicrobial and disease-control effects gradually became apparent during the flowering period. The coatings of CA-2 and CA-3, which contain lower concentrations of quaternary ammonium groups, were slightly less effective than the coating of CA-4 in suppressing powdery mildew.

[0093] Table 5 Comparison of dry matter content and yield of wheat under different treatment modes

[0094]

[0095] Comparison of the wheat yield and three yield factors (Table 5) revealed that, compared with the control (CA-1), the three polymer coating materials (CA-2, CA-3, and CA-4) increased the dry matter of Jimai 22 by 15.04%, 19.39%, and 15.03%, respectively; the dry matter of Shimai 26 by 7.34%, 9.05%, and 8.51%, respectively; the number of grains per ear increased by 9.34%, 5.03%, and 10.44%, respectively; and the yield increased by 12.48%, 9.72%, and 24.28%, respectively; while the number of grains per ear increased by 9.66%, 5.70%, and 12.77%, respectively; and the yield increased by 5.61%, 9.29%, and 18.27%, respectively, for Shimai 26. The yield increase for CA-5 did not reach a significant difference compared with the CK. It can be seen that the antibacterial, water-retaining and breathable effects of the high-molecular polymer coating applied to wheat plants can enhance the water retention of the leaves, thereby improving the water utilization rate of the crop, reducing diseases, enhancing photosynthesis, and promoting an increase in dry matter mass, thereby promoting an increase in the number of grains per ear, thereby increasing yield.

[0096] Application Example 2

[0097] Similar application trials were conducted in 2020-2021 at Thirteen Experimental Fields, a research facility at the Crop Research Institute of the Shandong Academy of Agricultural Sciences. The fields are loamy, have an annual wheat yield of 500 kg / mu, and are irrigated. The wheat varieties tested in this trial were Jimai 22 (provided by the Crop Research Institute of the Shandong Academy of Agricultural Sciences) and Shimai 26, a variety with a thicker wax layer (provided by the Shijiazhuang Academy of Agriculture and Forestry Sciences). Plantings were made on October 18, 2020, with a row spacing of 20 cm, a sowing rate of 11 kg / mu, and a sowing depth of 4 cm.

[0098] The two wheat varieties were treated with three treatments: water-retaining and breathable coating (CA-2), water-retaining and breathable erosion-resistant coating (CA-3), and antibacterial water-retaining and breathable coating (CA-4). Each treatment was repeated three times, and the plot area was 2m*8m=16m 2 , arranged in random blocks. On March 16, 2020, after the wheat entered the greening period, the polymers obtained in Examples 1 to 3 were evenly diluted with water at a mass ratio of 1:20, and the amount was about 50 L / mu. The leaves were evenly sprayed on the upper and lower surfaces of the wheat leaves with a spraying pot, avoiding rainy days. On April 10, the wheat entered the jointing stage, and the first topdressing was carried out at a dosage of about 50 L / mu. On May 6, the wheat began to enter the flowering stage, and the second supplementary spraying was carried out at a dosage of about 50 L / mu. The wheat of this season was harvested on June 16.

[0099] The control experiments in this study are as follows:

[0100] The control experiments consisted of a water treatment (CA-1) and an antimicrobial water-retaining weakened treatment (CA-5). The wheat sowing date and variety were the same as those in the previous experiments. The control treatments were sprayed with water at approximately 50 L / mu (approximately 50 L / mu) during the greening, jointing, and flowering stages. All other treatments were the same as those in the experimental experiments.

[0101] The test results of this experiment are compared as follows:

[0102] Table 6 Comparison of water production efficiency of tested wheat under different treatment modes

[0103]

[0104]

[0105] The comparison of the water production efficiency of wheat mentioned above showed that (Table 6, the three polymer coating material treatments (CA-2, CA-3, CA-4) and the weakened treatment CA-5 in this experiment can improve the water use efficiency of crops compared with the control (CA-1). The water use efficiency of Jimai 22 variety increased by 12.48%, 9.72% and 24.28% respectively; the water use efficiency of Shimai 26 with a thicker wax layer increased by 5.61%, 9.29% and 18.27% respectively compared with the ordinary water treatment. Material treatment can significantly improve crop water use efficiency. When plants experience drought stress, their leaves will close their stomata in an emergency to reduce transpiration and minimize water loss. Applying a high-molecular-weight polymer coating to the leaves effectively alleviates transpiration, retains moisture, and maintains normal photosynthesis, thereby improving water use efficiency and achieving the effect of saving water and increasing yields. Consistent with the experimental results of Application Example 1, CA-2, CA-3, and CA-4 performed better than CA-5, and the results of CA-5 treatment were better than CK, indicating that the molecular polymer coating has a water-saving effect.

[0106] Table 7 Comparison of net photosynthetic rate of tested wheat under different treatment modes

[0107]

[0108] Comparison (Table 7) revealed that the three polymer coating treatments (CA-2, CA-3, and CA-4) compared to the control (CA-1) increased the net photosynthetic rate of Jimai 22 by 7.26%, 5.32%, and 11.64% at the heading stage, and by 28.21%, 13.94%, and 10.14% at the mid-grain-filling stage, respectively. The net photosynthetic rate of Shimai 26 increased by 12.22%, 12.67%, and 8.28% at the heading stage, and by 9.78%, 6.05%, and 6.50% at the mid-grain-filling stage, respectively. The polymer coating treatments (CA-2, CA-3, and CA-4) did not significantly increase the net photosynthetic rate of Jimai 22 and Shimai 26 at the jointing and late-grain-filling stages, indicating that the polymer coatings primarily promote net photosynthetic rate during the critical growth periods of heading and mid-grain-filling.

[0109] Table 8 Comparison of transpiration rates of tested wheat under different treatment modes

[0110]

[0111] By comparison (Table 8), it was found that the transpiration rate of Jimai 22 treated with the three polymer coating materials (CA-2, CA-3 and CA-4) decreased by 12.99%, 16.01% and 9.40% respectively at the jointing stage, with an average decrease of 12.80%; at the heading stage, it decreased by 11.88%, 20.44% and 9.78% respectively, with an average decrease of 14.91%; at the mid-graining stage, it decreased by 7.88%, 25.07% and 23.15% respectively, with an average decrease of 18.70%, all of which reached significant differences. The transpiration rate of Shimai 26 was significantly reduced during the jointing, heading, and mid-grain filling stages: at the jointing stage, it decreased by 15.35%, 21.33%, and 18.07%, respectively, with an average decrease of 18.25%. At the heading stage, it decreased by 14.92%, 23.42%, and 17.80%, respectively, with an average decrease of 18.71%. At the mid-grain filling stage, it decreased by 5.13%, 14.99%, and 12.22%, respectively, with an average decrease of 10.78%. These differences were all significant, indicating that the polymer coating can significantly reduce leaf transpiration and water consumption, thereby saving water. The water-saving effect was not significant during the late grain filling stage. However, the polymer coating can inhibit leaf transpiration during the jointing-mid-grain filling period, when wheat has high water demand and is experiencing vigorous growth, reducing leaf water loss and alleviating the damage caused by drought stress to the plant.

[0112] Table 9 Comparison of powdery mildew incidence and disease index of wheat under different treatment modes

[0113]

[0114]

[0115] As shown in Table 9, the three polymer coatings used in this experiment—CA-2, CA-3, CA-4, and the weakened CA-5—were able to reduce the incidence and disease index of powdery mildew in wheat during both the middle and late stages of the disease. In the early stages of the disease, the inhibitory effects of CA-2, CA-3, CA-4, and CA-5 on the incidence and disease index were not significant. This is because the coatings were not effective until the initial application. By the middle stages of the disease, the effects of CA-3 and CA-4 were significantly different. While CA-2 and CA-5 reduced the incidence and disease index, the effects were not significant. In the late stages of the disease, CA-2, CA-3, and CA-4 all showed significant differences in reducing the incidence and disease index, while CA-5 showed some reduction, but the difference was not significant. This indicates that polymer coatings have an inhibitory effect on powdery mildew in winter wheat, especially in the late stages, effectively reducing the incidence and disease index, creating favorable conditions for increasing winter wheat yields.

[0116] Table 10 Comparison of dry matter content and yield of test varieties under different treatment modes

[0117]

[0118]

[0119] Comparison of the above results of wheat yield and the three yield factors (Table 10) showed that compared with the control (CA-1), the dry matter weight of Jimai 22 at maturity increased by 13.77%, 18.09% and 13.43% in the polymer coating material treatments (CA-2, CA-3 and CA-4); and the dry matter weight of Shimai 26 increased by 16.00%, 17.85% and 17.27%, respectively. The three treatments increased grain number per spike for Jimai 22 by 9.34%, 5.03%, and 10.44%, and yield by 12.48%, 9.72%, and 24.28%, respectively. The grain number per spike for Shimai 26 increased by 11.52%, 5.70%, and 12.77%, and yield by 5.61%, 9.29%, and 18.27%, respectively. The CA-5 treatment increased yield slightly compared to the CK (by 2.17% and 4.17%, respectively), but the difference was not significant. This suggests that the positive effect of the CA-5 treatment on yield was less pronounced than that of CA-2, CA-3, and CA-4. These results suggest that polymer coating treatment can enhance leaf resistance to drought stress, promote an increase in wheat dry matter, and ultimately increase grain number per spike, thereby boosting yield.

[0120] The present invention targets wheat leaves during the jointing and flowering stages, when water is relatively scarce. The coating protects wheat leaves and exploits the coating's water-retaining and antibacterial properties, allowing them to actively act on the wheat leaves and have a positive effect on wheat growth. Furthermore, the polymer coating matches the coating's water-retaining properties with the wheat's water-demand period, alleviating water shortages in wheat plants during critical periods, achieving its water-retaining and water-storing function and promoting wheat growth and development. The coating's antibacterial properties also match the high incidence of powdery mildew in the middle and late stages of wheat growth, significantly reducing the incidence of powdery mildew, alleviating the disease index, and achieving increased yields.

[0121] The management method of the present invention can match the water-retaining and antibacterial effect of the coating with the water-demand period of wheat and the high-incidence period of powdery mildew, thereby alleviating the water shortage and powdery mildew incidence rate during the critical growth period of wheat, improving water utilization rate, and reducing the powdery mildew incidence index, thereby promoting an increase in dry matter accumulation and an increase in the number of grains per ear, and ultimately achieving an increase in yield; whereas in the control example, the water-retaining and antibacterial effect of the coating without the addition of a high molecular weight polymer suffered severe water loss under the influence of water shortage and dry hot wind, resulting in slight dehydration and a relatively severe powdery mildew incidence rate during the critical growth period of wheat, and ultimately a lower yield.

Claims

1. A terpolymer, characterized in that The copolymer comprises structural unit A, structural unit B and structural unit C, and the structural formula is shown in A2: Formula A2 Among them, x / (x+y+z)=0.05~0.25; y / (x+y+z)=0.05~0.

25.

2. The terpolymer according to claim 1, characterized in that x / (x+y+z)=0.08~0.25, y / (x+y+z)=0.20~0.25, z / (x+y+z)=0.50~0.

72.

3. The terpolymer according to claim 1, characterized in that x / (x+y+z)=0.08~0.20; y / (x+y+z)=0.20; z / (x+y+z)=0.60~0.

72.

4. The terpolymer according to claim 1, characterized in that The number average molecular weight of the terpolymer is 200,000 to 500,000; 0<x≤20; and the ion exchange capacity of the terpolymer is 0.9 to 4.0 mmol / g.

5. The method for preparing the terpolymer according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) Add monomer acrylamide into the reaction vessel , vinylbenzyl chloride and an initiator, stirred, and filled with vinylidene fluoride monomer CH2=CF2 gas under a nitrogen atmosphere for polymerization reaction. After the reaction is completed, it is cooled to room temperature and the unreacted gas is released to obtain a uniform terpolymer emulsion; after the emulsion is demulsified with an ethanol solution, it is washed several times to remove the emulsifier and unreacted monomer, and dried to obtain an intermediate product, named A1, as shown in Formula I: ； Formula I (2) The product A1 obtained in step (1) is immersed in a trimethylamine aqueous solution, reacted at a certain temperature, then cooled to room temperature, repeatedly washed with deionized water until neutral, and dried to obtain the target product A2. The reaction formula is shown in Formula II: Formula II.

6. The method according to claim 5, characterized in that In step (1), the molar ratio of acrylamide, vinylbenzyl chloride and initiator is (1-5): (5-25): 1; The molar ratio of acrylamide to vinylidene fluoride is (0.4~5):1; The reaction pressure of the polymerization reaction is 1.05~1.55Mpa, and the reaction temperature is 60~100 o C, reaction time is 10~36h.

7. The method according to claim 6, characterized in that In step (1), the molar ratio of acrylamide, vinylbenzyl chloride and initiator is 2:(8-20):1; the molar ratio of acrylamide to vinylidene fluoride is (0.5-4):1; and the reaction time of the polymerization reaction is 24-30 hours.

8. The method according to claim 5, characterized in that The initiator in step (1) includes one of benzoyl peroxide, an azo compound or a persulfate.

9. The method according to claim 5, characterized in that Step (2) satisfies one or more of the following reaction conditions: (i) the mass percentage of the trimethylamine aqueous solution is 5-30%; (ii) the reaction temperature is 30-60°C and the reaction time is 24-50 hours; (iii) The product is dried at a temperature of 40 to 80°C and for a time of 12 to 30 hours.

10. Use of the terpolymer according to any one of claims 1 to 4 or the terpolymer prepared by the method according to any one of claims 5 to 9 in antibacterial and water-retaining properties of crops.

11. Use of the terpolymer according to any one of claims 1 to 4 or the terpolymer prepared by the method according to any one of claims 5 to 9 in the antibacterial and water-retaining effects on wheat leaves.

12. The use according to claim 11, characterized in that After the terpolymer is evenly diluted with water in a mass ratio of 1:10~50, avoid rainy days and spray it evenly on the upper and lower surfaces of wheat leaves. The dosage each time is 40~50L / mu.

13. The use according to claim 12, characterized in that The mass ratio of the terpolymer to water is 1:15-25.

14. The use according to claim 12, characterized in that Spray wheat three times during the greening stage, jointing stage and flowering stage.

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