Multi-headed cationic surfactants and their use in promoting the deposition of droplet spreading

Abstract

This invention discloses the preparation of a multiheaded cationic surfactant and its application in promoting droplet spreading and deposition. The method includes: assembling a 10-20 mM quaternary ammonium columnar aromatic hydrocarbon (QAP5) and a 10-20 mM high-molecular-weight surfactant octadecylamine polyoxyethylene ether (AC-1860) through hydrophobic interaction, followed by ultrasonication and stirring to prepare a multiheaded cationic superspreader with a spherical vesicle structure. This invention utilizes the multifunctional sites and excellent assembly properties of columnar aromatic hydrocarbons, using positively charged hydrophilic columnar aromatic hydrocarbons as the host molecule and a neutral high-molecular-weight surface aid as the guest molecule, to construct a novel multiheaded cationic surfactant spreading agent under van der Waals forces. This multi-headed cationic surfactant assembles into a positively charged spherical vesicle structure in water. It has high surface activity and strong migration ability. The nano-sized spherical vesicles can be effectively embedded into the micro-nano structure of rice leaves, which improves the liquid-solid interaction between droplets and rice striped leaf surfaces, and finally realizes the spreading and deposition of droplets on superhydrophobic rice striped leaf surfaces.

Description

Technical Field

[0001] This invention relates to the field of pesticide use reduction and efficiency enhancement technology, and particularly to multi-headed cationic surfactants, their preparation methods, and their application in promoting droplet spreading and deposition. Background Technology

[0002] Rice is one of the world's three major food crops and my country's most important food crop, playing a vital role in national food security and economic development. The spraying of pesticides to control pests and diseases is crucial for ensuring increased rice yields. However, rice leaves are composed of a multi-level micro-nano structure with parallel stripes and a hydrophobic waxy layer, exhibiting superhydrophobic properties. Therefore, when pesticide droplets impact rice leaves, severe splashing, rebounding, and drift occur, making deposition extremely difficult. Over 90% of pesticide formulations flow into the soil and lakes, causing environmental pollution and economic losses. Furthermore, due to the difficulty in droplet retention, pesticide formulations require repeated spraying, leading to excessive pesticide use and posing a significant threat to food safety and human health. Therefore, research on promoting droplet spreading and deposition has significant scientific and economic value.

[0003] Traditional single-headed small-molecule surfactants primarily achieve droplet spreading and deposition on superhydrophobic interfaces by reducing surface tension. However, the micelles formed by these single-headed surfactants are unstable, exhibit low surface activity, and have weak interactions with superhydrophobic leaf surfaces, making it difficult for their droplets to deposit on hydrophobic rice leaves. Multi-headed surfactants, on the other hand, possess advantages such as strong assembly capabilities, high surface activity, and strong migration ability. Their self-assembly structures can enhance the interaction between droplets and superhydrophobic plant leaves, showing significant promise for promoting droplet spreading and deposition. Here, based on the structure of rice leaves and their negatively charged surface, we chose to construct a multi-headed cationic surfactant. Utilizing its stable nanospherical vesicle assembly structure, high surface activity, and positive charge, we enhanced its interaction with the rice leaf surface, thereby regulating droplet spreading and deposition on striped rice leaves. Specifically, a positively charged water-soluble quaternary ammonium salt columnar aromatic hydrocarbon (QAP5)[5] was selected as the host, and a neutral polymeric surfactant, octadecylamine polyoxyethylene ether (AC-1860), was selected as the guest molecule. A novel multi-headed cationic surfactant was constructed using van der Waals forces. This multi-headed cationic surfactant was assembled in water into a positively charged stable nanosphere vesicle structure with high surface activity and a certain viscosity. The vesicle structure could be embedded into the micro-nano structure of rice leaves, which improved the interaction between droplets and rice striped leaf surfaces, increased the retention capacity of droplets, and finally achieved the spreading and deposition of droplets on superhydrophobic rice striped leaf surfaces. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a multiheaded cationic surfactant and its application in promoting droplet spreading and deposition. Utilizing the multifunctional sites and excellent assembly properties of columnar aromatic hydrocarbons, a novel multiheaded cationic surfactant spreading agent is constructed using the positively charged hydrophilic columnar aromatic hydrocarbon QAP5 as the host molecule and the neutral polymeric surfactant octadecylamine polyoxyethylene ether (AC-1860) as the guest molecule, through van der Waals forces. This multiheaded surfactant assembles in water to form a stable spherical vesicle structure with high surface activity and a certain viscosity. The vesicle structure of the assembly can be effectively embedded into the micro-nano structure of rice leaves, increasing the interaction force between droplets and the rice leaf surface and promoting droplet spreading and deposition on the rice leaf surface.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] In a first aspect of the present invention, a method for preparing a multi-headed cationic surfactant is provided, the method comprising:

[0007] An aqueous solution of a positively charged hydrophilic columnar aromatic hydrocarbon with a concentration of 10–20 mM and an aqueous solution of a neutral polymeric surfactant with a concentration of 10–20 mM are mixed in an equimolar ratio of (1–3):(1–3) by volume, followed by ultrasonication and stirring to obtain a multi-headed cationic surfactant.

[0008] Furthermore, the hydrophilic columnar aromatic hydrocarbon is a quaternary ammonium salt columnar aromatic hydrocarbon [5] (QAP5).

[0009] Furthermore, the polymeric surfactant is octadecylamine polyoxyethylene ether (AC-1860).

[0010] Furthermore, the ultrasound duration is 15–20 minutes.

[0011] Furthermore, the stirring time is 30–50 minutes.

[0012] Furthermore, the concentration of the aqueous solution of the hydrophilic columnar aromatic hydrocarbon is 10 mM.

[0013] Furthermore, the concentration of the aqueous solution of the polymeric surfactant is 10 mM.

[0014] Furthermore, the volume ratio of the aqueous solution of the hydrophilic columnar aromatic hydrocarbon to the aqueous solution of the polymeric surfactant is 1:1.

[0015] In a second aspect of the invention, a method for constructing multiheaded cationic surfactants using van der Waals weak interaction forces is provided.

[0016] In a third aspect of the invention, a multi-headed cationic surfactant is provided, which utilizes its high assembly capability to form a stable spherical vesicle structure, reducing the surface tension of the droplet, increasing the droplet viscosity, and can be embedded into the micro-nano structure of negatively charged rice leaf surface, increasing the interaction force between the droplet and the rice leaf surface and promoting the impact spreading and deposition of the droplet on the superhydrophobic striped leaf surface of rice.

[0017] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0018] (1) This invention provides a simple and efficient method for preparing multi-headed cationic surfactants. A multi-headed cationic surfactant is formed by assembling a positively charged quaternary ammonium columnar aromatic hydrocarbon (QAP5) with a neutral polymeric surfactant octadecylamine polyoxyethylene ether (AC-1860) under the weak van der Waals interaction.

[0019] (2) The multi-headed cationic surfactant provided by the present invention has strong assembly ability, can form a stable nano-spherical vesicle structure, can effectively reduce the surface tension of droplets, and has a certain viscosity.

[0020] (3) The present invention provides a positively charged multi-headed cationic surfactant assembly with a nanoscale spherical vesicle structure, which can be effectively embedded in the micro-nano structure of the striped rice leaf surface with negative charge, thereby improving the liquid-solid interaction force.

[0021] (4) The multi-headed cationic surfactant provided by the present invention enables rapid wetting and high-speed impact spreading of droplets on the striped leaf surface of rice. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of droplet impact and deposition on rice leaf surface regulated by multi-headed cationic surfactant (QAP5+AC-1860).

[0024] Figure 2 These are molecular structure diagrams of different water-soluble columnar aromatic host molecules and different polymeric surfactant guest molecules.

[0025] Figure 3 This is a screening diagram of binary host-guest assembly of water-soluble columnar aromatics with different structures and polymeric surfactants with different structures. Figure 3(a) Changes in the contact angle of a binary composite solution (10 mM: 10 mM) of water-soluble columnar aromatic hydrocarbons and polymeric surfactants on rice leaves. Figure 3 (b) shows the UV-Vis titration spectra of quaternary ammonium columnar aromatic hydrocarbon QAP5 and polymeric surfactants with different structures. Figure 3 (c) NMR titration binding constant plot of quaternary ammonium column aromatics QAP5 and octadecylamine polyoxyethylene ether AC-1860. Figure 3 (d) Assembly ratio diagram of quaternary ammonium salt columnar aromatics QAP5 and octadecylamine polyoxyethylene ether AC-1860.

[0026] Figure 4 This is a diagram showing the construction and characterization of the multiheaded cationic surfactant (QAP5+AC-1860). Figure 4 (a) is a schematic diagram of the construction of the multiheaded surfactant QAP5+AC-1860. Figure 4 (b) is a particle size analysis diagram of the assembly of multiheaded surfactant (QAP5+AC-1860). Figure 4 (c) is a schematic diagram of the zeta potential characterization of the multi-headed surfactant (QAP5+AC-1860), and 4(d) is a scanning electron microscope image of the assembly structure of the multi-headed surfactant (QAP5+AC-1860).

[0027] Figure 5 This is a dynamic wetting experiment diagram of multi-headed cationic surfactant (QAP5+AC-1860) droplets on rice leaf surface.

[0028] in Figure 5 (a) Dynamic contact angle variation of multi-headed cationic surfactant (QAP5+AC-1860) droplets on rice leaf surface. Figure 5 (b) is a graph showing the change in the wetting radius of multi-headed cationic surfactant (QAP5+AC-1860) droplets on rice leaves over time. Figure 5 (c) is a graph showing the change in the wetted area of ​​multi-headed cationic surfactant (QAP5+AC-1860) droplets on rice leaves over time.

[0029] Figure 6 This is a high-speed impact deposition diagram of multi-headed cationic surfactant (QAP5+AC-1860) droplets on the surface of rice leaves.

[0030] in Figure 6 (a) Scanning electron microscope image of the microstructure of rice leaves. Figure 6 (b) is a schematic diagram of the dynamic impact behavior of multi-headed cationic surfactant (QAP5+AC-1860) droplets on rice leaf surface. Figure 6(c) is the normalized impact diffusion diameter (D) of multi-headed cationic surfactant (QAP5+AC-1860) droplets on rice leaf surface. t / D o ) Schematic diagram showing the change over time. Figure 6 (d) is a schematic diagram of the impact diffusion area of ​​multi-headed cationic surfactant (QAP5+AC-1860) droplets on rice leaf surface.

[0031] Figure 7 This is a schematic diagram illustrating the erosion resistance of multi-headed cationic surfactant (QAP5+AC-1860) droplets after impact and deposition on rice leaf surfaces (laser confocal microscopy characterization was performed on the leaf surface after erosion; the stronger the fluorescence signal, the stronger the droplet retention ability). Figure 7 (a) is a fluorescence confocal visualization characterization of the impact deposition behavior of a multi-headed cationic surfactant (QAP5+AC-1860) complex sodium fluorescein solution on rice leaves. Figure 7 (b) Fluorescence intensity of the multi-headed cationic surfactant (QAP5+AC-1860) compound sodium fluorescein solution on rice leaves before and after rinsing. Figure 7 (c) The impact retention rate of the multi-headed cationic surfactant (QAP5+AC-1860) combined with sodium fluorescein solution on rice leaves.

[0032] Figure 8 This is a diagram illustrating the impact and deposition mechanism of multi-headed cationic surfactant (QAP5+AC-1860) droplets on rice leaf surfaces.

[0033] in Figure 8 (a) is a schematic diagram showing the change in surface tension of the multi-headed cationic surfactant (QAP5+AC-1860) as a function of concentration. Figure 8 (b) is a schematic diagram of the shear viscosity of the multi-headed surfactant (QAP5+AC-1860). Figure 8 (c) and Figure 8 (d) is a scanning electron microscope image of the microscopic deposition of multi-headed cationic surfactant (QAP5+AC-1860) droplets on rice leaf surface before and after impact. Detailed Implementation

[0034] The present invention will be described in detail below with reference to specific embodiments and examples, thereby making the advantages and various effects of the present invention more clearly apparent. Those skilled in the art should understand that these specific embodiments and examples are for illustrative purposes only and are not intended to limit the present invention.

[0035] Throughout this specification, unless otherwise specified, the terminology used herein should be understood as having the meaning commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In the event of any conflict, this specification shall prevail.

[0036] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be obtained by purchasing them from the market or by existing methods.

[0037] The technical solution of this application embodiment is to solve the above-mentioned technical problems, and the general idea is as follows:

[0038] According to a typical embodiment of the present invention, a method for preparing a multi-headed cationic surfactant is provided, such as... Figure 1 As shown, the method includes:

[0039] An aqueous solution of hydrophilic quaternary ammonium columnar aromatic hydrocarbon QAP5 with a concentration of 10–20 mM and an aqueous solution of octadecylamine polyoxyethylene ether AC-1860 with a concentration of 10–20 mM were mixed in an equimolar volume ratio, followed by ultrasonication and stirring. A multi-headed cationic surfactant was obtained through self-assembly.

[0040] The reason for choosing a concentration of 10-20 mM for the aqueous solution of hydrophilic columnar aromatics is that this concentration is conducive to the assembly of quaternary ammonium salt columnar aromatics and polymeric surfactants, and has a good impact spreading effect. If the concentration is too high, it will have the adverse effect of solid precipitation and waste raw materials. If the concentration is too low, the assembly will be unstable and unable to form an effective assembly.

[0041] The reason for choosing a concentration of 10-20 mM for the aqueous solution of the polymer surfactant is that this concentration is used to form a stable assembly structure. If the concentration is too high, it will have the adverse effect of solid precipitation, which will be detrimental to spraying. If the concentration is too low, it will have the adverse effect of unstable assembly and poor impact deposition effect.

[0042] The hydrophilic columnar aromatic hydrocarbon is a quaternary ammonium salt columnar aromatic hydrocarbon [5] (QAP5), which was synthesized in the laboratory.

[0043] The polymeric surfactant octadecylamine polyoxyethylene ether (AC-1860) was commercially available.

[0044] This invention selects positively charged quaternary ammonium salt columnar aromatics [5] (QAP5) hydrophilic columnar aromatics as the host molecule, and correspondingly uses neutral polymeric surfactant AC-1860 as the guest molecule. Under the action of van der Waals forces, a multi-headed surfactant is assembled to form a stable spherical vesicle structure in water, thereby realizing the superspreading deposition of liquid on the striped leaf surface of rice.

[0045] The inventors of this application discovered through experiments that QAP5 can only undergo host-guest assembly with AC-1860 to form a multi-headed surfactant. QAP5 cannot assemble with other surfactants to form a multi-headed surfactant; specific original experimental data can be found in Comparative Example 1.

[0046] The quaternary ammonium salt columnar aromatic hydrocarbon (QAP5) is preferably prepared by the following steps: 10 g of 1,4-bis(2-hydroxyethoxy)benzene, 39.8 g of carbon tetrabromide and 100 mL of acetonitrile solution are added to a 500 mL three-necked flask. Triphenylphosphine solution (31.5 g, dissolved in 150 mL of acetonitrile solution) is slowly added at 0 °C. The reaction is carried out at room temperature for 4 h under nitrogen protection. Then, 200 mL of cold water is added to the reaction mixture, and a white precipitate is precipitated. The precipitate is filtered, washed with methanol, and dried under vacuum to obtain a white solid bromine monomer (13.8 g). Subsequently, 3 g of bromine monomer, 0.35 g of paraformaldehyde and 150 mL of dichloroethane are added to a 250 mL three-necked flask. Under N2 protection, 1.6 g of boron trifluoride diethyl ether is slowly added. After reacting at room temperature for 3 h, methanol is added to quench the reaction. Vacuum filtration was performed, and the filtrate was purified by silica gel column chromatography using petroleum ether / dichloromethane (1:2) as the eluent to obtain a white powder, which was bromine[5]arene (1.3 g). Finally, 1 g of bromine[5]arene, 6.6 mL of trimethylamine ethanol solution (33% wt) and 100 mL of ethanol solution were added to a 250 mL three-necked flask, and the mixture was refluxed for 12 h. The solvent was removed by evaporation, deionized water was added, and the mixture was filtered. Then the water was removed by evaporation to obtain a white solid, which was quaternary ammonium salt[5]arene (QAP5, 1.1 g).

[0047] The sonication time is 15-20 minutes. Too short a sonication time is not conducive to the dissolution and dispersion of the sample, while too long a sonication time is not conducive to the assembly and formation of multi-headed cationic surfactants.

[0048] The stirring time is 20–50 minutes. Too short a stirring time is not conducive to complete assembly of the assembly, while too long a stirring time is not conducive to the formation of a stable multi-headed surfactant.

[0049] This invention utilizes the excellent host-guest assembly properties of macrocyclic molecules to assemble a multi-headed cationic surfactant (QAP5+AC-1860) by combining a quaternary ammonium salt columnar aromatic hydrocarbon (QAP5) and a high molecular weight surfactant octadecylamine polyoxyethylene ether (AC-1860) under van der Waals forces. 1The successful construction and assembly of multiheaded surfactants were characterized using 1H NMR spectroscopy, DLS particle size / potential analyzer, and scanning electron microscopy. The static and dynamic wetting effects, high-speed impact behavior, and erosion resistance of the multiheaded surfactants on rice leaves were investigated using a contact angle meter, high-speed photography, and laser confocal microscopy. The results showed that the designed and constructed multiheaded surfactants exhibited strong assembly capabilities, forming stable spherical vesicle structures and effectively reducing droplet surface tension while increasing droplet viscosity. The positively charged assemblies and nanoscale spherical vesicle structures effectively embedded themselves in the negatively charged micro / nanostructures of rice leaves, enhancing droplet-leaf interaction, increasing droplet retention, and promoting superspreading and deposition of droplets on the striped surface of rice leaves.

[0050] The following will provide a detailed description of a multiheaded cationic surfactant, its preparation method, and its application, in conjunction with embodiments, comparative examples, and experimental data.

[0051] The abbreviations in this embodiment of the invention are explained as follows:

[0052] QAP5: Quaternary ammonium salt column[5] aromatics;

[0053] AC-1860: Octadecylamine polyoxyethylene ether, CAS: 26635-92-7;

[0054] MAP5: Thioyl acetate columnar aromatic hydrocarbon;

[0055] AEO-9: Fatty alcohol polyoxyethylene ether, CAS: 68131-39-5;

[0056] NP-40: Nonylphenol polyoxyethylene ether, CAS: 26027-38-3;

[0057] Example 1: Spreading agent QAP5+AC-1860, its preparation method, and structural characterization

[0058] 1. Spreading agent QAP5+AC-1860 and its preparation method

[0059] (1) Synthesis of QAP5 host molecule

[0060] like Figure 2As shown, 10 g of 1,4-bis(2-hydroxyethoxy)benzene, 39.8 g of carbon tetrabromide, and 100 mL of acetonitrile solution were added to a 500 mL three-necked flask. Triphenylphosphine solution (31.5 g, dissolved in 150 mL of acetonitrile solution) was slowly added at 0 °C. The reaction was carried out at room temperature for 4 h under nitrogen protection. Then, 200 mL of cold water was added to the reaction mixture, resulting in a white precipitate. The precipitate was filtered, washed with methanol, and dried under vacuum to obtain a white solid bromine monomer (13.8 g). Subsequently, 3 g of the bromine monomer, 0.35 g of paraformaldehyde, and 150 mL of dichloroethane were added to a 250 mL three-necked flask. Under N2 protection, 1.6 g of boron trifluoride diethyl ether was slowly added. After reacting at room temperature for 3 h, the reaction was quenched by adding methanol. Vacuum filtration was performed, and the filtrate was purified by silica gel column chromatography using petroleum ether / dichloromethane (1:2) as the eluent to obtain a white powder, which was bromine[5]arene (1.3 g). Finally, 1 g of bromine[5]arene, 6.6 mL of trimethylamine ethanol solution (33% wt) and 100 mL of ethanol solution were added to a 250 mL three-necked flask, and the mixture was refluxed for 12 h. The solvent was removed by evaporation, deionized water was added, and the mixture was filtered. Then the water was removed by evaporation to obtain a white solid, which was quaternary ammonium salt[5]arene (QAP5, 1.1 g). 1 H NMR (600MHz, D2O) δ6.75 (s, 10H), 4.32 (d, J = 75.9Hz, 20H), 3.74 (s, 12H), 3.62 (s, 21H), 3.08 (d, J = 70.7Hz, 92H).

[0061] (2) Assembly of multi-headed surfactant QAP5+AC-1860

[0062] The structures of columnar aromatic hydrocarbon molecules (host) with different structures and surfactant molecules (guest) with different structures are as follows: Figure 2 As shown. 3 mL of quaternary ammonium salt column[5] aromatic QAP5 aqueous solution (10 mM) and 3 mL of AC-1860 (10 mM) aqueous solution were added to 10 mL glass sample bottles, sonicated for 20 min, and stirred at room temperature for 30 min. The QAP5+AC-1860 multi-headed cationic surfactant assembly was obtained by van der Waals forces.

[0063] 2. Assembly structure characterization of multiheaded surfactant QAP5+AC-1860

[0064] The assembly diagram of the multiheaded surfactant QAP5+AC-1860 is shown below. Figure 4 As shown in figure a. We first characterized the assembly particle size and potential of the multiheaded surfactant QAP5+AC-1860 using dynamic light scattering (DLS), as shown in figure a. Figure 4As shown in b and 4c, the particle size of the QAP5+AC-1860 assembly is approximately 360 nm, and the Zate potential ζ is +29.28 mV.

[0065] Transmission electron microscopy (TEM) was used to characterize the morphology and structure of the multiheaded surfactant QAP5+AC-1860 assembly, and the results showed that the QAP5+AC-1860 assembly was a spherical vesicle structure.

[0066] 2. Characterization of the host-guest interaction of the multi-headed surfactant QAP5+AC-1860

[0067] We through 1 The magnitude of the interaction between QAP5 and AC-1860 was characterized by 1H NMR titration experiments, such as Figure 3 As shown in Figure c, the binding constant between QAP5 and AC-1860 calculated from the NMR titration results is Ka = 2.09 × 10⁻⁶. 3 M -1 It has a strong host-guest role and can effectively perform self-assembly. The host-guest assembly ratio of QAP5 and AC-1860 is 1:1. Figure 3 d). The above results indicate that QAP5 and AC-1860 can perform host-guest assembly through weak interactions.

[0068] Comparative Example 1

[0069] The comparative examples are binary solutions formed by assembling MAP5 with surfactant AC-1860 and QAP5 with surfactant AC-1860.

[0070] The contact angles of binary solutions formed by the assembly of different host and guest molecules were characterized using a contact angle meter.

[0071] The results are as follows Figure 3 As shown in Figure a, it can be seen that the composite solutions assembled with MAP5 and surfactant AC-1860, as well as the composite solutions assembled with QAP5 and surfactant AC-1860, have relatively large contact angles. However, the composite solution assembled with QAP5 and AC-1860 in Example 1 of this invention has the smallest contact angle on the rice leaf surface, which can effectively reduce the water contact angle and achieve wetting on the leaf surface, thus possessing the characteristics of an excellent surfactant.

[0072] Comparative Example 2

[0073] The comparative example presents experimental data on the assembly of QAP5 with other surfactants (AEO-9, NP-40), specifically:

[0074] The fluorescence spectrometric titration experiment was used to test QAP5 (1×10⁻⁶) -5 M) and different surfactants, namely AEO-9, NP-40 (1×10)-5 The interaction between the subject and object (M) was explored.

[0075] The results are as follows Figure 3 As shown in b, QAP5(1×10 -5 There was no quenching attenuation phenomenon between QAP5A and surfactants AEO-9 (fatty alcohol polyoxyethylene ether) and NP-40. The above experimental results indicate that QAP5A cannot assemble with other surfactants to form multiheaded surfactants. Only when an equivalent amount of AC-1860 was added to the QAP5 solution did the fluorescence intensity of the QAP5 solution show a significant quenching attenuation, indicating a weak interaction between QAP5 and AC-1860.

[0076] Application Example 1: Application of spreading agent QAP5+AC-1860 in wetting and impact spreading on rice leaves.

[0077] (1) Dynamic wetting process of contact angle of multi-headed cationic surfactant (QAP5+AC-1860) on rice leaf surface.

[0078] Under the same conditions, the dynamic wetting changes of droplets in a 10mM multi-headed cationic surfactant solution (QAP5+AC-1860) at a certain concentration were studied over 4 minutes at the interface of a superhydrophobic rice leaf using an OCA20 contact angle meter. The changes in droplet wetting radius and spreading area over a certain time were calculated using the obtained contact angle changes. Figure 5 As shown in Figure a, the contact angles of the polymeric surfactant (AC-1860) and the quaternary ammonium salt [5] aromatic hydrocarbon (QAP5) remained almost unchanged within 4 minutes, exhibiting a hydrophobic state. However, the multi-headed cationic surfactant (QAP5+AC-1860) rapidly reduced the contact angle of water to 63±0.7° within 4 minutes, exhibiting a hydrophilic state. This indicates that the dynamic wetting ability of the multi-headed cationic surfactant QAP5+AC-1860 on the superhydrophobic rice leaf surface is significantly better than that of the polymeric surfactant (AC-1860) and the quaternary ammonium salt [5] aromatic hydrocarbon (QAP5). At the same time, the dynamic spreading area of ​​the multi-headed cationic surfactant on the hydrophobic rice leaf interface was studied and calculated using theoretical formulas and contact angle data, such as Figure 5 b and Figure 5 As shown in c. The results show that the self-assembled multiheaded cationic surfactant (QAP5+AC-1860) has the largest spreading area on rice leaves, which is much larger than the spreading area of ​​the polymeric surfactant droplets themselves, indicating that the multiheaded cationic surfactant QAP5+AC-1860 can effectively promote the wetting and spreading of droplets on hydrophobic rice leaves.

[0079] (2) High-speed impact behavior of multi-headed cationic surfactant (QAP5+AC-1860) on rice leaves.

[0080] Under the same conditions, a high-speed camera was used to study the dynamic impact behavior of a multi-headed cationic surfactant droplet (QAP5+AC-1860) at a certain concentration (10mM) impacting a superhydrophobic interface / leaf surface at a height of 20cm, in order to determine the dynamic impact deposition behavior of the multi-headed cationic surfactant.

[0081] Meanwhile, H2O, QAP5, AC-1860, and the superamphilic surfactant MAP5+CTAB from patent CN114982750B were used as comparisons.

[0082] like Figure 6 As shown in b, during the retraction process, H2O, QAP5, AC-1860, and MAP5+CTAB droplets begin to split along the central fringe, exhibiting significant anisotropic retraction, with small spherical droplets remaining on the rice surface. However, the retraction splashing behavior of QAP5+AC-1860 droplets is suppressed during the retraction process, indicating a close interaction with the rough rice fringe interface. The final state of the droplet is not retraction into a single sphere or multiple droplets, but rather it spreads across the interface, continuing to spread over time.

[0083] We also statistically analyzed the change in the droplet diffusion diameter (Dt / Do) on the leaf surface over time during the impact process, such as... Figure 6 As shown in Figure c, the QAP5+AC-1860 droplets have the largest diffusion diameter during the impact and spreading process on the leaf surface, thus achieving impact spreading and deposition on the leaf surface.

[0084] We also performed quantitative statistics on the final normalized impact spread area. For example... Figure 6 As shown in d, it was found that the final spreading area of ​​QAP5+AC-1860 was much larger than that of the other droplets, and the impact spreading effect was the best.

[0085] (3) Anti-erosion behavior of multi-headed cationic surfactant (QAP5+AC-1860) impacting rice leaf surface

[0086] Under the same conditions, the erosion resistance and retention capacity of droplets impacting rice leaves was studied using a laser confocal microscope. Figure 7 As shown. We added 1×10 to each of the following solutions: H2O, AC-1860, QAP5, MAP5+CTAB, and QAP5+AC-1860. -5 A droplet of 8 μL of sodium fluorescein at a height of 20 cm impacts a point 2 cm below the surface. 2Rice leaf surfaces (2cm long × 1cm wide). Five minutes after impaction, rice leaf surfaces containing different droplets were fixed on a 45° angled surface, and 3mL of water was vertically sprayed to wash the rice leaf surfaces from the morning. Laser confocal microscopy (LSCM) was then performed on the washed leaf surfaces. The model compound sodium fluorescein on the rice leaf was excited at 405nm, and the rice leaf surface was excited at 522nm.

[0087] The differences in the rain erosion resistance of various adjuvant droplets were illustrated by comparing the fluorescence intensity retained on rice leaf surfaces. Experimental results showed that, compared to the other four droplets, QAP5+AC-1860 exhibited the highest fluorescence intensity and the widest retention range on the rice leaf surface. This indicates that it can effectively embed itself into the micro-nano structures of the rice leaf, increasing the affinity between the droplet and the leaf surface, and thus possessing excellent rain erosion resistance.

[0088] Experiment 1: Physicochemical properties of spreading agent QAP5+AC-1860 and its spreading mechanism upon impacting rice leaves

[0089] (1) Physicochemical properties of multiheaded cationic surfactant (QAP5+AC-1860).

[0090] Under the same conditions, the surface tension changes of the multi-headed cationic surfactant (QAP5+AC-1860) at different concentrations were measured using an OCA20 contact angle meter. Figure 8 As shown in Figure a, the experiment revealed that the critical surface tension of the AC-1860 solution was 52.79 mN / m, while the surface tension of the QAP5+AC-1860 composite solution decreased continuously with increasing concentration, reaching a critical surface tension of 44.45 mN / m at 0.1 mM. The results indicate that the assembled multi-headed cationic surfactant QAP5+AC-1860 can effectively reduce the surface tension of the liquid, exhibiting high surface activity and strong migration ability, making the solution relatively easy to wet rice leaves. Simultaneously, we used a viscometer to test the viscosity of the QAP5+AC-1860 solution and found that the viscosity of the assembled QAP5+AC-1860 solution increased, which significantly reduced the breakup and splashing of droplets upon impact with the rice leaf surface. Figure 8 (b) To further illustrate the binding of QAP5+AC-1860 spreading agent to rice leaves, we observed the liquid-solid microstructure of QAP5+AC-1860 droplets after deposition on the rice leaf surface using SEM. The rice leaves were fixed and dehydrated before being subjected to SEM using a contact angle analyzer. After freeze-drying, the samples were observed under SEM. Figure 8As shown in Figure c, the surface of rice is composed of micron-sized striped structures and nano-sized papillae, exhibiting a multi-level micro / nano structure. When QAP5+AC-1860 composite droplets impact and deposit on the rice leaf surface, the assembled nanovesicle structures tightly wrap around the micron-sized papillae structures on the leaf surface and embed themselves within the nanosheet-like structures of the rice leaf surface. Figure 8 d) This increases the liquid-solid interaction force, ultimately achieving wetting and spreading on the rice leaf surface.

[0091] Finally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0092] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention.

[0093] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing a multi-headed cationic surfactant, characterized in that, The method includes: Quaternary ammonium salt columnar aromatics with a concentration of 10-20 mM and octadecylamine polyoxyethylene ether, a high molecular weight surfactant with a concentration of 10-20 mM, are mixed in a volume ratio of (1-3):(1-3), and then ultrasonicated and stirred to form a multi-headed cationic surfactant. The columnar aromatic hydrocarbon is a quaternary ammonium salt columnar aromatic hydrocarbon (QAP5), and the polymeric surfactant is octadecylamine polyoxyethylene ether AC-1860; The quaternary ammonium salt column[5] aromatic hydrocarbon (QAP5) was prepared by the following steps: 10 g of 1,4-bis(2-hydroxyethoxy)benzene, 39.8 g of carbon tetrabromide and 100 mL of acetonitrile solution were added to a 500 mL three-necked flask. Triphenylphosphine solution was slowly added at 0 °C. The triphenylphosphine solution was prepared by dissolving 31.5 g of triphenylphosphine in 150 mL of acetonitrile solution. The reaction was carried out at room temperature for 4 h under nitrogen protection. Then, 200 mL of cold water was added to the reaction mixture, and a white precipitate was precipitated. The precipitate was filtered, washed with methanol, and dried under vacuum to obtain a white solid bromine monomer. Subsequently, 3 g of bromine monomer and 0.35 g of acetonitrile were added to a 250 mL three-necked flask. g of paraformaldehyde and 150 mL of dichloroethane were added slowly under N2 protection with 1.6 g of boron trifluoride ether. After reacting at room temperature for 3 h, methanol was added to quench the reaction. The mixture was then filtered under vacuum. The filtrate was purified by silica gel column chromatography with petroleum ether / dichloromethane (1:2) as the eluent to obtain a white powder, which was bromine[5]arene. Finally, 1 g of bromine[5]arene, 6.6 mL of 33%wt trimethylamine ethanol solution and 100 mL of ethanol solution were added to a 250 mL three-necked flask. The mixture was refluxed for 12 h, the solvent was evaporated to remove the solvent, deionized water was added, the mixture was filtered, and then the water was evaporated to remove the water to obtain a white solid, which was quaternary ammonium salt[5]arene (QAP5).

2. The method for preparing a multi-headed cationic surfactant according to claim 1, characterized in that, The ultrasound session lasted 15 to 20 minutes.

3. The method for preparing a multi-headed cationic surfactant according to claim 1, characterized in that, The stirring time is 30 to 50 minutes.

4. The method for preparing a multi-headed cationic surfactant according to claim 1, characterized in that, The concentration of the aqueous solution of the quaternary ammonium salt columnar aromatic hydrocarbon is 10 mM.

5. The method for preparing a multi-headed cationic surfactant according to claim 1, characterized in that, The concentration of the aqueous solution of the polymeric surfactant is 10 mM.

6. The method for preparing a multi-headed cationic surfactant according to claim 1, characterized in that, The volume ratio of the aqueous solution of the quaternary ammonium salt columnar aromatic hydrocarbon to the aqueous solution of the polymeric surfactant is 1:

1.

7. A multi-headed cationic surfactant obtained by the method according to any one of claims 1-6.

8. The use of the multi-headed cationic surfactant of claim 7 in promoting droplet spreading and deposition.

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