Hydrophilic carboxyl modified siloxane as well as preparation method and application thereof

Abstract

The invention discloses hydrophilic carboxyl modified siloxane as well as a preparation method and application thereof. The chemical structural formula of the hydrophilic carboxyl modified siloxane is shown as a formula I or a formula II, in the formula I and the formula II, R1-R3 are respectively and independently selected from hydrogen atoms, C1-C30 alkyl groups, phenyl groups or phenyl groups substituted by methyl, ethyl and methoxyl; in the formula I and the formula II, R4 is selected from C1-C30 alkyl, C1-C30 alkyl containing heteroatoms in a carbon chain, phenyl or phenyl substituted by methyl, ethyl and methoxyl; in the formula I and the formula II, R5 is selected from hydrogen atoms, C1-C4 alkyl groups and indole methyl groups. The application of the reaction product of epoxy propoxy siloxane and amino acid in capillarity is deeply studied for the first time, it is found that the reaction product can effectively improve the capillary infiltration speed and height, and a new way is opened up for application of the compound in the fields of micro-fluidic chips, drug delivery, liquid transmission and the like.

Description

Technical Field

[0001] This invention belongs to the field of organosilicon chemistry and surface modification technology, specifically relating to a hydrophilic carboxyl-modified siloxane, its preparation method, and its application. Background Technology

[0002] Epoxypropoxysiloxanes possess excellent chemical stability, low surface tension, and reactivity due to the presence of both reactive silicon-oxygen bonds and epoxy groups in their molecular structure. They have significant application value in numerous fields such as coatings, adhesives, and electronic materials.

[0003] In the prior art, Chinese patent CN104086586B discloses a method for modifying the surface of fiber materials with epoxypropoxysiloxane to improve the wear resistance and corrosion resistance of fibers, but this patent does not involve the application of epoxypropoxysiloxane in the control of capillary phenomena.

[0004] Amino acids, as a class of organic compounds containing both amino and carboxyl bifunctional groups, possess excellent biocompatibility, hydrophilicity, and unique molecular recognition capabilities. Reacting epoxypropoxysiloxanes with amino acids yields products that promise to combine the advantages of both, opening up new application areas. For example, Chinese patent CN114555611A discloses siloxane derivatives of amino acids with surface-active properties. The amino acids are functionalized with siloxane groups to form compounds with surface-active properties. The amino acids used in this patent can have an alkyl chain with as few as one or as many as 12 carbons between the N-terminus and C-terminus. This alkyl chain can be further substituted by one or more substituents selected from hydroxyl, amino, amide, sulfonyl, sulfonate, carboxyl, and carboxyl groups. The N-terminal nitrogen can be acylated or alkylated with one or more alkyl groups. The compounds in this patent have low critical micelle concentrations and / or the ability to reduce liquid surface tension, making them suitable for use in shampoos, hair conditioners, car wash detergents, carpet cleaners, wetting agents in aerosol sprays, and additives in aerosol paints. Furthermore, the preparation of siloxane derivatives of amino acids with surface-active properties is disclosed, requiring a reflux reaction in toluene. Chinese Patent Publication No. CN107636048A discloses an organosilicon compound having an amino acid moiety and its preparation method, which involves... Structural formula or its combination The structured epoxy-functionalized organosilicon compounds are obtained by reacting amino acids with amino acids under reflux in the presence of aliphatic alcohols. These amino acid-containing organosilicon compounds are used in cosmetic formulations for skin and hair care, as surface treatments and finishing agents, as polishing agents for textiles and textile fibers, or as softeners during or after washing. Chinese Patent CN101460545B discloses amino acid-functionalized siloxanes, their preparation methods, and applications. It describes the reaction of amino acid derivatives selected from N-acyl and N-aromatic amino acids with amino-functionalized siloxanes to obtain salts of N-acyl or N-aromatic amino acids and aminosiloxanes, which can be applied to ointments, creams, gels, pastes, and foam aerosols. Chinese Patent CN111548501A discloses a method for preparing an amino acid-containing organosilicon surfactant. This involves reacting polyether-modified amino silicone oil with acrylates or chloroacetic acid esters, followed by hydrolysis under alkaline conditions under reflux to obtain the amino acid-containing organosilicon surfactant.

[0005] However, the above-mentioned prior art has at least one of the following shortcomings (see: CN114555611A, CN107636048A, CN101460545B and CN111548501A): 1. The reaction conditions are harsh, often requiring high temperature and high pressure; 2. Poor product selectivity and numerous side reactions; 3. The post-processing technology is complex and the yield is low; 4. It has not yet been applied to capillary phenomena.

[0006] Capillary action plays a crucial role in microfluidic chips, drug delivery, and liquid transport. In-depth research into how to increase the height of liquid rise in capillary action is of great practical significance for promoting technological progress in related fields.

[0007] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0008] The purpose of this invention is to provide a hydrophilic carboxyl-modified siloxane, its preparation method, and its application. This invention solves the problem of how to increase the liquid rise height in existing capillaries. By treating the capillary surface with the hydrophilic carboxyl-modified siloxane of this invention, the speed and height of capillary wetting are effectively improved. It can be widely used in microfluidic chips, drug delivery, liquid transport, and other fields.

[0009] To achieve the above objectives, the present invention provides a hydrophilic carboxyl-modified siloxane, the chemical structural formula of which is shown in Formula I or Formula II:

[0010]

[0011] In Formula I and Formula II, R1 to R3 are each independently selected from hydrogen atoms, C1 to C30 alkyl groups, phenyl groups, or phenyl groups substituted with methyl, ethyl, or methoxy groups; in Formula I and Formula II, R4 is selected from C1 to C30 alkyl groups, C1 to C30 alkyl groups containing heteroatoms in the carbon chain, phenyl groups, or phenyl groups substituted with methyl, ethyl, or methoxy groups; in Formula I and Formula II, R5 is selected from hydrogen atoms, C1 to C4 alkyl groups, or indolemethyl groups.

[0012] Preferably, R1 to R3 are each independently selected from methyl or ethyl.

[0013] Preferably, the R4 is selected from -(CH2)3OCH2-.

[0014] Preferably, R5 is selected from hydrogen atoms, methyl groups, and -(CH2). n NH2-, where n takes values ​​from 1 to 4.

[0015] A second objective of this invention is to provide a method for preparing the aforementioned hydrophilic carboxyl-modified siloxane, the method comprising:

[0016] Under inert gas protection, the siloxane as shown in Formula III, the amino acid as shown in Formula IV, and the catalyst are placed in an organic solvent, stirred, and reacted at 50℃~70℃. After post-treatment, hydrophilic carboxyl-modified siloxanes as shown in Formula I or II are obtained.

[0017] The method of the present invention monitors the reaction by infrared spectroscopy and finds that a reaction temperature of 50℃ to 70℃ can ensure the smooth progress of the ring-opening reaction between epoxypropoxysiloxane and amino acids, while avoiding side reactions caused by excessively high temperatures.

[0018] The use of different amino acids in this invention affects capillary action, which is related to differences in the polarity, charge, and molecular size of the amino acids. Amino acids can modify the properties of solid surfaces through adsorption.

[0019] Preferably, the organic solvent is selected from aromatic solvents, aliphatic hydrocarbon solvents, ether solvents, alcohol solvents, or ketone solvents.

[0020] More preferably, the aromatic solvent is selected from benzene, toluene, or xylene; the aliphatic hydrocarbon solvent is selected from hexaane or pentane; and the alcohol solvent is selected from anhydrous ethanol.

[0021] Preferably, the catalyst is selected from Lewis acid catalysts, organic base catalysts, or organotin catalysts.

[0022] More preferably, the Lewis acid catalyst is selected from aluminum trichloride or titanium tetrachloride; the organic base catalyst is selected from triethylamine; and the organotin catalyst is selected from dibutyltin dilaurate.

[0023] Preferably, the molar ratio of the siloxane to the amino acid is 1:(1~3); the mass of the catalyst is 0.5~4% of the mass of the siloxane.

[0024] Preferably, the amino acid is selected from at least one of glycine, alanine, and tryptophan.

[0025] Preferably, the reaction time is 1 to 5 hours, more preferably 2 to 5 hours. After multiple experiments, it has been verified that a reaction time of 2 to 5 hours can achieve a higher conversion rate.

[0026] Preferably, the post-treatment is as follows: after the reaction is completed, the reaction solution is cooled to room temperature, washed with water, ethyl acetate is added, the organic phase is separated, the organic phase is dried, the organic solvent is removed, and a crude product is obtained; the crude product is purified by column chromatography, using silica gel as the stationary phase and a mixture of petroleum ether and ethyl acetate as the eluent, the eluent containing the target product is collected, the eluent is removed, and the product is vacuum dried to finally obtain a hydrophilic carboxyl-modified siloxane.

[0027] More preferably, the volume ratio of petroleum ether to ethyl acetate in the eluent is (3~5):1; the vacuum drying temperature is 40~60℃, and the drying time is 8~12 h.

[0028] A third objective of this invention is to provide the application of the aforementioned hydrophilic carboxyl-modified siloxane in regulating liquid capillary behavior, wherein the hydrophilic carboxyl-modified siloxane can increase the speed and height of liquid ascent.

[0029] The hydrophilic carboxyl-modified siloxane of this invention possesses a unique molecular structure. Its siloxane portion imparts low surface tension to the material, while the amino acid portion can significantly alter the contact angle between the liquid and solid surfaces through interactions such as hydrogen bonding with liquid molecules. When the reaction product is added to a liquid, it reduces the surface tension of the liquid, increasing its wettability on the capillary wall, making it easier for the liquid to rise within the capillary. Furthermore, it lowers the contact angle between the liquid and the capillary wall, further influencing the speed and height of capillary ascent, thereby achieving effective control over liquid capillary phenomena.

[0030] Based on the above principles, the hydrophilic carboxyl-modified siloxane of the present invention can be used in microfluidic chips to optimize the liquid transport and distribution process, significantly improving the analytical performance of the chip; in the field of drug delivery, its regulatory effect on liquid capillary phenomena can be utilized to achieve targeted and efficient drug delivery, improving the therapeutic effect of the drug; in liquid transport pipelines, adding this reaction product can reduce the resistance of liquid transport, improve transport efficiency, and reduce energy consumption.

[0031] Preferably, the concentration of the hydrophilic carboxyl-modified siloxane in the liquid is 0.1 to 1.0%.

[0032] The hydrophilic carboxyl-modified siloxane, its preparation method, and its application of the present invention solve the problem of how to increase the liquid rise height in existing capillaries, and have the following advantages: (1) This invention is the first to conduct an in-depth study on the application of the reaction product of epoxypropoxysiloxane and amino acid in capillary phenomena. It found that it can effectively improve the speed and height of capillary wetting, opening up new avenues and methods for the application of this type of compound in multiple fields such as microfluidic chips, drug delivery, and liquid transport. It has important scientific research value and practical application value, and is expected to promote technological innovation and industrial development in related fields. (2) The preparation method of the present invention has mild reaction conditions and does not require extreme conditions such as high temperature and high pressure, which reduces the requirements for reaction equipment and energy consumption, making the production process safer and more environmentally friendly; the operation is simple and the reaction steps are concise, making it easy to carry out large-scale industrial production; through the optimization of the reaction process, a one-step synthesis method is adopted, the yield can reach more than 85%, and the product purity is as high as 98%, which effectively reduces the production cost, improves the product quality, and enhances the market competitiveness of the product. Attached Figure Description

[0033] Figure 1 The infrared spectrum of 3-(2,3-epoxypropoxy)propyltrimethoxysilane in Example 1 of this invention is shown.

[0034] Figure 2 The infrared spectrum of 3-(2,3-epoxypropoxy)propyltrimethoxysilane and glycine after reaction in Example 1 of this invention is shown. Detailed Implementation

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] It should be noted that: Unless otherwise specified in the examples, standard conditions or conditions recommended by the manufacturer should be followed. Instruments whose manufacturers are not specified are all commercially available products. Raw materials and reagents whose manufacturers are not specified are all commercially available goods or can be prepared using known methods.

[0037] In this invention, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are used only for simplicity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0038] The features mentioned in this invention can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification, provided that there is no contradiction in the combination of these features. Each feature disclosed in the specification can be replaced by any alternative feature that provides the same, equivalent, or similar purpose. Therefore, unless otherwise specified, the disclosed features are merely general examples of equivalent or similar features.

[0039] Examples 1-5 below illustrate a hydrophilic carboxyl-modified siloxane and its preparation method provided by the present invention, as detailed below: Example 1 A hydrophilic carboxyl-modified siloxane, the specific preparation method of which is as follows: Under nitrogen protection, 23.6 g (0.1 mol) of 3-(2,3-epoxypropoxy)propyltrimethoxysilane and 7.5 g (0.1 mol) of glycine were added to a 250 mL three-necked flask equipped with a stirrer, thermometer and reflux condenser. Then 0.5 g of dibutyltin dilaurate and 100 mL of anhydrous ethanol were added. The mixture was stirred and heated to 60 °C and reacted for 3 h. The reaction progress was monitored by infrared spectroscopy. When the characteristic peak of the epoxy group was significantly weakened, the reaction was considered to be basically completed.

[0040] After the above reaction was completed, the mixture was cooled to room temperature, deionized water was added, and then ethyl acetate, an organic solvent immiscible with water, was added to the reaction solution. The organic phase was separated, and anhydrous sodium sulfate was added to dry the mixture to remove water completely. After filtering to remove the drying agent, the solvent was removed by vacuum distillation to obtain the crude product. The crude product was purified by column chromatography using silica gel as the stationary phase and a mixture of petroleum ether and ethyl acetate in a volume ratio of 3:1 as the eluent. The eluent containing the target product was collected, and the eluent was removed by rotary evaporation. The product was then dried in a vacuum drying oven at 50°C for 10 h to obtain a hydrophilic carboxyl-modified siloxane as shown in Formula I (R1~R3 ​​are all methyl, R4 is -(CH2)3OCH2-, and R5 is H), with a yield of 86.8% and a purity of 98.5% as determined by high performance liquid chromatography.

[0041] The structural formula of 3-(2,3-epoxypropoxy)propyltrimethoxysilane used in this embodiment is as follows:

[0042] like Figure 1 The image shown is the infrared spectrum of 3-(2,3-epoxypropoxy)propyltrimethoxysilane in Example 1 of this invention. The infrared spectrum of 3-(2,3-epoxypropoxy)propyltrimethoxysilane exhibits several characteristic peaks: 3000 ~ 2800 cm⁻¹. -1 The CH stretching vibrations of methyl (-CH3) and methylene (-CH2-) groups exhibit absorption peaks in this region. Specifically, the CH stretching vibration of methyl forms shows an absorption peak at 2960 cm⁻¹. -1 2870cm -1 Nearby, the methylene group is at 2920 cm⁻¹ -1 2850cm -1 Around 1600-1400 cm⁻¹, these peaks represent the saturated hydrocarbon group structure in the molecule. -1 The CH bending vibrations of methyl and methylene groups produce absorption peaks in this region, with the asymmetric bending vibration of methyl groups at 1460 cm⁻¹. -1 Left and right, symmetrical bending vibration at 1380cm -1 Nearby. 1100~1000cm -1 The stretching vibration of the Si-OC bond exhibits a strong absorption peak here, which is one of the important characteristic peaks of this silane compound, reflecting the presence of siloxane groups. (900~800 cm⁻¹) -1 The characteristic absorption peak of the epoxy group is in the range of 910~900 cm⁻¹. -1 The presence of this peak nearby indicates that the molecule contains an epoxy structure.

[0043] like Figure 2 The image shown is the infrared spectrum of 3-(2,3-epoxypropoxy)propyltrimethoxysilane and glycine after their reaction in Example 1 of this invention. Si-O-Si stretching vibration peak: in the range of 1000~1100 cm⁻¹. -1 There are strong absorption peaks on both sides, which are characteristic peaks of the Si-O-Si bonds formed after the hydrolysis and condensation of silane. The CO stretching vibration peak: due to the presence of CO bonds formed after the ring opening of the epoxide in the reaction products, there is a peak in the range of 1050~1200 cm⁻¹. -1 An absorption peak is observed in this region, which partially overlaps with the peak of Si-O-Si. The NH stretching vibration peak is located at 3200–3500 cm⁻¹. -1 There is an absorption peak in the region. Simultaneously, there is an absorption peak at 1550–1650 cm⁻¹. -1 A bending vibration peak appears at 2800–3000 cm⁻¹. A stretching vibration peak (CH) appears at 2800–3000 cm⁻¹: This indicates the presence of an alkyl chain in the product. -1The presence of a moderately strong absorption peak due to the saturated CH stretching vibration in the region indicates the presence of an alkyl group.

[0044] Example 2 A hydrophilic carboxyl-modified siloxane is prepared using a method essentially the same as in Example 1, with the difference being: 27.0 g (0.1 mol) of 3-epoxypropoxypropylphenyl dimethoxysilane was used instead of 3-(2,3-epoxypropoxy)propyltrimethoxysilane, and 14.7 g (0.2 mol) of alanine was used instead of glycine; 0.2 g of aluminum trichloride was used; 120 mL of toluene was used instead of anhydrous ethanol; the reaction temperature was 70 °C, and the reaction time was 4 h. After the reaction, other treatments were basically the same as in Example 1, yielding a hydrophilic carboxyl-modified siloxane as shown in Formula I (R1~R2 are all methyl, R2 is phenyl, R4 is -(CH2)3OCH2-, and R5 is methyl), with a yield of 86.4% and a purity of 98.4%.

[0045] The structural formula of 3-epoxypropoxypropylphenyldimethoxysilane (i.e., 2-(3-(2-epoxypropoxy)propyl)-1-phenoxy-1,1-dimethoxysilane) is as follows:

[0046] Example 3 A hydrophilic carboxyl-modified siloxane is prepared using a method essentially the same as in Example 1, with the difference being: A mixture of 3.75 g (0.05 mol) glycine and 7.35 g (0.1 mol) alanine was used to replace glycine; 0.3 g triethylamine was used to replace dibutyltin dilaurate; 110 mL toluene was used to replace anhydrous ethanol; the reaction temperature was 65 °C, and the reaction was continued for 5 h; after the reaction, other treatments were basically the same as in Example 1, and hydrophilic carboxyl-modified siloxanes (a mixture of glycine and alanine, each with a siloxane attached to the N-terminus) were obtained with a yield of 88.4% and a purity of 98.8%.

[0047] Example 4 A hydrophilic carboxyl-modified siloxane is prepared using a method essentially the same as in Example 1, with the only difference being: The reaction time is 1 hour.

[0048] After the reaction was completed, the product was purified to obtain a hydrophilic carboxyl-modified siloxane with a yield of 80.5% and a purity of 98.5%.

[0049] Example 5 A hydrophilic carboxyl-modified siloxane is prepared using a method essentially the same as in Example 1, with the difference being: 14.6 g (0.1 mol) of lysine (lysine is a basic amino acid that can be dissolved in a small amount of anhydrous ethanol to form a homogeneous solution) was used to replace glycine. Other treatments were basically the same as in Example 1. Hydrophilic carboxyl-modified siloxanes were obtained with a yield of 87.8% and a purity of 98.2%.

[0050] Comparative Example 1 Referring to the relatively complex multi-step preparation method in the existing technology (taking the reaction of lysine with 3-(2,3-epoxypropoxy)propyltrimethoxysilane as an example), the specific steps are as follows: (1) Preparation of Cbz-protected lysine by protecting the α-amino group of lysine In a reaction vessel, L-lysine (146 g, 1.0 mol) and deionized water (300 mL) were added and stirred until dissolved. The mixture was then heated to 40 °C, and benzyloxycarbonyl chloride (Cbz-Cl, 180 g, 1.05 mol, α-amino protecting agent) was added dropwise. Simultaneously, 20% NaOH solution was added dropwise to maintain the pH at 9-10 (to promote the reaction between Cbz-Cl and the α-amino group). After the addition was complete, the reaction was maintained at this temperature for 3 hours. HPLC monitoring showed that the α-amino group protection rate was ≥99%. The reaction solution was adjusted to pH 5 with hydrochloric acid, and a white solid precipitated. This solid was centrifuged, filtered, and dried under vacuum at 40 °C to obtain Cbz-protected lysine (Cbz-NH-CH(COOH)-(CH)4-NH2, yield approximately 90%).

[0051] (2) Carboxyl group activation Cbz-protected lysine (28.2 g, 0.1 mol) was added to a reaction vessel, followed by dichloromethane (100 mL) and N,N-dimethylformamide (DMF, 0.5 mL, catalyst). The mixture was cooled to 0 °C, and oxalyl chloride (14.3 g, 0.11 mol) was added dropwise. The reaction was maintained at this temperature for 1 h to generate an acyl chloride-activated carboxyl intermediate (Cbz-NH-CH(COCl)-(CH)4-NH2). Excess oxalyl chloride and solvent were removed by rotary evaporation, and the intermediate was used directly in the next step without further purification.

[0052] (3) Selective ring-opening reaction with epoxypropoxy compounds In a reactor, under nitrogen protection, 3-(2,3-epoxypropoxy)propyltrimethoxysilane (236 g, 1.0 mol), acyl chloride activated carboxyl intermediate (0.95 mol), isopropanol (500 mL) and tetramethylguanidine (TMG, 5 g, alkaline catalyst, to promote nucleophilic attack of amino groups) were added. The temperature was raised to 65 °C and the reaction was stirred for 8 h (the disappearance rate of the characteristic peak of epoxy groups was ≥98% by infrared monitoring). During the reaction, the temperature was controlled by a jacket to avoid local overheating that could lead to epoxy group self-polymerization. (4) Remove the protective group The reaction solution from step (3) was transferred to a hydrogenation reactor, 10% palladium on carbon catalyst (5g) was added, hydrogen gas was introduced (pressure 0.3MPa), and the reaction was carried out at 30°C for 4h (the Cbz group was removed to benzyl alcohol under hydrogenation conditions). The catalyst was removed by filtration, and the isopropanol was removed by rotary evaporation of the filtrate to obtain the crude product.

[0053] (5) Column chromatography purification The crude product was dissolved in ethyl acetate (300 mL), and washed three times with 5% sodium chloride solution (200 mL) (to remove unreacted lysine). After separation, the organic phase was dehydrated (anhydrous sodium sulfate was added, and the recovered product was recycled). The low-boiling components (unreacted silane monomers) were separated by molecular distillation (temperature 80~100℃, pressure 100 Pa) to obtain the target product.

[0054] Following the steps above, the final yield was only 65%, and the purity was 90%.

[0055] Compared with the embodiments of the present invention, the traditional method has lower yield and purity, which fully demonstrates the superiority of the preparation method of the present invention.

[0056] Examples 6-10 and Comparative Example 2 below illustrate the application of the hydrophilic carboxyl-modified siloxanes prepared above in capillary action, as detailed below: Example 6 This embodiment demonstrates the application of the hydrophilic carboxyl-modified siloxane prepared in Example 1 above in capillary action, as detailed below: Prepare a capillary tube with an inner diameter of 0.2 mm, and prepare an aqueous solution of the hydrophilic carboxyl-modified siloxane prepared in Example 1 with a mass fraction of 0.5%. Vertically insert the cleaned capillary tube into the container containing the aqueous solution of the hydrophilic carboxyl-modified siloxane, and after 30 seconds, measure the height of the liquid rising in the capillary tube, which is 4.5 cm.

[0057] Under the same conditions, the height of the liquid rising in the capillary without treatment with the aqueous solution of the hydrophilic carboxyl-modified siloxane was 3.0 cm, indicating that the hydrophilic carboxyl-modified siloxane of the present invention can significantly promote the capillary rise of the liquid.

[0058] Example 7 This embodiment demonstrates the application of the hydrophilic carboxyl-modified siloxane prepared in Example 2 above in capillary action, as detailed below: A capillary tube with an inner diameter of 0.3 mm was prepared, and the hydrophilic carboxyl-modified siloxane prepared in Example 2 was dissolved in ethanol at a mass fraction of 1%. A capillary effect experiment was conducted. After 60 seconds, the liquid rose to a height of 4.0 cm in the capillary tube, while the height in the capillary tube without the hydrophilic carboxyl-modified siloxane aqueous solution was only 2.5 cm. This further verifies the promoting effect of the reaction product on liquid capillary action.

[0059] Example 8 This embodiment demonstrates the application of the hydrophilic carboxyl-modified siloxane prepared in Example 3 above in capillary action, as detailed below: A capillary tube with an inner diameter of 0.1 mm was prepared, and the hydrophilic carboxyl-modified siloxane prepared in Example 3 was dissolved in water to a concentration of 0.1% by mass. A capillary experiment was conducted, and after 60 seconds, the height the liquid rose in the capillary tube was measured to be 4.5 cm. Under the same conditions, the height the liquid rose in the capillary tube without the hydrophilic carboxyl-modified siloxane aqueous solution was 3.0 cm, indicating that the reaction product can significantly promote the capillary ascent of the liquid.

[0060] Example 9 This embodiment demonstrates the application of the hydrophilic carboxyl-modified siloxane prepared in Example 4 above in capillary action, as detailed below: A capillary tube with an inner diameter of 0.2 mm was prepared, and the hydrophilic carboxyl-modified siloxane prepared in Example 4 was dissolved in water to a concentration of 0.5% by mass. The cleaned capillary tube was vertically inserted into a container containing the hydrophilic carboxyl-modified siloxane aqueous solution. After 30 seconds, the height of the liquid rising in the capillary tube was measured to be 4.2 cm. Under the same conditions, the height of the liquid rising in the capillary tube without the hydrophilic carboxyl-modified siloxane aqueous solution was 3.0 cm, indicating that the reaction product can significantly promote the capillary ascent of the liquid.

[0061] Example 10 This embodiment demonstrates the application of the hydrophilic carboxyl-modified siloxane prepared in Example 5 above in capillary action, as detailed below: A capillary tube with an inner diameter of 0.2 mm was prepared, and the hydrophilic carboxyl-modified siloxane prepared in Example 5 was dissolved in water to a concentration of 0.5% by mass. The cleaned capillary tube was vertically inserted into a container containing the hydrophilic carboxyl-modified siloxane aqueous solution. After 30 seconds, the height of the liquid rising in the capillary tube was measured to be 4.2 cm. Under the same conditions, the height of the liquid rising in the capillary tube without the hydrophilic carboxyl-modified siloxane aqueous solution was 3.0 cm, indicating that the reaction product can significantly promote the capillary ascent of the liquid.

[0062] Comparative Example 2 This comparative example demonstrates the application of the hydrophilic carboxyl-modified siloxane prepared in Comparative Example 1 above in capillary action, as detailed below: Prepare a capillary tube with an inner diameter of 0.2 mm. Prepare a 0.5% (w / w) aqueous solution of the hydrophilic carboxyl-modified siloxane prepared in Comparative Example 1. Vertically insert the cleaned capillary tube into the container containing the hydrophilic carboxyl-modified siloxane aqueous solution. After 30 seconds, measure the height the liquid rises in the capillary tube; it is 4.0 cm. Under the same conditions, the height the liquid rises in the capillary tube without the hydrophilic carboxyl-modified siloxane aqueous solution is 3.0 cm. This indicates that the reaction product can significantly promote capillary ascent. However, the purity of the hydrophilic carboxyl-modified siloxane prepared in this comparative example is not as high as that of the present invention, and its capillary ascent effect is lower than that of the hydrophilic carboxyl-modified siloxane of the present invention.

[0063] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A hydrophilic carboxyl-modified siloxane, characterized in that, The chemical structural formula of the hydrophilic carboxyl-modified siloxane is shown in Formula I or Formula II: In Formula I and Formula II, R1 to R3 are each independently selected from hydrogen atoms, C1 to C30 alkyl or phenyl groups, or phenyl groups substituted with methyl, ethyl, or methoxy groups; In Formula I and Formula II, R4 is selected from C1 to C30 alkyl groups, C1 to C30 alkyl groups containing heteroatoms in the carbon chain, phenyl groups, or phenyl groups substituted with methyl, ethyl, or methoxy groups; In Formula I and Formula II, R5 is selected from hydrogen atoms, C1-C4 alkyl groups, and indolemethyl groups.

2. The hydrophilic carboxyl-modified siloxane according to claim 1, characterized in that, R1 to R3 are each independently selected from methyl or ethyl; R4 is selected from -(CH2)3OCH2-; R5 is selected from hydrogen atom, methyl and -(CH2). n NH2-, where n takes values ​​from 1 to 4.

3. The method for preparing the hydrophilic carboxyl-modified siloxane as described in claim 1 or 2, characterized in that, The method includes: Under inert gas protection, the siloxane as shown in Formula III, the amino acid as shown in Formula IV, and the catalyst are placed in an organic solvent, stirred, and reacted at 50℃~70℃. After post-treatment, hydrophilic carboxyl-modified siloxanes as shown in Formula I or II are obtained.

4. The preparation method according to claim 3, characterized in that, The organic solvent is selected from aromatic solvents, aliphatic hydrocarbon solvents, ether solvents, alcohol solvents, or ketone solvents.

5. The preparation method according to claim 4, characterized in that, The aromatic solvent is selected from benzene, toluene, or xylene; The aliphatic hydrocarbon solvent is selected from hexane or cyclohexane; The alcohol solvent is selected from anhydrous ethanol.

6. The preparation method according to claim 3, characterized in that, The catalyst is selected from Lewis acid catalysts, organic base catalysts, or organotin catalysts.

7. The preparation method according to claim 6, characterized in that, The Lewis acid catalyst is selected from aluminum trichloride or titanium tetrachloride; The organic base catalyst is selected from triethylamine; The organotin catalyst is selected from dibutyltin dilaurate.

8. The preparation method according to claim 3, characterized in that, The molar ratio of the siloxane to the amino acid is 1:(1~3); the mass of the catalyst is 0.5~4% of the mass of the siloxane.

9. The preparation method according to claim 3, characterized in that, The amino acid is selected from at least one of glycine, alanine, tryptophan, and lysine.

10. The application of the hydrophilic carboxyl-modified siloxane as described in claim 1 or 2 in regulating liquid capillary behavior, characterized in that, The hydrophilic carboxyl-modified siloxane can increase the speed and height of liquid ascent.

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