A rigid epoxy resin hydrophobic film and its preparation method

Abstract

The present invention discloses a rigid epoxy resin hydrophobic film and a preparation method thereof, belonging to the technical field of hydrophobic materials. When preparing the hydrophobic film, first prepare sodium tryptophan, then dissolve sodium tryptophan, a curing agent and an epoxy monomer in a solvent, and carry out a curing treatment on the obtained solution to obtain a rigid epoxy resin film; then put the prepared rigid epoxy resin film into a liquid culture medium containing Escherichia coli, and cultivate it at a constant temperature. The Escherichia coli etches the film, and thus the product is obtained. The present invention prepares a hydrophobic material by means of bacterial etching. Compared with the prior art scheme of using chemical reagents for etching, it is more environmentally friendly and efficient. The hydrophobic material prepared by the present invention has excellent hydrophobic properties, and at the same time also has good chemical stability and thermal stability, and can meet the use requirements of special occasions.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrophobic materials, and particularly relates to a rigid epoxy resin hydrophobic film and a preparation method thereof. Background Technique

[0002] Wettability, as an interfacial phenomenon widely existing in nature, is also one of the basic characteristics of solid surfaces and plays an important role in solving medical, transportation, energy, and environmental problems. Hydrophobicity is a common wettability. Hydrophobic surfaces show a water contact angle (WCA) greater than 90° in air. Natural biological surfaces such as lotus leaves, rose petals, and butterfly wings exhibit excellent hydrophobic properties. Inspired by nature, the preparation of artificial hydrophobic surfaces has become a highly regarded research topic. Artificial hydrophobic surfaces are often applied in fields such as self-cleaning, anti-corrosion, drag reduction, oil-water separation, and anti-icing due to their excellent properties.

[0003] So far, researchers have explored a variety of strategies for preparing hydrophobic surfaces, providing diverse choices for the preparation of hydrophobic surfaces. These strategies usually establish rough micro-nano structures and low surface energies provided by chemical modification. The design of surface roughness can capture air cavities in the gaps of micro-nano structures, and the low surface energy can further enhance the liquid repulsion performance. Currently, there are mainly three ways to prepare artificial hydrophobic surfaces: (1) Constructing sufficient roughness on low surface energy materials. This method is to roughen the surface of specific low surface energy materials. This method is limited by the number of low surface energy materials in nature and still has deficiencies in realizing the diversified and large-scale preparation of hydrophobic materials. (2) Reducing the surface energy of materials with sufficient roughness. This method is often achieved by molecular layer modification of the material surface, but the commonly used low surface energy substances for modification are fluorine-containing compounds, which are not only expensive but also environmentally unfriendly. (3) Creating rough micro-nano structures on the material surface and combining hydrophobic treatment to reduce the surface energy. This method is a combination of the first two methods and is the main method for current high-performance hydrophobic materials, but it also has the disadvantages of complex processes and demanding equipment. Summary of the Invention

[0004] In view of the above-mentioned prior art, the present invention provides a rigid epoxy resin hydrophobic film and a preparation method thereof to solve the technical problems of complex preparation processes and poor hydrophobic effects of existing hydrophobic films.

[0005] To achieve the above object, the technical solution adopted by the present invention is to provide a preparation method of a rigid epoxy resin hydrophobic film, including the following steps:

[0006] S1: Prepare sodium tryptophan;

[0007] S2: Dissolve sodium tryptophan, curing agent and epoxy monomer in a solvent, then pour the resulting solution onto a substrate and cure it at 75 - 85 °C for 10 - 15 h to obtain a rigid epoxy resin film;

[0008] S3: Prepare a liquid medium containing Escherichia coli;

[0009] S4: Sterilize the rigid epoxy resin film, then put the sterilized rigid epoxy resin film into the liquid medium containing Escherichia coli, incubate it at a constant temperature of 35 - 40 °C for 7 - 10 days, take out the rigid epoxy resin film, wash and dry it to obtain the product.

[0010] Based on the above technical solutions, the present invention can also be improved as follows.

[0011] Further, sodium tryptophan is prepared through the following steps:

[0012] Dissolve tryptophan in N,N - dimethylformamide, then add sodium hydroxide, and ultrasonically stir at room temperature until sodium hydroxide is completely dissolved to obtain it; the molar ratio of tryptophan to sodium hydroxide is 1:1.

[0013] Further, the curing agent is p - aminodiphenyl ether; the epoxy monomer is bisphenol A epoxy resin; the solvent is N,N - dimethylformamide.

[0014] Further, the molar ratio of sodium tryptophan, curing agent and epoxy monomer is 1:1:3.

[0015] Further, the curing temperature in S2 is 80 °C and the curing time is 12 h.

[0016] Further, the liquid medium containing Escherichia coli is prepared through the following steps:

[0017] S31: Dissolve beef extract, peptone and sodium chloride in water, boil it, and then cool it to room temperature to obtain a base liquid;

[0018] S32: Dissolve soluble starch medium and glucose in water, boil it, and then cool it to room temperature to obtain a nutrient solution;

[0019] S33: Mix the nutrient solution and the base liquid, sterilize it and then inoculate Escherichia coli, and incubate it at a constant temperature of 35 - 40 °C to obtain it.

[0020] Further, in S31, the material - liquid ratio of beef extract, peptone, sodium chloride to water is 1 g:2 g:1 g:200 mL; in S32, the material - liquid ratio of soluble starch medium, glucose to water is 0.85 g:0.5 g:50 mL; in S33, the volume ratio of the nutrient solution to the base liquid is 1:1.

[0021] Further, the sterilization in S4 is carried out by ultraviolet irradiation for half an hour.

[0022] Further, in S4, the culture temperature is 37 °C and the culture time is 8 days.

[0023] The present invention also discloses a rigid epoxy resin hydrophobic film prepared by the above preparation method.

[0024] The beneficial effects of the present invention are as follows:

[0025] 1. The present invention uses the method of bacterial etching to prepare hydrophobic materials, which is more environmentally friendly and efficient compared to the prior art method of using chemical reagents for etching.

[0026] 2. The hydrophobic material prepared by the present invention has excellent hydrophobic properties, and at the same time has good chemical stability and thermal stability, and can meet the usage requirements of special occasions.

[0027] 3. The present invention provides new ideas and methods for the hydrophobic modification of the epoxy resin surface by the bacterial etching technology, laying a foundation for subsequent research. Description of the Drawings

[0028] Figure 1 is the 1H NMR spectrum of tryptophan (Try) and sodium tryptophan (Try-Na + );

[0029] Figure 2 is the infrared spectrum of R-TAEP(DGEBA) films obtained at different curing times;

[0030] Figure 3 is the infrared spectrum of the R-TAEP(DGEBA) film cured for 12 h;

[0031] Figure 4 is the infrared spectrum of the R-TAEP(DGEBA) film before and after etching;

[0032] Figure 5 is the ultraviolet-visible spectrum of the liquid medium before and after etching the R-TAEP(DGEBA) film;

[0033] Figure 6 is the indole experiment result of the liquid medium;

[0034] Figure 7 is the fluorescence spectrum of the R-TAEP(DGEBA) film before and after etching;

[0035] Figure 8 is the EDS energy spectrum of the R-TAEP(DGEBA) film before and after etching;

[0036] Figure 9 is the water contact angle of different films before and after etching;

[0037] Figure 10 Graph of the ability of etched R-TAEP(DGEBA) film to capture air underwater;

[0038] Figure 11 SEM graphs of different films before and after etching;

[0039] Figure 12 Graph of the solvent performance of the etched R-TAEP(DGEBA) film;

[0040] Figure 13 Graph of the results of the thermal stability performance study of R-TAEP(DGEBA) film before and after etching. Detailed implementation mode

[0041] The raw materials and reagents used in the present invention are shown in Table 1.

[0042] Raw materials and reagents used in Table 1

[0043] Raw material Purity Source Beef extract BR Beijing Aoboxing Biotechnology Peptone BR Beijing Aoboxing Biotechnology Sodium chloride AR Chengdu Kelong Soluble starch medium BR Qingdao Haibo Biotechnology Glucose AR Tianjin Zhiyuan Chemical Reagent Escherichia coli —— Biological laboratory L-Tryptophan ≥98.0％ Aladdin Sodium hydroxide AR Chengdu Kelong p-Aminodiphenyl ether ≥98.0％ Alpha Chemical Industry Bisphenol A epoxy resin ≥98.0％ Alpha Chemical Industry E51 epoxy resin ≥98.0％ Alpha Chemical Industry N,N-Dimethylformamide AR Chengdu Kelong

[0044] The following combines examples to make a detailed description of the specific implementation mode of the present invention.

[0045] Example 1: Preparation of sodium tryptophan Try-Na +

[0046] The preparation route of sodium tryptophan is shown in Formula 1-1.

[0047]

[0048] The specific method is as follows: Dissolve tryptophan in N,N-dimethylformamide (DMF) solvent, and then add an equimolar amount (the same molar amount as tryptophan) of sodium hydroxide to the obtained solution. Stir it ultrasonically at room temperature to dissolve it to obtain a DMF solution of sodium tryptophan; Filter the obtained solution with a microporous filter, transfer the filtrate into a crystallization kettle, lower the temperature to 5°C, let it stand for crystallization for 5h, collect the crystals, and dry them at -0.09MPa and 85°C for 4h to obtain sodium tryptophan (Try-Na + ).

[0049] Perform nuclear magnetic resonance hydrogen spectrum analysis on tryptophan and sodium tryptophan, and the results are as Figure 1 shown. It can be seen from the figure that the proton hydrogen on the carboxylic acid in tryptophan is a broad peak, and the chemical shift is about ~13 ppm. The hydrogen on the carboxylic acid of sodium tryptophan is deprotonated, so the broad peak at this chemical shift disappears; The number of hydrogens in other positions remains unchanged, and the chemical environment remains basically unchanged, so the chemical shift does not change significantly. By comparing the nuclear magnetic resonance hydrogen spectra of the two, it can be confirmed that tryptophan is successfully deprotonated and sodium tryptophan is successfully prepared.

[0050] Example 2: Preparation of Rigid Epoxy Resin Film R-TAEP

[0051] Weigh 0.2 mmol of Try-Na + , 0.2 mmol of curing agent p-aminodiphenyl ether (ODA) and 0.6 mmol of bisphenol A type epoxy resin DGEBA. Dissolve them in 1.5 mL of DMF. After mixing evenly, filter the solution with cotton. Pour the filtrate onto a clean glass slide (75 mm * 25 mm) and carry out curing treatment in an oven at 80 °C. After curing is completed, slowly cool it to room temperature and carefully remove the film from the glass plate to obtain the rigid epoxy resin film R-TAEP (DGEBA).

[0052] Weigh 0.2 mmol of Try-Na + , 0.2 mmol of curing agent p-aminodiphenyl ether (ODA) and 0.6 mmol of bisphenol E51 type epoxy resin. Dissolve them in 1.5 mL of DMF. After mixing evenly, filter the solution with cotton. Pour the filtrate onto a clean glass slide (75 mm * 25 mm) and cure it in an oven at 80 °C for 12 h. After curing is completed, slowly cool it to room temperature and carefully remove the film from the glass plate to obtain the rigid epoxy resin film R-TAEP (E51).

[0053] Take the R-TAEP (DGEBA) films cured for 6 h, 8 h, 10 h, and 12 h respectively for infrared spectrum testing. The results are as Figure 2 shown. In the figure, the characteristic absorption peak of epoxy is at 870 cm -1 . It can be seen from Figure 2 that as time increases, the epoxy characteristic peak gradually decreases and completely disappears at 12 h, indicating that the degree of epoxy curing deepens with the extension of time and is completely cured at 12 h.

[0054] Take the R-TAEP (DGEBA) with a curing time of 12 h and conduct infrared characterization on it. The characterization results are as Figure 3 shown. In the figure, the stretching vibrations of hydroxyl O-H and imine group N-H are at 3411 cm -1 ; the stretching vibrations of methylene (-CH2-) are at 2930 cm -1 and 2865 cm -1 ; the skeletal vibrations of benzene rings are at 1657 cm -1 and 1685 cm -1 , and the peak shapes are sharp; the absorption position of the carbonyl group of carboxylate changes. The carboxylate ion (-CO2 - -) has symmetric vibration and antisymmetric vibration, which are located at 1396 cm -1 and 1455 cm -1 respectively, and the absorption peaks are both strong; 1120 cm-1 The peak at is the stretching vibration of the ether bond (C-O-C) in p-aminodiphenyl ether. Since the oxygen atom of this ether bond is connected to two benzene rings, this peak is a strong peak; at 870 cm -1 The peak at is the characteristic absorption peak of epoxy, and its disappearance basically indicates complete curing; since the carboxylate forms a salt with metal sodium ions, we can observe the absorption peak related to metal oxide at 740 cm -1 From this, it can be seen that the R-TAEP(DGEBA) film is successfully prepared.

[0055] Example 3: Preparation of a liquid medium containing Escherichia coli

[0056] The present invention utilizes bacterial etching technology to prepare hydrophobic materials. The bacterial etching technology is based on the decomposition of tryptophan by Escherichia coli. Escherichia coli has a unique metabolic mechanism, that is, through its endogenous tryptophanase, it can decompose tryptophan into indole, pyruvate and ammonia; among them, when indole undergoes a chemical reaction with dimethylaminobenzaldehyde in the indole reagent, a rose indole will be produced, thereby making the reaction solution turn red. This significant color change is called the indole positive test.

[0057] The liquid medium containing Escherichia coli used in the present invention is prepared through the following steps:

[0058] S1: Weigh 0.25 g of beef extract, 0.5 g of peptone, 0.25 g of NaCl and 50 mL of distilled water in a 100 mL beaker, stir and boil, then continue boiling for 10 minutes, and cool to room temperature to obtain an unsterilized beef extract-peptone culture solution (base solution);

[0059] S2: Weigh 0.85 g of soluble starch medium, 0.5 g of glucose and 50 mL of distilled water in a 100 mL beaker, stir and boil, then continue boiling for 10 minutes, and cool to room temperature to obtain a nutrient solution;

[0060] S3: Pour the base solution and the nutrient solution into a 250 mL conical flask, seal the conical flask with cotton gauze, and then place it in a vertical autoclave. Set the sterilization conditions to 121 °C for 20 minutes to carry out autoclave sterilization treatment to obtain a liquid medium; after the sterilization process is completed, let the conical flask cool to room temperature naturally, then take it out and transfer it to a laminar flow hood;

[0061] S4: The ultra-clean workbench, liquid medium, and inoculation loop are sterilized under ultraviolet light for half an hour, then the ultraviolet light is turned off, and bacterial inoculation is carried out 10 minutes later. Before inoculation, both hands are thoroughly disinfected with 75% (v / v) alcohol. During the inoculation process, both hands are kept inside the ultra-clean workbench at all times. In addition, the entire inoculation operation process needs to be carried out around the flame of the alcohol lamp. Before inoculation, the inoculation loop, the mouth of the conical flask, and the stopper are sterilized under the flame of the alcohol lamp. After the inoculation loop has cooled, Escherichia coli is taken and inoculated into the liquid medium. After inoculation is completed, the inoculation loop, the mouth of the conical flask, and the stopper are sterilized again with the flame of the alcohol lamp. The inoculated liquid medium is placed in a constant temperature incubator at 37 °C for cultivation until the logarithmic growth phase of Escherichia coli is reached, and a liquid medium containing Escherichia coli is obtained.

[0062] Example 4: Preparation of a rigid epoxy resin hydrophobic film

[0063] Take R-TAEP(DGEBA) with a curing time of 12 h, cut it into square pieces of 25 mm * 25 mm, place them in the ultra-clean workbench, and first carry out ultraviolet sterilization treatment for half an hour. Subsequently, place them in the liquid medium containing Escherichia coli prepared in Example 3 for bacterial etching. The liquid medium containing R-TAEP(DGEBA) is placed in a constant temperature incubator at 37 °C for eight days. After the cultivation is completed, the etched film is thoroughly washed with distilled water and ethanol in sequence. Finally, the washed film is dried at 50 °C for 4 h to obtain the etched R-TAEP(DGEBA) film, that is, the rigid epoxy resin hydrophobic film.

[0064] Infrared spectroscopy analysis is carried out on R-TAEP(DGEBA) before and after etching, and the results are as Figure 4 shown. Since the tryptophan fragment in the film is specifically recognized and decomposed by Escherichia coli after bacterial etching, the structure of the film changes slightly. As can be seen from Figure 4 , the O-H stretching vibration peak of the hydroxyl group and the N-H stretching vibration peak of the imine group originally at 3411 cm -1 decrease in intensity due to the disappearance of the imine group; the benzene ring skeletal vibration near 1600 cm -1 also changes due to the disappearance of indole; the decomposition of tryptophan salt causes the disappearance of carboxylate and sodium ions in the film structure, and the symmetric vibration, antisymmetric vibration of the carboxylate ion (-CO2 -1 , 1455 cm -1 -) at 1396 cm - and the absorption peak related to metal oxide at 740 cm -1 all show significant decreases or even disappearances. Except for the above several special structures, other structures of the film do not change, so other characteristic peaks do not change.

[0065] Take the liquid culture medium before and after etching, centrifuge it to separate the Escherichia coli and the solution in it, take the supernatant for liquid ultraviolet absorption test, and the test range is 230 nm to 350 nm. The test results are as Figure 5 shown. It can be seen from the figure that an ultraviolet absorption peak of indole appears at 270 nm, proving that indole groups in the thin film are etched off by Escherichia coli and dissolved in the liquid culture medium.

[0066] Take 5 mL of the liquid culture medium that has etched the R-TAEP(DGEBA) thin film into a glass bottle, add 1 mL of ether for extraction. After standing for a while, it is observed that the ether layer gradually floats on the surface of the liquid culture medium. At this time, the indole in the liquid culture medium has been effectively extracted into the ether layer. Subsequently, slowly add 5 to 10 drops of indole reagent (Kovacs indole reagent) along the bottle wall and observe the phenomenon. At the same time, indole tests were carried out on the indole monomer aqueous solution and the blank liquid culture medium, and the results are as Figure 6 shown. It can be seen from the figure that both the indole monomer and the indole test of the liquid culture medium that has etched the thin film show positive results, while the result of the blank liquid culture medium is negative. This result confirms that bacteria etching decomposes tryptophan in the thin film, resulting in the appearance of indole in the liquid culture medium.

[0067] Perform fluorescence spectrum analysis on the R-TAEP(DGEBA) thin film before and after etching, and the results are as Figure 7 shown. It can be seen from the figure that the intensity of the fluorescence spectrum absorption peak of the etched R-TAEP(DGEBA) thin film is significantly lower than that before etching, and the position of the fluorescence absorption peak also undergoes a red shift. This is because there is an indole structure of the luminescent group in the epoxy resin based on sodium tryptophan before etching, which has certain fluorescence properties. After etching, most of the sodium tryptophan fragments fall off, and the indole group of the luminescent group in the epoxy resin no longer exists. Therefore, the fluorescence intensity of the thin film after etching decreases significantly.

[0068] Perform EDS energy spectrum analysis on the R-TAEP(DGEBA) thin film before and after etching, and obtain the distribution of Na element on the surface of the thin film through surface scanning. The results are as Figure 8 shown, where (a) is the EDS energy spectrum diagram of the R-TAEP(DGEBA) thin film before etching, (b) is the EDS energy spectrum diagram of the etched R-TAEP(DGEBA) thin film, and the inset shows the distribution of Na element on the surface of the thin film. It can be seen from the figure that the R-TAEP(DGEBA) thin film before etching contains four elements: C, N, O, and Na, and the content of Na element is 10%; the types of elements in the etched R-TAEP(DGEBA) thin film remain unchanged, but the content of Na element decreases significantly, only 3%, further proving the decomposition of sodium tryptophan.

[0069] Experimental Example

[0070] I. Hydrophobicity Study of Rigid Epoxy Resin Hydrophobic Films

[0071] The water contact angle is one of the key indicators for measuring the wettability of material surfaces. The larger the water contact angle, the more difficult it is for water to wet the material surface, further indicating better surface hydrophobicity of the material; conversely, the smaller the water contact angle, the easier it is for water to wet the material surface, indicating poorer surface hydrophobicity. It is generally considered that a water contact angle below 90° is hydrophilic, above 90° is hydrophobic, and when it reaches above 150°, it is superhydrophobic.

[0072] The R-TAEP(E51) film was etched using the same etching process as in Example 4 to obtain the etched R-TAEP(E51) film. Then, the water contact angles of the rigid epoxy resin film R-AEP without the sodium tryptophan fragment, the etched R-TAEP(DGEBA) film, and the etched R-TAEP(E51) film were measured respectively. The results are as Figure 9 shown, and the inset is a photo of the water contact angle. Since the epoxy resin film using an amine curing agent contains oxygen atoms and nitrogen atoms with relatively large electronegativity, the polymer usually has a relatively high polarity. Therefore, it can be seen from the figure that the contact angles of the films without bacterial etching treatment are all less than 90°, showing medium wettability. After bacterial etching treatment, the water contact angles of the films containing the sodium tryptophan fragment increased significantly, exceeding 90°, showing hydrophobicity, while the water contact angle of the blank group R-AEP did not change significantly. Also, since the E51 type epoxy resin is more rigid than the bisphenol A type epoxy resin, the basic hydrophobicity of the formed R-TAEP(E51) film is relatively better, so the etching effect is also more obvious.

[0073] Due to the microscopically uneven structure on the hydrophobic surface, these structures can form tiny air pockets on the surface, enabling the hydrophobic surface to acquire the ability to capture air. The stronger the surface hydrophobic ability, the stronger the ability to capture air. The superhydrophobic surface can even directly form an air film. Figure 10 Shows an image of the etched R-TAEP(DGEBA) film completely immersed in water, capturing air underwater to form small bubbles.

[0074] II. Surface Morphology of the Etched R-TAEP Film

[0075] The influence of surface morphology on wettability cannot be ignored. Specifically, a relatively smooth surface often facilitates the uniform spreading of liquids, thereby enhancing the wetting performance. On the contrary, an increase in surface roughness may lead to an expansion of the contact angle, thereby weakening the wetting ability of the material.

[0076] The surface morphologies of the three groups of films before and after etching were observed by SEM. The results are as Figure 11As shown. It can be seen from the figure that the surface of the film without etching treatment is very smooth and flat, without the existence of micro-nano structures. Due to the bacterial etching effect on the etched film, some structures on the film surface fall off, so micron structures with a certain roughness are formed. The construction of the micron rough structure realizes the transformation of the film wettability. While in the blank group, due to the absence of specific sites (sodium tryptophan fragments) for bacterial etching, bacterial etching has no effect on it, and there are no changes in the wettability and surface morphology of the film before and after treatment.

[0077] III. Solvent Resistance of Etched R-TAEP Film

[0078] The etched R-TAEP (DGEBA) film was immersed in organic solvents such as DMF, DMSO, DMAc, NMP, and 5wt% HCl and NaOH solutions respectively, and left standing at room temperature for one week. The results are as Figure 12 shown. It can be seen from the figure that after one week of immersion, the size, color, and shape of the etched film have not changed significantly, and the solvent still remains clear and transparent, indicating that the etched R-TAEP film has excellent chemical stability.

[0079] IV. Thermal Stability of Etched R-TAEP Film

[0080] The thermal decomposition temperature and glass transition temperature of materials are important indicators in the actual application process. The thermal stability of the obtained R-TAEP (DGEBA) film before and after etching was studied by TGA and DSC. The results are as Figure 13 shown, where (a) is the TGA curve of the R-TAEP (DGEBA) film before and after etching, and (b) is the DSC curve of the R-TAEP (DGEBA) film before and after etching. From Figure 13 (a), it can be seen that the 5% weight loss temperature of the R-TAEP (DGEBA) film before etching is 283 °C. After etching, due to the decomposition of tryptophan and the disappearance of cation-π interaction, the 5% weight loss temperature decreases to 228 °C. Although the weight loss temperature decreases by 55 °C, it still has good heat resistance. From Figure 13 (b), it can be seen that the glass transition temperature of the R-TAEP (DGEBA) film before etching is 136 °C. After etching, due to the reduction of the rigid structure sodium tryptophan, the glass transition temperature decreases slightly, to 122 °C. Comprehensive TGA and DSC tests show that although bacterial etching will affect the thermal properties of the film, the influence is small. The thermal decomposition temperature and glass transition temperature of the etched film both remain at a relatively high level, showing excellent heat resistance.

[0081] Although the specific embodiments of the present invention have been described in detail in conjunction with the embodiments, it should not be construed as a limitation on the protection scope of this patent. Within the scope described in the claims, various modifications and variations that can be made by those skilled in the art without creative efforts still fall within the protection scope of this patent.

Claims

1. A method for preparing a rigid epoxy resin hydrophobic film, characterized in that, It includes the following steps: S1: Prepare sodium tryptophan; S2: Co - dissolve sodium tryptophan, curing agent and epoxy monomer in a solvent, then pour the obtained solution onto a substrate and cure it at 75 - 85 °C for 10 - 15 h to obtain a rigid epoxy resin film; S3: Prepare a liquid medium containing Escherichia coli; S4: Sterilize the rigid epoxy resin film, then put the sterilized rigid epoxy resin film into the liquid medium containing Escherichia coli, incubate it at 35 - 40 °C for 7 - 10 days, take out the rigid epoxy resin film, wash and dry it to obtain the product.

2. The preparation method according to claim 1, characterized in that, The sodium tryptophan is prepared through the following steps: Dissolve tryptophan in N,N - dimethylformamide, then add sodium hydroxide, and ultrasonically stir at room temperature until the sodium hydroxide is completely dissolved to obtain it; the molar ratio of tryptophan to sodium hydroxide is 1:

1.

3. The preparation method according to claim 1, characterized in that: The curing agent is p - aminodiphenyl ether; the epoxy monomer is bisphenol A type epoxy resin or E51 type epoxy resin; the solvent is N,N - dimethylformamide.

4. The preparation method according to claim 3, characterized in that: The molar ratio of sodium tryptophan, curing agent and epoxy monomer is 1:1:

3.

5. The preparation method according to claim 4, characterized in that: In S2, the curing temperature is 80 °C and the curing time is 12 h.

6. The preparation method according to claim 1, wherein The liquid medium containing Escherichia coli is prepared through the following steps: S31: Co - dissolve beef extract, peptone and sodium chloride in water, boil it, and then cool it to room temperature to obtain a base liquid; S32: Co - dissolve soluble starch medium and glucose in water, boil it, and then cool it to room temperature to obtain a nutrient solution; S33: Mix the nutrient solution and the base liquid, sterilize it, inoculate Escherichia coli, and incubate it at 35 - 40 °C to obtain the product.

7. The preparation method according to claim 6, characterized in that: In S31, the material - liquid ratio of beef extract, peptone, sodium chloride to water is 1 g:2 g:1 g:200 mL; in S32, the material - liquid ratio of soluble starch medium, glucose to water is 0.85 g:0.5 g:50 mL; in S33, the volume ratio of the nutrient solution to the base liquid is 1:

1.

8. The preparation method according to claim 7, characterized in that: In S4, the sterilization is carried out by ultraviolet irradiation for half an hour.

9. The preparation method according to claim 1, characterized in that: In S4, the incubation temperature is 37 °C and the incubation time is 8 days.

10. A rigid epoxy resin hydrophobic film prepared by the preparation method according to any one of claims 1 - 9.

Images