Epoxy resin film and preparation method thereof

Abstract

The present invention discloses an epoxy resin film and a preparation method thereof, belonging to the technical field of polymer films. By introducing an indole-grafted crown ether and potassium ions into the epoxy resin film, the present invention forms a cation-π interaction and a folded structure within the epoxy resin film. Due to the presence of the cation-π interaction and the folded structure, the mechanical properties, thermal stability, and solvent resistance of the epoxy resin film are significantly improved, thereby obtaining a film with excellent overall performance. The invention also provides a new approach for strengthening and toughening thermosetting epoxy resin films.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer films, and particularly relates to an epoxy resin film and a preparation method thereof. Background Art

[0002] The excellent mechanical properties of epoxy resin benefit from its high cross-linking density. At the same time, the high cross-linking density makes it difficult for its molecular chains to move, increasing its brittleness. Therefore, how to simultaneously improve the mechanical strength and toughness of epoxy resin is a challenging topic. The key issue is how to balance the strength and toughness of rigid skeleton polymers. In recent years, because the supramolecular structure formed by dynamic bonds has a controllable and special spatial structure, physical reversibility, and excellent physical and chemical properties, the construction of high-strength and tough polymers based on supramolecular network systems has become a new research hotspot. Many researchers have successfully constructed polymer materials with both strength and toughness based on dynamic bonds such as hydrogen bonds, ionic interactions, and coordination bonds. The advantage of dynamic bonds is that their destruction can dissipate external energy and ensure a certain mobility of the polymer chains, but it does not destroy the integrity of the polymer network. It can achieve the reinforcement and toughening of polymer materials without losing the mechanical properties of the polymer materials. However, the reinforcement and toughening of epoxy resins based on dynamic bonds is currently mainly used in flexible systems and is not suitable for rigid skeletons.

[0003] Cation-π interactions are dynamic, non-covalent interactions that differ from traditional hydrogen bonds and coordination bonds in that they operate on a "point-to-surface" basis, with a large surface area and wide range of action. When a material is subjected to external forces, cation-π interactions are easily formed and removed, dissipating a significant portion of the energy, making them highly effective in improving the mechanical properties of the material. Based on this, the researchers achieved enhanced toughness and reinforcement of the rigid polymer backbone by using the cation-π interactions between indole and cations as crosslinking points. Summary of the Invention

[0004] In view of the above-mentioned prior art, the present invention provides an epoxy resin film and a preparation method thereof to solve the technical problems of the prior art epoxy resin film having poor mechanical properties, thermal stability and solvent resistance.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is to provide a method for preparing an epoxy resin film, comprising the following steps:

[0006] S1: dissolving the indole-grafted crown ether in a solvent, then adding iodine salt to the resulting solution and mixing well to obtain a base solution;

[0007] S2: Add bisphenol A diglycidyl ether to the base liquid and mix well to obtain a precursor;

[0008] S3: Spread the precursor onto the substrate, and then cure it in a vacuum environment at a temperature of 115-125°C for 10-15h.

[0009] Based on the above technical solution, the present invention can also be further improved as follows.

[0010] Furthermore, the crown ether grafted with indole is bisindole crown ether diamine, which is prepared by the following steps:

[0011] (1) 4-Trimethylsilyl-3-butyn-1-ol, imidazole and tert-butyldimethylsilyl chloride are dissolved in anhydrous DMF and reacted at room temperature with stirring for 15 hours to obtain 3-tert-butyldimethylsilyloxy-trimethylsilyl-butyne; the mass ratio of 4-trimethylsilyl-3-butyn-1-ol, imidazole and tert-butyldimethylsilyl chloride is 0.85-0.86:0.8-0.82:1-1.1; the structural formula of 3-tert-butyldimethylsilyloxy-trimethylsilyl-butyne is as follows:

[0012]

[0013] (2) 2-iodo-4-nitroaniline, 3-tert-butyldimethylsilyloxy-trimethylsilyl-butyne, anhydrous lithium chloride, potassium acetate and palladium acetate are dissolved in anhydrous DMF, reacted at 70-80°C for 2-3 hours, and then separated and purified to obtain 3-[2-(tert-butyldimethylsilyloxy)ethyl]-5-nitro-2-trimethylsilylindole; the mass ratio of 2-iodo-4-nitroaniline, 3-tert-butyldimethylsilyloxy-trimethylsilyl-butyne, anhydrous lithium chloride, potassium acetate and palladium acetate is 2-3:0.7-0.8:0.2-0.3:2.5-3:0.1-0.15; the structural formula of 3-[2-(tert-butyldimethylsilyloxy)ethyl]-5-nitro-2-trimethylsilylindole is as follows:

[0014]

[0015] (3) 3-[2-(tert-butyldimethylsilyloxy)ethyl]-5-nitro-2-trimethylsilylindole was dissolved in anhydrous acetonitrile, and then a 48% by volume aqueous solution of hydrofluoric acid was added dropwise to the resulting solution. The mixture was stirred under sealed conditions at room temperature for 48 hours, and then separated and purified to obtain 3-hydroxyethyl-5-nitroindole. The material-liquid ratio of 3-[2-(tert-butyldimethylsilyloxy)ethyl]-5-nitro-2-trimethylsilylindole to the aqueous solution of hydrofluoric acid was 0.2-0.3 g:2 ml. The structural formula of 3-hydroxyethyl-5-nitroindole is as follows:

[0016]

[0017] (4) Carbon tetrabromide is dissolved in anhydrous acetonitrile, and the resulting solution is then added dropwise to a mixture of 3-hydroxyethyl-5-nitroindole and triphenylphosphine. The mixture is stirred at room temperature in the dark for 2 to 3 hours, and separated and purified to obtain 3-bromoethyl-5-nitroindole. The mass ratio of 3-hydroxyethyl-5-nitroindole, triphenylphosphine, and carbon tetrabromide is 0.9 to 1:1.7 to 1.8:2 to 2.3. The structural formula of 3-bromoethyl-5-nitroindole is as follows:

[0018]

[0019] (5) Dissolve diaza-18-crown-6-ether, sodium iodide and sodium carbonate in anhydrous acetonitrile to obtain a mixed solution; dissolve 3-bromoethyl-5-nitroindole in anhydrous acetonitrile and add the obtained solution dropwise to the mixed solution under a protective gas atmosphere; then react at 80-90° C. for 20-25 hours, and then separate and purify to obtain bisindole nitrocrown ether; the mass ratio of diaza-18-crown-6-ether, sodium iodide, sodium carbonate and 3-bromoethyl-5-nitroindole is 0.9-1:0.05-0.06:1.5-2.5:2-2.1; the structural formula of bisindole nitrocrown ether is as follows:

[0020]

[0021] (6) Dissolve bisindole nitrocrown ether and 10% palladium carbon in anhydrous ethanol, then dropwise add hydrazine hydrate to the resulting solution, and then reflux at a reflux temperature of 80-90° C. under a protective gas atmosphere for 12-16 hours, and then separate and purify to obtain bisindole crown ether diamine; the material-liquid ratio of bisindole nitrocrown ether, 10% palladium carbon and hydrazine hydrate is 0.2g:0.02g:1ml; the structural formula of bisindole crown ether diamine is as follows

[0022]

[0023] Furthermore, the material-liquid ratio of the crown ether grafted with indole to the solvent is 0.09-0.1 g:2 mL; and the solvent is dimethyl sulfoxide.

[0024] Furthermore, the iodine salt is potassium iodide; and the molar ratio of potassium iodide to the crown ether grafted with indole is 0.1-1.25:1.

[0025] Furthermore, the molar ratio of bisphenol A diglycidyl ether to the crown ether grafted with indole is 2:1.

[0026] Furthermore, the substrate is a cleaned glass plate.

[0027] Furthermore, in S3, the curing temperature is 120° C. and the curing time is 12 h.

[0028] The invention also discloses an epoxy resin film prepared by the preparation method.

[0029] The beneficial effects of the present invention are as follows: the present invention provides a method for preparing an epoxy resin film, by introducing a crown ether grafted with indole and potassium ions into the epoxy resin film, cation-π interaction and a folded structure can be formed inside the epoxy resin film, due to the presence of the cation-π interaction and the folded structure, the mechanical properties, thermal stability and solvent resistance of the epoxy resin film can be significantly improved, thereby obtaining a film with excellent comprehensive performance; at the same time, it provides a new idea for strengthening and toughening thermosetting epoxy resin films. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Is the structural formula of bisindole crown ether diamine;

[0031] Figure 2 This is the infrared spectrum characterization result of bisindole crown ether diamine;

[0032] Figure 3 This is the H-NMR characterization result of bis-bisindole crown ether diamine;

[0033] Figure 4 This is the C-NMR characterization result of bisindole crown ether diamine;

[0034] Figure 5 IR spectra of INCEAM-DG polymer film and DGEBA;

[0035] Figure 6 This is the solid-state NMR carbon spectrum of INCEAM-DG polymer film;

[0036] Figure 7 For INCEAM-DG and INCEAM-DG-K + SEM images of polymer films;

[0037] Figure 8 For INCEAM-DG and INCEAM-DG-K + Tensile stress-strain curves of polymer films;

[0038] Figure 9 For INCEAM-DG and INCEAM-DG-K + tensile strength and elongation at break of polymer films;

[0039] Figure 10 For INCEAM-DG and INCEAM-DG-K + Fracture energy of polymer films;

[0040] Figure 11 For INCEAM-DG and INCEAM-DG-K + Young's modulus of polymer films;

[0041] Figure 12 For INCEAM-DG and INCEAM-DG-K + DSC curves of polymer films;

[0042] Figure 13 For INCEAM-DG and INCEAM-DG-K + Thermogravimetric curves of polymer films;

[0043] Figure 14 INCEAM-DG-K + Figure 2 shows the results of solvent resistance test of polymer films;

[0044] Figure 15 For INCEAM-DG and INCEAM-DG-K + EDS test results of polymer film;

[0045] Figure 16 For INCEAM and INCEAM-K + The fluorescence emission spectrum of

[0046] Figure 17 For INCEAM and INCEAM-K + UV-visible absorption spectrum;

[0047] Figure 18 For INCEAM and INCEAM-K + H NMR spectrum;

[0048] Figure 19 INCEAM-DG-K + In situ stress relaxation-fluorescence spectroscopy of polymer films;

[0049] Figure 20 INCEAM-DG, INCEAM-DG-100%K + 、INCEAM-DG-100%K + After stretching and INCEAM-DG-100%K + UV-vis spectra after relaxation. DETAILED DESCRIPTION

[0050] The specific implementation methods of the present invention are described in detail below with reference to the embodiments.

[0051] Example 1: Preparation of bisindole crown ether diamine

[0052] 1. Weigh 854 mg of 4-trimethylsilyl-3-butyn-1-ol, 816 mg of imidazole, and 1.05 g of tert-butyldimethylsilyl chloride, dissolve them thoroughly in 15 ml of anhydrous DMF, and add them to a two-necked flask under a nitrogen atmosphere. Then, stir and react at room temperature for 15 hours. After the reaction is completed, prepare 15 ml of a 10 wt% sodium bicarbonate aqueous solution and slowly add it to the two-necked flask to quench the reaction for 10 minutes. The resulting solution is extracted three times with n-hexane, and the organic phase is washed three times with distilled water and saturated sodium chloride aqueous solution. Anhydrous sodium sulfate is then added to the resulting organic phase to remove residual moisture. After drying for 1 hour, the dehydrated solution is filtered and stirred to remove the absorbed sodium sulfate. The resulting organic phase is then poured into a round-bottom flask, concentrated under reduced pressure on a rotary evaporator at 40°C to remove the n-hexane, and finally dried in a vacuum oven at 45°C for 8 hours to obtain 3-tert-butyldimethylsilyloxy-trimethylsilyl-butyne (TMS-OTBDMS).

[0053] 2. Weigh 792 mg of TMS-OTBDMS, 2.60 g of 2-iodo-4-nitroaniline, 254 mg of anhydrous lithium chloride, 2.94 g of potassium acetate and 110 mg of palladium acetate; treat the two-necked flask with anhydrous and oxygen-free conditions, and then add the above reaction materials to the two-necked flask under a nitrogen atmosphere. When adding the materials, first add 2-iodo-4-nitroaniline, then add TMS-OTBDMS, then add anhydrous lithium chloride, potassium acetate and palladium acetate in sequence, and finally add 20 ml of anhydrous DMF. After the raw materials are fully dissolved, place the two-necked flask in an oil bath and heat to 75°C. Keep the temperature for reaction for 2.5 hours; monitor the degree of reaction by TLC. Stop heating after the raw materials are fully reacted. After the reaction solution is cooled to room temperature, add 20 ml of ethanol. The reaction solution was diluted with 20 ml of ice water and 20 ml of ether; the mixture was then poured into a separatory funnel to separate the aqueous and organic phases, the aqueous phase was extracted three times with ethyl acetate, the organic phases obtained twice were combined, and the organic phase was washed three times with distilled water and three times with a saturated sodium chloride aqueous solution. The organic phase was dried over anhydrous sodium sulfate for 2 hours, and then filtered under reduced pressure to remove the sodium sulfate, and then concentrated under reduced pressure to remove the solvent; a mixture of petroleum ether:ethyl acetate = 10:1 was used as the eluent, and 100-200 mesh silica gel powder was selected as the stationary phase of the chromatographic column. After purification by column chromatography, 3-[2-(tert-butyldimethylsilyloxy)ethyl]-5-nitro-2-trimethylsilylindole (IN-TMS-OTBDMS) was obtained.

[0054] 3. Dissolve 220 mg of IN-TMS-OTBDMS in acetonitrile, then pour the solution into a polytetrafluoroethylene reactor, and add 2 ml of a 48% (v / v) hydrofluoric acid aqueous solution dropwise to the polytetrafluoroethylene reactor under stirring; after the addition is complete, seal the polytetrafluoroethylene reactor to prevent HF and acetonitrile from volatilizing, and stir at room temperature for 48 hours, during which the progress of the reaction is monitored by TLC; after the raw materials are fully reacted, prepare a saturated sodium carbonate solution, and add the saturated sodium carbonate solution dropwise to the polytetrafluoroethylene reactor with a dropper under stirring, and adjust the pH of the reaction solution to 8; then transfer the reaction solution to a separatory funnel and add 50 ml of ethyl acetate was added to ensure that the aqueous phase and the organic phase were fully separated; after multiple extractions of the aqueous phase, the organic phases were mixed and washed three times with distilled water and then three times with saturated brine; anhydrous sodium sulfate was then added to dry the organic phase, and after drying for 2 hours, the anhydrous sodium sulfate was removed by filtration under reduced pressure; the organic phase obtained by filtration was poured into a round-bottom flask and concentrated under reduced pressure at 45°C to remove the ethyl acetate; a mixture of petroleum ether:ethyl acetate = 1:1-1:3 was used as the eluent, and 100-200 mesh silica gel powder was selected as the stationary phase of the chromatographic column, and wet loading separation and purification was performed to obtain 3-hydroxyethyl-5-nitroindole.

[0055] 4. Weigh 175 mg of triphenylphosphine, 221 mg of carbon tetrabromide, and 91.5 mg of 3-hydroxyethyl-5-nitroindole; first, evacuate the reaction apparatus to anhydrous and oxygen-free conditions and introduce nitrogen for a certain period of time. Then, add triphenylphosphine and 3-hydroxyethyl-5-nitroindole to the reaction apparatus under a nitrogen atmosphere; then, dissolve carbon tetrabromide in 6 ml of anhydrous acetonitrile and add the carbon tetrabromide-acetonitrile solution dropwise to the reaction apparatus in an ice-water bath; after the addition is complete, stir the reaction at room temperature in the dark for 2.5 hours; monitor the progress of the reaction by TLC. Afterwards, ethyl acetate was added to dilute the reaction solution, and the diluted reaction solution was transferred to a separatory funnel. The organic phase was washed three times with water and brine respectively. After washing, anhydrous sodium sulfate was added to dry the reaction solution. After drying for 2 hours, the sodium sulfate was removed by filtration under reduced pressure. The ethyl acetate was removed by concentration under reduced pressure at 45°C. A mixture of petroleum ether:ethyl acetate = 4:1-1:1 was used as the eluent, and 100-200 mesh silica gel powder was used as the stationary phase of the chromatographic column. The sample was wet loaded and purified by column chromatography to obtain 3-bromoethyl-5-nitroindole.

[0056] 5. Weigh 0.99 g of diaza-18-crown-6-ether, 0.0566 g of sodium iodide, 2.00 g of sodium carbonate and 2.03 g of 3-bromoethyl-5-nitroindole; add diaza-18-crown-6-ether to a round-bottom flask that has been vacuum-treated with anhydrous oxygen under a nitrogen atmosphere, dissolve it with 20 ml of anhydrous acetonitrile, and then add sodium iodide and sodium carbonate to the round-bottom flask; dissolve 3-bromoethyl-5-nitroindole in 20 ml of anhydrous acetonitrile, add the resulting solution dropwise to the round-bottom flask under a nitrogen atmosphere, and then react at 85° C. for 24 hours. Monitor the progress of the reaction by TLC; filter after the reaction is completed, and the filtrate is The reaction mixture was concentrated under reduced pressure at 45°C to remove acetonitrile, and then dissolved in dichloromethane. The resulting solution was washed three times with distilled water and dried over anhydrous magnesium sulfate for 1 hour. After drying, the mixture was filtered and concentrated under reduced pressure to remove the solvent. A mixture of acetone:ammonia water = 13.5:1 was used as the eluent, and 100-200 mesh silica gel powder was selected as the stationary phase of the chromatographic column. Separation and purification were carried out by wet loading to obtain a yellow solid. The solid particles were washed with anhydrous ethanol at reflux temperature for 12 hours, and filtered under reduced pressure to obtain the bisindole nitrocrown ether.

[0057] 6. Add 0.2 g of bisindole nitrocrown ether and 0.02 g of 10% palladium on carbon to a reaction apparatus, and then add 5 ml of anhydrous ethanol; add 1 ml of hydrazine hydrate dropwise to the reaction apparatus at reflux temperature over one hour; then, under a nitrogen atmosphere, react at a reflux temperature of 85° C. for 14 hours, and monitor the progress of the reaction by TLC. After the reaction is complete, filter the reaction solution at normal pressure, and then concentrate the filtrate under reduced pressure to remove the solvent; obtain an off-white crude product; then wash the crude product with tetrahydrofuran and anhydrous ethanol for 6 hours each to obtain bisindole crown ether diamine (INCEAM), the structural formula of which is as follows: Figure 1 The infrared spectrum characterization results, nuclear magnetic hydrogen spectrum characterization results and nuclear magnetic carbon spectrum characterization results are shown as follows: Figure 2 、 Figure 3 and Figure 4 shown.

[0058] Example 2: Preparation of bisindole crown ether-based epoxy resin film

[0059] 1. Preparation of INCEAM-DG polymer film

[0060] Mix bisindole crown ether diamine (INCEAM, 0.17 mmol, 0.098 g) with 2 mL of dimethyl sulfoxide (DMSO) and stir on a magnetic stirrer for 15 minutes to fully dissolve the bisindole crown ether diamine to obtain a bisindole crown ether diamine solution; then mix bisphenol A diglycidyl ether (DGEBA, 0.34 mmol, 0.115 g) with the bisindole crown ether diamine solution, stir on a magnetic stirrer for 30 minutes to fully mix, dissolve, and disperse, and then filter to obtain a slightly light yellow transparent solution.

[0061] A clean glass plate was placed in a leveled vacuum oven in a stable and orderly manner. The transparent solution obtained above was then added dropwise onto the glass plate using a glass dropper. The vacuum oven was heated to 120°C. After heating, the vacuum oven was turned off and the film was cured at this temperature for 12 hours. The heating and heat preservation function was then turned off. After the polymer film cooled to room temperature, the glass plate and film were immersed in deionized water. After 10 minutes, the polymer film was gently peeled off from the glass plate using a knife to obtain the INCEAM-DG polymer film, which was reddish-brown and transparent.

[0062] 2. Preparation of INCEAM-DG-K + polymer films

[0063] Five parts of bisindole crown ether diamine solutions were prepared according to the above method, and then 0.017 mmol (0.0028 g), 0.034 mmol (0.0056 g), 0.085 mmol (0.014 g), 0.17 mmol (0.028 g) and 0.21 mmol (0.035 g) of potassium iodide were added to the five parts of bisindole crown ether diamine solutions, respectively, and stirred at room temperature for 1 hour; bisphenol A diglycidyl ether (DGEBA, 0.34 mmol, 0.115 g) was then added to the resulting solution, stirred on a magnetic stirrer for 30 minutes to fully mix, dissolve and disperse it, and then filtered to obtain a transparent solution.

[0064] A clean glass plate was placed in a leveled vacuum oven in a stable and orderly manner. The transparent solution obtained above was then dripped onto the glass plate using a glass dropper. The vacuum oven was heated to 120°C. After the heating was complete, the vacuum oven was closed and the film was cured at this temperature for 12 hours. The heating and heat preservation function was then turned off. After the polymer film cooled to room temperature, the glass plate and the film were immersed in deionized water. After 10 minutes, the polymer film was gently peeled off from the glass plate with a knife to obtain INCEAM-DG-10%K. + 、INCEAM-DG-20%K + 、INCEAM-DG-50%K + 、INCEAM-DG-100%K + and INCEAM-DG-125%K + Polymer film.

[0065] Experimental Example 1: Structural Characterization of INCEAM-DG Polymer Film

[0066] The infrared spectrum of the bisindole crown ether epoxy resin film was characterized. Figure 5 As shown in Figure 2, bisphenol A diglycidyl ether (DGEBA) has a peak at 914 cm -1There is an obvious epoxy characteristic peak at 914 cm in the infrared spectrum of the polymer film. -1 The epoxy peak at 3430 cm-1 completely disappeared, indicating that the epoxy functional group has been completely reacted. -1 The absorption peak of the imino group of indole appeared at 1080 cm -1 The absorption peak at is the stretching vibration peak of the crown ether macrocycle COC. The disappearance of the epoxy characteristic peak and the appearance of the stretching vibration peaks of the imino group on the indole ring and the crown ether macrocycle COC prove the successful preparation of the polymer film.

[0067] In addition, the solid-state NMR carbon spectroscopy of the bisindole crown ether epoxy resin film was characterized, and the results were as follows: Figure 6 As shown in the figure, the carbon numbered 18 is the carbon on the methylene group connecting the crown ether to the indole, with a chemical shift of 22 ppm. The chemical shift of the other methylene carbon is 62 ppm, due to the greater deshielding effect on the methylene group directly connected to the nitrogen atom. Similarly, the two methylene carbons numbered 2 and 3 are directly connected to oxygen atoms, resulting in a larger chemical shift of around 72 ppm. The methylene carbons on the crown ether ring also have increased chemical shifts due to their direct connection to oxygen or nitrogen, ranging from 55 to 70 ppm. The chemical shift of the quaternary carbon numbered 9 is 45 ppm, and the chemical shift of the two methyl carbons on the quaternary carbon is 34 ppm. The chemical shifts of the carbon atoms in the aromatic ring are between 100 and 150 ppm. Among them, the chemical shifts of the carbons directly connected to oxygen and nitrogen are relatively large, with the carbon on the benzene ring directly connected to oxygen having the largest chemical shift, around 160 ppm. Based on the above analysis, the INCEAM-DG polymer film was successfully synthesized.

[0068] Experimental Example 2: INCEAM-DG polymer film and INCEAM-DG-K + Morphological characterization of polymer films

[0069] The prepared INCEAM-DG polymer film and INCEAM-DG-50%K + The polymer film was subjected to SEM analysis, and the results were as follows Figure 7 As shown, (a) is the SEM image of INCEAM-DG polymer film, (b) is the SEM image of INCEAM-DG-50%K + SEM images of polymer films. As can be seen from the figure, INCEAM-DG polymer films and INCEAM-DG-K + The surface of the polymer film is very smooth, K + The introduction of does not change the flatness of the film surface.

[0070] Experimental Example 3: INCEAM-DG polymer film and INCEAM-DG-K + Mechanical properties analysis of polymer films

[0071] The mechanical properties of the prepared polymer film were tested using an E44.104 electronic universal testing machine produced by Meister Industrial Systems (China). During the test, the film was cut into strips 50 mm long, 5 mm wide, and 0.05 mm thick. The test template was plastic tensile, the gauge length was 30 mm, the tensile rate was 2 mm / min, and the sensor used was 50 N.

[0072] INCEAM-DG and INCEAM-DG-K + The tensile stress-strain curve of polymer films is shown in Figure 2. Figure 8 As shown, the tensile strength and elongation at break are Figure 9 As shown in the figure, it can be seen that the tensile strength of the film without potassium ions is 75MPa, and the elongation at break is 7.9%. When potassium ions are not added, the film shows obvious brittle fracture. After the addition of potassium ions, the stress-strain curve of the film shows yield. As the potassium ion content increases from 0% to 100%, the mechanical strength of the film gradually increases. When the addition amount of potassium ions is 10% (the molar ratio of potassium ions to crown ether rings), the tensile strength of the film increases from 75MPa to 82MPa, an increase of 7.9%, and the elongation at break increases from 7.9% to 9.7%, an increase of 22.7%. When the addition amount of potassium ions increases to 20%, the film The tensile strength of the film was 82MPa, and the elongation at break increased from 7.9% to 12.7%, an increase of 60.8%; when the addition amount of potassium ions was 50%, the tensile strength of the film increased from 75MPa to 90MPa, an increase of 18.4%; the elongation at break increased from 7.9% to 13.9%, an increase of 75.9%; when the addition amount of potassium ions was 100%, the tensile strength of the film increased from 75MPa to 92MPa, an increase of 21.1%, and the elongation at break increased from 7.9% to 15.9%, an increase of 101.2%; when the addition amount of potassium ions was 125%, the mechanical properties of the film decreased.

[0073] INCEAM-DG and INCEAM-DG-K + The fracture energy of polymer films is Figure 10 As shown in Figure 11 As shown in the figure, the fracture energy of the film increases with the increase of potassium ion content, from 4.0MJ / m 3 Increased to 11.2MJ / m 3, an increase of 180.0%; the Young's modulus of the film increased from 1.52 GPa to 1.83 GPa, a 20.4% increase. Similarly, when the potassium ion addition reached 125%, the film's fracture energy and Young's modulus also decreased. The improved mechanical properties of the polymer film are attributed to the presence of a stretchable structure within the polymer network. When the film is stretched, the cation-π interaction is disrupted and the polymer chain structure is elongated, effectively dissipating external energy.

[0074] In addition, the mechanical properties of the film of the present invention were compared with those of other dynamically bonded reinforced and toughened epoxy resins. The results are shown in Table 1. It can be seen that the film of the present invention has a significant advantage in increasing the elongation at break.

[0075] Table 1 Comparison of mechanical properties of dynamic bond reinforced epoxy resin

[0076]

[0077] Experimental Example 4: INCEAM-DG polymer film and INCEAM-DG-K + Mechanical properties analysis of polymer films

[0078] The thermal stability of the polymer films was characterized using a TA Instruments TGA Q500 thermogravimetric analyzer. The films were dried in a vacuum oven at 120°C for 12 hours. The film weight was 5-8 mg, and the test atmosphere was nitrogen at a controlled flow rate of 20 ml / min. The heating rate was 10°C / min, and the test range was 25-800°C.

[0079] The heat resistance of polymer films was characterized using a TA Instruments DSC Q2000 differential scanning calorimeter. Prior to testing, the polymer films were dried in a vacuum oven at 100°C for 12 hours. The samples were chopped up and placed in aluminum crucibles, with an empty crucible placed to the left of the sample to be tested as a reference. The film mass ranged from 5 to 10 mg. The test atmosphere was nitrogen at a flow rate of 20 ml / min, with a heating rate of 10°C / min, and the test range was 25 to 200°C.

[0080] INCEAM-DG and INCEAM-DG-K + The DSC curves and thermogravimetric curves of the polymer films are shown in Figure 2. Figure 12 and Figure 13As shown. From the DSC curve in the figure, it can be seen that the glass transition temperature of the INCEAM-DG polymer film without the addition of potassium ions is 114°C. With the addition of potassium ions, the glass transition temperature of the film gradually increases; with the addition of 10% potassium ions (the molar ratio of potassium ions to crown ether rings), the glass transition temperature increases from 114°C to 129°C, an increase of 15°C; with the addition of 20%, 50%, and 100% potassium ions, the glass transition temperatures increase to 131°C, 134°C, and 141°C, respectively; the film with 100% potassium ions has a significantly higher glass transition temperature than the film without potassium ions, an increase of 27°C and 23.7%. From the thermogravimetric curve, it can be seen that when the addition of potassium ions increases from 0 to 100%, the thermal decomposition temperature of the film increases from 302°C to 315°C; after the addition of 100% potassium ions, the decomposition rate of the film also decreases, and the residual carbon rate increases. INCEAM-DG-K + The increase in the film's glass transition temperature is due to the formation of a folded structure, which reduces the flexibility of the polymer chain and reduces its mobility. The underlying mechanism is the complex interaction between potassium ions and the crown ether ring, as well as the cation-π interaction between potassium ions and the indole group attached to the crown ether ring, which forms the folded structure.

[0081] Experimental Example 5: INCEAM-DG polymer film and INCEAM-DG-K + Analysis of Solvent Resistance of Polymer Films

[0082] The prepared INCEAM-DG polymer film and INCEAM-DG-50%K + The polymer films were immersed in dichloromethane (DCM), petroleum ether (PE), ethyl acetate (EA), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC) and N-methylpyrrolidone (NMP) respectively. The results after immersion at room temperature for one week are shown in Figure 2. Figure 14 As shown, (a) is the immersion result of INCEAM-DG polymer film, (b) is the immersion result of INCEAM-DG-K + Immersion results of the polymer film. It can be seen that the polymer film basically maintains its original shape after being immersed in the solvent for one week. The solvent color and film shape have not changed, indicating that the polymer film has good solvent resistance.

[0083] Experimental Example 6: Analysis of the Strengthening and Toughening Mechanism of Bisindole Crown Ether Diamine on Polymer Films

[0084] For INCEAM-DG and INCEAM-DG-K + The polymer film was tested by energy dispersive X-ray spectroscopy (EDS). The test results are as follows: Figure 15As shown, (a) is the EDS image of INCEAM-DG polymer film, (b) is the EDS image of INCEAM-DG-K + EDS image of polymer film. It can be seen from the figure that potassium ions are evenly distributed in INCEAM-DG-K + EDS can prove that potassium ions are successfully introduced into the polymer film and are evenly distributed.

[0085] The fluorescence titration test of bis-indole crown ether diamine (INCEAM) was carried out, and the spectrum was as follows Figure 16 As shown in the figure, the fluorescence emission peak of the bisindole crown ether diamine monomer is at 354nm. After adding an equimolar amount of potassium ions, the fluorescence emission peak undergoes a red shift, and the peak intensity decreases. This is due to the cation-π interaction between potassium ions and indole, which causes electrons in the indole plane to transfer to the potassium ions, resulting in a decrease in the electron cloud density near the indole ring. Fluorescence titration confirms the existence of a cation-π interaction between potassium ions and indole, indirectly proving the existence of a folded structure.

[0086] Bisindole nitrocrown ether (INCENG) and INCENG-K + Liquid UV test was carried out in acetonitrile solution, and the UV absorption spectrum was as follows Figure 17 As shown in the figure, the addition of potassium ions causes a slight red shift in the characteristic UV absorption peak at 210 nm, representing indole, which is attributed to the cation-π interaction between the potassium ion and indole. The UV difference spectrum of the two shows distinct negative-positive bands at 227 nm and 246 nm, indicating a cation-π interaction between the potassium ion and the indole ring. The appearance of these negative-positive bands is due to the slight red shift in the indole ring and the weakening of the strong Bb transition.

[0087] Equimolar amounts of potassium iodide and bisindole crown ether diamine were mixed and tested for one-dimensional hydrogen spectrum. The test results are as follows: Figure 18 As shown. Figure 18 (b) It can be seen that after the addition of potassium ions, the chemical shift of the hydrogen at the position marked as 4 on indole moves to a low-field high displacement, indicating that a cation-π interaction is formed between indole and the potassium ion, resulting in a decrease in the electron cloud density of the hydrogen at this position; at the same time, the chemical shift of the hydrogen on the NH on indole also moves to a low-field high displacement. On the one hand, this is because the iodine ion forms a hydrogen bond with the NH on indole, which reduces the electron cloud density on the hydrogen; on the other hand, it is because the cation-π interaction between indole and potassium ions causes the electron to move toward the potassium ion, reducing the electron cloud density. Figure 18The chemical shifts of the hydrogens on the crown ether ring in (c) also shift to varying degrees. The chemical shift of the hydrogens of the methylene groups attached to the oxygens on the crown ether ring shifts downfield to a higher position. This indicates that the potassium ion enters the crown ether cavity and forms complex interactions with the four oxygens on the crown ether, reducing the electron density of the hydrogens on the methylene groups. The chemical shifts of the hydrogens on the methylene groups attached to the nitrogen groups also change, with peaks splitting. These results suggest that a folded structure is formed between the potassium ion and the bisindole crown diamine.

[0088] INCEAM-DG-100%K + The polymer film was tested for in-situ stress relaxation-fluorescence spectroscopy, and the results were as follows: Figure 19 As shown in the figure, the fluorescence emission peak is around 364nm when the film is unstretched; after stretching (10% strain), the fluorescence emission peak of the film undergoes a blue shift (350nm) and the intensity increases. This phenomenon is attributed to the opening of the embracing structure of the indole and crown ether rings under the action of external force, and the destruction of the cation-π interaction between indole and potassium ions. After five minutes of stretching, the fluorescence of the film begins to undergo a small red shift and the intensity decreases, indicating that the embracing structure between indole and crown ether is being regenerated; after 15 minutes of stretching, the fluorescence of the polymer film undergoes a significant red shift and a significant decrease in intensity, with the intensity and position close to returning to the unstretched state. The test results show that the folded structure of the indole and crown ether rings also exists in the polymer film. It is destroyed under the action of external force and can be reconstructed after the external force disappears.

[0089] Test INCEAM-DG and INCEAM-DG-100%K respectively + 、INCEAM-DG-100%K + After stretching and INCEAM-DG-100%K + The UV-vis spectrum after relaxation is as follows Figure 20 As shown, where (a) is INCEAM-DG and INCEAM-DG-100%K + UV-visible absorption spectra of the film before and after stretching; (b) INCEAM-DG and INCEAM-DG-100%K + Thin film UV-visible absorption spectrum and difference spectrum; (c) INCEAM-DG-100% K + and INCEAM-DG-100%K + UV-visible absorption spectrum and UV difference spectrum of the film after stretching; (d) is INCEAM-DG-100% K + and INCEAM-DG-100%K + UV-visible absorption spectra and UV difference spectra of the film after stretching and recovery; (e) INCEAM-DG and INCEAM-DG-100% K+ UV-visible absorption spectra and UV difference spectra of the film after stretching and recovery; (c) INCEAM-DG and INCEAM-DG-100% K + UV-visible absorption spectrum and UV difference spectrum of the film after stretching. As can be seen from the figure, INCEAM-DG-100%K + The UV-vis absorption peak of the film is blue-shifted compared with that of the INCEAM-DG film. The UV difference spectrum of the two films shows an obvious negative-positive band at 220 / 235nm. The appearance of this negative / positive band pair is due to the weakening of the strong Bb transition of the indole ring and the small red shift, indicating that INCEAM-DG-100% K + The presence of cation-π interactions in the film. INCEAM-DG-100% K + The UV absorption peak red-shifted after stretching, which was attributed to the opening of the original stretching structure. + and INCEAM-DG-100%K + The UV spectrum after stretching was also subtracted, and the subtraction spectrum also showed obvious negative and positive bands at 220 / 235nm. This result shows that INCEAM-DG-100%K + The films after stretching and without potassium ion addition are equivalent, which shows that INCEAM-DG-100% K + The cation-π interaction in the film itself is destroyed, which means that the folded structure is opened under the action of external force. + Film and INCEAM-DG-100%K + After stretching-relaxation (10 min), no obvious negative-positive bands appeared around 220 / 230 nm, which indicates that INCEAM-DG-100% K + The regeneration of cation-π interaction in the stretched film, i.e. the regeneration of the stretched structure. Similarly, INCEAM-DG-100%K + After stretching and relaxation (10 min), the difference spectrum of INCEAM-DG film showed obvious negative and positive bands, while INCEAM-DG-100% K + There are no obvious negative and positive bands in the difference spectra of the stretched and INCEAM-DG films. These two sets of results also indicate the existence of the folded structure, which can be opened and reconstructed.

[0090] Although the specific embodiments of the present invention have been described in detail in conjunction with the embodiments, this should not be construed as limiting the scope of protection of this patent. Within the scope described by the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.

Claims

1. A method for preparing an epoxy resin film, characterized in that: The following steps are involved: S1: dissolving an indole-grafted crown ether in a solvent, then adding an iodine salt to the resulting solution and mixing well to obtain a base solution; the indole-grafted crown ether is bisindole crown ether diamine, and the iodine salt is potassium iodide; the molar ratio of potassium iodide to indole-grafted crown ether is 0.1 to 1.25:1; S2: adding bisphenol A diglycidyl ether to the base liquid and mixing well to obtain a precursor; the molar ratio of the bisphenol A diglycidyl ether to the indole-grafted crown ether is 2:1; S3: Spread the precursor onto the substrate, and then cure it in a vacuum environment at a temperature of 115-125°C for 10-15h.

2. The preparation method according to claim 1, characterized in that The bisindole crown ether diamine is prepared by the following steps: (1) 4-trimethylsilyl-3-butyn-1-ol, imidazole and tert-butyldimethylsilyl chloride are dissolved in anhydrous DMF, and the mixture is stirred at room temperature for 15 hours to obtain 3-tert-butyldimethylsilyloxy-trimethylsilyl-butyne; the mass ratio of the 4-trimethylsilyl-3-butyn-1-ol, imidazole and tert-butyldimethylsilyl chloride is 0.85-0.86:0.8-0.82:1-1.1; (2) dissolving 2-iodo-4-nitroaniline, 3-tert-butyldimethylsilyloxy-trimethylsilyl-butyne, anhydrous lithium chloride, potassium acetate and palladium acetate in anhydrous DMF, reacting at 70-80° C. for 2-3 hours, and then separating and purifying to obtain 3-[2-(tert-butyldimethylsilyloxy)ethyl]-5-nitro-2-trimethylsilylindole; the mass ratio of the 2-iodo-4-nitroaniline, 3-tert-butyldimethylsilyloxy-trimethylsilyl-butyne, anhydrous lithium chloride, potassium acetate and palladium acetate is 2-3:0.7-0.8:0.2-0.3:2.5-3:0.1-0.15; (3) 3-[2-(tert-butyldimethylsilyloxy)ethyl]-5-nitro-2-trimethylsilylindole was dissolved in anhydrous acetonitrile, and then a 48% by volume aqueous solution of hydrofluoric acid was added dropwise to the resulting solution. The mixture was stirred under sealed conditions at room temperature for 48 hours, and then separated and purified to obtain 3-hydroxyethyl-5-nitroindole; the material-liquid ratio of 3-[2-(tert-butyldimethylsilyloxy)ethyl]-5-nitro-2-trimethylsilylindole to the aqueous solution of hydrofluoric acid was 0.2-0.3 g:2 ml; (4) dissolving carbon tetrabromide in anhydrous acetonitrile, then adding the resulting solution dropwise to a mixture of 3-hydroxyethyl-5-nitroindole and triphenylphosphine, stirring and reacting at room temperature for 2 to 3 hours in the dark, separating and purifying to obtain 3-bromoethyl-5-nitroindole; the mass ratio of the 3-hydroxyethyl-5-nitroindole, triphenylphosphine, and carbon tetrabromide is 0.9 to 1:1.7 to 1.8:2 to 2.3; (5) dissolving diaza-18-crown-6-ether, sodium iodide and sodium carbonate in anhydrous acetonitrile to obtain a mixed solution; dissolving 3-bromoethyl-5-nitroindole in anhydrous acetonitrile and adding the obtained solution dropwise to the mixed solution under a protective gas atmosphere; then reacting at 80-90° C. for 20-25 hours, and then separating and purifying to obtain bisindole nitrocrown ether; the mass ratio of the diaza-18-crown-6-ether, sodium iodide, sodium carbonate and 3-bromoethyl-5-nitroindole is 0.9-1:0.05-0.06:1.5-2.5:2-2.1; (6) Dissolving the bisindole nitrocrown ether and 10% palladium carbon in anhydrous ethanol, then adding hydrazine hydrate dropwise to the resulting solution, and then refluxing the reaction at a reflux temperature of 80 to 90° C. under a protective gas atmosphere for 12 to 16 hours, and then separating and purifying to obtain the product; the material-liquid ratio of the bisindole nitrocrown ether, 10% palladium carbon and hydrazine hydrate is 0.2 g:0.02 g:1 ml.

3. The preparation method according to claim 2, wherein: The material-liquid ratio of the crown ether grafted with indole to the solvent is 0.09-0.1 g:2 mL; and the solvent is dimethyl sulfoxide.

4. The preparation method according to claim 2, wherein: The substrate is a cleaned glass plate.

5. The preparation method according to claim 2, wherein: In S3, the curing temperature is 120°C and the curing time is 12 h.

6. The epoxy resin film obtained by the preparation method according to any one of claims 1 to 5.

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