Epoxy resin toughness curing agent containing catechol group and preparation method thereof

Abstract

The invention discloses a catechol group-containing epoxy resin toughness curing agent and a preparation method thereof.According to the method, a catechol group-containing thiol / carboxylic acid / amine epoxy resin curing agent is synthesized through a two-step method, and sites are provided for formation of further reversible catechol metal coordination bonds in a cross-linked network; and preparing the epoxy resin material containing the double cross-linked network through ring-opening reaction between sulfydryl and epoxy group, carboxyl and epoxy group or amino and epoxy group. The energy dissipation capacity of the epoxy resin material containing the coordination network is remarkably improved when the epoxy resin material is stimulated by the outside, and the catechol metal coordination structure uniformly dispersed in the network plays a key role in the balance of the rerigidity and the toughness under repeated loading-unloading cycles. In addition, the introduction of catechol metal coordination bonds causes the change of the ultraviolet absorption wavelength of the epoxy resin, and the epoxy resin can be used as a photothermal conversion material. According to the invention, the application of the thermosetting epoxy resin in the advanced fields of flexible robots, self-adaptive equipment and the like has important significance.

Description

Technical Field

[0001] The invention relates to an epoxy resin curing agent and a preparation method thereof, and in particular to a catechol group-containing thiol / carboxyl / amino-terminated epoxy resin curing agent and a preparation method thereof. Background Art

[0002] In recent years, epoxy resins have attracted great interest as promising thermosetting materials and have been widely used in mechanical manufacturing, electronic engineering and other fields. One of the most attractive features of epoxy resins is the designable manufacturing of molecular structures. By matching epoxy monomers and crosslinkers with different structures and functional groups, many interesting properties can be injected into the cured epoxy resins, including flame retardancy, degradation, reprocessing and self-healing properties. However, due to the high crosslinking density and entangled three-dimensional crosslinked network structure, the cured epoxy resin system has disadvantages such as brittleness or lack of crack propagation resistance, which limits its development in flexible and smart devices. It is generally believed that it is difficult to achieve high stiffness and elongation of materials at the same time. In order to obtain a feasible method to reduce the brittleness of materials and extend their service life, it is necessary to construct a flexible energy-consuming network against entropic forces while maintaining stability and excellent mechanical properties.

[0003] Organisms in nature provide a rich source of inspiration for creating multifunctional materials and systems due to their complex and delicate structures. In recent years, an important trend in polymer material design has been to mimic the functions or mechanisms of biological structures and behaviors, such as self-assembly and reversibility. Studies have found that in nature, materials with super-toughness, such as sea cucumbers, mussel foot silk and spider silk, achieve their high toughness through weak reversible bonds found in biological tissues, and compared with strong covalent bonds, only slightly lower forces are required to break them. The large amount of energy dissipation caused by the breaking and reorganization of reversible chemical bonds during external force interference can provide a way to balance the strength and toughness of materials, prepare materials with both high strength and toughness, and greatly expand the scope of material application. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a tough curing agent for epoxy resin containing catechol group and a preparation method thereof. The present invention can synthesize a thiol / carboxylic acid / amine epoxy curing agent containing catechol group by a simple two-step method, which can provide sites for the formation of further reversible catechol metal coordination bonds in the cross-linked network, and prepare an epoxy resin material containing a double cross-linked network by a ring-opening reaction between thiol-epoxy, carboxyl-epoxy or amino-epoxy. The energy dissipation capacity of the epoxy resin material containing the coordination network is significantly improved when it is stimulated by the outside world, and the catechol metal coordination structure uniformly dispersed in the network plays a key role in the balance of stiffness and toughness under repeated loading-unloading cycles. In addition, the introduction of catechol metal coordination bonds leads to changes in the wavelength of ultraviolet absorption of epoxy resin, which can be used as a photothermal conversion material. Combining a reasonable polymer design method with a bio-inspired concept, the thermosetting epoxy resin is endowed with high toughness and customizable functions, which is of great significance for its application in advanced fields such as flexible robots and adaptive equipment.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] A catechol-containing thiol / carboxyl / amino-terminated epoxy resin curing agent having the following molecular structure formula:

[0007] Mercapto-terminated epoxy resin curing agent containing catechol groups:

[0008]

[0009] Amino-terminated epoxy resin curing agent containing catechol groups:

[0010]

[0011] Carboxyl-terminated epoxy resin curing agent containing catechol groups:

[0012]

[0013] In the formula, R is not limited to one of methylene, dimethyl, cycloalkyl, etc.; R1, R2 and R3 are not limited to one of alkylene, alkyl, cycloalkyl, alkoxy, heterocyclic group, heterocycloalkyl, aromatic group, heteroaromatic group, oxyalkyleneoxy group, oxycycloalkyleneoxy group, oxyheterocycloalkyleneoxy group, oxycycloalkyleneoxy group, oxyheterocycloalkyleneoxy group, oxyaromaticeneoxy group, oxyheteroaromaticeneoxy group, aromaticene, alkylenearomaticene, alkylenearomaticene, heteroaromaticene, alkyleneheteroaromaticene; n=1 to 3.

[0014] A method for preparing the above-mentioned thiol / carboxyl / amino-terminated epoxy resin curing agent containing catechol groups is prepared according to the following reaction process:

[0015]

[0016] A two-step method is used to synthesize a thiol / carboxyl / amino-terminated epoxy resin curing agent containing a catechol group. The specific steps are as follows:

[0017] Step 1: Preparation of o-benzoquinone compounds

[0018] Step 1: dissolve the phenolic compound with R group and the high-valent iodine reagent in a certain amount of solvent, stir for 5 to 30 minutes after fully dissolved, wherein:

[0019] The structural formula of the phenolic compound with R group is:

[0020]

[0021] The amount of the high-valent iodine reagent is 1 to 5 times the amount of the phenolic compound with an R group;

[0022] The hypervalent iodine reagent is not limited to one of dichloroiodobenzene, dichloroiodosobenzene, iodosobenzene, 2-iodoacylbenzoic acid, iodosobenzene diacetate, and iodobenzene diacetate;

[0023] The solvent is at least one of methanol, ethanol, tetrahydrofuran, acetone, dichloromethane, acetonitrile, dioxane, N-methylpyrrolidone, N,N-dimethylformamide, and dimethyl sulfoxide;

[0024] Step 12: Cool the product obtained in step 11 in an ice water bath, filter the red crystalline precipitate, and wash it with a solvent for 2 to 4 times, wherein:

[0025] The solvent is at least one of methanol, ethanol, tetrahydrofuran, acetone, dichloromethane, acetonitrile, dioxane, N-methylpyrrolidone, N,N-dimethylformamide, and dimethyl sulfoxide;

[0026] Step 13: extracting the product of step 12 with a mixed solution of water and chloroform and removing unreacted 2-iodoacylbenzoic acid, and drying to obtain an o-benzoquinone compound;

[0027] The whole process was carried out under a nitrogen atmosphere to prevent the oxidation of the catechol groups;

[0028] Step 2: Preparation of thiol / carboxyl / amino-terminated epoxy resin curing agent containing catechol groups

[0029] A certain amount of o-benzoquinone compound is dissolved in a solvent, and thiol, thiol carboxylic acid or thiolamine is added dropwise, and stirred for 5 to 30 minutes under a nitrogen atmosphere. After the thiol, thiol carboxylic acid or thiolamine is added, the color of the solution containing the o-benzoquinone compound gradually changes from dark to light. When the color no longer changes, the reaction is stopped to obtain a thiol / carboxyl / amino-terminated epoxy resin curing agent containing a catechol group dissolved in the solvent, wherein:

[0030] The amount of the thiol / thiolamine / thiolcarboxylic acid is 2 times or more of the amount of the o-benzoquinone compound. Only at this ratio can a thiol curing agent terminated with a thiol group (-SH) / carboxyl group (-COOH) / amino group (-NH2) be synthesized;

[0031] The solvent may be at least one of methanol, ethanol, tetrahydrofuran, acetone, dichloromethane, acetonitrile, dioxane, N-methylpyrrolidone, N,N-dimethylformamide, and dimethyl sulfoxide;

[0032] The thiol / carboxyl / amino-terminated epoxy resin curing agent containing catechol groups dissolved in the solvent does not need to be purified, and can be further added with epoxy resin and compounded with other curing agents for use, and the final epoxy resin product can be obtained after curing.

[0033] A method for preparing an epoxy resin with high toughness and light-to-heat conversion performance is prepared according to the following reaction process:

[0034]

[0035] The specific steps are as follows:

[0036] Step 1: Preparation of o-benzoquinone compounds

[0037] Step 1: dissolve the phenolic compound with R group and the high-valent iodine reagent in a certain amount of solvent, stir for 5 to 30 minutes after fully dissolved, wherein:

[0038] The structural formula of the phenolic compound with R group is:

[0039]

[0040] The amount of the high-valent iodine reagent is 1 to 5 times the amount of the phenolic compound with an R group;

[0041] The hypervalent iodine reagent is not limited to one of dichloroiodobenzene, dichloroiodosobenzene, iodosobenzene, 2-iodoacylbenzoic acid, iodosobenzene diacetate, and iodobenzene diacetate;

[0042] The solvent is at least one of methanol, ethanol, tetrahydrofuran, acetone, dichloromethane, acetonitrile, dioxane, N-methylpyrrolidone, N,N-dimethylformamide, and dimethyl sulfoxide;

[0043] Step 12: Cool the product obtained in step 11 in an ice water bath, filter the red crystalline precipitate, and wash it with a solvent for 2 to 4 times, wherein:

[0044] The solvent is at least one of methanol, ethanol, tetrahydrofuran, acetone, dichloromethane, acetonitrile, dioxane, N-methylpyrrolidone, N,N-dimethylformamide, and dimethyl sulfoxide;

[0045] Step 13: extracting the product of step 12 with a mixed solution of water and chloroform and removing unreacted 2-iodoacylbenzoic acid, and drying to obtain an o-benzoquinone compound;

[0046] The whole process was carried out under a nitrogen atmosphere to prevent the oxidation of the catechol groups;

[0047] Step 2: Preparation of thiol / carboxyl / amino-terminated epoxy resin curing agent containing catechol groups

[0048] A certain amount of o-benzoquinone compound is dissolved in a solvent, and thiol, thiol carboxylic acid or thiolamine is added dropwise, and stirred for 5 to 30 minutes under a nitrogen atmosphere. After the thiol, thiol carboxylic acid or thiolamine is added, the color of the solution containing the o-benzoquinone compound gradually changes from dark to light. When the color no longer changes, the reaction is stopped to obtain a thiol / carboxyl / amino-terminated epoxy resin curing agent containing a catechol group dissolved in the solvent, wherein:

[0049] The molar ratio between the o-benzoquinone compound and different types of thiols is 1:2, and only under this ratio can the thiol curing agent terminated with thiol (-SH) be synthesized;

[0050] The molar ratio between the o-benzoquinone compound BQA and the thiol groups of different types of thiolamines is 1:2, and only under this ratio can the amino (-NH2)-terminated thiol curing agent be synthesized;

[0051] The molar ratio between the o-benzoquinone compound BQA and the thiol groups of different types of thiol carboxylic acids is 1:2, and only under this ratio can the carboxyl (-COOH)-terminated thiol curing agent be synthesized;

[0052] The solvent may be at least one of methanol, ethanol, tetrahydrofuran, acetone, dichloromethane, acetonitrile, dioxane, N-methylpyrrolidone, N,N-dimethylformamide, and dimethyl sulfoxide;

[0053] Step 3: Preparation of epoxy resin containing catechol groups

[0054] The epoxy resin, curing agent and accelerator are sequentially added to the solution of step 2, and stirred at 25-100° C. for 1-24 hours to obtain an epoxy resin containing a catechol group, wherein:

[0055] The weight ratio of the epoxy resin, the thiol / carboxyl / amino-terminated epoxy resin curing agent containing catechol groups, the curing agent and the accelerator is 1:0.1 to 1:0.9 to 0:0.01 to 0.05;

[0056] The epoxy resin includes one or more of glycidyl ether, glycidyl ester, glycidyl amine, aliphatic epoxy resin, alicyclic epoxy resin, trifunctional epoxy resin, tetrafunctional epoxy resin, phenolic epoxy resin, o-cresol epoxy resin, and nitrogen-containing epoxy resin;

[0057] The curing agent includes one or more of an amine curing agent, an anhydride curing agent, an anionic polymerization curing agent, a cationic polymerization curing agent, a polythiol curing agent, etc.;

[0058] The accelerator is not limited to 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30), benzyldimethylamine (BDMA) triethylamine, triethanolamine, o-hydroxybenzyldimethylamine (DMP-10), N-(2-hydroxyphenyl)-N',N'-dimethylurea; N-(2-hydroxy-4-nitrobenzene)-N',N'-dimethylurea; N-(5-chloro-2-hydroxybenzene)-N',N'-dimethylurea, N-(4-chlorophenyl)-N',N'-dimethylurea, N-(4-chloro-2-hydroxybenzene)-N',N'-dimethylurea, acetylacetone metal complex, boron trifluoride complex, one of imidazole accelerators;

[0059] Step 4: Preparation of Epoxy Resin Containing Catechol-Metal Coordination Bond

[0060] Add metal ions to the epoxy resin containing catechol groups in step 3, stir thoroughly for 0.5 to 12 hours, pour into a mold and solidify to obtain an epoxy resin containing catechol-metal coordination bonds, wherein:

[0061] The metal ions include but are not limited to Fe 3+ , Fe 2+ , Cu 2+ 、Co 2+ 、Zn 2+ 、Al 3+ 、Ni 2+ One or more of the above, the amount added is at most 1 / 3 to 1 / 2 times the molar amount of the o-benzoquinone compound;

[0062] The curing temperature is 50-200° C. and the curing time is 6-48 hours.

[0063] Compared with the prior art, the present invention has the following advantages:

[0064] 1. The present invention adopts a two-step method to synthesize a thiol-terminated thiol curing agent containing a catechol structure. The whole process is simple, has a high yield, and a fast reaction rate. Further, by adjusting the molar ratio of the curing agent with different types of epoxy resins, a series of epoxy resins with both rigid and flexible structures are prepared, and by introducing metal ions into the system, the dynamically reversible catechol metal coordination bond cross-linking sites can increase the energy dissipation of the resin system through the bond breaking-reorganization process when subjected to external forces. The epoxy resin obtained after curing not only has excellent mechanical properties, but can maintain stable operation in an environment within 250°C, and has excellent solvent resistance and UV resistance.

[0065] 2. The epoxy resin obtained by the present invention has good application in photothermal conversion. Due to the fluorescence quenching effect of heavy metal ions, the dark complex produced makes the absorption wavelength of the epoxy resin move toward the long-wave direction, resulting in the epoxy resin being able to increase the surface temperature of the epoxy resin under the irradiation of light sources such as xenon lamps / ultraviolet lamps, and having multiple cycles of photothermal conversion performance. DETAILED DESCRIPTION

[0066] The technical solution of the present invention is further described below in conjunction with the embodiments, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be included in the protection scope of the present invention.

[0067] Example 1: Preparation of o-benzoquinone compound I

[0068] Dissolve 12.0g of bisphenol Z and 39.0g of 2-iodobenzoic acid in 500mL of methanol and stir for 15min. Then cool the product in an ice-water bath for 10min. After the dark crystalline precipitate is separated, filter it and wash it three times with cold methanol. Extract the product with a mixed solution of water and chloroform and remove the unreacted IBX. After drying, obtain the o-benzoquinone compound BQZ with a yield of up to 70%. The molecular structure is as follows:

[0069]

[0070] Example 2: Preparation of Curing Agent I

[0071] 23.06g of bisphenol A and 88.45g of 2-iodobenzoic acid were dissolved in 500mL of methanol and stirred for 15min. The product was then cooled in an ice-water bath for 10min. After the red crystalline precipitate was precipitated, it was filtered and washed three times with cold methanol. The product was extracted with a mixed solution of water and chloroform and the unreacted IBX was removed. After drying, the o-benzoquinone compound BQA was obtained with a yield of up to 87%.

[0072] Take 11.3 g of the above-mentioned o-benzoquinone compound, dissolve it in 20 mL of DMF, slowly add 16.1 g of 3,6-dioxa-1,8-octanedithiol, and stir for 15 min under nitrogen protection. The solution changes from dark red brown to light yellow solution, which is the thiol curing agent I dissolved in DMF. The molecular structure is as follows:

[0073]

[0074] Example 3: Preparation of Curing Agent II

[0075] 23.06g of bisphenol A and 88.45g of 2-iodobenzoic acid were dissolved in 500mL of methanol and stirred for 15min. The product was then cooled in an ice-water bath for 10min. After the red crystalline precipitate was precipitated, it was filtered and washed three times with cold methanol. The product was extracted with a mixed solution of water and chloroform and the unreacted IBX was removed. After drying, the o-benzoquinone compound BQA was obtained with a yield of up to 87%.

[0076] Take 11.3 g of the above-mentioned o-benzoquinone compound, dissolve it in 20 mL of DMF, slowly drop 9.4 g of 3-mercaptopropionic acid, stir for 15 min under nitrogen protection, the solution changes from dark red brown to light yellow solution, which is the carboxylic acid curing agent II dissolved in DMF, and the molecular structure is as follows:

[0077]

[0078] Example 4: Preparation of Curing Agent III

[0079] 23.06g of bisphenol A and 88.45g of 2-iodobenzoic acid were dissolved in 500mL of methanol and stirred for 15min. The product was then cooled in an ice-water bath for 10min. After the red crystalline precipitate was precipitated, it was filtered and washed three times with cold methanol. The product was extracted with a mixed solution of water and chloroform and the unreacted IBX was removed. After drying, the o-benzoquinone compound BQA was obtained with a yield of up to 87%.

[0080] Take 11.3 g of the above-mentioned o-benzoquinone compound, dissolve it in 20 mL of DMF, slowly add 6.8 g of β-mercaptoethylamine, and stir for 15 min under nitrogen protection. The solution changes from dark red brown to light yellow solution, which is the amine curing agent III dissolved in DMF. The molecular structure is as follows:

[0081]

[0082] Example 5: Preparation of Thermosetting Epoxy Resin I by Compounding Curing Agent I with Polyetheramine D230

[0083] At room temperature, 10 g of epoxy resin E51 and 0.3 g of accelerator DMP-30 were added to the DMF solution of curing agent I after the reaction, and nitrogen protection was used throughout the process to prevent catechol from being oxidized. After reacting for 1 hour, 2.4 g of polyetheramine D230 was added and mixed, and reacted at room temperature overnight. Finally, a DMF solution of ferric chloride (1 / 3 of the amount of BQA) was added, and the mixture was transferred to an aluminum mold pre-coated with a release agent, and completely cured after degassing and heating in a vacuum oven at 80°C for 24 hours. After cooling to room temperature, a degradable epoxy resin I was obtained, and its thermodynamic properties are shown in Table 1.

[0084] Table 1 Thermodynamic properties of epoxy resin I

[0085] project performance Tensile strength(MPa) 25±3 Tensile modulus(GPa) 0.5±0.2 Tensile strain (%) 200±10 <![CDATA[T g (℃)]]> 60～70 <![CDATA[T d5％ (℃)]]> 240～250

[0086] Example 6: Preparation of thermosetting epoxy resin II by compounding curing agent I with 1,2-bis(2-aminoethoxy)ethane

[0087] At room temperature, 10 g of epoxy resin E51 and 0.3 g of accelerator DMP-30 were added to the DMF solution of curing agent I, and nitrogen protection was used throughout the process to prevent catechol from being oxidized. After reacting for 1 hour, 1.5 g of 1,2-bis(2-aminoethoxy)ethane was added and mixed, and reacted at room temperature overnight. Finally, a DMF solution of ferric chloride (1 / 3 of the amount of BQA) was added, and the mixture was transferred to an aluminum mold pre-coated with a release agent, and degassed and heated in a vacuum oven at 80°C for 24 hours before curing. After cooling to room temperature, a degradable epoxy resin II was obtained, and its thermodynamic properties are shown in Table 2.

[0088] Table 2 Thermodynamic properties of epoxy resin II

[0089] project performance Tensile strength(MPa) 30±5 Tensile modulus(GPa) 0.5±0.2 Tensile strain (%) 120±10 <![CDATA[T g (℃)]]> 60～70 <![CDATA[T d5％ (℃)]]> 250～260

[0090] Example 7: Preparation of Thermosetting Epoxy Resin III by Compounding Curing Agent I with 4,4-Diaminodiphenylmethane

[0091] At room temperature, 10 g of epoxy resin E51 and 0.3 g of accelerator DMP-30 were added to the DMF solution of curing agent I, and nitrogen protection was used throughout the process to prevent catechol from being oxidized. After reacting for 1 hour, 2.0 g of 4,4-diaminodiphenylmethane solution was added for mixing, and the mixture was reacted at room temperature overnight. Finally, a DMF solution of ferric chloride (1 / 3 of the amount of BQA) was added, and the mixture was transferred to an aluminum mold pre-coated with a release agent, and the mixture was completely cured after degassing and heating in a vacuum oven at 80°C for 24 hours. After cooling to room temperature, a degradable epoxy resin III was obtained, and its thermodynamic properties are shown in Table 3.

[0092] Table 3 Thermodynamic properties of epoxy resin III

[0093] project performance Tensile strength(MPa) 40±5 Tensile modulus(GPa) 1.0±0.2 Tensile strain (%) 50±10 <![CDATA[T g (℃)]]> 100～120 <![CDATA[T d5％ (℃)]]> 320～350

[0094] Example 8: Preparation of Thermosetting Epoxy Resin IV by Compounding Curing Agent II with 1,2-Bis(2-aminoethoxy)ethane

[0095] At room temperature, 11.1 g of epoxy resin CY183 and 0.3 g of accelerator DMP-30 were added to the DMF solution of curing agent II after the reaction. Nitrogen protection was used throughout the process to prevent the oxidation of catechol. After reacting for 1 hour, 1.5 g of 1,2-bis(2-aminoethoxy)ethane was added and mixed. The mixture was reacted at room temperature overnight. Finally, a DMF solution of ferric chloride (1 / 3 of the amount of BQA added) was added and the mixture was transferred to an aluminum mold pre-coated with a release agent. The mixture was degassed and heated in a vacuum oven at 100°C for 24 hours before being completely cured.

[0096] Example 9: Preparation of Thermosetting Epoxy Resin V by Compounding Curing Agent III with Polyetheramine D230

[0097] At room temperature, 11.4 g of bisphenol F epoxy resin and 0.3 g of accelerator DMP-30 were added to the DMF solution of curing agent III after the reaction. Nitrogen protection was used throughout the process to prevent the oxidation of catechol. After reacting for 1 hour, 2.4 g of polyetheramine D230 was added and mixed. The mixture was reacted at room temperature overnight. Finally, a DMF solution of ferric chloride (1 / 3 of the amount of BQA added) was added, and the mixture was transferred to an aluminum mold pre-coated with a release agent. The mixture was degassed and heated in a vacuum oven at 120°C for 24 hours before being completely cured.

[0098] Embodiment 10: Photothermal conversion type thermosetting epoxy resin 1

[0099] A xenon lamp with adjustable power was selected as the light source, the working distance was set to 15 cm, and a thermal imager was used to record the change in resin surface temperature over time. The surface temperature of thermosetting epoxy resin II can reach 50°C within 60 seconds, and the surface temperature can finally reach 75°C within 360 seconds of heating, confirming its good thermal conversion ability after absorbing sunlight.

[0100] Example 11: Photothermal conversion type thermosetting epoxy resin II

[0101] An adjustable power UV lamp was selected as the light source, the working distance was set to 15 cm, and a thermal imager was used to record the change in resin surface temperature over time. The surface temperature of thermosetting epoxy resin Ι can reach 45°C within 60 seconds, and the surface temperature can finally reach 60°C within 360 seconds of heating, confirming its good thermal conversion ability after absorbing sunlight.

[0102] Example 12: Photothermal conversion type thermosetting epoxy resin III

[0103] A xenon lamp with adjustable power was selected as the light source, the working distance was set to 15 cm, and a thermal imager was used to record the change of resin surface temperature over time. Thermosetting epoxy resin III was subjected to at least 5 cycles of on-off lighting under a certain power, and the resin surface temperature remained above 95% of the first on-light irradiation after 5 cycles, confirming its good thermal conversion retention ability after absorbing sunlight.

Claims

1. A thiol / carboxyl / amino-terminated epoxy resin curing agent containing a catechol group, characterized in that The curing agent has the following molecular structure formula: Mercapto-terminated epoxy resin curing agent containing catechol groups: Amino-terminated epoxy resin curing agent containing catechol groups: Carboxyl-terminated epoxy resin curing agent containing catechol groups: In the formula, R is one of methylene, dimethyl and cycloalkyl; R1, R2 and R3 are one of alkylene, alkyl, cycloalkyl, alkoxy, heterocyclic group, heterocyclic alkyl, aromatic group, heteroaromatic group, oxyalkyleneoxy group, oxycycloalkyleneoxy group, oxyheterocycloalkyleneoxy group, oxycycloalkyleneoxy group, oxyheterocycloalkyleneoxy group, oxyaromaticeneoxy group, oxyheteroaromaticeneoxy group, aromaticene, alkylenearomaticene, alkylenearomaticenealkylene, heteroaromaticene and alkyleneheteroaromaticene; n=1 to 3.

2. A method for preparing the catechol-containing thiol / carboxyl / amino-terminated epoxy resin curing agent according to claim 1, characterized in that The method comprises the following steps: Step 1: Preparation of o-benzoquinone compounds Step 11: dissolving a phenolic compound with an R group and a high-valent iodine reagent in a solvent, stirring for 5 to 30 minutes after being fully dissolved, wherein: The structural formula of the phenolic compound with R group is: The amount of the high-valent iodine reagent is 1 to 5 times the amount of the phenolic compound with an R group; Step 12, cooling the product obtained in step 11 in an ice water bath, filtering out the red crystalline precipitate, and washing with a solvent 2 to 4 times; Step 13: extracting the product of step 12 with a mixed solution of water and chloroform and removing unreacted 2-iodoacylbenzoic acid, and drying to obtain an o-benzoquinone compound; Step 2: Preparation of thiol / carboxyl / amino-terminated epoxy resin curing agent containing catechol groups The o-benzoquinone compound is dissolved in a solvent, and thiol, thiol carboxylic acid or thiolamine is added dropwise, and stirred for 5 to 30 minutes under a nitrogen atmosphere. After the thiol, thiol carboxylic acid or thiolamine is added, the color of the solution containing the o-benzoquinone compound gradually changes from dark to light. When the color no longer changes, the reaction is stopped to obtain a thiol / carboxyl / amino-terminated epoxy resin curing agent containing a catechol group dissolved in a solvent, wherein: The molar ratio of the o-benzoquinone compound to the thiol, the thiol group of the thiolamine or the thiol group of the thiolcarboxylic acid is 1:

2.

3. The method for preparing a thiol / carboxyl / amino-terminated epoxy resin curing agent containing a catechol group according to claim 2, characterized in that The high-valent iodine reagent is one of dichloroiodobenzene, dichloroiodosobenzene, iodosobenzene, 2-iodoacylbenzoic acid, iodosobenzene diacetate, and iodobenzene diacetate; the solvent is at least one of methanol, ethanol, tetrahydrofuran, acetone, dichloromethane, acetonitrile, dioxane, N-methylpyrrolidone, N,N-dimethylformamide, and dimethyl sulfoxide.

4. The method for preparing a thiol / carboxyl / amino-terminated epoxy resin curing agent containing a catechol group according to claim 2, characterized in that The entire process of step 1 is carried out under a nitrogen atmosphere.

5. A method for preparing an epoxy resin having high toughness and light-to-heat conversion performance, characterized in that The method comprises the following steps: Step 1: Preparation of o-benzoquinone compounds Step 11: dissolving a phenolic compound with an R group and a high-valent iodine reagent in a solvent, stirring for 5 to 30 minutes after being fully dissolved, wherein: The structural formula of the phenolic compound with R group is: The amount of the high-valent iodine reagent is 1 to 5 times the amount of the phenolic compound with an R group; Step 12, cooling the product obtained in step 11 in an ice water bath, filtering out the red crystalline precipitate, and washing with a solvent 2 to 4 times; Step 13: extracting the product of step 12 with a mixed solution of water and chloroform and removing unreacted 2-iodoacylbenzoic acid, and drying to obtain an o-benzoquinone compound; Step 2: Preparation of thiol / carboxyl / amino-terminated epoxy resin curing agent containing catechol groups Step 2:

1. Dissolve an o-benzoquinone compound in a solvent, add thiol, thiol carboxylic acid or thiolamine dropwise, and stir for 5 to 30 minutes under a nitrogen atmosphere. After the thiol, thiol carboxylic acid or thiolamine is added, the color of the solution containing the o-benzoquinone compound gradually changes from dark to light. When the color no longer changes, stop the reaction to obtain a thiol / carboxyl / amino-terminated epoxy resin curing agent containing a catechol group dissolved in a solvent, wherein: The amount of the thiol / thiolamine / thiolcarboxylic acid is 2 times or more of the amount of the o-benzoquinone compound; The catechol-containing thiol / carboxyl / amino-terminated epoxy resin curing agent has the following molecular structure formula: Mercapto-terminated epoxy resin curing agent containing catechol groups: Amino-terminated epoxy resin curing agent containing catechol groups: Carboxyl-terminated epoxy resin curing agent containing catechol groups: In the formula, R is one of methylene, dimethyl and cycloalkyl; R1, R2 and R3 are one of alkylene, alkyl, cycloalkyl, alkoxy, heterocyclic group, heterocyclic alkyl, aromatic group, heteroaromatic group, oxyalkyleneoxy group, oxycycloalkyleneoxy group, oxyheterocycloalkyleneoxy group, oxycycloalkyleneoxy group, oxyheterocycloalkyleneoxy group, oxyaromaticeneoxy group, oxyheteroaromaticeneoxy group, aromaticene, alkylenearomaticene, alkylenearomaticenealkylene, heteroaromaticene and alkyleneheteroaromaticene; n=1-3; Step 3: Preparation of epoxy resin containing catechol groups The epoxy resin, curing agent and accelerator are sequentially added to the solution of step 2, and stirred at 25-100° C. for 1-24 hours to obtain an epoxy resin containing a catechol group, wherein: The weight ratio of the epoxy resin, the thiol / carboxyl / amino-terminated epoxy resin curing agent containing catechol groups, the curing agent and the accelerator is 1:0.1 to 1:0.9 to 0:0.01 to 0.

05. Step 4: Preparation of Epoxy Resin Containing Catechol-Metal Coordination Bond Add metal ions to the epoxy resin containing catechol groups in step 3, stir thoroughly for 0.5 to 12 hours, pour into a mold and solidify to obtain an epoxy resin containing catechol-metal coordination bonds, wherein: The amount of the metal ion added is at most 1 / 3 to 1 / 2 times the molar amount of the o-benzoquinone compound; The curing temperature is 50-200° C. and the curing time is 6-48 hours.

6. The method for preparing the epoxy resin with high toughness and light-to-heat conversion performance according to claim 5, characterized in that The high-valent iodine reagent is one of dichloroiodobenzene, dichloroiodosobenzene, iodosobenzene, 2-iodoacylbenzoic acid, iodosobenzene diacetate, and iodobenzene diacetate; the solvent is at least one of methanol, ethanol, tetrahydrofuran, acetone, dichloromethane, acetonitrile, dioxane, N-methylpyrrolidone, N,N-dimethylformamide, and dimethyl sulfoxide.

7. The method for preparing the epoxy resin with high toughness and light-to-heat conversion performance according to claim 5, characterized in that The entire process of step 1 is carried out under a nitrogen atmosphere.

8. The method for preparing the epoxy resin with high toughness and light-to-heat conversion performance according to claim 5, characterized in that The epoxy resin is one or more of glycidyl ether, glycidyl ester, glycidyl amine, aliphatic epoxy resin, alicyclic epoxy resin, trifunctional epoxy resin, tetrafunctional epoxy resin, phenolic epoxy resin, o-cresol epoxy resin, nitrogen-containing epoxy resin; the curing agent is one or more of amine curing agent, acid anhydride curing agent, anionic polymerization curing agent, cationic polymerization curing agent, polythiol curing agent and the like; the accelerator is 2,4,6-tris(dimethylaminomethyl)phenol, Benzyldimethylamine triethylamine, triethanolamine, o-hydroxybenzyldimethylamine, N-(2-hydroxyphenyl)-N',N'-dimethylurea; N-(2-hydroxy-4-nitrobenzene)-N',N'-dimethylurea; N-(5-chloro-2-hydroxybenzene)-N',N'-dimethylurea, N-(4-chlorophenyl)-N',N'-dimethylurea, N-(4-chloro-2-hydroxybenzene)-N',N'-dimethylurea, acetylacetone metal complex, boron trifluoride complex, one of the imidazole accelerators.

9. The method for preparing the epoxy resin with high toughness and light-to-heat conversion performance according to claim 5, characterized in that The metal ion is Fe 3+ , Fe 2+ , Cu 2+ 、Co 2+ 、Zn 2+ 、Al 3+ 、Ni 2+ One or more of .

10. An epoxy resin with high toughness and photothermal conversion performance prepared by the method according to any one of claims 5 to 9.

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