A preparation method of functionalized graphene oxide based on alcohol-alkyne click reaction

Abstract

The invention discloses a method for preparing functional graphene oxide based on the alcohol-alkyne click reaction. Using the hydroxyl groups on graphene oxide as reaction sites, under the catalysis of an organic small molecule catalyst, after reaction at room temperature, the alcohol-alkyne click reaction between graphene oxide and a series of propargyl esters is successfully carried out, and a series of functional molecules are grafted and modified onto graphene oxide to obtain functional graphene oxide. The propargyl esters used in this method include allyl alcohol ester of propargylic acid, propargyl alcohol ester, dodecyl alcohol ester, mPEG ester, PCL ester, etc. Compared with the prior art, it not only has the advantageous features of room temperature reaction and fast reaction rate, but also directly uses commercial graphene oxide as raw material without prior functionalization. This method uses an organic small molecule catalyst without the need for metals or toxic reagents, ensuring the simple operability of the reaction and post-treatment. The dispersibility and stability of the prepared functional graphene oxide in common solvents have been significantly improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional materials, relates to the preparation of graphene oxide, and particularly relates to a method for preparing functional graphene oxide based on an alcohol-alkyne click reaction. Background Art

[0002] As a class of emerging materials that have received much attention, graphene has been widely used in the fields of energy storage, electronic devices, sensing materials, etc. due to its excellent high electrical conductivity, high thermal conductivity, and mechanical stability. However, due to the poor dispersibility, poor processability, and single functionality of graphene oxide (GO) itself, there are still huge challenges in the practical application and popularization of graphene materials. Therefore, chemically modifying graphene to improve its dispersibility, processability, and multifunctionality is an attractive method to expand the uses of GO.

[0003] Grafting chemical groups onto GO via click chemistry is one of the most common and effective methods for GO modification. For example, Cu(I)-catalyzed azide-alkyne click reaction, Diels-Alder click reaction, and thiol-ene click reaction. Because of its high efficiency, high selectivity, strong functional group tolerance, and mild reaction conditions. [Yang et al. Polymer 2011, 52, 3046] reported a method for polystyrenefunctionalizing GO using Cu(I)-catalyzed azide-alkyne click reaction. This method used azide-modified graphite oxide and alkyne-terminated polystyrene to graft polystyrene molecular chains onto the GO surface. The dispersibility of the modified GO was greatly changed and it had good dispersibility in organic solvents such as THF, DMF, and CHCl3. The prior art [Yuan et al. J. Mater. Chem. 2012, 22] functionalized graphene oxide in one step with methoxypolyethylene glycol with cyclopentadienyl end groups via Diels-Alder click reaction, and successfully prepared GO grafted and modified with polyethylene glycol. The obtained material had improved dispersibility in various solvents. [Salavagione et al. Macromolecules 2016, 49, 4948] reported a method for preparing conductive nanocomposites from poly(styrene-b-ethylene-co-butene-b-styrene) (SEBS) triblock copolymer and chemically modified graphene. This method functionalized graphene into short polyethylene brushes via thiol-ene click chemistry. Including the above three examples, the current methods for functionalizing GO via click reactions have some disadvantages, including high temperature, catalyst residue, and difficult post-treatment, the use of metals and toxic reagents, the need for pre-modification of azide groups, unsafe azo monomers, the pungent odor of thiol compounds, etc., which violate the principles of green chemistry and greatly limit their applications. Especially for the poor dispersibility and difficult post-treatment characteristics of GO itself, it is necessary to develop a more sustainable, mild-condition, simple, efficient, and highly operable GO modification method. Summary of the Invention

[0004] To overcome the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a method for preparing functionalized graphene oxide based on alcohol-alkyne click reaction. Using graphene oxide prepared by the Hummer method and propargylate as raw materials, through the hydroxyl groups on graphene oxide as reaction sites, under the catalysis of an organic small molecule catalyst, after reacting at room temperature, the alcohol-alkyne click reaction between graphene oxide and propargylate was successfully carried out, and a series of functionalized graphene oxides were prepared. This reaction exhibits great advantages such as high efficiency, mild reaction conditions, simple post-treatment, and stronger sustainability.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is:

[0006] A preparation method of functionalized graphene oxide based on the alcohol-alkyne click reaction, comprising the following steps at room temperature:

[0007] Step 1, dispersing graphene oxide in DMF to obtain a dispersion;

[0008] Step 2, adding an organic small molecule catalyst to the dispersion to obtain a mixed solution;

[0009] Step 3, adding propargyl esters in multiple batches to the mixed solution in sequence for reaction;

[0010] Step 4, after the reaction is completed, purifying and drying to obtain a functionalized graphene oxide material.

[0011] In one embodiment, in the dispersion of Step 1, the concentration of graphene oxide is 2-8 mg / mL.

[0012] In one embodiment, the graphene oxide is graphene oxide prepared by the commercial Hummer method, which contains a large number of hydroxyl groups.

[0013] In one embodiment, the organic small molecule catalyst is a Lewis base organic small molecule catalyst.

[0014] In one embodiment, the Lewis base organic small molecule catalyst is triethylenediamine.

[0015] In one embodiment, the propargyl ester is allyl propargylate, propargyl alcohol ester, dodecyl alcohol ester, mPEG ester, PCL ester, etc.

[0016] In one embodiment, in Step 3, the propargyl esters are added to the mixed solution in N batches at half-hour intervals in sequence, and the total reaction time is N / 2 hours.

[0017] In one embodiment, the mass ratio of the graphene oxide, the organic small molecule catalyst, and the propargyl ester is 1:(0.1-0.5):(1-4).

[0018] In one embodiment, the purification method is dialysis or high-speed centrifugation. Among them, the dialysis solvent is deionized water, and the solvents used for high-speed centrifugation are ethanol and water in sequence.

[0019] The functionalized graphene oxide material prepared by the present invention, through the grafted functional molecules, on the one hand, improves the dispersibility and processability of graphene oxide, and can be used in various conditions where traditional graphene oxide is not applicable (such as in chloroform and toluene solvents); on the other hand, it is applicable to various application scenarios of graphene, such as catalysis, sensing, conductivity, heat conduction, functional filler materials, etc.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] 1. High reaction efficiency, fast reaction speed, high reaction selectivity, mild reaction conditions, and high tolerance for reaction functional groups.

[0022] 2. This method directly uses commercial GO as the raw material, avoiding the pre-functionalization modification of GO (compared with other methods). This method reacts at room temperature, with more friendly operation. This method uses organic small molecule catalysts, avoiding the use of metals and toxic reagents, and is environmentally friendly. At the same time, these features ensure the simplicity and strong operability of the reaction and post-treatment operations, and have strong practicality.

[0023] 3. Through a series of alcohol-alkyne click reactions between propargyl esters and GO, it is a general and universal method that can graft a series of diverse functional molecules onto GO, with a wide application range, diverse functionalizations, and meeting various GO requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the key technology alcohol-alkyne click reaction process in the present invention.

[0025] Figure 2 It is a statistical graph of the reaction kinetics experiment of GO and allyl propargyl carbonate under different concentrations of the catalyst 1,4-diazabicyclo[2.2.2]octane, that is, the conversion rate-time relationship graph.

[0026] Figure 3 It is a photo of the dispersibility of GO in solvents such as tetrahydrofuran, N,N-dimethylformamide, toluene, and chloroform.

[0027] Figure 4 It is a photo of the dispersibility of the modified functional GO in solvents such as tetrahydrofuran, N,N-dimethylformamide, toluene, and chloroform.

[0028] Figure 5 It is the infrared spectrum of GO.

[0029] Figure 6 It is the infrared spectrum of the modified functional GO: (a) dodecyl propargyl carbonate for the click reaction, (b) mPEG propargyl carbonate for the click reaction. 5000 ester.

[0030] Figure 7 [[ID=)41]]It is the thermogravimetric curve of GO.

[0031] Figure 8 It is the thermogravimetric curve of the modified functional GO: (a) dodecyl propargyl carbonate for the click reaction, (b) mPEG propargyl carbonate for the click reaction. 5000 ester.

[0032] Figure 9It is the X-ray photoelectron spectroscopy analysis curve of GO.

[0033] Figure 10 It is the X-ray photoelectron spectroscopy analysis curve of modified functional GO: (a) dodecyl propiolate for click reaction, (b) mPEG propiolate for click reaction. 5000 ester. Specific embodiments

[0034] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings and examples.

[0035] The present invention relates to a method for synthesizing functional graphene oxide based on alcohol-alkyne click reaction, and the whole process can be carried out at room temperature, including the following steps:

[0036] Step 1: Disperse graphene oxide in the solvent DMF to obtain a dispersion.

[0037] Step 2: Add an organic small molecule catalyst to the dispersion obtained in Step 1.

[0038] Step 3: Add the propiolate ester in multiple batches at certain intervals successively to the mixture in Step 2.

[0039] Step 4: After the reaction in Step 3, purify and dry to obtain the functional graphene oxide material.

[0040] The principle of the present invention can be referred to Figure 1 As shown, by applying the alcohol-alkyne click reaction to the preparation of functional graphene oxide, using graphene oxide and a series of propiolate esters as raw materials, taking the hydroxyl groups on graphene oxide as reaction sites, under the catalysis of an organic small molecule catalyst, after the reaction at room temperature, the alcohol-alkyne click reaction between graphene oxide and a series of propiolate esters is successfully carried out, thereby grafting and modifying a series of functional molecules onto graphene oxide to obtain functional graphene oxide. Compared with the prior art, this method not only has the advantages of room temperature reaction and fast reaction speed, but also directly uses commercial graphene oxide as raw material without prior functionalization, and uses an organic small molecule catalyst without metal or toxic reagents, which ensures the simple operability of the reaction and post-treatment. The dispersibility and stability of the prepared modified graphene oxide in common solvents have been significantly improved.

[0041] In some embodiments of the present invention, the graphene oxide used in Step 1 is graphene oxide prepared by the commercial Hummer method, which contains a large number of hydroxyl groups, is more conducive to the alcohol-alkyne click reaction, and is free from pre-functionalization modification treatment. In the prepared dispersion, the concentration of graphene oxide in the solvent DMF is 2-8 mg / mL, and in this range, better reaction grafting effects can be obtained.

[0042] In some embodiments of the present invention, a Lewis base organic small molecule catalyst is selected to catalyze the completion of the key technology of the alcohol-alkyne click reaction. In the present invention, 1,4-diazabicyclo[2.2.2]octane is preferably selected as the catalyst because it has the advantages of low cost, excellent catalytic effect, small molecular weight, and easy separation and removal after the reaction.

[0043] In some embodiments of the present invention, propargylate is used as a modifier for graphene oxide, and an alcohol-alkyne click reaction occurs with graphene oxide and is bonded in the form of a covalent bond, so that the molecules carried in the propargylate are grafted and modified onto graphene oxide, realizing the preparation of functional graphene oxide materials. The propargylates used include but are not limited to allyl propargylate, propargyl alcohol ester, dodecyl alcohol ester, mPEG ester, PCL ester, etc. The propargylate used in step 3 can be the same propargylate or different propargylates for each batch. When the same propargylate is selected, single modification of graphene oxide can be achieved. When different propargylates are selected, multiple modifications of graphene oxide can be realized by one-pot method, that is, through click coupling of multiple propargylates, multiple functional molecules are grafted onto the same graphene oxide molecule.

[0044] In some embodiments of the present invention, the mass ratio of graphene oxide, organic small molecule catalyst, and propargylate can be controlled to be 1:0.1-0.5:1-4.

[0045] In some embodiments of the present invention, the propargylate can be added to the mixed solution in step 2 in N batches at intervals of half an hour, and the total reaction time is N / 2 hours. For example, N = 6. The batch here is related to the grafting rate. Adding the reaction substrate propargylate in small amounts and multiple times can, on the one hand, effectively reduce the intensity of the reaction and avoid the occurrence of side reactions, and improve the grafting rate; on the other hand, by increasing or decreasing the feeding batches, the purpose of increasing or decreasing the grafting rate can be achieved. The interval time here is related to the conversion rate of the reaction substrate propargylate. According to Figure 2 the reaction kinetics experiment shown, the reaction rate is relatively intense within the first 20 minutes, and a conversion rate of more than 80% of the reaction substrate propargylate can be achieved, and then the reaction slows down. Therefore, the interval time for each batch of feeding is 30 minutes.

[0046] In some embodiments of the present invention, the purification method is dialysis or high-speed centrifugation. The dialysis solvent is deionized water, and the solvents used for high-speed centrifugation are ethanol and water in sequence. The purification method of centrifugation or dialysis can be selected according to the experimental equipment conditions, and both methods are applicable.

[0047] The following are several specific embodiments of the present invention.

[0048] Example 1

[0049] A method for preparing functional graphene oxide based on alcohol-alkyne click reaction, comprising the following steps:

[0050] Step 1: Disperse 50 mg of graphene oxide in 10 mL of DMF to obtain a dispersion with a concentration of 5 mg / mL;

[0051] Step 2: Add 2.5 mg, 5 mg, and 10 mg of triethylenediamine to the dispersion obtained in step 1 at room temperature;

[0052] Step 3: At room temperature, 120 mg of allyl propiolate was added at once or in six batches at half-hour intervals to the mixture in step 2. The total reaction time was 3 hours.

[0053] Step 4: After the reaction is completed, the product is dialyzed and purified with deionized water and dried to obtain a functionalized graphene oxide material.

[0054] Example 2

[0055] Step 1: Disperse 64 mg of graphene oxide in 8 mL of DMF to obtain a dispersion with a concentration of 8 mg / mL;

[0056] Step 2: Add 10 mg of triethylenediamine to the dispersion obtained in step 1 at room temperature;

[0057] Step 3: At room temperature, 150 mg of propargyl propiolate was added to the mixture in step 2 in six batches at half-hour intervals. The total reaction time was 3 hours.

[0058] Step 4: After the reaction is completed, the product is dialyzed and purified with deionized water and dried to obtain a functionalized graphene oxide material.

[0059] Example 3

[0060] Step 1: Disperse 20 mg of graphene oxide in 10 mL of DMF to obtain a dispersion with a concentration of 2 mg / mL;

[0061] Step 2: Add 10 mg of triethylenediamine to the dispersion obtained in step 1 at room temperature;

[0062] Step 3: At room temperature, 50 mg of dodecanol propiolate was added to the mixture in step 2 in six batches at half-hour intervals. The total reaction time was 3 hours.

[0063] Step 4: After the reaction is completed, the product is purified by high-speed centrifugation with ethanol and water in sequence, and dried to obtain a functionalized graphene oxide material.

[0064] Example 4

[0065] Step 1: Disperse 50 mg of graphene oxide in 10 mL of DMF to obtain a dispersion with a concentration of 2.5 mg / mL.

[0066] Step 2: At room temperature, add 10 mg of triethylenediamine to the dispersion obtained in Step 1.

[0067] Step 3: At room temperature, add 150 mg of propargyl acrylate PCL ester to the mixture in Step 2 in six batches at half-hour intervals. The total reaction time is 3 hours.

[0068] Step 4: After the reaction is completed, dialyze and purify with deionized water, and after drying, obtain the functionalized graphene oxide material.

[0069] Example 5

[0070] Step 1: Disperse 50 mg of graphene oxide in 10 mL of DMF to obtain a dispersion with a concentration of 2.5 mg / mL.

[0071] Step 2: At room temperature, add 10 mg of triethylenediamine to the dispersion obtained in Step 1.

[0072] Step 3: At room temperature, add 150 mg of mPEG propargyl 5000 ester to the mixture in Step 2 in six batches at half-hour intervals. The total reaction time is 3 hours.

[0073] Step 4: After the reaction is completed, dialyze and purify with deionized water, and after drying, obtain the functionalized graphene oxide material.

[0074] The present invention confirmed the successful grafting of different functional groups on GO through infrared, X-ray photoelectron spectroscopy, and thermogravimetric characterization. For details, please refer to Figures 2 to 10 as shown.

[0075] Figure 2 is the statistical graph of the reaction kinetics experiment of GO and allyl propargyl acrylate under different concentrations of the catalyst triethylenediamine, that is, the conversion rate-time relationship graph. It can be seen that the reaction rate is relatively intense within the first 20 minutes, and a conversion rate of more than 80% of the reaction substrate propargyl acrylate can be achieved. Subsequently, the reaction slows down. Therefore, the interval time for each batch of feeding is 30 minutes. Figure 3 are the dispersion photos of the raw material graphene oxide in different solvents. It can be seen that the dispersion is better in DMF, and a stable dispersion can still be maintained after standing for 1 month. However, the dispersion in tetrahydrofuran, toluene, and chloroform is very poor.

[0076] Figure 4These are the photos of the dispersion of modified functionalized graphene oxide in different solvents. It shows excellent dispersion and stability in tetrahydrofuran, DMF, toluene, and chloroform, in sharp contrast to the original graphene oxide.

[0077] Figure 5 This is the infrared spectrum of the raw material GO. The band at 3221 cm -1 is very obvious, representing the -OH groups on GO. At 1721 cm -1 , 1652 cm -1 and 1060 cm -1 , the bands can be attributed to the C=O, C=C, and C-O-C stretching vibrations respectively.

[0078] Figure 6 (a) This is the infrared spectrum of GO modified with dodecyl propiolate. The significant decrease in the absorption intensity of the -OH groups at 3408 cm -1 proves that a large number of hydroxyl groups are consumed in the reaction. The two absorption peaks at 2922 cm -1 and 1142 cm -1 are attributed to the C-H of the grafted alkyl chain and the C-O-C vibration of the ester group respectively. (b) This is the infrared spectrum of the modification with mPEG 5000 ester. The two absorption peaks at 2876 cm -1 and 1107 cm -1 are attributed to the C-H and C-O-C vibrations of the grafted mPEG chain respectively.

[0079] Figure 7 This is the thermogravimetric curve of the raw material GO, with a char residue rate of 44.37%.

[0080] Figure 8 (a) This is GO modified with dodecyl propiolate, with a char residue rate of 41.72%. (b) This is GO modified with mPEG 5000 ester, with a char residue rate of 30.13%.

[0081] Figure 9 This is the X-ray photoelectron spectrum of the raw material GO, showing four characteristic peaks corresponding to four components in different functional groups: C-C / C=C (284.2 eV), C-O (285.7 eV), C=O (286.6 eV), and O-C=O (288.2 eV).

[0082] The following table shows the grafting rates of GO functionalized by click reaction with different propiolates in the above examples.

[0083]

[0084]

[0085] As can be seen from the above embodiments, through the described implementation steps, various propargyl esters with different functional groups are successfully grafted onto graphene oxide via an alcohol-alkyne click reaction, thereby successfully grafting and modifying different functional molecules onto graphene oxide, and successfully preparing a series of functional graphene oxide materials. This demonstrates the effectiveness and universality of the method for preparing functional graphene oxide based on the alcohol-alkyne click reaction proposed in the present invention.

Claims

1. A preparation method of functionalized graphene oxide based on alcohol-alkyne click reaction, characterized in that, Including the following steps at room temperature: Step 1: Dispersing graphene oxide in DMF to obtain a dispersion; Step 2: Adding an organic small molecule catalyst to the dispersion to obtain a mixture; Step 3: Adding propargyl esters in multiple batches to the mixture successively for reaction; Step 4: After the reaction, purifying and drying to obtain a functional graphene oxide material.

2. The preparation method of functionalized graphene oxide based on the alcohol-alkyne click reaction according to claim 1, wherein In Step 1, in the dispersion, the concentration of graphene oxide is 2-8 mg / mL.

3. The method for preparing functionalized graphene oxide based on the alcohol-alkyne click reaction according to claim 1 or 2, characterized in that, The graphene oxide is graphene oxide prepared by the commercial Hummer method, which contains a large number of hydroxyl groups.

4. The method for preparing functionalized graphene oxide based on the alcohol-alkyne click reaction according to claim 1, characterized in that, The organic small molecule catalyst is a Lewis base organic small molecule catalyst.

5. The preparation method of functionalized graphene oxide based on alcohol-alkyne click reaction according to claim 4, characterized in that, The Lewis base organic small molecule catalyst is 1,4-diazabicyclo[2.2.2]octane.

6. The method for preparing functionalized graphene oxide based on alcohol-alkyne click reaction according to claim 1, wherein The propargyl ester is allyl propargyl carbonate, propargyl alcohol ester, dodecyl alcohol ester, mPEG ester or PCL ester.

7. The preparation method of functionalized graphene oxide based on alcohol-alkyne click reaction according to claim 1, characterized in that, In Step 3, adding the propargyl ester in N batches to the mixture every half hour successively, and the total reaction time is N / 2 hours.

8. The preparation method of functionalized graphene oxide based on the alcohol-alkyne click reaction according to any one of claims 1 to 7, characterized in that, The mass ratio of the graphene oxide, the organic small molecule catalyst and the propargyl ester is 1:(0.1-0.5):(1-4).

9. The preparation method of functionalized graphene oxide based on the alcohol-alkyne click reaction according to claim 1, characterized in that, The purification method is dialysis or high-speed centrifugation. Among them, the dialysis solvent is deionized water, and the solvents used for high-speed centrifugation are ethanol and water in sequence.

10. A functional graphene oxide material obtained by the method for preparing functional graphene oxide based on the alcohol-alkyne click reaction according to any one of claims 1 to 9.

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