A method for preparing a Janus polysiloxane modified single-layer graphene oxide

Abstract

The application provides a preparation method of Janus polysiloxane modified monolayer graphene oxide, and belongs to the technical field of chemical modification of graphene oxide. First, toluene and water are mixed and then are allowed to stand to be layered, then monolayer graphene oxide is added into water, a cationic surfactant is added into toluene, and then is allowed to stand again; after the standing is completed, a single-end hydrogen-containing polysiloxane and trifluorophenyl boron are added into toluene to perform a standing reaction, part of toluene and water are extracted, and a remaining interfacial layer is obtained; finally, the interfacial layer is sequentially subjected to washing and drying to obtain Janus polysiloxane modified monolayer graphene oxide. The Janus polysiloxane modified monolayer graphene oxide prepared by the application has stronger amphiphilicity, and when used as a Pickering emulsifier, can make the emulsion more stable.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of chemical modification of graphene oxide, and in particular to a preparation method of Janus polysiloxane modified monolayer graphene oxide. BACKGROUND

[0002] Monolayer graphene oxide is an oxidation product of graphene, has the characteristics of high anisotropy, large specific surface area, solubility in water and easy chemical modification, and has become a two-dimensional nanomaterial that has attracted widespread attention. Janus graphene oxide refers to monolayer graphene oxide with different chemical structures on two sides. When the chemical structures on the two sides are hydrophilic and hydrophobic respectively, the Janus graphene oxide is called amphiphilic Janus graphene oxide. The amphiphilic Janus graphene oxide is often used as a Pickering emulsifier and a nano oil displacement material. The Janus graphene oxide has a large aspect ratio and a large specific surface area, is beneficial to adsorption at the oil-water interface, and forms a film structure with a certain strength, so the Janus graphene oxide performs better than other nanoparticles in the Pickering emulsifier and the nano oil displacement material.

[0003] At present, the methods for preparing Janus graphene oxide mainly include an emulsion template method (CN104386672A, 2015; CN113248669A, 2018; CN110713609A, 2020; CN110643000A, 2020) and a solid nanoparticle template method (CN108046244A, 2018). In the emulsion template method, graphene oxide is used as a Pickering emulsifier to obtain a water-in-oil or oil-in-water emulsion, and then a chemical modifier in the water phase and the oil phase reacts with the inner and outer interfaces of the graphene oxide to obtain Janus graphene oxide. In the solid nanoparticle template method, nanoparticles are dispersed in a solvent, graphene oxide is adsorbed to the surface of the nanoparticles, and then the chemical modifier is reacted, and finally the solid nanoparticles are removed to obtain Janus graphene oxide. Both the two methods have certain defects. In the emulsion template method, the amphiphilic property of the graphene oxide is not obvious before modification, the emulsification effect is poor, and therefore it is difficult to obtain a stable Pickering emulsion, so that many non-Janus structure modified graphene oxide impurities are contained in the prepared Janus graphene oxide. The nanoparticle template method has many steps and cannot modify both sides of the graphene oxide at the same time.

[0004] In addition, the commonly used Janus graphene oxide modifier is generally an amine group (or amino group) containing compound, such as octylamine, dodecylamine, octadecylamine, amino silane, dopamine, etc., which mainly utilizes ring-opening addition reaction of the amine group (or amino group) and the epoxy group in the graphene oxide to graft. The modifier can only modify the graphene oxide by using the epoxy group, and the grafting amount is limited by the content of the epoxy group, so it is necessary to modify the graphene oxide by using the abundant hydroxyl group.

[0005] In view of the above problems, the present application provides a new preparation method of Janus polysiloxane modified single-layer graphene oxide. SUMMARY

[0006] The present application aims to provide a preparation method of Janus polysiloxane modified single-layer graphene oxide to solve the technical problem that the Janus graphene oxide prepared in the prior art has many non-Janus structures.

[0007] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions:

[0008] The present application provides a preparation method of Janus polysiloxane modified single-layer graphene oxide, comprising the following steps:

[0009] (1) mixing toluene and water and then standing to separate into layers, then adding single-layer graphene oxide into the water and adding a cationic surfactant into the toluene, and standing again;

[0010] (2) after the standing is completed, adding a single-end hydrogen-containing polysiloxane and a trifluorophenyl boron into the toluene to carry out a standing reaction, extracting part of the toluene and water, and leaving a remaining interfacial layer;

[0011] (3) sequentially washing and drying the interfacial layer to obtain Janus polysiloxane modified single-layer graphene oxide.

[0012] Preferably, in the step (1), the volume ratio of toluene to water is 1-2:1-2.

[0013] Preferably, in the step (1), the mass fraction of the single-layer graphene oxide in the water is 0.1-5%.

[0014] Preferably, in the step (1), the cationic surfactant comprises hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide or dodecyltrimethylammonium bromide, wherein the concentration of the cationic surfactant in the toluene is 0.001-0.1 mol / L.

[0015] Preferably, in the step (2), the single-end hydrogen-containing polysiloxane has a molecular weight of 500-5000 g / mol; and the concentration of the single-end hydrogen-containing polysiloxane in toluene is 10-100 g / L.

[0016] Preferably, in the step (2), the concentration of the trifluorophenyl boron in toluene is 4-17 g / L.

[0017] Preferably, in the step (2), the temperature for the standing reaction is 20-30℃, and the time for the standing reaction is 1-2 h.

[0018] Preferably, in the step (2), the thickness of the interfacial layer is 2-4 mm.

[0019] The present application has the following advantages:

[0020] (1) The present application uses the method of electrostatic interfacial adsorption to prepare Janus single-layer graphene oxide, which can significantly reduce the modified graphene oxide impurities of non-Janus structure compared with the emulsion method and nano solid particle template method, and has fewer steps.

[0021] (2) Since the polysiloxane has low surface energy and stronger hydrophobicity compared with other organic amine modifiers, the Janus polysiloxane modified single-layer graphene oxide prepared by the present application has stronger amphiphilicity, and when used as a Pickering emulsifier, it can make the emulsion more stable.

[0022] (3) In the present application, the polysiloxane modified single-layer graphene oxide utilizes the abundant hydroxyl groups in the single-layer graphene oxide for reaction, which has high reactivity and good selectivity, greatly improves the modification efficiency, and shortens the reaction time. DETAILED DESCRIPTION

[0023] The present application provides a preparation method of Janus polysiloxane modified single-layer graphene oxide, which comprises the following steps:

[0024] (1) After toluene and water are mixed and then allowed to stand and separate, single-layer graphene oxide is added into the water, and a cationic surfactant is added into the toluene, and then allowed to stand again;

[0025] (2) After the standing is completed, single-end hydrogen-containing polysiloxane and trifluorophenyl boron are added into the toluene to perform a standing reaction, and part of the toluene and water are extracted, and the remaining interfacial layer is obtained;

[0026] (3) The interfacial layer is sequentially washed and dried to obtain the Janus polysiloxane modified single-layer graphene oxide.

[0027] In the present application, in the step (1), the volume ratio of toluene to water is 1-2:1-2, preferably 1-2:1, and further preferably 1:1.

[0028] In the present application, in the step (1), the mass fraction of the single-layer graphene oxide in water is 0.1-5%, preferably 0.2-4.5%, and further preferably 0.3-4%.

[0029] In the present application, in the step (1), the cationic surfactant comprises cetyltrimethylammonium chloride, cetyltrimethylammonium bromide or dodecyltrimethylammonium bromide, preferably cetyltrimethylammonium chloride and / or cetyltrimethylammonium bromide, and further preferably cetyltrimethylammonium bromide; wherein the concentration of the cationic surfactant in toluene is 0.001-0.1 mol / L, preferably 0.003-0.08 mol / L, and further preferably 0.01-0.05 mol / L.

[0030] In the present application, in the step (2), the molecular weight of the single-end hydrogen-containing polysiloxane is 500-5000 g / mol, preferably 1000-4000 g / mol, and further preferably 1500-3500 g / mol; and the concentration of the single-end hydrogen-containing polysiloxane in toluene is 10-100 g / L, preferably 15-95 g / L, and further preferably 20-90 g / L.

[0031] The single-end hydrogen-containing polysiloxane used in the present application is terminated by Si-H bond at one end and trimethylsilyl group at the other end.

[0032] In the present application, in the step (2), the concentration of the tris-pentafluorophenyl boron in toluene is 4-17 g / L, preferably 5-15 g / L, and further preferably 8-12 g / L.

[0033] In the present application, in the step (2), the temperature for standing reaction is 20-30℃, preferably 22-28℃, and further preferably 25℃; and the time for standing reaction is 1-2 h, preferably 1.5 h.

[0034] In the present application, in the step (2), the thickness of the interfacial layer is 2-4 mm, preferably 3 mm.

[0035] The technical solutions provided by the present application will be described in detail below in conjunction with examples, but they should not be understood as limiting the scope of protection of the present application.

[0036] Example 1

[0037] 100 mL of toluene and 100 mL of water were mixed and then allowed to stand and separate into layers, 0.5 g of single-layer graphene oxide (concentration of 0.5%) was added to the water, and 0.005 mol of cetyltrimethylammonium bromide (concentration of 0.05 mol / L) was added to the toluene, and then allowed to stand for 1 h again;

[0038] After the end of the standing, 1 g of monohydrogen-terminated polysiloxane with a molecular weight of 1000 g / mol (concentration of 10 g / L) and 0.5 g of tris-pentafluorophenyl boron (concentration of 5 g / L) were added to the toluene, and the reaction was allowed to proceed at 25 °C for 2 h. Then, part of the toluene and water were removed, and the remaining interfacial layer, with a thickness of 3 mm, was washed with 0.1 %wt NaOH solution and toluene in turn, and dried by centrifugation to obtain Janus polysiloxane-modified single-layer graphene oxide.

[0039] Example 2

[0040] After the mixture of 30 mL toluene and 30 mL water was allowed to stand and separate into layers, 0.3 g of single-layer graphene oxide (concentration of 0.99 %) was added to the water, and 0.003 mol of cetyltrimethylammonium bromide (concentration of 0.1 mol / L) was added to the toluene. The mixture was allowed to stand for another 0.5 h.

[0041] After the end of the standing, 1 g of monohydrogen-terminated polysiloxane with a molecular weight of 500 g / mol (concentration of 33.33 g / L) and 0.5 g of tris-pentafluorophenyl boron (concentration of 16.67 g / L) were added to the toluene, and the reaction was allowed to proceed at 20 °C for 1.5 h. Then, part of the toluene and water were removed, and the remaining interfacial layer, with a thickness of 4 mm, was washed with 0.1 %wt NaOH solution and toluene in turn, and dried by centrifugation to obtain Janus polysiloxane-modified single-layer graphene oxide.

[0042] Example 3

[0043] After the mixture of 100 mL toluene and 100 mL water was allowed to stand and separate into layers, 5 g of single-layer graphene oxide (concentration of 4.76 %) was added to the water, and 0.0001 mol of dodecyltrimethylammonium bromide (concentration of 0.001 mol / L) was added to the toluene. The mixture was allowed to stand for another 1 h.

[0044] After the end of the standing, 10 g of monohydrogen-terminated polysiloxane with a molecular weight of 5000 g / mol (concentration of 100 g / L) and 1 g of tris-pentafluorophenyl boron (concentration of 10 g / L) were added to the toluene, and the reaction was allowed to proceed at 30 °C for 1 h. Then, part of the toluene and water were removed, and the remaining interfacial layer, with a thickness of 2 mm, was washed with 0.1 %wt NaOH solution and toluene in turn, and dried by centrifugation to obtain Janus polysiloxane-modified single-layer graphene oxide.

[0045] Comparative Example 1

[0046] After mixing 100 mL of toluene and 100 mL of water and allowing them to separate, 0.5 g of single-layer graphene oxide (concentration of 0.5%) was added to the water, and 0.001 mol of cetyltrimethylammonium bromide (concentration of 0.01 mol / L) was added to the toluene, and then allowed to stand for 1 h again;

[0047] After standing, 1 g of octadecylamine was added to the toluene, and allowed to stand for 2 h at 25°C, and then part of the toluene and water was extracted, and the remaining interfacial layer was obtained, wherein the thickness of the interfacial layer was 3 mm, and then the interfacial layer was sequentially washed with 0.1%wt NaOH solution and toluene, and then centrifuged and dried to obtain Janus octadecylamine-modified single-layer graphene oxide.

[0048] Performance test:

[0049] The effects of the Janus polysiloxane-modified single-layer graphene oxide prepared in Test Example 1 and the Janus octadecylamine-modified single-layer graphene oxide prepared in Comparative Example 1 on Pickering emulsion stability were tested, and 0.1 g of the Janus polysiloxane-modified single-layer graphene oxide and 0.1 g of the Janus octadecylamine-modified single-layer graphene oxide were added to a mixture of 10 mL of n-hexane and 50 mL of water to obtain Pickering emulsions by vigorous stirring, and then the emulsions were allowed to stand for a long time, and the emulsion stability of the two was compared. The results showed that the Pickering emulsion emulsified by the Janus octadecylamine-modified single-layer graphene oxide gradually broke down after about 60 days, while the Pickering emulsion emulsified by the Janus polysiloxane-modified single-layer graphene oxide remained stable after 4 months.

[0050] As can be seen from the above examples, the present application provides a preparation method of Janus polysiloxane-modified single-layer graphene oxide. First, toluene and water are mixed and allowed to separate, and then single-layer graphene oxide is added to the water, and a cationic surfactant is added to the toluene, and then allowed to stand again. After standing, single-end hydrogen-containing polysiloxane and trifluorophenyl boron are added to the toluene for standing reaction, and part of the toluene and water is extracted, and the remaining interfacial layer is obtained. Finally, the interfacial layer is sequentially washed and dried to obtain Janus polysiloxane-modified single-layer graphene oxide. The method of preparing Janus single-layer graphene oxide by electrostatic interfacial adsorption can significantly reduce the impurities of non-Janus structure modified graphene oxide, and the steps are fewer. The Janus polysiloxane-modified single-layer graphene oxide prepared by the present application has stronger amphiphilicity, and when used as a Pickering emulsifier, it can make the emulsion more stable.

[0051] The above only describes the preferred embodiments of the present application, and it should be noted that those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered within the protection scope of the present application.

Claims

1. A method for preparing Janus polysiloxane-modified single-layer graphene oxide, characterized by, The method comprises the following steps: (1) mixing toluene and water and then allowing them to separate into layers, then adding single-layer graphene oxide into the water and adding cationic surfactant into the toluene, and then allowing them to stand again; (2) after the standing is completed, adding mono-end hydrogen-containing polysiloxane and trifluorophenyl boron into the toluene to allow them to stand and react, extracting part of the toluene and water, and leaving the remaining interfacial layer; (3) sequentially washing and drying the interfacial layer to obtain Janus polysiloxane-modified single-layer graphene oxide; in the step (2), the molecular weight of the mono-end hydrogen-containing polysiloxane is 500-5000 g / mol; and the concentration of the mono-end hydrogen-containing polysiloxane in the toluene is 10-100 g / L; in the step (2), the concentration of the trifluorophenyl boron in the toluene is 4-17 g / L; in the step (2), the temperature of the standing and reaction is 20-30 ℃, and the time of the standing and reaction is 1-2 h.

2. The production method according to claim 1, characterized by, in the step (1), the volume ratio of the toluene to the water is 1-2:1-2.

3. The production method according to claim 1 or 2, characterized by, in the step (1), the mass fraction of the single-layer graphene oxide in the water is 0.1-5%.

4. The production method according to claim 3, characterized by, in the step (1), the cationic surfactant comprises cetyltrimethylammonium chloride, cetyltrimethylammonium bromide or dodecyltrimethylammonium bromide, wherein the concentration of the cationic surfactant in the toluene is 0.001-0.1 mol / L.

5. The preparation method according to claim 4, characterized in that, in the step (2), the thickness of the interfacial layer is 2-4 mm.