CN114316318B

CN114316318B - Preparation method of polyurea/two-dimensional material/aluminum oxide super-assembled functional film

Info

Publication number: CN114316318B
Application number: CN202111635728.8A
Authority: CN
Inventors: 孔彪; 周姗; 谢磊; 何彦君; 曾洁
Original assignee: Fudan University
Current assignee: Fudan University
Priority date: 2021-12-29
Filing date: 2021-12-29
Publication date: 2023-08-29
Anticipated expiration: 2041-12-29
Also published as: CN114316318A

Abstract

The invention discloses a preparation method of a polyurea/two-dimensional material/alumina super-assembly functional film, which is characterized in that carboxylated graphene oxide is deposited on the surface of AAO under the auxiliary action of vacuum filtration, and the GO nano-sheet surface has rich hydroxyl and carboxyl functional groups, so that the GO nano-sheet and the hydroxyl on the surface of AAO form hydrogen bond-assisted interface super-assembly interaction, and the GO closely grows on the surface of AAO. In addition, in order to alleviate the phenomenon that GO is easy to peel in water, a layer of compact polyurea film grows on the surface of GO by an interfacial polymerization method. The final PGA composite film has a relatively hydrophobic surface, and the PU layer plays a role of a protective layer, so that the PGA is very stable in water, and the potential practical application value of the PGA is given. The PGA composite film with potential practical application value is prepared by the interface super-assembly and the interface polymerization method.

Description

Preparation method of polyurea/two-dimensional material/aluminum oxide super-assembled functional film

Technical Field

The invention belongs to the field of membrane science, and particularly relates to a preparation method of a polyurea/two-dimensional material/aluminum oxide super-assembled functional membrane.

Background

Two-dimensional materials refer to nano-sized sheet materials that have gained widespread attention in the field of film science in recent years when they can be stacked under vacuum assist to form films containing nano-or sub-nano-sized dimensions. The two-dimensional film material has the following advantages: 1) Can be prepared in large scale. The two-dimensional film material is usually formed by stacking two-dimensional materials by itself, and the simple film forming mode ensures that the thickness and the area of the film are not limited; 2) The pore canal is regular. The pore canal of the prepared two-dimensional membrane is formed by stacking nano sheets, and most of the pore canal has regular pore diameter and size, so that the membrane is endowed with certain selectivity; 3) And the controllability is good. Other functional groups can be modified on the surface of the nano sheet layer, a certain function is given to the nano sheet layer, in addition, the size is controllable, and the size of the nano channel can be increased or reduced by utilizing an intercalation technology. Based on the above advantages, various two-dimensional materials such as graphene oxide, reduced graphene oxide, mxens material, transition metal disulfide, and the like are currently widely used for constructing nanochannel membrane materials.

However, current two-dimensional materials still present challenges such as stability in water, anti-fouling properties, and the like. The two-dimensional nanoplatelets typically contain oxygen-containing functional groups thereon that are capable of binding water molecules, resulting in expansion of the two-dimensional nanochannel membrane, thereby degrading the membrane's performance.

Disclosure of Invention

The invention aims to solve the problems and provide a preparation method of a polyurea/two-dimensional material/alumina super-assembled functional film, which can stably exist in water and solve the problem of stability of a two-dimensional nano-channel film in water, and a PU layer is used as a protective layer, so that the GO film can be prevented from being peeled off in water and the PGA is endowed with excellent mechanical stability.

The aim of the invention is achieved by the following technical scheme:

a preparation method of a polyurea/two-dimensional material/aluminum oxide super-assembled functional film comprises the following steps:

(1) Preparing a dispersion liquid of carboxylated Graphene Oxide (GO);

(2) Growing GO on the AAO substrate with the aid of interface super-assembly by adopting a vacuum filtration method;

(3) Drying the pumped and filtered GO/AAO composite membrane;

(4) Preparing an aqueous-oil phase solution of a synthetic polyurea monomer;

(5) Dripping Polyethylenimine (PEI) on the surface of the GO/AAO film, and volatilizing the water to dryness;

(6) The 2, 4-Toluene Diisocyanate (TDI) solution is dripped on the GO/AAO surface containing PEI polymer chain, and the amino groups between two phases and isocyanate undergo interfacial polymerization reaction in an oven to generate a compact polyurea film, so as to obtain the PGA composite film with high mechanical property.

A polyurea protective layer grows on the surface of graphene oxide, so that PGA is very stable in water, and the PGA film prepared by the strategy of the invention adopts Anodic Aluminum Oxide (AAO) containing regular nano channels as a substrate, because the anodic aluminum oxide can be tightly combined with GO, and can provide rich ion or molecule transmission channels, thereby laying a foundation for practical application of the PGA film.

Further, the specific method of the step (1) is as follows: and weighing carboxylated graphene oxide, dispersing the carboxylated graphene oxide into deionized water, and performing ultrasonic dispersion, wherein the size of a nano sheet layer of the carboxylated graphene oxide is 3-5 mu m.

Further, the concentration of the dispersion of carboxylated graphene oxide was 1mg/ml.

Carboxylated graphene oxide is adopted, and mainly has two functions: on one hand, rich oxygen-containing functional groups on the GO nano sheet layer can perform super-assembly interaction with the AAO substrate, so that the oxygen-containing functional groups and the AAO substrate are tightly combined together; in addition, it can react with amino groups on the PEI chains, rivet PEI polymer chains on the surface of GO film.

Further, in the step (2), vacuum filtration is adopted, the filtration time is 6-7h, and GO is grown on the surface of AAO by adopting a vacuum filtration method, so that the method has the main advantage that a film with a highly ordered layered structure can be obtained.

Further, the GO/AAO composite membrane subjected to suction filtration in the step (3) is placed in an oven at 80 ℃ and dried for 2-3h.

Further, the specific method of the step (4) is as follows: firstly, preparing 1-2w/v% of Polyethyleneimine (PEI) aqueous solution, and dissolving 96-240mg of 50wt% of PEI solution into 58-60ml of deionized water; then, 0.4-0.6w/v% of 2, 4-Toluene Diisocyanate (TDI) is prepared, 0.02-0.04g of TDI is weighed and dissolved in 60ml of n-hexane, and the prepared two solutions are placed in an oven at 60 ℃. Preferably, 1.5w/v% PEI and 0.5w/v% TDI monomer are used to prepare the polyurea. Because PEI polymer chains contain rich amino groups, better formation of a polyurea film can be ensured, and a polyurea film with high bonding degree and more compactness can be obtained under the concentration condition.

Further, step (5) drops 80-100 μl of PEI onto the surface of the GO/AAO film until it volatilizes the water to dryness at 60 ℃.

Further, in the step (6), 80-100 mu L of TDI solution is dripped on the GO/AAO surface containing PEI polymer chains, the amino groups between two phases and isocyanate undergo interfacial polymerization reaction in an oven at 60 ℃, the reaction time is 5min, the whole reaction is carried out at 60 ℃, the PEI and TDI are guaranteed to have a relatively fast reaction rate, the interfacial polymerization reaction time is 5min, and the membrane is maintained to have certain permeability under the condition of keeping the membrane compact, so that the potential application value of the membrane is guaranteed.

The polyurea serving as a waterproof material has excellent stability in water and can relieve the expansion of the two-dimensional nano-channel film in water. According to the invention, polyurea is used as a waterproof protective layer of GO, and the PGA composite film is prepared by adopting an interface super-assembly and interface polymerization strategy, and has a hydrophobic outer surface, good stability in water and potential practical application value relative to GO/AAO.

According to the invention, through an interface super-assembly method, GO is assembled layer by layer, firstly, the GO is assembled on an AAO substrate rich in nano channels, then PEI is deposited on the GO surface, and after interfacial polymerization reaction, a layer of polyurea film grows on the GO surface, and finally, the PGA film is obtained. The prepared film has excellent stability in water and potential practical application value due to the hydrophobicity of the PU film.

According to the preparation method, the PGA composite film is prepared by carboxylated graphene oxide, and the rich carboxyl on the nano sheet layer can form hydrogen bond super-assembly interaction with the hydroxyl on the AAO, so that the PGA composite film can be stably attached to the AAO substrate; in addition, the carboxyl functional group on the nano-sheet layer can react with the amino group on the PEI chain, so that the occurrence of interfacial polymerization is promoted, and a layer of PU film grows on the GO surface. The invention adopts AAO as the substrate of the composite membrane, and the AAO contains abundant nano channels, so that abundant ways are provided for ion molecule transmission, and the AAO has potential practical application value. The invention adopts PEI and TDI as monomers for synthesizing polyurea, and mainly uses rich amino groups on PEI polymer chains, which can be fully polymerized with isocyanate functional groups on TDI molecules in a glue way so as to grow into a PU film. The invention adopts an interfacial polymerization method to prepare the polyurea film, which is mainly characterized by simple method and low byproducts. The concentration of the two monomers adopted by the invention can lead to the formation of a relatively compact PU layer, and simultaneously ensures that the PU layer contains abundant nano-pore channels, thereby laying a foundation for practical application. According to the preparation method, the PGA composite membrane is prepared through the strategies of interface super-assembly and interface polymerization, and the existence of PU reduces the permeation of water molecules, can increase the stability of the membrane in water, and has potential practical application value.

Drawings

FIG. 1 is a flow chart of the preparation of PGA composite membranes according to the present invention;

FIG. 2 is an optical picture of a PGA composite film prepared according to the present invention;

FIG. 3 is a scanning electron microscope contrast image of the surfaces of the GO/AAO film and the PGA composite film prepared by the present invention;

FIG. 4 is a cross-sectional view of a PU modified GO film made in accordance with the present invention;

FIG. 5 is a graph of a dot elemental analysis of the surface of the PGA composite film prepared according to the present invention;

FIG. 6 is a graph showing the surface element distribution of PGA composite films prepared according to the present invention;

FIG. 7 is a comparison of zeta potential of GO membranes prepared according to the present invention and polyurea modified GO membranes;

FIG. 8 is a Fourier transform infrared plot of the GO-modified polyurea before and after;

FIG. 9 is a graph of contact angle versus modification of polyurea with different layers;

FIG. 10 is a graph comparing the stability of PGA composite membrane and GO/AAO composite membrane in water.

Detailed Description

The invention will now be described in detail with reference to the drawings and specific examples.

Example 1

The preparation method of the PGA composite film specifically comprises the following steps:

step 1: firstly, preparing a dispersion liquid of carboxylated graphene oxide with the concentration of 1 mg/ml: weighing 3mg of carboxylated graphene oxide, dispersing the carboxylated graphene oxide into 3ml of deionized water, and performing ultrasonic dispersion for 3 hours, wherein the size of a nano sheet layer of the carboxylated graphene oxide is 3 mu m;

step 2: growing GO on an AAO substrate with the aid of interface super-assembly by adopting a vacuum filtration method, wherein the filtration time is about 6-7h;

step 3: then placing the pumped and filtered GO/AAO composite membrane in an oven at 80 ℃ and drying for 2-3h;

step 4: preparing an aqueous-oil phase solution of a synthetic polyurea monomer: firstly, preparing 1.5w/v% (mg/ml) of Polyethyleneimine (PEI) aqueous solution, and dissolving 180mg of 50wt% PEI solution into deionized water to 60ml; then, 0.5w/v% (mg/ml) of 2, 4-Toluene Diisocyanate (TDI) was prepared, about 0.03g of TDI was weighed and dissolved in 60ml of n-hexane, and the prepared two solutions were placed in an oven at 60 ℃;

step 5: firstly, dripping 100 mu L of PEI on the surface of the GO/AAO film, and volatilizing water to dryness at 60 ℃;

step 6: then, 100 mu L of TDI solution is dripped on the GO/AAO surface containing PEI polymer chains, and amino groups between two phases and isocyanate undergo interfacial polymerization reaction in an oven at 60 ℃ for 5min to generate a compact polyurea film;

step 7: the final PGA composite film with high mechanical properties is obtained.

FIG. 1 is a flow chart of example 1 for preparing PGA composite membranes by vacuum filtration interfacial super assembly and interfacial polymerization methods. Firstly, a layer of GO film grows on an AAO substrate by adopting a vacuum filtration method, and then a layer of polyurea thin protective film grows on the GO surface by adopting an interfacial polymerization method, so that a final PGA film can be obtained.

Fig. 2 is an optical picture of the PGA composite film prepared in example 1, and fig. 2a is a model view of the PGA composite film. FIG. 2 (b-f) is a polyurea film grown on GO/AAO surface in one to five layers, respectively.

Example 2

step 1: firstly, preparing a dispersion liquid of carboxylated graphene oxide with the concentration of 1 mg/ml: weighing 5mg of carboxylated graphene oxide, dispersing the carboxylated graphene oxide into 5ml of deionized water, and performing ultrasonic dispersion for 3 hours, wherein the size of a nano sheet layer of the carboxylated graphene oxide is 5 mu m;

step 4: preparing an aqueous-oil phase solution of a synthetic polyurea monomer: firstly, preparing 1w/v% (mg/ml) of Polyethyleneimine (PEI) aqueous solution, and dissolving 96mg of 50wt% PEI solution into deionized water to 58ml; then, 0.4w/v% (mg/ml) of toluene 2, 4-diisocyanate (TDI) was prepared, about 0.024g of TDI was weighed and dissolved in 60ml of n-hexane, and the prepared two solutions were placed in an oven at 60 ℃;

step 5: then, firstly, 80 mu L of PEI is dripped on the surface of the GO/AAO film, and the PEI is volatilized to be dry at 60 ℃;

step 6: then, 80 mu L of TDI solution is dripped on the GO/AAO surface containing PEI polymer chains, and amino groups between two phases and isocyanate undergo interfacial polymerization reaction in an oven at 60 ℃ for 5min to generate a compact polyurea film;

Example 3

step 1: firstly, preparing a dispersion liquid of carboxylated graphene oxide with the concentration of 1 mg/ml: 7mg of carboxylated graphene oxide is weighed, then dispersed into 7ml of deionized water, and subjected to ultrasonic dispersion for 3 hours, wherein the size of a nano sheet layer of the carboxylated graphene oxide is 5 mu m;

step 4: preparing an aqueous-oil phase solution of a synthetic polyurea monomer: firstly, preparing a 2w/v% (mg/ml) Polyethyleneimine (PEI) aqueous solution, and dissolving 240mg of a 50wt% PEI solution into deionized water to 60ml; then, 0.6w/v% of 2, 4-Toluene Diisocyanate (TDI) was prepared, about 0.036g of TDI was weighed and dissolved in 60ml of n-hexane, and the prepared two solutions were placed in an oven at 60 ℃;

step 5: then, firstly, 90 mu L of PEI is dripped on the surface of the GO/AAO film, and the PEI is volatilized to be dry at 60 ℃;

step 6: then, 90 mu L of TDI solution is dripped on the GO/AAO surface containing PEI polymer chains, and amino groups between two phases and isocyanate undergo interfacial polymerization reaction in an oven at 60 ℃ for 5min to generate a compact polyurea film;

The PGA composite film thus obtained was tested in accordance with example 1

1. Morphology characterization graph of PGA composite film

The GO or PU modified GO was carefully peeled from the AAO substrate and carefully cut into small pieces with small scissors, which were subjected to scanning electron microscopy. Fig. 3 compares the surface topography of GO and GO films grown with PU layers. Wherein fig. 3a, b are the surfaces without grown GO film, visible wrinkles; fig. 3c, d are GO films with PU layer grown on the surface, which can be seen to be rougher compared to GO film surface.

Fig. 4 is a cross section of a PU-modified GO membrane layer, it can be seen that GO still exhibits a layered stack structure, which contains rich interlayer nanochannels.

Fig. 5 is a graph showing that two points are respectively selected on the surface of the GO modified by the PU, and the points can be found to be rich in nitrogen elements, which indicates that the surface of the GO is successfully modified by the polyurea.

Fig. 6 is a surface scan of PU-modified GO surface, and shows that nitrogen is uniformly distributed on selected GO surface, which indicates that polyurea uniformly grows on the GO layer surface.

2. Characterization of PGA composite film

The GO or polyurea modified GO film was carefully peeled off from the AAO substrate, and then ground to a small pieces with a mortar to test for changes in fourier transform infrared and surface charge, respectively. FIG. 7 is a graph comparing the zeta potential of GO membrane with that of polyurea modified GO membrane before and after modification, FIGS. 7a and b are zeta potential profiles of GO membrane and polyurea modified GO membrane respectively, FIG. 7 compares the zeta potentials of both membranes, the zeta potential of the pure GO membrane is-25.8 mV, and the zeta potential of the pure GO membrane after modification of polyurea is about +55.1mV, which also demonstrates the successful modification of polyurea. FIG. 8 is a Fourier transform infrared comparison plot before and after modification, showing that the peak at 2800-2900cm-1 after modification of polyurea is expected to be compared with the previous peak, which is derived from saturated hydrocarbon peaks on the PEI chain, and 1500-1600cm-1 shows fine structural peaks of benzene rings, most importantly C-N vibrational peaks of polyurea at 1302cm-1, indicating successful modification of polyurea on GO.

3. Hydrophilic-hydrophobic testing of PGA composite films

Fig. 9 is a graph showing the hydrophilicity and hydrophobicity of PGA composite membranes prepared by an interfacial super-assembly and interfacial polymerization strategy. A drop of 0.2 μl of water was dropped onto the surface of the film, and the contact angle after stabilization was tested and photographed for recording. Fig. 9a is a contact angle test of the GO/AAO composite film, which can be seen to exhibit good hydrophilicity due to the rich oxygen-containing functional groups on the GO surface. Fig. 9b-f are hydrophilic and hydrophobic properties of PGA composite films modified with different layers (1-5 times) of polyurea, and it can be seen that the surface of GO film modified with polyurea has very good water repellency, indicating that the polyurea acts as a protective layer.

4. Stability test of PGA composite film

To test the stability of the PGA composite film, a GO/AAO composite film without modified polyurea was prepared, and then immersed in a 1M KCl solution to test its stability. Fig. 10a and b are pictures of the GO/AAO and PGA composite film just after soaking for 24 hours, it can be seen that the GO/AAO composite film has obvious cracks, but PGA remains very stable in the electrolyte solution, which indicates that PGA has very good stability and potential practical application value.

The previous description of the embodiments is provided to facilitate a person of ordinary skill in the art in order to make and use the present invention. It will be apparent to those skilled in the art that various modifications can be readily made to these embodiments and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above-described embodiments, and those skilled in the art, based on the present disclosure, should make improvements and modifications without departing from the scope of the present invention.

Claims

1. The preparation method of the polyurea/two-dimensional material/aluminum oxide super-assembled functional film is characterized by comprising the following steps of:

(1) Preparing a dispersion liquid of carboxylated graphene oxide GO;

(2) Growing GO on the anodic aluminum oxide AAO substrate with the aid of interface super-assembly by adopting a vacuum filtration method;

(3) Drying the pumped and filtered GO/AAO composite membrane;

(4) Preparing an aqueous-oil phase solution of a synthetic polyurea monomer;

(5) Dripping polyethylene imine PEI aqueous solution on the surface of the GO/AAO film, and volatilizing moisture until the water is dry;

(6) 2, 4-toluene diisocyanate TDI solution is dripped on the GO/AAO surface containing PEI polymer chain, and amino groups between two phases and isocyanate undergo interfacial polymerization reaction in an oven to generate a compact polyurea film, so that a PGA composite film with high mechanical property is obtained;

the specific method of the step (1) is as follows: weighing carboxylated graphene oxide, dispersing the carboxylated graphene oxide into deionized water, and performing ultrasonic dispersion, wherein the size of a nano sheet layer of the carboxylated graphene oxide is 3-5 mu m;

the specific method of the step (4) is as follows: firstly, preparing 1-2w/v% of polyethyleneimine PEI aqueous solution, and dissolving 96-240mg of 50wt% PEI solution into 58-60ml of deionized water; then preparing 0.4-0.6w/v% of 2, 4-toluene diisocyanate TDI solution, weighing 0.02-0.04g of TDI to be dissolved in 60ml of normal hexane, and placing the prepared two solutions in an oven at 60 ℃.

2. The method for preparing the polyurea/two-dimensional material/aluminum oxide super-assembled functional film according to claim 1, wherein the concentration of the dispersion liquid of carboxylated graphene oxide is 1mg/ml.

3. The method for preparing the polyurea/two-dimensional material/aluminum oxide super-assembled functional film according to claim 1, wherein the step (2) adopts vacuum filtration, and the filtration time is 6-7h.

4. The method for preparing the polyurea/two-dimensional material/aluminum oxide super-assembled functional film according to claim 1, wherein the GO/AAO composite film subjected to suction filtration in the step (3) is placed in an oven at 80 ℃ and dried for 2-3h.

5. The method for preparing the polyurea/two-dimensional material/alumina super-assembled functional film according to claim 1, wherein in the step (5), 80-100 μl of PEI aqueous solution is dripped on the surface of the GO/AAO film until the PEI aqueous solution volatilizes water to dryness at 60 ℃.

6. The method for preparing the polyurea/two-dimensional material/aluminum oxide super-assembled functional film according to claim 1, wherein in the step (6), 80-100 mu L of TDI solution is dripped on the GO/AAO surface containing PEI polymer chains, and the amino groups between two phases and isocyanate undergo interfacial polymerization reaction in an oven at 60 ℃ for 5min.