A method for preparing π-π conjugated molecularly confined polymerized graphene composite thin film materials

Abstract

This invention relates to a method for preparing π-π conjugated molecular confined polymerized graphene composite film materials. During the natural drying process, graphene oxide films undergo capillary shrinkage and weak interfacial interactions, resulting in low film orientation and density. Therefore, preparing graphene carbon films with high mechanical strength is a challenge. To address this, this invention employs a strategy of continuously stretching the graphene oxide film with external force to achieve a well-ordered orientation of the nanosheets. Long-chain molecules, 10,12-pentadecanediyne-1-ol (PCO), are introduced into the interlayer of graphene oxide to form covalent bonds and fix the well-ordered structure of the graphene oxide nanosheets. After reducing the graphene oxide to graphene, π-π long-chain molecules (BPATD) containing alkyne and phenanthroline rings are introduced into the interlayer of graphene to further fix the well-ordered structure of the graphene nanosheets, achieving ordered assembly of the graphene composite film (covalent bonds and π-π interactions). Finally, PCO and BPATD were confined and polymerized under ultraviolet light, and the resulting graphene composite film (US-SB-rGO) had a tensile strength of up to 1.97 GPa and a modulus of 107.67 GPa.

Description

Technical Field

[0001] This invention relates to a method for preparing π-π conjugated molecular confined polymerized graphene composite film materials, belonging to the field of nanocomposite material preparation. Background Technology

[0002] Currently, there are many reported assembly methods for assembling graphene nanosheets into macroscopic thin films, such as solution evaporation (ACSNano 2014, 8, 9511.), blade coating (Science 2024, 385, 62.), centrifugal casting (Adv. Mater. 2020, 32, 1907411.), superspreading orientation (Nature 2020, 580, 210.), layer-by-layer self-assembly (Science 2015, 348, 2491.), ordered assembly (Nat. Commun. 2018, 9, 1.), interfacial crosslinking (Science 2021, 374, 96.), pore filling (Nat. Commun. 2020, 11, 2077.), and confined assembly (Science 2024, Strategies such as those mentioned in 383, 771 have been used to improve the mechanical properties of two-dimensional nanomaterials and have achieved significant results. However, two-dimensional nanomaterials assembled by wet chemical methods inevitably undergo capillary shrinkage during the drying process as the solvent evaporates, resulting in more wrinkles on the nanosheets and severely affecting the mechanical properties of the materials. Researchers have reduced capillary shrinkage to some extent by increasing the contact angle between the nanosheets and the liquid and by solvent displacement, and have prepared self-supporting materials, but it is still impossible to simultaneously achieve high orientation and close packing of two-dimensional nanosheets (Science 2013, 341, 534).

[0003] Because the carbon in graphene nanosheets is sp. 2 Hybridization: Researchers prepared a bi-headed bispyrene butyryl ester (PSE-AP) with a pyrene ring to form π-π conjugation with graphene nanosheets and to combine it with Cr... 3+ Graphene composite films prepared by ionic crosslinking and interfacial synergy achieve a strength as high as 821 MPa (Adv. Mater. 2018, 30, 1802733.). Graphene composite films prepared through covalent bonding of PCO and PSE-AP and synergistic π-π conjugation at the interface achieve a strength as high as 945 MPa (PNAS2018, 115, 5359.). By preparing π-π conjugated long-chain molecules (BPDD) with pyrene rings and alkyne structures, a strength of 1054 MPa can be achieved under π-π conjugation (Matter 2019, 1, 389.).

[0004] In recent years, external force traction strategies have been widely used to eliminate wrinkles and defects in graphene nanomaterials (Nat. Mater. 2021, 20, 624.). Intercalation, plasticizing, and stretching of graphene oxide films prepared by blade coating have been proven to effectively eliminate wrinkles in GO nanosheets (Nat. Commun. 2020, 11, 1.), while reduction strategies are used to fix the ordered orientation structure of the nanosheets, achieving close packing of the nanosheets (Nat. Mater. 2021, 20, 624.).

[0005] Despite this, the tensile strength of graphene composite films obtained to date is far lower than that of intrinsic graphene monosheets. Therefore, obtaining high-performance macroscopic graphene composite films by assembling graphene oxide nanosheets remains a significant challenge. The degree of nanosheet orientation, interfacial interactions, and packing density are key factors affecting the mechanical properties of two-dimensional nanomaterials. Achieving highly ordered orientation, strong interfacial interactions, and densification of graphene nanosheets during assembly remains a substantial challenge.

[0006] Related studies have shown that interlayer water in graphene gels can maintain the ordered stacking of graphene nanosheets and prevent their aggregation. This is mainly because the surface of graphene nanosheets contains negatively charged hydrophilic functional groups. In the presence of interlayer water, electrostatic repulsion and hydration can separate the graphene nanosheets from each other, thereby maintaining an ordered stacking state (Adv. Mater. 2011, 23, 2833.). Based on this, reducing capillary shrinkage during the drying process can maintain the high orientation of the nanosheets, ensuring that the film has a high degree of orientation.

[0007] Currently, the relevant patents concerning the enhancement of the mechanical properties of graphene composite films by π-π conjugation include:

[0008] A method for preparing a high-strength, high-conductivity, fatigue-resistant, and corrosion-resistant graphene composite film (CN108622884A), a method for preparing a super-strong, high-conductivity graphene composite film with ordered cross-linking of π-π conjugation and covalent bonds (CN108516538A), a method for preparing a super-tough, high-conductivity graphene composite film with cross-linking of long-chain conjugated π bonds (CN109956465A), a method for preparing a highly oriented, dense graphene film with in-plane isotropic properties (CN111807355A), and a method for preparing graphene-titanium carbide cross-linked film materials and their application in supercapacitors (CN202211519772).

[0009] However, these patents only utilize simple bi-headed pyrene ring π-π conjugated molecular interfaces to prepare graphene composite films, and the improvement in mechanical properties is limited. No patents have been reported regarding the use of bi-headed phenanthroline ring π-π conjugated long-chain molecules containing alkyne structures to improve the mechanical properties of graphene composite films. Summary of the Invention

[0010] The problem this invention aims to solve is to overcome the shortcomings of existing technologies and provide a method for preparing graphene thin film materials, which can successfully prepare graphene thin films with high orientation, high strength, and high modulus.

[0011] This invention provides a method for enhancing graphene composite film materials through π-π confined molecular polymerization. First, a graphene oxide gel film is prepared. During film preparation, continuous external force is applied to suppress capillary shrinkage and induce high orientation of the nanosheets. Efficient stress transfer is achieved through the synergistic effect of covalent bonds and π-π interactions at the interface, resulting in a highly oriented and dense graphene composite film. The graphene composite film (US-SB-rGO) exhibits a tensile strength of 708.68-1968.01 MPa and a Young's modulus of 24.30-107.67 GPa. The increased tensile strength is mainly due to the formation of ester covalent bonds between the carboxyl groups at the edges of graphene oxide (GO) and the hydroxyl groups of 10,12-pentadecanediyn-1 alcohol (PCO) under continuous stretching, as well as the synergistic effect at the interface between the graphene nanosheets and the π-π conjugated long-chain molecules (BPATD) with phenanthroline rings at both ends. Furthermore, the confined polymerization of PCO and BPATD under UV irradiation effectively suppressed capillary shrinkage during the preparation process, ensuring a highly oriented and dense structure of the film. In addition, wide-angle X-ray scattering confirmed that suppressing capillary shrinkage effectively improves the film's orientation. Porosity calculations and scanning electron microscopy characterization of the film's cross-section also confirmed that suppressing capillary shrinkage effectively improves the film's density.

[0012] In this invention, the orientation degree is represented by the Herman orientation factor.

[0013] This invention is achieved through the following technical solution:

[0014] First, high-quality monolayer large-scale graphene oxide nanosheets (with a diameter of 5-60 nm) were obtained by low-temperature centrifugation exfoliation using a modified Hummers method. A GO gel film was prepared by first obtaining a 1 μm aqueous dispersion; then, nanosheets were assembled into a GO gel film by vacuum filtration, casting, and either blade coating or centrifugal casting; next, the nanosheets were stretched under continuous external force to induce high orientation and suppress capillary shrinkage during drying. Ester covalent bonds were formed between the carboxyl groups at the edges of graphene oxide and the hydroxyl groups of 10,12-pentadecyldiyne-1 alcohol (PCO). The covalently modified graphene oxide composite film (US-CGO) was then reduced to obtain a covalently modified graphene film material. Subsequently, the graphene nanosheets formed a π-π interface synergistic effect with π-π conjugated long-chain molecules (BPATD) containing phenanthroline rings at both ends. Under UV irradiation, PCO and BPATD were confined and polymerized, further effectively suppressing capillary shrinkage and ensuring a highly oriented and dense structure (US-Cπ-rGO). Finally, the ordered cross-linked film was irradiated with UV light at 254 nm and 365 nm for 2 hours. h, whose Herman orientation factor is between 0.871 and 0.970, preferably between 0.901 and 0.970; the porosity of the graphene crosslinked film (US-SB-rGO) material is 3.20-25.68%, preferably 3.2-10%.

[0015] A method for preparing graphene thin film material according to the present invention includes the following steps:

[0016] (1) The raw material 325 mesh graphite powder is reacted with concentrated sulfuric acid (H2SO4) and potassium permanganate (KMnO4) with a mass fraction of 98 wt% at low temperature, and then washed and centrifuged to prepare a single-layer graphene oxide (GO) nanosheet (sheet diameter of 5-60 μm) aqueous dispersion; preferably, the low temperature is 5 ℃~10 ℃;

[0017] (2) The aqueous dispersion of monolayer graphene oxide (GO) nanosheets (with a diameter of 5-30 μm) described in step (1) is subjected to closed shaking for 5-15 min, followed by centrifugation to obtain a graphene oxide (GO) gel with a concentration of 8-10 mg / ml.

[0018] (3) The graphene oxide (GO) gel obtained in step (2) is used to form a hydrogel membrane with a thickness of 100-1200 μm on a hydrophilic polyvinylidene fluoride (PVDF) porous substrate; preferably, the film forming process includes vacuum filtration, casting film formation, blade coating or centrifugal casting.

[0019] (4) In step (4), the graphene oxide gel film is plasticized and stretched under the action of external force and then kept in a stretched state.

[0020] (5) The graphene oxide (US-GO) film obtained in step (4) is subjected to continuous external stretching and covalently cross-linked with long-chain hydroxyl-containing molecules to obtain a covalently cross-linked graphene oxide film (US-CGO); preferably, the cross-linking agent is a dichloromethane (DCM) solution of 10,12-pentadecanediyne-1 alcohol (PCO).

[0021] Preferably, the crosslinking agent is a 15 mM dispersion of 10,12-pentadecanediyne-1-ol (PCO);

[0022] Preferably, the soaking reaction time is 1-3 h, and the PCO mass fraction is 0.5-3%.

[0023] (6) In step (5), under continuous stretching, covalently cross-linked graphene film (US-CrGO) is obtained by HI reduction. During the reduction and cleaning process, the continuous external force stretching inhibits the capillary shrinkage of the solvent; the preferred reduction time is 12 h.

[0024] (7) The covalently cross-linked graphene film (US-CrGO) in step (6) is immersed in BPATD dispersion to obtain an ordered cross-linked graphene film (US-CrGO). Preferably, the concentration of BPATD is 10 mM; preferably, the immersion reaction time is 12-48 h and the mass fraction of BPATD is 5-15%.

[0025] (8) The ordered cross-linked graphene film (US-Cπ-rGO) obtained in step (7) is subjected to external stretching, washed, and then subjected to confined polymerization under ultraviolet light at 254 nm and 365 nm, respectively, to form an ordered cross-linked graphene film (US-SB-rGO); preferably, the detergent is N,N-dimethylformamide (DMF), the ultraviolet light wavelength is 254 nm, the luminous efficacy is 30 W, and the irradiation time is 2 h; preferably, the ultraviolet light wavelength is 365 nm, the luminous efficacy is 500 W, and the irradiation time is 2 h;

[0026] (9) In step (8), the π-π conjugated molecular confined polymerization reinforced graphene composite film (US-SB-rGO) prepared by continuous external stretching has a Herman orientation factor of 0.718-0.970, preferably 0.901-0.970; the porosity of the graphene crosslinked film (US-SB-rGO) material is 3.20-25.68%, preferably 3.2-10%, and the thickness of the graphene crosslinked film material is 0.5-10 μm. The characteristic is that the tensile strength of the ordered crosslinked graphene composite film (US-SB-rGO) is 1.97 GPa and the modulus is 107.67 GPa.

[0027] The principle of this invention: First, high-quality monolayer graphene oxide (GO) nanosheets (5-60 μm in diameter) are used as raw materials. A GO gel film is prepared by concentrated coating. Then, capillary shrinkage is effectively suppressed by continuous stretching, resulting in a highly oriented graphene oxide film. Next, under continuous external stretching, the graphene oxide film reacts with PCO to form ester covalent bonds, effectively ensuring the highly oriented structure of the film. Then, the prepared graphene oxide film (US-CGO) undergoes reduction and π-π conjugated crosslinking with BPATD. Finally, the alkyne structures in the small molecule PCO and BPATD are polymerized under UV light confinement, introducing carbon-carbon double covalent bonds, thereby preparing a high-strength graphene composite film (US-SB-rGO).

[0028] Furthermore, compared with existing methods for preparing graphene composite film materials, the advantages of this invention are:

[0029] (1) The graphene gel film is stretched by continuous external force, which effectively suppresses capillary shrinkage during the film drying process, so that the film has a highly oriented structure.

[0030] (2) By utilizing the covalent bonds and π-π conjugation interactions formed between PCO and BPATD and graphene nanosheets, and the confined polymerization of the alkyne structure in PCO and BPATD under ultraviolet light, the capillary shrinkage of graphene during the drying process is effectively suppressed, further enhancing the highly oriented structure and effectively reducing the porosity of the film.

[0031] (3) The interfacial synergistic effect of covalent bonds and π-π interactions enables stress to be effectively transferred between nanosheets, thus giving the graphene composite film (US-SB-rGO) material excellent mechanical properties, including a tensile strength of 1.97 GPa and a modulus of 107.67 GPa. Attached Figure Description

[0032] Figure 1 This is a process flow diagram of a π-π conjugated molecular confined polymerized graphene composite film material according to the present invention.

[0033] Figure 2This diagram illustrates the preparation process of a π-π conjugated molecularly confined polymerized graphene composite film material according to the present invention. First, a graphene oxide gel film is subjected to continuous external force stretching to suppress capillary contraction of water molecules, resulting in a highly oriented graphene oxide film. Then, the graphene oxide film is covalently modified with PCO to prepare a US-CGO film. The US-CGO film is then reduced with hydroiodic acid (HI) to obtain a highly oriented US-CrGO. Subsequently, US-CrGO is π-π conjugated and crosslinked with BPATD to prepare the graphene composite film US-Cπ-rGO. Finally, the alkynes in the small molecule PCO and BPATD undergo confined polymerization under ultraviolet light irradiation, thereby preparing the highly oriented, dense, and mechanically strong graphene composite film US-SB-rGO.

[0034] Figure 3 Evidence for the improved film orientation and density in the preparation method of a π-π conjugated molecularly confined polymerized graphene composite film material of the present invention: A, Focused ion beam scanning electron microscope (FIB-SEM) image of the confined ordered cross-section of the graphene composite film (US-SB-rGO); B, Focused ion beam scanning electron microscope (FIB-SEM) image of the reduced graphene oxide film (rGO); C, Comparison of porosity between the reduced graphene oxide (rGO) film and the confined ordered cross-section of the graphene composite film (US-SB-rGO); D, Wide-angle X-ray scattering spectra of the reduced graphene oxide film (rGO) and the confined ordered cross-section of the graphene composite film (US-SB-rGO).

[0035] Figure 4 Evidence for the polymer-confined polymerization in the thin film in the preparation method of the π-π conjugated molecularly confined polymerized graphene composite thin film material of the present invention: A, the scattering vector q diagram of the thin film material was characterized by wide-angle X-ray scattering; B, the interlayer spacing of the thin film material was characterized by X-ray scattering instrumentation; C, differential scanning calorimetry characterization of polymer BPATD, the SB-rGO thin film of Example 6, and the US-SB-rGO thin film of Example 2; D, cross-sectional TEM image of the rGO thin film of Example 9; E, cross-sectional TEM image of the SB-rGO thin film of Example 6; F, cross-sectional TEM image of the US-SB-rGO thin film of Example 2.

[0036] Figure 5The mechanical properties of the graphene composite film prepared by the method of π-π confined polymerized graphene film of the present invention (Example 3) are shown. A, stress-strain curves of reduced graphene oxide film (rGO) and confined ordered assembled graphene composite film (US-SB-rGO); B, scanning electron microscope (SEM) image of the cross-section of confined ordered assembled graphene composite film (US-SB-rGO); C, in-situ tensile Raman peak shift spectrum of confined ordered crosslinked graphene composite film (US-SB-rGO); D, stress relaxation curves of reduced graphene oxide (rGO) film and confined ordered crosslinked graphene composite film (US-SB-rGO); E, scanning electron microscope (SEM) image of the cross-section of reduced graphene oxide (rGO) film; F, in-situ Raman spectrum of reduced graphene oxide (rGO) film; G, comparison of tensile strength-Young's modulus of confined ordered crosslinked graphene composite film (US-SB-rGO) and graphene films prepared by different preparation methods reported in the literature. Detailed Implementation

[0037] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. However, the following embodiments are only for explaining the present invention, and the scope of protection of the present invention should include all the contents of the claims. Moreover, through the description of the following embodiments, those skilled in the art can fully implement all the contents of the claims of the present invention.

[0038] The method of the present invention is implemented as follows: Figure 1 and Figure 2 As shown, Figure 1 This is a process flow diagram of a π-π conjugated molecular confined polymerization graphene composite film material according to the present invention. Figure 2 This diagram illustrates the preparation process of a π-π conjugated molecularly confined polymerized graphene composite film material according to the present invention. First, a graphene oxide gel film is subjected to continuous external force stretching to suppress capillary contraction of water molecules, resulting in a highly oriented graphene oxide film. Then, the graphene oxide film is covalently modified with PCO to prepare a US-CGO film. The US-CGO film is then reduced with hydroiodic acid (HI) to obtain a highly oriented US-CrGO. Subsequently, US-CrGO is π-π conjugated and crosslinked with BPATD to prepare the graphene composite film US-Cπ-rGO. Finally, the alkynes in the small molecule PCO and BPATD undergo confined polymerization under ultraviolet light irradiation, thereby preparing the highly oriented, dense, and mechanically strong graphene composite film US-SB-rGO.

[0039] The graphene oxide described in this invention is a two-dimensional nanosheet containing abundant oxygen-containing functional groups, which can form ester covalent bonds with small molecule PCO; the π-π conjugated long chain molecule (BPATD) with phenanthroline rings at both ends can form π-π interactions with the graphene nanosheet; the PCO and BPATD alkyne-linked structure are confined and polymerized under ultraviolet light to prepare a confined ordered crosslinked composite film (US-SB-rGO) with a thickness of 0.5-10 μm.

[0040] In the following embodiments of the present invention, the following testing methods are used:

[0041] A: The tensile strength test method includes the following steps: The prepared ordered cross-linked graphene composite film is cut into test strips with a length of 12 mm and a width of 3 mm. The strips are fixed on a paper test template with a span of 0.5 cm. A Shimadzu AGS-X tensile tester equipped with a 100 N sensor is used to test the tensile properties of the test strips at a tensile speed of 0.5 mm / min, thus obtaining the stress-strain curve of the film. Wherein, tensile strength = tensile force at break of the test strip / cross-sectional area of ​​the test strip.

[0042] B: The porosity testing method includes the following steps: Thin film porosity = 1 - Thin film measured density / Thin film theoretical density, where the thin film measured density = Thin film mass / Thin film volume, and the thin film theoretical density is calculated based on the content of each component of the composite thin film.

[0043] C: Young's modulus test method: Young's modulus is obtained by calculating the slope of the elastic region of the stress-strain curve.

[0044] Example 1

[0045] Add 24 mL of concentrated sulfuric acid (98 wt%) to a 1000 mL beaker and cool to 5 °C in an ice bath. Slowly add 1.0 g of graphite powder (325 mesh) (Qingdao Jinrilai Co., Ltd.), and magnetically stir at 5 °C for 1.5 h at a stirring speed of 500 rpm. Slowly add 3.0 g of KMnO4 over 2.0 h, maintaining the temperature at 5 °C throughout, and continue stirring for 10 h after the addition is complete. Add 50 mL of pre-frozen deionized water using a syringe pump, maintaining the temperature at 5 °C throughout, for approximately 8.0 h, and continue stirring for 1 h after the addition is complete. Pour the reaction mixture into 700 mL of pre-frozen deionized water to terminate the reaction. Slowly add 20 mL of H2O2 (30%) dropwise, stirring for 20 min. Place the mixture in a refrigerator to settle overnight (2-4 °C). Centrifuge three times with dilute HCl (3.7 wt%) at 10000 rpm for 5 min each time at 2-4 °C to remove Mn. 2+Centrifuge four times at 10,000 rpm for 5 min in deionized water at 2-4 °C to remove excess acid. Centrifuge three times at 3,000 rpm for 10 min to collect the supernatant and separate unseparated particles. Centrifuge the supernatant at 10,000 rpm for 10 min to obtain the precipitate. Disperse the precipitate in deionized water at 2-4 °C to prepare 2 mg / mL solutions. -1 The dispersion is stored in a refrigerator (2-5 ℃) to obtain a large monolayer GO dispersion with a sheet diameter of 5-60 μm.

[0046] Example 2

[0047] Take 30 mL of the GO dispersion prepared in Example 1 (2 mg / mL) -1 The GO gel was obtained by centrifuging at 10,000 rpm for 10 min in a 50 mL centrifuge tube. After removing air bubbles from the gel, graphene oxide gel film was prepared by coating it onto a hydrophilic polyvinylidene fluoride (PVDF) porous substrate. The gel film was then transferred to a stretching device and subjected to continuous stretching and natural drying to obtain a US-GO film. While in a stretched state, the film was immersed in a 15 mM PCO DCM solution for 2 h, followed by three DCM washes. Then, it was reduced with 38 wt% hydroiodic acid for 12 h and washed with anhydrous ethanol to obtain a covalently modified graphene film (US-CrGO). The film was then immersed in a 10 mM BPATD DMF solution for 24 h, followed by five DMF washes to remove BPATD from the film surface. Finally, it was irradiated under 254 nm and 365 nm UV lamps for 2 h each to obtain a confined, ordered cross-linked graphene composite film. By adjusting the coating height, US-SB-rGO films with a thickness range of 0.5-10 μm can be obtained. The resulting US-SB-rGO films have a tensile strength of 1.97 GPa and a modulus of 107.67 GPa.

[0048] Example 3

[0049] Take 30 mL of the GO dispersion prepared in Example 1 (2 mg / mL) -1The GO gel was obtained by centrifuging at 10,000 rpm for 10 min in a 50 mL centrifuge tube. After thoroughly removing air bubbles from the gel, graphene oxide gel membranes were prepared by coating the gel onto a hydrophilic polyvinylidene fluoride (PVDF) porous substrate. The gel membrane was transferred to a stretching device and stretched continuously until it was naturally dried to obtain a US-GO membrane. While under tension, the membrane was reduced with 38 wt% hydroiodic acid for 12 h, and then washed with anhydrous ethanol to obtain the graphene membrane (US-rGO). By adjusting the coating height, US-rGO membranes with thicknesses ranging from 0.5 to 5 μm can be obtained. The tensile strength of the obtained US-rGO membrane was 708.08 MPa, and the modulus was 24.3 GPa.

[0050] Example 4

[0051] Take 30 mL of the GO dispersion prepared in Example 1 (2 mg / mL) -1 The GO gel was obtained by centrifuging at 10,000 rpm for 10 min in a 50 mL centrifuge tube. After thoroughly removing air bubbles from the gel, graphene oxide gel membranes were prepared by coating the gel membrane onto a hydrophilic polyvinylidene fluoride (PVDF) porous substrate. The gel membrane was transferred to a stretching device and stretched continuously before natural drying to obtain a US-GO membrane. While in a stretched state, the membrane was immersed in a 15 mM PCO DCM solution for 2 h, followed by three DCM washes. Then, it was reduced with 38 wt% hydroiodic acid for 12 h, washed with anhydrous ethanol, and finally irradiated under a 254 nm UV lamp for 2 h to obtain a covalently modified graphene membrane (US-CrGO). By adjusting the coating height, US-CrGO membranes with thicknesses ranging from 0.5 to 5 μm can be obtained. The tensile strength of the obtained US-CrGO membrane was 1071.08 MPa, and the modulus was 55.68 GPa.

[0052] Example 5

[0053] Take 30 mL of the GO dispersion prepared in Example 1 (2 mg / mL) -1The GO gel was obtained by centrifuging at 10,000 rpm for 10 min in a 50 mL centrifuge tube. After thoroughly removing air bubbles from the gel, graphene oxide gel membranes were prepared by coating the gel membrane onto a hydrophilic polyvinylidene fluoride (PVDF) porous substrate. The gel membrane was transferred to a stretching device and stretched continuously before natural drying to obtain a US-GO membrane. While under stretching, the membrane was reduced with 38 wt% hydroiodic acid for 12 h, then washed with anhydrous ethanol, and then immersed in a 10 mM BPATD DMF solution for 24 h. After washing with DMF five times to remove BPATD from the membrane surface, the membrane was finally irradiated under a 365 nm UV lamp for 2 h to obtain an ordered cross-linked graphene composite membrane. By adjusting the coating height, US-πrGO membranes with thicknesses ranging from 0.5 to 10 μm can be obtained. The tensile strength of the obtained US-πrGO membrane was 1355.99 MPa, and the modulus was 65.42 GPa.

[0054] Example 6

[0055] Take 30 mL of the GO dispersion prepared in Example 1 (2 mg / mL) -1 The GO gel was obtained by centrifuging at 10,000 rpm for 10 min in a 50 mL centrifuge tube. After thoroughly removing air bubbles from the gel, graphene oxide gel membranes were prepared by coating the gel onto a hydrophilic polyvinylidene fluoride (PVDF) porous substrate. The membranes were then naturally dried to obtain graphene oxide films. The films were immersed in a 15 mM PCO DCM solution for 2 h, followed by three DCM washes. Next, the films were reduced with 38 wt% hydroiodic acid for 12 h, and then washed with anhydrous ethanol to obtain covalently modified graphene films (CrGO). The films were then immersed in a 10 mM BPATD DMF solution for 24 h, followed by five DMF washes to remove BPATD from the film surface. Finally, the films were irradiated under 254 nm and 365 nm UV lamps for 2 h each to obtain ordered cross-linked graphene composite films. By adjusting the coating height, SB-rGO films with thicknesses ranging from 0.5 to 10 μm could be obtained. The obtained SB-rGO film has a tensile strength of 1134.18 MPa and a modulus of 8.7 GPa.

[0056] Example 7

[0057] Take 30 mL of the GO dispersion prepared in Example 1 (2 mg / mL) -1The GO gel was obtained by centrifuging at 10,000 rpm for 10 min in a 50 mL centrifuge tube. After thoroughly removing air bubbles from the gel, graphene oxide gel membranes were prepared by coating the gel onto a hydrophilic polyvinylidene fluoride (PVDF) porous substrate. The membranes were then naturally dried to obtain graphene oxide films. The films were immersed in a 15 mM PCO solution in DCM for 1 h, 2 h, and 3 h, respectively, followed by three DCM washes. Next, the films were reduced with 38 wt% hydroiodic acid for 12 h, washed with anhydrous ethanol, and finally irradiated under a 254 nm UV lamp for 2 h to obtain covalently modified graphene films (CrGO). Adjusting the coating height allowed for obtaining CrGO films with thicknesses ranging from 0.5 to 10 μm. Thermogravimetric analysis revealed PCO contents of 0.67%, 2.29%, and 2.80%. The CrGO film with a PCO content of 2.29% exhibited a tensile strength of 564.03 MPa and a modulus of 4.85 GPa.

[0058] Example 8

[0059] Take 30 mL of the GO dispersion prepared in Example 1 (2 mg / mL) -1 The GO gel was obtained by centrifuging at 10,000 rpm for 10 min in a 50 mL centrifuge tube. After thoroughly removing air bubbles from the gel, graphene oxide gel membranes were prepared by coating the gel onto a hydrophilic polyvinylidene fluoride (PVDF) porous substrate. The membranes were then naturally dried to obtain graphene oxide films. The films were then reduced with 38 wt% hydroiodic acid for 12 h, washed with anhydrous ethanol, and then immersed in a 10 mM BPATD solution in DMF for 12 h, 24 h, 36 h, and 48 h, respectively. After washing with DMF five times to remove BPATD from the film surface, the films were finally irradiated under a 365 nm UV lamp for 2 h to obtain π-π conjugated crosslinked graphene composite films. Adjusting the coating height allows for the preparation of πrGO films with thicknesses ranging from 0.5 to 10 μm. Thermogravimetric analysis revealed BPATD contents of 7.8%, 10.7%, 11.2%, and 12.0%, respectively. When the BPATD content was 10.7%, the tensile strength of the πrGO film was 953.04 MPa and the modulus was 4.15 GPa.

[0060] Example 9

[0061] Take 30 mL of the GO dispersion prepared in Example 1 (2 mg / mL) -1The GO gel was obtained by centrifuging at 10,000 rpm for 10 min in a 50 mL centrifuge tube. After thoroughly removing air bubbles from the gel, graphene oxide gel membranes were prepared by coating the gel onto a hydrophilic polyvinylidene fluoride (PVDF) porous substrate. The membranes were then naturally dried to obtain graphene oxide films. The graphene oxide films were then reduced with 38 wt% hydroiodic acid for 12 h and washed with anhydrous ethanol to obtain graphene composite films (rGO). Adjusting the coating height allowed for the acquisition of rGO films with thicknesses ranging from 0.5 to 10 μm. The tensile strength of the obtained rGO films was 419.62 MPa, and the modulus was 5.09 GPa.

[0062] Example 10

[0063] The US-SB-rGO film prepared by confined ordered assembly (Example 2) exhibited a significantly higher Herman orientation factor than the rGO film (Example 9) due to suppressed capillary shrinkage. The orientation factor of the film material was characterized by wide-angle X-ray scattering (WAXS Xenocs Nanoinxider analyzer). The characterization results showed that the Herman orientation factor of the confined ordered assembled graphene film in Example 2 was 0.970 (…). Figure 3 In the middle D), the orientation factor of rGO thin film is only 0.718 ( Figure 3 (D). rGO film of Example 9 ( Figure 3 Cross-sectional FIB-SEM images of the US-SB-rGO films in Example B and Example 2 show that ( Figure 3 In contrast, the US-SB-rGO film (A) exhibits no significant pores and possesses a denser structure. A comparison of the porosity of the rGO film and the US-SB-rGO film (A) shows... Figure 3 The porosity of the rGO film (C) was 15.7%, while that of the US-SB-rGO film was 3.2%. This indicates that confined ordering effectively suppresses capillary shrinkage and improves the Herman orientation factor and density of the film.

[0064] Example 11

[0065] The US-SB-rGO film prepared by confined ordered assembly (Example 2) exhibits a significantly lower interlayer spacing than the SB-rGO film prepared by blade coating ordered assembly (Example 6) due to suppressed capillary shrinkage. Wide-angle X-ray scattering characterization of the film material's scattering vector q indicates that the interlayer spacing of the confined ordered assembled graphene film US-SB-rGO in Example 2 is 3.67 Å, ​​which is significantly lower than that of the SB-rGO film prepared by blade coating ordered assembly in Example 6. Figure 4 (A). The interlayer spacing of the thin film material was also characterized by X-ray scattering. The characterization results showed that the interlayer spacing of the confined ordered assembled graphene film US-SB-rGO in Example 2 was 3.78 Å (…). Figure 4 In Example B), the interlayer spacing of the SB-rGO thin film prepared by the orderly assembly of the blade coating in Example 6 was reduced to 3.67 Å ( Figure 4 The interlayer spacing of the rGO thin film is 3.67 Å (B). Figure 4 (B); Meanwhile, TEM images of the SB-rGO film in Example 6 and the US-SB-rGO film in Example 2 show that the US-SB-rGO film has a more regular orientation structure and a smaller lattice spacing. Figure 4 The irregular structures of rGO thin films and SB-rGO films due to capillary shrinkage result in a maximum lattice spacing of 3.78 Å. Figure 4 In addition to the graphene composite film US-SB-rGO, the rGO film also exhibits a more irregular structure due to capillary contraction. Figure 4 (D). Meanwhile, differential scanning calorimetry (DSC) Figure 4 Experiment C) shows that the glass transition temperature of the ordered graphene composite film US-SB-rGO film, which effectively suppresses capillary shrinkage through continuous external stretching, is 171.84 ℃, which is significantly higher than the glass transition temperature of 159.84 ℃ of the SB-rGO film prepared by orderly assembly by blade coating in Example 6. However, both are higher than the glass transition temperature of polymer BPATD (114.58 ℃), indicating that BPATD in the confined assembly US-SB-rGO film is more likely to undergo 1,4 addition polymerization under ultraviolet light, thereby introducing new carbon-carbon double covalent bonds. At the same time, the US-SB-rGO film has a smaller interlayer spacing due to the suppression of capillary shrinkage by continuous stretching, indicating that polymer BPATD and US-SB-rGO film have stronger π-π interaction.

[0066] Example 12

[0067] Confined ordered assembly of graphene composite films (US-SB-rGO) effectively suppresses capillary shrinkage and introduces interfacial synergistic effects, thereby improving the film orientation and density, resulting in high-mechanical-performance graphene composite films. Compared to the rGO film in Example 9, the tensile strength (419.62 MPa) and Young's modulus (5.09 GPa) of the US-SB-rGO film increased to 1.97 GPa, and the modulus to 107.67 GPa. Figure 5 (A). The frequency of the Raman G peak wavenumber decrease in in-situ tensile tests was used to characterize the stress transfer efficiency between nanosheets. Figure 5 The results show that, compared to rGO films (C, F), Figure 5 (F), US-SB-rGO composite membrane nanosheets ( Figure 5 The stress transfer efficiency between C and G bands shows a monotonically increasing trend; at a strain of 2.0%, the frequency in the G band decreases by 12.7 cm⁻¹.-1 It exhibits high stress transfer efficiency. The ability of the thin film to withstand dynamic loads is characterized by stress relaxation testing. Figure 5 The results showed that the US-SB-rGO film maintained 93.9% of its initial stress at a strain of 1% for 25,000 s, which is significantly higher than that of the rGO film (32.1%). SEM analysis revealed that the fracture surface of the rGO film was smooth. Figure 5 (E), but the US-SB-rGO film exhibits significant curling, indicating that the US-SB-rGO film possesses stronger interfacial forces ( Figure 5 (B) Mechanical properties were compared with those of other graphene films reported in the literature. Figure 5 As can be seen from G), the tensile strength and Young's modulus of the US-SB-rGO film prepared by the confined ordered assembly method are higher than those of similar films reported in the literature (Adv. Mater. 2020, 32, e1907411.; Nat. Commun. 2020, 11, 1.; Nat. Mater. 2021, 20, 624.).

[0068] It should be noted that, according to the above embodiments of the present invention, those skilled in the art can fully realize the scope of the independent claims and dependent claims of the present invention, and the implementation process and method are the same as those in the above embodiments; and the parts of the present invention not described in detail belong to the well-known technology in the art.

[0069] The above description is only a part of the specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a π-π conjugated molecularly confined polymerized graphene composite thin film material, characterized in that, Includes the following steps: Step 1: The raw graphite powder is reacted with concentrated sulfuric acid and potassium permanganate at a mass fraction of 98 wt% at low temperature, and then washed and centrifuged to prepare a single-layer graphene oxide dispersion. Step 2: The graphene oxide dispersion obtained in Step 1 is coated onto a hydrophilic polyvinylidene fluoride porous substrate to form a graphene oxide gel film with a thickness of 100-1000 micrometers. Step 3: The graphene oxide gel film obtained in Step 2 is used to prepare a graphene oxide film by continuous external force stretching. Step 4: The graphene oxide film obtained in Step 3 is subjected to continuous external stretching and then covalently cross-linked with a cross-linking agent solution containing long-chain hydroxyl molecules to obtain a covalently cross-linked graphene oxide film. The cross-linking agent solution is a dichloromethane solution of 10,12-pentadecanediyne-1 alcohol. Step 5: The covalently cross-linked graphene oxide film obtained in Step 4 is reduced with a reducing agent under external stretching to obtain a covalently cross-linked graphene film. Step 6: The covalently cross-linked graphene film obtained in Step 5 is washed with detergent under continuous external stretching, then immersed in a cross-linking agent solution for cross-linking, and dried to produce an ordered cross-linked graphene carbon film material. The cross-linking agent solution is an N,N-dimethylformamide solution of π-π conjugated long-chain molecules with phenanthroline rings at both ends. Step 7: The ordered cross-linked graphene film obtained in step 6 is subjected to external stretching, washed, and then polymerized under ultraviolet light at 254 nm and 365 nm, respectively, to prepare a π-π conjugated molecular confined polymerized graphene composite film material.

2. The method according to claim 1, characterized in that: In step 1, the low temperature is 5 ℃~10 ℃; the diameter of the single-layer graphene oxide nanosheet is 5-60 μm.

3. The method according to claim 1, characterized in that: In step 2, the coating speed is 10 mm / s to 100 mm / s, and the coating temperature is 25 ℃ to 35 ℃.

4. The method according to claim 1, characterized in that: In step 3, the graphene oxide gel film is regularly oriented under continuous external stretching.

5. The method according to claim 1, characterized in that: In step 4, the concentration of the 10,12-pentadecanediyne-1 alcohol is 15 mM, the mass fraction of the 10,12-pentadecanediyne-1 alcohol is 0.5-3%, and the crosslinking reaction time is 1-3 h.

6. The method according to claim 1, characterized in that: In step 5, the reducing agent is hydroiodic acid, and the reduction reaction takes 12 hours.

7. The method according to claim 1, characterized in that: In step 6, the detergent is anhydrous ethanol, the concentration of the π-π conjugated long-chain molecule with phenanthroline rings at both ends is 10 mM, the mass fraction of the π-π conjugated long-chain molecule with phenanthroline rings at both ends is 5-15%, and the soaking reaction time is 12-48 h.

8. The method according to claim 1, characterized in that: In step 7, the detergent used for washing is N,N-dimethylformamide, the luminous efficacy of ultraviolet light with a wavelength of 254 nm is 30 W, the irradiation time is 2 h, and the luminous efficacy of ultraviolet light with a wavelength of 365 nm is 500 W, the irradiation time is 2 h.

9. A π-π conjugated molecularly confined polymerized graphene composite film material prepared by the method according to any one of claims 1-8, characterized in that: The Herman orientation factor of the graphene composite film material is 0.970, the porosity of the graphene composite film material is 3.20%, the thickness of the graphene composite film material is 0.5-10 μm, the tensile strength of the graphene composite film material is 1.97 GPa, and the modulus of the graphene composite film material is 107.67 GPa.

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