A g-C3N4 / PLA-PPC type single-layer film with constant organic solvent-driven bidirectional deformation response, preparation method thereof and use thereof

Abstract

The present invention discloses a g-C3N4 / PLA-PPC type single-layer film with a constant organic solvent-driven bidirectional deformation response, a preparation method thereof, and uses thereof. The g-C3N4 / PLA-PPC type single-layer film with a constant organic solvent-driven bidirectional deformation response of the present invention has a single-layer membrane structure and undergoes continuous bidirectional deformation response under the stimulation of a constant organic solvent. The raw materials used include graphite-like carbon nitride (g-C3N4), polylactic acid (PLA), and polypropylene carbonate (PPC). In response to the demand for environmentally friendly social development, the present invention selects biodegradable polymer materials (PLA, PPC) and non-toxic g-C3N4 inorganic nanomaterials, and prepares organic solvent stimuli-responsive g-C3N4 / PLA-PPC films through a simple solution casting method. The g-C3N4 and PLA-PPC polymers are introduced to form an asymmetric film. Based on the expansion difference between the layered g-C3N4 inorganic material and the PLA-PPC polymer, autonomous and continuous bidirectional deformation response behavior is achieved under constant conditions, providing potential applications in the research field of organic solvent stimuli response.

Description

Technical Field

[0001] The present invention relates to a g-C3N4 / PLA-PPC type single-layer film with a constant organic solvent-driven bidirectional deformation response, a preparation method and uses thereof, and belongs to the technical field of intelligent polymer materials. Background Art

[0002] Stimuli-responsive polymers are a class of macromolecular systems that exhibit "intelligent" behavior. When the external environment (such as temperature, pH, light, humidity, organic solvents, electric field strength, and magnetic field strength) changes, the macromolecules undergo corresponding, observable changes in their macroscopic properties, converting other forms of energy into mechanical deformation. Organic solvent-driven actuation, as a form of intelligent actuation, has attracted widespread attention in fields such as actuators, smart devices, and sensors.

[0003] In recent years, achieving controllable deformation responses in green and environmentally friendly polymer materials has been a hot topic of research. To achieve stimulus-responsive motion, inorganic nanomaterials are often introduced into polymer systems to form asymmetric structures, leveraging their uneven expansion to achieve controllable deformation. However, traditional deformation is unidirectional, while bidirectional deformation is induced by changing the external environment. For example, in organic solvents, only unidirectional deformation occurs, and only after leaving the organic solvent will deformation occur again, meaning that bidirectional deformation is achieved in different environments. Furthermore, bilayer or multilayer films suffer from the problem of shedding and delamination between layers during expansion deformation or after multiple deformations.

[0004] Therefore, studying the continuous bidirectional deformation response behavior of polymer composites under a constant environment has important research significance for the application in the field of smart materials. Summary of the Invention

[0005] The present invention provides a g-C3N4 / PLA-PPC type single-layer film with a constant organic solvent-driven bidirectional deformation response, a preparation method thereof, and uses thereof. The film of the present invention has a single-layer asymmetric structure and can achieve continuous bidirectional deformation response under constant organic solvent drive. It can be applied to actuators and other fields, and the preparation process is simple.

[0006] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0007] A g-C3N4 / PLA-PPC type monolayer film with a constant organic solvent-driven bidirectional deformation response has a single-layer film structure; the g-C3N4 / PLA-PPC type monolayer film with a constant organic solvent-driven bidirectional deformation response undergoes continuous bidirectional deformation response under the stimulation of a constant organic solvent;

[0008] The raw materials used for the g-C3N4 / PLA-PPC type single-layer film with constant organic solvent-driven bidirectional deformation response include graphite-like carbon nitride (g-C3N4), polylactic acid (PLA) and polypropylene carbonate (PPC).

[0009] In this application, "constant" refers to maintaining the same organic solvent-stimulated environment. This means that the membranes of this application can undergo bidirectional deformation responses under the stimulation of the same organic solvent without requiring any changes in the environment, removal from the organic solvent environment, or other manipulations.

[0010] The above-mentioned g-C3N4 / PLA-PPC type single-layer film with constant organic solvent-driven bidirectional deformation response has an asymmetric structure.

[0011] The "stimulation of organic solvent" in this application can be soaking in an organic solvent or placing in an organic atmosphere (steam) environment.

[0012] Compared with traditional polymer films that can only respond to deformation in one direction, or achieve bidirectional deformation by changing the external environment, the present invention has never been reported to undergo continuous bidirectional deformation in a constant organic solvent environment.

[0013] In order to take both cost and deformability into consideration, the mass ratio of the graphite-like carbon nitride, polylactic acid and polypropylene carbonate is (2-8): (1-10): (0.1-20).

[0014] The g-C3N4 / PLA-PPC type single-layer film with a constant organic solvent-driven bidirectional deformation response in the present application undergoes a continuous bidirectional spiral curling response under the stimulation of a constant organic solvent.

[0015] The process of the above-mentioned continuous bidirectional helical coiling response is as follows: under the stimulation of a constant organic solvent, forward helical coiling occurs first, reaches a stable state in 2 to 10 seconds, and then returns to the original state in 2 to 10 seconds, then continues to coil in the reverse direction, reaches a stable state in 2 to 10 seconds, and then returns to the original state in 2 to 10 seconds; under the stimulation of a constant organic solvent, the above process is repeated to form a continuous bidirectional helical coiling response.

[0016] In this application, "forward" and "reverse" refer to two opposite directions. For example, if right is defined as "forward", then left is "reverse". If left is defined as "forward", then right is "reverse".

[0017] The organic solvent of the present application is at least one of ethyl acetate (EA), dichloromethane, chloroform, tetrahydrofuran or N,-N-dimethylformamide.

[0018] A method for preparing a g-C3N4 / PLA-PPC type single-layer film with a constant organic solvent-driven bidirectional deformation response comprises adding graphite-like carbon nitride (g-C3N4), polylactic acid (PLA) and polypropylene carbonate (PPC) to a 1,4-dioxane solvent (Diox), heating and stirring to obtain a membrane liquid, then laying a membrane, and heating to remove the 1,4-dioxane solvent to obtain a g-C3N4 / PLA-PPC type single-layer film with a constant organic solvent-driven bidirectional deformation response.

[0019] When the 1,4-dioxane solvent is removed by heating, the preferred heating temperature is 30-60°C.

[0020] The above-mentioned graphite-like carbon nitride (g-C3N4) is prepared as follows: melamine is poured into an alumina crucible and placed in a muffle furnace for calcination, then cooled to room temperature, washed, dried, ground into powder, and passed through a 200-mesh sieve to obtain graphite-like carbon nitride (g-C3N4).

[0021] The calcination process is as follows: heating to 500-600°C at a heating rate of 2-10°C / min, keeping the temperature for 3-4 hours, and then naturally cooling to room temperature.

[0022] During the above cleaning, a centrifuge is used for centrifugal cleaning, the number of cleaning times is 3-5 times, the speed of each cleaning is 8000-10000r / min, the time is 5-10min; the drying temperature is 60-80℃, and the time is 12-24h.

[0023] In the membrane liquid, the mass dosage of polylactic acid (PLA) is 1 to 10 wt% of the mass of 1,4-dioxane solvent, the mass ratio of polylactic acid (PLA) and polypropylene carbonate (PPC) is 1:(0.1 to 2), and the mass dosage of graphite-like carbon nitride (g-C3N4) is 2 to 8% of the mass of 1,4-dioxane solvent.

[0024] When preparing the film, the heating and stirring temperature is 50-80° C., the time is 1-24 hours, and the stirring speed is 100-500 r / min.

[0025] The above-mentioned g-C3N4 / PLA-PPC type single-layer film with constant organic solvent-driven bidirectional deformation response is used for actuators, or for smart sensors, or for soft robots, or for smart devices, etc.

[0026] To create an environmentally friendly thin film material with organic solvent-responsive deformation, this application uses PLA and PPC polymers. By introducing the inorganic nanomaterial g-C3N4 to form an asymmetric structure within the PLA-PPC system, it effectively achieves controllable deformation response behavior. The different organic expansion coefficients of g-C3N4 and PLA-PPC induce unique, autonomous, continuous, bidirectional deformation behavior, opening up new possibilities for the research of smart materials.

[0027] The above-mentioned g-C3N4 / PLA-PPC responsive film preparation can adjust the g-C3N4 content and polymer content as needed, which affects its organic solvent-driven response deformation behavior.

[0028] The technologies not mentioned in this invention are all referred to the prior art.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] (1) The present invention introduces g-C3N4 and PLA-PPC polymer composites to construct an asymmetric structure film. Under the stimulation of organic solvents, g-C3N4 and PLA-PPC have different expansion differences, and a special autonomous continuous bidirectional deformation response behavior is achieved under a constant environment.

[0031] (2) Compared with double-layer or multi-layer structures, the asymmetric single-layer structure can effectively avoid the problem of interlayer shedding during the expansion process.

[0032] (3) Select biodegradable polymer materials (PLA, PPC) and non-toxic g-C3N4 inorganic materials to meet the environmentally friendly needs of social development.

[0033] (4) The g-C3N4 / PLA-PPC stimuli-responsive film was prepared by a simple solution casting method, which is simple to operate and easy to achieve large-scale production. It has potential application prospects in actuators, smart devices, smart sensors and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Scanning electron microscope images of cross sections of g-C3N4 (A), PLA-PPC (B) and the g-C3N4 / PLA-PPC (C) composite film of the present invention;

[0035] Figure 2 Mechanical test diagram of g-C3N4 / PLA-PPC composite film with different g-C3N4 contents;

[0036] Figure 3 Graph showing the deformation process of PLA-PPC (A) and the g-C3N4 / PLA-PPC composite film of the present invention (B) driven by EA solvent;

[0037] Figure 4 Deformation motion diagrams of g-C3N4 / PLA, g-C3N4 / PPC and the g-C3N4 / PLA-PPC composite film of the present invention;

[0038] Figure 5 Graph showing the driving deformation process of the g-C3N4 / PLA-PPC composite film of the present invention in ethanol solvent;

[0039] Figure 6 Graphs showing the deformation motion of g-C3N4 / PLA-PPC composite films when the g-C3N4 content is 2.5wt% (A), 3.5wt% (B), 4.5wt% (C), 5.5wt% (D) and 6.5wt% (E) of the present invention;

[0040] Figure 7 Figure 3. Smart protective device assembled for g-C3N4 / PLA-PPC composite film.

[0041] Figure 8 Under the same environmental stimulus, the conventional unidirectional deformation response ( Figure 8 The upper middle part) and the bidirectional deformation response diagram of this application ( Figure 8 middle and lower half); DETAILED DESCRIPTION

[0042] In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with the examples, but the content of the present invention is not limited to the following examples.

[0043] Characterization and performance testing:

[0044] (1) Scanning electron microscopy (SEM) test: A scanning electron microscope (JEOLLtd JSM-7100F) was used to test the surface structure and cross-sectional structure of the samples.

[0045] (2) Mechanical property test: An electronic universal tensile testing machine is used for tensile testing of sample films: the sample film is cut into long strips and clamped on the fixture, which is fixed at both ends of the instrument. The film is stretched at a speed of 50 mm / min. During the test, the stress, strain and other parameters of the sample are obtained to evaluate the mechanical properties of the material.

[0046] (3) Deformation of the film: A 5 mm × 20 mm strip of g-C3N4-PLA / PPC film was placed in an organic solvent environment. The morphological changes of the film were recorded by video recording. The curling radius (r) of the film was measured using Image J software. The curling rate K (cm) was calculated using the formula K = 1 / r. -1 ), to achieve quantitative analysis of deformation curling.

[0047] In each case, polylactic acid (PLA, Mw: 110,000) and polypropylene carbonate (PPC, Mw: 100,000) were provided by Shanghai MacLean Biochemical Co., Ltd. and Jiangsu Zhongke Jinlong Chemical Co., Ltd., China, respectively, and melamine (CAS No. 108-78-1) was provided by Shanghai Yien Chemical Technology Co., Ltd.

[0048] Example 1

[0049] A method for preparing a g-C3N4 / PLA-PPC monolayer film with a constant organic solvent-driven bidirectional deformation response, the specific steps of which are as follows:

[0050] 1) Preparation of g-C3N4: Weigh 10g of melamine into an alumina crucible, place it in a muffle furnace, and calcine it at 550℃ at a heating rate of 2℃ / min for 4h. After cooling naturally to room temperature, use a centrifuge and deionized water to centrifuge and wash it three times. The centrifugal speed during each washing is 8000r / min and the centrifugal time is 10min. After washing, the obtained solid material is placed in an 80℃ oven for 24h, then ground into powder (g-C3N4), sieved through 200 mesh, and set aside.

[0051] 2) Preparation of PLA-PPC film: 0.15 g of PLA and PPC, 2.5 wt % of g-C3N4 (2.5 wt % means that the mass content of g-C3N4 in the obtained film liquid is 2.5 wt %), and 10 mL of Diox solvent were weighed separately, mixed, and heated at 60°C with magnetic stirring for 3 h (500 rpm) to obtain a film liquid. The film liquid was poured into a glass watch glass to a height of 0.15 cm. The glass watch glass was placed on a heating plate at 40°C for 2 h to remove the solvent, thereby obtaining a g-C3N4 / PLA-PPC film.

[0052] Example 2

[0053] A method for preparing a g-C3N4 / PLA-PPC monolayer film with a constant organic solvent-driven bidirectional deformation response, the specific steps of which are as follows:

[0054] 1) Preparation of g-C3N4: Weigh 10g of melamine into an alumina crucible, place it in a muffle furnace, and calcine it at 550℃ at a heating rate of 2℃ / min for 4h. After cooling naturally to room temperature, use a centrifuge and deionized water to centrifuge and wash it three times. The centrifugal speed during each washing is 8000r / min and the centrifugal time is 10min. After washing, the obtained solid material is placed in an 80℃ oven for 24h, then ground into powder (g-C3N4), sieved through 200 mesh, and set aside.

[0055] 2) Preparation of PLA-PPC film: 0.15 g of PLA and PPC, 3.5 wt% of g-C3N4 (3.5 wt% means that the mass content of g-C3N4 in the obtained film solution is 3.5 wt%), and 10 mL of Diox solvent were weighed separately, and heated at 60°C with magnetic stirring for 3 h (500 rpm) to obtain a film solution. The film solution was poured into a glass watch glass to a height of 0.2 cm. The glass watch glass was placed on a heating plate at 40°C for 2 h to remove the solvent, thereby obtaining a g-C3N4 / PLA-PPC film.

[0056] Example 3

[0057] A method for preparing a g-C3N4 / PLA-PPC monolayer film with a constant organic solvent-driven bidirectional deformation response, the specific steps of which are as follows:

[0058] 1) Preparation of g-C3N4: Weigh 10g of melamine into an alumina crucible, place it in a muffle furnace, and calcine it at 550℃ at a heating rate of 2℃ / min for 4h. After cooling naturally to room temperature, use a centrifuge and deionized water to centrifuge and wash it three times. The centrifugal speed during each washing is 8000r / min and the centrifugal time is 10min. After washing, the obtained solid material is placed in an 80℃ oven for 24h, then ground into powder (g-C3N4), sieved through 200 mesh, and set aside.

[0059] 2) Preparation of PLA-PPC bilayer film: 0.15 g of PLA and PPC, 4.5 wt % of g-C3N4 (4.5 wt % means that the mass content of g-C3N4 in the obtained film solution is 4.5 wt %), and 10 mL of Diox solvent were weighed separately, and heated at 60°C with magnetic stirring for 3 h (500 rpm) to obtain a film solution. The film solution was poured into a glass watch glass to a height of 0.25 cm. The glass watch glass was placed on a heating plate at 40°C for 2 h to remove the solvent, thereby obtaining a g-C3N4 / PLA-PPC film.

[0060] Example 4

[0061] A method for producing a g-C3N4 / PLA-PPC monolayer film with a constant organic solvent-driven bidirectional deformation response, the specific steps of which are as follows:

[0062] 1) Preparation of g-C3N4: Weigh 10g of melamine into an alumina crucible, place it in a muffle furnace, and calcine it at 550℃ at a heating rate of 2℃ / min for 4h. After cooling naturally to room temperature, use a centrifuge and deionized water to centrifuge and wash it three times. The centrifugal speed during each washing is 8000r / min and the centrifugal time is 10min. After washing, the obtained solid material is placed in an 80℃ oven for 24h, then ground into powder (g-C3N4), sieved through 200 mesh, and set aside.

[0063] 2) Preparation of PLA-PPC bilayer film: 0.15 g of PLA and PPC, 5.5 wt % of g-C3N4 (5.5 wt % indicates that the mass content of g-C3N4 in the resulting film solution is 5.5 wt %), and 10 mL of Diox solvent were weighed separately, and heated at 60°C with magnetic stirring for 3 h (500 rpm) to obtain a film solution. The film solution was poured into a glass watch glass to a height of 0.3 cm. The glass watch glass was placed on a hot plate at 40°C for 2 h to remove the solvent, thereby obtaining a g-C3N4 / PLA-PPC film.

[0064] Example 5

[0065] A method for preparing a g-C3N4 / PLA-PPC monolayer film with a constant organic solvent-driven bidirectional deformation response, the specific steps of which are as follows:

[0066] 1) Preparation of g-C3N4: Weigh 10g of melamine into an alumina crucible, place it in a muffle furnace, and calcine it at 550℃ at a heating rate of 2℃ / min for 4h. After cooling naturally to room temperature, use a centrifuge and deionized water to centrifuge and wash it three times. The centrifugal speed during each washing is 8000r / min and the centrifugal time is 10min. After washing, the obtained solid material is placed in an 80℃ oven for 24h, then ground into powder (g-C3N4), sieved through 200 mesh, and set aside.

[0067] 2) Preparation of PLA-PPC bilayer film: 0.15 g of PLA and PPC, 6.5 wt % of g-C3N4 (6.5 wt % means that the mass content of g-C3N4 in the obtained film solution is 6.5 wt %), and 10 mL of Diox solvent were weighed separately, and heated at 60°C with magnetic stirring for 3 h (500 rpm) to obtain a film solution. The film solution was poured into a glass watch glass to a height of 0.35 cm. The glass watch glass was placed on a heating plate at 40°C for 2 h to remove the solvent, thereby obtaining a g-C3N4 / PLA-PPC film.

[0068] Comparative Example 1

[0069] A method for preparing a PLA-PPC film comprises the following steps: weighing 0.15 g of PLA and PPC and 10 mL of Diox solvent, mixing the mixture, heating the mixture at 60° C. with magnetic stirring for 3 hours to obtain a film liquid, pouring the film liquid into a glass watch glass to a height of 0.3 cm, placing the glass watch glass on a heating plate at 40° C. for 2 hours to remove the solvent, and thus obtaining a PLA-PPC composite film.

[0070] Comparative Example 2

[0071] The preparation of g-C3N4 refers to Example 1. Weigh 0.3 g of PLA, 5.5 wt% of g-C3N4 (5.5 wt% means that the mass content of g-C3N4 in the obtained membrane liquid is 5.5 wt%), and 10 mL of Diox solvent, mix them, and heat with magnetic stirring at 60°C for 3 h to obtain a membrane liquid. Pour the membrane liquid into a glass watch glass to a height of 0.3 cm. Place the glass watch glass on a hot plate at 40°C for 2 h to remove the solvent, and a g-C3N4 / PLA composite membrane can be obtained.

[0072] Comparative Example 3

[0073] The preparation of g-C3N4 refers to Example 1. 0.3 g of PPC, 5.5 wt% of g-C3N4 (5.5 wt% means that the mass content of g-C3N4 in the obtained membrane liquid is 5.5 wt%), and 10 mL of Diox solvent were weighed and mixed. The mixture was heated at 60°C with magnetic stirring for 3 h to obtain a membrane liquid. The membrane liquid was poured into a glass watch glass to a height of 0.3 cm. The glass watch glass was placed on a hot plate at 40°C for 2 h to remove the solvent, thereby obtaining a g-C3N4 / PPC composite membrane.

[0074] Thin film characterization and performance analysis:

[0075] In order to understand the structure of the composite membrane most directly, the cross sections of g-C3N4, PLA-PPC and g-C3N4 / PLA-PPC composite membranes were tested by scanning electron microscopy. Figure 1 As shown in (A), g-C3N4 presents a tightly packed sheet structure. Figure 1 (B) is an image of the cross section of the PLA-PPC composite film (prepared in Comparative Example 1), showing that the PLA and PPC polymer chains are entangled to form a uniform and non-porous PLA-PPC composite film. Figure 1 (C) is an image of a cross section of a g-C3N4 / PLA-PPC composite film (prepared in Example 4). It can be seen that under the action of gravity, larger flaky g-C3N4 is deposited at the bottom of the composite film, and smaller flaky g-C3N4 is distributed among the PLA-PPC molecules, confirming that the g-C3N4 / PLA-PPC composite film has an asymmetric structure, which plays a vital role in achieving the drive response. The structures of the g-C3N4 / PLA-PPC composite films of the remaining examples are basically the same as those of the g-C3N4 / PLA-PPC composite film of this example and will not be repeated here.

[0076] Mechanical properties test can effectively evaluate the usability of composite films. A composite film with a size of 0.8×2.5 cm was fixed on an electronic universal tensile testing machine, and the film was stretched by applying external force to obtain a stress-strain curve. In order to understand the effect of the change of g-C3N4 content on the mechanical properties of the composite film, composite films with g-C3N4 contents of 2.5wt%, 3.5wt%, 4.5wt%, 5.5wt% and 6.5wt% were tested. Figure 2 As shown in the figure, it can be found that the maximum stress and strain of the g-C3N4 / PLA-PPC composite film decrease with the increase of g-C3N4 content, indicating that the introduction of g-C3N4 leads to the breakage of PLA-PPC molecular chains, thereby reducing the tensile properties of the composite film. Therefore, the excessive introduction of g-C3N4 is not conducive to the performance of the composite film.

[0077] Traditional stimulus-responsive polymer films can only undergo one-way deformation in one direction, or undergo two-way deformation response under conditions of changing environment. Therefore, achieving continuous two-way deformation under constant environmental stimulation has always been a huge challenge. The present invention is based on the principle of expansion differences between inorganic and polymeric materials with lamellar structures, and utilizes g-C3N4 and PLA-PPC with anisotropic organic solvent expansion response to construct an asymmetric structure composite film to achieve autonomous continuous two-way deformation under a constant organic solvent environment. Among them, the force between the organic solvent molecules and g-C3N4 may cause the g-C3N4 interlamellar spacing to increase, while the interaction between the solvent molecules and the PLA-PPC polymer causes the polymer chain to expand. Due to the difference in expansion of g-C3N4 and PLA-PPC polymers to organic solvents, continuous two-way competitive deformation occurs.

[0078] In order to determine the continuous bidirectional deformation mechanism of g-C3N4 / PLA-PPC composite membrane under constant organic solvent driving, further experimental research will help provide reliable evidence. First, the deformation process of PLA-PPC composite membrane (prepared in Comparative Example 1) and g-C3N4 / PLA-PPC composite membrane (prepared in Example 4) under ethyl acetate solvent driving was studied. Figure 3 As shown in (A), the PLA-PPC composite membrane undergoes swelling and deformation, but the deformation state is uncontrollable, while the deformation of the g-C3N4 / PLA-PPC composite membrane is controllable ( Figure 3(B)), indicating that the introduction of g-C3N4 provides a guiding role in the deformation of the composite film. As a two-dimensional nanomaterial, g-C3N4 forms a gradient network structure with a certain strength and rigidity in the composite film, which enhances the deformation stress of the PLA-PPC composite film and makes it more stable and controllable during the deformation process. Next, the deformation response behavior of g-C3N4 / PLA composite film (prepared in Comparative Example 2), g-C3N4 / PPC composite film (prepared in Comparative Example 3) and g-C3N4 / PLA-PPC composite film (prepared in Example 4) was studied. Figure 4 As shown, all three composite films exhibited a continuous "helical curling-recovery-reverse helical curling" response under constant environmental drive. This phenomenon clearly demonstrates that the interaction between the sheet-like g-C3N4 and PLA-PPC polymer plays a significant role in the continuous bidirectional motion. Practice has verified that compared with g-C3N4 / PLA and g-C3N4 / PPC composite films, the g-C3N4 / PLA-PPC composite film has significantly improved mechanical properties and a significantly faster response speed. The response performance can also be controlled by adjusting the PLA and PPC content.

[0079] In order to further confirm the important effect of the introduction of g-C3N4 on the continuous bidirectional deformation of g-C3N4 / PLA-PPC composite membrane, the driving deformation of g-C3N4 / PLA-PPC composite membrane in ethanol solvent ( Figure 5 The results showed that the g-C3N4 / PLA-PPC composite film (prepared in Example 4) only underwent unidirectional deformation. This was due to the expansion of the interlayer spacing of the flaky g-C3N4 in the presence of ethanol solvent, leading to deformation. However, the solubility parameters of ethanol and PLA-PPC polymer differ significantly. As an inert solvent, ethanol did not respond to the PLA-PPC polymer, and no reverse deformation occurred. This further confirmed that the volume expansion of g-C3N4 after adsorption of organic solvents caused the composite film to deform. This provides evidence for the continuous bidirectional deformation of g-C3N4 / PLA-PPC composite films driven by EA solvent.

[0080] In order to determine the factors affecting the biaxial deformation properties of g-C3N4 / PLA-PPC composite films, the effect of g-C3N4 content on the biaxial deformation properties of the composite films was investigated. Figure 6(AE) shows the optical and schematic diagrams of the deformation response of composite films (prepared by Examples 1-5, respectively) with g-C3N4 contents of 2.5wt%, 3.5wt%, 4.5wt%, 5.5wt% and 6.5wt% under EA solvent driving. The results show that different contents of g-C3N4 have a great influence on the deformation properties and deformation direction of the composite film within one cycle. When the content of g-C3N4 is 2.5wt%, the composite film undergoes continuous bidirectional deformation, and the response time of the composite film accelerates with the increase of g-C3N4 content. When the content of g-C3N4 is 6.5wt%, one cycle of deformation process can be completed in 13s. As the content of g-C3N4 increases from 2.5wt% to 6.5wt%, it is shown that the expansion force of the flake g-C3N4 after adsorbing EA solvent increases with the increase of g-C3N4 content, resulting in a gradual increase in the spiral curvature of the composite film. The second reverse helical curling rate reaches a maximum when the g-C3N4 content increases to 3.5wt%, and then decreases. This is likely due to the increased bending resistance caused by the introduction of excessive g-C3N4. Therefore, through Examples 1-5, the g-C3N4 / PLA-PPC films prepared with different contents have different response deformation properties, allowing the selection of appropriate films according to different application scenarios.

[0081] Application Examples

[0082] In recent years, intelligent protection devices have also been widely studied. Figure 7 As shown, the g-C3N4 / PLA-PPC composite film (prepared in Example 4) was cut into films with sizes of 2×1.5 cm, 1.5×1.5 cm, 1×1.5 cm, and 0.5×1.5 cm, and assembled into one, two, three, and four-piece smart protective devices, respectively. In order to demonstrate the accuracy and programmability of the protective device, the upper and lower surfaces of the g-C3N4 / PLA-PPC composite film were placed alternately in the smart protective device assembled from two or more pieces. Figure 7 As shown in (A), a g-C3N4 / PLA-PPC composite film is vertically fixed between two glass rods. When exposed to EA solvent, the 2×1.5 cm smart protective device first wraps around the left glass rod and then around the right glass rod. Multiple other smart protective devices exhibit the same response, but the wrapping positions alternate. This interesting alternating arrangement allows for more precise protection of any object, meeting diverse needs. This precision and programmability opens up a wider range of application scenarios for stimulus-responsive design.

Claims

1. A g-C3N4 / PLA-PPC monolayer film with a constant organic solvent-driven bidirectional deformation response, characterized by: It is a single-layer film structure; the g-C3N4 / PLA-PPC type single-layer film with a bidirectional deformation response driven by a constant organic solvent undergoes a continuous bidirectional helical curling response under the stimulation of a constant organic solvent; The process of continuous bidirectional helical coiling response is as follows: under the stimulation of a constant organic solvent, the forward helical coiling occurs first, reaching a stable state in 2-10 seconds, then recovering to the original state in the next 2-10 seconds, and then continuing to coil in the reverse direction and reaching a stable state in the next 2-10 seconds; "Constant" means maintaining the same organic solvent stimulation environment; "organic solvent stimulation" means immersing in an organic solvent or placing in an organic atmosphere environment; The raw materials used in the g-C3N4 / PLA-PPC type monolayer film with constant organic solvent driven bidirectional deformation response include graphite-like carbon nitride, polylactic acid and polypropylene carbonate; The mass ratio of graphite-like carbon nitride, polylactic acid and polypropylene carbonate is (2-8): (1-10): (0.1-20); The organic solvent is at least one of ethyl acetate, dichloromethane, chloroform, tetrahydrofuran or N,-N-dimethylformamide.

2. A method for preparing a g-C3N4 / PLA-PPC monolayer film with a constant organic solvent-driven bidirectional deformation response according to claim 1, characterized in that: Graphite-like carbon nitride, polylactic acid and polypropylene carbonate are added to 1,4-dioxane solvent, heated and stirred evenly to obtain a membrane liquid, and then the membrane is laid and the 1,4-dioxane solvent is removed by heating to obtain a g-C3N4 / PLA-PPC type single-layer film with a constant organic solvent-driven bidirectional deformation response.

3. The preparation method according to claim 2, wherein: The preparation of graphite-like carbon nitride is as follows: melamine is poured into an alumina crucible and calcined in a muffle furnace, then cooled to room temperature, cleaned, dried, and ground into powder to obtain graphite-like carbon nitride; wherein the calcination process is: heating to 500-600°C at a rate of 2-10°C / min, holding for 3-4 hours, and then naturally cooling to room temperature.

4. The preparation method according to claim 3, wherein: During cleaning, centrifuge cleaning is used, the number of cleaning times is 3-5 times, the speed of each cleaning is 8000-10000 r / min, and the time is 5-10 minutes; the drying temperature is 60-80 ° C, and the time is 12-24 hours.

5. The preparation method according to any one of claims 2 to 4, characterized in that: In the membrane solution, the mass amount of polylactic acid is 1~10 wt% of the mass of 1,4-dioxane solvent, the mass ratio of polylactic acid and polypropylene carbonate is 1:(0.1~2), and the mass amount of graphite-like carbon nitride is 2~8% of the mass of 1,4-dioxane solvent; the heating and stirring temperature is 50~80℃, the time is 1~24 h, and the stirring speed is 100~500 r / min.

6. Use of the g-C3N4 / PLA-PPC type monolayer film with constant organic solvent driven bidirectional deformation response according to claim 1, characterized in that: Used in actuators, or in smart sensors, or in soft robots, or in smart devices.

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