Bidirectional response E / EPG bimorphic shape memory composite film and preparation method thereof

Abstract

The invention belongs to the field of intelligent materials and shape memory materials, and discloses a bidirectional response E / EPG bimorphic shape memory composite film and a preparation method thereof. Epoxy resin, a curing agent, PEG and GO are used as raw materials, and the bidirectional response E / EPG bimorphic shape memory composite film is prepared through a PEG and GO dispersion technology, EPG hardening forming and EPG hardening-Ep coating-composite hardening forming. By adjusting the composite hardening forming technology, the bent and straight E / EPG composite film with two initial shapes is prepared, and the EPG layer and the Ep layer are mutually acted in the temperature change process by utilizing the difference between the thermal properties and the mechanical properties of the EPG layer and the Ep layer, so that the EPG / EPG composite film is prepared. The E / EPG with the two initial shapes achieves the thermal-optical double-stimulation bidirectional response shape memory function in the heating-cooling process. The developed E / EPG shows application potential in the fields of flexible actuators, soft robots, intelligent response unit structures and the like.

Description

Technical Field

[0001] The present invention relates to the field of smart materials and shape memory materials, and in particular to a shape memory composite film material. Background Art

[0002] Epoxy resin (Ep) is a commonly used engineering material with advantages such as high temperature resistance, high strength, dimensional stability, chemical corrosion resistance, and low cost. It is widely used in coatings, adhesives, composite materials, electronic materials, building materials and other fields. Although Ep has good mechanical properties and thermal stability, it needs to be properly modified according to specific application requirements to achieve the required performance and usage requirements. Ep has a low viscosity state before hardening, which is convenient for physical modification and further chemical modification through uniform dispersion of organic modifiers and inorganic particles, which makes SMEs developed based on Ep modification have greater application potential. The molding process of Ep is flexible and convenient, which makes Ep commonly used in the development of functional materials. It has been developed into SMEs and shows application potential in aerospace, automotive industry, electronic products, medical devices, smart materials and other fields. However, most SMEs have disadvantages such as only one-way response (cannot achieve circulation under non-external mechanical conditions), single stimulation mode (mostly temperature), high response temperature, single function, and high development cost, which greatly limits the development and functional application of SMEs.

[0003] According to the reversibility of the shape memory process, SMPs are further divided into traditional unidirectional SMPs (1W-SMPs) and bidirectional shape memory polymers (2W-SMPs). Among them, unidirectional SMPs need external mechanical action to achieve the shape memory cycle function, showing an irreversible shape memory effect; while 2W-SMPs can achieve the shape memory cycle function through external mechanical action, heat, light, humidity and other stimuli in the environment, showing a reversible shape memory effect, that is, the shape is not cycled by external mechanical action. The bidirectional shape memory function makes 2W-SMPs show great application potential in many high-tech fields such as smart clothing, sensor drive, aerospace, etc. At present, most SMEs have unidirectional shape memory response, and bidirectional shape memory response SMEs (2W-SMEs) face the problems of complex development process, high development cost, high response temperature, and difficult functional application. This research team previously disclosed a method for preparing a bidirectional corresponding shape memory composite material, but failed to obtain a controllable initial shape of the sample through process adjustment. It can only respond to thermal stimulation for shape memory bidirectional response, and the corresponding angle of the shape is small. Summary of the invention

[0004] In order to solve the technical problems that bidirectional shape memory polymers and their composite materials have a single initial shape or complex control process, a single response mode and a small response deformation angle, the present invention proposes a bidirectional responsive E / EPG dual-morphology shape memory composite film and a preparation method thereof.

[0005] To achieve the above object, the technical solution of the present invention is implemented as follows:

[0006] A method for preparing a bidirectionally responsive E / EPG dual-morphology shape memory composite film, the specific steps are as follows:

[0007] (1) Weigh epoxy resin (Ep, 5022A type epoxy resin) and add it to a beaker with a magnetic rotor, and place it on a constant temperature magnetic stirrer and stir it under certain temperature and speed conditions to obtain Ep liquid. Weigh polyethylene glycol (PEG) and add it to the Ep liquid and stir it to obtain Ep / PEG (EpP) solution. Weigh graphene oxide (GO), add it to the EpP solution and stir it for a certain time. After stirring evenly, transfer it to an ultrasonic disperser at a certain temperature for dispersion for a certain time, then transfer it to a constant temperature magnetic stirrer, and stir it again for a certain time to obtain Ep / PEG / GO (EPG) solution. Weigh the curing agent and add it to the EPG solution and stir it. After stirring for a certain time, transfer it to the PET release film and lay the film, then place it in a drying oven for heating treatment for a certain time, transfer it to room temperature and cool it to obtain a hardened EPG film.

[0008] (2) adding a curing agent to the Ep liquid obtained in step (1), and stirring for a period of time to obtain an Ep / curing agent mixed liquid;

[0009] (3) cutting the EPG film obtained in step (1) into EPG strips of a certain size, coating one side of the EPG strips with the Ep / curing agent mixture obtained in step (2) to obtain Ep / EPG (E / EPG) before curing;

[0010] (4) The Ep / EPG before hardening is placed in a drying oven for heating treatment under certain temperature conditions, and the hardened E / EPG is obtained after sufficient hardening and cooling at room temperature. The initial shape of the E / EPG obtained in this process is curved (curved E / EPG), which is recorded as bE / E; the Ep side of the obtained E / EPG before hardening is covered with a layer of non-stick paper (baking paper), and it is placed in a drying oven for heating treatment under certain temperature conditions, and the hardened E / EPG is obtained after sufficient hardening and cooling at room temperature. The initial shape of the E / EPG obtained in this process is straight (also called straight E / EPG), which is recorded as sE / E. Therefore, a bidirectionally responsive E / EPG dual-morphology shape memory composite film is obtained.

[0011] In the above step (1), the mass ratio of epoxy resin, polyethylene glycol and graphene oxide is 10:6:(0.1-0.5).

[0012] The polyethylene glycol in the above step (1) is polyethylene glycol 1000.

[0013] In the above step (1), the temperature of heating and stirring is 40-60°C, the speed of stirring is 200-400 r / min, and the temperature of ultrasonic dispersion is 50-60°C, the time is 0.5-1h.

[0014] In the above steps (1) and (2), the mass ratio of epoxy resin to curing agent is 100:33.

[0015] The above-mentioned curing agent is an amine curing agent, such as 273M type curing agent and the like.

[0016] In steps (1) and (4), heating refers to heating from room temperature to 90-100° C. at a heating rate of 7.5-15° C. / min and curing for 2-2.1 hours.

[0017] In the above step (4), the thickness ratio of the Ep layer to the EPG layer in the curved and straight E / EPG is 1:10.

[0018] The bidirectionally responsive E / EPG dual-morphology shape memory composite film is prepared using the above-mentioned preparation method.

[0019] Furthermore, the bidirectionally responsive E / EPG dual-morphology shape memory composite film has a curved or straight initial state, and the bidirectional response is achieved under thermal-optical dual stimulation.

[0020] The beneficial effects produced by the present invention are:

[0021] (1) The present invention not only improves the mechanical properties of the composite film material by introducing graphene oxide (GO), but also improves the thermal conductivity of the composite material, thereby achieving a higher thermal-optical dual stimulation bidirectional response sensitivity, so that the developed E / EPG composite material can respond and change shape faster when subjected to thermal-optical dual stimulation, achieving a higher thermal-optical dual stimulation bidirectional response sensitivity. Specifically, the bE / E prepared by the present invention can achieve a deformation of 34° within 50s by temperature increase stimulation, and recover a deformation of 32° within 50s by temperature reduction stimulation. In addition, bE / E can achieve a deformation of 19° within 20s by light stimulation, and recover a deformation of 18° within 25s by no light stimulation. The prepared sE / E can achieve a deformation of 30° within 50s by temperature increase stimulation, and recover a deformation of 28° within 35s by temperature reduction stimulation. In addition, sE / E can achieve a deformation of 16° within 20s by light stimulation, and recover a deformation of 15° within 25s by no light stimulation.

[0022] (2) The present invention uses the dispersion technology of PEG and GO to achieve efficient dispersion and uniform distribution of materials; the EPG hardening molding technology is used to optimize the mechanical properties and thermal response characteristics of the EPG layer; the EPG hardening-EP coating-composite hardening molding technology is used to achieve the synergistic effect of the EPG layer and the EP layer, ensuring that the composite film has excellent bidirectional response shape memory function under thermal-optical dual stimulation. Through the application of the above core technologies, a dual-morphology E / EPG film with two initial shapes, curved and straight, was prepared, and both of these two initial shape films showed a shape memory function of bidirectional response to thermal-optical dual stimulation during the heating-cooling process, which can meet the needs of more usage scenarios and modes.

[0023] (3) Compared with other shape memory polymers (SMPs), the SMEs involved in the present invention have the advantages of controllable dual initial morphology, dual stimulation mode (thermal-optical dual stimulation), bidirectional response effect (shape cycle under non-external mechanical action) and low cost (using industrial-grade epoxy resin and GO). BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 The figure is a flow chart for preparing the bidirectionally responsive E / EPG dual-morphological shape memory composite film of the present invention and the Ep film of comparative example 1; wherein, (a) is the EPG film preparation process; (b) is the bE / E film preparation process; (c) is the sE / E film preparation process; and (d) is the Ep film preparation process.

[0026] Figure 2 It is a bidirectional shape memory mechanism of bE / E.

[0027] Figure 3 It is the bidirectional shape memory mechanism of sE / E.

[0028] Figure 4 Stress-strain curves of EPG-1, EPG-3 and EPG-5.

[0029] Figure 5 Comparison of the shape response process of EPG-5 and EP under thermal stimulation conditions.

[0030] Figure 6 This is the bidirectional shape memory process of bE / G5 under room temperature-80℃-room temperature conditions.

[0031] Figure 7 These are the initial morphology, morphology after heating and morphology after cooling of bE / G5 under the conditions of room temperature-80℃-room temperature.

[0032] Figure 8 The angle change statistics of bE / G5 under the conditions of room temperature-80℃-room temperature.

[0033] Fig. 9 This is the bidirectional shape memory process of sE / E5 under room temperature-80℃-room temperature conditions.

[0034] Fig.10 These are the initial morphology, morphology after heating and morphology after cooling of sE / E5 under the conditions of room temperature-80℃-room temperature.

[0035] Fig.11 The angle change statistics of sE / E5 under the conditions of room temperature-80℃-room temperature.

[0036] Fig.12 This is the bidirectional shape memory process of bE / E5 under light stimulation conditions.

[0037] Fig.13 These are the initial morphology, morphology after illumination, and morphology after no illumination of bE / E5 under light stimulation conditions.

[0038] Fig.14 The angle change statistics of bE / E5 under light stimulation conditions.

[0039] Fig.15 This is the bidirectional shape memory process of sE / E5 under light stimulation conditions.

[0040] Fig.16 These are the initial morphology, morphology after illumination, and morphology after no illumination of sE / E5 under light stimulation conditions.

[0041] Fig.17 The angle change statistics of sE / E5 under light stimulation conditions. DETAILED DESCRIPTION

[0042] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] Example 1

[0044] The preparation method of the bidirectional responsive E / EPG dual-morphology shape memory composite film of this embodiment is as follows: Figure 1(ac) as described above, the steps are as follows:

[0045] (1) Add 6 g of PEG 1000 to 10 g of Ep liquid, stir for 5 min at 50 °C and 350 r / min, and stir until PEG is completely dissolved to obtain Ep / PEG (EpP) solution. Add 0.1 g of GO to the EpP solution, stir for 30 min at 50 °C and 350 r / min, transfer the uniformly stirred solution to an ultrasonic disperser at 50 °C and disperse for 1 h; transfer the completely dispersed solution to a constant temperature magnetic stirrer and stir for 30 min at 50 °C and 350 r / min to obtain EPG-1 solution. Add 3.3 g of curing agent (273M curing agent, purchased from Chuzhou Huisheng Electronic Materials Co., Ltd.) to the EPG-1 solution, stir for 30 min at 350 r / min, transfer to a PET release film and lay the film, and then place it in a drying oven for heating. The temperature of the drying oven was gradually increased from room temperature (25°C) to 100°C (at a heating rate of 15°C / min), and the drying process was carried out for 2 h. After cooling to room temperature, the hardened EPG-1 film (such as Figure 1 a).

[0046] (2) Add 3.3 g of curing agent (273M curing agent) to 10 g of Ep liquid in step (1), and stir for 5 min at a stirring speed of 350 r / min to obtain an Ep / curing agent mixed solution.

[0047] (3) The EPG-1 film in step (1) is cut into 8 mm × 80 mm EPG-1 strips, and the Ep / curing agent mixture is evenly coated on one side of the EPG-1 strip to obtain E / EPG-1 before hardening. The E / EPG-1 before hardening is placed in a drying oven for heating, and the temperature of the drying oven is gradually increased from room temperature 25°C to 100°C (heating rate is 15°C / min), and the heating and drying treatment is carried out for 2 hours. After cooling to room temperature, the hardened curved bE / E1 (such as Figure 1 b); Cover the Ep side of the E / EPG before hardening with a layer of non-stick paper, and repeat the above operation to obtain a straight sE / E1 after hardening (such as Figure 1 c). Thus, a bidirectionally responsive E / EPG dual-morphology (sE / E1, bE / E1) shape memory composite film was obtained. The film thicknesses of the Ep and EPG sides of the E / EPG dual-morphology (sE / E1, bE / E1) shape memory composite film were 0.1 mm and 1 mm, respectively.

[0048] Example 2

[0049] The preparation method of the bidirectionally responsive E / EPG dual-morphology shape memory composite film of this embodiment comprises the following steps:

[0050] (1) Add 6 g of PEG 1000 to 10 g of Ep liquid, stir for 5 min at 50 °C and 350 r / min, and stir until PEG is completely dissolved to obtain Ep / PEG (EpP) solution. Add 0.5 g of GO to the EpP solution, stir for 30 min at 50 °C and 350 r / min, transfer the uniformly stirred solution to an ultrasonic disperser at 50 °C and disperse for 1 h; transfer the completely dispersed solution to a constant temperature magnetic stirrer, stir for 30 min at 50 °C and 350 r / min, and obtain EPG-5 solution. Add 3.3 g of curing agent (273M curing agent) to the EPG-5 solution, stir for 30 min at 350 r / min, transfer to a PET release film and lay the film, and then place it in a drying oven for heating. The temperature of the drying oven was gradually increased from room temperature 25°C to 100°C (heating rate was 7.5°C / min), and the heating and drying treatment was performed for 2 hours. After being transferred to room temperature and cooled, a hardened EPG-5 film was obtained.

[0051] (2) Add 3.3 g of curing agent (273M curing agent) to 10 g of Ep liquid in step (1), and stir for 5 min at a stirring speed of 350 r / min to obtain an Ep / curing agent mixed solution.

[0052] (3) Cut the EPG-5 film in step (1) into 8mm×80mm EPG-5 strips, and evenly apply the Ep / curing agent mixture on one side of the EPG-5 strip to obtain the E / EPG-5 before hardening. Place the E / EPG-1 before hardening in a drying oven for heating, and gradually increase the temperature of the drying oven from room temperature 25°C to 100°C (heating rate of 15°C / min), heat and dry for 2 hours, and obtain the hardened curved bE / E5 after cooling to room temperature; cover the Ep side of the E / EPG before hardening with a layer of non-stick paper, and repeat the above operation to obtain the hardened straight sE / E5. Thus, a bidirectionally responsive E / EPG dual-morphology (sE / E5, bE / E5) shape memory composite film is obtained. The film thicknesses of the Ep and EPG sides of the E / EPG dual-morphology (sE / E5, bE / E5) shape memory composite film are 0.1mm and 1mm, respectively.

[0053] Example 3

[0054] The preparation method of the bidirectionally responsive E / EPG dual-morphology shape memory composite film of this embodiment comprises the following steps:

[0055] (1) Add 6 g of PEG 1000 to 10 g of Ep liquid, stir for 5 min at 50 °C and 350 r / min, and stir until PEG is completely dissolved to obtain Ep / PEG (EpP) solution. Add 0.3 g of GO to the EpP solution, stir for 30 min at 50 °C and 350 r / min, transfer the uniformly stirred solution to an ultrasonic disperser at 50 °C and disperse for 1 h; transfer the completely dispersed solution to a constant temperature magnetic stirrer, stir for 30 min at 50 °C and 350 r / min, and obtain EPG-3 solution. Add 3.3 g of curing agent (273M curing agent) to the EPG-3 solution, stir for 30 min at 350 r / min, transfer to a PET release film and lay the film, and then place it in a drying oven for heating. The temperature of the drying oven was gradually increased from room temperature 25°C to 100°C (heating rate was 10°C / min), and the heating and drying treatment was performed for 2 hours. After being transferred to room temperature and cooled, a hardened EPG-3 film was obtained.

[0056] (2) Add 3.3 g of curing agent (273M curing agent) to 10 g of Ep liquid in step (1), and stir for 5 min at a stirring speed of 350 r / min to obtain an Ep / curing agent mixed solution.

[0057] (3) Cut the EPG-3 film in step (1) into 8mm×80mm EPG-3 strips, and evenly coat the Ep / curing agent mixture on one side of the EPG-3 strip to obtain the E / EPG-3 before hardening. Place the E / EPG-1 before hardening in a drying oven for heating, and gradually increase the temperature of the drying oven from room temperature 25°C to 100°C (heating rate of 10°C / min), heat and dry for 2 hours, and obtain the hardened curved bE / E3 after cooling to room temperature; cover the Ep side of the E / EPG before hardening with a layer of non-stick paper, and repeat the above operation to obtain the hardened straight sE / E3. Thus, a bidirectionally responsive E / EPG dual-morphology (sE / E3, bE / E3) shape memory composite film is obtained. The film thicknesses of the Ep and EPG sides of the E / EPG dual-morphology (sE / E3, bE / E3) shape memory composite film are 0.1mm and 1mm, respectively.

[0058] Example 4

[0059] The preparation method of the bidirectionally responsive E / EPG dual-morphology shape memory composite film of this embodiment comprises the following steps:

[0060] (1) Add 6 g of PEG 1000 to 10 g of Ep liquid, stir at 60 ° C and 400 r / min for 5 min, stir until PEG is completely dissolved, and obtain Ep / PEG (EpP) solution. Add 0.5 g of GO to the EpP solution, stir at 60 ° C and 400 r / min for 30 min, transfer the uniformly stirred solution to an ultrasonic disperser at 50 ° C for 1 h; transfer the completely dispersed solution to a constant temperature magnetic stirrer, stir at 60 ° C and 400 r / min for 30 min, and obtain EPG-5 solution. Add 3.3 g of curing agent (273M curing agent) to the EPG-5 solution, stir at 400 r / min for 30 min, transfer to a PET release film and lay the film, and then place it in a drying oven for heating. The temperature of the drying oven was gradually increased from room temperature 25°C to 90°C (heating rate was 7.5°C / min), and the heating and drying treatment was carried out for 2.1 hours. After being transferred to room temperature and cooled, a hardened EPG-5 film was obtained.

[0061] (2) Add 3.3 g of curing agent (273M curing agent) to 10 g of Ep liquid in step (1), and stir for 5 min at a stirring speed of 350 r / min to obtain an Ep / curing agent mixed solution.

[0062] (3) The EPG-5 film in step (1) is cut into 8mm×80mm EPG-5 strips, and the Ep / curing agent mixture is evenly coated on one side of the EPG-5 strip to obtain the E / EPG-5 before hardening. The E / EPG-1 before hardening is placed in a drying oven for heating, and the temperature of the drying oven is gradually increased from room temperature 25°C to 90°C (heating rate is 15°C / min), and the heating and drying treatment is carried out for 2.1 hours. After cooling to room temperature, the curved bE / E5 after hardening is obtained; the Ep side of the E / EPG before hardening is covered with a layer of non-stick paper, and the above operation is repeated to obtain the straight sE / E5 after hardening. Thus, a bidirectionally responsive E / EPG dual-morphology (sE / E5, bE / E5) shape memory composite film is obtained. The film thicknesses of the Ep and EPG sides of the E / EPG dual-morphology (sE / E5, bE / E5) shape memory composite film are 0.1mm and 1mm respectively.

[0063] Example 5

[0064] The preparation method of the bidirectionally responsive E / EPG dual-morphology shape memory composite film of this embodiment comprises the following steps:

[0065] (1) Add 6 g of PEG 1000 to 10 g of Ep liquid, stir for 5 min at 40 °C and 200 r / min, and stir until PEG is completely dissolved to obtain Ep / PEG (EpP) solution. Add 0.5 g of GO to the EpP solution, stir for 30 min at 40 °C and 200 r / min, transfer the uniformly stirred solution to an ultrasonic disperser at 60 °C and disperse for 0.5 h; transfer the completely dispersed solution to a constant temperature magnetic stirrer, stir for 30 min at 40 °C and 200 r / min, and obtain EPG-5 solution. Add 3.3 g of curing agent (273M curing agent) to the EPG-5 solution, stir for 30 min at 200 r / min, transfer to a PET release film and lay the film, and then place it in a drying oven for heating. The temperature of the drying oven was gradually increased from room temperature 25°C to 90°C (heating rate was 7.5°C / min), and the heating and drying treatment was performed for 2 hours. After being transferred to room temperature and cooled, a hardened EPG-5 film was obtained.

[0066] (2) Add 3.3 g of curing agent (273M curing agent) to 10 g of Ep liquid in step (1), and stir for 5 min at a stirring speed of 350 r / min to obtain an Ep / curing agent mixed solution.

[0067] (3) The EPG-5 film in step (1) is cut into 8mm×80mm EPG-5 strips, and the Ep / curing agent mixture is evenly coated on one side of the EPG-5 strip to obtain the E / EPG-5 before hardening. The E / EPG-1 before hardening is placed in a drying oven for heating, and the temperature of the drying oven is gradually increased from room temperature 25°C to 90°C (heating rate is 15°C / min), and the heating and drying treatment is carried out for 2.1 hours. After cooling to room temperature, the curved bE / E5 after hardening is obtained; the Ep side of the E / EPG before hardening is covered with a layer of non-stick paper, and the above operation is repeated to obtain the straight sE / E5 after hardening. Thus, a bidirectionally responsive E / EPG dual-morphology (sE / E5, bE / E5) shape memory composite film is obtained. The film thicknesses of the Ep and EPG sides of the E / EPG dual-morphology (sE / E5, bE / E5) shape memory composite film are 0.1mm and 1mm respectively.

[0068] Comparative Example 1

[0069] The preparation method of the Ep film of this comparative example (such as Figure 1 d), the steps are as follows:

[0070] Add 3.3g of curing agent (273M type curing agent) to 10g of Ep liquid, stir for 5min at a stirring speed of 350r / min to obtain an Ep / curing agent mixed liquid. Transfer the obtained Ep / curing liquid mixture to a PET release film and lay the film, then place it in a drying oven for heating. The drying oven temperature is gradually increased from room temperature 25℃ to 100℃, heated and dried for 2h, and transferred to room temperature for cooling to obtain a hardened Ep film.

[0071] Implementation effect example

[0072] The preparation process of the EPG film of the present invention is as follows Figure 1 As shown in a, the present invention regulates the performance difference between EPG and Ep by Ep, PEG and GO, and prepares the EPG film by using the dispersion technology of PEG and GO and the EPG hardening molding technology. On the basis of the single-layer EPG film, the Ep coating and composite hardening treatment are innovatively carried out in sequence to form the final dual-morphology E / EPG composite film. During the temperature change process, the molecular motion state inside the E / EPG changes accordingly, thereby affecting its macroscopic morphology and achieving the function of shape switching.

[0073] The introduction of GO optimizes the rigidity, strength and ductility of the E / EPG composite membrane material. Figure 4Table 1 and Table 1 are respectively the stress-strain curves and stress-strain statistical results of EPG-1, EPG-3 and EPG-5 prepared in Examples 1-3 of the present invention, and it can be seen that with the increase of GO content, the elastic modulus of the E / EPG composite film is gradually increased from 0.46MPa of EPG-1 to 0.85MPa of EPG-5, and this change shows that the deformation resistance of the material is significantly enhanced. This improvement is mainly due to the high specific surface area and excellent mechanical properties of GO, which constructs a multi-level reinforcement network in the polymer matrix, effectively shares the applied load, and improves the rigidity and bearing capacity of the material. The yield stress of EPG-5 reaches 0.91MPa, which is significantly improved compared with EPG-1 and EPG-3, indicating that the material has better resistance to plastic deformation when subjected to high stress. This enhancement is not only reflected in the initial stress-strain response of the material, but also in the optimization of the internal structure. The introduction of GO enables the material to transfer stress more evenly when stressed, avoids local stress concentration, and thus delays the appearance of plastic deformation. In terms of ductility, the introduction of GO also performs well. The fracture strains of EPG-1, EPG-3 and EPG-5 are all higher than 440%, which indicates that the materials can withstand great deformation before fracture and show excellent toughness. The strong interface between the GO lamellar structure and the polymer matrix enables the composite film to effectively absorb energy during the stretching process and delay the occurrence of fracture, thereby achieving a significant improvement in ductility without sacrificing rigidity and strength. It is worth noting that although the yield stress (maximum tensile stress) of EPG-1, EPG-3 and EPG-5 is low, their extremely high fracture strain indicates that the introduction of GO improves the interfacial bonding properties of the material. The GO flakes play a bridging role in the polymer matrix, enhancing the interaction between the matrix and the filler, so that the material exhibits higher stability and deformation ability under dynamic loads.

[0074] Table 1 Stress-strain curves of EPG-1, EPG-3 and EPG-5

[0075]

[0076] The shape memory mechanism of bE / E5 is as follows Figure 2 As shown in Figure 2, during the composite hardening process, the EPG in bE / E5 is fully bent due to the hardening of Ep. When the temperature rises to the glass transition temperature (T g ) and above, the molecular chains in EPG tend to expand due to thermal motion, which makes bE / E5 gradually change from bending to straight. When the temperature decreases, the expansion tendency of EPG gradually decreases, Ep gradually recovers elasticity, which makes bE / E5 gradually change from straight to curved. Figure 5This is a comparison of the shape response processes of EPG-5 and EP under thermal stimulation conditions. From the figure, we can see the difference in the response of Ep and EPG-5 during the heating process, which provides a basis for constructing bE / E5 and sE / E5 with bidirectional shape memory function.

[0077] Figure 6-Figure 8 The shape memory process of bE / E5 from room temperature to 80℃ and then to room temperature, and the initial angle, temporary angle, angle after recovery, and angle change statistics are shown. It can be seen from the figure that during the heating process from room temperature to 80℃, bE / E5 can achieve a deformation of 34° within 50s through heating stimulation. During the cooling process from 80℃ to room temperature, bE / E5 can recover a deformation of 32° within 50s through cooling stimulation.

[0078] The shape memory mechanism of sE / E5 is as follows Figure 3 As shown in Figure 2, during the composite hardening process, the EPG in sE / E5 was not fully bent due to the limitation of non-sticking paper. When the temperature was raised to T g When the temperature drops to 0.04°C or above, the molecular chains in EPG tend to shrink due to thermal motion, causing sE / E5 to gradually change from straight to curved. When the temperature drops, the shrinkage trend of EPG gradually decreases, and Ep gradually recovers elasticity, causing sE / E5 to gradually change from curved to straight. Through process control, the developed E / EPG realizes the dual-morphology thermal-optical dual-stimulation bidirectional response shape memory function based on the performance difference between EPG and Ep, showing great application potential in the fields of flexible actuators, soft robots, and smart clothing. Figure 9-11 The shape memory process of sE / E5 from room temperature to 80℃ and then to room temperature, and the initial angle, temporary angle, angle after recovery, and angle change statistics are shown. It can be seen from the figure that during the heating process from room temperature to 80℃, sE / E5 can achieve a deformation of 30° within 50s through heating stimulation. During the cooling process from 80℃ to room temperature, sE / E5 can recover a deformation of 28° within 35s through cooling stimulation. In short, the developed bE / E and sE / E show excellent bidirectional shape memory function under thermal stimulation conditions.

[0079] Fig.12 and Fig.13 The light-stimulated shape memory process and result statistics of bE / E are shown respectively. During illumination, the developed bE / E can achieve a deformation of 19° within 20s through light stimulation. After stopping the illumination, the developed bE / E can recover a deformation of 18° within 25s through no light stimulation. Fig.14 The angle changes of bE / E during light-stimulated shape memory were statistically analyzed. In conclusion, the developed bE / E showed excellent bidirectional shape memory function under light-stimulated conditions.

[0080] Fig.15 and Fig.16 The light-stimulated shape memory process and result statistics of sE / E are shown respectively. During illumination, the developed sE / E can achieve a deformation of 16° within 20s through light stimulation. After stopping the illumination, the developed bE / E can recover a deformation of 15° within 25s through no light stimulation. Fig.17 The angle changes of sE / E during light-stimulated shape memory were statistically analyzed.In conclusion, the developed sE / E showed excellent bidirectional shape memory function under light-stimulated conditions.

[0081] The introduction of GO plays a key role in optimizing the mechanical properties of the E / EPG composite film, significantly improving the rigidity, strength and ductility of the material. By optimizing the dispersion and interface interaction of GO, the E / EPG composite film has excellent ductility and toughness while maintaining high strength, showing excellent comprehensive mechanical properties. This optimization not only improves the mechanical properties of the material, but also enhances its bidirectional response ability under thermal-optical dual stimulation, giving it broad application prospects in the fields of flexible actuators, soft robots, and intelligent response unit structures.

[0082] The present invention not only explains its basic principles, core characteristics and advantages, but also demonstrates its openness and scalability. Those skilled in the art should realize that the present invention is not limited to the specific embodiments described, but allows innovation and improvement without deviating from its main purpose and core scope, and its scope of protection is defined by the attached claims and their equivalents. The design concept of the present invention takes into account the diversity of practical applications. By adjusting the material ratio, optimizing the process parameters or introducing other functional components, its application scenarios and performance boundaries can be further expanded. For example, in the field of flexible electronic devices, the introduction of other nanomaterials or functional polymers can improve the conductivity, thermal stability or environmental adaptability of the composite film; in the intelligent response system, combined with stimulus response mechanisms such as humidity or magnetic response, more complex multimodal driving functions can be achieved.

[0083] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a bidirectionally responsive E / EPG dual-morphology shape memory composite film, characterized in that: Here are the steps: (1) under heating and stirring conditions, polyethylene glycol is added to the epoxy resin, and then graphene oxide is added, stirred and ultrasonically dispersed uniformly, and then a curing agent is added, and after film laying, heating, sufficient hardening and cooling, an Ep / PEG / GO membrane, i.e., an EPG membrane, is obtained; (2) adding a curing agent to the epoxy resin and stirring evenly to obtain an EP / curing agent mixed solution; (3) Cut the EPG film and apply the Ep / curing agent mixture on one side to obtain the Ep / EPG before curing; (4) heating the Ep / EPG before hardening, fully hardening and cooling to obtain a curved E / EPG; and covering the Ep side of the Ep / EPG before hardening with a layer of non-stick paper, and then heating, fully hardening and cooling to obtain a straight E / EPG; the curved and straight E / EPG are the E / EPG dual-morphological shape memory composite film with bidirectional response.

2. The method for preparing the bidirectionally responsive E / EPG dual-morphology shape memory composite film according to claim 1, characterized in that: In the step (1), the mass ratio of epoxy resin, polyethylene glycol and graphene oxide is 10:6:(0.1-0.5).

3. The method for preparing the bidirectionally responsive E / EPG dual-morphology shape memory composite film according to claim 1 or 2, characterized in that: The polyethylene glycol in step (1) is polyethylene glycol 1000.

4. The method for preparing the bidirectionally responsive E / EPG dual-morphology shape memory composite film according to claim 3, characterized in that: The heating and stirring temperature in step (1) is 40-60° C., and the stirring speed is 200-400 r / min.

5. The method for preparing the bidirectionally responsive E / EPG dual-morphology shape memory composite film according to claim 4, characterized in that: The mass ratio of epoxy resin to curing agent in steps (1) and (2) is 100:

33.

6. The method for preparing the bidirectionally responsive E / EPG dual-morphology shape memory composite film according to claim 5, characterized in that: The curing agent is an amine curing agent.

7. The method for preparing the bidirectionally responsive E / EPG dual-morphology shape memory composite film according to claim 6, characterized in that: The heating refers to heating from room temperature to 90-100° C. at a heating rate of 7.5-15° C. / min and curing for 2-2.1 hours.

8. The method for preparing the bidirectionally responsive E / EPG dual-morphology shape memory composite film according to claim 7, characterized in that: In the step (4), the thickness ratio of the Ep layer to the EPG layer in the curved and straight E / EPG is 1:

10.

9. A bidirectionally responsive E / EPG dual-morphology shape memory composite film prepared by the preparation method according to any one of claims 1 or 2 or 4 to 8.

10. The bidirectionally responsive E / EPG dual-morphology shape memory composite film according to claim 9, characterized in that: The bidirectionally responsive E / EPG dual-morphology shape memory composite film has a curved or straight initial state, and the bidirectional response is achieved under thermal-optical dual stimulation.

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