Novel temperature-driven bidirectional deformation response shape memory polymer

Abstract

The invention discloses a novel temperature-driven bidirectional deformation response shape memory polymer, and relates to the technical field of intelligent driving, a preparation method of the shape memory polymer comprises the following steps: sequentially stacking and arranging a polyacrylonitrile composite fabric, a shape memory functional layer film, a carbon fiber felt and an oriented graphene fiber film, and performing hot pressing by using a hot press to obtain the shape memory polymer. By introducing a polyethylene vinyl acetate copolymer matrix with high vinyl acetate content, a structural basis is provided for bidirectional deformation, temperature-driven bidirectional reversible deformation and multi-cycle repeated deformation capability are realized, and the flexibility of the material is improved.

Description

Technical Field

[0001] This invention relates to the field of intelligent drive technology, specifically to a novel temperature-driven bidirectional deformation-responsive shape memory polymer. Background Technology

[0002] Shape memory polymer materials, as a class of intelligent stimulus-responsive materials, can change shape in response to changes in external conditions, and are widely used in fields such as flexible robots, artificial muscles, and smart wearable devices. The shape memory effect is divided into unidirectional and bidirectional types. The unidirectional shape memory effect is relatively simple, only remembering a shape change once under external stimulus, which limits its application in fields such as actuators and artificial intelligence.

[0003] Compared to unidirectional shape memory polymers, bidirectional shape memory polymers can reversibly transform between the original shape and the temporary shape, achieving continuous deformation cycles without external intervention.

[0004] Patent CN109705313B discloses a thermally adaptable shape memory polymer and its application method. The above patent realizes the self-unfolding and self-folding function under heating stimulation conditions, which greatly improves the applicability of shape memory polymer.

[0005] The aforementioned patent has the advantage of being able to arbitrarily change its initial shape, and can change from a simple two-dimensional planar initial shape to a new three-dimensional permanent shape, solving the problem that traditional cross-linked polymers cannot be reprocessed after molding. However, there is still room for optimization in terms of bidirectional shape memory effect. This application solves the problem of limitations in traditional unidirectional shape memory polymers.

[0006] To this end, this application proposes a novel temperature-driven bidirectional deformation-responsive shape memory polymer that achieves bidirectional reversible deformation in response to multiple stimuli. Summary of the Invention

[0007] The purpose of this invention is to provide a novel temperature-driven bidirectional deformation-responsive shape memory polymer to solve the technical problems of the limitations of traditional unidirectional shape memory polymers mentioned in the background art.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a novel temperature-driven bidirectional deformation-responsive shape memory polymer, wherein the preparation method of the shape memory polymer includes the following steps:

[0009] S1. 20 g of polyethylene vinyl acetate copolymer with a vinyl acetate content of 40 wt% and 12 wt% benzamide peroxide are fed into a twin-screw extruder, melt-mixed and extruded and granulated. The melt temperature is 90℃-100℃ to obtain the blend extrudate.

[0010] S2. After the blended extrudate is cooled to room temperature, it is hot-pressed using a hot press at a temperature of 130 ℃, a pressure of 10 MPa, and a pressing time of 20 min to obtain a shape memory functional layer film.

[0011] S3. The polyacrylonitrile composite fabric, shape memory functional layer film, carbon fiber felt, and oriented graphene fiber film are sequentially stacked and hot-pressed for 30 minutes using a hot press to obtain the shape memory polymer.

[0012] Preferably, the polymer polyethylene vinyl acetate has an average number-average molecular weight of 2000 and the polymer benzoyl peroxide has an average number-average molecular weight of 242.23.

[0013] Preferably, step S3 further includes the preparation of a polyacrylonitrile composite fabric, the preparation method of which includes the following steps:

[0014] S31. Pour the flame retardant material into N,N-dimethylformamide to obtain a dispersion, and dissolve polyacrylonitrile in N,N-dimethylformamide to obtain a polyacrylonitrile solution;

[0015] S32. The polyacrylonitrile solution is ultrasonically stirred and the dispersion is slowly added dropwise. The solution is degassed under vacuum at 60°C for 60 min to obtain the spinning solution. The spinning solution is loaded into a syringe and electrospinned. A voltage of 20 kV is applied, the distance between the needle and the receiver is 10 cm, and the injection speed is 1 mL / h to obtain the polyacrylonitrile fabric.

[0016] S33. Add silane coupling agent to 0.25wt% acetic acid solution, stir with a magnetic stirrer to obtain modified solution, immerse polyacrylonitrile fabric in modified solution for 30 min, and dry in oven for 1.5 h to obtain modified fabric.

[0017] S34. Copper sulfate pentahydrate and sodium persulfate pentahydrate are poured into deionized water to obtain a mixed solution. The modified fabric is immersed in the mixed solution and heated in a water bath at 90°C for 120 minutes. After washing and drying, polyacrylonitrile composite fabric is obtained.

[0018] Preferably, the mass ratio of the polyacrylonitrile to the flame retardant material is 10:0.1-10:0.5.

[0019] Preferably, the mass ratio of the acetic acid solution to the silane coupling agent is 100:0.05-100:0.5.

[0020] Preferably, step S31 further includes the preparation of a flame-retardant material, and the method for preparing the flame-retardant material includes the following steps:

[0021] Step 1: Pour molybdenum disulfide powder into a reaction vessel containing 2wt% polyionic liquid aqueous solution, place the reaction vessel in an ice bath, and perform ultrasonic dispersion for 120 min. Then, process the mixture using a high-speed refrigerated centrifuge for 30 min at a speed of 6000 rpm / min, and collect the upper suspension.

[0022] Step 2: Transfer the upper suspension to a high-speed refrigerated centrifuge and centrifuge for 30 minutes at a speed of 12,000 rpm / min. Collect the precipitate, ultrasonically wash the precipitate, and freeze-dry it at -50℃ for 24 hours to obtain the flame retardant material.

[0023] Preferably, the method for preparing the polyionic liquid aqueous solution includes the following steps:

[0024] The ionic liquid monomer and azobisisobutyronitrile were poured into N,N-dimethylformamide for deoxygenation treatment to obtain a reaction solution. The reaction solution was placed in an oil bath at 70°C and reacted under a nitrogen atmosphere for 24 hours.

[0025] After cooling to room temperature, tetrahydrofuran was added dropwise. The precipitate was collected and washed with ethanol. The precipitate was dried at 60°C for 8 hours using a vacuum drying oven to obtain a solid powder. The solid powder was dissolved in deionized water to obtain a polyionic liquid aqueous solution.

[0026] Preferably, the mass ratio of the ionic liquid monomer to azobisisobutyronitrile is 50:1, and the ionic liquid monomer is 1-carboxymethyl-3-vinylimidazole bromide.

[0027] Preferably, step S3 further includes:

[0028] The graphene oxide slurry was loaded into a syringe, and anhydrous calcium chloride was used as a coagulation bath. The injection rate was 1 mL / h to obtain graphene fibers that were uniformly wound on the take-up tube. The fibers were washed with ethanol solution and vacuum dried at 50 °C for 6 h to obtain a graphene oxide fiber membrane.

[0029] The graphene oxide fiber membrane was immersed in hydroiodic acid for 12 hours and then washed to obtain an oriented graphene fiber membrane.

[0030] Preferably, in step S3, the hot pressing temperature of the hot press is 100 ℃ and the pressure is 10 MPa.

[0031] Compared with the prior art, the beneficial effects of the present invention are:

[0032] 1. This invention introduces a polyethylene vinyl acetate copolymer matrix with high vinyl acetate content, providing a structural basis for bidirectional deformation, realizing temperature-driven bidirectional reversible deformation and multi-cycle repeatable deformation capability, thereby improving the flexibility of the material.

[0033] 2. This invention improves the overall mechanical strength by combining polyacrylonitrile composite fabric and shape memory functional layer film, and loads copper sulfide particles on the surface of polyacrylonitrile fabric to realize the functions of photothermal and electrothermal conversion, and realizes multiple stimulus response.

[0034] 3. This invention improves the flame retardant properties of shape memory polymers by introducing flame retardant materials into polyacrylonitrile composite fabrics, thereby preventing the spread and diffusion of combustion, reducing the generation of toxic gases, and improving the safety of the material during use.

[0035] 4. This invention, through the design of introducing carbon fiber felt and oriented graphene fiber membrane, further ensures the electrothermal conversion function of shape memory polymer, improves the overall mechanical properties of shape memory polymer, and realizes rapid response of shape memory. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the shape memory polymer preparation process of the present invention;

[0037] Figure 2 This is a schematic diagram of the polyacrylonitrile fabric preparation process of the present invention;

[0038] Figure 3 This is a schematic diagram of the modified fabric preparation process of the present invention;

[0039] Figure 4 This is a schematic diagram of the polyacrylonitrile composite fabric preparation process of the present invention;

[0040] Figure 5 This is a schematic diagram of the flame-retardant material preparation process of the present invention;

[0041] Figure 6 This is a schematic diagram of the preparation process of the polyionic liquid aqueous solution of the present invention;

[0042] Figure 7 This is a schematic diagram of the preparation process of the graphene oxide fiber membrane of the present invention;

[0043] Figure 8 This is a schematic diagram of the oriented graphene fiber membrane preparation process of the present invention. Detailed Implementation

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] Example 1, please refer to Figure 1A novel temperature-driven bidirectional deformation-responsive shape memory polymer, the preparation method of which includes the following steps:

[0046] 20 g of polyethylene vinyl acetate copolymer with a vinyl acetate content of 40 wt% and 12 wt% benzamide peroxide were fed into a twin-screw extruder, melt-mixed and extruded and granulated at a melt temperature of 100 ℃ to obtain a blend extrudate.

[0047] After the blend extrudate was cooled to room temperature, it was hot-pressed using a hot press at a temperature of 130 ℃, a pressure of 10 MPa, and a pressing time of 20 min to obtain a shape memory functional layer film.

[0048] Flame retardant material and polyacrylonitrile were dissolved in N,N-dimethylformamide to obtain a dispersion and a polyacrylonitrile solution, respectively. The polyacrylonitrile solution was ultrasonically stirred, and the dispersion was slowly added dropwise. Vacuum degassing was performed at 60°C for 60 min to obtain a spinning solution. The mass ratio of polyacrylonitrile to flame retardant material was 10:0.5. The spinning solution was loaded into a syringe for electrospinning. A voltage of 20 kV was applied, the distance between the needle and receiver was 10 cm, and the injection rate was 1 mL / h, resulting in a polyacrylonitrile fabric. (The last sentence appears to be incomplete and possibly refers to a specific product or process.) A silane coupling agent was added to a % acetic acid solution at a mass ratio of 100:0.5. The mixture was stirred with a magnetic stirrer to obtain a modified solution. Polyacrylonitrile fabric was immersed in the modified solution for 30 minutes and then dried in an oven for 1.5 hours to obtain the modified fabric. Copper sulfate pentahydrate and sodium persulfate pentahydrate were added to deionized water to obtain a mixed solution. The modified fabric was immersed in the mixed solution and heated in a water bath at 90°C for 120 minutes. After washing and drying, polyacrylonitrile composite fabric was obtained.

[0049] Polyacrylonitrile composite fabric, shape memory functional layer film, carbon fiber felt, and oriented graphene fiber film are sequentially stacked and hot-pressed for 30 minutes to obtain shape memory polymer.

[0050] Furthermore, a polyethylene vinyl acetate copolymer with a vinyl acetate content of 40 wt% was used as the matrix material, and benzamide peroxide was selected as the initiator. The high vinyl acetate content endowed the material with high flexibility, transparency, and viscoelasticity. The increase in the high vinyl acetate content significantly improved the flexibility of the polyethylene vinyl acetate copolymer molecular chains, enabling the ethylene segments and vinyl acetate segments of the polyethylene vinyl acetate copolymer to form a microphase separation structure. The polyethylene vinyl acetate copolymer molecular chains were connected through a thermal crosslinking reaction, thereby forming a stable network crosslinked molecular network structure. Through the network crosslinked molecular network structure, the shape memory functional layer film can undergo shape changes when stimulated by temperature.

[0051] As the temperature rises, the interaction forces between molecular chains gradually weaken, and the crystalline phase of the ethylene segments in the shape memory functional layer film melts. The shape memory functional layer film becomes soft and easily deformable, at which point the shape memory polymer can be shaped into the desired shape by applying external force. When the temperature decreases, the interaction forces between molecular chains strengthen again, and the shape memory functional layer film recrystallizes, becoming hard again and returning to its original shape. When the shape memory polymer is subjected to temperature stimulation, it can transform from one shape to another, and when the temperature decreases, it can return to its original shape again. Through reversible shape changes that can be repeated in multiple cycles, the function of reversible bidirectional shape changes with temperature changes is realized, solving the problem of traditional unidirectional recovery and greatly improving the application flexibility and practicality of the material.

[0052] Example 2, please refer to Figure 1 , Figure 2 , Figure 3 and Figure 4 A novel temperature-driven bidirectional deformation-responsive shape memory polymer, the preparation method of which includes the following steps:

[0053] 20 g of polyethylene vinyl acetate copolymer with a vinyl acetate content of 40 wt% and 12 wt% benzamide peroxide were fed into a twin-screw extruder, melt-mixed and extruded and granulated at a melt temperature of 100 ℃ to obtain a blend extrudate.

[0054] After the blend extrudate was cooled to room temperature, it was hot-pressed using a hot press at a temperature of 130 ℃, a pressure of 10 MPa, and a pressing time of 20 min to obtain a shape memory functional layer film.

[0055] Flame retardant material and polyacrylonitrile were dissolved in N,N-dimethylformamide to obtain a dispersion and a polyacrylonitrile solution, respectively. The dispersion was slowly added dropwise to the polyacrylonitrile solution to obtain a spinning solution. The mass ratio of polyacrylonitrile to flame retardant material was 10:0.4. Electrospinning was performed to obtain polyacrylonitrile fabric. A silane coupling agent was added to a 0.25wt% acetic acid solution. The mass ratio of acetic acid solution to silane coupling agent was 100:0.4 to obtain a modification solution. The polyacrylonitrile fabric was immersed in the modification solution to obtain a modified fabric. Copper sulfate pentahydrate and sodium persulfate pentahydrate were poured into deionized water to obtain a mixed solution. The modified fabric was immersed in the mixed solution to obtain a polyacrylonitrile composite fabric.

[0056] Polyacrylonitrile composite fabric, shape memory functional layer film, carbon fiber felt, and oriented graphene fiber film are sequentially stacked and hot-pressed for 30 minutes using a hot press to obtain shape memory polymer.

[0057] Furthermore, polyacrylonitrile fabrics are modified with silane coupling agents to increase the interaction forces between fibers and improve the mechanical strength of the fabrics. Copper sulfide particles are uniformly distributed on the surface of the polyacrylonitrile fabric using a chemical water bath deposition method, forming a conductive network. These copper sulfide particles exhibit excellent photothermal conversion properties in the near-infrared region. When the material is exposed to a near-infrared light source, the copper sulfide particles absorb light energy and convert it into heat energy, thereby increasing the local temperature of the material. By combining the polyacrylonitrile composite fabric with a shape memory functional layer film, when the shape memory polymer is irradiated by a near-infrared light source, the copper sulfide particles absorb photon energy, and electrons transition from the valence band to the conduction band. Subsequently, the energy is converted into heat energy through a non-radiative relaxation process. The generated heat is transferred to the shape memory functional layer film, causing the molecular chain segments of the shape memory functional layer film to move, thus triggering the shape memory effect. This allows the shape memory polymer to deform under light irradiation.

[0058] Simultaneously, under the action of an applied voltage, a current is generated inside the polyacrylonitrile composite fabric loaded with copper sulfide particles. Due to the resistivity of the fabric, Joule heating is generated when the current passes through, thereby raising the temperature of the shape memory functional layer film, thus triggering the shape memory effect and realizing the electrically driven shape memory function. The polyacrylonitrile composite fabric loaded with copper sulfide particles on its surface provides photothermal and electrothermal conversion functions in the shape memory polymer composite material, while the fabric significantly enhances the mechanical properties of the shape memory polymer. By precisely controlling the light source or voltage, remote, non-contact shape memory control of the shape memory polymer can be realized.

[0059] Example 3, please refer to Figure 1 , Figure 5 and Figure 6 A novel temperature-driven bidirectional deformation-responsive shape memory polymer, the preparation method of which includes the following steps:

[0060] 20 g of a polyethylene vinyl acetate copolymer with a vinyl acetate content of 40 wt% and 12 wt% benzamide peroxide were fed into a twin-screw extruder, melt-mixed and extruded and granulated at a melt temperature of 95 ℃ to obtain a blend extrudate.

[0061] After the blend extrudate was cooled to room temperature, it was hot-pressed using a hot press at a temperature of 130 ℃, a pressure of 10 MPa, and a pressing time of 20 min to obtain a shape memory functional layer film.

[0062] Molybdenum disulfide powder was poured into a reaction vessel containing a 2wt% polyionic liquid aqueous solution. The reaction vessel was placed in an ice bath and ultrasonically dispersed for 120 min. Then, it was centrifuged using a high-speed refrigerated centrifuge for 30 min at a speed of 6000 rpm / min. The supernatant was collected and transferred to a high-speed refrigerated centrifuge for centrifugation for 30 min at a speed of 12000 rpm / min. The precipitate was collected, ultrasonically washed, and freeze-dried at -50℃ for 24 h to obtain the flame retardant material.

[0063] Flame retardant material and polyacrylonitrile were dissolved in N,N-dimethylformamide to obtain a dispersion and a polyacrylonitrile solution, respectively. The dispersion was slowly added dropwise to the polyacrylonitrile solution to obtain a spinning solution. The mass ratio of polyacrylonitrile to flame retardant material was 10:0.3. Electrospinning was performed to obtain polyacrylonitrile fabric. A silane coupling agent was added to a 0.25wt% acetic acid solution. The mass ratio of acetic acid solution to silane coupling agent was 100:0.3 to obtain a modification solution. The polyacrylonitrile fabric was immersed in the modification solution to obtain a modified fabric. The modified fabric was immersed in a mixed solution to obtain a polyacrylonitrile composite fabric.

[0064] Polyacrylonitrile composite fabric, shape memory functional layer film, carbon fiber felt, and oriented graphene fiber film are sequentially stacked and hot-pressed for 30 minutes using a hot press to obtain shape memory polymer.

[0065] Furthermore, molybdenum disulfide powder was combined with a polyionic liquid to prepare functionalized molybdenum disulfide nanosheets. These functionalized nanosheets were then added to polyacrylonitrile fibers as a flame retardant. The functionalized molybdenum disulfide nanosheets were uniformly dispersed within the polyacrylonitrile fibers, forming a nanoscale physical barrier that effectively blocked the penetration paths of heat and oxygen, significantly slowing down the heat and mass transfer rates during combustion. Simultaneously, molybdenum disulfide, as an excellent char-forming catalyst, rapidly catalyzes the formation of a dense and continuous char layer structure in the polyacrylonitrile fibers during high-temperature combustion, creating a heat insulation barrier and further inhibiting the spread of combustion. Under the combined effect of these two mechanisms, the flame retardant properties of the polyacrylonitrile fibers were significantly enhanced. The flame-retardant properties of acrylonitrile fibers effectively inhibit the spread and propagation of combustion. During the combustion of polyacrylonitrile composite fabrics, the carboxyl groups on functionalized molybdenum disulfide nanosheets promote the cyclization reaction of polyacrylonitrile molecular chains at lower temperatures through an ion-initiated mechanism, forming a stable ladder structure. This structure is further cross-linked through the bridging effect of functionalized molybdenum disulfide nanosheets, forming a network structure with a higher degree of cross-linking, reducing the generation of volatile oligomers and gases. As the temperature increases, the functionalized molybdenum disulfide nanosheets act as nucleation sites, promoting the transformation of the structure into an ordered graphitized carbon layer, thereby effectively isolating heat and oxygen, inhibiting the escape of flammable gases, and thus improving the flame-retardant properties of shape memory polymers.

[0066] Functionalized molybdenum disulfide nanosheets can form hydrogen bonds and dipole interactions with the -CN groups on the polyacrylonitrile fiber molecular chains, enhancing the cross-linking network inside the fiber, thereby improving the tensile strength and elongation at break of the fiber, and thus improving the mechanical properties of the shape memory polymer. Functionalized molybdenum disulfide nanosheets can capture free radicals in the gas phase during combustion, reducing chain breaking reactions and thus reducing the generation of toxic gases.

[0067] Example 4, please refer to Figure 1 , Figure 5 and Figure 6 A novel temperature-driven bidirectional deformation-responsive shape memory polymer, the preparation method of which includes the following steps:

[0068] 20 g of a polyethylene vinyl acetate copolymer with a vinyl acetate content of 40 wt% and 12 wt% benzamide peroxide were fed into a twin-screw extruder, melt-mixed and extruded and granulated at a melt temperature of 95 ℃ to obtain a blend extrudate.

[0069] After the blend extrudate was cooled to room temperature, it was hot-pressed using a hot press at a temperature of 130 ℃, a pressure of 10 MPa, and a pressing time of 20 min to obtain a shape memory functional layer film.

[0070] 1-Carboxymethyl-3-vinylimidazole bromide and azobisisobutyronitrile were added to N,N-dimethylformamide for deoxygenation treatment to obtain a reaction solution. The reaction solution was placed in an oil bath at 70°C and reacted under a nitrogen atmosphere for 24 hours. After cooling to room temperature, tetrahydrofuran was added dropwise, the precipitate was collected and washed with ethanol, and dried at 60°C for 8 hours in a vacuum drying oven to obtain a solid powder. The solid powder was dissolved in deionized water to obtain a polyionic liquid aqueous solution. Molybdenum disulfide powder was added to a 2wt% polyionic liquid aqueous solution, dispersed in an ice bath by ultrasonication, and centrifuged. The upper suspension was collected, centrifuged and the precipitate was collected, washed and freeze-dried to obtain a flame retardant material.

[0071] Flame retardant material and polyacrylonitrile were dissolved in N,N-dimethylformamide to obtain a dispersion and a polyacrylonitrile solution, respectively. The dispersion was slowly added dropwise to the polyacrylonitrile solution to obtain a spinning solution. The mass ratio of polyacrylonitrile to flame retardant material was 10:0.2. Electrospinning was performed to obtain polyacrylonitrile fabric. A silane coupling agent was added to a 0.25wt% acetic acid solution. The mass ratio of acetic acid solution to silane coupling agent was 100:0.2. The polyacrylonitrile fabric was immersed in a modification solution to obtain a modified fabric. The modified fabric was immersed in a mixed solution to obtain a polyacrylonitrile composite fabric.

[0072] Polyacrylonitrile composite fabric, shape memory functional layer film, carbon fiber felt, and oriented graphene fiber film are sequentially stacked and hot-pressed for 30 minutes to obtain shape memory polymer.

[0073] Furthermore, the polyionic liquid formed by the polymerization of 1-carboxymethyl-3-vinylimidazolium bromide monomer contains imidazole cations and carboxylate anions in its molecular structure, possessing the energy to catalyze char formation and capture free radicals in the gas phase. After modification with the polyionic liquid, the interlayer distance of molybdenum disulfide, which has a layered crystal structure, is significantly increased, thereby improving its specific surface area and significantly enhancing the interfacial bonding force between molybdenum disulfide and polyacrylonitrile fibers. Under high-temperature conditions, the imidazole rings and carboxyl groups in the polyionic liquid can effectively promote the cyclization reaction of polyacrylonitrile molecules, thus forming a stable ladder-like structure, enabling polyacrylonitrile to successfully transform into a robust char layer. Simultaneously, the phosphate esters generated by the high-temperature decomposition of the polyionic liquid further participate in the cross-linking reaction, consolidating the stability of the char layer. In addition, the orderly arrangement of molybdenum disulfide nanosheets within the formed char layer constructs a "brick-and-mortar" composite structure, where the molybdenum disulfide nanosheets act as the "bricks" and the char material generated by the pyrolysis of the polyionic liquid acts as the "mortar." This structure effectively blocks the transfer of oxygen and heat radiation, thereby significantly inhibiting the combustion process of the material.

[0074] Example 5, please refer to Figure 1 , Figure 7 and Figure 8 A novel temperature-driven bidirectional deformation-responsive shape memory polymer, the preparation method of which includes the following steps:

[0075] 20 g of a polyethylene vinyl acetate copolymer with a vinyl acetate content of 40 wt% and 12 wt% benzamide peroxide were fed into a twin-screw extruder, melt-mixed and extruded and granulated at a melt temperature of 95 ℃ to obtain a blend extrudate.

[0076] After the blend extrudate was cooled to room temperature, it was hot-pressed using a hot press at a temperature of 130 ℃, a pressure of 10 MPa, and a pressing time of 20 min to obtain a shape memory functional layer film.

[0077] Flame retardant material and polyacrylonitrile were dissolved in N,N-dimethylformamide to obtain a dispersion and a polyacrylonitrile solution, respectively. The dispersion was slowly added dropwise to the polyacrylonitrile solution to obtain a spinning solution. The mass ratio of polyacrylonitrile to flame retardant material was 10:0.1. Electrospinning was performed to obtain polyacrylonitrile fabric. A silane coupling agent was added to a 0.25wt% acetic acid solution. The mass ratio of acetic acid solution to silane coupling agent was 100:0.1 to obtain a modification solution. The polyacrylonitrile fabric was immersed in the modification solution to obtain a modified fabric. The modified fabric was immersed in a mixed solution to obtain a polyacrylonitrile composite fabric.

[0078] Graphene oxide slurry was loaded into a syringe, and anhydrous calcium chloride was used as the coagulation bath at an injection rate of 1 mL / h to obtain graphene fibers uniformly wound on a take-up tube. The fibers were washed with ethanol solution and vacuum dried at 50 °C for 6 h to obtain a graphene oxide fiber membrane. The graphene oxide fiber membrane was then immersed in hydroiodic acid for 12 h and washed to obtain an oriented graphene fiber membrane. Polyacrylonitrile composite fabric, shape memory functional layer film, carbon fiber felt, and oriented graphene fiber membrane were sequentially stacked and hot-pressed for 30 min using a hot press to obtain a shape memory polymer.

[0079] Furthermore, in shape memory polymers, the oriented graphene fiber film, acting as a conductive layer, can effectively generate an electrothermal conversion effect when a voltage is applied, raising the temperature of the shape memory polymer and activating its shape memory function, enabling it to change according to a preset shape. The axial thermal conductivity of the graphene fiber film is significantly higher than that of the shape memory functional layer film, allowing the graphene fibers to act as channels for rapid heat transfer, ensuring that heat can be uniformly diffused throughout the material. Thus, during the bidirectional deformation cycle of the shape memory polymer, the oriented graphene fiber film can shorten the response time of the heating stage and improve the response speed of the shape memory effect. In addition, the high axial modulus of the oriented graphene fiber film can effectively constrain the longitudinal expansion of the shape memory functional layer film during thermally driven deformation, thereby guiding the deformation along a preset direction and avoiding possible torsional deformation of the shape memory polymer during deformation, ensuring the accuracy and controllability of the deformation, and enhancing its precision and reliability.

[0080] Example 6, please refer to Figure 1 A novel temperature-driven bidirectional deformation-responsive shape memory polymer, the preparation method of which includes the following steps:

[0081] 20 g of polyethylene vinyl acetate copolymer with a vinyl acetate content of 40 wt% and 12 wt% benzamide peroxide were fed into a twin-screw extruder, melt-mixed and extruded and granulated. The melt temperature was 90 ℃ to obtain the blend extrudate.

[0082] After the blend extrudate was cooled to room temperature, it was hot-pressed using a hot press at a temperature of 130 ℃, a pressure of 10 MPa, and a pressing time of 20 min to obtain a shape memory functional layer film.

[0083] Flame retardant material and polyacrylonitrile were dissolved in N,N-dimethylformamide to obtain a dispersion and a polyacrylonitrile solution, respectively. The dispersion was slowly added dropwise to the polyacrylonitrile solution to obtain a spinning solution. The mass ratio of polyacrylonitrile to flame retardant material was 10:0.1. Electrospinning was performed to obtain polyacrylonitrile fabric. A silane coupling agent was added to a 0.25wt% acetic acid solution. The mass ratio of acetic acid solution to silane coupling agent was 100:0.05 to obtain a modification solution. The polyacrylonitrile fabric was immersed in the modification solution to obtain a modified fabric. The modified fabric was immersed in a mixed solution to obtain a polyacrylonitrile composite fabric.

[0084] Polyacrylonitrile composite fabric, shape memory functional layer film, carbon fiber felt, and oriented graphene fiber film are sequentially stacked and hot-pressed for 30 minutes using a hot press to obtain shape memory polymer.

[0085] Furthermore, the combination of carbon fiber felt and oriented graphene fiber membrane forms a complex and efficient conductive network. The carbon fiber felt provides the basis for high conductivity, while the oriented graphene fiber membrane further optimizes the conductive pathway through its anisotropic conductivity. This allows the shape memory polymer to maintain high conductivity while also possessing adjustable shielding performance, further enhancing the conductivity of the shape memory polymer.

[0086] Comparative Example 1: A novel temperature-driven bidirectional deformation-responsive shape memory polymer, the preparation method of which includes the following steps:

[0087] 20 g of polyethylene vinyl acetate copolymer with a vinyl acetate content of 40 wt% and 12 wt% benzamide peroxide were fed into a twin-screw extruder, melt-mixed and extruded and granulated at a melt temperature of 100 ℃ to obtain a blend extrudate.

[0088] After the blend extrudate was cooled to room temperature, it was hot-pressed using a hot press at a temperature of 130 ℃, a pressure of 10 MPa, and a pressing time of 20 min to obtain a shape memory functional layer film.

[0089] Polyacrylonitrile was dissolved in N,N-dimethylformamide to obtain a polyacrylonitrile solution. The polyacrylonitrile solution was subjected to ultrasonic mechanical stirring and vacuum degassing at 60°C for 60 min to obtain a spinning solution. Electrospinning was performed, and a silane coupling agent was added to a 0.25 wt% acetic acid solution at a mass ratio of 100:0.5 to obtain a modified solution. Polyacrylonitrile fabric was immersed in the modified solution to obtain a modified fabric. The modified fabric was then immersed in a mixed solution to obtain a polyacrylonitrile composite fabric.

[0090] Polyacrylonitrile composite fabric, shape memory functional layer film, carbon fiber felt, and oriented graphene fiber film are sequentially stacked and hot-pressed for 30 minutes using a hot press to obtain shape memory polymer.

[0091] Comparative Example 2: A novel temperature-driven bidirectional deformation-responsive shape memory polymer, the preparation method of which includes the following steps:

[0092] 20 g of polyethylene vinyl acetate copolymer with a vinyl acetate content of 40 wt% and 12 wt% benzamide peroxide were fed into a twin-screw extruder, melt-mixed and extruded and granulated at a melt temperature of 100 ℃ to obtain a blend extrudate.

[0093] After the blend extrudate was cooled to room temperature, it was hot-pressed using a hot press at a temperature of 130 ℃, a pressure of 10 MPa, and a pressing time of 20 min to obtain a shape memory functional layer film.

[0094] Flame retardant material and polyacrylonitrile are dissolved in N,N-dimethylformamide to obtain a dispersion and a polyacrylonitrile solution, respectively. The dispersion is slowly added dropwise to the polyacrylonitrile solution to obtain a spinning solution. The mass ratio of polyacrylonitrile to flame retardant material is 10:0.5. Electrospinning is performed to obtain polyacrylonitrile fabric. A silane coupling agent is added to a 0.25wt% acetic acid solution. The mass ratio of acetic acid solution to silane coupling agent is 100:0.5 to obtain a modification solution. The polyacrylonitrile fabric is immersed in the modification solution to obtain a modified fabric. The modified fabric is immersed in a mixed solution to obtain a polyacrylonitrile composite fabric.

[0095] Polyacrylonitrile composite fabric, shape memory functional layer film, and carbon fiber felt are sequentially stacked and hot-pressed for 30 minutes using a hot press to obtain shape memory polymer.

[0096] Performance testing

[0097] Test 1 Mechanical property test: The samples prepared in Examples 1-6 and Comparative Examples 1-2 were cut into dumbbell-shaped strips using a 4mm×50mm dumbbell-shaped cutter and tested using a universal tensile testing machine at a tensile rate of 10 mm / min to test the mechanical properties of the strips.

[0098] Test 2 Unidirectional shape memory performance test: The samples prepared in Examples 1-6 and Comparative Examples 1-2 were cut into 40mm×20mm specimens and tested using a thermomechanical analyzer. The temperature was raised to 100℃ and held for 5min. A stress of 0.3MPa was applied and held for 5min. The stress was kept constant and the temperature was lowered to 20℃. After holding for 5min, the stress was removed and the temperature was raised to 100℃. The unidirectional shape memory recovery rate was calculated.

[0099] Test 3: Bidirectional shape memory performance test: The samples prepared in Examples 1-6 and Comparative Examples 1-2 were cut into 40mm×20mm specimens and tested using a thermomechanical analyzer. The temperature was raised to 100℃ and held for 5min. A stress of 0.3MPa was applied and held for 5min. The stress was kept constant and the temperature was lowered to 20℃ and held for 5min. The temperature was then raised to 100℃ and the bidirectional shape memory recovery rate was calculated.

[0100] Test 4 Flame retardant performance test: The samples prepared in Examples 1-6 and Comparative Examples 1-2 were cut into 150mm×58mm specimens. The oxygen index was tested using a JF-3 limiting oxygen index meter according to GB / T5454-1997 standard, and the limiting oxygen index was recorded.

[0101] Table 1. Performance Test Results

[0102] Example Tensile strength (MPa) Unidirectional shape memory recovery rate (%) Bidirectional shape memory recovery rate (%) Limiting oxygen index (%) Example 1 36.4 97.5 96.8 34.5 Example 2 36.2 96.8 96.2 32.6 Example 3 35.9 96.2 95.4 30.2 Example 4 35.7 95.5 94.8 28.7 Example 5 35.5 94.7 94.1 26.3 Example 6 35.4 94.2 93.6 25.9 Comparative Example 1 28.7 96.7 96.2 18.8 Comparative Example 2 32.3 95.9 95.3 33.9

[0103] According to Examples 1-6, Comparative Examples 1-2 and Table 1, the shape memory functional layer film prepared by polyethylene vinyl acetate copolymer and benzamide peroxide has excellent thermal response shape memory properties when combined with the shape memory polymer. The introduction of polyacrylonitrile composite fabric and oriented graphene fiber film improves the overall mechanical properties of oriented graphene fiber film, and the flame retardant material introduced into polyacrylonitrile composite fabric improves the flame retardant properties of shape memory polymer.

[0104] Working principle: Polyvinyl acetate copolymer and benzamide oxide are introduced, and the copolymer molecular chains are connected by thermal crosslinking to build a stable cross-linked network structure. When stimulated by temperature, the shape changes, realizing reversible bidirectional shape change.

[0105] Polyacrylonitrile composite fabric is combined with shape memory functional layer film. The polyacrylonitrile composite fabric is loaded with copper sulfide particles, which provides photothermal and electrothermal conversion functions. The molybdenum disulfide nanosheets introduced into the polyacrylonitrile composite fabric improve the flame retardant properties of the shape memory polymer.

[0106] By combining oriented graphene fiber membranes, carbon fiber mats, and shape memory functional layer films, a conductive network is formed, generating an electrothermal conversion effect and further enhancing the mechanical properties of the shape memory polymer, thereby improving the application flexibility and practicality of the material.

[0107] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A novel temperature-driven bidirectional deformation-responsive shape memory polymer, characterized in that: The method for preparing the shape memory polymer includes the following steps: S1. 20 g of polyethylene vinyl acetate copolymer with a vinyl acetate content of 40 wt% and 12 wt% benzamide peroxide are fed into a twin-screw extruder, melt-mixed and extruded and granulated. The melt temperature is 90℃-100℃ to obtain the blend extrudate. S2. After the blended extrudate is cooled to room temperature, it is hot-pressed using a hot press at a temperature of 130 ℃, a pressure of 10 MPa, and a pressing time of 20 min to obtain a shape memory functional layer film. S3. The polyacrylonitrile composite fabric, shape memory functional layer film, carbon fiber felt, and oriented graphene fiber film are sequentially stacked and hot-pressed for 30 minutes using a hot press to obtain the shape memory polymer.

2. The novel temperature-driven bidirectional deformation-responsive shape memory polymer according to claim 1, characterized in that: The polymers, polyethylene vinyl acetate and benzoyl peroxide, have an average number-average molecular weight of 2000 and an average number-average molecular weight of 242.

23.

3. The novel temperature-driven bidirectional deformation-responsive shape memory polymer according to claim 1, characterized in that: Step S3 further includes the preparation of polyacrylonitrile composite fabric, and the preparation method of polyacrylonitrile composite fabric includes the following steps: S31. Pour the flame retardant material into N,N-dimethylformamide to obtain a dispersion, and dissolve polyacrylonitrile in N,N-dimethylformamide to obtain a polyacrylonitrile solution; S32. The polyacrylonitrile solution is ultrasonically stirred and the dispersion is slowly added dropwise. The solution is degassed under vacuum at 60°C for 60 min to obtain the spinning solution. The spinning solution is loaded into a syringe and electrospinned. A voltage of 20 kV is applied, the distance between the needle and the receiver is 10 cm, and the injection speed is 1 mL / h to obtain the polyacrylonitrile fabric. S33. Add silane coupling agent to 0.25wt% acetic acid solution, stir with a magnetic stirrer to obtain modified solution, immerse polyacrylonitrile fabric in modified solution for 30 min, and dry in oven for 1.5 h to obtain modified fabric. S34. Copper sulfate pentahydrate and sodium persulfate pentahydrate are poured into deionized water to obtain a mixed solution. The modified fabric is immersed in the mixed solution and heated in a water bath at 90°C for 120 minutes. After washing and drying, polyacrylonitrile composite fabric is obtained.

4. The novel temperature-driven bidirectional deformation-responsive shape memory polymer according to claim 3, characterized in that: The mass ratio of the polyacrylonitrile to the flame retardant material is 10:0.1-10:0.

5.

5. A novel temperature-driven bidirectional deformation-responsive shape memory polymer according to claim 3, characterized in that: The mass ratio of the acetic acid solution to the silane coupling agent is 100:0.05-100:0.

5.

6. The novel temperature-driven bidirectional deformation-responsive shape memory polymer according to claim 3, characterized in that: S31 further includes the preparation of flame-retardant materials, and the method for preparing flame-retardant materials includes the following steps: Step 1: Pour molybdenum disulfide powder into a reaction vessel containing 2wt% polyionic liquid aqueous solution, place the reaction vessel in an ice bath, and perform ultrasonic dispersion for 120 min. Then, process the mixture using a high-speed refrigerated centrifuge for 30 min at a speed of 6000 rpm / min, and collect the upper suspension. Step 2: Transfer the upper suspension to a high-speed refrigerated centrifuge and centrifuge for 30 minutes at a speed of 12,000 rpm / min. Collect the precipitate, ultrasonically wash the precipitate, and freeze-dry it at -50℃ for 24 hours to obtain the flame retardant material.

7. A novel temperature-driven bidirectional deformation-responsive shape memory polymer according to claim 6, characterized in that: The preparation method of the polyionic liquid aqueous solution includes the following steps: The ionic liquid monomer and azobisisobutyronitrile were poured into N,N-dimethylformamide for deoxygenation treatment to obtain a reaction solution. The reaction solution was placed in an oil bath at 70°C and reacted under a nitrogen atmosphere for 24 hours. After cooling to room temperature, tetrahydrofuran was added dropwise. The precipitate was collected and washed with ethanol. The precipitate was dried at 60°C for 8 hours using a vacuum drying oven to obtain a solid powder. The solid powder was dissolved in deionized water to obtain a polyionic liquid aqueous solution.

8. A novel temperature-driven bidirectional deformation-responsive shape memory polymer according to claim 7, characterized in that: The mass ratio of the ionic liquid monomer to azobisisobutyronitrile is 50:1, and the ionic liquid monomer is 1-carboxymethyl-3-vinylimidazole bromide.

9. A novel temperature-driven bidirectional deformation-responsive shape memory polymer according to claim 1, characterized in that: Step S3 further includes: The graphene oxide slurry was loaded into a syringe, and anhydrous calcium chloride was used as a coagulation bath. The injection rate was 1 mL / h to obtain graphene fibers that were uniformly wound on the take-up tube. The fibers were washed with ethanol solution and vacuum dried at 50 °C for 6 h to obtain a graphene oxide fiber membrane. The graphene oxide fiber membrane was immersed in hydroiodic acid for 12 hours and then washed to obtain an oriented graphene fiber membrane.

10. A novel temperature-driven bidirectional deformation-responsive shape memory polymer according to claim 1, characterized in that: In step S3, the hot pressing temperature of the hot press is 100 ℃ and the pressure is 10 MPa.

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