Cross-linking agent-free liquid crystal elastomer synthesis method, liquid crystal elastomer and body temperature driven actuator

Abstract

The invention provides a cross-linking agent-free liquid crystal elastomer synthesis method, a liquid crystal elastomer and a body temperature driven actuator, the liquid crystal elastomer with polymer chains aligned is prepared according to the cross-linking agent-free liquid crystal elastomer synthesis method, the energy storage modulus of the liquid crystal elastomer is 0.1-1 MPa, and the liquid crystal elastomer is a liquid crystal elastomer with polymer chains aligned. And the temperature TNI of the nematic phase to the isotropic phase of the liquid crystal elastomer is 60-62 DEG C. The actuator comprises the liquid crystal elastomer and a polyimide film, the liquid crystal elastomer is located on the surface of the polyimide film, and the polyimide film is bent through deformation of the liquid crystal elastomer. The polyimide film serves as a restraint layer and is used for enabling the liquid crystal elastomer to elastically reset. The liquid crystal elastomer can be driven by body temperature to deform.

Description

Technical Field

[0001] The present invention relates to the field of liquid crystal elastomers or actuators or low-temperature robots, and in particular to a method for synthesizing a liquid crystal elastomer without a cross-linking agent, a liquid crystal elastomer and an actuator driven by body temperature. Background Art

[0002] Liquid crystal elastomers are a type of thermally responsive smart material that can produce large reversible deformations under the action of heat. Fundamentally, by inputting energy to heat the liquid crystal elastomer, the liquid crystal polymer chains are transformed from the nematic phase to the isotropic phase and strain damping is overcome, thereby activating the material's programmable deformations such as bending, contraction and twisting.

[0003] In the prior art, the strain temperature window of liquid crystal elastomers is about 60-70°C or higher. Currently, there are mainly the following methods to reduce the driving energy of liquid crystal elastomers, i.e., the strain temperature window:

[0004] First, increase the pre-stretching ratio of liquid crystal elastomers. A large pre-stretching ratio will cause the liquid crystal molecular chains to form a more ordered single-domain structure, so that the material has a larger thermal response deformation. However, since the liquid crystal elastomer is basically stretched using a uniaxial stretching method, a large stretching ratio will cause stress concentration in the material, leading to stretching fracture. Currently, the maximum pre-stretching ratio of liquid crystal elastomers is about 1200%. However, a pre-stretching ratio of 1200% cannot reduce the strain temperature window.

[0005] Second, lower the nematic-isotropic transition temperature T of the liquid crystal elastomer NI . T of liquid crystal elastomer NI Also known as the clearing point temperature, lowering T NI The temperature required for the material to be heated to complete deformation and close to a transparent state can be reduced. In the prior art, liquid crystal elastomers are generally synthesized by thiol-acrylate reaction. In the traditional thiol-acrylate reaction, pentaerythritol tetrakis (3-mercaptopropionate) PETMP is used as a crosslinker for liquid crystal elastomers, and 2,2-(1,2-ethylenedioxy) diethyl mercaptan is used as a chain extender. The phase transition temperature of the synthesized liquid crystal elastomer is about 72°C, but it is impossible to achieve body temperature-driven liquid crystal elastomer deformation. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention provides a method for synthesizing a liquid crystal elastomer without a crosslinking agent, a liquid crystal elastomer and a body temperature-driven actuator. The liquid crystal elastomer synthesis route without a crosslinking agent significantly reduces the storage modulus of the material. In addition, a spiral stretching device is used to stretch the liquid crystal elastomer to a ratio of 2300% to 2500%, and the temperature T of the liquid crystal elastomer transitioning from the nematic phase to the isotropic phase is reduced. NI It is 60-62℃.

[0007] The present invention achieves the above technical objectives through the following technical means.

[0008] A method for synthesizing a liquid crystal elastomer without a crosslinking agent comprises the following steps:

[0009] 1.9-2.1 g of liquid crystal monomer is added to 0.76-0.84 g of toluene, and the liquid crystal monomer is heated to dissolve, and after dissolution, 0.538-0.595 g of 2,2'-(1,2-ethylenedioxy)bis(ethanethiol) is added, and after the solution is fully mixed by stirring, 0.0128-0.014 g of photoinitiator is added to obtain a liquid crystal precursor solution;

[0010] Diluting dipropylamine and toluene in a volume ratio of 1:50 to obtain a diluted catalyst solution;

[0011] Add 0.284-0.312 g of the diluted catalyst solution to the liquid crystal precursor solution and mix thoroughly, and place the solution in a vacuum environment to remove bubbles generated during the mixing process to obtain a mixed solution;

[0012] The mixed solution is poured into a glass mold, and placed away from light at room temperature, and then the glass mold is placed in a vacuum oven to evaporate the solvent, thereby obtaining a loosely cross-linked liquid crystal elastomer;

[0013] The loosely cross-linked liquid crystal elastomer is pre-stretched to 2300% to 2500% by a spiral stretching device, then removed and laid flat, and cured by ultraviolet irradiation to obtain a liquid crystal elastomer with oriented polymer chains.

[0014] Furthermore, the length of the loosely cross-linked liquid crystal elastomer is 70-80 mm, and the loosely cross-linked liquid crystal elastomer is pre-stretched to 1820-1950 mm by a spiral stretching device.

[0015] Furthermore, the liquid crystal monomer is added to toluene and heated at 80° C. for 5-10 minutes to dissolve the liquid crystal monomer.

[0016] Further, the mixed solution on the glass mold is placed in the dark at room temperature for 10-12 hours, and then placed in a vacuum oven at 80-82° C. to evaporate the solvent after 22-24 hours.

[0017] Furthermore, the rotation speed of the spiral stretching device is 0.25 to 0.28 r / s, so that the loosely cross-linked liquid crystal elastomer is pre-stretched to 2300% to 2500%.

[0018] A liquid crystal elastomer, a liquid crystal elastomer with polymer chain orientation prepared according to the crosslinking agent-free liquid crystal elastomer synthesis method, wherein the storage modulus of the liquid crystal elastomer is 0.1-1MPa, and the temperature T of the liquid crystal elastomer transitioning from the nematic phase to the isotropic phase NIIt is 60-62℃.

[0019] A body temperature driven actuator comprises the liquid crystal elastomer and a polyimide film, wherein the liquid crystal elastomer is located on the surface of the polyimide film, and the polyimide film is bent by deformation of the liquid crystal elastomer; the polyimide film is used as a constraint layer to elastically reset the liquid crystal elastomer.

[0020] Furthermore, under the action of a heat source above 25.2° C., the liquid crystal elastomer is deformed, thereby causing the polyimide film to bend.

[0021] The beneficial effects of the present invention are:

[0022] 1. The crosslinking agent-free liquid crystal elastomer synthesis method of the present invention significantly reduces the storage modulus of the material by not using a crosslinking agent. In addition, the liquid crystal elastomer is stretched to a ratio of 2300% to 2500% by using a spiral stretching device, and the temperature T of the liquid crystal elastomer transitioning from the nematic phase to the isotropic phase is lowered to 2300% to 2500%. NI It is 60-62℃.

[0023] 2. The cross-linking agent-free liquid crystal elastomer synthesis method described in the present invention, combined with the cross-linking agent-free liquid crystal elastomer synthesis route, significantly reduces the storage modulus of the material; the liquid crystal elastomer finally prepared can be directly driven by human body temperature, greatly reducing the thermal threshold of the material driving strain.

[0024] 3. The cross-linking agent-free liquid crystal elastomer synthesis method described in the present invention utilizes a spiral stretching device to allow the pre-stretching of the liquid crystal elastomer to occur within an extremely short distance, and the pre-stretched portion is evenly wound around the stretching axis, which greatly weakens the influence of stress concentration during uniaxial stretching and reduces the risk of stretching fracture. At the same time, it ensures that the width of the thin film formed by pre-stretching remains unchanged, greatly improving the pre-stretching ratio of the liquid crystal elastomer.

[0025] 4. The body temperature driven actuator described in the present invention can drive the actuator to deform using body temperature or a temperature slightly lower than low temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] 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. The drawings described below are some embodiments of the present invention. For ordinary technicians in this field, it is obvious that other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 Schematic diagram of the body temperature driven actuator according to the present invention.

[0028] Figure 2It is a schematic structural diagram of the spiral stretching device described in the present invention.

[0029] Figure 3 It is a top view of the spiral stretching device described in the present invention.

[0030] Figure 4 Infrared image of a body temperature-driven actuator driven by human body temperature (skin temperature).

[0031] Figure 5 Infrared image of a body temperature driven actuator driven by human body temperature (blowing temperature).

[0032] Figure 6 This is a graph showing the relationship between different molar ratios of PETMP cross-linking agent and the storage modulus of the sample during the synthesis of liquid crystal elastomers.

[0033] Figure 7 This is a graph of the loss tangent of the liquid crystal elastomer obtained by the cross-linking agent-free preparation method of the present invention.

[0034] In the figure:

[0035] 100-liquid crystal elastomer; 200-polyimide film;

[0036] 1-device housing; 2-device buckle plate; 3-rotating shaft; 4-worm gear; 5-worm; 6-rotatable cylindrical stage; 61-rotatable sleeve; 7-cylindrical sample stretching shaft; 8-baffle; 9-limiting block; 10-sample to be stretched; 11-stretched sample; 12-limiting plate. DETAILED DESCRIPTION

[0037] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0038] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "axial", "radial", "vertical", "horizontal", "inner", "outer" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0039] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0040] The crosslinking agent-free liquid crystal elastomer synthesis method of the present invention comprises the following steps:

[0041] 1.9-2.1 g of liquid crystal monomer is added to 0.76-0.84 g of toluene, and the liquid crystal monomer is heated to dissolve. After dissolution, 0.538-0.595 g of 2,2'-(1,2-ethylenedioxy)bis(ethanedithiol) is added, and after the solution is fully mixed by stirring, 0.0128-0.014 g of photoinitiator is added to obtain a liquid crystal precursor solution; the component of the liquid crystal monomer is 2-methyl-1,4-phenyl 4-(3-acryloxypropoxy)benzoate.

[0042] Diluting dipropylamine and toluene in a volume ratio of 1:50 to obtain a diluted catalyst solution;

[0043] Add 0.284-0.312 g of the diluted catalyst solution to the liquid crystal precursor solution and mix thoroughly, and place the solution in a vacuum environment to remove bubbles generated during the mixing process to obtain a mixed solution;

[0044] The mixed solution is poured into a glass mold, and placed away from light at room temperature, and then the glass mold is placed in a vacuum oven to evaporate the solvent, thereby obtaining a loosely cross-linked liquid crystal elastomer;

[0045] The loosely cross-linked liquid crystal elastomer is pre-stretched to 2300% to 2500% by a spiral stretching device, then removed and laid flat, and cured by ultraviolet irradiation to obtain a liquid crystal elastomer with oriented polymer chains.

[0046] The cross-linking agent-free liquid crystal elastomer synthesis method of the present invention significantly reduces the storage modulus of the material by not using a cross-linking agent. In addition, the liquid crystal elastomer is stretched to a ratio of 2300% to 2500% by using a spiral stretching device, and the temperature T of the liquid crystal elastomer transitioning from the nematic phase to the isotropic phase is reduced to 200%. NI It is 60-62℃.

[0047] like Figure 2 and 3 As shown, the spiral stretching device comprises a device housing 1, a worm gear assembly and a rotatable cylindrical stage 6; the worm gear assembly comprises a worm wheel 4, a worm 5 and a rotating shaft 3, a baffle 8 is arranged in the device housing 1, the baffle 8 divides the device housing 1 into two areas, a worm wheel 4 is installed in one area, and the worm 5 passes through one area and passes through the other area and is installed in the device housing 1. One end of the worm 5 passes through the baffle 8 and meshes with the worm wheel 4, one end of the worm 5 passes through the side hole of the device housing 1 and is limited by a limit plate 12, a rotating shaft 3 is installed on the worm wheel 4, and the rotation of the worm wheel 4 is promoted by holding the rotating shaft 3, and the rotation of the worm wheel 4 drives the worm 5 to rotate; the worm wheel 4 can also be connected to a stepping motor, and the speed can be accurately controlled by the stepping motor.

[0048] The other end of the rotating shaft worm 5 passes through the side hole of the device housing 1 and is limited by the limit block 9. The other end of the rotating shaft worm 5 passes through the side hole of the device housing 1. The outside is a cylindrical sample stretching shaft 7. A rotatable cylindrical stage 6 is set adjacent to the cylindrical sample stretching shaft 7. The rotatable cylindrical stage 6 is fixedly installed close to the side wall of the device housing 1. A rotatable sleeve 61 is sleeved on the rotatable cylindrical stage 6. The sample 10 to be stretched is placed on the rotatable cylindrical stage 6. The end of the sample 10 to be stretched is clamped by a sample clamp at the bottom. One end of the sample 10 to be stretched is wound around the cylindrical sample stretching shaft 7 and stretched into a stretched sample 11. A device buckle plate 2 is set above the device housing 1 to enclose the worm wheel 4 and the worm 5 in the device housing 1.

[0049] The hand-held shaft 3 is rotated, and the worm gear 4 rotates to drive the worm 5 to rotate. When the worm 5 rotates, the cylindrical sample stretching shaft 7 also rotates. The sample 10 to be stretched is fixed on the rotatable sleeve 61 with a sample clamp. As the sample is spirally stretched, the rotatable sleeve 61 can rotate slowly. The rotation of the rotatable sleeve 61 can release the sample to continue stretching, and finally a stretched sample 11 is formed on the cylindrical sample stretching shaft 7.

[0050] The spiral stretching device uses a winding stretching method in which the forces at both ends are the fixed force on the stage and the static friction force of the cylindrical stretching axis on the material. The spiral stretching device allows the pre-stretching of the liquid crystal elastomer to occur within the distance between the cylindrical sample stretching axis 7 and the rotatable cylindrical stage, and the pre-stretched part is evenly wound around the stretching axis, which greatly weakens the influence of stress concentration during uniaxial stretching, reduces the risk of stretching fracture, and ensures that the film width of the film formed by pre-stretching remains unchanged.

[0051] By adjusting the rotation speed of the cylindrical stretching axis, the stretching rate and the width of the formed film can be adjusted, thereby controlling the pre-stretching ratio of the material, as shown in Table 1:

[0052] Table 1

[0053]

[0054] Through experiments, it was found that under this device, the liquid crystal elastomer can reach a pre-stretching ratio of up to about 2500%.

[0055] Table 2: Relationship between the original length of the loosely cross-linked liquid crystal elastomer and the multiple length of the liquid crystal elastomer after ultra-stretching

[0056]

[0057] As shown in Table 2, the original length of the loosely cross-linked liquid crystal elastomer is 70-80 mm, and the length of the liquid crystal elastomer after ultra-stretching is stretched to 1820-1950 mm, resulting in a stretching multiple of 23.0-25.0 times.

[0058] Example 1

[0059] The crosslinking agent-free liquid crystal elastomer synthesis route of Example 1 comprises the following method:

[0060] 1.9 g of liquid crystal monomer (RM-257) was added to 0.76 g of toluene, and the mixture was heated at 80° C. for 5 minutes to dissolve the liquid crystal monomer. 0.538 g of 2,2'-(1,2-ethylenedioxy)diethylmercaptan (EDDET) was added, and the mixture was stirred in a magnetic stirrer for 1-2 minutes. After the solution was fully mixed, 0.0128 g of photoinitiator (HHMP) was added to obtain a liquid crystal precursor solution.

[0061] Diluting dipropylamine (DPA) and toluene in a volume ratio of 1:50 to obtain a diluted catalyst solution;

[0062] 0.284 g of the diluted catalyst was added to the liquid crystal precursor solution and mixed thoroughly, and the solution was placed in a vacuum chamber for 2 minutes to remove bubbles generated during the mixing process;

[0063] The mixture was poured into a glass mold and placed in a dark place at room temperature for 10 hours. Then, the glass mold was placed in a vacuum oven at 80°C to evaporate the solvent. After 22 hours, a loosely cross-linked liquid crystal elastomer was obtained.

[0064] The loosely cross-linked liquid crystal elastomer was pre-stretched to 2500% by a spiral stretching device, then removed from the device and laid flat, and cured by ultraviolet irradiation. After 25 minutes, a liquid crystal elastomer with oriented polymer chains was obtained.

[0065] Example 2

[0066] Example 2 A synthesis route of a liquid crystal elastomer without a crosslinking agent comprises the following method:

[0067] 2 g of liquid crystal monomer (RM-257) was added to 0.8 g of toluene, and the mixture was heated at 80° C. for 8 minutes to dissolve the liquid crystal monomer. 0.5665 g of 2,2'-(1,2-ethylenedioxy)diethylmercaptan (EDDET) was added, and the mixture was stirred in a magnetic stirrer for 1-2 minutes. After the solution was fully mixed, 0.0134 g of photoinitiator (HHMP) was added to obtain a liquid crystal precursor solution.

[0068] Diluting dipropylamine (DPA) and toluene in a ratio of 1:50 to obtain a diluted catalyst solution;

[0069] 0.298 g of the diluted catalyst was added to the liquid crystal precursor solution and mixed thoroughly, and the solution was placed in a vacuum chamber for 2 minutes to remove bubbles generated during the mixing process;

[0070] The mixture was poured into a glass mold and placed in a dark place at room temperature for 11 hours. Then, the glass mold was placed in a vacuum oven at 81°C to evaporate the solvent. After 23 hours, a loosely cross-linked liquid crystal elastomer was obtained.

[0071] The loosely cross-linked liquid crystal elastomer was pre-stretched to 2500% by a spiral stretching device, then removed from the device and laid flat, and cured by ultraviolet irradiation. After 28 minutes, a liquid crystal elastomer with oriented polymer chains was obtained.

[0072] Example 3

[0073] Example 3 A synthesis route of a liquid crystal elastomer without a crosslinking agent comprises the following method:

[0074] 2.1 g of liquid crystal monomer (RM-257) was added to 0.84 g of toluene, and the mixture was heated at 80° C. for 10 minutes to dissolve the liquid crystal monomer. 0.595 g of 2,2'-(1,2-ethylenedioxy)diethylmercaptan (EDDET) was added, and the mixture was stirred in a magnetic stirrer for 1-2 minutes. After the solution was fully mixed, 0.014 g of photoinitiator (HHMP) was added to obtain a liquid crystal precursor solution.

[0075] Diluting dipropylamine (DPA) and toluene in a volume ratio of 1:50 to obtain a diluted catalyst solution;

[0076] 0.312 g of the diluted catalyst was added to the liquid crystal precursor solution and mixed thoroughly, and the solution was placed in a vacuum chamber for 2 minutes to remove bubbles generated during the mixing process;

[0077] The mixture was poured into a glass mold and placed in a dark place at room temperature for 12 hours. Then, the glass mold was placed in a vacuum oven at 82°C to evaporate the solvent. After 24 hours, a loosely cross-linked liquid crystal elastomer was obtained.

[0078] The loosely cross-linked liquid crystal elastomer was pre-stretched to 2500% using an ultra-stretching device, then removed from the device and laid flat, and cured by ultraviolet irradiation. After 30 minutes, a liquid crystal elastomer with oriented polymer chains was obtained.

[0079] The liquid crystal elastomer prepared in Example 1 has a storage modulus of 0.12-1 MPa, and a temperature T at which the nematic phase of the liquid crystal elastomer transitions to the isotropic phase is NI It is 61.084-62℃.

[0080] The liquid crystal elastomer prepared in Example 2 has a storage modulus of 0.1-0.96 MPa, and a temperature T at which the nematic phase of the liquid crystal elastomer transitions to the isotropic phase is NI It is 60.322-61.722℃.

[0081] The liquid crystal elastomer prepared in Example 3 has a storage modulus of 0.14-0.97 MPa, and a temperature T at which the nematic phase of the liquid crystal elastomer transitions to the isotropic phase is NI It is 60-61.892℃.

[0082] The synthesis route of the cross-linking agent-free liquid crystal elastomer described in the present invention. Due to the reduction of the cross-linking agent, the liquid crystal elastomer of the present invention has a smaller tensile modulus, can produce a larger deformation under a smaller stress, and enhances the pre-stretching performance of the material. On the other hand, the sparser cross-linking network significantly reduces the storage modulus of the liquid crystal elastomer, which means that the molecular chains in the liquid crystal polymer material have higher flexibility and thermal responsive deformability, and the energy stored in the material due to elastic deformation during the strain process will be reduced, reducing the energy demand during thermal drive. At the same time, the liquid crystal elastomer also has a lower nematic phase to isotropic phase transition temperature T NI =60-62℃.

[0083] like Figure 1As shown, the body temperature driven actuator of the present invention comprises the liquid crystal elastomer 100 and the polyimide film 200. The liquid crystal elastomer 100 is located on the surface of the polyimide film 200 to form a double-layer actuator. The liquid crystal elastomer 100 is deformed by temperature change, so that the polyimide film 100 is bent. The polyimide film 100 is used as a constraint layer to elastically reset the liquid crystal elastomer. The double-layer actuator is bent when heated and automatically returns to its original shape after cooling.

[0084] like Figure 4 As shown, the straight spoke-shaped actuator is placed on the human skin ( Figure 4 The index finger is the index finger. The general human skin temperature is 35-37°C. When the straight spoke-shaped actuator is placed on the human skin, the spoke bends to the maximum angle of about 67° in 13 seconds.

[0085] like Figure 5 As shown, the actuator is a bionic crab soft robot. Under the action of the temperature of human body air (about 26-28°C), the actuator can bend and deform to about 57°C within 3.2 seconds, and return to its original shape after 9 seconds when the heat source is lost.

[0086] The present invention can cause the liquid crystal elastomer to deform under the action of a heat source above 25.2° C., thereby driving the polyimide film to bend. The actuator of the present invention reaches the level of body temperature drive.

[0087] Figure 6 The figure shows the relationship between different molar ratios of PETMP crosslinking agent and the storage modulus of the sample when synthesizing liquid crystal elastomer by thiol-acrylate reaction. When the PETMP crosslinking agent is 0 mol, that is, the storage modulus of the liquid crystal elastomer obtained by the preparation method without crosslinking agent = 0.1-1 MPa, that is, the storage modulus of the liquid crystal elastomer prepared by the present invention without crosslinking agent is 0.1-1 MPa.

[0088] Figure 7 The figure shows the loss tangent (the ratio of loss and storage modulus is called loss tangent) of the liquid crystal elastomer obtained by the crosslinking agent-free preparation method of the present invention, which reflects the viscoelastic ratio of the material. It can be seen that the viscosity peak of the liquid crystal elastomer appears at about 61°C (between 60-62°C). When heated at this temperature, the material loses the optical properties of liquid crystal and gradually changes from a turbid state to a transparent viscous state, that is, the phase transition temperature of the liquid crystal elastomer from the nematic phase to the isotropic phase is about 61°C.

[0089] The invention benefits from the ultra-stretching ratio of 2300% to 2500% and the liquid crystal elastomer synthesis route without crosslinking agent, which greatly reduces the threshold heat of deformation of the liquid crystal elastomer material. The liquid crystal elastomer synthesis route without crosslinking agent significantly reduces the storage modulus of the material, and the liquid crystal elastomer finally prepared can be directly driven by human body temperature, which greatly reduces the heat threshold of material driven strain.

[0090] It should be understood that although this specification is described according to various embodiments, not every embodiment contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0091] The series of detailed descriptions listed above are only specific descriptions of feasible embodiments of the present invention. They are not intended to limit the scope of protection of the present invention. All equivalent embodiments or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for synthesizing a liquid crystal elastomer without a crosslinking agent, characterized in that: The following steps are involved: 1.9-2.1 g of liquid crystal monomer is added to 0.76-0.84 g of toluene, and the liquid crystal monomer is heated to dissolve, and after dissolution, 0.538-0.595 g of 2,2'-(1,2-ethylenedioxy)bis(ethanethiol) is added, and after the solution is fully mixed by stirring, 0.0128-0.014 g of photoinitiator is added to obtain a liquid crystal precursor solution; Diluting dipropylamine and toluene in a volume ratio of 1:50 to obtain a diluted catalyst solution; Add 0.284-0.312 g of the diluted catalyst solution to the liquid crystal precursor solution and mix thoroughly, and place the solution in a vacuum environment to remove bubbles generated during the mixing process to obtain a mixed solution; The mixed solution is poured into a glass mold, and placed away from light at room temperature, and then the glass mold is placed in a vacuum oven to evaporate the solvent, thereby obtaining a loosely cross-linked liquid crystal elastomer; The loosely cross-linked liquid crystal elastomer is pre-stretched to 2300% to 2500% by a spiral stretching device, then removed and laid flat, and cured by ultraviolet irradiation to obtain a liquid crystal elastomer with oriented polymer chains.

2. The method for synthesizing a liquid crystal elastomer without a crosslinking agent according to claim 1, characterized in that: The length of the loosely cross-linked liquid crystal elastomer is 70-80 mm, and the loosely cross-linked liquid crystal elastomer is pre-stretched to 1820-1950 mm by a spiral stretching device.

3. The method for synthesizing a liquid crystal elastomer without a crosslinking agent according to claim 1, characterized in that: After the liquid crystal monomer is added to toluene, the mixture is heated at 80° C. for 5-10 minutes to dissolve the liquid crystal monomer.

4. The method for synthesizing a liquid crystal elastomer without a crosslinking agent according to claim 1, characterized in that: The mixed solution on the glass mold was placed in the dark at room temperature for 10-12 hours and then placed in a vacuum oven at 80-82°C for solvent evaporation after 22-24 hours.

5. The method for synthesizing a liquid crystal elastomer without a crosslinking agent according to claim 1, characterized in that: The rotation speed of the spiral stretching device is 0.25-0.28 r / s, so that the loosely cross-linked liquid crystal elastomer is pre-stretched to 2300%-2500%.

6. A liquid crystal elastomer, characterized in that: According to any one of claims 1 to 5, a liquid crystal elastomer (100) with oriented polymer chains is prepared by the method for synthesizing a liquid crystal elastomer without a crosslinking agent, wherein the storage modulus of the liquid crystal elastomer (100) is 0.1-1 MPa, and the temperature T at which the nematic phase of the liquid crystal elastomer (100) transitions to the isotropic phase is NI It is 60-62℃.

7. A body temperature driven actuator, characterized in that: The invention comprises the liquid crystal elastomer (100) and a polyimide film (200) as claimed in claim 6, wherein the liquid crystal elastomer (100) is located on the surface of the polyimide film (200), and the deformation of the liquid crystal elastomer (100) is driven by temperature change, thereby causing the polyimide film (200) to bend; and the polyimide film (200) is used as a constraint layer to elastically reset the liquid crystal elastomer (100).

8. The body temperature driven actuator according to claim 7, characterized in that Under the action of a heat source above 25.2° C., the liquid crystal elastomer (100) is deformed, thereby driving the polyimide film (200) to bend.

Images