SEBS-based liquid crystal elastomer and preparation method thereof

Abstract

The invention provides an SEBS (Styrene-Ethylene-Butylene-Styrene)-based liquid crystal elastomer and a preparation method thereof, and belongs to the field of synthesis and application of thermally-induced reversible deformation liquid crystal polymers. The liquid crystal elastomer is a low-degree cross-linked polymer network prepared from an ethylene-ethylene / butylene-styrene block copolymer SEBS and a double-end sulfydryl main chain type liquid crystal oligomer through photo-cross-linking curing, and a two-step secondary cross-linking mode is adopted. The material is prepared through a two-step method of PS segment physical structural domain pre-crosslinking and thiol-ene click reaction photo-crosslinking, and has bidirectional reversible deformation capability. By controlling the content of the liquid crystal units and the crosslinking and curing degree, the phase transition temperature and reversible deformation capability of the polymer material are regulated and controlled; a new thought and a new method are provided for preparing an intelligent flexible driver material with a novel function; on the basis of the liquid crystal polymer network, the SBS and SEBS materials can be developed towards high performance and intelligence.

Description

Technical Field

[0001] The invention belongs to the field of synthesis and application of thermo-induced reversible deformation liquid crystal polymers, and relates to a SEBS-based liquid crystal elastomer and a preparation method thereof. Background Art

[0002] With the rapid growth of scientific and technological development in human society, the importance of materials in social development is increasing day by day. At a time when the functions of traditional materials cannot cover various emerging fields and technical requirements, smart materials that integrate perception, drive and information processing have become a research hotspot. Liquid crystal elastomer (LCE) is a three-dimensional polymer network obtained by moderately cross-linking liquid crystal polymers. It can respond to the process of transition from liquid crystal phase to isotropic phase under external stimulation. It has the advantages of reversible bidirectional deformation memory function, rapid and large deformation, and programmable macroscopic deformation. It has broad application prospects in the fields of bionic devices, soft braking, biomedicine, etc.

[0003] Styrene-ethylene / butylene-styrene block copolymers (SEBS) with different degrees of hydrogenation are used as the main chain of liquid crystal elastomers and have a unique two-phase structure. The styrene segments used as physical crosslinks in styrene-butadiene-styrene triblock copolymers (SBS) are dispersed in a continuous polybutadiene phase, giving the material the dual advantages of room temperature elasticity and high temperature processability, making it a typical thermoplastic elastomer with superior performance. In addition, SBS rubber material is one of the rubber materials with the largest output, lowest cost and widest application. The development of high value-added downstream products can not only enrich the types of smart polymers, but also has important significance for improving the value chain.

[0004] At present, the preparation methods of LCE mainly include "one-step method" and "two-step method". The "one-step method" uses friction orientation, electrical orientation, magnetic orientation or optical orientation to induce the molten liquid crystal monomers to complete the orientation arrangement in the liquid crystal box, and then initiates free radical polymerization by light or heat to form a liquid crystal elastomer film. However, the "one-step method" is mainly limited by production conditions. The size of the liquid crystal box directly determines the size and shape of the prepared liquid crystal, so it is powerless in the case of large-scale production of non-small thin film liquid crystals. Secondly, in order to obtain the single domain orientation of the liquid crystal, the "one-step method" often needs to provide an in-situ orientation mechanism, otherwise, under external stimulation, the multi-domain oriented liquid crystal system cannot cause the material to produce reversible macroscopic deformation. The "two-step method" first obtains a lightly cross-linked liquid crystal network, and then uses light or heat to initiate free radical polymerization on the basis of mechanical stretching, thereby solidifying the orientation and arrangement of the liquid crystal primitives. The liquid crystal elastomer obtained by this method is not limited by the liquid crystal box, and can better show the advantages of programmable macroscopic deformation during the liquid crystal phase-isotropic phase transition. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides a SEBS-based liquid crystal elastomer and a preparation method thereof, the purpose of which is to prepare a double-terminal thiol main chain liquid crystal oligomer by Michael addition reaction, and prepare a styrene-ethylene / butylene-styrene block copolymer (SEBS) by hydrogenation reaction with a styrene-butadiene-styrene triblock copolymer (SBS) prepared by anionic polymerization reaction, and obtain a low-crosslinked polymer network by photocrosslinking and curing, and then prepare a SEBS-based liquid crystal elastomer with better thermal and mechanical properties. The present invention adjusts the performance of the liquid crystal elastomer by the proportion of components, and develops a new isotropic phase transition temperature control mode, specifically: by adjusting the ratio of the thiol component to the acrylate component, and the ratio of the liquid crystal unit to the chain extender in the acrylate component, the structure composition and performance of the liquid crystal oligomer are controlled, and the phase transition temperature and thermal driving performance of the LCE are further controlled.

[0006] To achieve the above object, the present invention adopts the following technical solution:

[0007] On the one hand, the present invention provides a SEBS-based liquid crystal elastomer, which is a low-crosslinked polymer network prepared by photo-crosslinking and curing of ethylene-ethylene / butylene-styrene block copolymer SEBS and a main-chain liquid crystal oligomer with double-terminal mercapto groups, and has a reversible two-way deformation memory function, providing a new possibility for preparing a more precise and controllable flexible driving device. The ethylene-ethylene / butylene-styrene block copolymer SEBS is prepared by hydrogenation reaction of styrene-butadiene-styrene triblock copolymer (SBS) prepared by anionic polymerization; the main-chain liquid crystal oligomer with double-terminal mercapto groups is prepared by Michael addition reaction.

[0008] Furthermore, the main chain liquid crystal oligomer with double-terminated thiol groups is a main chain liquid crystal oligomer composed of a liquid crystal unit 1,4-bis-[4-(6-acryloyloxyhexyloxy)benzoyloxy]-2-methylbenzene (RM82), a chain extender polyethylene glycol diacrylate (PEGDA), and a thiol-terminated component 2,2′-(1,2-ethylenedioxy)bis(ethylenethiol) (EDDT), and its liquid crystal formation interval is [T g (-20~50℃)-LC-T i (-10~85℃)].

[0009] Furthermore, the main chain liquid crystal oligomer with double-terminated thiol groups has a weight average molecular weight (M w ) is 1-20 kg·mol -1 , molecular weight distribution index (PDI) is 1.5-3.0, the glass transition temperature T of the main chain liquid crystal oligomer g The range is -20-50℃, the liquid crystal phase and the isotropic transition temperature T iThe range is -10-85℃, and its structural formula is as follows:

[0010]

[0011] Furthermore, in the main chain liquid crystal oligomer with double-terminated mercapto groups, the content of liquid crystal unit RM82 is 5-50 mol %, and its structural formula is as follows:

[0012]

[0013] Furthermore, in the main chain liquid crystal oligomer with double-terminated thiol groups, the content of chain extender PEGDA is 0-43 mol%, preferably 0-15 mol%, and its structural formula is as follows:

[0014]

[0015] Furthermore, the styrene-butadiene-styrene triblock copolymer (SBS) has a weight average molecular weight (M w ) is 50-400 kg·mol -1 , the molecular weight distribution index PDI is 1.05-1.40, and the mass fraction of styrene is 15-50% based on the total mass of styrene and butadiene as 100%.

[0016] Furthermore, the styrene-butadiene-styrene triblock copolymer (SEBS) with different hydrogenation degrees has a weight average molecular weight (M w ) is 50-400 kg·mol -1 , molecular weight distribution index (PDI) is 2.1-2.5, hydrogenation degree 50-100%, melting point T m The range is 45-90℃, and its structural formula is as follows:

[0017]

[0018] Furthermore, the SBS and SEBS preferably have a weight average molecular weight of 100-250 kg·mol -1 , SEBS hydrogenation degree is 50-70%.

[0019] In a second aspect, a method for preparing a SEBS-based liquid crystal elastomer comprises the following steps:

[0020] Step S1, synthesizing a main-chain liquid crystal oligomer with double-terminated thiol groups, specifically as follows:

[0021] Under the protection of anhydrous and oxygen-free argon, the liquid crystal element RM82, PEGDA, EDDT, and acetone were added to a three-necked flask equipped with a mechanical stirrer. In addition, a catalyst for the Michael addition reaction was added to the flask and reacted at room temperature for 20-25 hours. After the reaction, a main-chain liquid crystal oligomer with double-terminated thiol groups was obtained. In this step, the Michael addition reaction mainly occurred.

[0022] The molar ratio of RM82, PEGDA and EDDT is (0.3-1):(0-0.7):(1.1-2).

[0023] The synthetic route of the liquid crystal oligomer is as follows:

[0024]

[0025] Step S2, synthesizing a SEBS-based liquid crystal elastomer, specifically as follows:

[0026] The main chain liquid crystal oligomer and SEBS are dissolved in a solvent, and the mass fraction of the main chain liquid crystal oligomer is in the range of 20-50%, based on the total mass of the main chain liquid crystal oligomer and SEBS being 100%. After mechanical stirring and mixing, a photoinitiator is added to initiate a photocrosslinking reaction, and a film is coated after the reaction. After the solvent evaporates, a film material is obtained, which is cut into strips, stretched and oriented to 100-500% strain, and then a double-sided photocrosslinking reaction is further performed for 0.5-4h. After the reaction is completed, a SEBS-based liquid crystal elastomer with an adjustable phase transition temperature is obtained. In this step, a "thiol-ene" click reaction mainly occurs.

[0027] Furthermore, in step S2, the solvent may be toluene, chloroform, tetrahydrofuran, etc.

[0028] Further, in step S2, the initiator of the photocrosslinking reaction includes (2,4,6-trimethylbenzoyl) diphenylphosphine oxide (photoinitiator TPO), 2-methyl-4'-(methylthio)-2-morpholinyl benzophenone (photoinitiator 907), phenyl bis(2,4,6-trimethylbenzoyl) phosphine oxide (photoinitiator 819), preferably 2-methyl-4'-(methylthio)-2-morpholinyl benzophenone (photoinitiator 907); its structural formula is as follows:

[0029]

[0030] Furthermore, in step S2, the amount of photoinitiator added is: 0.3-0.6 g of main chain liquid crystal oligomer is added for every 1 μmol of photoinitiator.

[0031] Furthermore, in step S2, the strain of the spline is preferably 200-300%.

[0032] Furthermore, in step S2, the temperature of the photo-crosslinking reaction is room temperature, and the time is preferably 2-4 hours.

[0033] Furthermore, in step S1, the catalyst for the Michael addition reaction is di-n-propylamine (DPA), triethylamine (TEA) or N,N-diisopropylethylamine (DIPEA), preferably di-n-propylamine (DPA).

[0034] Furthermore, in step S1, the amount of the catalyst added for the Michael addition reaction is 2-4% of the total mass of the main chain liquid crystal oligomer with double-terminated mercapto groups, and its structural formula is as follows:

[0035]

[0036] Experimental tests of the present invention:

[0037] Liquid crystal performance analysis: The liquid crystal texture of SEBS-based liquid crystal elastomers was observed by polarizing microscope (POM) equipped with a hot stage and a digital camera. The molecular weight and molecular weight distribution index (ratio of weight average molecular weight to number average molecular weight) of the polymer were determined by gel permeation chromatography (GPC), and the glass transition temperature T of the liquid crystal oligomer was determined by differential scanning calorimetry (DSC). g and clear point T i .

[0038] The innovative features of the present invention are:

[0039] The present invention uses solvents such as toluene, chloroform, and tetrahydrofuran to dissolve a double-terminated mercapto liquid crystal oligomer and SEBS with different hydrogenation degrees for physical crosslinking, and a photoinitiator to perform secondary crosslinking by photocuring to prepare a SEBS-based liquid crystal elastomer, which has a bidirectional reversible change ability. By regulating the ratio of the mercapto component to the acrylate component, and the ratio of the liquid crystal unit to the chain extender in the acrylate component, the structure composition and performance of the liquid crystal oligomer can be regulated, and the phase transition temperature and thermal driving performance of the LCE can be further regulated, providing a new idea and method for preparing intelligent flexible driving materials with novel functions.

[0040] The beneficial effects of the present invention are:

[0041] The present invention synthesizes a liquid crystal oligomer with double-terminal thiol groups and SEBS with adjustable hydrogenation degree based on methods such as Michael addition, and obtains a SEBS-based liquid crystal elastomer by a two-step photocuring secondary crosslinking method. By controlling the content of liquid crystal primitives and the degree of crosslinking and curing, the phase transition temperature and reversible deformation ability of the polymer material are regulated. This provides a new idea and method for preparing intelligent flexible actuator materials with novel functions. Based on this liquid crystal polymer network, it is conducive to the development of SBS and SEBS materials towards high performance and intelligence. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 DSC curves of liquid crystal oligomers with different proportions of liquid crystal units; Figure 1 (a) DSC curves of liquid crystal oligomers with four molar ratios of RM82, PEGDA, and EDDT of 0.7:0.3:1.1, 0.7:0.3:1.3, 0.7:0.3:1.5, and 0.7:0.3:2; Figure 1 (b) DSC curves of liquid crystal oligomers with four molar ratios of RM82, PEGDA, and EDDT of 0.5:0.5:2, 0.7:0.3:2, 0.8:0.2:2, and 0.9:0.1:2.

[0043] Figure 2 Polarized texture photos of liquid crystal elastomers with a molar ratio of RM82, PEGDA, and EDDT of 0.9:0.1:2 under different strains; Figure 2 (a) is a photo of polarized liquid crystal texture under a strain of 50% and a deflection angle of 45°; Figure 2 (b) is a photo of polarized liquid crystal texture under strain of 100% and deflection angle of 45°; Figure 2 (c) is a photo of polarized liquid crystal texture under strain of 200% and deflection angle of 45°; Figure 2 (d) is a photo of polarized liquid crystal texture under a strain of 50% and a deflection angle of 90°; Figure 2 (e) is a photo of polarized liquid crystal texture under a strain of 100% and a deflection angle of 90°; Figure 2 (f) is a photo of polarized liquid crystal texture under strain of 200% and deflection angle of 90°; Figure 2 (g) is a photo of polarized liquid crystal texture under a strain of 300% and a deflection angle of 45°; Figure 2 (h) is a photo of polarized liquid crystal texture under a strain of 400% and a deflection angle of 45°; Figure 2 (i) is a photo of polarized liquid crystal texture under a strain of 500% and a deflection angle of 45°; Figure 2 (j) is a photo of polarized liquid crystal texture under a strain of 300% and a deflection angle of 90°; Figure 2 (k) is a photo of polarized liquid crystal texture under a strain of 400% and a deflection angle of 90°; Figure 2 (l) is a photograph of the polarized liquid crystal texture under a strain of 500% and a deflection angle of 90°. DETAILED DESCRIPTION

[0044] The present invention is further described in the following specific embodiments, but the embodiments are not intended to limit the scope of protection of the present invention.

[0045] Example 1

[0046] S1, Synthesis of Liquid Crystalline Oligomers with Double-Terminated Thiol Groups

[0047] Under the protection of anhydrous and oxygen-free argon, the liquid crystal element RM82 (6.179 g, 0.009 mol), EDDT (3.76 g, 0.02 mol), PEGDA (0.2 g, 0.001 mol) and 40 ml of acetone were added to a 250 ml three-necked flask equipped with a mechanical stirrer. In addition, TEA (0.1 g) was added to the flask as a catalyst and reacted at room temperature for 20 h. After the reaction was completed, the obtained product was dripped into ethanol, and the solution was discarded after standing for 12 h to obtain a liquid crystal oligomer with double-terminated thiol groups. The number average molecular weight (M n ) is 2.6 kg·mol -1 , molecular weight distribution index (PDI) is 2.4, and the liquid crystal formation interval is [T g (-40.1℃)-LC-T i (29.1℃)].

[0048] S2, Synthetic SEBS-based Liquid Crystalline Elastomer

[0049] SEBS (0.12 g) with a hydrogenation degree of 50% and a liquid crystal oligomer with double-terminated thiol groups (0.03 g) were dissolved in chloroform, mixed evenly, and 1 μmol of photoinitiator 907 were added, poured into a mold, and the solvent was evaporated to obtain a 0.04 mm film material. The film material was cut into strips and stretched to 200% strain for orientation, and then further double-sided photocrosslinking reaction was performed for 3 hours each. After the reaction was completed, a SEBS-based liquid crystal elastomer was obtained.

[0050] Depend on Figure 1 The DSC curve of the liquid crystal oligomer with a molar ratio of RM82, PEGDA, and EDDT of 0.8:0.2:2 shows that the liquid crystal formation interval is [T g (-40.1℃)-LC-T i (29.1℃)], the phase transition temperature of liquid crystal oligomers is correlated with the relative contents of mercapto groups and mesogens.

[0051] Depend on Figure 2 From the POM image, it can be seen that when the liquid crystal elastomer spline is stretched to 200%, it can show liquid crystal texture and has liquid crystal properties.

[0052] Example 2

[0053] S1, Synthesis of Liquid Crystalline Oligomers with Double-Terminated Thiol Groups

[0054] Under the protection of anhydrous and oxygen-free argon, the liquid crystal element RM82 (6.864g, 0.01mol), EDDT (3.76g, 0.02mol) and 40ml acetone were added to a 250ml three-necked flask equipped with a mechanical stirrer. In addition, DPA (2.025g) was added to the flask as a catalyst and reacted at room temperature for 25h. After the reaction was completed, the obtained product was dripped into ethanol, and the solution was discarded after standing for 12h to obtain a liquid crystal oligomer with a double-terminated thiol group. The number average molecular weight (M n ) is 2.9 kg·mol -1 , molecular weight distribution index (PDI) is 2.5, and the liquid crystal formation interval is [T g (-40.1℃)-LC-T i (29.1℃)].

[0055] S2, Synthetic SEBS-based Liquid Crystalline Elastomer

[0056] SEBS (0.12 g) with a hydrogenation degree of 50% and a liquid crystal oligomer with double-terminated thiol groups (0.03 g) were dissolved in toluene, mixed evenly, and 1 μmol of photoinitiator TPO was added, poured into a mold, and the solvent was evaporated to obtain a 0.04 mm film material. The film material was cut into strips and stretched to 300% strain for orientation, and then further double-sided photocrosslinking reaction was performed for 4 hours each. After the reaction was completed, a SEBS-based liquid crystal elastomer was obtained.

[0057] It can be seen from the POM image that the liquid crystal oligomer with a molar ratio of RM82, PEGDA, and EDDT of 1:0:2 exhibits a liquid crystal texture and has liquid crystal properties.

[0058] From the DSC curve, we can see that the liquid crystal formation interval is [T g (-40.1℃)-LC-T i (29.1℃)].

[0059] Example 3

[0060] S1, Synthesis of Liquid Crystalline Oligomers with Double-Terminated Thiol Groups

[0061] Under the protection of anhydrous and oxygen-free argon, the liquid crystal element RM82 (2.059 g, 0.003 mol), EDDT (2.068 g, 0.011 mol), PEGDA (1.4 g, 0.007 mol) and 40 ml of acetone were added to a 250 ml three-necked flask equipped with a mechanical stirrer. In addition, DIPEA (0.911 g) was added to the flask as a catalyst and reacted at room temperature for 24 h. After the reaction was completed, the obtained product was dripped into ethanol, and the solution was discarded after standing for 12 h to obtain a liquid crystal oligomer with a double-terminated thiol group. The number average molecular weight (M n ) is 2.5 kg·mol -1, molecular weight distribution index (PDI) is 2.1, and the liquid crystal formation interval is [T g (-50.9℃)-LC-T i (-3.2℃)].

[0062] S2, Synthetic SEBS-based Liquid Crystalline Elastomer

[0063] SEBS (0.12 g) with a hydrogenation degree of 50% and a liquid crystal oligomer with double-terminated thiol groups (0.03 g) were dissolved in chloroform, mixed evenly, and 1 μmol of photoinitiator 819 was added, poured into a mold, and the solvent was evaporated to obtain a 0.04 mm film material. The film material was cut into strips and stretched to 200% strain for orientation, and then further double-sided photocrosslinking reaction was performed for 2 hours each. After the reaction was completed, a SEBS-based liquid crystal elastomer was obtained.

[0064] It can be seen from the POM image that the liquid crystal oligomer with a molar ratio of RM82, PEGDA, and EDDT of 0.3:0.7:1.1 exhibits a liquid crystal texture and has liquid crystal properties.

[0065] From the DSC curve, we can see that the liquid crystal formation interval is [T g (-50.9℃)-LC-T i (-3.2℃)].

[0066] The above-described embodiments merely express the implementation methods of the present invention, but they cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A SEBS-based liquid crystal elastomer, characterized in that: The liquid crystal elastomer is a low-crosslinked polymer network prepared by photo-crosslinking and curing of ethylene-ethylene / butylene-styrene block copolymer SEBS and a main-chain liquid crystal oligomer with double-terminal mercapto groups, has a reversible two-way deformation memory function, and can prepare a controllable flexible driving device; the ethylene-ethylene / butylene-styrene block copolymer SEBS is prepared by hydrogenation reaction of a styrene-butadiene-styrene triblock copolymer SBS prepared by anionic polymerization; the main-chain liquid crystal oligomer with double-terminal mercapto groups is prepared by Michael addition reaction.

2. A SEBS-based liquid crystal elastomer according to claim 1, characterized in that: The main chain liquid crystal oligomer with double-terminated thiol groups is specifically as follows: The main chain liquid crystal oligomer of the double-terminated thiol group is composed of a liquid crystal unit 1,4-bis-[4-(6-acryloyloxyhexyloxy)benzoyloxy]-2-methylbenzene RM82, a chain extender polyethylene glycol diacrylate PEGDA, and a thiol-terminated component 2,2′-(1,2-ethylenedioxy)bis(ethylenethiol) EDDT, and the liquid crystal formation interval is [T g (-20~50℃)-LC-T i (-10~85℃)]; The main chain liquid crystal oligomer with double-terminated thiol groups has a weight average molecular weight M w 1-20kg·mol -1 , molecular weight distribution index PDI is 1.5-3.0, the glass transition temperature T of the main chain liquid crystal oligomer g The range is -20-50℃, the liquid crystal phase and the isotropic transition temperature T i The range is -10-85℃, and its structural formula is as follows:

3. A SEBS-based liquid crystal elastomer according to claim 2, characterized in that: In the main chain liquid crystal oligomer with double-terminated mercapto groups, the content of the liquid crystal unit RM82 is 5-50 mol %, and the content of the chain extender PEGDA is 0-43 mol %.

4. The SEBS-based liquid crystal elastomer according to claim 1, characterized in that: The styrene-butadiene-styrene triblock copolymer SBS has a weight average molecular weight (M w ) is 50-400 kg·mol -1 , the molecular weight distribution index PDI is 1.05-1.40, and the mass fraction of styrene is 15-50% based on the total mass of styrene and butadiene as 100%.

5. The SEBS-based liquid crystal elastomer according to claim 1, characterized in that: The styrene-butadiene-styrene triblock copolymer SEBS with different hydrogenation degrees has a weight average molecular weight M w 50-400 kg·mol -1 , molecular weight distribution index PDI is 2.1-2.5, hydrogenation degree 50-100%, melting point T m The range is 45-90℃, and its structural formula is as follows:

6. A SEBS-based liquid crystal elastomer according to claim 3, 4 or 5, characterized in that: The content of the chain extender PEGDA is preferably 0-15 mol%; the weight average molecular weight of the SBS is preferably 100-250 kg·mol -1 The SEBS preferably has a weight average molecular weight of 100-250 kg·mol -1 The SEBS hydrogenation degree is preferably 50-70%.

7. A method for preparing a SEBS-based liquid crystal elastomer according to any of claims 1 to 6, characterized in that: The following steps are involved: Step S1, synthesizing a main-chain liquid crystal oligomer with double-terminated thiol groups, specifically as follows: Under the protection of anhydrous and oxygen-free argon, the liquid crystal element RM82, PEGDA, EDDT and acetone are added into a reaction vessel equipped with a mechanical stirrer, and then a catalyst for Michael addition reaction is added to carry out Michael addition reaction, and the reaction is carried out at room temperature for 20-25 hours; after the reaction is completed, a main chain liquid crystal oligomer with double-terminated thiol groups is obtained; Step S2, synthesizing a SEBS-based liquid crystal elastomer, specifically as follows: The main chain liquid crystal oligomer and SEBS are dissolved in a solvent, and the mass fraction of the main chain liquid crystal oligomer is in the range of 20-50% based on the total mass of the main chain liquid crystal oligomer and SEBS being 100%; after mechanical stirring and mixing evenly, a photoinitiator is added to initiate a photocrosslinking reaction, and a film is coated after the reaction. After the solvent evaporates, a film material is obtained, which is cut into strips, stretched and oriented to a strain of 100-500%, and then a double-sided photocrosslinking reaction is carried out for 0.5-4h. After the reaction, a SEBS-based liquid crystal elastomer with an adjustable phase transition temperature is obtained.

8. The method for preparing a SEBS-based liquid crystal elastomer according to claim 7, characterized in that: In the step S1: The molar ratio of RM82, PEGDA and EDDT is (0.3-1):(0-0.7):(1.1-2); The catalyst is di-n-propylamine DPA, triethylamine TEA or N,N-diisopropylethylamine DIPEA, and the added amount of the catalyst is 2-4% of the total mass of the main chain liquid crystal oligomer with double-terminated mercapto groups.

9. The method for preparing a SEBS-based liquid crystal elastomer according to claim 8, characterized in that: The catalyst in step S1 is preferably di-n-propylamine DPA.

10. The method for preparing a SEBS-based liquid crystal elastomer according to claim 7, characterized in that: In the step S2: the solvent includes toluene, chloroform, and tetrahydrofuran; The initiator of the photocrosslinking reaction includes (2,4,6-trimethylbenzoyl) diphenylphosphine oxide, 2-methyl-4'-(methylthio)-2-morpholinyl benzophenone, phenyl bis(2,4,6-trimethylbenzoyl) phosphine oxide, preferably 2-methyl-4'-(methylthio)-2-morpholinyl benzophenone; The amount of the photoinitiator added is: 0.3-0.6 g of main chain liquid crystal oligomer is added for every 1 μmol of the photoinitiator; The strain of the spline is preferably 200-300%; The temperature of the photo-crosslinking reaction is room temperature, and the time is preferably 2-4 hours.

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