Thermoplastic polyurethane liquid crystal elastomer with molecular chain entanglement and preparation method and application thereof

Abstract

This invention relates to a thermoplastic polyurethane liquid crystal elastomer with molecular chain entanglement, its preparation method, and its applications. A thermoplastic polyurethane liquid crystal elastomer with high molecular weight and linear structure is prepared by mixing a dihydroxy liquid crystal monomer and a diisocyanate and then subjecting them to a thermal polymerization reaction. Subsequently, a stretching and orientation treatment is performed to align the molecular chains along the stretching direction, forming a thermally driven liquid crystal elastomer. The liquid crystal elastomer of this invention has the following advantages: utilizing the reversibility of molecular chain entanglement, the material can be processed by melt extrusion and hot pressing, greatly improving processing performance compared to traditional chemically cross-linked liquid crystal elastomers; by replacing chemical cross-linking with molecular chain entanglement, the mechanical strength and toughness of the material are improved, significantly enhancing its driving performance, with a maximum driving work capacity reaching 1,427 kJ / m. 3 It is far superior to traditional liquid crystal elastomers.

Description

Technical Field

[0001] This invention belongs to the field of organic polymer elastomer technology, and in particular relates to a thermoplastic polyurethane liquid crystal elastomer with molecular chain entanglement, its preparation method and application. Background Technology

[0002] Muscles play a vital role in the human body, supporting various life activities such as movement, respiration, and blood circulation. However, factors such as aging, diseases (such as stroke), surgery, or sports injuries can lead to weakening or loss of muscle function, thus affecting patients' quality of life. Therefore, the development of artificial muscles to assist rehabilitation or replace the function of damaged muscles is particularly important. Liquid crystal elastomers, as one of the most representative artificial muscles currently available, are typically composed of an ordered liquid crystal phase fixed by a covalently cross-linked network. These materials not only possess physical properties similar to human soft tissue (such as flexibility and density), but also can produce reversible deformation under external stimuli, effectively mimicking the contraction and relaxation of skeletal muscles (Nat. Rev. Mater. 2022, 7(1), 23).

[0003] Despite the great potential of liquid crystal elastomers in the field of artificial muscles, several problems remain to be solved. First, the mechanical strength of liquid crystal elastomers is relatively low: the tensile strength of most liquid crystal elastomers is less than 5 MPa, which results in insufficient actuation performance (<100 kJ / m). 3 This limitation restricts its ability to effectively lift or drive objects (Acc. Chem. Res. 2025, 58, 907). Secondly, liquid crystal elastomers have poor processing properties: the preparation process typically involves multiple reactions under harsh conditions, and their chemical cross-linking structure makes the material difficult to process further and mold into desired shapes. These problems severely restrict the practical application of the material (Chem. Rev. 2021, 122, 4927).

[0004] To address the above problems, existing research has proposed several solutions:

[0005] Chinese patent CN118496469A discloses a reusable and thermally driven liquid crystal elastomer, its preparation method, and its applications. A multi-domain liquid crystal elastomer is obtained by mixing a dihydroxy liquid crystal monomer, a diisocyanate chain extender, and a polyhydroxy (thiol) crosslinking agent, followed by thermal polymerization. The resulting multi-domain liquid crystal elastomer is then oriented to obtain a thermally driven single-domain liquid crystal elastomer. In the obtained liquid crystal elastomer, each structural unit contains a urethane bond, enabling the formation of strong hydrogen-bonded physical crosslinks to fix the liquid crystal orientation. The dynamic characteristics of hydrogen bonds can be utilized to impart reusable shaping properties to the material, and the synergistic enhancement effect of physical and chemical crosslinking can improve mechanical strength and driving performance. However, the liquid crystal elastomer disclosed in this patent is prepared through chemical crosslinking. Due to its chemically crosslinked structure, this structure makes it practically difficult to improve its processing performance, especially since the material is difficult to process using industrially common methods such as melt extrusion and hot pressing. Furthermore, the driving performance of this material is only 440 kJ / m³. 3 However, there is still room for improvement.

[0006] Chinese patent CN110373016B discloses a liquid crystal polyacrylate / liquid crystal polyurethane interpenetrating network liquid crystal elastomer, its preparation method, and its applications. The liquid crystal acrylate belongs to the first network, and the liquid crystal polyurethane belongs to the second network. Under conditions of simultaneous thermal polymerization and photoinitiation, the two independent liquid crystal systems are polymerized simultaneously, ultimately yielding a dual-liquid crystal system interpenetrating network liquid crystal elastomer (IPN-LCE). The interpenetrating network liquid crystal elastomer prepared by this method exhibits thermally driven properties. Under thermal stimulation, it can generate a driving force of 2.53 MPa and 1268 kJ / m². 3 The liquid crystal elastomer disclosed in this patent is also prepared through chemical cross-linking. Although it has excellent driving performance, its processing performance is severely limited due to the dual chemical cross-linking network.

[0007] Based on the above analysis, developing liquid crystal elastomers that are easy to process and have excellent driving and functional capabilities is a huge challenge. Summary of the Invention

[0008] In the prior art, liquid crystal elastomers are mostly prepared by chemical crosslinking. Therefore, most liquid crystal elastomers in the prior art contain chemical crosslinking structures. Due to the presence of chemical crosslinking structures, their processing performance is poor, which restricts their application scenarios. Therefore, liquid crystal elastomers prepared by chemical crosslinking in the prior art cannot simultaneously achieve both processing performance and driving performance. In order to solve this technical problem, the present invention provides a thermoplastic polyurethane liquid crystal elastomer with molecular chain entanglement, its preparation method and application.

[0009] Specifically, this invention proposes a molecularly entangled thermoplastic polyurethane liquid crystal elastomer, its preparation method, and its applications. This elastomer is simple and efficient to prepare, uses widely available raw materials, and is easily industrialized. Furthermore, the molecularly entangled thermoplastic polyurethane liquid crystal elastomer provided by this invention combines easy processing with excellent actuation performance, giving it broad application prospects in fields such as artificial muscles and soft robots.

[0010] The objective of this invention can be achieved through the following technical solutions:

[0011] Technical Solution 1: This invention first provides a method for preparing a thermoplastic polyurethane liquid crystal elastomer with multi-domain molecular chain entanglement, comprising the following steps:

[0012] A thermoplastic polyurethane liquid crystal elastomer with multi-domain molecular chain entanglement was obtained by mixing a dihydroxy liquid crystal monomer and a diisocyanate through a thermal polymerization reaction.

[0013] The binary hydroxyl liquid crystal monomer is selected from any one or a combination of several of the following structural formulas I-1 to I-3:

[0014]

[0015] The diisocyanate is selected from one or a combination of several of the following structural formulas II-1 to II-4:

[0016]

[0017] Based on total weight, the concentration of the dihydroxy liquid crystal monomer is 50wt% to 80wt%, the concentration of the diisocyanate is 20wt% to 50wt%, and the sum of the dihydroxy liquid crystal monomer and the diisocyanate is 100wt%.

[0018] In one embodiment of the present invention, the mixing temperature is 50°C to 100°C.

[0019] In one embodiment of the present invention, the temperature of the thermal polymerization reaction is 80°C to 150°C; the time of the thermal polymerization reaction is 3 hours to 20 hours.

[0020] In one embodiment of the present invention, the dihydroxy liquid crystal monomer is selected from the structure shown in Formula I-2, where m = 2, n = 6, and x = CH3, and the diisocyanate is selected from a mixture of the structures shown in Formula II-1 and Formula II-2 in equimolar ratios. The dihydroxy liquid crystal monomer and the diisocyanate are mixed in a molar ratio of 0.9 to 1.1:1.

[0021] The method for preparing multi-domain molecular chain entangled thermoplastic polyurethane liquid crystal elastomer provided by this invention uses simple and readily available raw materials. During the thermal polymerization reaction, no catalyst or solvent needs to be added, which helps to reduce side reactions and increase the concentration of reactants, thereby promoting the effective growth of molecular weight, increasing the polymerization rate, and thus obtaining a high molecular weight linear polymer.

[0022] Technical Solution 2: The present invention further provides a thermoplastic polyurethane liquid crystal elastomer with multi-domain molecular chain entanglement prepared by the above-mentioned Technical Solution 1.

[0023] Furthermore, the number-average molecular weight of the multi-domain molecular chain entangled thermoplastic polyurethane liquid crystal elastomer is 80,000 Da to 200,000 Da, which is determined by gel permeation chromatography.

[0024] The aforementioned multi-domain molecular chain entangled thermoplastic polyurethane liquid crystal elastomer, with its high molecular weight linear structure, can form molecular chain entanglements, thereby enhancing the strength and stability of the network structure. Furthermore, the urethane bonds in the structure can form strong hydrogen bonds, further strengthening the network structure, see [link to relevant documentation]. Figure 1 .

[0025] By utilizing the synergistic effect of hydrogen bonding and chain entanglement, the mechanical strength and driving performance of liquid crystal elastomers are significantly improved.

[0026] Since the liquid crystal elastomer of this invention does not contain a chemically cross-linked structure, it can be repeatedly processed using conventional melt processing techniques. These melt processing methods include hot pressing, extrusion, and injection molding, with processing temperatures ranging from 100°C to 200°C.

[0027] Technical Solution 3: The present invention further provides a method for preparing a single-domain liquid crystal elastomer, comprising the following preparation steps:

[0028] The thermoplastic polyurethane liquid crystal elastomer with multi-domain molecular chain entanglement described in technical solution 2 is subjected to stretching and orientation treatment so that its molecular chains are aligned along the stretching direction to form a thermally driven single-domain liquid crystal elastomer.

[0029] In one embodiment of the present invention, the multi-domain molecular chain entangled thermoplastic polyurethane liquid crystal elastomer described in technical solution 2 is mechanically stretched at room temperature, and the mechanical stretching range is 100% to 400%, to obtain a single-domain liquid crystal elastomer.

[0030] Technical Solution 4: The present invention further provides a single-domain liquid crystal elastomer, which is prepared based on the method of Technical Solution 3.

[0031] This single-domain liquid crystal elastomer can contract under heating stimulation, and when the heating is removed, the elastomer will recover and elongate. The heating stimulation temperature is 60℃~130℃.

[0032] Technical Solution 5: The present invention further provides the application of the single-domain liquid crystal elastomer.

[0033] Applications of the single-domain liquid crystal elastomer include, but are not limited to, the manufacture of artificial muscles, soft robots, and smart textiles.

[0034] The liquid crystal elastomer provided by this invention possesses a high molecular weight and linear structure, which facilitates the formation of dense molecular chain entanglements. Furthermore, the urethane bonds in the structure promote the formation of strong hydrogen bonds. Since both molecular chain entanglement and hydrogen bonding are reversible, this liquid crystal elastomer can be processed multiple times using conventional thermoplastic processing methods, significantly simplifying the processing flow. On the other hand, the molecular chain entanglement exhibits high stability, significantly enhancing the material's mechanical strength and ensuring its toughness, which is crucial for improving the material's actuation performance. In addition, the presence of hydrogen bonds further enhances the material's mechanical strength. By introducing molecular chain entanglement and hydrogen bonding, the strength and toughness of the material are improved while maintaining good processability. Therefore, the actual mechanical strength of the liquid crystal elastomer constructed by this invention can reach 219.6 MPa, and the work capacity during the actuation process can reach 1427 kJ / m. 3 It has high application value in fields such as artificial muscles and soft robots.

[0035] The structural design and polymerization method of this invention differ significantly from existing technologies. Existing liquid crystal elastomers typically employ chemical cross-linking structures, which not only complicates the preparation or polymerization process but also limits the material's processing performance. In contrast, the liquid crystal elastomer constructed in this invention possesses a linear structure and a high molecular weight. This design brings the following significant advantages: 1) The preparation process of the linear polymer is simple, requiring only one-step melt polymerization; 2) The linear polymer can be processed using simple methods (such as hot pressing, extrusion, and injection molding); 3) Utilizing spontaneously formed molecular chain entanglement instead of chemical cross-linking not only improves the material's mechanical properties but also enhances its toughness, thereby significantly improving the driving performance of the liquid crystal elastomer; unlike chemical cross-linking, molecular chain entanglement is reversible, capable of untangling through heating and shearing, and re-entering after the external force disappears, endowing the material with excellent processability (J. Compos. Sci., 2023, 7, 521). Compared with existing technologies, this invention has the following advantages and beneficial effects:

[0036] 1) The liquid crystal elastomer preparation method of this invention is simple. The multi-domain molecularly entangled thermoplastic polyurethane liquid crystal elastomer of this invention is prepared by one-step polymerization and then mechanically stretched and oriented at room temperature to obtain a thermally driven single-domain liquid crystal elastomer. In contrast, the preparation of existing liquid crystal elastomers usually involves multiple steps and harsh reaction conditions. Therefore, this invention significantly simplifies the preparation process and is more suitable for large-scale production.

[0037] 2) The liquid crystal elastomer described in this invention possesses excellent processing properties. Under high-temperature conditions, the molecular chain entanglement can disentangle under shear force. By utilizing this reversibility of entanglement and disentanglement, the liquid crystal elastomer can be processed using methods commonly used in industrial production, such as hot pressing, extrusion, and injection molding. In contrast, existing liquid crystal elastomers are difficult to process effectively due to limitations imposed by their chemical cross-linking structure. Therefore, this invention endows the material with superior processing properties, providing possibilities for expanding its application range.

[0038] 3) The liquid crystal elastomer described in this invention possesses excellent mechanical and actuation properties. Through the synergistic effect of molecular chain entanglement and hydrogen bonding, the material's actual mechanical strength can reach up to 219.6 MPa, and its actual elongation at break can reach 217%. Its work capacity during the thermal actuation process can reach 1427 kJ / m². 3 In contrast, the mechanical strength of existing liquid crystal elastomers is typically below 5 MPa, and their driving work capacity is below 100 kJ / m. 3 These superior mechanical and actuation properties demonstrate that heavier objects can be driven or supported using less material. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of molecular chain entanglement and hydrogen bonding in the structure of a liquid crystal elastomer before and after orientation.

[0040] Figure 2 The design concept for the aforementioned molecularly chain-entangled thermoplastic polyurethane liquid crystal elastomer;

[0041] Figure 3 The multi-domain liquid crystal elastomer material obtained in Example 1;

[0042] Figure 4 The actual stress-strain curve of the liquid crystal elastomer obtained in Example 1;

[0043] Figure 5 The method for preparing the soft robot described in Example 10;

[0044] Figure 6 This refers to the soft robot driving method described in Example 10;

[0045] Figure 7The single-domain liquid crystal elastomer obtained in Example 11 was repeatedly lifted with a 130g weight;

[0046] Figure 8 The driving performance test results of the single-domain liquid crystal elastomer obtained in Example 11 under different loads;

[0047] Figure 9 The artificial muscle preparation method described in Example 11;

[0048] Figure 10 The artificial muscle circulation obtained in Example 11 is used to lift the arm of an adult male;

[0049] Figure 11 The driving method for the tubular single-domain liquid crystal elastomer obtained in Example 13;

[0050] Figure 12 The filamentous multidomain liquid crystal elastomer obtained in Example 14. Detailed Implementation

[0051] This invention provides a method for preparing a multi-domain molecular chain entangled thermoplastic polyurethane liquid crystal elastomer, and the design concept of the molecular chain entangled thermoplastic polyurethane liquid crystal elastomer is as follows: Figure 2 As shown, the preparation method includes the following steps:

[0052] A thermoplastic polyurethane liquid crystal elastomer with multi-domain molecular chain entanglement was obtained by mixing a dihydroxy liquid crystal monomer and a diisocyanate through a thermal polymerization reaction.

[0053] The binary hydroxyl liquid crystal monomer is selected from any one or a combination of several of the following structural formulas I-1 to I-3:

[0054]

[0055] The diisocyanate is selected from one or a combination of several of the following structural formulas II-1 to II-4:

[0056]

[0057] Based on total weight, the concentration of the dihydroxy liquid crystal monomer is 50wt% to 80wt%, the concentration of the diisocyanate is 20wt% to 50wt%, and the sum of the dihydroxy liquid crystal monomer and the diisocyanate is 100wt%.

[0058] The mixing temperature is 50℃~100℃. The temperature of the thermal polymerization reaction is 80℃~150℃; the thermal polymerization reaction time is 3 hours~20 hours.

[0059] A single-domain liquid crystal elastomer can be obtained by mechanically stretching the multi-domain molecularly entangled thermoplastic polyurethane liquid crystal elastomer at room temperature with a stretch range of 100% to 400%. This single-domain liquid crystal elastomer can shrink under heating stimulation, and recover and elongate after the heating is removed. The heating stimulation temperature is 60°C to 130°C.

[0060] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. Unless otherwise specified, the methods described in the following embodiments are conventional methods. Unless otherwise specified, the raw materials are all available from publicly available commercial sources.

[0061] Examples 1-8 are examples of the preparation of multi-domain liquid crystal elastomers:

[0062] Example 1

[0063] 0.828 g (1 mmol) of a dihydroxy liquid crystal monomer (Formula I-2, m=2, n=6, x=CH3) was melted on a heating stage at 100 °C. Then, 0.84 g (0.5 mmol) of a diisocyanate (Formula II-1) and 0.105 g (0.5 mmol) of a diisocyanate (Formula II-2) were added. The diisocyanates act as chain extenders during the reaction. After thorough mixing, the mixture was poured into a mold (0.4 mm thick) and then polymerized in a hot press under the following conditions: 80 °C for 1 hour, followed by 130 °C for 8 hours. After the reaction was complete and cooled to room temperature, the resulting multidomain liquid crystal elastomer material was a white thin film, such as... Figure 3 As shown.

[0064] The stress-strain curve of the liquid crystal elastomer obtained in this embodiment is as follows: Figure 4 As shown, the actual mechanical strength of the liquid crystal elastomer can reach 219 MPa. This tensile test was conducted on a universal tensile testing machine, and the sample size used was 10 × 3 × 0.3 mm. 3 The stretching rate is 40 mm / min.

[0065] Example 2

[0066] In this embodiment, 6.3 mg (0.01 mmol) of dibutyltin dilaurate was added as a catalyst during the preparation of the multidomain liquid crystal elastomer material. The polymerization conditions were changed to 80°C for 1 hour and then 130°C for 3 hours. The rest was the same as in Example 1.

[0067] Example 3

[0068] In this embodiment, during the preparation of the multidomain liquid crystal elastomer material, the chain extender was changed to 0.05g (0.3mmol) chain extender (Formula II-1) and 0.147g (0.7mmol) chain extender (Formula II-2), and the polymerization conditions were changed to 90℃ for 1 hour and then 140℃ for 5 hours. The rest was the same as in Example 1.

[0069] Example 4

[0070] In this embodiment, during the preparation of the multidomain liquid crystal elastomer material, the chain extender was changed to 0.117g (0.7mmol) chain extender (Formula II-1) and 0.063g (0.3mmol) chain extender (Formula II-2), and the polymerization conditions were changed to 90℃ for 2 hours and then 140℃ for 3 hours. The rest was the same as in Example 1.

[0071] Example 5

[0072] In this embodiment, during the preparation of the multidomain liquid crystal elastomer material, the chain extender was changed to 0.84g (0.5mmol) chain extender (Formula II-1) and 0.111g (0.5mmol) chain extender (Formula II-4), and the polymerization conditions were changed to 80℃ for 3 hours first, and then 130℃ for 6 hours. The rest was the same as in Example 1.

[0073] Example 6

[0074] In this embodiment, during the preparation of the multidomain liquid crystal elastomer material, the liquid crystal monomer was changed to 0.801g (1mmol) of liquid crystal monomer (Formula I-2, m=2, n=6, x=H), the chain extender was changed to 0.131g (0.5mmol) of isocyanate monomer (Formula II-3) and 0.111g (0.5mmol) of chain extender (Formula II-4), and the polymerization conditions were changed to 80℃ for 2 hours first, and then 130℃ for 5 hours. The rest was the same as in Example 1.

[0075] Example 7

[0076] In this embodiment, during the preparation of the multidomain liquid crystal elastomer material, the liquid crystal monomer was changed to 0.468g (1mmol) of liquid crystal monomer (Formula I-1, m=2, n=6), the chain extender was changed to 0.105g (0.5mmol) of isocyanate monomer (Formula II-2) and 0.131g (0.5mmol) of isocyanate monomer (Formula II-3), and the polymerization conditions were changed to 80℃ for 2 hours first, and then 130℃ for 10 hours. The rest was the same as in Example 1.

[0077] Example 8

[0078] In this embodiment, during the preparation of the multidomain liquid crystal elastomer material, the liquid crystal monomer was changed to 0.458g (1mmol) of liquid crystal monomer (Formula I-3, m=2, n=3), the chain extender was changed to 0.084g (0.5mmol) of isocyanate monomer (Formula II-1) and 0.131g (0.5mmol) of isocyanate monomer (Formula II-3), the polymerization conditions were changed to 130℃-8 hours, and the rest were the same as in Example 1.

[0079] The characterization data of the multidomain liquid crystal elastomers prepared in Examples 1-8 are shown in Table 1. It can be seen that the multidomain liquid crystal elastomers prepared in Examples 1-8 all possess good driving performance and mechanical strength.

[0080] Table 1 Characterization data of the multidomain liquid crystal elastomers prepared in Examples 1-8

[0081]

[0082]

[0083] The driving amplitude was measured after stretching and orientation treatment.

[0084] Furthermore, comparing Example 1 and Example 2, it can be seen that the driving performance and mechanical strength of the multidomain liquid crystal elastomer obtained with and without the addition of a catalyst are not significantly different. This further proves that no catalyst or solvent needs to be added during the thermal polymerization process of this application. This helps to reduce side reactions and increase the concentration of reactants, thereby promoting the effective growth of molecular weight, increasing the polymerization rate, and thus obtaining a high molecular weight linear polymer.

[0085] Example 9 is a molding example of a multidomain liquid crystal elastomer:

[0086] Example 9

[0087] The multi-domain liquid crystal elastomer obtained in Example 1 was tightly wrapped around a stainless steel tube and heated at 130°C for 10 minutes. During the heating process, the material was continuously rolled to make the layers adhere together. After the heating was completed, the material was removed from the stainless steel tube after it gradually turned from transparent to white. The tubular multi-domain liquid crystal elastomer was then obtained.

[0088] Example 10 is an example of the fabrication of multi-domain liquid crystal elastomers in soft robots:

[0089] Example 10

[0090] Five thin film samples were obtained by cutting the multi-domain liquid crystal elastomer obtained in Example 1. One-fifth of the length of each sample was bonded together in an overlapping manner using dichloromethane solvent. Single-domain liquid crystal elastomers were then obtained by bending and stretching each multi-domain liquid crystal elastomer, as described in the following steps. Figure 5As shown. By repeatedly switching between 70°C and room temperature, the bonded soft robot can mimic the opening and closing of human fingers, forming a grasper, as shown. Figure 6 As shown.

[0091] Example 11 is an example of the application of multi-domain liquid crystal elastomers in the preparation of artificial muscles:

[0092] Example 11

[0093] The multi-domain liquid crystal elastomer obtained in Example 1 was mechanically stretched at room temperature to induce a 250% tensile deformation, thus obtaining a planar, elongated single-domain liquid crystal elastomer. This elastomer can bear heavy loads and perform work, such as... Figure 7 As shown.

[0094] The planar elongated single-domain liquid crystal elastomer obtained in this embodiment was subjected to driving performance tests under different loads, and the results are as follows: Figure 8 As shown, the work done in the thermally driven process can reach 1427 kJ / m. 3 The work performance is calculated using the following formula: P = mgL / V. Where P is the work performance, mg is the weight of the weight (N), L is the driving amplitude (m), and V is the volume of the elastic material (m³). 3 By changing the mass of the weights, the work performance of the liquid crystal elastomer under different loads can be obtained.

[0095] 30 planar strip-shaped single-domain liquid crystal elastomers were used as follows Figure 9 The steps shown are combined to create an artificial muscle device that can be applied to the human body, allowing it to lift an adult male's arm via electric heating cycles, such as... Figure 10 As shown.

[0096] Example 12 is a molding example of a tubular single-domain liquid crystal elastomer:

[0097] Example 12

[0098] The tubular multidomain liquid crystal elastomer obtained in Example 9 was heated at 80°C for 5 minutes, and then immediately subjected to mechanical stretching along the tube direction to induce a 300% tensile deformation, thus obtaining a tubular single-domain liquid crystal elastomer. By repeatedly switching between 70°C and room temperature, the elastomer was able to produce stretching motion with a reversible deformation of 30%.

[0099] The tubular single-domain liquid crystal elastomer was then heated at 130°C for 5 minutes to obtain a multi-domain liquid crystal elastomer. After cooling to room temperature, it was heated at 80°C for 5 minutes, followed immediately by mechanical expansion perpendicular to the tube direction, causing the tube to deform and increase in diameter by 100%, thus obtaining the tubular single-domain liquid crystal elastomer. By repeatedly switching between 70°C and room temperature, the elastomer could produce contractile motion, such as... Figure 11 As shown.

[0100] Example 13 is a reprocessing example of a multidomain liquid crystal elastomer:

[0101] Example 13

[0102] The multidomain liquid crystal elastomer obtained in Example 1 was shredded and then used to prepare filamentous multidomain liquid crystal elastomers using a twin-screw mixer. The chamber temperature of the twin-screw mixer was 150°C. The diameter of the filamentous multidomain liquid crystal elastomers could be varied, and the obtained filamentous multidomain liquid crystal elastomers with a diameter of 1 mm were shown below. Figure 12 As shown.

[0103] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A process for the preparation of a multi-domain, molecularly kinked, thermoplastic polyurethane liquid crystalline elastomer, characterized in that, Includes the following steps: A thermoplastic polyurethane liquid crystal elastomer with multi-domain molecular chain entanglement was obtained by mixing a dihydroxy liquid crystal monomer and a diisocyanate through a thermal polymerization reaction. The binary hydroxyl liquid crystal monomer is selected from any one or a combination of several of the following structural formulas I1 to I3: ； The diisocyanate is selected from one or a combination of several of the following structural formulas II1 to II4: ； Based on the total weight, the concentration of the dihydroxy liquid crystal monomer is 50wt% to 80wt%, the concentration of the diisocyanate is 20wt% to 50wt%, and the sum of the dihydroxy liquid crystal monomer and the diisocyanate is 100wt%.

2. The process for preparing a multi-domain, molecularly kinked, thermoplastic polyurethane liquid crystalline elastomer according to claim 1, characterized in that, The mixing temperature is 50 ℃~100 ℃; The temperature of the thermal polymerization reaction is 80 ℃ to 150 ℃; the time of the thermal polymerization reaction is 3 hours to 20 hours.

3. The method for preparing a multi-domain molecular chain entangled thermoplastic polyurethane liquid crystal elastomer according to claim 1, characterized in that, The dihydroxy liquid crystal monomer is selected from the structure shown in Formula I-2, and m=2, n=6, x=CH3. The diisocyanate is selected from a mixture of the structures shown in Formula II-1 and Formula II-2 in equal molar ratios. The molar ratio of hydroxyl groups to isocyanate groups in the dihydroxy liquid crystal monomer and the diisocyanate is 0.9 to 1.1:

1.

4. A multi-domain, molecularly kinked, thermoplastic polyurethane liquid crystalline elastomer characterized by, The liquid crystal elastomer prepared by the method described in claim 1 or 2 has a number-average molecular weight of 80,000 Da to 200,000 Da, which is determined by gel permeation chromatography.

5. A method for preparing a monodomain liquid crystal elastomer, characterized by, The thermoplastic polyurethane liquid crystal elastomer with multi-domain molecular chain entanglement described in claim 4 is subjected to stretching and orientation treatment so that its molecular chains are aligned along the stretching direction to form a thermally driven single-domain liquid crystal elastomer.

6. A process for the preparation of a monodomain liquid crystal elastomer according to claim 5, characterized in that, The multi-domain molecular chain entangled thermoplastic polyurethane liquid crystal elastomer of claim 4 is subjected to mechanical stretching at room temperature, with a stretching range of 100% to 400%, to obtain a single-domain liquid crystal elastomer.

7. A monodomain liquid crystal elastomer, characterized in that, It is prepared using the method described in claim 5 or 6.

8. A single-domain liquid crystal elastomer according to claim 7, characterized in that, The single-domain liquid crystal elastomer can contract under heating stimulation, and when the heating is removed, the elastomer will recover and elongate. The heating stimulation temperature is 60 ℃~130 ℃.

9. The application of the single-domain liquid crystal elastomer according to claim 7, characterized in that, Used to create artificial muscles, soft robots, or smart textiles.

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