Temperature-sensitive shape memory rubber material and application thereof in field of intelligent sealing

Abstract

The invention discloses a temperature-sensitive shape memory rubber material and application thereof in the field of intelligent sealing, and belongs to the technical field of rubber sealing. The invention relates to a temperature-sensitive shape memory rubber material and application thereof in the field of intelligent sealing, firstly, 4-cyano-4 '-pentylbiphenyl liquid crystal monomer is synthesized and then grafted with polydimethylsiloxane, then poly (N-isopropylacrylamide) is synthesized, and finally, 1, 2-propylene glycol is utilized to prepare the temperature-sensitive shape memory rubber material. The preparation method comprises the following steps: mixing a 1, 2-dichloroethylene solvent with ceramic powder, carbon nanotubes, poly (N-isopropylacrylamide) and liquid crystal monomer grafted polydimethylsiloxane, and carrying out hot press molding and annealing treatment to obtain the final temperature-sensitive shape memory rubber material. The material has excellent thermosensitivity, shape restorability and sealing performance, can quickly respond when the temperature changes, is suitable for various fields of intelligent pipeline valve sealing, aerospace heat insulation sealing rings and the like, has good thermal stability and mechanical properties, and is widely applied to intelligent sealing technologies with high requirements.

Description

Technical Field

[0001] The present invention relates to the technical field of rubber sealing, and more particularly to a temperature-sensitive shape memory rubber material and its application in the field of intelligent sealing. Background Art

[0002] With the rapid development of intelligent manufacturing and new materials technology, polymer elastomers with temperature-sensitive and shape-memory properties have received widespread attention in sealing engineering. Traditional rubber sealing materials mostly rely on a single physical or chemical structure, which is often difficult to achieve high-precision fitting when assembled at room temperature, and are prone to deformation failure under extreme high or low temperature conditions, resulting in leakage risks and increased maintenance costs. In recent years, temperature-sensitive shape memory polymers (SMAPs) have gradually become a research hotspot for solving the above-mentioned problems. Through molecular design, the organic combination of thermally responsive monomers, reversible cross-linking networks and flexible main chains can achieve self-regulating sealing properties that are soft to mold at low temperatures and "memory" to restore the original shape at high temperatures.

[0003] Currently, composite systems of liquid crystal monomer grafted structures, polydimethylsiloxane (PDMS) matrices, and thermosensitive poly(N-isopropylacrylamide) (PNIPAM) have found initial application in flexible electronic packaging, microfluidic chip valves, and automotive engine seals, demonstrating excellent reproducible assembly and thermal stability. However, existing materials still face limitations such as complex processing, insufficient interfacial adhesion between components, and slow deformation at high temperatures. Furthermore, uniform dispersion of nanofillers is difficult, affecting the material's mechanical uniformity and electrothermal response efficiency.

[0004] Looking ahead, the development trends of temperature-sensitive shape memory rubber materials are: first, molecular-level optimization, introducing multifunctional liquid crystal monomers and intelligent cross-linking agents to increase the shape memory rate and adjustable temperature range of response; second, nanostructure enhancement, achieving synergistic toughening of multiphase interfaces such as ceramic powders and carbon nanotubes, and improving mechanical strength and thermal conductivity; third, green and efficient processing, using ultrasonic dispersion and solvent evaporation microwave-assisted technology to achieve low-energy, scalable preparation; and fourth, multi-field coupling intelligence, triggering deformation through multiple external fields such as electricity, light, and magnetism to achieve remote self-adjustment and online monitoring of seals. These innovations will provide smart sealing solutions with higher reliability, lower energy consumption, and longer life for fields such as petrochemicals, aerospace, smart buildings, and medical devices. Summary of the Invention

[0005] The object of the present invention is to provide a temperature-sensitive shape memory rubber material and its application in the field of intelligent sealing, which has excellent temperature sensitivity, shape recovery and sealing performance, can respond quickly to temperature changes, and has good thermal stability and mechanical properties.

[0006] A temperature-sensitive shape memory rubber material, the preparation method of which is as follows:

[0007] S1. Preparation of 4-cyano-4'-pentylbiphenyl liquid crystal monomer: In a nitrogen atmosphere, chloroform solvent, 4-cyanobenzoic acid, and 4-n-pentylbiphenyl were added to a reaction vessel, and ultrasonically dissolved and dispersed uniformly. A catalyst, aluminum chloride, was slowly added under ultrasonication to react, and the mixture was naturally cooled to room temperature. The mixture was purified by column chromatography using a mixed solvent of chloroform / ethyl acetate as an eluent, and the solvent was removed from the purified solution by solvent evaporation to obtain a 4-cyano-4'-pentylbiphenyl liquid crystal monomer;

[0008] S2. Preparation of 4-cyano-4'-pentylbiphenyl liquid crystal monomer grafted polydimethylsiloxane: adding 1,2-dichloroethylene solvent and polydimethylsiloxane to a reaction vessel, dissolving and dispersing them uniformly through ultrasonication, adding 4-cyano-4'-pentylbiphenyl liquid crystal monomer, dissolving and dispersing them uniformly through ultrasonication, adding ammonium persulfate as a free radical initiator, dissolving and dispersing them uniformly through ultrasonication, reacting, and removing the solvent by solvent evaporation to obtain 4-cyano-4'-pentylbiphenyl liquid crystal monomer grafted polydimethylsiloxane;

[0009] S3. Preparation of poly(N-isopropylacrylamide): Deionized water and N-isopropylacrylamide are added to a reaction vessel, and the mixture is uniformly dissolved and dispersed by ultrasonication. Ammonium persulfate as an initiator is added, and the mixture is uniformly dissolved and dispersed by ultrasonication. The reaction is carried out, and ethanol is added to precipitate the poly(N-isopropylacrylamide) from the reaction solution by precipitation. The mixture is centrifuged, washed with ethanol, and dried to obtain the poly(N-isopropylacrylamide).

[0010] S4. Preparation of a temperature-sensitive shape memory rubber material: Add 1,2-dichloroethylene solvent, ceramic powder, carbon nanotubes, poly(N-isopropylacrylamide), and 4-cyano-4'-pentylbiphenyl liquid crystal monomer grafted polydimethylsiloxane into a reaction vessel, disperse them evenly by ultrasonication, remove the solvent by solvent evaporation, pour them into a mold, and process them by hot pressing at a temperature of 100-120°C and a pressure of 20-40 MPa, followed by annealing at 140-160°C for 100-140 minutes, and naturally cool them to room temperature to obtain a temperature-sensitive shape memory rubber material.

[0011] Preferably, in step S1, the formula ratio of chloroform, 4-cyanobenzoic acid, 4-n-pentylbiphenyl, and aluminum chloride is 400-600 mL: 100 g: 140-180 g: 2-4 g.

[0012] Preferably, the reaction conditions in step S1 are 70-90° C. for 10-14 h.

[0013] Preferably, in step S2, the formula ratio of 1,2-dichloroethylene, polydimethylsiloxane, 4-cyano-4'-pentylbiphenyl liquid crystal monomer, and ammonium persulfate is 1200-1600 mL: 100 g: 40-60 g: 0.1-0.5 g.

[0014] Preferably, the reaction conditions in step S2 are 50-70° C. for 5-7 hours.

[0015] Preferably, in step S3, the formula ratio of deionized water, N-isopropylacrylamide, and ammonium persulfate is 400-600 mL: 100 g: 0.1-0.5 g.

[0016] Preferably, the reaction conditions in step S3 are 60-80° C. for 8-12 h.

[0017] Preferably, the ceramic powder in step S4 is nano-silicon dioxide.

[0018] Preferably, in step S4, the formula ratio of 1,2-dichloroethylene, ceramic powder, carbon nanotubes, poly(N-isopropylacrylamide), and 4-cyano-4'-pentylbiphenyl liquid crystal monomer grafted polydimethylsiloxane is 400-600 mL:4-6 g:4-6 g:4-6 g:100 g.

[0019] A temperature-sensitive shape memory rubber material is used in the field of intelligent sealing. The temperature-sensitive shape memory rubber material can be applied to intelligent pipeline valve seals, aerospace thermal insulation seals, intelligent flexible connectors, automobile engine and chassis self-adjusting seals, microfluidic chips and intelligent valves, and building energy-saving intelligent window seals.

[0020] Compared with the prior art, the advantages of the present invention are:

[0021] (1) Excellent temperature-sensitive response, shape memory performance and high-precision sealing performance

[0022] The present invention grafts 4-cyano-4'-pentylbiphenyl liquid crystal monomers onto polydimethylsiloxane (PDMS) side chains through a free radical grafting method to form a temperature-sensitive composite material. The liquid crystal monomer has a spontaneous shrinkage force (strain>40%) in the liquid crystal phase transition range of 75-85°C, and can achieve precise dynamic sealing gap compensation when temperature is triggered, with an accuracy of ±0.1mm. This property gives the material excellent adaptability and shape memory during temperature changes. At the same time, this precision gives the material significant advantages in the field of intelligent sealing, especially in applications requiring high sealing accuracy and high temperature adaptability, such as intelligent pipeline valve seals and aerospace thermal insulation seals.

[0023] (2) Synergistic effect improves overall performance

[0024] A composite of poly(N-isopropylacrylamide) grafted with a 4-cyano-4'-pentylbiphenyl liquid crystal monomer (LCM) onto PDMS utilizes the synergistic effect of the thermoresponsive material and the LC monomer to optimize the material's shape memory and temperature responsiveness. The addition of poly(N-isopropylacrylamide) enhances the thermal stability and strain responsiveness of the composite, ensuring its long-term stability and reliability in multiple smart sealing applications.

[0025] At the same time, when carbon nanotubes and nano-silica are dispersed in the matrix at the same time, a "rigid-tough" complementary composite network structure can be formed: carbon nanotubes construct an efficient heat / force conduction skeleton to achieve rapid response and high strength; nano-silica acts as a microfiller to optimize the matrix interface bonding, rheological properties and thermal stability; the synergistic effect of the two can further improve the material's shape fixation rate, shape recovery rate and sealing stability, so that the temperature-sensitive shape memory rubber material of the present invention exhibits excellent performance under intelligent sealing, high temperature resistance and cyclic load conditions. DETAILED DESCRIPTION

[0026] Example 1:

[0027] S1. Preparation of 4-cyano-4'-pentylbiphenyl liquid crystal monomer: In a nitrogen atmosphere, 400 mL of chloroform solvent, 100 g of 4-cyanobenzoic acid, and 140 g of 4-n-pentylbiphenyl were added to a reaction vessel, and the mixture was uniformly dissolved and dispersed by ultrasonication. 2 g of aluminum chloride catalyst was slowly added under ultrasonication, and the mixture was reacted at 70° C. for 10 h. The mixture was naturally cooled to room temperature, and purified by column chromatography using a mixed solvent of chloroform / ethyl acetate as an eluent. The purified solution was subjected to a solvent evaporation method to remove the solvent to obtain a 4-cyano-4'-pentylbiphenyl liquid crystal monomer;

[0028] S2. Preparation of 4-cyano-4'-pentylbiphenyl liquid crystal monomer grafted polydimethylsiloxane: Add 1200 mL of 1,2-dichloroethylene solvent and 100 g of polydimethylsiloxane to a reaction container, dissolve and disperse them evenly by ultrasonication, add 40 g of 4-cyano-4'-pentylbiphenyl liquid crystal monomer, dissolve and disperse them evenly by ultrasonication, add 0.1 g of ammonium persulfate as a free radical initiator, dissolve and disperse them evenly by ultrasonication, react at 50°C for 5 h, and remove the solvent by solvent evaporation to obtain 4-cyano-4'-pentylbiphenyl liquid crystal monomer grafted polydimethylsiloxane;

[0029] S3. Preparation of poly(N-isopropylacrylamide): 400 mL of deionized water and 100 g of N-isopropylacrylamide were added to a reaction vessel, and the mixture was uniformly dissolved and dispersed by ultrasonication. 0.1 g of ammonium persulfate as an initiator was added, and the mixture was uniformly dissolved and dispersed by ultrasonication. The mixture was reacted at 60° C. for 8 h, and ethanol was added to precipitate the poly(N-isopropylacrylamide) from the reaction solution by precipitation. The mixture was centrifuged, washed with ethanol, and dried to obtain the poly(N-isopropylacrylamide).

[0030] S4. Preparation of temperature-sensitive shape memory rubber material: 400 mL of 1,2-dichloroethylene solvent, 4 g of ceramic powder nano-silica, 4 g of carbon nanotubes, 4 g of poly(N-isopropylacrylamide), and 100 g of 4-cyano-4'-pentylbiphenyl liquid crystal monomer grafted polydimethylsiloxane were added to a reaction container, and ultrasonically dispersed evenly. The solvent was removed by solvent evaporation method, and then poured into a mold. The mold was processed by hot pressing process at a temperature of 100°C and a pressure of 20 MPa, and then annealed at 140°C for 100 minutes. The material was naturally cooled to room temperature to obtain a temperature-sensitive shape memory rubber material.

[0031] Example 2:

[0032] S1. Preparation of 4-cyano-4'-pentylbiphenyl liquid crystal monomer: In a nitrogen atmosphere, 450 mL of chloroform solvent, 100 g of 4-cyanobenzoic acid, and 150 g of 4-n-pentylbiphenyl were added to a reaction vessel, and the mixture was uniformly dissolved and dispersed under ultrasound. 2.5 g of aluminum chloride catalyst was slowly added under ultrasound, and the mixture was reacted at 75° C. for 11 h. The mixture was naturally cooled to room temperature, and purified by column chromatography using a mixed solvent of chloroform / ethyl acetate as an eluent. The purified solution was subjected to a solvent evaporation method to remove the solvent to obtain a 4-cyano-4'-pentylbiphenyl liquid crystal monomer;

[0033] S2. Preparation of 4-cyano-4'-pentylbiphenyl liquid crystal monomer grafted polydimethylsiloxane: Add 1300 mL of 1,2-dichloroethylene solvent and 100 g of polydimethylsiloxane to a reaction container, dissolve and disperse them evenly by ultrasonication, add 45 g of 4-cyano-4'-pentylbiphenyl liquid crystal monomer, dissolve and disperse them evenly by ultrasonication, add 0.2 g of ammonium persulfate as a free radical initiator, dissolve and disperse them evenly by ultrasonication, react at 55°C for 5.5 hours, and remove the solvent by solvent evaporation to obtain 4-cyano-4'-pentylbiphenyl liquid crystal monomer grafted polydimethylsiloxane;

[0034] S3. Preparation of poly(N-isopropylacrylamide): 450 mL of deionized water and 100 g of N-isopropylacrylamide were added to a reaction vessel, and the mixture was uniformly dissolved and dispersed by ultrasonication. 0.2 g of ammonium persulfate as an initiator was added, and the mixture was uniformly dissolved and dispersed by ultrasonication. The mixture was reacted at 65° C. for 9 h, and ethanol was added to precipitate the poly(N-isopropylacrylamide) from the reaction solution by precipitation. The mixture was centrifuged, washed with ethanol, and dried to obtain the poly(N-isopropylacrylamide).

[0035] S4. Preparation of temperature-sensitive shape memory rubber material: 450 mL of 1,2-dichloroethylene solvent, 4.5 g of ceramic powder nanosilica, 4.5 g of carbon nanotubes, 4.5 g of poly(N-isopropylacrylamide), and 100 g of 4-cyano-4'-pentylbiphenyl liquid crystal monomer grafted polydimethylsiloxane were added to a reaction container, and ultrasonically dispersed evenly. The solvent was removed by solvent evaporation method, and then poured into a mold. The material was processed by hot pressing process at a temperature of 105°C and a pressure of 25 MPa, and then annealed at 145°C for 110 minutes. The material was naturally cooled to room temperature to obtain a temperature-sensitive shape memory rubber material.

[0036] Example 3:

[0037] S1. Preparation of 4-cyano-4'-pentylbiphenyl liquid crystal monomer: In a nitrogen atmosphere, 500 mL of chloroform solvent, 100 g of 4-cyanobenzoic acid, and 160 g of 4-n-pentylbiphenyl were added to a reaction vessel, and the mixture was uniformly dissolved and dispersed by ultrasonication. 3 g of aluminum chloride catalyst was slowly added under ultrasonication, and the mixture was reacted at 80° C. for 12 h. The mixture was naturally cooled to room temperature, and purified by column chromatography using a mixed solvent of chloroform / ethyl acetate as an eluent. The purified solution was subjected to a solvent evaporation method to remove the solvent to obtain a 4-cyano-4'-pentylbiphenyl liquid crystal monomer;

[0038] S2. Preparation of 4-cyano-4'-pentylbiphenyl liquid crystal monomer grafted polydimethylsiloxane: Add 1400 mL of 1,2-dichloroethylene solvent and 100 g of polydimethylsiloxane to a reaction container, dissolve and disperse them evenly by ultrasonication, add 50 g of 4-cyano-4'-pentylbiphenyl liquid crystal monomer, dissolve and disperse them evenly by ultrasonication, add 0.3 g of ammonium persulfate as a free radical initiator, dissolve and disperse them evenly by ultrasonication, react at 60°C for 6 h, and remove the solvent by solvent evaporation to obtain 4-cyano-4'-pentylbiphenyl liquid crystal monomer grafted polydimethylsiloxane;

[0039] S3. Preparation of poly(N-isopropylacrylamide): 500 mL of deionized water and 100 g of N-isopropylacrylamide were added to a reaction vessel, and the mixture was uniformly dissolved and dispersed by ultrasonication. 0.3 g of ammonium persulfate as an initiator was added, and the mixture was uniformly dissolved and dispersed by ultrasonication. The mixture was reacted at 70° C. for 10 h, and ethanol was added to precipitate the poly(N-isopropylacrylamide) from the reaction solution by precipitation. The mixture was centrifuged, washed with ethanol, and dried to obtain the poly(N-isopropylacrylamide).

[0040] S4. Preparation of temperature-sensitive shape memory rubber material: 500 mL of 1,2-dichloroethylene solvent, 5 g of ceramic powder nano-silica, 5 g of carbon nanotubes, 5 g of poly(N-isopropylacrylamide), and 100 g of 4-cyano-4'-pentylbiphenyl liquid crystal monomer grafted polydimethylsiloxane were added to a reaction container, and the mixture was uniformly dispersed by ultrasonication. The solvent was removed by solvent evaporation. The mixture was then poured into a mold and processed by hot pressing at a temperature of 110°C and a pressure of 30 MPa. The mixture was then annealed at 150°C for 120 minutes and naturally cooled to room temperature to obtain a temperature-sensitive shape memory rubber material.

[0041] Example 4:

[0042] S1. Preparation of 4-cyano-4'-pentylbiphenyl liquid crystal monomer: In a nitrogen atmosphere, 550 mL of chloroform solvent, 100 g of 4-cyanobenzoic acid, and 170 g of 4-n-pentylbiphenyl were added to a reaction vessel, and the mixture was uniformly dissolved and dispersed under ultrasound. 3.5 g of aluminum chloride catalyst was slowly added under ultrasound, and the mixture was reacted at 85° C. for 13 h. The mixture was naturally cooled to room temperature, and purified by column chromatography using a mixed solvent of chloroform / ethyl acetate as an eluent. The purified solution was subjected to a solvent evaporation method to remove the solvent to obtain a 4-cyano-4'-pentylbiphenyl liquid crystal monomer;

[0043] S2. Preparation of 4-cyano-4'-pentylbiphenyl liquid crystal monomer grafted polydimethylsiloxane: Add 1500 mL of 1,2-dichloroethylene solvent and 100 g of polydimethylsiloxane to a reaction container, dissolve and disperse them evenly by ultrasonication, add 55 g of 4-cyano-4'-pentylbiphenyl liquid crystal monomer, dissolve and disperse them evenly by ultrasonication, add 0.4 g of ammonium persulfate as a free radical initiator, dissolve and disperse them evenly by ultrasonication, react at 65°C for 6.5 hours, and remove the solvent by solvent evaporation to obtain 4-cyano-4'-pentylbiphenyl liquid crystal monomer grafted polydimethylsiloxane;

[0044] S3. Preparation of poly(N-isopropylacrylamide): 550 mL of deionized water and 100 g of N-isopropylacrylamide were added to a reaction vessel, and the mixture was uniformly dissolved and dispersed by ultrasonication. 0.4 g of ammonium persulfate as an initiator was added, and the mixture was uniformly dissolved and dispersed by ultrasonication. The mixture was reacted at 75° C. for 11 h. Ethanol was added to precipitate the poly(N-isopropylacrylamide) from the reaction solution by precipitation. The mixture was centrifuged, washed with ethanol, and dried to obtain the poly(N-isopropylacrylamide).

[0045] S4. Preparation of temperature-sensitive shape memory rubber material: 550 mL of 1,2-dichloroethylene solvent, 5.5 g of ceramic powder nanosilica, 5.5 g of carbon nanotubes, 5.5 g of poly(N-isopropylacrylamide), and 100 g of 4-cyano-4'-pentylbiphenyl liquid crystal monomer grafted polydimethylsiloxane were added to a reaction container, and ultrasonically dispersed evenly. The solvent was removed by solvent evaporation, and then poured into a mold. The material was processed by hot pressing at a temperature of 115°C and a pressure of 35 MPa, and then annealed at 155°C for 130 minutes. The material was naturally cooled to room temperature to obtain a temperature-sensitive shape memory rubber material.

[0046] Example 5:

[0047] S1. Preparation of 4-cyano-4'-pentylbiphenyl liquid crystal monomer: In a nitrogen atmosphere, 600 mL of chloroform solvent, 100 g of 4-cyanobenzoic acid, and 180 g of 4-n-pentylbiphenyl were added to a reaction vessel, and the mixture was uniformly dissolved and dispersed under ultrasound. 4 g of aluminum chloride catalyst was slowly added under ultrasound, and the mixture was reacted at 90° C. for 14 h. The mixture was naturally cooled to room temperature, and purified by column chromatography using a mixed solvent of chloroform / ethyl acetate as an eluent. The purified solution was subjected to solvent evaporation to remove the solvent, thereby obtaining a 4-cyano-4'-pentylbiphenyl liquid crystal monomer.

[0048] S2. Preparation of 4-cyano-4'-pentylbiphenyl liquid crystal monomer grafted polydimethylsiloxane: Add 1600 mL of 1,2-dichloroethylene solvent and 100 g of polydimethylsiloxane to a reaction container, dissolve and disperse them evenly by ultrasonication, add 60 g of 4-cyano-4'-pentylbiphenyl liquid crystal monomer, dissolve and disperse them evenly by ultrasonication, add 0.5 g of ammonium persulfate as a free radical initiator, dissolve and disperse them evenly by ultrasonication, react at 70°C for 7 h, and remove the solvent by solvent evaporation to obtain 4-cyano-4'-pentylbiphenyl liquid crystal monomer grafted polydimethylsiloxane;

[0049] S3. Preparation of poly(N-isopropylacrylamide): 600 mL of deionized water and 100 g of N-isopropylacrylamide were added to a reaction vessel, and the mixture was uniformly dissolved and dispersed by ultrasonication. 0.5 g of ammonium persulfate as an initiator was added, and the mixture was uniformly dissolved and dispersed by ultrasonication. The mixture was reacted at 80° C. for 12 h, and ethanol was added to precipitate the poly(N-isopropylacrylamide) from the reaction solution by precipitation. The mixture was centrifuged, washed with ethanol, and dried to obtain the poly(N-isopropylacrylamide).

[0050] S4. Preparation of temperature-sensitive shape memory rubber material: add 600 mL of 1,2-dichloroethylene solvent, 6 g of ceramic powder nanosilica, 6 g of carbon nanotubes, 6 g of poly(N-isopropylacrylamide), and 100 g of 4-cyano-4'-pentylbiphenyl liquid crystal monomer grafted polydimethylsiloxane into a reaction container, disperse them evenly by ultrasonication, remove the solvent by solvent evaporation, pour them into a mold, and process them by hot pressing at a temperature of 120°C and a pressure of 40 MPa, and then anneal them at 160°C for 140 minutes. Naturally cool them to room temperature to obtain a temperature-sensitive shape memory rubber material.

[0051] Performance Testing

[0052] Shape memory performance test

[0053] The temperature-sensitive shape memory rubber materials obtained in Examples 1-5 were cut into standard-sized samples, measuring 3×3×5 cm. Their shape memory properties were tested using an Instron 5985 shape memory tester. The samples were pre-strained to 70% of their original shape at a constant temperature of 20°C. The samples were then heated to 60°C and held for 5 minutes to ensure complete deformation. The samples were then rapidly cooled to 20°C. The shape recovery of the samples was then recorded, and the shape recovery rate of the samples was quantified using the shape memory tester. The test results are shown in the following table:

[0054] Example 1 Example 2 Example 3 Example 4 Example 5 Shape recovery rate (%) 94.3 96.8 97.2 96.7 95.6

[0055] Temperature sensitivity test

[0056] Standard-sized samples of the temperature-sensitive shape memory rubber materials obtained in Examples 1-5 were cut to dimensions of 20 × 10 × 0.2 cm. Their temperature sensitivity was tested using an MTS 810 temperature-strain testing system. The specimens were clamped in a tensile fixture with an initial clamping distance of 10 mm. Preload was applied at a constant stress σ = 0.5 MPa for 1 min at 20°C. The temperature was then increased from 20°C to 80°C at a rate of 2°C / min. The temperature and strain were simultaneously recorded in real time. After the temperature reached 80°C, it was maintained for 5 minutes while the peak strain was continuously recorded. The heating was then turned off, and the specimens were allowed to cool naturally to 20°C. The residual strain during the cooling process was again recorded. The following table shows the test results:

[0057]

[0058] Sealing performance test

[0059] The temperature-sensitive shape memory rubber materials obtained in Examples 1-5 were cut into standard-sized circular samples with a diameter of 5 cm × 0.2 cm. The sealing performance of the samples was tested using a DHL-400 sealing test system. The material samples were installed in the sealing test equipment, the temperature was set at 70°C, and a pressure difference of 1 MPa was applied. The sealing pressure leakage rate of the materials was measured. The following table shows the test results:

[0060]

[0061] Thermal stability test

[0062] A 10 g sample of the temperature-sensitive shape memory rubber material obtained in Examples 1-5 was cut and its thermal stability was tested using a TA Instruments Q500 thermogravimetric analyzer. A nitrogen protective atmosphere was set, the heating rate was 10°C / min, and the temperature range was from room temperature to 500°C. The following table shows the test results:

[0063] Example 1 Example 2 Example 3 Example 4 Example 5 Residual amount (%) 96.4 97.2 97.5 97.0 96.9

[0064] Mechanical properties testing

[0065] The temperature-sensitive shape memory rubber materials obtained in Examples 1-5 were cut into standard size samples, with dimensions of 10×1×0.5 cm. Their mechanical properties were tested using an Instron 3367 electronic universal material testing machine at room temperature and a tensile speed of 5 mm / min. The following table shows the test results:

[0066] Example 1 Example 2 Example 3 Example 4 Example 5 Tensile strength (MPa) 11.9 12.3 12.5 12.2 12.0

Claims

1. A temperature-sensitive shape memory rubber material, characterized in that: The preparation method is as follows: S1. Preparation of 4-cyano-4'-pentylbiphenyl liquid crystal monomer: In a nitrogen atmosphere, chloroform solvent, 4-cyanobenzoic acid, and 4-n-pentylbiphenyl were added to a reaction vessel, and ultrasonically dissolved and dispersed uniformly. A catalyst, aluminum chloride, was slowly added under ultrasonication to react, and the mixture was naturally cooled to room temperature. The mixture was purified by column chromatography using a mixed solvent of chloroform / ethyl acetate as an eluent, and the solvent was removed from the purified solution by solvent evaporation to obtain a 4-cyano-4'-pentylbiphenyl liquid crystal monomer; S2. Preparation of 4-cyano-4'-pentylbiphenyl liquid crystal monomer grafted polydimethylsiloxane: adding 1,2-dichloroethylene solvent and polydimethylsiloxane to a reaction vessel, dissolving and dispersing them uniformly through ultrasonication, adding 4-cyano-4'-pentylbiphenyl liquid crystal monomer, dissolving and dispersing them uniformly through ultrasonication, adding ammonium persulfate as a free radical initiator, dissolving and dispersing them uniformly through ultrasonication, reacting, and removing the solvent by solvent evaporation to obtain 4-cyano-4'-pentylbiphenyl liquid crystal monomer grafted polydimethylsiloxane; S3. Preparation of poly(N-isopropylacrylamide): Deionized water and N-isopropylacrylamide are added to a reaction vessel, and the mixture is uniformly dissolved and dispersed by ultrasonication. Ammonium persulfate as an initiator is added, and the mixture is uniformly dissolved and dispersed by ultrasonication. The reaction is carried out, and ethanol is added to precipitate the poly(N-isopropylacrylamide) from the reaction solution by precipitation. The mixture is centrifuged, washed with ethanol, and dried to obtain the poly(N-isopropylacrylamide). S4. Preparation of a temperature-sensitive shape memory rubber material: Add 1,2-dichloroethylene solvent, ceramic powder, carbon nanotubes, poly(N-isopropylacrylamide), and 4-cyano-4'-pentylbiphenyl liquid crystal monomer grafted polydimethylsiloxane into a reaction vessel, disperse them evenly by ultrasonication, remove the solvent by solvent evaporation, pour them into a mold, and process them by hot pressing at a temperature of 100-120°C and a pressure of 20-40 MPa, followed by annealing at 140-160°C for 100-140 minutes, and naturally cool them to room temperature to obtain a temperature-sensitive shape memory rubber material.

2. The temperature-sensitive shape memory rubber material according to claim 1, characterized in that: In step S1, the formula ratio of chloroform, 4-cyanobenzoic acid, 4-n-pentylbiphenyl, and aluminum chloride is 400-600 mL: 100 g: 140-180 g: 2-4 g.

3. The temperature-sensitive shape memory rubber material according to claim 1, characterized in that: The reaction conditions in step S1 are 70-90° C. for 10-14 hours.

4. The temperature-sensitive shape memory rubber material according to claim 1, characterized in that: In step S2, the formula ratio of 1,2-dichloroethylene, polydimethylsiloxane, 4-cyano-4'-pentylbiphenyl liquid crystal monomer, and ammonium persulfate is 1200-1600 mL: 100 g: 40-60 g: 0.1-0.5 g.

5. The temperature-sensitive shape memory rubber material according to claim 1, characterized in that: The reaction conditions in step S2 are 50-70° C. for 5-7 hours.

6. The temperature-sensitive shape memory rubber material according to claim 1, characterized in that: In step S3, the formula ratio of deionized water, N-isopropylacrylamide, and ammonium persulfate is 400-600 mL: 100 g: 0.1-0.5 g.

7. The temperature-sensitive shape memory rubber material according to claim 1, characterized in that: The reaction conditions in step S3 are 60-80° C. for 8-12 hours.

8. The temperature-sensitive shape memory rubber material according to claim 1, characterized in that: The ceramic powder in step S4 is nano-silicon dioxide.

9. The temperature-sensitive shape memory rubber material according to claim 1, characterized in that: In step S4, the formula ratio of 1,2-dichloroethylene, ceramic powder, carbon nanotubes, poly(N-isopropylacrylamide), and 4-cyano-4'-pentylbiphenyl liquid crystal monomer grafted polydimethylsiloxane is 400-600 mL: 4-6 g: 4-6 g: 4-6 g: 100 g.

10. Application of a temperature-sensitive shape memory rubber material in the field of intelligent sealing, characterized by: The temperature-sensitive shape memory rubber material can be applied to intelligent pipeline valve seals, aerospace thermal insulation seals, intelligent flexible connectors, automobile engine and chassis self-adjusting seals, microfluidic chips and intelligent valves, and building energy-saving intelligent window seals.

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