Surface-modified silicone rubber composite film and preparation method thereof

Abstract

The invention provides a surface-modified silicone rubber composite membrane and a preparation method thereof, and belongs to the technical field of composite membrane preparation. The polydimethylsiloxane is used as a flexible matrix and provides excellent gas permeability, and the reaction activity is improved by introducing a vinyl functional group, so that the polydimethylsiloxane can be grafted with a thermosensitive monomer and a photoresponse monomer, and the film material is endowed with temperature and photoresponse capability; the cellulose nanocrystals are modified by MOF, so that the specific surface area and pore structure of the filler are improved, the mechanical property and molecular sieve effect of the membrane are enhanced, and meanwhile, the uniform dispersity of the filler in a matrix is ensured; graphene oxide is modified by crown ether, so that the ion recognition capability, the mechanical enhancement effect and the separation selectivity of the membrane are further improved; through combination of the three, high efficiency and multifunctional adaptability of the surface-modified silicone rubber composite membrane in a complex separation task are realized.

Description

Technical Field

[0001] The invention belongs to the technical field of composite film preparation, and relates to a surface-modified silicone rubber composite film and a preparation method thereof. Background Art

[0002] Polydimethylsiloxane is a widely used silicone polymer favored for its excellent biocompatibility, good flexibility and low surface energy. This material has good thermal resistance and chemical stability. However, although polydimethylsiloxane performs well in many applications, it still has some shortcomings in mechanical properties and separation efficiency.

[0003] First, polydimethylsiloxane has weak mechanical properties, especially under high load or high impact conditions. Due to its high flexibility, polydimethylsiloxane easily deforms when subjected to tension and compression, resulting in lower tensile strength and tear strength than other high-performance materials. This makes polydimethylsiloxane perform poorly in some demanding engineering applications, especially those that require long-term loads or dynamic stresses.

[0004] Secondly, in terms of separation efficiency for organic hydrocarbon gases, the hydrophobicity and molecular selectivity of polydimethylsiloxane are insufficient, making it ineffective in gas separation applications. Especially in the separation of organic hydrocarbon gases such as gasoline and oil, the gas permeability and selective permeability of traditional polydimethylsiloxane membranes are low, and different types of hydrocarbon molecules cannot be effectively separated, resulting in unsatisfactory performance in high-efficiency separation applications. Summary of the invention

[0005] In view of the above problems, the purpose of the present invention is to provide a surface-modified silicone rubber composite membrane and a preparation method thereof. In the present invention, polydimethylsiloxane is used as a flexible matrix to provide excellent gas permeability, and the reaction activity is significantly improved by introducing vinyl functional groups, so that it can be grafted with thermosensitive monomers and photoresponsive monomers, giving the membrane material temperature and light responsiveness; cellulose nanocrystals are modified by MOF, which significantly improves the specific surface area and pore structure of the filler, enhances the mechanical properties and molecular sieve effect of the membrane, and ensures the uniform dispersion of the filler in the matrix; graphene oxide is modified by crown ethers, which further improves the ion recognition ability, mechanical enhancement and separation selectivity of the membrane. The combination of the three realizes the high efficiency and multifunctional adaptability of the composite membrane in complex separation tasks.

[0006] To achieve this object, the present invention adopts the following technical solutions: In a first aspect, the present invention provides a method for preparing a surface-modified silicone rubber composite film, the method for preparing the surface-modified silicone rubber composite film comprising: S1: reacting N-isopropylacrylamide with vinyltrimethoxysilane to obtain a thermosensitive monomer; S2: reacting p-aminoazobenzene with 3-isocyanatepropyltrimethoxysilane to obtain a photoresponsive monomer; S3: vinyl-modified polydimethylsiloxane is obtained by reacting polydimethylsiloxane with vinyl trimethoxysilane under the catalysis of dibutyltin dilaurate; the polydimethylsiloxane is dispersed in a hydrochloric acid solution to obtain pre-hydrolyzed vinyl-modified polydimethylsiloxane; the pre-hydrolyzed vinyl-modified polydimethylsiloxane is mixed with tetramethylammonium hydroxide, a thermosensitive monomer and a photoresponsive monomer to obtain a multi-modified polydimethylsiloxane; S21: dispersing cellulose nanocrystals in deionized water, adding copper nitrate and trimesic acid after ultrasonic dispersion to obtain a fifth reaction solution, centrifuging, washing, and drying after the reaction to obtain MOF-modified cellulose nanocrystals; S22: Under nitrogen protection, 18-crown ether-6 and potassium carbonate are dispersed in N,N-dimethylformamide, and then a solution of N-(3-chloropropyl)phthalimide in N,N-dimethylformamide is added to react to obtain a phthalimide-modified crown ether; the phthalimide-modified crown ether is mixed with hydrazine hydrate and reacted to obtain an amino crown ether; S23: dispersing graphene oxide in N,N-dimethylformamide solution, adding 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide to obtain a seventh reaction solution, adding amino crown ether after stirring at room temperature, continuing the reaction, centrifuging, washing, and vacuum drying to obtain crown ether-modified graphene oxide; S4: Disperse multi-modified polydimethylsiloxane, MOF-modified cellulose nanocrystals, and crown ether-modified graphene oxide in tetrahydrofuran, add a cross-linking agent and a catalyst to obtain a casting solution after ultrasonic dispersion, coat the solution on the surface of the supporting base membrane, and obtain a surface-modified silicone rubber composite membrane after heat treatment.

[0007] Specifically, S1: dispersing N-isopropylacrylamide and vinyltrimethoxysilane in anhydrous methanol to obtain a first reaction solution, and then subjecting the solution to a catalytic reaction with benzoyl peroxide under nitrogen protection, rotary evaporation, washing, and drying to obtain a thermosensitive monomer; S2: dispersing p-aminoazobenzene in dichloromethane, adding dropwise a dichloromethane solution of 3-isocyanatepropyltrimethoxysilane to obtain a second reaction solution, reacting at room temperature under nitrogen protection, filtering, concentrating under reduced pressure, and recrystallizing to obtain a photoresponsive monomer; S3: Dissolve polydimethylsiloxane in tetrahydrofuran, add vinyltrimethoxysilane and dibutyltin dilaurate to obtain a third reaction liquid, and perform vacuum distillation after the reaction to obtain vinyl-modified polydimethylsiloxane; disperse it in a hydrochloric acid solution to obtain pre-hydrolyzed vinyl-modified polydimethylsiloxane; prepare a tetrahydrofuran solution of the pre-hydrolyzed vinyl-modified polydimethylsiloxane, add tetramethylammonium hydroxide, a thermosensitive monomer and a photoresponsive monomer to obtain a fourth reaction liquid, and adjust the pH with a sodium bicarbonate solution after the reaction, stir, filter, wash, and rotary evaporate to obtain a multi-modified polydimethylsiloxane.

[0008] S21: dispersing cellulose nanocrystals in deionized water, adding copper nitrate and trimesic acid after ultrasonic dispersion to obtain a fifth reaction solution, centrifuging, washing, and drying after the reaction to obtain MOF-modified cellulose nanocrystals; S22: Disperse 18-crown ether-6 in N,N-dimethylformamide (DMF), add potassium carbonate under nitrogen protection and stir, then dropwise add DMF solution of N-(3-chloropropyl)phthalimide to obtain a sixth reaction solution, and react by stirring at a constant temperature; filter, rotary evaporate, and column chromatograph to obtain a phthalimide-modified crown ether; prepare a methanol solution of the phthalimide-modified crown ether, add hydrazine hydrate under stirring, and reflux reaction, and rotary evaporate and purify to obtain an amino crown ether; S23: dispersing graphene oxide in DMF, adding 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide after the dispersion is uniform to obtain a seventh reaction solution, adding amino crown ether after stirring at room temperature, continuing the reaction, centrifuging, washing, and vacuum drying to obtain crown ether-modified graphene oxide; S4: Disperse multi-modified polydimethylsiloxane, MOF-modified cellulose nanocrystals and crown ether-modified graphene oxide in tetrahydrofuran, and obtain a dispersion by ultrasonic dispersion. Then, add a cross-linking agent and a catalyst, and continue to disperse. Vacuum degassing is performed to obtain a casting liquid. The liquid is evenly coated on the surface of the supporting base membrane, and a surface-modified silicone rubber composite membrane is obtained after heat treatment.

[0009] As a preferred technical solution of the present invention, in step S1, the molar ratio of N-isopropylacrylamide to vinyltrimethoxysilane is (4.0-4.5):1, for example, it can be 4.00:1, 4.05:1, 4.10:1, 4.15:1, 4.20:1, 4.25:1, 4.30:1, 4.35:1, 4.40:1, 4.45:1 or 4.50:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0010] In some optional embodiments, the total concentration of N-isopropylacrylamide and vinyltrimethoxysilane in methanol is 10-15wt.%, for example, it can be 10.0wt.%, 10.5wt.%, 11.0wt.%, 11.5wt.%, 12.0wt.%, 12.5wt.%, 13.0wt.%, 13.5wt.%, 14.0wt.%, 14.5wt.% or 15.0wt.%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0011] In some optional embodiments, the reaction temperature of the first reaction liquid under nitrogen protection is 65-70°C, for example, it can be 65.0°C, 65.5°C, 66.0°C, 66.5°C, 67.0°C, 67.5°C, 68.0°C, 68.5°C, 69.0°C, 69.5°C or 70.0°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0012] In some optional embodiments, the reaction time of the first reaction liquid under nitrogen protection is 5-6h, for example, it can be 5.0h, 5.1h, 5.2h, 5.3h, 5.4h, 5.5h, 5.6h, 5.7h, 5.8h, 5.9h or 6.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0013] As a preferred technical solution of the present invention, in step S2, the concentration of p-aminoazobenzene in dichloromethane is 5-8wt.%, for example, it can be 5.0wt.%, 5.3wt.%, 5.6wt.%, 5.9wt.%, 6.2wt.%, 6.5wt.%, 6.8wt.%, 7.1wt.%, 7.4wt.%, 7.7wt.% or 8.0wt.%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0014] In some optional embodiments, the concentration of the dichloromethane solution of 3-isocyanatepropyltrimethoxysilane is 3-5wt%, for example, it can be 3.0wt.%, 3.2wt.%, 3.4wt.%, 3.6wt.%, 3.8wt.%, 4.0wt.%, 4.2wt.%, 4.4wt.%, 4.6wt.%, 4.8wt.% or 5.0wt.%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0015] In some optional embodiments, the molar ratio of 3-isocyanatepropyltrimethoxysilane to p-aminoazobenzene is (1.1-1.2):1, for example, it can be 1.10:1, 1.11:1, 1.12:1, 1.13:1, 1.14:1, 1.15:1, 1.16:1, 1.17:1, 1.18:1, 1.19:1 or 1.20:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0016] In some optional embodiments, the dripping speed of the dichloromethane solution of 3-isocyanatepropyltrimethoxysilane is 3-4 mL / min, for example, it can be 3.0 mL / min, 3.1 mL / min, 3.2 mL / min, 3.3 mL / min, 3.4 mL / min, 3.5 mL / min, 3.6 mL / min, 3.7 mL / min, 3.8 mL / min, 3.9 mL / min or 4.0 mL / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0017] In some optional embodiments, the reaction time of the second reaction liquid at room temperature under nitrogen protection is 18-20 hours, for example, it can be 18.0h, 18.2h, 18.4h, 18.6h, 18.8h, 19.0h, 19.2h, 19.4h, 19.6h, 19.8h or 20.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0018] As a preferred technical solution of the present invention, in step S3, the mass ratio of polydimethylsiloxane to tetrahydrofuran is 1:(5-8), for example, it can be 1:5.0, 1:5.3, 1:5.6, 1:5.9, 1:6.2, 1:6.5, 1:6.8, 1:7.1, 1:7.4, 1:7.7 or 1:8.0, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0019] In some optional embodiments, the molar ratio of the vinyltrimethoxysilane to polydimethylsiloxane is (1.2-1.5):1, for example, it can be 1.20:1, 1.23:1, 1.26:1, 1.29:1, 1.32:1, 1.35:1, 1.38:1, 1.41:1, 1.44:1, 1.47:1 or 1.50:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0020] In some optional embodiments, the dosage of dibutyltin dilaurate is 200-500ppm of the mass of polydimethylsiloxane, for example, it can be 200ppm, 230ppm, 260ppm, 290ppm, 320ppm, 350ppm, 380ppm, 410ppm, 440ppm, 470ppm or 500ppm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0021] In some optional embodiments, the reaction temperature of the third reaction liquid is 70-75°C, for example, it can be 70.0°C, 70.5°C, 71.0°C, 71.5°C, 72.0°C, 72.5°C, 73.0°C, 73.5°C, 74.0°C, 74.5°C or 75.0°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0022] In some optional embodiments, the reaction time of the third reaction liquid is 4-6h, for example, it can be 4.0h, 4.2h, 4.4h, 4.6h, 4.8h, 5.0h, 5.2h, 5.4h, 5.6h, 5.8h or 6.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0023] In some optional embodiments, the mass fraction of the tetrahydrofuran solution of vinyl-modified polydimethylsiloxane is 20-25wt.%, for example, it can be 20.0wt.%, 20.5wt.%, 21.0wt.%, 21.5wt.%, 22.0wt.%, 22.5wt.%, 23.0wt.%, 23.5wt.%, 24.0wt.%, 24.5wt.% or 25.0wt.%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0024] In some optional embodiments, the molar ratio of the vinyl-modified polydimethylsiloxane to the thermosensitive monomer and the photoresponsive monomer is (70-80):(15-10):(15-10), for example, it can be 70:15:15, 71:14.5:14.5, 72:14:14, 73:13.5:13.5, 74:13:13, 75:12.5:12.5, 76:12:12, 77:11.5:11.5, 78:11:11, 79:10.5:10.5 or 80:10:10, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0025] In some optional embodiments, the amount of tetramethylammonium hydroxide added is 0.1-0.2% of the total mass of the thermosensitive monomer and the photoresponsive monomer, for example, it can be 0.10%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19% or 0.20%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0026] In some optional embodiments, the reaction temperature of the fourth reaction liquid is 75-80°C, for example, it can be 75.0°C, 75.5°C, 76.0°C, 76.5°C, 77.0°C, 77.5°C, 78.0°C, 78.5°C, 79.0°C, 79.5°C or 80.0°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0027] In some optional embodiments, the reaction time of the fourth reaction liquid is 6-8h, for example, it can be 6.0h, 6.2h, 6.4h, 6.6h, 6.8h, 7.0h, 7.2h, 7.4h, 7.6h, 7.8h or 8.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0028] In some optional embodiments, the concentration of the sodium bicarbonate solution is 1-2 mol / L, for example, it can be 1.0 mol / L, 1.2 mol / L, 1.4 mol / L, 1.6 mol / L, 1.8 mol / L or 2.0 mol / L, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0029] In some optional embodiments, sodium bicarbonate solution is used to adjust the pH to 7-7.5, for example, 7.00, 7.05, 7.10, 7.15, 7.20, 7.25, 7.30, 7.35, 7.40, 7.45 or 7.50, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0030] As a preferred technical solution of the present invention, in S4, the cross-linking agent is any one of HMS-301, PMHS or D4H; The catalyst is any one of Karstedt catalyst and chloroplatinic acid; The supporting base film is any one of polypropylene, polyvinylidene fluoride or polysulfone; As a preferred technical solution of the present invention, in step S21, the mass fraction of the cellulose nanocrystals dispersed in deionized water is 1-2wt.%, for example, it can be 1.0wt.%, 1.1wt.%, 1.2wt.%, 1.3wt.%, 1.4wt.%, 1.5wt.%, 1.6wt.%, 1.7wt.%, 1.8wt.%, 1.9wt.% or 2.0wt.%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0031] In some optional embodiments, the power of the ultrasonic dispersion is 300-400 W, for example, it can be 300 W, 310 W, 320 W, 330 W, 340 W, 350 W, 360 W, 370 W, 380 W, 390 W or 400 W, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0032] In some optional embodiments, the ultrasonic dispersion time is 30-40 min, for example, it can be 30 min, 31 min, 32 min, 33 min, 34 min, 35 min, 36 min, 37 min, 38 min, 39 min or 40 min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0033] In some optional embodiments, the mass ratio of copper nitrate to cellulose nanocrystals is (0.3-0.5):1, for example, it can be 0.30:1, 0.32:1, 0.34:1, 0.36:1, 0.38:1, 0.40:1, 0.42:1, 0.44:1, 0.46:1, 0.48:1 or 0.50:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0034] In some optional embodiments, the molar ratio of trimesic acid to copper nitrate is (2-3):1, for example, it can be 2.0:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1 or 3.0:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0035] In some optional embodiments, the reaction time of the fifth reaction liquid is 4-6h, for example, it can be 4.0h, 4.2h, 4.4h, 4.6h, 4.8h, 5.0h, 5.2h, 5.4h, 5.6h, 5.8h or 6.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0036] As a preferred technical solution of the present invention, in step S22, the concentration of 18-crown ether-6 dispersed in N,N-dimethylformamide is 0.2-0.4M, for example, it can be 0.20M, 0.22M, 0.24M, 0.26M, 0.28M, 0.30M, 0.32M, 0.34M, 0.36M, 0.38M or 0.40M, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0037] In some optional embodiments, the temperature for adding potassium carbonate is 0-5°C, for example, it can be 0.0°C, 0.5°C, 1.0°C, 1.5°C, 2.0°C, 2.5°C, 3.0°C, 3.5°C, 4.0°C, 4.5°C or 5.0°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0038] In some optional embodiments, the molar ratio of potassium carbonate to 18-crown ether-6 is (1.2-1.5):1, for example, it can be 1.20:1, 1.23:1, 1.26:1, 1.29:1, 1.32:1, 1.35:1, 1.38:1, 1.41:1, 1.44:1, 1.47:1 or 1.50:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0039] In some optional embodiments, the molar ratio of N-(3-chloropropyl)phthalimide to 18-crown ether-6 is (1.2-1.5):1, for example, it can be 1.20:1, 1.23:1, 1.26:1, 1.29:1, 1.32:1, 1.35:1, 1.38:1, 1.41:1, 1.44:1, 1.47:1 or 1.50:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0040] In some optional embodiments, the concentration of the N,N-dimethylformamide solution of N-(3-chloropropyl)phthalimide is 0.3-0.5M, for example, it can be 0.30M, 0.32M, 0.34M, 0.36M, 0.38M, 0.40M, 0.42M, 0.44M, 0.46M, 0.48M or 0.50M, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0041] In some optional embodiments, the temperature of the sixth reaction liquid under constant temperature stirring reaction is 50-60°C, for example, it can be 50.0°C, 51.0°C, 52.0°C, 53.0°C, 54.0°C, 55.0°C, 56.0°C, 57.0°C, 58.0°C, 59.0°C or 60.0°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0042] In some optional embodiments, the stirring reaction time of the sixth reaction liquid at a constant temperature is 10-14h, for example, it can be 10.0h, 10.4h, 10.8h, 11.2h, 11.6h, 12.0h, 12.4h, 12.8h, 13.2h, 13.6h or 14.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0043] In some optional embodiments, the concentration of the methanol solution of the phthalimide-modified crown ether is 0.1-0.2 g / mL, for example, it can be 0.10 g / mL, 0.11 g / mL, 0.12 g / mL, 0.13 g / mL, 0.14 g / mL, 0.15 g / mL, 0.16 g / mL, 0.17 g / mL, 0.18 g / mL, 0.19 g / mL or 0.20 g / mL, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0044] In some optional embodiments, the molar ratio of hydrazine hydrate to phthalimide-modified crown ether is (3-4):1, for example, 3.0:1, 3.2:1, 3.4:1, 3.6:1, 3.8:1 or 4.0:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0045] In some optional embodiments, the temperature of the reflux reaction is 60-70°C, for example, it can be 60.0°C, 61.0°C, 62.0°C, 63.0°C, 64.0°C, 65.0°C, 66.0°C, 67.0°C, 68.0°C, 69.0°C or 70.0°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0046] In some optional embodiments, the reflux reaction time is 4-8h, for example, it can be 4.0h, 4.4h, 4.8h, 5.2h, 5.6h, 6.0h, 6.4h, 6.8h, 7.2h, 7.6h or 8.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0047] As a preferred technical solution of the present invention, in step S23, the mass fraction of the graphene oxide dispersed in N,N-dimethylformamide is 0.1-0.2wt.%, for example, it can be 0.10wt.%, 0.11wt.%, 0.12wt.%, 0.13wt.%, 0.14wt.%, 0.15wt.%, 0.16wt.%, 0.17wt.%, 0.18wt.%, 0.19wt.% or 0.20wt.%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0048] In some optional embodiments, the mass ratio of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, N-hydroxysuccinimide and graphene oxide is (2-3):2:1, for example, it can be 2:2:1, 2.1:2:1, 2.2:2:1, 2.3:2:1, 2.4:2:1, 2.5:2:1, 2.6:2:1, 2.7:2:1, 2.8:2:1, 2.9:2:1 or 3:2:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0049] In some optional embodiments, the seventh reaction liquid is stirred at room temperature for 2-3 h, for example, 2.0 h, 2.2 h, 2.4 h, 2.6 h, 2.8 h or 3.0 h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0050] In some optional embodiments, the mass ratio of the amino crown ether to graphene oxide is (2-3):1, for example, it can be 2.0:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1 or 3.0:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0051] In some optional embodiments, the continued reaction time is 20-24h, for example, it can be 20.0h, 20.4h, 20.8h, 21.2h, 21.6h, 22.0h, 22.4h, 22.8h, 23.2h, 23.6h or 24.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0052] As a preferred technical solution of the present invention, in step S4, the mass ratio of the multi-modified polydimethylsiloxane to tetrahydrofuran is 1:(3-4), for example, it can be 1:3.0, 1:3.2, 1:3.4, 1:3.6, 1:3.8 or 1:4.0, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0053] In some optional embodiments, the heat treatment temperature is 60-70°C, for example, it can be 60.0°C, 61.0°C, 62.0°C, 63.0°C, 64.0°C, 65.0°C, 66.0°C, 67.0°C, 68.0°C, 69.0°C or 70.0°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0054] In some optional embodiments, the heat treatment time is 4-5h, for example, it can be 4.0h, 4.2h, 4.4h, 4.6h, 4.8h or 5.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0055] In a second aspect, the present invention provides a surface-modified silicone rubber composite membrane. The surface-modified silicone rubber composite membrane comprises multi-modified polydimethylsiloxane, MOF-modified cellulose nanocrystals, crown ether-modified graphene oxide, a cross-linking agent and a catalyst, wherein the mass ratio of the multi-modified polydimethylsiloxane, MOF-modified cellulose nanocrystals, crown ether-modified graphene oxide, the cross-linking agent and the catalyst is: 100:(1-3):(1.5-3):(4-6):(0.1-0.2).

[0056] In the present invention, firstly, polydimethylsiloxane is selected as a matrix, and a vinyl functional group is introduced by chemical modification to improve the reactivity of the material, so as to lay a foundation for subsequent functionalization reactions. In specific operations, vinyl trimethoxysilane is used as a modifying agent, and a vinyl group is introduced into the molecular chain end of polydimethylsiloxane by silylation reaction. In order to promote the efficient conduction of this reaction and ensure the quality stability of the product, dibutyltin dilaurate is introduced as a homogeneous catalyst. Dibutyltin dilaurate is a typical organotin catalyst, which significantly improves the condensation reaction rate between the siloxane group and trimethoxysilane by reducing the reaction activation energy, while avoiding the occurrence of side reactions.

[0057] Through this reaction, vinyl-modified polydimethylsiloxane was successfully prepared. The vinyl functional group at the end of its molecular chain has high activity and can be chemically grafted with a variety of functional monomers. The core of this modification step is that by introducing vinyl groups, not only does it achieve efficient participation of polydimethylsiloxane in the functionalization reaction, but it also significantly improves its chemical bonding ability with subsequent thermosensitive monomers and photoresponsive monomers. The presence of vinyl groups enables these functional monomers to be stably grafted onto the molecular chain of polydimethylsiloxane by chemical bonds, avoiding the phase separation or uneven distribution problems that may occur in traditional physical mixing.

[0058] In addition, the introduction of vinyl groups also gives polydimethylsiloxane a higher degree of freedom in molecular design, enabling it to further participate in cross-linking reactions to form a multifunctional silicone rubber matrix with a network structure. This matrix not only maintains the inherent flexibility and excellent gas permeability of polydimethylsiloxane, but also enhances its dynamic regulation ability under external stimuli such as temperature response and light response through subsequent functionalization, laying a solid foundation for the multifunctionality and efficient separation performance of the composite membrane.

[0059] In the present invention, in order to give the material temperature responsive properties, a thermosensitive monomer is specially introduced to functionalize polydimethylsiloxane. The thermosensitive monomer selected is N-isopropylacrylamide, which is a typical thermosensitive monomer and is widely used in the design of temperature responsive materials due to its unique low critical solution temperature characteristics. The molecular structure of N-isopropylacrylamide contains a hydrophilic amide group and a hydrophobic isopropyl group, and its thermosensitive behavior comes from the competition between these two groups at a specific temperature. Specifically, at temperatures below the critical solution temperature, the amide group exhibits hydrophilicity by forming hydrogen bonds with water molecules; at temperatures above the critical solution temperature, the hydrogen bonds are broken, and the hydrophobic isopropyl group dominates, making the N-isopropylacrylamide group hydrophobic. This reversible hydrophilic-hydrophobic transition makes N-isopropylacrylamide an ideal thermosensitive functional monomer.

[0060] In order to stably introduce the thermosensitive properties of N-isopropylacrylamide into the silicone rubber matrix, the present invention combines N-isopropylacrylamide with vinyltrimethoxysilane through a free radical copolymerization reaction to generate a thermosensitive copolymer containing siloxane side chains. Specifically, the acryloyl double bond of N-isopropylacrylamide and the vinyl group of vinyltrimethoxysilane are copolymerized under the action of an initiator to form a polymer chain with a siloxane functional group. Subsequently, through the siloxane condensation reaction, the siloxane group of the thermosensitive copolymer forms a covalent bond with the silanol group of the pre-hydrolyzed vinyl-modified polydimethylsiloxane, thereby achieving stable grafting of the thermosensitive monomer. This method not only retains the thermosensitive properties of N-isopropylacrylamide, but also ensures the uniform distribution of the functional groups in the matrix through chemical bonding, significantly improving the stability of the material and the controllability of the function.

[0061] The temperature-responsive characteristics brought about by this thermosensitive monomer modification enable the performance of the membrane material to be dynamically regulated during use. Specifically, the modified polydimethylsiloxane matrix will show significant changes in hydrophilicity and hydrophobicity when the temperature rises or falls. This change directly affects the adsorption behavior and transmission capacity of the membrane for different molecules. For example, during the pervaporation process, when the temperature is higher than the critical solution temperature, the membrane surface becomes more hydrophobic, which can more effectively selectively permeate and separate organic vapors; at temperatures below the critical solution temperature, the membrane surface becomes hydrophilic, which may be more suitable for the penetration and separation of water molecules. Therefore, through this thermosensitive monomer modification, not only is the membrane material endowed with the ability to respond intelligently to changes in external temperature, but it also significantly increases the separation efficiency and scope of application of the membrane in different application scenarios.

[0062] In addition, the introduction of thermosensitive monomers also forms a synergistic effect with other functional modifications (such as the introduction of photoresponsive monomers), so that the final prepared composite membrane material can respond to multiple external stimulus conditions at the same time. This multifunctional response characteristic makes the membrane material more adaptable in complex operating environments, providing more possibilities for its application in oxygen-enriched separation, organic vapor recovery and pervaporation.

[0063] In the present invention, in order to give the membrane material photoresponsive properties, a photoresponsive monomer is specially introduced to functionalize polydimethylsiloxane. The selected photoresponsive molecule is p-aminoazobenzene, which is a classic photoresponsive compound whose core properties originate from the cis-trans isomerization behavior of the azobenzene group in the molecule. Under ultraviolet light, the structure of the azobenzene molecule changes from a thermodynamically stable trans state to a cis state; and under visible light or dark conditions, the cis state gradually returns to the trans state. This light-induced reversible isomerization process will cause significant changes in the molecular configuration and geometric structure, accompanied by changes in the intermolecular spatial arrangement and intermolecular forces. Therefore, azobenzene is an ideal photoresponsive functional monomer, which is widely used in the development of light-controlled switches, smart materials and photoresponsive separation membranes.

[0064] In order to introduce the photoresponsive properties of p-aminoazobenzene into the polydimethylsiloxane matrix, the present invention realizes the combination of p-aminoazobenzene and siloxane groups through chemical reaction. Specifically, the amino group in p-aminoazobenzene reacts with 3-isocyanate propyltrimethoxysilane to generate a silanized photoresponsive monomer. In this reaction, the isocyanate group reacts with the amino group to form a stable urea bond, while firmly connecting the azobenzene group to the siloxane molecule. Subsequently, the photoresponsive monomer is grafted onto the molecular chain of polydimethylsiloxane by covalent bonds so that it is embedded in the silicone rubber matrix. This chemical modification method not only ensures the efficient combination of the photoresponsive group in the matrix, but also significantly improves its dispersion uniformity and long-term stability in the matrix.

[0065] The introduction of photoresponsive monomers endows the membrane material with sensitivity to light stimulation. Under ultraviolet light irradiation, the azobenzene group changes from a trans structure to a cis structure. This isomerization process will lead to changes in molecular size and intermolecular arrangement, which in turn triggers adjustments in the internal microstructure of the membrane material. For example, the cis structure of azobenzene has a greater space occupancy effect than the trans structure. This configuration change may cause dynamic regulation of the membrane pores, thereby changing the permeability of the membrane to different molecules or ions. In addition, the isomerization of the azobenzene group may also affect the hydrophilicity distribution on the membrane surface, further regulating its separation performance. Therefore, by introducing photoresponsive monomers, the membrane material can not only achieve selective separation of specific molecules under external light stimulation, but also achieve dynamic regulation of separation behavior when switching between ultraviolet light and visible light.

[0066] This photoresponsive property has significant advantages in a variety of application scenarios. For example, in the pervaporation process, the membrane's selective separation of volatile organic compounds and water molecules can be dynamically adjusted by changing the lighting conditions; in the gas separation process, the photoresponsive property can be used to optimize the membrane's permeation rate for specific gases, thereby improving the separation efficiency. In addition, the bonding of the photoresponsive monomer to the membrane matrix is ​​achieved through covalent bonds. This stable chemical bonding method ensures the long-term durability of the photoresponsive function and maintains its performance advantages even in complex operating environments.

[0067] In the present invention, cellulose nanocrystals are introduced into the composite membrane as a functional filler to improve the mechanical properties and separation efficiency of the membrane. Cellulose nanocrystals are a type of nanoscale crystals prepared from natural cellulose by acid hydrolysis and other methods, and have unique structural characteristics and performance advantages. Its molecular skeleton is composed of β-1,4-glucose units and has a highly ordered crystal structure, so it exhibits extremely high crystallinity. Compared with traditional inorganic or synthetic fillers, cellulose nanocrystals have a series of excellent properties, including light weight, high strength, good biocompatibility, high thermal stability and renewability, and are therefore considered to be a very promising environmentally friendly nanomaterial.

[0068] The surface of cellulose nanocrystals is rich in a large number of hydroxyl groups, and these active groups provide great possibilities for surface chemical modification. Through appropriate chemical modification, functional groups can be introduced on the surface of cellulose nanocrystals, thereby achieving directional enhancement and functionalization in composite materials. In the present invention, in order to further improve the performance and functionality of cellulose nanocrystals, MOF modification technology is adopted. MOF is a type of porous material formed by metal ions or metal clusters and organic ligands through coordination bonds, which has an extremely high specific surface area, an adjustable pore structure and an excellent molecular sieve effect. Through MOF modification, cellulose nanocrystals not only have the ability to enhance the mechanical properties of the membrane, but also increase the separation selectivity and adsorption capacity of the material.

[0069] Specifically, the present invention realizes the preparation of MOF-modified cellulose nanocrystals through the following steps: first, cellulose nanocrystals are dispersed in deionized water, and copper nitrate and trimesic acid are introduced in the reaction process by utilizing the high reactivity of the surface hydroxyl groups. These chemical reagents form a MOF layer on the surface of the cellulose nanocrystals through coordination reaction. Copper nitrate provides a metal center, and trimesic acid, as a tridentate ligand, coordinates with the metal center, and finally forms a stable MOF structure. This MOF layer is evenly coated on the surface of the cellulose nanocrystals, so that it has the unique properties of MOF.

[0070] The introduction of MOF significantly enhances the functionality of cellulose nanocrystals. As a highly porous material, the MOF layer provides an extremely high specific surface area and a large number of controllable pores. These pores can not only efficiently adsorb specific molecules, but also act as a molecular sieve effect, making the material more selective for the separation of different molecules. In addition, the introduction of the MOF layer did not significantly increase the mass of the cellulose nanocrystals, because MOF itself has a lower density, which also ensures that the overall lightweight properties of the material are retained.

[0071] In the composite membrane system, the role of MOF-modified cellulose nanocrystals is multiple. On the one hand, the high strength and high crystallinity of cellulose nanocrystals significantly enhance the mechanical properties of the membrane, making the composite membrane have higher tensile strength and deformation resistance, thereby improving the stability and durability of the membrane under complex operating conditions. On the other hand, the porous structure of the MOF layer gives the composite membrane excellent selective separation performance. In the process of pervaporation or gas separation, MOF-modified cellulose nanocrystals can achieve efficient separation of specific molecules or gases through molecular sieve effect and adsorption selectivity. For example, MOF can preferentially adsorb or screen organic vapor molecules through its pore structure, while blocking larger unwanted molecules, thereby significantly improving the separation efficiency.

[0072] In addition, MOF-modified cellulose nanocrystals also exhibit good interfacial compatibility. Due to the rich hydroxyl groups on the surface of cellulose nanocrystals and the porous characteristics of the MOF layer, they have good dispersion in the composite membrane matrix and can effectively avoid structural defects caused by filler agglomeration. This uniform dispersion not only ensures the integrity of the composite membrane, but also further improves the separation performance and mechanical properties of the membrane material.

[0073] In the present invention, graphene oxide is introduced into the composite membrane as a filler to improve the mechanical properties, separation efficiency and selectivity of the membrane. Graphene oxide is an oxidized derivative of graphene, and its surface is rich in a variety of oxygen-containing functional groups, which give it unique chemical activity and good hydrophilicity. This makes graphene oxide have good dispersion stability in solution and provides abundant reaction sites for surface functionalization modification. In addition, the two-dimensional layered structure of graphene oxide gives it an extremely high specific surface area, providing sufficient active sites for molecular adsorption and transmission.

[0074] Graphene oxide also has excellent mechanical properties, and the carbon-carbon bonds in its single-layer structure have extremely high strength and rigidity, which enables it to play a significant reinforcing role in composite membranes. In particular, in separation membranes, the interlayer channels of graphene oxide have a molecular sieve effect, which can selectively permeate molecules based on molecular size, shape or polarity. This molecular sieve effect gives the composite membrane efficient separation performance, while being able to block larger or unwanted molecules from passing through the membrane, thereby achieving preferential separation of target molecules.

[0075] In order to further improve the dispersibility and functionality of graphene oxide in the composite film, the present invention chemically modifies the graphene oxide with amino crown ethers. Specifically, the amino crown ethers covalently bind to the carboxyl groups on the surface of graphene oxide through an amidation reaction to prepare crown ether-modified graphene oxide. The core of the amidation reaction is the dehydration condensation reaction between the carboxyl group and the amino group, which generates a stable amide bond under appropriate catalysts or reaction conditions. This chemical modification not only ensures the stable binding of the crown ether molecules on the surface of graphene oxide, but also significantly improves the surface properties of graphene oxide.

[0076] Crown ether molecules are a typical class of cyclic compounds, which contain multiple oxygen atoms in their molecular structure. These oxygen atoms can form complexes with specific cations or small molecules through lone pairs of electrons. By introducing crown ether molecules on the surface of graphene oxide, their unique ion recognition ability and complexation are successfully imparted to the composite membrane. Crown ether-modified graphene oxide can selectively adsorb and transport specific ions or small molecules, thereby significantly improving the separation selectivity of the membrane.

[0077] The introduction of crown ether molecules improves the dispersion of graphene oxide in the silicone rubber matrix. Since the oxygen atoms in the crown ether molecules can form a strong interaction with the siloxy groups in the silicone rubber matrix, the crown ether-modified graphene oxide can be more evenly distributed in the matrix, avoiding the agglomeration phenomenon that may occur in traditional graphene oxide. This uniform dispersion ensures the uniformity and stability of the composite film performance.

[0078] By dispersing multi-modified polydimethylsiloxane, MOF-modified cellulose nanocrystals and crown ether-modified graphene oxide in tetrahydrofuran and adding a crosslinker and a catalyst, chemical bonding between the matrix material and the filler can be achieved. The role of the crosslinker is to connect the functional groups between the PDMS molecular chains through chemical reactions to form a three-dimensional crosslinked network structure. The formation of this network structure not only enhances the mechanical properties of the composite membrane, but also significantly improves its stability under complex operating conditions. At the same time, the crosslinker reacts with the active functional groups on the surface of the filler, so that the filler is further embedded in the crosslinked network, strengthening the interfacial bonding between the matrix and the filler. The introduction of the catalyst accelerates the crosslinking reaction by reducing the activation energy of the crosslinking reaction, ensuring the complete formation of the network structure during the film formation process.

[0079] The obtained casting solution is coated on the surface of the base film, and the coated film is heat treated under specific temperature conditions. The heat treatment process plays two roles: on the one hand, the heat energy provided by the heat treatment further promotes the complete cross-linking reaction and ensures the integrity of the three-dimensional cross-linking network; on the other hand, as the solvent gradually evaporates and the chemical reaction deepens, the film surface gradually becomes dense and flat, forming a uniform ultra-thin film structure.

[0080] There is also a synergistic enhancement effect in the whole system: MOF-modified cellulose nanocrystals and crown ether-modified graphene oxide not only play their own enhancement and functionalization roles, but the interaction between them also significantly optimizes the performance of the membrane. MOF-modified cellulose nanocrystals have a highly regular porous structure and a high specific surface area, while crown ether-modified graphene oxide is characterized by a two-dimensional layered structure. The two can form a multi-scale separation channel network in the composite membrane. The micropores of MOF and the interlayer channels of crown ether-modified graphene oxide work together to enable the membrane to simultaneously achieve efficient separation of molecules of different sizes and different properties. For example, the microporous structure of MOF can screen out smaller molecules, while the two-dimensional channels of crown ether-modified graphene oxide can selectively adsorb and transport larger molecules or specific ions. The synergistic effect of this multi-scale separation mechanism enables the membrane to exhibit superior performance in more complex mixture separation tasks.

[0081] The surfaces of MOF-modified cellulose nanocrystals and crown ether-modified graphene oxide contain abundant active functional groups, which can form a strong interface bond with the reactive groups in the multi-modified polydimethylsiloxane matrix through chemical bonds or hydrogen bonds. This interface bond not only enhances the dispersion stability of the filler in the matrix, but also optimizes the stress transfer capacity between the filler and the matrix, thereby further improving the mechanical strength and long-term stability of the membrane. In addition, this interfacial synergy also effectively prevents the migration or shedding of the filler during operation, ensuring the durability of the separation performance of the membrane in long-term use.

[0082] Secondly, the porous structure of MOF-modified cellulose nanocrystals provides a smoother path for molecular diffusion in the matrix material. At the same time, the good compatibility of the MOF layer on its surface with polydimethylsiloxane also reduces the interfacial resistance, further improving the permeation flux of the membrane. The two-dimensional structure of crown ether-modified graphene oxide provides additional molecular selective screening capabilities through its interlayer channels, which complements the high permeability of polydimethylsiloxane. These interfacial synergistic effects ensure that the composite membrane maintains a high permeation efficiency while achieving highly selective separation.

[0083] Multiply modified polydimethylsiloxane is used as the matrix material, and its flexible molecular chain provides good processability and ductility for the composite membrane. However, flexible materials usually have deficiencies in mechanical strength and dimensional stability, and the introduction of MOF-modified cellulose nanocrystals and crown ether-modified graphene oxide forms an effective mechanical reinforcement effect on the matrix material through its rigid structure. The high crystallinity of MOF-modified cellulose nanocrystals and the high Young's modulus of crown ether-modified graphene oxide enable the composite membrane to achieve high-strength structural stability while maintaining flexibility. This synergistic balance of flexibility and rigidity enables the composite membrane to withstand higher mechanical stresses in complex operating environments while maintaining excellent separation performance.

[0084] Compared with the prior art, the present invention has the following beneficial effects: In the present invention, polydimethylsiloxane is used as a flexible matrix material, which provides excellent flexibility and gas permeability in the composite membrane, and at the same time provides a structural basis for functional modification and intelligent response characteristics. By introducing vinyl functional groups, the reactivity of hydroxy polydimethylsiloxane is significantly improved, enabling it to be efficiently combined with a variety of functional monomers. The grafting of thermosensitive monomers gives the membrane material temperature response characteristics, regulating the hydrophilicity and hydrophobicity of the membrane at different temperatures, thereby optimizing the separation performance; the introduction of photoresponsive monomers gives the membrane light responsiveness, and the membrane pore structure and separation behavior are regulated by switching between ultraviolet light and visible light.

[0085] In the present invention, cellulose nanocrystals are used as functional fillers to provide high mechanical strength and separation selectivity in the composite membrane. By modifying cellulose nanocrystals with MOF, a uniform porous MOF structure is introduced on the surface of the cellulose nanocrystals, which significantly increases the specific surface area and the number of pores of the cellulose nanocrystals, giving them a molecular sieve effect and adsorption selectivity. Secondly, the mechanical properties and selective separation capabilities of the composite membrane are improved, while its good dispersibility ensures the integrity of the membrane structure, providing important support for an efficient and stable separation process.

[0086] The present invention introduces graphene oxide as a functional filler of a two-dimensional structure, which provides mechanical reinforcement and molecular sieving effect in the composite membrane. By introducing crown ether molecules on the surface of graphene oxide, the ion recognition ability and dispersion stability of graphene oxide are significantly enhanced. Crown ether-modified graphene oxide combines mechanical reinforcement, ion selectivity and molecular sieving effects in the composite membrane system, forms a good synergistic effect with the matrix material, and provides excellent performance support for complex separation tasks. BRIEF DESCRIPTION OF THE DRAWINGS

[0087] Figure 1 A flow chart of a method for preparing a surface-modified silicone rubber composite membrane provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0088] The technical solution of the present invention is described in detail below in conjunction with specific embodiments and their accompanying drawings. The embodiments recorded herein are specific embodiments of the present invention, which are used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary and should not be construed as limitations on the embodiments of the present invention and the scope of protection of the present invention. In addition to the embodiments recorded herein, those skilled in the art can also adopt other obvious technical solutions based on the contents disclosed in the claims of this application and its specification, including technical solutions that adopt any obvious replacements and modifications to the embodiments recorded herein.

[0089] The chemical reagents used in the examples and comparative examples of the present invention are all commercially available products without further purification or treatment.

[0090] Example 1

[0091] This embodiment provides a surface-modified silicone rubber composite film and a preparation method thereof, see Figure 1 The preparation method of the surface-modified silicone rubber composite film specifically comprises the following steps: S1: N-isopropylacrylamide and vinyltrimethoxysilane are dispersed in anhydrous methanol at a molar ratio of 4:1 to obtain a first reaction solution, wherein the total concentration of N-isopropylacrylamide and vinyltrimethoxysilane in the first reaction solution is 12wt%, and the mixture is reacted at 67°C for 5.8h under the protection of nitrogen and then subjected to rotary evaporation, washing, and drying to obtain a thermosensitive monomer; S2: p-Aminoazobenzene was dispersed in dichloromethane at a concentration of 6 wt.%, and a dichloromethane solution of 3-isocyanatepropyltrimethoxysilane at a concentration of 4.5 wt.% was added at a dropping speed of 4 mL / min to obtain a second reaction solution, wherein the molar ratio of 3-isocyanatepropyltrimethoxysilane to p-aminoazobenzene was 1.16:1, and the reaction was carried out at room temperature under nitrogen protection for 18 h, and then filtered, concentrated under reduced pressure, and recrystallized to obtain a photoresponsive monomer; S3: dissolving polydimethylsiloxane in tetrahydrofuran at a mass ratio of 1:7, adding vinyltrimethoxysilane and dibutyltin dilaurate to obtain a third reaction solution, wherein the molar ratio of vinyltrimethoxysilane to polydimethylsiloxane is 1.42:1, and the amount of dibutyltin dilaurate added is 400ppm relative to the mass of polydimethylsiloxane, reacting at 72°C for 4.6h, and distilling under reduced pressure to obtain vinyl-modified polydimethylsiloxane; dispersing it in a hydrochloric acid solution to obtain pre-hydrolyzed vinyl-modified polydimethylsiloxane; preparing a mass fraction of A 22wt.% tetrahydrofuran solution of pre-hydrolyzed vinyl-modified polydimethylsiloxane is added with tetramethylammonium hydroxide, a thermosensitive monomer and a photoresponsive monomer to obtain a fourth reaction solution, wherein the molar ratio of vinyl-modified polydimethylsiloxane to the thermosensitive monomer and the photoresponsive monomer is 76:12:12, and the amount of tetramethylammonium hydroxide added is 0.16% of the total mass of the monomers. The reaction is carried out at 76°C for 7h, and then a 1.5mol / L sodium bicarbonate solution is used to adjust the pH to 7, and the solution is stirred, filtered, washed and rotary evaporated to obtain a multi-modified polydimethylsiloxane.

[0092] S21: Dispersing cellulose nanocrystals in deionized water at a mass fraction of 1.7 wt%, ultrasonically dispersing at a power of 370 W for 40 min, adding copper nitrate and trimesic acid to obtain a fifth reaction solution, wherein the mass ratio of copper nitrate to cellulose nanocrystals is 0.4:1, and the molar ratio of trimesic acid to copper nitrate is 2.7:1. After reacting for 5.4 h, centrifuging, washing, and drying to obtain MOF-modified cellulose nanocrystals; S22: 18-crown-6 is dispersed in DMF at a concentration of 0.3 M, potassium carbonate is added at 3° C. under nitrogen protection and stirred, wherein the molar ratio of potassium carbonate to 18-crown-6 is 1.3:1, and then a DMF solution of N-(3-chloropropyl)phthalimide with a concentration of 0.43 M is added dropwise to obtain a sixth reaction solution, wherein the molar ratio of N-(3-chloropropyl)phthalimide to 18-crown-6 is 1. 35:1, stirring and reacting at a constant temperature of 56°C for 12 hours; filtering, rotary evaporation, and column chromatography to obtain a phthalimide-modified crown ether; preparing a methanol solution of the phthalimide-modified crown ether with a concentration of 0.1 g / mL, adding hydrazine hydrate under stirring and then reflux reaction, wherein the molar ratio of hydrazine hydrate to the phthalimide-modified crown ether is 3.8:1, the reflux reaction temperature is 68°C, the time is 6 hours, and rotary evaporation and purification are performed to obtain an amino crown ether; S23: dispersing graphene oxide in DMF at a mass fraction of 0.18 wt.%, adding 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide after uniform dispersion to obtain a seventh reaction solution, wherein the mass ratio of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide to graphene oxide is 2.3:2:1, stirring at room temperature for 2.8 h, adding amino crown ether at a mass ratio of 2.5:1 to graphene oxide, continuing the reaction for 22 h, centrifuging, washing, and vacuum drying to obtain crown ether-modified graphene oxide; S4: Disperse multiply modified polydimethylsiloxane, MOF modified cellulose nanocrystals and crown ether modified graphene oxide in tetrahydrofuran, wherein the mass ratio of multiply modified polydimethylsiloxane to tetrahydrofuran is 1:3.5, and obtain a dispersion by ultrasonic dispersion. Then, add a crosslinker HMS-301 and a catalyst Karstedt, and continue to disperse. Vacuum degassing obtains a casting liquid, wherein the mass ratio of multiply modified polydimethylsiloxane, MOF modified cellulose nanocrystals, crown ether modified graphene oxide, crosslinker and catalyst is 100:2:2.5:5.4:0.15; uniformly coat it on the surface of a polypropylene support base membrane, and obtain a surface modified silicone rubber composite membrane after heat treatment at 67°C for 4.5h.

[0093] Example 2

[0094] This embodiment provides a surface-modified silicone rubber composite film and a preparation method thereof. The preparation method of the surface-modified silicone rubber composite film specifically comprises the following steps: S1: N-isopropylacrylamide and vinyltrimethoxysilane are dispersed in anhydrous methanol at a molar ratio of 4.5:1 to obtain a first reaction solution, wherein the total concentration of N-isopropylacrylamide and vinyltrimethoxysilane in the first reaction solution is 10wt%, and the mixture is reacted at 68°C for 6h under the protection of nitrogen and then subjected to rotary evaporation, washing, and drying to obtain a thermosensitive monomer; S2: p-Aminoazobenzene was dispersed in dichloromethane at a concentration of 7.2 wt%, and a dichloromethane solution of 3-isocyanatepropyltrimethoxysilane at a concentration of 3 wt% was added at a dropping speed of 3.4 mL / min to obtain a second reaction solution, wherein the molar ratio of 3-isocyanatepropyltrimethoxysilane to p-aminoazobenzene was 1.2:1, and the reaction was carried out at room temperature under nitrogen protection for 20 h, and then filtered, concentrated under reduced pressure, and recrystallized to obtain a photoresponsive monomer; S3: dissolving polydimethylsiloxane in tetrahydrofuran at a mass ratio of 1:6, adding vinyltrimethoxysilane and dibutyltin dilaurate to obtain a third reaction solution, wherein the molar ratio of vinyltrimethoxysilane to polydimethylsiloxane is 1.5:1, and the amount of dibutyltin dilaurate added is 500ppm relative to the mass of polydimethylsiloxane, reacting at 73°C for 5.6h, and distilling under reduced pressure to obtain vinyl-modified polydimethylsiloxane; dispersing it in a hydrochloric acid solution to obtain pre-hydrolyzed vinyl-modified polydimethylsiloxane; preparing a mass fraction of A 25wt.% tetrahydrofuran solution of pre-hydrolyzed vinyl-modified polydimethylsiloxane is added with tetramethylammonium hydroxide, a thermosensitive monomer and a photoresponsive monomer to obtain a fourth reaction liquid, wherein the molar ratio of vinyl-modified polydimethylsiloxane to the thermosensitive monomer and the photoresponsive monomer is 74:13:13, and the amount of tetramethylammonium hydroxide added accounts for 0.18% of the total mass of the monomers. The mixture is reacted at 78°C for 8h, and then a 2mol / L sodium bicarbonate solution is used to adjust the pH to 7.2, and the mixture is stirred, filtered, washed and rotary evaporated to obtain a multi-modified polydimethylsiloxane.

[0095] S21: Dispersing cellulose nanocrystals in deionized water at a mass fraction of 2 wt%, ultrasonically dispersing at a power of 350 W for 34 min, adding copper nitrate and trimesic acid to obtain a fifth reaction solution, wherein the mass ratio of copper nitrate to cellulose nanocrystals is 0.3:1, and the molar ratio of trimesic acid to copper nitrate is 2.3:1. After reacting for 6 h, centrifuging, washing, and drying to obtain MOF-modified cellulose nanocrystals; S22: Disperse 18-crown-6 in DMF at a concentration of 0.4M, add potassium carbonate under nitrogen protection at 5°C and stir, wherein the molar ratio of potassium carbonate to 18-crown-6 is 1.2:1, then dropwise add a DMF solution of N-(3-chloropropyl)phthalimide at a concentration of 0.5M to obtain a sixth reaction solution, wherein the molar ratio of N-(3-chloropropyl)phthalimide to 18-crown-6 is 1.42:1, and stir and react at a constant temperature of 60°C for 14h; filter, rotary evaporation, and column chromatography to obtain a phthalimide-modified crown ether; prepare a methanol solution of phthalimide-modified crown ether at a concentration of 0.2g / mL, add hydrazine hydrate under stirring and reflux reaction, wherein the molar ratio of hydrazine hydrate to phthalimide-modified crown ether is 3:1, the reflux reaction temperature is 70°C, and the time is 8h, and rotary evaporation and purification are performed to obtain an amino crown ether; S23: dispersing graphene oxide in DMF at a mass fraction of 0.12wt%, adding 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide after uniform dispersion to obtain a seventh reaction solution, wherein the mass ratio of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide to graphene oxide is 2.5:2:1, stirring at room temperature for 2.3h, adding amino crown ether at a mass ratio of 2.8:1 to graphene oxide, continuing the reaction for 23h, centrifuging, washing, and vacuum drying to obtain crown ether modified graphene oxide; S4: Disperse multiply modified polydimethylsiloxane, MOF modified cellulose nanocrystals and crown ether modified graphene oxide in tetrahydrofuran, wherein the mass ratio of multiply modified polydimethylsiloxane to tetrahydrofuran is 1:3.7, and obtain a dispersion by ultrasonic dispersion. Then, add a cross-linking agent and a catalyst, and continue to disperse. Vacuum degassing obtains a casting liquid, wherein the mass ratio of multiply modified polydimethylsiloxane, MOF modified cellulose nanocrystals, crown ether modified graphene oxide, cross-linking agent PMHS and catalyst chloroplatinic acid is 100:3:3:4.6:0.2; uniformly coat it on the surface of the polyvinylidene fluoride supporting base membrane, and obtain a surface modified silicone rubber composite membrane after heat treatment at 70°C for 4.8h.

[0096] Example 3

[0097] This embodiment provides a surface-modified silicone rubber composite film and a preparation method thereof. The preparation method of the surface-modified silicone rubber composite film specifically comprises the following steps: S1: N-isopropylacrylamide and vinyltrimethoxysilane are dispersed in anhydrous methanol at a molar ratio of 4.2:1 to obtain a first reaction solution, wherein the total concentration of N-isopropylacrylamide and vinyltrimethoxysilane in the first reaction solution is 14wt%, and the mixture is reacted at 65°C for 5h under the protection of nitrogen and then rotary evaporated, washed and dried to obtain a thermosensitive monomer; S2: p-Aminoazobenzene was dispersed in dichloromethane at a concentration of 5 wt.%, and a dichloromethane solution of 3-isocyanatepropyltrimethoxysilane at a concentration of 5 wt.% was added at a dropping speed of 3 mL / min to obtain a second reaction solution, wherein the molar ratio of 3-isocyanatepropyltrimethoxysilane to p-aminoazobenzene was 1.1:1, and the reaction was carried out at room temperature under nitrogen protection for 19.8 h, and then filtered, concentrated under reduced pressure, and recrystallized to obtain a photoresponsive monomer; S3: Dissolve polydimethylsiloxane in tetrahydrofuran at a mass ratio of 1:5, add vinyltrimethoxysilane and dibutyltin dilaurate to obtain a third reaction solution, wherein the molar ratio of vinyltrimethoxysilane to polydimethylsiloxane is 1.3:1, and the amount of dibutyltin dilaurate is 200ppm relative to the mass of polydimethylsiloxane, react at 70°C for 4h, and distill under reduced pressure to obtain vinyl-modified polydimethylsiloxane; disperse it in a hydrochloric acid solution to obtain pre-hydrolyzed vinyl-modified polydimethylsiloxane; prepare a mass fraction of 2 0wt.% of pre-hydrolyzed vinyl-modified polydimethylsiloxane in tetrahydrofuran solution, tetramethylammonium hydroxide, thermosensitive monomer and photoresponsive monomer are added to obtain a fourth reaction liquid, wherein the molar ratio of vinyl-modified polydimethylsiloxane to thermosensitive monomer and photoresponsive monomer is 70:15:15, and the amount of tetramethylammonium hydroxide is 0.1% of the total mass of monomers. The reaction is carried out at 75°C for 6h, and then the pH value is adjusted to 7.4 using a sodium bicarbonate solution with a concentration of 1.8mol / L, and the mixture is stirred, filtered, washed and rotary evaporated to obtain multiply modified polydimethylsiloxane.

[0098] S21: Dispersing cellulose nanocrystals in deionized water at a mass fraction of 1 wt%, and ultrasonically dispersing at a power of 300 W for 30 min, and then adding copper nitrate and trimesic acid to obtain a fifth reaction solution, wherein the mass ratio of copper nitrate to cellulose nanocrystals is 0.5:1, and the molar ratio of trimesic acid to copper nitrate is 2:1. After reacting for 4 hours, centrifuging, washing, and drying to obtain MOF-modified cellulose nanocrystals; S22: Disperse 18-crown-6 in DMF at a concentration of 0.2M, add potassium carbonate under nitrogen protection at 0°C and stir, wherein the molar ratio of potassium carbonate to 18-crown-6 is 1.5:1, then dropwise add a DMF solution of N-(3-chloropropyl)phthalimide at a concentration of 0.3M to obtain a sixth reaction solution, wherein the molar ratio of N-(3-chloropropyl)phthalimide to 18-crown-6 is 1.3:1, and stir and react at a constant temperature of 55°C for 10 hours; filter, rotary evaporation, and column chromatography to obtain a phthalimide-modified crown ether; prepare a methanol solution of phthalimide-modified crown ether at a concentration of 0.15g / mL, add hydrazine hydrate under stirring and reflux reaction, wherein the molar ratio of hydrazine hydrate to phthalimide-modified crown ether is 4:1, the reflux reaction temperature is 60°C, the time is 5h, and rotary evaporation and purification are performed to obtain an amino crown ether; S23: dispersing graphene oxide in DMF at a mass fraction of 0.1 wt.%, adding 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide after uniform dispersion to obtain a seventh reaction solution, wherein the mass ratio of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide to graphene oxide is 2:2:1, stirring at room temperature for 2 h, adding amino crown ether at a mass ratio of 2:1 to graphene oxide, continuing the reaction for 20 h, centrifuging, washing, and vacuum drying to obtain crown ether-modified graphene oxide; S4: Disperse multiply modified polydimethylsiloxane, MOF modified cellulose nanocrystals and crown ether modified graphene oxide in tetrahydrofuran, wherein the mass ratio of multiply modified polydimethylsiloxane to tetrahydrofuran is 1:3, and obtain a dispersion by ultrasonic dispersion. Then, add a cross-linking agent and a catalyst, and continue to disperse. Vacuum degassing obtains a casting solution, wherein the mass ratio of multiply modified polydimethylsiloxane, MOF modified cellulose nanocrystals, crown ether modified graphene oxide, cross-linking agent D4H and catalyst chloroplatinic acid is 100:1:1.5:4:0.18; uniformly coat it on the surface of the polysulfone supporting base membrane, and obtain a surface modified silicone rubber composite membrane after heat treatment at 60°C for 4h.

[0099] Example 4

[0100] This embodiment provides a surface-modified silicone rubber composite film and a preparation method thereof. The preparation method of the surface-modified silicone rubber composite film specifically comprises the following steps: S1: N-isopropylacrylamide and vinyltrimethoxysilane are dispersed in anhydrous methanol at a molar ratio of 4.4:1 to obtain a first reaction solution, wherein the total concentration of N-isopropylacrylamide and vinyltrimethoxysilane in the first reaction solution is 15wt%, and the mixture is reacted at 70°C for 5.4h under the protection of nitrogen and then subjected to rotary evaporation, washing and drying to obtain a thermosensitive monomer; S2: p-Aminoazobenzene was dispersed in dichloromethane at a concentration of 8 wt%, and a dichloromethane solution of 3-isocyanatepropyltrimethoxysilane at a concentration of 4.2 wt% was added at a dropping speed of 3.7 mL / min to obtain a second reaction solution, wherein the molar ratio of 3-isocyanatepropyltrimethoxysilane to p-aminoazobenzene was 1.12:1, and the reaction was carried out at room temperature under nitrogen protection for 19 h, and then filtered, concentrated under reduced pressure, and recrystallized to obtain a photoresponsive monomer; S3: dissolving polydimethylsiloxane in tetrahydrofuran at a mass ratio of 1:8, adding vinyltrimethoxysilane and dibutyltin dilaurate to obtain a third reaction solution, wherein the molar ratio of vinyltrimethoxysilane to polydimethylsiloxane is 1.2:1, and the amount of dibutyltin dilaurate added is 300ppm relative to the mass of polydimethylsiloxane, reacting at 75°C for 6h, and distilling under reduced pressure to obtain vinyl-modified polydimethylsiloxane; dispersing it in a hydrochloric acid solution to obtain pre-hydrolyzed vinyl-modified polydimethylsiloxane; preparing a mass fraction of 2 To a tetrahydrofuran solution of 3wt.% of pre-hydrolyzed vinyl-modified polydimethylsiloxane, tetramethylammonium hydroxide, a thermosensitive monomer and a photoresponsive monomer are added to obtain a fourth reaction liquid, wherein the molar ratio of vinyl-modified polydimethylsiloxane to the thermosensitive monomer and the photoresponsive monomer is 80:10:10, and the amount of tetramethylammonium hydroxide added accounts for 0.2% of the total mass of the monomers. The reaction is carried out at 80°C for 7.8h, and then the pH is adjusted to 7.5 using a 1mol / L sodium bicarbonate solution, and the reaction is carried out by stirring, filtering, washing and rotary evaporation to obtain multiply modified polydimethylsiloxane.

[0101] S21: Dispersing cellulose nanocrystals in deionized water at a mass fraction of 1.2 wt%, and ultrasonically dispersing at a power of 400 W for 38 min, and then adding copper nitrate and trimesic acid to obtain a fifth reaction solution, wherein the mass ratio of copper nitrate to cellulose nanocrystals is 0.43:1, and the molar ratio of trimesic acid to copper nitrate is 3:1. After reacting for 4.6 h, centrifuging, washing, and drying to obtain MOF-modified cellulose nanocrystals; S22: 18-crown-6 is dispersed in DMF at a concentration of 0.34 M, potassium carbonate is added under nitrogen protection at 4°C and stirred, wherein the molar ratio of potassium carbonate to 18-crown-6 is 1.4:1, and then a DMF solution of N-(3-chloropropyl)phthalimide with a concentration of 0.4 M is added dropwise to obtain a sixth reaction solution, wherein the molar ratio of N-(3-chloropropyl)phthalimide to 18-crown-6 is 1. 5:1, stirring and reacting at a constant temperature of 50°C for 13 hours; filtering, rotary evaporation, and column chromatography to obtain a phthalimide-modified crown ether; preparing a methanol solution of the phthalimide-modified crown ether with a concentration of 0.18 g / mL, adding hydrazine hydrate under stirring and then reflux reaction, wherein the molar ratio of hydrazine hydrate to the phthalimide-modified crown ether is 3.6:1, the reflux reaction temperature is 65°C, the time is 4 hours, and rotary evaporation and purification are performed to obtain an amino crown ether; S23: dispersing graphene oxide in DMF at a mass fraction of 0.2wt%, adding 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide after uniform dispersion to obtain a seventh reaction solution, wherein the mass ratio of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide to graphene oxide is 3:2:1, stirring at room temperature for 3h, adding amino crown ether in a mass ratio of 3:1 to graphene oxide, continuing the reaction for 24h, centrifuging, washing, and vacuum drying to obtain crown ether modified graphene oxide; S4: Disperse multiply modified polydimethylsiloxane, MOF modified cellulose nanocrystals and crown ether modified graphene oxide in tetrahydrofuran, wherein the mass ratio of multiply modified polydimethylsiloxane to tetrahydrofuran is 1:4, and obtain a dispersion by ultrasonic dispersion. Then add a crosslinker PMHS and a catalyst Karstedt, and continue to disperse. Vacuum degassing obtains a casting solution, wherein the mass ratio of multiply modified polydimethylsiloxane, MOF modified cellulose nanocrystals, crown ether modified graphene oxide, crosslinker and catalyst is 100:2.5:2.3:6:0.1; and uniformly coat it on the surface of a polyvinylidene fluoride supporting base membrane, and obtain a surface modified silicone rubber composite membrane after heat treatment at 62°C for 5h.

[0102] Comparative Example 1 This comparative example provides a surface-modified silicone rubber composite membrane, which differs from Example 1 in that in S3, the molar ratio of vinyltrimethoxysilane to polydimethylsiloxane is changed to 2:1, and the other operating steps and process parameters are exactly the same as those in Example 1.

[0103] Comparative Example 2 This comparative example provides a surface-modified silicone rubber composite membrane, which differs from Example 1 in that in S3, the molar ratio of vinyltrimethoxysilane to polydimethylsiloxane is changed to 1:1, and the other operating steps and process parameters are exactly the same as those in Example 1.

[0104] Comparative Example 3 This comparative example provides a surface-modified silicone rubber composite membrane, which differs from Example 1 in that, in S4, the mass ratio of multiply modified polydimethylsiloxane, MOF-modified cellulose nanocrystals, crown ether-modified graphene oxide, cross-linking agent and catalyst is 100:5:2.5:5.4:0.15, and the other operating steps and process parameters are exactly the same as those in Example 1.

[0105] Comparative Example 4 This comparative example provides a surface-modified silicone rubber composite membrane, which differs from Example 1 in that, in S4, the mass ratio of multiply modified polydimethylsiloxane, MOF-modified cellulose nanocrystals, crown ether-modified graphene oxide, cross-linking agent and catalyst is 100:0.1:2.5:5.4:0.15, and the other operating steps and process parameters are exactly the same as those in Example 1.

[0106] Comparative Example 5 This comparative example provides a surface-modified silicone rubber composite membrane, which differs from Example 1 in that, in S4, the mass ratio of multiply modified polydimethylsiloxane, MOF-modified cellulose nanocrystals, crown ether-modified graphene oxide, cross-linking agent and catalyst is 100:2:6:5.4:0.15, and the other operating steps and process parameters are exactly the same as those in Example 1.

[0107] Comparative Example 6 This comparative example provides a surface-modified silicone rubber composite membrane, which differs from Example 1 in that, in S4, the mass ratio of multiply modified polydimethylsiloxane, MOF-modified cellulose nanocrystals, crown ether-modified graphene oxide, cross-linking agent and catalyst is 100:2:0.5:5.4:0.15, and the other operating steps and process parameters are exactly the same as those in Example 1.

[0108] The performance test of the surface-modified silicone rubber composite films of the above-mentioned Examples 1 to 4 and Comparative Examples 1 to 6 was carried out, and the specific process is as follows: The tensile strength of the samples was tested according to GB / T 528-2009; The gas permeation flux and the separation performance of oxygen and nitrogen of the ultra-thin silicone rubber composite membrane were tested.

[0109] The test results are shown in Table 1.

[0110] Table 1: Performance test results of surface modified silicone rubber composite membrane

[0111] It can be obtained from the test results of Example 1 and Comparative Examples 1 and 2 that when the feeding amount of vinyltrimethoxysilane is too much, the residual unreacted groups will reduce the integrity of the cross-linked network, causing local stress concentration, thereby reducing the mechanical properties of the ultra-thin silicone rubber composite membrane. At the same time, too many unreacted groups form microscopic defects, which reduces the selectivity of the ultra-thin silicone rubber composite membrane; when the feeding amount is too low, it will lead to insufficient modification sites of polydimethylsiloxane and low subsequent functional group grafting amount, resulting in uneven cross-linking density of the ultra-thin silicone rubber composite membrane and decreased mechanical properties. At the same time, it will also lead to insufficient functionalization of polydimethylsiloxane, incomplete construction of mass transfer channels, and low selective gas transmission efficiency, resulting in poor overall separation performance of the ultra-thin silicone rubber composite membrane.

[0112] From the test results of Example 1 and Comparative Examples 3 and 4, it can be obtained that when the content of MOF-modified cellulose nanocrystals is too high, they are prone to agglomeration to form stress concentration points, thereby destroying the continuity of the polymer chain and greatly reducing the mechanical properties of the ultra-thin silicone rubber composite membrane. At the same time, agglomeration will form non-selective channels, resulting in a decrease in the gas selectivity of the ultra-thin silicone rubber composite membrane and a decrease in the overall separation efficiency. When the content of MOF-modified cellulose nanocrystals is too low, the mechanical properties of the ultra-thin silicone rubber composite membrane are less affected and the basic mechanical properties can be maintained, but the selective adsorption sites provided by MOF will be insufficient, resulting in a decrease in separation performance.

[0113] From the test results of Example 1 and Comparative Examples 5 and 6, it can be obtained that when the content of crown ether-modified graphene oxide is too high, the stacking of graphene oxide sheets leads to uneven stress, thereby reducing the mechanical properties of the ultra-thin silicone rubber composite membrane. At the same time, too many mass transfer channels destroy the density of the ultra-thin silicone rubber composite membrane, and its selectivity decreases significantly; when the content of crown ether-modified graphene oxide is too low, it has little effect on the mechanical properties of the matrix and basically maintains the original mechanical properties, but the selective transmission channels are insufficient and the separation performance is limited.

[0114] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a surface-modified silicone rubber composite film, characterized in that: The preparation method comprises: S1: reacting N-isopropylacrylamide with vinyltrimethoxysilane to obtain a thermosensitive monomer; S2: reacting p-aminoazobenzene with 3-isocyanatepropyltrimethoxysilane to obtain a photoresponsive monomer; S3: obtaining vinyl-modified polydimethylsiloxane by reacting polydimethylsiloxane with vinyl trimethoxysilane under the catalysis of dibutyltin dilaurate, wherein the molar ratio of the vinyl trimethoxysilane to the polydimethylsiloxane is (1.2-1.5):1; dispersing the polydimethylsiloxane in a hydrochloric acid solution to obtain pre-hydrolyzed vinyl-modified polydimethylsiloxane; mixing the pre-hydrolyzed vinyl-modified polydimethylsiloxane with tetramethylammonium hydroxide, a thermosensitive monomer and a photoresponsive monomer, and reacting the mixture to obtain a multi-modified polydimethylsiloxane; S4: Dispersing multi-modified polydimethylsiloxane, MOF-modified cellulose nanocrystals, and crown ether-modified graphene oxide in tetrahydrofuran, wherein the mass ratio of multi-modified polydimethylsiloxane to tetrahydrofuran is 1:(3-4), adding a cross-linking agent and a catalyst to obtain a casting solution after uniform dispersion, coating the solution on the surface of the supporting base film, and obtaining a surface-modified silicone rubber composite membrane after heat treatment, wherein the mass ratio of the multi-modified polydimethylsiloxane, MOF-modified cellulose nanocrystals, crown ether-modified graphene oxide, the cross-linking agent and the catalyst is: 100:(1-3):(1.5-3):(4-6):(0.1-0.2); The MOF-modified cellulose nanocrystals are prepared by dispersing the cellulose nanocrystals in deionized water, adding copper nitrate and trimesic acid after ultrasonic dispersion to obtain a fifth reaction solution, and centrifuging, washing and drying after the reaction; The cross-linking agent is any one of HMS-301, PMHS or D4H; the catalyst is any one of Karstedt catalyst or chloroplatinic acid; the supporting base membrane is any one of polypropylene, polyvinylidene fluoride or polysulfone; The preparation method of the crown ether modified graphene oxide is: Under nitrogen protection, 18-crown ether-6 and potassium carbonate are dispersed in N,N-dimethylformamide, and then a solution of N-(3-chloropropyl)phthalimide in N,N-dimethylformamide is added to react to obtain a phthalimide-modified crown ether; the phthalimide-modified crown ether is mixed with hydrazine hydrate and reacted to obtain an amino crown ether; The graphene oxide is dispersed in N,N-dimethylformamide, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide are added to obtain a seventh reaction solution, and the amino crown ether is added after stirring at room temperature, and the reaction is continued. The crown ether-modified graphene oxide is obtained by centrifugation, washing, and vacuum drying.

2. The method for preparing a surface-modified silicone rubber composite film according to claim 1, characterized in that: In S1: the molar ratio of N-isopropylacrylamide to vinyltrimethoxysilane is (4.0-4.5):

1.

3. The method for preparing a surface-modified silicone rubber composite film according to claim 1, characterized in that: In S2: the molar ratio of the 3-isocyanatepropyltrimethoxysilane to p-aminoazobenzene is (1.1-1.2):

1.

4. The method for preparing a surface-modified silicone rubber composite film according to claim 1, characterized in that: In S3: The feeding amount of the dibutyltin dilaurate is 200-500ppm of the mass of the polydimethylsiloxane; The molar ratio of the vinyl modified polydimethylsiloxane to the thermosensitive monomer and the photoresponsive monomer is (70-80):(15-10):(15-10); The feeding amount of the tetramethylammonium hydroxide accounts for 0.1-0.2% of the total mass of the thermosensitive monomer and the photoresponsive monomer.

5. The method for preparing a surface-modified silicone rubber composite film according to claim 1, characterized in that: In S4: The temperature of the heat treatment is 60-70°C; The heat treatment time is 4-5h.

6. The method for preparing a surface-modified silicone rubber composite film according to claim 1, characterized in that: In the preparation of the MOF-modified cellulose nanocrystals: The mass fraction of the cellulose nanocrystals dispersed in deionized water is 1-2wt.%; The power of the ultrasonic dispersion is 300-400W; The ultrasonic dispersion time is 30-40 min; The mass ratio of the copper nitrate to the cellulose nanocrystals is (0.3-0.5):1; The molar ratio of trimesic acid to copper nitrate is (2-3):1; The reaction time of the fifth reaction solution is 4-6 hours.

7. The method for preparing a surface-modified silicone rubber composite film according to claim 1, characterized in that: In the preparation method of the crown ether modified graphene oxide: The concentration of 18-crown ether-6 dispersed in N,N-dimethylformamide is 0.2-0.4M; The molar ratio of potassium carbonate to 18-crown ether-6 is (1.2-1.5):1; The molar ratio of N-(3-chloropropyl)phthalimide to 18-crown ether-6 is (1.2-1.5):1; The molar ratio of the hydrazine hydrate to the phthalimide modified crown ether is (3-4):

1.

8. The method for preparing a surface-modified silicone rubber composite film according to claim 1, characterized in that: In the preparation method of the crown ether modified graphene oxide: The mass fraction of the graphene oxide dispersed in N,N-dimethylformamide is 0.1-0.2wt.%; The mass ratio of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, N-hydroxysuccinimide and graphene oxide is (2-3):2:1; The mass ratio of the amino crown ether to graphene oxide is (2-3):

1.

9. A surface-modified silicone rubber composite film prepared by the method for preparing a surface-modified silicone rubber composite film according to any one of claims 1 to 8.

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