Shape memory hydrogel as well as preparation method and application thereof

Abstract

The invention discloses a shape memory hydrogel as well as a preparation method and application thereof, and belongs to the technical field of shape memory hydrogel preparation, N-isopropylacrylamide is used as a functional monomer, 4-vinylpyridine is used as a hydrophobic unit, methacrylic acid-beta-hydroxyethyl ester is used as a hydrophilic unit, N, N '-methylene bisacrylamide is used as a cross-linking agent, and the shape memory hydrogel is prepared by a hydrothermal method. Ammonium persulfate and N, N, N ', N'-tetramethylethylenediamine are used as a composite initiator; modified carbon quantum dots prepared from carboxyl carbon quantum dots, oxidized dextran and mixed ionic liquid are used as filling units. The hydrogel provided by the invention takes the modified carbon quantum dots as a nano reinforced phase and is combined with a composite cross-linking system, the tensile strength is greater than or equal to 0.45 MPa, and the elongation at break is greater than or equal to 400%. The hydrogel has good shape memory performance, the shape memory fixing rate is larger than or equal to 98%, and the shape memory recovery rate is larger than or equal to 97.5%; and after the hydrogel is subjected to swelling-shrinking / shape memory circulation for 10 times, the shape memory recovery rate is greater than or equal to 95.0%, and the circulation attenuation amplitude is greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of shape memory hydrogel preparation technology, specifically to a shape memory hydrogel, its preparation method, and its application. Background Technology

[0002] Shape memory hydrogels (SMHs) can maintain a temporary shape under specific conditions and recover their original shape in response to external stimuli. This switchable property of the structure has made it a hot research topic.

[0003] Currently, SMHs still face many challenges: 1. The mechanical properties of hydrogels are mostly insufficient to meet load-bearing requirements.

[0004] 2. Repeated deformation may lead to the breakage of the cross-linked network, and the problem of weak cycle stability needs to be solved.

[0005] Based on this, the present invention designs a shape memory hydrogel, its preparation method, and its application to solve the above problems. Summary of the Invention

[0006] In view of the above-mentioned shortcomings of the existing technology, the present invention provides a shape memory hydrogel, its preparation method and application.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A shape memory hydrogel uses N-isopropylacrylamide as a functional monomer, 4-vinylpyridine as a hydrophobic unit, β-hydroxyethyl methacrylate as a hydrophilic unit, N,N'-methylenebisacrylamide as a crosslinking agent, and ammonium persulfate and N,N,N',N'-tetramethylethylenediamine as a composite initiator; and modified carbon quantum dots prepared using carboxylated carbon quantum dots, oxidized dextran, and mixed ionic liquids as filling units.

[0008] Furthermore, the preparation method of modified carbon quantum dots includes the following steps: (1) Weigh 50-55 parts by weight of carboxyl carbon quantum dot powder, 50-80 parts by weight of mixed ionic liquid, and 0.8-1.2 parts by weight of oxidized dextran; the mixed ionic liquid is prepared by mixing 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and 1-ethyl-3-methylimidazolium tetrafluoroborate in a mass ratio of 0.2-0.5:1; (2) Add carbon quantum dot powder and mixed ionic liquid in sequence, stir at 50-60℃ and 400-600r / min for 15-30min, and use 250-350W ultrasonic to assist dispersion. Then add oxidized dextran and stir at 60-70℃ for 1.5-2h. (3) After the reaction is completed, modified carbon quantum dots are obtained by centrifugation, precipitation, washing and drying.

[0009] Furthermore, the mass ratio of β-hydroxyethyl methacrylate, 4-vinylpyridine, and N-isopropylacrylamide is 2-3:1-2:4-5.

[0010] Furthermore, the mass ratio of N,N'-methylenebisacrylamide, N,N,N',N'-tetramethylethylenediamine, and ammonium persulfate is 0.03-0.06:0.01-0.02:0.06-0.1.

[0011] Furthermore, in step (3), after the reaction is completed, the reaction solution is centrifuged at 8000-10000 r / min, and the precipitate is washed with ethanol and dried under vacuum at 60-65℃ to obtain modified carbon quantum dots.

[0012] Furthermore, the mixed ionic liquid is prepared by mixing 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and 1-ethyl-3-methylimidazolium tetrafluoroborate in a mass ratio of 0.2-0.5:1.

[0013] To better achieve the objectives of this invention, this invention also provides a method for preparing shape memory hydrogels, comprising the following steps: (1) Add β-hydroxyethyl methacrylate, 4-vinylpyridine and N-isopropylacrylamide sequentially to 50-80 mL of acetate-sodium acetate buffer solution, and stir magnetically at 22-25℃ for 20-30 min at a stirring speed of 300-500 rpm to form a monomer mixture. (2) Add modified carbon quantum dot powder to the monomer mixture and ultrasonically disperse for 30-45 min. The ultrasonic power is 200-300 W and the ultrasonic frequency is 45-50 kHz. At this time, the modified carbon quantum dot powder is completely dispersed and there are no obvious agglomerated particles. (3) Then add N,N'-methylenebisacrylamide and stir for 10-12 min; (4) First add N,N,N',N'-tetramethylethylenediamine and stir for 4-5 min. Then slowly add an ammonium persulfate aqueous solution with a mass concentration of 5-8.5% at a rate of 1-2 drops / second and stir for 5-10 min. (5) Inject the mixture into a mold pre-coated with a release agent, seal and let it stand at 22-25℃ for 3-5 hours to polymerize, and obtain shape memory hydrogel.

[0014] To better achieve the objectives of this invention, the present invention also provides an application of the shape memory hydrogel described herein in a temperature or acid / alkali gas recognition and response shape memory hydrogel product.

[0015] Compared with the prior art, the beneficial effects of this invention are as follows: 1. The hydrogel of this invention uses modified carbon quantum dots as the nano-reinforcing phase, combined with a composite crosslinking system, which solves the problems of insufficient mechanical properties and difficulty in load-bearing of traditional SMHs. The results show that its tensile strength is ≥0.45MPa and its elongation at break is ≥400%.

[0016] 2. The hydrogel of the present invention has excellent shape memory properties, with a shape memory fixation rate of ≥98% and a shape memory recovery rate of ≥97.5%. After 10 swelling-shrinkage / shape memory cycles (40℃ shaping → 25℃ recovery), the shape memory recovery rate of the hydrogel remains at ≥95.0%, only decreasing by 2.5% compared to the initial recovery rate, and the cycle attenuation is significantly reduced.

[0017] 3. It has acid / alkali gas recognition performance. The shape recovery response time is ≤50s in an acidic gas environment of 20% hydrochloric acid and ≤30s in an alkaline gas environment of 15% ammonia. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0019] Example 1: A method for preparing shape memory hydrogels, comprising the following steps: I. Preparation of modified carbon quantum dots, the steps are as follows: (1) Weigh 50 parts by weight of carboxyl carbon quantum dot powder, 50 parts by weight of mixed ionic liquid, and 0.8 parts by weight of oxidized dextran; the mixed ionic liquid is made by mixing 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and 1-ethyl-3-methylimidazolium tetrafluoroborate at a mass ratio of 0.2:1; the coating strength of oxidized dextran is improved by the formation of ionic complexes between imidazole cations and carboxyl groups on the surface of carbon quantum dots; (2) Add carbon quantum dot powder and mixed ionic liquid to a three-necked flask in sequence, stir at 50°C and 400r / min for 15min, and use 250W ultrasonic to assist dispersion, then add oxidized dextran, and stir at 60°C for 1.5h; (3) After the reaction is completed, the reaction solution is centrifuged at 8000r / min, the precipitate is washed with ethanol and dried under vacuum at 60°C to obtain modified carbon quantum dots.

[0020] 2. Add 2 parts by weight of β-hydroxyethyl methacrylate, 1 part by weight of 4-vinylpyridine, and 4 parts by weight of N-isopropylacrylamide to 50 mL of acetate-sodium acetate buffer solution (pH=5.5) in sequence, and stir magnetically for 20 min at 22℃ and 300 rpm to form a monomer mixture. 3. Add 0.3 parts by weight of modified carbon quantum dot powder to the monomer mixture, and ultrasonically disperse for 30 minutes. The ultrasonic power is 200W and the ultrasonic frequency is 45kHz. At this time, the modified carbon quantum dot powder is completely dispersed and there are no obvious agglomerated particles. 4. Then add 0.03 parts by weight of N,N'-methylenebisacrylamide and stir for 10 minutes; 5. First, add 0.01 parts by weight of N,N,N',N'-tetramethylethylenediamine and stir for 4 minutes. Then, slowly add a 5% ammonium persulfate aqueous solution (obtained by mixing 0.06 parts by weight of ammonium persulfate with water) at a rate of 1 drop / second and stir for 5 minutes. 6. Inject the mixture into a mold pre-coated with a release agent, seal and let it stand at 22°C for 3 hours to polymerize, and obtain shape memory hydrogel.

[0021] Example 2: A method for preparing shape memory hydrogels, comprising the following steps: I. Preparation of modified carbon quantum dots, the steps are as follows: (1) Weigh 55 parts by weight of carboxyl carbon quantum dot powder, 80 parts by weight of mixed ionic liquid, and 1.2 parts by weight of oxidized dextran; the mixed ionic liquid is made by mixing 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and 1-ethyl-3-methylimidazolium tetrafluoroborate at a mass ratio of 0.5:1; the coating strength of oxidized dextran is improved by the formation of ionic complexes between imidazole cations and carboxyl groups on the surface of carbon quantum dots; (2) Add carbon quantum dot powder and mixed ionic liquid to a three-necked flask in sequence, stir at 60°C and 600r / min for 30min, and use 350W ultrasonic to assist dispersion, then add oxidized dextran, and stir at 70°C for 2h; (3) After the reaction is completed, the reaction solution is centrifuged at 10000r / min, the precipitate is washed with ethanol and dried under vacuum at 65°C to obtain modified carbon quantum dots.

[0022] 2. Add 3 parts by weight of β-hydroxyethyl methacrylate, 2 parts by weight of 4-vinylpyridine, and 5 parts by weight of N-isopropylacrylamide to 80 mL of acetate-sodium acetate buffer solution (pH=6.0) in sequence, and stir magnetically for 30 min at 25 °C and 500 rpm to form a monomer mixture. 3. Add 1 part by weight of modified carbon quantum dot powder to the monomer mixture, and ultrasonically disperse for 45 min. The ultrasonic power is 300 W and the ultrasonic frequency is 50 kHz. At this time, the modified carbon quantum dot powder is completely dispersed and there are no obvious agglomerated particles. 4. Then add 0.06 parts by weight of N,N'-methylenebisacrylamide and stir for 12 minutes; 5. First, add 0.02 parts by weight of N,N,N',N'-tetramethylethylenediamine and stir for 5 minutes. Then, slowly add an 8.5% ammonium persulfate aqueous solution (obtained by mixing 0.1 parts by weight of ammonium persulfate with water) at a rate of 2 drops / second and stir for 10 minutes. 6. Inject the mixture into a mold pre-coated with a release agent, seal and let it stand at 25°C for 5 hours to polymerize, and obtain shape memory hydrogel.

[0023] Example 3: A method for preparing shape memory hydrogels, comprising the following steps: I. Preparation of modified carbon quantum dots, the steps are as follows: (1) Weigh 52 parts by weight of carboxyl carbon quantum dot powder, 70 parts by weight of mixed ionic liquid, and 1 part by weight of oxidized dextran; the mixed ionic liquid is made by mixing 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and 1-ethyl-3-methylimidazolium tetrafluoroborate at a mass ratio of 0.3:1; the coating strength of oxidized dextran is improved by forming ionic complexes between imidazole cations and carboxyl groups on the surface of carbon quantum dots; (2) Add carbon quantum dot powder and mixed ionic liquid to a three-necked flask in sequence, stir at 55°C and 500r / min for 20min, and simultaneously use 280W ultrasonic assisted dispersion, then add oxidized dextran, and stir at 65°C for 1.8h; (3) After the reaction is completed, the reaction solution is centrifuged at 9000r / min, the precipitate is washed with ethanol and dried under vacuum at 63°C to obtain modified carbon quantum dots.

[0024] 2. Add 2.8 parts by weight of β-hydroxyethyl methacrylate, 1.6 parts by weight of 4-vinylpyridine, and 4.5 parts by weight of N-isopropylacrylamide to 65 mL of acetate-sodium acetate buffer solution (pH=5.8) in sequence, and stir magnetically for 25 min at 23°C and 400 rpm to form a monomer mixture. 3. Add 0.5 parts by weight of modified carbon quantum dot powder to the monomer mixture, and ultrasonically disperse for 35 minutes. The ultrasonic power is 250W and the ultrasonic frequency is 48kHz. At this time, the modified carbon quantum dot powder is completely dispersed and there are no obvious agglomerated particles. 4. Then add 0.05 parts by weight of N,N'-methylenebisacrylamide and stir for 11 minutes; 5. First, add 0.02 parts by weight of N,N,N',N'-tetramethylethylenediamine and stir for 4.5 min. Then, slowly add a 6.5% ammonium persulfate aqueous solution (obtained by mixing 0.08 parts by weight of ammonium persulfate with water) at a rate of 2 drops / second and stir for 8 min. 6. Inject the mixture into a mold pre-coated with a release agent, seal and let it stand at 23°C for 4 hours to polymerize, and obtain shape memory hydrogel.

[0025] Experimental Example: Performance Testing of Hydrogels 1. Temperature response: Shape memory retention rate (temporary shape setting temperature 40℃, shape retention time 2h): ≥98%; Shape memory recovery rate (recovery trigger temperature 25℃, recovery time 120s): ≥97.5%; Shape memory cycle stability (after 10 swelling-shrinkage / shape memory cycles (40℃ shaping → 25℃ recovery)): recovery rate ≥95.0%; 2. Acid / base gas identification: Acid gas response performance (acid gas environment of 20% hydrochloric acid): shape recovery response time ≤50s.

[0026] Alkaline gas response performance (alkaline gas environment of 15% ammonia): shape recovery response time ≤30s.

[0027] 3. Mechanical properties: Tensile strength ≥ 0.45 MPa, elongation at break ≥ 400%.

[0028] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A shape memory hydrogel, characterized in that, The method uses N-isopropylacrylamide as the functional monomer, 4-vinylpyridine as the hydrophobic unit, β-hydroxyethyl methacrylate as the hydrophilic unit, N,N'-methylenebisacrylamide as the crosslinking agent, and ammonium persulfate and N,N,N',N'-tetramethylethylenediamine as the composite initiator; and modified carbon quantum dots prepared from carboxylated carbon quantum dots, oxidized dextran, and mixed ionic liquids as the filling unit.

2. The shape memory hydrogel according to claim 1, characterized in that, The preparation method of modified carbon quantum dots includes the following steps: (1) Weigh 50-55 parts by weight of carboxyl carbon quantum dot powder, 50-80 parts by weight of mixed ionic liquid, and 0.8-1.2 parts by weight of oxidized dextran; the mixed ionic liquid is prepared by mixing 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and 1-ethyl-3-methylimidazolium tetrafluoroborate in a mass ratio of 0.2-0.5:1; (2) Add carbon quantum dot powder and mixed ionic liquid in sequence, stir at 50-60℃ and 400-600r / min for 15-30min, and use 250-350W ultrasonic to assist dispersion. Then add oxidized dextran and stir at 60-70℃ for 1.5-2h. (3) After the reaction is completed, modified carbon quantum dots are obtained by centrifugation, precipitation, washing and drying.

3. The shape memory hydrogel according to claim 1, characterized in that, The mass ratio of β-hydroxyethyl methacrylate, 4-vinylpyridine, and N-isopropylacrylamide is 2-3:1-2:4-5.

4. The shape memory hydrogel according to claim 1, characterized in that, The mass ratio of N,N'-methylenebisacrylamide, N,N,N',N'-tetramethylethylenediamine, and ammonium persulfate is 0.03-0.06:0.01-0.02:0.06-0.

1.

5. The shape memory hydrogel according to claim 2, characterized in that, In step (3), after the reaction is completed, the reaction solution is centrifuged at 8000-10000 r / min, and the precipitate is washed with ethanol and dried under vacuum at 60-65℃ to obtain modified carbon quantum dots.

6. The shape memory hydrogel according to claim 1, characterized in that, The mixed ionic liquid is prepared by mixing 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and 1-ethyl-3-methylimidazolium tetrafluoroborate in a mass ratio of 0.2-0.5:

1.

7. A method for preparing a shape memory hydrogel according to any one of claims 1 to 6, characterized in that, Includes the following steps: (1) Add β-hydroxyethyl methacrylate, 4-vinylpyridine and N-isopropylacrylamide sequentially to 50-80 mL of acetate-sodium acetate buffer solution, and stir magnetically at 22-25℃ for 20-30 min at a stirring speed of 300-500 rpm to form a monomer mixture. (2) Add modified carbon quantum dot powder to the monomer mixture and ultrasonically disperse for 30-45 min. The ultrasonic power is 200-300 W and the ultrasonic frequency is 45-50 kHz. At this time, the modified carbon quantum dot powder is completely dispersed and there are no obvious agglomerated particles. (3) Then add N,N'-methylenebisacrylamide and stir for 10-12 min; (4) First add N,N,N',N'-tetramethylethylenediamine and stir for 4-5 min. Then slowly add an ammonium persulfate aqueous solution with a mass concentration of 5-8.5% at a rate of 1-2 drops / second and stir for 5-10 min. (5) Inject the mixture into a mold pre-coated with a release agent, seal and let it stand at 22-25℃ for 3-5 hours to polymerize, and obtain shape memory hydrogel.

8. The application of a shape memory hydrogel according to any one of claims 1 to 6 in a temperature or acid / alkali gas recognition-responsive shape memory hydrogel product.