Temperature-sensitive composite hydrogel as well as preparation method and application thereof
By preparing polysaccharide composite hydrogel, the existing PNIPAM hydrogel has solved the problems of low transparency and unadjustable phase transition temperature, and has achieved a hydrogel with high transparency and adjustable phase transition temperature, which is suitable for the manufacturing of smart windows.
Patent Information
- Application Number
- CN202510410070.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-02
- Publication Date
- 2025-07-11
AI Technical Summary
Existing PNIPAM-based thermochromic hydrogels have shortcomings in transparency and phase change temperature regulation, limiting their practical application in smart windows.
By preparing a temperature-sensitive composite hydrogel, the temperature-sensitive alkyl polysaccharide is obtained by reacting polysaccharides with an etherifying agent, and a mixed solution of N-isopropyl acrylamide and acrylic acid is added, followed by crosslinking to obtain a composite hydrogel with adjustable volume phase transition temperature.
It realizes the high transparency of the hydrogel, adjustable phase change temperature, excellent temperature sensitivity and hygroscopicity, low price, good biocompatibility, low toxicity, degradability and fast cooling, and is suitable for the manufacturing of thermally chromic smart windows.
Smart Images
Figure CN120289829A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of gel preparation, and specifically relates to a temperature-sensitive composite hydrogel, a preparation method thereof, and an application thereof. Background Art
[0002] Intelligent windows are mainly divided into four types according to different stimulus sources: electrochromic, photochromic, mechanochromic, and thermochromic. Among them, the low-cost thermochromic window that can automatically respond to temperature changes without energy input is considered the most cost-effective method that better meets the requirements of energy conservation and emission reduction. In the past decade, organic materials such as PNIPAM, HPC, and PNVCL have often been used in the design and synthesis of thermochromic hydrogel intelligent windows. These thermochromic hydrogels achieve the modulation of light transmittance through the reversible switching between hydrogen bonding (transparent) between water molecules and polymers and hydrophobic interaction (transparent) between polymer molecular chains near their lower critical solution temperature (LCST). Due to its low LCST (~32°C) and solar modulation ability, PNIPAM has become an excellent intelligent window material. However, the thermochromic hydrogels based on PNIPAM still have the defects of low transparency and the phase transition temperature cannot be adjusted according to the temperature requirements of different regions, which limits their practical application in intelligent windows. Therefore, some research teams have tried to introduce other substances into PNIPAM hydrogels to solve the above-mentioned thorny problems. For example, the transparency of intelligent windows can be significantly improved after PNIPAM is compounded with hydrophilic polymers such as gelatin, polyacrylamide (PAM), and hydroxypropyl cellulose (HPC). However, the defect that the phase transition temperature of the above-mentioned polymer-based hydrogel intelligent windows cannot be adjusted according to the temperature requirements of different regions limits their practical application in intelligent windows. Summary of the Invention
[0003] The object of the present invention is a temperature-sensitive composite hydrogel, a preparation method thereof, and an application thereof.
[0004] To achieve the above object, the technical solution adopted by the present invention is as follows:
[0005] A preparation method of a temperature-sensitive composite hydrogel, wherein the hydrogel is a temperature-sensitive alkyl polysaccharide obtained by reacting a polysaccharide with an etherifying agent; N-isopropylacrylamide and acrylic acid are added to the temperature-sensitive alkyl polysaccharide to obtain a mixed solution; the mixed solution is mixed with an auxiliary agent and crosslinked to obtain a temperature-sensitive composite hydrogel.
[0006] Furthermore,
[0007] (1) Preparation of temperature-sensitive alkyl polysaccharide: Alkalize the polysaccharide with alkali at 60 - 70 °C for 1 - 1.5 hours. After alkalization, add an etherifying agent to the reaction solution and stir and react at 70 - 90 °C for 4 - 8 hours. After the reaction, cool to room temperature and adjust the system to neutral. After adjustment, perform dialysis treatment with a dialysis bag until the conductivity of the reaction solution is less than 10 μs / cm, and then the temperature-sensitive alkyl polysaccharide is obtained.
[0008] (2) Mixed solution: Dissolve the temperature-sensitive alkyl polysaccharide obtained above in water, and then add N-isopropylacrylamide and acrylic acid, and react at a high temperature for 0.5 - 2 h to obtain a mixed solution.
[0009] (3) Crosslinking to prepare temperature-sensitive hydrogel: Add a crosslinking agent, an oxidizing agent, and a reducing agent to the above-obtained mixed solution in sequence. After addition, continue to stir in an ice-water bath for 3 - 5 min to obtain a temperature-sensitive composite hydrogel.
[0010] In the step (1), add sodium hydroxide accounting for 2% - 45% of the mass of the polysaccharide to a polysaccharide solution with a mass concentration of 10% - 60%, stir and mix evenly, and alkalize at 60 - 70 °C for 1 - 1.5 h; then dropwise add the etherifying agent according to the mass ratio of the etherifying agent to the polysaccharide of 0.3 - 3.5:1, and then stir and react at 70 - 90 °C for 4 - 8 h; then cool the reaction solution to room temperature by diluting with water, and then adjust the reaction solution to pH 7 with acid. After adjustment, place the reaction solution in a dialysis bag with a molecular weight of 7000 - 14000 for dialysis until the conductivity of the reaction solution is less than 10 μs / cm. After dialysis, concentrate and dry to obtain a powder or block solid alkyl polysaccharide; among them, the etherifying agent is alkyl glycidyl ether.
[0011] The polysaccharide is cellulose, starch or guar gum; the alkyl glycidyl ether is propyl glycidyl ether, isobutyl glycidyl ether or pentyl glycidyl ether.
[0012] In the step (2), crush the temperature-sensitive alkyl polysaccharide obtained above. After crushing, dissolve it in deionized water, and the concentration of the alkyl polysaccharide solution in the dissolution solution is 5 - 12 wt%; then add N-isopropylacrylamide and acrylic acid to the dissolution solution, and react in a water bath at 60 - 70 °C for 0.5 - 2 h to obtain a mixed solution; among them, the mass ratio of N-isopropylacrylamide, acrylic acid to the temperature-sensitive alkyl polysaccharide is 5 - 10:0.3 - 0.5:1.
[0013] In the step (3), add a crosslinking agent, an oxidizing agent, and a reducing agent to the above mixed solution under the condition of ice bath stirring, and then let it stand to obtain a hydrogel; among them, the mass ratio of the crosslinking agent to the mixed solution is 0.14 - 1.2:3, the mass ratio of the oxidizing agent to the mixed solution is 0.8 - 1.2:3, and the mass ratio of the reducing agent to the mixed solution is 0.8 - 1.2:3.
[0014] The prepared composite hydrogel product was rinsed with deionized water at 20 °C. This process mainly removed unreacted cross-linking agents and reactants such as sodium hydroxide. The above purification process was repeated several times until the conductivity of the hydrogel eluent was less than 10 μs / cm, and a temperature-sensitive polysaccharide hydrogel was obtained.
[0015] The cross-linking agent is one of N,N'-methylenebisacrylamide (hydroxyethyl acrylate, hydroxypropyl acrylate, methacrylic acid, hydroxyethyl methacrylate, hydroxypropyl methacrylate, divinylbenzene, N-hydroxymethylacrylamide, diacetone acrylamide); the redox system (redox initiation system) is potassium persulfate-sodium bisulfite. (Oxidants include hydrogen peroxide, persulfates, hydroperoxides, etc., and reductants include ferrous ions, sodium sulfite, sodium bisulfite, etc.)
[0016] A hydrogel prepared by the above method, and the volume phase transition temperature of the hydrogel obtained by the method can be adjusted in the range of 15.5 - 45.8 °C.
[0017] An application of the above hydrogel, and the application of the hydrogel in a thermochromic smart window.
[0018] The beneficial effects of the present invention are:
[0019] The hydrogel of the present invention is composed of pure polysaccharides and has excellent and adjustable thermosensitive properties and excellent hygroscopicity. Compared with petroleum-based thermosensitive hydrogels, it has the advantages of low cost, good biocompatibility, low toxicity, degradability, high transparency, fast cooling, and wide optical region modulation range. Description of the Drawings
[0020] Figure 1 It is a physical diagram of the thermosensitive composite hydrogel provided in the embodiment of the present invention at different temperatures.
[0021] Figure 2 It is a scanning electron microscope (SEM) diagram of the thermosensitive composite hydrogel provided in the embodiment of the present invention at different temperatures. Detailed Embodiments
[0022] The following further illustrates the specific embodiments of the present invention with reference to examples. It should be noted that the specific embodiments described herein are only for explaining and interpreting the present invention and are not limited to the present invention.
[0023] The determination of the temperature sensitivity of the polysaccharide hydrogel, that is, the determination of the volume phase transition temperature (VPTT), is as follows: In a water bath, the hydrogel was swollen in deionized water at a certain temperature range (0 - 60 °C) for at least 12 h. Then, the hydrogel was transferred to a dry glass container and weighed to determine the swelling weight at each temperature. The surface water was wiped off with filter paper before each measurement. The swelling ratio was calculated as follows:
[0024] SR=(Wt - Wd) / Wd
[0025] Wherein, Wt (g) is the weight of the gel at a certain temperature, and Wd (g) is the weight of the dry gel. The curve of the swelling ratio changing with temperature, and the temperature corresponding to the larger tangent slope of the curve is the volume phase transition temperature.
[0026] Example 1
[0027] (1) Preparation of 2-hydroxy-3-alkoxypropyl hydroxyethyl cellulose:
[0028] Add 10 g of cellulose into a 500 mL three-necked flask, add 60 mL of deionized water for dispersion, stir and heat to 70 °C. Dropwise add 4.4 g of sodium hydroxide with a mass concentration of 40% into the three-necked flask, and alkalize at 70 °C for 1 h. Then dropwise add 15 g of isobutyl glycidyl ether into the alkalized reaction solution, and react at 80 °C for 5 h. After the reaction is completed and cooled to room temperature, neutralize with hydrochloric acid to a pH value of 7, then put it into a dialysis bag with a molecular weight of 7000 - 14000 and dialyze in deionized water. The dialysis is completed when the conductivity of the deionized water is less than 10 μs / cm. Remove most of the water with a rotary evaporator, and then dry it with a freeze dryer to obtain blocky solid 2-hydroxy-3-alkoxypropyl hydroxyethyl cellulose.
[0029] (2) Pulverize the obtained 2-hydroxy-3-alkoxypropyl hydroxyethyl cellulose with a pulverizer and place it in a beaker. Take 1 g of the pulverized 2-hydroxy-3-alkoxypropyl hydroxyethyl cellulose and add it to 15 mL of deionized water at 70 °C, stir slowly until dissolved (try to avoid foaming). Then, add 6 g of N-isopropylacrylamide and 100 μL of acrylic acid to the dissolved solution, and react in a 70 °C water bath for 1 h to obtain a mixed solution.
[0030] (3) Preparation of the composite gel: In the above mixed solution, sequentially add 0.006 g of N,N-methylenebisacrylamide, 0.005 g of potassium persulfate and 0.003 g of sodium bisulfite, and stir for 5 minutes under ice bath conditions to obtain a composite hydrogel.
[0031] (4) Rinse the obtained composite gel with 20 °C deionized water to purify the composite gel. Repeat the treatment of the gel according to the above purification process until the conductivity of the eluent is less than 10 μs / cm to obtain a temperature-sensitive gel. The above purification process is mainly to remove unreacted cross-linking agents, oxidants, reducing agents and other reactants.
[0032] (5) After purification, a temperature-sensitive gel is obtained, denoted as D1 (see Figure 1 and 2), By measuring the curve of the swelling ratio changing with temperature, the temperature corresponding to the tangent line with a large slope is taken as the volume phase transition temperature, and the measured VPTT is 34.3 °C.
[0033] From Figure 1 and 2 It can be seen that the obtained hydrogel has obvious thermosensitive properties.
[0034] Example 2
[0035] This example is basically the same as Example 1. The difference is that in (1), the preparation conditions of 2-hydroxy-3-alkoxypropyl hydroxyethyl cellulose are shown in Table 1, and the obtained hydrogel is denoted as D2. The measured VPTT is 30.3 °C.
[0036] Table 1
[0037]
[0038] Example 3
[0039] This example is basically the same as Example 1. The difference is that in (1), the preparation conditions of 2-hydroxy-3-alkoxypropyl hydroxyethyl cellulose are shown in Table 2. The obtained hydrogel is denoted as D3. The measured VPTT is 22.3 °C.
[0040] Table 2
[0041]
[0042] Example 4
[0043] This example is basically the same as Example 1. The difference is that in (3), the amount of crosslinking agent used is 0.005 g, and the specific reaction conditions are shown in Table 3. The obtained hydrogel is denoted as D4. The measured VPTT is 20.1 °C.
[0044] Table 3
[0045]
[0046] Example 5
[0047] This example is basically the same as Example 1. The difference is that in (2), the amount of acrylic acid used is 50 μL, and the specific reaction conditions are shown in Table 4. The obtained hydrogel is denoted as D5. The measured VPTT is 42.1 °C.
[0048] Table 4
[0049]
[0050] Example 6
[0051] This example is basically the same as Example 1. The difference is that in (2), the amount of N-isopropylacrylamide used is 4 g, and the specific reaction conditions are shown in Table 5. The obtained hydrogel is denoted as D6. The VPTT is measured to be 24.3 °C.
[0052] Table 5
[0053]
[0054] Example 7
[0055] This example is basically the same as Example 1. The differences are as follows: in (1), the preparation conditions of 2-hydroxy-3-alkoxypropyl hydroxyethyl cellulose are shown in Table 6; in (2), the amount of N-isopropylacrylamide used is 4 g; in (3), the amount of crosslinking agent used is 0.005 g, and the specific reaction conditions are shown in Table 7. The obtained hydrogel is denoted as D7. The VPTT is measured to be 20.3 °C.
[0056] Table 6
[0057]
[0058] Table 7
[0059]
[0060] Example 8
[0061] This example is basically the same as Example 1. The differences are as follows: in (1), the preparation conditions of 2-hydroxy-3-alkoxypropyl hydroxyethyl cellulose are shown in Table 8; in (2), the amount of acrylic acid used is 50 μL; in (3), the amount of crosslinking agent used is 0.007 g, and the specific reaction conditions are shown in Table 9. The obtained hydrogel is denoted as D8. The VPTT is measured to be 27.3 °C.
[0062] Table 8
[0063]
[0064] Table 9
[0065]
[0066] In summary, the volume phase transition temperature (VPTT) of the hydrogel obtained by the present invention can be adjusted within the range of 15.5 - 45.8 °C. The hydrogel prepared by the present invention has excellent temperature sensitivity and hygroscopicity, and at the same time has the characteristics of low cost, good biocompatibility, low toxicity, degradability, high transparency, fast cooling, wide optical region modulation range, etc., and can be applied to the manufacture of thermochromic smart windows.
Claims
1. A preparation method of a temperature-sensitive composite hydrogel, characterized in that: The hydrogel is a temperature-sensitive alkyl polysaccharide obtained by reacting a polysaccharide with an etherifying agent; N-isopropylacrylamide and acrylic acid are added to the temperature-sensitive alkyl polysaccharide to obtain a mixed solution; the mixed solution is cross-linked with an auxiliary agent to obtain a temperature-sensitive composite hydrogel.
2. The method for preparing a temperature-sensitive composite hydrogel according to claim 1, characterized in that: (1) Preparation of temperature-sensitive alkyl polysaccharide: The polysaccharide is alkalized with alkali at 60-70 °C for 1-1.5 hours. After alkalization, an etherifying agent is added to the reaction solution, and the mixture is stirred and reacted at 70-90 °C for 4-8 hours. After the reaction, it is cooled to room temperature and adjusted to neutrality. After adjustment, it is dialyzed through a dialysis bag until the conductivity of the reaction solution is less than 10 μs / cm, and the temperature-sensitive alkyl polysaccharide is obtained. (2) Mixed solution: The temperature-sensitive alkyl polysaccharide obtained above is dissolved in water, and then N-isopropylacrylamide and acrylic acid are added, and the reaction is carried out at a high temperature for 0.5-2 h to obtain a mixed solution. (3) Cross-linking to prepare temperature-sensitive hydrogel: A cross-linking agent, an oxidizing agent and a reducing agent are sequentially added to the above-mentioned obtained mixed solution, and after addition, the mixture is continuously stirred in an ice-water bath for 3-5 min to obtain a temperature-sensitive composite hydrogel.
3. The preparation method of the temperature-sensitive composite hydrogel according to claim 2, characterized in that: In the step 1), sodium hydroxide with a mass concentration of 10% to 60% of the polysaccharide solution is added to the polysaccharide, stirred and mixed evenly, and alkalized at 60-70 °C for 1-1.5 h; then the etherifying agent is added dropwise at a ratio of the mass ratio of the etherifying agent to the polysaccharide of 0.3-3.5:1, and then stirred and reacted at 70-90 °C for 4-8 h; then the reaction solution is cooled to room temperature by diluting with water, and then the reaction solution is adjusted to pH 7 with acid. After adjustment, the reaction solution is placed in a dialysis bag with a molecular weight of 7000-14000 for dialysis until the conductivity of the reaction solution is less than 10 μs / cm. After dialysis, it is concentrated and dried to obtain a powder or block solid alkyl polysaccharide; wherein, the etherifying agent is alkyl glycidyl ether.
4. The preparation method of the temperature-sensitive composite hydrogel according to any one of claims 1-3, characterized in that: The polysaccharide is cellulose, starch or guar gum; the alkyl glycidyl ether is propyl glycidyl ether, isobutyl glycidyl ether or pentyl glycidyl ether.
5. The preparation method of the hydrogel according to claim 2, characterized in that: In the step 2), the obtained temperature-sensitive alkyl polysaccharide is crushed, and after crushing, it is dissolved in deionized water. The concentration of the alkyl polysaccharide solution in the dissolved solution is 5-12 wt%; then N-isopropylacrylamide and acrylic acid are added to the dissolved solution, and the reaction is carried out in a water bath at 60-70 °C for 0.5-2 h to obtain a mixed solution; wherein, the mass ratio of N-isopropylacrylamide, acrylic acid to the temperature-sensitive alkyl polysaccharide is 5-10:0.3-0.5:
1.
6. The preparation method of the temperature-sensitive composite hydrogel according to claim 2, characterized in that: In the step 3), a cross-linking agent, an oxidizing agent and a reducing agent are added to the above-mentioned mixed solution under the condition of ice bath stirring, and then left standing to obtain a hydrogel; wherein, the mass ratio of the cross-linking agent to the N-isopropylacrylamide, acrylic acid / polysaccharide mixture in the mixed solution is 0.14-1.2:3, the mass ratio of the oxidizing agent to the mixed solution is 0.8-1.2:3, and the mass ratio of the reducing agent to the mixed solution is 0.8-1.2:
3.
7. The hydrogel prepared by the method according to claim 1, characterized in that: The hydrogel obtained by the method of claim 1 has a volume phase transition temperature that can be adjusted within the range of 15.5-45.8 °C.
8. Use of the hydrogel according to claim 7, characterized in that: Application of the hydrogel in a thermochromic smart window.