Preparation method of photo-thermal response type composite hydrogel and intelligent window
By introducing graphene oxide into PNIPAM microgel and utilizing the photothermal effect and the small size effect of the microgel, the problems of high response temperature, slow speed and poor stability of PNIPAM hydrogel were solved, and a fast response and stable smart window effect was achieved.
Patent Information
- Application Number
- CN202510850364.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-24
- Publication Date
- 2025-09-19
AI Technical Summary
Existing PNIPAM hydrogels have high response temperature, slow response speed and poor dimensional stability, which makes it difficult to meet the application requirements of smart windows.
By introducing graphene oxide into PNIPAM microgel, its photothermal effect is used to isolate sunlight below the response temperature, and the small size effect of the microgel is combined to improve the response speed and maintain overall dimensional stability.
It achieved a rapid response (within 3 s) and transparency change at ambient temperature, maintained the dimensional stability of the gel device, and significantly improved the response speed and stability of the smart window.
Smart Images
Figure CN120665241A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the field of functional polymer materials, and in particular relates to a preparation method of a photothermal responsive composite hydrogel and a smart window. Background Art
[0002] Approximately 40% to 50% of global energy consumption comes from the building industry, and approximately 60% of energy exchange in buildings occurs through windows. Considerable effort has been invested in the construction industry to develop smart windows that can spontaneously modulate incident sunlight. Thermochromic windows utilize sunlight to heat-stimulate the phase change of color-changing materials, requiring no energy input. These windows are low-cost and have a simple structure, making them an ideal choice for building energy-saving windows. The core components of thermochromic windows are thermochromic light management materials, primarily including vanadium dioxide, perovskites, ionic liquids, and thermosensitive hydrogels. Among these, poly (N-isopropylacrylamide) (PNIPAM) thermosensitive hydrogels exhibit significant application potential in the field of smart windows due to their unique thermally responsive phase change behavior and excellent optical regulation properties.
[0003] However, current traditional PNIPAM hydrogels have some shortcomings that affect their application in smart windows. First, the response temperature of PNIPAM hydrogels (32°C) is still relatively high compared to the suitable indoor temperature range (20-26°C). When the indoor temperature is maintained at a comfortable level, smart windows made of conventional PNIPAM hydrogels have difficulty changing their transparency in a timely manner, and sunlight cannot be isolated and continues to heat the indoor space. Second, traditional PNIPAM hydrogels produce large volume changes during the phase transition process, which seriously affects the dimensional stability of the device. At the same time, this volume change depends on the diffusion and mass transfer process of water molecules, resulting in a slow response speed (usually taking several minutes to several hours), which makes it difficult to meet the real-time requirements of dynamic dimming.
[0004] Current PNIPAM hydrogels generally suffer from defects such as high response temperature, slow response speed, and poor dimensional stability, which greatly limit their application in smart windows. Therefore, it is necessary to improve the existing PNIPAM hydrogels. Summary of the Invention
[0005] The present invention aims to overcome the problems of high response temperature, slow response speed, and poor dimensional stability that currently exist in PNIPAM hydrogels when used in smart components. A photothermal-responsive composite hydrogel is proposed, along with a corresponding preparation method. The composite hydrogel provided by the present invention absorbs sunlight and heats up through graphene oxide (GO). When the ambient temperature is lower than the PNIPAM response temperature, it undergoes a temperature-sensitive transition, thereby isolating sunlight from entering the room. The small size effect of the microgels can significantly improve the response speed of the composite hydrogel. Furthermore, the temperature-sensitive transition occurs only in the microgels distributed in the matrix, without changing the overall volume of the composite gel, significantly improving the dimensional stability of the composite gel. The material prepared by this method can rapidly respond to light and change its own transparency. Furthermore, the preparation method is simple and inexpensive.
[0006] Specifically, the present invention adopts the following technical solutions: A method for preparing a photothermal responsive composite hydrogel comprises the following steps: Step 1: N-isopropylacrylamide, N,N'-methylenebisacrylamide and potassium persulfate are added to deionized water at room temperature and mixed and stirred to obtain a mixed solution. N2 is introduced into the mixed solution to remove dissolved oxygen. The mixed solution is then heated to 70-75°C and stirred for 6-8 hours. The solution is then washed by centrifugation and freeze-dried to obtain PNIPAM microgel. Step 2: At room temperature, graphene oxide, acrylamide and N,N'-methylenebisacrylamide are added to deionized water and mixed and stirred to obtain a mixed solution A; Step 3: First, the PNIPAM microgel obtained in step 1 is dispersed in the mixed solution A obtained in step 2 and stirred evenly, and then ammonium persulfate and tetramethylethylenediamine are added thereto; Step 4: Add the mixture from step 3 to at low temperature The composite hydrogel was obtained by reacting for 12-16 hours.
[0007] PNIPAM microgels are prepared through free radical polymerization. When the PNIPAM microgels are added to Mixture A and polymerized at low temperature, acrylamide primarily forms a cross-linked network within the microgel interstices. Simultaneously, graphene oxide is hydrogen-bonded to the newly formed polyacrylamide network. When the composite hydrogel is exposed to light, the graphene oxide converts the light into heat through a photothermal effect. When the temperature reaches the lowest solubility temperature (LCST) of PNIPAM, the microgels' light transmittance changes due to a hydrophilic-hydrophobic transition between the isopropyl groups.
[0008] Furthermore, in step 1, the concentration of N-isopropylacrylamide is 0.20-0.30 mol / L, the concentration of N,N'-methylenebisacrylamide is 0.5-0.75 mmol / L, and the concentration of potassium persulfate is 0.5 g / L.
[0009] Furthermore, in the mixed solution A obtained in step 2, the concentration of graphene oxide is 50-300 g / L, the concentration of acrylamide is 0-120 g / L, and the concentration of N,N'-methylenebisacrylamide is 0.9-1.2 g / L.
[0010] Furthermore, the ratio of PNIPAM microgel added to the mixed solution A in step 3 is 1-6 wt %.
[0011] Furthermore, in 1 L of mixed solution A in step 3, the amount of ammonium persulfate added is 0.2-0.6 g, and the amount of tetramethylethylenediamine added is 2.5-3.5 g.
[0012] Furthermore, the method comprises the following steps: Step 1: 1.13 g of N-isopropylacrylamide, 0.002 g of N,N'-methylenebisacrylamide, and 0.02 g of potassium persulfate were mixed and stirred with 100 mL of deionized water at room temperature to prepare a mixed solution. N2 was then introduced to remove dissolved oxygen. The solution was heated to 70°C and stirred at 300 rpm for 6 hours. Finally, the solution was centrifuged, washed, and freeze-dried to obtain PNIPAM microgels. Step 2: At room temperature, 1 mg of graphene oxide, 1 g of acrylamide, and 0.01 g of N,N'-methylenebisacrylamide were mixed with 10 mL of deionized water and stirred to obtain a mixed solution A; Step three: disperse 0.02 g of PNIPAM microgel in step one in the mixed solution A in step two, and then add 0.004 g of ammonium persulfate and 30 μL of tetramethylethylenediamine; Finally, the mixed reaction solution was quickly poured into a 1 mm thick glass sandwich and reacted at low temperature for 12 h to obtain a composite hydrogel.
[0013] A photothermal responsive composite hydrogel is prepared by the above method.
[0014] A smart window is prepared using the photothermal responsive composite hydrogel.
[0015] The graphene oxide in the composite hydrogel prepared by the present invention absorbs sunlight and heats up, and can undergo a temperature-sensitive transition when the ambient temperature is lower than the response temperature of PNIPAM to isolate sunlight from entering the room.
[0016] During the heating process, the composite hydrogel can undergo a reversible change from transparent to opaque within 3 s.
[0017] In addition, the hydrogel is dimensionally stable during the temperature response process, avoiding the potential application risks of gel devices caused by performance failure and structural instability, and further improving the application performance of the gel.
[0018] Compared with the prior art, the present invention has the following main advantages: (1) The material prepared by the present invention can reach the response temperature faster through the photothermal conversion of graphene oxide. 2 It is activated for 120s under light intensity; (2) The material prepared by the present invention responds quickly to temperature changes, the gel transparency changes significantly and has excellent dimensional stability; (3) The photothermal responsive composite hydrogel smart window prepared by the present invention has good application prospects and is expected to be used in smart optical components. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figure 1 This is a comparison diagram of the response processes of the GO / PAM / PNIPAM composite hydrogel prepared in Example 1 of the present invention and the PNIPAM hydrogel prepared in Comparative Example 3.
[0020] Figure 2 This is a physical picture of the GO / PAM / PNIPAM composite hydrogel prepared in Example 1 of the present invention before and after temperature response.
[0021] Figure 3 This is a full spectral transmittance diagram of the GO / PAM / PNIPAM composite hydrogel prepared in Example 1 of the present invention before and after temperature response.
[0022] Figure 4 This is a stability comparison chart of the GO / PAM / PNIPAM composite hydrogel prepared in Example 1 of the present invention and the PNIPAM hydrogel prepared in Comparative Example 3.
[0023] Figure 5 Schematic diagram of the light-to-heat conversion performance test and indoor temperature test device. Figure a is the light-to-heat conversion performance test, and figure b is the indoor temperature test. DETAILED DESCRIPTION
[0024] Representative embodiments will now be further refined. It should be understood that the following description is not intended to limit the embodiments to a preferred embodiment. On the contrary, it is intended to encompass alternatives, modifications, and equivalents that may be included within the spirit and scope of the embodiments defined by the appended claims.
[0025] Example 1: A photothermal responsive composite hydrogel smart window is prepared as follows: Step 1: 1.13 g of N-isopropylacrylamide, 0.002 g of N,N'-methylenebisacrylamide, and 0.02 g of potassium persulfate were mixed with 100 mL of deionized water at room temperature to prepare a mixed solution. N2 was then introduced to remove dissolved oxygen. The solution was heated to 70°C and stirred for 6 hours. Finally, the solution was centrifuged, washed, and freeze-dried to obtain PNIPAM microgels. Step 2: At room temperature, 1 mg of graphene oxide (GO), 1 g of acrylamide (PAM), and 0.01 g of N,N'-methylenebisacrylamide (PNIPAM) were mixed with 10 mL of deionized water and stirred to prepare a mixed solution A. Step 3: Disperse 0.02 g of PNIPAM microgel from Step 1 in mixed solution A from Step 2, then add 0.004 g of ammonium persulfate and 30 μL of tetramethylethylenediamine. Finally, quickly pour the reaction solution into a 1 mm thick glass sandwich and react at low temperature for 12 hours to obtain the GO / PAM / PNIPAM composite hydrogel smart window.
[0026] Example 2: A photothermal responsive composite hydrogel smart window is prepared as follows: Step 1: 1.13 g of N-isopropylacrylamide, 0.002 g of N,N'-methylenebisacrylamide, and 0.02 g of potassium persulfate were mixed with 100 mL of deionized water at room temperature to prepare a mixed solution. N2 was then introduced to remove dissolved oxygen. The solution was heated to 70°C and stirred for 6 hours. Finally, the solution was centrifuged, washed, and freeze-dried to obtain PNIPAM microgels. Step 2: At room temperature, 1 g of acrylamide (PAM) and 0.01 g of N,N'-methylenebisacrylamide (PNIPAM) were mixed with 10 mL of deionized water and stirred to obtain a mixed solution A. Step 3: Disperse 0.02 g of PNIPAM microgel from Step 1 in mixed solution A from Step 2, then add 0.004 g of ammonium persulfate and 30 μL of tetramethylethylenediamine. Finally, quickly pour the reaction solution into a 1 mm thick glass sandwich and react at low temperature for 12 hours to obtain the PAM / PNIPAM composite hydrogel smart window.
[0027] Example 3: A photothermal responsive composite hydrogel smart window is prepared as follows: Step 1: 21.13 g of N-isopropylacrylamide, 0.002 g of N,N'-methylenebisacrylamide, and 0.02 g of potassium persulfate were mixed and stirred with 100 mL of deionized water at room temperature to prepare a mixed solution. N2 was then introduced to remove dissolved oxygen. The solution was heated to 70°C and stirred for 6 hours. Finally, the solution was centrifuged, washed, and freeze-dried to obtain PNIPAM microgels. Step 2: At room temperature, 2 mg of graphene oxide (GO), 1 g of acrylamide (PAM), and 0.01 g of N,N'-methylenebisacrylamide (PNIPAM) were mixed with 10 mL of deionized water and stirred to prepare a mixed solution A. Step 3: Disperse 0.02 g of PNIPAM microgel from Step 1 in mixed solution A from Step 2, then add 0.004 g of ammonium persulfate and 30 μL of tetramethylethylenediamine. Finally, quickly pour the reaction solution into a 1 mm thick glass sandwich and react at low temperature for 12 hours to obtain the GO / PAM / PNIPAM composite hydrogel smart window.
[0028] Comparative Example 1: A polyacrylamide hydrogel window, the preparation process is as follows: Step 1: At room temperature, 1 g acrylamide and 0.01 g N,N'-methylenebisacrylamide were mixed with 10 mL of deionized water and stirred to obtain a mixed solution A. Step 2: Add 0.004 g of ammonium persulfate and 30 μL of tetramethylethylenediamine to mixed solution A. Finally, quickly pour the reaction solution into a 1 mm thick glass sandwich and react at low temperature for 12 hours to obtain a polyacrylamide (PAM) hydrogel window.
[0029] Comparative Example 2: A glass window, the preparation process is as follows: Step 1: Use 1 mm thick glass plywood as the glass window.
[0030] Comparative Example 3: A PNIPAM hydrogel window, the preparation process is as follows: Step 1: At room temperature, 1 g of N-isopropylacrylamide and 0.01 g of N,N'-methylenebisacrylamide were mixed with 10 mL of deionized water and stirred to obtain a mixed solution A. Step 2: Add 0.004 g of ammonium persulfate and 30 μL of tetramethylethylenediamine to mixed solution A. Finally, quickly pour the reaction solution into a 1 mm thick glass sandwich and react at low temperature for 12 hours to obtain a poly (N-isopropylacrylamide) (PNIPAM) hydrogel window.
[0031] Through the embodiments and three comparative examples, the indoor temperature control effects of ordinary glass windows, polyacrylamide gel windows, and N-isopropylacrylamide gel windows can be compared. The comparison results are detailed below.
[0032] Figure 1 This is a comparison chart of the response processes of the GO / PAM / PNIPAM composite hydrogel prepared in Example 1 and the PNIPAM hydrogel prepared in Comparative Example 3. It can be seen that the response process of the GO / PAM / PNIPAM composite hydrogel is completed within 3 s (50 s for the PNIPAM hydrogel).
[0033] Figure 2 These are the actual pictures of the GO / PAM / PNIPAM composite hydrogel prepared in Example 1 before and after temperature response. It can be seen that the GO / PAM / PNIPAM composite hydrogel is transparent before temperature response and becomes opaque and white after temperature response.
[0034] Figure 3 This is a graph of the full-spectrum transmittance of the GO / PAM / PNIPAM composite hydrogel prepared in Example 1 before and after temperature response. It can be seen that after temperature response, the full-spectrum transmittance of the sample decreases significantly.
[0035] Figure 4 This is a stability comparison chart of the GO / PAM / PNIPAM composite hydrogel prepared in Example 1 and the PNIPAM hydrogel prepared in Comparative Example 3. It can be seen that the GO / PAM / PNIPAM composite hydrogel is highly stable and not easily deformed.
[0036] The following is a light-to-heat conversion performance test of the products prepared in Examples 1-2. The specific test process is as follows: A xenon lamp (at the intensity of one sun) was used to illuminate the product surface. A thermocouple sensor was installed on the product surface. A computer collected the temperature rise data of the window under the xenon lamp to test the product's light-to-heat conversion performance. The test results are shown in the table below.
[0037] PNIPAM microgel (wt%) Graphene oxide (mg / L) Time required to reach 32 ºC (s) Example 1 2 100 320 Example 2 2 0 823 Example 3 2 200 269 The photothermal conversion performance test shows that the GO / PAM / PNIPAM composite hydrogel prepared in the present invention shortens the response time of the smart window prepared therefrom through the photothermal effect of graphene oxide.
[0038] The following is a test of the indoor temperature control ability of the products prepared in Examples 1-2 and Comparative Examples 1-2. The specific process of the test is as follows: A house model measuring 20 × 20 × 20 cm was constructed using PVC sheets and wrapped with insulation. A 10 × 10 cm notch was cut in the top and bottom to accommodate a window. A thermocouple sensor was installed at the geometric center of the simulated house to record indoor air temperature changes. Finally, a xenon lamp (with the intensity of one sun) was used to illuminate the room from top to bottom, and the sensor collected room temperature data for different window types. The materials from the previous example were placed in the notch and illuminated with the xenon lamp until the indoor temperature reached equilibrium. The test results are shown in the table below.
[0039] PNIPAM microgel (wt%) Graphene oxide (mg / L) Indoor temperature (°C) Example 1 2 100 30.4 Example 2 2 0 32.5 Comparative Example 1 0 0 38.6 Comparative Example 2 0 0 40.5 By testing the indoor temperature control ability of each sample, it can be seen that the GO / PAM / PNIPAM composite hydrogel window prepared by the present invention can maintain the indoor temperature at 30.4°C under one sunlight intensity, which is 10.1°C lower than that of ordinary glass windows.
[0040] To this end, the photothermal responsive composite hydrogel smart window prepared by the present invention is not only highly stable and structurally non-deformable, but also has rapid response characteristics. It can achieve rapid photothermal conversion when the ambient temperature changes, has outstanding indoor temperature regulation capabilities, and can effectively maintain the indoor temperature in a comfortable range.
[0041] It is obvious to those skilled in the art that certain modifications, combinations and variations can be made based on the above teachings.
Claims
1. A method for preparing a photothermal responsive composite hydrogel, characterized in that: The following steps are involved: Step 1: N-isopropylacrylamide, N,N'-methylenebisacrylamide and potassium persulfate are added to deionized water at room temperature and mixed and stirred to obtain a mixed solution. N2 is introduced into the mixed solution to remove dissolved oxygen. The mixed solution is then heated to 70-75°C and stirred for 6-8 hours. The solution is then washed by centrifugation and freeze-dried to obtain PNIPAM microgel. Step 2: At room temperature, graphene oxide, acrylamide and N,N'-methylenebisacrylamide are added to deionized water and mixed and stirred to obtain a mixed solution A; Step 3: First, the PNIPAM microgel obtained in step 1 is dispersed in the mixed solution A obtained in step 2 and stirred evenly, and then ammonium persulfate and tetramethylethylenediamine are added thereto; Step 4: Add the mixture from step 3 to Below 25℃ The composite hydrogel was obtained by reacting for 12-16 hours.
2. The preparation method according to claim 1, wherein: In step 1, the concentration of N-isopropylacrylamide is 0.20-0.30 mol / L, the concentration of N,N'-methylenebisacrylamide is 0.5-0.75 mmol / L, and the concentration of potassium persulfate is 0.5 g / L.
3. The preparation method according to claim 1, wherein: In the mixed solution A obtained in step 2, the concentration of graphene oxide is 50-300 g / L, the concentration of acrylamide is 0-120 g / L, and the concentration of N,N'-methylenebisacrylamide is 0.9-1.2 g / L.
4. The preparation method according to claim 1, wherein: The ratio of PNIPAM microgel added to the mixed solution A in step 3 is 1-6 wt %.
5. The preparation method according to claim 1, wherein: In 1 L of mixed solution A in step 3, the amount of ammonium persulfate added is 0.2-0.6 g, and the amount of tetramethylethylenediamine added is 2.5-3.5 g.
6. The preparation method according to claim 1, wherein: The following steps are involved: Step 1: 1.13 g of N-isopropylacrylamide, 0.002 g of N,N'-methylenebisacrylamide, and 0.02 g of potassium persulfate were mixed and stirred with 100 mL of deionized water at room temperature to prepare a mixed solution. N2 was then introduced to remove dissolved oxygen. The solution was heated to 70°C and stirred at 300 rpm for 6 hours. Finally, the solution was centrifuged, washed, and freeze-dried to obtain PNIPAM microgels. Step 2: At room temperature, 1 mg of graphene oxide, 1 g of acrylamide, and 0.01 g of N,N'-methylenebisacrylamide were mixed with 10 mL of deionized water and stirred to obtain a mixed solution A; Step three: disperse 0.02 g of PNIPAM microgel in step one in the mixed solution A in step two, and then add 0.004 g of ammonium persulfate and 30 μL of tetramethylethylenediamine; Finally, the mixed reaction solution was quickly poured into a 1 mm thick glass sandwich and reacted at 20 °C for 12 h to obtain a composite hydrogel.
7. A photothermal responsive composite hydrogel, characterized in that: The method is prepared by any one of claims 1 to 6.
8. A smart window, characterized in that: It is prepared using the photothermal responsive composite hydrogel described in claim 7.