A temperature-responsive gel, a temperature-controlled membrane, and corresponding preparation methods and applications

Abstract

The present invention relates to a temperature-responsive gel, which is prepared by the following steps: adding NIPAm, PVA and N,N′-methylenebis(acrylamide) to water to obtain an organic solution; adding nano-alumina particles to the organic solution, wherein the nano-alumina particles are bonded to the organic phase in the organic solution through the coupling agent; adding a coupling agent and an initiator to the precursor solution to construct a network structure to obtain the temperature-responsive gel. It also relates to a temperature-controlled film obtained from the temperature-responsive gel and its application. The temperature-responsive gel in the present invention has a reflectivity of up to 96.2%. The temperature-controlled film realizes fully automatic temperature regulation and can be widely used in the field of outdoor temperature control, achieving the purpose of low carbon and environmental protection.

Description

Technical Field

[0001] The invention relates to a gel, in particular to a temperature-responsive gel, a temperature-controlled film prepared by using the temperature-responsive gel, and a preparation method and application thereof. Background Art

[0002] Keeping the ambient temperature constant plays one of the most basic roles in many scenarios of human life, such as breeding and brewing industries. However, traditional temperature regulation mainly relies on air conditioning, which consumes a lot of energy. It is reported that the energy consumption of indoor temperature regulation devices for heating and cooling accounts for 20% of the world's total energy demand and generates a large amount of carbon dioxide emissions.

[0003] Based on the low temperature environment of the earth's outer space and the high temperature environment of the sun, people use outer space as a radiation cooling source and the sun as a heat source to achieve passive radiation cooling and passive solar heating with the smallest carbon footprint. This idea has attracted much attention. However, most passive devices are static and single-function, and cannot meet the actual requirements of dynamic cooling and heating under various conditions. Some efforts have been made in the prior art to achieve switchable radiation cooling and solar heating. For example, a porous silicone coating is used as an optical management platform for reversible mechanical forces, and a dual-mode thermal management device that switches the radiation cooling and solar heating functions through a pair of rotating actuators or rollers, but this mechanical switching cannot achieve intelligent temperature control. Summary of the invention

[0004] In order to solve the problems of high carbon emissions and unintelligent temperature control in the temperature regulating device in the prior art, the present invention provides an intelligent temperature regulating device directly triggered by temperature.

[0005] Based on this purpose, the present invention provides a temperature-responsive gel on one hand, including a gel network body and nano-alumina particles, wherein the nano-alumina particles are connected to the gel network body, and the gel network body is constructed by N-isopropylacrylamide (NIPAm), polyvinyl alcohol (PVA) and N,N′-methylenebis(acrylamide). The temperature-responsive gel has a temperature influence threshold. When the temperature is lower than the threshold, the gel is transparent, and when the temperature is higher than the threshold, the gel is white.

[0006] As a preferred solution, the temperature response threshold is 30-50°C.

[0007] As a preferred solution, the nano-alumina particles are bonded to the gel network body via a coupling agent.

[0008] In a second aspect, a method for preparing a temperature-responsive gel is provided, comprising the following steps: adding NIPAm, PVA and N,N′-methylenebis(acrylamide) to water to obtain an organic solution;

[0009] Adding nano-alumina particles and a coupling agent to the organic solution to obtain a precursor solution, wherein the nano-alumina particles are bonded to the organic phase in the organic solution through the coupling agent;

[0010] Adding a crosslinking agent and an initiator to the precursor solution, the NIPAm, PVA and N,N′-methylenebis(acrylamide) undergo a crosslinking reaction under the action of the crosslinking agent and the initiator;

[0011] The temperature-responsive gel is obtained.

[0012] As a preferred solution, the temperature-responsive gel is obtained by static molding.

[0013] As a preferred solution, the coupling agent includes a first end group capable of reacting and connecting with alumina and a second end group capable of reacting with the organic phase.

[0014] As a preferred solution, the coupling agent is bonded to the PVA in the organic solution, and the coupling agent is reacted to the hydroxyl groups on the PVA.

[0015] As a preferred embodiment, the coupling agent is tetrabutyl titanate, and the structural formula after the coupling agent reacts with the nano-alumina particles and the organic phase is

[0016]

[0017] Where * is the connected organic chain.

[0018] As a preferred solution, the cross-linking agent is TEMED.

[0019] As a preferred embodiment, the initiator is ammonium persulfate.

[0020] As a preferred embodiment, the NIPAm, PVA and N,N′-methylenebis(acrylamide) are mixed in deionized water.

[0021] As a preferred solution, the NIPAm, PVA and N,N′-methylenebis(acrylamide) are dissolved and mixed in deionized water at 50-60° C.

[0022] As a preferred embodiment, the mixing mass ratio of NIPAm and PVA is NIPAm:PVA (5-6):(1-2).

[0023] As a preferred solution, the mixing mass ratio of NIPAm and PVA is NIPAm:PVA is 6:(1-2).

[0024] As a preferred embodiment, the mixing mass ratio of the NIPAm and the N,N′-methylenebis(acrylamide) is NIPAm:N,N′-methylenebis(acrylamide) (34-38):1.

[0025] As a preferred solution, the size of nano-alumina particles is 20 to 40 nm.

[0026] As a preferred solution, the nano-alumina particle size is 30 nm.

[0027] As a preferred solution, the nano-alumina is added in the form of a nano-alumina dispersion, which is then heated in a water bath to couple the nano-alumina particles to the organic phase. The nano-alumina dispersion is an aqueous solution of nano-alumina.

[0028] As a preferred embodiment, the mass ratio of the temperature-responsive gel to the nano-alumina particles is (100-110):1.

[0029] As a preferred solution, water bath heating satisfies one or more of the following combinations:

[0030] The water bath heating temperature is 40°C;

[0031] The water bath heating time is 1 hour.

[0032] As a preferred embodiment, the conditions for adding the crosslinking agent and the initiator to the precursor solution satisfy one or more of the following combinations:

[0033] The precursor solution is purified by nitrogen;

[0034] The precursor solution was cooled to 25°C.

[0035] As a preferred solution, the gel forming method is to place the solution to be formed between two glass plates, clamp the two glass plates, and let it stand for forming.

[0036] As a preferred solution, the lower critical solution temperature (LCST) of the temperature-responsive gel is adjusted by adjusting the dosage ratio of the PVA to the NIPAm.

[0037] In a third aspect, a temperature control membrane is provided, comprising a gel layer and a graphene oxide layer, wherein the gel layer is a temperature-responsive gel obtained by any one of the above schemes or a combination of multiple schemes, and the graphene oxide layer is a carrier carrying graphene oxide.

[0038] As a preferred solution, the carrier is a fabric, and the graphene oxide layer is a fabric coated with graphene oxide.

[0039] As a preferred solution, the thickness of the gel layer is greater than 400 μm.

[0040] In a fourth aspect, the present invention provides a method for preparing a temperature control film, comprising the following steps:

[0041] (1) preparing a graphene oxide layer,

[0042] a Spraying graphene oxide solution on the preheated fabric;

[0043] b. baking the fabric sprayed with graphene oxide at high temperature in a vacuum;

[0044] (2) Assembling the gel layer and the graphene oxide layer together in a stacked form, wherein the gel layer is a temperature-responsive gel obtained by any one of the above schemes or a combination of multiple schemes.

[0045] As a preferred embodiment, the graphene oxide solution is obtained by dispersing graphene oxide nanosheets in deionized water.

[0046] As a preferred embodiment, the concentration of the graphene oxide solution is 3 mg / mL.

[0047] In its fifth aspect, the present invention provides the use of a temperature control film obtained by any one of the above schemes or a combination of multiple schemes in an outdoor temperature control device or a breeding room. When used, the gel layer faces the outdoors and the graphene oxide layer faces the indoors.

[0048] The beneficial effects of the present invention include:

[0049] (1) When the temperature of the temperature-responsive gel in the present invention is higher than the phase transition temperature (lower critical solution temperature), the gel turns white. Based on the high refractive index difference between alumina and the organic phase, the light is scattered, thereby achieving high reflectivity. At the same time, the gel has a high emissivity in the mid-infrared band. The combination of the two enables the gel to cool down in a high-temperature environment.

[0050] (2) When the temperature of the temperature-responsive gel in the present invention is lower than the phase transition temperature, a large number of hydrogen bonds exist in the gel, the gel pores are open, and the gel is transparent, achieving high transmittance.

[0051] (3) The temperature-responsive gel of the present invention achieves precise reflection or transmission.

[0052] (4) The reflectivity of the temperature-responsive gel in the present invention is as high as 96.2%.

[0053] (5) The temperature control membrane in the present invention realizes fully automatic temperature regulation. When the temperature is higher than the phase transition temperature of the gel, the high reflectivity of the gel layer reduces the sub-ambient temperature induced by the temperature control membrane. When the temperature is lower than the phase transition temperature of the gel, the high transmittance of the gel layer allows light to reach the graphene oxide underneath, where it is absorbed and the temperature rises, thereby achieving the purpose of heating.

[0054] (6) The temperature control film of the present invention achieves 100W m -2 The radiation cooling power can reach about 550W m in winter. -2 of solar heating power.

[0055] (7) Temperature control membranes have great advantages in potential energy saving. They will open up new ways to design zero-energy thermally responsive temperature adaptation devices and provide innovative ways to achieve sustainable energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 Transmittance switching diagram of the temperature-responsive gel in the present invention in a temperature cycle changing environment;

[0057] Figure 2 The corresponding transmittance of the temperature-responsive gel of Examples 1-3 of the present invention during cooling and heating;

[0058] Figure 3 The test device in Example 9;

[0059] Figure 4 Temperature variation curves corresponding to the containers in the experimental group, the containers in the control group and the outer container in Example 9;

[0060] Figure 5 Temperature variation curves corresponding to the containers in the experimental group, the containers in the control group and the outer container in Example 10;

[0061] Figure 6 Heating power diagram of temperature control film at different ambient temperatures;

[0062] Figure 7 Refrigeration effect diagram of temperature control film in summer;

[0063] Figure 8 Heating effect diagram of temperature control film in winter;

[0064] In the figure, 1, outer container, 2, inner container, 3, heating module, 4, refrigeration module, 5, temperature testing device, 6, double control membrane. DETAILED DESCRIPTION

[0065] The present invention will be further explained below in conjunction with specific implementation modes, but it should be understood that the protection scope of the present invention is not limited by the specific implementation modes.

[0066] A method for preparing a temperature-responsive gel comprises the following steps

[0067] Adding NIPAm, PVA and N,N′-methylenebis(acrylamide) to water to obtain an organic solution, preferably deionized water, to prevent ions in the water from affecting the gel cross-linking reaction;

[0068] Adding nano-alumina particles (Al2O3) and a coupling agent to the organic solution to obtain a precursor solution, wherein the nano-alumina particles are bonded to the organic phase in the organic solution through the coupling agent;

[0069] adding a crosslinking agent and an initiator to the precursor solution;

[0070] The NIPAm, PVA and N,N′-methylenebis(acrylamide) construct a network structure under the action of a crosslinking agent and an initiator to obtain the temperature-responsive gel.

[0071] If a gel of a specific shape is to be obtained, the solution can be poured into a mold after adding a crosslinker and an initiator and allowed to stand at room temperature for molding. The molding temperature can also be appropriately increased to increase the molding speed.

[0072] The coupling agent in the present invention includes a first end group capable of reacting with alumina and a second end group capable of reacting with the organic matter, and the inorganic alumina is connected with the organic matter, and the organic matter can be the product of any one or more reactions of NIPAm, PVA and N,N′-methylenebis(acrylamide). The preferred coupling agent is tetrabutyl titanate (TT), which reacts with the hydroxyl groups on the surface of the nano-alumina particles by cutting the butoxy chain, thereby forming a chemical bond with Al2O3. The same reaction also occurs between TT and the PVA chain in the organic phase, thereby bonding the nano-alumina particles in the organic phase. The structural formula after bonding is as follows:

[0073] Wherein * represents other organic chains.

[0074] The crosslinking agent and initiator of the present invention can be any component that can induce the organic phase to form a gel network structure. As a feasible measure, the crosslinking agent and initiator are respectively selected from tetramethylethylenediamine (TEMED) and ammonium persulfate. Under the joint action of the two, the organic phase in the solution is interconnected to form a porous network structure.

[0075] In order to form a uniform organic phase solution, the NIPAm, PVA and N,N′-methylenebis(acrylamide) are dissolved and mixed in deionized water at 50-60°C. At this temperature, the performance of the organic phase will not be affected, and the organic phase in the solution can be uniformly mixed, providing favorable conditions for the subsequent coupling reaction and cross-linking reaction. Based on the gel response temperature we need to obtain, the mixing mass ratio of NIPAm and PVA in the solution is NIPAm:PVA (5-6):(1-2), and the preferred mixing mass ratio of NIPAm and PVA is NIPAm:PVA is 6:(1-2), and the mixing ratio is further precisely controlled according to the required temperature. NIPAm and N,N′-methylenebis(acrylamide) undergo a cross-linking reaction to form the matrix of the responsive gel. The mixing mass ratio of NIPAm and N,N′-methylenebis(acrylamide) is (34-38):1. This mixing ratio stabilizes the network structure of the formed gel and provides the prerequisite for the combination of the gel with PVA and the modification of alumina. The selected nano-alumina particle size is 20-40nm, and the nano-sized alumina provides the prerequisite for the reaction of alumina with the organic phase. The preferred nano-alumina particle size is 30nm. Nano-alumina particles of this size have a high refractive index, which can achieve temperature sensitivity while effectively adjusting the sunlight reflectivity of the temperature-responsive gel.

[0076] The nano-alumina is added in the form of a nano-alumina dispersion, and after the nano-alumina dispersion is added, water bath heating is performed to couple the nano-alumina particles to the organic matter, and the water bath heating satisfies one or more of the following combinations: the water bath heating temperature is 40° C.; the water bath heating time is 1 hour. The nano-alumina dispersion is an aqueous solution of nano-alumina. The mass ratio of the temperature-responsive gel to the nano-alumina particles is (100-110):1.

[0077] Preferably, the conditions for adding the crosslinking agent and the initiator to the precursor solution satisfy one or more of the following combinations: the precursor solution is purified by nitrogen; the precursor solution is cooled to 25° C. Oxygen can affect the crosslinking process of the gel, and nitrogen purification can precipitate oxygen in the solution.

[0078] If the gel is to eventually form a temperature-responsive gel film, the solution to be formed can be poured between two glass plates with a fixed distance, and the gel film can be obtained by demolding after forming.

[0079] The temperature-responsive gel of the present invention adjusts the lower critical solution temperature (LCST) of the temperature-responsive gel by adjusting the dosage ratio of the PVA and the NIPAm. The strong light reflectivity of the gel mainly comes from the refractive index difference between the organic phase and the inorganic phase. The difference between the two can effectively scatter the light and achieve the high reflectivity of the gel. The temperature-responsive gel of the present invention has a loose chain structure at low temperatures, and a large number of hydrogen bonds are formed between the hydrophilic groups on the chain and the water molecules to maintain the stability of the structure. This structure can effectively allow light to pass through, thereby showing a higher light transmittance. When the temperature rises above the LCST, the hydrogen bonds between the molecular chains and the water molecules will break, and in order to achieve a low energy state, the molecular chains shrink to form a dense island structure. The island-like PNIPAm molecules can effectively scatter light, thereby showing a high reflectivity, and in appearance, the gel changes from transparent to white. The high reflectivity of the gel depends on (1) the breaking of hydrogen bonds between the gels, the gels agglomerate to form an island structure, and (2) the high refractive index nano-alumina particles attached to the gel, achieving a large refractive index difference between the organic phase and the inorganic phase. The combined effect of conditions (1) and (2) makes the gel show high reflectivity when the temperature is higher than the LCST. The nano-alumina particles introduced into the gel have a refractive index of 1.8 and a size of about 30 nm. The introduction of the nano-particles significantly increases the effective refractive index of the temperature-responsive gel in the present invention from 1.49 to about 1.69 relative to the gel without the introduction of nano-alumina particles, achieving a reflectivity of more than 90%, and the response temperature is 30 to 50°C.

[0080] A temperature control membrane based on the temperature responsive gel, comprising a stacked gel layer and a graphene oxide layer, wherein the thickness of the gel layer is greater than 400 μm, preferably 400 to 800 μm, and when the thickness is lower than this value and the temperature is higher than the LCST, the light scattering efficiency is low, and when the thickness is higher than this value and the temperature is lower than the LCST, the light transmission efficiency is low. The preparation method of the temperature control membrane comprises the following steps:

[0081] (1) preparing a graphene oxide layer,

[0082] a Spraying graphene oxide solution on the preheated fabric;

[0083] b. baking the fabric sprayed with graphene oxide at high temperature in a vacuum;

[0084] (2) Assembling a gel layer and a graphene oxide layer together in a stacked structure, wherein the gel layer is the gel prepared by the above method, and the outer layer may be provided with an optically transparent film for protecting the gel, which may specifically be glass or the like.

[0085] The graphene oxide solution is obtained by dispersing graphene oxide nanosheets in deionized water. The concentration of the graphene oxide solution is 3 mg / mL.

[0086] The above-mentioned temperature control film can be used in outdoor temperature control devices, such as the roof of a building, to ensure a constant indoor temperature, reduce the utilization rate of refrigeration and heating devices such as air conditioners, and can also be used in a breeding room to provide a constant temperature environment for seeds. The temperature control film has a gel layer as the top layer (outer layer), that is, the sunny side, and a graphene oxide layer as the bottom layer (inner layer), that is, the back-sun side. The top layer of the temperature control film can switch between transmission and reflection when the ambient temperature changes, while the bottom layer absorbs sunlight to the maximum extent. When the temperature is higher than the LCST (phase transition temperature), the top layer appears white, maximizing the backscattering of sunlight, and the reflectivity reaches 96.2%. At the same time, the top layer has a high emissivity of 90% in the mid-infrared band, so that it has good passive radiation cooling performance to reduce the temperature. When the temperature is lower than the LCST, the temperature control film switches to the heating mode. The top layer becomes transparent, allowing sunlight to pass through and be absorbed by the black graphene oxide layer, thereby achieving efficient passive solar heating performance and increasing the temperature. Therefore, the temperature control film in the present invention realizes automatic switching of thermal performance through passive radiation cooling and solar heating.

[0087] The following embodiments are listed for the above implementation mode. For the purpose of brevity, the present invention does not list all embodiments one by one. Simple replacements and all possible combinations of the listed embodiments are embodiments recorded in the present invention.

[0088] Example 1

[0089] The temperature-responsive gel was prepared by the following method:

[0090] (1) 7.91 g (0.07 mol) of NIPAm, 1.32 g (0.03 mol) of PVA, and 215.6 mg (0.0014 mol) of N,N′-methylenebis(acrylamide) were dissolved in deionized water at 50° C. to obtain a homogeneous 100 mL organic aqueous solution.

[0091] (2) Adding a nano-alumina dispersion solution, i.e., a solution of nano-alumina dispersed in water, wherein the nano-alumina particle size is 30 nm.

[0092] (3) adding tetrabutyl titanate (TT) as a coupling agent, and heating the solution in a water bath at 40° C. for 1 h, wherein the coupling agent connects the nano-alumina particles to the PVA chains, thereby obtaining a precursor solution;

[0093] (4) Cool down to room temperature (25°C), and purge the precursor solution with nitrogen (N2) to remove oxygen from the solution. (5) Add 1.35 mL of 30% TEMED (crosslinker) solution and 2.7 mL of 10% ammonium persulfate (initiator) solution to the precursor solution and stir evenly. NIPAm, PVA and N,N′-methylenebis(acrylamide) undergo crosslinking reaction under the action of the crosslinker and initiator.

[0094] (6) The temperature-responsive gel was obtained by static molding, and the content of the nano-alumina particles was adjusted so that the mass content of the nano-alumina in the gel was 1%.

[0095] If the temperature-responsive gel is to be prepared as a film, it can be formed by extrusion, specifically:

[0096] a. Seal the edges of the two glass slides with sealant and fix the distance between the two glass slides.

[0097] b. Inject the solution obtained in step 5 between two glass slides to form a sandwich structure.

[0098] c. Place the sample at room temperature and let it stand for at least 24 hours. After the reaction is completed, a temperature-responsive gel film is obtained, and the thickness of the gel film is the distance between the two glass slides.

[0099] The LCST of the temperature-responsive gel prepared in this example is 35°C.

[0100] Example 2

[0101] The difference from Example 1 is that the dosage of NIPAm is adjusted to increase the dosage of NIPAm by 20% relative to Example 1, and the other dosages are the same as Example 1. The LCST of the temperature-responsive gel obtained in this example is 30°C.

[0102] Example 3

[0103] The difference from Example 1 is that the amount of PVA is adjusted to increase the amount of PVA by 20% relative to Example 1, and the amounts of other components are the same as those in Example 1. The LCST of the temperature-responsive gel obtained in this example is 40°C.

[0104] Example 4

[0105] The difference from Example 1 is that (1) the dosage of PVA and N,N′-methylenebis(acrylamide) is adjusted so that the mass ratio of NIPAm to PVA is 6:1, the mass ratio of NIPAm to N,N′-methylenebis(acrylamide) is 34:1, and the dosage of NIPAm remains unchanged. (2) NIPAm, PVA and N,N′-methylenebis(acrylamide) are dissolved in deionized water at 60°C. (3) The size of the nano-alumina particles is 40nm. (4) The content of the nano-alumina particles in the gel is 0.9%. The obtained gel exhibits a reflectivity of 96% when the temperature is higher than the LCST, and exhibits a transmittance of 96% when the temperature is lower than the LCST.

[0106] Example 5

[0107] The difference from Example 1 is that (1) the dosage of PVA and N,N′-methylenebis(acrylamide) is adjusted so that the mass ratio of NIPAm to PVA is 5:2, the mass ratio of NIPAm to N,N′-methylenebis(acrylamide) is 38:1, and the dosage of NIPAm remains unchanged. (2) NIPAm, PVA and N,N′-methylenebis(acrylamide) are dissolved in deionized water at 55°C. (3) The size of the nanoalumina particles is 35nm. The obtained gel exhibits a reflectivity of 96% when the temperature is higher than the LCST, and a transmittance of 96% when the temperature is lower than the LCST.

[0108] Example 6

[0109] (1) 7.91 g (0.07 mol) of NIPAm, 1.32 g (0.03 mol) of PVA, and 215.6 mg (0.0014 mol) of N,N′-methylenebis(acrylamide) were dissolved in deionized water at 50° C. to obtain a homogeneous 100 mL organic aqueous solution.

[0110] (2) Adding a nano-alumina dispersion solution, that is, a solution of nano-alumina dispersed in water, wherein the nano-alumina particle size is 30 nm and the mass fraction of the solution is about 10%.

[0111] (3) adding tetrabutyl titanate (TT) as a coupling agent, and heating the solution in a water bath at 40° C. for 1 h, wherein the coupling agent connects the nano-alumina particles to the PVA chains, thereby obtaining a precursor solution;

[0112] (4) Cooling to room temperature (25°C), purging the precursor solution with nitrogen (N2) to remove oxygen in the solution to prevent the quenching effect of oxygen in the solution on free radicals during crosslinking.

[0113] (5) 1.35 mL of TEMED solution (crosslinker) and 2.7 mL of ammonium persulfate solution (initiator) were added to the precursor solution and stirred evenly. The mass fractions of TEMED solution and ammonium persulfate solution were 30% and 10%, respectively. NIPAm, PVA and N,N′-methylenebis(acrylamide) underwent crosslinking reaction under the action of the crosslinker and initiator.

[0114] (6) The temperature-responsive gel is statically molded into a film to obtain a gel layer, and the molding method is:

[0115] a. Seal the edges of the two glass slides with sealant and fix the distance between the two glass slides.

[0116] b. Inject the solution obtained in step 5 between two glass slides to form a sandwich structure.

[0117] c. Place the sample at room temperature and let it stand for at least 24 hours. After the reaction is completed, a temperature-responsive gel film is obtained, and the thickness of the gel film is the distance between the two glass slides.

[0118] (7) Assemble the gel layer obtained in step 6 and the graphene oxide layer together to obtain a temperature control membrane.

[0119] The thickness of the gel layer is 500 μm. The gel layer can be the gel after the glass slide is removed, or it can be assembled with the graphene oxide layer together with the glass slide.

[0120] The method for obtaining the graphene oxide layer is as follows: graphene oxide (GO) nanosheets are dispersed in deionized water by ultrasonic vibration for 2 hours to obtain a graphene oxide solution, the concentration of the graphene oxide solution is 3 mg / mL, and then the graphene oxide solution is sprayed on the preheated fabric using a commercial spray gun, and then the graphene oxide coated fabric is baked at 150°C in a vacuum to obtain a solar-absorbing graphene oxide coated fabric.

[0121] Example 7

[0122] The temperature-responsive gel obtained in Example 1 was placed in a 20°C to 50°C cyclic cooling and heating environment to obtain the transmittance of the temperature-responsive gel during the cycle. The results are as follows: Figure 1 As shown in the figure, the transmittance of the temperature-responsive gel switches between 5% and 96% with the temperature, and after 15 cycles, the temperature-responsive gel can still maintain its original transmittance.

[0123] Example 8

[0124] The temperature-responsive gel obtained in Example 1-3 was placed in a 20-50°C temperature environment for heating or cooling to test the transmittance of the gel. Figure 2 When the temperature is gradually increased from 20 to 50°C, the corresponding transmittance change points of Example 1, Example 2 and Example 3 are 35°C, 30°C and 40°C respectively, and the transmittances of the three are all reduced from 96% to 5%.

[0125] When the external temperature gradually decreases from 50 to 20°C, the corresponding transmittance change points of Example 1, Example 2 and Example 3 are 35°C, 30°C and 40°C respectively, and the transmittance of the three increases from 5% to 96%. The temperature-responsive gels all show precise temperature response values ​​and high transmittance or high reflectance.

[0126] Example 9

[0127] The refrigeration effect of the temperature control film obtained in Example 6 was tested. The test device is as follows: Figure 3, including an inner container 2 and an outer container 1, the outer container 1 is a large beaker, the inner container 2 is a small beaker, the outer container 1 is provided with a heating module 3 and a refrigeration module 4 for adjusting the temperature inside the outer container, the experiment includes an experimental group and a control group, the outer container 1 is used to simulate the external environment, the refrigeration module and the heating module are used to adjust the temperature inside the outer container, thereby simulating the temperature change of the external environment in which the inner container is located, and the inner container 2 is used to simulate the temperature control device to be thermostatically controlled.

[0128] The heating module was used to heat the environment to 55°C, and the environment was placed outdoors with light from 10:30 am to 1:30 pm. The difference between the experimental group and the control group is that the top layer of the small beaker in the experimental group is provided with the temperature control film 6 obtained in Example 6, and the side wall is provided with an insulation layer, specifically foam, while the top layer and side wall of the control group are both provided with insulation layers, which are not absolute insulation, and there is still a small amount of heat exchange with the outside world. The starting temperature in the container of the experimental group and the control group is the same, both 40°C. The test results are as follows Figure 4 The temperature of the experimental group dropped from 40℃ to 32℃, approaching 30℃, and the temperature of the control group rose steadily to 45℃, gradually approaching the external environment temperature. It can be seen that the temperature control film effectively reduces the temperature of the inner container.

[0129] Example 10

[0130] The heating efficiency of the temperature control film obtained in Example 6 was tested. The test device was the same as that in Example 9. The ambient temperature was adjusted to 1.5°C using a refrigeration module. The device was placed outdoors and the light was sunlight from 12:00 to 15:00. The initial temperature of the experimental group and the control group was 1.5°C. The temperature curves of the experimental group and the control group were as follows: Figure 5 ,From the figure, we can see that the temperature of the experimental group gradually rises to 24℃, and the temperature of the control group is close to the ambient temperature, with no obvious change. It can be seen that the temperature control film effectively increases the temperature of the inner container.

[0131] Embodiment 11

[0132] Since solar heating / radiative cooling power is a common and key factor in evaluating / comparing heating / cooling performance, we conducted outdoor measurements of the heat flux density of the temperature control film under actual outdoor conditions. Positive heat flux represents heating, and negative heat flux represents net cooling. We tested the cooling and heating efficiency of the temperature control film under a slow temperature increase from 15°C to 50°C, as shown in Figure 2. Figure 6 As shown in the figure, the heating power at 15℃, 20℃, and 25℃ is 550±55W m -2 , 400±40W m -2 、300±30W m -2When the temperature reaches LCST (30°C), the STG film automatically switches to the radiation cooling function. The average net cooling power of the temperature-controlled film at 35°C, 40°C, 45°C, and 50°C is 52±10W m -2 , 70±10W m -2 , 90±10W m -2 and 100±10W m -2 The results clearly show that the temperature control film in the present invention has good switchable cooling / heating performance.

[0133] Temperature control effect Figure 7 and Figure 8 In hot weather with an ambient air temperature of about 35°C, the average incident solar irradiance between 11:00 a.m. and 14:00 p.m. is 900 W m -2 In the case of temperature control film, the sub-ambient temperature induced by the temperature control film drops by (ΔT)≈5°C relative to the outside temperature and remains near 30°C. When it switches to heating mode in cold weather, the sub-ambient temperature induced by the temperature control film rises by 8°C relative to the outside temperature and remains near 30°C. This shows that the STG film shows effective heating / cooling effects in both winter and summer.

[0134] Finally, it should be noted that the above embodiments are only used to explain the present invention, rather than to limit it.

[0135] Solutions obtained by simple modifications, substitutions or reasonable inferences made by ordinary technicians in the relevant field based on the specific implementation methods of the present invention are all included in the protection scope of the present invention.

Claims

1. A method for preparing a temperature-responsive gel, characterized in that: The following steps are included NIPAm, PVA and N,N′-methylenebis(acrylamide) were added to water to obtain an organic solution; Adding nano-alumina particles and a coupling agent to the organic solution to obtain a precursor solution, wherein the nano-alumina particles are bonded to the organic phase in the organic solution through the coupling agent; adding a crosslinking agent and an initiator to the precursor solution; The NIPAm, PVA and N,N′-methylenebis(acrylamide) construct a network structure under the action of a crosslinking agent and an initiator to obtain the temperature-responsive gel.

2. The method for preparing the temperature-responsive gel according to claim 1, characterized in that: The precursor solution is added with a cross-linking agent and an initiator, and then allowed to stand for molding to obtain the temperature-responsive gel.

3. The method for preparing the temperature-responsive gel according to claim 1, characterized in that: The coupling agent includes a first terminal group capable of reacting and connecting with alumina and a second terminal group capable of reacting with the organic phase.

4. The method for preparing the temperature-responsive gel according to claim 1, characterized in that: The coupling agent is bonded to the PVA in the organic solution, and the coupling agent is reacted to the hydroxyl group on the PVA to connect.

5. The method for preparing the temperature-responsive gel according to claim 1, characterized in that: The coupling agent is tetrabutyl titanate, and the structural formula after the coupling agent reacts with the nano-alumina particles and the hydrogel is:

6. The method for preparing the temperature-responsive gel according to claim 1, characterized in that: The cross-linking agent is TEMED.

7. The method for preparing the temperature-responsive gel according to claim 1, characterized in that: The initiator is ammonium persulfate.

8. The method for preparing the temperature-responsive gel according to claim 1, characterized in that: The NIPAm, PVA and N,N′-methylenebis(acrylamide) were mixed in deionized water.

9. The method for preparing the temperature-responsive gel according to claim 1, characterized in that: The NIPAm, PVA and N,N′-methylenebis(acrylamide) are dissolved and mixed in deionized water at 50-60° C.

10. The method for preparing the temperature-responsive gel according to claim 1, characterized in that: The mixing mass ratio of NIPAm and PVA is NIPAm:PVA (5-6):(1-2).

11. The method for preparing the temperature-responsive gel according to claim 1, characterized in that: The mixing mass ratio of NIPAm and PVA is NIPAm:PVA is 6:(1-2).

12. The method for preparing the temperature-responsive gel according to claim 1, characterized in that: The mixing mass ratio of the NIPAm and the N,N′-methylenebis(acrylamide) is NIPAm:N,N′-methylenebis(acrylamide) (34-38):

1.

13. The method for preparing the temperature-responsive gel according to claim 1, characterized in that: The particle size of nano-alumina is 20-40 nm.

14. The method for preparing the temperature-responsive gel according to claim 1, characterized in that: The particle size of nano-alumina is 30nm.

15. The method for preparing the temperature-responsive gel according to claim 1, characterized in that: The nano-alumina is added in the form of a nano-alumina dispersion, and after adding the nano-alumina dispersion, water bath heating is performed to couple the nano-alumina particles to the organic matter. The nano-alumina dispersion is an aqueous solution of nano-alumina.

16. The method for preparing the temperature-responsive gel according to claim 1, characterized in that: The mass ratio of the temperature-responsive gel to the nano-alumina particles is (100-110):

1.

17. The method for preparing the temperature-responsive gel according to claim 15, characterized in that: Water bath heating satisfies one or more of the following combinations The water bath heating temperature is 40°C; The water bath heating time is 1 hour.

18. The method for preparing the temperature-responsive gel according to claim 1, characterized in that: The conditions for adding the crosslinking agent and the initiator to the precursor solution satisfy one or more of the following combinations: The precursor solution is purified by nitrogen; The precursor solution was cooled to 25°C.

19. The method for preparing the temperature-responsive gel according to claim 2, characterized in that: The gel forming method is to pour the solution to be formed between two glass plates with a fixed distance, and demould after forming.

20. The method for preparing the temperature-responsive gel according to claim 1, characterized in that: The lower critical solution temperature of the temperature-responsive gel is adjusted by adjusting the dosage ratio of the PVA and the NIPAm.

21. The method for preparing the temperature-responsive gel according to claim 1, characterized in that: The nano-alumina particles are coupled to at least one organic matter in an organic solution, and the organic matter coupled to the nano-alumina particles is one of NIPAm, PVA and N,N′-methylenebis(acrylamide) or their reaction products.

22. A temperature-responsive gel, characterized in that: It includes a gel network body and nano-alumina particles, wherein the nano-alumina particles are connected to the gel network body, and the gel network body is constructed by NIPAm, PVA and N,N′-methylenebis(acrylamide). The temperature-responsive gel has a temperature influence threshold. When the temperature is lower than the threshold, the gel is transparent, and when the temperature is higher than the threshold, the gel is white.

23. The temperature-responsive gel according to claim 22, characterized in that: The temperature response threshold is 30-50°C.

24. The temperature-responsive gel according to claim 22, characterized in that: The nano-alumina particles are bonded to the gel network body through a coupling agent.

25. A temperature-responsive gel, characterized in that: The temperature-responsive gel is prepared by the method for preparing the temperature-responsive gel according to claim 1.

26. A temperature control film, characterized in that: It comprises a gel layer and a graphene oxide layer, wherein the gel layer is the temperature-responsive gel according to claim 22 or the temperature-responsive gel according to claim 25, and the graphene oxide layer is a carrier carrying graphene oxide.

27. The temperature control film according to claim 26, characterized in that: The carrier is fabric, and the graphene oxide layer is fabric coated with graphene oxide.

28. The temperature control film according to claim 26, characterized in that: The gel layer has a thickness of 400 μm or more.

29. A method for preparing a temperature control film, characterized in that: The following steps are included (1) preparing a graphene oxide layer, a Spraying graphene oxide solution on the preheated fabric; b. baking the fabric sprayed with graphene oxide at high temperature in a vacuum; (2) Assembling a gel layer and a graphene oxide layer together in a stacked form, wherein the gel layer is the temperature-responsive gel according to claim 22 or the temperature-responsive gel according to claim 25.

30. The method for preparing a temperature control film according to claim 29, characterized in that: The graphene oxide solution is obtained by dispersing graphene oxide nanosheets in deionized water.

31. The method for preparing a temperature control film according to claim 29, characterized in that: The concentration of the graphene oxide solution is 3 mg / mL.

32. Use of the temperature control film according to claim 26 in an outdoor temperature control device.

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