CN113583635B

CN113583635B - Phase-change gel material with variable mechanical state

Info

Publication number: CN113583635B
Application number: CN202110837925.1A
Authority: CN
Inventors: 陈晓; 高鸿毅; 请求不公布姓名; 刘盼盼; 李昂
Original assignee: Suzhou Double Carbon New Material Co ltd
Current assignee: Suzhou Double Carbon New Material Co ltd
Priority date: 2021-07-23
Filing date: 2021-07-23
Publication date: 2023-01-24
Anticipated expiration: 2041-07-23
Also published as: CN113583635A

Abstract

The application discloses a phase-change gel material with variable mechanical state, which comprises: a poly (N-isopropylacrylamide) matrix having a three-dimensional crosslinked network structure; and the phase-change material is compounded in the poly N-isopropyl acrylamide matrix. The phase-change gel material has high phase-change latent heat, excellent stability, good elasticity and softness, is an energy storage material with better mechanical property, can change the shape and the rigidity according to the requirement, and can be applied to multi-scale adhesion and attachment of various three-dimensional surfaces.

Description

Phase-change gel material with variable mechanical state

Technical Field

The present application relates to the field of phase change materials, and more particularly, to a phase change gel material with variable mechanical state.

Background

Phase Change Materials (PCMs) are functional Materials capable of reversibly absorbing and releasing heat energy during a Phase Change process. These materials have been widely used in the fields of battery thermal management, solar heating systems, and electronic cooling. Among them, the solid-liquid organic PCMs have been widely studied due to their advantages of stable chemical and thermodynamic properties, small supercooling degree, no phase segregation during phase transition, etc. However, all solid-liquid PCMs have leakage problems during melting, which severely limits their large-scale practical applications.

Currently, the art has addressed the above-mentioned problems by preparing shaped composite phase change materials. For example, chinese patent application CN106590543A discloses a shaped composite phase change energy storage material and a preparation method thereof, which prepares a series of fatty acid-fatty alcohol eutectic/cellulose shaped/polymer-based composite materials by coating a phase change material with a molten polymer and tabletting; chinese patent application CN1513938 discloses a method for coating a phase change material with microcapsules, which comprises subjecting a phase change material as a core material and a polymer as a wall material to a polymerization reaction to prepare a microcapsule-coated phase change material with a compact structure; and the chinese patent application CN1587339A discloses a porous graphite-based phase change energy storage composite material and a preparation method thereof, wherein porous graphite is used as a base material, and then an organic phase change material is impregnated to obtain the phase change energy storage material.

However, for the above technologies such as polymer blending, microcapsule and porous material encapsulation, a large amount of supporting material is usually required to ensure the stability of the shape, and these materials usually maintain a single fixed mechanical state, i.e. shape-set composite phase change material, so that the rigidity of the composite phase change material cannot be changed significantly, and the composite phase change material is not suitable for applications in intelligent control and flexible electronic fields. In contrast, if the composite phase change material can change the mechanical state, the application fields thereof can be more diversified, and the composite phase change material has great potential particularly in the application fields of future electronics, robots and the like. Moreover, the manufacturing techniques for synthesizing the existing shaped composite phase change materials generally involve hydrothermal methods, freeze drying, vacuum impregnation, and the like, and these techniques are complicated and costly to operate. Therefore, it remains a great challenge for the art how to obtain phase change materials with high latent heat storage and good shape stability, and whose mechanical state can be changed depending on the requirements or operating conditions.

Disclosure of Invention

Aiming at the defects in the prior art, the application provides a phase-change gel composite phase-change material, which can be used for simply, conveniently and efficiently preparing a flexible three-dimensional cross-linked network poly N-isopropylacrylamide hydrogel by adopting a specific technological process, soaking the flexible three-dimensional cross-linked network poly N-isopropylacrylamide hydrogel in lower alcohol for alcoholization to obtain alcohol gel, and then replacing the lower alcohol in the alcohol gel with the molten phase-change material by adopting a low-cost solvent replacement method to prepare the phase-change gel material. The phase change gel material prepared by the preparation method has high phase change latent heat (enthalpy value) and excellent stability, has good elasticity and softness compared with other porous shape-stabilized composite phase change materials, is an energy storage material with better mechanical property, can change the shape and rigidity according to the needs, and can be applied to multi-scale adhesion and attachment of various three-dimensional surfaces.

To achieve the above object, in a first aspect, the present application provides a phase-change gel material with variable mechanical state, comprising: a poly (N-isopropylacrylamide) matrix with a three-dimensional cross-linked network structure; and the phase change material is compounded in the poly N-isopropyl acrylamide matrix.

In one possible embodiment, in combination with the first aspect, the phase-change gel material is prepared by the following method:

(1) Preparing poly N-isopropyl acrylamide hydrogel with a three-dimensional cross-linked network structure by taking an initiator/tetramethylethylenediamine oxidation-reduction system as an initiating system, and soaking the poly N-isopropyl acrylamide hydrogel in lower alcohol for alcoholization to obtain alcohol gel; and

(2) Heating and melting the phase-change material to perform solvent replacement with the alcogel, thereby obtaining the phase-change gel material.

In combination with the first aspect, in a possible embodiment, the step (1) may be: dissolving N-isopropyl acrylamide, methylene bisacrylamide and an initiator in a weight ratio of (1-5) to (0.5-1.5) in water, stirring, adding tetramethyl ethylenediamine, heating for reaction, and soaking with acetone, water and lower alcohol in sequence to obtain the alcohol gel.

In one possible embodiment in combination with the first aspect, in the step (1), the weight ratio of the N-isopropylacrylamide to the methylenebisacrylamide to the initiator is 100 (2-4) to 0.8-1.2.

In one possible embodiment in combination with the first aspect, in step (1), the amount of water dissolving the N-isopropylacrylamide, the methylenebisacrylamide and the initiator is (4 mL to 6 mL)/g of the N-isopropylacrylamide.

In combination with the first aspect, in one possible embodiment, in the step (1), the initiator is at least one selected from the group consisting of potassium persulfate, ammonium persulfate, and ammonium persulfate.

In a possible embodiment, in combination with the first aspect, in step (1), the stirring is performed under the condition of stirring at 15 ℃ to 30 ℃ for 20min to 40min under an inert gas atmosphere.

In one possible embodiment in combination with the first aspect, in the step (1), the amount of the tetramethylethylenediamine may be (4 μ L to 12 μ L)/g of N-isopropylacrylamide.

In one possible embodiment in combination with the first aspect, in step (1), the heating reaction is performed at 45 ℃ to 55 ℃ for 25min to 35min under the condition of air isolation.

With reference to the first aspect, in a possible embodiment, in the step (1), the soaking time with acetone is 8 to 16 hours; the soaking time of water is 8-16 h; and the soaking time by adopting lower alcohol can be 20-28 h.

Further, in the step (1), the lower alcohol is at least one selected from the group consisting of methanol, ethanol, n-propanol and isopropanol.

In a possible embodiment in combination with the first aspect, in step (1), the lower alcohol in the alcoholic gel is further replaced with an organic solvent. Preferably, the organic solvent is n-hexane or dichloromethane.

In a possible embodiment in combination with the first aspect, in step (1), graphene oxide is further added to the aqueous solution of N-isopropylacrylamide, methylenebisacrylamide and the initiator, and preferably, the weight ratio of the graphene oxide to the N-isopropylacrylamide is (0.01-0.1): 1.

With reference to the first aspect, in a possible embodiment, the step (2) may be: melting the phase-change material, adding the alcogel into the melted phase-change material to perform solvent replacement, and removing the phase-change material on the outer surface of the gel to obtain the phase-change gel material.

In combination with the first aspect, in a possible embodiment, in the step (2), the phase change material is at least one selected from the group consisting of stearyl alcohol, cetyl alcohol, myristyl alcohol, stearyl alcohol and arachidyl alcohol.

Further, in the step (2), the temperature for melting the phase change material is 70 ℃ to 90 ℃.

In one possible embodiment, in combination with the first aspect, in step (2), the weight ratio of the phase change material to the alcogel used is 1 (0.01-100).

In a possible embodiment in combination with the first aspect, in step (2), the temperature of the solvent replacement may be 70 ℃ to 90 ℃.

In a possible embodiment in combination with the first aspect, in step (2), the solvent replacement time is 8 to 16 hours.

In one possible embodiment in combination with the first aspect, in step (2), the phase change material on the outer surface of the gel is removed by wiping adsorption with paper, fabric, or nonwoven fabric.

In a second aspect, the present application provides a method for preparing the above phase-change gel material with variable mechanical state, which comprises the following steps:

(2) And heating and melting the phase-change material, and performing solvent replacement with the alcogel to obtain the phase-change gel material.

The technical scheme that this application provided compares prior art and has following beneficial effect at least:

the method for preparing the phase-change gel material with the variable mechanical state does not involve complicated operation processes such as freeze drying and vacuum-assisted impregnation, and is simple to operate and low in cost. The phase change gel material can prevent leakage of the contained phase change material, can maintain the gel structure of the material even at a temperature higher than the melting point of the phase change material, and has a high enthalpy value. In addition, the phase-change gel material can be tightly attached to the surfaces of various objects in a flexible state, so that the thermal resistance among the objects is reduced, the temperature adjusting and controlling performance is improved, and the grabbing function of the contact objects can be innovatively realized by utilizing the characteristic of changing the mechanical state.

Drawings

FIG. 1 is a photograph (a) and an SEM photograph (c) of a poly (N-isopropylacrylamide) hydrogel obtained in step (1) of example 1 of the present application before drying and a photograph (b) and an SEM photograph (d) of the hydrogel after drying;

FIG. 2 is a photograph of a phase-change gel material prepared in example 1 of the present application in a flexible state (a) and a rigid state (b); and

FIG. 3 is a Differential Scanning Calorimetry (DSC) chart of the phase change gel material obtained in example 1 of the present application.

Fig. 4 is a schematic flow chart of the phase-change gel material prepared by the present application for realizing the grabbing function.

Detailed Description

To make the objects, technical solutions and advantages of the embodiments of the present application clearer and more detailed description of the present application will be given below with reference to the embodiments and the accompanying drawings, but it should be understood that the following embodiments are only preferred embodiments of the present application, not all embodiments, and the scope of protection claimed in the present application shall be subject to the scope defined by the claims. Moreover, based on the embodiments in the present application, all other embodiments that can be obtained by a person skilled in the art without inventive work without the technical principle and inventive gist of the present application shall also belong to the scope of the present application.

Throughout the specification and claims, unless explicitly stated otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element or component but not the exclusion of any other element or component.

One embodiment of the application provides a phase change gel composite phase change material, which is prepared by a specific preparation method, and the phase change gel material is prepared by firstly simply, conveniently and efficiently preparing a flexible three-dimensional cross-linked network poly N-isopropyl acrylamide hydrogel by adopting a specific process, then soaking the hydrogel in lower alcohol for alcoholization to obtain alcohol gel, and then replacing the lower alcohol in the alcohol gel with a molten phase change material by adopting a low-cost solvent replacement method. The phase change gel material has high latent heat of phase change (enthalpy value) and excellent stability, has good elasticity and softness compared with other porous shaping composite phase change materials, is an energy storage material with better mechanical property, can change the shape and rigidity according to needs, and can be applied to multi-scale adhesion and attachment of various three-dimensional surfaces.

In a first aspect, the present application provides a phase change gel material of variable mechanical state, comprising: a poly (N-isopropylacrylamide) matrix with a three-dimensional cross-linked network structure; and the phase-change material is compounded in the poly N-isopropyl acrylamide matrix.

Solvent displacement in the present application, an easily implemented, novel and inexpensive three-dimensionally crosslinked gel-supported phase-change gel material is provided. Wherein the phase-change gel material has a gel of a three-dimensional cross-linked network as a support frame, and can prevent leakage of the phase-change material contained therein and maintain the structure of the gel of the material even at a temperature of the melting point or higher of the phase-change material. The prepared phase-change gel material has high enthalpy value, and the soft and hard variable states of the phase-change gel material are realized when the contained phase-change material is subjected to solid-liquid conversion under thermal stimulation. Compared with the shaped composite phase change material in the prior art, the phase change gel material according to the present application has the characteristics of good elasticity and softness in a flexible state (in this case, the phase change material is in a liquid state), and good hardness and mechanical strength in a rigid state (in this case, the phase change material is in a solid state). Therefore, the phase-change gel material can be tightly attached to the surfaces of various objects in a flexible state, the thermal resistance among the objects is reduced, the temperature adjusting and controlling performance is improved, and the grabbing function of the contact object can be innovatively realized by utilizing the characteristic of changing the mechanical state. In addition, the method for preparing the phase-change gel material does not involve complicated operation processes such as freeze drying, vacuum assisted impregnation and the like, and has simple operation and low cost.

The application firstly solves the problem that the solid-liquid phase-change material is easy to leak liquid when being melted, simultaneously breaks through the current situation that the existing shape-stabilized phase-change gel material only has a single fixed mechanical state, and develops the unique capability of switching the phase-change gel material between a hard state and a soft state. On one hand, the phase-change gel material can keep good contact with the three-dimensional outer surface of a contact object in a flexible state, so that the phase-change gel material can be ensured to be fully contacted with the surface of a power consumption type device in the aspect of heat management application of an electronic device, the thermal resistance between contact interfaces is reduced, better temperature regulation and control performance is achieved, and the phase-change gel material can be reassembled with the contact object; on the other hand, the rigid state can be hard enough to be firmly attached to the object, so that the variable rigidity of the rigid state can be utilized to realize the grabbing function of the contact object. For the grasping function, specifically, the phase-change gel material according to the present application is first brought into contact with a target object in a flexible state and then is converted into a rigid state so as to be closely attached to the contact object as a whole, at which time the target object can be moved, and when the phase-change gel material is converted into a flexible state again by thermal stimulation, the phase-change gel material can be separated from the contacted target object to release the object. The object is grabbed in a surface attaching or wrapping mode, the structure of the object cannot be damaged, and the grabbing force can be theoretically realized on the object in any shape. Therefore, the phase-change gel material with the variable mechanical state enables the application of the phase-change material to be more diversified and multipurpose, and is expected to be applied to the fields of future electronics, robots and intelligent self-adaption, thereby providing a new idea for the design and construction of the composite phase-change material.

Further, the phase-change gel material with variable mechanical state is prepared by the following method:

(2) And heating and melting the phase-change material to perform solvent replacement with the alcogel to obtain the phase-change gel material.

In the method of preparing the phase-change gel material of variable mechanical state according to the present application, the step (1) may be: dissolving N-isopropyl acrylamide, methylene bisacrylamide and an initiator in a weight ratio of (1-5) to (0.5-1.5) in water, stirring, adding tetramethyl ethylenediamine, heating for reaction, and soaking with acetone, water and lower alcohol in sequence to obtain the alcohol gel. In the present application, a specific amount ratio of the crosslinking agent (methylene bisacrylamide) is used, so that a gel having a specific crosslinking network density can be obtained. Compared with other gels with similar structures, the phase-change gel material prepared by the method is high in load and high in heat storage. When the consumption of the methylene bisacrylamide is too much, the network density in the gel is too high, which is not beneficial to the entering of solvents such as lower alcohol and the like, and further causes the replacement rate of the phase-change material to be too low during the subsequent solvent replacement; when the dosage of the methylene bisacrylamide is too small, the crosslinked network formed in the gel is less, the water absorption of the gel is poor, and the load of the phase-change material is not improved.

In the step (1), the weight ratio of the N-isopropylacrylamide, the methylenebisacrylamide and the initiator can be preferably 100 (2-4) to (0.8-1.2), and more preferably 100 (2-4) to 1. The structure of the phase-change gel material can be better regulated and controlled by adopting a specific material ratio.

In step (1), the amount of water that dissolves N-isopropylacrylamide, methylenebisacrylamide, and initiator may be (4 mL to 6 mL)/g of N-isopropylacrylamide (e.g., 4mL/g of N-isopropylacrylamide, 4.2mL/g of N-isopropylacrylamide, 4.4mL/g of N-isopropylacrylamide, 4.6mL/g of N-isopropylacrylamide, 4.8mL/g of N-isopropylacrylamide, 5mL/g of N-isopropylacrylamide, 5.2mL/g of N-isopropylacrylamide, 5.4mL/g of N-isopropylacrylamide, 5.8mL/g of N-isopropylacrylamide, or 6mL/g of N-isopropylacrylamide, or other specific values within the ranges).

In the step (1), the initiator may be at least one selected from the group consisting of potassium persulfate, ammonium persulfate, and ammonium persulfate.

In the step (1), the stirring condition may be that the stirring is performed for 20min to 40min (for example, may be 20min, 22min, 24min, 26min, 28min, 32min, 34min, 36min, 38min, or 40min, or other specific values within the range), preferably 30min, at 15 ℃ to 30 ℃ (for example, may be 15 ℃, 16 ℃, 17 ℃, 18 ℃, 19 ℃,20 ℃, 21 ℃, 22 ℃, 23 ℃, 24 ℃,25 ℃, 26 ℃, 27 ℃, 28 ℃, 29 ℃, or 30 ℃, or other specific values within the range), preferably 25 ℃ and under a protective atmosphere of an inert gas (such as nitrogen, argon, and the like).

In the crosslinking process in the step (1), tetramethylethylenediamine (TEMED) can catalyze an initiator to generate free radicals, so that polymerization of an acrylamide monomer is initiated, and methylene-bis-propylene and an acrylamide chain generate methylene bond crosslinking, so that a three-dimensional network structure is formed. The tetramethylethylenediamine may be used in an amount of (4. Mu.L to 12. Mu.L)/g of N-isopropylacrylamide (for example, 4. Mu.L/g of N-isopropylacrylamide, 4.5. Mu.L/g of N-isopropylacrylamide, 5. Mu.L/g of N-isopropylacrylamide, 5.5. Mu.L/g of N-isopropylacrylamide, 6. Mu.L/g of N-isopropylacrylamide, 6.5. Mu.L/g of N-isopropylacrylamide, 7. Mu.L/g of N-isopropylacrylamide, 7.5. Mu.L/g of N-isopropylacrylamide, 8. Mu.L/g of N-isopropylacrylamide, 8.5. Mu.L/g of N-isopropylacrylamide, 9. Mu.L/g of N-isopropylacrylamide, 9.5. Mu.L/g of N-isopropylacrylamide, 10. Mu.L/g of N-isopropylacrylamide, 10.5. Mu.L/g of N-isopropylacrylamide, 11. Mu.5. L/g of N-isopropylacrylamide, or other specific values within the range).

In the step (1), the heating reaction may be performed at 45 to 55 ℃ (for example, 45 ℃, 46 ℃, 47 ℃, 48 ℃, 49 ℃, 50 ℃, 51 ℃, 52 ℃, 53 ℃, 54 ℃ or 55 ℃ or other specific values in the range) in a state of isolating air, preferably at 50 ℃ (for 25 to 35min (for example, 25min, 26min, 27min, 28min, 29min, 30min, 31min, 32min, 33min, 34min or 35min or other specific values in the range), preferably at 30min.

In the step (1), the time for soaking with acetone may be 8h to 16h (for example, 8h, 8.5h, 9h, 9.5h, 10h, 10.5h, 11h, 11.5h, 12h, 12.5h, 13h, 13.5h, 14h, 14.5h, 15h, 15.5h or 16h, or other specific values within the range), and is preferably 12h; the soaking time with water can be 8h to 16h (for example, 8h, 8.5h, 9h, 9.5h, 10h, 10.5h, 11h, 11.5h, 12h, 12.5h, 13h, 13.5h, 14h, 14.5h, 15h, 15.5h or 16h, or other specific values in the range), and is preferably 12h; and the time for soaking with the lower alcohol may be 20 to 28 hours (for example, 20 hours, 20.5 hours, 21 hours, 21.5 hours, 22 hours, 22.5 hours, 23 hours, 23.5 hours, 24 hours, 24.5 hours, 25 hours, 25.5 hours, 26 hours, 26.5 hours, 27 hours, 27.5 hours, or 28 hours, or other specific values within the range), preferably 24 hours. By sequentially soaking in acetone, water and lower alcohol, unreacted monomers in the system can be removed, and the prepared crosslinked gel is fully alcoholized.

In step (1), the lower alcohol may be at least one selected from the group consisting of methanol, ethanol, n-propanol and isopropanol, and preferably ethanol.

Further, in step (1), the lower alcohol in the alcogel may be further replaced with an organic solvent. The organic solvent may be n-hexane or dichloromethane. Through further replacement with an organic solvent, the gel can be made to load the phase change material of the alkane with lower polarity. Thus, loading of various different types of phase change materials can be achieved by replacing the lower alcohol with different solvent species.

In addition, in the step (1), graphene oxide may be further added to an aqueous solution of N-isopropylacrylamide, methylenebisacrylamide and an initiator, so that it may be introduced into the prepared gel network to increase the thermal response speed of the phase-change gel. Further, the weight ratio of the graphene oxide to N-isopropylacrylamide may be (0.01 to 0.1) 1, and for example, may be 0.01.

In the method for preparing the phase-change gel material with variable mechanical state according to the present application, the step (2) may be: melting the phase-change material, adding the alcogel into the melted phase-change material to perform solvent replacement, and removing the phase-change material on the outer surface of the gel to obtain the phase-change gel material. Different from most physical impregnation methods for preparing composite phase-change materials, in the application, solvent replacement is adopted as a loading mode of the phase-change materials, specifically, after water in gel is removed to prepare alcohol gel, the alcohol gel is contacted with a molten liquid phase-change material, and lower alcohol in the alcohol gel is heated and evaporated, so that the phase-change materials can fully enter a gel network space left after the lower alcohol is evaporated.

In the step (2), the phase change material may be at least one selected from the group consisting of stearyl alcohol, cetyl alcohol, myristyl alcohol, tetradecane, octadecane and eicosane.

Further, the temperature at which the phase change material is melted may be 70 ℃ to 90 ℃ (e.g., may be 70 ℃, 72 ℃, 74 ℃, 78 ℃, 80 ℃, 82 ℃, 84 ℃, 86 ℃, 88 ℃, or 90 ℃, or other specific values within the stated range), preferably 80 ℃.

In the step (2), the weight ratio of the phase change material to the alcogel can be 1 (0.01-100), preferably 1 (0.1-10), and more preferably 1 (0.3-0.45).

In the step (2), the temperature of the solvent substitution may be not less than the melting point of the phase change material, and further, may be 70 to 90 ℃ (for example, may be 70 ℃, 72 ℃, 74 ℃, 78 ℃, 80 ℃, 82 ℃, 84 ℃, 86 ℃, 88 ℃, or 90 ℃, or other specific values within the range), preferably 80 to 90 ℃. At the temperature, the phase-change material is in a liquid state and has better solvent replacement and diffusion capacity.

In step (2), the solvent substitution time may be 8 to 16 hours (for example, 8 hours, 8.5 hours, 9 hours, 9.5 hours, 10 hours, 10.5 hours, 11 hours, 11.5 hours, 12 hours, 12.5 hours, 13 hours, 13.5 hours, 14 hours, 14.5 hours, 15 hours, 15.5 hours, or 16 hours, or other specific values within the range), and is preferably 12 hours. In this time frame, sufficient penetration and loading of the phase change material into the gel can be ensured.

In the step (2), the phase change material on the outer surface of the gel may be removed by wiping and adsorbing with a material such as paper, fabric, or nonwoven fabric, preferably with filter paper. And repeatedly adsorbing the liquid phase-change material on the surface of the gel by using the filter paper until no melting trace of the phase-change material exists on the filter paper, so that the phase-change material on the outer surface of the gel is removed, and finally the phase-change gel material is obtained.

In a second aspect, the present application further provides a method for preparing the above phase-change gel material with variable mechanical state, which comprises the following steps:

(1) Preparing poly N-isopropyl acrylamide hydrogel with a three-dimensional cross-linked network structure by taking an initiator/tetramethylethylenediamine oxidation-reduction system as an initiation system, and then soaking in lower alcohol for alcoholization to obtain alcohol gel; and

(2) Heating and melting the phase-change material, and performing solvent replacement with the alcogel to obtain the phase-change gel material.

The method for preparing the phase-change gel material with the variable mechanical state does not involve complicated operation processes such as freeze drying and vacuum-assisted impregnation, and is simple to operate and low in cost. In addition, the phase change gel material can prevent leakage of the phase change material contained therein, maintain the gel structure of the material even at a temperature equal to or higher than the melting point of the phase change material, and has a high enthalpy value. In addition, the phase-change gel material can be tightly attached to the surfaces of various objects in a flexible state, so that the thermal resistance among the objects is reduced, the temperature adjusting and controlling performance is improved, and the grabbing function of the contact objects can be innovatively realized by utilizing the characteristic of changing the mechanical state.

Thus, the effects of the variable mechanical state phase change gel material according to the present application include: (1) the phase-change gel material is soft enough at high temperature and can be attached to the three-dimensional surface of an electronic product, and the phase-change gel material becomes solid at low temperature so as to promote effective heat transfer; (2) the grabbing function of the object with any shape is realized through a reversible solid-liquid phase change process, namely, the phase change gel material contacts the object in a soft state, then the phase change gel material releases heat and solidifies, the phase change gel material is changed into a rigid solid state from the soft gel state, so that the phase change gel material and the object are tightly adhered together to form a whole, the dynamic adjustment of the bearing capacity can be carried out through responding to external thermal stimulation, and the object is released after the phase change gel is softened again. In particular, for example, only 2g of the phase-change gel material can lift about 25g of the grasping target material, which is 12.5 times its own weight, and the grasping hold time can reach 140 hours under the room temperature condition, which indicates that the phase-change gel material has an extremely excellent grasping function.

The technical solution of the present application is exemplarily described by specific embodiments as follows:

graphene oxide, model S26783, in the form of a monolayer solution at a concentration of 1wt%, was purchased from shanghai-sourced leaf biotechnology limited.

Other compounds used herein are commercially available or ordered and are commercially available to those skilled in the art on a market as desired.

< example >

Example 1

The preparation method of the phase-change gel material with the variable mechanical state comprises the following steps:

(1) 2.3g of N-isopropylacrylamide, 0.069g of methylenebisacrylamide and 0.023g of potassium persulfate as an initiator were dissolved in 10mL of deionized water and stirred in an oil bath at 25 ℃ for 30min under a nitrogen atmosphere. Subsequently, 20. Mu.L of tetramethylethylenediamine was added thereto, and the system was isolated from air and heated in an oil bath at 50 ℃ for 30min. Cooling to room temperature, adding acetone, soaking for 12h, soaking with deionized water for 12h, and soaking in ethanol for 24h for alcoholization to obtain alcogel;

(2) 2g of phase change material octadecanol was heated at 80 ℃ to complete melting, 0.66g of the said alcogel was added to the abovementioned octadecanol melt and incubated at 80 ℃ for 12h for solvent replacement. Then, repeatedly adsorbing the liquid phase-change material on the surface of the gel by using filter paper until no melting trace of the phase-change material exists on the filter paper, and finally obtaining the phase-change gel material.

FIG. 1 shows morphology photographs (a) and (c) of a poly (N-isopropylacrylamide) hydrogel obtained in step (1) of this example before drying and morphology photographs (b) and (d) after drying. As can be seen from SEM images (c) and (d), the gel is composed of a three-dimensionally crosslinked network.

Fig. 2 is photographs of the phase-change gel material prepared in this example in a flexible state (a) and a rigid state (b). It can be seen that above the phase transition temperature point, the phase change gel material is in a soft state and upon cooling, the phase change gel material changes to a hard state.

In addition, refer to fig. 3, which is a Differential Scanning Calorimetry (DSC) chart of the phase-change gel material prepared in this example. From the DSC test results, the phase transition latent heat of pure octadecanol is 221.01J/g (melting enthalpy) and 218.75J/g (solidification enthalpy), and the phase transition temperature is 63.98 deg.C (melting temperature) and 52.59 deg.C (solidification temperature), respectively. The actual latent heat of phase change for the 75% loading of octadecanol @ phase change gel material was 165.72J/g and 156.11J/g (melting enthalpy/freezing enthalpy), the phase change temperature was 68.03 ℃ (melting temperature) and 41.39 ℃ (freezing temperature), respectively; calculated as the theoretical latent heat of the phase-change gel material is 165.75/164.06J/g (melting enthalpy/solidification enthalpy), it can be found that the actual latent heat of the prepared phase-change gel material is very close to the theoretical latent heat of octadecanol, which indicates that the phase-change molecules can be sufficiently free-crystallized in the gel network, and the latent heat of the obtained phase-change gel material is high and has a high level.

Example 2

The preparation method of the phase-change gel material with variable mechanical state comprises the following steps:

(1) 1.8g of N-isopropylacrylamide, 0.072g of methylenebisacrylamide and 0.018g of potassium persulfate as initiator were dissolved in 10mL of deionized water and stirred in an oil bath at 25 ℃ for 30min under a nitrogen atmosphere. Subsequently, 10. Mu.L of tetramethylethylenediamine was added thereto, and the system was isolated from air and heated under an oil bath at 50 ℃ for 30min. Cooling to room temperature, adding acetone, soaking for 12h, soaking with deionized water for 12h, and soaking in ethanol for 24h for alcoholization to obtain alcogel; further, dichloromethane was used in place of ethanol.

(2) 2g of hexadecane, a phase change material, was heated to complete melting at 80 deg.C, 0.66g of the alcogel was added to the above hexadecane melt and incubated at 80 deg.C for 12h for solvent displacement. And then, repeatedly adsorbing the liquid phase-change material on the surface of the gel by using filter paper until no melting trace of the phase-change material exists on the filter paper, and finally obtaining the phase-change gel material.

Example 3

(1) 1.8g of N-isopropylacrylamide, 0.036g of methylenebisacrylamide and 0.018g of potassium persulfate as an initiator were dissolved in 10mL of deionized water and stirred in an oil bath at 25 ℃ for 30min under a nitrogen atmosphere. Subsequently, 10. Mu.L of tetramethylethylenediamine was added thereto, and the system was isolated from air and heated in an oil bath at 50 ℃ for 30min. Cooling to room temperature, adding acetone, soaking for 12h, soaking with deionized water for 12h, and soaking in ethanol for 24h for alcoholization to obtain alcogel;

(2) 2g of hexadecanol was heated at 80 ℃ to be completely melted, and 0.85g of the said alcogel was added to the above hexadecanol melt and incubated at 80 ℃ for 12 hours to effect solvent substitution. And then, repeatedly adsorbing the liquid phase-change material on the surface of the gel by using filter paper until no melting trace of the phase-change material exists on the filter paper, and finally obtaining the phase-change gel material.

Example 4

(1) 1.8g of N-isopropylacrylamide, 0.036g of methylenebisacrylamide and 0.018g of ammonium persulfate as an initiator are dissolved in 10mL of deionized water, 5mL of graphene oxide with the concentration of 1wt% is added thereto, and the mixture is stirred in an oil bath at 25 ℃ for 30min under a nitrogen protective atmosphere. Subsequently, 10. Mu.L of tetramethylethylenediamine was added thereto, and the system was isolated from air and heated in an oil bath at 50 ℃ for 30min. Cooling to room temperature, adding acetone, soaking for 12h, soaking with deionized water for 12h, and soaking in ethanol for 24h for alcoholization to obtain alcogel;

(2) 2g of phase change material octadecanol was heated at 80 ℃ to complete melting, 0.66g of the said alcogel was added to the abovementioned octadecanol melt and incubated at 80 ℃ for 12h for solvent replacement. And then, repeatedly adsorbing the liquid phase-change material on the surface of the gel by using filter paper until no melting trace of the phase-change material exists on the filter paper, and finally obtaining the phase-change gel material.

Comparative example 1

Referring to chem.Eng.J.396 (2020) 125206, zhou et al load a polyethylene glycol phase change material (CNC hydrogel-PEG 4000) with a cellulose nano-crystalline hydrogel as a carrier, and the obtained composite phase change material has latent heat of 151.8J/g and thermal conductivity of 0.44W/mk. But the phase change gel material has only a single mechanical state for a specific service purpose. However, dynamic materials with interchangeable mechanical states are an urgent need for future intelligent, adaptive application cases.

Effects of the embodiment

Test method

1. Loading of phase change material (%)

Calculating the load capacity of the phase-change material in the prepared phase-change gel material by adopting the following formula:

the load amount of the phase change material = [ mass of phase change material/(mass of phase change material + mass of alcogel material) ] × 100%

2. Latent heat of phase change and temperature of phase change

Thermal performance analysis of the samples in a nitrogen environment using Differential Scanning Calorimetry (DSC) in N ₂ The thermal performance of the sample was tested at a flow rate of 50mL/min and a temperature rise rate of 10 deg.C/min.

3. Mechanical Properties

Equiaxed compression testing of the samples was carried out using a universal material testing machine (Instron 4505) to obtain the stress-strain behaviour of the samples under compression, the maximum compressive strength of the samples was measured and the measurement was carried out at a compression of 1 mm/min.

4. Speed of thermal response

The experimental research of material thermal conductivity measurement is carried out by using a transient plane source method through a Hot Disk thermal analyzer, the thermal conductivity is researched by placing two flat plates containing the same type of samples and using a transient plane source technology, and the thermal conductivity coefficients of different samples are obtained

Results of the experiment

Using the above-described test and calculation methods, the prepared products of examples 1 to 4 and comparative example 1 were subjected to the performance or effect test, and the results are shown in Table 1 below

[ Table 1]

	Capacity of capacity		Enthalpy of fusion	Compressive strength	Speed of thermal response
						Example 1	75wt％	Octadecanol	165.72J/g	6.8kPa	0.32W/mk
Example 2	75wt％	Hexadecane (Hexadecane)	156.12J/g	6.2kPa	0.31W/mk
						Example 3	70wt％	Cetyl alcohol	167.66J/g	7.3kPa	0.39W/mk
Example 4	75wt％	Octadecanol	165.02J/g	38.1kPa	0.56W/mk
						Comparative example 1	-	Polyethylene glycol	151.8J/g	-	0.44W/mk

As shown in table 1 above, in examples 1 to 4 and comparative example 1, the method of preparing the phase change gel material with variable mechanical state according to the present application can prepare the phase change gel material with high load capacity, high heat storage density, no leakage of the phase change material, and high mechanical strength in a rigid state. In addition, compared with embodiment 2, in embodiment 4, graphene Oxide (GO) is further added to the gel carrier, so that the thermal response speed is further obviously improved, and the compressive strength is also greatly enhanced.

In addition, refer to fig. 4, which is a schematic flow chart of the phase-change gel material of the present application for achieving the grabbing function. The phase-change gel can be switched between a soft state and a hard state through a reversible solid-liquid phase change process, and the rigidity of the material is changed along with the phase-change gel. Specifically, the phase-change gel is contacted with the object to be taken in a soft state, so that the object to be taken is embedded into the phase-change gel in the soft state, and then the phase-change gel is solidified to form a whole with the object, so that the object to be taken can be successfully grabbed. To be moved to the target position, the phase change gel may be heated to become soft again, so that the object may be released. Therefore, the phase-change gel according to the present application is sufficiently soft at high temperatures, can conform to the three-dimensional surface of an electronic product, effectively reduces thermal resistance, and becomes solid at low temperatures to promote effective heat transfer; and the grabbing function of the object with any shape is realized through a reversible solid-liquid phase change process, namely, the phase change gel contacts the object in a soft state, the heat is released and solidified, the material is changed into a rigid solid state from the soft gel state, so that the material and the object are closely adhered together to form a whole, the bearing capacity is dynamically adjusted by responding to external thermal stimulation, and the object is released after the phase change gel is softened again. In conclusion, the phase-change gel material according to the present application can undergo an exceptionally large amplitude stiffness transition under thermal stimulation, and can fulfill the urgent need of current intelligent, adaptive applications.

The above-described embodiments of the present application are only preferred embodiments for explaining the present application, and are not limiting to the present application, and those skilled in the art can make modifications without inventive contribution as required after reading the present specification, however, any modifications, equivalents, improvements, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A phase change gel material of variable mechanical state comprising: a poly (N-isopropylacrylamide) matrix with a three-dimensional cross-linked network structure; and a phase change material compounded in the poly N-isopropyl acrylamide matrix;

the phase-change gel material is prepared by the following method:

(1) Dissolving N-isopropylacrylamide, methylene bisacrylamide and an initiator in a weight ratio of (1-5) to (0.5-1.5) in water, stirring, adding tetramethylethylenediamine, heating for reaction, and sequentially soaking by using acetone, water and lower alcohol to obtain alcohol gel; and

2. The phase-change gel material according to claim 1, wherein in the step (1), the initiator is at least one selected from the group consisting of potassium persulfate and ammonium persulfate.

3. The phase-change gel material as claimed in claim 1, wherein in step (1), the weight ratio of the N-isopropylacrylamide to the methylenebisacrylamide to the initiator is 100 (2-4) to (0.8-1.2).

4. The phase-change gel material as claimed in claim 1, wherein in the step (1), the amount of water for dissolving the N-isopropylacrylamide, the methylenebisacrylamide and the initiator is (4 mL-6 mL)/g of the N-isopropylacrylamide.

5. The phase-change gel material as claimed in claim 1, wherein in step (1), the amount of tetramethylethylenediamine is (4 μ L to 12 μ L)/g of N-isopropylacrylamide.

6. The phase-change gel material as claimed in claim 1, wherein in the step (1), the stirring is performed at 15-30 ℃ for 20-40 min under an inert gas atmosphere.

7. The phase-change gel material according to claim 1, wherein in the step (1), the heating reaction is carried out at 45-55 ℃ for 25-35 min under the condition of isolating air.

8. The phase-change gel material as claimed in claim 1, wherein in the step (1), the soaking time with acetone is 8-16 h; the soaking time of water is 8-16 h; and the soaking time by adopting lower alcohol is 20-28 h.

9. The phase-change gel material as claimed in claim 1, wherein in the step (1), the lower alcohol is at least one selected from the group consisting of methanol, ethanol, n-propanol and isopropanol.

10. The phase-change gel material as claimed in claim 1, wherein in step (1), graphene oxide is further added to the aqueous solution of N-isopropylacrylamide, methylenebisacrylamide and the initiator.

11. The phase-change gel material as claimed in claim 10, wherein the weight ratio of graphene oxide to N-isopropylacrylamide is (0.01-0.1): 1.

12. The phase-change gel material as claimed in claim 1, wherein in the step (1), the lower alcohol in the alcohol gel is further replaced with an organic solvent.

13. The phase change gel material of claim 12, wherein the organic solvent is n-hexane or dichloromethane.

14. The phase-change gel material as claimed in claim 1, wherein the step (2) is: melting the phase-change material, adding the alcogel into the melted phase-change material to perform solvent replacement, and removing the phase-change material on the outer surface of the gel to obtain the phase-change gel material.

15. The phase change gel material of claim 14, wherein in step (2), the phase change material is at least one selected from the group consisting of stearyl alcohol, cetyl alcohol, myristyl alcohol, stearyl alcohol and arachidyl alcohol.

16. The phase-change gel material as claimed in claim 14, wherein the temperature for melting the phase-change material in step (2) is 70-90 ℃.

17. The phase-change gel material of claim 14, wherein in step (2), the weight ratio of the phase-change material to the alcogel is 1 (0.01-100).

18. The phase-change gel material as claimed in claim 14, wherein the temperature of the solvent substitution in step (2) is 70 ℃ to 90 ℃.

19. The phase-change gel material as claimed in claim 14, wherein in the step (2), the solvent replacement time is 8h to 16h.

20. The phase-change gel material as claimed in claim 14, wherein in step (2), the phase-change material on the outer surface of the gel is removed by wiping with paper, fabric, or nonwoven.