CN108049241B - Preparation method of shape memory Janus material with energy conversion effect - Google Patents

Abstract

The invention discloses a preparation method of shape memory Janus material with energy conversion effect, aiming at designing and preparing paper sheets (Janus paper sheets) with asymmetric surface properties, so as to realize controllable asymmetric wetting and swelling behavior and In this way, the macroscopic reversible deformation of the material is driven to realize the conversion from swelling potential energy to mechanical energy. The invention includes the steps of building a working platform, preparing a Janus paper sheet, designing and evaluating an energy conversion device, and the like. The obtained Janus paper sheet material undergoes bending deformation for a short time in the water environment, and the curvature reaches 200m ^‑1 after deformation. The Janus paper sheet has stable deformation endpoints under both no-load and loaded conditions, and exhibits a good shape memory function. The paper also exhibits good stability and sensitivity during energy conversion. The invention has simple preparation process, readily available raw materials, non-toxic and environmental protection, low cost, strong stability, is suitable for large-area preparation, and has bright application prospects in the fields of future sensing devices and the like.

Description

A kind of preparation method of shape memory Janus material with energy conversion effect

technical field

The invention belongs to the technical field of preparation of asymmetric surface wetting materials, and particularly relates to a method for preparing a material with asymmetric wettability, asymmetric swelling and shape memory functions.

Background technique

Interfaces with asymmetric properties exist widely in nature, such as the huge difference in wettability between the upper and lower surfaces of lotus leaves, the selective permeability of biological cell membranes, and so on. The biomimetic design of this asymmetry in nature often endows interface materials with many unique properties, such as directional permeability of fluids, selective adhesion, etc., which can be applied to directional fluid transport, emulsion separation, membrane distillation and other fields.

Swelling is a process in which the volume of a polymer expands in a solvent. This process is relatively stable and easy to control. It can be used for superabsorbent materials on the macroscopic level, and can be used for controlling the surface morphology, microscopic size, structural network, etc. of the material on the microscopic level. For macroscopic swelling-driven shape memory materials, the design of the swelling end point is often focused on. This method is convenient and efficient, has high stability, strong controllability, and low cost. It has a bright future in the fields of energy conversion devices and environmental sensing devices. application prospects.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a simple and environmentally friendly method for preparing shape memory Janus paper sheet material with energy conversion effect. By exploiting its stable asymmetric wettability and swelling properties, the macroscopic deformation of the material is controlled, thereby realizing the transformation from swelling potential energy to mechanical potential energy. This process has strong controllability, high stability, readily available raw materials, low cost, and high practical application value.

The technical scheme for realizing the object of the present invention is: a preparation method of a shape memory Janus material with energy conversion effect, the steps of which are as follows:

A. Construction of the working platform: Tilt and fix the hair dryer at a certain angle to the horizontal plane, and fix the hollow stainless steel mesh frame along the air outlet to ensure that the stainless steel mesh is perpendicular to the airflow direction when the hair dryer is working, and the hollow part is facing out. The air outlet, the air outlet and the hollow are at a certain distance in the airflow direction;

B. Preparation of Janus paper: configure a certain proportion of polyvinylidene fluoride/N,N-dimethylformamide solution, cut the qualitative filter paper to a certain size, and fix the clean qualitative filter paper with clips at the hollow part of the working platform in step A. Filter paper sheet, keep the hair dryer working continuously, at the same time, the dropper draws the prefabricated polymer solution and drips it onto the upper surface of the paper sheet. Under the action of gravity, the polymer solution is cast to cover the entire upper surface. After the polymer on the upper surface is completely solidified, stop The hair dryer works, remove the paper, move it to a 60°C drying oven for annealing, and complete the preparation of the hydrophobic/superhydrophilic Janus paper;

C. Design and evaluation of the energy conversion device: fix one side of the paper sheet prepared in step B to hang it vertically, hang a certain mass of heavy objects at the lower edge, spray water on the hydrophilic side of the paper sheet, and record the bending deformation process and the maximum deformation state.

Further, in step A, the angle of inclination of the hair dryer is 30°.

Further, in step A, the distance between the air outlet and the hollow in the airflow direction is 3 cm.

Further, in step B, the polyvinylidene fluoride/N,N-dimethylformamide formulation ratio is 1.5 g of polyvinylidene fluoride powder dissolved in 10 ml of N,N-dimethylformamide.

Further, in step B, the cutting specification of the qualitative filter paper sheet is 2cm×4cm.

Further, in step C, the weight of the hanging heavy object in the energy conversion device is 2.5g.

The beneficial effects of the present invention are: compared with the prior art, the advantages of the present invention are:

1. The process is simple, the raw materials are readily available, non-toxic and environmentally friendly, and the cost is low.

2. The prepared asymmetric Janus paper sheet has high sensitivity to water, the curvature changes from 0m ^-1 to 200m ^-1 , and the deformation rate is large.

3. Display stable deformation end point in deformation and flattening cycle, with good shape memory function.

4. It is suitable for shape memory under unloaded and loaded conditions at the same time, and the maximum power per unit area of energy conversion under load conditions is 3.6×10 ^-3 W·m ^-2 .

5. High mechanical strength and long service life.

Description of drawings

Fig. 1 is the optical picture of the Janus paper sheet obtained in Example 1 of the present invention before and after deformation in water, (a) is before deformation, (b) is after deformation.

FIG. 2 is the curvature change of the Janus paper sheet obtained in Example 1 of the present invention after each deformation in the deformation-flattening cycle.

FIG. 3 is an optical picture of the obtained Janus paper sheet after bending in Example 2 of the present invention, and then swelling and deformation in water to reach the deformation end point. (a) is before bending, (b) is bending to the hydrophobic side, (c) is bending with crease, (d) is S-shaped bending, and (d) is the end point of deformation.

FIG. 4 is the example 3 of the present invention spraying water on a suspended Janus paper sheet with a load, and recording its deformation process and deformation end point.

FIG. 5 is the gravitational potential energy per unit area and the energy conversion power per unit area of the suspended Janus paper sheet with load in the deformation process in Example 3 of the present invention.

FIG. 6 is the variation of deflection angle of the suspended Janus paper sheet under load in the deformation-drying cycle in Example 3 of the present invention.

Detailed ways

In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with the embodiments, but the content of the present invention is not limited to the following embodiments. Those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms are also within the scope defined by the claims listed in this application.

Example 1

(1) Construction of the working platform:

The hair dryer is fixed at an angle of 30° from the horizontal plane, and the hollow stainless steel mesh frame is fixed along the air outlet to ensure that the stainless steel mesh plane is perpendicular to the airflow direction of the hair dryer when it is working, and the hollow part is facing the air outlet. The hollow is placed at a distance of 3cm in the direction of the airflow.

(2) Preparation of Janus paper sheets:

A polyvinylidene fluoride/N,N-dimethylformamide solution was prepared (1.5g PVDF dissolved in 10ml DMF), and the qualitative filter paper was cut into a size of 2cm×4cm. In step (1), fix the clean qualitative filter paper with clips at the hollow of the working platform, keep the hair dryer working continuously, and at the same time drop the prefabricated polymer solution onto the upper surface of the paper by the dropper. Under the action of gravity, the polymer solution flows Extend to cover the entire upper surface. After the polymer on the upper surface is completely cured, stop the hair dryer, remove the paper, and move it to a 60°C drying oven for annealing. So far, the preparation of hydrophobic/superhydrophilic Janus paper sheets is completed.

(3) Deformation of Janus paper sheet in water environment under no-load condition:

Put the Janus paper sheet prepared in step (2) on the water surface with the super-hydrophilic side facing down, record the deformation process of the paper sheet, and take it out when the maximum deformation is reached. The optical photos before and after the deformation are shown in Figure 1. The sheet is bent towards the hydrophobic surface, and when the deformation degree is large and has an obvious axial direction, the curved section can be equivalent to an arc, and the maximum curvature reaches 200m ^-1 .

(4) The shape memory of Janus paper in the deformation-flattening cycle under no-load condition:

Press the deformed paper sheet in step (3) under a 100g weight for 30 minutes to restore the smoothness and dryness of the paper sheet, put it on the water surface again, and take it out to measure the curvature when the maximum deformation is reached. The deformation-flattening cycle process was repeated 20 times, and its curvature change was shown in Fig. 2. Figure 2 shows that the Janus paper sheet maintains a relatively narrow range of maximum deformation curvature (197±5 m ^-1 ) and no obvious attenuation during the deformation-flattening cycle, showing that it has a stable swelling end point and good shape memory sex.

Example 2:

(1) Construction of the working platform:

The hair dryer is fixed at an angle of 30° from the horizontal plane, and the hollow stainless steel mesh frame is fixed along the air outlet to ensure that the stainless steel mesh plane is perpendicular to the airflow direction of the hair dryer when it is working, and the hollow part is facing the air outlet. The hollow is placed at a distance of 3cm in the direction of the airflow.

(2) Preparation of Janus paper sheets:

A polyvinylidene fluoride/N,N-dimethylformamide solution was prepared (1.5g PVDF dissolved in 10ml DMF), and the qualitative filter paper was cut into a size of 2cm×4cm. In step (1), fix the clean qualitative filter paper with clips at the hollow of the working platform, keep the hair dryer working continuously, and at the same time drop the prefabricated polymer solution onto the upper surface of the paper by the dropper. Under the action of gravity, the polymer solution flows Extend to cover the entire upper surface. After the polymer on the upper surface is completely cured, stop the hair dryer, remove the paper, and move it to a 60°C drying oven for annealing. So far, the preparation of hydrophobic/superhydrophilic Janus paper sheets is completed.

(3) Shape memory of Janus sheets under no-load conditions:

The Janus paper sheet prepared in step (2) is bent into different shapes, including bending toward the super-hydrophilic surface, bending at the crease, bending in an S shape, and then placing it on the water surface, and its maximum deformation state is shown in Figure 3 . Figure 3 shows that the paper sheet can still be deformed to a degree comparable to that in Example 1 during the deformation process by bending the paper sheet before swelling deformation, showing good shape memory.

Example 3:

(1) Construction of the working platform:

The hair dryer is fixed at an angle of 30° from the horizontal plane, and the hollow stainless steel mesh frame is fixed along the air outlet to ensure that the stainless steel mesh plane is perpendicular to the airflow direction of the hair dryer when it is working, and the hollow part is facing the air outlet. The hollow is placed at a distance of 3cm in the direction of the airflow.

(2) Preparation of Janus paper sheets:

A polyvinylidene fluoride/N,N-dimethylformamide solution was prepared (1.5g PVDF dissolved in 10ml DMF), and the qualitative filter paper was cut into a size of 2cm×4cm. In step (1), fix the clean qualitative filter paper with clips at the hollow of the working platform, keep the hair dryer working continuously, and at the same time drop the prefabricated polymer solution onto the upper surface of the paper by the dropper. Under the action of gravity, the polymer solution flows Extend to cover the entire upper surface. After the polymer on the upper surface is completely cured, stop the hair dryer, remove the paper, and move it to a 60°C drying oven for annealing. So far, the preparation of hydrophobic/superhydrophilic Janus paper sheets is completed.

(3) Design and evaluation of energy conversion device:

Fix one side of the paper sheet prepared in step (2) to hang it vertically, hang a weight of 2.5g vertically at the lower edge, spray water on the hydrophilic side of the paper sheet, and record the bending deformation process as shown in Figure 4, Measure the deflection angle caused by the bending of the paper, and calculate the gravitational potential energy and power converted per unit area of the paper. The gravitational potential energy and power converted per unit area are shown in Figure 5.

(4) Shape memory of Janus paper sheets in the deformation-drying cycle under loading conditions:

The paper sheet deformed in step (3) is kept dry under the load condition, the paper sheet is restored to be straight, water is sprayed on the superhydrophilic side again to make it swell and deformed, and the deformation-drying cycle process is repeated for 20 times. The deflection angle change in the cycle is shown in Fig. 6. Figure 6 shows that the Janus sheet was deformed in the deformation-drying cycle under the conditions of 1 and 2, and the maximum deflection angle was maintained in a relatively narrow range (26°±2°) without significant attenuation, showing good shape memory.

The present invention focuses on designing and fabricating paper sheets (Janus sheets) with asymmetric surface properties to achieve controllable asymmetric wetting and swelling behavior and thereby drive macroscopic reversible deformation of materials to achieve transition from swelling potential energy to mechanical energy transformation. The invention includes the steps of building a working platform, preparing a Janus paper sheet, designing and evaluating an energy conversion device, and the like. The obtained Janus paper sheet material undergoes bending deformation for a short time in the water environment, and the curvature reaches 200 m ^-1 after deformation. The Janus paper sheet has stable deformation endpoints under both no-load and loaded conditions, and exhibits a good shape memory function. The paper also exhibits good stability and sensitivity during energy conversion. The invention has simple preparation process, readily available raw materials, non-toxic and environmental protection, low cost, strong stability, is suitable for large-area preparation, and has bright application prospects in the fields of future sensing devices and the like.

Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than limiting the protection scope of the present invention. The essence and scope of the technical solution of the invention.

Claims (2)

1. A method for preparing a shape memory Janus material with an energy conversion effect is characterized by comprising the following steps:

A. building a working platform: the hairdryer is obliquely fixed at a certain angle with the horizontal plane, a hollowed stainless steel mesh frame is fixed on an air outlet of the hairdryer, the stainless steel mesh is guaranteed to be perpendicular to the air flow direction of the hairdryer during working, the hollowed part is opposite to the air outlet, and a certain distance is formed between the air outlet and the hollowed part in the air flow direction;

the inclination angle of the electric hair drier is 30 degrees; the distance between the air outlet and the hollow part in the airflow direction is 3 cm;

B. preparation of Janus paper sheet: preparing a certain proportion of polyvinylidene fluoride/N, N-dimethylformamide solution, cutting qualitative filter paper into a certain specification, fixing clean qualitative filter paper sheets at the hollow-out part of a working platform by using a clamp in the step A, keeping the electric hair drier to work continuously, simultaneously dripping prefabricated polymer solution from a dropper to the upper surface of the paper sheets, casting the polymer solution to cover the whole upper surface under the action of gravity, stopping the electric hair drier after the polymer on the upper surface is completely solidified, taking down the paper sheets, moving the paper sheets to a 60 ℃ drying box for annealing for later use, and thus finishing the preparation of hydrophobic/super-hydrophilic Janus paper sheets;

the preparation ratio of the polyvinylidene fluoride to the N, N-dimethylformamide is that 1.5g of polyvinylidene fluoride powder is dissolved in 10ml of N, N-dimethylformamide; the cutting specification of the qualitative filter paper sheet is 2cm multiplied by 4 cm;

C. design and evaluation of energy conversion device: and D, fixing one side of the paper sheet prepared in the step B to vertically hang the paper sheet, hanging a weight with certain mass at the lower edge, spraying water to the hydrophilic side of the paper sheet, and recording the bending deformation process and the maximum deformation state.

2. The method of preparing a shape memory Janus material with energy conversion effect as claimed in claim 1, wherein: in the step C, the weight of the suspended matter in the energy conversion device is 2.5 g.

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