High-strength polypyrrole in-situ growth napkin / natural rubber-hydrogel composite double-layer intelligent deformation material as well as preparation method and bionic driving application thereof

Abstract

The invention provides a high-strength polypyrrole in-situ growth napkin / natural rubber-hydrogel composite double-layer intelligent deformation material, a preparation method of the high-strength polypyrrole in-situ growth napkin / natural rubber-hydrogel composite double-layer intelligent deformation material and bionic driving application of the high-strength polypyrrole in-situ growth napkin / natural rubber-hydrogel composite double-layer intelligent deformation material. And polymerizing the natural rubber latex and the N-isopropylacrylamide hydrogel pre-polymerized solution on the polypyrrole modified napkin to obtain the double-layer composite hydrogel intelligent driving material. Polypyrrole is adopted to grow on the surface of the napkin in situ, the polypyrrole modified napkin is stretched by 10% and fixed, then the napkin, the natural rubber and the poly (N-isopropylacrylamide) composite hydrogel form a firm mechanical interlocking structure, the binding force is high, and the method is simple; meanwhile, the composite hydrogel is excellent in driving performance, high in photo-thermal conversion efficiency, good in mechanical property, simple in preparation method, controllable in technological parameter, low in cost and high in repeatability. Therefore, the material has a good application prospect in the field of photo-thermal driving bionic device materials.

Description

Technical Field

[0001] The invention relates to the field of functional polymer materials, and in particular to a high-strength polypyrrole in-situ grown napkin / natural rubber-hydrogel composite double-layer intelligent deformation material, a preparation method thereof, and a bionic driving application thereof. Background Art

[0002] Smart hydrogels have attracted great attention in the field of soft actuators and soft robots due to their large amount of water inside, good softness, and ability to respond to various external stimuli, and have broad application prospects in the biomedical field. As an important smart material, smart hydrogels can achieve controllable and reversible shape transformation under various external stimuli such as heat, pH, light, electricity, and magnetism. Moreover, smart hydrogel actuators are soft and wet materials, just like organisms, which enable them to adapt to different environments and loads, thereby achieving flexible movement and operation. Secondly, smart hydrogels are highly controllable and programmable. By changing the composition, structure, and external stimuli of the hydrogel, its mechanical properties, deformation behavior, and functional characteristics can be adjusted. This provides a wide range of possibilities for the design and manufacture of soft robots and soft actuators with different functions and performances. For example, Chinese patent CN115246263A discloses a method for preparing a dust-free paper-induced double-layer hydrogel actuator, wherein a mixture of synthetic lithium magnesium silicate, N-isopropylacrylamide (NIPAM), 1-hydroxycyclohexyl phenyl ketone and methanol is stirred to obtain a clear and transparent hydrogel precursor solution, and then a double-layer hydrogel actuator is obtained by photoinitiating in-situ polymerization on dust-free paper. The hydrogel can be cut into "Z", "S", "T" and "U" letter actuators, and the construction of a double-layer hydrogel letter actuator can achieve the deformation of "Z", "S", "T" and "U" in water at 60°C.

[0003] With the deepening of research, the research of scientific researchers on smart hydrogels has evolved from simple volume expansion / contraction to various complex drives. Smart hydrogels have become one of the most promising new bionic smart materials in recent years. Among them, smart hydrogels with photothermal response capabilities have become a research hotspot because of their remote controllability. Photothermal responsive smart hydrogels are fillers with photothermal effects introduced into temperature responsive hydrogels. Under the irradiation of visible light or near-infrared light, the photothermal fillers can absorb light energy and convert it into heat energy, causing the temperature responsive hydrogel to change in volume due to heat, thereby realizing the complex drive of photothermal responsive hydrogels.

[0004] However, existing smart composite hydrogels have problems with slow driving speed or poor mechanical strength, and most of the designed bionic actuators are spliced ​​together, resulting in relatively simple driving behaviors. Although the existing smart hydrogels have achieved certain improvements in complex deformation, driving speed, and mechanical properties, most of these improvements are based on bionic structures prepared from various purely synthetic raw materials. The preparation methods are also relatively cumbersome and not universal, and they can often only improve one of the properties, which seriously limits their further application. Most smart hydrogels have problems such as slow response rate, weak driving force, single driving mode, and difficulty in real-time detection and feedback of the driving process, which greatly limits their scope of application. Summary of the invention

[0005] In view of this, the purpose of the present invention is to propose a high-strength polypyrrole in-situ grown napkin / natural rubber-hydrogel composite double-layer intelligent deformation material and its preparation method and bionic drive application, so as to solve the problems of existing intelligent hydrogels such as slow response rate, weak driving force, and single driving mode.

[0006] The technical solution of the present invention is achieved in this way:

[0007] A high-strength polypyrrole in-situ grown napkin / natural rubber-hydrogel composite double-layer intelligent deformation material, comprising the following preparation steps:

[0008] S1: soaking a napkin in an ammonium persulfate solution with a concentration of 100 to 300 mmol / L, taking it out, spraying a pyrrole solution on the napkin to perform in-situ growth polymerization of polypyrrole, and obtaining a polypyrrole in-situ growth napkin; after the polymerization is completed, rinsing it with deionized water for three times to remove the incompletely reacted ammonium persulfate and pyrrole solution;

[0009] S2: taking monomer N-isopropylacrylamide, natural rubber emulsion and cross-linking agent, adding them into water and mixing them to prepare natural rubber emulsion-NIPAM hydrogel prepolymer solution, adding initiator and catalyst into the natural rubber emulsion-NIPAM hydrogel prepolymer solution to prepare natural rubber emulsion-NIPAM hydrogel coagulant solution;

[0010] S3: After stretching the polypyrrole in-situ grown napkin to a length of 8% to 15%, fix it on a quartz glass sheet, place a U-shaped silicone rubber mold on the polypyrrole in-situ grown napkin, pour natural rubber latex-NIPAM hydrogel coagulant into the U-shaped silicone rubber mold, cover it with a quartz glass sheet to seal, polymerize it at low temperature, add it to a weak acid solution for immersion polymerization, and obtain the high-strength polypyrrole in-situ grown napkin / natural rubber-hydrogel composite double-layer intelligent deformation material.

[0011] Preferably, in step S1, the dipping time is 1 to 3 hours; and the polymerization time is 1 to 6 minutes.

[0012] Preferably, in step S1, the ammonium persulfate solution is an initiator for initiating the in-situ growth polymerization of pyrrole monomers into polypyrrole.

[0013] Preferably, in step S2, the mass ratio of the monomer N-isopropylacrylamide, natural rubber latex, crosslinking agent, water, initiator and catalyst is 180-220 mg: 80-120 mL: 6-10 mg: 80-120 mL: 180-220 μL: 18-22 μL.

[0014] More preferably, the mass concentration of the natural rubber latex is 50% to 70%; the cross-linking agent includes N,N-methylenebisacrylamide, the initiator includes ammonium persulfate, and the catalyst includes tetramethylethylenediamine.

[0015] Preferably, in step S3, the temperature of the low-temperature polymerization is 3-6°C, and the time of the low-temperature polymerization is 5-15 min; the material is added to a weak acid solution for immersion polymerization for 1-3 hours, the concentration of the weak acid solution is 0.1-0.3 mol / L, and the weak acid solution includes an acetic acid solution. The natural rubber emulsion is polymerized by immersion in the acetic acid solution. Finally, the natural rubber emulsion polymerized material can be placed in a large amount of deionized water and immersed for 1-3 days to remove unreacted monomers and other impurities in the hydrogel.

[0016] Preferably, in step S3, the polypyrrole in-situ grown napkin is stretched to a length of 8% to 15% and then fixed.

[0017] Preferably, in step S3, the middle of the U-shaped silicone mold is hollowed out, and the natural rubber latex-NIPAM hydrogel coagulant is poured into the hollowed-out middle part, and a glass sheet is placed below the polypyrrole in-situ growth napkin and above the mold to fix the polypyrrole in-situ growth napkin and the mold.

[0018] On the one hand, the present invention provides a high-strength polypyrrole in-situ grown napkin paper / natural rubber-hydrogel composite double-layer intelligent deformation material prepared by the above-mentioned preparation method.

[0019] On the other hand, the present invention also provides the use of the above-mentioned high-strength polypyrrole in-situ grown napkin paper / natural rubber-hydrogel composite double-layer intelligent deformation material in the preparation of photothermal driven bionic device materials.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention provides a method for preparing a high-strength "polypyrrole in-situ grown napkin / natural rubber-hydrogel" composite double-layer intelligent deformation material, which uses a nozzle to spray a pyrrole solution onto a napkin soaked in ammonium persulfate, and then uses polypyrrole to modify the napkin and the natural rubber-poly N-isopropylacrylamide composite hydrogel to form a strong mechanical interlocking structure. It has strong binding force, simple method, and no interlayer peeling phenomenon will occur during the driving process. The polypyrrole in-situ grown napkin / natural rubber-poly N-isopropylacrylamide composite material prepared by the present invention has strong mechanical properties, strong driving force (lifting more than 100 times its own weight) and precisely programmable complex driving (complex deformations such as three-dimensional spirals at different angles); in addition, due to the interlocking structure, the polypyrrole in-situ grown napkin / natural rubber-poly N-isopropylacrylamide composite intelligent driving material will not peel off under complex driving and can restore its original shape.

[0022] The present invention adopts polypyrrole to grow in situ on the surface of napkin paper, stretches the polypyrrole modified napkin paper to a certain length and fixes it, and then forms a firm mechanical interlocking structure with natural rubber and poly N-isopropylacrylamide composite hydrogel, which has strong binding force and simple method; at the same time, the composite hydrogel has excellent driving performance, high photothermal conversion efficiency, good mechanical properties, simple preparation method, controllable process parameters, low cost, high repeatability, and is suitable for napkin paper of various specifications. Therefore, the composite double-layer intelligent deformation material of "polypyrrole in situ growth napkin paper / natural rubber-hydrogel" has a good application prospect in the field of photothermal driven bionic device materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram of the preparation of a high-strength polypyrrole in-situ grown napkin / natural rubber-hydrogel composite double-layer intelligent deformation material according to the present invention;

[0024] Figure 2 The contact angle test results of the in-situ growth time of polypyrrole on napkin paper;

[0025] Figure 3 The mechanical properties comparison diagram of the in-situ growth time of polypyrrole on the napkin paper and the pressure-strain curves of the napkin paper with in-situ growth of polypyrrole for 4 minutes in two directions respectively;

[0026] Figure 4 This is a light transmittance test result diagram of the polypyrrole modified napkin paper of Example 1;

[0027] Figure 5 This is a photothermal conversion efficiency test result diagram of the polypyrrole modified napkin paper of Example 1;

[0028] Figure 6This is a graph showing the mechanical properties test results of the polypyrrole in-situ grown napkin / natural rubber-hydrogel composite double-layer smart deformation material;

[0029] Figure 7 This is a scanning electron microscope (SEM) image of the polypyrrole in-situ grown napkin / natural rubber-hydrogel composite double-layer smart deformation material of Example 1;

[0030] Figure 8 The bending performance test diagram of the polypyrrole in-situ grown napkin / natural rubber-hydrogel composite double-layer smart deformable material under the irradiation of a surface light source in Example 1: (a) bending process, (b) recovery process, (c) reversible cycle test (scale: 5 mm);

[0031] Fig. 9 The bending performance test diagram of the polypyrrole in-situ grown napkin / natural rubber-hydrogel composite double-layer smart deformable material of Example 1 under the irradiation of a point light source: (a) bending process, (b) recovery process, (c) reversible cycle test (scale: 5 mm);

[0032] Fig.10 This is the programmable complex actuation of the polypyrrole in-situ grown napkin / natural rubber-hydrogel composite double-layer smart deformation material under near-infrared light irradiation of Example 1 (scale: 5 mm). DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0034] Unless otherwise specified, the experimental methods used in the embodiments of the present invention are all conventional methods.

[0035] Unless otherwise specified, the materials, reagents, etc. used in the embodiments of the present invention can be obtained from commercial sources.

[0036] The napkin paper involved in the embodiment of the present invention is purchased from Vinda Paper.

[0037] The natural rubber latex involved in the embodiment of the present invention was purchased from Guangdong Hongke Chemical Raw Materials Co., Ltd.

[0038] The specifications of the napkins in the embodiment of the present invention are only used as examples and are not limited to napkins of other specifications.

[0039] Example 1: Reference Figure 1 , a high-strength polypyrrole in-situ grown napkin / natural rubber-hydrogel composite double-layer intelligent deformation material, prepared by the following method:

[0040] S1: Cut the napkin into 2cm×3cm size, soak it in 200mmol / L ammonium persulfate (APS) solution for 2h; then take it out and spread it on a quartz glass plate, and then spray the pyrrole solution evenly on the upper surface of the napkin, and use ammonium persulfate to initiate the in-situ growth polymerization of pyrrole monomer for 4min to obtain polypyrrole in-situ growth napkin; after the polymerization is completed, rinse it with deionized water three times to remove the incompletely reacted ammonium persulfate and pyrrole solution;

[0041] S2: Weigh 200 mg of monomer N-isopropylacrylamide (NIPAM), 100 mL of natural rubber latex (mass concentration 60%) (Natural rubber latex, NRL), and 8 mg of cross-linking agent N,N'-Methylenebisacrylamide (BIS) into 100 mL of deionized water and place in a vortex rotator for 5 min to obtain a natural rubber latex-NIPAM hydrogel prepolymer solution;

[0042] S3: Stretch the polypyrrole in-situ growth napkin prepared in step S1 by 10% and place it on a quartz glass sheet for fixing, then place a U-shaped silicone rubber mold with a thickness of 200μm (the empty groove is 20mm×30mm) on the polypyrrole in-situ growth napkin. Add 200μL of ammonium persulfate and 20μL of tetramethylethylenediamine (N,N,N',N'-Tetramethylethylenediamine, TEMED) to the natural rubber emulsion-NIPAM hydrogel prepolymer prepared in step S2 and place it in a vortex rotator for mixing for 1min, then pour it into the U-shaped silicone rubber mold, and after the prepolymer liquid completely penetrates into one side of the in-situ growth pyrrole napkin, cover it with a quartz glass sheet, seal it with a clip and place it in a refrigerator for low-temperature polymerization at 4℃ for 10min. Soak the obtained hydrogel composite material in an acetic acid solution for 2h to polymerize the natural rubber emulsion, and the polypyrrole in-situ growth napkin / natural rubber-hydrogel composite material can be obtained. The obtained polypyrrole in situ grown napkin paper / natural rubber-hydrogel composite material was soaked in a large amount of deionized water for 2 days to remove the unreacted monomers and other impurities in the hydrogel. Finally, a polypyrrole in situ grown napkin paper / natural rubber-hydrogel (PMN / NR-PNIPAM bi-layer hydrogel) composite double-layer intelligent deformation material was obtained, such as Figure 1 As shown in b, it can be cut into different angles to achieve programmable complex drive.

[0043] Embodiment 2: The difference between Embodiment 2 and Embodiment 1 is that the growth time of polypyrrole on the napkin paper is different. The specific steps are as follows:

[0044] S1: Cut the napkin into 2cm×3cm size, soak it in 200mmol / L ammonium persulfate (APS) solution for 2h; then take it out and spread it on a quartz glass plate, and then spray the pyrrole solution evenly on the surface of the napkin to initiate the in-situ growth polymerization of pyrrole monomer by ammonium persulfate (0-6min); after the polymerization is completed, rinse it with deionized water three times to remove the incompletely reacted ammonium persulfate and pyrrole solution;

[0045] The remaining steps S2 and S3 are the same as those in the first embodiment.

[0046] The growth time of polypyrrole on napkins affects the hydrophilicity, mechanical properties and light transmittance of napkins. The experimental results show that the mechanical properties of napkins are improved the most when polypyrrole is grown in situ for 4 minutes, and the light transmittance is the lowest. At the same time, the hydrophilicity of napkins grown with polypyrrole in situ for 4 minutes is still in the super-hydrophilic category.

[0047] Comparative Example 1: PNIPAM hydrogel was prepared by the following method:

[0048] S1: 200 mg of monomer N-isopropylacrylamide and 8 mg of cross-linking agent N,N-methylenebisacrylamide were added to 200 mL of deionized water and placed in a vortex rotator for 5 min to obtain NIPAM hydrogel prepolymer solution;

[0049] S2: Place a U-shaped silicone rubber mold with a thickness of 200 μm (the hollow groove is 20 mm×30 mm) on a quartz glass sheet. Add 200 μL of ammonium persulfate and 20 μL of tetramethylethylenediamine to the NIPAM hydrogel prepolymer prepared in step S1 and place it in a vortex rotator to mix for 1 min, then pour it into the U-shaped silicone rubber mold, cover it with a quartz glass sheet, seal it with a clip, place it in a refrigerator, and polymerize it at low temperature at 4°C for 5 min to obtain PNIPAM hydrogel.

[0050] Example 3: Characterization and performance testing of the high-strength polypyrrole in-situ grown napkin / natural rubber-hydrogel composite double-layer intelligent deformation material prepared in Example 1:

[0051] (1) Contact angle test of the polypyrrole modified napkin prepared in step S1 of Example 1:

[0052] In this study, the contact angle of polypyrrole in-situ grown napkins with different polypyrrole growth times (0-6min) was tested. Figure 2As shown in a, as the polypyrrole growth time increases from 0 min to 6 min, the contact angle of the napkin paper gradually increases. This is because polypyrrole is hydrophobic, and the hydrophilicity of the napkin paper will decrease after the growth of polypyrrole. However, since the napkin paper is a superhydrophilic material, the polypyrrole-modified napkin paper is still a superhydrophilic material. Figure 2 b It can be seen that the contact angle of the napkin paper grown in situ for 4 minutes with polypyrrole dropped from 75.6° to 0° in just 0.396 s. This shows that the in situ grown polypyrrole napkin paper is a super hydrophilic material, and the natural rubber latex-NIPAM hydrogel prepolymer can completely penetrate into the napkin paper to complete polymerization and form a strong mechanical interlocking structure.

[0053] (2) Mechanical properties test of the polypyrrole modified napkin prepared in step S1 of Example 1:

[0054] like Figure 3 As shown in a, the tensile strength of the napkin paper without polypyrrole growth is 1.985MPa. Increasing the in-situ growth time of polypyrrole will improve the mechanical properties of the napkin paper. The tensile strength of the napkin paper reaches a maximum value (3.024MPa) when the polypyrrole growth time is 4 minutes; after 4 minutes, the tensile strength gradually decreases. The reason for this phenomenon may be that before the in-situ polymerization of pyrrole for 4 minutes, polypyrrole can tightly and evenly cover the surface of the napkin paper fiber, and effectively cover the microcracks on the surface of the napkin paper fiber, thereby reducing stress concentration, so the mechanical strength of the polypyrrole modified napkin paper is improved. After 4 minutes, polypyrrole agglomerated on the surface of the napkin paper fiber, causing stress concentration, thereby reducing the mechanical strength of the napkin paper with in-situ growth of polypyrrole. In addition, polypyrrole modified napkin paper has anisotropy in mechanical properties, such as Figure 3 As shown in b, the tensile strength of polypyrrole modified napkin paper in the parallel and perpendicular directions are 3.024MPa and 0.785MPa, respectively, which is 3.85 times different; the elongation at break is 30% and 5%, respectively, which is 6 times different, showing good anisotropy.

[0055] (3) Test on the light transmittance of the polypyrrole modified napkin prepared in step S1 of Example 1:

[0056] In order to make the composite hydrogel have a faster driving speed under the irradiation of near-infrared light, the temperature rise rate is particularly critical. Since white napkins reflect light sources, and black polypyrrole modified napkins can absorb light sources of various wavelengths. Therefore, the transmittance of polypyrrole modified napkins was tested in the wavelength range of 340-900nm using a UV-visible spectrophotometer. Figure 4The results show that the transmittance of white napkin paper is 42.9% at 808nm wavelength, showing good light wave transmittance, while the transmittance of black napkin paper with polypyrrole in situ growth for 4min is as low as 3.3%, which can absorb most of the light. Therefore, polypyrrole-modified napkin paper has excellent photothermal conversion efficiency, which makes the photothermal drive performance of the composite hydrogel even better and realizes remote controllable rapid photodrive.

[0057] (4) Test on the photothermal conversion efficiency of the polypyrrole modified napkin prepared in step S1 of Example 1:

[0058] like Figure 5 As shown in the results of a, under the same light spot (25 cm away from the test sample), the temperature of the polypyrrole-modified napkin increases with the increase of light power. From 0s to 60s, 1W / cm 2 When the light power is 7.5W / cm 2 When the temperature reaches 42.72℃ in 5s, it rises to 60.24℃ in 60s. Figure 5 As shown in the results (b), with the increase of light power, the heating rate and final temperature of polypyrrole modified napkin paper increased, indicating that polypyrrole modified napkin paper has excellent photothermal conversion efficiency.

[0059] (5) Mechanical properties test of high-strength polypyrrole in-situ grown napkin / natural rubber-hydrogel composite double-layer intelligent deformation material prepared in Example 1:

[0060] like Figure 6 The results show that the polypyrrole in situ grown napkin paper / natural rubber-hydrogel prepared in Example 1 has a tensile strength of 0.97 MPa and an elongation at break of 91.13%, which are much higher than the tensile strength of 30 KPa and the elongation at break of 56.75% of the PNIPAM hydrogel in Comparative Example 1. That is, the tensile strength of the polypyrrole in situ grown napkin paper / natural rubber-hydrogel prepared by polypyrrole in situ grown napkin paper is 32 times higher than that of pure PNIPAM hydrogel, providing a more excellent driving force for the polypyrrole in situ grown napkin paper / natural rubber-hydrogel.

[0061] (6) Scanning electron microscope (SEM) test was performed on the high-strength polypyrrole in-situ grown napkin / natural rubber-hydrogel composite double-layer intelligent deformation material prepared in Example 1:

[0062] Through Figure 7Scanning electron microscopy results showed that the polypyrrole in situ grown napkin paper / natural rubber-PNIPAM hydrogel had a double-layer structure, with the upper layer being polypyrrole-modified napkin paper and the lower layer being natural rubber-PNIPAM hydrogel. There was a strong bonding interface between the polypyrrole-modified napkin paper and the natural rubber-PNIPAM layer. This was because the polypyrrole-modified napkin paper had super hydrophilicity and a porous structure. The natural rubber-PNIPAM hydrogel was able to completely penetrate the polypyrrole-modified napkin paper and form a strong mechanical interlocking structure with the rough surface of the polypyrrole-modified napkin paper.

[0063] (7) Study on the bending properties of the high-strength polypyrrole in-situ grown napkin / natural rubber-hydrogel composite double-layer intelligent deformation material prepared in Example 1:

[0064] First, a long strip of polypyrrole in-situ grown napkin / natural rubber-hydrogel with a size of 12 mm in length, 2 mm in width and 0.20 mm in thickness was selected as the experimental sample. 2 Under the full irradiation of near-infrared light, the long strip of polypyrrole in-situ grown napkin / natural rubber-hydrogel can be bent quickly from 0° to 315° in 2.3s ( Figure 8 a). After the near-infrared light is removed, the polypyrrole in-situ grown napkin / natural rubber-hydrogel will continue to recover to its initial state within 64 seconds ( Figure 8 b). Compared with the PNIPAM smart hydrogel, which takes tens of seconds to several minutes to be driven by photothermal, the polypyrrole in-situ grown napkin / natural rubber-hydrogel of the present invention completed a 315° bend in 2.3 seconds. This shows that the driving speed of the polypyrrole in-situ grown napkin / natural rubber-hydrogel is significantly improved, and it can rise above the LCST in a short time, causing the hydrogel to shrink rapidly and produce driving behavior. In addition, the high reversibility of the hydrogel was verified based on a 20-cycle cycle experiment ( Figure 8 c).

[0065] (8) Study on the bending properties of the high-strength polypyrrole in-situ grown napkin / natural rubber-hydrogel composite double-layer intelligent deformation material prepared in Example 1:

[0066] A strip of polypyrrole in-situ grown napkin / natural rubber-hydrogel with a size of 12 mm in length, 1 mm in width and 0.20 mm in thickness was selected as the experimental sample, and the applied strength was 5 W / cm 2 Under the irradiation of near-infrared point light source, the long composite hydrogel only needs 1.2s ( Fig. 9 a), when the point light source is removed, the long composite hydrogel recovers from 90° to its initial shape within 52 s ( Fig. 9b). First, ensure that the diameter of the point light source spot is 1 mm. When changing the near-infrared light power, increase the distance to keep the spot size consistent. In addition, the bending process of the polypyrrole in-situ grown napkin / natural rubber-hydrogel is also reversible. After the entire bending-restoration process is repeated 20 times, the performance of the polypyrrole in-situ grown napkin / natural rubber-hydrogel is almost not affected ( Fig. 9 c). This experiment also confirmed that the polypyrrole in situ grown napkin / natural rubber-hydrogel has good fatigue resistance and structural stability.

[0067] (9) Study on the complex driving behavior of the high-strength polypyrrole in-situ grown napkin / natural rubber-hydrogel composite double-layer smart deformation material prepared in Example 1:

[0068] like Fig.10 , under near-infrared light irradiation (808nm, 7.5W / cm 2 ), due to the high photothermal conversion efficiency of polypyrrole in situ grown napkin paper / natural rubber-hydrogel (12mm×3mm×0.20mm) and the different cutting angles with the fiber direction, the smart hydrogel can be curled into spirals of different lengths. As the cutting angle increases, the spiral length of the polypyrrole in situ grown napkin paper / natural rubber-hydrogel actuator becomes longer. The spiral length of the polypyrrole in situ grown napkin paper / natural rubber-hydrogel at 60° is longer than that at 30°. In particular, at 90°, the polypyrrole in situ grown napkin paper / natural rubber-hydrogel rolls into a long tube, and at 0°, the polypyrrole in situ grown napkin paper / natural rubber-hydrogel rolls into a ring. And in the process of complex deformation, the polypyrrole in situ grown napkin paper / natural rubber-hydrogel maintains a certain distance from the near-infrared light, indicating good remote controllability. The in-situ grown polypyrrole napkin / natural rubber-hydrogel can accurately complete various complex photothermal response deformations.

[0069] In summary, the preparation method of the high-strength polypyrrole in-situ grown napkin / natural rubber-hydrogel composite double-layer intelligent deformation material provided by the present invention is used to grow polypyrrole in-situ on the napkin. The polypyrrole in-situ grown napkin can quickly form a strong mechanical interlocking structure with the natural rubber-poly N-isopropylacrylamide hydrogel, which has strong bonding force, simple method, and no interlayer peeling phenomenon will occur during the driving process. Furthermore, after the polypyrrole is grown in-situ on the napkin using this method, the photothermal conversion efficiency of the napkin can be significantly improved, and complex bionic driving behavior can be achieved under near-infrared irradiation.

[0070] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A high-strength polypyrrole in-situ grown napkin / natural rubber-hydrogel composite double-layer intelligent deformation material, characterized in that: The method comprises the following preparation steps: S1: soaking a napkin in a 100-300 mmol / L ammonium persulfate solution, taking it out, spraying the pyrrole solution on the napkin to perform in-situ growth polymerization of polypyrrole, and obtaining a polypyrrole in-situ growth napkin; S2: taking monomer N-isopropylacrylamide, natural rubber emulsion and cross-linking agent, adding them into deionized water and mixing them to prepare natural rubber emulsion-NIPAM hydrogel prepolymer solution, adding initiator and catalyst into the natural rubber emulsion-NIPAM hydrogel prepolymer solution to prepare natural rubber emulsion-NIPAM hydrogel coagulant solution; S3: After stretching the polypyrrole in-situ grown napkin to a certain length, fix it on a quartz glass sheet, place a U-shaped silicone rubber mold on the polypyrrole in-situ grown napkin, pour natural rubber latex-NIPAM hydrogel coagulant into the U-shaped silicone mold, cover it with a glass sheet to seal, polymerize it at low temperature, add it to a weak acid solution for immersion polymerization, and obtain the high-strength polypyrrole in-situ grown napkin / natural rubber-hydrogel composite double-layer intelligent deformation material.

2. The high-strength polypyrrole in-situ grown napkin / natural rubber-hydrogel composite double-layer intelligent deformation material according to claim 1, characterized in that: In step S1, the dipping time is 1 to 3 hours; the polymerization time is 1 to 6 minutes.

3. The high-strength polypyrrole in-situ grown napkin / natural rubber-hydrogel composite double-layer intelligent deformation material according to claim 1, characterized in that: In step S1, the ammonium persulfate solution is used as an initiator to initiate the in-situ growth polymerization of pyrrole monomers into polypyrrole.

4. The high-strength polypyrrole in-situ grown napkin / natural rubber-hydrogel composite double-layer intelligent deformation material according to claim 1, characterized in that: In step S2, the amounts of the monomer N-isopropylacrylamide, natural rubber latex, crosslinking agent, deionized water, initiator and catalyst are 180-220 mg: 80-120 mL: 7-10 mg: 80-120 mL: 180-220 μL: 18-22 μL.

5. The high-strength polypyrrole in-situ grown napkin / natural rubber-hydrogel composite double-layer intelligent deformation material according to claim 4, characterized in that: The mass concentration of the natural rubber latex is 50% to 70%; the cross-linking agent includes N,N-methylenebisacrylamide, the initiator includes ammonium persulfate, and the catalyst includes tetramethylethylenediamine.

6. The high-strength polypyrrole in-situ grown napkin / natural rubber-hydrogel composite double-layer intelligent deformation material according to claim 1, characterized in that: In step S3, the temperature of the low-temperature polymerization is 3-6°C, and the time of the low-temperature polymerization is 5-15 minutes; the mixture is added to a weak acid solution for immersion polymerization for 1-3 hours, and the concentration of the weak acid solution is 0.1-0.3 mol / L, and the weak acid solution includes an acetic acid solution.

7. The high-strength polypyrrole in-situ grown napkin / natural rubber-hydrogel composite double-layer intelligent deformation material according to claim 1, characterized in that: In step S3, the polypyrrole in-situ grown napkin is stretched to a length of 8% to 15% and then fixed.

8. The high-strength polypyrrole in-situ grown napkin / natural rubber-hydrogel composite double-layer intelligent deformation material according to claim 1, characterized in that: In step S3, the middle of the silicone rubber mold is hollowed out into a U-shape, and the natural rubber latex-NIPAM hydrogel condensate is poured into the middle hollow part. A quartz glass sheet is placed below the polypyrrole in-situ growth napkin and above the mold to fix the polypyrrole in-situ growth napkin and the silicone rubber mold.

9. A high-strength polypyrrole in-situ grown napkin / natural rubber-hydrogel composite double-layer intelligent deformation material prepared according to the preparation method according to any one of claims 1 to 8.

10. Use of the high-strength polypyrrole in-situ grown napkin / natural rubber-hydrogel composite double-layer intelligent deformation material according to claim 9 in the preparation of photothermal driven bionic device materials.

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