High-toughness and high-conductivity magnetic chitin-based composite hydrogel and preparation method thereof

Abstract

The invention discloses magnetic chitin-based composite hydrogel with high toughness and high conductivity and a preparation method of the magnetic chitin-based composite hydrogel. According to the preparation method, a bio-based natural polymer material chitin is taken as a main raw material, the bio-based natural polymer material chitin is compounded with a magnetic conductive Fe3O4 / C micromolecular carbon material, and a magnetic field assisted orientation strategy is innovatively adopted, so that the chitin-Fe3O4 / C composite hydrogel (CEF) with an oriented nanostructure is successfully prepared. The obtained hydrogel has excellent mechanical flexibility and high conductivity, and can be applied to preparation of flexible electronic systems (including electronic skin interfaces and advanced wearable biomedical equipment).

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of carbon nanocomposite material preparation, and particularly relates to a magnetic bio-based chitin-Fe3O4 / C composite hydrogel with high toughness and high conductivity as well as a preparation method and application thereof. BACKGROUND

[0002] The growing demand for intelligent portable devices has driven extensive research into wearable technology, including reusable patches and textile systems that integrate flexible, stretchable, and self-healing electronic components. These devices have great potential in applications such as prosthetics, biosignal detection, haptic feedback, and real-time health monitoring. One key requirement for such skin-conformable electronic components is biocompatibility with human tissues. However, traditional rigid materials such as metals and semiconductors lack these biomimetic properties, limiting their suitability for seamless integration with biological systems. Therefore, replicating the mechanical and functional properties of human skin, such as flexibility, dynamic stimulus responsiveness, and intrinsic stretchability, remains a challenge.

[0003] Hydrogels, as three-dimensional networks of crosslinked natural or synthetic polymers, are considered ideal candidates for skin-like materials in wearable technology due to their excellent flexibility and biocompatibility. Their network structure and mechanical properties can be precisely adjusted through chemical and physical methods, such as chemical crosslinking of chitin with epichlorohydrin (ECH) or non-covalent mediation with tannic acid (TA) to enhance crosslinking strength. This structural engineering enables hydrogels to mimic the flexibility and stretchability of biological skin. Although most hydrogels are electrical insulators, their conductivity can be enhanced by adding inorganic / organic fillers such as carbon nanotubes, graphene, MXenes, polypyrrole, or polyaniline. Metal-organic frameworks (MOFs) are a class of hybrid porous crystalline materials formed by bridging functional organic ligands with metal centers (ions or clusters). Due to their tunable metal centers, diverse organic ligands, and precisely adjustable pore structures, MOFs have great potential in energy storage, catalysis, and electrochemistry. Notably, MOFs can serve as precursors for deriving porous carbon-based metal oxide composite materials, a feature that has attracted significant attention in the field of electrochemistry. SUMMARY

[0004] The purpose of the present application is to provide a high-toughness and high-conductivity magnetic chitin-based composite hydrogel and a preparation method thereof. The hydrogel has excellent mechanical flexibility and high conductivity, and can be applied to the preparation of flexible electronic systems, including electronic skin interfaces and advanced wearable biomedical devices.

[0005] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: A high-toughness and high-conductivity magnetic chitin-based composite hydrogel, and a preparation method thereof, comprising the following steps: 1) FeCl3·6H2O and terephthalic acid were dissolved in N,N-dimethylformamide (DMF), and then the mixture was transferred to a Teflon-lined autoclave for hydrothermal treatment. After cooling to room temperature, a red-brown powder was collected by centrifugation, repeatedly washed with DMF and dried overnight to obtain a Fe-MOF in the shape of a spindle; 2) The Fe-MOF obtained in step 1) was placed in a high-temperature tube furnace for step-by-step calcination. After natural cooling to room temperature, a Fe3O4 / C small-molecule carbon material was obtained; 3) The Fe3O4 / C small-molecule carbon material obtained in step 2) was added to a chitin solution and crosslinked by adding epichlorohydrin. After that, the mixture was uniformly spread to realize stretching orientation, and secondary orientation was assisted by an applied magnetic field to form a chitin-Fe3O4 / C composite hydrogel with a directional nanostructure.

[0006] Further, the molar ratio of FeCl3·6H2O to terephthalic acid used in step 1) is 2-4:1.

[0007] Further, the temperature of the hydrothermal treatment in step 1) is 120-150°C, and the time is 12-24 h.

[0008] Further, the step-by-step calcination in step 2) is specifically heating to 280°C at a rate of 3°C / min in air, maintaining for 0.5-2 h to oxidize the framework, and then heating to 580°C at a rate of 3°C / min in a nitrogen atmosphere, maintaining for 1-2 h to convert the MOF into a magnetic Fe3O4 / C while maintaining its morphology and enhancing its conductivity.

[0009] Further, the mass concentration of the chitin solution in step 3) is 3-7 wt%.

[0010] Further, the amount of Fe3O4 / C small-molecule carbon material added to the chitin solution in step 3) is 0.06-0.18 g / 100 mL.

[0011] Further, the mass ratio of epichlorohydrin to chitin used in step 3) is 2-6:100.

[0012] Further, the crosslinking in step 3) is stirring at -10°C for 30 min.

[0013] Further, when the secondary orientation is assisted by an applied magnetic field in step 3), the environmental temperature is -10-0°C, the processing time is 5-10 min, and the direction of the applied magnetic field is parallel to the film plane, so that the spindle-shaped Fe3O4 / C small-molecule carbon material is arranged in parallel in the two-dimensional direction.

[0014] The tensile strength of the magnetic chitin-based composite hydrogel prepared by orientation in the extension film laying process, secondary orientation of magnetic filler rearrangement under the induction of an applied magnetic field is improved, and the Fe3O4 / C small molecule carbon material obtained after calcination can be used as an electronic conductor, and after magnetic field induction, a special conductive path can be formed in the composite hydrogel, so that the electrical conductivity is improved, so that the obtained composite hydrogel can be used for the preparation of flexible electronic systems (including electronic skin interface and advanced wearable biomedical devices).

[0015] The Fe-MOF with a spindle morphology is prepared by adjusting the ratio of metal precursor to ligand, and is converted into magnetic Fe3O4 / C small molecule carbon material through two-step calcination, and then is blended with a chitin solution and epichlorohydrin to crosslink and form a film, and at the same time, the Fe3O4 / C is induced by an applied magnetic field to arrange in the direction of magnetic induction lines to form an ordered conductive network. The directional arrangement induced by the magnetic field not only optimizes the conductive network, but also realizes the significant improvement of the mechanical properties by regulating the crystallization behavior. The directional arrangement of Fe3O4 / C can reduce the crystallinity of the hydrogel, so that the movement ability of the polymer chain segment is enhanced, and at the same time, the magnetic particles as physical crosslinking points can effectively disperse stress to improve the tensile properties of the material.

[0016] Compared with the prior art, the present application has the following advantages: (1) The raw materials of the present application are green and non-toxic, the synthesis process is simple, the process is green and environmentally friendly, and the cost is low.

[0017] (2) The present application does not need any template and pretreatment agent, and can synthesize spindle-shaped iron-based organic metal framework composite material from terephthalic acid and metal iron through one-step hydrothermal method, which is simple in operation and suitable for large-scale industrial production. (3) The composite material of the present application has better mechanical properties in the direction of auxiliary magnetic field construction, and the mechanical properties of the material are improved.

[0018] (4) The composite material of the present application has good electrical properties, shorter resistance response time and more sensitive current change, which promotes the application of natural polymer hydrogel in soft electronic devices and provides a new strategy to balance the mechanical strength and electrical performance functions. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 XRD patterns of Fe-MOF (A) and magnetic Fe3O4 / C (B) prepared in Example 1.

[0020] Figure 2 FESEM images of Fe-MOF (A) and magnetic Fe3O4 / C (B) prepared in Example 1.

[0021] Figure 3 FESEM images of Fe3O4 / C composite films prepared with and without magnetic field induced orientation for Example 2 (A) and Comparative Example 2 (B).

[0022] Figure 4 Tensile property graph of films prepared for Example 2 and Comparative Example 1.

[0023] Figure 5 Transverse and vertical conductivity of chitin-Fe3O4 / C composite films prepared for Example 2. DETAILED DESCRIPTION

[0024] A high-toughness and high-conductivity magnetic chitin-based composite hydrogel, and a preparation method thereof, comprises the following steps: 1) FeCl3·6H2O and terephthalic acid are dissolved in N,N-dimethylformamide (DMF) at a molar ratio of 2-4:1, and then the mixture is transferred to a Teflon-lined autoclave for hydrothermal treatment at 120-150°C for 12-24 h. After cooling to room temperature, a red-brown powder is collected by centrifugation, repeatedly washed with DMF, and dried at 60°C overnight to obtain a Fe-MOF in a spindle shape; 2) The Fe-MOF obtained in step 1) is placed in a high-temperature tube furnace, first heated to 280°C at a rate of 3°C / min in air, and then heated to 580°C at a rate of 3°C / min under a nitrogen atmosphere, and kept for 1-2 h. After natural cooling to room temperature, a Fe3O4 / C small molecular carbon material is obtained; 3) The Fe3O4 / C small molecular carbon material obtained in step 2) is added to a chitin solution with a mass concentration of 3-7 wt% at an amount of 0.06-0.18 g / 100 mL, and epoxy chloropropane (ECH) is added at a mass ratio of 100:2-6 with respect to the mass of the chitin used, and stirred at -10°C for 30 min. Then the mixture is uniformly spread on a flat plate, and placed in an external magnetic field environment at -10-0°C for 5-10 min (the direction of the external magnetic field is parallel to the plane of the film), to form a chitin-Fe3O4 / C composite hydrogel with oriented nanostructure. The C x E y F z represents, wherein x represents the mass percentage of chitin in the hydrogel film, and y and z respectively represent the mass percentage of ECH and Fe3O4 / C added to chitin. For example, C3E4F2 represents that 100 grams of hydrogel contains 3 grams of purified chitin, 0.12 grams of ECH, and 0.06 grams of Fe3O4 / C.

[0025] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0026] The preparation method of the chitin solution used in the embodiment is as follows: at room temperature, NaOH, urea and distilled water are mixed in a mass ratio of 11:4:82 to prepare an alkaline urea solution; then, under stirring, 3 g of chitin powder is dispersed in 97 mL of the obtained alkaline urea solution to form a uniform suspension, and the suspension is subjected to freeze-thaw circulation (i.e., freezing at -30°C for 5 h, stirring to disperse the frozen state to thaw, and repeating 1-2 times) to ensure complete dissolution, and then low-temperature centrifugation (4°C, 8000 rpm) is performed to obtain a transparent, bubble-free 3wt% chitin solution.

[0027] In the embodiment, the test conditions are as follows: the scanning electron microscope (SEM) test instrument is Regulus8100; the HER performance test is performed by using a Shanghai Chenhua CHI660e electrochemical workstation. X-ray powder diffraction (XRD) is tested by using a RIGAKU Ultima IV, and Cu-Ka (x=1.5406A) is used as the radiation source. The mechanical property data of the composite hydrogel are obtained by using a universal mechanical testing machine (UTM, CMT4104, China) with a 200N mechanical sensor, and the tensile test is performed at a tensile speed of 10 mm / min. -1

[0028] Embodiment 1 1) Under stirring, 5.406 grams (0.02 moles) of FeCl3·6H2O and 1.66 grams (0.01 moles) of terephthalic acid are dissolved in 30 milliliters of DMF, and then the mixture is transferred to a Teflon-lined autoclave, which is hydrothermally treated at 150°C for 24 hours. After cooling to room temperature, the red-brown powder is collected by centrifugation, repeatedly washed with DMF, and dried at 60°C overnight to obtain a spindle-shaped Fe-MOF.

[0029] 2) The synthesized Fe-MOF is then placed in a high-temperature tube furnace, first heated to 280°C (3°C / min) in air and kept for 1 hour to partially oxidize the framework, and then further heated to 580°C (3°C / min) under N2 atmosphere and kept for 1 hour to convert the MOF into a magnetic Fe3O4 / C, while maintaining its morphology and enhancing its electrical conductivity. After natural cooling to room temperature, a Fe3O4 / C small molecular carbon material is obtained.

[0030] Embodiment 2 ​0 g, 0.06 g, 0.12 g, 0.18 g of Fe3O4 / C obtained in Example 1 was added into 100 mL of chitin solution at -10 ℃, respectively, and 0.12 g of ECH was added dropwise, and after continuous stirring for 30 min, the mixture was uniformly spread on a flat plate to form a chitin-Fe3O4 / C composite hydrogel film with a directed nanostructure, which was labeled as C3E4F0, C3E4F2, C3E4F4, C3E4F6, respectively.

[0031] Comparative Example 1 0 g, 0.06 g, 0.12 g, 0.18 g of ECH was added dropwise into 100 mL of chitin solution at -10 ℃, respectively, and after continuous stirring for 30 min, the mixture was uniformly spread on a flat plate to form an epoxy chloropropane cross-linked chitin hydrogel film, which was labeled as C3E0F0, C3E2F0, C3E4F0, C3E6F0, respectively.

[0032] Comparative Example 2 0.06 g of Fe3O4 / C obtained in Example 1 was added into 100 mL of chitin solution at -10 ℃, followed by the addition of 0.12 g of epoxy chloropropane, and after continuous stirring for 30 min, the mixture was uniformly spread on a flat plate to form a chitin-Fe3O4 / C composite hydrogel film.

[0033] The phase composition of Fe-MOF and magnetic Fe3O4 / C prepared in Example 1 was analyzed by X-ray powder diffraction (XRD), and the results are shown in FIG. 1. Figure 1 As can be seen from FIG. 1, the Fe-MOF has clear diffraction peaks at 9.1°, 12.8°, 17.2°, 18.9°, 21.6°, 24.3° and 28.1°, which correspond to (020), (011), (040), (121), (031), (132) and (211) facets, respectively. The diffraction peaks of the magnetic Fe3O4 / C obtained after step-by-step calcination match the cubic Fe3O4. This proves that the Fe-MOF is converted to Fe3O4 after step-by-step calcination, and also proves the successful preparation of Fe3O4 / C. Figure 1

[0034] Figure 2 The high-magnification SEM images of Fe-MOF and magnetic Fe3O4 / C prepared in Example 1 are shown in FIG. 2. As can be seen from the figure, the obtained Fe-MOF presents a typical spindle shape, and its original structure is basically retained after step-by-step calcination.

[0035] Figure 3 ​FESEM images of the chitin-Fe3O4 / C composite film C3E4F2 prepared by external magnetic induction for Example 2 and the chitin-Fe3O4 / C composite film prepared without external magnetic induction for Comparative Example 2. As can be seen from the figure, after induction by the external magnetic field, Fe3O4 / C in the film is arranged in the direction of the two-dimensional magnetic field.

[0036] The mechanical properties of the prepared composite hydrogel film at-20℃ were quantitatively analyzed by using a universal tensile testing machine, and the results are shown in Figure 4 As can be seen from the figure, the original chitin hydrogel (C3E0F0) has a lower tensile breaking strength (0.33 MPa) and tensile breaking elongation (121.5%); the addition of epichlorohydrin improves the tensile breaking strength of the hydrogel to 0.59 MPa; and the simultaneous addition of epichlorohydrin and spindle Fe3O4 / C further improves the tensile breaking strength of the hydrogel to 0.82 MPa.

[0037] By installing a conductive copper foil with appropriate thickness on both sides of the composite hydrogel to connect an electrochemical workstation, a sandwich-structured sensing device is assembled, and then the horizontal and vertical conductivities of the hydrogel are measured, respectively. The conductivity is obtained by the formula , wherein L is the thickness of the material, R is the resistance of the material, and S is the cross-sectional area of the material between the electrodes.

[0038] As shown in Figure 5 , the horizontal average resistance of C3E0F0, C3E4F0, C3E4F2, C3E4F4 and C3E4F6 is 222.4, 191.2, 51.5, 107.8 and 136.3 Ω, respectively, and the conductivity thereof is 26.97, 31.38, 116.51, 55.65 and 44.02 S / m, respectively; the vertical average resistance thereof is 126.3, 100.2, 30.2, 58.1 and 70.6 Ω, respectively, and the conductivity thereof is 27.71, 34.12, 138.52, 63.23 and 52.24 S / m, respectively. It can be seen that the conductivity on the vertical path formed by magnetic field induction is greatly enhanced compared with the horizontal state, and the conductivity of the composite hydrogel C3E4F2 is the highest (138.52 S / m).

[0039] The above only describes the preferred embodiments of the present application, and any equivalent changes and modifications made within the scope of the patent application of the present application shall be included in the scope of the present application.

Claims

1. A method for preparing a high-toughness, high-conductivity magnetic chitin-based composite hydrogel, characterized in that: Includes the following steps: 1) Dissolve FeCl3·6H2O and terephthalic acid in N,N-dimethylformamide, then perform hydrothermal treatment. After cooling to room temperature, collect the reddish-brown powder by centrifugation, wash repeatedly with DMF and dry overnight to obtain spindle-shaped Fe-MOF; 2) The Fe-MOF obtained in step 1) is calcined in steps and then naturally cooled to room temperature to obtain Fe3O4 / C small molecule carbon material; 3) The Fe3O4 / C small molecule carbon material obtained in step 2) is added to the chitin solution, and epichlorohydrin is added for cross-linking. Then the mixture is uniformly laid to achieve stretching and orientation. At the same time, an external magnetic field is used to induce secondary orientation to form a chitin-Fe3O4 / C composite hydrogel with oriented nanostructure.

2. The preparation method according to claim 1, characterized in that: The molar ratio of FeCl3·6H2O and terephthalic acid used in step 1) is 2~4:

1.

3. The preparation method according to claim 1, characterized in that: The hydrothermal treatment in step 1) is performed at a temperature of 120~150℃ for 12~24 h.

4. The preparation method according to claim 1, characterized in that: The stepwise calcination described in step 2) specifically involves heating to 280°C in air at a rate of 3°C / min and holding for 0.5 to 2 hours, followed by heating to 580°C in a nitrogen atmosphere at a rate of 3°C / min and holding for 1 to 2 hours.

5. The preparation method according to claim 1, characterized in that: The chitin solution in step 3) has a mass concentration of 3-7%.

6. The preparation method according to claim 1, characterized in that: In step 3), the amount of Fe3O4 / C small molecule carbon material added to the chitin solution is 0.06~0.18 g / 100 mL; the mass ratio of epichlorohydrin to chitin used is 2~6:

100.

7. The preparation method according to claim 1, characterized in that: The crosslinking described in step 3) is performed by stirring at -10°C for 30 min.

8. The preparation method according to claim 1, characterized in that: In step 3), the ambient temperature for secondary orientation induced by an external magnetic field is -10 to 0°C, the processing time is 5 to 10 minutes, and the direction of the external magnetic field is parallel to the thin film plane.

9. A magnetic chitin-based composite hydrogel prepared by the method described in claim 1.

10. The application of the magnetic chitin-based composite hydrogel as described in claim 9 in a flexible electronic system.

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