Cellulose-based asymmetric conductive fiber and its preparation method

Abstract

The present invention discloses a cellulose-based asymmetric conductive fiber and a preparation method thereof. In the method, bacterial cellulose is first dissolved in a ZnCl2 solution, and then a conductive modified bacterial cellulose solution obtained by adding a conductive substance is used as spinning dope 1. At the same time, oxidized bacterial cellulose obtained by oxidation with sodium periodate is dissolved in a ZnCl2 solution, and the obtained oxidized bacterial cellulose solution is used as spinning dope 2. Finally, a cellulose-based asymmetric conductive fiber is prepared by a wet spinning process of coaxial spinning. The present invention uses renewable bacterial cellulose as a raw material, adopts a recyclable ZnCl2 solution as a dissolution system, and obtains an asymmetric conductive fiber with oxidized bacterial cellulose fibers on one side and conductive modified bacterial cellulose fibers on the other side through simple coaxial spinning, which is applicable to fields such as solar evaporation, seawater collection, actuators, sensors, and biomedicine.

Description

Technical Field

[0001] The present invention belongs to the technical field of biomedical materials, and relates to a cellulose-based asymmetric conductive fiber and a preparation method thereof. Background Art

[0002] There are many ways to conductively modify materials, such as material carbonization, conductive material doping, conductive material compounding, conductive layer coating, etc. Conductive polymers have excellent electrical conductivity and flexibility. By doping or post-treating materials with conductive polymers, the modified materials can meet specific requirements. Poly(3,4-ethylenedioxythiophene) (PEDOT) has attracted great attention due to its high electrical conductivity, excellent biocompatibility and biodegradability, easy synthesis and low cost. In Literature 1, by means of in-situ interfacial polymerization, bacterial cellulose pretreated by freezing was immersed in an ether solution containing 0.025 g / ml EDOT monomer and 0.05 g / ml FeCl3. After soaking for a period of time, the PEODT / BC composite nanofibers were washed with ethanol. The prepared PEODT / BC composite nanofibers have good cell compatibility and can enable the directional growth of nerve cells after applying corresponding electrical stimulation (Chuntao, Chen, Ting, et al. Three-Dimensional BC / PEDOT Composite Nanofibers with High Performance for Electrode–Cell Interface[J]. ACS Applied Materials&Interfaces, 2015, 7(51):28244-28253. DOI:10.1021 / acsami.5b07273.).

[0003] At present, the research on asymmetric materials mainly focuses on asymmetric nanoparticles, and there are few reports on asymmetric fibers. There are mainly two existing methods for preparing asymmetric fibers: (1) Electrospinning to prepare asymmetric conductive fibers. For example, in Reference 2, camphorsulfonic acid-doped polyaniline and polyethylene oxide were electrospun into side-by-side bicomponent fibers. This method uses a mixed solution of chloroform and dimethylformamide to dissolve polyaniline, camphorsulfonic acid, and polyethylene oxide to prepare a spinning dope. A large amount of organic matter is required, and the prepared asymmetric conductive fibers are brittle and have very poor mechanical properties. The breaking strength can only reach 5 ± 1 MPa (Liu W, Zhang J, Liu H. Conductive Bicomponent Fibers Containing Polyaniline Produced via Side-by-Side Electrospinning[J]. Polymers, 2019, 11(6):954-. DOI:10.3390 / polym11060954). However, in the traditional electrospinning process, a spinning dope with strong fluidity is required, and some spinning dopes with very high viscosities are not suitable for electrospinning; (2) Wet spinning to prepare asymmetric conductive fibers. For example, in Reference 3, polyacrylonitrile and polyaniline were dissolved in dimethyl sulfoxide, and dimethyl sulfoxide at 60 °C was used as a coagulation bath to prepare asymmetric fibers with polyacrylonitrile-doped polyaniline on one side and polyaniline on the other side. The asymmetric fibers prepared by this method have obvious boundaries, the binding strength of the asymmetric fibers on both sides is poor, and they are easily broken and separated. In addition, the solvents and coagulation baths used cannot be recycled (Liu W, Chang Y C, Zhang J, et al. Wet-Spun Side-by-Side Electrically Conductive Composite Fibers[J]. ACS Applied Electronic Materials, 2022, 4(4):1979-1988. DOI:10.1021 / acsaelm.2c00150.). Summary of the Invention

[0004] The object of the present invention is to provide a cellulose-based asymmetric conductive fiber with strong mechanical properties and a preparation method thereof. One side of the cellulose-based asymmetric conductive fiber is an oxidized bacterial cellulose fiber, and the other side is a conductive modified bacterial cellulose fiber.

[0005] The technical solution for achieving the object of the present invention is as follows:

[0006] A preparation method of a cellulose-based asymmetric conductive fiber, comprising the following steps:

[0007] Step 1, dissolve bacterial cellulose: Dissolve bacterial cellulose in a 65wt% - 70wt% ZnCl2 solution to obtain a uniformly dispersed bacterial cellulose solution with a bacterial cellulose concentration of 1.7 ± 0.1wt%.

[0008] Step 2, conductively modify bacterial cellulose: Add a conductive substance to the bacterial cellulose solution and stir well to disperse it evenly to obtain spinning dope 1.

[0009] Step 3, oxidize bacterial cellulose: Add sodium periodate to the aqueous bacterial cellulose solution and oxidize it at 50 ± 10°C for 3 - 5 h in the dark to obtain oxidized bacterial cellulose. Then dissolve the oxidized bacterial cellulose in a 65wt% - 70wt% ZnCl2 solution to obtain spinning dope 2 with a concentration of oxidized bacterial cellulose of 2 ± 0.1wt%.

[0010] Step 4, preparation of cellulose-based asymmetric conductive fibers: Use spinning dope 1 and spinning dope 2 as the spinning solutions and adopt a coaxial wet spinning method to collect the cellulose-based asymmetric conductive fibers obtained by wet spinning in an anhydrous ethanol coagulation bath.

[0011] Preferably, in step 2, the mass ratio of the conductive substance to bacterial cellulose is 1:4.

[0012] Preferably, in step 2, the conductive substance is selected from polypyrrole, polythiophene, polyaniline, poly(3,4-ethylenedioxythiophene), graphene oxide, carbon nanotubes, etc.

[0013] Preferably, in step 3, the solid content of the aqueous bacterial cellulose solution is 1%, and the mass ratio of sodium periodate to bacterial cellulose is 1.4:1.

[0014] Preferably, in step 4, the spinning speeds of the two axes are the same, both being 100 ml / h.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] (1) The present invention uses a coaxial wet spinning method to prepare cellulose-based asymmetric conductive fibers. Driven by the mechanical power of a peristaltic pump, the obtained cellulose-based asymmetric conductive fibers are coagulated and regenerated in anhydrous ethanol. This method is simple and easy to operate, and the solvents and coagulation baths used can be recycled. After the fibers are coagulated and regenerated, a large amount of ZnCl2 precipitates in the coagulation bath after standing for a period of time. Ethanol and ZnCl2 can be separated by simple filtration. The separated ethanol can be used as the coagulation bath again, and the separated ZnCl2 can be recycled after drying treatment.

[0017] (2) The present invention uses bacterial cellulose, which is rich in content, renewable, and has strong mechanical properties, as the basic raw material. The preparation method is simple and environmentally friendly, suitable for large-scale production. The prepared asymmetric microfibers are expected to be applied in fields such as actuators, textiles, biomedicine, and sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It shows a bacterial cellulose solution (a), a schematic diagram of the method for preparing asymmetric conductive fibers (b), a physical picture of the cellulose-based asymmetric fiber (c), and a physical picture of recovering ZnCl2 and ethanol in a static coagulation bath (d).

[0019] Figure 2 It shows a physical picture of wet bacterial cellulose fibers (a), a physical picture of wet conductive modified bacterial cellulose fibers (b), a physical picture of wet oxidized bacterial cellulose fibers (c), and a physical picture of wet asymmetric conductive fibers (d).

[0020] Figure 3 It shows the cyclic voltammogram (a) and the alternating current impedance spectrum (b) of bacterial cellulose, PEDOT, and GO conductive modified bacterial cellulose fibers.

[0021] Figure 4 It shows the tensile property diagram (a) of bacterial cellulose fibers prepared from bacterial cellulose solutions with different concentrations and the tensile property diagram (b) of pure bacterial cellulose fibers, conductive modified bacterial cellulose fibers, oxidized modified bacterial cellulose fibers, and asymmetric conductive modified bacterial cellulose fibers.

[0022] Figure 5 It shows the elemental mapping analysis diagram of the scanning electron microscope of Region 1 (oxidized modified side) of the cellulose-based asymmetric conductive fiber.

[0023] Figure 6 It shows the elemental mapping analysis diagram of the scanning electron microscope of Region 2 (conductive modified side) of the cellulose-based asymmetric conductive fiber. DETAILED DESCRIPTION OF THE INVENTION

[0024] The present invention will be further described below in conjunction with specific embodiments and the drawings.

[0025] Example 1

[0026] Preparation of bacterial cellulose fibers:

[0027] (1) Take 65 g of ZnCl2 and dissolve it in 35 g of deionized water. Stir at 80 °C until the solution is clear, then add 1.7 g of bacterial cellulose. Stir at 70 °C - 80 °C until the cellulose is completely dissolved to obtain a homogeneous, transparent bacterial cellulose solution with a bacterial cellulose concentration of 1.7 wt%.

[0028] (2) Using the bacterial cellulose solution as the spinning solution, set the spinning speed of the peristaltic pump to 100 ml / h. The solution ejected from the syringe directly enters the absolute ethanol coagulation bath to obtain bacterial cellulose fibers.

[0029] (3) Collect the coagulation bath, let it stand for 2 h, filter and dry to recover the solute ZnCl2 and the coagulation bath ethanol.

[0030] (4) Soak the bacterial cellulose fibers repeatedly with a large amount of deionized water, and collect the bacterial cellulose fibers at room temperature.

[0031] Example 2

[0032] Preparation of conductive modified bacterial cellulose fibers:

[0033] (1) Take 65 g of ZnCl2 and dissolve it in 35 g of deionized water. Stir at 80 °C until the solution is clear, then add 1.7 g of bacterial cellulose. Stir at 70 °C - 80 °C until the cellulose is completely dissolved to obtain a homogeneous and transparent bacterial cellulose solution with a bacterial cellulose concentration of 1.7 wt%.

[0034] (2) Add 0.04 g of PEDOT to 10 g of the bacterial cellulose solution and stir magnetically for 2 h to obtain a conductive modified bacterial cellulose solution.

[0035] (3) Using the conductive modified bacterial cellulose solution as the spinning solution, set the spinning speed of the peristaltic pump to 100 ml / h. The solution ejected from the syringe directly enters the absolute ethanol coagulation bath to obtain conductive modified bacterial cellulose fibers.

[0036] (4) Collect the coagulation bath, let it stand for 2 h, filter and dry to recover the solute ZnCl2 and the coagulation bath ethanol.

[0037] (5) Soak the conductive modified bacterial cellulose fibers repeatedly with a large amount of deionized water, and collect the conductive modified bacterial cellulose fibers at room temperature.

[0038] Example 3

[0039] Preparation of oxidized modified bacterial cellulose fibers:

[0040] (1) Add 5.6 g of sodium periodate to 400 g of a bacterial cellulose aqueous solution with a solid content of 1%. Under light-shielded conditions, oxidize at 50 °C for 5 h. Then add the oxidized bacterial cellulose aqueous solution into a dialysis bag and dialyze for 7 days, followed by freeze-drying to obtain solid oxidized bacterial cellulose.

[0041] (2) Dissolve 65 g of ZnCl₂ in 35 g of deionized water. Stir at 80 °C until the solution is clear, then add 2 g of oxidized bacterial cellulose. Stir in an environment of 70 °C - 80 °C until the oxidized bacterial cellulose is completely dissolved to obtain a homogeneous and transparent oxidized bacterial cellulose solution with an oxidized bacterial cellulose concentration of 2%.

[0042] (3) Using the oxidized modified bacterial cellulose solution as the spinning solution, set the spinning speed of the peristaltic pump to 100 ml / h. The solution ejected from the syringe directly enters the anhydrous ethanol coagulation bath to prepare oxidized modified bacterial cellulose fibers.

[0043] (4) Collect the coagulation bath, let it stand for 2 h, filter and dry to recover the solute ZnCl₂ and the coagulation bath ethanol.

[0044] (5) Soak the oxidized modified bacterial cellulose fibers repeatedly with a large amount of deionized water, and dry them at room temperature to collect the oxidized modified bacterial cellulose fibers.

[0045] Example 4

[0046] Preparation of cellulose-based asymmetric conductive fibers:

[0047] (1) Prepare the conductive modified bacterial cellulose solution in the same way as in Example 2.

[0048] (2) Prepare the oxidized modified bacterial cellulose solution in the same way as in Example 3.

[0049] (3) Using the conductive modified bacterial cellulose solution as spinning solution 1 and the oxidized modified bacterial cellulose solution as spinning solution 2, with a dual-channel peristaltic pump, set the spinning speed of both channels to 100 ml / h. The solution ejected from the Y-shaped needle directly enters the anhydrous ethanol coagulation bath to prepare cellulose-based asymmetric conductive fibers with oxidized bacterial cellulose fibers on one side and conductive modified bacterial cellulose fibers on the other side.

[0050] (4) Collect the coagulation bath, let it stand for 2 h, filter and dry to recover the solute ZnCl₂ and the coagulation bath ethanol.

[0051] (5) Soak the cellulose-based asymmetric conductive fibers repeatedly with a large amount of deionized water, and dry them at room temperature to collect the cellulose-based asymmetric conductive fibers.

[0052] Example 5

[0053] This example is substantially the same as Example 2, and the only difference is that PEDOT is replaced with graphene oxide (GO) to prepare GO conductive modified bacterial cellulose fibers.

[0054] Figure 1 (a) is a physical picture of the bacterial cellulose solution prepared in Example 1. It can be seen that the viscosity of the bacterial cellulose solution is very high. Figure 1(b) Schematic diagram of preparing asymmetric fibers by biaxial co - spinning, Figure 1 (c) Physical picture of the cellulose - based asymmetric conductive fiber prepared in Example 4, Figure 1 (d) Physical pictures of collecting the coagulation bath, standing and recycling ZnCl2 and ethanol.

[0055] Figure 2 (a) Physical picture of the wet bacterial cellulose fiber prepared in Example 1, Figure 2 (b) Physical picture of the wet conductive modified bacterial cellulose fiber prepared in Example 2, Figure 2 (c) Physical picture of the wet oxidation - modified bacterial cellulose fiber prepared in Example 3, Figure 2 (d) Physical picture of the wet cellulose - based asymmetric conductive fiber prepared in Example 4. It can be clearly observed that the surfaces of the four fibers are smooth and flat.

[0056] Figure 3 Cyclic voltammetry curves (a) and AC impedance diagrams (b) of bacterial cellulose, PEDOT - doped bacterial cellulose, and GO - doped bacterial cellulose. It can be seen from the figures that the electrochemical properties of bacterial cellulose doped with conductive substances have been greatly improved.

[0057] Figure 4 (a) Comparative diagram of the mechanical properties of fibers obtained by dissolving bacterial cellulose at different concentrations. It can be seen that as the mass concentration of bacterial fiber increases, the breaking strength of the fiber increases, while the elongation at break first increases and then decreases. Through comprehensive comparison, it can be concluded that the fiber prepared when the concentration of bacterial cellulose is 1.7% has the best mechanical properties. Figure 4 (b) Comparative diagram of the mechanical properties of the four fibers prepared in Examples 1 - 4. It can be seen from the figure that both conductive modification and oxidation modification will reduce the mechanical properties of the fiber. However, after making the two modified solutions into asymmetric fibers, the mechanical properties of the asymmetric fibers are improved to a certain extent.

[0058] Figure 5 、 6 Cross - sectional scanning electron microscopy images and elemental analysis diagrams of the oxidation - modified side and conductive - modified side of the cellulose - based asymmetric conductive fiber. Through elemental analysis, it can be seen that the oxidation - modified side does not contain the unique element S of PEDOT, while the conductive - modified side contains the unique element S of PEDOT. The chemical compositions on both sides of the asymmetric fiber are different, proving that the asymmetric - structured fiber has been successfully prepared. In addition, it can be seen from the figure that the content of Zn element is small, indicating that Zn in the fiber can be removed after soaking and washing with a large amount of deionized water.

Claims

1. Preparation method of cellulose-based asymmetric conductive fiber, characterized in that, It includes the following steps: Step 1, dissolve bacterial cellulose: Dissolve bacterial cellulose in a 65 wt% - 70 wt% ZnCl2 solution to obtain a bacterial cellulose solution with a uniformly dispersed bacterial cellulose concentration of 1.7 ± 0.1 wt%. Step 2, conductively modify bacterial cellulose: Add a conductive substance to the bacterial cellulose solution and stir well to make it uniformly dispersed to obtain spinning dope 1. Step 3, oxidize bacterial cellulose: Add sodium periodate to the aqueous bacterial cellulose solution, and under light - avoiding conditions, oxidize it at 50 ± 10 °C for 3 - 5 h to obtain oxidized bacterial cellulose. Then dissolve the oxidized bacterial cellulose in a 65 wt% - 70 wt% ZnCl2 solution to obtain spinning dope 2 with an oxidized bacterial cellulose concentration of 2 ± 0.1 wt%. Step 4, preparation of cellulose - based asymmetric conductive fiber: Using spinning dope 1 and spinning dope 2 as spinning solutions, adopt a co - axial wet spinning method to collect the cellulose - based asymmetric conductive fiber obtained by wet spinning in an absolute ethanol coagulation bath.

2. The preparation method according to claim 1, wherein In Step 2, the mass ratio of the conductive substance to bacterial cellulose is 1:

4.

3. The preparation method according to claim 1, characterized in that, In Step 2, the conductive substance is selected from polypyrrole, polythiophene, polyaniline, poly(3,4 - ethylenedioxythiophene), graphene oxide, or carbon nanotubes.

4. The preparation method according to claim 1, characterized in that, In Step 3, the solid content of the aqueous bacterial cellulose solution is 1%, and the mass ratio of sodium periodate to bacterial cellulose is 1.4:

1.

5. The preparation method according to claim 1, characterized in that, In Step 4, the spinning speeds of the two axes are the same, both being 100 ml / h.

6. A cellulose - based asymmetric conductive fiber prepared by the preparation method according to any one of claims 1 - 5.

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