A nanocellulose-based flexible thermoelectric material and its preparation method

Abstract

The present invention provides a nanocellulose-based flexible thermoelectric material and a preparation method thereof, belonging to the technical field of thermoelectric materials. The method comprises: adding an oxidant solution and a conductive polymer monomer to an anionic surfactant solution of a certain concentration. After reacting for a period of time at a certain temperature, the nanocellulose solution, the oxidant and the conductive polymer monomer are added in sequence. After reacting for a period of time, the material is centrifuged, the precipitate is removed, and the conductive polymer-nanocellulose material is obtained by repeated dissolution and centrifugation with a certain ratio of ethanol-water solution. The method of the present invention is simple and efficient, and the yield of the obtained conductive polymer-nanocellulose is high, the material has excellent thermoelectric properties, and has broad application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of thermoelectric materials, and in particular to a nano-cellulose-based flexible thermoelectric material and a preparation method thereof. Background Art

[0002] Solid-state power generation technology, a core technology for developing distributed clean energy or microgrids, can be categorized into three types: piezoelectric, triboelectric, and thermoelectric. Thermoelectric technology, currently widely used in thermoelectric power generation for military aerospace equipment, medical devices, and other applications, holds the greatest potential. Traditional thermoelectric devices are based on aluminum oxide and copper sheets, which are highly brittle. Environmental factors can lead to poor compatibility and significant performance degradation in microdevices during practical applications. Therefore, the development of flexible and micromachinable device materials is crucial for addressing challenges such as reduced thermoelectric efficiency associated with device miniaturization.

[0003] Organic semiconductors are a new type of material that combines high electrical conductivity with low thermal conductivity. Common types include acetylene, aniline, and thiophene. Among them, poly(3,4-ethylenedioxythiophene), an organic polymer belonging to the thiophene family, is a widely studied conductive material with characteristics such as adjustable molecular structure and band gap, as well as high electrical conductivity. However, the defects of high-purity poly(3,4-ethylenedioxythiophene) such as poor water solubility, low mechanical strength, and inability to form self-supporting films have seriously restricted its performance, application, and development. Traditional countermeasures, such as the use of surfactant coating (poly(3,4-ethylenedioxythiophene: poly(styrene sulfonate)), will reduce the overall conductivity of the material due to the wrapping of the low-conductivity surfactant component on the conductive host material. Therefore, people often hope to in situ polymerize poly(3,4-ethylenedioxythiophene) on the surface of organic materials to maintain the overall conductivity, flexibility, and film processability of the material for use in microdevices.

[0004] Nanocellulose is extracted from natural cellulose sources (wood, bamboo, etc.) and has the characteristics of high aspect ratio, high strength, low thermal conductivity and easy modification. This effectively meets the high strength, low thermal conductivity and lightweight flexibility requirements of thermoelectric device plates. Therefore, it is also widely used in devices such as solar cells, micro sensors and wearable devices. For example, Chinese patent CN117903471A prepares a bacterial cellulose flexible conductive gel film material with a dense surface layer and a loose inner layer by in-situ polymerization of conductive polymer monomers and doping with negatively ionized nanocrystals. The product has a conductivity of 10 -4 ~10 -1 S cm -1Order of magnitude; Chinese patent CN117558977A prepares highly conductive nanocellulose by introducing sulfosalicylic acid as an interface adhesive between 3,4-ethylenedioxythiophene and nanocellulose. In addition, there are also literature reports that polydopamine is added as an adhesive to prepare poly3,4-ethylenedioxythiophene-polydopamine-nanocellulose conductive nanofibers with a core-sheath structure.

[0005] However, the cellulose conductive materials reported so far have certain problems:

[0006] (1) Since cellulose itself is not conductive and its chemical reaction active sites are relatively dispersed, the current method of polymerizing conductive polymers on cellulose using in situ polymerization often makes it difficult to combine conductive polymer chains in the overall internal structure of cellulose (film, block, etc.) to form a uniform and coherent conductive path.

[0007] (2) Although the addition of viscous substances such as polymers can improve the compatibility between material components, most additives do not have good electrical conductivity. Therefore, the conductivity of the conductive material prepared by this method will decrease due to the decrease in the proportion of conductive components, which is not conducive to its application in the thermoelectric field.

[0008] Therefore, building a strong conductive network with cellulose as the skeleton is crucial for preparing flexible cellulose-based materials with high thermoelectric efficiency, and is also one of the key issues in further applying cellulose special materials in the thermoelectric field. Summary of the Invention

[0009] The purpose of the present invention is to provide a nanocellulose-based flexible thermoelectric material and a preparation method thereof, so as to achieve uniform polymerization of conductive polymer materials in the overall structure of nanocellulose without the need for additional adhesives, thereby obtaining a nanocellulose-based flexible thermoelectric material with high conductivity.

[0010] To achieve the above objectives, the present technical solution provides a method for preparing a nanocellulose-based flexible thermoelectric material, comprising the following steps:

[0011] An oxidant and a conductive polymer monomer are added to an anionic surfactant solution to react and obtain a fibrous conductive polymer, wherein the oxidant contains iron or amine radicals;

[0012] Nanocellulose solution, oxidant and conductive polymer monomer are sequentially added to the fibrous conductive polymer and reacted to obtain nanocellulose-based flexible thermoelectric material.

[0013] This scheme gradually adds an oxidant to the conductive polymer monomer to form latex particles, and uses the latex particles as templates to polymerize fibrous conductive polymers through the conductive polymer monomer. A large number of long-chain fibrous conductive polymers are polymerized on the surface of nanocellulose under the action of electric charge to form long-chain conductive polymer segments. These long-chain conductive polymers can not only evenly cover the surface of nanocellulose, but also act as bridges to promote electron transfer between nanocelluloses, so that the final nanocellulose-based flexible thermoelectric material has high conductivity.

[0014] Furthermore, the anionic surfactant of this embodiment is selected from one or any combination of sulfate anionic surfactant, sulfonic acid anionic surfactant or fatty acid salt anionic surfactant. Preferably, the anionic surfactant is selected from sulfonic acid anionic surfactant, and the sulfonic acid group (-OSO3 - Since sulfonate groups generally exist as counterions of conductive polymers, when sulfonate groups are present on the surface of nanocellulose, the fibrous conductive polymer can better exert its conductive effect.

[0015] Furthermore, when the anionic surfactant is a fatty acid salt anionic surfactant, the anionic surfactant is one or a combination of two or more of sodium fatty acid methyl ester sulfonate, fatty acid sulfoalkyl ester, fatty acid sulfoalkylamide, and sodium succinate sulfonate.

[0016] Furthermore, when the anionic surfactant is a sulfate-based anionic surfactant, the anionic surfactant is one or a combination of two or more of sulfated castor oil, sodium lauryl sulfate, sodium hexadecyl sulfate, sodium octadecyl sulfate, and sulfonated lignin.

[0017] Furthermore, when the anionic surfactant is a sulfonic acid anionic surfactant, the anionic surfactant is one or a combination of two or more of dioctyl sodium sulfosuccinate, sodium dodecylbenzenesulfonate, sodium hexadecylbenzenesulfonate, and sodium octadecylbenzenesulfonate.

[0018] Preferably, the anionic surfactant is selected from sodium lauryl sulfate, or the anionic surfactant is selected from a combination of sodium lauryl sulfate and one or more combinations of sodium fatty acid methyl ester sulfonate, fatty acid sulfoalkyl ester, fatty acid sulfoalkylamide, sodium succinate sulfonate, sulfated castor oil, sodium hexadecyl sulfate, sodium octadecyl sulfate, sulfonated lignin, dioctyl sodium sulfosuccinate, sodium dodecylbenzenesulfonate, sodium hexadecylbenzenesulfonate, and sodium octadecylbenzenesulfonate.

[0019] Furthermore, the concentration of the anionic surfactant is (5-100) mmol anionic surfactant / 100 mL water. Preferably, the concentration of the anionic surfactant is (5-30) mmol / 100 mL water.

[0020] Furthermore, the purpose of the oxidant containing iron or an amine radical is to initiate the polymerization reaction and simultaneously oxidize the conductive polymer monomer to help form the conductive polymer conjugated chain and charge carriers (such as holes). When the oxidant contains iron, the oxidant is selected from one or more combinations of ferric chloride, ferric p-toluenesulfonate, ferric hydroxide, and ferric nitrate. When the oxidant contains an amine radical, the oxidant is selected from ammonium persulfate.

[0021] Preferably, the oxidant is selected from ferric chloride, or a combination of ferric chloride and one or more of ferric p-toluenesulfonate, ammonium persulfate, ferric hydroxide, and ferric nitrate.

[0022] Furthermore, the molar ratio of the oxidant, the conductive polymer monomer, and the anionic surfactant is (1-50:1-50:1-100). This has the advantage of maintaining the stable formation of the oxidant-containing micelle particles to polymerize long-chain conductive polymer fibers.

[0023] Preferably, the molar ratio of the conductive polymer monomer to the oxidant is 8:16.

[0024] Furthermore, the conductive polymer monomer includes one or a combination of two or more of poly (3,4-ethylenedioxythiophene), polyaniline, polypyrrole and polythiophene.

[0025] Preferably, the conductive polymer monomer is selected from 3,4-ethylenedioxythiophene monomer, or a combination of 3,4-ethylenedioxythiophene monomer and one or more of polyaniline, polypyrrole and polythiophene.

[0026] Furthermore, an oxidant and a conductive polymer monomer are added to an anionic surfactant solution to react to obtain a fibrous conductive polymer, wherein the reaction conditions are a reaction temperature of 45 to 100° C. and a reaction time of 1 to 24 hours.

[0027] It should be noted that in this scheme, an oxidant is added dropwise to an anionic surfactant solution and a conductive polymer monomer is added, latex particles are formed between the oxidant and the anionic surfactant, and the conductive polymer monomer uses the latex particles as a template to grow rod-shaped fibrous conductive polymers. When the oxidant is ferric chloride and the anionic surfactant is sodium dodecyl sulfate, ferric chloride is added dropwise to the sodium dodecyl sulfate to form ferric chloride latex particles, and the conductive polymer monomer uses the ferric chloride latex particles as a template to polymerize into fibrous conductive polymers.

[0028] Furthermore, nanocellulose solution, oxidant and conductive polymer monomer are added to the fibrous conductive polymer in sequence, reacted at a set reaction temperature for a period of time and then centrifuged. The lower layer of the centrifuged precipitate is taken and repeatedly dissolved and centrifuged with ethanol aqueous solution to obtain a nanocellulose-based flexible thermoelectric material.

[0029] Furthermore, the nanocellulose solution is a solution containing -OSO3 - Functional groups of sulfurized nanocellulose.

[0030] Furthermore, the mass concentration of the nanocellulose solution is 0.1-1.0 wt %. This has the advantage of controlling the viscosity of the nanocellulose solution to prevent affecting the progress of the polymerization reaction system.

[0031] Furthermore, in the step of sequentially adding the nanocellulose solution, the conductive polymer monomer and the oxidant to the fibrous conductive polymer, the selection of the conductive polymer monomer and the oxidant is the same as that of the conductive polymer monomer and the oxidant when forming the fibrous conductive polymer.

[0032] Furthermore, the molar ratio of the conductive polymer monomer and the oxidant added sequentially to the fibrous conductive polymer is 8:16.

[0033] Furthermore, the nanocellulose solution, the oxidant and the conductive polymer monomer are sequentially added to the fibrous conductive polymer and reacted under the following reaction conditions: a reaction temperature of 45 to 100° C. and a reaction time of 1 to 24 hours.

[0034] Furthermore, after reacting for a period of time at the set reaction temperature, the centrifugal conditions are 6000-10000 r / min and the centrifugal time is 4-10 min. After centrifugation, the upper layer of the solution obtained is a clear orange-yellow solution, and the lower layer is a black precipitate.

[0035] Furthermore, the volume ratio of ethanol to water in the ethanol aqueous solution is 50:(0-100), preferably, the volume ratio of ethanol to water in the ethanol aqueous solution is 50:50.

[0036] Furthermore, the centrifugation conditions of repeated dissolution and centrifugation with ethanol aqueous solution are 6000-10000 r / min and the centrifugation time is 4-10 min. The solution after centrifugation is a clear colorless to light green solution on the upper layer and a black precipitate on the lower layer.

[0037] Furthermore, the yield of the nanocellulose-based flexible thermoelectric material is 50-85%.

[0038] It should be noted that the second addition of nanocellulose, oxidant and conductive polymer monomer in this scheme uses the nanocellulose in the solution as a new polymerization template. The fibrous conductive polymer is polymerized on the surface of the nanocellulose under the charge interaction force to form long-chain segments of conductive polymer. These long-chain conductive polymers can not only be evenly covered on the surface of the nanocellulose, but also act as bridges to promote electron transfer between different roots of nanocellulose to maintain the overall high conductivity of the material. Finally, the residual anionic surfactant in the material can be removed by centrifugation to further improve the overall conductivity of the material.

[0039] This solution additionally provides a nanocellulose-based flexible thermoelectric material, which is obtained according to the above-mentioned method for preparing the nanocellulose-based flexible thermoelectric material, and includes nanocellulose as a substrate and long-chain conductive polymer segments composed of fibrous conductive polymers polymerized on the surface of the nanocellulose.

[0040] Furthermore, the nanocellulose-based flexible thermoelectric materials provided by this solution are applied in the thermoelectric field, such as real-time monitoring equipment in extreme environments, wearable electrode treatment patches, heat recovery devices and other scenarios.

[0041] Compared with the existing technology, this technical solution has the following characteristics and beneficial effects:

[0042] This solution provides a method for preparing a nanocellulose-based flexible thermoelectric material. Unlike the simple in-situ polymerization reaction to prepare a conductive polymer-nanocellulose membrane or the simple mixing of nanocellulose with a conductive polymer, this solution uses the addition of anionic surfactants and oxidants to form a latex particle template, so that the conductive polymer monomer is polymerized with the latex particle template to obtain a rod-shaped fibrous conductive polymer. The conductive polymer monomer is then polymerized on the surface of the nanocellulose using the nanocellulose as a new polymerization template. The present invention ultimately obtains a nanocellulose-based flexible thermoelectric material with a more uniform distribution of conductive properties and a more stable structure. The material's electronic transmission and structural morphology can be effectively controlled by controlling the length of the conductive polymer chain segment and the degree of sulfonation on the nanocellulose. It has broad prospects in the application of thermoelectric materials, such as real-time monitoring equipment in extreme environments, wearable electrode treatment patches, and heat recovery devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 FIG. 1 is a scanning electron microscope (SEM) image of fibrous poly (3,4-ethylenedioxythiophene) according to one embodiment of the present invention.

[0044] Figure 2 This is the infrared spectrum (FT-IR) spectrum of poly (3,4-ethylenedioxythiophene)-nanocellulose material.

[0045] Figure 3This is the laser Raman spectrum (Raman) of poly (3,4-ethylenedioxythiophene)-nanocellulose material.

[0046] Figure 4 This is the X-ray diffraction (XRD) pattern of poly (3,4-ethylenedioxythiophene)-nanocellulose material.

[0047] Figure 5 This is the structural formula and preparation principle diagram of poly (3,4-ethylenedioxythiophene)-nanocellulose material.

[0048] Figure 6 This is the Zeta potential diagram of poly (3,4-ethylenedioxythiophene)-nanocellulose material.

[0049] Figure 7 This is the SEM image of poly (3,4-ethylenedioxythiophene)-nanocellulose material.

[0050] Figure 8 This is an atomic force microscope (AFM) image of poly (3,4-ethylenedioxythiophene)-nanocellulose material.

[0051] Figure 9 (a) Electrical conductivity, (b) Seebeck coefficient, (c) thermoelectric power factor, and (d) electron transition barrier diagram of poly (3,4-ethylenedioxythiophene)-nanocellulose material. DETAILED DESCRIPTION

[0052] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention are within the scope of protection of the present invention.

[0053] It is to be understood that the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element may be one, while in another embodiment, the number of the elements may be multiple, and the term "one" should not be understood as a limitation on the quantity.

[0054] Example 1

[0055] Preparation of poly (3,4-ethylenedioxythiophene)-nanocellulose-based materials

[0056] The structural formula of poly (3,4-ethylenedioxythiophene)-nanocellulose and the preparation principle diagram of poly (3,4-ethylenedioxythiophene)-nanocellulose are shown in the attached figure. Figure 5 shown.

[0057] (1) Preparation of Nanocellulose: 40 g of wood strips were immersed in a 4% peracetic acid solution at pH 4.5 and reacted at 85°C for 7 h to obtain delignified cellulose. The delignified cellulose was then immersed in a sulfamic acid / N,N-dimethylformamide solution with a molar ratio of sulfamic acid to cellulose (OH) functional groups of 1:1. After mixing, the mixture was subjected to a sulfation reaction in an 85°C water bath for 2 h to obtain sulfonated cellulose, which was then pulped using a blender to obtain nanocellulose.

[0058] (2) Preparation of poly (3,4-ethylenedioxythiophene)-nanocellulose: 30 mmol of sodium dodecyl sulfate was dissolved in 100 mL of water, 10 mL of 8 mmol of ferric chloride solution was added dropwise to the sodium dodecyl sulfate solution and stirred at 50°C for 10 min, 4 mmol of 3,4-ethylenedioxythiophene was added dropwise to the mixed solution and stirred at 50°C for 3 h. After 3 h, 27.4 g of 0.25 wt% nanocellulose solution, 10 mL of 8 mmol of ferric chloride solution and 4 mmol of 3,4-ethylenedioxythiophene were added dropwise to the mixed solution and stirred at 50°C for 3 h. At the end of the reaction, the solution was dark green or blue-black. The reaction liquid was transferred to a centrifuge tube and centrifuged at 9000 r / min for 5 min. The liquid was immediately poured out to obtain a black solid remaining on the tube wall. Then add 50% ethanol aqueous solution to the centrifuge tube and mix evenly. After centrifugation at 9000 r / min for 5 minutes, pour out the liquid immediately to obtain a black solid remaining on the tube wall. Repeat the above operation three times to obtain the poly (3,4-ethylenedioxythiophene)-nanocellulose product.

[0059] Structural characterization of poly (3,4-ethylenedioxythiophene)-nanocellulose-based materials:

[0060] The solution of poly (3,4-ethylenedioxythiophene)-nanocellulose was sampled after 3 hours of preparation and observed by scanning electron microscope (SEM). Figure 1 As shown, it can be seen that after 3 hours of reaction, the conductive polymer in the solution presents a fibrous morphology with a length of >5 μm, thereby verifying the generation of fibrous conductive PEDOT polymer.

[0061] The infrared spectrum scanning results of the prepared poly 3,4-ethylenedioxythiophene-nanocellulose material are as follows: Figure 2 As shown in the figure, it can be seen that the prepared poly 3,4-ethylenedioxythiophene-nanocellulose spectrum has a wavelength of 1236 cm -1 There is a stretching vibration peak of O=S=O at 826cm -1 The presence of COS bending vibration peak at 1484 cm-1 verifies the presence of nanocellulose components in poly(3,4-ethylenedioxythiophene)-nanocellulose. -1There is a stretching vibration peak of C=C; at 1325cm -1 There are CC bending vibration peaks at 1182, 1134, 1090, and 1054 cm -1 There is a bending vibration peak of COC at 970cm -1 and 929cm -1 The presence of a CSC bending vibration peak at , verified that fibrous 3,4-ethylenedioxythiophene was successfully polymerized on the surface of nanocellulose to synthesize poly (3,4-ethylenedioxythiophene)-nanocellulose.

[0062] The Raman spectrum of the prepared poly (3,4-ethylenedioxythiophene)-nanocellulose material was scanned, and the results were as follows: Figure 3 Shown, visible, at 438cm -1 、572cm -1 and 989cm -1 The three bands centered at 1101 cm reflect the deformation of the oxyethylene ring in the poly(3,4-ethylenedioxythiophene) structure; -1 There is a Raman peak related to the deformation of the COC bond at 1262 cm -1 There is C α -C α 'The Raman peak related to the inter-ring stretching; at 1368cm -1 、1429cm -1 and 1509cm -1 The Raman peaks at β -C β 'Stretch, C α -C β (-O)Stretch and Asymmetric C α -C β Stretching related.

[0063] The prepared poly (3,4-ethylenedioxythiophene)-nanocellulose material was subjected to X-ray diffraction, and the results were as follows: Figure 4 As shown in the figure, it can be seen that 2θ = 18.1° and 2θ = 22.7° are the (1-10 / 110) crystal plane and (200) crystal plane of nanocellulose respectively; the sharp peaks formed by the stacking crystallization between PEDOT chains appear at 2θ = 6.7° (d 100), 2θ = 12.8° (d 200), 2θ = 19.4° (d 300) and 2θ = 25.9°. Among them, the XRD peak at 2θ = 25.9° (lattice spacing ) is attributed to the distance between the π–π stacking of PEDOT chains (d 020).

[0064] The above experimental results all verify the successful synthesis of poly (3,4-ethylenedioxythiophene)-nanocellulose.

[0065] Performance test of poly (3,4-ethylenedioxythiophene)-nanocellulose-based materials:

[0066] The prepared poly (3,4-ethylenedioxythiophene) nanocellulose was subjected to Zeta potential test, and the results were as follows: Figure 6 As shown, the zeta of poly (3,4-ethylenedioxythiophene)-nanocellulose is 2.27 mV, indicating that poly (3,4-ethylenedioxythiophene) and nanocellulose are closely combined, the surface charge is low, and the attraction between particles is large.

[0067] The prepared poly (3,4-ethylenedioxythiophene)-nanocellulose was photographed by SEM, and the results are as follows: Figure 7 As shown, it can be seen that the surface of poly (3,4-ethylenedioxythiophene)-nanocellulose is relatively smooth and the fiber size is about 3-5 μm.

[0068] The prepared poly (3,4-ethylenedioxythiophene) nanocellulose was tested by atomic force microscopy (AFM). Figure 8 As shown, it can be seen that the size of poly (3,4-ethylenedioxythiophene)-nanocellulose fibers is about 3-5 μm, and the diameter of a single fiber is about 40 nm.

[0069] The above data all indicate that poly (3,4-ethylenedioxythiophene)-nanocellulose was successfully prepared, and a uniform poly (3,4-ethylenedioxythiophene) layer was successfully polymerized on the nanocellulose.

[0070] Example 2 Thermoelectric properties of poly (3,4-ethylenedioxythiophene)-nanocellulose

[0071] 0.0109 g of poly (3,4-ethylenedioxythiophene)-nanocellulose was weighed and dissolved in 300 mL of deionized water, and filtered on a filtration device to obtain a filter cake; a vacuum hot press was used to hot-press the filter cake into a poly (3,4-ethylenedioxythiophene)-nanocellulose film.

[0072] The thermoelectric performance of the prepared poly (3,4-ethylenedioxythiophene)-nanocellulose film was tested using a Seebeck resistance meter. Figure 9 (a) to Figure 9 As shown in (c), the conductivity of poly (3,4-ethylenedioxythiophene)-nanocellulose at 30°C is 5033 S·m -1 ; Seebeck coefficient is 19.0μV·K -1 The calculated thermoelectric power factor of poly (3,4-ethylenedioxythiophene) nanocellulose is 1.81 μW·m -1 K -2 As the temperature rises, the conductivity of the film decreases slightly, the Seebeck coefficient increases significantly, and the highest thermoelectric power factor can reach 2.45μW·m -1K -2 .

[0073] Further regression analysis of the measured thermoelectric performance values ​​showed that Figure 9 As shown in (d) in the figure, the energy required for electron transition in poly (3,4-ethylenedioxythiophene)-nanocellulose is 11 meV.

[0074] The above data all show that the prepared poly (3,4-ethylenedioxythiophene)-nanocellulose has good thermoelectric properties.

[0075] Example 3 Effect of different ratios on the reaction

[0076] Referring to Example 1, the ratio of the amount of 3,4-ethylenedioxythiophene added each time to the amount of ferric chloride added each time was changed, and other conditions remained unchanged. The reaction and treatment were carried out according to the scheme of Example 1. The specific results are shown in Table 1. It can be seen that when the molar ratio of 3,4-ethylenedioxythiophene to ferric chloride is 8:16, the yield of poly (3,4-ethylenedioxythiophene)-nanocellulose is the highest, reaching 75.4%, so this ratio is preferred for preparation.

[0077] Table 1 Effect of different ratios of 3,4-ethylenedioxythiophene and ferric chloride on the yield of poly (3,4-ethylenedioxythiophene)-nanocellulose

[0078]

[0079]

[0080] Example 4 Effect of different concentrations of ethanol-water ratio on product

[0081] Referring to Example 1, the ethanol-water ratio of the centrifuged solution was changed, while other conditions remained unchanged, and the reaction and treatment were carried out according to the scheme of Example 1. Specific results are shown in Table 2. As can be seen, when the ethanol-water volume ratio is 50:50, the yield of poly (3,4-ethylenedioxythiophene)-nanocellulose is the highest, reaching a yield of 75.4%, so this solvent is preferred for preparation.

[0082] Table 2 Effect of different ratios of ethanol aqueous solution on the yield of poly (3,4-ethylenedioxythiophene)-nanocellulose

[0083]

[0084] Comparative Example 1 Performance of commercially available poly (3,4-ethylenedioxythiophene) thermoelectric materials

[0085] Table 3 shows the performance results of several commonly reported commercially available or cellulose-based poly (3,4-ethylenedioxythiophene) thermoelectric materials.

[0086] Table 3 Comparison of thermoelectric properties of poly (3,4-ethylenedioxythiophene) nanocellulose and other materials

[0087]

[0088]

[0089] Compared with the performance of other materials in Table 3, the poly (3,4-ethylenedioxythiophene)-nanocellulose of the present invention has excellent thermoelectric performance.

[0090] Comparative Example 2: Effect of not adding anionic surfactant

[0091] Preparation of amorphous poly (3,4-ethylenedioxythiophene) nanocellulose: First, add 20 mL of a 16 mmol ferric chloride solution to 27.4 g of a 0.25 wt% nanocellulose solution and stir at 50°C for 30 minutes to disperse the solution evenly. Then, add 8 mmol of 3,4-ethylenedioxythiophene dropwise to the mixed solution and stir at 50°C for 3 hours. Other procedures were the same as in Example 1. The final product is amorphous poly (3,4-ethylenedioxythiophene) nanocellulose.

[0092] Referring to Example 2, the thermoelectric performance of amorphous poly (3,4-ethylenedioxythiophene)-nanocellulose was tested and compared with the poly (3,4-ethylenedioxythiophene)-nanocellulose prepared in the present invention. The corresponding performance results are shown in Table 4.

[0093] Table 4 Comparison of thermoelectric properties of poly (3,4-ethylenedioxythiophene) nanocellulose and amorphous poly (3,4-ethylenedioxythiophene) nanocellulose at different temperatures

[0094]

[0095] Comparing the thermoelectric properties of amorphous poly (3,4-ethylenedioxythiophene)-nanocellulose and poly (3,4-ethylenedioxythiophene)-nanocellulose at different temperatures in Table 4 without adding anionic surfactant, the electrical conductivity of the poly (3,4-ethylenedioxythiophene)-nanocellulose of the present invention is significantly higher than that of the amorphous poly (3,4-ethylenedioxythiophene)-nanocellulose synthesized by simple in situ polymerization reaction without adding anionic surfactant, which indicates that poly (3,4-ethylenedioxythiophene)-nanocellulose has more superior thermoelectric properties.

[0096] The present invention is not limited to the above-mentioned optimal implementation mode. Anyone can derive other forms of products under the inspiration of the present invention. However, no matter what changes are made in the shape or structure, any technical solution that is the same or similar to that of the present application falls within the scope of protection of the present invention.

Claims

1. A method for preparing a nanocellulose-based flexible thermoelectric material, characterized in that: The following steps are involved: An oxidant and a conductive polymer monomer are added to an anionic surfactant solution to react and obtain a fibrous conductive polymer, wherein the oxidant contains iron or ammonium radicals; Nanocellulose solution, oxidant and conductive polymer monomer are sequentially added to the fibrous conductive polymer and reacted to obtain the nanocellulose flexible thermoelectric material.

2. The method for preparing a nanocellulose-based flexible thermoelectric material according to claim 1, characterized in that: The anionic surfactant is selected from one or any combination of a sulfate anionic surfactant, a sulfonic acid anionic surfactant or a fatty acid salt anionic surfactant.

3. The method for preparing the nanocellulose-based flexible thermoelectric material according to claim 1, characterized in that: When the oxidant contains iron, the oxidant is selected from one or a combination of two or more of ferric chloride, ferric p-toluenesulfonate, ferric hydroxide, and ferric nitrate; when the oxidant contains an amine radical, the oxidant is selected from ammonium persulfate.

4. The method for preparing the nanocellulose-based flexible thermoelectric material according to claim 1, wherein: The concentration of anionic surfactant is (5~100) mmol anionic surfactant / 100 mL water.

5. The method for preparing the nanocellulose-based flexible thermoelectric material according to claim 1, wherein: The conductive polymer monomer includes one or a combination of two or more of 3,4-ethylenedioxythiophene, aniline, pyrrole and thiophene.

6. The method for preparing a nanocellulose-based flexible thermoelectric material according to claim 1, characterized in that: The molar ratio of the oxidant, the conductive polymer monomer and the anionic surfactant is 1-50:1-50:1-100.

7. The method for preparing a nanocellulose-based flexible thermoelectric material according to claim 1, characterized in that: Nanocellulose solution contains -OSO3 - Functional groups of sulfurized nanocellulose.

8. The method for preparing a nanocellulose-based flexible thermoelectric material according to claim 1, characterized in that: The mass concentration of the nanocellulose solution is 0.1~1.0wt%.

9. A nanocellulose-based flexible thermoelectric material, characterized in that: The preparation method of the nanocellulose-based flexible thermoelectric material according to any one of claims 1 to 8 comprises nanocellulose as a substrate, and long-chain conductive polymer segments composed of fibrous conductive polymers polymerized on the surface of the nanocellulose.

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