Functionalized aramid nanofiber and preparation method and application thereof

Abstract

The application discloses functionalized aramid nanofiber and a preparation method and application thereof. The preparation method comprises the following steps: mixing an organic solvent, a strong alkali, aramid fiber and a catalyst to perform a peeling activation reaction, and then adding a modification reagent to perform a Hofmann alkylation reaction, so as to obtain the functionalized aramid nanofiber. The application adopts a top-down method to peel the aramid fiber into aramid nanofiber, and then adds a modification reagent, so that the preparation of the functional aramid nanofiber is realized through a rapid Hofmann alkylation reaction. The inner molecular chain of the nanofiber is an aramid molecular chain, so that the crystalline structure of the aramid is not damaged, and the mechanical property of the nanofiber is ensured. The nanofiber prepared by the application is grafted with a large number of functional groups on the surface, and the grafted amount is greater than that of a polymerization method. The reaction process is mild, the reaction degree is controllable, the nanofiber has a good and perfect appearance, the functional group composition can be designed, and the functionalized application in multiple aspects such as biological medicine, environment and energy is possible.

Description

Technical Field

[0001] The present invention relates to an aramid nanofiber, in particular to a functionalized aramid nanofiber and a preparation method and application thereof, belonging to the technical field of new materials. Background Art

[0002] Aramid nanofibers are a new type of polymer nanofiber with excellent performance. Their high crystallinity and high internal rotational potential give them para-aramid properties such as high strength, high modulus, acid and alkali resistance, and high temperature resistance. They can be efficiently combined with polymer matrices through physical, chemical, and self-assembly processes, making them promising "reinforcement building blocks" for composite reinforcement. Existing aramid nanofiber preparation techniques primarily rely on alkali stripping and polymerization-induced assembly. Both methods produce unfunctionalized aramid nanofibers, limiting their application range and necessitating further modification.

[0003] Surface modification of aramid nanofibers can be divided into two methods: physical and chemical. In terms of physical modification, the surface of aramid nanofibers is mainly modified through methods such as plasma treatment, surface coating technology, ultraviolet radiation, gamma-ray radiation, and ultrasonic treatment. The purpose of these methods is to generate free radical active sites on the fiber surface, thereby improving the functionality of the fiber surface and achieving better compatibility with composite materials. For example, plasma treatment can introduce oxygen-containing functional groups on the surface of aramid nanofibers. After subsequent treatment, the rupture of chemical bonds leads to increased surface roughness of the fiber, thereby enhancing the interfacial shear force between the fiber and the matrix. Similarly, surface coating technology, ultraviolet radiation, gamma-ray radiation, and ultrasonic treatment methods all form active centers on the fiber surface through their own unique mechanisms, promoting the introduction of polar groups, thereby improving the surface wettability and roughness of the aramid nanofibers. These modification measures help to reduce problems such as stress defects caused by poor bonding between aramid nanofibers and composite materials.

[0004] Chemical modification technology has significantly improved the modification effect of aramid nanofibers by introducing a rich array of reactive groups onto the fiber surface, enhancing its surface activity. This technology primarily encompasses two methods: surface etching and surface grafting. During the surface etching process, the fibers are treated with acyl chlorides and acid-base compounds, which hydrolyze the amide bonds on the fiber surface, thereby increasing chemical activity and strengthening the interfacial interaction between the fiber and the composite material. Surface grafting, the mainstream technology for modifying aramid nanofibers, primarily involves grafting polar groups or reactive groups capable of undergoing secondary reactions onto the fiber surface. Depending on the position of the grafted functional group, it can be categorized as either benzene ring grafting or amide bond grafting. In aramid nanofibers, the ortho- and para-positioned hydrogen atoms on the benzene rings attached to amino groups are highly reactive and can undergo substitution reactions with electrophilic substituents. For example, -NH2 and -SO3H groups can be grafted onto the benzene rings through nitration-reduction and sulfonation reactions, respectively, thereby further grafting reactive groups. While amide bonds can also be grafted, their lower reactivity for nitration-reduction and sulfonation reactions results in less than ideal modification results. Using anhydrous, oxide-free metallization technology, efficient grafting can be achieved on amide bonds. Surface modification using alkali or alkaline earth metals and organic active substances (such as epoxides) can enhance surface activity. However, the highly reactive reactants during the reaction are dangerous and prone to explosions.

[0005] In summary, the modification strategies for aramid nanofibers, whether physical or chemical, exhibit different advantages and disadvantages. Physical modification methods can maintain the original properties of the fiber to the greatest extent and cause relatively little damage to the fiber structure. However, the physical modification process often requires more stringent environmental conditions, such as a vacuum environment or precise temperature control, which leads to higher energy consumption. In contrast, although chemical modification is simple to operate and has obvious modification effects, its process may cause a certain degree of damage to the intrinsic structure of the fiber. Summary of the Invention

[0006] The main purpose of the present invention is to provide a functionalized aramid nanofiber and a preparation method thereof, so as to overcome the deficiencies in the prior art.

[0007] Another object of the present invention is to provide applications of the functionalized aramid nanofibers.

[0008] To achieve the aforementioned object of the invention, the technical solutions adopted by the present invention include:

[0009] An embodiment of the present invention provides a method for preparing functionalized aramid nanofibers, comprising: mixing an organic solvent, a strong base, aramid fibers, and a catalyst, performing an exfoliation activation reaction, and then adding a modifying reagent to perform a Hofmann alkylation reaction to obtain the functionalized aramid nanofibers;

[0010] Wherein, the molecular formula of the modifying reagent includes C a H b O c X d S e M f 、C a H b O c X d N e P f At least one of the following, X is a halogen element, M is a metal element, and a=1~20, b≥2, c≥0, d≥1, e≥0, in formula C a H b O c X d S e M f f, f≥1, but in formula C a H b O c X d N e P f , f≥0.

[0011] The embodiment of the present invention also provides functionalized aramid nanofibers prepared by the above method.

[0012] The embodiments of the present invention also provide applications of the aforementioned functionalized aramid nanofibers in fields such as biomedicine, environment, or energy.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] 1) The present invention adopts a top-down method to strip aramid fibers into aramid nanofibers and then add a modification reaction reagent. Through a rapid Hofmann alkylation reaction, the functional aramid nanofibers are prepared. The internal molecular chains of the nanofibers are aramid molecular chains, the crystalline structure of the aramid is not destroyed, and the mechanical properties of the nanofibers are guaranteed.

[0015] 2) The nanofibers produced by the present invention have a large number of functional groups grafted onto their surfaces, which is greater than that obtained by the polymerization method. The reaction process is mild, the reaction degree is controllable, the nanofiber morphology is well-developed, and the composition of the functional groups can be designed, which has the potential for functional applications in biomedicine, environment, energy, and other fields.

[0016] 3) The method of the present invention has high reaction efficiency and eliminates the complex steps of drying, hydrolysis, acid washing, and plasma treatment of aramid nanofibers required in existing modification methods, thereby achieving a one-pot preparation and modification of nanofibers. The reaction is carried out at room temperature and atmospheric pressure, with mild reaction conditions, simple equipment, and the potential for rapid production expansion. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 is a flow chart for preparing a functionalized aramid nanofiber according to a typical embodiment of the present invention;

[0019] Figure 2 This is a photo of the modified aramid nanofiber slurry prepared in Example 1 of the present invention;

[0020] Figure 3 This is a scanning electron microscope image of the organometallic salt-modified aramid nanofiber prepared in Example 1 of the present invention;

[0021] Figure 4 This is a scanning electron microscope image of the organometallic salt-modified aramid nanofiber prepared in Example 2 of the present invention;

[0022] Figure 5 This is an AFM image of the organometallic salt-modified aramid nanofiber prepared in Example 1 of the present invention;

[0023] Figure 6 This is a scanning electron microscope image of the nitrogen-containing organic salt-modified aramid nanofiber prepared in Example 5 of the present invention. DETAILED DESCRIPTION

[0024] In view of the problems existing in the above-mentioned prior art, after long-term research and a large number of experiments, the inventors of this case proposed this technical solution, which mainly adopts a top-down approach to efficiently, safely and controllably prepare aramid nanofibers with functionalized functional groups on their surface through stripping-in-situ modification. This technology avoids the long and precisely controlled polymerization and assembly process, and realizes the spontaneous termination of the reaction and the unimodal distribution of the nanofiber diameter through mechanism design, without damaging the aramid molecular chain, ensuring the crystallinity and molecular weight of the nanofiber, so that it has higher strength and longer aspect ratio.

[0025] The technical solution, its implementation process and principles are further explained below.

[0026] The following terms require clarification:

[0027] Aramid nanofiber: A fiber material with a nanometer-scale diameter composed of aramid molecules (PPTA, poly(p-phenylene terephthalamide)).

[0028] Functionalized aramid nanofibers: aramid nanofibers that are modified or prepared by other methods and have certain functionality compared to aramid nanofibers.

[0029] As one aspect of the technical solution of the present invention, a method for preparing functionalized aramid nanofibers involves mixing an organic solvent, a strong base, aramid fibers and a catalyst, performing an exfoliation activation reaction, and then adding a modifying reagent to perform a Hofmann alkylation reaction to obtain functionalized aramid nanofibers.

[0030] In some embodiments, the molecular formula of the modifying reagent employed in the present invention follows C a H b O c X d S e M f , where: C is carbon, H is hydrogen, O is oxygen, X is a halogen (for example, F, Cl, Br, I, etc.), S is sulfur, M is a metal ion (for example, K, Na, Ca, Li, Mg, Zn, Fe, Sn, Cu, etc.), a ranges from 1 to 20, b ranges from 2 or more, c is 0 or more, d ranges from 1 or more, e ranges from 0 or more, and f ranges from 1 or more.

[0031] In other embodiments, the molecular formula of the modifying reagent used in the present invention can also follow C a H b O c X d N e P f , where: C is carbon, H is hydrogen, O is oxygen, X is a halogen (for example, any one of F, Cl, Br, I, etc.), N is nitrogen, P is phosphorus, a range is 1 to 20, b range is greater than or equal to 2, c is greater than or equal to 0, d range is greater than or equal to 1, e range is greater than or equal to 0, and f range is greater than or equal to 0.

[0032] The reaction principle of the present invention is that a strong base abstracts hydrogen to form a nitrogen anion, which is then grafted onto a functional group through an alkylation reaction. Different proportions of nitrogen anions can be formed on the aramid surface according to the ratio of the strong base to the aramid. At the same time, the amide bond on the aramid is a tertiary amine, so only one substituted functional group will be grafted.

[0033] In some embodiments, the mass ratio of the aramid fiber, the organic solvent, the strong base, the catalyst, and the modification reagent is 1:9-99:0.2-5:0.2-5:0.01-50. In another aspect, the mass ratio of the aramid fiber is 1, and the mass ratio of the other components is as follows: the organic solvent 9-99, the strong base 0.2-5, the catalyst 0.2-5, and the modification reagent 0.01-50.

[0034] In some embodiments, the aramid fiber can include any one of para-aramid fiber, meta-aramid fiber, aramid III fiber (heterocyclic aramid), or a combination of two or more thereof, but is not limited thereto.

[0035] In some embodiments, the organic solvent can include any one of dimethylformamide, dimethyl sulfoxide, N-methyl pyrrolidone, methanol, ethanol, water, or a combination of two or more thereof, but is not limited thereto.

[0036] In some embodiments, the strong base includes any one of an organic base and an inorganic base.

[0037] In some preferred embodiments, the inorganic base can include any one of a hydroxide, a hydride, or a combination of two or more thereof, but is not limited thereto.

[0038] In some more specific embodiments, the hydroxide can include any one of potassium hydroxide, sodium hydroxide, calcium hydroxide, or a combination of two or more thereof, but is not limited thereto.

[0039] In some more specific embodiments, the hydride can include any one of potassium hydride, calcium hydride, sodium hydride, or a combination of two or more thereof, but is not limited thereto.

[0040] In some preferred embodiments, the organic base can include any one of sodium tert-butoxide, potassium tert-butoxide, n-butyllithium, potassium methoxide, or a combination of two or more thereof, but is not limited thereto. The present application can excite different contents of nitrogen anion sites by adding the content of the base, and graft a hydrophilic functional group to the nitrogen anion site through Hofmann alkylation. The grafting amount can be controlled by the amount of the added base.

[0041] In some preferred embodiments, the catalyst can include any one of ethylene glycol, glycerol, formic acid, methanol, ethanol, water, or a combination of two or more thereof, but is not limited thereto.

[0042] In some embodiments, the modification reagent can be added in any one of a dropwise manner, a direct mixing manner, and the like.

[0043] In some embodiments, the preparation method specifically includes: mixing an organic solvent, a strong base, aramid fiber, and a catalyst for 1 to 48 hours to perform a stripping activation reaction.

[0044] In some embodiments, the Hofmann alkylation reaction is carried out at a temperature of 20 to 120° C. and for a time of 0.5 to 48 hours.

[0045] Among them, as one of the more specific embodiments, the present invention prepares water-based functionalized aramid nanofibers by a dynamic equilibrium stripping modification method, such as Figure 1 As shown, the method specifically implements the following steps: an organic solvent, a strong base, aramid fibers, and a catalyst are mixed for 1-48 hours to undergo a stripping activation reaction, obtaining an initial reaction solution. A modifying agent is added to the initial reaction solution, and the reaction is stirred until the color of the reaction system solution does not change after the addition of the modifying agent to obtain a reaction product. Unreacted strong base and modifying agent are filtered through a filter to obtain a cationic functionalized aramid nanofiber dispersion.

[0046] The functionalized aramid nanofiber preparation reaction process provided by the present invention is carried out in the wet phase throughout. The homogeneous reaction design eliminates the complex steps of drying, hydrolysis, pickling, plasma treatment, etc. required for the aramid nanofiber modification method, and achieves one-pot production, thereby greatly improving production efficiency.

[0047] In summary, the preparation method of the present invention utilizes a shaped polymer, which is stripped from top to bottom to obtain nanofibers. A modified reaction reagent is then added to obtain water-based nanofibers through a rapid Hofmann alkylation reaction. This technology avoids the lengthy and meticulously controlled polymerization and assembly processes. Through a designed mechanism, spontaneous reaction termination and a unimodal distribution of nanofiber diameter are achieved without damaging the aramid molecular chains, ensuring the crystallinity and molecular weight of the nanofibers, resulting in high strength and a long aspect ratio. Furthermore, the reaction is carried out at room temperature and atmospheric pressure, resulting in mild reaction conditions, simple equipment, and the potential for rapid production expansion.

[0048] Another aspect of an embodiment of the present invention further provides a functionalized aramid nanofiber prepared by the aforementioned preparation method, which has multiple functionalized functional groups on its surface, thus also bringing about differences in performance. In terms of performance, depending on the different functional groups, the nanofiber can achieve adsorption and affinity for different gases and liquids, luminescence under light stimulation, and higher flame retardant effect.

[0049] Specifically, the internal molecular chains of the functionalized aramid nanofibers of the present invention are aramid molecular chains, so the crystalline structure of aramid is not destroyed and the mechanical properties of the nanofibers are guaranteed; a large number of functional groups are grafted onto the surface of the nanofibers, and the grafted number is greater than that of the polymerization method.

[0050] The functionalized aramid nanofibers prepared by the present invention can be dispersed in different materials and have certain functionalities. The functionalities are manifested in the ability to adsorb specific substances or have properties such as luminescence and flame retardancy. This is caused by the functional groups corresponding to nitrogen, phosphorus or sulfur in the group, so that the materials obtained after the aramid nanofibers are composited with other materials have different properties and good compatibility with the base material.

[0051] Another aspect of the embodiments of the present invention further provides applications of the aforementioned functionalized aramid nanofibers.

[0052] Through the above technical solution, the reaction process of the present invention is mild, the reaction degree is controllable, the nanofiber morphology is well-developed, the functional group composition can be designed, and it has functional application possibilities in biomedicine, environment, energy and other fields.

[0053] Furthermore, the method of the present invention has high reaction efficiency and eliminates the complex steps of drying, hydrolyzing, pickling, and plasma treatment of aramid nanofibers required in existing modification methods, thereby achieving one-pot preparation and modification of nanofibers. The reaction is carried out at room temperature and atmospheric pressure, with mild reaction conditions and simple equipment, and has the potential for rapid production expansion.

[0054] The entire process is described in detail below using several examples and accompanying drawings. However, the scope of protection of the present invention is not limited by these examples. Furthermore, the examples merely provide some conditions for achieving the objectives, and do not necessarily require these conditions to be met. All variations that can be derived from or inferred from the present disclosure are considered to be within the scope of protection of the present invention.

[0055] Example 1

[0056] 10g of para-aramid fiber was mixed with 10g of potassium hydroxide, 980g of dimethyl sulfoxide, and 10g of ethanol and stirred for 20h. 50g of C2H4O2NaCl was added and stirred at room temperature (25°C) for 20h to obtain a reaction product. The excess unreacted salt was filtered out using a positive pressure filter to obtain a purified hydrophilic aramid nanofiber slurry. The obtained slurry is shown in the photo. Figure 2 The SEM images of the obtained organometallic salt modified aramid nanofibers are shown in Figure 3 As shown, the average diameter of the aramid nanofibers is 35 nm, and the AFM images of the obtained organometallic salt modified aramid nanofibers are shown in Figure 5 shown.

[0057] Example 2

[0058] 30g of para-aramid fiber was mixed with 20g of potassium hydroxide, 980g of dimethyl sulfoxide, and 20g of methanol and stirred for 20h to dissolve. 50g of C2H4O2NaCl was added and stirred at room temperature (25°C) for 30h to obtain a reaction product. The excess unreacted salt was filtered using a positive pressure filter to obtain a purified hydrophilic aramid nanofiber slurry. The SEM image of the obtained organometallic salt modified aramid nanofiber is shown in Figure 2. Figure 4 As shown, the average diameter of the nanofibers is 30 nm.

[0059] Example 3

[0060] Mix 10g of meta-aramid fiber with 10g of potassium hydride, 980g of dimethylformamide, and 10g of ethanol and stir to dissolve for 20h. Add 140g of C7H 17 N2Br and then stirred at 40 °C for 48 h to obtain the reaction product, and the excess unreacted salt was filtered out using a positive pressure filter to obtain purified CO2 adsorbing aramid nanofibers.

[0061] Example 4

[0062] 10g of aramid III fiber was mixed with 30g of potassium tert-butoxide, 980g of dimethyl sulfoxide, and 10g of water and stirred for 40h. 94g of C5H 14 NCl was added and stirred at 40° C. for 0.5 h to obtain a reaction product, and excess unreacted salts were filtered out using a positive pressure filter to obtain a purified aramid nanofiber slurry. The nanofiber had adsorption properties for acidic gases.

[0063] Example 5

[0064] 40g of para-fiber was mixed with 30g of potassium methoxide, 900g of N-methylpyrrolidone and 10g of ethanol and stirred for 40h. 3g of C 15 The H8O2NCl2 solution was heated to 80℃ and stirred for 14 hours. The reaction product was separated by high-speed centrifugation to obtain a purified aramid nanofiber slurry. The nanofiber had a fluorescence excitation effect. The SEM image of the obtained nitrogen-containing organic salt modified aramid nanofiber is shown in the figure. Figure 6 As shown, the average diameter of the nanofibers is 60 nm.

[0065] Example 6

[0066] 10g para-aramid fiber was mixed with 10g potassium hydroxide, 980g dimethyl sulfoxide and 10g methanol and stirred for 20h. 50g C9H 15 O4PCl3 and then stirred at room temperature (25°C) for 2h to obtain the reaction product. The excess unreacted salt was filtered out using a positive pressure filter to obtain a purified highly flame-retardant aramid nanofiber slurry. The oxygen index of the obtained aramid nanofiber reached 38%.

[0067] Example 7

[0068] 10g of para-aramid fiber was mixed with 50g of potassium hydroxide, 90g of dimethyl sulfoxide, and 2g of ethanol and stirred for 48 hours. 0.1g of CH3OCl was added and stirred at room temperature (25°C) for 1 hour to obtain a reaction product. Excess unreacted salts were filtered using a positive pressure filter to obtain a purified hydrophilic aramid nanofiber slurry. The resulting nanofibers had an average diameter of 800nm ​​and were easily dispersed in water.

[0069] Example 8

[0070] 10g para-aramid fiber was mixed with 10g potassium hydroxide, 980g dimethyl sulfoxide and 10g ethanol and stirred for 20h. 50g C 20 H 40 O2NaCl was then added, the temperature was raised to 90°C and stirred for 48h to obtain a reaction product, and excess unreacted salts were filtered out using a positive pressure filter to obtain a purified hydrophilic aramid nanofiber slurry.

[0071] Example 9

[0072] 10 g of para-aramid fiber was mixed with 50 g of sodium hydride, 990 g of N-methylpyrrolidone, and 2 g of propylene glycol, and stirred to dissolve for 1 h. 100 g of C2H6ClNaO4S was added, and the temperature was raised to 120 ° C and stirred for 15 h to obtain a reaction product. The excess unreacted salt was filtered out using a positive pressure filter to obtain a purified hydrophilic aramid nanofiber slurry.

[0073] Example 10

[0074] 10 g of para-aramid fiber was mixed with 20 g of n-butyl lithium, 980 g of N-methylpyrrolidone, and 3 g of formic acid, and stirred to dissolve for 24 h. 500 g of C4H8O4ClCa was added and stirred at 20°C for 48 h to obtain a reaction product. Excess unreacted salts were filtered out using a positive pressure filter to obtain a purified hydrophilic aramid nanofiber slurry.

[0075] Comparative Example 1

[0076] 10g of para-aramid fiber was mixed with 10g of potassium hydroxide, 980g of dimethyl sulfoxide, and 10g of methanol, stirred and dissolved for 20 hours, and 50g of propyne bromide was added and stirred at room temperature for 2 hours to obtain a reaction product. The resulting nanofiber had a diameter of 40nm. The obtained product did not show changes in affinity for gas, water, and organic reagents, stimulate luminescence, or change in flame retardant properties.

[0077] Comparative Example 2

[0078] 10g of para-aramid fiber was mixed with 10g of potassium hydroxide, 980g of dimethyl sulfoxide, and 10g of methanol, and stirred to dissolve for 20 hours. 20g of 1-bromo-2-butyne was added and stirred at room temperature for 2 hours to obtain a reaction product. The average diameter of the obtained nanofibers was 20nm. The obtained product did not show changes in affinity for gas, water, and organic reagents, stimulate luminescence, or change in flame retardant properties.

[0079] In addition, the inventors of this case also conducted experiments with other raw materials and conditions listed in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results.

[0080] The various aspects, embodiments, features and examples of the present invention should be considered as illustrative in all aspects and not intended to limit the present invention. Other embodiments, modifications and uses will be apparent to those skilled in the art without departing from the spirit and scope of the invention as claimed.

[0081] Although the present invention has been described with reference to illustrative embodiments, it will be understood by those skilled in the art that various other changes, omissions, and / or additions may be made and that substantially equivalents may be substituted for elements of the described embodiments without departing from the spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the scope of the invention.

Claims

1. A method for preparing functionalized aramid nanofibers, characterized in that: include: An organic solvent, a strong base, aramid fibers and a catalyst are mixed to carry out a stripping activation reaction, and then a modifying reagent is added to carry out a Hofmann alkylation reaction to prepare functionalized aramid nanofibers; Wherein, the molecular formula of the modifying reagent includes C a H b O c X d S e M f 、C a H b O c X d N e P f At least one of the following, X is a halogen element, M is a metal element, and a=1~20, b≥2, c≥0, d≥1, e≥0, in formula C a H b O c X d S e M f f, f≥1, but in formula C a H b O c X d N e P f wherein f≥0; and the mass ratio of the aramid fiber, the organic solvent, the strong base, the catalyst, and the modifying agent is 1:9-99:0.2-5:0.2-5:0.01-50.

2. The preparation method according to claim 1, wherein: In formula C a H b O c X d S e M f In the embodiment, X includes any one of F, Cl, Br, and I.

3. The preparation method according to claim 1, wherein: M includes any one of K, Na, Ca, Li, Mg, Zn, Fe, Sn, and Cu.

4. The preparation method according to claim 1, wherein: The aramid fiber includes any one of para-aramid fiber, meta-aramid fiber, and aramid III fiber, or a combination of two or more thereof.

5. The preparation method according to claim 1, wherein: The organic solvent includes any one or a combination of two or more of dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, methanol, ethanol, and water.

6. The preparation method according to claim 1, wherein: The strong base includes any one of an organic base and an inorganic base.

7. The preparation method according to claim 6, characterized in that: The inorganic base includes any one of hydroxide and hydride or a combination of the two.

8. The preparation method according to claim 7, characterized in that: The hydroxide includes any one of potassium hydroxide, sodium hydroxide, and calcium hydroxide, or a combination of two or more thereof.

9. The preparation method according to claim 7, characterized in that: The hydride includes any one of potassium hydride, calcium hydride, and sodium hydride, or a combination of two or more thereof.

10. The preparation method according to claim 6, characterized in that: The organic base includes any one of sodium tert-butoxide, potassium tert-butoxide, n-butyl lithium, and potassium methoxide, or a combination of two or more thereof.

11. The preparation method according to claim 1, characterized in that: The catalyst includes any one of ethylene glycol, glycerol, formic acid, methanol, ethanol and water, or a combination of two or more thereof.

12. The preparation method according to claim 1, characterized in that: The modifying agent may be added in any one of the following ways: dropwise addition and direct mixing.

13. The preparation method according to claim 1, characterized in that include: The organic solvent, strong base, aramid fiber and catalyst are mixed for 1 to 48 hours to perform a stripping activation reaction.

14. The preparation method according to claim 1, characterized in that: The Hofmann alkylation reaction is carried out at a temperature of 20 to 120° C. and for a time of 0.5 to 48 hours.

15. The functionalized aramid nanofiber prepared by the preparation method according to any one of claims 1 to 14, wherein the surface of the functionalized aramid nanofiber has multiple functional groups.

16. Use of the functionalized aramid nanofiber according to claim 15 in the fields of biomedicine, environment or energy.

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