Fluorescent polyionic liquid gel, its preparation method and application

Abstract

The application provides a fluorescent polyionic liquid gel and a preparation method and application thereof, relates to the technical field of polyionic liquid gels, and is prepared by free radical polymerization of an ionic liquid monomer containing a naphthylmethyl group, an ionic liquid monomer containing a carboxymethyl group and an ionic liquid monomer containing an ethyl group, and then introducing a copolymer of 4-thioctic acid (7-phenylbenzo[C][1,2,5]thiadiazole) ester and alpha-thioctic acid to obtain the fluorescent polyionic liquid gel through solvent evaporation; the novel polyionic liquid gel contains stable carbon-carbon covalent bonds and reactive dynamic sulfur-sulfur covalent bonds at the same time, so that the polyionic liquid gel has high mechanical strength and fatigue resistance, and in addition, has the characteristics and functions of fluorescence, antibiosis and the like, and can be used in the field of antibacterial materials and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of material preparation, and relates to a fluorescent polyionic liquid gel as well as a preparation method and application thereof. BACKGROUND

[0002] In recent years, polyionic liquids have been widely applied in the fields of catalysis, electrochemistry, material science and the like. The polyionic liquid is a functional polyelectrolyte containing anion and cation groups, the anion or cation groups of which are 'fixed' on a rigid main chain, and counterions are free in the network, so that the polyionic liquid has the characteristics of both ionic liquid and polymer. The polyionic liquid with stable structure can overcome the water absorption and fluidity of small molecule ionic liquid, and improve the mechanical properties and stability of the material. Therefore, the functional material has a wide application in the fields of intelligent responsive material, adsorption separation, catalytic reaction and the like. At present, the research on the fluorescent polyionic liquid gel functional material is still less.

[0003] Lipoic acid (LA) as a natural small molecule plays a crucial role in the aerobic metabolism of animals, and is also an ideal monomer for constructing a supramolecular system, which is mainly due to the fact that the molecule simultaneously has two characteristic functional groups of dynamic disulfide bond and carboxyl group. The lipoic acid can be initiated by free radicals or anions to form a polymer through ring-opening polymerization, and the hydrogen bonding between the carboxyl groups forms a crosslinked network structure. The terminal carboxyl group of the lipoic acid can be modified to functionalize and give more functional applications. SUMMARY

[0004] The first aspect of the application is to provide a fluorescent polyionic liquid gel, and the structural formula is as follows:

[0005]

[0006] In the formula, x=50-200; y=20-200; z=20-100; m=50-200; and n=20-100. The second aspect of the application is to provide a preparation method of the fluorescent polyionic liquid gel, comprising the following steps:

[0007] (1) Preparation of brominated 1-vinyl-3-ethyl imidazole ionic liquid:

[0008] Bromine ethane and 1-vinylimidazole are dissolved in methanol, and stirred at 25-30 DEG C for 24-48 h. After the reaction is completed, the product is purified by methanol-ethyl ether dissolution and precipitation, and vacuum dried to obtain a white powder solid product, which is the brominated 1-vinyl-3-ethyl imidazole ionic liquid [EVIm]Br. The molar ratio of 1-vinylimidazole to bromine ethane is 1:1-1:1.5.

[0009] (2) Preparation of brominated 1-vinyl-3-carboxymethyl imidazole ionic liquid:

[0010] Bromine acetic acid and 1-vinyl imidazole were dissolved in dichloromethane, and refluxed at 50-60°C for 45-50h under N2 atmosphere. After the reaction was completed, white solid was obtained by filtration, and then purified by methanol dissolution-ethyl ether precipitation. After vacuum drying, white solid product was obtained, which was brominated 1-vinyl-3-carboxymethyl imidazole ionic liquid [CMVIm]Br. The molar ratio of bromine acetic acid to 1-vinyl imidazole was 1:1-1:1.8.

[0011] (3) Preparation of brominated 1-vinyl-3-naphthalenemethyl imidazole ionic liquid:

[0012] 2-Bromomethyl naphthalene and 1-vinyl imidazole were dissolved in methanol under ice bath condition, and stirred at 25-30°C for 12-24h. After the reaction was completed, white solid was obtained by methanol dissolution-ethyl ether precipitation, which was brominated 1-vinyl-3-benzyl imidazole ionic liquid [NapMVIm]Br after vacuum drying. The molar ratio of 1-vinyl imidazole to 2-bromomethyl naphthalene was 1:1-1:1.8.

[0013] (4) Preparation of naphthalene-methyl-containing polyionic liquid:

[0014] [EVIm]Br, [CMVIm]Br, [NapMVIm]Br were dissolved in methanol, and stirred at 70-80°C for 48-72h under refluxing under N2 protection with azobisisobutyronitrile as initiator. After the reaction was completed, yellowish solid was obtained by methanol dissolution-ethyl acetate precipitation, which was polyionic liquid Nap-PIL after vacuum drying. The molar ratio of [EVIm]Br, [CMVIm]Br and [NapMVIm]Br was 1:1:1-1:3:3. The mass ratio of azobisisobutyronitrile to [CMVIm]Br was 1:50-1:100.

[0015] (5) Preparation of sodium lipoic acid:

[0016] Sodium hydroxide was dissolved in ethanol, and then lipoic acid was added into the sodium hydroxide ethanol solution. After stirring at room temperature for 4-6h, yellowish solid was obtained by suction filtration, which was sodium lipoic acid NaLA. The molar ratio of lipoic acid to sodium hydroxide was 1:1-1:1.2.

[0017] (6) Preparation of lipoic acid monomer containing fluorescent group:

[0018] The benzene boronic acid and 4,7-dibromobenzothiazole are dissolved in a mixture of toluene, ethanol and sodium carbonate aqueous solution, under the protection of N2, tetra(triphenylphosphine)palladium is added, and the reaction is stirred at 80-90 DEG C under reflux for 48-72h, after the reaction is completed, dichloromethane and saturated NaCl aqueous solution are extracted in sequence, the organic phase is taken, purified by silica gel column chromatography, and vacuum dried to obtain a yellow-green solid, which is 4-bromo-7-phenylbenzo[C][1,2,5]thiadiazole BPBTD; the BPBTD and NaLA are dissolved in DMF, under the protection of N2, the reaction is stirred at 60-70 DEG C under reflux for 48-72h, after the reaction is completed, dichloromethane and deionized water are extracted in sequence, the organic phase is taken, dehydrated by anhydrous magnesium sulfate, the solution is rotary evaporated, and vacuum dried to obtain a yellow-green solid, which is 4-lipoic acid (7-phenylbenzo[C][1,2,5]thiadiazole) ester LPBTDE; the molar ratio of benzene boronic acid and 4,7-dibromobenzothiazole is 1:2-1:1.5.

[0019] (7) Preparation of poly-lipoic acid containing fluorescent groups:

[0020] The LPBTDE and lipoic acid are dissolved in ethanol, dried at 60-70 DEG C to obtain a light yellow film PLPBTDE; the molar ratio of LPBTDE and lipoic acid is 1:1-1:9.

[0021] (8) Preparation of polyionic liquid gel:

[0022] The Nap-PIL and PLPBTDE are dissolved in anhydrous ethanol, stirred at room temperature for 3h, and the solvent is evaporated under natural conditions to obtain a yellow-brown gel, which is a fluorescent polyionic liquid gel Nap-PIL-PLPBTDE. The molar ratio of lipoic acid and Nap-PIL is 1:1-1:3; the molar ratio of PLPBTDE and Nap-PIL is 1:1-1:3.

[0023] The synthetic route of the present application is as follows:

[0024]

[0025] The third aspect of the present application is to provide a fluorescent polyionic liquid gel in the preparation of antibacterial materials. Experiments prove that the fluorescent polyionic liquid gel prepared in the present application has a significant inhibitory effect on aspergillus flavus.

[0026] The beneficial effects of the present application are as follows:

[0027] In summary, the present application obtains polyionic liquid by copolymerization of ion liquid monomer containing carboxyl, ethyl and naphthylmethyl, further combines polythioctic acid containing fluorescent group, evaporates solvent to obtain fluorescent polyionic liquid gel by polymerization of thioctic acid chain. The novel polyionic liquid contains stable carbon-carbon covalent bond, reactive dynamic sulfur-sulfur covalent bond and hydrogen bond of carboxyl, so that it has gel structure; the novel polyionic liquid gel contains stable carbon-carbon covalent bond and reactive dynamic sulfur-sulfur covalent bond, so that it has high mechanical strength and fatigue resistance, in addition, the action of naphthylmethyl and benzothiazole group makes the material produce strong blue fluorescence, and also has antibacterial property.

[0028] The application will be further described in connection with the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The infrared spectrum of Nap-PIL-PLPBTDE prepared in Example 1 1 H NMR spectrum.

[0030] Figure 2 The infrared spectrum of BPBTD prepared in Example 1 1 H NMR spectrum.

[0031] Figure 3 The infrared spectrum of LPBTDE prepared in Example 1 1 H NMR spectrum.

[0032] Figure 4 The infrared spectrum of Nap-PIL-PLPBTDE prepared in Example 1 1 HNMR spectrum.

[0033] Figure 5 The infrared spectrum of Nap-PIL-PLPBTDE prepared in Example 1.

[0034] Figure 6 The thermogravimetric analysis diagram of Nap-PIL-PLPBTDE prepared in Example 1.

[0035] Figure 7 The fluorescence effect diagram of Nap-PIL-PLPBTDE prepared in Example 1.

[0036] Figure 8 The antibacterial property experiment of culture medium prepared by Nap-PIL-PLPBTDE (a), Nap-PIL-PLA (b), glass glue (c) and blank group (d) prepared in Example 1.

[0037] Figure 9 The antibacterial property experiment of culture medium prepared by Nap-PIL-PLPBTDE, glass glue and blank group prepared in Example 1 on Aspergillus flavus.

[0038] Figure 10 Tensile cycle curve experiment of Nap-PIL-PLPBTDE prepared in Example 1. DETAILED DESCRIPTION

[0039] The preparation of the fluorescent polyionic liquid gel of the present application is further illustrated below by specific examples.

[0040] The materials and reagents used in the examples of the present application are as follows:

[0041] 1-vinylimidazole (VIm, analytical pure), bromoethane (analytical pure), bromoacetic acid (analytical pure) and 2,6-di-tert-butyl-p-cresol (BHT, analytical pure), 2-bromomethylnaphthalene (analytical pure) were purchased from Damas-beta, 1-vinylimidazole was purified by vacuum distillation and stored in a refrigerator. Lipoic acid (LA, analytical pure) was purchased from MERYER, azobis-isobutyronitrile was recrystallized with ethanol and stored in a refrigerator. Sodium hydroxide, anhydrous ethanol, methanol, ethyl acetate and anhydrous ether were all analytical pure reagents and were used directly without treatment.

[0042] The instruments used in the present application are as follows:

[0043] The structure of the materials was characterized by nuclear magnetic resonance spectrometer AVANCE AV400MHz (Bruker, Switzerland), Fourier transform infrared spectrometer Nicolet6700 (Thermo, USA) and thermal gravimetric analyzer TG209F3 (Netzsch, Germany), and the mechanical properties of the materials were tested by tensile testing machine INSTRON 6800 (Instron, USA).

[0044] Example 1

[0045] (1) Preparation of 1-vinyl-3-ethylimidazole ([EVIm]Br) salt ionic liquid

[0046] In a 50 mL round-bottom flask, 1-vinylimidazole 4.7749 g (50.74 mmol) was added, and then 20 mL of methanol was added to dissolve it. Then, bromoethane 5.8473 g (53.66 mmol) was slowly added dropwise to the above solution, and stirred at room temperature for 24 h. After the reaction was completed, the solution was added dropwise to 50 mL of ether, precipitated and filtered to obtain a white powder, which was purified by dissolving the precipitate in methanol-ether, repeated 3 times, and the solid was vacuum dried to obtain a white powder solid product, with a yield of 52%.

[0047] (2) Preparation of 1-vinyl-3-carboxymethyl imidazole ([CMVIm]Br) ionic liquid

[0048] In a 100 mL round-bottom flask, bromoacetic acid 6.9523 g (50.03 mmol) and 1- vinylimidazole 4.7841 g (50.83 mmol) were added, and then dichloromethane 50 mL was added to dissolve them. The solution was vacuumed and circulated with N2for 3 times, and then refluxed at 55 °C for 48 h under N2atmosphere. After the reaction was completed, the white solid was obtained by filtration, and then purified by methanol dissolution-ethyl ether precipitation for 3 times. The white solid product was obtained by vacuum drying, and the yield was 85%.

[0049] (3) Preparation of 1-vinyl-3-naphthylmethyl imidazole ([NapMVIm]Br) ionic liquid

[0050] In a 100 mL round-bottom flask, 1-vinylimidazole 5.8367 g (61.95 mmol) was added, and then 30 mL of methanol was added. The flask was placed in an ice bath, and then bromomethylnaphthalene 12.9343 g (58.50 mmol) was added in small portions for several times. The reaction was stirred at 25 °C for 24 h. After the reaction was completed, the product was purified by methanol dissolution-ethyl ether precipitation for 3 times. The white solid was obtained by vacuum drying, and the yield was 87%.

[0051] (4) Preparation of naphthylmethyl-containing polyionic liquid

[0052] In a 100 mL round-bottom flask, [EVIm]Br 2.0308 g (10.00 mmol), [CMVIm]Br 2.3308 g (10.00 mmol), [NapMVIm]Br 3.1521 g (10.00 mmol), and azobisisobutyronitrile 0.05 g were added in sequence, and then methanol 50 mL was added to dissolve them. The solution was vacuumed and circulated with N2for 3 times, and then stirred at 80 °C for 72 h under N2protection. After the reaction was completed, the product was purified by methanol dissolution-ethyl acetate precipitation for 3 times. The yellowish solid was obtained by vacuum drying, and the yield was 76%.

[0053] (5) Preparation of sodium lipoate (NaLA)

[0054] In a 100 mL beaker, sodium hydroxide 2.3972 g (59.93 mmol) was weighed, and then 50 mL of ethanol was added to dissolve the sodium hydroxide. Then lipoic acid 10.3030 g (49.94 mmol) was added to the sodium hydroxide ethanol solution, and then stirred at room temperature for 4 h. The yellowish solid was obtained by filtration, and the yield was 64%.

[0055] (6) Preparation of lipoic acid monomer containing a fluorescent group

[0056] Benzene boronic acid 5.5001 g (45.50 mmol) and 4,7-dibromobenzothiazole 20.0311 g (69.10 mmol) were dissolved in a mixture of 10 mL of toluene, 4 mL of ethanol and aqueous sodium carbonate solution (2 mol L –1 ,4 mL) under N2protection, and then tetra(triphenylphosphine)palladium 0.1403 g (0.1211 mmol) was added, and the reaction was stirred at 80 °C under reflux for 72 h. After the reaction was completed, dichloromethane and saturated NaCl aqueous solution were sequentially added for extraction, and the organic phase was taken and purified by silica gel column chromatography, and then dried in vacuum to obtain a yellow-green solid, which was 4-bromo-7-phenylbenzo[C][1,2,5]thiadiazole BPBTD, with a yield of 54%.

[0057] BPBTD 5.0115 g (17.21 mmol) and NaLA 3.9326 g (17.21 mmol) were dissolved in 40 mL of DMF in a 100 mL round-bottom flask, and then stirred at 60 °C under reflux for 48 h under N2protection. After the reaction was completed, dichloromethane and deionized water were sequentially added for extraction, and the organic phase was taken, dried over anhydrous magnesium sulfate, and then rotary evaporated and dried in vacuum to obtain a yellow-green solid, which was 4-lipoic acid (7-phenylbenzo[C][1,2,5]thiadiazole) ester LPBTDE, with a yield of 26%.

[0058] (7) Preparation of poly-lipoic acid containing fluorescent groups

[0059] LPBTDE 0.4207 g (1.00 mmol) and lipoic acid 1.8624 g (9.00 mmol) were dissolved in 10 mL of ethanol, and then dried at 60 °C to obtain a yellowish thin film PLPBTDE, with a yield of 98%.

[0060] (8) Preparation of polyionic liquid gel

[0061] Nap-PIL 6.3866 g (8.50 mmol) and lipoic acid 1.7538 g (8.50 mmol) were dissolved in 20 mL of anhydrous ethanol, and then stirred at room temperature for 3 h, and then the solvent was evaporated under natural conditions to obtain a yellow-brown gel, which was lipoic acid-containing polyionic liquid Nap-PIL-PLA, with a yield of 98%.

[0062] Nap-PIL 6.3091 g (8.40 mmol) and PLPBTDE 3.4992 g (8.40 mmol) were dissolved in 20 mL of anhydrous ethanol, and then stirred at room temperature for 3 h, and then the solvent was evaporated under natural conditions to obtain a yellow-brown gel, which was fluorescent polyionic liquid gel Nap-PIL-PLPBTDE, with a yield of 98%.

[0063] Structure characterization of the compound prepared in Example 1:

[0064] 1. Structural characterization of Nap-PIL

[0065] Figure 1 for Nap-PIL 1 HNMR spectra. From the figure, it can be seen that all peaks are broadened compared with [CMVIm]Br and [NapMVIm]Br monomers, especially the broad peaks at 5.7 and 1.50 ppm, which are the disappearance of the corresponding vinyl characteristic peaks, proving that the vinyl group has undergone polymerization.

[0066] 2. Structural characterization of BPBTD

[0067] Figure 2 for BPBTD 1 HNMR spectra. From the figure, it can be seen that all characteristic peaks are above 7.25, indicating that the hydrogen is in the conjugated system, the multiplet of hydrogen on the benzene ring is between 7.45-7.60 ppm, and the multiplet of hydrogen on the heterocycle is between 7.85-8.00 ppm. Proving the synthesis of BPBTD.

[0068] 3. Structural characterization of LPBTDE

[0069] Figure 3 for LPBTDE 1 HNMR spectra. From the figure, it can be seen that the multiplet of hydrogen of all fluorescent groups appears between 7.45-8.00 ppm, and the corresponding peak of the lipoic acid part appears in the high field. Proving the synthesis of LPBTDE.

[0070] 4. Structural characterization of Nap-PIL-PLPBTDE (provide 1 HNMR spectra)

[0071] Figure 4 for Nap-PIL-PLPBTDE 1 HNMR spectra. From the figure, there are no obvious monomer and small molecule peaks. The high field part is the peak of the poly-lipoic acid chain of the second network PLPBTDE, proving that both the first network (Nap-PIL) and the second network (PLPBTDE) have been formed.

[0072] Figure 5 Fourier transform infrared (FTIR) spectra of PLPBTDE, Nap-PIL, Nap-PIL-PLA and Nap-PIL-PLPBTDE, the stretching vibration of carboxyl group is at 1751 cm -1 , and shows a smaller peak in PLPBTDE and Nap-PIL-PLPBTDE, which is due to the modification of part of the carboxyl groups of lipoic acid repeating units by fluorescent molecule groups. In addition, the spectrum at 1550 cm -1 and 1172 cm-1 The Nap-PIL-PLPBTDE shows characteristic stretching vibrations of imidazole, which are assigned to the C=N and C-N bonds, respectively.

[0073] 6. Thermogravimetric analysis of Nap-PIL-PLPBTDE

[0074] Figure 6 The thermogravimetric analysis curve of Nap-PIL-PLPBTDE, with a water content of 3.28%, has high temperature stability, proving the formation of polyionic liquid gel.

[0075] 7. Fluorescence effect of Nap-PIL-PLPBTDE

[0076] Figure 7 The digital photos of Nap-PIL-PLPBTDE material under visible light, dark environment and ultraviolet light (365 nm) are shown, which shows yellow-brown color under visible light, no color can be observed in dark environment, and the material emits blue fluorescence under ultraviolet light, proving that Nap-PIL-PLPBTDE has fluorescence effect.

[0077] 8. Antibacterial performance of Nap-PIL-PLPBTDE

[0078] The antibacterial experiment of Nap-PIL-PLPBTDE prepared in Example 1 was carried out by the following method, as follows:

[0079] The antibacterial experiment of Nap-PIL-PLPBTDE compared with Nap-PIL-PLA, glass glue and blank group is shown, as Figure 8 The four concentric circles are shown, and a substrate (culture medium mixed with selected material, starch, glucose and agar) is added on each concentric circle, and a broad-spectrum bacteria is cultured, and after 0h, 24h, 48h and 72h (a~d), colonies appear in the culture medium added with blank group and glass glue, while the inner circle containing Nap-PIL-PLA and Nap-PIL-PLPBTDE has almost no colonies. Figure 8

[0080] As Figure 9 The antibacterial experiment of blank group, containing glass glue, containing Nap-PIL-PLPBTDE is designed on three same substrates (culture medium mixed with selected material, starch, glucose and agar), and Aspergillus flavus is cultured respectively. After 0h, 24h, 48h, colonies appear in the culture medium added with blank group and glass glue, while the culture medium containing Nap-PIL-PLPBTDE still has no colonies after 48h, proving that the material has antibacterial property and can be used for the preparation of antibacterial material.

[0081] 9. Fatigue resistance of Nap-PIL-PLPBTDE ​

[0082] The fatigue resistance test of Nap-PIL-PLPBTDE prepared in Example 1 was carried out using the following method, specifically as follows:

[0083] Nap-PIL-PLPBTDE was added at 10 mm min -1 The strain was tested under the tensile force of 200% strain for 50 consecutive cycles. Figure 10 It can be seen from the negative unloading stress-strain curve of Nap-PIL-PLPBTDE shown that Nap-PIL-PLPBTDE can still maintain the tensile strength and curve shape basically unchanged within 50 tensile cycles, and gradually tends to be stable as the tensile cycles increase, proving that it has good fatigue resistance.

[0084] Summarize:

[0085] In summary, the present invention copolymerizes ionic liquid monomers containing carboxyl, ethyl, and naphthylmethyl groups to produce a polyionic liquid, further combining it with polylipoic acid containing a fluorescent group, and evaporating the solvent to polymerize the lipoic acid chains to produce a fluorescent polyionic liquid gel. This novel polyionic liquid simultaneously contains stable carbon-carbon covalent bonds, reactive dynamic sulfur-sulfur covalent bonds, and hydrogen bonding of the carboxyl groups, resulting in high mechanical strength and fatigue resistance. Furthermore, the effects of the naphthylmethyl and phenylbenzothiazolyl groups allow the material to produce strong blue fluorescence and also exhibit antibacterial properties.

Claims

1. A fluorescent polyionic liquid gel, having the following structural formula: In the formula, x = 50-200; y = 20-200; z = 20-100; m = 50-200; n = 20-100.

2. A process for the preparation of the fluorescent polyionic liquid gel of claim 1, characterized by, Comprising the following steps: (1) Preparation of brominated 1-vinyl-3-ethyl imidazole ionic liquid: Dissolve bromoethane and 1-vinyl imidazole in methanol, stir at 25-30°C for 24-48h, after the reaction is completed, purify by methanol-ethyl ether dissolution and precipitation, vacuum dry to obtain white powder solid product, which is brominated 1-vinyl-3-ethyl imidazole ionic liquid [EVIm]Br; (2) Preparation of brominated 1-vinyl-3-carboxymethyl imidazole ionic liquid: Dissolve bromoacetic acid and 1-vinyl imidazole in dichloromethane, under N2 atmosphere, reflux at 50-60°C for 45-50h, after the reaction is completed, filter to obtain white solid, purify by methanol dissolution-ethyl ether precipitation, vacuum dry to obtain white solid product, which is brominated 1-vinyl-3-carboxymethyl imidazole ionic liquid [CMVIm]Br; (3) Preparation of brominated 1-vinyl-3-naphthylmethyl imidazole ionic liquid: Dissolve 2-bromomethyl naphthalene and 1-vinyl imidazole in methanol under ice bath condition, stir at 25-30°C for 12-24h, after the reaction is completed, purify by methanol dissolution-ethyl ether precipitation, vacuum dry to obtain white solid, which is brominated 1-vinyl-3-naphthylmethyl imidazole ionic liquid [NapMVIm]Br; (4) Preparation of naphthylmethyl-containing polyionic liquid: Dissolve [EVIm]Br, [CMVIm]Br, [NapMVIm]Br in methanol, use azobisisobutyronitrile as initiator, under N2 protection, reflux and stir at 70-80°C for 48-72h, after the reaction is completed, purify by methanol dissolution-ethyl acetate precipitation, vacuum dry to obtain light yellow solid, which is polyionic liquid Nap-PIL; In step (4), the molar ratio of [EVIm]Br, [CMVIm]Br and [NapMVIm]Br is 1:1:1-1:3:3, and the mass ratio of azobisisobutyronitrile and [CMVIm]Br is 1:50-1:100; (5) Preparation of sodium lipoic acid: Dissolve sodium hydroxide in ethanol, then add lipoic acid to the sodium hydroxide ethanol solution, stir at room temperature for 4-6h, and extract by filtration to obtain light yellow solid, which is sodium lipoic acid NaLA; (6) Preparation of lipoic acid monomer containing fluorescent groups: The benzene boronic acid and 4,7-dibromobenzothiazole are dissolved in a mixture of toluene, ethanol and aqueous sodium carbonate solution, under N2 protection, tetra (triphenylphosphine) palladium is added, and the reaction is stirred at 80-90℃ under reflux for 48-72h. After the reaction is completed, dichloromethane and saturated NaCl aqueous solution are sequentially extracted, the organic phase is taken, purified by silica gel column chromatography, and vacuum dried to obtain a yellow-green solid, which is 4-bromo-7-phenylbenzo[C][1,2,5]thiadiazole BPBTD. The BPBTD and NaLA are dissolved in DMF, under N2 protection, the reaction is stirred at 60-70℃ under reflux for 48-72h. After the reaction is completed, dichloromethane and deionized water are sequentially extracted, the organic phase is taken, dried over anhydrous magnesium sulfate, the solution is rotary evaporated, and vacuum dried to obtain a yellow-green solid, which is 4-lipoic acid (7-phenylbenzo[C][1,2,5]thiadiazole) ester LPBTDE; (7) Preparation of poly-lipoic acid containing fluorescent groups: LPBTDE and lipoic acid are dissolved in ethanol, dried at 60-70℃ to obtain a light yellow film PLPBTDE; In step (7), the molar ratio of LPBTDE and lipoic acid is 1:1-1:9; (8) Preparation of polyionic liquid gel: Nap-PIL and PLPBTDE are dissolved in anhydrous ethanol, stirred at room temperature for 3h, and the solvent is evaporated under natural conditions to obtain a yellow-brown gel, which is a fluorescent polyionic liquid gel Nap-PIL-PLPBTDE; In step (8), the molar ratio of PLPBTDE and Nap-PIL is 1:1-1:

3.

3. The process for the preparation of fluorescent polyionic liquid gel as claimed in claim 2, wherein: In step (1), the molar ratio of 1-vinylimidazole and bromoethane is 1:1-1:1.

5.

4. The process for the preparation of fluorescent polyionic liquid gel as claimed in claim 2, wherein: In step (2), the molar ratio of bromoacetic acid and 1-vinylimidazole is 1:1-1:1.

8.

5. The method for preparing a fluorescent polyionic liquid gel according to claim 2, wherein: In step (3), the molar ratio of 1-vinylimidazole and 2-bromomethyl naphthalene is 1:1-1:1.

8.

6. The method for preparing a fluorescent polyionic liquid gel according to claim 2, wherein: In step (6), the molar ratio of benzene boronic acid and 4,7-dibromobenzothiazole is 1:2-1:1.

5.

7. Use of the fluorescent polyionic liquid gel of claim 1 in the preparation of antibacterial materials.

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