CN116603268A - Polyion liquid double-aqueous-phase system for inducing reversible phase separation by host-guest interaction and application - Google Patents

Abstract

The application provides a polyion liquid double-aqueous-phase system for inducing reversible phase separation by host-guest interaction and application thereof, and belongs to the technical field of phase separation. The two aqueous phase system adopts PVImBn _x Et+PVImAzo ₅ Et+CB[8]As a component, the aqueous two-phase system has reversible response behavior under light/heat stimulation, wherein PVImBn _x Et is obtained by grafting benzyl (Bn) on a polyvinyl imidazole backbone structure, and the PVImAzo ₅ Et is obtained by grafting azobenzene (Azo) with polyvinyl imidazole as a main chain structure, and x is 10-40. The method is used for separating and purifying triphenylmethane and rhodamine B, can realize the temperature response and light correspondence in the purifying process, and has the advantages of no contact, quick response and the like.

Description

A polyionic liquid aqueous two-phase system with host-guest interaction-induced reversible phase separation and its application

Technical Field

The present application relates to a polyionic liquid two-phase aqueous system with host-guest interaction-induced reversible phase separation and its application, belonging to the technical field of phase separation.

Background Art

Aqueous two-phase system (ATPS) is formed by phase separation of a mixture of two immiscible substances, solute and water, above the critical concentration. It has the advantages of good biocompatibility, low interfacial tension, green environmental protection, and recyclability. It is widely used in various aspects such as extraction separation, mass transfer, and catalysis. It is an ideal medium for separating and purifying various compounds.

Polyionic liquids are very good solutes for constructing aqueous two-phase systems. The purpose of phase behavior regulation can be achieved by designing their structures or introducing functional groups. However, current research on polyionic liquids focuses more on how to use existing aqueous two-phase systems to achieve the distribution and extraction of substances, while there is less research on the intelligent and adjustable phase behavior of aqueous two-phase systems (based on the response of specific structures to external stimuli to achieve phase behavior changes).

Among the few studies on intelligent tunable phase behavior, most are based on covalent modification of component molecules, and no research has been found that uses non-covalent host-guest interactions to regulate double aqueous phases.

Summary of the invention

In view of this, the present application first provides a polyionic liquid two-phase aqueous system with host-guest interaction-induced reversible phase separation, which not only realizes non-covalent host-guest interaction to regulate the phase behavior of the two-phase aqueous system, but also realizes its stress response to temperature and ultraviolet light.

Specifically, the present application is implemented through the following scheme:

A polyionic liquid aqueous two-phase system with reversible phase separation induced by host-guest interaction, wherein the aqueous two-phase system is composed of PVImBn _x Et+PVImAzo ₅ Et+CB[8] and is reversible under light/heat stimulation, wherein the host is cucurbitac[8] uril and the guest is a benzyl group; PVImBn _x Et is obtained by grafting benzyl (Bn) with polyvinyl imidazole as the main chain structure, and x is 5 to 40; and PVImAzo ₅ Et is obtained by grafting azophenyl (Azo) with polyvinyl imidazole as the main chain structure.

The two-phase aqueous system of the above scheme uses benzyl-functionalized polyionic liquid PVImBn _x Et (x=5-40) and azophenyl-functionalized polyionic liquid PVImAzo ₅ Et with good water solubility as polyionic liquids, and cooperates with the main molecule cucurbitacin[8]uril (CB[8]) to form a stable two-phase aqueous system (ATPS), which is used for host-guest phase separation, endowed with temperature and light-induced response, and has up/down reversible phase inversion behavior, realizing adjustable phase separation and phase inversion effects, and has great application potential in the fields of future intelligent separation.

Further, as a preference:

In the thermal stimulation, a phase reversal occurs when the temperature rises to 70°C or above, and the original state is restored when the temperature drops to room temperature or below.

In the light stimulation, phase reversal occurs when ultraviolet light is used, and the original state is restored when visible light is used. More preferably, the ultraviolet light irradiation time is 2 to 20 seconds, and the visible light irradiation time is 2 to 40 minutes. The ultraviolet light wavelength is 325 to 400nm or 425 to 460nm, and the visible light wavelength is 320 to 400nm or 430 to 475nm. As the ultraviolet light irradiation time increases, the π→π* transition absorption peak gradually decreases, while the n→π* transition absorption peak gradually increases, indicating that the azobenzene group changes to the cis (cis configuration). When using visible light irradiation, the cis configuration will gradually return to a stable inverted configuration.

The two-phase aqueous system also includes N,N,N-trimethyl-1-adamantyl ammonium iodide. As a competitive object with a higher binding constant of cucurbit[8]uril, N,N,N-trimethyl-1-adamantyl ammonium iodide is more conducive to achieving phase reversibility of the two-phase aqueous system. At this time, in the polyionic liquid PVImBn _x Et, x is 15 to 30. The N,N,N-trimethyl-1-adamantyl ammonium iodide is prepared from 1-adamantaneamine, formaldehyde solution, formic acid and methyl iodide by the following reaction:

In the above scheme,

The PVImAzo ₅ Et is prepared from 6-bromohexyl-4-azophenyl ether and polyvinyl imidazole via the following reaction:

(1) Synthesis of 4-hydroxyazobenzene (Azo-OH): Aniline is mixed with concentrated hydrochloric acid in an ice-water bath to react, and sodium nitrite is added to react to obtain a diazonium salt solution. Phenol is added dropwise to a sodium hydroxide aqueous solution and stirred evenly, and then the diazonium salt solution is added dropwise in an ice-water bath to react and synthesize 4-hydroxyazobenzene.

(2) Synthesis of 6-bromohexyl-4-azophenyl ether (AzoC ₆ Br): 1,6-dibromohexane and potassium carbonate were added to 4-hydroxyazobenzene. After the reaction was completed, hydrochloric acid was added to dissolve the potassium carbonate to obtain 6-bromohexyl-4-azophenyl ether.

(3) Synthesis of polyvinylimidazole (PVIm): Polyvinylimidazole is obtained by reacting 1-vinylimidazole and azobisisobutyronitrile;

(4) Synthesis of azophenyl polyionic liquid (PVImAzo ₅ Et): The polyvinyl imidazole synthesized in step (3) was dissolved in methanol, and 6-bromohexyl-4-azophenyl ether was added. After the reaction was completed, ethyl bromide was added to continue the reaction, and the mixture was precipitated in ether to obtain PVImAzo ₅ Et.

The PVImBn _x Et is prepared from benzyl bromide, ethyl bromide and polyvinyl imidazole by the following reaction:

(1) Synthesis of polyvinylimidazole (PVIm): Polyvinylimidazole is obtained by reacting 1-vinylimidazole and azobisisobutyronitrile;

(2) Synthesis of azobenzene polyionic liquid PVImBn _x Et: The synthesized polyvinylimidazole was dissolved in methanol, and benzyl bromide was added to complete the reaction. Ethyl bromide was added to continue the reaction, and the mixture was precipitated in ether to obtain PVImBn _x Et.

The cucurbitacin [8] uril is prepared from urea, glyoxal and paraformaldehyde as raw materials through the following reaction:

1) After urea is dissolved in deionized water, concentrated sulfuric acid is added to adjust the pH to 1-2, glyoxal is added dropwise for reaction, and the pH is adjusted to neutral to obtain glycoluril;

2) Mix glycoluril and polyformaldehyde and add concentrated hydrochloric acid. After stirring for reaction, add methanol for precipitation to obtain cucurbituril [8].

Cucurbitacin[8]uril (CB[8]) is a non-toxic and non-reactive host molecule that can form homo-ternary or hetero-ternary complexes with guest molecules in aqueous media through cation-dipole interactions and hydrophobic interactions, which promotes its application as a supramolecular switch. This dynamic structure in aqueous media introduces stimulus responsiveness into the system. When combined with a specific guest, the system can achieve reversible conversion of the complex when subjected to external stimuli (such as light, redox potential or pH), and even achieve orthogonal stimulus responsiveness, which is predictable and designable.

The above scheme uses cucurbitacin[8]uril as the main molecule and polyvinyl imidazole as the main chain structure, and grafts low-grafting azophenyl (Azo) and benzyl (Bn) groups to synthesize a series of polyionic liquids, and forms a biphasic system with CB[8]. A biphasic system with dual stimulus responses to ultraviolet light and temperature was constructed. When the temperature rises (70°C) or ultraviolet light is applied, the biphasic system undergoes a phase reversal, and this phase behavior is reversible, realizing the regulation of the phase behavior of the biphasic system by external stimuli.

The polyionic liquid aqueous two-phase system is used for the separation and purification of triphenylmethane and rhodamine B, which can realize the temperature response and light response of the purification process, and has the advantages of non-contact and fast response.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a hydrogen nuclear magnetic resonance spectrum of the polyionic liquid PVImAzo ₅ Et (DMSO-d ₆ ) in Example 1;

FIG2 is the hydrogen nuclear magnetic resonance spectrum of PVImBn ₅ Et (DMSO-d ₆ ) in Example 1;

FIG3 is an FT-IR graph of the polyionic liquids PVImAzo ₅ Et and PVImBn ₅ Et in Example 1;

FIG4 is a TGA graph of polyionic liquids PVImAzo ₅ Et and PVImBn ₅ Et in Example 1;

FIG5 is a comparison of spectra of the PVImAzo ₅ Et aqueous solution in Example 1 under different UV irradiation times;

FIG6 is a comparison of spectra of the PVImAzo ₅ Et aqueous solution in Example 1 under different visible light irradiation times;

FIG7 is the hydrogen nuclear magnetic resonance spectrum of CB[8](D ₂ O) in Example 2;

FIG8 is a comparison of the stimulus response of the PVImBn _x Et + PVImAzo ₅ Et + CB[8] aqueous two-phase system with different _GDBn ;

FIG9 is a stimulus response diagram of the PVImBn ₅ Et+PVImAzo ₅ Et+CB[8] aqueous two-phase system;

FIG10 is a DLS curve of PVImBn _x Et (1.0 wt %) and PVImBn _x Et + CB [8] (1.0 wt %);

FIG11 is the DLS curves of PVImBn ₅ Et+0.4eq CB[8] (1.0wt%) at different temperatures;

FIG12 is a hydrogen nuclear magnetic resonance spectrum of N,N,N-trimethyl-1-adamantyl ammonium iodide (Chloroform-d) in Example 3;

FIG13 is a H-NMR spectrum of [MImBn]Br+CB[8]+[TMAda]I;

FIG. 14 is a comparison of the addition of the competing guest [TMAda]I into the PVImAzo ₅ Et+PVImBn _x Et+CB[8] aqueous two-phase system with different _GDBn .

DETAILED DESCRIPTION

The reagents and test equipment used in the following examples are shown in Table 1 and Table 2.

Table 1: Raw materials and reagents used in the examples

Table 2: Characterization and testing instruments used in the examples

name model factory Vacuum drying oven DZF-150 Zhengzhou Great Wall Science, Industry and Trade Co., Ltd. Oil bath pot DF-101S Zhengzhou Great Wall Science, Industry and Trade Co., Ltd. Analytical Balance YP402N Shanghai Precision Scientific Instrument Co., Ltd. Rotary evaporator RE-52AA Shanghai Yarong Company Infrared spectrometer Agilent Cary 660 Agilent Technologies UV-Vis Spectrometer UV-2600 Shimadzu Corporation Dynamic Light Scattering Zetasizer Nano-ZS 90 Malvern Thermogravimetric Analyzer DT Q600 V8.2 Build100 Birkin-Elmer Nuclear Magnetic Resonance Brucker 400MHz Brucke Biersbing

The scheme is explained below in conjunction with embodiments.

Example 1

The preparation of polyionic liquid (PVImBn _x Et, PVImAzo ₅ Et) in this embodiment comprises the following steps:

(1) Synthesis of 4-hydroxyazobenzene (Azo-OH)

① Dilute concentrated hydrochloric acid (36.5%) with 25 mL of deionized water, and mix with aniline (5.02 g, 53.9 mmol) purified by vacuum distillation in a 200 mL beaker in an ice-water bath. After mixing, react for 30 minutes.

② Weigh 3.7 g of sodium nitrite, dissolve it in 25 mL of water, add it to step ① and continue the reaction for 1 hour to obtain a diazonium salt solution.

③ Dissolve sodium hydroxide in 50 mL of water, drop the dissolved sodium hydroxide solution into phenol (7.8 g, 82.8 mmol) and stir to mix. Drop the diazonium salt solution in step ② into the above mixture under ice-water bath conditions and stir. After the addition is complete, continue the reaction for 2 hours.

④ Filter, wash with deionized water, and dry in a vacuum oven at 70°C for 12 h to obtain a yellow solid.

Yield: 9.53 g (89.03%).

The above preparation process can be represented by the following reaction formula:

(2) Synthesis of 6-bromohexyl-4-azophenyl ether (AzoC ₆ Br)

① Add 1,6-dibromohexane (13.73 g, 56.3 mmol), 4-hydroxyazobenzene (3.72 g, 18.8 mmol) and potassium carbonate (6.93 g, 50.1 mmol) to a 250 mL round-bottom flask in sequence, add 120 mL acetone and a magnetic stirrer. React in a 70 ° C oil bath in a nitrogen atmosphere for 24 hours. After the reaction is completed, hydrochloric acid is added dropwise to the flask to dissolve potassium carbonate to obtain a mixture.

② Take 150 mL of dichloromethane to extract the mixture, repeat the extraction of the organic phase 2-3 times and wash with deionized water and saturated brine, rotary evaporate, purify by column chromatography, the eluent is petroleum ether: ethyl acetate = 40:1 (volume ratio), rotary evaporate to remove the solvent, and vacuum dry at 70°C to obtain an orange solid powder.

Yield: 2.76 g (48.2%).

The above preparation process can be represented by the following reaction formula:

(3) Synthesis of polyvinyl imidazole (PVIm)

1-vinylimidazole (10.001 g, 106 mmol) and azobisisobutyronitrile (0.175 g, 1.063 mmol) were added to a round-bottom flask containing methanol (20 mL). The reaction system was refluxed at 70°C for 60 h under a nitrogen atmosphere. After the reaction was completed, the mixture was precipitated in ether, filtered, and dried at 80°C overnight to obtain a white-yellow solid.

The yield was 9.03 g (90.3%).

The above process is represented by the following reaction formula:

(4) Synthesis of azobenzene polyionic liquid (PVImAzo ₅ Et)

Polyvinyl imidazole (4.012 g, 42.6 mmol (imidazole monomer)) was weighed, dissolved in 20 mL of methanol, and then 6-bromohexyl-4-azophenyl ether (0.65 g, 2.13 mmol) was added, and refluxed at 70°C for reaction. After the reaction was completed, ethyl bromide (12.0149 g, 110.23 mmol) was added after cooling to room temperature, and the reaction was continued at 70°C for reflux. After the reaction was completed, the reaction system was precipitated in ether, filtered, and the product was dried at 70°C overnight to obtain an orange-yellow solid.

The yield was 3.93 g (84.2%).

The above process is represented by the following reaction formula:

(5) Synthesis of benzyl polyionic liquid (PVImBn _x Et)

Taking PVImBn ₅ Et as an example: polyvinyl imidazole (3.982 g, 42.3 mmol (imidazole monomer)) was weighed, dissolved in 20 mL of methanol, and then benzyl bromide (0.362 g, 2.12 mmol) was added, and refluxed at 70°C. After the reaction was completed, the mixture was cooled to room temperature, and then ethyl bromide (11.7541 g, 107.84 mmol) was added, and refluxed at 70°C. After the reaction was completed, the reaction system was precipitated in ether and dried at 70°C overnight to obtain a white solid.

The yield was 3.56 g (82.3%).

The above process is represented by the following reaction formula:

The above products were analyzed and tested as follows.

1) ¹ H NMR analysis:

The products PVImAzo ₅ Et and PVImBn _x Et were subjected to ¹ H NMR analysis, and the results are shown in Figures 1 and 2: The signal peak at δ = 7.0-8.3 ppm in the H NMR spectrum of PVImAzo ₅ Et is attributed to the signal peak of hydrogen on the benzene ring of the azobenzene group, indicating the successful grafting of the azobenzene group. The signal peak at δ = 5.0-5.7 ppm in the H NMR spectrum of PVImBn ₅ Et is attributed to the two hydrogens of the methylene group in the benzyl group, indicating the successful grafting of the benzyl group.

2) FT-IR and TGA analysis

FT-IR analysis is shown in Figure 3: 2832cm ^-1 and 2716cm ^-1 are the stretching vibration peaks of the CH in the alkyl substituent on the imidazole ring; 1584cm ^-1 and 1368cm ^-1 are the stretching vibration peaks of C＝C in the imidazole ring, proving the formation of the structure of the polyvinyl imidazole main chain. 1257cm ^-1 is the stretching vibration peak of Ar-O in PVImAzo ₅ Et, proving that the azobenzene group was successfully grafted onto the polymer. 3138cm ^-1 and 3071cm ^-1 are attributed to the CH stretching vibration peaks on the benzene ring of PVImBn ₅ Et, proving that the benzyl group was successfully grafted onto the polyvinyl imidazole.

Thermogravimetric analysis (TGA) results of polyionic liquid in nitrogen flow are shown in Figure 4: the polymer does not begin to decompose until 300°C, and has high thermal stability. The weight loss at around 100°C comes from the removal of the solvent.

3) Light response test

Since the azobenzene group is a photoresponsive group, PVImAzo ₅ Et is photoresponsive. The photoresponse of PVImAzo ₅ Et is characterized by UV-visible spectroscopy. As shown in Figures 5 and 6, in a stable state, the azobenzene polyionic liquid is in the trans configuration. When irradiated with ultraviolet light, the azobenzene group changes from the trans configuration to the cis configuration. When irradiated with visible light, the cis configuration returns to the stable trans configuration. In the aqueous two-phase system, under ultraviolet irradiation conditions, azobenzene is photoisomerized, the hydrophilicity of PVImAzo ₅ Et increases, the density of the PVImAzo ₅ Et-rich phase decreases, and a phase inversion occurs.

Example 2

This example is a synthesis of cucurbitac[8]uril (CB[8]), comprising the following two steps:

(1) Add urea (18 g, 0.3 mol) to a three-necked flask, add 25 mL of deionized water at 40°C and stir to dissolve it. After complete dissolution, add concentrated sulfuric acid to adjust the pH of the system to 1-2. Place a glyoxal solution (40 wt%) in a constant pressure dropping funnel, add all the glyoxal in a 50°C oil bath within 5 minutes, continue stirring for 5 minutes, then raise the temperature to 85°C and react for 2 hours. After the reaction is completed, cool to room temperature, prepare NaOH solution (15 wt%) to adjust the pH value of the reaction system to neutral, filter and wash with a large amount of deionized water, and place the obtained white solid in a vacuum drying oven to dry for 12 hours to obtain the product glycoluril. Yield: 14.56 g, 68.3%.

(2) Add paraformaldehyde (42 g, 2.8 mol) and glycoluril (100 g, 0.74 mol) obtained by the method of step (1) into a round-bottom flask, then add 150 mL of concentrated hydrochloric acid (36.5%), stir evenly, heat to 100°C, and react for 18 hours. After the reaction is completed, use a large amount of methanol to precipitate, filter, and wash the solid with a large amount of acetone. The obtained solid is placed in a vacuum drying oven at 100°C and dried for 24 hours. The dried solid was placed in a beaker, and three times the volume of hydrochloric acid (5 mol/L) was added. The mixture was stirred and filtered, and the filter cake was washed with acetone. The filtered solid was placed in a vacuum drying oven at 100°C for 24 hours to remove CB[6]. The dried solid was added to a formic acid solution (50 wt%), stirred and refluxed for 1 hour, and then filtered. The filter cake was washed with a large amount of acetone, and the obtained solid was dried in a vacuum drying oven at 100°C for 24 hours. The above operation was repeated to finally obtain a white solid product, namely cucurbitac[8]uril, and its ¹ H NMR analysis result is shown in Figure 7.

The above process is represented by the following reaction formula:

Example 3

In this example, a two-phase aqueous system is constructed, and the process is as follows:

0.15 g of each of PVImAzo ₅ Et and PVImBn _x Et prepared in Example 1 and 2 mL of deionized water were added to a sample bottle and stirred to dissolve; CB[8] prepared in Example 2 was added and continued to stir.

Taking _GDBn (Bn grafting degree) = 5% (x is 5), 15% (x is 15), 25% (x is 25), 35% (x is 35), and 45% (x is 45) as examples, _PVImBnxEt + _PVImAzo5Et +CB[8] aqueous two-phase systems with different _GDBn were prepared, and an equal amount (i.e., 1 eq) of CB[8] was added to the system.

In this case, the amount of CB[8] added was based on the molar number of benzyl groups in PVImBn ₅ Et (ie, 1 eq). For example, 13.6 mg CB[8] was added when 0.4 eq CB[8] was added.

The above two-phase aqueous system was tested.

1) Stimulus response test

The stimulus response results of the PVImBn _x Et + PVImAzo ₅ Et + CB[8] aqueous two-phase system with different _GDBn are shown in Figure 8: When _GDBn is 15-35%, the PVImBn _x Et-rich phase changes from the upper phase to the lower phase. For the aqueous two-phase system with _GDBn reaching 45%, the PVImBn _x Et-rich phase is obviously cross-linked and becomes an opaque gel, with a significantly reduced volume and located in the lower phase. In particular, the UV-temperature dual stimulus response of the aqueous two-phase system constructed with PVImBn ₅ Et + PVImAzo ₅ Et + CB[8], i.e., _GDBn is 5%, is particularly significant.

Stimulus response experiment was carried out on the PVImBn ₅ Et+PVImAzo ₅ Et+CB[8] aqueous two-phase system:

① Ultraviolet light stimulation response experiment: Under stirring conditions, use a 365nm fixed wavelength ultraviolet lamp to irradiate the two-phase aqueous system for 3 hours and let it stand to separate the layers.

② Temperature stimulus response experiment: Place the sample bottle containing the aqueous two-phase system in a 70°C drying oven for 20 minutes and observe the phenomenon.

From Figure 9, it can be seen that the aqueous two-phase system constructed by PVImAzo ₅ Et+PVImBn ₅ Et+CB[8] can undergo phase inversion under heating (70°C) or ultraviolet light (365nm), and this phenomenon is reversible. When the temperature drops to room temperature (25°C) or under visible light irradiation, the aqueous two-phase system will return to its initial state.

2) Dynamic light scattering characterization (DLS)

Dynamic light scattering tests were performed on aqueous solutions of PVImBn _x Et + CB[8] with different _GDBn . The test results are shown in Figure 10: With the increase of _GDBn , the size of the PVImBn _x Et@CB[8] aggregates gradually decreased. This is because the benzyl group combined with CB[8] to form a host-guest complex. The existence of hydrophobic interactions between the crosslinking points and the benzyl groups enhanced the interaction between the macromolecular chains, making the aggregation more compact and the aggregate size gradually decreasing. Since PVImBn _x Et@CB[8] further enhanced the interaction between the chains, the PVImBn _x Et-rich phase was relatively stable, making the two-phase aqueous system insensitive to UV light and temperature.

Take PVImBn ₅ Et (1wt%) + 0.4eq CB[8] as an example: As shown in Figure 11, the size of the PVImBn ₅ Et@CB[8] complex aggregates decreases significantly with increasing temperature. On the one hand, the increase in temperature weakens the non-covalent interaction between the host and guest complexes. On the other hand, the hydration capacity of the polyionic liquid PVImBn ₅ Et is also affected by temperature.

3) Effects of competing guest molecules on the aqueous two-phase system

In order to achieve phase reversibility of the two-phase aqueous system, an ionic liquid with a higher binding constant with CB[8] is added to the system as a competing object. Taking the ionic liquid N,N,N-trimethyl-1-adamantyl ammonium iodide ([TMAda]I) as an example, its synthesis process is as follows:

1-adamantanamine (1g, 6.6mmol), formaldehyde solution (37wt%, 1.6g, 19.8mmol) and formic acid (1.05g, 19.8mmol) were added to a round-bottom flask and placed in an oil bath at 100℃ for 18h. After the reaction, NaOH solution (40wt%) was added to adjust the pH value of the reaction system to 11-12, and the mixture was extracted with 30mL of ether. The organic phase was washed with saturated brine and the intermediate product N,N-dimethyl-1-adamantanylamine was obtained after rotary evaporation as a colorless oily liquid. Yield: 0.99g (90%). The intermediate product N,N-dimethyl-1-adamantylamine (0.5 g, 2.8 mmol) and 10 ml of dichloromethane were added to a round-bottom flask, and iodomethane (0.475 g, 3.35 mmol) was added under ice-water bath conditions, stirred at room temperature for 8 h, filtered, the filter cake was washed with dichloromethane, and dried in a vacuum oven at 40°C for 12 h to obtain a white solid product, namely N,N,N-trimethyl-1-adamantylammonium iodide ([TMAda]I), the ¹ HNMR analysis results of which are shown in Figure 12. Yield: 0.8 g (90.5%).

The above process is represented by the following reaction formula:

It can be clearly seen from Figure 13 that [BnMIm]Br was replaced to form a [TMAda]I@CB[8] complex, indicating that CB[8] preferentially binds to [TMAda]I.

As shown in Figure 14, when [TMAda]I is added to the aqueous two-phase system, in the system with lower _GDBn (15%, 25%), the competing guest combines with CB[8] to form [TMAda]I@CB[8], and the phase of the aqueous two-phase system is reversed and restored to the initial state. However, when _GDBn reaches 35%, [TMAda]I@CB[8] cannot precipitate from the system to reverse the phase of the aqueous two-phase system, which may be caused by the high viscosity of the system.

In the above case, polyionic liquids PVImBn _x Et (x = 5, 15, 25, 35, 45) and azobenzene functionalized polyionic liquids PVImAzo ₅ Et were synthesized by first polymerization and then modification, and the main molecule CB[8] and the competing guest N,N,N-trimethyl-1-adamantyl ammonium iodide were prepared. The constructed PVImAzo ₅ Et+PVImBn ₅ Et+CB[8] aqueous two-phase system can undergo phase inversion under ultraviolet light or heating conditions, and can be restored to the original state under visible light or temperature reduction conditions. When the competing guest N,N,N-trimethyl-1-adamantyl ammonium iodide is added to the aqueous two-phase system, the aqueous two-phase system with a lower _GDBn (≤25%) can be restored to the original state, while when the _GDBn is higher (35%), it cannot be restored due to the increased viscosity of the system.

Example 4

The PVImAzo ₅ Et+PVImBn ₅ Et+CB[8] aqueous two-phase system was used for the separation and purification of triphenylmethane dye (taking brilliant green as an example), and the process was as follows:

1) Prepare triphenylmethane aqueous solution (concentration: 10 mg/mL, pH: 8.0);

2) Take 0.15 g of each of PVImAzo ₅ Et and PVImBn _x Et prepared in Example 1, add them and 1.5 mL of deionized water into a sample bottle and stir to dissolve, then add 0.5 mL of triphenylmethane solution and stir until the solution separates into phases to form a two-phase aqueous system, in which the PVImAzo ₅ Et-rich phase is located in the lower layer, and the PVImBn _x Et-rich phase is located in the upper layer. Triphenylmethane is mainly distributed in the PVImAzo ₅ Et-rich phase, i.e., the lower layer. Take a small amount of the upper layer solution to determine the triphenylmethane concentration;

3) Add CB[8] prepared in Example 2 to the above aqueous two-phase system and continue stirring. The PVImAzo ₅ Et-rich phase is located in the upper layer, and triphenylmethane is also enriched in the upper layer. Take a small amount of the upper layer solution to measure the concentration of triphenylmethane. Combined with the second step, calculate the distribution ratio of triphenylmethane in the two phases.

The conventional purification process of triphenylmethane is:

1) Prepare triphenylmethane aqueous solution (concentration: 5 mg/mL, pH: 8.0);

2) Take 1 mL of triphenylmethane aqueous solution, add PVImBn _x Et (0.2 g) and K ₃ PO ₄ (0.2 g) to the solution, stir to dissolve, and let stand to form a two-phase aqueous system;

3) Use a separatory funnel to separate the two-phase solution, determine the concentration of triphenylmethane in the upper and lower phases respectively, and calculate the distribution ratio of triphenylmethane.

The difference between the two is shown in Table 3.

Table 3: Comparison of different purification methods of A

Example 5

The PVImAzo ₅ Et+PVImBn ₅ Et+CB[8] aqueous two-phase system was used for the separation and purification of rhodamine B. The process is as follows:

1) Prepare rhodamine B aqueous solution (concentration: 10 mg/mL);

2) Take 0.15 g of each of PVImAzo ₅ Et and PVImBn _x Et prepared in Example 1, add them and 1.5 mL of deionized water into a sample bottle and stir to dissolve, then add 0.5 mL of rhodamine B solution and stir until the solution separates into two phases to form a two-phase aqueous system, in which the PVImAzo ₅ Et-rich phase is located in the lower layer, and the PVImBn _x Et-rich phase is located in the upper layer. Rhodamine B is mainly distributed in the PVImAzo ₅ Et-rich phase, i.e., the lower layer. Take a small amount of the upper layer solution to determine the concentration of rhodamine B;

3) Add CB[8] prepared in Example 2 to the above two-phase aqueous system and continue stirring. The PVImAzo ₅ Et-rich phase is located in the upper layer, and rhodamine B is also enriched in the upper layer. Take a small amount of the upper layer solution to determine the concentration of rhodamine B. Combined with the second step, calculate the distribution ratio of rhodamine B in the two phases.

The conventional purification process of Rhodamine B is:

1) Prepare rhodamine B aqueous solution (concentration: 5 mg/mL, pH: 8.0);

2) Take 1 mL of Rhodamine B aqueous solution, add PVImBn _x Et (0.2 g) and K ₃ PO ₄ (0.2 g) to the solution, stir to dissolve, and let stand to form a two-phase aqueous system;

3) Use a separatory funnel to separate the two phases of the solution, determine the concentration of Rhodamine B in the upper and lower phases respectively, and calculate the distribution ratio of Rhodamine B.

The difference between the two is shown in Table 4.

Table 4: Comparison of different purification methods of Rhodamine B

Claims (10)

1. A polyionic liquid two-phase system capable of reversible phase separation induced by host-guest interaction, characterized in that: the two-phase system is composed of PVImBn _x Et + PVImAzo ₅ Et + CB [8], and the two-phase The system is reversible under light/heat stimulation, in which the host is cucurbit [8] urea, and the guest is a benzyl group; PVImBn _x Et is obtained by grafting benzyl groups with polyvinylimidazole as the main chain structure, and the x is 5-40; the PVImAzo ₅ Et is obtained by grafting azophenyl group with polyvinylimidazole main chain structure. 2. A polyionic liquid aqueous two-phase system in which host-guest interaction induces reversible phase separation according to claim 1, characterized in that: in the thermal stimulation, phase inversion occurs when the temperature rises to 70°C or above, and the temperature Return to original state when cooled to room temperature and below. 3. A polyionic liquid two-phase system in which host-guest interaction induces reversible phase separation according to claim 1, characterized in that: in the photostimulation, phase inversion occurs when ultraviolet light is irradiated, and when visible light is irradiated, phase inversion occurs. Return to original state. 4. A polyionic liquid aqueous two-phase system in which host-guest interaction induces reversible phase separation according to claim 3, characterized in that: the ultraviolet light irradiation time is 2-20s, and the visible light irradiation time is 2-40min. 5 . A polyionic liquid aqueous two-phase system in which host-guest interaction induces reversible phase separation according to claim 1 , characterized in that: in the polyionic liquid PVImBn _x Et , x is 15-35. 6. A polyionic liquid two-phase system in which host-guest interaction induces reversible phase separation according to claim 1, characterized in that: said two-phase system also includes N, N, N-trimethyl -1-adamantyl ammonium iodide, N, N, N-trimethyl-1-adamantyl ammonium iodide as competing object. 7 . A polyionic liquid aqueous two-phase system in which host-guest interaction induces reversible phase separation according to claim 7 , characterized in that: in the polyionic liquid PVImBn _x Et, x is 15-30. 8. A polyionic liquid two-phase system in which host-guest interaction induces reversible phase separation according to claim 7, characterized in that: said N, N, N-trimethyl-1-adamantyl iodide Ammonium is prepared from 1-adamantanamine, formaldehyde solution, formic acid and iodine salt. 9. A polyionic liquid two-phase system in which host-guest interaction induces reversible phase separation according to claims 1 to 8, characterized in that: the PVImAzo ₅ Et is 6-bromohexyl-4-azophenyl ether and polyvinylimidazole as raw materials, the PVImBn _x Et is prepared from benzyl bromide, ethyl bromide, and polyvinylimidazole as raw materials; the cucurbit [8] urea is prepared from urea, glyoxal and polymer Formaldehyde is produced as a raw material. 10. An application of a polyionic liquid two-phase aqueous system in which host-guest interaction induces reversible phase separation, characterized in that: the polyionic liquid two-phase aqueous system is used for the separation and purification of triphenylmethane or rhodamine B.