Liquid crystal polymer-aggregation-induced emission molecular fluorescent composite material with pH response

Abstract

The invention relates to the technical field of fluorescent liquid crystal, in particular to a liquid crystal polymer-aggregation-induced emission molecular fluorescent composite material with pH response, which comprises an SLCP film and TPE-4amide, an amidino group on the TPE-4amidine has response to pH, so that the fluorescence change of the material occurs; the SLCP film contains a hydrogen bond structure of carboxyl, and is easy to reversibly deconstruct under high temperature or alkaline solution treatment to form a regular transverse pore structure. The SLCP film is used as a main body, the electrostatic interaction in the SLCP film can be accurately controlled by adjusting the pH, fluorescent molecules are adsorbed, a self-assembly structure is formed, and the reversible change of the fluorescent color of the liquid crystal polymer-aggregation-induced emission molecular fluorescent composite material with pH response from yellow-green to blue is realized. The application limitation of a traditional liquid crystal unit is broken through, the stimulation responsiveness of the material is enhanced through the porous structure of the liquid crystal unit, and the liquid crystal unit has wide application prospects.

Description

Technical Field

[0001] The invention relates to the technical field of fluorescent liquid crystal, and in particular to a liquid crystal polymer-aggregation-induced luminescence molecule fluorescent composite material with pH response. Background Art

[0002] Fluorescent compounds have internal filter effect and self-absorption, and molecular aggregation can easily cause fluorescence quenching, which is called aggregation-induced fluorescence quenching (ACQ effect). Generally, the solution needs to be diluted to a concentration of less than 10 -5 mol / L is required to obtain an accurate spectrum of fluorescent molecules. Low concentrations severely limit the practical application of fluorescent sensors. Usually, researchers will avoid molecular aggregation by selecting fluorophores with high fluorescence quantum efficiency, introducing flexible groups such as alkyl chains to solve the problems of π-π stacking and material dissolution, and designing molecular structures with large steric hindrance such as dendrites to prevent aggregation. In 2001, Tang Benzhong's research group first proposed the AIE (aggregation-induced emission) mechanism. They found that fluorescent substances containing groups such as 1-methyl-1,2,3,4,5-tetraphenylthiole, substituted styrene, 9,10-diphenylethylene anthracene and tetraphenylethylene showed non-fluorescence or low fluorescence in solution. However, in the aggregated state, the intramolecular motion was restricted, which inhibited the energy attenuation of non-radiative channels, and excluded the torsional intramolecular charge transfer (TICT) process and J aggregation, thereby generating strong fluorescence. Aggregation-induced emission has expanded the application range of fluorescent sensors from being only suitable for dilute solution detection to aggregate detection, which greatly expands the scope of application of fluorescent sensors.

[0003] The research on AIE small molecules has achieved a series of important results, and the research on polymer materials with AIE properties has gradually become popular. When the AIE element is introduced into the polymer matrix, the polymer chain will inhibit the molecular motion of the AIE structural unit, resulting in a higher luminescence efficiency. Compared with AIE small molecules, AIE polymers have better plasticity, heat resistance and corrosion resistance. At the same time, through a variety of synthetic strategies, some specific functional groups can also be introduced into the polymer chain to obtain polymer materials that have fluorescent responses to external stimuli (light, force, acid, alkali, heat), which greatly develops its application in different fields such as stimulus-responsive materials, metal ion detection and biomedicine.

[0004] For example, the patent technical document CN115677890A discloses a dendritic fluorescent liquid crystal polymer with aggregation-induced emission properties and a preparation method thereof. First, a dendritic fluorescent monomer molecule I with an AIE effect is synthesized, and then the corresponding dendritic fluorescent liquid crystal polymer II is synthesized by a free radical polymerization method. This type of dendritic fluorescent liquid crystal polymer material has high temperature resistance and good processing properties, but cannot guarantee the sensitivity and reversibility of pH response.

[0005] Therefore, according to the above-mentioned related technologies, it is urgent to develop a liquid crystal polymer-aggregation-induced emission molecule fluorescent composite material with pH response. Summary of the invention

[0006] In view of this, the purpose of the present invention is to provide a liquid crystal polymer-aggregation-induced emission molecule fluorescent composite material with pH response to solve the problems of sensitivity and reversibility of pH response of aggregation-induced emission molecule fluorescent composite materials in the prior art.

[0007] Based on the above objectives, the present invention provides a liquid crystal polymer-aggregation-induced emission molecule fluorescent composite material with pH response.

[0008] A pH-responsive liquid crystal polymer-aggregation-induced emission molecule fluorescent composite material, comprising a SLCP film and TPE-4amidine;

[0009] The SLCP film has a hydrogen bonding structure containing carboxyl groups;

[0010] The structural formula of the TPE-4amidine is as follows:

[0011]

[0012] Preferably, the preparation method of the SLCP film is as follows:

[0013] Step A1: Mix the monomer and the cross-linking agent, add a photoinitiator and a polymerization inhibitor, dissolve them in dichloromethane, and heat at 50-70° C. for 3-5 hours in a dark environment to obtain a liquid crystal monomer mixture;

[0014] Step A2: Fill the liquid crystal monomer mixture into a liquid crystal box, place it at 90-100°C for 3-8 minutes in a yellow light environment without ultraviolet rays, irradiate it with a point light source with a wavelength of 365nm for 3-8 minutes, and further cure it at 135°C for 2-5 hours to obtain a SLCP film.

[0015] Preferably, the structural formula of the monomer in step A1 is as follows:

[0016]

[0017] The cross-linking agent structural formula is as follows:

[0018]

[0019] The structural formula of the photoinitiator is as follows:

[0020]

[0021] The polymerization inhibitor is p-methoxyphenol.

[0022] Preferably, the usage ratio of the monomer, cross-linking agent, photoinitiator, inhibitor and dichloromethane in step A1 is 0.8-1g: 0.1-0.2g: 8-12mg: 0.1-0.5mg: 10-12mL.

[0023] Preferably, the amount of the liquid crystal monomer mixture used in step A2 is 0.8-1.2 g.

[0024] Preferably, the preparation method of the TPE-4amidine is as follows:

[0025] Step B1: In a 500 mL flask, zinc powder and tetrahydrofuran are added, the flask is placed in an ice-salt bath and stirred for 20-30 min, titanium tetrachloride is slowly added dropwise to the flask at 0-2° C. under nitrogen protection, stirred at room temperature for 8-10 min, and then refluxed at 40-50° C. for 20-30 min to obtain a pre-treated solution;

[0026] Step B2: Pyridine and 4,4'-diaminobenzophenone are added to the pretreatment solution, refluxed at 40-50°C for 22-26 hours, cooled to room temperature, evaporated at 110-115°C for 20-30 minutes, dissolved in water, extracted twice with dichloromethane, and purified by column chromatography using dichloromethane and petroleum ether as eluents to obtain intermediate A;

[0027] Step B3: Intermediate A, 1,1-dimethoxy-N,N-dimethylethylamine and methanol are mixed, stirred at 60-80°C in a nitrogen atmosphere for 10-12 hours, purified by silica gel column chromatography using dichloromethane and petroleum ether, and heated at 60-80°C under vacuum for 6-8 hours to obtain TPE-4amidine.

[0028] Preferably, the ratio of zinc powder, tetrahydrofuran and titanium tetrachloride used in step B1 is 10-15 g: 300-350 mL: 8-10 mL.

[0029] Preferably, the usage ratio of pyridine, 4,4'-diaminobenzophenone and pretreatment solution in step B2 is 3-5 mL: 4-6 g: 300-350 mL;

[0030] The volume ratio of dichloromethane to petroleum ether in step B2 is 1:3;

[0031] The structural formula of the intermediate A is as follows:

[0032]

[0033] Preferably, the usage ratio of the intermediate A, 1,1-dimethoxy-N,N-dimethylethylamine and methanol in step B3 is 0.08-0.3 g: 0.1-0.4 g: 0.1-0.3 mL;

[0034] The volume ratio of dichloromethane to petroleum ether in step B3 is 3:1.

[0035] Preferably, the preparation method of the pH-responsive liquid crystal polymer-aggregation-induced emission molecule fluorescent composite material is as follows:

[0036] 2-5 mL of pH 12 phosphate buffer was added to the SLCP membrane, and the SLCP membrane was rinsed with distilled water. TPE-4amidine was prepared to a concentration of 10 -4 The 3 mol / L solution was applied to the SLCP film and allowed to stand for 6-8 hours to obtain a liquid crystal polymer-aggregation-induced emission molecule fluorescent composite material with pH response.

[0037] Beneficial effects of the present invention:

[0038] The present invention designs and synthesizes a novel aggregation-induced emission molecule TPE-4amidine containing four amidine groups as a guest, and integrates it into the network of hydrogen-bonded bridged SLCP membrane to achieve self-assembly, thereby forming a pH-responsive smectic liquid crystal polymer-aggregation-induced emission molecule fluorescent composite material.

[0039] The present invention provides a liquid crystal polymer-aggregation-induced luminescence molecule fluorescent composite material with pH response, and the amidine group on TPE-4amidine responds to pH, thereby causing a fluorescence change in the material. The SLCP film contains a hydrogen bond structure of carboxyl groups, which is easily reversibly decomposed under high temperature or alkaline solution treatment to form a regular lateral pore structure. With the help of this SLCP film as the main body, the electrostatic interaction within the SLCP film can be accurately controlled by adjusting the pH, and fluorescent molecules can be adsorbed and a self-assembled structure can be formed, so as to achieve a reversible change in the fluorescence color of the liquid crystal polymer-aggregation-induced luminescence molecule fluorescent composite material with pH response from yellow-green to blue. This not only breaks through the application limitations of traditional liquid crystal units, but also its porous structure enhances the stimulus responsiveness of the material, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only for the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0041] Figure 1 is a synthetic route diagram of TPE-4amidine in the present invention;

[0042] Figure 2 is the hydrogen nuclear magnetic resonance spectrum of intermediate A in the present invention;

[0043] Figure 3 is the carbon nuclear magnetic resonance spectrum of intermediate A in the present invention;

[0044] Figure 4 is the hydrogen nuclear magnetic resonance spectrum of TPE-4amidine in the present invention;

[0045] Figure 5 is the carbon nuclear magnetic resonance spectrum of TPE-4amidine in the present invention;

[0046] Figure 6 For different water contents 10 in Example 1 of the present invention -4 mol / L-TPE-4amidine solution fluorescence spectrum;

[0047] Figure 7 is a differential scanning calorimetry (DSC) curve of the liquid crystal monomer mixture in Example 1 of the present invention;

[0048] Figure 8 These are photos of the pH-responsive liquid crystal polymer-aggregation-induced emission molecule fluorescent composite material in Example 1 of the present invention after being treated with phosphate buffer solutions of different pH values;

[0049] Fig. 9 This is a patterned application diagram of the SLCP film in Example 1 of the present invention. DETAILED DESCRIPTION

[0050] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

[0051] The sources and properties of some of the raw materials used in the present invention are as follows:

[0052] 4,4'-Diaminobenzophenone was purchased from Shanghai Hansi Chemical Co., Ltd.; 1,1-dimethoxy-N,N-dimethylethylamine was purchased from Hubei Xinhongli Chemical Co., Ltd.

[0053] Example 1: A liquid crystal polymer-aggregation-induced emission molecule fluorescent composite material with pH response, comprising the following steps:

[0054] S1: 0.8-1g monomer and 0.1-0.2g cross-linking agent are mixed, and then 8-12mg photoinitiator and 0.1-0.5mg polymerization inhibitor are added, and the mixture is dissolved in 10-12mL dichloromethane, and heated at 50-70°C for 3-5h under light-proof conditions to obtain a liquid crystal monomer mixture;

[0055] S2: 0.8 g of the liquid crystal monomer mixture was filled into a liquid crystal box, and after standing at 90°C for 3 min in a yellow light environment without ultraviolet rays, it was irradiated with a point light source with a wavelength of 365 nm for 3 min, and further cured at 135°C for 2 h to obtain a SLCP film;

[0056] S3: In a 500 mL flask, add 10 g of zinc powder and 300 mL of tetrahydrofuran, place the flask in an ice-salt bath and stir for 20 min, under nitrogen protection, slowly drop 8 mL of titanium tetrachloride into the flask at 0°C, stir at room temperature for 8 min, and then reflux at 40°C for 20 min to obtain a pretreatment solution;

[0057] S4: Add 3 mL of pyridine and 4 g of 4,4'-diaminobenzophenone to 300 mL of the pretreatment solution, reflux at 40°C for 22 h, cool to room temperature, evaporate at 110°C for 20 min, dissolve in water, extract twice with dichloromethane, and purify by column chromatography using dichloromethane and petroleum ether as eluents to obtain intermediate A, wherein the volume ratio of dichloromethane to petroleum ether is 1:3;

[0058] S5: 0.08 g of intermediate A, 0.1 g of 1,1-dimethoxy-N,N-dimethylethylamine and 0.1 mL of methanol were mixed, stirred at 60° C. in a nitrogen atmosphere for 10 h, purified by silica gel column chromatography using dichloromethane and petroleum ether, and heated at 60° C. under vacuum for 6 h to obtain TPE-4amidine, wherein the volume ratio of dichloromethane to petroleum ether was 3:1;

[0059] S6: Add 2 mL of pH 12 phosphate buffer to the SLCP membrane and rinse the SLCP membrane with distilled water. -4 The 3 mol / L solution was coated on the SLCP film and allowed to stand for 8 h to obtain a liquid crystal polymer-aggregation-induced emission molecule fluorescent composite material with pH response.

[0060] Example 2: A liquid crystal polymer-aggregation-induced emission molecule fluorescent composite material with pH response, comprising the following steps:

[0061] S1: 0.8-1g monomer and 0.1-0.2g cross-linking agent are mixed, and then 8-12mg photoinitiator and 0.1-0.5mg polymerization inhibitor are added, and the mixture is dissolved in 10-12mL dichloromethane, and heated at 50-70°C for 3-5h under light-proof conditions to obtain a liquid crystal monomer mixture;

[0062] S2: 0.9 g of the liquid crystal monomer mixture was filled into the liquid crystal box, and after standing at 94°C for 5 min in a yellow light environment without ultraviolet rays, it was irradiated with a point light source with a wavelength of 365 nm for 5 min, and further cured at 135°C for 3 h to obtain a SLCP film;

[0063] S3: In a 500 mL flask, add 12 g of zinc powder and 320 mL of tetrahydrofuran, place the flask in an ice-salt bath and stir for 24 min, under nitrogen protection, slowly drop 8.5 mL of titanium tetrachloride into the flask at 0.5 ° C, stir at room temperature for 8.5 min, and then reflux at 44 ° C for 24 min to obtain a pretreatment solution;

[0064] S4: 3.5 mL of pyridine and 4.5 g of 4,4'-diaminobenzophenone were added to 320 mL of the pretreatment solution, refluxed at 44°C for 23 h, cooled to room temperature, evaporated at 112°C for 24 min, dissolved in water, extracted twice with dichloromethane, and purified by column chromatography using dichloromethane and petroleum ether as eluents to obtain intermediate A, wherein the volume ratio of dichloromethane to petroleum ether was 1:3;

[0065] S5: 0.1 g of intermediate A, 0.2 g of 1,1-dimethoxy-N,N-dimethylethylamine and 0.15 mL of methanol were mixed, stirred at 60-80° C. in a nitrogen atmosphere for 10.5 h, purified by silica gel column chromatography using dichloromethane and petroleum ether, and heated at 64° C. under vacuum for 6.5 h to obtain TPE-4amidine, wherein the volume ratio of dichloromethane to petroleum ether was 3:1;

[0066] S6: Add 3 mL of pH 12 phosphate buffer to the SLCP membrane, rinse the SLCP membrane with distilled water, and prepare TPE-4amidine at a concentration of 10 -4 The 30 mol / L solution was coated on the SLCP film and allowed to stand for 6.5 h to obtain a liquid crystal polymer-aggregation-induced emission molecule fluorescent composite material with pH response.

[0067] Example 3: A liquid crystal polymer-aggregation-induced emission molecule fluorescent composite material with pH response, comprising the following steps:

[0068] S1: 0.8-1g monomer and 0.1-0.2g cross-linking agent are mixed, and then 8-12mg photoinitiator and 0.1-0.5mg polymerization inhibitor are added, and the mixture is dissolved in 10-12mL dichloromethane, and heated at 50-70°C for 3-5h under light-proof conditions to obtain a liquid crystal monomer mixture;

[0069] S2: 1.1 g of the liquid crystal monomer mixture was filled into a liquid crystal box, and after standing at 98°C for 7 minutes under a yellow light environment without ultraviolet rays, it was irradiated with a point light source with a wavelength of 365 nm for 7 minutes, and further cured at 135°C for 4 hours to obtain a SLCP film;

[0070] S3: In a 500 mL flask, add 14 g zinc powder and 340 mL tetrahydrofuran, place the flask in an ice-salt bath and stir for 28 min, under nitrogen protection, slowly drop 9 mL titanium tetrachloride into the flask at 1 ° C, stir at room temperature for 9 min, and then reflux at 48 ° C for 28 min to obtain a pretreatment solution;

[0071] S4: 4 mL of pyridine and 5 g of 4,4'-diaminobenzophenone were added to 340 mL of the pretreatment solution, refluxed at 48°C for 25 h, cooled to room temperature, evaporated at 114°C for 28 min, dissolved in water, extracted twice with dichloromethane, and purified by column chromatography using dichloromethane and petroleum ether as eluents to obtain intermediate A, wherein the volume ratio of dichloromethane to petroleum ether was 1:3;

[0072] S5: 0.2 g of intermediate A, 0.3 g of 1,1-dimethoxy-N,N-dimethylethylamine and 0.2 mL of methanol were mixed, stirred at 68° C. in a nitrogen atmosphere for 11 h, purified by silica gel column chromatography using dichloromethane and petroleum ether, and heated at 78° C. under vacuum for 7 h to obtain TPE-4amidine, wherein the volume ratio of dichloromethane to petroleum ether was 3:1;

[0073] S6: Add 4 mL of pH 12 phosphate buffer to the SLCP membrane and rinse the SLCP membrane with distilled water. -4 The 30 mol / L solution was coated on the SLCP film and allowed to stand for 7 h to obtain a liquid crystal polymer-aggregation-induced emission molecule fluorescent composite material with pH response.

[0074] Example 4: A pH-responsive liquid crystal polymer-aggregation-induced emission molecule fluorescent composite material, comprising the following steps:

[0075] S1: 1 g of monomer and 0.2 g of cross-linking agent were mixed, and then 12 mg of photoinitiator and 0.5 mg of polymerization inhibitor were added, and the mixture was dissolved in 12 mL of dichloromethane, and heated at 70 ° C for 5 h in the dark to obtain a liquid crystal monomer mixture;

[0076] S2: 1.2 g of the liquid crystal monomer mixture was filled into a liquid crystal box, and after standing at 100°C for 8 min in a yellow light environment without ultraviolet rays, it was irradiated with a point light source with a wavelength of 365 nm for 8 min, and further cured at 135°C for 5 h to obtain a SLCP film;

[0077] S3: In a 500 mL flask, add 15 g of zinc powder and 350 mL of tetrahydrofuran, place the flask in an ice-salt bath and stir for 30 min, under nitrogen protection, slowly drop 10 mL of titanium tetrachloride into the flask at 2 ° C, stir at room temperature for 10 min, and then reflux at 50 ° C for 30 min to obtain a pretreatment solution;

[0078] S4: Add 5 mL of pyridine and 6 g of 4,4'-diaminobenzophenone to 350 mL of the pretreatment solution, reflux at 50°C for 26 h, cool to room temperature, evaporate at 115°C for 30 min, dissolve in water, extract twice with dichloromethane, and purify by column chromatography using dichloromethane and petroleum ether as eluents to obtain intermediate A, wherein the volume ratio of dichloromethane to petroleum ether is 1:3;

[0079] S5: 0.3 g of intermediate A, 0.4 g of 1,1-dimethoxy-N,N-dimethylethylamine and 0.3 mL of methanol were mixed, stirred at 80° C. in a nitrogen atmosphere for 12 h, purified by silica gel column chromatography using dichloromethane and petroleum ether, and heated at 80° C. under vacuum for 8 h to obtain TPE-4amidine, wherein the volume ratio of dichloromethane to petroleum ether was 3:1;

[0080] S6: Add 2-5 mL of pH 12 phosphate buffer to the SLCP membrane, rinse the SLCP membrane with distilled water, and prepare TPE-4amidine at a concentration of 10 -4 The 3 mol / L solution was applied to the SLCP film and allowed to stand for 6-8 hours to obtain a liquid crystal polymer-aggregation-induced emission molecule fluorescent composite material with pH response.

[0081] Performance Testing:

[0082] Fluorescence test of different water contents:

[0083] The TPE-4amidine prepared in Example 1 was dissolved in dimethylformamide to prepare a 10 - 2Then, the mother liquor was mixed with dimethylformamide and water in different proportions to prepare different water contents (0%, 10%, 80%, 90%, 99%) with a concentration of 10 -4 mol / L solution and tested its fluorescence properties.

[0084] When the water content is between 0% and 60%, the fluorescence of TPE-4amidine is very weak and almost no obvious fluorescence phenomenon can be observed. However, as the water content gradually increases from 70% to 99%, the fluorescence intensity of the solution increases significantly, the maximum emission wavelength of the fluorescence in the solution is 468nm, and the fluorescence is blue overall.

[0085] When the SLCP film treated with alkali was added to the TPE-4amidine solution with strong fluorescence, the fluorescence intensity of the solution decreased by 10 times, and the SLCP film also changed from a non-fluorescent state to a film with strong green fluorescence.

[0086] Phase transition test:

[0087] Take 20 mg of the liquid crystal monomer mixture in Example 1, preheat the differential scanning calorimeter to the working temperature, ensure that the instrument is accurately calibrated, put the liquid crystal monomer mixture in Example 1 and the reference material into the sample crucible of the differential scanning calorimeter, set the heating rate to 10°C / min, raise the temperature to 150°C, start the differential scanning calorimeter, and the instrument will heat the sample according to the preset temperature program, while monitoring and recording the heat difference between the sample and the reference material.

[0088] The results of differential scanning calorimetry (DSC) show that the prepared liquid crystal mixture undergoes a phase transition to a smectic phase at 88°C, and transforms into a nematic phase at 104.64°C. Further heating eventually leads to an isotropic state.

[0089] Fluorescence reversibility test:

[0090] After adding 2 drops of alkaline phosphate buffer to the pH-responsive liquid crystal polymer-aggregation-induced emission molecule fluorescent composite material prepared in Example 1, its fluorescence color was observed; then the surface of the pH-responsive liquid crystal polymer-aggregation-induced emission molecule fluorescent composite material was wiped clean, 2 drops of acidic phosphate buffer were added, and its fluorescence color was observed. The test was repeated 8 times.

[0091] The test results show that after adding alkaline phosphate buffer, the fluorescence color changes from green to yellow-green; and when acidic phosphate buffer is added, the fluorescence color changes to blue. After multiple cycles of introducing acid and alkali, the fluorescence color can still cycle between yellow-green and blue. This may be because TPE-4amidine has fluorescence quenching under alkaline conditions, and the fluorescence intensity decreases. However, the SLCP film in the pH-responsive liquid crystal polymer-aggregation-induced luminescence molecule fluorescent composite material can accurately control the electrostatic interaction within the SLCP film by adjusting the pH, adsorbing fluorescent molecules and forming a self-assembled structure, which can enhance the fluorescence intensity and emit green fluorescence. Based on this, by adjusting the pH value of each part of the fluorescent molecule conforming to the material, the information conversion application of different fluorescence signals in the same sample can be realized.

[0092] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention is limited to these examples. Under the concept of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

[0093] The present invention is intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A pH-responsive liquid crystal polymer-aggregation-induced emission molecule fluorescent composite material, characterized in that: Including SLCP membrane and TPE-4amidine; The SLCP film has a hydrogen bonding structure containing carboxyl groups; The structural formula of the TPE-4amidine is as follows:

2. The pH-responsive liquid crystal polymer-aggregation-induced emission molecule fluorescent composite material according to claim 1, characterized in that: The preparation method of SLCP film is as follows: Step A1: Mix the monomer and the cross-linking agent, add a photoinitiator and a polymerization inhibitor, dissolve them in dichloromethane, and heat at 50-70° C. for 3-5 hours in a dark environment to obtain a liquid crystal monomer mixture; Step A2: Fill the liquid crystal monomer mixture into a liquid crystal box, place it at 90-100°C for 3-8 minutes in a yellow light environment without ultraviolet rays, irradiate it with a point light source with a wavelength of 365nm for 3-8 minutes, and further cure it at 135°C for 2-5 hours to obtain a SLCP film.

3. The pH-responsive liquid crystal polymer-aggregation-induced emission molecule fluorescent composite material according to claim 2, characterized in that: The structural formula of the monomer in step A1 is as follows: The cross-linking agent structural formula is as follows: The structural formula of the photoinitiator is as follows: The polymerization inhibitor is p-methoxyphenol.

4. The pH-responsive liquid crystal polymer-aggregation-induced emission molecule fluorescent composite material according to claim 2, characterized in that: The usage ratio of the monomer, crosslinking agent, photoinitiator, inhibitor and dichloromethane in step A1 is 0.8-1g: 0.1-0.2g: 8-12mg: 0.1-0.5mg: 10-12mL.

5. The pH-responsive liquid crystal polymer-aggregation-induced emission molecule fluorescent composite material according to claim 2, characterized in that: The amount of the liquid crystal monomer mixture used in step A2 is 0.8-1.2 g.

6. The pH-responsive liquid crystal polymer-aggregation-induced emission molecule fluorescent composite material according to claim 1, characterized in that: The preparation method of the TPE-4amidine is as follows: Step B1: In a 500 mL flask, zinc powder and tetrahydrofuran are added, the flask is placed in an ice-salt bath and stirred for 20-30 min, titanium tetrachloride is slowly added dropwise to the flask at 0-2° C. under nitrogen protection, stirred at room temperature for 8-10 min, and then refluxed at 40-50° C. for 20-30 min to obtain a pre-treated solution; Step B2: Pyridine and 4,4'-diaminobenzophenone are added to the pretreatment solution, refluxed at 40-50°C for 22-26 hours, cooled to room temperature, evaporated at 110-115°C for 20-30 minutes, dissolved in water, extracted twice with dichloromethane, and purified by column chromatography using dichloromethane and petroleum ether as eluents to obtain intermediate A; Step B3: Intermediate A, 1,1-dimethoxy-N,N-dimethylethylamine and methanol are mixed, stirred at 60-80°C in a nitrogen atmosphere for 10-12 hours, purified by silica gel column chromatography using dichloromethane and petroleum ether, and heated at 60-80°C under vacuum for 6-8 hours to obtain TPE-4amidine.

7. The pH-responsive liquid crystal polymer-aggregation-induced emission molecule fluorescent composite material according to claim 6, characterized in that: The usage ratio of zinc powder, tetrahydrofuran and titanium tetrachloride in step B1 is 10-15 g: 300-350 mL: 8-10 mL.

8. The pH-responsive liquid crystal polymer-aggregation-induced emission molecule fluorescent composite material according to claim 6, characterized in that: The usage ratio of pyridine, 4,4'-diaminobenzophenone and pretreatment solution in step B2 is 3-5 mL: 4-6 g: 300-350 mL; The volume ratio of dichloromethane to petroleum ether in step B2 is 1:3; The structural formula of the intermediate A is as follows:

9. The pH-responsive liquid crystal polymer-aggregation-induced emission molecule fluorescent composite material according to claim 6, characterized in that: In step B3, the ratio of the intermediate A, 1,1-dimethoxy-N,N-dimethylethylamine and methanol is 0.08-0.3 g: 0.1-0.4 g: 0.1-0.3 mL; The volume ratio of dichloromethane to petroleum ether in step B3 is 3:

1.

10. The pH-responsive liquid crystal polymer-aggregation-induced emission molecule fluorescent composite material according to any one of claims 1 to 9, characterized in that: The preparation method of the pH-responsive liquid crystal polymer-aggregation-induced emission molecule fluorescent composite material is as follows: 2-5 mL of pH 12 phosphate buffer was added to the SLCP membrane, and the SLCP membrane was rinsed with distilled water. TPE-4amidine was prepared to a concentration of 10 -4 The 3 mol / L solution was applied to the SLCP film and allowed to stand for 6-8 hours to obtain a liquid crystal polymer-aggregation-induced emission molecule fluorescent composite material with pH response.

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