Fluorescent liquid crystal polyurethane material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of high polymer materials, and particularly relates to a fluorescent liquid crystal polyurethane material as well as a preparation method and application thereof. According to the invention, hydroxyl and a flexible spacer-CH2-are introduced to cyanostilbene to synthesize a dihydroxyl-containing cyanostilbene compound as a dihydroxyl fluorescent liquid crystal monomer. A linear polyurethane material is prepared by taking a dihydroxyl fluorescent liquid crystal monomer and diisocyanate as raw materials, and a structural unit of cyanostilbene is directly introduced into a main chain structure of polyurethane in a chemical bonding manner, so that fluorescent / liquid crystal units are uniformly and stably distributed in a polymer main chain; the fluorescent liquid crystal polyurethane material integrating high mechanical property, good processability and stable fluorescence characteristic is obtained. The fluorescent liquid crystal polyurethane material can provide a multifunctional solution in wider fields of data storage, coding anti-counterfeiting, intelligent sensing, flexible electronics, shape memory materials, photoelectric display devices, optical fiber communication, biomedicine and the like.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a fluorescent liquid crystal polyurethane material, its preparation method, and its application. Background Technology

[0002] Fluorescent polyurethanes are a class of polymeric materials with energy conversion and information transmission functions, showing significant application potential in fields such as intelligent sensing, medical diagnostics, and optical devices. Currently, fluorescent polyurethanes mainly include doped fluorescent polyurethanes and bonded fluorescent polyurethanes. Doped fluorescent polyurethanes are obtained by compounding polyurethane and fluorescent substances using methods such as in-situ polymerization, mechanical blending, melt blending, or solution blending. However, because the fluorescent substance and the polyurethane matrix are mainly bound by intermolecular forces, problems such as uneven distribution of the fluorescent substance, easy migration, or aggregation can easily occur. Moreover, compatibility issues between the polyurethane matrix and the fluorescent substance lead to brittleness and decreased toughness, thus affecting mechanical properties. Bonded fluorescent polyurethanes, on the other hand, link fluorescent molecules to the polyurethane molecular chain through chemical bonds, effectively improving the dispersibility of the fluorescent substance and the stability of the material. In bonded fluorescent polyurethanes, the fluorescent substance is often used as a chain extender, end-capping agent, polyol monomer, or isocyanate monomer.

[0003] However, most fluorescent molecules have a large rigid conjugated structure. Although the introduction of rigid fluorophores can enhance fluorescence performance, it will weaken the original high elasticity and toughness of polyurethane, resulting in a decrease in the mechanical properties of polyurethane materials. Moreover, because the rigid conjugated system has a strong π-π stacking effect, the solubility of the material decreases and the melting point increases, thereby affecting the processing performance. Summary of the Invention

[0004] To address the technical problem that existing fluorescent polyurethanes enhance fluorescence performance by introducing rigid fluorophores, but this weakens the original high elasticity and toughness of the polyurethane, resulting in a decrease in the mechanical properties and processing performance of the polyurethane material, this invention provides a fluorescent liquid crystal polyurethane material, its preparation method, and its application.

[0005] This invention introduces hydroxyl groups and flexible spacer groups (-CH2-) onto cyanobistanisole to synthesize a cyanobistanisole compound containing dihydroxyl groups, which serves as a dihydroxyl fluorescent liquid crystal monomer. Using the dihydroxyl fluorescent liquid crystal monomer and diisocyanate as raw materials, linear polyurethane materials are prepared. The structural units of cyanobistanisole are directly introduced into the main chain structure of the polyurethane through chemical bonding, resulting in a uniform and stable distribution of fluorescent / liquid crystal units within the polymer main chain. This yields a fluorescent liquid crystal polyurethane material that combines high mechanical properties, good processability, and stable fluorescence characteristics.

[0006] The first objective of this invention is to provide a fluorescent liquid crystal polyurethane material, which is prepared by a chain extension reaction of a fluorescent liquid crystal polyurethane prepolymer under chain extender conditions; the fluorescent liquid crystal polyurethane prepolymer is prepared by a polyaddition reaction of diisocyanate and dihydroxy fluorescent liquid crystal monomer under the action of a catalyst; the structural formula of the dihydroxy fluorescent liquid crystal monomer is as follows: .

[0007] Preferably, the chemical structural formula of the fluorescent liquid crystal polyurethane material is as follows: .

[0008] Preferably, the molar ratio of diisocyanate to dihydroxy fluorescent liquid crystal monomer is 1.1 to 4:1; the diisocyanate is hexamethylene diisocyanate, isoflurane diisocyanate or toluene diisocyanate.

[0009] Preferably, the molar ratio of the chain extender to the diisocyanate is 0.1 to 0.75:1; the chain extender is at least one selected from ethylene glycol, 1,4-butanediol, 1,6-hexanediol, ethylenediamine, and 1,6-hexanediamine.

[0010] Preferably, the catalyst is an organotin catalyst.

[0011] Preferably, the catalyst is dibutyltin dilaurate, stannous octoate, or dioctyltin.

[0012] Preferably, the specific preparation method of the dihydroxy fluorescent liquid crystal monomer is as follows: Under the action of an acid-binding agent and potassium iodide, p-hydroxybenzaldehyde, 6-bromo-1-hexanol, and a first solvent are placed at 60℃~90℃ to undergo a substitution reaction, yielding p-hydroxyhexyloxybenzaldehyde; under the action of an acid-binding agent and potassium iodide, p-hydroxyphenylacetonitrile, 6-bromo-1-hexanol, and a first solvent are placed at 60℃~90℃ to undergo a substitution reaction, yielding p-hydroxyhexyloxyphenylacetonitrile; under the conditions of 60℃~90℃, p-hydroxyhexyloxyphenylacetonitrile, p-hydroxyhexyloxybenzaldehyde, and the first solvent are mixed evenly, and then an alkaline solution is added, resulting in a carbanion condensation reaction, yielding a dihydroxy fluorescent liquid crystal monomer.

[0013] Preferably, the molar ratio of p-hydroxyhexyloxyphenylacetonitrile to p-hydroxyhexyloxybenzaldehyde is 1:1~2; and the molar ratio of the base to p-hydroxyhexyloxyphenylacetonitrile is 0.1~2:1.

[0014] Preferably, the alkaline solution is obtained by dissolving an alkali in a solvent, with the mass ratio of alkali to solvent being 1:20~50.

[0015] Preferably, the base is at least one selected from sodium hydroxide, potassium hydroxide, sodium ethoxide, potassium ethoxide, potassium tert-butoxide, triethylamine, pyridine, and piperidine.

[0016] Preferably, the time for the carbanion condensation reaction is 4h to 24h.

[0017] Preferably, in the preparation of p-hydroxyhexyloxybenzaldehyde, the molar ratio of p-hydroxybenzaldehyde to 6-bromo-1-hexanol, the acid-binding agent, and potassium iodide is 1:1~3:2~6:0.01~0.1; and the mass ratio of p-hydroxybenzaldehyde to the first solvent is 1:10~50.

[0018] Preferably, in the preparation of p-hydroxyhexyloxyphenylacetonitrile, the molar ratio of p-hydroxyphenylacetonitrile to 6-bromo-1-hexanol, the acid-binding agent and potassium iodide is 1:1~3:2~6:0.01~0.1; and the mass ratio of p-hydroxyphenylacetonitrile to the first solvent is 1:10~50.

[0019] Preferably, the acid-binding agent is at least one selected from anhydrous potassium carbonate, anhydrous sodium carbonate, anhydrous potassium bicarbonate, anhydrous sodium bicarbonate, triethylamine, and pyridine.

[0020] A second objective of this invention is to provide a method for preparing a fluorescent liquid crystal polyurethane material, comprising the following steps: A first mixed solution is obtained by mixing a dihydroxy fluorescent liquid crystal monomer, a catalyst, and a second solvent. A second mixed solution is obtained by mixing a diisocyanate and a second solvent. The second mixed solution is added to the first mixed solution, and under the action of the catalyst, the diisocyanate and the dihydroxy fluorescent liquid crystal monomer undergo a polyaddition reaction to obtain a fluorescent liquid crystal polyurethane prepolymer. The chain extender solution and the fluorescent liquid crystal polyurethane prepolymer are subjected to a chain extension reaction. After removing the solvent, a fluorescent liquid crystal polyurethane material is obtained.

[0021] Preferably, the molar ratio of the catalyst to the dihydroxy fluorescent liquid crystal monomer is 0.01~0.2:1.

[0022] Preferably, the concentration of the dihydroxy fluorescent liquid crystal monomer in the first mixed solution is 10%wt to 50%wt; and the concentration of the diisocyanate in the second mixed solution is 20%wt to 80%wt. The second mixed solution is added dropwise to the first mixed solution to avoid excessively high concentrations of the first and second mixed solutions, which could lead to an overly vigorous reaction.

[0023] Preferably, the temperature of the polyaddition reaction is 50℃~90℃ and the time is 3h~10h.

[0024] Preferably, the chain extension reaction is carried out at a temperature of 50℃ to 90℃ for 1 hour to 5 hours.

[0025] Preferably, the mass ratio of the dihydroxy fluorescent liquid crystal monomer to the solvent is 1:1 to 18.

[0026] The present invention prepares a first mixed solution by using a dihydroxy fluorescent liquid crystal monomer, a catalyst, and a second solvent; prepares a second mixed solution by using a diisocyanate and a second solvent; and then adds the second mixed solution dropwise to the first mixed solution to avoid an overly vigorous reaction that could lead to reaction failure.

[0027] Preferably, the chain extender solution is obtained by dissolving the chain extender in a solvent; the mass concentration of the chain extender solution is 1wt%~60wt%.

[0028] Preferably, the first solvent is ethanol.

[0029] Preferably, the second solvent is at least one selected from N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, 1,4-dioxane, and tetrahydrofuran.

[0030] Preferably, the solvent removal method is at least one of the following: forced-air drying, vacuum drying, rotary evaporation, distillation, and vacuum distillation.

[0031] The third objective of this invention is to provide an application of fluorescent liquid crystal polyurethane material in fields such as optical anti-counterfeiting, data storage, and intelligent sensing.

[0032] Compared with the prior art, the present invention has the following technical effects: 1. This invention introduces hydroxyl groups and flexible spacer groups (-CH2-) onto cyanostilbene to synthesize a cyanostilbene compound containing dihydroxyl groups, which serves as a dihydroxyl fluorescent liquid crystal monomer. Using the dihydroxyl fluorescent liquid crystal monomer and diisocyanate as raw materials, linear polyurethane materials are prepared. The structural units of cyanostilbene are directly introduced into the main chain structure of the polyurethane through chemical bonding, resulting in a uniform and stable distribution of fluorescent / liquid crystal units within the polymer main chain. This yields a fluorescent liquid crystal polyurethane material that combines high mechanical properties, good processability, and stable fluorescence characteristics.

[0033] 2. The cyanostilbene used in this invention has a rigid rod-like structure. After polymerization, it acts as a liquid crystal unit and serves as a rigid segment of the polymer backbone, effectively improving the material's strength, modulus, and heat resistance. Unlike existing technologies where the introduction of fluorescent groups often leads to a decrease in the material's mechanical properties, the introduction of fluorescent units in this invention plays a role in structural enhancement.

[0034] 3. This invention uses a dihydroxy fluorescent liquid crystal monomer with fluorescent units as a polymerizable monomer, which is firmly bonded to the polyurethane molecular backbone through covalent bonds, overcoming the defects of easy migration, aggregation, and uneven distribution of fluorophores in doped fluorescent materials. This results in the fluorescent liquid crystal polyurethane material of this invention having the advantages of high fluorescence stability and long service life.

[0035] 4. This invention utilizes the unique AIE effect of cyanostilbene, resulting in a fluorescent liquid crystal polyurethane material with weak fluorescence in solution, but significantly enhanced fluorescence intensity after being fabricated into a thin film or solid material. This characteristic makes it highly suitable for solid-state optoelectronic devices, solving the problem of fluorescence attenuation or quenching in the aggregated state of traditional fluorescent materials.

[0036] 5. This invention maintains excellent processing performance while ensuring high performance. Although a rigid structure is introduced, cyanostilbene, as a liquid crystal unit, endows the polymer melt / solution with good orientation and fluidity, resulting in low viscosity during processing. This makes it easy to process by injection molding, coating, spinning and other methods, overcoming the bottleneck of processing difficulties of most high-rigidity conjugated polymer materials.

[0037] 6. This invention combines the properties of liquid crystal and fluorescence to develop a fluorescent liquid crystal polyurethane material that has high mechanical properties, high processing performance, and fluorescence energy conversion and information transmission characteristics. It will provide multifunctional solutions in a wider range of fields such as data storage, anti-counterfeiting coding, smart sensing, flexible electronics, shape memory materials, optoelectronic display devices, optical fiber communication, and biomedicine. Attached Figure Description

[0038] Figure 1 The image shows the 1H NMR spectrum of the dihydroxy fluorescent liquid crystal monomer.

[0039] Figure 2 The infrared spectrum of the fluorescent liquid crystal polyurethane material prepared in Example 1 is shown.

[0040] Figure 3 The TG curve is shown for the fluorescent liquid crystal polyurethane material prepared in Example 1.

[0041] Figure 4 The DSC curve of the fluorescent liquid crystal polyurethane material prepared in Example 1 is shown.

[0042] Figure 5 The image shows a polarized light micrograph of the fluorescent liquid crystal polyurethane material prepared in Example 1.

[0043] Figure 6 The image shows the 1D-WAXD spectrum of the fluorescent liquid crystal polyurethane material prepared in Example 1.

[0044] Figure 7 The fluorescence spectra of the fluorescent liquid crystal polyurethane material prepared in Example 1 under different organic solvents are shown.

[0045] Figure 8 This describes the photochromic application of the fluorescent liquid crystal polyurethane material prepared in Example 1. Detailed Implementation

[0046] It should be noted that liquid crystal is a special phase between liquid and crystal, possessing both the flow characteristics of liquid and the order and anisotropy of crystalline components. Liquid crystal polyurethane, as a novel type of liquid crystal polymer material, achieves an organic combination of polyurethane segments and liquid crystal structural units by embedding liquid crystal units into the polyurethane molecular chain. This endows the material with high strength, high modulus, excellent heat resistance, and dimensional stability; its tensile strength and elastic modulus are typically several times or even an order of magnitude higher than ordinary polyurethane materials. Furthermore, the high fluidity of the liquid crystal units in liquid crystal polyurethane results in both the solution and melt exhibiting low viscosity and high fluidity, leading to better processing performance compared to traditional polyurethane.

[0047] Cyanostilbene is a class of small-molecule fluorescent compounds with aggregation-induced emission properties, emitting strong fluorescence in its aggregated state. Furthermore, cyanostilbene possesses a rigid rod-like structure, making it suitable as a liquid crystal building block for constructing liquid crystal polymers.

[0048] This invention synthesizes a cyanostilbene compound containing dihydroxyl groups by introducing hydroxyl groups and flexible spacer groups onto the structural units of cyanostilbene, serving as a dihydroxyl fluorescent liquid crystal monomer. Using the dihydroxyl fluorescent liquid crystal monomer and diisocyanate as raw materials, fluorescent liquid crystal polyurethane materials are constructed, achieving a balance between the high mechanical properties and high processability of liquid crystal polyurethane and the multifunctionality of fluorescent polyurethane. This makes it widely applicable in fields such as liquid crystal materials, optical information storage materials, photochromic materials, biological materials, nonlinear optical materials, and nanomaterials.

[0049] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments and accompanying drawings.

[0050] Unless otherwise specified, all reagents used in this invention are commercially available, and all methods used are conventional techniques in the art.

[0051] Example 1 A method for preparing a dihydroxy fluorescent liquid crystal monomer includes the following steps: Step 1: Synthesis of p-hydroxyhexyloxybenzaldehyde: 250 mL of ethanol, 10 g of p-hydroxybenzaldehyde, 40 g of anhydrous potassium carbonate, 1 g of potassium iodide, and 21.7 g of bromohexanol were added sequentially to a 500 mL single-necked flask. The flask was placed in a heated, temperature-controlled magnetically stirred bath and stirred at 75 °C for 24 h. After the reaction was complete, the filter residue was washed three times with ethanol, and the filtrates were combined. The filtrate was then evaporated to dryness to obtain the crude product. The crude product was purified by column chromatography using dichloromethane as the eluent. The second fraction was collected, evaporated to dryness, and dried to obtain p-hydroxyhexyloxybenzaldehyde. The specific synthetic route is as follows:

[0052] .

[0053] Step 2: Synthesis of p-hydroxyhexyloxyphenylacetonitrile: 250 mL of ethanol, 11 g of p-hydroxyphenylacetonitrile, 40 g of anhydrous potassium carbonate, 1 g of potassium iodide, and 21.7 g of bromohexanol were added to a 500 mL single-necked flask. The flask was placed in a heated, temperature-controlled magnetically stirred bath and stirred at 75 °C for 24 h. After the reaction was complete, the filter residue was washed three times with ethanol, and the filtrates were combined. The filtrate was dried to obtain the crude product. The crude product was purified by column chromatography using dichloromethane as the eluent. The second fraction was collected, evaporated to dryness, and then dried to obtain p-hydroxyhexyloxyphenylacetonitrile. The specific synthetic route is shown below:

[0054] .

[0055] Step 3: Synthesis of 4,4'-dihydroxyhexyloxy-α-cyanostilbene: 8 g of p-hydroxyhexyloxyphenylacetonitrile, 9 g of p-hydroxyhexyloxybenzaldehyde, and 100 mL of ethanol were added to a 500 mL three-necked flask. The mixture was heated to dissolve the acetonitrile at 75 °C, and then potassium tert-butoxide solution was added dropwise over 2 hours. The reaction was then carried out at 75 °C for 24 hours. The potassium tert-butoxide solution was prepared by dissolving 4 g of potassium tert-butoxide in 80 mL of ethanol. After the reaction was complete, the reaction solution was poured into water to precipitate the precipitate. The crude product was obtained by filtration and purified by column chromatography using a mixture of ethyl acetate and petroleum ether (5:1 v / v) as the eluent. The second fraction was collected, and after drying with the solvent evaporated, 4,4'-dihydroxyhexyloxy-α-cyanostilbene, i.e., a dihydroxy fluorescent liquid crystal monomer, was obtained.

[0056] Example 2 A method for preparing a fluorescent liquid crystal polyurethane material includes the following steps: 2g of dihydroxy fluorescent liquid crystal monomer, 0.15g of dibutyltin dilaurate and 8g of N,N-dimethylformamide were mixed to obtain the first mixed solution.

[0057] 1.15 g of hexamethylene diisocyanate was dissolved in 2 g of N,N-dimethylformamide to obtain a second mixed solution.

[0058] Under heating conditions of 80°C, the second mixed solution was added dropwise to the first mixed solution over a period of 2 hours. After the addition was completed, the reaction was continued for 4 hours to obtain a fluorescent liquid crystal polyurethane prepolymer reaction solution.

[0059] 0.2 g of butanediol was dissolved in 1 g of N,N-dimethylformamide to obtain a chain extender solution. This chain extender solution was then added to the fluorescent liquid crystal polyurethane prepolymer reaction solution, and the reaction was continued at 80°C for 2 hours to obtain a fluorescent liquid crystal polyurethane reaction solution. This solution was then poured into a polytetrafluoroethylene (PTFE) plastic tank and dried in a 60°C forced-air drying oven for 12 hours to remove the solvent, yielding the fluorescent liquid crystal polyurethane material. The specific synthetic route is shown below:

[0060] .

[0061] Test 1: use 1 The structure of the dihydroxy fluorescent liquid crystal monomer was characterized by H-NMR.

[0062] from Figure 1 It can be seen that peaks corresponding to hydrogen atoms at different positions in the dihydroxy fluorescent liquid crystal monomer can be found. In addition, no other impurity peaks were observed in the spectrum except for the solvents DMSO, H2O and TMS; thus, it is shown that Example 1 of the present invention successfully synthesized a dihydroxy fluorescent liquid crystal monomer with high purity.

[0063] Test 2: The fluorescent liquid crystal polyurethane material was characterized by FT-IR. Figure 2 It can be seen that at 2852cm -1 and 2922cm -1 Absorption peaks of the flexible spacer group -CH2- were observed nearby; 1687 cm⁻¹ -1 The absorption peak is -CN at 3317 cm⁻¹. -1 The nearby peak is the stretching vibration absorption peak of the imine group; 1573 cm⁻¹ -1 Nearby are carbon-carbon double bonds on the benzene ring; 1247 cm -1 The presence of -CO- stretching vibrations nearby indicates that hexamethylene diisocyanate has reacted completely, and the fluorescent liquid crystal polyurethane material has been successfully synthesized.

[0064] Test 3: The thermal stability of the fluorescent liquid crystal polyurethane material prepared in Example 2 was characterized by thermogravimetric analysis (TG). The specific testing procedure was as follows: 3-5 mg of the fluorescent liquid crystal polyurethane material was weighed and placed in a crucible, and the test was conducted under nitrogen atmosphere. Parameters were set, initially at 20 °C / min. -1 The temperature was increased to 120℃ and held for 5 minutes to remove moisture from the sample, followed by a further increase in temperature at 20℃ / min. -1 The heating rate was increased to 600℃. The temperature at which the sample lost 5% of its weight was taken as the decomposition temperature.

[0065] from Figure 3As can be seen, the decomposition temperature of the fluorescent liquid crystal polyurethane material is 196.6℃, indicating that the fluorescent liquid crystal polyurethane material prepared in the embodiments of the present invention has good thermal stability.

[0066] Test 4: The phase transition behavior of the fluorescent liquid crystal polyurethane material prepared in Example 2 was characterized by differential scanning calorimetry.

[0067] like Figure 4 As shown, the glass transition temperature of the fluorescent liquid crystal polyurethane material is 41.1℃, and the phase transition peak at 130℃ represents the transition from the liquid crystal phase to the isotropic phase, indicating that the fluorescent liquid crystal polyurethane material prepared in the embodiments of the present invention has a wide liquid crystal phase range.

[0068] Test 5: The liquid crystal phase of the fluorescent liquid crystal polyurethane material prepared in Example 2 was visually observed using a polarizing microscope.

[0069] like Figure 5 As shown, the fluorescent liquid crystal polyurethane material exhibits a birefringence phenomenon with seven colors under a polarizing microscope. This indicates that the fluorescent liquid crystal polyurethane material possesses liquid crystal properties.

[0070] Test 6: The liquid crystal phase structure of the fluorescent liquid crystal polyurethane material prepared in Example 2 was confirmed by one-dimensional wide-angle X-ray diffraction.

[0071] from Figure 6 As can be seen, the fluorescent liquid crystal polyurethane material exhibits two diffraction peaks in the low-angle region, corresponding to 2θ angles of 3.18° and 15.88°, with an angle ratio of approximately 1:5. This indicates that the fluorescent liquid crystal polyurethane material forms a smectic phase.

[0072] Test 7: The aggregation-induced emission phenomenon of the fluorescent liquid crystal polyurethane material prepared in Example 2 was characterized using a fluorescence spectrophotometer. Tests of the fluorescence intensity of a series of fluorescent liquid crystal polyurethane material samples with the same concentration but different water contents showed that, as... Figure 7 As shown, the fluorescence intensity of the sample continuously increases from 0% to 90%, exhibiting a clear aggregation-induced emission phenomenon.

[0073] Test 8: The application of the fluorescent liquid crystal polyurethane material prepared in Example 1 was investigated.

[0074] like Figure 8 As shown in a, a uniform fluorescent liquid crystal polyurethane coating was prepared on the bottom of the petri dish using a solution film-forming method, which exhibits bright yellow-green fluorescence under ultraviolet light. Figure 8As shown in b, an aluminum sheet with a hollowed-out school emblem pattern is placed on a fluorescent liquid crystal polyurethane coating. After irradiating with a UV lamp for 10 minutes, the school emblem pattern appears on the fluorescent liquid crystal polyurethane coating under UV light. Then, the fluorescent liquid crystal polyurethane coating with the school emblem pattern is placed in a 120℃ oven and heated for 30 minutes, as shown in Figure b. Figure 8 As shown in c, the school emblem pattern on the fluorescent liquid crystal polyurethane coating disappears. (See example c.) Figure 8 As shown in d, when a perforated aluminum sheet is placed on a fluorescent liquid crystal polyurethane coating and irradiated under a UV lamp for 10 minutes, the pattern on the fluorescent liquid crystal polyurethane coating will reappear.

[0075] This demonstrates that the fluorescent liquid crystal polyurethane material prepared in the embodiments of the present invention has the characteristics of photoresponse and thermal recovery, and can be applied to information storage to achieve repeated writing and erasure of information, and can also be used as an anti-counterfeiting material.

[0076] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range, as well as any value between the two endpoints, can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of this invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended scope of protection is intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of this invention.

[0077] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of protection of this invention and its equivalents, this invention also intends to include these modifications and variations.

Claims

1. A fluorescent liquid crystalline polyurethane material, characterized in that, The fluorescent liquid crystal polyurethane material is prepared by chain extension reaction of the fluorescent liquid crystal polyurethane prepolymer under the condition of a chain extender; The fluorescent liquid crystal polyurethane prepolymer is prepared by polyaddition reaction of diisocyanate and the double-hydroxyl fluorescent liquid crystal monomer under the action of a catalyst; the double-hydroxyl fluorescent liquid crystal monomer has the following structural formula: 。 2. The fluorescent liquid crystalline polyurethane material according to claim 1, characterized in that, The molar ratio of diisocyanate to the double-hydroxyl fluorescent liquid crystal monomer is 1.1-4:1; the molar ratio of the chain extender to diisocyanate is 0.1-0.75:1; and the diisocyanate is hexamethylene diisocyanate, isophorone diisocyanate or toluene diisocyanate.

3. The fluorescent liquid crystalline polyurethane material according to claim 1, wherein, The chain extender is at least one of ethylene glycol, 1,4-butanediol, 1,6-hexanediol, ethylenediamine and 1,6-hexanediamine; and the catalyst is an organic tin catalyst.

4. The fluorescent liquid crystalline polyurethane material according to claim 1, wherein, The specific preparation method of the double-hydroxyl fluorescent liquid crystal monomer is as follows: Under the action of an acid-binding agent and potassium iodide, p-hydroxybenzaldehyde, 6-bromo-1-hexanol and a first solvent are placed at 60-90 DEG C to undergo substitution reaction to obtain p-hydroxyhexyloxybenzaldehyde; Under the action of an acid-binding agent and potassium iodide, p-hydroxyphenylacetonitrile, 6-bromo-1-hexanol and a first solvent are placed at 60-90 DEG C to undergo substitution reaction to obtain p-hydroxyhexyloxyphenylacetonitrile; Under the condition of 60-90 DEG C, p-hydroxyhexyloxyphenylacetonitrile, p-hydroxyhexyloxybenzaldehyde and a first solvent are uniformly mixed, then a base solution is added to undergo carbon anion condensation reaction to obtain the double-hydroxyl fluorescent liquid crystal monomer.

5. The fluorescent liquid crystalline polyurethane material according to claim 4, characterized in that, The molar ratio of p-hydroxyhexyloxyphenylacetonitrile to p-hydroxyhexyloxybenzaldehyde is 1:1-2; the molar ratio of the base to p-hydroxyhexyloxyphenylacetonitrile is 0.1-2:1; and the base is at least one of sodium hydroxide, potassium hydroxide, sodium ethoxide, potassium ethoxide, potassium tert-butoxide, triethylamine, pyridine and piperidine.

6. The fluorescent liquid crystalline polyurethane material according to claim 4, wherein, In the preparation of p-hydroxyhexyloxybenzaldehyde, the molar ratio of p-hydroxybenzaldehyde to 6-bromo-1-hexanol, an acid-binding agent and potassium iodide is 1:1-3:2-6:0.01-0.1; in the preparation of p-hydroxyhexyloxyphenylacetonitrile, the molar ratio of p-hydroxyphenylacetonitrile to 6-bromo-1-hexanol, an acid-binding agent and potassium iodide is 1:1-3:2-6:0.01-0.1; the acid-binding agent is at least one of anhydrous potassium carbonate, anhydrous sodium carbonate, anhydrous potassium bicarbonate, anhydrous sodium bicarbonate, triethylamine and pyridine; and the first solvent is ethanol.

7. A method of producing the fluorescent liquid crystalline polyurethane material according to any one of claims 1 to 6, characterized in that, The method comprises the following steps: The double-hydroxyl fluorescent liquid crystal monomer, a catalyst and a second solvent are mixed to obtain a first mixed solution; Diisocyanate and the second solvent are mixed to obtain a second mixed solution; The second mixed solution is added to the first mixed solution, and under the action of the catalyst, polyaddition reaction of diisocyanate and the double-hydroxyl fluorescent liquid crystal monomer occurs to obtain the fluorescent liquid crystal polyurethane prepolymer; Chain extension reaction of the chain extender solution and the fluorescent liquid crystal polyurethane prepolymer is carried out, and after removal of the solvent, the fluorescent liquid crystal polyurethane material is obtained.

8. The method for preparing the fluorescent liquid crystal polyurethane material according to claim 7, characterized in that, The molar ratio of the catalyst to the double-hydroxyl fluorescent liquid crystal monomer is 0.01-0.2:1; the concentration of the double-hydroxyl fluorescent liquid crystal monomer in the first mixed solution is 10-50%wt; the concentration of diisocyanate in the second mixed solution is 20-80%wt; and the mass concentration of the chain extender solution is 1-60%wt.

9. The method for preparing the fluorescent liquid crystal polyurethane material according to claim 7, characterized in that, The temperature of the polyaddition reaction is 50-90 DEG C, and the temperature of the chain extension reaction is 50-90 DEG C; the second solvent is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, 1,4-dioxane and tetrahydrofuran.

10. A fluorescent liquid crystalline polyurethane material characterized in that, The fluorescent liquid crystal polyurethane material is the fluorescent liquid crystal polyurethane material according to any one of claims 1 to 6.

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