Polyvinyl alcohol derivative as well as preparation method and application thereof

Abstract

The invention provides a polyvinyl alcohol derivative as well as a preparation method and application thereof. The polyvinyl alcohol derivative comprises a structural unit of 1, 4-dihydropyridine, a structural unit of vinyl alcohol and a structural unit of vinyl acetate. The preparation method comprises the following steps: dissolving polyvinyl alcohol in an anhydrous organic solvent, adding an acetoacetic acid reagent for reaction to obtain a polyvinyl alcohol derivative containing beta-diketone, and in the presence of a catalyst, reacting an aldehyde compound containing an aggregation-induced emission structure, an ammonia source compound and 1, 2-diketone to obtain the beta-diketone-containing polyvinyl alcohol derivative. And adding a 1, 3-diketone compound into the obtained polyvinyl alcohol derivative containing beta-diketone, and carrying out Hantzsch reaction, so as to obtain the antioxidant aggregation-induced emission polyvinyl alcohol derivative containing the 1, 4-dihydropyridine structure. The polyvinyl alcohol derivative disclosed by the invention has excellent oxidation resistance and aggregation-induced emission performance, and can be applied to the fields of food packaging, biological medicine, health care and the like.

Description

Technical Field

[0001] The present invention relates to the field of functional polymer materials. Further, it relates to a polyvinyl alcohol derivative, a preparation method thereof, and an application thereof. Background Art

[0002] Polyvinyl alcohol (PVA) is a hydrophilic and environmentally friendly vinyl polymer, generally prepared by hydrolysis of polyvinyl acetate on a large industrial scale. It is inexpensive, biodegradable, and has good solvent resistance, film-forming property, low protein adsorption property, biocompatibility, and biodegradability. It can be used as products such as food packaging, contact lenses, vascular embolization particles, artificial pancreas, artificial cartilage, and meniscus, and has wide applications in the food packaging industry and the biomedical field.

[0003] In the fields of active food packaging and the treatment of diseases related to oxidative stress (such as neurodegenerative diseases, cardiovascular diseases, eye diseases, wound repair, etc.), materials with antioxidant properties have attracted much attention. Polyvinyl alcohol is often compounded with other antioxidant components to form functional antioxidant materials, such as preparing antioxidant hydrogels, PVA-based active packaging materials, etc. by combining with antioxidant components such as natural polyphenols. The method of co-mixing small molecule antioxidants into PVA materials has problems such as poor stability, fast migration, and affecting the processing performance of the materials. It is easy to migrate and dissolve during use, and the persistence is not good, which to a certain extent limits its development as a biomedical, packaging, and health care material. Therefore, modifying polyvinyl alcohol to make it have intrinsic antioxidant properties can significantly improve the stability and safety of the material, extend the metabolism or migration time, and improve the bioavailability of the material, which is of great significance. In addition, at present, many researchers have physically blended fluorescent probes with PVA-based materials, which are widely used in the fields of sensing detection, drug delivery, etc. However, traditional organic fluorescent probes have poor water solubility and biocompatibility, and are prone to fluorescence quenching due to local enrichment in the body. Modifying the structure of polyvinyl alcohol to endow it with aggregation-induced emission properties can effectively solve this problem. Summary of the Invention

[0004] In order to solve the technical problems existing in the prior art, the present invention provides a polyvinyl alcohol derivative containing a 1,4-dihydropyridine structure, having aggregation-induced emission and antioxidant properties, a preparation method thereof, and an application thereof.

[0005] The present invention can prepare antioxidant polyvinyl alcohol derivatives containing a 1,4-dihydropyridine structure with aggregation-induced emission properties in large quantities, simply, and efficiently. The present invention uses polyvinyl alcohol, which is widely sourced and inexpensive, as the main raw material, and under mild reaction conditions, through a simple preparation reaction process, obtains polyvinyl alcohol derivatives with aggregation-induced emission and excellent antioxidant properties in high yield.

[0006] By modifying and decorating polyvinyl alcohol, the present invention endows it with antioxidant ability and aggregation-induced emission property simultaneously, which can significantly improve the stability and safety of antioxidant groups, prolong the metabolism or migration time, and improve the utilization rate of the material. Meanwhile, endowing polyvinyl alcohol with the property of aggregation-induced emission facilitates the design of sensing and imaging strategies. In addition, polyvinyl alcohol units can be retained on the main chain, combining the properties of polyvinyl alcohol itself, such as good solvent resistance and film-forming property, and can be prepared into antioxidant film materials.

[0007] The first aspect of the present invention is to provide a polyvinyl alcohol derivative, which comprises a structural unit containing 1,4-dihydropyridine shown in Formula I, a vinyl alcohol structural unit shown in Formula II, and a vinyl acetate structural unit shown in Formula III;

[0008]

[0009] In Formula I, R is a group with the property of AIE motif.

[0010] According to the present invention, R is a group with the property of AIE motif, wherein the group with the property of AIE motif is derived from an aldehyde compound containing an AIE motif structure, and the aldehyde compound containing an AIE motif structure refers to an aldehyde compound containing an aggregation-induced emission unit.

[0011] By modifying and decorating polyvinyl alcohol, the present invention endows it with antioxidant ability and aggregation-induced emission property simultaneously, which can significantly improve the stability and safety of antioxidant groups, prolong the metabolism or migration time, and improve the utilization rate of the material. Meanwhile, endowing polyvinyl alcohol with the property of aggregation-induced emission facilitates the design of sensing and imaging strategies. In addition, polyvinyl alcohol units can be retained on the main chain, combining the properties of polyvinyl alcohol itself, such as good solvent resistance and film-forming property, and can be prepared into antioxidant film materials.

[0012] According to the present invention, R is a group with the property of AIE motif. According to some preferred embodiments of the present invention, R is one of, preferably

[0013] According to the present invention, the contents of the 1,4-dihydropyridine-containing structural unit represented by Formula I, the vinyl alcohol structural unit represented by Formula II, and the vinyl acetate structural unit represented by Formula III can be adjusted within a relatively wide range. Preferably, the molar percentages of the 1,4-dihydropyridine-containing structural unit, the vinyl alcohol structural unit, and the vinyl acetate structural unit are x, y, and z respectively, and x + y + z = 100 mol%; wherein, x + y = the degree of alcoholysis (i.e., the degree of alcoholysis of polyvinyl alcohol), and the degree of alcoholysis is 88-99 mol%; and / or, x is 4-20 mol% such as 4, 8, 10, 15, 20 mol%, and any two values or any interval of any two values, y is 60-95 mol% such as 60, 70, 80, 90, 95 mol%, and any two values or any interval of any two values, and the rest is z.

[0014] Polyvinyl alcohol is obtained by the alcoholysis of polyvinyl acetate. The degree of alcoholysis refers to the percentage of the number of vinyl alcohol units in the molecular chain to the total number of molecular structural units. The molar percentages of the structural units of Formula I and Formula II satisfy that the sum of the two is equal to the degree of alcoholysis.

[0015] The second aspect of the present invention is to provide a method for preparing a polyvinyl alcohol derivative, preferably for the method for preparing the polyvinyl alcohol derivative described in the first aspect, including reacting polyvinyl alcohol with an acetoacetylation reagent to obtain an intermediate of the polyvinyl alcohol derivative; and then, in the presence of a catalyst, carrying out a Hantzsch reaction on the intermediate of the polyvinyl alcohol derivative with an aldehyde compound containing an AIE motif structure, an ammonia source compound, and a 1,3-diketone compound to obtain the polyvinyl alcohol derivative;

[0016] Preferably, the intermediate of the polyvinyl alcohol derivative is a polyvinyl alcohol derivative containing β-diketone.

[0017] According to the present invention, the Hantzsch reaction refers to a process in which two molecules of β-carbonyl compounds (β-ketoesters) respectively undergo condensation reactions with one molecule of aldehyde and one molecule of ammonia, and then Michael addition is carried out to obtain a dihydropyridine derivative (for example, see Liu G, Pan R, Wei Y, et al. The Hantzsch Reaction in Polymer Chemistry: From Synthetic Methods to Applications [J]. Macromolecular Rapid Communications, 2020. DOI: 10.1002 / marc.202000459).

[0018] The present invention can prepare antioxidant polyvinyl alcohol derivatives containing 1,4-dihydropyridine structure with aggregation-induced emission properties in large quantities, simply and efficiently. The present invention uses polyvinyl alcohol, which is widely sourced and inexpensive and easy to obtain, as the main raw material. Under mild reaction conditions, through a simple preparation reaction process, polyvinyl alcohol derivatives with aggregation-induced emission and excellent antioxidant properties are obtained in high yield.

[0019] According to some preferred embodiments of the present invention, the preparation method of the polyvinyl alcohol derivative comprises the following steps:

[0020] (1) Dissolve polyvinyl alcohol in an anhydrous organic solvent, add an acetoacetylation reagent and react to obtain an intermediate of the polyvinyl alcohol derivative;

[0021] (2) In the presence of a catalyst, add an aldehyde compound containing an AIE motif structure, an ammonia source compound and a 1,3-diketone compound to the intermediate of the polyvinyl alcohol derivative obtained in step (1) to carry out the Hantzsch reaction to obtain the polyvinyl alcohol derivative.

[0022] In step (1):

[0023] According to some preferred embodiments of the present invention, the degree of polymerization of the polyvinyl alcohol is 500-1700, and the degree of alcoholysis is 88-99%, including but not limited to at least one of PVA1788, PVA1799, and PVA0588.

[0024] According to some preferred embodiments of the present invention, the anhydrous organic solvent is at least one of anhydrous N-methylpyrrolidone (NMP), anhydrous dimethyl sulfoxide (DMSO), and anhydrous N,N-dimethylformamide (DMF), and preferably anhydrous N-methylpyrrolidone. Anhydrous means that the water content is extremely low, usually requiring the water content to be less than or equal to 50 ppm.

[0025] According to some preferred embodiments of the present invention, the mass ratio of the polyvinyl alcohol to the volume of the anhydrous organic solvent is 0.03-0.2 g / ml, preferably 0.08-0.15 g / ml.

[0026] In step (1):

[0027] According to some preferred embodiments of the present invention, the acetoacetylation reagent is selected from at least one of diketene, 2,2,6-trimethyl-4H-1,3-dioxin-4-one, and tert-butyl acetoacetate.

[0028] According to some preferred embodiments of the present invention, the molar ratio of the hydroxyl group in the polyvinyl alcohol to the acetoacetylation reagent is 1:(0.01-1), preferably 1:(0.05-0.9).

[0029] According to some preferred embodiments of the present invention, the conditions for the reaction of the polyvinyl alcohol with the acetoacetylation reagent include: the reaction temperature is 25 to 40 °C, preferably 25 to 35 °C; and / or, the reaction time is 1 to 3 hours, preferably 1 to 2 hours.

[0030] In step (2):

[0031] According to some preferred embodiments of the present invention, the catalyst is a weakly acidic catalyst, preferably an amino acid catalyst, and more preferably at least one of glycine, proline, and phenylboronic acid.

[0032] According to the present invention, the aldehyde compound containing the AIE motif structure refers to an aldehyde compound containing an aggregation-induced emission unit. According to some preferred embodiments of the present invention, the aldehyde compound is an aromatic aldehyde having the properties of an AIE motif, preferably at least one of 4-(1,2,2-triphenylvinyl)benzaldehyde, tetraaldehyde tetraphenylethylene, 4-(diphenylamino)benzaldehyde, and 4-phenylthiophene-2-carbaldehyde, and more preferably 4-(1,2,2-triphenylethynyl)benzaldehyde (i.e., tetraphenylethylene carbaldehyde).

[0033] According to some preferred embodiments of the present invention, the ammonia source compound is at least one of ammonium acetate, ammonium carbonate, and ammonia water.

[0034] According to some preferred embodiments of the present invention, the 1,3-diketone compound is at least one of 1,3-cyclohexanedione and its derivatives, preferably at least one of 1,3-cyclohexanedione and C1-C4 alkyl-substituted 1,3-cyclohexanedione, and more preferably at least one of 1,3-cyclohexanedione, 5-methyl-1,3-cyclohexanedione, and 5,5-dimethyl-1,3-cyclohexanedione.

[0035] In step (2):

[0036] According to some preferred embodiments of the present invention, the molar ratio of the aldehyde compound, the ammonia source compound, and the 1,3-diketone compound in the feed is 1:(1 to 2):(1 to 1.2), preferably 1:(1.2 to 1.6):(1 to 1.2), and more preferably 1:(1.2 to 1.6):1.

[0037] According to some preferred embodiments of the present invention, the molar ratio of the aldehyde compound to the acetoacetylation reagent in step (1) in the feed is (1 to 2):1, preferably (1.1 to 1.5):1.

[0038] According to some preferred embodiments of the present invention, the molar ratio of the catalyst to the aldehyde compound in the feed is (0.05 to 0.2):1, preferably (0.1 to 0.15):1.

[0039] According to some preferred embodiments of the present invention, in step (2): the reaction temperature is 60 to 90 °C, preferably 70 to 80 °C; and / or, the reaction time is 2 to 5 hours, preferably 2 to 4 hours.

[0040] According to some preferred embodiments of the present invention, the intermediate of the polyvinyl alcohol derivative obtained by reacting polyvinyl alcohol with an acetoacetylation reagent does not need to be purified and directly enters step (2) for the Hantzsch reaction. In the prior art, the post-modification of polyvinyl alcohol generally requires the purification of intermediate products. However, the preparation method of the polyvinyl alcohol derivative of the present invention (i.e., the post-modification of polyvinyl alcohol) adopts a one-pot method, which does not require the purification of intermediate products, has mild reaction conditions, and a simple preparation method, and can obtain polyvinyl alcohol derivatives with both antioxidant and aggregation-induced emission properties in high yield.

[0041] According to some preferred embodiments of the present invention, after the Hantzsch reaction in step (2), the polyvinyl alcohol derivative is collected by the method of precipitation with an organic solvent;

[0042] Preferably, the reaction solution obtained after the Hantzsch reaction is mixed with an organic solvent, the precipitate is collected, washed and dried to obtain the polyvinyl alcohol derivative. As an example, after the Hantzsch reaction in step (2), the polyvinyl alcohol derivative containing a 1,4-dihydropyridine structure is collected by the method of precipitation with an organic solvent, that is, after the Hantzsch reaction, the reaction solution is poured into an organic solvent, and the precipitate is collected and washed repeatedly until the solvent is almost colorless, and the precipitate is air-dried naturally or the organic solvent is dried to obtain the polyvinyl alcohol derivative containing a 1,4-dihydropyridine structure.

[0043] Preferably, the organic solvent is at least one of methanol, ethanol, acetone, acetonitrile, dichloromethane, and methyl tert-butyl ether.

[0044] The third aspect of the present invention is to provide a polyvinyl alcohol derivative obtained by the preparation method described in the second aspect. Through the above preparation method, a 1,4-dihydropyridine structure with antioxidant and aggregation-induced emission functions is introduced into the side chain of polyvinyl alcohol, and the resulting modified polyvinyl alcohol derivative also has significant antioxidant ability and aggregation-induced emission characteristics.

[0045] The fourth aspect of the present invention is to provide an application of the polyvinyl alcohol derivative described in the first aspect or the third aspect in the fields of medicine and health, food packaging, such as specifically in the fields of biosensing and food packaging.

[0046] Compared with the prior art, the present invention has at least the following advantages:

[0047] The present invention can prepare antioxidant aggregation-induced emission polyvinyl alcohol derivatives containing 1,4-dihydropyridine structure in large quantities, simply and efficiently by using a one-pot method; the present invention uses commercially available polyvinyl alcohol as the main raw material, which is widely sourced, inexpensive and easily obtainable, and the preparation process is simple, with high yield and mild reaction conditions; the prepared polyvinyl alcohol derivatives have excellent antioxidant and aggregation-induced emission properties and have great application potential in the fields of food packaging, biomedicine, health care, etc. Description of the Drawings

[0048] Figure 1 It is the synthetic route diagram of the antioxidant aggregation-induced emission polyvinyl alcohol derivatives containing 1,4-dihydropyridine structure in Example 1, Example 5 and Example 6 of the present invention;

[0049] Figure 2 It is the synthetic route diagram of the antioxidant aggregation-induced emission polyvinyl alcohol derivatives containing 1,4-dihydropyridine structure in Example 2 of the present invention;

[0050] Figure 3 It is the synthetic route diagram of the antioxidant aggregation-induced emission polyvinyl alcohol derivatives containing 1,4-dihydropyridine structure in Example 3 of the present invention;

[0051] Figure 4 It is the synthetic route diagram of the antioxidant aggregation-induced emission polyvinyl alcohol derivatives containing 1,4-dihydropyridine structure in Example 4 of the present invention;

[0052] Figure 5 It is the infrared analysis spectrum of the polyvinyl alcohol derivative P1 and the intermediate in Example 1;

[0053] Figure 6 It is the antioxidant test curve of the polyvinyl alcohol derivatives described in Examples 1 to 6 and Comparative Example 1;

[0054] Figure 7 It is the photo of the polyvinyl alcohol derivative obtained in Example 1 under natural light and ultraviolet light (365 nm) excitation. Detailed Embodiments

[0055] The present invention will be specifically described below in conjunction with specific embodiments. It is necessary to point out here that the following embodiments are only for further illustration of the present invention and cannot be construed as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention still fall within the protection scope of the present invention.

[0056] In addition, it should be noted that in the following detailed embodiments, the various specific technical features described can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods.

[0057] In addition, any combination can be made among various different embodiments of the present invention as long as it does not violate the idea of the present invention. The technical solutions formed thereby belong to a part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0058] The present invention will be described in detail below through examples.

[0059] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods.

[0060] The materials, reagents, etc. used in the following examples can be obtained from commercial sources unless otherwise specified.

[0061] Specifications of some raw materials:

[0062] Polyvinyl alcohol 0588, degree of polymerization 500, degree of alcoholysis 88%;

[0063] Polyvinyl alcohol 1788, degree of polymerization 1700, degree of alcoholysis 88%;

[0064] Polyvinyl alcohol 1799, degree of polymerization 1700, degree of alcoholysis 99%;

[0065] The above polyvinyl alcohols were all purchased from Aladdin.

[0066] Example 1

[0067] The reaction equation is as Figure 1 shown.

[0068] Dissolve polyvinyl alcohol 0588 (1.1 g, hydroxyl molar amount about 22 mmol) in anhydrous N-methylpyrrolidone (10 mL) to form a clear and transparent solution. Add diketene (184.9 mg, 2.2 mmol), and stir at 25 °C for 1 hour to obtain acetylacetylated PVA modified by diketene. Then add 4-(1,2,2-triphenylvinyl)benzaldehyde (872.3 mg, 2.42 mmol), 5,5-dimethyl-1,3-cyclohexanedione (339.2 mg, 2.42 mmol), ammonium acetate (279.8 mg, 3.63 mmol), and glycine (18.2 mg, 0.24 mmol) to the reaction solution system, and raise the temperature of the reaction solution system to 80 °C and react for 4 hours. After the reaction is completed, precipitate the reaction solution in acetone solution, wash and dry to obtain a yellow film-like polyvinyl alcohol derivative P1.

[0069] The infrared spectrum of the modification step is shown in Figure 5, By comparing the infrared spectra of pure PVA (black line), acetoacetylated PVA obtained by diketene modification (red line), PVA grafted with antioxidant groups containing tetraphenylethylene structure, i.e., polyvinyl alcohol derivative P1, abbreviated as PVA-TPE (blue line) in the figure, and 4-(1,2,2-triphenylethynyl)benzaldehyde, i.e., TPE (green line), it can be seen that ACAC-PVA shows an obvious enhanced stretching vibration peak of -C=O at 1650 cm -1 , indicating that PVA has successfully reacted with diketene to obtain a polyvinyl alcohol derivative containing β-diketone; after grafting antioxidant groups containing tetraphenylethylene structure, PVA-TPE shows a stretching vibration peak of -C=C- at 1600 cm -1 , and characteristic peaks of aromatic rings appear at 750 cm -1 and 700 cm -1 , indicating that the target product P1 has been successfully prepared.

[0070] Example 2

[0071] The reaction equation is as Figure 2 shown.

[0072] Dissolve polyvinyl alcohol 0588 (1.1 g, hydroxyl molar amount about 22 mmol) in anhydrous N-methylpyrrolidone (10 mL) to form a clear and transparent solution. Add diketene (184.9 mg, 2.2 mmol) and stir at 25 °C for 1 hour. Then add tetraaldehyde tetraphenylethylene (1075.6 mg, 2.42 mmol), 5,5-dimethyl-1,3-cyclohexanedione (339.2 mg, 2.42 mmol), ammonium acetate (279.8 mg, 3.63 mmol), and glycine (18.2 mg, 0.24 mmol) to the reaction solution system. Heat the reaction solution system to 80 °C and react for 4 hours. After the reaction is completed, precipitate the reaction solution in acetone solution, wash and dry to obtain a yellow film-like polyvinyl alcohol derivative P2.

[0073] Example 3

[0074] The reaction equation is as Figure 3 shown.

[0075] Polyvinyl alcohol 0588 (1.1 g, hydroxyl molar amount about 22 mmol) was dissolved in anhydrous N-methylpyrrolidone (10 mL) to form a clear and transparent solution. Divinyl ketone (184.9 mg, 2.2 mmol) was added, and the mixture was stirred at 25 °C for 1 hour. Then, 4-phenylthiophene-2-carbaldehyde (455.6 mg, 2.42 mmol), 5,5-dimethyl-1,3-cyclohexanedione (339.2 mg, 2.42 mmol), ammonium acetate (279.8 mg, 3.63 mmol), and glycine (18.2 mg, 0.24 mmol) were added to the reaction solution system. The reaction solution system was heated to 80 °C and reacted for 4 hours. After the reaction was completed, the reaction solution was precipitated in an acetone solution, washed and dried to obtain a yellow film-like polyvinyl alcohol derivative P3.

[0076] Example 4

[0077] The reaction equation is as Figure 4 shown.

[0078] Polyvinyl alcohol 0588 (1.1 g, hydroxyl molar amount about 22 mmol) was dissolved in anhydrous N-methylpyrrolidone (10 mL) to form a clear and transparent solution. Divinyl ketone (184.9 mg, 2.2 mmol) was added, and the mixture was stirred at 25 °C for 1 hour. Then, 4-(diphenylamino)benzaldehyde (661.5 mg, 2.42 mmol), 5,5-dimethyl-1,3-cyclohexanedione (339.2 mg, 2.42 mmol), ammonium acetate (279.8 mg, 3.63 mmol), and glycine (18.2 mg, 0.24 mmol) were added to the reaction solution system. The reaction solution system was heated to 80 °C and reacted for 4 hours. After the reaction was completed, the reaction solution was precipitated in an acetone solution, washed and dried to obtain a yellow film-like polyvinyl alcohol derivative P4.

[0079] Example 5

[0080] The reaction equation is as Figure 1 shown.

[0081] Polyvinyl alcohol 1788 (1.1 g, hydroxyl molar amount about 22 mmol) was dissolved in anhydrous N-methylpyrrolidone (10 mL) to form a clear and transparent solution. Diacetone ketene (184.9 mg, 2.2 mmol) was added, and the mixture was stirred at 25 °C for 1 hour. Then, 4-(1,2,2-triphenylvinyl)benzaldehyde (872.3 mg, 2.42 mmol), 5,5-dimethyl-1,3-cyclohexanedione (339.2 mg, 2.42 mmol), ammonium acetate (279.8 mg, 3.63 mmol), and glycine (18.2 mg, 0.24 mmol) were added to the reaction solution system. The reaction solution system was heated to 80 °C and reacted for 4 hours. After the reaction was completed, the reaction solution was precipitated in an acetone solution, washed and dried to obtain a yellow film-like polyvinyl alcohol derivative P5.

[0082] Example 6

[0083] The reaction equation is as Figure 1 shown.

[0084] Polyvinyl alcohol 1799 (1.0 g, hydroxyl molar amount about 22.5 mmol) was dissolved in anhydrous N-methylpyrrolidone (10 mL) to form a clear and transparent solution. Diacetone ketene (184.9 mg, 2.2 mmol) was added, and the mixture was stirred at 25 °C for 1 hour. Then, 4-(1,2,2-triphenylvinyl)benzaldehyde (872.3 mg, 2.42 mmol), 5,5-dimethyl-1,3-cyclohexanedione (339.2 mg, 2.42 mmol), ammonium acetate (279.8 mg, 3.63 mmol), and glycine (18.2 mg, 0.24 mmol) were added to the reaction solution system. The reaction solution system was heated to 80 °C and reacted for 4 hours. After the reaction was completed, the reaction solution was precipitated in an acetone solution, washed and dried to obtain a yellow film-like polyvinyl alcohol derivative P6.

[0085] Example 7

[0086] Polyvinyl alcohol 0588 (1.1 g, hydroxyl molar amount about 22 mmol) was dissolved in anhydrous dimethyl sulfoxide (15 mL) to form a clear and transparent solution. tert-Butyl acetoacetate (348.0 mg, 2.2 mmol) was added, and the mixture was stirred at 25 °C for 1 hour. Then, 4-(1,2,2-triphenylvinyl)benzaldehyde (872.3 mg, 2.42 mmol), 5,5-dimethyl-1,3-cyclohexanedione (339.2 mg, 2.42 mmol), ammonium carbonate (348.8 mg, 3.63 mmol), and phenylboronic acid (29.3 mg, 0.24 mmol) were added to the reaction solution system. The reaction solution system was heated to 90 °C and reacted for 3 hours. After the reaction was completed, the reaction solution was precipitated in an acetone solution, washed and dried to obtain a yellow film-like polyvinyl alcohol derivative P7.

[0087] Example 8

[0088] Polyvinyl alcohol 0588 (1.1 g, hydroxyl molar amount about 22 mmol) was dissolved in anhydrous N,N-dimethylformamide (12 mL) to form a clear and transparent solution. Then tert-butyl acetoacetate (348.0 mg, 2.2 mmol) was added, and the mixture was stirred at 25 °C for 1 hour. Next, 4-(1,2,2-triphenylvinyl)benzaldehyde (872.3 mg, 2.42 mmol), 5,5-dimethyl-1,3-cyclohexanedione (339.2 mg, 2.42 mmol), ammonium carbonate (348.8 mg, 3.63 mmol), and proline (27.6 mg, 0.24 mmol) were added to the reaction solution system, and the reaction solution system was heated to 70 °C and reacted for 3.5 hours. After the reaction was completed, the reaction solution was precipitated in an acetone solution, washed and dried to obtain a yellow film-like polyvinyl alcohol derivative P8.

[0089] Verification was carried out by infrared analysis in the same way as in Example 1, and it was found that the target polyvinyl alcohol derivatives were obtained in Examples 2-8.

[0090] Adopt 1 1H nuclear magnetic resonance was used to confirm the content of the structural unit containing 1,4-dihydropyridine in the obtained polyvinyl alcohol derivatives. After detection, the content of the structural unit containing 1,4-dihydropyridine in polyvinyl alcohol derivatives P1-P8 was between 4-20 mol%, where the total content of the respective structural units of the polyvinyl alcohol derivatives was 100 mol%.

[0091] Comparative Example 1

[0092] Polyvinyl alcohol 0588 was used as Comparative Example 1, which does not contain the dihydropyridine structure (P7).

[0093] Test Example 1

[0094] The polyvinyl alcohol derivatives described in Examples 1-8 and Comparative Example 1 were subjected to an antioxidant test: The antioxidant test method is as follows:

[0095] Preparation of ABTS stock solution: Weigh 38.4 mg of ABTS and dissolve it in 10 mL of water to obtain Solution 1 with a concentration of 7 mM; weigh 6.6 mg of K2S2O8 and dissolve it in 10 mL of water to obtain Solution 2 with a concentration of 2.5 mM; directly mix Solution 1 and 2 in a volume ratio of 1:1 and store it in the dark for more than 14 hours to obtain the ABTS stock solution.

[0096] Preparation of ABTS working solution: Take 0.6 mL of the ABTS stock solution and dilute it to about 10 mL with ethanol; measure the absorbance of the solution at a wavelength of 734 nm, and adjust the solution concentration to an absorbance of about 0.7-0.8, which is the ABTS working solution.

[0097] Dissolve P1 - P8 in DMSO respectively to prepare solutions with a concentration of 1 mM. Subsequently, take 300 μL and add it to 3.5 mL of ABTS working solution, and record the change in absorbance at a wavelength of 734 nm using an ultraviolet spectrophotometer.

[0098] Comparison of antioxidant properties of Examples 1 - 6 and Comparative Example 1:

[0099] The results of the antioxidant test are as Figure 6 shown. After adding the samples prepared in the examples, the absorbance of the solution at 734 nm gradually decreased from the initial 0.74, indicating that the ABTS free radicals in the solution were gradually consumed by the antioxidant monomers. The faster the decrease rate and the lower the absorbance at the same time interval, the better the antioxidant effect. It can be seen that P1 - P6 all showed obvious antioxidant ability and could quickly quench the free radicals in the system. Among them, P1 - P4 had better effects when using PVA with the same low degree of polymerization. P1 had the fastest rate of quenching free radicals, and the absorbance was about 0.25 after 20 minutes, indicating that it had the strongest antioxidant ability. While polyvinyl alcohol without antioxidant modification (Comparative Example 1) could hardly quench free radicals.

[0100] Verify the polyvinyl alcohol derivatives obtained in Examples 7 - 8 according to the same method, and it is found that Examples 7 - 8 also showed obvious antioxidant ability and had a similar effect of quenching free radicals to Example 6.

[0101] Comparative Example 2

[0102] Replace 4-(1,2,2 - triphenylethynyl)benzaldehyde used in Example 1 with benzaldehyde, and the rest are the same as in Example 1 to prepare the polyvinyl alcohol derivative (P8).

[0103] The photos of the polyvinyl alcohol derivative obtained in Example 1 under natural light and ultraviolet light (365 nm) excitation are as Figure 7 shown, which has obvious aggregation - induced emission performance, while the polyvinyl alcohol derivative obtained in Comparative Example 2 has no aggregation - induced emission performance.

[0104] After verification, the polyvinyl alcohol derivatives obtained in Examples 2 - 8 of the present invention have similar effects to the polyvinyl alcohol derivative in Example 1 under natural light and ultraviolet light (365 nm) excitation, and all have obvious aggregation - induced emission performance.

[0105] This shows that through the modification method of the present invention, the obtained polyvinyl alcohol derivatives have aggregation - induced emission performance and are expected to be applied in the fields of food packaging, drug delivery, sensing detection, etc.

[0106] In summary, the present invention successfully prepared a polyvinyl alcohol derivative containing a 1,4-dihydropyridine structure with aggregation-induced emission and antioxidant properties. Compared with the composition obtained by the method of co-mixing a small molecule antioxidant into a PVA material, the polyvinyl alcohol derivative in the present invention has higher stability and safety, can extend the metabolism or migration time, and improve the utilization rate of the material. The polyvinyl alcohol derivative of the present invention can retain polyvinyl alcohol units on the main chain and has the properties of polyvinyl alcohol itself, such as good solvent resistance and film-forming properties, and can be prepared into an antioxidant film material.

[0107] The present invention has been described in detail above in combination with specific embodiments and exemplary examples, but these descriptions should not be construed as limiting the present invention. Those skilled in the art understand that without departing from the spirit and scope of the present invention, various equivalent substitutions, modifications or improvements can be made to the technical solutions and their implementation manners of the present invention, and these all fall within the scope of the present invention. The protection scope of the present invention is subject to the appended claims.

[0108] All publications, patent applications, patents and other references mentioned in this specification are hereby incorporated by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0109] When this specification uses prefixes such as "known to those skilled in the art", "prior art" or similar terms to derive materials, substances, methods, steps, devices or components, etc., the objects derived by such prefixes cover those commonly used in the art at the time when this application is filed, but also include those that are not commonly used at present but will become recognized in the art as suitable for similar purposes.

[0110] In the context of this specification, any matter or thing not mentioned, except as expressly stated, shall directly apply those known in the art without any change.

Claims

1. A polyvinyl alcohol derivative, which comprises a 1,4-dihydropyridine-containing structural unit shown in Formula I, a vinyl alcohol structural unit shown in Formula II, and a vinyl acetate structural unit shown in Formula III; In Formula I, R is a group having the properties of an AIE motif.

2. The polyvinyl alcohol derivative according to claim 1, wherein: R is one of; and / or, The molar percentage ratios of the 1,4-dihydropyridine-containing structural unit, the vinyl alcohol structural unit, and the vinyl acetate structural unit are x, y, and z respectively, and x + y + z = 100 mol%; wherein, x + y = the degree of alcoholysis, and the degree of alcoholysis is 88-99 mol%; and / or, x is 4-20 mol%, y is 60-95 mol%, and the rest is z.

3. A method for preparing a polyvinyl alcohol derivative, preferably a method for preparing the polyvinyl alcohol derivative according to claim 1 or 2, which comprises reacting polyvinyl alcohol with an acetoacetylation reagent to obtain an intermediate of the polyvinyl alcohol derivative; and then, in the presence of a catalyst, performing a Hantzsch reaction on the intermediate of the polyvinyl alcohol derivative with an aldehyde compound containing an AIE motif structure, an ammonia source compound, and a 1,3-diketone compound to obtain the polyvinyl alcohol derivative; Preferably, the intermediate of the polyvinyl alcohol derivative is a polyvinyl alcohol derivative containing β-diketone.

4. The preparation method according to claim 3, characterized in that It includes the following steps: (1) Dissolve polyvinyl alcohol in an anhydrous organic solvent, add an acetoacetylation reagent and react to obtain an intermediate of the polyvinyl alcohol derivative; (2) In the presence of a catalyst, add an aldehyde compound containing an AIE motif structure, an ammonia source compound, and a 1,3-diketone compound to the intermediate of the polyvinyl alcohol derivative obtained in step (1) to perform a Hantzsch reaction to obtain the polyvinyl alcohol derivative.

5. The preparation method according to claim 4, wherein: In step (1): The degree of polymerization of the polyvinyl alcohol is 500-1700, and the degree of alcoholysis is 88-99%; and / or, The anhydrous organic solvent is at least one of anhydrous N-methylpyrrolidone, anhydrous dimethyl sulfoxide, and anhydrous N,N-dimethylformamide; and / or, The mass ratio of the polyvinyl alcohol to the volume of the anhydrous organic solvent is 0.03-0.2 g / ml, preferably 0.08-0.15 g / ml.

6. The preparation method according to claim 4, wherein: In step (1): The acetoacetylation reagent is selected from at least one of diketene, 2,2,6-trimethyl-4H-1,3-dioxin-4-one, and tert-butyl acetoacetate; and / or, The molar ratio of the hydroxyl group in the polyvinyl alcohol to the acetoacetylation reagent is 1:(0.01-1), preferably 1:(0.05-0.9); and / or, The reaction conditions for the reaction of the polyvinyl alcohol with the acetoacetylation reagent include: the reaction temperature is 25-40 °C; and / or, the reaction time is 1-3 hours.

7. The preparation method according to claim 4, wherein: In step (2): The catalyst is a weakly acidic catalyst, preferably an amino acid catalyst, more preferably at least one of glycine, proline, and phenylboronic acid; and / or, The aldehyde compound is an aromatic aldehyde with AIE motif properties, preferably at least one of 4-(1,2,2-triphenylvinyl)benzaldehyde, tetrakis(4-formylphenyl)ethylene, 4-(diphenylamino)benzaldehyde, and 4-phenylthiophene-2-carbaldehyde; and / or, The ammonia source compound is at least one of ammonium acetate, ammonium carbonate, and ammonia water; and / or, The 1,3-diketone compound is at least one of 1,3-cyclohexanedione and its derivatives, preferably at least one of 1,3-cyclohexanedione and C1-C4 alkyl-substituted 1,3-cyclohexanedione, more preferably at least one of 1,3-cyclohexanedione, 5-methyl-1,3-cyclohexanedione, and 5,5-dimethyl-1,3-cyclohexanedione.

8. The preparation method according to claim 4, wherein: In step (2): The molar ratio of the aldehyde compound, ammonia source compound, and 1,3-diketone compound charged is 1:(1-2):(1-1.2), preferably 1:(1.2-1.6):(1-1.2); The molar ratio of the aldehyde compound to the acetoacetylation reagent in step (1) is (1-2):1, preferably (1.1-1.5):1; and / or, The molar ratio of the catalyst to the aldehyde compound is (0.05-0.2):1, preferably (0.1-0.15):1; and / or, The reaction temperature is 60-90 °C, preferably 70-80 °C; and / or, the reaction time is 2-5 hours, preferably 2-4 hours.

9. The preparation method according to any one of claims 3-8, wherein: The intermediate of the polyvinyl alcohol derivative obtained by reacting polyvinyl alcohol with the acetoacetylation reagent is directly subjected to the Hantzsch reaction without purification; and / or, After the Hantzsch reaction, the polyvinyl alcohol derivative is collected by precipitation with an organic solvent; Preferably, the reaction solution obtained after the Hantzsch reaction is mixed with an organic solvent, the precipitate is collected, washed, and dried to obtain the polyvinyl alcohol derivative; and / or, Preferably, the organic solvent is at least one of methanol, ethanol, acetone, acetonitrile, dichloromethane, and methyl tert-butyl ether.

10. A polyvinyl alcohol derivative obtained by the preparation method according to any one of claims 3-9.

11. Use of the polyvinyl alcohol derivative according to one of claims 1-2 or the polyvinyl alcohol derivative according to claim 10 in the fields of medicine and health and food packaging.

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