An antioxidant polyvinyl alcohol derivative containing a 1,4-dihydropyridine structure, and a preparation method and applications thereof

Abstract

The application provides an antioxidant polyvinyl alcohol derivative containing a 1,4-dihydropyridine structure and a preparation method and application thereof. The antioxidant polyvinyl alcohol derivative contains a 1,4-dihydropyridine structural unit, a vinyl alcohol structural unit and a vinyl acetate structural unit. The preparation method is as follows: polyvinyl alcohol is dissolved in anhydrous organic solvent, divinyl ketone is added for reaction to obtain a polyvinyl alcohol derivative containing a beta-diketone, in the presence of a catalyst, an aldehyde compound, an ammonia source compound and a 1,3-diketone compound are added into the obtained polyvinyl alcohol derivative containing a beta-diketone for Hantzsch reaction to obtain the antioxidant polyvinyl alcohol derivative containing the 1,4-dihydropyridine structure. The prepared polyvinyl alcohol derivative has excellent antioxidant performance and can be applied to the fields of food packaging, biological medicine, health care and the like.

Description

An antioxidant polyvinyl alcohol derivative containing a 1,4-dihydropyridine structure, its preparation method and application Technical Field

[0001] This invention relates to the field of functional polymer materials, and more specifically, to an antioxidant polyvinyl alcohol derivative containing a 1,4-dihydropyridine structure, its preparation method, and its application. Background Technology

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

[0003] Materials with antioxidant properties have attracted much attention in the fields of active food packaging and the treatment of oxidative stress-related diseases (such as neurodegenerative diseases, cardiovascular diseases, eye diseases, and wound repair). Polyvinyl alcohol (PVA) is often compounded with other antioxidant components to form functional antioxidant materials, such as antioxidant hydrogels and PVA-based active packaging materials prepared by combining it with antioxidant components such as natural polyphenols. However, PVA itself does not possess antioxidant properties and must be modified by adding active substances. For example, Sun Miao and Deng Jing et al. prepared inclusion complexes of eugenol essential oil and β-cyclodextrin, which were then blended and cast into films with PVA; Zhang Yan et al. modified PVA films with different contents of citric acid, etc. However, these methods of blending small-molecule antioxidants into PVA materials have problems such as poor stability, rapid migration, and impact on material processing performance. They are prone to migration and dissolution during use and have poor durability, which to some extent limits their development as biomedical, packaging, and health care materials. Therefore, modifying polyvinyl alcohol to give it antioxidant capacity can significantly improve the stability and safety of antioxidant groups, prolong metabolism or migration time, and improve the utilization of materials, which is of great significance. Summary of the Invention

[0004] To address the technical problems existing in the prior art, the present invention provides an antioxidant polyvinyl alcohol derivative containing a 1,4-dihydropyridine structure, its preparation method, and its application.

[0005] This invention enables the large-scale, simple, and efficient preparation of antioxidant polyvinyl alcohol derivatives containing a 1,4-dihydropyridine structure. Using readily available and inexpensive commercially available polyvinyl alcohol as the main raw material, this invention, under mild reaction conditions and through a simple preparation process, obtains polyvinyl alcohol derivatives with excellent antioxidant properties in high yield and confirms their antioxidant applications.

[0006] This invention modifies polyvinyl alcohol (PVA) to enhance its antioxidant capacity, significantly improving the stability and safety of antioxidant groups, prolonging metabolism or migration time, and increasing material utilization. Simultaneously, PVA units can be retained in the main chain, retaining the inherent properties of PVA, such as good solvent resistance and film-forming properties, making it suitable for preparing antioxidant film materials.

[0007] The polyvinyl alcohol derivatives prepared by this invention can have their antioxidant properties, water solubility, solvent resistance, and film-forming properties altered by adjusting the proportion of 1,4-dihydropyridine structural units. These derivatives can be applied in various fields such as biomedicine, packaging, and healthcare materials.

[0008] In the prior art, post-modification of polyvinyl alcohol generally requires purification of intermediate products. However, the preparation method of polyvinyl alcohol derivatives in this invention (i.e., post-modification of polyvinyl alcohol) adopts a one-pot method, which does not require purification of intermediate products. The reaction conditions are mild, the preparation method is simple, and polyvinyl alcohol derivatives with excellent antioxidant properties can be obtained in high yield.

[0009] One of the objectives of this invention is to provide an antioxidant polyvinyl alcohol derivative containing a 1,4-dihydropyridine structure.

[0010] The antioxidant polyvinyl alcohol derivative comprises structural units containing 1,4-dihydropyridine, vinyl alcohol structural units, and vinyl acetate structural units.

[0011] The structural unit containing 1,4-dihydropyridine is of formula I:

[0012]

[0013] The vinyl alcohol structural unit is of formula II:

[0014]

[0015] The vinyl acetate structural unit is of formula III:

[0016]

[0017] In Formula I, R is a phenyl, a substituted phenyl, a heterocyclic aryl, or a C1-C8 alkyl group, wherein the substituted phenyl is preferably 3-methoxy-4-hydroxyphenyl, p-hydroxyphenyl, or 3,4-dihydroxyphenyl, and the heterocyclic aryl is preferably 2-thiophene.

[0018] The molar percentages of the 1,4-dihydropyridine structural unit, the vinyl alcohol structural unit, and the vinyl acetate structural unit are x, y, and z, respectively, and x + y + z = 1; wherein x + y = degree of alcoholysis, and the degree of alcoholysis is 88-99%; preferably, x is 4-99 mol%, y is 0-95 mol%, and the remainder is z; more preferably, x is 4-91 mol%, y is 8-95 mol%, and the remainder is z; even more preferably, x is 4-60 mol%, y is 25-95 mol%, and the remainder is z.

[0019] Polyvinyl alcohol is obtained by alcoholysis of polyvinyl acetate. The degree of alcoholysis refers to the percentage of vinyl alcohol units in the molecular chain to the total number of molecular structural units. The molar percentages of structural units in Formula I and Formula II satisfy the condition that the sum of the two is equal to the degree of alcoholysis.

[0020] A second objective of this invention is to provide a method for preparing an antioxidant polyvinyl alcohol derivative containing a 1,4-dihydropyridine structure, comprising the following steps:

[0021] (1) Dissolve polyvinyl alcohol in an anhydrous organic solvent, add diketene and react to obtain a polyvinyl alcohol derivative containing β-diketone;

[0022] (2) In the presence of a catalyst, aldehydes, ammonia sources and 1,3-diones are added to the β-dione-containing polyvinyl alcohol derivative obtained in step (1) to carry out the Hantzsch reaction to obtain the antioxidant polyvinyl alcohol derivative containing the 1,4-dihydropyridine structure.

[0023] In a preferred embodiment of the present invention,

[0024] Step (1),

[0025] The degree of polymerization of the polyvinyl alcohol is 500-1700, and the degree of alcoholysis is 88-99%; preferably, at least one of PVA1788, PVA1799, and PVA0588.

[0026] The anhydrous organic solvent is preferably at least one of anhydrous N-methylpyrrolidone (NMP), anhydrous dimethyl sulfoxide (DMSO), and anhydrous N,N-dimethylformamide (DMF); anhydrous means having an extremely low water content, typically requiring a water content of less than or equal to 50 ppm.

[0027] In a preferred embodiment of the present invention,

[0028] Step (1),

[0029] The mass of the polyvinyl alcohol and the volume of the solvent are 0.05–0.3 g / ml, preferably 0.08–0.2 g / ml;

[0030] The molar ratio of the hydroxyl groups in the polyvinyl alcohol to the diketene is 1:(0.01-1), preferably 1:(0.1-0.9);

[0031] The reaction temperature is 25–40℃, preferably 25–35℃;

[0032] The reaction time is 1 to 3 hours, preferably 1 to 2 hours.

[0033] In a preferred embodiment of the present invention,

[0034] Step (2),

[0035] The catalyst is an amino acid catalyst or other weakly acidic catalyst, preferably glycine, proline or phenylboronic acid;

[0036] The aldehyde compound is preferably at least one of benzaldehyde, substituted benzaldehyde, heterocyclic aromatic aldehyde, and C1-C8 aliphatic aldehyde, wherein the substituted benzaldehyde is preferably at least one of vanillin, p-hydroxybenzaldehyde, and 3,4-dihydroxybenzaldehyde, and the heterocyclic aromatic aldehyde is preferably 2-thiophenealdehyde.

[0037] The ammonia source compound is preferably at least one of ammonium acetate, ammonium carbonate, and ammonia water;

[0038] The 1,3-dione compound is at least one of 1,3-cyclohexanedione and its derivatives, preferably at least one of 1,3-cyclohexanedione, 5-methyl-1,3-cyclohexanedione, and 5,5-dimethyl-1,3-cyclohexanedione.

[0039] In a preferred embodiment of the present invention,

[0040] Step (2),

[0041] The conditions for the Hantzsch reaction are as follows:

[0042] The molar ratio of the aldehyde compound, the ammonia source compound, and the 1,3-diketone compound is 1:(1-2):(1-1.2), preferably 1:(1.2-1.6):(1-1.2), and more preferably 1:(1.2-1.6):1;

[0043] The molar ratio of the aldehyde compound to diketene is (1-2):1, preferably (1.1-1.5):1;

[0044] The molar ratio of the catalyst to the aldehyde compound is (0.05–0.2):1, preferably (0.1–0.15):1;

[0045] The reaction temperature is 70–90℃, preferably 70–80℃;

[0046] The reaction time is 2 to 5 hours, preferably 2 to 4 hours.

[0047] In a preferred embodiment of the present invention,

[0048] After obtaining the polyvinyl alcohol derivative containing β-diketone in step (1), no purification is required, and it can be directly proceeded to step (2) for the Hantzsch reaction.

[0049] Step (2) After the Hantzsch reaction is completed, the polyvinyl alcohol derivative containing the 1,4-dihydropyridine structure is collected by organic solvent precipitation. That is, after the Hantzsch reaction is completed, the reaction solution is poured into an organic solvent and the precipitate is collected to obtain the polyvinyl alcohol derivative containing the 1,4-dihydropyridine structure.

[0050] In a preferred embodiment of the present invention,

[0051] The organic solvent is a commonly used organic solvent in the prior art, preferably at least one of methanol, ethanol, acetone, and acetonitrile.

[0052] The third objective of this invention is to provide an antioxidant polyvinyl alcohol derivative containing a 1,4-dihydropyridine structure obtained by the above preparation method.

[0053] The above preparation method introduces an antioxidant 1,4-dihydropyridine structure into the side chain of polyvinyl alcohol, and the resulting modified polyvinyl alcohol derivative also has significant antioxidant capacity.

[0054] The fourth objective of this invention is to provide an application of an antioxidant polyvinyl alcohol derivative containing a 1,4-dihydropyridine structure, such as its application in the fields of medicine and health, and food packaging.

[0055] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values; these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In the following, various technical solutions can, in principle, be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.

[0056] Compared with the prior art, the present invention has at least the following advantages:

[0057] This invention employs a one-pot method to prepare antioxidant polyvinyl alcohol derivatives containing 1,4-dihydropyridine structures in large quantities, simply, and efficiently. It uses commercially available polyvinyl alcohol as the main raw material, which is widely available, inexpensive, and readily accessible. The preparation process is simple, yields high, and the reaction conditions are mild. The prepared polyvinyl alcohol derivatives exhibit excellent antioxidant properties and have significant application potential in food packaging, biomedicine, and healthcare. Attached Figure Description

[0058] Figure 1 is a synthetic route diagram of the antioxidant polyvinyl alcohol derivative containing a 1,4-dihydropyridine structure in this invention;

[0059] Figure 2 shows the proton NMR spectrum of the antioxidant polyvinyl alcohol derivative (P1) containing a 1,4-dihydropyridine structure synthesized in Example 1. 1 H-NMR);

[0060] Figure 3 shows the proton NMR spectrum of the antioxidant polyvinyl alcohol derivative (P2) containing a 1,4-dihydropyridine structure synthesized in Example 2. 1 H-NMR);

[0061] Figure 4 shows the proton NMR spectrum of the antioxidant polyvinyl alcohol derivative (P3) containing a 1,4-dihydropyridine structure synthesized in Example 3. 1 H-NMR);

[0062] Figure 5 shows the hydrogen nuclear magnetic resonance spectrum of the antioxidant polyvinyl alcohol derivative (P4) containing a 1,4-dihydropyridine structure synthesized in Example 4. 1 H-NMR);

[0063] Figure 6 shows the proton NMR spectrum of the antioxidant polyvinyl alcohol derivative (P1′) containing a 1,4-dihydropyridine structure synthesized in Example 5. 1 H-NMR);

[0064] Figure 7 shows the proton NMR spectrum of the antioxidant polyvinyl alcohol derivative (P4′) containing a 1,4-dihydropyridine structure synthesized in Example 6. 1 H-NMR);

[0065] Figure 8 shows the ABTS of P1, P2, P3, and P4 in Examples 1-4. +· Quenching kinetics curve. Detailed Implementation

[0066] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection 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 are still within the scope of protection of the present invention.

[0067] It should also be noted that the various specific technical features described in the following embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the various possible combinations will not be described separately in this invention.

[0068] Furthermore, various embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention. The resulting technical solutions are part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0069] Test method:

[0070] α-Radical Quenching Ability Test Method: An aqueous solution of 2,2'-adiazonium 2,2'-bis(3-ethylbenzothiazoline-6-sulfonate) diammonium salt and an aqueous solution of potassium persulfate were mixed and left in the dark for 14 hours to obtain ABTS. +· Original solution. ABTS +· The stock solution was diluted with PBS buffer to an absorbance of approximately 0.7 to obtain ABTS. +· Working solution. Prepare a 2 mg / mL solution of P1-P4 polymers using PBS buffer. Mix the polymer solution with ABTS. +· The working solutions were mixed in equal proportions, and the change in absorbance of the solution at 734 nm was detected using an ELISA reader.

[0071] The references for this method are as follows:

[0072] 1. Jeddou, KB; Chaari, F.; Maktouf, S.; Nouri-Ellouz, O.; Helbert, CB; Ghorbel, RE, Structural, functional, and antioxidant properties of water-soluble polysaccharides from potatoes peels. Food Chem. 2016, 205, 97-105.

[0073] 2.Mao, T.; Yang, L.; Liu, G.; Wei, Y.; Gou, Y.; Wang, J.; Tao, L., Ferrocene-Containing Polymer via the Biginelli Reaction for In Vivo Treatment of Oxidative Stress Damage. ACS Macro Lett. 2019, 8(6), 639-645.

[0074] b. Test method for the molar percentage of each structural unit: In this invention, the following method can be used: 1 H NMR confirmed the structure of polyvinyl alcohol after antioxidant modification and the proportion of each structural unit.

[0075] The present invention will be described in detail below through embodiments.

[0076] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0077] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0078] Some raw material specifications:

[0079] Polyvinyl alcohol 0588, degree of polymerization 500, degree of alcoholysis 88%;

[0080] Polyvinyl alcohol 1788, degree of polymerization 1700, degree of alcoholysis 88%;

[0081] Polyvinyl alcohol 1799, degree of polymerization 1700, degree of alcoholysis 99%;

[0082] All of the polyvinyl alcohols mentioned above were purchased from Anhui Wanwei Group Co., Ltd.

[0083] Example 1

[0084] The reaction equation is shown in Figure 1.

[0085] Polyvinyl alcohol 0588 (1.1 g, hydroxyl molar amount approximately 22 mmol) was dissolved in anhydrous N-methylpyrrolidone (10 mL) to form a clear, transparent solution. Diketene (184.9 mg, 2.2 mmol) was added, and the mixture was stirred at 25 °C for 1 hour. Then, benzaldehyde (256.8 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 mixture, and the mixture was heated to 80 °C and reacted for 3.5 hours. After the reaction was complete, the reaction mixture was precipitated in acetone to obtain 1.5 g of polyvinyl alcohol derivative P1 containing a 1,4-dihydropyridine structure.

[0086] P1 contains the following structural units:

[0087]

[0088] Where R is the benzaldehyde side chain group, x is 0.07, y is 0.81, and z is 0.12.

[0089] As shown in Figure 2 1 The H-NMR spectrum shows that a characteristic peak of the benzene ring appears at a chemical shift of 6.95-7.15 ppm, and a nitrogen and hydrogen characteristic peak of the dihydropyridine ring appears at a chemical shift of around 8.97 ppm. Therefore, this example shows that the target polyvinyl alcohol derivative P1 containing the 1,4-dihydropyridine structure was obtained.

[0090] Example 2

[0091] The reaction equation is shown in Figure 1.

[0092] Polyvinyl alcohol 0588 (1.1 g, hydroxyl molar amount approximately 22 mmol) was dissolved in anhydrous N-methylpyrrolidone (10 mL) to form a clear, transparent solution. Diketene (184.9 mg, 2.2 mmol) was added, and the mixture was stirred at 25 °C for 1 hour. Vanillin (368.2 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 then added to the reaction mixture, and the mixture was heated to 80 °C and reacted for 3.5 hours. After the reaction was complete, the reaction mixture was precipitated in acetone to obtain 1.6 g of polyvinyl alcohol derivative P2 containing a 1,4-dihydropyridine structure.

[0093] P2 contains the following structural units:

[0094]

[0095] Where R is the vanillin side chain group, x is 0.07, y is 0.81, and z is 0.12.

[0096] As shown in Figure 3 1 The H-NMR spectrum shows that a characteristic peak of the benzene ring appears at a chemical shift of 6.43-6.67 ppm, and a nitrogen and hydrogen characteristic peak of the dihydropyridine ring appears at a chemical shift of around 8.92 ppm. Therefore, this example shows that the target polyvinyl alcohol derivative P2 containing the 1,4-dihydropyridine structure was obtained.

[0097] Example 3

[0098] The reaction equation is shown in Figure 1.

[0099] Polyvinyl alcohol 0588 (1.1 g, hydroxyl molar amount approximately 22 mmol) was dissolved in anhydrous N-methylpyrrolidone (10 mL) to form a clear, transparent solution. Diketene (184.9 mg, 2.2 mmol) was added, and the mixture was stirred at 25 °C for 1 hour. Then, p-hydroxybenzaldehyde (295.5 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 mixture, and the mixture was heated to 80 °C and reacted for 3.5 hours. After the reaction was complete, the reaction mixture was precipitated in acetone to obtain 1.5 g of polyvinyl alcohol derivative P3 containing a 1,4-dihydropyridine structure.

[0100] P3 contains the following structural units:

[0101]

[0102] Where R is the side chain group of p-hydroxybenzaldehyde, x is 0.04, y is 0.84, and z is 0.12.

[0103] As shown in Figure 4 1 The H-NMR spectrum shows that a characteristic peak of the benzene ring appears at a chemical shift of 6.45-6.93 ppm, and a nitrogen and hydrogen characteristic peak of the dihydropyridine ring appears at a chemical shift of around 8.90 ppm. Therefore, this example shows that the target polyvinyl alcohol derivative P3 containing the 1,4-dihydropyridine structure was obtained.

[0104] Example 4

[0105] The reaction equation is shown in Figure 1.

[0106] Polyvinyl alcohol 0588 (1.1 g, hydroxyl molar amount approximately 22 mmol) was dissolved in anhydrous N-methylpyrrolidone (10 mL) to form a clear, transparent solution. Diketene (184.9 mg, 2.2 mmol) was added, and the mixture was stirred at 25 °C for 1 hour. Then, 3,4-dihydroxybenzaldehyde (334.3 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 mixture, and the mixture was heated to 80 °C and reacted for 3.5 hours. After the reaction was complete, the reaction mixture was precipitated in acetone to obtain 1.6 g of polyvinyl alcohol derivative P4 containing a 1,4-dihydropyridine structure.

[0107] P4 contains the following structural units:

[0108]

[0109] Where R is a side chain group of 3,4-dihydroxybenzaldehyde, x is 0.04, y is 0.84, and z is 0.12.

[0110] As shown in Figure 5 1 The H-NMR spectrum shows that a characteristic peak of the benzene ring appears at a chemical shift of 6.30-6.55 ppm, and a nitrogen and hydrogen characteristic peak of the dihydropyridine ring appears at a chemical shift of about 8.87 ppm. Therefore, this example shows that the target polyvinyl alcohol derivative P4 containing the 1,4-dihydropyridine structure was obtained.

[0111] Example 5

[0112] The reaction equation is shown in Figure 1.

[0113] Polyvinyl alcohol 0588 (1.1 g, hydroxyl molar amount approximately 22 mmol) was dissolved in anhydrous N-methylpyrrolidone (10 mL) to form a clear, transparent solution. Diketene (1.66 g, 19.8 mmol) was added, and the mixture was stirred at 35 °C for 2 hours. Then, benzaldehyde (2.31 g, 21.78 mmol), 5,5-dimethyl-1,3-cyclohexanedione (3.66 g, 26.14 mmol), ammonium acetate (2.02 g, 26.14 mmol), and glycine (163.5 mg, 2.18 mmol) were added to the reaction mixture, and the mixture was heated to 80 °C and reacted for 3.5 hours. After the reaction was complete, the reaction mixture was precipitated in acetone to obtain 4.5 g of polyvinyl alcohol derivative P1′ containing a 1,4-dihydropyridine structure.

[0114] P1′ contains the following structural units:

[0115]

[0116] Where R is the benzaldehyde side chain group, x is 0.59, y is 0.29, and z is 0.12.

[0117] As shown in Figure 6 1 The H-NMR spectrum shows that a characteristic peak of the benzene ring appears at a chemical shift of 6.92-7.16 ppm, and a nitrogen and hydrogen characteristic peak of the dihydropyridine ring appears at a chemical shift of around 8.97 ppm. Therefore, this example shows that the target polyvinyl alcohol derivative P1′ containing the 1,4-dihydropyridine structure was obtained.

[0118] Example 6

[0119] The reaction equation is shown in Figure 1.

[0120] Polyvinyl alcohol 1799 (1.0 g, hydroxyl molar amount approximately 22.5 mmol) was dissolved in anhydrous N-methylpyrrolidone (10 mL) to form a clear, transparent solution. Diketene (283.7 mg, 3.38 mmol) was added, and the mixture was stirred at 25 °C for 1 hour. Then, 3,4-dihydroxybenzaldehyde (700.4 mg, 5.07 mmol), 5,5-dimethyl-1,3-cyclohexanedione (710.6 mg, 5.07 mmol), ammonium acetate (586.2 mg, 7.61 mmol), and glycine (38.5 mg, 0.51 mmol) were added to the reaction mixture, and the mixture was heated to 70 °C and reacted for 2.5 hours. After the reaction was complete, the reaction mixture was precipitated in acetone to obtain 1.8 g of polyvinyl alcohol derivative P4′ containing a 1,4-dihydropyridine structure.

[0121] P4′ contains the following structural units:

[0122]

[0123] Where R is a side chain group of 3,4-dihydroxybenzaldehyde, x is 0.06, y is 0.93, and z is 0.01.

[0124] As shown in Figure 7 1 The H-NMR spectrum shows that a characteristic peak of the benzene ring appears at a chemical shift of 6.30-6.58 ppm, and a nitrogen and hydrogen characteristic peak of the dihydropyridine ring appears at a chemical shift of about 8.87 ppm. Therefore, this example shows that the target polyvinyl alcohol derivative P4′ containing the 1,4-dihydropyridine structure was obtained.

[0125] Comparative Example 1

[0126] Polyvinyl alcohol 0588 was used as Comparative Example 1, which does not contain dihydropyridine structure.

[0127] Test example: The polyvinyl alcohol derivatives described in Examples 1-4 and Comparative Example 1 were subjected to antioxidant tests:

[0128] Comparison of antioxidant properties between Examples 1-4 and Comparative Example 1:

[0129] The antioxidant test results are shown in Figure 8. P2 and P4 quenched free radicals the fastest, eliminating 93% of free radicals within one minute; followed by P3, which quenched approximately 92.6% of free radicals within half an hour; while P1 quenched free radicals the slowest, eliminating only 63% within half an hour; unmodified polyvinyl alcohol failed to quench any free radicals at all. This demonstrates that the modification method of this invention imparts different levels of antioxidant capacity to the obtained polyvinyl alcohol derivatives, which are expected to have applications in food packaging, biomedicine, and healthcare.

[0130] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

[0131] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein 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.

[0132] When this specification uses the prefixes “known to those skilled in the art,” “prior art,” or similar terms to derive materials, substances, methods, steps, apparatus, or components, the objects derived from such prefixes cover those commonly used in the art at the time of this application, but also include those that are not currently commonly used but will become generally recognized in the art as suitable for similar purposes.

[0133] In the context of this specification, except where expressly stated, any matters or issues not mentioned shall apply directly to those known in the art without any modification.

Claims

1. An antioxidant polyvinyl alcohol derivative containing a 1,4-dihydropyridine structure, said antioxidant polyvinyl alcohol derivative comprising a 1,4-dihydropyridine structural unit, a vinyl alcohol structural unit, and a vinyl acetate structural unit; wherein the 1,4-dihydropyridine structural unit is of formula I: The vinyl alcohol structural unit described in Formula I is Formula II: The vinyl acetate structural unit described in Formula II is that of Formula III: In Formulas III and I, R is phenyl, substituted phenyl, heterocyclic aryl, or C1-C8 alkyl; the molar percentages of the structural units containing 1,4-dihydropyridine, vinyl alcohol, and vinyl acetate are x, y, and z, respectively, and x+y+z=1; wherein, x + y = degree of alcoholysis, where the degree of alcoholysis is 88~99%; x is 4~91 mol%, y is 8~95 mol%, and the remainder is z.

2. The antioxidant polyvinyl alcohol derivative containing a 1,4-dihydropyridine structure as described in claim 1, characterized in that: In Formula I, the substituted phenyl group is 3-methoxy-4-hydroxyphenyl, p-hydroxyphenyl, or 3,4-dihydroxyphenyl, and the heterocyclic aryl group is 2-thienyl; and / or, in Formula I, x is 4~60 mol%, y is 25~95 mol%, and the remainder is z.

3. A method for preparing an antioxidant polyvinyl alcohol derivative containing a 1,4-dihydropyridine structure as described in claim 1 or 2, comprising the following steps: (1) Polyvinyl alcohol is dissolved in an anhydrous organic solvent and diketene is added to react to obtain a polyvinyl alcohol derivative containing β-diketone; (2) Under the presence of a catalyst, aldehydes, ammonia sources and 1,3-diketones are added to the polyvinyl alcohol derivative containing β-diketone obtained in step (1) to carry out the Hantzsch reaction to obtain the antioxidant polyvinyl alcohol derivative containing 1,4-dihydropyridine structure.

4. The method for preparing the antioxidant polyvinyl alcohol derivative containing a 1,4-dihydropyridine structure as described in claim 3, characterized in that: 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.

5. The method for preparing the antioxidant polyvinyl alcohol derivative containing a 1,4-dihydropyridine structure as described in claim 3, characterized in that: In step (1), the mass of the polyvinyl alcohol and the volume of the solvent are 0.05~0.3 g / ml; and / or, the molar ratio of the hydroxyl groups in the polyvinyl alcohol to the diketene is 1:(0.01~1); and / or, the reaction temperature is 25~40℃; and / or, the reaction time is 1~3 hours.

6. The method for preparing the antioxidant polyvinyl alcohol derivative containing a 1,4-dihydropyridine structure as described in claim 5, characterized in that: In step (1), the mass of the polyvinyl alcohol and the volume of the solvent are 0.08~0.2 g / ml; and / or, the molar ratio of the hydroxyl groups in the polyvinyl alcohol to the diketene is 1:(0.1~0.9); and / or, the reaction temperature is 25~35℃; and / or, the reaction time is 1~2 hours.

7. The method for preparing the antioxidant polyvinyl alcohol derivative containing a 1,4-dihydropyridine structure as described in claim 3, characterized in that: In step (2), the catalyst is an amino acid catalyst or other weakly acidic catalyst; and / or, the aldehyde compound is at least one of benzaldehyde, substituted benzaldehyde, heterocyclic aromatic aldehyde, and C1-C8 aliphatic aldehyde; and / or, the ammonia source compound is at least one of ammonium acetate, ammonium carbonate, and ammonia water; and / or, the 1,3-dione compound is at least one of 1,3-cyclohexanedione and its derivatives.

8. The method for preparing the antioxidant polyvinyl alcohol derivative containing a 1,4-dihydropyridine structure as described in claim 7, characterized in that: In step (2), the catalyst is glycine, proline, or phenylboronic acid; and / or, the substituted benzaldehyde is at least one of vanillin, p-hydroxybenzaldehyde, and 3,4-dihydroxybenzaldehyde, and the heterocyclic aromatic aldehyde is 2-thiophenecarboxaldehyde; and / or, the 1,3-dione compound is at least one of 1,3-cyclohexanedione, 5-methyl-1,3-cyclohexanedione, and 5,5-dimethyl-1,3-cyclohexanedione.

9. The method for preparing the antioxidant polyvinyl alcohol derivative containing a 1,4-dihydropyridine structure as described in claim 3, characterized in that: In step (2), the molar ratio of the aldehyde compound, the ammonia source compound, and the 1,3-dione compound is 1:(1~2):(1~1.2)1; and / or, the molar ratio of the aldehyde compound to diketene is (1~2):1; and / or, the molar ratio of the catalyst to the aldehyde compound is (0.05~0.2):1; and / or, the reaction temperature is 70~90℃; and / or, the reaction time is 2~5 hours.

10. The method for preparing the antioxidant polyvinyl alcohol derivative containing a 1,4-dihydropyridine structure as described in claim 9, characterized in that: In step (2), the molar ratio of the aldehyde compound, the ammonia source compound, and the 1,3-dione compound is 1:(1.2~1.6):(1~1.2); and / or, the molar ratio of the aldehyde compound to diketene is (1.1~1.5):1; and / or, the molar ratio of the catalyst to the aldehyde compound is (0.1~0.15):1; and / or, the reaction temperature is 70~80℃; and / or, the reaction time is 2~4 hours.

11. The method for preparing the antioxidant polyvinyl alcohol derivative containing a 1,4-dihydropyridine structure as described in claim 10, characterized in that: In step (2), the molar ratio of the aldehyde compound, the ammonia source compound, and the 1,3-dione compound is 1:(1.2~1.6):

1.

12. The method for preparing the antioxidant polyvinyl alcohol derivative containing a 1,4-dihydropyridine structure as described in claim 3, characterized in that: After obtaining the polyvinyl alcohol derivative containing β-diketone in step (1), no purification is required, and it can be directly proceeded to step (2) for Hantzsch reaction; and / or, after the Hantzsch reaction in step (2) is completed, the polyvinyl alcohol derivative containing the 1,4-dihydropyridine structure is collected by organic solvent precipitation.

13. The method for preparing the antioxidant polyvinyl alcohol derivative containing a 1,4-dihydropyridine structure as described in claim 12, characterized in that: The organic solvent is at least one of methanol, ethanol, acetone, and acetonitrile.

14. The application of an antioxidant polyvinyl alcohol derivative containing a 1,4-dihydropyridine structure as described in claim 1 or 2, or an antioxidant polyvinyl alcohol derivative containing a 1,4-dihydropyridine structure obtained by the preparation method described in any one of claims 3 to 13, in the fields of medicine and health, and food packaging.

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