Photosensitive monomer, photosensitive polyurethane and preparation method and application thereof

Abstract

The invention relates to the technical field of photosensitive polymer synthesis, and discloses a photosensitive monomer, photosensitive polyurethane and a preparation method and application thereof. The photosensitive monomer is prepared by reacting 5-hydroxy-2-nitrobenzaldehyde with a compound M and a compound N capable of accepting external electron pairs in a first polar solvent. The photosensitive monomer has high cross-linking activity, can be subjected to efficient polycondensation with isocyanate and the like to synthesize a polyurethane holographic high polymer material, and can endow the material with physical cross-linking photoisomerization performance, a pyridine structure generated under ultraviolet irradiation can form intermolecular hydrogen bonds with a hydrogen-containing structure in a molecular chain, reversible cross-linking is achieved, and the photoisomerization performance is improved. And complexation with metal ions can be realized. According to the photosensitive monomer, the selection range of the photosensitive monomer required by production of a holographic high polymer material can be widened, and the development of holography is effectively promoted. The photosensitive monomer synthesis process is simple, the yield is high, the product is easy to separate, the controllability is high, and low-cost continuous production can be realized.

Description

Technical Field

[0001] The present application relates to the technical field of photosensitive polymer synthesis, and in particular to a photosensitive monomer, a photosensitive polyurethane, and a preparation method and application thereof. Background Art

[0002] With the rapid development of science and technology and the advent of the information age, information security issues have become increasingly prominent, especially in the fields of currency, certificates, commodities, etc., and the demand for anti-counterfeiting technology has been continuously upgraded. Although traditional anti-counterfeiting methods, such as watermarks and hot stamping, have played an anti-counterfeiting role to a certain extent, they have problems such as being easy to be counterfeited and difficult to identify on a large scale.

[0003] Using holographic materials as anti-counterfeiting encryption materials for anti-counterfeiting encryption is a safe and efficient encryption method. Holographic materials include inorganic holographic materials and organic holographic materials, among which organic holographic materials are prepared by reacting raw materials such as polymer matrix, photosensitive monomer and photoinitiator.

[0004] The photosensitive monomers used in existing organic holographic materials are usually composed of aromatic photosensitive structural units, co-initiator nitro structural units and hydroxyl active structural units, which can reduce the mobility and volatility of the photoinitiator and improve the photoinitiation efficiency and photocuring efficiency. However, the stability of the photosensitive monomer is poor, and it is easy to fail due to irreversible crosslinking induced by light and heat, resulting in a low synthesis yield, and the performance and safety in different application scenarios cannot be ensured. The application effect in anti-counterfeiting encryption polymer materials is poor. At the same time, organic holographic materials need to introduce photoreactive components such as free radical photosensitive monomers and photoinitiators, and the preparation process needs to regulate the free radical photosensitive monomers to undergo selective photopolymerization reactions. The preparation process is complicated, costly, and has a low degree of controllability and is not environmentally friendly, which is not conducive to industrial production, greatly limiting its application in optical anti-counterfeiting, decoration and other aspects.

[0005] There is an urgent need to develop an organic holographic material with a simple preparation process, good controllability, and good anti-counterfeiting and encryption effect. Summary of the invention

[0006] The present application provides a photosensitive monomer, a photosensitive polyurethane and a preparation method and application thereof, aiming to solve the problems of complex preparation process, poor controllability and poor azimuthal encryption effect of existing organic holographic materials.

[0007] In order to achieve the above objectives, the present application adopts the following technical solutions.

[0008] In a first aspect of the present application, a photosensitive monomer is provided, whose chemical structure is shown in formula (1):

[0009]

[0010] Preferably, the photosensitive monomer is prepared by reacting 5-hydroxy-2-nitrobenzaldehyde with a compound M and a compound N that can accept an external electron pair in a first polar solvent;

[0011] The chemical structure of the compound M is shown in formula (2):

[0012]

[0013] wherein R is selected from CH3, C2H5, CH(CH3)2, CH2CH2OCH3 or CH2CH(CH3)2;

[0014] The compound N is a Lewis acid or a Bronsted acid;

[0015] The first polar solvent includes any one of ethanol, acetic acid, tetrahydrofuran, methanol, trifluoroethanol, acetone, butanone, pyridine, acetonitrile or dichloromethane.

[0016] Preferably, the molar ratio of the 5-hydroxy-2-nitrobenzaldehyde, compound M and compound N is 1:2:5; the amount of the first polar solvent is at least 3 times the total mass of 5-hydroxy-2-nitrobenzaldehyde, compound M and compound N;

[0017] The reaction temperature is 0-15°C.

[0018] In a second aspect of the present application, a photosensitive polyurethane is provided, the chemical structure of which includes any one of the general formulas (3) to (5):

[0019]

[0020] R1 is selected from one of the following structural formulas:

[0021] R2 is selected from one of the following structural formulas:

[0022]

[0023] R3 is selected from

[0024] Wherein, n and m are the degree of polymerization, 1≤n≤20; 10≤m≤30.

[0025] The third aspect of the present application provides a method for preparing a photosensitive polyurethane, comprising:

[0026] Dissolving the diisocyanate, the chain extender and the soft segment in a second polar solvent, and reacting in an ice bath under an inert atmosphere to obtain an intermediate solution;

[0027] A photosensitive monomer solution dissolved in a second polar solvent is added to the intermediate solution, the temperature is raised to 35-45° C. for reaction, and then the temperature is raised to 55-65° C. for reaction to obtain a photosensitive polyurethane.

[0028] Preferably, the molar ratio of the photosensitive monomer, diisocyanate, chain extender and soft segment is 1:7.2:5:(0-3.6);

[0029] The amount of the second polar solvent used is at least twice the total amount of the photosensitive monomer, diisocyanate, chain extender and soft segment used.

[0030] Preferably, the diisocyanate comprises toluene diisocyanate or isophorone diisocyanate;

[0031] The chain extender is an amine chain extender or an amine chain extender; the alcohol chain extender includes any one of 1,4-butanediol (BDO), 1,6-hexanediol or glycerol; the amine chain extender includes ethylenediamine (DA) or N,N-dihydroxy (diisopropyl) aniline;

[0032] The soft segment comprises a polyester or polyether having at least two -OH / -NH2 functional groups;

[0033] The second polar solvent includes at least one of chloroform, dichloromethane, butyrolactone, butyl acetate, acetone, cyclopentanone, cyclohexanone, benzene, toluene, xylene, dioxane, dimethyl sulfoxide, cyclopentane, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone or N-vinyl-2-pyrrolidone.

[0034] Another aspect of the present application provides the use of the above-mentioned photosensitive monomer or photosensitive polyurethane in anti-counterfeiting encryption polymer materials.

[0035] In another aspect of the present application, a holographic polymer material is provided, which includes the above-mentioned photosensitive monomer or the above-mentioned photosensitive polyurethane.

[0036] Another aspect of the present application provides a method for preparing the above-mentioned holographic polymer material, comprising:

[0037] The photosensitive polyurethane material is exposed to ultraviolet light with a wavelength of 365nm through a mask plate with a target pattern of a grating structure engraved thereon, and then developed with a developer to obtain a holographic polymer material; wherein the voltage of the exposure light source is 10V, the current is 3A, and the exposure time is 10 to 30s;

[0038] The developer is acetonitrile or ethanol.

[0039] Compared with the prior art, the beneficial effects of this application are:

[0040] The photosensitive monomer of the present application has high cross-linking activity, and can be efficiently condensed with isocyanate and other materials to form polyurethane holographic polymer materials; and can give it the photoisomerization performance of physical cross-linking, and the pyridine structure generated under light conditions (365nm ultraviolet irradiation) can not only form intermolecular hydrogen bonds with hydrogen-containing structures in the molecular chain to achieve reversible cross-linking, but also produce complexation with metal ions. The photosensitive monomer of the present application can broaden the selection range of photosensitive monomers required for the production of holographic polymer materials, and effectively promote the development of holography.

[0041] The photosensitive monomer synthesis process of the present application is simple and has a high yield, with the yield reaching 85%; it is precipitated in a solid form, the product is easy to separate, has a high degree of controllability, and can achieve low-cost continuous production.

[0042] The photosensitive polyurethane of the present application introduces a photosensitive monomer as an end cap, and its polyurethane (urea) structural precursor forms a strong intermolecular force, which can avoid the diffusion of the monomer in the polymer, so that it has good film-forming properties. It has excellent photosensitivity, forms an ordered concave and convex plane grating under light conditions (365nm ultraviolet irradiation), and directly produces a high-resolution and angle-dependent color hologram, which is suitable for large-scale use in optical anti-counterfeiting, decoration and other industries. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments recorded in the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0044] Figure 1 This is the liquid phase mass spectrum of the photosensitive monomer NDHP of this invention;

[0045] Figure 2 This is the H-NMR spectrum of our photosensitive monomer NDHP;

[0046] Figure 3 This is the ultraviolet absorption spectrum of the photosensitive monomer NDHP of this invention;

[0047] Figure 4 This is a physical picture of the U-shaped effect of the photosensitive polyurethane holographic polymer material with dihydropyridine structure as end-capping prepared in Example 5;

[0048] Figure 5 This is a POM image of the U-shaped effect of the photosensitive polyurethane holographic polymer material with dihydropyridine structure as end-capping prepared in Example 5 observed under a microscope. DETAILED DESCRIPTION

[0049] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0050] In the following description of this embodiment, the terms "include", "comprising", "having" and "containing" are all open terms, meaning including but not limited to.

[0051] In the following description of this embodiment, the term "and / or" is used to describe the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, B exists alone, and A and B exist at the same time. A and B can be singular or plural. The character " / " generally indicates that the associated objects before and after are in an "or" relationship.

[0052] In the following description of this embodiment, the term "at least one" refers to one or more, and "plurality" refers to two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b or c", or "at least one of a, b and c", can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple, respectively.

[0053] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "an" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0054] Those skilled in the art should understand that in the following description of the embodiments of the present application, the order of serial numbers does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0055] Those skilled in the art will appreciate that the numerical ranges in the embodiments of the present application are to be construed as specifically disclosing each intermediate value between the upper and lower limits of the scope. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present application. The upper and lower limits of these smaller ranges may be independently included or excluded in the scope.

[0056] Unless otherwise specified, the technical / scientific terms used herein have the same meanings as those generally understood by those skilled in the art to which this application belongs. Although this application only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of this application. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0057] In a first aspect, the present application provides a photosensitive monomer, the chemical structure of which is shown in formula (1):

[0058]

[0059] The photosensitive monomer is prepared by reacting 5-hydroxy-2-nitrobenzaldehyde with a compound M and a compound N capable of accepting an external electron pair in a first polar solvent. In the present application, the photosensitive monomer is recorded as NDHP.

[0060] Specifically, 5-hydroxy-2-nitrobenzaldehyde, compound M and compound N are dissolved in a first polar solvent at a molar ratio of 1:2:5, and stirred at 0-15° C. for 2-5 hours, and the precipitated solid is the photosensitive monomer. Within this ratio range, the raw materials react completely, which not only saves raw materials but also reduces the generation of by-products.

[0061] In the present application, the amount of the first polar solvent is at least 3 times the total mass of 5-hydroxy-2-nitrobenzaldehyde, compound M and compound N. When the amount of the first polar solvent is within this range, the raw material can be well dissolved in the polar solvent, the yield can be improved and the by-products can be reduced.

[0062] In the present application, the chemical structure of the compound M is shown in formula (2):

[0063]

[0064] wherein R is selected from CH3, C2H5, CH(CH3)2, CH2CH2OCH3 or CH2CH(CH3)2;

[0065] In the present application, the compound N is a Lewis acid or a Bronsted acid, wherein the Lewis acid includes trifluoroacetic acid or acetic acid; in the present application, the preferred compound N is trifluoroacetic acid.

[0066] In the present application, the first polar solvent includes any one of ethanol, acetic acid, tetrahydrofuran, methanol, trifluoroethanol, acetone, butanone, pyridine, acetonitrile or dichloromethane.

[0067] The photosensitive monomer of the present application has high cross-linking activity and can be efficiently condensed with isocyanate to form polyurethane holographic polymer materials; and can give it the photoisomerization performance of physical cross-linking. The pyridine structure generated under light conditions (365nm ultraviolet irradiation) can not only form intermolecular hydrogen bonds with hydrogen-containing structures in the molecular chain to achieve reversible cross-linking, but also produce complexation with metal ions. The photoreaction mechanism of the photosensitive monomer is as follows:

[0068]

[0069] The present invention uses a one-pot Hantzsch reaction to prepare the photosensitive monomer NDHP, which has a simple preparation process and the reaction product is directly precipitated in a solid form, greatly simplifying the separation and purification operation, and does not require purification equipment, which is low in cost and convenient for large-scale continuous operation. The yield of the photosensitive monomer of the present invention can reach 85%.

[0070] In a second aspect, the present application provides a photosensitive polyurethane, the chemical structure of which includes any one of the general formulas (3)-(5):

[0071]

[0072] R1 is selected from one of the following structural formulas:

[0073]

[0074] R2 is selected from one of the following structural formulas:

[0075]

[0076] R3 is selected from

[0077] Wherein, n and m are the degree of polymerization, 1≤n≤20; 10≤m≤30.

[0078] The third aspect of the present application provides a method for preparing the above-mentioned photosensitive polyurethane, comprising:

[0079] Step 1, dissolving diisocyanate, chain extender and soft segment in a second polar solvent, reacting in an ice bath under an inert atmosphere to obtain an intermediate solution;

[0080] The diisocyanate is preferably toluene diisocyanate or isophorone diisocyanate;

[0081] The chain extender is an alcohol chain extender or an amine chain extender; the alcohol chain extender includes any one of 1,4-butanediol (BDO), 1,6-hexanediol or glycerol; the amine chain extender includes ethylenediamine (DA) or N,N-dihydroxy (diisopropyl) aniline;

[0082] The soft segment comprises a polyester or polyether having at least two -OH / -NH2 functional groups, and polytetrahydrofuran is preferred in the present application;

[0083] The second polar solvent includes at least one of chloroform, dichloromethane, butyrolactone, butyl acetate, acetone, cyclopentanone, cyclohexanone, benzene, toluene, xylene, dioxane, dimethyl sulfoxide, cyclopentane, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone or N-vinyl-2-pyrrolidone.

[0084] Step 2, adding the photosensitive monomer solution dissolved in the second polar solvent into the intermediate solution, heating to 35-45° C. for reaction, and then heating to 55-65° C. for reaction to obtain photosensitive polyurethane.

[0085] Wherein, the photosensitive monomer is the photosensitive monomer described in this application, and its chemical structure is:

[0086]

[0087] In the present application, the molar ratio of the photosensitive monomer, diisocyanate, chain extender and soft segment is preferably 1:7.2:5:(0-3.6);

[0088] Preferably, the amount of the second polar solvent is at least twice the total amount of the photosensitive monomer, diisocyanate, chain extender and soft segment.

[0089] The photosensitive polyurethane of the present application introduces a photosensitive monomer as an end cap, and its polyurethane (urea) structural precursor forms a strong intermolecular force, which can avoid the diffusion of the monomer in the polymer, making it have good film-forming properties. It has excellent photosensitivity and forms an ordered concave-convex plane grating under light conditions (365nm ultraviolet irradiation), directly generating a high-resolution and angle-dependent color hologram.

[0090] The photosensitive monomer or photosensitive polyurethane of the present application has excellent photosensitivity and can be used as or for preparing anti-counterfeiting encryption polymer macromolecular materials, which broadens the selection range of photosensitive monomers required for the production of holographic macromolecular materials and effectively promotes the development of holography.

[0091] The present application also provides a holographic polymer material, which includes the above-mentioned photosensitive polyurethane. The holographic polymer material of the present application has excellent photosensitivity, forms an ordered concave-convex plane grating under illumination conditions (365nm ultraviolet irradiation), and directly produces a high-resolution and angle-dependent color hologram, which is suitable for large-scale use in the fields of optical anti-counterfeiting, decoration, etc.

[0092] In the present application, the method for preparing the holographic polymer material comprises:

[0093] The photosensitive polyurethane material is exposed to ultraviolet light with a wavelength of 365nm through a mask plate with a target pattern of a grating structure engraved thereon, and then developed with a developer to obtain a holographic polymer material; wherein the voltage of the exposure light source is 10V, the current is 3A, and the exposure time is 10 to 30s;

[0094] The developer includes an organic solvent and a metal ion dissolved in the organic solvent, and the metal ion can react with the photosensitive molecule. The developer can be AR grade acetonitrile or AR grade ethanol, which can be directly obtained by purchasing the product. Preferably, metal ions such as palladium ions can be added to the developer, and the metal ions can react with the pyridine structure generated by the photosensitive monomer under light conditions (365nm ultraviolet irradiation) to achieve a better development effect.

[0095] The present application is further described below by way of examples.

[0096] Example 1

[0097] This embodiment provides a method for preparing a photosensitive monomer, comprising:

[0098] S1, add 10mmol of 5-hydroxy-2-nitrobenzaldehyde, 20mmol of 3-aminocrotonic acid methyl ester, 50mmol of trifluoroacetic acid and 31.56g of anhydrous ethanol to a single-necked flask under ice bath, and react for 3h under magnetic stirring under ice bath (0℃), collect the solid phase product by vacuum filtration after the reaction, rinse it with anhydrous ethanol, and dry it to obtain a solid powder, and obtain a photosensitive monomer, recorded as NDHP, with a yield of 87.7%. The synthesis route is as follows:

[0099]

[0100] Example 2

[0101] This embodiment provides a method for preparing a photosensitive polyurethane, comprising:

[0102] S1, in an inert environment without water or oxygen, weigh 3.6 mmol of toluene diisocyanate, 2.5 mmol of 1,4-butanediol, 0.5 mmol of NDHP and 2.57 g of N,N-dimethylacetamide for later use; dissolve toluene diisocyanate, 1,4-butanediol and NDHP in a portion of N,N-dimethylacetamide, react in an ice bath for 4 hours, and obtain an intermediate solution;

[0103] S2, dissolving NDHP in the remaining N,N-dimethylacetamide to obtain an NDHP solution, adding the NDHP solution to the intermediate solution, heating to 40°C and 60°C in turn, stirring and reacting overnight, to obtain a photosensitive polyurethane solution with a dihydropyridine structure as the end-capping, recorded as A-PU solution;

[0104] S3, at room temperature and in a dark environment, after filtering and removing impurities from the A-PU solution, the solution was spin-coated on a clean glass substrate, and then heated and purged with a hot air gun for 10 seconds to obtain a photosensitive polyurethane film terminated with a dihydropyridine structure, which was recorded as A-PU film.

[0105] Its synthetic reaction formula is:

[0106]

[0107] Example 3

[0108] This embodiment provides a method for preparing a photosensitive polyurethane, comprising:

[0109] S1, in an inert environment without water or oxygen, weigh 3.6 mmol of toluene diisocyanate, 2.5 mmol of 1,4-butanediol, 0.5 mmol of NDHP, 1.8 mmol of polytetrahydrofuran with a molecular weight of 2000 and 2.57 g of N,N-dimethylacetamide for use;

[0110] Dissolve toluene diisocyanate and polytetrahydrofuran in a portion of N,N-dimethylacetamide, and react in an ice bath for 4 hours; add 1,4-butanediol, and stir and react for another 4 hours to obtain an intermediate solution;

[0111] S2, dissolving NDHP in the remaining N,N-dimethylacetamide to obtain an NDHP solution, adding the NDHP solution to the intermediate solution, heating to 40°C and 60°C in turn, stirring and reacting overnight, to obtain a photosensitive polyurethane solution with a dihydropyridine structure as the end-capping, recorded as B-PU solution;

[0112] S3, at room temperature and in a dark environment, the B-PU solution was filtered and decontaminated and then spin-coated on a clean glass substrate, and then heated and purged with a hot air gun for 10 seconds to obtain a photosensitive polyurethane film terminated with a dihydropyridine structure, which was recorded as B-PU film.

[0113] Its synthetic reaction formula is:

[0114]

[0115] Example 4

[0116] This embodiment provides a method for preparing a photosensitive polyurethane, comprising:

[0117] S1, in an inert environment without water or oxygen, weigh 3.6 mmol of isophorone diisocyanate, 2.5 mmol of 1,4-butanediol, 0.5 mmol of NDHP, 1.8 mmol of polytetrahydrofuran with a molecular weight of 2000 and 2.57 g of N,N-dimethylacetamide for later use;

[0118] Dissolve isophorone diisocyanate and polytetrahydrofuran in a portion of N,N-dimethylacetamide, and react in an ice bath for 4 hours; add 1,4-butanediol, and stir and react for another 4 hours to obtain an intermediate solution;

[0119] S2, dissolving NDHP in the remaining N,N-dimethylacetamide to obtain an NDHP solution, adding the NDHP solution to the intermediate solution, heating to 40°C and 60°C in turn, stirring and reacting overnight, to obtain a photosensitive polyurethane solution with a dihydropyridine structure as a terminal, recorded as C-PU solution;

[0120] S3, at room temperature and in a dark environment, after filtering and removing impurities from the C-PU solution, the solution was spin-coated on a clean glass substrate, and then heated and purged with a hot air gun for 10 seconds to obtain a photosensitive polyurethane film terminated with a dihydropyridine structure, which was recorded as a C-PU film.

[0121] Its synthetic reaction formula is:

[0122]

[0123] Example 5

[0124] This embodiment provides a method for preparing a holographic polymer material, comprising:

[0125] The photosensitive polyurethane A-PU film prepared in Example 2 was exposed to an ultraviolet light source with a wavelength of 365 nm through a mask having a U-shaped target pattern for 30 seconds. After the exposure, the polymer holographic recording material A-PU was immersed in acetonitrile for adsorption and development treatment. After being taken out, it was rinsed with acetonitrile and dried at a temperature of 50°C for 10 seconds to obtain a holographic polymer material having holographic information recorded thereon.

[0126] The photosensitive monomer prepared in Example 1 was subjected to nuclear magnetic resonance testing, and its liquid phase mass spectrum was as follows: Figure 1 As shown, the H NMR spectrum is Figure 2 As shown in the UV absorption spectrum Figure 3 shown.

[0127] from Figure 1 It can be seen that the molecular weight test of the photosensitive monomer synthesized and purified is correct, and the photosensitive monomer is successfully prepared.

[0128] from Figure 2It can be seen from the NMR integral diagram of the photosensitive monomer that the value of the integral at the pyridinic hydrogen position is less than 1, proving that the content of pyridinic hydrogen has changed;

[0129] from Figure 3 It can be seen that with the increase of ultraviolet irradiation time, the absorption peak intensity at 225-260nm weakens, while the absorption peak intensity at 260-300nm increases, the absorption peak intensity at 300-375nm weakens, and the absorption peak intensity at 375-460nm increases, which proves the molecular photosensitivity and the transformation of molecular structure.

[0130] Figure 4 This is a physical picture of the photosensitive polyurethane holographic polymer material with dihydropyridine structure as the end-capping prepared in Example 5 of the present application, wherein the photosensitive polyurethane film is exposed for 30 seconds and developed once. Figure 4 It can be seen that the present application has successfully prepared a polymer film with adjustable desired patterns.

[0131] Figure 5 The structure of the holographic polymer material prepared in Example 5 is obtained under a microscope. Figure 5 It can be seen that the holographic polymer material forms adjustable periodic grating folds, which can directly produce high-resolution and angle-dependent color holograms, which are suitable for large-scale use in optical anti-counterfeiting, decoration and other fields.

[0132] Although the present application has been described in detail in general terms and in specific embodiments in this specification, it is obvious to those skilled in the art that some modifications or improvements may be made to the present application. Therefore, these modifications or improvements made without departing from the spirit of the present application are within the scope of protection claimed in the present application.

Claims

1. A photosensitive monomer, characterized in that: Its chemical structure is shown in formula (1):

2. The photosensitive monomer according to claim 1, characterized in that: It is prepared by reacting 5-hydroxy-2-nitrobenzaldehyde with a compound M and a compound N that can accept an external electron pair in a first polar solvent; The chemical structure of the compound M is shown in formula (2): wherein R is selected from CH3, C2H5, CH(CH3)2, CH2CH2OCH3 or CH2CH(CH3)2; The compound N is a Lewis acid or a Bronsted acid; The first polar solvent includes any one of ethanol, acetic acid, tetrahydrofuran, methanol, trifluoroethanol, acetone, butanone, pyridine, acetonitrile or dichloromethane.

3. The photosensitive monomer according to claim 2, characterized in that: The molar ratio of 5-hydroxy-2-nitrobenzaldehyde, compound M and compound N is 1:2:5; The amount of the first polar solvent is at least 3 times the total mass of 5-hydroxy-2-nitrobenzaldehyde, compound M and compound N; The reaction temperature is 0-15°C.

4. A photosensitive polyurethane, characterized in that: Its chemical structure includes any one of the general formulas (3)-(5): R1 is selected from one of the following structural formulas: R2 is selected from one of the following structural formulas: R3 is selected from Wherein, n and m are the degree of polymerization, 1≤n≤20; 10≤m≤30.

5. The method for preparing photosensitive polyurethane according to claim 4, characterized in that: include: Dissolving the diisocyanate, the chain extender and the soft segment in a second polar solvent, and reacting in an ice bath under an inert atmosphere to obtain an intermediate solution; A photosensitive monomer solution dissolved in a second polar solvent is added to the intermediate solution, the temperature is raised to 35-45° C. for reaction, and then the temperature is raised to 55-65° C. for reaction to obtain a photosensitive polyurethane.

6. The preparation method according to claim 5, characterized in that: The molar ratio of the photosensitive monomer, diisocyanate, chain extender and soft segment is 1:7.2:5:(0-3.6); The amount of the second polar solvent used is at least twice the total amount of the photosensitive monomer, diisocyanate, chain extender and soft segment used.

7. The preparation method according to claim 5, characterized in that: The diisocyanate includes toluene diisocyanate or isophorone diisocyanate; The chain extender is an amine chain extender or an amine chain extender; the alcohol chain extender includes any one of 1,4-butanediol (BDO), 1,6-hexanediol or glycerol; the amine chain extender includes ethylenediamine (DA) or N,N-dihydroxy (diisopropyl) aniline; The soft segment comprises a polyester or polyether having at least two -OH / -NH2 functional groups; The second polar solvent includes at least one of chloroform, dichloromethane, butyrolactone, butyl acetate, acetone, cyclopentanone, cyclohexanone, benzene, toluene, xylene, dioxane, dimethyl sulfoxide, cyclopentane, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone or N-vinyl-2-pyrrolidone.

8. Use of the photosensitive monomer according to claim 1 or the photosensitive polyurethane according to claim 4 in anti-counterfeiting encrypted polymer materials.

9. A holographic polymer material, characterized in that: It comprises the photosensitive monomer according to claim 1 or the photosensitive polyurethane according to claim 4.

10. The method for preparing the holographic polymer material according to claim 9, characterized in that: include: The photosensitive polyurethane material is exposed to ultraviolet light with a wavelength of 365nm through a mask plate with a target pattern of a grating structure engraved thereon, and then developed with a developer to obtain a holographic polymer material; wherein the voltage of the exposure light source is 10V, the current is 3A, and the exposure time is 10 to 30s; The developer is acetonitrile or ethanol.

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