Liquid crystalline polymers with programmable glass transition temperatures, methods of making and use thereof

Abstract

The application belongs to the technical field of photochromic materials, and discloses a liquid crystal polymer with programmable glass transition temperature and a preparation method and application thereof.The liquid crystal polymer has a glass transition temperature of 11-32 DEG C; the raw materials for preparing the liquid crystal polymer include, by weight fraction, 80.0-99.0 parts of liquid crystal polymerizable monomer material, 0.5-10.0 parts of spiropyran derivative, 0.1-5.0 parts of cyanostyrene derivative and 0.1-5.0 parts of photoinitiator.The liquid crystal polymer has a glass transition temperature of 11-32 DEG C and stepwise adjustable fluorescence; under ultraviolet irradiation, the fluorescence color changes from blue to pink and finally to bright red; under sufficient visible light irradiation, the red fluorescence can be weakened and gradually returned to blue. Different fading rates of the liquid crystal polymers with different T g The information can be encoded in the liquid crystal polymer in a 'time-locked' manner, and the correct information can only be identified at a specified time, that is, a 'time key' is used to decrypt the information.

Description

Technical Field

[0001] This application belongs to the field of photochromic materials technology, specifically relating to a liquid crystal polymer with a programmable glass transition temperature, its preparation method, and its application. Background Technology

[0002] In recent years, information security has become crucial in people's daily lives and production, making the protection of information increasingly important. Among numerous encryption technologies, encryption based on photoluminescent materials is widely recognized as one of the most ideal due to its high visibility, low requirements for stimulus response environment, ease of design, low cost, and high security level. When photoluminescent materials are subjected to specific external stimuli, the structure and excited-state energy levels of the material change, macroscopically exhibiting significant changes in material color and luminescence. Utilizing these color and luminescence changes can achieve secure information storage, thus protecting confidential information.

[0003] Currently, spiropyran-based organic photochromic materials are among the most commonly used photochromic materials. During the structural transition process, the molecular motion of spiropyran-based organic photochromic materials requires sufficient free volume, which varies at different glass transition temperatures (T0). g In liquid crystal polymers, the dynamic interconversion behavior of spiropyran derivatives with V-type and rod-shaped structures is different. In T... g In lower-grade spiropyran derivatives, reversible isomerization transitions between light-colored V-shaped structures and dark-colored rod-shaped structures are readily achieved; while in T... g In higher-T spiropyran derivatives, the transformation from a V-shaped structure to a rod-shaped structure is a process of releasing free volume and is relatively easy to achieve. However, the transformation from a dark-colored rod-shaped structure to a light-colored V-shaped structure is a process of competing for more free volume, especially at high T. g This is difficult to achieve in liquid crystal polymers.

[0004] Using a single T g Spiropyran-based organic photochromic materials are easily cracked due to their limited color change range and susceptibility to simple single-channel decryption methods. While multi-stimulus synergistic encryption / decryption techniques can improve information security, they often require complex processing or expensive equipment. Summary of the Invention

[0005] This application provides a liquid crystal polymer with a programmable glass transition temperature as an encryption material, which features high security, accuracy, and simple operation, aiming to solve the problem of using a single T in the prior art. g The encryption technology of spiropyran-based organic photochromic materials is easily cracked, while the encryption / decryption technology with high security through multiple stimuli is complex to operate and requires expensive equipment.

[0006] To achieve the above objectives, the present application adopts the following technical solution.

[0007] In a first aspect, this application provides a liquid crystal polymer having a programmable glass transition temperature, wherein the liquid crystal polymer having a programmable glass transition temperature has a glass transition temperature of 11°C to 32°C.

[0008] The raw materials for preparing the liquid crystal polymer with a programmable glass transition temperature, by weight, include:

[0009] Liquid crystal polymerizable monomers: 80.0-99.0 parts;

[0010] Spiropyran derivatives, 0.5-10.0 parts;

[0011] 0.1-5.0 parts of cyanostyrene derivatives;

[0012] Photoinitiator 0.1-5.0 parts.

[0013] In some embodiments, the liquid crystal polymer with a programmable glass transition temperature comprises multiple regions with different glass transition temperatures.

[0014] In some embodiments, the spiropyran derivative has the structural formula shown in formula (I):

[0015]

[0016] Where R is Or n is an integer between 2 and 18.

[0017] In some embodiments, the cyanostyrene derivative has the structural formula shown in formula (II):

[0018]

[0019] Where R is Or n is an integer from 1 to 18.

[0020] In some embodiments, the liquid crystal polymerizable monomer is one or more of the structural formulas shown in formula (III), (IV) or (V) mixed in any ratio;

[0021]

[0022] Where R is Or X is -CH3, -Cl, or -F; n is an integer from 1 to 18;

[0023]

[0024] Where R1 is Or R2 is -CN, -F, or -OC m H 2m+1 m is an integer from 1 to 18; n is an integer from 1 to 18;

[0025]

[0026] Among them, R3 is Or n is an integer from 1 to 18.

[0027] In some embodiments, the photoinitiator is one or more of 2-hydroxy-methylphenylpropane-1-one, 1-hydroxycyclohexylphenyl ketone, 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone, benzoin dimethyl ether, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and bis(2,6-difluoro-3-pyrrolidinyl)titanium oxide, mixed in any proportion.

[0028] A second aspect of this application provides a method for preparing the above-mentioned liquid crystal polymer having a programmable glass transition temperature, comprising:

[0029] S1, spiropyran derivative, cyano-styrene derivative, liquid crystal polymerizable monomer material and photoinitiator are mixed evenly in proportion to obtain a mixture;

[0030] S2, pour the mixture into the liquid crystal cell, heat it until the mixture is clear, then slowly cool it down and perform light irradiation curing;

[0031] S3, Remove the liquid crystal cell to obtain a liquid crystal polymer with a programmable glass transition temperature.

[0032] In some implementations, the photo-irradiation curing specifically refers to:

[0033] Irradiate the mixture with light of a single wavelength;

[0034] Alternatively, different regions of the mixture can be irradiated with light of different wavelengths;

[0035] The wavelength of the light is 365-520nm, and the light irradiance is 1-10mW / cm². 2 The irradiation time is 10-30 minutes.

[0036] A third aspect of this application provides the application of the aforementioned liquid crystal polymer with a programmable glass transition temperature as a material for time-dependent information encryption.

[0037] A fourth aspect of this application provides an encryption method based on the aforementioned liquid crystal polymer with a programmable glass transition temperature. Information is recorded on the liquid crystal polymer film with a programmable glass transition temperature using light of different wavelengths or different irradiation times through a photomask. Structural transformation is achieved by irradiation with short-wavelength light. The information is encoded in the time-dependent information encryption material in a "time-locked" manner. The encoded information self-erases over time, generating false or blank information. Correct information can only be identified at a specified time.

[0038] Compared with the prior art, the beneficial effects of this application are as follows:

[0039] The liquid crystal polymer of this application has a programmable glass transition temperature, which is in the range of 11°C to 32°C. The glass transition temperature T of the liquid crystal polymer can be changed by adjusting the ratio of the two configurations of the spiropyran derivative. g The FRET effect between spiropyran and cyanostyrene derivatives gives the liquid crystal polymer a progressively tunable fluorescence. Under the synergistic effect of the components, the fluorescence color of the liquid crystal polymer changes from blue to pink, and finally to bright red, under ultraviolet irradiation; under sufficient visible light irradiation, the red fluorescence weakens and gradually returns to blue; and different T... g The fading rates of liquid crystal polymers differ, with low T... g The fading rate of liquid crystal polymers is greater than that of high T g The fading rate of liquid crystal polymers.

[0040] This application utilizes different T g The varying fading rates of liquid crystal polymers (LCDs) and their progressively adjustable fluorescence properties allow information to be encoded in them using a "time-locked" method. This encoded information self-erases over time, generating false or blank information in the process; correct information can only be identified at a specified time, decrypted using a "time key." The liquid crystal polymer with a programmable glass transition temperature described in this application exhibits time-dependent characteristics, thus providing a higher level of security and offering a novel method for information encryption. Attached Figure Description

[0041] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1The image shows the fading state of the liquid crystal polymer film prepared in Example 1 after being irradiated with visible light, as observed in visible light mode.

[0043] Figure 2 The image shows the fading state of the liquid crystal polymer film prepared in Example 1 after being irradiated with visible light and observed under ultraviolet light mode.

[0044] Figure 3 The image shows the fading state of the liquid crystal polymer film prepared in Example 2 after being irradiated with visible light, as observed in visible light mode.

[0045] Figure 4 The image shows the fading state of the liquid crystal polymer film prepared in Example 2 after being irradiated with visible light and observed under ultraviolet light mode.

[0046] Figure 5 The image shows the fading state of the liquid crystal polymer film prepared in Example 3 after being irradiated with visible light, as observed in visible light mode.

[0047] Figure 6 The image shows the fading state of the liquid crystal polymer film prepared in Example 3 after being irradiated with visible light and observed under ultraviolet light mode.

[0048] Figure 7 This is an example diagram of a liquid crystal polymer film with a programmable glass transition temperature prepared in Example 4, used for encryption.

[0049] Figure 8 This is a schematic diagram of the light irradiation method for preparing a liquid crystal polymer film with a programmable glass transition temperature, as shown in Example 5. Figure 9 An example diagram of a liquid crystal polymer film with a programmable glass transition temperature prepared in Example 5 for encryption. Detailed Implementation

[0050] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0051] In the following description of this embodiment, the terms "including", "comprising", "having", and "containing" are all open-ended terms, meaning that they include but are not limited to.

[0052] In the following description of this embodiment, the term "and / or" is used to describe the association relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, B existing alone, and A and B existing simultaneously. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0053] In the following description of this embodiment, the term "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0054] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms "a" and "the" as used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0055] Those skilled in the art should understand that, in the following description of the embodiments of this application, the sequence of numbers does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. 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 this application.

[0056] Those skilled in the art will understand that the numerical ranges in the embodiments of this application should be understood to specifically disclose each intermediate value between the upper and lower limits of the range. Each smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this application. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0057] Unless otherwise stated, the technical / scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. While this application describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this application. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0058] In a first aspect, this application provides a liquid crystal polymer having a programmable glass transition temperature, wherein the liquid crystal polymer having a programmable glass transition temperature has a glass transition temperature of 11°C to 32°C.

[0059] The raw materials for preparing the liquid crystal polymer with a programmable glass transition temperature, by weight, include:

[0060] Liquid crystal polymerizable monomers: 80.0-99.0 parts;

[0061] Spiropyran derivatives, 0.5-10.0 parts;

[0062] 0.1-5.0 parts of cyanostyrene derivatives;

[0063] Photoinitiator 0.1-5.0 parts.

[0064] The liquid crystal polymer of this application has a programmable glass transition temperature, which is in the range of 11°C to 32°C. The glass transition temperature T of the liquid crystal polymer can be changed by adjusting the ratio of the two configurations of the spiropyran derivative. g The FRET effect between spiropyran and cyanostyrene derivative molecules gives the liquid crystal polymer a progressively tunable fluorescence. Under the synergistic effect of the components, the fluorescence color of the liquid crystal polymer changes from blue to pink, and finally to bright red, under ultraviolet irradiation; under sufficient visible light irradiation, the red fluorescence weakens and gradually returns to blue; and different T... g The fading rates of liquid crystal polymers differ, with low T... g The fading rate of liquid crystal polymers is greater than that of high T g The fading rate of liquid crystal polymers.

[0065] As a preferred embodiment, the liquid crystal polymer comprises multiple components with different glass transition temperatures T. g The region. Due to the different regions of T in the liquid crystal polymer. g Unlike other liquid crystal polymers, liquid crystal polymers have different fading rates in different regions, and each region of the liquid crystal polymer has progressively adjustable fluorescence. Information can be encoded in the liquid crystal polymer in a "time-locked" manner. The encoded information is self-erased over time, and false or blank information is generated in the process. Correct information can only be identified at a specified time, that is, the information is decrypted using a "time key".

[0066] In this application, the structural formula of the spiropyran derivative is shown in formula (I):

[0067]

[0068] Where R is Or n is an integer between 2 and 18.

[0069] Spiropyran derivatives with the structure of formula (I) are colorless or light-colored, non-fluorescent solids that do not exhibit liquid crystal properties under normal conditions. However, after irradiation with short-wavelength light, they transform into dark-colored, strongly fluorescent solids or liquids, exhibiting liquid crystal properties. Upon irradiation with bright visible light, they revert to their initial state. The principle is as follows: Spiropyran derivatives consist of two ester-like liquid crystal units. In their initial state, they have a V-shaped configuration, which is unfavorable for the regular arrangement of molecules, hence they do not exhibit liquid crystal properties. Upon stimulation by light or heat, the spiroring opens, greatly enhancing the degree of molecular conjugation. This results in strong absorption in the visible light region, producing color, and simultaneously exhibiting photofluorescence properties. After ring opening, the molecules adopt a rod-shaped configuration, which is conducive to the regular arrangement of molecules to form a liquid crystal phase, thus exhibiting liquid crystal properties.

[0070] In this application, the preferred spiropyran derivative R is... The structure with n=2, R is The structure with n=4 and R is Structures where n=6.

[0071] In this application, the structural formula of the cyanostyrene derivative is shown in formula (II):

[0072]

[0073] Where R is Or n is an integer from 1 to 18.

[0074] The cyanostyrene derivative initially exhibits blue fluorescence, which disappears after visible light irradiation. In this application, a FRET effect occurs between the cyanostyrene derivative molecule and the spiropyran derivative molecule, giving the liquid crystal polymer progressively tunable fluorescence.

[0075] In this application, the preferred cyanostyrene derivative R is... The structure is n=4, and R is... The structure of n=2 and R is Structures where n=6.

[0076] In this application, the liquid crystal polymerizable monomer is one or more of the structural formulas shown in formula (III), (IV) or (V) mixed in any ratio;

[0077]

[0078] Where R is Or X is -CH3, -Cl, or -F; n is an integer from 1 to 18;

[0079]

[0080] Where R1 is Or R2 is -CN, -F, or -OC m H 2m+1 m is an integer from 1 to 18; n is an integer from 1 to 18;

[0081]

[0082] Among them, R3 is Or n is an integer from 1 to 18.

[0083] It should be noted that the liquid crystal polymerizable monomer of this application has liquid crystal properties, has acrylate or methacrylate groups, and can undergo polymerization reactions or polymerize with spiropyran derivatives or cyanostyrene derivatives.

[0084] In the embodiments of this application, the liquid crystal polymerizable monomer is preferably a mixture of a liquid crystal polymerizable monomer with the structure of formula (III) and a liquid crystal polymerizable monomer with the structure of formula (IV).

[0085] Among them, the liquid crystal polymerizable monomer with the structure of formula (III) is preferably one of the following compounds:

[0086] R is X is a liquid crystal polymerizable monomer with Cl and n=6;

[0087] Or R is X is a liquid crystal polymerizable monomer of CH3 and n=4;

[0088] Or R is X is a liquid crystal polymerizable monomer of CH3 and n=6.

[0089] Liquid crystal polymerizable monomers with the structure of formula (IV), preferably the following compounds:

[0090] R1 is R2 is a liquid crystal polymerizable monomer of OCH3 and n=6;

[0091] Or R1 is R2 is a liquid crystal polymerizable monomer of OCH3 and n=4;

[0092] Or R1 is R2 is a liquid crystal polymerizable monomer with F and n=6;

[0093] Or R1 is R2 is a liquid crystal polymerizable monomer with CN and n=6.

[0094] In this application, the photoinitiator is one or more of 2-hydroxy-methylphenylpropane-1-one, 1-hydroxycyclohexylphenyl ketone, 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone, benzoin dimethyl ether, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and bis(2,6-difluoro-3-pyrrolephenyl)titanium oxide, mixed in any proportion. In the embodiments of this application, the photoinitiator is preferably a mixture of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and bis(2,6-difluoro-3-pyrrolephenyl)titanium oxide, a mixture of benzoin dimethyl ether and bis(2,6-difluoro-3-pyrrolephenyl)titanium oxide, or 2-hydroxy-methylphenylpropane-1-one. Of course, other combinations of the above photoinitiators can also be used. The photoinitiator is used to initiate photopolymerization reactions of liquid crystal polymerizable monomer materials and liquid crystal polymerizable monomer materials with spiropyran derivatives or cyanostyrene derivatives.

[0095] This application also provides a method for preparing the above-mentioned liquid crystal polymer with a programmable glass transition temperature, including:

[0096] S1, spiropyran derivative, cyano-styrene derivative, liquid crystal polymerizable monomer material and photoinitiator are mixed evenly in proportion to obtain a mixture;

[0097] S2, pour the mixture into the liquid crystal cell, heat it until the mixture is clear, then slowly cool it down and perform light irradiation curing;

[0098] S3, Remove the liquid crystal cell to obtain a liquid crystal polymer with a programmable glass transition temperature.

[0099] It should be noted that during photo-irradiation curing, the mixture is irradiated with light of wavelength 365-520nm, and the irradiation intensity is 1-10mW / cm². 2 The irradiation time is 10-30 minutes. After being irradiated and cured with light of different wavelengths and for different times, the liquid crystal polymer exhibits different T values ​​in the irradiated areas. g Depending on the specific requirements, different wavelengths of light can be used to irradiate different regions of the mixture, resulting in different glass transition temperatures (T0) in different regions of the liquid crystal polymer. g By adjusting the wavelength of light and the irradiation time, liquid crystal polymers with programmable glass transition temperatures can be prepared.

[0100] The liquid crystal polymer with a programmable glass transition temperature disclosed in this application can be used as a time-dependent information encryption material for information encryption.

[0101] This application also provides a time-dependent information encryption material, including the above-mentioned material with programmable T... gLiquid crystal polymers or liquid crystal polymers prepared by the above preparation methods with programmable T g The liquid crystal polymer. The T of the liquid crystal polymer... g The temperature can be adjusted between 11℃ and 32℃ depending on the wavelength of light and the irradiation time, and the low T temperature... g Liquid crystal polymers have a higher fading rate than high T g Liquid crystal polymers have a fast fading rate. By utilizing the different fading rates of liquid crystal polymers, information can be encoded in a "time-locked" manner in a liquid crystal polymer film. The encoded information is self-erased over time, and false or blank information is generated in the process.

[0102] A fourth aspect of this application provides an encryption method based on the aforementioned liquid crystal polymer with a programmable glass transition temperature. Information is recorded on the liquid crystal polymer film with a programmable glass transition temperature using light of different wavelengths or different irradiation times through a photomask. Structural transformation is achieved by irradiation with short-wavelength light. The information is encoded in the time-dependent information encryption material in a "time-locked" manner. The encoded information self-erases over time, generating false or blank information. Correct information can only be identified at a specified time.

[0103] The present application will be further illustrated by the following examples.

[0104] Example 1

[0105] This embodiment provides a T g The preparation method of the liquid crystal polymer at 13℃ is shown in Table 1.

[0106] Table 1. Raw materials and proportions for Example 1

[0107]

[0108]

[0109] Mix the components in Table 1 according to the specified proportions until homogeneous. Pour the mixture into a 50-micron liquid crystal cell, heat until the mixture becomes clear, and then slowly cool it down. Use light with a wavelength of 520 nm at a concentration of 5 mW / cm². 2 Irradiate the mixture with light at a certain intensity for 30 minutes to cause the monomers in the mixture to polymerize, yielding T. g It is a liquid crystal polymer film at 13℃.

[0110] The liquid crystal polymer film was irradiated with short-wavelength light, causing all the light-colored V-shaped structures of the spiropyran derivative to transform into dark-colored rod-shaped structures. Finally, it was exposed to visible light, and the fading of the liquid crystal polymer film was observed in both visible and ultraviolet light modes. The fading state diagram of the polymer film in visible light mode is shown below. Figure 1 As shown, the fading state diagram of the polymer film under ultraviolet light mode is as follows. Figure 2 As shown.

[0111] from Figure 1 It can be seen that at a wavelength of 520nm and a light intensity of 5mW / cm², 2 A liquid crystal polymer film prepared by irradiation with visible light for 30 minutes faded under visible light irradiation. The fading process was observed under ultraviolet light. Figure 2 As shown, the fluorescent color gradually changes from red to pink, then to blue, and the fading rate is very fast. This is because, under these polymerization conditions, the prepared liquid crystal polymer film T... g The temperature is 13℃, which is much lower than room temperature. In this liquid crystal polymer film, the two configurations of the spiropyran derivative molecule can freely switch, which macroscopically manifests as a very fast fading rate of the liquid crystal polymer film.

[0112] Example 2

[0113] This embodiment provides a T g The preparation method of the liquid crystal polymer at 24℃ is shown in Table 2.

[0114] Table 2 Raw materials and proportions for Example 2

[0115]

[0116] Mix the components in Table 2 according to the specified proportions until homogeneous. Pour the mixture into a 50-micron liquid crystal cell, heat until the mixture becomes clear, and then slowly cool it. Use light with a wavelength of 405 nm at 10 mW / cm². 2 Irradiate the mixture with light at a certain intensity for 20 minutes to cause the monomers in the mixture to polymerize, yielding T. g It is a liquid crystal polymer film at 24℃.

[0117] The liquid crystal polymer film was irradiated with short-wavelength light, causing all the light-colored V-shaped structures of the spiropyran derivative to transform into dark-colored rod-shaped structures. Finally, it was exposed to visible light, and the fading of the liquid crystal polymer film was observed in both visible and ultraviolet light modes. The fading state diagram of the polymer film in visible light mode is shown below. Figure 3 As shown, the fading state diagram of the polymer film under ultraviolet light mode is as follows. Figure 4 As shown.

[0118] from Figure 3 It can be seen that at a wavelength of 405nm and a light intensity of 5mW / cm², 2 A liquid crystal polymer film prepared by irradiation with visible light for 30 minutes faded under visible light irradiation. The fading process was observed under ultraviolet light. Figure 4As shown, the fluorescent color changes from red to pink, and then to blue, with a fading rate slower than that of the liquid crystal polymer film in Example 1. This is because, under these polymerization conditions, the prepared liquid crystal polymer film T... g The temperature was 24°C, close to room temperature. In this liquid crystal polymer film, the two configurations of the spiropyran derivative molecule can freely switch, but the switching rate is slow.

[0119] Example 3

[0120] This embodiment provides a T g The preparation method of liquid crystal polymer at 30℃ is shown in Table 3, and the raw material composition is as follows.

[0121] Table 3. Raw materials and proportions for Example 3

[0122]

[0123]

[0124] Mix the components in Table 3 according to the specified proportions until homogeneous. Pour the mixture into a 50-micron liquid crystal cell, heat until the mixture becomes clear, and then slowly cool it down. Use light with a wavelength of 365 nm at 5 mW / cm². 2 Irradiate the mixture with light at a certain intensity for 30 minutes to cause the monomers in the mixture to polymerize, yielding T. g It is a liquid crystal polymer film at 30℃.

[0125] The liquid crystal polymer film was irradiated with short-wavelength light, causing all the light-colored V-shaped structures of the spiropyran derivative to transform into dark-colored rod-shaped structures. Finally, it was exposed to visible light, and the fading of the liquid crystal polymer film was observed in both visible and ultraviolet light modes. The fading state diagram of the polymer film in visible light mode is shown below. Figure 5 As shown, the fading state diagram of the polymer film under ultraviolet light mode is as follows. Figure 6 As shown.

[0126] from Figure 5 It can be seen that at a wavelength of 365nm and a light intensity of 5mW / cm², 2 The liquid crystal polymer film prepared by irradiation with light for 30 minutes faded under visible light irradiation, but its fading rate was slower than that of Examples 1 and 2, and the liquid crystal polymer film did not completely fade in the end. The fading process was observed under ultraviolet light. Figure 6 As shown, the fluorescent color changed from red to pink, but did not completely fade. This is because, under these polymerization conditions, the prepared liquid crystal polymer film T... g The temperature is 30℃, which is higher than room temperature; at high T gIn liquid crystal polymer films, liquid crystal molecules have a strong anchoring effect on spiropyran derivative molecules, and it is difficult for the dark-colored rod-shaped configuration of spiropyran to be converted to the colorless V-shaped configuration.

[0127] Example 4

[0128] This embodiment provides a T g A method for preparing a liquid crystal polymer in the temperature range of 11℃ to 32℃ and an encryption method are disclosed. The raw material formulation of the liquid crystal polymer is shown in Table 4.

[0129] Table 4. Raw materials and proportions for Example 4

[0130]

[0131] Mix the components in Table 4 according to the specified ratios. Pour the mixture into a 50-micron liquid crystal cell and heat until the mixture becomes clear, then slowly cool it down. Divide the liquid crystal cell into three regions from left to right, and perform regional irradiation polymerization using photomasks. Specifically, for the first region from left to right, use a photomask with a pattern "F" and a wavelength of 365 nm with a light intensity of 5 mW / cm². 2 The first region was irradiated with light for 30 minutes to write the letter F; the second region was irradiated with a photomask patterned "E" and light with a wavelength of 405 nm and an intensity of 10 mW / cm². 2 The letter E was written by irradiating the area with light for 20 minutes. The third region was then illuminated using a photomask with a pattern of "I" and a wavelength of 520 nm and a light intensity of 5 mW / cm². 2 The letter 'I' was written by irradiating the area with light for 30 minutes. In the remaining areas, excluding the letters 'F', 'E', and 'I', light with a wavelength of 405 nm and an intensity of 5 mW / cm² was applied. 2 Irradiate light for 20 minutes.

[0132] After polymerization, the regions on the liquid crystal polymer film containing the letters F, E, and I, as well as the regions outside the letters, have different T values. g The liquid crystal polymer film was irradiated with short-wavelength light, causing all the light-colored V-shaped structures of the spiropyran derivative to be converted into dark-colored rod-shaped structures.

[0133] The liquid crystal polymer film was irradiated with visible light, and the fading of the film was observed in both visible light and ultraviolet light modes. Figure 7 As shown, in the initial state, the liquid crystal polymer film does not display any information; after being irradiated with visible light at times A, B, and C, the liquid crystal polymer film displays "FEI", "FE", and "F" respectively. This is because the glass transition temperature T of the regions containing "F", "E", and "I" on the liquid crystal polymer film is... gDue to differences in color intensity, the fading rate varies, resulting in the display of different information at different times. This liquid crystal polymer film exhibits time-dependent information encryption. Using a designated "time key," the correct information "FE" is decrypted at Time B. If the time interval is shorter or longer, false information "EFI" (Time A) or "F" (Time C) is identified. Utilizing these characteristics, information can be encoded in the liquid crystal polymer film in a "time-locked" manner. The encoded information self-erases over time, generating false or blank information in the process. Correct information can only be identified at a specified time, i.e., decrypted using the "time key."

[0134] Example 5

[0135] This embodiment provides a T g A method for preparing a liquid crystal polymer in the temperature range of 11℃ to 32℃ and an encryption method are disclosed. The raw material formulation of the liquid crystal polymer is shown in Table 5.

[0136] Table 5. Raw materials and proportions for Example 5

[0137]

[0138]

[0139] Mix the components in Table 5 according to the specified proportions. Pour the mixture into a 60-micron liquid crystal cell, heat until the mixture becomes clear, and then slowly cool it down. Using a photomask, irradiate the mixture with light of different wavelengths to write the letter "E". The irradiation method is as follows: Figure 8 As shown, the vertical line of the letter "E" uses light with a wavelength of 365nm and an intensity of 10mW / cm². 2 The image was written after 20 minutes of light irradiation. The two horizontal lines above were written using a wavelength of 405nm and a light intensity of 10mW / cm². 2 The image was written after 15 minutes of light irradiation. The horizontal line below was written using a wavelength of 405nm and a light intensity of 5mW / cm². 2 The light was irradiated for 15 minutes before writing. In the area outside the strokes of the letter "E", a light with a wavelength of 520nm and an intensity of 5mW / cm² was used. 2 Irradiation with light for 20 minutes. After polymerization, the vertical line of the letter E, the two horizontal lines above it, the horizontal line below it, and the area outside the strokes of the letter E on the liquid crystal polymer film have different T values. g The liquid crystal polymer film was irradiated with short-wavelength light, causing all the light-colored V-shaped structures of the spiropyran derivative to be converted into dark-colored rod-shaped structures.

[0140] The liquid crystal polymer film was irradiated with visible light, and the fading of the film was observed in both visible light and ultraviolet light modes. Figure 9 As shown, in the initial state, the liquid crystal polymer film does not display any information; after being illuminated by visible light at times A, B, and C, the liquid crystal polymer film displays "E", "F", and "I" respectively. This is because the T-wave pattern of the letter "E" on the liquid crystal polymer film varies with the number of strokes. g Due to differences in color intensity, the fading rate varies, resulting in the display of different information at different times. This liquid crystal polymer film exhibits time-dependent information encryption. Using a designated "time key," the correct information "F" is decrypted at Time B. If the time interval is shorter or longer, false information "E" (Time A) or "I" (Time C) is identified. Utilizing these characteristics, information can be encoded in the liquid crystal polymer film in a "time-locked" manner. The encoded information self-erases over time, generating false or blank information in the process. Correct information can only be recognized at a specified time, i.e., decrypted using the "time key."

[0141] Although this application has been described in detail in this specification with general descriptions and specific embodiments, some modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, such modifications or improvements made without departing from the spirit of this application are all within the scope of protection claimed in this application.

Claims

1. A liquid crystal polymer having a programmable glass transition temperature, characterized in that, The liquid crystal polymer with a programmable glass transition temperature has a temperature of 11°C. The glass transition temperature is 32 °C. The raw materials for preparing the liquid crystal polymer with a programmable glass transition temperature, by weight, include: Liquid crystal polymerizable monomers: 80.0-99.0 parts; Spiropyran derivatives, 0.5-10.0 parts; 0.1-5.0 parts of cyanostyrene derivatives; Photoinitiator 0.1-5.0 parts; The structural formula of the spiropyran derivative is shown in formula (I): (I) Where R is Or n is an integer between 2 and 18; The structural formula of the cyanostyrene derivative is shown in formula (II): (II) Where R is Or n is an integer from 1 to 18.

2. The liquid crystal polymer with a programmable glass transition temperature according to claim 1, characterized in that, The liquid crystal polymer with a programmable glass transition temperature comprises multiple regions with different glass transition temperatures.

3. The liquid crystal polymer with a programmable glass transition temperature according to claim 1, characterized in that: The liquid crystal polymerizable monomer is one or more of the structural formulas shown in formula (III), (IV) or (V) mixed in any ratio; (III) Where R is Or X is -CH3, -Cl, or -F; n is an integer from 1 to 18; (IV) Where R1 is Or R2 is -CN, -F, or -OC. m H 2m+1 m is an integer from 1 to 18; n is an integer from 1 to 18; (V) Among them, R3 is Or n is an integer from 1 to 18.

4. The liquid crystal polymer with a programmable glass transition temperature according to claim 1, characterized in that: The photoinitiator is one or more of 2-hydroxy-methylphenylpropane-1-one, 1-hydroxycyclohexylphenyl ketone, 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone, benzoin dimethyl ether, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and bis(2,6-difluoro-3-pyrrolephenyl)titanium decanoate, mixed in any proportion.

5. The method for preparing a liquid crystal polymer with a programmable glass transition temperature according to any one of claims 1 to 4, characterized in that, include: S1, spiropyran derivative, cyano-styrene derivative, liquid crystal polymerizable monomer material and photoinitiator are mixed evenly in proportion to obtain a mixture; S2, pour the mixture into the liquid crystal cell, heat it until the mixture is clear, then slowly cool it down and perform light irradiation curing; S3, Remove the liquid crystal cell to obtain a liquid crystal polymer with a programmable glass transition temperature.

6. The preparation method according to claim 5, characterized in that, The light irradiation curing specifically refers to: Irradiate the mixture with light of a single wavelength; Alternatively, different regions of the mixture can be irradiated with light of different wavelengths; The wavelength of the light is 365-520 nm, and the light irradiance is 1-10 mW / cm². 2 The irradiation time is 10-30 minutes.

7. The application of the liquid crystal polymer with a programmable glass transition temperature as described in any one of claims 1 to 4, or the liquid crystal polymer with a programmable glass transition temperature prepared by the preparation method described in claim 5 or 6, as a time-dependent information encryption material.

8. An encryption method based on a liquid crystal polymer with a programmable glass transition temperature as described in claim 1 or 2, characterized in that, Information is recorded on a liquid crystal polymer film with a programmable glass transition temperature using light of different wavelengths or irradiation times through a photomask. Structural transformation is achieved by irradiation with short-wavelength light. The information is encoded in the time-dependent information encryption material in a "time-locked" manner. The encoded information is self-erased over time and generates false or blank information. The correct information can only be identified at a specified time.

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