Thermochromic dye as well as preparation and application thereof

Abstract

The invention discloses thermochromic dye as well as preparation and application thereof, and belongs to the technical field of fine chemical engineering. The preparation method comprises the following steps: firstly, by taking a fluorane dye as a raw material, introducing an amino group into a fluorane dye structure by utilizing a reaction between lactone and alkyl diamine; and then preparing the lactam thermochromic dye by utilizing an aldehyde amine reaction between the amino fluorane dye and the phenolic hydroxyl benzaldehyde. By utilizing the characteristics that phenolic hydroxyl groups in a thermochromic dye structure release protons at low temperature and obtain protons at high temperature and utilizing the flexibility of alkyl chains in an alkyl diamine structure, a lactam structure in a fluorane dye structure is subjected to ring opening and ring closing reactions, the size of a conjugated system of the dye is adjusted, and the color change of the dye is realized.

Description

Technical Field

[0001] The invention relates to a thermochromic dye and preparation and application thereof, belonging to the technical field of fine chemical industry. Background Art

[0002] There are many types of thermochromic materials. Fluorane thermochromic materials can control their color by changing the electron donation and withdrawal properties, quantity and position of their substituents. They have become the current mainstream temperature-sensitive materials and are widely used in temperature-indicating coatings, color-changing inks, anti-counterfeiting and other aspects.

[0003] Fluorane thermochromic materials generally consist of three components: fluorane dye, developer and phase change material. Fluorane dye is a color former, which is an electron-donating substance in the color-changing system. It develops color by giving electrons to the developer, which determines the color of the color-changing system. The developer is a compound that causes thermochromism. It accepts electrons provided by the color former to change the color of the system, which determines whether the system changes color and the depth of the color change. The melting point of the phase change material determines the color change temperature of the system.

[0004] The color changing principle of the conventional thermochromic dye (ie, three-component system) is as follows.

[0005]

[0006] During the heating process, when the external temperature rises to the melting temperature of the phase change material, the phase change material is in a solution state, which can dissolve the leuco body and the chromophore. The two exist in their own independent molecular states, and the interaction between the two is destroyed by the solvent. The central carbon atom of the leuco body forms a ring, which is sp 3 The hybrid tetrahedral structure has poor molecular planarity, the conjugated system is destroyed, and the entire system appears colorless. During the cooling process, when the external temperature drops to the crystallization temperature of the phase change material, the phase change material is in a solid state, the color developer and the hidden color agent interact strongly, and electrons are converted between the two. The lactone ring opens, and the central carbon atom is converted to sp 2 The hybrid orbital and the entire system form a large π conjugated structure, which makes the dye absorb in the visible light region.

[0007] From the above color change principle, it can be known that the electron transfer rate between the color former and the developer affects the color change sensitivity of the system, i.e., the color change response time. The existing fluorane color change system is generally a three-component system, and the electron transfer between the color former and the developer is often intermolecular electron transfer, and the electron transfer rate is low. For example, in CN112852402A, a thermochromic material for textile printing is prepared using crystal violet lactone as a color former, bisphenol A as a developer, and alkyl alcohol as a phase change material. In CN115785599A, dyes such as 16 (3,3-bis (N-octyl-2-methylindole) phthalolactone) are used as colorants, bisphenol A is used as a color developer, and phenyl alcohol ((2-(4-phenylmethoxy)ethanol)) is used as a phase change material to prepare a bionic thermochromic material for high-spectral camouflage. In CN115888572A, crystal violet lactone and weak acid dyes are used as color developers, bisphenol A is used as a color developer, and alcohol esters are used as phase change materials to prepare a color-changing material with multi-color range indication and temperature adjustment functions. Summary of the invention

[0008] [Technical issues]

[0009] At present, most of the existing thermochromic dyes are three-component systems of color former, developer and phase change material. The color change of the system is caused by the intramolecular electron transfer between the color former and the color-changing body. However, the intramolecular electron transfer speed is low, which affects the color change sensitivity of the color change system and the application performance.

[0010] [Technical solution]

[0011] In order to solve the above problems, the present invention prepares a thermochromic dye that can form intramolecular electron transfer, which can significantly improve the electron transfer rate of the color-changing system, that is, significantly improve the color-changing sensitivity of the system. Moreover, since the color-changing system is transformed from three components to two components, the color-changing system is simple, and the color-changing performance is more stable and controllable.

[0012] The present invention first uses fluoran dye as a raw material, and utilizes the reaction between lactone and alkyl diamine to introduce an amino group into the fluoran dye structure; then utilizes the aldehyde amine reaction between the aminofluoran dye and phenolic hydroxybenzaldehyde to prepare a lactam thermochromic dye. The present invention utilizes the characteristics of the phenolic hydroxyl group in the thermochromic dye structure releasing protons at low temperatures and obtaining protons at high temperatures, and utilizes the flexibility of the alkyl chain in the alkyl diamine structure to cause the lactam structure in the fluoran dye structure to undergo ring opening and ring closing reactions, adjust the size of the conjugated system of the dye, and realize the color change of the dye. The color change mechanism of the lactam thermochromic dye of the present invention is as follows:

[0013]

[0014] The first object of the present invention is to provide a thermochromic dye, the structural formula of which is as follows:

[0015]

[0016] Where:

[0017] n is 1-17;

[0018] R1 and R2 are independently selected from: -H, C1-6 alkyl, substituted or unsubstituted phenyl;

[0019] R3 and R4 are independently selected from: -H, halogen (F, Cl, Br, I), C1-6 alkyl, halogenated C1-6 alkyl, substituted or unsubstituted phenyl, substituted or unsubstituted phenylamino;

[0020] R5, R6, R7 and R8 are independently selected from: -H, -OH, and at least one is -OH;

[0021] The substituents on the phenyl group may be selected from: halogen (F, Cl, Br, I), C1-6 alkyl, halogenated C1-6 alkyl.

[0022] In one embodiment of the present invention, the substituents on the phenyl group are monosubstituted, disubstituted, trisubstituted, or tetrasubstituted.

[0023] In one embodiment of the present invention, R1 and R2 are independently selected from: -H, -CH3, -C2H5, n-C3H7, i-C4H9, n-C4H9, n-C5H 11 ,

[0024] In one embodiment of the present invention, R3 and R4 are independently selected from: -H, Cl, -CH3, -C2H5, n-C4H9, n-C5H 11 ,

[0025] In one embodiment of the present invention, R5 and R8 are -OH, R6, R7 are H; or R8 is -OH, R5, R6, R7 are H.

[0026] In one embodiment of the present invention, n is further 6-9.

[0027] A second object of the present invention is to provide a method for thermochromic dyes, comprising the steps of:

[0028] (1) First, a certain amount of fluoran dye and ethanol are weighed, heated to 80° C., and stirred until completely dissolved; then a certain amount of diamine compound is added, refluxed for a certain period of time, and spin-dried; finally, the aminated dye is extracted with an aqueous solution of dichloromethane and ethanol, and dried to obtain the aminated dye;

[0029] (2) Weighing a certain amount of hydroxybenzaldehyde compound and dissolving it in a certain amount of chloroform, cooling the temperature to 0° C., adding a certain amount of anhydrous aluminum chloride, and stirring at room temperature for a certain period of time to obtain a hydroxybenzaldehyde solution;

[0030] (3) Weigh a certain amount of aminated dye, triethylamine and chloroform, stir until completely dissolved, and slowly add them dropwise to the above hydroxybenzaldehyde solution, continue stirring for a certain period of time at room temperature, add alkali to terminate the reaction, and stratification occurs; extract the aqueous layer with dichloromethane, and recrystallize in methanol solution to obtain a thermochromic dye.

[0031] In one embodiment of the present invention, the structure of the fluoran dye in step (1) is:

[0032]

[0033] Wherein, R1-R4 are as defined above.

[0034] In one embodiment of the present invention, the diamine compound in step (1) is: ethylenediamine, propylenediamine, diethylenetriamine, butylenediamine, pentanediamine, hexamethylenediamine, decanediamine, dodecanediamine, tetradecanediamine, hexadecanediamine, and octadecanediamine.

[0035] In one embodiment of the present invention, the molar ratio of the fluoran dye to the diamine compound in step (1) is 1:(15-40).

[0036] In one embodiment of the present invention, the mass ratio of the fluoran dye to ethanol in step (1) is 1:(10-50).

[0037] In one embodiment of the present invention, the reflux time in step (1) is 4 to 36 hours.

[0038] In one embodiment of the present invention, the mass ratio of ethanol to water in the aqueous solution of ethanol in step (1) is 1:(0.1-10).

[0039] In one embodiment of the present invention, the structure of the hydroxybenzaldehyde compound in step (2) is:

[0040]

[0041] Wherein, R5, R6, R7 and R8 are as defined above.

[0042] In one embodiment of the present invention, the molar ratio of the aminated dye to the hydroxybenzaldehyde compound in step (2) is 1:(1-1.1).

[0043] In one embodiment of the present invention, the mass ratio of the hydroxybenzaldehyde compound to chloroform in step (2) is 1:(30-60).

[0044] In one embodiment of the present invention, the molar ratio of the hydroxybenzaldehyde compound to anhydrous aluminum chloride in step (2) is 1:(1-1.5).

[0045] In one embodiment of the present invention, the stirring time in step (2) is 4 to 10 hours.

[0046] In one embodiment of the present invention, the molar ratio of the aminated dye to the hydroxybenzaldehyde compound in step (3) is 1:1.

[0047] In one embodiment of the present invention, the molar ratio of the aminated dye to triethylamine in step (3) is 1:(2-5).

[0048] In one embodiment of the present invention, the mass ratio of the aminated dye to chloroform in step (3) is 1:(10-15).

[0049] In one embodiment of the present invention, the stirring reaction time in step (3) is 6 to 15 hours.

[0050] The third object of the present invention is the use of the thermochromic dyes of the present invention in textile dyeing, printing and spinning.

[0051] In one embodiment of the present invention, the textile comprises polyester, nylon, cotton, viscose, linen or multiple blended fibers thereof and fabrics thereof.

[0052] In one embodiment of the present invention, the thermochromic fabric is obtained by dyeing, printing or spinning fibers with thermochromic dyes.

[0053] [Beneficial Effects]

[0054] The thermochromic dye of the present invention solves the problems of "the existing thermochromic dyes have poor color change sensitivity due to intermolecular electron transfer and poor controllability of complex color change of the three-component system", and expands the application in the direction of high-sensitivity color change and color change controllability. DETAILED DESCRIPTION

[0055] The preferred embodiments of the present invention are described below. It should be understood that the embodiments are for better explaining the present invention and are not used to limit the present invention.

[0056] The fluorane dye involved in the following examples can be purchased from Wuhan Shuer Biotechnology Co., Ltd., and its structure is shown below:

[0057]

[0058] Test method:

[0059] 1. H NMR spectroscopy (1 H-NMR):

[0060] Deuterated chloroform was used as solvent and a nuclear magnetic resonance spectrometer (AVANCE III) was used to characterize the samples.

[0061] 2. Temperature change sensitivity test:

[0062] Weigh 3g of the color-changing material in the colored state, add it to the tablet press, flatten it, and place it in a culture dish. Set the temperature of the temperature control platform to 50°C, and place the culture dish on the temperature control platform. Record the temperature change of the material from colored to colorless, and record the complete decolorization time.

[0063] 3. Temperature drop color change sensitivity test:

[0064] Weigh 3g of color-changing material and add it to the tablet press to flatten it. Place it in a culture dish and heat it to 60°C. The color-changing material shows a colorless state. Set the temperature of the temperature control platform to 50°C, place the culture dish on the temperature control platform, and record the cooling and color change of the material from colorless to colored by video, and record the complete color restoration time.

[0065] Example 1

[0066] A method for preparing a thermochromic dye comprises the following steps:

[0067] (1) Weigh 0.01 mol of fluoran dye (M = 402.5, 4.03 g) and 60 g of ethanol, heat to 80°C, and stir until completely dissolved; then add 0.36 mol of decanediamine (M = 174, 62.6 g), reflux for 24 hours, and spin dry; finally, use a mixture of dichloromethane and ethanol aqueous solution (the mass ratio of ethanol to water is 1:0.1) to extract the aminated dye, and dry it to obtain the aminated dye.

[0068] (2) Weigh 0.01 mol of p-hydroxybenzaldehyde (M = 122.12, 1.22 g) and dissolve it in 60 g of chloroform. Cool the mixture to 0°C, add 0.012 mol of anhydrous aluminum chloride (M = 122.12, 1.68 g), and stir the mixture at room temperature for 7 h.

[0069] (3) Weigh 0.01 mol of aminated dye (M = 556.5, 5.57 g), 0.03 mol of triethylamine (M = 101.19, 3.04 g) and 60 g of chloroform, stir until completely dissolved, and slowly add dropwise to the above p-hydroxybenzaldehyde solution, continue stirring at room temperature for 10 hours, add 1 mol / L sodium hydroxide solution to terminate the reaction, and stratification occurs. The aqueous layer is extracted with dichloromethane and recrystallized in methanol solution to obtain a thermochromic dye.

[0070] The structural formula of the obtained thermochromic dye is as follows:

[0071]

[0072] The synthesis steps of thermochromic dyes are as follows:

[0073]

[0074] The structural characterization is as follows:

[0075] 1 H-NMR (400MHz, CHCl3-d6): δ8.76 (s, 1H, N=C H ), δ7.91 (d, 2H, Ar-H), 7.78 (d, 2H, Ar-H), 7.58 (t, 1H, Ar-H), 7.18 (t, 1H, Ar-H), 7.10 (s, 1H, Ar-H), 7.00 (s, 1H, Ar -H), 6.85 (d, 2H, Ar-H), 6.54 (d, 1H, Ar-H), 6.38 (d, 1H, Ar-H), 6.34 (s, 1H, Ar-H), 5.35 (s, 1H, OH), 3.41 (q, 4H, -NC H 2CH3), 3.20 (q, 4H, NC H 2CH2), 2.34 (s, 3H, C H 3), 1.59-1.65 (m, 4H, NCH2C H 2), 1.29(s, 12H, C H 2), 1.15(s, 6H, C H 3).

[0076] Example 2

[0077] A method for preparing a thermochromic dye comprises the following steps:

[0078] (1) Weigh 0.01 mol of fluoran dye (M = 402.5, 4.03 g) and 60 g of ethanol, heat to 80°C, and stir until completely dissolved; then add 0.36 mol of decanediamine (M = 174, 62.6 g), reflux for 24 hours, and spin dry; finally, use a mixture of dichloromethane and ethanol aqueous solution (the mass ratio of ethanol to water is 1:0.1) to extract the aminated dye, and dry it to obtain the aminated dye.

[0079] (2) Weigh 0.01 mol of 2,5-dihydroxybenzaldehyde (M = 138.12, 1.38 g) and dissolve it in 65 g of chloroform. Cool the mixture to 0°C, add 0.012 mol of anhydrous aluminum chloride (M = 122.12, 1.68 g), and stir the mixture at room temperature for 7 h.

[0080] (3) Weigh 0.01 mol of aminated dye (M = 556.5, 5.57 g), 0.03 mol of triethylamine (M = 101.19, 3.04 g) and 60 g of chloroform, stir until completely dissolved, and slowly add dropwise to the above p-hydroxybenzaldehyde solution, continue stirring at room temperature for 10 hours, add 1 mol / L sodium hydroxide solution to terminate the reaction, and stratification occurs. The aqueous layer is extracted with dichloromethane and recrystallized in methanol solution to obtain a thermochromic dye.

[0081] The structural formula of the obtained thermochromic dye is as follows:

[0082]

[0083] The synthesis steps of thermochromic dyes are as follows:

[0084]

[0085] The structural characterization is as follows:

[0086] 1 H-NMR (400MHz, CHCl3-d6): δ8.56 (s, 1H, N=C H ), δ7.91 (d, 2H, Ar-H), 7.58 (t, 1H, Ar-H), 7.29 (s, 1H, Ar-H), 7.18 (t, 1H, Ar-H), 7.10 (s, 1H, Ar-H), 7.00 (s, 1H, Ar -H), 6.85 (d, 2H, Ar-H), 6.54 (d, 1H, Ar-H), 6.38 (d, 1H, Ar-H), 6.34 (s, 1H, Ar-H), 5.35 (s, 1H, OH), 3.41 (q, 4H, -NC H 2CH3), 3.20 (q, 4H, NC H 2CH2), 2.34 (s, 3H, C H 3), 1.59-1.65 (m, 4H, NCH2C H 2), 1.29(s, 12H, C H 2), 1.15(s, 6H, C H 3).

[0087] Comparative Example 1

[0088] The structure of a simple fluoran dye (commercially available) is shown below:

[0089]

[0090] Comparative Example 2

[0091] A method for preparing a thermochromic dye comprises the following steps:

[0092] (1) Weigh 0.01 mol of fluoran dye (M = 402.5, 4.03 g) and 60 g of ethanol, heat to 80°C, and stir until completely dissolved; then add 0.36 mol of ethylenediamine (M = 60.1, 21.64 g), reflux for 24 hours, and spin dry; finally, use a mixture of dichloromethane and ethanol aqueous solution (the mass ratio of ethanol to water is 1:0.1) to extract the aminated dye, and dry it to obtain the aminated dye.

[0093] (2) Weigh 0.01 mol of p-hydroxybenzaldehyde (M = 122.12, 1.22 g) and dissolve it in 70 g of chloroform. Cool the mixture to 0°C, add 0.012 mol of anhydrous aluminum chloride (M = 122.12, 1.68 g), and stir the mixture at room temperature for 7 h.

[0094] (3) Weigh 0.01 mol of aminated dye (M = 556.5, 5.57 g), 0.03 mol of triethylamine (M = 101.19, 3.04 g) and 60 g of chloroform, stir until completely dissolved, and slowly add dropwise to the above p-hydroxybenzaldehyde solution, continue stirring at room temperature for 10 h, add 1 mol / L sodium hydroxide to terminate the reaction, and stratification occurs. The aqueous layer is extracted with dichloromethane and recrystallized in a methanol solution to obtain a thermochromic dye.

[0095] The structural formula of the obtained thermochromic dye is as follows:

[0096]

[0097] Comparative Example 3

[0098] A method for preparing a thermochromic dye comprises the following steps:

[0099] (1) Weigh 0.01 mol of fluoran dye (M = 402.5, 4.03 g) and 60 g of ethanol, heat to 80°C, and stir until completely dissolved; then add 0.36 mol of decanediamine (M = 174, 62.6 g), reflux for 24 hours, and spin dry; finally, use a mixture of dichloromethane and ethanol aqueous solution (the mass ratio of ethanol to water is 1:0.1) to extract the aminated dye, and dry it to obtain the aminated dye.

[0100] (2) Weigh 0.01 mol of 3,5-dibromo-4-hydroxybenzaldehyde (M = 279.91, 2.80 g) and dissolve it in 60 g of chloroform. Cool the mixture to 0°C, add 0.012 mol of anhydrous aluminum chloride (M = 122.12, 1.68 g), and stir the mixture at room temperature for 7 h.

[0101] (3) Weigh 0.01 mol of aminated dye (M = 556.5, 5.57 g), 0.035 mol of triethylamine (M = 101.19, 3.54 g) and 65 g of chloroform, stir until completely dissolved, and slowly dropwise add to the above p-hydroxybenzaldehyde solution, continue stirring at room temperature for 10 h, add 1 mol / L sodium hydroxide to terminate the reaction, and stratification occurs. The aqueous layer is extracted with dichloromethane and recrystallized in a methanol solution to obtain a thermochromic dye.

[0102] The structural formula of the obtained thermochromic dye is as follows:

[0103]

[0104] Color change sensitivity test:

[0105] Example 1 and Example 2 were melt-blended with the phase change material hexadecanol (mass ratio of 1:24) at 80° C., cooled to room temperature, and the color change response time of the dye was tested at 50° C.

[0106] Comparative Example 1, bisphenol A and phase change material hexadecanol (mass ratio of 1:2:24) were melt-blended at 80°C, cooled to room temperature, and the color change response time of the dye was tested at 50°C.

[0107] The specific test results are shown in Table 1.

[0108] Table 1 Discoloration of Examples and Comparative Examples

[0109] sample Discoloration Temperature change response time Cooling color change response time Example 1 + hexadecanol system Red to colorless 15s 56s Example 2 + hexadecanol system Red to colorless 29s 42s Comparative Example 1 + Bisphenol A + Hexadecanol System Red to colorless 50s 120s Comparative Example 1 + Hexadecanol System Red remains unchanged -- -- Comparative Example 2 + Hexadecanol System Red remains unchanged -- -- Comparative Example 3 + Hexadecanol System Red remains unchanged -- --

[0110] As can be seen from the table, when the color body is comparative example 1, the cooling and heating color change response times of the three-component color change system are 120 and 50s respectively, and the color change response time is relatively long. When the color bodies are examples 1 and 2, the cooling and heating color change response times are significantly shortened, and the color change sensitivity is significantly improved. And when the color bodies are comparative examples 1, 2 and 3, the two-component color change system cannot achieve color change.

[0111] The above-mentioned embodiments are preferred examples of the present invention and are not intended to limit the protection scope of the present invention.

Claims

1. A thermochromic dye, the structural formula of which is as follows: Where: n is 1-17; R1 and R2 are independently selected from: -H, C1-6 alkyl, substituted or unsubstituted phenyl; R3 and R4 are independently selected from: -H, halogen, C1-6 alkyl, halogenated C1-6 alkyl, substituted or unsubstituted phenyl, substituted or unsubstituted phenylamino; R5, R6, R7 and R8 are independently selected from: -H, -OH, and at least one is -OH; The substituents on the phenyl group may be selected from: halogen, C1-6 alkyl, halogenated C1-6 alkyl.

2. The thermochromic dye according to claim 1, characterized in that The substituents on the phenyl group are monosubstituted, disubstituted, trisubstituted, or tetrasubstituted; R1 and R2 are independently selected from: -H, -CH3, -C2H5, n-C3H7, i-C4H9, n-C4H9, n-C5H 11 , R3 and R4 are independently selected from: -H, Cl, -CH3, -C2H5, n-C4H9, n-C5H 11 , R5 and R8 are -OH, and R6 and R7 are H; or R8 is -OH, and R5, R6 and R7 are H; n is 6-9.

3. A method for preparing a thermochromic dye according to claim 1 or 2, characterized in that: The steps include: (1) mixing a fluoran dye and ethanol, heating and stirring until completely dissolved; then adding a diamine compound, refluxing, and spin-drying; finally extracting the aminated dye with an aqueous solution of dichloromethane and ethanol, and drying to obtain the aminated dye; (2) dissolving a hydroxybenzaldehyde compound in chloroform, cooling the temperature to 0-5° C., adding anhydrous aluminum chloride, and stirring at room temperature for a certain period of time to obtain a hydroxybenzaldehyde solution; (3) mixing the aminated dye, triethylamine and chloroform, stirring until completely dissolved, and slowly adding dropwise to the hydroxybenzaldehyde solution obtained in step (2), continuing to stir at room temperature for a certain period of time, adding alkali to terminate the reaction, and stratification occurs; The aqueous layer was extracted with dichloromethane and recrystallized in methanol solution to obtain a thermochromic dye.

4. The method according to claim 3, characterized in that The structure of the fluoran dye in step (1) is: Wherein, the definitions of R1-R4 are the same as those in claim 1.

5. The method according to claim 3, characterized in that: The diamine compound in step (1) is: ethylenediamine, propylenediamine, diethylenetriamine, butylenediamine, pentanediamine, hexamethylenediamine, decanediamine, dodecanediamine, tetradecanediamine, hexadecanediamine, and octadecanediamine; the molar ratio of the fluorane dye to the diamine compound is 1:(15-40); and the mass ratio of the fluorane dye to ethanol is 1:(10-50).

6. The method according to claim 3, characterized in that The structure of the hydroxybenzaldehyde compound in step (2) is: Wherein, R5, R6, R7 and R8 are defined as in claim 11.

7. The method according to claim 3, characterized in that In step (2), the molar ratio of the aminated dye to the hydroxybenzaldehyde compound is 1:(1-1.1); the mass ratio of the hydroxybenzaldehyde compound to chloroform is 1:(30-60); and the molar ratio of the hydroxybenzaldehyde compound to anhydrous aluminum chloride is 1:(1-1.5).

8. The method according to claim 3, characterized in that In step (3), the molar ratio of the aminated dye to the hydroxybenzaldehyde compound is 1:1; the molar ratio of the aminated dye to triethylamine is 1:(2-5); and the mass ratio of the aminated dye to chloroform is 1:(10-15).

9. Use of the thermochromic dye according to claim 1 or 2 in textile dyeing, printing and spinning.

10. A thermochromic fabric, characterized in that: The thermochromic dye is obtained by dyeing, printing or spinning fibers with the thermochromic dye described in claim 1 or 2.

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