Environmental stimuli-responsive full-chromatographic color-changing microcapsule as well as preparation method and application thereof

Abstract

The invention discloses an environmental stimuli-responsive full-chromatographic color-changing double-chamber microcapsule, which is characterized in that a thermochromic organic pigment-loaded polymer microcapsule is synthesized by using a solvent evaporation method, and then a photochromic compound-loaded polystyrene nanocapsule is synthesized through miniemulsion polymerization. And then, electrostatically adsorbing the positively charged nanocapsule to the surface of the negatively charged thermochromic microcapsule, and carrying out ring-opening reaction crosslinking to prepare the strawberry-shaped double-chamber microcapsule. Under the stimulation of ultraviolet light and heat, the strawberry-shaped double-chamber microcapsule can present a full-chromatographic color, has good fatigue resistance to ultraviolet light, visible light and temperature, and is suitable for the application of luminescence anti-counterfeiting, information encryption and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical material preparation, and specifically relates to an environmental stimulus responsive full-chromatogram color-changing microcapsule and a preparation method and application thereof. Background Art

[0002] Counterfeiting of security documents is a global problem, and current anti-counterfeiting technologies, such as optical encryption using various materials (e.g., cerium-doped nanoparticles, semiconductors / carbon dots, organic dyes, photonic crystals, and fluorescent / phosphorescent materials), have some limitations. These technologies are easily copied due to their predictable color changes and single stimulus-response patterns. Therefore, there is a growing demand for high-security anti-counterfeiting materials with diverse colors and sophisticated authentication technologies to enhance document security and prevent copying and counterfeiting.

[0003] Stimuli-chromic materials are widely used as high-security anti-counterfeiting materials. These materials are able to change color under different stimuli, including but not limited to light, temperature, stress, pH, ions, and solvent polarity. However, most stimuli-chromic materials only change color in response to specific external stimuli. To enhance security measures, materials with multiple stimulus-responsive color switching modes are more ideal. Therefore, the development of multi-stimulus-responsive materials with full-color spectrum switching capabilities, using subtractive primary colors of cyan, magenta, and yellow, will significantly enhance anti-counterfeiting measures.

[0004] Microcapsules have attracted attention because they can protect active molecules such as fragrance oils, drugs and dyes from the influence of the external environment, and therefore have practical value in various applications. The invention of CN202211446963.5 discloses a three-color photochromic microcapsule and a preparation method thereof, wherein the microcapsule uses an organic photochromic material as a core material and a polymer material such as polyurethane as a wall material. The three-color photochromic microcapsule prepared by the invention not only has sensitive light responsiveness and light reversibility, but also has a certain resistance to light fatigue and excellent thermal stability. The invention of CN202211498988.X also discloses a microcapsule with multi-color gamut indication and temperature regulation functions, which uses a thermosensitive color-changing material, a water-soluble dye and a phase change material as a core material, and provides a method for preparing a microcapsule with a rich color spectrum and reversible changes between different tones and a multi-color gamut indication and temperature regulation function. Although these microcapsules can achieve color change between multiple colors, the color change spectrum is not full spectrum, and it is only the color change of the dye itself, and the color matching formed during the assembly process of nanoparticles has not been studied.

[0005] Traditional microcapsules can only encapsulate a single type of payload and respond to a single stimulus, a limitation that can be overcome by using multi-cavity microcapsules. In such microcapsules, each chamber is responsible for protecting a different stimulus-chromic material, thereby achieving independent encapsulation of multiple contents and avoiding cross-contamination. In addition, it is also crucial to ensure that different payloads from the same capsule can achieve independent, selective and controllable responses to different external stimuli. The structure of these microcapsules can be adjusted as needed to achieve the desired color change, making them versatile and suitable for a variety of application scenarios. Summary of the invention

[0006] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0007] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0008] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide an environmental stimulus responsive full-spectrum color-changing microcapsule.

[0009] (i) It has a strawberry-shaped dual-compartment structure formed by thermochromic microcapsules and photochromic nanocapsules;

[0010] (ii) Based on the coupling reaction between the imidazole ring on the surface of thermochromic microcapsules and the chloroalkane on the surface of photochromic nanocapsules, the assembly of full-spectrum color-changing microcapsules with a strawberry-like double-compartment structure is achieved.

[0011] As a preferred embodiment of the environmental stimulus responsive full-spectrum color-changing microcapsules described in the present invention, the core material of the thermochromic microcapsules is a thermochromic pigment, and the shell material is a polyacrylate-styrene polymer resin; the core material of the photochromic nanocapsules is a photosensitizing dye, and the shell material is a styrene polymer resin.

[0012] As a preferred embodiment of the environmental stimulus responsive full-chromatogram color-changing microcapsules described in the present invention, the particle size of the thermochromic microcapsules is 1 to 20 μm, and the particle size of the photochromic nanocapsules is 100 to 800 nm.

[0013] Another object of the present invention is to overcome the deficiencies in the prior art and provide a method for preparing the environmental stimulus responsive full-chromatogram color-changing microcapsules, which comprises:

[0014] 20.01-55.7 parts of polyacrylate-styrene polymer resin and 0.1-3 parts of thermochromic pigment are dissolved in 5-20 parts of dichloromethane to obtain dispersed phase I;

[0015] 0.5 to 10 parts of emulsifier are added to 100 to 500 parts of deionized water to obtain continuous phase I, dispersed phase I is added to continuous phase I under the action of mechanical shear force, and emulsion I is obtained after mixing;

[0016] 5 to 15 parts of styrene, 0.5 to 2 parts of 1-vinylimidazole, 0.01 to 0.5 parts of divinylbenzene, 0.1 to 0.5 parts of photosensitizing dye and 0.01 to 0.7 parts of azobisisobutyronitrile are reacted by stirring to obtain dispersed phase II;

[0017] 0.5-10 parts of emulsifier are added to 100-500 parts of deionized water to obtain continuous phase II, dispersed phase II is added to continuous phase II under mechanical shear force, and stirred at 40-80° C. for 3-10 hours to obtain emulsion II;

[0018] 1 to 5 parts of emulsion I and 10 to 30 parts of emulsion II are stirred and reacted at 20 to 60° C. for 4 to 12 hours, and then dried to obtain environmental stimulus responsive full chromatographic color-changing microcapsules.

[0019] As a preferred solution of the method for preparing the environmental stimulus responsive full-chromatographic color-changing microcapsules of the present invention, the method for preparing the polyacrylate-styrene polymer resin comprises:

[0020] The product is prepared by heating 15 to 25 parts of styrene, 2 to 10 parts of glycidyl methacrylate, 1 to 10 parts of butyl acrylate, 2 to 10 parts of 4-chloromethylstyrene and 0.01 to 0.7 parts of azobisisobutyronitrile in an oil bath at 75 to 80° C. for 6 to 8 hours.

[0021] As a preferred solution of the method for preparing the environmental stimulus responsive full-chromatogram color-changing microcapsules described in the present invention, the stirring temperature of the dispersed phase II is 75-80° C., and the stirring time is 4-6 hours.

[0022] As a preferred scheme for the preparation method of the environmental stimulus responsive full-chromatogram color-changing microcapsules described in the present invention, the emulsifier includes one or more of polyoxyethylene sorbitan monooleate, polyoxyethylene-8-octylphenyl ether, polyoxyethylene sorbitan monolaurate, sodium dodecylbenzene sulfonate, and sodium dodecyl sulfate.

[0023] As a preferred scheme for the preparation method of the environmental stimulus responsive full-chromatogram color-changing microcapsules described in the present invention, the photosensitizing dye includes one or more of cis-1,2-dicyano-1,2-bis(2,4,5-trimethyl-3-thienyl)ethylene, spiro[1,3,3-trimethylindole-(6'-nitrobenzodihydropyran), and 3,3-diphenyl-3H-naphtho[2,1-b]pyran.

[0024] As a preferred solution of the method for preparing the environmental stimulus responsive full-chromatogram color-changing microcapsules described in the present invention, the thermochromic pigment is a pigment that changes color with temperature.

[0025] Another object of the present invention is to overcome the deficiencies in the prior art and provide an application of an environmental stimulus responsive full-spectrum color-changing microcapsule, wherein: the environmental stimulus responsive full-spectrum color-changing microcapsule is applied to the fields of luminous anti-counterfeiting and information encryption, home textiles, sportswear, and leather products.

[0026] Beneficial effects of the present invention:

[0027] (1) The environmental stimulus responsive full-spectrum color-changing microcapsules prepared by the present invention can change color over the entire color range under the stimulation of ultraviolet light and temperature environmental conditions, and the microcapsules can be adjusted to present different colors by controlling the mass ratio of the photochromic nanocapsules.

[0028] (2) In the environmental stimulus responsive full-spectrum color-changing microcapsules of the present invention, a coupling reaction occurs between the chloroalkanes on the surface of the nanocapsules and the imidazole rings on the surface of the microcapsules to form a strawberry-shaped double-chamber microcapsule structure, which prolongs the service life of the microcapsules and increases the airtightness of the shell layer, making it less likely for the core material to leak, thereby ensuring that the double-chamber microcapsules change color evenly when the temperature or ultraviolet light changes.

[0029] (3) When the environmental stimulus responsive color-changing dual-chamber microcapsules of the present invention are used as ink for printing cotton fabrics, the printed pattern can achieve full-spectrum color change under ultraviolet and thermal stimulation, and has good fatigue resistance to temperature, ultraviolet light, and visible light. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0031] Figure 1 The scanning electron microscope images of the photochromic nanocapsules (a) and the thermochromic microcapsules (b) in Example 1 of the present invention are shown.

[0032] Figure 2 These are XPS analysis diagrams of the photochromic nanocapsules and thermochromic microcapsules before (b) and after (a) assembly in Example 1 of the present invention.

[0033] Figure 3 This is a diagram of the covalent bonding mechanism of the assembled surface of photochromic nanocapsules and thermochromic microcapsules in Example 1 of the present invention.

[0034] Figure 4 These are photos of the color change of the full-color color-changing microcapsule aqueous dispersion in Example 1 of the present invention under different stimuli, with a scale of 1 cm.

[0035] Figure 5 The color change photos and color change performance diagrams of the fabric printed with the full-color color-changing microcapsules in Example 1 of the present invention are shown.

[0036] Figure 6 Graph showing the assembly and color-changing performance of the full-spectrum color-changing microcapsules in Examples 1 and 2 of the present invention.

[0037] Figure 7 The color-changing photos and color-changing mechanism diagrams of the fabrics printed with the color-changing microcapsules in Example 1 of the present invention and Comparative Example 1 are shown.

[0038] Figure 8 This is a scanning electron microscope image of the microcapsules formed in Comparative Example 4 of the present invention, with a scale bar of 1 μm.

[0039] Fig. 9 This is a scanning electron microscope image of the microcapsules formed in Comparative Example 5 of the present invention, with a scale of 1 μm. DETAILED DESCRIPTION

[0040] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0041] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0042] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0043] The thermotropic pigments of different colors in the present invention are provided by Shenzhen Qiansebian New Material Technology Co., Ltd. (model: QSB).

[0044] Example 1

[0045] The invention provides a preparation method and application of environmental stimulus responsive full-chromatogram color-changing microcapsules based on thermochromic blue pigments.

[0046] 1) 15 parts of styrene, 2 parts of glycidyl methacrylate, 1 part of butyl acrylate, 2 parts of 4-chloromethylstyrene, and 0.01 parts of azobisisobutyronitrile were stirred in an oil bath at 75° C. for 8 hours to obtain polyacrylate-styrene resin (PS-CMSt);

[0047] Polyacrylate-styrene resin (PS-CMSt) and 0.1 parts of thermochromic blue pigment were dissolved in 5 parts of dichloromethane to obtain dispersed phase I;

[0048] 0.5 parts of sodium dodecylbenzene sulfonate are added to 100 parts of deionized water to obtain continuous phase I, dispersed phase I is added to continuous phase I under mechanical shear force, and dispersed at a speed of 5000 rpm for 50 minutes to obtain emulsion I (stirred at room temperature for 2 hours to volatilize dichloromethane to obtain thermochromic blue pigment microcapsules loaded with negative charges);

[0049] 2) 5 parts of styrene, 0.5 parts of 1-vinylimidazole, 0.01 parts of divinylbenzene, 0.1 parts of cis-1,2-dicyano-1,2-bis(2,4,5-trimethyl-3-thienyl)ethylene, and 0.01 parts of azobisisobutyronitrile were stirred and reacted at 80° C. for 6 hours to obtain dispersed phase II (thermochromic nanocapsules);

[0050] 0.5 parts of sodium dodecylbenzene sulfonate are added to 100 parts of deionized water to obtain continuous phase II, thermotropic nanocapsules are added to continuous phase II under mechanical shear force, dispersed at a speed of 5000 rpm for 10 minutes, and mechanically stirred at 40°C for 3 hours to obtain emulsion II;

[0051] 3) After 1 part of emulsion I and 10 parts of emulsion II are mixed evenly, the mixture is stirred and reacted at 20°C for 4 hours to obtain an aqueous dispersion of environmental stimulus responsive full chromatographic color-changing microcapsules, which are then dried to obtain environmental stimulus responsive full chromatographic color-changing microcapsules. The content of photochromic nanocapsules in the microcapsules is 40wt%.

[0052] Application Testing

[0053] Take 1 part of the full-chromatographic color-changing microcapsules prepared in this example and disperse them in water to prepare an aqueous dispersion (microcapsule content: 36%), mix it with 0.5 parts of a cellulose thickener, and print it on cotton fabric by printing to obtain an anti-counterfeiting color-changing fabric coating. A series of characterizations are performed on it. The results are as follows: Figures 1 to 5 shown.

[0054] Figure 1 The scanning electron microscope images of photochromic nanocapsules (a) and thermochromic microcapsules (b) show that the capsules are all regular spherical in shape and uniform in size, with the nanocapsules being about 100-800 nm and the microcapsules being 1-20 μm in size.

[0055] Figure 2 The XPS analysis diagrams of the photochromic nanocapsules and thermochromic microcapsules before (b) and after (a) assembly in Example 1 of the present invention are shown. It can be seen that the CN peak area of ​​the double-chamber microcapsules is larger, proving that the assembly of the double-chamber microcapsules is due to the coupling reaction between the chloroalkane on the surface of the nanocapsules and the imidazole ring on the surface of the microcapsules, and finally a series of strawberry-shaped double-chamber microcapsules are formed.

[0056] Figure 3 The covalent bonding mechanism diagram of the assembled surface of photochromic nanocapsules and thermochromic microcapsules. The positively charged nanocapsules and the negatively charged microcapsule surface show electrostatic attraction. This interaction lays the foundation for the subsequent substitution reaction, effectively attaching the nanocapsules firmly to the microcapsule surface. The assembly of the double-chamber microcapsules is based on the coupling reaction between the chloroalkane on the surface of the nanocapsule and the imidazole ring on the surface of the microcapsule, where the chloroalkane is 4-chloromethylstyrene and the imidazole ring is derived from 1-vinylimidazole.

[0057] The UV lamp (light intensity 30 μW / cm 2 ) irradiated at a distance of 5 cm from the sample for 5 seconds, and the color of the sample changed completely; the temperature was mainly raised by a hair dryer or a heating table, and the heating rate was 5℃ / min. When the color of the sample changed completely, the temperature was stopped. Two different color transition paths were observed under different stimuli (ultraviolet light or heating). The path of heating first and then ultraviolet light irradiation showed a wider range of color changes, from blue to green, then to yellow, and finally to light red. Figure 4 These are photos of the color change of the full-color color-changing microcapsule aqueous dispersion in Example 1 of the present invention under different stimuli.

[0058] Figure 5 Print fabric color-changing photos and color-changing performance diagrams for full-spectrum color-changing microcapsules.

[0059] Figure 5 a is a graph showing the color change of cotton fabric printed with thermochromic microcapsules under temperature changes. It can be seen that as the temperature increases, the "JNU" logo disappears, and when the temperature returns to room temperature, the previously disappeared logo reappears. This phenomenon highlights the potential application of these capsules in thermochromic anti-counterfeiting, where temperature-induced color changes can be used as security features.

[0060] Figure 5 b is a diagram showing the color change of printed fabric based on photochromic nanocapsules under ultraviolet irradiation. It can be seen that the photochromic nanocapsules printed on the fabric show bright colors, and the letters "JNU" show dynamic color changes after the ultraviolet irradiation stops at room temperature.

[0061] Figure 5 c is a multi-stimulus induced color change image of a printed fabric using full-color color-changing microcapsules inspired by a tree frog pattern. It can be seen that a tree frog pattern was printed using dual-chamber microcapsules (nanocapsule content: 40wt%), which showed multiple colors under different stimuli. The blue color of the tree frog pattern turned into yellow belonging to the photochromic nanocapsules when heated, which was attributed to the fading of the thermochromic microcapsules. At the same time, as these microcapsules faded, a new green color appeared. When the pattern was irradiated with UV light at high temperature, the color change behavior was similar to that of the photochromic nanocapsules.

[0062] Figure 5 d is a schematic diagram of the pattern color change mechanism under different stimuli. It can be seen that the color of the pattern is obtained by reflecting the color of the thermochromic microcapsules and photochromic nanocapsules, which conforms to the principle of subtractive color mixing. However, the color formed by simply mixing thermochromic and photochromic dyes or pigments on the cloth often shows unevenness or inconsistency during the color change process. This is mainly because each dye or pigment occupies a specific position on the surface of the cloth, resulting in uneven or defective colors after fading. In contrast, when multiple dyes or pigments are combined in dual-chamber microcapsules, the mixed color can be guaranteed to remain consistent and perfect after the color change. In addition, by repeating the printing process with different dual-chamber microcapsules, multicolor patterns with different colors and responses to stimuli can be easily created.

[0063] Figure 5 e is a seasonal color change diagram of printed fabrics using full-color color-changing microcapsules under various stimuli. It can be seen that the single-color "grapes" printed by microcapsules show significant dynamic color changes under different external stimuli (temperature, light), representing the change from spring to winter. These colors include various shades of purple and red.

[0064] Figure 5 f is the reflectance spectrum of the color-changing printed fabric printed with full-spectrum color-changing microcapsules under dual stimulation, and DCM-X represents the color revealed by the full-spectrum color-changing microcapsules under different stimulations. Figure 5 g is the chromaticity diagram of the corresponding color-changing printed fabric (CIE 1931 color space).

[0065] Figure 5h is a graph showing the thermal fatigue and light fatigue resistance characteristics of the tree frog pattern under repeated cycles of heating and cooling and alternating ultraviolet (365nm, 2 seconds) and visible light (20 minutes) irradiation, with a scale of 1 cm. It can be seen that the fatigue resistance results of the printed pattern under repeated heating and cooling cycles and alternating ultraviolet and visible light irradiation cycles show that with the increase in the number of cycles, when the number of cycles reaches 13 times, the absorbance of the cloth has almost no obvious change, indicating that the prepared printed cotton cloth has excellent fatigue resistance. The color change behavior observed in this process is very similar to the natural structural color in organisms. The dynamic response characteristics of these dual-chamber microcapsules under changing environmental conditions can be used for dynamic multidimensional anti-counterfeiting. The dynamic response characteristics of the dual-chamber microcapsules change with the changes in environmental conditions, providing valuable opportunities for dynamic multidimensional anti-counterfeiting strategies.

[0066] Example 2

[0067] The difference from Example 1 is that the content of the photochromic nanocapsules is adjusted to 10wt%, 80wt%, 100wt%, 140wt% and 15wt% to prepare different microcapsules.

[0068] Figure 6 a is a schematic diagram of different structures of full-spectrum color-changing double-chamber microcapsules.

[0069] Figure 6 b is a schematic diagram of the surface of thermochromic microcapsules covered by photochromic nanocapsules. It can be seen that by adjusting the proportion of photochromic nanocapsules, composite dual-chamber microcapsules of different colors can be prepared. With the increase of nanocapsule content, a higher density of nanocapsules was observed on the surface of the dual-chamber microcapsules. Therefore, the change in nanocapsule density leads to changes in the structure and color of the microcapsules.

[0070] Figure 6 c shows the color change of the microcapsules after adjusting the proportion of photochromic nanocapsules. It can be seen that by precisely manipulating the density structure of nanocapsules on the microcapsules, basic colors such as blue, yellow and cyan can be obtained.

[0071] Figure 6 d shows a wider range of color changes after heating / UV irradiation when the nanocapsule content is 40%. It can be seen that when the nanocapsule content is 40%, it changes from blue to green, then to yellow, and finally to light red after heating / UV irradiation. This change effectively covers the entire color spectrum, making it possible to fully control the spectral change.

[0072] Figure 6 e and Figure 6f is the reflectance spectrum and CIE 1931 color diagram, it can be seen that the color of the dual-chamber microcapsules can be controlled by adjusting the color and content of the dye loaded in the nano / microcapsules. In addition, the dual-chamber microcapsules can even show the full color spectrum after ultraviolet radiation or heating.

[0073] Example 3

[0074] The invention provides a preparation method and application of environmental stimulus responsive full-chromatogram color-changing microcapsules based on thermo-induced yellow pigments.

[0075] 17 parts of styrene, 3.5 parts of glycidyl methacrylate, 3 parts of butyl acrylate, 3.5 parts of 4-chloromethylstyrene and 0.1 part of azobisisobutyronitrile were stirred in an oil bath at 75°C for 8 hours to obtain PS-CMSt. PS-CMSt and 1 part of thermochromic yellow pigment were dissolved in 7 parts of dichloromethane to obtain dispersed phase I.

[0076] 3 parts of polyoxyethylene sorbitan monooleate are added to 150 parts of deionized water to obtain continuous phase I. Dispersed phase I is added to continuous phase I under mechanical shear force, and dispersed at a rotation speed of 8000 rpm for 80 minutes to obtain emulsion I. The mixture is stirred at room temperature for 4 hours to volatilize dichloromethane, thereby obtaining negatively charged thermochromic yellow pigment microcapsules.

[0077] 7 parts of styrene, 0.8 parts of 1-vinylimidazole, 0.15 parts of divinylbenzene, 0.2 parts of spiro[1,3,3-trimethylindole-(6'-nitrochroman)] and 0.2 parts of azobisisobutyronitrile were stirred and reacted at 80° C. for 4 hours to obtain thermochromic nanocapsules.

[0078] 3 parts of polyoxyethylene sorbitan monooleate were added to 200 parts of deionized water to obtain continuous phase II. Thermotropic nanocapsules were added to continuous phase II under mechanical shear force, dispersed at a speed of 8000 rpm for 12 minutes, and mechanically stirred at 50°C for 4 hours to obtain emulsion II.

[0079] Take 2 parts of emulsion I and 12 parts of emulsion II and mix them evenly, then stir and react at 30°C for 5 hours to obtain an aqueous dispersion of environmental stimulus responsive full-chromatogram color-changing microcapsules, and dry them to obtain environmental stimulus responsive full-chromatogram color-changing microcapsules.

[0080] Take 3 parts of the full-color color-changing microcapsules prepared in this example and disperse them in water to prepare an aqueous dispersion (microcapsule content: 35%), mix it with 1 part of a polyurethane thickener, and print it on cotton fabric by printing to obtain an anti-counterfeiting color-changing fabric coating.

[0081] Example 4

[0082] The invention provides a preparation method and application of environmental stimulus responsive full-chromatogram color-changing microcapsules based on thermochromic red pigments.

[0083] 20 parts of styrene, 5 parts of glycidyl methacrylate, 5 parts of butyl acrylate, 5 parts of 4-chloromethylstyrene and 0.3 parts of azobisisobutyronitrile were stirred in an oil bath at 75°C for 8 hours to obtain PS-CMSt. PS-CMSt and 1.5 parts of thermochromic red pigment were dissolved in 10 parts of dichloromethane to obtain dispersed phase I.

[0084] 5 parts of sodium dodecyl sulfate were added to 250 parts of deionized water to obtain continuous phase I. Dispersed phase I was added to continuous phase I under mechanical shear force, and dispersed at a rotation speed of 10000 rpm for 100 minutes to obtain emulsion I. The mixture was stirred at room temperature for 6 hours to volatilize dichloromethane, and negatively charged thermochromic red pigment microcapsules were obtained.

[0085] 10 parts of styrene, 1 part of 1-vinylimidazole, 0.25 parts of divinylbenzene, 0.25 parts of 3,3-diphenyl-3H-naphtho[2,1-b]pyran and 0.3 parts of azobisisobutyronitrile were stirred and reacted at 80° C. for 6 hours to obtain thermochromic nanocapsules.

[0086] 5 parts of sodium dodecyl sulfate were added to 250 parts of deionized water to obtain continuous phase II. Thermotropic nanocapsules were added to continuous phase II under mechanical shear force, dispersed at a speed of 10,000 rpm for 15 minutes, and mechanically stirred at 60°C for 5 hours to obtain emulsion II.

[0087] Take 2.5 parts of emulsion I and 20 parts of emulsion II and mix them evenly, then stir and react at 40°C for 8 hours to obtain an aqueous dispersion of environmental stimulus responsive full chromatogram color-changing microcapsules, and dry them to obtain environmental stimulus responsive full chromatogram color-changing microcapsules.

[0088] Take 5 parts of the full-color color-changing microcapsules prepared in this example and disperse them in water to prepare an aqueous dispersion (microcapsule content: 30%), mix it with 1.5 parts of an acrylic thickener, and print it on cotton fabric by printing to obtain an anti-counterfeiting color-changing fabric coating.

[0089] Example 5

[0090] The invention provides a preparation method and application of a thermo-induced purple pigment-based environmental stimulus-responsive full-chromatogram color-changing microcapsule.

[0091] 25 parts of styrene, 10 parts of glycidyl methacrylate, 10 parts of butyl acrylate, 10 parts of 4-chloromethylstyrene and 0.7 parts of azobisisobutyronitrile were stirred in an oil bath at 75°C for 8 hours to obtain polyacrylate-styrene resin (PS-CMSt). PS-CMSt and 3 parts of thermochromic purple pigment were dissolved in 20 parts of dichloromethane to obtain dispersed phase I.

[0092] 10 parts of polyoxyethylene sorbitan monolaurate were added to 500 parts of deionized water to obtain continuous phase I. The dispersed phase I was added to the continuous phase under mechanical shear force, and dispersed at a rotation speed of 20000 rpm for 200 minutes to obtain emulsion I. The mixture was stirred at room temperature for 12 hours to volatilize the dichloromethane, and negatively charged thermochromic purple pigment microcapsules were obtained.

[0093] 15 parts of styrene, 2 parts of 1-vinylimidazole, 0.5 parts of divinylbenzene, 0.5 parts of spiro[1,3,3-trimethylindole-(6'-nitrochroman)] and 0.7 parts of azobisisobutyronitrile were stirred and reacted at 80° C. for 6 hours to obtain thermochromic nanocapsules.

[0094] 10 parts of polyoxyethylene sorbitan monolaurate were added to 500 parts of deionized water to obtain continuous phase II. Thermotropic nanocapsules were added to continuous phase II under mechanical shear force, dispersed at a speed of 20,000 rpm for 30 minutes, and mechanically stirred at 80°C for 8 hours to obtain emulsion II.

[0095] Take 5 parts of emulsion I and 30 parts of emulsion II and mix them evenly, then stir and react at 60°C for 12 hours to obtain an aqueous dispersion of environmental stimulus responsive full-chromatogram color-changing microcapsules, and dry them to obtain environmental stimulus responsive full-chromatogram color-changing microcapsules.

[0096] Take 10 parts of the full-color color-changing microcapsules prepared in this example and disperse them in water to prepare an aqueous dispersion (microcapsule content: 33%), mix it with 3 parts of acrylic thickener, and print it on cotton fabric by printing to obtain an anti-counterfeiting color-changing fabric coating.

[0097] Example 6

[0098] The invention provides a preparation method and application of environmental stimulus responsive full-chromatogram color-changing microcapsules based on thermotropic green pigments.

[0099] 22 parts of styrene, 8 parts of glycidyl methacrylate, 7 parts of butyl acrylate, 7 parts of 4-chloromethylstyrene and 0.6 parts of azobisisobutyronitrile were stirred in an oil bath at 80°C for 6 hours to obtain PS-CMSt. PS-CMSt and 2 parts of thermochromic green pigment were dissolved in 16 parts of dichloromethane to obtain dispersed phase I.

[0100] 8 parts of polyoxyethylene-8-octylphenyl ether were added to 300 parts of deionized water to obtain continuous phase I. Dispersed phase I was added to continuous phase I under mechanical shear force. Emulsion I was obtained by dispersing at a rotation speed of 12000 rpm for 150 minutes. The mixture was stirred at room temperature for 10 hours to volatilize the dichloromethane, thereby obtaining negatively charged thermochromic green pigment microcapsules.

[0101] 12 parts of styrene, 1.6 parts of 1-vinylimidazole, 0.4 parts of divinylbenzene, 0.35 parts of cis-1,2-dicyano-1,2-bis(2,4,5-trimethyl-3-thienyl)ethylene and 0.6 parts of azobisisobutyronitrile were stirred and reacted at 80° C. for 6 hours to obtain thermochromic nanocapsules.

[0102] 8 parts of polyoxyethylene-8-octylphenyl ether were added to 400 parts of deionized water to obtain continuous phase II. Thermotropic nanocapsules were added to continuous phase II under mechanical shear force, dispersed at a speed of 12000 rpm for 25 minutes, and mechanically stirred at 75°C for 6 hours to obtain emulsion II.

[0103] Take 4 parts of emulsion I and 25 parts of emulsion II and mix them evenly, then stir and react at 50°C for 10 hours to obtain an aqueous dispersion of environmental stimulus responsive full-chromatogram color-changing microcapsules, and dry them to obtain environmental stimulus responsive full-chromatogram color-changing microcapsules.

[0104] Take 8 parts of the full-chromatography color-changing microcapsules prepared in this example and disperse them in water to prepare an aqueous dispersion (solid content: 35%), mix it with 2 parts of a cellulose thickener, and print it on cotton fabric by printing to obtain an anti-counterfeiting color-changing fabric coating.

[0105] Comparative Example 1

[0106] The difference between this comparative example and Example 1 is that the thermochromic microcapsules and photochromic nanocapsules prepared in Example 1 are simply mixed without being assembled. Specifically:

[0107] 1) 15 parts of styrene, 2 parts of glycidyl methacrylate, 1 part of butyl acrylate, 2 parts of 4-chloromethylstyrene, and 0.01 parts of azobisisobutyronitrile were stirred in an oil bath at 75°C for 8 hours to obtain PS-CMSt;

[0108] PS-CMSt and 0.1 part of thermochromic blue pigment were dissolved in 5 parts of dichloromethane to obtain dispersed phase I;

[0109] 0.5 parts of sodium dodecylbenzene sulfonate are added to 100 parts of deionized water to obtain continuous phase I, dispersed phase I is added to continuous phase I under mechanical shear force, dispersed at a speed of 5000 rpm for 50 minutes to obtain emulsion I, stirred at room temperature for 2 hours to volatilize dichloromethane, and obtained thermochromic blue pigment microcapsules loaded with negative charges;

[0110] 2) 5 parts of styrene, 0.5 parts of 1-vinylimidazole, 0.01 parts of divinylbenzene, 0.1 parts of cis-1,2-dicyano-1,2-bis(2,4,5-trimethyl-3-thienyl)ethylene, and 0.01 parts of azobisisobutyronitrile were stirred and reacted at 80° C. for 6 hours to obtain dispersed phase II, and then dried to obtain thermochromic nanocapsules;

[0111] 0.5 parts of sodium dodecylbenzene sulfonate are added to 100 parts of deionized water to obtain continuous phase II, thermotropic nanocapsules are added to continuous phase II under mechanical shear force, dispersed at a speed of 5000 rpm for 10 minutes, and mechanically stirred at 40°C for 3 hours to obtain emulsion II;

[0112] 3) Take 6 parts of thermochromic microcapsules and 4 parts of photochromic nanocapsules, add 3 parts of sodium carboxymethyl cellulose and disperse them in 20% deionized water to form a uniform slurry. Then, the slurry is applied on cotton fabric in the form of printing, and after drying, a color-changing anti-counterfeiting fabric coating is obtained.

[0113] Figure 7 The color-changing photos and color-changing mechanism diagrams of the fabrics printed with the color-changing microcapsules in Example 1 and Comparative Example 1 are shown.

[0114] Figure 7 a is a photograph of the color change process of the fabric printed with the mixed capsule color paste containing thermochromic dye and photochromic dye under heating conditions in Comparative Example 1. It can be seen that after the thermochromic and photochromic pigments are simply mixed and coated on the fabric, the color often shows unevenness or inconsistency during the color change process.

[0115] Figure 7 b is a diagram of the color generation mechanism of the fabric printed with the mixed capsule color paste containing thermochromic dye and photochromic dye under heating conditions in Comparative Example 1. It can be seen that each dye or pigment occupies a specific position on the fabric surface, resulting in uneven or defective coloring after fading.

[0116] Figure 7 c is a diagram of the color generation mechanism of the fabric printed with the color paste of the full-color color-changing microcapsules in Example 1 under heating conditions. It can be seen that only when multiple dyes or pigments are combined in the double-cavity microcapsules can the mixed colors be ensured to remain consistent and perfect after color change. The color of the pattern is formed by the combination of thermochromic microcapsules and photochromic nanocapsules, which conforms to the principle of subtractive color mixing.

[0117] Comparative Example 2

[0118] The difference between this embodiment and embodiment 1 is that the emulsion II in step 3) is adjusted to 0 parts, and the remaining steps and processes are all based on embodiment 1.

[0119] The microcapsules prepared by this method can only change color under temperature conditions, and the color change can only be a single color.

[0120] Comparative Example 3

[0121] The difference between this embodiment and embodiment 1 is that the emulsion II in step 3) is adjusted to 50 parts, and the remaining steps and processes are all based on embodiment 1.

[0122] Although the microcapsules prepared by this method have a double-chamber structure, they can only change color under light conditions, and the color change can only be a single color.

[0123] Comparative Example 4

[0124] The difference between this comparative example and Example 1 is that the 4-chloromethylstyrene in step 1) is adjusted to 1 part, and the remaining steps and processes are all referred to Example 1.

[0125] The microcapsule structure prepared by this method is not a double-chamber microcapsule, and the microcapsule ultimately cannot achieve full chromatographic color change. Figure 8 This is a scanning electron microscope image of the microcapsule. It can be seen that the microcapsule formed by this method is not a strawberry-shaped double-chamber structure.

[0126] Comparative Example 5

[0127] The difference between this comparative example and Example 1 is that the 1-vinylimidazole in step 2) is adjusted to 0.1 parts, and the remaining steps and processes are all referred to Example 1.

[0128] The microcapsule structure prepared by this method is not a double-chamber microcapsule, and the microcapsule ultimately cannot achieve full chromatographic color change. Fig. 9 This is a scanning electron microscope image of the microcapsule. It can be seen that the microcapsule formed by this method is not a strawberry-shaped double-chamber structure.

[0129] In summary, the environmental stimulus responsive full-chromatogram color-changing microcapsules prepared by the present invention can cover the entire color range under the stimulation of ultraviolet light and temperature environmental conditions, and the microcapsules can be adjusted to present different colors by controlling the mass proportion of photochromic nanocapsules. In the environmental stimulus responsive full-chromatogram color-changing microcapsules of the present invention, a coupling reaction occurs between the chloroalkanes on the surface of the nanocapsules and the imidazole rings on the surface of the microcapsules to form a strawberry-shaped double-chamber microcapsule structure, which prolongs the service life of the microcapsules and increases the airtightness of the shell layer, making it less likely for the core material to leak. When the environmental stimulus responsive color-changing double-chamber microcapsules of the present invention are used as ink and applied to printing cotton fabrics, the printed pattern can achieve full-chromatogram color change under ultraviolet and thermal stimulation, and has good fatigue resistance to temperature, ultraviolet light, and visible light.

[0130] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. An environmental stimulus responsive full-spectrum color-changing microcapsule, characterized in that: include, (i) It has a strawberry-shaped dual-compartment structure formed by thermochromic microcapsules and photochromic nanocapsules; (ii) Based on the coupling reaction between the imidazole ring on the surface of thermochromic microcapsules and the chloroalkane on the surface of photochromic nanocapsules, the assembly of full-spectrum color-changing microcapsules with a strawberry-like double-compartment structure is achieved.

2. The environmental stimulus responsive full-spectrum color-changing microcapsule according to claim 1, characterized in that: The core material of the thermochromic microcapsule is a thermochromic pigment, and the shell material is a polyacrylate-styrene polymer resin; the core material of the photochromic nanocapsule is a photosensitive dye, and the shell material is a styrene polymer resin.

3. The environmental stimulus responsive full-spectrum color-changing microcapsule according to any one of claims 1 or 2, characterized in that: The particle size of the thermochromic microcapsule is 1-20 μm, and the particle size of the photochromic nanocapsule is 100-800 nm.

4. The method for preparing the environmental stimulus responsive full-chromatogram color-changing microcapsules according to claim 1, characterized in that: include, 20.01-55.7 parts of polyacrylate-styrene polymer resin and 0.1-3 parts of thermochromic pigment are dissolved in 5-20 parts of dichloromethane to obtain dispersed phase I; 0.5 to 10 parts of emulsifier are added to 100 to 500 parts of deionized water to obtain continuous phase I, dispersed phase I is added to continuous phase I under the action of mechanical shear force, and emulsion I is obtained after mixing; 5 to 15 parts of styrene, 0.5 to 2 parts of 1-vinylimidazole, 0.01 to 0.5 parts of divinylbenzene, 0.1 to 0.5 parts of photosensitizing dye and 0.01 to 0.7 parts of azobisisobutyronitrile are reacted by stirring to obtain dispersed phase II; 0.5-10 parts of emulsifier are added to 100-500 parts of deionized water to obtain continuous phase II, dispersed phase II is added to continuous phase II under mechanical shear force, and stirred at 40-80° C. for 3-10 hours to obtain emulsion II; 1 to 5 parts of emulsion I and 10 to 30 parts of emulsion II are stirred and reacted at 20 to 60° C. for 4 to 12 hours, and then dried to obtain environmental stimulus responsive full-chromatographic color-changing microcapsules.

5. The method for preparing the environmental stimulus responsive full-chromatogram color-changing microcapsules according to claim 4, characterized in that: The preparation method of the polyacrylate-styrene polymer resin comprises: The product is prepared by heating 15 to 25 parts of styrene, 2 to 10 parts of glycidyl methacrylate, 1 to 10 parts of butyl acrylate, 2 to 10 parts of 4-chloromethylstyrene and 0.01 to 0.7 parts of azobisisobutyronitrile in an oil bath at 75 to 80° C. for 6 to 8 hours.

6. The method for preparing the environmental stimulus responsive full-chromatogram color-changing microcapsules according to claim 4, characterized in that: The stirring temperature of the dispersed phase II is 75-80° C., and the stirring time is 4-6 hours.

7. The method for preparing the environmental stimulus responsive full-chromatogram color-changing microcapsules according to claim 4, characterized in that: The emulsifier includes one or more of polyoxyethylene sorbitan monooleate, polyoxyethylene-8-octylphenyl ether, polyoxyethylene sorbitan monolaurate, sodium dodecylbenzene sulfonate, and sodium dodecyl sulfate.

8. The method for preparing the environmental stimulus responsive full-chromatogram color-changing microcapsules according to claim 4, characterized in that: The photosensitizing dye includes one or more of cis-1,2-dicyano-1,2-bis(2,4,5-trimethyl-3-thienyl)ethylene, spiro[1,3,3-trimethylindole-(6'-nitrobenzodihydropyran), and 3,3-diphenyl-3H-naphtho[2,1-b]pyran.

9. The method for preparing the environmental stimulus responsive full-chromatogram color-changing microcapsules according to claim 4, characterized in that: The thermochromic pigment is a pigment that changes color as the temperature changes.

10. The use of the environmental stimulus responsive full-spectrum color-changing microcapsules according to claim 1, characterized in that: The environmental stimulus responsive full-spectrum color-changing microcapsule is applied to the fields of luminous anti-counterfeiting and information encryption, home textiles, sportswear, and leather products.

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