Structural color system based on supercritical microemulsion phase separation, and preparation method therefor and use thereof

Abstract

A structural color system based on supercritical microemulsion phase separation, and a preparation method therefor and the use thereof. A working solution is formulated by using an amphiphilic emulsifier, water and a co-solvent as raw materials, such that a microemulsion having certain components is firstly formed in a supercritical fluid, and system conditions are gradually changed to perform phase separation, so as to obtain a structural color system. Patterns having different shapes can be further obtained by controlling different pressure and temperature conditions. In the present invention, a structural color is generated on the basis of supercritical microemulsion phase separation, non-pigmentary coloration, especially dark black, of a solution system is achieved, and the patterns having different shapes can be obtained by controlling process conditions, such that the present invention has relatively good application markets and prospects in the fields of related display or shading devices, other coloration, etc. The structural color system obtained in the present invention has flexible characteristics and can be used in the flexible wearable field. In addition, the technology of the present invention has the characteristics of convenient operation, simple process, low energy consumption, no need of using a large amount of pigments, such as dyes, no emissions of related pollutants, being green, ecological, environmentally friendly, etc.

Description

Structural color system based on supercritical microemulsion phase separation, preparation method and application Technical Field

[0001] The invention relates to a structural color generation method based on supercritical microemulsion phase separation, and belongs to the technical field of material processing or textile dyeing and finishing. Background Art

[0002] Currently, there are two main pathways for objects to exhibit color (i.e., object color). One pathway involves colorants containing conjugated systems or chromophores in their molecular structures. These selectively absorb incident light and then reflect the remaining wavelengths of visible light, producing color. This is exemplified by the various dyes and coatings commonly used in the textile industry. Printing and dyeing textiles with these dyes can produce a wide variety of colors and patterns. Another pathway involves the scattering, interference, and / or diffraction of incident light due to the unique surface structure of an object, or through specialized processing, allowing specific wavelengths of visible light to enter the human visual system, thereby producing color. This is known as structural chromogenesis. The use and emission of large amounts of chemicals, particularly residual colorants, during the coloring process pose significant challenges to ecological and environmental protection. Structural chromogenesis, on the other hand, is primarily a physical coloring method with favorable environmental and environmental characteristics. Consequently, structural chromogenesis has become a hot topic of research and attention both domestically and internationally in recent years.

[0003] Supercritical fluids, particularly supercritical carbon dioxide (SCF-CO2), use a critical state medium such as CO2 instead of water as a processing medium. This fundamentally changes traditional wet chemical processing methods, typically consuming little or no freshwater resources and producing and discharging no pollutants such as wastewater. These processes offer significant advantages, including clean production processes that are green, ecological, energy-efficient, and reduce emissions. Furthermore, these processes offer advantages such as a short process flow, convenient operation, low fluid viscosity, high diffusivity, high processing efficiency, and short processing times. Consequently, supercritical fluid technology, particularly SCF-CO2, has been widely promoted and applied in fields such as textile dyeing and finishing, biopharmaceuticals, natural product extraction, chemical reactions, and materials processing. The formation of microemulsions within supercritical fluids can overcome inherent limitations of the fluid (e.g., the hydrophobic nature of SCF-CO2), thereby expanding its application. For example, using supercritical CO2 fluid microemulsions can facilitate the transfer of polar target substances into a hydrophobic fluid medium through the hydrophilic core of the microemulsion, thereby achieving diverse application and processing goals. Existing literature reports on the use of supercritical CO2 fluid microemulsions for textile pretreatment processes such as desizing, degumming, scouring, and bleaching, as well as for the fixation of dyes on fibers. However, the use of this technology to generate structural colors and related patterns has not yet been reported. Technical Solutions

[0004] The purpose of the present invention is to provide a structural color system based on supercritical microemulsion phase separation, a preparation method and application, which is a new color-producing material with flexible and environmentally friendly characteristics.

[0005] The technical solution for achieving the purpose of the present invention is to provide a method for preparing a structural color system based on supercritical microemulsion phase separation, comprising the following steps:

[0006] (1) A working fluid is prepared with an amphiphilic emulsifier, water, and a cosolvent as raw materials, and placed in a working fluid unit of a supercritical fluid system. The circulating pump in the supercritical fluid system is turned on to force the fluid to circulate. The working fluid is mixed with the supercritical fluid medium, and a microemulsion is formed in situ in the microemulsion unit.

[0007] (2) By controlling the temperature and pressure of the supercritical fluid system, the microemulsion undergoes phase separation, resulting in a structural color system.

[0008] The working solution of the present invention comprises sodium di-(2-ethylhexyl) sulfosuccinate, water, ethanol, and a high-molecular-weight mixed protease. The high-molecular-weight mixed protease comprises one of cellulase, α-amylase, pectinase, lipase, or any combination thereof.

[0009] In step (1) of the present invention, the dynamic and static cycle time ratio of the forced circulation of the fluid is 1:1 to 1:10. In step (2), the temperature of the supercritical fluid system is controlled to be 0 to 200°C and the pressure is controlled to be 0 to 7 MPa.

[0010] The present invention discloses a method for preparing a structural color system based on supercritical microemulsion phase separation. By regulating the pressure of the supercritical fluid system between 4 MPa and 0 MPa and controlling the temperature, the structural color system exhibits a pattern-like shape. The pattern includes spherical, quasi-spherical, or quasi-three-dimensional polygonal shapes. The structural color system includes deep black, neutral colors, or various colors.

[0011] The technical solution of the present invention also includes a structural color system based on supercritical microemulsion phase separation obtained according to the above preparation method.

[0012] The present invention provides an application of a structural color system based on supercritical microemulsion phase separation, using it as a color-rendering material, preparing color-rendering or light-shielding devices, and in the field of flexible wearables.

[0013] The present invention utilizes supercritical fluid, especially supercritical CO2 fluid, to first form a certain type of microemulsion, and then adopts the method of changing the system conditions to make the system undergo a certain degree of phase separation and produce related structural coloration under certain conditions. At the same time, by controlling different conditions, different shapes of patterns can be obtained. Beneficial effects

[0014] The beneficial effects of the present invention are:

[0015] 1. The method of the present invention can effectively realize the generation of structural color systems based on supercritical microemulsion phase separation, providing new technical solutions and basic support for the preparation of new color-developing or light-shielding devices and the research and development of other related color-producing materials.

[0016] 2. The structural color system prepared by the method of the present invention can achieve the presentation of related tones such as deep black, and can also produce patterns of different shapes under appropriate control conditions. The alternating cycle of the two processes of color presentation and pattern formation can be achieved by increasing or reducing the system pressure.

[0017] 3. The greatest advantage of the structural color system produced by the method of the present invention is its flexibility. If the external packaging conditions are flexible and transparent, it can be applied in fields such as flexible wearables and can be easily reused.

[0018] 4. Since the method of the present invention does not involve the application of chemicals such as colorants, there are no environmental problems such as high emissions and high pollution. The process is simple and easy to operate. It has the characteristics of being green, ecological, environmentally friendly, energy-saving, and reducing emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG1 is a schematic diagram of a system for supercritical fluid microemulsion formation, phase separation, and structural color generation provided by the present invention;

[0020] Among them: (1) medium (such as CO2) gas cylinder; (2, 6, 9, 11, 13, 14) valve; (3) condenser; (4) pressure pump; (5) preheater; (7) additive (working fluid) unit; (8) filter; (10) microemulsion unit; (12) circulation pump; (15) fine-tuning valve; (16, 19) thermometer; (17, 20) pressure gauge; (18) separation unit; (21) purification unit; (22) online detection and window unit.

[0021] FIG2 is a diagram showing the formation, phase separation, structural color system formation, and pattern formation processes of the SCF-CO2 microemulsion system in Example 1 of the present invention;

[0022] FIG3 shows the formation, phase separation, structural color system formation, and pattern formation process of the SCF-CO2 microemulsion system in Example 2 of the present invention;

[0023] FIG4 shows the formation, phase separation, structural color system formation, and pattern formation process of the SCF-CO2 microemulsion system in Example 3 of the present invention;

[0024] FIG5 shows the formation, phase separation, structural color system formation, and pattern formation processes of the SCF-CO2 microemulsion system in Example 4 of the present invention. Modes for Carrying Out the Invention

[0025] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments. Example 1

[0026] This embodiment provides a method for preparing a structural color system, and the equipment system used is shown in FIG1 .

[0027] 1 , the steps for forming a microemulsion in a fluid such as supercritical carbon dioxide, generating structural color, and generating a pattern in this embodiment are as follows:

[0028] A working fluid consisting of the components required to form a microemulsion, such as an emulsifier, an appropriate amount of water, a cosolvent, and a polar target, is placed in additive unit 7, and the unit's top cover is then closed and sealed. The fine-tuning valve 15 and shut-off valve 14 in the system are closed, and shut-off valves 2, 6, 9, and 11 are opened sequentially. A predetermined amount of fluid medium, such as CO2, is introduced into the additive (working fluid) unit 7 and microemulsion unit 10, and the temperatures of the additive unit 7 and microemulsion unit 10 are raised to a preset target temperature. Simultaneously, a circulation pump 12 is activated to circulate the circuit connecting the additive unit 7 and microemulsion unit 10 in series, allowing the various additives in the additive unit 7 to fully interact with the medium, forming a uniform and stable microemulsion system in situ. This is then observed and recorded using the system's online monitoring and window unit 22. Then, the circulation pump 12 and the stop valve 9 are closed, and the fine-tuning valve 15 is slowly opened to systematically adjust the microemulsion unit 10, gradually carrying out phase separation under different conditions, thereby generating corresponding structural colors and spots, and using the online detection and window unit 22 for full observation and recording.

[0029] As needed, the shut-off valve 9 and / or the pressure pump 4 can be opened to replenish the pressure of the microemulsion unit 10, and the fine-tuning valve 15 can be used to achieve the alternating cycle of the two processes of structural intrinsic color and pattern formation.

[0030] After the structural color system and pattern are formed, the fine-tuning valve 15 is opened to release the pressure of the system, and the working fluid and the medium gas are separated and recovered by the separation and recovery system composed of the separation unit 18, the purification unit 21, the condenser 3, the medium gas cylinder 1, etc.

[0031] In this example, a working solution was prepared by mixing 0.5 g of sodium di-(2-ethylhexyl) sulfosuccinate (AOT), 40 mL of water, 10 mL of ethanol, and 0.4 g of a polymer mixed protease (0.1 g each of cellulase, α-amylase, pectinase, and lipase). This working solution was placed in additive unit 7, and the top cover was sealed. Experiments were conducted according to the specific implementation and operation described in this example. Under the process conditions of a fluid pressure of 15 MPa, a temperature of 60°C, and a fluid circulation and static ratio of 1:10, an SCF-CO2 microemulsion was formed for 60 minutes. The fine-tuning valve 15 was then slowly opened to allow phase separation, while the online observation and recording device was simultaneously activated. The experimental results are shown in Figure 2.

[0032] Referring to Figure 2, Figures a through f show the experimental results of in-situ generation of an SCF-CO2 microemulsion using the method described in this embodiment, followed by phase separation and the gradual generation of a structural color system and pattern in the apparatus system shown in Figure 1. (a) shows the SCF-CO2 microemulsion formed at 15 MPa, 60°C, and 60 min; (b) shows the obvious phase separation of the SCF-CO2 microemulsion at 4-5 MPa, 58.9°C; (c) shows the black structural color generated in the system at 1-2 MPa, 57.4°C; (d) shows the deep black structural color generated in the system at 0-1 MPa, 54.6°C; (e) shows a portion of a dark, fine pattern generated in the system at 0-0.5 MPa, 53.3°C; and (f) shows a portion of a spherical or quasi-spherical pattern generated in the system at 0-0.5 MPa, 52.4°C.

[0033] Figure 2 (a) shows that under the conditions of this example, the added working fluid can form an SCF-CO2 microemulsion in the SCF-CO2 system at 15 MPa, 60°C, and 60 min. The microemulsion is stable and evenly distributed in the SCF-CO2 system, appearing translucent. The bottom of the viewing window also partially exhibits white light, indicating that the incident white light from the light source opposite the viewing window can partially or mostly transmit the SCF-CO2 microemulsion system through the viewing window. Furthermore, the SCF-CO2 microemulsion at the viewing window interface also partially or mostly reflects the incident visible light. Figure (b) shows that when the system pressure is adjusted below the critical point of 7.38 MPa, such as 4-5 MPa, the SCF-CO2 microemulsion system exhibits a more obvious phase separation phenomenon, as shown in Figure (b). Some CO2 gas phase appears at the top of the viewing window, but the majority of the middle and lower portions of the window remain translucent SCF-CO2 microemulsion. However, when the system conditions are further adjusted, as shown in Figure 2(c), the translucent SCF-CO2 microemulsion in the system disappears, the lower half of the window becomes opaque, and a large amount of black structural color appears. Simultaneously, as the system continues to evolve, the entire window or system becomes increasingly blurred and darker, with the black structural color filling the entire window volume or system, and the hue becomes increasingly darker, ultimately producing a deep black structural color system, as shown in Figure (d). Furthermore, with further adjustments to the system conditions, the structural color produced in the system evolves further, with the system interface in the window weakly reflecting incident visible light and a large number of small spherical patterns appearing, as shown in Figure (e). Furthermore, with further adjustments to the system conditions, the system evolves further, with the window interface or system gradually becoming brighter and reflecting some incident light. The resulting spherical patterns become clearly visible and grow in size, as shown in Figure (f). The above shows that under the conditions of this embodiment, starting from the in situ formed SCF-CO2 microemulsion system, by regulating the system conditions, the system can undergo phase separation and effectively produce structural colors, and can further produce related patterns. Example 2

[0034] This example uses the equipment system shown in Figure 1 to generate an SCF-CO2 microemulsion in situ, followed by phase separation and the gradual generation of structural color and pattern patterns. Except for the system conditions used to record the phase separation, structural color, and pattern formation of the SCF-CO2 microemulsion system online, all other experimental conditions and procedures are identical to those in Example 1 and are described in detail in the detailed description.

[0035] Refer to Figure 3, in which Figures a to f are obtained by using the method described in this embodiment to change the conditions of the system, wherein: (a) Figure shows the SCF-CO2 microemulsion formed at 15 MPa×60℃×60 min; (b) Figure shows the obvious phase separation of the SCF-CO2 microemulsion at 3-4 MPa×58.4℃; (c) Figure shows the black structural color produced in the system at 1-1.5 MPa×57.4℃; (d) Figure shows the dark black structural color formed in the system at 0-0.5 MPa×41.8℃; (e) Figure shows a partial dark fine spot pattern formed in the system at 0-0.3 MPa×41.4℃; (f) Figure shows a partial spherical or quasi-spherical spot pattern formed in the system at 0-0.2 MPa×40.1℃.

[0036] Compared with Example 1, Figures 3 (a) and (b) show that under the conditions of this example, when the system pressure of the same SCF-CO2 microemulsion system is adjusted to a relatively lower value, such as 3-4 MPa in Figure 3 (b), the microemulsion system can continue to undergo phase separation, and its gas phase proportion is higher, while the microemulsion phase proportion continues to decrease. When the system pressure and temperature are further adjusted to 1-1.5 MPa×57.4°C, as shown in Figure 3 (c), a black structural color also appears, and the proportion is higher than that in Figure 2 (c). At the same time, when the system temperature and pressure conditions are adjusted to 0-0.5 MPa×41.8°C, the system appears a dark black structural color, as shown in Figure 3 (d). Furthermore, when the control system conditions were 0-0.3MPa × 41.4°C and 0-0.2MPa × 40.1°C, weak reflections of incident light began to appear at the window interface, and patterns of varying sizes gradually formed and appeared in the system. These patterns became increasingly clearer and brighter as the system conditions changed, and their size also continued to grow, as shown in Figures 3(e) and (f). These results demonstrate that varying the phase separation conditions in the SCF-CO2 microemulsion system results in reproducible phase separation, structural color formation, and pattern generation. Furthermore, the degree of phase separation, the proportion of structural color generation, and pattern formation and appearance are all related to the specific system conditions and have a wide adjustable range. Example 3

[0037] The experimental results show that SCF-CO2 microemulsion is in situ generated in the equipment system shown in Figure 1, followed by phase separation and gradual generation of structural color and pattern.

[0038] The method used in this example is as follows: 0.6 g of sodium di-(2-ethylhexyl) sulfosuccinate (AOT), 40 mL of water, 10 mL of ethanol, and 0.4 g of a polymer mixed protease (0.1 g each of cellulase, α-amylase, pectinase, and lipase) are prepared into a working solution. This solution is then placed in additive unit 7 and the top cover is sealed. The experiment is then conducted according to the above-described specific embodiments and procedures. The SCF-CO2 microemulsion is formed by treating the solution for 40 minutes at a fluid pressure of 13 MPa, a temperature of 50°C, and a fluid circulation and static ratio of 1:10. The fine-tuning valve 15 is then slowly opened to allow phase separation, while online observation and recording are performed.

[0039] The experimental results obtained are shown in Figure 4, in which: (a) the figure shows the SCF-CO2 microemulsion formed at 13MPa×50℃×40min; (b) the figure shows a large amount of black structural color produced by phase separation at 2~3MPa×46.5℃; (c) the figure shows the dark black structural color formed by the system at 0~0.3MPa×41.8℃; (d) the figure shows some dark fine spots formed by the system at 0~0.2MPa×40.5℃; (e) the figure shows some spherical or quasi-spherical spots formed by the system at 0~0.1MPa×40.0℃.

[0040] Figure 4(a) shows that, compared to Examples 1-2, under the conditions of this example, changing the working fluid composition and system formation conditions also yielded a good, nearly identical, stable SCF-CO2 microemulsion system. Figure 4(b) also demonstrates that accelerating the adjustment of system pressure and temperature conditions can also rapidly form a black structural color, shortening the process and time of structural color formation. Furthermore, a large amount of deep black structural color can be formed at 0-0.3 MPa × 41.8°C, as shown in Figure 4(c). Similar to Examples 1-2, further adjusting the system conditions to 0-0.2 MPa × 40.5°C and 0-0.1 MPa × 40.0°C, weak reflections of incident light appeared at the system interface, and dark speckles gradually became visible. As the system conditions were further adjusted, the speckles became increasingly clearer and brighter, and the speckles continued to grow, as shown in Figures 4(d) and 4(e). The above shows that by appropriately lowering the system pressure and temperature and shortening the formation time in the SCF-CO2 system, a stable SCF-CO2 microemulsion system can be effectively formed; at the same time, by quickly adjusting the system phase separation conditions, a deep black structural color can be quickly formed, and further a pattern can be formed. Example 4

[0041] Referring to Figure 5, panels a through f show the experimental results of in-situ generation of an SCF-CO2 microemulsion, followed by phase separation and the gradual generation of structural color and pattern patterns, using the method described below in this example, in the apparatus system shown in Figure 1. Except for the system conditions used for online recording of the SCF-CO2 microemulsion during phase separation, structural color, and pattern formation, all other experimental conditions and procedures are identical to those in Example 3 and are described in detail in the detailed description. Among them: (a) The figure shows the SCF-CO2 microemulsion formed at 14MPa×50℃×40min; (b) The figure shows the obvious phase separation of SCF-CO2 microemulsion at 5.5~7MPa×31.6℃; (c) The figure shows the dark black structural color formed by the system at 2~3MPa×25.0℃; (d) The figure shows the dark black structural color formed by the system at 0~2MPa×22.5℃; (e) The figure shows the polygonal pattern formed by the system at 0~0.3MPa×20.0℃; (f) The figure shows that the system forms a dark black structural color again when the system conditions are readjusted and the phase separation is reduced to 2~3MPa×30.0℃.

[0042] Compared to Examples 1-3, Figures 5(a) and (b) show that under the conditions of this example, the SCF-CO2 microemulsion system formed can undergo significant multi-layered phase separation even at relatively low temperatures, such as 5.5-7 MPa at 31.6°C in Figure 5(b). As the system pressure and temperature conditions are further adjusted to 2-3 MPa at 25.0°C, a large amount of deep black structural color appears, as shown in Figure 5(c). Furthermore, when the system conditions are further adjusted to 0-2 MPa at 22.5°C, the system is completely filled with deep black structural color, as shown in Figure 5(d). Furthermore, when the system conditions are continuously adjusted to 0-0.3 MPa at 20.0°C, polygonal patterns form and appear in the system, with the pattern size increasing as the system conditions change, as shown in Figure 5(e). If the system conditions are adjusted again and phase separation is initiated, deep black structural color will form again, as shown in Figure 5(f). This example demonstrates that by regulating different phase separation conditions in the SCF-CO2 microemulsion system, different phase separation behaviors may occur, but structural colors can still be effectively produced; however, the shape of the resulting pattern may also change; and by resetting the system conditions, structural colors and other phenomena can be cyclically produced again.

Claims

1. A method for preparing a structural color system based on supercritical microemulsion phase separation, characterized in that The steps include: (1) A working fluid is prepared with an amphiphilic emulsifier, water, and a co-solvent as raw materials, and is placed in a working fluid unit of a supercritical fluid system. A circulating pump in the supercritical fluid system is turned on to force the fluid to circulate, and the working fluid is mixed with the supercritical fluid medium to form a microemulsion in situ in the microemulsion unit; (2) By controlling the temperature and pressure of the supercritical fluid system, the microemulsion undergoes phase separation and a structural color system is obtained.

2. The method for preparing a structural color system based on supercritical microemulsion phase separation according to claim 1, characterized in that: The working solution comprises di-(2-ethylhexyl) sodium sulfosuccinate, water, ethanol and high molecular weight mixed protease.

3. The method for preparing a structural color system based on supercritical microemulsion phase separation according to claim 1, characterized in that: The dynamic-static cycle time ratio for forced circulation of the fluid is 1:1 to 1:

10.

4. The method for preparing a structural color system based on supercritical microemulsion phase separation according to claim 1, characterized in that: In step (2), the temperature of the supercritical fluid system is controlled to be 0 to 200° C. and the pressure is controlled to be 0 to 7 MPa.

5. The method for preparing a structural color system based on supercritical microemulsion phase separation according to claim 1, characterized in that: The pressure of the supercritical fluid system is regulated to vary between 4MPa and 0MPa, and the temperature conditions are controlled, so that the structural color system is in a pattern shape.

6. The method for preparing a structural color system based on supercritical microemulsion phase separation according to claim 1, characterized in that: The structural color system includes dark black neutral colors or various colors.

7. The method for preparing a structural color system based on supercritical microemulsion phase separation according to claim 2, characterized in that: The high molecular weight mixed protease comprises one of cellulase, α-amylase, pectinase, lipase, or any combination thereof.

8. The method for preparing a structural color system based on supercritical microemulsion phase separation according to claim 5, characterized in that: The pattern shape includes a sphere, a quasi-sphere, or a quasi-three-dimensional polygon.

9. A structural color system based on supercritical microemulsion phase separation obtained by the preparation method according to claim 1.

10. The use of a structural color system based on supercritical microemulsion phase separation as claimed in claim 9, characterized in that Used as color-rendering material, preparation of color-rendering or light-shielding devices, and flexible wearable field.

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