Method for preparing liquid photonic crystals based on monodisperse, highly stable colloidal particles

Abstract

The application belongs to the technical field of photonic crystal structure coloration, and discloses a preparation method of liquid photonic crystals based on monodisperse and high-stability colloidal particles, which comprises the following steps: S1, polymer monomer A and charged comonomer B are added into deionized water to perform copolymerization reaction by means of emulsion polymerization, and a crosslinking agent is added as needed, and polymer colloidal particles with high surface charge density characteristics are obtained through the reaction; S2, the polymer colloidal particles are dispersed into a dispersant, so that the polymer colloidal particles in the system are gradually reduced to a preset concentration state, and liquid photonic crystals with structural color and dynamic recovery are obtained. Through the application, the high stability requirement of the liquid photonic crystals can be met, and the structural color with high brightness and high saturation can still be presented even at a low concentration; the preparation method of the application is simple and easy to operate, the purification process is short in time consumption, the system has high stability, and is suitable for the application occasions of macro-preparation of liquid photonic crystals.

Description

Technical Field

[0001] This invention belongs to the field of colorimetric technology of photonic crystal structure, and more specifically, relates to a method for preparing liquid photonic crystals based on monodisperse, highly stable colloidal particles. Background Technology

[0002] Inspired by the formation mechanism of structural colors in nature, researchers have created photonic crystals by periodically arranging two or more materials with different dielectric constants into micro- and nano-structures that can produce biomimetic structural colors. Due to their high brightness, high color saturation, and the advantages of readily available materials, low pollution, high stability, and strong adjustability, these crystals have enormous potential value in numerous fields such as smart displays and sensors, and offer opportunities for sustainable development.

[0003] Liquid photonic crystals are pre-crystallized photonic crystals with long-range ordered periodic structures, formed by the self-assembly of colloidal particles in a liquid medium. They exhibit vibrant structural colors and exist in a dynamic equilibrium state. Colloidal particles in liquids spontaneously form and maintain an ordered arrangement through Brownian motion, electrostatic repulsion, and van der Waals forces, and their structure can dynamically adjust with external forces or environmental changes. Liquid photonic crystals can simplify the complex assembly process from colloidal particles to photonic crystals and can be applied in optical anti-counterfeiting labels, color decorations, trademarks, and other fields after encapsulation. However, in existing technologies, the surface charge density of the colloidal particles that form the building blocks of liquid photonic crystals is typically low, making it difficult to maintain long-term stability. Furthermore, they usually require high concentrations to exhibit bright structural colors, and the dispersant is typically a single aqueous solution.

[0004] More specifically, liquid photonic crystals with spherical colloidal particles as structural units are currently the most widely used, but the types of these colloidal particles are usually limited to silica particles. These colloidal particles have excellent monodispersity, but their surface charge density is usually low. The preparation of liquid photonic crystals requires complex purification processes such as dialysis and rotary evaporation, followed by the addition of additional stabilizers and light absorbers to form high-concentration liquid photonic crystals, thus exhibiting bright structural colors. For example, patent document CN201910350271.2 discloses the formation of liquid photonic crystals by supersaturating colloidal nanospheres under high volume fraction conditions. By adding different amounts of light absorbers, the saturation of the structural color can be controlled; by adding binders, physical adhesion is formed between the microspheres that make up the photonic crystal structure and between the photonic crystal and the substrate, thereby improving the stability of the photonic crystal structure and the durability of the structural color.

[0005] However, further research shows that while existing solutions of this type improve the stability of liquid photonic crystal systems to some extent, they require high concentrations of colloidal particle dispersions, resulting in higher costs. Furthermore, the presence of additives also affects the optical properties and stability of the photonic crystal composite film formed by combining the liquid photonic crystal with the polymer. Accordingly, how to prepare liquid photonic crystals that meet the high stability requirements at low concentrations and exhibit bright structural colors in various dispersants constitutes one of the urgent technical challenges to be addressed in this field. Summary of the Invention

[0006] To address one or more of the above-mentioned deficiencies or needs of existing technologies, this invention provides a method for preparing liquid photonic crystals based on monodisperse, highly stable colloidal particles. By specifically designing the types and characteristics of reactants throughout the preparation process, and especially by re-examining the entire reaction mechanism, polymer colloidal particles with high surface charge density and cross-linking properties can be effectively introduced. This not only meets the high stability requirements of liquid photonic crystals but also exhibits high brightness and high saturation structural color even at low concentrations. Furthermore, it is suitable for forming the desired liquid photonic crystals in various polar dispersants. The preparation method of this invention is simple, easy to operate, has a short purification process, and high system stability, making it particularly suitable for applications requiring large-scale preparation of liquid photonic crystals.

[0007] To achieve the above objectives, according to the present invention, a method for preparing a liquid photonic crystal based on monodisperse, highly stable colloidal particles is provided, characterized in that the method includes the following steps: S1, Generation of polymer colloidal particles Polymer monomer A and charged comonomer B are added to deionized water by emulsion polymerization. The mixture is heated to 70℃~85℃ and stirred continuously to carry out the copolymerization reaction, thereby obtaining polymer colloidal particles that constitute the basic unit of liquid photonic crystal. Wherein, the polymer monomer A is selected from one or any combination of the following substances: styrene (St), methyl methacrylate (MMA), hydroxyethyl acrylate (HEA), and butyl acrylate (BA); the charged copolymer monomer B is selected from one or any combination of the following substances: acrylic acid (AA), methacrylic acid (MAA), sodium styrene sulfonate (NaSS), methacryloyloxyethyltrimethylammonium chloride (MTC), 2-methacryloyloxyethyltrimethylammonium chloride (MTAC), and (3-acrylamidopropyl)trimethylammonium chloride (APTAC); and in the reaction system, the mass percentage concentration of the charged comonomer B is controlled to be 0.1wt%~0.3wt% of the polymer monomer A; S2. Preparation of Liquid Photonic Crystals The polymer colloidal particles obtained in step S1 are dispersed in a dispersant, so that the mass percentage concentration of the polymer colloidal particles in the system is gradually reduced to a preset concentration state, and a liquid photonic crystal with a pre-crystallized morphology is obtained. The liquid photonic crystal exhibits a flowing liquid state and has bright structural color and dynamic recovery. The dispersant is selected from one or any combination of the following substances: water (H2O), ethanol (EtOH), methanol (MeOH), glycerol (Glycerol), ethylene glycol (EG), polyethylene glycol (PEG200), polyethylene glycol diacrylate (PEGDA400), dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), diethylene glycol (DEG), honey, and malt syrup.

[0008] As a further preferred embodiment of the present invention, in step S1, the polymer colloidal particles are preferably obtained by an emulsifier-free soap-free emulsion polymerization method, and in the reaction system, the mass percentage concentration of the charged comonomer B is further controlled to be 0.1wt%~0.2wt% of the polymer monomer A.

[0009] As a further preferred embodiment of the present invention, in step S1, the functional groups of the polymer colloidal particles obtained by the reaction have high surface charge density characteristics to obtain sufficient electrostatic interaction, and the system stability can still be maintained at a low concentration of less than 20 wt%.

[0010] As a further preferred embodiment of the present invention, in step S1, a crosslinking agent is preferably added to the deionized water, thereby enabling the polymer colloidal particles obtained from the reaction to possess crosslinking properties. The crosslinking agent is selected from one or any combination of the following substances: ethylene glycol dimethacrylate (EGDMA), trimethylolpropane trimethacrylate (TMPTMA), divinylbenzene (DVB), and N,N'-methylenebisacrylamide (MBA); and in the reaction system, the mass percentage concentration of the crosslinking agent is controlled to be 3wt% to 10wt% of the polymer monomer A.

[0011] As a further preferred embodiment of the present invention, in step S1, the average diameter of the polymer colloidal particles is preferably 130 nm to 250 nm, the monodispersity index is less than 0.06, and the sphericity is also required.

[0012] As a further preferred embodiment of the present invention, in step S1, the surface charge of the polymer colloidal particles is preferably -40mV to -60mV or 40mV to 60mV.

[0013] As a further preferred embodiment of the present invention, in step S2, the dispersant is preferably a single dispersant or a mixture of multiple polar dispersants, and wherein the mass of the polar solvent is 50% to 100% of the aqueous phase.

[0014] As a further preferred embodiment of the present invention, in step S2, the mass percentage concentration of the liquid photonic crystal is preferably controlled to be 15wt% to 20wt%.

[0015] As a further preferred embodiment of the present invention, no additional additives, light absorbers or binders are required to maintain the stability of the system during the entire preparation process.

[0016] As a further preferred embodiment of the present invention, the above-mentioned liquid photonic crystal can be applied to optical anti-counterfeiting labels, color decorations, trademarks and other application fields after encapsulation.

[0017] As a further preferred embodiment of the present invention, the structural color of the liquid photonic crystal can be controlled by adjusting the system concentration and / or the size of the colloidal particles during the entire preparation process.

[0018] In summary, compared with the prior art, the above-described technical solutions conceived by this invention mainly possess the following technical advantages: (1) The technological innovation of this invention lies first in the targeted design of the reactant types and their characteristics in the entire preparation process, especially the re-study of the entire reaction mechanism, thereby solving the shortcomings of the existing technology such as low surface charge density and weak electrostatic interaction between particles of liquid photonic crystal monodisperse colloidal particles. The polymer colloidal particles obtained by the reaction have higher surface charge density and cross-linking characteristics, and can obtain sufficient electrostatic interaction to maintain the stability of the system. (2) The liquid photonic crystal prepared by the above reaction route designed in this invention not only has a certain fluidity and excellent dynamic reciprocity, but also can maintain system stability and exhibit bright structural color even at low concentration (e.g., below 20wt%). Furthermore, the structural color of the liquid photonic crystal can be quickly controlled by adjusting the system concentration and the size of the polymer colloidal particles. (3) In this invention, polymer colloidal particles with cross-linking characteristics can be prepared by delaying sample addition. This measure can further improve the thermal stability and solvent resistance of monodisperse, highly stable polymer colloidal particles, and significantly broaden the application of liquid photonic crystals in high temperature, organic solvents, strong acid and alkali and other application scenarios. (4) The polymer colloidal particles in this invention have a variety of high charge density surface functional groups and can be stably dispersed in different polar solvents or their mixtures, changing the state of the dispersant as a single hydrosol and obtaining a liquid photonic crystal with a bright structural color. (5) The preparation method of the present invention is green and environmentally friendly, without the need for additional additives to maintain system stability. The resulting liquid photonic crystal is eco-friendly and brightly colored, which can effectively reduce the use and emission of chemical colorants (dyes, pigments) and reduce environmental pollution. (6) The preparation method of the present invention is simple and easy to operate, the purification process is short and the system is highly stable, so it is particularly suitable for the application of large-scale preparation of liquid photonic crystals. Attached Figure Description

[0019] Figure 1 This is a process flow diagram of the liquid photonic crystal based on monodisperse, highly stable colloidal particles according to the present invention; Figure 2 This is an exemplary display of the particle size distribution of the polymer colloidal particles prepared according to Example 1 of the present invention; Figure 3 This is an exemplary scanning electron microscope image showing the polymer colloidal particles prepared according to Example 2 of the present invention; Figure 4a These are exemplary optical micrographs showing the liquid photonic crystal prepared according to Example 3 of the present invention; Figure 4b This is an exemplary display of the reflectance curve of the liquid photonic crystal prepared according to Example 3 of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0021] It should be understood that expressions such as "comprising" and "may include" as used in this application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In this application, terms such as "comprising" and / or "having" may be interpreted as indicating a specific characteristic, number, operation, constituent element, component, or combination thereof, but should not be interpreted as excluding the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0022] It should be understood that the terms “center,” “upper,” “lower,” “front,” “rear,” “left,” “right,” “vertical,” “horizontal,” “inner,” “outer,” “clockwise,” “counterclockwise,” “axial,” “radial,” and “circumferential” indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0023] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0024] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0025] Figure 1 This is a process flow diagram of the liquid photonic crystal based on monodisperse, highly stable colloidal particles according to the present invention. The following will refer to... Figure 1 This will be explained in more detail to illustrate the present invention.

[0026] First, there is the step of generating polymer colloidal particles.

[0027] In this step, polymer monomer A and charged comonomer B are added to deionized water by emulsion polymerization, and the temperature is raised to 70℃~85℃ and stirred continuously to carry out the copolymerization reaction, thereby obtaining polymer colloidal particles that constitute the basic unit of liquid photonic crystal. Wherein, the polymer monomer A is selected from one or any combination of the following substances: styrene (St), methyl methacrylate (MMA), hydroxyethyl acrylate (HEA), and butyl acrylate (BA); the charged copolymer monomer B is selected from one or any combination of the following substances: acrylic acid (AA), methacrylic acid (MAA), sodium styrene sulfonate (NaSS), methacryloyloxyethyltrimethylammonium chloride (MTC), 2-methacryloyloxyethyltrimethylammonium chloride (MTAC), and (3-acrylamidopropyl)trimethylammonium chloride (APTAC); and in the reaction system, the mass percentage concentration of the charged comonomer B is controlled to be 0.1wt% to 0.3wt% of the polymer monomer A.

[0028] It should be noted that the basic principles and other conventional conditions of emulsion polymerization are well known in the art and will not be elaborated upon here. Furthermore, the specific types of the reaction participants mentioned above can be appropriately combined and / or otherwise adjusted according to specific requirements, as long as they can ultimately react to generate polymer colloidal particle products with the desired properties.

[0029] More specifically, according to a preferred embodiment of the present invention, the polymer colloidal particles constituting the liquid photonic crystal building blocks are preferably obtained by an emulsifier-free soap-free emulsion polymerization method, and in the reaction system, the mass percentage concentration of the charged comonomer B is further controlled to be 0.1wt% to 0.2wt% of the polymer monomer A.

[0030] More specifically, according to another preferred embodiment of the invention, a crosslinking agent is preferably added to the deionized water, thereby enabling the polymer colloidal particles obtained from the reaction to possess the crosslinking properties of the same interest in this application; the crosslinking agent is selected from one or any combination of the following substances: ethylene glycol dimethacrylate (EGDMA), trimethylolpropane trimethacrylate (TMPTMA), divinylbenzene (DVB), N,N'-methylenebisacrylamide (MBA); and in the reaction system, the mass percentage concentration of the crosslinking agent is controlled to be 3wt% to 10wt% of the polymer monomer A.

[0031] Next is the preparation step of the liquid photonic crystal.

[0032] In this step, the polymer colloidal particles obtained above are dispersed in a dispersant, so that the mass percentage concentration of the polymer colloidal particles in the system gradually decreases to a preset concentration state, and a liquid photonic crystal with a pre-crystallized morphology is obtained. The liquid photonic crystal exhibits a flowing liquid state and has bright structural color and dynamic recovery. The dispersant is selected from one or any combination of the following substances: water (H2O), ethanol (EtOH), methanol (MeOH), glycerol (Glycerol), ethylene glycol (EG), polyethylene glycol (PEG200), polyethylene glycol diacrylate (PEGDA400), dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), diethylene glycol (DEG), honey, and malt syrup.

[0033] More specifically, according to another preferred embodiment of the invention, the dispersant is preferably a single dispersant or a mixture of multiple polar dispersants, and wherein the mass of the polar solvent is 50% to 100% of the aqueous phase.

[0034] Based on the above concept, this invention effectively avoids the reaction route in the prior art that requires a sufficiently high concentration to exhibit a bright structural color and where the dispersant is usually a single water solvent. The functional groups of the polymer colloidal particles obtained by the above reaction have high surface charge density characteristics (for example, the absolute value of the surface charge density is higher than 40mV, preferably in the range of -40mV to -60mV or 40mV to 60mV) to obtain sufficient electrostatic interaction, and accordingly, the system can still maintain stability under a preset low concentration state (for example, less than or equal to 20wt%, preferably in the range of 15wt% to 20wt%).

[0035] More specifically, by introducing polymer colloidal particles with high surface charge characteristics, this invention can obtain sufficient electrostatic interactions to maintain system stability. The resulting liquid photonic crystal not only has a certain degree of fluidity and excellent dynamic reciprocity, but also maintains system stability even at low concentrations, exhibiting a bright structural color. Furthermore, by adjusting the concentration of the system and the size of the polymer colloidal particles, the structural color of the liquid photonic crystal can be rapidly controlled.

[0036] It should also be noted that the delayed addition of samples in this invention can prepare polymer colloidal particles with cross-linking properties. This measure can further improve the thermal stability and solvent resistance of monodisperse, highly stable polymer colloidal particles, significantly broadening the application scope of liquid photonic crystals in high-temperature, organic solvent, and strong acid / alkali environments. Furthermore, the preparation method of this invention is green and environmentally friendly, requiring no additional additives (light absorbers, binders, etc.) to maintain system stability. The resulting liquid photonic crystals are eco-friendly and brightly colored, effectively reducing the use and emissions of chemical colorants (dyes, pigments), thus reducing environmental pollution.

[0037] The following are some specific embodiments to help to better understand the present invention.

[0038] Example 1 By using soap-free emulsion polymerization, monomer St and charged comonomer MTC were added to deionized water, heated to 85°C and stirred continuously to carry out the copolymerization reaction. In the reaction system, the mass percentage concentration of MTC was controlled to be 0.2 wt% of monomer St, and monodisperse, highly stable P(St-MTC) colloidal particles with a particle size of about 186 nm were obtained. The obtained P(St-MTC) colloidal particles were dispersed in a mixed dispersant (DMSO and PEGDA400 in a mass ratio of 1:1), and the mass concentration of the colloidal particles in the system was gradually diluted to 20wt% to obtain a liquid photonic crystal with bright and vivid structural color effect and dynamic recovery at a low concentration.

[0039] See Figure 2 The diagram shows the particle size distribution of the polymer colloidal particles prepared according to Example 1.

[0040] Example 2 By using soap-free emulsion polymerization, monomer St and charged comonomer AA were added to deionized water, heated to 75°C and continuously stirred to carry out the copolymerization reaction. The mass percentage concentration of AA was 0.18 wt% of monomer St, resulting in monodisperse, highly stable P(St-AA) colloidal particles with a particle size of approximately 195 nm. The obtained P(St-AA) colloidal particles were dispersed in a mixed dispersant (PEG200 and Glycerol in a mass ratio of 2:1), and the mass concentration of the colloidal particles in the system was gradually diluted to 20wt% to obtain liquid photonic crystals with bright and vivid structural color effects and dynamic recovery at different mass fractions.

[0041] See Figure 3 The image shows a scanning electron microscope (SEM) image of the polymer colloidal particles prepared according to Example 2.

[0042] Example 3 By using soap-free emulsion polymerization, monomer St and charged comonomer NaSS were added to deionized water, heated to 70°C and continuously stirred to carry out the copolymerization reaction. The mass percentage concentration of NaSS was 0.15 wt% of monomer St, resulting in monodisperse, highly stable P(St-NaSS) colloidal particles with a particle size of approximately 177 nm. The obtained P(St-NaSS) colloidal particles were dispersed in H2O dispersant, and the mass concentration of colloidal particles in the system was gradually diluted to 17 wt% to obtain liquid photonic crystals with bright and vivid structural color effects and dynamic recovery at different mass fractions.

[0043] See also Figure 4a and Figure 4b The images show optical micrographs and reflectance curves of the liquid photonic crystal prepared according to Example 3.

[0044] Example 4 The monomer MMA, charged comonomer AA, and crosslinking agent DVB were added to deionized water via emulsion polymerization. The mixture was heated to 80°C and stirred continuously to carry out the copolymerization reaction. The mass percentage concentration of AA was 0.1 wt% of the monomer MMA, and the mass percentage concentration of DVB was 5 wt% of the monomer MMA. Monodisperse, highly stable P(MMA-AA-DVB) colloidal particles with a particle size of approximately 158 nm were obtained. The obtained P(MMA-AA-DVB) colloidal particles were dispersed in H2O dispersant, and the mass concentration of colloidal particles in the system was gradually diluted to 15wt% to obtain liquid photonic crystals with bright and vivid structural color effects and dynamic recovery at different mass fractions.

[0045] Optical testing revealed that it can still rapidly self-assemble after being disturbed by external forces.

[0046] Example 5 The copolymerization reaction was carried out by adding monomers BA, MMA, charged comonomer MAA, and crosslinking agent EGDMA to deionized water via emulsion polymerization. The temperature was raised to 80°C and the mixture was continuously stirred. The mass percentage concentration ratio of monomers BA to MMA was 1:1, the mass percentage concentration of MAA was 0.2 wt% of monomers BA and MMA, and the mass percentage concentration of EGDMA was 7 wt% of monomers BA and MMA. Monodisperse, highly stable P(BA-MMA-MAA-EGDMA) colloidal particles with a particle size of approximately 153 nm were obtained. The obtained P(BA-MMA-MAA-EGDMA) colloidal particles were dispersed in a mixed dispersant of EtOH and DEG. The mass concentration of the colloidal particles in the system was gradually diluted to 16 wt% to obtain liquid photonic crystals with bright and vivid structural color effects and dynamic recovery at different mass fractions.

[0047] Example 6 The monomer HEA, the charged comonomer MTC, and the crosslinking agent EGDMA were added to deionized water via soap-free emulsion polymerization. The mixture was heated to 75°C and stirred continuously to carry out the copolymerization reaction. The mass percentage concentration of MTC was 0.2 wt% of the monomer HEA, and the mass percentage concentration of EGDMA was 5 wt% of the monomer HEA. Monodisperse, highly stable P(HEA-MTC-EGDMA) colloidal particles with a particle size of approximately 136 nm were obtained. The obtained P(HEA-MTC-EGDMA) colloidal particles were dispersed in a mixed dispersant of EtOH and EG, and the mass concentration of the colloidal particles in the system was gradually diluted to 16 wt% to obtain liquid photonic crystals with bright and vivid structural color effects and dynamic recovery at different mass fractions.

[0048] Example 7 By using soap-free emulsion polymerization, monomer St, charged comonomer MTAC, and crosslinking agent MBA were added to deionized water, heated to 85°C and continuously stirred to carry out the copolymerization reaction. The mass percentage concentration of MTAC was 0.1 wt% of monomer St, and the mass percentage of crosslinking agent MBA was 10 wt% of monomer St, resulting in monodisperse, highly stable P(St-MTAC-MBA) colloidal particles with a particle size of approximately 225 nm. The obtained P(St-MTAC-MBA) colloidal particles were dispersed in a mixed dispersant of EtOH and DEG, and the mass concentration of the colloidal particles in the system was gradually diluted to 15 wt% to obtain liquid photonic crystals with bright and vivid structural color effects and dynamic recovery at different mass fractions.

[0049] Example 8 By using a soap-free emulsion polymerization method, monomer MMA, charged comonomer APTAC, and crosslinking agent TMPTMA were added to deionized water, heated to 80°C, and continuously stirred to carry out the copolymerization reaction. The mass percentage concentration of APTAC was 0.2 wt% of monomer MMA, and the mass percentage concentration of crosslinking agent TMPTMA was 3 wt% of monomer MMA, resulting in monodisperse, highly stable P(MMA-APTAC-TMPTMA) colloidal particles with a particle size of approximately 190 nm. The obtained P(MMA-APTAC-TMPTMA) colloidal particles were dispersed in a mixed dispersant of polyethylene glycol (PEG200) and polyethylene glycol diacrylate (PEGDA400). The mass concentration of the colloidal particles in the system was gradually diluted to 15 wt% to obtain liquid photonic crystals with bright and vivid structural color effects and dynamic recovery at different mass fractions.

[0050] It should be noted that the free combinations of other specific types of monomers and specific embodiments with different dispersants are not listed one by one, as long as they meet the reaction route and mechanism of the present invention, the desired liquid photonic crystal can be obtained. In addition, the present invention can further achieve rapid control of the structural color of the above-mentioned liquid photonic crystal by adjusting the system concentration and the size of the polymer colloidal particles.

[0051] In summary, the preparation method of liquid photonic crystal based on monodisperse, highly stable colloidal particles designed according to this invention can effectively introduce polymer colloidal particles with high surface charge density and crosslinking properties. Consequently, it not only meets the high stability requirements of liquid photonic crystals, but also exhibits high brightness and high saturation structural color even at low concentrations. Furthermore, it is suitable for forming the desired liquid photonic crystal in various polar dispersants. The preparation method of this invention is simple, easy to operate, has a short purification process, and high system stability. Therefore, it is particularly suitable for applications involving large-scale preparation of liquid photonic crystals, and has good versatility and promotional value.

[0052] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a liquid photonic crystal based on monodisperse, highly stable colloidal particles, characterized in that, The method includes the following steps: S1, Generation of polymer colloidal particles Polymer monomer A and charged comonomer B are added to deionized water by emulsion polymerization. The mixture is heated to 70℃~85℃ and stirred continuously to carry out the copolymerization reaction, thereby obtaining polymer colloidal particles that constitute the basic unit of liquid photonic crystal. Wherein, the polymer monomer A is selected from one or any combination of the following substances: styrene (St), methyl methacrylate (MMA), hydroxyethyl acrylate (HEA), and butyl acrylate (BA); the charged copolymer monomer B is selected from one or any combination of the following substances: acrylic acid (AA), methacrylic acid (MAA), sodium styrene sulfonate (NaSS), methacryloyloxyethyltrimethylammonium chloride (MTC), 2-methacryloyloxyethyltrimethylammonium chloride (MTAC), and (3-acrylamidopropyl)trimethylammonium chloride (APTAC); and in the reaction system, the mass percentage concentration of the charged comonomer B is controlled to be 0.1wt%~0.3wt% of the polymer monomer A; S2. Preparation of liquid photonic crystals The polymer colloidal particles obtained in step S1 are dispersed in a dispersant, so that the mass percentage concentration of the polymer colloidal particles in the system is gradually reduced to a preset concentration state, and a liquid photonic crystal with a pre-crystallized morphology is obtained. The liquid photonic crystal exhibits a flowing liquid state and has bright structural color and dynamic recovery. The dispersant is selected from one or any combination of the following substances: water (H2O), ethanol (EtOH), methanol (MeOH), glycerol (Glycerol), ethylene glycol (EG), polyethylene glycol (PEG200), polyethylene glycol diacrylate (PEGDA400), dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), diethylene glycol (DEG), honey, and malt syrup.

2. The preparation method according to claim 1, characterized in that, In step S1, the polymer colloidal particles are preferably obtained by soap-free emulsion polymerization without emulsifiers, and in the reaction system, the mass percentage concentration of the charged comonomer B is further controlled to be 0.1wt%~0.2wt% of the polymer monomer A.

3. The preparation method according to claim 1 or 2, characterized in that, In step S1, the functional groups of the polymer colloidal particles obtained by the reaction have high surface charge density characteristics to obtain sufficient electrostatic interaction, and the system can still maintain stability at a low concentration of less than 20 wt%.

4. The preparation method according to any one of claims 1-3, characterized in that, In step S1, a crosslinking agent is preferably added to the deionized water, thereby giving the polymer colloidal particles obtained from the reaction crosslinking properties. The crosslinking agent is selected from one or any combination of the following substances: ethylene glycol dimethacrylate (EGDMA), trimethylolpropane trimethacrylate (TMPTMA), divinylbenzene (DVB), and N,N'-methylenebisacrylamide (MBA); and in the reaction system, the mass percentage concentration of the crosslinking agent is controlled to be 3wt% to 10wt% of the polymer monomer A.

5. The preparation method according to any one of claims 1-4, characterized in that, In step S1, the average diameter of the polymer colloidal particles is preferably 130 nm to 250 nm, the monodispersity index is less than 0.06, and they also have the required sphericity.

6. The preparation method according to claim 5, characterized in that, In step S1, the surface charge of the polymer colloidal particles is preferably -40mV to -60mV or 40mV to 60mV.

7. The preparation method according to any one of claims 1-6, characterized in that, In step S2, the dispersant is preferably a single dispersant or a mixture of multiple polar solvents, wherein the mass of the polar solvent is 50% to 100% of the aqueous phase.

8. The preparation method according to any one of claims 1-7, characterized in that, In step S2, the mass percentage concentration of the liquid photonic crystal is preferably controlled to be 15wt% to 20wt%.

9. The preparation method according to any one of claims 1-8, characterized in that, Throughout the preparation process, no additional additives, light absorbers, or binders are required to maintain system stability.

10. The preparation method according to any one of claims 1-9, characterized in that, The aforementioned liquid photonic crystals can be encapsulated and applied to fields such as optical anti-counterfeiting labels, color decorations, and trademarks.

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