A method for preparing a structural color pattern using a melanin photonic material

Abstract

This invention relates to a method for preparing structural color patterns using melanin photonic materials, belonging to the field of structural color technology. The method includes the following steps: S1, under alkaline conditions, PS microspheres and dopamine hydrochloride are reacted in a tris(hydroxymethyl)aminomethane-hydrochloric acid buffer solution, and the mixture is centrifuged to obtain PS@PDA microspheres; S2, the PS@PDA microspheres are prepared into a PS@PDA microsphere dispersion, dropped onto the surface of a silica gel plate, and dried to obtain PS@PDA structural color spheres; S3, the PS@PDA structural color spheres are prepared into a PS@PDA structural color sphere dispersion, and atomized using a masking process to obtain a structural color pattern. By controlling the particle size of the PS microspheres and the thickness of the PDA shell, structural color materials with uniform color, high color visibility, and high saturation can be prepared, ultimately achieving the preparation of full-spectrum structural colors covering the entire visible spectrum.

Description

Technical Field

[0001] This invention belongs to the field of structural color technology, and in particular relates to a method for preparing structural color patterns using melanin photonic materials. Background Technology

[0002] Colors in nature are divided into pigment colors and structural colors. Structural colors are produced by the interaction of light with the micro-nano structures on the surface of objects, which have optical scale. They have advantages such as high brightness, high saturation, environmental friendliness, and long-term chemical stability. Pigment colors, on the other hand, originate from the selective absorption of incident light by pigment molecules.

[0003] Currently, the construction of structural color-generating materials using colloidal nanospheres as assembly units has attracted widespread attention from researchers due to its simple technology and operation. However, the colors produced by these materials are relatively dull due to incoherent light scattering. Usually, black light-absorbing substances such as squid ink, carbon black, and graphene nanosheets are added to the colloidal microspheres to improve color visibility. Among them, carbon black is the most widely used. However, carbon black has a small particle size and is easy to agglomerate, making it difficult to disperse well around the colloidal particles, which can easily lead to uneven coloring of the structural color. Therefore, combining high light-absorbing substances directly with the microstructural units of colloidal microspheres has become a new approach to constructing structural color-generating materials.

[0004] Polydopamine (PDA), as a green and environmentally friendly biomimetic melanin material, can replace light-absorbing substances such as carbon black or black dyes. By coating it on the surface of colloidal microspheres, single-component color-generating structural color materials can be constructed, so that PDA can act as both a color-generating component and a light-absorbing component. Moreover, the structural color materials prepared in this way have bright colors, high saturation, and uniform color, and can develop color independently of a black background without the need for strong light source irradiation. Patent CN 110158315 A discloses a method for preparing a PDA structural color film. The method involves immersing a fabric flat or at an angle into a dopamine-tris(hydroxymethyl)aminomethane buffer solution, ensuring the solution completely covers the fabric surface. Dopamine is polymerized on the fabric surface using its self-polymerization film-forming properties. The desired structural color is obtained by controlling the polymerization reaction time. Finally, an adhesive layer is laid flat on the surface of the PDA structural color layer as a protective layer to complete the preparation. However, the above method has obvious drawbacks. First, it cannot flexibly control the color of the structural color film. Second, the prepared structural color has a low reflectivity. Third, directly immersing the fabric in the buffer solution affects the style characteristics of the fabric itself, such as damaging the fabric's breathability, softness, and hand feel.

[0005] Based on this, the present invention is proposed. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for preparing structural color patterns using melanin photonic materials. PDA is used as a biomimetic melanin-like light-absorbing material to modify the surface of PS microspheres, constructing a black light-absorbing material-PS microsphere composite structural color assembly unit. By controlling the particle size of the core layer PS microspheres and the thickness of the PDA shell, structural color materials with uniform color, high color visibility, and high saturation can be prepared. Furthermore, the presentation effect of the structural color can be flexibly adjusted, ultimately achieving the preparation of full-spectrum structural colors covering the entire visible spectrum.

[0007] The purpose of this invention is to provide a method for preparing structural color patterns using melanin photonic materials, comprising the following steps:

[0008] S1. Under alkaline conditions, PS microspheres and dopamine hydrochloride are reacted in a tris(hydroxymethyl)aminomethane-hydrochloric acid buffer solution, and PS@PDA microspheres are obtained by centrifugation.

[0009] S2. The PS@PDA microspheres described in S1 are prepared into a PS@PDA microsphere dispersion, dropped onto the surface of a silica gel plate, and dried to obtain PS@PDA structural color spheres;

[0010] S3. The PS@PDA structural color pellets described in S2 are formulated into a PS@PDA structural color pellet dispersion, and atomized deposition is performed using a masking process to obtain the structural color pattern.

[0011] In one embodiment of the present invention, in S1, the pH of the alkaline condition is 8-9.

[0012] In one embodiment of the present invention, in S1, the particle size of the PS microspheres is 140nm-250nm.

[0013] In one embodiment of the present invention, in S1, the concentration of the PS microspheres is 5.5 mg / mL-6.5 mg / mL, and the concentration of dopamine hydrochloride is 0.25 mg / mL-1 mg / mL.

[0014] In one embodiment of the present invention, in S1, the temperature of the reaction is 5°C-30°C and the time is 18h-22h.

[0015] In one embodiment of the present invention, in S2, the concentration of the PS@PDA microsphere dispersion is 8wt%-12wt%.

[0016] In one embodiment of the present invention, in S2, the drying temperature is 45℃-55℃; on the surface of the silicone plate, moisture is removed by drying, thereby achieving high-precision self-assembly of PS@PDA microspheres and optimizing the arrangement density and order of the microspheres.

[0017] In one embodiment of the present invention, in S3, the concentration of the PS@PDA structural chromophore dispersion is 8wt%-12wt%.

[0018] In one embodiment of the present invention, in S3, the substrate used for the atomization deposition is selected from paper, fabric, metal plate or ceramic.

[0019] In one embodiment of the present invention, in S3, the process parameters of the atomization deposition are: atomization pressure of 0.1MPa-0.5MPa, number of sprays of 3-9, and spraying distance of 5cm-10cm. By controlling the number of atomization depositions, the thickness of the structural color pattern is changed, thereby obtaining a more saturated and brighter color. At the same time, the atomization deposition method atomizes the dispersion liquid into tiny droplets for deposition, and the coating formation speed is stable and controllable. The prepared structural color pattern is not only saturated and uniform in color and has controllable performance, but also retains the original style of the substrate to the greatest extent.

[0020] The technical solution of the present invention has the following advantages compared with the prior art:

[0021] (1) The method described in this invention forms PS@PDA microspheres by uniformly coating polydopamine (PDA) on the surface of PS microspheres through in-situ oxidation self-polymerization. PDA is used as a biomimetic melanin light-absorbing layer, which avoids the problem of easy aggregation of traditional light-absorbing materials such as carbon black. The catechol anchoring group contained therein can also improve color uniformity, effectively reduce incoherent light scattering and make the structural color more vivid. Moreover, the in-situ polymerization method can avoid microsphere sedimentation, improve preparation efficiency and achieve uniform coating at the nanoscale.

[0022] (2) The method described in this invention constructs a dual regulation mechanism by precisely controlling the particle size of the core layer PS microspheres and the thickness of the PDA shell, which solves the problem of dull structural color and narrow color gamut of the assembly caused by wide microsphere size distribution or uneven PDA layer, and achieves full visible spectrum coverage from blue to red, and prepares structural color patterns with uniform color, high color visibility and saturation and flexible control.

[0023] (3) The method described in this invention optimizes the atomization deposition process parameters and controls the concentration of PS@PDA structural color pellet dispersion to reduce the "coffee ring effect" caused by droplet edge deposition during solvent evaporation, thereby achieving the preparation of highly saturated, patterned and substrate-friendly structural color patterns.

[0024] (4) The method described in this invention prepares an amorphous structural color pattern with sharp boundaries, no cross-penetration of colors and a three-dimensional visual effect. The entire coating process is simple, mild, environmentally friendly and controllable. Attached Figure Description

[0025] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein:

[0026] Figure 1 This is a schematic diagram illustrating the preparation of PS@PDA microspheres in Example 1 of the present invention;

[0027] Figure 2 This is a schematic diagram of the assembly of PS@PDA structured chromospheres in Embodiment 1 of the present invention;

[0028] Figure 3 This is a schematic diagram of the structural color pattern in Embodiment 1 of the present invention;

[0029] Figure 4 The image shows the SEM images of PS@PDA microspheres in Test Example 1 of this invention; where (a)-(e) represent low magnification, (f)-(j) represent high magnification, and the concentrations of DA from left to right are 0 mg / mL, 0.25 mg / mL, 0.5 mg / mL, 0.75 mg / mL, and 1 mg / mL, respectively.

[0030] Figure 5 This is an optical photograph of the PS@PDA structured chromosphere in Test Example 2 of this invention;

[0031] Figure 6 The reflection spectrum of the PS (190nm)@PDA structure chromosphere in Test Example 3 of this invention and the wavelengths corresponding to the reflection spectrum peaks;

[0032] Figure 7 The structural color patterns prepared on different substrates in Test Example 4 of the present invention are shown; where a is black dense twill fabric, b is black needle-punched nonwoven fabric, and cd is white meltblown nonwoven fabric. Detailed Implementation

[0033] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. It should be understood that the specific embodiments are only used to explain the present invention, but the embodiments are not intended to limit the present invention.

[0034] In this invention, unless otherwise stated, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0035] In this invention, unless otherwise stated, the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0036] In this invention, unless otherwise specified, the experimental methods used in the embodiments of this invention are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0037] In this invention, unless otherwise stated, the silicone plate in the embodiments of this invention needs to be ultrasonically cleaned and dried before use.

[0038] Example 1

[0039] The method for preparing structural color patterns using melanin photonic materials in this embodiment specifically includes the following steps:

[0040] Preparation of S1 PS microspheres: A certain volume (30mL, 40mL, 50mL) of styrene (St), 1mL of acrylic acid (AA) and 100mL of pure water were added to a three-necked flask. The three-necked flask was then placed in an oil bath at 100℃ and mechanically stirred continuously at 280r / min for 10min. Then, 0.15g of potassium persulfate (KPS) and 0.02g of sodium dodecyl sulfate (SDS) were added to the reaction system, and the reaction was continued for 2h under the same stirring conditions. The obtained product was washed four times by alternating centrifugation with alcohol and pure water. After drying, PS microsphere powders of different sizes (140nm, 190nm, 244nm) were obtained.

[0041] Preparation of S2, PS@PDA microspheres ( Figure 1 ): Measure 20 mL of pure water and add it to a 50 mL sample bottle. Weigh 0.12 g of PS microsphere powder and add it to the sample bottle. Sonicate the sample until the PS microspheres are completely dispersed in the water. Then weigh 0.4 g of tris(hydroxymethyl)aminomethane (Tris) and add it to the dispersion. Add hydrochloric acid to adjust the pH of the system to 8.5. Continue sonicating for 30 min. Finally, weigh a certain amount of dopamine hydrochloride (DA, with concentrations of 0 mg / mL, 0.25 mg / mL, 0.5 mg / mL, 0.75 mg / mL, and 1 mg / mL in the solution and add it to the sonicated solution. Stir magnetically at room temperature for 20 h. After multiple centrifugations and washings until the upper liquid is clear, PS@PDA microspheres of different sizes (PDA shell thickness of 0 nm, 1 nm, 3 nm, 5 nm, and 8 nm) are obtained.

[0042] Assembly of S3, PS@PDA structural color pellets ( Figure 2 First, PS@PDA microspheres were prepared into an aqueous dispersion with a concentration of 10wt%. After ultrasonic dispersion, a few drops were added to the surface of a silicone plate using a dropper. The silicone plate was then placed in a 50℃ oven to dry and remove moisture, thus obtaining PS@PDA structural color spheres.

[0043] S4. Preparation of structural color patterns ( Figure 3 First, PS (190nm)@PDA (3nm) structural color pellets are prepared into a 10wt% PS@PDA structural color pellet aqueous dispersion. The dispersion is placed in a mesh atomizer, and atomization deposition is performed using white or black paper as a substrate, combined with a masking process. The atomization pressure is controlled at 0.3MPa, the number of sprays is 6, and the spraying distance is 8cm to obtain the structural color pattern.

[0044] Test Example 1

[0045] SEM images of PS@PDA microspheres in Example 1 are shown below. Figure 4 As shown. From Figure 4 It can be seen that the surface of pure PS microspheres without the addition of dopamine hydrochloride (DA) is very smooth and the arrangement is tight and regular. However, when DA is added to the reaction system, the surface of PS microspheres gradually becomes rough due to the non-uniform coating of polydopamine (PDA). At the same time, the arrangement of microspheres no longer remains tight and regular, but begins to become disordered. As the DA concentration gradually increases from 0.25 mg / mL to 1 mg / mL, this disorder continues to intensify, especially when the DA concentration exceeds 0.5 mg / mL, the change in the disorder of the arrangement is more significant. Meanwhile, the overall size of PS@PDA microspheres also gradually increases with the increase of DA concentration. This size change and the evolution of surface morphology and arrangement can be mutually confirmed in both low-magnification and high-magnification SEM images.

[0046] Test Example 2

[0047] Optical photographs of PS@PDA structured chromospheres from Example 1 are shown below. Figure 5 As shown. From Figure 5 As can be seen, before the addition of dopamine hydrochloride (DA), the structural color spheres assembled from pure PS microspheres appear milky white due to interference from incoherent scattering light. However, when DA is added to the reaction system, it polymerizes on the surface of the PS microspheres under alkaline conditions to form a polydopamine (PDA) layer, resulting in PS@PDA structural color spheres. The structural color spheres assembled from these microspheres exhibit a bright and uniform color, thanks to PDA's biomimetic melanin-like properties, which combine color rendering and light absorption, effectively suppressing the influence of incoherent scattering. As the initial DA concentration gradually increases from 0.25 mg / mL to 1 mg / mL, the PDA coating thickness on the PS microsphere surface increases from 1 nm to 8 nm. During this process, the color of the structural color spheres assembled from PS@PDA microspheres not only gradually deepens but also exhibits a significant redshift. This stable color difference, controlled by DA concentration, ensures the adjustability of the structural color pattern and a good visual effect.

[0048] Test Example 3

[0049] The reflection spectrum of the PS (190nm)@PDA structure chromogran in Example 1 and the wavelengths corresponding to the reflection spectral peaks are as follows: Figure 6 As shown. From Figure 6 It can be seen that when dopamine hydrochloride (DA) is added to the reaction system, the reflectance of the structural color spheres assembled from PS@PDA microspheres shows a significant decreasing trend. This is because PDA, as a biomimetic melanin material, possesses excellent light absorption properties. The PDA layer formed by DA polymerization under alkaline conditions selectively captures a portion of incoherent scattered light, reducing the interference of scattered light on the structural color, resulting in a significant deepening of the color of the structural color spheres and a substantial improvement in color visibility. As the initial DA concentration gradually increases from 0.25 mg / mL to 1 mg / mL, and the PDA coating thickness on the PS microsphere surface increases from 1 nm to 8 nm, the reflectance of the PS@PDA structural color spheres also continuously decreases, and the color further deepens. This is because the increase in PDA layer thickness leads to a continuous increase in its absorption of incoherent scattered light. However, it should be noted that if the DA concentration exceeds 1 mg / mL, the absorption of light by PDA will be excessively enhanced, leading to a sharp decrease in the reflectance of the structural color, ultimately making the color dull and affecting the visual effect. When the concentration of DA is less than 0.5 mg / mL, the peak of the reflection spectrum shows only a slight red shift. This is because the PDA layer formed by polymerization on the surface of PS microspheres is relatively thin, and the average size of PS@PDA microspheres does not change significantly, resulting in minimal differences in the optical effects of the assembled structural color clusters. However, when the DA concentration is greater than 0.5 mg / mL, the red shift of the reflection spectrum peak is more significant. This is because the PDA layer formed by polymerization on the surface of PS microspheres not only significantly increases the overall size of PS@PDA microspheres but also leads to a more disordered arrangement of the microspheres. According to Bragg's law (the reflection wavelength of structural colors is closely related to the size and ordered arrangement of micro / nano structures), the combined effect of increased microsphere size and increased disordered arrangement causes a significant shift of the reflection spectrum peak towards longer wavelengths. This pattern is consistent with... Figure 5 The color changes shown in the optical photographs of the PS@PDA structured color spheres are completely consistent, further confirming that the DA concentration can achieve precise control over the structural color reflectivity and visual effects by adjusting the PDA layer thickness and the microsphere assembly state.

[0050] Test Example 4

[0051] Aqueous dispersions of PS@PDA structural color spheres (exhibiting blue, green, and red, respectively) were prepared based on PS microspheres with particle sizes of 180 nm, 210 nm, and 240 nm. Using 100% polyester fiber black dense twill fabric, black needle-punched nonwoven fabric, and white meltblown nonwoven fabric as substrates, atomization deposition was performed using a masking process to obtain… Figure 7 The structural color pattern shown. From Figure 7It can be seen that the boundaries between dyed and undyed areas in the structural color pattern are sharp, with no cross-penetration of colors, and the warp and weft yarns, and even individual fibers, in the dyed area are still clearly distinguishable without being immersed in liquid.

[0052] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a structural color pattern using a melanin photonic material, characterized by, Includes the following steps: S1. Under alkaline conditions, PS microspheres and dopamine hydrochloride are reacted in a tris(hydroxymethyl)aminomethane-hydrochloric acid buffer solution, and PS@PDA microspheres are obtained by centrifugation. S2. The PS@PDA microspheres described in S1 are prepared into a PS@PDA microsphere dispersion, dropped onto the surface of a silica gel plate, and dried to obtain PS@PDA structural color spheres; S3. The PS@PDA structural color pellets described in S2 are formulated into a PS@PDA structural color pellet dispersion, and atomized deposition is performed using a masking process to obtain the structural color pattern.

2. The method of claim 1, wherein the method is characterized by: In S1, the pH of the alkaline conditions is 8-9.

3. The method of claim 1, wherein the method is characterized by: In S1, the particle size of the PS microspheres is 140nm-250nm.

4. The method of claim 1, wherein the method is characterized by: In S1, the concentration of the PS microspheres is 5.5 mg / mL to 6.5 mg / mL, and the concentration of dopamine hydrochloride is 0.25 mg / mL to 1 mg / mL.

5. The method of claim 1, wherein the method is characterized by: In S1, the reaction temperature is 5℃-30℃ and the time is 18h-22h.

6. The method of claim 1, wherein the method is characterized by: In S2, the concentration of the PS@PDA microsphere dispersion is 8wt%-12wt%.

7. The method of claim 1, wherein the method is characterized by: In S2, the drying temperature is 45℃-55℃.

8. The method of claim 1, wherein the method is characterized by: In S3, the concentration of the PS@PDA structural chromophore dispersion is 8wt%-12wt%.

9. The method of claim 1, wherein the method is characterized by: In S3, the substrate used for the atomization deposition is selected from paper, fabric, metal plate or ceramic.

10. The method of claim 1, wherein the method is characterized by: In S3, the process parameters for atomization deposition are: atomization pressure of 0.1MPa-0.5MPa, number of sprays of 3-9, and spraying distance of 5cm-10cm.

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