Structural Color Fibers Based on Cholesteric Cellulose Liquid Crystals, Their Preparation Methods and Applications

Abstract

The present invention relates to a structural color fiber based on cholesteric cellulose liquid crystal, its preparation method and application. A cholesteric cellulose liquid crystal composed mainly of hydroxypropyl cellulose and a polymer hydrogel is constructed, and a fiber with structural color is prepared by using a dipping technique and an in-situ ultraviolet photopolymerization technique. Compared with the prior art, the present invention provides a cholesteric cellulose liquid crystal fiber with bright structural color, structural stability and good biocompatibility. The cholesteric cellulose liquid crystal material of the present invention and the technique for preparing fibers by the dipping method are convenient for realizing personalized customization of structural color fibers. The color and diameter of the fibers can be precisely adjusted, and the fibers have sensitive sensing characteristics to environmental temperature.

Description

Technical Field

[0001] The invention relates to the technical field of optical fiber material preparation, and in particular to a structural color fiber based on cholesteric cellulose liquid crystal and a preparation method and application thereof. Background Art

[0002] Polymer fibers are a type of material with a fiber structure processed from polymer compounds, with a uniform diameter and a certain mechanical strength. This type of material has a wide range of applications and promotes the interaction and coordinated development of materials science, engineering technology, and high-tech industries. The properties of polymer compounds are crucial to the processability, shape retention, and functionality of polymer fibers. There are many types of raw materials that can be used to prepare polymer fibers, including various types of chemical polymer materials. At present, color presentation is an important aspect of research in the field of polymer fiber preparation, because the color appearance of polymer fibers is crucial in practical applications in the fields of textiles, packaging materials, building materials, sensors, etc. However, most of the current processed raw materials are colored by doping chemical pigments, and there are still certain problems in color fidelity and stability. In addition, the interaction between pigments and raw materials will lead to changes in material properties, which will affect the mechanical properties of polymer fibers to a certain extent. In contrast, structural color is a coloring method inspired by nature, which produces color through the interaction between light and the inherent nanostructure of the material. Structural color materials are widely used in display devices, sensor devices, anti-counterfeiting labels, soft robots, etc. due to their unique color fidelity, brightness, and optical properties that are not affected by light degradation. However, the available raw materials and fiber preparation methods for constructing structural color polymer fibers have not yet been developed, so this field has not yet been developed. Therefore, developing a universal structural color raw material and based on it to realize the preparation of customizable structural color polymer fibers with high-fidelity color appearance is still a scientific problem that needs to be solved urgently. Summary of the invention

[0003] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and to provide a structural color fiber based on cholesteric cellulose liquid crystal and its preparation method and application. By constructing a cholesteric cellulose liquid crystal with hydroxypropyl cellulose and polymer hydrogel as the main components, and utilizing the pulling technology and in-situ ultraviolet polymerization technology, a fiber with structural color is prepared. The prepared structural color fiber has bright structural color, structural stability and good biocompatibility. The cholesteric cellulose liquid crystal material and the technology of preparing the fiber by the pulling method of the present invention facilitate the personalized customization of the structural color fiber. The color and diameter of the fiber can be precisely adjusted, and it has sensitive sensing characteristics to the ambient temperature.

[0004] The purpose of the present invention can be achieved by the following technical solutions:

[0005] The first object of the present invention is to provide a preparation method of a structural color fiber based on cholesteric cellulose liquid crystal, and the preparation method includes the following steps:

[0006] (1) Preparation of cholesteric cellulose liquid crystal: Mix hydroxypropyl cellulose, carbon nanotubes and a high molecular hydrogel prepolymer solution in deionized water, place them in a blender and stir in the dark for 3 days to disperse evenly to obtain a cholesteric cellulose liquid crystal dispersion. Then, centrifuge the above cholesteric cellulose liquid crystal dispersion in a high-speed centrifuge to remove air bubbles, and then store it in a refrigerator at 4°C in the dark for standby;

[0007] (2) Preparation of structural color fiber: Extrude the cholesteric cellulose liquid crystal dispersion prepared in step (1) onto a substrate using a syringe. Insert the needle of the lifting device into the cholesteric cellulose liquid crystal dispersion, and pull out the drawing liquid upward at a constant speed. During the pulling process, use ultraviolet light to cure the cholesteric cellulose liquid crystal dispersion into a structurally stable structural color fiber, and obtain a structural color fiber based on cholesteric cellulose liquid crystal.

[0008] Further, in step (1), the proportions of hydroxypropyl cellulose, high molecular hydrogel and carbon nanotubes in the cholesteric cellulose liquid crystal dispersion are 40-60 wt%, 6-10 wt% and 0.05-0.5 wt% respectively.

[0009] Further, in step (1), the high molecular hydrogel is composed of a high molecular monomer, a photoinitiator and a crosslinking agent.

[0010] Further, the high molecular monomer is one or a mixture of acrylamide, acrylic acid, N-isopropylacrylamide, hydroxyethyl methacrylate, etc., and the proportion of the high molecular monomer in the cholesteric cellulose liquid crystal dispersion is 6-10 wt%; the photoinitiator is 2-hydroxy-2-methylpropiophenone, and the proportion of the photoinitiator in the cholesteric cellulose liquid crystal dispersion is 0.5-1 wt%; the crosslinking agent is N-N'-dimethylenebisacrylamide, and the proportion of the crosslinking agent in the cholesteric cellulose liquid crystal dispersion is 0.15-0.25 wt%.

[0011] Further, the color of the structural color fiber is adjusted by the concentration of hydroxypropyl cellulose in step (1). The concentration of hydroxypropyl cellulose determines the color of the structural color fiber after ultraviolet curing. Different colors of structural color fibers can be obtained in step (2) by adjusting the concentration of hydroxypropyl cellulose.

[0012] Further, the color contrast of the structural color fiber is determined by the concentration of carbon nanotubes in step (1). The concentration of carbon nanotubes determines the color contrast of the structural color fiber obtained in step (2). The higher the concentration of carbon nanotubes, the higher the color contrast of the structural color fiber.

[0013] Furthermore, in step (2), the lifting device includes an electric z-axis elevator, a syringe, and a syringe needle; the electric z-axis elevator includes a lifting table; the syringe needle is installed on the syringe, and the syringe is vertically fixed on the lifting table of the electric z-axis elevator; below the lifting table is a substrate. When preparing the structural color fiber, the cholesteric cellulose liquid crystal dispersion is extruded onto the substrate. The lifting table is lowered to insert the syringe needle into the cholesteric cellulose liquid crystal dispersion, and then the lifting table of the electric z-axis elevator is manipulated to be lifted upward at a constant speed to extract the drawing liquid, and it is in-situ cured and formed above the liquid surface of the cholesteric cellulose liquid crystal dispersion with ultraviolet light to generate continuous structural color fibers.

[0014] Furthermore, during the process of lifting the drawing liquid, it extends, neck-snaps, and finally breaks; the in-situ curing needs to be completed before the break, and the breaking height is controlled by adjusting the liquid volume of the cellulose liquid crystal dispersion, the concentration of cellulose in the dispersion, the lifting speed, etc.

[0015] Furthermore, in step (2), when the liquid volume of the cholesteric cellulose liquid crystal dispersion is 1 ml, the displacement speed of the lifting device is 0.5 - 2 mm / s, and the diameter of the syringe needle is 0.5 - 2 mm, the ultraviolet light irradiation height is 1 - 3 mm / s above the liquid surface of the dispersion.

[0016] Furthermore, in step (2), the diameter of the structural color fiber is regulated by the displacement speed of the lifting device, the diameter of the syringe needle, and the ultraviolet light irradiation height. The diameter of the structural color fiber can be regulated as needed by changing the displacement speed of the lifting device, the diameter of the syringe needle, and the ultraviolet light irradiation position.

[0017] The second object of the present invention is to provide a structural color fiber based on cholesteric cellulose liquid crystal, and the structural color fiber based on cholesteric cellulose liquid crystal is prepared by the above preparation method.

[0018] The third object of the present invention is to provide an application of a structural color fiber based on cholesteric cellulose liquid crystal, and the structural color fiber based on cholesteric cellulose liquid crystal prepared by the above preparation method is used in the fields of biomedical sensors, food decoration, or smart fabrics.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1) The present invention reports for the first time a structural color fiber based on cholesteric cellulose, provides a method for processing structural color fibers from bottom to top, and the prepared structural color fiber has unique optical coloring, generating colors through the interaction of light with its own nanostructure. Therefore, the color of the fiber has its unique color fidelity, brightness, and optical properties that are not affected by photodegradation.

[0021] 2) The structural color fiber based on cholesteric cellulose liquid crystal prepared by the present invention adds a photocurable polymer hydrogel to the cholesteric cellulose liquid crystal, and the photocurable hydrogel can crosslink in situ through ultraviolet light to keep the fiber in the shape after pulling.

[0022] 3) For the structural color fiber based on cholesteric cellulose liquid crystal of the present invention, when a thermosensitive photocurable polymer hydrogel is selected, due to its synergistic thermal responsiveness with hydroxypropyl cellulose, the prepared structural color fiber has color tunability affected by the ambient temperature.

[0023] 4) The structural color fiber based on cholesteric cellulose liquid crystal prepared by the present invention, since the main component of the fiber is a cellulose derivative, has good biocompatibility and provides new research ideas for the development of environmentally friendly fiber processing and production technologies. Description of the Drawings

[0024] Figure 1 Reflectance spectra obtained after ultraviolet curing of cholesteric cellulose liquid crystals with different hydroxypropyl cellulose contents for Examples 1 to 3, where (a) Example 3, (b) Example 2, (c) Example 1.

[0025] Figure 2 Photographs of the generation process of the structural color fiber of Example 1.

[0026] Figure 3 Photographs of the structural color fibers with different colors for Examples 1 to 3.

[0027] Figure 4 Photographs of the structural color fiber with thermosensitive properties of Example 4, which can change color according to the change of ambient temperature. Detailed Embodiments

[0028] The present invention will be described in detail below with reference to the drawings and specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made. These all belong to the protection scope of the present invention.

[0029] In the technical solution of the present invention, features such as preparation means, materials, structures or composition ratios that are not clearly described are all regarded as common technical features disclosed in the prior art.

[0030] The applicant's design process is as follows:

[0031] In the present invention, the applicant proposes a cholesteric cellulose liquid crystal-based structural color fiber and a preparation method thereof. Cholesteric liquid crystal is a special form of material, composed of rod-shaped nanoparticles or molecules arranged in periodic parallel layers. Among them, hydroxypropyl cellulose is a long-chain cellulose derivative molecule with rich resources and good biocompatibility. The hydroxypropyl cellulose solution can self-assemble into cholesteric liquid crystal within a certain concentration range and exhibit bright and metallic luster structural color. The drawing method is a commonly used technique for preparing polymer fibers. In order to prepare fibers from the hydroxypropyl cellulose solution by the drawing method, we doped a photocurable polymer hydrogel in the hydroxypropyl cellulose solution to prepare a composite material. This composite material can generate cellulose fibers with uniform diameter and bright structural color through ultraviolet curing during the drawing process. In order to further enable the material to have a wider application range, we selected a photocurable polymer hydrogel to make a composite material. The photocurable polymer hydrogel can keep the shape of the composite material during irradiation through in-situ crosslinking by ultraviolet light. In addition, when a thermosensitive photocurable polymer hydrogel is selected, due to its synergistic thermal responsiveness with hydroxypropyl cellulose, the prepared structural color fiber has color tunability affected by the environmental temperature. More importantly, since the main component of this composite material is cellulose derivative, it has good biocompatibility and is an environmentally friendly fiber processing raw material. Based on the above characteristics, the present invention will provide new ideas and methods for the application of sustainable polymer fiber materials.

[0032] In the following examples, the raw materials used are all commercially available.

[0033] Examples 1 to 3

[0034] Examples 1 to 3 respectively provide a cholesteric cellulose liquid crystal-based structural color fiber, and the preparation method of the cholesteric cellulose liquid crystal-based structural color fiber includes the following steps:

[0035] (1) Prepare three cholesteric cellulose liquid crystal dispersions with different colors after molding.

[0036] 1.1) Prepare three polyacrylated gelatin hydrogel prepolymer solutions: Weigh three portions of 1.6 g of acrylated gelatin, 0.08 g of N-N'-dimethylacrylamide, and 0.2 mL of 2-hydroxy-2-methylpropiophenone, and mix them separately in three portions of deionized water to obtain three polyacrylated gelatin hydrogel prepolymer solutions (polymer hydrogel prepolymer solutions). The amounts of deionized water in the three polyacrylated gelatin hydrogel prepolymer solutions are 6.4 mL (Example 1), 7.2 mL (Example 2), and 8 mL (Example 3) respectively. After mixing, place them in a refrigerator at 4°C for standby.

[0037] 1.2) Add 0.2 mL of carbon nanotube dispersion (carbon nanotube content 0.1 wt%) to each of the three poly(methacryloylated gelatin) hydrogel prepolymer solutions described in (1.1), and then add hydroxypropyl cellulose powder until the total mass of each prepolymer solution is 20 g, thus obtaining three cholesteric cellulose liquid crystal dispersion liquids. In this way, in the three obtained cholesteric cellulose liquid crystal dispersion liquids, the hydroxypropyl cellulose contents are approximately 58 wt% (Example 1), 54 wt% (Example 2), and 50 wt% (Example 3), respectively. Place the three cholesteric cellulose liquid crystal dispersion liquids in a blender and stir them in the dark at a speed of 100 revolutions per minute for 3 days to uniformly disperse them. Then, centrifuge them at a speed of 10,000 revolutions per minute using a high-speed centrifuge to remove air bubbles. Finally, store them in a 4°C refrigerator in the dark for later use.

[0038] 2) Measure the reflection spectra of the three cholesteric cellulose liquid crystal dispersion liquids after polymerization.

[0039] Use a syringe to separately suck 1 mL of each of the three cholesteric cellulose liquid crystal dispersion liquids, and crosslink and cure them using ultraviolet light. It is found that their visual colors are, in order from high to low hydroxypropyl cellulose content, blue (Example 1), green (Example 2), and red (Example 3). Use a spectrometer to measure the reflection spectra of the three cholesteric cellulose liquid crystal dispersion liquids, and the results are as Figure 1 shown. Their reflection peak positions are: 524.8 nm (Example 1), 593.0 nm (Example 2), and 634.7 nm (Example 3).

[0040] 3) Prepare three structurally colored fibers of different colors by the pulling method.

[0041] Use a syringe to suck 1 mL of each of the three cholesteric cellulose ink dispersion liquids, and extrude them onto a substrate respectively. The diameter of the syringe needle is 1 mm. Lower the lifting platform so that the syringe needle is inserted into the dispersion liquid, and then operate the lifting platform of the electric z-axis elevator to lift it upward at a uniform speed of 1 mm / s to pull out the fiber. Use ultraviolet light to cure it in situ 1.5 cm above the liquid surface of the dispersion liquid to continuously generate structurally colored fibers. The pulling and forming process is as Figure 2 shown. The colors of the fibers are blue (Example 1), green (Example 2), and red (Example 3), and the results are as Figure 3 shown.

[0042] Example 4

[0043] This example provides a structurally colored fiber based on cholesteric cellulose liquid crystal. The preparation method of the structurally colored fiber based on cholesteric cellulose liquid crystal includes the following steps:

[0044] 1) Prepare a cholesteric cellulose liquid crystal dispersion liquid.

[0045] Weigh 10.8 g of hydroxypropyl cellulose, 0.8 g of acrylamide, 0.8 mL of acrylic acid, 0.08 g of N-N'-dimethylacrylamide, 0.2 mL of 2-hydroxy-2-methylpropiophenone, and 0.2 mL of carbon nanotube dispersion (carbon nanotube content 0.1 wt%). Mix them in deionized water to prepare 20 g of a cholesteric cellulose liquid crystal dispersion with a hydroxypropyl cellulose content of 54 wt%. Place the dispersion in a blender and stir it in the dark at a speed of 100 revolutions per minute for 3 days to disperse it evenly. Then, centrifuge it at a speed of 10,000 revolutions per minute using a high-speed centrifuge to remove air bubbles. Finally, store it in a refrigerator at 4°C in the dark for later use.

[0046] 2) Measure the reflection spectrum of the cholesteric cellulose liquid crystal dispersion after polymerization.

[0047] Use a syringe to separately suck 1 mL of the cholesteric cellulose liquid crystal dispersion, and crosslink and cure them using ultraviolet light. It is found that their visual color is green. Use a spectrometer to measure the reflection spectrum of the cholesteric cellulose after polymerization. The position of its reflection peak is: 635.1 nm.

[0048] 3) Prepare structural color fibers by the dip-coating method.

[0049] Use a syringe to suck 2 mL of the cholesteric cellulose dispersion with a hydroxypropyl cellulose content of 54 wt%, and extrude it onto a substrate. The diameter of the syringe needle is 1 mm. Lower the lifting platform so that the syringe needle is inserted into the dispersion. Then, operate the lifting platform of the electric z-axis elevator to lift it upward at a constant speed of 1.5 mm / s to pull out the fiber. Use ultraviolet light to cure it in situ 2 cm above the liquid surface of the dispersion to continuously generate structural color fibers. The color of the fibers is green.

[0050] 4) Temperature sensing characteristic evaluation experiment, record the color change of the structural color fibers at different ambient temperatures during the test.

[0051] When observed at room temperature of 20°C, the color of the fiber is green. When the ambient temperature gradually rises to 40°C, the color of the fiber changes from green to red, as Figure 4 shown, showing significant temperature sensing characteristics.

[0052] Example 5

[0053] This example provides a structural color fiber based on cholesteric cellulose liquid crystal. The difference in the preparation method of the structural color fiber based on cholesteric cellulose liquid crystal from that of Example 1 is that: in this example, 0.4 mL of carbon nanotube dispersion (carbon nanotube content 0.1 wt%) is added.

[0054] The color contrast of the structural color fiber based on cholesteric cellulose liquid crystal prepared in this example is significantly improved compared with that of the structural color fiber based on cholesteric cellulose liquid crystal prepared in Example 1.

[0055] Example 6

[0056] This example provides a structural color fiber based on cholesteric cellulose liquid crystal. The difference between the preparation method of the structural color fiber based on cholesteric cellulose liquid crystal and that of Example 1 is that: in this example, the lifting platform of the electric z-axis elevator is lifted upward at a uniform speed of 1.5 mm / s to draw out the fiber.

[0057] Compared with the diameter of the structural color fiber based on cholesteric cellulose liquid crystal prepared in Example 1, the diameter of the structural color fiber based on cholesteric cellulose liquid crystal prepared in this example is reduced by about 30%.

[0058] Example 7

[0059] This example provides a structural color fiber based on cholesteric cellulose liquid crystal. The difference between the preparation method of the structural color fiber based on cholesteric cellulose liquid crystal and that of Example 1 is that: in this example, the diameter of the syringe needle is 0.5 mm.

[0060] Compared with the diameter of the structural color fiber based on cholesteric cellulose liquid crystal prepared in Example 1, the diameter of the structural color fiber based on cholesteric cellulose liquid crystal prepared in this example is reduced by about 63%.

[0061] Example 8

[0062] This example provides a structural color fiber based on cholesteric cellulose liquid crystal. The difference between the preparation method of the structural color fiber based on cholesteric cellulose liquid crystal and that of Example 1 is that: in this example, ultraviolet light is used to in-situ cure and form it 1 cm above the liquid surface of the dispersion.

[0063] Compared with the diameter of the structural color fiber based on cholesteric cellulose liquid crystal prepared in Example 1, the diameter of the structural color fiber based on cholesteric cellulose liquid crystal prepared in this example is increased by about 200%.

[0064] The above description of the embodiments is for the convenience of those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative labor. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention should be within the protection scope of the present invention.

Claims

1. A preparation method of a structural color fiber based on cholesteric cellulose liquid crystal, characterized in that, The preparation method includes the following steps: (1) Preparation of cholesteric cellulose liquid crystal: Mix hydroxypropyl cellulose, carbon nanotubes, and a high-molecular hydrogel prepolymer solution in deionized water, and stir in the dark to disperse evenly to obtain a cholesteric cellulose liquid crystal dispersion. Then, centrifuge the above cholesteric cellulose liquid crystal dispersion to remove air bubbles, and store it refrigerated in the dark for later use; (2) Preparation of structural color fibers: Extrude the cholesteric cellulose liquid crystal dispersion prepared in step (1) onto a substrate using a syringe. Insert the needle of the lifting device into the cholesteric cellulose liquid crystal dispersion, and slowly pull it up at a uniform speed to obtain a drawn liquid. During the pulling process, use ultraviolet light to cure the cholesteric cellulose liquid crystal dispersion into structurally stable structural color fibers, and generate cellulose fibers with a uniform diameter and bright structural color through ultraviolet light curing to obtain structural color fibers based on cholesteric cellulose liquid crystal; The color of the structural color fibers is adjusted by the concentration of hydroxypropyl cellulose in step (1); The color contrast of the structural color fibers is determined by the concentration of carbon nanotubes in step (1); In step (2), the lifting device includes an electric z-axis elevator, a syringe, and a syringe needle; The electric z-axis elevator includes a lifting platform; The syringe needle is installed on the syringe, and the syringe is vertically fixed on the lifting platform of the electric z-axis elevator; Below the lifting platform is a substrate; In step (2), when the liquid volume of the cholesteric cellulose liquid crystal dispersion is 1 ml, the displacement speed of the lifting device is 0.5 - 2 mm / s, and the diameter of the syringe needle is 0.5 - 2 mm, the ultraviolet light irradiation height is 1 - 3 mm / s above the liquid surface of the dispersion; The diameter of the structural color fibers is regulated by the displacement speed of the lifting device, the diameter of the syringe needle, and the ultraviolet light irradiation height; In step (1), the high-molecular hydrogel includes a high-molecular monomer, a photoinitiator, and a crosslinking agent; The high-molecular monomer is one or a mixture of acrylamide, acrylic acid, N-isopropylacrylamide, and 2-hydroxyethyl methacrylate, and the proportion of the high-molecular monomer in the cholesteric cellulose liquid crystal dispersion is 6 - 10 wt%; The photoinitiator is 2-hydroxy-2-methylpropiophenone, and the proportion of the photoinitiator in the cholesteric cellulose liquid crystal dispersion is 0.5 - 1 wt%; The crosslinking agent is N-N'-bis(methylacryloyl)amide, and the proportion of the crosslinking agent in the cholesteric cellulose liquid crystal dispersion is 0.15 - 0.25 wt%.

2. The preparation method of a structural color fiber based on cholesteric cellulose liquid crystal according to claim 1, characterized in that In step (1), the proportions of hydroxypropyl cellulose, high-molecular hydrogel, and carbon nanotubes in the cholesteric cellulose liquid crystal dispersion are 40 - 60 wt%, 6 - 10 wt%, and 0.05 - 0.5 wt% respectively.

3. A structural color fiber based on cholesteric cellulose liquid crystal prepared by using the preparation method described in any one of claims 1 - 2.

4. An application of a structural color fiber based on cholesteric cellulose liquid crystal prepared by the preparation method according to any one of claims 1-2 or a structural color fiber based on cholesteric cellulose liquid crystal according to claim 3, characterized in that, Use the structural color fibers based on cholesteric cellulose liquid crystal in the fields of biomedical sensors, food decoration, or smart fabrics.

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