A method for preparing chiral photonic filaments

Abstract

The present invention discloses a method for preparing chiral photonic fibrils, which combines "confined self-assembly" and photochemical cross-linking technology, by using cellulose nanocrystals (CNC), polyethylene glycol diacrylate PEGDA (M n =1000) and a photoinitiator, injected into a polytetrafluoroethylene microtube under the shear force of a micropump. Combined with UV light cross-linking polymerization, chiral photonic fibers were prepared. These chiral photonic fibers exhibited interference color shifts in response to humidity, rotation angle, and stretching.

Description

Technical Field

[0001] The invention belongs to the technical field of material preparation, and particularly relates to a method for preparing chiral photonic filaments. Background Art

[0002] Textiles have played a vital role in human civilization since its inception, serving not only as protection against cold weather and warfare but also as vehicles for artistic expression and emotional sustenance. The emergence of modern smart textiles has given textiles a new mission: they can actively sense physiological information and respond to environmental stimuli. This concept has been widely applied in fields such as the Internet of Things, healthcare, energy storage, artificial intelligence, sports, and fashion. A notable trend is the combination of functional monomers (such as color-changing, luminescent, conductive, and phase-change materials) with synthetic polymers to create smart fibers through spinning or coating techniques, endowing textiles with unique functionalities. In contrast, responsive fibers composed of liquid crystals and shape memory polymers enable more proactive and convenient autonomous responses without relying on specialized equipment, complex power sources, or skilled technicians. However, designing next-generation smart textiles that integrate multiple stimuli and interactive responses while ensuring wearer comfort, washability, and cost-effectiveness remains a major challenge. Bio-derived CNCs (cellulose nanocrystals) can self-assemble into chiral nematic liquid crystal structures that respond to physical, chemical, or biological stimuli, changing their chiral-optical behavior. Processing them into photonic fibers holds promise for addressing these challenges.

[0003] Despite significant progress in developing the chiral photonic properties of CNCs, with applications in optics, sensors, and cosmetics, CNCs typically form thin films rather than continuous fibers due to Plateau-Rayleigh instability. Restricting the self-assembly of CNCs to tubular geometries could potentially yield long-distance fibers. However, the production of high-quality chiral optical fibers faces significant challenges, as ionic crosslinking or surface modification can destroy the chiral nematic organization of CNCs. Furthermore, striking a balance between high toughness, water stability, and vibrant optical color remains a long-standing challenge in the development of smart textiles. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the present invention aims to provide a method for preparing chiral photonic filaments. 1000By carrying out confined self-assembly, the traditional concept (that is, the self-assembly of CNC can only form chiral photonic films) was broken in the rapid photocuring reaction, thereby successfully preparing chiral photonic fibrils. Based on the synergistic effect of the shear force formed by continuous extrusion in the microtubes under the assistance of micropumps and the self-assembly of CNC, the chiral nematic structure of CNC can be retained in an infinitely extended axially symmetric space. More importantly, this chiral photonic fibril is endowed with high orientation through the action of shear force, thereby providing the material itself with excellent flexibility and interference. The obtained chiral photonic fibrils have the characteristics of multimodal optical interference color variation caused by humidity, rotation angle and stretching stimulation. The present invention has opened up a new field for the manufacture of intelligent optical textiles, which will promote the sustainable development of cellulose photonic materials and their practical application in the field of fiber science, thereby showing potential advantages in wearable textile sensors, intelligent soft optical fibers and green fashion clothing.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for preparing chiral photonic filaments comprises the following steps: injecting a precursor solution of a cellulose nanocrystal CNC solution, polyethylene glycol diacrylate PEGDA, and a photoinitiator into a polytetrafluoroethylene microtube under the action of shear fluid force assisted by a micropump, performing an ultraviolet light cross-linking reaction, and preparing the chiral photonic filaments.

[0007] Furthermore, after the ultraviolet light cross-linking reaction, the solidified filaments are drained into deionized water, washed, and dried to obtain chiral photonic filaments.

[0008] The cellulose nanocrystal (CNC) solution has a concentration of 7±0.2 wt%, preferably 7 wt%, which allows for the continuous production of chiral photonic fibers with diverse optical properties. Excessively low CNC solution concentrations, such as 3 wt%, 4 wt%, and 6 wt%, make it impossible to continuously produce chiral photonic fibers. Excessively high CNC solution concentrations, such as 8 wt%, result in a dechiralization effect in the chiral liquid crystal phase within the high-concentration CNC solution, making it impossible to produce chiral photonic fibers with diverse optical properties.

[0009] Among them, cellulose nanocrystal CNC solution is obtained by hydrolyzing cotton catalyzed by sulfuric acid.

[0010] Among them, polyethylene glycol diacrylate (PEGDA) has a number-average molecular weight of 800 to 1000, preferably 1000, and can continuously produce chiral photonic fibers with rich optical properties. However, PEGDA with lower number-average molecular weights, such as 200, 400, and 700, has several drawbacks in the chiral photonic fibers prepared by mixing it with CNC and a photoinitiator. First, it is impossible to continuously prepare chiral photonic fibers up to several meters in length, with the prepared length only reaching approximately 50 centimeters. Second, these chiral photonic fibers exhibit poor interference color properties and are unable to exhibit a wide-wavelength color shift from red to green to blue under hygroscopic stimulation.

[0011] Among them, the mass ratio of CNC and PEGDA is 1.0:1.5.

[0012] The mass ratio of CNC to photoinitiator is 1.0:0.05.

[0013] The photoinitiator is any one of Irgacure 2959, Irgacure 819 and Irgacure 1173.

[0014] The precursor solution obtained by mixing is fully stirred and then injected into the polytetrafluoroethylene microtube. The stirring time is 3-5 hours, preferably 4 hours.

[0015] The boost flow rate of the micropump is 20 μL min -1 ~60μL·min -1 , chiral photonic filaments with rich optical properties can be continuously obtained. When the flow rate is too low, less than 20μL·min -1 When the flow rate is too high, the precursor solution per unit area will undergo excessive photocuring reaction, and the generated solid crosslinks will block the microtubules, causing the chiral photonic filaments to deform and the process to stagnate. On the contrary, when the flow rate is too high, higher than 60 μL·min -1 When the photopolymerization temperature is too low, the precursor solution per unit area is insufficiently photocured, causing the chiral photonic filaments to decompose into filament fragments several centimeters long.

[0016] The diameter of the polytetrafluoroethylene microtubes is 100 to 300 microns, preferably 200 microns. This allows for continuous fibril production. For example, approximately 3 mL of precursor solution can produce over 30 meters of fibril at a time. However, if the tube diameter is too large, such as 500 or 1000 microns, fibrils can be produced over several tens of centimeters at a time, resulting in poor continuity.

[0017] The length of the polytetrafluoroethylene microtube can be 1 meter to 1.5 meters.

[0018] The chiral photonic filaments obtained by the above preparation method are used in the preparation of textiles. Through humidity, rotation angle and stretching stimulation, the chiral photonic filaments in the textiles undergo reversible interference color changes, which are used for fashion clothing design and anti-counterfeiting of high-end fabrics.

[0019] This invention combines confined self-assembly with photochemical crosslinking to produce chiral photonic filaments. These filaments exhibit bright interference colors, high orientation, strong mechanical toughness, and interference color variations in response to triple stimuli (moisture absorption, rotation angle, and stretching). Furthermore, they possess good weavability and excellent durability.

[0020] Technical advantages of the present invention:

[0021] By combining "confined self-assembly" and photochemical cross-linking technology, nanocellulose fibrils with chiral photonic structures and interference color variation characteristics are constructed; micropumps help connect microtubules, and combined with photocuring cross-linking reactions, ensure that the fibrils inherit the chiral nematic structure and obtain a high degree of orientation; this preparation process can achieve continuous and scalable processing at low cost; the chiral photonic fibrils have the ability to respond to humidity, rotation angle and stretching stimuli and undergo interference color variation. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a diagram showing the gradual growth of tactoid aggregates from the precursor solution of Example 1;

[0023] Figure 2 This is a schematic diagram of the device principle of the chiral photonic filament synthesis process of Example 1;

[0024] Figure 3 This is a photo of the 30-meter-long chiral photonic filament of Example 2;

[0025] Figure 4 This is a SEM image of the cross section of the chiral photonic filament of Example 2;

[0026] Figure 5 is the orientation curve of the chiral photonic filament of Example 2;

[0027] Figure 6 Circular dichroism spectrum of the chiral photonic filament of Example 2;

[0028] Figure 7 is the stress / strain curve of the chiral photonic filament of Example 2;

[0029] Figure 8 This is a real diagram of the hygroscopic stimulus-responsive variation of the chiral photonic filament of Example 2;

[0030] Figure 9 An optical fabric woven from the chiral photonic filaments of Example 2;

[0031] Figure 10 This is a real diagram of the variation in the responsiveness to stretching stimulation of the chiral photonic filament of Example 3;

[0032] Figure 11 This is a real picture of the chemical stability test of the chiral photonic filament in Example 3;

[0033] Figure 12 This is a diagram showing the stimulus-responsive variation of the optical fabric woven from the chiral photonic filaments of Example 3;

[0034] Figure 13 This is a curve showing the reversible optical response of the optical fabric woven with the chiral photonic filaments of Example 3;

[0035] Figure 14 This is the multimodal anti-counterfeiting pattern of the “WTU” embroidered letter optical fabric of Example 3. DETAILED DESCRIPTION

[0036] The present invention will be further described below with reference to specific implementation examples.

[0037] Example 1: A method for preparing chiral photonic filaments, comprising the following steps:

[0038] First, cellulose nanocrystal (CNC) suspension was prepared by sulfuric acid-catalyzed hydrolysis of degreasing cotton according to the method of ZL201910071858X. The hydrolyzed product was centrifuged and dialyzed, and then concentrated by rotary evaporation to obtain a 7 wt% CNC solution. Subsequently, the 7 wt% CNC solution, polyethylene glycol diacrylate PEGDA (M n =1000, denoted as PEGDA 1000 ) and 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone (Irgacure 2959) were mixed. In the system, CNC, PEGDA 1000 The mass ratio of PEG-100 and Irgacure 2959 was 1.0:1.5:0.05. After stirring for 4 hours, 10 mL of precursor solution was obtained. Then, about 3 mL of the precursor solution was loaded into a 5 mL syringe. The needle end of the syringe was connected to a polytetrafluoroethylene microtube with a diameter (inner diameter) of 200 μm and a length of 1 meter. The piston end of the syringe was installed on a micropump at a speed of 20 μL·min -1 At the same time, an ultraviolet lamp (λ max =365nm,13.6mW·cm -1 ) Implement photocuring reaction to prepare filaments. The filaments are continuously produced. Finally, the filaments are drained into deionized water to wash away the unreacted PEGDA. 1000and Irgacure 2959, and after washing, dried with a heating mantle at an internal temperature of 90°C, and chiral photonic filaments (about 30 meters long) were obtained. Figure 2 .

[0039] On the polarized light microscope (POM), the precursor solution (solution state is 0 seconds) gradually grows tactoid aggregates as the photocuring time increases, e.g. Figure 1 .

[0040] Example 2: A method for preparing chiral photonic filaments

[0041] The preparation method of this embodiment is the same as that of embodiment 1. The only difference is that the piston end of the syringe is installed on a micro pump with a flow rate of 40 μL·min. -1 Boost the flow rate.

[0042] At the same time, the PEGDA fibrils prepared in this example were used as blank control fibrils. 20 wt% PEGDA was directly prepared. 1000 , and add a certain amount of Irgacure 2959, PEGDA 1000 The mass ratio of PEG-10 to Irgacure 2959 was 30:1, and after stirring for 4 hours, a blank control precursor solution was obtained. PEGDA fibrils were then obtained according to the process parameters of this example.

[0043] A 30-meter-long roll of chiral photonic filament (obtained from about 3 mL of precursor solution at one time) was collected according to the method of this embodiment. Figure 3 .

[0044] The scanning electron microscope (SEM) image of the cross section of the chiral photonic filament obtained by the method of this embodiment is as follows: Figure 4 .

[0045] The orientation degree of the chiral photonic filaments obtained by the method of this embodiment is analyzed by two-dimensional X-ray diffraction pattern, as shown in FIG. Figure 5 .

[0046] The circular dichroism spectra of the chiral photonic filaments and PEGDA filaments obtained by the method of this embodiment are as follows: Figure 6 .

[0047] The stress / strain curves of the chiral photonic filaments and PEGDA filaments obtained by the method of this embodiment are as follows: Figure 7 , where wet chiral photonic filaments were sprayed with a small handheld humidifier for 20 seconds relative to dry chiral photonic filaments.

[0048] The chiral photonic filaments obtained by the method of this embodiment were placed in deionized water for swelling. The hygroscopic stimulus responsiveness variation is shown in the figure below. Figure 8As the chiral photonic filaments continue to absorb moisture, their interference colors under a polarized light microscope gradually change from wine red to grass green to sky blue, and the corresponding volume swelling ratios are 1.0, 1.1, and 1.2, respectively. A volume swelling ratio of 1.0 refers to the original unswollen state, and a volume swelling ratio of 1.2 means that the volume after swelling has increased by 20% compared to the initial volume.

[0049] The chiral photonic filaments obtained by the method of this embodiment are used as warp and black nylon yarn as weft, and are woven into a plain weave optical fabric using a Y200S electronic prototype. The optical fabric is placed under a polarizing microscope and the angle between the optical fabric and the polarizer is rotated to 45 degrees for observation. The optical fabric exhibits interference color phenomena, such as Figure 9 .

[0050] Example 3: A method for preparing chiral photonic filaments

[0051] The preparation method of this embodiment is the same as that of embodiment 1. The only difference is that the piston end of the syringe is installed on the micro pump with a flow rate of 60 μL·min. -1 Boost the flow rate.

[0052] According to the method of this embodiment, chiral photonic filaments of about 30 meters in length can also be collected at one time.

[0053] The chiral photonic filament obtained by the method of this embodiment is stretched, and the variation of its stretching stimulus response is shown in the figure. Figure 10 As the chiral photonic filament continues to stretch in the direction of the arrow, its interference color under the polarized light microscope gradually changes from burgundy to bright yellow, then to purple, and finally to blue. The corresponding strain rates are 0, 0.1, 0.2, 0.3 and 0.4, respectively, where 0.1 means that the length increases by 10% of the initial length after the strain occurs.

[0054] The chiral photonic filaments obtained by the method of this embodiment were used as warp and black nylon yarn as weft to weave a plain weave optical fabric using a Y200S electronic prototype machine. The chiral photonic filaments and optical fabric obtained by the method of this embodiment were immersed in five different solvents: chloroform, N,N-dimethylformamide, anhydrous ethanol, 1 mol / L hydrochloric acid, and 1 mol / L sodium hydroxide solution. After 24 hours, the samples remained unchanged. Figure 11 This indicates that the chiral photonic filaments have good chemical stability.

[0055] The chiral photonic filaments obtained by the method of this embodiment are used as warps and black nylon yarns as wefts, and are woven into plain optical fabrics using a Y200S electronic prototype. First, the optical fabric is moistened with a handheld humidifier, and under a polarizing microscope, the observation angle with the polarizer is adjusted to 45°, and the interference color of the optical fabric is observed to change from burgundy to green, and the reflectivity of the optical fabric is tested; then the optical fabric is rotated so that the observation angle with the polarizer is parallel to the polarizer, and its interference color disappears, and the reflectivity of the optical fabric is tested; finally, the moistened optical fabric is dried and re-rotated to a 45° angle with the polarizer, and its interference color can be restored to burgundy, and the reflectivity of the optical fabric is tested, which is one cycle. Ten cycles are completed continuously. The stimulus-responsive variation of the optical fabric is shown in the figure below. Figure 12 The reversible optical responsiveness change curve of the optical fabric is shown in Figure 2. Figure 13 .

[0056] The photonic filaments obtained by the method of this embodiment are patterned on shorts through embroidery technology. Under polarized light, the letters on the fabric are red; compared to fluorescent light, the photonic filaments are white and transparent; when the fabric is stretched horizontally, the chiral photonic filaments turn blue. The multimodal anti-counterfeiting real image of the "WTU" embroidered letter optical fabric is shown in the figure. Figure 14 .

[0057] The embodiments described are preferred implementations of the present invention, but the present invention is not limited to the above implementations. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essence of the present invention are within the scope of protection of the present invention.

Claims

1. A method for preparing chiral photonic filaments, characterized in that: The method comprises the following steps: injecting a precursor solution of 7±0.2 wt% cellulose nanocrystal CNC solution, polyethylene glycol diacrylate PEGDA with a number average molecular weight of 800-1000, and a photoinitiator into a polytetrafluoroethylene microtube under the action of shear fluid force assisted by a micropump, and performing an ultraviolet light cross-linking reaction to prepare chiral photonic fibers.

2. The preparation method according to claim 1, characterized in that The boost flow rate of the micropump is 20 μL∙min −1 ~60 μL∙min −1 .

3. The preparation method according to claim 1 or 2, characterized in that The diameter of microtubules is 100 microns to 300 microns.

4. The preparation method according to claim 1, characterized in that The mass ratio of CNC to PEGDA is 1.0: 1.5; and / or the mass ratio of CNC to photoinitiator is 1.0: 0.

05.

5. The preparation method according to claim 1, characterized in that The photoinitiator is any one of Irgacure 2959, Irgacure 819 and Irgacure 1173.

6. The preparation method according to claim 1, characterized in that Cellulose nanocrystals (CNC) solution was obtained by hydrolyzing cotton catalyzed by sulfuric acid.

7. The preparation method according to claim 1, characterized in that The concentration of the CNC solution was 7 wt%.

8. The preparation method according to claim 1, characterized in that After the ultraviolet light cross-linking reaction, the solidified filaments are drained into deionized water, washed, and dried to obtain chiral photonic filaments.

9. The preparation method according to claim 3, characterized in that The diameter of the microtubules is 200 microns.

10. Use of the chiral photonic filaments obtained by the preparation method according to any one of claims 1 to 9 in the preparation of textiles.

11. The use according to claim 10, characterized in that: Through humidity, rotation angle and stretching stimulation, chiral photonic filaments in textiles undergo reversible interference color changes, which are used in fashion clothing design and anti-counterfeiting of high-end fabrics.

Images