Preparation method of chiral photon filament

Abstract

The invention discloses a preparation method of a chiral photon fibril, which combines confinement self-assembly and photochemical crosslinking technologies, and comprises the following steps: injecting a precursor solution formed by mixing cellulose nanocrystals (CNC), polyethylene glycol diacrylate (PEGDA) (wherein n is equal to 1000) and a photoinitiator into a polytetrafluoroethylene microtube under the action of shear fluid force boosted by a micropump; and the chiral photon filament is prepared by cooperating with an ultraviolet light crosslinking polymerization reaction. The chiral photon filament has the capability of responsively interfering color variation in humidity, rotation angle and tensile stimulation.

Description

Technical Field

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

[0002] Textiles have played an important role in human civilization since its birth. They can be used to resist cold weather and war, and can also be used as a carrier of 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 used in the fields of Internet of Things, health care, energy storage, artificial intelligence, sports and fashion. A noteworthy trend is to combine functional monomers (such as color-changing, luminescent, conductive and phase-changing materials) with synthetic polymers to manufacture smart fibers through spinning or coating technology to give textiles unique functions. In contrast, responsive fibers composed of liquid crystals and shape memory polymers can achieve more active and convenient autonomous responses without relying on specialized equipment, complex power supplies and skilled technicians. However, it is still a major challenge to design the next generation of smart textiles that integrate multiple stimuli and interactive responses while ensuring their wearing comfort, washability and cost-effectiveness. Bio-derived CNCs (cellulose nanocrystals) can self-assemble into chiral nematic liquid crystal structures, thereby responding to physical, chemical or biological stimuli and changing their chiral light behavior. If they are processed into photonic fibers, they are expected to solve these challenges.

[0003] Despite the progress made in developing the chiral photonic properties of CNCs and their applications in optics, sensors and cosmetics, CNCs usually form films rather than continuous fibers due to Plateau-Rayleigh instability. Restricting the self-assembly of CNCs to tubular geometries may produce long-distance fibers. However, since ionic crosslinking or surface modification destroys the chiral nematic organization of CNCs, there are significant challenges in making high-quality chiral optical fibers. In addition, striking a balance between high toughness, water stability and bright optical colors remains a long-standing problem 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. 1000Confined self-assembly was carried out, breaking the traditional concept (i.e., CNC self-assembly can only form chiral photonic films) in the rapid photocuring reaction, thereby successfully preparing chiral photonic filaments. Based on the synergistic effect of the shear force formed by continuous extrusion in the microtube under the assistance of a micropump and the self-assembly of CNC, the chiral nematic structure of CNC can be retained in an infinitely extended axisymmetric space. More importantly, this chiral photonic filament 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 filament has 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, and will promote the sustainable development of cellulose photonic materials and their practical applications 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 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 crosslinking reaction, and preparing 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] Wherein, the concentration of cellulose nanocrystal CNC solution is 7±0.2wt%, preferably 7wt%, and chiral photonic filaments with rich optical properties can be continuously obtained. When the concentration of CNC solution is too low, such as 3wt%, 4wt% and 6wt%, it will result in the inability to achieve continuous preparation of chiral photonic filaments. When the concentration of CNC solution is too high, such as 8wt%, the chiral liquid crystal phase in the high concentration CNC solution exhibits a de-chiral effect, which will result in the inability to obtain chiral photonic filaments with rich optical properties.

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

[0010] Among them, the number average molecular weight of polyethylene glycol diacrylate PEGDA is 800-1000, preferably 1000, and chiral photonic fibers with rich optical properties can be continuously obtained. The number average molecular weight of PEGDA is relatively low, for example, 200, 400 and 700, and the chiral photonic fibers prepared by mixing it with CNC and photoinitiator have some defects: first, it is impossible to continuously prepare chiral photonic fibers up to several meters long, and the preparation length can only reach about 50 cm; second, the interference color performance of these chiral photonic fibers is poor, and they cannot show the wide wavelength color variation phenomenon 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] Among them, 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 fibers with rich optical properties can be continuously obtained. When the flow rate is too low, less than 20 μL·min -1 When the flow rate is too high, the precursor solution per unit area will undergo excessive photocuring reaction, and the solid cross-linked products produced 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 microtube is 100 microns to 300 microns, preferably 200 microns, and the filaments are continuously produced. For example, about 3 mL of the precursor solution can produce more than 30 meters of filaments at one time. When the diameter is too large, such as 500 microns and 1000 microns, the filaments can be produced for tens of centimeters at one time, and the continuity is poor.

[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 can be used for fashion clothing design and anti-counterfeiting of high-end fabrics.

[0019] The present invention combines "confined self-assembly" with photochemical cross-linking technology to prepare chiral photonic filaments, which exhibit bright interference colors, high orientation, strong mechanical toughness, and interference color variations in response to triple stimulation (moisture absorption, rotation angle, and stretching). In addition, it also has good weavability and excellent durability.

[0020] Technical advantages of the present invention:

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

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

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

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

[0025] Figure 4 This is a SEM image of a 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 is the 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 variation of the hygroscopic stimulus responsiveness of the chiral photonic filament of Example 2;

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

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

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

[0033] Fig.12 This is a real diagram of the stimulus responsiveness variation of the optical fabric woven with the chiral photonic filaments of Example 3;

[0034] Fig.13 The reversible optical responsiveness change curve of the optical fabric woven with the chiral photonic filaments of Example 3;

[0035] Fig.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 in conjunction with specific implementation examples.

[0037] Embodiment 1: A method for preparing a chiral photonic fiber, comprising the following steps:

[0038] First, a cellulose nanocrystal (CNC) suspension was prepared by hydrolyzing degreasing cotton with sulfuric acid according to the method of ZL201910071858X. The hydrolyzate was centrifuged and dialyzed, and then concentrated by a rotary evaporator 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 1:1:1:0:0.05 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 m. The piston end of the syringe was installed on a micropump at a speed of 20 μL min. -1 At the same time, a UV lamp (λ max =365nm,13.6mW·cm -1 ) A photocuring reaction is performed to prepare filaments. The filaments are continuously produced, and finally, the filaments are drained into deionized water to wash out the unreacted PEGDA. 1000and Irgacure 2959, and after washing, the mixture was dried with a heating jacket having an internal temperature of 90°C, and chiral photonic filaments (about 30 meters long) were obtained. Figure 2 .

[0039] On a 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 micropump at 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 to Irgacure 2959 was 30:1, and after stirring for 4 hours, a blank control precursor solution was obtained. Then, PEGDA fibrils were obtained according to the step parameters of this embodiment.

[0043] A roll of 30-meter-long chiral photonic filament (about 3 mL of precursor solution obtained 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 are 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 and then 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 to weave into plain optical fabric using a Y200S electronic prototype machine. The optical fabric is placed under a polarized light microscope and the optical fabric is rotated to an angle of 45° with the polarizer for observation. The optical fabric exhibits interference color phenomenon, such as Fig. 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 a micropump at 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 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. Fig.10 As the chiral photonic filaments continue to stretch in the direction of the arrow, their interference colors under the polarized light microscope gradually change from burgundy to bright yellow 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 yarns were used as weft to weave a plain 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, namely, chloroform, N,N-dimethylformamide, anhydrous ethanol, 1 mol / L hydrochloric acid and 1 mol / L sodium hydroxide solution. After 24 hours, the samples were taken out and remained unchanged. Fig.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 machine. First, the optical fabric is moistened with a handheld humidifier, and under a polarizing microscope, the observation angle between the fabric and the polarizer is adjusted to 45°, and it is observed that the interference color of the optical fabric changes from burgundy to green, and the reflectivity of the optical fabric is tested; then, the optical fabric is rotated so that the observation angle between the fabric and 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 in succession. The actual diagram of stimulus responsiveness variation of optical fabric is shown in the figure. Fig.12 The reversible optical responsiveness change curve of the optical fabric is shown in Fig.13 .

[0056] The photonic filaments obtained by the method of this embodiment are patterned on shorts through embroidery technology. When observed under polarized light, the letters on the fabric are red; compared with 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 picture of the "WTU" embroidered letter optical fabric is shown in the figure. Fig.14 .

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

Claims

1. A method for preparing a chiral photonic fiber, characterized in that: The method comprises the following steps: injecting a precursor solution of 7±0.2wt% 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 promoted by a micropump, performing ultraviolet light crosslinking reaction, and preparing chiral photonic filaments.

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

3. The preparation method according to claim 1 or 2, characterized in that: The diameter of the microtube is 100 to 300 micrometers, preferably 200 micrometers.

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. Use of the chiral photonic filaments obtained by the preparation method according to any one of claims 1 to 8 in the preparation of textiles.

10. The use according to claim 9, 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.

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