Self-repairing flexible photonic crystal material and preparation method thereof

Abstract

The invention relates to a self-repairing flexible photonic crystal material and a preparation method thereof. The preparation method comprises the following steps: 1) weighing microcrystalline cellulose, sulfuric acid, hexamethylene isocyanate, polytetrahydrofuran and other raw materials; 2) preparing a sulfonic cellulose nanocrystal suspension; (3) preparing polyurethane with a self-repairing function; and 4) blending the sulfonic acid-based cellulose nanocrystal suspension and the polyurethane dispersion liquid, and then co-assembling and curing to obtain the self-repairing flexible photonic crystal. The prepared self-repairing flexible photonic crystal material is excellent in mechanical performance, good in self-repairing performance and optical performance, mild in reaction condition, simple in process, low in cost, high in production efficiency and suitable for large-scale production.

Description

Technical Field

[0001] The present invention relates to a flexible photonic crystal material, in particular to a self-repairing flexible photonic crystal material and a preparation method thereof. Background Art

[0002] Due to their unique photonic bandgap characteristics, photonic crystals have shown important value in the fields of optical sensing, structural color display, optoelectronic devices, etc. Flexible photonic crystal materials have achieved stretchable and foldable functional expansion by introducing an elastic matrix, and have broad application prospects in wearable devices, flexible robot skin and other fields. However, after repeated mechanical deformation or external damage (such as scratches and cracks), the periodic photonic structure of traditional flexible photonic crystal materials is prone to irreversible damage, resulting in significant degradation or even failure of optical properties (such as structural color and reflective spectrum), which seriously limits the service life and reliability of the material. Summary of the Invention

[0003] In order to overcome the deficiencies in the prior art, the purpose of the present invention is to provide a flexible photonic crystal material that can avoid damage, aging, and cracking, and the photonic structure is not easily destroyed, and can self-repair, and a method for preparing the same. By introducing multiple dynamic bonds (disulfide bonds / hydrogen bond synergistic system) into the polyurethane main chain through molecular design, self-repair at room temperature (repair efficiency>85%) is achieved. At the same time, soft / hard segment microphase separation is achieved through block copolymerization, and a three-dimensional network structure of polyurethane with a gradient modulus is constructed, so that the material can still maintain the long-range ordered arrangement of the photonic crystal when subjected to large deformation (elongation at break>500%). In addition, the present invention forms ionic bonds and hydrogen bonds between the self-repairing interface and the photonic crystal nanoparticles by designing sulfonic acid groups and dynamic bond polymers (such as amino groups in polyurethane), and the damaged interface achieves rapid directional bonding, ensuring accurate reconstruction of the photonic band gap after damage.

[0004] To achieve the above objectives, the inventors provide a method for preparing a self-repairing flexible photonic crystal material, comprising the following steps:

[0005] 1) Weigh the following raw materials according to their amounts:

[0006] 0.6 parts of microcrystalline cellulose;

[0007] 8.55 parts of 98wt% sulfuric acid;

[0008] 2) diluting 98 wt % sulfuric acid to 64 wt % with water, heating to 40-50° C., adding microcrystalline cellulose, and stirring for at least 1 hour to obtain a mixture of sulfonated cellulose nanocrystals and sulfuric acid. The mixture is poured into at least 8 times the volume of deionized water to quench the reaction, and the quenched mixture is allowed to stand for separation;

[0009] 3) taking the milky white suspension phase at the bottom after the mixed solution in step 2) has been allowed to stand, centrifuging it at 4-10° C. to remove excess sulfuric acid, and then centrifuging it with deionized water until the supernatant exhibits a light blue characteristic. The supernatant from the last centrifugation (because some of the sulfonated cellulose nanocrystals are dispersed in the upper deionized water) and the lower precipitate (the lower precipitate from the last centrifugation) are mixed and stirred to uniformly disperse the sulfonated cellulose nanocrystals in the deionized water, thereby obtaining an aqueous suspension of sulfonated cellulose nanocrystals.

[0010] 4) placing the aqueous suspension of cellulose sulfonate nanocrystals obtained in step 3) into a dialysis bag and dialyzing it in deionized water for 5-7 days until the pH of the suspension remains stable, thereby obtaining an aqueous dispersion of cellulose sulfonate nanocrystals;

[0011] 5) placing the aqueous dispersion of cellulose sulfonate nanocrystals in step 4) in a 50-60° C. oven for 5-6 days to concentrate the dispersion to 5-7 wt %, and then adding sodium hydroxide solution to adjust the pH of the dispersion to 7 to obtain a cellulose sulfonate nanocrystal suspension;

[0012] 6) Weigh the following materials according to their quantity:

[0013]

[0014] 7) Under nitrogen protection, first dissolving the pretreated soft segment monomer and 2,2-dimethylolpropionic acid in an organic solvent and stirring and mixing at a temperature range of 50-60° C. until a homogeneous phase is obtained; then adding a catalytic amount of dibutyltin dilaurate as a catalyst to the system, and slowly adding the hard segment monomer; then heating to 80° C. and stirring and reacting under a nitrogen atmosphere for 3-5 hours to obtain a polyurethane prepolymer;

[0015] 8) Cooling the polyurethane prepolymer of step 7) to 60° C., then adding bis(2-hydroxyethyl) disulfide and stirring to dissolve, and keeping the temperature to react for 3-5 hours; after the reaction system is uniform, slowly dripping triethylamine into the reaction solution and stirring for 1-2 hours;

[0016] 9) lowering the temperature of the reaction solution obtained in step 8) to 6-10° C. and slowly adding 5-6 parts of deionized water dropwise while stirring to obtain a light blue polyurethane dispersion;

[0017] 10) According to the mass ratio of the sulfonated cellulose nanocrystals to polyurethane of 0.4-2.3:1, the sulfonated cellulose nanocrystal suspension prepared in step 5) and the polyurethane dispersion prepared in step 9) are mixed at room temperature, stirred and mixed uniformly at room temperature for 1-3 hours, and then ultrasonicated for 3-5 minutes to obtain a stable sulfonated cellulose nanocrystal dispersion; the sulfonated cellulose nanocrystal dispersion is poured into a polytetrafluoroethylene mold and allowed to stand and dry at room temperature for 3-5 days to obtain the self-healing flexible photonic crystal.

[0018] The present invention adopts the above-mentioned preparation method, which has the advantages of simple operation, mild reaction conditions, low cost, high production efficiency and suitability for large-scale production.

[0019] Because 98% concentrated sulfuric acid is too acidic, it can over-hydrolyze microcrystalline cellulose, destroying its crystalline regions. It also hinders the introduction of sulfonic acid groups onto the cellulose surface, affecting the dispersibility of sulfonated cellulose nanocrystals in the solvent. Therefore, the present invention first dilutes 98% sulfuric acid with water to 64% by weight as the hydrolysis solution. The 64% sulfuric acid protonates the hydroxyl groups in the microcrystalline cellulose molecules, catalyzing their reactivity and making the β-1,4-glycosidic bonds in the amorphous regions of the microcrystalline cellulose more susceptible to cleavage. The amorphous regions are hydrolyzed by sulfuric acid, while the crystalline regions of the microcrystalline cellulose are relatively intact due to their high chemical stability in 64% sulfuric acid, ultimately forming nanocrystals of the microcrystalline cellulose. During the sulfuric acid hydrolysis process, the hydroxyl groups on the microcrystalline cellulose molecules also undergo a sulfonation reaction with the sulfuric acid, forming sulfonic acid groups, ultimately producing sulfonated cellulose nanocrystals. The introduction of sulfonic acid groups increases the surface charge of the cellulose nanocrystals, improving their dispersibility and uniformity in the dispersant, resulting in a more vibrant and uniform color for the resulting photonic crystals.

[0020] The sulfonated cellulose nanocrystals obtained above can spontaneously arrange into a highly ordered chiral nematic liquid crystal structure, forming a periodic structure with photonic bandgap characteristics. When the sulfonated cellulose nanocrystal dispersion reaches a certain critical concentration, the rod-shaped colloidal particles of the sulfonated cellulose nanocrystals are driven by entropy to form a liquid crystal phase. Due to their high aspect ratio and high surface charge characteristics, the sulfonated cellulose nanocrystals undergo anisotropic phase separation when the critical concentration is exceeded in the aqueous phase, self-assembling into a left-handed chiral nematic structure, which is maintained after drying. The periodic structure, that is, the pitch, can be controlled by adjusting factors such as the concentration of the sulfonated cellulose nanocrystal suspension, pH value, temperature, ionic strength, and external field interference to influence the photonic bandgap characteristics of the photonic crystal and achieve precise control of different colors.

[0021] The rigid rod-like structure and surface-active groups of the sulfonic acid cellulose nanocrystals prepared by this method enhance their interfacial bonding with the polyurethane matrix. The sulfonic acid groups interact with dynamic bond polymers (such as amino groups in polyurethane) through ionic or hydrogen bonds, enabling rapid bond reconstruction at damaged interfaces, enabling self-repair of damaged surfaces and maintaining the structural integrity of the photonic crystal.

[0022] Furthermore, the hard segment monomer is one of the following: hexamethylene isocyanate or dicyclohexylmethane diisocyanate. Isocyanate, as a hard segment, affects the stiffness and strength of polyurethane. Polyurethanes prepared from aromatic isocyanates with rigid aromatic rings have stronger hard segment cohesion than aliphatic isocyanate-based polyurethanes, resulting in higher tensile strength. However, they are easily degraded and damaged by ultraviolet light, and are prone to yellowing, affecting the optical properties and lifespan of the photonic crystal material. Hexamethylene isocyanate or dicyclohexylmethane diisocyanate are aliphatic, and the polyurethanes prepared are less prone to yellowing and more flexible. As a result, the prepared flexible photonic crystal film will not have impurity colors, is less likely to affect the optical properties of the photonic crystal material, and has better flexibility, broadening its application scenarios.

[0023] Furthermore, the soft segment monomer is one of the following: polytetrahydrofuran with a molecular weight of 2000, polycaprolactone with a molecular weight of 2000, or polymethylsiloxane with a molecular weight of 2000. The molecular weights of the soft segment monomers in the present invention are all number average molecular weights. Polytetrahydrofuran, polycaprolactone, and polymethylsiloxane are polyols that can be polymerized with isocyanates to form polyurethanes, and the strength of the synthesized polyurethane decreases with the increase of the molecular weight of the polyether polyol, but the flexibility and elongation increase accordingly. That is, if a polyol with a molecular weight that is too high is used as the soft segment monomer, the strength of the prepared flexible photonic crystal film is improved, but the flexibility is reduced, and the self-healing effect is reduced. If a polyol with a molecular weight that is too low is used as the soft segment monomer, the strength of the prepared flexible photonic crystal film is reduced, but the flexibility is increased, and the self-healing effect is improved. In order to take into account the strength, flexibility, and self-healing effect of the prepared flexible photonic crystal film, the present invention preferably uses a polyol with a molecular weight of 2000.

[0024] Furthermore, the bis(2-hydroxyethyl) disulfide is a chain extender. The two terminal hydroxyl groups in the bis(2-hydroxyethyl) disulfide react with the isocyanate groups in the prepolymer to form a carbamate bond, extending the polymer chain and introducing a disulfide bond, becoming part of the hard segment. The dynamic disulfide bonds in the bis(2-hydroxyethyl) disulfide can achieve dynamic crosslinking at a lower temperature. At the same time, the NH in the polyurethane and the OH in the sulfonic acid cellulose nanocrystals can form hydrogen bonds. Therefore, the photonic crystal material of the present invention contains dynamic disulfide bonds and hydrogen bonds, which can simultaneously improve the mechanical strength and self-healing properties of the material.

[0025] Furthermore, the 2,2-dimethylolpropionic acid is a hydrophilic chain extender. The two hydroxyl groups of the 2,2-dimethylolpropionic acid react with isocyanate groups and are directly embedded in the polyurethane backbone. The carboxyl groups of the 2,2-dimethylolpropionic acid react with the neutralizing agent triethylamine to form carboxylates. The carboxylate ions impart strong hydrophilicity to the polyurethane chain, allowing the polyurethane to be emulsified and dispersed in water, facilitating the uniform dispersion of the polyurethane and sulfonic acid fiber nanocrystals in water.

[0026] Furthermore, the triethylamine is a neutralizing agent.

[0027] Furthermore, the centrifugal speed in step 3) is 6000-10000 r / min.

[0028] Furthermore, the molecular cutoff of the dialysis bag used in step 4) is 8000-14000Da or 12000-14000Da.

[0029] Furthermore, the pretreatment of the soft segment monomer and 2,2-dimethylolpropionic acid in step 7) is as follows: drying the soft segment monomer or 2,2-dimethylolpropionic acid under reduced pressure and vacuum at 80° C. to remove moisture.

[0030] Furthermore, the stirring speed in step 2) is 500-700 r / min, the stirring speed in step 7) is 200-400 r / min, the stirring speed in step 8) is 200-400 r / min, and the stirring speed in step 9) is 500-600 r / min.

[0031] Furthermore, the organic solvent in step 7) is one of the following: acetone, N,N-dimethylformamide.

[0032] The present invention also discloses the self-repairing flexible photonic crystal material prepared by the above-mentioned preparation method, which includes sulfonated cellulose nanocrystals and a polyurethane matrix. The sulfonated cellulose nanocrystals are dispersed in the polyurethane matrix as a photonic crystal skeleton, and the polyurethane matrix serves as a filler for the sulfonated cellulose nanocrystal skeleton. The mass ratio of the sulfonated cellulose nanocrystals to the polyurethane is 0.4-2.3:1.

[0033] The self-repairing flexible photonic crystal material prepared by the present invention has good optical properties, bright, vivid and uniform colors, and the structural color of the photonic crystal can be precisely controlled. By adjusting the solid mass ratio of sulfonate cellulose nanocrystals and polyurethane, the self-repairing flexible photonic crystal can present a series of colors covering the entire visible spectrum, including indigo, blue, green, yellow, orange and red.

[0034] The self-healing flexible photonic crystal material prepared by the present invention has a tensile strength of over 43.93 MPa, and after self-healing experiments, the tensile strength remains above 39.08 MPa. Therefore, the self-healing flexible photonic crystal material of the present invention retains the excellent optical properties of photonic crystals while adding the high-strength mechanical properties and self-healing properties of polyurethane materials. This can overcome the damage caused by cracking and scratching during use of the flexible photonic crystal material and extend the material's service life.

[0035] The beneficial effects of the present invention are: 1. The self-repairing flexible photonic crystal material prepared by the present invention has excellent optical properties on the one hand, and on the other hand, it gives the material excellent mechanical properties, self-repairing properties and processability; 2. The preparation method of the present invention has a simple process, mild reaction conditions, low cost, high production efficiency, and is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 These are photos of materials for Examples 1 to 5 and Comparative Example 2;

[0037] Figure 2 Fourier transform infrared spectra of the self-repairing flexible photonic crystal materials prepared in Examples 1 to 6. DETAILED DESCRIPTION

[0038] In order to explain the technical content, structural features, achieved objectives and effects of the technical solution in detail, the following is a detailed description in conjunction with specific embodiments and accompanying drawings.

[0039] Example 1: A method for preparing a self-repairing flexible photonic crystal material

[0040] A self-repairing flexible photonic crystal material comprises sulfonated cellulose nanocrystals and a polyurethane matrix, wherein the sulfonated cellulose nanocrystals are dispersed in the polyurethane matrix as a photonic crystal skeleton, and the polyurethane serves as a filler for the sulfonated cellulose nanocrystal skeleton, wherein the solid mass ratio of the sulfonated cellulose nanocrystals to the polyurethane is 2.3:1.

[0041] The preparation method comprises the following steps:

[0042] 1) Weigh the following raw materials according to their amounts:

[0043] 0.6 parts of microcrystalline cellulose;

[0044] 8.55 parts of 98wt% sulfuric acid;

[0045] 2) Adding an appropriate amount of deionized water to 8.55 mol of 98 wt % sulfuric acid to dilute it to 64 wt %, heating the mixture to 45° C., adding 0.6 mol of microcrystalline cellulose, and stirring at 610 rpm for 1 hour to obtain a mixture of sulfonated cellulose nanocrystals and sulfuric acid. The mixture is poured into 10 times the volume of deionized water to quench the reaction, and the quenched mixture is allowed to stand for 24 hours;

[0046] 3) taking the lower milky white suspension phase after standing, centrifuging it at 10° C. and 8000 r / min to remove residual sulfuric acid, and then centrifuging and washing it five times by adding deionized water continuously until the upper suspension of the centrifuge shows a light blue characteristic, taking the supernatant after centrifugation and mixing it with the precipitate to uniformly disperse the sulfonated cellulose nanocrystals in the deionized water to obtain an aqueous suspension of sulfonated cellulose nanocrystals;

[0047] 4) placing the obtained cellulose sulfonate nanocrystal suspension into a dialysis bag (with a cutoff of 12,000-14,000 Da) and dialyzing the suspension in deionized water for 5 days until the pH stabilizes, thereby obtaining an aqueous dispersion of cellulose sulfonate nanocrystals;

[0048] 5) The dispersion in step 4) was placed in a 50-60° C. oven and concentrated for 6 days to adjust its mass fraction to 7 wt %. Sodium hydroxide solution was added to adjust its pH to 7.

[0049] 6) Weigh the following materials according to their quantity:

[0050]

[0051] 7) Under nitrogen, 15 mmol of pretreated polytetrahydrofuran (molecular weight 2000) and 20 mmol of 2,2-dimethylolpropionic acid were dissolved in 681 parts of acetone and stirred at 55°C and 200 rpm until homogeneous. 0.3 mmol of dibutyltin dilaurate was then introduced into the system as a catalyst, and 70 mmol of hexamethylene isocyanate was slowly added. The reaction system temperature was adjusted to 80°C and mechanically stirred at 200 rpm for 3 hours under continuous nitrogen flow to obtain a polyurethane prepolymer.

[0052] 8) Cool the system described in step 7) to 60°C, then add 15 mmol of bis(2-hydroxyethyl) disulfide and stir to dissolve. The mixture is allowed to react at this constant temperature for 3 hours. Once the mixture is homogenized, slowly add 0.3 mmol of triethylamine dropwise to the mixture at a constant rate, stirring at 200 rpm for 1 hour.

[0053] 9) The temperature of the system obtained in step 8) was lowered to 8° C., and 5 mol of deionized water was added dropwise at a rate of 1 drop / second while stirring at a speed of 550 r / min to prepare a 30 wt % light blue polyurethane dispersion;

[0054] 10) 10g of the sulfonated cellulose nanocrystal suspension obtained in step 5) and 1g of the polyurethane dispersion obtained in step 9) were mixed at room temperature, stirred at room temperature for 2 hours, and sonicated for 3 minutes to produce a stable sulfonated cellulose nanocrystal dispersion. The sulfonated cellulose nanocrystal dispersion was poured into a polytetrafluoroethylene mold and allowed to dry at room temperature for 3 days to produce a self-healing flexible photonic crystal material.

[0055] Example 2: A method for preparing a self-repairing flexible photonic crystal material

[0056] A self-repairing flexible photonic crystal material comprises sulfonated cellulose nanocrystals and a polyurethane matrix, wherein the sulfonated cellulose nanocrystals are dispersed in the polyurethane matrix as a photonic crystal skeleton, and the polyurethane serves as a filler for the sulfonated cellulose nanocrystal skeleton, wherein the solid mass ratio of the sulfonated cellulose nanocrystals to the polyurethane is 1.5:1.

[0057] The preparation method comprises the following steps:

[0058] 1) Weigh the following raw materials according to their amounts:

[0059] 0.6 parts of microcrystalline cellulose;

[0060] 8.55 parts of 98wt% sulfuric acid;

[0061] 2) Adding an appropriate amount of deionized water to 8.55 mol of 98 wt % sulfuric acid to dilute it to 64 wt %, heating the mixture to 45° C., adding 0.6 mol of microcrystalline cellulose, and stirring at 610 rpm for 1 hour to obtain a mixture of sulfonated cellulose nanocrystals and sulfuric acid. The mixture is poured into 10 times the volume of deionized water to quench the reaction, and the quenched mixture is allowed to stand for 24 hours;

[0062] 3) taking the lower milky white suspension phase after standing, centrifuging it at 10° C. and 8000 r / min to remove residual sulfuric acid, and then centrifuging and washing it five times by adding deionized water continuously until the upper suspension of the centrifuge shows a light blue characteristic, taking the supernatant after centrifugation and mixing it with the precipitate to uniformly disperse the sulfonated cellulose nanocrystals in the deionized water to obtain an aqueous suspension of sulfonated cellulose nanocrystals;

[0063] 4) placing the obtained cellulose sulfonate nanocrystal suspension into a dialysis bag (with a cutoff of 8000-14000 Da) and dialyzing it in deionized water for 5 days until the pH stabilizes, thereby obtaining an aqueous dispersion of cellulose sulfonate nanocrystals;

[0064] 5) The dispersion in step 4) was placed in a 50-60° C. oven and concentrated for 6 days to adjust its mass fraction to 7 wt %. Sodium hydroxide solution was added to adjust its pH to 7.

[0065] 6) Weigh the following materials according to their quantity:

[0066]

[0067] 7) Under nitrogen, 15 mmol of pretreated polycaprolactone (molecular weight 2000) and 20 mmol of 2,2-dimethylolpropionic acid were dissolved in 681 parts of acetone and stirred at 55°C and 200 rpm until homogeneous. 0.3 mmol of dibutyltin dilaurate was then introduced into the system as a catalyst, and 70 mmol of dicycloethylmethane diisocyanate was slowly added. The reaction system temperature was adjusted to 80°C and mechanically stirred at 200 rpm for 3 hours under continuous nitrogen flow to obtain a polyurethane prepolymer.

[0068] 8) Cool the system described in step 7) to 60°C, then add 15 mmol of bis(2-hydroxyethyl) disulfide and stir to dissolve. The mixture is allowed to react at this constant temperature for 3 hours. Once the mixture is homogenized, slowly add 0.3 mmol of triethylamine dropwise to the mixture at a constant rate, stirring at 200 rpm for 1 hour.

[0069] 9) The temperature of the system obtained in step 8) was lowered to 8° C., and 6 mol of deionized water was added dropwise at a rate of 1 drop / second under stirring at a speed of 550 r / min to prepare a 30 wt % light blue polyurethane dispersion;

[0070] 10) 9.6 g of the sulfonated cellulose nanocrystal suspension obtained in step 5) and 1.5 g of the polyurethane dispersion obtained in step 9) were mixed at room temperature, stirred at room temperature for 2 hours, and sonicated for 3 minutes to produce a stable sulfonated cellulose nanocrystal dispersion. The sulfonated cellulose nanocrystal dispersion was poured into a polytetrafluoroethylene mold and allowed to dry at room temperature for 3 days to produce a self-healing flexible photonic crystal material.

[0071] Example 3: A method for preparing a self-repairing flexible photonic crystal material

[0072] A self-repairing flexible photonic crystal material comprises sulfonated cellulose nanocrystals and a polyurethane matrix, wherein the sulfonated cellulose nanocrystals are dispersed in the polyurethane matrix as a photonic crystal skeleton, and the polyurethane serves as a filler for the sulfonated cellulose nanocrystal skeleton, wherein the solid mass ratio of the sulfonated cellulose nanocrystals to the polyurethane is 1:1.

[0073] The preparation method comprises the following steps:

[0074] 1) Weigh the following raw materials according to their amounts:

[0075] 0.6 parts of microcrystalline cellulose;

[0076] 8.55 parts of 98wt% sulfuric acid;

[0077] 2) Adding an appropriate amount of deionized water to 8.55 mol of 98 wt % sulfuric acid to dilute it to 64 wt %, heating the mixture to 45° C., adding 0.6 mol of microcrystalline cellulose, and stirring at 610 rpm for 1 hour to obtain a mixture of sulfonated cellulose nanocrystals and sulfuric acid. The mixture is poured into 10 times the volume of deionized water to quench the reaction, and the quenched mixture is allowed to stand for 24 hours;

[0078] 3) taking the lower milky white suspension phase after standing, centrifuging it at 10° C. and 8000 r / min to remove residual sulfuric acid, and then centrifuging and washing it five times by adding deionized water continuously until the upper suspension of the centrifuge shows a light blue characteristic, taking the supernatant after centrifugation and mixing it with the precipitate to uniformly disperse the sulfonated cellulose nanocrystals in the deionized water to obtain an aqueous suspension of sulfonated cellulose nanocrystals;

[0079] 4) placing the obtained cellulose sulfonate nanocrystal suspension into a dialysis bag (with a cutoff of 8000-14000 Da) and dialyzing it in deionized water for 5 days until the pH stabilizes, thereby obtaining an aqueous dispersion of cellulose sulfonate nanocrystals;

[0080] 5) The dispersion in step 4) was placed in a 50-60° C. oven and concentrated for 6 days to adjust its mass fraction to 7 wt %. Sodium hydroxide solution was added to adjust its pH to 7.

[0081] 6) Weigh the following materials according to their quantity:

[0082]

[0083] 7) Under nitrogen, 15 mmol of pretreated polymethylsiloxane (molecular weight 2000) and 20 mmol of 2,2-dimethylolpropionic acid were dissolved in 681 parts of acetone and stirred at 55°C and 200 rpm until homogeneous. 0.3 mmol of dibutyltin dilaurate was then introduced into the system as a catalyst, and 70 mmol of hexamethylene isocyanate was slowly added. The reaction system temperature was adjusted to 80°C and mechanically stirred at 200 rpm for 3 hours under continuous nitrogen flow to obtain a polyurethane prepolymer.

[0084] 8) Cool the system described in step 7) to 40°C, then add 20 mmol of bis(2-hydroxyethyl) disulfide and stir to dissolve. The mixture is allowed to react at this constant temperature for 5 hours. Once the mixture is homogenized, slowly add 0.3 mmol of triethylamine dropwise to the mixture at a constant rate, stirring at 400 rpm for 1 hour.

[0085] 9) The temperature of the system obtained in step 8) was lowered to 6° C., and 6 mol of deionized water was added dropwise at a rate of 1 drop / second while stirring at 600 r / min to produce a 30 wt % light blue polyurethane dispersion;

[0086] 10) 8.6 g of the sulfonated cellulose nanocrystal suspension obtained in step 5) and 2 g of the polyurethane dispersion obtained in step 9) were mixed at room temperature, stirred at room temperature for 2 hours, and sonicated for 3 minutes to produce a stable sulfonated cellulose nanocrystal dispersion. The sulfonated cellulose nanocrystal dispersion was poured into a polytetrafluoroethylene mold and allowed to dry at room temperature for 3 days to produce a self-healing flexible photonic crystal material.

[0087] Example 4: A method for preparing a self-repairing flexible photonic crystal material

[0088] A self-repairing flexible photonic crystal material comprises sulfonated cellulose nanocrystals and a polyurethane matrix, wherein the sulfonated cellulose nanocrystals are dispersed in the polyurethane matrix as a photonic crystal skeleton, and the polyurethane serves as a filler for the sulfonated cellulose nanocrystal skeleton, wherein the solid mass ratio of the sulfonated cellulose nanocrystals to the polyurethane is 0.7:1.

[0089] The preparation method comprises the following steps:

[0090] 1) Weigh the following raw materials according to their amounts:

[0091] 0.6 parts of microcrystalline cellulose;

[0092] 8.55 parts of 98wt% sulfuric acid;

[0093] 2) Adding an appropriate amount of deionized water to 8.55 mol of 98 wt % sulfuric acid to dilute it to 64 wt %, heating the mixture to 45° C., adding 0.6 mol of microcrystalline cellulose, and stirring at 500 rpm for 2 hours to obtain a mixture of sulfonated cellulose nanocrystals and sulfuric acid. The mixture is poured into 10 times the volume of deionized water to quench the reaction, and the quenched mixture is allowed to stand for 24 hours;

[0094] 3) taking the lower milky white suspension phase after standing, centrifuging it at 4°C at a speed of 8000 r / min to remove residual sulfuric acid, and then continuously adding deionized water to wash it by centrifugation for 5 times until the upper suspension of the centrifuge shows a light blue characteristic, taking the supernatant after centrifugation and mixing it with the precipitate to uniformly disperse the sulfonated cellulose nanocrystals in the deionized water to obtain an aqueous suspension of sulfonated cellulose nanocrystals;

[0095] 4) placing the obtained cellulose sulfonate nanocrystal suspension into a dialysis bag (with a cutoff of 12,000-14,000 Da) and dialyzing the suspension in deionized water for 5 days until the pH stabilizes, thereby obtaining an aqueous dispersion of cellulose sulfonate nanocrystals;

[0096] 5) The dispersion in step 4) was placed in a 50-60° C. oven and concentrated for 5 days to adjust its mass fraction to 5 wt %. Sodium hydroxide solution was added to adjust its pH to 7.

[0097] 6) Weigh the following materials according to their quantity:

[0098]

[0099]

[0100] 7) Under nitrogen, 15 mmol of pretreated polytetrahydrofuran (molecular weight 2000) and 20 mmol of 2,2-dimethylolpropionic acid were dissolved in 720 parts of acetone and stirred at 55°C and 200 rpm until homogeneous. 0.3 mmol of dibutyltin dilaurate was then introduced into the system as a catalyst, and 70 mmol of hexamethylene isocyanate was slowly added. The reaction system temperature was adjusted to 80°C and mechanically stirred at 200 rpm for 5 hours under continuous nitrogen flow to obtain a polyurethane prepolymer.

[0101] 8) Cool the system described in step 7) to 60°C, then add 15 mmol of bis(2-hydroxyethyl) disulfide and stir to dissolve. The mixture is allowed to react at this constant temperature for 3 hours. Once the mixture is homogenized, slowly add 0.3 mmol of triethylamine dropwise at a constant rate and stir at 200 rpm for 2 hours.

[0102] 9) The temperature of the system obtained in step 8) was lowered to 10° C., and 6 mol of deionized water was added dropwise at a rate of 1 drop / second while stirring at a speed of 500 r / min to prepare a 30 wt % light blue polyurethane dispersion;

[0103] 10) 8.9 g of the sulfonated cellulose nanocrystal suspension obtained in step 5) and 2.1 g of the polyurethane dispersion obtained in step 9) were mixed at room temperature, stirred at room temperature for 1 hour, and sonicated for 5 minutes to produce a stable sulfonated cellulose nanocrystal dispersion. The sulfonated cellulose nanocrystal dispersion was poured into a polytetrafluoroethylene mold and allowed to dry at room temperature for 3 days to produce a self-healing flexible photonic crystal material.

[0104] Example 5: A method for preparing a self-repairing flexible photonic crystal material

[0105] A self-repairing flexible photonic crystal material comprises sulfonated cellulose nanocrystals and a polyurethane matrix, wherein the sulfonated cellulose nanocrystals are dispersed in the polyurethane matrix as a photonic crystal skeleton, and the polyurethane serves as a filler for the sulfonated cellulose nanocrystal skeleton, wherein the solid mass ratio of the sulfonated cellulose nanocrystals to the polyurethane is 0.4:1.

[0106] The preparation method comprises the following steps:

[0107] 1) Weigh the following raw materials according to their amounts:

[0108] 0.6 parts of microcrystalline cellulose;

[0109] 8.55 parts of 98wt% sulfuric acid;

[0110] 2) Adding an appropriate amount of deionized water to 8.55 mol of 98 wt % sulfuric acid to dilute it to 64 wt %, heating the mixture to 50° C., adding 0.6 mol of microcrystalline cellulose, and stirring at 610 rpm for 1 hour to obtain a mixture of sulfonated cellulose nanocrystals and sulfuric acid. The mixture is poured into 8 times the volume of deionized water to quench the reaction, and the quenched mixture is allowed to stand for 24 hours;

[0111] 3) taking the lower milky white suspension phase after standing, centrifuging it at 8°C and 10,000 r / min to remove residual sulfuric acid, and then centrifuging and washing it five times by adding deionized water continuously until the upper suspension of the centrifuge shows a light blue characteristic, taking the supernatant after centrifugation and mixing it with the precipitate to uniformly disperse the sulfonated cellulose nanocrystals in the deionized water to obtain an aqueous suspension of sulfonated cellulose nanocrystals;

[0112] 4) placing the obtained cellulose sulfonate nanocrystal suspension into a dialysis bag (cut-off of 8000-14000 Da) and dialyzing it in deionized water for 6 days until the pH stabilizes, thereby obtaining an aqueous dispersion of cellulose sulfonate nanocrystals;

[0113] 5) The dispersion liquid of step 4) was placed in a 50-60° C. oven and concentrated for 5 days to adjust its mass fraction to 7 wt %, and sodium hydroxide solution was added to adjust its pH to 7.

[0114] 6) Weigh the following materials according to their quantity:

[0115]

[0116] 7) Under nitrogen, 15 mmol of pretreated polytetrahydrofuran (molecular weight 2000) and 20 mmol of 2,2-dimethylolpropionic acid were dissolved in 681 parts of acetone and stirred at 50°C and 400 rpm until homogeneous. 0.3 mmol of dibutyltin dilaurate was then introduced into the system as a catalyst, and 70 mmol of hexamethylene isocyanate was slowly added. The reaction system temperature was adjusted to 80°C and mechanically stirred at 400 rpm for 3 hours under continuous nitrogen flow to obtain a polyurethane prepolymer.

[0117] 8) Cool the system described in step 7) to 60°C, then add 15 mmol of bis(2-hydroxyethyl) disulfide and stir to dissolve. The mixture is allowed to react at this constant temperature for 3 hours. Once the mixture is homogenized, slowly add 0.3 mmol of triethylamine dropwise to the mixture at a constant rate, stirring at 200 rpm for 1 hour.

[0118] 9) The temperature of the system obtained in step 8) was lowered to 8° C., and 6 mol of deionized water was added dropwise at a rate of 1 drop / second under stirring at a speed of 550 r / min to prepare a 30 wt % light blue polyurethane dispersion;

[0119] 10) 6.8 g of the sulfonated cellulose nanocrystal suspension obtained in step 5) and 4 g of the polyurethane dispersion obtained in step 9) were mixed at room temperature, stirred at room temperature for 3 hours, and sonicated for 3 minutes to produce a stable sulfonated cellulose nanocrystal dispersion. The sulfonated cellulose nanocrystal dispersion was poured into a polytetrafluoroethylene mold and allowed to dry at room temperature for 4 days to produce a self-healing flexible photonic crystal material.

[0120] Example 6: A method for preparing a self-repairing flexible photonic crystal material

[0121] A self-repairing flexible photonic crystal material comprises sulfonated cellulose nanocrystals and a polyurethane matrix, wherein the sulfonated cellulose nanocrystals are dispersed in the polyurethane matrix as a photonic crystal skeleton, and the polyurethane serves as a filler for the sulfonated cellulose nanocrystal skeleton, wherein the solid mass ratio of the sulfonated cellulose nanocrystals to the polyurethane is 2.3:1.

[0122] The preparation method comprises the following steps:

[0123] 1) Weigh the following raw materials according to their amounts:

[0124] 0.6 parts of microcrystalline cellulose;

[0125] 8.55 parts of 98wt% sulfuric acid;

[0126] 2) Adding an appropriate amount of deionized water to 8.55 mol of 98 wt % sulfuric acid to dilute it to 64 wt %, heating the mixture to 40° C., adding 0.6 mol of microcrystalline cellulose, and stirring at 700 rpm for 2 hours to obtain a mixture of sulfonated cellulose nanocrystals and sulfuric acid. The mixture is poured into 10 times the volume of deionized water to quench the reaction, and the quenched mixture is allowed to stand for 24 hours;

[0127] 3) taking the lower milky white suspension phase after standing, centrifuging it at 10° C. and 6000 r / min to remove residual sulfuric acid, and then centrifuging and washing it with deionized water for 5 times until the upper suspension of the centrifuge shows a light blue characteristic, taking the supernatant after centrifugation and mixing it with the precipitate to uniformly disperse the sulfonated cellulose nanocrystals in the deionized water to obtain an aqueous suspension of sulfonated cellulose nanocrystals;

[0128] 4) placing the obtained cellulose sulfonate nanocrystal suspension into a dialysis bag (with a cutoff of 12,000-14,000 Da) and dialyzing it in deionized water for 7 days until the pH stabilizes, thereby obtaining an aqueous dispersion of cellulose sulfonate nanocrystals;

[0129] 5) The dispersion in step 4) was placed in a 50-60° C. oven and concentrated for 6 days to adjust its mass fraction to 7 wt %. Sodium hydroxide solution was added to adjust its pH to 7.

[0130] 6) Weigh the following materials according to their quantity:

[0131]

[0132] 7) Under nitrogen, 15 mmol of pretreated polytetrahydrofuran (molecular weight 2000) and 20 mmol of 2,2-dimethylolpropionic acid were dissolved in 648 parts of N,N-dimethylformamide and stirred at 60°C and 300 rpm until homogeneous. 0.3 mmol of dibutyltin dilaurate was then introduced into the system as a catalyst, and 70 mmol of hexamethylene isocyanate was slowly added. The reaction system temperature was adjusted to 80°C and mechanically stirred at 300 rpm for 3 hours under continuous nitrogen flow to obtain a polyurethane prepolymer.

[0133] 8) Cool the system described in step 7) to 60°C, then add 15 mmol of bis(2-hydroxyethyl) disulfide and stir to dissolve. The mixture is allowed to react at a constant temperature for 3 hours. Once the mixture is homogenized, slowly add 0.45 mmol of triethylamine dropwise to the mixture at a constant rate, stirring at 200 rpm for 1 hour.

[0134] 9) The temperature of the system obtained in step 8) was lowered to 8° C., and 6 mol of deionized water was added dropwise at a rate of 1 drop / second under stirring at a speed of 550 r / min to prepare a 30 wt % light blue polyurethane dispersion;

[0135] 10) 10 g of the sulfonated cellulose nanocrystal suspension obtained in step 5) and 1 g of the polyurethane dispersion obtained in step 9) were mixed at room temperature, stirred at room temperature for 2 hours, and sonicated for 3 minutes to produce a stable sulfonated cellulose nanocrystal dispersion. The sulfonated cellulose nanocrystal dispersion was poured into a polytetrafluoroethylene mold and allowed to dry at room temperature for 4 days to produce a self-healing flexible photonic crystal material.

[0136] In each of the embodiments, the pretreatment of the soft segment monomer and 2,2-dimethylolpropionic acid in step 7) is: drying the soft segment monomer or 2,2-dimethylolpropionic acid under reduced pressure and vacuum at 80° C. to remove moisture.

[0137] Comparative Example 1

[0138] 1) Weigh the following raw materials according to their amounts:

[0139] 0.6 parts of microcrystalline cellulose;

[0140] 8.55 parts of 98wt% sulfuric acid;

[0141] 2) Adding an appropriate amount of deionized water to 8.55 mol of 98 wt % sulfuric acid to dilute it to 64 wt %, heating the mixture to 45° C., adding 0.6 mol of microcrystalline cellulose, and stirring at 610 rpm for 1 hour to obtain a mixture of sulfonated cellulose nanocrystals and sulfuric acid. The mixture is poured into 10 times the volume of deionized water to quench the reaction, and the quenched mixture is allowed to stand for 24 hours;

[0142] 3) taking the lower milky white suspension phase after standing, centrifuging it at 10° C. and 8000 r / min to remove residual sulfuric acid, and continuously adding deionized water for centrifugal washing, washing five times until the upper suspension of the centrifuged phase exhibits a light blue characteristic, until the upper supernatant of the centrifuged phase exhibits a light blue characteristic, taking the upper supernatant of the last centrifugation and the precipitate not dispersed in the upper supernatant of the last centrifugation and stirring evenly to uniformly disperse the sulfonated cellulose nanocrystals in the deionized water, thereby obtaining an aqueous suspension of sulfonated cellulose nanocrystals;

[0143] 4) placing the obtained cellulose sulfonate nanocrystal suspension into a dialysis bag and dialyzing it in deionized water for 5 days until the pH stabilizes, thereby obtaining an aqueous dispersion of cellulose sulfonate nanocrystals;

[0144] 5) placing the dispersion of step 4) in a 50-60° C. oven and concentrating for 6 days to adjust the mass fraction to 7 wt %;

[0145] 6) The dispersion obtained in step 5) was ultrasonically treated for 3 minutes to obtain an ultrasonic liquid. 3 g of the ultrasonic liquid was poured into a polytetrafluoroethylene mold and allowed to stand and dry at room temperature for 3 days to obtain a photonic crystal material.

[0146] Comparative Example 2

[0147] 1) Weigh the following raw materials according to their amounts:

[0148]

[0149] 2) Under nitrogen, 15 mmol of pretreated polytetrahydrofuran (molecular weight 2000) and 20 mmol of 2,2-dimethylolpropionic acid were dissolved in 681 parts of acetone and stirred at 55°C and 200 rpm until homogeneous. 0.3 mmol of dibutyltin dilaurate was then introduced into the system as a catalyst, and 70 mmol of hexamethylene isocyanate was slowly added. The reaction system temperature was adjusted to 80°C and mechanically stirred at 200 rpm for 3 hours under continuous nitrogen flow to obtain a polyurethane prepolymer.

[0150] 3) Cool the system from step 2) to 60°C, then add 15 mmol of bis(2-hydroxyethyl) disulfide and stir to dissolve. The reaction is continued at a constant temperature for 3 hours. Once the system is homogenized, slowly add 0.3 mmol of triethylamine dropwise to the system at a constant rate, stirring at 200 rpm for 1 hour.

[0151] 4) The temperature of the system obtained in step 3) was lowered to 8° C., and 6 mol of deionized water was added dropwise at a rate of 1 drop / second while stirring at a speed of 550 r / min to produce a 30 wt % light blue polyurethane dispersion;

[0152] 5) Take 3 g of the polyurethane dispersion obtained in step 4) and vacuum dry it in a polytetrafluoroethylene mold at 60° C. for 8 hours to obtain a self-healing polyurethane material.

[0153] The self-repairing flexible photonic crystal materials prepared in Examples 1 to 6 and the photonic crystal materials and polyurethane materials prepared in Comparative Examples 1-2 were subjected to various performance tests. The conditions for the various performance tests were as follows:

[0154] 1. Tensile test before and after self-repair: According to GB / T 528-2009, the specimens were cut into dumbbell-shaped specimens and the tensile strength and elongation at break were tested using a universal tensile testing machine at a speed of 100 mm / min. Each sample was measured three times and the average value was taken. A 2 mm deep crack was cut in the middle of the dumbbell-shaped specimen, placed in an 80°C thermostat for 6 hours, and then stored at 60°C for 24 hours. The repaired specimens were subjected to a tensile test, and the self-repair efficiency (SE) was calculated as follows:

[0155] SE=б2 / б1×100%

[0156] б2 is the tensile strength of the healed sample, and б1 is the tensile strength of the original sample.

[0157] According to the above detection method, the above detection was performed on the self-repairing flexible photonic crystal materials prepared in Examples 1 to 6 and the photonic crystal materials prepared in the comparative example. The specific monitoring data are shown in Table 1.

[0158] 2. Optical performance test: A DM6000B-M polarizing microscope (LAS 4.6.0 system) from Leica, Germany, was used to observe the structural color of the sample, and its optical properties were analyzed by comparing the structural color observed with the naked eye.

[0159] Table 1 Comparison of test data of products prepared in various embodiments

[0160]

[0161]

[0162] As shown in Table 1, the self-healing flexible photonic crystal material prepared by the present invention achieves a significant improvement in mechanical properties compared to Comparative Example 1 due to the addition of self-healing polyurethane. Compared to Comparative Example 2, the addition of sulfonic cellulose nanocrystals further enhances the mechanical strength of the present material, fully meeting the material's intended use. Furthermore, self-healing experiments show that the products prepared in Examples 1 through 6 all exhibit excellent self-healing efficiency, indicating that the self-healing flexible photonic crystal material prepared by the present invention possesses exceptional self-healing properties.

[0163] Therefore, the self-repairing flexible photonic crystal material of the present invention retains the mechanical properties and self-repairing properties of the self-repairing polyurethane material, can overcome the losses caused by friction and scratches during the use of the flexible photonic crystal material, and extend the service life of the material.

[0164] The photos of the materials prepared in Examples 1 to 5 and Comparative Example 2 are shown in Figure 1 As shown. Figure 1 As can be seen, the film prepared from the polyurethane without the addition of sulfonated cellulose nanocrystals in Comparative Example 2 is transparent. In Examples 1 to 5, increasing the polyurethane mass fraction yields a range of self-healing flexible photonic crystal materials covering the entire visible spectrum, including blue, green, yellow, orange, and red. This demonstrates that by manipulating the polyurethane mass fraction in the material, self-healing flexible photonic crystal materials with distinct and vivid structural colors can be precisely captured, providing a solid practical foundation for intelligent information encoding.

[0165] The infrared spectra of the self-repairing flexible photonic crystal materials prepared in Examples 1 to 6 are shown in FIG. Figure 2 .like Figure 2 As shown, the materials prepared in Examples 1 to 6 were -1 There is no signal at 2940 cm, indicating that the -NCO groups in the system have been completely reacted. -1 (CH asymmetric stretching vibration), 2853cm -1 (CH symmetric stretching vibration), 1700cm -1 (C=O stretching vibration) and 1103 cm -1 (COC stretching vibration) a characteristic peak appeared at 3200-3400cm -1 The broad peak in the range belongs to the NH stretching vibration, indicating that hydrogen bonds are formed between the NH of polyurethane and the OH of sulfonated cellulose nanocrystals in the sample.

[0166] It should be noted that although the above embodiments have been described herein, this does not limit the scope of patent protection of the present invention. Therefore, based on the innovative concept of the present invention, changes and modifications to the embodiments described herein, or equivalent structural or equivalent process transformations made using the contents of the present invention's specification and drawings, and direct or indirect application of the above technical solutions to other related technical fields, are all included in the scope of patent protection of the present invention.

Claims

1. A method for preparing a self-repairing flexible photonic crystal material, characterized in that: The following steps are involved: 1) Weigh the following raw materials according to their amounts: 0.6 parts of microcrystalline cellulose; 8.55 parts of 98wt% sulfuric acid; 2) diluting 98 wt % sulfuric acid to 64 wt % with water, heating to 40-50° C., adding microcrystalline cellulose, and stirring for at least 1 hour to obtain a mixture of sulfonated cellulose nanocrystals and sulfuric acid. The mixture is poured into at least 8 times the volume of deionized water to quench the reaction, and the quenched mixture is allowed to stand for separation; 3) taking the milky white suspension phase of the mixed solution from step 2) after standing, centrifuging it at 4-10° C. to remove excess sulfuric acid, and then centrifuging it with deionized water until the supernatant exhibits a light blue characteristic. The supernatant and the lower precipitate from the last centrifugation are mixed evenly to uniformly disperse the sulfonated cellulose nanocrystals in the deionized water, thereby obtaining an aqueous suspension of sulfonated cellulose nanocrystals. 4) placing the aqueous suspension of cellulose sulfonate nanocrystals obtained in step 3) into a dialysis bag and dialyzing it in deionized water for 5-7 days until the pH of the suspension remains stable, thereby obtaining an aqueous dispersion of cellulose sulfonate nanocrystals; 5) placing the aqueous dispersion of cellulose sulfonate nanocrystals in step 4) in a 50-60° C. oven for 5-6 days to concentrate the dispersion to 5-7 wt %, and then adding sodium hydroxide solution to adjust the pH of the dispersion to 7 to obtain a cellulose sulfonate nanocrystal suspension; 6) Weigh the following materials according to their quantity: 7) Under nitrogen protection, first dissolving the pretreated soft segment monomer and 2,2-dimethylolpropionic acid in an organic solvent and stirring and mixing at a temperature range of 50-60° C. until a homogeneous phase is obtained; then adding a catalytic amount of dibutyltin dilaurate as a catalyst to the system, and slowly adding the hard segment monomer; then heating to 80° C. and stirring and reacting under a nitrogen atmosphere for 3-5 hours to obtain a polyurethane prepolymer; 8) Cooling the polyurethane prepolymer of step 7) to 60° C., then adding bis(2-hydroxyethyl) disulfide and stirring to dissolve, and keeping the temperature to react for 3-5 hours; after the reaction system is uniform, slowly dripping triethylamine into the reaction solution and stirring for 1-2 hours; 9) lowering the temperature of the reaction solution obtained in step 8) to 6-10° C. and slowly adding 5-6 parts of deionized water dropwise while stirring to obtain a light blue polyurethane dispersion; 10) According to the mass ratio of the sulfonated cellulose nanocrystals to polyurethane of 0.4-2.3:1, the sulfonated cellulose nanocrystal suspension prepared in step 5) and the polyurethane dispersion prepared in step 9) are mixed at room temperature, stirred and mixed uniformly at room temperature for 1-3 hours, and then ultrasonicated for 3-5 minutes to obtain a stable sulfonated cellulose nanocrystal dispersion; the sulfonated cellulose nanocrystal dispersion is poured into a polytetrafluoroethylene mold and allowed to stand and dry at room temperature for 3-5 days to obtain the self-healing flexible photonic crystal.

2. The method for preparing the self-repairing flexible photonic crystal material according to claim 1, characterized in that: The hard segment monomer is one of the following: hexamethylene isocyanate or dicyclohexylmethane diisocyanate.

3. The method for preparing the self-repairing flexible photonic crystal material according to claim 1, characterized in that: The soft segment monomer is one of the following: polytetrahydrofuran with a molecular weight of 2000, polycaprolactone with a molecular weight of 2000 or polymethylsiloxane with a molecular weight of 2000.

4. The method for preparing the self-repairing flexible photonic crystal material according to claim 1, characterized in that: The triethylamine is a neutralizing agent, the bis(2-hydroxyethyl) disulfide is a chain extender, and the 2,2-dihydroxymethylpropionic acid is a hydrophilic chain extender.

5. The method for preparing the self-repairing flexible photonic crystal material according to claim 1, characterized in that: The centrifugal speed in step 3) is 6000-10000 r / min.

6. The method for preparing the self-repairing flexible photonic crystal material according to claim 1, characterized in that: The molecular cutoff of the dialysis bag used in step 4) is 8000-14000Da or 12000-14000Da.

7. The method for preparing the self-repairing flexible photonic crystal material according to claim 1, characterized in that: The pretreatment of the soft segment monomer and 2,2-dimethylol propionic acid in step 7) is as follows: the soft segment monomer or 2,2-dimethylol propionic acid is dried under reduced pressure and vacuum at 80° C. to remove moisture.

8. The method for preparing the self-repairing flexible photonic crystal material according to claim 1, characterized in that: The stirring speed in step 2) is 500-700 r / min, the stirring speed in step 7) is 200-400 r / min, the stirring speed in step 8) is 200-400 r / min, and the stirring speed in step 9) is 500-600 r / min.

9. The method for preparing the self-repairing flexible photonic crystal material according to claim 1, characterized in that: The organic solvent in step 7) is one of the following: acetone and N,N-dimethylformamide.

10. The self-repairing flexible photonic crystal material prepared by the preparation method according to any one of claims 1 to 9, characterized in that: The invention comprises sulfonic acid cellulose nanocrystals and a polyurethane matrix. The sulfonic acid cellulose nanocrystals are dispersed in the polyurethane matrix as a photonic crystal skeleton. The polyurethane matrix serves as a filler for the sulfonic acid cellulose nanocrystal skeleton. The mass ratio of the sulfonic acid cellulose nanocrystals to the polyurethane is 0.4-2.3:1.

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