Polyrotaxane, method for preparing the same, and mechanically color-changing material and application capable of responding to weak force in real time

Abstract

The present application belongs to the field of mechanical color-changing materials, and relates to a kind of polyrotaxane and its preparation method and mechanical color-changing material that can respond to weak force instantly and application.Polyrotaxane includes molecular ring and molecular shaft, molecular ring is provided with luminescent molecular group, and molecular shaft is provided with quencher molecular group;The luminescent molecule of the luminescent molecular group can be quenched;Each of the polyrotaxane provides two crosslinking sites, one of which is located on the molecular shaft, and the other is located on the molecular ring or luminescent molecular group.The present application synthesizes polyrotaxane with luminescent quencher on the molecular shaft and luminescent molecules on the molecular ring as crosslinking components, uses multi-arm polymer as matrix material to obtain reticular polymer material, and makes the material not luminescent in the relaxed state through the luminescent quencher on the molecular shaft, and the material changes color instantly due to the separation of the quencher and the luminescent molecules once the material is subjected to external force, and returns to the original color after the external force is removed.

Description

Technical Field

[0001] This invention belongs to the field of mechanical color-changing materials, specifically relating to a polyrotaxane, its preparation method, and a mechanical color-changing material that can respond instantly to weak forces and its applications. Background Technology

[0002] Polymers have been widely used, from simple rubber to high-performance plastics, due to their excellent designable properties. However, polymer products are inevitably subjected to mechanical forces during daily use, leading to irreversible changes in material properties. In addition to macroscopic damage, mechanical forces can also cause the breakage of individual chains, which can ultimately lead to failure due to fatigue, creep, or fracture. Therefore, an efficient and concise method is needed to detect stress and damage in materials.

[0003] Four mechanisms—changes in intermolecular interactions, changes in intramolecular conformation, the transition from a locally excited state to an intramolecular charge-transfer state, and intramolecular and intermolecular effects induced by hydrostatic pressure—can all induce material discoloration through changes in mechanical force. Mechanical discoloration makes it possible to visualize stress damage in materials. In typical mechanically discoloring materials, when polymers containing weakly covalent motifs are exposed to mechanical force, the covalent bonds break. The changes in optical properties during bond breakage can be used as signals to detect applied mechanical stress and strain. However, this mechanical discoloration is irreversible. Sometimes, materials need to be visualized in a reversible and highly sensitive manner to achieve stress and damage. Effective stress-sensing materials must respond to low deformation with detectable color changes, and these changes should be rapid and reversible upon force unloading. Summary of the Invention

[0004] The purpose of this invention is to solve the above-mentioned problems existing in the prior art, and to provide a polyrotaxane, its preparation method, and a mechanically color-changing material that can respond instantly to weak forces and its application. The polyrotaxane is a polyrotaxane with a luminescent quencher on the molecular axis and luminescent molecules on the molecular ring. It is used as a crosslinking component, and a multi-arm polymer is used as a polymer network precursor to crosslink and form an isotropic network polymer material. The luminescent quencher on the molecular axis makes the material non-luminescent in a relaxed state. Once the material is subjected to external force, the material changes color instantly due to the separation of the quencher and the luminescent molecules. After the external force is removed, the material returns to its original color.

[0005] To achieve the above objectives, a first aspect of the present invention provides a polyrotaxane comprising a molecular ring and a molecular axis, wherein the molecular ring has a luminescent molecular group and the molecular axis has a quencher molecular group; the quencher molecular group is capable of quenching the luminescence of the luminescent molecule; each of the polyrotaxanes provides two crosslinking sites, one of which is located on the molecular axis and the other is located on the molecular ring or on the luminescent molecular group.

[0006] A second aspect of the present invention provides a method for preparing the polyrotaxane, comprising the following steps:

[0007] (1) React luminescent molecules and molecular ring precursors to synthesize molecular rings with luminescent molecular groups;

[0008] (2) The quencher molecule reacts with the first part of the molecular axis, then the end is sealed, and the resulting product is self-assembled with the molecular ring with luminescent molecular groups obtained in step (1). The resulting product reacts with the second part of the molecular axis, and the end is sealed to synthesize the polyrotaxane.

[0009] A third aspect of the present invention provides a mechanically color-changing material that can respond instantly to weak forces, said material being a network polymer material comprising a multi-arm polymer as a matrix and the aforementioned polyrotaxane as a crosslinking component.

[0010] A fourth aspect of the present invention provides a method for preparing the aforementioned mechanically color-changing material capable of responding instantly to weak forces, the method comprising the following steps:

[0011] In the presence of a solvent, a multi-arm polymer, polyrotaxane, and a catalyst are reacted to obtain a mechanically color-changing material that can respond instantly to weak forces.

[0012] The fifth aspect of the present invention provides the application of the aforementioned polyrotaxane, or the aforementioned mechanically color-changing material that can respond instantly to weak forces, in the field of shape memory materials.

[0013] The beneficial effects of this invention are as follows: This invention uses polyrotaxane, which contains a luminescent quencher on its molecular axis and luminescent molecules on its molecular ring, as a crosslinking component, and a multi-arm polymer as the matrix material, to crosslink and form an isotropic network polymer material. The luminescent quencher on the molecular axis prevents the material from emitting light in a relaxed state. Once the material is subjected to external force, the quencher separates from the luminescent molecules, causing the material to change color instantaneously. After the external force is removed, the material returns to its original color.

[0014] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0015] Exemplary embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

[0016] Figure 1 The image shows the hydrogen NMR spectrum of the blue luminescent molecule in Example 1.

[0017] Figure 2 The image shows the hydrogen NMR spectrum of the yellow luminescent molecule in Example 4.

[0018] Figure 3The image shows the 1H NMR spectrum of BHEEEEN, the intermediate in the synthesis of crown ethers in Example 1.

[0019] Figure 4 A schematic diagram of the material's color-changing mechanism is shown.

[0020] Figure 5 The images show photographs of different luminescence intensities as the elongation of the P1 film changes in Embodiment 1 of the present invention. Detailed Implementation

[0021] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0022] To achieve the above objectives, a first aspect of the present invention provides a polyrotaxane comprising a molecular ring and a molecular axis, wherein the molecular ring has a luminescent molecular group and the molecular axis has a quencher molecular group; the quencher molecular group is capable of quenching the luminescence of the luminescent molecule; each of the polyrotaxanes provides two crosslinking sites, one of which is located on the molecular axis and the other is located on the molecular ring or on the luminescent molecular group.

[0023] According to the present invention, preferably, when the polyrotaxane is in a relaxed state, the quencher molecular group is close to the luminescent molecular group, and the luminescence of the luminescent molecule is quenched;

[0024] When the polyrotaxane is subjected to an external force, the quencher molecular groups move away from the luminescent molecular groups, and the luminescence of the luminescent molecules is restored.

[0025] According to the present invention, preferably, the molecular ring of the polyrotaxane is a crown ether;

[0026] The molecular axis of the polyrotaxane includes: a quencher molecular group, a first polymer chain and a second polymer chain respectively connecting the two ends of the quencher molecular group, and a first sterically hindered group and a second sterically hindered group respectively sealing the first polymer chain and the second polymer chain, wherein the first sterically hindered group provides a crosslinking site; the crosslinking site is preferably at least one of hydroxyl, amino and carboxyl groups.

[0027] According to the present invention, preferably, the monomer forming the crown ether is a single-arm sulfonated ethylene glycol; preferably, at least one of triethylene glycol monotoluenesulfonate, tetraethylene glycol monotoluenesulfonate, pentaethylene glycol monotoluenesulfonate and hexaethylene glycol monotoluenesulfonate.

[0028] According to the present invention, preferably, both the first polymer chain and the first polymer chain are polyethylene glycol-based segments;

[0029] The first steric hindrance end-capping agent is a steric hindrance molecule with two reactive groups; preferably, it is a steric hindrance molecule with two hydroxyl groups; more preferably, it is bis(p-tert-butylphenyl)bis(4-hydroxyphenyl)methane and / or 1,2-bis(4-hydroxyphenyl)-1,2-diphenylene;

[0030] The second steric hindrance end-capping agent is a steric hindrance molecule with a reactive group; preferably, it is a steric hindrance molecule with a hydroxyl group; more preferably, it is at least one of tris(p-tert-butylphenyl)(4-hydroxyphenyl)methane, 4-[bis[4-(1,1-dimethylethyl)phenyl][4-(1-methylethyl)phenyl]methyl]phenol, 4-[bis[4-(1,1-dimethylethyl)phenyl](4-ethylphenyl)methyl]phenol, bis(p-tert-butylphenyl)bis(4-hydroxyphenyl)methane, and 1,2-bis(4-hydroxyphenyl)-1,2-diphenylphenyl.

[0031] According to the present invention, preferably, the luminescent molecule is a yellow luminescent molecule and / or a blue luminescent molecule; the yellow luminescent molecule is preferably at least one of 4,7-dibromo-2,1,3-benzothiadiazole, 3,10-dibromoperylene, and dibromofluorescein; and the blue luminescent molecule is preferably at least one of 1,6-dibromopyrene, 2,6-dibromoanthracene, and 1,8-dibromoanthracene.

[0032] The quencher molecule is naphthalene-1,4,5,8-dianhydride.

[0033] According to a specific embodiment of the present invention, naphthalene-1,4,5,8-tetracarboxylic anhydride and diethylene glycolamine are reacted, and the ends are modified to azide to synthesize a quencher molecule. Subsequently, sterically hindered molecules with one and two hydroxyl groups are reacted with propynyl-tetraethylene glycol-methanesulfonate, respectively, and the products are then reacted with the quencher molecule to synthesize a one-end-capped molecular axis.

[0034] According to the present invention, preferably, the luminescent molecule is connected to the remaining components of the molecular ring of the polyrotaxane via a click chemistry reaction;

[0035] The quencher molecule is connected to the remaining components of the molecular axis of the polyrotaxane via a click chemistry reaction.

[0036] A second aspect of the present invention provides a method for preparing the polyrotaxane, comprising the following steps:

[0037] (1) React luminescent molecules and molecular ring precursors to synthesize molecular rings with luminescent molecular groups;

[0038] (2) The quencher molecule reacts with the first part of the molecular axis, then the end is sealed, and the resulting product is self-assembled with the molecular ring with luminescent molecular groups obtained in step (1). The resulting product reacts with the second part of the molecular axis, and the end is sealed to synthesize the polyrotaxane.

[0039] According to the present invention, preferably, the preparation method includes the following steps:

[0040] (a) Synthesizing crown ethers with luminescent molecular groups by reacting luminescent molecules with alkyne-based crown ethers;

[0041] (b) First, a polyethylene glycol polymer with propyne group and first reactive group at both ends is mixed with macro-blocking end-capping agent A to allow the first reactive group to react with macro-blocking end-capping agent A. Then, a quencher molecule with azide group at the end is added to react and synthesize a molecular axis with quencher molecule group and one end capped.

[0042] (c) The crown ether with luminescent molecular groups obtained in step (a) and the molecular axis with quencher molecular groups obtained in step (b) are self-assembled, and then the molecular axis is reacted with steric hindrance end-capping agent B to end-cap the other end of the molecular axis to synthesize the polyrotaxane.

[0043] According to the present invention, preferably, in step (a), the molar ratio of the luminescent molecule to the alkynylated crown ether is 0.85-1.5:1.

[0044] According to the present invention, preferably, in step (b), steric hindrance end-capping agent A and steric hindrance end-capping agent B are respectively a steric hindrance molecule with two reactive groups and a steric hindrance molecule with one reactive group;

[0045] The molar ratio of the quencher molecule and the steric hindrance end-capping agents A and B is independently 0.8-1.1:1.

[0046] According to the present invention, preferably, in step (c), the molar ratio of the crown ether with luminescent molecular groups to the molecular axis with quencher molecules is 0.8-1.2:1.

[0047] A third aspect of the present invention provides a mechanically color-changing material that can respond instantly to weak forces, characterized in that the material is a network polymer material comprising a multi-arm polymer as a matrix and the aforementioned polyrotaxane as a crosslinking component.

[0048] According to the present invention, preferably, in order to ensure the uniformity of the crosslinked network, the molar ratio of crosslinking sites in the polyrotaxane to hydroxyl groups in the multi-arm polymer is 0.5-1.5:1.

[0049] According to the present invention, preferably, the number-average molecular weight of the multi-arm polymer is 2 to 30 kDa, more preferably 4 to 16 kDa;

[0050] Preferably, the multi-armed polymer is a four-armed polycaprolactone and / or a three-armed polycaprolactone.

[0051] In this invention, the multi-arm polycaprolactone can be prepared using conventional polycaprolactone polymerization methods. The selected initiator is an initiator molecule containing more than two hydroxyl groups, such as pentaerythritol, glycerol, trimethylolpropane, bis(trimethylolpropane), trimethylolethane, etc. The catalyst can be a variety of catalysts for ring-opening polymerization, including tin salts such as stannous octoate, zinc salts such as zinc lactate, rare earth metal salts such as ytterbium trifluoromethanesulfonate, non-metallic compounds such as trifluoromethanesulfonate, enzymes, etc. The reaction can be carried out in solution or in bulk.

[0052] According to the present invention, preferably, the crosslinking sites of the polyrotaxane are connected to the multi-arm polymer by a crosslinking agent.

[0053] According to the present invention, preferably, the crosslinking agent is selected from at least one of hexamethylene diisocyanate, toluene diisocyanate, isophorone diisocyanate and lysine diisocyanate.

[0054] A fourth aspect of the present invention provides a method for preparing the aforementioned mechanically color-changing material capable of responding instantly to weak forces, the method comprising the following steps:

[0055] In the presence of a solvent, a multi-arm polymer, polyrotaxane, and a catalyst are reacted to obtain a mechanically color-changing material that can respond instantly to weak forces.

[0056] According to the present invention, preferably, the reaction is a crosslinking reaction, wherein the molar ratio of the crosslinking group of the crosslinking agent, the hydroxyl group of the multi-arm polycaprolactone, and the crosslinking site of the polyrotaxane is 80-120:100:0.01-0.1, and the conditions of the crosslinking reaction include: a temperature of 60-100°C and a time of 0.5-4h.

[0057] According to the present invention, preferably, the solvent is selected from at least one of tetrahydrofuran, dichloromethane, chloroform, dioxane, ethyl acetate and butyl acetate;

[0058] The concentration of the multi-arm polymer is 5-30 wt%.

[0059] According to the present invention, preferably, the catalyst is selected from at least one of dibutyltin dilaurate, dibutyltin oxide, dibutyltin maleate, dibutyltin diacetate, and di-n-butylbis(acetylacetonyl)tin;

[0060] The molar ratio of the catalyst to the multi-arm polymer is 0.0001-0.01:1.

[0061] According to the present invention, preferably, the reaction system further includes an antioxidant, wherein the antioxidant is selected from at least one of 2,6-di-tert-butyl-4-methylphenol, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and tris(2,4-di-tert-butyl)phosphite;

[0062] The molar ratio of the antioxidant to the multi-arm polymer is 0.0001-0.01:1.

[0063] The fifth aspect of the present invention provides the application of the aforementioned polyrotaxane, or the aforementioned mechanically color-changing material that can respond instantly to weak forces, in the field of shape memory materials.

[0064] The preferred application of this invention is in the field of stress damage detection.

[0065] The present invention will be further described below with reference to the embodiments, but the scope of the present invention is not limited to these embodiments.

[0066] All reagents used in the examples were commercially available, and the testing instruments included:

[0067] Nuclear magnetic resonance spectroscopy (NMR) 1 1H-NMR: The nuclear magnetic resonance spectrometer used was a Bruker AR×-500 from Bruker GmbH, Switzerland, with a resolution <0.2Hz and sensitivity >100. This experiment employed 1H NMR analysis, using deuterated chloroform and deuterated dimethyl sulfoxide as solvents, at a working frequency of 500MHz and a magnetic field strength of 7.05T, and was conducted at room temperature.

[0068] Fluorescence spectroscopy was performed using an FLS1000 steady-state and transient fluorescence spectrometer from Edinburgh, UK, with a xenon lamp as the excitation source and a P928P PMT detector as the detector.

[0069] Example 1

[0070] This embodiment illustrates the mechanically color-changing material that can instantly respond to weak forces according to the present invention and its preparation. The preparation method includes the following steps:

[0071] S1. A suspension was prepared by stirring and refluxing 0.25 g (1 mol) of 4-hydroxyphenylboronic acid pinacol ester, 0.215 g (1 mol) of 3-chloro-1-propanol, and 5 g of toluene at 70 °C for 24 h. The suspension was cooled to room temperature and poured into 500 mL of chloroform, and the solvent was evaporated. The crude product was purified by column chromatography using silica gel (elution: chloroform). A mixture of the product (1.84 g, 6.60 mol), 1,6-dibromopyrene (3.56 g, 9.90 mol), toluene (30 mL), ethanol (1 mL), potassium carbonate (3.64 g, 26.3 mmol), water (13 mL), and tetrakis(triphenylphosphine)palladium (382 mg, 0.330 mmol) under reflux for 19 h. The organic layer was separated, washed with H2O (2×100mL), dried and filtered with MgSO4, the solvent was evaporated, and the crude product was purified by column chromatography with silica gel (elution: chloroform) to obtain the blue luminescent molecule.

[0072] S2. 1,5-Dihydroxynaphthalene (DHNP) (5.23 g, 32.7 mmol) was added to tetraethylene glycol monotoluenesulfonate (MTTEG) (22.75 g, 65.3 mmol), K₂CO₃ (17.85 g, 129.2 mmol), and substoichiometric lithium bromide (LiBr) in anhydrous acetonitrile (MeCN) (250 mL). The reaction mixture was heated under reflux for 24 hours, cooled, and filtered. The residue was dissolved in water (200 mL), and the resulting solution was extracted with CH₂Cl₂ (2 × 50 mL). The organic layer was combined with the previously obtained filtrate, and the solvent was evaporated under vacuum. The resulting brown oily substance was dissolved in CH₂Cl₂ (200 mL), and the solution was washed with a mixture of brine and 10% NaOH aqueous solution (3:1, 3 × 100 mL). The organic layer was dried with MgSO4, the solvent was removed under reduced pressure, and the product was dried to obtain 1,5-bis(2-{2-[2-(2-hydroxyethoxy)ethoxy]ethoxy}ethoxy)naphthalene (BHEEEEN).

[0073] At 0 °C, a solution of tetrabromomethane (4.04 g, 12.2 mmol) in dichloromethane (15 mL) was added dropwise to a solution of BHEEEEN (2.50 g, 4.88 mmol) and triphenylphosphine (3.07 g, 11.7 mmol) in dichloromethane (200 mL). The reaction mixture was then stirred at room temperature for 2.5 h before most of the dichloromethane evaporated. The crude product was purified by rapid column chromatography on silica gel (elution: dichloromethane / ethyl acetate = 4:1 v / v). Subsequently, over 12 h, a solution of bromohydroquinone (518 mg, 2.74 mmol) and the product (1.75 g, 2.74 mmol) in DMF (25 mL) was added to a suspension of K₂CO₃ (7.57 g, 54.8 mmol) in DMF (300 mL) at 80 °C. After stirring at 80 °C for 24 h, the solvent was evaporated. Add chloroform (250 mL), and wash the organic layer with saturated NH4Cl aqueous solution (3 × 300 mL) and saturated NaCl aqueous solution (100 mL). Dry the organic layer with MgSO4 and filter, evaporating the solvent. Purify the crude product by silica gel rapid column chromatography (elution buffer: dichloromethane / acetone = 92:8 v / v) to give a crown ether with a bromine group.

[0074] Crown bromide (620 mg, 0.933 mmol), trimethylsilylacetylene (914 mg, 9.31 mmol), and Pd(PPh3)4 (54 mg, 4.7 × 10⁻⁶ mmol) were added. -2 mmol), CuI (8.89 mg, 4.67 × 10⁻⁶) -2A solution of 1 mmol) and i-Pr2NH (30 mL) in THF (20 mL) was stirred at 70 °C for 18 h under a nitrogen atmosphere. After cooling to room temperature, the reaction mixture was poured into ethyl acetate (150 mL). The organic layer was washed with 5% hydrochloric acid aqueous solution (2 × 100 mL), saturated NaHCO3 aqueous solution (100 mL), and saturated NaCl aqueous solution, dried over MgSO4 and filtered, and the solvent was evaporated. The crude product was purified by rapid column chromatography on silica gel (eluent: gradient dichloromethane / acetone = 95:5 V / V to dichloromethane / acetone = 92:8 V / V) to give sulfonated crown ether. Then, tetrabutylammonium fluoride (tetrahydrofuran solution) (1 mol / L, 0.98 mL, 0.98 mmol) was added to a solution of sulfonated crown ether (560 mg, 0.820 mmol) in THF (30 mL). After stirring the reaction mixture at room temperature for 2 hours, ethyl acetate (150 mL) and water (200 mL) were added. The organic layer was separated and washed with saturated aqueous solution. NaCl (100 mL) was added, dried over MgSO4, and filtered, with the solvent evaporated. The crude product was purified by silica gel rapid column chromatography (eluent: a gradient from dichloromethane / acetone = 95:5 V / V to dichloromethane / acetone = 92:8 V / V) with alkynylated crown ether.

[0075] A solution of a blue luminescent molecule (439 mg, 1.18 mmol), an alkynylated crown ether (718 mg, 1.18 mmol), tetrakis(triphenylphosphine)palladium (136 mg, 118 mmol), CuI (22.5 mg, 0.118 mmol), and Et₂NH (30 mL) in THF (20 mL) was stirred under nitrogen at 70 °C for 12 h. After cooling to room temperature, the reaction mixture was poured into ethyl acetate (150 mL). The organic layer was separated, washed with 5% hydrochloric acid solution (2 × 100 mL), saturated sodium bicarbonate solution (100 mL), and saturated NaCl (100 mL), dried over MgSO₄, filtered, and the solvent was evaporated. The crude product was purified by rapid column chromatography on silica gel (eluent: dichloromethane / acetone = 9:1 V / V) to give a crown ether containing the luminescent molecule, designated as compound 6.

[0076] S3. Naphthalene-1,4,5,8-tetracarboxylic anhydride (1.50 g, 5.59 mmol) and diethylene glycolamine (2.35 g, 22.4 mmol) were refluxed and stirred in 1,4-dioxane (70 mL) for 18 hours. After cooling to room temperature, the reaction mixture was poured into a 5% hydrochloric acid solution (200 mL). The precipitate was filtered and washed with water (3 × 50 mL) and methanol (3 × 50 mL), and then dried under vacuum. Subsequently, PBr3 (1.86 mL, 19.8 mmol) was added to a DMF (200 mL) solution of the product (3.80 g, 8.59 mmol), and the mixture was stirred at 70 °C for 4 hours. After cooling to room temperature, the reaction mixture was slowly poured into a 5% NaHCO3 (200 mL) solution. The resulting precipitate was filtered and washed with water (5 × 50 mL) and methanol (3 × 50 mL). The solid residue was dissolved in chloroform, the solution was dried over MgSO4 and filtered, and then the solvent was evaporated. The crude product was purified by rapid column chromatography on silica gel (eluent: chloroform). Finally, NaN3 (1.72 g, 26.4 mmol) was added to a DMF (200 mL) solution of the purified sample (1.50 g, 2.64 mmol), and the mixture was stirred at 60 °C for 24 h. After cooling to room temperature, the reaction mixture was poured into water (200 mL). The resulting precipitate was filtered and washed with water (5 × 50 mL). The solid residue was dissolved in chloroform, the solution was dried over MgSO4 and filtered, and then the solvent was evaporated. The crude product was purified by rapid column chromatography on silica gel (eluent: chloroform) to give the quencher molecule.

[0077] A mixture of tris(p-tert-butylphenyl)(4-hydroxyphenyl)methane and bis(p-tert-butylphenyl)bis(4-hydroxyphenyl)methane (500 mg, 0.864 mmol), propynyl-tetraethylene glycol-methanesulfonate (501 mg, 1.30 mmol), and K₂CO₃ (358 mg, 2.65 mmol) in DMF (100 mL) was stirred vigorously at 80 °C for 18 hours under a nitrogen atmosphere. The organic layer was separated by washing with saturated NH₄Cl solution (200 mL) and ethyl acetate (100 mL), dried over MgSO₄, filtered, and then the solvent was evaporated. The crude product was purified by rapid silica gel column chromatography (eluent: dichloromethane / acetone = 6:1 V / V) to give a molecule with a sterically hindered group at one end, designated compound 8.

[0078] A mixture of sodium ascorbate (496 mg, 2.50 mmol) and copper(II) sulfate (200 mg, 1.25 mmol) in water (4 mL) was added to a solution of a sterically hindered molecule without hydroxyl groups (600 mg, 0.834 mmol) and a quencher (616 mg, 1.25 mmol) in chloroform (15 mL), and the mixture was stirred vigorously at room temperature for 12 hours. The suspension was poured into a mixture of water (100 mL) and chloroform (100 mL). The organic layer was separated, washed with saturated NaCl solution (2 × 100 mL), dried over MgSO4, filtered, and the solvent was evaporated. The crude product was purified by silica gel rapid column chromatography (elution buffer: gradient from dichloromethane / acetone = 9:1 to dichloromethane / acetone = 1:1 V / V) and cyclic GPC (elution buffer: chloroform) to give a molecular axis with the quencher molecule and one end capped, designated as compound 12.

[0079] S4. A mixture of sodium ascorbate and copper(II) sulfate in water was added to a chloroform solution of compounds 8, 12, and 6, and the mixture was stirred vigorously at room temperature for 24 hours. The suspension was poured into a mixture of water and chloroform, and the organic layer was separated, washed with saturated NaCl solution, dried over MgSO4, filtered, and the solvent was evaporated. The crude product was purified by silica gel rapid column chromatography to obtain a bifunctional polyrotaxane, designated as polyrotaxane 1.

[0080] Polyrotaxane 1, tetra-armed polycaprolactone (4 kDa), and toluene diisocyanate were dissolved in tetrahydrofuran in a specific ratio. The ratio of hydroxyl groups in polyrotaxane 1 to isocyanate groups to hydroxyl groups in tetra-armed polycaprolactone was 0.8:1.8:1. One drop of dibutyltin dilaurate (DBTDL) and 0.78 mg of the antioxidants 2,6-di-tert-butyl-4-methylphenol and 2,6-di-tert-butyl-p-cresol (BHT) were added, and the mixture was reacted in an open polytetrafluoroethylene circular mold at 70°C for 10 hours. Partial evaporation of the solvent yielded a gel. The gel was then dried under vacuum at 70°C for 5 hours to obtain a mechanically chromogenic film P1. P1 showed no fluorescence under UV irradiation but exhibited significant fluorescence when stretched to 50% of its original length. The fluorescence spectrum showed that the fluorescence intensity increased 50 times that of the original sample. Figure 5 The images show the different luminescence patterns under different tensile strengths.

[0081] Example 2

[0082] This embodiment illustrates the mechanically color-changing material that can instantly respond to weak forces according to the present invention and its preparation. The preparation method includes the following steps:

[0083] Polyrotaxane 1, tetra-armed polycaprolactone (8 kDa), and toluene diisocyanate were dissolved in tetrahydrofuran in a specific ratio. The ratio of hydroxyl groups in polyrotaxane 1 to isocyanate groups to hydroxyl groups in tetra-armed polycaprolactone was 0.8:1.8:1. One drop of DBTDL and 0.78 mg of BHT were added, and the mixture was reacted in an open polytetrafluoroethylene circular mold at 70°C for 10 hours. Partial evaporation of the solvent yielded a gel. The gel was then dried under vacuum at 70°C for 5 hours to obtain a mechanically color-changing film material P2. P2 showed no fluorescence under UV irradiation but exhibited significant fluorescence when stretched to 50% of its original length. The fluorescence spectrum showed that the fluorescence intensity increased to 26 times that of the original sample.

[0084] Example 3

[0085] This embodiment illustrates the mechanically color-changing material that can instantly respond to weak forces according to the present invention and its preparation. The preparation method includes the following steps:

[0086] Polyrotaxyl 1, tetra-armed polycaprolactone (16 kDa), and hexamethylene diisocyanate were dissolved in tetrahydrofuran in a specific ratio. The ratio of hydroxyl groups in polyrotaxyl 1 to isocyanate groups to hydroxyl groups in tetra-armed polycaprolactone was 0.9:1.9:1. One drop of dibutyltin diacetate and 1 mg of antioxidant 1010 were added, and the mixture was reacted in an open polytetrafluoroethylene circular mold at 70°C for 10 hours. Partial evaporation of the solvent yielded a gel. The gel was then dried under vacuum at 70°C for 5 hours to obtain a mechanically color-changing film P3. P3 showed no fluorescence under UV irradiation but exhibited significant fluorescence when stretched to 50% of its original length. The fluorescence spectrum showed that the fluorescence intensity increased to 25 times that of the original sample.

[0087] Example 4

[0088] This embodiment illustrates the mechanically color-changing material that can instantly respond to weak forces according to the present invention and its preparation. The preparation method includes the following steps:

[0089] S1. A mixture of 4,7-dibromo-2,1,3-benzothiadiazole (917 mg, 3.12 mmol), 1-ethynyl-4-propoxybenzene (500 mg, 3.12 mmol), tetrakis(triphenylphosphine)palladium (180 mg, 0.156 mmol), copper iodide (29.7 mg, 0.156 mmol), and ethylenediamine (20 mL) in THF (20 mL) was stirred at 70 °C for 22 hours under a nitrogen atmosphere. After cooling to room temperature, the reaction mixture was poured into ethyl acetate (150 mL), and the organic layer was washed with 5% hydrochloric acid solution (2100 mL), saturated NaHCO3 solution (100 mL), and saturated sodium chloride solution (100 mL). The organic layer was dried over MgSO4 and filtered, and the solvent was evaporated. The crude product was purified by rapid column chromatography on silica gel (eluent gradient from hexane / chloroform = 1:1 V / V to hexane / chloroform = 1:2 V / V), followed by precipitation from a mixture of chloroform and hexane to obtain a yellow luminescent molecule.

[0090] S2. 1,5-Dihydroxynaphthalene (DHNP) (5.23 g, 32.7 mmol) was added to tetraethylene glycol monotoluenesulfonate (MTTEG) (22.75 g, 65.3 mmol), K₂CO₃ (17.85 g, 129.2 mmol), and substoichiometric lithium bromide (LiBr) in anhydrous acetonitrile (MeCN) (250 mL). The reaction mixture was heated under reflux for 24 hours, cooled, and filtered. The residue was dissolved in water (200 mL), and the resulting solution was extracted with CH₂Cl₂ (2 × 50 mL). The organic layer was combined with the previously obtained filtrate, and the solvent was evaporated under vacuum. The resulting brown oily substance was dissolved in CH₂Cl₂ (200 mL), and the solution was washed with a mixture of brine and 10% NaOH aqueous solution (3:1, 3 × 100 mL). The organic layer was dried with MgSO4, the solvent was removed under reduced pressure, and the product was dried to obtain 1,5-bis(2-{2-[2-(2-hydroxyethoxy)ethoxy]ethoxy}ethoxy)naphthalene (BHEEEEN).

[0091] At 0 °C, a solution of tetrabromomethane (4.04 g, 12.2 mmol) in dichloromethane (15 mL) was added dropwise to a solution of BHEEEEN (2.50 g, 4.88 mmol) and triphenylphosphine (3.07 g, 11.7 mmol) in dichloromethane (200 mL). The reaction mixture was then stirred at room temperature for 2.5 h before most of the dichloromethane evaporated. The crude product was purified by rapid column chromatography on silica gel (elution: dichloromethane / ethyl acetate = 4:1 v / v). Subsequently, over 12 h, a solution of bromohydroquinone (518 mg, 2.74 mmol) and the product (1.75 g, 2.74 mmol) in DMF (25 mL) was added to a suspension of K₂CO₃ (7.57 g, 54.8 mmol) in DMF (300 mL) at 80 °C. After stirring at 80 °C for 24 h, the solvent was evaporated. Add chloroform (250 mL), wash the organic layer with saturated NH4Cl aqueous solution (3 × 300 mL) and saturated NaCl aqueous solution (100 mL). Dry the organic layer with MgSO4 and filter, evaporating the solvent. Purify the crude product by silica gel rapid column chromatography (elution buffer: dichloromethane / acetone = 92:8 v / v) to give a crown ether with a bromine group.

[0092] Crown bromide (620 mg, 0.933 mmol), trimethylsilylacetylene (914 mg, 9.31 mmol), and Pd(PPh3)4 (54 mg, 4.7 × 10⁻⁶ mmol) were added. -2 mmol), CuI (8.89 mg, 4.67 × 10⁻⁶) -2A solution of 1 mmol) and i-Pr2NH (30 mL) in THF (20 mL) was stirred at 70 °C for 18 h under a nitrogen atmosphere. After cooling to room temperature, the reaction mixture was poured into ethyl acetate (150 mL). The organic layer was washed with 5% hydrochloric acid aqueous solution (2 × 100 mL), saturated NaHCO3 aqueous solution (100 mL), and saturated NaCl aqueous solution, dried over MgSO4 and filtered, and the solvent was evaporated. The crude product was purified by rapid column chromatography on silica gel (eluent: gradient dichloromethane / acetone = 95:5 V / V to dichloromethane / acetone = 92:8 V / V) to give sulfonated crown ether. Then, tetrabutylammonium fluoride (tetrahydrofuran solution) (1 mol / L, 0.98 mL, 0.98 mmol) was added to a solution of sulfonated crown ether (560 mg, 0.820 mmol) in THF (30 mL). After stirring the reaction mixture at room temperature for 2 hours, ethyl acetate (150 mL) and water (200 mL) were added. The organic layer was separated and washed with saturated aqueous solution. NaCl (100 mL) was added, dried over MgSO4, and filtered. The solvent was evaporated. The crude product was purified by silica gel rapid column chromatography (eluent: a gradient from dichloromethane / acetone = 95:5 V / V to dichloromethane / acetone = 92:8 V / V) with alkynylated crown ether.

[0093] A solution of a yellow luminescent molecule (439 mg, 1.18 mmol), an alkynylated crown ether (718 mg, 1.18 mmol), tetrakis(triphenylphosphine)palladium (136 mg, 118 mmol), CuI (22.5 mg, 0.118 mmol), and Et₂NH (30 mL) in THF (20 mL) was stirred under nitrogen at 70 °C for 12 h. After cooling to room temperature, the reaction mixture was poured into ethyl acetate (150 mL). The organic layer was separated, washed with 5% hydrochloric acid solution (2 × 100 mL), saturated sodium bicarbonate solution (100 mL), and saturated NaCl (100 mL), dried over MgSO₄, filtered, and the solvent was evaporated. The crude product was purified by rapid column chromatography on silica gel (eluent: dichloromethane / acetone = 9:1 V / V) to give the crown ether containing the luminescent molecule, compound 6.

[0094] S3. Naphthalene-1,4,5,8-tetracarboxylic anhydride (1.50 g, 5.59 mmol) and diethylene glycolamine (2.35 g, 22.4 mmol) were refluxed and stirred in 1,4-dioxane (70 mL) for 18 hours. After cooling to room temperature, the reaction mixture was poured into a 5% hydrochloric acid solution (200 mL). The precipitate was filtered and washed with water (3 × 50 mL) and methanol (3 × 50 mL), and then dried under vacuum. Subsequently, PBr3 (1.86 mL, 19.8 mmol) was added to a DMF (200 mL) solution of the product (3.80 g, 8.59 mmol), and the mixture was stirred at 70 °C for 4 hours. After cooling to room temperature, the reaction mixture was slowly poured into a 5% NaHCO3 (200 mL) solution. The resulting precipitate was filtered and washed with water (5 × 50 mL) and methanol (3 × 50 mL). The solid residue was dissolved in chloroform, the solution was dried over MgSO4 and filtered, and then the solvent was evaporated. The crude product was purified by rapid column chromatography on silica gel (eluent: chloroform). Finally, NaN3 (1.72 g, 26.4 mmol) was added to a DMF (200 mL) solution of the purified sample (1.50 g, 2.64 mmol), and the mixture was stirred at 60 °C for 24 h. After cooling to room temperature, the reaction mixture was poured into water (200 mL). The resulting precipitate was filtered and washed with water (5 × 50 mL). The solid residue was dissolved in chloroform, the solution was dried over MgSO4 and filtered, and then the solvent was evaporated. The crude product was purified by rapid column chromatography on silica gel (eluent: chloroform) to give the quencher molecule.

[0095] A mixture of tris(p-tert-butylphenyl)(4-hydroxyphenyl)methane and bis(p-tert-butylphenyl)bis(4-hydroxyphenyl)methane (500 mg, 0.864 mmol), propynyl-tetraethylene glycol-methanesulfonate (501 mg, 1.30 mmol), and K₂CO₃ (358 mg, 2.65 mmol) in DMF (100 mL) was stirred vigorously at 80 °C for 18 hours under a nitrogen atmosphere. The organic layer was separated by washing with saturated NH₄Cl solution (200 mL) and ethyl acetate (100 mL), dried over MgSO₄, filtered, and then the solvent was evaporated. The crude product was purified by rapid silica gel column chromatography (eluent: dichloromethane / acetone = 6:1 V / V) to give a molecule with a sterically hindered group at one end, designated compound 8.

[0096] A mixture of sodium ascorbate (496 mg, 2.50 mmol) and copper(II) sulfate (200 mg, 1.25 mmol) in water (4 mL) was added to a solution of a sterically hindered molecule without hydroxyl groups (600 mg, 0.834 mmol) and a quencher (616 mg, 1.25 mmol) in chloroform (15 mL), and the mixture was stirred vigorously at room temperature for 12 hours. The suspension was poured into a mixture of water (100 mL) and chloroform (100 mL). The organic layer was separated, washed with saturated NaCl solution (2 × 100 mL), dried over MgSO4, filtered, and the solvent was evaporated. The crude product was purified by silica gel rapid column chromatography (elution buffer: gradient from dichloromethane / acetone = 9:1 to dichloromethane / acetone = 1:1 V / V) and cyclic GPC (elution buffer: chloroform) to give compound 12 with a molecular axis.

[0097] S4. A mixture of sodium ascorbate and copper(II) sulfate in water was added to a chloroform solution of compounds 8, 12, and 6, and the mixture was stirred vigorously at room temperature for 24 hours. The suspension was poured into a mixture of water and chloroform, and the organic layer was separated, washed with saturated NaCl solution, dried over MgSO4, filtered, and the solvent was evaporated. The crude product was purified by silica gel rapid column chromatography to give bifunctional polyrotaxane 2.

[0098] Polyrotaxane 2, tetra-armed polycaprolactone (4 kDa), and toluene diisocyanate were dissolved in tetrahydrofuran in a specific ratio. The ratio of hydroxyl groups in polyrotaxane 2 to isocyanate groups to hydroxyl groups in tetra-armed polycaprolactone was 0.8:1.8:1. One drop of DBTDL and 0.78 mg of BHT were added, and the mixture was reacted in an open polytetrafluoroethylene circular mold at 60°C for 10 hours. Partial solvent evaporation yielded a gel. The gel was then dried under vacuum at 70°C for 5 hours to obtain a mechanically chromogenic film P4. P4 showed no fluorescence under UV irradiation but exhibited significant fluorescence when stretched to 50% of its original length. The fluorescence spectrum showed that the fluorescence intensity increased to 35 times that of the original sample.

[0099] Example 5

[0100] This embodiment illustrates the mechanically color-changing material that can instantly respond to weak forces according to the present invention and its preparation. The preparation method includes the following steps:

[0101] Polyrotaxane 2, tetra-armed polycaprolactone (8 kDa), and hexamethylene diisocyanate were dissolved in chloroform in a specific ratio. The ratio of hydroxyl groups in polyrotaxane 2 to isocyanate groups to hydroxyl groups in tetra-armed polycaprolactone was 1:2:1. One drop of DBTDL and 0.78 mg of BHT were added, and the mixture was reacted in an open polytetrafluoroethylene circular mold at 50°C for 10 hours. Partial evaporation of the solvent yielded a gel. The gel was then dried under vacuum at 70°C for 5 hours to obtain a mechanically chromogenic film P5. P5 showed no fluorescence under UV irradiation but exhibited significant fluorescence when stretched to 50% of its original length. The fluorescence spectrum showed that the fluorescence intensity increased to 15 times that of the original sample.

[0102] Example 6

[0103] This embodiment illustrates the mechanically color-changing material that can instantly respond to weak forces according to the present invention and its preparation. The preparation method includes the following steps:

[0104] Polyrotaxane 2, tetra-armed polycaprolactone (16 kDa), and isophorone diisocyanate were dissolved in tetrahydrofuran in a certain ratio. The ratio of hydroxyl groups in polyrotaxane 1 to isocyanate groups to hydroxyl groups in tetra-armed polycaprolactone was 0.8:1.8:1. One drop of DBTDL and 0.78 mg of BHT were added, and the mixture was reacted in an open polytetrafluoroethylene circular mold at 60°C for 10 hours. Partial evaporation of the solvent yielded a gel. The gel was then dried under vacuum at 70°C for 5 hours to obtain the mechanochromic material P6. P6 showed no fluorescence under UV irradiation but exhibited significant fluorescence when stretched to 50% of its original length. The fluorescence spectrum showed that the fluorescence intensity increased to 13 times that of the original sample.

[0105] Example 7

[0106] Polyrotaxane 1, three-armed polycaprolactone with a molecular weight of 10 kDa, and lysine diisocyanate were dissolved in tetrahydrofuran in a certain ratio. The ratio of hydroxyl groups in polyrotaxane 1 to isocyanate groups to hydroxyl groups in three-armed polycaprolactone was 0.9:1.8:1. One drop of DBTDL and 0.78 mg of BHT were added, and the mixture was reacted in an open polytetrafluoroethylene circular mold at 60°C for 10 hours. Partial evaporation of the solvent yielded a gel. The gel was then dried under vacuum at 70°C for 5 hours to obtain a mechanically chromogenic film P7. P7 showed no fluorescence under UV irradiation but exhibited significant fluorescence when stretched to 50% of its original length. The fluorescence spectrum showed that the fluorescence intensity increased tenfold compared to the original sample.

[0107] Example 8

[0108] Polyrotaxane 2, three-armed polycaprolactone with a molecular weight of 10 kDa, and toluene diisocyanate were dissolved in tetrahydrofuran in a certain ratio. The ratio of hydroxyl groups in polyrotaxane 1 to isocyanate groups to hydroxyl groups in the three-armed polycaprolactone was 0.8:1.8:1. One drop of DBTDL and 0.78 mg of BHT were added, and the mixture was reacted in an open polytetrafluoroethylene circular mold at 60°C for 10 hours. Partial evaporation of the solvent yielded a gel. The gel was then dried under vacuum at 70°C for 5 hours to obtain a mechanically chromogenic film P8. P8 showed no fluorescence under UV irradiation but exhibited significant fluorescence when stretched to 50% of its original length. The fluorescence spectrum showed that the fluorescence intensity increased to six times that of the original sample.

[0109] Example 9

[0110] Polyrotaxane 1, three-armed polycaprolactone (4 kDa), and isophorone diisocyanate were dissolved in chloroform in a certain ratio. The ratio of hydroxyl groups in polyrotaxane 1 to isocyanate groups to hydroxyl groups in the three-armed polycaprolactone was 0.9:1.9:1. One drop of DBTDL and 0.78 mg of BHT were added, and the mixture was reacted in an open polytetrafluoroethylene circular mold at 60°C for 10 hours. Partial evaporation of the solvent yielded a gel. The gel was then dried under vacuum at 70°C for 5 hours to obtain a mechanically chromogenic film P9. P9 showed no fluorescence under UV irradiation but exhibited significant fluorescence when stretched to 50% of its original length. The fluorescence spectrum showed that the fluorescence intensity increased to seven times that of the original sample.

[0111] Example 10

[0112] Polyrotaxane 2, tetra-armed polycaprolactone (15 kDa), and isophorone diisocyanate were dissolved in chloroform in a certain ratio. The ratio of hydroxyl groups in polyrotaxane 1 to isocyanate groups to hydroxyl groups in tetra-armed polycaprolactone was 1:2:1. One drop of DBTDL and 0.78 mg of BHT were added, and the mixture was reacted in an open polytetrafluoroethylene circular mold at 50°C for 10 hours. Partial evaporation of the solvent yielded a gel. The gel was then dried under vacuum at 70°C for 5 hours to obtain the mechanochromic material P10. P10 showed no fluorescence under UV irradiation but exhibited significant fluorescence when stretched to 50% of its original length. The fluorescence spectrum showed that the fluorescence intensity increased to four times that of the original sample.

[0113] Comparative Example 1

[0114] The only difference between this comparative example and Example 1 is that the four-armed polycaprolactone was replaced with dihydroxy polycaprolactone with a molecular weight of 4KD, resulting in Comparative Material 1, which showed no color under UV light before and after stretching.

[0115] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

[0116] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

Claims

1. A polyrotaxane, characterized in that, The polyrotaxane comprises a molecular ring and a molecular axis, wherein the molecular ring has a luminescent molecular group and the molecular axis has a quencher molecular group; the quencher molecular group is capable of quenching the luminescence of the luminescent molecule; each polyrotaxane provides two crosslinking sites, one of which is located on the molecular axis and the other is located on the molecular ring or on the luminescent molecular group.

2. The polyrotaxane according to claim 1, wherein, When the polyrotaxane is in a relaxed state, the quencher molecular groups approach the luminescent molecular groups, and the luminescence of the luminescent molecules is quenched. When the polyrotaxane is subjected to an external force, the quencher molecular groups move away from the luminescent molecular groups, and the luminescence of the luminescent molecules is restored.

3. The polyrotaxane according to claim 1, wherein, The molecular ring of the polyrotaxane is a crown ether; The molecular axis of the polyrotaxane includes: a quencher molecular group, a first polymer chain and a second polymer chain respectively connecting the two ends of the quencher molecular group, and a first sterically hindered group and a second sterically hindered group respectively sealing the first polymer chain and the second polymer chain, wherein the first sterically hindered group provides a crosslinking site; the crosslinking site is preferably at least one of hydroxyl, amino and carboxyl groups.

4. The polyrotaxane according to claim 3, wherein, The monomer forming the crown ether is a single-arm sulfonated ethylene glycol; preferably at least one of triethylene glycol monotoluenesulfonate, tetraethylene glycol monotoluenesulfonate, pentaethylene glycol monotoluenesulfonate, and hexaethylene glycol monotoluenesulfonate.

5. The polyrotaxane according to claim 3, wherein, Both the first polymer chain and the first polymer chain are polyethylene glycol-based segments; The first steric hindrance end-capping agent is a steric hindrance molecule with two reactive groups; preferably, it is a steric hindrance molecule with two hydroxyl groups; more preferably, it is bis(p-tert-butylphenyl)bis(4-hydroxyphenyl)methane and / or 1,2-bis(4-hydroxyphenyl)-1,2-diphenylene; The second steric hindrance end-capping agent is a steric hindrance molecule with a reactive group; preferably, it is a steric hindrance molecule with a hydroxyl group; more preferably, it is at least one of tris(p-tert-butylphenyl)(4-hydroxyphenyl)methane, 4-[bis[4-(1,1-dimethylethyl)phenyl][4-(1-methylethyl)phenyl]methyl]phenol, 4-[bis[4-(1,1-dimethylethyl)phenyl](4-ethylphenyl)methyl]phenol, bis(p-tert-butylphenyl)bis(4-hydroxyphenyl)methane, and 1,2-bis(4-hydroxyphenyl)-1,2-diphenylphenyl.

6. The polyrotaxane according to claim 1, wherein, The luminescent molecule is a yellow luminescent molecule and / or a blue luminescent molecule; the yellow luminescent molecule is preferably at least one of 4,7-dibromo-2,1,3-benzothiadiazole, 3,10-dibromoperylene, and dibromofluorescein; the blue luminescent molecule is preferably at least one of 1,6-dibromopyrene, 2,6-dibromoanthracene, and 1,8-dibromoanthracene. The quencher molecule is naphthalene-1,4,5,8-dianhydride.

7. The polyrotaxane according to claim 1, wherein, The luminescent molecule is connected to the remaining components of the molecular ring of the polyrotaxane through a click chemistry reaction; The quencher molecule is connected to the remaining components of the molecular axis of the polyrotaxane via a click chemistry reaction.

8. The method for preparing polyrotaxane according to any one of claims 1-7, characterized in that, Includes the following steps: (1) React luminescent molecules and molecular ring precursors to synthesize molecular rings with luminescent molecular groups; (2) The quencher molecule reacts with the first part of the molecular axis, then the end is sealed, and the resulting product is self-assembled with the molecular ring with luminescent molecular groups obtained in step (1). The resulting product reacts with the second part of the molecular axis, and the end is sealed to synthesize the polyrotaxane.

9. The preparation method according to claim 8, wherein, The preparation method includes the following steps: (a) Synthesizing crown ethers with luminescent molecular groups by reacting luminescent molecules with alkyne-based crown ethers; (b) First, a polyethylene glycol polymer with propyne group and first reactive group at both ends is mixed with macro-blocking end-capping agent A to allow the first reactive group to react with macro-blocking end-capping agent A. Then, a quencher molecule with azide group at the end is added to react and synthesize a molecular axis with quencher molecule group and one end capped. (c) The crown ether with luminescent molecular groups obtained in step (a) and the molecular axis with quencher molecular groups obtained in step (b) are self-assembled, and then the molecular axis is reacted with steric hindrance end-capping agent B to end-cap the other end of the molecular axis to synthesize the polyrotaxane.

10. The preparation method according to claim 8, wherein, In step (a), the molar ratio of the luminescent molecule to the alkynylated crown ether is 0.85-1.5:

1.

11. The preparation method according to claim 8, wherein, In step (b), steric hindrance end-capping agent A and steric hindrance end-capping agent B are respectively a steric hindrance molecule with two reactive groups and a steric hindrance molecule with one reactive group; The molar ratio of the quencher molecule and the steric hindrance end-capping agents A and B is independently 0.8-1.1:

1.

12. The preparation method according to claim 8, wherein, In step (c), the molar ratio of crown ether with luminescent molecular groups to molecular axis with quencher molecules is 0.8-1.2:

1.

13. A mechanically color-changing material capable of responding instantly to weak forces, characterized in that, The material is a network polymer material, including a multi-arm polymer as the matrix and polyrotaxane as the crosslinking component according to any one of claims 1-7.

14. The mechanically color-changing material capable of responding instantly to weak forces according to claim 13, wherein, The molar ratio of crosslinking sites in the polyrotaxane to hydroxyl groups in the multi-arm polymer is 0.5-1.5:

1.

15. The mechanically color-changing material that can instantly respond to weak forces according to claim 13, wherein, The number-average molecular weight of the multi-arm polymer is 2 to 30 kDa, preferably 4 to 16 kDa; Preferably, the multi-armed polymer is a four-armed polycaprolactone and / or a three-armed polycaprolactone.

16. The mechanically color-changing material capable of responding instantly to weak forces according to claim 13, wherein, The crosslinking sites of the polyrotaxane are connected to the multi-arm polymer by a crosslinking agent.

17. The mechanically color-changing material that can respond instantly to weak forces according to claim 16, wherein, The crosslinking agent is selected from at least one of hexamethylene diisocyanate, toluene diisocyanate, isophorone diisocyanate, and lysine diisocyanate.

18. A method for preparing a mechanically color-changing material capable of instantaneous response to weak forces as described in any one of claims 13-17, characterized in that, The method includes the following steps: In the presence of a solvent, a multi-arm polymer, polyrotaxane, and a catalyst are reacted to obtain a mechanically color-changing material that can respond instantly to weak forces.

19. The preparation method according to claim 18, wherein, The reaction is a crosslinking reaction, and the molar ratio of the crosslinking groups of the crosslinking agent, the hydroxyl groups of the multi-arm polycaprolactone, and the crosslinking sites of the polyrotaxane is 80-120:100:0.01-0.

1. The conditions for the crosslinking reaction include: a temperature of 60-100℃ and a time of 0.5-4h.

20. The preparation method according to claim 18, wherein, The solvent is selected from at least one of tetrahydrofuran, dichloromethane, chloroform, dioxane, ethyl acetate, and butyl acetate; The concentration of the multi-arm polymer is 5-30 wt%.

21. The preparation method according to claim 18, wherein, The catalyst is selected from at least one of dibutyltin dilaurate, dibutyltin oxide, dibutyltin maleate, dibutyltin diacetate, and di-n-butylbis(acetylacetonyl)tin; The molar ratio of the catalyst to the multi-arm polymer is 0.0001-0.01:

1.

22. The preparation method according to claim 18, wherein, The reaction system also includes an antioxidant, which is selected from at least one of 2,6-di-tert-butyl-4-methylphenol, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and tris(2,4-di-tert-butyl)phosphite. The molar ratio of the antioxidant to the multi-arm polymer is 0.0001-0.01:

1.

23. The application of the polyrotaxane according to any one of claims 1-7, or the mechanically color-changing material that can respond instantly to weak forces according to any one of claims 13-17, in the field of shape memory materials, preferably in the field of stress damage detection.

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