Persistent force-induced color-changing crystal material with low force response threshold value and ultraviolet light resistance and force response threshold value regulation and control method of persistent force-induced color-changing crystal material
The preparation of force-causing crystal materials by phenolsulfophthalein derivatives solves the problem that existing materials are difficult to last for long-term discoloration and ultraviolet light sensitivity under low pressure, and achieves long-lasting discoloration response and ultraviolet light resistance below 4GPa, which is suitable for aerospace equipment and external sensing.
Patent Information
- Application Number
- CN202510611830.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-13
- Publication Date
- 2025-08-22
AI Technical Summary
Existing powerful crystal materials are difficult to experience a persistent discoloration response under conditions below 4GPa, and are sensitive to ultraviolet light, affecting the accuracy and reliability of the response.
The force-induced chromatographic crystal material was prepared by recrystallization purification, and a force-induced chromatographic system with different colors and threshold pressures was constructed by regulating the electronic properties and steric hindrance properties of the substituents, reducing the force response threshold to 2.7GPa, and resistant to ultraviolet light interference.
Force-induced crystal materials with a persistent discoloration response under conditions below 4GPa are realized, and can operate stably in ultraviolet light environments, suitable for aerospace equipment and building external sensing materials.
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Abstract
Description
Technical Field
[0001] The present invention belongs to the field of mechanochromic materials, and specifically relates to the development of a class of long-lasting mechanochromic crystal materials with a low force response threshold and resistance to ultraviolet light, as well as an effective method for regulating the force response threshold thereof. Background Art
[0002] Mechanical force is a form of energy that is widely present and easy to apply in daily production and life. Through reasonable structural design, a series of force-responsive smart materials can be constructed, which have important application value in the fields of damage detection, stress sensing and information storage. Currently, the most commonly used material types are crystals (including powder crystals), polymer bulk materials, polymer solutions, etc., among which the research on crystal materials is of great significance. Compared with other materials, crystals or powder crystals usually have a simple preparation process and do not require complex polymerization processes. At the same time, they have the characteristics of structural determination and long-range order. On the one hand, they give the material performance better controllability, stability and repeatability. On the other hand, they are conducive to in-depth and clear research on the structure-activity relationship of the material and the understanding of the nature of the response behavior.
[0003] Among the reported force-responsive crystal materials, the system that exhibits irreversible mechanochromism has a series of advantages, such as the response behavior can be observed with the naked eye, no external excitation light source is required, the signal contrast is high, and the response history can be effectively and persistently retained. It can be applied to mechanical memory, offline force measurement and other fields.
[0004] Currently, the main problems with the systems developed by researchers that undergo persistent mechanochromic changes under hydrostatic pressure include: (1) the force threshold required for the color change response is high, generally above 4 GPa, which limits its application range; (2) the materials are generally highly sensitive to ultraviolet light. When irradiated with ultraviolet light, the materials will undergo a color change response similar to that under the action of force, which affects the accuracy and reliability of the analysis of the system's force behavior. In general, there is currently a lack of force-specific responsive materials that can undergo persistent color changes under conditions below 4 GPa and can withstand ultraviolet light. Summary of the Invention
[0005] In response to the above problems, the purpose of the present invention is to provide a long-lasting mechanochromic crystal material with a low force response threshold and resistance to ultraviolet light, expand the library of force-sensitive materials that respond in the low-pressure region (less than 4 GPa) and are not interfered with by ultraviolet light, and at the same time deeply analyze the intrinsic structure-activity relationship to provide an effective method for regulating the force response threshold of the material.
[0006] To achieve the above technical objectives, the present invention provides a mechanochromic crystal material having a low force response threshold and being resistant to ultraviolet light, the structure of which is shown in Formula I:
[0007]
[0008] In formula I, R1 and R2 are each independently a hydrogen atom, an alkyl group, a cycloalkyl group, a silyl group, an alkoxy group, an alkylsiloxy group, a hydroxyl group, or a halogen group; R3 and R4 are each independently a hydrogen atom, an alkyl group, a cycloalkyl group, a silyl group, an alkoxy group, an alkylsiloxy group, or a halogen group.
[0009] Furthermore, the above-mentioned alkyl group is preferably a C1-C20 straight-chain or branched alkyl group, more preferably a C1-C10 straight-chain or branched alkyl group, and most preferably a C1-C6 straight-chain or branched alkyl group, such as methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, isobutyl, tert-butyl, pentyl, etc.
[0010] The cycloalkyl group is preferably a C3-C20 cycloalkyl group, more preferably a C3-C10 cycloalkyl group, such as cyclopropyl, cyclobutyl, cyclopentyl, cyclobutyl, adamantane, and the like.
[0011] The silyl group is preferably a C1-C20 silyl group, more preferably a C1-C10 silyl group, such as a trimethylsilyl group, a triethylsilyl group, and the like.
[0012] The alkoxy group is preferably a C1-C20 alkoxy group, more preferably a C1-C10 alkoxy group, and most preferably a C1-C6 alkoxy group, such as a methoxy group, an ethoxy group, and the like.
[0013] The alkylsilyl group is preferably a C1-C20 alkyl-substituted silyl group, and more preferably a C1-C10 polyalkyl-substituted silyl group.
[0014] The halogen is preferably Br or Cl.
[0015] For the molecular structure shown in Formula I, when R2 is a hydroxyl group, the corresponding compound can be obtained by recrystallization and purification from commercially available raw materials. The resulting crystalline material has significant mechanochromic properties, and its structure is shown in Formula II:
[0016]
[0017] In formula II, R1 is a hydrogen atom, an alkyl group, a cycloalkyl group, a silyl group, an alkoxy group, an alkylsiloxy group, a hydroxyl group, or a halogen group; R3 and R4 are each independently a hydrogen atom, an alkyl group, a cycloalkyl group, a silyl group, an alkoxy group, an alkylsiloxy group, or a halogen group.
[0018] Furthermore, the above-mentioned alkyl group is preferably a C1-C20 straight-chain or branched alkyl group, more preferably a C1-C10 straight-chain or branched alkyl group, and most preferably a C1-C6 straight-chain or branched alkyl group, such as methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, isobutyl, tert-butyl, pentyl, etc.
[0019] The cycloalkyl group is preferably a C3-C20 cycloalkyl group, more preferably a C3-C10 cycloalkyl group, such as cyclopropyl, cyclobutyl, cyclopentyl, cyclobutyl, adamantane, and the like.
[0020] The silyl group is preferably a C1-C20 silyl group, more preferably a C1-C10 silyl group, such as a trimethylsilyl group, a triethylsilyl group, and the like.
[0021] The alkoxy group is preferably a C1-C20 alkoxy group, more preferably a C1-C10 alkoxy group, and most preferably a C1-C6 alkoxy group, such as a methoxy group, an ethoxy group, and the like.
[0022] The alkylsilyl group is preferably a C1-C20 alkyl-substituted silyl group, and more preferably a C1-C10 polyalkyl-substituted silyl group.
[0023] The halogen is preferably Br or Cl.
[0024] Some typical mechanochromic crystal materials shown in formula II are listed below:
[0025]
[0026] In an embodiment of the present invention, the above-mentioned mechanochromic crystal material is prepared by the following method:
[0027] The corresponding commercial raw materials are purified by recrystallization using dichloromethane, and then the corresponding dichloromethane or ethyl acetate solutions are prepared, and the poor solvent is slowly added to the liquid surface, wherein the volume ratio of the good solvent (dichloromethane or ethyl acetate) to the poor solvent (n-hexane) is controlled at 1:3 to 1:5. The system is then left to stand at room temperature, and the target crystalline material is obtained after 3 to 7 days.
[0028] The present invention selects phenolsulfonphthalein as the force-sensitive core structure for the first time, and obtains a phenolsulfonphthalein derivative single crystal material with force-sensitive properties as shown in Formula I, which contains a five-membered ring lactone and has sp 3 The twisted spiro ring structure connected by hybrid carbon atoms, in addition, the sulfonate ion has a high stability, and the CO weak bond in the corresponding structure can be broken at a lower pressure to obtain a stable open ring structure ( Figure 1 ), while sp 3 The carbon atom transforms into sp 2 The product structure tends to be planar, with a larger conjugated area. The corresponding absorption spectrum of the system is red-shifted to the visible light region, allowing the response signal to be directly monitored by the naked eye. The force response threshold of the selected force-sensitive molecules is reduced to 2.7GPa, and their mechanochromic process is not affected by ultraviolet light. They are expected to be used as force-specific sensing materials in outdoor sunlight scenarios such as turbine blades for aerospace equipment, wind tunnel equipment, and building side beams.
[0029] Furthermore, the electronic and steric properties of the substituents in the force-sensitive structure will affect the force-responsive behavior of the molecule. Changing the substituents at specific sites is an effective method to regulate the threshold pressure of the molecular color change, thereby constructing a series of mechanochromic systems corresponding to different colors and threshold pressures. For example, appropriately increasing the steric hindrance of the substituents can reduce the threshold pressure at which the system undergoes a color change response; the length of the carbon-oxygen weak bond at the ester ring of the molecule is consistent with the size of the molecule's response threshold pressure. The shorter the weak bond, the higher the strength and the corresponding higher threshold pressure, while the electronic properties of the substituents will affect the length of the carbon-oxygen weak bond; the strength of the hydrogen bond between adjacent molecules is also significantly correlated with the molecular mechanochromic threshold pressure. The stronger the hydrogen bond, the lower the system response threshold pressure.
[0030] Compared with existing force-induced long-lasting color-changing materials, the present invention has the following technical advantages:
[0031] (1) For the first time, a phenolsulfonphthalein derivative containing a sulfonate structure was proposed as a force-sensitive core and applied to the color change response to hydrostatic pressure.
[0032] (2) For the first time, the single crystal structure of a force-sensitive phenolsulfonphthalein derivative was obtained, clarifying the specific mechanism by which it changes color under the action of force.
[0033] (3) A force-sensitive material system with a stress response threshold of only 2.7 GPa was developed, which is significantly lower than the response threshold (p = 4 GPa) corresponding to the currently reported system that undergoes persistent force-induced color change under hydrostatic pressure. In addition, the color change process is not affected by ultraviolet light and can be used as force-specific sensing materials in outdoor sunlight scenes such as turbine blades of aerospace equipment, wind tunnel equipment, and building side beams.
[0034] (4) By regulating the electronic and steric properties of the substituents in the force-sensitive structure, a series of mechanochromic systems corresponding to different colors and threshold pressures were constructed, and an effective method for regulating the mechanochromic threshold pressure of mechanochromic molecules was proposed. BRIEF DESCRIPTION OF THE DRAWINGS
[0035] Figure 1 This is a schematic diagram of the stable open-ring structure obtained by breaking the CO weak bond in the force-sensitive core structure of the mechanochromic crystal material of the present invention under relatively low pressure.
[0036] Figure 2 This is the in-situ UV-visible absorption spectrum of the PSP-Me crystal pressurization process in Example 5.
[0037] Figure 3 This is the in-situ UV-visible absorption spectrum of the PSP-Me crystal decompression process in Example 5.
[0038] Figure 4 These are in-situ micrographs obtained during the process of pressurizing and depressurizing the PSP-Me crystal in Example 5.
[0039] Figure 5 Comparison of the UV-visible diffuse reflectance spectra of the piezochromic product of PSP-Me crystals in Example 6 and phenol red (PR) powder.
[0040] Figure 6 This is the in-situ infrared spectrum under high pressure obtained during the pressurization of the PSP-Me crystal in Example 6.
[0041] Figure 7 This is the in-situ UV-visible absorption spectrum of the PSP-Pr crystal pressurization process in Example 7.
[0042] Figure 8 This is the in-situ UV-visible absorption spectrum of the PSP-Pr crystal pressure relief process in Example 7.
[0043] Figure 9 These are in-situ micrographs obtained during the process of pressurizing and depressurizing the PSP-Pr crystal in Example 7.
[0044] Figure 10 This is the in-situ UV-visible absorption spectrum of the PSP-Cl crystal during the pressurization process in Example 8, and the inset is the in-situ micrograph under the corresponding pressure.
[0045] Figure 11 This is the in-situ UV-visible absorption spectrum of the PSP-Cl crystal during the pressure relief process in Example 8, and the inset is the in-situ micrograph under the corresponding pressure.
[0046] Figure 12 This is the in-situ UV-visible absorption spectrum of the pressurized PSP-Br crystal in Example 8, and the inset is the in-situ micrograph under the corresponding pressure.
[0047] Figure 13 This is the in-situ UV-visible absorption spectrum of the PSP-Br crystal during the pressure relief process in Example 8, and the inset is the in-situ micrograph under the corresponding pressure.
[0048] Figure 14 Schematic diagram of the molecular conformation and weak bond length in the single crystal structures of PSP-Me, PSP-Pr, PSP-Cl, and PSP-Br in Example 9.
[0049] Figure 15 Schematic diagram of the number and length of intermolecular hydrogen bonds in the single crystal structures of PSP-Me, PSP-Pr, PSP-Cl, and PSP-Br in Example 9.
[0050] Figure 16This is the UV-visible diffuse reflectance spectrum of the PSP-Me crystal before and after UV irradiation in Example 10.
[0051] Figure 17 This is the UV-visible diffuse reflectance spectrum of the PSP-Pr crystal before and after UV irradiation in Example 10.
[0052] Figure 18 1 is the UV-visible diffuse reflectance spectrum of the PSP-Cl crystal before and after UV irradiation in Example 10.
[0053] Figure 19 This is the UV-visible diffuse reflectance spectrum of the PSP-Br crystal before and after UV irradiation in Example 10. DETAILED DESCRIPTION
[0054] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.
[0055] In Examples 1 to 4, the following four crystalline materials were obtained from commercially available raw materials through recrystallization purification and single crystal growth. The obtained crystalline materials have significant mechanochromic properties.
[0056]
[0057] Example 1. Preparation of PSP-Me single crystal material
[0058] PSP-Me molecules were purchased from Beijing Inokai Technology Co., Ltd. 100 mg of the obtained PSP-Me sample was added to a round-bottom flask, and then 25 mL of dichloromethane solvent and 50 mL of n-hexane solvent were added and stirred to dissolve it completely. The round-bottom flask was then connected to a rotary evaporator and the solvent was slowly removed at room temperature. When about 25 mL of solvent remained in the system, the round-bottom flask was removed and the solid-liquid mixture in the flask was poured into a ceramic Büchner funnel for filtration to obtain a purified powdered sample.
[0059] Take 20 mg of the purified PSP-Me powder sample, add 5 mL of dichloromethane solvent, heat to 35 ° C and stir to dissolve it completely, then take 1 mL of the clear liquid, filter it through a 0.22 μm polytetrafluoroethylene filter membrane and transfer it to a 10 mL flat-bottom sample bottle, then use a syringe to slowly add 5 mL of n-hexane solvent to the upper layer of the PSP-Me solution along the wall of the sample bottle, and then let the system stand at room temperature. The target material will be obtained after 3 to 7 days.
[0060] Example 2: Preparation of PSP-Pr single crystal material
[0061] PSP-Pr molecules were purchased from Shanghai Bid Pharmaceutical Technology Co., Ltd. 100 mg of the obtained PSP-Pr sample was added to a round-bottom flask, and then 25 mL of dichloromethane solvent and 50 mL of n-hexane solvent were added and stirred to dissolve it completely. The round-bottom flask was then connected to a rotary evaporator and the solvent was slowly removed at room temperature. When about 25 mL of solvent remained in the system, the round-bottom flask was removed and the solid-liquid mixture in the flask was poured into a ceramic Büchner funnel for filtration to obtain a purified powdered sample.
[0062] Take 20 mg of the purified PSP-Pr powder sample, add 5 mL of ethyl acetate solvent, heat to 35 ° C and stir to dissolve it completely, then take 1 mL of the clear liquid, filter it through a 0.22 μm polytetrafluoroethylene filter membrane and transfer it to a 10 mL flat-bottom sample bottle, then use a syringe to slowly add 5 mL of n-hexane solvent to the upper layer of the PSP-Pr solution along the wall of the sample bottle, and then let the system stand at room temperature. The target material will be obtained after 3 to 7 days.
[0063] Example 3: Preparation of PSP-Cl single crystal material
[0064] PSP-Cl molecules were purchased from Shanghai TiCI Chemical Industry Development Co., Ltd. 100 mg of the obtained PSP-Cl sample was added to a round-bottom flask, and then 25 mL of dichloromethane solvent and 50 mL of n-hexane solvent were added and stirred to dissolve it completely. The round-bottom flask was then connected to a rotary evaporator and the solvent was slowly removed at room temperature. When about 25 mL of solvent remained in the system, the round-bottom flask was removed and the solid-liquid mixture in the flask was poured into a ceramic Büchner funnel for filtration to obtain a purified powdered sample.
[0065] Take 20 mg of the purified PSP-Cl powder sample, add 5 mL of dichloromethane solvent, heat to 35 ° C and stir to dissolve it completely, then take 1 mL of the clear liquid, filter it through a 0.22 μm polytetrafluoroethylene filter membrane and transfer it to a 10 mL flat-bottom sample bottle, then use a syringe to slowly add 5 mL of n-hexane solvent to the upper layer of the PSP-Cl solution along the wall of the sample bottle, and then let the system stand at room temperature. The target material is obtained after 3 to 7 days.
[0066] Example 4. Preparation of PSP-Br single crystal material
[0067] PSP-Br molecules were purchased from Tianjin Xiens Biochemical Technology Co., Ltd. 100 mg of the obtained PSP-Br sample was added to a round-bottom flask, and then 25 mL of dichloromethane solvent and 50 mL of n-hexane solvent were added and stirred to dissolve it completely. The round-bottom flask was then connected to a rotary evaporator and the solvent was slowly removed at room temperature. When about 25 mL of solvent remained in the system, the round-bottom flask was removed and the solid-liquid mixture in the flask was poured into a ceramic Büchner funnel for filtration to obtain a purified powdered sample.
[0068] Take 20 mg of the purified PSP-Br powder sample, add 5 mL of dichloromethane solvent, heat to 35 ° C and stir to dissolve it completely, then take 1 mL of the clear liquid, filter it through a 0.22 μm polytetrafluoroethylene filter membrane and transfer it to a 10 mL flat-bottom sample bottle, then use a syringe to slowly add 5 mL of n-hexane solvent to the upper layer of the PSP-Br solution along the wall of the sample bottle, and then let the system stand at room temperature. The target material will be obtained after 3 to 7 days.
[0069] In the following Examples 5 to 8, a diamond anvil was used to analyze the response behavior of the mechanochromic crystal material of the present invention under hydrostatic pressure. The anvil face diameter of the diamond anvil was 400 μm, a T301 steel gasket was used, the gasket thickness was about 50 μm, the hole diameter of the middle sample cavity was 150 μm, the pressure transmission medium was silicone oil, and ruby particles were used for in-situ pressure calibration.
[0070] Example 5: Piezochromic Properties of PSP-Me Crystals
[0071] Based on the hydrostatic pressure provided by the diamond anvil cell technology, the response behavior of the PSP-Me crystal under high pressure was obtained, and the process was monitored in real time by in-situ UV-visible absorption spectroscopy. During the initial pressurization process, the absorption spectrum did not change much. When the pressure increased to 3.2 GPa, a new absorption peak appeared at a wavelength of 555 nm ( Figure 2 ). As the pressure increases further, the intensity of the absorption spectrum gradually increases, indicating that the number of molecules undergoing ring-opening reactions gradually increases. At the same time, since the intermolecular interaction is enhanced with the increase of pressure, the absorption peak gradually red-shifts with the increase of pressure. During the pressure release process, the newly appeared absorption peak in the visible light region still remains, but the position of the absorption peak gradually blue-shifts with the decrease of pressure ( Figure 3 ), which is caused by the increase in the distance between molecules and the weakening of the force. During the process, the partially open-ring molecules return to the closed state, which slightly reduces the intensity of the absorption spectrum. After the pressure is completely removed, the absorption peak corresponding to the open-ring product still exists, indicating that the color change response brought about by the opening of the PSP-Me ring under high pressure can effectively retain the history of mechanical force. The color of the crystal also changes significantly during the pressurization and decompression process ( Figure 4 ), corresponding to changes in the absorption spectrum. In situ micrographs show that the initial sample is colorless and transparent crystals. As the pressure increases to 3.2 GPa, the crystals turn light pink. The color gradually deepens with increasing pressure, reaching deep purple at 12.1 GPa and black at 15.0 GPa. During decompression, the color of the crystals gradually lightens. After complete pressure removal, the crystals retain their red color, having not returned to their initial colorless state.
[0072] Example 6: Analysis of the corresponding products of the piezochromic reaction of PSP-Me crystals
[0073] The UV-visible absorption spectrum of the corresponding product of the pressure-induced color change of PSP-Me crystals was compared with the UV-visible diffuse reflectance spectrum of phenol red (PR) powder, which has been confirmed to have an open-ring structure. It can be seen that the two are basically consistent, and the color of the macroscopic sample is also similar ( Figure 5 ), it is reasonable to infer that the PSP-Me crystal undergoes a heterolytic bond cleavage reaction under high pressure, forming an open ring structure similar to PR. In addition, in order to obtain specific information on the evolution of the system structure during the pressurization process, the infrared spectrum of the system was tested in situ ( Figure 6 ). Initially, the crystal is at 3500cm -1 There is a sharp absorption peak at 3470 cm-1, which corresponds to the stretching vibration of phenolic hydroxyl groups. When the pressure is increased to 3.0 GPa, which is close to the threshold pressure of 3.2 GPa corresponding to the mechanochromism of the crystal, the system -1 A new absorption peak appears at 1705cm -1 A new absorption peak appears at , which corresponds to the stretching vibration peak of the carbon-oxygen double bond, and the peak intensity gradually increases with increasing pressure, which is consistent with the formation of a keto structure by a ring-opening reaction of the molecule.
[0074] Example 7: Effect of Substituent Steric Properties on the Force Response Behavior of the Molecular Formula I
[0075] The PSP-Pr crystals with larger alkyl substituents initially have weak absorption in the visible light region and appear colorless macroscopically. However, when the pressure reaches 2.7 GPa, a new absorption peak appears at 560 nm ( Figure 7 ), the corresponding crystal turns light pink, and then the absorption peak gradually increases with the increase of pressure, corresponding to the increase in the number of molecules undergoing ring-opening reaction, and the color of the crystal also deepens to purple, and finally turns to brown-black. The absorption peak weakens during the pressure release process ( Figure 8 ), the crystal still appears bright red even after the pressure is completely released, indicating that it can also retain the pressure history ( Figure 9 It is worth noting that compared with the pressure threshold of 3.2 GPa corresponding to the color change of PSP-Me, the color change threshold of PSP-Pr with larger alkyl substituents is further reduced to 2.7 GPa. This threshold pressure is lower than the irreversible mechanochromic system reported so far, and therefore is expected to be applicable to a wider variety of practical scenarios. It also shows that appropriately increasing the steric hindrance of the substituent can reduce the threshold pressure for the system to undergo color change response.
[0076] Example 8: Effect of Substituent Electronic Properties on the Force Response Behavior of the Molecular Formula I
[0077] The alkyl group at the R1 position in the molecule of Formula I was replaced with a chlorine substituent (PSP-Cl) and a bromine substituent (PSP-Br) with strong electron-withdrawing properties. The high-pressure test results showed that both of them also had piezochromic properties, but the pressure threshold corresponding to their color change was significantly increased. The PSP-Cl crystal corresponds to 15.0 GPa ( Figure 10 ), PSP-Br crystal corresponds to 16.6GPa ( Figure 12 ), at this pressure, the absorption spectrum of the system showed a broad absorption peak covering the entire visible light region, and it continued to red-shift with increasing pressure. During the decompression process, the intensity of the corresponding absorption peak of the system gradually decreased and blue-shifted. When the pressure was completely released, a new absorption peak at 545nm was clearly observed, corresponding to the ring-opening reaction product, and the crystal macroscopic appearance was light orange-red ( Figure 11 , Figure 13 The above results show that the electronic properties of the substituents on the aromatic ring in the phenolsulfonphthalein structure have an important influence on the difficulty of the ring-opening reaction in the system. The introduction of electron-withdrawing groups will significantly increase the threshold pressure for the color change response of the system.
[0078] Example 9: Relationship between material color change response threshold pressure and crystal structure
[0079] The single crystal structure of the mechanochromic crystal material was analyzed and the results showed that the carbon-oxygen bond at the ester ring of the four molecules PSP-Me, PSP-Pr, PSP-Cl, and PSP-Br is longer than the ordinary carbon-oxygen bond length. This indicates that they have weak bond characteristics ( Figure 14 ), and the specific weak bond length order is consistent with the response threshold pressure of the molecule. For example, the carbon-oxygen weak bond in the PSP-Pr molecule is the longest, reaching The corresponding threshold pressure is also the lowest (2.7 GPa), and this length also exceeds the reported pressure-induced chromic molecule benzoxazine based on covalent bond breaking. Spiropyran Phenolphthalein and naphthopyrans The weak bond in the PSP-Br molecule is the shortest. This indicates that the bond has a relatively high strength, corresponding to the highest threshold pressure (16.6 GPa). In addition, there is a strong hydrogen bond between the sulfonyl oxygen on the lactone ring and the phenolic hydroxyl group of another molecule in all four molecules ( Figure 15). Considering that the molecular motion in the crystal is highly restricted, the intermolecular hydrogen bonding is further enhanced under pressure, resulting in an increase in the negative charge on the phenolic hydroxyl oxygen. Due to the conjugation effect of the aromatic ring, the positive charge of the spirocyclic carbon increases, making it more likely to undergo heterolytic cleavage of the carbon-oxygen weak bond. That is, stronger hydrogen bonding can reduce the reaction energy barrier and correspondingly reduce the threshold pressure corresponding to the color change of the system. A detailed analysis of the intermolecular hydrogen bonding in the four crystals shows that in the PSP-Pr crystal, the two phenolic hydroxyl groups in each molecule are hydrogen bonded with the sulfonyl oxygen of the adjacent molecule, corresponding to an OH...O length of and This multi-site strong hydrogen bonding is expected to significantly reduce the energy barrier of its ring-opening reaction, which corresponds to its actual lowest response threshold pressure. In contrast, the closest distance between the phenolic hydroxyl group of a molecule and the sulfonyl oxygen of an adjacent molecule in the PSP-Br crystal is There is only weak hydrogen bonding, which is consistent with the highest response threshold pressure. In PSP-Me and PSP-Cl crystals, there is a phenolic hydroxyl group in each molecule that has a hydrogen bond with the adjacent molecule, and the two adjacent molecules form a dimer associated with a double hydrogen bond, and the corresponding OH...O lengths are and The stronger intermolecular hydrogen bonding in the former gives it higher ring-opening reactivity, corresponding to a lower threshold pressure. Overall, there is a significant correlation between the strength of the corresponding hydrogen bonding in the four crystals and the threshold pressure of molecular mechanochromism. The stronger the hydrogen bonding, the lower the threshold pressure of the system response.
[0080] In summary, for application scenarios that require color change response to higher pressure, R1, R3, and R4 in the corresponding molecular structure II should preferably be selected from alkyl substituents with less steric hindrance and halogen substituents with strong electron-withdrawing properties; for application scenarios that require color change response to lower pressure, R1, R3, and R4 in the corresponding molecular structure II should preferably be selected from alkyl substituents with greater steric hindrance and substituents with weak electron-withdrawing properties.
[0081] Example 10: Ultraviolet light tolerance of crystalline materials
[0082] To test whether the selected four molecules PSP-Me, PSP-Pr, PSP-Cl, and PSP-Br are sensitive to ultraviolet light, their solids were irradiated for 2 hours under a high-pressure mercury lamp with a power of 250W and an emission wavelength of mainly 365nm. There was no obvious difference in the UV-visible diffuse reflectance spectra of the solids before and after illumination, indicating that the color change response of this type of structure is not interfered by ultraviolet light ( Figure 16 , Figure 17 , Figure 18 , Figure 19 ), and is less affected by the environment in practical applications.
[0083] The above describes the long-lasting mechanochromic crystal material with a low force response threshold and resistance to ultraviolet light provided by the present invention and the effective method for regulating its force response threshold through detailed embodiments. It should be understood by those skilled in the art that certain changes or modifications may be made to the present invention without departing from the essence of the present invention, and are not limited to the contents disclosed in the embodiments.
Claims
1. Application of the phenolsulfonphthalein derivatives containing a sulfonate structure shown in Formula I as mechanochromic materials: In formula I, R1 and R2 are each independently a hydrogen atom, an alkyl group, a cycloalkyl group, a silyl group, an alkoxy group, an alkylsiloxy group, a hydroxyl group, or a halogen group; R3 and R4 are each independently a hydrogen atom, an alkyl group, a cycloalkyl group, a silyl group, an alkoxy group, an alkylsiloxy group, or a halogen group.
2. The use according to claim 1, characterized in that The alkyl group is a C1-C20 straight chain or branched alkyl group; the cycloalkyl group is a C3-C20 cycloalkyl group; the silyl group is a C1-C20 silyl group; the alkoxy group is a C1-C20 alkoxy group; the alkylsiloxy group is a C1-C20 alkyl-substituted siloxy group; and the halogen group is Br or Cl.
3. The use according to claim 1, characterized in that In formula I, R2 is a hydroxyl group.
4. The use according to claim 3, characterized in that The phenolsulfonphthalein derivative containing a sulfonate structure is selected from one or more of the following compounds:
5. The use according to any one of claims 1 to 4, characterized in that A phenolsulfonphthalein derivative containing a sulfonate structure shown in Formula I is made into a single crystal material and applied to color change response to hydrostatic pressure.
6. The use according to any one of claims 1 to 4, characterized in that The single crystal material of the phenolsulfonphthalein derivative containing a sulfonate structure shown in Formula I is used as a force-specific sensing material under sunlight, and its mechanochromic process is not interfered by ultraviolet light.
7. The use according to any one of claims 1 to 4, characterized in that By regulating the electronic properties and / or steric properties of the substituents in the molecular structure shown in Formula I, a series of mechanochromic materials corresponding to different colors and threshold pressures are constructed.
8. The use according to claim 7, characterized in that When R2 is a hydroxyl group, the threshold pressure of the mechanochromic material at which the color change response occurs is lowered by introducing substituents with greater steric hindrance and / or weaker electron-withdrawing properties at positions R1, R3, and R4 in Formula I; alternatively, the threshold pressure of the mechanochromic material at which the color change response occurs is increased by introducing substituents with less steric hindrance and / or stronger electron-withdrawing properties at positions R1, R3, and R4 in Formula I.
9. A method for regulating the chromatic threshold pressure of a mechanochromic material, wherein the molecular structure of the mechanochromic material is as shown in Formula I: In Formula I, R1 and R2 are each independently a hydrogen atom, an alkyl group, a cycloalkyl group, a silyl group, an alkoxy group, an alkylsiloxy group, a hydroxyl group, or a halogen group; R3 and R4 are each independently a hydrogen atom, an alkyl group, a cycloalkyl group, a silyl group, an alkoxy group, an alkylsiloxy group, or a halogen group; By introducing substituents with different electronic and / or steric properties into the molecular structure shown in Formula I, mechanochromic materials corresponding to different color change threshold pressures are constructed.
10. The method according to claim 9, wherein When R2 is a hydroxyl group, the threshold pressure of the mechanochromic material at which the color change response occurs is lowered by introducing substituents with greater steric hindrance and / or weaker electron-withdrawing properties at positions R1, R3, and R4 in Formula I; alternatively, the threshold pressure of the mechanochromic material at which the color change response occurs is increased by introducing substituents with less steric hindrance and / or stronger electron-withdrawing properties at positions R1, R3, and R4 in Formula I.