Self-repairable thermochromic polydimethylsiloxanes and methods of making

Abstract

The present application relates to a kind of self-repairable thermochromic polydimethylsiloxane and preparation method, which utilizes amino silicone oil (PDMS-NH2) as main material, adds metal salt and polyaldehyde to form coordination bond and imine bond, so that amino silicone oil is crosslinked and cured with mechanical properties.The metal coordination bond and dynamic imine bond jointly give PDMS temperature change and self-repair function.The self-repairable thermochromic PDMS prepared by the present application has the advantages of simple preparation process, short process flow, environmental protection, less equipment investment, high cost performance, recyclable and the like.

Description

Technical Field

[0001] This invention belongs to the field of organosiloxane preparation technology, and relates to a self-healing thermochromic PDMS and its preparation method. Technical Background

[0002] Polydimethylsiloxane (PDMS) has become an ideal material for light modulation due to its high optical transparency, good thermal stability, excellent mechanical strength, non-toxicity, ease of processing, and low cost. Its transparency and / or color can be reversibly altered by changing its surface and internal microstructure or by using a doping medium. However, the current manufacturing processes for thermochromic smart optical materials based on PDMS are complex, costly, and inefficient, posing significant challenges to their practical application. Therefore, there is an urgent need to develop simple and effective strategies for designing novel thermochromic smart optical materials.

[0003] Thermochromism refers to the phenomenon where the color of certain substances changes with temperature. Currently, thermochromic materials are mainly divided into inorganic and organic materials. For example, invention patent (ZL201811339325.7) discloses a vanadium dioxide-based thermochromic composite material with adjustable color development and its application. The vanadium dioxide-based thermochromic composite material includes vanadium dioxide-based thermochromic materials and ultraviolet photochromic materials. Alternatively, organic thermochromic materials can be combined with inorganic thermochromic materials. For example, invention patent (CN201810301698.9) discloses a method for preparing thermochromic coatings, using a combination of inorganic and organic thermochromic materials. However, inorganic thermochromic materials are in powder form, have poor processability, are difficult to mold, are highly toxic to humans, and are expensive, making them difficult to apply to wearable skin devices.

[0004] Compared with inorganic thermochromic materials, organic thermochromic materials have many advantages such as easy modification, adjustable color, obvious color change, and strong flexibility. Among them, small-molecule organic thermochromic materials have poor stability, which limits their practical application, while organic polymer thermochromic materials have good stability and a wide variety, making them a research hotspot in recent years. The article "Research Progress of Thermochromic Polymers" introduces the applications of thermochromic polymers prepared using polyacetylene, polythiophene, etc. Invention patent (CN202110264261.4) discloses a thermochromic organosilicon resin prepared using polyacids, phenylsiloxanes, silane coupling agents, and lower alcohols. However, due to the inherent softness of PDMS, it is prone to mechanical damage during long-term use, leading to a decline in the material's original mechanical and electrochemical properties, and even loss of its original function. Therefore, extending the service life of PDMS has become an important research problem. Imparting self-healing properties to PDMS is an effective method to solve this problem. Summary of the Invention

[0005] One of the objectives of this invention is to provide a self-healing thermochromic polydimethylsiloxane and its preparation method, which enhances the mechanical properties of PDMS elastomers by employing a synergistic crosslinking mechanism of imine bonds and metal coordination bonds, while simultaneously endowing PDMS with self-healing properties.

[0006] To achieve the above-mentioned objectives, the technical solution of this invention is as follows:

[0007] A method for preparing a self-healing thermochromic polydimethylsiloxane includes the following steps:

[0008] (1) Dissolve amino silicone oil PDMS-NH2 in an organic solvent under magnetic stirring to obtain a mixed organic solution;

[0009] (2) Dissolve the polyaldehyde raw material in an organic solvent under magnetic stirring, and then add it dropwise to the organic solution in step (1) while stirring for 3 minutes.

[0010] (3) Dissolve the metal salt in an organic solvent, mix it evenly, and then add it to the solution obtained in step (2). Stir continuously for 2 minutes.

[0011] (4) Place the final mixed solution obtained in step (3) in a fume hood and evaporate at room temperature for 24 hours to remove organic solvents. After curing, self-healing thermochromic PDMS is obtained.

[0012] As a preferred method, the amino silicone oil used has amino groups on its side chains, an ammonia value of 0.4, a viscosity of 800-5000 cPs, and is not further purified; its molecular formula is:

[0013]

[0014] As a preferred embodiment, the organic solvent in step (1) is one or more of tetrahydrofuran, ethyl acetate, chloroform, dichloromethane, toluene, and N,N-dimethylformamide. The solvent is volatile and can dissolve amino silicone oil. Sufficient amount of solvent is used.

[0015] As a preferred method, the polyaldehyde mentioned in step (2) is one or more of terephthalaldehyde, pyromellitic aldehyde, isophthalaldehyde, o-phthalaldehyde, and malondialdehyde, which are soluble in organic solvents. First, it is dissolved in an organic solvent and dispersed evenly to form an organic solution of 50 mg / ml. Then, it is added dropwise to the diluted amino silicone oil mixed solution. The concentration of polyaldehyde in the final mixed solution obtained in step (2) is 1 wt% to 3 wt%.

[0016] As a preferred method, the metal salt in step (3) is a copper salt that is soluble in an organic solvent. Before use, it is dissolved in the organic solvent in step (3) to form an organic solution of 50 mg / ml. The copper salt content in the final solution obtained in step (3) is 1 wt% to 3 wt%.

[0017] As a preferred method, step (4) is carried out at room temperature for a period of not less than 24 hours to ensure that the solvent is completely evaporated.

[0018] A second objective of this invention is to provide a self-healing thermochromic polydimethylsiloxane obtained by the preparation method described above.

[0019] The beneficial effects of this invention are as follows:

[0020] (1) The thermochromic PDMS prepared by the present invention has the advantages of obvious color change at 30℃~90℃, easy preparation, easy modification, and high cost performance.

[0021] (2) The preparation process of this invention is simple, the process flow is short, it is environmentally friendly, and the equipment investment is low.

[0022] (3) The present invention has a self-healing function, which can extend the service life and can be recycled and reused. Attached Figure Description

[0023] Figure 1 This is a schematic diagram illustrating the fabrication process of the self-healing thermochromic polydimethylsiloxane (PDMS) of the present invention.

[0024] Figure 2 This is a schematic diagram of the self-healing process of PDMS after shear wave damage in the present invention. Detailed Implementation

[0025] The present invention will now be described in detail with reference to specific implementation examples and accompanying drawings. It should be noted that the following implementation examples are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0026] All raw materials used in the examples are commercial products and have not been further purified.

[0027] The embodiments provide a method for preparing a self-healing thermochromic polydimethylsiloxane, comprising the following steps:

[0028] (1) Under magnetic stirring, amino silicone oil PDMS-NH2 is dissolved in an organic solvent to obtain a mixed organic solution; preferably, the amino silicone oil used has amino groups on its side chains, an ammonia value of 0.4, a viscosity of 800-5000 cPs, and is not further purified, with the molecular formula:

[0029]

[0030] Preferably, the organic solvent in step (1) is one or more of tetrahydrofuran, ethyl acetate, chloroform, dichloromethane, toluene, and N,N-dimethylformamide. The solvent is volatile and can dissolve amino silicone oil. Sufficient amount of solvent is used.

[0031] (2) Dissolve the polyaldehyde raw material in an organic solvent under magnetic stirring, and then add it dropwise to the organic solution in step (1) while stirring continuously for 3 minutes; preferably, the polyaldehyde in step (2) is one or more of terephthalaldehyde, trimesophthalaldehyde, isophthalaldehyde, o-phthalaldehyde, and malondialdehyde that are soluble in organic solvents. First, dissolve it in an organic solvent and disperse it evenly to form an organic solution of 50 mg / ml, and then add it dropwise to the diluted amino silicone oil mixed solution. The concentration of polyaldehyde in the final mixed solution obtained in step (2) is 1 wt% to 3 wt%.

[0032] (3) Dissolve the metal salt in an organic solvent, mix it evenly, and add it to the solution obtained in step (2). Stir continuously for 2 minutes. Preferably, the metal salt in step (3) is a copper salt that is soluble in an organic solvent. Before use, it is dissolved in the organic solvent in step (3) to form an organic solution of 50 mg / ml. The copper salt content in the final solution obtained in step (3) is 1 wt% to 3 wt%.

[0033] (4) Place the final mixed solution obtained in step (3) in a fume hood and evaporate at room temperature for 24 hours to remove organic solvents. After curing, self-healing thermochromic PDMS is obtained. Preferably, step (4) is evaporated at room temperature for no less than 24 hours to ensure that the solvent is completely evaporated.

[0034] Example 1

[0035] This embodiment provides a method for preparing a self-healing thermochromic polydimethylsiloxane, comprising the following steps:

[0036] (1) 5g of amino silicone oil PDMS-NH2 was dissolved in 10ml of tetrahydrofuran under magnetic stirring to obtain a mixed organic solution; the amino silicone oil used had amino groups on its side chains, an ammonia value of 0.4, a viscosity of 800-5000 cPs, and was not further purified; its molecular formula was:

[0037]

[0038] (2) Dissolve terephthalaldehyde in tetrahydrofuran under magnetic stirring to form an organic solution of 50 mg / ml. Then, while stirring, add 1 ml of the 50 mg / ml terephthalaldehyde and tetrahydrofuran mixed solution to the organic solution in step (1). The concentration of terephthalaldehyde in the final mixed solution obtained in step (2) is 1 wt%. Continue stirring for 3 min.

[0039] (3) Dissolve copper chloride in tetrahydrofuran to form an organic solution of 50 mg / ml. After mixing evenly, add 1 ml of 50 mg / ml CuCl2 tetrahydrofuran solution to the solution obtained in step (2). The CuCl2 content in the final solution obtained in step (3) is 1 wt%. Stir continuously for 2 min.

[0040] (4) The final mixed solution obtained in step (3) was placed in a fume hood and evaporated at room temperature for 24 hours to remove the organic solvent. After curing, self-healing thermochromic PDMS was obtained. The PDMS sample after evaporation and curing was heated at 30℃, 60℃ and 90℃, and its color change was observed. At 30℃, PDMS was dark blue. After heating to 60℃, the color turned blue-cyan. After heating to 90℃, the color turned green.

[0041] Example 2

[0042] The difference between this embodiment and Example 1 is that the terephthalaldehyde content in the final mixed solution obtained in step (2) is 2 wt%. The PDMS sample after volatilization and curing was heated at 30℃, 60℃, and 90℃, and its color change was observed. After heating to 30℃, the PDMS was dark blue, after heating to 60℃ it became light blue, and after continuing to heat to 90℃ the color became dark green.

[0043] Example 3

[0044] The difference between this embodiment and Example 1 is that the terephthalaldehyde content in the final mixed solution obtained in step (2) is 3 wt%. The PDMS sample after volatilization and curing was heated at 30℃, 60℃, and 90℃, and its color change was observed. At 30℃, PDMS was dark blue, turned blue after being heated to 60℃, and turned cyan-green after being heated to 90℃.

[0045] Example 4

[0046] The difference between this embodiment and Example 1 is that the CuCl2 content is 100mg, and the copper salt content in the final solution obtained in step (3) is 2wt%. The PDMS sample after volatilization and curing was heated at 30℃, 60℃, and 90℃, and its color change was observed. At 30℃, PDMS was sky blue, turned blue-black after being heated to 60℃, and turned dark green after being heated to 90℃.

[0047] Example 5

[0048] The difference between this embodiment and Example 1 is that the terephthalaldehyde content in the final mixed solution obtained in step (2) is 2wt%, the CuCl2 content is 100mg, and the copper salt content in the final solution obtained in step (3) is 2wt%. The PDMS sample after volatilization and curing was heated at 30℃, 60℃, and 90℃, and its color change was observed. At 30℃, PDMS was bluish-white; after heating to 60℃, it turned sky blue; and after further heating to 90℃, the color turned dark green.

[0049] Example 6

[0050] The difference between this embodiment and Example 1 is that the terephthalaldehyde content in the final mixed solution obtained in step (2) is 3wt%, the CuCl2 content is 100mg, and the copper salt content in the final solution obtained in step (3) is 2wt%. The PDMS sample after volatilization and curing was heated at 30℃, 60℃, and 90℃, and its color change was observed. At 30℃, PDMS was bluish-white; after heating to 60℃, it turned light blue; and after continuous heating to 90℃, the color turned dark green.

[0051] Example 7

[0052] The difference between this embodiment and Example 1 is that the CuCl2 content is 150 mg, and the copper salt content in the final solution obtained in step (3) is 3 wt%. The PDMS sample after volatilization and curing was heated at 30℃, 60℃, and 90℃, and its color change was observed. At 30℃, PDMS was green, and after heating to 60℃, the color turned dark green, and after heating to 90℃, the dark green color deepened further.

[0053] Example 8

[0054] The difference between this embodiment and Example 1 is that the terephthalic acid content in the polydimethylsiloxane product in the final mixed solution obtained in step (2) is 2 wt%, and the CuCl2 content in the final solution obtained in step (3) is 3 wt%. The PDMS sample after volatilization and curing was heated at 30℃, 60℃, and 90℃, and its color change was observed. At 30℃, PDMS was dark green; after heating to 60℃, the dark green deepened; and after further heating to 90℃, the dark green deepened further, turning into dark black.

[0055] Example 9

[0056] The difference between this embodiment and Example 1 is that the terephthalaldehyde content in the final mixed solution obtained in step (2) is 3 wt%, the CuCl2 content is 150 mg, and the copper salt content in the final solution obtained in step (3) is 3 wt%. The PDMS sample after volatilization and curing was heated at 30℃, 60℃, and 90℃, and its color change was observed. At 30℃, PDMS was dark green; after heating to 60℃, the dark green deepened; and after continuously raising the temperature to 90℃, the dark green deepened further, turning into dark black.

[0057] Example 10

[0058] PDMS prepared according to Example 1 was divided into two parts. The broken ends were then tightly joined together and heated at 90°C for 30 minutes. The broken ends showed obvious healing. The self-healing PDMS could be stretched and restored to its original shape at will. Figure 2 A schematic diagram of its self-healing process is shown. This indicates that the obtained polydimethylsiloxane product has good self-healing properties and recyclable processing performance.

[0059] Example 11

[0060] The difference between this embodiment and Embodiment 1 is that the organic solvent in step (1) is ethyl acetate, which is volatile and can dissolve amino silicone oil, and the amount of solvent used is sufficient.

[0061] The polyaldehyde mentioned in step (2) is pyromellitic aldehyde, which is soluble in organic solvents. The concentration of the polyaldehyde in the final mixed solution obtained in step (2) is 2 wt%, and the copper salt content in the final solution obtained in step (3) is 2 wt%. The final polydimethylsiloxane is dark blue at 30°C, turns cyan-green when heated to 60°C, and turns gray-green when heated to 90°C.

[0062] Example 12

[0063] The difference between this embodiment and Embodiment 1 is that the organic solvent in step (1) is chloroform, which is volatile and can dissolve amino silicone oil, and the amount of solvent used is sufficient.

[0064] The polyaldehyde mentioned in step (2) is isophthalaldehyde, which is soluble in organic solvents. The concentration of polyaldehyde in the final mixed solution obtained in step (2) is 2 wt%, and the copper salt content in the final solution obtained in step (3) is 2 wt%. The color change of the final polydimethylsiloxane upon heating is the same as in Example 5.

[0065] Example 13

[0066] The difference between this embodiment and Embodiment 1 is that the organic solvent in step (1) is chloroform, which is volatile and can dissolve amino silicone oil, and the amount of solvent used is sufficient.

[0067] The polyaldehyde mentioned in step (2) is phthalaldehyde, which is soluble in organic solvents. The concentration of polyaldehyde in the final mixed solution obtained in step (2) is 2 wt%, and the copper salt content in the final solution obtained in step (3) is 2 wt%. The color change of the final polydimethylsiloxane upon heating is the same as in Example 5.

[0068] Example 14

[0069] The difference between this embodiment and Embodiment 1 is that the organic solvent in step (1) is toluene, which is volatile and can dissolve amino silicone oil, and the amount of solvent used is sufficient.

[0070] The polyaldehyde mentioned in step (2) is terephthalaldehyde, which is soluble in organic solvents. The concentration of the polyaldehyde in the final mixed solution obtained in step (2) is 2 wt%, and the copper salt content in the final solution obtained in step (3) is 2 wt%. The color change of the final polydimethylsiloxane upon heating is the same as in Example 5.

[0071] Example 15

[0072] The difference between this embodiment and Embodiment 1 is that the organic solvent in step (1) is toluene solvent, which is volatile and can dissolve amino silicone oil, and the amount of solvent used is sufficient.

[0073] The polyaldehyde mentioned in step (2) is bromomalondialdehyde, which is soluble in organic solvents. The concentration of the polyaldehyde in the final mixed solution obtained in step (2) is 2 wt%, and the copper salt content in the final solution obtained in step (3) is 2 wt%. The final polydimethylsiloxane is blue at 30°C, turns green when heated to 60°C, and turns dark green when heated to 90°C.

Claims

1. A method for preparing a self-healing thermochromic polydimethylsiloxane, characterized in that... Includes the following steps: (1) Under magnetic stirring, amino silicone oil PDMS-NH2 was dissolved in an organic solvent to obtain a mixed organic solution; the amino silicone oil PDMS-NH2 has amino groups in its side chain, an ammonia value of 0.4, a viscosity of 800-5000 cPs, and was not further purified; (2) Dissolve the polyaldehyde raw material in an organic solvent under magnetic stirring, and then add it dropwise to the organic solution in step (1) while stirring continuously for 3 min; the polyaldehyde is one or more of terephthalaldehyde, trimesophthalaldehyde, isophthalaldehyde, o-phthalaldehyde, and malondialdehyde, which are soluble in organic solvents; first dissolve it in an organic solvent and disperse it evenly to form an organic solution of 50 mg / ml, and then add it dropwise to the diluted amino silicone oil mixed solution; the concentration of polyaldehyde in the final mixed solution obtained in step (2) is 1wt%~3wt%; (3) Dissolve the metal salt in an organic solvent, mix well, and add it to the solution obtained in step (2). Stir continuously for 2 minutes. The metal salt is a copper salt that is soluble in organic solvents. Before use, dissolve it in the organic solvent described in step (3) to form an organic solution of 50 mg / ml. The copper salt content in the final solution obtained in step (3) is 1 wt% to 3 wt%. (4) Place the final mixed solution obtained in step (3) in a fume hood and evaporate at room temperature for 24 hours to remove organic solvents. After curing, self-healing thermochromic PDMS is obtained.

2. The method for preparing self-healing thermochromic polydimethylsiloxane according to claim 1, characterized in that: The amino silicone oil used contains amino groups in its side chains, has an ammonia value of 0.4, a viscosity of 800-5000 cPs, and is not further purified. Its molecular formula is: , where the repeating units a and b are positive integers.

3. The method for preparing self-healing thermochromic polydimethylsiloxane according to claim 1, characterized in that: The organic solvent mentioned in step (1) is one or more of tetrahydrofuran, ethyl acetate, chloroform, dichloromethane, toluene, and N,N-dimethylformamide. The solvent is volatile and can dissolve amino silicone oil. Sufficient amount of solvent is used.

4. The method for preparing self-healing thermochromic polydimethylsiloxane according to claim 1, characterized in that, Step (4) Evaporate at room temperature for no less than 24 hours to ensure complete evaporation of the solvent.

5. The self-healing thermochromic polydimethylsiloxane obtained by the preparation method according to any one of claims 1 to 4.

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