Multi-synergistic self-repairing polysiloxane elastomer and preparation method thereof

Abstract

The invention relates to the technical field of organic silicon elastomers, in particular to a multi-synergistic self-repairing polysiloxane elastomer and a preparation method thereof, and the preparation method is based on a dynamic borate bond and imine bond synergistic preparation process and a hydrogen bond and dynamic borate bond / imine bond synergistic preparation process. Compared with a single dynamic imine bond or borate bond self-repairing system, the preparation method of the multi-synergetic self-repairing polysiloxane elastomer has the advantages that the mechanical property and the self-repairing efficiency of a material are improved by utilizing a strong and weak dynamic bond synergetic system, the process for preparing the organic silicon elastomer is simple, convenient and feasible, the reaction period is short, and the cost is low. The reaction can be completed under the room temperature condition, the self-healing condition is mild, a sample can be self-repaired only under the room temperature condition, industrial production and practical application are greatly facilitated, and the method is expected to be applied to sealing materials and flexible electronic devices. The used raw materials are commercially available, so that large-scale production in industrialization is facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of silicone elastomers, and in particular to a multi-synergistic self-healing polysiloxane elastomer and a preparation method thereof. Background Art

[0002] Silicone elastomers have been widely used in biomedicine, flexible electronic devices, high-performance coatings and other fields due to their excellent properties such as stability, aging resistance, biocompatibility and low surface energy. However, during use, silicone elastomers will inevitably wear and blemish, resulting in reduced material performance and safety hazards, seriously affecting the service life of the material, which greatly limits the scope of use of silicone elastomers. Therefore, it is particularly important to obtain polysiloxane elastomers with better mechanical properties and stronger self-healing ability through structural design. At present, most of the research focuses on introducing dynamic bonds or hydrogen bonds into polymer material systems through certain means to achieve the effect of self-healing. Among them, polysiloxane elastomers constructed in a multiple synergistic manner are very different from single dynamic bonds in terms of preparation methods and self-healing conditions.

[0003] For example, CN110092911B discloses a polysiloxane elastomer material based on the Diels-Alder reaction. After the material is damaged by an incision, the self-healing process requires a long and strict heat treatment of the material sample at a temperature of up to 130 degrees Celsius, and then it needs to be repeatedly carried out in an air atmosphere at 80 degrees Celsius for more than 60 hours, which greatly limits the actual production and application.

[0004] Another example is a method for preparing a self-healing polysiloxane elastomer based on strong and weak hydrogen bonds disclosed in CN115819776B. By blending linear functional polysiloxane and hyperbranched silica spheres, multiple strong and weak hydrogen bond interactions are introduced. Although the polysiloxane elastomer prepared by this method can achieve good self-healing at room temperature, the synthesis process is complicated and the reaction cycle of a single step is as long as more than 4 days.

[0005] Therefore, developing a polysiloxane elastomer with a simple preparation process, short reaction cycle and the ability to self-heal under mild conditions has become a research hotspot and is of great significance for the actual production and application of such materials. Therefore, we proposed a method for preparing a multi-synergistic self-healing polysiloxane elastomer. Summary of the invention

[0006] The main purpose of the present invention is to provide a multi-synergistic self-healing polysiloxane elastomer and a preparation method thereof, which can effectively solve the problems in the background technology.

[0007] One of the purposes of the present invention is to provide a method for preparing a multi-synergistic self-healing polysiloxane elastomer, and the technical scheme adopted is:

[0008] A method for preparing a multi-synergistic self-healing polysiloxane elastomer, the method is based on a synergistic preparation process of a dynamic borate bond and an imine bond or a synergistic preparation process of a hydrogen bond and a dynamic borate bond / imine bond.

[0009] The collaborative preparation process based on dynamic borate ester bond and imine bond includes the following steps:

[0010] S1A: Low molecular weight linear polydimethylsiloxane (PDMS-NH2) was used to coordinate with boronic acid groups or undergo reductive amination with aldehyde groups to prepare two types of polysiloxane prepolymers;

[0011] Furthermore, the polydimethylsiloxane is terminated with aminopropyl groups, and the molecular weight of the polydimethylsiloxane includes but is not limited to 1000, 2000 and 5000.

[0012] Furthermore, the boric acid compound is selected from at least one of o-formylphenylboronic acid, p-formylphenylboronic acid, m-formylphenylboronic acid, 5-formyl 2-hydroxyphenylboronic acid, and 3-formyl 2-methylphenylboronic acid.

[0013] Furthermore, the benzaldehyde compound is selected from at least one of terephthalaldehyde, o-phthalaldehyde, isophthalaldehyde, and 2,5-diethylterephthalaldehyde.

[0014] S2A: The obtained two types of polydimethylsiloxane prepolymers are blended to obtain two types of dynamically bonded polysiloxane elastomers;

[0015] Furthermore, the obtained polysiloxane elastomer was placed in a vacuum defoaming box to remove bubbles, and then the remaining solvent was removed in an oven at 60°C.

[0016] Preferably, aminopropyl-terminated linear polydimethylsiloxane with a molecular weight of 1000 and o-formylphenylboronic acid are selected in S1A, stirred and dissolved in ultra-dry tetrahydrofuran, poured into a mold, and left open for 18 hours to obtain a light yellow viscous liquid sample.

[0017] Preferably, aminopropyl-terminated linear polydimethylsiloxane with a molecular weight of 1000 and terephthalaldehyde are selected in S1A, stirred and dissolved in ultra-dry tetrahydrofuran, poured into a mold, and left open for 18 hours to obtain a sample of light yellow viscous liquid.

[0018] Preferably, the boric acid compound and the benzaldehyde compound in S1A have different reactivity, and the blending ratio needs to be adjusted according to the actual reaction conditions and the performance requirements of the target elastomer.

[0019] The synergistic preparation process based on hydrogen bonding and dynamic borate ester bonding / imine bonding includes the following steps:

[0020] S1B: Low molecular weight linear polydimethylsiloxane (PDMS-NH2) reacts with isocyanate groups to prepare polysiloxane prepolymers containing hydrogen bonds;

[0021] Furthermore, the isocyanate is selected from one or more of hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, and isophorone diisocyanate.

[0022] S2B: The obtained prepolymer is reacted with o-formylphenylboronic acid / terephthalaldehyde to obtain a polysiloxane with coordinated hydrogen bonds and dynamic borate ester bonds / imine bonds through boron nitrogen coordination or reductive amination reaction.

[0023] Furthermore, the boric acid compound is selected from one or more of o-formylphenylboronic acid, p-formylphenylboronic acid, and m-formylphenylboronic acid.

[0024] Furthermore, the benzaldehyde compound is selected from one or more of terephthalaldehyde, o-phthalaldehyde, and isophthalaldehyde.

[0025] Preferably, aminopropyl-terminated linear polydimethylsiloxane with a molecular weight of 1000 and hexamethylene isocyanate are selected in S1B, reacted in super-dry dichloromethane, and then the excess solvent is evaporated to obtain a light yellow viscous liquid sample.

[0026] Preferably, the prepolymer of S1B and o-formaldehyde phenylboronic acid are selected in S2B, stirred and dissolved in ultra-dry THF, poured into a mold, and left open for 18 hours to obtain a sample of light yellow transparent polysiloxane elastomer.

[0027] Preferably, the prepolymer of S1B and terephthalaldehyde are selected in S2B, stirred and dissolved in super-dry THF, poured into a mold, and left open for 18 hours to obtain a sample of a colorless and transparent polysiloxane elastomer.

[0028] The second object of the present invention is to provide a multi-synergistic self-healing polysiloxane elastomer, and the technical solution adopted is:

[0029] A multi-synergistic self-healing polysiloxane elastomer is prepared by adopting the preparation method of the multi-synergistic self-healing polysiloxane elastomer.

[0030] The polysiloxane elastomer contains any of the following technical features:

[0031] A. Dynamic borate ester bond and imide bond,

[0032] B. Hydrogen bonds and dynamic borate ester bonds,

[0033] C. Hydrogen bond and dynamic imine bond.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. Compared with a single dynamic imine bond or borate ester bond self-repairing system, the present invention utilizes a system of strong and weak dynamic bonds to improve the mechanical properties and self-repairing efficiency of the material.

[0036] 2. The process for preparing the organosilicon elastomer of the present invention is simple and easy, the reaction cycle is short, and the reaction can be completed at room temperature.

[0037] 3. The self-healing conditions are mild, and the sample can achieve self-repair only at room temperature, which is greatly convenient for industrial production and practical applications, and is expected to be applied to sealing materials and flexible electronic devices. The raw materials used are all commercially available, which is conducive to scale-up production in industrialization. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Schematic diagram of the synthesis route of polysiloxane elastomer with dynamic borate bond and dynamic imine bond;

[0039] Figure 2 Schematic diagram of the synthesis route of polysiloxane elastomers with coordinated hydrogen bonds and dynamic borate bonds / imine bonds;

[0040] Figure 3 is the structural formula of phenylboric acid, benzaldehyde and isocyanate that can be used;

[0041] Figure 4 These are optical microscope images of the self-healing polysiloxane elastomers of Example 7 (Figure a), Example 8 (Figure b) and Example 9 (Figure c);

[0042] Figure 5 is the rheological diagram of the polysiloxane elastomer of Example 7;

[0043] Figure 6 is a stress-strain curve diagram of the polysiloxane elastomer before and after healing of Example 7;

[0044] Figure 7 The self-healing optical microscope images of the polysiloxane elastomers of Example 10 (Figure a) and Example 11 (Figure b);

[0045] Figure 8 is the rheological diagram of the polysiloxane elastomer of Example 10;

[0046] Fig. 9 Graph showing the stress-strain curve of the polysiloxane elastomer of Example 10 before and after healing. DETAILED DESCRIPTION

[0047] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0048] (I) Polysiloxane elastomer with dynamic borate ester bond and imine bond

[0049] Example 1

[0050] Weigh PDMS-NH2 (4 g, 4 mmol) with a molecular weight of 1000, stir and dissolve it in 10 mL of redistilled tetrahydrofuran, add o-formaldehyde phenylboronic acid (1.2 g, 8 mmol), stir evenly and pour into a mold, leave it open for 18 hours to finally obtain a light yellow viscous liquid which is a borate-modified polysiloxane prepolymer.

[0051] Example 2

[0052] Weigh PDMS-NH2 (4 g, 2 mmol) with a molecular weight of 2000, stir and dissolve it in 10 mL of redistilled tetrahydrofuran, add o-formaldehyde phenylboronic acid (0.6 g, 4 mmol), stir evenly and pour into a mold, leave it open for 18 h to finally obtain a light yellow viscous liquid which is a borate-modified polysiloxane prepolymer.

[0053] Example 3

[0054] Weigh PDMS-NH2 (4 g, 4 mmol) with a molecular weight of 1000, stir and dissolve it in 10 mL of redistilled dichloromethane, add o-formaldehyde phenylboronic acid (1.2 g, 8 mmol), stir evenly and pour into a mold, leave it open for 18 hours to finally obtain a light yellow viscous liquid which is a borate-modified polysiloxane prepolymer.

[0055] Example 4

[0056] Weigh PDMS-NH2 (4 g, 4 mmol) with a molecular weight of 1000, stir and dissolve it in 10 mL of redistilled tetrahydrofuran, add terephthalaldehyde (0.54 g, 4 mmol), stir evenly and pour into a mold, leave it open for 18 hours to finally obtain a light yellow viscous liquid which is an imine bond-modified polysiloxane prepolymer.

[0057] Example 5

[0058] Weigh PDMS-NH2 (4 g, 4 mmol) with a molecular weight of 1000, stir and dissolve it in 10 mL of redistilled dichloromethane, add terephthalaldehyde (0.54 g, 4 mmol), stir evenly and pour into a mold, leave it open for 18 hours to finally obtain a light yellow viscous liquid which is an imine bond-modified polysiloxane prepolymer.

[0059] Example 6

[0060] Weigh PDMS-NH2 (4 g, 2 mmol) with a molecular weight of 2000, stir and dissolve it in 10 mL of redistilled tetrahydrofuran, add terephthalaldehyde (0.27 g, 2 mmol), stir evenly and pour into a mold, leave it open for 18 hours to finally obtain a light yellow viscous liquid which is an imine bond-modified polysiloxane prepolymer.

[0061] Example 7

[0062] Weigh 0.9 g of the borate-modified polysiloxane prepolymer obtained in Example 1 and 0.1 g of the imine-modified polysiloxane prepolymer obtained in Example 4, add 2 mL of ultra-dry tetrahydrofuran and stir to dissolve, pour into a mold, leave it open for 18 hours, place it in a vacuum defoaming box to remove bubbles, and then place it in a 60°C oven to remove the remaining solvent to obtain a light yellow transparent elastomer.

[0063] Example 8

[0064] Weigh 0.7 g of the borate-modified polysiloxane prepolymer obtained in Example 1 and 0.3 g of the imine-modified polysiloxane prepolymer obtained in Example 4, add 2 mL of ultra-dry tetrahydrofuran and stir to dissolve, pour into a mold, leave it open for 18 hours, place it in a vacuum defoaming box to remove bubbles, and then place it in a 60°C oven to remove the remaining solvent to obtain a light yellow transparent elastomer.

[0065] Example 9

[0066] Weigh 0.5 g of the borate-modified polysiloxane prepolymer obtained in Example 1 and 0.5 g of the imine-modified polysiloxane prepolymer obtained in Example 4, add 2 mL of ultra-dry tetrahydrofuran and stir to dissolve, pour into a mold, leave it open for 18 hours, place it in a vacuum defoaming box to remove bubbles, and then place it in a 60°C oven to remove the remaining solvent to obtain a light yellow transparent elastomer.

[0067] (II) Polysiloxane elastomers with synergistic hydrogen bonds and dynamic borate / imide bonds

[0068] Example 10

[0069] Weigh PDMS-NH2 (8.0 g, 2.67 mmol) and stir to dissolve in 85 mL of redistilled dichloromethane. Under ice bath and nitrogen protection, use a constant pressure funnel to slowly drop a dichloromethane (25 mL) solution of hexamethylene diisocyanate (224.27 mg, 1.33 mmol) into the reaction system to prevent local gelation of the reaction system. Then remove the ice bath, react at room temperature for 16 hours, and then remove excess solvent by rotary evaporation to obtain a transparent viscous liquid containing hydrogen bonded polysiloxane prepolymer. Weigh 1 g of hydrogen bonded prepolymer and o-formylphenylboronic acid (47.6 mg, 0.32 mmol), dissolve both in about 2 mL of tetrahydrofuran, stir to dissolve, pour into a mold, leave it open for 18 hours, and volatilize tetrahydrofuran to obtain a polysiloxane elastomer containing hydrogen bonds and dynamic borate bonds.

[0070] Embodiment 11

[0071] Weigh PDMS-NH2 (8.0 g, 2.67 mmol) and stir to dissolve in 85 mL of redistilled tetrahydrofuran. Under ice bath and nitrogen protection, use a constant pressure funnel to slowly drop a dichloromethane (25 mL) solution of hexamethylene diisocyanate (224.27 mg, 1.33 mmol) into the reaction system to prevent local gelation of the reaction system. Then remove the ice bath, react at room temperature for 16 hours, and then remove the excess solvent by rotary evaporation to obtain a transparent viscous liquid containing hydrogen bonded polysiloxane prepolymer. Weigh 1 g of hydrogen bonded prepolymer and terephthalaldehyde (21.29 mg, 0.16 mmol), dissolve both in about 2 mL of tetrahydrofuran, stir to dissolve, pour into a mold, leave it open for 18 hours, and volatilize the tetrahydrofuran to obtain a polysiloxane elastomer containing hydrogen bonds and dynamic imine bonds.

[0072] Application experiments of multiple synergistic self-healing polysiloxane elastomers:

[0073] (1) Use a polarizing microscope (DM2700P) produced by Leica of Germany to take optical photos of the polysiloxane elastomer before and after self-healing. Place the polysiloxane elastomers prepared in Examples 7, 8, 9, 10, and 11 on a storage table, select a 10x lens, adjust the focal length and light source brightness, and make the image clear in the paper field of view. Take photos of the elastomer fracture, and take optical photos of the elastomer after healing after an interval of 4 hours. Figure 4 (Example 7, Example 8 and Example 9) and Figure 7 (Example 10 and Example 11) are shown.

[0074] Depend on Figure 4 It can be seen that after 4 hours of self-repairing process, the fracture marks at the incision of the samples of Example 7, Example 8 and Example 9 basically disappeared, indicating that the samples have good self-repairing ability;

[0075] Depend on Figure 7 It can be seen that after 4 hours of self-repair process, the incisions of the samples in Example 10 and Example 11 are partially healed. Although there is still a "scar"-like morphology, it has little effect on the subsequent mechanical properties, and the samples still have good self-repair ability.

[0076] (2) Using an MCR 302 rheometer produced by Anton Paar, Austria, the storage modulus (G') and loss modulus (G") of the elastomer under different environments were monitored and recorded as a function of shear strain. The polysiloxane elastomers prepared in Examples 7 and 10 were placed on the test platform of the rheometer, a rotor with a platen diameter of 15 mm, a test gap of 0.3 mm, and a test temperature of 20°C were used. The rheological properties of the elastomer were tested by cyclic strain tests at a frequency of 5 rad·s-1 and strains of 0.0001% and 10%, as shown in FIG. Figure 5 (Example 7) and Figure 8 (Example 10) is shown.

[0077] Depend on Figure 5 It can be found that: when the applied strain is small, its storage modulus is significantly higher than the loss modulus, indicating that the elasticity of the sample is dominant at low strain, and the rheological properties are in the linear viscoelastic region. When a large strain is applied, the storage modulus drops rapidly and approaches the loss modulus, indicating that the sample shows viscous characteristics due to the destruction of the cross-linked network constructed by the internal dynamic bonds, and the rheological properties are in the nonlinear viscoelastic region, that is, the mechanical properties of this polysiloxane elastomer material coordinated by dynamic borate bonds and imine bonds can be stably maintained at small strains.

[0078] Depend on Figure 8 It can be found that: when the applied strain is small, its storage modulus is significantly higher than the loss modulus, indicating that the elasticity of the sample is dominant at low strain, and the rheological properties are in the linear viscoelastic region. When a large strain is applied, the storage modulus drops rapidly and approaches the loss modulus, indicating that the sample shows viscous characteristics due to the destruction of the cross-linked network constructed by the internal dynamic bonds, and the rheological properties are in the nonlinear viscoelastic region, that is, the mechanical properties of this polysiloxane elastomer material coordinated by hydrogen bonds and dynamic borate bonds can be stably maintained at small strains.

[0079] (3) The test was conducted using a 594 series single-column tabletop frame produced by Instro Corporation of the United States. The size of the elastomer was 15 mm, 5 mm, and 0.3 mm. A 500N sensor was used to measure the tensile strength and elongation at break of the polysiloxane elastomers prepared in Examples 7 and 10 before and after self-healing at a tensile speed of 10 mm·min-1. The test temperature was 25°C. Figure 6 (Example 7) and Fig. 9 (Example 10) is shown.

[0080] Depend on Figure 6 It can be seen that the elongation at break (strain) and maximum tensile strength (stress) of this polysiloxane elastomer with dynamic borate bonds and imine bonds synergistically after self-repair are similar to those before damage, indicating that it has good self-repair ability.

[0081] Depend on Fig. 9 It can be seen that the elongation at break (strain) of this polysiloxane elastomer with coordinated hydrogen bonds and dynamic borate bonds will decrease after self-repair, but the maximum tensile strength (stress) is basically similar to that before damage, indicating that it has good self-repair ability.

[0082] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for preparing a multi-synergistic self-healing polysiloxane elastomer, characterized in that: The preparation method is based on a dynamic borate ester bond and imine bond collaborative preparation process and a hydrogen bond or a dynamic borate ester bond / imine bond collaborative preparation process. The collaborative preparation process based on dynamic borate ester bond and imine bond includes the following steps: S1A: Low molecular weight linear polydimethylsiloxane (PDMS-NH2) was used to coordinate with boronic acid groups or undergo reductive amination with aldehyde groups to prepare two types of polysiloxane prepolymers; S2A: The obtained two types of polydimethylsiloxane prepolymers are blended to obtain two types of dynamically bonded polysiloxane elastomers; The synergistic preparation process based on hydrogen bonding and dynamic borate ester bonding / imine bonding includes the following steps: S1B: Low molecular weight linear polydimethylsiloxane (PDMS-NH2) reacts with isocyanate groups to prepare polysiloxane prepolymers containing hydrogen bonds; S2B: The obtained prepolymer is reacted with o-formylphenylboronic acid / terephthalaldehyde to obtain a polysiloxane with coordinated hydrogen bonds and dynamic borate ester bonds / imine bonds through boron nitrogen coordination or reductive amination reaction.

2. The method for preparing a multi-synergistic self-healing polysiloxane elastomer according to claim 1, characterized in that: In the S1A, the polydimethylsiloxane is terminated with aminopropyl groups, and the molecular weight of the polydimethylsiloxane includes but is not limited to 1000, 2000 and 5000.

3. The method for preparing a multi-synergistic self-healing polysiloxane elastomer according to claim 1, characterized in that: In the S1A, the boronic acid compound is selected from at least one of o-formylphenylboronic acid, p-formylphenylboronic acid, m-formylphenylboronic acid, 5-formyl 2-hydroxyphenylboronic acid, and 3-formyl 2-methylphenylboronic acid.

4. The method for preparing a multi-synergistic self-healing polysiloxane elastomer according to claim 1, characterized in that: In the S1A, the benzaldehyde compound is selected from at least one of terephthalaldehyde, o-phthalaldehyde, isophthalaldehyde, and 2,5-diethylterephthalaldehyde.

5. The method for preparing a multi-synergistic self-healing polysiloxane elastomer according to claim 1, characterized in that: In the above S2A, the obtained polysiloxane elastomer was subjected to a vacuum defoaming box to remove bubbles, and then the remaining solvent was removed in an oven at 60°C.

6. The method for preparing a multi-synergistic self-healing polysiloxane elastomer according to claim 1, characterized in that: In the S1B, the isocyanate is selected from one or more of hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, and isophorone diisocyanate.

7. The method for preparing a multi-synergistic self-healing polysiloxane elastomer according to claim 1, characterized in that: In the S2B, the boric acid compound is selected from one or more of o-formylphenylboronic acid, p-formylphenylboronic acid, and m-formylphenylboronic acid.

8. The method for preparing a multi-synergistic self-healing polysiloxane elastomer according to claim 1, characterized in that: In the S2B, the benzaldehyde compound is selected from one or more of terephthalaldehyde, o-phthalaldehyde, and isophthalaldehyde.

9. A multi-synergistic self-healing polysiloxane elastomer, characterized in that: The elastomer is prepared by the method for preparing a multi-synergistic self-healing polysiloxane elastomer as described in any one of claims 1 to 8.

10. The multi-synergistic self-healing polysiloxane elastomer according to claim 9, characterized in that: The polysiloxane elastomer contains any of the following technical features: A. Dynamic borate ester bond and imide bond, B. Hydrogen bonds and dynamic borate ester bonds, C. Hydrogen bond and dynamic imine bond.

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