Functionalized elastomers and applications

Abstract

This invention discloses a functionalized elastomer and its applications, belonging to the field of new materials technology. This invention introduces a multi-layered dynamic network composed of abundant H bonds, disulfide bonds, and metal coordination bonds into the elastomer. The H bonds are provided by urethane bonds and the UPy segment of U2-diol, while the metal coordination bonds are formed by ligands provided by dimethylglyoxime and metal ions. A one-pot method is used to prepare a functionalized elastomer capable of low-temperature self-healing. The resulting functionalized elastomer exhibits good mechanical properties and can achieve self-healing at -15°C, showing great promise for applications in low-temperature resistant flexible wearables and other fields.

Description

Technical Field

[0001] This invention belongs to the field of new materials technology and relates to a functionalized elastomer and its applications. Background Technology

[0002] Self-healing is a characteristic of biological tissues, enabling them to effectively repair themselves after mechanical damage. Therefore, inspired by nature, incorporating self-healing properties into elastomers has significantly improved their lifespan and stability, reduced maintenance costs, and enabled novel applications. Consequently, self-healing materials have attracted considerable attention and shown great promise in many fields, including automotive coatings, electronic skin, and soft robotics. Exogenous self-healing, due to its reliance on self-healing agents, has limited healing capabilities, restricting its widespread application. Therefore, intrinsic self-healing materials based on dynamic non-covalent interactions or reversible covalent bonds are currently a research focus. However, intrinsic healing processes typically require external energy input, such as heat, light, pressure, or other agents. Since many materials in real life are damaged under environmental conditions without available external stimuli, there is a strong need to develop elastomer materials that can spontaneously heal themselves at room temperature or even low temperatures.

[0003] Developing elastomer materials with low-temperature self-healing properties remains a significant challenge. A common approach to designing self-healing materials combines dynamic covalent bonds (disulfide bonds, imine bonds, etc.) and dynamic non-covalent bonds (H bonds, metal coordination bonds, ionic interactions, etc.). However, materials obtained using this method are typically relatively weak. In contrast, a large number of non-covalent interactions may lead to better mechanical properties but may compromise the material's self-healing ability, tensile strength, and toughness. Furthermore, due to their linear molecular structure, these materials may be subject to limited elasticity and potential creep. Therefore, some researchers have used chemical cross-linking structures based on dynamic covalent bonds such as urea bonds, boron-oxygen bonds, and disulfide bonds to construct relatively strong healable materials. However, cross-linked networks restrict chain movement and reduce healing capacity. Overall, the self-healing ability and mechanical properties of a material are inherently mutually exclusive. Achieving both high mechanical robustness and healing efficiency simultaneously remains a significant challenge, especially under environmental conditions, as their requirements for molecular structure are often contradictory. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention adopts the following technical solution:

[0005] The purpose of this invention is to provide a method for preparing a low-temperature self-healing functionalized elastomer, comprising the following steps:

[0006] (1) Hydroxyl-terminated bio-based aliphatic prepolymers were obtained by reacting bio-based dicarboxylic acids and diols;

[0007] (2) The hydroxyl-terminated bio-based aliphatic prepolymer is mixed and reacted with isocyanate, diol components, glycerol, metal salts and ligands to obtain a functionalized elastomer.

[0008] In one embodiment of the present invention, a low-temperature self-healing functionalized elastomer is obtained by reacting glycol, glycerol, isocyanate and metal ions. Its topological structure contains a rich multi-dynamic network composed of hydrogen bonds, urethane esters, disulfide bonds and metal coordination bonds, which endows the elastomer with low-temperature self-healing properties.

[0009] In one embodiment of the present invention, the bio-based diol is one or a combination of propylene glycol, butylene glycol, rubber seed oil-based diol, palm oil-based diol, sunflower seed oil-based diol, isosorbide, pentylene glycol, ethylene glycol, and dimerol.

[0010] In one embodiment of the present invention, the bio-based dicarboxylic acid is one or a combination of itaconic acid, sebacic acid, succinic acid, azelaic acid, dimeric fatty acid (DAA), dodecyl dicarboxylic acid, and fumaric acid.

[0011] In one embodiment of the present invention, the molar ratio of bio-based diol to dicarboxylic acid is (1-2):1.

[0012] In one embodiment of the present invention, the polymerization inhibitor mentioned in step (1) is any one of 4-methoxyphenol and hydroquinone, and the amount added is 0.05-0.5 wt%.

[0013] In one embodiment of the present invention, the catalyst in step (1) is tetrabutyl titanate, p-toluenesulfonic acid, antimony acetate, and dibutyltin laurate; the amount used is 0.05-0.5 wt% of the total mass.

[0014] In one embodiment of the present invention, the temperature of the reaction in step (1) is 130-190°C and the time is 1-8 hours.

[0015] In one embodiment of the present invention, the number average molecular weight of the hydroxyl-terminated bio-based aliphatic prepolymer in step (1) is 1000-13000.

[0016] In one embodiment of the present invention, the diol component in step (2) is U2-diol, or a combination of U2-diol and other diol reagents; the other diol reagents are any one or more of bis(2-hydroxyethyl) disulfide, dimethylglyoxime, butanediol, propylene glycol, and isosorbide.

[0017] In one embodiment of the present invention, the total amount of the hydroxyl-terminated bio-based aliphatic prepolymer and diol component in step (2) is in a molar ratio of 2 to 8:1 to glycerol.

[0018] In one embodiment of the present invention, the total molar ratio of hydroxyl groups to isocyanate groups in the hydroxyl-terminated bio-based aliphatic prepolymer and diol component in step (2) is 1:1 to 2.

[0019] In one embodiment of the present invention, the isocyanate in step (2) is one or a combination of isoflurone isocyanate, hexamethylene diisocyanate, toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), dicyclohexylmethane diisocyanate (HMDI), and lysine diisocyanate (LDI).

[0020] In one embodiment of the present invention, the ligand in step (2) is dimethylglyoxime, which can form metal coordination bonds with metal ions.

[0021] In one embodiment of the present invention, the molar ratio of the ligand to glycerol in step (2) is (2-5):1.

[0022] In one embodiment of the present invention, the metal salt in step (2) is one of copper chloride and zinc chloride.

[0023] In one embodiment of the present invention, the molar ratio of the metal salt to the ligand in step (2) is 1:10 to 30.

[0024] In one embodiment of the present invention, the reaction in step (2) is first stirred at 50°C to 80°C for 1-6 hours, then reacted at 40°C to 60°C under nitrogen atmosphere for 12-24 hours, and then the temperature is raised to 70°C to 90°C to continue the reaction for 12-36 hours.

[0025] In one embodiment of the present invention, the elastomer preparation method specifically includes:

[0026] (1) Preparation of hydroxyl-terminated bio-based aliphatic prepolymer: Bio-based dicarboxylic acid, diol, polymerization inhibitor and catalyst are added to the reactor, the reaction temperature is 130-190℃, the esterification time is 1-8h, and then the esterification system is changed to a vacuum system, and the reaction is carried out for 2-8h to obtain hydroxyl-terminated bio-based aliphatic prepolymer.

[0027] (2) Place the prepolymer under vacuum at 90℃-120℃ for 1-3 hours to remove water. Then adjust the reaction temperature to 50℃~80℃ and add isocyanate, bis(2-hydroxyethyl) disulfide, U2-diol, glycerol and metal ions. Stir for 1-6 hours. Then pour the reactants into a mold and place it in a nitrogen-filled environment at 40℃-60℃ for 12-24 hours. Then react at 70~90℃ for 12~36 hours.

[0028] Based on the above method, this invention provides a functionalized elastomer capable of low-temperature self-healing.

[0029] The present invention also provides the application of the above-mentioned low-temperature self-healing functionalized elastomer in the fields of self-powered triboelectric generators and wearable devices.

[0030] The present invention also provides the application of the above-mentioned low-temperature self-healing functionalized elastomer in the fields of automotive coatings, electronic skin and soft robots.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] This invention provides a one-pot method for the efficient preparation of bio-based crosslinked elastomers containing multiple dynamic networks. Its key feature is the introduction of a multi-dynamic network composed of abundant H bonds, disulfide bonds, and metal coordination bonds into the elastomer. The H bonds are provided by urethane bonds and the UPy segment of U2-diol, while the metal coordination bonds are formed by ligands provided by dimethylglyoxime and metal ions, thus creating a strong and weak crosslinking network, thereby endowing the elastomer with excellent mechanical properties. Furthermore, the bio-based prepolymer, acting as a soft segment, provides the elastomer with sufficient flexibility and a low glass transition temperature.

[0033] Compared to previously reported self-healing elastomers, the low-temperature self-healing bio-based crosslinked elastomer of this invention exhibits self-healing capabilities at -15°C due to its abundant hydrogen bonds, metal coordination bonds, and low bond energy disulfide bonds, coupled with a lower glass transition temperature. This makes it a promising candidate for applications in low-temperature resistant flexible wearable devices and other fields. Detailed Implementation

[0034] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0035] Example 1

[0036] (1) Add 7.8 g (0.060 mol) itaconic acid, 8.09 g (0.040 mol) sebacic acid, 4.18 g (0.055 mol) 1,3-propanediol, 4.95 g (0.055 mol) 1,4-butanediol, 0.05 wt% 4-methoxyphenol and 0.05 wt% tetrabutyl titanate to a 100 mL three-necked flask. Collect the water generated by the reaction using a water separator and a condenser. Set the nitrogen flow rate to 0.15 L / min, the magnetic stirring speed to 380 r / min, the reaction temperature to 180 °C, and the reaction time to 2 h. Then change the reaction system to a vacuum system and continue the reaction for 5 h to obtain a pale yellow hydroxyl-terminated bio-based unsaturated aliphatic prepolymer with a number average molecular weight of 3680 g / mol.

[0037] (2) Add 10 mmol of prepolymer, 10 mmol of dimethyl ethyl oxime, 3 mmol of bis(2-hydroxyethyl) disulfide, 1 mmol of U2-diol and 3 mmol of glycerol to a 100 ml three-necked flask at 50 °C according to a molar ratio of 8:1 for the total amount of diol components and prepolymer to glycerol. Add 28.5 mmol of isoflurane isocyanate, 3 drops of dibutyltin laurate and 0.32 mmol of copper chloride and 40 ml of acetone according to a molar ratio of 1:1 for the total amount of diol components and prepolymer to isocyanate. Stir and react for 2 h. Pour into a mold and dry at 50 °C for 24 h. Then raise the temperature to 75 °C and dry for 24 h. The drying process is carried out under a nitrogen atmosphere to obtain a cross-linked polyurethane elastomer with low-temperature self-healing properties.

[0038] Example 2

[0039] (1) Same as in Example 1, the corresponding pale yellow hydroxyl-terminated bio-based unsaturated aliphatic prepolymer was prepared.

[0040] (2) Add 10 mmol of prepolymer, 10 mmol of dimethylglyoxime, 2 mmol of bis(2-hydroxyethyl) disulfide, 2 mmol of U2-diol and 3 mmol of glycerol to a 100 ml three-necked flask at 50 °C. Add 28.5 mmol of isoflurane isocyanate, 3 drops of dibutyltin laurylate and 0.32 mmol of copper chloride and 40 ml of acetone at a ratio of 1:1. Stir and react for 2 h. Pour into a mold and dry at 50 °C for 24 h. Then raise the temperature to 75 °C and dry for 24 h. The drying process is carried out under a nitrogen atmosphere to obtain a cross-linked polyurethane elastomer with low-temperature self-healing properties.

[0041] Example 3

[0042] (1) Same as in Example 1, the corresponding pale yellow hydroxyl-terminated bio-based unsaturated aliphatic prepolymer was prepared.

[0043] (2) Add 10 mmol of prepolymer, 10 mmol of prepolymer, 10 mmol of dimethylglyoxime, 1 mmol of bis(2-hydroxyethyl) disulfide, 3 mmol of U2-diol and 3 mmol of glycerol to a 100 ml three-necked flask at 50 °C. Add 28.5 mmol of isoflurane isocyanate, 3 drops of dibutyltin laurylate and 0.32 mmol of copper chloride and 40 ml of acetone at a ratio of 1:1. Stir and react for 2 h. Pour into a mold and dry at 50 °C for 24 h. Then raise the temperature to 75 °C and dry for 24 h. The drying process is carried out under a nitrogen atmosphere to obtain a cross-linked polyurethane elastomer with low-temperature self-healing properties.

[0044] Example 4

[0045] (1) Same as in Example 1, the corresponding pale yellow hydroxyl-terminated bio-based unsaturated aliphatic prepolymer was prepared.

[0046] (2) Add 10 mmol of prepolymer, 10 mmol of dimethyl ethyl oxime, 4 mmol of U2-diol and 3 mmol of glycerol to a 100 ml three-necked flask at 50 °C. Add 28.5 mmol of isoflurane isocyanate, 3 drops of dibutyltin laurate and 0.32 mmol of copper chloride and 40 ml of acetone at a ratio of 1:1. Stir and react for 2 h. Pour into a mold and dry at 50 °C for 24 h. Then raise the temperature to 75 °C and dry for 24 h. The drying process is carried out under a nitrogen atmosphere to obtain a cross-linked polyurethane elastomer with low-temperature self-healing properties.

[0047] Comparative Example 1

[0048] The diol components contain no U2-diol and no sulfur-containing components.

[0049] (1) Same as in Example 1, the corresponding pale yellow hydroxyl-terminated bio-based unsaturated aliphatic prepolymer was prepared.

[0050] (2) Add 10 mmol of prepolymer, 14 mmol of dimethylglyoxime, and 3 mmol of glycerol to a 100 ml three-necked flask at 50 °C. Add 28.5 mmol of isoflurane isocyanate, 3 drops of dibutyltin laurate, 0.32 mmol of copper chloride, and 40 ml of acetone in a ratio of 1:1 of total hydroxyl to isocyanate. Stir and react for 2 h. Pour into a mold and dry at 50 °C for 24 h. Then raise the temperature to 75 °C and dry for 24 h. The drying process is carried out under a nitrogen atmosphere to obtain a cross-linked polyurethane elastomer with low-temperature self-healing properties.

[0051] Comparative Example 2

[0052] Diol components contain sulfur components but lack U2-diol:

[0053] (1) Same as in Example 1, the corresponding pale yellow hydroxyl-terminated bio-based aliphatic prepolymer was prepared.

[0054] (2) Add 10 mmol of prepolymer, 10 mmol of dimethylglyoxime, 4 mmol of bis(2-hydroxyethyl) disulfide, and 3 mmol of glycerol to a 100 ml three-necked flask at 50 °C. Add 28.5 mmol of isoflurane isocyanate, 3 drops of dibutyltin laurylate, 0.32 mmol of copper chloride, and 40 ml of acetone in a 1:1 ratio of total hydroxyl group to isocyanate group. Stir and react for 2 h. Pour into a mold and dry at 50 °C for 24 h. Then raise the temperature to 75 °C and dry for 24 h. The drying process is carried out under a nitrogen atmosphere to obtain a cross-linked polyurethane elastomer with low-temperature self-healing properties.

[0055] The performance of the elastomers obtained in Examples 1-4 and Comparative Examples 1-2 was tested, and the results are shown in Table 1.

[0056] Table 1 Performance Test Results

[0057]

[0058] As shown in Table 1, the low-temperature self-healing bio-based crosslinked elastomer of the present invention, due to its abundant hydrogen bonds, metal coordination bonds, and low bond energy disulfide bonds, combined with a relatively low glass transition temperature, enables it to achieve self-healing at low temperatures of -10 to -15°C. In contrast, the elastomer in Comparative Example 2, without the addition of U2-diol, only achieved self-healing at 30°C; below 30°C, it could not effectively self-heal. Furthermore, while disulfide bonds, being low-energy bonds, impart self-healing properties when introduced into the elastomer, they also reduce its strength. With increasing U2-diol content, the tensile strength of the elastomer gradually increases, while the elongation at break gradually decreases.

[0059] Example 5

[0060] Referring to Example 2, the preparation temperature of the hydroxyl-terminated bio-based unsaturated aliphatic prepolymer was changed while other parameters remained unchanged, and the corresponding elastomer films were obtained. The results are shown in Table 2.

[0061] Table 2

[0062]

[0063] As shown in Table 2, the molecular weight of the low-temperature self-healing bio-based crosslinked elastomer of the present invention gradually increases with the increase of the prepolymer preparation temperature, and the mechanical properties of the obtained low-temperature self-healing bio-based crosslinked elastomer gradually increase. This is because, under the condition of constant crosslinking density, the chain entanglement effect between crosslinking points is enhanced, resulting in improved mechanical properties.

[0064] Example 6

[0065] Comparative optimization of different diol components:

[0066] Referring to Example 2, U2-diol was replaced with other diols while other parameters remained unchanged, and the corresponding crosslinked polyurethane elastomers were obtained.

[0067] The properties of the obtained crosslinked polyurethane elastomers were tested, and the results are shown in Table 3.

[0068] Table 3

[0069]

[0070] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A method for preparing a low temperature self-healing functionalized elastomer, characterized in that, Includes the following steps: (1) Hydroxyl-terminated bio-based aliphatic prepolymers were obtained by reacting bio-based dicarboxylic acids and bio-based diols; (2) The hydroxyl-terminated bio-based aliphatic prepolymer is mixed and reacted with isocyanate, glycol components, glycerol, metal salts, and ligands to obtain a functionalized elastomer; The diol component is a combination of U2-diol and other diol reagents; the other diol reagents are bis(2-hydroxyethyl) disulfides; The ligand is dimethylglyoxime.

2. The method of claim 1, wherein, The bio-based diol is one or a combination of propylene glycol, butylene glycol, rubber seed oil-based diol, palm oil-based diol, sunflower seed oil-based diol, isosorbide, pentylene glycol, ethylene glycol, and dimerol; the bio-based dicarboxylic acid is one or a combination of itaconic acid, sebacic acid, succinic acid, azelaic acid, dimer fatty acid, dodecyl dicarboxylic acid, and fumaric acid; the molar ratio of bio-based diol to bio-based dicarboxylic acid is (1-2):

1.

3. The method of claim 1, wherein, In step (1), the reaction process also requires a polymerization inhibitor and a catalyst. The polymerization inhibitor is any one of 4-methoxyphenol and hydroquinone, and the amount added is 0.05-0.5 wt%. The catalyst is tetrabutyl titanate, p-toluenesulfonic acid, antimony acetate, and dibutyltin laurate, and the amount used is 0.05-0.5 wt% of the total mass.

4. The method of claim 1, wherein, The total amount of the hydroxyl-terminated bio-based aliphatic prepolymer and diol components in step (2) is in a molar ratio of 2 to 8:1 to glycerol.

5. The method of claim 1, wherein, In step (2), the total molar ratio of hydroxyl groups to isocyanates in the hydroxyl-terminated bio-based aliphatic prepolymer and diol components is 1:1~2; the isocyanate is one or a combination of isophorone diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, and lysine diisocyanate.

6. The method according to any one of claims 1 to 5, characterized in that, The metal salt mentioned in step (2) is one of copper chloride and zinc chloride; the molar ratio of the metal salt to the ligand is 1:10~30; the molar ratio of the ligand to glycerol is (2-5):

1.

7. A low-temperature self-healing functionalized elastomer prepared by the method described in any one of claims 1-6.

8. The application of the low-temperature self-healing functionalized elastomer as described in claim 7 in the fields of self-powered triboelectric generators and wearable devices.

9. The application of the low-temperature self-healing functionalized elastomer of claim 7 in the fields of automotive coatings, electronic skin, and soft robotics.

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