A polysiloxane-based shape memory polymer and its preparation method

Abstract

A polysiloxane-based shape memory polymer and its preparation method are disclosed, belonging to the field of shape memory polymer synthesis technology. The method involves sequentially adding formaldehyde solution, a solution containing siloxane, and 2-naphthol to a container, reacting at 90℃-100℃ for 1.5h-3h; removing the solvent by vacuum distillation, then washing the liquid residue multiple times with deionized water to obtain the product, drying the product at 60℃ for 6h to obtain a viscous liquid; placing the liquid in a mold, then transferring the mold to an oven, heating it to 120℃ and then 140℃, holding each temperature for 1h, and finally heating it to 190℃-220℃ and holding it for 5h-6.5h to complete curing. The shape memory polymer formed by the polymerization of siloxane and 2-naphthol contains numerous Si-O groups, benzene rings, and oxazine rings. These groups enhance the polymer's high-temperature resistance. Chemical or physical crosslinking points act as a stationary phase to remember the permanent shape, while flexible alkyl-siloxane units act as switching segments to fix the temporary shape.

Description

Technical Field

[0001] This invention belongs to the field of shape memory polymer synthesis technology, and particularly relates to a polysiloxane-based shape memory polymer and its preparation method. Background Technology

[0002] Shape memory polymers (SMPs) are smart materials that respond to external stimuli. Due to their ability to recover from a temporary shape to a permanent shape after being stimulated by light, heat, or electricity, they have been widely used in aerospace, biomedicine, and sensor fields in recent years. While traditional shape memory polymers (SMPs) have made some progress in materials such as polyurethane, polyester, and vinyl polymers, they still have many shortcomings in practical applications. For example, polyurethane, polyester, and vinyl polymers are prone to degradation and loss of shape recovery ability under high temperature or extreme climatic conditions; polyurethane absorbs a large amount of water in high humidity environments, leading to poor shape stability and a significant decrease in performance. Therefore, the high-temperature stability, moisture effects, processability, and room-temperature properties of traditional shape memory polymers limit their widespread adoption in certain applications.

[0003] Polysiloxanes possess an alternating organic-inorganic molecular structure, giving them excellent high-temperature resistance, climate change resistance, and outstanding hydrophobicity. As a novel matrix material, they are attracting increasing attention from researchers. Unlike traditional shape memory polymers, polysiloxane-based shape memory polymers maintain good shape memory properties at high temperatures. Simultaneously, they exhibit excellent room temperature flexibility and processability, enabling them to operate in more demanding environments, such as high-temperature, humid, or extreme climate applications. Summary of the Invention

[0004] The purpose of this invention is to address the problem that existing shape memory polymers cannot meet practical applications, and to provide a polysiloxane-based shape memory polymer and its preparation method. This invention designs at the molecular level, further enhancing the high-temperature stability of the polysiloxane by introducing thermally stable functional groups such as benzene rings and oxazine groups. The resulting polymer exhibits good shape memory properties and high temperature tolerance, making it suitable for harsh environments such as automotive or aerospace components or aerospace applications.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing a polysiloxane-based shape memory polymer, the method comprising:

[0007] Step 1: Add formaldehyde solution to the container, then add solution containing siloxane, and finally add 2-naphthol. Increase the temperature to promote the reaction of formaldehyde, siloxane and 2-naphthol. React at 90℃-100℃ for 1.5h-3h.

[0008] Step 2: Remove the solvent by vacuum distillation, then wash the liquid residue with deionized water several times to obtain the product, and dry the product in a vacuum oven at 60°C for 6 hours to obtain a viscous liquid;

[0009] Step 3: Place the liquid in the mold, then transfer the mold to the oven and heat it to 120℃ and 140℃ respectively, holding each temperature for 1 hour. Finally, heat it to 190℃-220℃ and hold it for 5-6.5 hours to complete the curing.

[0010] Furthermore, in step one, the structural formula of the siloxane is:

[0011]

[0012] In equation (I), R1 is NH2, and R2, R3, R4, R5, R6, and R7 are independent of each other and are selected from H and C. 1-10 Alkyl, C 6-14 One or more of the aryl groups.

[0013] Further, in step one, the structural formula of the 2-naphthol is:

[0014]

[0015] In formula (II), R1 is selected from H and C. 1-10 One of the alkyl groups.

[0016] Furthermore, in step one, the solvent of the solution is a solvent with a solubility parameter between 2-naphthol and siloxane, preferably one or more of toluene, o-xylene, and p-xylene.

[0017] Further, in step one, the mass ratio of 2-naphthol, formaldehyde, and siloxane is 14:6:5 to 7, preferably, the mass ratio of 2-naphthol, formaldehyde, and siloxane is 14:6:6.

[0018] Furthermore, the shape memory polymer reaction process involves an equation as shown in equation (III):

[0019]

[0020] In equation (III), R1, R2, R3, R4, R5, R6, and R7 are independent of each other and are selected from H and C. 1-10 Alkyl, C 6-14 One or more of the aryl groups, where R8 is NH2.

[0021] Furthermore, in step one, the reaction temperature is 90℃-95℃, and the time is 2.0h-2.5h. The heating temperature can be 90℃, 91℃, 92℃, 93℃, 94℃, 95℃ or any value in between; the heating time can be 1.5h, 1.6h, 1.7h, 1.8h, 1.9h, 2.0h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h, 3.0h or any value in between.

[0022] Furthermore, in step three, the curing temperature is 210℃-215℃, and the curing time is 5.0h-6h. The curing temperature can be 200℃, 201℃, 202℃, 203℃, 204℃, 215℃, 216℃, 217℃, 218℃, 219℃, or any value in between; the heating time can be 5.5h, 5.6h, 5.7h, 5.8h, 5.9h, 6.0h, 6.1h, 6.2h, 6.3h, 6.4h, 6.5h, or any value in between.

[0023] A polysiloxane-based shape memory polymer prepared by the above preparation method.

[0024] Compared to existing technologies, this invention has the following advantages: the shape memory polymer formed by the polymerization of siloxane and 2-naphthol contains a large number of Si-O groups, benzene rings, and oxazine rings. These groups can enhance the polymer's resistance to high temperatures. Chemical or physical crosslinking points act as a stationary phase to remember the permanent shape, while flexible alkyl-siloxane units act as switching segments to fix the temporary shape. These alkyl-siloxane units, as effective switching segments, have high glass transition temperatures, resulting in a high transition temperature for the shape memory polymer. Furthermore, it exhibits good shape memory performance, recovering the permanent shape from the temporary shape at 140°C, with a shape memory rate of up to 94%. Detailed Implementation

[0025] As used herein: The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof as used herein are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0026] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0027] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0028] The technical solution of the present invention will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0029] Example 1

[0030] A method for preparing a polysiloxane-based shape memory polymer includes the following steps:

[0031] (1) Add 20 mL of a mixture of p-xylene and 12 mL of formaldehyde to a round-bottom flask. Then, weigh 10 g of siloxane and dissolve it in 20 mL of p-xylene solution. Add the p-xylene solution containing the siloxane dropwise to the above solution mixture. Finally, add 28 g of 2-naphthol and stir the mixture. Gradually increase the temperature to 90 °C and continue stirring for 2 h.

[0032] (2) After the reaction was completed, the solvent p-xylene was removed by vacuum distillation, and the liquid residue was washed three times with deionized water. The washed liquid was dried in a vacuum oven at 60°C for 6 hours to obtain the product liquid.

[0033] (3) Place the above product into a mold. You can use vacuuming or freezing centrifugation to remove air bubbles from the product. Then transfer it to an oven and keep it at 120°C for 1 hour. Then raise the temperature to 140°C and keep it at 1 hour.

[0034] (4) Finally, the oven is heated to 200°C at a heating rate of 5°C / min and kept at that temperature for 6 hours to complete the curing process and obtain the shape memory polymer.

[0035] Example 2

[0036] A method for preparing a polysiloxane-based shape memory polymer includes the following steps:

[0037] (1) Add 20 mL of a mixture of p-xylene and 12 mL of formaldehyde to a round-bottom flask. Then, weigh 12 g of siloxane and dissolve it in 20 mL of p-xylene solution. Add the p-xylene solution containing the siloxane dropwise to the above solution mixture. Finally, add 28 g of 2-naphthol and stir the mixture. Gradually increase the temperature to 90 °C and continue stirring for 2 h.

[0038] (2) After the reaction was completed, the solvent p-xylene was removed by vacuum distillation, and the liquid residue was washed three times with deionized water. The washed liquid was dried in a vacuum oven at 60°C for 6 hours to obtain the product liquid.

[0039] (3) Place the above product into a mold. You can use vacuuming or freezing centrifugation to remove air bubbles from the product. Then transfer it to an oven and keep it at 120°C for 1 hour. Then raise the temperature to 140°C and keep it at 1 hour.

[0040] (4) Finally, the oven is heated to 200°C at a heating rate of 5°C / min and kept at that temperature for 6 hours to complete the curing process and obtain the shape memory polymer.

[0041] Example 3

[0042] A method for preparing a polysiloxane-based shape memory polymer includes the following steps:

[0043] (1) Add 20 mL of a mixture of p-xylene and 12 mL of formaldehyde to a round-bottom flask. Then, weigh 14 g of siloxane and dissolve it in 20 mL of p-xylene solution. Add the p-xylene solution containing the siloxane dropwise to the above mixture. Finally, add 28 g of 2-naphthol and stir the mixture. Gradually increase the temperature to 90 °C and continue stirring for 2 h.

[0044] (2) After the reaction was completed, the solvent p-xylene was removed by vacuum distillation, and the liquid residue was washed three times with deionized water. The washed liquid was dried in a vacuum oven at 60°C for 6 hours to obtain the product liquid.

[0045] (3) Place the above product into a mold. You can use vacuuming or freezing centrifugation to remove air bubbles from the product. Then transfer it to an oven and keep it at 120°C for 1 hour. Then raise the temperature to 140°C and keep it at 1 hour.

[0046] (4) Finally, the oven is heated to 200°C at a heating rate of 5°C / min and kept at that temperature for 6 hours to complete the curing process and obtain the shape memory polymer.

[0047] A certain mass of sample was cut for differential scanning calorimetry (DSC) experiment. First, it was heated to 200℃ to eliminate thermal history, and then cooled naturally before a heating-cooling scan was performed. The response temperature of the sample was determined based on the obtained data. All the above experiments were conducted under nitrogen protection.

[0048] First, the prepared sample strip of a certain size is placed in a drying oven at 90℃ for 30 minutes, then folded 180°, and the bending angle θ0 (θ0≈180) of the sample strip is recorded. Afterward, while maintaining external force, the sample strip is allowed to cool to room temperature, and then the external force is removed, and the bending angle θ1 of the sample strip is recorded. Therefore, the shape fixation rate of the prepared sample can be calculated using the following formula.

[0049]

[0050] First, standard specimens of the required dumbbell-shaped polymer and its composite materials are prepared using a mechanical testing machine. Then, static mechanical property tests are conducted at room temperature, with the loading speed of the testing machine clamps at 1-5 mm / min. -1 Three parallel samples were used for each group of test samples, and the average value was taken to calculate the tensile strength, elongation at break and Young's modulus.

[0051] Table 1 Response Temperature of Examples

[0052]

[0053]

[0054] Table 2. Shape fixation temperature and shape fixation rate in the embodiments.

[0055] product Shape fixed temperature (°C) Shape fixation rate Example 1 169 91％ Example 2 190 94％ Example 3 197 96％

[0056] Table 3 Mechanical properties of the embodiments

[0057] product Tensile strength (MPa) Elongation at break (100%) Young's modulus (kPa) Example 1 4.4 183％ 2530 Example 2 5.1 164％ 2689 Example 3 5.0 179％ 2447

[0058] As shown in the table, the response temperature and mechanical properties of shape memory polymers prepared from siloxanes and 2-naphthol can be adjusted within a certain range. With increasing siloxane mass, the polymer's response temperature increased from 170℃ to 179℃, and the shape retention rate also slightly improved, from 91% to 94%. However, with further increases in siloxane mass, its Young's modulus decreased slightly.

Claims

1. A method for preparing a polysiloxane-based shape memory polymer, characterized in that: The method is as follows: Step 1: Add formaldehyde solution to a container, followed by a solution containing siloxane, and finally add the compound shown in formula (II). React at 90 ℃~100 ℃ for 1.5 h~3 h; the structural formula of the siloxane is: Formula (I) In equation (I), R1 is NH2, and R2, R3, R4, R5, R6, and R7 are independent of each other and are selected from H and C. 1-10 Alkyl, C 6-14 One or more of the aryl groups; the mass ratio of the compound shown in formula (II), formaldehyde, and siloxane is 14:6:5~7; the structural formula of formula (II) is as follows: Equation (II) In formula (II), R1 is selected from H and C. 1-10 One of the alkyl groups; Step 2: Remove the solvent by vacuum distillation, then wash the liquid residue with deionized water several times to obtain the product, and dry the product in a vacuum oven at 60 °C for 6 h to obtain a viscous liquid; Step 3: Place the liquid in the mold, then transfer the mold to the oven and heat it to 120 ℃ and 140 ℃ respectively, holding each temperature for 1 h. Finally, heat it to 190 ℃~220 ℃ and hold it for 5 h~6.5 h to complete the curing.

2. The method for preparing a polysiloxane-based shape memory polymer according to claim 1, characterized in that: In step one, the solvent of the solution is a solvent with a solubility parameter between that of 2-naphthol and siloxane.

3. The method for preparing a polysiloxane-based shape memory polymer according to claim 1, characterized in that: In step one, the reaction temperature is 90 ℃~95 ℃ and the time is 2.0 h~2.5 h.

4. The method for preparing a polysiloxane-based shape memory polymer according to claim 1, characterized in that: In step three, the curing temperature is 210 ℃~215 ℃, and the curing time is 5.0 h~6 h.

5. A polysiloxane-based shape memory polymer prepared by the preparation method according to any one of claims 1 to 4.

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