Polysiloxane-based shape memory polymer and preparation method thereof

Abstract

The invention discloses a polysiloxane-based shape memory polymer and a preparation method thereof, and belongs to the technical field of shape memory polymer synthesis. The method comprises the following steps: sequentially adding a formaldehyde solution, a solution dissolved with siloxane and 2-naphthol into a container, and reacting at 90-100 DEG C for 1.5-3 hours; removing the solvent through reduced pressure distillation, then washing liquid residues for multiple times by using deionized water to obtain a product, and drying the product at 60 DEG C for 6 hours to obtain viscous liquid; the liquid is placed in a mold, then the mold is transferred into a drying oven, the temperature is increased to 120 DEG C and 140 DEG C in sequence, heat preservation is conducted for 1 h, finally, the temperature is increased to 190 DEG C to 220 DEG C, the temperature is kept for 5 h to 6.5 h, and curing is completed. The shape memory polymer formed by polymerizing siloxane and 2-naphthol has more Si-O groups, benzene rings and oxazine rings, the groups can enhance the tolerance of the polymer to high temperature, chemical or physical crosslinking points serve as a stationary phase to memorize a permanent shape, and a flexible alkyl-siloxane unit serves as a switching section to fix a temporary shape.

Description

Technical Field

[0001] The invention belongs to the technical field of shape memory polymer synthesis, and in particular relates to a polysiloxane-based shape memory polymer and a preparation method thereof. Background Art

[0002] Shape memory polymers are smart materials that can respond to external stimuli. Because they can recover from a temporary shape to a permanent shape after being stimulated by light, heat, electricity, etc., they have been widely used in aerospace, biomedicine, sensors and other fields in recent years. Although traditional shape memory polymers (SMPs) have made certain progress in materials such as polyurethane, polyester, and vinyl polymers, they still have many shortcomings in practical applications. For example, under high temperature or extreme climate conditions, polyurethane, polyester and vinyl polymers are easily degraded and lose their shape recovery ability; polyurethane will absorb a lot of water in a high humidity environment, resulting in poor shape stability and significantly reduced performance. Therefore, the high temperature stability, moisture influence, processability and room temperature performance of traditional shape memory polymers limit their widespread promotion in certain applications.

[0003] Polysiloxane has an organic-inorganic alternating molecular structure, which makes it have excellent high temperature resistance, climate change resistance and excellent hydrophobicity. As a new type of matrix material, it has attracted more and more attention from researchers. Different from the performance of traditional shape memory polymers, polysiloxane-based shape memory polymers can still maintain good shape memory performance at high temperatures. At the same time, it has excellent room temperature flexibility and processability. These characteristics enable it to work in more harsh environments, such as high temperature, humidity or extreme climate application scenarios. Summary of the invention

[0004] The purpose of the present invention is to solve the problem that existing shape memory polymers cannot meet practical applications, and to provide a polysiloxane-based shape memory polymer and a preparation method thereof. The present invention is designed at the molecular level, and its high temperature stability is further improved by introducing functional groups such as benzene rings and oxazine with good thermal stability into polysiloxane. The prepared polymer has good shape memory performance and high temperature tolerance, and can be used in harsh environments such as automobiles or aerospace parts or in the aerospace field.

[0005] To achieve the above purpose, 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 into a container, then add a solution containing siloxane, and finally add 2-naphthol, raise the temperature to promote the reaction of formaldehyde, siloxane and 2-naphthol, and react at 90°C-100°C for 1.5h-3h;

[0008] Step 2: removing the solvent by distillation under reduced pressure, then washing the liquid residue with deionized water for multiple times to obtain a product, and drying the product in a vacuum oven at 60° C. for 6 h to obtain a viscous liquid;

[0009] Step 3: Place the liquid in a mold, then transfer the mold to an oven, heat it to 120°C and 140°C, keep it warm for 1 hour respectively, and finally heat it to 190°C-220°C and keep it for 5h-6.5h to complete the curing.

[0010] Furthermore, in step 1, the structural formula of the siloxane is:

[0011]

[0012] In formula (I), R1 is NH2, R2, R3, R4, R5, R6, and R7 are independently selected from H, C 1-10 Alkyl, C 6-14 One or more of aromatic groups.

[0013] Further, in step 1, the structural formula of the 2-naphthol is:

[0014]

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

[0016] Furthermore, in step 1, the solvent of the solution is a solvent having a solubility parameter between 2-naphthol and siloxane, preferably one or more of toluene, o-xylene, and p-xylene.

[0017] Furthermore, in step 1, the mass ratio of 2-naphthol, formaldehyde and siloxane is 14:6:5-7, preferably, the mass ratio of 2-naphthol, formaldehyde and siloxane is 14:6:6.

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

[0019]

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

[0021] Further, in step one, the reaction temperature is 90°C-95°C, the time is 2.0h-2.5h, the heating temperature can be 90°C, 91°C, 92°C, 93°C, 94°C, 95°C 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] Further, in step 3, the curing temperature is 210°C-215°C, and the curing time is 5.0h-6h. The curing temperature can be 200°C, 201°C, 202°C, 203°C, 204°C, 215°C, 216°C, 217°C, 218°C, 219°C or any value therebetween; 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 therebetween.

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

[0024] Compared with the prior art, the present invention has the following advantages: the shape memory polymer formed by the polymerization of siloxane and 2-naphthol contains more Si-O groups, benzene rings and oxazine rings, which can enhance the polymer's tolerance to high temperatures, chemical or physical crosslinking points as fixed phases to memorize permanent shapes, and flexible alkyl-siloxane units as switch segments to fix temporary shapes. These alkyl siloxane units act as effective switch segments, and their higher glass transition temperatures give shape memory polymers a higher transition temperature. In addition, it exhibits good shape memory properties, and can restore permanent shapes from temporary shapes at 140°C, with a shape memory rate of up to 94%. DETAILED DESCRIPTION

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

[0026] When an amount, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper preferred values ​​and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pairing of any range upper limit or preferred value with any range lower limit or preferred value, regardless of whether the range is disclosed separately. For example, when a range of "1 to 5" is disclosed, the described range should be interpreted as including ranges "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described in this article, unless otherwise stated, the range is intended to include its end values ​​and all integers and fractions within the range.

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

[0028] The technical scheme of the present invention will be described in detail below in conjunction with specific embodiments, but those skilled in the art will appreciate that the following embodiments are only used to illustrate the present invention and should not be considered to limit the scope of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0029] Example 1

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

[0031] (1) Add 20 mL of p-xylene and 12 mL of formaldehyde mixture into a round-bottom flask, then weigh 10 g of siloxane and dissolve it in 20 mL of p-xylene solution, drop the p-xylene solution containing siloxane into the above solution mixture, and 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 is completed, the solvent p-xylene is removed by distillation under reduced pressure, and the liquid residue is washed three times with deionized water. The washed liquid is dried in a vacuum oven at 60° C. for 6 hours to obtain a product liquid.

[0033] (3) The above product is placed in a mold, and the bubbles in the product can be removed by vacuuming or freezing centrifugation. Then, it is transferred to an oven and kept at 120°C for 1 hour, and then the temperature is increased to 140°C and kept for another 1 hour.

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

[0035] Example 2

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

[0037] (1) Add 20 mL of p-xylene and 12 mL of formaldehyde mixture into a round-bottom flask, then weigh 12 g of siloxane and dissolve it in 20 mL of p-xylene solution, drop the p-xylene solution containing siloxane into the above solution mixture, and 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 is completed, the solvent p-xylene is removed by distillation under reduced pressure, and the liquid residue is washed three times with deionized water. The washed liquid is dried in a vacuum oven at 60° C. for 6 hours to obtain a product liquid.

[0039] (3) The above product is placed in a mold, and the bubbles in the product can be removed by vacuuming or freezing centrifugation. Then, it is transferred to an oven and kept at 120°C for 1 hour, and then the temperature is increased to 140°C and kept for another 1 hour.

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

[0041] Example 3

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

[0043] (1) Add 20 mL of p-xylene and 12 mL of formaldehyde mixture into a round-bottom flask, then weigh 14 g of siloxane and dissolve it in 20 mL of p-xylene solution, drop the p-xylene solution containing siloxane into the above solution mixture, and 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 is completed, the solvent p-xylene is removed by distillation under reduced pressure, and the liquid residue is washed three times with deionized water. The washed liquid is dried in a vacuum oven at 60° C. for 6 hours to obtain a product liquid.

[0045] (3) The above product is placed in a mold, and the bubbles in the product can be removed by vacuuming or freezing centrifugation. Then, it is transferred to an oven and kept at 120°C for 1 hour, and then the temperature is increased to 140°C and kept for another 1 hour.

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

[0047] A certain mass of sample was cut for differential scanning calorimetry experiment. First, it was heated to 200°C to eliminate the thermal history. After natural cooling, heating and cooling scans were performed. The response temperature of the sample was determined based on the obtained data. The above experiments were all carried out under nitrogen protection.

[0048] First, the prepared sample strip with a certain size is placed in a drying oven at 90°C for 30 minutes and then folded 180°, and the bending angle θ0 of the sample strip is recorded (θ0≈180). After that, the sample strip is cooled to room temperature while maintaining the external force, 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 by the following formula.

[0049]

[0050] First, the required dumbbell-shaped polymer and composite material samples were prepared according to the mechanical testing machine, and then the static mechanical properties were tested at room temperature. The loading speed of the mechanical testing machine chuck was 1-5mm min -1 There are 3 parallel samples in each group of test samples, and the average value is taken to calculate the tensile strength, elongation at break and Young's modulus.

[0051] Table 1 Response temperature of the embodiment

[0052]

[0053]

[0054] Table 2 Shape fixing temperature and shape fixing rate of the embodiment

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

[0056] Table 3 Mechanical properties of the examples

[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 below, the response temperature and mechanical properties of the shape memory polymer prepared with siloxane and 2-naphthol as raw materials can be adjusted within a certain range. As the mass of siloxane increases, the response temperature of the polymer increases from 170°C to 179°C, and the shape fixation rate also increases slightly from 91% to 94%. However, as the mass of siloxane continues to increase, its Young's modulus decreases slightly.

Claims

1. A method for preparing a polysiloxane-based shape memory polymer, characterized in that: The method is: Step 1: Add formaldehyde solution into a container, then add a solution containing siloxane, and finally add 2-naphthol, and react at 90℃-100℃ for 1.5h-3h; Step 2: removing the solvent by distillation under reduced pressure, then washing the liquid residue with deionized water for multiple times to obtain a product, and drying the product in a vacuum oven at 60° C. for 6 h to obtain a viscous liquid; Step 3: Place the liquid in a mold, then transfer the mold to an oven, heat it to 120°C and 140°C, keep it warm for 1 hour respectively, and finally heat it to 190°C-220°C and keep it for 5h-6.5h to complete the curing.

2. The method for preparing a polysiloxane-based shape memory polymer according to claim 1, characterized in that: In step 1, the structural formula of the siloxane is: In formula (I), R1 is NH2, R2, R3, R4, R5, R6, and R7 are independently selected from H, C 1-10 Alkyl, C 6-14 One or more of aromatic groups.

3. The method for preparing a polysiloxane-based shape memory polymer according to claim 1, characterized in that: In step 1, the structural formula of the 2-naphthol is: In formula (II), R1 is selected from H, C 1-10 One of the alkyl groups.

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

5. The method for preparing a polysiloxane-based shape memory polymer according to claim 1, characterized in that: In step 1, the mass ratio of 2-naphthol, formaldehyde and siloxane is 14:6:5-7.

6. The method for preparing a polysiloxane-based shape memory polymer according to claim 1, characterized in that: The reaction process of shape memory polymer involves the equation shown in formula (III): In formula (III), R1, R2, R3, R4, R5, R6, and R7 are independently selected from H, C 1-10 Alkyl, C 6-14 One or more of the aromatic groups, R8 is NH2.

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

8. 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°C-215°C, and the curing time is 5.0h-6h.

9. A polysiloxane-based shape memory polymer prepared by the preparation method according to any one of claims 1 to 8.

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