Self-healing polymer as well as preparation method and application thereof

Abstract

The invention relates to a self-healing polymer as well as a preparation method and application thereof, and belongs to the technical field of preparation of environment-friendly flexible polymer materials, and the prepared self-healing polyurethane elastomer has rapid self-healing property, high mechanical strength and recyclable processability of materials.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials, and specifically relates to a self-healing polymer, its preparation method, and its application. Background Technology

[0002] Traditional polyurethanes, polymerized from petroleum-based polyols and isocyanates, are widely used in aerospace and medical devices. However, the contradiction between the application demands of polyurethanes and the scarcity of fossil fuels as raw materials is becoming increasingly severe. Furthermore, the rapid development of flexible electronics, wearable devices, and smart sensing technologies places higher demands on the environmental adaptability, durability, and functional repairability of polyurethanes. Against this backdrop, the preparation of self-healing polyurethanes using bio-based or recycled raw materials has become a research hotspot in green chemistry. Polyester polyols obtained from the alcoholysis of waste PET, as an environmentally friendly raw material, can not only replace traditional petroleum-based polyols but also introduce reversible π-π interactions through benzene ring stacking in the molecular chain to construct green self-healing polyurethanes. However, the dynamic nature of these π-π interactions requires activation by external stimuli, making room-temperature self-healing impossible. Among various self-healing polyurethane design strategies, polyurethanes based on oxime-carbamate bonds have attracted considerable attention due to their ability to achieve dynamic bond dissociation and recombination under mild conditions.

[0003] However, there are few reports on the preparation of green room temperature self-healing polyurethane by combining alcoholysis polyester polyols with oxime-carbamate bonds. Furthermore, how to achieve dynamic synergy between the soft segments of alcoholysis polyester polyols and oxime-carbamate bonds through molecular design, while taking into account the rapid self-healing properties, high mechanical strength, and recyclability of the material, is a key problem that urgently needs to be solved. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a self-healing polyoxime urethane, its preparation method and application.

[0005] This invention provides a self-healing polymer, the general structural formula of which is:

[0006] Where y = (1~3), z is 20 or higher; Furthermore, z is (20 or more).

[0007] Where R is an isocyanate residue; The isocyanate residues are the groups remaining after the isocyanate groups are removed.

[0008] The M is

[0009] Where n = (1, 2, 3); x = (6~8).

[0010] Furthermore, n=1, x=2, y=1, and z is 20 or more.

[0011] The isocyanate is one or more of isophorone diisocyanate (IPDI), dicyclohexylmethane diisocyanate (HMDI), and diphenylmethane diisocyanate (MDI).

[0012] The corresponding structure of isocyanate: , , .

[0013] The preparation of polyoxime esters involves reacting polyester polyol and dimethylglyoxime as soft segments and chain extenders, respectively, with different isocyanates under the action of a catalyst.

[0014] This invention provides a method for preparing polyoxime urethane, comprising: mixing polyester polyol, solvent and catalyst, adding isocyanate dropwise for reaction, then adding dimethylglyoxime solution for reaction, and post-treatment to obtain polyoxime urethane.

[0015] The preferred embodiment of the above preparation method is as follows: The structure of the polyester polyol:

[0016] Where n = (1, 2, 3); x = (6~8); Furthermore, the polyester polyol is an alcoholysis polyester polyol.

[0017] The isocyanate is one or more of isophorone diisocyanate (IPDI), dicyclohexylmethane diisocyanate (HMDI), and diphenylmethane diisocyanate (MDI).

[0018] The solvent includes N,N-dimethylformamide; the catalyst includes dibutyltin dilaurate; and the solvent for the dimethylglyoxime solution includes N,N-dimethylformamide.

[0019] The molar ratio of the polyester polyol to the isocyanate is 1:4~6.

[0020] The catalyst is fed in an amount of 0.4% to 0.5% of the total mass of polyester polyol, isocyanate, and dimethylglyoxime; the dimethylglyoxime is 2 to 4 times the molar amount of polyester polyol.

[0021] The preparation process includes: heating the polyester polyol to 110-120℃ and then evacuating it under vacuum; cooling it to 80-90℃ and then adding solvent and catalyst; stirring; adding isocyanate dropwise for 2-4 hours; then cooling it to 55-65℃ and adding dimethylglyoxime solution for 14-18 hours; all reactions are carried out under protective gas conditions.

[0022] The post-treatment involves reacting at 55-65℃ for 12-24 hours, followed by heating to 80-85℃ and vacuuming for 20-30 hours.

[0023] This invention provides an application of any of the self-healing polymers described herein in the field of self-healing elastomers.

[0024] Compared with the prior art, the technical effects and advantages provided by the present invention in the above technical solution are as follows: The present invention uses polyester polyol and dimethylglyoxime as soft segment and chain extender, respectively, and the polyoxime elastomer obtained by reacting with isocyanates of different structures has good self-healing and mechanical properties.

[0025] This invention belongs to the field of environmentally friendly flexible polymer material preparation technology, and also relates to a low-cost, high-value-added recycling process for waste plastic products. The self-healing polyoxime elastomer of this invention also possesses rapid self-healing properties. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0027] Figure 1 These are the UV-Vis spectral test curves for Examples 1-3; Figure 2 Examples 1-3 are surface height maps and phase curves obtained from atomic force microscopy (AFM). Figure 3 These are the stress-strain curves for Examples 1-3; Figure 4 These are images of the self-healing scratches in Example 3 under a digital microscope; Figure 5 This is the self-healing efficiency of the specimens at different temperatures in Example 3.

[0028] Figure 6 This is a flowchart of the synthesis process of POU elastomer. Detailed Implementation

[0029] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0030] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0031] The sources and specifications of the raw materials and reagents used in the experiment are shown in Table 1.

[0032] Table 1 Experimental materials and reagents

[0033] Example 1 In this embodiment, isophorone diisocyanate (IPDI) was used for synthesis.

[0034] Preparation of polyoxime urethane containing isophorone diisocyanate (IPDI): Alcohololyzed polyester polyol (2.362 g, 0.500 mmol) was added to a reaction flask, and the mixture was heated to 120 °C and vacuum-treated to remove water and residual anhydrous ethanol for 2 h. While maintaining a nitrogen atmosphere, the mixture was cooled to 85 °C, and N,N-dimethylformamide (DMF, 2 mL) and dibutyltin dilaurate (DBTDL, 0.5 wt%, 0.015 g) were added to the reaction flask. After magnetic stirring at 600 r / min for 20 min, isophorone diisocyanate (IPDI, 0.467 g, 2.1 mmol) was added dropwise using a syringe, and the reaction proceeded for 3 h. Subsequently, the temperature was lowered to 60 °C, and a solution of dimethylglyoxime (DMG, 0.174 g, 1.5 mmol) dissolved in 2 mL of DMF was added to the flask, and the reaction proceeded for 16.5 h. Finally, the product was poured into a polytetrafluoroethylene mold and transferred to a 60°C vacuum oven to continue the reaction for 24 h. The oven was then heated to 80°C and vacuumed for 27 h to obtain a yellow solid, which is POU-IPDI.

[0035] Example 2 In this embodiment, dicyclohexylmethane diisocyanate (HMDI) was used for synthesis.

[0036] Preparation of polyoxime urethane containing dicyclohexylmethane diisocyanate (HMDI): Alcohololyzed polyester polyol (2.362 g, 0.500 mmol) was added to a reaction flask, and the mixture was heated to 120 °C and vacuum-treated to remove water and residual anhydrous ethanol for 2 h. While maintaining a nitrogen atmosphere, the mixture was cooled to 85 °C, and N,N-dimethylformamide (DMF, 2 mL) and dibutyltin dilaurate (DBTDL, 0.5 wt%, 0.015 g) were added to the reaction flask. After magnetic stirring at 600 r / min for 20 min, dicyclohexylmethane diisocyanate (HMDI, 0.551 g, 2.1 mmol) was added dropwise using a syringe, and the reaction proceeded for 3 h. Subsequently, the temperature was lowered to 60 °C, and a solution of dimethylglyoxime (DMG, 0.174 g, 1.5 mmol) dissolved in 2 mL of DMF was added to the flask, and the reaction proceeded for 16.5 h. Finally, the product was poured into a polytetrafluoroethylene mold and transferred to a 60 °C vacuum oven to continue the reaction for 24 h. The oven was then heated to 80 °C and vacuumed for 27 h to obtain a yellow solid, which is POU-HMDI.

[0037] Example 3 In this embodiment, diphenylmethane diisocyanate (MDI) was used for synthesis.

[0038] Preparation of polyoxime urethane containing diphenylmethane diisocyanate (MDI): Alcohololyzed polyester polyol (2.362 g, 0.500 mmol) was added to a reaction flask, and the mixture was heated to 120 °C and vacuum-treated to remove water and residual anhydrous ethanol for 2 h. While maintaining a nitrogen atmosphere, the mixture was cooled to 85 °C, and N,N-dimethylformamide (DMF, 2 mL) and dibutyltin dilaurate (DBTDL, 0.5 wt%, 0.015 g) were added to the reaction flask. After magnetic stirring at 600 r / min for 20 min, diphenylmethane diisocyanate (MDI, 0.526 g, 2.1 mmol) was added dropwise using a syringe, and the reaction proceeded for 3 h. Subsequently, the temperature was lowered to 60 °C, and a solution of dimethylglyoxime (DMG, 0.174 g, 1.5 mmol) dissolved in 2 mL of DMF was added to the flask, and the reaction proceeded for 16.5 h. Finally, the product was poured into a polytetrafluoroethylene mold and transferred to a 60 °C vacuum oven to continue the reaction for 24 h. The oven was then heated to 80 °C and vacuumed for 27 h to obtain a yellow solid, which is POU-MDI.

[0039] Performance tests were conducted on Examples 1, 2, and 3. 1. Gel permeation chromatography (GPC) test: The molecular weight of POU was determined using a GPC equipped with an RI detector and an MG300 column. All solvents used were N-methylpyrrolidone, and the concentration was prepared at 1.0 mg / mL.

[0040] 2. Ultraviolet-Vis Spectroscopy (UV-Vis) Testing: The intensity of π-π interactions in POU was characterized using UV-Vis with a slow response rate, a scan rate of 100 nm / min, and a scan range of 230–300 nm.

[0041] 3. Atomic Force Microscope (AFM): The surface morphology and phase separation of POU were determined by AFM characterization of height maps and phase maps. The scanning range was 500 nm. The images were processed and analyzed using Nano-Scope-Analysis and Gwyddion software.

[0042] 4. Uniaxial tensile test: The tensile properties of POU were characterized using a universal testing machine. The sample was a rectangular strip of 15×3×0.5 mm3, and the tensile rate was 50 mm / min. The results were taken as the average of three data points.

[0043] 5. Surface scratch self-healing test: The self-healing property of scratches on the surface of POU-MDI was characterized using a digital microscope. The PU surface was scratched with a razor blade, and the scratches were about 1.2 mm long. The changes of the scratches over time were observed at room temperature (25℃).

[0044] 6. Spline cutting self-healing test: The tensile properties of the cut and self-healing specimens of Example 3 were characterized using a universal testing machine. The cut rectangular specimens of Example 3 were placed in ovens at 25 ℃, 55 ℃ and 70 ℃ for 24 h and then removed. The self-healing performance of POU-MDI was evaluated by the tensile strength of the healed specimens. The average of the three tensile strengths was taken as the result, and the ratio of the tensile strength after self-healing to the original tensile strength was defined as the self-healing efficiency.

[0045] Examples 1-3 were characterized by GPC to determine the molecular weight and distribution of POU, as shown in Table 2. Under the same reaction conditions and ratios, the reactivity of alcoholysis polyester polyols with different isocyanates varied. In Example 3, the Mn and Mw were 23535 and 62374 g / mol, respectively, which were significantly higher than those of the other two examples. This indicates that the alcoholysis polyols have higher reactivity with MDI, and the reaction between the two readily yields products with excellent mechanical properties.

[0046] Table 2. Molecular weight and distribution of POU

[0047] Examples 1-3 characterized the samples using UV-Vis spectra, such as... Figure 1 As shown, under essentially the same solution concentration, a broad characteristic absorption peak appeared in all three sets of POU spectra, indicating the presence of π-π interactions in the materials. Furthermore, the absorption peak intensities of Examples 1 and 2 were essentially the same, with the highest values ​​both around 243.8 nm. The absorption peak signal of Example 3 was significantly stronger than that of Examples 1 and 2, with its highest absorption peak value near 246.1 nm, exhibiting a clear red shift, indicating that the π-π interactions in Example 3 were stronger than in the other two sets of POUs.

[0048] Examples 1-3 used AFM to test the height map and corresponding phase map of the material surface at a scanning size of 500×500 nm2, as shown below. Figure 2 As shown. The adhesion strength of the material surface determines the phase value of the corresponding region. Generally, bright areas in the phase diagram represent domains aggregated by interactions, while broad dark areas represent soft segments with lower modulus. From Figure 2 It can be seen that no obvious hard segment microdomains appeared in any of the three sets of examples, indicating that the domains in the material are uniformly distributed in the soft segments. To further compare the degree of microphase separation among the three sets of examples while keeping the material color range consistent, it can be seen that the color of Example 1 is the brightest, followed by Example 3, while the color of Example 2 is the darkest. In addition, a 500 nm long straight line region with the largest phase difference was selected in the phase diagram of the three sets of examples, and the average phase value of this region was calculated. The average phase value of Example 1 is the largest and two sets of phase difference peaks appear, indicating the largest degree of microphase separation; Example 3 has only one set of phase difference peaks and the peak value is smaller than that of Example 1, indicating a relatively small degree of microphase separation; Example 2 has a basically consistent average phase and no obvious phase difference peaks appear, indicating the smallest degree of microphase separation.

[0049] The mechanical properties of Examples 1-3 can be investigated using stress-strain curves, such as... Figure 3 As shown in Table 3, POU exhibits different mechanical properties with changes in isocyanate structure. The Young's modulus of POU is negatively correlated with chain segment regularity. However, with increasing elongation and stress, the physical crosslinking points (hydrogen bonds and π-π interactions) in POU begin to dissipate mechanical energy. Examples 1 and 3 have relatively more physical crosslinking points, thus their tensile strength is higher than that of Example 2. Compared to Example 2, Example 3 exhibits a higher tensile strength (6.6 ± 0.1 MPa), an increase of 2.0 times; compared to Example 1, the elongation at break of Example 3 (903.6 ± 50.8%) is significantly increased by 1.4 times. Therefore, Example 3 has the best mechanical properties.

[0050] Table 3 Mechanical properties of POU

[0051] The reversible hydrogen bonds, oxime-carbamate bonds, and π-π interactions in Example 3 enable it to possess good room-temperature self-healing ability, which is investigated through room-temperature scratch self-healing and spline cut self-healing experiments. Figure 4 As shown in Table 4, the healing process of the scratched film of Example 3 was observed under a digital microscope at room temperature (25 °C). The micrographs show that only a small portion of the deepest scratches remained unhealed at 25 min, and the scratches completely disappeared at 30 min, indicating that Example 3 has good room temperature scratch self-healing ability. The self-healing ability of Example 3 was further evaluated by testing the mechanical properties of cut rectangular specimens of Example 3 after healing at different temperatures. The cut rectangular specimens were placed at the fracture surfaces in contact and then placed in environments at room temperature, 55 °C, and 70 °C for 24 h before being removed. The mechanical properties of the specimens after cooling are shown in Table 4. Figure 5 As shown, under the same healing time, the tensile strength, elongation at break, and self-healing efficiency of Example 3 all increased with increasing temperature. After healing at 70 °C for 24 h, the self-healing efficiency of Example 3 reached 83.0 ± 4.9%, which was 24.1% higher than that of the self-healing specimen at 55 °C. This is because heating can promote the dissociation and recombination rate of reversible dynamic bonds at the fracture site of Example 3, which macroscopically manifests as an improvement in material mechanics and self-healing efficiency. The above research shows that Example 3 is a room-temperature self-healing elastomer with temperature response capability, which can effectively repair material damage and extend service life.

[0052] Table 4 Self-healing performance of Example 3

[0053] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A self-healing polymer, characterized in that, The general structural formula of the polymer is: ； Where y = (1~3), z is 20 or higher; Where R is an isocyanate residue; The M is ； Where n = (1, 2, 3); x = (6~8).

2. The self-healing polymer according to claim 1, characterized in that, The isocyanate is one or more of isophorone diisocyanate (IPDI), dicyclohexylmethane diisocyanate (HMDI), and diphenylmethane diisocyanate (MDI).

3. A method for preparing a self-healing polymer, comprising: Polyester polyol, solvent, and catalyst are mixed, and isocyanate is added dropwise for reaction. Then, dimethylglyoxime solution is added for reaction, followed by post-treatment to obtain polyoxime urethane.

4. The preparation method according to claim 3, characterized in that, The structure of the polyester polyol: ； Where n = (1, 2, 3); x = (6~8); the isocyanate is one or more of isophorone diisocyanate IPDI, dicyclohexylmethane diisocyanate HMDI, and diphenylmethane diisocyanate MDI.

5. The preparation method according to claim 3, characterized in that, The solvent includes N,N-dimethylformamide; the catalyst includes dibutyltin dilaurate; and the solvent for the dimethylglyoxime solution includes N,N-dimethylformamide.

6. The preparation method according to claim 3, characterized in that, The molar ratio of the polyester polyol to the isocyanate is 1:4~6.

7. The preparation method according to claim 3, characterized in that, The catalyst is fed in an amount of 0.4-0.5% of the mass of polyester polyol, isocyanate, and dimethylglyoxime; the dimethylglyoxime is 2-4 times the molar amount of polyester polyol.

8. The preparation method according to claim 3, characterized in that, Preparation includes: After the polyester polyol is heated to 110-120℃, a vacuum is drawn, and after cooling to 80-90℃, solvent and catalyst are added, stirred, and isocyanate is added dropwise for 2-4 hours. Then, the temperature is lowered to 55-65℃ and dimethylglyoxime solution is added for 14-18 hours. All reactions are carried out under protective gas conditions.

9. The preparation method according to claim 3, characterized in that, The post-treatment involves reacting at 55-65℃ for 12-24 hours, followed by heating to 80-85℃ and vacuuming for 20-30 hours.

10. The application of the self-healing polymer according to any one of claims 1-2 in the field of self-healing elastomers.

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