Self-healing polyurethane elastomers having a bicontinuous phase structure and methods of making the same

Abstract

The application discloses a self-repairing polyurethane elastomer with a bicontinuous phase structure and a preparation method thereof. The structural formula of the self-repairing polyurethane elastomer is one-step synthesized by amino-terminated polydimethylsiloxane, isophorone diisocyanate and 5-(2-hydroxyethyl)-6-methyl-2-aminouracil with a molar ratio of 1:1.1-1.5:0.1-0.5 and dibutyltin dilaurate as a catalyst. The self-repairing polyurethane elastomer has a bicontinuous network structure, high elasticity, excellent fatigue resistance and good thermal stability.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials and relates to a self-healing polyurethane elastomer with a dual continuous phase structure and its preparation method. Background Technology

[0002] Throughout history, humankind has never ceased its exploration and learning of the natural world's organisms, resulting in the invention of numerous biomimetic materials. These materials have played a crucial role in the progress of human society. For vast biological systems, nothing is more captivating than their self-healing capabilities. In 2001, White published a report on self-healing epoxy resins in Nature [Nature, 2001, 409, 794-797], sparking a research boom in self-healing polymer materials. With the deepening research into component dynamic chemistry (supramolecular chemistry and dynamic covalent bonds), researchers have developed an increasing number of self-healing materials with different moduli (different hardnesses) to meet practical application needs.

[0003] Flexible (low modulus) polymer materials have been widely used in flexible electronic devices due to their excellent stretchability and bendability. However, flexible electronic devices are easily damaged in everyday use environments, making the development of self-healing flexible electronic devices essential. Based on the above reports, Professor Zhenan Bao of Stanford University developed a self-healing polyurethane elastomer through layered hydrogen bonding [Adv. Mater., 2018, 30, 1706846]. This elastomer is synthesized from amino-terminated polydimethylsiloxane, 4,4′-methylene bis(phenyl isocyanate), and isophorone diisocyanate. It can recover 78% of its mechanical properties after 48 hours of repair at room temperature. In addition, this material also has high resistance to damage and crack propagation, but these properties gradually decrease during repeated use. Furthermore, this elastomer does not possess excellent thermodynamic stability. Assessing crack propagation resistance solely based on a single tensile test is insufficient. As is well known, flexible electronic devices often undergo bending and stretching thousands of times in real-world applications. Cracks can easily propagate and even penetrate the entire material during these high-frequency reciprocating movements, causing the material to fail completely before it can repair itself. Therefore, developing thermally stable, room-temperature fatigue-resistant, flexible self-healing materials is of paramount importance for flexible electronic devices. Summary of the Invention

[0004] The purpose of this invention is to provide a self-healing polyurethane elastomer with a dual continuous phase structure and its preparation method.

[0005] The technical solution for achieving the objective of this invention is as follows:

[0006] A self-healing polyurethane elastomer with a bicontinuous phase structure is synthesized in one step from amino-terminated polydimethylsiloxane (NH2-PDMS-NH2), isophorone diisocyanate (IPDI), and 5-(2-hydroxyethyl)-6-methyl-2-aminouracil in a molar ratio of 1:1.1-1.5:0.1-0.5, with dibutyltin dilaurate as a catalyst. The structural formula of the self-healing polyurethane elastomer is as follows:

[0007] n≥22.

[0008] The preparation method of a self-healing polyurethane elastomer with a dual continuous phase structure includes the following specific steps:

[0009] The molar ratio of amino-terminated polydimethylsiloxane, isophorone diisocyanate, and 5-(2-hydroxyethyl)-6-methyl-2-aminouracil was 1:1.1-1.5:0.1-0.5. 5-(2-hydroxyethyl)-6-methyl-2-aminouracil powder, amino-terminated polydimethylsiloxane, isophorone diisocyanate, and dibutyltin dilaurate were dissolved in N,N-dimethylformamide. The mixture was refluxed at 70±10℃ under a nitrogen atmosphere with stirring. After the reaction was completed, the mixture was cooled to room temperature to obtain a self-healing polyurethane elastomer material.

[0010] Preferably, 5-(2-hydroxyethyl)-6-methyl-2-aminouracil is prepared by the following steps: 2-acetylbutyrolactone, triethylamine and guanidine carbonate are refluxed in ethanol for 4-6 h. After the reaction, a yellow powder solid is obtained by suction filtration, further washed with ethanol and dried at 60 °C for 12-24 h to obtain a white 5-(2-hydroxyethyl)-6-methyl-2-aminouracil powder.

[0011] Preferably, the amino-terminated polydimethylsiloxane has a number average molecular weight of 3000.

[0012] Preferably, the molar ratio of amino-terminated polydimethylsiloxane, isophorone diisocyanate, and 5-(2-hydroxyethyl)-6-methyl-2-aminouracil is 1:1.3:0.3.

[0013] Preferably, the reflux reaction time is 12–18 h.

[0014] Preferably, the concentration of amino-terminated polydimethylsiloxane in the reaction system is 30 wt%.

[0015] Preferably, the mass of dibutyltin dilaurate is 1% of the mass of isophorone diisocyanate.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] This invention uses 5-(2-hydroxyethyl)-6-methyl-2-aminouracil as a chain extender to modulate the phase structure of a self-healing polyurethane elastomer, giving it a bicontinuous network structure. This bicontinuous network structure effectively improves the resilience of the self-healing polyurethane elastomer (it can recover to its original length within 5 minutes when stretched to 500% strain) and its fatigue resistance (fatigue threshold of 1010 J / m). -2 ) and thermal stability (when stretched to 50% strain at 50°C, it can still return to its original length within 2 minutes). Attached Figure Description

[0018] Figure 1 The atomic force microscopy phase diagram of SHPU-SNS-0.3 in Example 2;

[0019] Figure 2 Infrared images of SHPU-SNS-0.1, SHPU-SNS-0.3, SHPU-SNS-0.5, and SHPU-WNS in Examples 1, 2, 3, and Comparative Example 1;

[0020] Figure 3 The mechanical repair curves of SHPU-SNS-0.3 and SHPU-WNS in Example 2 and Comparative Example 1 are shown.

[0021] Figure 4 These are actual images showing the broken samples obtained in Example 2 and Comparative Example 1;

[0022] Figure 5 Tensile stress-strain curves of SHPU-SNS-0.1, SHPU-SNS-0.3, SHPU-SNS-0.5 and SHPU-WNS in Examples 1, 2, 3 and Comparative Example 1;

[0023] Figure 6 The fatigue threshold diagrams for SHPU-SNS-0.3 and SHPU-WNS in Example 2 and Comparative Example 1 are shown.

[0024] Figure 7 This is a comparison chart of the elasticity of SHPU-SNS-0.3 and SHPU-WNS in Example 2 and Comparative Example 1;

[0025] Figure 8 The strain recovery curves of SHPU-SNS-0.3 and SHPU-WNS at 50°C are shown in Example 2 and Comparative Example 1. Detailed Implementation

[0026] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings.

[0027] 5-(2-hydroxyethyl)-6-methyl-2-aminouracil was prepared according to the reference [J. Am. Chem. Soc., 2018, 140, 5280], and the specific steps are as follows:

[0028] 5.12 g of 2-acetylbutyrolactone, 11 ml of triethylamine, and 3.60 g of guanidine carbonate were weighed and refluxed in 40 ml of ethanol at 60 °C for 4 hours. After the reaction, a yellow powder solid was obtained by suction filtration, which was further washed with ethanol. The product was then placed in an oven at 60 °C for 12 hours to obtain a white 5-(2-hydroxyethyl)-6-methyl-2-aminouracil powder.

[0029] Example 1

[0030] White 5-(2-hydroxyethyl)-6-methyl-2-aminouracil powder (0.0169 g), amino-terminated polydimethylsiloxane (3 g), isophorone diisocyanate (0.2442 g), and dibutyltin dilaurate were placed in a three-necked flask containing 10 ml of N,N-dimethylformamide solvent. The mixture was refluxed at 70 °C for 12 hours. After the solution cooled to room temperature, the resulting solid was dissolved in chloroform solution and then poured into a polytetrafluoroethylene mold to evaporate the solvent at room temperature for 12 hours, resulting in a self-healing polyurethane elastomer SHPU-SNS-0.1 with a bicontinuous phase structure.

[0031] Example 2

[0032] White 5-(2-hydroxyethyl)-6-methyl-2-aminouracil powder (0.0507 g), amino-terminated polydimethylsiloxane (3 g), isophorone diisocyanate (0.2886 g), and dibutyltin dilaurate were placed in a three-necked flask containing 10 ml of N,N-dimethylformamide solvent. The mixture was refluxed at 70 °C for 12 hours. After the solution cooled to room temperature, the resulting solid was dissolved in chloroform solution and then poured into a polytetrafluoroethylene mold to evaporate the solvent at room temperature for 12 hours, resulting in a self-healing polyurethane elastomer SHPU-SNS-0.3 with a bicontinuous phase structure.

[0033] Example 3

[0034] White 5-(2-hydroxyethyl)-6-methyl-2-aminouracil powder (0.0845 g), amino-terminated polydimethylsiloxane (3 g), isophorone diisocyanate (0.333 g), and dibutyltin dilaurate were placed in a three-necked flask containing 10 ml of N,N-dimethylformamide solvent. The mixture was refluxed at 70 °C for 12 hours. After the solution cooled to room temperature, the resulting solid was dissolved in chloroform solution and then poured into a polytetrafluoroethylene mold to evaporate the solvent at room temperature for 12 hours, resulting in a self-healing polyurethane elastomer SHPU-SNS-0.5 with a bicontinuous phase structure.

[0035] Comparative Example 1

[0036] Amino-terminated polydimethylsiloxane (3g) and isophorone diisocyanate (0.222g) were placed in a three-necked flask containing 10ml of N,N-dimethylformamide solvent and refluxed at 70°C for 12 hours. After the solution cooled to room temperature, the resulting solid was dissolved in chloroform solution and then poured into a polytetrafluoroethylene mold to evaporate the solvent at room temperature for 12 hours, resulting in a self-healing polyurethane elastomer SHPU-WNS that does not have a bicontinuous phase structure.

[0037] Figure 1 The image shows an atomic force microscopy phase diagram of SHPU-SNS-0.3 in Example 2. As can be seen from the image, the material has a phase with a bicontinuous network structure.

[0038] Figure 2 The infrared spectra of SHPU-SNS-0.1, SHPU-SNS-0.3, SHPU-SNS-0.5, and SHPU-WNS in Examples 1, 2, 3, and Comparative Example 1 are shown. Peak 1 is the carbonyl peak in the carbamate. SHPU-WNS does not have peak 1, while SHPU-SNS-0.1, SHPU-SNS-0.3, and SHPU-SNS-0.5 have peak 1.

[0039] Figure 3 The mechanical repair curves are those of SHPU-SNS-0.3 in Example 2 and SHPU-WNS in Comparative Example 1.

[0040] Figure 4 The images show the actual products of SHPU-SNS-0.3 in Example 2 and SHPU-WNS in Comparative Example 1 after they were broken.

[0041] Figure 5The tensile stress-strain curves for SHPU-SNS-0.1, SHPU-SNS-0.3, SHPU-SNS-0.5, and SHPU-WNS in Examples 1, 2, 3, and Comparative Example 1 are shown. The stress and strain of SHPU-SNS-0.1 are 0.95 MPa and 1135%, respectively; the stress and strain of SHPU-SNS-0.5 are 3.4 MPa and 1650%, respectively. Compared to SHPU-WNS (stress of 0.6 MPa and strain of 970%), the stress and strain of SHPU-SNS-0.3 are increased by 4.1 and 1.7 times, respectively, reaching 2.60 MPa and 1680%.

[0042] Figure 6 The fatigue threshold diagrams are for SHPU-SNS-0.3 (Example 2) and SHPU-WNS (Comparative Example 1). The fatigue thresholds of SHPU-SNS-0.3 and SHPU-WNS are 1010 J / m. -2 With 29J m -2 The fatigue threshold of SHPU-SNS-0.3 is 34.8 times higher than that of SHPU-WNS.

[0043] Figure 7 The image shows a comparison of the elasticity of SHPU-SNS-0.3 in Example 2 and SHPU-WNS in Comparative Example 1. Under 500% tensile strain, SHPU-SNS-0.3 can return to its original length within 5 minutes, while SHPU-WNS cannot.

[0044] Figure 8 The figures show the strain recovery curves of SHPU-SNS-0.3 in Example 2 and SHPU-WNS in Comparative Example 1 at 50°C. SHPU-SNS-0.3 can return to its original length within 2 minutes after being stretched to 50% at 50°C, but SHPU-WNS cannot return to its original length after being stretched to 50% at 50°C.

Claims

1. A self-healing polyurethane elastomer with a dual continuous phase structure, characterized in that, Its structural formula is as follows: ，n≥22。 2. The method for preparing a self-healing polyurethane elastomer with a dual continuous phase structure as described in claim 1, characterized in that, The specific steps are as follows: The molar ratio of amino-terminated polydimethylsiloxane, isophorone diisocyanate, and 5-(2-hydroxyethyl)-6-methyl-2-aminouracil was 1:1.1~1.5:0.1~0.

5. 5-(2-hydroxyethyl)-6-methyl-2-aminouracil powder, amino-terminated polydimethylsiloxane, isophorone diisocyanate, and dibutyltin dilaurate were dissolved in N,N-dimethylformamide. The mixture was refluxed at 70±10 °C under a nitrogen atmosphere with stirring. After the reaction was completed, the mixture was cooled to room temperature to obtain a self-healing polyurethane elastomer material.

3. The preparation method according to claim 2, characterized in that, 5-(2-hydroxyethyl)-6-methyl-2-aminouracil was prepared by the following steps: 2-acetylbutyrolactone, triethylamine and guanidine carbonate were refluxed in ethanol for 4-6 h. After the reaction, a yellow powder solid was obtained by suction filtration. The powder solid was further washed with ethanol and dried at 60 °C for 12-24 h to obtain a white 5-(2-hydroxyethyl)-6-methyl-2-aminouracil powder.

4. The preparation method according to claim 2, characterized in that, The number-average molecular weight of amino-terminated polydimethylsiloxane is 3000.

5. The preparation method according to claim 2, characterized in that, The molar ratio of amino-terminated polydimethylsiloxane, isophorone diisocyanate, and 5-(2-hydroxyethyl)-6-methyl-2-aminouracil is 1:1.3:0.

3.

6. The preparation method according to claim 2, characterized in that, The reflux reaction time is 12-18 hours.

7. The preparation method according to claim 2, characterized in that, In the reaction system, the concentration of amino-terminated polydimethylsiloxane is 30 wt%.

8. The preparation method according to claim 2, characterized in that, The mass of dibutyltin dilaurate is 1% of the mass of isophorone diisocyanate.

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