A polyurethane material, its preparation and use

Abstract

The application belongs to the technical field of polymers, and particularly relates to a polyurethane material and a preparation method and application thereof. The polyurethane material comprises the following components in parts by weight: polycaprolactone diol 10-50 parts, hexamethylene diisocyanate 1-10 parts, catalyst 0.05-0.3 parts, spiro-pyran diol 0.5-5 parts, and crosslinking agent 1-6 parts. The molecular formula of the spiro-pyran diol is shown in the description. The polyurethane material prepared by the application can realize two response functions under a single stimulus, and significantly expands the development potential and application field of the double-way shape memory material.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of polymers, and particularly relates to a polyurethane material and a preparation method and application thereof. BACKGROUND

[0002] Shape Memory Polymer (SMP) refers to an intelligent polymer material which has an initial shape, is transformed into a temporary shape and is fixed under a specific condition, and can be restored to the initial shape through external stimulation (such as heat, electricity, magnetism, light, etc.). According to the functionality, it can be divided into one-way and two-way shape memory effect, and both of them can realize two-stage, three-stage or multi-stage shape. One-way shape memory effect is irreversible, and if the material is to be deformed from the original shape to the temporary shape again, the sample needs to be trained again. On the contrary, two-way shape memory effect is reversible, and the sample can be reversibly converted between the original shape and the temporary shape without retraining, so it has a broad application prospect in the fields of biomedical, intelligent textiles, sensors and actuators, etc.

[0003] At present, almost all two-way shape memory polymers only have a single function of reversible deformation or color change, and the materials with two-way shape memory effect, such as liquid crystal elastomers, have the disadvantages of complex synthesis process, high cost and difficult to adjust the transition temperature, which seriously limit the mass production and practical application of shape memory polymer materials. Therefore, the development of multi-response (such as light, electric field, magnetic field, solution response, etc.) and multi-functional (such as combined with self-repairing) two-way shape memory materials will significantly improve the application field of two-way shape memory materials in real life. SUMMARY

[0004] The present application aims to provide a polyurethane material and a preparation method and application thereof. The polyurethane material prepared by the present application can realize two response functions under a single stimulus, which significantly expands the development potential and application field of two-way shape memory materials.

[0005] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: a polyurethane material, comprising the following components in parts by weight: polycaprolactone diol 10-50 parts, hexamethylene diisocyanate 1-10 parts, catalyst 0.05-0.3 parts, spiropyran diol 0.5-5 parts, crosslinking agent 1-6 parts.

[0006] The molecular formula of the spiropyran diol is as follows:

[0007]

[0008] Preferably, the relative molecular weight of the polycaprolactone diol is 2000-7500. When the relative molecular weight of the polycaprolactone diol is low, the crystallinity of the synthesized polyurethane material is insufficient, resulting in a decrease in the reversible shape memory effect of the trained polyurethane sample; when the relative molecular weight is high, the crosslinking density of the prepared polyurethane is too low, and the internal stress significantly decays during the conduction process, which also reduces the final reversible shape memory effect.

[0009] Preferably, the polyurethane material comprises at least one of the following (1)-(2):

[0010] (1) the crosslinking agent comprises at least one of trimethylolpropane tris(3-mercaptopropionate), glycerol, trimethylolpropane, pentaerythritol, hexamethylene diammonium, diethanolamine;

[0011] (2) the catalyst comprises dibutyltin dilaurate.

[0012] The application also claims a preparation method of the polyurethane material, comprising the following steps:

[0013] S1, preparation of spiropyran diol;

[0014] S2, preparation of polyurethane material:

[0015] S21, synthesis: dehydrating, dissolving the polycaprolactone diol to obtain a polycaprolactone diol solution, mixing hexamethylene diisocyanate and a catalyst, slowly adding the polycaprolactone diol solution, stirring uniformly, then adding the spiropyran diol, stirring, adding the crosslinking agent, and air drying to obtain a polyurethane film;

[0016] S22, training: heating the prepared polyurethane film, then elongating the polyurethane film to generate strain, cooling under constant strain, finally removing the external force, and heating and then cooling the polyurethane film to obtain the polyurethane material.

[0017] Hydrogen bond is a common physical interaction between functional groups. Single hydrogen bond can be regarded as a physical crosslinking point in the material. The application takes advantage of the fact that polyurethane contains a considerable number of hydrogen bonds, and uses the physical crosslinking network formed by hydrogen bonds to prepare a polyurethane material with double-way shape memory provided by the internal stress of the hydrogen bond network. When the temperature is raised to above the melting point of the sample and below the breaking temperature of the hydrogen bond, the internal orientation of the crystalline region of the polyurethane material melts, resulting in shrinkage of the sample; when the temperature drops to room temperature, the melted crystalline region re-forms orientation crystallization under the action of the internal stress provided by the hydrogen bond network, and the sample elongates. Through the above principle, the double-way shape memory effect is realized, and the prepared polyurethane material has obvious double-way shape memory effect.

[0018] The ordinary spiropyran structure in the prior art changes from colorless to colored state by molecular structure rearrangement under the stimulation of ultraviolet light, but then needs to be heated to change from colored to colorless state. The excitation conditions of the ordinary spiropyran structure for color change are quite different, and usually need to respond under multiple stimulation conditions, which cannot realize multiple responses under one stimulation, and is not conducive to actual use. By introducing the spiropyran diol structure into the polyurethane main chain with double-way shape memory effect, the spiropyran diol exists in the open ring state during the reaction, can interact with the polyurethane as a chain extender, not only effectively promotes the synthesis of the polyurethane material, but also due to the specific spiropyran structure of the spiropyran diol and the property that the response temperature of the spiropyran diol is approximately the same as the transition temperature of the polyurethane driving phase, so that the finally prepared polyurethane material can have reversible deformation and reversible color functions under a single thermal stimulation, and the mechanical properties are also improved.

[0019] Preferably, the preparation method of the polyurethane material at least includes one of the following (1)-(5):

[0020] (1) the dehydration conditions of the polycaprolactone diol in step S21 are drying at 100-120℃ for 10-12h;

[0021] (2) the solvent of the polycaprolactone diol solution in step S21 is tetrahydrofuran, and the mass ratio of the polycaprolactone diol to tetrahydrofuran is (10-30):(10-30);

[0022] (3) the mixing conditions of the hexamethylene diisocyanate and dibutyltin dilaurate in step S21 are mixing under nitrogen protection at 50-60℃;

[0023] (4) the temperature of the stirring in step S21 is 60-80℃;

[0024] (5) the time of the air drying in step S21 is 48-72h.

[0025] It should be noted that the polycaprolactone diol solution in step S21 needs to be added dropwise within 30min.

[0026] Preferably, the preparation method of the polyurethane material at least includes one of the following (1)-(4):

[0027] (1) the heating temperature of the polyurethane film in step S22 is 40-80℃, and the time is 5-20min;

[0028] (2) the strain range of the strain in step S22 is 500-1000%;

[0029] (3) The temperature reduction in step S22 is to reduce the temperature to 25-30°C;

[0030] (4) The temperature reduction in step S22 is to reduce the temperature to 25-30°C;

[0031] Preferably, the preparation of the spiropyran diol comprises the following steps:

[0032] S11, preparation of cyclized indole: mix 2-bromoethanol solution and indoline, add acetonitrile, stir the reaction under nitrogen protection, rotary evaporation, washing, vacuum drying, to obtain a purple red solid powder (hydroxyindole); weigh the hydroxyindole, KOH, add deionized water, stir, extract, take the filtrate, to obtain cyclized indole;

[0033] S12, preparation of hydroxylated salicylaldehyde: weigh 3-chloromethyl-5-nitrosalicylaldehyde and dissolve it, reflux and stir, dropwise add NaOH solution, react for 3-5 h, cool the solution to room temperature, rotary evaporation, recrystallize the product in water, filter, and dry to obtain hydroxylated salicylaldehyde;

[0034] S13, synthesis of spiropyran diol: mix cyclized indole and hydroxylated salicylaldehyde, add solvent, stir under nitrogen protection, reflux, react for 5-7 h, rotary evaporation, recrystallization, and dry to obtain spiropyran diol.

[0035] Preferably, the preparation method of the spiropyran diol at least comprises one of the following (1)-(8):

[0036] (1) The molar ratio of the 2-bromoethanol solution to the indoline in step S11 is 5:(3-4);

[0037] (2) The stirring reaction condition in step S11 is to stir the reaction under 70-80°C oil bath condition for 24-48 h;

[0038] (3) The washing condition in step S11 is to wash with n-hexane for 2-3 times;

[0039] (4) The vacuum drying temperature in step S11 is 30-60°C;

[0040] (5) The molar ratio of the hydroxyindole to KOH in step S11 is 5:(7-8);

[0041] (6) The amount of deionized water added in step S11 is 50-60 ml;

[0042] (7) The stirring condition in step S11 is to stir at room temperature for 20-30 min;

[0043] (8) The solvent used in the extraction in step S11 is methyl tert-butyl ether, and the number of times of extraction is 3-5.

[0044] Preferably, the preparation method of the spiropyran diol at least comprises one of the following (1)-(8):

[0045] (1) The solvent used for dissolving the 3-chloromethyl-5-nitrosalicylaldehyde in step S12 is acetone, and the ratio of the 3-chloromethyl-5-nitrosalicylaldehyde to the solvent is 10 mmol:40 mL;

[0046] (2) The reflux stirring condition in step S12 is reflux stirring at 80℃ for 30-60 min;

[0047] (3) The amount of the NaOH solution added in step S12 is 3-5 ml, and the concentration of the NaOH solution is 1-5 mol / L;

[0048] (4) The molar ratio of the cyclization indole to the hydroxylated salicylaldehyde in step S13 is 4.9:4.1;

[0049] (5) The solvent in step S13 is 30 mL of ethanol and 30 mL of water;

[0050] (6) The reflux stirring condition in step S13 is oil bath reflux stirring at 80℃;

[0051] (7) The recrystallization condition in step S13 is recrystallization in a solution of acetonitrile:water=7:3;

[0052] (8) The drying temperature in step S12 is 40-60℃, and the drying temperature in step S13 is 40-80℃.

[0053] The application also claims the use of the polyurethane material in preparing indicators, drivers, soft robots, intelligent substrates and the like.

[0054] Compared with the prior art, the application has the following beneficial effects:

[0055] The polyurethane material prepared by the application has reversible deformation and color change effects and multiple responsiveness, which can effectively overcome the defect that the traditional double-path shape memory polymer can only make a single response to external stimulation, significantly expanding the development potential and application field of the double-path shape memory material. Meanwhile, the preparation process of the application is simple, the cost is low, and it is conducive to large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0056] Figure 1 The effect schematic diagram of the polyurethane prepared by the embodiment of the application. DETAILED DESCRIPTION

[0057] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0058] In the examples and comparative examples, the experimental methods used are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0059] The spiropyran diols selected in the examples and comparative examples are prepared by the following method.

[0060] Preparation of spiropyran diols:

[0061] (1) Preparation of hydroxyindole: 20 mmol of 2-bromoethanol solution and 16 mmol of indoline were weighed into a three-necked flask, acetonitrile was added, nitrogen was passed, a reflux device was installed, and stirring was performed under an 80°C oil bath for 24 h. Acetonitrile was removed by rotary evaporation, washed with n-hexane for 3 times, and dried in a vacuum oven to obtain 3.01 g of purple red solid powder with a yield of 70.7%;

[0062] (2) Preparation of cyclized indole: 10 mmol of hydroxyindole and 16 mmol of KOH were weighed into a 100 mL beaker, 50 mL of deionized water was added after stirring at room temperature for 20 min to mix thoroughly, the solution was extracted with methyl tert-butyl ether three times, the filtrate was taken, and the methyl tert-butyl ether was removed to obtain 1.67 g of yellow oil with a yield of 80.1%;

[0063] (3) Preparation of hydroxylated salicylaldehyde: 3-chloromethyl-5-nitrosalicylaldehyde 10 mmol was dissolved in 40 mL of acetone, and stirring was performed under reflux at 80°C for 30 min. 3 mL of NaOH was added dropwise into the flask, and the solution was allowed to react for 3 h. After the solution was cooled to room temperature, the solvent was removed by rotary evaporation. The product was recrystallized in water, filtered and dried to obtain 1.42 g of light yellow powder with a yield of 79.5%;

[0064] (4) Synthesis of dihydroxylated spiropyran: 4.9 mmol of cyclized indole and 4.1 mmol of hydroxylated salicylaldehyde were weighed into a 250 mL three-necked flask, 30 mL of ethanol and 30 mL of water were added, a reflux device was installed, nitrogen was protected, and stirring was performed under an 80°C oil bath reflux for 5 h. After the reaction, the solvent was removed by a rotary evaporator, recrystallized in acetonitrile: water = 7:3, and dried to obtain 1.3 g of purple crystals with a yield of 69.6%.

[0065] Example 1, preparation of polyurethane material

[0066] Formulation components: polycaprolactone diol 30 parts, hexamethylene diisocyanate 5 parts, dibutyltin dilaurate 0.1 part, spiropyran diol 3 parts, trimethylolpropane tris(3-mercaptopropionate) 3 parts.

[0067] Preparation method: (1) synthesis: first, polycaprolactone diol (PCL3000) with a molecular weight of 3000 was placed in a vacuum oven at 100°C for 12h, and then dissolved in tetrahydrofuran. Hexamethylene diisocyanate (HDI) and dibutyltin dilaurate (DBTDL) were placed in a three-necked flask under nitrogen protection at 60°C. The obtained PCL3000 tetrahydrofuran solution was placed in a constant pressure funnel, and the HDI in the three-necked flask was slowly added dropwise and mixed uniformly with the HDI under magnetic stirring. The PCL3000 tetrahydrofuran solution was added dropwise within 30min. The reaction generated a polycaprolactone with isocyanate groups at both ends, which was polyurethane prepolymer 1 (PU prepolymer 1). Then, spiropyran diol (SP(OH)2) was added to PU prepolymer 1 for chain extension to obtain polyurethane prepolymer 2 (PU prepolymer 2). Trimethylolpropane tris(3-mercaptopropionate) was added to polyurethane prepolymer 2 for crosslinking under the conditions of 60°C and magnetic stirring. The obtained solution was stirred uniformly and then injected into a polytetrafluoroethylene mold. After air drying at room temperature for 48h, a polyurethane film was prepared.

[0068] (2) training: the obtained polyurethane film was cut into a dumbbell-shaped sample with a cutter of 50mm*4mm. The obtained dumbbell-shaped sample was placed in a 60°C oven for 10min, then stretched to a strain of 1000%, and then cooled to room temperature under constant strain. Finally, the external force was removed, the sample was heated to 55°C and kept for 5min, and then cooled to room temperature to prepare a polyurethane material with double-way shape memory effect.

[0069] Example 2, preparation of polyurethane material

[0070] Formulation components: polycaprolactone diol 30 parts, hexamethylene diisocyanate 5 parts, dibutyltin dilaurate 0.1 part, spiropyran diol 3 parts, trimethylolpropane tris(3-mercaptopropionate) 3 parts.

[0071] Preparation method: (1) Synthesis: first, polycaprolactone diol (PCL3000) with a molecular weight of 3000 was placed in a vacuum oven at 100°C for 12h, and then dissolved in tetrahydrofuran. Hexamethylene diisocyanate (HDI) and dibutyltin dilaurate (DBTDL) were placed in a three-necked flask under nitrogen protection at 60°C. The obtained tetrahydrofuran solution of PCL3000 was placed in a constant pressure funnel, and the HDI in the three-necked flask was slowly added dropwise and mixed uniformly with the HDI under magnetic stirring. The tetrahydrofuran solution of PCL3000 was added dropwise within 30min. The reaction generated a polyurethane prepolymer 1 (PU prepolymer 1) with isocyanate groups at both ends. Then SP(OH)2 was added to PU prepolymer 1 for chain extension to obtain a polyurethane prepolymer 2 (PU prepolymer 2). Glycerol was added to the polyurethane prepolymer 2 (PU prepolymer 2) for crosslinking under the conditions of 60°C and magnetic stirring. The obtained solution was stirred uniformly and then poured into a polytetrafluoroethylene mold. After air drying at room temperature for 48h, a polyurethane film was prepared.

[0072] (2) Training: the obtained polyurethane film was cut into a dumbbell-shaped sample with a size of 50mm*4mm using a cutter. The obtained dumbbell-shaped sample was placed in a 60°C oven for 10min, and then the sample was elongated to a strain of 500%. The sample was then cooled to room temperature under constant strain. Finally, the external force was removed, the sample was heated to 55°C and kept constant for 5min, and then cooled to room temperature to prepare a polyurethane with a double-way shape memory effect.

[0073] Example 3, preparation of a polyurethane material

[0074] Formulation components: polycaprolactone diol 50 parts, hexamethylene diisocyanate 10 parts, dibutyltin dilaurate 0.3 parts, spiropyran diol 5 parts, diethanolamine 6 parts.

[0075] Preparation method: (1) Synthesis: first, the polycaprolactone diol with a molecular weight of 2000 (PCL2000) was placed in a vacuum oven at 100°C for 12h, and then dissolved in tetrahydrofuran. Hexamethylene diisocyanate (HDI) and dibutyltin dilaurate (DBTDL) were placed in a three-necked flask under nitrogen protection at 60°C. The tetrahydrofuran solution of PCL2000 was placed in a constant pressure funnel, and the HDI in the three-necked flask was slowly added dropwise and mixed uniformly with the HDI under magnetic stirring. The tetrahydrofuran solution of PCL2000 was added dropwise within 30min. The reaction generated a polyurethane prepolymer 1 (PU prepolymer 1) with isocyanate groups at both ends. Then, spiropyran diol (SP(OH)2) was added to PU prepolymer 1 for chain extension to obtain a polyurethane prepolymer 2 (PU prepolymer 2). Diethanolamine was added to the polyurethane prepolymer 2 for crosslinking under the conditions of 60°C and magnetic stirring. The obtained solution was stirred uniformly and then poured into a polytetrafluoroethylene mold. After being air-dried at room temperature for 48h, a polyurethane film was prepared.

[0076] (2) Training: the obtained polyurethane film was cut into a dumbbell-shaped sample with a size of 50mm*4mm using a cutter. The obtained dumbbell-shaped sample was placed in a 60°C oven for 10min, and then the sample was stretched to a strain of 1000%. After that, the sample was cooled to room temperature under constant strain. Finally, the external force was removed, and the sample was heated to 55°C and kept constant for 5min, and then cooled to room temperature to prepare a polyurethane material with a double-way shape memory effect.

[0077] Example 4, preparation of a polyurethane material

[0078] Formulation components: polycaprolactone diol 30 parts, hexamethylene diisocyanate 5 parts, dibutyltin dilaurate 0.1 parts, spiropyran diol 3 parts, trimethylolpropane tris(3-mercaptopropionate) 3 parts.

[0079] Preparation method: (1) Synthesis: first, the polycaprolactone diol (PCL7500) with a molecular weight of 7500 was placed in a vacuum oven at 100°C for 12h, and then dissolved in tetrahydrofuran. Hexamethylene diisocyanate (HDI) and dibutyltin dilaurate (DBTDL) were placed in a three-necked flask under nitrogen protection at 60°C. The obtained tetrahydrofuran solution of PCL7500 was placed in a constant pressure funnel, and the HDI in the three-necked flask was slowly added dropwise and mixed uniformly with the HDI under magnetic stirring. The tetrahydrofuran solution of PCL7500 was added dropwise within 30min. The reaction generated a polyurethane prepolymer 1 with isocyanate groups at both ends, which was polyurethane prepolymer 1. Then, spiropyran diol (SP(OH)2) was added to PU prepolymer 1 for chain extension to obtain polyurethane prepolymer 2. Trimethylolpropane tris(3-mercaptopropionate) was added to the polyurethane prepolymer 2 for crosslinking under the conditions of 60°C and magnetic stirring. The obtained solution was stirred uniformly and then injected into a polytetrafluoroethylene mold. After air drying at room temperature for 48h, a polyurethane film was prepared.

[0080] (2) Training: the obtained polyurethane film was cut into a dumbbell-shaped sample with a size of 50mm*4mm using a cutter. The obtained dumbbell-shaped sample was placed in a 60°C oven for 10min, and then the sample was elongated to have a strain of 1000%. Then, the sample was cooled to room temperature under constant strain. Finally, the external force was removed, the sample was heated to 55°C and kept constant for 5min, and then cooled to room temperature to prepare a polyurethane material with a double-way shape memory effect.

[0081] Comparative Example 1

[0082] Compared with Example 1, the only difference of the present comparative example is that an equal amount of 1,4-butanediol is used instead of spiropyran diol.

[0083] The preparation method is referred to Example 1.

[0084] Comparative Example 2

[0085] Compared with Example 1, the only difference of the present comparative example is that a polycaprolactone diol with a relative molecular weight of 1000 is used.

[0086] The preparation method is referred to Example 1.

[0087] Comparative Example 3

[0088] Preparation method:

[0089] (1) Synthesis: same as Example 1;

[0090] (2) Training: the obtained polyurethane film was cut into dumbbell-shaped samples with a cutter. The obtained dumbbell-shaped samples were heated in an oven at 60°C for 10 min, then the samples were elongated to have a strain of 1200%, then the samples were cooled to room temperature under constant strain. Finally, the external force was removed, the samples were heated to 55°C and kept for 5 min, then cooled to room temperature, thereby obtaining a polyurethane material having a double-way shape memory effect.

[0091] Compared with Example 1, the only difference of the present comparative example is that the training process is that the sample is elongated to have a strain of 1200%.

[0092] The preparation method is referred to Example 1.

[0093] Comparative Example 4

[0094] Compared with Example 1, the only difference of the present comparative example is that the training step is absent.

[0095] The preparation method is referred to Example 1.

[0096] Comparative Example 5

[0097] Compared with Example 1, the only difference of the present comparative example is that an equal amount of a single-double bond spiropyran is used to replace the spiropyran diol.

[0098] The preparation method is referred to Example 1.

[0099] Test Example 1

[0100] The polyurethane materials prepared in the examples and comparative examples were subjected to excitation operation, and the reversible strain capacity of the corresponding samples was determined. The specific operation of excitation is as follows:

[0101] Excitation: the trained sample was heated from 0°C to 55°C and kept for 5 min, and the deformation and color change of the sample were observed. Then the sample was continuously cooled from 55°C to 0°C and kept for 5 min, and the deformation and color change of the sample were observed. The reversible shape memory effect of the sample was tested by using a dynamic mechanical analyzer Q800 (TA Instruments, USA), seven cycles were tested, and the corresponding data were recorded. The reversible strain capacity data of the sample were directly obtained by the dynamic mechanical analyzer.

[0102] The experimental data are shown in Table 1.

[0103] Table 1

[0104] Deformation and color change of the samples Reversible strain capacity of the samples (%) Example 1 Ability to reversibly deform and change color 11.99 Example 2 Ability to reversibly deform and change color 8.42 Example 3 Ability to reversibly deform and change color 6.41 Example 4 Ability to reversibly deform and change color 11.02 Comparative Example 1 No ability to reversibly change color 10.14 Comparative Example 2 Ability to reversibly deform and change color 4.25 Comparative Example 3 Ability to reversibly deform and change color 9.32 Comparative Example 4 Ability to reversibly change color only /

[0105] From the data in Table 1, it can be seen that the polyurethane material prepared in the examples of the present application can simultaneously realize the effects of reversible deformation and color change, and has good reversible strain capacity.

[0106] The polyurethane material prepared in Comparative Example 1 cannot realize the reversible color change function because 1,4-butanediol is used instead of spiropyran diol; the relative molecular weight of the polycaprolactone diol used in Comparative Example 2 is too small, so that the crystallinity of the synthesized polyurethane material is insufficient, thereby resulting in the decrease of the reversible shape memory effect of the trained polyurethane sample; in Comparative Example 3, the strain value of the sample during the training process is not appropriate, resulting in the decrease of the reversible strain capacity of the prepared polyurethane material; the polyurethane film prepared in Comparative Example 4 is not subjected to the training operation, so that the polyurethane material does not have the reversible deformation effect; in Comparative Example 5, a single-double bond spiropyran is used instead of the spiropyran diol component, because it does not have the structure of the diol used as a chain extender in the polyurethane, so that the synthesized polyurethane is prone to breakage due to the too short rigid chain, and cannot be subjected to the subsequent training and testing process.

[0107] The above examples only illustrate the principles and effects of the present application, and are not used to limit the present application. Any person skilled in the art can modify or change the above examples without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes completed by those skilled in the art without departing from the spirit and technical thought disclosed by the present application should be covered by the claims of the present application.

Claims

1. A polyurethane material, characterized in that, The polyurethane material is prepared by the following steps: The polyurethane material is prepared by the following steps: ； The polyurethane material is prepared by the following steps: The polyurethane material is prepared by the following steps: S1, preparation of the spiropyran diol; S2, preparation of the polyurethane material: S21, synthesis: the polycaprolactone diol is dehydrated and dissolved to obtain a polycaprolactone diol solution, the hexamethylene diisocyanate and the catalyst are mixed, the polycaprolactone diol solution is slowly added dropwise, stirred uniformly, then the spiropyran diol is added, stirred, the crosslinking agent is added, air dried, and a polyurethane film is prepared; S22, training: the prepared polyurethane film is heated, then the polyurethane film is elongated, strained, cooled under constant strain, and finally the external force is removed, the polyurethane film is first heated and then cooled, and the polyurethane material is prepared.

2. The polyurethane material of claim 1, wherein, At least one of the following (1)~(2) is included: (1) the crosslinking agent includes at least one of trimethylolpropane tris(3-mercaptopropionate), glycerol, trimethylolpropane, pentaerythritol, hexamethylene diamine, and diethanolamine; (2) the catalyst includes dibutyltin dilaurate.

3. The polyurethane material of claim 1, wherein, The preparation of the spiropyran diol includes the following steps: S11, preparation of the cyclized indole: 2-bromoethanol solution and indoline are mixed, acetonitrile is added, stirred under nitrogen protection, rotary evaporation, washed, vacuum dried, and hydroxyindole is obtained; hydroxyindole and KOH are weighed, deionized water is added, stirred, extracted, and the filtrate is obtained to obtain the cyclized indole; S12, preparation of the hydroxylated salicylaldehyde: 3-chloromethyl-5-nitrosalicylaldehyde is weighed and dissolved, refluxed and stirred, NaOH solution is added dropwise, reacted for 3~5h, the solution is cooled to room temperature, rotary evaporation, the product is recrystallized in water, filtered, and dried to obtain the hydroxylated salicylaldehyde; S13, synthesis of the spiropyran diol: the cyclized indole and the hydroxylated salicylaldehyde are mixed, a solvent is added, stirred under nitrogen protection, refluxed, reacted for 5~7h, rotary evaporation, recrystallized, and dried to obtain the spiropyran diol.

4. The polyurethane material of claim 3, wherein, At least one of the following (1)~(8) is included: (1) the molar ratio of the 2-bromoethanol solution to the indoline in step S11 is 5:(3~4); (2) the stirring reaction in step S11 is carried out at 70~80℃ under oil bath conditions for 24~48h; (3) the washing in step S11 is carried out with n-hexane for 2~3 times; (4) the vacuum drying in step S11 is carried out at 30~60℃; (5) the molar ratio of the hydroxyindole to KOH in step S11 is 5:(7~8); (6) the amount of the deionized water added in step S11 is 50~60ml; (7) the stirring in step S11 is carried out at room temperature for 20~30min; (8) the solvent for the extraction in step S11 is methyl tert-butyl ether, and the extraction is carried out for 3~5 times.

5. The polyurethane material of claim 3, wherein, At least one of the following (1)~(8) is included: (1) The solvent for dissolving the 3-chloromethyl-5-nitrosalicylaldehyde in step S12 is acetone, and the ratio of the 3-chloromethyl-5-nitrosalicylaldehyde to the solvent is 10 mmol:40 mL; (2) The reflux stirring condition in step S12 is reflux stirring at 80℃ for 30~60 min; (3) The amount of the NaOH solution added in step S12 is 3~5 ml, and the concentration of the NaOH solution is 1~5 mol / L; (4) The molar ratio of the cyclization indole to the hydroxylated salicylaldehyde in step S13 is 4.9:4.1; (5) The solvent in step S13 is 30 mL of ethanol and 30 mL of water; (6) The reflux stirring condition in step S13 is oil bath reflux stirring at 80℃; (7) The recrystallization condition in step S13 is recrystallization in a solution of acetonitrile:water=7:3; (8) The drying temperature in step S12 is 40~60℃, and the drying temperature in step S13 is 40~80℃.

6. The polyurethane material of claim 1, wherein, At least one of the following (1)~(5) is included: (1) The dehydrating condition of the polycaprolactone diol in step S21 is drying at 100~120℃ for 10~12 h; (2) The solvent of the polycaprolactone diol solution in step S21 is tetrahydrofuran, and the mass ratio of the polycaprolactone diol to tetrahydrofuran is (10~30):(10~30); (3) The mixing condition of the hexamethylene diisocyanate and dibutyltin dilaurate in step S21 is mixing under nitrogen protection at 50~60℃; (4) The stirring temperature in step S21 is 60~80℃; (5) The air-drying time in step S21 is 48~72 h.

7. The polyurethane material of claim 1, wherein, At least one of the following (1)~(4) is included: (1) The heating temperature of the polyurethane film in step S22 is 40~80℃, and the time is 5~20 min; (2) The strain range of the strain in step S22 is 500~1000%; (3) The cooling in step S22 is to reduce the temperature to 25~30℃; (4) The condition of first heating and then cooling in step S22 is to heat the polyurethane film to 55℃ for 5 min, and then to reduce to room temperature.

8. Use of the polyurethane material according to any one of claims 1~2 in the preparation of indicators, actuators, soft robots and intelligent substrates.

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