Branched polyamide and preparation method therefor

Abstract

The present invention relates to the technical field of functional polymer materials and stimuli-responsive smart polymer materials, and particularly relates to a branched polyamide and a preparation method therefor. The main chain of the branched polyamide has a pyrrolidone ring and is of a dendritic hyperbranched structure; and the lowest critical solution temperature of an aqueous solution thereof varies with concentration, and the range of changes in the lowest critical solution temperature is 16-37°C. In the preparation method of the present invention, itaconic acid and a diamine are used for preparing linear polyamide having a pyrrolidone ring on the main chain by means of a salt monomer method, and then a hyperbranched structure is formed by means of thermal shock. The preparation method is simple and convenient, easy in terms of post-treatment, and environmentally friendly. The prepared temperature-sensitive color-changing hyperbranched polyamide can provide different temperature response solutions to adapt to complex application scenarios.

Description

Branched polyamide and its preparation method Technical Field

[0001] This invention relates to the field of functional polymer materials and smart responsive polymer materials, and in particular to a branched polyamide and its preparation method. Background Technology

[0002] Thermochromic materials are functional materials in which the visible absorption spectrum changes in response to changes in ambient temperature. Over the past 80 years, the types and properties of these materials have greatly improved, leading to their widespread application in various fields such as industry, textiles, military, printing, and anti-counterfeiting.

[0003] Temperature-responsive polymers currently mainly include bio-derived hydroxypropyl cellulose and petroleum-based poly(N-isopropylacrylamide). Hydroxypropyl cellulose has an excessively high minimum critical cosolubility temperature, resulting in poor solubility when adjusted in salt solutions. Furthermore, the molecular weight of hydroxypropyl cellulose is difficult to control, which is another reason for its poor solubility. Poly(N-isopropylacrylamide), on the other hand, exhibits a minimum critical temperature closest to human comfort, but it suffers from poor biocompatibility and high cost.

[0004] Therefore, there is an urgent need for a new type of thermosensitive color-changing temperature-responsive material with an easily adjustable minimum critical co-solution temperature to expand its application scenarios. Summary of the Invention

[0005] To address the shortcomings of existing temperature-responsive polymer materials, such as poor solubility, poor biocompatibility, and high cost, this invention provides a novel thermosensitive color-changing temperature-responsive material with an easily adjustable minimum critical co-solution temperature.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] The first objective of this invention is to provide a branched polyamide having a pyrrolidone ring on its main chain and having a dendritic hyperbranched structure (hereinafter referred to as hyperbranched polyamide).

[0008] Furthermore, the hyperbranched polyamide has the structural units shown in the figure below:

[0009] Where x takes the value of an integer from 2 to 20, and m, n, and p take the value of an integer from 10 to 1660.

[0010] Furthermore, the hyperbranched polyamide has a molecular weight of 6,000 to 1,000,000;

[0011] In some embodiments of the present invention, the hyperbranched polyamide has a branching degree of 0.67% to 10%.

[0012] Furthermore, the minimum critical co-solution temperature of the hyperbranched polyamide aqueous solution varies with concentration;

[0013] Furthermore, the minimum critical eutectic temperature varies in the range of 16-37℃.

[0014] In some embodiments of the present invention, the hyperbranched polyamide is a rope-type hyperbranched polyamide; having the structure shown in the figure below:

[0015] Where x takes the value of an integer from 2 to 20, and m and n take the value of an integer from 10 to 1660.

[0016] In one embodiment of the present invention, the hyperbranched polyamide prepared by the salt monomer method and the thermal shock method has a pyrrolidone ring on the main chain and forms a dendritic branched chain.

[0017] In some embodiments of the present invention, the thermochromic hyperbranched polyamide has a molecular weight of 6,000 to 1,000,000 and a branching degree of 0.67% to 10%.

[0018] In some embodiments, hyperbranched polyamides are prepared into aqueous solutions of hyperbranched polyamides in different mass fraction ratios. The resulting aqueous solutions of hyperbranched polyamides, with concentrations ranging from 0.5% to 2.0% by mass, exhibit a minimum critical cosolubility temperature that gradually decreases from 35°C to 17°C as the concentration changes.

[0019] In some embodiments of the present invention, the hyperbranched polyamide aqueous solution undergoes a reversible change in visible transmittance before and after the minimum co-solution temperature, with transmittance ranging from 97% to 5%.

[0020] In some embodiments of the present invention, when the concentration of the hyperbranched polyamide aqueous solution is increased from 0.5% to 2.0% by mass, the minimum critical cosolubility temperature decreases from 36°C to 18°C.

[0021] In some embodiments of the present invention, when the concentration of the hyperbranched polyamide aqueous solution is increased from 0.5% to 2.0% by mass, the minimum critical cosolubility temperature decreases from 34°C to 17°C.

[0022] In some embodiments of the present invention, when the concentration of the hyperbranched polyamide aqueous solution is increased from 0.5% to 2.0% by mass, the minimum critical cosolubility temperature decreases from 32°C to 16°C.

[0023] In some embodiments of the present invention, when the concentration of the hyperbranched polyamide aqueous solution is increased from 0.5% to 2.0% by mass, the minimum critical cosolubility temperature decreases from 33°C to 18°C.

[0024] In some embodiments of the present invention, when the concentration of the hyperbranched polyamide aqueous solution is increased from 0.5% to 2.0% by mass, the minimum critical cosolubility temperature decreases from 37°C to 19°C.

[0025] In some embodiments of the present invention, when the concentration of the hyperbranched polyamide aqueous solution is increased from 0.5% to 2.0% by mass, the minimum critical cosolubility temperature decreases from 29°C to 17°C.

[0026] The second objective of this invention is to provide a method for preparing the thermosensitive color-changing hyperbranched polyamide, comprising steps S1, S2, and S3:

[0027] S1. Itaconic acid and diamine are dissolved in solvents respectively. After mixing them evenly, they are allowed to stand and precipitate to obtain a white salt monomer. After separation and drying, itaconic acid diamine salt monomer is obtained.

[0028] S2. Place the salt monomer obtained in step S1 into a reaction vessel and heat it under an inert atmosphere to obtain linear polyamide;

[0029] S3. The linear polyamide obtained in step S2 is subjected to a thermal shock hyperbranching reaction under an inert atmosphere to obtain a hyperbranched polyamide. By subjecting the linear polyamide to thermal shock, the two terminal amino groups undergo deamination to form secondary amines, while the rear carboxyl group reacts with the secondary amine to form a hyperbranched structure.

[0030] Further, in step S1, the diamine is one or a combination of straight-chain or branched diamines of C2-C20.

[0031] Furthermore, the branched diamine is a diamine whose main chain carbon contains 1-2 branched groups; the branched groups are methyl, ethyl, propyl or isopropyl.

[0032] In some embodiments, the branched diamine is one or a combination of (NH2(CH2)3CHXNH2), (NH2(CH2)2CHXCH2NH2) (X = CH3, CH2CH3);

[0033] In some embodiments, the heating conditions in step S2 are 170-190°C; the reaction time is 4-20 h.

[0034] In some embodiments, in step S3, the thermal shock reaction temperature is 210–250°C; the reaction time is 1–10 h.

[0035] In some embodiments, the inert atmosphere is provided by nitrogen or argon;

[0036] In step S1, the solvent includes, but is not limited to, ethanol, water, methanol, etc.

[0037] In some preferred embodiments, the method for preparing hyperbranched polyamide includes the following steps:

[0038] (1) Itaconic acid and 1,5-diaminopentane were dissolved in anhydrous ethanol, and after mixing them evenly, they were allowed to stand to precipitate and obtain a white salt monomer. After filtration and drying, powdered itaconic acid 1,5-diaminopentane salt monomer was obtained.

[0039] (2) Place the dried salt monomer in a three-necked flask, heat it to 170-190℃ under nitrogen, stir for 4-20h to carry out condensation polymerization, and obtain linear polyamide.

[0040] (3) After linear polyamide is formed, thermal shock hyperbranching reaction is carried out under nitrogen atmosphere. The reaction is heated to 210-250℃ and the reaction is carried out for 1-10 hours to obtain hyperbranched polyamide.

[0041] A third objective of this invention is to provide applications of the thermochromic hyperbranched polyamide in the field of smart response materials, such as smart response windows and thermochromic glass.

[0042] This invention can adapt to complex application scenarios by controlling the concentration of hyperbranched polyamide and regulating the minimum critical co-solution temperature of the hyperbranched polyamide aqueous solution.

[0043] The beneficial effects of this invention are:

[0044] This invention prepares a novel thermochromic temperature-responsive material with a minimum critical co-solution temperature adjustable by concentration. The thermochromic hyperbranched polyamide has a molecular weight of 6,000 to 1,000,000 and a branching degree of 0.67% to 10%.

[0045] The hyperbranched polyamide of this invention can control the lowest critical co-solution temperature of the hyperbranched polyamide aqueous solution by controlling its concentration. Furthermore, the lowest critical co-solution temperature and its range can also be adjusted by using different diamines; the lowest critical co-solution temperature range is 37℃-16℃.

[0046] The preparation method of the present invention utilizes itaconic acid and diamine to first prepare linear polyamides with pyrrolidone rings on the main chain via a salt monomer method, and then thermally shocks them to form hyperbranched structures; the preparation method is simple, the post-processing is easy, and it is environmentally friendly.

[0047] The thermosensitive color-changing hyperbranched polyamide prepared by this invention can provide different response temperature schemes to adapt to complex application scenarios. Attached Figure Description

[0048] The accompanying drawings are provided to further illustrate the present application and form part of the specification. They are used together with the embodiments of the present application to explain the present application, but do not constitute a limitation thereof; in the drawings:

[0049] Figure 1 is a structural diagram of the branched polyamide prepared in this invention;

[0050] Figure 2 is a schematic diagram of the steps for preparing the thermosensitive color-changing hyperbranched polyamide in Example 1 of the present invention.

[0051] Figure 3 shows the 13-carbon nuclear magnetic resonance spectra of the linear polyamide of Comparative Example 1 and the hyperbranched polyamide prepared in Example 1.

[0052] Figure 4 shows the 13-carbon nuclear magnetic resonance spectrum of the rope-type polyamide in Example 5;

[0053] Figure 5 shows images of the 0.50% hyperbranched polyamide solution prepared in Example 1 at 25°C and 35°C;

[0054] Figure 6 shows the transmittance of the linear polyamide of Comparative Example 1 and the hyperbranched polyamide prepared in Example 1 with a mass fraction of 0.50% under visible light at a wavelength of 550 nm at different temperatures.

[0055] Figure 7 shows the transmittance of the linear polyamide of Comparative Example 3 and the hyperbranched polyamide prepared in Example 7 with a mass fraction of 0.50% under visible light at a wavelength of 550 nm at different temperatures;

[0056] Figure 8 shows images of smart windows prepared with hyperbranched polyamide solutions of comparative examples 1-0.5% at 25℃ and 35℃;

[0057] Figure 9 shows the indoor temperature curves of the smart windows prepared in the comparative example and the comparative example with hyperbranched polyamide solution (1-0.5%) under summer conditions. Detailed Implementation

[0058] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Unless otherwise specified, the experimental methods in the following embodiments are conventional methods in the art. However, those skilled in the art will readily understand that the specific material ratios, process conditions and results described in the embodiments are only for illustrating the present invention, and should not and will not limit the present invention as described in detail in the claims.

[0059] Example 1

[0060] Preparation of hyperbranched polyamide: 6.505 g (50 mmol) itaconic acid, 5.089 g (50 mmol) 1,5-diaminopentane, 50 mL anhydrous ethanol, the method includes the following steps:

[0061] (1) Dissolve 6.505g itaconic acid and 5.089g 1,5-diaminopentane in 25mL of anhydrous ethanol. After mixing them evenly, let them stand to precipitate and obtain white salt monomers. After filtration and drying, powdered itaconic acid and 1,5-pentanediamine salt monomers are obtained.

[0062] (2) The dried salt monomer was placed in a three-necked flask and stirred and condensed under nitrogen at 180°C for 6 hours to obtain linear polyamide.

[0063] (3) Linear polyamide was subjected to thermal shock hyperbranching reaction at 210°C for 5 h under nitrogen atmosphere to obtain hyperbranched polyamide;

[0064] (4) The prepared hyperbranched polyamide was prepared into hyperbranched polyamide solutions of 0.5%, 0.75%, 1.0%, 1.5% and 2.0% by mass fraction.

[0065] Example 2

[0066] Preparation of hyperbranched polyamide: 6.505 g (50 mmol) itaconic acid, 5.089 g (50 mmol) 1,5-diaminopentane, 50 mL anhydrous ethanol, the method includes the following steps:

[0067] (1) Dissolve 6.505g itaconic acid and 5.089g 1,5-diaminopentane in 25mL of anhydrous ethanol. After mixing them evenly, let them stand to precipitate and obtain white salt monomers. After filtration and drying, powdered itaconic acid and 1,5-pentanediamine salt monomers are obtained.

[0068] (2) The dried salt monomer was placed in a three-necked flask and stirred and condensed under nitrogen at 180°C for 6 hours to obtain linear polyamide.

[0069] (3) Linear polyamide was subjected to thermal shock hyperbranching reaction at 220°C for 4 hours under nitrogen atmosphere to obtain hyperbranched polyamide;

[0070] (4) The prepared hyperbranched polyamide was prepared into hyperbranched polyamide solutions of 0.5%, 0.75%, 1.0%, 1.5% and 2.0% by mass fraction.

[0071] Example 3

[0072] Preparation of hyperbranched polyamide: 6.505 g (50 mmol) itaconic acid, 5.089 g (50 mmol) 1,5-diaminopentane, 50 mL anhydrous ethanol, the method includes the following steps:

[0073] (1) Dissolve 6.505g itaconic acid and 5.089g 1,5-diaminopentane in 25mL of anhydrous ethanol. After mixing them evenly, let them stand to precipitate and obtain white salt monomers. After filtration and drying, powdered itaconic acid and 1,5-pentanediamine salt monomers are obtained.

[0074] (2) The dried salt monomer was placed in a three-necked flask and stirred and condensed under nitrogen at 180°C for 6 hours to obtain linear polyamide.

[0075] (3) Linear polyamide was subjected to thermal shock hyperbranching reaction at 230°C for 3 hours under nitrogen atmosphere to obtain hyperbranched polyamide;

[0076] (4) The prepared hyperbranched polyamide was prepared into hyperbranched polyamide solutions of 0.5%, 0.75%, 1.0%, 1.5% and 2.0% by mass fraction.

[0077] Example 4

[0078] Preparation of hyperbranched polyamide: 6.505 g (50 mmol) itaconic acid, 5.089 g (50 mmol) 1,5-diaminopentane, 50 mL anhydrous ethanol, the method includes the following steps:

[0079] (1) Dissolve 6.505g itaconic acid and 5.089g 1,5-diaminopentane in 25mL of anhydrous ethanol. After mixing them evenly, let them stand to precipitate and obtain white salt monomers. After filtration and drying, powdered itaconic acid and 1,5-pentanediamine salt monomers are obtained.

[0080] (2) The dried salt monomer was placed in a three-necked flask and stirred and condensed under nitrogen at 180°C for 6 hours to obtain linear polyamide.

[0081] (3) Linear polyamide was subjected to thermal shock hyperbranching reaction at 240°C for 2 hours under nitrogen atmosphere to obtain hyperbranched polyamide;

[0082] (4) The prepared hyperbranched polyamide was prepared into hyperbranched polyamide solutions of 0.5%, 0.75%, 1.0%, 1.5% and 2.0% by mass fraction.

[0083] Example 5

[0084] Preparation of hyperbranched polyamide: 6.505 g (50 mmol) itaconic acid, 5.089 g (50 mmol) 1,5-diaminopentane, 50 mL anhydrous ethanol, the method includes the following steps:

[0085] (1) Dissolve 6.505g itaconic acid and 5.089g 1,5-diaminopentane in 25mL of anhydrous ethanol. After mixing them evenly, let them stand to precipitate and obtain white salt monomers. After filtration and drying, powdered itaconic acid and 1,5-pentanediamine salt monomers are obtained.

[0086] (2) The dried salt monomer was placed in a three-necked flask and stirred and condensed under nitrogen at 180°C for 6 hours to obtain linear polyamide.

[0087] (3) Linear polyamide was subjected to thermal shock hyperbranching reaction at 250°C for 1 hour under nitrogen atmosphere to obtain special hyperbranched polyamide, rope-type hyperbranched polyamide.

[0088] (4) The prepared rope-type hyperbranched polyamide was prepared into rope-type hyperbranched polyamide solutions of 0.5%, 0.75%, 1.0%, 1.5% and 2.0% by mass fraction.

[0089] Example 6

[0090] Preparation of hyperbranched polyamide: 6.505 g (50 mmol) itaconic acid, 2.204 g (25 mmol) 1,4-diaminobutane, 2.905 g (25 mmol) 1,6-diaminohexane, 50 mL anhydrous ethanol. The method includes the following steps:

[0091] (1) Dissolve 6.505g itaconic acid, 2.204g 1,4-diaminobutane, and 2.905g 1,6-diaminohexane in 25mL of anhydrous ethanol. After mixing them evenly, let them stand to precipitate and obtain white salt monomers. After filtration and drying, powdered itaconic acid and 1,4-diaminobutane / 1,6-diaminohexane salt monomers are obtained.

[0092] (2) The dried salt monomer was placed in a three-necked flask and stirred and condensed under nitrogen at 180°C for 6 hours to obtain linear polyamide.

[0093] (3) Linear polyamide was subjected to thermal shock hyperbranching reaction at 210°C for 5 h under nitrogen atmosphere to obtain hyperbranched polyamide;

[0094] (4) The prepared hyperbranched polyamide was prepared into hyperbranched polyamide solutions of 0.5%, 0.75%, 1.0%, 1.5% and 2.0% by mass fraction.

[0095] Example 7

[0096] Preparation of hyperbranched polyamide: 13.010 g (100 mmol) itaconic acid, 4.509 g (75 mmol) 1,2-diaminoethane, 7.864 g (25 mmol) 1,20-diaminoeicosane, and 50 mL anhydrous ethanol. The method includes the following steps:

[0097] (1) 13.010 g itaconic acid, 4.509 g 1,2-diaminoethane, and 7.864 g 1,20-diaminoeicosane were dissolved in 25 mL of anhydrous ethanol. After mixing them evenly, the mixture was allowed to stand and precipitate to obtain a white salt monomer. After filtration and drying, powdered itaconic acid and 1,2-diaminoethane / 1,20-diaminoeicosane salt monomers were obtained.

[0098] (2) The dried salt monomer was placed in a three-necked flask and stirred and condensed under nitrogen at 180°C for 6 hours to obtain linear polyamide.

[0099] (3) Linear polyamide was subjected to thermal shock hyperbranching reaction at 210°C for 5 h under nitrogen atmosphere to obtain hyperbranched polyamide;

[0100] (4) The prepared hyperbranched polyamide was prepared into hyperbranched polyamide solutions of 0.5%, 0.75%, 1.0%, 1.5% and 2.0% by mass fraction.

[0101] Comparative Example 1

[0102] Preparation of linear polyamide: Using 6.505 g (50 mmol) itaconic acid, 5.089 g (50 mmol) 1,5-diaminopentane, and 50 mL anhydrous ethanol, the method includes the following steps:

[0103] (1) Dissolve 6.505g itaconic acid and 5.089g 1,5-diaminopentane in 25mL of anhydrous ethanol. After mixing them evenly, let them stand to precipitate and obtain white salt monomers. After filtration and drying, powdered itaconic acid and 1,5-pentanediamine salt monomers are obtained.

[0104] (2) The dried salt monomer was placed in a three-necked flask and stirred and condensed under nitrogen at 180°C for 6 hours to obtain linear polyamide.

[0105] (3) Then, linear polyamide solutions of 0.5%, 0.75%, 1.0%, 1.5% and 2.0% were prepared according to mass fraction.

[0106] Comparative Example 2

[0107] The formula and steps (1) and (2) are the same as in Example 6;

[0108] (3) The linear polyamide obtained in step (2) of Example 6 was prepared into linear polyamide solutions of 0.5%, 0.75%, 1.0%, 1.5% and 2.0% by mass fraction.

[0109] Comparative Example 3

[0110] The formula and steps (1) and (2) are the same as in Example 7;

[0111] (3) The linear polyamide obtained in step (2) of Example 7 was prepared into linear polyamide solutions of 0.5%, 0.75%, 1.0%, 1.5% and 2.0% by mass fraction.

[0112] Test case

[0113] (1) Synthesis of hyperbranched polyamide

[0114] The synthesis of hyperbranched structures was demonstrated by gel permeation chromatography and 13-carbon nuclear magnetic resonance characterization of linear polyamides and hyperbranched polyamides.

[0115] As shown in Figure 3, after the thermal shock hyperbranching reaction, the absorption peaks of the carbonyl carbon in the comparative linear polyamide and the hyperbranched polyamide of Example 1 were analyzed using 13-carbon nuclear magnetic resonance (NMR) testing. Compared with the linear polyamide, the absorption peak a of the terminal carboxyl group in the hyperbranched polyamide decreased in intensity, while the absorption peak b of the amide bond increased significantly, consistent with the results of the hyperbranching reaction. For the rope-type polyamide of Example 5, the appearance of the new carbonyl absorption peak d was clearly visible, representing the formation of a rope-type polyamide structure.

[0116] As shown in Table 1, the molecular weight increased significantly after the thermal shock hyperbranching reaction, especially the weight-average molecular weight. The weight-average molecular weight of the linear polyamide in Comparative Example 1 increased from 12988 to 278785 in Example 1, 271660 in Example 2, 236918 in Example 3, 218052 in Example 4, and 202136 in Example 5.

[0117] Meanwhile, the molecular weight distribution of Comparative Example 2 increased from 11696 to 269947 in Example 6 and Comparative Example 3 increased from 14619 to 344984 in Example 7. Compared with the comparative examples, the molecular weight distribution of the examples also became wider, which is consistent with the changes in molecular weight and molecular weight distribution after branching.

[0118] Table 1. Number-average molecular weight, weight-average molecular weight, and molecular weight distribution index of the comparative linear polyamides and the hyperbranched polyamides of Examples 1-2.

[0119] (2) Thermochromic properties of hyperbranched polyamides

[0120] By measuring the minimum critical co-solution temperatures of the comparative linear polyamide and hyperbranched polyamide of different concentrations in Example 1, as shown in Table 2, it can be seen that the comparative linear polyamide, due to its excessively low molecular weight and strong hydrophilicity, does not exhibit temperature-responsive behavior. However, by using the thermal shock hyperbranching method, its molecular weight can be increased, bringing it to a state of hydrophilicity-repellency equilibrium, thus resulting in temperature-responsive color change behavior, as shown in Figure 5. At 25°C, the hyperbranched polyamide solution remains transparent, while at 35°C, the hyperbranched polyamide solution becomes turbid.

[0121] Table 2-1 Comparative examples of linear polyamides and hyperbranched polyamides of different concentrations from Example 1: minimum critical cosolubility temperatures

[0122] Table 2-2 Comparative examples of linear polyamides and hyperbranched polyamides of different concentrations from Example 1: minimum critical cosolubility temperatures

[0123] To further verify the thermosensitive color-changing response performance, the linear polyamide prepared in the comparative example and the hyperbranched polyamide sample prepared in Example 1 with a mass fraction of 0.50% were tested using a UV-Vis spectrophotometer. As shown in Figure 6, the transmittance of the linear polyamide in the comparative example remained constant at 96.5% at 550 nm between 25-45 °C, while the transmittance of the 0.50% hyperbranched polyamide rapidly decreased from 95% to 5% around the response temperature of 35 °C. As shown in Figure 7, the transmittance of the hyperbranched polyamide prepared in Example 7 changed rapidly between 27-30 °C. With increasing concentration, the hyperbranched polyamide exhibits easier formation of hydrogen bonds between molecular chains, easier polymer chain aggregation, and a lower minimum critical co-solution temperature.

[0124] To verify the performance of the prepared hyperbranched polyamide under practical application conditions, smart windows prepared with comparative examples 1-0.5% and 1-0.5% of the hyperbranched polyamide solution were tested under simulated indoor temperatures in summer. As shown in Figure 8, the smart window prepared with comparative example 1-0.5% of the hyperbranched polyamide solution remained transparent at 25 degrees Celsius, but became completely cloudy when the outdoor temperature was raised to 35 degrees Celsius. Figure 9 shows a significant temperature difference between the smart windows prepared in the comparative example and the actual example, with an average temperature difference of 7.8 degrees Celsius, indicating good temperature regulation capabilities in summer.

[0125] In summary, this invention provides a novel thermosensitive color-changing temperature-responsive material—hyperbranched polyamide—with an easily adjustable minimum critical co-solution temperature. The method involves first preparing a linear polyamide with a pyrrolidone ring on the main chain using itaconic acid and a linear or branched diamine via a salt monomer method, followed by thermal shock to form a hyperbranched structure. The preparation method is simple, easy to process, and environmentally friendly. The minimum critical co-solution temperature of the hyperbranched polyamide aqueous solution varies with concentration; for example, the minimum critical dissolution temperature of the hyperbranched polyamide prepared in Example 1 changes from 35°C to 17°C when the concentration increases from 0.5% to 2.0% by mass.

[0126] The thermosensitive color-changing hyperbranched polyamide prepared by this invention has an adjustable minimum critical co-solution temperature, which can provide different response temperature schemes to adapt to complex application scenarios; it has high application value in terms of intelligent response performance.

[0127] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A branched polyamide, characterized in that, The main chain has a pyrrolidone ring and a dendritic hyperbranched structure, with the structural units shown in the figure below: Where x takes the value of an integer from 2 to 20, and m, n, and p take the value of an integer from 10 to 1660.

2. The branched polyamide according to claim 1, characterized in that, Molecular weight ranges from 6,000 to 1,000,000; And / or, the degree of branching is 0.67% to 10%.

3. The branched polyamide according to claim 1, characterized in that, The minimum critical co-solution temperature of the branched polyamide aqueous solution varies with concentration.

4. The branched polyamide according to claim 3, characterized in that, The minimum critical eutectic temperature is 16-37℃.

5. The branched polyamide according to claim 1, characterized in that, The branched polyamide is a rope-type hyperbranched polyamide; it has the structural unit shown in the figure below: Where x takes the value of an integer from 2 to 20, and m and n take the value of an integer from 10 to 1660.

6. The method for preparing branched polyamide according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Itaconic acid and diamine are dissolved in solvents respectively. After mixing them evenly, they are allowed to stand and precipitate to obtain a white salt monomer. After separation and drying, itaconic acid diamine salt monomer is obtained. S2. Place the salt monomer obtained in step S1 into a reaction vessel and heat it under an inert atmosphere to obtain linear polyamide; S3. The linear polyamide obtained in step S2 is subjected to a thermal shock hyperbranching reaction under an inert atmosphere to obtain branched polyamide.

7. The method for preparing branched polyamide according to claim 6, characterized in that, In step S1, the diamine is one or a combination of straight-chain or branched diamines of C2-C20. The branched diamine is a diamine whose main chain carbon contains 1-2 branched groups; the branched groups are methyl, ethyl, propyl or isopropyl.

8. The method for preparing branched polyamide according to claim 6, characterized in that, In step S1, the solvent includes, but is not limited to, ethanol, water, and methanol.

9. The method for preparing branched polyamide according to claim 6, characterized in that, In step S2, the heating conditions are 170-190℃; the reaction time is 4-20h. And / or, in step S3, the thermal shock reaction temperature is 210–250°C; the reaction time is 1–10 h.

10. The use of the branched polyamide according to any one of claims 1-5 in temperature-responsive materials.

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