Branched polyamide and preparation method

Abstract

The invention relates to the technical field of functional polymer materials and intelligent response polymer materials, in particular to branched polyamide and a preparation method thereof. The branched polyamide main chain has a pyrrolidone ring and is of a dendritic hyperbranched structure; the lowest critical solution temperature of the aqueous solution changes along with the change of the concentration, and the change range of the lowest critical solution temperature is 16-37 DEG C. According to the preparation method, itaconic acid and diamine are used for preparing linear polyamide with a pyrrolidone ring on a main chain through a salt monomer method, and then a hyperbranched structure is formed through thermal shock; the preparation method is simple and convenient, easy in post-treatment and environment-friendly. The prepared temperature-sensitive color-changing hyperbranched polyamide can provide different response temperature schemes to adapt to complex application scenes.

Description

Technical Field

[0001] The invention relates to the technical field of functional polymer materials and intelligent response polymer materials, in particular to a branched polyamide and a preparation method thereof. Background Art

[0002] Thermochromic materials refer to functional materials whose visible absorption spectra change when the surrounding temperature changes. In the past 80 years of development, the types and properties of materials have been greatly developed and widely used in various fields such as industry, textiles, military, printing, anti-counterfeiting, etc.

[0003] The main temperature-responsive polymer materials currently include biologically derived hydroxypropyl cellulose and petroleum-based poly(N-isopropylacrylamide). The minimum critical solubility temperature of hydroxypropyl cellulose is too high, and if it is adjusted in a salt solution, it has the defect of poor solubility. On the other hand, the molecular weight of hydroxypropyl cellulose is difficult to control, which is also one of the reasons for its poor solubility. Poly(N-isopropylacrylamide) shows a minimum critical temperature that is closest to the comfortable temperature of the human body, but it has poor biocompatibility and high cost.

[0004] Therefore, there is an urgent need for a new type of thermochromic temperature-responsive material that can easily adjust the minimum critical eutectic temperature to expand its application scenarios. Summary of the invention

[0005] In order to solve the defects of poor solubility and biocompatibility as well as high cost of existing temperature-responsive polymer materials, the present invention provides a novel temperature-responsive material with a temperature-sensitive color-changing property and a conveniently adjustable minimum critical eutectic temperature.

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

[0007] The first object of the present invention is to provide a branched polyamide having a pyrrolidone ring on the main chain and a dendritic hyperbranched structure (hereinafter referred to as a hyperbranched polyamide);

[0008] Furthermore, the hyperbranched polyamide has a structural unit shown in the following formula:

[0009]

[0010] The value of x is an integer from 2 to 20, and the values ​​of m, n, and p are integers from 10 to 1660.

[0011] Further, the molecular weight of the hyperbranched polyamide is 6000 to 1000000;

[0012] In some embodiments of the present invention, the hyperbranched polyamide has a branching degree of 0.67% to 10%.

[0013] Further, the lowest critical solution temperature of the hyperbranched polyamide aqueous solution varies with the concentration;

[0014] Furthermore, the minimum critical solution temperature varies in the range of 16-37°C.

[0015] In some embodiments of the present invention, the hyperbranched polyamide is a rope-type hyperbranched polyamide having a structure as shown in the following formula:

[0016]

[0017] The value of x is an integer between 2 and 20, and the values ​​of m and n are integers between 10 and 1660.

[0018] 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.

[0019] In some embodiments of the present invention, the molecular weight of the thermochromic hyperbranched polyamide is 6,000 to 1,000,000, and the degree of branching is 0.67% to 10%.

[0020] In some embodiments, the hyperbranched polyamide is prepared into a hyperbranched polyamide aqueous solution according to different mass fraction ratios. The prepared hyperbranched polyamide aqueous solution has a concentration ranging from 0.5% to 2.0% by mass fraction, and a minimum critical solution temperature gradually decreases from 35°C to 17°C as the concentration changes.

[0021] In some embodiments of the present invention, the hyperbranched polyamide aqueous solution undergoes a reversible change in visible transmittance around the lowest co-solubility temperature, with the transmittance changing from 97% to 5%.

[0022] In some embodiments of the present invention, when the concentration of the hyperbranched polyamide aqueous solution increases from 0.5% by mass to 2.0% by mass, the lowest critical solution temperature decreases from 36° C. to 18° C.

[0023] In some embodiments of the present invention, when the concentration of the hyperbranched polyamide aqueous solution increases from 0.5% by mass to 2.0% by mass, the lowest critical solution temperature decreases from 34° C. to 17° C.

[0024] In some embodiments of the present invention, when the concentration of the hyperbranched polyamide aqueous solution increases from 0.5% by mass to 2.0% by mass, the lowest critical solution temperature decreases from 32° C. to 16° C.

[0025] In some embodiments of the present invention, when the concentration of the hyperbranched polyamide aqueous solution increases from 0.5% by mass to 2.0% by mass, the lowest critical solution temperature decreases from 33° C. to 18° C.

[0026] In some embodiments of the present invention, when the concentration of the hyperbranched polyamide aqueous solution increases from 0.5% by mass to 2.0% by mass, the lowest critical solution temperature decreases from 37° C. to 19° C.

[0027] In some embodiments of the present invention, when the concentration of the hyperbranched polyamide aqueous solution increases from 0.5% by mass to 2.0% by mass, the lowest critical solution temperature decreases from 29° C. to 17° C.

[0028] The second object of the present invention is to provide a method for preparing the thermosensitive color-changing hyperbranched polyamide, comprising steps S1, S2, and S3:

[0029] S1. Dissolving itaconic acid and a diamine in a solvent respectively, mixing the two uniformly and then standing to precipitate to obtain a white salt monomer, which is separated and dried to obtain an itaconic acid diamine salt monomer;

[0030] S2. The salt monomer obtained in step S1 is placed in a reaction vessel, heated under an inert atmosphere, and reacted to obtain a linear polyamide;

[0031] S3. The linear polyamide obtained in step S2 is subjected to a heat shock hyperbranching reaction under an inert atmosphere to obtain a hyperbranched polyamide. By subjecting the linear polyamide to a heat shock, the two terminal amino groups undergo a deamination reaction to form secondary amines, and the rear end carboxyl group reacts with the secondary amine to form a hyperbranched structure.

[0032] Further, in step S1, the diamine is one or a combination of C2-C20 straight-chain or branched diamines;

[0033] Furthermore, the branched diamine is a diamine having 1-2 branched groups on the diamine main chain carbon; the branched groups are methyl, ethyl, propyl or isopropyl.

[0034] In some embodiments, the branched diamine is (NH2(CH2)3CHXNH2), (NH2(CH2)

[0035] 2CHXCH2NH2)(X=CH3, CH2CH3) or a combination thereof;

[0036] In some embodiments, the heating condition in step S2 is 170-190° C. and the reaction time is 4-20 h.

[0037] In some embodiments, in step S3, the thermal shock reaction temperature is 210-250° C. and the reaction time is 1-10 h.

[0038] In some embodiments, the inert atmosphere is provided by nitrogen or argon;

[0039] In step S1, the solvent includes but is not limited to ethanol, water, methanol, etc.

[0040] In some preferred embodiments, the method for preparing hyperbranched polyamide comprises the following steps:

[0041] (1) dissolving itaconic acid and 1,5-diaminopentane in anhydrous ethanol respectively, mixing the two evenly and then standing to precipitate to obtain a white salt monomer, which is then filtered and dried to obtain a powdery itaconic acid 1,5-diaminopentane salt monomer;

[0042] (2) placing the dried salt monomer in a three-necked flask, heating to 170-190° C. under nitrogen, stirring for 4-20 hours, and performing condensation polymerization to obtain a linear polyamide;

[0043] (3) The linear polyamide is then subjected to a heat shock hyperbranching reaction in a nitrogen atmosphere, heated to 210-250° C., and reacted for 1-10 hours to obtain a hyperbranched polyamide.

[0044] The third object of the present invention is to provide an application of the temperature-sensitive color-changing hyperbranched polyamide, which is applied to the field of smart response materials, such as smart response windows, temperature-sensitive color-changing glass, etc.

[0045] The present invention can adapt to complex application scenarios by controlling the concentration of the hyperbranched polyamide and regulating the minimum critical co-solubility temperature of the hyperbranched polyamide aqueous solution.

[0046] Beneficial effects of the present invention:

[0047] The invention prepares a novel temperature-sensitive color-changing temperature-responsive material whose minimum critical co-solution temperature is adjusted by concentration. The molecular weight of the temperature-sensitive color-changing hyperbranched polyamide is 6000 to 1000000, and the branching degree is 0.67% to 10%.

[0048] The hyperbranched polyamide of the present invention can regulate the minimum critical solution temperature of the hyperbranched polyamide aqueous solution by controlling the concentration. At the same time, the hyperbranched polyamide of the present invention can also adjust the minimum critical solution temperature and its variation range by using different diamines; the minimum critical solution temperature range is 37°C-16°C.

[0049] The preparation method of the invention uses itaconic acid and diamine to first prepare a linear polyamide with a pyrrolidone ring on the main chain through a salt monomer method, and then forms a hyperbranched structure through thermal shock. The preparation method is simple, easy to post-process, and environmentally friendly.

[0050] The temperature-sensitive color-changing hyperbranched polyamide prepared by the present invention can provide different response temperature schemes to adapt to complex application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The accompanying drawings are used to provide a further understanding of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the present application and do not constitute a limitation of the present application. In the accompanying drawings:

[0052] Figure 1 The structure diagram of the branched polyamide prepared by the present invention;

[0053] Figure 2 The steps of preparing the thermochromic hyperbranched polyamide according to Example 1 of the present invention are shown in FIG.

[0054] Figure 3 13 carbon nuclear magnetic resonance spectra of the linear polyamide of Comparative Example 1 and the hyperbranched polyamide prepared in Example 1;

[0055] Figure 4 This is the 13 carbon nuclear magnetic resonance spectrum of the rope-type polyamide of Example 5;

[0056] Figure 5 These are pictures of a 0.50% by weight hyperbranched polyamide solution prepared in Example 1 at 25° C. and 35° C.;

[0057] Figure 6 The transmittance of the linear polyamide of Comparative Example 1 and the hyperbranched polyamide with a mass fraction of 0.50% prepared in Example 1 under visible light with a wavelength of 550nm at different temperatures;

[0058] Figure 7 The transmittance of the linear polyamide of Comparative Example 3 and the hyperbranched polyamide with a mass fraction of 0.50% prepared in Example 7 under visible light of 550nm wavelength at different temperatures. DETAILED DESCRIPTION

[0059] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are only a part of embodiments of the present invention, rather than all embodiments. The experimental methods in the following embodiments, unless otherwise specified, are conventional methods in the art. However, it is easy for those skilled in the art to understand that the specific material proportions, process conditions and results described in the embodiments are only used to illustrate the present invention, and should not and will not limit the present invention described in detail in the claims.

[0060] Example 1

[0061] Preparation of hyperbranched polyamide: itaconic acid 6.505 g (50 mmol), 1,5-diaminopentane 5.089 g (50 mmol), anhydrous ethanol 50 mL, the method comprising the following steps:

[0062] (1) 6.505 g of itaconic acid and 5.089 g of 1,5-diaminopentane were dissolved in 25 mL of anhydrous ethanol respectively, the two were mixed evenly and allowed to stand to precipitate to obtain a white salt monomer, which was then filtered and dried to obtain powdery itaconic acid and 1,5-pentanediamine salt monomers.

[0063] (2) The dried salt monomer is placed in a three-necked flask, and stirred for condensation polymerization at 180° C. under nitrogen conditions for 6 hours to obtain a linear polyamide.

[0064] (3) subjecting the linear polyamide to a thermal shock hyperbranching reaction at 210° C. under a nitrogen atmosphere for 5 h to obtain a hyperbranched polyamide;

[0065] (4) The prepared hyperbranched polyamide is prepared according to mass fraction to obtain 0.5%, 0.75%, 1.0%, 1.5% and 2.0% hyperbranched polyamide solutions.

[0066] Example 2

[0067] Preparation of hyperbranched polyamide: itaconic acid 6.505 g (50 mmol), 1,5-diaminopentane 5.089 g (50 mmol), anhydrous ethanol 50 mL, the method comprising the following steps:

[0068] (1) 6.505 g of itaconic acid and 5.089 g of 1,5-diaminopentane were dissolved in 25 mL of anhydrous ethanol respectively, the two were mixed evenly and allowed to stand to precipitate to obtain a white salt monomer, which was then filtered and dried to obtain powdery itaconic acid and 1,5-pentanediamine salt monomers.

[0069] (2) The dried salt monomer is placed in a three-necked flask, and stirred for condensation polymerization at 180° C. under nitrogen conditions for 6 hours to obtain a linear polyamide.

[0070] (3) subjecting the linear polyamide to a thermal shock hyperbranching reaction at 220° C. under a nitrogen atmosphere for 4 h to obtain a hyperbranched polyamide;

[0071] (4) The prepared hyperbranched polyamide is prepared according to mass fraction to obtain 0.5%, 0.75%, 1.0%, 1.5% and 2.0% hyperbranched polyamide solutions.

[0072] Example 3

[0073] Preparation of hyperbranched polyamide: itaconic acid 6.505 g (50 mmol), 1,5-diaminopentane 5.089 g (50 mmol), anhydrous ethanol 50 mL, the method comprising the following steps:

[0074] (1) 6.505 g of itaconic acid and 5.089 g of 1,5-diaminopentane were dissolved in 25 mL of anhydrous ethanol respectively, the two were mixed evenly and allowed to stand to precipitate to obtain a white salt monomer, which was then filtered and dried to obtain powdery itaconic acid and 1,5-pentanediamine salt monomers.

[0075] (2) The dried salt monomer is placed in a three-necked flask, and stirred for condensation polymerization at 180° C. under nitrogen conditions for 6 hours to obtain a linear polyamide.

[0076] (3) subjecting the linear polyamide to a thermal shock hyperbranching reaction at 230° C. under a nitrogen atmosphere for 3 h to obtain a hyperbranched polyamide;

[0077] (4) The prepared hyperbranched polyamide is prepared according to mass fraction to obtain 0.5%, 0.75%, 1.0%, 1.5% and 2.0% hyperbranched polyamide solutions.

[0078] Example 4

[0079] Preparation of hyperbranched polyamide: itaconic acid 6.505 g (50 mmol), 1,5-diaminopentane 5.089 g (50 mmol), anhydrous ethanol 50 mL, the method comprising the following steps:

[0080] (1) 6.505 g of itaconic acid and 5.089 g of 1,5-diaminopentane were dissolved in 25 mL of anhydrous ethanol respectively, the two were mixed evenly and allowed to stand to precipitate to obtain a white salt monomer, which was then filtered and dried to obtain powdery itaconic acid and 1,5-pentanediamine salt monomers.

[0081] (2) The dried salt monomer is placed in a three-necked flask, and stirred for condensation polymerization at 180° C. under nitrogen conditions for 6 hours to obtain a linear polyamide.

[0082] (3) subjecting the linear polyamide to a thermal shock hyperbranching reaction at 240° C. for 2 h under a nitrogen atmosphere to obtain a hyperbranched polyamide;

[0083] (4) The prepared hyperbranched polyamide is prepared according to mass fraction to obtain 0.5%, 0.75%, 1.0%, 1.5% and 2.0% hyperbranched polyamide solutions.

[0084] Example 5

[0085] Preparation of hyperbranched polyamide: itaconic acid 6.505 g (50 mmol), 1,5-diaminopentane 5.089 g (50 mmol), anhydrous ethanol 50 mL, the method comprising the following steps:

[0086] (1) 6.505 g of itaconic acid and 5.089 g of 1,5-diaminopentane were dissolved in 25 mL of anhydrous ethanol respectively, the two were mixed evenly and allowed to stand to precipitate to obtain a white salt monomer, which was then filtered and dried to obtain powdery itaconic acid and 1,5-pentanediamine salt monomers.

[0087] (2) The dried salt monomer is placed in a three-necked flask, and stirred for condensation polymerization at 180° C. under nitrogen conditions for 6 hours to obtain a linear polyamide.

[0088] (3) subjecting the linear polyamide to a heat shock hyperbranching reaction at 250° C. for 1 h under a nitrogen atmosphere to obtain a special hyperbranched polyamide, a rope-type hyperbranched polyamide;

[0089] (4) The prepared rope-type hyperbranched polyamide is prepared according to mass fraction to obtain 0.5%, 0.75%, 1.0%, 1.5% and 2.0% rope-type hyperbranched polyamide solutions.

[0090] Example 6

[0091] Preparation of hyperbranched polyamide: itaconic acid 6.505 g (50 mmol), 1,4-diaminobutane 2.204 g (25 mmol), 1,6-diaminohexane 2.905 g (25 mmol), anhydrous ethanol 50 mL, the method comprising the following steps:

[0092] (1) 6.505 g of itaconic acid, 2.204 g of 1,4-diaminobutane, and 2.905 g of 1,6-diaminohexane were respectively dissolved in 25 mL of anhydrous ethanol, the two were mixed evenly and allowed to stand to precipitate to obtain a white salt monomer, which was then filtered and dried to obtain powdery itaconic acid and 1,4-diaminobutane / 1,6-diaminohexane salt monomers.

[0093] (2) The dried salt monomer is placed in a three-necked flask, and stirred for condensation polymerization at 180° C. under nitrogen conditions for 6 hours to obtain a linear polyamide.

[0094] (3) subjecting the linear polyamide to a thermal shock hyperbranching reaction at 210° C. under a nitrogen atmosphere for 5 h to obtain a hyperbranched polyamide;

[0095] (4) The prepared hyperbranched polyamide is prepared according to mass fraction to obtain 0.5%, 0.75%, 1.0%, 1.5% and 2.0% hyperbranched polyamide solutions.

[0096] Example 7

[0097] Preparation of hyperbranched polyamide: itaconic acid 13.010 g (100 mmol), 1,2-diaminoethane 4.509 g (75 mmol), 1,20-diaminoeicosane 7.864 g (25 mmol), anhydrous ethanol 50 mL, the method comprising the following steps:

[0098] (1) 13.010 g of itaconic acid, 4.509 g of 1,2-diaminoethane, and 7.864 g of 1,20-diaminoeicosane were respectively dissolved in 25 mL of anhydrous ethanol, the two were mixed evenly and allowed to stand to precipitate to obtain a white salt monomer, which was then filtered and dried to obtain powdery itaconic acid and 1,2-diaminoethane / 1,20-diaminoeicosane salt monomers.

[0099] (2) The dried salt monomer is placed in a three-necked flask, and stirred for condensation polymerization at 180° C. under nitrogen conditions for 6 hours to obtain a linear polyamide.

[0100] (3) subjecting the linear polyamide to a thermal shock hyperbranching reaction at 210° C. under a nitrogen atmosphere for 5 h to obtain a hyperbranched polyamide;

[0101] (4) The prepared hyperbranched polyamide is prepared according to mass fraction to obtain 0.5%, 0.75%, 1.0%, 1.5% and 2.0% hyperbranched polyamide solutions.

[0102] Comparative Example 1

[0103] Preparation of linear polyamide: using itaconic acid 6.505g (50mmol), 1,5-diaminopentane 5.089g (50mmol), anhydrous ethanol 50mL, the method comprises the following steps:

[0104] (1) 6.505 g of itaconic acid and 5.089 g of 1,5-diaminopentane were respectively dissolved in 25 mL of anhydrous ethanol, the two were mixed evenly and then allowed to stand to precipitate to obtain a white salt monomer, which was then filtered and dried to obtain powdery itaconic acid and 1,5-pentanediamine salt monomers;

[0105] (2) placing the dried salt monomer in a three-necked flask, stirring and condensing the mixture under nitrogen at 180° C. for 6 h to obtain a linear polyamide;

[0106] (3) Then, the linear polyamide solutions of 0.5%, 0.75%, 1.0%, 1.5% and 2.0% were prepared according to the mass fraction.

[0107] Comparative Example 2

[0108] The formula and steps (1) and (2) are the same as those in Example 6;

[0109] (3) The linear polyamide prepared in step (2) of Example 6 was mixed according to mass fraction to obtain linear polyamide solutions of 0.5%, 0.75%, 1.0%, 1.5% and 2.0%.

[0110] Comparative Example 3

[0111] The formula and steps (1) and (2) are the same as those in Example 7;

[0112] (3) The linear polyamide prepared in step (2) of Example 7 was mixed according to mass fraction to obtain linear polyamide solutions of 0.5%, 0.75%, 1.0%, 1.5% and 2.0%.

[0113] Test Case

[0114] (1) Synthesis of hyperbranched polyamide

[0115] The synthesis of the hyperbranched structures was demonstrated by gel permeation chromatography and 13C NMR characterization tests for linear and hyperbranched polyamides.

[0116] like Figure 3 As shown, by 13C NMR test, after the heat shock hyperbranching reaction, the absorption peaks of carbonyl carbon of the comparative linear polyamide and the hyperbranched polyamide of Example 1 were analyzed. Compared with the linear polyamide, the absorption peak a of the terminal carboxyl group of the hyperbranched polyamide decreased in intensity, and the absorption peak b of the amide bond increased significantly, which is consistent with the result of the hyperbranching reaction. For the rope-type polyamide of Example 5, the appearance of the new carbonyl absorption peak d can be clearly seen, representing the formation of the rope-type structure polyamide.

[0117] As shown in Table 1, after the thermal shock hyperbranching reaction, the molecular weight increased significantly, especially the weight average molecular weight. The weight average molecular weight of the linear polyamide of Comparative Example 1 increased from 12988 to 278785 of Example 1, 271660 of Example 2, 236918 of Example 3, 218052 of Example 4, and 202136 of Example 5;

[0118] At the same time, the 11696 of comparative example 2 increased to 269947 of example 6 and the 14619 of comparative example 3 increased to 344984 of example 7, and the molecular weight distribution of the examples also became wider than that of the comparative examples, which is consistent with the molecular weight change and molecular weight distribution change after the branched structure.

[0119] Table 1 Number average molecular weight, weight average molecular weight and molecular weight distribution index of the comparative linear polyamide and the hyperbranched polyamide of Examples 1-2

[0120]

[0121] (2) Thermosensitive color change properties of hyperbranched polyamide

[0122] By measuring the lowest critical solution temperature of the comparative linear polyamide and the hyperbranched polyamide of Example 1 at different concentrations, as shown in Table 2, it can be found that the comparative linear polyamide has too low molecular weight and too strong hydrophilicity, and does not show temperature response behavior. However, by using the thermal shock method to hyperbranch, its molecular weight can be increased, so that it is in a state of affinity and hydrophobicity balance, thereby showing temperature response color change behavior, such as Figure 5 , at 25 °C, the hyperbranched polyamide solution remained transparent, while at 35 °C, the hyperbranched polyamide solution became turbid.

[0123] Table 2-1 Minimum critical solution temperature of linear polyamide in comparative example and hyperbranched polyamide in Example 1 at different concentrations

[0124]

[0125]

[0126] Table 2-2 Minimum critical solution temperature of linear polyamide and hyperbranched polyamide of Example 1 with different concentrations

[0127]

[0128] In order to further verify the thermosensitive color response performance, the linear polyamide prepared in the comparative example and the hyperbranched polyamide sample with a mass fraction of 0.50% prepared in Example 1 were tested by UV-visible spectrophotometer. Figure 6 As shown, it can be seen that the transmittance of 550nm visible light of the comparative linear polyamide remains unchanged at 96.5% at 25-45°C, while the transmittance of 0.50% hyperbranched polyamide rapidly drops from 95% to 5% around the response temperature of 35°C. Figure 7 As shown, the transmittance of the hyperbranched polyamide prepared in Example 7 changes rapidly at 27-30° C. As the concentration of the hyperbranched polyamide increases, hydrogen bonds between its molecular chains are more easily formed, polymer chains are more likely to agglomerate, and the hyperbranched polyamide has a lower minimum critical solution temperature.

[0129] In summary, the present invention prepares a new type of temperature-sensitive color-changing temperature-responsive material-hyperbranched polyamide that is easy to adjust the minimum critical solution temperature; it uses itaconic acid and straight-chain diamine or branched diamine to first prepare a linear polyamide with a pyrrolidone ring on the main chain through a salt monomer method, and then thermally shocks to form a hyperbranched structure; the preparation method is simple, easy to post-process, and environmentally friendly. The minimum critical solution temperature of the hyperbranched polyamide aqueous solution changes with the concentration. For example, when the concentration of the hyperbranched polyamide prepared in Example 1 is from 0.5% to 2.0% by mass, the minimum critical solution temperature changes from 35°C to 17°C.

[0130] The thermosensitive color-changing hyperbranched polyamide with an adjustable minimum critical solution temperature prepared by the present invention can provide different response temperature schemes to adapt to complex application scenarios; and has high application value in terms of intelligent response performance.

[0131] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as 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 a structural unit as shown in the following formula: The value of x is an integer from 2 to 20, and the values ​​of m, n, and p are integers from 10 to 1660.

2. The branched polyamide according to claim 1, characterized in that Molecular weight is 6000 to 1000000; And / or, the degree of branching is from 0.67% to 10%.

3. The branched polyamide according to claim 1, characterized in that The lower critical solution temperature of the branched polyamide aqueous solution changes with the concentration.

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

5. The branched polyamide according to claim 1, characterized in that The branched polyamide is a rope-type hyperbranched polyamide having a structural unit as shown in the following formula: The value of x is an integer between 2 and 20, and the values ​​of m and n are integers between 10 and 1660.

6. The method for preparing branched polyamide according to any one of claims 1 to 5, characterized in that: The steps include: S1. Dissolving itaconic acid and a diamine in a solvent respectively, mixing the two uniformly and then standing to precipitate to obtain a white salt monomer, which is separated and dried to obtain an itaconic acid diamine salt monomer; S2. The salt monomer obtained in step S1 is placed in a reaction vessel and heated under an inert atmosphere to react to obtain a linear polyamide; S3. The linear polyamide prepared in step S2 is subjected to a thermal shock hyperbranching reaction under an inert atmosphere to obtain a 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 C2-C20 straight-chain or branched diamines; The branched diamine is a diamine having 1 to 2 branched groups on the diamine main chain carbon; 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 condition is 170-190°C; 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. Use of the branched polyamide according to any one of claims 1 to 5 in a temperature responsive material.

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