Multielement branched polyamide and preparation method thereof

Abstract

The invention relates to the technical field of functional polymer materials, in particular to multi-element branched polyamide and a preparation method thereof. The main chain of the multi-element branched polyamide is provided with a pyrrolidone ring, and the multi-element branched polyamide is of a controllable multi-element branched structure; the lowest critical solution temperature of the aqueous solution is changed along with the change of concentration, molecular weight, number of branched units and variety and concentration of salt, and the change range of the lowest critical solution temperature is 10-80 DEG C. The preparation method comprises the following steps: preparing an amino acid monomer with a pyrrolidone ring by utilizing itaconic acid and diamine through a salt monomer method, then preparing linear polyamide with the pyrrolidone ring on a main chain, and then adding branching centers in different proportions to form multi-element branched polyamide; the preparation method is simple, convenient, easy in post-treatment and environment-friendly. The prepared temperature-sensitive color-changing type multielement branched polyamide can provide different response temperature schemes to adapt to complex application scenes.

Description

Technical Field

[0001] The present invention relates to the technical fields of branched functional polymer materials and intelligent responsive polymer materials, and particularly relates to a branched polyamide and a preparation method thereof. Background Art

[0002] Intelligent responsive polymer materials refer to polymer materials that can undergo reversible deformations, color changes, volume expansions, etc. in response to external stimuli (such as temperature, light, magnetic field, etc.). Among them, thermochromic polymer materials are functional materials that are accompanied by changes in the visible absorption spectrum. In the past 80-year development process, due to the great development of their material types and properties, they have been widely used in various fields such as industry, textiles, military, printing, anti-counterfeiting, etc.

[0003] Currently, temperature-responsive polymer materials mainly include hydroxypropyl cellulose of biological origin and poly(N-isopropylacrylamide) of petroleum origin. The lower critical solution temperature of hydroxypropyl cellulose is too high, and it has the defect of poor solubility when adjusted in a salt solution. 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 the lowest critical temperature 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 temperature-responsive material with thermochromic properties that is easy to adjust the lower critical solution temperature to expand the usage scenarios. Summary of the Invention

[0005] In order to solve the defects of poor solubility, poor biocompatibility, and high cost of existing temperature-responsive polymer materials, the present invention provides a new type of temperature-responsive material with thermochromic properties that is easy to adjust the lower critical solution temperature.

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

[0007] A multi-branched polyamide having a pyrrolidone ring on the main chain and a controllable multi-branched structure, and having the following structural units:

[0008]

[0009]

[0010] Wherein the values of x and y are integers from 2 to 20, and the values of m, n, p, q, r, s, t, and v are independently integers from 10 to 1660.

[0011] In one embodiment, x is 2, 4, 5, 6, or 20.

[0012] In one embodiment, y is 2 or 5.

[0013] In one embodiment, the values of m, n, p, q, r, s, t, and v are independently 15 - 80.

[0014] In one embodiment, the degree of branching of the multi - branched polyamide is from 0.0075% to 50%.

[0015] In one embodiment, the lower critical solution temperature of the multi - branched polyamide aqueous solution varies with concentration; the variation range of the lower critical solution temperature is 10 - 80 °C;

[0016] In one embodiment, the lower critical solution temperature of the branched polyamide varies in the range of 5 - 80 °C in salt ion solutions with different concentrations and types.

[0017] In one embodiment, the prepared hyper - branched polyamide has a pyrrolidone ring on the main chain and forms a multi - branched chain.

[0018] In one embodiment, the multi - branched polyamide is configured into a multi - branched polyamide aqueous solution according to different mass fraction ratios; for the prepared multi - branched polyamide aqueous solution, the concentration ranges from 0.5% to 2.0% by mass fraction, and the lower critical solution temperature that varies with concentration gradually decreases from 80 °C to 63 °C.

[0019] In one embodiment, the multi - branched polyamide aqueous solution undergoes a reversible change in visible transmittance before and after the lowest critical solution temperature, and the transmittance changes from 97% to 5%.

[0020] In one embodiment, when the concentration of the multi - branched polyamide aqueous solution is increased from 0.5% to 2.0% by mass fraction, the lower critical solution temperature decreases from 55 °C to 35 °C.

[0021] In one embodiment, when the concentration of the multi - branched polyamide aqueous solution is increased from 0.5% to 2.0% by mass fraction, the lower critical solution temperature decreases from 38 °C to 25 °C.

[0022] In one embodiment, when the concentration of the multi - branched polyamide aqueous solution is increased from 0.5% to 2.0% by mass fraction, the lower critical solution temperature decreases from 32 °C to 16 °C.

[0023] In some embodiments of the present invention, when the concentration of the multi - branched polyamide aqueous solution is increased from 0.5% to 2.0% by mass fraction, the lower critical solution temperature decreases from 30 °C to 10 °C.

[0024] In one embodiment, when the concentration of the multi - branched polyamide aqueous solution is increased from 0.5% to 2.0% by mass fraction, the lower critical solution temperature decreases from 27 °C to 46 °C.

[0025] In one embodiment, when the concentration of the multi-branched polyamide aqueous solution is increased from 0.5% by mass to 2.0%, the lowest critical solution temperature is decreased from 15 °C to 35 °C.

[0026] In one embodiment, when the concentration of the multi-branched polyamide aqueous solution is increased from 0.5% by mass to 2.0%, the lowest critical solution temperature is decreased from 48 °C to 70 °C.

[0027] In one embodiment, in a sodium chloride solution in which the concentration of the multi-branched polyamide is decreased from 4.0 mol / L to 0.1 mol / L, the lowest critical solution temperature is increased from 5 °C to 30 °C; in a calcium chloride solution in which the concentration is decreased from 2.0 mol / L to 0.1 mol / L, the lowest critical solution temperature is decreased from 80 to 36 °C.

[0028] The second object of the present invention is to provide a method for preparing a multi-branched polyamide, comprising the following steps:

[0029] Step 1, itaconic acid and a diamine are respectively dissolved in a solvent, mixed evenly, and allowed to stand and precipitate to obtain a white salt monomer. After separation and drying, an itaconic acid diamine salt monomer is obtained; the diamine is one or a combination of straight-chain or branched diamines having 2 to 20 carbon atoms; the branched diamine is a diamine having 1 to 2 branched groups on the main chain carbon of the diamine; the branched group is methyl, ethyl, propyl or isopropyl;

[0030] Step 2, the itaconic acid diamine salt monomer prepared in Step 1 is heated and reacted in a solvent to obtain an amino acid monomer with a pyrrolidone ring;

[0031] Step 3, the amino acid monomer with a pyrrolidone ring prepared in Step 2 is heated under an inert atmosphere to obtain a linear polyamide;

[0032] Step 4, the linear polyamide prepared in Step 3 is heated and reacted with a branching center under an inert atmosphere to form a controllable multi-branched structure, obtaining a branched polyamide; the branching center includes a straight-chain or branched diamine, triamine, tetraamine, hexaamine or octaamine having 2 to 20 carbon atoms; the branched diamine is a diamine having 1 to 2 branched groups on the main chain carbon of the diamine, and the branched group is methyl, ethyl, propyl or isopropyl; the triamine is tris(2-aminoethyl)amine; the tetraamine, hexaamine and octaamine are dendritic polyamide amines.

[0033] In one embodiment, the diamine includes 1,2-diaminoethane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane or 1,20-diaminotetracosane.

[0034] In one embodiment, the branching center includes 1,2-diaminoethane, 1,5-diaminopentane, tris(2-aminoethyl)amine, tetraamino PAMAM, hexaamino PAMAM, octaamino PAMAM, or tris(2-aminoethyl)amine.

[0035] In one embodiment, in Steps 1 and 2, the solvent includes ethanol, water, or methanol.

[0036] In one embodiment, in Steps 3 and 4, the heating condition is 170 - 240 °C; the reaction time is 1 - 20 h.

[0037] In one embodiment, the method is specifically as follows:

[0038] Step 2-1: Dissolve itaconic acid and 1,5-diaminopentane in absolute ethanol respectively. After mixing them evenly and standing for precipitation, a white salt monomer is obtained. After filtration and drying, a powdery itaconic acid 1,5-diaminopentane salt monomer is obtained.

[0039] Step 2-2: Dissolve the dried itaconic acid 1,5-diaminopentane salt monomer in deionized water and place it in a single-neck flask. Heat it to 110 °C for reflux condensation, and magnetically stir and react for 24 h. Then, through drying, an amino acid monomer with a slightly viscous liquid pyrrolidone ring is obtained.

[0040] Step 2-3: Place the dried amino acid monomer with a pyrrolidone ring in a three-neck flask. Under nitrogen conditions, heat it to 170 - 240 °C, stir and react for 1 - 20 h for condensation polymerization to obtain a linear polyamide.

[0041] Step 2-4: Add tris(2-aminoethyl)amine and conduct a thermal shock hyperbranched reaction under a nitrogen atmosphere. Heat it to 170 - 240 °C and react for 1 - 20 h to obtain a hyperbranched polyamide.

[0042] The third object of the present invention is to provide the application of the above-mentioned multi-branched polyamide in temperature-responsive materials.

[0043] The multi-branched polyamide can change color in response to temperature and can be applied to the field of intelligent response materials, such as intelligent response windows, thermochromic glass, etc.

[0044] The present invention can control the concentration of the hyperbranched polyamide to regulate the lower critical solution temperature of the hyperbranched polyamide aqueous solution to adapt to complex application scenarios.

[0045] Beneficial effects:

[0046] The present invention prepares a novel temperature-responsive material with thermochromic properties and a minimum critical solution temperature (LCST) adjustable by concentration. The thermochromic multi-branched polyamide has a molecular weight of 4,000 to 1,000,000 and a branching degree of 0.0075% to 50%.

[0047] The multi-branched polyamide of the present invention can control the LCST 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 LCST and its variation range by using different diamines and different types and concentrations of salts; the LCST range is 80 °C - 10 °C.

[0048] The preparation method of the present invention uses itaconic acid and diamine to first prepare an amino acid monomer with a pyrrolidone ring on the main chain by the salt monomer method, and then forms a linear polyamide by melt polymerization, and then adds a branching center to form a multi-branched structure; the preparation method is simple, the post-treatment is easy, and it is environmentally friendly.

[0049] The thermochromic multi-branched polyamide prepared by the present invention can provide different response temperature schemes to adapt to complex application scenarios. Description of the Drawings

[0050] The 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 to the present application; in the drawings:

[0051] Figure 1 is the structural diagram of the multi-branched polyamide prepared by the present invention;

[0052] Figure 2 is the step schematic diagram of the thermochromic multi-branched polyamide prepared in Examples 2, 3, and 4 of the present invention;

[0053] Figure 3 is the 1H nuclear magnetic resonance spectrum of the linear polyamide in Comparative Example 2 and the three-branched polyamide prepared in Example 3;

[0054] Figure 4 is the picture of the 2.00% multi-branched polyamide solution prepared in Example 3 at 25 °C and 35 °C;

[0055] Figure 5 is the transmittance of the 2.00% multi-branched polyamide prepared in Comparative Example 2 and Example 3 at different temperatures at a visible light wavelength of 550 nm;

[0056] Figure 6 is the transmittance of the 1.00% multi-branched polyamide prepared in Comparative Example 3 and Example 7 at different temperatures at a visible light wavelength of 550 nm. Detailed implementation manners

[0057] The technical solutions 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 the embodiments of the present invention, rather than all of the embodiments. The experimental methods in the following embodiments are all conventional methods in the art unless otherwise specified. However, those skilled in the art can easily understand that the specific material ratios, process conditions and their 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.

[0058] Example 1

[0059] Preparation of hyperbranched polyamide: 6.505 g (50 mmol) of itaconic acid, 3.005 g (50 mmol) of 1,2-diaminoethane, 50 mL of absolute ethanol. The method includes the following steps:

[0060] (1) Dissolve 6.505 g of itaconic acid and 3.005 g of 1,2-diaminoethane in 25 mL of absolute ethanol respectively. After mixing them evenly and standing for precipitation to obtain white salt monomers, and then after filtration and drying, powdery itaconic acid and ethylenediamine monomers are obtained.

[0061] (2) Dissolve the dried salt monomers in deionized water and place them in a single-neck flask. Heat to 110 °C for reflux condensation, stir magnetically for 24 h, and then through drying, amino acid monomers of pyrrolidone ring with slightly viscous liquid are obtained;

[0062] (3) Place the dried salt monomers in a three-neck flask, and carry out stirring condensation polymerization at 180 °C under nitrogen for 4 h to obtain linear polyamide.

[0063] (4) Add the branching center 1,2-diaminoethane and react at 180 °C for 1 h under nitrogen atmosphere to obtain binary branched polyamide, such as Figure 1 ① in, where x is 2, y is 2, n is 50, and m is 50;

[0064] (5) Prepare binary branched polyamide solutions of 0.5%, 0.75%, 1.0%, 1.5% and 2.0% by mass fraction from the prepared hyperbranched polyamide.

[0065] Example 2

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

[0067] (1) Dissolve 6.505 g of itaconic acid and 5.089 g of 1,5-diaminopentane in 25 mL of absolute ethanol respectively. After mixing them evenly and allowing them to stand for precipitation, a white salt monomer is obtained. After filtration and drying, a powdery itaconic acid and 1,5-pentanediamine salt monomer is obtained.

[0068] (2) Dissolve the dried salt monomer in deionized water and place it in a single-necked flask. Heat it to 110 °C for reflux condensation, and stir the reaction magnetically for 24 h. Then, through drying, an amino acid monomer with a slightly viscous liquid pyrrolidone ring is obtained;

[0069] (3) Place the dried salt monomer in a three-necked flask, and carry out stirring condensation polymerization at 190 °C under nitrogen conditions for 4 h to obtain a linear polyamide.

[0070] (4) Add the branching center 1,5-diaminopentane and react at 180 °C for 1 h under a nitrogen atmosphere to obtain a binary-branched polyamide, such as Figure 1 ① in which x is 5, y is 5, n is 45, and m is 50;

[0071] (5) Prepare binary-branched polyamide solutions of 0.5%, 0.75%, 1.0%, 1.5%, and 2.0% by mass fraction from the prepared hyperbranched polyamide.

[0072] Example 3

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

[0074] (1) Dissolve 6.505 g of itaconic acid and 5.089 g of 1,5-diaminopentane in 25 mL of absolute ethanol respectively. After mixing them evenly and allowing them to stand for precipitation, a white salt monomer is obtained. After filtration and drying, a powdery itaconic acid and 1,5-pentanediamine salt monomer is obtained.

[0075] (2) Dissolve the dried salt monomer in deionized water and place it in a single-necked flask. Heat it to 110 °C for reflux condensation, and stir the reaction magnetically for 24 h. Then, through drying, an amino acid monomer with a slightly viscous liquid pyrrolidone ring is obtained;

[0076] (3) Place the dried salt monomer in a three-necked flask, and carry out stirring condensation polymerization at 190 °C under nitrogen conditions for 4 h to obtain a linear polyamide.

[0077] (4) Add the branching center tris(2-aminoethyl)amine and react at 180 °C for 1 h under a nitrogen atmosphere to obtain a ternary-branched polyamide, such as Figure 1② in it, where x is 5, m is 30, n is 30, and p is 33;

[0078] (5) Prepare ternary branched polyamide solutions with mass fractions of 0.5%, 0.75%, 1.0%, 1.5%, and 2.0% from the prepared hyperbranched polyamide.

[0079] Example 4

[0080] Preparation of hyperbranched polyamide: 6.505 g (50 mmol) of itaconic acid, 5.089 g (50 mmol) of 1,5-diaminopentane, 50 mL of absolute ethanol. The method includes the following steps:

[0081] (1) Dissolve 6.505 g of itaconic acid and 5.089 g of 1,5-diaminopentane in 25 mL of absolute ethanol respectively. After mixing them evenly and standing for precipitation to obtain white salt monomers, and then through filtration and drying, powdery itaconic acid and 1,5-pentanediamine salt monomers are obtained.

[0082] (2) Dissolve the dried salt monomers in deionized water and place them in a single-neck flask. Heat to 110 °C for reflux condensation, and magnetically stir and react for 24 h. Then through drying, amino acid monomers of pyrrolidone rings in the form of slightly viscous liquids are obtained;

[0083] (3) Place the dried salt monomers in a three-neck flask, and carry out stirring condensation polymerization at 190 °C under nitrogen for 4 h to obtain linear polyamide.

[0084] (4) Add branched center tetraamino PAMAM and react at 180 °C for 1 h under a nitrogen atmosphere to obtain quaternary branched polyamide, such as Figure 1 ③ in it, where x is 5, m is 20, n is 22, p is 21, and q is 20;

[0085] (5) Prepare quaternary branched polyamide solutions with mass fractions of 0.5%, 0.75%, 1.0%, 1.5%, and 2.0% from the prepared hyperbranched polyamide.

[0086] Example 5

[0087] Preparation of hyperbranched polyamide: 6.505 g (50 mmol) of itaconic acid, 5.089 g (50 mmol) of 1,5-diaminopentane, 50 mL of absolute ethanol. The method includes the following steps:

[0088] (1) Dissolve 6.505 g of itaconic acid and 5.089 g of 1,5-diaminopentane in 25 mL of absolute ethanol respectively. After mixing them evenly and standing for precipitation to obtain white salt monomers, and then through filtration and drying, powdery itaconic acid and 1,5-pentanediamine salt monomers are obtained.

[0089] (2) Dissolve the dried salt monomer in deionized water and place it in a single-necked flask. Heat it to 110 °C for reflux condensation, stir magnetically for 24 h, and then obtain the amino acid monomer of pyrrolidone ring in the form of a slightly viscous liquid through drying.

[0090] (3) Place the dried salt monomer in a three-necked flask, and carry out stirring condensation polymerization at 190 °C under nitrogen for 4 h to obtain a linear polyamide.

[0091] (4) Add the branched center hexaamino PAMAM and react at 180 °C for 1 h under a nitrogen atmosphere to obtain a six-arm branched polyamide, such as Figure 1 ④ in which x is 5, m is 15, n is 18, p is 15, q is 20, r is 18, s is 18;

[0092] (5) Prepare six-arm branched polyamide solutions with mass fractions of 0.5%, 0.75%, 1.0%, 1.5% and 2.0% from the prepared hyperbranched polyamide.

[0093] Example 6

[0094] Preparation of hyperbranched polyamide: 6.505 g (50 mmol) of itaconic acid, 5.089 g (50 mmol) of 1,5-diaminopentane, 50 mL of absolute ethanol. The method comprises the following steps:

[0095] (1) Dissolve 6.505 g of itaconic acid and 5.089 g of 1,5-diaminopentane in 25 mL of absolute ethanol respectively. After mixing them evenly and standing for precipitation to obtain a white salt monomer, and then through filtration and drying, a powdery itaconic acid and 1,5-pentanediamine salt monomer are obtained.

[0096] (2) Dissolve the dried salt monomer in deionized water and place it in a single-necked flask. Heat it to 110 °C for reflux condensation, stir magnetically for 24 h, and then obtain the amino acid monomer of pyrrolidone ring in the form of a slightly viscous liquid through drying.

[0097] (3) Place the dried salt monomer in a three-necked flask, and carry out stirring condensation polymerization at 190 °C under nitrogen for 4 h to obtain a linear polyamide.

[0098] (4) Add the branched center octaamino PAMAM and react at 180 °C for 1 h under a nitrogen atmosphere to obtain an eight-arm branched polyamide, such as Figure 1 ⑤ in which x is 5, m is 20, n is 18, p is 21, q is 20, r is 21, s is 20, t is 19, v is 22;

[0099] (5) The prepared hyperbranched polyamide was formulated into octa-branched polyamide solutions with mass fractions of 0.5%, 0.75%, 1.0%, 1.5% and 2.0%.

[0100] Example 7

[0101] Preparation of hyperbranched polyamide: 6.505 g (50 mmol) of itaconic acid, 2.204 g (25 mmol) of 1,4-diaminobutane, 2.905 g (25 mmol) of 1,6-diaminohexane, 50 mL of absolute ethanol. The method comprises the following steps:

[0102] (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 absolute ethanol. After mixing them evenly and standing for precipitation to obtain a white salt monomer, and then after filtration and drying, a powdery itaconic acid and 1,4-diaminobutane / 1,6-diaminohexane salt monomer was obtained.

[0103] (2) The dried salt monomer was dissolved in deionized water and placed in a single-necked flask, heated to 110 °C for condensation reflux, and magnetically stirred for reaction for 24 h, and then through drying, an amino acid monomer with a slightly viscous liquid pyrrolidone ring was obtained;

[0104] (3) The dried salt monomer was placed in a three-necked flask, and under nitrogen conditions, it was stirred and condensation polymerized at 190 °C for 4 h to obtain a linear polyamide.

[0105] (4) 1,5-Diaminopentane as the branching center was added and reacted at 180 °C for 1 h under a nitrogen atmosphere to obtain a binary-branched polyamide, as shown in Figure 1 ①, where x is 4 and 6, y is 5, m is 70, and n is 80;

[0106] (5) The prepared hyperbranched polyamide was formulated into binary-branched polyamide solutions with mass fractions of 0.5%, 0.75%, 1.0%, 1.5% and 2.0%.

[0107] Example 8

[0108] Preparation of hyperbranched polyamide: 13.010 g (100 mmol) of itaconic acid, 4.509 g (75 mmol) of 1,2-diaminoethane, 7.864 g (25 mmol) of 1,20-diaminodocosane, 50 mL of absolute ethanol. The method comprises the following steps:

[0109] (1) Dissolve 13.010 g of itaconic acid, 4.509 g of 1,2-diaminoethane, and 7.864 g of 1,20-diaminodecane in 25 mL of absolute ethanol respectively. After mixing them evenly and allowing them to stand for precipitation, a white salt monomer is obtained. After filtration and drying, a powdery itaconic acid and 1,2-diaminoethane / 1,20-diaminodecane salt monomer is obtained.

[0110] (2) Dissolve the dried salt monomer in deionized water and place it in a single-necked flask. Heat it to 110 °C for reflux condensation, and stir magnetically for 24 h. Then, through drying, an amino acid monomer of pyrrolidone ring in the form of a slightly viscous liquid is obtained;

[0111] (3) Place the dried salt monomer in a three-necked flask, and under nitrogen conditions, stir and condense and polymerize at 190 °C for 4 h to obtain a linear polyamide.

[0112] (4) Add the branching center tris(2-aminoethyl)amine and react at 180 °C for 1 h under a nitrogen atmosphere to obtain a ternary branched polyamide, as shown in ② in Figure 1 where x is 2 and 20, m is 30, n is 65, and p is 50;

[0113] (5) Prepare 0.5%, 0.75%, 1.0%, 1.5%, and 2.0% ternary branched polyamide solutions by configuring the prepared hyperbranched polyamide according to the mass fraction.

[0114] Comparative Example 1

[0115] Prepare 0.5%, 0.75%, 1.0%, 1.5%, and 2.0% linear polyamide solutions by configuring the linear polyamide prepared in step (2) of Example 1 according to the mass fraction.

[0116] Comparative Example 2

[0117] Prepare 0.5%, 0.75%, 1.0%, 1.5%, and 2.0% linear polyamide solutions by configuring the linear polyamide prepared in step (2) of Example 2 according to the mass fraction.

[0118] Comparative Example 3

[0119] Prepare 0.5%, 0.75%, 1.0%, 1.5%, and 2.0% linear polyamide solutions by configuring the linear polyamide prepared in step (2) of Example 7 according to the mass fraction.

[0120] Comparative Example 4

[0121] Prepare 0.5%, 0.75%, 1.0%, 1.5%, and 2.0% linear polyamide solutions by configuring the linear polyamide prepared in step (2) of Example 8 according to the mass fraction.

[0122] Comparative Example 5

[0123] Compared with the previously published patent CN119350641A, "Branched Polyamide and Preparation Method"

[0124] Preparation of hyperbranched polyamide: 6.505 g (50 mmol) of itaconic acid, 5.089 g (50 mmol) of 1,5-diaminopentane, 50 mL of absolute ethanol. The method includes the following steps:

[0125] (1) Dissolve 6.505 g of itaconic acid and 5.089 g of 1,5-diaminopentane in 25 mL of absolute ethanol respectively. After mixing them evenly and standing for precipitation to obtain white salt monomers, and then through filtration and drying, powdery itaconic acid and 1,5-pentanediamine salt monomers are obtained.

[0126] (2) Place the dried salt monomers in a three-necked flask, and carry out stirring condensation polymerization at 180 °C under nitrogen for 6 h to obtain linear polyamide.

[0127] (3) Carry out thermal shock hyperbranched reaction on the linear polyamide at 210 °C for 5 h under nitrogen atmosphere to obtain hyperbranched polyamide;

[0128] (4) Prepare 0.5%, 0.75%, 1.0%, 1.5% and 2.0% hyperbranched polyamide solutions according to the mass fraction of the prepared hyperbranched polyamide.

[0129] Previously, we proposed a polyamide with a hyperbranched structure obtained by thermal shock, but its structure is difficult to control. At the same time, in the synthesis process, it has high energy consumption, long reaction time, cumbersome steps, and a small performance adjustment range. For example, the lowest critical solution temperature range is only 16 - 37 °C. Therefore, in this invention patent, amino acid monomers with pyrrolidone rings on the main chain are first prepared by the salt monomer method using itaconic acid and diamine, and then linear polyamide is formed by melt polymerization, and then a branching center is added to form a multi-branched structure; the multi-branched polymer synthesized by this method has a clear structure, and the molecular weight and degree of branching can be simply controlled by adjusting the feeding ratio of the branching center, with a wide molecular weight distribution range and a wide lowest critical solution temperature adjustment range.

[0130] Test Example

[0131] (1) Synthesis of multi-branched polyamide

[0132] The synthesis of a controllable multi-branched structure is demonstrated by gel permeation chromatography and 1H nuclear magnetic resonance characterization tests on linear polyamide and hyperbranched polyamide.

[0133] Such as Figure 3As shown in the figure, through 1H nuclear magnetic resonance testing, after adding the branching center reaction, the absorption peaks of the hydrogen spectrum of the linear polyamide in the comparative example and the terpolymer-branched polyamide in Example 3 were analyzed. Compared with the linear polyamide, the terpolymer-branched polyamide significantly showed a methylene absorption peak belonging to the branching center, which was consistent with the results of the terpolymerization reaction.

[0134] As shown in Table 1, after adding different branching centers to carry out the branching reaction, the molecular weight increased significantly, especially the weight-average molecular weight. The weight-average molecular weight of the linear polyamide in Comparative Example 1 increased from 6750 to 22500 in Example 1. The weight-average molecular weight of the linear polyamide in Comparative Example 2 increased from 7800 to 23800 in Example 2, 21500 in Example 3, 23000 in Example 4, 24000 in Example 5, and 24900 in Example 6. At the same time, the weight-average molecular weight of 7500 in Comparative Example 3 increased to 24800 in Example 7, and the weight-average molecular weight of 7900 in Comparative Example 4 increased to 26500 in Example 8. Moreover, compared with the comparative examples, the molecular weight distribution of the examples also became wider, which was in line with the molecular weight change and molecular weight distribution change after the branching structure. At the same time, the molecular weight controllability of Examples 1-8 was greater than that of Comparative Example 5, and the range was wider. Thus, it was convenient to obtain a polymer with a clearer and more controllable structure. At the same time, the multi-branched polyamide had a wider range of lower critical solution temperatures.

[0135] Table 1 Number-average molecular weight, weight-average molecular weight, and molecular weight distribution index of linear polyamide in the comparative example and multi-branched polyamide in the example

[0136]

[0137]

[0138] (2) Thermochromic properties of multi-branched polyamide

[0139] By measuring the lower critical solution temperature of the linear polyamide in Comparative Example 2 and the terpolymer-branched polyamide in Example 3 with different concentrations, as shown in Table 2, it can be obtained that due to the too low molecular weight of the linear polyamide in Comparative Example 2, its hydrophilicity was too strong, and no temperature-responsive behavior occurred. However, by adding a branching center and then carrying out a branching reaction, its molecular weight could be increased, making it in a hydrophilic-hydrophobic balance state, thus showing a temperature-responsive color change behavior. Moreover, compared with Comparative Example 5, the adjustment range of the lower critical solution temperature was wide. For example, Figure 5 , at 25 °C, the terpolymer-branched polyamide solution remained transparent, while at 35 °C, the terpolymer-branched polyamide solution became turbid.

[0140] Table 2-1 Lower critical solution temperature of the linear polyamide in Comparative Example 2 and the terpolymer-branched polyamide in Example 3 with different concentrations

[0141]

[0142] Table 2-2 Lower critical solution temperature of linear polyamide in the comparative example and multi-branched polyamides with different concentrations in the examples

[0143]

[0144]

[0145] To further verify the thermochromic response performance, the linear polyamide prepared in the comparative example and the hyperbranched polyamide sample with a mass fraction of 2.00% prepared in Example 2 were tested by an ultraviolet-visible spectrophotometer. As Figure 6 shown, it can be seen that for the linear polyamide in the comparative example, the visible light transmittance at 550 nm remained unchanged at 96.5% at 25 - 45 °C, while for the ternary branched polyamide with 2.00%, the transmittance rapidly decreased from 95% to 5% before and after the response temperature of 35 °C. As Figure 6 shown, for the binary branched polyamide prepared in Example 7, the light transmittance changed rapidly at 27 - 30 °C. As the concentration of the multi-branched polyamide increases, the intermolecular hydrogen bonds between its molecular chains are more likely to form, and the aggregation of polymer chains is more likely to occur, resulting in a lower lower critical solution temperature.

[0146] In addition, to explore the effect of salts on the lower critical solution temperature of multi-branched polyamides, the lower critical solution temperatures of the ternary branched polyamide in Example 3 were measured under different concentrations and types of salts. As shown in Tables 3-1 and 3-2, it can be seen that in sodium chloride solutions, the higher the concentration, the higher the ionic strength and the stronger the ionic hydration ability, resulting in a decrease in the binding ability between the ternary branched polyamide and water, thus bringing a lower lower critical solution temperature. In the case of calcium chloride, the same-charge repulsion effect dominates. The higher the concentration, the more uniformly the ternary branched polyamide is dispersed, the stronger its binding ability with water, and the higher the temperature at which aggregation occurs, resulting in a higher lower critical solution temperature.

[0147] Table 3-1 Lower critical solution temperature of the ternary branched polyamide in Example 3 in sodium chloride solutions with different concentrations

[0148]

[0149] Table 3-2 Lower critical solution temperature of the ternary branched polyamide in Example 3 in calcium chloride solutions with different concentrations

[0150]

[0151]

[0152] In summary, the present invention prepares a novel temperature-responsive material, multi-branched polyamide with thermochromic property and easy adjustment of the lowest critical solution temperature. It uses itaconic acid and linear diamine or branched diamine to first prepare amino acid monomers with pyrrolidone rings on the main chain through the salt monomer method, and then forms linear polyamide through melt polymerization, and then adds a branching center to form a multi-branched structure. The preparation method is simple, the post-treatment is easy, and it is environmentally friendly. The lowest critical solution temperature of the aqueous solution of the multi-branched polyamide varies with the concentration. For example, when the concentration of the hyperbranched polyamide prepared in Example 3 ranges from 0.5% to 2.0% by mass fraction, the lowest critical solution temperature changes from 55 °C to 35 °C.

[0153] The thermochromic multi-branched polyamide with an adjustable lowest 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 intelligent response performance.

[0154] The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A multi-branched polyamide, characterized in that, It has a pyrrolidone ring on the main chain and is a controllable multi-branched structure, having the structural units shown below: Wherein the values of x and y are integers from 2 to 20, and the values of m, n, p, q, r, s, t, and v are integers from 10 to 1660.

2. The preparation method of the multi-branched polyamide described in claim 1, characterized in that, It includes the following steps: Step 1, dissolve itaconic acid and diamine in a solvent respectively, mix them evenly, let them stand and precipitate to obtain a white salt monomer, after separation and drying, obtain the itaconic acid diamine salt monomer; the diamine is one or a combination of linear or branched diamines with C2-C20; the branched diamine is a diamine having 1-2 branched groups on the main chain carbon of the diamine; the branched group is methyl, ethyl, propyl or isopropyl; Step 2, heat and react the itaconic acid diamine salt monomer prepared in Step 1 in a solvent to obtain an amino acid monomer with a pyrrolidone ring; Step 3, heat the amino acid monomer with a pyrrolidone ring prepared in Step 2 under an inert atmosphere to react to obtain a linear polyamide; Step 4, heat and react the linear polyamide prepared in Step 3 with a branching center under an inert atmosphere to form a controllable multi-branched structure to obtain a branched polyamide; the branching center includes a linear or branched diamine, triamine, tetraamine, hexaamine or octaamine with C2-C20; the branched diamine is a diamine having 1-2 branched groups on the main chain carbon of the diamine, and the branched group is methyl, ethyl, propyl or isopropyl; the triamine is tris(2-aminoethyl)amine; the tetraamine, hexaamine and octaamine are dendritic polyamide amines.

3. The preparation method of a multi-branched polyamide according to claim 2, characterized in that, In Steps 1 and 2, the solvent includes ethanol, water or methanol.

4. The preparation method of a multi-branched polyamide according to claim 2, characterized in that, In Steps 3 and 4, the heating condition is 170-240 °C; the reaction time is 1-20 h.

5. The preparation method of a multi-branched polyamide according to claim 2, characterized in that, In Step 4, the reaction ratio of the branching center to the linear polyamide is 1:13280 to 1:

20.

6. The preparation method of a multi-branched polyamide according to claim 2, characterized in that, The method specifically is: Step 2-1, dissolve itaconic acid and 1,5-diaminopentane in absolute ethanol respectively, mix them evenly and let them stand and precipitate to obtain a white salt monomer, and after filtration and drying, obtain a powdery itaconic acid 1,5-diaminopentane salt monomer; Step 2-2, dissolve the dried itaconic acid 1,5-diaminopentane salt monomer in deionized water and place it in a single-neck flask, heat it to 110 °C for reflux condensation, stir magnetically and react for 24 h, and then through drying, obtain an amino acid monomer with a slightly viscous liquid pyrrolidone ring; Step 2-3, place the dried amino acid monomer with a pyrrolidone ring in a three-neck flask, heat it to 170-240 °C under nitrogen conditions, stir and react for 1-20 h to carry out condensation polymerization to obtain a linear polyamide; Step 2-4, add tris(2-aminoethyl)amine to carry out a thermal shock hyperbranched reaction under a nitrogen atmosphere, heat it to 170-240 °C, and react for 1-20 h to obtain a hyperbranched polyamide.

7. Application of a multi-branched polyamide prepared by the method of Claim 1 or any one of Claims 2-6 in a temperature-responsive material.

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