A core-shell type multi-arm azide polyether, a preparation method and application thereof

Abstract

This invention belongs to the field of energetic adhesives technology, and provides a core-shell multi-arm azido polyether, its preparation method, and its applications. The core-shell multi-arm azido polyether of this invention has the structure shown in Formula I. The core-shell multi-arm azido polyether of this invention uses a hyperbranched polyether as the core and an azido polyether as the arms, and is stable under neutral and alkaline conditions, expanding its application range; simultaneously, the branching degree of the core can be significantly controlled, causing the originally linear azido polyether to exhibit a highly branched state. Examples show that the branching degree of the core-shell multi-arm azido polyether of this invention can be controlled within the range of 0.3 to 0.6; when used as an energetic adhesive, the core-shell multi-arm azido polyether provided by this invention can better combine with isocyanate curing agents to form polyurethane elastomers.

Description

Technical Field

[0001] This invention relates to the field of energetic adhesives, and more particularly to a core-shell type multi-arm azidopolyether, its preparation method, and its application. Background Technology

[0002] As a crucial component of solid propellants, binders react with curing agents to form a three-dimensional cross-linked network structure, effectively binding other components in the solid propellant together. Therefore, the performance of the binder directly affects the mechanical properties, low-temperature performance, and storage resistance of the solid propellant. Thus, the preparation and application of novel binder materials are a vital foundation for the development of solid propellants. Due to the advantages of azide binders compared to other binders, such as low sensitivity, no smoke, high burning rate, and low signal characteristics, azide-based functional binders are attracting increasing attention.

[0003] Liu Jianxin et al. (Liu Jianxin, Wang Cundong, Pan Hongbo, Zhang Lihua. Research progress on energetic azido polymer adhesives [J]. Polymer Bulletin, 2014(09):10-18.) introduced homopolymerized energetic azido polyether adhesives such as glycidyl azidoether (GAP), poly-3-azidomethyl-3-methyloxetane (PAMMO), and 3,3-bisazidomethyloxetane (PBAMO). Homopolymerized azido polyethers are linear polymers, and after reacting with isocyanate curing agents, they basically maintain a linear state, which limits the mechanical properties of polyurethane elastomers cured from linear azido polyethers. Therefore, modifying linear azido polyethers into branched structures, so that they form a three-dimensional network structure during the curing process, can result in better mechanical properties. Therefore, how to modify energetic adhesives to have branched structures is an urgent need.

[0004] Ehsan Mohammadifar et al. (Ehsan Mohammadifar, Ali Bodaghi, Abbas Dadkhahtehrani, Ali Nemati Kharat, Mohsen Adeli, and Rainer Haag. Green Synthesis of Hyperbranched Polyglycerol at Room Temperature[J].ACS Macro Letters, 2017(6):35-40.) studied a method for the cationic polymerization of glycidol initiated by citric acid to form hyperbranched polyethers. By changing the monomer feed ratio and reaction temperature, the degree of branching of the hyperbranched polyethers can be controlled from 0.32 to 0.56. However, since its polymerization center is a citric acid unit containing ester groups, it is easily hydrolyzed and unstable under neutral and alkaline conditions, which limits its application development. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a core-shell multi-arm azido polyether, its preparation method, and its applications. The core-shell multi-arm azido polyether provided by this invention contains only ether bonds in its structure, is chemically stable, insoluble in water, soluble only in organic solvents, and stable under neutral and alkaline conditions.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a core-shell type multi-arm azidopolyether having the structure shown in Formula I:

[0008]

[0009] In Equation I, n is 1 to 5.

[0010] This invention also provides a method for preparing the core-shell multi-arm azido polyether described above, comprising the following steps:

[0011] Raw material 1 with the structure shown in Formula 5, Lewis acid catalyst and first polar organic solvent are mixed and subjected to cationic ring-opening polymerization to obtain product 1 with the structure shown in Formula 1.

[0012] The raw material 2 having the structure shown in Formula 6 and the product 1 are copolymerized in a second polar organic solvent to obtain the product 2 having the structure shown in Formula 7.

[0013] The product 2, alkali metal azide salt, and third polar organic solvent are mixed and subjected to an azide reaction to obtain the core-shell multi-arm azide polyether.

[0014]

[0015]

[0016] In Formula 6, X includes -F, -Cl, -Br, or -I;

[0017]

[0018] In Formula 7, X includes -F, -Cl, -Br, or -I.

[0019] Preferably, the molar ratio of the raw material 1 to the Lewis acid catalyst is (1-5):1.

[0020] Preferably, the temperature of the cationic ring-opening polymerization reaction is -20 to 30°C, and the time is 36 to 72 hours.

[0021] Preferably, the molar ratio of raw material 2 to product 1 is (1-20):1.

[0022] Preferably, the copolymerization reaction is carried out at a temperature of -10 to 10°C for a time of 12 to 48 hours.

[0023] Preferably, the molar ratio of product 2 to alkali metal azide salt is 1:(1.1 to 1.5).

[0024] Preferably, the temperature of the azide reaction is 60–98°C and the time is 15–48 h.

[0025] The present invention also provides the application of the core-shell multi-arm azido polyether described in the above technical solution or the core-shell multi-arm azido polyether prepared by the preparation method described in the above technical solution as an energetic adhesive.

[0026] This invention provides a core-shell type multi-arm azidopolyether having the structure shown in Formula I:

[0027]

[0028] In Equation I, n is 1 to 5.

[0029] The core-shell multi-arm azidopolyether provided by this invention is a hyperbranched polyether With a core of azide polyether The branching mechanism allows the hyperbranched polyether core to be stable under neutral and alkaline conditions, expanding the application range of core-shell multi-arm azido polyethers. Simultaneously, the branching degree of the core can be significantly controlled, enabling the originally linear azido polyether to exhibit a highly branched state. The results of the examples show that the branching degree of the core-shell multi-arm azido polyether provided by this invention can be controlled within a range of 0.3–0.6. When used as an energetic adhesive, the core-shell multi-arm azido polyether provided by this invention can better combine with isocyanate curing agents to form polyurethane elastomers.

[0030] This invention also provides a method for preparing the core-shell multi-arm azido polyether described in the above technical solution, comprising the following steps: mixing raw material 1 having the structure shown in Formula 5, a Lewis acid catalyst, and a first polar organic solvent to perform a cationic ring-opening polymerization reaction to obtain product 1 having the structure shown in Formula 1; performing a copolymerization reaction between raw material 2 having the structure shown in Formula 6 and product 1 in a second polar organic solvent to obtain product 2 having the structure shown in Formula 7; and mixing product 2, an alkali metal azide salt, and a third polar organic solvent to perform an azide reaction to obtain the core-shell multi-arm azido polyether. The preparation method provided by this invention effectively controls the branching degree of the hyperbranched polyether core by adjusting the temperature of the cationic ring-opening polymerization reaction of 3-ethyl-3-hydroxymethylepoxybutane with the structure shown in Formula 5 to -20 to 30°C, thereby obtaining core-shell multi-arm azido polyethers with different degrees of branching. The results of the embodiments show that the branching degree of the core-shell multi-arm azido polyether provided by the present invention can be controlled within the range of 0.3 to 0.6. Specifically, when the cationic ring-opening polymerization reaction of 3-ethyl-3-hydroxymethylepoxybutane is at -20°C, the branching degree of the core-shell multi-arm azido polyether is 0.23; when the cationic ring-opening polymerization reaction of 3-ethyl-3-hydroxymethylepoxybutane is at 0°C, the branching degree of the core-shell multi-arm azido polyether is 0.34; and when the cationic ring-opening polymerization reaction of 3-ethyl-3-hydroxymethylepoxybutane is at 30°C, the branching degree of the core-shell multi-arm azido polyether is 0.56. When used as an energetic binder, the preparation method of the core-shell multi-arm azido polyether provided by the present invention can select a suitable branching degree of the core-shell multi-arm azido polyether according to the actual mechanical performance requirements of solid fuels. Attached Figure Description

[0031] Figure 1 The NMR spectra of the hyperbranched polyether cores prepared in Examples 1-4;

[0032] Figure 2 The NMR spectra of the core-shell multi-arm azido polyethers prepared in Examples 1-4 are shown.

[0033] Figure 3 Infrared spectra of the core-shell multi-arm azido polyethers prepared in Examples 1-4;

[0034] Figure 4 The DSC temperature curves of the core-shell multi-arm azido polyethers prepared in Examples 1-4 are shown.

[0035] Figure 5 The thermogravimetric curves of the core-shell multi-arm azido polyethers prepared in Examples 1-4 are shown. Detailed Implementation

[0036] This invention provides a core-shell type multi-arm azidopolyether having the structure shown in Formula I:

[0037]

[0038] In this invention, n in Formula I is 1 to 5.

[0039] The core-shell multi-arm azidopolyether provided by this invention is a hyperbranched polyether With a core of azide polyether The arms allow the hyperbranched polyether core to be stable under neutral and alkaline conditions, expanding the application range of core-shell multi-arm azido polyethers; at the same time, the branching degree of the core can be greatly controlled, making the originally linear azido polyether exhibit a highly branched state.

[0040] In this invention, the molar percentage of the azide polyether in the core-shell multi-arm azide polyether is preferably ≥75%, and more preferably 75-85%.

[0041] In this invention, the arms of the core-shell multi-arm azidopolyether preferably further include... In the formula, X includes -F, -Cl, -Br, or -I. In this invention, the... The molar percentage of the core-shell multi-arm azido polyether is preferably ≤5%, and more preferably 1-5%.

[0042] This invention also provides a method for preparing the core-shell multi-arm azido polyether described above, comprising the following steps:

[0043] Raw material 1 with the structure shown in Formula 5, Lewis acid catalyst and first polar organic solvent are mixed and subjected to cationic ring-opening polymerization to obtain product 1 with the structure shown in Formula 1.

[0044] The raw material 2 having the structure shown in Formula 6 and the product 1 are copolymerized in a second polar organic solvent to obtain the product 2 having the structure shown in Formula 7.

[0045] The product 2, alkali metal azide salt, and a third polar organic solvent are mixed and subjected to an azide reaction to obtain the core-shell multi-arm azide polyether.

[0046] Unless otherwise specified, all raw materials used in this invention are preferably commercially available products.

[0047] In this invention, a raw material 1 having the structure shown in Formula 5, a Lewis acid catalyst, and a first polar organic solvent are mixed and subjected to a cationic ring-opening polymerization reaction to obtain a product 1 having the structure shown in Formula 1.

[0048] In this invention, the raw material 1 has the structure shown in Formula 5:

[0049] In this invention, the Lewis acid catalyst preferably comprises a boron trifluoride diethyl ether complex and / or a boron trifluoride tetrahydrofuran complex, and more preferably a boron trifluoride diethyl ether complex.

[0050] In this invention, the first polar organic solvent preferably includes one or more of dichloromethane, trichloromethane, and dichloroethane, and more preferably dichloromethane. In this invention, the water content of the first polar organic solvent is preferably <50 ppm.

[0051] In this invention, the molar ratio of the raw material 1 to the Lewis acid catalyst is preferably (1-5):1, more preferably (2-4):1, and even more preferably 3:1. In this invention, the volume of the first polar organic solvent is preferably 5-20 times the volume of the raw material 1, and more preferably 10 times.

[0052] In this invention, the cationic ring-opening polymerization reaction is preferably carried out in an anhydrous and oxygen-free environment.

[0053] In this invention, mixing the raw material 1 having the structure shown in Formula 5, the Lewis acid catalyst, and the first polar organic solvent preferably includes the following steps:

[0054] The first polar organic solvent is placed into the reaction vessel and subjected to dehydration and deoxygenation operations to obtain the starting solution.

[0055] A portion of the initiator solution and the Lewis acid catalyst are first mixed to obtain a first mixture;

[0056] The raw material 1 and the remaining starting solution are mixed to obtain the raw material 1 solution;

[0057] The raw material 1 solution is added dropwise to the first mixture.

[0058] In this invention, the temperature of the starting solution is preferably -20 to 30°C.

[0059] In this invention, the first mixing is preferably carried out under stirring conditions, and the stirring speed is preferably 500-800 rpm; the first mixing time is preferably 0.5 h.

[0060] In this invention, the raw material 1 solution is preferably added dropwise.

[0061] In this invention, during the dripping process, the temperature of the first mixture is preferably -20 to 30°C.

[0062] In this invention, the temperature of the cationic ring-opening polymerization reaction is preferably -20 to 30°C, and the time is preferably 36 to 72 hours, more preferably 48 hours.

[0063] After the cationic ring-opening polymerization reaction, the present invention preferably proceeds directly to the subsequent polymerization reaction without any further treatment.

[0064] In this invention, product 1 has the structure shown in Formula 1:

[0065]

[0066] In this invention, the degree of branching of product 1 is preferably 0.2 to 0.6.

[0067] After obtaining product 1 with the structure shown in Formula 1, the present invention performs a copolymerization reaction between raw material 2 with the structure shown in Formula 6 and product 1 in a second polar organic solvent to obtain product 2 with the structure shown in Formula 7.

[0068] In this invention, the raw material 2 has the structure shown in Formula 6:

[0069] In Formula 6, X includes -F, -Cl, -Br, or -I.

[0070] In this invention, the second polar organic solvent preferably comprises N,N-dimethylformamide and / or dimethyl sulfoxide. In this invention, the water content of the second polar organic solvent is preferably <50 ppm.

[0071] In this invention, the molar ratio of raw material 2 to product 1 is preferably (1-20):1, more preferably 5:1. In this invention, the volume of the second polar organic solvent is preferably 5-20 times the volume of product 2, more preferably 10 times.

[0072] In this invention, the copolymerization reaction of raw material 2 having the structure shown in Formula 6 and product 1 in a second polar organic solvent preferably includes the following steps:

[0073] The raw material 2 is mixed with the second polar organic solvent to obtain a solution of raw material 2;

[0074] The solution of raw material 2 is added dropwise to product 1.

[0075] In this invention, the third mixing is preferably carried out under stirring conditions, and the stirring speed is preferably 500 to 800 rpm.

[0076] In this invention, the preferred rate of adding the raw material 2 solution is 3 to 5 mL / h.

[0077] In this invention, the temperature of the copolymerization reaction is preferably -10 to 10°C, more preferably 0°C; the time is preferably 12 to 48 hours, more preferably 24 hours.

[0078] Following the copolymerization reaction, the present invention preferably further includes a quenching reaction and a post-treatment. In this invention, the quenching agent for the quenching reaction is preferably an aqueous solution of sodium carbonate; the mass percentage of the aqueous solution of sodium carbonate is preferably 5%.

[0079] In this invention, the post-treatment preferably includes: sequentially washing, drying, and removing the second polar organic solvent from the organic phase obtained by separating the reaction solution after the quenching reaction. In this invention, the washing preferably includes sequential washing with sodium carbonate aqueous solution, deionized water, and saturated sodium chloride aqueous solution. In this invention, the reagent used for washing with the sodium carbonate aqueous solution is preferably an aqueous sodium carbonate solution; the mass percentage of the sodium carbonate aqueous solution is preferably 5%. In this invention, the drying is preferably drying with a desiccant; the desiccant used for drying with the desiccant is preferably anhydrous sodium sulfate. In this invention, the method for removing the second polar organic solvent is preferably vacuum distillation; this invention does not specifically limit the parameters of the vacuum distillation, as long as the second polar organic solvent can be removed.

[0080] In this invention, product 2 has the structure shown in Formula 7:

[0081]

[0082] In Equation 7, X includes -F, -Cl, -Br, or -I.

[0083] After obtaining product 2 with the structure shown in Formula 7, the present invention mixes product 2, alkali metal azide salt and third polar organic solvent to carry out azide reaction to obtain the core-shell type multi-arm azide polyether.

[0084] In this invention, the alkali metal azide salt preferably includes sodium azide.

[0085] In this invention, the third polar organic solvent preferably comprises N,N-dimethylformamide and / or dimethyl sulfoxide, more preferably dimethyl sulfoxide. In this invention, the water content of the third polar organic solvent is preferably <50 ppm.

[0086] In this invention, the molar ratio of product 2 to the alkali metal azide salt is preferably 1:1.1 to 1.5. This invention does not specifically limit the amount of the third polar organic solvent used, as long as it is sufficient to fully dissolve product 2 and the alkali metal azide salt.

[0087] In this invention, mixing the product 2, the alkali metal azide salt, and the third polar organic solvent preferably includes the following steps:

[0088] The product 2 and the third polar organic solvent were mixed to obtain a solution of product 2;

[0089] The alkali metal azide salt is mixed with the product 2 solution in batches for the fifth time.

[0090] In this invention, the fourth mixing is preferably carried out under stirring conditions. In this invention, the temperature of the product 2 solution is preferably 60°C.

[0091] In this invention, the fifth mixing is preferably carried out under stirring conditions.

[0092] In this invention, the temperature of the azide reaction is preferably 60-98°C, and the time is preferably 15-48 h, more preferably 30 h.

[0093] Following the azide reaction, the present invention preferably further includes post-treatment. In the present invention, the post-treatment preferably includes: sequentially performing solid-liquid separation, removal of a third polar organic solvent, dichloromethane extraction, washing the dichloromethane extract phase, drying the dichloromethane extract phase, and removing dichloromethane. In the present invention, the solid-liquid separation is preferably filtration. In the present invention, the method for removing the third polar organic solvent is preferably vacuum distillation. In the present invention, the washing preferably includes sequential washing with deionized water and washing with saturated sodium chloride. In the present invention, the drying is preferably drying with a desiccant, and the desiccant preferably includes anhydrous sodium sulfate. In the present invention, the method for removing dichloromethane is preferably vacuum distillation.

[0094] This invention provides the application of the core-shell multi-arm azido polyether described in the above technical solution or the core-shell multi-arm azido polyether prepared by the preparation method described in the above technical solution as an energetic adhesive.

[0095] When the core-shell multi-arm azido polyether provided by this invention is used as an energetic binder, this invention does not specifically limit the amount of the core-shell multi-arm azido polyether used. The appropriate degree of branching of the core-shell multi-arm azido polyether can be selected according to the actual mechanical performance requirements of the solid fuel.

[0096] The following detailed description, in conjunction with embodiments, illustrates the core-shell multi-arm azido polyether, its preparation method, and its applications provided by the present invention. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0097] Example 1

[0098] After drying the three-necked flask to remove trace amounts of moisture, 50 mL of ultra-dry dichloromethane was added to the flask. The flask was then placed in a low-temperature constant-temperature reaction bath, maintaining the reaction system at -20°C. 2.82 g (0.02 mol) of boron trifluoride diethyl ether complex was added, and the mixture was stirred for 0.5 h. 4.64 g (0.04 mol) of 3-ethyl-3-oxabutane methanol was dissolved in 50 mL of ultra-dry dichloromethane and added dropwise through a constant-pressure dropping funnel. After the addition was complete, the reaction was allowed to proceed for 48 h to obtain hyperbranched polyether. 1 mL of the hyperbranched polyether was extracted using a syringe for characterization. The reaction temperature was then adjusted to 0℃, and 18.5 g of epichlorohydrin (0.2 mol) was dissolved in 50 mL of ultra-dry dichloromethane. The solution was placed in a constant pressure dropping funnel and added dropwise over 10 h. The polymerization reaction was carried out for 24 h. After the polymerization reaction was completed, the reaction was quenched with a 5% sodium carbonate aqueous solution. The organic phase was washed successively with a 5% sodium carbonate aqueous solution, deionized water, and saturated sodium chloride solution. After drying with anhydrous sodium sulfate, the organic solvent was removed by vacuum distillation to obtain a core-shell multi-arm polyether with a branching degree of 0.23.

[0099] 2 g (0.1 mol) of core-shell multi-arm polyether was added to a round-bottom flask, followed by 30 mL of anhydrous N,N-dimethylformamide. After stirring until homogeneous, the reaction system temperature was raised to 60 °C. While stirring, 0.845 g (0.13 mol) of sodium azide was added in batches. After all the sodium azide was added, the temperature was raised to 98 °C, and the reaction was stirred for 30 h. After the reaction was completed, the mixture was cooled to room temperature. Excess sodium azide and the salt produced in the reaction were removed by filtration. The mixture was then distilled under reduced pressure to remove a large amount of N,N-dimethylformamide. Dichloromethane was added, and the remaining small amount of N,N-dimethylformamide was extracted with deionized water and saturated sodium chloride solution. After drying with anhydrous sodium sulfate, the mixture was distilled under reduced pressure to obtain a core-shell multi-arm azide polyether with a branching degree of 0.23.

[0100] Based on the feed ratio, in core-shell multi-arm azidopolyether In this case, n is 5, and the molar percentage content is 83%.

[0101] Example 2

[0102] After drying the three-necked flask to remove trace amounts of moisture, 50 mL of ultra-dry dichloromethane was added to the flask. The flask was then placed in a low-temperature constant-temperature reaction bath, maintaining the reaction system at 0°C. 2.82 g (0.02 mol) of boron trifluoride diethyl ether complex was added and stirred for 0.5 h. 4.64 g (0.04 mol) of 3-ethyl-3-oxabutane methanol was dissolved in 50 mL of ultra-dry dichloromethane and added dropwise through a constant-pressure dropping funnel. After the addition was complete, the reaction was allowed to proceed for 48 h to obtain hyperbranched polyether. 1 mL of the hyperbranched polyether was extracted using a syringe for characterization. The reaction temperature was then adjusted to 0°C. 18.5 g (0.2 mol) of epichlorohydrin was dissolved in 50 mL of ultra-dry dichloromethane and added dropwise through a constant-pressure dropping funnel over 10 h. The polymerization reaction was then allowed to proceed for 24 h. After the polymerization reaction was completed, the reaction was quenched with a 5% sodium carbonate aqueous solution. The organic phase was washed sequentially with a 5% sodium carbonate aqueous solution, deionized water and saturated sodium chloride solution. After drying with anhydrous sodium sulfate, the organic solvent was removed by vacuum distillation to obtain a core-shell multi-arm polyether with a branching degree of 0.34.

[0103] 2 g (0.1 mol) of core-shell multi-arm polyether was added to a round-bottom flask, followed by 30 mL of anhydrous N,N-dimethylformamide. After stirring until homogeneous, the reaction system temperature was raised to 60 °C. While stirring, 0.845 g (0.13 mol) of sodium azide was added in batches. After all the sodium azide was added, the temperature was raised to 98 °C, and the reaction was stirred for 30 h. After the reaction was completed, the mixture was cooled to room temperature. Excess sodium azide and the salt produced in the reaction were removed by filtration. The mixture was then distilled under reduced pressure to remove a large amount of N,N-dimethylformamide. Dichloromethane was added, and the remaining small amount of N,N-dimethylformamide was extracted with deionized water and saturated sodium chloride solution. After drying with anhydrous sodium sulfate, the mixture was distilled under reduced pressure to obtain a core-shell multi-arm azide polyether with a branching degree of 0.34.

[0104] Based on the feed ratio, in core-shell multi-arm azidopolyether In this case, n is 5, and the molar percentage content is 83%.

[0105] Example 3

[0106] After drying the three-necked flask to remove trace amounts of moisture, 50 mL of ultra-dry dichloromethane was added to the flask. The flask was then placed in a low-temperature constant-temperature reaction bath, maintaining the reaction system at 20°C. 2.82 g (0.02 mol) of boron trifluoride diethyl ether complex was added, and the mixture was stirred for 0.5 h. 4.64 g (0.04 mol) of 3-ethyl-3-oxabutane methanol was dissolved in 50 mL of ultra-dry dichloromethane and added dropwise through a constant-pressure dropping funnel. After the addition was complete, the reaction was allowed to proceed for 48 h to obtain hyperbranched polyether. 1 mL of the hyperbranched polyether was extracted using a syringe for characterization. The reaction temperature was then adjusted to 0°C, and 18.5 g (0.2 mol) of epichlorohydrin was dissolved in 50 mL of ultra-dry dichloromethane and added dropwise through a constant-pressure dropping funnel over 10 h. The polymerization reaction was then allowed to proceed for 24 h. After the polymerization reaction was completed, the reaction was quenched with a 5% sodium carbonate aqueous solution. The organic phase was washed sequentially with a 5% sodium carbonate aqueous solution, deionized water and saturated sodium chloride solution. After drying with anhydrous sodium sulfate, the organic solvent was removed by vacuum distillation to obtain a core-shell multi-arm polyether with a branching degree of 0.43.

[0107] 2 g (0.1 mol) of core-shell multi-arm polyether was added to a round-bottom flask, followed by 30 mL of anhydrous N,N-dimethylformamide. After stirring until homogeneous, the reaction system temperature was raised to 60 °C. While stirring, 0.845 g (0.13 mol) of sodium azide was added in batches. After all the sodium azide was added, the temperature was raised to 98 °C, and the reaction was stirred for 30 h. After the reaction was completed, the mixture was cooled to room temperature. Excess sodium azide and the salt produced in the reaction were removed by filtration. The mixture was then distilled under reduced pressure to remove a large amount of N,N-dimethylformamide. Dichloromethane was added, and the remaining small amount of N,N-dimethylformamide was extracted with deionized water and saturated sodium chloride solution. After drying with anhydrous sodium sulfate, the mixture was distilled under reduced pressure to obtain a core-shell multi-arm azide polyether with a branching degree of 0.43.

[0108] Based on the feed ratio, in core-shell multi-arm azidopolyether In this case, n is 5, and the molar percentage content is 83%.

[0109] Example 4

[0110] After drying a three-necked flask to remove trace amounts of moisture, 50 mL of ultra-dry dichloromethane was added to the flask. The flask was then placed in a low-temperature constant-temperature reaction bath, maintaining the reaction system at 30°C. 2.82 g (0.02 mol) of boron trifluoride diethyl ether complex was added, and the mixture was stirred for 0.5 h. 4.64 g (0.04 mol) of 3-ethyl-3-oxabutane methanol was dissolved in 50 mL of ultra-dry dichloromethane and added dropwise through a constant-pressure dropping funnel. After the addition was complete, the reaction was allowed to proceed for 48 h to obtain hyperbranched polyether. 1 mL of the hyperbranched polyether was extracted using a syringe for characterization. The reaction temperature was then adjusted to 0°C, and 18.5 g (0.2 mol) of epichlorohydrin was dissolved in 50 mL of ultra-dry dichloromethane and added dropwise through a constant-pressure dropping funnel over 10 h. The polymerization reaction was then allowed to proceed for 24 h. After the polymerization reaction was completed, the reaction was quenched with a 5% sodium carbonate aqueous solution. The organic phase was washed sequentially with a 5% sodium carbonate aqueous solution, deionized water and saturated sodium chloride solution. After drying with anhydrous sodium sulfate, the organic solvent was removed by vacuum distillation to obtain a core-shell multi-arm polyether with a branching degree of 0.56.

[0111] 2 g (0.1 mol) of core-shell multi-arm polyether was added to a round-bottom flask, followed by 30 mL of anhydrous N,N-dimethylformamide. After stirring until homogeneous, the reaction system temperature was raised to 60 °C. While stirring, 0.845 g (0.13 mol) of sodium azide was added in batches. After all the sodium azide was added, the temperature was raised to 98 °C, and the reaction was stirred for 30 h. After the reaction was completed, the mixture was cooled to room temperature. Excess sodium azide and the salt produced in the reaction were removed by filtration. The mixture was then distilled under reduced pressure to remove a large amount of N,N-dimethylformamide. Dichloromethane was added, and the remaining small amount of N,N-dimethylformamide was extracted with deionized water and saturated sodium chloride solution. After drying with anhydrous sodium sulfate, the mixture was distilled under reduced pressure to obtain a core-shell multi-arm azide polyether with a branching degree of 0.56.

[0112] Based on the feed ratio, in core-shell multi-arm azidopolyether In this case, n is 5, and the molar percentage content is 83%.

[0113] Figure 1 The NMR spectra of the hyperbranched polyether cores prepared in Examples 1-4 are shown below. Figure 1 It can be seen that: 21.2–22.2 ppm is the carbon atom absorption peak of the terminal unit T in the hyperbranched polyether structure, 22.2–23 ppm is the carbon atom absorption peak of the linear unit L in the hyperbranched polyether structure, and 23–23.5 ppm is the carbon atom absorption peak of the branched unit D in the hyperbranched polyether structure. The area intensities of the three peaks, S1 and S2, were obtained using integral curves. 21.2-22.2 S 22.2-23 With S 23-23.5 Then, according to Formula 1, the degree of branching of the hyperbranched polyether core in the core-shell multi-arm azido polyether can be calculated.

[0114]

[0115] The branching degree of the hyperbranched polyether core obtained in Example 1 was calculated to be 0.23, the branching degree of the hyperbranched polyether core obtained in Example 2 was 0.34, the branching degree of the hyperbranched polyether core obtained in Example 3 was 0.43, and the branching degree of the hyperbranched polyether core obtained in Example 4 was 0.56.

[0116] Figure 2 The NMR spectra of the core-shell multi-arm azido polyethers prepared in Examples 1-4 are shown; from Figure 2 It can be seen that the peaks at 68.00-69.00 ppm and 77.75-78.05 ppm belong to the characteristic peaks of the methylene groups bonded to the carbon atoms on the backbone of the core-shell multi-arm azido polyether. The characteristic peaks at 60.50-62.00 ppm, belonging to the carbon atoms bonded to the hydroxyl groups, disappear in the NMR spectrum of the core-shell multi-arm azido polyether, indicating that the primary hydroxyl groups have completely reacted. The characteristic peaks at 44.13 and 47.13 ppm are the characteristic peaks of the chloromethyl carbon atoms. After the azidation reaction, the characteristic shift of the chloromethyl group disappears, and new chemical shifts appear at 51.45 and 53.21 ppm, which are the proton absorption peaks and carbon atom absorption peaks of the methylene groups bonded to the azido groups, indicating successful azidation.

[0117] Figure 3 The infrared spectra of the core-shell multi-arm azido polyethers prepared in Examples 1-4 are shown below. Figure 3 It can be seen that: 3450cm -1 The broad peak at 2100 cm⁻¹ is the absorption peak of the stretching vibration of the hydroxyl group. -1 The absorption peak is due to the stretching vibration of the azide group, at 745 cm⁻¹. -1 The complete disappearance of the C-Cl stretching vibration absorption peak indicates complete azidation. (1109 cm⁻¹) -1 The absorption peaks are due to the stretching vibrations of the ether bonds. The appearance of these stretching vibration absorption peaks indicates that a core-shell multi-arm azido polyether has been successfully prepared.

[0118] Figure 4 The DSC temperature rise curves of the core-shell multi-arm azido polyethers prepared in Examples 1-4 are shown below. Figure 4 It can be seen that the glass transition temperature of the prepared core-shell multi-arm azido polyether is -56.0℃ to -57.4℃, indicating that it has good low-temperature mechanical properties.

[0119] Figure 5 The thermogravimetric curves of the core-shell multi-arm azido polyethers prepared in Examples 1-4 are shown below. Figure 5It can be seen that the prepared core-shell multi-arm azido polyether loses less than 5% of its weight at 200℃. The first stage of decomposition occurs in the temperature range of 269–301℃, and the second stage of decomposition occurs in the temperature range of 454–472℃. This indicates that the prepared core-shell multi-arm azido polyether has good high-temperature performance.

[0120] 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. Use of a core-shell type multi-arm azido polyether as an energetic binder, characterized in that, The preparation method of the core-shell multi-arm azido polyether is as follows: After drying the three-necked flask to remove trace amounts of moisture, add 50 mL of ultra-dry dichloromethane to the flask. Then place the flask in a low-temperature constant-temperature reaction bath, maintaining the reaction system at 30°C. Add 2.82 g of boron trifluoride diethyl ether complex and stir for 0.5 h; then add 4.64 g of... 3-Ethyl-3-oxabutane methanol was dissolved in 50 mL of ultra-dry dichloromethane and added dropwise through a constant-pressure dropping funnel. After the addition was complete, the reaction was carried out for 48 h to obtain hyperbranched polyether. 1 mL of the hyperbranched polyether was extracted with a syringe for characterization. Then, the reaction temperature was adjusted to 0 °C, and 18.5 g of epichlorohydrin was dissolved in 50 mL of ultra-dry dichloromethane and added dropwise through a constant-pressure dropping funnel over 10 h. The polymerization reaction was carried out for 24 h. After the polymerization reaction was completed, the reaction was quenched with a 5% sodium carbonate aqueous solution. The organic phase was washed successively with a 5% sodium carbonate aqueous solution, deionized water, and saturated sodium chloride solution. After drying with anhydrous sodium sulfate, the organic solvent was removed by vacuum distillation to obtain a core-shell multi-arm polyether with a branching degree of 0.

56. 2g of core-shell multi-arm polyether was added to a round-bottom flask, followed by 30mL of anhydrous N,N-dimethylformamide. After stirring until homogeneous, the reaction system temperature was raised to 60℃. While stirring, 0.845g of sodium azide was added in batches. After all the sodium azide was added, the temperature was raised to 98℃, and the reaction was stirred for 30h. After the reaction was completed, the mixture was cooled to room temperature. Excess sodium azide and the salt produced in the reaction were removed by filtration. The mixture was then distilled under reduced pressure to remove a large amount of N,N-dimethylformamide. Dichloromethane was added, and the remaining small amount of N,N-dimethylformamide was extracted with deionized water and saturated sodium chloride solution. After drying with anhydrous sodium sulfate, the mixture was distilled under reduced pressure to obtain a core-shell multi-arm azide polyether with a branching degree of 0.56.

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