A multifunctional phthalonitrile resin containing a biphenyl dither and an internal alkynyl group structure, and a preparation method and application thereof

Abstract

This invention provides a multifunctional phthalonitrile resin containing biphenyl diether and internal alkyne groups, its preparation method, and its applications, belonging to the field of high-temperature thermosetting resin technology. The resin uses polyarylene ether phenylacetylene as a modifier, and through alkyne modification and the introduction of multiple phthalonitrile functional groups, it can achieve dual crosslinking and curing via nitrile cyclization and alkyne addition. The preparation method of the resin is as follows: synthesis of hydroxyl-terminated polyarylene ether phenylacetylene, nitrile end-capping modification, preparation of halogenated phthalonitrile monomers, alkyne-phthalonitrile coupling and purification; the resin is first prepolymerized, then cured after programmed temperature rise. The resin of this invention has a low melting point, a wide processing window, good solubility, a maximum thermal decomposition temperature >530℃ after curing, a high carbon residue at 800℃, and excellent thermo-oxidative stability and ablation resistance. It can be widely used in high-temperature lightweight structural and functional materials fields such as aerospace, hypersonic vehicles, deep space exploration, and advanced thermal protection.

Description

Technical Field

[0001] This invention relates to the field of high-temperature thermosetting resin technology, and particularly to a multifunctional phthalonitrile resin containing biphenyl diether and endynyl group structures, its preparation method, and its application. Background Technology

[0002] Phthalonil resin is a significant high-performance thermosetting resin. Its nitrile groups can undergo cyclization trimerization at high temperatures, forming a stable cross-linked network of aromatic heterocyclic rings such as triazine rings, isoindoline rings, and phthalocyanine rings. This results in excellent thermo-oxidative stability, high carbon residue, good mechanical strength, and flame retardant properties, making it an ideal matrix for ultra-high temperature structural materials. With the rapid development of hypersonic vehicles, deep space exploration, and other fields, higher requirements are being placed on resins for lightweighting, high temperature resistance, high carbon residue, ablation resistance, and long-term stable service.

[0003] Currently, traditional phthalonitrile resins have obvious technical shortcomings: (1) The upper limit of heat resistance of conventional resins is insufficient, making it difficult to meet the long-term service requirements of high temperature above 400℃; (2) The monomers have high melting points, poor solubility, narrow processing windows, and limited molding processes; (3) The curing temperature of single nitrile crosslinking systems is high, the rate is slow, and the crosslinking density is low; (4) The molecular chains are rigid and brittle, and the high temperature mechanical retention rate is insufficient, making them prone to cracking; (5) There is a lack of resin systems that combine low melting point, easy processing, high crosslinking, and ultra-high temperature resistance into an integrated structure.

[0004] Alkyne groups offer advantages such as low-temperature crosslinking, high-temperature non-degradation, and significantly improved carbon residue. They can form a dual crosslinking system with nitrile groups, significantly broadening the processing window and enhancing thermal stability. However, existing technologies lack integrated high-temperature resistant resins modified with polyarylene ether phenylacetylene as a modifier, containing multiple phthalonitrile functional groups, and also lack a complete and controllable preparation route from polymerization, end-capping, halogenation to coupling, making it difficult to achieve precise structural control and stable performance improvement.

[0005] To address the aforementioned issues, this invention provides a multifunctional phthalonitrile resin containing biphenyl diether and an internal alkyne group. Through alkyne modification and molecular structure design, it achieves a synergistic improvement in low melting point, easy processing, high crosslinking density, and high-temperature heat resistance, meeting the urgent needs of cutting-edge fields such as aerospace for high-temperature resins. Summary of the Invention

[0006] The main objective of this invention is to provide a multifunctional phthalonitrile resin containing biphenyl diether and internal alkyne groups. Using polyarylene ether phenylacetylene as a modifier, the resin undergoes alkyne modification and the introduction of multiple phthalonitrile functional groups to form a multifunctional phthalonitrile resin with a nitrile-alkyne dual crosslinking system. This resin features a low melting point, good processability, moderate curing temperature, excellent thermal stability, and high carbon residue at 800℃.

[0007] To achieve the above objectives, the present invention provides a multifunctional phthalonitrile resin containing a biphenyl diether and an endynyl group structure, wherein the multifunctional phthalonitrile resin comprises a structural unit of the following general formula (I): (I).

[0008] The method for preparing a multifunctional phthalonitrile resin containing biphenyl diether and an endynyl group provided by the present invention specifically includes the following steps: S1. Preparation of hydroxyl-terminated polyarylene phenylacetylene: In an anhydrous and inert gas protected system, using biphenyl monomers, hydroquinone, and halogenated aromatic acetylene monomers as raw materials, an alkaline catalyst was added, and hydroxyl-terminated polyarylene phenylacetylene was obtained through nucleophilic aromatic substitution and stepwise polymerization. S2. Preparation of nitrile-terminated polyarylene phenylacetylene: Using a nitrile-modifying reagent as the nitrile group source, nucleophilic substitution is performed with the hydroxyl-terminated polyarylene phenylacetylene to achieve the conversion of hydroxyl to nitrile group, thereby obtaining nitrile-terminated polyarylene phenylacetylene; S3. Preparation of halogenated phthalonitrile monomers: Using aminophthalonitrile derivatives as raw materials, halogenated phthalonitriles are obtained through diazotization-halogenation substitution reaction.

[0009] S4. Preparation of multifunctional phthalonitrile: Halogenated phthalonitrile and nitrile-terminated polyarylene phenylacetylene undergo a halogenated aromatic hydrocarbon-alkynyl hydrocarbon coupling reaction to complete alkynyl modification and obtain crude multifunctional phthalonitrile. S5. The above-mentioned crude multifunctional phthalonitrile product was purified and dried under vacuum to obtain multifunctional phthalonitrile resin.

[0010] Further, in step S1, the molar ratio of the biphenyl monomer, hydroquinone, and halogenated aromatic acetylene monomer is 1:(0.2-0.3):(1.0-1.2); The molar ratio of the biphenyl monomer to the alkaline catalyst is 1:(1.5-3.0).

[0011] Further, in step S2, the molar ratio of the hydroxyl-terminated polyarylene ether phenylacetylene to the nitrifying agent is 1:(1.2-3.0); The nitrile-modifying agent is a nitro-activated phthalonitrile monomer.

[0012] Further, in step S3, the molar ratio of the aminophthalonitrile derivative to the diazotizing reagent and the halogenating reagent in the diazotization-halogenation reaction is 1:(1.0-1.5):(1.5-4.0); During the diazotization reaction, the reaction temperature is -10 to 5℃, and the reaction time is 30 min to 2 h. During the halogenation substitution reaction, the reaction temperature is 20–80℃ and the reaction time is 2–6 h.

[0013] Further, the aminophthalonitrile derivative is any one of 3-aminophthalonitrile, 4-aminophthalonitrile, 4-(3-aminophenoxy)phthalonitrile, 4-(4-aminophenoxy)phthalonitrile, and polyaminophthalonitrile; The diazotizing agent is any one of potassium nitrite, potassium nitrite, and isoamyl nitrite; The halogenated reagent is any one of potassium halide, sodium halide, ammonium halide, and cuprous halide.

[0014] Further, in step S4, the molar ratio of the halophthalonitrile to the nitrile-terminated polyarylene ether phenylacetylene is 1:(1.0~2.0); In the aforementioned haloaromatic-alkyne coupling reaction, the amount of catalyst used is 0.5–5 mol%. The catalyst is a nickel-based catalyst or a palladium-based catalyst.

[0015] Further, the multifunctional phthalonitrile resin is cured. The curing process is as follows: a curing agent is added to the multifunctional phthalonitrile resin, prepolymerization is carried out at ≥205℃ for 20-90 min, and then a gradient temperature program is used for curing. The gradient temperature program is as follows: first, heat to 210℃ and hold for 2 hours; then heat to 240℃ and hold for 4 hours; then heat to 250℃ and hold for 5 hours; then heat to 280℃ and hold for 2 hours; then heat to 320℃ and hold for 4 hours; then heat to 350℃ and hold for 2 hours; then heat to 360℃ and hold for 2 hours; finally, heat to 380℃ and hold for 2 hours to complete curing.

[0016] Furthermore, the mass ratio of the multifunctional phthalonitrile resin to the curing agent is 100:(5-20). The curing agent is one or more of the following: self-catalytic phthalonitrile, Lewis acid curing agent, and aromatic diamine curing agent.

[0017] The multifunctional phthalonitrile resin containing biphenyl diether and endynyl group structures provided by this invention can be applied to aerospace ultra-high temperature structural composite materials (including aircraft thermal protection systems, high temperature resistant protective structures for deep space exploration equipment, aircraft fuselage and wing sandwich structures, and lightweight high temperature resistant protective structures for deep space exploration equipment), ablation-resistant coatings, high temperature resistant encapsulation materials, and adhesives. It is particularly suitable for resin matrices, composite materials, and their thermal protection materials in high-temperature service scenarios above 400°C, such as aerospace, hypersonic vehicles, and deep space exploration equipment.

[0018] The beneficial effects of this invention are as follows: 1. The molecular design and modification method of this invention is novel, adopting a five-step coupling route of "hydroxyl-terminated polymerization - nitrile-terminated - halogenation activation - alkynyl coupling - temperature-programmed curing". That is, through a five-step controllable synthesis route, nucleophilic substitution, diazotization halogenation, coupling reaction and gradient curing kinetics are matched and coupled to achieve synergistic action of nitrile cyclization and alkynyl addition crosslinking. The resulting alkynyl-modified multifunctional phthalonitrile resin has low melting point, good processability, good solubility, high crosslinking density, and excellent ablation resistance and thermal stability.

[0019] 2. This invention employs stepwise controllable synthesis and atmospheric pressure gradient curing. The raw materials are readily available in commercially available markets, requiring no special or expensive equipment, which significantly reduces synthesis and curing costs and improves resource utilization.

[0020] 3. This invention uses a gradient-programmed temperature rise followed by curing to prepare a multifunctional phthalonitrile resin, which exhibits excellent thermal stability and high-temperature resistance. Its T... d5% With a maximum thermal decomposition temperature of >450℃, a maximum thermal decomposition temperature of >530℃, and a carbon residue rate of >55% at 800℃, it has a wide processing window, excellent overall performance, and can be used stably for a long time in high-temperature environments.

[0021] 4. The process of this invention is controllable, the conditions are mild, and the repeatability is good. It does not require special equipment and is suitable for laboratory preparation and large-scale engineering applications. It can be widely used in the fields of high-temperature lightweight structural and functional materials such as aerospace, hypersonic vehicles, deep space exploration, and advanced thermal protection. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0023] Figure 1 This is a synthetic route diagram of multifunctional phthalonitrile according to Example 1 of the present invention; Figure 2 The FTIR spectrum of the hydroxyl-terminated polyarylene ether phenylacetylene of Example 1 of the present invention is shown below. Figure 3 This is the 1H NMR spectrum of the hydroxyl-terminated polyarylene ether phenylacetylene of Example 1 of the present invention; Figure 4 This is the carbon NMR spectrum of the hydroxyl-terminated polyarylene ether phenylacetylene of Example 1 of the present invention; Figure 5 This is the two-dimensional NMR spectrum of the hydroxyl-terminated polyarylene phenylacetylene of Example 1 of the present invention; Figure 6The following are the XPS full spectrum and peak fitting diagrams of the hydroxyl-terminated polyarylene phenylacetylene of Example 1 of the present invention, wherein (a) is the XPS full spectrum of the hydroxyl-terminated polyarylene phenylacetylene; (b) is the XPS C1s peak diagram of the hydroxyl-terminated polyarylene phenylacetylene; and (c) is the XPS O1s peak diagram of the hydroxyl-terminated polyarylene phenylacetylene. Figure 7 The XRD pattern of the hydroxyl-terminated polyarylene ether phenylacetylene of Example 1 of this invention is shown below. Figure 8 The MALDI-TOF mass spectrum of the hydroxyl-terminated polyarylene ether phenylacetylene of Example 1 of the present invention is shown below. Figure 9 This is the TGA curve of the hydroxyl-terminated polyarylene ether phenylacetylene of Example 1 of the present invention; Figure 10 The image shows the FTIR spectrum of the nitrile-terminated polyarylene ether phenylacetylene of Example 1 of this invention. Figure 11 This is the 1H NMR spectrum of the nitrile-terminated polyarylene ether phenylacetylene of Example 1 of the present invention; Figure 12 This is the carbon NMR spectrum of the nitrile-terminated polyarylene ether phenylacetylene of Example 1 of the present invention; Figure 13 The image shows the FTIR spectrum of the halophthalonitrile of Example 1 of this invention. Figure 14 The above is the 1H NMR spectrum of the halophthalonitrile of Example 1 of the present invention; Figure 15 The carbon NMR spectrum of the halophthalonitrile of Example 1 of the present invention; Figure 16 This is the XPS X3d peak fitting diagram of the halogenated phthalonitrile of Example 1 of the present invention; Figure 17 The XRD pattern of the halophthalonitrile of Example 1 of the present invention is shown below. Figure 18 The above is the HRMS mass spectrum of the halophthalonitrile of Example 1 of the present invention; Figure 19 This is a graph showing the elemental mass ratio (EA) of the halophthalonitriles in Example 1 of the present invention; Figure 20 This is the DSC curve of the halogenated phthalonitrile of Example 1 of the present invention; Figure 21 The image shows the FTIR spectrum of the multifunctional phthalonitrile resin of Example 1 of this invention. Figure 22 The above is the 1H NMR spectrum of the multifunctional phthalonitrile resin of Example 1 of the present invention; Figure 23The carbon NMR spectrum of the multifunctional phthalonitrile resin of Example 1 of the present invention; Figure 24 The XPS full spectrum and peak fitting diagrams of the multifunctional phthalonitrile resin in Example 1 of the present invention are shown, wherein (a) is the XPS full spectrum of the multifunctional phthalonitrile; (b) is the XPS C1s peak diagram of the multifunctional phthalonitrile; (c) is the XPS O1s peak diagram of the multifunctional phthalonitrile; and (d) is the XPS N1s peak diagram of the multifunctional phthalonitrile. Figure 25 The above is an HRMS mass spectrum of the multifunctional phthalonitrile resin of Example 1 of the present invention. Figure 26 The MALDI-TOF mass spectrum of the multifunctional phthalonitrile resin of Example 1 of the present invention is shown. Figure 27 This is a graph showing the elemental mass ratio of the multifunctional phthalonitrile resin in Example 1 of the present invention. Figure 28 This is a DSC curve of the multifunctional phthalonitrile resin of Example 1 of the present invention; Figure 29 This is a curing process analysis diagram of the DSC curves of the multifunctional phthalonitrile resin under different heating rates in Example 1 of the present invention. Figure 30 This is a curing process analysis diagram of the fitting curves of the multifunctional phthalonitrile resin at different heating rates in Example 1 of the present invention. Figure 31 The TGA / DTG curves of the multifunctional phthalonitrile resin in Example 1 of this invention are shown. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0026] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention, as well as the prior art known to those skilled in the art and the description of this invention, may be implemented using any prior art methods, devices, and materials similar to or equivalent to those described, used, or made of materials in the embodiments of this invention.

[0027] Research has found that the low efficiency of conventional phthalonitrile resin curing and molding processes is mainly due to the fact that traditional phthalonitrile resins have high melting and curing temperatures, which are incompatible with conventional alkynyl modification, coupling, and curing conditions. This can easily lead to problems such as alkynyl side reactions, incomplete nitrile substitution, and insufficient crosslinking during the process, ultimately resulting in defects such as low thermal stability of the material.

[0028] Based on this, the present invention provides a multifunctional phthalonitrile resin containing biphenyl diether and endynyl group structures, which comprises structural units of the following general formula (Ⅰ): (I).

[0029] The resin contains biphenyl diether and alkynyl groups in its structure, as well as multiple phthalonitrile functional groups. It can achieve double cross-linking and curing through nitrile cyclization trimerization and alkynyl addition, thereby making the cross-linking density of the present invention high, improving the thermal stability and mechanical properties of the present invention, and making the thermal decomposition temperature >530℃ and the carbon residue rate at 800℃ high.

[0030] The present invention provides a method for preparing and curing a multifunctional phthalonitrile resin containing biphenyl diether and endynyl groups, specifically comprising the following steps: S1. Preparation of hydroxyl-terminated polyaryl ether phenylacetylene: In an anhydrous system and under inert gas protection, biphenyl monomers were added to a reaction vessel, and an anhydrous polar aprotic solvent was added and stirred until completely dissolved. Then, an alkaline catalyst was added, and the temperature was raised to 100-120℃ and stirred for 1-2 hours to allow the phenolic hydroxyl groups to be fully deprotonated to form phenolic anions. Halogenated aromatic acetylene monomers were then added to the reaction vessel, and the temperature was raised to 140-200℃ and kept at this temperature for 6-24 hours to carry out nucleophilic aromatic substitution and stepwise polymerization. Hydroquinone was added 1 hour before the end of the reaction to carry out the end-capping reaction. After the reaction was completed, the mixture was cooled to room temperature, precipitated, filtered, washed, and vacuum dried to obtain hydroxyl-terminated polyaryl ether phenylacetylene (α).

[0031] Research has revealed that conventional resin synthesis processes involving polyarylene ether phenylacetylene are inefficient. The fundamental reason lies in the high melting points and reaction temperature requirements of polyarylene ether phenylacetylene monomers, which far exceed the temperature and environmental range provided by traditional stepwise polymerization. The low-to-medium temperature conditions of conventional processes are insufficient to meet the high-temperature polymerization requirements of these monomers, easily leading to problems such as low molecular weight, incomplete hydroxyl end-capping, insufficient chain growth, and poor solubility and processability. Unlike conventional preparation methods, this invention specifically selects rigid biphenyl monomers and halogenated aromatic acetylene monomers as reactants, and adds hydroquinone before the reaction ends to further improve the hydroxyl end-capping rate of the polymer. Through a synergistic route of nucleophilic aromatic substitution and stepwise polymerization, hydroxyl-terminated polyarylene ether phenylacetylene oligomers are precisely prepared, significantly improving the system's molecular weight and subsequent reactivity. Furthermore, by strictly controlling the raw material molar ratio, reaction temperature, reaction time, and polymerization method, the molecular chain length and degree of polymerization can be controlled and adjusted. Compared with traditional polyarylene ether phenylacetylene, the hydroxyl-terminated polyarylene ether phenylacetylene prepared by this invention has a more suitable molecular weight, a higher and more stable hydroxyl-termination rate, higher structural regularity and better solubility. It can not only effectively improve the efficiency of subsequent nitrile-terminated substitution, but also provide a more stable and efficient reaction basis for subsequent halogenation activation and alkynyl-aryl coupling reaction, significantly improving the crosslinking density, heat resistance and mechanical properties of the final resin.

[0032] In this embodiment of the invention, the biphenyl monomer is 4,4'-dihydroxybiphenyl (DHBP, or dihydroxybiphenyl), which provides the phenolic hydroxyl group and aromatic ring skeleton, exhibiting high rigidity, high heat resistance, and good reactivity. In some embodiments, this invention selects a DHBP and hydroquinone (HQ) complex system, which improves hydroxyl end-capping efficiency and chain growth uniformity while ensuring the rigidity of the main chain.

[0033] In this embodiment of the invention, the halogenated aromatic acetylene monomer is a chlorinated aromatic acetylene monomer, or it may be an aromatic acetylene monomer containing other halogens. In some embodiments of the invention, the halogenated aromatic acetylene monomer is selected as 3,4-dichlorophenylacetylene (DCEA), which contains both chlorine atoms and acetylene groups in its molecular structure. After nucleophilic substitution in step S1, the crosslinkable acetylene group is retained, providing sites for subsequent coupling reactions.

[0034] In this embodiment of the invention, the molar ratio of biphenyl monomers, hydroquinone, and halogenated aromatic acetylene monomers is 1:(0.2-0.3):(1.0-1.2). Controlling the molar ratio of biphenyl monomers to halogenated aromatic acetylene monomers at 1:1.0-1.2 ensures that phenolic monomers participate in the reaction in a slightly excess or equivalent amount, allowing the polymer to stably retain hydroxyl groups (-OH) at the ends, achieving a high hydroxyl end-capping rate and providing sufficient reaction sites for subsequent nitrile end-capping. Furthermore, it ensures that the polymer has a moderate and uniform molecular weight, avoiding problems such as end-group closure, chain termination, and low molecular weight caused by excessive halogenated monomers. It also avoids raw material waste and post-processing difficulties caused by excessive phenolic monomers. In addition, a high hydroxyl end-capping rate significantly improves the substitution efficiency of nitrile end-capping in step S2, making the conversion of -OH to -CN more complete. It also improves molecular weight and structural uniformity, making the halogenation reaction in step S3 and the acetylene-aryl coupling in step S4 more stable and controllable, with fewer side reactions and higher coupling efficiency.

[0035] In some embodiments of the present invention, the molar ratio of biphenyl monomers to halogenated aromatic acetylene monomers is kept within the range of 1:(1.0 to 1.2). The amount of monomers fed can be selected according to the volume of the reaction vessel. It is necessary to ensure that the substrate is completely dissolved and fully contacted, and also to ensure that there is no large amount of boiling or agglomeration during the reaction process, and that the polymer is generated uniformly.

[0036] In this invention, the anhydrous polar aprotic solvent is one or more of N-methylpyrrolidone (NMP), N,N-dimethylamide (DMF), N,N-dimethylacetamide (DMAc), and sulfolane to ensure complete dissolution of biphenyl monomers.

[0037] In step S1 of this invention, the alkaline catalyst is selected from anhydrous alkali metal carbonates, including one or more of potassium carbonate (K2CO3), sodium carbonate (Na2CO3), and cesium carbonate (Cs2CO3), and is used to deprotonate the phenolic hydroxyl group to form an oxygen anion, thereby initiating a nucleophilic aromatic substitution reaction.

[0038] In some embodiments of the present invention, the alkaline catalyst is anhydrous potassium carbonate, which is mildly alkaline. Stepwise polymerization is carried out in an inert atmosphere and an anhydrous system, effectively avoiding problems such as monomer oxidation, chlorine atom hydrolysis, alkynyl side reactions, and deactivation of terminal hydroxyl groups. It also reduces residual metal ions and system impurities. While effectively improving hydroxyl end-capping efficiency, molecular chain length, and polymerization repeatability, it maintains the product with a low melting point and good solubility, laying a stable structural foundation for subsequent nitrile end-capping, alkynyl coupling, and high-temperature curing.

[0039] In this invention, the molar ratio of biphenyl monomer to alkaline catalyst is 1:(1.5-3.0). Preferably, the molar ratio of biphenyl monomer to alkaline catalyst is 1:2.0.

[0040] In some embodiments of the present invention, the temperature of the heat preservation reaction is 160-190°C. Appropriately increasing the reaction temperature can be beneficial to chain growth and complete substitution. The heat preservation time is 10-18h. Appropriately extending the reaction time can make the molecular chain extend more fully.

[0041] Step S1 of the present invention is carried out entirely under an anhydrous system and inert gas protection. The anhydrous system can avoid hydrolysis of chlorinated monomers and ensure the activity of substitution reaction. The inert gas is nitrogen (N2) or argon (Ar) to prevent monomer oxidation and side reactions.

[0042] S2. Preparation of nitrile-terminated polyarylene ether phenylacetylene: Hydroxyl-terminated polyarylene ether phenylacetylene was added to a reaction vessel, and anhydrous high-boiling solvent was added and stirred until completely dissolved; then a catalyst was added, and the temperature was raised to 100-120℃, and stirred for 1-2 h to allow the terminal phenolic hydroxyl groups to be fully deprotonated to form phenoxy anions; a nitrification reagent was added, and the temperature was further raised to 160-220℃, and a nucleophilic aromatic substitution reaction was carried out under inert gas protection for 4-12 h; after the reaction was completed, the mixture was cooled to room temperature, precipitated, filtered, washed, and vacuum dried to obtain nitrile-terminated polyarylene ether phenylacetylene (α-CN).

[0043] Studies have shown that conventional hydroxyl nitrification processes are inefficient, primarily because the hydroxyl groups at the ends of the polymers are inherently less reactive. Furthermore, traditional nitrification conditions are incompatible with the coexisting alkynyl groups in the molecule, leading to incomplete substitution, main chain damage, alkynyl side reactions, and low nitrile grafting efficiency. In step S2 of this invention, a nitrile-based reagent is used as the nitrile source to undergo a nucleophilic aromatic substitution reaction with the hydroxyl-terminated polyarylene ether phenylacetylene obtained in step S1. Without damaging the alkynyl group or initiating side reactions, the terminal hydroxyl group (-OH) is converted to a nitrile group (-CN), yielding a nitrile-terminated polyarylene ether phenylacetylene. This achieves a high degree of substitution from hydroxyl to nitrile, improving the system's crosslinking activity and high-temperature stability. Step 2 employs a stepwise activation method, first forming phenol-oxygen anions, then adding nitrile reagents to reduce side reactions and improve substitution selectivity; and the entire process is protected by inert gas (nitrogen or argon) to prevent high-temperature oxidation, cross-linking, and side reactions of the alkynyl group; no transition metal catalysts are used to avoid coupling side reactions of the alkynyl group; at the same time, the reaction temperature is strictly controlled at ≤220℃ to prevent thermal cross-linking of the alkynyl group at high temperatures.

[0044] In this invention, the nitrifying agent (electrophilic agent) is a nitrile-activated phthalonitrile monomer, including mononitrophthalonitrile and polynitrophthalonitrile. In some embodiments of this invention, 4-nitrophthalonitrile is selected as the nitrifying agent based on heat resistance and processability requirements. Its substitution site is specific, it has few side reactions, retains the nitrile group intact, and the nitro group is a strong electron-withdrawing group, which can efficiently activate the ortho / para positions of the benzene ring, achieving nucleophilic substitution under mild conditions, thereby improving the efficiency of nucleophilic substitution.

[0045] In some embodiments of the present invention, the molar ratio of hydroxyl-terminated polyarylene ether phenylacetylene to nitrile-activated phthalonitrile monomer is 1:(1.2-3.0). Preferably, the molar ratio of hydroxyl-terminated polyarylene ether phenylacetylene to 4-nitrophthalonitrile is 1:(2.0-3.0). Using an excess of nitrile reagent can promote a more complete substitution reaction. In the specific production process, the mass of raw materials is adjusted according to the volume of the reaction vessel to ensure uniform dissolution of the system, no local overheating, and no clumping.

[0046] In step S2 of this invention, the catalyst is an anhydrous alkali metal salt, including one or more of potassium carbonate (K2CO3), sodium carbonate (Na2CO3), cesium carbonate (Cs2CO3), and tertiary amine bases (including triethylamine, diisopropylamine, etc.). This deprotonates the terminal phenolic hydroxyl group to form a phenoxy anion, increasing nucleophilic activity and simultaneously neutralizing the nitro byproducts generated in the reaction.

[0047] In step S2 of some embodiments of the present invention, anhydrous potassium carbonate, which is mildly alkaline and does not damage the nitrile and alkynyl groups, is selected as the catalyst. The substitution is carried out under inert anhydrous conditions, which effectively avoids problems such as nitrile hydrolysis, alkynyl crosslinking, main chain breakage, and increased by-products. While significantly improving the degree of substitution of -OH to -CN, the resin structure is kept intact, the heat resistance is improved, and the processing window is widened.

[0048] In this invention, the anhydrous high-boiling-point solvent is a high-boiling-point polar aprotic solvent, including one or more of NMP, DMAc, DMF, sulfolane, and diphenyl sulfone.

[0049] It is worth noting that step S2 is also in an anhydrous system to avoid protonation of phenol oxide anions and ensure substitution efficiency.

[0050] In step S2 of some embodiments of the present invention, the nucleophilic aromatic substitution reaction temperature is 180-200°C, which balances substitution efficiency and alkynyl stability, and avoids alkynyl self-polymerization; the reaction time is 6-10 h, which can ensure a high degree of substitution while avoiding alkynyl side reactions, main chain degradation and impurity generation. Appropriately extending the reaction time can increase the degree of substitution of hydroxyl groups to nitrile groups. However, excessively long reaction time (>12 h) can easily trigger side reactions, leading to alkynyl self-polymerization, product degradation and increased impurities, which reduces the efficiency of subsequent bonding and the overall performance of the final resin. Therefore, the reaction time is controlled at 6-10 h.

[0051] S3. Preparation of halophthalonitrile monomers: The aminophthalonitrile derivative was added to an acidic medium and stirred to disperse it evenly; the temperature was lowered to -10 to 5℃, and a diazotizing reagent was slowly added dropwise, and the mixture was kept at this temperature and stirred for 30 min to 2 h to carry out the diazotization reaction and complete the preparation of the diazonium salt; then a halogenating reagent was added to the system, and the temperature was naturally raised to 20 to 80℃, and the mixture was stirred for 2 to 6 h to carry out the halogenation reaction, in which the diazonium group was replaced by a halogen atom; after the reaction was completed, the mixture was cooled to room temperature, filtered, washed, ethanol-washed, and vacuum dried to obtain the crude product; finally, the crude product was purified by recrystallization, column chromatography, or vacuum distillation to obtain high-purity halophthalonitrile (XPN).

[0052] Conventional diazonium salt-halogenation processes are inefficient and have low yields, mainly because the diazonium salt formed from aminophthalonitrile is very unstable, while traditional halogenation conditions are relatively harsh (such as heating and strong acidity). This mismatch leads to problems such as diazonium salt decomposition, numerous side reactions, incomplete halogen substitution, and damage to the nitrile group. This invention uses aminophthalonitrile derivatives as raw materials and employs a low-temperature diazotization + mild halogenation process. The amino group is efficiently converted to halogen, effectively avoiding problems such as diazonium salt explosion, nitrile group hydrolysis, halogen residue, and excessive byproducts. The prepared halogenated phthalonitrile has high purity, low melting point, high activity, and good processability. Throughout the reaction, the nitrile group (-CN) structure remains intact, stable, has good solubility, and moderate crystallinity, providing reaction sites for subsequent alkynyl coupling.

[0053] In this invention, the aminophthalonitrile derivative is one or more of 4-aminophthalonitrile, 3-aminophthalonitrile, 4-(3-aminophenoxy)phthalonitrile, 4-(4-aminophenoxy)phthalonitrile, and polyaminophthalonitrile. In the embodiments of this invention, the preferred aminophthalonitrile derivative is 4-(3-aminophenoxy)phthalonitrile, because it has a specific reaction site and high substitution selectivity; the steric hindrance and electronic effect matching between the 4-position amino group and the two nitrile groups are optimal, resulting in fewer side reactions, higher conversion rates, and a simpler product structure, facilitating subsequent precise coupling; the nitrile group exhibits strong stability, and the 4-position substitution has minimal impact on the nitrile group on the benzene ring. Under acidic, low-temperature, and heating conditions, the nitrile group does not hydrolyze, undergo addition, or break bonds, resulting in high structural integrity.

[0054] In this invention, the acidic medium is one of concentrated hydrochloric acid, dilute sulfuric acid, fluoroboric acid, phosphoric acid, and glacial acetic acid, used to provide the acidic environment required for diazotization. In embodiments of this invention, the acidic medium is preferably concentrated hydrochloric acid or dilute sulfuric acid, as these acids can stably supply the H₂ required for the reaction. +This method efficiently achieves the protonation of aromatic amino groups, improving the stability and reaction conversion rate of diazonium salts. Compared to the problems of insufficient acidity and low diazotization conversion rate of weak acids (glacial acetic acid, phosphoric acid) and high cost of fluoroboric acid, dilute hydrochloric acid and dilute sulfuric acid are suitable for the diazotization requirements of this system. The acidity is controllable and the reaction rate is stable and moderate. This avoids the incomplete diazotization reaction caused by excessively low acidity, and also avoids the defects of excessively strong acidity in concentrated strong acid systems, which cause thermal decomposition of diazonium salts and increased side reactions.

[0055] In this invention, the diazotizing agent is one or more of sodium nitrite (NaNO2), potassium nitrite, and isoamyl nitrite. In the embodiments of this invention, sodium nitrite is preferred as the diazotizing agent due to its high diazotizing efficiency and mild reaction. The reasons for this preference are: sodium nitrite can stably release nitrosyl ions in an acidic system, rapidly forming a diazonium salt with 4-(3-aminophenoxy)phthalonitrile, resulting in high conversion rate, few side reactions, no oxidation of the nitrile group, and no damage to the nitrile group (-CN); under low-temperature diazotizing conditions, sodium nitrite exhibits weak oxidizing properties and mild acidity, preventing side reactions such as nitrile group hydrolysis, addition, and bond breaking, thus ensuring the integrity of the product structure.

[0056] In this invention, the halogenating agent is one or more of potassium halide, sodium halide, cuprous halide, and ammonium halide. In some embodiments of this invention, potassium halide (KX, X = F, Cl, Br, I) is selected as the halogenating agent based on activity and purification requirements. Potassium halide has moderate halide ion activity and higher substitution efficiency, resulting in a product halogenated phthalonitrile monomer with a low melting point, moderate activity, and ease of subsequent coupling. The preferred reason is that potassium ions (K... + With a large radius and weak polarization, it can fully dissociate and release halide ions (X). - Potassium halides exhibit strong nucleophilic substitution ability, capable of completely replacing the diazonium group under mild conditions, with a substitution conversion rate significantly higher than that of sodium and ammonium salts. They also have fewer side reactions, and the nitrile group is not easily destroyed. Furthermore, potassium halides are neutral to mild in diazonium salt substitution systems, preventing side reactions such as hydrolysis, addition, and elimination of the nitrile group, thus maximizing the preservation of the -CN structure and ensuring product purity.

[0057] In some embodiments of the present invention, the molar ratio of aminophenoxyphthalonitrile derivative to diazotizing agent and halogenating agent is 1:(1.0-1.5):(1.5-4.0). An appropriate excess of halogenating agent can improve the halogenation yield and the degree of substitution. However, an excessively high excess ratio can easily introduce impurities and side reactions, so it is controlled within the range of 1.5-4.0.

[0058] In some embodiments of the present invention, the diazotization temperature is 0°C and the time is 1 hour; the halogenation substitution temperature is 50°C and the time is 4 hours, which can optimize the yield and purity of the product of step 3 of the present invention.

[0059] In step S3 of this invention, the solvent is one or more of deionized water, an ethanol / water mixture, N,N-dimethylformamide (DMF), acetone, dichloromethane, and acetonitrile, suitable for low-temperature diazotization and homogeneous reaction. In the embodiments of this invention, the solvent is selected as deionized water or an ethanol / water mixture (volume ratio of ethanol to water 1:1 to 4, preferably 1:2), because diazotization must be carried out at -10 to 5°C. The deionized water and ethanol / water mixture has a low freezing point and good low-temperature fluidity, does not freeze or separate into layers, and can ensure the stable formation of diazonium salts without decomposition or explosion. 4-(3-aminophenoxy)phthalonitrile, sodium nitrite, and potassium halide have moderate solubility in deionized water or an ethanol / water mixture, which can react fully without causing difficulties in subsequent purification due to excessive solubility.

[0060] It is worth noting that the raw materials used in step S3 of this invention are all high-purity reagents to ensure the stability of the diazonium salt, complete halogen substitution, and that the nitrile group is not damaged.

[0061] S4. Preparation of multifunctional phthalonitrile: Halogenated phthalonitrile, nitrile-terminated polyarylene ether phenylacetylene and anhydrous alkali were added to a reaction vessel. The reaction vessel was then evacuated and filled with inert gas. This process was repeated at least 3 times to ensure the reaction system was under anhydrous conditions and inert gas protection. Anhydrous solvent was added and stirred to dissolve the mixture. Then, catalyst and ligand were added, and the temperature was raised to 80–140 °C. The mixture was stirred for 6–24 h to carry out the coupling of halogenated aromatic hydrocarbons and alkynes. After the reaction was completed, the mixture was cooled to room temperature, poured into water to settle, and filtered to obtain the crude multifunctional phthalonitrile (MPN) product.

[0062] Conventional Sonogashira coupling processes struggle to achieve coexistence of nitrile and alkynyl groups, primarily because the reactivity of halogenated monomers and alkynyl compounds is mismatched, leading to problems such as catalyst deactivation, alkynyl self-polymerization, nitrile group destruction, and excessively wide molecular weight distribution.

[0063] This invention utilizes XPN and nitrile-terminated polyaryl ether phenylacetylene as raw materials to prepare MPN via a haloaryl-alkynyl coupling reaction. The MPN exhibits controllable structure, high heat resistance, and a wide processing window, making it suitable for high-end applications such as composite materials and thermal protection structures. The entire reaction is conducted under anhydrous inert conditions and mild selective catalysis, effectively avoiding problems such as alkynyl self-polymerization, nitrile decomposition, halogen removal, metal residue, and uncontrolled crosslinking. This achieves precise coupling between the halogenated monomer and the alkynyl compound, maintaining the structural integrity of the nitrile (-CN) and alkynyl (-C≡C-) groups. The resulting multifunctional phthalonitrile (i.e., alkynyl-modified polyphthalonitrile) is a multifunctional oligomer with a moderate molecular weight distribution, low melting point, good processability, and excellent high-temperature thermal stability. It can be further cured to form a highly heat-resistant network structure.

[0064] In step S4 of this invention, the catalyst is a nickel-based catalyst (Ni(COD)2, NiCl2(PPh3)2) or a palladium-based catalyst (Pd(PPh3)4, PdCl2(PPh3)2, Pd(OAc)2). In some embodiments of this invention, palladium-based catalysts are preferred, mainly because: palladium-based catalysts have high catalytic activity and strong selectivity, do not damage nitrile and alkynyl groups, and ensure the integrity of functional groups; the reaction conditions are mild (80-140°C), which can avoid the side reactions of alkynyl self-polymerization and nitrile groups caused by high temperature, resulting in fewer side reactions; the conversion efficiency is high, the dosage is low (0.5-5 mol%), and the cost is controllable.

[0065] In step S4 of this invention, the ligand is any one of tricyclohexylphosphine, 1,10-phenanthroline, 2,2'-bipyridine, and triphenylphosphine (PPh3). In embodiments of this invention, the ligand is preferably triphenylphosphine, which coordinates stably with the palladium catalyst, effectively inhibiting metal aggregation and catalyst deactivation; it has moderate steric hindrance and electronic effects, which can improve coupling selectivity and reduce side reactions; it has good solubility and can exist stably in DMF, N,N-dimethylacetamide (DMAc), and N-methylpyrrolidone (NMP).

[0066] In step S4 of this invention, the anhydrous alkali is any one of sodium carbonate, cesium carbonate, potassium phosphate, organic amines, and potassium carbonate. In some embodiments of this invention, the anhydrous alkali is one of potassium carbonate, triethylamine (TEA), or diisopropylamine, because these three anhydrous alkalis are mildly alkaline, which can neutralize the acid generated in the reaction without destroying the nitrile group or initiating alkynyl isomerization / addition; they have good solubility / dispersibility in polar solvents, resulting in a homogeneous system and stable reaction; and they are highly compatible with palladium catalysis systems, which can significantly improve coupling conversion and yield.

[0067] In step S4 of this invention, the solvent is any one of dioxane, acetonitrile, ultra-dry tetrahydrofuran (THF), or anhydrous polar aprotic solvent. In some embodiments of this invention, the solvent is NMP, DMF, or DMAc, anhydrous polar aprotic solvents, which have high solubility for monomers, catalysts, and ligands, achieving homogeneous reactions and high conversion rates; they also exhibit good high-temperature stability, not decomposing, oxidizing, or participating in side reactions at 80–140°C.

[0068] In some embodiments of the present invention, the Pd(PPh3)4+PPh3+K2CO3+NMP system is selected because it has the highest coupling efficiency and the most stable structure.

[0069] In step S4 of this invention, the molar ratio of halophthalonitrile to nitrile-terminated polyarylene ether phenylacetylene is 1:(1.0-2.0), and the amount of catalyst used is 0.5-5 mol%. The halophthalonitrile obtained in step S3 has specific reaction sites, high coupling selectivity, few side reactions, simple product structure, low melting point (<100℃), and good solubility. It matches the activity of nitrile-terminated polyarylene ether phenylacetylene, resulting in high coupling efficiency, mild reaction, and high precision in obtaining multifunctional phthalonitriles.

[0070] It is worth noting that the amount of catalyst used refers to the percentage of the amount of catalyst relative to the amount of halophthalonitrile.

[0071] In some embodiments of the present invention, the coupling temperature of the haloaryl-alkyne is 100-120°C, the time is 12h, and the molar ratio of halophthalonitrile to nitrile-terminated polyarylene ether phenylacetylene is 1:1, which can make the coupling in step S4 complete and without side reactions.

[0072] S5. The crude multifunctional phthalonitrile product obtained in step S4 is recrystallized using an ethanol / methanol mixed solvent (ethanol to methanol volume ratio of 1 to 2:1, preferably 1:1); it is then washed sequentially with deionized water, ethanol, and acetone to remove residual catalyst, salts, and unreacted monomers; then it is vacuum dried at 50 to 80°C for 6 to 12 hours to obtain highly purified multifunctional phthalonitrile; the highly purified multifunctional phthalonitrile is then mixed with a curing agent and prepolymerized at ≥205°C for 20 to 90 minutes; finally, it is cured using a gradient temperature program to obtain multifunctional phthalonitrile resin.

[0073] This invention employs a three-step coupling process of purification and impurity removal, prepolymerization and thickening, and gradient curing. This process achieves a high degree of matching between nitrile curing, alkynyl addition, and thermal crosslinking kinetics, solving problems such as high-temperature curing cracking, cell defects, uneven crosslinking, and low heat resistance. The resulting cured resin has a dense structure, low internal stress, high temperature resistance, and high carbon residue, making it suitable for critical applications such as aircraft interlayers, thermal protection, and deep space exploration equipment.

[0074] In this invention, the curing agent is one or more of Lewis acid curing agents, aromatic diamine curing agents, and self-catalytic phthalonitriles. The Lewis acid curing agent can be selected from phenolic Lewis acids, zinc chloride, ferric chloride, boron trifluoride complexes, etc.; the aromatic diamine curing agent can be selected from m-phenylenediamine, diaminodiphenyl sulfone, diaminodiphenylmethane, etc.; and the self-catalytic phthalonitrile can be a self-catalytic phthalonitrile monomer containing phenolic hydroxyl, amino, or benzoxazine structures.

[0075] In the embodiments of the present invention, the curing agent is a self-catalytic phthalonitrile (preferably, 4-(3-aminophenoxy)phthalonitrile), which can achieve self-curing without the need for an external catalyst, reducing small molecule residues and improving thermal stability.

[0076] In embodiments of the present invention, the mass ratio of purified MPN (i.e., highly purified multifunctional phthalonitrile) to curing agent is 100:(5-20). In specific embodiments, the preferred mass ratio of purified MPN to curing agent is 100:(8-12), which balances curing degree, toughness, and heat resistance. If the mass of the curing agent is too low (based on 100 parts by mass of purified MPN, the mass of the curing agent < 5), it will lead to insufficient catalysis, incomplete curing, and a 5% loss in mass at the thermal decomposition temperature (T). d5% The residual carbon content is low at 800℃.

[0077] In some embodiments of the present invention, the melting temperature of the purified MPN is the same as the prepolymerization temperature, preferably 210°C, and the prepolymerization time is 30–60 min, which can stabilize the system and reduce bubbles and internal stress. Prepolymerization before programmed temperature curing in this invention is performed to increase the viscosity of the system, avoid foaming and collapse; to perform preliminary crosslinking, reduce internal stress during subsequent curing; and to ensure curing uniformity, thereby improving mechanical properties and heat resistance.

[0078] In this invention, the curing process employs a gradient temperature program as follows: first, heat to 210°C and hold for 2 hours; then heat to 240°C and hold for 4 hours; then heat to 250°C and hold for 5 hours; then heat to 280°C and hold for 2 hours; then heat to 320°C and hold for 4 hours; then heat to 350°C and hold for 2 hours; then heat to 360°C and hold for 2 hours; finally, heat to 380°C and hold for 2 hours to complete curing. Heating within the 210–250°C range allows for gradual activation of the nitrile groups, resulting in gentle crosslinking at low temperatures and eliminating internal stress; holding at 280°C allows for full addition of the alkynyl groups, forming a double crosslinked network; and heating within the 320–380°C range allows for deep curing, full formation of the aromatic heterocyclic structure, and optimal heat resistance.

[0079] This invention utilizes biphenyl monomers, hydroquinone, and halogenated aromatic acetylene monomers as raw materials. Hydroxyl-terminated polyaryl ether phenylacetylene is synthesized through nucleophilic aromatic substitution and stepwise polymerization. The reactivity is then enhanced by nitrile end-capping and halogenation activation. Subsequently, alkynyl-aryl coupling constructs multifunctional phthalonitrile. Finally, curing via programmed temperature rise achieves dual crosslinking of nitrile cyclization and alkynyl addition. This stepwise controllable synthesis achieves a matched coupling of reactivity, coupling kinetics, and curing kinetics, solving the problems of high melting point, high curing temperature, easy functional group destruction, and narrow processing window. The resulting resin exhibits low melting point, good processability, high crosslinking density, and excellent thermal stability.

[0080] The multifunctional phthalonitrile resin containing biphenyl diether and endynyl group structures and its cured material prepared by the above method are a new type of high-temperature resistant resin-based material. It can be applied to aerospace ultra-high temperature structural composite materials (including aircraft thermal protection systems, high-temperature resistant protective structures for deep space exploration equipment, aircraft fuselage and wing sandwich structures, and lightweight high-temperature resistant protective structures for deep space exploration equipment), ablation-resistant coatings, high-temperature resistant encapsulation materials, and adhesives. It is particularly suitable for resin matrices, composite materials, and thermal protection materials for high-temperature service scenarios above 400°C, such as aerospace, hypersonic vehicles, and deep space exploration equipment.

[0081] The following describes the multifunctional phthalonitrile resin containing biphenyl diether and endynyl group structures and its curing method according to specific embodiments of the present invention.

[0082] Scanning electron microscope (SEM): Model MIRA4, TESCAN Corporation.

[0083] Thermogravimetric analyzer (TG-DSC): METTLER TOLEDO TGA / DSC1, nitrogen atmosphere, heating rate of 10℃ / min, temperature scan range of 25~1000℃.

[0084] Example 1 A method for preparing a multifunctional phthalonitrile resin containing biphenyl diether and an endynyl group is as follows: S1. In an anhydrous system and under nitrogen protection, 8 g of 4,4'-dihydroxybiphenyl was added to a reaction vessel, followed by 60 mL of NMP and stirring until completely dissolved. Then, 11.2 g of anhydrous potassium carbonate was added, and the mixture was heated to 120 °C and stirred for 2 hours to allow the phenolic hydroxyl groups to fully deprotonate and form phenoxy anions. Then, 9.2 g of [unspecified substance] was added to the reaction vessel. 3,4-Dichlorophenylacetylene was heated to 150°C and kept at that temperature for 12 hours to carry out nucleophilic aromatic substitution and stepwise polymerization. 1.1 g of hydroquinone was added 1 hour before the end of the reaction. After the reaction was completed, the mixture was cooled to room temperature, and the reaction solution was slowly added dropwise to excess deionized water to precipitate the polymer. The mixture was stirred thoroughly for 30 minutes to allow the polymer to settle completely. The crude solid product was collected by vacuum filtration. The filter cake was washed repeatedly with deionized water until the filtrate was neutral, and then washed 2-3 times with ethanol to remove residual solvent and inorganic salts. Finally, the washed solid was placed in a vacuum drying oven and dried at 60°C for 24 hours to constant weight to obtain hydroxyl-terminated polyarylene ether phenylacetylene (α).

[0085] The functional group structure of hydroxyl-terminated polyarylene ether phenylacetylene was characterized using Fourier transform infrared spectroscopy (FTIR), such as... Figure 2 As shown. From Figure 2 It can be seen that the two curves are at approximately 3500cm -1The presence of broad absorption peaks in the vicinity corresponds to the stretching vibration of the terminal hydroxyl group (-OH) in the polymer, confirming that the product successfully retains the hydroxyl-terminated structure; the absorption peaks in the 1200–1000 cm⁻¹ range are also significant. -1 The presence of strong absorption peaks in the 1600–1450 cm⁻¹ range is attributed to the stretching vibrations of the aryl ether bond (-COC-), indicating that the nucleophilic aromatic substitution reaction successfully constructed the polyaryl ether backbone structure; the absorption peaks in the 1600–1450 cm⁻¹ range are also significant. -1 The multiple absorption peaks in the region (within the dashed box in the figure) correspond to the skeletal vibrations of the aromatic ring, confirming the existence of the benzene ring structure in the molecular chain; both curves α-1 and α-2 retain the complete -OH and -COC- characteristic peaks, indicating that hydroxyl-terminated polyarylene ether phenylacetylene was successfully synthesized under both process conditions.

[0086] Nuclear magnetic resonance spectroscopy (NMR) was employed, including proton (H) spectroscopy. 1 H NMR, carbon spectrum ( 13 Using C NMR and two-dimensional NMR spectra, the precise molecular structure of hydroxyl-terminated polyarylene phenylacetylene was determined, such as... Figures 3-5 As shown. From Figures 3-5 It can be seen that, 1 In the 1H NMR spectrum, the multiplets at δ 7.2–7.6 ppm correspond to the aromatic hydrogen signals of the polyarylene backbone, and the characteristic peak at δ 3.18 ppm is attributed to the alkynyl hydrogen of the phenylacetylene unit, confirming the successful introduction of the target structural unit. 13 In the 120–160 ppm NMR spectrum, the multiplets correspond to the aromatic ring and aryl ether carbon signals, while the characteristic peak at 79–82 ppm further confirms the presence of the alkynyl carbon. The two-dimensional NMR spectrum clearly shows the hydrogen-carbon coupling relationship, verifying the connection mode of the Ar-O-Ar backbone structure. Based on the combined NMR analysis results, it can be confirmed that this invention successfully synthesized a well-defined, high-purity hydroxyl-terminated polyaryl ether phenylacetylene, with a molecular structure completely consistent with the design.

[0087] X-ray photoelectron spectroscopy (XPS) was used to analyze the elemental composition and chemical valence states of the surface of hydroxyl-terminated polyarylene ether phenylacetylene using full-spectrum and peak fitting methods. Figure 6 As shown, (a) is the XPS full spectrum of hydroxyl-terminated polyarylene ether phenylacetylene; (b) is the XPS C1s peak spectrum of hydroxyl-terminated polyarylene ether phenylacetylene; and (c) is the XPS O1s peak spectrum of hydroxyl-terminated polyarylene ether phenylacetylene. Figure 6 As can be seen from the full spectrum, the product mainly contains C and O elements, with extremely low residual chlorine. The C1s peaks at 284.80 eV, 286.10 eV, 286.49 eV, 287.96 eV, and 291.73 eV correspond to CC / CH, Ar-C, Ar-O-Ar, C≡C, and aromatic ring π-π, respectively. The structure was confirmed by the O1s fractions at 532.09 eV and 533.43 eV, which indicated the presence of the Ar-O-Ar ether bond and the terminal -OH group, respectively. The XPS results were in perfect agreement with the target structure, verifying the successful synthesis of hydroxyl-terminated polyaryl ether phenylacetylene.

[0088] X-ray diffraction (XRD) was used to analyze the crystal structure and phase composition of hydroxyl-terminated polyarylene ether phenylacetylene, such as... Figure 7 As shown. From Figure 7 It can be seen that the sample exhibits a wide and diffuse peak near 2θ≈20°, indicating that it is mainly in an amorphous / semi-crystalline state. At the same time, weak characteristic diffraction peaks appear at 2θ≈29° and 41°, corresponding to the (110) / (200) and (210) / (112) crystal planes, respectively, indicating that there is a certain degree of ordered aggregation in the polymer, but the overall crystallinity is low, which is beneficial to improving the processing fluidity and solubility of the material.

[0089] The molecular weight and molecular weight distribution of hydroxyl-terminated polyarylene ether phenylacetylene were determined using matrix-assisted laser desorption / ionization time-of-flight mass spectrometry (MALDI-TOF MS). Figure 8 As shown. From Figure 8 As can be seen, the main signal peaks in the spectrum are clear and evenly distributed, indicating that the polymer is mainly in the form of oligomers, with molecular weight concentrated in the range of m / z 200 to 1000. The distribution is narrow and there are no obvious high molecular weight impurities, indicating that the degree of polymerization of the product is controllable and the structure is uniform, which is consistent with the designed oligomer structure.

[0090] Thermogravimetric analysis (TGA) was used to evaluate the thermal stability and thermal decomposition behavior of hydroxyl-terminated polyarylene ether phenylacetylene, such as... Figure 9 As shown. From Figure 9 It can be seen that the sample did not lose significant weight before 200℃, indicating that it has good thermal stability at medium and low temperatures; the main decomposition stage is concentrated in the range of 250-500℃, corresponding to the thermal decomposition of the polyarylether main chain and side groups; the char residue rate at 800℃ is about 35%, indicating that the polymer has a certain thermal decomposition char residue capacity, which can meet the requirements of subsequent high-temperature curing and heat-resistant applications.

[0091] S2. Add 7g of hydroxyl-terminated polyarylene ether phenylacetylene to a reaction vessel, add 50mL of DMF, and stir until completely dissolved; then add 5.6g of anhydrous potassium carbonate, heat to 120℃, and stir for 2h to allow the terminal phenolic hydroxyl groups to fully deprotonate and form phenoxy anions; add 3.2g of 4-nitrophthalonitrile, and continue heating to 200℃ to carry out a nucleophilic aromatic substitution reaction under inert gas protection, and maintain the reaction temperature for 8h; after the reaction is completed, cool to room temperature, precipitate, filter, wash, and vacuum dry to obtain nitrile-terminated polyarylene ether phenylacetylene (α-CN).

[0092] The functional group structure of nitrile-terminated polyarylene ether phenylacetylene was characterized using Fourier transform infrared spectroscopy (FTIR), such as... Figure 10 As shown. From Figure 10 It can be seen that at approximately 2230cm -1 The characteristic stretching vibration peak of the nitrile group (-CN) appeared at 1600–1500 cm⁻¹. -1 The region contains aromatic ring skeletal vibration peaks, 1250–1000 cm⁻¹. -1 The presence of a characteristic peak for an aryl ether bond (-COC-) at 2230 cm⁻¹ confirms the successful synthesis of nitrile-terminated polyaryl ether phenylacetylene. After curing, the nitrile group (-CN) exhibits a characteristic peak at 2230 cm⁻¹. -1 The characteristic peak at 1600–1500 cm⁻¹ is significantly weakened, while the characteristic peak at 1600–1500 cm⁻¹ is significantly weakened. -1 The appearance of new absorption peaks in the region, attributed to characteristic vibrations of crosslinking structures such as triazine or phthalocyanine rings, indicates that the nitrile groups underwent addition polymerization during curing, forming a thermosetting crosslinked network structure. Combined FTIR analysis confirms the successful introduction of nitrile-terminated structures into the prepolymer, and the expected crosslinking reaction after curing, verifying the curing behavior and structural evolution of the system.

[0093] Nuclear magnetic resonance spectroscopy (NMR) was employed, including proton (H) spectroscopy. 1 H NMR, carbon spectrum ( 13 (C10 NMR) to resolve the precise molecular structure of nitrile-terminated polyarylene ether phenylacetylene, such as Figures 11-12 As shown. From Figures 11-12 It can be seen that, 1 In the 1H NMR spectrum, the multiplets at δ 6.71–5.55 ppm correspond to the aromatic hydrogen signals of the polyarylene backbone; the characteristic peaks at δ 3.36–2.85 ppm are consistent with the chemical shifts of the alkynyl hydrogen, confirming the retention of the phenylacetylene unit. 13 In the C NMR spectrum, the characteristic peak near δ110 ppm corresponds to the nitrile (-CN) carbon signal, the multiplets in the δ 120–160 ppm range are attributed to the aromatic ring and aryl ether bonds, and the signal near δ77 ppm is the solvent peak. (Summary) 1 H NMR and 13 C10 NMR analysis confirmed that the present invention successfully synthesized a nitrile-terminated polyarylene acetylene with a well-defined molecular structure, which is completely consistent with the design target.

[0094] S3. Mix 5g of 4-(3-aminophenoxy)phthalonitrile and 30mL of dilute hydrochloric acid (2mol / L), cool to 0℃, add 2.1g of sodium nitrite aqueous solution (2mol / L) dropwise and react for 1h; add 7.5g of potassium chloride, heat to 50℃ and react for 4h. After the reaction is completed, cool to room temperature, dilute with deionized water, and filter to remove inorganic salts; then wash with deionized water, ethanol and acetone in sequence to remove unreacted raw materials and by-products; then dry the product under vacuum at 60℃ for 12h and recrystallize with ethanol to obtain halophthalonitrile.

[0095] The functional group structures of halophthalonitriles were characterized using Fourier transform infrared spectroscopy (FTIR), such as... Figure 13 As shown. From Figure 13 It can be seen that the raw material 4-(3-aminophenoxy)phthalonitrile is at 3300-3500 cm⁻¹ -1 The characteristic doublet of amino groups at the xanthan site completely disappears in products XPN-1 and XPN-2, proving that the amino group has been completely converted; all samples show a peak value of ~2230 cm⁻¹. -1 The presence of nitrile characteristic peaks at all locations indicates that the phthalonitrile structure is stably retained during the reaction; simultaneously, the product exhibits characteristic peaks in the fingerprint region (1000–800 cm⁻¹). -1 The appearance of a new CX bond characteristic absorption peak confirmed the successful halogenation reaction and the successful synthesis of the target halophthalonitrile.

[0096] Nuclear magnetic resonance spectroscopy (NMR) was employed, including proton (H) spectroscopy. 1 H NMR, carbon spectrum ( 13 (C10 NMR) to resolve the precise molecular structure of halophthalonitriles, such as Figures 14-15 As shown. From Figures 14-15 It can be seen that, 1 In the H NMR spectrum, the multiplets with chemical shifts in the range of 6.89 to 8.16 ppm are all aromatic hydrogen signals, which perfectly match the chemical environment of the hydrogen atoms on the benzene ring in the target molecule, and there are no amino hydrogen or other impurity hydrogen signals from the starting material. 13 In the C NMR spectrum, the characteristic peaks at δ 114–116 ppm correspond to the nitrile carbon of the phthalonitrile unit, while the multiplets in the δ 110–165 ppm range coincide with the signals of the aromatic carbon and ether bond carbon in the aromatic ether structure. 1 H NMR and 13 C10 NMR analysis confirmed that the molecular structure of the synthesized product was completely consistent with the structure of the target halophthalonitrile, and the product had high purity and no obvious byproducts.

[0097] X-ray photoelectron spectroscopy (XPS) X3d peak fitting was used to analyze the chemical valence states and relative proportions of elements on the surface of halophthalonitriles, such as... Figure 16 As shown. From Figure 16 It can be seen that the high-resolution X3d spectrum exhibits characteristic double peaks at 620.8 eV and 632.3 eV, corresponding to the X(3d) of the CX bond, respectively. 5 / 2 ) and X(3d 3 / 2 The spin orbital splitting peak indicates that the halogen element exists in the molecule in the form of a bond with carbon, confirming the successful construction of the CX bond in the halophthalonitrile structure.

[0098] X-ray diffraction (XRD) was used to analyze the crystal structure and phase composition of halophthalonitriles, such as... Figure 17 As shown. From Figure 17 It can be seen that a series of sharp and high-intensity characteristic diffraction peaks appeared in the spectrum, corresponding to crystal planes such as (001), (110), (020), and (200), indicating that the synthesized halophthalonitrile has good crystallinity, complete crystal structure, single crystal phase, and no obvious amorphous impurities, proving that the product has high purity and regular crystal form.

[0099] High-resolution mass spectrometry (HRMS) was used to accurately identify the molecular weight and molecular formula of halophthalonitriles, such as... Figure 18 As shown. From Figure 18 As can be seen, the spectrum shows the highest intensity characteristic molecular ion peak, whose mass-to-charge ratio (m / z=437) is in perfect agreement with the theoretical molecular weight of the target halophthalonitrile, and there are no obvious impurity peaks, proving that the molecular formula of the synthesized product is consistent with the theoretical design, the product has high purity, and the structure has been accurately verified.

[0100] The elemental composition and mass ratio of halophthalonitriles were determined using an elemental analyzer (EA), such as... Figure 19 As shown. From Figure 19 As can be seen from the analysis results, the mass fractions of C, N, H, O and halogen element (X) in the sample are highly consistent with the theoretical elemental composition of the target molecule, and there are no obvious impurity element signals, which further confirms that the elemental composition of the halophthalonitrile is consistent with the theoretical structure and the product has high purity.

[0101] The thermal transition properties of halogenated phthalonitriles were detected using differential scanning calorimetry (DSC), such as... Figure 20 As shown. From Figure 20 It can be seen that the raw material PN-A (4-(3-aminophenoxy)phthalonitrile) shows a significant melting endothermic peak at about 140℃, while the melting endothermic peak of XPN shifts significantly to a lower temperature (about 95℃) and has a sharp peak shape, indicating that halogenation modification significantly reduces the melting temperature of phthalonitrile and improves its melt flowability. At the same time, XPN does not show a significant crosslinking exothermic peak during the heating process, indicating that it has good thermal stability within the melting temperature range, which is beneficial to subsequent processing and curing.

[0102] S4: 4g of the above-mentioned halophthalonitrile, 6g of nitrile-terminated polyarylene ether phenylacetylene, 0.06g of Pd(PPh3)4, 0.12g of triphenylphosphine, 4.2g of potassium carbonate, and 50mL of anhydrous DMF were mixed and reacted at 110℃ for 12h under anhydrous conditions and nitrogen protection. After the reaction was completed, the mixture was cooled to room temperature, poured into water to settle, and filtered to obtain the crude product. The crude product was then recrystallized with an ethanol / methanol mixed solvent (ethanol to methanol volume ratio of 1:1). The product was then washed successively with deionized water, ethanol, and acetone to remove residual catalyst, salts, and unreacted monomers. The washed product was then vacuum dried at 70℃ for 10h to obtain the purified multifunctional phthalonitrile resin (MPN).

[0103] like Figure 1 The figure shows the chemical reaction equation between halophthalonitrile and nitrile-terminated polyarylene ether phenylacetylene.

[0104] The functional group structure of multifunctional phthalonitrile resins was characterized using Fourier transform infrared spectroscopy (FTIR), such as... Figure 21 As shown. From Figure 21 It can be seen that the MPN before curing is approximately 2230cm. -1 A distinct characteristic stretching vibration peak of the nitrile group (-CN) was observed at the 1600 cm⁻¹. After curing, the intensity of this peak decreased significantly, and it also decreased at 1600 cm⁻¹. -1 A new characteristic absorption peak appears nearby, corresponding to the triazine ring structure formed by the curing of phthalonitrile; in addition, the cured product shows a peak at 1724 cm⁻¹. -1 The absence of a distinct carbonyl peak at 815 cm⁻¹ indicates that no oxidation side reaction occurred in the system; while at 815 cm⁻¹... -1 The absorption peak at the specified location is consistent with the characteristic vibrations of the biphenyl diether structure, confirming that the main chain structure was preserved during the curing process. Comprehensive analysis indicates that the nitrile groups of the MPN resin underwent the expected cross-linking reaction during curing, forming a stable triazine ring cross-linking network, while the main chain structure remained intact, verifying the curing behavior and structural evolution of the resin.

[0105] Nuclear magnetic resonance spectroscopy (NMR) was employed, including proton (H) spectroscopy. 1 H NMR, carbon spectrum ( 13 (C10 NMR) to resolve the precise molecular structure of multifunctional phthalonitrile resins, such as... Figure 22 and Figure 23 As shown. From Figure 22 and Figure 23 It can be seen that, 1 In the 1H NMR spectrum, the multiplets in the δ6.0–8.2 ppm range were all aromatic hydrogen signals, which perfectly matched the chemical environment of the benzene ring hydrogen in the target structure; the characteristic peak near δ2.5 ppm was attributed to the ≡CH hydrogen signal of the internal alkyne group, confirming the successful introduction of the alkyne structure. 13In the C NMR spectrum, the characteristic peak at δ 110–116 ppm corresponds to the nitrile (-CN) carbon signal; the strong peak at δ 90.6 ppm is the alkynyl carbon signal, directly verifying the existence of the internal alkynyl structure; the multiplets in the δ 115–165 ppm range are consistent with the aromatic carbon and ether bond carbon signals in the aromatic ether structure. In summary… 1 H NMR and 13 C10 NMR analysis confirmed that the molecular structure of the synthesized multifunctional phthalonitrile resin was completely consistent with the design target, and the product had high purity and no obvious by-products.

[0106] X-ray photoelectron spectroscopy (XPS) was used to analyze the elemental composition and chemical valence states of multifunctional phthalonitriles using full-spectrum and peak fitting methods. Figure 24 As shown, (a) is the XPS full spectrum of multifunctional phthalonitriles; (b) is the XPS C1s peak spectrum of multifunctional phthalonitriles; (c) is the XPS O1s peak spectrum of multifunctional phthalonitriles; and (d) is the XPS N1s peak spectrum of multifunctional phthalonitriles. Figure 24 Full-spectrum analysis shows that the sample is mainly composed of C, O, and N, with no obvious impurity element signals. High-resolution peak fitting further reveals the bonding states of each element: the characteristic peaks at 284.8 eV, 285 eV, 286.2 eV, and 286.8 eV in the C1s spectrum correspond to CC / CH, C≡C, C≡N, and COC bonds, respectively; the signal at 533.1 eV in the O1s spectrum belongs to the aryl ether bond (COC), and the signal at 531.8 eV corresponds to the terminal hydroxyl group (-OH); the single peak at 399.2 eV in the N1s spectrum clearly confirms the existence of the nitrile group (C≡N) structure. The chemical valence states and bonding states of the above elements are completely consistent with the theoretical structure of the target resin, further verifying the successful synthesis of the multifunctional phthalonitrile resin.

[0107] High-resolution mass spectrometry (HRMS) was used to accurately identify the molecular weight and molecular formula of multifunctional phthalonitrile resins, such as... Figure 25 As shown. From Figure 25 As can be seen, a series of characteristic peaks with mass-to-charge ratios (m / z) of 339, 481 and 623 appeared in the spectrum, which correspond to the molecular ion peaks of oligomers with different degrees of polymerization. The measured values ​​of each peak are in high agreement with the theoretical molecular weight, and there are no obvious impurity peaks. This confirms that the molecular formula of the target multifunctional phthalonitrile resin is consistent with the theoretical structure, the product has high purity, and the degree of polymerization distribution is controllable.

[0108] The molecular weight and molecular weight distribution of multifunctional phthalonitrile resins were determined using matrix-assisted laser desorption / ionization time-of-flight mass spectrometry (MALDI-TOF MS). Figure 26 As shown. From Figure 26It can be seen that both resins exhibited a series of characteristic peaks with mass-to-charge ratios (m / z) of 339, 481, and 623, corresponding to the molecular ion peaks of oligomers with different degrees of polymerization. The peak positions are highly consistent with the theoretical molecular weight, and there are no obvious impurity peaks. In comparison, the signal intensity of the oligomers in MPN-2 is higher, indicating that its degree of polymerization distribution is more concentrated and the overall product structure is well uniform. This confirms that the multifunctional phthalonitrile resin has a controllable degree of polymerization and a narrow molecular weight distribution.

[0109] The elemental composition and mass ratio of multifunctional phthalonitrile resins were determined using an elemental analyzer (EA), such as... Figure 27 As shown. From Figure 27 It can be seen that the mass fractions of C, N, H and O elements in the resin are highly consistent with the theoretical elemental composition of the target molecule. Among them, the mass fraction of carbon element is the highest, and the contents of nitrogen, oxygen and hydrogen elements also match the contents of functional groups such as nitrile groups and aromatic ether bonds in the molecular structure. No extra impurities were detected, which further confirms that the elemental composition of the synthesized multifunctional phthalonitrile resin is consistent with the theoretical structure and the product has high purity.

[0110] Differential scanning calorimetry (DSC) was used to detect the thermal transition properties and curing reactivity of multifunctional phthalonitrile resins at different heating rates, such as... Figures 28-30 As shown. From Figures 28-30 It can be seen that, from Figure 28 As can be seen, the MPN resin before curing showed a significant melting endothermic peak at about 180℃, while the melting peak of the cured MPN-C sample disappeared, and a sharp curing exothermic peak appeared in the range of 300-320℃, indicating that the resin can undergo a cross-linking curing reaction after melting; the disappearance of the exothermic peak after curing indicates that the resin has completed the cross-linking reaction and formed a stable thermosetting network. Figure 29 The DSC curves are shown for different heating rates (5, 10, 15, 20℃ / min). As the heating rate increases, the onset temperature (T0) and peak temperature (T) of the curing exothermic peak increase. p ) and termination temperature (T) e The peaks all shift towards higher temperatures, and the peak shape gradually widens. This is because the increased heating rate leads to a stronger thermal hysteresis effect, and the resin curing reaction does not have enough time to proceed fully in the low-temperature region. Figure 30 Linear fitting curves of the curing characteristic temperature at different heating rates were obtained. The curing activation energy of the resin can be further calculated using kinetic methods such as Kissinger or Ozawa, providing a theoretical basis for formulating the curing process. Comprehensive analysis shows that this multifunctional phthalonitrile resin exhibits a well-defined melt-curing process, high curing reactivity, and a characteristic curing temperature that changes regularly with the heating rate. Therefore, the curing process parameters can be optimized by controlling the heating rate.

[0111] Thermogravimetric analysis (TGA) was used to evaluate the thermal stability and thermal decomposition behavior of multifunctional phthalonitrile resins, such as... Figure 31 As shown. From Figure 31 As can be seen from the TGA curve, the cured resin experiences only a small amount of mass loss below 100℃, corresponding to the removal of residual moisture or trace small molecules in the system. Subsequently, the mass remains basically stable in the range of 100–450℃, exhibiting excellent thermal stability. The main thermal decomposition process of the resin begins at approximately 450℃, reaching the maximum decomposition rate at 531.6℃, and still exhibits a high char residue at 800℃. The DTG curve further verifies the single-step decomposition characteristics of the resin, with no obvious low-temperature decomposition peak, indicating that the cross-linked and cured multifunctional phthalonitrile resin forms a highly stable cross-linked network structure, possessing excellent thermal stability and thermal decomposition resistance.

[0112] The obtained multifunctional phthalonitrile resin was cured: 5g of MPN was blended with 0.5g of 4-(3-aminophenoxy)phthalonitrile and prepolymerized at 210℃ for 30min, followed by post-curing according to the following program: 210℃-2h, 240℃-4h, 250℃-5h, 280℃-2h, 320℃-4h, 350℃-2h, 360℃-2h, 380℃-2h, to obtain a thermosetting material.

[0113] Testing revealed that the melting point of the multifunctional phthalonitrile resin of this invention is 180℃; the maximum thermal decomposition temperature of the thermosetting material obtained after curing is 531.6℃, and the residual carbon rate at 800℃ is 72%. d5% The curing temperature is 460℃, and the peak curing exothermic temperature is 310~320℃.

[0114] Example 2 The difference between this Example 2 and Example 1 is that: In step S1, the reaction temperature is 175℃ and the reaction time is 14h; In step S2, the reaction temperature is 185℃ and the reaction time is 9 hours. In step S3, the halogenating agent is potassium bromide, and the amount added is 8.7g; In step S4, anhydrous NMP is used to replace anhydrous DMF; The curing process of the multifunctional phthalonitrile resin is the same as in Example 1, and is described in Example 1.

[0115] Testing revealed that the melting point of the multifunctional phthalonitrile resin of this invention is 176℃; the maximum thermal decomposition temperature of the thermosetting material obtained after curing is 512℃, and the residual carbon rate at 800℃ is 58.3%. d5% The temperature is 435℃, and the peak temperature of curing exothermic reaction is 302℃.

[0116] Example 3 The difference between Example 1 and Example 3 is that: In step S2, the amount of 4-nitrophthalonitrile added is 3.5g; In step S4, the amount of nitrile-terminated polyarylene ether phenylacetylene added was 6.3 g, the amount of Pd(PPh3)4 added was 0.07 g, the amount of triphenylphosphine added was 0.14 g, the reaction temperature was 115 °C, the reaction time was 10 h, and anhydrous DMAc was used instead of anhydrous DMF. During the curing process, the amount of 4-(3-aminophenoxy)phthalonitrile added was 0.7g, and the prepolymerization time was 40min.

[0117] Testing revealed that the melting point of the multifunctional phthalonitrile resin of this invention is 184℃; the maximum thermal decomposition temperature of the thermosetting material obtained after curing is 527℃, and the residual carbon rate at 800℃ is 69.5%. d5% The temperature is 452℃, and the peak temperature of curing exothermic reaction is 305℃.

[0118] Example 4 The difference between Example 1 and Example 4 is that: In step S1, the amount of anhydrous potassium carbonate added is 12.6g; In step S2, the amount of anhydrous potassium carbonate added is 6.3g; During the curing process, the curing agent is 4,4'-diaminodiphenyl sulfone, and the amount added is 0.5g.

[0119] Testing revealed that the melting point of the multifunctional phthalonitrile resin of this invention is 178℃; the maximum thermal decomposition temperature of the thermosetting material obtained after curing is 524℃, and the residual carbon rate at 800℃ is 67.2℃. d5% The temperature is 446℃, and the peak temperature of curing exothermic reaction is 286℃.

[0120] Example 5 The difference between Example 1 and Example 5 is that: In step S1, the reaction temperature is 185℃ and the reaction time is 10h; In step S4, anhydrous NMP is used to replace anhydrous DMF; During the curing process, the prepolymerization temperature is 215℃.

[0121] Testing revealed that the melting point of the multifunctional phthalonitrile resin of this invention is 168℃; the maximum thermal decomposition temperature of the thermosetting material obtained after curing is 528℃, and the residual carbon rate at 800℃ is 70%. d5% The temperature is 454℃, and the peak temperature of curing exothermic reaction is 308℃.

[0122] Example 6 The difference between Example 1 and Example 6 is that: In step S4, anhydrous DMAc is used to replace anhydrous DMF, and the reaction time is 14 hours.

[0123] Testing revealed that the melting point of the multifunctional phthalonitrile resin of this invention is 182℃; the maximum thermal decomposition temperature of the thermosetting material obtained after curing is 542℃, and the residual carbon rate at 800℃ is 74.6%. d5% Its temperature is 471℃, and its curing exothermic peak temperature is 318℃. It has the highest crosslinking density and the best heat resistance.

[0124] Comparative Example 1 Compared with Example 1, Comparative Example 1 did not involve the preparation of nitrile-terminated polyarylene ether phenylacetylene (i.e., there was no product from step 2). In step S4, halophthalonitrile was directly coupled with hydroxyl-terminated polyarylene ether phenylacetylene to obtain unnitrile-modified resin.

[0125] The resin obtained in this comparative example has a maximum thermal decomposition temperature of only 426℃, and cannot yield a polyfunctional phthalonitrile resin.

[0126] Comparative Example 2 Compared with Example 1, Comparative Example 2 did not involve the preparation of halogenated phthalonitrile monomers (i.e., there was no product in step 3). In step S4, 4-(3-aminophenoxy)phthalonitrile was directly coupled with nitrile-terminated polyarylene ether phenylacetylene to obtain the modified resin.

[0127] The resin obtained in this comparative example is actually phthalonitrile with biphenyl diether as the main chain cured by 4-(3-aminophenoxy)phthalonitrile. It is only a traditional phthalonitrile resin with a high melting point (>200℃), a narrow processing window, low coupling efficiency, and a carbon residue rate of only 39.7% at 800℃.

[0128] Comparative Example 3 Compared with Example 1, Comparative Example 3 did not involve the preparation of halogenated phthalonitrile monomers from multifunctional phthalonitriles (i.e., the reaction in step 4 was not carried out). During the curing process, the halogenated phthalonitriles and nitrile-terminated polyarylene ether phenylacetylene were directly cured using the curing process in Example 1.

[0129] The product obtained in this comparative example is only a common nitrile-terminated phthalonitrile monomer, not a resin. It has neither a curing peak nor a curing temperature, and certainly no maximum decomposition temperature, etc. d5% Only 382℃.

[0130] Comparative Example 4 Compared with Example 1, in the curing process of Comparative Example 4, the prepolymer was not cured using a gradient curing procedure, but was directly cured at a constant temperature of 380°C for 8 hours.

[0131] The resin obtained in this comparative example has high internal stress, is prone to cracking, and is not completely cured, resulting in damage to the macroscopic structure of the product.

[0132] Comparative Example 5 Compared with Example 1, in step S4 of Comparative Example 5, potassium carbonate was used instead of Pd(PPh3)4 in the coupling reaction.

[0133] This comparative example cannot prepare a multifunctional phthalonitrile resin because Pd(PPh3)4 is the main catalyst for the Sonogashira coupling reaction between the haloaromatic hydrocarbon and the terminal alkyne group. When only a base catalyst is used, the CX bond cannot be effectively activated, the coupling reaction is difficult to proceed fully, the reaction conversion rate is low, the product molecular weight is small, there are many impurities in the system, and no product is generated.

[0134] Comparative Example 6 In this comparative example, 4-(3-aminophenoxy)phthalonitrile was directly used as a self-catalytic curing agent blend (without the S1-S4 modification steps), and the resin was prepared according to the same curing procedure.

[0135] The resin obtained in this comparative example has a high melting point, poor processability, and a high curing temperature; the resin melting point is 240℃; the maximum thermal decomposition temperature of the cured material is 450℃, and the residual carbon rate at 800℃ is 60.3%. d5% The temperature is 429℃, and the peak temperature of curing exothermic reaction is 350℃.

[0136] The above technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made under the technical concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A method for preparing a multifunctional phthalonitrile resin containing a biphenyl diether and an endynyl group, characterized in that, Specifically, the following steps are included: S1. Preparation of hydroxyl-terminated polyarylene phenylacetylene: In an anhydrous and inert gas protected system, using biphenyl monomers, hydroquinone, and halogenated aromatic acetylene monomers as raw materials, an alkaline catalyst was added, and hydroxyl-terminated polyarylene phenylacetylene was obtained through nucleophilic aromatic substitution and stepwise polymerization. S2. Preparation of nitrile-terminated polyarylene phenylacetylene: Using a nitrile-modifying reagent as the nitrile group source, nucleophilic substitution is performed with the hydroxyl-terminated polyarylene phenylacetylene to achieve the conversion of hydroxyl to nitrile group, thereby obtaining nitrile-terminated polyarylene phenylacetylene; S3. Preparation of halophthalonitrile monomers: Using aminophthalonitrile derivatives as raw materials, halophthalonitriles are obtained through diazotization-halogenation substitution reaction; S4. Preparation of multifunctional phthalonitrile: Halogenated phthalonitrile and nitrile-terminated polyarylene phenylacetylene undergo a halogenated aromatic hydrocarbon-alkynyl hydrocarbon coupling reaction to complete alkynyl modification and obtain crude multifunctional phthalonitrile. S5. The above-mentioned crude multifunctional phthalonitrile product was purified and dried under vacuum to obtain multifunctional phthalonitrile resin.

2. The method for preparing the multifunctional phthalonitrile resin containing biphenyl diether and endynyl group structures according to claim 1, characterized in that, In step S1, the molar ratio of the biphenyl monomer, hydroquinone, and halogenated aromatic acetylene monomer is 1:(0.2-0.3):(1.0-1.2). The molar ratio of the biphenyl monomer to the alkaline catalyst is 1:(1.5-3.0).

3. The method for preparing the multifunctional phthalonitrile resin containing biphenyl diether and endynyl group structures according to claim 1, characterized in that, In step S2, the molar ratio of the hydroxyl-terminated polyarylene ether phenylacetylene to the nitrifying agent is 1:(1.2-3.0); The nitrile-modifying agent is a nitro-activated phthalonitrile monomer.

4. The method for preparing the multifunctional phthalonitrile resin containing biphenyl diether and endynyl group structures according to claim 1, characterized in that, In step S3, during the diazotization-halogenation substitution reaction, the molar ratio of the aminophthalonitrile derivative to the diazotizing reagent and the halogenating reagent is 1:(1.0-1.5):(1.5-4.0). During the diazotization reaction, the reaction temperature is -10 to 5℃, and the reaction time is 30 min to 2 h. During the halogenation substitution reaction, the reaction temperature is 20–80℃ and the reaction time is 2–6 h.

5. The method for preparing the multifunctional phthalonitrile resin containing biphenyl diether and endynyl group structures according to claim 4, characterized in that, The aminophthalonitrile derivative is any one of 3-aminophthalonitrile, 4-aminophthalonitrile, 4-(3-aminophenoxy)phthalonitrile, 4-(4-aminophenoxy)phthalonitrile and polyaminophthalonitrile; The diazotizing agent is any one of sodium nitrite, potassium nitrite, and isoamyl nitrite; The halogenated reagent is any one of potassium halide, sodium halide, ammonium halide, and cuprous halide.

6. The method for preparing the multifunctional phthalonitrile resin containing biphenyl diether and endynyl group structures according to claim 1, characterized in that, In step S4, the molar ratio of the halophthalonitrile to the nitrile-terminated polyarylene ether phenylacetylene is 1:(1.0-2.0). In the coupling reaction of haloaromatics and alkynes, the amount of catalyst used is 0.5–5 mol%; The catalyst is a nickel-based catalyst or a palladium-based catalyst.

7. A multifunctional phthalonitrile resin containing biphenyl diether and an endynyl group structure prepared by the preparation method according to any one of claims 1-6, characterized in that, The multifunctional phthalonitrile resin comprises structural units of the following general formula (Ⅰ): （Ⅰ）。 8. The multifunctional phthalonitrile resin containing biphenyl diether and endynyl group structures according to claim 7, characterized in that, The multifunctional phthalonitrile resin is cured by adding a curing agent to the multifunctional phthalonitrile resin, prepolymerizing at ≥205℃ for 20-90 min, and then curing by gradient temperature program. The gradient temperature program is as follows: first, heat to 210℃ and hold for 2 hours; then heat to 240℃ and hold for 4 hours; then heat to 250℃ and hold for 5 hours; then heat to 280℃ and hold for 2 hours; then heat to 320℃ and hold for 4 hours; then heat to 350℃ and hold for 2 hours; then heat to 360℃ and hold for 2 hours; finally, heat to 380℃ and hold for 2 hours to complete curing.

9. The multifunctional phthalonitrile resin containing biphenyl diether and endynyl group structures according to claim 8, characterized in that, The mass ratio of the multifunctional phthalonitrile resin to the curing agent is 100:(5-20). The curing agent is one or more of the following: self-catalytic phthalonitrile, Lewis acid curing agent, and aromatic diamine curing agent.

10. The application of the multifunctional phthalonitrile resin prepared by the preparation method according to any one of claims 1-6 or the multifunctional phthalonitrile resin according to claim 7, characterized in that, It is used in the fields of aerospace ultra-high temperature structural composite materials, ablation-resistant coatings, high temperature resistant packaging materials and adhesives.

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