A liquid crystal oligomer, an intrinsic high-thermal-conductivity liquid crystal phthalonitrile resin and a preparation method and application thereof

Abstract

The application provides a liquid crystal oligomer, a liquid crystal phthalonitrile resin with intrinsic high thermal conductivity and a preparation method and application thereof. The liquid crystal oligomer is obtained by condensation polymerization of the following raw materials: diphenyl ether compounds, biphenyl compounds and nitro phthalonitrile; the raw material of the liquid crystal phthalonitrile resin of the application comprises the liquid crystal oligomer. The liquid crystal phthalonitrile of the application can be used in the fields of aerospace, military and national defense, rail transit, electronic appliances and the like, and is expected to make high-temperature-resistant and high-thermal-conductivity structural parts (such as aerospace vehicles) more lightweight, and can improve the heat dissipation capacity of equipment (such as radars, vehicle-mounted thermal control systems and integrated chips) and maintain the insulation properties, thereby prolonging the service life of the equipment.

Description

Technical Field

[0001] This invention relates to the field of thermally conductive polymer materials, specifically to a liquid crystal oligomer, a liquid crystal phthalonitrile resin with intrinsically high thermal conductivity, its preparation method, and its application. Background Technology

[0002] Thermally conductive polymers possess advantages such as lightweight, high strength, chemical resistance, and ease of processing, and are widely used in aerospace, electronics and electrical industries, and various sectors of the national economy. In recent years, the rapid development of technologies such as high-frequency high-speed integrated circuits and high-power-density devices has placed higher demands on thermally conductive polymers. Most polymers are electron-saturated systems, relying on lattice vibrations (phonons) as the primary heat conduction carriers. Due to the random entanglement between polymer chain segments and the weak van der Waals interactions between chains, heat conduction between molecular chains is greatly limited, resulting in a low intrinsic thermal conductivity of polymers, typically between 0.1 and 0.5 W / (m·K), which is insufficient to meet the needs of high-tech development. Therefore, there is an urgent need to develop high thermal conductivity polymers.

[0003] Currently, methods for improving the thermal conductivity of polymers are divided into filling methods and intrinsic methods. The filling method involves introducing high thermal conductivity fillers into the polymer matrix, utilizing the fillers to form thermally conductive pathways within the matrix, thereby increasing the polymer's thermal conductivity. However, the significant interfacial thermal resistance between the thermally conductive filler and the polymer matrix, along with the extremely low thermal conductivity of the polymer matrix, severely limits the extent to which the thermal conductivity of polymer materials can be improved. Furthermore, the introduction of large amounts of fillers leads to a sharp decline in the processability and mechanical properties of filled polymer materials. Therefore, improving the intrinsic thermal conductivity of polymer materials is the core approach to obtaining high thermal conductivity polymers.

[0004] Phthalonil resin is a novel high-performance thermosetting resin with excellent heat resistance, mechanical properties, and processing characteristics, and is widely used in aerospace, shipbuilding, electronics, and new energy fields. However, the intrinsic thermal conductivity of phthalonitrile resin is relatively low, typically around 0.3 W / (m·K), which cannot meet the requirements of aerospace, military defense, and electronics industries for high-temperature resistant and high-thermal-conductivity polymer materials. Currently, the main method for improving the thermal conductivity of phthalonitrile is the filling method, and there are no reports on improving the intrinsic thermal conductivity of phthalonitrile. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention provides an intrinsically high thermal conductivity liquid crystal phthalonitrile resin, its preparation method and application, which has excellent intrinsic thermal conductivity.

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

[0007] A liquid crystal oligomer, which is obtained by condensation polymerization of the following raw materials: diphenyl ether compounds, biphenyl compounds, and nitrophthalonitrile.

[0008] According to an embodiment of the present invention, the diphenyl ether compound is selected from dihydroxydiphenyl ether, dichlorodiphenyl ether, dibromodiphenyl ether, for example 4,4'-dihydroxydiphenyl ether.

[0009] According to an embodiment of the present invention, the biphenyl compound is selected from dihydroxybiphenyl, dichlorobiphenyl, dibromobiphenyl, for example 4,4'-dibromobiphenyl.

[0010] According to an embodiment of the present invention, the nitrophthalonitrile is selected from at least one of 3-nitrophthalonitrile and 4-nitrophthalonitrile, for example, 4-nitrophthalonitrile.

[0011] According to a preferred embodiment of the present invention, the molar ratio of the diphenyl ether compound and the biphenyl compound is 1.1 to 2, and the molar ratio of the diphenyl ether compound and the nitrophthalonitrile is 0.9-1.1:0.9-1.1, for example, 1:1.

[0012] According to a preferred embodiment of the present invention, the liquid crystal oligomer is obtained by condensation polymerization of the following raw materials: 4,4'-dihydroxydiphenyl ether, 4,4'-dibromobiphenyl, and 4-nitrophthalonitrile. Preferably, the molar ratio of 4,4'-dihydroxydiphenyl ether to 4,4'-dibromobiphenyl is 1.1 to 2, and the molar ratio of 4,4'-dihydroxydiphenyl ether to 4-nitrophthalonitrile is 1.

[0013] For example, the liquid crystal oligomer has the structure shown in Formula I:

[0014]

[0015] In Formula I, m = 1 to 10, for example, 2, 3, 4, 5, 6, 7, 8, 9; n = 1 to 10, for example, 2, 3, 4, 5, 6, 7, 8, 9.

[0016] This invention also provides a method for preparing the above-mentioned liquid crystal oligomers, comprising the following steps:

[0017] In an inert atmosphere, diphenyl ether compounds, biphenyl compounds, and a catalyst are subjected to a first condensation polymerization reaction; subsequently, nitrophthalonitrile is added to carry out a second condensation polymerization reaction to obtain the liquid crystal oligomer.

[0018] According to an embodiment of the present invention, the catalyst is selected from alkaline catalysts.

[0019] According to an embodiment of the present invention, the catalyst is specifically selected from at least one of anhydrous sodium carbonate, anhydrous potassium carbonate, anhydrous cesium carbonate, anhydrous calcium oxide, anhydrous sodium bicarbonate, sodium hydroxide, or potassium hydroxide.

[0020] According to an embodiment of the present invention, the molar ratio of the catalyst to the diphenyl ether compound is 0.5-1.5, preferably 1:1.

[0021] According to an embodiment of the present invention, the diphenyl ether compound, the biphenyl compound, and the catalyst are first mixed in an organic solvent before the first condensation polymerization reaction is carried out.

[0022] According to an embodiment of the present invention, the organic solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, acetonitrile, or N-methylpyrrolidone.

[0023] According to an embodiment of the present invention, the inert atmosphere is nitrogen and / or argon.

[0024] According to an embodiment of the present invention, the conditions for the first condensation polymerization reaction include: a reaction temperature of 100-140°C and a reaction time of 3-8 hours. Preferably, the reaction temperature is 130-140°C and the reaction time is 7-8 hours.

[0025] According to an embodiment of the present invention, the conditions for the second condensation polymerization reaction include: a reaction temperature of 60-90°C and a reaction time of 6-12 hours. Preferably, the reaction temperature is 70-80°C and the reaction time is 8-12 hours.

[0026] According to an embodiment of the present invention, after the reaction is complete, the pH value can be adjusted to a weakly acidic level, for example, 5-7; preferably, the pH value is 6.5. In this invention, methods known in the art can be used to adjust the pH value, for example, using a dilute hydrochloric acid aqueous solution, exemplarily, the volume fraction of the dilute hydrochloric acid aqueous solution is 5%.

[0027] According to an embodiment of the present invention, the obtained liquid crystal oligomer may also be washed and / or dried in the method, for example, by washing with water (e.g., deionized water) and vacuum drying.

[0028] The present invention also provides the application of the above-mentioned liquid crystal oligomers in the preparation of liquid crystal phthalonitrile resins.

[0029] The present invention also provides a liquid crystal phthalonitrile resin, the raw materials of which include the above-mentioned liquid crystal oligomer and curing agent.

[0030] According to an embodiment of the present invention, the mass ratio of curing agent to liquid crystal oligomer is 1:0.01-0.1, preferably 1:0.05-0.08.

[0031] According to an embodiment of the present invention, the curing agent is selected from at least one of metal salt curing agents, organic acid curing agents, inorganic acid curing agents, and organic amine curing agents.

[0032] Preferably, the metal salt curing agent is selected from at least one of stannous chloride, stannous chloride, copper chloride, zinc chloride, and cuprous chloride.

[0033] Preferably, the organic acid curing agent is selected from at least one of sulfonic acid, carboxylic acid, sulfinic acid, and thiocarboxylic acid.

[0034] Preferably, the inorganic acid curing agent is selected from at least one of hydrochloric acid, sulfuric acid, and nitric acid.

[0035] Preferably, the organic amine curing agent includes at least one of 4-(4-aminophenoxy)phthalonitrile, 1,3-bis(3-aminophenoxy)benzene, and p-phenylenediamine.

[0036] According to an embodiment of the present invention, the liquid crystal temperature of the liquid crystal phthalonitrile resin is 140–280°C, for example, 150°C, 200°C, or 250°C. In this invention, the liquid crystal temperature refers to the temperature range during which the liquid crystal phthalonitrile resin transforms from an amorphous phase to a liquid crystal phase, and then from the liquid crystal phase to an isotropic liquid phase.

[0037] According to an embodiment of the present invention, the liquid crystal phthalonitrile resin can be cured under liquid crystal temperature conditions.

[0038] The present invention also provides a method for preparing the above-mentioned liquid crystal phthalonitrile resin, comprising: mixing the curing agent with a liquid crystal oligomer, and curing to obtain the liquid crystal phthalonitrile resin.

[0039] According to an embodiment of the present invention, the mixing can be carried out by a solution method or a melt method.

[0040] According to an embodiment of the present invention, the mixing conditions are: high-speed stirring for 2-5 hours.

[0041] According to an embodiment of the present invention, when mixing is performed using a solution method, a solvent also needs to be added. Preferably, after mixing using the solution method, the solvent needs to be removed (e.g., by vacuum drying). Preferably, the solvent is selected from at least one of acetone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and N-methylpyrrolidone.

[0042] According to an embodiment of the present invention, the curing temperature is 180 to 280°C, for example, 180°C, 200°C, 220°C, or 250°C.

[0043] According to an embodiment of the present invention, the curing temperature is matched with the liquid crystal temperature of the liquid crystal phthalonitrile resin, that is, there is a significant overlap between the curing temperature and the liquid crystal temperature. For example, the curing temperature is selected from any temperature value greater than 150°C within the liquid crystal temperature range of the liquid crystal phthalonitrile resin, preferably a temperature close to the upper limit of the liquid crystal temperature. For example, when the liquid crystal temperature is 140 to 280°C, the curing temperature is 180 to 280°C.

[0044] The present invention also provides the application of the above-mentioned liquid crystal phthalonitrile resin in the fields of aerospace, military defense, rail transportation, and electronics.

[0045] Compared with the prior art, the intrinsically high thermal conductivity liquid crystal phthalonitrile resin of the present invention has the following beneficial effects:

[0046] (1) This invention proposes to introduce "rigid-flexible" liquid crystal units from the perspective of resin matrix molecular structure design. For example, the molecular structure of liquid crystal phthalonitrile resin contains rigid mesocrystalline biphenyl units and flexible ether bonds, giving the liquid crystal phthalonitrile resin thermotropic liquid crystal behavior. Within the liquid crystal temperature range, the molecular chains of the liquid crystal phthalonitrile resin remain highly ordered. By controlling the curing temperature of the liquid crystal phthalonitrile resin to match the liquid crystal temperature, a relatively ordered resin microstructure is constructed to reduce the scattering of phonons between its molecular chains, thereby improving the intrinsic thermal conductivity of the liquid crystal phthalonitrile resin and thus broadening the applications of high thermal conductivity phthalonitrile.

[0047] (2) The aromatic ether-biphenyl type thermotropic liquid crystal phthalonitrile oligomer proposed in this invention has good solubility in common solvents such as acetone, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide and dimethyl sulfoxide, with a melt viscosity of less than 1 Pascal second, good processability, and is suitable for the requirements of various composite material molding processes such as compression molding and RTM.

[0048] (3) The intrinsically high thermal conductivity liquid crystal phthalonitrile resin proposed in this invention has a thermal conductivity as high as 1.14 W / (m·K), which is 2.92 times higher than that of conventional phthalonitrile resin. Furthermore, the 5% thermal weight loss temperature (T0) of the cured liquid crystal phthalonitrile resin is also high. d 5 It has a temperature rating of ≥500℃ and a heat resistance rating of ≥300℃, exhibiting excellent thermal stability.

[0049] (4) The liquid crystal phthalonitrile of the present invention can replace metals in aerospace, military defense, rail transportation, electronics and electrical appliances and other fields. It is expected to make high temperature and high thermal conductivity structural components (such as in aerospace vehicles) lighter and improve the heat dissipation capacity of equipment (such as radar, vehicle thermal control system and integrated chip) and maintain insulation properties, thereby extending the service life of the equipment. Attached Figure Description

[0050] Figure 1 The image shows the hydrogen NMR spectrum of the aromatic ether-biphenyl type thermotropic liquid crystal phthalonitrile oligomer prepared in Example 1 of this invention.

[0051] Figure 2 The image shows the GPC curve of the aromatic ether-biphenyl type thermotropic liquid crystal phthalonitrile oligomer (LCPN) prepared in Example 1 of this invention.

[0052] Figure 3 The image shows the DSC curve of the aromatic ether-biphenyl type thermotropic liquid crystal phthalonitrile oligomer (LCPN) prepared in Example 1 of this invention.

[0053] Figure 4 The image shows the POM diagram of the aromatic ether-biphenyl type thermotropic liquid crystal phthalonitrile oligomer (LCPN) prepared in Example 1 of this invention.

[0054] Figure 5 The image shows the TGA test results of the intrinsically high thermal conductivity liquid crystal phthalonitrile resin (LCPN8) prepared in Example 1 of this invention under a nitrogen atmosphere.

[0055] Figure 6 The test results of the in-plane and thickness directions of the intrinsic high thermal conductivity liquid crystal phthalonitrile resin (LCPN8) prepared in Example 1 of the present invention and the aromatic ether type phthalonitrile resin prepared in Comparative Example 1 are shown. Detailed Implementation

[0056] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0057] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0058] Example 1

[0059] (1) Synthesis of aromatic ether-biphenyl type thermotropic liquid crystal phthalonitrile oligomer (LCPN): 17.33 g (85.8 mmol) of 4,4'-dihydroxydiphenyl ether, 20.59 g (66.0 mmol) of 4,4'-dibromobiphenyl (molar ratio 1.3) and 300 mL of N,N-dimethylformamide were added to a three-necked flask. The mixture was stirred at 60 °C for 20-40 min under an inert atmosphere until completely dissolved. Then, the temperature was raised to 140 °C, and 18.22 g (132 mmol) of anhydrous potassium carbonate was added. The reaction was carried out at this temperature for 6 h. The temperature was lowered to 80 °C, and 14.84 g (85.8 mmol) of 4-nitrophthalonitrile, 100 mL of N,N-dimethylformamide and 9.11 g (66 mmol) of anhydrous potassium carbonate were added. The reaction was carried out at this temperature for 8 h. After cooling to room temperature, the alkaline catalyst insoluble in organic solvents was removed by filtration. The reaction solution was then added dropwise to deionized water to precipitate the product. The pH was adjusted to 6.5 using a dilute hydrochloric acid aqueous solution (the volume fraction of the dilute hydrochloric acid aqueous solution was 5%). After stirring at room temperature for 4-5 hours, the product was filtered under reduced pressure. The product was washed 3-5 times with deionized water and dried under vacuum to obtain aromatic ether-biphenyl type thermotropic liquid crystal phthalonitrile oligomer (LCPN).

[0060] (2) Preparation of liquid crystal phthalonitrile resin (LCPN8): 20g of the aromatic ether-biphenyl type thermotropic liquid crystal phthalonitrile oligomer (LCPN) prepared in step (1) and 1.6g of organic amine 4-(4-aminophenoxy)phthalonitrile curing agent (Formula (II)) were added to a three-necked flask, wherein the mass ratio of curing agent to phthalonitrile oligomer was 1:0.08. The mixture was stirred at 140℃ for 2h under an inert atmosphere and poured into a clean aluminum box while hot to obtain an intermediate product. According to the sample size required for thermal conductivity testing, 4g of the intermediate product was placed in a cylindrical metal mold with a diameter of 30mm and a height of 10mm. The product was cured according to a step heating program of 180℃ / 2h, 220℃ / 2h, and 250℃ / 4h. After cooling, the mold was opened and the product was removed to obtain a dense intrinsically high thermal conductivity liquid crystal phthalonitrile resin (LCPN8). According to the testing standards for thermally conductive samples, circular samples with a diameter of 22.5 mm and a thickness of 0.5 mm were prepared using a metallographic pre-grinding machine, and their thermal conductivity was measured. The samples were then retained for testing to assess their heat resistance after curing at 315℃ for 5 hours and 375℃ for 5 hours.

[0061] The structural formula of the organic amine phthalonitrile curing agent 4-(4-aminophenoxy)phthalonitrile is shown in formula (II) below:

[0062]

[0063] Example 2

[0064] The preparation method of the liquid crystal phthalonitrile resin in this embodiment is basically the same as that in Example 1, except that:

[0065] In step (1), the molar ratio of 4,4'-dihydroxydiphenyl ether to 4,4'-dibromobiphenyl was adjusted to 1.1, i.e., 14.67 g (72.6 mmol) of 4,4'-dihydroxydiphenyl ether and 20.59 g (66.0 mmol) of 4,4'-dibromobiphenyl; in step (2), the liquid crystal oligomer prepared in this example was used; the remaining conditions and steps were the same as in Example 1.

[0066] Example 3

[0067] The preparation method of the liquid crystal phthalonitrile resin in this embodiment is basically the same as that in Example 1, except that:

[0068] In step (1), the molar ratio of 4,4'-dihydroxydiphenyl ether to 4,4'-dibromobiphenyl is adjusted to 1.5, i.e., 20.00 g (99 mmol) of 4,4'-dihydroxydiphenyl ether and 20.59 g (66.0 mmol) of 4,4'-dibromobiphenyl; in step (2), the liquid crystal oligomer prepared in this example is used; the remaining conditions and steps are the same as in Example 1.

[0069] Example 4

[0070] The preparation method of the liquid crystal phthalonitrile resin in this embodiment is basically the same as that in Example 1, except that:

[0071] In step (2), the mass ratio of curing agent to liquid crystal oligomer resin matrix is ​​adjusted to 1:0.05, that is, 20g of aromatic ether-biphenyl type thermotropic liquid crystal phthalonitrile oligomer (LCPN) and 1.0g of organic amine 4-(4-aminophenoxy)phthalonitrile curing agent; the remaining conditions and steps are the same as in Example 1.

[0072] Example 5

[0073] The preparation method of the liquid crystal phthalonitrile resin in this embodiment is basically the same as that in Example 2, except that:

[0074] In step (2), the mass ratio of curing agent to phthalonitrile oligomer is adjusted to 1:0.05, that is, 20g of aromatic ether-biphenyl type thermotropic liquid crystal phthalonitrile oligomer (LCPN) and 1.0g of organic amine 4-(4-aminophenoxy)phthalonitrile curing agent; the remaining conditions and steps are the same as in Example 2.

[0075] Example 6

[0076] The preparation method of the liquid crystal phthalonitrile resin in this embodiment is basically the same as that in Example 3, except that:

[0077] In step (2), the mass ratio of curing agent to phthalonitrile oligomer is adjusted to 1:0.05, that is, 20g of aromatic ether-biphenyl type thermotropic liquid crystal phthalonitrile oligomer (LCPN) and 1.0g of organic amine 4-(4-aminophenoxy)phthalonitrile curing agent; the remaining conditions and steps are the same as in Example 3.

[0078] Comparative Example 1

[0079] Preparation of aromatic ether-type phthalonitrile resin: 20g of aromatic ether-type phthalonitrile monomer (MPN) (Formula (III)) and 1.6g of organic amine 4-(4-aminophenoxy)phthalonitrile curing agent (Formula (II)) were added to a three-necked flask, wherein the mass ratio of curing agent to phthalonitrile monomer was 1:0.08. The mixture was stirred at 140℃ for 2h under an inert atmosphere and poured into a clean aluminum box while hot to obtain an intermediate product. According to the sample size required for thermal conductivity testing, 4g of the intermediate product was placed in a cylindrical metal mold with a diameter of 30mm and a height of 10mm. Curing was performed according to a stepped heating program of 180℃ / 2h, 220℃ / 2h, and 250℃ / 4h. After cooling, the mold was opened and the resin was removed to obtain dense phthalonitrile resin. According to the testing standards for thermal conductivity samples, a circular sample with a diameter of 22.5mm and a thickness of 0.5mm was prepared using a metallographic pre-grinding machine, and its thermal conductivity was measured.

[0080] The structural formula of the aromatic ether type phthalonitrile monomer is shown below:

[0081]

[0082] Test Example 1

[0083] Figure 1 The image shows the 1H NMR spectrum of the aromatic ether-biphenyl type thermotropic liquid crystal phthalonitrile oligomer (LCPN) prepared in Example 1 of this invention. The instrument used was a Bruker AVIII 400HD, and the solvent used was deuterated dimethyl sulfoxide (DMSO-d6). The disappearance of the hydroxyl hydrogen signal and the low-field hydrogen signal under the interaction of nitro groups in the reactant monomers proves that the reaction proceeded successfully, and the hydrogen signals of the products correspond well.

[0084] Figure 2 The image shows the GPC curve of the aromatic ether-biphenyl type thermotropic liquid crystal phthalonitrile oligomer (LCPN) prepared in Example 1 of this invention. The mobile phase used in the instrument was N-methylpyrrolidone, and the stationary phase was polystyrene spheres. The flow rate of the mobile phase was 10 mL / min, and the temperature was 35 °C. The oligomer exhibits polydispersity, with a weight-average molecular weight of 6189 and a number-average molecular weight of 1534, indicating that the polymerization reaction proceeded smoothly.

[0085] Figure 3The image shows the DSC curve of the aromatic ether-biphenyl type thermotropic liquid crystal phthalonitrile oligomer (LCPN) prepared in Example 1 of this invention. A Mettler Toledo DSC 822e differential scanning calorimeter was used with nitrogen as the test atmosphere, a flow rate of 50 mL / min, and a heating rate of 10 °C / min. In Example 1, the aromatic ether-biphenyl type thermotropic liquid crystal phthalonitrile oligomer (LCPN) exhibited two DSC endothermic peaks during the heating process (peaks located at 140 °C and 280 °C, respectively). These peaks are attributed to the transition from the amorphous phase to the liquid crystal phase and the transition from the liquid crystal phase to the isotropic liquid phase, respectively. Therefore, the liquid crystal temperature of the LCPN prepared in Example 1 is 140–280 °C.

[0086] Figure 4 The image shows the POM (Positive Oxidation Method) images of the aromatic ether-biphenyl type thermotropic liquid crystal phthalonitrile oligomer prepared in Example 1 of this invention. From left to right and top to bottom, the POM images represent 120℃, 150℃, 200℃, and 250℃, respectively. Temperature-dependent polarized light observation was performed using an OLYMPVSBX53 upright microscope with a THMS600 hot stage. When the aromatic ether-biphenyl type thermotropic liquid crystal phthalonitrile oligomer prepared in Example 1 was heated to 120℃, no bright spots appeared in the field of view. At 150℃, numerous bright green spots appeared. At 200℃, the spots shrank and changed to a bright blue-green color as the resin changed color. At 250℃, the spots still existed and changed to a bright blue color as the resin changed color. Figure 3 The results are consistent with the DSC results.

[0087] Test Example 2

[0088] Figure 5 The TGA test image of the intrinsically high thermal conductivity liquid crystal phthalonitrile resin (LCPN8) prepared in Example 1 of this invention under a nitrogen atmosphere was obtained. The instrument model was Netzsch TG209F1-Is10, the heating rate was 10℃ / min, the flow rate was 50mL / min, the protective gas was nitrogen, and the flow rate was 20mL / min. After a stepped temperature curing program of 180℃ / 2h, 220℃ / 2h, 250℃ / 4h, 315℃ / 5h, and 375℃ / 5h, the resin's 5% thermogravimetric temperature (Tg) was determined. d 5 The temperature is 506℃, and the 10% thermal weight loss temperature (T) is... d 10 It has a temperature of 551℃ and excellent heat resistance.

[0089] Figure 6The thermal conductivity test results are for the intrinsically high thermal conductivity liquid crystal phthalonitrile resin (LCPN8) prepared in Example 1 and the aromatic ether type phthalonitrile resin (APN) prepared in Comparative Example 1. The testing instrument was a NETZSCH LFA467, and the testing atmosphere was nitrogen. The thermal conductivity of APN was 0.39 W / (m·K), and the thermal conductivity of LCPN8 was 1.14 W / (m·K), representing a 2.92-fold increase in thermal conductivity compared to APN.

[0090] Furthermore, in Examples 2-6, liquid crystal phthalonitrile resins were prepared by changing the monomer feed ratio of diphenyl ether compounds and biphenyl compounds, or by changing the mass ratio of curing agent to liquid crystal oligomer. The test results were basically the same as those in Example 1. The inventors believe that:

[0091] 1) Since the reactivity of 4,4-dibromobiphenyl with 4,4-dihydroxydiphenyl ether is limited, its chain extension ability remains basically the same within a certain reaction temperature. Therefore, even if the monomer feed ratio is changed, the molecular weight distribution of the liquid crystal oligomer obtained after full reaction does not change significantly. The test results are basically the same as those in Example 1.

[0092] 2) The inventors believe that, under the conditions of the mass ratio of curing agent to liquid crystal oligomer of the present invention, the curing process using a stepped temperature increase program of 180℃ / 2h, 220℃ / 2h, and 250℃ / 4h can satisfy the curing of liquid crystal phthalonitrile resin. By adjusting the mass ratio of curing agent to liquid crystal oligomer within the range of the present invention, the curing time of the resin from a fluid state to a viscous state can be changed without affecting the performance of the final sample. Therefore, the test results are basically the same as those in Example 1.

[0093] The exemplary embodiments of the present invention have been described above. However, the scope of protection of this application is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A liquid crystal oligomer, characterized in that, The liquid crystal oligomer is obtained by condensation polymerization of the following raw materials: diphenyl ether compounds, biphenyl compounds, and nitrophthalonitrile.

2. The liquid crystal oligomer according to claim 1, characterized in that, The diphenyl ether compounds are selected from dihydroxydiphenyl ether, dichlorodiphenyl ether, and dibromodiphenyl ether. Preferably, the biphenyl compound is selected from dihydroxybiphenyl, dichlorobiphenyl, and dibromobiphenyl. Preferably, the nitrophthalonitrile is selected from at least one of 3-nitrophthalonitrile and 4-nitrophthalonitrile. Preferably, the molar ratio of the diphenyl ether compound and the biphenyl compound is 1.1 to 2.

3. The method for producing liquid crystal oligomers according to claim 1 or 2, characterized in that, Includes the following steps: In an inert atmosphere, diphenyl ether compounds, biphenyl compounds, and a catalyst are subjected to a first condensation polymerization reaction; subsequently, nitrophthalonitrile is added to carry out a second condensation polymerization reaction to obtain the liquid crystal oligomer.

4. The method according to claim 3, characterized in that, The catalyst is selected from basic catalysts. Preferably, the catalyst is specifically selected from at least one of anhydrous sodium carbonate, anhydrous potassium carbonate, anhydrous cesium carbonate, anhydrous calcium oxide, anhydrous sodium bicarbonate, sodium hydroxide, or potassium hydroxide. Preferably, the molar ratio of the catalyst to the diphenyl ether compound is 0.5-1.

5. Preferably, the diphenyl ether compound, the biphenyl compound, and the catalyst are first mixed in an organic solvent before the first condensation polymerization reaction is carried out. Preferably, the organic solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, acetonitrile, or N-methylpyrrolidone. Preferably, the inert atmosphere is nitrogen and / or argon. Preferably, the conditions for the first condensation polymerization reaction include: a reaction temperature of 100-140°C and a reaction time of 3-8 hours. Preferably, the conditions for the second condensation polymerization reaction include: a reaction temperature of 60-90°C and a reaction time of 6-12 hours.

5. The use of the liquid crystal oligomer according to claim 1 or 2 in the preparation of liquid crystal phthalonitrile resin.

6. A liquid crystal phthalonitrile resin, characterized in that, Its raw materials include the liquid crystal oligomer and curing agent as described in claim 1 or 2.

7. The liquid crystal phthalonitrile resin according to claim 6, characterized in that, The mass ratio of curing agent to liquid crystal oligomer is 1:0.01-0.

1. Preferably, the curing agent is selected from at least one of metal salt curing agents, organic acid curing agents, inorganic acid curing agents, and organic amine curing agents. Preferably, the metal salt curing agent is selected from at least one of stannous chloride, stannous chloride, copper chloride, zinc chloride, and cuprous chloride. Preferably, the organic acid curing agent is selected from at least one of sulfonic acid, carboxylic acid, sulfinic acid, and thiocarboxylic acid. Preferably, the inorganic acid curing agent is selected from at least one of hydrochloric acid, sulfuric acid, and nitric acid. Preferably, the organic amine curing agent includes at least one of 4-(4-aminophenoxy)phthalonitrile, 1,3-bis(3-aminophenoxy)benzene, and p-phenylenediamine. Preferably, the liquid crystal temperature of the liquid crystal phthalonitrile resin is 140–280°C.

8. The method for preparing the liquid crystal phthalonitrile resin according to claim 6 or 7, characterized in that, The preparation method includes: mixing the curing agent with the liquid crystal oligomer, and then curing to obtain the liquid crystal phthalonitrile resin.

9. The preparation method according to claim 8, characterized in that, The mixing can be carried out by solution mixing or melting. Preferably, the mixing conditions are: high-speed stirring for 2-5 hours. Preferably, the curing temperature is 180–280°C.

10. The application of the liquid crystal phthalonitrile resin according to claim 6 or 7 in the fields of aerospace, military defense, rail transportation, and electronics.

Images