Intrinsic heat-conducting liquid crystal polymer material as well as preparation method and application thereof

Abstract

The invention provides an intrinsic heat-conducting liquid crystal polymer material and a preparation method and application thereof, the preparation method comprises the following steps: (1) mixing a raw material A, a raw material B, a catalyst and an organic solvent, and reacting to obtain a first compound; (2) mixing the raw material C, the raw material B, a catalyst and an organic solvent, and reacting to obtain a second compound; and (3) mixing a first compound, an optional second compound, hydrogen-containing polysiloxane, a hydrosilylation catalyst and a solvent, carrying out hydrosilylation reaction, and carrying out hot pressing to obtain the intrinsic heat-conducting liquid crystal polymer material. The intrinsic heat conduction liquid crystal polymer material prepared by the preparation method provided by the invention has a relatively high heat conduction coefficient.

Description

Technical Field

[0001] The invention belongs to the technical field of liquid crystal polymers and relates to an intrinsic thermal conductive liquid crystal polymer material and a preparation method and application thereof. Background Art

[0002] With the high integration, miniaturization and functionalization of microelectronic devices, the heat generated by chips and power devices during operation is difficult to be effectively dissipated in a small enclosed space, resulting in excessive device temperature and accelerated equipment aging. Efficient heat dissipation has become a technical bottleneck in the development of the microelectronics field. Although traditional thermal conductive materials such as metals and inorganic fillers have high thermal conductivity, they are heavy, difficult to process and easily lead to a decrease in electrical insulation performance, which limits their application in electronic packaging and other fields. In the process of exploring multifunctional materials suitable for electrical devices, semiconductors and thermal interface materials (TIMs), polymers have become a very promising choice due to their easy processing, low cost, excellent mechanical properties and rich variety. However, the thermal conductivity (TC) of polymers in their pure state is poor, which is a key problem that needs to be solved urgently. Block polymers usually present a partially amorphous structure, with random curling of molecular chains and defects such as voids and entanglements. These defects not only become stress concentration points, but also serve as phonon scattering sites, resulting in their thermal conductivity (λ: about 0.1 W·m -1 K -1 ) is low. Therefore, developing polymer materials with high thermal conductivity to meet thermal management needs has become an important and urgent task.

[0003] Thermally conductive polymers are generally divided into two categories based on their preparation process: intrinsic and filled. Filled thermally conductive polymer composites are made by adding highly thermally conductive metals, inorganic particles or carbon-based materials to the polymer matrix. Typically, the purpose of using these fillers is to build thermal conductive paths in the polymer matrix, but high filler loadings are usually required to reach the percolation threshold of a continuous thermally conductive network. In fact, the matrix in the polymer mixture mainly acts as a thermal insulator, and interfacial thermal resistance hinders heat conduction. Although these filled polymer systems are widely used, they often face many challenges, such as the need for high filler loadings, difficulty in manufacturing, and high costs.

[0004] In contrast, intrinsic thermally conductive polymers are achieved by changing the structure of chain units (such as orientation, liquid crystal properties, and crystal structure) during polymer synthesis. Most traditional bulk polymers are composed of saturated systems without free electrons, where phonons are the main carriers of heat conduction. Phonons can be regarded as a quantized form of thermal energy, and phonon scattering at interfaces is one of the important reasons limiting the thermal conductivity of polymer composites. The arrangement of polymer chains is similar to that of a manila rope, with a random and entangled structure, which leads to a high probability of phonon scattering, thus forming a thermal resistance and a low thermal conductivity (TC). According to Bruggeman's theory (Bruggeman effective medium theory), the thermal conductivity of a composite material depends more on the thermal conductivity of the matrix rather than that of the filler. Therefore, improving the thermal conductivity of the polymer itself has become the research focus.

[0005] Therefore, in this field, there is a desire to develop an intrinsic thermally conductive polymer material that not only has good thermal conductivity but also has a simple preparation method. Summary of the Invention

[0006] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide an intrinsic thermally conductive liquid crystal polymer material, its preparation method, and its application. That is, to solve problems such as the deterioration of the mechanical properties of polymers, the decrease in electrical insulation, and the reduction in destructive strength, the present invention turns the research focus to the thermal conductivity of the polymer itself and proposes an intrinsic thermally conductive liquid crystal polymer material, its preparation method, and its application.

[0007] Compared with the traditional technology, the advantage of the preparation method provided by the present invention is that no filler is required. The present invention introduces mesogenic units into the side chain of polysiloxane and successfully prepares an intrinsic thermally conductive liquid crystal polymer material (LCPM) through chemical cross-linking graft copolymerization. Utilizing the high flexibility of polysiloxane, while introducing a rigid biphenyl liquid crystal structure, an ordered arrangement of liquid crystal polymer molecules is achieved. Selecting a dinitrile mesogenic unit with partial charged characteristics enables the existence of π-π interactions between adjacent groups, and these interactions are regarded as weak cross-links, which helps to improve the liquid crystal orientation and crystallinity of LCPM. In addition, the cross-linking intermediate monomer S-CL induces strong intermolecular chain interactions, thereby increasing the crystallinity and reducing the thermal resistance to phonon conduction along the polymer chain. To a certain extent, the microcirculation orientation of crystalline polymers can effectively inhibit phonon scattering. The flexible chain segments of polysiloxane and alkyl provide flexibility and processability to the material. Preparing intrinsic thermally conductive polymers through molecular design provides new ideas and directions for improving the thermal conductivity of polymers and their composites.

[0008] The preparation method provided by the present invention successfully synthesizes a series of intrinsic thermally conductive liquid crystal polymer materials (LCPM) through a chemical cross-linking method, and proves that the LCPM materials have excellent thermal conductivity and mesomorphic properties. Through molecular design and structural regulation (introducing mesogenic units (biphenyl, cyanobiphenyl) and regulating the spatial distribution of self-assembled liquid crystal domains, using the microscale ordered structure of the cross-linking agent and increasing the non-covalent interaction between cross-linking points), high thermal conductivity is achieved without relying on fillers, while retaining the advantages of polymer materials such as light weight, flexibility and easy processing. Due to its unique molecular ordered structure, liquid crystal polymer materials can effectively inhibit phonon scattering and improve thermal conductivity, becoming a research hotspot of intrinsic thermally conductive materials.

[0009] To achieve the object of this invention, the following technical solutions are adopted in the present invention:

[0010] In the first aspect, the present invention provides a preparation method of an intrinsic thermally conductive liquid crystal polymer material, and the preparation method includes the following steps:

[0011] (1) Mix raw material A, raw material B, a catalyst and an organic solvent, and react to obtain a first compound (denoted as S-CL);

[0012] (2) Mix raw material C, raw material B, a catalyst and an organic solvent, and react to obtain a second compound (denoted as H-B);

[0013] (3) Mix the first compound, the optional second compound, hydrogen-containing polysiloxane (H-PMDS), a hydrosilylation catalyst and a solvent, carry out a hydrosilylation reaction, and hot press to obtain the intrinsic thermally conductive liquid crystal polymer material;

[0014] Among them, raw material A has the structure shown in the following formula I:

[0015]

[0016] The raw material B in step (1) and step (2) each independently has the structure shown in the following formula II:

[0017]

[0018] In formula II, X is a halogen (such as -F, -Cl, -Br or -I), and a is an integer from 0 to 2 (such as 0, 1 or 2);

[0019] Raw material C has the structure shown in the following formula III:

[0020]

[0021] In the present invention, the reactions in step (1) and step (2) are both Williamson ether reactions.

[0022] The intrinsic thermally conductive liquid crystal polymer material prepared by the preparation method provided by the present invention has a structure including mesogenic groups (biphenyl groups, cyanobiphenyl groups) and flexible polysiloxane chains, and has thermally conductive liquid crystal properties. By introducing rigid biphenyl and mesogenic units with partially charged properties of diphenyl cyanide on the flexible polydimethylsiloxane chain, the stacking of side chains and the π-π interaction between molecules are achieved, realizing the ordered arrangement of liquid crystal polymer molecules. The ordered microstructure forms an excellent continuous heat conduction network, so that the liquid crystal polymer material has a high thermal conductivity. The thermal conductivity of the intrinsic thermally conductive liquid crystal polymer material provided by the present invention can reach up to 0.58 W·m -1 K -1 , which is 2.9 times that of the general PDMS thermal conductivity (0.20 W·m -1 K -1 ).

[0023] Preferably, the raw material A is

[0024] Preferably, in formula II, X is -Br.

[0025] Preferably, in formula II, a is 0.

[0026] Preferably, the raw material B in steps (1) and (2) is both (allyl bromide).

[0027] Preferably, the raw material C is

[0028] Preferably, the hydrogen-containing polysiloxane has the structure shown in the following formula IV:

[0029]

[0030] In formula IV, n and z are each independently an integer from 0 to 30 (such as 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, etc.), and n and z are not both 0; m is an integer from 0 to 30 (such as 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, etc.); R is -H or a straight-chain or branched-chain alkyl group of C1-C10 (such as C1, C2, C3, C4, C5, C6, C7, C8, C9 or C10).

[0031] Preferably, R is -H or -CH3.

[0032] It should be noted that the hydrogen-containing polysiloxane having the structure shown in formula IV of the present invention can be prepared by a conventional method according to the prior art.

[0033] When the second compound is included in step (2), the intrinsic thermally conductive liquid crystal polymer material synthesized in the present invention has a structure shown in the following formula V:

[0034]

[0035] In formula V, n and z are each independently an integer from 0 to 30 (such as 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, etc.), and n and z are not both 0; m is an integer from 0 to 30 (such as 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, etc.); R is -H or a linear or branched alkyl group of C1-C10 (such as C1, C2, C3, C4, C5, C6, C7, C8, C9 or C10); o is an integer from 1 to 3 (such as 1, 2 or 3), and p is an integer from 1 to 3 (such as 1, 2 or 3).

[0036] Preferably, the number average molecular weight of the intrinsic thermally conductive liquid crystal polymer material is 5000, and o and p are 1.5.

[0037] Preferably, the molar ratio of raw material A to raw material B in step (1) is 1:(1-3), such as 1:1, 1:1.2, 1:1.4, 1:1.6, 1:1.8, 1:2, 1:2.2, 1:2.4, 1:2.6, 1:2.8, 1:3, etc.

[0038] Preferably, the catalyst in step (1) includes any one or a combination of at least two of potassium carbonate, sodium carbonate, and sodium hydride.

[0039] Preferably, the molar ratio of raw material A to the catalyst in step (1) is 1:(1.5-3), such as 1:1.5, 1:1.6, 1:1.8, 1:2, 1:2.2, 1:2.4, 1:2.6, 1:2.8, 1:3, etc.

[0040] Preferably, the organic solvent in step (1) includes dichloromethane and / or acetone.

[0041] Preferably, the temperature of the reaction in step (1) is 55-75°C, such as 55°C, 60°C, 65°C, 70°C, 75°C, etc., and the reaction time is 8-12 h, such as 8 h, 9 h, 10 h, 11 h, 12 h, etc.

[0042] Preferably, the molar ratio of raw material C to raw material B in step (2) is 1:(1-3), such as 1:1, 1:1.2, 1:1.4, 1:1.6, 1:1.8, 1:2, 1:2.2, 1:2.4, 1:2.6, 1:2.8, 1:3, etc.

[0043] Preferably, the catalyst described in step (2) includes any one or a combination of at least two of potassium carbonate, sodium carbonate, and sodium hydride.

[0044] Preferably, the molar ratio of raw material C to the catalyst in step (2) is 1:(1.5 - 3), such as 1:1.5, 1:1.6, 1:1.8, 1:2, 1:2.2, 1:2.4, 1:2.6, 1:2.8, 1:3, etc.

[0045] Preferably, the organic solvent described in step (2) includes any one or a combination of at least two of dichloromethane, acetone, and tetrahydrofuran.

[0046] Preferably, the temperature of the reaction in step (2) is 55 - 75°C, such as 55°C, 60°C, 65°C, 70°C, 75°C, etc., and the reaction time is 8 - 12 h, such as 8 h, 9 h, 10 h, 11 h, 12 h, etc.

[0047] As a preferred technical solution of the present invention, both step (1) and step (2) are carried out under magnetic stirring, but there are no special limitations on the rate and time of magnetic stirring, and it is only necessary to mix each component evenly.

[0048] As a preferred technical solution of the present invention, in both step (1) and step (2), after mixing other components, raw material B is added to the system. Preferably, the addition method of raw material B is dropwise addition through a constant pressure dropping funnel, and the dropping rate is preferably one drop every 3 - 5 seconds.

[0049] As a preferred technical solution of the present invention, the reactions in both step (1) and step (2) are carried out under an oil bath condition; after the above reactions are completed, the present invention preferably washes, first dries, recrystallizes, and second dries the reaction products in sequence to obtain the first compound and the second compound.

[0050] Preferably, the washing liquid used for washing is preferably saturated sodium bicarbonate aqueous solution or pure water; the present invention preferably washes with saturated sodium bicarbonate aqueous solution and pure water in sequence; the washing method preferably uses a beaker and magnetic stirring, and the washing times for each washing liquid are preferably 1 - 2 times.

[0051] Preferably, after the washing is completed, the present invention preferably dries the washed material; in the present invention, the first drying and the second drying preferably use an oven for drying, the drying temperature is preferably 70 - 80°C (such as 70°C, 75°C, 80°C, etc.), and the drying time is preferably 6 - 9 h (such as 6 h, 7 h, 8 h, 9 h, etc.).

[0052] Preferably, the solvent used for recrystallization in the present invention is a mixed solution of methanol and ethanol, and the recrystallization temperature is preferably 55 - 65°C, such as 55°C, 60°C, 65°C, etc.

[0053] Preferably, the molar ratio of the Si-H groups in the hydrogen-containing polysiloxane in step (3) to the first compound and the second compound is 2:(0.4-2):(0-2). 0.4-2 can be, for example, 0.4, 0.6, 0.8, 1, 1.2, 1.4, 1.6, 1.8, 2, etc., and 0-2 can be, for example, 0 (i.e., without adding the second compound), 0.2, 0.4, 0.6, 0.8, 1, 1.2, 1.4, 1.6, 1.8, 2, etc.

[0054] Preferably, the hydrosilylation catalyst in step (3) includes any one or a combination of at least two of chloroplatinic acid, Karstedt catalyst, and chloroplatinic acid complex, and chloroplatinic acid is preferred.

[0055] Preferably, based on the total feed amount in step (3) being 100 wt.% (i.e., based on the total amount of the first compound, the optional second compound, the hydrogen-containing polysiloxane, the hydrosilylation catalyst, and the solvent in step (3) being 100 wt.%), the amount of the hydrosilylation catalyst used is 2-100 ppm, such as 2 ppm, 4 ppm, 6 ppm, 8 ppm, 10 ppm, 12 ppm, 14 ppm, 16 ppm, 18 ppm, 20 ppm, 30 ppm, 40 ppm, 50 ppm, 60 ppm, 70 ppm, 80 ppm, 90 ppm, 100 ppm, etc., and 3-50 ppm is preferred.

[0056] Preferably, the solvent in step (3) includes chloroform.

[0057] Preferably, the temperature of the hydrosilylation reaction in step (3) is 75-110 °C, such as 75 °C, 80 °C, 85 °C, 90 °C, 95 °C, 100 °C, 105 °C, 110 °C, etc., and the time of the hydrosilylation reaction is 10-12 h, such as 10 h, 10.5 h, 11 h, 11.5 h, 12 h, etc.

[0058] Preferably, after the hydrosilylation reaction in step (3), it further includes a step of removing the solvent by vacuum heating.

[0059] Preferably, the temperature for removing the solvent by vacuum heating is 60-80 °C, such as 60 °C, 65 °C, 70 °C, 75 °C, 80 °C, etc., and the time is 3-5 h, such as 3 h, 3.5 h, 4 h, 4.5 h, 5 h, etc.

[0060] Preferably, the pressure of the hot pressing in step (3) is 0.05 - 0.1 MPa, such as 0.05 MPa, 0.06 MPa, 0.07 MPa, 0.08 MPa, 0.09 MPa, 0.1 MPa, etc.; the temperature of the hot pressing is 100 - 125 °C, such as 100 °C, 105 °C, 110 °C, 115 °C, 120 °C, 125 °C, etc.; and the time of the hot pressing is 10 - 20 min, such as 10 min, 15 min, 20 min, etc.

[0061] In a second aspect, the present invention provides an intrinsic thermally conductive liquid crystal polymer material, which is prepared by the preparation method as described in the first aspect.

[0062] In a third aspect, the present invention provides an application of the intrinsic thermally conductive liquid crystal polymer material as described in the second aspect in an interface material.

[0063] Compared with the prior art, the present invention has the following beneficial effects:

[0064] The intrinsic thermally conductive liquid crystal polymer material prepared by the preparation method provided by the present invention has a structure including mesogenic groups (biphenyl groups, cyanobiphenyl groups) and flexible polysiloxane chains, and has thermally conductive liquid crystal properties. Rigid biphenyl and partially charged cyanobiphenyl mesogenic units are introduced onto the flexible polydimethylsiloxane chains. The stacking of the side chains and the π-π interaction between molecules achieve the ordered arrangement of liquid crystal polymer molecules. The ordered microstructure forms an excellent continuous heat conduction network, thereby enabling the liquid crystal polymer material to have a high thermal conductivity. The highest thermal conductivity of the intrinsic thermally conductive liquid crystal polymer material provided by the present invention can reach 0.58 W·m -1 K -1 , which is 2.9 times that of the general PDMS thermal conductivity (0.20 W·m -1 K -1 ). BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 1H NMR spectra of the first compound and the second compound prepared in Example 1 of the present invention.

[0066] Figure 2 Schematic structural diagrams of the intrinsic thermally conductive liquid crystal polymer materials provided in Examples 2 - 4 of the present invention.

[0067] Figure 3 Infrared spectra of the intrinsic thermally conductive liquid crystal polymer materials provided in Examples 1 - 4 and Comparative Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0068] The technical solution of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0069] In the preparation method of the intrinsic thermally conductive liquid crystal polymer material provided in the following specific embodiments of the present invention, first, through main raw materials such as hydroxybiphenyl, raw material B (such as allyl bromide, etc.), cyanobiphenol, and a catalyst, liquid crystal monomers (S-CL, H-B) are prepared by Williamson ether reactions. The Williamson ether reaction products and hydrogen-containing polydimethylsiloxane are synthesized into a series of intrinsic thermally conductive liquid crystal polysiloxanes (i.e., intrinsic thermally conductive liquid crystal polymer materials) through hydrosilylation reactions. The rigid and partially electron-bearing mesogenic unit side chains are arranged in an orderly manner and the π-π stacking structure between molecules inhibits the random orientation of the chains, thereby realizing the orderliness of the layered arrangement structure.

[0070] Unless otherwise specified, the H-PMDS used in the following examples of the present invention is prepared by the following method:

[0071] PHMS (H% = 1.25%) (1.500 g), D4 (octamethylcyclotetrasiloxane, 0.250 g), and MM (hexamethyldisiloxane, 0.125 g) are added to a three-necked round-bottom flask equipped with a magnetic stirrer, a spherical condenser refluxer, a thermometer, and a constant-pressure dropping funnel. Sulfuric acid (0.0357 g) is contained in the constant-pressure dropping funnel. Sulfuric acid is added dropwise, and the mixture is stirred at 50 °C for 6 hours. After telomerization, the flask is cooled to room temperature, and sodium bicarbonate (0.0607 g) is added in batches. After filtration, the crude product is rotary evaporated under reduced pressure at 40 °C to remove low-boiling products to obtain H-PDMS (H% = 1.0%).

[0072] Example 1

[0073] In this example, a preparation method of an intrinsic thermally conductive liquid crystal polymer material is provided. The preparation method includes the following steps:

[0074] (1) A mixture of 4,4'-dihydroxybiphenyl (10.0 g, 0.0537 mol), potassium carbonate (22.27 g, 0.1615 mol) and sodium hydride (0.1 g) was added to a three-necked flask equipped with a magnetic stirrer. 100 mL of acetone solvent was added, and the mixture was stirred for 30 min under a nitrogen atmosphere. Then, allyl bromide (19.49 g, 0.1625 mol) was slowly added to the above reaction system through a constant-pressure dropping funnel, and the temperature was gradually raised to 65 °C. The mixture was kept reacting with stirring for 12 h. After that, the reaction was cooled to room temperature, most of the solvent was removed by rotary evaporation, and the product was washed successively with saturated aqueous sodium hydroxide solution and distilled water. The final product was placed in an oven and dried for 6 h to obtain the final first compound (S-CL).

[0075] (2) A mixture of 4-cyanobiphenyl-4'-ol (20 g, 0.1025 mol), potassium carbonate (28.32 g, 0.2053 mol) and sodium hydride (0.1 g) was added to a three-necked flask equipped with a magnetic stirrer. 100 mL of acetone solvent was added, and the mixture was stirred for 30 min under a nitrogen atmosphere. Then, allyl bromide (13.01 g, 0.1084 mol) was slowly added to the above reaction system through a constant-pressure dropping funnel, and the temperature was gradually raised to 65 °C. The mixture was kept reacting with stirring for 12 h. After that, the reaction was cooled to room temperature, most of the solvent was removed by rotary evaporation, and the product was washed successively with saturated aqueous sodium hydroxide solution and distilled water. The final product was placed in an oven and dried for 6 h to obtain the final second compound (H-B).

[0076] (3) H-PMDS (0.20 g, containing 2.0 mmol Si-H groups) and S-CL (0.55 g, 2.07 mmol) were dissolved in 10 mL of chloroform and sonicated at high power for 5 min to ensure uniform dispersion. Then, after injecting 2.0 mg of a pre-prepared chloroplatinic acid solution (1 g of chloroplatinic acid dissolved in 50 g of isopropanol), the mixture solution was poured into a polytetrafluoroethylene (PTFE) square mold (60 mm long, 60 mm wide, 20 mm high). The PTFE mold was sonicated for 5 minutes to remove air bubbles in the mixture solution, and then heated in an oven at 80 °C for 12 h to complete the hydrosilylation cross-linking process. After cooling to room temperature, the LCPM sample was taken out of the PTFE mold, and then the above gel was hot-pressed at 0.05 MPa and 125 °C for 10 min. Finally, an intrinsic thermally conductive liquid crystal polymer material, denoted as LCPM1, was obtained and cooled at room temperature.

[0077] The 1H NMR spectra of the first compound and the second compound prepared in this example are as Figure 1As shown, it can be seen that the characteristic singlet peak of the methylene group connected to the alkenyl group is at 4.60 - 4.62 ppm, the two doublets at 5.3 - 5.5 ppm and the multiplet at 6.1 ppm are characteristic peaks of the alkenyl group, and the peaks at 7.0 - 7.7 ppm are characteristic peaks of the hydrogen protons on the benzene ring, which proves that the first compound and the second compound are successfully synthesized.

[0078] Example 2

[0079] In this example, a preparation method of an intrinsic thermally conductive liquid crystal polymer material is provided. The preparation method includes the following steps:

[0080] Steps (1) and (2) are the same as those in Example 1. Step (3) includes the following steps:

[0081] Dissolve H-PMDS (0.20 g, containing 2.0 mmol Si-H groups), S-CL (0.44 g, 1.65 mmol) and H-B (0.11 g, 0.47 mmol) in 10 mL of chloroform, and ultrasonically treat with high power for 5 min to ensure uniform dispersion. Then, after injecting 2.0 mg of a pre-prepared chloroplatinic acid solution (1 g of chloroplatinic acid dissolved in 50 g of isopropanol), pour the mixture solution into a polytetrafluoroethylene (PTFE) square mold (60 mm in length, 60 mm in width, 20 mm in height). Ultrasonically treat the PTFE mold for 5 minutes to remove the bubbles in the mixture solution, and then heat it in an oven at 80 °C for 12 h to complete the hydrosilylation cross-linking process. After cooling to room temperature, take out the LCPM sample from the PTFE mold, and then hot press the above gel at 0.05 MPa and 125 °C for 10 min. Finally, obtain the intrinsic thermally conductive liquid crystal polymer material, denoted as LCPM 2, and cool it at room temperature.

[0082] Example 3

[0083] In this example, a preparation method of an intrinsic thermally conductive liquid crystal polymer material is provided. The preparation method includes the following steps:

[0084] Steps (1) and (2) are the same as those in Example 1. Step (3) includes the following steps:

[0085] Dissolve H-PMDS (0.20 g, containing 2.0 mmol Si-H groups), S-CL (0.27 g, 1.01 mmol), and H-B (0.26 g, 1.11 mmol) in 10 mL of chloroform and ultrasonicate at high power for 5 min to ensure uniform dispersion. Then, after injecting 2.0 mg of a pre-prepared chloroplatinic acid solution (1 g of chloroplatinic acid dissolved in 50 g of isopropanol), pour the mixture solution into a polytetrafluoroethylene (PTFE) square mold (60 mm in length, 60 mm in width, and 20 mm in height). Ultrasonicate the PTFE mold for 5 minutes to remove air bubbles in the mixture solution, and then heat it in an oven at 80 °C for 12 h to complete the hydrosilylation cross-linking process. After cooling to room temperature, take out the LCPM sample from the PTFE mold, and then hot-press the above gel at 0.05 MPa and 125 °C for 10 min to finally obtain an intrinsic thermally conductive liquid crystal polymer material, denoted as LCPM 3, and cool it at room temperature.

[0086] Example 4

[0087] In this example, a method for preparing an intrinsic thermally conductive liquid crystal polymer material is provided, and the preparation method includes the following steps:

[0088] Steps (1) and (2) are the same as those in Example 1, and step (3) includes the following steps:

[0089] Dissolve H-PMDS (0.20 g, containing 2.0 mmol Si-H groups), S-CL (0.11 g, 0.41 mmol), and H-B (0.48 g, 2.04 mmol) in 10 mL of chloroform and ultrasonicate at high power for 5 min to ensure uniform dispersion. Then, after injecting 2.0 mg of a pre-prepared chloroplatinic acid solution (1 g of chloroplatinic acid dissolved in 50 g of isopropanol), pour the mixture solution into a polytetrafluoroethylene (PTFE) square mold (60 mm in length, 60 mm in width, and 20 mm in height). Ultrasonicate the PTFE mold for 5 minutes to remove air bubbles in the mixture solution, and then heat it in an oven at 80 °C for 12 h to complete the hydrosilylation cross-linking process. After cooling to room temperature, take out the LCPM sample from the PTFE mold, and then hot-press the above gel at 0.05 MPa and 125 °C for 10 min to finally obtain an intrinsic thermally conductive liquid crystal polymer material, denoted as LCPM 4, and cool it at room temperature.

[0090] Comparative Example 1

[0091] In this comparative example, a method for preparing an intrinsic thermally conductive liquid crystal polymer material is provided, and the preparation method includes the following steps:

[0092] Steps (1) and (2) are the same as those in Example 1, and step (3) includes the following steps:

[0093] Dissolve H-PMDS (0.20 g, containing 2.0 mmol Si-H groups) and H-B (0.52 g, 2.21 mmol) in 10 mL of chloroform, and ultrasonically treat them at high power for 5 min to ensure uniform dispersion. Then, after injecting 2.0 mg of the pre-prepared chloroplatinic acid solution (1 g of chloroplatinic acid dissolved in 50 g of isopropanol), pour the mixture solution into a polytetrafluoroethylene (PTFE) square mold (60 mm in length, 60 mm in width, and 20 mm in height). Ultrasonically treat the PTFE mold for 5 minutes to remove the bubbles in the mixture solution, and then heat it in an oven at 80 °C for 12 h to complete the hydrosilylation cross-linking process. After cooling to room temperature, take out the LCPM sample from the PTFE mold, and then hot press the above gel at 0.05 MPa and 125 °C for 10 min to finally obtain the intrinsic thermally conductive liquid crystal polymer material, denoted as LCPM 5, and cool it at room temperature.

[0094] Comparative Example 2

[0095] In this comparative example, a conventional PDMS (RH-H512, hydrogen content 1.15 - 1.25%) is provided.

[0096] The structural schematic diagrams of the intrinsic thermally conductive liquid crystal polymer materials provided in Examples 2 - 4 of the present invention are as Figure 2 shown.

[0097] The infrared spectra of the intrinsic thermally conductive liquid crystal polymer materials provided in Examples 1 - 4 of the present invention and Comparative Example 1 are as Figure 3 shown.

[0098] Use a Ruiying thermal conductivity tester to measure the thermal conductivity (λ) of the intrinsic thermally conductive liquid crystal polymer materials provided in the examples and comparative examples of the present invention, and the test results are shown in Table 1.

[0099] Table 1

[0100] <![CDATA[λ (W·m -1 K -1 )]]> Example 1 0.58 Example 2 0.46 Example 3 0.31 Example 4 0.24 Comparative Example 1 0.18 Comparative Example 2 0.20

[0101] As can be seen from Table 1, compared with the conventional PDMS (Comparative Example 2), the intrinsic thermally conductive liquid crystal polymer materials provided in the examples of the present invention all have relatively high thermal conductivities (0.24 - 0.58 W·m -1 K -1 ).

[0102] Compared with Example 1, the thermal conductivity of the intrinsic thermally conductive liquid crystal polymer material provided in Comparative Example 1 is significantly reduced.

[0103] The applicant declares that the present invention uses the above embodiments to illustrate the intrinsic thermally conductive liquid crystal polymer material and its preparation method and application of the present invention. However, the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent substitution of the raw materials selected for the present invention, the addition of auxiliary components, the selection of specific methods, etc. all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for preparing an intrinsically thermally conductive liquid crystal polymer material, characterized in that: The preparation method comprises the following steps: (1) mixing raw material A, raw material B, a catalyst and an organic solvent, and reacting them to obtain a first compound; (2) mixing raw material C, raw material B, a catalyst and an organic solvent, and reacting to obtain a second compound; (3) mixing the first compound, the optional second compound, the hydrogen-containing polysiloxane, the hydrosilylation catalyst and the solvent, performing a hydrosilylation reaction, and hot pressing to obtain the intrinsically thermally conductive liquid crystal polymer material; Wherein, the raw material A has the structure shown in the following formula I: The raw material B in step (1) and step (2) each independently has a structure shown in the following formula II: In formula II, X is a halogen, and a is an integer from 0 to 2; Raw material C has the structure shown in the following formula III:

2. The intrinsic thermal conductive liquid crystal polymer material according to claim 1, characterized in that: The raw material A is Preferably, in formula II, X is -Br; Preferably, in formula II, a is 0; Preferably, the raw materials B in step (1) and step (2) are Preferably, the raw material C is 3. The preparation method according to claim 1 or 2, characterized in that: The hydrogen-containing polysiloxane has a structure shown in the following formula IV: In formula IV, n and z are each independently an integer of 0 to 30, and n and z are not simultaneously 0; m is an integer of 0 to 30; R is -H or a C1-C10 straight or branched alkyl group; Preferably, R is -H or -CH3.

4. The preparation method according to any one of claims 1 to 3, characterized in that The molar ratio of raw material A to raw material B in step (1) is 1:(1-3); Preferably, the catalyst in step (1) comprises any one of potassium carbonate, sodium carbonate, sodium hydride, or a combination of at least two thereof; Preferably, the molar ratio of the raw material A to the catalyst in step (1) is 1:(1.5-3); Preferably, the organic solvent in step (1) comprises dichloromethane and / or acetone; Preferably, the reaction temperature in step (1) is 55-75° C., and the reaction time is 8-12 h.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The molar ratio of raw material C to raw material B in step (2) is 1:(1-3); Preferably, the catalyst in step (2) comprises any one of potassium carbonate, sodium carbonate, sodium hydride, or a combination of at least two thereof; Preferably, the molar ratio of the raw material C to the catalyst in step (2) is 1:(1.5-3); Preferably, the organic solvent in step (2) comprises any one of dichloromethane, acetone, tetrahydrofuran, or a combination of at least two thereof; Preferably, the reaction temperature in step (2) is 55-75° C., and the reaction time is 8-12 h.

6. The preparation method according to any one of claims 1 to 5, characterized in that: In step (3), the molar ratio of Si-H groups in the hydrogen-containing polysiloxane to the first compound and the second compound is 2:(0.4-2):(0-2); Preferably, the hydrosilylation catalyst in step (3) comprises any one of chloroplatinic acid, Karstedt catalyst, and chloroplatinic acid complex, or a combination of at least two thereof; Preferably, based on the total feed amount in step (3) being 100 wt.%, the amount of the hydrosilylation catalyst used is 2-100 ppm; Preferably, the solvent in step (3) comprises chloroform; Preferably, the temperature of the hydrosilylation reaction in step (3) is 75-110° C., and the time of the hydrosilylation reaction is 10-12 h.

7. The preparation method according to any one of claims 1 to 6, characterized in that: After the hydrosilylation reaction in step (3), the step further comprises the step of removing the solvent by vacuum heating; Preferably, the temperature of the vacuum heating to remove the solvent is 60-80° C. and the time is 3-5 h.

8. The preparation method according to any one of claims 1 to 7, characterized in that: The hot pressing pressure in step (3) is 0.05-0.1 MPa, the hot pressing temperature is 100-125° C., and the hot pressing time is 10-20 min.

9. An intrinsically thermally conductive liquid crystal polymer material, characterized in that: The intrinsic thermal conductive liquid crystal polymer material is prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the intrinsic thermal conductive liquid crystal polymer material according to claim 9 in interface materials.

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