Epoxy resin-based liquid crystal polymer with low glass transition temperature as well as preparation method and application of epoxy resin-based liquid crystal polymer

Abstract

The invention discloses an epoxy resin-based liquid crystal polymer with low glass transition temperature and a preparation method and application thereof. The epoxy resin-based liquid crystal polymer with low glass transition temperature is prepared from the following raw materials: an epoxy resin-based liquid crystal polymerizable monomer, a chain extender, a cross-linking agent, a thermal polymerization catalyst, a cationic polymerization initiator, a cationic polymerization sensitizer and a cationic polymerization additive. The epoxy resin-based liquid crystal polymerizable monomer comprises at least three of a compound shown as a formula 1, a compound shown as a formula 2, a compound shown as a formula 3, a compound shown as a formula 4, a compound shown as a formula 5, a compound shown as a formula 6, a compound shown as a formula 7, a compound shown as a formula 8 and a compound shown as a formula 9. The epoxy resin-based liquid crystal polymer has the advantages of low glass transition temperature, high mechanical strength, high elastic modulus, high elongation at break and high thermal stability.

Description

Technical Field

[0001] This application belongs to the field of liquid crystal polymer materials technology, specifically relating to an epoxy resin-based liquid crystal polymer with a low glass transition temperature, its preparation method, and its application. Background Technology

[0002] Liquid crystal polymer composites combine the properties of liquid crystal polymers with the useful properties of other composite components, which is beneficial for improving the performance of materials and expanding their application fields.

[0003] However, the most researched acrylate-based liquid crystal polymers currently suffer from low strength, making them unsuitable for high-strength structural materials. Epoxy resin-based liquid crystal polymers, on the other hand, have high glass transition temperatures, resulting in brittleness, low elongation at break, and poor mechanical properties, significantly hindering their practical applications. To apply epoxy resin-based liquid crystal polymers to advanced resin engineering materials, the glass transition temperature of the polymer should be further reduced while maintaining high strength. Therefore, there is an urgent need to develop an epoxy resin-based liquid crystal polymer with high strength and a low glass transition temperature. Summary of the Invention

[0004] To address the problems mentioned in the background section, the present invention aims to provide an epoxy resin-based liquid crystal polymer with a low glass transition temperature, its preparation method, and its applications. The epoxy resin-based liquid crystal polymer of the present invention exhibits a low glass transition temperature, high mechanical strength, high elastic modulus, high elongation at break, and high thermal stability.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: On the one hand, the present invention provides an epoxy resin-based liquid crystal polymer with a low glass transition temperature, wherein the raw materials for preparing the epoxy resin-based liquid crystal polymer with a low glass transition temperature include epoxy resin-based liquid crystal polymerizable monomers, chain extenders, crosslinking agents, thermal polymerization catalysts, cationic polymerization initiators, cationic polymerization sensitizers, and cationic polymerization auxiliaries. The epoxy resin-based liquid crystal polymerizable monomer includes at least three (preferably at least five) compounds from the following formulas: Formula 1, Formula 2, Formula 3, Formula 4, Formula 5, Formula 6, Formula 7, Formula 8, and Formula 9.

[0006] Formula 1

[0007] Formula 2

[0008] Formula 3

[0009] Formula 4

[0010] Formula 5

[0011] Formula 6

[0012] Formula 7

[0013] Formula 8

[0014] Formula 9 In formulas 1 to 9, X1 is selected from groups. or X2 is selected from the group or m is an integer from 1 to 10, and n is an integer from 1 to 10.

[0015] The epoxy resin-based liquid crystal polymer with low glass transition temperature of the present invention preferably uses an aromatic ester type of liquid crystal unit of an epoxy resin-based liquid crystal polymerizable monomer, which not only broadens the temperature range of the liquid crystal, but also increases the compatibility of the mixed liquid crystal.

[0016] Furthermore, the epoxy resin-based liquid crystal polymerizable monomer has a liquid crystal phase transition point below 60°C and a clearing point above 120°C. This wider liquid crystal phase temperature range is beneficial, firstly, for broadening the processing temperature range of the material preparation, and secondly, for lowering the glass transition temperature of the liquid crystal polymer.

[0017] Furthermore, the glass transition temperature of the epoxy resin-based liquid crystal polymer with a low glass transition temperature is preferably 0-20°C.

[0018] Furthermore, the glass transition temperature of the epoxy resin-based liquid crystal polymer with a low glass transition temperature is preferably 20-40°C.

[0019] Furthermore, the glass transition temperature of the epoxy resin-based liquid crystal polymer with a low glass transition temperature is preferably 40-60°C.

[0020] Furthermore, the chain extender is selected from at least one of the following compounds: , where m is an integer from 1 to 10, and n is an integer from 1 to 10.

[0021] Furthermore, the crosslinking agent is selected from at least one of the following compounds: , Capcure3800, where a is an integer from 1 to 8, b is an integer from 1 to 8, c is an integer from 1 to 8, and d is an integer from 1 to 8.

[0022] Furthermore, the thermal polymerization catalyst is selected from at least one of diethylamine, ethylenediamine, dihexyltriamine, polyethylenepolyamine, polyetherdiamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, hexanediamine, and 2,4,6-tris(dimethylaminomethyl)phenol; The cationic polymerization initiator is selected from at least one of the following: di[4-diphenylthiophenyl]sulfide dihexafluoroantimonate, bis(4-tert-butylphenyl)iodohexafluorophosphate, di-tert-butylphenyliodomonium hexafluorophosphate, bis(4-tert-butylphenyl)iodomonium hexafluorophosphate, benzoin ether, 4-isobutylphenyl-4'-methylphenyliodohexafluorophosphate, isopropylphenylcyclopentadiene iron hexafluorophosphate, bis(4-dodecylbenzene)iodohexafluoroantimonate, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, and diphenyl-(4-phenylthio)phenylsulfonium hexafluoroantimonate. The cationic polymerization sensitizer is selected from at least one of the following: benzoin diethyl ether, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexylphenyl ketone, isopropylthioxanthone (2,4 isomer mixture), bis(2,6-difluoro-3-pyrrolephenyldicyclopentadiene), and 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone; The cationic polymerization aid is selected from at least one of alicyclic epoxy resin 1700, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylic acid ester, and diglycidyl hexahydrophthalic acid ester.

[0023] Furthermore, the content of the chain extender, crosslinking agent, and thermal polymerization catalyst is 0-50% of the total weight of the epoxy resin-based liquid crystal polymerizable monomers, preferably 0-30%. The content of the cationic polymerization initiator, cationic polymerization sensitizer, and cationic polymerization auxiliaries is 0-30% of the total weight of the epoxy resin-based liquid crystal polymerizable monomers, preferably 0-25%.

[0024] Further, the mass ratio of the chain extender, crosslinking agent, and thermal polymerization catalyst is (0-10):(0-10):(0-5); The mass ratio of the cationic polymerization initiator, cationic polymerization sensitizer and cationic polymerization auxiliary is (0-1):(0-1):(0-10).

[0025] On the other hand, the present invention provides a method for preparing an epoxy resin-based liquid crystal polymer with a low glass transition temperature as described above, comprising the following steps: The epoxy resin-based liquid crystal polymerizable monomer, chain extender, crosslinking agent, thermal polymerization catalyst, cationic polymerization initiator, cationic polymerization sensitizer, and cationic polymerization auxiliaries are mixed evenly to obtain a mixture; The mixture is injected into a sealed container to obtain a sample; wherein the upper and lower surfaces of the sealed container have a friction interface that induces the parallel alignment of liquid crystals; or the upper and lower surfaces of the sealed container have a friction interface that induces the parallel alignment of liquid crystals and a magnetic field or electric field is applied along the direction of liquid crystal alignment induced by the friction interface; or the upper and lower surfaces of the sealed container do not have a friction interface that induces the parallel alignment of liquid crystals, and a magnetic field or electric field perpendicular to the thickness direction is applied. The sample was cured to obtain an epoxy resin-based liquid crystal polymer with a low glass transition temperature.

[0026] The preparation method of the present invention uses surface induction or the anisotropy of liquid crystal to orient the sample, thereby orienting the mesocrystalline units in the polymer.

[0027] Furthermore, the thickness of the sealed container is 0.5-2000 μm.

[0028] Furthermore, the curing process involves first performing thermal polymerization at 40-150℃ for 0-120 h, followed by curing at (-20)-150℃ with 10-500 mW / cm 2 UV-polymerization 0-10 6 The process involves cationic photopolymerization, wherein the durations of thermal polymerization and cationic photopolymerization are not both 0.

[0029] The above numerical range should be understood to mean that each intermediate value between the upper and lower limits of the range is not specifically disclosed.

[0030] On the other hand, the present invention provides an application of the epoxy resin-based liquid crystal polymer with a low glass transition temperature as described above, or the epoxy resin-based liquid crystal polymer with a low glass transition temperature prepared by any of the above-described preparation methods, in advanced resin engineering materials.

[0031] Compared with the prior art, the present invention has the following beneficial effects: (1) The epoxy resin-based liquid crystal polymer of the present invention has a low glass transition temperature, high mechanical strength, high elastic modulus, high elongation at break and high thermal stability.

[0032] (2) The preparation method of the present invention is simple, which makes it have broad application prospects in advanced resin engineering materials. Attached Figure Description

[0033] Figure 1 These are DSC curves of epoxy resin-based liquid crystal polymerizable monomers from Examples 1-3 of this invention; Figure 2 This is a stress-strain curve of epoxy resin-based liquid crystal polymer Al with a low glass transition temperature prepared in Example 1 of the present invention. Figure 3 This is a DSC curve of epoxy resin-based liquid crystal polymer A1 with a low glass transition temperature prepared in Example 1 of the present invention. Figure 4 This is a TGA curve of epoxy resin-based liquid crystal polymer A1 with a low glass transition temperature prepared in Example 1 of the present invention. Figure 5 This is a stress-strain curve of epoxy resin-based liquid crystal polymer A2 with a low glass transition temperature prepared in Example 2 of the present invention. Figure 6 This is a DSC curve of epoxy resin-based liquid crystal polymer A2 with a low glass transition temperature prepared in Example 2 of the present invention. Figure 7 This is a TGA curve of epoxy resin-based liquid crystal polymer A2 with a low glass transition temperature prepared in Example 2 of the present invention. Figure 8 This is a stress-strain curve of epoxy resin-based liquid crystal polymer A3 with a low glass transition temperature prepared in Example 3 of the present invention. Figure 9 This is a DSC curve of epoxy resin-based liquid crystal polymer A3 with a low glass transition temperature prepared in Example 3 of the present invention. Figure 10 This is a TGA curve of epoxy resin-based liquid crystal polymer A3 with a low glass transition temperature prepared in Example 3 of the present invention. Figure 11 This is a stress-strain curve of the acrylate-thiol polymer S1 prepared in Comparative Example 1 of this invention. Figure 12 This is a stress-strain curve of the epoxy resin-based liquid crystal polymer S2 prepared in Comparative Example 2 of this invention. Figure 13 This is a DSC curve of the epoxy resin-based liquid crystal polymerizable monomer used in Comparative Example 2 of this invention. Figure 14 This is a DSC curve of the epoxy resin-based liquid crystal polymer S2 prepared in Comparative Example 2 of this invention. Figure 15 This is a TGA curve of the epoxy resin-based liquid crystal polymer S2 prepared in Comparative Example 2 of this invention. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings. The described embodiments should not be regarded as limitations on this application. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0035] It should be noted that all raw materials and / or reagents in the embodiments and comparative examples of this application were purchased commercially or prepared according to conventional methods known to those skilled in the art.

[0036] The mechanical properties of liquid crystal polymers in this invention's embodiments and comparative examples were tested using an electronic universal testing machine (CMT4503, Shenzhen Branch of MTECH Industrial Systems (China) Co., Ltd.). The specimen gauge length was 20 mm, width was 5 mm, thickness was 100 micrometers, and the tensile rate was 10 mm / min. Fracture strength was defined as the maximum stress in the stress-strain curve, elastic modulus was the ratio of maximum stress to strain in the elastic phase of the stress-strain curve, and elongation at break referred to the strain at which fracture strength was achieved.

[0037] The thermal properties of liquid crystal polymers were tested using a differential scanning calorimeter (Q2000, TA) in the embodiments and comparative examples of this invention. The temperature change rate was 10℃ / min. The phase transition point refers to the temperature at which the polymer undergoes a phase transition, and the glass transition temperature refers to the temperature at which it transforms into a glassy state.

[0038] The thermal stability of liquid crystal polymers in the embodiments and comparative examples of this invention was tested using a thermogravimetric analyzer (SDT Q600, TA) at a heating rate of 10℃ / min. The thermal stability temperature is the temperature at which the polymer loses 5% (mass percentage) of weight.

[0039] The epoxy resin-based liquid crystal polymerizable monomers used in the embodiments of the present invention include 2-methyl-1,4-phenylene bis(4-(4-(ethylene oxide-2-yl)butoxy)benzoate) (E6M-mi), 2-methyl-1,4-phenylene bis(4-((7-(ethylene oxide-2-yl)heptyl)oxy)benzoate) (E9M-mi), and 2-methyl-1,4-phenylene bis(4-((9-(ethylene oxide-2-yl)nonyl) The following benzoates are listed: 2-methyl-1,4-phenylenebis(4-((8-(ethylene oxide-2-yl)octanoyl)oxy)benzoate (E9M-zhi), and 2-methyl-1,4-phenylenebis(4-((10-(ethylene oxide-2-yl)decanoyl)oxy)benzoate (E11M-zhi), with a mass ratio of 1:1:1:1:1. Their molecular structures are shown below: , , , , .

[0040] The epoxy resin-based liquid crystal polymerizable monomers in the examples were thermally characterized using differential scanning calorimetry, and the results are as follows: Figure 1 As shown. According to Figure 1 It is known that its crystal / liquid crystal transition point is around -15℃, and its clearing point is around 150℃. This broadens the processing temperature range of liquid crystal polymers and may also be beneficial for lowering the glass transition temperature of liquid crystal polymers.

[0041] Example 1 Epoxy resin-based liquid crystal polymer A1 with a low glass transition temperature: its raw materials include 2-methyl-1,4-phenylene bis(4-(4-(ethylene oxide-2-yl)butoxy)benzoate (E6M-mi), 2-methyl-1,4-phenylene bis(4-((7-(ethylene oxide-2-yl)heptyl)oxy)benzoate (E9M-mi), 2-methyl-1,4-phenylene bis(4-((9-(ethylene oxide-2-yl)nonyl)oxy)benzoate (E11M-mi), 2-methyl-1,4-phenylene bis(4-((8-(ethylene oxide-2-yl)octanoyl)oxy)benzoate (E9M-zhi), 2-methyl-1, 4-Phenylidene bis(4-((10-(ethylene oxide-2-yl)decanoyl)oxy)benzoate) (E11M-zhi), chain extender 3,6-dioxa-1,8-octanedithiol (DODT), crosslinking agent pentaerythritol tetrakis(3-mercaptopropionic acid) (PETMP), thermal polymerization catalyst 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30), cationic polymerization initiator di[4-diphenylthiophenyl]thioether dihexafluoroantimonate (1176), cationic polymerization sensitizer 2-hydroxy-2-methyl-1-phenyl-1-propanone (1173), cationic polymerization aid 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate (06E).

[0042] The preparation method of epoxy resin-based liquid crystal polymer A1 with a low glass transition temperature is as follows: (1) 2-methyl-1,4-phenylene bis(4-(4-(ethylene-2-yl)butoxy)benzoate) (E6M-mi), 2-methyl-1,4-phenylene bis(4-((7-(ethylene-2-yl)heptyl)oxy)benzoate) (E9M-mi), 2-methyl-1,4-phenylene bis(4-((9-(ethylene-2-yl)nonyl)oxy)benzoate) (E11M-mi), 2-methyl-1,4-phenylene bis(4-((8-(ethylene-2-yl)octanoyl)oxy)benzoate) (E9M-zhi), 2-methyl-1,4-phenylene bis(4-((10-(ethylene-2-yl)decanoyl)oxy)benzoate) (E11M-zhi) The following ingredients were mixed according to the mass fractions in Table 1: chain extender 3,6-dioxa-1,8-octanedithiol (DODT), crosslinking agent pentaerythritol tetrakis(3-mercaptopropionic acid) (PETMP), thermal polymerization catalyst 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30), cationic polymerization initiator di[4-diphenylthiophenyl]thioether dihexafluoroantimonate (1176), cationic polymerization sensitizer 2-hydroxy-2-methylphenylacetone (1173), and cationic polymerization aid 3,4-epoxycyclohexylcarboxylic acid-3',4'-epoxycyclohexylmethyl ester (06E). After thorough mixing, the mixture was injected into a liquid crystal cell made of two pieces of glass with a polyimide parallel orientation coating on the surface. The thickness of the liquid crystal cell was 100 μm.

[0043] (2) The liquid crystal cell in step 1 was cured at 80°C for 24 hours to prepare an epoxy resin-based liquid crystal polymer with a low glass transition temperature, denoted as A1.

[0044] Table 1. Mass fraction of each raw material in Example 1

[0045] The mechanical properties of the epoxy resin-based liquid crystal polymer A1 prepared in Example 1 were characterized using an electronic universal testing machine. The results are as follows: Figure 2 As shown. According to Figure 2 It can be seen that the tensile strength of epoxy resin-based liquid crystal polymer A1 is 45.28 MPa, the elastic modulus is 146.67 MPa, and the elongation at break is 30.87%.

[0046] The epoxy resin-based liquid crystal polymer A1 prepared in Example 1 was thermally characterized using differential scanning calorimetry, and the results are as follows: Figure 3 As shown. According to Figure 3 It is known that the glass transition temperature of epoxy resin-based liquid crystal polymer Al is 16℃ when heated and 12℃ when cooled. The glass transition temperature is relatively low. At room temperature (25℃), it is in a non-glassy state and is not a brittle material.

[0047] The thermal stability of the epoxy resin-based liquid crystal polymer A1 prepared in Example 1 was characterized using a thermogravimetric analyzer, and the results are as follows: Figure 4 As shown. According to Figure 4 It can be seen that the epoxy resin-based liquid crystal polymer A1 loses 5% of its weight at 295℃, indicating that the epoxy resin-based liquid crystal polymer A1 has good thermal stability.

[0048] Example 2 Epoxy resin-based liquid crystal polymer A2 with a low glass transition temperature: its raw materials include 2-methyl-1,4-phenylene bis(4-(4-(ethylene oxide-2-yl)butoxy)benzoate (E6M-mi), 2-methyl-1,4-phenylene bis(4-((7-(ethylene oxide-2-yl)heptyl)oxy)benzoate (E9M-mi), 2-methyl-1,4-phenylene bis(4-((9-(ethylene oxide-2-yl)nonyl)oxy)benzoate (E11M-mi), 2-methyl-1,4-phenylene bis(4-((8-(ethylene oxide-2-yl)octanoyl)oxy)benzoate (E9M-zhi), 2-methyl-1, 4-Phenylidene bis(4-((10-(ethylene oxide-2-yl)decanoyl)oxy)benzoate) (E11M-zhi), chain extender 3,6-dioxa-1,8-octanedithiol (DODT), crosslinking agent pentaerythritol tetrakis(3-mercaptopropionic acid) (PETMP), thermal polymerization catalyst 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30), cationic polymerization initiator di[4-diphenylthiophenyl]thioether dihexafluoroantimonate (1176), cationic polymerization sensitizer 2-hydroxy-2-methyl-1-phenyl-1-propanone (1173), cationic polymerization aid 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate (06E).

[0049] The preparation method of epoxy resin-based liquid crystal polymer A2 with a low glass transition temperature is as follows: (1) 2-methyl-1,4-phenylene bis(4-(4-(ethylene-2-yl)butoxy)benzoate) (E6M-mi), 2-methyl-1,4-phenylene bis(4-((7-(ethylene-2-yl)heptyl)oxy)benzoate) (E9M-mi), 2-methyl-1,4-phenylene bis(4-((9-(ethylene-2-yl)nonyl)oxy)benzoate) (E11M-mi), 2-methyl-1,4-phenylene bis(4-((8-(ethylene-2-yl)octanoyl)oxy)benzoate) (E9M-zhi), 2-methyl-1,4-phenylene bis(4-((10-(ethylene-2-yl)decanoyl)oxy)benzoate) (E11M-zhi) The following ingredients were mixed according to the mass fractions in Table 2: chain extender 3,6-dioxa-1,8-octanedithiol (DODT), crosslinking agent pentaerythritol tetrakis(3-mercaptopropionic acid) (PETMP), thermal polymerization catalyst 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30), cationic polymerization initiator di[4-diphenylthiophenyl]thioether dihexafluoroantimonate (1176), cationic polymerization sensitizer 2-hydroxy-2-methylphenylacetone (1173), and cationic polymerization aid 3,4-epoxycyclohexylcarboxylic acid-3',4'-epoxycyclohexylmethyl ester (06E). After thorough mixing, the mixture was injected into a liquid crystal cell made of two pieces of glass with a polyimide parallel orientation coating on the surface. The thickness of the liquid crystal cell was 100 μm.

[0050] (2) First, keep the liquid crystal cell in step 1 at 80℃ for 24 hours, and then heat it at 100mW / cm. 2 An epoxy resin-based liquid crystal polymer with a low glass transition temperature was prepared by irradiating it at room temperature for 5 minutes under ultraviolet light intensity, denoted as A2.

[0051] Table 2. Mass fraction of each raw material in Example 2

[0052] The mechanical properties of the epoxy resin-based liquid crystal polymer A2 prepared in Example 2 were characterized using an electronic universal testing machine. The results are as follows: Figure 5 As shown. According to Figure 5 It can be seen that the tensile strength of epoxy resin-based liquid crystal polymer A2 is 53.35 MPa, the elongation at break is 21.28%, and the elastic modulus is 250.70 MPa.

[0053] The epoxy resin-based liquid crystal polymer A2 prepared in Example 2 was thermally characterized using differential scanning calorimetry, and the results are as follows: Figure 6 As shown. According to Figure 6It is known that the glass transition temperature of epoxy resin-based liquid crystal polymer A2 is 23℃ when heated and 16℃ when cooled. It is not in a glassy state at room temperature, that is, it is not a brittle material.

[0054] The thermal stability of the epoxy resin-based liquid crystal polymer A2 prepared in Example 2 was characterized using a thermogravimetric analyzer, and the results are as follows: Figure 7 As shown. According to Figure 7 It can be seen that the epoxy resin-based liquid crystal polymer A2 loses 5% of its weight at 292℃, indicating that the epoxy resin-based liquid crystal polymer A2 has good thermal stability.

[0055] Example 3 Epoxy resin-based liquid crystal polymer A3 with a low glass transition temperature: its raw materials include 2-methyl-1,4-phenylene bis(4-(4-(ethylene oxide-2-yl)butoxy)benzoate (E6M-mi), 2-methyl-1,4-phenylene bis(4-((7-(ethylene oxide-2-yl)heptyl)oxy)benzoate (E9M-mi), 2-methyl-1,4-phenylene bis(4-((9-(ethylene oxide-2-yl)nonyl)oxy)benzoate (E11M-mi), 2-methyl-1,4-phenylene bis(4-((8-(ethylene oxide-2-yl)octanoyl)oxy)benzoate (E9M-zhi), 2-methyl-1, 4-Phenylidene bis(4-((10-(ethylene oxide-2-yl)decanoyl)oxy)benzoate) (E11M-zhi), chain extender 3,6-dioxa-1,8-octanedithiol (DODT), crosslinking agent pentaerythritol tetrakis(3-mercaptopropionic acid) (PETMP), thermal polymerization catalyst 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30), cationic polymerization initiator di[4-diphenylthiophenyl]thioether dihexafluoroantimonate (1176), cationic polymerization sensitizer 2-hydroxy-2-methyl-1-phenyl-1-propanone (1173), cationic polymerization aid 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate (06E).

[0056] The preparation method of epoxy resin-based liquid crystal polymer A3 with a low glass transition temperature is as follows: (1) 2-methyl-1,4-phenylene bis(4-(4-(ethylene-2-yl)butoxy)benzoate) (E6M-mi), 2-methyl-1,4-phenylene bis(4-((7-(ethylene-2-yl)heptyl)oxy)benzoate) (E9M-mi), 2-methyl-1,4-phenylene bis(4-((9-(ethylene-2-yl)nonyl)oxy)benzoate) (E11M-mi), 2-methyl-1,4-phenylene bis(4-((8-(ethylene-2-yl)octanoyl)oxy)benzoate) (E9M-zhi), 2-methyl-1,4-phenylene bis(4-((10-(ethylene-2-yl)decanoyl)oxy)benzoate) (E11M-zhi) The following ingredients were mixed according to the mass fractions in Table 3: chain extender 3,6-dioxa-1,8-octanedithiol (DODT), crosslinking agent pentaerythritol tetrakis(3-mercaptopropionic acid) (PETMP), thermal polymerization catalyst 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30), cationic polymerization initiator di[4-diphenylthiophenyl]thioether dihexafluoroantimonate (1176), cationic polymerization sensitizer 2-hydroxy-2-methylphenylacetone (1173), and cationic polymerization aid 3,4-epoxycyclohexylcarboxylic acid-3',4'-epoxycyclohexylmethyl ester (06E). After thorough mixing, the mixture was injected into a liquid crystal cell made of two pieces of glass with a polyimide parallel orientation coating on the surface. The thickness of the liquid crystal cell was 100 μm.

[0057] (2) Set the liquid crystal cell from step 1 to 100mW / cm 2 An epoxy resin-based liquid crystal polymer with a low glass transition temperature was prepared by irradiating it at room temperature for 5 minutes under ultraviolet light intensity, denoted as A3.

[0058] Table 3. Mass fraction of each raw material in Example 3

[0059] The mechanical properties of the epoxy resin-based liquid crystal polymer A3 prepared in Example 3 were characterized using an electronic universal testing machine. The results are as follows: Figure 8 As shown. According to Figure 8 It can be seen that the tensile strength of epoxy resin-based liquid crystal polymer A3 is 43.29 MPa, the elongation at break is 8.57%, and the elastic modulus is 505.13 MPa.

[0060] The epoxy resin-based liquid crystal polymer A3 prepared in Example 3 was thermally characterized using differential scanning calorimetry, and the results are as follows: Figure 9 As shown. According to Figure 9 It can be seen that the glass transition temperature of epoxy resin-based liquid crystal polymer A3 is 51℃ when heated and 46℃ when cooled, which is relatively low.

[0061] The thermal stability of the epoxy resin-based liquid crystal polymer A3 prepared in Example 3 was characterized using a thermogravimetric analyzer, and the results are as follows: Figure 10 As shown. According to Figure 10 It can be seen that the epoxy resin-based liquid crystal polymer A3 loses 5% of its weight at 302℃, indicating that the epoxy resin-based liquid crystal polymer A3 has good thermal stability.

[0062] Comparative Example 1 Acrylate-thiol polymer S1: Its raw materials include 1,4-butanediol diacrylate, 1,4-cyclohexanediethanol diacrylate, 3,6-dioxa-1,8-octanedithiol (DODT), pentaerythritol tetrakis(3-mercaptopropionic acid) ester (PETMP), triethylamine, and benzoin dimethyl ether (Irg 651).

[0063] The preparation method of acrylate-thiol polymer S1 is as follows: (1) 1,4-Butanediol diacrylate, 1,4-cyclohexanediethanol diacrylate, 3,6-dioxa-1,8-octanedithiol (DODT), pentaerythritol tetrakis(3-mercaptopropionic acid) (PETMP), triethylamine, and benzoin dimethyl ether (Irg 651) were mixed according to the mass fractions in Table 4. After being thoroughly stirred, the mixture was injected into a liquid crystal cell made of two pieces of glass with a polyimide parallel orientation coating on the surface. The thickness of the liquid crystal cell was 100 μm.

[0064] (2) First, keep the liquid crystal cell from step 1 at 60°C for 24 hours, then heat it at 5 mW / cm². 2 An acrylate-thiol polymer, denoted as S1, was prepared by irradiating the polymer at room temperature for 5 minutes under ultraviolet light intensity.

[0065] Table 4. Mass fraction of each raw material in Comparative Example 1

[0066] The mechanical properties of the acrylate-thiol polymer S1 prepared in Comparative Example 1 were characterized using an electronic universal testing machine. The results are as follows: Figure 11 As shown. According to Figure 11 It can be seen that the material has a fracture strength of 1.29 MPa, a fracture elongation of 18.04%, and an elastic modulus of 7.15 MPa. Its mechanical properties are significantly lower than those of Examples 1-3.

[0067] Comparative Example 2 Epoxy resin-based liquid crystal polymer S2: Its raw materials include 2-methyl-1,4-phenylene bis(4-((10-(epoxy-2-yl)decanoyl)oxy)benzoate (E11M-zhi), chain extender 3,6-dioxa-1,8-octanedithiol (DODT), crosslinking agent pentaerythritol tetrakis(3-mercaptopropionic acid) (PETMP), thermal polymerization catalyst 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30), cationic polymerization initiator di[4-diphenylthiophenyl]thioether dihexafluoroantimonate (1176), cationic polymerization sensitizer 2-hydroxy-2-methyl-1-phenyl-1-propanone (1173), and cationic polymerization aid 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate (06E).

[0068] The preparation method of epoxy resin-based liquid crystal polymer S2 is as follows: (1) 2-methyl-1,4-phenylene bis(4-((10-(ethylene oxide-2-yl)decanoyl)oxy)benzoate) (E11M-zhi), chain extender 3,6-dioxa-1,8-octanedithiol (DODT), crosslinking agent pentaerythritol tetrakis(3-mercaptopropionic acid) (PETMP), thermal polymerization catalyst 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30), and cationic polymerization initiator di[4-diphenylene]

[1176] di(2-hydroxy-2-methylphenylacetone) thioether (1176), 2-hydroxy-2-methylphenylacetone (1173) cationic polymerization sensitizer, and 3,4-epoxycyclohexylcarboxylic acid-3',4'-epoxycyclohexylmethyl ester (06E) cationic polymerization aid were mixed according to the mass fractions in Table 5. After thorough mixing, the mixture was injected into a liquid crystal cell made of two pieces of glass with parallel-aligned polyimide coatings on their surfaces. The thickness of the liquid crystal cell was 100 μm.

[0069] (2) First, keep the liquid crystal cell from step 1 at 80°C for 24 hours, then heat it at 100mW / cm². 2 An epoxy resin-based liquid crystal polymer, denoted as S2, was prepared by irradiating the product at room temperature for 5 minutes under ultraviolet light intensity.

[0070] Table 5. Mass fraction of each raw material in Comparative Example 2

[0071] The mechanical properties of the epoxy resin-based liquid crystal polymer S2 prepared in Comparative Example 2 were characterized using an electronic universal testing machine. The results are as follows: Figure 12 As shown. According to Figure 12 It can be seen that the tensile strength of epoxy resin-based liquid crystal polymer S2 is 34.55 MPa, the elongation at break is 19.12%, and the elastic modulus is 180.7 MPa. The comprehensive mechanical properties of epoxy resin-based liquid crystal polymer S2 are lower than those of Examples 1-3.

[0072] The epoxy resin-based liquid crystal polymerizable monomer in Comparative Example 2 was thermally characterized using differential scanning calorimetry, and the results are as follows: Figure 13 As shown.

[0073] The epoxy resin-based liquid crystal polymer S2 prepared in Comparative Example 2 was thermally characterized using differential scanning calorimetry, and the results are as follows: Figure 14 As shown. According to Figure 14 It can be seen that the glass transition temperature of epoxy resin-based liquid crystal polymer S2 is 58°C when heated and 62°C when cooled. The glass transition temperature is higher than that of Examples 1-3, and the material is more brittle at room temperature.

[0074] The thermal stability of the epoxy resin-based liquid crystal polymer S2 prepared in Comparative Example 2 was characterized using a thermogravimetric analyzer, and the results are as follows: Figure 15 As shown. According to Figure 15 It is known that the temperature at which epoxy resin-based liquid crystal polymer S2 loses 5% of its weight is 290℃.

[0075] In summary, due to the use of epoxy resin-based liquid crystal polymerizable monomers with mixed components, the temperature range of these monomers is broadened, resulting in polymers with glass transition temperatures all below 55℃. This leads to improved elongation at break (all above 8%), increased tensile strength (all above 40 MPa), and higher elastic modulus in the material's mechanical properties. Furthermore, by adjusting other polymer components and preparation methods, the material can achieve continuously varying glass transition temperatures, compositions, structures, and properties.

[0076] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An epoxy resin-based liquid crystal polymer with a low glass transition temperature, characterized in that, The raw materials for preparing the epoxy resin-based liquid crystal polymer with a low glass transition temperature include epoxy resin-based liquid crystal polymerizable monomers, chain extenders, crosslinking agents, thermal polymerization catalysts, cationic polymerization initiators, cationic polymerization sensitizers, and cationic polymerization auxiliaries. The epoxy resin-based liquid crystal polymerizable monomer includes at least three of the following compounds: compound 1, compound 2, compound 3, compound 4, compound 5, compound 6, compound 7, compound 8, and compound 9. Formula 1 Formula 2 Formula 3 Formula 4 Formula 5 Formula 6 Formula 7 Formula 8 Formula 9 In formulas 1 to 9, X1 is selected from groups. or X2 is selected from the group or m is an integer from 1 to 10, and n is an integer from 1 to 10.

2. The epoxy resin-based liquid crystal polymer with a low glass transition temperature according to claim 1, characterized in that, The chain extender is selected from at least one of the following compounds. , where m is an integer from 1 to 10, and n is an integer from 1 to 10.

3. The epoxy resin-based liquid crystal polymer with a low glass transition temperature according to claim 1, characterized in that, The crosslinking agent is selected from at least one of the following compounds. , Capcure 3800, where a is an integer from 1 to 8, b is an integer from 1 to 8, c is an integer from 1 to 8, and d is an integer from 1 to 8.

4. The epoxy resin-based liquid crystal polymer with a low glass transition temperature according to claim 1, characterized in that, The thermal polymerization catalyst is selected from at least one of diethylamine, ethylenediamine, dihexyltriamine, polyethylene polyamine, polyether diamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, hexanediamine, and 2,4,6-tris(dimethylaminomethyl)phenol; The cationic polymerization initiator is selected from at least one of the following: di[4-diphenylthiophenyl]sulfide dihexafluoroantimonate, bis(4-tert-butylphenyl)iodohexafluorophosphate, di-tert-butylphenyliodomonium hexafluorophosphate, bis(4-tert-butylphenyl)iodomonium hexafluorophosphate, benzoin ether, 4-isobutylphenyl-4'-methylphenyliodohexafluorophosphate, isopropylphenylcyclopentadiene iron hexafluorophosphate, bis(4-dodecylbenzene)iodohexafluoroantimonate, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, and diphenyl-(4-phenylthio)phenylsulfonium hexafluoroantimonate. The cationic polymerization sensitizer is selected from at least one of the following: benzoin diethyl ether, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexylphenyl ketone, isopropylthioxanthone (2,4 isomer mixture), bis(2,6-difluoro-3-pyrrolephenyldicyclopentadiene), and 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone; The cationic polymerization aid is selected from at least one of alicyclic epoxy resin 1700, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylic acid ester, and diglycidyl hexahydrophthalic acid ester.

5. The epoxy resin-based liquid crystal polymer with a low glass transition temperature according to claim 1, characterized in that, The content of the chain extender, crosslinking agent, and thermal polymerization catalyst is 0-50% of the total weight of the epoxy resin-based liquid crystal polymerizable monomer; The content of the cationic polymerization initiator, cationic polymerization sensitizer, and cationic polymerization auxiliaries is 0-30% of the total weight of the epoxy resin-based liquid crystal polymerizable monomers.

6. The epoxy resin-based liquid crystal polymer with a low glass transition temperature according to claim 5, characterized in that, The mass ratio of the chain extender, crosslinking agent and thermal polymerization catalyst is (0-10):(0-10):(0-5); The mass ratio of the cationic polymerization initiator, cationic polymerization sensitizer and cationic polymerization auxiliary is (0-1):(0-1):(0-10).

7. The method for preparing the epoxy resin-based liquid crystal polymer with a low glass transition temperature according to any one of claims 1-6, characterized in that, Includes the following steps: The epoxy resin-based liquid crystal polymerizable monomer, chain extender, crosslinking agent, thermal polymerization catalyst, cationic polymerization initiator, cationic polymerization sensitizer, and cationic polymerization auxiliaries are mixed evenly to obtain a mixture; The mixture is injected into a sealed container to obtain a sample; wherein the upper and lower surfaces of the sealed container have a friction interface that induces the parallel alignment of liquid crystals; or the upper and lower surfaces of the sealed container have a friction interface that induces the parallel alignment of liquid crystals and a magnetic field or electric field is applied along the direction of liquid crystal alignment induced by the friction interface; or the upper and lower surfaces of the sealed container do not have a friction interface that induces the parallel alignment of liquid crystals, and a magnetic field or electric field perpendicular to the thickness direction is applied. The sample was cured to obtain an epoxy resin-based liquid crystal polymer with a low glass transition temperature.

8. The preparation method according to claim 7, characterized in that, The thickness of the sealed container is 0.5-2000 μm.

9. The preparation method according to claim 7, characterized in that, The curing process involves first thermal polymerization at 40-150℃ for 0-120 h, followed by curing at (-20)-150℃ with 10-500 mW / cm². 2 UV-polymerization 0-10 6 The process involves cationic photopolymerization, wherein the durations of thermal polymerization and cationic photopolymerization are not both 0.

10. The application of the epoxy resin-based liquid crystal polymer with low glass transition temperature as described in any one of claims 1-5 or the epoxy resin-based liquid crystal polymer with low glass transition temperature prepared by any one of claims 6-9 in advanced resin engineering materials.

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