Macromolecule based on side chain liquid crystal polynorbornene as well as preparation method and application thereof

Abstract

The invention discloses a polymer based on side-chain liquid crystal polynorbornene as well as a preparation method and application thereof, a monomer based on side-chain liquid crystal polynorbornene has a structure as shown in a general formula 1, and the polymer based on side-chain liquid crystal polynorbornene has a repeating unit as shown in a general formula 8. According to the monomer structure, a benzamide group is introduced into a side chain liquid crystal molecular structure, adjacent liquid crystal side chains generate hydrogen bond interaction after polymerization, on one hand, the mechanical property of the material is improved, on the other hand, stacking arrangement of a layered structure can be promoted during film preparation, and the gas barrier performance is improved.

Description

Technical Field

[0001] This application belongs to the technical field of liquid crystal polymer materials, and particularly relates to a polymer based on side-chain liquid crystal polynorbornene, a preparation method thereof, and an application thereof. Background Art

[0002] With the rapid development of fields such as flexible electronic devices, pharmaceutical packaging, and precision device encapsulation, the performance requirements for gas barrier film materials are becoming increasingly stringent. Currently, commercially available gas barrier film materials generally use polyimide films, polyester films, liquid crystal polymer films, etc. The common problem with these materials is that it is difficult to balance high barrier properties and deformation adaptability, especially unable to meet the requirement of maintaining stable gas resistance for a long time under bending and stretching conditions for future flexible electronic devices. Therefore, the development of high-gas-barrier flexible polymer films with excellent tensile properties has important value, which will hopefully break through the application bottleneck of existing gas barrier materials in flexible scenarios. Summary of the Invention

[0003] The purpose of this application is to provide a polymer based on side-chain liquid crystal polynorbornene, a preparation method thereof, and an application thereof, so as to solve the technical problem that the gas barrier film materials in the prior art are difficult to balance high barrier properties and deformation adaptability and cannot meet the requirement of maintaining stable gas resistance for a long time under bending and stretching conditions for future flexible electronic devices.

[0004] To achieve the above purpose, the first aspect of this application provides a monomer based on side-chain liquid crystal polynorbornene, having the following general formula 1:

[0005]

General formula 1

[0006]

[0007] In the general formula 1, R1, R2, and R3 are each independently selected from the following groups: H, OR', and R1, R2, and R3 are not simultaneously H, and R' is a straight-chain alkyl, branched-chain alkyl, or cycloalkyl with more than 1 carbon atom;

[0008] n is 2, 3, 4, 5, or 6.

[0009] In one or more embodiments, it has the following general formula 2:

[0010]

General formula 2

[0011]

[0012] In the general formula 2, n is 2, 3, 4, 5, or 6.

[0013] To achieve the above purpose, the second aspect of this application provides a preparation method of the monomer as described in any of the above embodiments, including:

[0014] Disperse the substituted benzoic acid having the following general formula 3 and a chlorinating reagent in a first solvent and react them to obtain a first intermediate having the following general formula 4;

[0015] Disperse the first intermediate in a second solvent, and then add 4-((tert-butyldimethylsilyl)oxy)aniline and triethylamine and react them to obtain a second intermediate having the following general formula 5;

[0016] Disperse the second intermediate in a third solvent, and then add tetrabutylammonium fluoride and react them to obtain a third intermediate having the following general formula 6;

[0017] React the third intermediate and bromohydrocarbon C n H 2n Br2 in a nucleophilic substitution reaction to obtain a fourth intermediate having the following general formula 7;

[0018] React the fourth intermediate and N-hydroxy-5-norbornene-2,3-dicarboximide in a nucleophilic substitution reaction to obtain the monomer having the general formula 1;

[0019]

General formula 3

General formula 4

[0020]

General formula 5

General formula 6

[0021]

General formula 7

[0022] Among them, in the general formulas 3 to 7, R1, R2, and R3 are each independently selected from the following groups: H, OR', and R1, R2, and R3 are not simultaneously H, and R' is a straight-chain alkyl, branched-chain alkyl, or cycloalkyl having more than 1 carbon atom;

[0023] In the bromohydrocarbon C n H 2n Br2 and the general formula 7, n is 2, 3, 4, 5, or 6.

[0024] In one or more embodiments, in the step of dispersing the substituted benzoic acid and the chlorinating reagent in the first solvent and reacting them,

[0025] The chlorinating reagent is oxalyl chloride, and the molar ratio of the substituted benzoic acid to oxalyl chloride is (0.8 to 1.2):(1.2 to 1.5).

[0026] In one or more embodiments, the first solvent is anhydrous dichloromethane.

[0027] In one or more embodiments, the reaction conditions for the reaction are an ice bath, and the reaction time is 3 to 4 h.

[0028] In one or more embodiments, in the step of dispersing the first intermediate in a second solvent and then adding 4-((tert-butyldimethylsilyl)oxy)aniline and triethylamine for reaction,

[0029] The second solvent is anhydrous dichloromethane.

[0030] In one or more embodiments, the molar ratio of the substituted benzoic acid, 4-((tert-butyldimethylsilyl)oxy)aniline, and triethylamine is (0.8 to 1.2):(1.1 to 1.3):(1.3 to 1.6).

[0031] In one or more embodiments, the temperature of the reaction is room temperature, and the reaction time is 4 to 6 h.

[0032] In one or more embodiments, in the step of dispersing the second intermediate in a third solvent and then adding tetrabutylammonium fluoride for reaction,

[0033] The third solvent is tetrahydrofuran.

[0034] In one or more embodiments, the reaction specifically comprises adding tetrabutylammonium fluoride under an ice bath, reacting for 1.5 to 3 h, rotary evaporating and concentrating after the reaction is completed, then dropping the reaction system into water, stirring overnight for reaction, filtering by suction, and drying to obtain the third intermediate.

[0035] In one or more embodiments, the molar ratio of the second intermediate to tetrabutylammonium fluoride is (0.8 to 1.2):(1.1 to 1.3).

[0036] In one or more embodiments, the step of subjecting the third intermediate and bromohydrocarbon C n H 2n Br2 to a nucleophilic substitution reaction specifically comprises:

[0037] Dispersing the third intermediate, bromohydrocarbon C n H 2n Br2, potassium carbonate, and TBAB in a fourth solvent, and carrying out a reflux reaction to obtain the fourth intermediate;

[0038] Among them, the reaction temperature of the reflux reaction is 75 to 80 °C, and the reaction time is 24 to 72 h.

[0039] In one or more embodiments, the third intermediate, bromohydrocarbon C n H 2nThe molar ratio of Br2 to potassium carbonate is (0.8 to 1.2):(5.5 to 10.5):(5.5 to 7.5), and the mass ratio of the TBAB to the third intermediate is 1:(5 to 8).

[0040] In one or more embodiments, the fourth solvent is acetone.

[0041] In one or more embodiments, the step of subjecting the fourth intermediate and N-hydroxy-5-norbornene-2,3-dicarboximide to a nucleophilic substitution reaction to obtain the monomer having the general formula 1 is specifically as follows:

[0042] Disperse the fourth intermediate, N-hydroxy-5-norbornene-2,3-dicarboximide, potassium carbonate, and TBAB in a fifth solvent, carry out a reflux reaction, and after the reaction is completed, extract and rotary evaporate to obtain the monomer having the general formula 1;

[0043] Among them, the molar ratio of the fourth intermediate, N-hydroxy-5-norbornene-2,3-dicarboximide, and potassium carbonate is (0.8 to 1.2):(1.1 to 1.3):(5.5 to 7.5), and the mass ratio of the TBAB to the fourth intermediate is 1:(5 to 8).

[0044] In one or more embodiments, the reaction time of the reflux reaction is 12 to 24 h, and the reaction temperature is 70 to 80 °C.

[0045] In one or more embodiments, the fifth solvent is anhydrous DMF.

[0046] To achieve the above object, a third aspect of the present application provides a polymer based on side-chain liquid crystal polynorbornene, which is obtained by polymerizing the monomer according to any one of the above embodiments. The polymer has a repeating unit shown in the following general formula 8, and the number of the repeating units is greater than or equal to 10;

[0047]

General formula 8

[0048]

[0049] In the general formula 8, R1, R2, and R3 are each independently selected from the following groups: H, OR', and R1, R2, and R3 are not simultaneously H, and R' is a linear alkyl group, a branched alkyl group, or a cyclic alkyl group with more than 1 carbon atom;

[0050] n is 2, 3, 4, 5, or 6.

[0051] To achieve the above object, a fourth aspect of the present application provides a preparation method of a polymer according to any one of the above embodiments, including:

[0052] Disperse the monomer with the general formula 1 in the sixth solvent under an inert atmosphere, and then add the Grubbs third-generation catalyst. Polymerize under an inert atmosphere to obtain the polymer.

[0053] In one or more embodiments, the reaction time of the polymerization reaction is 2 to 4 h, and the reaction temperature is room temperature.

[0054] In one or more embodiments, the molar ratio of the Grubbs third-generation catalyst to the monomer is (0.8 to 1.2):(20 to 60).

[0055] In one or more embodiments, the sixth solvent is anhydrous dichloromethane.

[0056] To achieve the above object, the fifth aspect of the present application provides an application of the monomer based on side-chain liquid crystal polynorbornene or the polymer based on side-chain liquid crystal polynorbornene according to any of the above embodiments in the preparation of a flexible gas barrier film.

[0057] To achieve the above object, the sixth aspect of the present application provides a method for preparing a flexible gas barrier film, including:

[0058] Melt the polymer according to any of the above embodiments into a block, and pre-press at the first temperature to obtain an intermediate sample;

[0059] Press the intermediate sample at the second temperature, and cool to obtain the flexible gas barrier film;

[0060] Wherein, the first temperature is higher than the isotropic transition temperature of the polymer, and the second temperature is 5 to 15 °C lower than the isotropic transition temperature of the polymer.

[0061] In one or more embodiments, the step of pressing at the second temperature is specifically:

[0062] Heat and keep the intermediate sample at the second temperature, apply a pressure of 13.5 to 16.5 MPa, stop heating after maintaining the pressure for 30 to 50 min, and remove the pressure after cooling to the temperature to obtain the flexible gas barrier film.

[0063] In one or more embodiments, the second temperature is 113 to 123 °C.

[0064] To achieve the above object, the seventh aspect of the present application provides a flexible gas barrier film prepared by using the preparation method according to any of the above embodiments.

[0065] Different from the prior art, the beneficial effects of the present application are:

[0066] The monomer structure of this application introduces a "benzene - amide - benzene" rod - like motif in the side groups and an alkyl tail chain at the end of the side chain. By introducing a benzamide group into the side - chain liquid - crystal molecular structure, hydrogen - bond interactions will occur between adjacent liquid - crystal side chains after polymerization. On the one hand, the introduction of hydrogen - bond interactions can provide mechanical support for the side - chain liquid - crystal polymer system, enhance the stacking stability of liquid - crystal motifs, and thus significantly improve the mechanical properties of the material. On the other hand, the side - chain benzamide structure can promote the development of layered structures. The layered structure is beneficial to the improvement of mechanical properties, and the layered - structure characteristics can promote the stacking arrangement of layered structures during the preparation of thin films, improving the gas - barrier performance.

[0067] In the polymer structure of this application, hydrogen - bond interactions will occur between the benzamide groups of adjacent side chains. The introduction of hydrogen - bond interactions can provide mechanical support for the side - chain liquid - crystal polymer system, enhance the stacking stability of liquid - crystal motifs, and thus significantly improve the mechanical properties of the material. At the same time, when applying to prepare thin films, the large polarity and stacking arrangement structure of amide bonds can be utilized to significantly improve the gas - barrier performance of the thin films.

[0068] The flexible gas - barrier thin film of this application has both excellent gas - barrier performance and mechanical properties. Among them, the oxygen permeability is as low as 6300 cm 3 ·μm / (m 2 ·d·atm), significantly superior to existing commercial thin films. The film modulus at 30 °C is 352 MPa, the fracture stress is 28.1 MPa, and the fracture strain is 287%, which can meet the requirements of future flexible electronic devices for maintaining stable gas resistance under bending and stretching states for a long time. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] In order to more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in this application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0070] Figure 1 It is a schematic flow chart of an embodiment of the preparation method of the monomer based on side - chain liquid - crystal polynorbornene of this application;

[0071] Figure 2 It is a schematic flow chart of an embodiment of the preparation method of the polymer based on side - chain liquid - crystal polynorbornene of this application;

[0072] Figure 3 It is a schematic flow chart of an embodiment of the preparation method of the flexible gas - barrier thin film of this application;

[0073] Figure 41H NMR spectrum of monomer 1M6-2 prepared in Example 1 of the present application;

[0074] Figure 5 1H NMR spectrum of polymer 1P6-2 prepared in Example 1 of the present application;

[0075] Figure 6 1H NMR spectrum of monomer 1M6-4 prepared in Example 2 of the present application;

[0076] Figure 7 1H NMR spectrum of polymer 1P6-4 prepared in Example 2 of the present application;

[0077] Figure 8 1H NMR spectrum of monomer 1M6-6 prepared in Example 3 of the present application;

[0078] Figure 9 1H NMR spectrum of polymer 1P6-6 prepared in Example 3 of the present application;

[0079] Figure 10 Photograph and two-dimensional X-ray scattering pattern of the thin film sample of Example 4 of the present application;

[0080] Figure 11 Photograph and two-dimensional X-ray scattering pattern of the thin film sample of Example 5 of the present application;

[0081] Figure 12 Differential scanning calorimetry chart of polymer 1P6-2 prepared in Example 1 of the present application;

[0082] Figure 13 Two-dimensional X-ray scattering pattern of polymer 1P6-2 of Example 1 of the present application;

[0083] Figure 14 Stress-strain curve diagrams of the thin films of Example 4 and Example 5 of the present application at 30 °C. Detailed implementation manners

[0084] In order to enable those skilled in the art to better understand the technical solutions in the present application, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0085] Existing gas barrier films are difficult to balance high gas barrier performance and deformation adaptability, especially unable to meet the requirement of maintaining stable gas resistance under bending and stretching states for future flexible electronic devices in the long term.

[0086] Liquid crystals are a class of substances between crystals and liquids, possessing both processability and orderliness. The substances that form liquid crystals are called liquid crystal units. According to the position of the flexible chain segment and the unit, they can be divided into main-chain and side-chain liquid crystal polymers. Side-chain liquid crystal polymers can form diverse liquid crystal phase structures due to the rich and adjustable side-chain units and high degrees of freedom of movement. They can effectively fix liquid crystal molecules and prepare processable thin films, making them ideal materials for preparing high-gas-barrier flexible polymer films.

[0087] To solve the problems existing in the current gas-barrier film materials, this application provides a monomer based on side-chain liquid crystal polynorbornene and the polymer obtained by its polymerization. This material can be applied in the preparation of gas-barrier films, significantly improving the gas-barrier performance and mechanical properties of the gas-barrier films.

[0088] Specifically, the monomer based on side-chain liquid crystal polynorbornene in this application has the following general formula 1:

[0089]

General formula 1

[0090]

[0091] In general formula 1, R1, R2, and R3 are each independently selected from the following groups: H, OR', and R1, R2, and R3 are not all H at the same time, and R' is a straight-chain alkyl, branched-chain alkyl, or cyclic alkyl with more than 1 carbon atom.

[0092] n is 2, 3, 4, 5, or 6.

[0093] In one embodiment, the monomer based on side-chain liquid crystal polynorbornene can have the following general formula 2. This monomer is named 1M6-n, where 1 represents the number of alkyl groups connected to the phenyl group at the side-chain end, 6 represents the carbon chain length of the alkyl group connected to the phenyl group at the side-chain end, and n represents the number of carbon atoms in the alkyl chain between N-hydroxy-5-norbornene-2,3-dicarboximide and the benzamide structure.

[0094]

General formula 2

[0095]

[0096] In general formula 2, n is 2, 3, 4, 5, or 6.

[0097] It should be noted that the monomer structure of this application is not limited to the above general formula 2. In other embodiments, other numbers of alkyl groups can be connected to the side-chain end, and each alkyl group can be independently selected from a straight-chain alkyl, branched-chain alkyl, or cyclic alkyl with a carbon chain length greater than 1, all of which can achieve the effects of this embodiment.

[0098] Exemplarily, the monomer based on side-chain liquid crystal polynorbornene in this application can also be selected from the following structures:

[0099]

[0100] The monomer structure of the present application introduces a "benzene - amide - benzene" rod - like motif in the side - group and an alkyl tail - chain at the end of the side - chain. By introducing a benzamide group into the side - chain liquid - crystal molecular structure, hydrogen - bond interactions will occur between adjacent liquid - crystal side - chains after polymerization.

[0101] On the one hand, the introduction of hydrogen - bond interactions can provide mechanical support for the side - chain liquid - crystal polymer system, enhance the stacking stability of liquid - crystal motifs, and thus significantly improve the mechanical properties of the material. On the other hand, the side - chain benzamide structure can promote the development of the lamellar structure. The lamellar structure is beneficial to the improvement of mechanical properties, and the lamellar - structure characteristics can promote the stacking arrangement of the lamellar structure when preparing films, improving the gas - barrier performance.

[0102] The present application also provides a polymer based on side - chain liquid - crystal polynorbornene obtained by polymerizing the above - mentioned monomer. This polymer has a repeating unit shown in the following general formula 8, where the number of repeating units is greater than or equal to 10.

[0103]

General formula 8

[0104]

[0105] In general formula 8, R1, R2, and R3 are each independently selected from the following groups: H, OR', and R1, R2, and R3 are not simultaneously H, and R' is a straight - chain alkyl, branched - chain alkyl, or cyclic - chain alkyl with more than 1 carbon atom;

[0106] n is 2, 3, 4, 5, or 6.

[0107] For the polymer based on side - chain liquid - crystal polynorbornene of the present application, a benzamide group is introduced on the side - chain, and hydrogen - bond interactions will occur between the benzamide groups of adjacent side - chains. The introduction of hydrogen - bond interactions can provide mechanical support for the side - chain liquid - crystal polymer system, enhance the stacking stability of liquid - crystal motifs, and thus significantly improve the mechanical properties of the material. At the same time, when applying to prepare films, the large polarity of the amide bond and the stacking arrangement structure can be utilized to significantly improve the gas - barrier performance of the film.

[0108] The present application also provides a preparation method of the above - mentioned monomer. Please refer to Figure 1 , Figure 1 is a schematic flow chart of an embodiment of the preparation method of the monomer based on side - chain liquid - crystal polynorbornene of the present application.

[0109] As Figure 1 shown, this preparation method includes:

[0110] S100, Disperse a substituted benzoic acid with general formula 3 and a chlorinating reagent in a first solvent and react to obtain a first intermediate product with general formula 4.

[0111] General formula 3 General formula 4

[0112] First, a substituted benzoic acid is used as a raw material to react with a chlorinating reagent to replace the hydroxyl group of the carboxylic acid with Cl. Among them, the substituents R1, R2, and R3 of the substituted benzoic acid can be selected based on the structure of the target monomer.

[0113] In one embodiment, the chlorinating reagent can be oxalyl chloride, and the molar ratio of the substituted benzoic acid to oxalyl chloride is (0.8 - 1.2):(1.2 - 1.5); in other embodiments, other chlorinating reagents can also be selected, such as thionyl chloride, etc., and the effects of this embodiment can be achieved.

[0114] In one embodiment, the first solvent can be anhydrous dichloromethane.

[0115] In one embodiment, the reaction can be carried out under an ice bath, and the reaction time can be 3 - 4 h.

[0116] In one embodiment, the specific synthesis reaction formula can be as follows:

[0117]

[0118] In the above reaction, the raw material substituted benzoic acid can be prepared from a benzoic acid ester in which the phenyl group is substituted with 1, 2, or 3 hydroxyl groups. The benzoic acid ester and a halogenated hydrocarbon including the target alkyl group are subjected to a hydroxyalkylation reaction under the action of anhydrous potassium carbonate and a phase transfer catalyst TBAB to obtain the substituted benzoic acid, which will not be elaborated here.

[0119] S200. Disperse the first intermediate in the second solvent, and then add 4-((tert-butyldimethylsilyl)oxy)aniline and triethylamine to react to obtain a second intermediate having General formula 5.

[0120] General formula 5

[0121] In General formula 5, OTBDMS is tert-butyldimethylsilyl.

[0122] Furthermore, a second intermediate is obtained by a nucleophilic substitution reaction between an acyl chloride and an amine.

[0123] In one embodiment, the second solvent can be anhydrous dichloromethane.

[0124] In one embodiment, the molar ratio of the substituted benzoic acid, 4-((tert-butyldimethylsilyl)oxy)aniline, and triethylamine can be (0.8 - 1.2):(1.1 - 1.3):(1.3 - 1.6).

[0125] In one embodiment, the reaction temperature can be room temperature and the reaction time can be 4 - 6 h.

[0126] In one embodiment, the specific synthesis reaction formula can be as follows:

[0127]

[0128] S300. Disperse the second intermediate product in a third solvent, then add tetrabutylammonium fluoride for reaction to obtain a third intermediate product with general formula 6.

[0129]

General formula 6

[0130] In one embodiment, the third solvent can be tetrahydrofuran.

[0131] In one embodiment, the reaction process can be specifically as follows: Add tetrabutylammonium fluoride under an ice bath, react for 1.5 - 3 h, after the reaction is completed, concentrate by rotary evaporation, then drop the reaction system into water, stir overnight, filter, and dry to obtain the third intermediate product.

[0132] In one embodiment, the reaction process can be monitored by thin-layer chromatography. When the reaction is completed, rotary evaporate until there is a slight residue in the solution, then slowly drop the solution into water, stir overnight, and then filter and dry to obtain the solid third intermediate product.

[0133] In one embodiment, the molar ratio of the second intermediate product to tetrabutylammonium fluoride can be (0.8 - 1.2) : (1.1 - 1.3).

[0134] In one embodiment, the specific synthesis reaction formula can be as follows:

[0135]

[0136] S400. Carry out a nucleophilic substitution reaction on the third intermediate product and bromohydrocarbon C n H 2n Br2 to obtain a fourth intermediate product with general formula 7.

[0137]

General formula 7

[0138] Among them, in bromohydrocarbon C n H 2n Br2 and general formula 7, n is 2, 3, 4, 5 or 6.

[0139] In one embodiment, anhydrous potassium carbonate can be used to provide an alkaline environment, and TBAB can be used as a phase transfer catalyst to react the third intermediate product with bromohydrocarbon C n H2n Nucleophilic substitution is carried out with Br2, and the specific reaction process can be as follows:

[0140] Disperse the third intermediate product, bromohydrocarbon C n H 2n Br2, potassium carbonate and TBAB in the fourth solvent, and carry out a reflux reaction to obtain the fourth intermediate product.

[0141] In one embodiment, after the reaction is completed, the solvent can be removed by filtration and rotary evaporation to obtain a solid. The solid is dissolved in DCM, washed with saturated NaCl solution, and after liquid separation, the organic phase is dried with anhydrous Na2SO4, and DCM is removed by rotary evaporation to obtain the purified fourth intermediate product.

[0142] In one embodiment, the reaction temperature of the reflux reaction can be 75 - 80 °C, and the reaction time can be 24 - 72 h.

[0143] In one embodiment, the molar ratio of the third intermediate product, bromohydrocarbon C n H 2n Br2 and potassium carbonate can be (0.8 - 1.2):(5.5 - 10.5):(5.5 - 7.5).

[0144] In one embodiment, the mass ratio of TBAB to the third intermediate product is 1:(5 - 8).

[0145] In one embodiment, the fourth solvent can be acetone.

[0146] In one embodiment, the specific synthesis reaction formula can be as follows:

[0147]

[0148] S500. Carry out a nucleophilic substitution reaction on the fourth intermediate product and N-hydroxy-5-norbornene-2,3-dicarboximide to obtain a monomer with general formula 1.

[0149] In one embodiment, anhydrous potassium carbonate can be used to provide an alkaline environment, and TBAB can be used as a phase transfer catalyst to carry out nucleophilic substitution on the fourth intermediate product and N-hydroxy-5-norbornene-2,3-dicarboximide. The specific reaction process can be as follows:

[0150] Disperse the fourth intermediate product, N-hydroxy-5-norbornene-2,3-dicarboximide, potassium carbonate and TBAB in the fifth solvent, carry out a reflux reaction, and after the reaction is completed, extract and rotary evaporate to obtain a monomer with general formula 1.

[0151] In one embodiment, the steps of extraction and rotary evaporation can be specifically as follows: after the reaction is completed, DCM and saturated sodium bicarbonate solution are added, the organic and inorganic phases are separated, the organic phase is extracted with saturated NaCl solution and then dried with anhydrous Na2SO4, DCM is removed by rotary evaporation, and recrystallization is carried out with DCM:EtOH to obtain the purified monomer.

[0152] In one embodiment, the molar ratio of the fourth intermediate, N-hydroxy-5-norbornene-2,3-dicarboximide and potassium carbonate can be (0.8~1.2):(1.1~1.3):(5.5~7.5), and the mass ratio of TBAB to the fourth intermediate can be 1:(5~8).

[0153] In one embodiment, the reaction time of the reflux reaction can be 12~24h, and the reaction temperature can be 70~80°C.

[0154] In one embodiment, the fifth solvent can be anhydrous DMF.

[0155] In one embodiment, the specific synthesis reaction formula can be as follows:

[0156]

[0157] Based on the preparation methods of the above embodiments, the target structure monomer is prepared, with high reaction yield and mild reaction conditions.

[0158] The present application also provides a preparation method of the above polymer based on side-chain liquid crystal polynorbornene. Please refer to Figure 2 , Figure 2 which is a schematic flow chart of an embodiment of the preparation method of the polymer based on side-chain liquid crystal polynorbornene of the present application.

[0159] As Figure 2 shown, the preparation method includes:

[0160] S10. Disperse the monomer with the general formula 1 in a sixth solvent under an inert atmosphere, then add a Grubbs third-generation catalyst, and carry out a polymerization reaction under an inert atmosphere to obtain a polymer.

[0161] In one embodiment, the sixth solvent can be anhydrous dichloromethane.

[0162] In one embodiment, the inert atmosphere can be nitrogen.

[0163] In one embodiment, the molar ratio of the Grubbs third-generation catalyst to the monomer can be (0.8~1.2):(20~60).

[0164] In one embodiment, the reaction time of the polymerization reaction can be 2~4h, and the reaction temperature can be room temperature.

[0165] In one embodiment, the Grubbs third-generation catalyst can be dissolved in anhydrous dichloromethane and then rapidly injected into the dispersion of the monomer.

[0166] In one embodiment, the specific synthesis reaction formula can be as follows:

[0167]

[0168] Among them, x is the number of repeating units, and x is greater than or equal to 10.

[0169] The present application also provides a flexible gas-barrier film prepared from the above-mentioned polymer based on side-chain liquid crystal polynorbornene. This flexible gas-barrier film has both excellent mechanical properties and oxygen barrier properties, and is expected to break through the application bottleneck of existing gas-barrier materials in flexible scenarios.

[0170] Specifically, in one embodiment, in order to further optimize the oxygen barrier performance and mechanical properties of the film, the above-mentioned flexible gas-barrier film can be an oriented film, and its preparation method can be referred to Figure 3 .

[0171] Please refer to Figure 3 , Figure 3 which is a schematic flow chart of an embodiment of the preparation method of the flexible gas-barrier film of the present application.

[0172] As Figure 3 shown, the preparation method includes:

[0173] S1. Melting the polymer based on side-chain liquid crystal polynorbornene into a block and pre-pressing it at a first temperature to obtain an intermediate sample;

[0174] S2. Pressing the intermediate sample at a second temperature and cooling to obtain a flexible gas-barrier film.

[0175] Among them, the first temperature is higher than the isotropic transition temperature of the polymer, so that the polymer material of the present application can be pre-pressed in the isotropic liquid state to obtain a relatively thick intermediate sample, forming a homogeneous non-oriented structure.

[0176] The second temperature is 5-15 °C lower than the isotropic transition temperature of the polymer of the present application, so that the intermediate sample is secondarily pressed and formed in the liquid crystal state, and the molecular chains are oriented to obtain an oriented film.

[0177] It should be understood that in the above preparation method, the first temperature only needs to ensure that all parts of the polymer material are in the isotropic liquid state, and there is no limit to the maximum value of the first temperature; the second temperature is used to ensure that the polymer material is in the liquid crystal state, and it can be 5-15 °C lower than the isotropic transition temperature.

[0178] In one embodiment, the second temperature may be 113 to 123 °C.

[0179] In one embodiment, the step of pressing at the second temperature may specifically be:

[0180] Heat and keep the intermediate sample at the second temperature, apply a pressure of 13.5 to 16.5 MPa, stop heating after maintaining the pressure for 30 to 50 min, cool to the temperature and then remove the pressure to obtain a flexible gas-barrier film.

[0181] Of course, in other embodiments, the flexible gas-barrier film of the present application can also be prepared by other commonly used methods in the art, and the effects of this embodiment can also be achieved.

[0182] The effects of the technical solution of the present application will be further elaborated in detail below with reference to specific examples.

[0183] Example 1:

[0184] A polymer 1P6-2 has the following structural formula:

[0185]

[0186] The synthesis route of polymer 1P6-2 is as follows:

[0187]

[0188] The synthesis method of polymer 1P6-2 is as follows:

[0189] (1) Synthesis of p-octyloxybenzoic acid (C6O-ph-COOH)

[0190] Take 15.22 g (100 mmol) of methyl p-hydroxybenzoate, 19.81 g (120 mmol) of bromohexane, 27.64 g (200 mmol) of anhydrous potassium carbonate (K2CO3) and 2.63 g of tetrabutylammonium bromide (TBAB) and mix them in a 500 mL round-bottom flask. After adding 180 mL of acetone, reflux for 16 h and monitor the reaction by TLC. Filter off K2CO3 by suction, rotary evaporate to remove acetone to obtain the product.

[0191] Add 150 mL of absolute ethanol (EtOH) to the above product. Dissolve 8.42 g (150 mmol) of potassium hydroxide (KOH) in water and drop it into the reaction system. After refluxing for 12 h, monitor the reaction by TLC. Rotary evaporate to remove EtOH. After adding 60 mL of tetrahydrofuran (THF), adjust the pH to acidic with dilute hydrochloric acid (HCl), extract with diethyl ether (Et2O) and then dry with anhydrous Na2SO4. Rotary evaporate to remove the solvent and recrystallize from Et2O to obtain 17.34 g of white crystals with a yield of 78%.

[0192] (2) Synthesis of N-4-tert-butyldimethylsilyloxyphenyl-4-hexyloxybenzamide (C6O-amide-OTBDMS)

[0193] In anhydrous DCM, 8.0 g (36 mmol) of C6O-ph-COOH was added, and 3.7 mL (43.2 mmol) of oxalyl chloride ((COCl)2) was added in an ice bath, and the reaction was carried out at room temperature. After monitoring the reaction by TLC and completion of the reaction, the solvent and (COCl)2 were removed by rotary evaporation. After dissolution with anhydrous DCM, rotary evaporation was carried out again, and this operation was repeated 2 times, and then it was dissolved with anhydrous DCM. 10.05 g (45 mmol) of H2N-ph-OTBDMS and 5.46 g (54 mmol) of triethylamine (Et3N) were dissolved in anhydrous DCM and then slowly dropped into the above solution, and the reaction was carried out at room temperature. After monitoring the reaction by TLC and completion of the reaction, an appropriate amount of water was added and then separated by liquid separation. The organic phase was washed with saturated sodium chloride (NaCl) solution, dried over anhydrous Na2SO4, and DCM was removed by rotary evaporation to obtain 10.8 g of white solid, with a yield of 70.3%.

[0194] (3) Synthesis of N-4-hydroxyphenyl-4-hexyloxybenzamide (C6O-amide-OH)

[0195] 7.28 g (17.0 mmol) of C6O-amide-OTBDMS was dissolved in THF, and 20.4 mL of 1 M tetrabutylammonium fluoride (TBAF) in THF solution was slowly added under ice bath. The reaction was carried out at room temperature. After monitoring the reaction by TLC and completion of the reaction, rotary evaporation was carried out until the solution was slightly left, and then it was slowly dropped into water and stirred at room temperature overnight. After filtration and drying, 5.32 g of white powdery solid was obtained, with a yield of 100%.

[0196] (4) Synthesis of N-4-bromoethoxyphenyl-4-hexyloxybenzamide (C6O-amide-OC2Br)

[0197] 2.5 g (8.0 mmol) of C6O-amide-OH, 12.02 g (64.0 mmol) of 1,2-dibromoethane, 7.28 g (52.7 mmol) of K2CO3 and 500 mg of TBAB were dissolved in 100 mL of acetone, refluxed at 75 °C for 36 h, and the reaction was monitored by TLC. After filtration, the organic solvent was removed by rotary evaporation. The obtained solid was dissolved in DCM, washed with saturated NaCl solution, and after liquid separation, the organic phase was dried over anhydrous Na2SO4, and DCM was removed by rotary evaporation to obtain 2.89 g of white powdery solid (yield 86.2%).

[0198] (5) Synthesis of monomer 1M6-2

[0199] Dissolve 2.25 g (5.35 mmol) of C6O-amide-OC2Br, 1.13 g (6.31 mmol) of N-hydroxy-5-norbornene-2,3-dicarboximide, 4.44 g (32.1 mmol) of K2CO3 and 410 mg of TBAB in 45 mL of dry N,N-dimethylformamide (DMF). After refluxing for 18 h, monitor the reaction by TLC until completion. Add DCM and saturated sodium bicarbonate solution, separate the organic and inorganic phases, extract the organic phase with saturated NaCl solution and then dry it over anhydrous Na2SO4. Rotavapor to remove DCM. Recrystallize with DCM:EtOH to obtain 2.31 g of white powdery solid (yield 83.3%) 1M6-2.

[0200] Its 1 The 1H NMR results are shown in Figure 4 , Figure 4 which is the 1H NMR spectrum of monomer 1M6-2 prepared in Example 1 of this application.

[0201] The 1H NMR data and 13C NMR data of monomer 1M6-2 are as follows, which are in line with the characteristics of the target monomer:

[0202] 1 1H NMR (400 MHz, CDCl3, δ, ppm): 7.81 (m, 2H), 7.64 (s, 1H), 7.53 (m, 2H), 6.96 (m, 2H), 6.92 (m, 2H), 6.15 - 6.10 (m, 2H), 4.46–4.43 (m, 2H), 4.19 (t, 2H), 4.01 (t, 2H), 2.93 (t, 2H), 2.28 (m, 2H), 1.97–1.92 (m, 1H), 1.54–1.47 (m, 1H), 1.45 - 1.23 (m, 8H), 0.89 (t, 3H).

[0203] 13 13C NMR (100 MHz, CDCl3, δ, ppm): 176.27, 164.15, 162.06, 155.39, 135.74, 131.71, 128.79, 126.83, 121.98, 115.12, 114.45, 68.28, 66.44, 62.77, 52.74, 46.34, 43.08, 41.68, 31.82, 30.40, 29.35, 29.24, 29.15, 26.01, 22.67, 14.12.

[0204] (6) Synthesis of polymer 1P6-2

[0205] 414 mg (0.80 mmol) of 1M6-2 was added to a dry Schlenk tube. The tube was evacuated and filled with nitrogen three times. While stirring, 3 mL of dry DCM was injected into the tube using a syringe. After the monomer dissolved, 17.69 mg (0.02 mmol) of Grubbs' third-generation catalyst was dissolved in 1 mL of dry DCM and quickly injected into the monomer solution (the molar ratio of Grubbs' third-generation catalyst to 1M6-2 was 1:40). The polymerization reaction was carried out at room temperature under a nitrogen atmosphere for 2 hours.

[0206] After the reaction, 3-5 drops of vinyl ethyl ether were injected into the polymerization tube to quench the reaction. The reaction solution was diluted with 5 mL of DCM and then added dropwise to 125 mL of anhydrous methanol with stirring. The polymer precipitated. The precipitate was collected by centrifugation and dried under vacuum at room temperature to obtain a white block sample with a mass of 411 mg and a yield of 99%.

[0207] See also Figure 5 , Figure 5 This is the hydrogen nuclear magnetic resonance spectrum of the polymer 1P6-2 prepared in Example 1 of the present application.

[0208] like Figure 4 and Figure 5 As shown, the chemical shift of hydrogen on the double bond of norbornene in the monomer appears at 6.10-6.16 ppm, and the peak disappears after polymerization. At the same time, the chemical shift of the double bond in the polynorbornene main chain appears at 5.1-5.5 ppm, proving that the polymerization is successful.

[0209] The number average molecular weight (Mn) of 1P6-2 was 28.7×10 4 The molecular weight distribution index (PDI) is 1.38, the molecular weight distribution is narrow, the chain length is uniform, the molecular chains are closely arranged, and there are few gas permeation paths.

[0210] Example 2:

[0211] A polymer 1P6-4 has the following structural formula:

[0212]

[0213] The synthetic route of polymer 1P6-4 is as follows:

[0214]

[0215] The synthesis method of polymer 1P6-4 is basically the same as that of polymer 1P6-2 in Example 1, except that:

[0216] In step (4), 1,4-dibromobutane was used instead of 1,2-dibromoethane in Example 1;

[0217] In step (2), the amount of oxalyl chloride used was 3.1 mL (36.2 mmol), the amount of H2N-ph-OTBDMS used was 37.7 mmol, and the amount of triethylamine used was 45.2 mmol;

[0218] In step (3), 23.9 mL of a 1 M solution of tetrabutylammonium fluoride (TBAF) in THF was added;

[0219] In step (4), the amount of TBAB used was 375 mg, and the reflux reaction temperature was 80 °C;

[0220] In step (6), the amount of Grubbs third-generation catalyst used was 0.01 mmol, and the polymerization reaction was carried out at room temperature for 3 h.

[0221] For the monomer 1M6-4 synthesized in Example 2 1 The 1H NMR results are shown in Figure 6 , Figure 6 which is the 1H NMR spectrum of the monomer 1M6-4 prepared in Example 2 of this application.

[0222] The 1H NMR data and 13C NMR data of the monomer 1M6-4 are as follows, which are in line with the characteristics of the target monomer:

[0223] 1 1H NMR (400 MHz, CDCl3, δ, ppm): 7.81 (m, 2H), 7.62 (s, 1H), 7.51 (m, 2H), 6.96 (m, 2H), 6.99 (m, 2H), 6.15 - 6.10 (m, 2H), 4.17 (t, 2H), 4.01 (m, 4H), 3.27 (t, 2H), 2.92 (m, 2H), 2.23 (m, 1H), 1.95–1.72 (m, 4H), 1.56 - 1.44 (m, 1H), 1.40 - 1.23 (m, 8H), 0.89 (t, J = 6.8 Hz, 3H).

[0224] 13 13C NMR (100 MHz, CDCl3, δ, ppm): 176.33, 165.13, 162.02, 155.80, 135.78, 131.25, 128.78, 126.90, 122.00, 114.85, 114.43, 68.27, 67.63, 52.12, 46.64, 45.80, 31.82, 29.35, 26.01, 23.32, 22.68, 14.12.

[0225] For the polymer 1P6-4 synthesized in Example 21 The \(^1H\) NMR results are shown in Figure 7 , Figure 7 which is the \(^1H\) NMR spectrum of the polymer 1P6-4 prepared in Example 2 of this application.

[0226] As Figure 6 and Figure 7 shown, the chemical shift of the hydrogen on the norbornene double bond in the monomer appears at 6.10 - 6.15 ppm. After polymerization, this peak disappears. At the same time, the chemical shift belonging to the double bond in the poly(norbornene) main chain appears at 5.1 - 5.5 ppm, proving that the polymerization is successful.

[0227] Through gel permeation chromatography (GPC) testing, the number average molecular weight (\(M_n\)) of P6-4 is 24.6×10 4 , and the polydispersity index (PDI) is 1.37. The molecular weight distribution is narrow, the chain lengths are uniform, the molecular chains are closely arranged, and there are fewer gas permeation paths.

[0228] Example 3:

[0229] A polymer 1P6-6 has the following structural formula:

[0230]

[0231] The synthesis route of the polymer 1P6-6 is as follows:

[0232]

[0233] The synthesis method of this polymer 1P6-6 is basically the same as that of the polymer 1P6-2 in Example 1, except that:

[0234] In step (4), 1,6-dibromohexane is used instead of 1,2-dibromoethane in Example 1;

[0235] In step (2), the amount of oxalyl chloride used is 4.3 mL (50.2 mmol), the amount of H2N-ph-OTBDMS used is 52.2 mmol, and the amount of triethylamine used is 62.6 mmol;

[0236] In step (3), 13.5 mL of a 1 M solution of tetrabutylammonium fluoride (TBAF) in THF is added;

[0237] In step (4), the amount of TBAB used is 500 mg;

[0238] In step (6), the amount of Grubbs third-generation catalyst used is 0.03 mmol.

[0239] For the monomer 1M6-6 synthesized in Example 3, the 1 \(^1H\) NMR results are shown in Figure 8 ,Figure 8 1H NMR spectrum of monomer 1M6-6 prepared in Example 3 of this application.

[0240] The 1H NMR data and 13C NMR data of monomer 1M6-6 are as follows, which conform to the characteristics of the target monomer:

[0241] 1 H NMR(400MHz,CDCl3,δ,ppm):7.81(m,2H),7.70(s,1H),7.51(m,2H),6.94(m,2H),6.88(m,2H),6.15 - 6.10(m,2H),4.10(t,J=6.6Hz,2H),4.00(t,J=6.6Hz,2H),3.95(t,J=6.4Hz,2H),3.32(m,2H),2.92(m,2H),2.23(m,1H),1.95–1.90(m,1H),1.88 - 1.72(m,4H),1.55 - 1.42(m,4H),1.39 - 1.26(m,8H),0.89(t,J=6.6Hz,3H).

[0242] 13 C NMR(100MHz,CDCl3,δ,ppm):176.33,165.13,162.02,155.80,135.78,131.25,128.78,126.90,122.00,114.85,114.43,68.27,52.12,46.64,45.80,31.82,30.36,29.35,29.24,27.15,25.98,25.52,22.68,14.12.

[0243] For the polymer 1P6-6 synthesized in Example 3 1 The 1H NMR results are shown in Figure 9 , Figure 9 1H NMR spectrum of polymer 1P6-6 prepared in Example 3 of this application.

[0244] As Figure 8 and Figure 9 shown, the chemical shift of the hydrogen on the norbornene double bond in the monomer appears at 6.10 - 6.15 ppm, and this peak disappears after polymerization. At the same time, the chemical shift belonging to the double bond in the poly(norbornene) main chain appears at 5.1 - 5.5 ppm, proving successful polymerization.

[0245] The number-average molecular weight (Mn) of P6-4 obtained by gel permeation chromatography (GPC) test is 34.1×10 4, the molecular weight distribution index (PDI) is 1.36, with a narrow molecular weight distribution, uniform chain length, closely arranged molecular chains, and few gas permeation paths.

[0246] Example 4:

[0247] An oriented polymer film is prepared from the polymer 1P6-2 prepared in Example 1. The preparation method includes:

[0248] Take an appropriate amount of the polymer 1P6-2 sample and melt it into a block, and pre-press it into a relatively thick disc-shaped sample at 150 °C; then press the film at 120 °C, apply a stress of 15 MPa, stop heating after waiting for 40 min, and remove the pressure after cooling to room temperature to obtain an oriented polymer 1P6-2 film with a thickness of 163 μm.

[0249] The photograph of the film sample prepared in Example 4 and its two-dimensional X-ray diffraction characterization data are as Figure 10 shown, Figure 10 is the photograph and two-dimensional X-ray scattering pattern of the film sample of Example 4 of this application, proving that the prepared film has good orientation, where the layer normal direction is perpendicular to the plane of the film.

[0250] Example 5:

[0251] An unoriented polymer film is prepared from the polymer 1P6-2 prepared in Example 1. The preparation method includes:

[0252] Pre-melt a slightly excessive amount of the polymer 1P6-2 sample into a block, and then add a square mold with a certain thickness made of folded aluminum foil and with a hole in the middle, and fix it with aluminum plates on both sides. The tablet press is pre-heated to 160 °C. Place the above-mentioned aluminum plate with the sample on the hot plate of the tablet press, apply a pressure of 15 MPa, wait for 40 min, then turn off the heating, and remove the pressure after cooling to room temperature to obtain a sample film with a size of 5 cm × 5 cm × 188 μm.

[0253] The photograph of the film sample prepared in Example 5 and its two-dimensional X-ray diffraction characterization data are as Figure 10 shown, Figure 11 is the photograph and two-dimensional X-ray scattering pattern of the film sample of Example 5 of this application, proving that the prepared film is unoriented.

[0254] Effect Example 1:

[0255] Differential scanning calorimetry (DSC) analysis was performed on the polymer 1P6-2 prepared in Example 1 to investigate its phase transition behavior, and Figure 12 , Figure 12 is the differential scanning calorimetry chart of the polymer 1P6-2 prepared in Example 1 of this application.

[0256] AsFigure 12 As shown in the figure, during the first cooling process, a phase transition peak appears at 117°C, and a phase transition peak appears at 128°C during the second heating process. The temperature difference between the two peaks (11°C) reflects the thermal hysteresis effect, which is a typical characteristic of the phase transition kinetics of liquid crystal materials. Therefore, it is possible that the surface polymer 1P6-2 forms a liquid crystal phase.

[0257] Next, in order to further determine the phase structure of the sample, we performed a two-dimensional X-ray scattering experiment on the oriented polymer 1P6-2 and obtained Figure 13 , Figure 13 which is the two-dimensional X-ray scattering pattern of the polymer 1P6-2 in Example 1 of this application. As Figure 13 shown, the polymer 1P6-2 forms a typical smectic C phase, and there is a 27° angle between the layer normal direction and the stretching direction.

[0258] Effect Example 2: Gas Barrier Performance Analysis

[0259] The applicant analyzed the gas barrier performance of the films prepared in Examples 4 and 5, measured the oxygen transmission rate (OTR), permeability coefficient (P), diffusion coefficient (D), and solubility coefficient (S) of the films, and obtained the data in Table 1.

[0260] Table 1 Gas Permeation Properties of Oriented and Unoriented Films of Polymer 1P6-2

[0261]

[0262] Furthermore, the applicant compared the gas barrier performance of the films prepared in Examples 4 and 5 with that of existing commercial films and obtained the data in Table 2.

[0263] Table 2 Gas Permeation Properties of Films of Polymer 1P6-2 and Existing Commercial Films

[0264]

[0265] As can be seen from the data in Table 1 and Table 2 above, the films in Examples 4 and 5 both have excellent oxygen barrier properties. Among them, the gas barrier performance of the film in Example 4 is significantly better than that of existing commercial films, and the gas barrier performance of Example 5 can reach the level of better commercial films. The reason is that a benzamide group is introduced into the side-chain liquid crystal molecular structure of the polymer 1P6-2 in Example 1, and hydrogen bond interactions will occur between adjacent liquid crystal side chains after polymerization. After being prepared into a film, the gas barrier performance is significantly improved by using the stacked arrangement structure and the high polarity of the amide bond.

[0266] Furthermore, by comparing the data of Example 4 and Example 5, it is found that the oxygen permeability coefficient of the oriented film in Example 4 is reduced by one order of magnitude compared with the unoriented film in Example 5. By analyzing the solubility coefficient S and the diffusion coefficient D, it is found that the solubility coefficients of the oriented film and the unoriented film are similar, which indicates that the same molecular structure of the two leads to similar gas adsorption properties. However, due to the layered phase structure stacked layer by layer in the oriented film, the diffusion of oxygen in the film is blocked, resulting in a much smaller diffusion coefficient than that of the unoriented film sample.

[0267] Effect Example 3: Mechanical Property Analysis

[0268] To verify the mechanical properties of the film of the present application, the applicant conducted stress-stretching experiments on the films of Example 4 and Example 5 and obtained Figure 14 , Figure 14 which is the stress-strain curve diagram of the films of Example 4 and Example 5 of the present application at 30°C.

[0269] As Figure 14 shown, the films of Example 4 and Example 5 both exhibit excellent mechanical properties. Among them, the fracture stress of the film of Example 4 reaches 28.1 MPa, yielding occurs at about 50% strain, and the fracture strain is 287%; the fracture stress of the film of Example 5 reaches 20 MPa, yielding occurs at about 30% strain, and the fracture strain is 450%, both having excellent strength and tensile properties.

[0270] Specifically, by comparing the data of Example 4 and Example 5, the strength of the film of Example 4 is better than that of Example 5, but the tensile property is weaker than that of Example 5. This is mainly because the mechanical properties of the film improve when the oriented film is uniaxially stretched in the direction parallel to the layer.

[0271] From the above various effect examples, it can be seen that the polymer of the present application can improve the interaction between the side chains of the liquid crystal polymer, achieve a high glass transition temperature, enhance the stacking stability of the liquid crystal units, and further improve the gas barrier property and mechanical property of the film by introducing benzamide units into the side chain. Furthermore, through specific orientation, the liquid crystal polymer film can achieve both excellent gas barrier property and mechanical property.

[0272] For those skilled in the art, it is obvious that the present application is not limited to the details of the above exemplary embodiments, and the present application can be implemented in other specific forms without departing from the spirit or basic characteristics of the present application. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present application is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present application. Any reference signs in the claims should not be regarded as limiting the claimed rights.

[0273] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A monomer based on side-chain liquid crystal polynorbornene, characterized in that, Has the following general formula 1: [General formula 1] In the general formula 1, R1, R2, and R3 are each independently selected from the following groups: H, OR', and R1, R2, and R3 are not simultaneously H, and R' is a straight-chain alkyl, branched-chain alkyl, or cycloalkyl group with more than 1 carbon atom; n is 2, 3, 4, 5, or 6.

2. The monomer according to claim 1, characterized in that Has the following general formula 2: [General formula 2] In the general formula 2, n is 2, 3, 4, 5, or 6.

3. A method for preparing a monomer as described in claim 1, characterized in that, Includes: Disperse the substituted benzoic acid with the following general formula 3 and a chlorinating reagent in a first solvent for reaction to obtain a first intermediate with the following general formula 4; Disperse the first intermediate in a second solvent, and then add 4-((tert-butyldimethylsilyl)oxy)aniline and triethylamine for reaction to obtain a second intermediate with the following general formula 5; Disperse the second intermediate in a third solvent, and then add tetrabutylammonium fluoride for reaction to obtain a third intermediate with the following general formula 6; React the third intermediate product with bromohydrocarbon C n H 2n Br2 in a nucleophilic substitution reaction to obtain a fourth intermediate product with the following general formula 7; Perform a nucleophilic substitution reaction on the fourth intermediate and N-hydroxy-5-norbornene-2,3-dicarboximide to obtain the monomer with the general formula 1; 【General formula 3】 【General formula 4】 【General formula 5】 【General formula 6】 【General formula 7】 Among them, in the general formulas 3 to 7, R1, R2, and R3 are each independently selected from the following groups: H, OR', and R1, R2, and R3 are not simultaneously H, and R' is a straight-chain alkyl, branched-chain alkyl, or cycloalkyl group with more than 1 carbon atom; The bromohydrocarbon C n H 2n In Br2 and general formula 7, n is 2, 3, 4, 5 or 6.

4. The preparation method according to claim 3, wherein In the step of dispersing the substituted benzoic acid and the chlorinating reagent in the first solvent for reaction, The chlorinating reagent is oxalyl chloride, and the molar ratio of the substituted benzoic acid to oxalyl chloride is (0.8 - 1.2):(1.2 - 1.5); and / or, The first solvent is anhydrous dichloromethane; and / or, The reaction conditions of the reaction are an ice bath, and the reaction time is 3 - 4 h.

5. The preparation method according to claim 3, wherein In the step of dispersing the first intermediate in the second solvent, and then adding 4-((tert-butyldimethylsilyl)oxy)aniline and triethylamine for reaction, The second solvent is anhydrous dichloromethane; and / or, The molar ratio of the substituted benzoic acid, 4-((tert-butyldimethylsilyl)oxy)aniline, and triethylamine is (0.8 - 1.2):(1.1 - 1.3):(1.3 - 1.6); and / or, The reaction temperature of the reaction is room temperature, and the reaction time is 4 - 6 h.

6. The preparation method according to claim 3, characterized in that, In the step of dispersing the second intermediate in the third solvent, and then adding tetrabutylammonium fluoride for reaction, The third solvent is tetrahydrofuran; and / or, The reaction specifically is to add tetrabutylammonium fluoride under an ice bath, react for 1.5 - 3 h, spin evaporate and concentrate after the reaction is completed, then drop the reaction system into water, stir overnight for reaction, filter, and dry to obtain the third intermediate; and / or, The molar ratio of the second intermediate to the tetrabutylammonium fluoride is (0.8 - 1.2):(1.1 - 1.3).

7. The preparation method according to claim 3, wherein, The step of subjecting the third intermediate and the bromohydrocarbon C n H 2n to a nucleophilic substitution reaction with Br2 is specifically as follows: Disperse the third intermediate product, bromohydrocarbon C n H 2n Br2, potassium carbonate and TBAB in a fourth solvent, and carry out a reflux reaction to obtain the fourth intermediate product; Among them, the reaction temperature of the reflux reaction is 75 - 80 °C, and the reaction time is 24 - 72 h; and / or, The molar ratio of the third intermediate, bromohydrocarbon C n H 2n to Br2 and potassium carbonate is (0.8 to 1.2):(5.5 to 10.5):(5.5 to 7.5), and the mass ratio of the TBAB to the third intermediate is 1:(5 to 8); and / or, The fourth solvent is acetone.

8. The preparation method according to claim 3, characterized in that, The step of subjecting the fourth intermediate product and N-hydroxy-5-norbornene-2,3-dicarboximide to a nucleophilic substitution reaction to obtain the monomer having the general formula 1 is specifically as follows: Disperse the fourth intermediate product, N-hydroxy-5-norbornene-2,3-dicarboximide, potassium carbonate and TBAB in a fifth solvent, carry out a reflux reaction, and after the reaction is completed, carry out extraction and rotary evaporation to obtain the monomer having the general formula 1; Wherein, the molar ratio of the fourth intermediate product, N-hydroxy-5-norbornene-2,3-dicarboximide and potassium carbonate is (0.8 to 1.2):(1.1 to 1.3):(5.5 to 7.5), and the mass ratio of TBAB to the fourth intermediate product is 1:(5 to 8); and / or, The reaction time of the reflux reaction is 12 to 24 h, and the reaction temperature is 70 to 80 °C; and / or, The fifth solvent is anhydrous DMF.

9. A polymer based on side-chain liquid crystal polynorbornene, characterized in that, Obtained by polymerizing the monomer according to claim 1, the polymer has a repeating unit shown in the following general formula 8, and the number of the repeating units is greater than or equal to 10; 【General formula 8】 In the general formula 8, R1, R2, and R3 each independently selected from the following groups: H, OR', and R1, R2, and R3 are not simultaneously H, and R' is a straight-chain alkyl, branched-chain alkyl or cycloalkyl group with more than 1 carbon atom; n is 2, 3, 4, 5 or 6.

10. A method for preparing a polymer as described in claim 9, characterized in that, Comprising: Disperse the monomer having the general formula 1 in a sixth solvent under an inert atmosphere, and then add a Grubbs third-generation catalyst, and carry out a polymerization reaction under an inert atmosphere to obtain the polymer.

11. The preparation method according to claim 10, characterized in that, The reaction time of the polymerization reaction is 2 to 4 h, and the reaction temperature is room temperature; and / or, The molar ratio of the Grubbs third-generation catalyst to the monomer is (0.8 to 1.2):(20 to 60); and / or, The sixth solvent is anhydrous dichloromethane.

12. Use of the monomer based on side-chain liquid crystal polynorbornene according to claim 1 or 2 or the polymer based on side-chain liquid crystal polynorbornene according to claim 9 in the preparation of a flexible gas barrier film.

13. A preparation method of a flexible gas-barrier film, characterized in that, Comprising: Melt the polymer according to claim 9 into a block, and pre-press it at a first temperature to obtain an intermediate sample; Press the intermediate sample at a second temperature, and cool to obtain the flexible gas barrier film; Wherein, the first temperature is higher than the isotropic transition temperature of the polymer, and the second temperature is 5 to 15 °C lower than the isotropic transition temperature of the polymer.

14. The preparation method according to claim 1, wherein The step of pressing at the second temperature is specifically as follows: Heat and keep the intermediate sample at the second temperature, and apply a pressure of 13.5 to 16.5 MPa, stop heating after maintaining the pressure for 30 to 50 min, and remove the pressure after cooling to the temperature to obtain the flexible gas barrier film; and / or, The second temperature is 113 to 123 °C.

15. A flexible gas barrier film prepared by using the preparation method according to claim 13 or 14.

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