Liquid crystal molecule, preparation method and application

Abstract

The invention belongs to the technical field of functional materials, and particularly relates to a liquid crystal molecule, a preparation method and application, a biheterocycle substituted pyridine element is used as a rigid core of the liquid crystal molecule, side groups of different types and lengths are used as flexible modification parts, and a pyridine derivative is endowed with liquid crystal characteristics, so that the pyridine derivative has excellent fluidity and long-range orderliness; the liquid crystal molecule is a banana-shaped liquid crystal small molecule, has a unique molecular structure, is adjustable in liquid crystal phase state type and phase change temperature, and has application value in the fields of display, luminescence and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional materials, and in particular relates to a liquid crystal molecule, a preparation method and an application thereof. Background Art

[0002] Liquid crystal is a soft material with both liquid fluidity and crystal anisotropy, discovered by Austrian botanist Reinitzer and German physicist Lehmann in 1888. Due to its unique response to external fields such as electricity, light, heat, and magnetism, liquid crystal has been widely used in high-tech fields such as flat-panel displays, smart windows, optical brakes, augmented reality, high-end anti-counterfeiting, and high thermal conductivity materials.

[0003] According to the molecular shape, liquid crystal molecules are usually divided into rod-shaped liquid crystals, disc-shaped liquid crystals and banana-shaped liquid crystals. Banana-shaped liquid crystal molecules are mainly composed of a curved rigid part and a flexible carbon chain connected to its two ends. Due to the special geometric shape of banana-shaped liquid crystal molecules, they can self-assemble to form a variety of novel phase structures, showing the mutual coupling of molecular bending, intra-layer tilt and molecular layer chirality. The liquid crystal phase formed by banana-shaped liquid crystal molecules can produce ferroelectric, antiferroelectric switching effects and secondary harmonics, and has potential application value in the fields of photoelectric switches, nonlinear optical materials and new optical fibers. The existing technology lacks research on banana-shaped liquid crystals. Summary of the invention

[0004] The purpose of the present invention is to provide a liquid crystal molecule, a preparation method and an application thereof based on the current situation that there is a lack of research on banana-shaped liquid crystals. By modifying a flexible chain outside a rigid bicyclic-substituted pyridine moiety, a banana-shaped (bow-shaped) liquid crystal molecule with the long axis direction of the molecule as a characteristic direction is obtained. The liquid crystal molecule has liquid crystal properties and the characteristics of a wide liquid crystal temperature range and an adjustable liquid crystal phase temperature range, and has broad application prospects in the fields of display and light-emitting devices.

[0005] The first aspect of the present invention provides a liquid crystal molecule having a structure shown in formula (I):

[0006]

[0007] In Formula I,

[0008] n1 is 1 or 2;

[0009] n2 is 1 or 2;

[0010] Ring A and Ring B are the same or different and are each independently selected from a saturated or unsaturated monocyclic heterocycle;

[0011] R1 and R2 are the same or different, and R1 and R2 are independently selected from any one of a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted oxaalkyl group, and a liquid crystal unit.

[0012] The molecular weight of the liquid crystal molecules of the present invention is less than 1500, and the liquid crystal molecules are small liquid crystal molecules.

[0013] According to some embodiments of the present invention, the substituent is selected from halogen, cyano, phenyl, C1-C10 alkyl and C1-C10 alkoxy;

[0014] According to some embodiments of the present invention, the halogen is selected from fluorine, chlorine, bromine and iodine; and / or,

[0015] The C1-C10 alkyl group is selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, isobutyl, n-pentyl, isopentyl, n-hexyl and n-heptyl; and / or,

[0016] The C1-C10 alkoxy group is selected from the group consisting of methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, tert-butoxy, isobutoxy, n-pentoxy, isopentyloxy, n-hexyloxy and n-heptyloxy.

[0017] According to some embodiments of the present invention, the type of liquid crystal phase and the phase transition temperature range can be regulated by one or more of the length of the flexible chain and the type of the flexible chain.

[0018] According to some embodiments of the present invention, the liquid crystal molecules are selected from any one of a columnar liquid crystal phase, a smectic A liquid crystal phase and a smectic C liquid crystal phase.

[0019] According to some embodiments of the present invention, the liquid crystal phase temperature range of the liquid crystal molecules is 0°C to 200°C.

[0020] According to some embodiments of the present invention, the liquid crystal molecules are banana-shaped (bow-shaped) with the long axis direction of the molecules as a characteristic direction.

[0021] According to some embodiments of the invention, Ring A and Ring B are the same or different and are each independently selected from a 3- to 7-membered saturated or unsaturated monocyclic heterocycle;

[0022] Preferably, the 3- to 7-membered saturated or unsaturated monocyclic heterocycle is selected from the group consisting of a triazepine ring, an azetidine ring, an oxetane ring, a tetrahydrofuran ring, a tetrahydrothiophene ring, a tetrahydropyrrole ring, a piperidine ring, a pyrroline ring, an oxazolidine ring, a piperazine ring, a dioxolane ring, a dioxane ring, a morpholine ring, a thiomorpholine ring, a thiomorpholine-1,1-dioxide, a tetrahydropyran ring, an azetidine-2-one ring, an oxetane-2-one ring, a pyrrolidine-2-one ring, a pyrrolidine-2,5-dione ring, a piperidine-2-one ring, a dihydrofuran-2(3H)-one ring, a dihydrofuran-2,5-dione ring, a tetrahydro-2H-pyran-2-one ring, a piperazine-2-one ring, a morpholine-3-one ring, a 1,2-dihydroazacyclic ring butadiene ring, 1,2-dihydrooxacyclobutadiene ring, 2,5-dihydro-1H-pyrrole ring, 2,5-dihydrofuran ring, 2,3-dihydrofuran ring, 2,3-dihydro-1H-pyrrole ring, 3,4-dihydro-2H-pyran ring, 1,2,3,4-tetrahydropyridine ring, 3,6-dihydro-2H-pyran ring, 1,2,3,6-tetrahydropyridine ring, 4,5-dihydro-1H-imidazole ring, 1,4,5,6-tetrahydropyrimidine ring, 3,4,7,8-tetrahydro-2H-1,4,6-oxadiazolidine ring, 1,6-dihydropyrimidine ring, 4,5,6,7-tetrahydro-1H-1,3-diazacyclopentadiene ring, 2,5,6,7-tetrahydro-1,3,5-oxadiazacyclopentadiene ring.

[0023] According to some embodiments of the present invention, the ring A and the ring B are

[0024] According to some embodiments of the invention, n1 is 1; and / or

[0025] n2 is 1; and / or

[0026] R1 and R2 are the same or different, and R1 and R2 are each independently selected from any one of a substituted or unsubstituted C1-C10 alkyl group, a substituted or unsubstituted C1-C10 alkoxy group, a substituted or unsubstituted C1-C10 oxaalkyl group, and a mesogen;

[0027] Preferably, the C1-C10 alkyl group is selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, isobutyl, n-pentyl, isopentyl, n-hexyl and n-heptyl; and / or,

[0028] The C1-C10 alkoxy group is selected from methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, tert-butoxy, isobutoxy, n-pentoxy, isopentyloxy, n-hexyloxy and n-heptyloxy; and / or,

[0029] The C1-C10 oxaalkyl group is selected from methoxypropoxy, 3,6,9-trioxadecanyl; and / or

[0030] R1 and R2 are the same.

[0031] In some embodiments of the present invention, the structure of the liquid crystal unit is shown in any one of Formula II, Formula III, Formula IV, Formula V and Formula VI:

[0032]

[0033] Among them, 1≤m1≤18; 1≤m2≤18;

[0034] Z1 and Z2 are the same or different, and are independently selected from any one of a substituted or unsubstituted alkylene group, a substituted or unsubstituted alkyleneoxy group, and a substituted or unsubstituted imido group;

[0035] R4 to R7 are the same or different and are independently selected from any one of hydrogen, cyano, alkyl with or without substitution and alkoxy with or without substitution;

[0036] The substituent is selected from halogen, cyano, phenyl, C1-C10 alkyl and C1-C10 alkoxy,

[0037] More preferably, the halogen is selected from fluorine, chlorine, bromine and iodine; and / or,

[0038] The C1-C10 alkyl group is selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, isobutyl, n-pentyl, isopentyl, n-hexyl and n-heptyl; and / or,

[0039] The C1-C10 alkoxy group is selected from the group consisting of methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, tert-butoxy, isobutoxy, n-pentoxy, isopentyloxy, n-hexyloxy and n-heptyloxy.

[0040] In some embodiments of the present invention, Z1 is selected from any one of a substituted or unsubstituted C1-C20 alkyl group, a substituted or unsubstituted C1-C20 alkyleneoxy group, and a substituted or unsubstituted C1-C20 imido group;

[0041] Preferably, Z1 is selected from any one of -CH2-(methylene), -CH2CH2-(ethylene), -CH2CH2CH2-(propylene), -C(CH3)2-(isopropylene), -CH2CH2CH2CH2-(butylene), -CF2CF2CF2CF2-(perfluorosubstituted butylene), -OCH2CF2-(difluorosubstituted ethyleneoxy), and -NHC(=O)CH2-(acetimidyl).

[0042] In some embodiments of the present invention, Z2 is selected from any one of a substituted or unsubstituted C1-C20 alkyl group, a substituted or unsubstituted C1-C20 alkyleneoxy group, and a substituted or unsubstituted C1-C20 imido group;

[0043] Preferably, Z1 is selected from any one of -CH2-(methylene), -CH2CH2-(ethylene), -CH2CH2CH2-(propylene), -C(CH3)2-(isopropylene), -CH2CH2CH2CH2-(butylene), -CF2CF2CF2CF2-(perfluorosubstituted butylene), -OCH2CF2-(difluorosubstituted ethyleneoxy), and -NHC(=O)CH2-(acetimidyl).

[0044] In some embodiments of the present invention, R4 is cyano.

[0045] In some embodiments of the present invention, R5 is hydrogen.

[0046] In some embodiments of the present invention, R6 is any one of hydrogen, a C1-C20 alkyl group which may be substituted or not substituted, or a C1-C20 alkoxy group which may be substituted or not substituted;

[0047] Preferably, the C1-C20 alkyl group is selected from any one of methyl, ethyl, propyl, 1-methylethyl, butyl, 1-methylpropyl, 2-methylpropyl, 1,1-dimethylethyl, pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 2,2-dimethylpropyl, 1-ethylpropyl, hexyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1,1-dimethylbutyl, 1,2-dimethylbutyl, 1,3-dimethylbutyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl, 3,3-dimethylbutyl, 1-ethylbutyl, 2-ethylbutyl, 1,1,2-trimethylpropyl, 1,2,2-trimethylpropyl, 1-ethyl-1-methylpropyl and 1-ethyl-2-methylpropyl; and / or,

[0048] The C1-C20 alkoxy group is selected from any one of methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, 1-methyl-propoxy, 2-methyl-propoxy, tert-butoxy, n-pentoxy, 1-methylbutoxy, 2-methylbutoxy, 3-methylbutoxy, 1,1-dimethylpropoxy, 1,2-dimethylpropoxy, 2,2-dimethyl-propoxy, 1-ethylpropoxy, n-hexyloxy, 1-methylpentoxy, 2-methylpentoxy, 3-methylpentoxy, 4-methylpentoxy, 1,1-dimethylbutoxy, 1,2-dimethylbutoxy, 1,3-dimethylbutoxy, 2,2-dimethylbutoxy, 2,3-dimethylbutoxy, 3,3-dimethylbutoxy, 1-ethylbutoxy, 2-ethylbutoxy, 1,1,2-trimethylpropoxy, 1,2,2-trimethylpropoxy, 1-ethyl-1-methylpropoxy and 1-ethyl-2-methylpropoxy;

[0049] R6 is preferably any one of a substituted or unsubstituted C1-C8 alkyl group or a substituted or unsubstituted C1-C8 alkoxy group.

[0050] In some embodiments of the present invention, R7 is hydrogen.

[0051] According to some embodiments of the present invention, the liquid crystal molecule has a structure shown in Formula VII,

[0052]

[0053] In Formula VII,

[0054] X is selected from any one of C1-C10 alkyl, C1-C10 alkoxy, and C1-C10 oxaalkyl;

[0055] Preferably, the C1-C10 alkyl group is selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, isobutyl, n-pentyl, isopentyl, n-hexyl and n-heptyl; and / or,

[0056] The C1-C10 alkoxy group is selected from methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, tert-butoxy, isobutoxy, n-pentoxy, isopentyloxy, n-hexyloxy and n-heptyloxy; and / or,

[0057] The C1-C10 oxaalkyl group is selected from methoxypropoxy and 3,6,9-trioxadecyl.

[0058] The second aspect of the present invention provides a method for preparing the liquid crystal molecule according to the first aspect, comprising: mixing raw materials for reaction, wherein the raw materials include a 2,6-pyridine derivative, a reducing agent and a flexible side chain precursor;

[0059] Preferably, the molar ratio of the 2,6-pyridine derivative to the reducing agent is 1:1.5 to 1:4;

[0060] The molar ratio of the flexible side chain precursor to the 2,6-pyridine derivative is 1:1 to 1.5:1; and / or

[0061] The 2,6-pyridine derivative is 2,6-pyridinedicarbonitrile; and / or

[0062] The reducing agent is hydrazine hydrate; and / or

[0063] The flexible side chain precursor is selected from one or more of a halogenated oxaalkyl-containing compound, a long-chain alcohol and a halogenated alkane;

[0064] More preferably, the compound containing halogenated oxaalkyl is a halogenated acid anhydride or an acyl halide; the halogenated acid anhydride is preferably trifluoroacetic anhydride; and / or, the acyl halide is preferably any one of decanoyl chloride, hexanoyl chloride, butyryl chloride and octanoyl chloride; and / or,

[0065] The long-chain alcohol is a C1-C10 alcohol; and / or the halogenated alkane is a C1-C10 halogenated alkane.

[0066] According to some embodiments of the present invention, the preparation method specifically comprises:

[0067] 1) mixing a 2,6-pyridine derivative, a reducing agent and a solvent A to react to obtain an intermediate product;

[0068] 2) The intermediate product, solvent B and flexible side chain precursor are mixed and reacted.

[0069] Preferably, the solvent A is ethanol; the molar ratio of the solvent A to the reducing agent is preferably 50 to 5:1; and / or

[0070] The solvent B is an ether solvent, and the ether solvent is preferably diethylene glycol dimethyl ether; the molar ratio of the solvent B to the 2,6-pyridine derivative is 1:15 to 1:30; and / or

[0071] The reaction temperature of step 1) is 15°C to 35°C; and / or

[0072] The reaction temperature of step 2) is 100°C to 120°C.

[0073] According to some embodiments of the present invention, the preparation method comprises:

[0074] (1) Dissolve 2,6-pyridinedicarbonitrile in a single-necked flask containing ethanol, stir evenly at room temperature, then add hydrazine hydrate dropwise overnight; after a light yellow precipitate is precipitated, filter it, rinse the filter cake three times with ethanol, and dry it in vacuum to obtain a light yellow powder product;

[0075] (2) The yellow powder product obtained in step (1) is mixed with an ether solvent, ultrasonically dispersed uniformly, and then anhydride or acid chloride is added dropwise. After the mixed solution is clarified, it is heated, stirred and refluxed, cooled to room temperature (15-35°C), and distilled water and concentrated hydrochloric acid are added in sequence, and the temperature is continued to be raised, stirred and refluxed overnight; the temperature is continued to be lowered to room temperature (15-35°C), and after a white precipitate is precipitated, it is filtered by suction, and the filter cake is rinsed with deionized water and an ether solvent for multiple times, and finally vacuum dried to obtain a white powder product, thereby obtaining the liquid crystal molecule.

[0076] According to some specific embodiments of the present invention, the acid anhydride or acid chloride in step (2) contains 1 to 10 carbon atoms.

[0077] The term "oxaalkyl" as used herein is -(O-alkyl-) n -saturated ends (such as hydroxyl, methyl, etc.).

[0078] As used herein, the term "alkoxy" refers to an -O-alkyl group.

[0079] The term "halo" used in the present invention refers to halogen substitution, and "halogen" refers to fluorine, chlorine, bromine and iodine.

[0080] The fifth aspect of the present invention provides the use of the liquid crystal molecules described in the first aspect or the liquid crystal molecules prepared by the method described in the second aspect in the preparation of display and light-emitting devices.

[0081] Compared with the prior art, the present invention provides a liquid crystal molecule, a preparation method and an application.

[0082] The present invention has the following beneficial effects:

[0083] (1) The present invention provides a liquid crystal molecule core of a structure shown in formula (I), wherein the liquid crystal molecule core is a rigid bicyclic substituted pyridine core. The liquid crystal molecule of the present invention is a banana-like liquid crystal small molecule, wherein the liquid crystal molecule core and the flexible chain are combined by covalent bonding, respectively serving as a rigid core and a flexible modification part, and imparting liquid crystal properties to pyridine derivatives, so that the obtained banana-like liquid crystal small molecule has excellent fluidity and long-range order, and the liquid crystal phase temperature range is adjustable from 0°C to 200°C, and the liquid crystal phase type and liquid crystal phase temperature range of the banana-like liquid crystal small molecule can be regulated by the length and type of the flexible chain. The longer the flexible chain length, the weaker the molecular crystallinity, and the easier it is to form a liquid crystal phase structure with a lower degree of order; conversely, the liquid crystal has a high degree of order and even crystallization. In addition, different types of flexible chains affect the mutual stacking of molecules due to different intermolecular interactions and energy disturbances, thereby obtaining liquid crystal phase structures with different degrees of order.

[0084] (2) The present invention obtains liquid crystal molecules with a lower clearing point, which can achieve the transition from solid to liquid at a lower temperature, so as to facilitate bulk processing.

[0085] (3) The method for preparing liquid crystal molecules provided by the present invention has readily available raw materials, low cost, and mild preparation conditions, and can be applied to the fields of display and light-emitting devices in the future. BRIEF DESCRIPTION OF THE DRAWINGS

[0086] Figure 1 This is a polarizing microscope image of the banana-shaped liquid crystal small molecule obtained in Example 1;

[0087] Figure 2 This is the mass spectrum of the banana-shaped liquid crystal small molecule obtained in Example 1;

[0088] Figure 3 It is a schematic diagram of the structure of the banana-shaped liquid crystal small molecule obtained in Example 1 by molecular simulation calculation;

[0089] Figure 4 is the X-ray diffraction (XRD) spectrum of the banana-shaped liquid crystal small molecule prepared in Example 2;

[0090] Figure 5 The differential scanning calorimetry (DSC) curve of the banana-shaped liquid crystal small molecule prepared in Example 3 is shown. DETAILED DESCRIPTION

[0091] The present invention will be further described below in conjunction with specific implementation methods. The protection scope of the present invention is not limited by the following embodiments but is determined by the claims.

[0092] It should be particularly noted that two or more aspects (or implementation methods) disclosed in the context of this specification can be arbitrarily combined with each other, and the technical solution thus formed is part of the original disclosure of this specification and also falls within the scope of protection of the present invention.

[0093] Example

[0094] Exemplary embodiments of the present invention are described below, including various details of the embodiments of the present invention to aid understanding, which should be considered as merely exemplary. Therefore, it should be appreciated by those of ordinary skill in the art that various changes and modifications may be made to the embodiments described herein without departing from the scope and spirit of the present invention. Similarly, for clarity and simplicity, descriptions of known functions and structures are omitted in the following description. The experimental methods used in the following embodiments are conventional methods unless otherwise specified. The materials, reagents, etc. used in the following embodiments, unless otherwise specified, can all be obtained from commercial sources.

[0095] In an exemplary embodiment of the present invention,

[0096] The detection method of the present invention is a conventional technical method in the art.

[0097] Room temperature refers to 15-35°C, and the reaction is at normal pressure (one standard atmosphere).

[0098] In an exemplary embodiment of the present invention, the detection method is a conventional technical method in the art.

[0099] In an exemplary embodiment of the present invention, the liquid crystal molecule has a structure shown in formula (III),

[0100]

[0101] In formula III,

[0102] X is selected from any one of C1-C10 alkyl, C1-C10 alkoxy and C1-C10 oxaalkyl.

[0103] In an exemplary embodiment of the present invention, a method for preparing a liquid crystal molecule includes: reacting a liquid crystal molecule core with a flexible side chain precursor; the flexible side chain precursor is selected from one of a halogenated oxoalkyl compound (corresponding to a C1-C10 oxoalkyl chain), a long-chain alcohol (corresponding to a C1-C10 alkoxy chain) and a halogenated alkane (corresponding to a C1-C10 alkyl chain); when the carbon chain length is the same, its flexibility gradually decreases; and for the same type of flexible chain, the longer the carbon chain, the higher the flexibility. Under the same conditions, the higher the flexibility of the flexible chain, the lower its liquid crystal phase temperature, and vice versa.

[0104] In an exemplary embodiment of the present invention, the liquid crystal molecule is a banana-shaped liquid crystal small molecule, wherein the bicyclic substituted pyridine core and the flexible chain modified on its outer surface act together to make the molecule have both liquid crystal properties and bulk luminescence properties, and the liquid crystal phase temperature range of the liquid crystal molecule can be regulated by regulating one or more of the length of the flexible chain and the type of the flexible chain. The liquid crystal phase temperature range of the liquid crystal molecule provided by the present invention is adjustable within 0 to 200°C.

[0105] In an exemplary embodiment of the present invention, a method for preparing banana-shaped liquid crystal small molecules is provided, comprising the following steps:

[0106] (1) Dissolve 2,6-pyridinedicarbonitrile in a single-necked flask containing ethanol, stir evenly at room temperature, then add hydrazine hydrate dropwise overnight; after a light yellow precipitate is precipitated, filter it, rinse the filter cake three times with ethanol, and dry it in vacuum to obtain a light yellow powder product;

[0107] (2) The yellow powder product obtained in step (1) is mixed with an ether solvent, ultrasonically dispersed uniformly, and then anhydride or acid chloride is added dropwise. After the mixed solution is clarified, it is heated, stirred and refluxed, and after the system is cooled to room temperature, distilled water and concentrated hydrochloric acid are added in sequence, and the temperature is continued to be raised, stirred and refluxed overnight; the temperature is continued to be lowered to room temperature, and after a white precipitate is precipitated, it is filtered by suction, and the filter cake is rinsed with deionized water and ether for multiple times, and finally vacuum dried to obtain a white powder product, thereby obtaining the banana-shaped liquid crystal small molecule.

[0108] According to some specific embodiments of the present invention, the molar ratio of 2,6-pyridinedicarbonitrile to hydrazine hydrate in step (1) is 1:1.5 to 1:4.

[0109] According to some specific embodiments of the present invention, the acid anhydride or acid chloride in step (2) contains 1 to 10 carbon atoms.

[0110] The following are examples:

[0111] Example 1

[0112] A banana-shaped liquid crystal small molecule, which consists of a rigid bicyclic substituted pyridine core and a surface-modified flexible chain, is prepared by the following steps:

[0113] a) Dissolve 5g of 2,6-pyridine dicarbonitrile in a single-necked flask containing 100mL of ethanol, stir evenly at room temperature, and then add 40mL of hydrazine hydrate dropwise overnight. After a light yellow precipitate is precipitated, filter it, rinse the filter cake three times with ethanol, and dry it in vacuum to obtain a light yellow powder product with a yield of 98%;

[0114] b) Mix 2.27g of the light yellow powder obtained in the previous step with 30mL of diethylene glycol dimethyl ether, disperse evenly by ultrasonication, and then add 5.44g of trifluoroacetic anhydride dropwise. After the mixed solution is clarified, heat to 120°C and stir and reflux for 6h. After the system cools to room temperature, add 70mL of distilled water and 2mL of concentrated hydrochloric acid in sequence, continue to heat to 90°C, stir and reflux, and spend the night. Continue to cool to room temperature, filter after the white precipitate is precipitated, rinse the filter cake with deionized water and petroleum ether several times, and finally vacuum dry to obtain a white powder product with a yield of 75%.

[0115] Figure 1 This is a polarizing microscope photograph of the banana-shaped liquid crystal small molecule prepared in Example 1 after being heated to a clearing point and then cooled to room temperature. It can be seen that the banana-shaped liquid crystal small molecule has not crystallized, showing the birefringence phenomenon of liquid crystal. Figure 2 The mass spectrum of the banana-shaped liquid crystal small molecule prepared in Example 1 shows that its molecular weight is 350.0586.

[0116] Figure 3This is a schematic diagram of the structure of the banana-shaped liquid crystal small molecule obtained in Example 1, and the side chain is simplified during the calculation.

[0117] Example 2

[0118] A banana-shaped liquid crystal small molecule, which consists of a rigid bicyclic substituted pyridine core and a surface-modified flexible chain, is prepared by the following steps:

[0119] a) Dissolve 2.5 g of 2,6-pyridine dicarbonitrile in a single-necked flask containing 50 mL of ethanol, stir evenly at room temperature, and then add 20 mL of hydrazine hydrate dropwise overnight. After a light yellow precipitate is precipitated, filter it, rinse the filter cake three times with ethanol, and vacuum dry it to obtain a light yellow powder product with a yield of 95%;

[0120] b) Mix 1.2g of the light yellow powder obtained in the previous step with 15mL of diethylene glycol dimethyl ether, disperse evenly by ultrasonication, and then add 2.7g of butyryl chloride dropwise. After the mixed solution is clarified, heat to 100°C and stir and reflux for 6h. After the system cools to room temperature, add 35mL of distilled water and 1mL of concentrated hydrochloric acid in sequence, continue to heat to 90°C, stir and reflux overnight. Continue to cool to room temperature, filter after the white precipitate is precipitated, rinse the filter cake with deionized water and petroleum ether several times, and finally vacuum dry to obtain a white powder product with a yield of 80%.

[0121] Figure 4 This is the X-ray diffraction (XRD) spectrum of the banana-shaped liquid crystal small molecule. From the peak shape in the spectrum, it can be seen that the molecule can form a columnar liquid crystal phase.

[0122] Example 3

[0123] A banana-shaped liquid crystal small molecule, which consists of a rigid bicyclic substituted pyridine core and a surface-modified flexible chain, is prepared by the following steps:

[0124] a) Dissolve 2.5 g of 2,6-pyridine dicarbonitrile in a single-necked flask containing 50 mL of ethanol, stir evenly at room temperature, and then add 20 mL of hydrazine hydrate dropwise overnight. After a light yellow precipitate is precipitated, filter it, rinse the filter cake three times with ethanol, and vacuum dry it to obtain a light yellow powder product with a yield of 95%;

[0125] b) Mix 1.2g of the light yellow powder obtained in the previous step with 15mL of diethylene glycol dimethyl ether, disperse evenly by ultrasonication, and then add 2.7g of hexanoyl chloride dropwise. After the mixed solution is clarified, heat to 100°C and stir and reflux for 6h. After the system cools to room temperature, add 35mL of distilled water and 1mL of concentrated hydrochloric acid in sequence, continue to heat to 90°C, stir and reflux overnight. Continue to cool to room temperature, filter after the white precipitate is precipitated, rinse the filter cake with deionized water and petroleum ether several times, and finally vacuum dry to obtain a white powder product with a yield of 80%.

[0126] Figure 5 The differential scanning calorimetry (DSC) curve of the prepared banana-shaped liquid crystal small molecule shows that the temperature range of the liquid crystal phase of the molecule is 0°C to 38°C. When heated to above 38°C, an isotropic liquid fluid can be obtained, which is convenient for bulk processing.

[0127] Example 4

[0128] A banana-shaped liquid crystal small molecule, which consists of a rigid bicyclic substituted pyridine core and a surface-modified flexible chain, is prepared by the following steps:

[0129] a) Dissolve 2.5 g of 2,6-pyridine dicarbonitrile in a single-necked flask containing 50 mL of ethanol, stir evenly at room temperature, and then add 20 mL of hydrazine hydrate dropwise overnight. After a light yellow precipitate is precipitated, filter it, rinse the filter cake three times with ethanol, and vacuum dry it to obtain a light yellow powder product with a yield of 95%;

[0130] b) Mix 1.2g of the light yellow powder obtained in the previous step with 15mL of diethylene glycol dimethyl ether, disperse evenly by ultrasonication, and then add 2.7g of octanoyl chloride dropwise. After the mixed solution is clarified, heat to 100°C and stir and reflux for 6h. After the system cools to room temperature, add 35mL of distilled water and 1mL of concentrated hydrochloric acid in sequence, continue to heat to 90°C, stir and reflux, and stay overnight. Continue to cool to room temperature, filter after the white precipitate is precipitated, rinse the filter cake with deionized water and petroleum ether several times, and finally dry it in vacuum to obtain a white powder product with a yield of 70%.

[0131] Example 5

[0132] A banana-shaped liquid crystal small molecule, which consists of a rigid bicyclic substituted pyridine core and a surface-modified flexible chain, is prepared by the following steps:

[0133] a) Dissolve 5g of 2,6-pyridine dicarbonitrile in a single-necked flask containing 100mL of ethanol, stir evenly at room temperature, and then add 40mL of hydrazine hydrate dropwise overnight. After a light yellow precipitate is precipitated, filter it, rinse the filter cake three times with ethanol, and dry it in vacuum to obtain a light yellow powder product with a yield of 98%;

[0134] b) Mix 2.27g of the light yellow powder obtained in the previous step with 30mL of diethylene glycol dimethyl ether, disperse evenly by ultrasonication, and then add 5.44g of decanoyl chloride dropwise. After the mixed solution is clarified, heat to 120°C and stir and reflux for 6h. After the system cools to room temperature, add 70mL of distilled water and 2mL of concentrated hydrochloric acid in sequence, continue to heat to 90°C, stir and reflux overnight. Continue to cool to room temperature, filter after the white precipitate is precipitated, rinse the filter cake with deionized water and petroleum ether several times, and finally vacuum dry to obtain a white liquid product with a yield of 75%.

[0135] Comparative Example 1

[0136] A banana-shaped liquid crystal small molecule, which consists of a rigid bicyclic substituted pyridine core and a surface-modified flexible chain, is prepared by the following steps:

[0137] a) Dissolve 2.5 g of 2,6-pyridine dicarbonitrile in a single-necked flask containing 50 mL of ethanol, stir evenly at room temperature, and then add 20 mL of hydrazine hydrate dropwise overnight. After a light yellow precipitate is precipitated, filter it, rinse the filter cake three times with ethanol, and vacuum dry it to obtain a light yellow powder product with a yield of 95%;

[0138] b) Mix 1.2g of the light yellow powder obtained in the previous step with 15mL of diethylene glycol dimethyl ether, disperse evenly by ultrasonication, and then add 1.3g of acetic acid dropwise. After the mixed solution is clarified, heat to 100°C and stir and reflux for 6h. After the system cools to room temperature, add 35mL of distilled water and 1mL of concentrated hydrochloric acid in sequence, continue to heat to 90°C, stir and reflux, and spend the night. Continue to cool to room temperature, filter after the white precipitate is precipitated, rinse the filter cake with deionized water and petroleum ether several times, and finally dry in vacuum to obtain a white powder product with a yield of 80%.

[0139] In Comparative Example 1, the molecular structure has no modified flexible part, and banana-shaped liquid crystal molecules cannot be obtained. Only crystalline banana-shaped molecules can be obtained, and liquid fluid cannot be obtained by increasing the temperature.

[0140] The phase temperature range and phase structure of the banana-like molecules prepared in Examples 1 to 4 of the present invention and Comparative Example 1 are shown in Table 1. It can be seen that the banana-like liquid crystal small molecules prepared in the embodiments of the present invention have an adjustable liquid crystal phase temperature range between 0 and 200° C., and the liquid crystal phase type is adjustable, which can meet the application requirements of various application scenarios.

[0141] Table 1 Liquid crystal phase temperature range and luminescent color of banana-like liquid crystal molecules

[0142]

[0143]

[0144] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A liquid crystal molecule having a structure represented by formula (I), In Formula I, n1 is 1 or 2; n2 is 1 or 2; Ring A and Ring B are the same or different and are independently selected from a saturated or unsaturated monocyclic heterocycle; R1 and R2 are the same or different, and R1 and R2 are independently selected from any one of a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted oxaalkyl group, and a liquid crystal unit; Preferably, the molecular weight of the liquid crystal molecule is less than 1500, and the liquid crystal molecule is a small liquid crystal molecule; and / or The substituent is selected from halogen, cyano, phenyl, C1-C10 alkyl and C1-C10 alkoxy; More preferably, the halogen is selected from fluorine, chlorine, bromine and iodine; and / or, The C1-C10 alkyl group is selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, isobutyl, n-pentyl, isopentyl, n-hexyl and n-heptyl; and / or, The C1-C10 alkoxy group is selected from the group consisting of methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, tert-butoxy, isobutoxy, n-pentoxy, isopentoxy, n-hexoxy and n-heptoxy. The liquid crystal molecule according to claim 1, characterized in that: The liquid crystal phase type and phase transition temperature range can be regulated by one or more of the length of the flexible chain and the type of the flexible chain; Preferably, the liquid crystal molecules are selected from any one of a columnar liquid crystal phase, a smectic A liquid crystal phase and a smectic C liquid crystal phase.

2. The liquid crystal molecule according to claim 1 or 2, characterized in that: The liquid crystal phase temperature range of the liquid crystal molecules is 0°C to 200°C.

3. The liquid crystal molecule according to any one of claims 1 to 3, characterized in that: The liquid crystal molecules are banana-shaped with the molecular long axis direction as the characteristic direction.

4. The liquid crystal molecule according to any one of claims 1 to 3, characterized in that: Ring A and Ring B are the same or different and are independently selected from a 3- to 7-membered saturated or unsaturated monocyclic heterocycle; Preferably, the 3- to 7-membered saturated or unsaturated monocyclic heterocycle is selected from the group consisting of a triazepine ring, an azetidine ring, an oxetane ring, a tetrahydrofuran ring, a tetrahydrothiophene ring, a tetrahydropyrrole ring, a piperidine ring, a pyrroline ring, an oxazolidine ring, a piperazine ring, a dioxolane ring, a dioxane ring, a morpholine ring, a thiomorpholine ring, a thiomorpholine-1,1-dioxide, a tetrahydropyran ring, an azetidine-2-one ring, an oxetane-2-one ring, a pyrrolidine-2-one ring, a pyrrolidine-2,5-dione ring, a piperidine-2-one ring, a dihydrofuran-2(3H)-one ring, a dihydrofuran-2,5-dione ring, a tetrahydro-2H-pyran-2-one ring, a piperazine-2-one ring, a morpholine-3-one ring, a 1,2-dihydroazepine Cyclobutadiene ring, 1,2-dihydrooxetadiene ring, 2,5-dihydro-1H-pyrrole ring, 2,5-dihydrofuran ring, 2,3-dihydrofuran ring, 2,3-dihydro-1H-pyrrole ring, 3,4-dihydro-2H-pyran ring, 1,2,3,4-tetrahydropyridine ring, 3,6-dihydro-2H-pyran ring, 1,2,3,6-tetrahydropyridine ring, 4,5-dihydro-1H-imidazole ring, 1,4,5,6-tetrahydropyrimidine ring, 3,4,7,8-tetrahydro-2H-1,4,6-oxadiazolidine ring, 1,6-dihydropyrimidine ring, 4,5,6,7-tetrahydro-1H-1,3-diazacyclopentadiene ring, 2,5,6,7-tetrahydro-1,3,5-oxadiazacyclopentadiene ring.

5. The liquid crystal molecule according to any one of claims 1 to 4, characterized in that: The ring A and the ring B are 6. The liquid crystal molecule according to any one of claims 1 to 5, characterized in that: n1 is 1; and / or n2 is 1; and / or R1 and R2 are the same or different, and R1 and R2 are each independently selected from any one of a substituted or unsubstituted C1-C10 alkyl group, a substituted or unsubstituted C1-C10 alkoxy group, a substituted or unsubstituted C1-C10 oxaalkyl group, and a mesogen; Preferably, the C1-C10 alkyl group is selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, isobutyl, n-pentyl, isopentyl, n-hexyl and n-heptyl; and / or, The C1-C10 alkoxy group is selected from methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, tert-butoxy, isobutoxy, n-pentoxy, isopentyloxy, n-hexyloxy and n-heptyloxy; and / or, The C1-C10 oxaalkyl group is selected from methoxypropoxy, 3,6,9-trioxadecanyl; and / or R1 and R2 are the same.

7. The liquid crystal molecule according to any one of claims 1 to 6, characterized in that: The structure of the liquid crystal unit is shown in any one of Formula II, Formula III, Formula IV, Formula V and Formula VI: Among them, 1≤m1≤18; 1≤m2≤18; Z1 and Z2 are the same or different, and are independently selected from any one of a substituted or unsubstituted alkylene group, a substituted or unsubstituted alkyleneoxy group, and a substituted or unsubstituted imido group; R4 to R7 are the same or different and are independently selected from any one of hydrogen, cyano, alkyl with or without substitution and alkoxy with or without substitution; Preferably, the substituent is selected from halogen, cyano, phenyl, C1-C10 alkyl and C1-C10 alkoxy, More preferably, the halogen is selected from fluorine, chlorine, bromine and iodine; and / or, The C1-C10 alkyl group is selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, isobutyl, n-pentyl, isopentyl, n-hexyl and n-heptyl; and / or, The C1-C10 alkoxy group is selected from the group consisting of methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, tert-butoxy, isobutoxy, n-pentoxy, isopentyloxy, n-hexyloxy and n-heptyloxy.

8. The method for preparing a liquid crystal molecule according to any one of claims 1 to 7, characterized in that: include: Mixing raw materials for reaction, the raw materials comprising a 2,6-pyridine derivative, a reducing agent and a flexible side chain precursor; Preferably, the molar ratio of the 2,6-pyridine derivative to the reducing agent is 1:1.5 to 1:4; The molar ratio of the flexible side chain precursor to the 2,6-pyridine derivative is 1:1 to 1.5:1; and / or The 2,6-pyridine derivative is 2,6-pyridinedicarbonitrile; and / or The reducing agent is hydrazine hydrate; and / or The flexible side chain precursor is selected from one or more of a halogenated oxaalkyl-containing compound, a long-chain alcohol and a halogenated alkane; More preferably, the compound containing halogenated oxaalkyl is a halogenated acid anhydride or an acyl halide; the halogenated acid anhydride is preferably trifluoroacetic anhydride; and / or the acyl halide is preferably any one of decanoyl chloride, hexanoyl chloride, butyryl chloride and octanoyl chloride; and / or The long-chain alcohol is a C1-C10 alcohol; and / or the halogenated alkane is a C1-C10 halogenated alkane.

9. The method for preparing liquid crystal molecules according to claim 8, characterized in that: The preparation method specifically comprises: 1) mixing a 2,6-pyridine derivative, a reducing agent and a solvent A to react to obtain an intermediate product; 2) The intermediate product, solvent B and flexible side chain precursor are mixed and reacted. Preferably, the solvent A is ethanol; the molar ratio of the solvent A to the reducing agent is preferably 50 to 5:1; and / or The solvent B is an ether solvent, and the ether solvent is preferably diethylene glycol dimethyl ether; the molar ratio of the solvent B to the 2,6-pyridine derivative is 1:15 to 1:30, and / or The reaction temperature of step 1) is 15°C to 35°C; and / or The reaction temperature of step 2) is 100°C to 120°C.

10. Use of the liquid crystal molecule according to any one of claims 1 to 7 or the liquid crystal molecule prepared by the method according to claim 8 or 9 in preparing display and light-emitting devices.

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