CN118759769A - Two-dimensional lamellar liquid crystals and their alignment methods and applications - Google Patents

Abstract

The present application discloses a two-dimensional lamellar liquid crystal and an orientation method and application thereof. The orientation method comprises the following steps: providing a first substrate having a first surface and a second substrate having a second surface, defining a liquid crystal accommodation space between the first surface and the second surface, and placing the two-dimensional lamellar liquid crystal into the liquid crystal accommodation space; the first surface and the second surface are incompletely hydrophilic interfaces; applying a disturbance factor to induce the two-dimensional lamellar liquid crystal to be vertically oriented. The preparation method is simple to operate, has mild conditions, and has low energy consumption. The prepared two-dimensional liquid crystal has excellent uniformity and stability, and the realized liquid crystal orientation direction is unique, and the orientation effect is good and uniform.

Description

Two-dimensional lamellar liquid crystals and their alignment methods and applications

Technical Field

The present application relates to the field of two-dimensional liquid crystal technology, and in particular to two-dimensional lamellar liquid crystals and alignment methods and applications thereof.

Background Art

The rapid development of materials science has promoted the progress of liquid crystal science. Two-dimensional lamellar liquid crystals have shown great application value in optoelectronic devices, biomedicine, separation technology and other fields due to their unique physical and chemical properties and wide application potential. In high-performance applications such as optical devices and mass transfer membranes, due to the complexity and arrangement diversity of the lamellar structure of two-dimensional lamellar liquid crystals, their orientation uniformity and anisotropy directly affect the overall optical axis of the material or the channel orientation of the separation membrane, which in turn determines the final performance of related devices, such as transmittance, uniformity of the optical axis, optical phase regulation ability, and mass transfer efficiency. Key parameters. Therefore, achieving a uniform and directional arrangement structure is crucial to improving device performance.

Traditional liquid crystal orientation technology mainly focuses on the regulation of one-dimensional molecular arrangement, such as the parallel or vertical orientation of nematic liquid crystals, mainly a single electric field or orientation layer induced orientation. However, in the field of two-dimensional lamellar liquid crystals, especially the precise control of their microstructure and macroscopic properties, there are still many challenges. The electric field orientation mentioned above is difficult to apply to the vertical orientation process of large-area two-dimensional lamellar liquid crystals, because excessively high electric fields usually break up the lamellar phase structure. At the same time, the method of orientation layer induction is difficult to meet the requirements of large-area, high-precision, and controllable orientation. Moreover, these methods are also difficult to achieve vertical orientation of the two-dimensional layer while achieving anisotropic arrangement of the two-dimensional lamellar liquid crystal layer, and the stability is insufficient in specific application environments.

Summary of the invention

The present application aims to solve at least one of the technical problems existing in the prior art. To this end, the present application proposes a two-dimensional lamellar liquid crystal and its orientation method and application, which can meet the large-area, high-precision, and controllable orientation requirements of the two-dimensional lamellar liquid crystal material, and realize the vertical orientation of the two-dimensional layer while achieving anisotropic arrangement, and has high stability.

In a first aspect of the present application, a method for aligning two-dimensional lamellar liquid crystals is provided, the method comprising the following steps:

A first substrate having a first surface and a second substrate having a second surface are provided, a liquid crystal accommodation space is defined between the first surface and the second surface, and two-dimensional lamellar liquid crystals are placed in the liquid crystal accommodation space, and the first surface and the second surface are incompletely hydrophilic interfaces;

Applying disturbance factors induces vertical orientation of two-dimensional lamellar liquid crystals;

The disturbance factors include at least one of tangential force factors, fluid flow factors, temperature factors, electric field factors, magnetic field factors, pressure factors, additive factors, and thermal radiation factors.

The beneficial effects of the embodiments of the present application are:

The two-dimensional layered liquid crystal material obtained by the above-mentioned orientation method exhibits a unique vertical orientation structure and a uniform orientation effect, which can meet the large-area, high-precision and controllable orientation requirements of the two-dimensional layered liquid crystal material, realize the vertical orientation of the two-dimensional layer while achieving anisotropic arrangement, and has high stability.

In some embodiments, the first surface and the second surface are solid interfaces.

In some embodiments, the first surface and the second surface are independently selected from any one of a flexible solid interface and a non-flexible solid interface.

In some embodiments, the contact angle between the first surface and water and the contact angle between the second surface and water are greater than 45°.

In some embodiments, the materials of the first surface and the second surface are independently selected from at least one of metal, inorganic non-metal, and organic matter.

In some embodiments, the first surface and the second surface are independently selected from any one of a coating and a film.

In some embodiments, the two-dimensional lamellar liquid crystal includes a single-component liquid crystal or a mixed-component liquid crystal.

In some embodiments, the two-dimensional lamellar liquid crystal includes any one of a lamellar monolayer structure and a lamellar bilayer structure.

In some embodiments, the two-dimensional lamellar liquid crystal includes any one of a thermotropic liquid crystal and a lyotropic liquid crystal.

In some embodiments, the two-dimensional lamellar liquid crystal includes at least one of a surfactant-type thermotropic two-dimensional lamellar liquid crystal containing a hydrophilic segment and a hydrophobic segment, and a thermotropic two-dimensional lamellar liquid crystal containing a cyclic rigid structure.

In some embodiments, the two-dimensional lamellar liquid crystal is a two-dimensional lamellar liquid crystal formed by mixing the following A1 and A2:

A1: at least one of smectic A phase liquid crystal, smectic B phase liquid crystal, smectic C phase liquid crystal, smectic D phase liquid crystal, blue phase liquid crystal, and lamellar phase liquid crystal;

A2: At least one of salt, water, liquid organic matter, and liquid acid.

In some embodiments, the temperature range of the two-dimensional lamellar liquid crystal presenting a liquid crystal phase is -10°C to 300°C.

In some of the embodiments, the viscosity of the two-dimensional lamellar liquid crystal is in the range of 10 ³ mPa·s to 10 ¹⁰ mPa·s.

In some of the embodiments, the first substrate or the second substrate is moved relative to the two-dimensional lamellar liquid crystal to induce anisotropic arrangement of liquid crystal domains of the two-dimensional lamellar liquid crystal.

In some embodiments, the direction of the relative movement of the first substrate or the second substrate includes at least one of a tangential movement and a normal movement along the first surface or the second surface.

In some embodiments, the type of relative motion includes any one of unidirectional motion, circular motion, and reciprocating motion.

In some embodiments, the trajectory of the relative motion includes at least one of a linear motion and an arc motion.

In some embodiments, the speed of the relative motion is 0.1 mm/s to 50 mm/s.

In some of the embodiments, the relative movement of the two-dimensional layered liquid crystal includes relative movement driven by at least one of gravity, centrifugal force, shear stress, pressure difference, capillary force, temperature difference, and cross magnetic and electric fields.

In some embodiments, the relative movement of the first substrate or the second substrate with respect to the two-dimensional lamellar liquid crystal includes: fixing the second substrate to allow the first substrate to move relative to the two-dimensional lamellar liquid crystal.

In some embodiments, the first surface and the second surface are independently selected from any one of a plane and a curved surface.

In some embodiments, the approach angle of the first substrate relative to the two-dimensional lamellar liquid crystal is 5° to 90°, and the departure angle is 3° to 175°.

In some of these embodiments, the perturbation factor is applied via a tunable force field generator.

According to a second aspect of the present application, a two-dimensional lamellar liquid crystal is provided, wherein the two-dimensional lamellar liquid crystal is oriented by any one of the aforementioned orientation methods.

According to a third aspect of the present application, a device is provided, which includes the aforementioned two-dimensional layered liquid crystal.

In some of the embodiments, the device is any one of an optical filter, an optical phase modulator, a display, a sensor, an ion separation membrane, and an energy conversion device.

The purpose of this application is to propose a liquid crystal orientation technology that can induce vertical orientation of two-dimensional lamellar liquid crystals, and to provide a liquid crystal orientation solution for molecular assembly structure regulation, optical signal modulation, and mass transfer process enhancement under special working conditions. This application is particularly aimed at two-dimensional lamellar liquid crystal materials, and realizes the vertical orientation and anisotropic arrangement of the two-dimensional layer in the two-dimensional lamellar liquid crystal by precisely controlling the solid-liquid interface characteristics, introducing disturbance factors, and applying characteristic stress fields and cross fields. This innovative method not only greatly improves the accuracy and controllability of liquid crystal orientation, but also expands the range of liquid crystal types applicable to liquid crystal orientation technology, giving two-dimensional lamellar liquid crystals potential in optical devices, mass transfer membranes and many high-tech applications.

The core of this application is to propose and construct a new liquid crystal orientation method, realize the vertical orientation and macroscopic ordered arrangement of the two-dimensional layer in the two-dimensional lamellar liquid crystal, and comprehensively use the characteristic surface interface, characteristic stress field, magnetoelectric cross field, two-dimensional lamellar phase liquid crystal material and specially designed liquid crystal orientation device. Through the interaction between the preferred interface and the liquid crystal material, combined with a variety of disturbance factors, the two-dimensional lamellar liquid crystal arrangement and its order degree are regulated, thereby inducing the desired vertical orientation and anisotropic structure. This technical solution of the present application is not only applicable to single-component two-dimensional lamellar liquid crystals, but also covers complex mixed component systems, significantly enhancing the versatility and scope of application of the technology.

Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an alignment device for two-dimensional lamellar liquid crystals in one embodiment of the present application.

FIG. 2 is a schematic diagram of the molecular self-assembly structure in a single-layer two-dimensional lamellar liquid crystal in an embodiment of the present application.

FIG. 3 is a schematic diagram of the molecular self-assembly structure in a bilayer two-dimensional lamellar liquid crystal in an embodiment of the present application.

Figure 4 shows the bright field and dark field images of the polarized light microtexture of the two-dimensional liquid crystal domain after the anisotropic vertical uniform orientation in different embodiments of the present application. Among them, (A)~(H) are polarized light microtextures under the factors of tangential force, fluid flow, temperature, electric field, magnetic field, pressure, additives, and thermal radiation, respectively; (I)~(N) are polarized light microtextures of lyotropic liquid crystal, thermotropic liquid crystal, smectic A~D, blue phase liquid crystal, single component liquid crystal, and complex mixed component liquid crystal orientation, respectively. P and A in the figure represent the polarization direction and analysis direction of the polarizing microscope, respectively.

FIG. 5 is a stability test result of the two-dimensional lamellar liquid crystal orientation effect in one embodiment of the present application.

FIG. 6 is a schematic diagram showing the principle of two-dimensional lamellar liquid crystal alignment in one embodiment of the present application.

FIG7 is a comparison of contact angles of different solid surfaces with deionized water in one embodiment of the present application, wherein (A) is hydrophilic glass, (B) is hydrophobic glass, (C) is stainless steel, and (D) is polytetrafluoroethylene.

FIG8 shows different types of solid interface structures used in an embodiment of the present application, wherein (A) is a plane/plane structure, (B) is a plane/arc structure, (C) is a plane/inclined structure, and (D) is an arc/arc structure.

FIG. 9 is a schematic diagram of the structure of a force field applying device used in an embodiment of the present application.

Figure 10 is an application of aligned two-dimensional layered liquid crystal to adjust the phase of polarized light in one embodiment of the present application, wherein (A) is a schematic diagram of the principle of the test device, and (B) is a diagram showing the variation of the phase difference of polarized light with the rotation angle of the liquid crystal box.

Reference numerals: first substrate 110 , electric field generating device 120 , magnetic field generating device 130 , second substrate 140 , two-dimensional layered liquid crystal 150 , injection port 160 , liquid crystal molecules 210 , hydrophilic segments 211 , hydrophobic segments 212 , two-dimensional layer 220 .

DETAILED DESCRIPTION

The following will clearly and completely describe the concept of the present application and the technical effects produced in combination with the embodiments, so as to fully understand the purpose, features and effects of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of them. Based on the embodiments of the present application, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present application.

The embodiments of the present application are described in detail below. The described embodiments are exemplary and are only used to explain the present application, and should not be understood as limiting the present application.

In the description of this application, "several" means more than one, "many" means more than two, "greater than", "less than", "exceed", etc. are understood to exclude the number itself, "above", "below", "within", etc. are understood to include the number itself, and "about" means within the range of ±20%, 10%, 8%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.2%, 0.1%, etc. of the number itself. If there is a description of "first" or "second", it is only used to distinguish the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

In the description of the present application, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

Referring to FIG1 , an orientation device for implementing an orientation method provided in an embodiment of the present application is shown, which includes a first substrate 110 and a second substrate 140. The first substrate 110 has a first surface, and the second substrate 140 has a second surface. The first surface and the second surface are arranged opposite to each other and define a liquid crystal accommodation space. During the orientation process, a two-dimensional lamellar liquid crystal 150 is placed in the liquid crystal accommodation space. The first surface and the second surface are incompletely hydrophilic interfaces. A disturbance factor is applied to induce a vertical orientation of the two-dimensional lamellar liquid crystal. Thus, a vertical and anisotropic orientation of the two-dimensional liquid crystal domain is achieved. Among them, the disturbance factor may optionally include at least one of a tangential force factor, a fluid flow factor, a temperature factor, an electric field factor, a magnetic field factor, a pressure factor, an additive factor, and a thermal radiation factor.

The term "two-dimensional lamellar liquid crystal" means that the liquid crystal presents a two-dimensional layered structure on a microscopic scale. In some embodiments, the two-dimensional lamellar liquid crystal is formed by a single component, and the component independently forms a two-dimensional lamellar structure. In some other embodiments, the two-dimensional lamellar liquid crystal is formed by multiple components, and these components are mixed to form a two-dimensional lamellar structure. Thus, the two-dimensional lamellar liquid crystal includes any one of a single-component liquid crystal and a mixed-component liquid crystal. In some embodiments, the two-dimensional lamellar structure includes, but is not limited to, a lamellar monolayer structure and a lamellar bilayer structure. In some embodiments, the liquid crystal molecules 210 in the two-dimensional lamellar liquid crystal of the lamellar monolayer structure and the lamellar bilayer structure include a hydrophilic segment 211 and a hydrophobic segment 212, and the liquid crystal molecules are surfactant-type, the hydrophilic segment 211 and the two-dimensional layer 220 are mutually affinity, and the hydrophobic segment 212 is away from the two-dimensional layer 220. It can be understood that in this case, the composition of the two-dimensional layer 220 includes hydrophilic components, such as at least one polar solvent among water, alcohols, ketones, esters, acids, etc., specifically including but not limited to water, butyl acetate, ethyl acetate, n-butanol, phenol, methyl ethyl alcohol, tert-butanol, tetrahydrofuran, dioxane, acetone, ethanol, methanol, etc.

In some embodiments, a single-component two-dimensional lamellar liquid crystal contains surfactant-type molecules of a hydrophilic segment-hydrophobic segment structure or molecules of a rigid structure (e.g., rigid rod-shaped, disc-shaped, or ring-shaped); in a mixed-component two-dimensional lamellar liquid crystal, the liquid crystal molecules contain hydrophilic segments and hydrophobic segments and are mixed with at least one of salt, water, liquid organic matter, and liquid acid. Thus, the liquid crystal molecules themselves or the liquid substances added to the liquid crystal molecule material can induce lamellar microphase separation of the liquid crystal molecule layer and self-assemble to form a lamellar structure.

In some embodiments, hydrophilic segments (such as at least one functional group such as amino, hydroxyl, imidazole, pyridyl, quaternary ammonium) and hydrophobic segments (such as at least one functional group such as alkyl chain) are introduced into liquid crystal molecules to synthesize liquid crystal molecules that meet the preparation of two-dimensional lamellar liquid crystals, and two-dimensional lamellar liquid crystals with a bilayer structure are prepared in this way. In some embodiments, molecular segments containing typical rigid liquid crystal primitives (such as rigid rod-shaped, disc-shaped, and ring-shaped molecular segments) are used as liquid crystal phase induction sources (i.e., hydrophobic segments), and hydrophilic segments are connected to one end of the liquid crystal primitive to synthesize liquid crystal small molecules, which can induce the formation of two-dimensional lamellar liquid crystals with bilayer characteristics. Hydrophilic segments are connected to both ends of the primitive to synthesize liquid crystal small molecules, which can induce the formation of two-dimensional lamellar liquid crystals with monolayer characteristics. In some embodiments, uniform mixing can be achieved by at least one method such as centrifugation, heating, stirring, and shaking. In some embodiments, organic small molecules, solvents, soluble salts, and other components are further added to the system to further regulate the structure and orientability of the two-dimensional lamellar liquid crystal.

Referring to FIG2 , the liquid crystal molecules in the two-dimensional lamellar liquid crystal of the lamellar monomolecular structure include a hydrophobic segment 212 in the middle and hydrophilic segments 211 on both sides, and the hydrophilic segments 211 on both sides are respectively affinity with the adjacent two-dimensional layer 220 so that the hydrophobic segment 212 is located therebetween. Referring to FIG3 , the liquid crystal molecules 210 in the two-dimensional lamellar liquid crystal of the lamellar bimolecular structure include a hydrophobic segment 212 on one side and a hydrophilic segment 211 on the other side. The hydrophilic segment 211 of one of the two liquid crystal molecules 210 is affinity with one two-dimensional layer 220, and the hydrophilic segment 211 of the other liquid crystal molecule is affinity with another adjacent two-dimensional layer 220, and the lamellar structure of the two-dimensional layer 220 is formed by the two liquid crystal molecules. It can be understood that the above two liquid crystal molecules can be the same liquid crystal molecules or different liquid crystal molecules, and the latter specifically includes but is not limited to at least one of different hydrophilic segments and different hydrophobic segments.

In some embodiments, the liquid crystal molecules in the two-dimensional lamellar liquid crystal are any one of thermotropic liquid crystal and lyotropic liquid crystal, so the two-dimensional lamellar liquid crystal can also be divided into thermotropic liquid crystal and lyotropic liquid crystal. Thermotropic liquid crystals include the surfactant-type thermotropic two-dimensional lamellar liquid crystals containing hydrophilic segments and hydrophobic segments, and also include thermotropic two-dimensional lamellar liquid crystals containing cyclic rigid structures. Among them, the cyclic rigid structure includes but is not limited to aromatic ring structures such as benzene rings, naphthalene rings, and tribenzo rings.

In some embodiments, the two-dimensional lamellar liquid crystal is a two-dimensional lamellar liquid crystal formed by a mixture of the following A1 and A2: A1: at least one of smectic A phase liquid crystal, smectic B phase liquid crystal, smectic C phase liquid crystal, smectic D phase liquid crystal, blue phase liquid crystal, and lamellar phase liquid crystal; A2: at least one of salt, water, liquid organic matter, and liquid acid. Among them, the liquid organic matter includes but is not limited to liquid organic small molecules and liquid polymers, and the salt includes but is not limited to inorganic salts and organic salts.

In some embodiments, the temperature range at which the two-dimensional lamellar liquid crystal presents a liquid crystal phase is -10°C to 300°C, for example, it can be -10°C, 0°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 120°C, 140°C, 160°C, 180°C, 200°C, 220°C, 240°C, 260°C, 280°C, or 300°C.

In some embodiments, the viscosity of the two-dimensional lamellar liquid crystal is in the range of 10 ³ mPa·s to 10 ¹⁰ mPa·s, for example, 10 ³ mPa·s, 10 ⁴ mPa·s, 10 ⁵ mPa·s, 10 ⁶ mPa·s, 10 ⁷ mPa·s, 10 ⁸ mPa·s, 10 ⁹ mPa·s, or 10 ¹⁰ mPa·s.

Referring to FIG1 , the first substrate 110 has a first surface, the second substrate 140 has a second surface, the first surface and the second surface are arranged opposite to each other and define a liquid crystal accommodation space, and the two-dimensional layered liquid crystal is placed in the liquid crystal accommodation space. It can be understood that the liquid crystal accommodation space defined by the first surface and the second surface is usually an open accommodation space, but in some embodiments it can also be a closed type. Open or closed means that it is open or closed in the direction of the first surface and the second surface.

In some embodiments, the first surface and the second surface are solid interfaces, including but not limited to flexible solid interfaces and non-flexible (rigid) solid interfaces. For example, the first surface and the second surface can be independently selected from any one of flexible solid interfaces and non-flexible solid interfaces, thereby adapting to different materials and process requirements for different first surfaces and second surfaces.

In some embodiments, the first surface and the second surface are incompletely hydrophilic interfaces. It is understood that the hydrophilic and hydrophobic properties of the interface can be obtained by the intrinsic properties of the material, or by physical, chemical, or coating treatment. In some embodiments, the contact angle between the first surface and water and the contact angle between the second surface and water are independently greater than 45°, for example, the contact angles can be independently 50°, 60°, 70°, 80°, 90°, 100°, 110°, 120°, etc. This specific hydrophilic and hydrophobic interface design is conducive to controlling the hydrophobic segments or liquid crystal unit segments of the liquid crystal molecules close to the first surface of the first substrate or the second surface of the second substrate to fully contact and fit with the hydrophobic interface, and to induce the rearrangement and sequence of non-near-surface liquid crystal molecules by means of the weak interaction force between the same segments or segments between adjacent liquid crystal molecules, control the arrangement of molecules near the interface, and enhance the vertical orientation effect.

In some embodiments, to achieve the above-mentioned contact angle requirements, the materials of the first surface and the second surface are independently selected from at least one of metal, inorganic non-metal, and organic matter. In some embodiments, the materials of the first surface of the first substrate and the second surface of the second substrate include but are not limited to platinum, titanium and titanium alloys, gold, titanium oxide, and resin, wherein the materials of the first surface and the second surface can be the same or different. In some embodiments, the first surface and the second surface are independently selected from any one of a coating and a film.

In some embodiments, when a tangential force factor is applied for disturbance, the shear stress of the tangential force acting on the liquid crystal surface is ≥1.5 N/ ^cm2 , and the normal stress is ≥0.7 N/ ^cm2 , for example, the shear stress is 1.5 N/ ^cm2 , 2 N/ ^cm2 , 2.5 N/ ^cm2 , 3 N/ ^cm2 , 3.5 N/ ^cm2 , 4 N/ ^cm2 , 4.5 N/cm2, ⁵ N/ ^cm2 , and the normal stress is 0.7 N/ ^cm2 , 0.8 N/ ^cm2 , 0.9 N/ ^cm2 , 1 N/ ^cm2 , 2 N/ ^cm2 , 3 N/ ^cm2 , 4 N/ ^cm2 , 5 N/ ^cm2 .

In some embodiments, when a fluid flow factor is applied for disturbance, the flow rate of the two-dimensional lamellar liquid crystal is ≥1 mm/s, for example, it can be 1 mm/s, 2 mm/s, 3 mm/s, 4 mm/s, 5 mm/s, 6 mm/s, 8 mm/s, or 10 mm/s.

In some embodiments, when the temperature factor is applied for disturbance, the temperature action condition is 60-200°C, for example, 60°C, 70°C, 80°C, 90°C, 100°C, 120°C, 140°C, 160°C, 180°C, 200°C. In some embodiments, the temperature action time is more than 1 min, for example, 2 min, 3 min, 5 min, 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, 80 min, 100 min.

In some embodiments, when the electric field factor is applied for disturbance, the electric field strength is ≥500 V/cm, for example, 500 V/cm, 600 V/cm, 800 V/cm, 1000 V/cm. In some embodiments, the electric field action time is ≥5s, for example, 5s, 10s, 20s, 30s, 40s, 45s, 50s, 60s, 2min, 3min, 5min.

In some embodiments, when a magnetic field factor is applied for disturbance, the magnetic field strength is ≥0.5 T, for example, it can be 0.5 T, 1 T, 2 T, 3 T, 4 T, 5 T. In some embodiments, the magnetic field action time is ≥5 s, for example, it can be 5 s, 10 s, 20 s, 30 s, 40 s, 45 s, 50 s, 60 s, 2 min, 3 min, 5 min.

In some embodiments, when a pressure factor is applied for disturbance, the pressure is ≥100 Pa, for example, 100 Pa, 200 Pa, 300 Pa, 400 Pa, 500 Pa, 600 Pa, 800 Pa, 1000 Pa. In some embodiments, the frequency of pressure application is ≥0.5 Hz, for example, 0.5 Hz, 1 Hz, 2 Hz, 3 Hz, 4 Hz, 5 Hz. In some embodiments, the frequency of pressure application is ≥3 times, for example, 3 times, 4 times, 5 times, 6 times, 8 times, 10 times.

In some embodiments, when the additive factor is applied for disturbance, the additive includes a few-layer two-dimensional inorganic magnetic nanosheet. In some embodiments, the number of layers of the two-dimensional inorganic magnetic nanosheet includes but is not limited to 1 to 10 layers, for example, it can be 10 layers, 9 layers, 8 layers, 7 layers, 6 layers, 5 layers, 4 layers, 3 layers, 2 layers, 1 layer. In some embodiments, the two-dimensional inorganic magnetic nanosheet includes but is not limited to defective graphene (such as point defects, nitrogen doping, sulfur doping, fluorination, hydroxylation, edge states), defective boron nitride (such as point defects, carbon doping), transition metal halides (such as _CrX3 , _X = I, _Br , Cl; _VI3 ), transition metal phosphorus sulfide compounds (such as _TMPX3 , TM = Fe, Mn, Ni, Co, Cr, X = S, Se), transition metal tellurides _CrXTe3 ( _CrSiTe3 , _CrGeTe3 ), FexGeTe2 (x = 3 to 5), _Fe3O4 , _{Ti2O3 , etc.} In some embodiments, the lateral size of the two-dimensional inorganic magnetic nanosheet is ≥10 μm, for example, it can be 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 100 μm. In some embodiments, the amount of the two-dimensional inorganic magnetic nanosheet added to the two-dimensional lamellar liquid crystal is 0.01 wt%~30 wt%, for example, 0.01 wt%, 0.02 wt%, 0.05 wt%, 0.1 wt%, 0.2 wt%, 0.5 wt%, 1 wt%, 2 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%. In some embodiments, after adding the additive, the two-dimensional lamellar liquid crystal is left to stand for ≥1 h, for example, it can be 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 8 h, 10 h.

In some embodiments, when the thermal radiation factor is applied for disturbance, the radiation power is ≥100 W, for example, it can be 100 W, 200 W, 300 W, 400 W, 500 W, 600 W, 800 W, 1000 W. In some embodiments, the radiation time is ≥5 min, for example, it can be 5 min, 10 min, 15 min, 20 min, 30 min, 45 min, 60 min. In some embodiments, the wavelength of the radiation light source is 850 nm~940 nm. In some embodiments, the distance between the radiation light source and the two-dimensional lamellar liquid crystal is ≤10 cm, for example, it can be 10 cm, 9 cm, 8 cm, 7 cm, 6 cm, 5 cm, 4 cm, 3 cm, 2 cm, 1 cm.

It is understandable that the above disturbance factors can be added individually, or in combination at the same time or in a certain order.

In some embodiments, the disturbance factors applied generally include, but are not limited to, applying at least one of alternating tangential forces to the two-dimensional layered liquid crystal, increasing the temperature, applying multi-directional cross-magnetic electric fields, applying alternating pressure, applying infrared thermal radiation, and adding thickeners. Among them, the alternating tangential force refers to the shear stress generated by reciprocating shearing, and the direction of the shear stress is parallel to the substrate; it can be understood that when the substrate is a curved surface, the shear stress is parallel to the tangent direction of the curved surface. Alternating pressure refers to the pressure or positive stress caused by reciprocating extrusion, and the direction of the compressive stress is perpendicular to the substrate; it can be understood that when the substrate is a curved surface, the compressive stress is perpendicular to the tangent direction of the curved surface. For example, referring to Figure 1, an alternating electric field is applied by the electric field generating device 120, and an alternating magnetic field is applied by the magnetic field generating device 130.

Through this method, the materials and hydrophilicity and hydrophobicity of the first surface and the second surface are designed, the interfacial interactions between the two-dimensional lamellar liquid crystal and the first surface and the second surface are controlled, and the hydrophilic segments/components and hydrophobic segments/components in the two-dimensional lamellar liquid crystal are induced to undergo orderly microphase separation and arrange into a vertically oriented structure.

The interaction at the solid-liquid interface is the driving force for the vertical alignment of two-dimensional lamellar liquid crystals. The application of disturbance factors is an energy source that intensifies the thermal motion of molecules in the two-dimensional lamellar liquid crystal domains and induces the rearrangement of the two-dimensional lamellar liquid crystal domains, thereby breaking through the high energy barrier for the movement of small liquid crystal molecules and liquid crystal domains in high viscosity systems. By controlling the type and intensity of the disturbance factors involved, the speed of molecular assembly, the speed of vertical orientation, and the effect of vertical orientation can be quantitatively controlled to meet the needs of different liquid crystal orientation process conditions and different liquid crystal orientation effects. It can also optimize its macroscopic performance and meet the needs of liquid crystal optics, structural, and mass transfer functions in different application scenarios. The flexible use of the above disturbance factors ensures precise control of the microscopic assembly behavior, assembly process, and assembly results of liquid crystals.

In some embodiments, the alignment method further includes inducing the liquid crystal domain to further anisotropically align in the normal direction. Specifically, when the two-dimensional lamellar liquid crystal domain is vertically oriented or tending to be vertically oriented, a tangential stress is applied to induce the two-dimensional liquid crystal domains with different normal directions to rotate under the action of the tangential stress and present a macroscopic orderly arrangement of the liquid crystal domains in the plane.

In some embodiments, the first substrate 110 or the second substrate 140 is moved relative to the two-dimensional lamellar liquid crystal 150 to induce anisotropic arrangement of the two-dimensional lamellar liquid crystal domains.

In some embodiments, the direction of the relative motion of the first substrate or the second substrate includes at least one of tangential motion and forward motion along the first surface or the second surface. Wherein, forward motion refers to an extrusion motion perpendicular to the substrate. In some embodiments, the type of relative motion includes any one of unidirectional motion, circumferential motion and reciprocating motion. In some embodiments, the trajectory of the relative motion includes at least one of linear motion and arc motion. In some embodiments, the speed of the relative motion is 0.1 mm/s~50 mm/s.

In some embodiments, the anisotropic arrangement of the two-dimensional lamellar liquid crystal depends on the force-applying device composed of the first substrate and the second substrate, so that the first substrate or the second substrate moves relative to the two-dimensional lamellar liquid crystal. In some embodiments, the second substrate is fixed so that the first substrate moves relative to the two-dimensional lamellar liquid crystal. In some embodiments, referring to FIG6, the first surface of the first substrate 110 and the second surface of the second substrate 140 are independently selected from any one of a plane and an arc surface, that is, a variety of different combinations such as plane/plane, plane/arc surface, arc surface/plane, arc surface/arc surface can be formed. In some embodiments, referring to FIG9, the approach angle of the first substrate 110 relative to the two-dimensional lamellar liquid crystal 150 is 5°~90°, and the departure angle is 3°~175°. In some embodiments, the relative movement of the two-dimensional lamellar liquid crystal that induces tangential stress includes relative movement driven by at least one of gravity, centrifugal force, shear stress, pressure difference, capillary force, temperature difference, and cross-magnetic electric field. In some embodiments, the disturbance factor is applied by a tunable force field generator. Therefore, in these embodiments, through the geometric shapes of the first surface and the second surface (a combination of plane/curved surfaces), the approach and departure angles of the first surface, and an integrated tunable force field generator, cross magnetic and electric fields and mechanical shear forces are provided to assist in achieving a more precise liquid crystal domain orientation.

In some embodiments, the two-dimensional lamellar liquid crystal is subjected to relative movement of the two-dimensional lamellar liquid crystal through the first substrate and the second substrate, and the orientation is completed by shearing at a set shear rate and for a set time. In some embodiments, the shear rate is ≥0.1 mm/s, for example, it can be 0.1 mm/s, 0.2 mm/s, 0.3 mm/s, 0.4 mm/s, 0.5 mm/s, 0.6 mm/s, 0.7 mm/s, 0.8 mm/s, 0.9 mm/s, 1 mm/s. In some embodiments, the shearing time is ≥1 s, for example, it can be 1 s, 2 s, 3 s, 4 s, 5 s, 6 s, 7 s, 8 s, 9 s, 10 s. In some embodiments, the ambient temperature of shearing is above 20 ° C, for example, it can be 20 ° C, 25 ° C, 30 ° C, 40 ° C, 50 ° C, 60 ° C, 70 ° C, 80 ° C, 90 ° C, 100 ° C.

The second aspect of the present application further provides a two-dimensional lamellar liquid crystal, which is oriented by any of the aforementioned orientation methods.

The third aspect of the present application also provides a device, which includes the aforementioned two-dimensional layered liquid crystal.

In some embodiments, the device is any one of an optical filter, an optical phase modulator, a display, a sensor, an ion separation membrane, and an energy conversion device.

The alignment method provided in the embodiments of the present application has the following advantages and effects over the prior art:

(1) Technical uniqueness: The two-dimensional layered liquid crystal material obtained by the above-mentioned orientation method exhibits a unique vertical orientation structure with uniform orientation effect, which is suitable for large-area and precise orientation processes.

(2) Mild and efficient preparation process: The proposed preparation process is implemented under mild conditions, which not only ensures energy efficiency but also is suitable for large-scale production. It ensures the uniform orientation structure of the two-dimensional lamellar liquid crystal material and the orientation effect is stable and reliable.

(3) Wide range of application fields: The two-dimensional lyotropic liquid crystal material of the present application is very suitable for use in multiple high-tech fields such as optical filters, optical phase retarders, display technology, sensors, special vertical channel high-efficiency separation membranes and energy conversion devices due to its unique vertical orientation structure and excellent performance, showing broad application prospects.

(4) Flexibility and customizability: The specific implementation of the method, device or material can be flexibly adjusted according to the specific application requirements to ensure optimal performance in different scenarios, further highlighting the practical value and technological innovation of this application.

Example 1: Preparation of two-dimensional lamellar liquid crystal

Tetradecylvinyl imidazole hydrogen sulfate (abbreviated as VImHS) molecules were selected as liquid crystal molecules and deionized water was used as polar solvent to induce the preparation of two-dimensional lamellar liquid crystals with a monomer hydration degree of 15 (VImHS-15) and a bilayer structure. The specific steps are as follows:

(1) Take an appropriate amount of VImHS powder and place it in a centrifuge tube, and add deionized water at a molar ratio of VImHS: _H2O of 1:15;

(2) Stir thoroughly with a glass rod;

(3) Ultrasonic oscillation at room temperature;

(4) Repeat steps (2) and (3) multiple times;

(5) Centrifuge at 60,000 rpm for 5 min at room temperature;

(6) The mouth of the centrifuge tube was sealed with a sealing film and allowed to stand for 24 hours to achieve full and uniform self-assembly of the VImHS molecules.

The above steps can be used to fully mix the raw materials, remove bubbles inside the system, prevent solvent evaporation, prevent the intrusion of external impurities, and relax the stirring and mixing process to form micro stress between two-dimensional liquid crystal domains.

Example 2

The two-dimensional lamellar liquid crystal prepared in Example 1 was morphologically observed under a polarizing microscope, and the polarizing microstructural characteristics of its functional slurry were recorded under various temperature conditions. X-ray diffraction (XRD) technology was used to accurately measure the key structural parameters of the system, covering the single-period interlayer distance of the two-dimensional lamellar liquid crystal, the VImHS layer thickness, and the water layer thickness information.

The EMPYREANX X-ray diffractometer from Panalytical of the Netherlands was used, with a Cu-Kα target (λ=0.154 nm), a loading voltage of 40 kV, a loading current of 40 mA, and a scanning range of θ=0.5~30°. The Bragg formula was used to calculate the bilayer spacing:

d = nλ/2sinθ

Where, d is the interplanar spacing (nm); θ is the diffraction half-angle (rad); n is the diffraction order, n = 1, 2,···; λ is the target wavelength, nm;

The average thickness of the water layer and the VImHS layer can be determined by the molecular layer spacing, solvent/solute ratio and physical properties.

The volume fraction (φs) of VImHS can be calculated by the following formula:

φ _s =(W _s /ρ _s )/(W _s /ρ _s )+(W _w /ρ _w )

W _s is the mass percentage of VImHS; W _w is the mass percentage of deionized water; ρ _s is the mass density of VImHS; ρ _w is the density of VImHS;

The method of casting molten VImHS in a constant volume crucible was used to measure _ρs, which was 0.586 g/ ^cm3 , and the water density was 1 g/ ^cm3 . The average thickness of the hydrophobic layer _dL and the average thickness of the water layer _dw can be calculated by the following formula.

d _{L =} φ·d

d _w =dd _L

The calculation results of molecular layer spacing, VImHS layer and water layer thickness are shown in Table 1:

Table 1. Parameter calculation results

Example 3

The interface properties of solid substrate materials are important factors that determine the affinity between VImHS-15 two-dimensional lamellar liquid crystal slurry and solid surface, and directly affect the feasibility and effect of vertical orientation of two-dimensional layers in VImHS-15 two-dimensional lamellar liquid crystal slurry. This example uses the contact angle analysis method to achieve the design and optimization of solid-liquid interface properties. The compatibility is analyzed by measuring the contact angle (CA) of deionized water dropped on the surface of the solid base. The smaller the CA, the better the solid-liquid compatibility.

The test process was carried out at a temperature of >5°C and a humidity of 40% to 90%. The above method was used to test the surface contact angles of hydrophilic glass, hydrophobic glass, stainless steel, and polytetrafluoroethylene. Referring to Figure 7, the contact angles were measured to be 40°, 79°, 70°, and 120°, respectively.

The types of solid interface structures used in this embodiment include plane/plane structure, plane/inclined structure, plane/arc structure, and arc/arc structure. The structure is shown in FIG8 . The thickness of the two-dimensional layered liquid crystal 150 is 5 μm~500 μm, and the thickness can be uniform or non-uniform. In FIG8 , (A) α1≤90°; (B) 0°<α2≤360°; (C) α3≤90°; (D) 0°<α4≤360°, and l1 can be any length; the structure in the figure can be a combination of any n similar units, where 0°＜αn≤360°, and ln can be any length. In FIG8 , the first substrate 110 and the second substrate 140 can be made of any material and any size; the structure outside the edge amorphous transition area can be of any shape.

Example 4

The VImHS-15 two-dimensional lamellar liquid crystal slurry prepared in Example 1 has good reversible shear deformation characteristics. Therefore, referring to Figure 1, the first substrate 110 and the second substrate 140 are both hydrophobic glass plates with a contact angle of 79° with water, the distance between the first substrate 110 and the second substrate 140 is 100 μm, the system temperature is 25°C, the second substrate 140 is fixed, the VImHS-15 two-dimensional lamellar liquid crystal prepared in Example 1 is injected from the injection port 160, the first substrate 110 is moved at a shear rate of 1.3 mm/s, and the two-dimensional lamellar liquid crystal 150 placed between the first substrate 110 and the second substrate 140 is subjected to unidirectional shear for 10 s.

The polarization texture of the VImHS-15 two-dimensional lamellar liquid crystal slurry after shearing is shown in (A) in Figure 4. It is fully bright in the field of view, and becomes fully dark after deflection of 45°, and it changes periodically, indicating that the shearing action makes the two-dimensional layer in the VImHS-15 two-dimensional lamellar liquid crystal slurry anisotropically oriented vertically and uniformly. The possible molecular arrangement transformation process is shown in Figure 3, and the normal vectors of the bilayer are arranged uniformly. The key to the success of shear orientation lies in the viscosity of the VImHS-15 two-dimensional lamellar liquid crystal (under the test condition of 100rad/s, the elastic modulus of VImHS-15: 20000Pa, the viscous modulus 4000 Pa, and the viscosity 10000 mPa·s). The shear stress can be transmitted from the surface of the VImHS-15 two-dimensional lamellar liquid crystal slurry to the inside, realizing the uniform orientation of the VImHS-15 two-dimensional lamellar liquid crystal slurry along the thickness direction.

In addition, taking polytetrafluoroethylene material as a comparison, its contact angle with water was adjusted to gradually decrease to hydrophilic through plasma treatment, so as to set up experimental groups with different gradient contact angles, and oriented as a substitute for the above-mentioned 79° hydrophobic glass plate. The results showed that when the contact angle between the substrate material and water was less than 45°, the two-dimensional lamellar liquid crystal showed incomplete, uneven or failed orientation. Therefore, it was determined that the critical point of the contact angle between the substrate material and water was 45°, and the substrate with a contact angle with water of not less than 45° could obtain a good orientation effect by the orientation method of the embodiment.

Embodiments 5 to 17

Referring to Example 4, the orientation was performed according to the components or orientation conditions shown in Tables 2 to 3 below, and the polarization textures were respectively shown in (B) to (N) in FIG. 4 :

Table 2. Working conditions of different orientations

The preparation method of VImHS-13 two-dimensional lamellar liquid crystal is similar to that of Example 1, except that the degree of hydration is reduced to 13.

Table 3. Different liquid crystals and orientation conditions

Among them, the preparation method of VImHS-11 two-dimensional lamellar liquid crystal refers to Example 1, except that the hydration degree is reduced to 11; VImHS is pure tetradecyl vinyl imidazole hydrogen sulfate without any additives; MImBr is tetradecyl methyl imidazole bromide, which is obtained by quaternization reaction of 1-methyl imidazole and tetradecane bromide at 60°C and multiple recrystallization using ethyl acetate; MImCl is tetradecyl methyl imidazole chloride, which is obtained by quaternization reaction of 1-methyl imidazole and tetradecane chloride at 60°C and multiple recrystallization using ethyl acetate.

Example 18: Stability Test

According to Example 4, after orientation for 0 to 1000 h, the POM optical anisotropy of the VImHS-15 two-dimensional lamellar liquid crystal slurry showed a continuous and stable pattern. After 250 h of shearing, the optical anisotropy increased, and high-power microscopic observation revealed that a uniform striped texture appeared perpendicular to the shear direction, indicating that after unloading the shear stress, the oriented liquid crystal domains slowly relaxed and further assembled into an oriented structure with a higher degree of order. After standing for 1000 h, referring to Figure 5, the POM texture of the shear-oriented VImHS-15 two-dimensional lamellar liquid crystal slurry still maintained significant light and dark changes after deflection by 45°, indicating that the macroscopic orientation of the liquid crystal domains in the VImHS-15 two-dimensional lamellar liquid crystal slurry can be stable for more than 1000 h under constant temperature and sealing conditions, which is attributed to the hydrophobic properties of the upper and lower substrate interfaces to the stability of the vertical orientation structure of the VImHS-15 two-dimensional lamellar liquid crystal domains.

After orientation, the VImHS-15 two-dimensional lamellar liquid crystal constructs anisotropic vertically uniformly oriented long-range ordered lamellar channels along the transmembrane direction, which is expected to achieve applications and performance enhancement in the fields of optics and mass transfer.

The aligned two-dimensional lamellar liquid crystals of Examples 5 to 17 were tested using the above method. The macroscopic orientation of the liquid crystal domains in the two-dimensional lamellar liquid crystals can also be stable for more than 1000 h under constant temperature and sealed conditions.

Example 19: Application of polarized light phase adjustment

Polarized light is light whose vibration direction is limited to a certain plane. Polarizers can filter light with a specific vibration direction to achieve polarization of light. The transparent dimming plate produces a phase delay on the polarized light passing through it through its internal structure. This delay varies with the rotation angle of the dimming plate and can be used to modulate the interference, diffraction and other properties of the light. In this embodiment, the anisotropic vertically uniformly oriented two-dimensional layered liquid crystal after orientation in Example 4 is placed in a liquid crystal box made of transparent quartz glass, and it is used as a dimming plate with a phase adjustment function to adjust the phase of polarized light.

Referring to (A) in FIG10 , the optical signal transmitter in this embodiment is a monochromatic laser with a wavelength set to 520 nm. A polarizer is selected as the starting polarizer, and the light beam of the regulating tube transmitter is polarized light to ensure that the incident light is in a single polarization state. The center of the anisotropic vertically uniformly oriented two-dimensional layered liquid crystal box is overlapped with the optical path and is perpendicular to the optical path. A photodetector is selected as an optical signal receiver to detect the light intensity or phase information after passing through the dimming film. A rotating table for clamping the anisotropic vertically uniformly oriented two-dimensional layered liquid crystal box is set to accurately control the rotation angle of the dimming film. A data acquisition system is set to record the relationship between the output signal of the photodetector and the rotation angle.

Initial calibration: adjust the system to ensure that the light path is correct and the photodetector is in the best receiving position. Angle rotation and data recording: rotate the dimming plate in small angle steps (such as every 15°), and record the output signal of the photodetector after each rotation (the signal here is an indirect reflection of the phase difference, or directly use a phase measurement device). Repeat the measurement. To improve data accuracy, measure each angle at least three times and take the average value.

The results are shown in FIG10 . It is observed that as the liquid crystal box rotates along the center point, the phase difference of the 520nm polarized light passing through the dimming film presents a sinusoidal variation trend, indicating that the phase delay effect of the dimming film on light is periodically related to the rotation angle.

The sinusoidal change of the phase difference shows that this phenomenon conforms to the modulation principle in optics. The change of the internal structure of the liquid crystal box (the arrangement of liquid crystal molecules) with the rotation angle leads to different phase delays when light passes through, thus forming a sinusoidal phase difference, refer to (B) in Figure 10. The calculation of phase delay found that the experimental data can be fitted to the sine function to obtain the specific function expression of the phase difference with the rotation angle, and further calculate the phase delay of the dimming film at different angles. This application not only verifies the phase adjustment ability of anisotropic vertically uniformly oriented two-dimensional layered liquid crystals, but also provides an experimental basis for the use of dimming films in optical information processing, optical computing and other fields.

The present application is described in detail above in conjunction with the embodiments, but the present application is not limited to the above embodiments, and various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present application. In addition, the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

Claims (10)

1. The method for aligning the two-dimensional lamellar liquid crystal is characterized by comprising the following steps of:

Providing a first substrate with a first surface and a second substrate with a second surface, wherein a liquid crystal accommodating space is defined between the first surface and the second surface, and two-dimensional lamellar liquid crystal is placed in the liquid crystal accommodating space, and the first surface and the second surface are incompletely hydrophilic interfaces;

applying disturbance factors to induce the two-dimensional lamellar liquid crystal to generate vertical orientation;

wherein the disturbance factor comprises at least one of tangential force factor, fluid flow factor, temperature factor, electric field factor, magnetic field factor, pressure factor, additive factor, and heat radiation factor.

2. The orientation method according to claim 1, characterized in that the contact angle of the first face with water and the contact angle of the second face with water are larger than 45 °.

3. The alignment method according to claim 1, wherein the two-dimensional lamellar liquid crystal comprises at least one of smectic a phase liquid crystal, smectic B phase liquid crystal, smectic C phase liquid crystal, smectic D phase liquid crystal, blue phase liquid crystal, lamellar phase liquid crystal.

4. The method of aligning according to claim 1, wherein the first substrate or the second substrate is caused to relatively move with respect to the two-dimensional lamellar liquid crystal to induce anisotropic arrangement of liquid crystal domains of the two-dimensional lamellar liquid crystal.

5. The method of aligning according to claim 4, wherein the relative motion of the two-dimensional lamellar liquid crystal includes at least one of gravity, centrifugal force, shear stress, pressure difference, capillary force, temperature difference, and crossed magnetic electric field.

6. The method of claim 4, wherein the relative movement of the first substrate or the second substrate with respect to the two-dimensional lamellar liquid crystal comprises: and fixing a second substrate to enable the first substrate to perform relative motion relative to the two-dimensional lamellar liquid crystal.

7. The method of orientation according to claim 4, characterized in that the perturbation factor is applied by a tunable force field generator.

8. A two-dimensional lamellar liquid crystal which is aligned by the alignment method according to any one of claims 1 to 7.

9. A device comprising the two-dimensional lamellar liquid crystal according to claim 8.

10. The device of claim 9, wherein the device is any one of an optical filter, an optical phase modulator, a display, a sensor, an ion separation membrane, an energy conversion device.