Covalently crosslinked circularly polarized network topology and applications thereof

Abstract

The application discloses a covalently cross-linked circular polarization network topology structure and application thereof, and the structure is a double-layer structure prepared by covalently cross-linking a liquid crystal polymer layer and an inorganic luminescent layer, the covalently cross-linking between interfaces is realized by using a liquid crystal polymer with a spiral structure and a reaction monomer dispersed in inorganic fluorescent powder in fluorine rubber, a network topology structure with high-quality circular polarization luminescence is obtained, and the structure still has considerable chiral optical activity under continuous deformation. The application overcomes the compatibility and dispersibility problems of inorganic fluorescent powder in a liquid crystal system, and provides a universal method for research and application of the inorganic fluorescent powder in the chiral luminescence field.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of circularly polarized luminescent material preparation, and particularly relates to a covalently cross-linked circularly polarized network topology and application thereof. BACKGROUND

[0002] Circularly polarized light, as a kind of polarized light with a constant or regular change in the direction of vibration, is a way of expressing the chirality of light, including left-handed circularly polarized light propagating clockwise along the helical trajectory of light waves, and right-handed circularly polarized light propagating counterclockwise. Due to this unique optical property, circularly polarized light has broad application prospects in asymmetric synthesis, chiral sensing, chiral optoelectronics, 3D display, information encryption and other fields. Traditional circularly polarized light can be generated by continuously passing non-polarized light through a linear polarizer and a quarter-wave plate, but this method has problems such as serious loss of light energy and complex integration of devices. Chiral luminescent materials can directly produce circularly polarized luminescence, which can effectively reduce energy loss and facilitate the integration of device preparation. The main parameters for evaluating the circularly polarized luminescence performance are luminescent efficiency and luminescent asymmetry factor, among which the luminescent asymmetry factor determines the practicability of circularly polarized luminescent materials. Therefore, constructing circularly polarized luminescent materials with high luminescent asymmetry factor has become a research hotspot in recent years.

[0003] Cholesteric liquid crystal is a kind of helical supramolecule that can be orderly self-assembled, and has a significant amplification effect on chirality, and is widely used in circularly polarized luminescent material systems. At present, the main means to construct high-quality circularly polarized luminescent materials is to compound cholesteric liquid crystal with achiral luminescent materials, which mainly includes direct physical mixing (cholesteric liquid crystal is directly co-assembled with luminescent materials in a spiral) and physical stacking (cholesteric liquid crystal and luminescent materials are stacked into a double-layer structure). However, direct physical mixing will reduce the self-assembly ability of liquid crystals, and the luminescent body has problems such as unstable physical properties, uneven dispersion, and physical mixing will cause damage to the luminescent body, reducing its luminescence; physical stacking has the problem of phase separation, which is not conducive to the device integration of materials and does not have the deformation ability required in actual application process.

[0004] Therefore, it is still a challenging task to find a more suitable preparation method to make the circularly polarized luminescent material have high asymmetric luminescent factor, high physical and chemical stability, and have the deformation ability required in actual application. SUMMARY

[0005] The present application aims to provide a covalently cross-linked circularly polarized network topology and application thereof, which uses a covalent cross-linking strategy to tightly combine the liquid crystal layer and the luminescent layer together, and obtains high-quality circularly polarized luminescent performance.

[0006] In one aspect of the present application, a covalently cross-linked circularly polarized network topology is provided. According to an embodiment of the present application, the structure is a bilayer structure prepared by covalent cross-linking of a liquid crystal polymer layer and an inorganic luminescent layer, i.e., the network topology includes a liquid crystal polymer layer, an inorganic luminescent layer and an interfacial covalent chemical bond. The structure has high quality circularly polarized luminescence properties, with a luminescence asymmetry factor (g lum ) maximum of 1.31. The structure does not exhibit delamination under continuous deformation and maintains a relatively high chiral optical activity (g lum = 10 -1 ).

[0007] In addition, the covalently cross-linked circularly polarized network topology according to the above-mentioned embodiment of the present application can also have the following additional technical features:

[0008] In some embodiments of the present application, the liquid crystal polymer layer includes 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene (RM257), (3R,3aS,6aS)-hexahydrofuro[3,2-b]furan-3,6-diyl bis(4-(4-((4-(acryloyloxy)butoxy)carbonyloxybenzoyloxy)benzoate) (LC756). The interfacial covalent bond is generated by polymerization of RM257, LC756 and polyethylene glycol diacrylate (PEGDA, M w = 400 Da) under ultraviolet light.

[0009] In some embodiments of the present application, the inorganic luminescent layer uses inorganic fluorescent powder, specifically long afterglow fluorescent powder.

[0010] In some embodiments of the present application, the inorganic fluorescent powder is one of blue fluorescent powder, green fluorescent powder or red fluorescent powder, wherein the blue fluorescent powder is Sr2MgSi2O7:Eu, the green fluorescent powder is SrAl2O4:Eu, Dy and the red fluorescent powder is Y2O2S:Eu, Mg, Ti.

[0011] In another aspect of the present application, a preparation method of a circularly polarized luminescent film is provided. According to an embodiment of the present application, the method includes the following steps:

[0012] (1) mixing 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene and (3R,3aS,6aS)-hexahydrofuro[3,2-b]furan-3,6-diyl bis(4-(4-((4-(acryloyloxy)butoxy)carbonyloxybenzoyloxy)benzoate), dissolving after heating and cooling to room temperature, adding a crosslinking agent, a chain extender, a photoinitiator and a catalyst, stirring to obtain a cholesteric reaction mixture, laying the cholesteric reaction mixture on a glass substrate, and standing at room temperature to obtain a cholesteric phase pre-polymer, and irradiating the cholesteric phase pre-polymer in a UV curing box to obtain a liquid crystal polymer layer;

[0013] (2) dissolving a copolymer of polyvinylidene fluoride and hexafluoropropylene in a solvent tetraethylammonium chloride, sequentially adding a crosslinking agent, a photoinitiator, silicon dioxide and an inorganic fluorescent powder, and mixing uniformly to obtain a luminescent precursor;

[0014] (3) pouring the luminescent precursor on the surface of the liquid crystal polymer and spreading, and curing in a UV curing box to obtain the circularly polarized luminescent film, wherein the circularly polarized luminescent film has the covalently crosslinked circularly polarized network topology.

[0015] In addition, the method for preparing a circularly polarized luminescent film according to the above-mentioned embodiment of the present application can further have the following additional technical features:

[0016] In some embodiments of the present application, in step (1), the weight ratio of 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene and (3R,3aS,6aS)-hexahydrofuro[3,2-b]furan-3,6-diyl bis(4-(4-((4-(acryloyloxy)butoxy)carbonyloxybenzoyloxy)benzoate) is (143-250):100, the crosslinking agent is pentaerythritol tetra(3-mercaptopropionate) (PETMP), the chain extender is ethylenediaminetetraacetic acid (EDDET), the photoinitiator is I-651, the catalyst is docosapentaenoic acid (TPO), and the irradiation time is 5-10 min.

[0017] In some embodiments of the present application, in step (2), the crosslinking agent is polyethylene glycol diacrylate, and the photoinitiator is trimethylbenzoyl-diphenylphosphine oxide.

[0018] In another aspect of the present application, a method for preparing one-dimensional core-shell fibers is provided. According to an embodiment of the present application, the method comprises the following steps:

[0019] (1) mixing 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene and (3R,3aS,6aS)-hexahydrofuro[3,2-b]furan-3,6-diyl bis(4-(4-((4-(acryloyloxy)butoxy)carbonyloxybenzoyloxy)benzoate), dissolving after heating and cooling to room temperature, adding a crosslinking agent, a chain extender, a photoinitiator and a catalyst, stirring to obtain a cholesteric reaction mixture;

[0020] (2) dissolving a copolymer of polyvinylidene fluoride and hexafluoropropylene (PVDF-HFP) in a solvent tetraethylammonium chloride (TEAc), sequentially adding a crosslinking agent, a photoinitiator, silica and an inorganic fluorescent powder, mixing uniformly to obtain a luminescent precursor;

[0021] (3) injecting the luminescent precursor into a low-density polyethylene tube by using a syringe pump, placing in a UV curing box for curing, then immersing in toluene at 90-100℃ to dissolve the polyethylene tube to obtain a pre-bonded luminescent fiber; wherein the injection rate of the syringe pump is 500 μL / min, and the inner diameter of the low-density polyethylene tube is 1.0 mm;

[0022] (4) dip-coating the cholesteric reaction mixture on the surface of the pre-bonded luminescent fiber, placing at room temperature, promoting the self-assembly of the coating layer into a radial spiral structure and evaporating toluene, then curing in a UV curing box to obtain a one-dimensional core-shell fiber, wherein the one-dimensional core-shell fiber has the covalently cross-linked circularly polarized network topology structure.

[0023] In addition, the preparation method of the one-dimensional core-shell fiber according to the above-mentioned embodiments of the present application can also have the following additional technical features:

[0024] In some embodiments of the present application, in step (1), the weight ratio of 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene and (3R,3aS,6aS)-hexahydrofuro[3,2-b]furan-3,6-diyl bis(4-(4-((4-(acryloyloxy)butoxy)carbonyloxybenzoyloxy)benzoate) is (143-250):100, the crosslinking agent is pentaerythritol tetra(3-mercaptopropionate) (PETMP), the chain extender is ethylenediaminetetraacetic acid (EDDET), the photoinitiator is I-651, and the catalyst is docosapentaenoic acid (TPO).

[0025] In some embodiments of the present application, in step (2), the crosslinking agent is polyethylene glycol diacrylate, and the photoinitiator is trimethylbenzoyl-diphenylphosphine oxide.

[0026] Compared with the prior art, the present application has the following beneficial effects:

[0027] 1) The present application uses a covalent cross-linking strategy to tightly combine the liquid crystal polymer layer and the inorganic light-emitting layer together, obtaining high-quality circularly polarized luminescence performance. The structure still maintains considerable chiral optical activity under continuous deformation, and can be prepared into a two-dimensional film or a one-dimensional fiber according to application requirements, fully realizing the wearability of circularly polarized luminescence materials.

[0028] 2) In the present application, the fluorescent powder is separated from the liquid crystal layer, and by constructing a double-layer structure, the compatibility and dispersion problems can be directly avoided. At the same time, the inorganic fluorescent powder used in the present application has a relatively large particle size (tens to hundreds of microns) compared with complexes and quantum dots, which is almost not considered in the circularly polarized luminescence material of the liquid crystal system. Therefore, the method provided by the present application overcomes the compatibility and dispersion problems of inorganic fluorescent powder in the liquid crystal system, and provides a universal method for the research and application of chiral luminescence.

[0029] 3) The preparation method provided by the present application is suitable for a variety of inorganic long-afterglow fluorescent powder, and can construct a series of high-quality circularly polarized luminescence materials, providing a rich material library for exploring the application of circularly polarized light. At the same time, the circularly polarized luminescence material prepared by the method has excellent processability, and can be easily prepared into a film or a fiber according to application requirements. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 Stability test of the circularly polarized luminescence film synthesized in Example 1 of the present application; a-c are the thermogravimetric-differential scanning calorimetry (TG-DSC) curves of the liquid crystal polymer layer (a), the luminescent precursor (b), and the circularly polarized luminescence film (c) in a N2 atmosphere at 30-800 DEG C, d-f are the DSC curves of the liquid crystal polymer layer (d), the luminescent precursor (e), and the circularly polarized luminescence film (f) in a N2 atmosphere at 30-200 DEG C under heating-cooling cycles;

[0031] Figure 2 The transmission spectra (a-c) and the actual photos (d-f) of the liquid crystal polymer synthesized in Example 1 of the present application, wherein a, d are the transmission spectrum and the actual photo of the liquid crystal polymer in Example 1, b, e are the transmission spectrum and the actual photo of the liquid crystal polymer in Example 2, and c, f are the transmission spectrum and the actual photo of the liquid crystal polymer in Example 3;

[0032] Figure 3 The cross-sectional SEM image of the red circularly polarized luminescence film synthesized in Example 3 of the present application;

[0033] Figure 4 a, b, c are the circularly polarized fluorescence spectra of the circularly polarized luminescence films synthesized in Examples 1-3 of the present application;

[0034] Figure 5 A cross-sectional SEM image of the red circularly polarized luminescent fiber prepared in Example 4 of the present application;

[0035] Figure 6 a, b, c are circularly polarized fluorescence spectra of the blue, green, and red circularly polarized luminescent fibers prepared in Example 4 of the present application;

[0036] Figure 7 A photo of the brightness difference of the circularly polarized luminescent fiber prepared in Example 4 of the present application under left-handed (L) and right-handed (R) polarizers. DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative labor fall within the protection scope of the present application.

[0038] Example 1

[0039] A preparation method of a circularly polarized luminescent film, comprising the following steps:

[0040] (1) Preparation of a liquid crystal polymer layer

[0041] 1.132 g of RM257 was mixed with LC756 (the weight ratio of LC756 to RM257 was 7.0 wt%), heated and dissolved in a toluene solvent, the heating temperature was 80°C, and the heating time was 5 minutes, and then cooled to room temperature. Then, 0.0658 g of PETMP, 0.1392 g of EDDET, 0.008 g of Irgacure 651 (I-651), and 0.2971 g of DPA (diluted with toluene at a ratio of 1:100) were added to the mixed solution and stirred for 5 min to obtain a cholesteric reaction mixture. The obtained cholesteric reaction mixture was vacuumed for 1 min, laid flat on a glass substrate and left to stand for 24 h to obtain a cholesteric prepolymer. The obtained cholesteric prepolymer was photo-cured under an ultraviolet light (365 nm) with an intensity of 40 W / cm2for 5 min to obtain a liquid crystal polymer, and a liquid crystal polymer film with a photonic band gap of about 460 nm and a structural color of blue. 2 1.132 g of RM257 was mixed with LC756 (the weight ratio of LC756 to RM257 was 7.0 wt%), heated and dissolved in a toluene solvent, the heating temperature was 80°C, and the heating time was 5 minutes, and then cooled to room temperature. Then, 0.0658 g of PETMP, 0.1392 g of EDDET, 0.008 g of Irgacure 651 (I-651), and 0.2971 g of DPA (diluted with toluene at a ratio of 1:100) were added to the mixed solution and stirred for 5 min to obtain a cholesteric reaction mixture. The obtained cholesteric reaction mixture was vacuumed for 1 min, laid flat on a glass substrate and left to stand for 24 h to obtain a cholesteric prepolymer. The obtained cholesteric prepolymer was photo-cured under an ultraviolet light (365 nm) with an intensity of 40 W / cm2for 5 min to obtain a liquid crystal polymer, and a liquid crystal polymer film with a photonic band gap of about 460 nm and a structural color of blue.

[0042] (2) Preparation of a luminescent precursor

[0043] 1.0 g PVDF-HFP was dissolved in 40 mL TEAc with magnetic stirring for 24 h, then 1 wt% PEGDA, 1 wt% TPO, 2 wt% SiO2, 10 wt% inorganic blue fluorescent powder Sr2MgSi2O7:Eu were added and mixed for 5 min to obtain the luminescent precursor with blue emission color.

[0044] (3) Preparation of circularly polarized luminescent film

[0045] The liquid crystal polymer prepared in step (1) has a front surface (with strong structural color) and a back surface (with weak structural color). The luminescent precursor prepared in step (2) was laid flat on the back surface of the liquid crystal polymer, and cured with 365 nm ultraviolet light for 5 min to obtain a blue circularly polarized luminescent film.

[0046] As shown in Figure 1 , the heat-resistant temperature of the prepared liquid crystal polymer layer, luminescent precursor and circularly polarized luminescent film is as high as 300℃, indicating that the sample has high thermal stability.

[0047] Example 2

[0048] A method for preparing a circularly polarized luminescent film, the difference between this embodiment and Example 1 is that in step (1), the weight ratio of LC756 is 6.3 wt%, and the photonic band gap of the obtained liquid crystal polymer film is about 525 nm, and the structural color is green; in step (2), the inorganic fluorescent powder is green fluorescent powder SrAl2O4:Eu,Dy, and mixed for 5 min to obtain a luminescent precursor with green emission color; and in step (3), a green circularly polarized luminescent film is obtained.

[0049] Example 3

[0050] A method for preparing a circularly polarized luminescent film, the difference between this embodiment and Example 1 is that in step (1), the weight ratio of LC756 and RM257 is 5.0 wt%, and the photonic band gap of the obtained liquid crystal polymer film is about 630 nm, and the structural color is red; in step (2), the inorganic fluorescent powder is red fluorescent powder Y2O2S:Eu,Mg,Ti, and mixed for 5 min to obtain a luminescent precursor with red emission color; and in step (3), a red circularly polarized luminescent film is obtained.

[0051] As shown in Figure 2 , the transmission spectrum of the prepared liquid crystal polymer has the maximum degree of overlap with the emission peak of the inorganic long-afterglow fluorescent powder, and the liquid crystal polymer exhibits obvious structural color.

[0052] As shown in Figure 3 , the covalently crosslinked interface of the liquid crystal polymer layer and the inorganic luminescent layer is tightly connected.

[0053] AsFigure 4 As shown, the circularly polarized luminescent film has an asymmetric luminescence factor glum of up to 1.31.

[0054] Example 4

[0055] A method for preparing one-dimensional core-shell fibers, comprising the following steps:

[0056] (1) The luminescent precursors prepared in Examples 1-3 were respectively injected into a low-density polyethylene tube with an inner diameter of 1.0 mm at a rate of 500 μL / min by a syringe pump (LSP-02), and stored in a UV curing box for 5 min; then immersed in toluene at 95 ℃ for 30 min to dissolve the low-density polyethylene tube, and a pre-bonded luminescent fiber was obtained.

[0057] (2) The pre-bonded luminescent fiber was immersed in the corresponding cholesteric reaction mixture in Examples 1-3 for 10 min; after taking out, it was left to stand at room temperature for 24 h to promote the helical self-assembly of the liquid crystal layer, and toluene was evaporated, and then cured in a UV curing box for 5 min to obtain a blue, green and red circularly polarized luminescent fiber.

[0058] The SEM image of the cross section of the circularly polarized luminescent fiber prepared in Example 4 is shown in Figure 5 .

[0059] The circularly polarized fluorescence spectrum of the circularly polarized luminescent fiber prepared in Example 4 is shown in Figure 6 , and the asymmetric luminescence factor g lum is close to 1.0.

[0060] The photos of the circularly polarized luminescent fiber prepared in Example 4 under left-handed (L) and right-handed (R) polarizers are shown in Figure 7 , showing a visible brightness difference.

[0061] The above is only an example and description of the present application, and those skilled in the art can make various modifications or supplements to the described specific embodiments or use similar ways to replace, as long as they do not deviate from the structure of the present application or exceed the scope defined by the present claims, which shall belong to the protection scope of the present application.

Claims

1. A method for preparing a circularly polarized luminescent film, characterized in that, The method comprises the following steps: (1) mixing 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene and (3R,3aS,6aS)-hexahydrofuran[3,2-b]furan-3,6-diyl bis(4-(4-((4-(acryloyloxy)butoxy)carbonyloxybenzoyloxy)benzoate), dissolving after heating and cooling to room temperature, adding a crosslinking agent, a chain extender, a photoinitiator and a catalyst, stirring to obtain a cholesteric reaction mixture, laying the cholesteric reaction mixture on a glass substrate, and standing at room temperature to obtain a cholesteric phase prepolymer, and irradiating the cholesteric phase prepolymer in an ultraviolet curing box to obtain a liquid crystal polymer layer; (2) dissolving a copolymer of polyvinylidene fluoride and hexafluoropropylene in a solvent tetraethylammonium chloride, and sequentially adding a crosslinking agent, a photoinitiator, silicon dioxide and inorganic fluorescent powder to obtain a luminescent precursor, wherein the inorganic fluorescent powder comprises one of blue fluorescent powder, green fluorescent powder or red fluorescent powder, wherein the blue fluorescent powder is Sr2MgSi2O7:Eu, the green fluorescent powder is SrAl2O4:Eu,Dy, and the red fluorescent powder is Y2O2S:Eu,Mg,Ti; (3) pouring the luminescent precursor on the surface of the liquid crystal polymer and spreading, and curing in an ultraviolet curing box to obtain the circularly polarized luminescent film, wherein the circularly polarized luminescent film has a double-layer covalently cross-linked circularly polarized network topology structure.

2. The method of claim 1, wherein the method further comprises: In step (1), the weight ratio of 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene and (3R,3aS,6aS)-hexahydrofuran[3,2-b]furan-3,6-diyl bis(4-(4-((4-(acryloyloxy)butoxy)carbonyloxybenzoyloxy)benzoate) is (143-250):100, the crosslinking agent is pentaerythritol tetra(3-mercaptopropionate), the chain extender is ethylenediaminetetraacetic acid, the photoinitiator is I-651, the catalyst is docosapentaenoic acid, and the irradiation time is 5-10 min.

3. The method of claim 1, wherein the method further comprises: In step (2), the crosslinking agent is polyethylene glycol diacrylate, and the photoinitiator is trimethylbenzoyl-diphenylphosphine oxide. ​ 4. A process for the preparation of one-dimensional core-shell fibers, characterized in that, The method comprises the following steps: (1) mixing 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene and (3R,3aS,6aS)-hexahydrofuran[3,2-b]furan-3,6-diyl bis(4-(4-((4-(acryloyloxy)butoxy)carbonyloxybenzoyloxy)benzoate), dissolving after heating and cooling to room temperature, adding a crosslinking agent, a chain extender, a photoinitiator and a catalyst, stirring to obtain a cholesteric reaction mixture; (2) Dissolve the copolymer of polyvinylidene fluoride and hexafluoropropylene in the solvent tetraethylammonium chloride, add crosslinking agent, photoinitiator, silica and inorganic fluorescent powder in turn, mix uniformly to obtain a luminescent precursor, wherein the inorganic fluorescent powder comprises one of blue fluorescent powder, green fluorescent powder or red fluorescent powder, wherein the blue fluorescent powder is Sr2MgSi2O7:Eu, the green fluorescent powder is SrAl2O4:Eu,Dy and the red fluorescent powder is Y2O2S:Eu,Mg,Ti; (3) Inject the luminescent precursor into a low-density polyethylene tube, place it in an ultraviolet curing box for curing, then immerse it in toluene at 90-100℃ to dissolve the polyethylene tube, and obtain a pre-bonded luminescent fiber; (4) Dip coat the cholesteric reaction mixture on the surface of the pre-bonded luminescent fiber, place it at room temperature, promote the self-assembly of the coating layer into a radial spiral structure and evaporate toluene, then cure it in an ultraviolet curing box to obtain a one-dimensional core-shell fiber, wherein the one-dimensional core-shell fiber has a double-layer covalently cross-linked circularly polarized network topology.

5. The method of claim 4, wherein: In step (1), the weight ratio of 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene and (3R,3aS,6aS)-hexahydrofuro[3,2-b]furan-3,6-diyl bis(4-(4-((4-(acryloyloxy)butoxy)carbonyloxybenzoyloxy)benzoate) is (143-250):100, the crosslinking agent is pentaerythritol tetra(3-mercaptopropionate), the chain extender is ethylenediaminetetraacetic acid, the photoinitiator is I-651, and the catalyst is docosapentaenoic acid.

6. The method of claim 4, wherein: In step (2), the crosslinking agent is polyethylene glycol diacrylate, and the photoinitiator is trimethylbenzoyl-diphenylphosphine oxide.

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