A dynamic control method of chirality flipping of circularly polarized room temperature phosphorescence based on soft helical superstructure

Abstract

The invention discloses a chirality reversal dynamic control method based on soft helical superstructure circularly polarized room temperature phosphorescence, which belongs to the field of optical materials and comprises the following steps: step 1, dissolving nematic liquid crystal 5CB and chiral optical switch M1 in solvent dichloromethane to obtain a mixed solution, and evaporating the solvent to obtain cholesteric liquid crystal; step 2, preparing vertically oriented and parallel oriented liquid crystal boxes coated with room temperature phosphorescent polymer-polyvinyl alcohol films; step 3, under capillary action, respectively injecting cholesteric liquid crystals into the parallel oriented or vertical oriented liquid crystal boxes to prepare cholesteric liquid crystal room temperature phosphorescent polymer film CLC-M1-RTP doped with chiral optical switch; step 4, irradiating the film prepared in step 3 with light of different wavelengths, and realizing dynamic control of chirality reversal and asymmetry factor in the room temperature phosphorescent polymer system by controlling the wavelength and illumination time.

Description

Technical Field

[0001] The present invention belongs to the field of optical materials, and in particular is a chiral flipping dynamic control method based on soft helical superstructure circularly polarized room temperature phosphorescence. Background Art

[0002] Organic room temperature phosphorescent materials with circularly polarized luminescence properties have a wide range of applications in three-dimensional optical display, information storage technology, and anti-counterfeiting. Previously reported circularly polarized organic ultra-long room temperature phosphorescent materials were mainly achieved through crystallization, copolymerization, and host-guest doping. However, in the room temperature phosphorescent system, the circularly polarized luminescence asymmetry factor is low and the chirality flip and dynamic reversible regulation of the asymmetry factor cannot be achieved.

[0003] The existing solutions to the above problems include: (1) Combining room temperature phosphorescent polymers with soft helical superstructures can significantly increase the asymmetric factor of circularly polarized luminescence, such as cholesteric liquid crystals, which have the effect of amplifying chirality due to the photon bandgap effect of cholesteric liquid crystals. (2) By introducing molecular motors and constructing a double-layer structure of liquid crystal phosphorescent polymers, the asymmetric factor can be dynamically controlled under the synergistic effect of light and temperature.

[0004] However, due to the poor compatibility between molecular motors and liquid crystals and the relatively small helical twisting force, dynamic reversible regulation of chirality reversal and asymmetry factors cannot be achieved.

[0005] Therefore, the present invention proposes a method for dynamically controlling the chirality reversal of circularly polarized room temperature phosphorescence based on a soft helical superstructure. A specially designed chiral light switch is doped into a nematic liquid crystal to construct a cholesteric liquid crystal layer and a phosphorescent polymer layer. Through illumination of different wavelengths, the chiral light switch molecules will emit light photoisomerization, thereby changing the helical structure of the cholesteric liquid crystal, and finally realizing dynamic reversible control of chirality reversal and asymmetry factor in a circularly polarized room temperature phosphorescence system. Summary of the invention

[0006] Purpose of the invention: The purpose of the present invention is to solve the problem that the existing circularly polarized room temperature phosphorescent system cannot achieve chirality reversal, and to provide a method for dynamically controlling chirality reversal of circularly polarized room temperature phosphorescent light based on a soft helical superstructure. The present invention dopes a specially designed chiral light switch into a nematic liquid crystal, constructs a chiral light-switch-doped cholesteric liquid crystal layer and a phosphorescent polymer layer, and changes the helical structure of the cholesteric liquid crystal under the action of light of different wavelengths by controlling the photoisomerization process of the chiral light switch, and finally realizes dynamic reversible control of chirality reversal and asymmetry factor in the circularly polarized room temperature phosphorescent system.

[0007] Technical solution: A chiral flipping dynamic control method based on soft helical superstructure circularly polarized room temperature phosphorescence, comprising the following steps:

[0008] Step 1: dissolving the nematic liquid crystal 5CB and the chiral optical switch M1 in a solvent of dichloromethane to obtain a mixed solution, and evaporating the solvent to obtain a cholesteric liquid crystal (CLC);

[0009] Step 2, preparing a vertically oriented and parallelly oriented liquid crystal cell coated with a room temperature phosphorescent polymer-polyvinyl alcohol film;

[0010] Step 3: Under the capillary action, the cholesteric liquid crystal is injected into the parallel-oriented or vertical-oriented liquid crystal box to prepare the cholesteric liquid crystal room temperature phosphorescent polymer film CLC-M1-RTP doped with the chiral optical switch;

[0011] Step 4: Expose the film prepared in step 3 to light of different wavelengths, and achieve dynamic regulation of chirality reversal and asymmetry factor in the room temperature phosphorescent polymer system by controlling the wavelength and illumination time.

[0012] Furthermore, the mass percentage concentration of the nematic liquid crystal 5CB in the mixed solution is 58.9 wt %, the mass percentage concentration of the chiral optical switch M1 in the mixed solution is 4.2 wt %, the volume of dichloromethane is 2 ml, and the solvent may also be chloroform.

[0013] Furthermore, the step 2 is specifically as follows:

[0014] Step 2.1, preparing a room temperature phosphorescent polymer-polyvinyl alcohol solution;

[0015] A mixture of 100 mg of room temperature phosphorescent polymer and 400 mg of polyvinyl alcohol was dissolved in 5 mL of deionized water, stirred vigorously at 108 °C for 3 hours, and then cooled to room temperature to obtain a room temperature phosphorescent polymer-polyvinyl alcohol solution (RTP-PVA solution);

[0016] Step 2.2, spin-coat the room temperature phosphorescent polymer-polyvinyl alcohol solution onto the glass substrate, place it in a vacuum drying oven at 50°C, and then rub it with nylon cloth for orientation to ensure uniform arrangement;

[0017] Step 2.3, assembling the two parallel-oriented glass substrates prepared in step 2.2 into a parallel-oriented liquid crystal box to prepare a parallel-oriented liquid crystal box; assembling the two vertically-oriented glass substrates prepared in step 2.2 into a vertically-oriented liquid crystal box; the thickness of the liquid crystal box is controlled by ultraviolet glue doped with nanoparticles, and the thickness of the liquid crystal box is 15.4 µm.

[0018] Furthermore, in step 2.1, the room temperature phosphorescent polymer is P1 or P2, and the polyethanol is PVA-1799.

[0019] Furthermore, step four is specifically as follows: in the cholesteric liquid crystal room temperature phosphorescent polymer film doped with the chiral light switch, in the initial state, the cholesteric liquid crystal doped with the light switch is left-handed, and after irradiation with 460 nm for 2 minutes, the soft helical structure of the cholesteric phase changes from left-handedness to right-handedness, and the luminescence asymmetry factor increases, and then after irradiation with 340 nm for 2 minutes, the soft helical structure of the cholesteric phase changes from right-handedness to left-handedness, and the luminescence asymmetry factor decreases.

[0020] Beneficial effects: (1) The cholesteric liquid crystal room temperature phosphorescent polymer film doped with a chiral optical switch prepared by the present invention is composed of a cholesteric liquid crystal (CLC) layer doped with an optical switch (M1) and a room temperature phosphorescent (RTP) polymer layer. Under irradiation with 460 nm and 340 nm light, the film can exhibit dynamic chirality reversal. (2) The luminescence asymmetry factor ( g lum ) is as high as 0.4. (3) The present invention has the advantages of easy operation, low price and good fatigue resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is the chemical structural formula of the nematic liquid crystal 5CB, polyvinyl alcohol PVA, chiral light switch M1, green phosphorescent polymer (P1), and yellow phosphorescent polymer (P2) in the present invention.

[0022] Figure 2 The luminescence asymmetry factor of CLC-M1-P1 prepared for the parallel-aligned and vertical-aligned liquid crystal cells in Example 1 ( g lum ) of the dynamic reversible modulation.

[0023] Figure 3 These are photos of CLC-M1-P1 and CLC-M1-P2 prepared in Example 1 and Example 2 after the 365 nm ultraviolet light irradiation was turned off for a period of time. DETAILED DESCRIPTION

[0024] The technical solution of the present invention is described in detail below through embodiments, but the protection scope of the present invention is not limited to the embodiments.

[0025] The present invention proposes a chiral flip dynamic control method based on soft helical superstructure circularly polarized room temperature phosphorescence. A specially designed chiral light switch is doped into the nematic liquid crystal to construct a cholesteric liquid crystal layer and a phosphorescent polymer layer. Through the control of light of different wavelengths, the chiral light switch molecules will emit light photoisomerization, thereby changing the helical structure of the cholesteric liquid crystal, and finally realizing the dynamic reversible control of chiral flip and asymmetry factor in the circularly polarized room temperature phosphorescence system.

[0026] In the embodiment of the present invention, the nematic liquid crystal 5CB is from Nanjing Leyao Technology Co., Ltd., and the polyvinyl alcohol PVA-1799 is from Shanghai Aladdin Biochemical Technology Co., Ltd. The room temperature phosphorescent polymers P1, P2, and the chiral optical switch M1 are all from Nanjing Leyao Technology Co., Ltd.

[0027] Example 1: A chiral flipping dynamic control method based on soft helical superstructure circularly polarized room temperature phosphorescence. In this example, the room temperature phosphorescent polymer is P1, and the specific steps are as follows:

[0028] 1) Dissolve nematic liquid crystal 5CB (58.9 wt%) and chiral photoswitch M1 (4.2 wt%) in 2 mL of dichloromethane, and evaporate the solvent at 70°C to obtain cholesteric liquid crystal.

[0029] 2) Prepare vertically oriented and parallel oriented liquid crystal cells coated with room temperature phosphorescent polymer-polyvinyl alcohol film;

[0030] A room temperature phosphorescent polymer-polyvinyl alcohol solution was prepared; a mixture of 100 mg of room temperature phosphorescent polymer P1 and 400 mg of polyvinyl alcohol PVA-1799 was dissolved in 5 mL of deionized water, and after vigorous stirring at 108° C. for 3 hours, the mixture was cooled to room temperature to obtain a room temperature phosphorescent polymer-polyvinyl alcohol solution;

[0031] The room temperature phosphorescent polymer-polyvinyl alcohol solution was spin-coated onto glass substrates, placed in a vacuum drying oven at 50°C, and then rubbed with nylon cloth for orientation to ensure uniform alignment;

[0032] The two prepared parallel-oriented glass substrates were assembled into a parallel-oriented liquid crystal cell, and a parallel-oriented liquid crystal cell and a vertical-oriented liquid crystal cell were prepared respectively; the preparation method was as follows: a layer of room temperature phosphorescent polymer-polyvinyl alcohol film was pre-coated on one glass substrate, and then assembled with another parallel-oriented glass substrate into a liquid crystal cell; the thickness of the liquid crystal cell (15.4 µm) was controlled by ultraviolet glue doped with nanoparticles. Similarly, another glass sheet coated with a room temperature phosphorescent polymer-polyvinyl alcohol film was assembled with a vertically-oriented glass substrate into a liquid crystal cell, and the cell thickness was 15.0 µm, which was controlled by ultraviolet glue doped with nanoparticles.

[0033] 3) Inject the prepared cholesteric liquid crystal (M1-doped CLC) into the parallel-oriented and vertical-oriented liquid crystal cells prepared above, respectively, to prepare a circularly polarized organic ultra-long room-temperature phosphorescent film CLC-M1-P1 doped with green phosphorescence.

[0034] Example 2: A chiral flipping dynamic control method based on soft helical superstructure circularly polarized room temperature phosphorescence. In this example, the room temperature phosphorescent polymer is P2, and the specific steps are as follows:

[0035] 1) Dissolve nematic liquid crystal 5CB (58.9 wt%) and chiral photoswitch M1 (4.2 wt%) in 2 mL of dichloromethane, and evaporate the solvent at 70°C to obtain cholesteric liquid crystal.

[0036] 2) Prepare vertically oriented and parallel oriented liquid crystal cells coated with room temperature phosphorescent polymer-polyvinyl alcohol film;

[0037] A mixture of 100 mg of room temperature phosphorescent polymer P2 and 400 mg of poly(vinyl alcohol) PVA-1799 was dissolved in 5 mL of deionized water, stirred vigorously at 108 °C for 3 hours, and then cooled to room temperature to obtain a room temperature phosphorescent polymer-polyvinyl alcohol solution;

[0038] The room temperature phosphorescent polymer-polyvinyl alcohol solution was spin-coated onto glass substrates, placed in a vacuum drying oven at 50°C, and then rubbed with nylon cloth for orientation to ensure uniform alignment;

[0039] The two prepared parallel-oriented glass substrates were assembled into a parallel-oriented liquid crystal cell, and a parallel-oriented liquid crystal cell and a vertical-oriented liquid crystal cell were prepared respectively; the preparation method was as follows: a layer of room temperature phosphorescent polymer-polyvinyl alcohol film was pre-coated on one glass substrate, and then assembled with another parallel-oriented glass substrate into a liquid crystal cell; the thickness of the liquid crystal cell (15.4 µm) was controlled by ultraviolet glue doped with nanoparticles. Similarly, another glass sheet coated with a room temperature phosphorescent polymer-polyvinyl alcohol film was assembled with a vertically-oriented glass substrate into a liquid crystal cell, and the cell thickness was 15.0 µm, which was controlled by ultraviolet glue doped with nanoparticles.

[0040] 3) Inject the prepared cholesteric liquid crystal (M1-doped CLC) into the parallel-oriented and vertical-oriented liquid crystal cells prepared above, respectively, to prepare a circularly polarized organic ultra-long room temperature phosphorescent film CLC-M1-P2 doped with yellow phosphorescence.

[0041] Test Case

[0042] The films prepared in Examples 1 and 2 were irradiated with 460 nm and 340 nm light, respectively, and the irradiation time was controlled to finally achieve chirality reversal in the CP-OURTP structure. Figure 2 and Figure 3 shown.

[0043] Figure 2 The optical asymmetry factor of CLC-M1-P1 prepared in Example ( g lum ) is dynamically reversibly modulated. Where a is the initial state of the two CLC-M1-P1 prepared in the parallel and vertical orientation liquid crystals.g lum Spectrum; b is the CLC-M1-P1 in a parallel-oriented liquid crystal cell under 460 nm light and 340 nm light respectively. g lum Spectrum; c is the CLC-M1-P1 in a vertically aligned liquid crystal cell under 460 nm light and 340 nm light respectively. g lum (d), (e), and (f) are the circular polarization spectra corresponding to (a), (b), and (c), respectively.

[0044] Depend on Figure 2 It can be seen that in the parallel-oriented liquid crystal cell, the cholesteric liquid crystal doped with the optical switch M1 is left-handed in the initial state, and the circularly polarized luminescence asymmetry factor is -0.38 (see Figure 2 a); After 2 min of 460 nm illumination, the soft helical structure of the cholesteric phase changes from left-handedness to right-handedness, and the luminescence asymmetry factor becomes +0.37 ( Figure 2 b); then after irradiation with 340 nm light for 2 min, the cholesteric phase liquid crystal changed from right-handed to left-handed, and the luminescence asymmetry factor became -0.37 (as shown in Figure 2 b); This shows that in the parallel-oriented liquid crystal cell, for the CLC-M1-P1 film, by controlling the wavelength of light, the chirality flipping of the cholesteric phase liquid crystal and the dynamic regulation of the luminescence asymmetry factor can be controlled. In the vertically oriented liquid crystal cell, the cholesteric phase liquid crystal doped with the optical switch M1 is left-handed in the initial state, and the circularly polarized luminescence asymmetry factor is -0.25 (see Figure 2 a in the figure). After 2 min of irradiation at 460 nm, the soft helical structure of the cholesteric phase changes from left-handedness to right-handedness, and the emission asymmetry factor becomes +0.19 ( Figure 2 c). After irradiation with 340 nm light for 2 min, the cholesteric liquid crystal changes from right-handed to left-handed, and the asymmetric factor of the emission changes to -0.21 (e.g. Figure 2 c). This shows that in a vertically oriented liquid crystal cell, for the CLC-M1-P1 film, by controlling the wavelength of light, the chirality flipping of the cholesteric liquid crystal and the dynamic regulation of the luminescence asymmetry factor can be controlled.

[0045] Chirality reversal can be achieved in both parallel-oriented liquid crystal cells and vertical-oriented liquid crystal cells, but the luminescence asymmetry factor is slightly larger in the parallel-oriented liquid crystal cell.

[0046] The test results of CLC-M1-P2 prepared in Example 2 are as follows: in the parallel-oriented liquid crystal box, the cholesteric liquid crystal doped with the optical switch M1 is left-handed in the initial state, and the circularly polarized luminescence asymmetry factor is -0.48 at this time; after 2 minutes of 460 nm illumination, the soft helical structure of the cholesteric phase changes from left-handed to right-handed, and the luminescence asymmetry factor becomes +0.29; then after 2 minutes of 340 nm illumination, the cholesteric liquid crystal changes from right-handed to left-handed, and the luminescence asymmetry factor becomes -0.30 again; this shows that in CLC-M1-P2, by controlling the wavelength of illumination, the chirality reversal of the cholesteric liquid crystal and the dynamic regulation of the luminescence asymmetry factor can be controlled. In the vertically oriented liquid crystal box and in the parallel oriented liquid crystal box, the cholesteric phase liquid crystal doped with the optical switch M1 is left-handed in the initial state, and the circularly polarized luminescence asymmetry factor is -0.38; after 2 minutes of 460 nm illumination, the soft helical structure of the cholesteric phase changes from left-handed to right-handed, and the luminescence asymmetry factor becomes +0.15; then after 2 minutes of 340 nm illumination, the cholesteric phase liquid crystal changes from right-handed to left-handed, and the luminescence asymmetry factor becomes -0.20; this shows that in CLC-M1-P2, by controlling the wavelength of light, the chirality reversal of the cholesteric phase liquid crystal and the dynamic regulation of the luminescence asymmetry factor can be controlled.

[0047] Figure 3 The following are photos of the films doped with green phosphor (CLC-M1-P1) and yellow phosphor (CLC-M1-P2) after turning off the 365nm UV light. Figure 3 The two CLC-M1-P1 and CLC-M1-P2 in the figure are prepared in a parallel alignment liquid crystal cell. Figure 3 It can be seen that for the CLC-M1-P1 film, the afterglow time seen by the naked eye is about 3.2 s, and for the CLC-M1-P2 film, the afterglow time seen by the naked eye is about 0.8 s.

[0048] In summary, based on the structure of optical switch-doped cholesteric liquid crystal-room temperature phosphorescent polymer (CLC-M1-RTP), the present invention realizes dynamic reversible regulation of chirality reversal and asymmetry factor in the CP-OURTP system by changing the illumination of different wavelengths.

[0049] As described above, although the present invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the present invention itself. Various changes in form and details may be made without departing from the spirit and scope of the present invention.

Claims

1. A chiral flipping dynamic control method based on soft helical superstructure circularly polarized room temperature phosphorescence, characterized in that: The steps include: Step 1: dissolving the nematic liquid crystal 5CB and the chiral optical switch M1 in a solvent of dichloromethane to obtain a mixed solution, and evaporating the solvent to obtain a cholesteric liquid crystal; the chemical structures of 5CB and M1 are as follows: ； Step 2, preparing a vertically oriented or parallel oriented liquid crystal cell coated with a room temperature phosphorescent polymer-polyvinyl alcohol film; Step 3: Under the capillary action, the cholesteric liquid crystal is injected into the parallel-oriented or vertical-oriented liquid crystal box to prepare a cholesteric liquid crystal room temperature phosphorescent polymer film doped with a chiral optical switch; Step 4: Expose the film prepared in step 3 to light of different wavelengths, and dynamically control the chirality reversal and asymmetry factor by controlling the wavelength and illumination time.

2. The control method according to claim 1, characterized in that: In the step 1, the mass percentage concentration of the nematic liquid crystal 5CB in the mixed solution is 58.9 wt %, and the mass percentage concentration of the chiral optical switch M1 in the mixed solution is 4.2 wt %.

3. The control method according to claim 1, characterized in that: The step 2 is specifically as follows: Step 2.1, preparing a room temperature phosphorescent polymer-polyvinyl alcohol solution; A mixture of 100 mg of room temperature phosphorescent polymer and 400 mg of polyvinyl alcohol was dissolved in 5 mL of deionized water, stirred vigorously at 108°C for 3 hours, and then cooled to room temperature to obtain a room temperature phosphorescent polymer-polyvinyl alcohol solution; Step 2.2, spin-coat the room temperature phosphorescent polymer-polyvinyl alcohol solution onto the glass substrate, place it in a vacuum drying oven at 50°C, and then rub it with nylon cloth for orientation to ensure uniform arrangement; Step 2.3, assembling the two parallel-oriented glass substrates prepared in step 2.2 into a parallel-oriented liquid crystal box to prepare a parallel-oriented liquid crystal box; assembling the two vertically-oriented glass substrates prepared in step 2.2 into a vertically-oriented liquid crystal box; the thickness of the liquid crystal box is controlled by ultraviolet glue doped with nanoparticles, and the thickness of the liquid crystal box is 15.4 µm.

4. The control method according to claim 3, characterized in that: In the step 2.1, the room temperature phosphorescent polymer is P1 or P2, and the polyvinyl alcohol is PVA-1799; the chemical structures of P1 and P2 are as follows: 。 5. The control method according to claim 3, characterized in that: Step four is specifically as follows: in the cholesteric liquid crystal room temperature phosphorescent polymer film doped with a chiral light switch, in an initial state, the cholesteric liquid crystal doped with the light switch is left-handed, and after irradiation with 460 nm for 2 minutes, the soft helical structure of the cholesteric phase changes from left-handedness to right-handedness, and the luminescence asymmetry factor increases, and then after irradiation with 340 nm for 2 minutes, the soft helical structure of the cholesteric phase changes from right-handedness to left-handedness, and the luminescence asymmetry factor decreases.

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