A method for dynamic regulation of circularly polarized room temperature phosphorescence based on cholesteric liquid crystal elastomer

Abstract

The present invention provides a method for dynamic regulation of circularly polarized room temperature phosphorescence based on cholesteric liquid crystal elastomer, which belongs to the technical field of optical materials, and the steps are as follows: step 1, dissolving a liquid crystal monomer, a chiral agent, a cross-linking agent, a chain extender, a photoinitiator, a catalyst and a room temperature phosphorescent polymer in a solvent of dichloromethane, and evaporating the solvent to obtain a red cholesteric liquid crystal elastomer room temperature phosphorescent oligomer; step 2, polymerizing the cholesteric liquid crystal elastomer room temperature phosphorescent oligomer with ultraviolet light at room temperature to obtain a CLCE-RTP film; step 3, regulating the circularly polarized phosphorescent asymmetry factor by controlling the degree of tensile deformation of the CLCE-RTP film. The present invention dopes P1, P2 or P3 with a cholesteric liquid crystal elastomer to achieve dynamic reversible regulation of the circularly polarized room temperature phosphorescent asymmetry factor between 0.8 and 0.15.

Description

Technical Field

[0001] The invention belongs to the technical field of optical materials, and in particular is a method for dynamically controlling circularly polarized room temperature phosphorescence of a cholesteric liquid crystal elastomer. 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, optoelectronic devices, and anti-counterfeiting. Previously reported circularly polarized organic ultralong room temperature phosphorescent materials were mainly achieved through crystallization, copolymerization, and host-guest doping strategies. However, most phosphorescent materials have an asymmetry factor of 10 -3 Up to 10 -2 The circularly polarized luminescence asymmetry factor is fixed, which greatly limits their practical applications.

[0003] In response to the above problems, existing technologies include: combining room temperature phosphorescent materials with cholesteric liquid crystals to increase the luminescence asymmetry factor by 1-2 orders of magnitude. Constructing a double-layer structure of chiral liquid crystal phosphorescent polymers, the asymmetry factor can be dynamically controlled through ultraviolet light and temperature control. However, the current technology has poor processability, limited scalability, and relies on rigid substrates such as glass, which is not conducive to its practical application. Summary of the invention

[0004] Purpose of the invention: The purpose of the present invention is to solve the problem that the asymmetry factor of the existing circularly polarized room temperature phosphorescence is fixed, and to provide a method for dynamically controlling the circularly polarized room temperature phosphorescence based on a cholesteric liquid crystal elastomer. The method constructs a mixed system of a cholesteric liquid crystal elastomer and an organic room temperature phosphorescent material, changes the helical structure of the cholesteric liquid crystal elastomer under the action of an external force, thereby changing the photonic bandgap, and ultimately achieving dynamic and reversible control of the asymmetry factor of a high circularly polarized room temperature phosphorescence.

[0005] Technical solution: A method for dynamically controlling circularly polarized room temperature phosphorescence of cholesteric liquid crystal elastomers, comprising the following steps:

[0006] Step 1: dissolving a raw material composition containing a liquid crystal monomer, a chiral agent, a cross-linking agent, a chain extender, a photoinitiator, a catalyst and a room temperature phosphorescent polymer in a solvent of dichloromethane, mixing them evenly after they are fully dissolved, and evaporating the solvent to obtain a red cholesteric liquid crystal elastomer room temperature phosphorescent oligomer; the room temperature phosphorescent polymer is P1, P2 or P3 respectively.

[0007] Step 2: polymerizing the red cholesteric liquid crystal elastomer room temperature phosphorescent oligomer under ultraviolet light at room temperature to obtain a cholesteric liquid crystal elastomer-room temperature phosphorescent polymer film, which is referred to as CLCE-RTP film;

[0008] Step 3: Regulate the circularly polarized phosphorescence asymmetry factor by controlling the degree of tensile deformation of the CLCE-RTP film.

[0009] Furthermore, in the step 1, in the raw material composition, the liquid crystal monomer is RM257, the chiral agent is LC756, the cross-linking agent is PETMP, the chain extender is EDDET, the photoinitiator is IRG651, and the catalyst is DPA.

[0010] Furthermore, in the step 1, the content of the liquid crystal monomer and the chiral agent in the raw material composition is 71.2 wt%, the content of the chiral agent in the raw material composition is 3.2 wt%; and the content of the room temperature phosphorescent polymer in the raw material composition is 1.5 wt%.

[0011] Further, the solvent is evaporated in the following manner:

[0012] The mixed solution is poured into a glass culture dish (90 mm in diameter) and evaporated at room temperature for 4-6 hours to obtain a cholesteric liquid crystal elastomer room temperature phosphorescent oligomer.

[0013] Furthermore, the specific operation of step 2 is: polymerizing the cholesteric liquid crystal elastomer room temperature phosphorescent oligomer at room temperature with ultraviolet light of wavelength 365 nanometers for 10-30 minutes, and the power of the ultraviolet light is 20-50 mW / cm 2 , a cholesteric liquid crystal elastomer-room temperature phosphorescent polymer film was obtained, which was recorded as CLCE-RTP film.

[0014] Furthermore, the specific operations of step three are:

[0015] Apply tension to both ends of the CLCE-RTP film, and the length of the stretch increase is 0-100% of the CLCE-RTP film;

[0016] As the stretching length increases, the photon bandgap shifts to the blue, and the structural color of the film continuously transitions from red to green and finally to blue. At the same time, the circularly polarized phosphorescence asymmetry factor g lum As the stretching length increases, it gradually becomes lower and the wavelength blue-shifts; when the tension is removed, as the film length shrinks, the structural color of the film will transition from blue to green and finally to red. g lum Gradually becomes higher and the wavelength redshifts.

[0017] Furthermore, when the room temperature phosphorescent polymer is P3, the circularly polarized phosphorescence asymmetry factor can be achieved in the CLCE-RTP film. g lum Dynamically reversible regulation between 0.15 and 0.8.

[0018] Furthermore, when the room temperature phosphorescent polymer is P2, the circularly polarized phosphorescence asymmetry factor can be achieved in the CLCE-RTP film. g lum Dynamically reversible regulation between 0.02 and 0.8.

[0019] Furthermore, when the room temperature phosphorescent polymer is P1, the circularly polarized phosphorescence asymmetry factor can be achieved in the CLCE-RTP film. g lum Dynamically reversible regulation between 0.12 and 0.4.

[0020] Beneficial effects: (1) The present invention dopes room temperature phosphorescent polymer into cholesteric liquid crystal elastomer, utilizes the flexibility and stretchability of the elastomer, and controls the movement of the photon bandgap by controlling the change of the pitch of the CLCE-RTP film under the action of external force, thereby achieving g lum When the external force is removed, the pitch of the CLCE-RTP film will recover and the photon bandgap will redshift. Therefore, it is possible to achieve g lum (2) The present invention achieves excellent processing performance and high g lum , and can be g lum Full-color CLCE-RTP film with dynamic and reversible control. (3) The present invention has the advantages of easy large-area preparation, high flexibility, low price and good fatigue resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The chemical structures of liquid crystal monomer (RM257), chiral agent (LC756), cross-linking agent (PETMP), chain extender (EDDET), photoinitiator (IRG651), catalyst (DPA), blue phosphorescent polymer (P1), green phosphorescent polymer (P2), and red phosphorescent polymer (P3) are shown in FIG.

[0022] Figure 2 When doped with red afterglow room temperature phosphorescent polymer (P3), the structural color change and reflection spectrum of the CLCE-RTP film under tensile deformation.

[0023] Figure 3 When the red afterglow room temperature phosphorescent polymer (P3) is doped, the circularly polarized room temperature phosphorescence asymmetry factor ( g lum ) Dynamic reversible regulation diagram.

[0024] Figure 4 When the doped room temperature phosphorescent polymer is a blue afterglow room temperature phosphorescent polymer (P1), the dynamic change graph of the luminescence asymmetry factor and the dynamic change graph of the circularly polarized luminescence spectrum of the CLCE-RTP film.

[0025] Figure 5 When the doped room temperature phosphorescent polymer is a green afterglow room temperature phosphorescent polymer (P2), the dynamic change graph of the luminescence asymmetry factor and the dynamic change graph of the circularly polarized luminescence spectrum of the CLCE-RTP film. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is described in detail below with reference to the accompanying drawings, but the protection scope of the present invention is not limited to the embodiments.

[0027] The present invention discloses a dynamic control method based on cholesteric liquid crystal elastomer-room temperature phosphorescent polymer (CLCE-RTP). The method is based on the change of the helical superstructure of the cholesteric liquid crystal elastomer caused by stress, and by controlling the stretching length, the photon bandgap of the CLCE-RTP film is changed to achieve dynamic and reversible control of the asymmetric factor of circularly polarized room temperature phosphorescence.

[0028] In the embodiment of the present invention, the molecular structures of RM257, LC756, PETMP, EDDET, IRG651, DPA, P1, P2 and P3 are as follows: Figure 1 RM257, LC756, IRG651 were from Nanjing Leyao Technology Co., Ltd., PETMP, EDDET, DPA were from Merck, Germany; P1, P2, and P3 were from Nanjing Leyao Technology Co., Ltd.

[0029] Example 1: The room temperature phosphorescent polymer is P3, and the dynamic reversible control method based on the asymmetric factor of the cholesteric liquid crystal elastomer-room temperature phosphorescent polymer is as follows:

[0030] (1) Dissolve 960 mg of liquid crystal monomer (RM257), 42.5 mg of chiral agent (LC756), 65 mg of cross-linking agent (PETMP), 249 mg of chain extender (EDDET), 7.5 mg of photoinitiator (IRG651), 3.5 mg of catalyst (DPA) and 20 mg of red phosphorescent polymer (P3) in dichloromethane (CH2Cl2), fully dissolve and mix well.

[0031] (2) The obtained solution was poured into a glass culture dish (the diameter of the culture dish was 90 mm) and placed at room temperature for 4 hours to allow the dichloromethane to completely evaporate, thereby preparing a cholesteric liquid crystal elastomer room temperature phosphorescent oligomer (CLCE-RTP film).

[0032] (3) Use ultraviolet light with a wavelength of 365 nanometers (power of 50 mW / cm 2 ) to irradiate the oligomer obtained in the previous step for 10 min, and then peel the obtained film from the culture dish with a spatula and cut it into long strips.

[0033] (4) Under the action of external force, the pitch of the CLCE-RTP film will change at both ends of the stretched film, causing its photon bandgap to change and causing the reflection color of the CLCE-RTP film to change; as the stretching length increases, the photon bandgap blueshifts, and the structural color of the film continuously transitions from red to green and finally to blue; at the same time, the circularly polarized phosphorescence asymmetry factor g lum As the stretching length increases, it gradually becomes lower and the wavelength blue-shifts; when the tension is removed, as the film length shrinks, the structural color of the film will transition from blue to green and finally to red. g lum gradually becomes higher and the wavelength redshifts. The specific results are as follows Figure 2 and Figure 3 shown.

[0034] Figure 2 a in the figure is a CLCE-RTP film with a red initial structural color. The structural color of the CLCE-RTP film changes continuously from red to blue through stretching deformation. Figure 2 b in the figure is the reflection spectrum of CLCE-RTP film at different stretching lengths. Figure 2 As can be seen in Figure a, as the stretching length increases, the structural color of the cholesteric liquid crystal elastomer changes from red to green, and finally to blue, resulting in a blue shift. The corresponding reflection spectrum center wavelength changes from 625 nanometers to 490 nanometers, as shown in Figure 5. Figure 2 As shown in b.

[0035] Figure 3 a is the dynamic change of circularly polarized phosphorescence (CPL) spectrum with the increase of stretching length when the doped room temperature polymer is red phosphorescent (P3). Figure 3 b is the circularly polarized luminescence asymmetry factor ( g lum )’s dynamic change diagram. Figure 3 The c in the equation is the value under the conditions of applying and removing external force. g lum Dynamic reversible change diagram. Figure 3 The d in the figure is the maximum value as the number of cycles increases. g lum and minimum g lum The dynamic change diagram of . Figure 3 It can be seen that when the stretch length is 0%, glum The maximum value is 0.8. As the stretching length increases, glum gradually decreases. When the stretching length reaches the maximum (100%), g lum The minimum value reached is 0.15.

[0036] Example 2: A method for dynamically reversibly regulating the asymmetric factor of a cholesteric liquid crystal elastomer-room temperature phosphorescent polymer, wherein the room temperature phosphorescent polymer is P1, and the rest is the same as in Example 1.

[0037] As the stretching length increases, the photon bandgap shifts to the blue. The structural color of the film continuously transitions from red to green and finally to blue. At the same time, the circularly polarized phosphorescence asymmetry factor g lum As the stretching length increases, it first increases and then decreases, and the wavelength shifts to the blue; when the tension is removed, as the film length shrinks, the structural color of the film will transition from blue to green and finally to red. g lum It gradually increases, then decreases, and the wavelength redshifts. The specific results are as follows Figure 4 shown.

[0038] As the stretching length increases, when the doped room temperature phosphorescent polymer is blue phosphorescent (P1), the dynamic change of the luminescence asymmetry factor of the CLCE-RTP film is shown in Figure 2. Figure 4 The dynamic change of the circularly polarized luminescence spectrum of the CLCE-RTP film is shown in a. Figure 4 As shown in b. Figure 4 It can be seen that when the stretch length is 20%, g lum The maximum value is 0.4. As the stretching length increases, g lum Gradually decrease, when the stretch length reaches the maximum (100%), g lum The minimum value reached is 0.12.

[0039] Example 3: A method for dynamically reversibly regulating the asymmetric factor of a cholesteric liquid crystal elastomer-room temperature phosphorescent polymer, wherein the room temperature phosphorescent polymer is P2, and the rest is the same as Example 1.

[0040] As the stretching length increases, the photon bandgap shifts to the blue. The structural color of the film changes from red to green and finally to blue. At the same time, the circularly polarized phosphorescence asymmetry factor g lum As the stretching length increases, it first increases and then decreases, and the wavelength shifts to the blue; when the tension is removed, as the film length shrinks, the structural color of the film will transition from blue to green and finally to red. glum It gradually increases, then decreases, and the wavelength redshifts. The specific results are as follows: Figure 5 shown.

[0041] As the stretching length increases, when the doped room temperature phosphorescent polymer is blue phosphorescent (P2), the dynamic change of the CLCE-RTP luminescence asymmetry factor is shown in the figure below: Figure 5 As shown in a in Figure 1, the dynamic change of the circularly polarized luminescence spectrum of CLCE-RTP is shown in Figure 5 As shown in b, when the stretch length is 20%, g lum The maximum value is 0.8. As the stretching length increases, g lum First increase and then decrease, when the stretch length reaches the maximum (100%), g lum The minimum value reached is 0.02.

[0042] The contents of the components in the above three embodiments are shown in the following table:

[0043]

[0044] Changing the concentration of the chiral agent LC756 will change the structural color of the cholesteric liquid crystal elastomer. When the content of the chiral agent in the raw material composition is 3.2 wt%, the room temperature phosphorescent polymer, whether it is P1, P2 or P3, the structural color of the cholesteric liquid crystal elastomer room temperature phosphorescent oligomer is red.

[0045] When the concentration of chiral agent LC756 in the raw material composition is 3.8 wt% and the doped room temperature phosphorescent polymer is P2, the structural color of the cholesteric liquid crystal elastomer is green; when the concentration of LC756 is 4.2 wt% and the doped room temperature phosphorescent polymer is P1, the structural color of the cholesteric liquid crystal elastomer is blue.

[0046] The present invention proposes a dynamic control method for the asymmetric factor of circularly polarized room temperature phosphorescence of cholesteric liquid crystal elastomer, which dopes three room temperature phosphorescent polymers of blue (P1), green (P2) or red (P3) with cholesteric liquid crystal elastomer, and regulates the photon bandgap of cholesteric liquid crystal by generating tensile deformation. In a full-color cholesteric liquid crystal elastomer room temperature phosphorescent polymer system, dynamic reversible control of the asymmetric factor of circularly polarized room temperature phosphorescence between 0.8 and 0.02 is achieved, and the processability is good, so large-scale production can be achieved.

[0047] The circularly polarized phosphorescence asymmetry factor g lum :

[0048] ;

[0049] in, I L , I R represent the intensity of left-handed and right-handed circularly polarized light, respectively. .

[0050] g lum It can be used to measure the polarization degree and rotation direction of light. Its value range is -2 to 2, where 2 represents pure left-handed circularly polarized light, -2 represents pure right-handed circularly polarized light, and 0 represents linearly polarized light or unpolarized light. The closer the absolute value of the circularly polarized luminescence asymmetry factor is to 2, the higher the polarization degree of the light.

[0051] 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 may be made to it in form and detail without departing from the spirit and scope of the present invention as defined in the appended claims.

Claims

1. A method for dynamically controlling the asymmetric factor of circularly polarized room temperature phosphorescence of a cholesteric liquid crystal elastomer, characterized in that: The steps include: Step 1, dissolving a raw material composition containing a liquid crystal monomer, a chiral agent, a cross-linking agent, a chain extender, a photoinitiator, a catalyst and a room temperature phosphorescent polymer in a solvent of dichloromethane, mixing them evenly after fully dissolving to obtain a mixed solution, and evaporating the solvent to obtain a red cholesteric liquid crystal elastomer room temperature phosphorescent oligomer; the liquid crystal monomer is RM257, the chiral agent is LC756, the cross-linking agent is PETMP, the chain extender is EDDET, the photoinitiator is IRG651, the catalyst is DPA, and the room temperature phosphorescent polymer is P1, P2 or P3 respectively; The chemical structures of P1, P2 and P3 are as follows: ； Step 2: polymerize the red cholesteric liquid crystal elastomer room temperature phosphorescent oligomer at room temperature using ultraviolet light with a wavelength of 365 nanometers for 10-30 minutes, and the power of the ultraviolet light is 20 ~ 50 mW / cm 2 , a cholesteric liquid crystal elastomer-room temperature phosphorescent polymer film is obtained, which is denoted as CLCE-RTP film; Step 3: Controlling the asymmetric factor of circularly polarized phosphorescence by controlling the degree of tensile deformation of the CLCE-RTP film; The content of the liquid crystal monomer and the chiral agent in the raw material composition is 71.2 wt %, the content of the chiral agent in the raw material composition is 3.2 wt %; the content of the room temperature phosphorescent polymer in the raw material composition is 1.5 wt %.

2. The method according to claim 1, characterized in that In the step 1, the solvent is evaporated by pouring the mixed solution into a glass culture dish and evaporating the mixture at room temperature for 4-6 hours to obtain a cholesteric liquid crystal elastomer room temperature phosphorescent oligomer.

3. The method according to claim 1, characterized in that The specific operations of step three are: Tension was applied to both ends of the CLCE-RTP film, and the length of the stretching was 0-100% of the CLCE-RTP film. As the stretching length increased, the photon bandgap shifted to the blue, and the structural color of the film continuously transitioned from red to green and finally to blue. At the same time, the circularly polarized phosphorescence asymmetry factor g lum As the stretching length increases, it gradually becomes lower and the wavelength blue-shifts; when the tension is removed, as the film length shrinks, the structural color of the film transitions from blue to green and finally to red. g lum Gradually becomes higher and the wavelength redshifts.

4. The method according to claim 1, characterized in that When the room temperature phosphorescent polymer is P3, the circularly polarized phosphorescence asymmetry factor can be achieved in the CLCE-RTP film. g lum Dynamically reversible regulation between 0.15 and 0.

8.

5. The method according to claim 3, characterized in that: When the room temperature phosphorescent polymer is P2, the circularly polarized phosphorescence asymmetry factor can be achieved in the CLCE-RTP film. g lum Dynamically reversible regulation between 0.02 and 0.

8.

6. The method according to claim 3, characterized in that When the room temperature phosphorescent polymer is P1, the circularly polarized phosphorescence asymmetry factor can be achieved in the CLCE-RTP film. g lum Dynamically reversible regulation between 0.12 and 0.4.

Images