Functionalized liquid crystal polymer dimming film and preparation method thereof

Abstract

The invention discloses a functional liquid crystal polymer dimming film and a preparation method thereof, and belongs to the technical field of functional liquid crystal materials and preparation thereof. The problems that an existing dimming film is complex in structure, slow in response and prone to being polluted outdoors are solved. A micron-sized conical or columnar surface structure is formed on the surface of a liquid crystal polymer film through laser etching, and then after surface modification is conducted through a modifier, the super-hydrophobic property (the static contact angle is larger than 150 degrees, and the rolling angle is smaller than 10 degrees) is obtained, meanwhile, the super-hydrophobic liquid crystal polymer film has the remarkable light or thermal stimulation response property, deformation is generated within a short time (smaller than 1 min), and the super-hydrophobic liquid crystal polymer film has the super-hydrophobic property. The surface microstructure is changed, so that the transmittance of the thin film is changed.

Description

Technical Field

[0001] The invention relates to a functionalized liquid crystal polymer dimming film and a preparation method thereof, belonging to the technical field of functional liquid crystal materials and preparation thereof. Background Art

[0002] As a functional material that enables dynamic control of optical and thermal properties, switchable film has significant application value in areas such as building energy conservation, transportation, and aerospace. Currently, mainstream switchable film technologies rely on liquid media or multi-layer composite structures to achieve optical switching, but they generally face technical challenges such as slow response speed and insufficient environmental stability. This is particularly true in outdoor applications, where long-term exposure to complex environmental factors such as rain and dust can easily lead to optical degradation, seriously shortening the film's service life.

[0003] Superhydrophobic surface technology, with its unique self-cleaning properties, offers a new approach to addressing the environmental adaptability challenges of switchable film. However, conventional superhydrophobic coatings (such as those modified with SiO2 nanoparticles) have significant limitations in their application: dynamic wetting control for photo- and thermal-responsiveness is difficult, while complex fabrication processes hinder high-precision processing. Therefore, a liquid crystal polymer switchable film with self-cleaning properties is highly desirable. Summary of the Invention

[0004] In order to solve the problems of the existing dimming film having a complex structure, slow response and susceptibility to outdoor pollution, the present invention provides a functionalized liquid crystal polymer dimming film and a preparation method thereof.

[0005] The technical solution of the present invention: One of the purposes of the present invention is to provide a method for preparing a functionalized liquid crystal polymer dimming film, the method comprising the following steps: (1) The surface of the cleaned liquid crystal polymer film is subjected to laser etching to form a micron-scale conical structure or columnar structure on the surface of the liquid crystal polymer film, and then the film is cleaned and dried at room temperature; (2) The etched liquid crystal polymer film is subjected to plasma treatment and then immersed in a modifier solution for surface modification. After being taken out and dried, a functionalized liquid crystal polymer dimming film is obtained.

[0006] It is further defined that the liquid crystal polymer film in (1) is an azobenzene liquid crystal polymer film, a fluorescent dye-doped liquid crystal polymer film, a carbon nanotube-doped liquid crystal polymer film or a graphene-doped liquid crystal polymer film.

[0007] It is further specified that the mass proportion of azobenzene liquid crystal in the azobenzene liquid crystal polymer film is 30-100%.

[0008] It is further defined that the mass proportion of the fluorescent dye in the fluorescent dye-doped liquid crystal polymer film is 0.5%-2%.

[0009] It is further defined that the mass proportion of carbon nanotubes in the carbon nanotube-doped liquid crystal polymer film is 0.01-10%.

[0010] It is further defined that the mass proportion of graphene in the graphene-doped liquid crystal polymer film is 0.01-10%.

[0011] It is further defined that the laser etching processing conditions in (1) are: power of 0.1-0.7W, frequency of 1000-1200KHz, scanning speed of 1000-1200mm / s, processing path of two sets of mutually perpendicular parallel straight lines, line spacing between adjacent parallel straight lines of 10-15μm, and processing number of passes of 4-9.

[0012] It is further defined that the laser etching processing conditions in (1) are: power of 0.18 W, frequency of 1000 kHz, scanning speed of 1000 mm / s, processing path of two sets of mutually perpendicular parallel straight lines, line spacing between adjacent parallel straight lines of 10 μm, and processing number of 5 times.

[0013] It is further defined that the laser etching processing conditions in (1) are: power of 0.28 W, frequency of 1000 kHz, scanning speed of 1000 mm / s, processing path of two sets of mutually perpendicular parallel straight lines, line spacing between adjacent parallel straight lines of 12 μm, and processing number of 4 passes.

[0014] It is further defined that the laser etching processing conditions in (1) are: power of 0.35 W, frequency of 1000 kHz, scanning speed of 1000 mm / s, processing path of two sets of mutually perpendicular parallel straight lines, line spacing between adjacent parallel straight lines of 10 μm, and processing number of 6 times.

[0015] It is further defined that the laser used in the laser etching process in (1) is a picosecond laser with a wavelength of 355 nm or a femtosecond laser with a wavelength of 1080 nm.

[0016] It is further defined that the spot radius of the laser etching process in (1) is 5-7 μm.

[0017] It is further defined that the liquid crystal polymer film after laser etching in (1) is ultrasonically cleaned in anhydrous ethanol for 5-10 minutes.

[0018] It is further defined that the modifier in (2) is perfluoropolyether PFPE, octadecyltrichlorosilane OTS, perfluorooctanesulfonyl compound PFOS or linear polydimethylsiloxane LPDMS.

[0019] The second purpose of this solution is to provide a functional liquid crystal polymer dimming film prepared by the above method, which has light or heat responsive dimming properties and super hydrophobicity.

[0020] Beneficial effects: (1) The present invention forms a micron-scale conical or columnar surface structure on the surface of a liquid crystal polymer film by laser etching, and then obtains superhydrophobic properties (static contact angle greater than 150°, rolling angle less than 10°) after surface modification with a modifier. At the same time, it also has significant light or heat stimulus response characteristics, causing deformation in a short time (<1 minute), resulting in changes in the surface microstructure, thereby bringing about changes in the transmittance of the film.

[0021] (2) The laser etching method used in the present invention can be formed in one step, with fast processing speed, simple steps and high efficiency. In addition, the prepared super-hydrophobic liquid crystal polymer dimming film does not require complex components and can achieve multifunctional coupling on a thin film. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a microstructure morphology of the surface of the functionalized liquid crystal polymer dimming film prepared in Example 1; Figure 2 This is a static contact angle diagram of the surface of the functionalized liquid crystal polymer dimming film prepared in Example 1; Figure 3 This is a microstructure morphology of the surface of the functionalized liquid crystal polymer dimming film prepared in Example 2; Figure 4 This is a static contact angle diagram of the surface of the functionalized liquid crystal polymer dimming film prepared in Example 2; Figure 5 Schematic diagram of the ultraviolet light response of the functionalized liquid crystal polymer dimming film prepared in Example 2; Figure 6 This is a graph showing the change in transmittance and haze of the functionalized liquid crystal polymer dimming film prepared in Example 2 in response to ultraviolet light; Figure 7 This is a graph showing the change in hydrophobic angle in response to ultraviolet light of the functionalized liquid crystal polymer dimming film prepared in Example 2; Figure 8 This is a microstructure morphology of the surface of the functionalized liquid crystal polymer dimming film prepared in Example 3; Figure 9 This is a static contact angle diagram of the surface of the functionalized liquid crystal polymer dimming film prepared in Example 3; Figure 10 This is a graph showing the thermal response transmittance variation of the functionalized liquid crystal polymer dimming film prepared in Example 3; Figure 11 This is a microstructure morphology of the surface of the functionalized liquid crystal polymer dimming film prepared in Comparative Example 1; Figure 12 This is a static contact angle diagram of the surface of the functionalized liquid crystal polymer dimming film prepared in Comparative Example 1; Figure 13 This is a microstructure morphology of the surface of the functionalized liquid crystal polymer dimming film prepared in Comparative Example 2; Figure 14 This is a static contact angle diagram of the surface of the functionalized liquid crystal polymer dimming film prepared in Comparative Example 2. DETAILED DESCRIPTION

[0023] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0024] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0025] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0026] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods, and instruments used are conventional in the art and can be obtained commercially by those skilled in the art unless otherwise specified.

[0027] Example 1: Step 1: ultrasonically cleaning the surface of the liquid crystal polymer film to obtain a liquid crystal polymer film with a clean and smooth surface; The liquid crystal polymer film was prepared by dissolving 1g of RM257 in 750μL of DMF at 80°C. Subsequently, 0.17g of EDDET, 0.15g of PETMP, and 0.056g of photoinitiator I651 were added and mixed thoroughly. After cooling to room temperature, 0.003g of DPA (pre-dissolved in toluene at a mass ratio of 1:20) was added to the mixture. The mixture was evenly cast into a 200μm polytetrafluoroethylene mold, which was then placed in an oven at 80°C for 24 hours to allow for the Michael addition reaction. After demolding, the film was uniaxially stretched to 1.5 times its original length to induce alignment of the liquid crystal molecules, while simultaneously undergoing photopolymerization under 365nm UV light.

[0028] Step 2: Place the liquid crystal polymer film cleaned in Step 1 on the work surface of a picosecond laser with a wavelength of 355nm. Set the picosecond laser spot radius to 10μm, the output power to 0.18W, the repetition rate to 1000kHz, the scanning speed to 1000mm / s, the number of processing passes to 5, and the laser processing path to two sets of mutually perpendicular parallel lines with a line spacing of 10μm between adjacent parallel lines. After the laser parameters and processing path are determined, turn on the picosecond laser and laser ablate the liquid crystal polymer surface, so that the surface of the liquid crystal polymer is etched with micron-scale cone structures or columnar structures.

[0029] Step 3: The laser-etched liquid crystal polymer film was ultrasonically cleaned in anhydrous ethanol for 10 minutes and then naturally dried at room temperature.

[0030] Step 4: PFPE modification is performed on the surface of the etched liquid crystal polymer film. The specific operation process is as follows: the liquid crystal polymer film with microstructure is treated with plasma at a power of 30W for 2 minutes for surface activation, and then immersed in a 1% mass concentration PFPE hexane solution for 15 seconds. After taking it out, it is dried in a 130°C oven for 30 minutes to obtain a functionalized liquid crystal polymer dimming film.

[0031] The microstructure of the surface of the functionalized liquid crystal polymer dimming film prepared in this embodiment was characterized, and the SEM photos are as follows: Figure 1 As shown, cone-shaped microstructures were successfully etched on the surface of the liquid crystal polymer film by laser processing.

[0032] The static contact angle of the surface of the functionalized liquid crystal polymer dimming film prepared in this embodiment is as follows: Figure 2 As shown, the static contact angle is 151.2°, which has superhydrophobic properties.

[0033] Example 2: Step 1: ultrasonically cleaning the surface of the azobenzene liquid crystal polymer film to obtain a liquid crystal polymer film with a clean and smooth surface; The azobenzene liquid crystal polymer film was prepared as follows: 0.2g RM257 and 0.059g D6AB were dissolved in 250μL DMF at 80°C. Subsequently, 0.045g EDDET, 0.04g PETMP, and 0.0124g photoinitiator I784 were added and mixed thoroughly. After cooling to room temperature, 0.0008g DPA (pre-dissolved in toluene at a mass ratio of 1:20) was added to the mixture. The mixture was evenly cast into a 200μm polytetrafluoroethylene mold, which was then placed in an oven at 80°C for 24 hours to allow for the Michael addition reaction. After demolding, the film was uniaxially stretched to 1.5 times its original length to induce alignment of the liquid crystal molecules, while simultaneously undergoing photopolymerization under 455nm UV light.

[0034] Step 2: Place the liquid crystal polymer film cleaned in Step 1 on the work surface of a picosecond laser with a wavelength of 355nm. Set the picosecond laser spot radius to 10μm, the output power to 0.28W, the repetition rate to 1000kHz, the scanning speed to 1000mm / s, the number of processing passes to 4, and the laser processing path to two sets of mutually perpendicular parallel lines with a line spacing of 12μm between adjacent parallel lines. After the laser parameters and processing path are determined, turn on the picosecond laser and laser ablate the liquid crystal polymer surface, so that the surface of the liquid crystal polymer is etched with micron-scale cone structures or columnar structures.

[0035] Step 3: The laser-etched liquid crystal polymer film was ultrasonically cleaned in anhydrous ethanol for 10 minutes and then naturally dried at room temperature.

[0036] Step 4: Perform OTS modification on the surface of the etched liquid crystal polymer film. The specific operation process is: treat the liquid crystal polymer film with microstructure with plasma at a power of 30W for 2 minutes for surface activation, and then soak it in a 2% OTS toluene solution for 30 minutes. After taking it out, clean the surface with anhydrous ethanol, and then dry it in an oven at 120°C for 30 minutes to obtain a functionalized liquid crystal polymer dimming film.

[0037] The microstructure of the surface of the functionalized liquid crystal polymer dimming film prepared in this embodiment was characterized, and the SEM photos are as follows: Figure 3 As shown, cone-shaped microstructures were successfully etched on the surface of the liquid crystal polymer film by laser processing.

[0038] The static contact angle of the surface of the functionalized liquid crystal polymer dimming film prepared in this embodiment is as follows: Figure 4 As shown in the figure, the static contact angle is 157.5°, indicating superhydrophobicity, and the sliding angle is 9.5°.

[0039] The UV response performance of the functionalized liquid crystal polymer dimming film prepared in this example was characterized. Figure 5 Schematic diagram of ultraviolet light response, where (a) is before ultraviolet light irradiation, and (b) is after ultraviolet light irradiation. By comparing Figure (a) and Figure (b), it can be seen that ultraviolet light stimulation can cause the film to shrink and wrinkle.

[0040] The transmittance of the functionalized liquid crystal polymer dimming film before and after UV irradiation was further characterized. Figure 6 As shown in the figure, after being stimulated by ultraviolet light, the transmittance of the functionalized liquid crystal polymer dimming film decreased by 12% and the haze increased by 30%.

[0041] The hydrophobicity changes of functionalized liquid crystal polymer dimming film before and after UV irradiation were compared. Figure 7 The graph of the hydrophobic angle change in response to UV light is repeated multiple times, where 0.5, 1.5, 2.5 and 3.5 times represent the period before UV light irradiation, and 1, 2 and 3 times represent the period after UV light irradiation. Figure 7 It can be seen that after being stimulated by ultraviolet light, the hydrophobic angle on the surface of the functionalized liquid crystal polymer dimming film will decrease by about 15°, and the hydrophobic angle returns to its initial state after the structure is restored.

[0042] Example 3: Step 1: ultrasonically cleaning the surface of the carbon nanotube-doped liquid crystal polymer film to obtain a liquid crystal polymer film with a clean and smooth surface; The carbon nanotube-doped liquid crystal polymer film was prepared as follows: 0.59g of RM257 and 0.4g of RM82 were dissolved in 750μL of DMF at 80°C. Subsequently, 0.17g of EDDET, 0.15g of PETMP, and 0.056g of photoinitiator I651 were added and thoroughly mixed. 2wt% of carbon nanotubes were doped as a photothermal responsive filler. After cooling to room temperature, 0.003g of DPA (pre-dissolved in toluene at a mass ratio of 1:20) was added to the mixture. The mixture was evenly cast into a 200μm polytetrafluoroethylene mold, which was then placed in an oven at 80°C for 24 hours to allow for Michael addition reaction. After demolding, the film was uniaxially stretched to 1.5 times its original length to induce alignment of the liquid crystal molecules, while photopolymerization was carried out under 365nm UV light.

[0043] Step 2: Place the liquid crystal polymer film cleaned in Step 1 on the work surface of a femtosecond laser with a wavelength of 1080nm. Set the picosecond laser spot radius to 10μm, the output power to 0.35W, the repetition rate to 1000kHz, the scanning speed to 1000mm / s, the number of processing passes to 6, and the laser processing path to two sets of mutually perpendicular parallel lines with a line spacing of 10μm between adjacent parallel lines. After the laser parameters and processing path are determined, turn on the picosecond laser and laser ablate the liquid crystal polymer surface, so that the surface of the liquid crystal polymer is etched with micron-scale conical or columnar structures.

[0044] Step 3: The laser-etched liquid crystal polymer film was ultrasonically cleaned in anhydrous ethanol for 10 minutes and then naturally dried at room temperature.

[0045] Step 4: PFOS modification is performed on the surface of the etched liquid crystal polymer film. The specific operation process is as follows: the liquid crystal polymer film with microstructure is treated with plasma at a power of 30W for 2 minutes for surface activation, and then it is immersed in a 2% mass concentration of PFOS hexane solution for 30 minutes. After taking it out, the surface is cleaned with anhydrous ethanol, and then dried in an oven at 120°C for 30 minutes to obtain a functionalized liquid crystal polymer dimming film.

[0046] The microstructure of the surface of the functionalized liquid crystal polymer dimming film prepared in this embodiment was characterized, and the SEM photos are as follows: Figure 8 As shown, columnar microstructures were successfully etched on the surface of the liquid crystal polymer film by laser processing.

[0047] The static contact angle of the surface of the functionalized liquid crystal polymer dimming film prepared in this embodiment is as follows: Figure 9 As shown in the figure, the static contact angle is 153.4°, indicating superhydrophobicity, and the sliding angle is 4.8°.

[0048] The photothermal response performance of the functionalized liquid crystal polymer dimming film prepared in this example was characterized. Figure 10 This is a diagram showing the transmittance change of the functionalized liquid crystal polymer dimming film in response to light and heat. As can be seen from the figure, the transmittance of the liquid crystal polymer film gradually decreases with the increase of infrared light exposure time. The infrared light wavelength is 808nm and the power is 200mW.

[0049] Comparative Example 1 The difference between this comparative example and Example 2 is that in step 2, the output power is 0.05W, the repetition frequency is 8000KHz, the scanning speed is 1000mm / s, and the number of processing passes is 5; the remaining process steps and parameter settings are the same as those in Example 2.

[0050] The microstructure of the functionalized liquid crystal polymer dimming film obtained in this comparative example was characterized, and the SEM photos are as follows: Figure 11 As shown in FIG, the reduced laser power resulted in the processed structure being too shallow, and no surface microstructure of microcones or microcolumns was formed.

[0051] The static contact angle of the surface of the functionalized liquid crystal polymer dimming film prepared in this comparative example is as follows: Figure 12 As shown in the figure, the static contact angle is 99°, which does not have superhydrophobic properties.

[0052] Comparative Example 2 The difference between this comparative example and Example 1 is that in step 2, the output power is 2.38W, the repetition frequency is 8000KHz, the scanning speed is 1000mm / s, and the number of processing passes is 5; the remaining process steps and parameter settings are the same as those in Example 1.

[0053] The microstructure of the functionalized liquid crystal polymer dimming film obtained in this comparative example was characterized, and the SEM photos are as follows: Figure 13 As shown in the figure, the structure is severely ablated due to the high laser power, and the surface microstructure is destroyed.

[0054] The static contact angle of the surface of the functionalized liquid crystal polymer dimming film prepared in this comparative example is as follows: Figure 14 As shown in FIG, the static contact angle is 119°, which does not have superhydrophobic properties.

[0055] The above description is only a preferred embodiment of the present invention. In view of the fact that those skilled in the art can make appropriate changes and modifications to the above embodiments, the present invention is not limited to the specific embodiments described above. Some modifications and changes to the present invention should also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a functionalized liquid crystal polymer dimming film, characterized in that: include: (1) The surface of the cleaned liquid crystal polymer film is subjected to laser etching to form a micron-scale conical structure or columnar structure on the surface of the liquid crystal polymer film, and then the film is cleaned and dried at room temperature; (2) The etched liquid crystal polymer film is subjected to plasma treatment and then immersed in a modifier solution for surface modification. After being taken out and dried, a functionalized liquid crystal polymer dimming film is obtained.

2. The preparation method according to claim 1, characterized in that (1) The liquid crystal polymer film is an azobenzene liquid crystal polymer film, a fluorescent dye-doped liquid crystal polymer film, a carbon nanotube-doped liquid crystal polymer film or a graphene-doped liquid crystal polymer film.

3. The preparation method according to claim 1, characterized in that (1) The laser etching processing conditions are: power of 0.1-0.7W, frequency of 1000-1200KHz, scanning speed of 1000-1200mm / s, processing path of two sets of mutually perpendicular parallel straight lines, the line spacing between adjacent parallel straight lines is 10-15μm, and the number of processing passes is 4-9.

4. The preparation method according to claim 3, characterized in that (1) The laser etching processing conditions are as follows: power of 0.18 W, frequency of 1000 kHz, scanning speed of 1000 mm / s, processing path of two sets of mutually perpendicular parallel straight lines, line spacing between adjacent parallel straight lines of 10 μm, and processing number of 5 times.

5. The preparation method according to claim 3, characterized in that (1) The laser etching processing conditions are as follows: power of 0.28 W, frequency of 1000 kHz, scanning speed of 1000 mm / s, processing path of two sets of mutually perpendicular parallel straight lines, line spacing between adjacent parallel straight lines of 12 μm, and processing number of 4 passes.

6. The preparation method according to claim 3, characterized in that (1) The laser etching processing conditions are as follows: power of 0.35 W, frequency of 1000 kHz, scanning speed of 1000 mm / s, processing path of two sets of mutually perpendicular parallel straight lines, line spacing between adjacent parallel straight lines of 10 μm, and processing number of 6 times.

7. The preparation method according to claim 1, characterized in that (1) The laser used in the laser etching process is a picosecond laser with a wavelength of 355 nm or a femtosecond laser with a wavelength of 1080 nm.

8. The preparation method according to claim 1, characterized in that (1) The spot radius of the laser etching process is 5-7 μm.

9. The preparation method according to claim 1, characterized in that (2) The modifier is PFPE, OTS, PFOS or LPDMS.

10. A functionalized liquid crystal polymer dimming film prepared by the method according to any one of claims 1 to 9, characterized in that: It has light- or heat-responsive dimming properties and superhydrophobicity.

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