A functionalized liquid crystal polymer dimming film and its preparation method

Abstract

This invention discloses a functionalized liquid crystal polymer dimming film and its preparation method, belonging to the technical field of functional liquid crystal materials and their preparation. This invention solves the problems of existing dimming films, such as complex structure, slow response, and susceptibility to outdoor contamination. The invention involves forming a micron-scale conical or columnar surface structure on the surface of a liquid crystal polymer film through laser etching, followed by surface modification with a modifier, resulting in superhydrophobic properties (static contact angle greater than 150°, roll-off angle less than 10°). Simultaneously, it exhibits significant light or heat stimulation response characteristics, undergoing deformation within a short time (<1 min), leading to changes in the surface microstructure and thus altering the film's transmittance.

Description

Technical Field

[0001] This invention relates to a functionalized liquid crystal polymer dimming film and its preparation method, belonging to the technical field of functional liquid crystal materials and their preparation. Background Technology

[0002] As a functional material capable of dynamically controlling photothermal performance, dimming films have significant application value in fields such as building energy conservation, transportation, and aerospace. Currently, most mainstream dimming film technologies rely on liquid media or multilayer composite structures to achieve optical switching, generally facing technical challenges such as slow response speed and insufficient environmental stability. Especially in outdoor applications, long-term exposure to complex environmental factors such as rain and dust can easily lead to optical performance degradation, severely impacting service life.

[0003] Currently, superhydrophobic surface technology offers a new approach to solving the environmental adaptability problem of dimming films due to its unique self-cleaning properties. However, traditional superhydrophobic coatings (such as SiO2 nanoparticle modified coatings) have significant limitations in dimming film applications: on the one hand, it is difficult to achieve dynamic wetting control of light / heat response; on the other hand, the complex preparation process makes high-precision processing difficult. Therefore, it is essential to provide a liquid crystal polymer dimming film with self-cleaning function. Summary of the Invention

[0004] To address the problems of existing dimming films being complex in structure, slow in response, and easily contaminated outdoors, this invention provides a functionalized liquid crystal polymer dimming film and its preparation method.

[0005] The technical solution of this invention: One objective of this 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 make the surface of the liquid crystal polymer film have a micron-sized conical or columnar structure, and then cleaned and dried at room temperature. (2) After the etched liquid crystal polymer film is subjected to plasma treatment, it is immersed in a modifier solution for surface modification treatment, and then dried to obtain a functionalized liquid crystal polymer dimming film.

[0006] Further specifying, (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.

[0007] Furthermore, the mass percentage of azobenzene liquid crystal in the azobenzene liquid crystal polymer film is 30-100%.

[0008] Furthermore, the mass percentage of fluorescent dye in the fluorescent dye-doped liquid crystal polymer film is 0.5%-2%.

[0009] Furthermore, the mass percentage of carbon nanotubes in the carbon nanotube-doped liquid crystal polymer film is 0.01-10%.

[0010] Furthermore, the mass percentage of graphene in the graphene-doped liquid crystal polymer film is 0.01-10%.

[0011] Further, the laser etching 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 pass of 4-9 passes.

[0012] Further specifying, the laser etching conditions in (1) are: power of 0.18W, frequency of 1000KHz, scanning speed of 1000mm / s, processing path of two sets of mutually perpendicular parallel straight lines, line spacing between adjacent parallel straight lines of 10μm, and processing pass of 5 passes.

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

[0014] Further specifying, the laser etching conditions in (1) are: power of 0.35W, frequency of 1000KHz, scanning speed of 1000mm / s, processing path of two sets of mutually perpendicular parallel straight lines, line spacing between adjacent parallel straight lines of 10μm, and processing pass of 6 passes.

[0015] Further specifying, (1) the laser used for laser etching is a picosecond laser with a wavelength of 355nm or a femtosecond laser with a wavelength of 1080nm.

[0016] Further, the laser etching spot radius in (1) is 5-7 μm.

[0017] Further specify that (1) the liquid crystal polymer film after laser etching is ultrasonically cleaned in anhydrous ethanol for 5-10 min.

[0018] Further specifying, the modifier in (2) is perfluoropolyether PFPE, octadecyltrichlorosilane OTS, perfluorooctane sulfonyl compound PFOS or linear polydimethylsiloxane LPDMS.

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

[0020] Beneficial effects: (1) In this invention, a micron-sized conical or columnar surface structure is formed on the surface of a liquid crystal polymer film by laser etching. After surface modification with a modifier, the film obtains superhydrophobic properties (static contact angle greater than 150° and roll-off angle less than 10°). It also has significant light or heat stimulation response characteristics and deforms in a short time (<1min), resulting in changes in the surface microstructure and thus changes in the film transmittance.

[0021] (2) The laser etching method used in this invention can form a film in one step, with fast processing speed, simple steps, and high efficiency. Moreover, the superhydrophobic liquid crystal polymer dimming film prepared does not require complex components and can achieve multifunctional coupling on a single film. Attached Figure Description

[0022] Figure 1 Microstructure morphology of the surface of the functionalized liquid crystal polymer dimming film prepared in Example 1; Figure 2 A static contact angle diagram of the surface of the functionalized liquid crystal polymer dimming film prepared in Example 1; Figure 3 The microstructure morphology of the surface of the functionalized liquid crystal polymer dimming film prepared in Example 2; Figure 4 Static contact angle diagram of the surface of the functionalized liquid crystal polymer dimming film prepared in Example 2; Figure 5 A schematic diagram of the ultraviolet light response of the functionalized liquid crystal polymer dimming film prepared in Example 2; Figure 6 The graph shows the changes in ultraviolet light response transmittance and haze of the functionalized liquid crystal polymer dimming film prepared in Example 2. Figure 7 The graph shows the change in hydrophobic angle of the functionalized liquid crystal polymer dimming film prepared in Example 2 under ultraviolet light response. Figure 8 Microstructure morphology of the surface of the functionalized liquid crystal polymer dimming film prepared in Example 3; Figure 9 Static contact angle diagram of the surface of the functionalized liquid crystal polymer dimming film prepared in Example 3; Figure 10 The graph shows the change in thermal response transmittance of the functionalized liquid crystal polymer dimming film prepared in Example 3. Figure 11 The image shows the microstructure morphology of the surface of the functionalized liquid crystal polymer dimming film prepared for Comparative Example 1. Figure 12 Static contact angle diagram of the surface of the functionalized liquid crystal polymer dimming film prepared for Comparative Example 1; Figure 13 The image shows the microstructure morphology of the surface of the functionalized liquid crystal polymer dimming film prepared for Comparative Example 2. Figure 14 The static contact angle diagram of the surface of the functionalized liquid crystal polymer dimming film prepared for Comparative Example 2. Detailed Implementation

[0023] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0024] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art may make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0025] Secondly, the term "one embodiment" or "embodiment" as used 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 different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

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

[0027] Example 1: Step 1: Perform ultrasonic cleaning on the surface of the liquid crystal polymer film to obtain a clean and smooth liquid crystal polymer film. The liquid crystal polymer film was prepared as follows: 1 g of RM257 was dissolved in 750 μL of DMF at 80°C. Then, 0.17 g of EDDET, 0.15 g of PETMP, and 0.056 g of photoinitiator I651 were added and thoroughly mixed. After cooling to room temperature, 0.003 g of DPA (pre-dissolved in toluene, with a DPA to toluene mass ratio of 1:20) was added to the mixture. The mixture was uniformly poured into a 200 μm polytetrafluoroethylene mold, and the mold was then placed in an oven at 80°C for 24 h to allow for Michael addition reaction. After demolding, the film was uniaxially stretched to 1.5 times its original length to induce liquid crystal molecule alignment, and simultaneously photopolymerization was carried out under 365 nm ultraviolet light.

[0028] Step Two: Place the liquid crystal polymer film cleaned in Step One onto the stage of a 355nm picosecond laser. Set the laser spot radius to 10μm, output power to 0.18W, repetition rate to 1000kHz, scanning speed to 1000mm / s, and the number of passes to 5. The laser processing path consists of two sets of mutually perpendicular parallel straight lines with a spacing of 10μm between adjacent parallel lines. After determining the laser parameters and processing path, turn on the picosecond laser to ablate the liquid crystal polymer surface, resulting in a micron-scale conical or columnar structure.

[0029] Step 3: Ultrasonically clean the laser-etched liquid crystal polymer film in anhydrous ethanol for 10 minutes, and then let it air dry 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 activated by plasma treatment at a power of 30W for 2 minutes, then it is immersed in a 1% PFPE hexane solution for 15 seconds, and then dried in an oven at 130℃ for 30 minutes to obtain a functionalized liquid crystal polymer dimming film.

[0031] The microstructure of the functionalized liquid crystal polymer dimming film prepared in this embodiment was characterized, and the SEM images are shown below. Figure 1 As shown, a conical microstructure was successfully etched onto the surface of a liquid crystal polymer film using laser processing.

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

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

[0034] Step Two: Place the liquid crystal polymer film cleaned in Step One onto the stage of a 355nm picosecond laser. Set the laser spot radius to 10μm, output power to 0.28W, repetition rate to 1000kHz, scanning speed to 1000mm / s, and the number of passes to 4. The laser processing path consists of two sets of mutually perpendicular parallel straight lines with a spacing of 12μm between adjacent parallel lines. After determining the laser parameters and processing path, turn on the picosecond laser to ablate the liquid crystal polymer surface, resulting in a micron-scale conical or columnar structure.

[0035] Step 3: Ultrasonically clean the laser-etched liquid crystal polymer film in anhydrous ethanol for 10 minutes, and then let it air dry at room temperature.

[0036] Step 4: Perform OTS modification 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 activated by plasma treatment at a power of 30W for 2 minutes, then it is immersed in a 2% OTS toluene solution for 30 minutes, then the surface is cleaned with anhydrous ethanol, and then dried in an oven at 120℃ for 30 minutes to obtain a functionalized liquid crystal polymer dimming film.

[0037] The microstructure of the functionalized liquid crystal polymer dimming film prepared in this embodiment was characterized, and the SEM images are shown below. Figure 3 As shown, a conical microstructure was successfully etched onto the surface of a liquid crystal polymer film using laser processing.

[0038] The static contact angle of the functionalized liquid crystal polymer dimming film surface prepared in this embodiment is as follows: Figure 4 As shown, the static contact angle is 157.5°, exhibiting superhydrophobic properties. The roll-off angle is 9.5°.

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

[0040] Further characterization of the transmittance of the functionalized liquid crystal polymer dimming film before and after ultraviolet light irradiation was performed, and the results are as follows: Figure 6 As shown, 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 changes in hydrophobicity of functionalized liquid crystal polymer dimming films before and after ultraviolet light irradiation were compared. Figure 7 This is a graph showing the change in hydrophobic angle in response to ultraviolet light after repeated exposures. The 0.5, 1.5, 2.5, and 3.5 times represent before ultraviolet light exposure (i.e., before irradiation), and the 1st, 2nd, and 3rd times represent after ultraviolet light exposure (i.e., after irradiation). Figure 7 It is known that after being stimulated by ultraviolet light, the hydrophobic angle of the functionalized liquid crystal polymer dimming film surface will decrease by about 15°, and the hydrophobic angle will return to the initial state after the structure is restored.

[0042] Example 3: Step 1: The surface of the carbon nanotube-doped liquid crystal polymer film is ultrasonically cleaned to obtain a clean and smooth liquid crystal polymer film. The preparation method of carbon nanotube-doped liquid crystal polymer film is as follows: 0.59 g of RM257 and 0.4 g of RM82 were dissolved in 750 μL of LDM at 80°C. Then, 0.17 g of EDDET, 0.15 g of PETMP, and 0.056 g of photoinitiator I651 were added and thoroughly mixed. 2 wt% carbon nanotubes were doped as photothermal responsive fillers. After cooling to room temperature, 0.003 g of DPA (pre-dissolved in toluene, with a DPA to toluene mass ratio of 1:20) was added to the mixture. The mixture was uniformly poured into a 200 μm polytetrafluoroethylene mold, and the mold was then placed in an oven at 80°C for 24 h to carry out the Michael addition reaction. After demolding, the film was uniaxially stretched to 1.5 times its original length to induce liquid crystal molecule alignment, and simultaneously photopolymerization was carried out under 365 nm ultraviolet light.

[0043] Step Two: Place the liquid crystal polymer film cleaned in Step One onto the stage of a 1080nm femtosecond laser. Set the laser spot radius to 10μm, output power to 0.35W, repetition rate to 1000kHz, scanning speed to 1000mm / s, and the number of passes to 6. The laser processing path consists of two sets of mutually perpendicular parallel straight lines with a spacing of 10μm between adjacent parallel lines. After determining the laser parameters and processing path, turn on the picosecond laser to ablate the liquid crystal polymer surface, resulting in a micron-scale conical or columnar structure.

[0044] Step 3: Ultrasonically clean the laser-etched liquid crystal polymer film in anhydrous ethanol for 10 minutes, and then let it air dry 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 activated by plasma treatment at a power of 30W for 2 minutes, then it is immersed in a 2% PFOS hexane solution for 30 minutes, then the surface is cleaned with anhydrous ethanol, and then dried in an oven at 120℃ for 30 minutes to obtain a functionalized liquid crystal polymer dimming film.

[0046] The microstructure of the functionalized liquid crystal polymer dimming film prepared in this embodiment was characterized, and the SEM images are shown below. Figure 8 As shown, columnar microstructures were successfully etched onto the surface of a liquid crystal polymer film using laser processing.

[0047] The static contact angle of the functionalized liquid crystal polymer dimming film surface prepared in this embodiment is as follows: Figure 9 As shown, the static contact angle is 153.4°, exhibiting superhydrophobic properties. The roll-off angle is 4.8°.

[0048] The photothermal response properties of the functionalized liquid crystal polymer dimming film prepared in this embodiment were characterized. Figure 10 The graph shows the change in photothermal transmittance of the functionalized liquid crystal polymer dimming film. As can be seen from the graph, the transmittance of the liquid crystal polymer film gradually decreases with the increase of infrared light irradiation 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 the output power in step two 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 in Example 2.

[0050] The microstructure of the functionalized liquid crystal polymer dimming film obtained in this comparative example was characterized, and the SEM images are shown below. Figure 11 As shown, the reduced laser power resulted in a shallow processed structure, failing to form surface microstructures such as microcones or micropillars.

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

[0052] Comparative Example 2 The difference between this comparative example and Example 1 is that the output power in step two 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 in Example 1.

[0053] The microstructure of the functionalized liquid crystal polymer dimming film obtained in this comparative example was characterized, and the SEM images are shown below. Figure 13 As shown, the excessively high laser power resulted in severe structural ablation, and the surface microstructure morphology was destroyed.

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

[0055] The above description is only a preferred embodiment of the present invention. Given 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, and some modifications and changes to the present invention should also fall within the protection scope 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 make the surface of the liquid crystal polymer film have a micron-sized conical or columnar structure, and then cleaned and dried at room temperature; 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. (2) After the etched liquid crystal polymer film is subjected to plasma treatment, it is immersed in a modifier solution for surface modification treatment, and then dried to obtain a functionalized liquid crystal polymer dimming film.

2. The preparation method according to claim 1, characterized in that, The laser etching processing conditions are as follows: 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 pass of 4-9 passes.

3. The preparation method according to claim 2, characterized in that, The laser etching conditions are as follows: power of 0.18W, frequency of 1000KHz, scanning speed of 1000mm / s, processing path of two sets of mutually perpendicular parallel straight lines, line spacing between adjacent parallel straight lines of 10μm, and processing pass of 5 times.

4. The preparation method according to claim 2, characterized in that, The laser etching conditions are as follows: power of 0.28W, frequency of 1000KHz, scanning speed of 1000mm / s, processing path of two sets of mutually perpendicular parallel straight lines, line spacing between adjacent parallel straight lines of 12μm, and processing pass of 4 times.

5. The preparation method according to claim 2, characterized in that, The laser etching conditions are as follows: power of 0.35W, frequency of 1000KHz, scanning speed of 1000mm / s, processing path of two sets of mutually perpendicular parallel straight lines, line spacing between adjacent parallel straight lines of 10μm, and processing pass of 6 times.

6. The preparation method according to claim 1, characterized in that, The laser used for the laser etching process is a 355nm picosecond laser or a 1080nm femtosecond laser.

7. The preparation method according to claim 1, characterized in that, The laser etching process has a spot radius of 5-7 μm.

8. The preparation method according to claim 1, characterized in that, The modifier is PFPE, OTS, PFOS, or LPDMS.

9. A functionalized liquid crystal polymer dimming film prepared by the method according to any one of claims 1 to 8, characterized in that, It has light or heat-responsive dimming properties, as well as superhydrophobicity.

Images