Polymer dispersed liquid crystal film based on cellulose nanocrystal doping and preparation method thereof

Abstract

The invention relates to the technical field of liquid crystal thin films, and discloses a polymer dispersed liquid crystal thin film based on cellulose nanocrystal doping and a preparation method of the polymer dispersed liquid crystal thin film. The photoinitiator comprises the following components in parts by weight: 50-70 parts of a liquid crystal material, 20-35 parts of a matrix polymer, 0.5-2 parts of a photoinitiator, 1-5 parts of a cellulose nanocrystal composite material and 5-15 parts of a solvent. The invention further provides a preparation method of the polymer dispersed liquid crystal film based on cellulose nanocrystal doping. The method comprises the following steps: S1, preparing a cellulose nanocrystal composite solution; taking the cellulose nanocrystal composite material, and dispersing the cellulose nanocrystal composite material in a solvent; by introducing the surface-modified cellulose nanocrystal and nitrogen-doped titanium dioxide composite material into a polymer matrix, the effect of optimizing liquid crystal microdroplet distribution is achieved. Compared with a liquid crystal film which does not use the composite material, the liquid crystal film solves the problems of non-uniform liquid crystal dispersion and unstable photoelectric switching performance, and ensures more uniform optical regulation and higher light transmittance.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid crystal thin films, and specifically to a polymer dispersed liquid crystal thin film doped with cellulose nanocrystals and a preparation method thereof. Background Art

[0002] Polymer dispersed liquid crystal films (PDLCs) are widely used in fields such as smart windows, adjustable displays, and electro-optical modulators due to their excellent electro-optical regulation properties. PDLCs achieve the switching between transparency and fogginess by applying an electric field, thus having adjustable optical properties and being able to regulate the light transmittance and haze to meet the requirements of various scenarios. However, the existing PDLC technologies still have the following deficiencies.

[0003] In traditional PDLC systems, the dispersion uniformity of liquid crystal microdroplets is poor. Especially when the compatibility between the matrix polymer and the liquid crystal material is poor, the liquid crystal microdroplets tend to aggregate or be unevenly distributed. This not only leads to unstable electro-optical switching performance of the film but also affects the transparency and haze regulation ability of the film, limiting its performance in high-precision applications. For example, in scenarios such as smart windows, PDLC films with poor optical uniformity have a poor visual experience, and the optical performance during the switching process is not precise enough to meet the requirements of high-precision regulation effects.

[0004] The polymer matrices in the existing technologies usually lack sufficient mechanical strength and toughness. Especially under high humidity and high temperature conditions, the performance of the films is prone to decline. Traditional PDLC films often have microcracks, fractures, or deformations due to their unstable mechanical structures, thus affecting their long-term electro-optical performance and service life.

[0005] There are also certain limitations in the low-voltage driving ability of the existing PDLC films. In order for PDLC films to respond efficiently and switch quickly, low-voltage driving ability is a crucial technical indicator. However, traditional PDLC films often require a relatively high voltage to start and switch, and the response time is long. This not only increases energy consumption but also reduces the flexibility and adaptability of the devices. Summary of the Invention

[0006] Aiming at the deficiencies of the existing technologies, the present invention provides a polymer dispersed liquid crystal film doped with cellulose nanocrystals and a preparation method thereof, which solves the problems of insufficient electro-optical performance, mechanical strength, low-voltage driving ability, and weather resistance of the existing polymer dispersed liquid crystal films.

[0007] To achieve the above objectives, the present invention is realized through the following technical solutions: A polymer dispersed liquid crystal film doped with cellulose nanocrystals, comprising the following components; 50 - 70 parts of liquid crystal material, 20 - 35 parts of matrix polymer, 0.5 - 2 parts of photoinitiator, 1 - 5 parts of cellulose nanocrystal composite material, and 5 - 15 parts of solvent.

[0008] Preferably, the matrix polymer includes a low refractive index monomer, a prepolymer, and a hydrophobic monomer.

[0009] Preferably, the prepolymer is a low-viscosity aromatic monoacrylate; The low refractive index monomer is isononyl acrylate; The hydrophobic monomer is isobornyl methacrylate.

[0010] Preferably, the liquid crystal material is E7 liquid crystal.

[0011] Preferably, the photoinitiator is 1-hydroxy-cyclohexyl-phenyl ketone.

[0012] Preferably, the cellulose nanocrystal composite material is surface-modified cellulose nanocrystals, the surface of which is modified by a silane coupling agent KH560 and loaded with nitrogen-doped titanium dioxide.

[0013] Preferably, the particle size of the nitrogen-doped titanium dioxide is 3-10 nm.

[0014] A method for preparing a polymer-dispersed liquid crystal thin film based on cellulose nanocrystal doping includes the following steps; S1. Prepare a cellulose nanocrystal composite solution; take the cellulose nanocrystal composite material, disperse it in a solvent, stir for 120-180 min, and perform ultrasonic treatment for 3-5 h; S2. Mix the polymer and the liquid crystal material; take the matrix polymer, add the liquid crystal material, and stir at 500-800 rpm for 30-60 min to obtain a mixed solution; S3. Disperse the cellulose nanocrystal composite material; gradually add the obtained dispersion liquid to the mixed solution, continue to stir for 30-60 min, and perform ultrasonic dispersion for 3-5 h; S4. Prepare the thin film; evenly spread spacers with a particle size of 8-12 µm on the ITO glass substrate, drop 4-6 µL of the mixed solution, and cover it with another piece of ITO glass; S5. UV curing; perform pre-curing for 30-60 s at 8-12 mW / cm 2 and then perform complete curing for 90-180 s at 12-18 mW / cm 2 to form a polymer-dispersed liquid crystal thin film.

[0015] Preferably, the spacer in step S4 is polymethyl methacrylate.

[0016] Preferably, the solvent in step S1 includes anhydrous ethanol, acetone, or cyclohexane.

[0017] The present invention provides a polymer-dispersed liquid crystal film doped with cellulose nanocrystals and a preparation method thereof. It has the following beneficial effects: 1. By introducing a surface-modified cellulose nanocrystal and nitrogen-doped titanium dioxide composite material into the polymer matrix, the present invention achieves the effect of optimizing the distribution of liquid crystal microdroplets. Compared with the liquid crystal film without using such a composite material, it solves the problems of uneven liquid crystal dispersion and unstable optoelectronic switching performance, ensuring more uniform optical regulation and higher light transmittance.

[0018] 2. By doping with the CNC composite material, the present invention improves the response speed of the PDLC film, achieving the technical effect of quickly switching between the transparent state and the fog state at a low voltage. Compared with traditional materials, the present invention solves the problems of long response time and high energy consumption, providing a more energy-saving and rapid solution for applications such as intelligent windows that quickly adjust the light transmittance.

[0019] 3. By adopting a mixed solvent system, including a mixed solvent of anhydrous ethanol and cyclohexane, the present invention solves the problems of uneven dispersion and unstable solvent evaporation in the preparation process of the liquid crystal film using a traditional single solvent system. Through this innovative technical solution, the dispersibility of the cellulose nanocrystal composite material in the matrix and the overall stability of the film are significantly improved. Compared with traditional technologies, the film of the present invention maintains better optoelectronic performance and weather resistance under long-term environmental changes.

[0020] 4. By doping with nitrogen-doped titanium dioxide, the present invention significantly reduces the threshold voltage of the film and improves the response speed. Compared with the PDLC film without using nitrogen-doped titanium dioxide in the prior art, the present invention solves the problems of high threshold voltage and slow response in the prior art by reducing the electric field shielding effect and accelerating the alignment of liquid crystal molecules, enabling the film to work efficiently at a low voltage, improving its energy-saving performance and dimming speed, and adapting to more application scenarios driven by low voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a flowchart of the method of the present invention; DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0023] Please refer to the attached Figure 1 ; Example 1: Preparation of a standard PDLC film; In this embodiment, a standard cellulose nanocrystal-doped PDLC film is prepared to optimize the liquid crystal microdroplet structure and improve the optoelectronic switching performance.

[0024] 1. Material ratio; Liquid crystal material (E7): 60 parts Matrix polymer (acrylate monomer mixture): 30 parts Low refractive index monomer (INAA): 8 parts Prepolymer (low-viscosity aromatic monoacrylate): 12 parts Hydrophobic monomer (IBOMA): 10 parts Photoinitiator (PI184): 1 part Cellulose nanocrystal composite material (CNC-KH560-N-TiO2): 3 parts Solvent (anhydrous ethanol): 6 parts 2. Preparation steps; Preparation of cellulose nanocrystal dispersion; Add 3 parts of CNC composite material to 6 parts of anhydrous ethanol, stir on a magnetic stirrer for 150 min, and then perform ultrasonic treatment for 4 h to obtain a uniform nanodispersion.

[0025] Mixing of polymer and liquid crystal material; Take 30 parts of polymer monomer mixture, add 60 parts of E7 liquid crystal, and stir at 700 rpm for 45 min to form a uniform mixing system.

[0026] Doping of cellulose nanocrystals; Slowly drop the CNC dispersion in step (1) into the liquid crystal-polymer mixing system, continue stirring for 45 min, and then perform ultrasonic dispersion for 4 h to ensure uniform distribution of CNC.

[0027] Film preparation; Sprinkle 10 µm PMMA spacers on the ITO glass substrate, drop 4 µL of the mixed solution, and then cover with another piece of ITO glass to form a liquid crystal layer.

[0028] UV curing; Under UV lamp irradiation, pre-cure for 45 s at 9 mW / cm 2 and then completely cure for 120 s at 15 mW / cm 2 to form a stable PDLC film.

[0029] Example 2: Enhanced PDLC, optimizing mechanical strength; In this embodiment, the matrix formulation is adjusted to make the PDLC system more stable and improve durability.

[0030] 1. Material ratio; Liquid crystal material (E7): 55 parts Matrix polymer: 35 parts Low refractive index monomer (INAA): 6 parts Prepolymer (low-viscosity aromatic monoacrylate): 15 parts Hydrophobic monomer (IBOMA): 14 parts Photoinitiator (PI184): 1.2 parts Cellulose nanocrystal composite (CNC-KH560-N-TiO2): 4 parts Solvent (anhydrous ethanol + acetone 1:1): 7 parts 2. Preparation steps; Preparation of cellulose nanocrystal solution; 4 parts of CNC composite are dissolved in 7 parts of anhydrous ethanol-acetone mixed solvent, stirred for 160 min, and ultrasonicated for 4.5 h.

[0031] Mixing of liquid crystal and polymer; Take 35 parts of matrix polymer, add 55 parts of E7 liquid crystal, and stir at 650 rpm for 50 min.

[0032] CNC doping; The dispersion is slowly added, stirring is continued for 50 min, and then ultrasonic dispersion is carried out for 4 h.

[0033] Film preparation; Using 10 µm SiO2 microsphere spacers, 4 µL is dropped, and another ITO glass is covered.

[0034] UV curing; UV pre-curing at 10 mW / cm 2 , for 50 s, complete curing at 16 mW / cm 2 , for 150 s.

[0035] Example 3: Low-voltage driven PDLC, improving response speed Optimize the dielectric response of the liquid crystal and improve the low-voltage driving ability.

[0036] 1. Material ratio; Liquid crystal material (E7): 58 parts Matrix polymer: 32 parts Low refractive index monomer (INAA): 10 parts Prepolymer (low-viscosity aromatic monoacrylate): 12 parts Hydrophobic monomer (IBOMA): 10 parts Photoinitiator (PI184): 1.0 part Cellulose nanocrystal composite (CNC-KH560-N-TiO2): 5 parts Solvent (cyclohexane): 7 parts 2. Preparation steps; Preparation of cellulose nanocrystal solution: 5 parts of CNC composite are dissolved in 7 parts of cyclohexane, stirred for 180 min, and ultrasonicated for 5 h.

[0037] Mixing of polymer and liquid crystal; 32 parts of polymer are added to 58 parts of E7, and stirred at 750 rpm for 40 min.

[0038] CNC doping; The dispersion is added slowly, and stirring is continued for 40 min, followed by ultrasonic dispersion for 5 h.

[0039] Film preparation; Using 10 µm SiO2 microsphere spacers, 4 µL is dropped and another ITO glass is covered.

[0040] UV curing; UV pre-curing at 9 mW / cm 2 , for 40 s, and complete curing at 14 mW / cm 2 , for 130 s.

[0041] Example 4: High-stability PDLC, enhancing weather resistance Aiming at the influence of environmental humidity and temperature changes on the performance of PDLC, this example optimizes the matrix polymer structure to improve the weather resistance and long-term stability of the film.

[0042] 1. Material ratio; Liquid crystal material (E7): 57 parts Matrix polymer: 33 parts Low refractive index monomer (INAA): 7 parts Prepolymer (low-viscosity aromatic monoacrylate): 13 parts Hydrophobic monomer (IBOMA): 13 parts Photoinitiator (PI184): 1.1 parts Cellulose nanocrystal composite material (CNC-KH560-N-TiO2): 4 parts Solvent (anhydrous ethanol + cyclohexane 2:1): 8 parts 2. Preparation steps; Preparation of cellulose nanocrystal solution; Take 4 parts of CNC composite material and dissolve it in a mixed solvent of 8 parts of anhydrous ethanol and cyclohexane, stir for 160 min, and then ultrasonicate for 4 h to obtain a stable nano-dispersion.

[0043] Mixing of polymer and liquid crystal; Take 33 parts of matrix polymer, add 57 parts of E7 liquid crystal, and stir at 700 rpm for 50 min to obtain a homogeneous mixing system.

[0044] CNC nanocomposite doping; Slowly add the dispersion from step (1) to the liquid crystal-polymer mixing system, continue stirring for 50 min, and then ultrasonicate for 4 h to ensure uniform distribution of CNC.

[0045] Film preparation; Disperse 10 µm PMMA microsphere spacers on the ITO glass substrate, drop 4 µL of the mixed solution, and cover with another piece of ITO glass.

[0046] UV curing; UV pre-cure at 10 mW / cm 2 for 50 s, full cure at 16 mW / cm 2 for 150 s to form a stable PDLC film.

[0047] Comparative Example 1 (corresponding to Example 1, without doping CNC composite material) This comparative example uses a conventional PDLC formulation without doping cellulose nanocrystal composite material (CNC-KH560-N-TiO2), and compares its effects on the liquid crystal microdroplet structure and optoelectronic properties.

[0048] 1. Material ratio; Liquid crystal material (E7): 60 parts Matrix polymer: 30 parts Low refractive index monomer (INAA): 8 parts Prepolymer (low viscosity aromatic monoacrylate): 12 parts Hydrophobic monomer (IBOMA): 10 parts Photoinitiator (PI184): 1 part Solvent (anhydrous ethanol): 6 parts 2. Preparation steps; The same as in Example 1, except that the CNC composite material is not added. The remaining steps, including the mixing, stirring, ultrasonic treatment, film preparation, and UV curing method of the liquid crystal and polymer, remain the same.

[0049] Comparative Example 2 (corresponding to Example 2, without optimizing the proportion of hydrophobic monomer) This comparative example uses a PDLC system with an unoptimized proportion of hydrophobic monomer (IBOMA) and compares its effects on mechanical properties and moisture resistance.

[0050] 1. Material ratio; Liquid crystal material (E7): 55 parts Matrix polymer: 35 parts Low refractive index monomer (INAA): 6 parts Prepolymer (low viscosity aromatic monoacrylate): 18 parts Hydrophobic monomer (IBOMA): 8 parts (6 parts less) Photoinitiator (PI184): 1.2 parts CNC-KH560-N-TiO2 composite material: 4 parts Solvent (anhydrous ethanol + acetone 1:1): 7 parts 2. Preparation steps; Same as Example 2, only the proportion of the hydrophobic monomer (IBOMA) is adjusted and reduced to 8 parts, and the remaining steps including CNC dispersion, liquid crystal mixing, ultrasonic treatment, film preparation, and UV curing method remain the same.

[0051] Comparative Example 3 (corresponding to Example 3, without doping N-TiO2) This comparative example uses a formulation without doped nitrogen-doped titanium dioxide (N-TiO2) to compare its effects on the dielectric response characteristics and low-voltage driving ability of PDLC.

[0052] 1. Material ratio; Liquid crystal material (E7): 58 parts Matrix polymer: 32 parts Low refractive index monomer (INAA): 10 parts Prepolymer (low-viscosity aromatic monoacrylate): 12 parts Hydrophobic monomer (IBOMA): 10 parts Photoinitiator (PI184): 1.0 part CNC-KH560 composite material (without nitrogen-doped titanium dioxide N-TiO2): 5 parts (removing N-TiO2) Solvent (cyclohexane): 7 parts 2. Preparation steps; Same as Example 3, only without doping nitrogen-doped titanium dioxide, and the remaining steps such as CNC dispersion, liquid crystal mixing, ultrasonic treatment, film preparation, and UV curing method remain the same.

[0053] Comparative Example 4 (corresponding to Example 4, without using a mixed solvent system) This comparative example uses a single solvent system (absolute ethanol) and does not use the 2:1 mixed solvent of absolute ethanol + cyclohexane to compare its effects on the dispersion stability of CNC and the weather resistance of the film.

[0054] 1. Material ratio; Liquid crystal material (E7): 57 parts Matrix polymer: 33 parts Low refractive index monomer (INAA): 7 parts Prepolymer (low-viscosity aromatic monoacrylate): 13 parts Hydrophobic monomer (IBOMA): 13 parts Photoinitiator (PI184): 1.1 parts CNC-KH560-N-TiO2 composite material: 4 parts Solvent (absolute ethanol): 8 parts (removing cyclohexane) 2. Preparation steps; Same as Example 4, except that the mixed solvent is not used and replaced with a single anhydrous ethanol, and the remaining steps such as CNC dispersion, liquid crystal mixing, ultrasonic treatment, film preparation, and UV curing method remain the same.

[0055] Experiment 1: Optoelectronic performance test (transmittance and haze) Objective: To verify the effect of CNC composite doping on the optical properties of the PDLC system. Control groups: Example 1 and Comparative Example 1 (without CNC doping).

[0056] Experimental method: Sample preparation: Prepare PDLC films according to Example 1 and Comparative Example 1 respectively, with a unified size of 2 cm × 2 cm, and place them for 24 h to ensure structural stability.

[0057] Transmittance measurement: Use a spectrophotometer (λ = 550 nm) to measure the transmittance in the transparent state (applying an 80 V AC electric field, 1 kHz) and the haze state (no electric field).

[0058] Haze test: Use a haze meter to measure the change in transmittance and calculate the optoelectronic modulation ability of the PDLC.

[0059] Comparative analysis: Record the transmittance in the transparent state and the haze state and calculate the contrast ratio.

[0060] Experiment 2: Response speed Purpose: To evaluate the response speed of polymer-dispersed liquid crystal films doped with cellulose nanocrystals at low voltages and verify their fast dimming ability in applications such as smart windows and optical modulators; Experimental method: Sample preparation: Prepare PDLC films according to the formulations of Example 2 and Comparative Example 2, with a unified size of 15 mm × 15 mm, a thickness controlled at 100 μm, and a curing time of 24 hours.

[0061] Response speed test: Fix the sample in the test equipment, apply an alternating current of 0 - 100 V (frequency 1 kHz), and record the response time (T_on) from the haze state to the transparent state and the recovery time (T_off) from the transparent state to the haze state.

[0062] Comparative analysis: Record the response time of each sample, conduct comparative analysis, and evaluate the effect of different formulations on the response speed of the film.

[0063] Experiment 3: Low-voltage drive test (threshold voltage) Objective: To verify the effect of N-TiO2 doping on the dielectric response performance of PDLC and reduce the threshold voltage. Control groups: Example 3 and Comparative Example 3 (without N-TiO2 doping).

[0064] Experimental method: Sample preparation: Prepare PDLC films according to Example 3 and Comparative Example 3, and cut them into test pieces of 15 mm × 15 mm.

[0065] Driving voltage test: Apply 0 - 100 V alternating current (frequency 1 kHz) using an LCR tester, and record the lowest voltage at which the light transmittance reaches 90%, i.e., the threshold voltage (Vth).

[0066] Response time measurement: At a voltage of 50 V, record the response time (T_on) of PDLC from the foggy state to the transparent state and the recovery time (T_off) from the transparent state to the foggy state.

[0067] Comparative analysis: Record the threshold voltage and response time, and analyze the optimization effect of N-TiO2 on the low-voltage driving characteristics of PDLC.

[0068] Experiment 4: Weather resistance test (environmental stability) Objective: Evaluate the stability of the PDLC system under high humidity and high temperature conditions. Control group: Example 4 and Comparative Example 4 (without using a mixed solvent) Experimental method: Sample preparation: Prepare PDLC films according to Example 4 and Comparative Example 4, and cut them into specimens of 2 cm × 2 cm.

[0069] Aging experiment: Place the samples in a thermo-hygrostat (85% RH, 60 °C) and continuously test for 168 h.

[0070] Optoelectronic property monitoring: Record the change in light transmittance every 24 h and calculate the optical stability.

[0071] Apply a 50 V alternating voltage every 24 h and detect whether the driving voltage increases.

[0072] Comparative analysis: Observe the structural changes of the PDLC film (optical microscope) and evaluate the long-term stability.

[0073] Experiment 1: Optoelectronic property test (light transmittance and haze) Experimental description Objective: Evaluate the effect of CNC composite doping on the light transmittance and haze of PDLC, and verify its advantages in smart window applications.

[0074] Experimental control group: Example 1 (doped with CNC composite) Comparative Example 1 (not doped with CNC composite) Experimental equipment: Spectrophotometer (λ = 550 nm), used to measure the light transmittance at different voltages Haze meter, used to measure the degree of light scattering in the foggy state Adjustable power supply (0 - 100V, 1kHz AC), controlling the transparent state and fog state of PDLC Experimental procedures Sample preparation: Prepare PDLC films according to the formulations of Example 1 and Comparative Example 1, cut them into test pieces of 2 cm × 2 cm, and place them in an environment of 25°C and 50% RH for 24 h to ensure stable structure.

[0075] Transmittance measurement: Fix the sample on the sample holder of the spectrophotometer and measure the transmittance at 0V (fog state) and 20V (transparent state) respectively, and record multiple measurement points to reduce errors.

[0076] Haze measurement: Use a haze meter to measure the haze value of PDLC at 0V to evaluate the scattering ability in the fog state.

[0077] Data recording: Repeat the measurement 5 times, take the average value, and calculate the transmittance contrast ratio (transparent state vs fog state).

[0078] Experimental data Table 1: Transmittance and haze test results of PDLC at different voltages Summary The addition of CNC composites makes the distribution of liquid crystal microdroplets in the PDLC system more uniform, reduces the agglomeration phenomenon, and significantly improves the transmittance. In the transparent state, CNC optimizes the refractive index matching of the polymer matrix, improves the optical uniformity of the film, and reduces the interface scattering loss. Compared with the PDLC system without doped CNC, the transmittance in the transparent state is increased by 13% - 16%, which means higher light utilization rate and more comfortable visual experience in application scenarios such as smart windows.

[0079] In the fog state, the presence of CNC composites makes the liquid crystal microdroplets form a more stable scattering structure, enhances the light scattering ability, and increases the haze. Experimental data shows that the transmittance in the fog state of Example 1 decreases, while the haze value increases by 7 - 10%, which means the fog state is denser, effectively blocking the line of sight and enhancing the privacy protection ability.

[0080] Experiment 2: Response speed test Experimental description: Purpose: To evaluate the response speed of polymer dispersed liquid crystal films doped with cellulose nanocrystals at low voltages and verify their fast dimming ability in applications such as smart windows and light modulators.

[0081] Experimental control groups Example 2 (optimizing the content of IBOMA to improve the response speed) Comparative Example 2 (reducing the content of IBOMA, traditional formulation) Experimental equipment Experimental equipment Voltage source (0 - 100V, 1kHz, alternating current) Transmittance tester (records the change in PDLC transmittance) Response time measurement device (measures the response time and recovery time from the foggy state to the transparent state) Experimental procedure: Sample preparation: Prepare PDLC films according to the formulations of Example 2 and Comparative Example 2, with a uniform size of 15 mm × 15 mm, a thickness controlled at 100 μm, and a curing time of 24 hours.

[0082] Response speed test: Fix the sample in the test equipment, apply an alternating current of 0 - 100V (frequency 1kHz), and record the response time (T_on) from the foggy state to the transparent state and the recovery time (T_off) from the transparent state to the foggy state.

[0083] During the test, keep switching between the transparent state (80V) and the foggy state (0V), and use the transmittance tester to record the change in the transmittance of the film in real time.

[0084] Test the response speed at 50V voltage and record the T_on and T_off times.

[0085] Repeat the test 5 times to ensure the reliability of the data.

[0086] Data recording and analysis: Record the response time of each sample, conduct a comparative analysis, and evaluate the influence of different formulations on the response speed of the film.

[0087] Table 2: Response speed test results of different PDLC formulations Summary The high IBOMA content in Example 2 enhances the cross - link density of the polymer matrix, thereby improving the interaction between the polymer matrix and liquid crystal molecules and increasing the alignment speed of liquid crystal molecules. This optimization enables the liquid crystal molecules to rearrange more quickly, thus shortening the response time under the action of an electric field. This characteristic allows Example 2 to switch between the transparent state and the foggy state more quickly under low - voltage drive, reducing the energy consumption of the device and significantly increasing the dimming speed.

[0088] Compared with Comparative Example 2, the film of Example 2 exhibits better electric - field responsiveness, which means it can provide higher efficiency and performance in applications such as smart windows and optical modulators that require frequent transparency switching. A fast response time is crucial for these applications, which can improve the user experience, especially in scenarios where rapid adjustment of light transmittance is needed, such as automatically adjusting window light and in - vehicle displays.

[0089] The fast-responsive film also has important advantages in energy conservation. Since it can complete the conversion between transparency and fogginess in a shorter time, it can reduce unnecessary energy consumption, extend the service life of the device, and improve the overall efficiency of the system. Generally speaking, the optimized PDLC film not only has fast response ability, but also performs excellently in low-voltage driving and energy conservation, and is especially suitable for intelligent control systems that require fast dimming.

[0090] Experiment 3: Low-voltage driving test (threshold voltage) Experiment description Purpose: By testing the influence of N-TiO2 doping on the low-voltage driving performance of PDLC, verify its advantages in reducing the threshold voltage and improving the response speed.

[0091] Experimental comparison group: Example 3 (doped with N-TiO2) Comparative example 3 (not doped with N-TiO2) Experimental equipment: LCR tester (applying 0-100V alternating current, frequency 1kHz) Voltage source (0-100V, alternating current) Transmittance tester (recording the change of PDLC transmittance) Response time measurement device (recording the response time from fogginess to transparency) Experimental steps Sample preparation: Prepare PDLC films according to Example 3 and Comparative Example 3, with a unified size of 15mm×15mm, a thickness controlled at 100μm, and a curing time of 24h.

[0092] The samples are stably placed in a normal temperature and humidity environment for 48h to ensure that the samples are fully stable.

[0093] Threshold voltage measurement: Fix the sample on the LCR tester, apply 0-100V alternating current, and set the frequency to 1kHz.

[0094] Record the lowest voltage at which the transmittance reaches 90%, that is, the threshold voltage (Vth).

[0095] Response time measurement: At a voltage of 50V, record the time from fogginess to transparency (T_on) and the recovery time from transparency to fogginess (T_off).

[0096] Repeat the test 5 times to ensure the reliability of the data.

[0097] Data recording and analysis: Record the threshold voltage and response time of each sample for comparative analysis.

[0098] Experimental data Table 3: Test results of low-voltage driving performance of different PDLC formulations Summary The doping of N-TiO2 significantly affects the electrical properties of PDLC. By doping N-TiO2, Example 3 exhibits a lower threshold voltage, which is 8 - 9 V lower than that of Comparative Example 3. This enables the PDLC film to be activated at a lower voltage, saving energy and improving the driving efficiency. This phenomenon can be attributed to the fact that the introduction of N-TiO2 reduces the electric field shielding effect between liquid crystal molecules, enhances the alignment speed of liquid crystal molecules, and thus achieves a lower driving voltage.

[0099] In terms of response time, the PDLC system of Example 3 shows a faster response speed, especially during the switching process in the transparent state. The times of T_on and T_off are respectively reduced by 30% - 35% compared to Comparative Example 3. This is because N-TiO2 provides a better charge transfer channel in PDLC, accelerating the formation of the electric field and the rotation of liquid crystal molecules, thereby enhancing the regulation efficiency. In addition, the nanoparticles of N-TiO2 enhance the conductivity of the film, making the rotational response of liquid crystal molecules under the action of the electric field more rapid.

[0100] This performance optimization has significant advantages for optical devices that require frequent switching (such as smart windows, light modulators, etc.). Low-voltage driving and fast response make PDLC more energy-efficient and flexible, suitable for application scenarios that require high-efficiency light regulation and high response speed. With the increasing demand for battery and energy efficiency, Example 3 provides a more energy-efficient and faster-response optoelectronic regulation solution.

[0101] Experiment 4: Weather resistance test (environmental stability) Experiment description Purpose: To evaluate the stability of the PDLC system in high-humidity and high-temperature environments, test its long-term performance under different environmental conditions, and ensure its reliability in practical applications, especially for long-term use in smart windows and building glass.

[0102] Experimental control groups: Example 4 (using a mixed solvent system) Comparative Example 4 (not using a mixed solvent system) Experimental equipment: Thermostatic and humidistatic chamber (85% RH, 60 °C) Spectrophotometer (for measuring the change in transmittance) Microscope (for observing surface changes and possible structural damage) Voltage source (for measuring the change in driving voltage) Experimental procedure Sample preparation: Prepare PDLC films according to Example 4 and Comparative Example 4. The sample size is 2 cm × 2 cm, and ensure that the thickness of both groups of samples is 100 μm.

[0103] Place the samples in an environment of 25°C and 50% RH for 24 h to ensure initial stability.

[0104] Aging experiment: Put the samples into a thermo-hygrostat chamber, set the temperature to 60°C and the humidity to 85% RH, and continuously test for 168 h (7 days).

[0105] Optoelectronic property monitoring: Measure the change in transmittance every 24 h and record the change in transmittance at different time points.

[0106] Use a spectrophotometer to measure the change in transmittance from the transparent state to the foggy state.

[0107] Voltage change test: Record the transmittance when applying 50 V alternating current every 24 h to monitor whether there is a significant change in the driving voltage.

[0108] Microscope observation: Use a microscope to observe whether there are cracks, peeling, or other possible material deterioration on the surface.

[0109] Data recording and analysis: Record the transmittance data at different aging stages and analyze the difference in the weather resistance of PDLC under different solvent systems.

[0110] Experimental data Table 4: Weather resistance test results of PDLC under different solvent systems Summary After long-term aging in a high-temperature and high-humidity environment, the PDLC film of Example 4 showed relatively good stability. The change in transmittance was very small, only 2% - 3%, and the voltage change was also relatively small, indicating that its optoelectronic properties were basically stable in a high-humidity and high-temperature environment. This is closely related to the increase in the crosslinking density of the polymer matrix after using the mixed solvent system. The crosslinked structure effectively reduced the influence of moisture and temperature on the material, improving the weather resistance and stability of the film.

[0111] Compared with Comparative Example 4, the PDLC film without using the mixed solvent showed poor performance under high humidity and high temperature conditions. The light transmittance decreased by 5%-6%, and obvious cracks and material deterioration appeared on the surface. Microscopic observation showed that the liquid crystal molecules or the polymer matrix might have undergone delamination or detachment, further confirming the structural instability caused by the low cross-linking density. These changes significantly affected the long-term service life of the material.

[0112] This difference emphasizes the importance of the cross-linked structure of the polymer matrix for the weather resistance of PDLC. Adopting the mixed solvent system can enhance the stability of the polymer, reduce the influence brought by environmental factors, and thus improve the reliability of the material in practical applications. For applications such as smart windows, Example 4 provides a solution with long life and high stability, which can still maintain good performance under complex environmental conditions.

[0113] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A polymer dispersed liquid crystal film doped with cellulose nanocrystals, characterized in that: The invention comprises the following components: 50-70 parts of liquid crystal material, 20-35 parts of matrix polymer, 0.5-2 parts of photoinitiator, 1-5 parts of cellulose nano-crystal composite material and 5-15 parts of solvent.

2. The polymer dispersed liquid crystal film doped with cellulose nanocrystals according to claim 1, characterized in that: The matrix polymer includes a low refractive index monomer, a prepolymer and a hydrophobic monomer.

3. The polymer dispersed liquid crystal film doped with cellulose nanocrystals according to claim 2, characterized in that: The prepolymer is a low-viscosity aromatic monoacrylate; The low refractive index monomer is isononyl acrylate; The hydrophobic monomer is isobornyl methacrylate.

4. The polymer dispersed liquid crystal film doped with cellulose nanocrystals according to claim 1, characterized in that: The liquid crystal material is E7 liquid crystal.

5. The polymer dispersed liquid crystal film doped with cellulose nanocrystals according to claim 1, characterized in that: The photoinitiator is 1-hydroxy-cyclohexane-phenyl ketone.

6. The polymer dispersed liquid crystal film doped with cellulose nanocrystals according to claim 1, characterized in that: The cellulose nanocrystal composite material is surface-modified cellulose nanocrystals, the surface of which is modified by a silane coupling agent KH560 and loaded with nitrogen-doped titanium dioxide.

7. The polymer dispersed liquid crystal film doped with cellulose nanocrystals according to claim 6, characterized in that: The particle size of the nitrogen-doped titanium dioxide is 3-10 nm.

8. A method for preparing a polymer dispersed liquid crystal film doped with cellulose nanocrystals, according to the polymer dispersed liquid crystal film doped with cellulose nanocrystals according to any one of claims 1 to 7, characterized in that: The steps include: S1. preparing a cellulose nanocrystal composite solution; taking a cellulose nanocrystal composite material, dispersing it in a solvent, stirring it for 120-180 minutes, and performing ultrasonic treatment for 3-5 hours; S2, mixing a polymer and a liquid crystal material; taking a base polymer, adding a liquid crystal material, and stirring at 500-800 rpm for 30-60 min to obtain a mixed solution; S3, dispersing the cellulose nanocrystal composite material; gradually adding the obtained dispersion into the mixed solution, continuing stirring for 30-60 minutes, and ultrasonically dispersing for 3-5 hours; S4, thin film preparation: evenly spread spacers with a particle size of 8-12µm on the ITO glass substrate, drop 4-6µL of the mixed solution, and cover with another ITO glass; S5, UV curing; 8-12mW / cm 2 Pre-cure for 30-60s, followed by 12-18mW / cm 2 Fully cure for 90-180s to form a polymer dispersed liquid crystal film.

9. The method for preparing a polymer dispersed liquid crystal film doped with cellulose nanocrystals according to claim 8, characterized in that: In step S4, the spacer is polymethyl methacrylate.

10. The method for preparing a polymer dispersed liquid crystal film doped with cellulose nanocrystals according to claim 8, characterized in that: The solvent in step S1 includes anhydrous ethanol, acetone or cyclohexane.

Images