Transparent and shape-controllable and reversible pmma film, preparation method and application thereof

Abstract

The application belongs to the technical field of material engineering, and discloses a PMMA film with controllable and reversible transparency and shape, a preparation method and application. The preparation method comprises the following steps: modifying PMMA by carboxylation to obtain carboxylated PMMA; dissolving the carboxylated PMMA in trifluoroethanol, stirring until completely dissolved after 12-24 hours to obtain a carboxylated PMMA solution; and pouring the carboxylated PMMA solution on a polyimide film, and standing until the trifluoroethanol solution is completely volatilized to obtain a PMMA film. The preparation method is simple and suitable for industrialization. The obtained PMMA film has controllable and reversible transparency and shape, and can be used to prepare a PMMA material with controllable and reversible transparency and shape at low cost.

Description

Technical Field

[0001] This invention belongs to the field of materials engineering technology, and relates to a PMMA film with controllable and reversible transparency and shape, its preparation method and application. Background Technology

[0002] Polymethyl methacrylate (PMMA), commonly known as plexiglass, is an important acrylic polymer. Due to its aesthetic appeal, high transparency, and good mechanical properties, it is widely used in catalysis, sensors, and other fields. However, the processing of plastics like PMMA faces several common problems. Currently, plastic processing is mainly carried out through temperature manipulation, which typically involves harsh conditions, complex machinery, and high energy consumption. Water can serve as an effective plasticizer to soften both natural and synthetic polymers. Wu et al. utilized water-assisted methods to achieve sustainable plastics with arbitrary plasticity (Advanced Materials, 2022, 34(19)). On the other hand, materials with controllable transparency can respond to changes in the external environment, providing broad application prospects for smart windows, privacy protection, and electronic screens. Various methods have been developed to control the transparency of materials. One approach is to utilize electromagnetic effects to modulate the optical properties of metamaterials (Nature Communications, 2012, 3; Carbon, 2019, 142: 354-362). Another approach is to utilize the photothermal conversion effect of graphene oxide to change the transparency of smart glass (Solar Energy Materials and SolarCells, 2017, 166: 45-51). Furthermore, the transparency can be controlled by injecting adaptive fluids into porous films and then mechanically stimulating them (Acs Nano, 2016, 10(10): 9387-9396). However, both approaches suffer from high technical requirements, difficult operation, and high costs. Summary of the Invention

[0003] In view of this, the present invention provides a PMMA film with controllable and reversible transparency and shape, a preparation method and an application. The PMMA film has the characteristics of controllable transparency, reversibility and controllable shape, and the preparation method is simple and the application is wide.

[0004] The technical solution provided by this invention is as follows:

[0005] A method for preparing a PMMA film with controllable and reversible transparency and shape includes the following steps:

[0006] S1. PMMA was carboxylated by immersing it in a sodium hydroxide alcohol solution to obtain carboxylated PMMA;

[0007] S2. Dissolve the carboxylated PMMA in trifluoroethanol, and after 12-24 hours, stir until completely dissolved to obtain a carboxylated PMMA solution;

[0008] S3. The carboxylated PMMA solution is poured onto a polyimide film and allowed to stand until the trifluoroethanol solution has completely evaporated to obtain the PMMA film.

[0009] Further, step S1 specifically involves: soaking PMMA powder in a 0.5M sodium hydroxide 75% ethanol solution for 1-2 hours, removing it, washing it with distilled water, and allowing it to stand and dry to obtain carboxylated PMMA.

[0010] Further, step S1 specifically involves: soaking PMMA powder in a 0.5M sodium hydroxide 75% ethanol solution for 2 hours, removing it, washing it with distilled water, and allowing it to stand and dry to obtain carboxylated PMMA.

[0011] Furthermore, the solvent for the sodium hydroxide solution is 75% ethanol.

[0012] Furthermore, the concentration of the carboxylated PMMA solution is 0.15-0.25 g / mL.

[0013] The present invention also provides a PMMA film obtained by the above preparation method.

[0014] The present invention also provides an application of the above-mentioned PMMA film in the preparation of PMMA materials with controllable transparency and shape and reversibility.

[0015] The present invention also provides a method for preparing irregularly shaped PMMA material, wherein the above-mentioned PMMA film is placed in water or anhydrous ethanol at 50°C, and after the PMMA film becomes soft, the PMMA film is shaped and then left for a while to obtain an irregularly shaped PMMA material with a preset shape.

[0016] Furthermore, the preset shape is a spiral, M-shape, or N-shape.

[0017] The present invention also provides a method for controlling the transparency of PMMA film, wherein the above-mentioned PMMA film is immersed in water at 50°C for 5 to 20 minutes to obtain an opaque PMMA film with a transparency of 0-10%, and the opaque PMMA film is immersed in anhydrous ethanol at 50°C for 5 to 20 minutes to obtain a transparent film with a transparency of 65-90%.

[0018] Compared with existing technologies, this invention uses a 75% sodium hydroxide ethanol solution to modify PMMA by carboxylation, which can easily control the carboxyl content in carboxylated PMMA to maintain it at 1.583 × 10⁻⁶. -5With a constant mol / g concentration and using trifluoroethanol as the solvent, the resulting PMMA film exhibits high transparency. Custom shapes can be achieved through treatment with water or anhydrous ethanol at 50°C. Water treatment at 50°C converts high transparency to opacity, while anhydrous ethanol treatment at 50°C converts opacity to high transparency; these conversions are reversible. Furthermore, the shape changes are also reversible, allowing for repeated design of different shapes. Attached Figure Description

[0019] Figure 1 The graph shows the calculated carboxyl content of PMMA powder after soaking in a 0.5M sodium hydroxide 75% ethanol solution for 0 h, 0.5 h, 1 h, 2 h, 2.5 h, and 3 h. Graph A shows untreated PMMA powder (Sample 1: soaking time 0 h), Graph B shows PMMA powder soaked for 0.5 h (Sample 2), Graph C shows PMMA powder soaked for 1 h (Sample 3), Graph D shows PMMA powder soaked for 2 h (Sample 4), Graph E shows PMMA powder soaked for 2.5 h (Sample 5), and Graph F shows PMMA powder soaked for 3 h (Sample 6).

[0020] Figure 2 The hydrophilic angles of samples 1-4;

[0021] Figure 3 The graph shows the changes in transparency for samples 1 and 4.

[0022] Figure 4 This is a diagram showing the changes in the physical state of sample 4 before and after shape control in Example 5;

[0023] Figure 5 This is a graph showing the carboxyl content of commercially available carboxylated polymethyl methacrylate used in Comparative Example 2.

[0024] Figure 6 The image shows the PMAA membrane prepared in Comparative Example 2 before and after being immersed in water for 20 minutes, bearing a 5g weight. Detailed Implementation

[0025] The present invention will be further explained below with reference to the embodiments and accompanying drawings. The following embodiments are only used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0026] Example 1

[0027] 2g of PMMA powder was immersed in 100mL of 0.5M NaOH ethanol solution for carboxylation treatment. After washing three times with distilled water, it was dried to obtain carboxylated PMMA.

[0028] Soaking times were 0h, 0.5h, 1h, 2h, 2.5h, and 3h, respectively, resulting in sample 1, sample 2, sample 3, sample 4, sample 5, and sample 6.

[0029] The carboxyl content of the water-insoluble component was measured by conductivity titration. 0.3 g of dried sample 1-4 was weighed, and 55 mL of distilled water and 5 mL of 0.01 M sodium chloride solution were added. The mixture was stirred thoroughly with a magnetic stirrer to obtain a homogeneous solution. Then, 0.1 M HCl was added to adjust the pH of the mixture to 2.5–3.0, and the mixture was stirred magnetically for 1 h. Subsequently, 0.04 M NaOH solution was titrated at a rate of 0.1 mL / min. The conductivity of the mixture was monitored during the reaction using a conductivity meter. Titration was stopped when the pH of the solution reached 11. The carboxyl content was calculated using the formula: Carboxyl content = 0.04 mol / L * (V B -V A The carboxyl content is calculated based on 0.3g / mL, where V A and V B The figures represent the volumes of NaOH solution consumed at the intersections of the tangent lines to the horizontal lines representing the lowest points of the conductivity curves on the left and right sides, respectively. The conductivity variation formulas and carboxyl group contents for samples 1-5 are shown below. Figure 1 As shown in the figure, the carboxyl content increases with the soaking time in NaOH alcohol solution, reaching its highest level of 1.583 × 10⁻⁶ when the treatment time is 2 hours. -5 mol / g. The treatment time was further increased, and the carboxyl content remained at 1.583 × 10⁻⁶ mol / g. -5 The mol / g remains constant.

[0030] Example 2

[0031] 2g of samples 1-4 obtained in Example 1 were dissolved in 10mL of trifluoroethanol to a concentration of 0.2g / mL. The solution was stirred overnight and then poured onto a polyimide film. After the trifluoroethanol evaporated, a carboxylated polymethyl methacrylate film was obtained.

[0032] Hydrophilicity tests were conducted on the PMMA films prepared using samples 1-4, and the results were... Figure 2 As shown, it can be observed that the carboxyl content on the material surface increases with increasing immersion time, leading to enhanced hydrophilicity. Sample 4 has the highest carboxyl content and the best hydrophilicity.

[0033] Example 3

[0034] The PMMA film prepared using sample 4 (immersion time 2h) was immersed in water at 50℃ for 20min to obtain an opaque film with ~2% opacity. After complete drying, its transparency was measured by placing it on a flower. Figure 3 As shown in the image below.

[0035] Example 4

[0036] The opaque film obtained in Example 4 was immersed in anhydrous ethanol at 50°C for 5 minutes to obtain a transparent film with approximately 65% ​​transparency. After complete drying, the film was placed on a flower to measure its transparency. Figure 3 The following figure (corresponding to carboxylated PMMA) is shown.

[0037] As shown in Examples 4 and 5, the PMMA film prepared by the present invention has extremely high transparency (about 90%) and controllable transparency. When the film is immersed in water at 50°C for 20 minutes, the film will change from highly transparent to opaque (about 2%). Further immersion of the opaque film in anhydrous ethanol at 50°C for 5 minutes will change the film from opaque (about 2%) back to highly transparent (about 65%). After immersion for 20 minutes, the transparency can reach 90%. Repeating this operation can achieve controllable transparency of the carboxylated PMMA film.

[0038] Figure 3 In the image below, the leftmost image shows the original transparent PMMA, the middle image shows the image after water treatment at 50°C for 20 minutes, where the transparency of the material is significantly reduced, and the rightmost image shows the PMMA after treatment with anhydrous ethanol at 50°C for 5 minutes, where the transparency is significantly improved again. Below is the corresponding quantitative analysis of transparency: the original PMMA film has a transparency of about 90%, which decreases to about 2% after water treatment, and recovers to about 65% after further treatment with anhydrous ethanol at 50°C.

[0039] Example 5

[0040] The PMMA film prepared from sample 4 (immersion time 2h) can support a 5g weight (see sample 4). Figure 4 (Figure B, left image) Place it in a 50°C water or ethanol solution for about 5 minutes. The film becomes soft and can hardly support its own weight (see Figure B). Figure 4 (See right image B). At this point, shape customization is performed, such as spiral, M-shape, N-shape, etc. The shape will be fixed after standing for a moment after removing it from water or ethanol (e.g., ...). Figure 4 A).

[0041] Comparative Example 1

[0042] Commercially available polymethyl methacrylate (PMMA) was dissolved in trifluoroethanol at a concentration of 0.2 g / mL and stirred overnight. The solution was then cast onto a polyimide film, and the PMMA film (sample 1) was obtained after the trifluoroethanol evaporated. Immersing sample 1 in water at 50°C slightly decreased the film's transparency. Subsequent immersion in anhydrous ethanol at 50°C slightly increased the transparency. The actual image and transparency test results are shown below. Figure 3As shown in the image above (corresponding to PMMA), the transparency does not change significantly after water treatment and anhydrous ethanol treatment.

[0043] Comparative Example 2

[0044] Commercially available carboxylated PMMA (PMAA) with a carboxyl content of 2.657 × 10⁻⁶ was used. -5 mol / g, such as Figure 5 The solution (as shown) was dissolved in acetone, with a PMMA concentration of 0.2 g / mL. The solution was stirred overnight to dissolve, and then poured onto a polyimide film. After the acetone evaporated, a PMAA film was obtained. This PMAA film can support a 5 g weight (see...). Figure 6 A) After being immersed in water or anhydrous ethanol at 50°C for 20 minutes, it can still support a 5g weight (see...). Figure 6 B) It can be seen that when the carboxyl content is higher than a certain level, it cannot become soft and can be customized in shape.

Claims

1. A method for preparing a PMMA thin film with controllable and reversible transparency and shape, characterized in that, Includes the following steps: S1. Soak PMMA powder in 0.5 M sodium hydroxide alcohol solution for 1-2 h, remove it, wash it with distilled water, let it stand and dry to obtain carboxylated PMMA; S2. Dissolve the carboxylated PMMA in trifluoroethanol, and after 12-24 hours, stir until completely dissolved to obtain a carboxylated PMMA solution with a concentration of 0.15-0.25 g / mL; S3. The carboxylated PMMA solution is poured onto a polyimide film and left to stand until the trifluoroethanol solution has completely evaporated to obtain the PMMA film.

2. The preparation method according to claim 1, characterized in that, The solvent for the sodium hydroxide alcohol solution is 75% alcohol.

3. The PMMA film obtained by the preparation method according to any one of claims 1-2.

4. The application of the PMMA film according to claim 3 in the preparation of PMMA materials with controllable transparency and shape and reversibility.

5. A method for preparing an irregularly shaped PMMA material, characterized in that, The PMMA film described in claim 3 is placed in a water or ethanol solution at 50°C. After the PMMA film becomes soft, the PMMA film is shaped and then left to stand for a while to obtain a pre-shaped irregular PMMA material.

6. The preparation method according to claim 5, characterized in that, The preset shape is a spiral, M-shaped, or N-shaped.

7. A method for controlling the transparency of a PMMA film, characterized in that, The PMMA film of claim 3 is soaked in water at 50°C for 5-20 min to obtain an opaque PMMA film with a transparency of 2-10%. The opaque PMMA film is then soaked in anhydrous ethanol at 50°C for 5-20 min to obtain a transparent film with a transparency of 65-90%.

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