PMMA (polymethyl methacrylate) film with controllable and reversible transparency and shape as well as preparation method and application of PMMA film

Abstract

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

Description

Technical Field

[0001] The invention belongs to the technical field of material engineering, and relates to a PMMA film with controllable and reversible transparency and shape, a preparation method and application thereof. Background Art

[0002] Polymethyl methacrylate (PMMA), commonly known as organic glass, is an important acrylic polymer. Due to its advantages such as beauty, high transparency and good mechanical properties, it is widely used in catalysis, sensors and other fields. At the same time, there are some common problems in the processing of plastics such as polymethyl methacrylate. At present, plastic processing is mainly carried out by temperature manipulation, which usually involves harsh conditions, complex machines and high energy consumption. Water can be used as an effective plasticizer to soften natural and synthetic polymers. Wu et al. used water to assist in the realization of 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 in fields such as smart windows, privacy protection and electronic screens. At present, a variety of methods have been developed to achieve material transparency control. One method is to use electromagnetic effects to regulate the optical properties of metamaterials (Nature Communications, 2012, 3; Carbon, 2019, 142: 354-362), and another method is to use the photothermal conversion effect of graphene oxide to change the transparency of smart glass (Solar Energy Materials and Solar Cells, 2017, 166: 45-51.); in addition, adaptive fluids are injected into porous films and their transparency is controlled by mechanical stimulation (Acs Nano, 2016, 10 (10): 9387-9396). However, both methods have the disadvantages of high technical requirements, high operational difficulty, and high cost consumption. Summary of the invention

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

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

[0005] A method for preparing a PMMA film with controllable transparency and shape and reversibility, comprising the following steps:

[0006] S1. The PMMA is immersed in a sodium hydroxide alcohol solution for carboxylation modification to obtain carboxylated PMMA;

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

[0008] S3. pouring the carboxylated PMMA solution onto the polyimide film and allowing it to stand until the trifluoroethanol solution is completely evaporated to obtain the PMMA film.

[0009] Furthermore, step S1 specifically includes: adding PMMA powder into a 0.5M sodium hydroxide 75% ethanol solution and soaking for 1-2 hours, taking it out and washing it with distilled water, standing it to dry, and obtaining carboxylated PMMA.

[0010] Furthermore, step S1 specifically includes: adding PMMA powder into 0.5M sodium hydroxide 75% ethanol solution and soaking for 2 hours, taking it out and washing it with distilled water, standing it to dry, so as to obtain carboxylated PMMA.

[0011] Furthermore, the solvent of 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 invention also provides a PMMA film obtained by the above preparation method.

[0014] The present invention also provides an application of the PMMA film in preparing a PMMA material with controllable transparency and shape and which is reversible.

[0015] The present invention also provides a method for preparing a special-shaped PMMA material, which comprises placing the PMMA film into water or anhydrous ethanol at 50° C., and after the PMMA film becomes soft, customizing the shape of the PMMA film, and then leaving it for a while to obtain a special-shaped PMMA material with a preset shape.

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

[0017] The present invention also provides a method for controlling the transparency of a PMMA film. The 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 to 10%. 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 to 90%.

[0018] Compared with the prior art, the present invention uses 75% sodium hydroxide ethanol solution to carboxylate PMMA, which can simply control the carboxyl content in the carboxylated PMMA to maintain the carboxyl content at 1.583×10 -5mol / g remains unchanged, and trifluoroethanol is used as the solvent. The PMMA film finally prepared has high transparency. It can be customized into any shape through 50℃ water or anhydrous ethanol auxiliary treatment. It can be transformed from high transparency to opaque through 50℃ water treatment, and from opaque to high transparency through 50℃ anhydrous ethanol treatment, and these transformations are reversible. In addition, the change of shape is also reversible, that is, different shapes can be designed repeatedly. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The figure is a calculation result diagram of the carboxyl content of PMMA powder after immersion in 0.5M sodium hydroxide 75% ethanol solution for 0h, 0.5h, 1h, 2h, 2.5h and 3h; wherein, Figure A is untreated PMMA powder (sample 1: immersion time is 0h), Figure B is PMMA powder with immersion time of 0.5h (sample 2), Figure C is PMMA powder with immersion time of 1h (sample 3), Figure D is PMMA powder with immersion time of 2h (sample 4); Figure E is PMMA powder with immersion time of 2.5h (sample 5), and Figure F is PMMA powder with immersion time of 3h (sample 6);

[0020] Figure 2 is the hydrophilic angle of samples 1-4;

[0021] Figure 3 It is the transparency change diagram of sample 1 and sample 4;

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

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

[0024] Figure 6 This is a physical picture of the PMAA membrane prepared in Comparative Example 2 carrying a 5 g weight before and after being immersed in water for 20 minutes. DETAILED DESCRIPTION

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

[0026] Example 1

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

[0028] The immersion time is 0h, 0.5h, 1h, 2h, 2.5h and 3h, and sample 1, sample 2, sample 3, sample 4, sample 5 and sample 6 are obtained respectively.

[0029] The carboxyl content of the water-insoluble component was measured by conductivity titration. 0.3 g of the dried sample 1-4 to be tested was weighed, 55 mL of distilled water and 5 mL of 0.01 M sodium chloride solution were added, and the mixture was stirred evenly with a magnetic stirrer to obtain a mixed solution. Then 0.1 M HCI was added to adjust the pH value of the mixed solution to 2.5-3.0, and the mixture was stirred magnetically for 1 hour. Subsequently, 0.04 M NaOH solution was titrated at a rate of 0.1 mL / min, and the conductivity of the mixed solution during the reaction was monitored by a conductivity meter. The titration was stopped when the pH value of the solution reached 11. According to the formula: carboxyl content = 0.04 mol / L*(V B -V A )mL / 0.3g to calculate the carboxyl content, where V A and V B The volume of NaOH solution consumed at the intersection of the tangent line of the conductivity curve on the left and right sides and the lowest horizontal line. The conductivity change formula and carboxyl content of samples 1-5 are as follows: Figure 1 It can be found that the carboxyl content increases with the increase of the NaOH alcohol solution immersion treatment time. When the treatment time is 2h, the carboxyl content is the highest, reaching 1.583×10 -5 mol / g. As the treatment time continued to increase, the carboxyl content remained at 1.583×10 -5 mol / g remains unchanged.

[0030] Example 2

[0031] 2 g of sample 1-4 obtained in Example 1 was dissolved in 10 mL of trifluoroethanol at a concentration of 0.2 g / mL, and stirred overnight to dissolve. The solution was cast on a polyimide film, and a carboxylated polymethyl methacrylate film was obtained after the trifluoroethanol evaporated.

[0032] The hydrophilicity test of PMMA films prepared by using samples 1-4 was carried out. Figure 2 As shown in the figure, it can be found that with the increase of immersion treatment time, the carboxyl content on the surface of the material will also increase, resulting in an increase in hydrophilicity. Among them, sample 4 has the highest carboxyl content and the best hydrophilicity.

[0033] Example 3

[0034] The PMMA film prepared by using sample 4 (immersion time of 2h) was immersed in 50℃ water for 20min to obtain an opaque film of 2%. After being completely dried, it was placed on a flower to measure its transparency. Figure 3 As shown in the figure below.

[0035] Example 4

[0036] The opaque film obtained in Example 4 was immersed in 50°C anhydrous ethanol for 5 minutes to obtain a transparent film of about 65%. After it was completely dried, it was placed on a flower to measure its transparency. Figure 3 As shown in the figure below (corresponding to carboxylated PMMA).

[0037] According to Examples 4 and 5, the PMMA film prepared by the present invention has extremely high transparency (about 90%) and has the property of controllable transparency. When the film is immersed in 50°C water for 20 minutes, the film will change from highly transparent to opaque (about 2%). The opaque film is further immersed in 50°C anhydrous ethanol for 5 minutes, and the film changes from opaque (about 2%) 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 figure below, the leftmost picture is the actual picture of the original carboxylated PMMA transparency, the middle picture is the actual picture after 50℃ water treatment for 20 minutes, it can be found that the transparency of the material is significantly reduced, and the right picture below is the actual picture of the carboxylated PMMA after 50℃ anhydrous ethanol treatment for 5 minutes. It can be found that the transparency is significantly improved after anhydrous ethanol treatment. The following is the corresponding quantitative analysis of transparency. The transparency of the original PMMA film is about 90%. After water treatment, the transparency is reduced to about 2%. After further treatment with 50℃ anhydrous ethanol, the transparency is restored to about 65%.

[0039] Example 5

[0040] The PMMA film prepared from sample 4 (immersion time 2 h) can bear a weight of 5 g (see Figure 4 B (left), put it in 50℃ water or ethanol solution for about 5 minutes, the film becomes soft and can hardly bear its own weight (see Figure 4 B right), at this time, the shape can be customized, such as spiral, M-shaped, N-shaped, etc., and the shape can be fixed after leaving water or ethanol and standing for a while (such as Figure 4 A).

[0041] Comparative Example 1

[0042] Dissolve commercially available polymethyl methacrylate in trifluoroethanol at a concentration of 0.2 g / mL, stir overnight to dissolve, cast the solution on a polyimide film, and wait for the trifluoroethanol to evaporate to obtain a polymethyl methacrylate film (sample 1). Sample 1 was immersed in 50°C water, and the transparency of the film decreased slightly. It was then placed in 50°C anhydrous ethanol, and the transparency increased slightly. The actual picture and transparency test results are shown in the figure. Figure 3As shown in the figure above (corresponding to PMMA), it can be seen that the transparency does not change much after water treatment and anhydrous ethanol treatment.

[0043] Comparative Example 2

[0044] Commercially available carboxylated PMMA (PMAA, carboxyl content 2.657×10 -5 mol / g, such as Figure 5 (shown) was dissolved in acetone with a PMMA concentration of 0.2 g / mL, stirred overnight to dissolve, and the solution was cast on a polyimide film. After the acetone evaporated, a PMAA film was obtained. The PMAA film can carry a 5 g weight (see Figure 6 A), after soaking it in 50℃ water or anhydrous ethanol for 20min, it can still bear 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 cannot be customized in shape.

Claims

1. A method for preparing a PMMA film with controllable transparency and shape and reversibility, characterized in that: The following steps are involved: S1. The PMMA is immersed in a sodium hydroxide alcohol solution for carboxylation modification to obtain carboxylated PMMA; S2. The carboxylated PMMA is dissolved in trifluoroethanol, and after 12-24 hours, stirred until completely dissolved to obtain a carboxylated PMMA solution; S3. pouring the carboxylated PMMA solution onto the polyimide film and allowing it to stand until the trifluoroethanol solution is completely evaporated to obtain the PMMA film.

2. The preparation method according to claim 1, characterized in that: Step S1 specifically includes: adding PMMA powder into 0.5M sodium hydroxide alcohol solution and soaking for 1-2 hours, taking it out and washing it with distilled water, standing it to dry, and obtaining carboxylated PMMA.

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

4. The preparation method according to claim 1, characterized in that: The concentration of the carboxylated PMMA solution is 0.15-0.25 g / mL.

5. The PMMA film obtained by the preparation method according to any one of claims 1 to 4.

6. Use of the PMMA film according to claim 5 in preparing PMMA materials with controllable transparency and shape and reversibility.

7. A method for preparing a special-shaped PMMA material, characterized in that: The PMMA film of claim 5 is placed in a water or ethanol solution at 50° C., and after the PMMA film becomes soft, the PMMA film is customized in shape, and then left for a while to obtain a special-shaped PMMA material with a preset shape.

8. The preparation method according to claim 7, characterized in that: The preset shape is a spiral shape, an M shape or an N shape.

9. A method for controlling the transparency of a PMMA film, characterized in that: The PMMA film of claim 5 is immersed in 50°C water for 5 to 20 minutes to obtain a PMMA opaque film with a transparency of 2-10%. The PMMA opaque film is immersed in 50°C anhydrous ethanol for 5 to 20 minutes to obtain a transparent film with a transparency of 65-90%.

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