Janus film directionally constructed by light driving and method

Abstract

The invention discloses a light-driven directionally constructed Janus film and a method, and belongs to the technical field of functional film materials.Hydrophobic molecules and hydrophilic molecules are dispersed in a macromolecular prepolymer solution, and after coating and film forming, light with specific wavelength is utilized for irradiation, so that the hydrophobic molecules migrate to the upper surface under light driving, and the functional film is formed. The hydrophilic molecules migrate to the lower surface under the action of gravity, and meanwhile, the prepolymer is photo-initiated to be cured, so that the Janus film with a hydrophobic upper surface and a hydrophilic lower surface is formed. The method is simple and efficient, and is suitable for the fields of microfluidics, separation membranes, intelligent coatings and the like.

Description

Technical Field

[0001] This invention belongs to the field of functional thin film materials technology, specifically relating to a Janus thin film with asymmetric surface properties and its light-driven directional construction method. Background Technology

[0002] Janus films, due to their different physical or chemical properties on both sides, have wide applications in microfluidics, sensing, catalysis, and smart coatings. Current methods for preparing Janus films mainly include layer-by-layer assembly, electrospinning, interfacial polymerization, and asymmetric modification. However, these methods are often cumbersome, costly, or difficult to achieve precise molecular orientation. Furthermore, existing methods largely rely on external physical fields (such as electric fields or temperature gradients) or complex chemical reactions, limiting their control precision and efficiency.

[0003] Therefore, there is an urgent need to develop a simple, efficient, and controllable method for preparing Janus thin films, which can achieve directional migration and distribution control of molecules along the thickness direction of the film. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing Janus thin films in one step by utilizing the synergistic effect of light-driven and gravity-based molecular directional migration, combined with photopolymerization technology. This method is simple, efficient, environmentally friendly, and suitable for large-area thin film preparation.

[0005] This invention provides a method for optically driven directional construction of Janus thin films, comprising the following steps:

[0006] Hydrophobic and hydrophilic molecules are dispersed in a polymer prepolymer solution containing a photoinitiator;

[0007] The resulting solution is coated onto a substrate to form a liquid film;

[0008] When the film is irradiated with light of a specific wavelength, the light energy drives the hydrophobic molecules to migrate to the upper surface, and gravity drives the hydrophilic molecules to migrate to the lower surface. At the same time, the light induces the curing of the polymer prepolymer.

[0009] After curing, a Janus film with asymmetric surface properties is obtained.

[0010] Furthermore, the polymer prepolymer includes, but is not limited to, one or more of acrylic resin, epoxy resin, silicone resin, and polyurethane prepolymer.

[0011] Furthermore, the hydrophobic molecule includes one or more of fluorinated compounds, silane coupling agents, and long-chain alkyl compounds;

[0012] Furthermore, the hydrophilic molecule includes one or more of polyethylene glycol, polyvinyl alcohol, carboxylates, and sulfonates.

[0013] Furthermore, the light of the specific wavelength is ultraviolet light or visible light, with a wavelength range of 250 nm–450 nm.

[0014] Furthermore, the light intensity is 10–200 mW / cm², and the illumination time is 10 seconds to 30 minutes.

[0015] Furthermore, the mass fractions of the hydrophobic and hydrophilic molecules in the polymer prepolymer solution are 0.1%–10% and 0.1%–15%, respectively.

[0016] Furthermore, the substrate is glass, silicon wafer, polymer film, or metal foil.

[0017] Furthermore, the Janus thin film prepared using the light-driven directional construction method of the present invention comprises:

[0018] The polymer matrix is ​​formed by curing a polymer prepolymer solution;

[0019] Hydrophobic molecules distributed on the surface of a polymer matrix;

[0020] Hydrophilic molecules distributed in the lower surface region of the polymer matrix;

[0021] The water contact angle on the upper surface of the film is ≥90°, and the water contact angle on the lower surface is ≤60°.

[0022] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0023] 1. Driven by the synergy of light and gravity: Light energy drives hydrophobic molecules to float upwards, while gravity drives hydrophilic molecules to sink downwards, achieving efficient directional migration;

[0024] 2. Simultaneous photocuring: Light irradiation drives molecular migration and promotes curing, completing film formation and structure construction in one step;

[0025] 3. Simple and controllable process: No complex equipment or multi-step processing is required, making it suitable for continuous production;

[0026] 4. Tunable structure: By adjusting the types and concentrations of molecules and the illumination parameters, the degree of asymmetry and performance of the thin film can be controlled. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a diagram illustrating the process of optically driven directional fabrication of Janus thin films.

[0029] Figure 2 This is a schematic diagram of the contact angles of the upper and lower surfaces in Example 2;

[0030] Figure 3 This is a schematic diagram of the contact angles of the upper and lower surfaces in Example 3; Detailed Implementation

[0031] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0032] Example 1

[0033] This invention provides a method for optically driven directional construction of Janus thin films, comprising the following steps:

[0034] Step 1: Prepare the mixed solution;

[0035] Hydrophobic and hydrophilic molecules are dispersed in a polymer prepolymer solution containing a photoinitiator to form a homogeneous mixed solution.

[0036] The polymer prepolymer includes, but is not limited to, one or more of acrylic resin, epoxy resin, silicone resin, and polyurethane prepolymer; the hydrophobic molecule includes, or is not limited to, one or more of fluorinated compounds, silane coupling agents, and long-chain alkyl compounds; the hydrophilic molecule includes, or is not limited to, polyethylene glycol, polyvinyl alcohol, carboxylates, and sulfonates.

[0037] The mass fractions of the hydrophobic and hydrophilic molecules in the polymer prepolymer solution are 0.1%–10% and 0.1%–15%, respectively. By adjusting the mass fractions of the hydrophobic and hydrophilic molecules in the polymer prepolymer solution, the water contact angles of the upper and lower surfaces of the Janus film can be controlled.

[0038] Step 2, film formation;

[0039] The resulting solution is coated onto a substrate to form a liquid film; the substrate is glass, silicon wafer, polymer film, or metal foil.

[0040] Step 3, light-driven directional migration and curing;

[0041] When a liquid film is irradiated with light of a specific wavelength, the light energy drives the hydrophobic molecules to migrate to the upper surface, while gravity drives the hydrophilic molecules to migrate to the lower surface. At the same time, the light induces the curing of the polymer prepolymer, resulting in a Janus film with asymmetric surface properties, where the upper surface is hydrophobic and the lower surface is hydrophilic.

[0042] The light of the specific wavelength is ultraviolet light or visible light, with a wavelength range of 250 nm–450 nm;

[0043] The light intensity is 10–200 mW / cm², and the illumination time is 10 seconds to 30 minutes;

[0044] Step 4: After curing, peel the Janus film off the substrate.

[0045] During the photo-driven directional migration and curing process, the photoinitiator exhibits strong absorption of light of a specific wavelength. When this specific wavelength of light irradiates the polymer prepolymer solution, the light energy is efficiently absorbed by the photoinitiator near the upper surface of the prepolymer solution and rapidly converted into heat energy. This results in a significant and rapid increase in temperature on the upper surface of the prepolymer solution, while the lower region remains cooler due to light attenuation and lag in heat conduction. This temperature difference creates a surface tension gradient within the prepolymer solution, with higher-temperature regions exhibiting lower surface tension and lower-temperature regions exhibiting higher surface tension. In other words, the upper surface of the prepolymer solution has low surface tension, and the lower surface has high surface tension. Fluid flows from the region of low surface tension to the region of high surface tension to balance this difference. Hydrophobic molecules dissolved or dispersed in the prepolymer solution, due to their lower surface energy, tend to migrate and accumulate towards the gas-liquid interface to reduce the overall surface energy of the system. Hydrophilic molecules settle downwards due to gravity and convection compensation.

[0046] The Janus film prepared by the method of the present invention comprises:

[0047] The polymer matrix is ​​formed by curing a polymer prepolymer solution.

[0048] Hydrophobic molecules are distributed on the upper surface region (hydrophobic layer) of a polymer matrix. This upper surface region is rich in hydrophobic functional molecules, which gives the upper surface of the polymer matrix hydrophobic properties.

[0049] Hydrophilic molecules are distributed in the lower surface region (hydrophilic layer) of the polymer matrix; this lower surface region is rich in hydrophilic functional molecules, which makes the upper surface of the polymer matrix hydrophobic.

[0050] The Janus film has an overall thickness of 100μm to 1mm, is colorless and transparent, and has good flexibility; the water contact angle of the upper surface of the Janus film is ≥90°, and the water contact angle of the lower surface is ≤60°.

[0051] Example 2

[0052] This embodiment describes a method for optically driven directional construction of Janus thin films, such as... Figure 1 As shown, it includes the following steps:

[0053] Step 1: Prepare the mixed solution;

[0054] Hydrophobic and hydrophilic molecules are dispersed in a polymer prepolymer solution containing a photoinitiator to form a homogeneous mixed solution.

[0055] In this embodiment, 1 g of epoxy acrylate prepolymer and an appropriate amount of photoinitiator 184 are dissolved in 5 g of acetone, and 0.05 g of perfluorooctyltriethoxysilane (hydrophobic molecule) and 0.1 g of polyethylene glycol (PEG-1000, hydrophilic molecule) are added and stirred until a mixed solution is formed; the appropriate amount of photoinitiator 184 can be 0.01 g.

[0056] Step 2, film formation;

[0057] The mixed solution was spin-coated onto a glass substrate to form a liquid film with a thickness of approximately 10 μm;

[0058] Step 3, light-driven directional migration and curing;

[0059] The film was irradiated with a 365 nm UV lamp (intensity 50 mW / cm²) for 5 minutes. Under illumination, hydrophobic molecules migrated to the upper surface mainly driven by light, while hydrophilic molecules migrated to the lower surface mainly driven by gravity. During this process, the light irradiation also induced the curing of the polymer prepolymer. After curing, a Janus film was obtained, and the following measurements were taken: Figure 2 As shown in (a), the water contact angle of the upper surface is 108.5°, as... Figure 2 As shown in (a), the lower surface is 42.8°.

[0060] Step 4: After curing, the Janus film is peeled off from the substrate to obtain a Janus film with a stable asymmetric structure.

[0061] Example 3

[0062] This embodiment of a method for optically driven directional construction of Janus thin films includes the following steps:

[0063] Step 1: Prepare the mixed solution;

[0064] Mix 2 g of polyurethane acrylate prepolymer, 0.1 g of octadecyltrimethoxysilane (hydrophobic molecule), and 0.15 g of sodium dodecyl sulfate (hydrophilic molecule), and add 0.01 g of photoinitiator 184;

[0065] Step 2, film formation;

[0066] The mixed solution is coated onto a PET film to form a liquid film with a thickness of approximately 30 μm;

[0067] Step 3, light-driven directional migration and curing;

[0068] Irradiation with 385 nm ultraviolet light (intensity 80 mW / cm²) for 10 minutes; under illumination, hydrophobic molecules migrate to the upper surface mainly driven by light, while hydrophilic molecules migrate to the lower surface mainly under gravity; during this process, the light irradiation simultaneously induces the curing of the polyurethane acrylate prepolymer, resulting in a Janus film, such as... Figure 3 As shown in (a), the contact angle of the upper surface of the film is 104.9°, as... Figure 2 As shown in (b), the lower surface is 35.6°.

[0069] Step 4: After curing, the Janus film is peeled off from the substrate to obtain a Janus film with a stable asymmetric structure.

Claims

1. A method of constructing a Janus film, characterized by, The method comprises the following steps: dispersing hydrophobic molecules and hydrophilic molecules in a high polymer prepolymer solution containing a photoinitiator; coating the obtained solution on a substrate to form a liquid film; irradiating the liquid film with light of a specific wavelength to make the hydrophobic molecules migrate to the upper surface under the driving of light and the hydrophilic molecules migrate to the lower surface under the action of gravity, and meanwhile initiate the photocuring of the high polymer prepolymer; after curing, a Janus film with a hydrophobic upper surface and a hydrophilic lower surface is obtained.

2. The method of claim 1, wherein the Janus film is constructed by, The high polymer prepolymer is selected from one or more of acrylic resin, epoxy resin, silicone resin, and polyurethane prepolymer.

3. The method of claim 1, wherein the Janus film is constructed by, The hydrophobic molecules are selected from one or more of fluorine-containing compounds, silane coupling agents, and long-chain alkyl compounds.

4. The method of claim 1, wherein the Janus film is constructed by, The hydrophilic molecules are selected from one or more of polyethylene glycol, polyvinyl alcohol, carboxylate, and sulfonate.

5. The method of claim 1, wherein the Janus film is constructed by, The light of the specific wavelength is ultraviolet light or visible light, and the wavelength range is 250 nm-450 nm.

6. The method of claim 1, wherein the Janus film is constructed by, The light intensity is 10-200 mW / cm², and the irradiation time is 10 seconds to 30 minutes.

7. The method of claim 1, wherein the Janus film is constructed by, The mass fraction of the hydrophobic molecules in the high polymer prepolymer solution is 0.1%-10%, and the mass fraction of the hydrophilic molecules is 0.1%-15%.

8. The method of claim 1, wherein the Janus film is constructed by, The substrate is glass, a silicon wafer, a polymer film, or a metal foil.

9. A Janus film prepared according to the method of any one of claims 1-8, characterized by, The Janus film comprises: a high polymer matrix; hydrophobic molecules distributed in the upper surface region of the high polymer matrix; and hydrophilic molecules distributed in the lower surface region of the high polymer matrix.

10. The Janus film of claim 9, wherein, The high polymer matrix is formed by curing a high polymer prepolymer solution.

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