Flexible packaging material and preparation method and application thereof

Abstract

The invention discloses a flexible packaging material and a preparation method and application thereof. The flexible packaging material comprises a sandwich structure formed by sequentially stacking a polymer elastomer with a viscoplastic surface layer, a self-adaptive gas barrier layer and a polymer elastomer with a viscoplastic surface layer, wherein the viscoplastic surface layer of the polymer elastomer consists of a non-polar viscoelastic molecular network and a plastic polar polymer microdomain; the self-adaptive gas barrier layer is at least one of liquid metal, hygroscopic gel and viscous hygroscopic liquid; and the viscoplastic surface layers of the upper and lower polymer elastomers are respectively contacted with two surfaces of the self-adaptive gas barrier layer, so that a sandwich structure is formed. The flexible packaging material not only can be flexibly stretched, but also has ultrahigh gas barrier property, and has important significance and value for promoting the practical application and industrialization process of flexible electronic devices.

Description

Technical Field

[0001] This application relates to the field of flexible electronics technology, and in particular to a flexible packaging material, its preparation method, and its application. Background Technology

[0002] Flexible electronics technology is driving the development of biomedical engineering, human-computer interaction, and artificial intelligence. In this technological field, the barrier properties of flexible encapsulation materials, i.e., encapsulation films, are crucial for the translation of devices from laboratory research to practical applications. This is especially true for flexible electronic devices made from highly sensitive materials such as halide perovskites, organic semiconductors, and organic electrolytes, which are extremely sensitive to water, oxygen, and biological fluids. Therefore, the ultra-high barrier properties of the encapsulation film become a key factor in their stable operation.

[0003] When designing wearable or implantable flexible electronic devices, the encapsulation layer often employs elastic and stretchable flexible encapsulation materials. Their core advantage lies in their ability to deform synchronously with the electronic device, thus fully leveraging the device's flexible functionality. Existing flexible encapsulation materials are typically polymer elastomers. The inherent looseness of the molecular structure of polymer elastomers allows them to achieve strong tensile properties; however, this also results in insufficient barrier properties. Therefore, achieving an elastomer sealing layer that maintains high tensile strength while also providing ultra-high barrier performance has become a pressing technical challenge in the development of flexible electronic devices.

[0004] To effectively reduce the gas permeability of elastic materials, research has largely focused on integrating high-barrier gas-blocking materials, such as liquid metals or adsorbents, into the elastomer matrix. However, in practical applications, it has been found that the gas permeability of these composite materials does not exhibit the expected order-of-magnitude reduction compared to the original elastomer.

[0005] Another approach involves fabricating a macroscopic polymer container from the elastic material and filling it with liquid metal. The liquid metal provides a physical barrier, effectively reducing the gas permeability of the elastic material. However, this method comes at the cost of increased container size and reduced seal stretchability. Therefore, while adding liquid metal improves gas barrier performance, this design requires more space to accommodate the liquid barrier material, sacrificing seal flexibility and compactness, and limiting the range of deformation the seal can withstand.

[0006] In conclusion, developing an elastomer encapsulation film that is both flexible and stretchable and possesses ultra-high gas barrier properties is of significant research importance and application value for promoting the practical application and industrialization of flexible electronic devices. Summary of the Invention

[0007] The purpose of this application is to provide a new flexible packaging material, its preparation method, and its application.

[0008] To achieve the above objectives, this application adopts the following technical solution:

[0009] One aspect of this application discloses a flexible encapsulation material comprising a sandwich structure formed by sequentially stacking a polymer elastomer having a viscoplastic surface layer, an adaptive gas barrier layer, and another polymer elastomer having a viscoplastic surface layer; wherein the viscoplastic surface layer of the polymer elastomer is composed of a nonpolar viscoelastic molecular network and plastic polar polymer microdomains; the adaptive gas barrier layer is at least one of liquid metal, hygroscopic gel, and viscous hygroscopic liquid; the upper and lower viscoplastic surface layers of the polymer elastomer are respectively in contact with the two surfaces of the adaptive gas barrier layer, thereby forming the sandwich structure.

[0010] It should be noted that this application creatively transforms the surface properties of the polymer elastomer film from traditional elasticity to viscoplasticity. Utilizing the characteristic of viscoplastic surfaces to form defect-free and deformable interfaces with various materials, a gas barrier layer (i.e., an adaptive gas barrier layer) such as liquid metal, hygroscopic gel, or viscous hygroscopic liquid is layered with a polymer elastomer possessing a viscoplastic surface to form a flexible film with ultra-high barrier performance—the flexible encapsulation material of this application. Furthermore, this gas barrier layer adaptively deforms with the elastic film during stretching without weakening the gas barrier performance or affecting the stretchability of the elastic film itself, thus preserving the flexibility and compactness of the flexible encapsulation material. Therefore, the flexible encapsulation material of this application maintains both flexibility and stretchability while providing excellent gas barrier performance, which is of great significance and value in promoting the practical application and industrialization of flexible electronic devices. It provides key technical support for the development of flexible electronics technology and lays the foundation for opening new application paths in wearable devices, biomedical sensors, flexible energy storage, and other fields.

[0011] In one embodiment of this application, the raw material for the polymer elastomer is a styrene-based block copolymer.

[0012] Preferably, the styrene-based block copolymer is a styrene-based triblock copolymer.

[0013] Preferably, the styrene-based triblock copolymer used in this application is at least one of styrene-isobutylene-styrene block copolymer (SIBS), styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), styrene-ethylene / butene-styrene block copolymer (SEBS), and styrene-ethylene / propylene-styrene block copolymer (SEPS).

[0014] It should be noted that styrene-based block copolymers, such as SIBS, are only one specific elastic film material used in this application. Under the same inventive concept, it is not excluded that other raw materials may also be used.

[0015] In one implementation of this application, the polymer elastomer further contains a plasticizer.

[0016] In one embodiment of this application, the plasticizer is one or a combination of several olefin polymers such as polyisobutylene, maleic anhydride-grafted polyisobutylene, petroleum resin, rosin resin, terpene resin, amorphous α-olefin copolymer (APAO), maleic anhydride-grafted APAO, and amorphous polyolefin (APO).

[0017] It should be noted that the key to this application is to change the surface properties of the polymer elastomer film from traditional elasticity to viscoplasticity. As for the preparation of the elastic film, existing technologies can be referenced. For example, polyisobutylene can be added as a plasticizer to styrene block copolymer elastomer to adjust the mechanical properties and barrier properties of styrene block copolymer elastomer.

[0018] In one implementation of this application, the polar grafted polymer selected for the polar polymer microdomains is at least one of maleic anhydride-grafted polypropylene (MA-PP), maleic anhydride-grafted polyethylene (MA-PE), glycidyl methacrylate-grafted polypropylene (GMA-PP), and glycidyl methacrylate-grafted polyolefin elastomer (GMA-POE).

[0019] Preferably, the polar grafted polymer selected for the polar polymer nanodomains is MA-PP or GMA-PP with a high content of grafted maleic anhydride.

[0020] In one implementation of this application, the hygroscopic gel is an ionic gel and / or an alcohol gel.

[0021] In one embodiment of this application, the ionogel is an ionogel composed of poly(acrylic acid-co-2-acrylamide-2-methylpropanesulfonic acid) and 1-ethyl-3-methylimidazolium acetate, and the alcohol gel is an alcohol gel composed of polyvinyl alcohol and glycerol.

[0022] In one implementation of this application, the viscous hygroscopic liquid is pure glycerol or a mixture of glycerol and ectoin.

[0023] Another aspect of this application discloses the application of the flexible packaging material in flexible electronic devices.

[0024] Another aspect of this application discloses a flexible electronic device using the flexible packaging material of this application.

[0025] It should be noted that the flexible electronic device of this application, due to the use of the flexible encapsulation material for sealing, has better gas barrier performance, thereby improving the quality and stability of the flexible electronic device; furthermore, because the flexible encapsulation material of this application is used, it does not affect the tensile properties of the flexible electronic device, enabling the flexible electronic device to have a wider range of applications. It is understood that the flexible electronic device of this application includes, but is not limited to, wearable devices, biomedical sensors, and flexible energy storage, as specifically referred to in existing flexible electronic devices.

[0026] Another aspect of this application discloses a method for preparing the flexible packaging material, including the following steps:

[0027] (1) A polymer elastomer preparation step with a viscoplastic surface layer includes using at least one of solution casting, blade coating, slot coating, dip coating, and screen printing to generate a surface layer on one side of a polymer elastomer film composed of a nonpolar viscoelastic molecular network and plastic polar polymer microdomains.

[0028] (2) Adaptive gas barrier layer preparation steps, (21) When the adaptive gas barrier layer is a hygroscopic gel, its preparation method includes placing the alcohol gel in an ethanol solution of γ-aminopropyltriethoxysilane to obtain an alcohol gel with a surface grafted silane coupling agent; or, initiating a polymerization reaction in an inert gas atmosphere and carrying out sealed thermal polymerization to promote gelation and form an ionic gel.

[0029] (22) When the adaptive gas barrier layer is a viscous hygroscopic liquid, its preparation method includes embedding micro-nano-sized solid particles into a designated area of ​​a polymer elastomer film with surface grafted polar polymer microdomains by hot pressing technology, adding viscous hygroscopic liquid to the position where the solid particles are embedded, and obtaining a polymer elastomer film with a surface covered by viscous hygroscopic liquid.

[0030] (23) When the adaptive gas barrier layer is liquid metal, its preparation method includes forming a silver film with a thickness of nanoscale in a designated area of ​​a polymer elastomer film grafted with polar polymer microdomains on the surface, and coating the liquid metal onto the silver film area to obtain a polymer elastomer film with liquid metal on the surface.

[0031] (3) Multilayer composite step, (31) When the adaptive gas barrier layer is a hygroscopic gel, the hygroscopic gel is sandwiched between the polar polymer microdomains of two polymer elastomer films and hot-pressed composite is performed to obtain the flexible encapsulation material of this application.

[0032] (32) When the adaptive gas barrier layer is a viscous hygroscopic liquid, two polymer elastomer films with surfaces covered by the viscous hygroscopic liquid are used, and the sides covered by the viscous hygroscopic liquid are stacked facing each other and physically pressed. While promoting the spread of droplets, the gas is discharged, thus obtaining the flexible encapsulation material of this application.

[0033] (33) When the adaptive gas barrier layer is liquid metal, two polymer elastomer films with liquid metal covering their surfaces are stacked facing each other and physically pressed to promote droplet spreading while expelling gas, thus obtaining the flexible encapsulation material of this application.

[0034] In one implementation of this application, the solution casting method includes dissolving the raw material particles of the polymer elastomer film and the polar grafted polymer used for the polar polymer microdomains in an organic solvent, allowing it to stand in a sealed environment to achieve preliminary gelation; then, opening the sealed environment to allow the organic solvent to evaporate and form a film; and placing the film in a vacuum oven to dry it, removing the residual organic solvent, and obtaining a polymer elastomer film with surface grafted polar polymer microdomains.

[0035] Due to the adoption of the above technical solutions, the beneficial effects of this application are as follows:

[0036] The flexible encapsulation material of this application creatively transforms the surface properties of the polymer elastomer film from the traditional elasticity to a viscoplastic polar polymer microdomain surface. Liquid metal, hygroscopic gel, or viscous hygroscopic liquid is then sandwiched between two layers of polar polymer microdomains. This allows the flexible encapsulation material of this application to maintain flexible stretchability while providing excellent gas barrier properties, which is of great significance and value for promoting the practical application and industrialization of flexible electronic devices. Attached Figure Description

[0037] Figure 1 These are the mechanical property test results of the elastic film in the embodiments of this application;

[0038] Figure 2 These are the test results of the wetting ridge height of the elastic film in the embodiments of this application;

[0039] Figure 3 This is a schematic diagram of the adhesion between the surface of the viscoplastic elastomer and the substrate in an embodiment of this application;

[0040] Figure 4 These are the water vapor transmission rate test results and barrier diagrams of the flexible packaging material in the embodiments of this application;

[0041] Figure 5 It is a summary of test results on the mechanical properties and oxygen permeability of different types of films;

[0042] Figure 6This is the water vapor transmission rate test result of the flexible packaging material in Embodiment 2 of this application. Detailed Implementation

[0043] To effectively address the gas permeation problem in encapsulation layers, the core strategy of this application aims to integrate an adaptive gas barrier layer into the sealing elastomer matrix. This effectively prevents gas molecules from penetrating and ensures the sealing integrity of the encapsulation layer under various environmental conditions. However, due to the limited segment mobility and chemical inertness of traditional sealing elastomer surfaces, it is difficult to construct a completely defect-free interface with heterogeneous materials (including nanoparticles and thin film materials) at the microscopic level, thereby forming a conformal and robust bond between the sealing elastomer matrix and the gas barrier layer, especially when the heterogeneous surface is non-planar or undergoes significant deformation.

[0044] Therefore, this application proposes a method for regulating the surface molecular conformation, transforming the surface properties of sealing elastomers from traditional elasticity to viscoplasticity. By controlling the phase separation process, this application introduces a viscoplastic surface effect into the sealing elastomer, significantly enhancing the mobility and polarity of surface segments. The resulting surface viscoplastic effect endows the material with the ability to form defect-free and deformable interfaces with various materials. Furthermore, this surface viscoplastic sealing elastomer can be seamlessly integrated with solid / liquid physicochemical barriers, such as liquid metals, hygroscopic gels, or viscous hygroscopic liquids, thereby constructing a stretchable sealing platform with extremely low water vapor transmission rate (WVTR) and oxygen transmission rate (OTR).

[0045] The polymer elastomer encapsulation substrate used in this application possesses a deformable, viscoplastic surface, allowing the elastic film to adhere tightly to various material surfaces without limitations in size, material properties, or geometry. Under stress, this material better adapts to and fills the microscopic irregularities at the interface, reducing gas molecule permeation. Furthermore, the viscoplastic surface also facilitates the integration of the elastomer film, providing a solid foundation for developing highly stretchable multilayer composite barrier film systems. This design of a sealing elastomer viscoplastic surface layer not only significantly improves the interfacial sealing performance of the material but also greatly expands the application of flexible encapsulation materials in ultra-high barrier performance encapsulation, particularly suitable for applications with extremely high requirements for sealing and stretchability. It provides a new technical path for developing highly stretchable multilayer composite barrier films and expands its application in the field of soft electronics with ultra-high sealing requirements.

[0046] The present application will be further described in detail below with reference to specific embodiments and accompanying drawings. The following embodiments are only for further illustration of the present application and should not be construed as limiting the present application.

[0047] Unless otherwise specified, the terms used in this application generally have the meanings commonly understood by those skilled in the art. Unless otherwise specified, the methods used in the following embodiments are conventional methods, and the raw materials used are all available from publicly available commercial sources. Unless otherwise specified, all operations are performed at room temperature and pressure.

[0048] Example 1

[0049] In this example, an elastic film is prepared using styrene-isobutylene-styrene block copolymer (SIBS) and maleic anhydride-grafted polypropylene (MA-PP). By controlling the phase separation process of the two materials, a viscoplastic surface layer is formed on the bottom surface of the elastic film. A viscous hygroscopic liquid is sandwiched between the two viscoplastic surface layers as an adaptive gas barrier layer to form the flexible encapsulation material in this example. The viscous hygroscopic liquid used in this example is a mixture of glycerol and ectoin (Shanghai Yuanye Biotechnology Co., Ltd., S2578), in which the mass fraction of ectoin is 23%.

[0050] The specific preparation method of the flexible packaging material in this example includes:

[0051] Preparation steps of the viscoplastic surface layer: First, disperse 1.0 g of MA-PP masterbatch (Sigma-Aldrich, 25722-45-6) in 200 mL of toluene solvent, stir at 125 °C for 2 hours, and use cold water circulation condensation to achieve reflux. After the masterbatch is completely dissolved, add 40 g of SIBS particles (Kaneka, SIBSTAR) to the solution. TM The mixture was stirred at room temperature for 2 hours to achieve homogeneous mixing (102T). The resulting MA-PP / SIBS precursor solution was then poured into a 15cm diameter glass petri dish pretreated with oxygen plasma and sealed with aluminum foil at room temperature. The dish was allowed to stand for 2–5 hours (3 hours in this example) to promote uniform solvent distribution and initial gelation of the material. To precisely control the solvent evaporation rate, tiny pinholes were created on the aluminum foil to allow the toluene solvent to slowly evaporate in a fume hood, thus forming a thin film. After complete solvent evaporation, the formed film was peeled from the petri dish and stored in a vacuum oven at 110°C for 8 hours to thoroughly remove residual solvent, ensuring the purity and performance stability of the resulting elastomer material, thus obtaining the viscoplastic surface layer in this example. This process not only ensures the uniformity and viscoplastic surface properties of the material but also provides a high-quality elastomer substrate for subsequent lamination and integration processes.

[0052] Adaptive gas barrier layer preparation and multilayer composite steps: A rectangular perforated mask (customized template dimensions are 8cm*3cm*0.5mm, material is PTFE) is precisely placed on the previously prepared SIBS viscoplastic surface; a layer is uniformly coated in the perforated area of ​​the mask (coating density is 1.6μg / cm³). 2 3A molecular sieve powder (Tianjin Xiens, L05335) was used. Next, a hot press was used to heat the powder to 140°C to achieve hot-press bonding between the molecular sieve powder and the viscoplastic surface area. The molecular sieve particles, with a size of approximately 1 micrometer, have two key functions: first, they efficiently adsorb trace amounts of permeated water molecules, thus reducing water vapor permeability; second, after the molecular sieve particles are embedded in the hollow areas, they can transform the viscoplastic surface into an inert state, preventing the upper and lower film layers from sticking together due to stress, thereby preventing the formation of "short-circuit" channels in the thickness direction and ensuring that the barrier performance is not affected. This powder layer is essential and plays a crucial role in the structure; ultimately, the powder particles are embedded in the surface of the viscoplastic film. Besides molecular sieves, other types of nano-desiccant can be used for the powder layer, such as inorganic salt particles (e.g., LiCl, CaCl2) and metal oxide nanoparticles (e.g., activated Al2O3, CaO), but 3A molecular sieves are significantly more effective than other materials.

[0053] Subsequently, the mask is removed; a fixed volume of glycerol / ectoin is added to the surface of the heat-pressed molecular sieve powder layer. Another identical membrane is prepared following the same procedure (note: no further glycerol / ectoin drops are needed on this second membrane, as this would increase the difficulty of subsequent lamination), and it is flipped over to face the membrane with the glycerol droplet already applied. A gas duct is placed at the edge; the two membranes are firmly bonded at the edge by physical pressing, promoting the spread of the glycerol droplet and slowly expelling air from the membrane along the gas duct. Finally, the gas duct is removed, and the membrane is heat-sealed again (heat-sealing process parameters: 80℃, 40kPa, 2 minutes) to ensure the integrity and sealing of the laminated structure, thus obtaining the flexible encapsulation material of this example.

[0054] Example 2

[0055] This example uses the same viscoplastic surface layer as in Example 1. The only difference is that this example uses EGaIn liquid metal as an adaptive gas barrier layer to form the flexible encapsulation material.

[0056] The specific preparation method of the flexible packaging material in this example includes:

[0057] The preparation steps for the viscoplastic surface layer are the same as in Example 1.

[0058] Adaptive gas barrier layer preparation and multilayer composite steps: A surface viscoplastic elastomer (i.e., viscoplastic surface layer) that has undergone 100% coaxial stretching is placed on a plastic PET substrate, and then a rectangular cutout mask is precisely placed on it; in the area not covered by the mask, a silver film with a thickness of 200 nm is uniformly deposited by vapor deposition technology; then, the mask is removed and the film is released from the coaxial stretching state; then, a drop of a predetermined volume (5 μL) of liquid metal is dropped onto the area with the silver film on the surface. Prepare another identical film according to the above process, and flip it over so that it is face-to-face with the film on which liquid metal droplets have been dropped. At the same time, place a gas duct in the edge area. The two films are firmly bonded in the edge area by physical pressing. During this process, the EGaIn droplets are spread and the air inside the film is slowly discharged along the gas duct. Finally, the gas duct is removed and hot-press sealing is performed (hot-press sealing process parameters are 80℃, pressure is 40kPa, and time is 2 minutes) to ensure the integrity and sealing of the laminated structure, thus obtaining the flexible encapsulation material in this example.

[0059] In this process, because the vapor deposition process requires attaching the film to the deposition table, directly attaching the adhesive film without a plastic substrate would contaminate the film. The type of plastic is irrelevant; any plastic substrate other than PET can be used. In this example, the coaxial stretching treatment can, on the one hand, regulate the microstructure of the elastomer substrate, allowing the vapor-deposited silver film to penetrate deeply into the substrate's microstructure, thus significantly enhancing the adhesion between the film and the substrate. On the other hand, in practical applications, the elastomer substrate may undergo repeated stretching and bending deformation. By pre-stretching the substrate coaxially, the silver film can better adapt to the substrate's deformation during stretching, effectively dispersing stress concentration caused by substrate deformation, thereby preventing the film from cracking or peeling due to excessive stress. Releasing the film from the coaxial stretching state—this operation pre-stretches the elastomer film and releases it after vapor deposition—not only enhances the adhesion between the silver film and the elastomer film and optimizes the elastomer film's deformation capability, but also improves the film's uniformity.

[0060] Example 3

[0061] This example uses the same viscoplastic surface layer as in Example 1. The only difference is that this example uses an alcohol gel composed of polyvinyl alcohol and glycerin as an adaptive gas barrier layer to form the flexible encapsulation material in this example.

[0062] The specific preparation method of the flexible packaging material in this example includes:

[0063] The preparation steps for the viscoplastic surface layer are the same as in Example 1.

[0064] Preparation of the adaptive gas barrier layer and multilayer composite steps: Polyvinyl alcohol (PVA) powder (Aladdin, PVA-1799) was dissolved in dimethyl sulfoxide (DMSO) solution and stirred at 80°C for 3 hours to obtain a PVA / DMSO mixture with a PVA mass fraction of 15%. The prepared PVA / DMSO mixture was poured into a rectangular polytetrafluoroethylene (PTFE) mold (10 cm long, 5 cm wide, and 1 cm high), and then the mold was placed in a glycerol solution environment at room temperature to promote the exchange reaction between DMSO and glycerol. After 40 hours, the sample was removed to obtain a PVA / glycerol gel. The obtained PVA / glycerol gel was subjected to wet annealing at 120°C. The wet-annealed sample was immersed in an ethanol solution containing 2% by mass of γ-aminopropyltriethoxysilane (APTES) to graft a silane coupling agent onto the gel surface. The alcohol gel with silane coupling agent grafted onto its surface is sandwiched between two identical elastomers with viscoplastic surfaces (i.e., viscoplastic surface layers) and hot-pressed at 75°C for 20 minutes to obtain a composite film with a laminated structure, which is the flexible encapsulation material in this example.

[0065] Example 4

[0066] This example uses the same viscoplastic surface layer as in Example 1. The only difference is that this example uses an ionogel composed of poly(acrylic acid-co-2-acrylamide-2-methylpropanesulfonic acid) and 1-ethyl-3-methylimidazolium acetate as an adaptive gas barrier layer to form the flexible encapsulation material in this example.

[0067] The specific preparation method of the flexible packaging material in this example includes:

[0068] The preparation steps for the viscoplastic surface layer are the same as in Example 1.

[0069] Preparation of the adaptive gas barrier layer and multilayer composite steps: 5 wt% graphene oxide slurry was uniformly dispersed in 1-ethyl-3-methylimidazolium acetate using ultrasonic dispersion under ice bath conditions to form a homogeneous mixed solution. Subsequently, 2 g of acrylic acid (AA) powder (Aladdin, A1200), 0.5 g of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) (Aladdin, A106798), and 0.04 g of glycidyl methacrylate (GMA) (Sigma-Aldrich, 779342) were mixed into the above mixture. Next, 0.14 g of ammonium persulfate (APS) was added under an inert gas atmosphere to initiate the polymerization reaction. The above solution was then poured into a custom-made Teflon mold (10 cm long, 5 cm wide, 1 cm high) and subjected to sealed thermal polymerization at 60 °C to promote the gelation process. After polymerization, the sample was removed and placed in a vacuum oven at 95 °C to remove residual moisture. The dried ionogel was sandwiched between two identical elastomers with viscoplastic surfaces (i.e., viscoplastic surface layers) and hot-pressed at 85°C for 20 minutes to prepare a composite film with a layered structure, namely the flexible encapsulation material in this example.

[0070] Material characterization analysis

[0071] The following is a structural characterization of the viscoplastic surface elastomer prepared in Example 1: This study used an electronic universal testing machine (model CMT6203, equipped with a 100N load sensor, tensile speed set to 100 mm / min) to determine the stress-strain curves and perform mechanical testing to characterize the elastomer film properties before and after the addition of MA-PP. The samples were cut into dumbbell shapes (5 mm width, 80 mm gauge length) using a custom-made sheet metal punch. The behavior of the elastomer film before and after the addition of MA-PP was characterized. Based on Example 1, without adding MA-PP masterbatch, 40 g of SIBS particles were directly dispersed in 200 mL of toluene solvent. The subsequent steps were the same as in Example 1, preparing an ungrafted SIBS elastic film. The mechanical properties of the MA-PP-grafted and ungrafted elastic films were compared. The results... Figure 1 As shown in Figure A.

[0072] Test results show that the elastic modulus (1.1 MPa) and elongation at break (~800%) of the elastomer film after adding MA-PP are comparable to those of the original SIBS material, indicating that the bulk properties of the material are almost unaffected by the surface design. The inset in Figure A shows that the elastomer film did not crack after being punctured by scissors, thus demonstrating the excellent toughness of the elastomer film.

[0073] Nanoindentation tests were performed on sample surfaces using a Hysitron TI 950 nanoindenter (equipped with a Berkovich indenter manufactured by Bruker, USA). The Berkovich diamond indenter was calibrated using standard fused silica. During the test, the sample was placed on an iron base and fixed to a magnetic stage, and the indentation area was precisely located using a visible light microscope. A trapezoidal loading function was used, with loading, holding, and unloading times set to 10 seconds, 60 seconds, and 800 seconds, respectively, and load-depth curves were recorded. To ensure the indentation depth did not exceed the instrument's detection limit of 5 micrometers, the maximum load was set to 30 micronewtons. The characteristics of the elastic surface without MA-PP grafting and the viscoplastic surface with MA-PP grafting were tested, and the results are as follows: Figure 1 As shown in Figure B.

[0074] The results show that for SIBS materials, the force applied at the indenter tip increases linearly with increasing indentation depth, consistent with the conventional elastic deformation of elastomer surfaces. In contrast, the viscoplastic surface layer exhibits an atypical response pattern: when the indentation depth is less than 2860 nm, the applied force remains near zero, subsequently increasing monotonically but nonlinearly with further increases in indentation depth, corresponding to viscous and elastic / plastic deformation behaviors, respectively. Furthermore, the initial slope (i.e., contact stiffness) of the enlarged unloading curve in the inset of Figure B becomes negative at low unloading rates, a characteristic of the "nose tip" effect caused by the viscoplasticity of the polymer.

[0075] The surface viscoplastic properties of the elastomer were further verified through self-adhesion experiments. In the experiment, two elastic films grafted with MA-PP were placed opposite each other at room temperature, and the interface fused easily by lightly pressing with a finger for 3 seconds. Figure 1 As shown in Figure C, the interface boundary between the two fused films becomes difficult to discern, and upon attempting to peel them apart, a fibrous structure resembling cheese is formed, as shown in Figure C. Figure 1 As shown in Figure C, this surface fiber-like phenomenon provides direct experimental evidence for the existence of a viscoplastic surface layer.

[0076] Place immiscible [EIm]BF4 ionic liquid droplets on a viscoplastic surface, such as Figure 2 As shown in Figure A, the viscous flow of polymer chains on the surface leads to nanoscale surface creep through interfacial wetting when a droplet comes into contact with the polymer substrate. This is visualized using scanning white light interference microscopy, such as... Figure 2 As shown in Figure B, we found that at 30°C, the wetting ridge height of the viscoplastic surface reached 170 nm, more than twice that of SIBS. This difference in wetting ridge height further amplified as the temperature increased from 30°C to 80°C. These combined findings confirm the existence of viscoplastic surfaces and reveal the influence of temperature on their wetting behavior.

[0077] SIBS exhibits a viscoplastic surface that demonstrates the ability to form conformal, tough, and stretchable adhesions to a variety of material surfaces. This conformality and stretchability stem from highly mobile polymer chains in the surface layer, which adapt to the microstructure of the contact surface, achieving a tight fit. The toughness of the adhesion is attributed to the dispersed MA-PP polar domains in the subsurface layer. For example... Figure 3 As shown, these polar regions can trigger the formation of covalent bonds and, as energy dissipation regions, improve the toughness of adhesion by dispersing stress concentration at the adhesion interface.

[0078] To effectively address the problem of water molecule permeation, and leveraging the ease of integration provided by surface viscoplasticity, Example 1 developed a composite barrier membrane with high tensile strength and water impermeability. This barrier membrane's intermediate gas barrier layer consists of an embedded layer composed of molecular sieve particles and a high-viscosity liquid layer composed of glycerol and ectoine. Figure 4 As shown in Figure A.

[0079] This study used an ultra-precision water vapor permeability analyzer (Mocon, AQUATRAN 3) to detect the water vapor permeability of the flexible packaging material in Example 1. The sample size was 5cm × 6cm (the measurement area was limited to 5.64cm² by the window size). 2 The sample is positioned between two parts of the test chamber. One side is continuously supplied with 99.9999% pure dry nitrogen carrier gas, while the other side is continuously exposed to a water vapor environment. When water vapor passes through the sample, it mixes with the carrier gas and is transported to a detection limit of 10. -5 g / m 2 A high-precision water vapor sensor with a lifespan of [number] days. To prevent interference from external air, the film edges were tightly sealed with O-rings. Simultaneously, following the method of Example 1, a similar three-layer barrier film was prepared using a SIBS elastic film without MA-PP grafting for comparative testing. The test results are as follows: Figure 4 As shown in Figure B.

[0080] The results showed that, under conditions of 25°C and 90% relative humidity (RH), the water vapor transmission rate of the 0.65 mm thick three-layer barrier membrane was below the detection limit of the MoconAQUATRAN Model 3 device (~10). -5 g / m -2 / day), compared to a three-layer barrier membrane integrated with SIBS using a non-adhesive plastic surface, its water vapor permeability is reduced by three orders of magnitude, such as Figure 4 As shown in Figure B, this significant difference is primarily attributed to the direct contact between the two SIBS films, resulting in a "short circuit" that allows water molecules to permeate through this region, as... Figure 4As shown in Figure C. Because the SIBS surface is elastic, it cannot effectively encapsulate the molecular sieve, nor can it maintain a continuous liquid removal layer, especially after repeated mechanical stimulation, such as... Figure 4 As shown in Figure D. In contrast, the viscoplastic surface, due to its viscoplasticity and polarity, can stably and uniformly coat the molecular sieve, avoiding the occurrence of "short circuits" and thus maintaining a high barrier against moisture diffusion. These results highlight the importance of viscoplastic surface design in improving barrier performance. The film thickness was measured by scanning electron microscopy, and the liquid layer thickness was measured by optical microscopy using fluorescence staining. The results show that the 0.65 mm thick three-layer barrier film consists of a 0.25 mm elastomer film, a 0.15 mm liquid layer, and a 0.25 mm elastomer film. All embodiments have this thickness and structure.

[0081] Composite design strategies utilizing viscoplastic surface elastomers are not limited to the integration of chemisorbent liquid layers. By replacing the chemisorbent liquid layer with a physically barrier liquid metal, seals that are both airtight and highly stretchable can be developed, such as the flexible encapsulation material of Example 2. Figure 5 This paper summarizes our measurements of oxygen transmission rate (OTR) for common elastomers and plastics with a standardized film thickness of 1 mm under conditions of 23°C and 0% relative humidity (RH). The common elastomers and plastics tested in this experiment specifically include: elastomers PDMS and SEBS; and plastics PS, HDPE, PC, Parylene C, PET, PVC, PA, and PVDC.

[0082] This study used an ultra-precision oxygen permeation analyzer (Mocon, OX-TRAN 2 / 22L) to detect oxygen transmission rate (OTR) under test conditions of 23℃ and 0% relative humidity. During testing, the pressure difference across the film was set to one standard atmosphere. The results showed that the OTR of the single viscoplastic surface elastomer film was comparable to that of high-density polyethylene plastic, but its elastic modulus was much lower. Dissolving a 1300 molecular weight polyisobutylene (PIB) oligomer in toluene and slowly injecting it onto the top surface of the viscoplastic elastomer further reduced the modulus of the single film to approximately 100 kPa at the cost of a slight increase in oxygen permeability. Similar to integrated chemisorption barrier films, the physical barrier three-layer composite film has a thin-film structure that can withstand large deformations without increasing OTR, thanks to the high integrated stability provided by its viscoplastic surface.

[0083] Furthermore, we assembled a three-layer composite barrier membrane (composed of a 0.125 mm thin film, a 0.4 mm liquid metal, and a 0.125 mm thin film) (with surface grafted MA-PP) onto the sample after adding plasticizer. Its steady-state OTR reached the detection limit of our equipment (~10). -4 cm 3 / m 2 / day), such as Figure 6 As shown, under conditions of 38°C and 90% relative humidity (RH), the WVTR value is as low as 1.8 × 10⁻⁶. -3 g / m -2 / day.

[0084] Following the above method, this experiment tested the elastic modulus, elongation at break, water vapor permeability, and oxygen permeability of the flexible packaging materials prepared in Examples 1 to 4, respectively. The same tests were also conducted using SISB elastic films without MA-PP grafting, which were assembled into three composite barrier films using the same method as in Examples 1 to 4. The test results are shown in Table 1.

[0085] Table 1. Test results of tensile and barrier properties of flexible packaging materials.

[0086] elastic modulus Fracture growth rate Water vapor transmission rate oxygen transmission rate Example 1 2.2MPa 780％ <![CDATA[<9*10 -5 g / m 2 / day]]> <![CDATA[0.85cm 3 / m 2 / day]]> Example 1 Comparison 2.6MPa 692％ <![CDATA[0.068g / m 2 / day]]> <![CDATA[2.8cm 3 / m 2 / day]]> Example 2 1.4MPa 804％ <![CDATA[1.8*10 -3 g / m 2 / day]]> <![CDATA[<9*10 -4 cm 3 / m 2 / day]]> Example 2 Comparison 1.4MPa 787％ <![CDATA[0.078g / m 2 / day]]> <![CDATA[0.142cm 3 / m 2 / day]]> Example 3 2.7MPa 792％ <![CDATA[5.8*10 -3 g / m 2 / day]]> <![CDATA[0.59cm 3 / m 2 / day]]> Example 3 (Comparative Study) 1.8MPa 812％ <![CDATA[0.086g / m 2 / day]]> <![CDATA[5.26cm 3 / m 2 / day]]> Example 4 2.4MPa 802％ <![CDATA[<9*10 -5 g / m 2 / day]]> <![CDATA[0.74cm 3 / m 2 / day]]> Example 4 (Comparative) 1.9MPa 755％ <![CDATA[0.054g / m 2 / day]]> <![CDATA[3.86cm 3 / m 2 / day]]>

[0087] In Table 1, Example 1 is the control, which uses a SISB elastic film without MA-PP grafting and is assembled in the manner of Example 1 to obtain a three-dimensional composite barrier film. Examples 2 to 4 are similar.

[0088] The test data in Table 1 show that the water and oxygen barrier properties of the flexible encapsulation film can be precisely adjusted by controlling the type of interlayer in the viscoplastic elastic film. Specifically, when the interlayer is a glycerol / ectoine viscous hygroscopic liquid layer, the water vapor transmission rate (WVTR) of the film is less than 10%. -5 g / m2 / day; while when a liquid metal layer is used in the interlayer, the oxygen permeability (OTR) can be controlled at 10. -4 cm 3 / m 2 Below / day. Furthermore, this flexible encapsulation film exhibits an elastic modulus of approximately 2 MPa and an elongation at break of around 800%, demonstrating excellent elastic mechanical properties, making it a promising universal solution for the protection of stretchable electronic devices.

[0089] The above description, in conjunction with specific embodiments, provides a further detailed explanation of this application and should not be construed as limiting the specific implementation of this application to these descriptions. Those skilled in the art to which this application pertains can make several simple deductions or substitutions without departing from the concept of this application.

Claims

1. A flexible encapsulation material, characterized in that: The invention comprises a sandwich structure formed by sequentially stacking a polymer elastomer with a viscoplastic surface layer, an adaptive gas barrier layer, and another polymer elastomer with a viscoplastic surface layer; the viscoplastic surface layer is composed of a nonpolar viscoelastic molecular network and plastic polar polymer microdomains; the adaptive gas barrier layer is at least one of liquid metal, hygroscopic gel, and viscous hygroscopic liquid; the viscoplastic surface layers of the upper and lower polymer elastomers are respectively in contact with the two surfaces of the adaptive gas barrier layer.

2. The flexible packaging material according to claim 1, characterized in that: The raw material for the polymer elastomer is a styrene-based block copolymer; Preferably, the styrene-based block copolymer is a styrene-based triblock copolymer; Preferably, the styrene-based triblock copolymer is at least one of styrene-isobutylene-styrene block copolymer, styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, styrene-ethylene / butene-styrene block copolymer, and styrene-ethylene / propylene-styrene block copolymer; Preferably, the polymer elastomer further contains a plasticizer; Preferably, the plasticizer is one or a combination of several of the following: polyisobutylene, maleic anhydride-grafted polyisobutylene, petroleum resin, rosin resin, terpene resin, amorphous α-olefin copolymer, maleic anhydride-grafted amorphous α-olefin copolymer, and amorphous polyolefin.

3. The flexible packaging material according to claim 1, characterized in that: The polar polymer microdomains are selected from at least one of the following polar grafted polymers: maleic anhydride-grafted polypropylene, maleic anhydride-grafted polyethylene, glycidyl methacrylate-grafted polypropylene, and glycidyl methacrylate-grafted polyolefin elastomer. Preferably, the polar polymer microdomains are selected from maleic anhydride-grafted polypropylene or glycidyl methacrylate-grafted polypropylene.

4. The flexible encapsulation material according to any one of claims 1-3, characterized in that: The hygroscopic gel is an ionic gel and / or an alcohol gel.

5. The flexible packaging material according to claim 4, characterized in that: The ionogel is an ionogel composed of poly(acrylic acid-co-2-acrylamide-2-methylpropanesulfonic acid) and 1-ethyl-3-methylimidazolium acetate, and the alcohol gel is an alcohol gel composed of polyvinyl alcohol and glycerol.

6. The flexible encapsulation material according to any one of claims 1-3, characterized in that: The viscous, hygroscopic liquid is pure glycerol or a mixture of glycerol and ectoine.

7. The application of the flexible packaging material according to any one of claims 1-6 in flexible electronic devices.

8. A flexible electronic device using the flexible packaging material according to any one of claims 1-6.

9. A method for preparing the flexible encapsulation material according to any one of claims 1-6, characterized in that: Includes the following steps, (1) A polymer elastomer preparation step with a viscoplastic surface layer includes using at least one of solution casting, blade coating, slot coating, dip coating, and screen printing to generate a surface layer on one side of a polymer elastomer film composed of a nonpolar viscoelastic molecular network and plastic polar polymer microdomains. (2) Adaptive gas barrier layer preparation steps, (21) When the adaptive gas barrier layer is a hygroscopic gel, its preparation method includes placing the alcohol gel in an ethanol solution of γ-aminopropyltriethoxysilane to obtain an alcohol gel with a surface grafted silane coupling agent; or, initiating a polymerization reaction in an inert gas atmosphere and carrying out sealed thermal polymerization to promote gelation and form an ionic gel. (22) When the adaptive gas barrier layer is a viscous hygroscopic liquid, its preparation method includes embedding micro-nano-sized solid particles into a designated area of ​​a polymer elastomer film with surface grafted polar polymer microdomains by hot pressing technology, and dripping the viscous hygroscopic liquid onto the position where the solid particles are embedded to obtain a polymer elastomer film with a surface covered by viscous hygroscopic liquid. (23) When the adaptive gas barrier layer is liquid metal, its preparation method includes forming a silver film with a thickness of nanoscale in a designated area of ​​a polymer elastomer film grafted with polar polymer microdomains on the surface, and dropping liquid metal onto the silver film area to obtain a polymer elastomer film with liquid metal covering the surface. (3) Multilayer composite step, (31) When the adaptive gas barrier layer is a hygroscopic gel, the hygroscopic gel is sandwiched between the polar polymer microdomains of two polymer elastomer films and hot-pressed composite is performed to obtain the flexible encapsulation material. (32) When the adaptive gas barrier layer is a viscous hygroscopic liquid, two polymer elastomer films with surfaces covered by the viscous hygroscopic liquid are used, and the sides covered by the viscous hygroscopic liquid are stacked facing each other and physically pressed to promote the spread of droplets while expelling gas, thus obtaining the flexible encapsulation material. (33) When the adaptive gas barrier layer is liquid metal, two polymer elastomer films with liquid metal covering their surfaces are stacked facing each other and physically pressed to promote droplet spreading while expelling gas, thus obtaining the flexible encapsulation material.

10. The preparation method according to claim 9, characterized in that: The solution casting method includes dissolving the raw material particles of the polymer elastomer film and the polar grafted polymer used for the polar polymer microdomains in an organic solvent, allowing it to stand in a sealed environment to achieve preliminary gelation; then, opening the sealed environment to allow the organic solvent to evaporate and form a film; placing the film in a vacuum oven to dry it and remove the residual organic solvent to obtain a polymer elastomer film with surface grafted polar polymer microdomains.

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