Stretchable polymer packaging material based on heterostructure hydrogen bond network and preparation method and application thereof

Abstract

The invention discloses a stretchable polymer packaging material based on a heterostructure hydrogen bond network and a preparation method and application thereof, and belongs to the technical field of stretchable packaging materials. The stretchable polymer packaging material based on the heterostructure hydrogen bond network is obtained by combining amino-functionalized hexagonal boron nitride (hBN-NH2) nanosheets and polyurethane (PU) through a solution mixing method, and the heterogeneous hydrogen bond network is formed by surface amino groups (-NH2) of hBN-NH2 and carbamate carbonyl groups (-C = O) of PU, so that the interfacial compatibility, stability and dynamic property are enhanced; therefore, high stretchability, low modulus, high toughness and excellent barrier property are realized. According to the invention, the contradiction among the flexibility, toughness and barrier property of the traditional packaging material is solved, and a new solution is provided for the packaging of the next generation of wearable electronic equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of stretchable packaging materials, and in particular to a stretchable polymer packaging material based on a heterostructure hydrogen bond network, and a preparation method and application thereof. Background Art

[0002] Wearable electronic devices have shown tremendous potential in areas such as health monitoring, human-computer interaction, and personalized health management. These devices achieve functionality and intelligence by closely adhering to the structure of human skin, placing stringent demands on the mechanical and electrical stability of encapsulation materials. However, existing encapsulation materials face significant bottlenecks in mechanical adaptability, environmental stability, and multi-performance integration. While traditional inorganic materials and rigid polymers (such as polyimide and polyethylene terephthalate) exhibit excellent water / oxygen barrier properties due to their high crystallinity and dense molecular arrangement, their inherent rigidity results in insufficient stretchability and high modulus, making them unable to meet the core requirements of wearable devices for skin compatibility (modulus <800 kPa) and dynamic deformation adaptability (strain ≥20%). Traditional polymer elastomers (such as polydimethylsiloxane (PDMS), styrene-ethylene-butylene-styrene (SEBS), and polyurethane (PU)) achieve high stretchability through flexible segments and loose molecular structures, but they generally suffer from excessive modulus (≥400 kPa), insufficient fracture toughness, and weak barrier properties, making it difficult to ensure long-term device stability in humid or dynamic environments. While emerging soft materials (such as hydrogels) possess low modulus and biocompatibility, their weak fracture energy strength and environmental sensitivity (structural collapse after water absorption) also limit their practical applications. The core contradiction lies in the inherent conflict between low modulus requirements (skin compatibility) and high barrier performance (environmental stability): the former requires a loose polymer network to reduce modulus, while the latter relies on a dense structure to hinder penetration, resulting in an irreconcilable contradiction in material design. Although nanofillers (such as hexagonal boron nitride nanosheets) can reduce water / oxygen permeability due to their atomically dense structure, their surface inertness leads to weak interfacial bonding with the polymer matrix, causing key problems such as filler agglomeration, strain concentration, and rapid failure under cyclic loading, hindering their practical application in elastomers.

[0003] Therefore, there is an urgent need to develop a packaging material with high stretchability, low modulus, high toughness and high barrier properties to ensure the stable operation of wearable devices in high humidity environments. Summary of the Invention

[0004] The present invention aims to provide a stretchable polymer encapsulation material based on a heterogeneous hydrogen-bonded network, as well as its preparation method and application, to address the aforementioned problems in the prior art. By combining amino-functionalized hexagonal boron nitride (hBN-NH2) nanosheets with polyurethane (PU), the present invention utilizes the heterogeneous hydrogen-bonded network to enhance interfacial compatibility, stability, and dynamics, thereby achieving high stretchability, low modulus, high toughness, and excellent water barrier properties.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] One of the technical solutions of the present invention is a stretchable polymer packaging material based on a heterostructure hydrogen bond network, which is formed by amino-functionalized hexagonal boron nitride nanosheets and polyurethane through the action of a heterostructure hydrogen bond network.

[0007] The amino groups (-NH2) on the surface of amino-functionalized hexagonal boron nitride (hBN-NH2) nanosheets form a heterogeneous hydrogen-bonding network with the carbamate carbonyl groups (-C=O) in polyurethane (PU), resulting in the hBN-NH2 / PU composite. This heterogeneous hydrogen-bonding network enhances the composite's interfacial compatibility, stability, and dynamics, resulting in high stretchability, low modulus, high toughness, and excellent barrier properties.

[0008] Preferably, the polyurethane is obtained by reacting hydroxy-terminated polydimethylsiloxane (PDMS-OH) and 4,4'-diphenylmethane diisocyanate (MDI) as monomers.

[0009] Furthermore, the preparation steps of the polyurethane include:

[0010] Mix the hydroxy-terminated polydimethylsiloxane, 4,4'-diphenylmethane diisocyanate, catalyst and solvent 1, heat at 35-45°C for 3-4 hours, then cool the reaction system to 0-5°C, add the chain extender, and continue the reaction (at 0-5°C) for 30-40 minutes.

[0011] Furthermore, the catalyst includes dibutyltin dilaurate (DBTDL).

[0012] Furthermore, the solvent 1 includes N,N-dimethylformamide (DMF).

[0013] Furthermore, the chain extender includes 1,4-butanediol.

[0014] Furthermore, the number average molecular weight of the hydroxyl-terminated polydimethylsiloxane is 4000-6000 Da. The molecular chain of the high molecular weight hydroxyl-terminated polydimethylsiloxane is longer, which can reduce the stacking interaction of the polymer chains and reduce the hydrogen bond density in the polyurethane chain, thereby reducing the Young's modulus of the polyurethane.

[0015] Furthermore, the usage ratio of the hydroxy-terminated polydimethylsiloxane, 4,4'-diphenylmethane diisocyanate, catalyst and chain extender is 5-15 g: 0.38-1.5 g: 15-45 μL: 45-180 mg.

[0016] Furthermore, the molar ratio of the 4,4'-diphenylmethane diisocyanate to the hydroxy-terminated polydimethylsiloxane is greater than 1, that is, the 4,4'-diphenylmethane diisocyanate is excessive.

[0017] The purpose of using an excess of 4,4'-diphenylmethane diisocyanate is to improve the elasticity of the polyurethane. This excess 4,4'-diphenylmethane diisocyanate provides more reactive sites, allowing it to fully react with the hydroxyl groups in the hydroxyl-terminated polydimethylsiloxane, forming a richer and more uniform crosslinked network. This crosslinked structure effectively restricts polymer chain slippage, improving the material's resistance to deformation under stress, and thus enhancing the polyurethane's elasticity. Generally speaking, the amount of 4,4'-diphenylmethane diisocyanate used is just the theoretical amount required for complete reaction with the hydroxyl groups in the hydroxyl-terminated polydimethylsiloxane, i.e., a 1:1 molar ratio between the two, which is considered the standard amount. If the amount of 4,4'-diphenylmethane diisocyanate exceeds this theoretical value, it is considered excessive.

[0018] Furthermore, the usage ratio of the hydroxy-terminated polydimethylsiloxane and the solvent 1 (excluding the portion used to dissolve the chain extender) is 5-15 g:20-80 mL.

[0019] Preferably, the step of mixing the hydroxy-terminated polydimethylsiloxane, 4,4'-diphenylmethane diisocyanate, a catalyst and solvent 1 and heating the mixture at 35-45° C. for 3-4 hours comprises:

[0020] Add the hydroxy-terminated polydimethylsiloxane and the catalyst to the reaction vessel, then add a mixed solution of part of 4,4'-diphenylmethane diisocyanate and part of solvent 1, heat and react at 35-45°C for 1 hour, then add the remaining mixed solution of 4,4'-diphenylmethane diisocyanate and the remaining solvent 1, and continue heating and reacting at 35-45°C for 2-3 hours.

[0021] Furthermore, the chain extender is added in the form of a mixed solution of the chain extender and solvent 1, that is, the chain extender and solvent 1 are first mixed and then added to the reaction system, and the amount ratio of the chain extender to solvent 1 is 45-180 mg:2.5-10 mL.

[0022] Optionally, after the reaction (reaction after adding the chain extender) is completed, the step of adding solvent 3 (for the purpose of dissolving the reaction product) to the reaction solution obtained by the reaction to obtain a mixed solution, and dropping the mixed solution into methanol for precipitation, followed by filtering and vacuum drying is further included.

[0023] Optionally, the solvent 3 comprises tetrahydrofuran (THF).

[0024] Furthermore, the preparation steps of the amino-functionalized hexagonal boron nitride nanosheets include:

[0025] Hexagonal boron nitride (hBN) nanosheets and urea are mixed and ball-milled to obtain a mixture; the mixture is sequentially subjected to centrifugal washing, dialysis and freeze-drying to obtain the amino-functionalized hexagonal boron nitride nanosheets.

[0026] The present invention introduces amino groups (-NH2) into hBN by ball milling to achieve amino surface functionalization.

[0027] Furthermore, the mass ratio of the hexagonal boron nitride nanosheets to urea is 0.9-3.6:15-60.

[0028] Furthermore, the parameters of the ball milling include: a ball mass ratio of 15.9-63.6:160-750, a rotation speed of 500-1000 rpm, and a time (specifically, the overall operation time) of 20-25 hours.

[0029] Optionally, the ball milling process is paused for 5 minutes every 30 minutes.

[0030] Optionally, the ball milling is performed under a nitrogen environment to prevent oxidation.

[0031] Optionally, the centrifugal washing includes: first centrifugal washing at a speed of 500 rpm for 15-30 minutes, and then centrifugal washing at a speed of 8000 rpm for 1-2 hours.

[0032] Optionally, the dialysis is performed for 7-10 days, during which the water is changed every 8 hours.

[0033] Centrifugal washing and dialysis are designed to completely remove residual urea and ensure the purity of surface functional groups of hBN-NH2 nanosheets.

[0034] The second technical solution of the present invention: The method for preparing the above-mentioned stretchable polymer packaging material based on the heterostructure hydrogen bond network comprises the following steps:

[0035] The amino-functionalized hexagonal boron nitride nanosheets, polyurethane and solvent 2 are mixed to obtain a mixed solution; the mixed solution is cast into a mold to form the stretchable polymer encapsulation material based on the heterostructure hydrogen bond network (i.e., hBN-NH2 / PU composite material).

[0036] The present invention obtains a stretchable polymer encapsulation material based on a heterostructured hydrogen bond network by a simple solution blending and solution casting method, wherein the hBN-NH2 nanosheets interact with the carbamate groups in PU through the heterostructured hydrogen bond network.

[0037] Further preferably, the stretchable polymer packaging material based on the heterostructure hydrogen bond network is a hBN-NH2 / PU composite film.

[0038] Furthermore, the mass ratio of the amino-functionalized hexagonal boron nitride nanosheets to the polyurethane is 5-15:100.

[0039] Furthermore, the solvent 2 includes tetrahydrofuran.

[0040] Furthermore, the usage ratio of the polyurethane and the solvent 2 is 0.7-1.5 g:5-8 mL.

[0041] The third technical solution of the present invention: Application of the above-mentioned stretchable polymer packaging material based on heterostructure hydrogen bond network in the preparation of wearable electronic devices.

[0042] Furthermore, the application includes: using the stretchable polymer encapsulation material based on the heterostructure hydrogen bond network to encapsulate light-emitting organic molecules, thin films containing light-emitting organic molecules, or stretchable electrodes.

[0043] The present invention develops a stretchable polymer packaging material with high stretchability, low modulus, high toughness (high stretchability, low modulus, and high toughness indicate that the polymer is soft and tough) and high barrier properties. High-molecular-weight PDMS-OH containing silane functional groups is selected as the basic component. Its low Young's modulus and the presence of silicon-oxygen bonds in the molecular chain can significantly reduce the rigidity of the material and improve its flexibility, so that the material exhibits excellent deformation ability during stretching. At the same time, MDI with multiple conformational degrees of freedom and a symmetrical structure is selected to provide the material with the necessary strength and modulus by forming crystalline regions to balance flexibility and mechanical properties. Afterwards, hBN nanosheets are introduced, and amino groups are introduced on their surface by mechanical ball milling, so that they form interfacial hydrogen bonds with the carbamate groups in the polyurethane, significantly enhancing the interfacial interaction. Finally, a soft, tough, and stretchable polymer packaging material with high barrier properties is constructed.

[0044] In the present invention, the amino groups (-NH2) on the surface of hBN-NH2 nanosheets form a heterogeneous hydrogen bond network with the carbamate carbonyl groups (-C=O) in PU, and the principle diagram of the barrier to water and oxygen is shown in the figure. Figure 1The improved barrier performance of this composite material stems from two factors: the small size of hBN-NH2 allows for uniform dispersion within the polyurethane matrix, creating tortuous diffusion pathways for water and oxygen, forming a dense barrier layer and reducing permeability. Furthermore, interfacial hydrogen bonding between the hBN-NH2 nanosheets and the polyurethane matrix inhibits nanosheet aggregation and enhances interfacial stability through a hydrogen-bonded network. This results in tighter entanglement of polymer chains at the interface, significantly extending the diffusion pathways for water and oxygen, thereby improving barrier performance.

[0045] The packaging material prepared by the present invention, especially when the content of hBN-NH2 nanosheets is 15wt%, achieves high stretchability (510%), low modulus (75.8kPa), high fracture energy (2.44kJ·m -2 ) and excellent water barrier properties (20.69g·m -2 day -1 ).

[0046] The present invention discloses the following technical effects:

[0047] (1) The present invention successfully developed a soft and tough stretchable polymer encapsulation material through a heterogeneous structure hydrogen bond network strategy. The material has high stretchability, low modulus, and high toughness. In particular, when the hBN-NH2 content is 15wt%, high stretchability (510%), low modulus (75.8kPa), and high fracture energy (2.44kJ·m -2 ) is significantly superior to traditional polymer composites. This performance combination effectively resolves the contradiction between softness, toughness and mechanical strength of existing materials, meeting the needs of wearable devices in complex environments.

[0048] (2) The present invention significantly improves the water vapor transmission rate (WVTR) and oxygen transmission rate (OPC) of the packaging material through the uniform dispersion of hBN-NH2 nanosheets and the enhancement of the heterogeneous hydrogen bond network. The WVTR of the 15wt% hBN-NH2 / PU composite material is as low as 20.69g·m -2 day, OPC as low as 188.7cm 3 ·m -2 day -1 bar -1 , far superior to hBN / PU composite materials under the same load. This excellent barrier property ensures the long-term stability of the packaging material in high humidity environments, effectively protecting wearable electronic devices from corrosion by water vapor and oxygen.

[0049] (3) Under the harsh conditions of high humidity (90% RH) and mechanical strain (20%), the packaging material of the present invention exhibits excellent environmental stability. The resistance of the encapsulated silver paste electrode device changes by less than 5% within 30 days, and the electromagnetic interference shielding effect (EMI SE) changes by less than 3% within 5 days, while the performance of the unencapsulated sample drops sharply within 5 days. This stability is crucial to ensure the reliable operation of wearable devices in harsh environments.

[0050] (4) The present invention uses a solution blending method to prepare the hBN-NH2 / PU composite material, which is simple and easy to scale up. By controlling the content of hBN-NH2 nanosheets, the mechanical and barrier properties of the material can be flexibly adjusted to meet the needs of different application scenarios.

[0051] (5) The encapsulation material of the present invention is not only suitable for encapsulating stretchable electrodes and light-emitting organic molecules, but can also be extended to protect other flexible electronic components. Its stability and mechanical durability in high-humidity environments make it an ideal encapsulation solution for the next generation of high-performance wearable electronic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0053] Figure 1 Schematic diagram of the principle of forming a heterogeneous hydrogen bond network between amino groups (-NH2) on the surface of hBN-NH2 nanosheets and carbamate carbonyl groups (-C=O) in PU to achieve water and oxygen barrier;

[0054] Figure 2 Schematic diagram of the preparation principle of polyurethane;

[0055] Figure 3 This is the gel permeation chromatogram of the PU prepared in step (1) of Example 1;

[0056] Figure 4 Schematic diagram of the structure of hBN-NH2 nanosheets prepared in step (2) of Example 1;

[0057] Figure 5High-resolution N1s nuclear energy level spectrum of hBN nanosheets (a), high-resolution B1s nuclear energy level spectrum of hBN nanosheets (b), high-resolution N1s nuclear energy level spectrum of hBN-NH2 nanosheets (c), high-resolution B1s nuclear energy level spectrum of hBN-NH2 nanosheets (d), full-spectrum XPS measurement scan of hBN nanosheets and hBN-NH2 nanosheets (e), infrared spectra of hBN nanosheets and hBN-NH2 nanosheets (f);

[0058] Figure 6 Physical images of raw material hBN nanosheets (a) and hBN-NH2 nanosheets (b), SEM images of raw material hBN nanosheets (c) and hBN-NH2 nanosheets (d), AFM images of raw material hBN nanosheets (e) and hBN-NH2 nanosheets (f);

[0059] Figure 7 X-ray diffraction (XRD) spectra (a), Raman spectra (b), and a local magnified view of the Raman spectra (c) of hBN-NH2 nanosheets and raw material hBN nanosheets;

[0060] Figure 8 XRD spectra of the pure PU film prepared in Comparative Example 1, the hBN-NH2 / PU composite film prepared in Example 3, and the hBN / PU composite film prepared in Comparative Example 4;

[0061] Figure 9 The dispersion of hBN-NH2 nanosheets and raw material hBN nanosheets in PU solution;

[0062] Figure 10 SEM images of the pure PU film (a) prepared in Comparative Example 1, the hBN / PU composite film (b) prepared in Comparative Example 4, and the hBN-NH2 / PU composite film (c) prepared in Example 3;

[0063] Figure 11 Thermogravimetric measurement results of hBN-NH2 / PU, hBN / PU and pure PU with different nanosheet contents (a), differential thermal analysis results of hBN-NH2 / PU, hBN / PU and pure PU with different nanosheet contents (b), and the function relationship of Tanδ of pure PU, 15wt% hBN / PU and 15wt% hBN-NH2 / PU as a function of temperature (c);

[0064] Figure 12 Stress-strain curves (a), elongation at break (b), energy at break (c), and Young's modulus (d) of hBN-NH2 / PU, hBN / PU, and pure PU with different nanosheet contents;

[0065] Figure 13Cyclic curves of pure PU (a), 5wt% hBN-NH2 / PU (b), 10wt% hBN-NH2 / PU (c), 15wt% hBN-NH2 / PU (d), 5wt% hBN / PU (e), 10wt% hBN / PU (f) and 15wt% hBN / PU (g) stretched by 50%, 100%, 150%, 200%, 250% and 300%, respectively;

[0066] Figure 14 WVTR test results (a) and OPC test results (b) of hBN-NH2 / PU composite films with different nanosheet contents, pure PU films, and hBN / PU composite films with different nanosheet contents;

[0067] Figure 15 Schematic diagram of the preparation and packaging of the light-emitting film in Application Example 1 (a), and the luminescence of the encapsulated film under undeformed conditions in air (a), 50% strain in air (c), twisted conditions in air (d), undeformed conditions in water (e), 50% strain in water (f), and twisted conditions in water (g);

[0068] Figure 16 The lighting conditions of a bulb connected to a wire under the following conditions: (a) undeformed in air; (b) 20% strain in air; (c) torsion in air; (d) undeformed in water; (e) 20% strain in water; and (f) torsion in water.

[0069] Figure 17 Resistance change of electrodes packaged with different materials and unpackaged electrodes under 20°C, 90% humidity and unstretched conditions within 30 days (a), resistance change of electrodes packaged with different materials and unpackaged electrodes under 20°C, 90% humidity and 20% strain conditions within 30 days (b), electromagnetic interference shielding effectiveness of electrodes with different packaging conditions at 20°C, 90% humidity and unstretched conditions (c), electromagnetic interference shielding effectiveness of electrodes with different packaging conditions at 20°C, 90% humidity and 20% strain conditions (d). DETAILED DESCRIPTION

[0070] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0071] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0072] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0073] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0074] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0075] It should be pointed out that the matters not described in detail in the present invention are conventional operating means in this field and are not the focus of the present invention.

[0076] When referring to room temperature or normal temperature in the specific embodiments of the present invention, it specifically refers to 20-30°C.

[0077] All raw materials involved in the specific embodiments of the present invention are common commercial products.

[0078] The schematic diagram of the preparation principle of polyurethane in the specific embodiment of the present invention (ie, Example 1) is as follows Figure 2 As shown, the 5000Da silane-containing PDMS-OH (brand name MER-DMS-C21, CAS number: 156327-07-0) was selected to utilize long-chain siloxane to weaken the stacking between molecular chains and enhance flexibility. MDI, with its high symmetry, was selected as a monomer to enhance the rigidity of the material. To prevent implosion during the reaction, MDI was added in batches to slow the reaction rate.

[0079] Example 1

[0080] A stretchable polymer encapsulation material based on a heterogeneous structured hydrogen bond network (i.e., hBN-NH2 / PU composite material) is prepared as follows:

[0081] (1) Preparation of PU

[0082] 10g of 5000Da number-average molecular weight PDMS-OH and 30μL of DBTDL were added to a dry round-bottom flask equipped with a magnetic stir bar. A mixed solution of 0.525g of MDI and 25mL of DMF was then added. After reacting at 40°C for 1 hour, a mixed solution of 0.225g of MDI and 15mL of DMF was added (MDI was added in batches to slow the reaction and prevent implosion). The reaction was continued at 40°C for 2 hours. After the reaction was complete, the flask was cooled to 0°C. A mixed solution of 1,4-butanediol and DMF (prepared by dissolving 90.1mg of 1,4-butanediol in 5mL of DMF at room temperature) was then added. The reaction was continued at 0°C for 30-40 minutes. After the reaction was complete, tetrahydrofuran was added to the resulting reaction solution to dissolve the reaction product. The resulting mixture was then added dropwise to methanol for precipitation. The resulting mixture was then filtered and vacuum-dried to remove the solvent, yielding the polyurethane (PU).

[0083] (2) Preparation of hBN-NH2 nanosheets

[0084] Under nitrogen, 1.8 g of hBN and 30 g of urea were placed in a 500 mL jar along with 325 g of zirconium oxide balls for grinding. Ball milling was performed at 500 rpm for 20 hours (with a 5-minute pause every 30 minutes). Afterwards, the mixture was centrifuged (centrifugal washing was performed twice, first at 500 rpm for 15 minutes and then at 8000 rpm for 1.5 hours) and dialyzed in water for 7 days (changing the water every 8 hours) to remove urea. Finally, the mixture was freeze-dried to obtain hBN-NH2 nanosheets.

[0085] (3) Preparation of hBN-NH2 / PU composite film

[0086] 800 mg of polyurethane (PU) was dissolved in 5 mL of tetrahydrofuran to form a PU solution. 40 mg of hBN-NH2 nanosheets were then added to the PU solution (i.e., a mass ratio of hBN-NH2 nanosheets to PU of 5:100). The mixture was stirred at room temperature to obtain a mixed solution. The mixed solution was then cast into a 3.5 cm × 3.5 cm mold and dried at room temperature to form a film, resulting in a 5 wt% hBN-NH2 / PU composite film (abbreviated as 5 wt% hBN-NH2 / PU, with an average thickness of 500 μm).

[0087] Example 2

[0088] The same as Example 1, except that in step (3), the amount of PU used is 750 mg, the amount of tetrahydrofuran used is 5 mL, the amount of hBN-NH2 nanosheets used is 75 mg (i.e., the mass ratio of hBN-NH2 nanosheets to PU is 10:100), and the obtained composite material film is referred to as 10 wt% hBN-NH2 / PU (average thickness is 500 μm).

[0089] Example 3

[0090] The same as Example 1, except that in step (3), the amount of PU used is 700 mg, the amount of tetrahydrofuran used is 5 mL, the amount of hBN-NH2 nanosheets used is 105 mg (i.e., the mass ratio of hBN-NH2 nanosheets to PU is 15:100), and the obtained composite material film is referred to as 15wt% hBN-NH2 / PU (average thickness is 500μm).

[0091] Comparative Example 1

[0092] (1) Preparation of PU

[0093] The preparation steps of PU are the same as step (1) in Example 1.

[0094] (2) Preparation of pure PU film

[0095] 1 g of PU was dissolved in 5 mL of tetrahydrofuran to form a PU solution, which was then cast into a 3.5 cm × 3.5 cm mold and dried at room temperature to form a film, thereby obtaining a pure PU film (average thickness of 500 μm).

[0096] Comparative Example 2

[0097] (1) Preparation of PU

[0098] The preparation steps of PU are the same as step (1) in Example 1.

[0099] (2) Preparation of hBN / PU composite film

[0100] 800 mg of PU was dissolved in 5 mL of tetrahydrofuran to form a PU solution. 40 mg of hBN was then added to the PU solution and stirred at room temperature to obtain a mixed solution. The mixed solution was then cast into a 3.5 cm x 3.5 cm mold to form a film, resulting in an hBN / PU composite film (abbreviated as 5 wt% hBN / PU, with an average thickness of 500 μm).

[0101] Comparative Example 3

[0102] The same as Comparative Example 2, except that in step (2), the amount of PU used is 750 mg, the amount of tetrahydrofuran used is 5 mL, and the amount of hBN nanosheets used is 75 mg (i.e., the mass ratio of hBN nanosheets to PU is 10:100). The obtained composite film is referred to as 10 wt% hBN / PU (average thickness is 500 μm).

[0103] Comparative Example 4

[0104] The same as Comparative Example 2, except that the amount of PU used in step (2) is 700 mg, the amount of tetrahydrofuran used is 5 mL, and the amount of hBN nanosheets used is 105 mg (i.e., the mass ratio of hBN nanosheets to PU is 15:100). The obtained composite film is referred to as 15 wt% hBN / PU (average thickness is 500 μm).

[0105] Test Example 1

[0106] Morphology, structure, and composition characterization

[0107] Figure 3 The gel permeation chromatogram of the PU prepared in step (1) of Example 1 proves that the number average molecular weight of the PU is about 140,000.

[0108] Figure 4 Schematic diagram of the structure of hBN-NH2 nanosheets prepared in step (2) of Example 1, wherein amino groups exist on the surface of hBN.

[0109] Figure 5The X-ray photoelectron spectroscopy (XPS) spectra and infrared spectra of the hBN-NH2 nanosheets prepared in step (2) of Example 1 and the raw material hBN nanosheets. Among them, a is the high-resolution N1s nuclear energy level spectrum of the hBN nanosheet, b is the high-resolution B1s nuclear energy level spectrum of the hBN nanosheet, c is the high-resolution N1s nuclear energy level spectrum of the hBN-NH2 nanosheet, d is the high-resolution B1s nuclear energy level spectrum of the hBN-NH2 nanosheet, e is the full spectrum measurement scan of the XPS of the hBN nanosheet and the hBN-NH2 nanosheet, and f is the infrared spectrum of the hBN nanosheet and the hBN-NH2 nanosheet. It can be seen from the N1s nuclear energy level spectra a and c that the original hBN nanosheet has only one strong peak at 397.6eV, which originates from the N-B bond, which means that the hBN nanosheet has a very simple molecular structure and the nitrogen atom does not have any functional groups. The hBN-NH2 nanosheets showed another peak at 399.1eV, indicating that an amino modifier was attached to the surface and edge of the original hBN nanosheets. Similarly, from the B1s nuclear energy level spectra b and d, it can be seen that in hBN nanosheets and hBN-NH2 nanosheets, the characteristic peaks are both located at 190.0eV, which are assigned to BN bonds. From the XPS full spectrum scan e, it can also be seen that hBN nanosheets and hBN-NH2 nanosheets contain N and B elements. In addition, it can be seen from the infrared spectrum f that hBN nanosheets have N and B elements at 1380cm -1 The strong transmittance at 816 cm -1 The peak at 3400 cm-1 is less intense, which is related to the bending mode of the BNB bond. -1 The broad peak near the NH stretching is attributed to the NH stretching. The above results indicate that the amino groups are successfully connected to the surface of the hBN nanosheets, that is, the amino surface functionalization of the hBN nanosheets is achieved.

[0110] Figure 6 The physical images, scanning electron microscope (SEM) images and atomic force microscope (AFM) images of the hBN-NH2 nanosheets and raw material hBN nanosheets prepared in step (2) of Example 1, wherein a is a physical image of the hBN nanosheets, b is a physical image of the hBN-NH2 nanosheets, c is an SEM image of the hBN nanosheets, d is an SEM image of the hBN-NH2 nanosheets, e is an AFM image of the hBN nanosheets, and f is an AFM image of the hBN-NH2 nanosheets. It can be seen from the physical images that there is no difference in the morphology and appearance of the samples before and after ball milling. The SEM images show that the size of the hBN-NH2 nanosheets is significantly smaller than that of the hBN nanosheets, and the AFM images show that the thickness of the hBN-NH2 nanosheets is thinner than that of the hBN nanosheets.

[0111] Figure 7The X-ray diffraction (XRD) spectra (a), Raman spectra (b) and a local magnified view of the Raman spectra (c) of the hBN-NH2 nanosheets and raw material hBN nanosheets prepared in step (2) of Example 1. It can be seen from the XRD spectra that the characteristic peaks of hBN can still be seen in the hBN-NH2 nanosheets, which shows that the strong mechanical force during the ball milling process did not destroy the crystal structure of hBN. The characteristic diffraction peak of hBN at 26.6° corresponds to the (002) lattice plane with high peak intensity and sharp peak shape. After ball milling, the peak intensity of hBN-NH2 on the (002) crystal plane has been reduced to a certain extent. This is because the normal impact force and tangential shear force generated when the ball milling beads collide with the layered crystal hBN during ball milling overcome the interlayer force of hBN, thereby reducing the thickness and crystallinity of hBN. It can be seen from the Raman spectrum that at about 1367cm -1 There is a characteristic peak at each layer, which can be assigned to the BN vibration mode (E 2g phonon mode). It is noteworthy that the peak intensity of hBN-NH2 is significantly weaker and broader than that of unmodified hBN. This result can be attributed to the peak at about 1367 cm -1 The reduction of multiple peaks superposition further verifies the significant reduction in hBN particle thickness after ball milling.

[0112] Figure 8 The XRD spectra of the pure PU film prepared in Comparative Example 1, the hBN-NH2 / PU composite film prepared in Example 3, and the hBN / PU composite film prepared in Comparative Example 4. It can be seen that the (002) peak intensity of hBN-NH2 / PU is weakened compared with hBN / PU, which indicates that functionalization reduces the stacking interaction between hBN.

[0113] Test Example 2

[0114] Performance Testing

[0115] (1) Dispersion performance

[0116] The hBN-NH2 nanosheets prepared in step (2) of Example 1 and the raw material hBN nanosheets were dispersed into the PU solution (wherein PU is the PU prepared in step (1) of Example 1, the solvent is THF, the concentration of PU is 125 mg / mL, and the concentration of nanosheets is 18 mg / mL), stirred evenly, and the dispersion conditions after standing for 0 h, 2 h, and 12 h were observed. The results are as follows: Figure 9As shown in the figure, after standing for a period of time, hBN settles to the bottom of the bottle and separates from the PU. However, hBN-NH2 nanosheets are well dispersed in the PU solution. This is due to the interfacial hydrogen bonding between the amino groups on the hBN-NH2 surface and the PU, resulting in good compatibility. In contrast, unmodified hBN, due to its relatively inert surface, lacks interaction with the PU and easily separates from it.

[0117] Figure 10 SEM images of the pure PU film (a) prepared in Comparative Example 1, the hBN / PU composite film (b) prepared in Comparative Example 4, and the hBN-NH2 / PU composite film (c) prepared in Example 3. It can be seen that the size of the hBN-NH2 nanosheets is significantly reduced and its dispersion in PU is good.

[0118] (2) Thermogravimetric analysis

[0119] Figure 11 Thermogravimetric analysis results of hBN-NH2 / PU composite films prepared in Examples 1-3, PU films prepared in Comparative Example 1, and hBN / PU composite films prepared in Comparative Examples 2-4, wherein a is the thermogravimetric (TGA) measurement results of hBN-NH2 / PU, hBN / PU, and pure PU with different nanosheet contents, b is the differential thermal analysis (DTG) results of hBN-NH2 / PU, hBN / PU, and pure PU with different nanosheet contents, and c is the function relationship between Tanδ and temperature for pure PU, 15wt% hBN / PU, and 15wt% hBN-NH2 / PU. The TGA and DTG results show that the increase in thermal stability is related to the addition amount of nanosheets. For hBN / PU and hBN-NH2 / PU composite materials, the decomposition temperature (T 5％ ) increases in proportion to the filler content. Specifically, the hBN-NH2 / PU system reaches ΔT at 15 wt% loading. 5％ = +7.4°C (from 319.0°C for pure PU to 326.4°C for 15wt% hBN-NH2 / PU), exceeding that of pure PU and hBN / PU composites. Dynamic mechanical analysis (DMA) quantified the incremental increase in glass transition temperature (ΔT g = +3.0 °C, from -110.0 °C of pure PU to -107.0 °C of 15 wt% hBN-NH2 / PU), indicating that the interfacial interaction between the nanosheets and PU limits the mobility of the segments.

[0120] (3) Mechanical properties test

[0121] Mechanical properties tests were performed on the hBN-NH2 / PU composite films prepared in Examples 1-3, the PU film prepared in Comparative Example 1, and the hBN / PU composite films prepared in Comparative Examples 2-4. Specifically, the stress-strain curve and elongation at break, toughness, and Young's modulus of each sample were evaluated using a tensile testing system (this test is mainly based on GB / T 528-2009, and the test steps and sample dimensions are standardized in combination with the characteristics of polymer materials. The tensile rate is 0.5 mm / s, the sample length is 10.0±1.0 mm, the sample width is 6.0±1.0 mm, and the sample thickness is 0.5±0.1 mm). Figure 12 The mechanical properties test results of hBN-NH2 / PU, hBN / PU and pure PU (i.e., the nanosheet content is 0) with different nanosheet contents, where a is the stress-strain curve, b is the elongation at break, c is the fracture energy, and d is the Young's modulus. It can be seen that the tensile strength of the composite material increases with the increase of hBN or hBN-NH2 content, while the elongation at break decreases. It is worth noting that the hBN-NH2 / PU composite material achieves an ideal balance between modulus and fracture energy. The Young's modulus of 15wt% hBN / PU soared from 25.2kPa of PU to 155.1kPa, while the Young's modulus of 15wt% hBN-NH2 / PU increased slightly to 75.8kPa. In contrast, the fracture energy of hBN-NH2 / PU increased from 0.9kJ·m -2 Significantly increased to 2.44 kJ·m -2 , while the fracture energy of hBN / PU is only 0.9 kJ·m -2 Slightly increased to 1.2 kJ·m -2 This indicates that the hBN-NH2 / PU composites can achieve high fracture energy while maintaining low modulus.

[0122] In addition, cyclic tensile tests were performed on the hBN-NH2 / PU composite films prepared in Examples 1-3, the PU films prepared in Comparative Example 1, and the hBN / PU composite films prepared in Comparative Examples 2-4 (the test was mainly based on GB / T528-2009, and the test steps and sample dimensions were standardized in combination with the characteristics of polymer materials. The tensile rate was 0.5 mm / s, the sample length was 10.0 ± 1.0 mm, the sample width was 6.0 ± 1.0 mm, and the sample thickness was 0.5 ± 0.1 mm). The results are as follows: Figure 13As shown. Among them, ag are the cycle curves of pure PU, 5wt% hBN-NH2 / PU, 10wt% hBN-NH2 / PU, 15wt% hBN-NH2 / PU, 5wt% hBN / PU, 10wt% hBN / PU and 15wt% hBN / PU stretched by 50%, 100%, 150%, 200%, 250% and 300% respectively. It can be seen that with the increase in the number of stretching cycles, the 15wt% hBN / PU composite material exhibits stress softening in repeated cycles, while the 15wt% hBN-NH2 / PU maintains a stress hardening behavior similar to that of pure PU. This shows that the hBN-NH2 / PU composite material has excellent cyclic stability, which is attributed to the interfacial hydrogen bonding interaction between the nanosheets and the PU matrix. These interactions greatly enhance the interfacial stability of the composite material, thereby improving the cyclic durability of the material.

[0123] (4) Barrier performance test

[0124] Figure 14 The water vapor permeability test results (a) and oxygen permeability test results (b) of the hBN-NH2 / PU composite film with different nanosheet contents prepared in Examples 1-3, the pure PU film (i.e., the nanosheet content is 0) prepared in Comparative Example 1, and the hBN / PU composite film with different nanosheet contents prepared in Comparative Examples 2-4 are shown. It can be seen that with the increase of hBN-NH2 nanosheet content, the water vapor barrier and oxygen barrier properties of hBN-NH2 / PU composites are improved by up to 2.36 times and 2.5 times respectively compared with pure PU. It is worth noting that the WVTR of 15wt% hBN-NH2 / PU reaches 20.69g·m -2 day -1 , OPC reaches 188.7cm 3 ·m -2 day -1 bar -1, outperforming hBN / PU composites with the same loading. This improvement is due to the smaller size of hBN-NH2, which allows for uniform dispersion within the PU matrix. Furthermore, interfacial hydrogen bonding between hBN-NH2 and the PU matrix inhibits nanosheet aggregation and enhances interfacial stability through a heterogeneous interfacial hydrogen bond network. This results in tighter entanglement of polymer chains at the interface, significantly extending the diffusion path for water (or oxygen) molecules, thereby improving barrier properties.

[0125] Application Example 1

[0126] The pure PU prepared in step (1) of Example 1 was prepared into a luminescent film. The specific preparation process was as follows: three luminescent organic small molecules: (1,10-phenanthroline) tris[4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione] europium (III), 9,10-diphenylanthracene, and 1,8-naphtholactam were mixed with PU and a solvent, tetrahydrofuran, to obtain a mixed solution, and the luminescent film was obtained by film laying. The mass ratio of the organic small molecule to the PU was 100 mg:1 g, the concentration of the PU in the mixed solution was 125 mg / mL, and the concentration of the organic small molecule in the mixed solution was 12.5 mg / mL. Moreover, the (1,10-phenanthroline) tris[4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione] europium (III) organic small molecule emits red light, the 9,10-diphenylanthracene organic small molecule emits blue light, and the 1,8-naphtholactam organic small molecule emits green light.

[0127] The three prepared luminescent films were then cut into the shapes of the English letters "T," "J," and "U," respectively, and encapsulated with the 15 wt% hBN-NH2 / PU (500 μm thick) prepared in Example 3 on the top and bottom layers. Fluorescence measurements were performed on the encapsulated luminescent films under different conditions.

[0128] Schematic diagram of the preparation and packaging of light-emitting thin films Figure 15 As shown in a, the luminescence of the encapsulated film under different conditions when irradiated with a wavelength of 254nm is as follows Figure 15 As shown in bg, b is the condition of no deformation in air, c is the condition of 50% strain in air, d is the condition of twisting in air, e is the condition of no deformation in water, f is the condition of 50% strain in water, and g is the condition of twisting in water. Experiments have shown that under the protection of 254nm light irradiation, the encapsulated pattern can maintain continuous luminescence. Even under stretching (reaching 50% strain), twisting or underwater stretching and twisting conditions, the luminescence can remain stable. That is, the film containing luminescent small molecules encapsulated by the encapsulation material of the present invention can maintain stable luminescence performance under stretching and twisting operations under normal (air) conditions and in underwater environments, confirming its reliable barrier ability under extreme mechanical conditions.

[0129] Application Example 2

[0130] Conductive silver paste electrodes were printed on the surface of the 15 wt% hBN-NH2 / PU composite film (500 μm thick) prepared in Example 3 using inkjet printing technology. Wires were used to connect the electrodes to the external circuit of a small light bulb, and the top layer was encapsulated with the 15 wt% hBN-NH2 / PU composite film. This resulted in an encapsulated conductive silver paste electrode device.

[0131] Figure 16 The conductive silver paste electrode device encapsulated with the 15wt% hBN-NH2 / PU composite material prepared in Application Example 2 illuminates when connected to a wire under conditions of no deformation in air (a), 20% strain in air (b), torsion in air (c), no deformation in water (d), 20% strain in water (e), and torsion in water (f). The encapsulated conductive silver paste electrode device illuminates normally under normal air conditions, 20% strain in air, and torsion in air. It maintains stable conductivity even when submerged in water and under 20% strain and torsion underwater.

[0132] Application Example 3

[0133] Conductive silver paste electrodes were printed on the pure PU film (i.e., 0wt% hBN / PU) prepared in Comparative Example 1, the 15wt% hBN / PU composite film prepared in Comparative Example 4, the 15wt% hBN-NH2 / PU composite film prepared in Example 3, the PDMS (Dow Corning 184) film, and the SEBS (H1221) film (the thickness of each film was 500 μm, wherein the PDMS film was a commercially available film purchased directly; the preparation method of the SEBS film was the same as the preparation method of the pure PU film in Comparative Example 1, except that the tetrahydrofuran solvent was replaced by toluene solvent in equal volume, and the PU was replaced by SEBS in equal mass) using inkjet printing technology. The electrodes were led to the outside with copper wires, and the same materials were used for top-layer packaging. Conductive silver paste electrode devices encapsulated with different materials were obtained. The stability performance of the prepared conductive silver paste electrode devices encapsulated with different materials was tested, and the unencapsulated conductive silver paste electrode (printed on the 15wt% hBN-NH2 / PU composite film) was used as a control. Specifically, the resistance tests involved are all performed using a multimeter, and the electromagnetic interference shielding effectiveness (EMI SE) is tested using a vector network analyzer.

[0134] Figure 17The resistance change of electrodes encapsulated with different materials and unencapsulated electrodes under 20°C, 90% humidity and unstretched conditions within 30 days (a); the resistance change of electrodes encapsulated with different materials and unencapsulated electrodes under 20°C, 90% humidity and 20% strain conditions within 30 days (b); the electromagnetic interference shielding effectiveness of electrodes with different encapsulation conditions under 20°C, 90% humidity and unstretched conditions (c); the electromagnetic interference shielding effectiveness of electrodes with different encapsulation conditions under 20°C, 90% humidity and 20% strain conditions (d). PDMS in a and b represents PDMS (Dow Corning 184); Encapsulated in c and d represents 15wt% hBN-NH2 / PU encapsulated in a high humidity environment for 5 days; Unencapsulated represents unencapsulated in a high humidity environment for 5 days; Original represents the test immediately after preparation. The results show that the resistance of the unencapsulated electrode changed by 55% within 5 days, while the resistance of the PDMS and SEBS encapsulated electrodes changed by 19% and 5%, respectively. In contrast, the resistance change of the electrode encapsulated with 15wt% hBN-NH2 / PU is negligible. After 30 days, the unencapsulated electrode completely lost its conductivity, the conductivity of the electrodes encapsulated with PDMS and SEBS decreased significantly, but the electrode encapsulated with 15wt% hBN-NH2 / PU showed only slight resistance fluctuations (<5%). In addition, at 20°C and 90% humidity, the EMI SE of the encapsulated electrode remained at 38.7dB after 5 days, with only a 2% decrease, while that of the unencapsulated electrode was 29.5dB. Under a strain of 20%, the EMI SE of the encapsulated electrode remained at 19.8dB, with a fluctuation of less than 5%, while the unencapsulated electrode failed. It can be seen that the electrode device encapsulated with the encapsulation material of the present invention exhibits excellent environmental mechanical stability in a high humidity environment (90% humidity environment).

[0135] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A stretchable polymer encapsulation material based on a heterostructure hydrogen bond network, characterized in that: It is formed by amino-functionalized hexagonal boron nitride nanosheets and polyurethane through a heterostructured hydrogen bond network.

2. The stretchable polymer encapsulation material based on heterostructure hydrogen bond network according to claim 1, characterized in that: The polyurethane is obtained by reacting terminal hydroxyl polydimethylsiloxane and 4,4'-diphenylmethane diisocyanate as monomers.

3. The stretchable polymer packaging material based on heterostructure hydrogen bond network according to claim 2, characterized in that: The preparation steps of the polyurethane include: Mix the hydroxy-terminated polydimethylsiloxane, 4,4'-diphenylmethane diisocyanate, catalyst and solvent 1, heat at 35-45°C for 3-4 hours, then cool the reaction system to 0-5°C, add the chain extender, and continue the reaction for 30-40 minutes.

4. The stretchable polymer packaging material based on heterostructure hydrogen bond network according to claim 3, characterized in that: The catalyst includes dibutyltin dilaurate; and / or, the solvent 1 comprises N,N-dimethylformamide; And / or, the chain extender comprises 1,4-butanediol.

5. The stretchable polymer packaging material based on heterostructure hydrogen bond network according to claim 3, characterized in that: The number average molecular weight of the hydroxy-terminated polydimethylsiloxane is 4000-6000Da; And / or, the amount ratio of the hydroxy-terminated polydimethylsiloxane, 4,4'-diphenylmethane diisocyanate, catalyst and chain extender is 5-15g:0.38-1.5g:15-45μL:45-180mg.

6. The stretchable polymer packaging material based on heterostructure hydrogen bond network according to claim 1, characterized in that: The preparation steps of the amino-functionalized hexagonal boron nitride nanosheets include: The hexagonal boron nitride nanosheets and urea are mixed and ball-milled to obtain a mixture; the mixture is sequentially subjected to centrifugal washing, dialysis and freeze-drying to obtain the amino-functionalized hexagonal boron nitride nanosheets.

7. The stretchable polymer packaging material based on heterostructure hydrogen bond network according to claim 6, characterized in that: The mass ratio of the hexagonal boron nitride nanosheets to urea is 0.9-3.6:15-60; And / or, the parameters of the ball milling include: a ball mass ratio of 15.9-63.6:160-750, a rotation speed of 500-1000 rpm, and a time of 20-25 hours.

8. A method for preparing a stretchable polymer encapsulation material based on a heterostructure hydrogen bond network according to any one of claims 1 to 7, characterized in that: The following steps are involved: The amino-functionalized hexagonal boron nitride nanosheets, polyurethane and solvent 2 are mixed to obtain a mixed solution; the mixed solution is cast into a mold to form the stretchable polymer packaging material based on the heterostructure hydrogen bond network.

9. The preparation method according to claim 8, wherein The mass ratio of the amino-functionalized hexagonal boron nitride nanosheets to the polyurethane is 5-15:100; And / or, the solvent 2 comprises tetrahydrofuran.

10. Use of the stretchable polymer packaging material based on the heterostructure hydrogen bond network according to any one of claims 1 to 7 in the preparation of wearable electronic devices.

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