Humidity-responsive polydisulfide adhesive materials, methods of making and using the same

Abstract

This invention provides a humidity-responsive polydisulfide adhesive, its preparation method, and its applications. The preparation method includes: preparing guanidine-modified thioctic acid or its derivatives (monomer A) and thioctic acid carboxylates, their derivatives, or polymeric carboxylates (component B) into aqueous solutions, then mixing them to form a condensed phase through salt bridging between the guanidine salt groups and the carboxylate groups, and inducing ring-opening polymerization of the disulfide five-membered ring in the condensed phase; followed by solid-liquid separation, vacuum drying, and hot pressing to obtain the polydisulfide adhesive. This invention enables broad-spectrum continuous control from hot melt adhesive to pressure-sensitive adhesive in a single material system by changing the ambient humidity, and the aqueous phase polymerization process requires no heating or catalyst.

Description

Technical Field

[0001] This invention relates to the field of humidity-responsive materials technology, specifically to a humidity-responsive polydisulfide adhesive material, its preparation method, and its application. Background Technology

[0002] Adhesive materials play an indispensable role in modern industry and daily life, encompassing numerous fields such as structural bonding in aerospace engineering, encapsulation of flexible electronic devices, and immediate fixation of medical dressings. Traditional polymer adhesives are typically formulated and optimized for specific applications. For example, traditional high-strength adhesives (such as cyanoacrylates and epoxy resins) provide strong adhesion; however, the network structure of these materials is usually permanently fixed after curing, making it difficult to reconfigure or adjust according to changes in the external environment. This means that their excellent performance in a single context cannot be directly translated into applications in other contexts. To overcome the limitations of traditional adhesives, stimulus-responsive smart adhesives have been developed in recent years. These adhesives can regulate their internal network structure and chain dynamics in response to external stimuli (such as light, heat, pH, and humidity), thereby achieving dynamic control over adhesive behavior. However, existing stimulus-responsive adhesives still face two technological bottlenecks. First, the adjustable range of adhesive strength is often extremely limited. Most systems primarily exhibit discrete "on / off" switching modes (i.e., a binary state of adhesion and debonding), rather than a broad-spectrum continuous transition between different adhesive modes (such as hot melt adhesive mode and pressure-sensitive adhesive mode). Second, many stimulus-induced reactions lack continuous and programmable structural evolution mechanisms. In a single material system, it is difficult to achieve continuous and precise control over weak adhesion, strong structural adhesion, and pressure-sensitive adhesion. Furthermore, some existing high-performance polymer adhesives often rely on complex synthesis processes, toxic organic solvents, or harsh catalytic / heating conditions during preparation, which is inconsistent with the development trend of green chemistry and limits their large-scale application.

[0003] Therefore, developing a smart adhesive with a green and simple preparation process that can achieve a wide range of continuously adjustable adhesion mode transitions within a single material system is a core challenge that urgently needs to be addressed in the field of smart adhesives. Summary of the Invention

[0004] This invention provides a humidity-responsive polydisulfide adhesive material, its preparation method, and its application. It provides a smart adhesive material that can achieve continuous control from strong structural adhesion (hot melt adhesive) to pressure-sensitive adhesion (pressure-sensitive adhesive) in a single material system through simple changes in environmental humidity. At the same time, it solves the problems of traditional polymer adhesive preparation processes relying on organic solvents, requiring heating, or using catalysts.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A humidity-responsive polydisulfide adhesive material, said polydisulfide adhesive material being prepared by a method comprising the following steps: Step S1, providing monomer A and component B, wherein monomer A is guanidine salt modified thioctic acid or its derivative, and component B is thioctic acid carboxylate, thioctic acid carboxylate derivative or polymer carboxylate; Step S2: After preparing monomer A and component B into aqueous solutions, they are mixed to form a condensed phase through salt bridging of guanidine salt groups and carboxylate salt groups, and the ring-opening polymerization of disulfide five-membered rings is induced in the condensed phase; then, after solid-liquid separation, vacuum drying and hot pressing, the humidity-responsive polydisulfide adhesive material is obtained.

[0006] To achieve the above objectives, the present invention also provides the following technical solutions: A method for preparing the above-mentioned polydisulfide adhesive material, the method comprising the following steps: S1, providing monomer A and component B, wherein monomer A is guanidine salt modified thioctic acid or a derivative thereof, and component B is thioctic acid carboxylate, thioctic acid carboxylate derivative or polymeric carboxylate; S2, monomer A and component B are respectively prepared into aqueous solutions and then mixed to form a condensed phase by the salt bridge effect of guanidine salt groups and carboxylate salt groups. The condensed phase is then induced to undergo ring-opening polymerization of disulfide five-membered rings. Subsequently, the mixture is subjected to solid-liquid separation, vacuum drying and hot pressing to obtain the humidity-responsive polydisulfide adhesive material.

[0007] To achieve the above objectives, the present invention also provides the following technical solutions: The application of the above-mentioned polydisulfide adhesive material or the polydisulfide adhesive material obtained by the above-mentioned preparation method in the preparation of adhesive materials, impact-resistant materials, coating materials or biodegradable materials.

[0008] Compared with the prior art, the present invention has achieved the following beneficial effects: 1. Broad-spectrum continuous control: endows materials with humidity-triggered structural self-evolution behavior, enabling wide-range continuous control of glass transition temperature and modulus.

[0009] 2. Green and mild preparation: Based on the non-covalent salt bridging effect to drive molecular self-assembly and aggregation, the aqueous phase polymerization process does not require heating or catalysts, and is energy-saving and environmentally friendly throughout.

[0010] 3. Intrinsic dynamics and biodegradability: The intrinsic dynamic properties of disulfide bonds endow the material with excellent comprehensive properties such as self-healing, recyclability, reprocessability and biodegradability. Attached Figure Description

[0011] To more clearly illustrate the technical solution in one embodiment of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0012] Figure 1 This is a macroscopic photograph of the mixture of the two monomer aqueous solutions during the preparation process of Example 1 of the present invention; Figure 2 These are confocal microscope images taken during liquid-liquid phase separation during the preparation process in Example 1 of this invention; Figure 3 This is a comparison of the Raman spectra of the polymer prepared in Example 1 of the present invention and the two monomers; Figure 4 X-ray energy dispersive spectroscopy (EDS) image of the polymer prepared in Example 1 of this invention; Figure 5 The X-ray diffraction (XRD) patterns of the polymer obtained in Example 1 of this invention under different humidity conditions are shown. Figure 6 Differential scanning calorimetry (DSC) curves of the polymer prepared in Example 1 of this invention under different humidity conditions; Figure 7 The tensile stress-strain curves of the polymer obtained in Example 1 of this invention under different humidity conditions are shown. Figure 8 The results show the overlap shear adhesion strength test results of the polymer prepared in Example 1 of this invention to glass under different humidity conditions. Detailed Implementation

[0013] The technical solution of one embodiment of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. It should be understood that the specific embodiments described herein are only for illustration and explanation of the present invention and are not intended to limit the present invention.

[0014] Any specific numerical value (including the endpoints of the numerical range) disclosed in this invention is not limited to the exact value, but should be understood to also cover values ​​close to the exact value, such as all possible values ​​within ±5% of the exact value. Furthermore, for the disclosed numerical range, one or more new numerical ranges can be obtained by arbitrarily combining the endpoint values ​​of the range, the endpoint values ​​with specific point values ​​within the range, and the specific point values. These new numerical ranges should also be considered as specifically disclosed in this invention.

[0015] The terminology used in this invention is for the purpose of describing specific exemplary embodiments only and is not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” as used herein are intended to include the plural forms as well. The terms “comprising,” “including,” “containing,” and “having” are inclusive and thus describe the presence of said features, elements, compositions, steps, integers, operations, and / or components, but do not exclude the presence or inclusion of one or more other features, integers, steps, operations, elements, components, and / or sets thereof. Although the open-ended term “comprising” should be understood as a non-limiting term used to describe and claim the various embodiments described in this invention, in some aspects it may instead be understood as a more restrictive and limiting term, such as “consisting of” or “essentially composed of.” Thus, for any given embodiment describing a composition, material, component, element, feature, integer, operation, and / or process step, the invention also particularly includes embodiments consisting of or substantially consisting of such compositions, materials, components, elements, features, integers, operations, and / or process steps. In the case of “consisting of…”, the alternative embodiments exclude any additional compositions, materials, components, elements, features, integers, operations and / or process steps. In the case of “essentially composed of…”, any additional compositions, materials, components, elements, features, integers, operations and / or process steps that substantially affect the essential and novel characteristics are excluded from such embodiments. However, any compositions, materials, components, elements, features, integers, operations and / or process steps that do not substantially affect the essential and novel characteristics may be included in the embodiments.

[0016] Any method steps, processes, and operations described in this invention should not be construed as necessarily requiring them to be performed in the specific order discussed or shown, unless explicitly specified. It should also be understood that, unless otherwise stated, additional or alternative steps may be used.

[0017] In this invention, except where expressly stated, any matters or issues not mentioned are directly applicable to those known in the art without any modification. Furthermore, any embodiment described in this invention can be freely combined with one or more other embodiments described in this invention, and the resulting technical solutions or concepts are considered part of the original disclosure or original record of this invention, and should not be regarded as new content not disclosed or anticipated by this invention, unless those skilled in the art consider the combination to be clearly unreasonable.

[0018] Unless otherwise stated, the terminology used in this invention has the same meaning as commonly understood by those skilled in the art. If a term is defined in this invention and its definition differs from the common understanding in the art, the definition of this invention shall prevail.

[0019] As mentioned earlier, there is an urgent need for a smart adhesive material that can continuously adjust its adhesion from strong structural adhesion (hot melt adhesive) to pressure-sensitive adhesion (pressure-sensitive adhesive) within a single material system through simple changes in ambient humidity. Simultaneously, it is necessary to address the problems of traditional polymer adhesive preparation processes that rely on organic solvents, require heating, or use catalysts. Therefore, this invention proposes the following technical solution to address the aforementioned issues.

[0020] First aspect This invention provides a humidity-responsive polydisulfide adhesive material, which is prepared by a method comprising the following steps: Step S1, providing monomer A and component B, wherein monomer A is guanidine salt-modified thioctic acid or its derivative, and component B is thioctic acid carboxylate, thioctic acid carboxylate derivative, or polymeric carboxylate; Step S2, mixing monomer A and component B separately in aqueous solutions, thereby forming a condensed phase through salt bridging of guanidine salt groups and carboxylate groups, and inducing ring-opening polymerization of the disulfide five-membered ring in the condensed phase; subsequently, through solid-liquid separation, vacuum drying, and hot pressing, the humidity-responsive polydisulfide adhesive material is obtained. It should be noted that the above-mentioned condensed phase-induced polymerization mechanism can fundamentally change the traditional synthesis approach of polymer adhesives. Specifically, the strong non-covalent salt bridge effect generated by guanidine salt and carboxyl salt groups in the aqueous phase can spontaneously drive molecular self-assembly and form a locally hydrophobic condensed phase microenvironment. Under room temperature conditions without any catalyst or external heating, the ring-opening polymerization of the disulfide five-membered ring can be driven. The final polymer network, due to the hydrophobic disulfide backbone embedding some hydrophilic sites, endows the material with extremely high sensitivity to environmental humidity and structural self-evolution behavior, thus breaking through the bottleneck that a single material cannot simultaneously achieve the properties of high-strength hot melt adhesive and instant pressure-sensitive adhesive.

[0021] In some embodiments of the present invention, the structure of monomer A is as shown in Formula I or Formula II; (Formula I); (Formula II); When component B is lipoic acid carboxylate or a derivative thereof, its structure is as shown in Formula III or Formula IV: (Formula III); (Formula IV); In Formulas I to IV, n is an integer from 1 to 6, and m is an integer from 2 to 6; R1 is hydrogen, a C1-C4 straight-chain alkyl group, or a C1-C4 branched alkyl group; R2 is hydrogen, a C1-C4 straight-chain alkyl group, a C1-C4 branched alkyl group, or a carboxyl group; R3 and R4 are each independently selected from any one of hydrogen, a C1-C4 straight-chain alkyl group, a C1-C4 branched alkyl group, an amino group, an ester group, an acyl group, or an alkoxy group; Nu - Selected from any one of chloride ions, bromide ions, or sulfate ions; E + It is selected from any one of sodium ions, potassium ions, or calcium ions. When the monomer substituent is limited to a short-chain alkyl group of C1 to C4 or a specific functional group, the hydrophilicity and hydrophobicity of the monomer molecule can be better controlled, ensuring good salt bridge crosslinking in the early stage of aqueous mixing, and ensuring that the polymer network has suitable chain segment activity space after final curing into a film, thereby maximizing the modulus adjustment tolerance of the adhesive under different humidity conditions.

[0022] In some embodiments of the present invention, when monomer A is guanidine salt-modified lipoic acid or a derivative thereof, its structural formula includes, but is not limited to, the following specific examples: .

[0023] In some embodiments of the present invention, when component B is thioctic acid carboxylate or a derivative thereof, its structural formula includes, but is not limited to, the following specific examples.

[0024] In some embodiments of the present invention, when component B is a polymer carboxylate, the polymer carboxylate is selected from at least one of sodium hyaluronate, sodium alginate, sodium polyacrylate, sodium polystyrene sulfonate, and sodium polymethacrylate. Introducing the aforementioned specific natural or synthetic macromolecular polymer carboxylates as rigid framework templates can create excellent synergistic effects with the dynamic polydisulfide network. The combined effect of the long macromolecular chains and multi-site salt bridge crosslinking not only enhances the macroscopic cohesive strength and mechanical dissipation capacity of the material but also further endows it with excellent underwater adhesion and interfacial anchoring force.

[0025] In some embodiments of the present invention, when component B is a polymer carboxylate, its structural formula includes, but is not limited to, the following specific examples:

[0026] .

[0027] In the above formula, n is an integer from 1 to 6.

[0028] In some embodiments of the present invention, in step S2, the concentrations of the aqueous solutions of monomer A and component B are each independently 50–400 mmol / L; the mixing temperature is 10–45°C. Controlling the reactant concentrations and system temperature within these specific ranges is crucial to ensuring stable liquid-liquid phase separation, guaranteeing the smooth formation of the condensed phase while avoiding uncontrolled aggregation caused by excessively high concentrations.

[0029] In some embodiments of the present invention, in step S2, the solid-liquid separation includes centrifugation at 4000–8000 rpm and standing for 3–24 hours; the drying temperature is 50–100°C. The specific centrifugal force and standing time described above promote the complete separation of the condensed phase and the physical entanglement of the polymer long chains; the subsequent medium-to-high temperature drying further removes moisture, causing the originally loose aggregates to undergo irreversible densification and shrinkage, ultimately transforming them into a tough adhesive film with extremely high initial peel strength.

[0030] In some embodiments of the present invention, in step S2, the molar ratio of monomer A to component B is 1:1 to 2:1. Using this specific ratio ensures that the guanidine salt groups in monomer A and the carboxyl salt groups in component B undergo sufficient salt-bridge crosslinking, thereby guaranteeing the stability of the final polymer network structure and its sensitive humidity response characteristics.

[0031] In some embodiments of the present invention, monomer A is guanidine-modified lipoic acid prepared by reacting lipoic acid, N,N'-carbonyldiimidazole, ethylenediamine, and 1H-pyrazole-1-formamidinium hydrochloride; component B is sodium lipoate. This specific precursor combination provides the material system with stronger thermodynamic driving force for ring-opening polymerization. Specifically, the guanidine-modified lipoic acid and sodium lipoate can form extremely stable salt bridges and electrostatic interactions, promoting good self-assembly aggregation of the monomers before polymerization. Tests show that the polymer prepared based on this specific combination can achieve a maximum lap shear strength of over 11.2 MPa on a glass surface at 65% RH humidity, exhibiting strong structural hot melt adhesive properties.

[0032] In some embodiments of the present invention, the structural formulas of lipoic acid and its derivatives used as starting materials for preparing monomer A are shown in Formulas V and VI: (Form V); (Form VI).

[0033] In formulas V and VI, n is an integer from 1 to 6; R1 is hydrogen, C1-C4 straight-chain alkyl, or C1-C4 branched alkyl; R2 is hydrogen, C1-C4 straight-chain alkyl, C1-C4 branched alkyl, or carboxyl.

[0034] It is worth noting that in some embodiments of the present invention, monomer A is prepared by the following steps: thioctic acid or its derivative and N,N'-carbonyldiimidazole are dissolved in an organic solvent, and a solution containing ethylenediamine or butanediamine is added dropwise under ice bath conditions to obtain an intermediate (for example, when the reactants are thioctic acid and ethylenediamine, the intermediate is specifically thioctic amide ethylenediamine; generally, they can be collectively referred to as thioctic amide or its derivative intermediates); the intermediate is dissolved in an organic solvent, and 1H-pyrazole-1-formamidinium hydrochloride is added under a protective atmosphere and ice bath conditions to obtain monomer A.

[0035] The structural formulas of the above-mentioned thioctic amide or its derivative intermediates are shown in formulas VII and VIII below: (Formula VII); (Form VIII).

[0036] In formulas VII and VIII, n is an integer from 1 to 6; R1, R2, R3, and R4 are hydrogen, C1-C4 straight-chain alkyl, or C1-C4 branched alkyl.

[0037] Second aspect This invention provides a method for preparing a polydisulfide adhesive material as described in the first aspect. The preparation method includes the following steps: S1, providing monomer A and component B, wherein monomer A is guanidine salt-modified thioctic acid or its derivative, and component B is thioctic acid carboxylate, thioctic acid carboxylate derivative, or polymeric carboxylate; S2, mixing monomer A and component B separately in aqueous solutions, allowing the guanidine salt groups and carboxylate groups to form a condensed phase through salt bridging, and inducing the ring-opening polymerization of the disulfide five-membered ring in the condensed phase, followed by solid-liquid separation, vacuum drying, and hot pressing to obtain the humidity-responsive polydisulfide adhesive material. This method eliminates the dependence on toxic organic solvents, high-energy external heating, and toxic metal catalysts in traditional polymer synthesis. High-performance polymers can be obtained simply through aqueous phase mixing and centrifugal separation. This not only cuts off VOC emissions at the source, achieving green chemical manufacturing, but also significantly simplifies product purification and post-processing, possessing extremely high industrial scale-up potential and cost advantages.

[0038] In some embodiments of the present invention, after solid-liquid separation and before obtaining the humidity-responsive polydisulfide adhesive material, the process parameters for vacuum drying and hot pressing are as follows: vacuum drying temperature is 60–75°C, vacuum degree is 0.15 mbar, vacuum drying time is 12–24 h, hot pressing temperature is 60–75°C, hot pressing pressure is 4–6 MPa, and hot pressing time is 2–6 h.

[0039] In some embodiments of the present invention, monomer A is prepared by the following steps: lipoic acid or its derivative and N,N'-carbonyldiimidazole are dissolved in an organic solvent, and a solution containing ethylenediamine or butanediamine is added dropwise under ice bath conditions to obtain an intermediate; the intermediate is dissolved in an organic solvent, and 1H-pyrazole-1-formamidinium hydrochloride is added under a protective atmosphere and ice bath conditions to obtain monomer A. The ice bath and protective atmosphere conditions in the above multi-step synthesis process effectively suppress the thermal ring-opening or oxidation side reactions of the sensitive dithiopentane structure during the reaction. Simultaneously, the use of N,N'-carbonyldiimidazole as a mild condensing agent allows the amidation reaction to proceed mildly and efficiently, thereby ensuring the high purity of the synthesized monomer A, which is a necessary condition for the formation of a defect-free condensed phase in the subsequent aqueous phase.

[0040] In some embodiments of the present invention, when component B is lipoic acid carboxylate or a derivative thereof, it is prepared by the following steps: lipoic acid or a derivative thereof is dissolved with an inorganic base in a mixed solvent of water and ethanol, reacted at 50–90°C for 2–8 hours, acetone or diethyl ether is added to precipitate the product, and after separation and drying, component B is obtained. The neutralization reaction in the mixed solvent of water and ethanol not only ensures the complete dissolution of the inorganic base and efficient proton transfer but also maintains the integrity of the lipoic acid skeleton. Subsequent recrystallization by adding a poor solvent (acetone or diethyl ether) can extremely quickly and thoroughly remove unreacted inorganic salts and organic impurities, ensuring the high purity of component B powder, thereby ensuring the precise controllability of the two-component ratio in the subsequent polymerization reaction.

[0041] Third aspect This invention provides the application of polydisulfide adhesive materials as described in the first aspect or prepared by the method described in the second aspect in the preparation of adhesive materials, impact-resistant materials, coating materials, or biodegradable materials. Benefiting from the intrinsic dynamic exchange characteristics of disulfide bonds and the humidity-responsive evolution mechanism of the supramolecular network within the material, this material breaks through the functional boundaries of traditional static adhesives. It not only achieves excellent energy dissipation (impact resistance) through network rearrangement under impact loads but also undergoes complete chemical degradation in alkaline or alcoholic solvents, thus demonstrating irreplaceable application value in cutting-edge fields such as flexible electronic packaging, wearable medical dressings, and sustainable green coatings.

[0042] Example The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0043] The sources of some of the raw materials used in the examples are as follows: The lipoic acid was purchased from Aladdin, its full name is (±)-α-lipoic acid (racemic), CAS number is 1077-28-7, purity is 99%, grade is reagent grade (RG); N,N'-carbonyldiimidazole was purchased from Adamas, CAS number 530-62-1, purity 99%, reagent grade (RG); Ethylenediamine was purchased from Shanghai Testing & Inspection Group, CAS number 107-15-3, purity 99%, grade analytical grade (AR); 1H-pyrazole-1-methylamidine hydrochloride was purchased from Bid Pharmaceuticals, CAS number 4023-02-3, with a purity of 97% and a reagent grade (RG).

[0044] It should be noted that the other raw materials, testing equipment, instruments, etc. mentioned in this invention specification can all be obtained through general commercial channels.

[0045] Example 1 This embodiment provides a humidity-responsive polydisulfide adhesive material, the preparation method of which is as follows: (1) Preparation of monomer A (guanidine salt modified lipoic acid): Dissolve 5 g of lipoic acid in 150 mL of dichloromethane, slowly add 5.25 g of N,N'-carbonyldiimidazole, and stir until clear. Slowly add the solution dropwise to a 37 mL dichloromethane solution containing 13 mL of ethylenediamine under ice bath conditions, stir for 1 h under ice bath conditions, and then stir for 2 h at room temperature. Wash three times with saturated saline, dry with anhydrous sodium sulfate, filter, and remove the solvent under reduced pressure to obtain the intermediate lipoic acid ethylenediamine. Dissolve 5 g of the above intermediate in 150 mL of dichloromethane, slowly add 2.95 g of 1H-pyrazole-1-formamidinium hydrochloride under ice bath conditions, stir for 1 h under ice bath conditions, and then stir for 2 h at room temperature. Remove the solvent under reduced pressure, and separate by column chromatography to obtain the yellow solid product guanidine salt modified lipoic acid (monomer A).

[0046] (2) Preparation of component B (sodium lipoate): Dissolve 10g of lipoic acid in 66mL of a mixed solvent of ethanol and water (ethanol to water volume ratio of 10:1), add 2g of sodium hydroxide, and stir under reflux at 75℃ for 4h. After cooling to room temperature, dropwise add the reaction solution into a large amount of acetone, stir for 30min, and filter. Collect the pale yellow powder, and vacuum dry it at room temperature, with a vacuum degree of 0.15mbar and a vacuum drying time of 24h to obtain sodium lipoate (component B).

[0047] (3) Preparation of humidity-responsive adhesive material: 5g of monomer A and 3.49g of component B were dissolved in 76mL of water to prepare a 200mmol / L aqueous solution. The two solutions were mixed (resulting in a clear liquid-liquid phase separation), centrifuged, and allowed to stand for 3 hours. The supernatant was discarded, and the mixture was vacuum dried and then hot-pressed. The vacuum drying temperature was 60℃, the vacuum degree was 0.15mbar, and the vacuum drying time was 12 hours. The hot-pressing temperature was 40℃, the hot-pressing pressure was 4MPa, and the hot-pressing time was 2 hours, yielding a pale yellow transparent film (i.e., polydisulfide adhesive material). By placing the film in different humidity environments for equilibration, materials with different adhesion properties can be obtained.

[0048] Table 1 shows the types and ratios of monomer A and component B used in Examples 2-8 of this invention.

[0049] Example 2 This embodiment provides a humidity-responsive polydisulfide adhesive material, the preparation method of which is as follows: (1) Provide monomer A and component B: The chemical structure of monomer A is shown as shown in Table 1 above for the monomer A corresponding to Example 2, and the chemical structure of component B is shown in Table 1 above for the component B corresponding to Example 2.

[0050] (2) Preparation of humidity-responsive adhesive material: The monomer A and component B were dissolved in water to prepare an aqueous solution with a concentration of 200 mmol / L. The two solutions were mixed in a molar ratio of 1:1 between monomer A and component B. After mixing, the system underwent liquid-liquid phase separation. After centrifugation, the mixture was allowed to stand for 3 hours, the supernatant was discarded, and the mixture was vacuum dried and then hot-pressed. The vacuum drying temperature was 70°C, the vacuum degree was 0.15 mbar, the vacuum drying time was 24 hours, the hot-pressing temperature was 70°C, the hot-pressing pressure was 5 MPa, and the hot-pressing time was 3 hours to obtain a polydisulfide adhesive film.

[0051] Example 3 This embodiment provides a humidity-responsive polydisulfide adhesive material, the preparation method of which is as follows: (1) Provide monomer A and component B: The chemical structure of monomer A is shown as shown in Table 1 above for the monomer A corresponding to Example 3, and the chemical structure of component B is shown in Table 1 above for the component B corresponding to Example 3.

[0052] (2) Preparation of humidity-responsive adhesive material: The monomer A and component B were dissolved in water to prepare an aqueous solution with a concentration of 200 mmol / L. The two solutions were mixed in a molar ratio of 1:1 between monomer A and component B. After mixing, the system underwent liquid-liquid phase separation. After centrifugation, the mixture was allowed to stand for 3 hours, the supernatant was discarded, and the mixture was vacuum dried and then hot-pressed. The vacuum drying temperature was 70°C, the vacuum degree was 0.15 mbar, the vacuum drying time was 24 hours, the hot-pressing temperature was 70°C, the hot-pressing pressure was 5 MPa, and the hot-pressing time was 3 hours to obtain a polydisulfide adhesive film.

[0053] Example 4 This embodiment provides a humidity-responsive polydisulfide adhesive material, the preparation method of which is as follows: (1) Provide monomer A and component B: The chemical structure of monomer A is shown as shown in the monomer A corresponding to Example 4 in Table 1 above, and the chemical structure of component B is shown as shown in the component B corresponding to Example 4 in Table 1 above.

[0054] (2) Preparation of humidity-responsive adhesive material: The monomer A and component B were dissolved in water to prepare an aqueous solution with a concentration of 200 mmol / L. The two solutions were mixed at a molar ratio of 2:1 for monomer A to component B. After mixing, the system underwent liquid-liquid phase separation. After centrifugation, the mixture was allowed to stand for 3 hours, the supernatant was discarded, and the mixture was vacuum dried and then hot-pressed. The vacuum drying temperature was 70°C, the vacuum degree was 0.15 mbar, the vacuum drying time was 24 hours, the hot-pressing temperature was 70°C, the hot-pressing pressure was 6 MPa, and the hot-pressing time was 3 hours to obtain a polydisulfide adhesive film.

[0055] Example 5 This embodiment provides a humidity-responsive polydisulfide adhesive material, the preparation method of which is as follows: (1) Provide monomer A and component B: The chemical structure of monomer A is shown as shown in the monomer A corresponding to Example 5 in Table 1 above, and the chemical structure of component B is shown as shown in the component B corresponding to Example 5 in Table 1 above.

[0056] (2) Preparation of humidity-responsive adhesive material: The monomer A and component B were dissolved in water to prepare an aqueous solution with a concentration of 200 mmol / L. The two solutions were mixed in a molar ratio of 1:1 between monomer A and component B. After mixing, the system underwent liquid-liquid phase separation. After centrifugation, the mixture was allowed to stand for 3 hours, the supernatant was discarded, and the mixture was vacuum dried and then hot-pressed. The vacuum drying temperature was 70°C, the vacuum degree was 0.15 mbar, the vacuum drying time was 24 hours, the hot-pressing temperature was 70°C, the hot-pressing pressure was 4 MPa, and the hot-pressing time was 4 hours to obtain a polydisulfide adhesive film.

[0057] Example 6 This embodiment provides a humidity-responsive polydisulfide adhesive material, the preparation method of which is as follows: (1) Provide monomer A and component B: The chemical structure of monomer A is shown as shown in the monomer A corresponding to Example 6 in Table 1 above, and component B is a polymer carboxylate, the chemical structure of which is shown as shown in the component B corresponding to Example 6 in Table 1 above.

[0058] (2) Preparation of humidity-responsive adhesive material: The monomer A and component B were dissolved in water to prepare an aqueous solution with a concentration of 200 mmol / L. The two solutions were mixed in a molar ratio of 1:1 between monomer A and component B. After mixing, the system underwent liquid-liquid phase separation. After centrifugation, the mixture was allowed to stand for 3 hours, the supernatant was discarded, and the mixture was vacuum dried and then hot-pressed. The vacuum drying temperature was 70°C, the vacuum degree was 0.15 mbar, the vacuum drying time was 24 hours, the hot-pressing temperature was 70°C, the hot-pressing pressure was 5 MPa, and the hot-pressing time was 5 hours to obtain a polydisulfide adhesive film.

[0059] Example 7 This embodiment provides a humidity-responsive polydisulfide adhesive material, the preparation method of which is as follows: (1) Provide monomer A and component B: The chemical structure of monomer A is shown as shown in the monomer A corresponding to Example 7 in Table 1 above, and component B is a polymer carboxylate, the chemical structure of which is shown as shown in the component B corresponding to Example 7 in Table 1 above.

[0060] (2) Preparation of humidity-responsive adhesive material: The monomer A and component B were dissolved in water to prepare an aqueous solution with a concentration of 200 mmol / L. The two solutions were mixed in a molar ratio of 1:1 between monomer A and component B. After mixing, the system underwent liquid-liquid phase separation. After centrifugation, the mixture was allowed to stand for 3 hours, the supernatant was discarded, and the mixture was vacuum dried and then hot-pressed. The vacuum drying temperature was 70°C, the vacuum degree was 0.15 mbar, the vacuum drying time was 24 hours, the hot-pressing temperature was 70°C, the hot-pressing pressure was 5 MPa, and the hot-pressing time was 5 hours to obtain a polydisulfide adhesive film.

[0061] Example 8 This embodiment provides a humidity-responsive polydisulfide adhesive material, the preparation method of which is as follows: (1) Provide monomer A and component B: The chemical structure of monomer A is shown as shown in the monomer A corresponding to Example 8 in Table 1 above, and component B is a polymer carboxylate, the chemical structure of which is shown as shown in the component B corresponding to Example 8 in Table 1 above.

[0062] (2) Preparation of humidity-responsive adhesive material: The monomer A and component B were dissolved in water to prepare an aqueous solution with a concentration of 200 mmol / L. The two solutions were mixed in a molar ratio of 1:1 between monomer A and component B. After mixing, the system underwent liquid-liquid phase separation. After centrifugation, the mixture was allowed to stand for 3 hours, the supernatant was discarded, and the mixture was vacuum dried and then hot-pressed. The vacuum drying temperature was 75°C, the vacuum degree was 0.15 mbar, the vacuum drying time was 24 hours, the hot-pressing temperature was 75°C, the hot-pressing pressure was 5 MPa, and the hot-pressing time was 6 hours to obtain a polydisulfide adhesive film.

[0063] Test case The polydisulfide adhesive material prepared in Example 1 was subjected to the following structural characterization and performance tests.

[0064] 1. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) tests The films prepared in Example 1 were tested after being equilibrated under different humidity levels (25%RH, 45%RH, 65%RH, 85%RH, 95%RH).

[0065] XRD tests were performed using an 18KW / D / max2550VB / PC X-ray diffractometer.

[0066] The DSC test was conducted using a TA Instruments modulated DSC2910,1090B differential scanning calorimeter, under the following conditions: heating and cooling rate of 10℃ / min.

[0067] 2. Tensile mechanical testing The film prepared in Example 1 was cut into strips of 60mm*6mm*1mm. Stress-strain tests were performed using an INSTRON 34TM-5 universal testing machine at different humidity levels (25%RH to 95%RH) and a tensile speed of 50mm / min.

[0068] 3. Overlap Shear Adhesion Strength Test The adhesive material prepared in Example 1 was placed between two glass substrates with a bonding area of ​​1.5 cm², and the sample was prepared at 60°C. An INSTRON 34TM-5 universal testing machine was used to perform lap shear tests under different humidity conditions, with a tensile speed of 50 mm / min.

[0069] 4. Impact resistance test The polymer material obtained in Example 1 was hot-pressed into a 1 mm thick film and subjected to a drop ball impact test at 65% RH. A 5 g steel ball was dropped from a height of 50 cm to impact the film, and the damage to the film was observed.

[0070] 5. Degradability Experiment Dissolve 0.4 g of sodium hydroxide in 10 mL of methanol-water solution (methanol to water volume ratio 1:1) to prepare a 1 mol / L alkaline-alcohol solution. Take 1 g of the polymer material obtained in Example 1 and immerse it in the prepared alkaline-alcohol solution at room temperature to observe the degradation time.

[0071] Test Results (1) For the polydisulfide adhesive material prepared in Example 1, the test results show that: 1. In terms of microstructure and thermal properties, no sharp XRD diffraction peaks were observed under different humidity levels, the network was uniform and there was no obvious microphase separation; as humidity increased, its glass transition temperature (Tg) shifted significantly to the low-temperature region (Tg was 49.9℃ at 25%RH and -10.24℃ at 95%RH).

[0072] 2. In terms of tensile mechanical properties, as the humidity increases from 25%RH to 95%RH, the elastic modulus of the material gradually decreases from 140MPa to 0.5MPa, while the elongation at break increases from 5.8% to 508.6%.

[0073] 3. In terms of overlap shear adhesion performance, the adhesion strength is the highest at 65%RH, reaching about 11.2MPa (exhibiting hot melt adhesive characteristics); at 95%RH, the adhesion strength drops to about 1.0MPa (transforming into pressure-sensitive adhesive mode).

[0074] 4. In terms of impact resistance and biodegradability, the 1 mm thick film showed no obvious cracks or damage on the surface after being subjected to a falling ball impact (5 g steel ball, 50 cm drop height) at 65% RH, and could effectively absorb impact energy; when the sample (1 g) was immersed in a 1 mol / L alkaline alcohol solution, it was completely degraded after about 12 h at 25 ℃.

[0075] (2) For the polydisulfide adhesive material prepared in Example 2, the test results show that: 1. In terms of microstructure and thermal properties, its Tg at 25%RH is 36.4℃ and its Tg at 95%RH is -15.4℃.

[0076] 2. In terms of tensile mechanical properties, as the humidity increases from 25%RH to 95%RH, the elastic modulus of the material changes from 103MPa to 0.1MPa, and the elongation at break changes from 10.9% to 670.3%.

[0077] 3. Regarding the lap shear adhesion properties, the adhesion strength is 9.8 MPa at 65% RH and 0.8 MPa at 95% RH.

[0078] 4. In terms of impact resistance and biodegradability, the 1 mm thick film showed no obvious cracks or damage on the surface after being subjected to a falling ball impact at 65% RH; when immersed in a 1 mol / L alkaline alcohol solution, the complete degradation time was 12 h.

[0079] (3) For the polydisulfide adhesive material prepared in Example 3, the test results show that: 1. In terms of microstructure and thermal properties, its Tg at 25%RH is 39.4℃ and its Tg at 95%RH is -12.6℃.

[0080] 2. In terms of tensile mechanical properties, as the humidity increases from 25%RH to 95%RH, the elastic modulus of the material changes from 108MPa to 0.2MPa, and the elongation at break changes from 9.8% to 547.5%.

[0081] 3. Regarding the lap shear adhesion properties, the adhesion strength is 8.9 MPa at 65% RH and 0.9 MPa at 95% RH.

[0082] 4. In terms of impact resistance and biodegradability, the 1 mm thick film showed no obvious cracks or damage on the surface after being subjected to a falling ball impact at 65% RH; when immersed in a 1 mol / L alkaline alcohol solution, the complete degradation time was 12 h.

[0083] (4) For the polydisulfide adhesive material prepared in Example 4, the test results show that: 1. In terms of microstructure and thermal properties, its Tg at 25%RH is 69.3℃ and its Tg at 95%RH is 8.9℃.

[0084] 2. In terms of tensile mechanical properties, as the humidity increases from 25%RH to 95%RH, the elastic modulus of the material changes from 258MPa to 3.9MPa, and the elongation at break changes from 5.4% to 286.7%.

[0085] 3. Regarding the lap shear adhesion properties, the adhesion strength is 7.8 MPa at 65% RH and 2.6 MPa at 95% RH.

[0086] 4. In terms of impact resistance and biodegradability, the 1 mm thick film showed no obvious cracks or damage on the surface after being subjected to a falling ball impact at 65% RH; when immersed in a 1 mol / L alkaline alcohol solution, the complete degradation time was 12 h.

[0087] (5) For the polydisulfide adhesive material prepared in Example 5, the test results show that: 1. In terms of microstructure and thermal properties, its Tg at 25%RH is 62.3℃ and its Tg at 95%RH is 3.4℃.

[0088] 2. In terms of tensile mechanical properties, as the humidity increases from 25%RH to 95%RH, the elastic modulus of the material changes from 248.6MPa to 8.9MPa, and the elongation at break changes from 4.8% to 327.6%.

[0089] 3. Regarding the lap shear adhesion properties, the adhesion strength is 7.8 MPa at 65% RH and 2.1 MPa at 95% RH.

[0090] 4. In terms of impact resistance and biodegradability, the 1 mm thick film showed no obvious cracks or damage on the surface after being subjected to a falling ball impact at 65% RH; when immersed in a 1 mol / L alkaline alcohol solution, the complete degradation time was 12 h.

[0091] (6) For the polydisulfide adhesive material prepared in Example 6, the test results show that: 1. In terms of microstructure and thermal properties, its Tg at 25%RH is 76.8℃ and its Tg at 95%RH is -2.5℃.

[0092] 2. In terms of tensile mechanical properties, as the humidity increases from 25%RH to 95%RH, the elastic modulus of the material changes from 318MPa to 2.8MPa, and the elongation at break changes from 3.9% to 412.5%.

[0093] 3. Regarding the lap shear adhesion properties, the adhesion strength is 6.8 MPa at 65% RH and 1.6 MPa at 95% RH.

[0094] 4. In terms of impact resistance and biodegradability, the 1 mm thick film showed no obvious cracks or damage on the surface after being subjected to a falling ball impact at 65% RH; when immersed in a 1 mol / L alkaline alcohol solution, the complete degradation time was 18 h.

[0095] (7) For the polydisulfide adhesive material prepared in Example 7, the test results show that: 1. In terms of microstructure and thermal properties, its Tg at 25%RH is 55.6℃ and its Tg at 95%RH is -18.2℃.

[0096] 2. In terms of tensile mechanical properties, as the humidity increases from 25%RH to 95%RH, the elastic modulus of the material changes from 186MPa to 0.7MPa, and the elongation at break changes from 7.2% to 615.4%.

[0097] 3. Regarding the lap shear adhesion properties, the adhesion strength is 7.2 MPa at 65% RH and 1.1 MPa at 95% RH.

[0098] 4. In terms of impact resistance and biodegradability, the 1 mm thick film showed no obvious cracks or damage on the surface after being subjected to a falling ball impact at 65% RH; when immersed in a 1 mol / L alkaline alcohol solution, the complete degradation time was 14 h.

[0099] (8) For the polydisulfide adhesive material prepared in Example 8, the test results show that: 1. In terms of microstructure and thermal properties, its Tg at 25%RH is 75.6℃ and its Tg at 95%RH is 4.8℃.

[0100] 2. In terms of tensile mechanical properties, as the humidity increases from 25%RH to 95%RH, the elastic modulus of the material changes from 342MPa to 6.5MPa, and the elongation at break changes from 3.4% to 298.7%.

[0101] 3. Regarding the lap shear adhesion properties, the adhesion strength is 6.4 MPa at 65% RH and 2.4 MPa at 95% RH.

[0102] 4. In terms of impact resistance and biodegradability, the 1 mm thick film showed no obvious cracks or damage on the surface after being subjected to a falling ball impact at 65% RH; when immersed in a 1 mol / L alkaline alcohol solution, the complete degradation time was 18 h.

[0103] The structure and properties of the polydisulfide adhesive material prepared in Example 1 of the present invention will be further described in detail below with reference to the accompanying drawings.

[0104] like Figure 1 As shown, after mixing aqueous solutions of monomer A and component B, a clear liquid-liquid phase separation phenomenon was observed macroscopically, with a thick condensed phase appearing at the bottom. Figure 2 The confocal microscopy images further confirmed the formation of distinct droplet-like condensates at the microscale, indicating that the molecular self-assembly and aggregation were driven by strong salt bridging between the two monomers.

[0105] like Figure 3 As shown in the Raman spectrum comparison, the spectral characteristics of the prepared polymer material changed significantly compared to the two monomers, which fully demonstrates that the disulfide five-membered ring in the monomer was successfully induced to undergo ring-opening polymerization in the condensed phase microenvironment. Figure 4 As shown in the X-ray energy dispersive spectroscopy (EDS) image, the detection results further confirmed that the final polymer material contained sulfur segments derived from the two monomers.

[0106] like Figure 5The X-ray diffraction (XRD) pattern shows that the polymer material exhibits broad amorphous diffuse peaks under different humidity conditions (25%RH to 95%RH) without any sharp crystalline diffraction peaks. This indicates that the polymer network constructed by salt bridges and disulfide bonds is highly uniform and there is no obvious microphase separation.

[0107] like Figure 6 As shown in the differential scanning calorimetry (DSC) curve, the glass transition temperature (Tg) of the polymer material shifts significantly to the low-temperature region with the increase of ambient humidity. This proves that the hydrophilic sites embedded in the disulfide hydrophobic backbone can effectively sense water molecules, giving the material a humidity-sensitive and continuous thermal response characteristic.

[0108] like Figure 7 As shown in the tensile stress-strain curves, at a tensile speed of 50 mm / min, the tensile modulus of the material gradually decreases as the ambient humidity increases from 25%RH to 95%RH, while the elongation at break significantly increases. This indicates that the plasticizing effect of water molecules enhances the mobility of polymer network segments, and the material exhibits significant humidity-dependent mechanical behavior.

[0109] like Figure 8 The lap shear adhesion strength test results show that the polymer material exhibits a broad-spectrum adhesion mode transition to the glass substrate under different humidity conditions. At a humidity level of 65% RH, its adhesion strength reaches a peak of approximately 11.2 MPa, exhibiting typical characteristics of a high-strength structural hot melt adhesive. However, as the humidity continues to rise to 95% RH, its adhesion strength gradually decreases to approximately 1.0 MPa, at which point the material transitions to a pressure-sensitive adhesive adhesion mode. These results directly demonstrate that the material of this invention can achieve broad-spectrum and continuous control of adhesion performance within a single system.

[0110] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims. Furthermore, specific examples have been used in the specification to illustrate the principles and implementation methods of the present invention. The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention, and the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A humidity-responsive polydisulfide adhesive material, characterized in that, The polydisulfide adhesive material is prepared by a method comprising the following steps: Step S1, providing monomer A and component B, wherein monomer A is guanidine salt modified lipoic acid or its derivative, and component B is lipoic acid carboxylate, lipoic acid carboxylate derivative or polymeric carboxylate; Step S2: After preparing monomer A and component B into aqueous solutions, they are mixed to form a condensed phase through salt bridging of guanidine salt groups and carboxylate salt groups, and the ring-opening polymerization of disulfide five-membered rings is induced in the condensed phase; then, after solid-liquid separation, vacuum drying and hot pressing, the humidity-responsive polydisulfide adhesive material is obtained.

2. The polydisulfide adhesive material as described in claim 1, characterized in that, The structure of monomer A is shown in Formula I or Formula II; (Formula I); (Formula II); When component B is lipoic acid carboxylate or a derivative thereof, its structure is as shown in Formula III or Formula IV: (Formula III); (Formula IV); In Equations I to IV, n is an integer from 1 to 6, and m is an integer from 2 to 6; R1 is hydrogen, a C1-C4 straight-chain alkyl group, or a C1-C4 branched alkyl group; R2 is hydrogen, C1-C4 straight-chain alkyl, C1-C4 branched alkyl, or carboxyl group; R3 and R4 are each independently selected from any one of hydrogen, C1-C4 straight-chain alkyl, C1-C4 branched alkyl, amino, ester, acyl or alkoxy chain; Nu - Selected from any one of chloride ions, bromide ions, or sulfate ions; E + It is selected from any one of sodium ions, potassium ions, or calcium ions.

3. The polydisulfide adhesive material as described in claim 1, characterized in that, When component B is a polymer carboxylate, the polymer carboxylate is selected from at least one of sodium hyaluronate, sodium alginate, sodium polyacrylate, sodium polystyrene sulfonate, and sodium polymethacrylate.

4. The polydisulfide adhesive material as described in claim 1, characterized in that, In step S2, the aqueous solutions of monomer A and component B each have an independent concentration of 50–400 mmol / L; The mixing temperature is 10–45°C.

5. The polydisulfide adhesive material as described in claim 4, characterized in that, In step S2, the solid-liquid separation includes centrifugation at 4000-8000 rpm and standing for 3-24 hours; The drying temperature is 50–100°C.

6. The polydisulfide adhesive material as described in claim 1, characterized in that, In step S2, the molar ratio of monomer A to component B is 1:1 to 2:

1.

7. The polydisulfide adhesive material as described in claim 2, characterized in that, The monomer A is a guanidine salt modified lipoic acid prepared by reacting lipoic acid, N,N'-carbonyldiimidazole, ethylenediamine and 1H-pyrazole-1-formamidinium hydrochloride; Component B is sodium thioctic acid.

8. A method for preparing the polydisulfide adhesive material as described in claim 1, characterized in that, The preparation method includes the following steps: S1, providing monomer A and component B, wherein monomer A is guanidine salt modified thioctic acid or a derivative thereof, and component B is thioctic acid carboxylate, thioctic acid carboxylate derivative or polymeric carboxylate; S2, monomer A and component B are respectively prepared into aqueous solutions and then mixed to form a condensed phase by the salt bridge effect of guanidine salt groups and carboxylate salt groups. The condensed phase is then induced to undergo ring-opening polymerization of disulfide five-membered rings. Subsequently, the mixture is subjected to solid-liquid separation, vacuum drying and hot pressing to obtain the humidity-responsive polydisulfide adhesive material.

9. The preparation method according to claim 8, characterized in that, The monomer A is prepared by the following steps: lipoic acid or its derivative and N,N'-carbonyldiimidazole are dissolved in an organic solvent, and a solution containing ethylenediamine or butanediamine is added dropwise under ice bath conditions to obtain an intermediate; the intermediate is dissolved in an organic solvent, and 1H-pyrazole-1-formamidinium hydrochloride is added under a protective atmosphere and ice bath conditions to obtain the monomer A. And / or, when component B is lipoic acid carboxylate or a derivative thereof, it is prepared by the following steps: dissolving lipoic acid or a derivative thereof with an inorganic base in a mixed solvent of water and ethanol, reacting at 50-90°C for 2-8 hours, adding acetone or diethyl ether to precipitate the product, and obtaining component B after separation and drying.

10. The use of a polydisulfide adhesive material as described in any one of claims 1 to 7, or a polydisulfide adhesive material obtained by the preparation method as described in claim 8 or 9, in the preparation of adhesive materials, impact-resistant materials, coating materials, or biodegradable materials.

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