Multifunctional underwater adhesive based on deep eutectic solvent and preparation method of multifunctional underwater adhesive

Abstract

The invention discloses a multifunctional underwater adhesive based on a deep eutectic solvent and a preparation method thereof, and the preparation method comprises the following steps: (1) mixing fatty acid and quaternary ammonium salt, heating and stirring until a uniform and transparent DES solution is formed; and (2) adding an acrylamide monomer and a fluorine-containing acrylate monomer into the DES solution to form a precursor solution, then adding a photoinitiator, and irradiating with an ultraviolet lamp to obtain the underwater adhesive. The adhesive prepared by the invention provides strong adhesion to different substrates by utilizing various interactions among carbonyl, amide and trifluoromethyl contained in eutectic gel, such as hydrogen bonds, metal complexation and hydrophobic interaction, and meanwhile, the surface energy of the adhesive can be reduced by utilizing the fluorine-substituted polyacrylate copolymer, so that the adhesive can be applied to the field of chemical engineering. And the adhesive capacity of the adhesive on a low-surface-energy material is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesives, and in particular to a multifunctional underwater adhesive based on a low eutectic solvent and a preparation method thereof. Background Art

[0002] Adhesive is a substance that can connect the surfaces of two or more objects together. It usually exists in the form of liquid, paste or tape, and bonds objects together through physical or chemical action. There are many types of adhesives at present, such as common transparent tape, 502 glue, hot melt adhesive, cement and natural rubber, etc. Underwater adhesive, as the name suggests, is an adhesive used in water environment. Underwater adhesive is widely used in many underwater environment operations such as underwater sensing, marine environment exploration, underwater coating and underwater emergency treatment. However, in the underwater environment, a hydration layer will form on the surface of the material. This hydration layer will hinder the adhesive from forming an effective interaction force with the surface of the material, which greatly reduces the effect of the adhesive. Moreover, long-term exposure of underwater adhesives to the water environment will cause problems such as swelling and degradation of the adhesive, resulting in failure of the bonding effect. In addition, underwater adhesives often face the problem of non-toxicity and environmental protection.

[0003] Someone proposed a method for preparing underwater adhesives using rosin-based diol chain extenders. The adhesive prepared by this method has the advantages of simple preparation, green and sustainable, but the rosin group will accelerate the oxidation process in a humid environment, affecting its performance. Adhesive protein mussels are a natural ideal underwater adhesive. Inspired by this, people have developed an underwater adhesive containing catechol groups for widespread use. However, the catechol group has the disadvantage of being easily oxidized, which affects its storage process. In addition, the poor mechanical properties of catechol group adhesives also limit the application of this adhesive.

[0004] In summary, the current underwater adhesives still have many problems such as poor bonding strength, poor environmental stability, weak mechanical strength, and poor electrical conductivity. There is an urgent need for an adhesive with good mechanical properties, electrochemical properties, environmental stability, and underwater adhesion properties. Summary of the invention

[0005] The object of the present invention is to provide a multifunctional underwater adhesive based on a deep eutectic solvent and a preparation method thereof, to solve the problems of poor bonding strength, poor environmental stability, weak mechanical strength and poor electrical conductivity of the above-mentioned underwater adhesive. The present invention designs a hydrophobic eutectic gel composed of a quaternary ammonium salt hydrophobic deep eutectic solvent (DES) and a fluorinated polymer network, using the obtained DES as a solvent, introducing an acrylate monomer, because polyacrylate has excellent water resistance and adhesion properties as a typical hydrophobic polymer, is suitable for preparing a gel with good anti-swelling properties and self-adhesive properties, and the obtained ion gel (adhesive) has good mechanical properties, electrochemical properties, environmental stability and underwater adhesion properties. These properties benefit from the low surface energy of fluorinated polymers, the excellent hydrophobicity of DES and the rich dynamic interactions between DES and polymers, and it is difficult for water molecules and DES to interpenetrate each other, so that the adhesive has excellent waterproof ability and long-term durability in a variety of environments.

[0006] To achieve the above object, the first aspect of the present invention provides a method for preparing a multifunctional underwater adhesive based on a deep eutectic solvent, comprising the following steps:

[0007] (1) Mixing fatty acid and quaternary ammonium salt, heating and stirring until a uniform and transparent DES solution is formed;

[0008] (2) Adding acrylamide monomers and fluorinated acrylate monomers to a DES solution to form a precursor solution, then adding a photoinitiator and irradiating with an ultraviolet lamp to obtain an underwater adhesive.

[0009] Preferably, in step (1), the quaternary ammonium salt is selected from at least one of tetrabutylammonium bromide and tetraoctylammonium bromide; and the fatty acid is selected from at least one of heptanoic acid, octanoic acid, nonanoic acid and decanoic acid.

[0010] More preferably, in step (1), the quaternary ammonium salt is tetraoctylammonium bromide and the fatty acid is capric acid.

[0011] Preferably, in step (1), the molar ratio of the quaternary ammonium salt to the fatty acid is 1:(2-3).

[0012] Preferably, in step (1), the heating temperature is 30-80° C., the heating time is 1-4 h, and the stirring speed is 100-800 rpm.

[0013] More preferably, in step (1), the heating temperature is 70° C., the heating time is 2 h, and the stirring speed is 500 rpm.

[0014] Preferably, in step (2), the acrylamide monomer is selected from at least one of N-hydroxyethyl acrylamide, acrylamide, N-methyl acrylamide, N,N-dimethyl acrylamide, N-hydroxymethyl acrylamide, and N-tert-butyl acrylamide; and the fluorine-containing acrylate monomer is selected from at least one of 2,2,2-trifluoroethyl acrylate, hexafluorobutyl acrylate, 2,2,3,3-tetrafluoroethyl acrylate, perfluorohexyl ethyl acrylate, perfluorooctyl ethyl acrylate, and 2-(perfluorobutyl) ethyl acrylate.

[0015] The concept of deep eutectic solvent (DES) was first proposed by Abbott in 2003. He proposed that a deep eutectic solvent is a liquid mixture with a melting point significantly lower than that of each component. The DES-based ion gel not only has the excellent properties of traditional ionic liquids (such as non-volatile, non-reactive with water and non-flammable, etc.), but also has lower cost, simpler preparation and better biodegradability than ionic liquids. It has excellent biocompatibility and degradability, conforms to the concept of sustainable development of green environmental protection, and has been widely used in energy storage devices, biopharmaceuticals and catalytic synthesis since its discovery. At present, the more commonly used is hydrophilic DES-based ion gel. Since it is hydrophilic, it is difficult to avoid absorbing water in the air. It is easy to absorb a large amount of environmental moisture. There is a risk of gel swelling and phase separation, which leads to gel softening, adversely affecting the durability of the device, and also causing a significant decrease in the performance of the adhesive. Hydrophobic deep eutectic solvents (HDESs) are a new type of green solvents. Through certain chemical modifications, hydrophobic groups or structures are added, thereby reducing the interaction with water and solubility, and improving the stability and application potential in non-aqueous environments. In this paper, a quaternary ammonium salt hydrophobic DES is designed, and hydrophobic DES (HDESs) is prepared by utilizing the non-polarity of the four butyl groups in tetrabutyl quaternary ammonium salt and the long-chain alkyl groups in the quaternary ammonium salt molecule.

[0016] Then, in this patent, the prepared hydrophobic DES (HDESs) is used as a solvent, an acrylate monomer is introduced, and a fluorinated polymer is added to form a hydrophobic eutectic gel (HDESs gel). Since polyacrylate, as a typical hydrophobic polymer, has excellent water resistance and adhesion properties, it is suitable for preparing a gel with good anti-swelling properties and self-adhesiveness. The obtained ion gel has good mechanical properties, electrochemical properties, environmental stability and underwater adhesion properties. Thanks to the low surface energy of the fluorinated polymer, the excellent hydrophobicity of DES, and the rich dynamic interactions between DES and the polymer, it is difficult for water molecules and DES to penetrate each other, so that the ion gel has excellent waterproof ability and long-term durability in a variety of environments.

[0017] Preferably, in step (2), the photoinitiator is selected from at least one of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, 1-hydroxycyclohexyl phenyl ketone and 2-hydroxy-2-methyl-1-phenyl-1-propanone.

[0018] More preferably, the photoinitiator is 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone.

[0019] Preferably, in step (2), the mass fraction of the DES solution is 30% to 70% of the total mass of the precursor solution, and the molar ratio of the acrylamide monomer to the fluorinated acrylate monomer is 30 to 70:30 to 70.

[0020] More preferably, the mass fraction of DES solution is 30%, 40%, 50%, 60%, 70%, the molar ratio of decanoic acid to tetraoctylammonium bromide is 2:1 and 3:1 respectively, and DES solution accounts for 30%, 40%, 50%, 60%, 70% of the mass fraction of the entire precursor solution.

[0021] Preferably, in step (2), the ultraviolet irradiation time is 10 to 30 minutes.

[0022] More preferably, the ultraviolet irradiation time is 20 min.

[0023] The second aspect of the present invention provides a multifunctional underwater adhesive based on a low eutectic solvent, which is prepared by the above-mentioned preparation method.

[0024] The adhesive prepared by the present invention has good mechanical properties, electrochemical properties, environmental stability and underwater adhesion properties, specifically, transparency: visible light> 90%, underwater adhesion: ~70kPa, high stretchability: ~1300%, high mechanical strength: 0.3MPa.

[0025] The third aspect of the present invention provides an application of a multifunctional underwater adhesive based on a low eutectic solvent, and the multifunctional underwater adhesive is used in the fields of underwater sensing, marine environment exploration, underwater coating, underwater emergency treatment and battery electrode adhesive.

[0026] Therefore, the present invention adopts the above-mentioned multifunctional underwater adhesive based on a low eutectic solvent and a preparation method thereof, which has the following beneficial effects:

[0027] (1) The present invention uses green, environmentally friendly, low-cost quaternary ammonium salts and fatty acids to form DES, which has similar properties to ionic liquids and has the advantages of easy synthesis, biodegradability, good biocompatibility, high conductivity and non-toxicity, and has a wider application than ion gels.

[0028] (2) The present invention uses fluorine-containing acrylate monomers (such as 2,2,2-trifluoroethyl acrylate) and acrylamide monomers (such as N-hydroxyethyl acrylamide) to prepare the required ion gel adhesive. Among them, for 2,2,2-trifluoroethyl acrylate (TFEA), the fluorine atoms contained in it play an important hydrophobic role. The fluorine atoms have high electronegativity, and due to the high bond energy and low polarizability of the CF bond, the fluorine compound has a low surface energy, thus showing hydrophobicity, and the fluorine atoms can also improve the adhesion effect. In addition, the many groups such as amine groups contained in TFEA and various interactions can play a role in enhancing the cross-linking density and improving the adhesion ability. The amide group in N-hydroxyethyl acrylamide (HEAA) provides good hydrolysis resistance and adhesion, so that the product has good chemical stability and adhesion. And HEAA also has many interactions such as hydrogen bonds and double bonds, which help to improve the adhesion and mechanical properties of the ion gel. The adhesive prepared by the present invention has good adhesion effects on many substrates such as glass, polytetrafluoroethylene, wood, steel, polyvinyl chloride, rubber, plastic and pig skin.

[0029] (3) The present invention prepares a DES solution by the interaction between a quaternary ammonium salt and a fatty acid, and then introduces HEAA and TFEA to obtain the desired hydrophobic eutectic gel (HDESs gel) as an adhesive by photoinitiation. The entire preparation process is simple to operate and has low cost. The prepared hydrophobic eutectic gel has excellent underwater adhesion, environmental stability, biocompatibility, functional stability and self-healing properties, and can be desorbed under alkaline conditions. It can be applied to many fields such as underwater adhesion, flexible sensors, underwater emergency devices, and battery electrode binders.

[0030] (4) The adhesive prepared by the present invention has good transparency (visible light> 90%), good underwater adhesion (~70kPa), high stretchability (~1300%), high mechanical strength (0.3MPa), good conductivity, etc., and has good application prospects in underwater surveying, underwater communication, and optical camouflage. At the same time, it will provide a multifunctional underwater adhesive with excellent comprehensive performance for underwater wearable devices and sensing applications.

[0031] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a characterization of the permeability of adhesives of different proportions prepared in the present invention;

[0033] Figure 2 The adhesion conditions of the adhesive obtained by the present invention on different substrates in the air and underwater; the substrates are glass, polytetrafluoroethylene, wood, steel, polyvinyl chloride, rubber, plastic and pig skin;

[0034] Figure 3 It is a continuous stretching cycle curve diagram of the adhesive obtained by the present invention;

[0035] Figure 4 A Morse code table for underwater communication made of a sensor made of the adhesive obtained by the present invention;

[0036] Figure 5 This is a simulated diagram of the stretched state of the sensor made of the adhesive obtained by the present invention under water;

[0037] Figure 6 This is a signal curve diagram obtained when the adhesive obtained by the present invention is used as an underwater sensor. DETAILED DESCRIPTION

[0038] The present invention will be further described below. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and a specific operation process, but the present invention is not limited to this embodiment.

[0039] Example 1

[0040] A method for preparing a multifunctional underwater adhesive based on a low eutectic solvent comprises the following steps:

[0041] (1) fatty acid capric acid and quaternary ammonium salt tetraoctylammonium bromide were mixed in a molar ratio of 2:1, and stirred at 70° C. and 500 rpm for 2 h until a uniform and transparent DES solution was formed;

[0042] (2) The obtained DES solution is stirred with N-hydroxyethyl acrylamide (HEAA) and 2,2,2-trifluoroethyl acrylate (TFEA) at room temperature and mixed evenly until a transparent precursor solution is formed, wherein the DES solution accounts for 30% of the mass of the precursor solution, and HEAA and TFEA account for 70% of the mass of the precursor solution, wherein the molar ratio of HEAA to TFEA is 50:50, i.e., 1:1, and then irradiated with an ultraviolet lamp for 20 minutes to perform free radical polymerization to obtain an adhesive.

[0043] Example 2

[0044] The difference between this embodiment and embodiment 1 is that the DES solution accounts for 40%, 50%, 60% or 70% of the mass of the precursor solution.

[0045] Comparative Example 1

[0046] The difference between this comparative example and Example 1 is that the types of DES solutions are different.

[0047] The preparation process of DES solution in this comparative example is:

[0048] The low eutectic solvent includes a hydrogen bond acceptor and a hydrogen bond donor, wherein the hydrogen bond acceptor is selected from choline chloride, and the hydrogen bond donor is selected from ethylene glycol. Choline chloride and ethylene glycol are mixed in a mass ratio of 1:2 and stirred at 50 degrees Celsius until a transparent DES solution is formed.

[0049] Comparative Example 2

[0050] The difference between this comparative example and Example 1 is that the DES solvent in step (2) is replaced by water.

[0051] Test example

[0052] The performance tests were performed on the adhesives prepared in Examples 1-2 and Comparative Examples 1-2.

[0053] from Figure 1 It can be seen that when adding different mass percentages of DES solution, the permeability of the adhesive prepared in Example 1-2 can be obtained. When the thickness of the film is 1 mm, the average transmittance exceeds 90% in the visible light range of 400-800 nm, which reflects the high compatibility of DES and P(TFEA-HEAA), and no aggregation of chain segments occurs after polymerization, and no phase separation occurs.

[0054] from Figure 2 It can be seen that the adhesive prepared in Example 1 can achieve good adhesion on different substrates and can also maintain its adhesion effect basically unchanged underwater. This is because there are a large number of polar groups such as hydroxyl, carbonyl, amide, trifluoromethyl, etc. inside the eutectic gel (adhesive), which can produce various interactions with the interface, mainly including hydrogen bonding, metal complexation, ion dipole and hydrophobic interaction, etc. For fluorine-substituted acrylic polymers, the -CF3 therein is conducive to reducing the surface energy of the eutectic gel and can provide strong adhesion to different substrates.

[0055] from Figure 3It can be seen that the uninterrupted stretching cycle performance of the adhesive prepared in Example 1, the tensile performance of the adhesive is 100%, 0.07MPa. Different curves represent stretching cycles 1, 2, 3, 5, 10, 15 and 20 times, respectively. Under 100% deformation, after 20 consecutive stretching-recovery cycles, the decoupled non-covalent interactions cannot be reorganized in time, and the peak stress of the stress-strain curve decreases, which indicates that the material is gradually fatigued and damaged; after unloading, the strain does not completely recover to zero, which indicates that the material has residual strain, and a large hysteresis loop appears after 20 cycles of stretching, which indicates that the material dissipates a lot of energy. Adhesion is determined by both cohesion and interfacial adhesion. This energy dissipation is conducive to increasing adhesion. When the interface is subjected to force, part of it enters the adhesive and is consumed, and part of it acts on the adhesive surface. Therefore, this energy dissipation can increase the interfacial adhesion to a certain extent.

[0056] The maximum tensile properties of the adhesives prepared in Example 1-2 and Comparative Example 1-2 were tested. The test results are shown in Table 1.

[0057] Table 1 Tensile properties of adhesives prepared in Examples and Comparative Examples

[0058]

[0059]

[0060] Figure 4 The adhesive obtained in Example 1 is used to make a sensor for underwater communication using a Morse code table. A "point signal" and a "long signal" are respectively sent out by controlling the speed of finger bending. The change in resistance is controlled by controlling the bending of the finger. When the finger bends quickly, the resistance changes quickly and a sharp peak appears, corresponding to the point signal. When the finger bends slowly, the resistance changes relatively slowly and a wide peak appears, corresponding to the "long signal".

[0061] Figure 5 The state diagram and stretching state simulation diagram of the adhesive prepared in Example 1 as an underwater sensor. When the eutectic gel is stretched, the cross-sectional area of ​​ions passing through the gel becomes smaller, which is not conducive to the transmission of ions and increases its resistance. When it recovers, the resistance returns to its original state.

[0062] Figure 6 The signal curve diagram obtained when the adhesive obtained in Example 1 is used as an underwater sensor is shown in FIG. Figure 6 It can be seen that the prepared gel has an obvious response to the given stimulus, and the gel can respond differently to different stimuli.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for preparing a multifunctional underwater adhesive based on a low eutectic solvent, characterized in that: The following steps are involved: (1) Mix the fatty acid and the quaternary ammonium salt, heat and stir until a uniform and transparent DES solution is formed; (2) Adding acrylamide monomers and fluorinated acrylate monomers to the DES solution to form a precursor solution, and then adding a photoinitiator and irradiating with ultraviolet light to obtain an underwater adhesive.

2. The method for preparing a multifunctional underwater adhesive based on a deep eutectic solvent according to claim 1, characterized in that: In step (1), the quaternary ammonium salt is selected from at least one of tetrabutylammonium bromide and tetraoctylammonium bromide; and the fatty acid is selected from at least one of heptanoic acid, octanoic acid, nonanoic acid and decanoic acid.

3. The method for preparing a multifunctional underwater adhesive based on a deep eutectic solvent according to claim 1, characterized in that: In step (1), the molar ratio of the quaternary ammonium salt to the fatty acid is 1:(2-3).

4. The method for preparing a multifunctional underwater adhesive based on a deep eutectic solvent according to claim 1, characterized in that: In step (1), the heating temperature is 30-80° C., the heating time is 1-4 h, and the stirring speed is 100-800 rpm.

5. The method for preparing a multifunctional underwater adhesive based on a deep eutectic solvent according to claim 1, characterized in that: In step (2), the acrylamide monomer is selected from at least one of N-hydroxyethyl acrylamide, acrylamide, N-methyl acrylamide, N,N-dimethyl acrylamide, N-hydroxymethyl acrylamide, and N-tert-butyl acrylamide; the fluorine-containing acrylate monomer is selected from at least one of 2,2,2-trifluoroethyl acrylate, hexafluorobutyl acrylate, 2,2,3,3-tetrafluoroethyl acrylate, perfluorohexyl ethyl acrylate, perfluorooctyl ethyl acrylate, and 2-(perfluorobutyl) ethyl acrylate.

6. The method for preparing a multifunctional underwater adhesive based on a deep eutectic solvent according to claim 1, characterized in that: In step (2), the photoinitiator is selected from at least one of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, 1-hydroxycyclohexyl phenyl ketone and 2-hydroxy-2-methyl-1-phenyl-1-propanone.

7. The method for preparing a multifunctional underwater adhesive based on a deep eutectic solvent according to claim 1, characterized in that: In step (2), the mass fraction of the DES solution is 30% to 70% of the total mass of the precursor solution, and the molar ratio of the acrylamide monomer to the fluorinated acrylate monomer is 30 to 70:30 to 70.

8. The method for preparing a multifunctional underwater adhesive based on a deep eutectic solvent according to claim 1, characterized in that: In step (2), the ultraviolet irradiation time is 10 to 30 minutes.

9. A multifunctional underwater adhesive based on a low eutectic solvent, characterized in that: Prepared by the preparation method according to any one of claims 1 to 8.

10. The use of a multifunctional underwater adhesive based on a deep eutectic solvent according to claim 9, characterized in that: Multifunctional underwater adhesives are used in underwater sensing, marine environment exploration, underwater coatings, underwater emergency treatment and battery electrode adhesives.

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