Water-resistant conductive hydrogel and method for producing the same

Abstract

This provides a hydrogel with improved durability and water resistance, and a method for producing the same. [Solution] The present invention relates to a hydrogel having both an ionic conductive portion based on an acrylic polymer and an electrically conductive portion of PEDOT:PSS (poly(3,4-ethylenedioxythiophene)polystyrene sulfonate), and further, the present invention provides a hydrogel to which PEG or PEGME is added in order to enhance the water resistance (or durability) of the hydrogel.

Description

Technical Field

[0001] The present invention relates to a hydrogel. In particular, the present invention relates to a hydrogel containing both a part having ion conductivity based on an acrylic polymer and a part having electrical conductivity of PEDOT:PSS (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate), and more particularly, to a hydrogel having excellent water resistance (or durability).

Background Art

[0002] Polymer conductive hydrogels are generally substances used in various applications such as medical electrodes, diapers, contact lenses, and cell culture. A hydrogel is a hydrophilic polymer crosslinked by cohesive forces such as covalent bonds, hydrogen bonds, van der Waals bonds or physical bonds, and has a network structure that can contain a large amount of water inside and swell on an aqueous solution.

[0003] The present invention relates to a hydrogel used for medical electrodes among hydrogels. Conventional hydrogel adhesive patches for ECG (electrocardiogram) and EMG (electromyography) sensors have ion conductive properties based on an acrylic adhesive, but as shown in FIG. 1, swelling or shrinkage of the hydrogel volume occurs due to penetration or dissolution by moisture, resulting in unstable ion conductivity, causing a decrease in sensing ability and generation of noise. In addition, conventional hydrogel patches have the problem that as the usage time increases, they peel off from the user's skin during use due to weakening of water resistance and durability, making long-term measurement impossible and giving discomfort to the user.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] Conventional hydrogels undergo de-swelling or swelling due to the evaporation or absorption of water, which alters their ionic conductivity. This alteration in ionic conductivity generates noise in electrical signals, making it difficult to transmit accurate electrical signals. The present invention aims to solve these problems of conventional hydrogels.

[0006] In particular, the present invention aims to solve the problems caused by the evaporation and absorption of water in hydrogels mainly composed of ion-conducting acrylic polymers.

[0007] In particular, the present invention aims to provide a hydrogel with improved durability and water resistance. [Means for solving the problem]

[0008] The present invention provides a hydrogel comprising an ion-conductive acrylic polymer, PEDOT:PSS, and one or more additives selected from PEG and PEGME, in order to improve electrical conductivity, water resistance, and durability.

[0009] In particular, the hydrogel may contain 1 to 100 parts by weight of PEDOT:PSS and 1 to 30 parts by weight of additives, based on 100 parts by weight of an acrylic polymer.

[0010] In particular, the molecular weight of the additive PEG or PEGME is between 500 and 20,000.

[0011] In particular, the acrylic polymer is a monopolymer of a first monomer having an acrylic group, or a copolymer of a first monomer having an acrylic group and a second monomer having a different functional group.

[0012] In particular, the first monomer having an acrylic group is acrylic acid, and the second monomer is 2-acrylamido-2-methylpropane sulfonic acid.

[0013] Furthermore, the present invention provides a method for producing a hydrogel, comprising the steps of: (1) preparing a first solution containing a monomer including a first monomer containing an acrylic group, a crosslinking agent, a photoinitiator, an electrolyte, and deionized water; (2) preparing a second solution of PEDOT:PSS and an alcohol solvent; (3) preparing a mixed solution of the first and second solutions; (4) adding additives by mixing one or more of PEG and PEGME as additives into the mixed solution; and (5) irradiating the mixed solution containing the additives with ultraviolet light to cause crosslinking.

[0014] In particular, the mixed solution may contain 1 to 100 parts by weight of PEDOT:PSS and 1 to 30 parts by weight of the additive, based on 100 parts by weight of the monomer.

[0015] In particular, the molecular weight of the additive is between 500 and 20,000.

[0016] In particular, the monomer may include a first monomer having an acrylic group and a second monomer having a functional group other than an acrylic group.

[0017] In particular, the first monomer having an acrylic group is acrylic acid, and the second monomer is 2-acrylamido-2-methylpropane sulfonic acid. [Effects of the Invention]

[0018] In the present invention, a hydrogel was produced by mixing PEDOT:PSS, an alcohol-based solvent-based electrically conductive polymer that is miscible with an ion-conductive acrylic polymer. The mixed hydrogel patch of the acrylic polymer and PEDOT:PSS of the present invention contains both ion conductivity and electrical conductivity and can transmit a stable signal when applied to an ECG or EMG sensor. In addition, it is possible to produce a hydrogel product with water resistance and durability ensured through an additive such as PEG or PEGME, and it is possible to produce a hydrogel product that transmits a stable electrical signal for a long time.

Brief Description of the Drawings

[0019] [Figure 1] It is a diagram explaining the swelling and de-swelling phenomena of a conventional hydrogel containing an ion-conductive acrylic polymer due to moisture. [Figure 2] It is a diagram explaining the difference between a conventional hydrogel and the hydrogel of the present invention. [Figure 3] It is a photograph of the mixed solutions of the comparative example and Examples 1 to 8. [Figure 4] It is a photograph of the samples of the comparative example and Examples 1 to 8 after curing. [Figure 5] It is a photograph showing the results of the water resistance test of the samples of the comparative example and Examples 1 to 8 after curing.

Modes for Carrying Out the Invention

[0020] In the following description, "polymer" is used in an inclusive sense that includes "copolymer" and has the same meaning as "polymer".

[0021] Figure 2 is a diagram for explaining the difference between a conventional hydrogel and the hydrogel of the present invention. The present invention is characterized in that, in order to improve the electrical conduction characteristics of an acrylic-based polymer hydrogel based on ion conductivity, PEDOT:PSS (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate), which has excellent electrical conductivity in addition to acrylic-based polymers, is added.

[0022] The ":" in PEDOT:PSS means a hydrogen bond, but it is a mixture of PEDOT and PSS rather than a copolymer. PSS and PEDOT compensate for each other's charges, and the PEDOT oligomer is strongly bonded to the PSS polymer chain. Depending on the mixing ratio of PEDOT and PSS, the PEDOT:PSS solution can selectively have hydrophilic or hydrophobic properties. In the present invention, PEDOT:PSS with excellent electrical conductivity is used as a component for imparting electrical conductivity to the hydrogel.

[0023] Also, in the present invention, it is characterized in that an "alcohol" solvent is used when producing the mixed solution of PEDOT:PSS. When the solvent of PEDOT:PSS is water-based, its miscibility with the acrylic monomer solution is very low and it is not suitable as a hydrogel. However, in the present invention, the use of alcohol-based PEDOT:PSS is characterized by improving the miscibility with the acrylic monomer solution.

[0024] Also, in the present invention, as a component for improving water resistance or durability, an additive of PEG (poly(ethylene glycol)) or PEGME (poly(ethylene glycol) methyl ether) is included as an essential component. Although PEG or PEGME is understood to improve the water resistance and durability of the hydrogel by chemical bonding with PEDOT:PSS, further research on the theoretical basis is necessary.

[0025] In the present invention, PEDOT:PSS can be used in amounts of 1 to 100 parts by weight and the additive in amounts of 1 to 30 parts by weight per 100 parts by weight of the acrylic polymer. In particular, the molecular weight of the additive is 500 to 20,000.

[0026] The acrylic polymer is a monopolymer of a first monomer having an acrylic group, or a copolymer of a first monomer having an acrylic group and a second monomer having a different functional group. In particular, the first monomer having an acrylic group is acrylic acid, and the second monomer is 2-acrylamido-2-methylpropane sulfonic acid.

[0027] Furthermore, the present invention provides a method for producing a hydrogel, comprising the steps of: (1) preparing a first solution containing a monomer having an acrylic group as a functional group, a crosslinking agent, a photoinitiator, an electrolyte, and deionized water; (2) preparing a second solution of PEDOT:PSS and an alcohol solvent; (3) preparing a mixed solution of the first and second solutions; (4) adding additives by mixing one or more of PEG and PEGME as additives into the mixed solution; and (5) irradiating the mixed solution containing the additives with ultraviolet light to cause crosslinking.

[0028] In particular, the mixed solution contains 1 to 100 parts by weight of PEDOT:PSS and 1 to 30 parts by weight of the additive, based on 100 parts by weight of the monomer. Specifically, the molecular weight of the additive is 500 to 20,000. The monomer is a mixed monomer of acrylic acid, which is a first monomer having an acrylic group as a functional group, and 2-acrylamido-2-methylpropane sulfonic acid (AMPS), which is a second monomer.

[0029] The present invention will be explained in more detail below through experiments.

[0030] Examples Figure 3 shows photographs of the comparative examples and the mixed solutions of Examples 1-8. A total of nine samples were prepared as shown in the table below.

[0031] [Table 1]

[0032] Here, the monomer solution in Table 1 above is a total of 8 g of solution containing 0.96 g of acrylic acid as the first monomer, 1.28 g of AMPS as the second monomer, 0.008 g of photoinitiator, and other components such as electrolyte (KCl) and deionized water. The PEDOT:PSS solution in Table 1 above is a 2 g solution in which PEDOT:PSS is dissolved at a concentration of 0.5 wt% in IPA (isoprophyllite) as the solvent.

[0033] Experiment example: Water resistance (durability) experiment Water resistance tests were conducted on the nine samples mentioned above. For the experiment, an aluminum plate was used as a substrate, coated with the nine solutions listed in Table 1, and then cured by UV irradiation. Figure 4 shows photographs of the comparative example and samples 1-8 after curing.

[0034] The water resistance test involved observing the morphology of the sample after exposing it to running water for approximately 2 seconds, and this test was repeated three times. Figure 5 shows photographs of the results of the water resistance test. In the comparative example sample on the far left of the top row, it was confirmed that the hydrogel disappeared and the color faded, but the other samples from Examples 1 to 8 of the present invention remained intact without dissolving in water. In other words, the samples from the examples of the present invention were found to have excellent water resistance (and durability).

[0035] Thus, the water resistance tests revealed that the adhesive patches without the additives (PEG or PEGME) in the comparative examples had poor water resistance, while the adhesive patches containing the additives in Examples 1-8 were resistant to moisture and possessed water resistance. This indicates that the hydrogel patches can be worn for extended periods and can be used as medical hydrogel patches that stably deliver signals.

Claims

1. Acrylic polymers and PEDOT:PSS and, A hydrogel characterized by containing one or more additives selected from PEG and PEGME.

2. Within the hydrogel, based on 100 parts by weight of an acrylic polymer, The hydrogel according to claim 1, characterized in that 1 to 100 parts by weight of PEDOT:PSS and 1 to 30 parts by weight of the additive are mixed together.

3. The hydrogel according to claim 1, characterized in that the molecular weight of the additive is 500 to 20,000.

4. The hydrogel according to claim 1, characterized in that the acrylic polymer is a monopolymer of a first monomer having an acrylic group, or a copolymer of a second monomer having a different functional group from the first monomer having an acrylic group.

5. The first monomer having an acrylic group is acrylic acid. The hydrogel according to claim 4, characterized in that the second monomer is 2-acrylamido-2-methylpropanesulfonic acid.

6. Step (1) of preparing a first solution comprising a monomer containing an acrylic group, a crosslinking agent, a photoinitiator, an electrolyte and deionized water, PEDOT: Preparation step (2) of the second solution of PSS and alcohol solvent, The preparation step (3) of the mixed solution of the first solution and the second solution, Additive mixing step (4) involves mixing one or more of PEG and PEGME as additives into the aforementioned mixed solution, A method for producing a hydrogel, comprising the step (5) of irradiating a mixed solution containing the aforementioned additives with ultraviolet light to cause crosslinking.

7. The method for producing a hydrogel according to claim 6, characterized in that the mixed solution contains 1 to 100 parts by weight of PEDOT:PSS and 1 to 30 parts by weight of the additive per 100 parts by weight of the monomer.

8. The method for producing a hydrogel according to claim 6, characterized in that the molecular weight of the additive is 500 to 20,000.

9. The method for producing a hydrogel according to claim 6, characterized in that the monomer is a mixed monomer of a first monomer having an acrylic group and a second monomer having a functional group other than an acrylic group.

10. The first monomer having an acrylic group is acrylic acid. The method for producing a hydrogel according to claim 9, characterized in that the second monomer is 2-acrylamido-2-methylpropanesulfonic acid.

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