KR102025864B1 - Hydrogel actuator haning acrylic acid and method for fabricating hydrogel actuator - Google Patents

Abstract

A hydrogel actuator according to an embodiment of the present invention forms a three-dimensional network structure as an acrylic monomer is polymerized, comprises a double layer hydrogel capable of adjusting a linking density, wherein the acrylic monomer contains an acrylic acid and a hydrogel is patterned.

Description

HYDROGEL ACTUATOR HANING ACRYLIC ACID AND METHOD FOR FABRICATING HYDROGEL ACTUATOR}

Provided are a hydrogel actuator including acrylic acid and a method of manufacturing the same.

Superabsorbent polymer (SAP) is a hydrogel that absorbs more than 10 ~ 1000 times water or volume ratio when exposed to aqueous solution and shows 95% or more absorbency. The main super absorbent polymer used in disposable diapers or sanitary napkins is a super absorbent polymer made of polyacrylic acid, which is partially neutralized by caustic soda. According to new applications, the physical properties are being improved through neutralizing agents or surface treatment methods, but the superabsorbent polymer may adversely affect the wearer's skin due to the severe toxicity of the monomer.

In addition, disposable diapers with polyacrylic acid can cause potential environmental pollution during post-treatment. For example, about 20 states in the United States prohibit the use of disposable diapers on the ground or have a VAT.

On the other hand, studies on polyacrylic acid-starch graft polymers in which starch is grafted to polyacrylic acid or biodegradable polymers in which natural polymers and synthetic polymers are mixed, but pollute the environment and guarantee stability It may not be. Therefore, it is necessary to develop a hygienic and safe eco-friendly absorbent that does not use synthetic polymers.

In addition, the swelling rate is very slow because the conventional hydrogel swelling by the diffusion of the solvent through the polymer chain. It takes a long time from several hours to several days to reach complete swelling in the dried state. While hydrogels with this slow swelling behavior are useful for controlled drug release, their utilization may be low in many applications requiring complete swelling in minutes.

Hydrogel actuator comprising acrylic acid according to an embodiment of the present invention and its manufacturing method is to improve the expansion rate.

Hydrogel actuator including acrylic acid according to an embodiment of the present invention and its manufacturing method is to improve the absorbency.

Hydrogel actuator comprising acrylic acid according to an embodiment of the present invention and a method for producing the same is to control the crosslinking density.

Hydrogel actuator comprising acrylic acid according to an embodiment of the present invention and its manufacturing method is to increase the utilization of the hydrogel actuator.

Hydrogel actuator including acrylic acid according to an embodiment of the present invention and a method for manufacturing the same is for producing an environmentally friendly resin.

In addition to the above object, embodiments according to the present invention can be used to achieve other objects not specifically mentioned.

Hydrogel actuator (hydrogel actuator) according to an embodiment of the present invention, the acrylic monomer is polymerized to form a three-dimensional network structure, the cross-linking density is adjusted to include a double layer hydrogel (hydrogel), the acrylic monomer Acrylic acid, and the hydrogel is patterned.

Here, the hydrogel may be crosslinked through radical polymerization.

The hydrogel is represented by the following Structural Formula 1, and sodium (Na +) ions may be bonded to the carboxyl group (COO−) of acrylic acid.

 [Formula 1]

The crosslinking density may include 0.2 wt% to 0.80wt% of diethylene glycol diacrylate (Di (ethylene glycol) diacrylate) which is a cross-linker.

The polymerization may proceed with the initiation reaction due to potassium persulfate (KPS) as an initiator.

The hydrogel includes bilayers having different crosslinking densities, and the curvature may be adjusted according to pH.

Method for producing a hydrogel actuator according to an embodiment of the present invention, the step of preparing an acrylic acid monomer solution, adding a sodium hydroxide solution to the monomer solution, adding a crosslinking agent and an initiator to the monomer solution to prepare a polymerization solution Heating the polymerization solution in the template to form a hydrogel, injecting the polymerization solution onto the hydrogel into a patterned mold and forming a double layer hydrogel, and heating the double layer hydrogel to polymerize. Include.

In the preparing of the polymerization solution, the crosslinking agent may include 0.2 wt% to 0.80 wt%, and may include hydrogel having different crosslinking densities by controlling the amount of the crosslinking agent.

The crosslinking agent may include diethylene glycol diacrylate (Di (ethylene glycol) diacrylate).

The initiator may comprise potassium persulfate (KPS).

In the heating step, the polymerization may be carried out by heating at a temperature of 55 ° C. for 2 hours.

Hydrogel actuator comprising acrylic acid according to an embodiment of the present invention and a method of manufacturing the same can improve the expansion rate, improve the absorbency, adjust the crosslinking density, increase the utilization rate of the hydrogel actuator It can be, and to manufacture an environmentally friendly resin.

Figure 1a is a SEM picture of a hydrogel film according to one embodiment, Figure 1b is a view showing a SEM picture of the hydrogel film inflated in water for 48 hours according to one embodiment.
2 is a view showing a manufacturing process of a hydrogel film according to an embodiment.
3 is a view showing a manufacturing process of a double-layer hydrogel according to an embodiment.
4 is a view showing a manufacturing process of a hydrogel actuator according to an embodiment.
5 is a graph showing the expansion ratio of the hydrogel film according to an embodiment.
6 is a graph showing the expansion ratio according to the dispersion dye of the double-layer hydrogel according to an embodiment.
7 is a graph showing the expansion ratio according to the dispersion dye of the double-layer hydrogel according to an embodiment.
8 is a graph showing Young's modulus and elongation at break of a bilayer hydrogel according to one embodiment.
9 is an image showing the curvature change of the bilayer hydrogel for about 0.1 to 15 minutes in the pH 7 buffer according to one embodiment.
FIG. 10 is an image of a bilayer hydrogel observed for about 3 hours in a pH 7 buffer according to one embodiment.
11 is a graph showing the curvature change according to pH 3, 7 and 10 of the bilayer hydrogel according to an embodiment.
FIG. 12 is an image showing curvature with time in a pH 7 buffer solution of a bilayer hydrogel according to one embodiment. FIG.
FIG. 13 is an image showing curvature with time in a pH 3 buffer solution of a bilayer hydrogel according to one embodiment. FIG.
FIG. 14 is an image showing curvature with time in a pH 10 buffer solution of a bilayer hydrogel according to one embodiment. FIG.
It is a state before the electric current of the hydrogel actuator according to an embodiment of Figure 15 (left photo), and the image (current photo) through which the current flows.

DETAILED DESCRIPTION Embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily practice the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. The drawings and description are to be regarded as illustrative in nature and not restrictive. Like reference numerals designate like elements throughout the specification. In addition, in the case of well-known technology, a detailed description thereof will be omitted.

In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. When a part of a layer, film, region, plate, etc. is said to be "on" another part, this includes not only the other part being "right over" but also another part in the middle. On the other hand, when a part is "just above" another part, there is no other part in the middle. Conversely, when a part of a layer, film, region, plate, etc. is "below" another part, this includes not only the other part "below" but also another part in the middle. On the other hand, when a part is "just below" another part, it means that there is no other part in the middle.

Throughout the specification, when a part is said to "include" a certain component, it means that it can further include other components, without excluding other components unless specifically stated otherwise.

Figure 1a is a SEM picture of the hydrogel film, Figure 1b shows a SEM picture of the hydrogel film inflated in water for 48 hours. At this time, each hydrogel film was lyophilized for 48 hours before being measured.

1A and B, the hydrogel film 100 according to the embodiment includes an acrylic monomer 10 based on acrylic acid, and the acrylic monomer 10 is polymerized to form a hydrogel film 100. The structure of sodium polyacrylate crosslinked with each other dimensionally is shown.

The acrylic monomer 10 may represent a sodium acrylate structure in which a carboxyl group (COO −) of acrylic acid and sodium (Na +) ions of sodium hydroxide are combined, but is not limited thereto. For example, acrylamide, vinyl alcohol, N-isopropylacrylamide, N, N-diethylacrylamide and sodium 4-hydroxy -2-methylenebutanoate (sodium 4-hydroxy-2-methylenebutanoate) and the like. In this case, the acrylic monomer 10 may be formed by neutralizing by adding sodium hydroxide to acrylic acid. In this case, about 80% may be neutralized, but is not limited thereto.

Subsequently, the acrylic monomer 10 is polymerized to form sodium polyacrylate. The neutralized acrylic monomer 10 undergoes a radical polymerization reaction by a crosslinking agent and an initiator, and three-dimensional sodium polyacrylate is formed as the monomers crosslink each other. The film having such a sodium polyacrylate structure is defined as a hydrogel film 100.

The hydrogel film 100 may be represented by the following structural formula 1.

[Formula 1]

In the polymerization reaction, the cross-linker may be di (ethylene glycol) diacrylate, and when the polymer chain crosslinks, a three-dimensional network structure is formed to exhibit water absorption characteristics. And, the swelling effect of the hydrogel film 100 may appear. At this time, according to the crosslinking density, the water absorbency can be adjusted, the mechanical strength can be adjusted.

In addition, the initiator may be potassium persulfate (KPS), which is a water-soluble thermal initiator, and free radicals may be formed through pyrolysis in an aqueous solution.

Hydrogel film 100 may be made by a variety of physical and chemical methods depending on the crosslinking method. For example, it exhibits physical gel formation such as intermolecular entanglement, hydrogen bonding, ionic bonding, and hydrophobic interaction, and chemical gel formation due to covalent bonds, and various manufacturing methods have various properties such as size, surface properties, structure, and composition. The particle | grains which have can be manufactured.

As such, while the acrylic monomer 10 is radically polymerized, gelation characteristics may be expressed, and the hydrogel film 100 forming a three-dimensional network structure may be formed by gelation. The hydrogel film 100 is flat and transparent without serious cavitation, and has a soft strength including solid and liquid properties due to the hydrophilic functional groups on the surface. The hydrogel film 100 is insoluble in water but has a property of absorbing a large amount of water and swelling. The cross-linked three-dimensional connection network exhibits a super absorbent property capable of absorbing a large amount of water, and an expansion effect may be exhibited. This is because the hydrophilic functional group of the hydrogel film 100 is hydrolyzed by water molecules and water is absorbed while filling the space in the three-dimensional crosslinked network by capillary force and osmotic pressure. It may be. The pore size formed by the crosslinked network may be about 3-20 μm, but is not limited thereto.

Therefore, due to the absorption of water, the weight of the hydrogel film 100 can be increased hundreds to thousands times more than the dry film, and the mechanical properties of the material such as elasticity or expansion ratio can be adjusted according to the crosslinking density. In this case, the shape of the hydrogel film 100 may be maintained even during expansion.

2 is a view showing a manufacturing process of the hydrogel film.

Referring to FIG. 2, the hydrogel film 100 is formed through polymerization of free radicals. A polymerization solution is prepared by mixing a sodium hydroxide solution, a crosslinking agent and an initiator with an acrylic acid solution.

The method for producing the hydrogel film 100 includes preparing an acrylic acid solution, adding a sodium hydroxide solution, adding a crosslinking agent and an initiator, and polymerizing in a template.

First, a step of preparing an acrylic acid solution is performed. The acrylic acid solution may be prepared by mixing about 14 g (0.204 mol, 1490 equiv) of acrylic acid in about 8 mL of water. At this time, water and acrylic acid represent two phases separated without being mixed with each other due to density difference.

Subsequently, the step of adding sodium hydroxide solution is performed. The sodium hydroxide solution may be supplied by mixing by adding about 6.6 g (0.165 mol, 1190 equiv) of sodium hydroxide to about 16 mL of water. When the sodium hydroxide solution is added to the acrylic acid solution, the acrylic acid solution is neutralized while the acrylic acid solution is neutralized to remove the phase separation phenomenon. At this time, the acrylic acid solution may be neutralized by about 80% by sodium hydroxide solution, and may have a molar concentration of about 8 mM. In this step, the solution may be subjected to nitrogen bubbling (N ₂ bubbling) for about 1 hour to remove the gas in the solution.

Next, the step of adding a crosslinking agent and an initiator is performed. The crosslinking agent may be, for example, diethylene glycol diacrylate, and may be added at a ratio of about 0.20 to 0.80 wt% relative to the acrylic acid monomer (monomer). The initiator may be, for example, potassium persulfate (KPS), and oxygen free radicals may form when heated in aqueous solution. Such free radicals may be covalently bonded to the acrylic monomer 10 to cause a polymerization reaction.

Subsequently, the step of polymerizing in a template is performed. The polymerization solution transferred to the template with a syringe may be polymerized on a heating plate set at about 55 ° C. for about 2 hours, and the hydrogel film 100 may be formed. At this time, the template may be a glass template of 11.5 cm x 15 cm x 0.1 cm (width x length x thickness), may have a high specific surface area and volume, and may be excellent in heat transfer. This is similar to controlling the autoacceleration process in a sheet-type mold.

Therefore, the hydrogel film 100 according to the embodiment has a three-dimensional network and may have a different crosslinking density depending on the amount of the crosslinking agent. According to the crosslinking density, the mechanical properties of the hydrogel film 100, for example, elasticity or expansion ratio may be adjusted, the hydrogel film 100 may be expanded, and water may be absorbed. In this case, the water may be absorbed by capillary force or osmotic pressure.

In the following description, the description may be omitted for the contents overlapping with the above description.

3 is a view showing a manufacturing process of a double-layer hydrogel.

Referring to FIG. 3, the hydrogel film 100 may deposit a polymerization solution to form a double layer hydrogel 200. At this time, it is possible to distinguish each layer of the bilayer by adding a disperse dye of different colors to the polymerization solution.

The bilayer hydrogel 200 according to the embodiment has a linear bilayer structure and may be bent in a circle in a liquid. At this time, each layer of the bilayer may be formed with a different crosslinking density according to the ratio of the crosslinking agent, the curvature of the bilayer hydrogel 200 can be adjusted according to the pH. For example, the first layer contains relatively few crosslinking agents, and a crosslinked hydrogel layer can be formed with loose density and can absorb large amounts of water. The second layer contains a relatively large number of crosslinking agents, and a high density of hard crosslinked hydrogel layer can be formed and can absorb a small amount of water. As such, the bilayer hydrogel film 200 having a different density exhibits different expansion characteristics in the liquid, and may be rolled into a circle due to a difference in water pressure of absorbing water. In general, the more crosslinking agent is included, the dilation effect can be reduced. Therefore, due to the difference in the expansion ratio, the bending phenomenon occurs in the direction of the hydrogel containing a large amount of the crosslinking agent, and may form a circle shape. This bilayer structure may consist of homogeneous species and may consist of crosslinked polymers (enlarged portion of FIG. 3). In addition, the bilayer hydrogel 200 can be prepared through continuous radical polymerization without the need for an auxiliary adhesive, thereby eliminating interfacial complexity that causes the bond to break.

The method of manufacturing the double layer hydrogel 200 according to the embodiment includes preparing a hydrogel film 100, forming a second layer on the hydrogel film 100, and polymerizing by heating. .

First, the step of manufacturing the hydrogel film 100 is performed. In this case, color may appear on the hydrogel film 100 by adding a disperse dye to the polymerization solution. The disperse dye may be, for example, navy blue, but is not limited thereto. Disperse dyes may affect the expansion ratio of the hydrogel film 100, it is possible to control the reduction of the expansion ratio. At this time, navy blue dye (10 mg, 0.2 wt%) may be added to the acrylic monomer (10) solution of acrylic acid (14.71 g, 0.204 mol, 1378.4 equiv) neutralized 80%, the amount of crosslinking agent is Di (ethylene glycol) Diacrylate (50 mg, 0.233 mmol, 1.7 equiv, about 0.34 wt%), initiator, KPS (37 mg, 0.137 mmol, 1.0 equiv) may be added to prepare the first polymerization solution, but is not limited thereto. In this case, the hydrogel film 100 may be radically polymerized while being heated at a temperature of about 55 ° C. for about 2 hours, and a hydrogel film 100 having a relatively low crosslinking density may be formed.

Next, forming a second layer on the hydrogel film 100 is performed. At this time, the polymerization solution for forming the second layer may be prepared in the same manner as the hydrogel film 100, but by adding more crosslinking agent to form a second layer having a higher crosslink density. For example, a crosslinker di (ethylene glycol) diacrylate (93 mg, 0.434 mmol, 3.2 equiv, about 0.63 wt%) may be included, and a crosslinked layer that is relatively harder and denser than the first layer may be formed. Disperse dyes of different colors, for example red (10 mg, 0.2 wt%), may be added to distinguish this layer. The initiator KPS and the acrylic monomer 10 solution may be added in the same amount as the hydrogel film 100. In this step, the second polymerization solution is carefully injected into the gap between the first layer hydrogel film 100 and the glass lid.

Subsequently, a step of heating to polymerize is performed. The second polymerization solution may be heated at a temperature of about 55 ° C. for about 2 hours to cause a radical polymerization reaction and a hydrogel may be formed. In this case, two adjacent hydrogels may have mutually penetrating properties, and the hydrogel film 100 and the second layer may be closely deposited with each other. Therefore, the double layer hydrogel 200 having different crosslinking densities may be formed. The thickness of the first layer (navy blue) and the second layer (red) of the bilayer hydrogel 200 may be 1.2 mm and 0.8 mm, respectively, but is not limited thereto.

In the following description, the description may be omitted for the contents overlapping with the above description.

The hydrogel actuator 210 may be manufactured by patterning the double layer hydrogel 200.

The hydrogel actuator 210 according to the embodiment may be formed by patterning the dual layer hydrogel 200 having different crosslinking densities from each other. The crosslink density plays an important role in doubling the expansion ratio as well as the mechanical strength. The difference in crosslinking density controls the water absorbing properties, and the bilayer of the hydrogel actuator 210 exhibits heterogeneous deformation. Accordingly, bending of the hydrogel actuator 210 may occur in the liquid, and may represent a programmed reaction. This is because the change in shape can be controlled according to pH, temperature, salinity, metal ion, light or electrical potential. In this case, two hydrogels having different crosslinking densities in the hydrogel actuator 210 may be continuously polymerized in place.

In addition, the hydrogel actuator 210 may exhibit a characteristic that the linear hydrogel is folded into a circle according to pH. For example, it may be markedly fast (within about 11 minutes) at pH 10, but complete, but not limited to. Bending of the bilayer occurs due to the difference in expansion ratio. For example, hydrogels with less crosslinker expand more and hydrogels with higher crosslinker expand less. Therefore, due to the difference in expansion, a bending phenomenon occurs in the direction of the hydrogel containing a large amount of the crosslinking agent, and may form a circle shape.

4 is a view illustrating a manufacturing process of the hydrogel actuator 210.

Referring to FIG. 4, a method of manufacturing a hydrogel actuator 210 according to an embodiment includes manufacturing a hydrogel film 100, forming a patterned second layer, and polymerizing by heating. do.

First, the step of manufacturing the hydrogel film 100 is performed. In this case, color may appear on the hydrogel film 100 by adding a disperse dye to the polymerization solution. The disperse dye may be, for example, navy blue, but is not limited thereto. In addition, the amount of the crosslinking agent may be included from 0.20wt% to 0.80wt%, for example, 0.34wt% may be included to form a hydrogel having a loose crosslink. At this time, while being heated for about 2 hours at a temperature of about 55 ℃ can be radically polymerized, the hydrogel film 100 can be formed.

Next, the step of forming the patterned second layer is performed. A glass mask may be placed on the hydrogel film 100, and a second patterned layer may be formed by depositing a polymerization solution between the glass masks. In addition, it may be prepared by adding a disperse dye, for example, red, in the second polymerization solution to distinguish it from the first layer, but is not limited thereto. In this case, the amount of the crosslinking agent may be included in the range of 0.20wt% to 0.80wt%, for example, 0.63wt% may be included to form a hydrogel having a hard crosslink.

Subsequently, a step of heating to polymerize is performed. The second polymerization solution may be heated at a temperature of about 55 ° C. for about 2 hours to cause a radical polymerization reaction and a hydrogel may be formed. Accordingly, a double layer hydrogel actuator 210 having different crosslinking densities may be formed, and bending of the hydrogel actuator 210 may occur due to a difference in crosslinking density when expanded in a liquid.

In summary, the hydrogel actuator 210, which is a superabsorbent hydrogel, may be prepared by polymerizing the biocompatible acrylic monomer 10. In addition, the hydrogel actuator 210 may form a double layer having a different crosslinking density by adjusting the amount of the crosslinking agent, and may be quickly and easily manufactured through polymerization.

The hydrogel actuator 210 is a superabsorbent hydrogel, and may be used as an expandable material, an elastomer, a hydrophilic matrix, a container, a support, a film, and the like from a polymer material point of view. In addition, it can be applied variously in various fields such as soil improver, tissue design, desalination, catalyst and health care. In particular, irritant superabsorbent hydrogels contain components (eg, cellulose, alginate, starch, chitosan, polysaccharides, and biocompatibility and utility in water, including a wide range of functional monomers / cost-effective natural products). Proteins), the use of water as an environmentally friendly, ubiquitous stimulus, the use of a wide range of well-established chemistries for synthesis (eg, radical polymerization), identifiable volume changes, and synergistic effects through hybridization The properties that represent the processability of the smart components integrated with the mineral components that make them can be improved. In addition, the combination of various functional groups of the hydrogel actuator 210 may facilitate the development of crosslinked polymer systems characterized by smart reactions for many biomedical or environmentally friendly applications. For example, LED switches, microlenses capable of controlled emission, and functional membranes that remove certain pollutants (eg, mitroplastics) from the sea can be used in a variety of applications.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the following Examples are merely examples of the present invention, and the present invention is not limited to the following Examples.

In the examples, acrylic acid, diethylene glycol diacrylate, potassium persulfate were obtained from Sigma Aldrich. Disperse dyes such as Synolon N / Blue S-GLS (navy blue color) and Synolon Rubine S-GEL (red color) were obtained from KIMCO. Acrylic acid was distilled under reduced pressure before use. Deionized water was prepared using a water purification system (Pure Power I +, DAIHAN Scientific). All other reagents and solvents were used as commonly purchased, unless otherwise noted. Proton nuclear magnetic resonance (1H NMR) spectra were recorded on a Bruker 300 MHz NMR spectrometer at 25 ° C. Proton chemical shifts are expressed in parts per million (ppm, δ scale) and refer to tetramethylsilane ((CH ₃ ) ₄ Si, δ 0.00 ppm) or residual protium (D 2 O, δ 4.70 ppm) in solvent. It is expressed by words such as chemical shift, doublet (s = singlet, d = doublet, t = triplet, q = quartet, m = multiplet and / or multiple resonances, br = broad peak), and integration. Carbon nuclear magnetic resonance (13 C NMR) was recorded on a Bruker 500 MHz NMR spectrometer at 25 ° C. The chemical × chemical shift of carbon is expressed in parts per million (ppm, δ scale) and refers to tetramethylsilane ((CH ₃ ) ₄ Si, δ 0.00 ppm). For the tensile test, the prepared hydrogel film was cut with a laser cutter. The film was bonded between two PMMA forceps with a super glue similar to the previously reported method. The resulting specimens have dimensions of 10 mm x 10 mm x 1 mm (length x width x thickness). Uniaxial tensile test was performed using an Instron 5543 universal testing machine (UTM) with a 1000-N load cell in air at 25 ° C. Specimens were stretched at a rate of 5 mm / min before fracture. Each hydrogel film sample was connected during the measurement. Stress-strain curves were recorded. Ultimate tensile strength was determined by the pressure at the point of fracture. The ultimate strain was determined by the strain at the point of fracture. Young's modulus was obtained from the initial 10% to 30% slope of the stress-strain curve. Tensile force was obtained from the point under the stress-strain curve. Data points were obtained five times from five independent experiments. The microstructure of the dried hydrogel film was observed with a Carl Zeiss SUPRA 55VP scanning electron microscope (SEM) at an acceleration voltage of 2 kV. Before being measured, the sample was dried for 3 days by lyophilization and coated with a thin platinum layer. Attenuated total reflection-infrared spectroscopy (ATRFTIR) measurement was performed with a Nicolet-6700 instrument (Thermo Scientific) at room temperature. Spectra were obtained at an average rate of 32 scans in the range of 4000 cm 1 to 400 cm 1.

Example  One - Hydrogel  film

Prepare a solution of acrylic acid (14.7 g, 0.204 mol, 1490 equiv) in water (8 mL). In addition, prepare a solution of sodium hydroxide (NaOH, 6.6 g, 0.165 mol, 1190 equiv) in water (16 mL). The two solutions were mixed to neutralize about 80% acrylic acid.

Nitrogen bubbling is carried out to the neutralized solution for about 1 hour to remove the gas in the solution.

To the degassed solution was added potassium persulfate (KPS) as an initiator, 37 mg, 0.14 mmol, 1.0 equiv and di (ethylene glycol) diacrylate (50 mg, 0.23 mmol, 1.7 equiv) as crosslinker. Transfer to a glass template with a size of 11.5 cm x 15 cm x 0.1 cm (width x length x thickness) and mix. The monomer solution is then polymerized on a heat plate at about 55 ° C. for about 2 hours. At this time, the amount of the crosslinking agent may be adjusted from about 0.20 wt% to about 0.80 wt%, and the amount of the crosslinking agent is adjusted relative to the amount of the acrylic acid monomer.

The hydrogel film was obtained by subtracting from the quantitative yield of the mold. IR (cm- ¹ ) 3361, 2932, 2852, 1685.8, 1552, 1405, 1294; 1 H NMR (300 MHz, D 2 O): δ 1.82 (br s, methine protons), 1.23 (br s, methylene protons); 13 C NMR (125 MHz, D 2 O): δ 183.6, 44.8, 37.3, 36.1.

Experimental Example 1-hydrogel  Expansion ratio of film

Hydrogel films according to Example 1 were prepared, and expansion ratios according to their crosslinking agent ratios were compared, which are shown in FIG. 5 and Table 1. In this case, the hydrogel film according to Example 1 was compared to the initial hydrogel film and the hydrogel film after absorbing water. At this time, the acrylic acid monomer solution contained in water is continuously supplied at 0.8M.

5 represents the ratio (%) of the crosslinking agent to the acrylic acid monomer, and the vertical axis represents the expansion ratio (%) of the hydrogel film.

Table 1 shows the cross-linker content (wt%), the degree of swelling (%) and the cross-linking density (mmol / L) of the hydrogel film according to the example.

Referring to FIG. 5 and Table 1, hydrogel films 1-6 include different amounts of crosslinking agents under the same conditions, wet the film in deionized water, and expand the expansion ratio (Equation 1) and crosslink density (ρ) (Equation 2). Calculations were made to determine the effect of crosslinking agents on absorbency.

In the case of the initial hydrogel film (as-prepared samples), regardless of the amount of crosslinking agent it can be seen that there is a similar expansion ratio and about 44% to about 47% expansion.

On the other hand, in the case of the hydrogel film (after absorption of water) after absorbing water, it can be seen that the expansion ratio decreases as the amount of the crosslinking agent increases (film 2-6). For example, in the case of film 2 (0.34% crosslinking agent), it can be seen that the film expands up to 200 times. However, the hydrogel film containing the minimum crosslinking agent is excluded (film 1). This may be inferred that the film 1 contains too little cross-linking agent, so that loose cross-linking is formed, and part is dissolved and capillary force for absorbing water is inhibited. In this case, the hydrogel film may be obtained after the initial hydrogel film is dried and then expanded for about 48 hours in deionized water to absorb water.

Therefore, it can be seen that the hydrogel film according to the embodiment exhibits different expansion ratios according to the amount of the crosslinking agent, that is, the crosslinking density, and the expansion ratio decreases as the crosslinking density increases. The film shows anisotropic dimensional change, the film in its initial state has a length of 1.15 cm, and is reduced by about 26% in freeze drying. However, after the exposure to water for about 48 hours it can be seen that about 4.1 times increase.

The expansion ratio is calculated from Equation 1 below.

Equation 1: degree of swelling (%) =

The crosslinking density is calculated from the following equation.

Equation 2:

Where X represents the weight of the analyte sample and X ₀ represents the weight of the sample dried in vacuo by freeze drying for 48 hours. Vsol represents the molar volume of water. In addition, v _p , ie, the equilibrium polymer volume fraction, is determined by the expansion ratio. And x, that is, 0.46 as the solvent-polymer interaction index.

hydrogel film cross-linker
(wt%) degree of swelling
(%) cross-linking density
(mmol / L) One 0.20 15900 0.71 2 0.34 20200 0.47 3 0.42 16300 0.68 4 0.50 10000 1.55 5 0.63 7500 2.54 6 0.80 7100 2.77

Example  2 - Double layer Hydrogel

Bilayer hydrogels are prepared by continuous radical polymerization. Di (ethylene glycol) diacrylate (50 mg, 0.233 mmol, 1.7 equiv), KPS (37 mg, 0.137 mmol, 1.0 equiv) and navy blue dye (10 mg, 0.2 wt%) were 80% neutralized acrylic acid (14.71 g, 0.204). mol, 1378.4 equiv) solution to make the first polymerization solution.

The first polymerization solution is poured into a glass template (11.5 cm x 15 cm x 0.1 cm). This template was covered with a glass lid and the template was heated at 55 ° C. for 2 hours to form a first layer on the glass lid (film 2).

The second layer is synthesized in a similar way on the first layer. After the first layer is made in the glass template, additional glass thicknesses (0.1 cm) are placed as spaced spacers.

The second polymerization solution was di (ethylene glycol) diacrylate (93 mg, 0.434 mmol, 3.2 equiv), KPS (37 mg, 0.137 mmol, 1.0 equiv), and 80% neutralized acrylic acid solution to give red dye (10 mg, 0.2 wt%). ) Is added and prepared (film 5).

The second solution is carefully injected into the gap between the first layer and the glass lid and then heated at a temperature of 55 ° C. for 2 hours.

The finished free-standing double layer hydrogel is taken out of the mold and then cut to desired size with a laser cutter or razor to obtain quantitative quantities. The thicknesses of the first layer (navy blue) and the second layer (red) of the bilayer hydrogel actuators were measured to be 1.2 mm and 0.8 mm, respectively.

Experimental Example 2-double layer Hydrogel  Expansion ratio

The bilayer hydrogel according to Example 2 was prepared, and the expansion ratio of each layer was observed, which is shown in FIGS. 6 and 7. The expansion ratios were confirmed by comparing the bilayer hydrogels 2 and 5 before adding the disperse dyes and the bilayer hydrogels after adding the disperse dyes (navy blue dye or red dye).

A graph comparing the double layer hydrogel comprising the hydrogels 2 and 5 before dyeing and the first layer (2 + navy blue dye) stained with navy blue and the second layer (5 + red dye) stained in red in FIG. 6. The horizontal axis of the graph represents time (min), and the vertical axis represents the degree of swelling (%).

FIG. 7 is a graph comparing bilayer hydrogels comprising hydrogels 2 and 5 before dyeing and a first layer dyed red (2 + red dye) and a second layer dyed navy blue (5 + navy blue dye) The horizontal axis of the graph represents time (min), and the vertical axis represents the degree of swelling (%).

Referring to FIG. 6, compared to hydrogels 2 (first layer) and 5 (second layer) before dyeing, hydrogel 2 + navy blue dye and hydrogel 5 + red dye synthesized with a hydrophobic (insoluble) disperse dye were completely removed. When solved, it can be seen that the expansion ratio decreases by half.

Therefore, the disperse dye affects the expansion ratio of the two hydrogel layers, the hydrogel 2 decreases the expansion ratio from 193% / min before dyeing to 177% / min after dyeing, and hydrogel 5 has an expansion ratio of 161% / min before dyeing. After staining can be seen to decrease to 96% / min. This was calculated from the linear slope of the initial region.

On the other hand, referring to Figure 7, compared with hydrogel 2 + navy blue dye and hydrogel 5 + red dye, hydrogel 2 + red dye and hydrogel 5 + navy blue dye synthesized with a hydrophobic (insoluble) disperse dye is less The expansion ratio difference was shown. The expansion ratio is calculated from the initial line of the enlarged picture, the expansion ratio of hydrogel 2 + red dye is 114% min ^−1, and the expansion ratio of hydrogel 5 + navy blue dye is 65% min ⁻¹ .

Because of this, it can be inferred that synthesizing the bilayer with hydrogel 2 + navy blue dye and hydrogel 5 + red dye shows a more effective expansion effect. Therefore, when two adjacent parts with different crosslinking densities are joined together, the contact between the two shows a difference in the expansion ratio in the water medium, and it can be confirmed that the bilayer hydrogel may cause heterogeneous deformation by utilizing the difference. .

Experimental Example 3-double layer Hydrogel  Mechanical toughness

The bilayer hydrogel according to Example 2 was prepared, and the mechanical toughness of the bilayer hydrogel was confirmed when staining was performed, and these are shown in FIGS. 8 and 2.

8 shows the Young's modulus (MPa), and the bottom shows the elongation at fracture (%).

Table 2 shows the mean (Avg.) Of Young's modulus (MPa), elongation at fracture (%) and toughness (MJ / m ³ ) of the hydrogel film. The comparison is shown.

Referring to FIG. 8 and Table 2, the dispersion dyes improved the elongation and toughness at break of the hydrogels 2 and 5, and the crosslinked structure was maintained while stretching under tensile force. In addition, the Young's modulus change was not large, it can be seen that the elongation at break of the bilayer (average of each navy blue 2 and red 5).

hydrogel film Young's modulus (MPa) elongation at fracture (%) toughness (MJ / m ³ ) Avg. Std. Avg. Std. Avg. Std. 2 0.15 0.01 295.2 26.9 0.28 0.03 5 0.12 0.01 192.0 14.1 0.14 0.02 navy blue 2 0.09 0.01 688.0 46.5 0.79 0.06 red 5 0.14 0.01 334.0 23.0 0.43 0.04 bilayer 0.09 0.00 451.9 31.1 0.39 0.04

Experimental Example 4-double layer Hydrogel  Bending properties

The bilayer hydrogel according to Example 2 was prepared, and the bending change of the hydrogel at pH 7 was observed, which is shown in FIGS. 9 and 10.

9 is an image showing the curvature change of the bilayer hydrogel for about 0.1 to 15 minutes in a pH 7 buffer.

 10 is an image showing the bilayer hydrogel observed for about 3 hours in pH 7 buffer.

9 and 10, the bilayer bent in neutral pH 7 buffer is shown. The buffer was used to prevent changes in pH due to hydrogels.

As soon as the buffer was added (0.1 min), the linear materials began to bend, and after 15 minutes the bilayer hydrogel turned round. The navy blue layer (2, 0.34 wt% cross-linker) was more bloated than the inner red layer (5, 0.63 wt% cross-linker), which compared to the red layer, the navy blue layer contained less cross-linker. It can be inferred because it forms a loose crosslink and absorbs more water.

As a result of observing the bilayer hydrogel in pH 7 buffer for about 3 hours, it can be seen that the volume of the bilayer hydrogel was slightly increased but the round shape was maintained.

Experimental Example 5-pH  According Double layer Hydrogel  curvature

The bilayer hydrogel according to Example 2 was prepared, and the curvature change of the bilayer hydrogel according to pH was observed, which is shown in FIGS. 11 to 14, Table 3, and Table 4.

11 shows the change in curvature of the bilayer hydrogel according to pH 3, 7 and 10. The horizontal axis represents time min, and the vertical axis represents curvature m ^{- 1} .

12 is a pH 7 buffer solution at 25, the image of the curvature of the bilayer hydrogel over time, the curvature was measured every minute.

FIG. 13 is a pH 3 buffer solution at 25, and shows an image of curvature of a bilayer hydrogel over time, and the curvature was measured every minute.

FIG. 14 is a pH 10 buffer solution at 25, and is an image of the curvature of the bilayer hydrogel over time, and the curvature was measured every minute.

Table 3 is a table showing the curvature (m- ¹ ) change of the bilayer hydrogel according to pH 3, 7 and 10 with time (min).

Table 4 is a table showing the degree of swelling with hydrogel 2, navy blue 2, red 2, 5, navy blue 5 and red 5 over time (min) at pH 7.

Referring to Figures 11 to 14, Table 3 and Table 4, the double-layer hydrogel can be seen that the curvature increases with time. The bilayer hydrogels were dried in circles within 15 minutes at pH 7, dried in circles within about 13 minutes at pH 3, and dried within about 11 minutes at pH 10. At this time, the length 2.8 cm, width 0.3 cm and thickness 2 mm of the double-layer hydrogel was measured in the same manner.

The curvature increased slightly faster at pH 3 than at pH 7 (the folding speed was found to be 28.1 m ^-1 s ^-1 and calculated from the range of the initial line), but the final curvature was somewhat lower than the value from pH 7 but at the same time less Pulled

The curvature increased fastest at pH 10 (speed, 33.6 m ^-1 s ^-1 ; 1.3 times faster than pH 7), and the final curvature was at 224 m ^-1 in 9 minutes (theoretical curvature of a circle with a 2.8 cm circumference). Reached.

At this time, it can be inferred that protonation of carboxylate at pH 3 can prevent the complete folding of the bilayer. It can be inferred that at pH 10 the remaining acid functionalities can be deprotonated, which can promote folding.

time
(min) curvature (m ^-1 ) pH 3 pH 7 pH 10 0.1 82 66 105 One 110 98 142 2 136 117 169 3 144 129 183 4 161 137 196 5 168 148 200 6 172 157 209 7 183 164 216 8 189 174 225 9 190 182 224 10 191 187 224 11 193 195 224 12 190 199 13 190 204 14 208 15 208

time
(min) 2 navy blue 2 red 2 5  navy blue 5 red 5 0 0 0 0 0 0 0 5 530 341 360 360 279 246 10 1146 784 646 932 592 566 15 2052 1479 1122 1757 866 1137 20 3059 2570 1598 2376 1062 1440 25 4045 3442 2392 3329 1571 2013 30 4538 4342 2916 4154 1897 2413 35 5117 5362 3551 5297 2341 2823 40 5697 5965 4043 5614 2733 3053 45 6567 6544 4662 5773 3164 3233 50 7291 7100 4979 5932 3490 3316 55 8161 7472 5170 6090 3764 3336 60 9030 7822 5329 6249 4012 3373 70 10335 8203 5741 6408 4339 3438 80 11204 8533 6170 6567 4600 3448 90 12219 8771 6329 6725 4730 3516 100 13233 8842 6487 6805 4861 3518 110 14103 8850 6567 6884 4926 3536 120 14972 8900 6583 6884 4926 3556 150 16422 8933 6598 6884 4939 3695 180 17436 9000 6598 7043 4939 3700 210 18016 9017 6614 7043 4939 3718 240 18596 9033 6630 7043 4939 3755 300 18741 9033 6630 7043 4939 3791 360 18741 9067 6646 7043 4952 3791 480 18741 9183 6646 7043 4952 3809

Example 3-hydrogel  Actuator

Each polymerization solution was dyed using navy blue and red dispersion dyes to distinguish the layers before the polymerization was performed.

A first layer was prepared comprising 0.34 wt% of crosslinker (film 2). On top of that, we directly deposited a second polymerization solution containing 0.63 wt% of crosslinking agent (film 5). And polymerized under the same conditions in the presence of 0.25 wt% KPS. The first layer is then covered with a piece of glass when the patterned bilayer is ready. In addition, the second solution is carefully injected into the gap between the first layer and the glass lid and then heated at a temperature of 55 ° C. for 2 hours. Pulled out of the glass mold to obtain a bilayer hydrogel actuator, with a volume of 2.8 cm × 0.2 cm × 0.3 cm, exhibiting anisotropic shape change.

The thickness of the first layer (navy blue) and the second layer (red) of the hydrogel actuator was measured to be 1.3 mm and 0.7 mm, respectively.

In summary, patterning was done with a glass mask to create a hydrogel actuator. Small layers were used to pattern the first layer (navy blue film 2; size 3 cm × 0.5 cm × 1.3 mm) during the second layer polymerization, and the second layer, small patch (red film 5; size, 0.5 cm × 0.5 cm × 0.7) mm) was left on the first layer.

Hydrogel actuators comprise bilayers with different crosslink densities, and the second layer causes the entire hydrogel to bend in distilled water. Compared to the second layer with tight crosslinks, the first layer with loose crosslinks absorbs and expands a lot of water. Therefore, bending may occur due to a difference in expansion ratio between the first layer having a relatively small expansion ratio and the second layer having a large expansion ratio.

The hydrogel layers adhered closely to each other because they could penetrate each other. This interpenetration occurs during the second polymerization reaction in two adjacent portions.

Experimental Example  6-circuit switch

A double layer hydrogel actuator according to Example 3 was prepared and an electronic circuit test was performed, which is shown in FIG. 15.

The left picture of FIG. 15 is a picture before a current flows, and the right picture is a picture of a current.

Referring to FIG. 15, a patterned bilayer hydrogel was placed between two parallel copper plates and the copper plate was fixed using an alligator clip. The copper plates were connected with LED bulbs and dry cell batteries.

At the beginning (0 min), the double-layer hydrogel actuator in the distilled water did not bend and the electronic circuit was opened, and no current flowed through the LED bulb.

However, two minutes later, the double layer hydrogel actuator bends in water and the circuit starts to close, and the LED bulb turns red when the current flows. At this time, the double-layer hydrogel actuator was touched from the inside of about 1 cm of the copper plate length, it can be seen that the circuit is closed.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

10: acrylic monomer 100: hydrogel film
200: bilayer hydrogel 210: hydrogel actuator

Claims (11)

Acryl monomer is polymerized to form a three-dimensional network structure, and a double layer hydrogel having a controlled crosslinking density
Including,
The acrylic monomer,
Contains acrylic acid,
The hydrogel is represented by the following Structural Formula 1, and sodium (Na +) ions are bonded to the carboxyl group (COO-) of the acrylic acid,
[Formula 1]

The hydrogel is patterned,
Hydrogel actuators.
In claim 1,
The hydrogel is a hydrogel actuator that is cross-linked through a radical polymerization (radical polymerization).
delete delete In claim 1,
The polymerization is a hydrogel actuator in which the initiation reaction proceeds due to the initiator (potassium persulfate, KPS).
In claim 1,
The hydrogel includes a bilayer having different crosslinking densities, and a hydrogel actuator having curvature adjusted according to pH.
Preparing an acrylic acid monomer solution,
Adding sodium hydroxide solution to the monomer solution,
Preparing a polymerization solution by adding a crosslinking agent and an initiator to the monomer solution,
Heating the polymerization solution in a template to form a hydrogel,
Injecting a polymerization solution onto the hydrogel into a patterned mold and forming a bilayer hydrogel; and
Heating the hydrogel of the bilayer to polymerize
Including,
The crosslinking agent includes diethylene glycol diacrylate (Di (ethylene glycol) diacrylate)
Method for producing a hydrogel actuator.
In claim 7,
In the step of preparing the polymerization solution, the crosslinking agent comprises 0.2wt% to 0.80wt%, the method of producing a hydrogel actuator comprising a hydrogel having a different crosslinking density by controlling the amount of the crosslinking agent.
delete In claim 7,
The initiator is a method of producing a hydrogel actuator comprising potassium persulfate (KPS).
In claim 7,
In the heating step, a method of manufacturing a hydrogel actuator is heated by polymerization at a temperature of 55 ℃ for 2 hours.

Images