WO2024248354A1 - Boronic acid functional pressure-sensitive adhesive and manufacturing method therefor - Google Patents

Abstract

The present invention relates to a boronic acid functional pressure-sensitive adhesive. More specifically, the present invention provides a method for manufacturing a boronic acid functional pressure-sensitive adhesive, the method comprising the steps of: synthesizing a scaffold pressure-sensitive adhesive by reacting butyl acrylate with glycidyl methacrylate; and synthesizing a boronic acid pressure-sensitive adhesive by reacting a scaffold pressure-sensitive adhesive with 4-mercaptophenylboronic acid. In addition, the present invention provides a boronic acid functional pressure-sensitive adhesive comprising a boronic acid group and a butyl group. In addition, the present invention provides a functional coating material and an antifouling coating composition, comprising the boronic acid pressure-sensitive adhesive according to the present invention.

Description

Boronic acid functional pressure-sensitive adhesive and its manufacturing method

The present invention relates to a boronic acid functional pressure-sensitive adhesive, and more specifically, to a boronic acid functional pressure-sensitive adhesive and a method for producing the same, wherein a pressure-sensitive adhesive (PSA) is produced by synthesizing butyl acrylate (BA) and glycidyl methacrylate (GMA), and the pressure-sensitive adhesive is functionalized with boronic acid (4-Mercaptophenylboronic acid, 4-pMPBA).

Most biomedical materials are non-functional materials, so additional functionalization steps are inevitably required. However, these steps are generally material-dependent, and only a few methods have been reported for surface functionalization, such as polydopamine coating, regardless of the material.

When designing and synthesizing biomaterials, interface properties are as important as body properties. This is because the surface of the biomaterial directly interacts with the external substrate. However, commonly used biocompatible materials such as metals, ceramics, and polysaccharides are non-functional and have limited availability. Surface modification technology can maximize the functionality of biomaterials by upgrading the properties of biomaterials or imparting new capabilities. Representative abilities include: (1) antibacterial and antifouling properties, (2) cell adhesion and growth promotion, (3) immune response suppression, and (4) improved mechanical properties of materials.

However, the range of groups that can be functionalized is limited due to the dependence on materials for surface modification. For example, when gold is used as a raw material for biomaterials, it is common to use molecules containing thiol anchoring groups for functionalization, and for functionalization of silica-based materials, special molecules such as APTMS (3-aminopropyltrimethoxysilane) must be used.

Inspired by mussels, polydopamine coating technology was reported in 2007 as an innovative methodology that enables surface modification regardless of the surface type. Specifically, dopamine, which contains both amine and catechol groups, interacts with the surrounding substrate while undergoing spontaneous oxidative polymerization in a weakly basic state. Since catechol can undergo various chemical interactions such as hydrogen bonding, electrostatic interaction, and pi-related bonding, the polymer structure of dopamine (i.e., polydopamine) can be successfully coated on the target substrate. The polydopamine coating layer acts as a molecular bonding agent that can chemically conjugate nucleophiles (e.g., -NH2, -SH) through Michael-type addition and Schiff-base formation on the coated substrate due to the remaining unreacted catechol groups. This enables the introduction of additional functional materials with nucleophilic groups, thereby enabling easy secondary modification. Recently, galol (1,2,3-trihydroxybenzene)-functionalized coating materials, such as poly(carboxylic acid) and poly(pyrogallol), have been found to play a similar role, and related materials have attracted considerable attention due to their versatility in various applications. However, polyphenol coatings have the following disadvantages: (1) the functionality is limited to catechol and galol, (2) the molar composition of unreacted functional groups is difficult to control and varies from batch to batch, and (3) they are not transparent, which limits their applications requiring transparency.

Despite these drawbacks, the application of material-independent multifunctional coatings is quite limited to polyphenol materials, which limits the potential applications related to surface modification. If the above-mentioned problems can be solved by introducing new technologies that can diversify the functionality of the surface with controllable molar ratio and transparency, the possible applications by surface modification can be further expanded.

In particular, boronic acid is an interesting functional group that is continuously being adopted in various applications, especially in the field of biomaterials. The advantage of boronic acid group lies in the dynamic covalent bond formation with diol groups that are abundant in natural molecules (e.g., glucose) and polymers (e.g., polysaccharides). For example, boronic acid group can rapidly form boronic acid-diol complexes to form cross-linked structures, and the bond dissociation can be easily controlled by adjusting the pH. Inspired by this chemistry, pH-sensitive drug delivery systems and biosensors have been successfully developed. However, boronic acid-containing biopolymers cannot be applied to surface functionalization.

Several surface modification methods for boronic acid functionalization have been reported, but none of them can be applied to a variety of surfaces and remain permanently in physiological (aqueous) conditions. For example, a method has been used to apply a coating composed of polyethyleneimine and boronic acid to a glass surface for detecting diabetic biomarkers. Similarly, alginate-boronic acid has been utilized as an adhesive for substrate coating. However, both methods can only be used on specific substrates (e.g., glass), and the universality of the surface modification has not been tested.

In this invention, the present invention has been completed to provide a surface modification method for boric acid functionalization.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a boronic acid functional pressure-sensitive adhesive composed of a butyl group and a boronic acid group for surface functionalization on various substrates, and a one-step boronic acid functionalization method using the same.

The technical problems to be solved by the invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by a person having ordinary skill in the technical field to which the present invention belongs from the description below.

In order to achieve the above object, the present invention provides a method for producing a boronic acid functional pressure-sensitive adhesive, comprising the steps of: synthesizing a scaffold pressure-sensitive adhesive by reacting butyl acrylate and glycidyl methacrylate; and synthesizing a boronic acid pressure-sensitive adhesive by reacting the scaffold pressure-sensitive adhesive with 4-mercaptophenylboronic acid.

In the step of synthesizing the scaffold pressure-sensitive adhesive, the molar ratio of the glycidyl methacrylate to the butyl acrylate may be 1:12 to 15.

In the step of synthesizing the above butyl acrylate and the above glycidyl methacrylate, azobisisobutyronitrile and dimethylformamide can be added and reacted at 50 to 70 °C.

The hydroxyl group of the above 4-mercaptophenylboronic acid can be protected using pinacol.

The step of reacting the scaffold pressure-sensitive adhesive with the 4-mercaptophenylboronic acid to synthesize a boronic acid pressure-sensitive adhesive may include the steps of: dissolving the scaffold pressure-sensitive adhesive and the 4-mercaptophenylboronic acid in tetrahydrofuran, respectively; adding the 4-mercaptophenylboronic acid solution to the scaffold pressure-sensitive adhesive solution; adding DBU (1,8-Diazabicyclo[5.4.0]undec-7-ene) as a catalyst to the mixed solution and reacting at 50 to 60 °C for 22 to 26 hours; and after the reaction step, precipitating the mixed solution using a methanol/water common solvent and then centrifuging the obtained mixture and dissolving the obtained mixture in tetrahydrofuran.

After the step of synthesizing the above-mentioned boronic acid pressure-sensitive adhesive, a step of deprotecting the pinacol group may be additionally included.

In addition, the present invention provides a boronic acid functional pressure-sensitive adhesive comprising a boronic acid group and a butyl group.

The above-mentioned boronic acid functional pressure-sensitive adhesive can be manufactured by polymerizing butyl acrylate and glycidyl methacrylate.

The above-mentioned boronic acid functional pressure-sensitive adhesive can be applied to one or more substrates selected from the group consisting of polymers, metals, and ceramics.

In addition, the present invention provides an antifouling coating composition comprising a boronic acid functional pressure-sensitive adhesive manufactured by the manufacturing method of claims 1 to 6.

By means of solving the above problem, the present invention can provide a boronic acid functional pressure-sensitive adhesive composed of a butyl group and a boronic acid group for surface functionalization on various substrates and a method for producing the same.

In addition, the present invention can provide a one-step boronic acid functionalization method using the pressure-sensitive adhesive.

In addition, the boronic acid functional pressure-sensitive adhesive according to the present invention can be utilized as an implant coating material, and more specifically, the synthesized alginate-catechol (Alg-Ca), known as an antifouling natural polymer, can be reversibly bonded to a substrate functionalized with boronic acid through catechol-boronate complexation.

In addition, the boronic acid functional pressure-sensitive adhesive according to the present invention can introduce a boronic acid functional group onto the surface of a specific material and can be utilized in various application fields.

The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims.

Figure 1 is ^{a 1} H NMR spectrum of a scaffold pressure-sensitive adhesive (PSA).

Figure 2 is the ¹ H NMR spectrum of 4-pMPBA (4-Mercaptophenylboronic acid).

Figure 3 is a ¹ H NMR spectrum after the reaction between phenyl boronic acid and the scaffold pressure-sensitive adhesive is completed.

Figure 4 shows (A) the ¹ H NMR spectrum of PSA-BA, (B) the ¹ H NMR spectrum comparing the pinacol peaks of PSA-pBA before and after deprotection, and (C) the UV-vis spectra of PSA-pBA and PSA-BA.

Figure 5 shows XPS peaks of a bare silicon wafer and a PSA-BA coated silicon wafer.

Figure 6 shows the contact angle patterns before and after PSA-BA coating on various substrates (PLLA, PDMS, Au, Aluminum).

Figure 7 shows (A) a schematic diagram of Alg-Ca synthesis, (B) ¹ H NMR spectrum of Alg-Ca, (C) the degree of catechol substitution of alginate, and the results of measuring ultraviolet absorbance at 280 nm (A280) using a UV-vis spectrophotometer.

Figure 8 shows the results of in vitro cytotoxicity tests on bare glass, PSA-BA primary-coated glass, and PSA-BA/Alg-Ca secondary-coated glass.

Figure 9 shows (A) a schematic diagram of repeated Alg-Ca coating on a boric acid-functionalized substrate, (B) changes in the atomic percentage of Si2p when PSA-BA (first coating) and Alg-Ca (second coating) are sequentially applied to a bare substrate (silicon wafer), and (C, D, E, F, G, H) fluorescent images of stained bacteria, live and dead bacteria, on each substrate.

The terms used in the present invention are selected from the most widely used general terms possible while considering the functions of the present invention, but they may vary depending on the intention of engineers working in the field, precedents, the emergence of new technologies, etc. In addition, in certain cases, there are terms arbitrarily selected by the applicant, and in this case, the meanings thereof will be described in detail in the description of the relevant invention. Therefore, the terms used in the present invention should be defined based on the meanings of the terms and the overall contents of the present invention, rather than simply the names of the terms.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms defined in commonly used dictionaries, such as those defined in common usage, should be interpreted as having a meaning consistent with the meaning they have in the context of the relevant art, and will not be interpreted in an idealized or overly formal sense unless expressly defined in this application.

When a part of a specification is said to “include” a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise stated.

Below, with reference to the attached drawings, embodiments of the present invention are described in detail so that those skilled in the art can easily practice the present invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

Hereinafter, the present invention will be described in detail.

The present invention provides a method for producing a boronic acid functional pressure-sensitive adhesive, comprising the steps of: synthesizing a scaffold pressure-sensitive adhesive by reacting butyl acrylate and glycidyl methacrylate; and synthesizing a boronic acid pressure-sensitive adhesive by reacting the scaffold pressure-sensitive adhesive with 4-mercaptophenylboronic acid.

The above scaffold pressure-sensitive adhesive can be obtained through free radical polymerization of the butyl acrylate and the glycidyl methacrylate. Here, butyl acrylate can induce a low glass transition temperature (Tg) of the pressure-sensitive adhesive, thereby improving flexibility and facilitating chemical interaction with the surface. On the other hand, glycidyl methacrylate can act as a block for introducing special functional molecules.

In the step of synthesizing the scaffold pressure-sensitive adhesive, the molar ratio of the glycidyl methacrylate: the butyl acrylate may be 1:12 to 15, more preferably 1:13 to 14, but is not limited thereto. The molar ratio of the glycidyl methacrylate and the butyl acrylate may be set to maximize the functionality while minimizing the influence on the unique glass transition temperature (Tg) (~ -30°C) required for use as a pressure-sensitive adhesive.

In the step of synthesizing the above butyl acrylate and the above glycidyl methacrylate, azobisisobutyronitrile and dimethylformamide are added and the reaction can be performed at 50 to 70 °C. More specifically, the reaction can be performed at 60 °C, but is not limited thereto.

The above 4-mercaptophenylboronic acid can protect the hydroxyl group using pinacol. In general, a nucleophile having a thiol group can be easily covalently bonded to a scaffold by a ring-opening reaction of an epoxide. However, in the case of 4-mercaptophenylboronic acid containing both a thiol group and a boronic acid group, the ring-opening of the epoxide can be activated not only by the thiol but also by the boronic acid, which may cause unexpected competition. As a result, the reaction rate between unprotected phenyl boronic acid and the scaffold pressure-sensitive adhesive may be significantly reduced. In order to prevent this phenomenon, the hydroxyl group of 4-mercaptophenylboronic acid can be protected using pinacol in the present invention.

The step of reacting the scaffold pressure-sensitive adhesive with the 4-mercaptophenylboronic acid to synthesize a boronic acid pressure-sensitive adhesive may include the steps of: dissolving the scaffold pressure-sensitive adhesive and the 4-mercaptophenylboronic acid in tetrahydrofuran, respectively; adding the 4-mercaptophenylboronic acid solution to the scaffold pressure-sensitive adhesive solution; adding DBU (1,8-Diazabicyclo[5.4.0]undec-7-ene) as a catalyst to the mixed solution and reacting at 50 to 60 °C for 22 to 26 hours; and after the reaction step, precipitating the mixed solution using a methanol/water common solvent and then centrifuging the obtained mixture and dissolving the obtained mixture in tetrahydrofuran.

After the step of synthesizing the above-mentioned boronic acid pressure-sensitive adhesive, a step of deprotecting the pinacol group may be additionally included.

The step of deprotecting the pinacol group of the above boronic acid pressure-sensitive adhesive can obtain the final product, a boronic acid functional pressure-sensitive adhesive, by deprotecting the pinacol group by treating with 5% TFA and MeB(OH) ₂ . Here, MeB(OH) ₂ can act as a sacrificial molecule because it has a higher binding affinity than phenyl boronic acid. As a result, the pinacol group bonded to the original position is removed and can be replaced by phenyl boronic acid through ester exchange (Fig. 4).

In addition, the present invention provides a boronic acid functional pressure-sensitive adhesive comprising a boronic acid group and a butyl group.

The above-mentioned boronic acid functional pressure-sensitive adhesive can be manufactured by polymerizing butyl acrylate and glycidyl methacrylate.

The above-mentioned boronic acid functional pressure-sensitive adhesive can be applied to one or more substrates selected from the group consisting of polymers, metals, and ceramics.

According to one embodiment of the present invention, the coating possibility of a boronic acid functional pressure-sensitive adhesive on not only a silicon substrate but also various polymer and metal substrates can be evaluated using contact angle measurements, and it can be confirmed that the boronic acid functional pressure-sensitive adhesive is successfully coated on all substrates, thereby changing the polarity of the surface.

In addition, the present invention provides an antifouling coating composition utilizing a boronic acid functional pressure-sensitive adhesive manufactured by the manufacturing method of claims 1 to 6.

Introducing a functionalized boronic acid group on the surface of a material can enable various applications. According to one embodiment of the present invention, a new repetitive antifouling technology can be developed by focusing on the reversible bonding characteristics between catechol and boronic acid functional groups. The reason why repetitive coating is necessary is that surrounding organic substances continuously accumulate on the surface over time. For example, if an implant material is continuously used in a physiological environment, even if it exhibits anti-biofouling properties, it will eventually be covered with an organic layer over time. In particular, in the case of dental implant materials, they can be easily coated with polyphenol substances when food is consumed. After being covered with an organic layer, external pathogens such as bacteria can attach to the surface and grow. In other words, the anti-biofouling function of the existing surface can be disabled by being covered with an additional layer.

This problem can be solved by repeatedly switching and attaching the bio-fouling prevention layer. Even if an organic layer is deposited on the surface, it can be naturally removed by removing the bio-fouling prevention layer underneath. After that, the existing surface can be re-coated with a contamination prevention material to restore the bio-fouling prevention function.

Hereinafter, in order to help understand the present invention, examples will be given and described in detail. However, the following examples are only intended to illustrate the content of the present invention, and the scope of the present invention is not limited to the following examples. The examples of the present invention are provided to more completely explain the present invention to a person having average knowledge in the art.

<Manufacturing Example 1> PSA-BA Synthesis

Step 1. Synthesis of scaffold pressure-sensitive adhesive (PSA)

Scaffold pressure-sensitive adhesives (PSAs) were synthesized using butyl acrylate (BA; ≥99%) and glycidyl methacrylate (GMA; ≥97.0%) via free radical polymerization. Before polymerization, the two acrylates were passed through a column filled with inhibitor remover. The radical initiator, azobisisobutyronitrile (AIBN, 12 wt %) in acetone, was dried by rotary evaporation. Anhydrous dimethylformamide (DMF; Sigma-Aldrich, USA, 99.8%), AIBN (1.2 g, 7.3 mmol), BA (80.46 g, 627.8 mmol), and GMA (6.45 g, 45.4 mmol) (225 mL) were added to a 500 mL Schlenk flask and stirred for 10 min. To remove the gas from the solution mixture, the freeze-pump-thaw cycle was repeated three times, and then the flask was filled with an inert gas. The flask was immersed in an oil bath at 60°C for polymerization and left overnight. The mixture was immersed in liquid N ₂ to terminate the reaction. The polymer was precipitated with a common solvent of methanol/water 95:5 (%, v/v) to remove the residual reactants. The precipitate was centrifuged, and the polymer was redissolved in tetrahydrofuran (THF). After repeating this precipitation process three times, the polymer was dried under high vacuum to remove the solvent. The synthesis of the scaffold PSA was confirmed by ¹ H NMR spectroscopy.

Step 2. Synthesis of 4-pMPBA

The hydroxyl group of 4-mercaptophenylboronic acid (4-MPBA; 350 mg, 2.3 mmol) was protected using pinacol. Sodium sulfate (Na ₂ SO ₄ , 1 g, 8.76 mmol) and pinacol (403 mg, 3.4 mmol) were added to a solution of 4-MPBA in diethyl ether (7 mL). The solution mixture was stirred at room temperature for 16 h. When the reaction was completed, the residual sodium sulfate in the mixture was removed through reduced pressure filtration. And the filtered solution was dried using a rotary evaporator. The obtained powder was purified using silica gel column chromatography (AcOEt/hexane = 1:4). Spot-on thin layer chromatography (TLC) was stained yellow using Ellman's reagent. The solution collected through chromatography was recrystallized using a rotary evaporator to remove the solvent, obtaining a white powder.

Step 3. PSA-pBA synthesis

To synthesize PSA-pBA, 4-pMPBA was introduced into the epoxide ring of the scaffold PSA. Specifically, scaffold PSA (2 g, 1.24 mmol, 1 eq.) was dissolved in anhydrous THF (18 mL) in a round bottom flask, and then purged with inert nitrogen gas. In a separate step, 4-pMPBA (0.388 g, 1.64 mmol, 1.33 eq.) was also dissolved in anhydrous THF (2 mL) and then slowly added dropwise to the PSA solution. Then, 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU; 38 μL, 0.250 mmol, 0.2 eq.) as a catalyst was slowly added dropwise to the PSA and 4-pMPBA solutions. The mixture was reacted in a 55 °C oil bath for 24 h, and a yellow solution was obtained. A co-solvent of methanol/water 95:5 (%, v/v) was used to precipitate the solution. After centrifugation, the supernatant was discarded and the obtained polymer was dissolved in THF. This precipitation process was repeated three times. Finally, the solvent was removed from the polymer using a Schlenk line.

Step 4. Production of PSA-BA by removing pinacol from PSA-pBA

Pinacol deprotection of PSA-pBA was performed. First, PSA-pBA (230 mg) was mixed with anhydrous THF (2.75 mL) and dissolved in an oil bath at 50 °C using a Teflon stirring bar. When PSA-pBA was completely dissolved, a solution of methylboronic acid (MeB(OH) ₂ ; 1 eq, 60 mg) dissolved in anhydrous THF (2 mL) was added dropwise to the mixture with stirring. Then, trifluoroacetic acid (TFA; 250 μL) was slowly added dropwise to the mixture, and the reaction was carried out at room temperature for 2 h. To remove the residual reactants, the polymer was precipitated with a common solvent of methanol/water 95:5 (%, v/v). After centrifugation of the precipitate, the polymer was redissolved in tetrahydrofuran (THF). Finally, the obtained polymer was solvent-removed using a Schlenk line. The unprotected pinacol group in PSA-pBA was confirmed by ¹ H NMR and UV-Vis spectroscopy (UV-1800, Shimadzu, Japan). The conversion was calculated by comparing the integrals of the pinacol peaks before and after the deprotection step, and the distinct peak right next to the pinacol peak was used as a standard. For UV-vis analysis, the absorbance spectra of the polymers before and after the deprotection step were analyzed in the range of 200 nm to 400 nm (solvent: THF). For accurate comparison, the obtained spectra were normalized using Excel software. Steps 1 to 4 of Preparation Example 1 are schematically illustrated in FIG. 11.

<Manufacturing Example 2> Synthesis of Alg-Ca

Alg-Ca was synthesized via EDC/NHS coupling reaction. For conjugation of dopamine, alginate (1 g, approximately 5 mmol) was dissolved in 100 mL of 0.1 M MES buffer (pH 5.2), and the mixture was purged with inert N ₂ gas. Next, EDC-HCl (5 mmol, 0.9585 g) and NHS (5 mmol, 0.575 g) were individually added dropwise to the alginate solution at 10 min intervals. After bubbling N ₂ with the alginate mixture for 5 min, dopamine hydrochloride (5 mmol, 0.9482 g) dissolved in 3 mL of MES buffer (0.1 M, pH 5.2) was added dropwise to the alginate/EDC/NHS solution. The reaction was performed at room temperature for 1 h. After the reaction, the mixed solution was dialyzed against 5 L of DDW (pH 6) containing 20 g of NaCl for 3 days. After 3 days, the mixed solution was dialyzed against pure DDW for 4 h using a 3.5 kDa MWCO membrane and then freeze-dried for 3 days.

<Example 1> Boronic acid functionalization using PSA-BA

PSA-BA was coated on a Si wafer (1 cm × 1 cm) using a spin coater (SC-300, EHC.Co., Ltd, Japan). Specifically, a PSA-BA solution (20 mg/mL) was dissolved in THF in an oil bath at 50°C. Then, the completely dissolved PSA-BA solution (60 μL) was dropped all at once onto the Si wafer, and the substrate was spin-coated. Specifically, the first and second coating steps were performed at 1000 rpm for 10 s and 4000 rpm for 20 s, respectively. Finally, the coating was confirmed by contact angle and X-ray photoelectron spectroscopy (see Figure 12).

<Example 2>

The same procedure as Example 1 was followed, except that a PLLA substrate was used instead of a Si wafer.

<Example 3>

The same procedure as in Example 1 was followed except that a PDMS substrate was used instead of a Si wafer.

<Example 4>

The same procedure as in Example 1 was followed except that an Au substrate was used instead of a Si wafer.

<Example 5>

The same procedure as Example 1 was followed, except that an aluminum substrate was used instead of a Si wafer.

<Example 6> Secondary modification of boronic acid functionalized substrate using Alg-Ca

Alg-Ca was coated on Si wafers modified with PSA-BA. A solution of Alg-Ca (5 mg/mL) dissolved in pH 8.5 Tris buffer was prepared. Next, the PSA-BA-coated substrates were immersed in the solution (4 mL) using a petri dish for each piece. After shaking the dish at 50 rpm for 24 h, the substrates were washed with distilled water and dried with N ₂ gas. Finally, the coating of Alg-Ca was confirmed using X-ray photoelectron spectroscopy.

<Example 7> Repeated coating of Alg-Ca by PSA-BA

After removing the Alg-Ca layer from the Si wafer modified with PSA-BA and Alg-Ca, Alg-Ca was newly coated. To remove the Alg-Ca layer, the substrate was held obliquely with tweezers and washed with pH 4 PBS buffer for 5 min. Then, the substrate was rinsed with distilled water and dried using nitrogen gas. Alg-Ca recoating of the substrate with only the PSA-BA layer remaining was performed by the previously mentioned method. Both the removal and recoating of Alg-Ca were analyzed by X-ray photoelectron spectroscopy (Nexsa, Thermo Fisher, USA).

<Comparative Example 1>

Bare silicon wafers were prepared for comparison with PSA-BA coated silicon wafers.

<Comparative Example 2>

Bare glass was prepared for comparison of cytotoxicity tests with PSA-BA coated glass.

<Experimental Example 1> ¹ H NMR Analysis of Scaffold Pressure-Sensitive Adhesive (PSA)

The synthesis of the scaffold PSA was confirmed by ¹ H NMR spectroscopy.

Figure 1 shows the ¹ H NMR spectrum of the scaffold PSA synthesized in Manufacturing Example 1.

The optimal ratio of two monomers, butyl acrylate (BA) and glycidyl methacrylate (GMA), was set to 93:7 to maximize the functional portion while minimizing the effect on the inherent glass transition temperature (Tg) (~ -30°C) required for use as a pressure-sensitive adhesive, and this ratio (93:7) was confirmed through ¹ H NMR analysis (Fig. 1).

The ratio of BA and GMA side chains in the scaffold PSA was calculated using ¹ H NMR spectroscopy by the following formula:

3Hx (h)+3Hy (d)=43.43 Hy

Using the above equation, the ratio of Hx and Hy, which represent the normalized integral areas (1H) of the BA and GMA side chains, respectively, can be deduced as follows:

Hx:Hy = 13.48:1= 93:7

<Experimental Example 2> Analysis of 4-pMPBA (4-Mercaptophenylboronic acid)

The synthesis of 4-pMPBA was confirmed by ¹ H NMR spectroscopy.

Figure 2 shows the ¹ H NMR spectrum of 4-pMPBA synthesized in Manufacturing Example 1.

The synthesized 4-pMPBA can be seen to be grafted via the ring-opening reaction of epoxide.

<Experimental Example 3> ¹ H NMR analysis after reaction of 4-MPBA and scaffold PSA

In general, a nucleophile having a thiol group can easily be covalently bonded to a scaffold by the ring-opening reaction of the epoxide group. However, in the case of 4-MPBA containing both a thiol group and a boronic acid group, the ring-opening of the epoxide group can be activated not only by the thiol but also by the boronic acid, resulting in an unexpected competition. As a result, the reaction rate of phenyl boronic acid (unprotected) and the scaffold PSA was significantly reduced, as confirmed in the ¹ H NMR results (Fig. 3).

<Experimental Example 4> Analysis of PSA-pBA and PSA-BA

The final product, PSA-BA, was obtained by deprotecting the pinacol group by treating PSA-pBA with 5% TFA and MeB(OH) ₂ , and the conversion was about 60% calculated from the ¹ H NMR results (Fig. 4 (A), (B)). Here, MeB(OH) ₂ acts as a sacrificial molecule because it has a higher binding affinity than phenyl boronic acid. As a result, the pinacol group conjugated to the original position was removed and replaced by phenyl boronic acid through ester exchange.

Successful deprotection of the pinacol group was also confirmed by UV-vis results. Compared with the original peak of pinacol-protected PSA-pBA, the absorbance peak of the deprotected PSA-BA was slightly red-shifted, which is a signal of the elongated pi-conjugated band in the boronic acid group (Figure 4 (C)).

<Experimental Example 5> XPS Analysis of PSA-BA Coated Silicon Wafer

The surfaces of bare silicon wafers and PSA-BA-coated silicon wafers were analyzed by XPS.

Fig. 5 is an XPS spectrum of the surface of a bare silicon wafer and a silicon wafer coated with PSA-BA. As can be seen in Fig. 5, it can be confirmed that the Si2p peak is significantly reduced after PSA-BA coating.

<Experimental Example 6> Contact angle analysis before and after PSA-BA coating on various substrates

The average contact angle on the bare silicon wafer was 35.7° (n=5), which increased to 74.8° (n=5) after PSA-BA coating, providing evidence for the introduction of a nonpolar PSA-BA coating containing a significant amount of hydrocarbon chains.

In addition to Si wafers, PSA-BA can be applied to various surfaces. This is because of the presence of butyl groups in PSA, which are known to exhibit adhesion to a wide range of substrates and strong van der Waals forces. In addition to the previously coated SiO ₂ (ceramic material), the possibility of PSA-BA coating on representative polymer and metal (PLLA, PDMS, Au, aluminum) substrates was evaluated using contact angle measurements (Fig. 6). As observed in the experimental results, the contact angle values of all substrates converged to approximately 80° after PSA-BA coating. In particular, the contact angles on relatively polar surfaces (e.g., PLLA, Au, aluminum) increased after coating, whereas those on relatively nonpolar surfaces (e.g., PDMS) decreased.

The contact angle values changed as follows. PLLA increased from 70.8° to 84.9°, PDMS decreased from 98.4° to 86.1°, Au increased from 59.0° to 74.7°, and Aluminum also increased from 35.0° to 71.9° (n=5). As a result, it was confirmed that the polarity of the surface was changed by the successful coating of PSA-BA.

<Experimental Example 7> Synthetic Analysis of Alg-Ca

The synthesis of Alg-Ca was confirmed by ¹ H NMR spectroscopy. The degree of catechol substitution (DOS) of alginate was measured by UV absorbance at 280 nm (A280) using a UV-Vis spectrophotometer (UV-1800, Shimadzu, Japan). A calibration curve was obtained using dopamine hydrochloride solution.

Figure 7(A) is a schematic diagram of the synthesis of Alg-Ca, and Figure 7(B) is a ¹ H NMR spectrum of Alg-Ca. Figure 7(C) shows the results of measuring the degree of catechol substitution of alginate by measuring the UV absorbance at A280 nm using a UV-vis spectrophotometer.

<Experimental Example 8> Cytotoxicity Test

Cytotoxicity tests were performed according to the ISO 10993-5 guideline. L929 cells were used for cytotoxicity tests to confirm the biocompatibility of the samples (Bare glass, PSA-BA primary coating, PSA-BA/Alg-Ca secondary coating). The cells were maintained in a medium at 37°C in a 5% CO ₂ humidified incubator. Cells that were passaged twice were harvested and seeded in a 24-well plate at a density of 0.05 x 10 ⁵ cells per well. The samples cut into 10 mm × 10 mm pieces were placed in the well plates, and the cell suspension was slowly dispensed. After that, they were cultured for 24 h in a 5% CO ₂ humidified incubator at 37°C. For cytotoxicity tests, one drop of CCK-8 assay solution was added to each well, and 100 μL of the supernatant from each well was transferred to a 96-well plate. Absorbance was read at 450 nm using a microplate reader (Infinite 200 Pro, Tecan, Mannedorf, Switzerland).

According to CCK analysis, both modified surfaces (primary coating, secondary coating) showed biocompatibility and similar cell viability compared to the bare substrate (Fig. 8).

<Experimental Example 9> Anti-fouling test

The antifouling properties of the coated glass were evaluated based on the degree of adhesion of E. coil (KRIBB, Korea). Specifically, the modified substrate was placed in a 24-well plate, and the bacterial solution (5.3 × 10 ⁹ CFU/mL) was dispensed. The plate was then incubated at 37°C for 24 h. After overnight, the plate was removed from the incubator, and the substrate was washed three times with sterile PBS. The washed sample was then transferred to a new 24-well plate, and 1 mL of sterile PBS was dispensed into each well. Then, the bacterial live/dead reagent (3 μL per mL, Invitrogen, USA) was added to each well, and the plate was placed back into the 37°C incubator for 15 min. After incubation, the substrate surface was covered with a bare glass substrate, and fluorescence images were observed using a confocal microscope (ECLIPSE Ts2-FL, Nikon, Japan).

As shown in Fig. 9(A), (B), the atomic ratio of the high-resolution Si2p peak decreased from 5.74% (1 coating) to 1.72% (2 coating) after the first Alg-Ca coating. This suggests that Alg-Ca composed of carbon and oxygen was additionally deposited on the exposed surface (SiO ₂ ). After pH 4 PBS treatment, the second coating of Alg-Ca showed a similar decreasing pattern as the first coating, decreasing from 5.2% (1' coating) to 2.19% (2' coating). This demonstrates that Alg-Ca can be repeatedly applied to the SiO ₂ surface functionalized with boronic acid.

Figure 9(C, D, E, F, G, H) shows the results of bacterial attachment based on sequential coating (1, 2, 1', 2' coating). To quantify the degree of bacterial attachment, the area of the exposed substrate (SiO ₂ ) was set as 1, and the degrees of attachment of the remaining substrates were compared and analyzed using ImageJ. After functionalizing the bare substrate with PSA-BA (1 coating), the degree of bacterial attachment was reduced to 92.0%. Acrylic adhesives are generally resistant to microbial communities due to their smooth texture and nutrient-poor properties. However, the adhesive alone cannot completely prevent bacterial attachment. The observation results showed that bacteria attached to the surface and began to form an organic layer during 24 hours of incubation.

Because of the presence of an organic layer formed by dead bacteria, live bacteria can rapidly regrow. To address this, the antifouling material Alg-Ca was additionally introduced (twice coated), and as a result, the attachment rate was significantly reduced to 99.4% compared to the bare substrate (Fig. 9 (F)). After Alg-Ca was removed using a pH 4 PBS solution, the degree of bacterial attachment on the surface (1' coating) was reduced by 89.5% compared to the bare substrate, which was similar to the effect of 1 coating (92.0%). After Alg-Ca was re-coated (2' coating), the previous biofouling prevention function was restored (Fig. 9 (H)), and it could be observed that the bacterial attachment rate was significantly reduced to 99.8% compared to the bare substrate.

To simulate the conditions under which an actual organic layer accumulates, the antifouling coating surface (2 coating) was exposed to a tank containing living marine life (squid) for a week. Then, bacteria were cultured on the surface according to the same procedure as before. As a result, it was confirmed that the bacterial adhesion ability was significantly increased by about 3.4 times (Fig. 9(G)). After treatment with a pH 4 PBS solution for 5 min to remove the antifouling and organic layers, when the Alg-Ca coating was reapplied, it was confirmed that the adhesion rate decreased again to 99.8% compared to the bare surface. In other words, it was proven that repetitive modification of a biofouling surface is possible through PSA-BA functionalization (see Fig. 14).

Claims (10)

A step of synthesizing a scaffold pressure-sensitive adhesive by reacting butyl acrylate and glycidyl methacrylate; and A method for producing a boronic acid functional pressure-sensitive adhesive, comprising the step of reacting the scaffold pressure-sensitive adhesive with 4-mercaptophenylboronic acid to synthesize a boronic acid pressure-sensitive adhesive. In paragraph 1, A method for producing a boronic acid functional pressure-sensitive adhesive, characterized in that in the step of synthesizing the scaffold pressure-sensitive adhesive, the molar ratio of the glycidyl methacrylate: the butyl acrylate is 1:12 to 15. In paragraph 1, A method for producing a boronic acid functional pressure-sensitive adhesive, characterized in that in the step of synthesizing the butyl acrylate and the glycidyl methacrylate, azobisisobutyronitrile and dimethylformamide are added and reacted at 50 to 70 °C. In paragraph 1, A method for manufacturing a boronic acid functional pressure-sensitive adhesive, characterized in that the hydroxyl group of the above 4-mercaptophenylboronic acid is protected using pinacol. In paragraph 1, The step of synthesizing a boronic acid pressure-sensitive adhesive by reacting the above scaffold pressure-sensitive adhesive and the above 4-mercaptophenylboronic acid is as follows. A step of dissolving the scaffold pressure-sensitive adhesive and the 4-mercaptophenylboronic acid in tetrahydrofuran, respectively; A step of adding the above 4-mercaptophenylboronic acid solution to the above scaffold pressure-sensitive adhesive solution; A step of adding DBU (1,8-Diazabicyclo[5.4.0]undec-7-ene) as a catalyst to the above mixed solution and reacting at 50 to 60 °C for 22 to 26 hours; and A method for producing a boronic acid functional pressure-sensitive adhesive, characterized in that it comprises a step of dissolving the mixture obtained by precipitating the mixed solution using a methanol/water common solvent after the above reaction step and then centrifuging the mixture in tetrahydrofuran. In paragraph 1, A method for producing a boronic acid functional pressure-sensitive adhesive, characterized in that it further comprises a step of deprotecting a pinacol group after the step of synthesizing the above boronic acid pressure-sensitive adhesive. A boronic acid functional pressure-sensitive adhesive containing a boronic acid group and a butyl group. In Article 7, The above-mentioned boronic acid functional pressure-sensitive adhesive is a boronic acid functional pressure-sensitive adhesive characterized in that it is manufactured by polymerizing butyl acrylate and glycidyl methacrylate. In Article 7, A boronic acid functional pressure-sensitive adhesive characterized in that the above boronic acid functional pressure-sensitive adhesive can be applied to one or more substrates selected from the group consisting of polymers, metals, and ceramics. An antifouling coating composition comprising a boronic acid functional pressure-sensitive adhesive manufactured by the manufacturing method of claims 1 to 6.

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