KR102495336B1 - Crosslinking agent comprising polymer brush containing aziridine, manufacturing method thereof, and their use as crosslinking agent - Google Patents

Abstract

The present invention relates to a crosslinking agent comprising a polymer brush containing an aziridine group, a manufacturing method thereof, and uses thereof, wherein the crosslinking agent can effectively control the crosslinking density without changing the concentration by adjusting the length and density of the polymer brush, can exhibit various mechanical and adhesive properties, and can use both solvent-type and water-based adhesives by containing polyethylene glycol with amphipathic properties.

Description

Crosslinking agent comprising polymer brush containing aziridine, manufacturing method thereof, and their use as crosslinking agent

The present invention relates to a crosslinking agent comprising a polymer brush containing an aziridine group, a method for preparing the same, and a use thereof.

Adhesives are ubiquitous in all industries, from household products to cutting-edge electronics and pharmaceuticals. Considering this enormous economic ripple effect, extensive research is being conducted to develop next-generation adhesives. In addition to achieving cost-effective mass production, securing the ability to efficiently control cohesion (mechanical strength), adhesion and tack is a key point in adhesive research, as these properties are often interrelated in complex ways. Cohesive force represents mechanical strength, structural durability and thermal stability and is controlled by crosslinking density. On the other hand, adhesion, the ability to rapidly adhere to a surface, is governed primarily by preferential interaction of adhesion molecules with the surface rather than internal cohesion and thus decreases with increasing cross-linking density. Adhesion, which describes the ability to maintain surface bonding against external shear forces, initially improves by increasing cohesion, which prevents premature structural collapse, but as cohesion continues to increase, stiffness increases and cohesion is lost, resulting in a decrease in adhesion.

Existing crosslinkers for adhesives are mostly small molecules or oligomers containing one or more reactive functional groups. Generally included in small amounts in the prepolymer mixture, their sole purpose is to cross-link the base polymer to increase cohesion. On the other hand, adhesive properties are mostly given by the physical properties of the polymer system. Their limited role is mainly due to a rather rapid loss of adhesion (and concomitant increase in cohesion) with increasing concentration, since their relatively small size compared to the base polymer leads to high reactivity. To enhance cohesion individually, nanoparticles as fillers are often incorporated to create composite structures.

Therefore, in order to overcome the limitations of current crosslinking technology, it is necessary to develop a crosslinking agent capable of controlling the crosslinking density and influencing adhesive properties by physicochemical interactions. In this regard, macromolecular crosslinkers ('macrocrosslinkers') are considered promising alternatives to small molecule crosslinkers because they offer several properties. First, a larger, controllable number of reactive functional groups can be conjugated to the polymer backbone. Therefore, the crosslinking density can be adjusted in a wide range without a large change in the total concentration. Second, different types of functional groups can be conjugated to the same polymer chain to exhibit multifunctionality. Third, as long as sufficient physical interaction and miscibility are ensured, the polymeric crosslinking agent itself can be used as a macromonomer. Thus, within a concentration range of a homogeneous solution, two or more polymeric crosslinking agents can react with each other to form a polymeric network. Fourth, unlike small molecules that provide few pathways for physical interactions, the chemical composition and physical dimensions of polymeric crosslinkers can be controlled to optimize the resulting mechanical and adhesive properties by inducing different physical interactions with other macromonomers. there is. For example, by adopting a grafted or branched shape to the polymer crosslinker instead of the conventional linear shape, the physical interaction with the surrounding polymer network can be controlled. Charged or hydrophobic moieties may additionally be included to create electrostatic or hydrophobic interactions, respectively.

Republic of Korea Patent Registration No. 10-1708074 (2017.02.17. Publication)

The present invention relates to a crosslinking agent comprising a polymer brush, and provides a crosslinking agent for controlling the length and density of a polymer brush comprising an aziridine group and polyethylene glycol acrylate.

The present invention includes a brush copolymer comprising a first brush monomer and a second brush monomer comprising an amphiphilic polymer having an aziridine group terminal group, wherein the second brush monomer is polyethylene glycol methyl ether acrylate (poly(ethylene glycol) methyl ether acrylate), polyethylene glycol phenyl ether acrylate (poly(ethylene glycol) phenyl ether acrylate), polyethylene glycol methyl ether methacrylate (poly(ethylene glycol) methyl ether methacrylate), polyethylene glycol acrylate (poly(ethylene glycol) glycol) acrylate) and polyethylene glycol methacrylate (poly(ethylene glycol) methacrylate).

In addition, the present invention comprises a first step of preparing a first brush monomer by mixing an aziridine compound and an amphiphilic polymer; and a second step of preparing a brush copolymer by mixing and reacting the prepared first brush monomer, second brush monomer, and initiator, wherein the second brush monomer is polyethylene glycol methyl ether acrylate (poly(ethylene glycol) ) methyl ether acrylate), polyethylene glycol phenyl ether acrylate (poly(ethylene glycol) phenyl ether acrylate), polyethylene glycol methyl ether methacrylate (poly(ethylene glycol) methyl ether methacrylate), polyethylene glycol acrylate (poly(ethylene glycol) ) acrylate) and polyethylene glycol methacrylate (poly (ethylene glycol) methacrylate).

In addition, the present invention provides an adhesive comprising the above-described crosslinking agent and a prepolymer, wherein the prepolymer includes an aqueous or solvent-type prepolymer.

The crosslinking agent of the present invention can effectively control the crosslinking density without changing the concentration by adjusting the length and density of the polymer brush, and can exhibit various mechanical and adhesive properties.

In addition, the crosslinking agent of the present invention includes polyethylene glycol having amphipathic properties, and thus has the advantage of being usable for both solvent-type and water-based adhesives.

Figure 1 is a schematic image of the structure and crosslinking agent of the compound included in the crosslinking agent according to the present invention: (a) Poly (mPEG-co-AzPEG) was synthesized, a brush copolymer composed of Az-PEG and mPEG brush (P(AzPEG)), (b) the structure of P(AzPEG) was controlled by adjusting the length and density of the AzPEG brush.
2 is a ¹ H-NMR spectrum result of P (AzPEG400) according to various substitution degrees of aziridine brush (DS _Az ).
Figure 3 is the result of measuring the rheological properties of the crosslinking agent according to the present invention: (a) a schematic diagram of the crosslinking reaction between poly (EHA-co-AA) and P (AzPEG); and (be) physical appearance images of poly(EHA-co-AA) with and without P(AzPEG) crosslinking, and (be) crosslinked poly(EHA-co-AA) at various concentrations (0-10%) and DSAz (DS1, DS3, DS5, and DS7). are the storage modulus (G') and loss modulus (G") of (EHA-co-AA).
Figure 4 is the result of measuring the storage modulus and loss modulus of the crosslinking agent according to the present invention: (ac) maximum storage modulus (G' _MAX ) measured after crosslinking between poly (EHA-co-AA) and P (AzPEG) and (df) the loss tangent (Tan δ) calculated from G' _MAX and G” _MAX .
5 is a result of a lap shear test performed to measure the shear modulus and adhesive strength of P(AzPEG) crosslinked poly(EHA-co-AA) to a glass substrate: (a, d) P(AzPEG250), ( b, e) P(AzPEG400) and (c, f) P(AzPEG 700) (*p<0.05). Poly(EHA-co-AA) without P(AzPEG) cross-linking was used as a control.
6 is a result of a lap shear test to measure the shear modulus and adhesive strength of P(AzPEG) crosslinked poly(EHA-co-AA) to a plastic substrate: (a, d) P(AzPEG250), ( b, e) P(AzPEG400) and (c, f) P(AzPEG 700) (*p<0.05). Poly(EHA-co-AA) without P(AzPEG) cross-linking was used as a control.
7 is a result of a lap shear test to measure the shear modulus and adhesive strength of P(AzPEG) crosslinked poly(EHA-co-BA-co-MMA-co-AA-co-HEMA) to a glass substrate. : (a, d) P(AzPEG250), (b, e) P(AzPEG400) and (c, f) P(AzPEG 700) (*p<0.05). Poly(EHA-co-AA) without P(AzPEG) cross-linking was used as a control.

Hereinafter, the present invention is described in detail.

The present invention provides a crosslinking agent comprising a brush copolymer comprising a first brush monomer and a second brush monomer comprising an amphiphilic polymer having an aziridine terminal group.

The crosslinking agent of the present invention may include a brush copolymer in which the first brush monomer and the second brush monomer are randomly copolymerized at a constant ratio.

The first brush monomer may be one in which an aziridine group is substituted at the end of an amphiphilic polymer. Specifically, the amphiphilic polymer may be poly(ethylene glycol) diacrylate.

By including the amphiphilic polymer as described above, the crosslinking agent of the present invention can be used for both aqueous or solvent type adhesives.

The molecular weight of the first brush monomer may be 100 to 1,000 g/mol. Specifically, the molecular weight of the first brush monomer may be 200 to 1,000 g/mol, 200 to 700 g/mol, or 400 to 700 g/mol.

The degree of substitution of the first brush monomer may be 10% to 85%. Specifically, the degree of substitution of the first brush monomer may be 15% to 85%, 15% to 70%, or 20% to 85%.

As described above, the crosslinking agent of the present invention including the first brush monomer can effectively control the crosslinking density without changing the concentration by controlling the length and density of the brush.

The second brush monomer is polyethylene glycol methyl ether acrylate (poly (ethylene glycol) methyl ether acrylate), polyethylene glycol phenyl ether acrylate (poly (ethylene glycol) phenyl ether acrylate), polyethylene glycol methyl ether methacrylate (poly( ethylene glycol) methyl ether methacrylate), polyethylene glycol acrylate (poly(ethylene glycol) acrylate), and polyethylene glycol methacrylate (poly(ethylene glycol) methacrylate). More specifically, the second brush monomer may be polyethylene glycol methyl ether acrylate.

The molecular weight of the second brush monomer may be 100 to 1,000 g/mol. Specifically, the molecular weight of the second brush monomer may be 200 to 1,000 g/mol, 200 to 700 g/mol, or 400 to 700 g/mol.

In addition, the present invention comprises a first step of preparing a first brush monomer by mixing an aziridine compound and an amphiphilic polymer; and a second step of preparing a brush copolymer by mixing and reacting the prepared first brush monomer, second brush monomer, and initiator.

The first step is a step of capping an aziridine group at the end of the amphiphilic polymer. Specifically, in the first step, the first brush monomer may be prepared by mixing the amphiphilic polymer at a molar ratio of 1 to 1.5 based on the aziridine compound and stirring for 20 to 30 hours in a nitrogen atmosphere at room temperature. More specifically, the first step is to prepare a first brush monomer by mixing the amphiphilic polymer at a molar ratio of 1 to 1.2 or 1 to 1.5 based on the aziridine compound and stirring for 20 to 25 hours in a nitrogen atmosphere at room temperature. can do.

The aziridine compound may include at least one selected from the group consisting of aziridine, 2-methylaziridine, 2-phenylaziridine, and 2-methyl-3-phenylaziridine. Specifically, the aziridine compound may be 2-methylaziridine.

The amphiphilic polymer may be polyethylene glycol diacrylate.

By including the amphiphilic polymer as described above, the crosslinking agent of the present invention can be used for both aqueous or solvent type adhesives.

The amphiphilic polymer may have a molecular weight of 100 to 1,000 g/mol. Specifically, the amphiphilic polymer may have a molecular weight of 200 to 1,000 g/mol, 200 to 700 g/mol, or 400 to 700 g/mol.

In addition, the crosslinking agent of the present invention, including the above molecular weight amphiphilic polymer, can effectively control the crosslinking density without changing the concentration by controlling the length and density of the first brush monomer.

The second step is a step of preparing a brush copolymer by mixing and polymerizing a first brush monomer, a second brush monomer, and an initiator, and the brush copolymer prepared through the second step is the first brush monomer and the second brush. It may be in the form of randomly copolymerized monomers at a constant ratio.

The second brush monomer is polyethylene glycol methyl ether acrylate (poly (ethylene glycol) methyl ether acrylate), polyethylene glycol phenyl ether acrylate (poly (ethylene glycol) phenyl ether acrylate), polyethylene glycol methyl ether methacrylate (poly( ethylene glycol) methyl ether methacrylate), polyethylene glycol acrylate (poly(ethylene glycol) acrylate), and polyethylene glycol methacrylate (poly(ethylene glycol) methacrylate). More specifically, the second brush monomer may be polyethylene glycol methyl ether acrylate.

The molecular weight of the second brush monomer may be 100 to 1,000 g/mol. Specifically, the molecular weight of the second brush monomer may be 200 to 1,000 g/mol, 200 to 700 g/mol, or 400 to 700 g/mol.

The initiator is 2,2'-azobis (isobutyronitrile) (AIBN), 4,4'-azobis (4-cyanopentanoic acid), 2,2'-azobis (2-cyano-2- butane), 1,1'-azobis (cyclohexanecarbanitrile), potassium persulfate, sodium persulfate, ammonium persulfate, benzoyl peroxide, and at least one selected from the group consisting of di-tert-butyl peroxide can include Specifically, the initiator may be 2,2'-azobis(isobutyronitrile) (AIBN).

In the second step, the first and second brush monomers and the initiator are mixed and degassed with nitrogen for 30 minutes to 2 hours, and the temperature is 50 to 100 ° C or 60 to 80 ° C under a nitrogen atmosphere for 15 to 30 hours or 15 to 80 ° C. A brush copolymer can be prepared by reacting for 25 hours. Additionally, the solvent can be removed with a rotary evaporator and then washed twice or more with an excess of solvent (diethyl ether).

In the second step, the concentration of the first and second brush monomers may be 0.1 to 1.0 M, and in the second step, the molar ratio of the first brush monomer and the second brush monomer is 0 to 80:20 to 100. can Specifically, the concentration of the first and second brush monomers may be 0.1 to 0.5 M, and the molar ratio between the first brush monomer and the second brush monomer may be 0 to 70:30 to 100.

In the brush copolymer prepared through the second step, the degree of substitution of the first brush monomer may be 10% to 85%. Specifically, the degree of substitution of the first brush monomer may be 15% to 85%, 15% to 70%, or 20% to 85%.

As described above, the crosslinking agent of the present invention including the first brush monomer can effectively control the crosslinking density without changing the concentration by controlling the length and density of the brush.

In addition, the present invention provides an adhesive comprising the above-described crosslinking agent and prepolymer.

Corresponding features are replaced by the above-mentioned parts, and are omitted below.

The crosslinking agent may be included in an amount of 1 to 20 phr (parts per hundred resin) based on 100 phr of the prepolymer. Specifically, the crosslinking agent may be included in an amount of 1 to 15 phr or 1 to 10 phr based on 100 phr of the prepolymer.

The prepolymer includes an aqueous or solvent-type prepolymer, and the aqueous prepolymer includes poly(EHA-co-BA-co-MMA-co-AA-co-HEMA), poly(EHA-co-AA-co- MMA), poly(EHA-co-AA-co-HEMA), poly(EHA-co-MMA-co-AA), poly(BA-co-AA-co-HEMA) and poly(BA-co-AA- co-MMA) may be one or more selected from the group consisting of. The solvent-type prepolymer is poly(ethyl hexyl acrylate-co-acrylic acid; poly(EHA-co-AA)), poly(EHA-co-AA-co-BA ) (BA: Butyl Acrylate), poly(EHA-co-AA-co-MMA), poly(EHA-co-AA-co-Sty) (Sty: Styrene) and poly(EHA-co-AA-co-VAc ) (VAc: Vinyl Acetate).

The adhesive according to the present invention includes the crosslinking agent described above and exhibits improved storage modulus and loss modulus compared to adhesives without the crosslinking agent, which may be affected by the length of the first brush monomer of the crosslinking agent.

In addition, the adhesive according to the present invention includes the above-mentioned crosslinking agent, and the shear modulus and adhesive strength increase depending on the concentration of the crosslinking agent, which means that the crosslinking density affects the adhesive strength, so that the adhesive strength can increase as the crosslinking density increases. there is.

Hereinafter, the present invention will be described in more detail through examples. These examples are only for explaining the present invention in more detail, and it will be apparent to those skilled in the art that the scope of the present invention is not limited by these examples according to the gist of the present invention. .

ingredient

4-dimethylaminopyridine (DMAP), 4-methoxyphenol, glycidyl methacrylate (GMA), poly(ethylene glycol) diacrylate (Mn 250, 400 and 700 g/mol) (PEGDA250, PEGDA400 and PEGDA700) , poly(ethylene glycol) methyl ether acrylate (mPEGA, Mn 480 g/mol), n-butyl acrylate (n-BA), ammonium persulfate (APS) and N,N,N',N'-tetramethylethylene Diamine (TEMED) was purchased from Sigma-Aldrich. Dimethylsulfoxide (DMSO), 2-butanone, 2-ethylhexylacrylate (EHA), acrylic acid (AA), ethylacetate (EtAc), 2-hydroxyethylmethacrylate (HEMA), tetrahydrofuran (THF) ), and sodium carbonate was purchased from Samjeon Chemical (Seoul, Korea). 2-methylaziridine was purchased from Hanul Chemical (Ulsan, Korea). 2,2′-azobis(2-methylpropioniril) (AIBN) was purchased from Junsei Chemical Co. (Tokyo, Japan). Anhydrous toluene was purchased from Alfa Aesar. mPEGA was purified by passing through a basic alumina column to remove the inhibitor, and AIBN was used after recrystallization from methanol.

Example 1

1-1) Synthesis of aziridine-PEG-acrylate (AzPEGA)

The aziridine functional group was conjugated to PEGDA by Michael addition. 2-methylaziridine (3.57g, 62.6mmol) was slowly added to PEGDA250 (14.2g, 56.9mmol), and stirred for 24 hours under a dry nitrogen (N ₂ ) atmosphere at room temperature. After the reaction, excess 2-methylaziridine was removed by rotary evaporation to synthesize AzPEGA250, and the product was a colorless liquid with a yield of 91%. AzPEGA400 and AzPEGA700 were synthesized in the same manner as above using PEGA400 and PEGA700 of different molecular weights, and the products were colorless liquids, respectively, with yields of 93.4% and 93.7%.

1-2) Aziridine-PEG-brush copolymer (poly(mPEG-co-AzPEG) synthesis)

m-PEGA and AzPEGA were copolymerized by free radical polymerization. Various molar ratios of mPEGA and AzPEG were dissolved in anhydrous toluene (monomer concentration = 0.35 M, molar ratio of mPEGA to AzPEG = 95:5, 90:10, 80:20, 70:30, 50:50, 30:70, 10 :90 and 0:100), then AIBN was added as an initiator such that the mole ratio of monomer to initiator was 50.

The mixture was degassed with dry nitrogen (N ₂ ) for 1 hour, and reacted at 70° C. for 20 hours under a dry nitrogen (N ₂ ) atmosphere. After polymerization, the solvent was removed with a rotary evaporator, and the remaining mixture was precipitated and washed twice with an excess of diethyl ether. Drying in vacuo gave the final product. The chemical structure of poly(mPEG-co-AzPEG) was confirmed using ¹ H-NMR spectroscopy. The degree of substitution of AzPEG (DSAz) was calculated using the integral of the characteristic peaks corresponding to the AzPEG brush and the mPEG brush. Similarly, the molecular weight was calculated using AIBN and the integral of the characteristic peaks corresponding to the two brushes.

Example 2

2-1) Solvent type adhesive

A solvent-based adhesive prepolymer, poly(2-ethylhexyl acrylate-co-acrylic acid) (poly(EHA-co-AA)), was synthesized by solution polymerization. Monomers, EHA, AA, and initiator AIBN were dissolved in ethyl acetate (EtAc) in a three-necked round bottom flask equipped with a mechanical stirrer and condenser, with a monomer to solvent ratio of 1:1 and EHA to AA ratio of 95 :5, and the initiator was dissolved in a ratio of 0.3wt% of the monomer. The mixture was stirred for 3 hours at 60° C. under dry nitrogen (N ₂ ) atmosphere for 1 hour. After polymerization, the mixture was cooled to room temperature and vacuum dried to obtain the product.

2-2) Water-based adhesive

The water-based adhesive prepolymer was synthesized by emulsion polymerization. First, 18.5 mL DI water, 2 g SDS and 53.3 g of total monomers consisting of 65% EHA, 20% n-BA, 10% MMA, 3% AA and 2% HEMA were vigorously mixed to form a pre-emulsion. has manufactured A buffered solution consisting of 0.33 g sodium carbonate and 0.084% sodium bicarbonate in 18.5 mL deionized water was placed in a three-necked flask under a nitrogen (N ₂ ) atmosphere and heated to 80°C. Then, 10% (v/v) of the total amount of the pre-emulsion and APS was added to the buffer and 10% of the total amount of the APS initiator solution (0.33 g APS in 1 mL of deionized water) was added to start the reaction. The rest of the pre-emulsion and initiator were added over 2 hours at 80°C. After further stirring for 1 hour, the reaction was terminated at room temperature. The mixture was cooled to room temperature and dried in vacuo to give the product.

Example 3

The adhesive prepolymer and poly(mPEG-co-AzPEG) crosslinker were dissolved in a solvent at 25% (w/v). The solvent for the solvent-based adhesive was THF, and the solvent for the water-based adhesive was deionized water. The amount of crosslinker was 1, 5 and 10 parts per 100 parts resin (phr). The solution was placed between overlapping areas (25 mm × 25 mm) of two substrates (75 mm × 25 mm), dried and thermally cured at 80 °C for 20 min in vacuum. Cooled at room temperature for 3 hours for further curing and allowed to equilibrate before mechanical testing.

A lap shear test was performed to measure adhesive properties, and the adhesive-bonded substrate was uniaxially stretched at 12 mm/min until the adhesive was completely broken, and a stress-strain plot was obtained (Model 3343, Instron). The shear modulus was calculated with an initial slope of 10%. The highest stress value obtained during the experiment was selected as the adhesive strength.

Example 4

Changes in rheological properties during curing were monitored using a rotating disk rheometer (Kinexus, Malvern). The prepolymer solution was placed on a sample stage and the storage modulus (G') and loss modulus (G") over time were measured at 80°C in a small amplitude oscillatory shear mode. The frequency and strain of the rotating disk were 1 Hz and 10%, respectively.

Experimental Example 1

As a method of synthesizing AzPEG brush copolymers (poly(mPEG-co-AzPEG), crosslinkers containing aziridine moieties have long been used as crosslinkers for a variety of polymeric materials. Like other crosslinkers, most are small molecules or limited number is an oligomer with aziridine groups of 2. On the other hand, having a larger and tunable number of aziridine groups in the polymer platform can allow greater control over the cross-link density at a given concentration, thus increasing the number of tunable aziridine groups. The indicated polymer can be regarded as a promising macro-crosslinking agent, which enables mass production by using radical copolymerization of acrylic monomers containing aziridine rather than post-modification of polymers having aziridine moieties and molecular weight And the degree of substitution was adjustable.

First, aziridine-PEG-acrylate (AzPEGA) was prepared by synthesizing an aziridine-containing monomer by a facile Michael addition reaction of 2-methylaziridine to poly(ethylene glycol) diacrylate (PEGDA). In this study, three different PEGDAs with molecular weights of 250, 400 and 700 g/mol were used to synthesize AzPEGA (i.e. AzPEGA250, AzPEGA400 and AzPEGA700), so the resulting polymers have different brush lengths. Then, poly(mPEG-co-AzPEG), a copolymer with AzPEGA and mPEG brushes, was synthesized by polymerizing AzPEGA and methoxy polyethyleneglycol acrylate (mPEG) as comonomers (Figure 1a). For simplicity, poly(mPEG-co-AzPEG) is referred to here as P(AzPEG) and the different molecular weights of AzPEGA are denoted as P(AzPEG250), P(AzPEG400) and P(AzPEG700).

The degree of substitution of aziridine groups (DS _Az ), which is the ratio of aziridine groups to the total number of brushes, was controlled simply by changing the ratio of AzPEGA to mPEGA to eight different combinations (DS1 to DS8), as shown in Table 1 below. Regardless of the molecular weight (MW) of AzPEGA, the DS _Az range of P(AzPEG) was similarly controlled up to about 82% (Table 1). Also, the length of the P(AzPEG) backbone remained constant regardless of DS _Az . These results demonstrated that the free radical copolymerization of mPEGA and AzPEGA is not hindered by the size and relative concentration of AzPEGA.

In addition, an advantage of the crosslinker of the present invention is the amphiphilic nature of PEG as a brush linker. The widespread presence of PEG makes all P(AzPEG) soluble in water as well as in most organic solvents. As a result, P(AzPEG) can be used as a crosslinking agent in both solvent-based and aqueous adhesive materials despite having a hydrophobic polyethylene backbone.

# DS _Az (%) AzPEGA250 AzPEGA400 AzPEGA700 DS 1 4 4 10 DS 2 8 6 14 DS 3 18 14 22 DS4 24 20 34 DS 5 36 36 47 DS 6 64 54 56 DS 7 74 64 66 DS8 82 78 74

Experimental Example 2

With the ability to efficiently control the structure of polymer brushes, P(AzPEG) is used to determine the rheological properties (mechanical and adhesive properties) of various adhesive materials, and P(AzPEG) is used for poly(ethyl hexyl, a well-known acrylic adhesive). acrylate-co-acrylic acid) (poly(ethyl hexyl acrylate-co-acrylic acid; poly(EHA-co-AA)) was used as a crosslinker. Due to the presence of carboxylic acid, poly(EHA-co-AA) can react with P(AzPEG) through a ring-opening nucleophilic reaction with aziridine.4 different DS _Az (DS1, DS3, DS5 and DS7) and molecular weight These different AzPEGs (AzPEG250, AzPEG400, AzPEG700) were used, and the concentration of P(AzPEG) was adjusted up to 10 phr.

Changes in rheological properties during the crosslinking reaction between poly(EHA-co-AA) and P(AzPEG) were investigated by measuring the storage modulus (G') and loss modulus (G”) during the crosslinking reaction (FIG. 3). As DS _Az increased, the increase in G' over time was more pronounced compared to G”. Also, G' increased with P(AzPEG) concentration at higher DS _Az (DS5 and DS7). These results clearly indicate that P(AzPEG) can effectively control the cross-linking density of poly(EHA-co-AA). The difference in G' was not noticeable at low DS _Az (DS1 and DS3), possibly because the limited number of aziridine groups do not confer significant mechanical strength.

The effect of AzPEG brush length was demonstrated by the maximum storage shear modulus ( _G'MAX ) after completion of the cross-linking reaction, which correlated with the shear modulus (Figure 4). At the same DS _Az , G'MAX decreased with the length of _AzPEG at all P(AzPEG) concentrations. This result confirmed that the length of the AzPEG brush had a significant effect on the cross-linking reaction. Increasing the brush length from AzPEG250 to AzPEG700 reduced the shape mobility of the longer AzPEG brushes, resulting in reduced responsiveness (Fig. 4).

Loss tangents calculated from the maximum G' and G” values, which represent the degree of conversion from a viscous precursor (sol) to a cross-linked structure (gel), also decreased significantly with increasing DS _Az and concentration for DS5 and DS7 (Fig. 4d–f). . Loss tangents showed no significant change at low DSAz (DS1 and DS3) consistent with low _G'MAX values. These results further confirmed the control of cross-linking density by P(AzPEG).

Experimental Example 3

The adhesive properties of poly(EHA-co-AA) cross-linked with P(AzPEG) were investigated to evaluate the effectiveness of P(AzPEG) in controlling aggregation and adhesion behavior in a sophisticated manner through the density and brush structure of reactive functional groups. The adhesive was cured between glass substrates and lap shear tests were performed to measure shear moduli and adhesive strength (FIG. 5).

It was evident that the shear modulus and adhesive strength gradually increased with increasing DS _Az regardless of the brush length, which showed a maximum at the highest DS _Az (DS7). These results imply that the increased cross-linking density and resulting increase in cohesive force promoted mechanical strength and helped prevent premature structural collapse. In addition, excessive cohesive force increase, which often leads to a weakening of the adhesive force at the substrate interface due to the cohesive region critically dominating the adhesive region, did not occur with increasing DS _Az , especially at low P(AzPEG) concentrations.

However, the maximum adhesive strength and shear modulus in DS7 appeared at the lowest P(AzPEG) concentration of 1 phr and decreased with P(AzPEG) concentration. The reduced adhesive strength at higher P(AzPEG) concentrations severely impairs adhesion, as higher DS _Az resulted in a greater degree of crosslinking, as evidenced by the higher G′ _MAX and loss tangent in FIG. 4 . It is highly likely that the adhesive force has substantially increased. However, at lower DS _Az , shear modulus and adhesive strength increased with P(AzPEG) concentration as the increased cohesive force was not high enough to impair adhesion. Nevertheless, by incorporating P(AzPEG) with different concentrations and DS _Az , the adhesive properties could be controlled over a wide range.

The increase in shear modulus and adhesive strength with DS _Az is more gradual for P( _AzPEG250 ), whereas higher DS _Az was more pronounced in In particular, in the case of P (AzPEG700), the shear modulus and adhesive strength did not show a significant increase as DS _Az was lower (DS1, DS3). This means that the cross-linking density controlled by P(AzPEG) has a direct effect on the adhesive properties, and it can be seen that a certain density of aziridine groups is required for more sufficient aggregation.

Although the adhesive strength was the lowest at the same DS _Az , it was the highest at P (AzPEG700), so the effect of the brush length was also confirmed (df in FIG. 5). Adhesion may be enhanced due to the ability of the longer brushes to deform through morphological flexibility at high strain and help maintain adhesion through larger chain entanglement with the surrounding polymer chains.

Experimental Example 4

The adhesive properties of P(AzPEG)-crosslinked poly(EHA-co-AA) were evaluated on poly(methyl methacrylate), a widely used acrylic plastic substrate, and compared to those evaluated on glass substrates (FIG. 6). First, at a given DS _Az , both the shear modulus and adhesive strength increased with P(AzPEG) regardless of the brush length, which was not the case for glass substrates, where the highest values were demonstrated at the lowest P(AzPEG) concentration. This is most likely due to the larger interfacial bonding to the polymer surface (polymer-polymer interactions) than to the glass surface (polymer-glass interactions), and the higher shear modulus to the plastic substrate at each DS _Az and P(AzPEG) concentration. and adhesive strength. As a result, it was confirmed that the increase in cohesive force by the concentration of DS _Az and P(AzPEG) continued to promote the adhesive force.

Similar to the glass substrate, the adhesive strength increased with the brush length to the plastic substrate as the maximum value increased from 81 kPa for P(AzPEG250) to 130 kPa for P(AzPEG700), despite having similar shear modulus (Fig. 6d-f). The ability of longer brushes to undergo more extensive structural changes allows greater resistance to externally applied forces and more extensive mechanical deformation.

Experimental Example 5

Water-based adhesives are mainly used because they are considered environmentally friendly and harmless compared to solvent-based adhesives containing organic solvents or other volatile organic compounds. In order to make a water-based adhesive, resin components including basic monomers and cross-linking agents must be completely dissolved or stably dispersed in an aqueous medium like an emulsion. In this regard, P(AzPEG) of the present invention has an advantage in that P(AzPEG) is easily dissolved in water due to the amphiphilic PEG brush. Use of P(AzPEG) as a crosslinker for poly(EHA-co-BA-co-MMA-co-AA-co-HEMA), an aqueous acrylic adhesive, on glass substrates to evaluate the performance of P(AzPEG) in an aqueous environment. did (FIG. 7).

For P(AzPEG250), maximum shear modulus and adhesive strength were obtained in the intermediate DSAz at all concentrations (1 phr and 5 phr in DS5 and 10 phr in DS3) (Figs. 7a and 7d). The decrease at higher DS _Az was more pronounced at 10 phr than at 5 phr. These results indicate that a higher amount of hydrophobic aziridine compared to hydrophilic PEG in aqueous conditions can shift the hydrophilic-lipophilic balance (HLB) downward, resulting in inefficient cross-linking (eg hydrophobic disruption). there is.

For P(AzPEG400), a similar biphasic trend was observed at 1 phr and 5 phr, with a maximum at the middle DS _Az . However, at 10%, both shear modulus and adhesive strength continued to increase with DS _Az (Figs. 7b and 7e). Due to the increased hydrophilicity with increased PEG brush length, P(AzPEG400) can accommodate a larger number of aziridines without compromising the hydrophilic-lipophilic balance (HLB). As a result, even at high DS _Az , the cross-linking density and consequent adhesive properties can continue to increase.

Considering the highest PEG content per weight, P(AzPEG700) was expected to have the highest HLB, but as the PEG brush length for AzPEG700 further increased, the shear modulus and adhesive strength increased with DS _Az up to DS5, but not DS7. , especially at the highest concentration of 10 phr (Figures 7c and 7f). This suggests that the structural mobility of the PEG brush at the highest DS _Az probably pushed the aziridine moiety inward through hydrophobic collapse to the point where a significant amount of aziridine became inaccessible to the crosslinking reaction and the cohesion decreased, resulting in Cohesion seems to decrease. Overall, these results indicate that the cohesive and adhesive properties of both solvent-type and water-based adhesives can be effectively controlled by adjusting the length of the PEG brush and the aziridine content in the P(AzPEG) crosslinker.

Accordingly, the present invention provides an aziridine capped poly(ethylene glycol) (PEG) brush, namely poly(AzPEG-co-mPEG) ('P(AzPEG)'), which is a multifunctional copolymer to prepare a crosslinker of an adhesive polymer and , while keeping the length of the main polymer backbone constant to control the crosslinking density through radical copolymerization of various ratios of aziridine-PEG-acrylate (AzPEGA) and methyl-PEG-acrylate (mPEGA) You can control the degree of displacement of the AzPEG brush. The crosslinker of the present invention controlled the length of the AzPEG brush to mediate the physical interaction with the macromer. In addition, it has the advantage that P(AzPEG) is soluble in both aqueous and organic solvents, including amphiphilic PEG.

Having described specific parts of the present invention in detail above, it is clear that these specific techniques are only preferred embodiments for those skilled in the art, and the scope of the present invention is not limited thereto. Accordingly, the substantial scope of the present invention will be defined by the appended claims and equivalents thereof.

The scope of the present invention is indicated by the following claims, and all changes or modifications derived from the meaning and scope of the claims and equivalent concepts thereof should be construed as being included in the scope of the present invention.

Claims (11)

A brush copolymer comprising a first brush monomer and a second brush monomer comprising an amphiphilic polymer having an aziridine terminal group,
The second brush monomer is polyethylene glycol methyl ether acrylate (poly (ethylene glycol) methyl ether acrylate), polyethylene glycol phenyl ether acrylate (poly (ethylene glycol) phenyl ether acrylate), polyethylene glycol methyl ether methacrylate (poly( ethylene glycol) methyl ether methacrylate), polyethylene glycol acrylate (poly (ethylene glycol) acrylate), and polyethylene glycol methacrylate (poly (ethylene glycol) methacrylate). According to claim 1,
The first brush monomer is a crosslinking agent, characterized in that the aziridine group is substituted at the terminal of polyethylene glycol. According to claim 1,
The crosslinking agent, characterized in that the molecular weight of the first brush monomer is 100 to 1,000 g / mol. According to claim 1,
A crosslinking agent, characterized in that the degree of substitution of the first brush monomer is 10% to 85% based on the total copolymer. A first step of preparing a first brush monomer by mixing an aziridine compound and an amphiphilic polymer; and
A second step of mixing and reacting the prepared first brush monomer, second brush monomer, and initiator to prepare a brush copolymer,
The second brush monomer is polyethylene glycol methyl ether acrylate (poly (ethylene glycol) methyl ether acrylate), polyethylene glycol phenyl ether acrylate (poly (ethylene glycol) phenyl ether acrylate), polyethylene glycol methyl ether methacrylate (poly( ethylene glycol) methyl ether methacrylate), polyethylene glycol acrylate (poly (ethylene glycol) acrylate), polyethylene glycol methacrylate (poly (ethylene glycol) methacrylate). According to claim 5,
In the second step, the molar ratio of the first brush monomer and the second brush monomer is 0 to 80: 20 to 100. According to claim 5,
The first step is a method for producing a crosslinking agent, characterized in that the amphiphilic polymer is mixed at a molar ratio of 1 to 1.5 based on the aziridine compound and stirred for 20 to 30 hours in a nitrogen atmosphere and at room temperature. According to claim 5,
In the second step, the concentration of the first and second brush monomers is 0.1 to 1.0 M. According to claim 5,
In the first step, the molecular weight of the amphiphilic polymer is 100 to 1,000 g / mol. Comprising a crosslinking agent and a prepolymer according to any one of claims 1 to 4,
The prepolymer is an adhesive comprising an aqueous or solvent-type prepolymer. According to claim 10,
The adhesive comprising 1 to 20 phr (parts per hundred resin) based on 100 phr of the crosslinking agent.

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