Block copolymer

Abstract

A block copolymer, a method for preparing a block copolymer, a resin composition, and a film are provided. The block copolymer can be useful in inhibiting complete separation of the hard segment even under a severe high-temperature condition by increasing the chemical cross-linking density around the hard segment without causing an increase in glass transition temperature of the hard segment, thereby maintaining high-temperature durability.

Claims

1. A cured product of a curable resin composition, wherein the curable resin composition comprises a block copolymer comprising: a hard segment having a glass transition temperature of 25 C. or more; and a soft segment having a glass transition temperature of 10 C. or less, wherein the soft segment comprises a polymerization unit derived from a cross-linkable monomer, and the polymerization unit derived from the cross-linkable monomer has a higher concentration in a region adjacent to the hard segment than in a region which is not adjacent to the hard segment, wherein the cured product of the curable resin composition has a phase-separated structure comprising a shell layer and a spherical domain, wherein the shell layer comprises the soft-segment, and the spherical domain comprises the hard segment, and the shell layer has a higher cross-linking density in a region adjacent to the hard segment than in a region which is not adjacent to the hard segment.

2. The cured product of claim 1, wherein the hard segment comprises a polymerization unit derived from a methacrylic monomer.

3. The cured product of claim 1, wherein the soft segment comprises polymerization units derived from an acrylic monomer and a cross-linkable monomer.

4. The cured product of claim 1, wherein the glass transition temperature of the hard segment is in a range of 30 C. to 200 C.

5. The cured product of claim 1, wherein the glass transition temperature of the soft segment is in a range of 80 C. to 0 C.

6. The cured product of claim 1, wherein the cross-linkable monomer comprises at least one functional group selected from the group consisting of a hydroxyl group, a carboxyl group, an epoxy group, a glycidyl group, an isocyanate group, an amide group, an amino group, and an alkoxysilyl group.

7. The cured product of claim 1, wherein the content of the hard segment is in a range of 5 to 25% by weight, based on the total weight of the block copolymer.

8. The cured product of claim 1, which has a number average molecular weight of 5,000 to 500,000.

9. The cured product of claim 1, which has a molecular weight distribution of greater than 1 and 3 or less.

10. A film comprising the cured product of claim 1.

11. The film of claim 10, wherein the film is a pressure-sensitive adhesive film.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic diagram showing a block copolymer according to one exemplary embodiment of the present application; and

(2) FIG. 2 is a schematic diagram showing a phase-separated structure including spherical domains occurring when a phase-separated film is formed using the block copolymer according to one exemplary embodiment of the present application.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

(3) Hereinafter, exemplary embodiments of the present application will be described in detail. However, the present application is not limited to the embodiments to be disclosed below, but can be implemented in various forms. The following embodiments are described in order to enable those of ordinary skill in the art to embody and practice the present application.

Preparation of Copolymer

Preparative Example 1

(4) 50 g of methyl methacrylate (MMA) and 50 g of n-butyl methacrylate (BMA) as monomers used to prepare a hard segment, 100 g of an ethyl acetate (EA) solvent, and 0.65 g of an ethyl 2-bromoisobutyrate (EBiB) ATRP initiator was added to a 500-mL round-bottom flask, and the flask was sealed. A reaction flask was bubbled with nitrogen for 30 minutes to remove oxygen, and dipped in an oil bath which is heated at 60 C. 0.24 g of CuBr was put into a separately arranged 10-mL vial to remove oxygen, and 0.44 g of N,N,N,N,N-pentamethyldiethylenetriamine (PMDETA) and 7 mL of oxygen-free N,N-dimethylformamide (DMF) were then added to prepare an ATRP catalyst solution. The catalyst solution prepared under a nitrogen atmosphere was put into the flask, and a reaction was initiated. The previously prepared flask was bubbled with nitrogen for 30 minutes to remove oxygen from the solution, and then heated at 60 C. in an oil bath. After 7 hours of heating, the flask was opened and exposed to oxygen, and a reaction was then terminated. As a result, a P(MMA-co-BMA) macroinitiator (MI1) having a monomer conversion rate of 72%, a number average molecular weight (Mn) of 26,000, a PDI (Mw/Mn) of 1.22, and a glass transition temperature of 55 C. was prepared. 30 g of MI1 purified by precipitation with methanol, 27 g of n-butyl acrylate (BA), 15 g of 4-hydroxybutyl acrylate (HBA), and 72 g of EA were put into a 1 L reactor, and bubbled with nitrogen for 30 minutes to remove oxygen. The reaction temperature was controlled to be 60 C. while maintaining a nitrogen atmosphere. A catalyst solution including 0.016 g of CuBr.sub.2, 0.052 g of tris(2-pyridylmethyl)amine (TPMA), and 1.4 mL of DMF was prepared and put into a reactor, and 0.75 g of tin dioctoate was added as a catalyst reducing agent to initiate a reaction. The reaction conversion rate was measured using .sup.1H-NMR, and, when the conversion rate of BA reached 30%, a mixture of 250 g of BA and 250 g of EA from which oxygen was previously removed was put into a reaction bath, and the temperature of the reaction bath was maintained at 60 C. After 15 hours, the reaction was terminated, and a P(MMA-co-BMA)-b-P(BA-co-HBA) copolymer solution in which cross-linking functional groups are unevenly distributed around a hard segment was prepared. In this case, it was revealed that the copolymer had a monomer conversion rate of 68%, a number average molecular weight (Mn) of 189,000, a PDI (Mw/Mn) of 1.31, and a P(MMA-co-BMA) content (.sup.1H-NMR) of 14%.

Preparative Example 2

(5) 30 g of MI1 prepared in Preparative Example 1, 30 g of BA, 20 g of 2-hydroxypropyl methacrylate (HPMA), and 65 g of EA were put into a 1 L reactor, and bubbled with nitrogen for 30 minutes to remove oxygen. The reaction temperature was controlled to be 60 C. while maintaining a nitrogen atmosphere. A catalyst solution including 0.016 g of CuBr.sub.2, 0.052 g of TPMA, and 1.4 mL of DMF was prepared and put into a reactor, and 0.75 g of tin dioctoate was added as a catalyst reducing agent to initiate a reaction. The reaction conversion rate was measured using .sup.1H-NMR, and, when the conversion rate of BA reached 50%, a mixture of 250 g of BA and 250 g of EA from which oxygen was previously removed was put into a reaction bath, and the temperature of the reaction bath was maintained at 60 C. After 15 hours, the reaction was terminated, and a P(MMA-co-BMA)-b-P(BA-co-HPMA) copolymer solution in which cross-linking functional groups are unevenly distributed around a hard segment was prepared. In this case, it was revealed that the copolymer had a monomer conversion rate of 65%, a number average molecular weight (Mn) of 163,000, a PDI (Mw/Mn) of 1.34, and a P(MMA-co-BMA) content (.sup.1H-NMR) of 13%.

Preparative Example 3

(6) 50 g of MMA, 84 g of cyclohexyl methacrylate (CHMA), 134 g of EA, 0.65 g of EBiB, 0.24 g of CuBr, and 0.44 g of PMDETA were added, and a P(MMA-co-CHMA) macroinitiator (MI2) (having a monomer conversion rate of 79%, an Mn of 33,000, a PDI (Mw/Mn) of 1.18, and a Tg of 91 C.) was prepared in the same manner as in Preparative Example 1. 30 g of MI2 purified by precipitation with methanol, 58 g of 2-ethylhexyl acrylate (EHA), 12 g of 4-hydroxybutyl acrylate (HBA), and 100 g of EA were put into a 1 L reactor, and bubbled with nitrogen for 30 minutes to remove oxygen. The reaction temperature was controlled to be 60 C. while maintaining a nitrogen atmosphere. A catalyst solution including 0.016 g of CuBr.sub.2, 0.052 g of TPMA, and 1.4 mL of DMF was prepared and put into a reactor, and 0.75 g of tin dioctoate was added as a catalyst reducing agent to initiate a reaction. The reaction conversion rate was measured using .sup.1H-NMR, and, when the conversion rate of BA reached 50%, a mixture of 250 g of BA and 250 g of EA from which oxygen was previously removed was put into a reaction bath, and the temperature of the reaction bath was maintained at 60 C. After 15 hours, the reaction was terminated, and a P(MMA-co-CHMA)-b-P(EHA-co-HBA) copolymer solution in which cross-linking functional groups are unevenly distributed around a hard segment was prepared. In this case, it was revealed that the copolymer had a monomer conversion rate of 75%, a number average molecular weight (Mn) of 260,000, a PDI (Mw/Mn) of 1.42, and a P(MMA-co-CHMA) content (.sup.1H-NMR) of 11%.

Preparative Example 4

(7) 100 g of MMA, 100 g of EA, 0.65 g of EBiB, 0.24 g of CuBr, and 0.44 g of PMDETA were added, and a PMMA macroinitiator (MI3) (having a monomer conversion rate of 75%, an Mn of 25,500, a PDI (Mw/Mn) of 1.21, and a Tg of 105 C.) was prepared in the same manner as in Preparative Example 1. 30 g of MI3 purified by precipitation with methanol, 92 g of BA, 15 g of glycidyl methacrylate (GMA), and 107 g of EA were put into a 1 L reactor, and bubbled with nitrogen for 30 minutes to remove oxygen. The reaction temperature was controlled to be 60 C. while maintaining a nitrogen atmosphere. A catalyst solution including 0.016 g of CuBr.sub.2, 0.052 g of TPMA, and 1.4 mL of DMF was prepared and put into a reactor, and 0.75 g of tin dioctoate was added as a catalyst reducing agent to initiate a reaction. The reaction conversion rate was measured using .sup.1H-NMR, and, when the conversion rate of BA reached 30%, a mixture of 185 g of BA and 185 g of EA from which oxygen was previously removed was put into a reaction bath, and the temperature of the reaction bath was maintained at 60 C. At this point, the conversion rate of GMA was 67%. After 15 hours, the reaction was terminated, and a PMMA-b-P(BA-co-GMA) copolymer solution in which cross-linking functional groups are unevenly distributed around a hard segment was prepared. In this case, it was revealed that the copolymer had a monomer conversion rate of 72%, a number average molecular weight (Mn) of 194,000, a PDI (Mw/Mn) of 1.33, and a PMMA content (.sup.1H-NMR) of 13%.

Preparative Example 5

(8) 30 g of MI3 prepared in Preparative Example 4, 92 g of BA, 15 g of N,N-dimethylaminoethyl methacrylate (DMAEA), 107 g of EA, 0.016 g of CuBr.sub.2, 0.052 g of TPMA, and 0.75 g of tin dioctoate were added, and a reaction was performed in the same manner as in Preparative Example 4. When the conversion rates of BA and DMAEA reached approximately 30% and 65%, respectively, 185 g of BA and 185 g of EA were further added to prepare a PMMA-b-P(BA-co-DMAEA) copolymer solution (having a monomer conversion rate of 77%, an Mn of 182,000, a PDI (Mw/Mn) of 1.36, and a PMMA content (.sup.1H-NMR) of 12%).

Comparative Preparative Example 1

(9) 30 g of MI1 prepared in Preparative Example 1, 277 g of BA, 15 g of HBA, and 292 g of EA were put into a 1 L reactor, and bubbled with nitrogen for 30 minutes to remove oxygen. The reaction temperature was controlled to be 60 C. while maintaining a nitrogen atmosphere. A catalyst solution including 0.016 g of CuBr.sub.2, 0.052 g of TPMA, and 1.4 mL of DMF was prepared and put into a reactor, and 0.75 g of tin dioctoate was added as a catalyst reducing agent to initiate a reaction. After 15 hours, the reaction was terminated, and a P(MMA-co-BMA)-b-P(BA-co-HBA) copolymer solution in which cross-linking functional groups are uniformly distributed in a soft segment was prepared. In this case, it was revealed that the copolymer had a monomer conversion rate of 69%, a number average molecular weight (Mn) of 191,000, a PDI (Mw/Mn) of 1.31, and a P(MMA-co-BMA) content (.sup.1H-NMR) of 14%.

Comparative Preparative Example 2

(10) 30 g of MI3 prepared in Preparative Example 4, 277 g of BA, 15 g of GMA, and 292 g of EA were put into a 1 L reactor, and bubbled with nitrogen for 30 minutes to remove oxygen. The reaction temperature was controlled to be 60 C. while maintaining a nitrogen atmosphere. A catalyst solution including 0.016 g of CuBr.sub.2, 0.052 g of TPMA, and 1.4 mL of DMF was prepared and put into a reactor, and 0.75 g of tin dioctoate was added as a catalyst reducing agent to initiate a reaction. After 15 hours, the reaction was terminated, and a PMMA-b-P(BA-co-GMA) copolymer solution in which cross-linking functional groups are uniformly distributed in a soft segment was prepared. In this case, it was revealed that the copolymer had a monomer conversion rate of 69%, a number average molecular weight (Mn) of 191,000, a PDI (Mw/Mn) of 1.31, and a PMMA content (.sup.1H-NMR) of 14%.

Comparative Preparative Example 3

(11) A mixture of 15 g of MMA, 15 g of BMA, 190 g of BA, 10 g of HBA, and 292 g of EA was put into a 1 L reactor, and bubbled with nitrogen for 30 minutes to remove dissolved oxygen. The reaction temperature was controlled to be 70 C., and 0.18 g of a thermal polymerization initiator, 2,2-azobisisobutyronitrile (AIBN), was added, and then reacted for 15 hours. Then, the reaction was terminated. As a result, a random copolymer solution was prepared. In this case, it was revealed that the random copolymer had a monomer conversion rate of 96%, a number average molecular weight (Mn) of 98,000, a PDI (Mw/Mn) of 5.82, and a PMMA content (.sup.1H-NMR) of 13%.

Comparative Preparative Example 4

(12) 100 g of styrene (S), 100 g of EA, and 0.65 g of EBiB were put into a round-bottom flask, and the flask was sealed. A reaction flask was bubbled with nitrogen for 30 minutes to remove oxygen, and dipped in an oil bath which is heated at 60 C. 0.24 g of CuBr was put into a separately arranged 10-mL vial to remove oxygen, and 0.44 g of PMDETA and 7 mL of oxygen-free DMF were then added to prepare an ATRP catalyst solution. The catalyst solution prepared under a nitrogen atmosphere was put into the flask, and a reaction was initiated. The previously prepared flask was bubbled with nitrogen for 30 minutes to remove oxygen from the solution, and then heated at 60 C. in an oil bath. After 7 hours of heating, the flask was opened and exposed to oxygen, and a reaction was then terminated. As a result, a PS macroinitiator (MI4) having a monomer conversion rate of 70%, a number average molecular weight (Mn) of 23,800, a PDI (Mw/Mn) of 1.24, and a glass transition temperature of 100 C. was prepared. A reaction was performed in the same manner as in Preparative Example 4 to prepare a PS-b-P(BA-co-GMA) copolymer solution in which cross-linking functional groups are unevenly distributed around a hard segment, except that MI4 purified by precipitation with methanol was used instead of MI3. In this case, it was revealed that the copolymer had a monomer conversion rate of 77%, a number average molecular weight (Mn) of 134,000, a PDI (Mw/Mn) of 2.75, and a PS content (.sup.1H-NMR) of 12%.

Preparation of Cross-Linkable Resin Composition and Phase-Separated Film

Example 1

(13) 10 g (based on the solid content) of the block copolymer prepared in Preparative Example 1, 0.2 g of toluene diisocyanate as a cross-linking agent, and 0.01 g of dibutyltin dilaurate as a curing accelerator, were added, and EA was then added as a solvent to prepare a solution having a solid content of 30%. A release-treated surface of a poly(ethylene terephthalate) (PET) film (thickness: 38 m, MRF-38 commercially available from Mitsubishi Corporation) release-treated with a silicon compound was coated with the solution so that a coating layer could have a thickness after drying of approximately 25 m, and dried at 130 C. for 30 minutes in a convection oven. Phase separation and cross-linking were simultaneously induced in a drying process. A surface of the test sample prepared thus was observed in a phase mode of an atomic force microscopy (AFM) to obtain an image. As a result, it could be seen that a spherical phase was formed properly.

Examples 2 and 3

(14) Cross-linked phase-separated films in which a spherical phase was formed properly were prepared in the same manner as in Example 1, except that the block copolymers prepared in Preparative Examples 2 and 3 were used, respectively, instead of the block copolymer of Preparative Example 1 used in Example 1.

Examples 4 and 5

(15) 10 g (based on the solid content) of the block copolymer prepared in Preparative Example 4 or 5, 0.2 g of a succinic anhydride, and 0.03 g of 2-methylimidazole were added, and EA was then added as a solvent to prepare a solution having a solid content of 30%. A release-treated surface of a PET film (thickness: 38 m, MRF-38 commercially available from Mitsubishi Corporation) release-treated with a silicon compound was coated with the solution so that a coating layer could have a thickness after drying of approximately 25 m, and dried at 130 C. for 30 minutes in a convection oven. Phase separation and cross-linking were simultaneously induced in a drying process. As a result, a phase-separated film having a spherical phase formed therein was prepared.

Comparative Example 1

(16) A composition solution having a solid content of 30% was prepared in the same manner as in Example 1, except that the block copolymer prepared in Comparative Preparative Example 1 was used. Thereafter, a phase-separated film was prepared using the solution in the same manner as in Example 1.

Comparative Example 2

(17) A composition solution having a solid content of 30% was prepared in the same manner as in Example 4, except that the block copolymer prepared in Comparative Preparative Example 2 was used. Thereafter, a phase-separated film was prepared using the solution in the same manner as in Example 1.

Comparative Example 3

(18) A composition solution having a solid content of 30% was prepared in the same manner as in Example 4, except that the random copolymer prepared in Comparative Preparative Example 3 was used. Thereafter, a film was prepared using the solution in the same manner as in Example 1. In this case, no fine phase was observed due to the use of the random copolymer resin.

Comparative Example 4

(19) A composition solution having a solid content of 30% was prepared in the same manner as in Example 4, except that the block copolymer prepared in Comparative Preparative Example 4 was used. Thereafter, a film was prepared using the solution in the same manner as in Example 1. In this case, no spherical phase formation was observed since the copolymer had a relatively high molecular weight distribution value (Mw/Mn).

(20) Evaluation of Durability Upon Application as Pressure-Sensitive Adhesive for Polarizing Plates

(21) 1. Preparation of Polarizing Plate Specimen

(22) A pressure-sensitive adhesive layers was formed between a glass substrate and a polarizing plate using the resin composition including each of the block copolymers and random copolymers prepared in Examples 1 and 2 and Comparative Examples 1 and 3. Each of the resin films prepared in Example 1 and Comparative Examples 1 and 3 was attached to the polarizing plate to prepare a polarizing plate specimen. The polarizing plate specimen was cut into pieces having a size of 180 cm320 cm (lengthwidth), and attached to a commercially available LCD panel having a thickness of 0.7 mm. Thereafter, the panel was stored at 50 C. and 5 atmospheric pressures for 20 minutes to prepare a sample polarizing plate.

(23) 2. Evaluation of Heat-Resistant Durability

(24) To evaluate heat-resistant durability of the sample polarizing plate prepared thus, the prepared sample polarizing plate was kept for approximately 300 hours under a temperature condition of 90 C., and formation of bubbles on a surface of a pressure-sensitive adhesive and peeling of the pressure-sensitive adhesive were observed with the naked eye. The heat-resistant durability was evaluated according to the following evaluation criteria.

(25) <Criteria for Evaluation of Heat-Resistant Durability>

(26) : There are no bubble formation and peeling

(27) : Bubble formation and peeling are slightly observed

(28) x: Bubble formation and peeling are slightly observed in larger numbers

(29) The durability evaluation results are listed in the following Table 1.

(30) TABLE-US-00001 TABLE 1 Type of polymer Tg of hard segment Durability Example 1 Block polymer 55 C. Example 2 Block polymer 55 C. Comparative Block polymer 55 C. x Example 1 Comparative Random polymer x Example 3

(31) Evaluation of Durability Upon Application as a Pressure-Sensitive Adhesive for Attaching Hard Coating Layer-Protective Film Used During ITO Glass Annealing

(32) Each of the compositions including the block copolymers prepared in Examples 3, 4 and 5 and Comparative Examples 2 and 4 was applied to a pressure-sensitive adhesive for attaching a film used to protect a hard coating layer of ITO glass. Each of the films prepared using the resin compositions prepared in Examples 3, 4 and 5 and Comparative Examples 2 and 4 was attached to a hard coating layer opposite to the hard coating layer of ITO glass, and subjected to ITO annealing at 150 C. for an hour.

(33) The criteria for evaluation of durability were applied in the same manner as in the pressure-sensitive adhesive for polarizing plates. The durability evaluation results are listed in the following Table 2.

(34) TABLE-US-00002 TABLE 2 Type of polymer Tg of hard segment Durability Example 3 Block polymer 91 C. Example 4 Block polymer 105 C. Example 5 Block polymer 105 C. Comparative Block polymer 105 C. x Example 2 Comparative Block polymer 100 C. x Example 4

(35) As listed in Table 2, it was revealed that the block copolymer according to one exemplary embodiment of the present application maintained excellent durability and exhibited higher durability than the random copolymer due to the presence of the physical cross-linking points since the hard segment was not completely dismantled even at a severe temperature condition higher than the glass transition temperature of the hard segment.