Block copolymer

Abstract

Provided is a lactic acid-based block copolymer which is biodegradable while having excellent mechanical properties.

Claims

1. A block copolymer, comprising a first block and a second block, wherein: the first block is a lactic acid-polymerized repeating unit; the second block is a 3-hydroxypropionic acid (3-HP)-polymerized repeating unit; and the first block and the second block are linked to each other via a group —X.sub.1-L-X.sub.2—, wherein: X.sub.1 and X.sub.2 are each independently an ester bond, an amide bond, a urethane bond, a urea bond, or a carbonate bond; and L is a substituted or unsubstituted C.sub.1-10 alkylene, a substituted or unsubstituted C.sub.6-60 arylene, or a substituted or unsubstituted C.sub.2-60 heteroarylene containing one or more heteroatoms selected from the group consisting of O, N, Si, and S.

2. The block copolymer of claim 1, wherein a number (m) of lactic acid-polymerized repeating units is an integer from 1 to 10,000, and a number (n) of 3-HP-polymerized repeating units is an integer from 1 to 10,000.

3. The block copolymer of claim 2, wherein a ratio of n to m is 1:1 to 1:10.

4. The block copolymer of claim 1, wherein: the first block is a lactic acid-polymerized repeating unit of the following Chemical Formula 3; and the second block is a 3-HP-polymerized repeating unit of the following Chemical Formula 4: ##STR00006##

5. A block copolymer, comprising a first block and a second block, wherein: the first block is a lactic acid-polymerized repeating unit; the second block is a 3-hydroxypropionic acid (3-HP)-polymerized repeating unit; and the block copolymer has the following Chemical Formula 1: ##STR00007## wherein in Chemical Formula 1: X.sub.1 and X.sub.2 are each independently an ester bond, an amide bond, a urethane bond, a urea bond, or a carbonate bond; L is a substituted or unsubstituted C.sub.1-10 alkylene, a substituted or unsubstituted C.sub.6-60 arylene, or a substituted or unsubstituted C.sub.2-60 heteroarylene including one or more heteroatoms selected from the group consisting of O, N, Si, and S; and n and m are each independently an integer from 1 to 10,000.

6. A block copolymer, comprising a first block and a second block, wherein: the first block is a lactic acid-polymerized repeating unit; the second block is a 3-hydroxypropionic acid (3-HP)-polymerized repeating unit; and the block copolymer has the following Chemical Formula 2: ##STR00008## wherein in Chemical Formula 2: L is a substituted or unsubstituted C.sub.1-10 alkylene, a substituted or unsubstituted C.sub.6-60 arylene, or a substituted or unsubstituted C.sub.2-60 heteroarylene including one or more heteroatoms selected from the group consisting of O, N, Si, and S; and n and m are each independently an integer from 1 to 10,000.

7. The block copolymer of claim 5, wherein in Chemical Formula 1, L is a linear C.sub.8 alkylene.

8. The block copolymer of claim 5, wherein in Chemical Formula 1, a ratio of n to m is 1:1 to 1:10.

9. The block copolymer of claim 1, wherein the block copolymer has a weight average molecular weight of 1000 g/mol or more.

10. The block copolymer of claim 1, wherein the block copolymer has a first peak at a melting point (Tm) of 60° C. to 80° C. and a second peak at a melting point (Tm) of 125° C. to 150° C. in DSC (Differential Scanning Calorimeter) patterns.

11. The block copolymer of claim 1, wherein the block copolymer has a tensile strength of 40 MPa to 55 MPa.

12. The block copolymer of claim 1, wherein the block copolymer has a tensile modulus of 1 GPa to 3.3 GPa.

13. The block copolymer of claim 1, wherein the block copolymer has an elongation at break of 1.8% to 540%.

14. The block copolymer of claim 2, wherein a ratio of n to m is 1:1.5 to 1:9.

15. The block copolymer of claim 2, wherein a ratio of n and m is 1:2 to 1:8.

16. The block copolymer of claim 1, wherein a molar ratio of lactic acid-polymerized repeating units to 3-HP-polymerized repeating units is 1:0.1 to 1:1.

17. The block copolymer of claim 1, wherein a molar ratio of lactic acid-polymerized repeating units to 3-HP-polymerized repeating units is 1:0.3 to 1:0.9.

18. The block copolymer of claim 1, wherein a molar ratio of lactic acid-polymerized repeating units to 3-HP-polymerized repeating units is 1:0.4 to 1:0.7.

19. The block copolymer of claim 1, wherein the block copolymer is prepared by reacting polylactic acid and poly(3-hydroxypropionic acid) to form the block copolymer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIGS. 1A and 1B are graphs showing NMR results of analyzing HDI (FIG. 1A) and a block copolymer of Example 1 (FIG. 1B); and

(2) FIG. 2 is a graph showing DSC results of analyzing PLA, P3HP, and the block copolymer of Example 1.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(3) The present invention will be described in more detail in the following examples. However, the following examples are for illustrative purposes only, and the present invention is not intended to be limited by the following examples.

Example 1

(4) To a 500 mL round-bottom flask, 11 g (number of moles: 0.055 mmol, MW: 200,000 g/mol) of polylactic acid, 2.75 g (number of moles: 0.028 mmol, MW: 100,000 g/mol) of poly(3-hydroxypropionic acid), and 50 ml of toluene were introduced, and stirred at 180° C. for 1 hour. Thereafter, 1,6-hexamethylene diisocyanate (HDI, number of moles: 0.110 mmol, MW: 168.2 g/mol) was added thereto, and allowed to react at 180° C. for 30 minutes. Thereafter, the reaction product was dissolved in chloroform, and then extracted with methanol to recover a block copolymer of the following Chemical Formula 5.

(5) ##STR00004##

Comparative Example 1

(6) To a 500 mL round-bottom flask, 11 g (number of moles: 0.055 mmol, MW: 200,000 g/mol) of polylactic acid and 50 ml of toluene were introduced, and stirred at 180° C. for 1 hour. To the round-bottom flask, 1,6-hexamethylene diisocyanate (HDI, number of moles: 0.110 mmol, MW: 168.2 g/mol) was added thereto, and allowed to react at 175° C. for 40 minutes under a nitrogen atmosphere. Thereafter, the reaction product was dissolved in chloroform, and then extracted with methanol to recover a copolymer of the following Chemical Formula 6.

(7) ##STR00005##

(8) Evaluation

(9) 1) NMR (Nuclear Magnetic Resonance) Analysis

(10) NMR analysis was performed at room temperature using an NMR spectrometer containing Varian Unity Inova (500 MHz) equipped with a 5 mm triple-resonance probe. HDI and the block copolymer of Example 1 were used as analytes after being diluted with a solvent (CDCl.sub.3) for NMR measurement at a concentration of about 10 mg/ml, respectively, and chemical shifts were expressed as ppm.

(11) FIGS. 1A and 1B are graphs showing NMR results of analyzing HDI (FIG. 1A) and the block copolymer of Example 1 (FIG. 1B). According to FIGS. 1A and 1B, the NMR peaks of HDI were shifted to the left.

(12) Further, according to the NMR result of the block copolymer of Example 1, a peak corresponding to the N—H bond was observed at about 3.1 ppm, indicating that the PLA block and the P3HP block were linked via a urethane bond.

(13) 2) DSC (Differential Scanning Calorimeter) Analysis

(14) DSC analysis was performed using a PerkinElmer DSC 800 instrument. PLA, P3HP, and the block copolymer of Example 1 as analytes were heated using the instrument at a heating rate of 10° C. per minute from 25° C. to 250° C. under a nitrogen atmosphere, respectively, and then cooled at a cooling rate of −10° C. per minute from 250° C. to −50° C., and heated again at a heating rate of 10° C. per minute from −50° C. to 250° C. to obtain endothermic curves.

(15) FIG. 2 is a graph showing DSC results of analyzing PLA, P3HP, and the block copolymer of Example 1. Further, the resulting graph of FIG. 2 was analyzed to determine a glass transition temperature (Tg), a melting temperature (Tm), and an enthalpy of melting (ΔH.sub.melt) of each compound, which are shown in Table 1 below.

(16) TABLE-US-00001 TABLE 1 Tg (° C.) Tm (° C.) ΔH.sub.melt (J/g) PLA 61.85 145.37 2.669 P3HP −25.92 66.99 54.68 Example 1 34.22 62.03 9.296 139.62 12.21

(17) According to Table 1, it was confirmed mat the copolymer of Example 1 showed the melting temperatures of both PLA and P3HP. Random copolymers show no crystallinity, and thus no melting temperatures are observed, whereas block copolymers show melting temperatures of respective blocks. Accordingly, the DSC analysis results confirmed that the compound of Example 1 was a block copolymer.

(18) Further, Example 1 showed a glass transition temperature of 34.22° C. which is between the glass transition temperatures of PLA and P3HP.