Title Page
Contents
요약 11
Chapter 1. Introduction 12
Chapter 2. Theoretical background 15
2.1. Biodegradable polymers 15
2.2. Polylactide 18
2.2.1. Synthesis of PLA 20
2.2.2. Properties of PLA 22
2.2.3. Stereochemical PLA 24
2.3. Polyether polyol 25
2.3.1. Synthesis of Polyether polyol 26
2.3.2. Properties of polyether polyol 27
2.4. Poly(propylene carbonate) 29
2.4.1. Synthesis of PPC 30
2.4.2. Properties of PPC 32
2.5. Surface energy 34
2.6. Langmuir-Blodgett technique 36
2.6.1. Surface pressure-area isotherms 37
2.6.2. Kinetic curve 38
2.7. Degradation of polymers 40
2.8. Degradation control of biodegradable polymers 41
2.8.1. Chemical modifications 43
2.8.2. Physical modifications 45
Chapter 3. Enzymatic degradation of triblock copolymers of polylactide and polyether polyol 46
3.1. Experimental 46
3.1.1. Materials 46
3.1.2. Synthesis 47
3.1.3. Measurements 48
3.2. Results and discussion 49
3.2.1. Chemical compositions 49
3.2.2. Thermal properties 51
3.2.3. Surface wettability 53
3.2.4. Surface pressure-area isotherms of monolayers 55
3.2.5. Enzymatic degradations 57
3.3. Conclusions 62
Chapter 4. Mechanical, thermal properties and degradation behaviors of polylactide/poly(propylene carbonate) blends 63
4.1. Experimental 63
4.1.1. Materials 63
4.1.2. Blend preparation 64
4.1.3. Measurements 65
4.2. Results and discussion 66
4.2.1. Mechanical properties 66
4.2.2. Thermal properties 68
4.2.3. Hydrolytic and enzymatic degradations 70
4.2.4. Morphological study 78
4.3. Conclusions 80
References 81
Table 1. Properties of PLA 23
Table 2. Properties of polyether polyol 28
Table 3. Properties of PPC 33
Table 4. Mn and composition of synthesized copolymers 50
Table 5. Characteristics of synthesized copolymers and blend 52
Table 6. Surface energies of liquids 54
Table 7. Contact angles and estimated surface energies of synthesized l-PLA and copolymers 54
Table 8. Mechanical properties of l-PLA, PPC, and l-PLA/PPC blend films 67
Table 9. Thermal properties of l-PLA, PPC, and l-PLA/PPC blends 69
Table 10. Thermal properties of l-PLA, PPC, and l-PLA/PPC blends after hydrolytic (pH 11) and enzymatic (1 mg proteinase K) degradations for 42... 76
Figure 1. Cyclic biological process of biodegradable polymers. 16
Figure 2. Classification of biodegradable polymers based on their resources. 17
Figure 3. Schematic representation of PLA production. 19
Figure 4. Low carbon footprint of PLA and its applications. 19
Figure 5. Synthetic tools for polymerization of PLA. 21
Figure 6. Stereoisomeric forms of lactides. 24
Figure 7. Growth of domestic emission trading volume and price. 29
Figure 8. Synthetic tools for synthesis of PPC. 31
Figure 9. A sessile drop of liquid on a solid showing a three-phase force line. 35
Figure 10. Polymeric monolayers on a water subphase. 36
Figure 11. Surface pressure-area (π-A) isotherm of monolayer. 37
Figure 12. Schematic representation of hydrolysis of polymeric monolayers on the water subphase. 39
Figure 13. Modification methods of PLA. 42
Figure 14. Types of copolymerization. 44
Figure 15. ¹H-NMR spectra of (A) polyether polyol and (B) 2LLA-87. 50
Figure 16. DSC curves of (A) synthesized l-PLA with different Mn, and (B) synthesized copolymers, polyether polyol, and blend. 52
Figure 17. Contact angle images of synthesized polymers. 53
Figure 18. Pressure-area isotherms of l-PLA and copolymer monolayers on subphase at a pH of 6.8. 56
Figure 19. Area ratio vs time for monolayer films maintained at (A) 3 mN/m and (B) 5 mN/m on subphase with 0.02 mg of proteinase K. 59
Figure 20. AFM images and corresponding line profiles of homopolymers and copolymers before/after enzymatic degradation:... 61
Figure 21. Chemical structures of l-PLA and PPC. 63
Figure 22. Stress-strain curves of l-PLA, PPC, and l-PLA/PPC blend films. 67
Figure 23. (A) Tg and (B) Tm of DSC curves of l-PLA, PPC, and l-PLA/PPC blends. 69
Figure 24. (A) Stress-strain curves of l-PLA/PPC (20/80) blend with different degradation times, (B) % weight loss, (C) tensile strength, and (D)... 73
Figure 25. (A) Stress-strain curves of l-PLA/PPC (80/20) blend with different degradation times, (B) % weight loss, (C) tensile strength, and (D)... 74
Figure 26. Area ratio vs time for monolayer films maintained at 5 mN/m on subphases (A) at pH 11 and (B) with 0.02 mg of proteinase K. 77
Figure 27. AFM images and corresponding line profiles of homopolymers and l-PLA/PPC blend films before/after enzymatic degradation: (A) l-PLA,... 79
Scheme 1. Synthesis of PLA from L- and D-lactic acids. 21
Scheme 2. Synthesis of polyether polyol from biomass. 26
Scheme 3. Copolymerization route of PPC using CO₂ and PO. 31
Scheme 4. Synthetic routes of copolymerization of LA with polyether polyol. 47