Catalytic Synthesis and Characterization of Biodegradable ...

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Chapter 1 provide polycarbonates. (Figure 1.2.9). 28 They use (Salen)M III X as a catalyst for the copolymerization of CO2 and cyclohexene oxide in the presence of N-MeIm. At 80 and 58.5 bar CO2 pressure, (Salen)M III X alone copolymerized cyclohexene oxide and carbon dioxide to poly(cyclohexylenecarbonate), void of polyether linkages, with a TOF of 10.4 h-1. 1.2.4 Lanthanide-Based Catalysts Figure 1.2.9. (Salen)M III X catalyst for epoxides ring opening. Yttrium, aluminum, rare-earth metals, and combinations of multiple metal reagents have shown activity for the copolymerization of epoxides and CO2. For example, PO–CO2 copolymerization was effected by a rare-earth metal system comprised of yttrium tris[bis(2-ethylhexyl)phosphate], AliBu3, and glycerol. The PPC produced contained only 10–30% carbonate linkages, although molecular weights of up to 476000 gmol -1 were achieved. 31 This system also exhibited activity for the alternating copolymerization of CO2 with epichlorohydrin 32 and glycidyl ether monomers. 33 Other rare-earth metal systems consisted of yttrium carboxylates [Y(CO2CF3)3 or Y(CO2RC6H4)3 where R is H, OH, Me, or NO2], ZnEt2, and glycerine. 34-36 The alternating copolymerization of CO2 and PO yielded PPC with up to 98.5% carbonate linkages, turnover frequencies up to 2.5 h -1 , and molecular weights reaching 100 000 gmol -1 . CHO–CO2 copolymerization produced PCHC with 100% carbonate linkages, molecular weights of 19000–330000 gmol -1 , and Mw/Mn’s of 3.5–12.5. It must be noted that control experiments indicated that ZnEt2, but not Y(CO2CF3)3, was essential for polymerization. Finally, ternary catalysts composed of Nd(CO2CCl3)3, ZnEt2, and glycerol were also reported to copolymerize PO and CO2. 37 ‐ 10 ‐
1.3 Polylactide 1.3.1 Introduction - 11 - Polymerization and Applications of Biodegradable Polyesters Polylactide (PLA) is biodegradable, thermoplastic, aliphatic polyester derived from lactic acid, which is made from renewable resources, such as corn starch or sugarcanes. 38 PLA has similar mechanical properties to polyethylene terephthalate, but has a significantly lower maximum continuous use temperature. Poly(L-lactide) (PLLA) is the most important PLA. It is a semicrystalline polymer and has a crystallinity around 37%, a glass transition temperature ~67 and a melting temperature ~180 . PLA can be processed like all other thermoplastic polymers with extrusion, injection molding, blow molding, or fiber spinning processes into various products. The products can be recycled after use either by remelting and processing the material a second time or they can be hydrolyzed into lactic acid, the basic chemical. The last possibility is to compost the polylactide to introduce it into the natural life cycle of all biomass, where it degrades into CO2 and water. PLA can be recycled following the traditional ways, composted like all other organic matter, and it will do no harm if burned in an incineration plant or introduced into a classical waste management system. PLA becomes of commercial interest in recent years, in light of its biodegradability. 1.3.2 Synthesis of PLA Figure 1.3.1 synthesis of PLA by the polycondensation of lactic acid. PLA can be prepared by direct polycondensation of lactic acid (Figure 1.3.1), which is produced from the bacterial fermentation of corn starch or cane sugar. 39 However, it is usually difficult to obtain high molecular weight polymer by polycondensation. Because each polymerization reaction generates one molecule of water, the presence of which degrades the forming polymer chain and results in the generation of low molecular weight PLA. So water has to be removed during the polycondensation in order to generate PLA with high molecular weight. Yamaguchi et al. has reported the synthesis of high molecular weight PLA by using molecular sieve to dry water during direct polycondensation. 40 However long reaction times and high temperatures are required in lactic acid polycondensation. 41
Page 1 and 2: Catalytic Synthesis and Characteriz
Page 3 and 4: Preface Biodegradable polyesters ha
Page 5 and 6: Chapter 3 Polymerization of Lactic
Page 7 and 8: Chapter 1 Polymerization and Applic
Page 9 and 10: - 3 - Polymerization and Applicatio
Page 11 and 12: - 5 - Polymerization and Applicatio
Page 13 and 14: 1.2.2 Aluminum Catalysts - 7 - Poly
Page 15: - 9 - Polymerization and Applicatio
Page 19 and 20: - 13 - Polymerization and Applicati
Page 21 and 22: 1.3.4 Application of PLA Figure 1.3
Page 27 and 28: 1.5.1.4 Polyaniline (PANi) - 21 - P
Page 47 and 48: 1.6.1 Radical Polymers for Organic
Page 51 and 52: initialization of the device by app
Page 55 and 56: 1.6.2.4 Others - 49 - Polymerizatio
Page 63 and 64: 182. R. B. Weller, J. Invest. Derma
Page 65 and 66: Chapter 2 Synthesis and Electrochem
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Synthesis and Electrochemistry of S
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Chapter 3 3.1 Introduction Poly(lac
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Chapter 3 polydispersity index (PDI
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Chapter 3 aluminum based complexes
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Chapter 3 3.5 Conclusions Co(III) c
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Chapter 3 22. Z. H. Tang, X. S. Che
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Chapter 4 4.1 Introduction Stimulus
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Chapter 4 the proton of methenyl gr
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Chapter 4 attributed to the amide g
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Chapter 4 4.4 Thermal Properties Th
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Chapter 4 Figure 4.8 MTT assay for
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Chapter 4 The 1 H NMR and 13 C NMR
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Chapter 4 Cell viability (%) = (Asa
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Chapter 5 Synthesis of Triblock Cop
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5.2 Synthesis of Triblock Copolymer
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Sample Table 1. Feed and result com
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= 25 μm. B: MTT assay for the cyto
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‐ 109 ‐ Synthesis of Triblock C
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‐ 111 ‐ Synthesis of Triblock C
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Chapter 6 6.1 Introduction Since th
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Chapter 6 6.3 Synthesis of MPEG-b-P
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Chapter 6 used to characterize the
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Chapter 6 Figure 6.6 Cyclic voltamm
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Chapter 6 vivo cytotoxicity was als
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Chapter 6 NMR. Characterization of
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Chapter 6 CO2 for 24 h. RSC96 cells
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Chapter 7 Conclusion and Future Pro
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‐ 131 ‐ Conclusion and Future P
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‐ 133 ‐ Conclusion and Future P
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13. Xuan Pang, Xuesi Chen, Xiuli Zh
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Acknowledgments The present thesis
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