Catalytic Synthesis and Characterization of Biodegradable ...

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Chapter 1 The next major breakthrough in the area of propylene oxide and CO2 copolymerization came with the uncovering of air-stable dicarboxylic acid derivatives of zinc by Soga and co-workers. 10 These catalysts were prepared by the reaction of zinc hydroxide or zinc oxide with dicarboxylic acids in toluene. Although the zinc glutarate analogue was found to be catalytically most active, producing significant quantities of polypropylene carbonate from propylene oxide and CO2, the percent of active zinc sites on this heterogeneous catalyst was quite low (
- 5 - Polymerization and Applications of Biodegradable Polyesters in the presence of a quaternary organic salt or triphenylphosphine. At ambient temperature and a relatively high catalyst loading, reaction rates were slow, generally requiring 12-23 days and thereby affording rather low molecular weight polymers. Nevertheless, copolymers from ethylene oxide, propylene oxide, or cyclohexene oxide and carbon dioxide with very narrow molecular weight distributions (1.06-1.14) were isolated. Approximately a decade later, Kruper and Dellar investigated the use of (tpp)CrX complexes in the presence of 4-10 equiv of nitrogen donors, such as N-methylimidazole (N-MeIm) or (4-dimethylamino)pyridine (DMAP), for the coupling of a wide variety of epoxides and carbon dioxide to provide cyclic carbonates. 15 For example, propylene oxide readily afforded propylene carbonate at 50 bar of CO2 pressures with a TOF of 158 h -1 at 80 . Conversely, cyclohexene oxide and CO2 yielded predominantly copolymer under similar reaction conditions. In more recent studies, Holmes and co-workers have reported the copolymerization of cyclohexene oxide and CO2 in the presence of a fluorinated (tpp)CrCl catalyst (Figure 1.2.2) along with a cocatalyst such as DMAP. 16 TOFs greater than 150 h -1 were observed for reactions performed at 110 in scCO2 (225 bar) where the catalyst solubility is greatly enhanced over its (tpp)CrCl analogue, with the resulting copolymers having a high percentage of carbonate linkages (>97%) and narrow polydispersities (PDIs). The rapid advances currently being experienced in the copolymerization of cyclohexene oxide and carbon dioxide were fueled by Darensbourg’s development of a series of discrete zinc phenoxide derivatives as catalysts in 1995. 17 A typical bis(phenoxide)Zn(THF)2 complex (where THF = tetrahydrofuran) used in these studies is illustrated in Figure 1.2.3, where the steric bulk of the phenoxide ligands limits aggregate formation. Figure 1.2.2 Fluorinated porphyrin derivative of chromium(III) chloride. These catalysts were extremely effective for homopolymerizing epoxides to polyether;
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: - 3 - Polymerization and Applicatio
Page 13 and 14: 1.2.2 Aluminum Catalysts - 7 - Poly
Page 15 and 16: - 9 - Polymerization and Applicatio
Page 17 and 18: 1.3 Polylactide 1.3.1 Introduction
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
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- 55 - Polymerization and Applicati
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182. R. B. Weller, J. Invest. Derma
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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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