Catalytic Synthesis and Characterization of Biodegradable ...

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Chapter 3 aluminum based complexes were totally inactive for the ROP of LacOCA. 3.4 Characterization of the Obtained PLA Figure 3.3 Structures of aluminum based complexes. The 1 H NMR spectrum of the obtained PLA was shown in Figure 3.4. The doublet peaks at 1.73 ppm was assigned to CH3 resonance of the polymer chain. The quartet peaks at 5.15 ppm was attributed to that of the CHCH3 of PLA. 13 C NMR spectrum of the PLA was displayed in Figure 3.5. The signals at 169.5, 69.0 and 16.6 ppm corresponded to the carbon resonances of carbonyl, methine, and methyl groups of the PLA chain, respectively. These results were consistent with the reported NMR spectra of PLA, 28 which demonstrated that PLA was formed by the polymerization of LacOCA. The carbonyldioxy group was eliminated from the polymerization system by the liberation of carbon dioxide. 8 6 4 2 0 ppm Figure 3.4 1 H NMR spectrum of poly(lactic acid) from LacOCA. The DSC thermogram of the obtained PLA was shown in Figure 3.6. The glass transition ‐ 80 ‐
Polymerization of Lactic O‐Carboxylic Anhydride using Organometallic Catalysts temperature (Tg) of the corresponding PLA was 55 °C. This was in consistent with the reported data in a literature (Tg ~ 55 °C). 31 The melting point Tm of the PLA was 154 °C, which was lower than that for the poly(L-lactide) reported in the literature (Tm ~ 175 °C). 31 TGA revealed that T5%, the temperature corresponding to 5% weight loss, was 231°C for the PLA produced by the LacOCA polymerization. This was lower than that of the previously reported poly(L-lactide) (T5% ~ 320 °C). 32 These lower characteristic thermal transition temperatures were ascribed to the relatively low molecular weights of the PLA produced by the LacOCA polymerization. Increasing the molecular weights by suppressing the proposed side reactions such as the transesterification by tuning the catalytic activity with a suitably designed ligand around the cobalt center will be the topics of our continuous research. 200 150 100 50 0 ppm Figure 3.5 13 C NMR spectrum of poly(lactic acid) from LacOCA. Heat flow (W/g) 0.5 0.0 -0.5 -1.0 -1.5 -2.0 50 100 150 Temperature ( o C) Figure 3.6. DSC thermogram of poly(lactic acid) (Table 3.1, Entry 3). ‐ 81 ‐
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Catalytic Synthesis and Characteriz
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Preface Biodegradable polyesters ha
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Chapter 3 Polymerization of Lactic
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Chapter 1 Polymerization and Applic
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- 3 - Polymerization and Applicatio
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1.2.2 Aluminum Catalysts - 7 - Poly
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1.3 Polylactide 1.3.1 Introduction
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- 13 - Polymerization and Applicati
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1.3.4 Application of PLA Figure 1.3
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1.5.1.4 Polyaniline (PANi) - 21 - P
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Page 67 and 68: Synthesis and Electrochemistry of S
Page 79: Synthesis and Electrochemistry of S
Page 84 and 85: Chapter 3 3.1 Introduction Poly(lac
Page 86 and 87: Chapter 3 polydispersity index (PDI
Page 90 and 91: Chapter 3 3.5 Conclusions Co(III) c
Page 92 and 93: Chapter 3 22. Z. H. Tang, X. S. Che
Page 94 and 95: Chapter 4 4.1 Introduction Stimulus
Page 96 and 97: Chapter 4 the proton of methenyl gr
Page 98 and 99: Chapter 4 attributed to the amide g
Page 100 and 101: Chapter 4 4.4 Thermal Properties Th
Page 102 and 103: Chapter 4 Figure 4.8 MTT assay for
Page 104 and 105: Chapter 4 The 1 H NMR and 13 C NMR
Page 106 and 107: Chapter 4 Cell viability (%) = (Asa
Page 109 and 110: Chapter 5 Synthesis of Triblock Cop
Page 111 and 112: 5.2 Synthesis of Triblock Copolymer
Page 113 and 114: Sample Table 1. Feed and result com
Page 115 and 116: = 25 μm. B: MTT assay for the cyto
Page 117 and 118: ‐ 109 ‐ Synthesis of Triblock C
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Page 124 and 125: Chapter 6 6.1 Introduction Since th
Page 126 and 127: Chapter 6 6.3 Synthesis of MPEG-b-P
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Page 130 and 131: Chapter 6 Figure 6.6 Cyclic voltamm
Page 132 and 133: Chapter 6 vivo cytotoxicity was als
Page 134 and 135: Chapter 6 NMR. Characterization of
Page 136 and 137: 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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