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Chapter 3 polydispersity index (PDI) of PLA was in the range of 1.1–1.5. The Mn of the obtained PLA was low in all experiments except the Co(III)-c-(NO2)2 initiating system, which gave PLA with a high Mn (9.6×10 3 ). The molecular weight distribution of the product obtained with the Co(III)-c-(NO2)2 catalyst was relatively broad (PDI = 1.4). When the Co(III)-b-NO2/ i PrOH initiating system (where i PrOH was isopropanol) was employed, the Mn of PLA increased from 3.3×103 to 6.0×103 and the PDI broadened from 1.1 to 1.5 as the monomer/initiator ratio increased from 100/1 to 200/1 (Table 3.1, Entries 5 and 6). The Co(III)-b-NO2 initiating system without i PrOH also catalyzed the polymerization of LacOCA. Compared with the Co(III)-b-NO2/ i PrOH initiating system, the Mn of the resulting PLA using the Co(III)-b-NO2 initiating system was slightly higher (Mn = 7.6×10 3 ). The molecular weight distribution of PLA was also broad (PDI = 1.4), which was similar to that of the Co(III)-b-NO2/ i PrOH initiating system. These demonstrated that the Co(III) complexes with Schiff base ligands acted as the catalysts for the ROP of LacOCA. The present ROP method somehow allowed the control of the molecular weight of PLA, but the molecular weight distribution was broad in most cases of the polymerization examined in this study, especially in longer polymerization time. The large polydispersity implies that the ROP may have been accompanied by undesired intra- and/or inter-transesterification reactions. Table 3.1 Polymerizations of LacOCA Entry Initiating system [M]/[I] Temp. ‐ 78 ‐ /°C Time 1 Co(III)-a-(NO2)2/ i PrOH 100/1 70 35 4.0 1.3 2 Co(III)-b-(NO2)2/ i PrOH 100/1 70 35 4.3 1.2 3 Co(III)-c-(NO2)2/ i PrOH 100/1 70 35 9.6 1.4 4 Co(III)-a-NO2/ i PrOH 100/1 70 35 6.4 1.4 5 Co(III)-b-NO2/ i PrOH 100/1 70 35 3.3 1.1 6 Co(III)-b-NO2/ i PrOH 200/1 70 60 6.0 1.5 /hr Mn /10 3 PDI
Polymerization of Lactic O‐Carboxylic Anhydride using Organometallic Catalysts 7 Co(III)-b-NO2 200/1 70 60 7.6 1.4 8 Co(III)-c-NO2/ i PrOH 100/1 70 35 3.6 1.2 9 Stannous benzoate/ i PrOH 120/1 70 15 6.4 1.2 10 Stannous benzoate 120/1 70 15 7.0 1.3 11 Stannous octoate/ i PrOH 150/1 60 15 7.9 1.4 12 (Cyclohexylsalen)AlEt/BnOH 150/1 70 11 N/A N/A 13 (Dimethylsalen)AlEt/BnOH 150/1 70 11 N/A N/A i PrOH: isopropyl alcohol. BnOH: benzyl alcohol. 3.3 Polymerization of LacOCA using Tin(II) or Al(III) Based Complexes Tin(II) and Al(III) complexes are also widely used as catalysts for the ROP of lactides. Based on the activity of the Co(III) complexes (vide supra), we decided to examine the ROP of LacOCA using these metal complexes with the similar (or identical) ligands as the catalysts. Stannous benzoate, stannous octate, (cyclohexylsalen)AlEt, and (dimethylpropylsalen)AlEt (Figure 3.3) were employed in this chapter. Both stannous benzoate and stannous octate were efficient catalysts for the ROP of LacOCA. When the stannous benzoate/ i PrOH initiating system was used as the catalyst and the monomer/initiator ratio was 120/1, the Mn and PDI of the obtained PLA were 6.4×10 3 and 1.2, respectively (Table 3.1, Entry 9). When the stannous benzoate initiating system was applied, the resulting Mn of 7.0×10 3 was slightly higher than that obtained with the benzoate/ i PrOH initiating system (Table 3.1, Entry 9). This result suggested that the addition of i PrOH was not effective to control the Mn of the product of the LacOCA polymerization when stannous benzoate was used as the catalyst, which was in contrast to the DMAP/alcohol mediated ROP of LacOCA 10, 11 where the alcohol was able to control the Mn of PLA. (Cyclohexylsalen)AlEt 29, 30 and (dimethylpropylsalen)AlEt 28 (Figure 3.3) are efficient Al based catalysts for the ROP of lactides. However, no polymer was isolated from the ROP of LacOCA using those catalysts (Table 3.1, Entries 12 and 13), which indicated that the ‐ 79 ‐
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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 35 and 36: - 29 - Polymerization and Applicati
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
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 88 and 89: Chapter 3 aluminum based complexes
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
Page 119: ‐ 111 ‐ Synthesis of Triblock C
Page 124 and 125: Chapter 6 6.1 Introduction Since th
Page 126 and 127: Chapter 6 6.3 Synthesis of MPEG-b-P
Page 128 and 129: Chapter 6 used to characterize the
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
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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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