Catalytic Synthesis and Characterization of Biodegradable ...

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Chapter 6 NMR. Characterization of MPEG-CPAD: IR: � ~ (cm-1) 1737 (C=O) 1044 (C=S). 1 H NMR (300M, CDCl3, δ ppm): 7.89 7.57 7.40 (5H, CH×3 in benzene), 4.27 (2H, CH2OC(O)-), 3.64 (CH2 in PEG), 3.38 (3H, CH3O-), 2.46~2.75 (4H, CH2×2 in CPAD), 1.94 (3H, CH3 in CPAD). Characterization of MPEG-b-PLA-CPAD: IR: � ~ (cm-1) 1755 (C=O) 1044 (C=S). 1 H NMR (300M, CDCl3, δ ppm): 7.88 7.57 7.40 (5H, CH×3 in benzene), 5.15 (CH in PLA), 4.26 (2H, CH2OC(O)-), 3.62 (CH2 in PEG), 3.36 (3H, CH3O-), 2.46~2.75 (4H, CH2×2 in CPAD), 1.95 (3H, CH3 in CPAD). Synthesis of MPEG-b-poly(2,2,6,6-tetramethylpiperidinyloxy acrylamide) (PEG-b-PTAm). For kinetic study, 0.22 g MPEG-CPAD (0.042 mmol), 0.53 g TAP (2.5 mmol) and 3.4 mg AIBN (0.021 mmol) were dissolved in 8 mL 1,4-dioxane/methanol (v/v, 3:1). The mixture was deaerated by applying three times freeze-pump-thaw cycle. Afterwards, the tube was immerged in 90 o C oil bath. Samples were taken out at various time intervals and quenched immediately into liquid nitrogen. The freezing samples were lyophilized to gain pink powders under reduced pressure and then used for 1 H NMR analysis to determine the monomer conversions. Molecular weights and molecular weight distributions were determined by GPC after the oxidation of the samples by m-chloroperbenzoic acid (mCPBA) in THF. The detailed oxidation processes are as follow. For preparation of MPEG-b-PTAm, 0.10 g MPEG-CPAD (0.019 mmol), 0.25 g TAP monomer (1.2 mmol) and 1.6 mg AIBN (0.01 mmol) were dissolved in 4mL 1,4-dioxane/methanol (v/v, 3:1). The mixture was deaerated by applying three times freeze-pump-thaw cycle. Afterwards, the tube was immerged in 90 o C oil bath and stirred for 8 hours. After cooling to room temperature, the mixture was precipitated from cold ethyl ether. The slight pink precipitate was collected and washed twice with ethyl ether. The product was obtained after vacuum drying for 24 h with a yield of 81% (0.29 g). In order to gain MPEG-b-PTAm, an oxidation step was needed. Typically, 110 mg of the aforementioned product dissolved in 5 mL THF and stirred in ice-cold bath, to which 500 mg of mCPBA was added. The mixture was allowed to move to the room temperature and stirred for further 4 hours. The final product was obtained by precipitating the mixture into 120 mL ethyl ether/n-hexane (v/v, 1:1), yield 92%. (Mn=25200, PDI=1.38 by GPC). ‐ 124 ‐
Synthesis of MPEG-b-PLA-b-PTAm. Synthesis of Amphiphilic Triblock Copolymers of Acrylamide, Lactate, and Ethyleneoxide 0.56 g MPEG-b-PLA-CPAD (0.04 mmol), 0.50 g (2.4 mmol) TAP monomer and 3.3 mg AIBN (0.02 mmol) ware dissolved in 6mL 1,4-dioxane/methanol (9:1, v/v). The mixture was deaerated by applying three times freeze-pump-thaw cycle. Afterwards, the tube was immerged in 90 o C oil bath and stirred for 8 hours. After cooling to room temperature, the mixture was precipitate in cold ethyl ether. The pale pink precipitate was collected and washed twice with ethyl ether. The product was obtained after vacuum drying for 24 h with a yield of 79% (0.84 g). An additional oxidation procedure was also needed to gain the final product MPEG-b-PLA-b-PTAm in good yield. (Mn=32300, PDI=1.42 by GPC) Micelles preparation and characterization. The preparation procedures for the MPEG-b-PTAm and MPEG-b-PLA-b-PTAm micelles are the same. Typically, 50 mg of the block copolymer was firstly dissolved in 5 mL of THF and then added dropwise into 10 mL deionized water. The mixture was then transferred into a dialysis bag (molecular weight cut-off = 3500 Da) and dialyzed against deionized water for 24h. Afterwards, the micelles solution was diluted to 50 mL with deioinized water. The final concentrations of the micelles were 1.0 mg mL -1 . The structure of the micelles was characterized by DLS and TEM. EPR study. To evaluate the stability of the nitroxyl radicals containing micelles in the reducing environment, EPR study of the micelles in PBS buffering solution containing ascorbic acid at high concentration was conducted. 0.5 mL of the prepared micelle solution (1.0 mg.mL -1 ) was mixed vigorously with 0.5 mL of PBS solution (pH 7.4, 0.2 M containing 10.0 mM ascorbic acid). The mixture was then transferred into capillary tube immediately for EPR measurement over time. The final concentrations of the micelle and the ascorbic acid were 0.5 mg.mL -1 and 5.0 mM, respectively. The same assay was performed toward TEMPOL at concentration of 0.5 mg mL -1 in the same buffer as the control. Cytotoxicity assay. The cytotoxicity of the block copolymers were assessed using MTT method. Polymer samples were dispersed in DMEM medium (Dulbecco's Modified Eagle Medium) supplemented with 10% fetal calf serum (Gibco) in a humidified incubator at 37 and 5% ‐ 125 ‐
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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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1.6.1 Radical Polymers for Organic
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initialization of the device by app
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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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Page 84 and 85: Chapter 3 3.1 Introduction Poly(lac
Page 86 and 87: Chapter 3 polydispersity index (PDI
Page 88 and 89: Chapter 3 aluminum based complexes
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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
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Page 115 and 116: = 25 μm. B: MTT assay for the cyto
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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
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Page 136 and 137: Chapter 6 CO2 for 24 h. RSC96 cells
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Page 147 and 148: 13. Xuan Pang, Xuesi Chen, Xiuli Zh
Page 149: Acknowledgments The present thesis
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