Catalytic Synthesis and Characterization of Biodegradable ...

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Chapter 4 The 1 H NMR and 13 C NMR measurements were performed on Bruker DMX300 spectrometer with tetramethylsilane (TMS) as an internal reference. FTIR spectra were measured on a Bruker Vertex 70 Fourier Transform Infrared spectrometer using the KBr disk method. Atomic force microscopy (AFM) images were acquired in a commercial SPA300HV/SPI3800N Probe Station, Seiko Instruments, Japan, in tapping mode. A silicon microcantilever (spring constant 2 N/m and resonance frequency ~ 70 kHz, Olympus, Japan) with an etched conical tip was used for scan. Silicon wafers were cleaned by a 30 min dip in fresh 1:1 H2SO4 (concentrated)/H2O2 (30%) solution. Subsequently, the acids were removed by a thorough rinse in Millipore water. Polymer thin films were obtained by spin-coating a copolymer chloroform solution onto silicon wafers. Magnetization and magnetic susceptibility of the powder polymer sample were measured using a Quantum Design MPMS-7 SQUID (superconducting quantum interference device) magnetometer. The magnetic susceptibility was measured from 10 to 300 K under a 1.0 T field. Cyclic voltammetry was performed using a normal potentiostat system (BAS Inc. ALS660B) with a conventional three-electrode cell under a dry argon atmosphere. A platinum disk, coiled platinum wire, and Ag/AgCl were used as the working, auxiliary and reference electrode, respectively. The cyclic voltammogram was measured in a dichloromethane solution in the presence of 0.1 M tetrabutylammonium tetrafluoroborate as the supporting electrolyte. The film of copolymer was 100 nm in thickness. The formal potential of the ferrocene/ferrocenium redox couple was 0.45 V vs the Ag/AgCl reference electrode. The GPC analysis was performed using TOSOH HLC-8220 with 0.1 M LiCl DMF as solvent. Synthesis of PLA-HEMA PLA-HEMA was easily prepared by the ring-opening polymerization of L-lactide in the presence of HEMA and stannous octoate (Sn(Oct)2). First, 0.48 g HEMA, 5.0 g L-lactide, 8 mg hydroquinone, and 5 mg Sn(Oct)2 were added into a dried glass reactor already flame-dried and nitrogen-purged three times. After injection of 35 mL toluene, the reactor was sealed and maintained at 120 o C for 24 h. The product was precipitated with an excess of ethanol, purified by precipitating twice into ethanol from chloroform solution, to give a white product. Yield: 34%. Synthesis of PTAP-g-PLA Typically, 0.15 g PLA-HEMA and 0.35 g 2,2,6,6-tetrametylpiperidine-4-yl acrylamide ‐ 96 ‐
‐ 97 ‐ Synthesis of Lactide‐Grafted Poly(TEMPO‐acrylamide) and its Electrochemical Property and Biocompatibility (TAP) were added into a dried glass reactor already flame-dried and nitrogen-purged three times. After injection of 6 mL dioxane, 6 mg AIBN was added to the glass in glove box. Then the system was degassed by three freeze-vacuum-thaw cycles. Finally, the glass reactor was sealed under Ar atmosphere and then immersed in an oil bath at 85 o C under stirring. After 24 h, the reaction solution was poured into excessive methanol. The homopolymer of PLA-HEMA was precipitated and filtered. The poly(2,2,6,6-tetrametylpiperidine-4-yl acrylamide)-g-polylactide (PTAP-g-PLA) was dispersed in the methanol solution and collected by evaporation of methanol under reduced pressure. Then the product was purified by precipitating twice into diethyl ether from chloroform solution, and eventually dried under vacuum at room temperature for 24 h. Synthesis of PTAm-g-PLA PTAP-g-PLA was added to an ice-cold solution of 3-chloroperoxybenzoic acid in THF and stirred for 3 h at room temperature. The weight ratio of PTAP to 3-chloroperoxybenzoic acid was 1:4. The polymer was solved in THF with oxidation progress. The solution was added dropwise to diethyl ether/hexane (1/1 v/v 200 ml). The precipitate was collected by filtration, and dried under reduced pressure for 12 h. Yield: 77%. Cytotoxicity assay The cytotoxicity of the various polymer complexes were assessed using the MTT assay. PTAm-g-PLA, PLA and PTAm 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% CO2, respectively. After 24 h, extracted solutions of polymers were diluted into different concentrations. RSC96 cells were seeded at 1.2 ×10 4 cells/well in 96-well plates and cultured for 24 h. Then the culture media were replaced by the extracted solutions and the plates were returned to the incubator for an additional 24 h. At the end of the experiments, 20 μL of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) solution (5 mg/mL) was added to each well. The plates were returned to the incubator. After 4 h, the MTT solutions were carefully removed from each well, and 200 mL DMSO was added to dissolve the MTT formazan crystals. The plate was incubated for an additional 10 min before the absorbance at 492nm was recorded by an ELISA microplate reader (Bio-Rad). The cell viability (%) was calculated according to the following equation:
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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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Page 63 and 64: 182. R. B. Weller, J. Invest. Derma
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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 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 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
Page 136 and 137: Chapter 6 CO2 for 24 h. RSC96 cells
Page 141 and 142: Chapter 7 Conclusion and Future Pro
Page 143 and 144: ‐ 131 ‐ Conclusion and Future P
Page 145 and 146: ‐ 133 ‐ Conclusion and Future P
Page 147 and 148: 13. Xuan Pang, Xuesi Chen, Xiuli Zh
Page 149: Acknowledgments The present thesis
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