Catalytic Synthesis and Characterization of Biodegradable ...

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Chapter 1 the device is switched to a low resistance near –4.5 V as the threshold voltage. The low resistance state is maintained during the reverse sweep of the voltage from –5 to +1.4 V. The low-resistance or ON state was observed for repeated sweeps, regardless of the sweep direction. When a bias of –1.5 V was applied, the device sharply switched to the high-resistance or OFF state again. In the hysteretic curve, the ON–OFF ratio amounted to four orders of magnitude. The retention cycles of the ON and OFF states under open-circuit conditions persisted for more than 10 4 times. Furthermore, each state survived for a month after the corresponding once-time-only pulse as well as consecutive pulses. The charge injection at the radical polymer/electrode interface and transport in the bulk of the radical polymer layer are dominated by the Schottky barrier and the Poole–Frenkel mechanism. In the ON state, charges are trapped at the radical polymer/PVDF interfaces, and induce accumulation of the opposite charge at the radical polymer/electrode interfaces and reduction the Schottky barriers, allowing charges to transfer across the radical polymer/electrode interfaces even at low voltages. 192 The SOMO levels of the p-type PTMA and the n-type PGSt are near 5.4 and 4.7 eV, respectively. Figure 1.6.5 p-type and n-type radical polymer-based memory architecture, and charge injection, transporting, and trapping configuration. The p-type layer accepts holes, and electrons are injected into the n-type layer. The injected holes and electrons are transported by the hopping mechanism, and are stored at the radical polymer/PVDF interfaces. Under open-circuit conditions, the trapped holes and electrons were nonvolatile due to charge trapping at the radical polymer/PVDF interfaces and to blocking of the charge transfer in the polymer layers having sufficient resistances. The asymmetric configuration of the electrodes with the different work functions allows ‐ 44 ‐
initialization of the device by applying an inverse voltage. 1.6.2 Radical Polymers for Biomedical Applications 1.6.2.1 Nitric Oxide Release Systems - 45 - Polymerization and Applications of Biodegradable Polyesters Nitric oxide (NO•) is a small but highly reactive free radical with expanding known biological activities. Its essential roles involve the regulatory agent for normal physiological activities and cytotoxic species in diseases and their treatments. There have been numerous examples of application of the nitric oxide on disease treatments, such as antiviral compounds, cancer treatment, anti-inflammatory drugs and other nitric oxide-related diseases treatment. However, the excess introduction of nitric oxide into body may induce significant adverse side effects like microvascular leakage, tissue damage in cystic fibrosis, septic shock, B-cell destruction, and possible mutagenic risk. 193 Therefore, it is very important to develop smart delivery vehicles for control release of the nitric oxide. Biodegradable polymers are known to be biocompatible and degradable in physiological conditions which have been widely utilized as drug delivery vehicles in the forms of matrices or nanoparticles. Accordingly, pioneered works by C. C. Chu and co-workers have reported to incorporate of stable nitric oxide radicals to either the chain end or backbone of the biodegradable polymers. 193-196 In such contributions, nitric oxide derivative, tampamine nitroxyl radical (4-amino-2,2,6,6-tetramethylpiperidine-1-oxy, TAM) have been chemically coupled with various biodegradable polymers such as polyglycolide (PGA), poly(acrylic acid/lactide/ε-caprolactone) (PBLCA) and poly(ester amide)s (PEAs). The biological activities of these TAM-incorporated polymers and the release kinetic of the TAM from the polymer matrices have also been evaluated. For example, the level of the retardation of smooth muscle cell (SMC) of the TAM-PGA was conducted in vitro cell culture (Figure 1.6.6). The TAM-PGA was found to show profound retardation of the proliferation of SMC as similar with the TAM free nitroxyl radicals at concentration of 1 μg/mL. Thus, it appeared that the long PGA segments had no evidently interference on the biological functions of nitroxyl radicals incorporated. However, the incorporation of TAM into the polymer chain end have limitation in the TAM content in the polymer, improved strategies have also been proposed by the authors via conjugating the TAM to the backbone of the biodegradable polymers such as PBLCA and PEAs. 193, 194 Up to 8.32% (wt %) of the TAM content in
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 and 10: - 3 - Polymerization and Applicatio
Page 13 and 14: 1.2.2 Aluminum Catalysts - 7 - Poly
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 49: - 43 - Polymerization and Applicati
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 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
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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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