Catalytic Synthesis and Characterization of Biodegradable ...

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Chapter 4 the proton of methenyl groups in the lactide backbone. The molecular weight of PLA-HEMA was 3000, calculated from the integration area ratio of peaks 1 and 6 (Figure 4.1A). To prevent the possible polymerization of HEMA under the high temperature, hydroquinone was used as an inhibitor which was removed during the purification step of the polymeric product. After the copolymerization with the TAP monomer, the peak associated with the double bond disappeared, as shown in Figure 4.1B, which suggested the polymerization of PLA-HEMA. The structure of copolymer was also confirmed by 13 C NMR (Figure 4.2). Figure 4.1 1 H NMR of PLA-HEMA (A) and PTAP-g-PLA2 (B). Figure 4.2 13 C NMR spectra of PTAP (A), PTAP-g-PLA (B) and PLA-HEMA (C). The contents of PTAP in the copolymers were determined by the integration area ratio of the peaks at 5.19 and 4.19 ppm. It was noted that the peak at 4.19 ppm contained the resonance from the –CH2CH2- groups capped at the PLA chain end, so this part of integration ‐ 88 ‐
‐ 89 ‐ Synthesis of Lactide‐Grafted Poly(TEMPO‐acrylamide) and its Electrochemical Property and Biocompatibility was subtracted to determine the monomer composition (Figure 4.1B). The compositions of the copolymers evaluated by the 1 H NMR spectra were summarized in Table 4.1. All the copolymer had a relatively lower PLA content compared with the feeding ratio. Presumably the PLA-HEMA macromonomers had a relatively low reactive efficiency and only part of the macromonomers copolymerized with the 2,2,6,6-tetrametylpiperidine-4-yl acrylamide monomer. The low yield of the copolymerization can also be attributed to the low reactivity of the macromonomers. The GPC results showed that the molecular weight of the copolymers decreased as the PLA content increased, indicating that the introduction of the PLA lowered the reactivity of the propagating copolymer radical, making them more readily terminated during the polymerization. Sample Table 4.1 Feed and result compositions of copolymers. a PLA-HEMA/Monomer (w/w) Feed Result b Yield (%) Mn c PDI c Unpaired electron density (spin/g) d 1 3 : 7 1 : 9.0 42.0 7.0 × 10 4 1.98 2.14 × 10 21 2 5 : 5 1 : 4.3 32.5 3.9 × 10 4 2.03 1.64 × 10 21 3 7 : 3 1 : 2.4 40.8 1.2 × 10 4 1.97 1.39 × 10 21 a Reaction temperature was 85 o C and duration was 24 h;. b Calculated from 1 H NMR; c Determined from GPC in DMF. d Determined from SQUID after oxidation. TEMPO are generally prepared through the oxidation of 2,2,6,6-tetramethylpiperidine. Several oxidants, including hydrogen peroxide, peracids and lead(IV) oxide, can be used to obtain the nitrooxide radical. In this chapter, the oxidation of PTAP-g-PLA was accomplished in the presence of 3-chloroperoxybenzoic acid. The obtained PTAm-g-PLA was orange powder. To further investigate the oxidation reaction of copolymer, the FTIR spectra before and after the oxidation were obtained (Figure 4.3). The peak at 1359 cm -1 was obviously enhanced after the oxidation, which was assigned to the characteristic peak of the nitroxide radical. 21, 22 The peak at 1758 cm -1 (νCO) was characteristic peak of the PLA segment, which did not change after the oxidation. The peaks at 1653 cm -1 (νCO) and 1548 cm -1 (νCO-NH) were
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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 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 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
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
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13. Xuan Pang, Xuesi Chen, Xiuli Zh
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Acknowledgments The present thesis
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