Catalytic Synthesis and Characterization of Biodegradable ...

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Chapter 5 5.6 Conclusions Triblock copolymers composed of PLA and PTAm with well-defined structure was prepared by combination of ROP and RAFT methods. Since the living characteristics of the RAFT polymerization, the triblock copolymers could be obtained with well-defined structure and compositions, which was confirmed by the comparison of their yields and PDIs with that of graft copolymers synthesized in Chapter 4. Biological evaluation of the material showed that the material has good biocompatibility and low cytotoxicity. Electrospinning technology was then adopted to prepare the electro-active porous polymer matrices with relatively large surface area for biomedical applications. The morphology of electrospun copolymers is mainly attributed to the viscosity difference from tyre-like shape at lower concentration to fibroid shape at higher concentration. 5.7 Experimental Section Materials Lactide was purchased from Purac, Holland. Stannous octoate (Sn(Oct)2, 95%) and 1,4-butanediol (BDO) were purchased from Aldrich. 2, 2'-Azoisobutyronitrile (AIBN, Beijing Chemical Co., China) was recrystallized twice from methanol. 4-Cyanopentnoic acid dithiobenzoate (CPAD) was prepared as described in literature. 4-Amino-2,2,6,6-tetramethylpiperidine (TCI, >97%) and Acrylyl chloride (Alfa Aesar, 96%) were used to prepare the 2,2,6,6-tetra-methylpiperidinyl acrylamide (TAP) monomer. N,N'-Dicyclohexylcarbodiimide (DCC, 99%) and 4-dimethylaminopyridine (DMAP, 98%) were purchased from Sigma Chemical Co. and used as received. All other reagents were used without further purification. Instrument 1 H NMR spectra were recorded on Bruker AV 400 NMR spectrometer in CDCl3. Gel permeation chromatography was performed with a DMF eluent using a Tosoh HLC-8220 instrument, and the molecular weight and polydispersity were calibrated with polystyrene standards. Scanning electron microscope (SEM) images were obtained by using an ESEM (Model XL 30 ESEM FEG from Micro FEI Philips). The specimens were mounted on metal stubs using a double-sided adhesive tape and vacuum coated with a platinum layer prior to examination. Samples for cyclic voltammetry were prepared by depositing thin LM PAP film ‐ 108 ‐
‐ 109 ‐ Synthesis of Triblock Copolymers of TEMPO‐Acrylamide and Lactate by RAFT Polymerization on an indium tin oxide (ITO) electrode as working electrode and Ag/Ag + as reference electrode. Cyclic voltammograms were recorded on a CHI 630 potentiostat with different scanning rate. Synthesis of Hydroxyl-capped PLA After recrystallization in ethyl acetate for three times, lactide (1 mol) was added to a flame-dried and nitrogen-purged glass ampoule, into which a 150 mL toluene solution of BDO (7.2 mmol) and Sn(Oct)2 (0.3% of the BDO, mol/mol) was then transferred. The reaction vessel was immersed into a thermostatic oil bath maintained at 120 o C, under magnetic stirring for 24 h. The reaction product was precipitated into ethanol, filtered and dried at 40 o C in vacuum for 48 h. Synthesis of Macromolecular CTA: CPAD-PLA-CPAD Typically, PLA 5 g (0.5 mmol), CPAD 0.28 g (1mmol), DCC 0.42 g (2 mmol) and DMAP 0.025 g (0.2 mmol) were dissolved in 20 mL anhydrous methylene chloride. The solution was stirred at room temperature for 48 hours. After filtration of the precipitate, the solution was poured into 200 mL cold ethyl ether, yielding pink precipitate. The pink precipitate was redissolved in methylene chloride and precipitated again in cold ethyl ether. After washing with additional two times with ethyl ether, the pink product CPAD-PLA-CPAD was finally obtained, Yield 92%. Synthesis of PTAm-b-PLA-b-PTAm Typically, 0.20 g CPAD-PLA-CPAD (0.02 mmol), 0.29 g (1.4 mmol) TAP monomer and 1.6 mg AIBN (0.01 mmol) ware dissolved in 2 mL THF. 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 12 hours. After cooling to room temperature, the mixture was precipitate in 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%. In order to obtain PTAm-b-PLA-b-PTAm, an oxidation step was needed. Typically, 110 mg of the aforementioned PTAP-b-PLA-b-PTAP dissolved in 5 mL THF and stirred in ice-cold bath, to which 500 mg of m-chloroperbenzoic acid (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 precipitate the mixture into 120 mL ethyl ether/n-hexane (v/v, 1:1), Yield: 92%.
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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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1.6.2.4 Others - 49 - Polymerizatio
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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 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: = 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
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
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Page 149: Acknowledgments The present thesis
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