| In this thesis, covalent modification of multi-walled carbon nanotubes (MWNT) by some novel well-defined copolymer through atom transfer nitroxide radical coupling (ATNRC) reaction was studied, which were prepared by, atom transfer radical polymerization (ATRP), and so on. Samples were characterized by FTIR, TEM and TGA etc. The results are listed as follows:1. MWNT with2,2,6,6-tetramethylpiperidine-l-oxy (MWNT-TEMPO) groups was prepared first by esterification of4-hydroxy-2,2,6,6-tetramethylpiperidine-l-oxy (HO-TEMPO) and carboxylic acid group on the surface of MWNT, and then PEG with bromide end group (PEG-Br) were obtained by esterification of PEG and ethyl2-bromoisobutyryl bromide, while PDMAEMA-Br/PtBA-Br achieved by ATRP reaction. The polymer (PEG/PDMAEMA/PtBA) grafted MWNT were successfully produced by bromo-ended polymers and2,2,6,6-tetramethylpiperidine (TEMPO) groups attached on the MWNT surface via ATNRC reaction.The products were characterized by FTIR and TGA. The efficiency of ATNRC reaction in MWNT-TEMPO/PDMAEMA-Br/PtBA-Br reached75.4%,89.1%, Nevertheless, in MWNT-TEMPO/PEG-Br was41%, which showed not higher than systerm MWNT-TEMPO/PEG-Br/St and MWNT/PEG-Br.Usually, the higher activity for PEG-Br would lead to the easier termination via disproportionation during the ATNRC procedure. Even adding St monomer which played a role in transferring radical and delaying the theinactivation time in homogeneous polymerization system,, however, it can not improve the grafting efficiency due to the heterogeneous system.it can be resulted that ATNRC system was not applicable to PEG-Br. But grafting efficiency of MWNT-TEMPO/PEG-Br was much higher than that of other ATRNC/PEG-Br system reported in the literature ascribed to the strong free scavergency of MWNT.2. MWNT-g-PDMAEMA was synthesized by MWNT-TEMPO with different molecular weight PDMAEMA-Br. The target products were characterized by GPC, TGA,1H NMR spectroscopy. Rheological measurements were used to characterize the rheological properties in different pH. It was found that the lower critical solution temperature (LCST) decreased with the increase of pH. Compared with pure PDMAEMA solution with same concentration, MWNT-g-PDMAEMA had higher modulus and strength; the shear thickening of MWNT-g-PDMAEMA/PDMAEMA solutions was studied. The results showed that shear thickening could be observed under certain conditions:1) high solution concentration;2) enough chain length of PDMAEMA;3) high PDMAEMA content in solvent;4) high pH. The self-assembly studiesshowed that the LCST of the aqueous solution decreased with the increase of pH and ionic strength, and the diameter of the formed micelles increased with the increase of pH and ionic strength.3. MWNT-g-PDMAEMA-mPEG/a-cyclodextrin (a-CD) formed by stimulus-responsive MWNT-g-PDMAEMA-mPEG and a-CD was studied.The stoichiometry value of [EO]/α-CD calculated from’H-NMR data was2.06. The structures of the as-obtained hydrogels were confirmed by1H-NMR, TGA and DSC analyses. The rheological measurement shows that the Inclusion Complex was pH/temperature-responsive. Meanwhile, the introduction of MWNT nanoparticles positively affected the strength and viscosity of the hydrogels. More importantly, the hybrid hydrogels also showed a shear thinning effect attributed to the supramolecular physical nature of the supra-cross-links. Thermal analysis showed that the thermal stability of the hybrid hydrogel was substantially improved by up to50℃higher than that of native hydrogel. |
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