Abstract:

The novel thermo-sensitive fluorine-containing amphiphilic graft copolymer was prepared by graft copolymerization of poly(ethylene glycol) methyl ether methacrylate(MPEGMA) macromonomer, 2,2,3,4,4,4-hexafluorobutyl methacrylate(HFMA) and N-isopropylacrylamide(NIPAAm). The molecular structures of the graft copolymer were characterized by FTIR, ¹H NMR, ¹⁹F NMR and gel permeation chromatography(GPC). The low critical solution temperature(LCST) was measured by UV-Vis spectrophotometer. The result shows that the LCST is about 38.9 ℃ and above the normal human physiological temperature. The critical micelle concentrations(cmc) were determined by the fluorescent probe technique. When the copolymer aqueous solution temperature was above the LCST, the cmc decreased significantly. The average hydrodynamic radius and size distribution of the copolymer micelles were measured by laser light scattering(LLS). The micelle size decreased greatly when the copolymer aqueous solution temperature reached the LCST. However, when the temperature was too high, the micelles became larger instead. The morphology of the copolymer micelles was observed by transmission electron microscopy(TEM). The result shows that P(NIPAAm-co-HFMA)-g-PEG can self-assemble into spherical micelles. When the temperature was under the LCST, the micelles had a loose core-shell structure. When the temperature was above the LCST, the micelle became compact and the core-shell structure was not obvious. In a word, the micelles were sensitive to the change of temperature.

Key words: Thermo-sensitive, Fluoropolymer, Amphiphilic graft copolymer, Micellization