Fabrication Of PNIPAM Hydrogel Nanoparticles And Preliminary Study Of Their Applications

In this thesis, monodispersed and thermosensitive poly (N-isopropylacrylamide) (PNIPAM) hydrogel nanoparticles were prepared by emulsion polymerization with NIPAM as reaction material and N, N'-methylenebisacrylamide (BIS) as crosslinker in water. Their rapid responding to external stimuli and phase transition by suspension concentration's transition were studied in this thesis. After preparation, these hydrogel nanoparticles were dialyzed by distilled water-dialysis and electro-dialysis respectively. Compared of these two dialysis methods, electro-dialysis was better than distilled water-dialysis. The reasons were short time and high efficiency of electro-dialysis. The electro-dialysis was used in all following experiments.The mean diameter of PNIPAM nanoparticles was measured by dynamic laser light scattering at different temperatures, its lower critical solution temperature (LCST) we obtained was 33～34℃. After PNIPAM nanoparticles were dried at 100℃, we added water then these dried nanoparticles' concentration came back to the previous level. They remained themosensitivity and the LCST did not change. It indicated that PNIPAM nanoparticles were themoreversible and their themosensitivity was inherent. In addition, PNIPAM nanoparticles had rapid and reversible color phenomena. The hydrogel nanoparticles solution was transparent and exhibited an iridescent pattern at 15℃, and the temperature was raised to 55℃, at which point the pattern became invisible.In this thesis, controlled diameter which had 50～600 nm range and controlled LCST PNIPAM nanoparticles with different experiment conditions were obtained. The LCST of these different PNIPAM nanoparticles was measured by dynamic laser light scattering at different temperatures, and their thermosensitive figures were obtained. In addition, PNIPAM hydrogel nanoparticles network was obtained by high electro-dialysis under some experiments'conditions, maybe the network was crosslinked by covalent bond.The PNIPAM nanoparticles suspension was hydrolyzed by alkaline solution, and we got pH-sensitive gel nanoparticles. These hydrolyzed particles were measured by laser light scattering under different pH conditions. At about pH 7.2 to pH 8.0, the whole system's random intensity was broken and diameter of hydrolyzed particles changed rapidly, but at other pH values, diameters of hydrolyzed particles didn't change so rapidly.The PNIPAM nanoparticles suspension had specific NaCl sensitivity that caused phase transition, meanwhile normal saline's sensitivity could be measured, so we utilized Na~+, Cl~- to measure critical phase transition NaCl solution concentration in different PNIPAM nanoparticles suspension concentration. In...