| Poly(N-isopropylacrylamide) (PNIPAAm) nanogel dispersions of high concentration exhibit rich phase behaviors while temperature changes. The molecular structure, the diameter of the nanogel and the medium of the nanogel dispersion are of great influence on the phase behaviors. Given by these special phase behaviors and rheological property, PNIPAAm nanogel dispersion has a great prospect of been used in biomedical field, for example, used as injectable in situ-forming gel stuff, and embolic materials. In this thesis, we research the PNIPAAm nanogels with a dimeter of 150~ 600nm. The dispersions of the nanogels are of great thixotropy and are highly temperature responsive. Main contents and results are as follows:(1)PNIPAAm nanogels were prepared by precipitation polymerization in the presence of various amount of surfactant. The sizes of PNIPAAm nanogels were narrowly distributed with diameters of 573.4 nm,340.6 nm,247.7 nm,192.5 nm characterized by dynamic light scattering (DLS). Scanning electron microscope (SEM) was employed to character nanogel particles dried at a temperature which was far beneath the volume phase transition temperature (VPPT). SEM images of the nanogel particles were in coincidence with the DLS result. Atomic force microscopy (AFM) was employed to character nanogel particles dried at a temperature higher than VPTT. PNIPAAm nanogel was shrinked with the increasing temperature. PNIPAAm nanogel with a diameter of 192.5 nm kept its spherical form while the nanogel particle with a diameter of 573.4 nm became an irregular shrinkage.(2)DLS was employed to determine the diameter of nanogel particles as temperature changed. The VPPT of nanogel particles were 32℃, despite of the diameter. Volume phase transition was reversible though swelling was slower than deswelling. The temperature range required for equilibrium swelling increased while the diameter of the nanogel particles increased. Equilibrium swelling ratio decreased while the diameter of the nanogel particles increased. Kinetics of the thermosensitive volume phase transitions of PNIPAAm nanogel particles were investigated by time-course UV-vis spectroscopy, VPT completed in 100s despite of the diameter. Swelling kinetics curves were delayed than that of deswelling.(3)The vial inverting with visual method was employed to study the phase behaviors of PNIPAAm nanogel dispersions of high concentration. The nanogel dispersions exhibited 6 phases while temperature increased: semi translucent swollen gel, homogeneous fluid, viscous fluid, opaque swollen gel, physically bonded nanogel network, phase-separated colloidal fluid. Besides, PNIPAAm nanogel(247.4 nm and 192.5 nm) 15% dispersions formed physically bonded nanogel networks at 37℃and kept its structure in water, as a embolism in interventional therapy. The viscosity of nanogel dispersions decreased while temperature increased, until VPPT. The nanogel dispersions which formed physically bonded nanogel network exhibited a sharp increase of viscosity at VPTT. Other dispersions decreased in viscosity constantly. All of the nanogel dispersions had the property of shear thinning.(4)The influence of iopamidol on PNIPAAm nanogel was researched. Iopamidol resulted in the increase of the diameter and the VPTT of nanogel particles in diluted dispersions. The vial inverting with visual method was employed to study the phase behaviors of nanogel high concentration dispersions with iopamidol. The separate temperature was increased by 5℃. The viscosity and shear thinning property of the nanogel dispersions were not changed by Iopamidol.In a word, the resultant PNIPAAm nanogel dispersions were novel thermosensitive materials which exhibited multi-phase behavior with the change of temperature. The studies on its multi-phase behavior are very important on its application.
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