The nano-composite hydrogels were prepared by the radical graft copolymerization of N- isopropylacrylamide onto the surface of Nano-SiO2 particles treated with vinyhrimethoxysilane in a mixture solvent of H2O/THF at 25℃

and N

N’-methylene bisacrylamide (BIS) was used as the crosslinking agent The products were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy These composite hydrogels exhibit higher swelling ratio than the usual poly(N-isopropylacrylamide) hydrogels at fow temperature(15℃) and more excellent water release behavior at high temperature(50℃)．The swelling ratio of hydrogel H1

which has no nano-SiO2 component

is about 29 at 15℃

by contrast

the swelling ratio of hydrogel H4 which contents 5％nano-SiO2 component is about 35 at the sanle temperature At the same time

the water release behavior of hydrogel H4 shows an almost linear form

which is very essential to the controlled drug delivery systems．The reasons causing the properly improvement of the hydrogels were discussed．