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Poly(N-isopropylacrylamide)(PNIPAAm)-modified silica bead with varied grafting density and same length was prepared via atom transfer radical polymerization(ATRP).The grafting ratio of PNIPAAm was characterized by thermogravimetric analysis(TGA),and length of them was determined by gel permeation chromatography(GPC).Our results showed that all of these stationary phases exhibit a lower critical solution temperature(LCST),it is between 30℃ to 40℃.The elution behavior of five steroids was investigated by using water as mobile phase.The results showed that PIPAAm grafting density has a crucial influence on separation efficiency of thermosensitive chromatographic stationary phase.On less PNPAAm chains on silica surface,short retention time,narrower peak width was observed compared with more PNIPAAm.But if the grafting density was too more,the column efficiently would be get worse.So the proper grafting ratio of the PNIPAAm on the suface of the silica is crucial.