Thermosensitive core-shell particles were synthesized through grafting copolymerization of N-isopropylacrylamide (NIPAM) with ［3-(methacryloyloxy) propyl］ trimethoxysilane (MPT) coupled on the surface of ultra fine silica dioxide beads.The grafting copolymerization was carried out at the present of polyvinyl alcohol as a surfactant

H2O/cyclohexanol as mixed solvents

and 2

2′-azobis(isobutyronitrile) as an initiator.The effect of surfactant concentration and the composition of mixed solvents on the grafting rate was investigated.The infrared spectrum has confirmed the structure of the modified silica.Differential scanning calorimetry (DSC) has indicated the thermosensitivity of the particles.The thermosensitive particles were used as packing materials of high-performance liquid chromatography (HPLC) for separating naphthalin derivatives.The results revealed that satisfactory separation was attained by controlling temperature of the column.As a comparison the packing material of silica-MPT has no such separating efficiency due to absence of thermosensitivety.The mechanism for the temperature-controlled separation is attributed to the polarity change of the PNIPAM on silica surface when PNIPAM undergoes volume phase transition.