Modification of porous silica particles with poly(acrylic acid)

The surface of porous silica particles was modified with poly(acrylic acid) by reacting the carboxyl groups on poly(acrylic acid) with the amino group s of pregrafted aminopropyltriethoxysilane (APS). The chemical modification s by APS and polymer were characterized by infrared spectroscopy and the am ount of APS and poly(acrylic acid) grafted to the surface were determined b y thermal gravimetric analyses. The wettability of the modified silica part icles, based on the rate of water penetration, was pH-dependent with PAA; a t pH 1.5 the wettability increased but at pH 5.5 it decreased dramatically. The pore size and size distribution of the silica particles decreased with APS and polymer grafting. Copyright (C) 2000 John Wiley & Sons, Ltd.