Abstract. The surface modification of the anatase titania nanoparticles prepared via a controlled nonhydrolytic sol-gel process is achieved by the formation of the bidentate coordination between titania and methacrylic acid (MAA) molecules. The in situ photocatalytic polymerization of methyl methacrylate (MMA) monomer is initiated by surface modified anatase titania nanoparticles under Xe lamp irradiation. A variety of techniques including differential scanning calorimetry (DSC), thermo-gravimetric analysis (TGA) and scanning electron microscopy (SEM) are employed to characterize the resulting materials. The glass transition temperatures and the thermal stabilities of polymethyl methacrylate (PMMA) composite materials prepared via photocatalytic polymerization are enhanced compared with pure polymer. The partial aggregation of titania nanoparticles in PMMA composite films is derived from the surface polymerization of MMA, which makes the inorganic particles hydrophobic and drives them to the water/oil interfaces.