Surface modification of silica, titania, and zinc oxide micro particles with epoxidized soybean oil for preparation of polystyrene composite films

A novel and convenient procedure is presented for bilayered encapsulation of silica, ZnO, and TiO₂ microparticles using highly adhesive unsaturated polyester, poly (2-hydroxy propylene maleate) (PHM) and epoxidized soybean oil (ESO). Thus, adsorption of PHM onto the particle surfaces from acetone solution (under sonication) and followed curing at 180°C resulted in self crosslinking of the polyester layer by thermally induced addition of its free-hydroxy groups to the maleate double bonds. The adsorption of the polyester onto particle surfaces was demonstrated to obey typical Langmuir isotherms. The oil was tethered onto particle surfaces through residual hydroxy groups of the crosslinked polyester layer at 180°C. Thermo gravimetrical analyses (TGA), FTIR spectra, and transmission electron microscopy (TEM) images of the oil-modified pigments clearly indicated presence of organic layers (26.4-37.3% w/w) with 0.1-0.15 lm thicknesses. The resulting organically modified particles were demonstrated to give fairly stable and homogenous dispersions in concentrated polystyrene solutions. Those dispersions were employed for preparing nearly transparent cast films on glass substrates. Scanning electron microscopy (SEM) images of the freestanding films did not show any phase separation.