Hydrophilic/hydrophobic properties of silica surfaces modified with metal oxides and polydimethylsiloxane

Abstract

Microcalorimetry and measurements of the contact angle of water were performed to investigate the hydrophilic/hydrophobic properties of silica surfaces modified with metal oxides and polydimethylsiloxane (PDMS) at 20-500°C. Fumed silicas whose surfaces contained grafted oxygen compounds of metals were used as adsorbents, with VOCl 3, CrO2Cl2, TiCl4, SnCl4, AlCl3 and Zn(acac)2 vapours being applied as modifiers. It was found that the hydrophobic coating of silicas modified with metal oxides and PDMS (8-40 wt%) was stable over the temperature range 100-350°C. With a titania coating, the hydrophobic properties were retained at temperatures up to 500°C for an adsorbed polymer content of 20-40 wt%.