Optimizing Hydrophobicity and Photocatalytic Activity of PDMS-Coated Titanium Dioxide

Polydimethylsiloxane (PDMS) can be linked to the surface of metal-oxide photocatalysts by immersion and UV illumination. The surfaces become hydrophobic and keep their hydrophobicity even under extended UV exposure. Titanium dioxide (TiO₂) is a prominent example of a metal-oxide photocatalyst. Here, we studied the influence of a grafted PDMS layer on the photocatalytic activity and wetting properties of TiO₂. By varying the molecular weight of PDMS, we controlled the thickness of the polymer layer from 0.6 to 5.5 nm. We recommend a PDMS molecular weight of 6.0 kDa. It leads to a grafted PDMS layer thickness of 2.2 nm, a receding contact angle of 94°, a low contact angle hysteresis of 9°, and the layer is still photocatalytically active.