Polydimethylsiloxanes-modified TiO2 coatings: The role of structural, morphological and optical characteristics in a self-cleaning surface

The surface modification of TiO2 thin film with hydrophobic agents has been a good strategy for modulation properties of this versatile material, allowing it to be compatible with a wider range of applications. This is a promising approach in the developing of improved self-cleaning materials; since films prepared with this modification are expected to exhibit photocatalytic and hydrophobic properties. However, these strategies still need to be improved, seeking the design of hydrophobic and photocatalytic structures through faster and simpler procedures, using non-fluorinated polymers. This work proposed the synthesis and characterization of self-cleaning coatings, involving a polydimethylsiloxane (PDMS)/TiO2 system. TiO2 thin films were modified with two different types of PDMS: hydroxyl and vinyl-terminated - and prepared by two distinct routes: Route A, which involved a modified TiO2 sol-gel process, and route B, consisting in the functionalization of TiO2 films after their calcination. Each route was best suited for a different type of PDMS. The PDMS modification occurred by a covalent linkage, which can allow a better durability of the functionalization on TiO2 surface. In some cases, the functionalization was heterogeneous and promoted a significant increase in surface roughness, allowing these samples to present hydrophobicity and photocatalytic activity.