(188w) A Simple Methodology for Producing Super-Hydrophobic Composite Films on Various Substrates

The use of coating materials with low surface energy and the creation of surface roughness is known to amplify the hydrophobic character of a surface. Within this framework a simple methodology for enhanced hydrophobicity is presented. Various nanoparticles (silica, tin and alumina) were dispersed in a poly(alkyl siloxane) (Rhodorsil 224). The mixtures were sprayed on silicon substrates resulting in the formation of a rough, two-length-scaled hierarchical structure which resembles to the surface morphology of the lotus-leaf.

We report that: i) Super-hydrophobic composite films were produced with all the different kind particles mixed with the polymer ii) The measured maximum equilibrium contact angles were found to be independent of the nature of the polymer-particle binary mixture. iii) The equilibrium contact angles measured on surfaces which were prepared from dilute dispersions were increased rapidly with particle concentration reaching some maximum values (162±2^ο) and iv) When the equilibrium contact angle is maximum, the contact angle hysteresis reaches some minimum values (2-4^ο) providing evidence that the composites prepared with high particle concentrations are super hydrophobic and exhibit augmented water repellence.

The methodology was also tested on various substrates (glass, marble, concrete, aluminum, silk, wood). The equilibrium contact angle measurements revealed that the substrate has no significant effect on the superhydrophobic character of the applied coatings.

The suggested strategy has some important advantages: i) It is a low cost and simple method ii) It can be used on large surfaces, such as facades and stone monuments.

Acknowledgements

This research project (PENED 2003) with MIS 03ΕΔ91 is co-financed by E.U.-European Social Fund (75%) and the Greek Ministry of Development-GSRT (25%). The support of Greek State Scholarship's Foundation to Mr. P. Manoudis is also gratefully acknowledged.