Increasing surface roughness of coatings to promote high-hydrophobicity

ABSTRACT: We have developed a simple sol-gel route to produce organic-inorganic hybrid nanomaterials without Volatile Organic Compounds (VOCs). Our materials are obtained by mixing a silica oligomer and an aqueous solution of n-octylamine under ultrasonic agitation. Moreover, an organic component (polydimethylsiloxane, PDMS) is added to give hydrophobic properties to the product. In order to evaluate the effect of the organic component on hydrophobicity, we use different PDMS contents. The addition of PDMS to the starting sol creates a dual scale of roughness, which is increased as PDMS content is higher. We conclude that PDMS plays an important role in the hydrophobic behavior of the product by two mechanisms: by reducing surface energy and by creating a dual type of roughness. Finally, we have demonstrated the hydrophobic effectiveness of these products on two popular monumental stones.