Superhydrophobicity of composite surfaces created from polymer blends.

Hypothesis: When they are used alone, some polymers, such as polypropylene, Carnauba wax or polycarbonate allow the creation of superhydrophobic surfaces by spin coating or casting. On the other hand, some other polymers, such as polystyrene, polyvinylacetate or polychloroprene, are unable to render a superhydrophobic surface by these techniques. Using binary mixtures of these two types of polymers in a single common solvent, superhydrophobic composite surfaces can be created. We aim to show that superhydrophobicity is depending on the ratio between the two polymers in the initial blend and their intrinsic wettability.

Experiments: The transition towards superhydrophobicity is studied on composite surfaces made of various polymers. Surfaces are created with simple coating methods, such as casting or spin-coating, of polymer solutions and letting the solvent evaporate at ambient conditions.

Findings: Transitions are sharp and the amount of polypropylene in the blend to achieve superhydrophobicity decreases with the hydrophobicity of the second polymer. Topographic and wettability measurements are performed that show that both effects, topographical and chemical, interplay in the property of superhydrophobicity.