| Abstract
| - Molecular dynamics simulations were used to study the wetting of nanogrooved PE and PVC polymer surfaces.The contact angles, equilibrium states, and equilibrium shapes of two nanosized water droplets were analyzed onsurfaces with 1D-arranged periodic roughness of various dimensions. The composite solid−liquid contact, which ispreferred in practical applications and in which a droplet rests on top of the surface asperities, was observed on theroughest PE surfaces, whereas water filled the similar but slightly deeper grooves on PVC surfaces. The transitionfrom the wetted to composite contact regime occurred when the contact angle with a flat surface reached the valueat which the apparent Wenzel and Cassie contact angles are equal. Droplets on grooved PE surfaces with the compositecontact exhibited contact angles in agreement with Cassie's equation, but the increase in hydrophobicity on smoothersurfaces with the wetted contact was less than expected from Wenzel's equation. The difference between the simulatedand theoretical values decreased as the dimensions of the surface grooves increased. Only a slight increase or evena slight decrease in the contact angles was observed on the grooved PVC surfaces, owing to the less hydrophobicnature of the flat PVC surface. On both polymers, the nanodroplet assumed a spherical shape in the composite contact.Only minor anisotropy was observed in the wetted contact on PE surfaces, whereas even a highly anisotropic shapewas seen on the grooved PVC surfaces. The contact angle in the direction of the grooves was smaller than that inthe perpendicular direction, and the difference between the two angles decreased with the increasing size of the waterdroplet.
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