The role of hydration in the wetting of a soluble polymer

By forcing a contact line to advance on the polymeric deposit left by a drying polymer droplet, we have been able to measure the contact angle of water on an hydrosoluble polymer substrate. Measuring simultaneously the contact angle and the hydration of the polymer, we show that a dry layer of hydrosoluble polymer is poorly wetting because of the hydrophobic backbone of the polymer, which segregates at the surface.