From superhydrophobicity and water repellency to superhydrophilicity: smart polymer-functionalized surfaces

pH-responsive surfaces, reversibly switching between superhydrophilicity and superhydrophobicity/water repellency, are developed by grafting from'' a pH-sensitive polymer onto a hierarchically micro/nano-structured substrate. We quantify the water repellency by investigating the restitution coefficient of water droplets bouncing off the surfaces. The water repellent state requires appropriate hydrophobicity of the functionalizing polymer as well as very low values of contact angle hysteresis.