Surface mobility and structural transitions of poly(n-alkyl methacrylates) probed by dynamic contact angle measurements

Dynamic contact angles and contact-angle hysteresis of a series of poly(n-alkyl methacrylates) (PAMA) were investigated using the Wilhelmy plate technique. The mobility of polymer surface chains, segments, and side groups affected the measured contact angles and their hysteresis. A model is presented in which contact-angle hysteresis of PAMA's is explained in terms of the reorientation of polymer chains and segments at the interface of the polymers with water and air. The contact angles observed also indicated structural transitions in the polymer surfaces of PAMA's that were dependent on alkyl side chain length and temperature.