Low-rate dynamic contact angles on poly(methyl methacrylate/ethyl methacrylate, 30/70) and the determination of solid surface tensions

Abstract

Low-rate dynamic contact angles of 12 liquids on a poly(methyl methacrylate/ethyl methacrylate, 30/70) P(MMA/EMA, 30/70) copolymer were measured by an automated axisymmetric drop shape analysis-profile (ADSA-P). It was found that five liquids yield nonconstant contact angles, and/or dissolve the polymer on contact. From the experimental contact angles of the remaining seven liquids, it is found that the liquid-vapor surface tension times cosine of the contact angle changes smoothly with the liquid-vapor surface tension (i.e., γlυ cos θ depends only on γlυ for a given solid surface or solid surface tension). This contact angle pattern is in harmony with those from other methacrylate polymer surfaces previously studied. 45,50 The solid-vapor surface tension calculated from the equation-of-state approach for solid-liquid interfacial tensions 14 is found to be 35.1 mJ/m 2 , with a 95% confidence limit of ± 0.3 mJ/m 2 , from the experimental contact angles of the seven liquids.