Wetting behavior and solid surface tensions for a 70 : 30 copolymer of polystyrene and poly(methyl methacrylate)

Low-rate dynamic contact angles of 12 liquids on a poly(styrene/methyl meth acrylate, 70/30) P(S/MMA, 70/30) copolymer were measured by an automated ax isymmetric drop shape analysis profile (ADSA-P). It was found that 8 liquid s yield non-constant contact angles, and/or dissolve the polymer on contact . From the experimental contact angles of the remaining 4 liquids, it was f ound that the product of the liquid-vapor surface tension and the cosine of the contact angle changes smoothly with the liquid-vapor surface tension, i.e., gamma(lv)cos theta depends only on gamma(lv) for a given solid surfac e (or solid surface tension). This contact angle pattern is in harmony with that of the corresponding homopolymers, polystyrene and poly(methyl methac rylate), previously studied [42, 47]. The solid-vapor surface tension calcu lated from the equation-of-state approach for solid-liquid interfacial tens ions [14] is found to be 33.0 mJ/m(2), with a 95% confidence limit of +/-0. 3 mJ/m(2), from the experimental contact angles of the 4 liquids.