Low-rate dynamic contact angles on poly[styrene-alt-(hexyl/10-carboxydecyl(90/10)maleimide)] and the determination of solid surface tensions

Abstract

Low-rate dynamic contact angles of 14 liquids on a poly[styrene-alt-(hexyl/10-carboxydecyl(90/10)maleimide)] P[S-(H/CM)] were measured by means of an automated axisymmetric drop shape analysis-profile (ADSA-P). It was found that 9 liquids yield non-constant contact angles, and/or dissolve the polymer. From the experimental contact angles of the remaining 5 liquids, it was found that the product of the liquid-vapour surface tension and the cosine of the contact angle changes smoothly with the liquid-vapour surface tension, i. e. γlv cos θ depends only on γlv for a given solid surface (or solid surface tension). This contact angle pattern is in harmony with those from other inert and non-inert (polar and non-polar) surfaces. The solid-vapour surface tension calculated from the equation-of-state approach for solid-liquid interfacial tensions was found to be 31.0 mJ/m2, with a 95% confidence limit of ±0.6 mJ/m2 from the experimental contact angles of the 5 liquids in Laboratory 1, and γsv = 29.9 mJ/m2 from measurements with two liquids in Laboratory 2. The difference is essentially due to actual physical differences between the polymer films prepared in the two laboratories.