Estimation of the surface tension components of thiodiglycol

The total surface tension of thiodiglycol was determined experimentally, and its surface tension components were estimated: γ^LW = 42 ± 1 mJ m^-2, γ⁺ = 1.1 ± 0.5 mJ m^-2, and γ^- = 25.0 ± 0.5 mJ m^-2. The Lifshitz - van der Waals component was estimated from experimental values of thiodiglycol/n-alkane interfacial tensions, measured by the pendant drop method. The γ⁺ and γ^- were estimated using the additional information of the contact angle of thiodiglycol on a solid substrate with known surface energy components. Three polymeric substrates were used independently with this purpose: PS, SAN2, and PMMA. The most consistent set of values was obtained using PMMA. The final establishment of the values for the surface tension components of thiodiglycol involved a trial and error procedure where the parameters were slightly changed to reproduce the previously calculated surface energy components of the three polymer substrates. This study reinforced the idea that the estimation of the surface free energy components of a liquid (or solid) is highly dependent on the calculation method and on the systems used to perform the calculations.