Prediction of the surface tension of deep eutectic solvents

Surface tension is one of the important deep eutectic solvents (DESs) physical properties which provides considerable information related to the molecular influence on the intensity of interactions in the mixture. Due to the absence of DESs surface tension experimental data, prediction methods of this property become of high importance. In this work, two simple methods for the prediction of DESs surface tension are presented. The first method reports the use of the parachor to predict surface tension. In the second method, the effect of temperature variation on surface tension was predicted using the Othmer equation. The parachor of nine different DESs based on ammonium and phosphunium salts were determined experimentally as well as calculated from the molecular structure of their constituting components using available parachor contribution data for neutral compounds. The results showed that calculated and experimental parachor of DESs were notably close and that the parachor contribution data developed for neutral compounds can be successfully utilized for deep eutectic solvents with an average surface tension prediction percentage error of 6.4%. The average prediction percentage error using the Othmer equation was 2.57%. This proves that surface tension of DESs can be predicted efficiently using either one of the two suggested methods. (C) 2012 Elsevier B.V. All rights reserved.