A QSPR model for the prediction of the "fish-tail" temperature of C(i)E4/water/polar hydrocarbon oil systems.

The fish-tail temperatures denoted as T* have been determined or collected for 85 ternary systems based on three tetraethylene glycol monoalkyl ethers C(i)E(4) (i = 6, 8, 10), water, and 43 hydrocarbon oils of various hydrophobicities. Fourteen fragrant mono- and sesquiterpenes in addition to 29 model oils, including n-alkanes, cyclohexenes, cyclohexanes, and alkylbenzenes, were investigated in order to establish a QSPR model for the prediction of T* as a function of the chemical structure of the oils. Only two molecular descriptors related to branching and molecular size (Kier A3) and polarizability (average negative softness) of the molecules are necessary to model and predict the values of T* and EACN (equivalent alkane carbon number) of unsaturated and/or cyclic and/or branched hydrocarbons exhibiting an EACN ranging from -4 and +35. Results are discussed in terms of evolution of the effective packing parameter of the surfactants according to temperature and oil penetration into the interfacial film.