Solubilization of n-alkylbenzene and n-perfluoroalkylbenzene in hydrogenated and fluorinated surfactants micelles

The maximum solubilities of homologous series of n-alkylbenzene and n-perfluoroalkylbenzene in aqueous solutions of surfactants n-tetradecyltrimethylammonium chloride (TTAC) and N  -(1,1-dihydroperfluorodecyl)-N,N,NN,N,N-trimethylammonium chloride (C10F-TAC) were measured as a function of the surfactant concentration at 298.2 K. There are four solubilization systems in viewpoints of hydrocarbons and fluorocarbons. In general, in all systems, the maximum solubility decreased with an increase in the alkyl carbon length of the solubilizates. The homogeneous combinations of solubilizates and solubilizers have higher affinity than heterogeneous combinations. The affinity between a hydrocarbon and a fluorocarbon can be clarified by determining the Gibbs free energy (ΔG0ΔG0) on solubilization by thermodynamic analysis. The largest negative value of ΔG0ΔG0 was obtained for the homogeneous system of n-perfluoroalkylbenzene and C10F-TAC, whereas the smallest value was obtained for the heterogeneous system of n  -perfluoroalkylbenzene and TTAC. The contributions of methylene and perfluoromethylene to Gibbs energy, namely, ΔGCH20 and ΔGCF20, were found to be −2.6 and −2.9 kJ mol−1, respectively, for the TTAC solution, whereas the respective values for the C10F-TAC solution were −2.0 and −3.3 kJ mol−1.

Incremental free energy of solubilization per methylene group and perperfluoromethylene group.Figure optionsDownload as PowerPoint slide