INTERACTIONS BETWEEN OCTYLMETHYLSULFOXIDE AND IONIC SURFACTANTS IN AQUEOUS SOLUTIONS

The interactions between nonionic surfactant octylmethylsulfoxide (OMS) and ionic surfactants sodium decylsulfate(SDeS), sodium perfluorooctanoate(SPFO), and decyltrimethylammonium bromide (DeTAB) in aqueous solutions have been investigated. The following results are obtained: 1) The critical micelll concentration (cmc)-mole fraction(alpha) curves of all mixtures discussed are lower than the ideal ones. 2) The surface absorptions at cmc(Gamma(cmc,T)) of OMS-SDeS, OMS-SPFO mixtures have maximum values. But those of OMS-DeTAB mixtures have not. 3) The surface tension at cmc (gamma(cmc)) of OMS-SPFO solution can reach a value below 16 mNm(-1) which is lower than those of single OMS and SPFO. However, gamma(cmc) of the other two kinds of mixtures are lower than that of single SDeS or DeTAB, but higher than that of single OMS. 4) All of the molecular interaction parameters of surfactants in micells (beta) and in surface layers (beta) are negtive. Their variations are also discussed. 5) Interactions of OMS-SDeS, and OMS-SPFO are much stronger than that of OMS-DeTAB. It is explained with protonation of some of the oxygen atoms of OMS molecules in aqueous solutions.