Micellization And Synergistic Effects In Mixed Anionic/Nonionic Surfactant Systems

Firstly, dodecyl benzene sulfonate (MDBS) and lauryl sulfate MDS were selected as anionic surfactants. DDM and Brij30were selected as non-ionic surfactants respectively.And then an anionic surfactant was mixed with a non-ionic surfactan to form binary surfactants system.The mixed critical micelle concentration (cmc) of the binary surfactants systems was determined by surface tension measurement. The cmc data was used to calculate the molecular interaction parameters according to regular solution theory. Test results show that:(1) The NH4DS/DDM, NH4DS/Brij30, SDS/Brij30mixed systems have significantly excellent surface activity compared with a single surface active agent system.(2) The NH4DS/DDM, MDS/Brij30mixed systems all had micellization and reduced the surface tension.(3) The MDBS/DDM mixed system has the micelle synergy. The SDBS/Brij30and the IDBS/Brij30mixed systems also have the micelle synergy when αMDBS=0.3.(4)Thermodynamics investigation of mixed micelles showed that the Gibbs free energy values of all the mixed systems were negative, and micellization is a spontaneous process. At the same time, the aggregation numbers of micelles for deferent ratio mixed systems were determined by steady-state fluorescence probe method with pyrene as fluorescence probe and benzophenone as quencher.(5)The aggregation numbers of micelles for the mixed systems(NH4DS/DDM、NH4DS/Brij30、Mg(DS)2/DDM、Mg(DS)2/Brij30) were all smaller than that of the pure anionic surfactants, but bigger than that of pure non-ionic surfactants.(6)The aggregation numbers of micelles for the mixed systems (MDBS/DDM^MDBS/Brij30) just opposite results. And the study based on pyrene I1/I3ratio index reported information on the microenvironmental properties of mixed micelles at the same composition supports the explanation.Secondly, the cmc of the binary mixtures at SDBS molar fraction (αSDBS) from0.0to1.0has been quantitatively estimated by steady-state fluorescence measurements. The micellar characteristics had been estimated following two different theoretical treatments. Investigation shows that the interaction parameter (β12) were obtained are negative values for the three mixtures at all composition, and the negative degree of average value β12ave for the three mixtures followed the order of SDBS/TX-100> SDBS/Brij35> SDBS/Brij58. The negative β12values for the three systems imply that the interaction between the SDBS and the three nonionic surfactants is attractive in nature, being more intense in the case of SDBS/Brij58.The aggregation numbers of micelles for the mixed systems were all bigger than that of the pure anionic surfactants, but smaller than that of pure non-ionic surfactants. Zeta potential measurement shows that the absolute value of Zeta potential|(?)|decrease abruptly for the three mixtures confirmed the synergistic interaction between the binary surfectants. The|(?)|value decreased most markedly for the SDBS/Brij58which means the synergistic interaction is most intense in SDBS/Brij58.The behavior of mixed surfactant solutions, that was, the binary and ternary surfactant combinations of SDBS, TX100and Brij30had been studied by surface tension in aqueous medium. The physicochemical properties of the systems observed to depend on the solution composition. The results suggested that the values on the basis of Rosen approaches proved that there is synergism in the mixed micelle. Different systems had been compared. There is synergism in the reduction of the surface tension of aqueous solutions of different binary mixture.The theory about the synergic effect of the non-ideal ternary mixture agreed well with the experimental results.