Determination of the second CMCs of dodecyl polyoxyethylene polyoxypropylene ether by the methods of cloud point, fluorescence, and viscosity

The second critical micellar concentrations (CMCs) of nonionic surfactant dodecyl polyoxyethylene polyoxypropylene ether C12H25O(EO)m(PO)nH (LS54: m=5, n=4; LS45: m=4, n=5; LS36: m=3, n=6) were determined by three methods: cloud point, steady-state fluorescence and viscosity in paper. A comparison of the results obtained from different experiment shows that the cloud point method is easier than the steady-state fluorescence, and the viscosity method is not a good method for the second CMCs’ determination.