Surface properties of cationic bolaamphiphiles and their mixed systems with oppositely charged conventional surfactant

Surface properties of three cationic bolaamphiphile eicosanediyl 1,20-bis(pyridinium bromide) [Py+(CH2)20Py+]2Br−, phenyl 1,4-bis(oxyhexyl trimethyl ammonium bromide) (C6PhC6), phenyl 1,4-bis(oxydecyl trimethyl ammonium bromide) (C10PhC10), and their mixed systems with oppositely charged conventional surfactant sodium dodecyl sulfite (SDS) were studied. The results showed that bolaamphiphiles with rigid group also adopted reverse U-shape conformation at the air/water interface as those with flexible skeleton. Micellization in these bolaamphiphile systems is easier than those of the comparable conventional surfactants. Micellization thermodynamic parameters were calculated according to the phase separation model and entropy was found to be the main driving force in the process of micellization. Diagrams for the C6PhC6/SDS and C20Py2/SDS mixed systems were constructed based on the regular solution theory. It was found that the structural difference between the two bolaamphileles affects the interaction between the two components in each mixed systems greatly.