Theoretical and experimental studies on interactions of cationic-anionic surfactants

Typical cationic and anionic surfactants were chosen and their interactions were calculated by quantum chemical method. Interaction energies are -0.2378 kJ.mol(-1), -3.3394 kJ.mol(-1) and 0.1204 kJ.mol(-1) for the molecular pairs with fluocarbon and hydrocarbon chain: C4H10/C5H12, C4F10/C5H12, and C4F10/C5F12, respectively. When hydrophilic group with cationic and anionicions is introduced, interaction energies are -287.40 kJ.mol(-1), -311.18 kJ.mol(-1) and -345.83 kJ.mol(-1). The results show that there is strong static interaction between cationic and anionic surfactants. It has been predicted that mixed monolayer may be formed and surface activity is enhanced favorably, especially for mixtures of cationic and anionic surfactants with fluocarbon and hydrocarbon chains. The anionic surfactants, sodium octadecylbenzenesulfonate perfluopolyetherbenzenesulonate(ANF-I) was synthesized, mixture effects of ANF-I with sodium octadecylbenzenesulfonate or dodecyldimethyl benzylammonium bromide were studied. The results indicate that the efficiency of mixing increased and the theoretical prediction was testified. These results can provide useful information for the design of new surfactants.