THE INTERACTION OF SOME NOVEL DIQUATERNARY GEMINI SURFACTANTS WITH ANIONIC SURFACTANTS

The interactions of a series of novel cationic gemini surfactants, H2n +1(CH3)(2)N+CH2CHOHCHOHCH2(CH3)(2)N+CnH2n+1](2) 2Br(-) (symbolized (Cn N)(2)), with conventional surfactants (containing a single hydrophilic and a single hydrophobic group in the molecule) have been investigate d. It is found that (C8N)(2) and (C10N)(2) have very strong interactio ns with the anionic surfactants C10H21SO3Na, C12H25SO3Na, and C12H25SO 3Na, and C12H25(C2H4O)(4)SO4Na, producing marked synergism in surface tension reduction efficiency and effectiveness and in mixed micelle fo rmation in H2O, 0.1 M NaBr, and 0.1 M NaCl. In contrast to this, (C12N )(2) shows no synergism at all with C12H25SO3Na and has a much weaker synergistic interaction with C12H25(C2H4O)(4)SO4Na It is proposed that extraordinarily strong interaction between the (C12N)(2) and C12H25SO 3Na produces small, soluble, nonmicellar aggregates having no surface activity that decrease the monomer concentrations of the component sur factants, thereby reducing the surface activity of the system. Equilib rium constant calculations for this aggregate formation indicate that the two surfactants are present in a 1:1 molar ratio. (C) 1996 Academi c Press, Inc.