Micellar Morphology in the Presence of Salts and Organic Additives

Viscometry under Newtonian flow conditions has been used to study morphological changes in 0.3 M sodium dodecyl sulfate (SDS) micellar solutions in the presence of aliphatic amines ( n -heptyl, C 7 NH 2, or n -octyl, C 8 NH 2 ) and different inorganic (MCl, M = Li, Na, K, or Rb; and NaX, X = Cl, Br, or SCN), organic salts (NaY, Y = salicylate (Sal), benzoate (Ben), anthranilate (An), or tosylate (Tos)), symmetrical quaternary bromides (R 4 NBr, R = H, CH 3, C 2 H 5, n- C 3 H 7, n -C 4 H 9, or n -C 5 H 11 ) or tetrabutylphosphonium bromide, ( n -C 4 H 9 ) 4 PBr, at 30 °C. Addition of amines with or without organic/inorganic salts causes the usual viscosity increase until the phase boundary of the L 1 phase is reached. However, in the presence of quaternary bromides, viscosity−[amine] profiles show an increase, a plateau, and slower decrease regions. The appearance of these regions has been found to be dependent on the chain length of the R-part and [quaternary bromide]. These effects have been discussed on the basis of solubilization of aliphatic amines in a micellar palisade layer or micellar exterior and their possible effects on the packing parameter and micellar morphology.