Bj. Shiau et al., PRECIPITATION OF MIXTURES OF ANIONIC AND CATIONIC SURFACTANTS .3. EFFECT OF ADDED NONIONIC SURFACTANT, Journal of colloid and interface science, 167(2), 1994, pp. 332-345
The precipitation of an anionic surfactant by a cationic surfactant in
the presence of a nonionic surfactant is examined. The precipitation
domains for sodium dodecyl sulfate/dodecylpyridinium chloride were mea
sured over a wide range of surfactant concentrations as a function of
nonylphenol polyethoxylate concentration. Increasing the nonylphenol p
olyethoxylate concentration decreases the tendency for precipitation t
o occur. A model for predicting precipitation domains in ternary surfa
ctant mixtures has been developed and verified experimentally. The mod
el allows the nonionic surfactant to affect the precipitation behavior
only by lowering the critical micelle concentration of the mixture. S
mall deviations between theory and experiments along part of the anion
ic-rich micelle boundary result from adsorption of SDS on the precipit
ate which gives the microcrystals a negative charge and prevents their
growth to a visible size. (C) 1994 Academic Press, Inc.