GROWTH OF SODIUM DODECYL-SULFATE MICELLES IN THE PRESENCE OF N-OCTYLAMINE

The effect of addition of n-octylamine (OA) on structural transition i n aqueous (D2O) micellar solutions of SDS (sodium dodecyl sulfate) was studied by viscosity and small-angle neutron scattering (SANS) at var ious temperatures. The distinct rise in relative viscosity of SDS solu tion on the addition of a certain OA concentration (similar to 0.03 M) has been attributed to change in micellar shape from a sphere to a ro d, At higher OA concentration, these rods overlap giving rise to large increase in viscosity. SANS distribution showed a well-defined peak f or 0.3 M SDS. With the OA addition (0.02-0.065 M) shift in the peak po sition toward low and-values was observed. This is due to increase in intermicellar distance. The SANS distribution of 0.3 M SDS + 0.065 M O A, studied as a function of temperature; showed that micellar size dec reases on heating. The SANS spectra were analyzed using various existi ng models. The micelle dimension (bla) and mean aggregation number (ii ) were computed over a range of OA concentrations and temperatures. Th e observed results are interpreted in terms of mixed micelle formation with concomitant micellar growth.