EFFECT OF NAOH AND NACL ON THE DISODIUM N-DECANE PHOSPHONATE MICELLARAGGREGATION NUMBER

The diffusion coefficient of disodium n-decane phosphonate micelles wa s studied by polarography at 25 degrees C in NaCl and in NaOH solution s, and the size and aggregation number of the micelles was computed as a function of Na+ concentration. All other conditions being equal, th e addition of NaCl produces micelles with an aggregation number one or der of magnitude larger than the NaOH addition. This is due to the inc rease of the effective charge per micellized head group produced by th e reaction of OH- with the hydrolized head groups which are mainly pre sent as -PO3H- in the micellar Stern layer.