S. Sotiropoulos et al., ADSORPTION OF SODIUM DODECYL-SULFATE ON MERCURY AS AN EXAMPLE OF MICELLIZATION WITHIN A MULTILAYER INTERPHASE, Journal of electroanalytical chemistry [1992], 356(1-2), 1993, pp. 201-223
The adsorption of sodium dodecylsulphate from aqueous electrolytic sol
utions on a polarized mercury electrode was studied by means of differ
ential capacitance measurements over a wide range of concentration and
potential, and in the presence of different supporting electrolytes w
ith different ionic strengths. An interpretation of the differential c
apacitance vs. applied potential curves is given, based on theoretical
treatments developed previously. It is shown that at concentrations b
elow the cmc, two-dimensional aggregates are formed on the electrode s
urface within a polarization region which is bounded by two capacitanc
e peaks at extreme positive and negative polarizations. This film is n
ot particularly stable and is transformed into a compact layer at pola
rizations close to the potential of maximum adsorption, resulting in a
capacitance pit. With increasing bulk concentration the aggregation p
rocess extends across the interphase and at least two layers of aggreg
ates-micelles are formed at concentrations around and above the cmc. T
his three-dimensional aggregation is characterized by the appearance o
f deformed and/or split capacitance peaks which determine the polariza
tion region where this phenomenon occurs.