S. Sotiropoulos et al., INTERFACIAL MICELLIZATION OF CETYL-DIMETHYL-BENZYLAMMONIUM CHLORIDE AND TWEEN-80(R) AT THE HG ELECTROLYTE SOLUTION INTERPHASE/, Journal of electroanalytical chemistry [1992], 356(1-2), 1993, pp. 225-243
The adsorption of a cationic micelle-forming surfactant, cetyl-dimethy
l-benzylammonium chloride, and of a neutral surfactant, Tween 80R, fro
m aqueous electrolyte solutions on a polarized mercury electrode was s
tudied by means of differential capacitance measurements in order to e
xamine the influence of the structure and charge of the adsorbate on i
nterfacial micellization. For both surfactants, deformed capacitance p
eaks were recorded, accompanied by capacitance plateaux. These are suf
ficient criteria for the occurrence of a two- or three-dimensional agg
regation process of the adsorbate molecules within the electrical doub
le layer. The adsorption behaviour of cetyl-dimethyl-benzylammonium ca
tions shows striking similarities with that of sodium dodecylsulphate.
Their aggregates on the electrode surface collapse to a compact layer
at potentials negative of the ecm and a polylayer is formed under fav
ourable conditions at far negative or positive polarizations respectiv
ely. Since these adsorbates have quite different structures, these sim
ilarities are attributed to their ionic character. In contrast, the su
rface aggregates of Tween 80R do not collapse to a compact layer but a
re stable over an extended potential range, forming two micellar plate
aux. Finally, general conclusions of our theoretical and experimental
studies on micellization at charged interphases are also presented.