Aggregation number of alkanediyl-α,ω-bis(dimethylalkylammonium bromide) surfactants determined by static light scattering

Aggregation number of alkanediyl-α,ω-bis(dimethylalkylammonium bromide) surfactants in aqueous solutions has been determined at different number of carbon atoms in the alkyl tail ‘m’ and in spacer ‘s’ by using static light scattering. Values of aggregation number at different spacer numbers s=2–10 lie between 17 and 33 and between 18 and 55 for alkyl tail lengths m=9–16, respectively. Data for variable parameter s correspond to results obtained by neutron scattering technique. In all cases but s=2 and m=16, the slopes of Debye plots were found to be increasing and the value of the second virial coefficient B was found to be in the range 1.3×10−3–13×10−3 cm3 mol g−2 indicating the spherical shape of micelles. Increased aggregation number and negative B of surfactant with the shortest spacer s=2 indicates the rod-like micelle shape. Aggregation number of surfactant with the longest alkyl tail m=16 is too small to predict the rod-like shape of the micelle.