Abstract: Effect of spacer chain length on aggregation of C₁₂-s-C₁₂·2Br dimeric surfactants in aqueous solutions has been investigated by using conductivity and viscosity measurements as well as steady fluorescence quench technique. The results showed the ability for the micelle formation of C₁₂-s-C₁₂·2Br dimeric surfactants is much better than that of their monomer, dodecyltrimethylammonium bromide(C₁₂ TABr). The values of cmc for the former are lower than an order compared with the latter. The aggregation number Nof C₁₂-s-C₁₂·2Br micelles decreases with increasing concentration c, specially for s=2, the value of Nincreases rapidly at c>7.7 mmol/L. The calculated result indicates a significant change in the micellar shape and the formation of prolate ellipsoid micelles at c>7.7 mmol/L. The viscosity measurement for C₁₂-2-C₁₂·2Br micellar solutions demonstrates the calculated results.

Key words: Dimeric surfactants, Effect of spacer chain length, Micelle formation, Micelle structure