A series of symmetrical cationic gemini surfactants of the type N,N 0 -didodecyl-N,N,N 0 ,N 0 -tetramethylalkane-R, ω-diammonium dibromide "12-s-12" (s = 2, 4, 6, 8, 10, and 12) are synthesized, and their micellization study in aqueous solution is systematically reported. Specific conductivity as a function of surfactant concentration was measured, and critical micelle concentration (CMC), degree of counterion dissociation (R) of the micelle, and thermodynamic parameters, namely, Gibbs energy (ΔG m ), enthalpy (ΔH m ), and entropy (ΔS m ), of micellization were evaluated using this data at various temperatures. Surface tension studies at 298.15 K provided similar CMCs as given by conductometry along with information on the efficiency/ effectiveness and the area occupied per molecule. Small-angle neutron scattering (SANS) inferred the presence of few morphological geometries ranging from spherical to rodlike micelles. Results are explained in terms of the hydrophobicity of spacer chain length along with the electrostatic repulsion between the cationic centers of gemini surfactant molecules.

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The interaction between mixtures of nonionic surfactant polyethylene glycol p-(1,1,3,3-tetramethyl butyl)-phenyl ether and cationic gemini surfactants alkanediyl-a,x-bis(dimethyldodecylammonium bromide) (12-s-12, where s = 2, 4 and 6) was studied using surface tension and small-angle neutron scattering measurements. Marked interaction was observed for the investigated surfactants mixtures which depend upon the hydrophobic spacer length of the gemini surfactant and also on the fraction of nonionic surfactant in the mixed systems. The results are discussed in terms of interaction parameters calculated according to the theory of regular solutions which uses the critical micelle concentration determined tensiometrically to calculate the molecular interaction parameter and the mole fractions of the two components in the mixed micelles. A relatively high negative molecular interaction parameter value (up to -3.40) obtained for mixtures of nonionic and cationic gemini surfactant indicates a presence of strong attractive interaction in the mixed system that increases with the spacer length of the gemini surfactant. Micellar parameters deduced from small-angle neutron scattering measurements also compliment the surface tension results.