Synergism in cationic gemini – additive systems

A series of dicationic gemini surfactants with the general formula C16H33(CH3)2N+−(CH2)s−N+(CH3)2C16H33, 2Br− (where s = 4–6), designated as 16-s-16, were synthesised. Their interaction with organic additives: n-alcohols (C3H7OH, C7H15OH, C8H17OH) and the corresponding amines (C3H7NH2, C7H15NH2, C8H17NH2) in the absence and presence of KNO3 at 30°C was studied viscometrically to observe their effect on assembly formation and micellar transition. The simultaneous presence of KNO3 and organics induced rich aggregates morphologies in the gemini micellar systems by giving high viscosity values. On comparing the behaviour of the gemini surfactant series for a given alkyl chain length of the organic additive, the spacer is found to markedly influence the behaviour; shorter the spacer, earlier the sphere-to-rod transition. In the case of the conventional surfactant, CTAB, the concentration of KNO3 used with the geminis was insufficient to induce any transition.