Surface properties of gemini surfactant dsdbs in aqueous solution

The surface properties of gemini surfactant aqueous solution, referred to as dimeric sodium dodecyl benzene sulfonate DSDBS-x, where x was the carbon numbers of the spacer(x=2 and 6), were investigated by using the determinations of surface tension, conductivity and freeze-fracture-transmission-electron-microscopy(FF-TEM) method. It was found that the critical micelle concentration(CMC) at 30°C for DSDBS-2 and DSDBS-6 were 1.3×10-5 and 2.5×10-5 mol/L, respectively, and their micelle structures were more compact than that of corresponding conventional monomer sodium dodecyl benzene sulfonate(SDBS). With DSDBS concentration increased more than four times of its CMC, the solution conductivity deviated from the expected linear relationship as the consequence of spheroidal micelles transferring into rod-micelles. Furthermore, the influence of NaCl on the surface excess concentration (ΓCMC) of DSDBS-6 was stronger than that of DSDBS-2, owing to the former's longer carbon chain bending toward to interface easily.