ESR Studies on the Micellization Behaviors of a Series of Novel Asymmetric Gemini Surfactants

The synthesis of a new series of asymmetric cationic gemini surfactant and the investigation of their micellization behaviors by electronic spin resonance (ESR) as well as the surface tension measurements were reported. 4-Oxo-2,2,6,6-tetramethylpiperidine-N-oxyl (4-oxo-TEMPO) is used as the spin probe. The surfactants studied have the general formula [C_nH_2n+1 N⁺ (CH₃)₂C₆H₁₂N⁺(CH₃)₂C_mH_2m+1]Br₂⁻, referred to as dimeric n-6-m surfactants, in which n and m are the numbers of carbon atoms in the asymmetric side alkyl chains. From the experimental data, rotational correlation time τ_c, surface tension and critical micelle concentration (cmc) values, the physical properties of these new surfactants have preliminarily been e-valuated. It is shown that this new series of asymmetric gemini surfactants has interesting micellization behaviors, and they are very different in aggregating tendency from their asymmetric analogues.