Rate-dependent lowering of surface tension during transformations of water-soluble surfactants from bolaform to monomeric structures

摘要

We report the synthesis of water-soluble, bolaform surfactants containing disulfide bonds (Br-N+(CH3)(3)(CH2)(8)SS(CH2)(8)N+(CH3)(3)Br-, 1) and measurements of the surface tensions of aqueous solutions of these surfactants during their reduction to monomeric, thiol-containing fragments (Br-N+(CH3)(3)(CH2)(8)SH, 2). Surface tensions measured during the redox induced transformation of 1 to 2 were found to he tower, by up to 10 mN/m, as compared to surface tensions of solutions of 1 or 2. The extent of lowering of the surface tension was dependent on the rate of transformation of 1 to 2. These results and others suggest that, during the transformation of 1 to 2 at the surface of the solution, slow desorption of 2 leads to a transient accumulation of 2 at the surface of the solution and thus to low surface tensions. We believe that redox-induced transformations of surfactants may form the basis of a general principle to create low (transient) surface tensions. References: 27