Small-angle neutron-scattering study and micellar model of the gemini (phenylenedimethylene)bis(n-octylammonium)dibromide surfactant micelles in water

The microstructure of the micelles formed in aqueous solution by gemini sur factants with aromatic spacers, [Br(CH3)(2)N+(CmH2m+1)- (Ph)-(CmH2m+l)N+(CH 3)(2)Br, m = 8 and Ph - o-, m- or p-phenylenedimethylene] has been examined by small-angle neutron scattering. Aggregation of the gemini surfactants w ith an o-phenylenedimethylene spacer brings about formation of premicelles and small micelles at concentrations below the second critical micelle conc entration, while above this concentration marked micellar growth and variat ion in shape occurs. It is suggested that the minimum aggregate formed at t his critical micelle concentration may be the trimer or tetramer and that t his result supports the mechanism of "gemini --> submicelle --> assembly" f or micellar growth.