title: Synthesis and Properties of Multiarmed Geminis.
abstract: Three families of multiarmed and multicationic gemini surfactants, having pentaerythritol, dipentaerythritol, or adamantane cores, were synthesized and examined for their colloidal properties in water. Geminis with four or six six-carbon chains are highly water-soluble and do not self-assemble. But surface tension and conductivity measurements show that the geminis with four or six eight-carbon chains form micelles in the 3-6 mM range (compared to 0.5 M for a corresponding surfactant with a single chain). According to dynamic light scattering, these micelles are small (<30 Å diameter); no evidence of dendritic growth below 25 mM is evident. Geminis with four or six 12-carbon chains are too water-insoluble to examine for micelle formation. It is concluded the outward projection of the hydrocarbon chains in water greatly enhances the propensity of the surfactants to self-assemble. Micellar growth is seemingly restricted by chain pairing, chain looping, and associative ring formation. Since the aggregates have, despite these effects, greater residual water-hydrocarbon contact than found in typical micelles, water solubility of surfactants having longer chains is impaired.
authors.affiliation: Department of Chemistry, Emory University, Atlanta, Georgia 30322.
authors.forename: Fredric M.
authors.initials: FM
authors.lastname: Menger
authors.forename: Vasily A.
authors.initials: VA
authors.lastname: Migulin