The role of counterions on the elasticity of highly charged lamellar phases: a small-angle x-ray and neutron-scattering determination.

摘要: The structure and fluctuations of the swollen Lα lamellar phase highly charged surfactant didodecyldimethylammonium halide fluid bilayers (DDA+X−) are studied using high-resolution small-angle x-ray scattering medium-resolution, high-contrast neutron-scattering. Caille parameter η, as a function swelling (Lα periodicity d), was determined from full q-range fits measured profiles for three different counterions (X−=Cl−, Br−, NO3−). This quantifies amplitude membrane within Landau–de Gennes smectic-A linear elasticity theory. anions used gave strong specific effects at maximum phase, while lower swellings two-phase coexistence collapsed lamellae (d∼30 ∼80A) observed bromide nitrate ions. Over intermediate dilution range all counterions, single can be continuously with pure water which is governed by an equation...