Self-assembly and adsorption of cetyltrimethylammonium bromide and didodecyldimethylammonium bromide surfactants at the mica-water interface.

摘要: The self-assembly and adsorption of the surfactants cetyltrimethylammonium bromide (CTAB) didodecyldimethylammonium (DDAB) at muscovite mica–water interface are studied using molecular-dynamics simulations. Adsorption takes place by an ion-exchange mechanism, in which K+ ions replaced organic alkylammonium cations from solution. Simulations performed with without surface ions, pure water, aqueous CTAB DDAB form micellar structures bulk solution, absence they quickly adsorb bilayer structures. ordering is not perfect, there a competition formation cylindrical micelles. DDAB, on other hand, forms well-ordered structure, innermost layer showing strong orientational ordering, outermost being more disordered. simulations water highlight molecular electrostatic interactions mica-surface atoms. Using simulated scattering length density profiles, results compared directly critically existing neutron reflectivity measurements. simulation generally consistent experiments, yield new insights molecular-scale interface.