Polyelectrolyte–surfactant complexes on solid surface

Abstract

Polyelectrolyte–surfactant complexes have been deposited on hydrophilic silicon substrates by using a horizontal deposition technique. DNA and carboxymethyl cellulose (carboxyMC) were used as short and long polyelectrolyte and dodecyltrimethylammonium bromide (DTAB) was used as water-soluble surfactant. Varying the surfactant concentration, the structural and morphological information have been obtained for these polyelectrolyte–surfactant complexes. Morphology and out-of-plane structures have been obtained by atomic force microscopy and X-ray reflectivity studies. Electron density profiles obtained from the reflectivity study show that DNA–DTAB complexes form lamellar like multilayered structure but carboxyMC–DTAB complexes form coil-like structure. At lower DTAB concentration, these DNA–DTAB and carboxyMC–DTAB complexes form Gibbs layer, whereas at higher surfactant concentration, DTAB molecules themselves form lamellar like multilayered structure that coexists with the structure formed by the complexes.