orabase and dodecyltrimethylammonium

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.

Topics: Animals; Carboxymethylcellulose Sodium; Cattle; DNA; Electrolytes; Particle Size; Polymers; Quaternary Ammonium Compounds; Surface Properties; Surface-Active Agents

Surface tension measurements show that at low concentrations a surfactant bearing two ester groups in its chain assembles into small aggregates or else rearranges at the air/water interface to occupy less area per molecule. Only at higher surfactant concentrations do bona fide micelles form. The air/water interface, it is argued, saturates abruptly and cooperatively (as does the aggregation into micelles at the higher concentrations) to give a "critical monolayer concentration". Yet saturation does not reduce the surface tension a great deal. The bulk of surface tension reduction is imparted by monomeric surfactant in the solution via a mechanism that is obscure but may be related in part to the mechanical perturbation of the saturated film during measurement.

Topics: Adsorption; Air; Carboxymethylcellulose Sodium; Hydrophobic and Hydrophilic Interactions; Micelles; Quaternary Ammonium Compounds; Surface Tension; Surface-Active Agents; Water; Wettability