title: Novel amphiphiles with preorganized functionalities-formation of Langmuir-films and efficiency in mineral flotation.
abstract: Based on the principle of supramolecular preorganization, three different types of new oligofunctional surfactants have been designed and prepared differing in both the degree of conformational flexibility and the hydrophilic-lipophilic balance of their structures due to the chosen building blocks including rather rigid and shape-persistent backbones or a dendritic subunit. Surface-active properties of the oligofunctional surfactants involving critical micellization concentration, surface tension at cmc, effectiveness of surface tension reduction, and the efficiency of adsorption were determined by use of the surface tension isotherms, respectively. In particular the amino-acid-based amphiphiles show remarkable surface-active properties with the adsorption at the air/water interface and also the aggregation to micelles starting at very low concentration. By analysis of the surface pressure-surface area isotherms interesting information on the packing behavior and orientation of the amphiphilic molecules in relation to the molecular structure could be obtained. Moreover, limiting area and collapse pressure of the Langmuir-films were determined. Morphological observation of the dynamic process of monolayer compression at the air/water interface was carried out by Brewster angle microscopy illustrating several phase states visualized as snap shots. Furthermore, the effectiveness of the new surfactants acting as collecting agents in the process of flotation using the model mineral fluorite was studied. A surprisingly high recovery of the mineral was obtained for the surfactants with constricted flexibility. The flotation plots clearly manifest that bundling of surfactant subunits by tethering to an aromatic core or by dendritic branching is profitable, indicating that effects of preorganization of the oligofunctional surfactant molecules are important.
authors.affiliation: Institute of Organic Chemistry, Freiberg University of Mining and Technology, Freiberg/Saxony, Germany.
authors.forename: P U
authors.initials: PU
authors.lastname: Müller
authors.forename: C C
authors.initials: CC
authors.lastname: Akpo
authors.forename: K W
authors.initials: KW
authors.lastname: Stöckelhuber
authors.forename: E
authors.initials: E
authors.lastname: Weber
mesh_terms: D000327:Adsorption; D000388:Air; D004305:Dose-Response Relationship, Drug; D008823:Micelles; D008853:Microscopy / Q000379:methods*; D008956:Models, Chemical; D008968:Molecular Conformation; D012492:Salts / Q000494:pharmacology; D012964:Sodium / Q000737:chemistry; D013499:Surface Properties; D013500:Surface Tension; D013501:Surface-Active Agents / Q000737:chemistry*; D014867:Water
chemical_list: D008823:Micelles; D012492:Salts; D013501:Surface-Active Agents; D014867:Water; D012964:Sodium