Abstract
This review illustrates applications of the surface forces measurement for characterizing interactions of surfactant assemblies. The measurement provided new insights into dispersion properties of surfactants at the molecular level. Phenomena discussed include: (1) spontaneous vesicle formation upon changing counterions of an ammonium surfactant from bromide to acetate; (2) the cloud point of nonionic (polyoxyethylene) surfactant micelles; (3) salt (NaCl) induced fusion and aggregation of vesicles containing the ammonium or the phosphate group as a hydrophilic part; (4) an unusually long-range attraction (>200 nm) between hydrophobic surfaces. The forces measurement was employed also to study the adsorption of polyions. The obtained force profiles revealed that polystyrene sulfonate adsorbed onto the ammonium monolayers at 1:1 stoichiometry in a flat configuration. Another new study used polyelectrolyte-functionalized surfactants to prepare brush layers of polyelectrolytes. The brush layer structures of polyelectrolytes such as poly (glutamic acid) were inferred from the analysis of the steric components of the force profiles. The analysis permitted the determination of the elastic compressibility modulus of an oriented, single polymer brush layer in a solvent.
