STABILIZATION OF WATER-SOLUBLE SURFACTANTS AT THE AIR-WATER-INTERFACEWITH GEGENION COMPLEXATION

In this study the stability of Langmuir layers of tetradecyl benzoic a cid (TDBA) interacting with poly(ethyleneimine) (PEI) in the subphase is analyzed as a function of PEI concentration, PEI molecular weight a nd surface pressure. Stable Gegenion complex, Langmuir monolayers were obtained in the PEI concentration range of 0.75 to 1.5 mM PEI monomer , and the surface pressure vs. specific area isotherms were independen t of the PEI concentration. The isotherms were expanded indicating sig nificant molecular interactions between TDBA and PEI. No effect of the molecular weight of PEI on the isotherms was observed. Outside this c oncentration range the Gegenion complex, Langmuir monolayers were eith er unstable or the isotherms were dependent on the PEI concentration, The structure of the Gegenion complex, Langmuir-Blodgett films were in vestigated using IR spectroscopy.