Dendrimer and polystyrene surfactant structure at the air-water interface

The Π-A isotherms at the air-water interface and 25°C for monomolecular films of the recently synthesized dendrimer surfactants are reported and compared with those of polystyrene terminated with a single hydroxyl group. There is a strong dependence of the isotherms on molecular weight (MW) for both systems, the lower MWs typified by an increase in the surface pressure through a liquid expanded phase, followed by a peaked collapse transition, indicating a nucleation and growth process, to a liquid condensed, phase. The higher molecular weight dendrimer and polystyrene isotherms are also similar, with a steep increase in the surface pressure being due to a direct transition to a solid phase.