Europium(III)-cored fluorinated dendrimers at the air–water surface

A series of lanthanide (Eu3+) cored fluorinated dendrimers of generations 1 through 4 (G1–G4) have been studied with respect to their film-forming properties at the air–water surface. All dendrimers studied here formed stable films at the air–water surface. At the air–water surface, the dendrimers are likely to adopt asymmetric “funnel-like” conformations wherein the lanthanide core is directed towards the water surface and the fluorinated phenyl groups are directed away from the bulk phase. This hypothesis was further tested by addition of an electrolyte (0.01 M MgSO4) to the subphase. The added electrolyte was found to (i) advance the onset of network formation, as well as completion of monolayers, and (ii) increase the collapse pressure. Both features support the asymmetric conformation hypothesis, in that addition of an electrolyte promotes further conformational changes and shields electrostatic repulsion between lanthanide cores, thus allowing for closer packing of the molecules.