Molecular reorganization of paired assemblies of T-shaped rod-coil amphiphilic molecule at the air-water interface.

A T-shaped aromatic amphiphilic molecule based on linear oligo(ethylene oxide) was synthesized. We suggest that its peculiar interfacial behavior at the air-water interface and the structure of the Langmuir-Blodgett monolayer are associated with its peculiar T-shape and competing steric and amphiphilic interactions at different surface pressures. At low surface pressure, uniform and smooth monolayers were formed. Upon compression, the molecular reorganization from spherical to cylindrical transformation occurred, as caused by the submerging of the oligo(ethylene oxide) chains, providing for efficient pi-pi interactions of the central core. At the highest surface pressure, the monolayer collapses into bilayer domains, following a bicontinuous network formation which tends to transform into a perforated film. The unique shape of T-like rigid aromatic cores makes their structural reorganization very peculiar with paired, dimerlike molecular packing dominating in gas and solid states. This paired aggregation is so strong that it is preserved in the course of flipping and formation of vertically oriented backbones.