Supramolecular organisation of oligo(p-phenylenevinylene) at the air–water interface and in water

Abstract

Two novel chiral (bola)amphiphilic oligo(p-phenylenevinylene)s (OPVs) have been synthesised and fully characterised. Decoration of the hydrophobic OPV backbone with a hydrophilic tris[tetra(ethylene oxide)]benzene wedge on one side and a hydrophobic tris(alkoxy)benzene wedge on the other side, resulted in amphiphilic OPV1. In bolaamphiphile OPV2, two hydrophilic tris[tetra(ethylene oxide)]benzene wedges are connected at both ends of the OPV backbone. The organisation of the amphiphiles has been investigated at the air–water interface and in water. Langmuir monolayers of OPV1 showed that these amphiphiles are perpendicularly oriented at the air–water interface. In the case of OPV2, the OPV units are lying flat on the subphase with the hydrophilic ethylene glycol wedges pointing into the water phase. In chloroform, the OPV derivatives are present as molecularly dissolved species. In water, the amphiphilic OPV derivatives aggregate in chiral stacks, as can be concluded from UV–vis, fluorescence and CD spectroscopy. Temperature dependent measurements showed for OPV1 a transition at 50 °C from a chiral aggregated state to disordered aggregates. In the case of bolaamphiphilic OPV2, the transition at 55 °C between those states is a less cooperative process. The chiral order in the assemblies of the bolaamphiphiles can be influenced by the addition of salt.