Bipyridyl-modified phosphonium polyelectrolytes: synthesis, photophysics, metal ion coordination and layer-by-layer assembly with anionic conjugated polymers

A novel class of chromophoric polyelectrolytes bearing phosphonium moieties in their backbones has been prepared to incorporate metal-binding 2,2′-bipyridyl (bipy) units. The effect of metal ion binding on the photophysical properties of the polyelectrolyte was probed. By binding metal ions to the polycation, the relative charge loading could be progressively increased as a strategy to control its supramolecular assembly with polyanions. The metallated and metal-free polyelectrolytes were utilized in layer-by-layer self-assembly with poly(acrylic acid) or anionic conjugated polymers including a poly(p-phenylene vinylene) and polythiophene derivative. The photophysical properties, nanomorphology, and substrate dependence of the resultant multilayer films were examined, and indicate that layer density, composition, and morphology can be tuned by metallation and ion pairing effects.