Blue-Emitting Poly(2,7-pyrenylene)s: Synthesis and Optical Properties

The first 2,7-linked conjugated polypyrene tethering four aryl groups has been synthesized, and the photophysical properties of the polymer have been characterized. Due to the unique substitution with bulky aryl groups at the 4,5,9,10-positions of pyrene, the polymer although comprising large T-units is readily soluble in common organic solvents. The polymer has a blue fluorescence in solution with an emission band maximum at lambda = 429 nm, fulfilling the requirements for a blue-emitting polymer. To a first approximation, this can be attributed to electronically decoupled pyrene subunits due to the nodal properties of their frontier orbitals. Furthermore, in solution the intriguing blue fluorescence is combined with solvent-dependent features, which could be used as a probe for local solvent polarity. Finally, in the solid state, the red-shifted emission of the polymer could be strongly reduced by blending with a nonconjugated polymer such as polystyrene.