High Ionization Potential Conjugated Polymers

We report the synthesis of a series of poly(p-phenylene ethynylene)s (PPEs) with high ionization
potentials and associated high excited-state electron affinities. Their photophysical properties were
investigated using steady-state and time-resolved fluorescence techniques. The ionization potentials of
the polymer thin films were determined using ultraviolet photoelectron spectroscopy (UPS), and those with
the highest ionization potentials displayed high sensitivity for the detection of electron-donating aromatic
compounds. The effects of sterics, chemical structure, and electronic properties on the polymers' sensory
responses were investigated by fluorescence quenching experiments in both solution and solid thin films.
In addition, we report that in some cases the excited-state charge-transfer complexes (exciplexes) of the
PPEs with analytes were observed. These latter effects provide promising opportunities for the formation
of sensitive and selective chemical sensors.