Highly Emissive Conjugated Polymer Excimers

Conjugated polymers often display a decrease of fluorescence efficiency upon aggregation due
in large part to enhanced interpolymer interactions that produce weakly emissive species generally described
as having excimer-like character. We have found that poly(phenylene ethynylene)s with fused pendant
[2.2.2] ring structures having alkene bridges substituted with two ester groups function to give highly emissive,
broad, and red-shifted emission spectra in the solid state. To best understand the origin of this new solid-state emissive species, we have performed photophysical studies of a series of different materials in solution,
spin-coated thin films, solid solutions, and Langmuir films. We conclude that the new, red-shifted, emissive
species originate from excimers produced by interchain interactions being mediated by the particular [2.2.2]
ring system employed. The ability to design structures that can reliably produce highly emissive conjugated
polymer excimers offers new opportunities in the emission tailoring of electroluminescence and sensory
devices.