Photophysical study of a conjugated-non-conjugated PPV-type electroluminescent copolymer

This paper reports the photo- and electroluminescence studies of emitting species of one of the first reported blue emitters, the conjugated-non-conjugated multi-block copolymer, poly[1,8-octanedioxy-2,6-dimethoxy-1,4-phenylene-1,2-ethenylene-1,4-phenylene-1,2-ethenylene-3,5-dimethoxy-1,4-phenylene]. Because the conjugation length of the emissive center is very well defined (two and half phenylene-vinylene units) the differences found between the fluorescence profile of the fluorophore in solution, at several concentrations and that in the solid state allowed us to conclude that in solid the emission comes from associated forms, such as ground-state dimers and/or excimers. Time-resolved fluorescence in a nanosecond time scale recorded at ϖem=24,096 cm−1 showed a monoexponential decay of 1.5 ns, which is compatible with rigid forms of stilbene derivatives.