Ladder-type oligo(p-phenylene)s tethered to a poly(alkylene) main chain: The orthogonal approach to functional light-emitting polymers

We report a series of light-emitting polymers with ladder-type oligo(p-phenylene) units orthogonally and periodically tethered to a polyalkylene main chain via a substitution-type condensation polymerization reaction. This involved the reaction between lithiated fluoreneacene oligomers and a homologous series of α,ω-dibromoalkanes. The fluoreneacene oligomers were synthesized using a step by-step procedure involving the Suzuki coupling method, Grignard reaction, and Friedel-Crafts type ring closure (alkylation). The polymerization involved lithiation of the reactive hydrogens in the middle phenyl group followed by an S_N2-type condensation polymerization with the dibromoalkanes. The oligomers have spectral properties consistent with that of other ladder-type p-pheneneylene structures. The alkylene chain length influenced the luminophore aggregation and excimer formation in the solid state. These materials showed high photoluminescence efficiencies in both solution and solid state, making them good candidates as organic materials for light-emitting devices.