Control of the conjugation length and solubility in electroluminescent polymers

A new type of cyclolinear polymer, poly(phenylene vinylene-alt-cyclotriphosphazene), was synthesized through Heck-type coupling reactions to produce π-conjugated macromolecules with excellent solubility and precise electronic control of the band-gap energy. This synthesis method is capable of producing well-defined alternating polymers. The method is highly adaptable and can be readily used for other chromophore systems. The resulting polymers were also capable of accommodating a wide variety of substituents on the cyclophosphazene rings with minimal effect on the electronic properties. The band gap and electron affinities of the polymer were varied through the manipulation of the π-conjugated unit located between the insulating phosphazene rings. Each chromophore matched the intended conjugation length consistently throughout the macromolecules. The polymers were good film formers because of the chosen substituents on the phosphazene rings. The absorbance of the polymers indicated minimal spectral shift from the monomer absorbance. This suggested an effective insulation of each chromophore unit from its neighbors by the phosphazene rings. Solution photoluminescence efficiencies were found to be up to 44.1%.