Blue solid-state photoluminescence and electroluminescence from novel poly(para-phenyleneethynylene) copolymers

We report the synthesis of a series of random copolymers composed of phenyleneethynylene and 3,7-di-tert-butylnaphthalene units by alkyne metathesis with simple catalyst systems, formed from MO(CO)(6) and 4-chlorophenol in situ. These novel copolymers give rise to efficient (Phi = 0.16-0.76) blue solid-state emission (lambda (max) = 422-443 nm) which can be fine-tuned according to their naphthalene content differing greatly from that of standard dialkyl-PPE (lambda (max) 500-520 nm). The effective and blue-shifted solid-state emission is a result of disrupting the solid-state alignment thereby diminishing pi-pi interactions of the copolymers in addition to the efficient interruption of planarization of the conjugated backbone. Electroluminescent multilayer devices showed low turn-on voltages (5.5 V) and a maximum brightness of 100 cd/m(2).