Phenothiazine-S,S-dioxide- and fluorene-based light-emitting polymers: Introduction of e(-)-deficient S,S-dioxide into e(-)-rich phenothiazine

Abstract

A novel series of poly(10-hexyl-phenothiazine-S,S-dioxide-3,7-diyl) and poly(9,9'-dioetyl-fluorene-2,7-diyl-alt-10-hexyl-3,7-phenothiazine-S,S-dioxide) (PFPTZSS) compounds were synthesized through Ni(0)-mediated Yamamoto polymerization and Pd(II)-catalyzed Suzuki polymerization. The synthesized polymers were characterized by H-1 NMR spectroscopy and elemental analysis and showed higher glass transition temperatures than that of pristine polyfluorene. In terms of photoluminescence (PL), the PFPTZ-SS compounds were highly fluorescent with bright blue emissions in the solid state. Light-emitting devices were fabricated with these polymers in an indium tin oxide/poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate)/ polymer/Ca/Al configuration. The electroluminescence (EL) of the copolymers differed from the PL characteristics: the EL device exhibited a redshifted greenish-blue emission in contrast to the blue emission observed in the PL. Additionally, this unique phenothiazine-S,S-dioxide property, triggered by the introduction of an electron-deficient SO2 unit into the electron-rich phenothiazine, gave rise to improvements in the brightness, maximum luminescence intensity, and quantum efficiency of the EL devices fabricated with PFPTZ-SS. (c) 2007 Wiley Periodicals, Inc.