Vinyl polymer containing 1,4-distyrylbenzene chromophores: Synthesis, optical, electrochemical properties and its blend with PVK and Ir(ppy)₃

Vinyl polymer PDSB containing pendant 1,4-distyrylbenzene derivatives was prepared from its precursor poly(4-vinylbenzyl chloride) (PVBC: M_w = 10,400, PDI = 1.12), which had been synthesized by the controlled radical polymerization (RAFT). PDSB is readily soluble in common organic solvents and basically amorphous material with 5% weight-loss temperature higher than 390 °C. The HOMO level of PDSB, estimated from cyclic voltammetric data, is -5.15 eV, which is higher than -5.8 eV of PVK and thus effective in reducing the hole injection barrier between the PEDOT:PSS and emitting layer. The blend films of fluorescent isolated blue emitter (PDSB) and phosphorescent green system [PVK/Ir(ppy)₃] were prepared to tune color emission. The blend films [PVK:PDSB:Ir(ppy)₃] show composition-dependent behavior in PL spectral properties and EL characteristics. The PL spectra of the blend films [PVK:PDSB:Ir(ppy)₃] show a major emission at 515 nm and a minor peak at 454 nm, which are attributed to Ir(ppy)₃ and PDSB, respectively. The C.I.E. 1931 coordinates of the blend LED devices shift from (0.29, 0.61) for PVK:PDSB = 10:0 to (0.25, 0.35) for PVK:PDSB = 0:10 with the increase of PDSB content.