Two soluble poly(1,4-phenylene vinylene-4,4-biphenylene vinylene)s (PI, P2) were synthesized through the Wittig condensation, in which P1 and P2 contain flexible oligo(ethylene oxide) and hexyloxy side groups, respectively. Furthennore, a blend of P1 with lithium perchlorate (Pl-LP) was obtained to investigate the effect of doping. The polymers show good solubility in common organic solvents and are thermally stable (Td > 315 degreesC. The optical properties of the polymers, both in solution and as cast films, were investigated by absorption and photoluminescence (PL) spectra, whereas the electrochemical characteristics were obtained using cyclic voltammetric measurement. The LUMO levels of P1, P2, and Pl-LP are - 3.18, - 3.21 and - 3.79 eV and the band-gaps are 1.95, 2.18, and 1.27 eV, respectively. Double-layer light-emitting diodes (ITO/PEDOT/Polymer/Al) were successfully fabricated to investigate their electroluminescent (EL) properties. The PL and EL spectral maxima of PL P2, and PI-LP locate at 507-509 nm and 511-516 nm, indicating that they are yellowishgreen emitting materials. The tum-on electric field was 4.2 X 10(5), 5.6 X 10(5), and 34 X 10(5) V/cm and maximum luminance was 175, 268, and 620 cd/m(2) for pl, P2, and Pl-LP, respectively. (C) 2004 Elsevier Ltd. All rights reserved.