A novel hyperbranched copolymer, poly(2,4,6-tributyloxy-1,3,5-trivinylenephenylene-co-2-methoxy-5-octyloxy-p-phenyelenevinylene) PTBOTV-co-PMOPV, and a linear counterpart poly(2-methoxy-5-octyloxy-p-phenyelenevinylene) (PMOPV) were synthesized by the Gilch polymerization and characterized with UV-vis, FT-IR, H-1 NMR and Photoluminescence (PL) spectroscopy. PTBOTV-co-PMOPV showed excellent solubility, good film-formation ability, and high thermal stability. The UV-vis, PL, and electroluminescence (EL) spectra of PTBOTV-co-PMOPV were blue-shifted approximately 9-15 nm on comparison with those of PMOPV. The polymer light-emitting diode (PLED) was fabricated in ITO/PEDOT (50 nm)/polymer (60 nm)/ Alq(3) (30 nm)/LiF (1 nm)/Al (200 nm) configuration. The PTBOTV-co-PMOPV exhibited the maximum external quantum efficiency (EQE) of 0.26% at 60.7 cd/m(2), while the PMOPV device showed the maximum EQE of 0.17% at 88 cd/m(2).