Two new soluble block copolymers are reported in which chromophores and hexa(ethylene oxide) units alternate along the polymer backbone. In polymer I the chromophore was the distyrylbenzene unit. The polymer was synthesised via the Wittig reaction and the ionisation potential of 5.4 +/- 0.2 eV was measured by cyclic voltammetry and photoelectron spectroscopy. Polymer I showed a high solid-state photoluminescence efficiency (34%) and was used to make efficient (0.5 cd/A) light emitting diodes (LEDs). Polymer I was also used in light emitting cells; these showed luminescence in reverse bias and a reduced turn-on voltage compared to the LEDs. Polymer 2, in which the chromophore was dodecafluoro-distryrylbenzene, was prepared via the Horner-Wittig reaction and showed an ionisation potential of 6.25 +/-0.15 eV and a solid-state photoluminescence efficiency of 17%. It was used as electron-conducting layer in a LED but failed to give significant electroluminescence. The optical energy gap for both polymers was 3.0 eV.