4-hexylbithieno[3,2-b:2′3′-elpyridine:: An efficient electron-accepting unit in fluorene and indenofluorene copolymers for light-emitting devices - Sonar, P; Zhang, JY; Grimsdale, AC; Müllen, K; Surin, M; Lazzaroni, R; Leclère, P; Tierney, S; Heeney, M; McCulloch, I (MACROMOLECULES, 2004)