Light-emitting diodes based on poly(methacrylates) with distyrylbenzene and oxadiazole side chains

We report investigations on the use of singly and doubly functionalised poly(methacrylates) (PMA) for the fabrication of polymeric light-emitting diodes (LEDs). The functional groups we used were distyrylbenzene (DSB) as blue chromophore and 2-phenyl-5-phenyl-1,3,4-oxadiazole (PPD) or 2-phenyl-5-biphenyl-1,3,4-oxadiazole (PBD) as charge-transport groups to produce three homopolymers (with one functional group only) and a copolymer bearing both DSB and PBD groups (PMA-DSB-PBD). The polymers have been used alone or blended together in single-layer devices or in double-layer devices, for which a thin poly(p-phenylene vinylene) (PPV) layer was used as a hole-transporting material. Despite the high photoluminescence yield of these DSB-based materials, successful fabrication of blue-emitting LEDs has only been achieved by using the copolymer, both in single- and double-layer devices.