Synthesis, electron mobility, and electroluminescence of a polynorbornene-supported silole

A solution-processable polynorbornene with pendant fluorescent and electron-transport silole groups was synthesized using ruthenium-complex-initiated ring-opening metathesis polymerization. A weight-average molecular weight around 59,300 and a low polydispersity index of 1.4 were estimated for the polymer using gel permeation chromatography. The thermal, electronic, photo- and electroluminescence properties of the polymer were investigated and compared with those of a small-molecule reference compound. The polymer exhibits better thermal stability than the small molecule and exhibits a glass transition temperature of 91 °C, while retaining the optical and electronic properties of the corresponding small-molecule silole. The room temperature electron mobility was measured using the time-of-flight technique to be 3.5 × 10−5 cm2/V/s at an applied electric field of 7.5 × 105 V/cm. Organic light-emitting diodes fabricated using the polymer as the electron transport and emissive layer have low efficiencies; introduction of an additional tris(8-hydroxyquinolinato)aluminum (Alq3) electron-transport layer leads not only to increased efficiency, but also to increased contributions to the electroluminescence from the Alq3.