A new hole injecting polymer for an electroluminescent element was prepared by radical polymerization of a methacrylate monomer that contains an N’-bipheny-N,N-diphenylamine unit as a pendent side chain. Cyclic voltammetry of the polymer coated on an ITO electrode shows a chemically irreversible oxidation at 1.2 V. Subsequent cycles reveal that the newly formed species is electrochemically stable. The polymer was used as both an electroluminescent layer and a hole injection layer in single- and double-layered devices, respectively. The double-layered device using ITO as the anode, Al as the cathode, and poly[methyl(2-(1-pyrenyl)ethyl)siloxane] as the electroluminescent layer gave bright blue-green light with a maximum brightness level of 168 cd/m(2) and an internal quantum efficiency of 0.20%.