Copolymer architectures containing donor and acceptor units for blue light-emitting diodes

Here we describe a study of the properties of some polyoxadiazoles containing bulky fluorene units suitable for blue polymer light emitting diodes (LEDs). These copolymers present good solubility in convenient solvents such as NMP, DMF, DMAc and THF, allowing to obtain thin films by pouring the solutions of polymers onto glass substrates or silicon wafers. Very thin films as-deposited onto glass plates studied by AFM technique exhibit a free pinhole, very smooth surface and practically without defects, over a scanning range of 3 - 10 mu m. All the copolymers show good thermal stability, up to 400 degrees C and glass transition temperature in the range of 144-173 degrees C. UV-vis absorption spectra of these polymers performed in very dilute solutions exhibit absorption peaks and shoulders in the range of 280 - 340 nm. Excited with UV light peaking at 360 nm, the polymers in solutions and in solid state show photoluminescence in the blue domain.