Synthesis and properties of hyperbranched poly(triphenylamine)s prepared by palladium catalyzed C-N coupling reaction

Abstract

Hyperbranched poly(triphenylamine)s with various end functional groups were prepared starting from 4, 4′-diamino-4″-bromotriphenylamine through palladium catalyzed C-N coupling reaction. The self-polycondensation of the monomer afforded secondary amino groups predominantly. End-capped polymers were isolated by the chemical modification of unreacted amino groups by acid chlorides. The properties of the hyperbranched poly(triphenylamine)s, such as solubility, thermal stability and ionization potential, were dependent on the end functional groups. The hyper-branched poly(triphenylamine)s were examined as a hole transporting material for organic light emitting diodes. The multi-layered device composed of ITO/hyperbranched poly(triphenylamine)/Alq3/Mg-Ag showed yellow-green emission derived from Alq3. The device performance was improved when the polymer end-capped with alkyl chlorides were used as a hole transporting material. Since the ionization potentials of the hyperbranched polymer with alkyl amide end groups were higher than that with aromatic amide end groups, efficient hole injection from ITO/hyperbranched poly(triphenylamine)/Alq3 might be achieved to improve the device performance.