Nanostructured semiconductor block copolymers:: π-π Stacking, optical and electrochemical properties

The structural and optical properties of semiconductor block copolymers containing triphenylamine as hole transport material and perylene bisimide as dye and electron transport material are reported. The polymers were prepared by nitroxide mediated controlled radical polymerisation and characterized with GPC, DSC, and TGA. The electrochemical properties as determined by cyclic voltammetry show the HOMO and LUMO values of the block copolymers to be -5.23 eV and -3.65 eV, respectively. The perylene bisimide units aggregate by pi-pi stacking which could be analyzed with wide-angle X-ray scattering. The absorption and fluorescence properties of the perylene bisimide polymers and monomers in solution and film were investigated. It could be shown that they are strongly influenced by intramolecular coupling between different perylene bisimide units in polymers. The block copolymers exhibit a microphase separation on a nanometer scale with a constant perylene bisimide domain width of 13 nm and lengths of up to several micrometers. (C) 2006 Elsevier B.V. All rights reserved.