The solid-state organization of 'self-doped' PPV oligomers

Using a combination of multi-frequency EPR and NMR spectroscopy and quantum-chemical calculations at the level of Density Functional Theory (DFT), the organization of self-doped PPV oligomers in their solid state is investigated. The analysis of the different spectra shows that the electrochemical procedure used to self-dope these materials produces positive radicals (polarons) in an almost quantitative way, but still magnetically isolated polarons are observed. The difference between chemical and electrochemical oxidation of the oligomers is studied in detail. Furthermore, ageing of the electrochemically oxidized oligomers may be accompanied by a stacking of the oligomers.