Synthetic Metals, 31 (1989) 147 - 153 147 MAGNETIC RESONANCE AND ELECTROCHEMICAL STUDIES OF POLY(PHENYLENE VINYLENE) A. PRON*, F. GENOUD**, M. NECHTSCHEIN and A. ROUSSEAU CENG, DRF, SPh/DSPE ER CNRS 216; 85X, 38041 Grenoble Cddex (France) (Received November 30, 1988; in revised form January 23, 1989; accepted January 30, 1989) Abstract The structure of poly(p-phenylene vinylene) (PPV) is investigated by 13C solid-state n.m.r. Electrochemical oxidative doping of PPV is studied by cyclic voltammetry and in situ e.s.r, experiments: both methods give evidence for a reversible oxidation process at 1.23 V superimposed on an irreversible one. The electrochemical response of the 'reversible' spins is consistent with polaron formation upon doping. Introduction Poly(p-phenylene vinylene) (PPV) prepared by the soluble polymeric precursor has been the subject of significant research interest in recent years, mainly due to the fact that the precursor film may be stretched-aligned during thermal transformation. The oriented films obtained can, in turn, be oxidatively doped to give conducting polymers. Several papers con- cerning molecular orientation [1, 2], doping [3], structure [4] and optical properties [5, 6] of PPV have been published. Since PPV can be formally considered as a copolymer of polyacetylene and poly(p-phenylene), it has a non-degenerate ground state. In general, in polymers of this type one observes spin generation upon charge injection, followed by spin annihilation for higher charges [7, 8]. Such behaviour can be interpreted in terms of polaron-bipolaron transition and it can easily be monitored by an in situ e.s.r.-electrochemical experiment. It is therefore interesting to verify whether a similar spin-charge relationship exists in the case of PPV. In this communication we present the structure of PPV investigated by 13C n.m.r, studies and the results of spin concentration measurements carried out during electrochemical cycling of PPV placed in an e.s.r, cavity. *Permanent address: Department of Chemistry, Technical University of Warsaw, 00664 Warsaw, Poland. **Universit6 J. Fourier, Grenoble. 0379-6779/89/$3.50 © Elsevier Sequoia/Printed in The Netherlands