Effect of structural features of polypyrrole (PPy) on electrical conductivity reflected on 13C ssNMR parameters

Polypyrroles are widely used in the chemical industry because of their variable conductivity and stability. Their precise structural description and understanding of their electronic structure are crucial steps for targeted synthesis and specific use. Herein, we present an experimental strategy using solid-state C-13 NMR spectroscopy allowing detailed structural characterization of a wide range of polypyrrole systems with considerably differing conductivity ranging from 5.3 x 10(-7) S cm(-1) to 103 S cm(-1). In this regard, we have optimized an experimental strategy combining traditional as well as advanced NMR techniques allowing reliable detection of spectra for all samples in this heterogeneous group of systems. From all recorded C-13 NMR spectra the relative content of quinoid form present in each sample is determined and correlated with observed conductivity. Furthermore, the correlation among content of quinoid form, sample conductivity and half-width of corresponding C-13 NMR signal was revealed. We show that by obtaining one of the three experimentally obtained parameters, the other two can be quickly and easily estimated.