Side by Side, but Not Together: Simultaneous Polymerization of Aniline and Pyrrole Yields a Homopolymer Blend

Abstract The present work shows that simultaneous polymerization of aniline and pyrrole does not lead to formation of the respective copolymer (PANI-PPy), despite hundreds of research papers claiming otherwise. For the first time, solid-state 15N magic-angle spinning nuclear magnetic resonance (NMR) of the polymerization products synthesized from 15N-monomers was used to complement conventional methods of conducting polymer characterization (scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, and Raman spectroscopy) to confirm the material composition. The NMR analysis showed that PANI-PPy contains two individual conducting polymer domains coupled through π–π interactions, which was also supported by vibrational spectroscopy. The block copolymer structure of PANI-PPy, which cannot be directly excluded by the results of spectroscopic characterization, contradicts the SEM data, showing distinct micrometer-size individual phases with morphologies similar to pristine homopolymers. Therefore, it is concluded that PANI-PPy produced by simultaneous polymerization of the respective monomers is not a genuine copolymer, but rather a domain-separated blend of homopolymers.