An electron and X-ray diffraction study of conducting polypyrrole/dodecyl sulfate

Electron diffraction patterns have been obtained for thin crystals of polypyrrole doped with dodecyl sulfate. The data show six-fold symmetry and have been indexed to a hexagonal crystal structure with a = 0.92 nm. X-ray diffraction patterns of the bulk polymer were also obtained and indexed to a hexagonal structure, giving a = 0.90 nm and c = 1.24 nm. These results are consistent with those obtained for poly(3-methylthiophene) for which a helical structure has been proposed. Convergent beam electron diffraction patterns suggest that the observed structure continues into the bulk polymer but in a less ordered manner. It is suggested that although most of the published experimental data on the structure of polypyrroles has been interpreted as consistent with the trans linear chain formation, the cis helical structure cannot be excluded.