31P and 19F solid state NMR have been used to study the nature of the PF6− anion in polypyrrole films at various levels of oxidation. It appears that the symmetric PF6− unit remains undistorted and unchanged throughout, suggesting that it is predominantly acting only as a counterion and not as a true ‘dopant’, since any distortion in the phosphorous environments would result at the very least in chemical shift anisotropy of the 31P nucleus. A second set of phosphorous and fluorine resonances, which are consistent with a difluoride phosphorous compound, appeared in the films. Upon electrochemical reduction of the polymer, the undistorted PF6− anion leaves the film whereas the second phosphorous species remains. Re-oxidation of the polymer reverses the processes observed during reduction.
Field of Research
039999 Chemical Sciences not elsewhere classified
Socio Economic Objective
970103 Expanding Knowledge in the Chemical Sciences