Vibrational analysis as a tool for detecting electronic mobility. The case of the alternating Ethylene- tetrafluoroethylene copolymers.

Frequency and intensity spectroscopies have been used in the reanalysis of the vibrational spectrum (IR and Raman) of alternate copolymers of ethylene and tetrafluoroethylene. A new assignment of the CH stretching fundamental is proposed. The seeming anomalies of the infrared spectrum in the CH stretching range are accounted for in terms of equilibrium atomic charges and charge fluxes. In particular, the analysis of the dichroic ratios shows that there exists a relevant mobility of the electronic charge along the C-C bonds.