Relaxation Spectrum of Polytetrafluoroethylene Obtained from Electron Paramagnetic Resonance and Nuclear Magnetic Resonance Spectra

Abstract

Distribution of the correlation time in solid polymers was taken into consideration in the analysis of the magnetic resonance data. Motional narrowing of the line width of the EPR spectrum of fluoroalkyl radicals in polytetrafluoroethylene and that of broad line NMR spectrum (fluorine resonance) were observed on the same samples at the temperatures ranging from 260 to 320K. Since EPR and NMR measurements are measurements with different characteristic times of observation, representative correlation times corresponding to respective measurements were found to agree with the relaxation theory proposed by Miyake [J. Polym. Sci. 28: 476 (1958)] in which distributions of correlation time were taken into consideration. Based on these values, the real activation energy of the molecular motion associated with the motional narrowings of EPR and NMR studies were found to be 310 KJ/mol. On the other hand, the activation energy which gives the same relaxation spectrum as obtained from EPR and NMR data was found to be 318 KJ/mol. This reflects that the analysis in the present paper is a proper analysis. The present paper presents an example in which the consideration of the distribution of the correlation time was successfully applied.