NMR line-shape analysis of swollen crosslinked poly(ethylene oxide) using an orientation-dependent Gaussian broadening function with varying width

Abstract

NMR line shapes of swollen crosslinked poly(oxyethylene) were analysed as a convolution of a narrow Lorentzian function governed by rapid segmental motions, and a dipolar broadening function. An orientation-dependent Gaussian function with some distribution of its width was chosen for the dipolar broadening function. For the distribution of the width a function similar to the χ2 distribution was used. An appreciable improvement compared to the previous analysis with the orientation-dependent Lorentz function was only obtained if the distribution used contained an essential amount of narrow widths close to zero. With this approach, it was possible to simulate the experimental spectra obtained in the CDCl3 swelling agent at various temperatures within experimental accuracy. With the CCl4 swelling agent, the agreement was slightly worse in the peak area, apparently due to the distribution of the width of the narrow Lorentzian function governed by rapid segmental motions. Even in this case, an improvement compared to the previous analysis was obtained. It was found that a simple Gaussian distribution function with the maximum at zero width, which is a special case of the general distribution function used, can reproduce the experimental spectra with almost the same accuracy as the general distribution function.