Molecular motions of polymers having helical conformation. I. Poly(ethylene glycol) and polyoxymethylene

In order to study molecular motion characteristic of a helical polymer, proton magnetic resonance spectra and the complex dielectric constants ε * for a wide frequency range have been measured in the temperature region between 90°K. and the melting point for poly(ethylene glycol), which is thought to be helical in the solid state. The molecular weights of the samples are 4000, 1000, and 400. These results suggest that a molecular motion such as rotation or oscillation is able to occur even in crystalline regions well below the melting point. The temperature at which this type of molecular motion begins seems to be independent of the molecular weight of the samples, although the melting point is found to depend markedly on molecular weight. X‐ray and dilatometric measurements were carried out for the same samples and indicate the absence of a crystalline phase transition (first‐order transformation) at the temperature region where the narrowing of the NMR line width of PEG is observed. The results for another helical polymer, polyoxymethylene, are also presented.