Long-ranged relaxations in poly(ethylene oxide) melts: Evidence for network behavior

Abstract

Two slow, long-ranged relaxations in melts of poly(ethylene oxide) (PEO) were studied using the noninvasive dynamic light-scattering technique of photon correlation spectroscopy (PCS). Measurements were made for two PEO samples, one with a molecular weight distinctly above the entanglement value and a second sample with a molecular weight distinctly below the entanglement value. Based on several lines of evidence, it is concluded that the faster of these relaxations, which can be identified with the “cluster” or “Fischer” mode observed earlier in other homopolymer melts, results from the gel-like behavior of a physical network formed by the polymer in the melt, while larger-scale rearrangements in the polymer network structure are responsible for the slower relaxation.