Macromolecule self-diffusion in poly(ethylene glycol) melts

Macromolecule self-diffusion in poly(ethylene glycol)s with Mn = 3 × 102 to 4 × 104 and Mw Mn ≈ 1.1 was investigated by pulsed field gradient nuclear magnetic resonance. Samples with Mn < 3 × 103 were characterized by a single self-diffusion coefficient, D. In the fraction with high Mn, a spectrum of values of D was found, its width depending on the diffusion time. The existence of the spectrum of D is explained by the existence of macromolecule dynamic clusters with a finite lifetime in melts. The dependence of the average self-diffusion coefficients on molecular weights is described by a curve with two linear regions, the change in slope occurring where the entanglement network first appears. © 1986