Tube Renewal versus Reptation: Polymer Diffusion in Molten Poly(Propylene Oxide)

Abstract

The translational diffusion coefficient $D$ of labeled poly(propylene oxide) chains in molten poly(propylene oxide) has been measured by fluorescence redistribution after pattern photobleaching both below and above the critical molecular weight for entanglement. Labeled poly(propylene oxide) was synthesized with exactly one fluorophore per molecule. The dependence of $D$ on solvent molecular weight in the entangled system is evidence that tube renewal is an important mechanism for self-diffusion in this moderate-molecular-weight polymer melt.